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New submissions for Mon, 13 Jan 20

[1]  arXiv:2001.03171 [pdf, other]

Title: Striped Blandford/Znajek jets from advection of small scale magnetic field

Authors: J. F. Mahlmann (1), A. Levinson (2), M. A. Aloy (1) ((1) Departament d'Astronomia i Astrofísica, Universitat de València, 46100, Burjassot, Spain, (2) The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel)

Comments: 25 pages, 17 figures of which 17 are in color. 1 animated figure. Submitted to MNRAS

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

Black hole - accretion disc systems are the central engines of relativistic jets from stellar to galactic scales. We numerically quantify the unsteady outgoing Poynting flux through the horizon of a rapidly spinning black hole endowed with a rotating accretion disc. The disc supports small-scale, concentric, flux tubes with zero net magnetic flux. Our General Relativistic force-free electrodynamics simulations follow the accretion onto the black hole over several hundred dynamical timescales in 3D. For the case of counter-rotating accretion discs, the average process efficiency reaches up to $\left\langle\epsilon\right\rangle\approx 0.43$, compared to a stationary energy extraction by the Blandford/Znajek process. The process efficiency depends on the cross-sectional area of the loops, i.e. on the product $l\times h$, where $l$ is the radial loop thickness and $h$ its vertical scale height. We identify a strong correlation between efficient electromagnetic energy extraction and the quasi-stationary setting of ideal conditions for the operation of the Blandford/Znajek process (e.g. optimal field line angular velocity and fulfillment of the so-called Znajek condition). Remarkably, the energy extraction operates intermittently (alternating episodes of high and low efficiency) without imposing any large-scale magnetic field embedding the central object. Scaling our results to supermassive black holes, we estimate that the typical variability timescale of the system is of the order of days to months. Such timescales may account for the longest variability scales of TeV emission observed, e.g. in M87.

[2]  arXiv:2001.03176 [pdf, other]

Title: 3\%-accurate predictions for the clustering of dark matter, haloes and subhaloes, over a wide range of cosmologies and scales

Authors: S. Contreras, R. E. Angulo M. Zennaro, G. Aricó, M. Pellejero-Ibañez

Comments: 12 pages, 8 figures. Submitted. Comments are welcome

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

Predicting the spatial distribution of objects as a function of cosmology is an essential ingredient for the exploitation of future galaxy surveys. In this paper we show that a specially-designed suite of gravity-only simulations together with cosmology-rescaling algorithms can provide the clustering of dark matter, haloes, and subhaloes with high precision. Specifically, with only 3 $N$-body simulations we obtain the power spectrum of dark matter at $z=0$ and $z=1$ to better than 3\% precision for essentially all currently viable values of 8 cosmological parameters, including massive neutrinos and dynamical dark energy, and over the whole range of scales explored, 0.03 < $k/h^{-1}Mpc$ < 5. This precision holds at the same level for mass-selected haloes and for subhaloes selected according to their peak maximum circular velocity. As an initial application of these predictions, we successfully constrain $\Omega_{\rm m}$, $\sigma_8$, and the scatter in subhalo-abundance-matching employing the projected correlation function of mock SDSS galaxies.

[3]  arXiv:2001.03177 [pdf, other]

Title: The Chemical Compositions of Accreted and {\it in situ} Galactic Globular Clusters According to SDSS/APOGEE

Authors: Danny Horta, Ricardo P. Schiavon, J. Ted Mackereth, Timothy C. Beers, José G. Fernández-Trincado, Peter M. Frinchaboy, Doug Geisler, Sten Hasselquist, Henrik Jönsson, Richard R. Lane, Steven R. Majewski, Szabolcs Mészáros, Christian Moni Bidin, David M. Nataf, Alexandre Roman-Lopes, Christian Nitschelm, Gail Zasowski

Comments: 18 pages, 10 figures, 3 tables. Re-submitted to MNRAS following moderate revisions

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

The advent of large surveys is making possible the unravelling of the mass assembly history of the Milky Way. Studies of the kinematics and chemical compositions of Galactic globular clusters (GCs) enable the reconstruction of the history of star formation, chemical evolution, and mass assembly of the Galaxy. Using the latest data release (DR16) of the SDSS/APOGEE survey, we identify 3,090 stars associated with 46 GCs. Using a previously defined kinematic association, we break the sample down into eight separate groups and examine how the kinematics-based classification maps into chemical composition space, considering only $\alpha$ (mostly Si and Mg) elements and Fe. Our results show that: (i) The loci of both \textit{in situ} and accreted subgroups in chemical space match those of their field counterparts; (ii) GCs from different individual accreted subgroups occupy the same locus in chemical space. This could either mean that they share a similar origin or that they are associated with distinct satellites which underwent similar chemical enrichment histories; (iii) The chemical compositions of the GCs associated with the low orbital energy subgroup defined by Massari and collaborators is broadly consistent with an \textit{in situ} origin. However, at the low metallicity end, the distinction between accreted and \textit{in situ} populations is blurred; (iv) Regarding the status of GCs whose origin is ambiguous, we conclude the following: the position in Si-Fe plane suggests an \textit{in situ} origin for Liller 1 and a likely accreted origin for NGC 5904 and NGC 6388. The case of NGC 288 is unclear, as its orbital properties suggest an accretion origin, its chemical composition suggests it may have formed {\it in situ}.

[4]  arXiv:2001.03178 [pdf, other]

Title: Growing Pains: The Formation Times and Building Blocks of Milky Way-mass Galaxies in the FIRE Simulations

Authors: Isaiah B. Santistevan, Andrew Wetzel, Kareem El-Badry, Joss Bland-Hawthorn, Michael Boylan-Kolchin, Jeremy Bailin, Claude-Andre Faucher-Giguere, Samantha Benincasa

Comments: 18 pages, 8 figures, submitted to MNRAS

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

Surveys of the Milky Way (MW) and M31 enable detailed studies of stellar populations across ages and metallicities, with the goal of reconstructing formation histories across cosmic time. These surveys motivate key questions for galactic archaeology in a cosmological context: when did the main progenitor of a MW/M31-mass galaxy form, and what were the galactic building blocks that formed it? We investigate the formation times and progenitor galaxies of MW/M31-mass galaxies using the FIRE-2 cosmological simulations, including 6 isolated MW/M31-mass galaxies and 6 galaxies in Local Group (LG)-like pairs at z = 0. We examine main progenitor "formation" based on two metrics: (1) transition from primarily ex-situ to in-situ stellar mass growth and (2) mass dominance compared to other progenitors. We find that the main progenitor of a MW/M31-mass galaxy emerged typically at z ~ 3-4 (11.6-12.2 Gyr ago), while stars in the bulge region (inner 2 kpc) at z = 0 formed primarily in a single main progenitor at z < 5 (< 12.6 Gyr ago). Compared with isolated hosts, the main progenitors of LG-like paired hosts emerged significantly earlier (\Delta z ~ 2, \Delta t ~ 1.6 Gyr), with ~ 4x higher stellar mass at all z > 4 (> 12.2 Gyr ago). This highlights the importance of environment in MW/M31-mass galaxy formation, especially at early times. Overall, about 100 galaxies with M_star > 10^5 M_sun formed a typical MW/M31-mass system. Thus, surviving satellites represent a highly incomplete census (by ~ 5x) of the progenitor population.

[5]  arXiv:2001.03179 [pdf, other]

Title: The Gaia-ESO Survey: a new approach to chemically characterising young open clusters

Authors: M. Baratella, V. D'Orazi, G. Carraro, S. Desidera, S. Randich, L. Magrini, V. Adibekyan, R. Smiljanic, L. Spina, M. Tsantaki, G. Tautvaisiene, S. G. Sousa, P. Jofré, F. M. Jiménes-Esteban, E. Delgado-Mena, S. Martell, M. Van der Swaelmen, V. Roccatagliata, G. Gilmore, E. J. Alfaro, A. Bayo, T. Bensby, A. Bragaglia, E. Franciosini, A. Gonneau, U. Heiter, A. Hourihane, R. D. Jeffries, S. E. Koposov, L. Morbidelli, L. Prisinzano, G. Sacco, L. Sbordone, C. Worley, S. Zaggia, J. Lewis

Comments: 16 pages, 11 figures, accepted by A&A

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

Open clusters (OCs) are recognised as excellent tracers of Galactic thin-disc properties. At variance with intermediate-age and old OCs, for which a significant number of studies is now available, clusters younger than 150 Myr have been mostly overlooked in terms of their chemical composition, with few exceptions. On the other hand, previous investigations seem to indicate an anomalous behaviour of young clusters, which includes slightly sub-solar iron (Fe) abundances and extreme, unexpectedly high barium (Ba) enhancements. In a series of papers, we plan to expand our understanding of this topic and investigate whether these chemical peculiarities are instead related to abundance analysis techniques. We present a new determination of the atmospheric parameters for 23 dwarf stars observed by the Gaia-ESO survey in five young OCs (younger than 150 Myr) and one star-forming region (NGC 2264). We exploit a new method based on titanium (Ti) lines to derive the spectroscopic surface gravity, and most importantly, the microturbulence parameter. A combination of Ti I and Fe I lines is used to obtain effective temperatures. We also infer the abundances of Fe II, Ti II, Na I, Mg I, Al I, Si I, Ca I, Cr I and Ni I. Our findings are in fair agreement with Gaia-ESO iDR5 results for effective temperatures and surface gravities, but suggest that for very young stars, the microturbulence parameter is over-estimated when Fe lines are employed. This affects the derived chemical composition and causes the metal content of very young clusters to be under-estimated. Our clusters display a metallicity [Fe/H] between +0.04 and +0.12; they are not more metal poor than the Sun. Although based on a relatively small sample size, our explorative study suggests that we may not need to call for ad hoc explanations to reconcile the chemical composition of young OCs with Galactic chemical evolution models.

[6]  arXiv:2001.03180 [pdf, other]

Title: MSTAR -- a fast parallelised algorithmically regularised integrator with minimum spanning tree coordinates

Authors: Antti Rantala, Pauli Pihajoki, Matias Mannerkoski, Peter H. Johansson, Thorsten Naab

Comments: 20 pages, 16 figures, accepted for publication in MNRAS

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

We present the novel algorithmically regularised integration method MSTAR for high accuracy ($|\Delta E/E| \gtrsim 10^{-14}$) integrations of N-body systems using minimum spanning tree coordinates. The two-fold parallelisation of the $\mathcal{O}(N_\mathrm{part}^2)$ force loops and the substep divisions of the extrapolation method allows for a parallel scaling up to $N_\mathrm{CPU} = 0.2 \times N_\mathrm{part}$. The efficient parallel scaling of MSTAR makes the accurate integration of much larger particle numbers possible compared to the traditional algorithmic regularisation chain (AR-CHAIN) methods, e.g. $N_\mathrm{part} = 5000$ particles on $400$ CPUs for $1$ Gyr in a few weeks of wall-clock time. We present applications of MSTAR on few particle systems, studying the Kozai mechanism and N-body systems like star clusters with up to $N_\mathrm{part} =10^4$ particles. Combined with a tree or a fast multipole based integrator the high performance of MSTAR removes a major computational bottleneck in simulations with regularised subsystems. It will enable the next generation galactic-scale simulations with up to $10^9$ stellar particles (e.g. $m_\star = 100 M_\odot$ for a $M_\star = 10^{11} M_\odot$ galaxy) including accurate collisional dynamics in the vicinity of nuclear supermassive black holes.

[7]  arXiv:2001.03181 [pdf, other]

Title: The Dust Attenuation Law in Galaxies

Authors: Samir Salim, Desika Narayanan

Comments: To be published in Annual Reviews of Astronomy and Astrophysics

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

Understanding the properties and physical mechanisms that shape dust attenuation curves in galaxies is one of the fundamental questions of extragalactic astrophysics, with a great practical significance for deriving the physical properties of galaxies, such as the star formation rate and stellar mass. Attenuation curves result from a combination of dust grain properties, dust content, and the spatial arrangement of dust and different populations of stars. In this review we assess the current state of the field, paying particular attention to the importance of extinction curves as the building blocks of attenuation laws. We introduce a quantitative framework to characterize and compare extinction and attenuation curves, present a theoretical foundation for interpreting empirical results, overview an array of observational methods, and review the observational state of the field at both low and high redshift. Our main conclusions are: Attenuation curves exhibit a large range of slopes, from curves with shallow (Milky Way-like) slopes to those exceeding the slope of the SMC extinction curve. The slopes of the curves correlate strongly with the effective optical opacities, in the sense that galaxies with low dust column density (lower visual attenuation) tend to have steeper slopes, whereas the galaxies with high dust column density have shallower (grey) slopes. Galaxies appear to exhibit a diverse range of 2175A UV bump strengths, but on average have suppressed bumps compared to the average Milky Way extinction curve. Theoretical studies indicate that variations in bump strength may result from similar geometric and radiative transfer effects that drive the correlation between the slope and the dust column.

[8]  arXiv:2001.03184 [pdf, other]

Title: Gamma-ray observations of low-luminosity active galactic nuclei

Authors: Raniere de Menezes, Rodrigo Nemmen, Justin D. Finke, Ivan Almeida, Bindu Rani

Comments: 12 pages, 4 figures

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

The majority of the activity around nearby (z ~ 0) supermassive black holes is found in low-luminosity active galactic nuclei (LLAGN), the most of them being classified as low ionization nuclear emission regions. Although these sources are well studied from radio up to X-rays, they are poorly understood in gamma-rays. In this work we take advantage of the all sky-surveying capabilities of the Large Area Telescope on board Fermi Gamma ray Space Telescope to study the whole Palomar sample of LLAGN in gamma-rays. Precisely, the four radio-brightest LLAGN in the sample are identified as significant gamma-ray emitters, all of which are recognized as powerful Fanaroff-Riley I galaxies. These results suggest that the presence of powerful radio jets is of substantial importance for observing a significant gamma-ray counterpart even if these jets are misaligned with respect to the line of sight. We also find that most of the X-ray-brightest LLAGN do not have a significant gamma-ray and strong radio emission, suggesting that the X-rays come mainly from the accretion flow in these cases. A detailed analysis of the spectral energy distributions (SEDs) of NGC 315 and NGC 4261, both detected in gamma-rays, is provided where we make a detailed comparison between the predicted hadronic gamma-ray emission from a radiatively inefficient accretion flow (RIAF) and the gamma-ray emission from a leptonic jet-dominated synchrotron self-Compton (SSC) model. Both SEDs are better described by the SSC model while the RIAF fails to explain the gamma-ray observations.

