We gratefully acknowledge support from
the Simons Foundation and Leiden University.

Astrophysics

New submissions

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New submissions for Tue, 24 Mar 20

[1]  arXiv:2003.09420 [pdf, other]
Title: Model independent results for the inflationary and reheating epochs
Authors: Gabriel German
Comments: 7 pages, three tables, one figure. arXiv admin note: text overlap with arXiv:2002.11091
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

We address the problem of determining inflationary characteristics in a model independent way and then study constraints for reheating. We start from a recently proposed equation which allows to accurately calculate the value of the inflaton at horizon crossing $\phi_k$. We then use an equivalent form of this equation to write a formula that relates the tensor-to-scalar index $ r $ to the number of e-folds during inflation $ N_k $, hence a general bound for $ N_k $ follows. In particular, at present $r < 0.063$ implies $N_k < 56.3$. We also give an upper bound to the size of the universe, during the inflationary epoch, that gave rise to the current observable universe. The reheating epoch is discussed and a bound is given for the effective number of relativistic degrees of freedom $ g_ {re} $ which translates into a bound for the reheat temperature. From here bounds for the number of e-folds during reheating and also during the radiation dominated epoch follow. A criteria to know whether the constraint for the effective number of degrees of freedom exists is given in terms of the ratio $ V_e / V_k $ where $V_e$ is the potential at the end of inflation and $V_k$ at the horizon crossing scale $k$. Finally we study two particular models: Starobinsky model, which was studied before and is mostly used here for comparison, and a Mutated Hilltop Inflation (MHI) model. Tables \ref {table2} and \ref {table3} show results for the two specific models of inflation.

[2]  arXiv:2003.09427 [pdf, other]
Title: Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event
Comments: 20 pages, 7 figures, 4 tables. Submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report the discovery of the first unambiguous case of resolved double-peaked Balmer emission in a tidal disruption event (TDE), AT~2018hyz, that serves as a clear indication of an accretion disk. We modelled the \Ha\ emission line with a low eccentricity ($e\approx0.1$) accretion disk extending out to $\sim$100 $R_{p}$ and a Gaussian component originating from non-disk clouds. Our analysis indicates that in AT~2018hyz, disk formation took place promptly after the most-bound debris returned to pericenter, which we estimate to be roughly tens of days before the first detection. Redistribution of angular momentum and mass transport, possibly through shocks, must occur on the observed timescale of about a month to create the large \Ha-emitting disk that comprises $\lesssim$10\% of the initial stellar mass. With these new insights from AT~2018hyz, we infer that efficient circularization may be common among optically-detected TDEs despite their lack of double-peaked emission, which can be largely affected by the disk inclination angle and the relative strength of the disk contribution to the non-disk component.

[3]  arXiv:2003.09437 [pdf, other]
Title: A Deep CFHT Optical Search for a Counterpart to the Possible Neutron Star - Black Hole Merger GW190814
Comments: 20 pages, 14 figures including appendices; submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a wide-field optical imaging search for electromagnetic counterparts to the likely neutron star - black hole (NS-BH) merger GW190814/S190814bv. This compact binary merger was detected through gravitational waves by the LIGO/Virgo interferometers, with masses suggestive of a NS-BH merger. We imaged the LIGO/Virgo localization region using the MegaCam instrument on the Canada-France-Hawaii Telescope. We describe our hybrid observing strategy of both tiling and galaxy-targeted observations, as well as our image differencing and transient detection pipeline. Our observing campaign produced some of the deepest multi-band images of the region between 1.7 and 8.7 days post-merger, reaching a 5sigma depth of g > 22.8 (AB mag) at 1.7 days and i > 23.0 and i > 23.9$ at 3.7 and 8.7 days, respectively. These observations cover a mean total integrated probability of 68.8% of the localization region. We find no compelling candidate transient counterparts to this merger in our images, which suggests that either the lighter object was tidally disrupted inside of the BH's innermost stable circular orbit, the transient lies outside of the observed sky footprint, or the lighter object is a low-mass BH. We use 5sigma source detection upper limits from our images in the NS-BH interpretation of this merger to constrain the mass of the kilonova ejecta to be Mej < 0.015Msun for a 'blue' (kappa = 0.5 cm^2 g^-1) kilonova, and Mej < 0.04Msun for a 'red' (kappa = 5-10 cm^2 g^-1) kilonova. Our observations emphasize the key role of large-aperture telescopes and wide-field imagers such as CFHT MegaCam in enabling deep searches for electromagnetic counterparts to gravitational wave events.

[4]  arXiv:2003.09442 [pdf, other]
Title: Combining FOF and halo-based algorithms for the identification of galaxy groups
Comments: 11 pages and 9 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Galaxy groups provide the means for a great diversity of studies that contribute to a better understanding of the structure of the universe on a large scale and allow the properties of galaxies to be linked to those of the host halos. However, the identification of galaxy systems is a challenging task and therefore it is necessary to improve the techniques involved as much as possible. In view of the large present and forthcoming galaxy catalogues, we propose, implement, and evaluate an algorithm that combines the two most popular techniques used to identify galaxy systems. The algorithm can be easily applied to any spectroscopic galaxy catalogue, but here we demonstrate its use on the Sloan Digital Sky Survey. Assuming that a galaxy group is a gravitationally bounded system that has at least one bright galaxy, we begin by identifying groups with a Friends-Of-Friends algorithm adapted to fit this definition. In view of the shortcomings of this method, particularly the lack of ability to identify low-number groups, and consequently the inability to study the occupation of halos throughout the mass range, we improve it by adding a halo-based procedure. To assess the performance, we construct a mock catalogue from a semi-analytical model to compare the groups identified using our method with those obtained from the simulation. The comparison of groups extracted using our method with those of a mock catalogue shows that the proposed algorithm provides excellent results. The modifications introduced to the Friends-Of-Friends algorithm in the first part of the procedure to fit the adopted group definition gave reliable groups. Furthermore, the incorporation of the halo-based method reduces the interlopers while more accurately reproducing the number of galaxies per group. As a specific application, we use the algorithm to extract groups from the Sloan Digital Sky Survey.

[5]  arXiv:2003.09452 [pdf, other]
Title: Mass loss in tidally stripped systems; the energy-based truncation method
Comments: 20 pages, 14 figures, accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The ability to accurately predict the evolution of tidally stripped haloes is important for understanding galaxy formation and testing the properties of dark matter. Most studies of substructure evolution make predictions based on empirical models of tidal mass loss that are calibrated using numerical simulations. This approach can be accurate in the cases considered, but lacks generality and does not provide a physical understanding of the processes involved. Recently, we demonstrated that truncating NFW distribution functions sharply in energy results in density profiles that resemble those of tidally stripped systems, offering a path to constructing physically motivated models of tidal mass loss. In this work, we review calculations of mass loss based on energy truncation alone, and then consider what secondary effects may modulate mass loss beyond this. We find that a combination of dependence on additional orbital parameters and variations in individual particle energies over an orbit results in a less abrupt truncation in energy space as a subhalo loses mass. Combining the energy truncation approach with a simple prediction for the mass-loss rate, we construct a full model of mass loss that can accurately predict the evolution of a subhalo in terms of a single parameter $\eta_{\rm eff}$. This parameter can be fully determined from the initial orbital and halo properties, and does not require calibration with numerical simulations.

[6]  arXiv:2003.09464 [pdf, other]
Title: Addressing via N-body simulations the distribution of the satellite tidal debris in the Milky Way environment
Comments: 13 pages, 12 figures, 3 tables, accepted for publication by Astronomy & Astrophysics
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the distribution of the Milky Way satellites stellar and dark matter debris. For the first time we address the question of the tidal disruption of satellites in simulations by utilising simultaneously a) a realistic set of orbits extracted from cosmological simulations, b) a three component host galaxy with live halo, disc and bulge components, and c) satellites from hydrodynamical simulations. We analyse the statistical properties of the satellite debris of all massive galaxies reaching the inner Milky Way on a timescale of 2 Gyr. Up to 80$\%$ of the dark matter is stripped from the satellites, while this happens for up to 30$\%$ of their stars. The stellar debris ends mostly in the inner Milky Way halo, whereas the dark matter debris shows a flat mass distribution over the full main halo. The dark matter debris follows a density profile with inner power law index $\alpha_{\rm DM}=-0.66$ and outer index $\beta_{\rm DM}=2.94$, while for stars $\alpha_{*}=-0.44$ and $\beta_{*}=6.17$. In the inner 25 kpc, the distribution of the stellar debris is flatter than that of the dark matter debris and the orientations of their short axes differ significantly. Changing the orientation of the stellar disc by 90$^{\rm{o}}$ has only a minor impact on the distribution of the satellite debris. Our results indicate that the dark matter is more easily stripped than stars from the Milky Way satellites. The structure of the debris is dominated by the satellite orbital properties. The radial profiles, the flattening and the orientation of the stellar and dark matter debris are significantly different, which prevents the prediction of the dark matter distribution from the observed stellar component.

[7]  arXiv:2003.09469 [pdf, other]
Title: Spectral classification of B stars: The empirical sequence using SDSS-IV/APOGEE near-IR data
Comments: 11 pages, 7 figures and 1 table
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We present a semi-empirical spectral classification scheme for normal B-type stars using near-infrared spectra (1.5-1.7 $\mu$m) from the SDSS APOGEE2-N DR14 database. The main motivation for working with B-type stars is their importance in the evolution of young stellar clusters, however we also take advantage of having a numerous sample (316 stars) of B-type star candidates in APOGEE2-N, for which we also have optical (3600-9100 \angstrom) counterparts from the LAMOST survey. By first obtaining an accurate spectral classification of the sources using the LAMOST DR3 spectra and the canonical spectral classification scheme Gray & Corbally 2009, we found a linear relation between optical spectral types and the equivalent widths of the hydrogen lines of the Brackett series in the APOGEE2-N NIR spectra. This relation extends smoothly from a similar relation for O and early-B stars found by Roman-Lopes et al. (2018). This way, we obtain a catalog of B-type sources with features in both the optical and NIR, and a classification scheme refined down to one spectral sub-class.

[8]  arXiv:2003.09473 [pdf, other]
Title: Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud V: Multiple Populations in ancient Globular Clusters
Comments: Accepted in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We examine four ancient Large Magellanic Cloud (LMC) globular clusters (GCs) for evidence of multiple stellar populations using the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope Programme GO-14164. NGC 1466, NGC 1841, and NGC 2257 all show evidence for a redder, secondary population along the main-sequence. Reticulum does not show evidence for the presence of a redder population, but this GC has the least number of stars and Monte Carlo simulations indicate that the sample of main sequence stars is too small to robustly infer whether a redder population exists in this cluster. The second, redder, population of the other three clusters constitutes $\sim30-40\%$ of the total population along the main-sequence. This brings the total number of ancient LMC GCs with known split or broadened main-sequences to five. However, unlike for Hodge 11 and NGC 2210 (see arXiv:1904.01434), none of the clusters show evidence for multiple populations in the horizontal branch. We also do not find evidence of a second population along the Red Giant Branch (RGB).

[9]  arXiv:2003.09492 [pdf, other]
Title: First spectroscopic study of ionized gas emission lines in the extreme low surface brightness galaxy Malin 1
Comments: 18 pages, 15 figures, accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Malin 1 is the largest known low surface brightness (LSB) galaxy, the archetype of so-called giant LSBs. The structure and the origin of such galaxies are still poorly understood, especially due to the lack of high-resolution kinematics and spectroscopic data. We use emission lines from spectroscopic observations of Malin 1 aiming to bring new constraints on the internal dynamics and star formation history of Malin 1. We have extracted a total of 16 spectra from different regions of Malin 1 and calculated the rotational velocities of these regions from the wavelength shifts and star formation rates from the observed H$\alpha$ emission line fluxes. We compare our data with existing data and models for Malin 1. For the first time we present the inner rotation curve of Malin 1, characterized in the radial range r < 10 kpc by a steep rise in the rotational velocity up to at least 350 km/s (with a large dispersion), which had not been observed previously. We use these data to study a suite of new mass models for Malin 1. We show that in the inner regions dynamics may be dominated by the stars (although none of our models can explain the highest velocities measured) but that at large radii a massive dark matter halo remains necessary. The H$\alpha$ fluxes derived star formation rates are consistent with an early-type disk for the inner region, and with the level found in extended UV galaxies for the outer parts of the giant disk of Malin 1. We also find signs of high metallicity but low dust content for the inner regions.

[10]  arXiv:2003.09511 [pdf, other]
Title: Accretion in low-mass members of the Orion Nebula Cluster with young transition disks
Comments: 12 pages, 6 figures (17 pages, 11 figures if appendix included). Accepted by Astronomy and Astrophysics on 24/02/2020
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

Although the Orion Nebula Cluster is one of the most studied clusters in the solar neighborhood, the evolution of the very low-mass members ($M_* < 0.25 \, M_\odot$) has not been fully addressed due to their faintness. Our goal is to verify if some young and very low-mass objects in the Orion Nebula Cluster show evidence of ongoing accretion using broadband VLT/X-Shooter spectra. For each target, we determined the corresponding stellar parameters, veiling, observed Balmer jump, and accretion rates. Additionally, we searched for the existence of circumstellar disks through available on-line photometry. We detected accretion activity in three young stellar objects in the Orion Nebula Cluster, two of them being in the very low-mass range. We also detected the presence of young transition disks with ages between 1 and 3.5 Myr.

[11]  arXiv:2003.09563 [pdf, other]
Title: The Average Physical Properties of A-G Stars Derived from uvby-H$β$ Strömgren-Crawford Photometry as the Basis for a Spectral-Classification Synthetical Approach
Comments: 20 pages, 22 figures, 9 tables, accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We have revisited and updated the $uvby$ Str\"omgren colour and colour-index distributions of A, F and early G-type main sequence stars. For this aim, we selected 7054 dwarf stars along with 65 MK standard stars within the same spectral range but covering all luminosity classes. The standard stars were selected following the MK mandate strictly, using spectra taken at classification resolution recorded on photographic plates. We used the colours of these stars to determine the effective temperature and surface gravity. After correcting for systematic offsets using fundamental parameters and considering a few exceptions, we find an one-to-one correspondence, among MK spectral types, Str\"omgren photometry, and their associated physical properties.
We have applied a principal component analysis to the mean Str\"omgren indices for dwarf stars complemented by MK standards for higher luminosity classes. We have used the projections to introduce three new photometric metaindices, namely SM1, SM2, and SM3. We have defined a 3D-box, which allowed us to segregate dwarf stars from bright giants and supergiant stars, with the aid of the metaindices. Two of the planes show that the projections of dwarfs and supergiants are ordered by temperature; however, the temperature dependence for the supergiants is not as well defined as for the dwarfs. Following the MK Process, we were able to form an automatic classifier. We present some applications and assigned synthetical spectral types. We suggest that our metaindices formalism allows the extension of Str\"omgren photometric outside its original mandate (i.e., later types), without requiring the introduction of additional photometric filters.

