Astrophysics

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New submissions for Fri, 6 Dec 19

[1]  arXiv:1912.02180 [pdf, other]

Title: Simultaneous detection of an intrinsic absorber and a compact jet emission in the X-ray binary IGR J17091-3624 during a hard accretion state

Authors: E. Gatuzz, M. Díaz Trigo, J.C.A. Miller-Jones, S. Migliari

Comments: 13 pages, 10 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a detailed analysis of three XMM-Newton observations of the black hole low-mass X-ray binary IGR~J17091-3624 taken during its 2016 outburst. Radio observations obtained with the Australia Telescope Compact Array (ATCA) indicate the presence of a compact jet during all observations. From the best X-ray data fit results we concluded that the observations were taken during a transition from a hard accretion state to a hard-intermediate accretion state. For Observations 1 and 2 a local absorber can be identified in the EPIC-pn spectra but not in the RGS spectra, preventing us from distinguishing between absorption local to the source and that from the hot ISM component. For Observation 3, on the other hand, we have identified an intrinsic ionized static absorber in both EPIC-pn and RGS spectra. The absorber, observed simultaneously with a compact jet emission, is characterized by an ionization parameter of 1.96< log({\xi}) <2.05 and traced mainly by Ne X, Mg XII, Si XIII and Fe XVIII.

[2]  arXiv:1912.02183 [pdf, other]

Title: Multi-Gaussian fitting Algorithm to determine multi-band photometry and photometric redshifts of LABOCA and Herschel sources in proto-cluster environments

Authors: Youngik Lee

Comments: 13 pages, 25 figures

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

This research focuses on identifying high redshift galaxies from LABOCA(LArge APEX BOlometer CAmera) and SPIRE(The Spectral and Photometric Imaging Receiver) maps towards proto-cluster candidates initially selected from the SPT (South pole telescope) survey. Based on the Multi-Gaussian fitting algorithm, we cross-match all significant LABOCA sources at SPIRE wavelengths based on their coordinates and signal to noise ratio to derive their photometry at 250, 350, 500 and 870 $\mu m$. We use this information to calculate a photometric redshift for SPT sources towards cluster fields. The code was developed in the Python programming environment.

[3]  arXiv:1912.02185 [pdf, ps, other]

Title: Proton-synchrotron as the radiation mechanism of the prompt emission of GRBs?

Authors: G. Ghisellini (1), G. Ghirlanda (1), G. Oganesyan (2,3,4), S. Ascenzi (1), L. Nava (1,5,6,7), A. Celotti (8,1,6,7), O.S. Salafia (1), E.M. Ravasio (1,9), M. Ronchi (1) (1:OA Brera, 2: GSSI, 3: INFN L'Aquila, 4: OA Teramo, 5: OA Trieste, 6: INFN 7: IFPU Trieste, 8: SISSA Trieste, 9: Univ. Bicocca Milano)

Comments: 7 pages, 3 figures, Submitted to A&A

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We discuss the new surprising observational results that indicate quite convincingly that the prompt emission of Gamma-Ray Bursts (GRBs) is due to synchrotron radiation produced by a particle distribution that has a low energy cut-off. The evidence of this is provided by the low energy part of the spectrum of the prompt emission, that shows the characteristic F(nu) \propto nu^(1/3) shape followed by F(nu) \propto nu^(-1/2) up to the peak frequency. This implies that although the emitting particles are in fast cooling, they do not cool completely. This poses a severe challenge to the basic ideas about how and where the emission is produced, because the incomplete cooling requires a small value of the magnetic field, to limit synchrotron cooling, and a large emitting region, to limit the self-Compton cooling, even considering Klein-Nishina scattering effects. Some new and fundamental ingredient is required for understanding the GRBs prompt emission. We propose proton-synchrotron as a promising mechanism to solve the incomplete cooling puzzle.

[4]  arXiv:1912.02186 [pdf, other]

Title: Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies

Authors: Evan N. Kirby (1), Karoline M. Gilbert (2 and 3), Ivanna Escala (1 and 4), Jennifer Wojno (3), Puragra Guhathakurta (5), Steven R. Majewski (6), Rachael L. Beaton (4 and 7) ((1) Caltech, (2) Space Telescope Science Institute, (3) Johns Hopkins, (4) Princeton, (5) UC Santa Cruz, (6) University of Virginia, (7) Carnegie Observatories)

Comments: 26 pages, 13 figures. Accepted to AJ. Table 2 is available as a machine-readable table under "Other Formats."

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present deep spectroscopy from Keck/DEIMOS of Andromeda I, III, V, VII, and X, all of which are dwarf spheroidal satellites of M31. The sample includes 256 spectroscopic members across all five dSphs. We confirm previous measurements of the velocity dispersions and dynamical masses, and we provide upper limits on bulk rotation. Our measurements confirm that M31 satellites obey the same relation between stellar mass and stellar metallicity as Milky Way (MW) satellites and other dwarf galaxies in the Local Group. The metallicity distributions show similar trends with stellar mass as MW satellites, including evidence in massive satellites for external influence, like pre-enrichment or gas accretion. We present the first measurements of individual element ratios, like [Si/Fe], in the M31 system, as well as measurements of the average [alpha/Fe] ratio. The trends of [alpha/Fe] with [Fe/H] also follow the same galaxy mass-dependent patterns as MW satellites. Less massive galaxies have more steeply declining slopes of [alpha/Fe] that begin at lower [Fe/H]. Finally, we compare the chemical evolution of M31 satellites to M31's Giant Stellar Stream and smooth halo. The properties of the M31 system support the theoretical prediction that the inner halo is composed primarily of massive galaxies that were accreted early. As a result, the inner halo exhibits higher [Fe/H] and [alpha/Fe] than surviving satellite galaxies.

[5]  arXiv:1912.02189 [pdf, other]

Title: The correlations between optical/UV broad lines and X-ray emission for a large sample of quasars

Authors: J. D. Timlin, W. N. Brandt, Q. Ni, B. Luo, Xingting Pu, D. P. Schneider, M. Vivek, W. Yi

Comments: 24 pages, 16 Figures

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<z<2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14), that do not contain broad absorption lines (BAL) in their rest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandra observations to our previously published sample of 139 quasars from SDSS DR5 which is still used to correlate X-ray and optical/UV emission in typical quasars. We fit the SDSS spectra for 753 of the quasars in our sample that have high-quality (exposure time $\gtrapprox$10 ks and off-axis observation angle <10 arcmin) X-ray observations, and analyze their X-ray-to-optical SED properties ($\alpha_{ox}$ and $\Delta\alpha_{ox}$) with respect to the measured CIV and MgII emission-line rest-frame equivalent width (EW) and the CIV emission-line blueshift. We find significant correlations (at the >99.99% level) between $\alpha_{ox}$ and these emission-line parameters, as well as between $\Delta\alpha_{ox}$ and CIV EW. Slight correlations are found between $\Delta\alpha_{ox}$ and CIV blueshift, MgII EW, and the CIV EW to MgII EW ratio. The best-fit trend in each parameter space is used to compare the X-ray weakness ($\Delta\alpha_{ox}$) and optical/UV emission properties of typical quasars and weak-line quasars (WLQs). The WLQs typically exhibit weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs compared to our typical quasars can be explained by an X-ray "shielding" model.

[6]  arXiv:1912.02191 [pdf, other]

Title: Is the expansion of the universe accelerating? All signs still point to yes

Authors: David Rubin, Jessica Heitlauf

Comments: Submitted to ApJ

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Type Ia supernovae (SNe Ia) provided the first strong evidence that the expansion of the universe is accelerating. With SN samples now more than ten times larger than those used for the original discovery and joined by other cosmological probes, this discovery is on even firmer ground. Two recent, related studies (Nielsen et al. 2016 and Colin et al. 2019, hereafter N16 and C19, respectively) have claimed to undermine the statistical significance of the SN Ia constraints. Rubin & Hayden (2016) (hereafter RH16) showed N16 made an incorrect assumption about the distributions of SN Ia light-curve parameters, while C19 also fails to remove the impact of the motion of the solar system from the SN redshifts, interpreting the resulting errors as evidence of a dipole in the deceleration parameter. Building on RH16, we outline the errors C19 makes in their treatment of the data and inference on cosmological parameters. Reproducing the C19 analysis with our proposed fixes, we find that the dipole parameters have little effect on the inferred cosmological parameters. We thus affirm the conclusion of RH16: the evidence for acceleration is secure.

[7]  arXiv:1912.02194 [pdf, other]

Title: Detailed Characterization of Low Activity Comet 49P/Arend-Rigaux

Authors: Laurie E. U. Chu (1), Karen J. Meech (1), Tony L. Farnham (2), Ekkehard Kührt (3), Stefano Mottola (3), Jacqueline V. Keane (1), Stephan Hellmich (3), Olivier R. Hainaut (4), Jan T. Kleyna (1) ((1) Institute for Astronomy University of Hawaii, (2) University of Maryland, (3) DLR German Aerospace Center, (4) European Southern Observatory)

Comments: 18 pages, 8 figures, Accepted for publication by Icarus

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Comet 49P/Arend-Rigaux is a well known low-activity Jupiter Family comet. Despite the low activity, we have witnessed outgassing activity in 1992, 2004, and 2012. In 2012 a broad tail-like feature (PA$\sim270^\circ, \sim2.3\times10^5$ km) and a narrow jet-like feature (PA$\sim180^\circ, \sim9.3\times10^4$ km) were seen simultaneously. Using Finson-Probstein (FP) dust dynamical models we determine: grain sizes released in each event; duration of activity; when activity peaked; and velocity of the dust particles, allowing us to make comparisons between the events. We find that the tail feature in 2012 is similar to the tail in 1992 with large grains (40-4000 $\mu$m) peaking in activity near perihelion with a long outgassing duration greater than 150 days. The jet feature from 2012, however, is more similar to the 2004 event which we model with small grains (1-8 $\mu$m) with a short duration of activity ($\sim$1 month). The main difference between these two features is that the 2004 event occurs prior to perihelion, while the 2012 event is post-perihelion. We use the grain sizes from the FP models to constrain ice sublimation models. Between 1985 and 2018 we cover 6 apparitions with 26 nights of our own observations plus data from the literature and the Minor Planet Center, which together, allow us to model the heliocentric light curve. We find that the models are consistent with H$_2$O ice sublimation as the volatile responsible for driving activity over most of the active phases and a combination of H$_2$O and CO$_2$ ices are responsible for driving activity near perihelion. We measure the fractional active area over time for H$_2$O and discover that the activity decreases from an average active area of $\sim3\%$ to $\sim0.2\%$. This secular decrease in activity implies that the comet is becoming depleted of volatiles and is in the process of transitioning to a dormant or dead state.

[8]  arXiv:1912.02195 [pdf, other]

Title: Exploring the outskirts of globular clusters: the peculiar kinematics of NGC 3201

Authors: P. Bianchini, R. Ibata, B. Famaey

Comments: 9 pages, 4 figure, 1 table. Accepted for publication to ApJ Letters

Subjects: Astrophysics of Galaxies (astro-ph.GA)

The outskirts of globular clusters (GCs) simultaneously retain crucial information about their formation mechanism and the properties of their host galaxy. Thanks to the advent of precision astrometry both their morphological and kinematic properties are now accessible. Here we present the first dynamical study of the outskirts of the retrograde GC NGC 3201 until twice its Jacobi radius (< 100 pc), using specifically-selected high-quality astrometric data from Gaia DR2. We report the discovery of a stellar overdensity along the South-East/North-West direction that we identify as tidal tails. The GC is characterized globally by radial anisotropy and a hint of isotropy in the outer parts, with an excess of tangential orbits around the lobes corresponding to the tidal tails, in qualitative agreement with an N-body simulation. Moreover, we measure flat velocity dispersion profiles, reaching values of $3.5\pm0.9$ km/s until beyond the Jacobi radius. While tidal tails could contribute to such a flattening, this high velocity dispersion value is in disagreement with the expectation from the sole presence of potential escapers. To explain this puzzling observation, we discuss the possibility of an accreted origin of the GC, the presence of a dark matter halo --leftover of its formation at high redshift -- and the possible effects of non-Newtonian dynamics. Our study uncovers a new path for the study of GC formation and of the properties of the Milky Way potential in the era of precision astrometry.

[9]  arXiv:1912.02196 [pdf, other]

Title: Exploiting flux ratio anomalies to probe warm dark matter in future large scale surveys

Authors: David Harvey, Wessel Valkenburg, Amelie Tamone, Alexey Boyarsky, Frederic Courbin, Mark Lovell

Comments: Accepted MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Flux ratio anomalies in strong gravitationally lensed quasars constitute a unique way to probe the abundance of non-luminous dark matter haloes, and hence the nature of dark matter. In this paper we identify double imaged quasars as a statistically efficient probe of dark matter, since they are 20 times more abundant than quadruply imaged quasars. Using N-body simulations that include realistic baryonic feedback, we measure the full distribution of flux ratios in doubly imaged quasars for cold (CDM) and warm dark matter (WDM) cosmologies. Through this method, we fold in two key systematics - quasar variability and line-of-sight structures. We find that WDM cosmologies predict a ~6 per cent difference in the cumulative distribution functions of flux ratios relative to CDM, with CDM predicting many more small ratios. Finally, we estimate that ~600 doubly imaged quasars will need to be observed in order to be able to unambiguously discern between CDM and the two WDM models studied here. Such sample sizes will be easily within reach of future large scale surveys such as Euclid. In preparation for this survey data we require discerning the scale of the uncertainties in modelling lens galaxies and their substructure in simulations, plus a strong understanding of the selection function of observed lensed quasars.

[10]  arXiv:1912.02199 [pdf, ps, other]

Title: The dynamical history of the evaporating or disrupted ice giant planet around white dwarf WD J0914+1914

Authors: Dimitri Veras, Jim Fuller

Comments: Submitted to MNRAS

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Robust evidence of an ice giant planet shedding its atmosphere around the white dwarf WD J0914+1914 represents a milestone in exoplanetary science, allowing us to finally supplement our knowledge of white dwarf metal pollution, debris discs and minor planets with the presence of a major planet. Here, we discuss the possible dynamical origins of this planet, WD J0914+1914b. The very young cooling age of the host white dwarf (13 Myr) combined with the currently estimated planet-star separation of about 0.07 au imposes particularly intriguing and restrictive coupled constraints on its current orbit and its tidal dissipation characteristics. The planet must have been scattered from a distance of at least a few au to its current location, requiring the current or former presence of at least one more major planet in the system. We show that WD J0914+1914b could not have subsequently shrunk its orbit through chaotic f-mode tidal excitation (characteristic of such highly eccentric orbits) unless the planet was or is highly inflated and had at least partially thermally self-disrupted from mode-based energy release. We also demonstrate that if the planet is currently assumed to reside on a near-circular orbit at 0.07 au, then non-chaotic equilibrium tides impose unrealistic values for the planet's tidal quality factor. We conclude that WD J0914+1914b either resembles a disrupted "Super-Puff" whose remains reside on a circular orbit, or a larger or denser ice giant on a currently eccentric orbit. Distinguishing these two possibilities strongly motivates follow-up observations.

[11]  arXiv:1912.02200 [pdf, other]

Title: Constraining Galactic Structure with the LISA White Dwarf Foreground

Authors: Katelyn Breivik, Chiara M. F. Mingarelli, Shane L. Larson

Comments: 9 pages, 5 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

White dwarfs comprise 95% of all stellar remnants, and are thus an excellent tracer of old stellar populations in the Milky Way. Current and planned telescopes are not able to directly probe the white dwarf population in its entirety due to its inherently low luminosity. However, the Galactic population of double white dwarf binaries gives rise to a millihertz gravitational-wave foreground detectable by the Laser Interferometer Space Antenna (LISA). Here we show how characterizing this foreground's angular power spectrum will enable us to probe the Galactic structure in a novel way and measure the vertical scale height of the Galaxy's oldest stellar populations. We do this using a binary population synthesis study that incorporates different Galactic spatial distributions for the double white dwarf population. We find that the level of anisotropy in the white dwarf foreground's angular power spectrum is strongly dependent on the vertical scale height of the population. Finally, we show that LISA can probe the vertical scale height of the Galactic double white dwarf population with an accuracy of 50 pc-200pc, depending on angular resolution limits, using the angular power spectrum of the white dwarf foreground.

