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New submissions for Thu, 12 Mar 20

[1]  arXiv:2003.04897 [pdf, other]

Title: Distribution of Water Vapor in Molecular Clouds. II

Authors: Gary J. Melnick (CfA), Volker Tolls (CfA), Ronald L. Snell (UMass), Michael J. Kaufman (SJSU), Edwin A. Bergin (UMich), Javier R. Goicoechea (CSIC), Paul F. Goldsmith (JPL), Eduardo González-Alfonso (Universidad de Alcalá), David J. Hollenbach (SETI), Dariusz C. Lis (CalTech), David A. Neufeld (JHU)

Comments: 59 pages, including 23 figures, Accepted for publication in ApJ

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

The depth-dependent abundance of both gas-phase and solid-state water within dense, quiescent, molecular clouds is important to both the cloud chemistry and gas cooling. Where water is in the gas phase, it's free to participate in the network of ion-neutral reactions that lead to a host of oxygen-bearing molecules, and its many ortho and para energy levels make it an effective coolant for gas temperatures greater than 20K. Where water is abundant as ice on grain surfaces, and unavailable to cool the gas, significant amounts of oxygen are removed from the gas phase, suppressing the gas-phase chemical reactions that lead to a number of oxygen-bearing species, including O2. Models of FUV-illuminated clouds predict that the gas-phase water abundance peaks in the range Av ~3 and 8mag of the cloud surface, depending on the gas density and FUV field strength. Deeper within such clouds, water is predicted to exist mainly as ice on grain surfaces. More broadly, these models are used to analyze a variety of other regions, including outflow cavities associated with young stellar objects and the surface layers of protoplanetary disks. In this paper, we report the results of observational tests of FUV-illuminated cloud models toward the Orion Molecular Ridge and Cepheus B using data obtained from the Herschel Space Observatory and the Five College Radio Astronomy Observatory. Toward Orion, 2220 spatial positions were observed along the face-on Orion Ridge in the H2O 110-101 557GHz and NH3 J,K=1,0-0,0 572GHz lines. Toward Cepheus B, two strip scans were made in the same lines across the edge-on ionization front. These new observations demonstrate that gas-phase water exists primarily within a few magnitudes of dense cloud surfaces, strengthening the conclusions of an earlier study based on a much smaller data set, and indirectly supports the prediction that water ice is quite abundant in dense clouds.

[2]  arXiv:2003.04904 [pdf, other]

Title: Cometary Activity Discovered on a Distant Centaur: A Non-Aqueous Sublimation Mechanism

Authors: Colin Orion Chandler, Jay K. Kueny, Chadwick A. Trujillo, David E. Trilling, William J. Oldroyd

Comments: 19 pages, 4 figures, submitted to Astrophysical Journal Letters

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

Centaurs are minor planets thought to have originated in the outer Solar System region known as the Kuiper Belt. Active Centaurs enigmatically display comet-like features (e.g., tails, comae) even though they orbit in the gas giant region where it is too cold for water to readily sublimate. Only 18 active Centaurs have been identified since 1927 and, consequently, the underlying activity mechanism(s) have remained largely unknown up to this point. Here we report the discovery of activity emanating from Centaur 2014 OG392, based on archival images we uncovered plus our own new observational evidence acquired with the Dark Energy Camera (Cerro Tololo Inter-American Observatory Blanco 4 m telescope), the Inamori-Magellan Areal Camera & Spectrograph (Las Campanas Observatory 6.5 m Walter Baade Telescope) and the Large Monolithic Imager (Lowell Observatory 4.3 m Discovery Channel Telescope). We detect a coma as far as 400,000 km from 2014 OG392, and our novel analysis of sublimation processes and dynamical lifetime suggest carbon dioxide and/or ammonia are the most likely candidates for causing activity on this and other active Centaurs. We find 2014 OG392 is optically red, but CO2 and NH3 are spectrally neutral in this wavelength regime so the reddening agent is as yet unidentified.

[3]  arXiv:2003.04905 [pdf, other]

Title: Constraining the reionization history using deep learning from 21cm tomography with the Square Kilometre Array

Authors: Tumelo Mangena (UWC/SARAO), Sultan Hassan (NMSU/UWC), Mario G. Santos (UWC/SARAO)

Comments: Accepted for publication in MNRAS

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

Upcoming 21cm surveys with the SKA1-LOW telescope will enable imaging of the neutral hydrogen distribution on cosmological scales in the early Universe. These surveys are expected to generate huge imaging datasets that will encode more information than the power spectrum. This provides an alternative unique way to constrain the reionization history, which might break the degeneracy in the power spectral analysis. Using Convolutional Neural Networks (CNN), we create a fast estimator of the neutral fraction from the 21cm maps that are produced by our large semi-numerical simulation. Our estimator is able to efficiently recover the neutral fraction ($x_{\rm HI}$) at several redshifts with a high accuracy of 99\% as quantified by the coefficient of determination $R^{2}$. Adding the instrumental effects from the SKA design slightly increases the loss function, but nevertheless we are still able to recover the neutral fraction with a similar high accuracy of 98\%, which is only 1 per cent less. Our results show the promise of directly using 21cm-tomography to constrain the reionization history in a model independent way, complementing similar efforts, such as those of the optical depth measurements from the Cosmic Microwave Background (CMB) observations by ${\it Planck}$.

[4]  arXiv:2003.04925 [pdf, other]

Title: Perfectly parallel cosmological simulations using spatial comoving Lagrangian acceleration

Authors: Florent Leclercq, Baptiste Faure, Guilhem Lavaux, Benjamin D. Wandelt, Andrew H. Jaffe, Alan F. Heavens, Will J. Percival

Comments: 23 pages, 8 figures, 2 tables

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

Existing cosmological simulation methods lack a high degree of parallelism due to the long-range nature of the gravitational force, which limits the size of simulations that can be run at high resolution. To solve this problem, we propose a new, perfectly parallel approach to simulate cosmic structure formation, based on the spatial COmoving Lagrangian Acceleration (sCOLA) framework. Building upon a hybrid analytical and numerical description of particles' trajectories, our algorithm allows an efficient tiling of a cosmological volume, where the dynamics within each tile is computed independently. As a consequence, the degree of parallelism is equal to the number of tiles. We optimise the accuracy of sCOLA by the use of a buffer region around tiles, and of appropriate Dirichlet boundary conditions around sCOLA boxes. As a result, we show that cosmological simulations at the degree of accuracy required for the analysis of the next generation of surveys can be run in drastically reduced wall-clock times and with very low memory requirements. The perfect scalability of our algorithm unlocks profoundly new possibilities of computing larger and higher-resolution cosmological simulations, taking advantage of a variety of hardware architectures.

[5]  arXiv:2003.04931 [pdf, other]

Title: Resonance in the K2-19 system is at odds with its high reported eccentricities

Authors: Antoine C. Petit, Erik A. Petigura, Melvyn B. Davies, Anders Johansen

Comments: Submitted to MNRAS

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

K2-19 hosts a planetary system composed of two outer planets, b and c, with size of $7.0\pm 0.2~R_\oplus$ and $4.1\pm0.2~R_\oplus$ , and an inner planet, d, with a radius of $1.11\pm 0.05 R_\oplus$. A recent analysis of Transit-Timing Variations (TTVs) suggested b and c are close to but not in 3:2 mean motion resonance (MMR) because the classical resonant angles circulate. Such an architecture challenges our understanding of planet formation. Indeed, planet migration through the protoplanetary disk should lead to a capture into the MMR. Here, we show that the planets are in fact, locked into the 3:2 resonance despite circulation of the conventional resonant angles and aligned periapses. However, we show that such an orbital configuration cannot be maintained for more than a few hundred million years due to the tidal dissipation experienced by planet d. The tidal dissipation remains efficient because of a secular forcing of the innermost planet eccentricity by planets b and c. While the observations strongly rule out an orbital solution where the three planets are on close to circular orbits, it remains possible that a fourth planet is affecting the TTVs such that the four planet system is consistent with the tidal constraints.

[6]  arXiv:2003.04935 [pdf, other]

Title: Cosmic Discordance: Planck and luminosity distance data exclude LCDM

Authors: Eleonora Di Valentino, Alessandro Melchiorri, Joseph Silk

Comments: 5 pages, 2 figures

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

We show that a combined analysis of CMB anisotropy power spectra obtained by the Planck satellite and luminosity distance data simultaneously excludes a flat universe and a cosmological constant at $99 \%$ C.L. These results hold separately when combining Planck with three different datasets: the two determinations of the Hubble constant from Riess et al. 2019 and Freedman et al. 2020, and the Pantheon catalog of high redshift supernovae type-Ia. We conclude that either LCDM needs to be replaced by a drastically different model, or else there are significant but still undetected systematics. Our result calls for new observations and stimulates the investigation of alternative theoretical models and solutions.

[7]  arXiv:2003.04940 [pdf, other]

Title: The Chemical Nature of the Young 120-Myr-old Nearby Pisces-Eridanus Stellar Stream Flowing through the Galactic Disk

Authors: Keith Hawkins, Madeline Lucey, Jason Curtis

Comments: 13 Pages, 9 Figures, 3 Tables. Submitted to MNRAS, Comments Welcome

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

Recently, a new cylindrical-shaped stream of stars, up to 700 pc long, was discovered hiding in the Galactic disk using kinematic data enabled by the Gaia mission. This curious stream of stars, dubbed the Pisces-Eridanus stream, was initially thought to be as old as 1 Gyr, yet its stars shared a rotation period distribution consistent with the 120-Myr-old Pleiades cluster. In this work, we explore the detailed chemical nature of this stellar stream. We carried out high-resolution spectroscopic follow-up of 42 Pisces-Eridanus stream stars using McDonald Observatory, and combined these data with information for 40 members observed with the low-resolution LAMOST spectroscopic survey. Together, these data enabled us to measure the abundance distribution of light/odd-Z (Li, C, Na, Al, Sc, V), $\alpha$ (Mg, Si, Ca, Ti), Fe-peak (Cr, Mn, Fe, Co, Ni, Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, Eu) elements across the Pisces-Eridanus stream. We find that the stream is (1) near solar metallicity with [Fe/H] = -0.03 dex and (2) has a metallicity spread of 0.07 dex. We also find that (3) the abundance of Li indicates that Pisces-Eridanus is $\sim$120 Myr old, consistent with the gyrochronology result. We find that (4) the stream has a [X/Fe] abundance spreads of 0.06 $< \sigma$[X/Fe] $< $ 0.20 dex in most elements, and (5) no significant abundance gradients across its major axis except a potentially weak gradient in [Si/Fe]. These results together show that the Pisces-Eridanus stream is a uniquely close, young, chemically interesting laboratory for testing our understanding of star and planet formation.