[12]  arXiv:2003.09567 [pdf, ps, other]
Title: Observations of a quasi-periodic pulsation in the coronal loop and microwave flux during a solar preflare phase
Comments: 13 pages, 4 figures, accepted by the ApJL
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report a quasi-periodic pulsation (QPP) event simultaneously detected from the spatial displacements of coronal loop at both EUV images and microwave emission during the preflare phase of a C1.1 flare on 2016 March 23. Using the motion magnification technique, a low-amplitude transverse oscillation with the growing period is discovered in a diffuse coronal loop in Atmospheric Imaging Assembly (AIA) image sequences at wavelength of 171 A, and the initial oscillation period is estimated to be ~397 s with a slow growth rate of 0.045. At the same time, a QPP with growing periods from roughly 300 s to nearly 500 s is discovered in the microwave flux in the same active region. Based on the imaging observations measured at EUV wavelengths by the AIA and at microwave 17 GHz by Nobeyama Radioheliograph, the diffuse coronal loop and the microwave radiation source are found to be connected through a hot loop seen in AIA images at wavelength of 94 A. The growing period of the QPP should be related to the modulation of LRC-circuit oscillating process in a current-carrying plasma loop. The existence of electric currents may imply the non-potentialities in the source region during the preflare phase.

[13]  arXiv:2003.09581 [pdf, other]
Title: Census of young stellar population in the Galactic H II region Sh2-242
Comments: 17 pages, 12 figures, Published in the Astronomical Journal
Journal-ref: AJ 159 (2020) 153
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present here identification and characterization of the young stellar population associated with an active star-forming site Sh2-242. We used our own new optical imaging and spectroscopic observational data, as well as several archival catalogs, e.g., Pan-STARRS 1, $Gaia$ DR2, IPHAS, WIRCam, 2MASS, and $Spitzer$. Slit spectroscopic results confirm the classification of the main ionizing source BD+26 980 as an early-type star of spectral type B0.5 V. The spectrophotometric distance of the star is estimated as 2.08 $\pm$ 0.24 kpc, which confirms the source as a member of the cluster. An extinction map covering a large area (diameter $\sim$ 50') is generated with $H$ and $K$ photometry toward the region. From the map, three distinct locations of peak extinction complexes ($A_{V}$ $\simeq$ 7$-$17 mag) are identified for the very first time. Using the infrared color excess, a total of 33 Class I and 137 Class II young objects are classified within the region. The IPHAS photometry reveals classification of 36 H$\alpha$ emitting sources, which might be class II objects. Among 36 H$\alpha$ emitting sources, 5 are already identified using infrared excess emission. In total, 201 young objects are classified toward S242 from this study. The membership status of the young sources is further windowed with the inclusion of parallax from the $Gaia$ DR2 catalog. Using the optical and infrared color-magnitude diagrams, the young stellar objects are characterized with an average age of $\sim$ 1 Myr and the masses in the range 0.1$-$3.0 $M_\odot$. The census of the stellar content within the region is discussed using combined photometric and spectroscopic data.

[14]  arXiv:2003.09591 [pdf, ps, other]
Title: The Effect of Ram-Pressure Stripping on Dwarf Galaxies
Authors: Patrick Steyrleithner (1), Gerhard Hensler (1), Alessandro Boselli (2) ((1) University of Vienna, (2) Aix Marseille Universitæ)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot intra-cluster medium (ICM) of galaxy clusters. For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to gas-poor systems by RPS is not easily observed and must happen in the outskirts of clusters. In a few objects in close by galaxy clusters and the field, RPS has been observed. Since cluster early-type DGs also show a large variety of internal structures (unexpected central gas reservoirs, blue stellar cores, composite radial stellar profiles), we aim in this study to investigate how ram pressure (RP) affects the interstellar gas content and therefore the star-formation (SF) activity. Using a series of numerical simulations, we quantify the dependence of the stripped-off gas on the velocity of the infalling DGs and on the ambient ICM density. We demonstrated that SF can be either suppressed or triggered by RP depending on the ICM density and the DGs mass. Under some conditions, RP can compress the gas, so that it is unexpectedly retained in the central DG region and forms stars. When gas clouds are still bound against stripping but lifted from a thin disk and fall back, their new stars form an ellipsoidal (young) stellar population already with a larger velocity dispersion without the necessity of harassment. Most spectacularly, star clusters can form downstream in stripped-off massive gas clouds in the case of strong RP. We compare our results to observations.

[15]  arXiv:2003.09613 [pdf, ps, other]
Title: Cardiopulmonary Arrest and Resuscitation of a Nearby Super Massive Black Hole
Comments: 8 pages, 4 figures and 1 table, accepted by AJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

The discovery of spectral type transition of active galactic nuclei (AGNs), the so-called changing-look(CL) phenomenon, challenges the widely accepted AGN paradigm, not only in the orientation based Unified Model, but also in the standard disk model. In past decades, only a couple of nearby repeat "changing-look" active galactic nuclei (CL-AGNs) have been identified. Here we report spectroscopic observations of UGC 3223 over the course of 18 years, from 2001 onwards. Combining the spectrum taken in 1987 by Stirpe, we have witnessed its type transitions from $1.5\rightarrow2.0\rightarrow1.8$ over 32 years, and captured a long-lived (at least 10 years) thorough "turn-off" state with a spectrum typical of a Seyfert 2 galaxy. The long-term thorough "turn-off" state probably suggests a once-dormant and an awakening central engine in UGC3223. We argue the (dis)appearance of the broad Balmer emission lines can be explained by the disk-wind BLR model given the evolution of the calculated Eddington ratio of accretion of the supermassive black hole.

[16]  arXiv:2003.09639 [pdf, other]
Title: Opportunities to Search for Extra-Terrestrial Intelligence with the Five-hundred-meter Aperture Spherical radio Telescope
Comments: 14 pages, 8 figures, Accepted by Research in Astron. Astrophys. (FAST special issue)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The discovery of ubiquitous habitable extrasolar planets, combined with revolutionary advances in instrumentation and observational capabilities, has ushered in a renaissance in the search for extra-terrestrial intelligence (SETI). Large scale SETI activities are now underway at numerous international facilities. The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the largest single-aperture radio telescope in the world, well positioned to conduct sensitive searches for radio emission indicative of exo-intelligence. SETI is one of the five key science goals specified in the original FAST project plan. A collaboration with the Breakthrough Listen Initiative has been initiated in 2016 with a joint statement signed both by Dr. Jun Yan, the then director of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC), and Dr. Peter Worden, the Chairman of the Breakthrough Prize Foundation. In this paper, we highlight some of the unique features of FAST that will allow for novel SETI observations. We identify and describe three different signal types indicative of a technological source, namely, narrow-band, wide-band artificially dispersed, and modulated signals. We here propose observations with FAST to achieve sensitivities never before explored.

[17]  arXiv:2003.09646 [pdf]
Title: Unveiling the secrets of the mid-infrared Moon
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The Moon's optical characteristics in visible and long-wavelength infrared (LWIR) have long been observed with our eyes or with instruments. What the mid-infrared (MIR) Moon looks like is still a mystery. For the first time we present detailed appearance of the MIR Moon observed by a high-resolution geostationary satellite and reveal the essence behind its appearance. The appearance of the MIR Moon is opposite to its normal visible appearance. In addition the MIR Moon shows limb darkening. Both the absolute and the relative brightness distribution of the MIR lunar disk changes with the solar incidence angle. The signatures of the MIR Moon are controlled by both the reflection and emission of the lunar surface. We also show first-ever brightness temperature maps of the lunar disk without needing a mosaic, which better show the temperature variation across the lunar disk. They reveal that the relationship between brightness temperature and solar incidence angle i is cos1/bi, and the power parameter is smaller than the Lambertian temperature model of cos1/4i observed for lunar orbit-based measurements. The slower decrease of the brightness temperature when moving away from the sub-solar point than the Lambertian model is due to topographic effects. The brightness temperature is dominated by albedo and the solar incidence angle and influenced by the topography. Our results indicate that the Moon in the MIR exhibits many interesting phenomena which were previously unknown, and contains abundant information about lunar reflection and thermal emission for future study.

[18]  arXiv:2003.09655 [pdf, other]
Title: Intensity Mapping as a Probe of Axion Dark Matter
Authors: Jurek B. Bauer (U Göttingen), David J. E. Marsh (U Göttingen), Renée Hložek (U Toronto), Hamsa Padmanabhan (CITA), Alex Laguë (U Toronto/CITA)
Comments: 16 pages, 14 figures, 2 tables, code to reproduce our results is publicly available at this https URL
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)

Intensity mapping (IM) of spectral lines has the potential to revolutionize cosmology by increasing the total number of observed modes by several orders of magnitude compared to the cosmic microwave background (CMB) anisotropies. In this paper, we consider IM of neutral hydrogen (HI) in the redshift range $0 \lesssim z \lesssim 3$ employing a halo model approach where HI is assumed to follow the distribution of dark matter (DM) halos. If a portion of the DM is composed of ultralight axions then the abundance of halos is changed compared to cold dark matter below the axion Jeans mass. With fixed total HI density, $\Omega_{\rm HI}$, assumed to reside entirely in halos, this effect introduces a scale-independent increase in the HI power spectrum on scales above the axion Jeans scale, which our model predicts consistent with N-body simulations. Lighter axions introduce a scale-dependent feature even on linear scales due to its suppression of the matter power spectrum near the Jeans scale. We use the Fisher matrix formalism to forecast the ability of future HI surveys to constrain the axion fraction of DM and marginalize over astrophysical and model uncertainties. We find that a HIRAX-like survey is a very reliable IM survey configuration, being affected minimally by uncertainties due to non-linear scales, while the SKA1MID configuration is the most constraining as it is sensitive to non-linear scales. Including non-linear scales and combining a SKA1MID-like IM survey with the Simons Observatory CMB, the benchmark ''fuzzy DM'' model with $m_a = 10^{-22}\text{ eV}$ can be constrained at the 10% level. For lighter ULAs this limit improves below 1%, and allows the possibility to test the connection between axion models and the grand unification scale across a wide range of masses.

[19]  arXiv:2003.09656 [pdf, other]
Title: 3D Radiative MHD simulations of starspots
Comments: Accepted to ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

There are no direct spatially resolved observations of spots on stars other than the Sun and starspot properties are inferred indirectly through lightcurves and spectropolarimetric data. We present the first self-consistent 3D radiative MHD computations of starspots on G2V, K0V and M0V stars, which will help to better understand observations of activity, variability and magnetic fields in late-type main-sequence stars. We used the MURaM code, which has been extensively used to compute "realistic" sunspots, for our simulations. We aim to study how fundamental starspot properties such as intensity contrast, temperature and magnetic field strength vary with spectral type. We first simulated in 2D, multiple spots of each spectral type to find out appropriate initial conditions for our 3D runs. We find that with increasing stellar effective temperature, there is an increase in the temperature difference between the umbra of the spot and its surrounding photosphere, from 350K on the M0V star to 1400K on the G2V star. This trend in our simulated starspots is consistent with observations. The magnetic field strengths of all the starspot umbrae are in the 3-4.5 kG range. The G2V and K0V umbrae have comparable magnetic field strengths around 3.5 kG, while the M0V umbra has a relatively higher field strength around 4 kG. We discuss the physical reasons behind both these trends. All of the three starspots develop penumbral filament-like structures with Evershed flows. The average Evershed flow speed drops from 1.32 km s$^{-1}$ in the G2V penumbra to 0.6 km s$^{-1}$ in the M0V penumbra.

[20]  arXiv:2003.09663 [pdf, other]
Title: Testing the Kerr black hole hypothesis using X-ray reflection spectroscopy and a thin disk model with finite thickness
Comments: 15 pages, 9 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

X-ray reflection spectroscopy is a powerful tool for probing the strong gravity region of black holes and can be used for testing general relativity in the strong field regime. Simplifications of the available relativistic reflection models limit the capability of performing accurate measurements of the properties of black holes. In this paper, we present an extension of the model RELXILL_NK in which the accretion disk has a finite thickness rather than being infinitesimally thin. We employ the accretion disk geometry proposed by Taylor & Reynolds (2018) and we construct relativistic reflection models for different values of the mass accretion rate of the black hole. We apply the new model to high quality Suzaku data of the X-ray binary GRS 1915+105 to explore the impact of the thickness of the disk on tests of the Kerr metric.

[21]  arXiv:2003.09697 [pdf, other]
Title: Populations of filaments from the distribution of galaxies in numerical simulations
Comments: submitted to A&A, 12 pages, 13 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

We present a statistical study of the filamentary structures of the Cosmic Web in the large hydro-dynamical simulations TNG300-1 and MAGNETICUM at redshift z=0. We focus on the radial distribution of the galaxy density around filaments detected using the Discrete Persistent Structure Extractor (DisPerSE). We show that the average profile of filaments presents an excess of galaxy density (> 5 sigma) up to radial distances of 27 Mpc from the core. The relation between galaxy density and the length of filaments is further investigated showing that short (L_f < 9 Mpc) and long (L_f > 20 Mpc) filaments are two statistically different populations. Short filaments are puffier, denser and more connected to massive objects, whereas long filaments are thinner, less dense and more connected to less massive structures. These two populations trace different environments and may correspond to bridges of matter between over-dense structures (short filaments) and to the cosmic filaments shaping the skeleton of the Cosmic Web (long filaments). Through MCMC explorations, we find that the density profiles of both short and long filaments can be described by the same empirical models (GNFW, beta-model, a single and a double power law) with different and distinct sets of parameters.

[22]  arXiv:2003.09701 [pdf, other]
Title: Deep search for hydrogen peroxide toward pre- and protostellar objects -- Testing the pathway of grain surface water formation
Comments: 13 pages, 4 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Context: In the laboratory, hydrogen peroxide (HOOH) was proven to be an intermediate product in the solid-state reaction scheme that leads to the formation of water on icy dust grains. When HOOH desorbs from the icy grains, it can be detected in the gas phase. In combination with water detections, it may provide additional information on the water reaction network. Hydrogen peroxide has previously been found toward $\rho$ Oph A. However, further searches for this molecule in other sources failed. Hydrogen peroxide plays a fundamental role in the understanding of solid-state water formation and the overall water reservoir in young stellar objects (YSOs). Without further HOOH detections, it is difficult to assess and develop suitable chemical models that properly take into account the formation of water on icy surfaces. Aims: The objective of this work is to identify HOOH in YSOs and thereby constrain the grain surface water formation hypothesis. Methods: Using an astrochemical model based on previous work in combination with a physical model of YSOs, the sources R CrA-IRS\,5A, NGCC1333-IRAS\,2A, L1551-IRS\,5, and L1544 were identified as suitable candidates for an HOOH detection. Long integration times on the APEX 12m and IRAM 30m telescopes were applied to search for HOOH signatures in these sources. Results: None of the four sources under investigation showed convincing spectral signatures of HOOH. The upper limit for HOOH abundance based on the noise level at the frequency positions of this molecule for the source R CrA-IRS\,5A was close to the predicted value. For NGC1333-IRAS 2A, L1544, and L1551-IRS\,5, the model overestimated the hydrogen peroxide abundances.

[23]  arXiv:2003.09705 [pdf, other]
Title: Askaryan radiation from neutrino-induced showers in ice
Comments: 18 pages, 11 figures. Accepted in Phys. Rev. D
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a semi-analytical method for the calculation of coherent Askaryan radiation in showers induced by neutrinos of any flavor in ice. We compare our results with those of a full Monte Carlo simulation based on the ZHAireS code. This approach is able to reproduce the vector potential and hence electric field at any experimentally relevant observer position in the time domain. This work extends published results only valid for electron-induced showers. We establish the validity of the semi-analytical calculation of the radio signal produced by all types of neutrino-induced showers in ice. The method is computationally efficient and only requires as inputs the longitudinal charge excess profile of the showers and a parameterization of the vector potential in the far-field region of the shower at the Cherenkov angle that we also provide. Our methodology avoids tracking the contributions to the electric field from millions of particles every time the radio pulse has to be calculated at a given observer position. These results can be readily used in the interpretation of the data taken by experiments, and in the planning and design of future initiatives based on the radio technique in ice.

