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Astrophysics

New submissions

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New submissions for Wed, 27 May 20

[1]  arXiv:2005.12265 [pdf, other]
Title: Discovery of an ultra-young stellar "snake" with two dissolving cores in the solar neighborhood
Authors: Hai-Jun Tian
Comments: 6 pages, 4 figures, 1 table, submitted on ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

In this Letter we report the discovery of an ultra-young (only 30-40\,Myr) quasi-tidal tail (dubbed a stellar "snake") nearby the region of Orion complex from {\it Gaia} DR2. The average distance of this structure is about 310\,pc from the Sun. Both the length and width are over 200\,pc, but the thickness is only about 80\,pc. Oddly it has only one tail. Its head includes two dissolving cores, which can be clearly distinguished in the 6D phase space. The two cores are probably broken from an open cluster of initially thousands of members with a total mass of larger than 2000$M_{\odot}$ in the same stellar population. This population is so young (an order of magnitude younger than the ages of any previously known tidal tails) that it can not be well explained with the classical theory of tidal tails. In addition, we check the theory of mass segregation, but do not find any strong evidence for this theory within 125\,pc from the cluster center. Our finding challenges the current theory of the formation and evolution of tidal tails. Its age is well consistent with the history of the Gould Belt. So it may fill the observational gap between the history of the Gould Belt and the star formation near the Orion complex.

[2]  arXiv:2005.12275 [pdf, other]
Title: Is diffuse intracluster light a good tracer of the galaxy cluster matter distribution?
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We explore the relation between diffuse intracluster light (central galaxy included) and the galaxy cluster (baryonic and dark) matter distribution using a sample of 528 clusters at $0.2\leq z \leq 0.35$ found in the Dark Energy Survey (DES) Year 1 data. The surface brightness of the diffuse light shows an increasing dependence on cluster total mass at larger radius, and appears to be self-similar with a universal radial dependence after scaling by cluster radius.We also compare the diffuse light radial profiles to the cluster (baryonic and dark) matter distribution measured through weak lensing and find them to be comparable. The IllustrisTNG galaxy formation simulation offers further insight into the connection between diffuse stellar mass and cluster matter distributions -- the simulation radial profile of the diffuse stellar component does not have a similar slope with the total cluster matter content, although that of the cluster satellite galaxies does. Regardless of the radial trends, the amount of diffuse stellar mass has a low-scatter scaling relation with cluster's total mass in the simulation, out-performing the total stellar mass of cluster satellite galaxies. We conclude that there is no consistent evidence on whether or not diffuse light is a faithful radial tracer of the cluster matter distribution. Nevertheless, both observational and simulation results reveal that diffuse light is an excellent indicator of the cluster's total mass.

[3]  arXiv:2005.12276 [pdf, other]
Title: GalaxyNet: Connecting galaxies and dark matter haloes with deep neural networks and reinforcement learning in large volumes
Comments: 21 pages, 21 figures, 6 tables, submitted
Subjects: Astrophysics of Galaxies (astro-ph.GA); Data Analysis, Statistics and Probability (physics.data-an)

We present the novel wide & deep neural network GalaxyNet, which connects the properties of galaxies and dark matter haloes, and is directly trained on observed galaxy statistics using reinforcement learning. The most important halo properties to predict stellar mass and star formation rate (SFR) are halo mass, growth rate, and scale factor at the time the mass peaks, which results from a feature importance analysis with random forests. We train different models with supervised learning to find the optimal network architecture. GalaxyNet is then trained with a reinforcement learning approach: for a fixed set of weights and biases, we compute the galaxy properties for all haloes and then derive mock statistics (stellar mass functions, cosmic and specific SFRs, quenched fractions, and clustering). Comparing these statistics to observations we get the model loss, which is minimised with particle swarm optimisation. GalaxyNet reproduces the observed data very accurately ($\chi_\mathrm{red}=1.05$), and predicts a stellar-to-halo mass relation with a lower normalisation and shallower low-mass slope at high redshift than empirical models. We find that at low mass, the galaxies with the highest SFRs are satellites, although most satellites are quenched. The normalisation of the instantaneous conversion efficiency increases with redshift, but stays constant above $z\gtrsim0.7$. Finally, we use GalaxyNet to populate a cosmic volume of $(5.9~\mathrm{Gpc})^3$ with galaxies and predict the BAO signal, the bias, and the clustering of active and passive galaxies up to $z=4$, which can be tested with next-generation surveys, such as LSST and Euclid.

[4]  arXiv:2005.12280 [pdf, other]
Title: Searching for Black Holes in the Outer Solar System with LSST
Comments: 4 pages, 2 figures; submitted for publication in ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Earth and Planetary Astrophysics (astro-ph.EP)

Planet Nine has been proposed to potentially be a black hole in the outer solar system. We investigate the accretion flares that would result from impacts of small Oort cloud objects, and find that the upcoming LSST observing program will be able to either rule out or confirm Planet Nine as a black hole within a year. We also find that LSST could rule out or confirm the existence of trapped planet-mass black holes out to the edge of the Oort cloud, indirectly probing the dark matter fraction in primordial black holes and potentially improving upon current limits by orders of magnitude.

[5]  arXiv:2005.12281 [pdf, other]
Title: A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) -- II. Search for exoplanets in open clusters of the southern ecliptic hemisphere and their frequency
Comments: 19 pages, 12 figures, 3 tables. Accepted for publication in MNRAS on May 20, 2020. PATHOS light curves are available at MAST as HLSP at this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The scope of the project "A PSF-based Approach to TESS High Quality data Of Stellar clusters" (PATHOS) is the extraction and analysis of high-precision light curves of stars in stellar clusters and young associations for the identification of candidate exoplanets and variable stars. The cutting-edge tools used in this project allow us to measure the real flux of stars in dense fields, minimising the effects due to contamination by neighbour sources. We extracted about 200 000 light curves of stars in 645 open clusters located in the southern ecliptic hemisphere and observed by TESS during the first year of its mission. We searched for transiting signals and we found 33 objects of interest, 11 of them are strong candidate exoplanets. Because of the limited S/N, we did not find any Earth or super-Earth. We identified two Neptune-size planets orbiting stars with $R_{\star}<1.5\,R_{\odot}$, implying a frequency $f_{\star}=1.34 \pm 0.95\,\%$, consistent with the frequency around field stars. The 7 Jupiter candidates around stars with $R_{\star}<\,1.5R_{\odot}$ imply a frequency $f_{\star}=0.19\pm 0.07\,\%$, smaller than in the field. A more complete estimate of the survey completeness and false positive rate is needed to confirm these results. Light curves used in this work will be made available to the astronomical community on the Mikulski Archive for Space Telescope under the project PATHOS.

[6]  arXiv:2005.12289 [pdf, other]
Title: CLEAR II: Evidence for Early Formation of the Most Compact Quiescent Galaxies at High Redshift
Authors: Vicente Estrada-Carpenter (1), Casey Papovich (1), Ivelina Momcheva (2), Gabriel Brammer (3), Raymond Simons (2), Joanna Bridge (4), Nikko J. Cleri (5), Henry Ferguson (2), Steven L. Finkelstein (6), Mauro Giavalisco (7), Intae Jung (8), Jasleen Matharu (1), Jonathan R. Trump (5), Benjamin Weiner (9) ((1) Texas A&M, (2) STScI, (3) Cosmic Dawn Centre, (4) University of Louisville, (5) University of Connecticut, (6) University of Texas at Austin, (7) University of Massachusetts, (8) The Catholic University of America, (9) MMT/Steward Observatory)
Comments: 13 pages, 7 figures, accepted for publication in ApJ. Includes an interactive online appendix (this https URL)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The origin of the correlations between mass, morphology, quenched fraction, and formation history in galaxies is difficult to define, primarily due to the uncertainties in galaxy star-formation histories. Star-formation histories are better constrained for higher redshift galaxies, observed closer to their formation and quenching epochs. Here we use "non-parametric" star-formation histories and a nested sampling method to derive constraints on the formation and quenching timescales of quiescent galaxies at $0.7<z<2.5$. We model deep HST grism spectroscopy and photometry from the CLEAR (CANDELS Lyman$-\alpha$ Emission at Reionization) survey. The galaxy formation redshifts, $z_{50}$ (defined as the point where they had formed 50\% of their stellar mass) range from $z_{50}\sim 2$ (shortly prior to the observed epoch) up to $z_{50} \simeq 5-8$. \editone{We find that early formation redshifts are correlated with high stellar-mass surface densities, $\log \Sigma_1 / (M_\odot\ \mathrm{kpc}^{-2}) >$10.25, where $\Sigma_1$ is the stellar mass within 1~pkpc (proper kpc). Quiescent galaxies with the highest stellar-mass surface density, $\log\Sigma_1 / (M_\odot\ \mathrm{kpc}^{-2}) > 10.25$, } show a \textit{minimum} formation redshift: all such objects in our sample have $z_{50} > 2.9$. Quiescent galaxies with lower surface density, $\log \Sigma_1 / (M_\odot\ \mathrm{kpc}^{-2}) = 9.5 - 10.25$, show a range of formation epochs ($z_{50} \simeq 1.5 - 8$), implying these galaxies experienced a range of formation and assembly histories. We argue that the surface density threshold $\log\Sigma_1/(M_\odot\ \mathrm{kpc}^{-2})>10.25$ uniquely identifies galaxies that formed in the first few Gyr after the Big Bang, and we discuss the implications this has for galaxy formation models.

[7]  arXiv:2005.12290 [pdf, other]
Title: The PHLEK Survey: A New Determination of the Primordial Helium Abundance
Comments: 32 pages, 11 figures, Accepted for publication in the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present Keck NIRSPEC and Keck NIRES spectroscopy of sixteen metal-poor galaxies that have pre-existing optical observations. The near-infrared (NIR) spectroscopy specifically targets the HeI 10830A emission line, due to its sensitivity to the physical conditions of the gas in HII regions. We use these NIR observations, combined with optical spectroscopy, to determine the helium abundance of sixteen galaxies across a metallicity range 12 + log (O/H) = 7.13 - 8.00. This data set is combined with two other samples where metallicity and helium abundance measurements can be secured: star-forming galaxies selected from the Sloan Digital Sky Survey spectroscopic database and existing low-metallicity systems in the literature. We calculate a linear fit to these measurements, accounting for intrinsic scatter, and report a new determination of the primordial helium number abundance, y_P = 0.0805+/-0.0017, which corresponds to a primordial helium mass fraction Y_P = 0.2436+/-0.0040. Using our determination of the primordial helium abundance in combination with the latest primordial deuterium measurement, (D/H)_P x 10^5 =2.527+/-0.030, we place a bound on the baryon density Omega_bh^2 = 0.0215+/-0.0005 and the effective number of neutrino species Neff = 2.85+/-0.28. These values are in 1.3-sigma agreement with those deduced from the Planck satellite observations of the temperature fluctuations imprinted on the Cosmic Microwave Background.

[8]  arXiv:2005.12295 [pdf, other]
Title: H0LiCOW XI. A weak lensing measurement of the external convergence in the field of the lensed quasar B1608+656 using HST and Subaru deep imaging
Comments: Accepted MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We investigate the environment and line of sight of the H0LiCOW lens B1608+656 using Subaru Suprime-Cam and the Hubble Space Telescope (HST) to perform a weak lensing analysis. We compare three different methods to reconstruct the mass map of the field, i.e. the standard Kaiser-Squires inversion coupled with inpainting and Gaussian or wavelet filtering, and $\tt{Glimpse}$ a method based on sparse regularization of the shear field. We find no substantial difference between the 2D mass reconstructions, but we find that the ground-based data is less sensitive to small-scale structures than the space-based observations. Marginalising over the results obtained with all the reconstruction techniques applied to the two available HST filters F606W and F814W, we estimate the external convergence, $\kappa_{\rm ext}$ at the position of B1608+656 is $\kappa_{\rm ext} = 0.11^{+0.06}_{-0.04}$, where the error bars corresponds respectively to the 16th and 84th quartiles. This result is compatible with previous estimates using the number-counts technique, suggesting that B1608+656 resides in an over-dense line of sight, but with a completely different technique. Using our mass reconstructions, we also compare the convergence at the position of several groups of galaxies in the field of B1608+656 with the mass measurements using various analytical mass profiles, and find that the weak lensing results favor truncated halo models.

[9]  arXiv:2005.12298 [pdf, other]
Title: High-resolution VLA low radio frequency observations of the Perseus cluster: radio lobes, mini-halo and bent-jet radio galaxies
Comments: 17 pages, 12 figures, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

We present the first high-resolution 230-470 MHz map of the Perseus cluster obtained with the Karl G. Jansky Very Large Array. The high dynamic range and resolution achieved has allowed the identification of previously-unknown structures in this nearby galaxy cluster. New hints of sub-structures appear in the inner radio lobes of the brightest cluster galaxy NGC 1275. The spurs of radio emission extending into the outer X-ray cavities, inflated by past nuclear outbursts, are seen for the first time at these frequencies, consistent with spectral aging. Beyond NGC 1275, we also analyze complex radio sources harbored in the cluster. Two new distinct, narrowly-collimated jets are visible in IC 310, consistent with a highly-projected narrow-angle tail radio galaxy infalling into the cluster. We show how this is in agreement with its blazar-like behavior, implying that blazars and bent-jet radio galaxies are not mutually exclusive. We report the presence of filamentary structures across the entire tail of NGC 1265, including two new pairs of long filaments in the faintest bent extension of the tail. Such filaments have been seen in other cluster radio sources such as relics and radio lobes, indicating that there may be a fundamental connection between all these radio structures. We resolve the very narrow and straight tail of CR 15 without indication of double jets, so that the interpretation of such head-tail sources is yet unclear. Finally, we note that only the brightest western parts of the mini-halo remain, near NGC 1272 and its bent double jets.