[8]  arXiv:2003.04944 [pdf, other]

Title: Potential Vorticity Mixing in a Tangled Magnetic Field

Authors: Chang-Chun Chen, Patrick H. Diamond

Comments: 17 pages, 10 figures, 2 tables

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

A theory of potential vorticity (PV) mixing in a disordered (tangled) magnetic field is presented. The analysis is in the context of $\beta$-plane MHD, with a special focus on the physics of momentum transport in the stably stratified, quasi-2D solar tachocline. A physical picture of mean PV evolution by vorticity advection and tilting of magnetic fields is proposed. In the case of weak-field perturbations, quasi-linear theory predicts that the Reynolds and magnetic stresses balance as turbulence Alfv\'enizes for a larger mean magnetic field. Jet formation is explored quantitatively in the mean field-resistivity parameter space. However, since even a modest mean magnetic field leads to large magnetic perturbations for large magnetic Reynolds number, the physically relevant case is that of a strong but disordered field. We show that numerical calculations indicate that the Reynolds stress is modified well before Alfv\'enization -- i.e. before fluid and magnetic energies balance. To understand these trends, a double-average model of PV mixing in a stochastic magnetic field is developed. Calculations indicate that mean-square fields strongly modify Reynolds stress phase coherence and also induce a magnetic drag on zonal flows. The physics of transport reduction by tangled fields is elucidated and linked to the related quench of turbulent resistivity. We propose a physical picture of the system as a resisto-elastic medium threaded by a tangled magnetic network. Applications of the theory to momentum transport in the tachocline and other systems are discussed in detail.

[9]  arXiv:2003.04951 [pdf, other]

Title: Relationship between rotation curves and matter distribution in spiral galaxy discs

Authors: Gonzalo Fernandez-Torija Daza, Martin Lopez-Corredoira

Comments: 44 pages, 13 figures, Master thesis, Department of Astrophysics, University of La Laguna (Tenerife, Spain), July 2016

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

Feng & Gallo (2011) developed a numerical method of deriving rotation curves from the density distribution and, in particular, the inverse problem while considering just a self-gravitating disc and the thin disc approximation. Our first aim here is to reproduce the same analysis and expand it with various ideas and examples. The main obstacles to building this numerical implementation are certain singularities. We try to fix the instabilities using different methods. Moreover, we add a final chapter extending the problem and its method to a third dimension through the perpendicular to the galactic plane.
The dark halo (whose density is usually represented by a nearby spherical distribution) is supposed to support the outer parts of the rotation curves of spiral galaxies. Here, however, we work only with a self-gravitation disc. To treat this topic we first calculate the disc density distribution from measured rotation curve data of the Milky Way. We then compare this distribution with the observed exponential stellar density, and the difference is attributed to a dark disc. This representation of Feng & Gallo of the Galaxy with a dark disc instead of a dark halo is controversial.
When we analyse the effect of flares on rotation curves, the thin disc approximation fails, and we need to introduce a vertical dimension to measure and predict the effects of the flare through different heights. Just by spreading the mass perpendicularly to the plane -- without adding any further mass -- the flare provokes no severe changes on the rotation curve. The flare mainly provokes a faster velocity decrease in the outer part of the Galaxy ($r\gtrsim 14$ kpc). But we also have obtained a slight velocity increase in the first kiloparsecs after the starting point of the flare.

[10]  arXiv:2003.04955 [pdf]

Title: Volatile evolution and atmospheres of Trans-Neptunian Objects

Authors: Leslie A. Young, Felipe Braga-Ribas, Robert E. Johnson

Journal-ref: The Trans-Neptunian Solar System, Edited by Dina Prialnik, Maria Antoinetta Barucci, Leslie Young. ISBN: 9780128164907. Elsevier, 2020., p.127-151

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)

At 30-50 K, the temperatures typical for surfaces in the Kuiper Belt (e.g. Stern & Trafton 2008), only seven species have sublimation pressures higher than 1 nbar (Fray & Schmitt 2009): Ne, N$_2$, CO, Ar, O$_2$, CH$_4$, and Kr. Of these, N$_2$, CO, and CH$_4$ have been detected or inferred on the surfaces of Trans-Neptunian Objects (TNOs). The presence of tenuous atmospheres above these volatile ices depends on the sublimation pressures, which are very sensitive to the composition, temperatures, and mixing states of the volatile ices. Therefore, the retention of volatiles on a TNO is related to its formation environment and thermal history. The surface volatiles may be transported via seasonally varying atmospheres and their condensation might be responsible for the high surface albedos of some of these bodies. The most sensitive searches for tenuous atmospheres are made by the method of stellar occultation, which have been vital for the study of the atmospheres of Triton and Pluto, and has to-date placed upper limits on the atmospheres of 11 other bodies. The recent release of the Gaia astrometric catalog has led to a "golden age" in the ability to predict TNO occultations in order to increase the observational data base.

[11]  arXiv:2003.04962 [pdf, other]

Title: Science with the X-ray Imaging and Spectroscopy Mission (XRISM)

Authors: XRISM Science Team

Comments: White paper, 30 pages, not including references

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

This white paper was prepared by members of the XRISM Science Team for the benefit of the general astronomical community. This paper describes the capabilities of XRISM, offers a sampling of the many science topics that the mission will address, and discusses the synergies of XRISM with the plethora of planned and existing facilities in the 2020s and beyond.

[12]  arXiv:2003.05007 [pdf, other]

Title: Subsecond Spikes in Fermi GBM X-ray Flux as a Probe for Solar Flare Particle Acceleration

Authors: Trevor Knuth, Lindsay Glesener

Comments: 22 pages, 11 figures, 2 tables; Submitted to ApJ

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

Solar flares are known to release a large amount of energy into accelerating electrons. Studying small timescale ($\leq$ 2s) fluctuations in nonthermal X-ray flux offers the opportunity to probe the nature of those acceleration mechanisms. By comparing the durations, differences in timing between energy bands, and the periodicity of these spikes against the relevant timescales called for by various acceleration mechanisms, a test for each mechanism's validity can be made. This work details the analysis of fast fluctuations in Fermi Gamma-ray Burst Monitor (Fermi GBM) data from 2 M9.3 class solar flares that occurred on SOL2011-07-30 and SOL2011-08-04. This study shows the usefulness of Fermi GBM data as a means of examining these small timescale spikes and presents a rigorous method of identifying, counting, and measuring the temporal properties of these subsecond X-ray spikes. In the 2 flares examined we found spikes to primarily occur in spans of 60-100 seconds in the impulsive phase. The relative spike intensity ranged from 5% to 46% of the total counts, depending on the energy band the spike was measured in. The average spike durations were 0.96 and 0.66 seconds and the median durations were 0.79 and 0.32 seconds for the 2 flares. The spike duration distribution for the SOL2011-08-04 flare was found to follow a power law with a -1.8 $\pm$ 0.5 index. Of the 3 spiking intervals identified, only 1 was found to have a periodicity, showing significant power at the 1.7 $\pm$ 0.1 Hz frequency.

[13]  arXiv:2003.05010 [pdf, other]

Title: Collision between Molecular Clouds I. The effect of the cloud virial ratio in head-on collisions

Authors: Tabassum S Tanvir, James E Dale

Comments: 13 pages, 15 figures; Accepted by MNRAS

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

In a series of papers we investigate the effect of collisions between turbulent molecular clouds on their structure, evolution and star formation activity. In this paper we look into the role of the clouds' initial virial ratios. Three different scenarios were examined: both clouds initially bound, one cloud bound and one unbound, and both clouds initially unbound. Models in which one or both clouds are bound generate filamentary structures aligned along the collision axis and discernible in position-position and position--velocity space. If neither cloud is bound, no filaments result. Unlike in previous simulations of collisions between smooth clouds, owing to the substructure created in the clouds by turbulence before the collisions, dissipation of kinetic energy by the collision is very efficient and in none of our simulations is sufficient bulk kinetic energy lost to render the clouds bound. Simulations where both clouds are bound created twice as much stellar mass than the bound-unbound model, and both these scenarios produced much more stellar mass than the simulation in which both clouds are unbound. Each simulation was also compared with a control run in which the clouds do not collide. We find the bound-bound collision increases the overall star formation efficiency by a factor of approximately two relative to the control, but that the bound-unbound collision produces a much smaller increase, and the collision has very little effect on the unbound--unbound cloud collision.

[14]  arXiv:2003.05040 [pdf, other]

Title: Dynamical instabilities in systems of multiple short-period planets are likely driven by secular chaos: a case study of Kepler-102

Authors: Kathryn Volk, Renu Malhotra

Comments: submitted to AAS journals

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

We investigated the dynamical stability of high-multiplicity Kepler and K2 planetary systems. Our numerical simulations find instabilities in $\sim20\%$ of the cases on a wide range of timescales (up to $5\times10^9$ orbits) and over an unexpectedly wide range of initial dynamical spacings. To identify the triggers of long-term instability in multi-planet systems, we investigated in detail the five-planet Kepler-102 system. Despite having several near-resonant period ratios, we find that mean motion resonances are unlikely to directly cause instability for plausible planet masses in this system. Instead, we find strong evidence that slow inward transfer of angular momentum deficit (AMD) via secular chaos excites the eccentricity of the innermost planet, Kepler-102 b, eventually leading to planet-planet collisions in $\sim80\%$ of Kepler-102 simulations. Kepler-102 b likely has a mass $>\sim0.1M_{\oplus}$, hence a bulk density exceeding about half Earth's, in order to avoid dynamical instability. To investigate the role of secular chaos in our wider set of simulations, we characterize each planetary system's AMD evolution with a "spectral fraction" calculated from the power spectrum of short integrations ($\sim5\times10^6$ orbits). We find that small spectral fractions ($\lesssim0.01$) are strongly associated with dynamical stability on long timescales ($5\times10^9$ orbits) and that the median time to instability decreases with increasing spectral fraction. Our results support the hypothesis that secular chaos is the driver of instabilities in many non-resonant multi-planet systems, and also demonstrate that the spectral analysis method is an efficient numerical tool to diagnose long term (in)stability of multi-planet systems from short simulations.