[9]  arXiv:2001.03209 [pdf, other]

Title: Internal structure of superclusters of galaxies from pattern recognition techniques

Authors: I. Santiago-Bautista, C. A. Caretta, H. Bravo-Alfaro, E. Pointecouteau, F. Madrigal

Comments: Proceedings of The Conference of Computational Interdisciplinary Science (CCIS 2019), Atlanta (GA) USA, Georgia Tech - School of Physics, March 19th - 22th, 2019, 13 pages, 15 figures

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

The Large-Scale Structure (LSS) of the Universe is a homogeneous network of galaxies separated in dense complexes, the superclusters of galaxies, and almost empty voids. The superclusters are young structures that did not have time to evolve into dynamically relaxed systems through the age of the Universe. Internally, they are very irregular, with dense cores, filaments and peripheral systems of galaxies. We propose a methodology to map the internal structure of superclusters of galaxies using pattern recognition techniques. Our approach allows to: i) identify groups and clusters in the LSS distribution of galaxies; ii) correct for the "fingers of God" projection effect, caused by the partial knowledge of the third space coordinate; iii) detect filaments of galaxies and trace their skeletons. In this paper, we present the algorithms, discuss the optimization of the free parameters and evaluate the results of its application. With this methodology, we have mapped the internal structure of 42 superclusters in the nearby universe (up to $z=0.15$).

[10]  arXiv:2001.03214 [pdf, other]

Title: NuSTAR observations of the Transient Galactic Black Hole Binary Candidate Swift J1858.6-0814: A New Sibling of V404 Cyg and V4641 Sgr?

Authors: Jeremy Hare, John A. Tomsick, Douglas J. K. Buisson, Maica Clavel, Poshak Gandhi, Javier A. Garcia, Brian W. Grefenstette, Dominic J. Walton, Yanjun Xu

Comments: Accepted for publication in the Astrophysical Journal

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

Swift J1858.6-0814 was discovered by Swift-BAT on October 25, 2018. Here we report on the first follow-up NuSTAR observation of the source, which shows variability spanning two orders of magnitude in count rate on timescales of ~10-100 s. The power-spectrum of the source does not show any quasi-periodic oscillations or periodicity, but has a large fractional rms amplitude of 147%$\pm3$%, exhibiting a number of large flares throughout the observation. The hardness ratio (defined as $R_{10-79 \rm keV}/R_{3-10 \rm keV}$) of the flares tends to be soft, while the source spans a range of hardness ratios during non-flaring periods. The X-ray spectrum of the source shows strong reflection features, which become more narrow and peaked during the non-flaring intervals. We fit an absorbed relativistic reflection model to the source spectra to place physical constraints on the system. Most notably, we find that the source exhibits a large and varying intrinsic absorbing column density ($N_{\rm H}=1.4-4.2\times10^{23}$ cm$^{-2}$). This large intrinsic absorption is further supported by the energy spectra extracted from two flares observed simultaneously by NuSTAR and NICER. We find that the inner accretion disk of the source has a low inclination, $i<29^{\circ}$ ( 3$\sigma$ upper-limit), while the iron abundance in the disk is close to solar, $A_{\rm Fe}=1.0\pm0.3$. We set a 90% confidence upper limit on the inner radius of the accretion disk of $r_{\rm in}<8 \ r_{\rm ISCO}$, and, by fixing $r_{\rm in}$ to be at $r_{\rm ISCO}$, a 90% confidence lower-limit on the spin of the black hole of $a^{*}>0.0$. Lastly, we compare the properties of Swift J1858.6$-$0814 to those of V404 Cygni and V4641 Sgr, which both show rapid flaring and a strong and variable absorption.

[11]  arXiv:2001.03223 [pdf, other]

Title: Investigation of Deferred Charge Effects in LSST ITL Sensors

Authors: Adam Snyder, Aaron Roodman

Comments: 12 pages, 7 figures; published in JATIS

Journal-ref: J. Astron. Telesc. Instrum. Syst. 5(4), 041509 (2019)

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

The traditional characterization of charge transfer inefficiency (CTI) in charge-coupled devices (CCDs) can suffer from a number of deficiencies: CTI is often only calculated for a limited number of signal levels, CTI is calculated from a limited number of pixels, and the sources of CTI are usually assumed to occur at every pixel-to-pixel transfer. A number of serial CTI effects have been identified during preliminary testing of CCDs developed by Imaging Technology Laboratory (ITL) for use in the Large Synoptic Survey Telescope (LSST) camera focal plane that motivate additional study beyond the traditional CTI characterization. This study describes a more detailed examination of the serial deferred charge effects in order to fully characterize the deferred charge measured in the serial overscan pixels of these sensors. The results indicate that in addition to proportional CTI loss that occurs at each pixel transfer, ITL CCDs have additional contributions to the deferred charge measured in serial overscan pixels, likely caused by fixed CTI loss due to charge trapping, and an electronic offset drift at high signal.

[12]  arXiv:2001.03234 [pdf, other]

Title: Tidal Disruptions of Main Sequence Stars -- V. The Varieties of Disruptions

Authors: Julian Krolik, Tsvi Piran, Taeho Ryu

Comments: 10 pages, 2 figures, comments welcome!

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

Tidal disruption events (TDEs), events in which a star passes very close to a supermassive black hole, are generally imagined as leading either to the star's complete disruption or to its passage directly into the black hole. In the former case it is widely believed that in all cases the bound portion of the debris quickly "circularizes" due to relativistic apsidal precession, i.e., forms a compact accretion disk, and emits a flare of standardized lightcurve and spectrum. We show here that TDEs are more diverse and can be grouped into several distinct categories on the basis of stellar pericenter distance $r_p$; we calculate the relative frequency of these categories. In particular, because rapid circularization requires $r_p \lesssim 10r_g$ ($r_g \equiv GM_{\rm BH}/c^2$), it can happen in only a minority of total disruptions, $\lesssim 1/4$ when the black hole has mass $M_{\rm BH} = 10^6 M_\odot$. For larger pericenter distances, $10 < r_p/r_g < 27$ (for $M_{\rm BH}=10^6M_\odot$), main sequence stars are completely disrupted, but the bound debris orbits are highly eccentric and possess semimajor axes $\sim 100\times$ the scale of the expected compact disk. Partial disruptions with fractional mass-loss $\gtrsim 10\%$ should occur with a rate similar to that of total disruptions; for fractional mass-loss $\gtrsim 50\%$, the rate is $\approx 1/3$ as large. Partial disruptions---which must precede total disruptions when the stars' angular momenta evolve in the "empty loss-cone" regime---change the orbital energy by factors $\gtrsim O(1)$. Remnants of partial disruptions are in general far from thermal equilibrium. Depending on the orbital energy of the remnant and conditions within the stellar cluster surrounding the SMBH, it may return after hundreds or thousands of years and be fully disrupted, or it may rejoin the stellar cluster.

[13]  arXiv:2001.03235 [pdf, other]

Title: Berkeley Supernova Ia Program: Data Release of 637 Spectra from 247 Type Ia Supernovae

Authors: Benjamin E. Stahl, WeiKang Zheng, Thomas de Jaeger, Thomas G. Brink, Alexei V. Filippenko, Jeffrey M. Silverman, S. Bradley Cenko, Kelsey I. Clubb, Melissa L. Graham, Goni Halevi, Patrick L. Kelly, Io Kleiser, Isaac Shivvers, Heechan Yuk, Bethany E. Cobb, Ori D. Fox, Michael T. Kandrashoff, Jason J. Kong, Jon C. Mauerhan, Xianggao Wang, Xiaofeng Wang

Comments: 22 pages, 9 figures, accepted for publication in MNRAS

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

We present 637 low-redshift optical spectra collected by the Berkeley Supernova Ia Program (BSNIP) between 2009 and 2018, almost entirely with the Kast double spectrograph on the Shane 3~m telescope at Lick Observatory. We describe our automated spectral classification scheme and arrive at a final set of 626 spectra (of 242 objects) that are unambiguously classified as belonging to Type Ia supernovae (SNe~Ia). Of these, 70 spectra of 30 objects are classified as spectroscopically peculiar (i.e., not matching the spectral signatures of "normal" SNe~Ia) and 79 SNe~Ia (covered by 328 spectra) have complementary photometric coverage. The median SN in our final set has one epoch of spectroscopy, has a redshift of 0.0208 (with a low of 0.0007 and high of 0.1921), and is first observed spectroscopically 1.1 days after maximum light. The constituent spectra are of high quality, with a median signal-to-noise ratio of 31.8 pixel$^{-1}$, and have broad wavelength coverage, with $\sim 95\%$ covering at least 3700--9800~\AA. We analyze our dataset, focusing on quantitative measurements (e.g., velocities, pseudo-equivalent widths) of the evolution of prominent spectral features in the available early-time and late-time spectra. The data are available to the community, and we encourage future studies to incorporate our spectra in their analyses.

[14]  arXiv:2001.03276 [pdf, other]

Title: Studying Anisotropy of Compressible Magnetohydrodynamic Turbulence by Synchrotron Polarization Intensity

Authors: Ru-Yue Wang, Jian-Fu Zhang, Fu-Yuan Xiang (Xiangtan Univ.)

Comments: 13 pages with 12 Figures and 1 Table. Accepted by ApJ

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

Based on statistical analysis of synchrotron polarization intensity, we study the anisotropic properties of compressible magnetohydrodynamic (MHD) turbulence. The second-order normalized structure function, quadrupole ratio modulus and anisotropic coefficient are synergistically used to characterize the anisotropy of the polarization intensity. On the basis of pre-decomposition data cubes, we first explore the anisotropy of the polarization intensity in different turbulence regimes and find that the most significant anisotropy occurs in the sub-Alfv\'enic regime. Using post-decomposition data cubes in this regime, we then study the anisotropy of the polarization intensity from Alfv\'en, slow and fast modes. Statistics of polarization intensity from Alfv\'en and slow modes demonstrate the significant anisotropy while statistics of polarization intensity from fast modes show isotropic structures, which is consistent with the earlier results provided in Cho & Lazarian (2002). As a result, both quadrupole ratio modulus and anisotropic coefficient for polarization intensities can quantitatively recover the anisotropy of underlying compressible MHD turbulence. The synergistic use of the two methods helps enhance the reliability of the magnetic field measurement.

[15]  arXiv:2001.03307 [pdf]

Title: Single Shot Spectroscopic Design Aspects

Authors: Harsh Mathur

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

High time cadence Spectro Polarimetry allows the feasibility of studying magnetic field evolution coupled with the plasma flows. Such a high cadence solar spectropolarimetry if developed will allow one to study magnetic field evolution in eruptive processes like solar flares, prominence eruptions, etc. A single shot solar spectroscopy was recently demonstrated at Multi Application Solar Telescope (MAST) at Udaipur Solar Observatory. The snapshot spectroscopy is performed by sampling the pupil plane using the lenslet array to get multiple images of the field of view (FOV), which are then collimated and the collimated beam is made to pass through an FP Etalon in collimated mode. As the distance from the FP axis increases, the peak transmitted wavelength shift towards the bluer side. Using a prefilter with a full width half maximum (FWHM) less than the free spectral range (FSR) of FP, combined with an imaging lens, we can get multiple images of FOV on image plane with a blue shift in spectra as we move radially outwards from the optical axis.

[16]  arXiv:2001.03315 [pdf, other]

Title: Atomic carbon, nitrogen, and oxygen forbidden emission lines in the water-poor comet C/2016 R2 (Pan-STARRS)

Authors: S. Raghuram, D. Hutsemékers, C. Opitom, E. Jehin, A. Bhardwaj, J. Manfroid

Comments: 15 pages,11 Figures, 7 Tables

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

The N$_2$ and CO-rich and water-depleted comet C/2016 R2 (Pan-STARRS) (hereafter `C/2016 R2') is a unique comet for detailed spectroscopic analysis. We aim to explore the associated photochemistry of parent species, which produces different metastable states and forbidden emissions, in this cometary coma of peculiar composition. We re-analyzed the high-resolution spectra of comet C/2016 R2, which were obtained in February 2018, using the UVES spectrograph of the European Southern Observatory (ESO) Very Large Telescope (VLT). Various forbidden atomic emission lines of [CI], [NI], and [OI] were observed in the optical spectrum of this comet when it was at 2.8 au from the Sun. The observed forbidden emission intensity ratios are studied in the framework of a couple-chemistry emission model. The model calculations show that CO$_2$ is the major source of both atomic oxygen green and red-doublet emissions in the coma of C/2016 R2 (while for most comets it is generally H$_2$O), whereas, CO and N$_2$ govern the atomic carbon and nitrogen emissions, respectively. Our modelled oxygen green to red-doublet and carbon to nitrogen emission ratios are higher by a factor {of 3}, when compared to the observations. These discrepancies can be due to uncertainties associated with photon cross sections or unknown production/loss sources. Our modelled oxygen green to red-doublet emission ratio is close to the observations, when we consider an O$_2$ abundance with a production rate of 30\% relative to the CO production rate. The collisional quenching is not a significant loss process for N($^2$D) though its radiative lifetime is significant ($\sim$10 hrs). Hence, the observed [NI] doublet-emission ratio ([NI] 5198/5200) of 1.22, which is smaller than the terrestrial measurement by a factor {1.4}, is mainly due to the characteristic radiative decay of N($^2$D).