[12]  arXiv:1912.02201 [pdf, other]

Title: The impact of star formation sampling effects on the spectra of lensed $z>6$ galaxies detectable with $\textit{JWST}$

Authors: Anton Vikaeus, Erik Zackrisson, Christian Binggeli

Comments: 8 pages, 5 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

The upcoming $\textit{James Webb Space Telescope}$ ($\textit{JWST}$) will allow observations of high-redshift galaxies at fainter detection levels than ever before, and $\textit{JWST}$ surveys targeting gravitationally lensed fields are expected to bring $z\gtrsim 6$ objects with very low star formation rate (SFR) within reach of spectroscopic studies. As galaxies at lower and lower star formation activity are brought into view, many of the standard methods used in the analysis of integrated galaxy spectra are at some point bound to break down, due to violation of the assumptions of a well-sampled stellar initial mass function (IMF) and a slowly varying SFR. We argue that galaxies with SFR$\sim 0.1\ M_\odot$ yr$^{-1}$ are likely to turn up at the spectroscopic detection limit of $\textit{JWST}$ in lensed fields, and investigate to what extent star formation sampling may affect the spectral analysis of such objects. We use the $\small{\text{SLUG}}$ spectral synthesis code to demonstrate that such effects are likely to have significant impacts on spectral diagnostics of, for example, the Balmer emission lines. These effects are found to stem primarily from SFRs varying rapidly on short ($\sim$ Myr) timescales due to star formation in finite units (star clusters), whereas the effects of an undersampled IMF is deemed insignificant in comparison. In contrast, the ratio between the HeII- and HI-ionizing flux is found to be sensitive to IMF-sampling as well as ICMF-sampling (sampling of the stellar initial cluster mass function), which may affect interpretations of galaxies containing Population III stars or other hot ionizing sources.

[13]  arXiv:1912.02205 [pdf, other]

Title: Global 21-cm Signal Extraction from Foreground and Instrumental Effects II: Efficient and Self-Consistent Technique for Constraining Nonlinear Signal Models

Authors: David Rapetti, Keith Tauscher, Jordan Mirocha, Jack O. Burns

Comments: 19 pages, 11 figures, 5 tables. Submitted to ApJ. Code available at this https URL

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present the completion of a data analysis pipeline that self-consistently separates global 21-cm signals from large systematics using a pattern recognition technique. In the first paper of this series, we obtain optimal basis vectors from signal and foreground training sets to linearly fit both components with the minimal number of terms that best extracts the signal given its overlap with the foreground. In this second paper, we utilize the spectral constraints derived in the first paper to calculate the full posterior probability distribution of any signal parameter space of choice. The spectral fit provides the starting point for a Markov Chain Monte Carlo (MCMC) engine that samples the signal without traversing the foreground parameter space. At each MCMC step, we marginalize over the weights of all linear foreground modes and suppress those with unimportant variations by applying priors gleaned from the training set. This method drastically reduces the number of MCMC parameters, augmenting the efficiency of exploration, circumvents the need for selecting a minimal number of foreground modes, and allows the complexity of the foreground model to be greatly increased to simultaneously describe many observed spectra without requiring extra MCMC parameters. Using two nonlinear signal models, one based on EDGES observations and the other on phenomenological frequencies and temperatures of theoretically expected extrema, we demonstrate the success of this methodology by recovering the input parameters from multiple randomly simulated signals at low radio frequencies (10-200 MHz), while rigorously accounting for realistically modeled beam-weighted foregrounds.

[14]  arXiv:1912.02212 [pdf, other]

Title: Gas flows in galactic centre environments: cloud evolution and star formation in the Central Molecular Zone

Authors: Maya A. Petkova, J. M. Diederik Kruijssen

Comments: Conference proceedings of "GCWS 2019 - New Horizons in Galactic Center Astronomy and Beyond"

Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Central Molecular Zone (CMZ) is the most extreme star-forming environment in the Milky Way in terms of gas pressures, densities, temperatures, and dynamics. It acts as a critical test bed for developing star formation theories applicable to the (high-redshift-like) conditions under which most stars in the Universe formed. We present a set of numerical simulations of molecular clouds orbiting on the 100-pc stream that dominates the molecular gas reservoir of the CMZ, with the goal of characterising their morphological and kinematic evolution in response to the external gravitational potential and their eccentric orbital motion. These simulations capture the evolution of single clouds in a strong and plausibly dominant background potential. We find that the evolution of the clouds is closely coupled to the orbital dynamics and their arrival on the 100-pc stream marks a transformative event in their lifecycle. The clouds' sizes, aspect ratios, position angles, filamentary structure, column densities, velocity dispersions, line-of-sight velocity gradients, angular momenta, and overall kinematic complexity are controlled by the background potential and their passage through the orbit's pericentre. We compare these predictions of our simulations to observations of clouds on the Galactic Centre `dust ridge' and find that the inclusion of galactic dynamics naturally reproduces a surprisingly wide variety of key observed morphological and kinematic features. We argue that the accretion of gas clouds onto the central regions of galaxies, where the rotation curve turns over and the tidal field becomes fully compressive, is likely to lead to their collapse and associated star formation. This can generate an evolutionary progression of cloud collapse with a common zero point. Together, these processes may naturally give rise to the synchronised starbursts observed in numerous galactic nuclei.

[15]  arXiv:1912.02214 [pdf, other]

Title: Monte Carlo radiative transfer for the nebular phase of Type Ia supernovae

Authors: L. J. Shingles, S. A. Sim, M. Kromer, K. Maguire, M. Bulla, C. Collins, C. P. Ballance, A. S. Michel, C. A. Ramsbottom, F. K. Roepke, I. R. Seitenzahl, N. B. Tyndall

Comments: 15 pages, 12 figures. Accepted for publication by MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We extend the range of validity of the ARTIS 3D radiative transfer code up to hundreds of days after explosion, when Type Ia supernovae are in their nebular phase. To achieve this, we add a non-local thermodynamic equilibrium (non-LTE) population and ionisation solver, a new multi-frequency radiation field model, and a new atomic dataset with forbidden transitions. We treat collisions with non-thermal leptons resulting from nuclear decays to account for their contribution to excitation, ionisation, and heating. We validate our method with a variety of tests including comparing our synthetic nebular spectra for the well-known one-dimensional W7 model with the results of other studies. As an illustrative application of the code, we present synthetic nebular spectra for the detonation of a sub-Chandrasekhar white dwarf in which the possible effects of gravitational settling of Ne22 prior to explosion have been explored. Specifically, we compare synthetic nebular spectra for a 1.06 M$_\odot$ white dwarf model obtained when 5.5 Gyr of very-efficient settling is assumed to a similar model without settling. We find that this degree of Ne22 settling has only a modest effect on the resulting nebular spectra due to increased Ni58 abundance. Due to the high ionisation in sub-Chandrasekhar models, the nebular [Ni II] emission remains negligible, while the [Ni III] line strengths are increased and the overall ionisation balance is slightly lowered in the model with Ne22 settling. In common with previous studies of sub-Chandrasekhar models at nebular epochs, these models overproduce [Fe III] emission relative to [Fe II] in comparison to observations of normal Type Ia supernovae.

[16]  arXiv:1912.02216 [pdf, ps, other]

Title: Electrons in the Young Solar Wind: First Results from the Parker Solar Probe

Authors: J. S. Halekas, P. Whittlesey, D. E. Larson, D. McGinnis, M. Maksimovic, M. Berthomier, J. C. Kasper, A. W. Case, K. E. Korreck, M. L. Stevens, K. G. Klein, S. D. Bale, R. J. MacDowall, M. P. Pulupa, D. M. Malaspina, K. Goetz, P. R. Harvey

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations utilizing a combination of fitting to model distributions and numerical integration for $\sim 100,000$ electron distributions measured near the Sun on the first two PSP orbits, which reached heliocentric distances as small as $\sim 0.17$ AU. As expected, the electron core density and temperature increase with decreasing heliocentric distance, while the ratio of electron thermal pressure to magnetic pressure ($\beta_e$) decreases. These quantities have radial scaling consistent with previous observations farther from the Sun, with superposed variations associated with different solar wind streams. The density in the strahl also increases; however, the density of the halo plateaus and even decreases at perihelion, leading to a large strahl/halo ratio near the Sun. As at greater heliocentric distances, the core has a sunward drift relative to the proton frame, which balances the current carried by the strahl, satisfying the zero-current condition necessary to maintain quasi-neutrality. Many characteristics of the electron distributions near perihelion have trends with solar wind flow speed, $\beta_e$, and/or collisional age. Near the Sun, some trends not clearly seen at 1 AU become apparent, including anti-correlations between wind speed and both electron temperature and heat flux. These trends help us understand the mechanisms that shape the solar wind electron distributions at an early stage of their evolution.

[17]  arXiv:1912.02228 [pdf, other]

Title: Simulated Direct Imaging Detection of Water Vapor For Exo-Earths

Authors: Anna Sage Ross, Tyler D. Robinson

Comments: 2.5 pages, 1 figure, Research Notes of the AAS

Journal-ref: Res. Notes AAS 3, 177, 2019

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Habitable planets are often defined as terrestrial worlds capable of maintaining surface liquid water. As a result, atmospheric water vapor can be a critical indicator of habitability. Thus, habitability-themed exoplanet investigations emphasize detection of water vapor signatures for their targets. A variety of concept missions for exoplanet direct imaging in reflected light have seen recent study, including the HabEx and LUVOIR concepts. Here, it is important to understand how direct imaging in reflected light --- coupled with moderate-resolution spectroscopy --- could be used to detect various water vapor amounts in Earth-like exoplanetary atmospheres. To investigate water vapor detection for terrestrial exoplanets, we generated reflectance spectra over a grid of water vapor column masses and used an instrument model to explore requisite integration times for spectral feature detection at either visible or near-infrared wavelengths. Lower-resolution near-infrared spectroscopy is generally optimal for detecting water vapor in the atmospheres of Earth-like exoplanets when using direct imaging in reflected light. This holds true for dry or cold terrestrial planets, whose atmospheres would contain relatively little water vapor. Atmospheres richer in water vapor, such as planets undergoing a moist or runaway greenhouse, could have water vapor efficiently detected at visible wavelengths. Understanding details like an exoplanet's size, temperature, and location relative to the habitable zone can aid in determining appropriate wavelength ranges for atmospheric characterization. Overall, water vapor detection for Earth-like exoplanets is quite feasible for future direct imaging missions.

[18]  arXiv:1912.02229 [pdf, other]

Title: The East Asian Observatory SCUBA--2 survey of the COSMOS field: unveiling 1147 bright sub-millimeter sources across 2.6 square degrees

Authors: J. M. Simpson (EACOA: ASIAA), Ian Smail (Durham University), A. M. Swinbank, S. C. Chapman, Chian-Chou Chen, J. E. Geach, Y. Matsuda, R. Wang, Wei-Hao Wang, Y. Yang, Y. Ao, R. Asquith, N. Bourne, R. T. Coogan, K. Coppin, B. Gullberg, N. K. Hine, L. C. Ho, H. S. Hwang, R. J. Ivison, Y. Kato, K.Lacaille, A. J. R. Lewis, D. Liu, M. J. Michałowski, I. Oteo, M. Sawicki, J. Scholtz, D. Smith, A. P. Thomson, J. L. Wardlow

Comments: Published in ApJ July 2019

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present sensitive 850$\mu$m imaging of the COSMOS field using 640hr of new and archival observations taken with SCUBA-2 at the East Asian Observatory's James Clerk Maxwell Telescope. The SCUBA-2 COSMOS survey (S2COSMOS) achieves a median noise level of $\sigma_{850\mu{\mathrm{m}}}$=1.2mJy/beam over an area of 1.6 sq. degree (MAIN; HST/ACS footprint), and $\sigma_{850\mu{\mathrm{m}}}$=1.7mJy/beam over an additional 1 sq. degree of supplementary (SUPP) coverage. We present a catalogue of 1020 and 127 sources detected at a significance level of >4$\sigma$ and >4.3$\sigma$ in the MAIN and SUPP regions, respectively, corresponding to a uniform 2% false-detection rate. We construct the single-dish 850$\mu$m number counts at $S_{850}$>2mJy and show that these S2COSMOS counts are in agreement with previous single-dish surveys, demonstrating that degree-scale fields are sufficient to overcome the effects of cosmic variance in the $S_{850}$=2-10mJy population. To investigate the properties of the galaxies identified by S2COSMOS sources we measure the surface density of near-infrared-selected galaxies around their positions and identify an average excess of 2.0$\pm$0.2 galaxies within a 13$''$ radius (~100kpc at $z$~2). The bulk of these galaxies represent near-infrared-selected SMGs and/or spatially-correlated sources and lie at a median photometric redshift of $z$=2.0$\pm$0.1. Finally, we perform a stacking analysis at sub-millimeter and far-infrared wavelengths of stellar-mass-selected galaxies ($M_{\star}$=10$^{10}$-10$^{12}{\rm M_{\odot}}$) from $z$=0-4, obtaining high-significance detections at 850um in all subsets (SNR=4-30), and investigate the relation between far-infrared luminosity, stellar mass, and the peak wavelength of the dust SED. The publication of this survey adds a new deep, uniform sub-millimeter layer to the wavelength coverage of this well-studied COSMOS field.

[19]  arXiv:1912.02234 [pdf, other]

Title: Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single Star and Binary Merger Progenitor Models for SN 1987A

Authors: Masaomi Ono, Shigehiro Nagataki, Gilles Ferrand, Koh Takahashi, Hideyuki Umeda, Takashi Yoshida, Salvatore Orlando, Marco Miceli

Comments: Accepted for publication in The Astrophysical Journal, 62 pages, 26 figures, 3 tables

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We perform three-dimensional hydrodynamic simulations of aspherical core-collapse supernovae focusing on the matter mixing in SN 1987A. The impacts of four progenitor (pre-supernova) models and parameterized aspherical explosions are investigated. The four pre-supernova models include a blue supergiant (BSG) model based on a slow merger scenario developed recently for the progenitor of SN 1987A (Urushibata et al. 2018). The others are a BSG model based on a single star evolution and two red supergiant (RSG) models. Among the investigated explosion (simulation) models, a model with the binary merger progenitor model and with an asymmetric bipolar-like explosion, which invokes a jetlike explosion, best reproduces constraints on the mass of high velocity $^{56}$Ni, as inferred from the observed [Fe II] line profiles. The advantage of the binary merger progenitor model for the matter mixing is the flat and less extended $\rho \,r^3$ profile of the C+O core and the helium layer, which may be characterized by the small helium core mass. From the best explosion model, the direction of the bipolar explosion axis (the strongest explosion direction), the neutron star (NS) kick velocity, and its direction are predicted. Other related implications and future prospects are also given.

[20]  arXiv:1912.02235 [pdf, other]

Title: Streaming Classification of Variable Stars

Authors: Lukas Zorich, Karim Pichara, Pavlos Protopapas

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR); Machine Learning (cs.LG)

In the last years, automatic classification of variable stars has received substantial attention. Using machine learning techniques for this task has proven to be quite useful. Typically, machine learning classifiers used for this task require to have a fixed training set, and the training process is performed offline. Upcoming surveys such as the Large Synoptic Survey Telescope (LSST) will generate new observations daily, where an automatic classification system able to create alerts online will be mandatory. A system with those characteristics must be able to update itself incrementally. Unfortunately, after training, most machine learning classifiers do not support the inclusion of new observations in light curves, they need to re-train from scratch. Naively re-training from scratch is not an option in streaming settings, mainly because of the expensive pre-processing routines required to obtain a vector representation of light curves (features) each time we include new observations. In this work, we propose a streaming probabilistic classification model; it uses a set of newly designed features that work incrementally. With this model, we can have a machine learning classifier that updates itself in real time with new observations. To test our approach, we simulate a streaming scenario with light curves from CoRot, OGLE and MACHO catalogs. Results show that our model achieves high classification performance, staying an order of magnitude faster than traditional classification approaches.

[21]  arXiv:1912.02238 [pdf, other]

Title: The role of environment in galaxy evolution in the SERVS Survey I: density maps and cluster candidates

Authors: Nick Krefting, Anna Sajina, Mark Lacy, Kristina Nyland, Duncan Farrah, Behnam Darvish, Steven Duivenvoorden, Ken Duncan, Violeta Gonzalez-Perez, Claudia del P. Lagos, Seb Oliver, Raphael Shirley, Mattia Vaccari

Comments: 26 pages, 12 figures, accepted for publication in ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use photometric redshifts derived from new $u$-band through 4.5$\mu$m Spitzer IRAC photometry in the 4.8\,deg$^2$ of the XMM-LSS field to construct surface density maps in the redshift range 0.1-1.5. Our density maps show evidence for large-scale structure in the form of filaments spanning several tens of Mpc. Using these maps, we identify 339 overdensities that our simulated lightcone analysis suggests are likely associated with dark matter haloes with masses, $M_{\rm halo}$, log($M_{\rm halo}/M_{\odot})>$13.7. From this list of overdensities we recover 43 of 70 known X-ray detected and spectroscopically confirmed clusters. The missing X-ray clusters are largely at lower redshifts and lower masses than our target log($M_{\rm halo}/M_{\odot})>$13.7. The bulk of the overdensities are compact, but a quarter show extended morphologies which include likely projection effects, clusters embedded in apparent filaments as well as at least one potential cluster merger (at $z\sim1.28$). The strongest overdensity in our highest redshift slice (at $z\sim1.5$) shows a compact red galaxy core potentially implying a massive evolved cluster.