[15]  arXiv:2003.05052 [pdf, other]

Title: Formation of single-moon systems around gas giants

Authors: Yuri I. Fujii, Masahiro Ogihara

Comments: Published in A&A letter

Journal-ref: A&A 635, L4 (2020)

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

Several mechanisms have been proposed to explain the formation process of satellite systems, and relatively large moons are thought to be born in circumplanetary disks. Making a single-moon system is known to be more difficult than multiple-moon or moonless systems. We aim to find a way to form a system with a single large moon, such as Titan around Saturn. We examine the orbital migration of moons, which change their direction and speed depending on the properties of circumplanetary disks. We modeled dissipating circumplanetary disks with taking the effect of temperature structures into account and calculated the orbital evolution of Titan-mass satellites in the final evolution stage of various circumplanetary disks. We also performed N-body simulations of systems that initially had multiple satellites to see whether single-moon systems remained at the end. The radial slope of the disk-temperature structure characterized by the dust opacity produces a patch of orbits in which the Titan-mass moons cease inward migration and even migrate outward in a certain range of the disk viscosity. The patch assists moons initially located in the outer orbits to remain in the disk, while those in the inner orbits fall onto the planet. We demonstrate for the first time that systems can form that have only one large moon around giant planet. Our N-body simulations suggest satellite formation was not efficient in the outer radii of circumplanetary disks.

[16]  arXiv:2003.05069 [pdf, other]

Title: Timing of the accreting millisecond pulsar IGR J17591-2342: evidence of spin-down during accretion

Authors: A. Sanna, L. Burderi, K. C. Gendreau, T. Di Salvo, P. S. Ray, A. Riggio, A. F. Gambino, R. Iaria, L. Piga, C. Malacaria, G. K. Jaisawal

Comments: Submitted to MNRAS. 10 pages, 6 figures, 2 tables

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

We report on the phase-coherent timing analysis of the accreting millisecond X-ray pulsar IGR J17591-2342, using Neutron Star Interior Composition Explorer (NICER) data taken during the outburst of the source between 2018 August 15 and 2018 October 17. We obtain an updated orbital solution of the binary system. We investigate the evolution of the neutron star spin frequency during the outburst, reporting a refined estimate of the spin frequency and the first estimate of the spin frequency derivative ($\dot{\nu} \sim -7\times 10^{-14}$ Hz s$^{-1}$), confirmed independently from the modelling of the fundamental frequency and its first harmonic. We further investigate the evolution of the X-ray pulse phases adopting a physical model that accounts for the accretion material torque as well as the magnetic threading of the accretion disc in regions where the Keplerian velocity is slower than the magnetosphere velocity. From this analysis we estimate the neutron star magnetic field $B_{eq} = 2.8(3)\times10^{8}$ G. Finally, we investigate the pulse profile dependence on energy finding that the observed behaviour of the pulse fractional amplitude and lags as a function of energy are compatible with a thermal Comptonisation of the soft photons emitted from the neutron star caps.

[17]  arXiv:2003.05110 [pdf, other]

Title: H--He collision-induced satellite in the Lyman-$α$ profile of DBA white dwarf stars

Authors: Nicole F. Allard, John F. Kielkopf, Siyi Xu, Grégoire Guillon, Bilel Mehnen, Roberto Linguerri, Muneerah Mogren Al Mogren, Majdi Hochlaf, Ivan Hubeny

Comments: 9 pages, 7 figures

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

The spectra of helium-dominated white dwarf stars with hydrogen in their atmosphere present a distinctive broad feature centered around 1160~\AA\/ in the blue wing of the Lyman-$\alpha$ line. It is extremely apparent in WD 1425+540 recently observed with HST COS. With new theoretical line profiles based on ab initio atomic interaction potentials we show that this feature is a signature of a collision-induced satellite due to an asymptotically forbidden transition. This quasi-molecular spectral satellite is crucial to understanding the asymmetrical shape of Lyman-$\alpha$ seen in this and other white dwarf spectra. Our previous work predicting this absorption feature was limited by molecular potentials that were not adequate to follow the atomic interactions with spectroscopic precision to the asymptotic limit of large separation. A new set of potential energy curves and electronic dipole transition moments for the lowest electronic states of the H--He system were developed to account accurately for the behavior of the atomic interactions at all distances, from the chemical regime within 1~\AA\/ out to where the radiating H atoms are not significantly perturbed by their neighbors. We use a general unified theory of collision-broadened atomic spectral lines to describe a rigorous treatment of hydrogen Lyman-$\alpha$ with these potentials and present a new study of its broadening by radiative collisions of hydrogen and neutral helium. These results enable ab initio modeling of radiative transport in DBA white dwarf atmospheres.

[18]  arXiv:2003.05116 [pdf, other]

Title: Noise Temperature of Phased Array Radio Telescope: The Murchison Widefield Array and the Engineering Development Array

Authors: Daniel C. X. Ung, Marcin Sokolowski, Adrian T. Sutinjo, David B. Davidson

Comments: IEEE Trans. Antennas. Propagat., accepted, 6 Mar. 2020. 10 pages, 13 figures

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

This paper presents a framework to compute the receiver noise temperature (Trcv) of two low-frequency radio telescopes, the Murchison Widefield Array (MWA) and the Engineering Development Array (EDA). The MWA was selected because it is the only operational low-frequency Square Kilometre Array (SKA) precursor at the Murchison Radio-astronomy Observatory, while the EDA was selected because it mimics the proposed SKA-Low station size and configuration. It will demonstrated that the use of an existing power wave based framework for noise characterization of multiport amplifiers is sufficiently general to evaluate Trcv of phased arrays. The calculation of Trcv was done using a combination of measured noise parameters of the low-noise amplifier (LNA) and simulated S-parameters of the arrays. The calculated values were compared to measured results obtained via astronomical observation and both results are found to be in agreement. Such verification is lacking in current literature. It was shown that the receiver noise temperatures of both arrays are lower when compared to a single isolated element. This is caused by the increase in mutual coupling within the array which is discussed in depth in this paper.

[19]  arXiv:2003.05121 [pdf, other]

Title: The reliability of the Titius-Bode relation and its implications for the search for exoplanets

Authors: Patricia Lara, Guadalupe Cordero-Tercero, Christine Allen

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

The major semiaxes of the planets in our Solar System obey a simple geometric progression known as the Titius-Bode Relation (TBR), whose physical origin remains disputed. It has been shown that the exoplanetary systems follow a similar (but not identical) progression of the form a_n= a_0 e^(bn), where a_0, b are constants to be determined for each system. Since its formulation, the Titius-Bode Relation has proved to be highly predictive in our Solar System. Using data from 27 exoplanetary systems with 5 or more planets and applying a proposed method, we conclude that reliable TB-like fits can be obtained for systems with at least 4 planets and that the precision of the TBR is 78%. By means of a statistical test we show that the periods of planets in real exoplanetary systems are not consistent with a random distribution. Rather, they show signs that their configuration is shaped by their mutual interactions.

[20]  arXiv:2003.05134 [pdf]

Title: Wind- and Operation-Induced Vibration Measurements of the Main Reflector of the Nobeyama 45 m Radio Telescope

Authors: Ikumi Hashimoto, Masakatsu Chiba, Nozomi Okada, Hideo Ogawa, Ryohei Kawabe, Tetsuhiro Minamidani, Yoichi Tamura, Kimihiro Kimura

Comments: Accepted for publication in Journal of Vibration Engineering & Technologies

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

As deformations of the main reflector of a radio telescope directly affect the observations, the evaluation of the deformation is extremely important. Dynamic characteristics of the main reflector of the Nobeyama 45 m radio telescope, Japan, are measured under two conditions: The first is when the pointing observation is in operation, and the second is when the reflector is stationary and is subjected to wind loads when the observation is out of operation. Dynamic characteristics of the main reflector are measured using piezoelectric accelerometers. When the telescope is in operation, a vibration mode with one nodal line horizontally or vertically on the reflector is induced, depending on whether the reflector is moving in the azimuthal or elevational planes, whereas under windy conditions, vibration modes that have two to four nodal lines are simultaneously induced. The predominant mode is dependent on the direction of wind loads.

[21]  arXiv:2003.05137 [pdf, other]

Title: Relating the structure of dark matter halos to their assembly and environment

Authors: Yangyao Chen, H.J. Mo, Cheng Li, Huiyuan Wang, Xiaohu Yang, Youcai Zhang, Kai Wang

Comments: 23 pages, 16 figures, 1 table. Submitted to ApJ. Comments are welcomed

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

We use the ELUCID N-Body simulation to study the relation of structural properties of dark matter halos to their assembly history and environment. We find that the complexity of halo assembly histories can be well described by a small number of principal components. Using decision trees built with the random ensemble method, we find that the correlation between halo concentration and assembly history is tight: more than 60% of the variance in halo concentration can be explained by assembly history alone. Halo shape and spin parameters are found to depend not only on assembly history, but also on environment and initial condition, and these dependencies are not orthogonal. The structures of more massive halos depend more strongly on higher-order components of the assembly history. The relations between halo intrinsic properties and environment are weak compared to their variances, with the anisotropy of local tidal fields having the strongest correlation with halo properties. Our method of dimension reduction and regression can help simplify the characterization of the halo population and clarify the degeneracy among halo properties.

[22]  arXiv:2003.05150 [pdf, other]

Title: Illuminating the dark ages: Cosmic backgrounds from accretion onto primordial black hole dark matter

Authors: G. Hasinger

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

Cold dark matter as the sum of different mass Primordial Black Hole (PBH) could explain a number of mysteries, like the massive seed BH needed for the earliest QSOs, the massive LIGO/VIRGO binary BH, or the putative "Planet X" PBH in our Solar System. The most abundant PBH should be around the Chandrasekhar mass. This may already have been vindicated by the recent OGLE/GAIA population of putative BH of 1-10 Msun. I assume that all dark matter exists in the form of 1.4 Msun PBH and estimate the contribution of baryon accretion onto PBH to the cosmic backgrounds, concentrating on the Cosmic X-ray/Cosmic infrared background fluctuations discovered in deep Chandra and Spitzer surveys. Bondi accretion over cosmic time, assuming appropriate values of baryon density and effective relative velocity, as well as accretion and radiation efficiencies, predict a PBH contribution consistent with the residual X-ray fluctuations, peaking at z~17-30 consistent with other constraints requiring high redshifts for this signal. The PBH contribution to the Cosmic Infrared fluctuations is only about 1%, thus these are likely from star formation processes associated with the PBH. Other phenomena could be affected by the PBH accretion. Magnetic fields are an essential ingredient in the accretion process, and PBH can play an important role in amplifying magnetic seed fields in the early universe. The contribution of PBH to the re-ionization history of the universe does not conflict with the stringent limits from the most recent Planck data. X-ray heating from PBH can contribute to the entropy floor observed in groups of galaxies. The redshifted 21-cm absorption line feature observed by EDGES could be connected to the PBH radio emission. The diffuse X-ray emission in the Galactic Center region is not violated by PBH; some of the discrete sources in the Chandra Galactic Ridge observations could be PBH.