[24]  arXiv:2003.09709 [pdf, other]
Title: The Carnegie Supernova Project II. The shock wave revealed through the fog: the strongly interacting Type IIn SN 2013L
Comments: Accepted for publication on Astronomy and Astrophysics, 43 pages, 29 figures. Abstract abridged
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We present ultra-violet to mid-infrared observations of the long-lasting Type IIn supernova (SN) 2013L obtained by the Carnegie Supernova Project II (CSP-II). The spectra of SN 2013L are dominated by H emission features characterized by three components attributed to different regions. A unique feature of this Type IIn SN is that the blue shifted line profile is dominated by the macroscopic velocity of the expanding shock wave of the SN. We are therefore able to trace the evolution of the shock velocity in the dense and partially opaque circumstellar medium (CSM), from $\sim 4800~km~s^{-1}$ at +48 d, decreasing as $t^{-0.23}$ to $\sim 2700~km~s^{-1}$ after a year. We perform spectral modeling of both the broad- and intermediate-velocity components of the H$\alpha$ line profile. The high-velocity component is consistent with emission from a radially thin, spherical shell located behind the expanding shock with emission wings broadened by electron scattering. We propose that the intermediate component originates from pre-ionized gas from the unshocked dense CSM with the same velocity as the narrow component, $\sim 100~km~s^{-1}$, but also broadened by electron scattering. The spectral energy distributions (SEDs) of SN 2013L after +132 d are well reproduced by a two-component black-body (BB) model. The circumstellar-interaction model of the bolometric light curve reveals a mass-loss rate history with large values ($1.7\times 10^{-2} - 0.15~M_\odot~yr^{-1}$) over the $\sim $25 - 40 years before explosion. The drop in the light curve at $\sim 350$ days and presence of electron scattering wings at late epochs indicate an anisotropic CSM. The mass-loss rate values and the unshocked CSM velocity are consistent with the characteristics of a massive star, like a luminous blue variable (LBV) undergoing strong eruptions, similar to $\eta$ Carina.

[25]  arXiv:2003.09718 [pdf, other]
Title: Dynamic Scheduling: Target of Opportunity Observations of Gravitational Wave Events
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

The simultaneous detection of electromagnetic (EM) and gravitational waves from the coalescence of two neutron stars (GW/GRB170817A) has ushered in a new era of "multi-messenger" astronomy, with EM detections spanning from gamma to radio. This great opportunity for new scientific investigations raises the issue of how the available multi-messenger tools can best be integrated to constitute a powerful method to study the transient universe in particular. To facilitate the classification of possible optical counterparts to gravitational-wave events, it is important to optimize the scheduling of observations and the filtering of transients, both key elements of the follow-up process. In this work, we describe the existing workflow whereby telescope networks such as GRANDMA and GROWTH are currently scheduled; we then present modifications we have developed for the scheduling process specifically, identifying the relevant challenges that have appeared during the latest observing run. We address issues with scheduling more than one epoch for multiple fields within a skymap, especially for large and disjointed localizations. This is done in two ways: by optimizing the maximum number of fields that can be scheduled, and by splitting up the lobes within the skymap by right ascension to be scheduled individually. In addition, we implement the ability to take previously observed fields into consideration when rescheduling. We show the improvements that these modifications produce in making the search for optical counterparts more efficient, and we point to areas needing further improvement.

[26]  arXiv:2003.09732 [pdf, other]
Title: WIYN Open Cluster Study. LXXVII. Radial-Velocity Measurements and Spectroscopic Binary Orbits in the Open Cluster NGC 7789
Comments: 47 pages, 16 figures. Submitted to AJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

We introduce the stellar sample of the WIYN Open Cluster Study radial-velocity survey for the rich open cluster NGC 7789 (1.6 Gyr, [Fe/H] = +0.02). This sample lies within an 18$'$ circular radius from the cluster center (10 pc in projection, or about 2 core radii), and includes giants, red-clump stars, blue stragglers, red stragglers, sub-subgiants, and main-sequence stars down to one mag below the turnoff. Our survey began in 2005 and comprises more than 9,000 radial-velocity measurements from the Hydra Multi-Object Spectrograph on the WIYN 3.5m telescope. We identify 564 likely cluster members and present the orbital solutions for 83 cluster binary stars with periods between 1.45$\,$d and 4200$\,$d. From the main-sequence binary solutions we fit a circularization period of 8.22$^{+3.51}_{-1.35}\,$d. We calculate an incompleteness-corrected main-sequence binary frequency of 31% $\pm$ 3% for binaries with periods less than 10$^{4}$ days, similar to other WOCS open clusters of all ages. We detect a blue straggler binary frequency of 31% $\pm$ 15%, consistent with the similarly aged cluster NGC 6819.

[27]  arXiv:2003.09738 [pdf, other]
Title: Self-gravitating barotropic equilibrium configurations of rotating bodies with SPH
Comments: 12 pages, 6 figures, 4 Tables, accepted for publication in Astronomy and Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present a novel relaxation method to build three-dimensional rotating structures of barotropic bodies using the SPH technique. The method is able to relax gaseous structures in rigid as well as differential rotation. The relaxation procedure strongly relies on the excellent conservation of angular momentum that characterizes the SPH technique. The method has been successfully applied to a variety of zero-temperature white dwarfs and polytropic self-gravitating structures. Our SPH results have been validated by comparing the main features (energies, central densities and the polar to equatorial radius ratio) to those obtained with independent, albeit grid-based methods, as for example, the self-consistent field method, showing that both methods agree within few percents.

[28]  arXiv:2003.09760 [pdf, other]
Title: Fluctuation dynamo in a weakly collisional plasma
Comments: 62 pages, 25 figures, 1 table, submitted for publication to Journal of Plasma Physics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph)

The turbulent amplification of cosmic magnetic fields depends upon the material properties of the host plasma. In many hot, dilute astrophysical systems, such as the intracluster medium (ICM) of galaxy clusters, the rarity of particle--particle collisions allows departures from local thermodynamic equilibrium. These departures exert anisotropic viscous stresses on the plasma motions that inhibit their ability to stretch magnetic-field lines. We present a numerical study of the fluctuation dynamo in a weakly collisional plasma using magnetohydrodynamic (MHD) equations endowed with a field-parallel viscous (Braginskii) stress. When the stress is limited to values consistent with a pressure anisotropy regulated by firehose and mirror instabilities, the Braginskii-MHD dynamo largely resembles its MHD counterpart. If instead the parallel viscous stress is left unabated -- a situation relevant to recent kinetic simulations of the fluctuation dynamo and to the early stages of the dynamo in a magnetized ICM -- the dynamo changes its character, amplifying the magnetic field while exhibiting many characteristics of the saturated state of the large-Prandtl-number (${\rm Pm}\gtrsim{1}$) MHD dynamo. We construct an analytic model for the Braginskii-MHD dynamo in this regime, which successfully matches magnetic-energy spectra. A prediction of this model, confirmed by our simulations, is that a Braginskii-MHD plasma without pressure-anisotropy limiters will not support a dynamo if the ratio of parallel and perpendicular viscosities is too large. This ratio reflects the relative allowed rates of field-line stretching and mixing, the latter of which promotes resistive dissipation of the magnetic field. In all cases that do exhibit a dynamo, the generated magnetic field is organized into folds that persist into the saturated state and bias the chaotic flow to acquire a scale-dependent spectral anisotropy.

[29]  arXiv:2003.09776 [pdf, ps, other]
Title: Characteristic masses in galaxy quenching: environmental versus internal effects
Comments: 7 pages, 4 figures, submitted to AAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

A clear transition of galaxy quenching is identified in the multi-parameter space of stellar mass ($M_*$), bulge to total mass ratio ($B/T_{\rm m}$), halo mass ($M_{\rm h}$) and halo-centric distance ($r/r_{180}$). For a given halo mass, the characteristic stellar mass ($M_{*, \rm c}$) for the transition is about one-fifth of the stellar mass of the corresponding central galaxy, and almost independent of $B/T_{\rm m}$. Once $B/T_{\rm m}$ is fixed, the quenched fraction of galaxies with $M_*<M_{*, \rm c}$ increases with $M_h$, but {\it decreases} with $M_*$ in the inner part of halos ($r/r_{180}<0.5$). In the outer part ($r/r_{180}>0.5$), the trend with $M_{\rm h}$ remains but the correlation with $M_*$ is absent or becomes positive. For galaxies above $M_{\rm *, c}$ and with $B/T_{\rm m}$ fixed, the quenched fraction increases with $M_{\rm *}$, but depends only weakly on $M_{\rm h}$ in both the inner and outer regions. In general the quenched fraction increases with $B/T_{\rm m}$ when other parameters are fixed. We discuss the implications of the characteristic stellar mass for internal and environmental quenching processes. Our results suggest that environmental quenching is important only for galaxies with $M_*<M_{*, \rm c}$, while internal quenching plays the dominating role for high-mass galaxies. The efficiencies of internal and environmental quenching both depend on $B/T_{\rm m}$.

[30]  arXiv:2003.09780 [pdf, other]
Title: The Parkes Pulsar Timing Array Project: Second data release
Comments: 26 pages, 6 figures. Accepted for publication in PASA. The data release can be downloaded from this https URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We describe 14 years of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements of pulse times of arrival from 26 millisecond pulsars using the 64-m Parkes radio telescope with a cadence of approximately three weeks in three observing bands. A comprehensive description of the pulsar observing systems employed at the telescope since 2004 is provided, including the calibration methodology and an analysis of the stability of system components. We attempt to provide full accounting of the reduction from the raw measured Stokes parameters to pulse times of arrival to aid third parties in reproducing our results. This conversion is encapsulated in a processing pipeline designed to track provenance. Our data products include pulse times of arrival for each of the pulsars along with an initial set of pulsar parameters and noise models. The calibrated pulse profiles and timing template profiles are also available. These data represent almost 21,000 hrs of recorded data spanning over 14 years. After accounting for processes that induce time-correlated noise, 22 of the pulsars have weighted root-mean-square timing residuals of < 1 ${\mu}$s in at least one radio band. The data should allow end users to quickly undertake their own gravitational-wave analyses (for example) without having to understand the intricacies of pulsar polarisation calibration or attain a mastery of radio-frequency interference mitigation as is required when analysing raw data files.

[31]  arXiv:2003.09811 [pdf, other]
Title: First embedded cluster formation in California molecular cloud
Comments: 6 pages, 5 figures, accepted for publication in ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We performed a multi-wavelength observation toward LkHa 101 embedded cluster and its adjacent 85arcmin*60arcmin region. The LkHa 101 embedded cluster is the first and only one significant cluster in California molecular cloud (CMC). These observations have revealed that the LkHa 101 embedded cluster is just located at the projected intersectional region of two filaments. One filament is the highest-density section of the CMC, the other is a new identified filament with a low-density gas emission. Toward the projected intersection, we find the bridging features connecting the two filaments in velocity, and identify a V-shape gas structure. These agree with the scenario that the two filaments are colliding with each other. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we measured that the RRL velocity of the LkHa 101 H II region is 0.5 km/s, which is related to the velocity component of the CMC filament. Moreover, there are some YSOs distributed outside the intersectional region. We suggest that the cloud-cloud collision together with the fragmentation of the main filament may play an important role in the YSOs formation of the cluster.

[32]  arXiv:2003.09818 [pdf, ps, other]
Title: Emergent gravity fails to explain color-dependent galaxy-galax lensing signals from SDSS Dr7
Comments: 7 pages, 3 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We test the Emergent Gravity(EG) theory using the galaxy-galaxy lensing technique based on SDSS DR7 data. In the EG scenario, we do not expect color dependence of the galaxy sample in the 'apparent dark matter' predicted by EG, which is exerted only by the baryonic mass. If the baryonic mass is similar, then the predicted lensing profiles from the baryonic mass should be similar according to the EG, regardless of the color of the galaxy sample. We use the stellar mass of the galaxy as a proxy of its baryonic mass. We divide our galaxy sample into 5 stellar mass bins, and further classify them as red and blue subsamples in each stellar mass bin. If we set halo mass and concentration as free parameters, $\Lambda$CDM is favored by our data in terms of the reduced $\chi^2$ while EG fails to explain the color dependence of ESDs from the galaxy-galaxy lensing measurement.

[33]  arXiv:2003.09825 [pdf, other]
Title: Reconstruction of Radio Relics and X-ray Tails in an Off-axis Cluster Merger: Hydrodynamical Simulations of A115
Comments: 14 pages, 11 figures, Submitted to ApJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

Although a merging galaxy cluster is a useful laboratory to study many important astrophysical processes and fundamental physics, only limited interpretations are possible without careful analysis of the merger scenario. However, the study is demanding because a thorough comparison of multi-wavelength observations with detailed numerical simulations is required. In this paper, we present such a study for the off-axis binary merger A115. The system possesses a number of remarkable observational features, but no convincing merger scenario, explaining the shape and location of the radio relic in harmony with the orientation of the cometary X-ray tails, has been presented. Our hydrodynamical simulation, with adaptive mesh refinement, suggests that the cometary X-ray tail of A115 might be a slingshot tail and can arise $\sim0.3$ Gyrs after the impact and before the two subclusters reach their apocenters. This scenario can predict the location and orientation of the giant radio relic, which is parallel to the northern X-ray tail. In addition, our study indicates that diffusive shock acceleration alone cannot generate the observed radio power unless aided by stronger magnetic fields and/or more significant presence of fossil electrons.

[34]  arXiv:2003.09842 [pdf]
Title: Near-Infrared Photometry of Superthin Edge-on Galaxies
Comments: 10 pages, 6 figures, accepted for publication in Astronomische Nachrichten
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We perform near-infrared photometry of a large sample of 49 superthin edge-on galaxies. These galaxies are selected based on optical photometry because of high radial-to-vertical scale ratio in their stellar disks. The Near Infrared (NIR) H and K observations were conducted with the cryogenic-cooled camera ASTRONIRCAM on the 2.5m telescope at the Caucasus Mountain Observatory of Lomonosov Moscow State University. A majority of galaxies in our sample show comparable or better photometric depth than the Sloan Digital Sky Survey (SDSS) optical images. We estimate the structural parameters of stellar disks in the galaxies and find that the NIR scale height of stellar disks is comparable to that estimated from the optical, SDSS g, r and i, whereas the H and K scale length of the stellar disks is significantly shorter than in the g, r and i. We investigate if a realistic distribution of dust alone can explain the difference in the scale length and find that in the majority of the galaxies the radial variation of the stellar population is actually responsible for the color distribution. The latter suggests a younger age of the disks periphery, and the inside out building up of stellar disks in the superthin galaxies.