[10]  arXiv:2005.12300 [pdf, other]
Title: The former companion of the hyper-velocity star S5-HVS1
Authors: Wenbin Lu (1), Jim Fuller (1), Yael Raveh (2), Hagai B. Perets (2), Ting S. Li (3, 4), Matthew W. Hosek Jr. (5), Tuan Do (5) ((1) Caltech, (2) Technion, (3) Carnegie Observatories, (4) Princeton, (5) UCLA)
Comments: 10 pages, 6 figures, 2 tables. MNRAS submitted. Comments welcome!
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The hyper-velocity star S5-HVS1, ejected 5 Myr ago from the Galactic Center at 1800 km/s, was most likely produced by tidal break-up of a tight binary by the supermassive black hole SgrA*. Taking a Monte Carlo approach, we show that the former companion of S5-HVS1 was likely a main-sequence star between 1.5 and 6 solar masses and was captured into a highly eccentric orbit with pericenter distance in the range 1-10 AU and semimajor axis about $10^3$ AU. We then explore the fate of the captured star. We find that the heat deposited by tidally excited stellar oscillation modes leads to runaway disruption if the pericenter distance is smaller than about 3 AU. Over the past 5 Myr, its angular momentum has been significantly modified by orbital relaxation, which may stochastically drive the pericenter inwards below 3 AU and cause tidal disruption. We find an overall survival probability in the range 5% to 50%, depending on the local relaxation time in the close environment of the captured star, and the initial pericenter at capture. The pericenter distance of the surviving star has migrated to 10-100 AU, making it potentially the most extreme member of the S-star cluster. From the ejection rate of S5-HVS1-like stars, we estimate that there may currently be a few stars in such highly eccentric orbits. They should be detectable (typically Ks < 18.5 mag) by the GRAVITY instrument and by future Extremely Large Telescopes and hence provide an extraordinary probe of the spin of SgrA*.

[11]  arXiv:2005.12315 [pdf, other]
Title: JoXSZ: Joint X-SZ fitting code for galaxy clusters
Comments: 11 pages, 9 figures, accepted for publication in Astronomy and Astrophysics. Code available on GitHub at this https URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The thermal Sunyaev-Zeldovich (SZ) effect and the X-ray emission offer separate and highly complementary probes of the thermodynamics of the intracluster medium. We present JoXSZ, the first publicly available code designed to jointly fit SZ and X-ray data coming from various instruments to derive the thermodynamic profiles of galaxy clusters. JoXSZ follows a fully Bayesian forward-modelling approach, accounts for the SZ calibration uncertainty and X-ray background level systematic. It improves upon most state-of-the-art, and not publicly available, analyses because it adopts the correct Poisson-Gauss expression for the joint likelihood, makes full use of the information contained in the observations, even in the case of missing values within the datasets, has a more inclusive error budget, and adopts a consistent temperature across the various parts of the code, allowing for differences between X-ray and SZ gas mass weighted temperatures when required by the user. JoXSZ accounts for beam smearing and data analysis transfer function, accounts for the temperature and metallicity dependencies of the SZ and X-ray conversion factors, adopts flexible parametrization for the thermodynamic profiles, and on user request allows either adopting or relaxing the assumption of hydrostatic equilibrium (HE). When HE holds, JoXSZ uses a physical (positive) prior on the radial derivative of the enclosed mass and derives the mass profile and overdensity radii $r_\Delta$. For these reasons, JoXSZ goes beyond simple SZ and electron density fits. We illustrate the use of JoXSZ by combining Chandra and NIKA data on the high-redshift cluster CL J1226.9+3332. The code is written in Python, it is fully documented and the users are free to customize their analysis in accordance with their needs and requirements. JoXSZ is publicly available on GitHub.

[12]  arXiv:2005.12336 [pdf]
Title: Exploration of the outer solar system with fast and small sailcraft
Comments: A White Paper to the National Academy of Sciences Planetary Science and Astrobiology Decadal Survey 2023-2032. 13 pages, 5 figures and 2 tables
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)

Two new interplanetary technologies have advanced in the past decade to the point where they may enable exciting, affordable missions that reach further and faster deep into the outer regions of our solar system: (i) small and capable interplanetary spacecraft and (ii) light-driven sails. Combination of these two technologies could drastically reduce travel times within the solar system. We discuss a new paradigm that involves small and fast moving sailcraft that could enable exploration of distant regions of the solar system much sooner and faster than previously considered. We present some of the exciting science objectives for these miniaturized intelligent space systems that could lead to transformational advancements in the space sciences.

[13]  arXiv:2005.12343 [pdf, other]
Title: Multi-wavelength observations of 2HWC J1928+177: dark accelerator or new TeV gamma-ray binary?
Comments: accepted to ApJ, 8 pages, 7 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

2HWC J1928+177 is a Galactic TeV gamma-ray source detected by the High Altitude Water Cherenkov (HAWC) Observatory up to ~ 56 TeV. The HAWC source, later confirmed by H.E.S.S., still remains unidentified as a dark accelerator since there is no apparent supernova remnant or pulsar wind nebula detected in the lower energy bands. The radio pulsar PSR J1928+1746, coinciding with the HAWC source position, has no X-ray counterpart. Our SED modeling shows that inverse Compton scattering in the putative pulsar wind nebula can account for the TeV emission only if the unseen nebula is extended beyond r ~ 4 [arcmin]. Alternatively, TeV gamma rays may be produced by hadronic interactions between relativistic protons from an undetected supernova remnant associated with the radio pulsar and a nearby molecular cloud G52.9+0.1. NuSTAR and Chandra observations detected a variable X-ray point source within the HAWC error circle, potentially associated with a bright IR source. The X-ray spectra can be fitted with an absorbed power-law model with $N_{\rm H} = (9\pm3)\times10^{22}$ cm$^{-2}$ and $\Gamma_X = 1.6\pm0.3$ and exhibit long-term X-ray flux variability over the last decade. If the X-ray source, possibly associated with the IR source (likely an O star), is the counterpart of the HAWC source, it may be a new TeV gamma-ray binary powered by collisions between the pulsar wind and stellar wind. Follow-up X-ray observations are warranted to search for diffuse X-ray emission and determine the nature of the HAWC source.

[14]  arXiv:2005.12352 [pdf, other]
Title: Is Fornax 4 the nuclear star cluster of the Fornax dwarf spheroidal galaxy?
Comments: Accepted for publication in MNRAS. 12 pages, 11 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Fornax 4 is the most distinctive globular cluster in the Fornax dwarf spheroidal. Located close to the centre of the galaxy, more metal-rich and potentially younger than its four companions (namely, Fornax clusters number 1, 2, 3 and 5), it has been suggested to have experienced a different formation than the other clusters in the galaxy. Here we use HST/WFC3 photometry to characterize the stellar population content of this system and shed new light on its nature. By means of a detailed comparison of synthetic horizontal branch and red giant branch with the observed colour-magnitude diagrams, we find that this system likely hosts stellar sub-populations characterized by a significant iron spread up to $\Delta$[Fe/H]$\sim$0.4 dex and possibly by also some degree of He abundance variations $\Delta$Y$\sim0.03$. We argue that this purely observational evidence, combined with the other peculiarities characterizing this system, supports the possibility that Fornax 4 is the nuclear star cluster of the Fornax dwarf spheroidal galaxy. A spectroscopic follow-up for a large number of resolved member stars is needed to confirm this interesting result and to study in detail the formation and early evolution of this system and more in general the process of galaxy nucleation.

[15]  arXiv:2005.12357 [pdf, other]
Title: Recovering the city street lighting fraction from skyglow measurements in a large-scale municipal dimming experiment
Comments: 44 pages, 9 figures; accepted by Journal of Quantitative Spectroscopy and Radiative Transfer
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Anthropogenic skyglow dominates views of the natural night sky in most urban settings, and the associated emission of artificial light at night (ALAN) into the environment of cities involves a number of known and suspected negative externalities. One approach to lowering consumption of ALAN in cities is dimming or extinguishing publicly owned outdoor lighting during overnight hours; however, there are few reports in the literature about the efficacy of these programs. Here we report the results of one of the largest municipal lighting dimming experiments to date, involving $\sim$20,000 roadway luminaires owned and operated by the City of Tucson, Arizona, U.S. We analyzed both single-channel and spatially resolved ground-based measurements of broadband night sky radiance obtained during the tests, determining that the zenith sky brightness during the tests decreased by ($-5.4\pm0.9$)% near the city center and ($-3.6\pm0.9$)% at an adjacent suburban location on nights when the output of the street lighting system was dimmed from 90% of its full power draw to 30% after local midnight. Modeling these changes with a radiative transfer code yields results suggesting that street lights account for about ($14\pm1$)% of light emissions resulting in skyglow seen over the city. A separate derivation from first principles implies that street lighting contributes only 2-3% of light seen at the zenith over Tucson. We discuss this inconsistency and suggest routes for future work.

[16]  arXiv:2005.12358 [pdf, ps, other]
Title: Understanding the rotational variability of K2 targets. HgMn star KIC 250152017 and blue horizontal branch star KIC 249660366
Comments: 8 pages, accepted for publication in Astronomy & Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Ultraprecise space photometry enables us to reveal light variability even in stars that were previously deemed constant. A large group of such stars show variations that may be rotationally modulated. This type of light variability is of special interest because it provides precise estimates of rotational rates. We aim to understand the origin of the light variability of K2 targets that show signatures of rotational modulation. We used phase-resolved medium-resolution XSHOOTER spectroscopy to understand the light variability of the stars KIC~250152017 and KIC~249660366, which are possibly rotationally modulated. We determined the atmospheric parameters at individual phases and tested the presence of the rotational modulation in the spectra. KIC 250152017 is a HgMn star, whose light variability is caused by the inhomogeneous surface distribution of manganese and iron. It is only the second HgMn star whose light variability is well understood. KIC 249660366 is a He-weak, high-velocity horizontal branch star with overabundances of silicon and argon. The light variability of this star is likely caused by a reflection effect in this post-common envelope binary.

[17]  arXiv:2005.12383 [pdf, other]
Title: Origin of sub-TeV afterglow emission from gamma-ray bursts GRB 190114C and GRB 180720B
Comments: 7 pages, 2 figures, APJ style, to be published in Astrophysical Journal Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

The detection of GRB 180722B and GRB 190114C in sub-TeV gamma-rays has opened up a new window to study gamma-ray bursts in high energy gamma-rays. Recently it is shown that the synchrotron and inverse Compton processes are responsible for the production of these high energy gamma-rays during the afterglow. Here, for the first time we demonstrate that, the photohadronic scenario which is successful in explaining the multi-TeV flaring in high energy blazars is also applicable for gamma-ray bursts. We show that the sub-TeV spectra of GRB 190114C and GRB 180720B are due to the interaction of high energy protons with the background photons in the synchrotron self-Compton region and synchrotron region respectively. The nature of the background photon distributions help us to constraint their bulk Lorentz factors.

[18]  arXiv:2005.12391 [pdf, other]
Title: Redshift evolution of the hot intracluster gas metallicity in the C-EAGLE cluster simulations
Comments: 18 pages, 16 figures, submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

The abundance and distribution of metals in galaxy clusters contains valuable information about their chemical history and evolution. By looking at how metallicity evolves with redshift, it is possible to constrain the different metal production channels. We use the C-EAGLE clusters, a sample of 30 high resolution ($m_{gas} \simeq 1.8\times 10^{6}$ M$_{\odot}$) cluster zoom simulations, to investigate the redshift evolution of metallicity, with particular focus on the cluster outskirts. The early enrichment model, in which the majority of metals are produced in the core of cluster progenitors at high redshift, suggests that metals in cluster outskirts have not significantly evolved since $z=2$. With the C-EAGLE sample, we find reasonable agreement with the early enrichment model as there is very little scatter in the metallicity abundance at large radius across the whole sample, out to at least $z=2$. The exception is Fe for which the radial dependence of metallicity was found to evolve at low redshift as a result of being mainly produced by Type Ia supernovae, which are more likely to be formed at later times than core-collapse supernovae. We also found considerable redshift evolution of metal abundances in the cores of the C-EAGLE clusters which has not been seen in other simulations or observation based metallicity studies. Since we find this evolution to be driven by accretion of low metallicity gas, it suggests that the interaction between outflowing, AGN heated material and the surrounding gas is important for determining the core abundances in clusters.

[19]  arXiv:2005.12406 [pdf, other]
Title: Forecasting Solar Cycle 25 using Deep Neural Networks
Comments: 17 pages, 16 figures
Journal-ref: Solar Physics volume 295, Article number: 65 (2020)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

With recent advances in the field of machine learning, the use of deep neural networks for time series forecasting has become more prevalent. The quasi-periodic nature of the solar cycle makes it a good candidate for applying time series forecasting methods. We employ a combination of WaveNet and LSTM neural networks to forecast the sunspot number using the years 1749 to 2019 and total sunspot area using the years 1874 to 2019 time series data for the upcoming Solar Cycle 25. Three other models involving the use of LSTMs and 1D ConvNets are also compared with our best model. Our analysis shows that the WaveNet and LSTM model is able to better capture the overall trend and learn the inherent long and short term dependencies in time series data. Using this method we forecast 11 years of monthly averaged data for Solar Cycle 25. Our forecasts show that the upcoming Solar Cycle 25 will have a maximum sunspot number around 106 $\pm$ 19.75 and maximum total sunspot area around 1771 $\pm$ 381.17. This indicates that the cycle would be slightly weaker than Solar Cycle 24.

[20]  arXiv:2005.12408 [pdf, ps, other]
Title: Simulating the outer layers of rapidly rotating stars
Comments: 9 pages, 9 Figues and one table
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

This paper presents the results of a set of radiative hydrodynamic (RHD) simulations of convection in the near-surface regions of a rapidly rotating star. The simulations use microphysics consistent with stellar models, and include the effects of realistic convection and radiative transfer. We find that the overall effect of rotation is to reduce the strength of turbulence. The combination of rotation and radiative cooling creates a zonal velocity profile in which the motion of fluid parcels near the surface is independent of rotation. Their motion is controlled by the strong up and down flows generated by radiative cooling. The fluid parcels in the deeper layers, on the other hand, are controlled by rotation.