[23]  arXiv:2003.05153 [pdf, other]

Title: The Open Universe survey of Swift-XRT GRB fields: a complete sample of HBL blazars

Authors: P. Giommi, Y.L. Chang, S. Turriziani, T. Glauch, C. Leto, F. Verrecchia, P. Padovani, A.V. Penacchioni, F. Arneodo, U. Barres de Almeida, C.H. Brandt, M. Capalbi, O. Civitarese, V. D'Elia, A. Di Giovanni, M. De Angelis, J. Del Rio Vera, S. Di Pippo, R. Middei, M. Perri, A.M.T. Pollock, S. Puccetti, N. Ricard, R. Ruffini, N. Sahakyan

Comments: Submitted to A&A. 8 pages, 7 figures

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

We have analysed all the X-ray images centred on Gamma Ray Bursts generated by Swift over the last 15 years using automatic tools that do not require any expertise in X-ray astronomy, producing results in excellent agreement with previous findings. This work, besides presenting the largest medium-deep survey of the X-ray sky and a complete sample of blazars, wishes to be a step in the direction of achieving the ultimate goal of the Open Universe Initiative, that is to enable non expert people to fully benefit of space science data, possibly extending the potential for scientific discovery, currently confined within a small number of highly specialised teams, to a much larger population. We have used the Swift_deepsky Docker container encapsulated pipeline to build the largest existing flux-limited and unbiased sample of serendipitous X-ray sources. Swift_deepsky runs on any laptop or desktop computer with a modern operating system. The tool automatically downloads the data and the calibration files from the archives, runs the official Swift analysis software and produces a number of results including images, the list of detected sources, X-ray fluxes, SED data, and spectral slope estimations. We used our source list to build the LogN-LogS of extra-galactic sources, which perfectly matches that estimated by other satellites. Combining our survey with multi-frequency data we selected a complete radio flux-density limited sample of High Energy Peaked (HBL) blazars.

[24]  arXiv:2003.05156 [pdf, ps, other]

Title: Properties of gamma-ray decay lines in 3D core-collapse supernova models, with application to SN 1987A and Cas A

Authors: A. Jerkstrand, A. Wongwathanarat, H.-T. Janka, M. Gabler, D. Alp, R. Diehl, K. Maeda, J. Larsson, C. Fransson, A. Menon, A. Heger

Comments: 29 pages, accepted for publication in MNRAS

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

Comparison of theoretical line profiles to observations provides important tests for supernova explosion models. We study the shapes of radioactive decay lines predicted by current 3D core-collapse explosion simulations, and compare these to observations of SN 1987A and Cas A. Both the widths and shifts of decay lines vary by several thousand kilometers per second depending on viewing angle. The line profiles can be complex with multiple peaks. By combining observational constraints from 56Co decay lines, 44Ti decay lines, and Fe IR lines, we delineate a picture of the morphology of the explosive burning ashes in SN 1987A. For M_ZAMS=15-20 Msun progenitors exploding with ~1.5 *10^51 erg, ejecta structures suitable to reproduce the observations involve a bulk asymmetry of the 56Ni of at least ~400 km/s and a bulk velocity of at least ~1500 km/s. By adding constraints to reproduce the UVOIR bolometric light curve of SN 1987A up to 600d, an ejecta mass around 14 Msun is favoured. We also investigate whether observed decay lines can constrain the neutron star (NS) kick velocity. The model grid provides a constraint V_NS > V_redshift, and applying this to SN 1987A gives a NS kick of at least 500 km/s. For Cas A, our single model provides a satisfactory fit to the NuSTAR observations and reinforces the result that current neutrino-driven core-collapse SN models can achieve enough bulk asymmetry in the explosive burning material. Finally, we investigate the internal gamma-ray field and energy deposition, and compare the 3D models to 1D approximations.

[25]  arXiv:2003.05158 [pdf, other]

Title: An all-photonic focal-plane wavefront sensor

Authors: Barnaby R. M. Norris, Jin Wei, Christopher H. Betters, Alison Wong, Sergio G. Leon-Saval

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

Adaptive optics (AO) is critical in modern astronomy, as well as in optical communications and remote sensing, to deal with the rapid blurring caused by the Earth's turbulent atmosphere. But even the best AO systems are limited by their wavefront sensors, which need to be in an optical plane non-common to the science image, unavoidably leading to errors that limit the reach of current astronomy. They are also insensitive to certain wavefront-error modes, and are poorly suited to injecting light into single-mode optical fibres, important for applications such as high-resolution spectroscopy of extra-solar planets. Here we present a new type of wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning. This new wavefront sensor can be placed at the same focal plane as the science image, and is also optimal for single-mode fibre injection. By only measuring the intensities of an array of single-mode outputs, both phase and amplitude information on the incident wavefront can be reconstructed. We demonstrate the concept with both simulations and an experimental realisation of this novel wavefront sensor, wherein Zernike wavefront errors are recovered from focal-plane measurements to a precision of $2.6\times10^{-5}$ radians mean-squared-error.

[26]  arXiv:2003.05190 [pdf, other]

Title: Suppressed or enhanced central star formation rates in late-type barred galaxies

Authors: Jing Wang, E. Athanassoula, Si-Yue Yu, Christian Wolf, Li Shao, Hua Gao, T. H. Randriamampandry

Comments: 22 pages, 11 figures, accepted for publication in ApJ

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

Bars in disc-dominated galaxies are able to drive gas inflow inside the corotation radius, thus enhancing the central star formation rate (SFR). Previous work, however, has found that disc-dominated galaxies with centrally suppressed SFR frequently host a bar. Here we investigate possible causes for the suppression of central SFR in such cases. We compare physical properties of a sample of disc-dominated barred galaxies with high central SFR (HC galaxies) with those of a sample of disc-dominated barred galaxies with low central SFR (LC galaxies). We find that the two samples have on average similar HI content and bars of similar strength. But we also find that the HCs have bluer colors than LCs, and that outside the bar region they host stronger spiral arms than the LCs where closed rings are more often seen. We discuss and evaluate the possible causes for the suppression of the central SFR in the LC galaxies as opposed to its enhancement in the HC galaxies.

[27]  arXiv:2003.05197 [pdf, other]

Title: Acceleration of charged particles in rotating magnetized star

Authors: Debojoti Kuzur, Rupamoy Bhattacharyya, Ritam Mallick

Comments: 9 pages, 10 figures

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

Charged particles at the crust of compact stars may be ejected and accelerated by the electric field generated due to the rotation of the magnetized star. For neutron or hybrid stars, the negatively charged particles are usually electrons, and the positively charged particles are mainly protons and Iron. Whereas the existence of strange stars also includes the possibility of ejection of strangelets from the star surface. The flux of such strangelets emitted from all known pulsars is in the range of $10^9-10^{10}$ GeV. Therefore, such massive strangelets can be one of the candidates for the sources of the highest-energy cosmic rays that have still eluded us. Our model proposes a possible origin of these ultra high energy cosmic rays.

[28]  arXiv:2003.05220 [pdf, other]

Title: Tidal disruption events around spherically symmetric compact boson stars

Authors: Matheus C. Teodoro, Lucas G. Collodel, Jutta Kunz

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

We report simulations regarding tidal disruption clouds orbiting spherically symmetric compact boson stars in two different regimes. First we consider clouds in three different bound orbits close to the boson star and analyze the mechanisms of debris formation for these. We infer from the simulations that the lifetimes of these hot-spots are longer for circularly orbiting clouds than for clouds on eccentric orbits. Next we compare the evolution of more extended and less dense clouds on circular orbits around a boson star and a Schwarzschild black hole. As an outcome of the simulations we observe the formation of a ring-like structure around the boson star endowed with a spiralling shock structure and a constant thermal bremsstrahlung total luminosity. This final configuration contrasts strongly with the black hole scenario where the gas is totally captured behind the event horizon.

[29]  arXiv:2003.05226 [pdf, other]

Title: Phase mixing and wave heating in a complex coronal plasma

Authors: Thomas Howson, Ineke De Moortel, Jack Reid

Comments: 14 pages, 19 figures

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

Aims. We investigate the formation of small scales and the dissipation of MHD wave energy through non-linear interactions of counter-propagating, phase-mixed Alfvenic waves in a complex magnetic field. Methods. We conducted fully 3-D, non-ideal MHD simulations of transverse waves in complex magnetic fields. Continuous wave drivers were imposed on the foot points of magnetic field lines and the system was evolved for several Alfven travel times. Phase-mixed waves were allowed to reflect off the upper boundary and the interactions between the resultant counter-streaming wave packets were analysed. Results. The complex nature of the background magnetic field encourages the development of phase mixing, leading to a growth in currents and vorticities. Counter-propagating phase-mixed waves induce a cascade of energy to small scales and result in more efficient energy dissipation. This effect is enhanced in simulations with more complex magnetic fields. High-frequency drivers excite localised field line resonances and produce efficient wave heating. However, this relies on the formation of large amplitude oscillations on resonant field lines. Drivers with smaller frequencies than the fundamental frequencies of field lines are not able to excite resonances and thus do not inject sufficient Poynting flux to power coronal heating. Even in the case of high-frequency oscillations, the rate of dissipation is likely too slow to balance coronal energy losses, even within the quiet Sun. Conclusions. For the generalised phase-mixing presented here, complex background field structures enhance the rate of wave energy dissipation. However, it remains difficult for realistic wave drivers to inject sufficient Poynting flux to heat the corona. Indeed, significant heating only occurs in cases which exhibit amplitudes that are much larger than those currently observed in the solar atmosphere.