[35]  arXiv:2003.09863 [pdf, other]
Title: Analysis of absorption lines in the high resolution spectra of five hot post-AGB candidates
Authors: A. Herrero (1 and 2), M. Parthasarathy (3 and 4), S. Simon-Diaz (1 and 2), S. Hubrig (5), G. Sarkar (6), S. Muneer (3) ((1) Instituto de Astrofisíca de Canarias, La Laguna, Tenerife, Spain, (2) Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain, (3) Indian Institute of Astrophysics, Koramangala, Bangalore, India, (4) National Astronomical Observatory of Japan (NAOJ), Mitaka, Tokyo, Japan, (5) Leibniz-Institute for Astrophysik, Potsdam (AIP), Potsdam, Germany, (6) Indian Institute of Technology, Kanpur, India)
Comments: 15 pages, 10 figures accepted for MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

From an analysis of absorption lines in the high resolution spectra we have derived the radial velocities, stellar parameters (Teff, gravity, wind-strength parameter logQ and projected rotational velocity) and abundances (C, N, O, and Si ) of IRAS 17460-3114, IRAS 18131-3008, IRAS 19336-0400, LSE 45 and LSE 163. Abundances are found to be solar, except for a low Si abundance in IRAS 19336-0400 and a mild CNO pattern in LSE 163, that rotates at an unusual large rotational velocity for its spectral classification. Combining the stellar parameters information with Gaia DR2 data we are able to derive absolute magnitudes, radii and luminosities and clarify the possible post-AGB nature of the objects. IRAS 17460-3114 and IRAS 18131-3008 are found to be massive OB stars, whereas IRAS 19336-0400 is found to be a post-AGB star, already showing nebular lines in the spectrum. However, we could not confirm the nature of LSE 45 and LSE 163 as post-AGB stars, although their parameters are much more inconsistent with those of massive stars. In both cases, we find a discrepancy between the spectroscopic mass and that derived from the predictions of post-AGB evolutionary tracks. In addition, LSE 45 lacks nebular lines, that are present in IRAS 19336-0400 at a similar temperature. In the case of LSE 163 the rotational velocity (259+/-15 km/s) would be extremely large for a star evolving to CSPN. The combination of this rotational velocity, the high Galactic latitude, slightly large radial velocity and mild CNO enhancement suggests a history of binary interaction.

[36]  arXiv:2003.09900 [pdf, other]
Title: Cosmic ray feedback from supernovae in dwarf galaxies
Comments: 19 pages, 15 figures, submitted
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The regulation of the baryonic content in dwarf galaxies is a long-standing problem. Supernovae (SNe) are supposed to play a key role in forming large-scale galactic winds by removing important amounts of gas from galaxies. SNe are efficient accelerators of non-thermal particles, so-called cosmic rays (CRs), which can substantially modify the dynamics of the gas and conditions to form large-scale galactic winds. We investigate how CR injection by SNe impacts the star formation and the formation of large-scale winds in dwarf galaxies, and whether it can produce galaxy star formation rates (SFR) and wind properties closer to observations. We run CR magneto-hydrodynamical simulations of dwarf galaxies at high resolution (9 pc) with the adaptive mesh refinement code ramses. Those disc galaxies are embedded in isolated halos of mass $10^{10}$ and $10^{11} \, \rm M_{\odot}$, and CRs are injected by SNe. We include CR isotropic and anisotropic diffusion with various diffusion coefficients, CR radiative losses, and CR streaming.The injection of CR energy into the interstellar medium smooths out the highest gas densities, which reduces the SFR by a factor of 2-3. Mass outflow rates are significantly greater with CR diffusion, by 2 orders of magnitudes for the higher diffusion coefficients. Without diffusion and streaming, CRs are inefficient at generating winds. CR streaming alone allows for the formation of winds but which are too weak to match observations. The formation of galactic winds strongly depends on the diffusion coefficient: for low coefficients, CR energy stays confined in high density regions where CR energy losses are highest, and higher coefficients, which allow for a more efficient leaking of CRs out of dense gas, produce stronger winds. CR diffusion leads to colder and denser winds than without CRs, and brings outflow rates and mass loading factors much closer to observations.

[37]  arXiv:2003.09925 [pdf]
Title: Formation of embryos of the Earth and the Moon from the common rarefied condensation and their subsequent growth
Authors: S. I. Ipatov
Comments: 16 pages
Journal-ref: Solar System Research, 2018, v. 52, N 5, p. 401-416
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Embryos of the Moon and the Earth may have formed as a result of contraction of a common parental rarefied condensation. The required angular momentum of this condensation could largely be acquired in a collision of two rarefied condensations producing the parental condensation. With the subsequent growth of embryos of the Moon and the Earth taken into account, the total mass of as-formed embryos needed to reach the current angular momentum of the Earth-Moon system could be below 0.01 of the Earth mass. For the low lunar iron abundance to be reproduced with the growth of originally iron-depleted embryos of the Moon and the Earth just by the accretion of planetesimals, the mass of the lunar embryo should have increased by a factor of 1.3 at the most. The maximum increase in the mass of the Earth embryo due to the accumulation of planetesimals in a gas-free medium is then threefold, and the current terrestrial iron abundance is not attained. If the embryos are assumed to have grown just by accumulating solid planetesimals (without the ejection of matter from the embryos), it is hard to reproduce the current lunar and terrestrial iron abundances at any initial abundance in the embryos. For the current lunar iron abundance to be reproduced, the amount of matter ejected from the Earth embryo and infalling onto the Moon embryo should have been an order of magnitude larger than the sum of the overall mass of planetesimals infalling directly on the Moon embryo and the initial mass of the Moon embryo, which had formed from the parental condensation, if the original embryo had the same iron abundance as the planetesimals. The greater part of matter incorporated into the Moon embryo could be ejected from the Earth in its multiple collisions with planetesimals (and smaller bodies).

[38]  arXiv:2003.09965 [pdf, other]
Title: A statistical study of the plasma and composition distribution inside magnetic clouds: 1998-2011
Comments: 11 pages,3 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

A comprehensive analysis of plasma and composition characteristics inside magnetic clouds (MCs) observed by the Advanced Composition Explorer (ACE) spacecraft from 1998 February to 2011 August is presented. The results show that MCs have specific interior structures, and MCs of different speeds show differences in composition and structure. Compared with the slow MCs, fast MCs have enhanced mean charge states of iron, oxygen, silicon, magnesium, $\mathrm{O^{7+}/O^{6+}}$, $\mathrm{C^{6+}/C^{5+}}$, $\mathrm{C^{6+}/C^{4+}}$ and $\mathrm{Fe^{\geq16+}/Fe_{total}}$ values. For ionic species in fast MCs, a higher atomic number represents a greater enhancement of mean charge state than slow MCs. We also find that both the fast and slow MCs display bimodal structure distribution in the mean iron charge state ($\mathrm{\langle Q\rangle Fe}$), which suggests that the existence of flux rope prior to the eruption is common. Furthermore, the $\mathrm{\langle Q\rangle Fe} $, $\mathrm{Fe^{\geq16+}/Fe_{total}}$, and $\mathrm{O^{7+}/O^{6+}}$ ratio distribution inside fast MCs have the feature that the posterior peak is higher than the anterior one. This result agrees with the "standard model" for CME/flares, by which magnetic reconnection occurs beneath the flux rope, thereby ionizing the ions of the posterior part of flux rope sufficiently by high-energy electron collisions or by direct heating in the reconnection region.

[39]  arXiv:2003.09982 [pdf]
Title: Delivery of water and volatiles to the terrestrial planets and the Moon
Comments: 9 pages
Journal-ref: Solar System Research, 2018, v. 52, N 5, p. 392-400
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

From modeling the evolution of disks of planetesimals under the influence of planets, it has been shown that the mass of water delivered to the Earth from beyond Jupiter's orbit could be comparable to the mass of terrestrial oceans. A considerable portion of the water could have been delivered to the Earth's embryo, when its mass was smaller than the current mass of the Earth. While the Earth's embryo mass was growing to half the current mass of the Earth, the mass of water delivered to the embryo could be near 30% of the total amount of water delivered to the Earth from the feeding zone of Jupiter and Saturn. Water of the terrestrial oceans could be a result of mixing the water from several sources with higher and lower D/H ratios. The mass of water delivered to Venus from beyond Jupiter's orbit was almost the same as that for the Earth, if normalized to unit mass of the planet. The analogous per-unit mass of water delivered to Mars was two-three times as much as that for the Earth. The mass of water delivered to the Moon from beyond Jupiter's orbit could be less than that for the Earth by a factor not more than 20.

[40]  arXiv:2003.09991 [pdf, other]
Title: Magnetohydrodynamic modelling of star-planet interaction and associated auroral radio emission
Comments: 13 pages, 10 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We present calculations of auroral radio powers of magnetised hot Jupiters orbiting Sun-like stars, computed using global magnetohydrodynamic (MHD) modelling of the magnetospheric and ionospheric convection arising from the interaction between the magnetosphere and the stellar wind. Exoplanetary auroral radio powers are traditionally estimated using empirical or analytically-derived relations, such as the Radiometric Bode's Law (RBL), which relates radio power to the magnetic or kinetic energy dissipated in the stellar wind-planet interaction. Such methods risk an oversimplification of the magnetospheric electrodynamics giving rise to radio emission. As the next step toward a self-consistent picture, we model the stellar wind-magnetosphere-ionosphere coupling currents using a 3D MHD model. We compute electron-cyclotron maser instability-driven emission from the calculated ionospheric field-aligned current density. We show that the auroral radio power is highly sensitive to interplanetary magnetic field (IMF) strength, and that the emission is saturated for plausible hot Jupiter Pedersen conductances, indicating that radio power may be largely independent of ionospheric conductance. We estimate peak radio powers of $10^{14}$ W from a planet exposed to an IMF strength of $10^3$ nT, implying flux densities at a distance of 15 pc from Earth potentially detectable with current and future radio telescopes. We also find a relation between radio power and planetary orbital distance that is broadly consistent with results from previous analytic models of magnetosphere-ionosphere coupling at hot Jupiters, and indicates that the RBL likely overestimates the radio powers by up to two orders of magnitude in the hot Jupiter regime

[41]  arXiv:2003.10029 [pdf, other]
Title: Excitation and charge transfer in low-energy hydrogen atom collisions with neutral manganese and titanium
Comments: 9 pages, 3 figures, 5 tables; accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Atomic Physics (physics.atom-ph)

Data for inelastic processes due to hydrogen atom collisions with manganese and titanium are needed for accurate modeling of the corresponding spectra in late-type stars. Excitation and charge transfer in low-energy Mn+H and Ti+H collisions is studied theoretically using a method based on an asymptotic two-electron linear combination of atomic orbitals model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multi-channel Landau-Zener model to treat the dynamics. Extensive calculations of charge transfer (mutual neutralization, ion-pair production), excitation and de-excitation processes in the two collisional systems are carried out for all transitions between covalent states dissociating to energies below the first ionic limit, and the dominating ionic states. Rate coefficients are determined for temperatures in the range 1000 - 20 000 K in steps of 1000 K. Like for earlier studies of other atomic species, charge transfer processes are found to lead to much larger rate coefficients than excitation processes.

[42]  arXiv:2003.10035 [pdf, ps, other]
Title: Time Variability of Nonthermal X-ray Stripes in Tycho's Supernova Remnant with Chandra
Comments: 8 pages, 3 figures, 2 tables, accepted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Analyzing Chandra data of Tycho's supernova remnant (SNR) taken in 2000, 2003, 2007, 2009, and 2015, we search for time variable features of synchrotron X-rays in the southwestern part of the SNR, where stripe structures of hard X-ray emission were previous found. By comparing X-ray images obtained at each epoch, we discover a knot-like structure in the northernmost part of the stripe region becomes brighter particularly in 2015. We also find a bright filamentary structure gradually becomes fainter and narrower as it moves outward. Our spectral analysis reveal that not only the nonthermal X-ray flux but also the photon indices of the knot-like structure change from year to year. During the period from 2000 to 2015, the small knot shows brightening of $\sim 70\%$ and hardening of $\Delta \Gamma \sim 0.45$. The time variability can be explained if the magnetic field is amplified to $\sim 100~\mathrm{\mu G}$ and/or if magnetic turbulence significantly changes with time.

[43]  arXiv:2003.10052 [pdf, other]
Title: Anisotropic separate universe simulations
Comments: 19 pages, 9 figures, 1 table, submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The long-wavelength coherent overdensity and tidal force, which are not direct observables for a finite-volume survey, affect time evolution of cosmic structure formation and therefore clustering observables through the mode coupling. In this paper we develop an "anisotropic" separate universe (SU) simulation technique to simulate large-scale structure formation taking into account the effect of large-scale tidal force into the anisotropic expansion of local background. We modify the TreePM N-body simulation code to implement the anisotropic SU simulations, and then study the "response" function of matter power spectrum that describes how the matter power spectrum responds to the large-scale tidal effect as a function of wavenumber and redshift for a given global cosmology. We test and validate the SU simulation results from the comparison with the perturbation theory predictions and the results from high-resolution PM simulation. We find that the response function displays characteristic scale dependences over the range of scales down to nonlinear scales, up to k ~ 6 h/Mpc.

[44]  arXiv:2003.10070 [pdf, other]
Title: Satellite Alignment: III. Satellite Galaxies Spatial Distribution and their Dependence on Redshift with A Novel Galaxy Finder
Comments: 15 pages,11 figures and 3 tables; accepted for publication in The Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

After extensively explored, broad agreement between observations and theories has been reached that satellites are preferentially aligned with major axes of their host centrals. There are still some issues unsolved on this topic. In this paper, we present studies on satellite spatial distribution. To fairly compare with observations, we develop a novel galaxy finder and reconstruction algorithm in hydrodynamical simulation, which is based on the projected mock image, taking into account the full consideration of the point spread function, pixel size, surface brightness limit, resolution and redshift dimming effects. With galaxy samples constructed using such an algorithm, the satellite alignment is examined by comparing with observational results. It is found that the observational alignment can be reproduced for red galaxies, which dominate the sample in this study, but not for blue galaxies. Satellites' radial distribution is also investigated. It exhibits that outer satellites within host halos show stronger alignment signal than satellites in the inner regions, especially for red satellites, which is in contrast with previous studies. The disagreement is mainly due to extra galaxies identified by our new galaxy finder, which are mainly located in the inner region of host halos. Our study illustrates that at lower redshift, the alignment strength becomes stronger, while radial distribution curve becomes flatter. This suggests differences in the evolution of the angular distribution between satellites residing in the inner and outer halos, and implies that the post-infall evolution reduces the original alignment signal, that the impact decreases for satellites with later infall times.

[45]  arXiv:2003.10077 [pdf, other]
Title: Ly$α$ forest power spectrum as an emerging window into the epoch of reionization and cosmic dawn
Comments: Comments welcome, 11 pages, 8 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Conventional wisdom was that thermal relics from the epoch of reionization (EOR) would vanish swiftly and hence the usual intergalactic medium (IGM) temperature-density relation would be recovered rapidly. Thus the Ly$\alpha$ forest is one of the primary cosmological probes at the post-reionization epoch. Recently, however, it was shown that the imprint of cosmic reionization can survive to lower redshifts ($z \sim 2$) than previously thought. Given the high sensitivities of upcoming Ly$\alpha$ forest surveys, this effect will be a novel broadband systematic that must be tackled for cosmological application. From the astrophysical point of view, however, the imprint of inhomogeneous reionization can shed light on the EOR and cosmic dawn. We utilize a hybrid method --- which includes two different simulation codes capable of handling the huge dynamical range --- to show the impact of patchy reionization on the Ly$\alpha$ forest and its dependence on different astrophysical scenarios. We found small, but statistically significant, deviations in the 1D Ly$\alpha$ power spectrum that range from a tenth of per cent at $z = 2$ to a few per cent at $z = 4$. The deviations in the 3D Ly$\alpha$ power spectrum are considerably large and range from a few per cent at $z = 2$ up to tens of per cent at $z = 4$. By exploiting different $k$-dependence of power spectrum among various astrophysical scenarios, the effect of patchy reionization on the Ly$\alpha$ forest power spectrum can open a new window into the cosmic reionization and possibly even the cosmic dawn.