[22]  arXiv:1912.02244 [pdf, other]

Title: Magnetic connectivity of the ecliptic plane within 0.5 AU : PFSS modeling of the first PSP encounter

Authors: Samuel T. Badman, Stuart D. Bale, Juan C. Martinez Oliveros, Olga Panasenco, Marco Velli, David Stansby, Juan C. Buitrago-Casas, Victor Reville, John W. Bonnell, Anthony W. Case, Thierry Dudok de Wit, Keith Goetz, Peter R. Harvey, Justin C. Kasper, Kelly E. Korreck, Davin E. Larson, Roberto Livi, Robert J. MacDowall, David M. Malaspina, Marc Pulupa, Michael L. Stevens, Phyllis L. Whittlesey

Comments: 19 Pages, 8 Main Figures, 3 Appendix Figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

We compare magnetic field measurements taken by the FIELDS instrument on Parker Solar Probe (PSP) during its first solar encounter to predictions obtained by Potential Field Source Surface (PFSS) modeling. Ballistic propagation is used to connect the spacecraft to the source surface. Despite the simplicity of the model, our results show striking agreement with PSPs first observations of the heliospheric magnetic field from 0.5 AU (107.5 Rs) down to 0.16 AU (35.7 Rs). Further, we show the robustness of the agreement is improved both by allowing the photospheric input to the model to vary in time, and by advecting the field from PSP down to the PFSS model domain using in situ PSP/SWEAP measurements of the solar wind speed instead of assuming it to be constant with longitude and latitude. We also explore the source surface height parameter (RSS) to the PFSS model finding that an extraordinarily low source surface height (1.3-1.5Rs) predicts observed small scale polarity inversions which are otherwise washed out with regular modeling parameters. Finally, we extract field line traces from these models. By overlaying these on EUV images we observe magnetic connectivity to various equatorial and mid-latitude coronal holes indicating plausible magnetic footpoints and offering context for future discussions of sources of the solar wind measured by PSP.

[23]  arXiv:1912.02246 [pdf, other]

Title: Microlensing and Photon Bunching: The impact of decoherence

Authors: Geraint F. Lewis, Peter Tuthill

Comments: 4 pages, 1 figure, accepted for publication in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Gravitational microlensing within the Galaxy offers the prospect of probing the details of distant stellar sources, as well as revealing the distribution of compact (and potentially non-luminous) masses along the line-of-sight. Recently, it has been suggested that additional constraints on the lensing properties can be determined through the measurement of the time delay between images through the correlation of the bunching of photon arrival times; an application of the Hanbury-Brown Twiss effect. In this paper, we revisit this analysis, examining the impact of decoherence of the radiation from a spatially extended source along the multiple paths to an observer. The result is that, for physically reasonable situations, such decoherence completely erases any correlation that could otherwise be used to measure the gravitational lensing time delay. Indeed, the divergent light paths traverse extremely long effective baselines at the lens plane, corresponding to extremes of angular resolving power well beyond those attainable with any terrestrial technologies; the drawback being that few conceivable celestial objects would be sufficiently compact with high enough surface brightness to yield usable signals.

[24]  arXiv:1912.02255 [pdf, other]

Title: WISPR Imaging of a Pristine CME

Authors: Phillip Hess, Alexis Rouillard, Athanasios Kouloumvakos, Paulett C. Liewer, Jie Zhang, Suman Dhakal, Guillermo Stenborg, Robin C. Colaninno, Russell A. Howard

Comments: 12 Pages, 9 Figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

The Wide-field Imager for Solar Probe (WISPR) on board the Parker Solar Probe (PSP) observed a CME on 2018 November 01, the first day of the initial PSP encounter. The speed of the CME, approximately 200-300 km s$^{-1}$ in the WISPR field of view, is typical of slow, streamer blowout CMEs. This event was also observed by the LASCO coronagraphs. WISPR and LASCO view remarkably similar structures that enable useful cross-comparison between the two data sets as well as stereoscopic imaging of the CME. Analysis is extended to lower heights by linking the white-light observations to EUV data from AIA, which reveal a structure that erupts more than a full day earlier before the CME finally gathers enough velocity to propagate outward. This EUV feature appears as a brightness enhancement in cooler temperatures such as 171 \AA, but as a cavity in nominal coronal temperatures such as 193 \AA. By comparing this circular, dark feature in 193 \AA \ to the dark, white-light cavity at the center of the eruption in WISPR and LASCO, it can be seen that this is one coherent structure that exists prior to the eruption in the low corona before entering the heliosphere and likely corresponds to the core of the magnetic flux rope. It is also believed that the relative weakness of the event contributed to the clarity of the flux rope in WISPR, as the CME did not experience impulsive forces or strong interaction with external structures that can lead to more complex structural evolution.

[25]  arXiv:1912.02261 [pdf, other]

Title: A Catalog of Emission-Line Galaxies from the Faint Infrared Grism Survey: Studying Environmental Influence on Star Formation

Authors: John Pharo, Sangeeta Malhotra, James E. Rhoads, Norbert Pirzkal, Steven L. Finkelstein, Russell Ryan, Andrea Cimatti, Lise Christensen, Nimish Hathi, Anton Koekemoer, Santosh Harish, Mark Smith, Amber Straughn, Rogier Windhorst, Ignacio Ferreras, Caryl Gronwall, Pascale Hibon, Rebecca Larson, Robert O'Connell, Anna Pasquali, Vithal Tilvi

Comments: Accepted to ApJ. 36 pages, 14 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a catalog of 208 $0.3 < z < 2.1$ Emission Line Galaxies (ELG) selected from 1D slitless spectroscopy obtained using Hubble's WFC3 G102 grism, as part of the Faint Infrared Grism Survey (FIGS). We identify ELG candidates by searching for significant peaks in all continuum-subtracted G102 spectra, and, where possible, confirm candidates by identifying consistent emission lines in other available spectra or with published spectroscopic redshifts. We provide derived emission line fluxes and errors, redshifts, and equivalent widths (EW) for H$\alpha$ $\lambda6563$, [OIII]$\lambda\lambda4959,5007$, and [OII]$\lambda\lambda3727$ emission lines, for emission line galaxies down to AB(F105W) $ > 28$ and $> 10^{-17}$ erg cm$^{-2}$ s$^{-1}$ line flux. We use the resulting line catalog to investigate a possible relationship between line emission and a galaxy's environment. We use 7th-nearest-neighbor distances to investigate the typical surroundings of ELGs compared to non-ELGs, and we find that [OIII] emitters are preferentially found at intermediate galaxy densities near galaxy groups. We characterize these ELGs in terms of the galaxy specific star formation rate (SSFR) versus stellar mass, and find no significant influence of environment on that relation. We calculate star formation rates (SFR), and find no dependence of SFR on local galaxy surface density for $0.3 < z < 0.8$ H$\alpha$ emitters and for $0.8<z<1.3$ [OIII] emitters. We find similar rates of close-pair interaction between ELGs and non-ELGs. For galaxy surface densities $\Sigma \leq 30$ Mpc$^{-2}$, we find no consistent effect of environment on star formation.

[26]  arXiv:1912.02264 [pdf, other]

Title: A New Likely Redback Millisecond Pulsar Binary with a Massive Neutron Star: 4FGL J2333.1--5527

Authors: Samuel J. Swihart, Jay Strader, Ryan Urquhart, Jerome A. Orosz, Laura Shishkovsky, Laura Chomiuk, Ricardo Salinas, Elias Aydi, Kristen C. Dage, Adam M. Kawash

Comments: Submitted to ApJ; 8 pages, 6 figures, 1 table

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present the discovery of a likely new redback millisecond pulsar binary associated with the Fermi $\gamma$-ray source 4FGL J2333.1--5527. Using optical photometric and spectroscopic observations from the SOAR telescope, we identify a low-mass, main sequence-like companion in a 6.9-hr, highly inclined orbit around a suspected massive neutron star primary. Archival XMM-Newton X-ray observations show this system has a hard power-law spectrum $\Gamma = 1.6\pm0.3$ and $L_X \sim 5 \times 10^{31}$ erg s$^{-1}$, consistent with redback millisecond pulsar binaries. Our data suggest that the system harbors a massive ($1.88\pm 0.24\,M_{\odot}$) neutron star whose properties can be much better constrained with its future detection as a millisecond radio pulsar. This work shows that a bevy of nearby compact binaries still await discovery, and that unusually massive neutron stars continue to be common in redbacks.

[27]  arXiv:1912.02268 [pdf, other]

Title: Signatures of Clouds in Hot Jupiter Atmospheres: Modeled High Resolution Emission Spectra from 3D General Circulation Models

Authors: Caleb K. Harada, Eliza M.-R. Kempton, Emily Rauscher, Michael Roman, Marah Brinjikji

Comments: 20 pages, 9 figures, 2 tables, 1 animation (Fig. 6: this https URL), submitted to ApJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Observations of scattered light and thermal emission from hot Jupiter exoplanets have suggested the presence of inhomogeneous aerosols in their atmospheres. 3D general circulation models (GCMs) that attempt to model the effects of aerosols have been developed to understand the physical processes that underlie their dynamical structures. In this work, we investigate how different approaches to aerosol modeling in GCMs of hot Jupiters affect high-resolution thermal emission spectra throughout the duration of the planet's orbit. Using results from a GCM with temperature-dependent cloud formation, we calculate spectra of a representative hot Jupiter with different assumptions regarding the vertical extent and thickness of clouds. We then compare these spectra from models in which clouds are absent or simply post-processed (i.e., added subsequently to the completed clear model). We show that the temperature-dependent treatment of clouds in the GCM produces high-resolution emission spectra that are markedly different from the clear and post-processed cases---both in the continuum flux levels and line profiles---and that increasing the vertical extent and thickness of clouds leads to bigger changes in these features. We evaluate the net Doppler shifts of the spectra induced by global winds and the planet's rotation and show that they are strongly phase-dependent, especially for models with thicker and more extended clouds. This work further demonstrates the importance of radiative feedback in cloudy atmospheric models of hot Jupiters, as this can have a significant impact on interpreting spectroscopic observations of exoplanet atmospheres.

[28]  arXiv:1912.02313 [pdf]

Title: O2- and CO-Rich Atmospheres for Potentially Habitable Environments on TRAPPIST-1 Planets

Authors: Renyu Hu, Luke Peterson, Eric T. Wolf

Comments: ApJ accepted

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Small exoplanets of nearby M dwarf stars present the possibility to find and characterize habitable worlds within the next decade. TRAPPIST-1, an ultracool M dwarf star, was recently found to have seven Earth-sized planets of predominantly rocky composition. The planets e, f, and g can have a liquid water ocean on their surface given appropriate atmospheres of N2 and CO2. Particularly, climate models have shown that the planets e and f can sustain a global liquid water ocean, for >=0.2 bar CO2 plus 1 bar N2, or >=2 bars CO2, respectively. These atmospheres are irradiated by ultraviolet emission from the star's moderately active chromosphere, and the consequence of this irradiation is unknown. Here we show that chemical reactions driven by the irradiation can produce and maintain more than 0.2 bar O2 and 0.05 bar CO if the CO2 is >=0.1 bar. The abundance of O2 and CO can rise to more than 1 bar under certain boundary conditions. Because of this O2-CO runaway, habitable environments on the TRAPPIST-1 planets entail an O2- and CO-rich atmosphere with coexisting O3. The only process that would prevent the runaway is direct recombination of O2 and CO in the ocean, a reaction that is facilitated biologically. Our results indicate that O2, O3, and CO should be considered together with CO2 as the primary molecules in the search for atmospheric signatures from temperate and rocky planets of TRAPPIST-1 and other M dwarf stars.

[29]  arXiv:1912.02319 [pdf, ps, other]

Title: Hi-C 2.1 Observations of Small-Scale Miniature-Filament-Eruption-Like Cool Ejections in Active Region Plage

Authors: Alphonse C. Sterling, Ronald L. Moore, Navdeep K. Panesar, Kevin P. Reardon, Momchil Molnar, Laurel A. Rachmeler, Sabrina L. Savage, Amy R. Winebarger

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We examine 172 Ang ultra-high-resolution images of a solar plage region from the Hi-C 2.1 ("Hi-C") rocket flight of 2018 May 29. Over its five-minute flight, Hi-C resolves a plethora of small-scale dynamic features that appear near noise level in concurrent Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 171 Ang images. For ten selected events, comparisons with AIA images at other wavelengths and with the Interface Region Imaging Spectrograph (IRIS) images indicate that these features are cool (compared to the corona) ejections. Combining Hi-C 172 Ang, AIA 171 Ang, IRIS 1400 Ang, and H$\alpha$, we see that these ten cool ejections are similar to the H$\alpha$ "dynamic fibrils" and Ca ii "anemone jets" found in earlier studies. The front of some of our cool ejections are likely heated, showing emission in IRIS 1400 Ang. On average, these cool ejections have approximate widths: $3''.2 \pm 2''.1$, (projected) maximum heights and velocities: $4''.3 \pm 2''.5$ and $23 \pm 6$ km/s, and lifetimes: $6.5 \pm 2.4$ min. We consider whether these Hi-C features might result from eruptions of sub-minifilaments (smaller than the minifilaments that erupt to produce coronal jets). Comparisons with SDO's Helioseismic and Magnetic Imager (HMI) magnetograms do not show magnetic mixed-polarity neutral lines at these events' bases, as would be expected for true scaled-down versions of solar filaments/minifilaments. But the features' bases are all close to single-polarity strong-flux-edge locations, suggesting possible local opposite-polarity flux unresolved by HMI. Or, it may be that our Hi-C ejections instead operate via the shock-wave mechanism that is suggested to drive dynamic fibrils and the so-called type I spicules.

[30]  arXiv:1912.02333 [pdf, other]

Title: Distribution and Energy Balance of Pluto's Nitrogen Ice, as seen by New Horizons in 2015

Authors: Briley Lewis, John Stansberry, Bryan Holler, William Grundy, Bernard Schmitt, Silvia Protopapa, Carey Lisse, S. Alan Stern, Leslie Young, Harold Weaver, Catherine Olkin, Kimberly Ennico, the New Horizons Science Team

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Pluto's surface is geologically complex because of volatile ices that are mobile on seasonal and longer time scales. Here we analyzed New Horizons LEISA spectral data to globally map the nitrogen ice, including nitrogen with methane diluted in it. Our goal was to learn about the seasonal processes influencing ice redistribution, to calculate the globally averaged energy balance, and to place a lower limit on Pluto's N2 inventory. We present the average latitudinal distribution of nitrogen and investigate the relationship between its distribution and topography on Pluto by using maps that include the shifted bands of methane in solid solution with nitrogen to more completely map the distribution of the nitrogen ice. We find that the global average bolometric albedo is 0.83 +\- 0.11, similar to that inferred for Triton, and that a significant fraction of Pluto's N2 is stored in Sputnik Planitia. Under the assumption that Pluto's nitrogen-dominated 11.5 microbar atmosphere is in vapor pressure equilibrium with the nitrogen ice, the ice temperature is 36.93 +/- 0.10 K, as measured by New Horizons. Combined with our global energy balance calculation, this implies that the average bolometric emissivity of Pluto's nitrogen ice is probably in the range 0.47 - 0.72. This is consistent with the low emissivities estimated for Triton based on Voyager, and may have implications for Pluto's atmospheric seasonal variations, as discussed below. The global pattern of volatile transport at the time of the encounter was from north to south, and the transition between condensation and sublimation within Sputnik Planitia is correlated with changes in the grain size and CH4 concentration derived from the spectral maps. The low emissivity of Pluto's N2 ice suggests that Pluto's atmosphere may undergo an extended period of constant pressure even as Pluto recedes from the Sun in its orbit.

[31]  arXiv:1912.02345 [pdf, other]

Title: Cold giant planets evaporated by hot white dwarfs

Authors: Matthias R. Schreiber, Boris T. Gaensicke, Odette Toloza, Mercedes-S. Hernandez, Felipe Lagos

Comments: ApJL in press

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

Atmospheric escape from close-in Neptunes and hot Jupiters around sun-like stars driven by extreme ultraviolet (EUV) irradiation plays an important role in the evolution of exo-planets and in shaping their ensemble properties. Intermediate and low mass stars are brightest at EUV wavelengths at the very end of their lives, after they have expelled their envelopes and evolved into hot white dwarfs. Yet the effect of the intense EUV irradiation of giant planets orbiting young white dwarfs has not been assessed. We show that the giant planets in the solar system will experience significant hydrodynamic escape caused by the EUV irradiation from the white dwarf left behind by the Sun. A fraction of the evaporated volatiles will be accreted by the solar white dwarf, resulting in detectable photospheric absorption lines. As a large number of the currently known extra-solar giant planets will survive the metamorphosis of their host stars into white dwarfs, observational signatures of accretion from evaporating planetary atmospheres are expected to be common. In fact, one third of the known hot single white dwarfs show photospheric absorption lines of volatile elements, which we argue are indicative of ongoing accretion from evaporating planets. The fraction of volatile contaminated hot white dwarfs strongly decreases as they cool. We show that accretion from evaporating planetary atmospheres naturally explains this temperature dependence if more than 50 per cent of hot white dwarfs still host giant planets.