[30]  arXiv:2003.05260 [pdf, other]

Title: A search for dark matter in Triangulum II with the MAGIC telescopes

Authors: MAGIC Collaboration: V. A. Acciari (1), S. Ansoldi (2,23), L. A. Antonelli (3), A. Arbet Engels (4), D. Baack (5), A. Babić (6), B. Banerjee (7), U. Barres de Almeida (8), J. A. Barrio (9), J. Becerra González (1), W. Bednarek (10), L. Bellizzi (11), E. Bernardini (12,16), A. Berti (13), J. Besenrieder (14), W. Bhattacharyya (12), C. Bigongiari (3), A. Biland (4), O. Blanch (15), G. Bonnoli (11), Ž. Bošnjak (6), G. Busetto (16), R. Carosi (17), G. Ceribella (14), Y. Chai (14), A. Chilingarian (18), S. Cikota (6), S. M. Colak (15), U. Colin (14), E. Colombo (1), J. L. Contreras (9), J. Cortina (19), S. Covino (3), V. D'Elia (3), P. Da Vela (17), F. Dazzi (3), A. De Angelis (16), B. De Lotto (2), M. Delfino (15,26), J. Delgado (15,26), D. Depaoli (13), F. Di Pierro (13), et al. (132 additional authors not shown)

Comments: 14 pages, 8 figures, accepted for publication in Physics of the Dark Universe

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

We present the first results from very-high-energy observations of the dwarf spheroidal satellite candidate Triangulum II with the MAGIC telescopes from 62.4 hours of good-quality data taken between August 2016 and August 2017. We find no gamma-ray excess in the direction of Triangulum II, and upper limits on both the differential and integral gamma-ray flux are presented. Currently, the kinematics of Triangulum II are affected by large uncertainties leading to a bias in the determination of the properties of its dark matter halo. Using a scaling relation between the annihilation J-factor and heliocentric distance of well-known dwarf spheroidal galaxies, we estimate an annihilation J-factor for Triangulum II for WIMP dark matter of $\log[J_{\text{ann}}({0.5^{\circ}})/$ GeV$^{2}$ cm$^{-5}] = 19.35 \pm 0.37$. We also derive a dark matter density profile for the object relying on results from resolved simulations of Milky Way sized dark matter halos. We obtain 95% confidence-level limits on the thermally averaged annihilation cross section for WIMP annihilation into various Standard Model channels. The most stringent limits are obtained in the $\tau^{+}\tau^{-}$ final state, where a cross section for annihilation down to $\langle \sigma_{\text{ann}} v \rangle = 3.05 \times 10^{-24}$ cm$^{3}$ s$^{-1}$ is excluded.

[31]  arXiv:2003.05262 [pdf, other]

Title: Constraints on features in the inflationary potential from future Euclid data

Authors: Ivan Debono, Dhiraj Kumar Hazra, Arman Shafieloo, George F. Smoot, Alexei A. Starobinsky

Comments: 22 pages

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

With Planck CMB observations, we established the spectral amplitude and tilt of the primordial power spectrum. Evidence of a red spectral tilt ($n_\mathrm{s}=0.96$) at $8\sigma$ provides strong support for the inflationary mechanism, especially the slow-roll of the effective scalar field in its nearly flat potential as the generator of scalar primordial perturbations. With the next generation of Large Scale Structure surveys, we expect to probe primordial physics beyond the overall shape and amplitude of the main, smooth and slowly-changing part of the inflaton potential. Using the specifications for the upcoming Euclid survey, we investigate to what extent we can constrain the inflation potential beyond its established slow-roll behaviour. We provide robust forecasts with Euclid and Planck mock data from 9 fiducial power spectra that contain suppression and wiggles at different cosmological scales, using the Wiggly Whipped Inflation framework to generate these features in the primordial spectrum. We include both Euclid cosmic shear and galaxy clustering, with a conservative cut-off for non-linear scales. Using MCMC simulations, we obtain an improvement in constraints in the WWI potential, as well an improvement for the background cosmology parameters. We find that apart from improving the constraints on the overall scale of the inflationary potential by 40-50\%, we can also identify oscillations in the primordial spectrum that are present within intermediate to small scales ($k\sim0.01-0.2\,\mathrm{Mpc^{-1}}$).

[32]  arXiv:2003.05276 [pdf, other]

Title: Rossby modes in slowly rotating stars: depth dependence in distorted polytropes with uniform rotation

Authors: C. Damiani, R. H. Cameron, A. C. Birch, L. Gizon

Comments: 10 pages, 8 figures, accepted in A&A

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

Large-scale Rossby waves have recently been discovered from measurements of horizontal surface and near-surface solar flows (L\"optien at al. 2018). We are interested in understanding why only the sectoral modes are seen in the observations and also in modelling the radial structure of the observed modes. To do so, we characterise here the radial eigenfunctions of r modes for slowly-rotating polytropes in uniform rotation. We find that for free-surface boundary conditions on a spheroid of non-vanishing surface density, r modes can only exist for $\ell=m$ spherical harmonics in the inviscid case, and we compute their depth dependence and frequencies to leading order. For quasi-adiabatic stratification the sectoral modes with no radial nodes are the only modes which are almost toroidal and the depth dependence of the corresponding horizontal motion scales as $r^m$. For all r modes except the zero radial order sectoral ones, non-adiabatic stratification plays a crucial role in the radial force balance. The lack of quasi-toroidal solutions when stratification is close to neutral, except for the sectoral modes without nodes in radius, follows from the statement that the system needs to be in both horizontal and radial force balance. In the absence of super- or subadiabatic stratification and viscosity, both the horizontal and radial force balances independently determine the pressure perturbation. The only quasi-toroidal cases in which the two determinations of the pressure perturbation are consistent are the special cases where $\ell=m$, and the horizontal displacement scales with $r^m$.

[33]  arXiv:2003.05337 [pdf, ps, other]

Title: Study of slowly rotating CP stars observed with TESS

Authors: O. Kobzar, V. Khalack, D. Bohlender, A. David-Uraz, P. Kashko, D.M. Bowman, C. Lovekin, D. Tvardovskyi, M. Perron-Cormier, E. Paunzen, J. Sikora, P. Lampens, O. Richard

Comments: 5 pages, 1 figure, PTA Proceedings

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

Since the end of 2018, the Transiting Exoplanet Survey Satellite (TESS) provides high-quality space data on stellar photometry to the astronomical community. We present the results of an analysis of TESS photometric data for known slowly rotating magnetic chemically peculiar (mCP) stars. In general, mCP stars show an inhomogeneous distribution of elements in their stellar atmospheres that leads to spectroscopic (line profile) and photometric (light curve) variations over the rotation period. In the frame of the oblique magnetic rotator (OMR) model, patches of enhanced chemical abundance on the stellar surface reveal the frequency of stellar rotation. Using this approach, we have compiled a list of slowly rotating mCP stars with rotation periods longer than two days from the analysis of the photometric data provided by TESS for the first eight sectors of observations. Slowly rotating mCP stars usually possess a hydrodynamically stable stellar atmosphere where a magnetic field can amplify the process of atomic diffusion and leads to the horizontal and vertical stratification of chemical abundances.

[34]  arXiv:2003.05354 [pdf, other]

Title: Atmospheric compositions and observability of nitrogen dominated ultra-short period super-Earths

Authors: Mantas Zilinskas, Yamila Miguel, Paul Molliére, Shang-Min Tsai

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

We explore the chemistry and observability of nitrogen dominated atmospheres for ultra-short-period super-Earths. We base the assumption, that super-Earths could have nitrogen filled atmospheres, on observations of 55 Cnc e that favour a scenario with a high-mean-molecular-weight atmosphere. We take Titan's elemental budget as our starting point and using chemical kinetics compute a large range of possible compositions for a hot super-Earth. We use analytical temperature profiles and explore a parameter space spanning orders of magnitude in C/O \& N/O ratios, while always keeping nitrogen the dominant component. We generate synthetic transmission and emission spectra and assess their potential observability with the future James Webb Space Telescope and ARIEL. Our results suggest that HCN is a strong indicator of a high C/O ratio, which is similar to what is found for H-dominated atmospheres. We find that these worlds are likely to possess C/O > 1.0, and that HCN, CN, CO should be the primary molecules to be searched for in thermal emission. For lower temperatures (T < 1500 K), we additionally find NH3 in high N/O ratio cases, and C2H4, CH4 in low N/O ratio cases to be strong absorbers. Depletion of hydrogen in such atmospheres would make CN, CO and NO exceptionally prominent molecules to look for in the 0.6 - 5.0 $\mu$m range. Our models show that the upcoming JWST and ARIEL missions will be able to distinguish atmospheric compositions of ultra-short period super-Earths with unprecedented confidence.

[35]  arXiv:2003.05366 [pdf, other]

Title: Normalized Angular Momentum Deficit: a tool for comparing the violence of the dynamical histories of planetary systems

Authors: D. Turrini, A. Zinzi, J. A. Belinchon

Comments: 6 pages, 1 table, 3 figures. Submitted to Astronomy & Astrophysics

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

Population studies of the orbital characteristics of exoplanets in multi-planet systems highlighted the existence of an anti-correlation between the average orbital eccentricity of planets and the number of planets of their host system (i.e. its multiplicity). This effect was proposed to reflect the different violence of the dynamical evolution of the planetary systems. Previous work suggested that the relative violence of the dynamical evolution of planetary systems with similar orbital architectures can be compared through the computation of their angular momentum deficit (AMD). We investigated the possibility of using a more general metric to perform analogous comparisons between planetary systems with different orbital architectures. We considered a modified version of the AMD, the normalized angular momentum deficit (NAMD), and used it to study a sample of 99 multi-planet systems containing both the currently best-characterized extrasolar systems and the Solar System, i.e. planetary systems with both compact and wide orbital architectures. We verified that the NAMD allows to compare the violence of the dynamical histories of multi-planet systems with different orbital architectures. We identified an anti-correlation between the NAMD and the multiplicity of the planetary systems, of which the previously observed eccentricity--multiplicity anti--correlation is a reflection. Our results seem to indicate that phases of dynamical instabilities and chaotic evolution are not uncommon among planetary systems. They also suggest that the efficiency of the planetary formation process in producing high-multiplicity systems is likely higher that suggested by their currently known population.