[46]  arXiv:2003.10078 [pdf, other]
Title: AGNs are not that cool: revisiting the intrinsic AGN far-infrared spectral energy distribution
Authors: Jun Xu (USTC), Mouyuan Sun (XMU, USTC), Yongquan Xue (USTC)
Comments: 15 pages, 14 figures, Accepted to ApJ. Tables 2 & 3 and the fitting results can be downloaded from this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

We investigate the intrinsic spectral energy distribution (SED) of active galactic nuclei (AGNs) at infrared (IR) bands with 42 $z < 0.5$ optically luminous Palomar Green survey quasars through SED decomposition. We decompose the SEDs of the 42 quasars by combining an AGN IR template library Siebenmorgen2015 that covers a wide range of the AGN parameter space with three commonly used galaxy template libraries. We determine the median AGN SED from the best-fitting results. The far-IR (FIR) contribution of our median AGN SED is significantly smaller than that of Symeonidis et al. 2016, but roughly consistent with that of Lyu et al. 2017. The AGN IR SED becomes cooler with increasing bolometric luminosity, which might be due to that more luminous AGNs might have stronger radiative feedback to change torus structures and/or their tori might have higher metallicities. Our conclusions do not depend on the choice of galaxy template libraries. However, since the predicted polycyclic aromatic hydrocarbon (PAH) emission line flux is galaxy template-dependent, cautions should be taken on deriving galaxy FIR contribution from PAH fluxes.

[47]  arXiv:2003.10095 [pdf, other]
Title: Can $f(T)$ gravity resolve the $H_0$ tension?
Authors: Deng Wang, David Mota
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

We investigate whether the simplest representative of teleparallel gravity $f(T)$ can resolve the current $H_0$ tension between the direct local measurement and the indirect global inference under the assumption of standard cosmology. Through constraining three popular $f(T)$ scenarios with Planck-2018 cosmic microwave background data, we find that the $f(T)$ power law model can alleviate the large discrepancy in $H_0$ from $4.4\sigma$ to $1.9\sigma$ confidence level, in opposition to the two exponential models. When considering the neutrino effects in the power-law model, we obtain constraints on the effective number of relativistic species $N_{eff}$ and the mass sum of three active neutrinos $\Sigma m_\nu$ in $f(T)$ gravity. Using the correlation between $H_0$ and the neutrino parameters, we can improve and alleviate the tension from $1.9\sigma$ to $1.8\sigma$ confidence level. Furthermore, we explain why the power-law model mitigates the $H_0$ tension more efficiently than two exponential ones. Finally, we find that whether a viable $f(T)$ theory can resolve the $H_0$ tension depends on the mathematical structure of the distortion factor $y$, this could provides a clue for theorists to write a better expression of $f(T)$ function.

[48]  arXiv:2003.10114 [pdf, ps, other]
Title: Perturbative description of bias tracers using consistency relations of LSS
Comments: 24 pages, 1 figure, 1 table
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We develop a simple formalism of biased tracers that we dub $\mathit{Monkey\ bias}$. In this formalism, a biased tracer field is constructed directly in terms of the linear matter fluctuation field and the set of derivative operators acting on it. Such bias expansion is first organized based on the general structure of non-linear dynamical equations for the biased tracers. Further physical conditions, like the equivalence principle, are imposed on tree-level correlators utilising the consistency relations. We obtain the bias expansion up to the third-order in linear matter fluctuation in the generalized $\Lambda$CDM background, which reproduces the previous results in the limit of the EdS universe. This algorithmic construction of our bias operator basis is well suited for extensions towards higher-order bias fields. Moreover, this formalism reveals that biased tracer dynamics in generalized $\Lambda$CDM background is not entirely degenerate with the rest of bias parameters, thus opening a possibility of testing the background cosmology through the observations of biased tracers.

[49]  arXiv:2003.10135 [pdf, ps, other]
Title: The path to Z And-type outbursts: The case of V426 Sagittae (HBHA 1704-05)
Comments: 19 pages, 12 figures, 9 tables, 2 appendices, accepted for A&A, Tables A.1, A.2 and A.3 are only available at the CDS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

The star V426 Sge (HBHA~1704-05), originally classified as an emission-line object and a semi-regular variable, brightened at the beginning of August 2018, showing signatures of a symbiotic star outburst. We aim to confirm the nature of V426 Sge as a classical symbiotic star, determine the photometric ephemeris of the light minima, and suggest the path from its 1968 symbiotic nova outburst to the following 2018 Z And-type outburst. We re-constructed an historical light curve (LC) of V426 Sge from approximately the year 1900, and used original low- and high-resolution spectroscopy complemented with Swift-XRT and UVOT, optical UBVRcIc and near-infrared JHKL photometry obtained during the 2018 outburst and the following quiescence. The historical LC reveals no symbiotic-like activity from 1900 to 1967. In 1968, V426~Sge experienced a symbiotic nova outburst that ceased around 1990. From approximately 1972, a wave-like orbitally related variation with a period of $493.4\pm 0.7$ days developed in the LC. This was interrupted by a Z And-type outburst from the beginning of August 2018 to the middle of February 2019. At the maximum of the 2018 outburst, the burning white dwarf (WD) increased its temperature to $>2\times 10^5$ K, generated a luminosity of $\sim 7\times 10^{37}(d/3.3kpc)^2$ erg/s, and blew a wind at the rate of $\sim 3\times 10^{-6}$ M$_{\odot}$/yr. The donor is a normal M4-5 III giant and the accretor is a low-mass $\sim$0.5 M$_{\odot}$ WD. During the transition from the symbiotic nova outburst to the quiescent phase, a pronounced sinusoidal variation along the orbit develops in the LC of most symbiotic novae. The following eventual outburst is of Z And-type, when the accretion by the WD temporarily exceeds the upper limit of the stable burning. At this point the system becomes a classical symbiotic star.

[50]  arXiv:2003.10153 [pdf, other]
Title: Universal properties of primary and secondary cosmic ray energy spectra
Comments: 5 pages, 2 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Atomic nuclei appearing in cosmic rays are typically classified as primary or secondary. However, a better understanding of their origin and propagation properties is still necessary. We analyse the flux of primary (He, C, O) and secondary nuclei (Li, Be, B) detected with rigidity (momentum/charge) between 2 GV and 3 TV by the Alpha Magnetic Spectrometer (AMS) on the International Space Station. We show that $q$-exponential distribution functions, as motivated by generalized versions of statistical mechanics with temperature fluctuations, provide excellent fits for the measured flux of all nuclei considered. Primary and secondary fluxes reveal a universal dependence on kinetic energy per nucleon for which the underlying energy distribution functions are solely distinguished by their effective degrees of freedom. All given spectra are characterized by a universal mean temperature parameter $\sim$ 200 MeV which agrees with the Hagedorn temperature. Our analysis suggests that QCD scattering processes together with nonequilibrium temperature fluctuations imprint heavily and universally onto the measured cosmic ray spectra, and produce a similar shape of energy spectra as high energy collider experiments on the Earth.

[51]  arXiv:2003.10154 [pdf, ps, other]
Title: Boltzmann's $H$-theorem, entropy and the strength of gravity in theories with a nonminimal coupling between matter and geometry
Comments: 5 pages, no figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

In this paper we demonstrate that, contrary to recent claims, Boltzmann's $H$-theorem does not necessarily hold in the context of theories of gravity with nonminimally coupled matter fields if the effective gravitational constant increases with time. We also suggest a possible link between the high entropy of the Universe and the weakness of gravity in the context of these theories.

[52]  arXiv:2003.10198 [pdf, other]
Title: Merger-inspired rotation laws and the low-T/W instability in neutron stars
Comments: 12 pages, 8 figures and 3 tables. Submitted to MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Implementing a family of differential rotation laws inspired by binary neutron-star merger remnants, we consider the impact of the rotation profile on the low-T/W instability. We use time evolutions of the linearised dynamical equations, in Newtonian gravity, to study non-axisymmetric oscillations and identify the unstable modes. The presence and evolution of the low-T/W instability is monitored with the canonical energy and angular momentum, while the growth time is extracted from the evolved kinetic energy. The results for the new rotation laws highlight similarities with the commonly considered j-constant law. The instability sets in when an oscillation mode co-rotates with the star (i.e. whenever there is a point where the mode's pattern speed matches the bulk angular velocity) and grows faster deep inside the co-rotation region. However, the new profiles add features, like an additional co-rotation point to the problem, which affect the onset of instability. The rotation laws influence more drastically the oscillation frequencies of the l=m=2 f-mode in fast rotating models, but affect the instability growth time at any rotation rate. We also identify models where the low-T/W instability appears to be triggered by inertial modes. We discuss to what extent the inferred qualitative behaviour is likely to be of observational relevance.

[53]  arXiv:2003.10203 [pdf, ps, other]
Title: Violation of slow-roll in non-minimal inflation
Comments: 25 pages, 10 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

We show that a non-minimal coupling to gravity can not only make some inflationary models consistent with cosmological data, similar to the case of Higgs inflation, but can also invoke slow-roll violation to realize graceful exit from inflation. In particular, this is the case in models where a destabilizing mechanism that ends inflation should be assumed when the model is minimally coupled to gravity. As explicit examples, we consider the power-law and inverse monomial inflation models with a non-minimal coupling to gravity. While these models are excluded in the minimally coupled case, we show that they can become viable again in non-minimally coupled scenarios. We also argue that in most scenarios we consider reheating can be naturally realized via gravitational particle production but that this depends on the underlying theory of gravity in a non-trivial way.

[54]  arXiv:2003.10225 [pdf, other]
Title: Robustness of prediction for extreme adaptive optics systems under various observing conditions: An analysis using VLT/SPHERE adaptive optics data
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

For high-contrast imaging (HCI) systems, such as VLT/SPHERE, the performance of the system at small angular separations is contaminated by the wind-driven halo in the science image. This halo is a result of the servo-lag error in the adaptive optics (AO) system due to the finite time between measuring the wavefront phase and applying the phase correction. One approach to mitigating the servo-lag error is predictive control. We aim to estimate and understand the potential on-sky performance that linear data-driven prediction would provide for VLT/SPHERE under various turbulence conditions. We used a linear minimum mean square error predictor and applied it to 27 different AO telemetry data sets from VLT/SPHERE taken over many nights under various turbulence conditions. We evaluated the performance of the predictor using residual wavefront phase variance as a performance metric. We show that prediction always results in a reduction in the temporal wavefront phase variance compared to the current VLT/SPHERE AO performance. We find an average improvement factor of 5.1 in phase variance for prediction compared to the VLT/SPHERE residuals. When comparing to an idealised VLT/SPHERE, we find an improvement factor of 2.0. Under our 27 different cases, we find the predictor results in a smaller spread of the residual temporal phase variance. Finally, we show there is no benefit to including spatial information in the predictor in contrast to what might have been expected from the frozen flow hypothesis. A purely temporal predictor is best suited for AO on VLT/SPHERE.

[55]  arXiv:2003.10260 [pdf, ps, other]
Title: Radial Star Formation Histories in 32 Nearby Galaxies
Comments: Accepted for publication in the Astronomical Journal. arXiv admin note: text overlap with arXiv:1511.03285
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The spatially resolved star formation histories are studied for 32 normal star-forming galaxies drawn from the the Spitzer Extended Disk Galaxy Exploration Science survey. At surface brightness sensitivities fainter than 28 mag arcsec$^{-2}$, the new optical photometry is deep enough to complement archival ultraviolet and infrared imaging and to explore the properties of the emission well beyond the traditional optical extents of these nearby galaxies. Fits to the spectral energy distributions using a delayed star formation history model indicate a subtle but interesting average radial trend for the spiral galaxies: the inner stellar systems decrease in age with increasing radius, consistent with inside-out disk formation, but the trend reverses in the outermost regions with the stellar age nearly as old as the innermost stars. These results suggest an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and accretions of satellite dwarf galaxies. The subset of S0 galaxies studied here show the opposite trend compared to what is inferred for spirals: characteristic stellar ages that are increasingly older with radius for the inner portions of the galaxies, and increasingly younger stellar ages for the outer portions. This result suggests that either S0 galaxies are not well modeled by a delayed-$\tau$ model, and/or that S0 galaxies have a more complicated formation history than spiral galaxies.

[56]  arXiv:2003.10262 [pdf, other]
Title: Search for non-thermal X-ray emission in the colliding wind binary Cyg OB2 #8A
Comments: 12 pages, 8 figures, A&A accepted
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

Cyg OB2 #8a is a massive O-type binary displaying strong non-thermal radio emission. Owing to the compactness of this binary, emission of non-thermal X-ray photons via inverse Compton scattering is expected. We first revised the orbital solution for Cyg OB2 #8a using new optical spectra. We then reduced and analysed X-ray spectra obtained with XMM-Newton, Swift, INTEGRAL, and NuSTAR. The analysis of the XMM-Newton and Swift data allows us to better characterise the X-ray emission from the stellar winds and colliding winds region at energies below 10 keV. We confirm the variation of the broad-band light curve of Cyg OB2 #8a along the orbit with, for the first time, the observation of the maximum emission around phase 0.8. The minimum ratio of the X-ray to bolometric flux of Cyg OB2 #8a remains well above the level expected for single O-type stars, indicating that the colliding wind region is not disrupted during the periastron passage. The analysis of the full set of publicly available INTEGRAL observations allows us to refine the upper limit on the non-thermal X-ray flux of the Cyg OB2 region between 20 and 200 keV. Two NuSTAR observations (phases 0.028 and 0.085) allow us to study the Cyg OB2 #8a spectrum up to 30 keV. These data do not provide evidence of the presence of non-thermal X-rays, but bring more stringent constraints on the flux of a putative non-thermal component. Finally, we computed, thanks to a new dedicated model, the anisotropic inverse Compton emission generated in the wind shock region. The theoretical non-thermal emission appears to be compatible with observational limits and the kinetic luminosity computed from these models is in good agreement with the unabsorbed flux observed below 10 keV.

[57]  arXiv:2003.10272 [pdf, other]
Title: Stellar wind effects on the atmospheres of close-in giants: a possible reduction in escape instead of increased erosion
Authors: A. A. Vidotto, A. Cleary (Trinity College Dublin, the University of Dublin)
Comments: 13 pages, MNRAS in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The atmospheres of highly irradiated exoplanets are observed to undergo hydrodynamic escape. However, due to strong pressures, stellar winds can confine planetary atmospheres, reducing their escape. Here, we investigate under which conditions atmospheric escape of close-in giants could be confined by the large pressure of their host star's winds. For that, we simulate escape in planets at a range of orbital distances ([0.04, 0.14] au), planetary gravities ([36%, 87%] of Jupiter's gravity), and ages ([1, 6.9] Gyr). For each of these simulations, we calculate the ram pressure of these escaping atmospheres and compare them to the expected stellar wind external pressure to determine whether a given atmosphere is confined or not. We show that, although younger close-in giants should experience higher levels of atmospheric escape, due to higher stellar irradiation, stellar winds are also stronger at young ages, potentially reducing escape of young exoplanets. Regardless of the age, we also find that there is always a region in our parameter space where atmospheric escape is confined, preferably occurring at higher planetary gravities and orbital distances. We investigate confinement of some known exoplanets and find that the atmosphere of several of them, including pi Men c, should be confined by the winds of their host stars, thus potentially preventing escape in highly irradiated planets. Thus, the lack of hydrogen escape recently reported for pi Men c could be caused by the stellar wind.