[17]  arXiv:2001.03335 [pdf, other]

Title: Nonaxisymmetric Hall instability: A key to understanding magnetars

Authors: Konstantinos N. Gourgouliatos, José A. Pons

Comments: 5 pages, 3 Figures, Published in Physical Review Research, Rapid Communication

Journal-ref: Phys. Rev. Research 1, 032049(R) (2019)

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

It is generally accepted that the non-linear, dynamical evolution of magnetic fields in the interior of neutron stars plays a key role in the explanation of the observed phenomenology. Understanding the transfer of energy between toroidal and poloidal components, or between different scales, is of particular relevance. In this letter, we present the first 3D simulations of the Hall instability in a neutron star crust, confirming its existence for typical magnetar conditions. We confront our results to estimates obtained by a linear perturbation analysis, which discards any interpretation as numerical instabilities and confirms its physical origin. Interestingly, the Hall instability creates locally strong magnetic structures that occasionally can make the crust yield to the magnetic stresses and generates coronal loops, similarly as solar coronal loops find their way out through the photosphere. This supports the viability of the mechanism, which has been proposed to explain magnetar outbursts.

[18]  arXiv:2001.03337 [pdf, other]

Title: Observational Constraints on the Common Envelope Phase

Authors: David Jones (IAC, Spain)

Comments: 29 pages, 8 figures. To appear in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds. Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-035562

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

The common envelope phase was first proposed more than forty years ago to explain the origins of evolved, close binaries like cataclysmic variables. It is now believed that the phase plays a critical role in the formation of a wide variety of other phenomena ranging from type Ia supernovae through to binary black holes, while common envelope mergers are likely responsible for a range of enigmatic transients and supernova imposters. Yet, despite its clear importance, the common envelope phase is still rather poorly understood. Here, we outline some of the basic principles involved, the remaining questions as well as some of the recent observational hints from common envelope phenomena - namely planetary nebulae and luminous red novae - which may lead to answering these open questions.

[19]  arXiv:2001.03348 [pdf, other]

Title: A first attempt to differentiate between modified gravity and modified inertia with galaxy rotation curves

Authors: Jonas Petersen, Federico Lelli

Comments: To be published in Astronomy & Astrophysics, 12 pages, 7 figures

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

The phenomenology of modified Newtonian dynamics (MOND) on galaxy scales may point to more fundamental theories of either modified gravity (MG) or modified inertia (MI). In this paper, we test the applicability of the global deep-MOND parameter $Q$ which is predicted to vary at the $10\%$ level between MG and MI theories. Using mock-observed analytical models of disk galaxies, we investigate several observational uncertainties, establish a set of quality requirements for actual galaxies, and derive systematic corrections in the determination of $Q$. Implementing our quality requirements to the SPARC database yields $15$ galaxies, which are close enough to the deep-MOND regime as well as having rotation curves that are sufficiently extended and sampled. For these galaxies, the average and median values of $Q$ seem to favor MG theories, albeit both MG and MI predictions are in agreement with the data within $1.5\sigma$. Improved precision in the determination of $Q$ can be obtained by measuring extended and finely-sampled rotation curves for a significant sample of extremely low-surface-brightness galaxies.

[20]  arXiv:2001.03370 [pdf, other]

Title: Detrending Exoplanetary Transit Light Curves with Long Short-Term Memory Networks

Authors: Mario Morvan, Nikolaos Nikolaou, Angelos Tsiaras, Ingo P. Waldmann

Comments: 12 pages, 10 figures, 4 tables, accepted for publication in The Astronomical Journal

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

The precise derivation of transit depths from transit light curves is a key component for measuring exoplanet transit spectra, and henceforth for the study of exoplanet atmospheres. However, it is still deeply affected by various kinds of systematic errors and noise. In this paper we propose a new detrending method by reconstructing the stellar flux baseline during transit time. We train a probabilistic Long Short-Term Memory (LSTM) network to predict the next data point of the light curve during the out-of-transit, and use this model to reconstruct a transit-free light curve - i.e. including only the systematics - during the in-transit. By making no assumption about the instrument, and using only the transit ephemeris, this provides a general way to correct the systematics and perform a subsequent transit fit. The name of the proposed model is TLCD-LSTM, standing for Transit Light Curve Detrending LSTM. Here we present the first results on data from six transit observations of HD 189733b with the IRAC camera on board the Spitzer Space Telescope, and discuss some of its possible further applications.

[21]  arXiv:2001.03379 [pdf, other]

Title: The peculiar emission line spectra of core-Extremely Red BOSS Quasars at $z\sim$2-3: orientation and/or evolution?

Authors: Montse Villar Martin, Michele Perna, Andrew Humphrey, Nieves Castro Rodriguez, Luc Binette, Pablo Perez Gonzalez, Silvia Mateos, Antonio Cabrera Lavers

Comments: 23 pages, 10 figures. Accepted for publication in A&A

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

Core-extremely red quasars (core-ERQ) have been proposed to represent an intermediate evolutionary phase in which a heavily obscured quasar is blowing out the circumnuclear interstellar medium with very energetic outflows prior to becoming an optical quasar. We revise the general UV and optical emission line properties of core-ERQ in the context of the AGN orientation-based unification scenario. We use diagnostic diagrams based on ultraviolet (UV) emission line ratios and UV-optical line kinematic information to compare the physical and kinematic gas properties of core-ERQ with those of other luminous narrow and broad line AGN. In particular, we provide a revised comparison of the [OIII] kinematics in 21 core-ERQ with other samples of quasars matched in luminosity with the aim of evaluating whether core-ERQ host the most extreme [OIII] outflows.
The UV line ratios suggest that the physical properties (for instance, density, metallicity) of the ionised gas in core-ERQ are similar to those observed in the BLR of blue Nitrogen-loud QSOs. The [OIII] outflow velocities of core-ERQ are, on average, consistent with those of very luminous blue QSO1, although extreme outflows are much more frequent in core-ERQ. These similarities can be explained in the context of the AGN unification model, assuming that core-ERQ are viewed with an intermediate orientation between type 2 (edge-on) and type 1 (face-on) QSOs. We propose that core-ERQ are very luminous but otherwise normal quasars viewed at an intermediate orientation. Such orientation allows a direct view of the outer part of the large BLR, from which core-ERQ UV emission originates; the extreme [OIII] outflow velocities are instead a consequence of the very high luminosity of core-ERQ.

[22]  arXiv:2001.03385 [pdf, ps, other]

Title: Faint and fading tails : the fate of stripped HI gas in Virgo cluster galaxies

Authors: Rhys Taylor, Joachim Köppen, Pavel Jáchym, Robert Minchin, Jan Palouš, Richard Wünsch

Comments: Accepted for publication in AJ. 15 pages, 10 figures, 3 tables (plus 10 page appendix with 18 figures)

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

Although many galaxies in the Virgo cluster are known to have lost significant amounts of HI gas, only about a dozen features are known where the HI extends significantly outside its parent galaxy. Previous numerical simulations have predicted that HI removed by ram pressure stripping should have column densities far in excess of the sensitivity limits of observational surveys. We construct a simple model to try and quantify how many streams we might expect to detect. This accounts for the expected random orientation of the streams in position and velocity space as well as the expected stream length and mass of stripped HI. Using archival data from the Arecibo Galaxy Environment Survey, we search for any streams which might previously have been missed in earlier analyses. We report the confident detection of ten streams as well as sixteen other less sure detections. We show that these well-match our analytic predictions for which galaxies should be actively losing gas, however the mass of the streams is typically far below the amount of missing HI in their parent galaxies, implying that a phase change and/or dispersal renders the gas undetectable. By estimating the orbital timescales we estimate that dissolution rates of 1-10 Msolar/yr are able to explain both the presence of a few long, massive streams and the greater number of shorter, less massive features.

[23]  arXiv:2001.03388 [pdf, other]

Title: Physical conditions and chemical abundances in photoionized nebulae from optical spectra

Authors: Jorge García-Rojas (Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, Dept. Astrofísica. Univ. La laguna, Tenerife, Spain)

Comments: Book Chapter. 31 pages. 6 Figures. Accepted for publication in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-035562

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

This chapter presents a review on the latest advances in the computation of physical conditions and chemical abundances of elements present in photoionized gas H II regions and planetary nebulae). The arrival of highly sensitive spectrographs attached to large telescopes and the development of more sophisticated and detailed atomic data calculations and ionization correction factors have helped to raise the number of ionic species studied in photoionized nebulae in the last years, as well as to reduce the uncertainties in the computed abundances. Special attention will be given to the detection of very faint lines such as heavy-element recombination lines of C, N and O in H II regions and planetary nebulae, and collisionally excited lines of neutron-capture elements (Z >30) in planetary nebulae.

[24]  arXiv:2001.03389 [pdf, other]

Title: Real-Time RFI Mitigation for the Apertif Radio Transient System

Authors: Alessio Sclocco, Dany Vohl, Rob V. van Nieuwpoort

Comments: 6 pages, 10 figures. To appear in Proceedings from the 2019 Radio Frequency Interference workshop (RFI 2019), Toulouse, France (23-26 September)

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

Current and upcoming radio telescopes are being designed with increasing sensitivity to detect new and mysterious radio sources of astrophysical origin. While this increased sensitivity improves the likelihood of discoveries, it also makes these instruments more susceptible to the deleterious effects of Radio Frequency Interference (RFI). The challenge posed by RFI is exacerbated by the high data-rates achieved by modern radio telescopes, which require real-time processing to keep up with the data. Furthermore, the high data-rates do not allow for permanent storage of observations at high resolution. Offline RFI mitigation is therefore not possible anymore. The real-time requirement makes RFI mitigation even more challenging because, on one side, the techniques used for mitigation need to be fast and simple, and on the other side they also need to be robust enough to cope with just a partial view of the data.
The Apertif Radio Transient System (ARTS) is the real-time, time-domain, transient detection instrument of the Westerbork Synthesis Radio Telescope (WSRT), processing 73 Gb of data per second. Even with a deep learning classifier, the ARTS pipeline requires state-of-the-art real-time RFI mitigation to reduce the number of false-positive detections. Our solution to this challenge is RFIm, a high-performance, open-source, tuned, and extensible RFI mitigation library. The goal of this library is to provide users with RFI mitigation routines that are designed to run in real-time on many-core accelerators, such as Graphics Processing Units, and that can be highly-tuned to achieve code and performance portability to different hardware platforms and scientific use-cases. Results on the ARTS show that we can achieve real-time RFI mitigation, with a minimal impact on the total execution time of the search pipeline, and considerably reduce the number of false-positives.

[25]  arXiv:2001.03413 [pdf, other]

Title: Chromospheric Heating by Acoustic Waves Compared to Radiative Cooling: II -- Revised Grid of Models

Authors: Vahid Abbasvand, Michal Sobotka, Petr Heinzel, Michal Svanda, Jan Jurcák, Dario del Moro, Francesco Berrilli

Comments: 9 pages, 8 figures

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

Acoustic and magnetoacoustic waves are considered to be possible agents of chromospheric heating. We present a comparison of deposited acoustic energy flux with total integrated radiative losses in the middle chromosphere of the quiet Sun and a weak plage. The comparison is based on a consistent set of high-resolution observations acquired by the IBIS instrument in the Ca II 854.2 nm line. The deposited acoustic-flux energy is derived from Doppler velocities observed in the line core and a set of 1737 non-LTE 1D hydrostatic semi-empirical models, which also provide the radiative losses. The models are obtained by scaling the temperature and column mass of five initial models VAL B-F to get the best fit of synthetic to observed profiles. We find that the deposited acoustic-flux energy in the quiet-Sun chromosphere balances 30-50 % of the energy released by radiation. In the plage, it contributes by 50-60 % in locations with vertical magnetic field and 70-90 % in regions where the magnetic field is inclined more than 50 degrees to the solar surface normal.

[26]  arXiv:2001.03422 [pdf, other]

Title: Electrodynamics and radiation from rotating neutron star magnetospheres

Authors: Jérôme Pétri

Comments: Accepted for publication in the journal Universe

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

Neutron stars are compact objects rotating at high speed, up to a substantial fraction of the speed of light (up to 20\% for millisecond pulsars) and possessing ultra-strong electromagnetic fields (close to and sometimes above the quantum critical field of \numprint{4.4e9}~\SIunits{\tesla}). Moreover, due to copious $e^\pm$ pair creation within the magnetosphere, the relativistic plasma surrounding the star is forced into corotation up to the light cylinder where the corotation speed reaches the speed of light. The neutron star electromagnetic activity is powered by its rotation which becomes relativistic in the neighbourhood of this light cylinder. These objects naturally induce relativistic rotation on macroscopic scales about several thousands of kilometers, a crucial ingredient to trigger the central engine as observed on Earth. In this paper, we elucidate some of the salient features of this corotating plasma subject to efficient particle acceleration and radiation, emphasizing several problems and limitations concerning current theories of neutron star magnetospheres. Relativistic rotation in these systems is indirectly probed by the radiation produced within the magnetosphere. Depending on the underlying assumptions about particle motion and radiation mechanisms, different signatures on their light-curves, spectra, pulse profiles and polarisation angles are expected in their broadband electromagnetic emission. We show that these measurements put stringent constraints on the way to describe particle electrodynamics in a rotating neutron star magnetosphere.