[32]  arXiv:1912.02348 [pdf, ps, other]

Title: The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere

Authors: C. H. K. Chen, S. D. Bale, J. W. Bonnell, D. Borovikov, T. A. Bowen, D. Burgess, A. W. Case, B. D. G. Chandran, T. Dudok de Wit, K. Goetz, P. R. Harvey, J. C. Kasper, K. G. Klein, K. E. Korreck, D. Larson, R. Livi, R. J. MacDowall, D. M. Malaspina, A. Mallet, M. D. McManus, M. Moncuquet, M. Pulupa, M. Stevens, P. Whittlesey

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)

The first two orbits of the Parker Solar Probe (PSP) spacecraft have enabled the first in situ measurements of the solar wind down to a heliocentric distance of 0.17 au (or 36 Rs). Here, we present an analysis of this data to study solar wind turbulence at 0.17 au and its evolution out to 1 au. While many features remain similar, key differences at 0.17 au include: increased turbulence energy levels by more than an order of magnitude, a magnetic field spectral index of -3/2 matching that of the velocity and both Elsasser fields, a lower magnetic compressibility consistent with a smaller slow-mode kinetic energy fraction, and a much smaller outer scale that has had time for substantial nonlinear processing. There is also an overall increase in the dominance of outward-propagating Alfv\'enic fluctuations compared to inward-propagating ones, and the radial variation of the inward component is consistent with its generation by reflection from the large-scale gradient in Alfv\'en speed. The energy flux in this turbulence at 0.17 au was found to be ~10% of that in the bulk solar wind kinetic energy, becoming ~40% when extrapolated to the Alfv\'en point, and both the fraction and rate of increase of this flux towards the Sun is consistent with turbulence-driven models in which the solar wind is powered by this flux.

[33]  arXiv:1912.02350 [pdf, other]

Title: A Linear Formation Flying Astronomical Interferometer in Low Earth Orbit

Authors: Jonah T. Hansen, Michael J. Ireland

Comments: 11 Pages, 7 Figures, submitted to Publications of the Astronomical Society of Australia

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)

Space interferometry is the inevitable endpoint of high angular resolution astrophysics, and a key technology that can be leveraged to analyse exoplanet formation and atmospheres with exceptional detail. However, the anticipated cost of large missions such as Darwin and TPF-I, and inadequate technology readiness levels have resulted in limited developments since the late 2000s. Here, we present a feasibility study into a small scale formation flying interferometric array in Low Earth Orbit, that will aim to prove the technical concepts involved with space interferometry while still making unique astrophysical measurements. We will detail the proposed system architecture and metrology system, as well as present orbital simulations that show that the array should be stable enough to perform interferometry with < 50m/s/year delta-v and one thruster per spacecraft. We also conduct observability simulations to identify which parts of the sky are visible for a given orbital configuration. We conclude with optimism that this design is achievable, but a more detailed control simulation factoring in a demonstrated metrology system is the next step to demonstrate full mission feasibility.

[34]  arXiv:1912.02361 [pdf, other]

Title: Ion Scale Electromagnetic Waves in the Inner Heliosphere

Authors: Trevor Bowen, Alfred Mallet, Jia Huang, Kristopher G. Klein, David M. Malaspina, Michael L. Stevens, Stuart D. Bale, John W. Bonnell, Anthony W. Case, Benjamin D. Chandran, Christopher Chaston, Christopher H. Chen, Thierry Dudok de Wit, Keith Goetz, Peter R. Harvey, Gregory G. Howes, Justin C. Kasper, Kelly Korreck, Davin E. Larson, Roberto Livi, Robert J. MacDowall, Michael McManus, Marc Pulupa, J Verniero, Phyllis Whittlesey

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

Understanding the physical processes in the solar wind and corona which actively contribute to heating, acceleration, and dissipation is a primary objective of NASA's Parker Solar Probe (PSP) mission. Observations of coherent electromagnetic waves at ion scales suggests that linear cyclotron resonance and non-linear processes are dynamically relevant in the inner heliosphere. A wavelet-based statistical study of coherent waves in the first perihelion encounter of PSP demonstrates the presence of transverse electromagnetic waves at ion resonant scales which are observed in 30-50\% of radial field intervals. Average wave amplitudes of approximately 4 nT are measured, while the mean duration of wave events is of order 20 seconds; however long duration wave events can exist without interruption on hour-long timescales. Though ion scale waves are preferentially observed during intervals with a radial mean magnetic field, we show that measurement constraints, associated with single spacecraft sampling of quasi-parallel waves superposed with anisotropic turbulence, render the measured quasi-parallel ion-wave spectrum unobservable when the mean magnetic field is oblique to the solar wind flow; these results imply that the occurrence of coherent ion-scale waves is not limited to a radial field configuration. The lack of strong radial scaling of characteristic wave amplitudes and duration suggests that the waves are generated {\em{in-situ}} through plasma instabilities. Additionally, observations of proton distribution functions indicate that temperature anisotropy may drive the observed ion-scale waves.

[35]  arXiv:1912.02376 [pdf, other]

Title: Hemispherical Variance Anomaly and Reionization Optical Depth

Authors: Marcio O'Dwyer, Craig J. Copi, Johanna M. Nagy, C. Barth Netterfield, John Ruhl, Glenn D. Starkman

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

CMB full-sky temperature data show a hemispherical asymmetry in power nearly aligned with the Ecliptic. In real space, this anomaly can be quantified by the temperature variance in the northern and southern Ecliptic hemispheres, with the north displaying an anomalously low variance while the south appears consistent with expectations from the best-fitting theory, LCDM. While this is a well-established result in temperature, the low signal-to-noise ratio in current polarization data prevents a similar comparison. Even though temperature and polarization are correlated, polarization realizations constrained by temperature data show that the lack of variance is not expected to be present in polarization data. Therefore, a natural way of testing whether the temperature result is a fluke is to measure the variance of CMB polarization components. In anticipation of future CMB experiments that will allow for high-precision large-scale polarization measurements, we study how variance of polarization depends on LCDM parameters' uncertainties by forecasting polarization maps with Planck's MCMC chains. We find that, unlike temperature variance, polarization variance is noticeably sensitive to present uncertainties in cosmological parameters. This comes mainly from the current poor constraints on the reionization optical depth, tau, and the fact that tau drives variance at low multipoles. In this work we show how the variance of polarization maps generically depends on the cosmological parameters. We demonstrate how the improvement in the tau measurement seen between Planck's two latest data releases results in a tighter constraint on polarization variance expectations. Finally, we consider even smaller uncertainties on tau and how more precise measurements of tau can drive the expectation for polarization variance in a hemisphere close to that of the cosmic-variance-limited distribution.

[36]  arXiv:1912.02393 [pdf, other]

Title: On the origin of the asymmetric dwarf galaxy distribution around Andromeda

Authors: Zhen Wan, William H. Oliver, Geraint F. Lewis, Justin I. Read, Michelle L. M. Collins

Comments: 12 pages, 10 figures, accepted by MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

The dwarf galaxy distribution surrounding M31 is significantly anisotropic in nature. Of the 30 dwarf galaxies in this distribution, 15 form a disc-like structure and 23 are contained within the hemisphere facing the Milky Way. Using a realistic local potential, we analyse the conditions required to produce and maintain these asymmetries. We find that some dwarf galaxies are required to have highly eccentric orbits in order to preserve the presence of the hemispherical asymmetry with an appropriately large radial dispersion. Under the assumption that the dwarf galaxies originate from a single association or accretion event, we find that the initial size and specific energy of that association must both be relatively large in order to produce the observed hemispherical asymmetry. However if the association was large in physical size, the very high-energy required would enable several dwarf galaxies to escape from the M31 and be captured by the Milky Way. Furthermore, we find that associations that result in this structure have total specific energies concentrated around $E = V_{esc}^{2} - V_{init}^{2} \sim 200^2$ -- $300^2\ \rm{km^2\ s^{-2}}$, implying that the initial velocity and initial position needed to produce the structure are strongly correlated. The overlap of initial conditions required to produce the radial dispersion, angular dispersion, and the planar structure is small and suggests that either they did not originate from a single accretion event, or that these asymmetric structures are short-lived.

[37]  arXiv:1912.02403 [pdf, ps, other]

Title: The HASHTAG project I. A Survey of CO(3-2) Emission from the Star Forming Disc of M31

Authors: Zongnan Li, Zhiyuan Li, Matthew W. L. Smith, Christine D. Wilson, Yu Gao, Stephen A. Eales, Yiping Ao, Martin Bureau, Aeree Chung, Timothy A. Davis, Richard de Grijs, David J. Eden, Jinhua He, Tom M. Hughes, Xuejian Jiang, Francisca Kemper, Isabella Lamperti, Bumhyun Lee, Chien-Hsiu Lee, Michal J. Michalowski, Harriet Parsons, Sarah Ragan, Peter Scicluna, Yong Shi, Xindi Tang, Neven Tomicic, Sebastien Viaene, Thomas G. Williams, Ming Zhu

Comments: 21 pages, 10 figures, accepted by MNRAS for publication

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a CO(3-2) survey of selected regions in the M31 disc as part of the JCMT large programme, HARP and SCUBA-2 High-Resolution Terahertz Andromeda Galaxy Survey (HASHTAG). The 12 CO(3-2) fields in this survey cover a total area of 60 square arcminutes, spanning a deprojected radial range of 2 - 14 kpc across the M31 disc. Combining these observations with existing IRAM 30m CO(1-0) observations and JCMT CO(3-2) maps of the nuclear region of M31, as well as dust temperature and star formation rate surface density maps, we are able to explore the radial distribution of the CO(3-2)/CO(1-0) integrated intensity ratio (R31) and its relationship with dust temperature and star formation. We find that the value of R31 between 2 - 9 kpc galactocentric radius is 0.14, significantly lower than what is seen in the nuclear ring at ~1 kpc (R31 ~ 0.8), only to rise again to 0.27 for the fields centred on the 10 kpc star forming ring. We also found that R31 is positively correlated with dust temperature, with Spearman's rank correlation coefficient $\rho$ = 0.55. The correlation between star formation rate surface density and CO(3--2) intensity is much stronger than with CO(1-0), with $\rho$ = 0.54 compared to -0.05, suggesting that the CO(3-2) line traces warmer and denser star forming gas better. We also find that R31 correlates well with star formation rate surface density, with $\rho$ = 0.69.

[38]  arXiv:1912.02408 [pdf, ps, other]

Title: Obscuring fraction of active galactic nuclei implied by supernova and radiative feedbacks

Authors: Nozomu Kawakatu, Keiichi Wada, Kohei Ichikawa

Comments: 17 pages, 11 figures, Accepted for publication in ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the obscuring structure of circumnuclear disks (CNDs) by considering supernova (SN) feedbacks from nuclear starburst and the effect of anisotropic radiative pressure from AGNs. We suppose that the mass accretion onto a central supermassive black hole (SMBH) is triggered by SN-driven turbulence within CNDs, and we explore how the structures of CNDs depend on the BH mass ($M_{\rm BH}$) and AGN luminosity ($L_{\rm AGN}$). We find that the obscuring fraction ($f_{\rm obs}$) peaks at $\sim10\%$ of the Eddington luminosity ($L_{\rm Edd}$), and its maximal value is $f_\mathrm{obs} \sim 0.6$ for less massive SMBHs (e.g., $M_{\rm BH} < 10^{8}M_{\odot}$). This is because the scale height of CNDs is determined by the SN-driven accretion for a smaller $L_{\rm AGN}$, while the dusty molecular gas in CNDs is blown away by the radiation pressure from AGNs beyond the critical luminosity. On the other hand, for massive SMBHs (e.g., $M_{\rm BH} > 10^{8}M_{\odot}$), $f_{\rm obs}$ is always smaller than $0.2$, and it is almost independent of $L_{\rm AGN}$ because the scale height of CNDs is mainly controlled by the maximal star-formation efficiency ($C_{\rm *, max}$) in CNDs. By comparison with the obscuring fractions suggested from the mid-infrared observations of nearby AGNs, the SN plus radiative feedback model with $C_{\rm *, max} = 10^{-7}\, {\rm yr}^{-1}$ well reproduces the observations for $M_\mathrm{BH} = 10^8 M_\odot$. We also find that the intense starburst or the existence of dust-free absorbers inside CNDs are necessary, to explain X-ray observations.

[39]  arXiv:1912.02415 [pdf, other]

Title: Modelling Double Neutron Stars: Radio and Gravitational Waves

Authors: Debatri Chattopadhyay, Simon Stevenson, Jarrod R. Hurley, Luca J. Rossi, Chris Flynn

Comments: 25 pages, submitted to MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We have implemented prescriptions for modelling pulsars in the rapid binary population synthesis code COMPAS. We perform a detailed analysis of the double neutron star (DNS) population, accounting for radio survey selection effects. The surface magnetic field decay timescale (${\approx}1000$\,Myr) and mass scale (${\approx}0.02$\,M$_\odot$) are the dominant uncertainties in our model. Mass accretion during common envelope evolution plays a non-trivial role in recycling pulsars. We find a best-fit model that is in broad agreement with the observed Galactic DNS population. Though the pulsar parameters (period and period derivative) are strongly biased by radio selection effects, the observed orbital parameters (orbital period and eccentricity) closely represent the intrinsic distributions. The number of radio observable DNSs in the Milky Way at present is $\approx$\,2500 in our model, only $\approx$\,10\% of the predicted total number of DNSs in the galaxy. Using our model calibrated to the Galactic DNS population, we make predictions for DNS mergers observed in gravitational waves. The median DNS chirp mass is 1.14\,M$_\mathrm{\odot}$ and $\approx$40\% of DNSs have a chirp mass $\geq$ 1.2\,M$_\mathrm{\odot}$. The expected effective spin $\chi_\mathrm{eff}$ for isolated DNSs is $\lesssim$0.03 from our model. We predict that $\approx$34\% of the current Galactic isolated DNSs will merge within a Hubble time, and have a median total mass of 2.7\,M$_\mathrm{\odot}$. Finally, we discuss implications for fast radio bursts and post-merger remnant gravitational-waves.

[40]  arXiv:1912.02454 [pdf, ps, other]

Title: Sardinia Radio Telescope observations of Local Group dwarf galaxies -- I. The cases of NGC6822, IC1613, and WLM

Authors: A. Tarchi, P. Castangia, G. Surcis, A. Brunthaler, C. Henkel, M. Pawlowski, K. M. Menten, A. Melis, S. Casu, M. Murgia, A. Trois, R. Concu, J. Darling

Comments: 15 pages, 7 figures, accepted for publication by MNRAS. A high-resolution version of the paper can be found at the link this http URL

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Almost all dwarf galaxies in the Local Group that are not satellites of the Milky Way or M31, belong to either one of two highly-symmetric planes. It is still a matter of debate, whether these planar structures are dynamically stable or whether they only represent a transient alignment. Proper motions, if they could be measured, could help to discriminate between these scenarios. Such motions could be determined with multi-epoch Very Long Baseline Interferometry (VLBI) of sources that show emission from water and methanol at frequencies of 22 and 6.7 GHz, respectively. We report searches for such masers. We have mapped three Local Group galaxies, NGC6822, IC1613 and WLM in the bands covering the water vapor and methanol lines. These systems are members of the two above mentioned planes of galaxies. We have produced deep radio continuum (RC) maps and spectral line cubes. The former have been used to identify star forming regions and to derive global galactic star formation rates (SFRs). These SFRs turn out to be lower than those determined at other wavelengths in two of our sources. This indicates that dwarf galaxies may follow predictions on the RC-SFR relation only in individual regions of enhanced radio continuum emission, but not when considering the entire optical body of the sources. No methanol or water maser emission has been confidently detected, down to line luminosity limits of ~0.004 and 0.01 solar luminosities, respectively. This finding is consistent with the small sizes, low SFRs and metallicities of these galaxies.