[58]  arXiv:2003.10278 [pdf, other]
Title: Using variability and VLBI to measure cosmological distances
Comments: Accepted for publication in MNRAS Letters, 5 pages, 2 figures, 1 table
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

In this paper, we propose a new approach to determining cosmological distances to active galactic nuclei (AGN) via light travel-time arguments, which can be extended from nearby sources to very high redshift sources. The key assumption is that the variability seen in AGN is constrained by the speed of light and therefore provides an estimate of the linear size of an emitting region. This can then be compared with the angular size measured with very long baseline interferometry (VLBI) in order to derive a distance. We demonstrate this approach on a specific well studied low redshift (z = 0.0178) source 3C84 (NGC 1275), which is the bright radio core of the Perseus Cluster. We derive an angular diameter distance including statistical errors of $D_{A} = 72^{+5}_{-6}$ Mpc for this source, which is consistent with other distance measurements at this redshift. Possible sources of systematic errors and ways to correct for them are discussed.

[59]  arXiv:2003.10288 [pdf, other]
Title: Energy Optimization in Binary Star Systems: Explanation for Equal Mass Members in Close Orbits
Comments: 13 pages, 2 figures, accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

Observations indicate that members of close stellar binaries often have mass ratios close to unity, while longer-period systems exhibit a more uniform mass-ratio distribution. This paper provides a theoretical explanation for this finding by determining the tidal equilibrium states for binary star systems --- subject to the constraints of conservation of angular momentum and constant total mass. This work generalizes previous treatments by including the mass fraction as a variable in the optimization problem. The results show that the lowest energy state accessible to the system corresponds to equal mass stars on a circular orbit, where the stellar spin angular velocities are both synchronized and aligned with the orbit. These features are roughly consistent with observed properties of close binary systems. We also find the conditions required for this minimum energy state to exist: [1] The total angular momentum must exceed a critical value, [2] the orbital angular momentum must be three times greater than the total spin angular momentum, and [3] the semimajor axis is bounded from above. The last condition implies that sufficiently wide binaries are not optimized with equal mass stars, where the limiting binary separation occurs near $a_0\approx16R_\ast$.

[60]  arXiv:2003.10310 [pdf, other]
Title: Dynamical Environment and Surface Characteristics of Asteroid (16) Psyche
Comments: 19 pages
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Radar observations show that (16) Psyche is one of the largest and most massive asteroids of the M-class located in the main belt, with a diameter of approximately 230 km. This fact makes Psyche a unique object since observations indicated an iron-nickel composition. It is believed that this body may be what was left of a metal core of an early planet that would have been fragmented over millions of years due to violent collisions. In this work we study a variety of dynamical aspects related to the surface, as well as, the environment around this asteroid. We use computational tools to explore the gravitational field generated by this body, assuming constant values for its density and rotation period. We then determine a set of physical and dynamical characteristics over its entire surface. The results include the geometric altitude, geopotential altitude, tilt, slope, among others. We also explore the neighborhood around the asteroid (16) Psyche, so that the location and linear stability of the equilibrium points were found. We found four external equilibrium points, two of them linearly stable. We confirmed the stability of these points by performing numerical simulations of massless particles around the asteroid, which also showed an asymmetry in the size of the stable regions. In addition, we integrate a cloud of particles in the vicinity of (16) Psyche in order to verify in which regions of its surface the particles are most likely to collide.

[61]  arXiv:2003.10311 [pdf, ps, other]
Title: Galactic Center IRS13E: Colliding Stellar Winds or an Intermediate Mass Black Hole?
Comments: 23 pages, 9 figures, Submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

A small cluster of massive stars residing in the Galactic center, collectively known as IRS13E, is of special interest due to its close proximity to Sgr A* and the possibility that an embedded intermediate-mass black hole (IMBH) binds its member stars. It has been suggested that colliding winds from two member stars, both classified as Wolf-Rayet type, are responsible for the observed X-ray, infrared and radio emission from IRS13E. We have conducted an in-depth study of the X-ray spatial, temporal and spectral properties of IRS13E, based on 5.6 Ms of ultra-deep Chandra observations obtained over 20 years. These X-ray observations show no significant evidence for source variability. We have also explored the kinematics of the cluster members, using Keck near-infrared imaging and spectroscopic data on a 14-yr baseline that considerably improve the accuracy of stars' proper motions. The observations are interpreted using 3-dimensional hydrodynamical simulations of colliding winds tailored to match the physical conditions of IRS13E, leading us to conclude that the observed X-ray spectrum and morphology can be well explained by the colliding wind scenario, in the meantime offering no support for the presence of a putative IMBH. An IMBH more massive than a few $10^3{\rm~M_\odot}$ is also strongly disfavored by the stellar kinematics.

[62]  arXiv:2003.10314 [pdf, other]
Title: A remnant planetary core in the hot Neptunian desert
Comments: Accepted for publication in Nature. This is a preprint of the article, before minor changes made during the refereeing and editing process
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to major uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary pathways provide a new route to understanding planetary interiors. We present the discovery of TOI-849b, the remnant core of a giant planet, with a radius smaller than Neptune but an anomalously high mass $M_p=40.8^{+2.4}_{-2.5}M_{\oplus}$ and density of $5.5\pm0.8$gcm$^{-3}$, similar to the Earth. Interior structure models suggest that any gaseous envelope of pure hydrogen and helium consists of no more than $3.9^{+0.8}_{-0.9}$% of the total mass of the planet. TOI-849b transits a late G type star (T$_{\rm mag}=11.5$) with an orbital period of 18.4 hours, leading to an equilibrium temperature of 1800K. The planet's mass is larger than the theoretical threshold mass for runaway gas accretion. As such, the planet could have been a gas giant before undergoing extreme mass loss via thermal self-disruption or giant planet collisions, or it avoided substantial gas accretion, perhaps through gap opening or late formation. Photoevaporation rates cannot provide the mass loss required to reduce a Jupiter-like gas giant, but can remove a few $M_\oplus$ hydrogen and helium envelope on timescales of several Gyr, implying that any remaining atmosphere is likely to be enriched by water or other volatiles from the planetary interior. TOI-849b represents a unique case where material from the primordial core is left over from formation and available to study.

[63]  arXiv:2003.10318 [pdf, other]
Title: Microlensing of radially pulsating stars
Comments: 10 pages, 6 figures; Accepted to be published by MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Here, we study the microlensing of radially pulsating stars. Discerning and characterizing the properties of distant, faint pulsating stars is achievable through high-cadence microlensing observations. Combining stellar variability period with microlensing gives the source distance, type, and radius and helps better determine the lens parameters. Considering periodically variations in their radius and surface temperature, their microlensing light curves are resulted from multiplication of the magnification factor with variable finite size effect by the intrinsic brightness curves of pulsing source. The variable finite source size due to pulsation can be significant for transit and single microlensing and while caustic-crossing features. This kind of deviation in the magnification factor is considerable when the ratio of the source radius to the projected lens-source distance is in the range of $\rho_{\star}/u \in[0.4,10]$ and its duration is short and in the same order of the time of crossing the source radius. Other deviations due to variable source intensity and its area make colored and periodic deviations which are asymmetric with respect to the signs of pulsation phase. The positive phases makes deviations with larger amplitude that negative phase. These deviations dominate in filters with short wave lengths (e.g., $B-$band). The position of magnification peaks in microlensing of variable stars varies and this displacement differs in different filters.

[64]  arXiv:2003.10319 [pdf, other]
Title: The Magellan/PFS Exoplanet Search: A 55-day period dense Neptune transiting the bright ($V=8.6$) star HD 95338
Comments: 12 pages, 11 figures, submitted to MNRAS. Comments welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We report the detection of a transiting, dense Neptune planet candidate orbiting the bright ($V=8.6$) K0.5V star HD 95338. Detection of the 55-day periodic signal comes from the analysis of precision radial velocities from the Planet Finder Spectrograph (PFS) on the Magellan II Telescope. Follow-up observations with HARPS also confirm the presence of the periodic signal in the combined data. HD 95338 was also observed by the Transiting Exoplanet Survey Satellite ({\it TESS}), and we identify a clear single transit at the period corresponding to the signal detected in the radial velocity data. A Markov Chain Monte Carlo period search on the velocities allows strong constraints on the expected transit time, matching well the epoch calculated using {\it TESS}. A joint fit model yields an absolute mass of 39.43$^{+6.04}_{-4.13} M_{\oplus}$ and a radius of 3.98$^{+0.09}_{-0.08}$ $R_{\oplus}$ which translates to a density of 3.41$^{+0.56}_{-0.40}$ g cm$^{-3}$, for the planet. Given the planet mass and radius, structure models suggest it is fully composed of ice. HD 95338 b is one of the most dense Neptune planets yet detected, indicating a heavy element enrichment of $\sim$90% ($\sim35\, M_{\oplus}$). This system presents a unique opportunity for future follow-up observations that can further constrain structure models of cool gas giant planets.

[65]  arXiv:2003.10322 [pdf, ps, other]
Title: Catalogue with visual morphological classification of 32,616 radio galaxies with optical hosts
Comments: Proceedings paper under the IAU symposium "Nuclear Activity in Galaxies Across Cosmic Time", eds. M. Povic, P. Marziani, J. Masegosa, H. Netzer, S. H. Negu, and S. B. Tessema
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the catalogue of Radio sources associated with Optical Galaxies and having Unresolved or Extended morphologies I (ROGUE I). It was generated by cross-matching galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR 7) as well as radio sources from the First Images of Radio Sky at Twenty Centimetre (FIRST) and the National Radio Astronomical Observatory VLA Sky Survey (NVSS) catalogues. We created the largest handmade catalogue of visually classified radio objects and associated with them optical host galaxies, containing 32,616 galaxies with a FIRST core within 3 arcsec of the optical position. All listed objects possess the good quality SDSS DR 7 spectra with the signal-to-noise ratio $>$10 and spectroscopic redshifts up to $z=0.6$. The radio morphology classification was performed by a visual examination of the FIRST and the NVSS contour maps overlaid on a DSS image, while an optical morphology classification was based on the 120 arcsec snapshot images from SDSS DR 7.
The majority of radio galaxies in ROGUE I, i.e. $\sim$ 93%, are unresolved (compact or elongated), while the rest of them exhibit extended morphologies, such as Fanaroff-Riley (FR) type I, II, and hybrid, wide-angle tail, narrow-angle tail, head-tail sources, and sources with intermittent or reoriented jet activity, i.e. double-double, X-shaped, and Z-shaped. Most of FR IIs have low radio luminosities, comparable to the luminosities of FR Is. Moreover, due to visual check of all radio maps and optical images, we were able to discover or reclassify a number of radio objects as giant, double-double, X-shaped, and Z-shaped radio galaxies. The presented sample can serve as a database for training automatic methods of identification and classification of optical and radio galaxies.

[66]  arXiv:2003.10326 [pdf, other]
Title: The explanation for the mysterious hot solar corona
Comments: 5 pages, 1 Figure
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)

The coronal heating has remained a puzzle for decades since its observation in 1940. Several space missions have been planned to resolve this conundrum in the past and many more intend to target this issue in the future. The unfolding of this issue will not only advance the fundamentals of astrophysical science but also promise an improvement in space weather prediction. Its origin has been debated without complete convergence; the acoustic waves, magneto-hydrodynamic waves, and micro/nano-flares are the strongest candidates so far to explain the mystery of coronal heating. However, none of these processes significantly justifies the million-degree temperature of the solar corona and the problem remains unsolved to date. Here, we propose a new physical mechanism to explain the observed heating of the solar corona. The statistical energy created during the interaction of the spin magnetic moment of the plasma particles with the turbulent and continuously evolving coronal magnetic field could substantiate the observed million-degree coronal temperature.

[67]  arXiv:2003.10352 [pdf, other]
Title: Timing stability of black widow pulsars
Authors: Ann-Sofie Bak Nielsen (1,2,4), Gemma H. Janssen (3,5), Golam Shaifullah (3), Joris P. W. Verbiest (2,1), David J. Champion (1), Grégory Desvignes (11), Lucas Guillemot (6,7), Ramesh Karuppusamy (1), Michael Kramer (1), Andrew G. Lyne (8), Andrea Possenti (9,12), Ben W. Stappers (8), Cees Bassa (3), Ismaël Cognard (6,7), Kuo Liu (1), Gilles Theureau (6,7,10) ((1) Max-Planck-Institut für Radioastronomie, (2) Fakultät für Physik, Universität Bielefeld, (3) ASTRON, (4) Leiden University, (5) Radboud University, (6) Laboratoire de Physique et Chimie de l'Environnement et de l'Espace LPC2E CNRS-Université d'Orléans, (7) Station de radioastronomie de Nancay, (8) Jodrell Bank Centre for Astrophysics, (9) INAF - Osservatorio Astronomico di Cagliari, (10) LUTH, Observatoire de Paris, (11) LESIA, Observatoire de Paris, (12) Università di Cagliari)
Comments: Submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study the timing stability of three black widow pulsars, both in terms of their long-term spin evolution and their shorter-term orbital stability. The erratic timing behaviour and radio eclipses of the first two black widow pulsar systems discovered (PSRs B1957+20 and J2051$-$0827) was assumed to be representative for this class of pulsars. With several new black widow systems added to this population in the last decade, there are now several systems known that do not show these typical orbital variations or radio eclipses. We present timing solutions using 7$-$8 yrs of observations from four of the European Pulsar Timing Array telescopes for PSRs\,J0023+0923, J2214+3000 and J2234+0944, and confirm that two of these systems do not show any significant orbital variability over our observing time span, both in terms of secular or orbital parameters. The third pulsar PSR J0023+0923 shows orbital variability and we discuss the implications for the timing solution. Our results from the long-term timing of these pulsars provide several new or improved parameters compared to earlier works. We discuss our results regarding the stability of these pulsars, and the stability of the class of black widow pulsars in general, in the context of the binary parameters, and discuss the potential of the Roche-lobe filling factor of the companion star being an indicator for stability of these systems.