[27]  arXiv:2001.03424 [pdf, other]

Title: Vetting the optical transient candidates detected by the GWAC network using convolutional neural networks

Authors: Damien Turpin, M. Ganet, S. Antier, E. Bertin, L. P. Xin, N. Leroy, C. Wu, Y. Xu, X. H. Han, H. B. Cai, H. L. Li, X. M. Lu, J. Y. Wei

Comments: 12 pages, 8 figures, 5 tables

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

The observation of the transient sky through a multitude of astrophysical messengers hasled to several scientific breakthroughs these last two decades thanks to the fast evolution ofthe observational techniques and strategies employed by the astronomers. Now, it requiresto be able to coordinate multi-wavelength and multi-messenger follow-up campaign withinstruments both in space and on ground jointly capable of scanning a large fraction of thesky with a high imaging cadency and duty cycle. In the optical domain, the key challengeof the wide field of view telescopes covering tens to hundreds of square degrees is to dealwith the detection, the identification and the classification of hundreds to thousands of opticaltransient (OT) candidates every night in a reasonable amount of time. In the last decade, newautomated tools based on machine learning approaches have been developed to perform thosetasks with a low computing time and a high classification efficiency. In this paper, we presentan efficient classification method using Convolutional Neural Networks (CNN) to discard anybogus falsely detected in astrophysical images in the optical domain. We designed this toolto improve the performances of the OT detection pipeline of the Ground Wide field AngleCameras (GWAC) telescopes, a network of robotic telescopes aiming at monitoring the opticaltransient sky down to R=16 with a 15 seconds imaging cadency. We applied our trainedCNN classifier on a sample of 1472 GWAC OT candidates detected by the real-time detectionpipeline. It yields a good classification performance with 94% of well classified event and afalse positive rate of 4%.

[28]  arXiv:2001.03425 [pdf, other]

Title: Mass limits for stationary protoplanetary accretion disks

Authors: Florian Ragossnig, Lukas Gehrig, Ernst Dorfi, Daniel Steiner, Alexander Stökl

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

The collapse of interstellar gaseous clouds towards a protostar leads to the formation of accretion disks around the central star. Such disks can be dynamically stable if they settle in an axisymmetric state. In this letter, we investigate the long-term stability of astrophysical viscous disks around various protostars by utilizing an implicit numerical code which solves the equations of radiation hydrodynamics and treats turbulence-induced viscosity according to the $\alpha$-viscosity model. We show how the viscosity is related to the disk mass. A stability criterion to determine the maximum disk mass can be formulated. We analyse such instabilities for a variety of radial points with different orbital distances from the host star and discuss the feedback on the disk in the event of an unstable protoplanetary disk. Additionally, we examine the critical disk mass for disks with variable outer boundaries. We derive an easily applicable method to obtain an estimate for maximum disk masses when the outer disk radius ins known.

[29]  arXiv:2001.03450 [pdf, other]

Title: Arm-interarm gas abundance variations explored with MUSE: the role of spiral structure in the chemical enrichment of galaxies

Authors: Laura Sánchez-Menguiano, Sebastián F. Sánchez, Isabel Pérez, Tomás Ruiz-Lara, Lluís Galbany, Joseph P. Anderson, Hanindyo Kuncarayakti

Comments: 15 pages, 10 figures. Accepted for publication in MNRAS

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

Spiral arms are the most characteristic features of disc galaxies, easily distinguishable due to their association with ongoing star formation. However, the role of spiral structure in the chemical evolution of galaxies is unclear. Here we explore gas-phase abundance variations between arm and interarm regions for a sample of 45 spiral galaxies using high spatial resolution VLT/MUSE Integral Field Spectroscopy data. We report the presence of more metal-rich HII regions in the spiral arms with respect to the corresponding interarm regions for a large subsample of galaxies ($45-65\%$ depending on the adopted calibrator for the abundance derivation). A small percentage of the sample is observed to display the opposite trend, that is, more metal-poor HII regions in the spiral arms compared to that of the interarms ($5-20\%$ depending on the calibrator). We investigate the dependence of the variations with three galaxy properties: the stellar mass, the presence of bars, and the flocculent/grand design appearance of spiral arms. In all cases, we observe that the arm-interarm abundance differences are larger (positive) in more massive and grand-design galaxies. This is confirmed by an analogous spaxel-wise analysis, which also shows a noticeable effect of the presence of galactic bars, with barred systems presenting larger (positive) arm-interarm abundance variations than unbarred systems. The comparison of our results with new predictions from theoretical models exploring the nature of the spirals would highly impact on our knowledge on how these structures form and affect their host galaxies.

[30]  arXiv:2001.03470 [pdf, other]

Title: SPCANet: Stellar Parameters and Chemical Abundances Network for LAMOST-II Medium Resolution Survey

Authors: Rui Wang, A-Li Luo, Jian-Jun Chen, Wen Hou, Shuo Zhang, Yong-Heng Zhao, Xiang-Ru Li, Yong-Hui Hou, LAMOST MRS Collaboration

Comments: Accepted by ApJ, 16 pages, 14 figures, 2 tables

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

The fundamental stellar atmospheric parameters T_eff and log g and 13 chemical abundances are derived for medium-resolution spectroscopy from LAMOST Medium-Resolution Survey (MRS) data sets with a deep-learning method. The neural networks we designed, named as SPCANet, precisely map LAMOST MRS spectra to stellar parameters and chemical abundances. The stellar labels derived by SPCANet are with precisions of 119 K for T_eff and 0.17 dex for log g. The abundance precision of 11 elements including [C/H], [N/H], [O/H], [Mg/H], [Al/H], [Si/H], [S/H], [Ca/H], [Ti/H], [Cr/H], [Fe/H], and [Ni/H] are 0.06~0.12 dex, while of [Cu/H] is 0.19 dex. These precisions can be reached even for spectra with signal-to-noise as low as 10. The results of SPCANet are consistent with those from other surveys such as APOGEE, GALAH and RAVE, and are also validated with the previous literature values including clusters and field stars. The catalog of the estimated parameters is available at \url{this http URL}.

[31]  arXiv:2001.03476 [pdf, other]

Title: Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe

Authors: Vratislav Krupar, Adam Szabo, Milan Maksimovic, Oksana Kruparova, Eduard P. Kontar, Laura A. Balmaceda, Xavier Bonnin, Stuart D. Bale, Marc Pulupa, David M. Malaspina, John W. Bonnell, Peter R. Harvey, Keith Goetz, Thierry Dudok de Wit, Robert J. MacDowall, Justin C. Kasper, Anthony W. Case, Kelly E. Korreck, Davin E. Larson, Roberto Livi, Michael L. Stevens, Phyllis L. Whittlesey, Alexander M. Hegedus

Comments: 12 pages, 10 figures, accepted for publication in ApJS

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

Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted than the actual ones. Since the scattering depends on the spectrum of density turbulence, better understanding of the radio wave propagation provides indirect information on the relative density fluctuations $\epsilon=\langle\delta n\rangle/\langle n\rangle$ at the effective turbulence scale length. Here, we have analyzed 30 type III bursts detected by Parker Solar Probe (PSP). For the first time, we have retrieved type III burst decay times $\tau_{\rm{d}}$ between 1 MHz and 10 MHz thanks to an unparalleled temporal resolution of PSP. We observed a significant deviation in a power-law slope for frequencies above 1 MHz when compared to previous measurements below 1 MHz by the twin-spacecraft Solar TErrestrial RElations Observatory (STEREO) mission. We note that altitudes of radio bursts generated at 1 MHz roughly coincide with an expected location of the Alfv\'{e}n point, where the solar wind becomes super-Alfv\'{e}nic. By comparing PSP observations and Monte Carlo simulations, we predict relative density fluctuations $\epsilon$ at the effective turbulence scale length at radial distances between 2.5$R_\odot$ and 14$R_\odot$ to range from $0.22$ and $0.09$. Finally, we calculated relative density fluctuations $\epsilon$ measured in situ by PSP at a radial distance from the Sun of $35.7$~$R_\odot$ during the perihelion \#1, and the perihelion \#2 to be $0.07$ and $0.06$, respectively. It is in a very good agreement with previous STEREO predictions ($\epsilon=0.06-0.07$) obtained by remote measurements of radio sources generated at this radial distance.

[32]  arXiv:2001.03484 [pdf, other]

Title: Near-ultraviolet detections of four dwarf nova candidates in the globular cluster 47 Tucanae

Authors: David Modiano, Aastha S. Parikh, Rudy Wijnands

Comments: 12 pages, 6 figures. Accepted to A&A on 15/12/2019

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

We investigate near-ultraviolet (NUV) variability in the Galactic globular cluster (GC) 47 Tucanae (47 Tuc). This work was undertaken within the GC sub-project of the Transient UV Objects project, a programme which aims to find and study transient and strongly variable UV sources. Globular clusters are ideal targets for transient searches because of their high stellar densities and large populations of variable systems. Using all archival observations of 47 Tuc obtained with the UV/optical telescope (UVOT) aboard the Neil Gehrels Swift observatory with the uvm2 filter, we searched for UV variability using a specialised pipeline which utilises difference image analysis. We found four clear transients, hereafter SW1-4, with positions consistent with those of known cataclysmic variables (CVs) or CV candidates identified previously using Hubble Space Telescope observations. All four sources exhibit significant outbursts. Based on the inferred outburst properties and the association with known CVs, we tentatively identify the UV transients as CV-dwarf novae (DNe). Two DNe have been previously observed in 47 Tuc: V2, which has a position consistent with that of SW4; and AKO 9, which was not in outburst during any of the UVOT observations. We thus increase the known number of DNe in 47 Tuc to 5 and the total number of detected DNe in all Galactic GCs combined from 14 to 17. We discuss our results in the context of the apparent scarcity of DNe in GCs. We suggest that the likely cause is observational biases, such as limited sensitivity due to the high background from unresolved stars in the GC and limited angular resolution of the telescopes used. We additionally detected one strongly variable source in 47 Tuc, which could be identified as the known RR Lyrae star HV 810. We found its period to have significantly increased with respect to that measured from data taken in 1988.

[33]  arXiv:2001.03497 [pdf, other]

Title: The prototype star $γ$ Doradus observed by TESS

Authors: S. Christophe, V. Antoci, E. Brunsden, R.-M. Ouazzani, S.J.A.J. Salmon

Comments: 2 pages, 2 figures, poster contribution at the conference "Stars and their variability observed from space - Celebrating the 5th anniversary of BRITE-Constellation", Vienna, Austria, August 19 - 23, 2019. Eds: C. Neiner, W. Weiss, D. Baade, E. Griffin, C. Lovekin, A. Moffat

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

$\gamma$ Doradus is the prototype star for the eponymous class of pulsating stars that consists of late A-early F main-sequence stars oscillating in low-frequency gravito-inertial modes. Being among the brightest stars of its kind (V = 4.2), $\gamma$ Dor benefits from a large set of observational data that has been recently completed by high-quality space photometry from the TESS mission. With these new data, we propose to study $\gamma$ Dor as an example of possibilities offered by synergies between multi-technical ground and space-based observations. Here, we present the preliminary results of our investigations.

[34]  arXiv:2001.03498 [pdf, ps, other]

Title: The Faint Host Galaxies of C IV Absorbers at z > 5

Authors: Kristian Finlator, Caitlin Doughty, Zheng Cai, Gonzalo Díaz

Comments: 15 pages, 16 figures, resubmitted to MNRAS with improvements following first referee report

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

We explore the expected galaxy environments of CIV absorbers at z>5 using the Technicolor Dawn simulations. These simulations reproduce the observed history of reionization, the z~6 galaxy stellar mass function, the Ly{\alpha} forest transmission at z>5, and the SiIV column density distribution (CDD) at z=5.5. Nonetheless, the CIV CDD remains underproduced. Comparison with observed CII/SiII equivalent width ratios and the CII line incidence suggests that a low carbon yield accounts for some, but not all, of the CIV discrepancy. Alternatively, a density-bounded escape scenario could harden the metagalactic ionizing background more dramatically even than binary stellar evolution, boosting the CIV CDD into near-agreement with observations. In this case galaxies ionize more efficiently and fewer are required to host a given high-ionization absorber. Absorbers' environments therefore constrain ionizing escape. Regardless of the escape scenario, galaxies correlate with CIV absorbers out to 300 proper kpc (pkpc). The correlation strengthens independently with galaxy luminosity and CIV column density. Around strong systems (log(N_CIV) > 14)), the overdensity of galaxies with M_UV < -18 or log(L_Ly{\alpha}) > 41.9 declines from 200-300 within 100 pkpc to 40-60 within 250 pkpc. The previously-suggested association between strong CIV absorbers and Ly{\alpha} emitters at z>5 is not expected. It may arise if both populations inhabit large-scale voids, but for different reasons. Although most neighboring galaxies are too faint for HST, JWST will, with a single pointing, identify ~10 neighboring galaxies per strong CIV absorber at z>5. Ground-based tests of these predictions are possible via deep surveys for Ly{\alpha} emission using integral field units.