[21]  arXiv:2005.12416 [pdf, other]
Title: Diagnostics of Parameters for the X-ray Jets of SS 433 from High-Resolution Chandra Spectroscopy
Comments: 17 pages, 12 figures, published in Astronomy Letters; the ftp link was changed due to technical reasons
Journal-ref: Astron. Lett. 45, 299-320 (2019)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The X-ray spectrum of the Galactic microquasar SS 433 contains a rich set of emission lines of highly ionized atoms of heavy elements whose significant Doppler shift leaves no doubt that they are produced in collimated relativistic jets of outflowing material. We have performed a systematic analysis of the high-resolution X-ray spectra obtained by the Chandra observatory to determine the parameters of the jets within the multitemperature model of their emission that self-consistently predicts the source's line and continuum spectrum. The spectrum of SS 433 at energies below 3 keV is shown to be statistically satisfactorily described by the jet emission model, while the introduction of an additional hard component is required above 3 keV. We summarize the jet parameters (bulk velocity, opening angle, kinetic luminosity, base temperature, and relative elemental abundances) derived by fitting the data below 3 keV and describe the revealed degeneracies and systematic effects due to the presence of an additional component. Using the derived parameters, we show that the hard component is compatible with the emission from the hot (up to 40 keV) extension of the visible part of the jets moderately absorbed ($N_H \sim 2 \times 10^{23}$ cm$^{-2}$) in the cold-wind material. The combined X-ray emission model constructed in this way allows the broadband spectrum of SS 433 to be described self-consistently.

[22]  arXiv:2005.12426 [pdf, other]
Title: GRB 170817A as a Refreshed Shock Afterglow viewed off-axis
Comments: 11 pages, 6 figures - Submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Energy injection into the external shock system that generates the afterglow to a gamma-ray burst (GRB) can result in a re-brightening of the emission. Here we investigate the off-axis view of a re-brightened refreshed shock afterglow. We find that the afterglow light-curve, when viewed from outside of the jet opening angle, could be characterised by a slow rise, or long-plateau, with a maximum flux determined by the total system energy. Using the broadband afterglow data for GRB 170817A, associated with the gravitational wave detected binary neutron star merger GW170817, we show that a refreshed shock model with a simple top-hat jet can reproduce the observed afterglow features. The best fit model parameters give a jet opening angle $\theta_j=5^\circ.2^{+1.1}_{-0.6}$, an inclination to the line of sight $\iota=16^\circ.0^{+3.4}_{-1.1}$, an initial isotropic kinetic energy $E_1=0.3^{+3.5}_{-0.3}\times10^{52}$ erg and a total, refreshed shock energy $E_{\rm total}=0.42^{+5.6}_{-0.4}\times10^{53}$ erg. The model fitting prefers an initial bulk Lorentz factor $\Gamma_{0,1}<60$, with a comparatively low central value of $\Gamma_{0,1}=19.5$, indicating that the on-axis jet could have been a `failed-GRB' and that the associated $\gamma$-ray emission was the result of a shock-breakout or some other process.

[23]  arXiv:2005.12459 [pdf, other]
Title: The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder I. The Spectral Feature Finder and Catalogue
Comments: 20 pages, 8 figures, 8 tables, accepted by MNRAS March 2020
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

We provide a detailed description of the Herschel SPIRE Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF). The FF is an automated process designed to extract significant spectral features from SPIRE FTS data products. Optimising the number of features found in SPIRE FTS spectra is challenging. The wide SPIRE FTS frequency range (447-1568 GHz) leads to many molecular species and atomic fine structure lines falling within the observed bands. As the best spectral resolution of the SPIRE FTS is ~1.2 GHz, there can be significant line blending, depending on the source type. In order to find, both efficiently and reliably, features in spectra associated with a wide range of sources, the FF iteratively searches for peaks over a number of signal-to-noise ratio (SNR) thresholds. For each threshold, newly identified features are rigorously checked before being added to the fitting model. At the end of each iteration, the FF simultaneously fits the continuum and features found, with the resulting residual spectrum used in the next iteration. The final FF products report the frequency of the features found and the associated SNRs. Line flux determination is not included as part of the FF products, as extracting reliable line flux from SPIRE FTS data is a complex process that requires careful evaluation and analysis of the spectra on a case-by-case basis. The FF results are 100% complete for features with SNR greater than 10 and 50-70% complete at SNR of 5. The FF code and all FF products are publicly available via the Herschel Science Archive.

[24]  arXiv:2005.12460 [pdf, other]
Title: The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder II. Estimating Radial Velocity of SPIRE Spectral Observation Sources
Comments: 12 pages, 16 figures, 1 table, accepted by MNRAS March 2020
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

The Herschel SPIRE FTS Spectral Feature Finder (FF) detects significant spectral features within SPIRE spectra and employs two routines, and external references, to estimate source radial velocity. The first routine is based on the identification of rotational CO emission, the second cross-correlates detected features with a line template containing most of the characteristic lines in typical far infra-red observations. In this paper, we outline and validate these routines, summarise the results as they pertain to the FF, and comment on how external references were incorporated.

[25]  arXiv:2005.12461 [pdf, other]
Title: The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder III. Line Identification and Off-Axis Spectra
Comments: 15 pages (+2 appendix pages), 14 figures, 7 tables, accepted by MNRAS April 2020
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

The ESA Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF) project is an automated spectral feature fitting routine developed within the SPIRE instrument team to extract all prominent spectral features from all publicly available SPIRE FTS observations. We present the extension of the FF to include the off-axis detectors of the FTS in sparsely sampled single-pointing observations, the results of which have been ingested into the catalogue. We also present the results from an automated routine for identifications of the atomic/molecular transitions that correspond to the spectral features extracted by the FF. We use a template of 307 atomic fine structure and molecular lines that are commonly found in SPIRE FTS spectra for the cross-match. The routine makes use of information provided by the line identification to search for low signal-to-noise ratio features that have been excluded or missed by the iterative FF. In total, the atomic/molecular transitions of 178,942 lines are identified (corresponding to 83% of the entire FF catalogue), and an additional 33,840 spectral lines associated with missing features from SPIRE FTS observations are added to the FF catalogue.

[26]  arXiv:2005.12462 [pdf, other]
Title: The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder IV. Neutral Carbon Detection in the SPIRE FTS Spectra
Comments: 8 pages, 9 figures, 2 tables, accepted by MNRAS March 2020
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The SPIRE FTS Spectral Feature Finder (FF), developed within the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer (FTS) instrument team, is an automated spectral feature fitting routine that attempts to find significant features in SPIRE FTS spectra. The $^3$P$_1$ - $^3$P$_0$ and $^3$P$_2$ - $^3$P$_1$ neutral carbon fine structure lines are common features in carbon rich far-infrared astrophysical sources. These features can be difficult to detect using an automated feature detection routine due to their typically low amplitude and line blending. In this paper we describe and validate the FF sub-routine designed to detect the neutral carbon emission observed in SPIRE spectral data.

[27]  arXiv:2005.12471 [pdf, other]
Title: K-CLASH: spatially-resolving star-forming galaxies in field and cluster environments at $z \approx 0.2$-$0.6$
Authors: Alfred L. Tiley (1,2,3), Sam P. Vaughan (4,5,3), John P. Stott (6), Roger L. Davies (3), Laura J. Prichard (7), Andrew Bunker (3), Martin Bureau (3,8), Michele Cappellari (3), Matt Jarvis (3,9), Aaron Robotham (1), Luca Cortese (1,5), Sabine Bellstedt (1), Behzad Ansarinejad (2) ((1) ICRAR/UWA, (2) CEA Durham University, (3) University of Oxford, (4) SIfA University of Sydney, (5) ASTRO3D, (6) Lancaster University, (7) STScI, (8) Yonsei University, (9) University of the Western Cape)
Comments: Accepted for publication in MNRAS, 31 pages, 15 figures, 2 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the KMOS-CLASH (K-CLASH) survey, a K-band Multi-Object Spectrograph (KMOS) survey of the spatially-resolved gas properties and kinematics of 191 (predominantly blue) H$\alpha$-detected galaxies at $0.2 \lesssim z \lesssim 0.6$ in field and cluster environments. K-CLASH targets galaxies in four Cluster Lensing And Supernova survey with Hubble (CLASH) fields in the KMOS $IZ$-band, over $7'$ radius ($\approx2$-$3$ Mpc) fields-of-view. K-CLASH aims to study the transition of star-forming galaxies from turbulent, highly star-forming disc-like and peculiar systems at $z\approx1$-$3$, to the comparatively quiescent, ordered late-type galaxies at $z\approx0$, and to examine the role of clusters in the build-up of the red sequence since $z\approx1$. In this paper, we describe the K-CLASH survey, present the sample, and provide an overview of the K-CLASH galaxy properties. We demonstrate that our sample comprises star-forming galaxies typical of their stellar masses and epochs, residing both in field and cluster environments. We conclude K-CLASH provides an ideal sample to bridge the gap between existing large integral-field spectroscopy surveys at higher and lower redshifts. We find that star-forming K-CLASH cluster galaxies at intermediate redshifts have systematically lower stellar masses than their star-forming counterparts in the field, hinting at possible ``downsizing'' scenarios of galaxy growth in clusters at these epochs. We measure no difference between the star-formation rates of H$\alpha$-detected, star-forming galaxies in either environment after accounting for stellar mass, suggesting that cluster quenching occurs very rapidly during the epochs probed by K-CLASH, or that star-forming K-CLASH galaxies in clusters have only recently arrived there, with insufficient time elapsed for quenching to have occured.

[28]  arXiv:2005.12481 [pdf, ps, other]
Title: Magnetic field generation by an inhomogeneous return current
Authors: Yutaka Ohira
Comments: 6 pages, 2 figures, accepted for publication in ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Plasma Physics (physics.plasm-ph)

A new generation mechanism of the magnetic field in an inhomogeneous collisionless plasma with a beam component is proposed. We show that even though the current and charge neutralities are initially satisfied, the current neutrality is eventually violated if there is an inhomogeneity, so that the magnetic field is generated. By conducting ab initio two-dimensional particle-in-cell simulations, we demonstrate that the magnetic field is generated as expected. The new generation mechanism of the magnetic field can play an important role in the current universe because cosmic rays can be regarded as the beam component in the astrophysical plasma. We propose that the first cosmic rays generate the magnetic field with a large scale at the redshift of z ~ 20.

[29]  arXiv:2005.12498 [pdf, ps, other]
Title: Focal Surface Attitude Detection for LAMOST
Comments: 9 pages,8 figures,accepted for publication in Research in Astronomy and Astrophysics
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

With telescope apertures becoming larger and larger, the deployment of large-field telescopes is becoming increasingly popular. However, optical path calibration is necessary to ensure the image quality of large-field and large-diameter telescopes. In particular, focal plane attitude calibration is an essential optical path calibration technique that has a direct impact on image quality. In this paper, a focal plane attitude detection method using eight acquisition cameras is proposed based on the calibration requirements of the wide-field telescope, LAMOST. Comparison of simulation and experimental results shows that the detection accuracy of the proposed method can reach 30 arcsec. With additional testing and verification, this method could be used to facilitate regular focal plane attitude calibration for LAMOST as well as other large-field telescopes.

[30]  arXiv:2005.12507 [pdf, other]
Title: Selection of massive evolved galaxies at $3 \leq z \leq 4.5$ in the CANDELS fields
Comments: 20 pages, 11 figures, Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Using the CANDELS photometric catalogs for the \textit{HST}/ACS and WFC3, we identified massive evolved galaxies at $3 < z < 4.5$, employing three different selection methods. We find the comoving number density of these objects to be $\sim 2 \times 10^{-5}$ and $8 \times 10^{-6}Mpc^{-3}$ after correction for completeness for two redshift bins centered at $z=3.4, 4.7$. We quantify a measure of how much confidence we should have for each candidate galaxy from different selections and what are the conservative error estimates propagated into our selection. Then we compare the evolution of the corresponding number densities and their stellar mass density with numerical simulations, semi-analytical models, and previous observational estimates, which shows slight tension at higher redshifts as the models tend to underestimate the number and mass densities. By estimating the average halo masses of the candidates ($M_h \approx 4.2, 1.9, 1.3 \times 10^{12} M_\odot$ for redshift bins centered at $z=3.4, 4.1, 4.7$), we find them to be consistent with halos that were efficient in turning baryons to stars and were relatively immune to the feedback effects and on the verge of transition into hot-mode accretion. This can suggest the relative cosmological starvation of the cold gas followed by an overconsumption phase in which the galaxy consumes the available cold gas rapidly as one of the possible drivers for the quenching of the massive evolved population at high redshift.

[31]  arXiv:2005.12510 [pdf, ps, other]
Title: The radio-loud narrow-line Seyfert 1 galaxy 1H 0323+342 in a galaxy merger
Comments: 10 pages, 4 figures. Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The supermassive black holes (SMBHs) of narrow-line Seyfert 1 galaxies (NLS1s) are at the lowest end of mass function of active galactic nuclei (AGNs) and preferentially reside in late-type host galaxies with pseudobulges, which are thought to be formed by internal secular evolution. On the other hand, the population of radio-loud NLS1s presents a challenge for the relativistic jet paradigm that powerful radio jets are exclusively associated with very high mass SMBHs in elliptical hosts, which are built-up through galaxy mergers. We investigated distorted radio structures associated with the nearest gamma-ray emitting, radio-loud NLS1 1H 0323+342. This provides supporting evidence for the merger hypothesis based on the past optical/near-infrared observations of its host galaxy. The anomalous radio morphology consists of two different structures, the inner curved structure of currently active jet and the outer linear structure of low-brightness relics. Such a coexistence might be indicative of the stage of an established black hole binary with precession before the black holes coalesce in the galaxy merger process. 1H 0323+342 and other radio-loud NLS1s under galaxy interactions may be extreme objects on the evolutionary path from radio-quiet NLS1s to normal Seyfert galaxies with larger SMBHs in classical bulges through mergers and merger-induced jet phases.