[41]  arXiv:1912.02464 [pdf, other]

Title: Self-Induced Dust Traps Around Snow Lines in Protoplanetary Discs

Authors: Arnaud Vericel, Jean François Gonzalez

Comments: 14 pages, 14 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Dust particles need to grow efficiently from micrometre sizes to thousands of kilometres to form planets. With the growth of millimetre to meter sizes being hindered by a number of barriers, the recent discovery that dust evolution is able to create `self-induced' dust traps shows promises. The condensation and sublimation of volatile species at certain locations, called snow lines, is also thought to be an important part of planet formation scenarios. Given that dust sticking properties change across a snow line, this raises the question: how do snow lines affect the self-induced dust trap formation mechanism? The question is particularly relevant with the multiple observations of the carbon monoxide (CO) snow line in protoplanetary discs, since its effect on dust growth and dynamics is yet to be understood. In this paper, we present the effects of snow lines in general on the formation of self-induced dust traps in a parameter study, then focus on the CO snow line. We find that for a range of parameters, a dust trap forms at the snow line where the dust accumulates and slowly grows, as found for the water snow line in previous work. We also find that, depending on the grains sticking properties on either side of the CO snow line, it could either be a starting or braking point for dust growth and drift. This could provide clues to understand the link between dust distributions and snow lines in protoplanetary disc observations.

[42]  arXiv:1912.02476 [pdf]

Title: Voyager 2 enters interstellar space

Authors: R. Du Toit Strauss

Journal-ref: Nature Astronomy volume 3, pages 963-964(2019)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

After 41 years of travel, the Voyager 2 spacecraft joins its twin in interstellar space. A suite of papers report Voyager 2's experience of its transition through the heliosheath and heliopause to what lies beyond.

[43]  arXiv:1912.02496 [pdf, ps, other]

Title: Emergence of small-scale magnetic flux in the quiet Sun

Authors: I. Kontogiannis, G. Tsiropoula, K. Tziotziou, C. Gontikakis, C. Kuckein, M. Verma, C. Denker

Comments: Accepted for publication in Astronomy & Astrophysics 14 pages, 14 figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We study the evolution of a small-scale emerging flux region (EFR) in the quiet Sun, from its emergence to its decay. We track processes and phenomena across all atmospheric layers, explore their interrelations and compare our findings with recent numerical modelling studies. We used imaging, spectral and spectropolarimetric observations from space-borne and ground-based instruments. The EFR appears next to the chromospheric network and shows all characteristics predicted by numerical simulations. The total magnetic flux of the EFR exhibits distinct evolutionary phases, namely an initial subtle increase, a fast increase and expansion of the region area, a more gradual increase, and a slow decay. During the initial stages, bright points coalesce, forming clusters of positive- and negative-polarity in a largely bipolar configuration. During the fast expansion, flux tubes make their way to the chromosphere, producing pressure-driven absorption fronts, visible as blueshifted chromospheric features. The connectivity of the quiet-Sun network gradually changes and part of the existing network forms new connections with the EFR. A few minutes after the bipole has reached its maximum magnetic flux, it brightens in soft X-rays forming a coronal bright point, exhibiting episodic brightenings on top of a long smooth increase. These coronal brightenings are also associated with surge-like chromospheric features, which can be attributed to reconnection with adjacent small-scale magnetic fields and the ambient magnetic field. The emergence of magnetic flux even at the smallest scales can be the driver of a series of energetic phenomena visible at various atmospheric heights and temperature regimes. Multi-wavelength observations reveal a wealth of mechanisms which produce diverse observable effects during the different evolutionary stages of these small-scale structures.

[44]  arXiv:1912.02518 [pdf, other]

Title: First in-situ Measurements of Electron Density and Temperature from Quasi-Thermal Noise Spectroscopy with Parker Solar Probe/FIELDS

Authors: Michel Moncuquet, Nicole Meyer-Vernet, Karine Issautier, Marc Pulupa, J. W. Bonnell, Stuart D. Bale, Thierry Dudok de Wit, Keith Goetz, Léa Griton, Peter R. Harvey, Robert J. MacDowall, Milan Maksimovic, David M. Malaspina

Comments: 17 pages, 7 figures, accepted in ApJS (Parker Solar Probe special issue)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM); Space Physics (physics.space-ph)

Heat transport in the solar corona and wind is still a major unsolved astrophysical problem. Because of the key role played by electrons, the electron density and temperature(s) are important prerequisites for understanding these plasmas. We present such in situ measurements along the two first solar encounters of Parker Solar Probe (PSP), between 0.5 and 0.17 AU from the Sun, revealing different states of the emerging solar wind near solar activity minimum. These preliminary results are obtained from a simplified analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the Radio Frequency Spectrometer (RFS/FIELDS). The local electron density is deduced from the tracking of the plasma line, which enables accurate measurements, independent of calibrations and spacecraft perturbations, whereas the temperatures of the thermal and supra-thermal components of the velocity distribution, as well as the average kinetic temperature are deduced from the shape of the plasma line. The temperature of the weakly collisional thermal population, similar for both encounters, decreases with distance as $R^{-0.74}$, much slower than adiabatic. In contrast, the temperature of the nearly collisionless suprathermal population exhibits a virtually flat radial variation. The 7-second resolution of the density measurements enables us to deduce the low-frequency spectrum of compressive fluctuations around perihelion, varying as $f^{-1.4}$. This is the first time that QTN spectroscopy is implemented with an electric antenna length not exceeding the plasma Debye length. As PSP will approach the Sun, the decrease in Debye length is expected to considerably improve the accuracy of the temperature measurements.

[45]  arXiv:1912.02533 [pdf]

Title: Photometry of an unusual small distant object 2016 ND21

Authors: Tetiana Hromakina, Sergey Velichko, Irina Belskaya, Yurij Krugly, Aleksandr Sergeev

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present the first-ever measurements of the surface colors and rotational properties of a recently discovered distant object in an unusual orbit 2016 ND21. In 2017, this object was close to its perihelion, which allowed us to observe it with a 2.0-m telescope at the Peak Terskol observatory. Broadband photometric observations of 2016 ND21 were carried out in October and December of 2017 in standard BVR filters of the Johnson-Cousins photometric system. During our observations, we did not detect any cometary activity. We found the rotational period of 17.53{\pm}0.02 hr, while another a little longer value of 17.65{\pm}0.02 hr is also possible. Assuming an equatorial aspect of observations, a peak-to-peak amplitude of A = 0.31{\pm}0.05 mag (or even higher since only one maximum and one minimum were well-measured) corresponds to an elongated body with an axis ratio a/b ~1.3. The lightcurve behavior indicates a complex, possibly non-convex, shape of this object. The visible absolute magnitude is HV =12.4{\pm}0.1 mag, which was estimated by using the linear phase slope 0.04 mag/deg as the most probable value from our observations. Assuming a surface albedo in the range of 0.04-0.10, the size of 2016 ND21 should be about 15-23 km. From our multi-color observations, we determined surface colors V-R = 0.69{\pm}0.04 mag, B-R = 1.79{\pm}0.08 mag, and B-V = 1.10{\pm}0.08 mag. The measured colors indicate an extremely red surface of this object. A very red surface is unusual for comets, which is in agreement with the fact, that no cometary activity was detected for 2016 ND21. The B-R color is higher than the typical B-R colors of the red D-type asteroids, but it is consistent with colors of the red Centaurs and TNOs classified as RR type in TNOs classification. This result gives a first evidence of a possible outer belt origin of this small body.

[46]  arXiv:1912.02538 [pdf, other]

Title: On the spectroscopic detection of periodic plasma flows in loops undergoing thermal non-equilibrium

Authors: Gabriel Pelouze, Frédéric Auchère, Karine Bocchialini, Clara Froment, Susanna Parenti, Elie Soubrié

Comments: Accepted for publication in A&A. 16 pages, 16 figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Context: Long-period intensity pulsations were recently detected in the EUV emission of coronal loops, and have been attributed to cycles of plasma evaporation and condensation driven by thermal non-equilibrium (TNE). Numerical simulations that reproduce this phenomenon also predict the formation of periodic flows of plasma at coronal temperatures along some of the pulsating loops. Aims: In this paper, we aim at detecting these predicted flows of coronal-temperature plasma in pulsating loops. Methods: To this end, we use time series of spatially resolved spectra from the EUV imaging spectrometer (EIS) onboard Hinode, and track the evolution of the Doppler velocity in loops in which intensity pulsations have previously been detected in images of SDO/AIA. Results: We measure signatures of flows that are compatible with the simulations, but only in a fraction of the observed events. We demonstrate that this low detection rate can be explained by line of sight ambiguities, combined with instrumental limitations such as low signal to noise ratio or insufficient cadence.

[47]  arXiv:1912.02565 [pdf, other]

Title: A dusty benchmark brown dwarf near the ice line of HD 72946

Authors: A.-L. Maire, J.-L. Baudino, S. Desidera, S. Messina, W. Brandner, N. Godoy, F. Cantalloube, R. Galicher, M. Bonnefoy, J. Hagelberg, J. Olofsson, O. Absil, G. Chauvin, T. Henning, M. Langlois

Comments: Accepted for publication in A&A, 10 pages, 10 figures, 1 table. Includes language editing

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Context. HD72946 is a bright and nearby solar-type star hosting a low-mass companion at long period (P~16 yr) detected with the radial velocities (RV) method. The companion has a minimum mass of 60.4+/-2.2 MJ and might be a brown dwarf. Its expected semi-major axis of ~243 mas makes it a suitable target for further characterization with high-contrast imaging, in particular to measure its inclination, mass, and spectrum and thus definitely establish its substellar nature. Aims. We aim to further characterize the orbit, atmosphere, and physical nature of HD72946B. Methods. We present high-contrast imaging data in the near-infrared with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. We also use proper motion measurements of the star from Hipparcos and Gaia. Results. The SPHERE data reveal a point source with a contrast of ~9 mag at a projected separation of ~235 mas. No other point sources are detected in the field of view. By jointly fitting the RV, imaging, and proper motion data, we constrain all the orbital parameters of HD72946B and assess a dynamical mass of 72.4+/-1.6 MJ and a semi-major axis of 6.45$^{+0.08}_{-0.07}$ au. Empirical comparison of its IFS spectrum to template dwarfs indicates a spectral type of L5.0+/-1.5. The J-H3 color is close to the expectations of the DUSTY models and suggests a cloudy atmosphere. Comparison with atmospheric models of the spectrophotometry suggests an effective temperature of ~1700 K. The bolometric luminosity (log(L/LS)=-4.11+/-0.10 dex) and dynamical mass of HD72946B are more compatible with evolutionary models for an age range of ~0.9-3 Gyr. The formation mechanism of the companion is currently unclear as it appears slightly away from the bulk of model predictions. HD72946B is currently the closest benchmark brown dwarf companion to a solar-type star with imaging, RV, and proper motion measurements.

[48]  arXiv:1912.02581 [pdf, other]

Title: The Solar Probe Cup on Parker Solar Probe

Authors: Anthony W. Case, Justin C. Kasper, Michael L. Stevens, Kelly E. Korreck, Kristoff Paulson, Peter Daigneau, Dave Caldwell, Mark Freeman, Thayne Henry, Brianna Klingensmith, Miles Robinson, Peter Berg, Chris Tiu, Kenneth H. Wright Jr., David Curtis, Michael Ludlam, Davin Larson, Phyllis Whittlesey, Roberto Livi, Kristopher G. Klein, Mihailo M. Martinović

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)

The Solar Probe Cup (SPC) is a Faraday Cup instrument onboard NASA's Parker Solar Probe (PSP) spacecraft designed to make rapid measurements of thermal coronal and solar wind plasma. The spacecraft is in a heliocentric orbit that takes it closer to the Sun than any previous spacecraft, allowing measurements to be made where the coronal and solar wind plasma is being heated and accelerated. The SPC instrument was designed to be pointed directly at the Sun at all times, allowing the solar wind (which is flowing primarily radially away from the Sun) to be measured throughout the orbit. The instrument is capable of measuring solar wind ions with an energy/charge between 100 V and 6000 V (protons with speeds from $139-1072~km~s^{-1})$. It also measures electrons with an energy between 100 V and 1500 V. SPC has been designed to have a wide dynamic range that is capable of measuring protons and alpha particles at the closest perihelion (9.86 solar radii from the center of the Sun) and out to 0.25 AU. Initial observations from the first orbit of PSP indicate that the instrument is functioning well.

[49]  arXiv:1912.02593 [pdf, other]

Title: Non-Linear Convergence of Solar-like Stars Chromospheres using Millimeter, Sub-millimeter, and Infrared Observations

Authors: F. Tapia-Vazquez, V. De la Luz

Comments: Accepted to The Astrophysical Journal Supplement

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In this work, we present a new methodology to fit the observed and synthetic spectrum of solar-like stars at millimeter, submillimeter and infrared wavelengths through semiempirical models of the solar chromosphere. We use the Levenberg-Marquardt algorithm as a Non-Linear method, PakalMPI as the semiempirical model of the solar chromosphere, and recent observations from the Atacama Large Millimeter/submillimeter Array (ALMA) of Alpha Centauri A as a test case. Our results show that we can use solar chromospheric semiempirical models as an input model to reproduce the observed spectrum of solar-like stars. The new profiles show similarities to the solar chromosphere as a minimum of temperature (without the restriction from CO emission) and a plateau in the high chromosphere. Our method provides a new fast numerical tool to estimate the physical conditions of solar-like stars.

[50]  arXiv:1912.02599 [pdf, other]

Title: The mass of our Milky Way

Authors: Wenting Wang, Jiaxin Han, Marius Cautun, Zhaozhou Li, Miho N. Ishigaki

Comments: Any comments or additional references are welcomed

Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We perform an extensive review of the numerous studies and methods used to determine the total mass of the Milky Way. We group the various methods into seven broad classes, including: i) estimating Galactic escape velocity using high velocity objects; ii) measuring the rotation curve through terminal and circular velocities; iii) modeling halo stars, globular clusters and satellite galaxies with the Spherical Jeans equation and iv) with phase-space distribution functions; v) simulating and modeling the dynamics of stellar streams and their progenitors; vi) modeling the motion of the Milky Way, M31 and other distant satellites under the framework of Local Group timing argument; and vii) measurements made by linking the brightest Galactic satellites to their counterparts in simulations. For each class of methods, we introduce their theoretical and observational background, the method itself, the sample of available tracer objects, model assumptions, uncertainties, limits and the corresponding measurements that have been achieved in the past. Both the measured total masses within the radial range probed by tracer objects and the extrapolated virial masses are discussed and quoted. We also discuss the role of modern numerical simulations in terms of helping to validate model assumptions, understanding systematic uncertainties and calibrating the measurements. While measurements in the last two decades show a factor of two scatters, recent measurements using \textit{Gaia} DR2 data are approaching a higher precision. We end with a detailed discussion of future developments, especially as the size and quality of the observational data will increase tremendously with current and future surveys. In such cases, the systematic uncertainties will be dominant and thus will necessitate a much more rigorous testing and characterization of the various mass determination methods.

[51]  arXiv:1912.02622 [pdf, other]

Title: Science Case for the Einstein Telescope

Authors: Michele Maggiore, Chris van den Broeck, Nicola Bartolo, Enis Belgacem, Daniele Bertacca, Marie Anne Bizouard, Marica Branchesi, Stefano Foffa, Juan García-Bellido, Stefan Grimm, Jan Harms, Tanja Hinderer, Sabino Matarrese, Cristiano Palomba, Marco Peloso, Angelo Ricciardone, Mairi Sakellariadou

Comments: 41 pages, 19 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

The Einstein Telescope (ET), a proposed European ground-based gravitational-wave detector of third-generation, is an evolution of second-generation detectors such as Advanced LIGO, Advanced Virgo, and KAGRA which could be operating in the mid 2030s. ET will explore the universe with gravitational waves up to cosmological distances. We discuss its main scientific objectives and its potential for discoveries in astrophysics, cosmology and fundamental physics.

[52]  arXiv:1912.02649 [pdf, ps, other]

Title: 3DMAP-VR, a project to visualize 3-dimensional models of astrophysical phenomena in virtual reality

Authors: Salvatore Orlando, Ignazio Pillitteri, Fabrizio Bocchino, Laura Daricello, Laura Leonardi

Comments: Published on Research Notes of the AAS, Volume 3, Number 11

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

In this research note, we present 3DMAP-VR,(3-Dimensional Modeling of Astrophysical Phenomena in Virtual Reality), a project aimed at visualizing 3D MHD models of astrophysical simulations, using virtual reality sets of equipment. The models account for all the relevant physical processes in astrophysical phenomena: gravity, magnetic-field-oriented thermal conduction, energy losses due to radiation, gas viscosity, deviations from proton-electron temperature equilibration, deviations from the ionization equilibrium, cosmic rays acceleration, etc.. We realized an excellent synergy between our 3DMAP-VR project and Sketchfab (one of the largest open access platforms to publish and share 3D virtual reality and augmented reality content) to promote a wide dissemination of results for both scientific and public outreach purposes.