[35]  arXiv:2001.03501 [pdf, other]

Title: Tidal Disruptions of Main Sequence Stars -- I. Observable Quantities and their Dependence on Stellar and Black Hole Mass

Authors: Taeho Ryu, Julian Krolik, Tsvi Piran, Scott C. Noble

Comments: 14 pages, 7 figures, comments welcome! Supersedes arXiv:1907.08205

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

This paper introduces a series of papers presenting a quantitative theory for the tidal disruption of main sequence stars by supermassive black holes. Using fully general relativistic hydrodynamics simulations and MESA-model initial conditions, we explore the pericenter-dependence of tidal disruption properties for eight stellar masses ($0.15 \leq M_*/M_\odot \leq 10$) and six black hole masses ($10^5 \leq M_{BH}/M_\odot \leq 5 \times 10^7$). We present here the results most relevant to observations. The effects of internal stellar structure and relativity decouple for both the disruption cross section and the characteristic energy width of the debris. Moreover, the full disruption cross section is almost independent of $M_*$ for $M_*/M_\odot \lesssim 3$. Independent of $M_*$, relativistic effects increase the critical pericenter distance for full disruptions by up to a factor $\sim 3$ relative to the Newtonian prediction. The probability of a direct capture is also independent of $M_*$; at $M_{BH}/M_\odot \simeq 5 \times 10^6$ this probability is equal to that of a complete disruption. The width of the debris energy distribution $\Delta E$ can differ from the standard estimate by factors from 0.35 to 2, depending on $M_*$ and $M_{BH}$, implying a corresponding change in the characteristic mass-return timescale. The "frozen-in approximation" is inconsistent with $\Delta E$, and mass-loss continues over a long span of time. We provide analytic forms, suitable for use in both event rate estimates and parameter inference, to describe all these trends. For partial disruptions, we find a nearly-universal relation between the star's angular momentum and the fraction of $M_*$ remaining. Within the "empty loss-cone" regime, partial disruptions must precede full disruptions. These partial disruptions can drastically affect the rate and appearance of subsequent total disruptions.

[36]  arXiv:2001.03502 [pdf, other]

Title: Tidal disruptions of main sequence stars -- II. Simulation methodology and stellar mass dependence of the character of full tidal disruptions

Authors: Taeho Ryu, Julian Krolik, Tsvi Piran, Scott C. Noble

Comments: 19 pages, 10 figures, 3 tables, comments welcome! Supersedes arXiv:1907.11883

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

This is the second in a series of papers presenting the results of fully general relativistic simulations of stellar tidal disruptions in which the stars' initial states are realistic main-sequence models. In the first paper (Paper I), we gave an overview of this program and discussed the principal observational implications of our work. Here we describe our calculational method and provide details about the outcomes of full disruptions, focusing on the stellar mass dependence of the outcomes for a black hole of mass $10^{6}\rm{M}_{\odot}$. We consider eight different stellar masses, from $0.15~{\rm M}_\odot$ to $10~{\rm M}_\odot$. We find that, relative to the traditional order-of-magnitude estimate $r_{\rm t}$, the physical tidal radius of low-mass stars ($M_{\star} \lesssim 0.7~ {\rm M}_\odot$) is larger by tens of percent, while for high-mass stars ($M_{\star} \gtrsim1~ {\rm M}_\odot$) it is smaller by a factor 2--2.5. The traditional estimate of the range of energies found in the debris is $\approx 1.4\times$ too large for low-mass stars, but is a factor $\sim 2$ too small for high-mass stars; in addition, the energy distribution for high-mass stars has significant wings. For all stars undergoing tidal encounters, we find that mass-loss continues for many stellar vibration times because the black hole's tidal gravity competes with the instantaneous stellar gravity at the star's surface until the star has reached a distance from the black hole $\sim O(10)r_{\rm t}$.

[37]  arXiv:2001.03503 [pdf, other]

Title: Tidal disruptions of main sequence stars -- III. Stellar mass dependence of the character of partial disruptions

Authors: Taeho Ryu, Julian Krolik, Tsvi Piran, Scott C. Noble

Comments: 14 pages, 8 figures, comments welcome! Supersedes arXiv:1909.04041

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

In this paper, the third in this series, we continue our study of tidal disruption events of main-sequence stars by a non-spinning $10^{6}~\rm{M}_\odot$ supermassive black hole. Here we focus on the stellar mass dependence of the outcomes of partial disruptions. As the encounter becomes weaker, the debris mass is increasingly concentrated near the outer edges of the energy distribution. As a result, the mass fallback rate can deviate substantially from a $t^{-5/3}$ power-law, becoming more like a single peak with a tail declining as $t^{-p}$ with $p\simeq2-5$. Surviving remnants are spun-up in the prograde direction and are hotter than main sequence stars of the same mass. Their specific orbital energy is $\simeq10^{-3}\times$ that of the debris, but of either sign with respect to the black hole potential, while their specific angular momentum is close to that of the original star. Even for strong encounters, remnants have speeds at infinity relative to the black hole potential $\lesssim 300$ km s$^{-1}$, so they are unable to travel far out into the galactic bulge. The remnants most deeply bound to the black hole go through a second tidal disruption event upon their first return to pericenter; if they have not thermally relaxed, they will be completely disrupted.

[38]  arXiv:2001.03504 [pdf, other]

Title: Tidal disruptions of main sequence stars -- IV. Relativistic effects and dependence on black hole mass

Authors: Taeho Ryu, Julian Krolik, Tsvi Piran, Scott C. Noble

Comments: 13 pages, 10 figures, 2 tables, comments welcome!

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

Using a suite of fully relativistic hydrodynamic simulations applied to main-sequence stars with realistic internal density profiles, we examine full and partial tidal disruptions across a wide range of black hole mass ($10^{5}\leq M_{\rm BH}/\mathrm{M}_{\odot}\leq 5\times 10^{7}$) and stellar mass ($0.3 \leq M_{\star} /\mathrm{M}_{\odot}\leq 3$) as larger $M_{\rm BH}$ leads to stronger relativistic effects. For fixed $M_{\star}$, as $M_{\rm BH}$ increases, the ratio of the maximum pericenter distance yielding full disruptions ($\mathcal{R}_{\rm t}$) to its Newtonian prediction rises rapidly, becoming triple the Newtonian value for $M_{\rm BH} = 5\times10^{7}~{\rm M}_\odot$, while the ratio of the energy width of the stellar debris for full disruptions to the Newtonian prediction decreases steeply, resulting in a factor of two correction at $M_{\rm BH} = 5 \times 10^7~{\rm M}_\odot$. We find that for partial disruptions, the fractional remnant mass for a given ratio of the pericenter to $\mathcal{R}_{\rm t}$ is higher for larger $M_{\rm BH}$. These results have several implications. As $M_{\rm BH}$ increases above $\sim 10^7~{\rm M}_\odot$, the cross section for complete disruptions is suppressed by competition with direct capture. However, the cross section ratio for partial to complete disruptions depends only weakly on $M_{\rm BH}$. The relativistic correction to the debris energy width delays the time of peak mass-return rate and diminishes the magnitude of the peak return rate. For $M_{\rm BH} \gtrsim 10^7~{\rm M}_\odot$, the $M_{\rm BH}$-dependence of the full disruption cross section and the peak mass-return rate and time is influenced more by relativistic effects than by Newtonian dynamics.

[39]  arXiv:2001.03516 [pdf]

Title: The effects of atmospheric entry heating on organic matter in interplanetary dust particles

Authors: My E.I. Riebe, Dionysis I. Foustoukos, Conel M.O'D. Alexander, Andrew Steele, George D. Cody, Bjorn Mysen, Larry R. Nittler

Comments: 31 pages, 6 figures. Submitted to Earth and Planetary Science Letters (EPSL)

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

Interplanetary dust particles (IDPs) were likely major sources of extraterrestrial organics to the early Earth. However, IDPs experience heating to > 500 ${\deg}$C for up to several seconds during atmospheric entry. In this study, we aim to understand the effects of atmospheric entry heating on the dominant organic component in IDPs by conducting flash heating experiments (4 s to 400 {\deg}C, 600 {\deg}C, 800 {\deg}C, and 1000 {\deg}C) on insoluble organic matter (IOM) extracted from the meteorite Cold Bokkeveld (CM2). For each of the experimental charges, the bulk isotopic compositions of H, N, and C were analyzed using IRMS, the H isotopic heterogeneities (occurrence of hotspots) of the samples were measured by NanoSIMS, and the functional group chemistry and ordering of the IOM was evaluated using FTIR and Raman spectroscopy, respectively. IOM in particles heated to > 600 {\deg}C experienced loss of isotopically heavy, labile H and N groups, resulting in decreases in bulk ${\delta}$D, ${\delta}$15N, H/C and, upon heating > 800 {\deg}C, in N/C. The H heterogeneity was not greatly affected by flash heating to < 600 {\deg}C, although the hotspots tended to be less isotopically anomalous in the 600 {\deg}C sample than in the 400 {\deg}C sample. However, the hotspots all but disappeared in the 800 {\deg}C sample. Loss of C=O groups occurred at 800 {\deg}C. Based on the Raman G-band characteristics, the heating resulted in increased ordering of the polyaromatic component of the IOM. The data presented in this study show that all aspects of the composition of IOM in IDPs are affected by atmospheric entry heating. Modelling and temperature estimates from stepwise release of He has shown that most IDPs are heated to > 500{\deg}C (Love and Brownlee, 1991; Nier and Schlutter, 1993), hence, atmospheric entry heating is expected to have altered the organic matter in most IDPs.

[40]  arXiv:2001.03522 [pdf, ps, other]

Title: VERITAS Detection of LS 5039 and HESS J1825-137

Authors: VERITAS Collaboration: A. U. Abeysekara (1), W. Benbow (2), R. Bird (3), R. Brose (4 and 5), J. L. Christiansen (6), A. J. Chromey (7), W. Cui (8 and 9), M. K. Daniel (2), A. Falcone (10), L. Fortson (11), D. Hanna (12), T. Hassan (5), O. Hervet (13), J. Holder (14), G. Hughes (2), T. B. Humensky (15), P. Kaaret (16), P. Kar (1), N. Kelley-Hoskins (5), M. Kertzman (17), D. Kieda (1), M. Krause (5), M. J. Lang (18), G. Maier (5), P. Moriarty (18), D. Nieto (19), M. Nievas-Rosillo (e), R. A. Ong (3), D. Pandel (20), M. Pohl (4 and 5), R. R. Prado (5), E. Pueschel (5), J. Quinn (21), K. Ragan (12), P. T. Reynolds (22), G. T. Richards (14), E. Roache (2), I. Sadeh (5), M. Santander (23), G. H. Sembroski (8), A. Weinstein (7), P. Wilcox (16), D. A. Williams (13), T. J Williamson (14) ((1) Department of Physics and Astronomy, University of Utah, Salt Lake City, UT, USA, (2) Center for Astrophysics j Harvard & Smithsonian, Cambridge, MA, USA, (3) Department of Physics and Astronomy, University of California, Los Angeles, CA, USA, (4) Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany, (5) DESY, Platanenallee 6, 15738 Zeuthen, Germany, (6) Physics Department, California Polytechnic State University, San Luis Obispo, CA, USA, (7) Department of Physics and Astronomy, Iowa State University, Ames, IA, USA, (8) Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA, (9) Department of Physics and Center for Astrophysics, Tsinghua University, Beijing, China, (10) Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA, USA, (11) School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA, (12) Physics Department, McGill University, Montreal, Canada, (13) Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA, USA, (14) Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE, USA, (15) Physics Department, Columbia University, New York, NY, USA, (16) Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA, USA, (17) Department of Physics and Astronomy, DePauw University, Greencastle, IN, USA, (18) School of Physics, National University of Ireland Galway, University Road, Galway, Ireland, (19) Institute of Particle and Cosmos Physics, Universidad Complutense de Madrid, Madrid, Spain, (20) Department of Physics, Grand Valley State University, Allendale, MI, USA, (21) School of Physics, University College Dublin, Belfield, Dublin 4, Ireland, (22) Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland, (23) Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL, USA)

Comments: 4 pages, 2 figures

Journal-ref: Astroparticle Physics (2020), Volume 117, article id. 102403

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

With 8 hours of observations, VERITAS confirms the detection of two very high energy gamma-ray sources. The gamma-ray binary LS 5039 is detected with a statistical significance of $8.8\sigma$. The measured flux above 1 TeV is $(2.5 \pm 0.4) \times 10^{-12} \rm \, cm^{-2} \, s^{-1}$ near inferior conjunction and $(7.8 \pm 2.8) \times 10^{-13} \rm \, cm^{-2} \, s^{-1}$ near superior conjunction. The pulsar wind nebula HESS J1825-137 is detected with a statistical significance of $6.7\sigma$ and a measured flux above 1 TeV of $(3.9 \pm 0.8) \times 10^{-12} \rm \, cm^{-2} \, s^{-1}$.

[41]  arXiv:2001.03524 [pdf, other]

Title: In-Flight Performance and Calibration of the LOng Range Reconnaissance Imager (LORRI) for the New Horizons Mission

Authors: H. A. Weaver, A. F. Cheng, F. Morgan, H. W. Taylor, S. J. Conard, J. I. Nunez, D. J. Rodgers, T. R. Lauer, W. M. Owen, J. R. Spencer, O. Barnouin, A. S. Rivkin, C. B. Olkin, S. A. Stern, L. A. Young, M. B. Tapley, M. Vincent

Comments: Accepted by PASP, January 2020

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

The LOng Range Reconnaissance Imager (LORRI) is a panchromatic (360--910 nm), narrow-angle (field of view = 0.29 deg), high spatial resolution (pixel scale = 1.02 arcsec) visible light imager used on NASA's New Horizons (NH) mission for both science observations and optical navigation. Calibration observations began several months after the NH launch on 2006 January 19 and have been repeated annually throughout the course of the mission, which is ongoing. This paper describes the in-flight LORRI calibration measurements, and the results derived from our analysis of the calibration data. LORRI has been remarkably stable over time with no detectable changes (at the 1% level) in sensitivity or optical performance since launch. By employing 4 by 4 re-binning of the CCD pixels during read out, a special spacecraft tracking mode, exposure times of 30 sec, and co-addition of approximately 100 images, LORRI can detect unresolved targets down to V = 22 (SNR=5). LORRI images have an instantaneous dynamic range of 3500, which combined with exposure time control ranging from 0ms to 64,967 ms in 1ms steps supports high resolution, high sensitivity imaging of planetary targets spanning heliocentric distances from Jupiter to deep in the Kuiper belt, enabling a wide variety of scientific investigations. We describe here how to transform LORRI images from raw (engineering) units into scientific (calibrated) units for both resolved and unresolved targets. We also describe various instrumental artifacts that could affect the interpretation of LORRI images under some observing circumstances.