[36]  arXiv:2003.05381 [pdf, other]

Title: Abundance analyses of Li-enriched and normal giants in the GALAH survey

Authors: Deepak, David L. Lambert, Bacham Eswar Reddy

Comments: 20 pages, 14 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society on March 09, 2020

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

Compositions of lithium-enriched and normal giants among the GALAH survey are compared. Except for Li, the only detectable abundance difference between lithium-enriched and normal giants among the investigated elements from carbon to europium occurs for carbon. Among Li-rich giants with A(Li) = 1.8 to 3.1, the C deficiency is very similar to that reported for the normal giants (with A(Li) $<$ 1.8) where the slight C deficiency arises from the first dredge-up. Carbon is slightly under abundant relative to normal giants among the super Li-rich giants where the Li abundance exceeds A(Li) = 3.2. The C abundance as well as the $^{12}$C/$^{13}$C ratios from the literature suggest that addition of Li to create a Li-rich giant may occur independently of the abundance changes wrought by the first dredge-up. Creation of a super Li-rich giant, however, appears to occur with additional CN-cycle conversion of C to N. The probability of becoming a Li-rich giant is approximately independent of a star's mass, although the majority of the Li-rich giants are found to be low mass ($M \leq$ 2 M$_\odot$). The frequency of occurrence of Li-enriched giants among normal giants is about one percent and slightly dependent on metallicity ([Fe/H]). Li-enriched and normal giants are found to have similar projected rotational velocity which suggest that Li-enrichment in giants is not linked to scenarios such as mergers and tidal interaction between binary stars.

[37]  arXiv:2003.05384 [pdf, other]

Title: Dense Gas in a Giant Molecular Filament

Authors: Y. Wang, H. Beuther, N. Schneider, S. E. Meidt, H. Linz, S. Ragan, C. Zucker, C. Battersby, J. D. Soler, E. Schinnerer, F. Bigiel, D. Colombo, Th. Henning

Comments: 15 pages, 10 figures, submitted to A&A

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

Recent surveys of the Galactic plane in the dust continuum and CO emission lines reveal that large ($\gtrsim 50$~pc) and massive ($\gtrsim 10^5$~$M_\odot$) filaments, know as giant molecular filaments (GMFs), may be linked to galactic dynamics and trace the mid-plane of the gravitational potential in the Milky Way. We have imaged one entire GMF located at $l\sim$52--54$^\circ$ longitude, GMF54 ($\sim$68~pc long), in the dense gas tracers using the HCN(1--0), HNC(1--0), HCO$^+$(1--0) lines, and their $^{13}$C isotopologue transitions, as well as the N$_2$H$^+$(1--0) line. We study the dense gas distribution, the column density probability density functions (N-PDFs) and the line ratios within the GMF. The dense gas molecular transitions follow the extended structure of the filament with area filling factors between 0.06 and 0.28 with respect to $^{13}$CO(1--0). We constructed the N-PDFs of H$_2$ for each of the dense gas tracers based on their column densities and assumed uniform abundance. The N-PDFs of the dense gas tracers appear curved in log-log representation, and the HCO$^+$ N-PDF has the largest log-normal width and flattest power-law slope index. Studying the N-PDFs for sub-regions of GMF54, we found an evolutionary trend in the N-PDFs that high-mass star forming and Photon-Dominate Regions (PDRs) have flatter power-law indices. The integrated intensity ratios of the molecular lines in GMF54 are comparable to those in nearby galaxies. In particular, the N$_2$H$^+$/$^{13}$CO ratio, which traces the dense gas fraction, has similar values in GMF54 and all nearby galaxies except ULIRGs.

[38]  arXiv:2003.05397 [pdf, other]

Title: A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L-band

Authors: Rebecca K. Webb, Matteo Brogi, Siddharth Gandhi, Michael R. Line, Jayne L. Birkby, Katy L. Chubb, Ignas A. G. Snellen, Sergey N. Yurchenko

Comments: Accepted for publication in MNRAS; 13 pages, 10 figures

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

High resolution spectroscopy (R > 20,000) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES (R = 100,000) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 microns. We observe a weak (3.0 sigma, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K-band, we measure a detection significance of 8.4 sigma for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken three years apart, this points to the absence of strong radial-velocity anomalies due, e.g., to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 +- 2.0)kms^{-1} (1 sigma) and improve the error bars on this parameter by ~70%. However, we only marginally tighten constraints on orbital inclination (66.2 +3.7 -3.1 degrees) and planet mass (0.963 +0.036 -0.031 Jupiter masses), due to the dominant uncertainties of stellar mass and semi-major axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterisation via high resolution spectroscopy.

[39]  arXiv:2003.05404 [pdf, other]

Title: The GRAVITY young stellar object survey. II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO

Authors: GRAVITY Collaboration: A. Caratti o Garatti (1,2,3), R. Fedriani (1,3,4), R. Garcia Lopez (1,2,3), M. Koutoulaki (1,3,5), K. Perraut (6), H. Linz (2), W. Brandner (2), P. Garcia (7,8,9), L. Klarmann (2), T. Henning (2), L. Labadie (10), J. Sanchez-Bermudez (2,11), B. Lazareff (6), E.F. van Dishoeck (12,14), P. Caselli (12), P.T. de Zeeuw (12,14), A. Bik (13), M. Benisty (6,9), C. Dougados (6), T.P. Ray (1), A. Amorim (8), J.-P. Berger (6), Y. Clénet (15), V. Coudé du Foresto (15), G. Duvert (6), A. Eckart (10), F. Eisenhauer (12), F. Gao (12), E. Gendron (15), R. Genzel (12,16), S. Gillessen (12), P. Gordo (8), L. Jocou (6), M. Horrobin (10), P. Kervella (15), S. Lacour (15), J.-B. Le Bouquin (6), P. Léna (15), R. Grellmann (10), T. Ott (12), T. Paumard (15), G. Perrin (15), et al. (10 additional authors not shown)

Comments: Accepted for publication in A&A letters

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

The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. We deploy near-infrared (NIR) spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 $\mu$m). We present the first GRAVITY/VLTI observations at high spectral (R=4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS2. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases ($\leq$8$^{\circ}$). Our best ellipsoid model provides a disc inclination of 34$^{\circ}$$\pm$1$^{\circ}$, a disc major axis position angle of 166$^{\circ}$$\pm$1$^{\circ}$, and a disc diameter of 3.99$\pm$0.09 mas (or 1.69$\pm$0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74$\pm^{0.08}_{0.07}$ mas (1.16$\pm$0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and $PA$ matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of $M_*\sim$14.7$^{+2}_{-3.6}$ M$_{\odot}$ by combining our interferometric and spectral modelling results.

[40]  arXiv:2003.05416 [pdf, other]

Title: A new proxy to estimate the cosmic-ray ionisation rate in dense cores

Authors: Stefano Bovino, Simon Ferrada-Chamorro, Alessandro Lupi, Dominik R.G. Schleicher, Paola Caselli

Comments: Accepted on MNRAS Letters

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

Cosmic rays are a global source of ionisation, and the ionisation fraction represents a fundamental parameter in the interstellar medium. Ions couple to magnetic fields, affect the chemistry, and the dynamics of star-forming regions as well as planetary atmospheres. However, the cosmic-ray ionisation rate represents one of the bottlenecks for astrochemical models, and its determination is one of the most puzzling problems in astrophysics. While for diffuse clouds reasonable values have been provided from H$_3^+$ observations, for dense clouds, due to the lack of rotational transitions, this is not possible, and estimates are strongly biased by the employed model. We present here an analytical expression, obtained from first principles, to estimate the cosmic-ray ionisation rate from observational quantities. The theoretical predictions are validated with high-resolution three-dimensional numerical simulations and applied to the well known core L1544; we obtained an estimate of $\zeta_2 \sim 2-3 \times 10^{-17}$ s$^{-1}$. Our results and the analytical formulae provided represent the first model-independent, robust tool to probe the cosmic-ray ionisation rate in the densest part of star-forming regions (on spatial scales of $R \leq 0.05$ pc). An error analysis is presented to give statistical relevance to our study.

Cross-lists for Thu, 12 Mar 20

[41]  arXiv:2003.04303 (cross-list from gr-qc) [pdf, ps, other]

Title: A local self-tuning mechanism for the cosmological constant

Authors: Daniel Sobral-Blanco, Lucas Lombriser

Comments: 14 pages

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

Recently the global variation of the Planck mass in the General Relativistic Einstein-Hilbert action was proposed as a self-tuning mechanism of the cosmological constant preventing vacuum energy from freely gravitating. We show that this global mechanism emerges for generic local scalar-tensor theories with additional coupling of the scalar field to the field strength of a three-form gauge field that turns the scalar field constant on the domain of the action. Evaluation of the resulting integral constraint equation over the observable Universe yields a self-consistent framework with General Relativistic field equations and arbitrary radiatively stable residual cosmological constant. We argue that the expectation value for this residual is in good agreement with the magnitude of the observed cosmic acceleration.

[42]  arXiv:2003.04304 (cross-list from gr-qc) [pdf, ps, other]

Title: Canonical Analysis of Brans-Dicke Theory Addresses Hamiltonian Inequivalence between Jordan and Einstein Frames

Authors: Gabriele Gionti, S.J

Comments: 11 pages, letter, latex

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

Jordan and Einstein frames are studied under the light of Hamiltonian formalism. Dirac's constraint theory for Hamiltonian systems is applied to Brans-Dicke theory. In both Jordan and Einstein frames, Brans-Dicke theory has four secondary first class constraints, whose constraint algebra is different. The Weyl (conformal) transformation between the two frames results not to be a canonical transformation, addressing a quantum mechanical non equivalence as well.

[43]  arXiv:2003.04903 (cross-list from hep-ph) [pdf, other]

Title: The QCD Axion at Finite Density

Authors: Reuven Balkin, Javi Serra, Konstantin Springmann, Andreas Weiler

Comments: 39 pages + appendices and references, 6 figures

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

We show how the properties of the QCD axion change in systems at finite baryonic density, such as neutron stars. At nuclear saturation densities, where corrections can be reliably computed, we find a mild reduction of the axion mass and up to an order of magnitude enhancement in the model-independent axion coupling to neutrons. At moderately higher densities, if realized, meson (kaon) condensation can trigger axion condensation. We also study the axion potential at asymptotically large densities, where the color-superconducting phase of QCD potentially leads to axion condensation, and the mass of the axion is generically several orders of magnitude smaller than in vacuum due to the suppressed instantons. Several phenomenological consequences of the axion being sourced by neutron stars are discussed, such as its contribution to their total mass, the presence of an axionic brane, or axion-photon conversion in the magnetosphere.

[44]  arXiv:2003.04908 (cross-list from hep-ph) [pdf, other]

Title: Gravitational Origin for Neutrino Masses

Authors: Hooman Davoudiasl

Comments: 6 pages, 3 figures

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

We describe a scenario where the smallness of neutrino masses is related to a global symmetry that is only violated by quantum gravitational effects. The proposed implementation of our scenario leads to axion particles that decay into neutrinos, which could be probed through cosmological measurements and may help explain the Hubble parameter tension. Depending on the details of the implementation, the scenario could provide axion dark matter candidates.