[53]  arXiv:1912.02653 [pdf, other]

Title: The Enhancement of Proton Stochastic Heating in the near-Sun Solar Wind

Authors: Mihailo M. Martinović, Kristopher G. Klein, Justin C. Kasper, Anthony W. Case, Kelly E. Korreck, Davin Larson, Roberto Livi, Michael Stevens, Phyllis Whittlesey, Benjamin D. G. Chandran, Ben L. Alterman, Jia Huang, Christopher H. K. Chen, Stuart D. Bale, Marc Pulupa, David M. Malaspina, John W. Bonnell, Peter R. Harvey, Keith Goetz, Thierry Dudok de Wit, Robert J. MacDowall

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph)

Stochastic heating is a non-linear heating mechanism driven by the violation of magnetic moment invariance due to large-amplitude turbulent fluctuations producing diffusion of ions towards higher kinetic energies in the direction perpendicular to the magnetic field. It is frequently invoked as a mechanism responsible for the heating of ions in the solar wind. Here, we quantify for the first time the proton stochastic heating rate $Q_\perp$ at radial distances from the Sun as close as $0.16$ au, using measurements from the first two Parker Solar Probe encounters. Our results for both the amplitude and radial trend of the heating rate, $Q_\perp \propto r^{-2.5}$, agree with previous results based on the Helios data set at heliocentric distances from 0.3 to 0.9 au. Also in agreement with previous results, $Q_\perp$ is significantly larger in the fast solar wind than in the slow solar wind. We identify the tendency in fast solar wind for cuts of the core proton velocity distribution transverse to the magnetic field to exhibit a flat-top shape. The observed distribution agrees with previous theoretical predictions for fast solar wind where stochastic heating is the dominant heating mechanism.

[54]  arXiv:1912.02673 [pdf, other]

Title: PIC Simulation Methods for Cosmic Radiation and Plasma Instabilities

Authors: Martin Pohl, Masahiro Hoshino, Jacek Niemiec

Comments: Review paper, 102 pages, accepted for publication in "Progress in Particle and Nuclear Physics"

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)

Particle acceleration in collisionless plasma systems is a central question in astroplasma and astroparticle physics. The structure of the acceleration regions, electron-ion energy equilibration, preacceleration of particles at shocks to permit further energization by diffusive shock acceleration, require knowledge of the distribution function of particles besides the structure and dynamic of electromagnetic fields, and hence a kinetic description is desirable. Particle-in-cell simulations offer an appropriate, if computationally expensive method of essentially conducting numerical experiments that explore kinetic phenomena in collisionless plasma. We review recent results of PIC simulations of astrophysical plasma systems, particle acceleration, and the instabilities that shape them.

[55]  arXiv:1912.02680 [pdf]

Title: Local Turbulence: Effects and causes

Authors: Olivier Lai (LAGRANGE), Kanoa Withington, Romain Laugier (LAGRANGE), Mark Chun

Journal-ref: AO4ELT6, Jun 2019, Quebec, Canada

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Dome seeing is a known source of image quality degradation, but despite tremendous progress in wavefront control with the development of adaptive optics and environmental control through implementation of dome venting, surprisingly little is known about it quantitatively. We have found evidence of non-Kolmogorov dome turbulence from our observations with the imaka wide field adaptive optics system; PSFs seem to indicate an excess of high spatial frequencies and turbulence profiles reveal turbulence at negative conjugations. This has motivated the development of a new type of optical turbulence sensor called AIR-FLOW, Airborne Interferometric Recombiner: Fluctuations of Light at Optical Wavelengths. It is a non-redundant mask imaging interferometer that samples the optical turbulence passing through a measurement cell and it measures the two-dimensional optical Phase Structure Function. This is a useful tool to characterise different types of turbulence (e.g. Kolmogorov, diffusive turbulence, etc.). By fitting different models, we can determine parameters such as Cn 2 , r0, L0 or deviation from fully developed turbulence. The instrument was tested at the Canada France Hawaii Telescope, at the University of Hawaii 2.2-meter telescope (UH88'') and at the Observatoire de la C{\^o}te d'Azur. It is ruggedised and sensitive enough to detect changes with different dome vent configurations, as well as slow local variations of the index of refraction in the UH88'' telescope tube. The instrument is portable enough that it can be used to locate sources of turbulence inside and around domes, but it can also be used in an operational setting without affecting observations to characterise the local optical turbulence responsible for dome seeing. Thus, it could be used in real-time observatory control systems to configure vents and air handlers to effectively reduce dome seeing. We believe it could also be a tool for site surveys to evaluate dome seeing mitigation strategies in situ.

[56]  arXiv:1912.02682 [pdf, other]

Title: Primordial Black Holes as Dark Matter through Higgs Criticality

Authors: Samuel Passaglia, Wayne Hu, Hayato Motohashi

Comments: 22 pages, 10 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

We study the dynamics of a spectator Higgs field which stochastically evolves during inflation onto near-critical trajectories on the edge of a runaway instability. We show that its fluctuations do not produce primordial black holes in sufficient abundance to be the dark matter, nor do they produce significant second-order gravitational waves. First we show that the Higgs produces larger fluctuations on CMB scales than on PBH scales, itself a no-go for a viable PBH scenario. Then we track the superhorizon perturbations nonlinearly through reheating using the delta N formalism to show that they are not converted to large curvature fluctuations. Our conclusions hold regardless of any fine-tuning of the Higgs field for both the Standard Model Higgs and for Higgs potentials modified to prevent unbounded runaway.

[57]  arXiv:1912.02687 [pdf, other]

Title: MOBSTER: Establishing a Picture of Magnetic Massive Stars as a Population

Authors: Alexandre David-Uraz (1), Coralie Neiner (2), James Sikora (3), James Barron (4 and 5), Dominic M. Bowman (6), Pınar Cerrahoğlu (1), David H. Cohen (7), Christiana Erba (1), Oleksandr Kobzar (8), Oleg Kochukhov (9), Véronique Petit (1), Matthew E. Shultz (1), Asif ud-Doula (10), Gregg A. Wade (5), the MOBSTER Collaboration ((1) Department of Physics and Astronomy, University of Delaware, Newark, DE USA, (2) LESIA, Paris Observatory, PSL University, CNRS, Sorbonne University, Université de Paris, Meudon, France, (3) Physics and Astronomy Department, Bishop's University, Sherbrooke, Canada, (4) Department of Physics, Engineering Physics & Astronomy, Queen's University, Kingston, ON, Canada, (5) Department of Physics and Space Science, Royal Military College of Canada, Kingston, ON, Canada, (6) Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, Belgium, (7) Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA, USA, (8) Département de Physique et d'Astronomie, Université de Moncton, Moncton, NB, Canada, (9) Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden, (10) Penn State Scranton, Dunmore, PA, USA)

Comments: 7 pages, 1 figure, Conference proceedings: "Stellar Magnetic Fields - A workshop in honour of the career and contributions of John Landstreet", London, Canada, 2019 (to be published in the Proceedings of the Polish Astronomical Society)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Magnetic massive and intermediate-mass stars constitute a separate population whose properties are still not fully understood. Increasing the sample of known objects of this type would help answer fundamental questions regarding the origins and characteristics of their magnetic fields. The MOBSTER Collaboration seeks to identify candidate magnetic A, B and O stars and explore the incidence and origins of photometric rotational modulation using high-precision photometry from the Transiting Exoplanet Survey Satellite (\textit{TESS}) mission. In this contribution, we present an overview of our methods and planned targeted spectropolarimetric follow-up surveys.

[58]  arXiv:1912.02701 [pdf, other]

Title: Superabundance of Exoplanet Sub-Neptunes Explained by Fugacity Crisis

Authors: Edwin S. Kite, Bruce Fegley Jr., Laura Schaefer, Eric B. Ford

Comments: Accepted by Astrophysical Journal Letters

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)

Transiting planets with radii 2-3 $R_\bigoplus$ are much more numerous than larger planets. We propose that this drop-off is so abrupt because at $R$ $\sim$ 3 $R_\bigoplus$, base-of-atmosphere pressure is high enough for the atmosphere to readily dissolve into magma, and this sequestration acts as a strong brake on further growth. The viability of this idea is demonstrated using a simple model. Our results support extensive magma-atmosphere equilibration on sub-Neptunes, with numerous implications for sub-Neptune formation and atmospheric chemistry.

[59]  arXiv:1912.02702 [pdf, other]

Title: RELICS: A Very Large ($θ_{E}\sim40"$) Cluster Lens -- RXC J0032.1+1808

Authors: Ana Acebron, Adi Zitrin, Dan Coe, Guillaume Mahler, Keren Sharon, Masamune Oguri, Maruša Bradač, Larry Bradley, Brenda Frye, Christine J. Forman, Victoria Strait, Yuanyuan Su, Keiichi Umetsu, Felipe Andrade-Santos, Roberto J. Avila, Daniela Carrasco, Catherine Cerny, Nicole G. Czakon, William A. Dawson, Carter Fox, Austin T. Hoag, Kuang-Han Huang, Traci L. Johnson, Shotaro Kikuchihara, Daniel Lam, Lorenzo Lovisari, Ramesh Mainali, Mario Nonino, Pascal A. Oesch, Sara Ogaz, Masami Ouchi, Matthew Past, Rachel Paterno-Mahler, Avery Peterson, Russell E. Ryan, Brett Salmon, Daniel P. Stark, Sune Toft, Michele Trenti, Benedetta Vulcani, Brian Welch

Comments: 16 pages, submitted to ApJ

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

Extensive surveys with the \textit{Hubble Space Telescope} (HST) over the past decade, targeting some of most massive clusters in the sky, have uncovered dozens of galaxy-cluster strong lenses. The massive cluster strong-lens scale is typically $\theta_{E}\sim10"$ to $\sim30-35"$, with only a handful of clusters known with Einstein radii $\theta_{E}\sim40"$ or above (for a source at $z_{s}\sim2$, nominally). Here we report another very large cluster lens, RXC J0032.1+1808 (at $z=0.3956$), the second richest cluster in the redMapper cluster catalog and the 85th most massive cluster in the Planck Sunyaev-Zel'dovich catalog. With both our Light-Traces-Mass and fully parametric (dPIEeNFW) approaches, we construct strong lensing models based on 18 multiple images of 5 background galaxies in the \textit{HST} data from the \textit{Reionization Lensing Cluster Survey} (RELICS; using also data also from a previous snapshot program), in addition to a previously found sextuply imaged system in this cluster. Furthermore, we compare these models to the Lenstool and GLAFIC models, which were produced independently as part of the RELICS program. All models reveal a large effective Einstein radius of $\theta_{E}\simeq40"$ ($z_{s}=2$). The central region of the cluster shows an obvious concentration of substructures, which together account for the large critical area. Although RXC J0032.1+1808 has a very large critical area and lensing strength, only three magnified high-redshift candidates are found within the field targeted by RELICS. Nevertheless, given its exceptional lensing strength, we expect many more high-redshift candidates will be seen in an additional coverage with \textit{HST}, and in deeper, longer-wavelength observations with \textit{JWST}.

[60]  arXiv:1912.02730 [pdf, ps, other]

Title: Strong Soft X-ray Excess in 2015 XMM-Newton Observation of BL--Lac OJ~287

Authors: Main Pal, Pankaj Kushwaha, Gulab C. Dewangan, M. Sami, P. K. Pawar

Comments: 12 pages, 5 figures, 2 tables; revised version submitted to ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

We report a strong soft X-ray excess in the BL--Lacartae $\gamma$-ray blazar OJ~287 during the long exposure in May 2015, amongst two of the latest \xmm~{} observations performed in May 2015 and 2018. In case of May 2015 observation, a logparabola model fits the EPIC-pn data well while a logparabola plus powerlaw describes the overall simultaneous optical to X-ray spectra, suggesting the excess as the synchrotron tail. This interpretation, however, is inconsistent with the observed spectral break between near-infrared and optical spectra, attributed to standard disk around a supermassive black hole (SMBH). Based on this, we considered two commonly invoked accretion disk based models in AGNs to explain the soft excess: the cool Comptonization component in the accretion disk and the blurred reflection from the partially ionized accretion disk. We found that both cool Comptonization and blurred reflection models provide equally good fit to the data and favor a super-heavy SMBH of mass $\sim 10^{10}~M_\odot$. Further investigation of about a month long simultaneous X-ray and UV pointing observations revealed a delayed UV emission with respect to the 1.5-10 keV band, favoring X-ray reprocessing phenomenon as the dominant mechanism. The results suggest that the soft excess is probably caused by strong light bending close to the SMBH. The detected soft excess in 2015 data and its disappearance in 2018 data is also consistent with the presence of accretion disk emission, inferred from the NIR-optical spectral} break between May 2013 to March 2016.

[61]  arXiv:1912.02741 [pdf, other]

Title: A HARPS RV search for planets around young nearby stars

Authors: A. Grandjean, A.-M. Lagrange, M. Keppler, N. Meunier L. Mignon, S. Borgniet, G. Chauvin, S. Desidera F. Galland, S. Messina, M. Sterzik, B. Pantoja, L. Rodet, N. Zicher

Comments: 19 pages, 15 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Young nearby stars are good candidates in the search for planets with both radial velocity (RV) and direct imaging techniques. This, in turn, allows for the computation of the giant planet occurrence rates at all separations. The RV search around young stars is a challenge as they are generally faster rotators than older stars of similar spectral types and they exhibit signatures of magnetic activity (spots) or pulsation in their RV time series. Specific analyses are necessary to characterize, and possibly correct for, this activity. Our aim is to search for planets around young nearby stars and to estimate the giant planet (GP) occurrence rates for periods up to 1000 days. We used the HARPS spectrograph on the 3.6m telescope at La Silla Observatory to observe 89 A-M young (< 600 Myr) stars. We used our SAFIR (Spectroscopic data via Analysis of the Fourier Interspectrum Radial velocities ) software to compute the RV and other spectroscopic observables. Then, we computed the companion occurrence rates on this sample. We confirm the binary nature of HD177171, HD181321 and HD186704. We report the detection of a close low mass stellar companion for HIP36985. No planetary companion was detected. We obtain upper limits on the GP (< 13 MJup) and BD (13-80 MJup) occurrence rates based on 83 young stars for periods less than 1000 days, which are set, 2_-2^+3 % and 1_-1^+3 %.

[62]  arXiv:1912.02743 [pdf, other]

Title: Toward Filament Segmentation Using Deep Neural Networks

Authors: Azim Ahmadzadeh, Sushant S. Mahajan, Dustin J. Kempton, Rafal A. Angryk, Shihao Ji

Comments: 10 pages, 10 figures, 1 table, accepted in IEEE BigData 2019

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Computer Vision and Pattern Recognition (cs.CV); Machine Learning (cs.LG)

We use a well-known deep neural network framework, called Mask R-CNN, for identification of solar filaments in full-disk H-alpha images from Big Bear Solar Observatory (BBSO). The image data, collected from BBSO's archive, are integrated with the spatiotemporal metadata of filaments retrieved from the Heliophysics Events Knowledgebase (HEK) system. This integrated data is then treated as the ground-truth in the training process of the model. The available spatial metadata are the output of a currently running filament-detection module developed and maintained by the Feature Finding Team; an international consortium selected by NASA. Despite the known challenges in the identification and characterization of filaments by the existing module, which in turn are inherited into any other module that intends to learn from such outputs, Mask R-CNN shows promising results. Trained and validated on two years worth of BBSO data, this model is then tested on the three following years. Our case-by-case and overall analyses show that Mask R-CNN can clearly compete with the existing module and in some cases even perform better. Several cases of false positives and false negatives, that are correctly segmented by this model are also shown. The overall advantages of using the proposed model are two-fold: First, deep neural networks' performance generally improves as more annotated data, or better annotations are provided. Second, such a model can be scaled up to detect other solar events, as well as a single multi-purpose module. The results presented in this study introduce a proof of concept in benefits of employing deep neural networks for detection of solar events, and in particular, filaments.

[63]  arXiv:1912.02746 [pdf, other]

Title: The disc-like host galaxies of radio-loud Narrow-Line Seyfert 1s

Authors: Alejandro Olguín-Iglesias, Jari Kotilainen, Vahram Chavushyan

Comments: 17 pages, 9 figures, 3 tables

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Until recently, relativistic jets were ubiquitously found to be launched from giant elliptical galaxies. However, the detection by the Fermi-LAT of gamma-ray emission from radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxies raised doubts on this relation. Here, we morphologically characterize a sample of 29 RL-NLSy1s (including 12 gamma-ray emitters, gamma-NLSy1s) in order to find clues on the conditions needed by AGN to produce relativistic jets. We use deep near-infrared images from the Nordic Optical Telescope and the ESO VLT to analyze the surface brightness distribution of the galaxies in the sample. We detected 72% of the hosts (24% classified as gamma-NLSy1s). Although we cannot rule out that some RL-NLSy1s are hosted by dispersion supported systems, our findings strongly indicate that RL-NLSy1s hosts are preferentially disc galaxies. 52% of the resolved hosts (77% non-gamma-emitters and 20% gamma-emitters) show bars with morphological properties (long and weak) consistent with models that promote gas inflows, which might trigger nuclear activity. The extremely red bulges of the gamma-NLSy1s, and features that suggest minor mergers in 75% of their hosts might hint to the necessary conditions for gamma-rays to be produced. Among the features that suggest mergers in our sample, we find 6 galaxies that show offset stellar bulges with respect to their AGN. When we plot the nuclear versus the bulge magnitude, RL-NLSy1s locate in the low-luminosity end of flat-spectrum radio quasars (FSRQs), suggesting a similar accretion mode between these two AGN types.