[42]  arXiv:2001.03550 [pdf]

Title: Debiased albedo distribution for Near Earth Objects

Authors: Alessandro Morbidelli, Marco Delbo, Mikael Granvik, William F. Bottke, Robert Jedicke, Bryce Bolin, Patrick Michel, David Vokrouhlický

Comments: In press in Icarus

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

We extend the most recent orbital and absolute magnitude Near Earth Object (NEO) model (Granvik et al., 2018) to provide a statistical description of NEO geometric albedos. Our model is calibrated on NEOWISE albedo data for the NEO population and reproduces these data very well once a simple model for the NEOWISE observational biases is applied. The results are consistent with previous estimates. There are about 1,000 NEOs with diameter D>1km and the mean albedo to convert absolute magnitude into diameter is 0.147. We do not find any statistically significant evidence that the albedo distribution of NEOs depends on NEO size. Instead, we find evidence that the disruption of NEOs at small perihelion distances found in Granvik et al. (2016) occurs preferentially for dark NEOs. The interval between km-sized bodies striking the Earth should occur on average once every 750,000 years. Low and high albedo NEOs are well mixed in orbital space, but a trend remains with higher albedo objects being at smaller semimajor axes and lower albedo objects more likely found at larger semimajor axes.

[43]  arXiv:2001.03552 [pdf, other]

Title: Trend Filtering -- II. Denoising Astronomical Signals with Varying Degrees of Smoothness

Authors: Collin A. Politsch, Jessi Cisewski-Kehe, Rupert A. C. Croft, Larry Wasserman

Comments: Part 2 of 2, Link to Part 1: arXiv:1908.07151; 15 pages, 7 figures

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Applications (stat.AP)

Trend filtering---first introduced into the astronomical literature in Paper I of this series---is a state-of-the-art statistical tool for denoising one-dimensional signals that possess varying degrees of smoothness. In this work, we demonstrate the broad utility of trend filtering to observational astronomy by discussing how it can contribute to a variety of spectroscopic and time-domain studies. The observations we discuss are (1) the Lyman-$\alpha$ forest of quasar spectra; (2) more general spectroscopy of quasars, galaxies, and stars; (3) stellar light curves with planetary transits; (4) eclipsing binary light curves; and (5) supernova light curves. We study the Lyman-$\alpha$ forest in the greatest detail---using trend filtering to map the large-scale structure of the intergalactic medium along quasar-observer lines of sight. The remaining studies share broad themes of: (1) estimating observable parameters of light curves and spectra; and (2) constructing observational spectral/light-curve templates. We also briefly discuss the utility of trend filtering as a tool for one-dimensional data reduction and compression.

[44]  arXiv:2001.03555 [pdf, ps, other]

Title: Centrifugal acceleration of protons by a supermassive black hole

Authors: Ya. N. Istomin, A. A. Gunya

Comments: 9 pages, 7 figures, 1 table

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

The centrifugal acceleration is due to the rotating poloidal magnetic field in the magnetosphere creates the electric field which is orthogonal to the magnetic field. Charged particles with finite cyclotron radii can move along the electric field and receive energy. Centrifugal acceleration pushes particles to the periphery, where their azimuthal velocity reaches the light speed. We have calculated particle trajectories by numerical and analytical methods. The maximum obtained energies depend on the parameter of the particle magnetization $ \kappa $, which is the ratio of rotation frequency of magnetic field lines in the magnetosphere $ \Omega_F $ to non-relativistic cyclotron frequency of particles $ \omega_c $, $ \kappa = \Omega_F /\omega_c << 1 $, and from the parameter $ \alpha $ which is the ratio of toroidal magnetic field $ B_T $ to the poloidal one $ B_P $, $ \alpha = B_T / B_P $. It is shown that for small toroidal fields, $ \alpha <\kappa^{1/4} $, the maximum Lorentz factor $ \gamma_m $ is only the square root of magnetization, $ \gamma_m = \kappa^{-1/2} $, while for large toroidal fields, $ \alpha >\kappa^{1/4} $, the energy increases significantly, $ \gamma_m = \kappa^{-2/3} $. However, the maximum possible acceleration, $ \gamma_m = \kappa^{-1} $, is not achieved in the magnetosphere. For a number of active galactic nuclei, such as M87, maximum values of Lorentz factor for accelerated protons are found. Also for special case of Sgr. A* estimations of the maximum proton energy and its energy flux are obtained. They are in agreement with experimental data obtained by HESS Cherenkov telescope.

[45]  arXiv:2001.03558 [pdf, other]

Title: Thirty Years of Radio Observations of Type Ia SN 1972E and SN 1895B: Constraints on Circumstellar Shells

Authors: Yvette Cendes, Maria R. Drout, Laura Chomiuk, Sumit K. Sarbadhicary

Comments: Accepted for publication in the Astrophysical Journal

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

We have imaged over 35 years of archival Very Large Array (VLA) observations of the nearby (d$_{\rm{L}}$ $=$ 3.15 Mpc) Type Ia supernovae SN\,1972E and SN\,1895B between 9 and 121 years post-explosion. No radio emission is detected, constraining the 8.5 GHz luminosities of SN\,1972E and SN\,1895B to be L$_{\nu,8.5\rm{GHz}}$ $<$ 6.0 $\times$ 10$^{23}$ erg s$^{-1}$ Hz$^{-1}$ 45 years post-explosion and L$_{\nu,8.5\rm{GHz}}$ $<$ 8.9 $\times$ 10$^{23}$ erg s$^{-1}$ Hz$^{-1}$ 121 years post-explosion, respectively. These limits imply a clean circumstellar medium (CSM), with $n$ $<$ 0.9 cm$^{-3}$ out to radii of a few $\times$ 10$^{18}$ cm, if the SN blastwave is expanding into uniform density material. Due to the extensive time coverage of our observations, we also constrain the presence of CSM shells surrounding the progenitor of SN\,1972E. We rule out essentially all medium and thick shells with masses of 0.05$-$0.3 M$_\odot$ at radii between $\sim$10$^{17}$ and 10$^{18}$ cm, and thin shells at specific radii with masses down to $\lesssim$0.01 M$_\odot$. These constraints rule out swaths of parameter space for a range of single and double degenerate progenitor scenarios, including recurrent nova, core-degenerate objects, ultra-prompt explosions and white dwarf (WD) mergers with delays of a few hundred years between the onset of merger and explosion. Allowed progenitors include WD-WD systems with a significant ($>$ 10$^{4}$ years) delay from the last episode of common envelope evolution and single degenerate systems undergoing recurrent nova, provided that the recurrence timescale i short and the system has been in the nova phase for $\gtrsim$10$^{4}$ yr, such that a large ($>$ 10$^{18}$ cm) cavity has been evacuated. Future multi-epoch observations of additional intermediate-aged Type Ia SNe will provide a comprehensive view of the large-scale CSM environments around these explosions.

[46]  arXiv:2001.03565 [pdf, other]

Title: Detectability of embedded protoplanets from hydrodynamical simulations

Authors: E. Sanchis, G. Picogna, B. Ercolano, L. Testi, G. Rosotti

Comments: Accepted for publication on January 8, 2020 in MNRAS. 15 pages of main text with 14 figures, and 5 pages of appendices A and B with 4 figures

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

We predict magnitudes for young planets embedded in transition discs, still affected by extinction due to material in the disc. We focus on Jupiter-size planets at a late stage of their formation, when the planet has carved a deep gap in the gas and dust distributions and the disc starts being transparent to the planet flux in the infrared (IR). Column densities are estimated by means of three-dimensional hydrodynamical models, performed for several planet masses. Expected magnitudes are obtained by using typical extinction properties of the disc material and evolutionary models of giant planets. For the simulated cases located at $5.2$ AU in a disc with local unperturbed surface density of $127$ $\mathrm{g} \cdot \mathrm{cm}^{-2}$, a $1$ $M_J$ planet is highly extincted in J-, H- and K-bands, with predicted absolute magnitudes $\ge 50$ mag. In L- and M-bands extinction decreases, with planet magnitudes between $25$ and $35$ mag. In the N-band, due to the silicate feature on the dust opacities, the expected magnitude increases to $40$ mag. For a $2$ $M_J$ planet, the magnitudes in J-, H- and K-bands are above $22$ mag, while for L-, M- and N-bands the planet magnitudes are between $15$ and $20$ mag. For the $5$ $M_J$ planet, extinction does not play a role in any IR band, due to its ability to open deep gaps. Contrast curves are derived for the transition discs in CQ Tau, PDS70, HL Tau, TW Hya and HD163296. Planet mass upper-limits are estimated for the known gaps in the last two systems.

[47]  arXiv:2001.03575 [pdf, ps, other]

Title: Average radial structures of gas convection in the solar granulation

Authors: T. Oba, Y. Iida, T. Shimizu

Comments: 29 pages, 10 figures, accepted for publication in ApJ

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

Gas convection is observed in the solar photosphere as the granulation, i.e., having highly time-dependent cellular patterns, consisting of numerous bright cells called granules and dark surrounding-channels called intergranular lanes. Many efforts have been made to characterize the granulation, which may be used as an energy source for various types of dynamical phenomena. Although the horizontal gas flow dynamics in intergranular lanes may play a vital role, but they are poorly understood. This is because the Doppler signals can be obtained only at the solar limb, where the signals are severely degraded by a foreshortening effect. To reduce such a degradation, we use Hinode's spectroscopic data, which are free from a seeing-induced image degradation, and improve its image quality by correcting for straylight in the instruments. The dataset continuously covers from the solar disk to the limb, providing a multidirectional line-of-sight (LOS) diagnosis against the granulation. The obtained LOS flow-field variation across the disk indicates a horizontal flow speed of 1.8-2.4 km/s. We also derive the spatial distribution of the horizontal flow speed, which is 1.6 km/s in granules and 1.8 km/s in intergranular lanes, and where the maximum speed is inside intergranular lanes. This result newly suggests the following sequence of horizontal flow: A hot rising gas parcel is strongly accelerated from the granular center, even beyond the transition from the granules to the intergranular lanes, resulting in the fastest speed inside the intergranular lanes, and the gas may also experience decelerations in the intergranular lane.

[48]  arXiv:2001.03581 [pdf, other]

Title: Observations of a GX 301-2 Apastron Flare with the X-Calibur Hard X-Ray Polarimeter Supported by NICER, the Swift XRT and BAT, and Fermi GBM

Authors: Q. Abarr (1), M. Baring (2), B. Beheshtipour (3,4), M. Beilicke (4), G. deGeronimo (5), P. Dowkontt (1), M. Errando (1), V. Guarino (6), N. Iyer (7), (8), F. Kislat (9), M. Kiss (7), (8), T. Kitaguchi (10), H. Krawczynski (1), J. Lanzi (11), S. Li (12), L. Lisalda (1), T. Okajima (13), M. Pearce (7), (8), L. Press (1), B. Rauch (1), D. Stuchlik (11), H. Takahashi (14), J. Tang (1), N. Uchida (14), A. West (1), P. Jenke (15), H. Krimm (16), A. Lien (17), (18), C. Malacaria (19), (20), J. M. Miller (21), C. Wilson-Hodge (19) ((1) Washington University in St. Louis, (2) Rice University, (3) Max Planck Institute for Gravitational Physics, (4) Former affiliation: Washington University in St. Louis, (5) DG CIrcuits, (6) Guarino Engineering, (7) KTH Royal Institute of Technology, (8) Oskar Klein Centre for Cosmoparticle Physics, (9) University of New Hampshire, (10) RIKEN Nishina Center, (11) NASA Wallops Flight Facility, (12) Brookhaven National Laboratory, (13) NASA's Goddard Space Flight Center, (14) Hiroshima University, (15) University of Alabama in Huntsville, (16) National Science Foundation, (17) Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, (18) University of Maryland, (19) NASA Marshall Space Flight Center, (20) Universities Space Research Association, NSSTC, (21) University of Michigan)

Comments: Accepted for publication in the Astrophysical Journal. 20 pages, 19 figures, 4 tables

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

The accretion-powered X-ray pulsar GX 301-2 was observed with the balloon-borne X-Calibur hard X-ray polarimeter during late December 2018, with contiguous observations by the NICER X-ray telescope, the Swift X-ray Telescope and Burst Alert Telescope, and the Fermi Gamma-ray Burst Monitor spanning several months. The observations detected the pulsar in a rare apastron flaring state coinciding with a significant spin-up of the pulsar discovered with the Fermi GBM. The X-Calibur, NICER, and Swift observations reveal a pulse profile strongly dominated by one main peak, and the NICER and Swift data show strong variation of the profile from pulse to pulse. The X-Calibur observations constrain for the first time the linear polarization of the 15-35 keV emission from a highly magnetized accreting neutron star, indicating a polarization degree of (27+38-27)% (90% confidence limit) averaged over all pulse phases. We discuss the spin-up and the X-ray spectral and polarimetric results in the context of theoretical predictions. We conclude with a discussion of the scientific potential of future observations of highly magnetized neutron stars with the more sensitive follow-up mission XL-Calibur.