[45]  arXiv:2003.04921 (cross-list from nucl-ex) [pdf, other]

Title: Direct measurement of the terrestrial $^7$Be $L/K$ capture ratio in cryogenic tantalum

Authors: S. Fretwell, K.G. Leach, C. Bray, G.B. Kim, J. Dilling, A. Lennarz, X. Mougeot, F. Ponce, C. Ruiz, J. Stackhouse, S. Friedrich

Comments: 5 pages, 3 figures. Submitted to Physical Review Letters

Subjects: Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)

We report a high-statistics measurement of the $L/K$ orbital electron capture (EC) ratio in $^7$Be embedded in cryogenic Ta. The thin Ta film formed part of a high-resolution superconducting tunnel junction (STJ) radiation detector that was used to identify the signals from different decay channels. The measured $L/K$ capture ratio of 0.070(7) is significantly larger than the only previous measurement of this quantity and the theoretical predictions that include in-medium effects. This result brings into question the accuracy of the extrapolated $L/K$ ratio currently used in calculations of the $^7$Be destruction rate in astrophysical environments relevant to solar and galactic neutrino modeling, and the cosmological lithium problem. This Letter presents the first experiment that uses STJs for nuclear-recoil detection, opening a new experimental avenue for low-energy precision measurements with rare isotopes.

[46]  arXiv:2003.05339 (cross-list from hep-ph) [pdf, other]

Title: Revisiting Neutrino Self-Interaction Constraints from $Z$ and $τ$ decays

Authors: Vedran Brdar, Manfred Lindner, Stefan Vogl, Xun-Jie Xu

Comments: 13 pages, 5 figures

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

Given the elusive nature of neutrinos, their self-interaction is particularly difficult to probe. Nevertheless, upper limits on the strength of such an interaction can be set by using data from terrestrial experiments. In this work we focus on additional contributions to the invisible decay width of $Z$ boson as well as the leptonic $\tau$ decay width in the presence of a neutrino coupling to a relatively light scalar. For invisible $Z$ decays we derive a complete set of constraints by considering both three-body bremsstrahlung as well as the loop correction to two-body decays. While the latter is usually regarded to give rather weak limits we find that through the interference with the Standard Model diagram it actually yields a competitive constraint. As far as leptonic decays of $\tau$ are concerned, we derive a first limit on neutrino self-interactions that is valid across the whole mass range of a light scalar mediator. Our bounds on the neutrino self-interaction are leading for $m_\phi \gtrsim 300$ MeV and interactions that prefer $\nu_\tau$. Bounds on such $\nu$-philic scalar are particularly relevant in light of the recently proposed alleviation of the Hubble tension in the presence of such couplings.

[47]  arXiv:2003.05342 (cross-list from gr-qc) [pdf, ps, other]

Title: Dynamics of Chiral Cosmology

Authors: Andronikos Paliathanasis

Comments: 19 pages, 9 figures, 1 table

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

We perform a detailed analysis for the dynamics of Chiral cosmology in a spatially flat Friedmann-Lema\^{\i}tre-Robertson-Walker universe with a mixed potential term. The stationary points are categorized in four families. Previous results in the literature are recovered while new phases in the cosmological evolution are found. From our analysis we find nine different cosmological solutions, the eight describe scaling solutions, where the one is that of a pressureless fluid, while only one de Sitter solution is recovered.

[48]  arXiv:2003.05407 (cross-list from physics.space-ph) [pdf, ps, other]

Title: Dependence of Intensities of Major Geomagnetic Storms (Dst $\le$ -100 nT) on Associated Solar Wind Parameters

Authors: Gui-Ming Le, Gui-Ang Liu, Ming-Xian Zhao

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

A geomagnetic storm is the result of sustained interaction between solar wind with a southward magnetic field and the magnetosphere. To investigate the influence of various solar wind parameters on the intensity of major geomagnetic storm, 67 major geomagnetic storms that occurred between 1998 and 2006 were used to calculate the correlation coefficients (CCs) between the intensities of major geomagnetic storms and the time integrals of southward interplanetary magnetic field $B_s$, solar wind electric field ($E_y$) and injection function (Q) during the main phase of the associated geomagnetic storms. SYM-H$_{min}$ was used to indicate the intensity of the associated major geomagnetic storm, while I($B_z$), I($E_y$) and I(Q) were used to indicate the time integrals of $B_z$, $E_y$ and Q during the main phase of associated major geomagnetic storm respectively. The derived CC between I($B_z$) and SYM-H$_{min}$ is 0.33, while the CC between I($E_y$) and SYM-H$_{min}$ is 0.57 and the CC between I(Q) and SYM-H$_{min}$ is 0.86. The results provide statistical evidence that solar wind dynamic pressure or solar wind density plays a significant role in transferring solar wind energy into the magnetosphere, in addition to the southward magnetic field and solar wind speed. Solar wind that has a strong geoeffectiveness requires solar wind dynamic pressure $>$3 nPa or solar wind density $>3$ nPa$/V_{sw}^2$. Large and long duration $B_s$ alone cannot ensure a major geomagnetic storm, especially if the solar wind dynamic pressure is very low, as large and long duration Bs is not a full condition, only a necessary condition to trigger a major geomagnetic storm.

[49]  arXiv:2003.05409 (cross-list from physics.space-ph) [pdf, other]

Title: Localized magnetic field structures and their boundaries in the near-Sun solar wind from Parker Solar Probe measurements

Authors: V. Krasnoselskikh (1 and 2), A. Larosa (1), O. Agapitov (2), T. Dudok de Wit (1), M. Moncuquet (3), F. S. Mozer (2 and 4), M. Stevens (5), S. D. Bale (2 and 4 and 6 and 7), J. Bonnell (2), C. Froment (1), K. Goetz (8), K. Goodrich (2), P. Harvey (2), J. Kasper (5 and 9), R. MacDowall (10), D. Malaspina (11), M. Pulupa (2), N. Raouafi (12), C. Revillet (1), M. Velli (13), J. Wygant (8), ((1) LPC2E, CNRS and University of Orléans, 3A avenue de la Recherche Scientifique, Orléans, France, (2) Space Sciences Laboratory, University of California, Berkeley, CA USA, (3) LESIA, Observatoire de Paris-Meudon, Meudon, France, (4) Physics Department, University of California, Berkeley, CA, USA, (5) Smithsonian Astrophysical Observatory, Cambridge, MA, 02138, USA, (6) he Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK, (7) School of Physics and Astronomy, Queen Mary University of London, London, UK, (8) School of Physics and Astronomy, University of Minnesota, Minneapolis, MN USA, (9) Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI USA, (10) Solar System Exploration Division, NASA/Goddard Space Flight Center, Greenbelt, MD, USA, (11) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, US, (12) Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA, (13) Institute of Geophysics & Planetary Physics, Department of Earth, Planetary & Space Sciences, University of California, Los Angeles, CA, USA)

Comments: 27 pages, 18 Figures, submitted to ApJ Supplement

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

One of the discoveries made by Parker Solar Probe during first encounters with the Sun is the ubiquitous presence of relatively small-scale structures standing out as sudden deflections of the magnetic field. They were called switchbacks as some of them show up the full reversal of the radial component of the magnetic field and then return to regular conditions. Analyzing the magnetic field and plasma perturbations associated with switchbacks we identify three types of structures with slightly different characteristics: 1. Alfvenic structures, where the variations of the magnetic field components take place while the magnitude of the field remains constant; 2. Compressional, the field magnitude varies together with changes of the components; 3. Structures manifesting full reversal of the magnetic field (extremal class of Alfvenic structures). Processing of structures boundaries and plasma bulk velocity perturbations lead to the conclusion that they represent localized magnetic field tubes with enhanced parallel plasma velocity and ion beta moving together with respect to surrounding plasma. The magnetic field deflections before and after the switchbacks reveal the existence of total axial current. The electric currents are concentrated on the relatively narrow boundary layers on the surface of the tubes and determine the magnetic field perturbations inside the tube. These currents are closed on the structure surface, and typically have comparable azimuthal and the axial components. The surface of the structure may also accommodate an electromagnetic wave, that assists to particles in carrying currents. We suggest that the two types of structures we analyzed here may represent the local manifestations of the tube deformations corresponding to a saturated stage of the Firehose instability development.

Replacements for Thu, 12 Mar 20

[50]  arXiv:1804.05861 (replaced) [pdf, other]

Title: Differentiating Disk and Black Hole Driven Jets with EHT Images of Variability in M87

Authors: Britton Jeter (1,2,4), Avery E. Broderick (1,2,4), Roman Gold (3,4), ((1) University of Waterloo, (2) Waterloo Centre for Astrophysics, (3) Perimeter Institute, (4) Institute for Theoretical Physics)

Comments: 12 pages, 14 figures, Submitted to MNRAS

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

[51]  arXiv:1903.08348 (replaced) [pdf, other]

Title: Global Stability Properties of the Climate: Melancholia States, Invariant Measures, and Phase Transitions

Authors: Valerio Lucarini, Tamas Bodai

Comments: 48 Pages, 10 Figures

Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Earth and Planetary Astrophysics (astro-ph.EP); Statistical Mechanics (cond-mat.stat-mech); Chaotic Dynamics (nlin.CD)

[52]  arXiv:1904.01029 (replaced) [pdf, other]

Title: Probing Primordial Chirality with Galaxy Spins

Authors: Hao-Ran Yu, Pavel Motloch, Ue-Li Pen, Yu Yu, Huiyuan Wang, Houjun Mo, Xiaohu Yang, Yipeng Jing

Comments: 6 pages (including Supplemental Material), 3 figures. Matched accepted version in PRL

Journal-ref: Phys. Rev. Lett. 124, 101302 (2020)

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

[53]  arXiv:1905.11279 (replaced) [pdf, other]

Title: Simulations of the 3-Dimensional Velocity Distribution of Halo Weakly Interacting Massive Particles for Directional Dark Matter Detection Experiments

Authors: Chung-Lin Shan

Comments: 193 pages, 132 figures (599 pdf plots, 18 png skteches), 36 tables; v2: materials added and improved, typos fixed

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

[54]  arXiv:1906.05812 (replaced) [pdf, ps, other]

Title: Type IIn supernova light-curve properties measured from an untargeted survey sample