[68]  arXiv:2003.10377 [pdf, other]
Title: Extended lens reconstructions with Grale: exploiting time domain, substructural and weak-lensing information
Comments: 24 pages, 19 figures, accepted for publication in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The information about the mass density of galaxy clusters provided by the gravitational lens effect has inspired many inversion techniques. In this article, updates to the previously introduced method in Grale are described, and explored in a number of examples. The first looks into a different way of incorporating time delay information, not requiring the unknown source position. It is found that this avoids a possible bias that leads to "over-focusing" the images, i.e. providing source position estimates that lie in a considerably smaller region than the true positions. The second is inspired by previous reconstructions of the cluster of galaxies MACS J1149.6+2223, where a multiply-imaged background galaxy contained a supernova, SN Refsdal, of which four additional images were produced by the presence of a smaller cluster galaxy. The inversion for the cluster as a whole, was not able to recover sufficient detail interior to this quad. We show how constraints on such different scales, from the entire cluster to a single member galaxy, can now be used, allowing such small scale substructures to be resolved. Finally, the addition of weak lensing information to this method is investigated. While this clearly helps recover the environment around the strong lensing region, the mass sheet degeneracy may make a full strong and weak inversion difficult, depending on the quality of the ellipticity information at hand. We encounter ring-like structure at the boundary of the two regimes, argued to be the result of combining strong and weak lensing constraints, possibly affected by degeneracies.

[69]  arXiv:2003.10391 [pdf, other]
Title: The heavier the better: how to constrain mass ratios and spins of high-mass neutron-star mergers
Comments: 6 pages, 4 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The first binary neutron-star merger event, GW170817, and its bright electromagnetic counterpart have provided a remarkable amount of information. By contrast, the second event, GW190425, with $M_{\rm tot}=3.4^{+0.3}_{-0.1}\,M_{\odot}$ and the lack of an electromagnetic counterpart, has hardly improved our understanding of neutron-star physics. While GW190425 is compatible with a scenario in which the merger has lead to a prompt collapse to a black hole and little ejected matter to power a counterpart, determining the mass ratio and the effective spin $\tilde{\chi}$ of the binary remains difficult. This is because gravitational waveforms cannot yet well constrain the component spins of the binary. However, since the mass of GW190425 is significantly larger than the maximum mass for nonrotating neutron stars, $M_{_{\rm TOV}}$, the mass ratio $q$ cannot be too small, as the heavier star would not be gravitationally stable. Making use of universal relations and a large number of equations of state, we provide strict limits in the $(\tilde{\chi},q)$ plane for GW190425, namely: $q_{\rm min} \geq 0.48$ and $ \tilde{\chi}_{\rm max}\leq 0.16$, that help to rule out the most-extreme configurations. Finally, we show how future observations of high-mass binaries can provide a lower bound on $M_{_{\rm TOV}}$.

[70]  arXiv:2003.10420 [pdf, other]
Title: The impact of peculiar velocities on supernova cosmology
Comments: 9 pages, 8 figures, 1 table. To be submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We study correlated fluctuations of Type~Ia supernova observables due to peculiar velocities of both the observer and the supernova host galaxies, and their impact on cosmological parameter estimation. We demonstrate using the CosmicFlows-3 dataset that at low redshifts the corrections for peculiar velocities in the JLA catalogue have been systematically underestimated. By querying a horizon-size N-body simulation we find that compared to a randomly placed Copernican observer, an observer in an environment like our local universe will see 2--5 times stronger correlations between supernovae in the JLA catalogue. Hence the covariances usually employed which assume a Copernican observer underestimate the effects of coherent motion of the supernova host galaxies. Although previous studies have suggested that this should have $<2\%$ effect on cosmological parameter estimation, we find that when peculiar velocities are treated consistently the JLA data favours significantly smaller values of matter and dark energy density than in the standard $\Lambda$CDM model. A joint fit to simultaneously determine the cosmological parameters and the bulk flow finds a bulk flow faster than 200 km~s$^{-1}$ continuing beyond 200~Mpc. This demonstrates that the local bulk flow is an essential nuisance parameter which must be included in cosmological model fitting when analysing supernova data.

Cross-lists for Tue, 24 Mar 20

[71]  arXiv:1909.07199 (cross-list from gr-qc) [pdf]
Title: Oscillating cosmological force modifies Newtonian dynamics
Comments: 17 pages, 3 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA)

In the Newtonian limit of general relativity force acting on a test mass in a central gravitational field is conventionally defined by the attractive Newtonian gravity (inverse square) term plus a small repulsive cosmological force, which is proportional to the slow acceleration of the universe expansion. In this paper we consider the cosmological force correction due to fast quantum oscillations of the universe scale factor, which were suggested recently by Wang et al. (Phys. Rev. D 95, 103504 (2017)) as a potential solution of the cosmological constant problem. These fast fluctuations of the cosmological scale factor induce strong changes to the current sign and magnitude of the average cosmological force, thus making it one of the potential probable causes of the modification of Newtonian dynamics in galaxy-scale systems. The modified cosmological force may be responsible for the recently discovered "cosmic clock" behaviour of disk galaxies in the low redshift universe.

[72]  arXiv:2003.09659 (cross-list from physics.space-ph) [pdf]
Title: Narrowband large amplitude whistler-mode waves in the solar wind and their association with electrons: STEREO waveform capture observations
Comments: astro-ph.EP - Earth and Planetary Astrophysics
Subjects: Space Physics (physics.space-ph); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Large amplitude whistler waves at frequencies of 0.2 to 0.4 times electron cyclotron frequency are frequently observed in the solar wind. The waves are obliquely propagating close to the resonance cone, with significant electric fields parallel to the background magnetic field, enabling strong interactions with electrons. Propagation angles are distinctly different from whistlers usually observed in the solar wind, and amplitudes are significantly larger. Waves occur most often in association with stream interaction regions (SIRs), and are often close-packed. 68 percent of the 54 SIRs had narrowband whistler groups; 33 percent of the nine interplanetary coronal mass ejections had coherent groups. Although wave occurrence as a function of the electron temperature anisotropy and parallel beta is constrained by the thresholds for the whistler temperature anisotropy and firehose instabilities, neither is consistent with observed wave properties. We show for the first time that comparisons of wave data to thresholds for the electron beam driven instability (beam speed greater than twice the electron Alfven speed) and to the whistler heat flux fan instability indicate that either might destabilize the narrowband waves. In contrast, the less coherent waves, on average, are associated with zero or near zero heat flux and much higher electron Alfven speeds, without higher energy beams. This suggests that the less coherent waves may be more effective in regulating the electron heat flux, or that the scattering and energization of solar wind electrons by the narrowband waves results in broadening of the waves. The highly oblique propagation and large amplitudes of both the narrowband and less coherent whistlers enable resonant interactions with electrons over a broad energy range, and, unlike parallel whistlers does not require that the electrons and waves counter-propagate.

[73]  arXiv:2003.09751 (cross-list from gr-qc) [pdf, ps, other]
Title: Cosmic strings in hybrid metric-Palatini gravity
Comments: 15 pages, 9 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

We consider static and cylindrically symmetric interior string solutions in the scalar-tensor representation of the hybrid metric-Palatini modified theory of gravity. As a first step in our study, we obtain the gravitational field equations and further simplify the analysis by imposing Lorentz invariance along the $t$ and $z$ axes, which reduces the number of unknown metric tensor components to a single function. In this case, the general solution of the field equations can be obtained, for an arbitrary form of the scalar field potential, in an exact closed parametric form, with the scalar field $\phi$ taken as a parameter. We consider in detail several exact solutions of the field equations, corresponding to a null and constant potential, and to a power-law potential of the form $V(\phi)=V_0\phi ^{3/4}$, in which the behavior of the scalar field, metric tensor component and string tension can be described in a simple mathematical form. We also investigate the string models with exponential and Higgs type scalar field potentials by using numerical methods. In this way we obtain a large class of novel stable stringlike solutions in the context of hybrid metric-Palatini gravity, in which the basic parameters, such as the scalar field, metric tensor and string tension, depend essentially on the initial values of the scalar field, and of its derivative, along the string axis.

[74]  arXiv:2003.09768 (cross-list from hep-ph) [pdf, other]
Title: Axions in neutron star mergers
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)

Supernovae and cooling neutron stars have long been used to constrain the properties of axions, such as their mass and interactions with nucleons and other Standard Model particles. We investigate the prospects of using neutron star mergers as a similar location where axions can be probed in the future. We examine the impact axions would have on mergers, considering both the possibility that they free-stream through the dense nuclear matter and the case where they are trapped. We calculate the mean free path of axions in merger conditions, and find that they would free-stream through the merger in all thermodynamic conditions. In contrast to previous calculations, we integrate over the entire phase space while using a relativistic treatment of the nucleons, assuming the matrix element is momentum-independent. In particular, we use a relativistic mean field theory to describe the nucleons, taking into account the precipitous decrease in the effective mass of the nucleons as density increases above nuclear saturation density. We find that within current constraints on the axion-neutron coupling, axions could cool nuclear matter on timescales relevant to neutron star mergers. Our results may be regarded as first steps aimed at understanding how axions affect merger simulations and potentially interface with observations.

[75]  arXiv:2003.10046 (cross-list from physics.space-ph) [pdf, ps, other]
Title: Effects of Radial Distances on Small-scale Magnetic Flux Ropes in the Solar Wind
Authors: Yu Chen, Qiang Hu
Comments: Accepted by ApJ (22 March)
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

Small-scale magnetic flux ropes (SFRs), in the solar wind, have been studied for decades. Statistical analysis utilizing various in situ spacecraft measurements is the main observational approach which helps investigate the generation and evolution of these small-scale structures. Based on the Grad-Shafranov (GS) reconstruction technique, we use the automated detection algorithm to build the databases of these small-scale structures via various spacecraft measurements at different heliocentric distances. We present the SFR properties including the magnetic field and plasma parameters at different radial distances from the sun near the ecliptic plane. It is found that the event occurrence rate is still in the order of a few hundreds per month, the duration and scale size distributions follow power laws, and the flux rope axis orientations are approximately centered around the local Parker spiral directions. In general, most SFR properties exhibit radial decays. In addition, with various databases established, we derive scaling laws for the changes of average field magnitude, event counts, and SFR scale sizes, with respect to the radial distances, ranging from $\sim$ 0.3 au for Helios to $\sim$ 7 au for the Voyager spacecraft. The implications of our results for comparisons with the relevant theoretical works and for the application to the Parker Solar Probe (PSP) mission are discussed.

[76]  arXiv:2003.10127 (cross-list from gr-qc) [pdf, other]
Title: Model Comparison tests of modified gravity from the Eöt-Wash experiment
Comments: 6 pages, 1 figure. Link to analysis code available at this https URL
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Perivolaropoulos et al (arXiv:1904.09462) have argued that the residual torque data in the E\"ot-Wash experiment shows evidence for an oscillating potential, which could be a signature of non-local modified gravity theories. We independently assess the viability of this claim by analyzing the same data. We fit this data to three different parametrizations (an offset Newtonian, Yukawa model, oscillating model) and assess the significance of the oscillating model using four distinct model comparison techniques: frequentist, Bayesian, and information theoretic criterion such as AIC and BIC. We find that the frequentist test favors the Newtonian model over the oscillating one. The other techniques on the other hand favor the oscillating potential. However, only the BIC test decisively favors the oscillating parametrization as compared to a constant offset model. Our analysis codes have been made publicly available.

[77]  arXiv:2003.10205 (cross-list from hep-ph) [pdf, ps, other]
Title: Geometric optics in the presence of axion-like particles in curved space-time
Comments: 3 pages
Subjects: High Energy Physics - Phenomenology (hep-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)

We present a concise derivation of geometric optics in the presence of axionic fields in a curved space-time. Whenever light can be described via geometric optics (the eikonal approximation), the only difference to the situation without axionic field is the phenomenon of achromatic birefringence. Consequently, redshift of light and distance estimates based on propagating light rays, as well as shear and magnification due to gravitational lensing are not affected by the interaction of light with an axionic field.

[78]  arXiv:2003.10284 (cross-list from gr-qc) [pdf, ps, other]
Title: Relativistic stars in 4D Einstein-Gauss-Bonnet gravity
Comments: 9 pages, 3 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

In the present paper we investigate the structure of relativistic stars in 4D Einstein-Gauss-Bonnet gravity. The mass-radius relations are obtained for realistic hadronic and for strange quark star equations of state, and for a wide range of the Gauss-Bonnet coupling parameter $\alpha$. Even though the deviations from general relativity for nonzero values of $\alpha$ can be large enough, they are still comparable with the variations due to different modern realistic equations of state if we restrict ourselves to moderate value of $\alpha$. That is why the current observations of the neutron star masses and radii alone can not impose stringent constraints on the value of the parameter $\alpha$. Nevertheless some rough constraints on $\alpha$ can be put. The existence of stable stellar mass black holes imposes $\sqrt{\alpha}\lesssim 2.6 {\rm km}$ for $\alpha>0$ while the requirement that the maximum neutron star mass should be greater than two solar masses gives $\sqrt{|\alpha|}\lesssim 3.9 {\rm km}$ for $\alpha<0$. We also present an exact solution describing the structure of relativistic stars with uniform energy density in 4D Einstein-Gauss-Bonnet gravity.

[79]  arXiv:2003.10403 (cross-list from physics.flu-dyn) [pdf, other]
Title: Stress-driven spin-down of a viscous fluid within concentric shells
Comments: Submitted to J. Fluid Mechanics
Subjects: Fluid Dynamics (physics.flu-dyn); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We investigate the linear properties of the steady stress-driven spin-down flow of a viscous fluid inside a spherical shell, both within the incompressible and anelastic approximations, and in the asymptotic limit of small viscosities. Neglecting buoyancy force, we find a steady-state to settle in a viscous time for the incompressible flow. From boundary layer analysis, we derive an analytical geostrophic solution for the 3D incompressible steady flow, inside and outside a cylinder $\mathcal{C}$ that is tangent to the inner shell. The meridional circulation associated with the spin-down flow in these two regions scales with the Ekman number $E$. A power expansion of the fields with the small parameter $E^{1/3}$ corresponding to the width of the inner Stewartson shear layer laying along the tangent cylinder, reveals it to be the site of an upwelling flow of amplitude $O(E^{1/3})$. Despite its narrowness, this shear layer concentrates most of the global meridional kinetic energy of the system. Furthermore, a stable stratification does not perturb the spin-down flow provided the Prandtl number is small enough. If this is not the case, the Stewartson layer disappears and meridional circulation is confined within the thermal layers. The scalings for the amplitude of the anelastic secondary flow have been found to be the same as for the incompressible flow in all three regions, at the lowest order. However, because the velocity no longer conforms the Taylor-Proudman theorem, its shape differs outside the tangent cylinder $\mathcal{C}$, that is, where differential rotation takes place. Finally, we find the settling of the steady-state to be reached on a viscous time for the weakly, strongly and thermally unstratified incompressible flows. Large density variations relevant to astro- and geophysical systems, tend to slightly shorten the transient.

[80]  arXiv:2003.10416 (cross-list from hep-ph) [pdf, other]
Title: Strong constraints on thermal relic dark matter from Fermi-LAT observations of the Galactic Center
Comments: 23 pages, 14 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

The extended excess towards the Galactic Center (GC) in gamma rays inferred from Fermi-LAT observations has been interpreted as being due to dark matter (DM) annihilation. Here, we perform new likelihood analyses of the GC and show that when including templates for the stellar galactic and nuclear bulges, the GC shows no significant detection of a DM annihilation template, even after generous variations in the Galactic diffuse emission models and a wide range of DM halo profiles. We include Galactic diffuse emission models with combinations of 3D inverse Compton maps, variations of interstellar gas maps, and a central source of electrons. For the DM profile, we include both spherical and ellipsoidal DM morphologies and a range of radial profiles from steep cusps to kiloparsec-sized cores, motivated in part by hydrodynamical simulations. Our derived upper limits on the dark matter annihilation flux place strong constraints on DM properties. In the case of the pure $b$-quark annihilation channel, our limits on the annihilation cross section are more stringent than those from the Milky Way dwarfs up to DM masses of $\sim$TeV, and rule out the thermal relic cross section up to $\sim$300 GeV. Better understanding of the DM profile, as well as the Fermi-LAT data at its highest energies, would further improve the sensitivity to DM properties.