[49]  arXiv:2001.03594 [pdf, other]

Title: A broadband look of the Accreting Millisecond X-ray Pulsar SAX J1748.9-2021 using AstroSat and XMM-Newton

Authors: Rahul Sharma, Aru Beri, Andrea Sanna, Anjan Dutta

Comments: 9 pages, 8 figures. Accepted for publication in MNRAS

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

SAX J1748.9-2021 is a transient accretion powered millisecond X-ray pulsar located in the Globular cluster NGC 6440. We report on the spectral and timing analysis of SAX J1748.9-2021 performed on AstroSat data taken during its faint and short outburst of 2017. We derived the best-fitting orbital solution for the 2017 outburst and obtained an average local spin frequency of 442.361098(3) Hz. The pulse profile obtained from 3-7 keV and 7-20 keV energy bands suggest constant fractional amplitude ~0.5% for fundamental component, contrary to previously observed energy pulse profile dependence. Our AstroSat observations revealed the source to be in a hard spectral state. The 1-50 keV spectrum from SXT and LAXPC on-board AstroSat can be well described with a single temperature blackbody and thermal Comptonization. Moreover, we found that the combined spectra from XMM-Newton (EPIC-PN) and AstroSat (SXT+LAXPC) indicated the presence of reflection features in the form of iron (Fe K${\alpha}$) line that we modeled with the reflection model xillvercp. One of the two X-ray burst observed during the AstroSat/LAXPC observation showed hard X-ray emission (>30 keV) due to Compton up-scattering of thermal photons by the hot corona. Time resolved analysis performed on the bursts revealed complex evolution in emission radius of blackbody for second burst suggestive of mild photospheric radius expansion.

[50]  arXiv:2001.03595 [pdf, other]

Title: Nine New Repeating Fast Radio Burst Sources from CHIME/FRB

Authors: E. Fonseca, B. C. Andersen, M. Bhardwaj, P. Chawla, D. C. Good, A. Josephy, V. M. Kaspi, K. W. Masui, R. Mckinven, D. Michilli, Z. Pleunis, K. Shin, S. P. Tendulkar, K. M. Bandura, P. J. Boyle, C. Brar, T. Cassanelli, D. Cubranic, M. Dobbs, F. Q. Dong, B. M. Gaensler, G. Hinshaw, T. L. Landecker, C. Leung, D. Z. Li, H.-H. Lin, J. Mena-Parra, M. Merryfield, A. Naidu, C. Ng, C. Patel, U. Pen, M. Rafiei-Ravandi, M. Rahman, S. M. Ransom, P. Scholz, K. M. Smith, I. H. Stairs, K. Vanderlinde, P. Yadav, A. V. Zwaniga

Comments: Submitted to ApJL on 24 December 2019

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

We report on the discovery and analysis of bursts from nine new repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These sources span a dispersion measure (DM) range of 195 to 1380 pc cm$^{-3}$. We detect two bursts from three of the new sources, three bursts from four of the new sources, four bursts from one new source, and five bursts from one new source. We determine sky coordinates of all sources with uncertainties of $\sim$10$^\prime$. We detect Faraday rotation measures (RMs) for two sources, with values $-20(1)$ and $-499.8(7)$ rad m$^{-2}$. We find that the DM distribution of our events, combined with the nine other repeaters discovered by CHIME/FRB, is indistinguishable from that of thus far non-repeating CHIME/FRB events. However, as previously reported, the burst widths appear statistically significantly larger than the thus far non-repeating CHIME/FRB events, further supporting the notion of inherently different emission mechanisms and/or local environments. We identify candidate galaxies that may contain the low-DM FRB 190110.J1353+48.

[51]  arXiv:2001.03599 [pdf, other]

Title: GeV-TeV Counterparts of SS 433/W50 from Fermi-LAT and HAWC Observations

Authors: Ke Fang, Eric Charles, Roger Blandford

Comments: 10 pages, 3 figures, 2 tables. To appear in ApJ Letters

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

The extended jets of the microquasar SS 433 have been observed in optical, radio, X-ray, and recently very-high-energy (VHE) $\gamma$-rays by HAWC. The detection of HAWC $\gamma$-rays with energies as great as 25 TeV motivates searches for high-energy $\gamma$-ray counterparts in the Fermi-LAT data in the 100 MeV--300 GeV band. In this paper, we report on the first-ever joint analysis of Fermi-LAT and HAWC observations to study the spectrum and location of $\gamma$-ray emission from SS~433. Our analysis finds common emission sites of GeV-to-TeV $\gamma$-rays inside the eastern and western lobes of SS 433. The total flux above 1 GeV is $\sim 1\times10^{-10}\,\rm cm^{-2}\,s^{-1}$ in both lobes. The $\gamma$-ray spectrum in the eastern lobe is consistent with inverse-Compton emission by an electron population that is accelerated by jets. To explain both the GeV and TeV flux, the electrons need to have a soft intrinsic energy spectrum, or undergo a quick cooling process due to synchrotron radiation in a magnetized environment.

[52]  arXiv:2001.03602 [pdf, other]

Title: Investigating a Deep Learning Method to Analyze Images from Multiple Gamma-ray Telescopes

Authors: Aryeh Brill, Qi Feng, T. Brian Humensky, Bryan Kim, Daniel Nieto, Tjark Miener

Comments: 4 pages, 4 figures, Proceedings of the 2019 New York Scientific Data Summit (NYSDS)

Journal-ref: Proceedings of the 2019 New York Scientific Data Summit (NYSDS), 12-14 June 2019, New York, NY, USA. Available: IEEE Xplore, http://www.ieee.org

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

Imaging atmospheric Cherenkov telescope (IACT) arrays record images from air showers initiated by gamma rays entering the atmosphere, allowing astrophysical sources to be observed at very high energies. To maximize IACT sensitivity, gamma-ray showers must be efficiently distinguished from the dominant background of cosmic-ray showers using images from multiple telescopes. A combination of convolutional neural networks (CNNs) with a recurrent neural network (RNN) has been proposed to perform this task. Using CTLearn, an open source Python package using deep learning to analyze data from IACTs, with simulated data from the upcoming Cherenkov Telescope Array (CTA), we implement a CNN-RNN network and find no evidence that sorting telescope images by total amplitude improves background rejection performance.

Cross-lists for Mon, 13 Jan 20

[53]  arXiv:1904.08184 (cross-list from hep-ph) [pdf, other]

Title: Real-time dynamics of axion particle production due to spontaneous decay of a coherent axion field

Authors: Xu-Guang Huang, Dmitri E. Kharzeev, Hidetoshi Taya

Comments: 17 pages, 10 figures; v2: more explanations on the validity of the formulation are added, typos are corrected, to be published in PRD

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Nuclear Theory (nucl-th)

We show that the coherent axion field spontaneously decays by emitting axion particles via quantum tunneling if axion potential has more than one minimum. By employing the $\hbar$-expansion and mean field approximation, we develop a formalism to trace the real-time dynamics of the axion particle production including its backreaction to the coherent axion field. We also present numerical results for the time evolution of various physical quantities including the strength of the coherent axion field, phase-space density of produced axion particles, energy density, and pressure. Phenomenological implications of our results are also discussed.

[54]  arXiv:2001.00159 (cross-list from physics.hist-ph) [pdf]

Title: The Great Debate

Authors: I. Horvath

Comments: In Hungarian. This article was published in the 2020 Astronomical Yearbook (Hungarian, MCSE)

Subjects: History and Philosophy of Physics (physics.hist-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

A hundred years ago (1920) in the auditorium of the Smithsonian Institution's U.S. National Museum there were two lectures under the auspices of the George Ellery Hale Lecture series, what has come to be called the 'Great Debate'. In the debate, Harlow Shapley and Heber Curtis argued over the 'Scale of the Universe'. Curtis argued that the Universe is composed of many galaxies like our own and they are relatively small. Shapley argued that the Universe was composed of only one big Galaxy. In Shapley's model, our Sun was far from the center of this great island Universe.

[55]  arXiv:2001.03290 (cross-list from gr-qc) [pdf, other]

Title: Gravitational deflection angle of light: Definition by an observer and its application to an asymptotically nonflat spacetime

Authors: Keita Takizawa, Toshiaki Ono, Hideki Asada

Comments: 7 pages, 5 figures

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

The gravitational deflection angle of light for an observer and source at finite distance from a lens object has been studied by Ishihara et al. [Phys. Rev. D, 94, 084015 (2016)], based on the Gauss-Bonnet theorem with using the optical metric. Their approach to finite-distance cases is limited within an asymptotically flat spacetime. By making several assumptions, we give an interpretation of their definition from the observer's viewpoint: The observer assumes the direction of a hypothetical light emission at the observer position and makes a comparison between the fiducial emission direction and the direction along the real light ray. The angle between the two directions at the observer location can be interpreted as the deflection angle by Ishihara et al. The present interpretation does not require the asymptotic flatness. Motivated by this, we avoid such asymptotic regions to discuss another integral form of the deflection angle of light. This form makes it clear that the proposed deflection angle can be used not only for asymptotically flat spacetimes but also for asymptotically nonflat ones. We examine the proposed deflection angle in two models for the latter case; Kottler (Schwarzschild-de Sitter) solution in general relativity and a spherical solution in Weyl conformal gravity.

[56]  arXiv:2001.03473 (cross-list from physics.plasm-ph) [pdf, ps, other]

Title: Particle trajectories in Weibel filaments: influence of external field obliquity and chaos

Authors: A Bret, M E Dieckmann

Comments: 10 pages, 6 figures, to appear in Journal of Plasma Physics

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

When two collisionless plasma shells collide, they interpenetrate and the overlapping region may turn Weibel unstable for some values of the collision parameters. This instability grows magnetic filaments which, at saturation, have to block the incoming flow if a Weibel shock is to form. In a recent paper [J. Plasma Phys. (2016), vol. 82, 905820403], it was found implementing a toy model for the incoming particles trajectories in the filaments, that a strong enough external magnetic field $\mathbf{B}_0$ can prevent the filaments to block the flow if it is aligned with. Denoting $B_f$ the peak value of the field in the magnetic filaments, all test particles stream through them if $\alpha=B_0/B_f > 1/2$. Here, this result is extended to the case of an oblique external field $B_0$ making an angle $\theta$ with the flow. The result, numerically found, is simply $\alpha > \kappa(\theta)/\cos\theta$, where $\kappa(\theta)$ is of order unity. Noteworthily, test particles exhibit chaotic trajectories.

[57]  arXiv:2001.03530 (cross-list from stat.CO) [pdf, other]

Title: Dynamic Gauss Newton Metropolis Algorithm

Authors: Mehmet Ugurbil

Comments: 21 pages, 5 figures

Subjects: Computation (stat.CO); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Data Analysis, Statistics and Probability (physics.data-an)

GNM: The MCMC Jagger. A rocking awesome sampler. This python package is an affine invariant Markov chain Monte Carlo (MCMC) sampler based on the dynamic Gauss-Newton-Metropolis (GNM) algorithm. The GNM algorithm is specialized in sampling highly non-linear posterior probability distribution functions of the form $e^{-||f(x)||^2/2}$, and the package is an implementation of this algorithm. On top of the back-off strategy in the original GNM algorithm, there is the dynamic hyper-parameter optimization feature added to the algorithm and included in the package to help increase performance of the back-off and therefore the sampling. Also, there are the Jacobian tester, error bars creator and many more features for the ease of use included in the code. The problem is introduced and a guide to installation is given in the introduction. Then how to use the python package is explained. The algorithm is given and finally there are some examples using exponential time series to show the performance of the algorithm and the back-off strategy.

[58]  arXiv:2001.03531 (cross-list from nucl-th) [pdf, other]

Title: Supercritical charged objects and $e^+e^-$ pair creation

Authors: Cheng-Jun Xia, She-Sheng Xue, Ren-Xin Xu, Shan-Gui Zhou

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

We investigate the stability and $e^+e^-$ pair creation of supercritical charged superheavy nuclei, $ud$QM nuggets, strangelets, and strangeon nuggets based on Thomas-Fermi approximation. The model parameters are fixed by reproducing their masses and charge properties reported in earlier publications. It is found that $ud$QM nuggets, strangelets, and strangeon nuggets may be more stable than ${}^{56}$Fe at $A\gtrsim 315$, $5\times10^4$, and $1.2\times10^8$, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number $\sim$965, while $ud$QM nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than $39$, 433, and $2.7\times10^5$. The $e^+e^-$ pair creation will inevitably start for superheavy nuclei with charge numbers $Z\geq177$, $ud$QM nuggets with $Z\geq163$, strangelets with $Z\geq 192$, and strangeon nuggets with $Z\geq 212$. A universal relation $Q/R_e = \left(m_e - \bar{\mu}_e\right)/\alpha$ is obtained at a given electron chemical potential $\bar{\mu}_e$, where $Q$ is the total charge and $R_e$ the radius of electron cloud. This predicts the maximum charge number by taking $\bar{\mu}_e=-m_e$. For supercritical charged objects with $\bar{\mu}_e<-m_e$, the decay rate for $e^+e^-$ pair production is estimated based on the JWKB approximation. It is found that most positrons are emitted at $t\lesssim 10^{-15}$ s, while a long lasting positron emission is observed for large objects with $R\gtrsim 1000$ fm. The emission and annihilation of positrons from supercritical charged objects may be partially responsible for the short $\gamma$-ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in X-ray spectra from galaxies and galaxy clusters.

[59]  arXiv:2001.03559 (cross-list from physics.plasm-ph) [pdf, other]

Title: A quantitative study of some sources of uncertainty in opacity measurements

Authors: Jean-Christophe Pain, Franck Gilleron

Comments: submitted to "High Energy Density Physics"

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

Laboratory (laser and Z-pinch) opacity measurements of well-characterized plasmas provide data to assist inertial confinement fusion, astrophysics and atomic-physics research. In order to test the atomic-physics codes devoted to the calculation of radiative properties of hot plasmas, such experiments must fulfill a number of requirements. In this work, we discuss some sources of uncertainty in absorption-spectroscopy experiments, concerning areal mass, background emission, intensity of the backlighter and self-emission of the plasma. We also study the impact of spatial non-uniformities of the sample.