Authors: A. Nyholm, J. Sollerman, L. Tartaglia, F. Taddia, C. Fremling, N. Blagorodnova, A. V. Filippenko, A. Gal-Yam, D. A. Howell, E. Karamehmetoglu, S. R. Kulkarni, R. Laher, G. Leloudas, F. Masci, M. M. Kasliwal, K. Morå, T. J. Moriya, E. O. Ofek, S. Papadogiannakis, R. Quimby, U. Rebbapragada, S. Schulze

Comments: Accepted for publication (A&A) 2019 Sep 30. Figures 3, 4 & 7 updated (erroneous standard deviations shown in earlier versions). Abstract abridged. 33 pages, 22 figures, 7 tables

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

[55]  arXiv:1906.08826 (replaced) [pdf, other]

Title: Automated crater shape retrieval using weakly-supervised deep learning

Authors: Mohamad Ali-Dib, Kristen Menou, Alan P. Jackson, Chenchong Zhu, Noah Hammond

Comments: 59 pages, 13 figures, Accepted for publication in Icarus

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Computer Vision and Pattern Recognition (cs.CV); Machine Learning (cs.LG)

[56]  arXiv:1908.02647 (replaced) [pdf]

Title: Climate simulations of early Mars with estimated precipitation, runoff, and erosion rates

Authors: Ramses M. Ramirez, Robert A. Craddock, Tomohiro Usui

Comments: Published in JGR:Planets (61 pages, 12 Figures, 2 Tables; Supp Info: 7 pages, 5 figures)

Journal-ref: Journal of Geophysical Research: Planets, 125, e2019JE006160 (2020)

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

[57]  arXiv:1908.08902 (replaced) [pdf, other]

Title: The CatWISE Preliminary Catalog: Motions from ${\it WISE}$ and ${\it NEOWISE}$ Data

Authors: Peter R. M. Eisenhardt (1), Federico Marocco (1,2), John W. Fowler (3), Aaron M. Meisner (4), J. Davy Kirkpatrick (2), Nelson Garcia (2), Thomas H. Jarrett (5), Renata Koontz (6), Elijah J. Marchese (6), S. Adam Stanford (7), Dan Caselden (8), Michael C. Cushing (9), Roc M. Cutri (2), Jacqueline K. Faherty (10), Christopher R. Gelino (2), Anthony H. Gonzalez (11), Amanda Mainzer (1), Bahram Mobasher (12), David J. Schlegel (13), Daniel Stern (1), Harry I. Teplitz (2), Edward L. Wright (14) ((1) Jet Propulsion Laboratory, Caltech, USA, (2) IPAC, Caltech, USA, (3) 230 Pacific St., Apt. 205, Santa Monica, CA, USA, (4) National Optical Astronomy Observatory, USA, (5) University of Cape Town, South Africa, (6) UC Riverside, USA, (7) UC Davis, USA, (8) Gigamon ATR, USA, (9) University of Toledo, USA, (10) American Museum of Natural History, USA, (11) University of Florida, USA, (12) UC Riverside, USA, (13) Lawrence Berkeley National Laboratory, USA, (14) UCLA, USA)

Comments: 53 pages, 20 figures, 5 tables. Accepted by ApJS

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

[58]  arXiv:1908.09240 (replaced) [pdf, other]

Title: Thermal Components in Gamma-ray Bursts. II. Constraining the Hybrid Jet Model

Authors: Liang Li

Comments: 31 pages, 13 figures including 94 panels, 1 table, accepted for publication in ApJ

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

[59]  arXiv:1908.11265 (replaced) [pdf, other]

Title: Non-linear Schrödinger-type formulation of scalar field cosmology: two barotropic fluids and exact solutions

Authors: Chonticha Kritpetch (IF Naresuan), Jarunee Sanongkhun (IF Naresuan), Pichet Vanichchapongjaroen (IF Naresuan), Burin Gumjudpai (IF Naresuan)

Comments: 11 pages, 2 figures

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

[60]  arXiv:1910.02361 (replaced) [pdf, ps, other]

Title: Detectability of 21cm signal during the Epoch of Reionization with 21cm-Lyman-$α$ emitter cross-correlation. III. Model dependence

Authors: Kenji Kubota, Akio. K. Inoue, Kenji Hasegawa, Keitaro Takahashi

Comments: 11 pages, 10 figures, submitted to Monthly Notices of the Royal Astronomical Society

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

[61]  arXiv:1910.04779 (replaced) [pdf, other]

Title: Cosmological implications of electromagnetically interacting dark matter: milli-charged particles and atoms with singly and doubly charged dark matter

Authors: Gautham A P, Shiv Sethi

Comments: Version 2: 27 pages, 6 figures, 2 Tables

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

[62]  arXiv:1910.11345 (replaced) [pdf, other]

Title: Semi-analytic forecasts for JWST -- III. Intrinsic production efficiency of Lyman-continuum radiation

Authors: L. Y. Aaron Yung, Rachel S. Somerville, Gergö Popping, Steven L. Finkelstein

Comments: 17 pages, 12 figures, accepted for publication in MNRAS

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

[63]  arXiv:1912.10792 (replaced) [pdf]

Title: A compact multi-planet system around a bright nearby star from the Dispersed Matter Planet Project

Authors: D. Staab, C.A. Haswell, J.R. Barnes, G. Anglada-Escudé, L. Fossati, J.P.J. Doherty, J. Cooper, J.S. Jenkins, M.R. Díaz, M.G. Soto

Comments: Accepted for publication by Nature Astronomy on 12th November 2019 (Main article, Methods and Supplementary Information; 24 pages, 10 figures, 3 tables)

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

[64]  arXiv:1912.12006 (replaced) [pdf, other]

Title: Erratum: Nonlinear spherical perturbations in quintessence models of dark energy

Authors: Manvendra Pratap Rajvanshi, J. S. Bagla

Comments: 8 pages, 10 figures. Erratum for 1802.05840

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

[65]  arXiv:1912.12499 (replaced) [pdf, other]

Title: Non-linear damping of superimposed primordial oscillations on the matter power spectrum in galaxy surveys

Authors: Mario Ballardini, Riccardo Murgia, Marco Baldi, Fabio Finelli, Matteo Viel

Comments: 23 pages, 10 figures, 1 table

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

[66]  arXiv:2001.11564 (replaced) [pdf, other]

Title: The Milky Way's stellar streams and globular clusters do not align in a Vast Polar Structure

Authors: Alexander H. Riley, Louis E. Strigari

Comments: 10+8 pages, 4 figures, 4+5 tables. Accepted for publication in MNRAS

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

[67]  arXiv:2002.01064 (replaced) [pdf, ps, other]

Title: Quantum nature of Wigner function for inflationary tensor perturbations

Authors: Jinn-Ouk Gong, Min-Seok Seo

Comments: (v1) 24 pages, (v2) 27 pages, discussions expanded and references added, to appear in Journal of High Energy Physics

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

[68]  arXiv:2002.10737 (replaced) [pdf, other]

Title: The HSC-SSP Transient Survey: Implications from Early Photometry and Rise Time of Normal Type Ia Supernovae

Authors: Ji-an Jiang, Naoki Yasuda, Keiichi Maeda, Mamoru Doi, Toshikazu Shigeyama, Nozomu Tominaga, Masaomi Tanaka, Takashi J. Moriya, Ichiro Takahashi, Nao Suzuki, Tomoki Morokuma, Ken'ichi Nomoto

Comments: 13 pages, 5 figures, accepted for publication in ApJ

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

[69]  arXiv:2002.11091 (replaced) [pdf, other]

Title: Precise determination of the inflationary epoch and constraints for reheating

Authors: Gabriel German

Comments: 5 pages, one figure. The main equation Eq.(4) has been replaced by a more compact looking formula, although equivalent to the originally presented (v2). The numbers in Eqs.(24)-(27) have been adjusted after a calculation with improved precision (v2). In v3 we have added a figure a table and two particular models in addition to Starobinsky model

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

[70]  arXiv:2003.03059 (replaced) [pdf, ps, other]

Title: Magnetic filed structure of the Galactic plane from differential analysis of interstellar polarization

Authors: Tetsuya Zenko, Tetsuya Nagata, Mikio Kurita, Masaru Kino, Shogo Nishiyama, Noriyuki Matsunaga, Yasushi Nakajima

Comments: 32 pages, 17 figures, accepted in PASJ

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

[71]  arXiv:2003.04565 (replaced) [pdf, other]

Title: The Locus Algorithm III: A Grid Computing system to generate catalogues of optimised pointings for Differential Photometry

Authors: Oisń Creaner, Kevin Nolan, John Walsh, Eugene Hickey

Comments: 12 Pages, 9 Figures, 1 reference corrected, cross-references for arxiv links updated

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Distributed, Parallel, and Cluster Computing (cs.DC)

[72]  arXiv:2003.04570 (replaced) [pdf, other]

Title: The Locus Algorithm IV: Performance metrics of a grid computing system used to create catalogues of optimised pointings

Authors: Oisín Creaner, John Walsh, Kevin Nolan, Eugene Hickey

Comments: 6 Pages, 1 Figure, arxiv references updated with correct links

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Performance (cs.PF)

[73]  arXiv:2003.04574 (replaced) [pdf, other]

Title: The Locus Algorithm II: A robust software system to maximise the quality of fields of view for Differential Photometry

Authors: Kevin Nolan, Eugene Hickey, Oisín Creaner

Comments: 11 Pages, 13 Figures, Updated arxiv references with URLs for other papers in series

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Distributed, Parallel, and Cluster Computing (cs.DC)

[74]  arXiv:2003.04582 (replaced) [pdf, other]

Title: The Locus Algorithm I: A technique for identifying optimised pointings for differential photometry

Authors: Oisín Creaner, Kevin Nolan, Eugene Hickey, Niall Smith

Comments: 11 Pages, 6 Figures, simultaneous-release papers updated with arxiv cross-references

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

[75]  arXiv:2003.04590 (replaced) [pdf, other]

Title: A Catalogue of Locus Algorithm Pointings for Optimal Differential Photometry for 23,779 Quasars

Authors: Oisín Creaner, Kevin Nolan, David Grennan, Niall Smith, Eugene Hickey

Comments: 7 pages, 5 figures, cross-references to other papers in the series edited with arxiv links

Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM); Distributed, Parallel, and Cluster Computing (cs.DC); Digital Libraries (cs.DL)

• New submissions
• Cross-lists
• Replacements