[32]  arXiv:2005.12527 [pdf, ps, other]
Title: Understanding the Fundamental Plane and the Tully Fisher Relation
Authors: Jeremy Mould
Comments: For publication in Frontiers in Astronomy and Space Sciences
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The relation between early type galaxy size, surface brightness and velocity dispersion, "the fundamental plane", has long been understood as resulting from equilibrium in their largely pressure supported stellar dynamics. The dissipation and feedback involved in reaching such an equilibrium through merger formation of these galaxies over cosmic time can be responsible for the orientation of the plane. We see a correlation between surface brightness enhancement and youth in the 6dF Galaxy Survey. Correlations of this `tilt' with stellar mass, age, concentration, shape and metallicity now point the direction for further work on the resolved kinematics and structure of these nearby galaxies and on their initial mass function and dark matter component.
On the face of it, the Tully Fisher relation is a simpler one dimensional scaling relation. However, as late type galaxies have bulges as well as disks, and, as the surface density of disks is only standard for the more massive galaxies, additional parameters are involved.

[33]  arXiv:2005.12528 [pdf, other]
Title: The Process of Stellar Tidal Disruption by Supermassive Black Holes. The first pericenter passage
Comments: Review chapter in book: 'The Tidal Disruption of Stars by Massive Black Holes', Space Science Reviews, Springer. Comments welcome
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Tidal disruption events (TDEs) are among the brightest transients in the optical, ultraviolet, and X-ray sky. These flares are set into motion when a star is torn apart by the tidal field of a massive black hole, triggering a chain of events which is -- so far -- incompletely understood. However, the disruption process has been studied extensively for almost half a century, and unlike the later stages of a TDE, our understanding of the disruption itself is reasonably well converged. In this Chapter, we review both analytical and numerical models for stellar tidal disruption. Starting with relatively simple, order-of-magnitude physics, we review models of increasing sophistication, the semi-analytic ``affine formalism,'' hydrodynamic simulations of the disruption of polytropic stars, and the most recent hydrodynamic results concerning the disruption of realistic stellar models. Our review surveys the immediate aftermath of disruption in both typical and more unusual TDEs, exploring how the fate of the tidal debris changes if one considers non-main sequence stars, deeply penetrating tidal encounters, binary star systems, and sub-parabolic orbits. The stellar tidal disruption process provides the initial conditions needed to model the formation of accretion flows around quiescent massive black holes, and in some cases may also lead to directly observable emission, for example via shock breakout, gravitational waves or runaway nuclear fusion in deeply plunging TDEs.

[34]  arXiv:2005.12530 [pdf, ps, other]
Title: Smooth stochastic density field reconstruction
Comments: Submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We introduce a method for generating a continuous, mass-conserving and high-order differentiable density field from a discrete point distribution such as particles or halos from an N-body simulation or galaxies from a spectroscopic survey. The method consists on generating an ensemble of point realizations by perturbing the original point set following the geometric constraints imposed by the Delaunay tessellation in the vicinity of each point in the set. By computing the mean field of the ensemble we are able to significantly reduce artifacts arising from the Delaunay tessellation in poorly sampled regions while conserving the features in the point distribution. Our implementation is based on the Delaunay Tessellation Field Estimation (DTFE) method, however other tessellation techniques are possible. The method presented here shares the same advantages of the DTFE method such as self-adaptive scale, mass conservation and continuity, while being able to reconstruct even the faintest structures of the point distribution usually dominated by artifacts in Delaunay-based methods. Additionally, we also present preliminary results of an application of this method to image denoising and artifact removal, highlighting the broad applicability of the technique introduced here.

[35]  arXiv:2005.12549 [pdf, other]
Title: Change of a Weibel-type to an Alfvénic shock in pair plasma by upstream waves
Comments: 11 pages, 10 figures, accepted for publication in Physics of Plasmas
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph)

We examine with particle-in-cell (PIC) simulations how a parallel shock in pair plasma reacts to upstream waves, which are driven by escaping downstream particles. Initially, the shock is sustained in the two-dimensional simulation by a magnetic filamentation (beam-Weibel) instability. Escaping particles drive an electrostatic beam instability upstream. Modifications of the upstream plasma by these waves hardly affect the shock. In time, a decreasing density and increasing temperature of the escaping particles quench the beam instability. A larger thermal energy along than perpendicular to the magnetic field destabilizes the pair-Alfv\'en mode. In the rest frame of the upstream plasma, the group velocity of the growing pair-Alfv\'en waves is below that of the shock and the latter catches up with the waves. Accumulating pair-Alfv\'en waves gradually change the shock in the two-dimensional simulation from a Weibel-type shock into an Alfv\'enic shock with a Mach number that is about 6 for our initial conditions.

[36]  arXiv:2005.12555 [pdf]
Title: Star formation in thin disks of spiral galaxies seen face-on
Comments: Published in Astrophysics, 2020, v.63, pp.151-165
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Estimates of the integrated (SFR) and specific (sSFR) rates of star formation are given for 181 galaxies of later Sc, Scd, and Sd types seen almost face-on. Their SFRs were determined from FUV fluxes in the GALEX survey. The median values of the sSFR are: -10.66 dex for Sc, -10.44 dex for Scd, and -10.40 dex for Sd types in units of yr-1. The average value of the sSFR for these galaxies falls off smoothly from lowmass to giant disks. After accounting for photometric errors, the specific star formation rate has a small cosmic variation of 0.16 dex. In order to reproduce the observed stellar mass on a cosmic time of 13.8 Gyr, the galaxies without bulges viewed face-on must have had an SFR two-three times higher in the past than observed now.

[37]  arXiv:2005.12560 [pdf, other]
Title: Ultra-Long Gamma-Ray Bursts detection with SVOM/ECLAIRs
Comments: Accepted in Experimental Astronomy; 32 pages, 18 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Ultra-long Gamma-Ray Bursts (ulGRBs) are Gamma-Ray Bursts (GRBs) with an unusually long emission in X and gamma rays, reaching durations of thousands of seconds. They could form a specific class of high-energy transient events, whose origin is still under discussion. The current sample of known ulGRBs consists of a few tens of events which have been detected so far by the Burst Alert Telescope (BAT) aboard the Neil Gehrels Swift Observatory and some other instruments. The SVOM mission which is scheduled to begin operations after 2021 could help to detect and observe more ulGRBs thanks to its soft gamma-ray telescope ECLAIRs. After an introduction on ulGRBs and the SVOM mission, we present the results of our simulations on the capabilities of ECLAIRs to detect ulGRBs. First we use the sample of ulGRBs detected by Swift/BAT and simulate these events through a model of the instrument and the prototype trigger software that will be implemented onboard ECLAIRs. Then we present a study of the ECLAIRs capabilities to detect a synthetic population of ulGRBs built by transporting the ulGRBs detected by Swift/BAT to higher redshifts. Finally we give an estimate of the ulGRB rate expected to be detected by ECLAIRs and show that ECLAIRs can detect at least as much ulGRBs as BAT.

[38]  arXiv:2005.12587 [pdf, other]
Title: Dark Energy with Phantom Crossing and the $H_0$ tension
Comments: 7 pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We investigate the possibility of phantom crossing in the dark energy sector and solution for the Hubble tension between early and late Universe observations. We use robust combinations of different cosmological observations, namely the CMB, local measurement of Hubble constant ($H_0$), BAO and SnIa for this purpose. For a combination of CMB+BAO data which is related to early Universe physics, phantom crossing in the dark energy sector is confirmed at $95$\% confidence level and we obtain the constraint $H_0=71.0^{+2.9}_{-3.8}$ km/s/Mpc at 68\% confidence level which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combination of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtain the constraint $H_0=70.25\pm 0.78$ km/s/Mpc at 68\% confidence level and the phantom crossing happening at the scale factor $a_m=0.851^{+0.048}_{-0.031}$ at 68\% confidence level.

[39]  arXiv:2005.12594 [pdf, other]
Title: Simulation study on the effects of diffractive collisions on the prediction of the observables in ultra-high-energy cosmic ray experiments
Comments: 26 pages, 15 figures,9 tables
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The mass composition of ultra-high-energy cosmic rays is important for understanding their origin. Owing to our limited knowledge of the hadronic interaction, the interpretations of the mass composition from observations have several open problems, such as the inconsistent interpretations of $\langle X_{\mathrm{max}}\rangle $ and $\langle X_{\mathrm{max}}^{\mu}\rangle $ and the large difference between the predictions by the hadronic interaction models. Diffractive collision is one of the proposed sources of the uncertainty. In this paper, we discuss the effect of the detailed characteristics of diffractive collisions on the observables of ultra-high-energy cosmic-ray experiments by focusing on three detailed characteristics. These are the cross-sectional fractions of different collision types, diffractive-mass spectrum, and diffractive-mass-dependent particle productions. We demonstrated that the current level of the uncertainty in the cross-sectional fraction can affect 8.9$\mathrm{g/cm^2}$ of $\langle X_{\mathrm{max}}\rangle $ and 9.4$\mathrm{g/cm^2}$ of $\langle X_{\mathrm{max}}^{\mu}\rangle $, whereas the other details of the diffractive collisions exhibit relatively minor effects.

[40]  arXiv:2005.12595 [pdf, ps, other]
Title: Phase-dependent study of near-infrared disk emission lines in LB-1
Comments: To be submitted to ApJ. Comments are welcome
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The mass, origin and evolutionary stage of the binary system LB-1 has been the subject of intense debate, following the claim that it hosts an $\sim$70$M_{\odot}$ black hole, in stark contrast with the expectations for stellar remnants in the Milky Way. We conducted a high-resolution, phase-resolved spectroscopic study of the near-infrared Paschen lines in this system, using the 3.5-m telescope at Calar Alto Observatory. We find that Pa$\beta$ and Pa$\gamma$ (after proper subtraction of the stellar absorption component) are well fitted with a standard double-peaked model, typical of disk emission. We measured the velocity shifts of the red and blue peaks at 28 orbital phases: the line center has an orbital motion in perfect antiphase with the stellar motion, and the radial velocity amplitude ranges from 8 to 13 km/s for different choices of lines and profile modelling. We interpret this curve as proof that the disk is tracing the orbital motion of the primary, ruling out the circumbinary disk and the hierarchical triple scenarios. The phase-averaged peak-to-peak half-separation (proxy for the projected rotational velocity of the outer disk) is $\sim$70 km s$^{-1}$, larger than the stellar orbital velocity and also inconsistent with a circumbinary disk. From those results, we infer a primary mass 4--8 times higher than the secondary mass. Moreover, we show that the ratio of the blue and red peaks (V/R intensity ratio) has a sinusoidal behaviour in phase with the secondary star, which can be interpreted as the effect of external irradiation by the secondary star on the outer disk. Finally, we briefly discuss our findings in the context of alternative scenarios recently proposed for LB-1. Definitive tests between alternative solutions will require further astrometric data from $Gaia$.

[41]  arXiv:2005.12596 [pdf, other]
Title: ARCHI: pipeline for light curve extraction of CHEOPS background star
Comments: 14 pages, 13 figures, accepted for publication in MNRAS, all code available at this https URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

High precision time series photometry from space is being used for a number of scientific cases. In this context, the recently launched CHEOPS (ESA) mission promises to bring 20 ppm precision over an exposure time of 6 hours, when targeting nearby bright stars, having in mind the detailed characterization of exoplanetary systems through transit measurements. However, the official CHEOPS (ESA) mission pipeline only provides photometry for the main target (the central star in the field). In order to explore the potential of CHEOPS photometry for all stars in the field, in this paper we present archi, an additional open-source pipeline module{\dag}to analyse the background stars present in the image. As archi uses the official Data Reduction Pipeline data as input, it is not meant to be used as independent tool to process raw CHEOPS data but, instead, to be used as an add-on to the official pipeline. We test archi using CHEOPS simulated images, and show that photometry of background stars in CHEOPS images is only slightly degraded (by a factor of 2 to 3) with respect to the main target. This opens a potential for the use of CHEOPS to produce photometric time series of several close-by targets at once, as well as to use different stars in the image to calibrate systematic errors. We also show one clear scientific application where the study of the companion light curve can be important for the understanding of the contamination on the main target.

[42]  arXiv:2005.12616 [pdf, other]
Title: Spectroscopic and Photometric Periods of Six Ultracompact Accreting Binaries
Comments: 22 pages, 21 figures. Accepted for publication by MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Ultracompact accreting binary systems each consist of a stellar remnant accreting helium-enriched material from a compact donor star. Such binaries include two related sub-classes, AM CVn-type binaries and helium cataclysmic variables, in both of which the central star is a white dwarf. We present a spectroscopic and photometric study of six accreting binaries with orbital periods in the range of 40--70 min, including phase-resolved VLT spectroscopy and high-speed ULTRACAM photometry. Four of these are AM CVn systems and two are helium cataclysmic variables. For four of these binaries we are able to identify orbital periods (of which three are spectroscopic). SDSS J1505+0659 has an orbital period of 67.8 min, significantly longer than previously believed, and longer than any other known AM CVn binary. We identify a WISE infrared excess in SDSS J1505+0659 that we believe to be the first direct detection of an AM CVn donor star in a non-direct impacting binary. The mass ratio of SDSS J1505+0659 is consistent with a white dwarf donor. CRTS J1028-0819 has an orbital period of 52.1 min, the shortest period of any helium cataclysmic variable. MOA 2010-BLG-087 is co-aligned with a K-class star that dominates its spectrum. ASASSN-14ei and ASASSN-14mv both show a remarkable number of echo outbursts following superoutbursts (13 and 10 echo outbursts respectively). ASASSN-14ei shows an increased outburst rate over the years following its superoutburst, perhaps resulting from an increased accretion rate.