[64]  arXiv:1912.02763 [pdf, other]

Title: LyaCoLoRe: Synthetic Datasets for Current and Future Lyman-$α$ Forest BAO Surveys

Authors: James Farr, Andreu Font-Ribera, Hélion du Mas des Bourboux, Andrea Muñoz-Gutiérrez, Francisco Javier Sanchez Lopez, Andrew Pontzen, Alma Xochitl González-Morales, David Alonso, David Brooks, Peter Doel, Thomas Etourneau, Julien Guy, Jean-Marc Le Goff, Axel de al Macorra, Nathalie Palanque-Delabrouille, Ignasi Pérez-Ràfols, James Rich, Anže Slosar, Gregory Tarle, Duan Yutong, Kai Zhang

Comments: 29 pages, 7 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The statistical power of Lyman-${\alpha}$ forest Baryon Acoustic Oscillation (BAO) measurements is set to increase significantly in the coming years as new instruments such as the Dark Energy Spectroscopic Instrument deliver progressively more constraining data. Generating mock datasets for such measurements will be important for validating analysis pipelines and evaluating the effects of systematics. With such studies in mind, we present LyaCoLoRe: a package for producing synthetic Lyman-${\alpha}$ forest survey datasets for BAO analyses. LyaCoLoRe transforms initial Gaussian random field skewers into skewers of transmitted flux fraction via a number of fast approximations. In this work we explain the methods of producing mock datasets used in LyaCoLoRe, and then measure correlation functions on a suite of realisations of such data. We demonstrate that we are able to recover the correct BAO signal, as well as large-scale bias parameters similar to literature values. Finally, we briefly describe methods to add further astrophysical effects to our skewers - high column density systems and metal absorbers - which act as potential complications for BAO analyses.

[65]  arXiv:1912.02787 [pdf, other]

Title: Wind of Change: retrieving exoplanet atmospheric winds from high-resolution spectroscopy

Authors: J. V. Seidel (1), D. Ehrenreich (1), L. Pino (2), V. Bourrier (1), B. Lavie (1), R. Allart (1), A. Wyttenbach (3), C. Lovis (1) (Observatoire astronomique de l'Université de Genève, CH (1), Anton Pannekoek Institute for Astronomy, University of Amsterdam, NL (2), Leiden Observatory, Leiden University, NL (3))

Comments: 17 pages, 30 figures, accepted for publication in Astronomy & Astrophysics (04.12.2019)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Context. The atmosphere of exoplanets has been studied extensively in recent years, using numerical models to retrieve chemical composition, dynamical circulation or temperature from data. One of the best observational probes in transmission is the sodium doublet, due to its large cross section. However, modelling the shape of the planetary sodium lines has proven to be challenging. Models with different assumptions regarding the atmosphere have been employed to fit the lines in the literature, yet statistically sound direct comparisons of different models are needed to paint a clear picture. Aims. We will compare different wind and temperature patterns and provide a tool to distinguish them driven by their best fit for the sodium transmission spectrum of the hot Jupiter HD 189733b. We parametrise different possible wind patterns already tested in literature and introduce the new option of an upwards driven vertical wind. Methods. We construct a forward model where the wind speed, wind geometry and temperature are injected into the calculation of the transmission spectrum. We embed this forward model in a nested sampling retrieval code to rank the models via their Bayesian evidence. Results. We retrieve a best-fit to the HD 189733b data for vertical upward winds $|\vec{v}_{\mathrm{ver}}(\mathrm{mean})|=40\pm4$ km/s at altitudes above $10^{-6}$ bar. With the current data from HARPS, we cannot distinguish wind patterns for higher pressure atmospheric layers. Conclusions. We show that vertical upwards winds in the upper atmosphere are a possible explanation for the broad sodium signature in hot Jupiters. We highlight other influences on the width of the doublet and explore strong magnetic fields acting on the lower atmosphere as one possible origin of the retrieved wind speed.

[66]  arXiv:1912.02800 [pdf, other]

Title: Traits for chemical evolution in solar twins: Trends of neutron-capture elements with stellar age

Authors: Paula Jofre, Holly Jackson, Marcelo Tucci Maia

Comments: Accepted by A&A Letters

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

The physical processes driving chemical evolution in the Milky Way can be probed using the distribution of abundances in low-mass FGK type stars in space phase at different times. During their final stages of evolution stars experience nucleosynthesis several times, each at different timescales and producing different chemical elements, so finding abundance ratios that have simple variations across cosmic times remains a challenge. Using the sample of 80 solar twins for which ages and abundances of 30 elements were measured with high precision by Bedell et al 2018, we searched for all possible abundance ratios combinations that show linear trends with age. We found 55 such ratios, all combining a neutron-capture element and another one produced by different nucleosynthesis channels. We recovered the ratios of [Y/Mg], [Ba/Mg] and [Al/Y] reported previously in the literature, and found that [C/Ba] had the largest dependency with age with a slope of $0.049 \pm 0.003~\mathrm{dex/Gyr}$, imposing constraints on the magnitude of time dependency of abundance ratios in solar twins. Our results suggest using s-process elements, in lieu of Fe, as a reference for constraining chemical evolution models of the solar neighbourhood. Our study illustrates hows a large variety of chemical elements measured from high resolution spectra is key in facing current challenges in understanding the formation and evolution of our Galaxy.

[67]  arXiv:1912.02806 [pdf, other]

Title: Spectral library of age-benchmark low-mass stars and brown dwarfs

Authors: E. Manjavacas, N. Lodieu, V. J. S. Béjar, M. R. Zapatero-Osorio, S.Boudreault, M. Bonnefoy

Comments: Accepted for publication in MNRAS. The spectra will be available in the publisher version of this paper and in GitHub: &lt;this https URL&gt;

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

In the past years, some extremely red brown dwarfs were found. They were believed to have low surface gravity, but many of their spectral characteristics were similar to those of high surface gravity brown dwarfs, showing that youth (or low surface gravity) spectral characteristics are poorly understood. We aim to test surface gravity indicators in late-M and early-L brown dwarf spectra using data obtained with the X-shooter spectrograph at the Very Large Telescope. We selected a benchmark sample of brown dwarfs members of Chamaeleon\,I ($\sim$2 Myr), Upper Scorpius (5$-$10~Myr), Pleiades (132$\pm$27 Myr), and Praesepe (590$-$790 Myr) with well-constrained ages, and similar metallicities. We provided a consistent spectral classification of the sample in the optical and in the near-infrared. We measured the equivalent widths of their alkali lines, finding that they have a moderate correlation with age, especially for objects with spectral types M8 and later. We used spectral indices defined in the literature to estimate surface gravity, finding that their gravity assignment is accurate for 75\% of our sample. We investigated the correlation between red colours and age, finding that after $\sim$10~Myr, the colour does not change significantly for our sample {with spectral types M6.0-L3.0}. In this case, red colours might be associated with circumstellar disks, {ring structures, extinction, or viewing angle}. Finally, we calculated the {bolometric luminosity}, {and $J$ and $K$ bolometric corrections} for our sample. We found that six objects are overluminous compared to other members of the same association. Those objects are also flagged as binary candidates by the $Gaia$ survey.

[68]  arXiv:1912.02808 [pdf, other]

Title: Coronal Jets, and the Jet-CME Connection

Authors: Alphonse C. Sterling

Journal-ref: Journal of Physics: Conference Series, Volume 1100, Issue 1, article id. 012024 (2018)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Solar coronal jets have been observed in detail since the early 1990s. While it is clear that these jets are magnetically driven, the details of the driving process has recently been updated. Previously it was suspected that the jets were a consequence of magnetic flux emergence interacting with ambient coronal field. New evidence however indicates that often the direct driver of the jets is erupting field, often carrying cool material (a "minifilament"), that undergoes interchange magnetic reconnection with preexisting field ([1]). More recent work indicates that the trigger for eruption of the minifilament is frequently cancelation of photospheric magnetic fields at the base of the minifilament. These erupting minifilaments are analogous to the better-known larger-scale filament eruptions that produce solar flares and, frequently, coronal mass ejections (CMEs). A subset of coronal jets drive narrow "white-light jets," which are very narrow CME-like features, and apparently a few jets can drive wider, although relatively weak, "streamer-puff" CMEs. Here we summarize these recent findings.

[69]  arXiv:1912.02812 [pdf, other]

Title: Cloud Atlas: Weak color modulations due to rotation in the planetary-mass companion GU Psc b and 11 other brown dwarfs

Authors: Ben W.P. Lew, Dániel Apai, Yifan Zhou, Jacqueline Radigan, Mark Marley, Glenn Schneider, Nicolas B. Cowan, Paulo A. Miles-Páez, Elena Manjavacas, Theodora Karalidi, L. R. Bedin, Patrick J. Lowrance, Adam J. Burgasser

Comments: 15 pages, 7 figures, accepted for publication in AJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Among the greatest challenges in understanding ultra-cool brown dwarf and exoplanet atmospheres is the evolution of cloud structure as a function of temperature and gravity. In this study, we present the rotational modulations of GU Psc b -- a rare mid-T spectral type planetary-mass companion at the end of the L/T spectral type transition. Based on the HST/WFC3 1.1-1.67$\rm\, \mu m$ time-series spectra, we observe a quasi-sinusoidal light curve with a peak-to-trough flux variation of 2.7 % and a minimum period of eight hours. The rotation-modulated spectral variations are weakly wavelength-dependent, or largely gray between 1.1-1.67$\rm\,\mu$m. The gray modulations indicate that heterogeneous clouds are present in the photosphere of this low-gravity mid-T dwarf. We place the color and brightness variations of GU Psc b in the context of rotational modulations reported for mid-L to late-T dwarfs. Based on these observations, we report a tentative trend: mid-to-late T dwarfs become slightly redder in $J-H$ color with increasing $J$-band brightness, while L dwarfs become slightly bluer with increasing brightness. If this trend is verified with more T-dwarf samples, it suggests that in addition to the mostly gray modulations, there is a second-order spectral-type dependence on the nature of rotational modulations.

[70]  arXiv:1912.02816 [pdf, other]

Title: Age Demographics of the Milky Way Disk and Bulge

Authors: J. Grady, V. Belokurov, N.W. Evans (IoA, Cambridge)

Comments: MNRAS, submitted

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use the extensive $Gaia$ Data Release 2 set of Long Period Variables to select a sample of Oxygen-rich Miras throughout the Milky Way disk and bulge for study. Exploiting the relation between Mira pulsation period and stellar age/chemistry, we slice the stellar density of the Galactic disk and bulge as a function of period. We find the morphology of both components evolves as a function of stellar age/chemistry with the stellar disk being stubby at old ages, becoming progressively thinner and more radially extended at younger stellar ages, consistent with the picture of inside-out and upside-down formation of the Milky Way's disk. We see evidence of a perturbed disk, with large-scale stellar over-densities visible both in and away from the stellar plane. We find the bulge is well modelled by a triaxial boxy distribution with an axis ratio of $\sim [1:0.4:0.3]$. The oldest of the Miras ($\sim$ 9-10 Gyr) show little bar-like morphology, whilst the younger stars appear inclined at a viewing angle of $\sim 21^{\circ}$ to the Sun-Galactic Centre line. This suggests that bar formation and buckling took place 8-9 Gyr ago, with the older Miras being hot enough to avoid being trapped by the growing bar. We find the youngest Miras to exhibit a strong peanut morphology, bearing the characteristic X-shape of an inclined bar structure.

Cross-lists for Fri, 6 Dec 19

[71]  arXiv:1912.02187 (cross-list from hep-th) [pdf, other]

Title: 4-volume cutoff measure of the multiverse

Authors: Alexander Vilenkin, Masaki Yamada

Comments: 13 pages, 3 figures

Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Predictions in an eternally inflating multiverse are meaningless unless we specify the probability measure. The scale-factor cutoff is perhaps the simplest and most successful measure which avoid catastrophic problems such as the youngness paradox, runaway problem, and Boltzmann brain problem, but it is not well defined in contracting regions with a negative cosmological constant. In this paper, we propose a new measure with properties similar to the scale-factor cutoff which is well defined everywhere. The measure is defined by a cutoff in the 4-volume spanned by infinitesimal comoving neighborhoods in a congruence of timelike geodesics. The probability distributions for the cosmological constant and for the curvature parameter in this measure are similar to those for the scale factor cutoff and are in a good agreement with observations.

[72]  arXiv:1912.02213 (cross-list from physics.geo-ph) [pdf, other]

Title: Constraints on the magnetic field within a stratified outer core

Authors: Colin M Hardy, Philip W Livermore, Jitse Niesen

Comments: 27 pages, 10 figures

Subjects: Geophysics (physics.geo-ph); Earth and Planetary Astrophysics (astro-ph.EP); Fluid Dynamics (physics.flu-dyn)

Mounting evidence from both seismology and experiments on core composition suggests the existence of a layer of stably stratified fluid at the top of Earth's outer core. In this work we examine the structure of the geomagnetic field within such a layer, building on the important but little known work of Malkus (1979). We assume (i) an idealised magnetostrophic spherical model of the geodynamo neglecting inertia, viscosity and the solid inner core, and (ii) a strongly stratified layer of constant depth immediately below the outer boundary within which there is no spherically radial flow. Due to the restricted dynamics, Malkus showed that the geomagnetic field must obey a certain condition which is a more restrictive version of the condition of Taylor (1963). The nonlinear nature of these constraints makes finding a magnetic field that obeys them, here termed a Malkus state, a challenging task. Nevertheless, such Malkus states when constrained further by geomagnetic observations have the potential to probe the interior of the core. By focusing on a particular class of magnetic fields for which the Malkus constraints are linear, we describe a constructive method that turns any purely-poloidal field into an exact Malkus state by adding a suitable toroidal field. We consider poloidal fields following a prescribed smooth profile within the core that match observation-derived models of the magnetic field in either epoch 2015 or the 10000-yr time averaged field. Multiple possible solutions for the toroidal field exist, hence we determine the Malkus state of miumum toroidal energy and we find that it has a strong azimuthal toroidal field, larger than the observed poloidal component at the core-mantle boundary. For the 2015 field for a layer of depth 300 km, we estimate a root mean squared azimuthal toroidal field of 3 mT with a pointwise maximum of 8 mT occurring at a depth of about 70 km.

[73]  arXiv:1912.02271 (cross-list from physics.space-ph) [pdf]

Title: Global-scale Observations and Modeling of Far-Ultraviolet Airglow During Twilight

Authors: Stanley C. Solomon1, Laila Andersson, Alan G. Burns, Richard W. Eastes, Carlos Martinis, William E. McClintock, Arthur D. Richmond

Comments: Manuscript submitted to the Journal of Geophysical - Space Physics on 14 November 2019

Subjects: Space Physics (physics.space-ph); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The NASA Global-scale Observations of the Limb and Disk (GOLD) ultraviolet imaging spectrograph performs observations of upper-atmosphere airglow from the sunlit disk and limb of the Earth, in order to infer quantities such as the composition and temperature of the thermosphere. To interpret the measurements, the observational and solar illumination geometry must be considered. We use forward models of upper atmosphere density and composition, photoelectron impact, airglow emissions, radiative transfer, and line-of-sight integration, to describe the expected observations, and here test those calculations against observations near the terminator, and near the limb. On the night side of the terminator, broad regions of faint airglow are seen, particularly near the winter solstice. These are caused by photoelectrons that were transported along field lines from magnetically conjugate areas in the other hemisphere, where those areas are still illuminated. We perform model calculations to demonstrate that this process is the source of the emission, and obtain good agreement with its morphology and intensity. In some regions, the observed emissions are not as intense as the model simulations. Some of the reductions in electron flux are explained by changes in magnetic field strength; in other cases, particularly at high magnetic latitude, the cause is unknown, but must occur along extended field lines as they reach into the plasma sheet.