[60]  arXiv:2001.03571 (cross-list from gr-qc) [pdf, other]

Title: Numerical relativity simulation of GW150914 in Einstein dilaton Gauss-Bonnet gravity

Authors: Maria Okounkova

Comments: 6 pages, 5 figures

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

A present challenge in testing general relativity (GR) with binary black hole gravitational wave detections is the inability to perform model-dependent tests due to the lack of merger waveforms in beyond-GR theories. In this study, we produce the first numerical relativity binary black hole gravitational waveform in Einstein dilaton Gauss-Bonnet (EDGB) gravity, a higher-curvature theory of gravity with motivations in string theory. We evolve a binary black hole system in order-reduced EDGB gravity, with parameters consistent with GW150914. We focus on the merger portion of the waveform, due to the presence of secular growth in the inspiral phase. We compute mismatches with the corresponding general relativity merger waveform, finding that from a post-inspiral-only analysis, we can constrain the EDGB lengthscale to be $\sqrt{\alpha_\mathrm{GB}} \lesssim 11$ km.

[61]  arXiv:2001.03600 (cross-list from nucl-ex) [pdf, other]

Title: Gamma-ray emission in alpha-particle reactions with C, Mg, Si, Fe

Authors: J. Kiener, J. Bundesmann, I. Deloncle, A. Denker, V. Tatischeff, A. Gostojic, C. Hamadache, J. Röhrich, H. Benhabiles, I. Bougaoub, A. Coc, F. Hammache, J. Peyré

Comments: 5 pages, 5 figures, contribution to the XXIII International School on Nuclear Physics, Neutron Physics and Applications, Varna, Bulgaria, September 22-28, 2019

Subjects: Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE)

Cross sections for the strongest gamma-ray emission lines produced in alpha-particle reactions with C, Mg, Si, Fe have been measured in the range E_alpha = 50 - 90 MeV at the center for proton therapy at the Helmholtz-Zentrum Berlin. Data for more than 60 different gamma-ray lines were determined, with particular efforts for lines that are in cross section compilations/evaluations with astrophysical purpose, and where data exist at lower projectile energies. The data are compared with predictions of a modern nuclear reaction code and cross-section curves of the latest evaluation for gamma-ray line emission in accelerated-particle interactions in solar flares.

Replacements for Mon, 13 Jan 20

[62]  arXiv:1609.04485 (replaced) [pdf, other]

Title: Perturbations and quantum relaxation

Authors: Adithya Kandhadai, Antony Valentini

Comments: 28 pages, 15 figures, minor amendments in v3

Journal-ref: Found. Phys. 49, 1 (2019)

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

[63]  arXiv:1712.08619 (replaced) [pdf, other]

Title: Detection of missing baryons in galaxy groups with kinetic Sunyaev-Zel'dovich effect

Authors: Seunghwan Lim, Houjun Mo, Huiyuan Wang, Xiaohu Yang

Comments: Significantly revised from the previous version. Accepted for publication in ApJ

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

[64]  arXiv:1806.02819 (replaced) [pdf, other]

Title: Probing non-Gaussian Stochastic Gravitational Wave Backgrounds with LISA

Authors: Nicola Bartolo, Valerie Domcke, Daniel G. Figueroa, Juan Garcia-Bellido, Marco Peloso, Mauro Pieroni, Angelo Ricciardone, Mairi Sakellariadou, Lorenzo Sorbo, Gianmassimo Tasinato

Comments: Corrections added in the 3-point response function(s); Note added to discuss observability of the non-Gaussian signal; 33 pages + appendices, 5 Figures

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

[65]  arXiv:1810.12946 (replaced) [pdf, ps, other]

Title: The Robustness of Cosmological Hydrodynamic Simulation Predictions to Changes in Numerics and Cooling Physics

Authors: Shuiyao Huang, Neal Katz, Romeel Davé, Mark Fardal, Juna Kollmeier, Benjamin D. Oppenheimer, Molly S. Peeples, Shawn Roberts, David H. Weinberg, Philip F. Hopkins, Robert Thompson

Comments: 29 pages, 25 figures, accepted by MNRAS

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

[66]  arXiv:1811.06545 (replaced) [pdf, other]

Title: Early-type galaxy density profiles from IllustrisTNG: I. Galaxy correlations and the impact of baryons

Authors: Yunchong Wang (1,2), Mark Vogelsberger (1), Dandan Xu (3), Shude Mao (2,4), Volker Springel (5), Hui Li (1), David Barnes (1), Lars Hernquist (6), Annalisa Pillepich (7), Federico Marinacci (6), Rüediger Pakmor (8), Rainer Weinberger (6), Paul Torrey (9) ((1) MIT, (2) Tsinghua, (3) IASTU, (4) NAOC, (5) MPA, (6) Harvard, (7) MPIA, (8) HITS, (9) UF)

Comments: 31 pages, 20 figures, 9 tables. Accepted for publication in MNRAS. Major revision, added the effects of feedback on the total density profile in Section 4. Pay attention to changes in Figures 7, 10, 12, and 16

Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 4, February 2020, Pages 5188-5215

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

[67]  arXiv:1906.02217 (replaced) [pdf, other]

Title: A null test to probe the scale-dependence of the growth of structure as a test of General Relativity

Authors: Felipe Oliveira Franco, Camille Bonvin, Chris Clarkson

Comments: v1: 6 pages, 3 figures. v2: 6 pages, 4 figures, new paragraph on non-linearities, matches version published in MNRAS Letters

Journal-ref: MNRAS Letters 492 (2020), L34-L39

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

[68]  arXiv:1906.04181 (replaced) [pdf, other]

Title: 3D simulations of clump formation in stellar wind collisions

Authors: Diego Calderón, Jorge Cuadra, Marc Schartmann, Andreas Burkert, Joaquín Prieto, Christopher M. P. Russell

Comments: 21 pages, 20 Figures, 2 Tables. Accepted for publication in MNRAS

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

[69]  arXiv:1906.10302 (replaced) [pdf, other]

Title: Rapid Particle Acceleration due to Recollimation Shocks and Turbulent Magnetic Fields in Injected Jets with Helical Magnetic Fields

Authors: Kenichi Nishikawa, Yosuke Mizuno, Jose L. Gomez, Ioana Dutan, Jacek Niemiec, Oleh Kobzar, Nicholas MacDonald, Athina Meli, Martin Pohl, Kouichi Hirotani

Comments: 8 pages, 5 figures, submitted to ApJL, movie will be added if possible (dBtotByz11MF_011.mp4 5.8MB), significantly revised with corrected figures. After rejected by ApJL, submitted to MNRAS, revised, 8 pages, 6 figures

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

[70]  arXiv:1906.10421 (replaced) [pdf, other]

Title: A Toy Model for the Dynamical Discrepancies on Galactic Scales

Authors: Jonas Petersen, Martin Rosenlyst

Comments: 5 pages, 2 figures

Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 490, Issue 3, December 2019, Pages 3493-3497

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Theory (hep-th)

[71]  arXiv:1907.12958 (replaced) [pdf, other]

Title: Wave excitation by energetic ring-distributed electron beams in the solar corona

Authors: X. Zhou, P. A. Muñoz, J. Büchner, S. Liu

Comments: ApJ, accepted

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

[72]  arXiv:1908.05042 (replaced) [pdf, ps, other]

Title: Understanding CMB physics through the exploration of exotic cosmological models: a classroom study using CLASS

Authors: Tanja Rindler-Daller

Comments: Revised and corrected version; subm. to European Journal of Physics; 21 pages, 5 figures

Subjects: Physics Education (physics.ed-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[73]  arXiv:1908.07151 (replaced) [pdf, other]

Title: Trend Filtering -- I. A Modern Statistical Tool for Time-Domain Astronomy and Astronomical Spectroscopy

Authors: Collin A. Politsch, Jessi Cisewski-Kehe, Rupert A. C. Croft, Larry Wasserman

Comments: Part 1 of 2; 15 pages, 3 figures

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Applications (stat.AP)

[74]  arXiv:1909.00791 (replaced) [pdf, other]

Title: The impact of braiding covariance and in-survey covariance on next-generation galaxy surveys

Authors: Fabien Lacasa

Comments: 10+1 pages, 12+2 figures. Matches version accepted in A&A. Notebook on github also updated to match

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

[75]  arXiv:1909.02019 (replaced) [pdf, other]

Title: A simple supergravity model of inflation constrained with Planck 2018 data

Authors: Gabriel Germán, Juan Carlos Hidalgo, Francisco X. Linares Cedeño, Ariadna Montiel, J. Alberto Vázquez

Comments: 8 pages, 2 tables, 5 figures. Final version accepted for publication in PRD

Journal-ref: Phys. Rev. D 101, 023507 (2020)

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

[76]  arXiv:1910.02959 (replaced) [pdf, other]

Title: The evolution of rest-frame UV properties, Lya EWs and the SFR-Stellar mass relation at z~2-6 for SC4K LAEs

Authors: Sérgio Santos, David Sobral, Jorryt Matthee, João Calhau, Elisabete da Cunha, Bruno Ribeiro, Ana Paulino-Afonso, Pablo Arrabal Haro, Josh Butterworth

Comments: Accepted for publication in MNRAS. 23 pages, 11 figures, 3 tables + appendices. The full SC4K catalogue of LAEs with PSF photometry, stellar masses, SFRs and other properties for individual LAEs, is available at this https URL

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

[77]  arXiv:1910.04113 (replaced) [pdf, other]

Title: AMS-02 beryllium data and its implication for cosmic ray transport

Authors: Carmelo Evoli, Giovanni Morlino, Pasquale Blasi, Roberto Aloisio

Comments: 11 pages, 6 figures. Accepted for publication on Physical Review D

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

[78]  arXiv:1910.07541 (replaced) [pdf, other]

Title: Testing Galaxy Formation Simulations with Damped Lyman-$α$ Abundance and Metallicity Evolution

Authors: Sultan Hassan (NMSU/UWC), Kristian Finlator (NMSU/DAWN), Romeel Davé (Edinburgh/UWC/SAAO), Christopher W. Churchill (NMSU), J. Xavier Prochaska (UCSC/Kavli IPMU)

Comments: Accepted for publication in MNRAS

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

[79]  arXiv:1910.08199 (replaced) [pdf, ps, other]

Title: The Impact of Wind Scalings on Stellar Growth and the Baryon Cycle in Cosmological Simulations

Authors: Shuiyao Huang, Neal Katz, Romeel Davé, Benjamin D. Oppenheimer, David H. Weinberg, Mark Fardal, Juna A. Kollmeier, Molly S. Peeples

Comments: 31 pages, 19 figures, accepted by MNRAS

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

[80]  arXiv:1911.05179 (replaced) [pdf, other]

Title: WASP-52b. The effect of starspot correction on atmospheric retrievals

Authors: Giovanni Bruno, Nikole K. Lewis, Munazza K. Alam, Mercedes López-Morales, Joanna K. Barstow, Hannah R. Wakeford, David Sing, Gregory W. Henry, Gilda E. Ballester, Vincent Bourrier, Lars A. Buchhave, Ofer Cohen, Thomas Mikal-Evans, Antonio García Muñoz, Panayotis Lavvas, Jorge Sanz-Forcada

Comments: 16 pages, 11 figures, 1 table. Updated figure 5

Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 4, February 2020, Pages 5361-5375

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

[81]  arXiv:1912.00399 (replaced) [pdf, other]

Title: Constraining the long-lived magnetar remnants in short gamma-ray bursts from late-time radio observations

Authors: Liang-Duan Liu, He Gao, Bing Zhang

Comments: 23 pages, 6 figures, 3 tables, ApJ accepted

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

[82]  arXiv:1912.05627 (replaced) [pdf, other]

Title: The Hubble Space Telescope Advanced Camera for Surveys Emission Line Survey of Andromeda. I: Classical Be Stars

Authors: M. Peters, J.P. Wisniewski, B.F. Williams, J.R. Lomax, Y. Choi, M. Durbin, L.C. Johnson, A.R. Lewis, J. Lutz, T.A.A. Sigut, A. Wallach, J.J. Dalcanton

Comments: Accepted to AJ

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

[83]  arXiv:1912.06478 (replaced) [pdf, ps, other]

Title: The quantum black hole as a gravitational hydrogen atom

Authors: Christian Corda, Fabiano Feleppa

Comments: 20 pages. Submitted to JHEP

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

[84]  arXiv:1912.06671 (replaced) [pdf, ps, other]

Title: Neutron-capture elements in dwarf galaxies II: Challenges for the s- and i-processes at low metallicity

Authors: Ása Skúladóttir, Camilla Juul Hansen, Arthur Choplin, Stefania Salvadori, Melanie Hampel, Simon W. Campbell

Comments: Accepted in A&A, 16 pages, 10 figures, Paper II in series

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

[85]  arXiv:1912.12539 (replaced) [pdf]

Title: Betelgeuse at the end of 2019: an historical minimum about to end

Authors: Costantino Sigismondi

Comments: 4 pages, 2 figures, 1 table

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

[86]  arXiv:1912.12632 (replaced) [pdf, other]

Title: MCMCI: A code to fully characterise an exoplanetary system

Authors: Andrea Bonfanti, Michaël Gillon

Comments: 18 pages, 6 figures, 6 tables. Accepted for publication in A&A. Source code link: this https URL

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

[87]  arXiv:2001.01209 (replaced) [pdf, other]

Title: Dark Matter in CCDs at Modane (DAMIC-M) : A silicon detector apparatus searching for low-energy physics processes

Authors: Steven Juhyung Lee, Ben Kilminster, Anna Macchiolo

Comments: Proceedings to be submitted to JINST for IPRD19 conference

Subjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)

• New submissions
• Cross-lists
• Replacements