[43]  arXiv:2005.12617 [pdf, other]
Title: Cosmological constraints from HII starburst galaxy apparent magnitude and other cosmological measurements
Comments: 16 pages, 6 figures, submitted to MNRAS
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 use HII starburst galaxy apparent magnitude measurements to constrain cosmological parameters in six cosmological models. A joint analysis of HII galaxy, quasar angular size, baryon acoustic oscillations peak length scale, and Hubble parameter measurements result in relatively model-independent and restrictive estimates of the current values of the non-relativistic matter density parameter \om\ and the Hubble constant $H_0$. These estimates favor a 2.0$\sigma$ to 3.4$\sigma$ (depending on cosmological model) lower $H_0$ than what is measured from the local expansion rate. The combined data are consistent with dark energy being a cosmological constant and with flat spatial hypersurfaces, but do not strongly rule out mild dark energy dynamics or slightly non-flat spatial geometries.

[44]  arXiv:2005.12624 [pdf, other]
Title: Submillimetre water masers at 437, 439, 471, and 474 GHz towards evolved stars. APEX observations and radiative transfer modelling
Comments: Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Here we aim to characterise submillimetre water masers at 437, 439, 471, and 474 GHz towards a sample of evolved stars.
We used the Atacama Pathfinder Experiment (APEX) to observe submillimetre water transitions and the CO (4-3) line towards 11 evolved stars. The sample included semi-regular and Mira variables, plus a red supergiant star. We performed radiative transfer modelling for the water masers. We also used the CO observations to determine mass loss rates for the stars.
From the sample of 11 evolved stars, 7 display one or more of the masers at 437, 439, 471, and 474 GHz. We therefore find that these masers are common in evolved star circumstellar envelopes. The fact that the maser lines are detected near the stellar velocity indicates that they are likely to originate from the inner circumstellar envelopes of our targets. We tentatively link the presence of masers to the degree of variability of the target star, that is, masers are more likely to be present in Mira variables than in semi-regular variables. We suggest that this indicates the importance of strong shocks in creating the necessary conditions for the masers. Typically, the 437 GHz line is the strongest maser line observed among those studied here. We cannot reproduce the above finding in our radiative transfer models. In general, we find that maser emission is very sensitive to dust temperature in the lines studied here. To produce strong maser emission, the dust temperature must be significantly lower than the gas kinetic temperature. In addition to running grids of models in order to determine the optimum physical conditions for strong masers in these lines, we performed smooth wind modelling for which we cannot reproduce the observed line shapes. This also suggests that the masers must originate predominantly from the inner envelopes.

[45]  arXiv:2005.12655 [pdf, other]
Title: A probabilistic approach to phase calibration: I. Effects of source structure on fringe-fitting
Comments: accepted for publication in MNRAS
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We propose a probabilistic framework for performing simultaneous estimation of source structure and fringe-fitting parameters in Very Long Baseline Interferometry (VLBI) observations. As a first step, we demonstrate this technique through the analysis of synthetic short-duration Event Horizon Telescope (EHT) observations of various geometric source models at 230 GHz, in the presence of baseline-dependent thermal noise. We perform Bayesian parameter estimation and model selection between the different source models to obtain reliable uncertainty estimates and correlations between various source and fringe-fitting related model parameters. We also compare the Bayesian posteriors with those obtained using widely-used VLBI data reduction packages such as CASA and AIPS, by fringe-fitting 200 Monte Carlo simulations of each source model with different noise realisations, to obtain distributions of the Maximum A Posteriori (MAP) estimates. We find that, in the presence of resolved asymmetric source structure and a given array geometry, the traditional practice of fringe-fitting with a point source model yields appreciable offsets in the estimated phase residuals, potentially biasing or limiting the dynamic range of the starting model used for self-calibration. Simultaneously estimating the source structure earlier in the calibration process with formal uncertainties improves the precision and accuracy of fringe-fitting and establishes the potential of the available data especially when there is little prior information. We also note the potential applications of this method to astrometry and geodesy for specific science cases and the planned improvements to the computational performance and analyses of more complex source distributions.

[46]  arXiv:2005.12677 [pdf, other]
Title: Mapping the radio to mid-infrared spectral index of Cas A: evidence for flattening and a cooling break
Comments: 12 pages, 10 figures, submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Non-linear shock acceleration models predict a flattening of synchrotron radiation spectrum at higher frequencies. For Cassiopeia A a synchrotron spectral flattening was previously reported for a small part of the remnant in the mid-infrared regime. Here we present new measurements for spectral flattening using the archival radio (4.72~GHz) and mid-infrared (3.6~$\mu$m) data, and produce a complete spectral index map to investigate the spatial variations within the remnant. Our result shows overall spectral flattening across the remnant ($\alpha \sim -0.5$ to $-0.7$), with the flattest values coinciding with the locations of most recent particle acceleration. In addition to overall flattening, we also detect a relatively steeper region in the Southeast of the remnant ($\alpha \sim -0.67$). We argue that this could be a signature of a cooling break, and estimate the lower limit of magnetic field to be $B \sim 420$~$\mu$G, consistent with other magnetic-field strength estimates.

[47]  arXiv:2005.12707 [pdf, other]
Title: A Ly-alpha nebula at z~3.3
Comments: Accepted to A&A, 8 pages, 4 figures. arXiv admin note: text overlap with arXiv:1708.00447 by other authors
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Context. Searching for high-redshift galaxies is a field of intense activity in modern observational cosmology that will continue to grow with future ground-based and sky observatories. Over the last few years, a lot has been learned about the high-z Universe. Aims. Despite extensive Ly-alpha Blobs (LAB) surveys from low to high redshifts, giant LABs over 100 kpc have been found mostly at z~2-4. This redshift range is coincident with the transition epoch of galactic gas-circulation processes from inflows to outflows at z~2.5-3. This suggests that the formation of giant LABs may be related to a combination of gas inflows and outflows. Their extreme youth makes them interesting objects in the study of galaxy formation as they provide insight into some of the youngest known highly star forming galaxies, with only modest time investments using ground-based telescopes. Methods. Systematic narrow-band Ly-alpha nebula surveys are ongoing, but they are limited in their covered redshift range and their comoving volume. This poses a significant problem when searching for such rare sources. To address this problem, we developed a systematic searching tool, ATACAMA (A Tool for seArChing for lArge LyMan Alpha nebulae) designed to find large Ly-alpha nebulae at any redshift within deep multi-wavelength broad-band imaging. Results. We identified a Ly-alpha nebula candidate at zphot~3.3 covering an isophotal area of 29.4sq.arcsec. Its morphology shows a bright core and a faint core which coincides with the morphology of previously known Ly-alpha blobs. A first estimation of the Ly-alpha equivalent width and line flux agree with the values from the study led by several groups.

[48]  arXiv:2005.12717 [pdf, other]
Title: IRIS and ALMA Observations Uncovering a Type-II Spicule and the Dynamic Nature of a Chromospheric Plage Region
Comments: 36 pages, 15 figures, submitted to the Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present observations of the solar chromosphere obtained simultaneously with the Atacama Large Millimeter/submillimeter Array (\emph{ALMA}) and the Interface Region Imaging Spectrograph (\emph{IRIS}). The observatories targeted a chromospheric plage region of which the spatial distribution (split between strongly and weakly magnetized regions) allowed the study of linear-like structures in isolation, free of contamination from background emission. Using these observations in conjunction with a radiative magnetohydrodynamic 2.5D model covering the upper convection zone all the way to the corona that considers non-equilibrium ionization effects, we report the detection of an on-disk chromospheric spicule with \emph{ALMA} and confirm its multithermal nature. In addition, we discuss the strikingly high degree of similarity between chromospheric plage features observed in \emph{ALMA}/Band6 and \emph{IRIS}/\ion{Si}{4} (also reproduced in our model) suggesting that \emph{ALMA}/Band6 does not observe in the low chromosphere as previously thought but rather observes the upper chromospheric parts of structures such as spicules and other bright structures above plage at geometric heights near transition region temperatures. We also show that \emph{IRIS}/\ion{Mg}{2} is not as well correlated with \emph{ALMA}/Band6 as was previously thought. For these comparisons, we propose and employ a novel empirical method for the determination of plage regions, which seems to better isolate plage from its surrounding regions as compared to other methods commonly used. We caution that isolating plage from its immediate surroundings must be done with care to mitigate stastistical bias in quantitative comparisons between different chromospheric observables. Lastly, we report indications for chromospheric heating due to traveling shocks supported by the \emph{ALMA}/Band6 observations.

[49]  arXiv:2005.12744 [pdf, ps, other]
Title: Circumnuclear regions of different BPT types in star-forming MaNGA galaxies: AGN detectability
Comments: 17 pages, 14 figures, accepted for publication in the A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We consider the circumnuclear regions of MaNGA galaxies. The spectra are classified as AGN-like, HII-region-like (or SF-like), and intermediate (INT) spectra according to their positions on the BPT diagram. There are the following four configurations of the radiation distributions in the circumnuclear regions: 1) AGN+INT, the innermost region of the AGN-like radiation is surrounded by a ring of radiation of the intermediate type; 2) INT, the central area of radiation of the intermediate type; 3) SF+INT, the inner region of the HII-region-like radiation is surrounded by a ring of radiation of the intermediate type; and 4) SF, the HII-region-like radiation only. The LINERS of configurations 1 and 2 are examined. The spaxel spectra of the LINERs form a sequences on the BPT diagram. The line ratios change smoothly with radius, from AGN-like at the center to HII-region-like at larger distances. This is in agreement with the paradigm that the LINERs are excited by AGN activity. The AGN and INT radiation in the circumnuclear region is accompanied by an enhanced gas velocity dispersion, s_g. The radius of the area of the AGN and INT radiation is similar to the radius of the area with enhanced s_g, and the central s_g,c correlates with the luminosity of the AGN+INT area. We assume that the gas velocity dispersion can serve as an indicator of the AGN activity. The values of s_g,c for the SF-type centers partly overlap with those of the AGN-type centers. We find that there is a demarcation line between the positions of the AGN-type and SF-type objects on the s_g,c - central Halpha surface brightness diagram.

[50]  arXiv:2005.12757 [pdf, other]
Title: Measurement of magnetic field and relativistic electrons along a solar flare current sheet
Comments: 16 pages, 8 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Space Physics (physics.space-ph)

In the standard model of solar flares, a large-scale reconnection current sheet is postulated as the central engine for powering the flare energy release and accelerating particles. However, where and how the energy release and particle acceleration occur remain unclear due to the lack of measurements for the magnetic properties of the current sheet. Here we report the measurement of spatially-resolved magnetic field and flare-accelerated relativistic electrons along a current-sheet feature in a solar flare. The measured magnetic field profile shows a local maximum where the reconnecting field lines of opposite polarities closely approach each other, known as the reconnection X point. The measurements also reveal a local minimum near the bottom of the current sheet above the flare loop-top, referred to as a "magnetic bottle". This spatial structure agrees with theoretical predictions and numerical modeling results. A strong reconnection electric field of ~4000 V/m is inferred near the X point. This location, however, shows a local depletion of microwave-emitting relativistic electrons. These electrons concentrate instead at or near the magnetic bottle structure, where more than 99% of them reside at each instant. Our observations suggest that the loop-top magnetic bottle is likely the primary site for accelerating and/or confining the relativistic electrons.

[51]  arXiv:2005.12758 [pdf, other]
Title: Axisymmetric equilibrium models for magnetised neutron stars in Scalar-Tensor Theories
Comments: accepted for publication by A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

Among the possible extensions of General Relativity that have been put forward in order to address some long standing issues in our understanding of the Universe, Scalar-Tensor Theories have received a lot of attention for their simplicity. Interestingly, some of these predict a potentially observable non-linear phenomenon, known as \textit{spontaneous scalarisation}, in the presence of highly compact matter distributions, like the case of neutron stars. Neutron stars are ideal laboratories to investigate the properties of matter under extreme conditions, and in particular they are known to harbour the strongest magnetic fields in the Universe. Here, for the first time, we present a detailed study of magnetised neutron stars in Scalar-Tensor Theories. First, we show that the formalism developed for the study of magnetised neutron stars in General Relativity, based on the \textit{eXtended Conformally Flat Condition}, can easily be extended in the presence of a non-minimally coupled scalar field, retaining many of its numerical advantages. We then carry out a study of the parameter space considering the two extreme geometries of purely toroidal and purely poloidal magnetic fields, varying both the strength of the magnetic field and the intensity of scalarisation. We compare our results with magnetised general-relativistic solutions and un-magnetised scalarised solutions, showing how the mutual interplay between magnetic and scalar fields affect the magnetic and the scalarisation properties of neutron stars. In particular, we focus our discussion on magnetic deformability, maximum mass and range of scalarisation.

[52]  arXiv:2005.12761 [pdf, other]
Title: iDQ: Statistical Inference of Non-Gaussian Noise with Auxiliary Degrees of Freedom in Gravitational-Wave Detectors
Comments: 29 pages, 10 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)

Gravitational-wave detectors are exquisitely sensitive instruments and routinely enable ground-breaking observations of novel astronomical phenomena. However, they also witness non-stationary, non-Gaussian noise that can be mistaken for astrophysical sources, lower detection confidence, or simply complicate the extraction of signal parameters from noisy data. To address this, we present iDQ, a supervised learning framework to autonomously detect noise artifacts in gravitational-wave detectors based only on auxiliary degrees of freedom insensitive to gravitational waves. iDQ has operated in low latency throughout the advanced detector era at each of the two LIGO interferometers, providing invaluable data quality information about each detection to date in real-time. We document the algorithm, describing the statistical framework and possible applications within gravitational-wave searches. In particular, we construct a likelihood-ratio test that simultaneously accounts for the presence of non-Gaussian noise artifacts and utilizes information from both the observed gravitational-wave strain signal and thousands of auxiliary degrees of freedom. We also present several examples of iDQ's performance with modern interferometers, showing iDQ's ability to autonomously reproduce known data quality monitors and identify noise artifacts not flagged by other analyses.