[81]  arXiv:2003.10424 (cross-list from eess.IV) [pdf, other]
Title: Learning a Probabilistic Strategy for Computational Imaging Sensor Selection
Comments: This paper has been accepted to the IEEE International Conference on Computational Photography (ICCP) 2020. Keywords: Computational Imaging, Optimized Sensing, Ising Model, Deep Learning, VLBI, Interferometry
Subjects: Image and Video Processing (eess.IV); Instrumentation and Methods for Astrophysics (astro-ph.IM); Computer Vision and Pattern Recognition (cs.CV); Machine Learning (cs.LG); Signal Processing (eess.SP)

Optimized sensing is important for computational imaging in low-resource environments, when images must be recovered from severely limited measurements. In this paper, we propose a physics-constrained, fully differentiable, autoencoder that learns a probabilistic sensor-sampling strategy for optimized sensor design. The proposed method learns a system's preferred sampling distribution that characterizes the correlations between different sensor selections as a binary, fully-connected Ising model. The learned probabilistic model is achieved by using a Gibbs sampling inspired network architecture, and is trained end-to-end with a reconstruction network for efficient co-design. The proposed framework is applicable to sensor selection problems in a variety of computational imaging applications. In this paper, we demonstrate the approach in the context of a very-long-baseline-interferometry (VLBI) array design task, where sensor correlations and atmospheric noise present unique challenges. We demonstrate results broadly consistent with expectation, and draw attention to particular structures preferred in the telescope array geometry that can be leveraged to plan future observations and design array expansions.

[82]  arXiv:2003.10427 (cross-list from gr-qc) [pdf, other]
Title: Gravitomagnetic tidal resonance in neutron-star binary inspirals
Authors: Eric Poisson
Comments: 35 pages, 6 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

A compact binary system implicating at least one rotating neutron star undergoes gravitomagnetic tidal resonances as it inspirals toward its final merger. These have a dynamical impact on the phasing of the emitted gravitational waves. The resonances are produced by the inertial modes of vibration of the rotating star. Four distinct modes are involved, and the resonances occur within the frequency band of interferometric gravitational-wave detectors when the star spins at a frequency that lies within this band. The resonances are driven by the gravitomagnetic tidal field created by the companion star; this is described by a post-Newtonian vector potential, which is produced by the mass currents associated with the orbital motion. These resonances were identified previously by Flanagan and Racine [Phys. Rev. D 75, 044001 (2007)], but these authors accounted only for the response of a single mode, the r-mode, a special case of inertial modes. All four relevant modes are included in the analysis presented in this paper. The total accumulated gravitational-wave phase shift is shown to range from approximately $10^{-2}$ radians when the spin and orbital angular momenta are aligned, to approximately $10^{-1}$ radians when they are anti-aligned. Such phase shifts will become measurable in the coming decades with the deployment of the next generation of gravitational-wave detectors (Cosmic Explorer, Einstein Telescope); they might even come to light within this decade, thanks to planned improvements in the current detectors. With good constraints on the binary masses and spins gathered from the inspiral waveform, the phase shifts deliver information regarding the internal structure of the rotating neutron star, and therefore on the equation of state of nuclear matter.

Replacements for Tue, 24 Mar 20

[83]  arXiv:1808.00080 (replaced) [pdf, other]
Title: Testing General Relativity with Black Hole-Pulsar Binaries
Comments: 12 figures, 18 pages, fixed 2 minor typos
Journal-ref: Phys. Rev. D 98, 124007 (2018)
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
[84]  arXiv:1809.01474 (replaced) [src]
Title: Tracking down R Coronae Borealis stars using the WISE All-Sky survey
Comments: Article withdraw as its contents was merged into the following article arXiv:1809.01743 titled "A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey"
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[85]  arXiv:1809.01743 (replaced) [pdf, other]
Title: A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey
Comments: 34 pages, 20 figures
Journal-ref: published A&A 635, A14 (2020)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[86]  arXiv:1811.05998 (replaced) [pdf, other]
Title: Thermal Emission in the Southwest Clump of VY CMa
Comments: Published in AJ, February 2019. 14 pages, 5 figures, 2 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
[87]  arXiv:1811.12416 (replaced) [pdf, other]
Title: Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR
Comments: 14 pages, 8 figures, ApJ, in press
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[88]  arXiv:1901.03439 (replaced) [pdf, other]
Title: First-principles demonstration of diffusive-advective particle acceleration in kinetic simulations of relativistic plasma turbulence
Comments: 7 pages, 5 figures, Accepted to Astrophysical Journal Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)
[89]  arXiv:1902.00589 (replaced) [pdf, other]
Title: Testing systematics of Gaia DR2 parallaxes with empirical surface brightness -- color relations applied to eclipsing binaries
Comments: Like original version but with updated grant numbers
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[90]  arXiv:1902.05738 (replaced) [pdf, other]
Title: Perturbative Resonance during Dark Matter Production and Its Cosmological Implications
Authors: Changhong Li
Comments: 22 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[91]  arXiv:1904.09439 (replaced) [pdf, other]
Title: New types of the chromospheric anemone microflares: Case study
Comments: LaTeX2e, solarphysics documentclass, 10 pages, 3 PDF figures, submitted to Solar Physics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[92]  arXiv:1906.04989 (replaced) [pdf, other]
Title: A scalar field inducing a non-metrical contribution to gravitational acceleration and a compatible add-on to light deflection
Authors: Erhard Scholz
Comments: 39 pages, 2 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)
[93]  arXiv:1906.08748 (replaced) [pdf, other]
Title: Relativistic effects in the large-scale structure with effective dark energy fluids
Comments: 21 pages, 3 figures, comments on dark energy anisotropic stress added, results unchanged. Matches published version
Journal-ref: JCAP 03 (2020) 037
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[94]  arXiv:1906.11388 (replaced) [pdf, other]
[95]  arXiv:1907.04929 (replaced) [pdf, other]
Title: Multiband Probabilistic Cataloging: A Joint Fitting Approach to Point Source Detection and Deblending
Comments: 25 pages, 15 figures. Incorporated comments from referee process
Journal-ref: The Astronomical Journal (2020), Volume 159, Number 4,
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[96]  arXiv:1907.07522 (replaced) [pdf, other]
Title: Real-time cosmology with SKA
Comments: 12 pages, 5 figures; accepted for publication in the European Physical Journal C
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[97]  arXiv:1907.07642 (replaced) [pdf, other]
Title: Accelerating the search for Axion-Like Particles with machine learning
Comments: Version accepted for publication in JCAP
Journal-ref: JCAP03(2020)046
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[98]  arXiv:1907.10068 (replaced) [pdf, other]
Title: Inferred timescales for common envelope ejection using wide astrometric companions
Comments: 17 pages, 20 figures, accepted to the MNRAS on 23 March 2020
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
[99]  arXiv:1909.02908 (replaced) [pdf, ps, other]
Title: Two Numerical Methods for the 3D Anisotropic Propagation of Galactic Cosmic Rays
Comments: 11 pages, 5 figures
Journal-ref: published by ApJ, 892:6 (7pp), 2020
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[100]  arXiv:1909.09169 (replaced) [pdf, ps, other]
Title: Massive Warm/Hot Galaxy Coronae: II. Isentropic Model
Comments: 24 pages, 15 figures. Accepted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[101]  arXiv:1910.00398 (replaced) [pdf, other]
Title: The Gaia DR2 parallax zero point: Hierarchical modeling of red clump stars
Comments: Submitted to MNRAS on 29 September 2019; Revised 3 February 2020; Accepted 24 February 2020
Journal-ref: Volume 493, Issue 3, April 2020, Pages 4367-4381
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
[102]  arXiv:1910.01646 (replaced) [pdf, other]
Title: Searching for Solar Siblings in APOGEE and $Gaia$ DR2 with N-body Simulations
Comments: 12 pages, 9 figures, 3 tables, Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[103]  arXiv:1910.04036 (replaced) [pdf, other]
Title: Numerical-relativity simulations of long-lived remnants of binary neutron star mergers
Comments: 20 pages, 16 figures. Improved text and one appendix added
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
[104]  arXiv:1910.13947 (replaced) [pdf, other]
Title: Small scale direct dark matter search experiments
Authors: Susana Cebrián
Comments: TAUP2019 proceedings
Journal-ref: Susana Cebrian, 2020 J. Phys.: Conf. Ser. 1468 012033
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
[105]  arXiv:1910.13957 (replaced) [pdf, other]
Title: The TREX-DM experiment at the Canfranc Underground Laboratory
Comments: TAUP2019 proceedings
Journal-ref: J Castel et al 2020 J. Phys.: Conf. Ser. 1468 012063
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
[106]  arXiv:1911.06334 (replaced) [pdf, other]
Title: Warming Nuclear Pasta with Dark Matter: Kinetic and Annihilation Heating of Neutron Star Crusts
Comments: 42 pages, 7 figures, 1 table, JCAP version
Journal-ref: JCAP03(2020)038
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
[107]  arXiv:1911.06456 (replaced) [pdf, other]
Title: Is there really a `Hubble tension'?
Comments: 6 pages, 3 figures, 1 table; Expanded to include details of data discrepancies and their impact on the inferred Hubble constant; Incorporates the contents of arXiv:1905.00221 as suggested by editor. Code : this https URL
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[108]  arXiv:1912.02837 (replaced) [pdf, other]
Title: The BAT AGN Spectroscopic Survey -- XVIII. Searching for Supermassive Black Hole Binaries in the X-rays
Comments: 17 pages, 8 figures, and 3 tables. Resubmitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[109]  arXiv:1912.04257 (replaced) [pdf, other]
Title: A response to Rubin & Heitlauf: "Is the expansion of the universe accelerating? All signs still point to yes"
Comments: 6 pages, 2 figures, 3 tables; Expanded to respond to v.2 of arXiv:1912.02191
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[110]  arXiv:1912.05528 (replaced) [pdf, other]
Title: Evidence for cosmic acceleration with next-generation surveys: A model-independent approach
Comments: 5 pages, 4 figures. Minor edition, MNRAS accepted
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[111]  arXiv:1912.06139 (replaced) [pdf, other]
Title: Gravitational Waves from Supercool Axions
Comments: 29 pages, 9 figures. v2) Refs added, typos fixed, matches JHEP version
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[112]  arXiv:1912.07847 (replaced) [pdf, other]
Title: Which bright fast radio bursts repeat?
Comments: 12 pages, 7 figures, 5 tables. Updated after error discovered in original (v1) submission
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[113]  arXiv:2001.00043 (replaced) [pdf, other]
Title: Strengthening the TCC Bound on Inflationary Cosmology
Comments: 5 pages, 1 figure; v2: references added and updated, v3: minor clarifications added
Journal-ref: JCAP 03 (2020) 047
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[114]  arXiv:2001.05648 (replaced) [pdf, other]
Title: Probability Density Functions of Observed Intensities in Self-Absorbing Molecular Clouds
Comments: 13 pages, 11 figures, 2 tables, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[115]  arXiv:2001.10005 (replaced) [pdf, ps, other]
Title: Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light-curve flattening
Authors: Doron Kushnir, Eli Waxman (WIS)
Comments: 9 pages, 5 figures. Minor revisions following referee's report
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[116]  arXiv:2001.11199 (replaced) [pdf, ps, other]
Title: Gaia's Detectability of Black Hole-Main Sequence Star Binaries Formed in Open Clusters
Comments: 10 pages, 9 figures, submitted to PASJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
[117]  arXiv:2002.01881 (replaced) [pdf, ps, other]
Title: Fingerprints of the cosmological constant: Folds in the profiles of the axionic dark matter distribution in a dyon exterior
Comments: 12 pages, 5 figures, revised version published in the Special Issue of the Journal Symmetry
Journal-ref: Symmetry, 2020, 12(3), 455
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[118]  arXiv:2002.03204 (replaced) [pdf, other]
Title: Evolution of porous dust grains in protoplanetary discs -- I. Growing grains
Comments: MNRAS 493, 1788 (2020). 13 pages, 13 figures. Correction of a typo in the algorithm of Appendix A4
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[119]  arXiv:2002.12689 (replaced) [pdf, other]
Title: A major optical & X-ray outburst from the Magellanic Bridge source RX J0209.6-7427
Comments: 6 pages, 6 figures. Accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[120]  arXiv:2003.00019 (replaced) [pdf, other]
Title: Venturing beyond the ISCO: Detecting X-ray emission from the plunging regions around black holes
Comments: 20 pages, 12 figures. Accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[121]  arXiv:2003.01723 (replaced) [pdf, other]
Title: Neutrino Portal to FIMP Dark Matter with an Early Matter Era
Comments: 39 pages, 11 figures, references added, typos corrected
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[122]  arXiv:2003.02326 (replaced) [pdf, ps, other]
Title: The Curious Case of the North Star: the continuing tension between evolution models and measurements of Polaris
Comments: 5 pages, 1 figure, submitted for Astronomical Society of the Pacific Conference Series "RRLyrae/Cepheid2019: Frontiers of Classical Pulsators: Theory and Observations", Cloudcroft, NM, USA October 13-18, 2019, Corrected references
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[123]  arXiv:2003.05366 (replaced) [pdf, other]
Title: Normalized angular momentum deficit: A tool for comparing the violence of the dynamical histories of planetary systems
Comments: 6 pages, 1 table, 3 figures. Accepted for publication on Astronomy & Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[124]  arXiv:2003.06874 (replaced) [pdf, other]
Title: A dark matter telescope probing the 6 to 60 GHz band
Comments: 25 pages, 7 figures
Subjects: Instrumentation and Detectors (physics.ins-det); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)
[125]  arXiv:2003.07187 (replaced) [pdf, other]
Title: Chemodynamics of Green Pea galaxies -- I. Outflows and turbulence driving the escape of ionising photons and chemical enrichment
Comments: 23 pages, 21 figures. Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
[126]  arXiv:2003.07472 (replaced) [pdf, other]
Title: ALMA High-frequency Long Baseline Campaign in 2017: Band-to-band Phase Referencing in Submillimeter Waves
Comments: 61 pages, 17 figures, 8 tables
Journal-ref: 2020ApJS..247...23A
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[127]  arXiv:2003.07830 (replaced) [pdf, other]
Title: Discovery of GeV $γ$-ray emission from M33 and Arp 299 with Fermi-LAT
Comments: 8 pages, 9 figures, 2 tables; typo corrected
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
[128]  arXiv:2003.08658 (replaced) [pdf, other]
Title: ALMA 0.88 mm Survey of Disks around Planetary-mass Companions
Comments: Accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[129]  arXiv:2003.09069 (replaced) [pdf, other]
Title: Forecasts for Next Generation tSZ Surveys: the Impact of a Cosmology-Dependent Selection Function
Comments: 12 pages, 9 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[130]  arXiv:2003.09188 (replaced) [pdf, other]
Title: Identification of pre-biotic molecules containing Peptide-like bond in a hot molecular core, G10.47+0.03
Comments: Accepted for the publication in the Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
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