[74]  arXiv:1912.02349 (cross-list from physics.space-ph) [pdf, other]

Title: Identification of Magnetic Flux Ropes from Parker Solar Probe Observations during the First Encounter

Authors: L.-L. Zhao, G. P. Zank, L. Adhikari, Q. Hu, J. C. Kasper, S. D. Bale, K. E. Korreck, A. W. Case, M. Stevens, J. W. Bonnell, T. Dudok de Wit, K. Goetz, P. R. Harvey, R. J. MacDowall, D. M. Malaspina, M. Pulupa, D. E. Larson, R. Livi, P. Whittlesey, K. G. Klein

Comments: 22 pages, 5 figures, accepted in ApJS

Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

The Parker Solar Probe (PSP) observed an interplanetary coronal mass ejection (ICME) event during its first orbit around the sun, among many other events. This event is analyzed by applying a wavelet analysis technique to obtain the reduced magnetic helicity, cross helicity, and residual energy, the first two of which are magnetohydrodynamics (MHD) invariants. Our results show that the ICME, as a large scale magnetic flux rope, possesses high magnetic helicity, very low cross helicity, and highly negative residual energy, thus pointing to a magnetic fluctuation dominated structure. Using the same technique, we also search for small-scale coherent magnetic flux rope structures during the period from 2018/10/22--2018/11/21, which are intrinsic to quasi-2D MHD turbulence in the solar wind. Multiple structures with duration between 8 and 300 minutes are identified from PSP in-situ spacecraft measurements. The location and scales of these structures are characterized by wavelet spectrograms of the normalized reduced magnetic helicity, normalized cross helicity and normalized residual energy. Transport theory suggests that these small-scale magnetic flux ropes may contribute to the acceleration of charged particles through magnetic reconnection processes, and the dissipation of these structures may be important for understanding the coronal heating processes.

[75]  arXiv:1912.02569 (cross-list from hep-ph) [pdf, other]

Title: Beyond the Standard Models with Cosmic Strings

Authors: Yann Gouttenoire, Géraldine Servant, Peera Simakachorn

Comments: 68 pages, 25 figures

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We examine which information on the early cosmological history can be extracted from the potential measurement by third-generation gravitational-wave observatories of a stochastic gravitational wave background (SGWB) produced by cosmic strings. We consider a variety of cosmological scenarios breaking the scale-invariant properties of the spectrum, such as early long matter or kination eras, short intermediate matter and inflation periods inside a radiation era, and their specific signatures on the SGWB. This requires to go beyond the usually-assumed scaling regime, to take into account the transient effects during the change of equation of state of the universe. We compute the time evolution of the string network parameters and thus the loop-production efficiency during the transient regime, and derive the corresponding shift in the turning-point frequency. We consider the impact of particle production on the gravitational-wave emission by loops. We estimate the reach of future interferometers LISA, BBO, DECIGO, ET and CE and radio telescope SKA to probe the new physics energy scale at which the universe has experienced changes in its expansion history. We find that a given interferometer may be sensitive to very different energy scales, depending on the nature and duration of the non-standard era, and the value of the string tension. It is fascinating that by exploiting the data from different GW observatories associated with distinct frequency bands, we may be able to reconstruct the full spectrum and therefore extract the values of fundamental physics parameters.

[76]  arXiv:1912.02616 (cross-list from physics.pop-ph) [pdf, other]

Title: Interstellar communication network. I. Overview and assumptions

Authors: Michael Hippke

Comments: AJ in press

Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

It has recently been suggested in this journal by Benford (2019) that "Lurkers" in the form of interstellar exploration probes could be present in the solar system. Similarly, extraterrestrial intelligence could send long-lived probes to many other stellar systems, to report back science and surveillance. If probes and planets with technological species exist in more than a handful of systems in our galaxy, it is beneficial to use a coordinated communication scheme. Due to the inverse square law, data rates decrease strongly for direct connections over long distances. The network bandwidth could be increased by orders of magnitude if repeater stations (nodes) are used in an optimized fashion. This introduction to a series of papers makes the assumptions of the communication scheme explicit. Subsequent papers will discuss technical aspects such as transmitters, repeaters, wavelengths, and power levels. The overall purpose is to gain insight into the physical characteristics of an interstellar communication network, allowing us to describe the most likely sizes and locations of nodes and probes.

[77]  arXiv:1912.02639 (cross-list from physics.space-ph) [pdf]

Title: The Near-Sun Dust Environment: Initial Observations from Parker Solar Probe

Authors: J. R. Szalay, P. Pokorný, S. D. Bale, E. R. Christian, K. Goetz, K. Goodrich, M. E. Hill, M. Kuchner, R. Larsen, D. Malaspina, D. J. McComas, D. Mitchell, B. Page, N. Schwadron

Comments: 34 pages, 10 figures, 3 tables

Subjects: Space Physics (physics.space-ph); Earth and Planetary Astrophysics (astro-ph.EP)

The Parker Solar Probe (PSP) spacecraft has flown into the most dense and previously unexplored region of our solar system's zodiacal cloud. While PSP does not have a dedicated dust detector, multiple instruments onboard are sensitive to the effects of meteoroid bombardment. Here, we discuss measurements taken during PSP's first two orbits and compare them to models of the zodiacal cloud's dust distribution. Comparing the radial impact rate trends and the timing and location of a dust impact to an energetic particle detector, we find the impactor population to be consistent with dust grains on hyperbolic orbits escaping the solar system. Assuming PSP's impact environment is dominated by hyperbolic impactors, the total quantity of dust ejected from our solar system is estimated to be 1-14 tons/s. We expect PSP will encounter an increasingly more intense impactor environment as its perihelion distance and semi-major axis are decreased.

[78]  arXiv:1912.02689 (cross-list from hep-ph) [pdf, other]

Title: Gravity-mediated Dark Matter in Clockwork/Linear Dilaton Extra-Dimensions

Authors: Miguel G. Folgado, Andrea Donini, Nuria Rius

Comments: 26 pages, 6 figures. arXiv admin note: text overlap with arXiv:1907.04340

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

We study for the first time the possibility that Dark Matter (represented by particles with spin $0,1/2$ or $1$) interacts gravitationally with Standard Model particles in an extra-dimensional Clockwork/Linear Dilaton model. We assume that both, the Dark Matter and the Standard Model, are localized in the IR-brane and only interact via gravitational mediators, namely the Kaluza-Klein (KK) graviton and the radion/KK-dilaton modes. We analyse in detail the Dark Matter annihilation channel into Standard Model particles and into two on-shell Kaluza-Klein towers (either two KK-gravitons, or two radion/KK-dilatons, or one of each), finding that it is possible to obtain the observed relic abundance via thermal freeze-out for Dark Matter masses in the range $m_{\rm DM} \in [1, 15]$ TeV for a 5-dimensional gravitational scale $M_5$ ranging from 5 to a few hundreds of TeV, even after taking into account the bounds from LHC Run II and irrespectively of the DM particle spin.

Replacements for Fri, 6 Dec 19

[79]  arXiv:1205.0052 (replaced) [pdf, other]

Title: A Multi-wavelength Study of the Sunyaev-Zel'dovich Effect in the Triple-Merger Cluster MACS J0717.5+3745 with MUSTANG and Bolocam

Authors: Tony Mroczkowski, Simon Dicker, Jack Sayers, Erik D. Reese, Brian Mason, Nicole Czakon, Charles Romero, Alexander Young, Mark Devlin, Sunil Golwala, Phillip Korngut, Craig Sarazin, James Bock, Patrick M. Koch, Kai-Yang Lin, Sandor M. Molnar, Elena Pierpaoli, Keiichi Umetsu, Michael Zemcov

Comments: 10 Figures, 18 pages. this version corrects issues with the previous arXiv version

Journal-ref: 2012 ApJ, 761, 47

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

[80]  arXiv:1808.05265 (replaced) [pdf, ps, other]

Title: Gravitational Radiation From Pulsar Creation

Authors: Leonard S. Kisslinger, Bijit Singha, Zhou Li-juan

Comments: 7 pages,2 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[81]  arXiv:1809.10478 (replaced) [pdf, other]

Title: Electrodynamics of double neutron star mergers

Authors: Maxim Lyutikov (Purdue University)

Comments: This ArXive version corrects a sign error in the published paper in Eq. (15). Equations (15)-(18) and figures 2 and 3 are affected. Overall results and conclusions remain the same

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[82]  arXiv:1811.10084 (replaced) [pdf, other]

Title: The Density Structure of Simulated Stellar Streams

Authors: Raymond G. Carlberg

Comments: ApJ accepted. Fig1 movies available at this https URL and movie10_461.mmp4 (+/-60 and 10 kpc boxes centered on star cluster)

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[83]  arXiv:1812.11341 (replaced) [pdf, ps, other]

Title: Prompt atmospheric neutrinos in the quark-gluon string model

Authors: S. I. Sinegovsky, M. N. Sorokovikov (Joint Institute for Nuclear Research & Irkutsk State University)

Comments: 15 pages, 18 figures; corrected text and figures, added references

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

[84]  arXiv:1901.03430 (replaced) [pdf, other]

Title: Dual MeV Gamma-Ray and Dark Matter Observatory -- GRAMS Project

Authors: Tsuguo Aramaki, Per Hansson Adrian, Georgia Karagiorgi, Hirokazu Odaka

Comments: 10 pages, 10 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)

[85]  arXiv:1902.03054 (replaced) [pdf, other]

Title: Non-sphericity of ultralight axion dark matter haloes in the Galactic dwarf spheroidal galaxies

Authors: Kohei Hayashi, Ippei Obata

Comments: 20 pages, 12 figures, accepted for publication in MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)

[86]  arXiv:1903.02003 (replaced) [pdf, other]

Title: The Milky Way bar/bulge in proper motions: a 3D view from VIRAC & Gaia

Authors: Jonathan P. Clarke, Christopher Wegg, Ortwin Gerhard, Leigh C. Smith, Phil W. Lucas, Shola M. Wylie

Comments: 22 pages, 21 figures, Accepted for publication in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[87]  arXiv:1903.04957 (replaced) [pdf, other]

Title: Sheer shear: weak lensing with one mode

Authors: Emilio Bellini, David Alonso, Shahab Joudaki, Ludovic van Waerbeke

Comments: 15 pages, 16 figures. Accepted version on OJA

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[88]  arXiv:1903.06654 (replaced) [pdf, other]

Title: Probing hot gas around luminous red galaxies through the Sunyaev-Zel'dovich effect

Authors: Hideki Tanimura, Gary Hinshaw, Ian G. McCarthy, Ludovic Van Waerbeke, Nabila Aghanim, Yin-Zhe Ma, Alexander Mead, Tilman Tröster, Alireza Hojjati, Bruno Moraes

Comments: 12 pages, 6 figures, accepted by MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[89]  arXiv:1906.03272 (replaced) [pdf, other]

Title: Efficient Production of Sound Waves by AGN Jets in the Intracluster Medium

Authors: Christopher J. Bambic, Christopher S. Reynolds

Comments: 17 pages, 14 figures, accepted for publication in ApJ

Journal-ref: The Astrophysical Journal, Volume 886, Issue 2, article id. 78, 16 pp. (2019)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

[90]  arXiv:1906.11170 (replaced) [pdf, other]

Title: The 320 EeV Fly's Eye event: a key messenger or a statistical oddity ?

Authors: Thomas Fitoussi, Gustavo Medina-Tanco, Juan-Carlos D'Olivo

Comments: 18 pages, 7 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[91]  arXiv:1907.13135 (replaced) [pdf, other]

Title: Analyzing Atmospheric Temperature Profiles and Spectra of M dwarf Rocky Planets

Authors: Matej Malik, Eliza M.-R. Kempton, Daniel D. B. Koll, Megan Mansfield, Jacob L. Bean, Edwin Kite

Comments: published in ApJ. Also see these three companion papers: 1. Mansfield et al. 2019 (ApJ, 886, 2), "Identifying Atmospheres on Rocky Exoplanets Through Inferred High Albedo", 2. Koll et al. 2019 (ApJ, 886, 2), "Identifying candidate atmospheres on rocky M dwarf planets via eclipse photometry", 3. Koll (submitted) "A Scaling Theory for Atmospheric Heat Redistribution on Rocky Exoplanets"

Journal-ref: ApJ, 2019, 886, 2

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[92]  arXiv:1908.06558 (replaced) [pdf, ps, other]

Title: Non-strange quark stars from NJL model with proper-time regularisation

Authors: Qingwu Wang, Chao Shi, Hong-Shi Zong

Journal-ref: Physical Review D 100, 123003 (2019)

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

[93]  arXiv:1908.11448 (replaced) [pdf, other]

Title: Testing the Accuracy of Halo Occupation Distribution Modelling using Hydrodynamic Simulations

Authors: Gillian D. Beltz-Mohrmann, Andreas A. Berlind, Adam O. Szewciw

Comments: 20 pages, 9 figures, accepted by MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

[94]  arXiv:1909.02014 (replaced) [pdf, other]

Title: Electroweak phase transition with composite Higgs models: calculability, gravitational waves and collider searches

Authors: Ligong Bian, Yongcheng Wu, Ke-Pan Xie

Comments: 36 pages, 5 figures. The version to be appear on JHEP

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[95]  arXiv:1910.04156 (replaced) [pdf, other]

Title: Large-Volume Centimeter-Wave Cavities for Axion Searches

Authors: Chao-Lin Kuo

Comments: Expanded, now at 7 pages & 7 figures

Subjects: Instrumentation and Detectors (physics.ins-det); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)

[96]  arXiv:1910.08799 (replaced) [pdf, other]

Title: Variable Stars: A Net of Complementary Methods for Time Series Analysis. Application to RY UMa

Authors: Ivan L. Andronov, Lidia L. Chinarova

Comments: Astronomical and Astrophysical Transactions (AApTr), 2020, v.33, No. 4 (in press)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

[97]  arXiv:1910.14250 (replaced) [pdf, other]

Title: Quantifying the Influence of Jupiter on the Earth's Orbital Cycles

Authors: Jonathan Horner, Pam Vervoort, Stephen R. Kane, Alma Y. Ceja, David Waltham, James Gilmore, Sandra Kirtland Turner

Comments: 19 pages; 11 figures; accepted for publication in the Astronomical Journal Version 2 - incorporates typo corrections and minor changes noted at the proofing stage, after acceptance

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[98]  arXiv:1911.00903 (replaced) [pdf, other]

Title: COSMIC Variance in Binary Population Synthesis

Authors: Katelyn Breivik, Scott C. Coughlin, Michael Zevin, Carl L. Rodriguez, Kyle Kremer, Claire S. Ye, Jeff J. Andrews, Michael Kurkowski, Matthew C. Digman, Shane L. Larson, Frederic A. Rasio

Comments: reflects the version submitted to ApJ; 17 pages, 2 Tables, 4 Figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

[99]  arXiv:1911.01233 (replaced) [pdf, ps, other]

Title: Asymptotic behavior of a matter filled universe with exotic topology

Authors: Puskar Mondal

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Mathematical Physics (math-ph)

[100]  arXiv:1911.02955 (replaced) [pdf, ps, other]

Title: Dark energy as a large scale quantum gravitational phenomenon

Authors: Tejinder P. Singh

Comments: v2: 11 pages, material added at the end (Eqn. 8 onwards): (i) a quantum-classical duality (ii) role of Planck length in explaining the quantum-classical transition

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)

[101]  arXiv:1911.03305 (replaced) [pdf, other]

Title: The DNNLikelihood: enhancing likelihood distribution with Deep Learning

Authors: Andrea Coccaro, Maurizio Pierini, Luca Silvestrini, Riccardo Torre

Comments: 44 pages, 17 figures, 8 tables; v2: 46 pages, appendix on coverage changed, figures and bibliography improved, references added

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex); Data Analysis, Statistics and Probability (physics.data-an)

[102]  arXiv:1911.03915 (replaced) [pdf, ps, other]

Title: Generation of massive stellar black holes by rapid gas accretion in primordial dense clusters

Authors: Zacharias Roupas, Demosthenes Kazanas

Journal-ref: A&A, 632 L8, 2019

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[103]  arXiv:1911.11450 (replaced) [pdf, other]

Title: Expanding Core-Collapse Supernova Search Horizon of Neutrino Detectors

Authors: Odysse Halim, Carlo Vigorito, Claudio Casentini, Giulia Pagliaroli, Marco Drago, Viviana Fafone

Comments: 4 pages, 2 figures. this contribution was accepted by IOP Conference Series for the conference: TAUP2019, Toyama, Japan. this http URL

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex); Data Analysis, Statistics and Probability (physics.data-an)

[104]  arXiv:1912.01660 (replaced) [pdf, other]

Title: The [α/Fe]-[Fe/H] relation in the E-MOSAICS simulations: its connection to the birth place of globular clusters and the fraction of globular cluster field stars in the bulge

Authors: Meghan E. Hughes, Joel L. Pfeffer, Marie Martig, Marta Reina-Campos, Nate Bastian, Robert A. Crain, J. M. Diederik Kruijssen

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[105]  arXiv:1912.01895 (replaced) [pdf, other]

Title: Where Did They Come From, Where Did They Go. Grazing Fireballs

Authors: P.M. Shober, T. Jansen-Sturgeon, E.K. Sansom, H.A.R. Devillepoix, M.C. Towner, P.A. Bland, M. Cupák, R.M. Howie, B.A.D. Hartig

Comments: Submitted to AJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

• New submissions
• Cross-lists
• Replacements