[53]  arXiv:2005.12767 [pdf, ps, other]
Title: Space VLBI 2020: Science and Technology Futures Conference Summary
Authors: T. Joseph W. Lazio (1), Walter Brisken (2), Katherine Bouman (3), Sheperd Doeleman (4), Heino Falcke (5), Satoru Iguchi (6), Yuri Y. Kovalev (7), Colin J. Lonsdale (8), Zhiqiang Shen (9), Anton Zensus (10), Anthony J. Beasley (2) ( (1) Jet Propulsion Laboratory, California Institute of Technology, (2) National Radio Astronomy Observatory, (3) California Institute of Technology, (4) Harvard-Smithsonian Center for Astrophysics, (5) Radboud University, (6) Graduate University of Advanced Studies, National Astronomical Observatory of Japan, (7) Astro Space Center of Lebedev Physical Institute, Moscow Institute of Physics & Technology, (8) Massachusetts Institute of Technology/Haystack Observatory, (9) Shanghai Astronomical Observatory, (10) Universität zu Köln, Max-Planck-Institut fuer Radioastronomie)
Comments: Nine pages + references and conference schedule appendix; conference Web site this http URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

The "Space VLBI 2020: Science and Technology Futures" meeting was the second in The Future of High-Resolution Radio Interferometry in Space series. The first meeting (2018 September 5--6; Noordwijk, the Netherlands) focused on the full range of science applications possible for very long baseline interferometry (VLBI) with space-based antennas. Accordingly, the observing frequencies (wavelengths) considered ranged from below 1~MHz (> 300 m) to above 300~GHz (< 1 mm). For this second meeting, the focus was narrowed to mission concepts and the supporting technologies to enable the highest angular resolution observations at frequencies of 30~GHz and higher (< 1 cm).
This narrowing of focus was driven by both scientific and technical considerations. First, results from the RadioAstron mission and the Event Horizon Telescope (EHT) have generated considerable excitement for studying the inner portions of black hole (BH) accretion disks and jets and testing elements of the General Theory of Relativity (GR). Second, the technologies and requirements involved in space-based VLBI differ considerably between 100~MHz and 100~GHz; a related consideration is that there are a number of existing instruments or mission concepts for frequencies of approximately 100~MHz and below, while it has been some time since attention has been devoted to space VLBI at frequencies above 10~GHz.
This conference summary attempts to capture elements of presentations and discussions that occurred.

[54]  arXiv:2005.12785 [pdf, other]
Title: Collisional heating and compaction of small bodies: Constraints for their origin and evolution
Comments: 34 pages, 11 figures. Accepted for publication in Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The current properties of small bodies provide important clues to their origin and history. However, how much small bodies were processed by past collisions and to what extent they retain a record of processes that took place during the formation and early evolution of the Solar System is still poorly understood. Here we study the degree of collisional heating and compaction by analysing the large set of previous simulations of small body break-ups by Jutzi et al. (2019), which used porous targets of 50 - 400 km in diameter and investigated a large range of impact velocities, angles as well as energies. We find that the degree of impact processing is generally larger than found in previous studies which considered smaller objects (e.g. Jutzi et al., 2017; Schwartz et al., 2018). However, there is a clear dichotomy in terms of impact processing: the escaping material always experiences stronger heating than the material bound to the largest remnant. Assuming they originate from the same parent body, some of the observed differences between the recently visited asteroids Ryugu and Bennu may be explained by a different location of the material eventually forming these asteroids in the original parent body. Our results also provide constraints on the initial size of cometary nuclei.

[55]  arXiv:2005.12827 [pdf, ps, other]
Title: XMM-Newton observations of eleven intermediate polars and possible candidates
Comments: 21 pages, 13 figs
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We aim to identify new intermediate polars (IPs) in XMM-Newton observations from a list of promising candidates. By selecting targets not previously known to be X-ray bright we aim to uncover evidence for an X-ray underluminous IP subpopulation. We performed period searches on the XMM-Newton X-ray and optical data of our targets to seek both the spin and orbital periods, which differ in IPs. We also investigated the X-ray spectra to find the hot plasma emission shown by these objects. With archival Swift data we coarsely investigated the long-term X-ray variability, and with archival optical data from a variety of catalogues, we compared the optical to X-ray luminosity to identify X-ray faint objects. This paper presents the first XMM-Newton observation of the prototype IP, DQ Her. We find firm evidence for HZ~Pup, V349 Aqr, and IGR J18151-1052 being IPs, with likely white dwarf spin periods of 1552, 390, and 390 s, respectively. The former two have luminosities typical of IPs, and the latter is strongly absorbed and with unknown distance. GI~Mon and V1084~Her are apparently non-magnetic CVs with interesting short-term variability unrelated to WD spin. V533~Her is probably a magnetic CV and remains a good IP candidate, while V1039 Cen is possibly a polar. The remaining candidates were too faint to allow for any firm conclusions.

[56]  arXiv:2005.12839 [pdf, other]
Title: Formation and Dynamics of Transequatorial Loops
Comments: Accepted by Astronomy and Astrophysics (May 26, 2020) 17 pages, 15 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

To study the dynamical evolution of trans-equatorial loops (TELs) using imaging and spectroscopy. We have used the images recorded by the Atmospheric Imaging Assembly and the Helioseismic Magnetic Imager on-board the Solar Dynamics Observatory and spectroscopic observations taken from the Extreme-Ultraviolet Imaging Spectrometer on-board Hinode. The data from AIA 193 {\AA} channel show that TELs are formed between AR 12230 and a newly emerging AR 12234 and evolved during December 10-14, 2014. The xt-plots for December 12, 2014 obtained using AIA 193 {\AA} data reveal signatures of inflow and outflow towards an X-region. High cadence AIA images also show recurrent intensity enhancements in close proximity to the X-region (P2), which is observed to have higher intensities for spectral lines formed at log T[K] =6.20 and voids at other higher temperatures. The electron densities and temperatures in the X-region (and P2) are maintained steadily at log N_e =8.5-8.7 /cc and log T[K] =6.20, respectively. Doppler velocities in the X-region show predominant redshifts by about 5-8 km/s when closer to the disk centre but blueshifts (along with some zero-velocity pixels) when away from the centre. The Full-Width-Half-Maxima (FWHM) maps reveal non-thermal velocities of about 27-30 km/s for Fe XII, Fe XIII and Fe XV lines. However, the brightest pixels have non-thermal velocities of about 62 km/s for Fe XII and Fe XIII lines. On the contrary, the dark X-region for Fe XV line have the highest non-thermal velocity (roughly 115 km/s). We conclude that the TELs are formed due to magnetic reconnection. We further note that the TELs themselves undergo magnetic reconnection leading to reformation of loops of individual ARs. Moreover, this study, for the first time, provides measurements of plasma parameters in X-regions thereby providing essential constraints for theoretical studies.

[57]  arXiv:2005.12843 [pdf, other]
Title: An elliptic expansion of the potential field source surface model
Comments: 11 pages, 7 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Context. The potential field source surface model is frequently used as a basis for further scientific investigations where a comprehensive coronal magnetic field is of importance. Its parameters, especially the position and shape of the source surface, are crucial for the interpretation of the state of the interplanetary medium. Improvements have been suggested that introduce one or more additional free parameters to the model, for example, the current sheet source surface (CSSS) model.
Aims. Relaxing the spherical constraint of the source surface and allowing it to be elliptical gives modelers the option of deforming it to more accurately match the physical environment of the specific period or location to be analyzed.
Methods. A numerical solver is presented that solves Laplace's equation on a three-dimensional grid using finite differences. The solver is capable of working on structured spherical grids that can be deformed to create elliptical source surfaces.
Results. The configurations of the coronal magnetic field are presented using this new solver. Three-dimensional renderings are complemented by Carrington-like synoptic maps of the magnetic configuration at different heights in the solar corona. Differences in the magnetic configuration computed by the spherical and elliptical models are illustrated.

[58]  arXiv:2005.12854 [pdf, other]
Title: Spitzer Variability Properties of Low-Gravity L Dwarfs
Comments: Accepted for publication in AJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We present \textit{Spitzer Space Telescope} variability monitoring observations of three low-gravity L dwarfs with previous detections of variability in the near-IR, 2MASS J0045+16, 2MASS J0501-00 and 2MASS J1425-36. We detect significant, periodic variability in two of our targets, 2MASS J0045+16 and 2MASS J0501-00. We do not detect variability in 2MASS J1425-36. Combining our new rotation periods with rotational velocities, we calculate inclination angles of $22\pm1^{\circ}$, ${60^{+13 }_{-8}} ^{\circ}$ and $52^{+19}_{-13}~^{\circ}$ for 2MASS J0045+16, 2MASS J0501-00 and 2MASS J1425-36 respectively. Our three new objects are consistent with the tentative relations between inclination, amplitude and color anomaly previously reported. Objects with the highest variability amplitudes are inclined equator-on, while the maximum observed amplitude decreases as the inclination angle decreases. We also find a correlation between the inclination angle and $(J-K)_{\mathrm{2MASS}}$ color anomaly for the sample of objects with measured inclinations. Compiling the entire sample of brown dwarfs with \textit{Spitzer} variability detections, we find no enhancement in amplitude for young, early-L dwarfs compared to the field dwarf population. We find a possible enhancement in amplitude of low-gravity late-L dwarfs at $4.5~\mu$m. We do not find a correlation between amplitude ratio and spectral type for field dwarfs or for the young population. Finally, we compile the rotation periods of a large sample of brown dwarfs with ages 1 Myr to 1 Gyr and compare the rotation rates predicted by evolutionary models assuming angular momentum conservation. We find that the rotation rates of the current sample of brown dwarfs fall within the expected range set by evolutionary models and breakup limits.

[59]  arXiv:2005.12858 [pdf, other]
Title: New multi-part collisional model of the main belt: The contribution to near-Earth asteroids
Comments: 14 pages, 12 Figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Aims. We developed a six-part collisional evolution model of the main asteroid belt (MB) and used it to study the contribution of the different regions of the MB to the near-earth asteroids (NEAs). Methods. We built a statistical code called ACDC that simulates the collisional evolution of the MB split into six regions (namely Inner, Middle, Pristine, Outer, Cybele and High-Inclination belts) according to the positions of the major resonances present there ($\nu_{6}$, 3:1J, 5:2J, 7:3J and 2:1J). We consider the Yarkovsky effect and the mentioned resonances as the main mechanism that removes asteroids from the different regions of the MB and delivers them to the NEA region. We calculated the evolution of the NEAs coming from the different source regions by considering the bodies delivered by the resonances and mean dynamical timescales in the NEA population. Results. Our model is in agreement with the major observational constraints associated with the MB, such as the size distributions of the different regions of the MB and the number of large asteroid families. It is also able to reproduce the observed NEAs with H < 16 and agrees with recent estimations for H < 20, but deviates for smaller sizes. We find that most sources make a significant contribution to the NEAs; however the Inner and Middle belts stand out as the most important source of NEAs followed by the Outer belt. The contributions of the Pristine and Cybele regions are minor. The High-Inclination belt is the source of only a fraction of the actual observed NEAs with high inclination, as there are dynamical processes in that region that enable asteroids to increase and decrease their inclinations.

[60]  arXiv:2005.12867 [pdf, other]
Title: A Systematic Study on the Absorption Features of Interstellar Ices in Presence of Impurities
Comments: Accepted for Publication in the ACS Earth and Space Chemistry Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chemical Physics (physics.chem-ph)

Spectroscopic studies play a key role in the identification and analysis of interstellar ices and their structure. Some molecules have been identified within the interstellar ices either as pure, mixed, or even as layered structures. Absorption band features of water ice can significantly change with the presence of different types of impurities (CO, CO2, CH3OH, H2CO, etc.). In this work, we carried out a theoretical investigation to understand the behavior of water band frequency, and strength in the presence of impurities. The computational study has been supported and complemented by some infrared spectroscopy experiments aimed at verifying the effect of HCOOH, NH3 , and CH3 OH on the band profiles of pure H2O ice. Specifically, we explored the effect on the band strength of libration, bending, bulk stretching, and free-OH stretching modes. Computed band strength profiles have been compared with our new and existing experimental results, thus pointing out that vibrational modes of H2O and their intensities can change considerably in the presence of impurities at different concentrations. In most cases, the bulk stretching mode is the most affected vibration, while the bending is the least affected mode. HCOOH was found to have a strong influence on the libration, bending, and bulk stretching band profiles. In the case of NH3, the free-OH stretching band disappears when the impurity concentration becomes 50%. This work will ultimately aid a correct interpretation of future detailed spaceborne observations of interstellar ices by means of the upcoming JWST mission.

[61]  arXiv:2005.12869 [pdf, other]
Title: Global X-Ray Properties of the Vela and Puppis A Supernova Remnants
Comments: accepted for publication in The Astronomical Journal, 8 pages, 4 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The Vela and Puppis A supernova remnants (SNRs) comprise a large emission region of $\sim 8^{\circ}$ diameter in the soft X-ray sky. The HaloSat CubeSat mission provides the first soft X-ray ($0.4-7$ keV) observation of the entire Vela SNR and Puppis A SNR region with a single pointing and moderate spectral resolution. HaloSat observations of the Vela SNR are best fit with a two-temperature thermal plasma model consisting of a cooler component with $kT_{1} = 0.19^{+0.01}_{-0.01}$ keV in collisional ionization equilibrium and a hotter component with $kT_{2} = 1.06^{+0.45}_{-0.27}$ keV in non-equilibrium ionization. Observations of the Puppis A SNR are best fit with a single-component plane-parallel shocked plasma model with $kT = 0.86^{+0.06}_{-0.05}$ keV in non-equilibrium ionization. For the first time, we find the total X-ray luminosities of both components of the Vela SNR spectrum in the $0.5-7$ keV energy band to be $L_X = 4.4^{+1.4}_{-1.4} \times 10^{34}$ erg s$^{-1}$ for the cooler component and $L_X = 4.1^{+1.8}_{-1.5} \times 10^{34}$ erg s$^{-1}$ for the hotter component. We find the total X-ray luminosities of the Vela and Puppis A SNRs to be $L_{\text{X}} = 8.4 \times 10^{34}$ erg s$^{-1}$ and $L_X = 6.7^{+1.1}_{-0.9} \times 10^{36}$ erg s$^{-1}$.

[62]  arXiv:2005.12871 [pdf, other]
Title: Vortices evolution in the solar atmosphere: A dynamical equation for the swirling strength
Comments: 12 pages, to be published in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We study vortex dynamics in the solar atmosphere by employing and deriving the analytical evolution equations of two vortex identification criteria. The two criteria used are vorticity and the swirling strength. Vorticity can be biased in the presence of shear flows, but its dynamical equation is well known; the swirling strength is a more precise criterion for the identification of vortical flows, but its evolution equation is not known yet. Therefore, we explore the possibility of deriving a dynamical equation for the swirling strength. We then apply the two equations to analyze radiative MHD simulations of the solar atmosphere produced with the CO5BOLD code. We present a detailed review of the swirling strength criterion and the mathematical derivation of its evolution equation. This equation did not exist in the literature before and it constitutes a novel tool that is suitable for the analysis of a wide range of problems in (magneto-)hydrodynamics. By applying this equation to numerical models, we find that hydrodynamical and magnetic baroclinicities are the driving physical processes responsible for vortex generation in the convection zone and the photosphere. Higher up in the chromosphere, the magnetic terms alone dominate. Moreover, we find that the swirling strength is produced at small scales in a chaotic fashion, especially inside magnetic flux concentrations. The swirling strength represents an appropriate criterion for the identification of vortices in turbulent flows, such as those in the solar atmosphere. Moreover, its evolution equation, which is derived in this paper, is pivotal for obtaining precise information about the dynamics of these vortices and the physical mechanisms responsible for their production and evolution. Since this equation is available, the swirling strength is now the ideal quantity to study the dynamics of vortices in (magneto-)hydrodynamics.

[63]  arXiv:2005.12887 [pdf, ps, other]
Title: Dynamical History of the Uranian System
Comments: Accepted for Planetary Science Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We numerically simulate the past tidal evolution of the five large moons of Uranus (Miranda, Ariel, Umbriel, Titania, and Oberon). We find that the most recent major mean-motion resonance (MMR) between any two moons, the Ariel-Umbriel 5:3 MMR, had a large effect on the whole system. Our results suggest that this resonance is responsible for the current 4.3$^{\circ}$ inclination of Miranda (instead of previously proposed 3:1 Miranda-Umbriel MMR), and that all five moons had their inclinations excited during this resonance. Miranda experienced significant tidal heating during the Ariel-Umbriel 5:3 MMR due to its eccentricity being excited by Ariel's secular perturbations. This tidal heating draws energy from shrinking of Miranda's orbit, rather than Ariel's outward evolution, and can generate heat flows in excess of 100 mW m$^{-2}$, sufficient to produce young coronae on Miranda. We find that this MMR was followed by a sequence of secular resonances, which reshuffled the moons' eccentricities and inclinations. We also find that the precession of Oberon's spin axis is close to a resonance with the precession of Umbriel's orbital plane, and that this spin-orbit resonance was likely excited during the Ariel-Umbriel 5:3 MMR. After the exit from the MMR, subsequent Ariel-Umbriel secular resonance and Oberon-Umbriel spin-orbit resonance may be able to explain the current low inclinations of Ariel and Umbriel. The age of Miranda's surface features tentatively suggests Uranian tidal $Q=15,000-20,000$, which can be further refined in future work.

[64]  arXiv:2005.12888 [pdf, other]
Title: Interactions among intermediate redshift galaxies. The case of SDSSJ134420.86+663717.8
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the properties of the central supermassive black holes and the host galaxies of the interacting object SDSSJ134420.86+663717.8. We obtained optical long slit spectroscopy data from the Large Binocular Telescope (LBT) using the Multi Object Double Spectrograph (MODS). Analysing the spectra revealed several strong broad and narrow emission lines of ionised gas in the nuclear region of one galaxy, whereas only narrow emission lines were visible for the second galaxy. The optical spectra were used to plot diagnostic diagrams, deduce rotation curves of the two galaxies, and calculate the masses of the central supermassive black holes. We find that the galaxy with broad emission line features has Seyfert~1 properties, while the galaxy with only narrow emission line features seems to be star-forming in nature. Furthermore, we find that the masses of the central supermassive black holes are almost equal at a few times 10^7 solar mass. Additionally, we present a simple N-body simulation to shed some light on the initial conditions of the progenitor galaxies. We find that for an almost orthogonal approach of the two interacting galaxies, the model resembles the optical image of the system.

[65]  arXiv:2005.12891 [pdf, ps, other]
Title: Dispersion measure components within host galaxies of Fast Radio Bursts: observational constraints from statistical properties of FRBs
Authors: Yuu Niino
Comments: 13 pages, 10 figures, submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Dispersion measure (DM) of Fast Radio Bursts (FRBs) are commonly used as a indicator of distance assuming that DM in excess of the expected amount within the Milky Way in the direction of each FRB arise mostly from the inter-galactic medium. However, the assumption might not be true if, for example, most FRB progenitors are embedded in ionized circumstellar material (CSM, e.g. supernova remnant). In this study, we jointly analyze distributions of DM, flux density, and fluence of the FRB samples observed by the Parkes telescope and the Australian Square Kilometre Array Pathfinder (ASKAP) using analytical models of FRBs, to constrain fractions of various DM components that shape the overall DM distribution and emission properties of FRBs. Comparing the model predictions with the observations we find that the typical amount of DM in each FRB host galaxy is $\sim 120$ cm$^{-3}$pc which is naturally explained as a combination of interstellar medium (ISM) and halo of an ordinary galaxy, without additional contribution from ionized CSM that is directly associated with an FRB progenitor. Furthermore, we also find that observed flux densities of FRBs do not statistically suffer strong $K$-correction, i.e. the typical luminosity density of FRBs does not significantly change within the range of emitting frequency $\nu_{\rm rest} \sim$ 1--4 GHz.

Cross-lists for Wed, 27 May 20

[66]  arXiv:1711.08329 (cross-list from gr-qc) [pdf, other]
Title: Statefinder diagnostic and constraints on the Palatini f(R) gravity theories
Comments: 19 pages, 10 figures, arXiv admin note: text overlap with arXiv:1002.3867
Journal-ref: RAA 2018 Vol. 18 No.3, 26(16pp)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

We focus on a series of $f(R)$ gravity theories in Palatini formalism to investigate the probabilities of producing the late-time acceleration for the flat Friedmann-Robertson-Walker (FRW) universe. We apply statefinder diagnostic to these cosmological models for chosen series of parameters to see if they distinguish from one another. The diagnostic involves the statefinder pair $\{r,s\}$, where $r$ is derived from the scale factor $a$ and its higher derivatives with respect to the cosmic time $t$, and $s$ is expressed by $r$ and the deceleration parameter $q$. In conclusion, we find that although two types of $f(R)$ theories: (i) $f(R) = R + \alpha R^m - \beta R^{-n}$ and (ii) $f(R) = R + \alpha \ln R - \beta$ can lead to late-time acceleration, their evolutionary trajectories in the $r-s$ and $r-q$ planes reveal different evolutionary properties, which certainly justify the merits of statefinder diagnostic. Additionally, we utilize the observational Hubble parameter data (OHD) to constrain these models of $f(R)$ gravity. As a result, except for $m=n=1/2$ of (i) case, $\alpha=0$ of (i) case and (ii) case allow $\Lambda$CDM model to exist in 1$\sigma$ confidence region. After adopting statefinder diagnostic to the best-fit models, we find that all the best-fit models are capable of going through deceleration/acceleration transition stage with late-time acceleration epoch, and all these models turn to de-Sitter point ($\{r,s\}=\{1,0\}$) in the future. Also, the evolutionary differences between these models are distinct, especially in $r-s$ plane, which makes the statefinder diagnostic more reliable in discriminating cosmological models.

[67]  arXiv:2005.08071 (cross-list from gr-qc) [pdf, ps, other]
Title: There is no coincidence after all!
Authors: Saurya Das (University of Lethbridge)
Comments: This essay received an Honorable Mention in the 2020 Gravity Research Foundation Essay Competition
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

We show that if Dark Matter is made up of light bosons, they form a Bose-Einstein condensate in the early Universe. This in turn naturally induces a Dark Energy of approximately equal density and exerting negative pressure.This explains the so-called coincidence problem.

[68]  arXiv:2005.11337 (cross-list from physics.space-ph) [pdf, other]
Title: Assessment of the Performance of Ionospheric Models with NavIC Observations during Geomagnetic Storms
Comments: 4 pages, 4 figures, accepted for publication in the proceedings of the 2020 URSI Regional Conference on Radio Science(URSI-RCRS 2020)
Subjects: Space Physics (physics.space-ph); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The paper presents an assessment of the performances of the global empirical models: International Reference Ionosphere (IRI)-2016 and the NeQuick2 model derived ionospheric Total Electron Content (TEC) with respect to the Navigation with Indian Constellation (NavIC)/ Indian Regional Navigation Satellite System(IRNSS) estimated TEC under geomagnetic storm conditions. The present study is carried out over Indore (Geographic: 22.52$^{\circ}$N 75.92$^{\circ}$E and Magnetic Dip: 32.23$^{\circ}$N, located close to the northern crest of the Equatorial Ionization Anomaly (EIA) region of the Indian sector). Analysis has been performed for an intense storm (September 6-10, 2017), a moderate storm (September 26-30, 2017) and a mild storm (January 17-21, 2018) that fall in the declining phase of the present solar cycle. It is observed that both IRI-2016 and NeQuick2 derived TEC are underestimates when compared with the observed TEC from NavIC and therefore fail to predict storm time changes in TEC over this region and requires real data inclusion from NavIC for better prediction over the variable Indian longitude sector.

[69]  arXiv:2005.12278 (cross-list from hep-ph) [pdf, other]
Title: A Cosmic Microscope for the Preheating Era
Comments: 30 pages
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

Light fields with spatially varying backgrounds can modulate cosmic preheating, and imprint the nonlinear effects of preheating dynamics at tiny scales on large scale fluctuations. This provides us a unique probe into the preheating era which we dub the "cosmic microscope.'' We identify a distinctive effect of preheating on scalar perturbations that turns the Gaussian primordial fluctuations of a light scalar field into square waves, like a diode. The effect manifests itself as local non-Gaussianity. We present a model, "modulated partial preheating," where this nonlinear effect is consistent with current observations and can be reached by near future cosmic probes.

[70]  arXiv:2005.12287 (cross-list from gr-qc) [pdf, other]
Title: Gravitational Decoherence of Dark Matter
Comments: 40 pages, 5 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)

Decoherence describes the tendency of quantum sub-systems to dynamically lose their quantum character. This happens when the quantum sub-system of interest interacts and becomes entangled with an environment that is traced out. For ordinary macroscopic systems, electromagnetic and other interactions cause rapid decoherence. However, dark matter (DM) may have the unique possibility of exhibiting naturally prolonged macroscopic quantum properties due to its weak coupling to its environment, particularly if it only interacts gravitationally. In this work, we compute the rate of decoherence for light DM in the galaxy, where a local density has its mass, size, and location in a quantum superposition. The decoherence is via the gravitational interaction of the DM overdensity with its environment, provided by ordinary matter. We focus on relatively robust configurations: DM perturbations that involve an overdensity followed by an underdensity, with no monopole, such that it is only observable at relatively close distances. We use non-relativistic scattering theory with a Newtonian potential generated by the overdensity to determine how a probe particle scatters off of it and thereby becomes entangled. As an application, we consider light scalar DM, including axions. In the galactic halo, we use diffuse hydrogen as the environment, while near the earth, we use air as the environment. For an overdensity whose size is the typical DM de Broglie wavelength, we find that the decoherence rate in the halo is higher than the present Hubble rate for DM masses $m_a \lesssim 5 \times 10^{-7}$eV and in earth based experiments it is higher than the classical field coherence rate for $m_a \lesssim 10^{-6}$eV. When spreading of the states occurs, the rates can become much faster, as we quantify. Also, we establish that DM BECs decohere very rapidly and so are very well described by classical field theory.

[71]  arXiv:2005.12306 (cross-list from gr-qc) [pdf, other]
Title: Gravitational Waves Induced by Scalar Perturbations with a Lognormal Peak
Authors: Shi Pi, Misao Sasaki
Comments: 16 pages, 3 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

We study the stochastic gravitational wave (GW) background induced by the primordial scalar perturbation with the spectrum having a lognormal peak of width $\Delta$ at $k=k_*$. We derive an analytical formula for the GW spectrum $\Omega_\text{GW}$ for both narrow ($\Delta\ll1$) and broad ($\Delta\gtrsim1$) peaks. In the narrow-peak case, the spectrum has a double peak feature with the sharper peak at $k= 2k_*/\sqrt{3}$. On the infrared (IR) side of the spectrum, we find power-law behavior with a break at $k=k_b$ in the power-law index where it chages from $k^3$ on the far IR side to $k^2$ on the near IR side. We find the ratio of the break frequency to the peak frequency is determined by $\Delta$ as $f_b/f_p\approx\sqrt{3}\Delta$, where $f_b$ and $f_p$ are the break and peak frequencies, respectively. In the broad-peak case, we find the GW spectrum also has a lognormal peak at $k=k_*$ but with a smaller width of $\Delta/\sqrt2$. Using these derived analytic formulae, we also present expressions for the maximum values of $\Omega_\text{GW}$ for both narrow and broad cases. Our results will provide a useful tool in searching for the induced GW signals in the coming decades.

[72]  arXiv:2005.12314 (cross-list from gr-qc) [pdf, other]
Title: Induced gravitational waves as a probe of thermal history of the universe
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

The scalar perturbation induced gravitational waves are a probe of the primordial density perturbation spectrum on small scales. In this paper, we show that they can also probe the thermal history of the universe. We assume the universe underwent a stage with a constant equation of state parameter $w$, followed by the radiation-dominated stage of the conventional bigbang universe. We find that the infrared slope of the power spectrum of the induced stochastic gravitational wave background for decelerating cosmologies is related to the equation of state of the universe. Furthermore, the induced gravitational wave spectrum has in general a broken power-law shape around the scale of reheating. Interestingly, below the threshold $w=0$ of the equation of state parameter, the broken power-law presents a peak for a dirac delta peak in the scalar spectrum. For a finite width peak, the threshold changes to $w=-1/15$ depending on the value of the width. In some cases, such a broken power-law gravitational wave spectrum may degenerate to the spectrum from other sources like phase transitions or global cosmic strings.

[73]  arXiv:2005.12372 (cross-list from physics.space-ph) [pdf, other]
Title: Alfvénic Slow Solar Wind Observed in the Inner Heliosphere by Parker Solar Probe
Comments: submitted to ApJS, welcome comments
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

The slow solar wind is typically characterized as having low Alfv\'enicity. However, Parker Solar Probe (PSP) observed predominately Alfv\'enic slow solar wind during several of its initial encounters. From its first encounter observations, about 55.3\% of the slow solar wind inside 0.25 au is highly Alfv\'enic ($|\sigma_C| > 0.7$) at current solar minimum, which is much higher than the fraction of quiet-Sun-associated highly Alfv\'enic slow wind observed at solar maximum at 1 au. Intervals of slow solar wind with different Alfv\'enicities seem to show similar plasma characteristics and temperature anisotropy distributions. Some low Alfv\'enicity slow wind intervals even show high temperature anisotropies, because the slow wind may experience perpendicular heating as fast wind does when close to the Sun. This signature is confirmed by Wind spacecraft measurements as we track PSP observations to 1 au. Further, with nearly 15 years of Wind measurements, we find that the distributions of plasma characteristics, temperature anisotropy and helium abundance ratio ($N_\alpha/N_p$) are similar in slow winds with different Alfv\'enicities, but the distributions are different from those in the fast solar wind. Highly Alfv\'enic slow solar wind contains both helium-rich ($N_\alpha/N_p\sim0.045$) and helium-poor ($N_\alpha/N_p\sim0.015$) populations, implying it may originate from multiple source regions. These results suggest that highly Alfv\'enic slow solar wind shares similar temperature anisotropy and helium abundance properties with regular slow solar winds, and they thus should have multiple origins.

[74]  arXiv:2005.12606 (cross-list from physics.plasm-ph) [pdf, other]
Title: On quasi-parallel whistler waves in the solar wind
Comments: submitted to Physics of Plasmas
Subjects: Plasma Physics (physics.plasm-ph); Solar and Stellar Astrophysics (astro-ph.SR)

The recent simulations showed that the whistler heat flux instability, which presumably produces the most of quasi-parallel coherent whistler waves in the solar wind, is not efficient in regulating the electron heat conduction. In addition, recent spacecraft measurements indicated that some fraction of coherent whistler waves in the solar wind may propagate anti-parallel to the electron heat flux, being produced due to a perpendicular temperature anisotropy of suprathermal electrons. We present analysis of properties of parallel and anti-parallel whistler waves unstable at electron heat fluxes and temperature anisotropies of suprathermal electrons typical of the pristine solar wind. Assuming the electron population consisting of counter-streaming dense thermal core and tenuous suprathermal halo populations, we perform a linear stability analysis to demonstrate that anti-parallel whistler waves are expected to have smaller frequencies, wave numbers and growth rates compared to parallel whistler waves. The stability analysis is performed over a wide range of parameters of core and halo electron populations. Using the quasi-linear scaling relation we show that anti-parallel whistler waves saturate at amplitudes of one order of magnitude smaller than parallel whistler waves, which is at about $10^{-3}\;B_0$ in the pristine solar wind. The analysis shows that the presence of anti-parallel whistler waves in the pristine solar wind is more likely to be obscured by turbulent magnetic field fluctuations, because of lower frequencies and smaller amplitudes compared to parallel whistler waves. The presented results will be also valuable for numerical simulations of the electron heat flux regulation in the solar wind.

[75]  arXiv:2005.12684 (cross-list from gr-qc) [pdf, ps, other]
Title: Big Rip: heating by Hawking radiation and a possible connection to conformal cyclic cosmology
Authors: Rafael Ruggiero
Comments: 4 pages, 1 figure. To be submitted to Phys. Rev. D, comments welcome
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In the Big Rip cosmological scenario, a FRW universe containing dark energy with $w < -1$ in its equation of state (phantom energy) expands in such way that, in a finite timespan, the scale factor diverges to infinity and the size of the cosmic horizon goes to zero. Here we revisit this scenario in light of the fact that Hawking radiation is expected to be generated at the apparent horizon of a FRW universe, and show that the energy density and temperature of that radiation both diverge at the Big Rip. We then use this fact to propose a new variant of Penrose's conformal cyclic cosmology model in which the future spacetime metric becomes conformally invariant at the Big Rip instead of in the remote future of a de Sitter universe; this removes the need for mass decay from the model and makes it consistent with current physical laws.

[76]  arXiv:2005.12747 (cross-list from gr-qc) [pdf, ps, other]
Title: Transformation of Primordial Cosmological Perturbations Under the General Extended Disformal Transformation
Comments: 19 pages, for submission to JCAP
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

Primordial cosmological perturbations are the seeds that were cultivated by inflation and the succeeding dynamical processes, eventually leading to the current Universe. In this work, we investigate the behaviour of the gauge-invariant scalar and tensor perturbations under the general extended disformal transformation, namely, $g_{\mu\nu} \rightarrow A(X,Y,Z)g_{\mu\nu} + \Phi_\mu\Phi_\nu$, where $X \equiv -\tfrac{1}{2}\phi^{;\mu}\phi_{;\mu}, Y \equiv \phi^{;\mu}X_{;\mu}, Z \equiv X^{;\mu}X_{;\mu} $ and $\Phi_\mu \equiv C\phi_{;\mu} + DX_{;\mu}$, with $C$ and $D$ being a general functional of $(\phi,X,Y,Z)$. We find that the tensor perturbation is invariant under this transformation. On the other hand, the scalar curvature perturbation receives a correction due the conformal term only; it is independent of the disformal term at least up to linear order. Within the framework of the full Horndeski theory, the correction terms turn out to depend linearly on the gauge-invariant comoving density perturbation and the first time-derivative thereof. In the superhorizon limit, all these correction terms vanish, leaving only the original scalar curvature perturbation. In other words, it is invariant under the general extended disformal transformation in the superhorizon limit, in the context of full Horndeski theory. Our work encompasses a chain of research studies on the transformation or invariance of the primordial cosmological perturbations, generalising their results under our general extended disformal transformation. Apart from the cosmological perturbations, this work and the transformation considered herein, give us strong impetus to go beyond the current horizon of scalar-tensor theories.

[77]  arXiv:2005.12804 (cross-list from gr-qc) [pdf, ps, other]
Title: Inflationary Attractors in $F(R)$ Gravity
Comments: PLB Accepted
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

In this letter we shall demonstrate that the viable $F(R)$ gravities can be classified mainly into two classes of inflationary attractors, either the $R^2$ attractors or the $\alpha$-attractors. To show this, we shall derive the most general relation between the tensor-to-scalar ratio $r$ and the spectral index of primordial curvature perturbations $n_s$, namely the $r-n_s$ relation, by assuming that the slow-roll condition constrains the values of the slow-roll indices. As we show, the relation between the tensor-to-scalar ratio and the spectral index of the primordial curvature perturbations has the form $r\simeq \frac{48 (1-n_s)^2}{(4-x)^2}$, where the dimensionless parameter $x$ contains higher derivatives of the $F(R)$ gravity function with respect to the Ricci scalar, and it is a function of the $e$-foldings number $N$ and may also be a function of the free parameters of the various $F(R)$ gravity models. For $F(R)$ gravities which have a spectral index compatible with the observational data and also yield $x\ll 1$, these belong to the $R^2$-type of attractors, with $r\sim 3 (1-n_s)^2$, and these are viable theories. Moreover, in the case that $x$ takes larger values in specific ranges and is constant for a given $F(R)$ gravity, the resulting $r-n_s$ relation has the form $r\sim 3 \alpha (1-n_s)^2$, where $\alpha$ is a constant. Thus we conclude that the viable $F(R)$ gravities may be classified into two limiting types of $r-n_s$ relations, one identical to the $R^2$ model at leading order in $x$, and one similar to the $\alpha$-attractors $r-n_s$ relation, for the $F(R)$ gravity models that yield $x$ constant. Finally, we also discuss the case that $x$ is not constant.

[78]  arXiv:2005.12808 (cross-list from hep-th) [pdf, other]
Title: On catalyzed vacuum decay around a radiating black hole and the crisis of the electroweak vacuum
Comments: 25 pages, 8 figures
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)

False vacuum decay is a key feature in quantum field theories and exhibits a distinct signature in the early Universe cosmology. It has recently been suggested that the false vacuum decay is catalyzed by a black hole (BH), which might cause the catastrophe of the Standard Model Higgs vacuum if primordial BHs are formed in the early Universe. We investigate vacuum phase transition of a scalar field around a radiating BH with taking into account the effect of Hawking radiation. We find that the vacuum decay rate slightly decreases in the presence of the thermal effect since the scalar potential is stabilized near the horizon. However, the stabilization effect becomes weak at the points sufficiently far from the horizon. Consequently, we find that the decay rate is not significantly changed unless the effective coupling constant of the scalar field to the radiation is extremely large. This implies that the change of the potential from the Hawking radiation does not help prevent the Standard Model Higgs vacuum decay catalyzed by a BH.

[79]  arXiv:2005.12829 (cross-list from hep-ex) [pdf, other]
Title: Sensitivity to neutrinos from the solar CNO cycle in Borexino
Comments: 15 pages, 12 figures
Subjects: High Energy Physics - Experiment (hep-ex); Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Detectors (physics.ins-det)

Neutrinos emitted in the carbon, nitrogen, oxygen (CNO) fusion cycle in the Sun are a sub-dominant, yet crucial component of solar neutrinos whose flux has not been measured yet. The Borexino experiment at the Laboratori Nazionali del Gran Sasso (Italy) has a unique opportunity to detect them directly thanks to the detector's radiopurity and the precise understanding of the detector backgrounds. We discuss the sensitivity of Borexino to CNO neutrinos, which is based on the strategies we adopted to constrain the rates of the two most relevant background sources, \(pep\) neutrinos and \(^{210}\)Bi beta decays. Finally, the relevance of a detection of CNO neutrinos is extensively discussed in the context of the solar metallicity problem.

[80]  arXiv:2005.12885 (cross-list from hep-ph) [pdf, other]
Title: Higgs chameleon
Comments: 5 pages+references, 1 figure
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

The existing constraints from particle colliders reveal a suspicious but nonlethal meta-stability for our current electroweak vacuum of Higgs potential in the standard model of particle physics, which is, however, disfavored in the early Universe if the inflationary Hubble scale is larger than the instability scale when Higgs quartic self-coupling runs into negative value. Alternative to previous trials of acquiring a positive effective mass-squared from Higgs quadratic couplings to Ricci scalar or inflaton field, we propose a third approach to stabilize the Higgs potential in the early Universe by regarding Higgs as chameleon coupled to inflaton alone without conflicting to the present constraints on either Higgs or chameleon.

Replacements for Wed, 27 May 20

[81]  arXiv:1809.03528 (replaced) [pdf, other]
Title: GW$\times$LSS: Chasing the Progenitors of Merging Binary Black Holes
Comments: 34 pages, 8 figures. Matches the published version. Added link to Multi_CLASS code
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[82]  arXiv:1901.05170 (replaced) [pdf, ps, other]
Title: Possibility Of Concentration of Glycine Near The Surface Of Comet 67P/Churyumov-Gerasimenko
Comments: submitted to A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[83]  arXiv:1907.01485 (replaced) [pdf, other]
Title: A transition from parabolic to conical shape as a common effect in nearby AGN jets
Authors: Y. Y. Kovalev (Lebedev, MIPT, MPIfR), A. B. Pushkarev (CrAO, Lebedev), E. E. Nokhrina (MIPT), A. V. Plavin (Lebedev, MIPT), V. S. Beskin (Lebedev, MIPT), A. Chernoglazov (Lebedev, MIPT), M. L. Lister (Purdue U.), T. Savolainen (Aalto U., MPIfR)
Comments: 18 pages; electronic table 3 is available from the preprint source; a typo in the abstract is corrected; accepted by MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
[84]  arXiv:1908.01195 (replaced) [pdf, other]
Title: Five dimensional charged rotating minimally gauged supergravity black hole cannot be over-spun and/or over-charged in non-linear accretion
Comments: 12 pages, 2 figures; accepted for publication in Eur. Phys. J. C. Figures and further references have been added
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[85]  arXiv:1908.09856 (replaced) [pdf, other]
Title: Reionization optical depth determination from Planck HFI data with ten percent accuracy
Comments: 11 pages, 18 figures; matches published version. Maps and simulations available at this http URL, likelihood at this https URL
Journal-ref: A&A 635, A99 (2020)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[86]  arXiv:1909.05515 (replaced) [pdf, other]
Title: Axion boson stars
Comments: 16 pages, 4 figures. v2: Matches published version. v3: added a reference to give credits for Fig. 1
Journal-ref: JCAP 09 061 (2019)
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[87]  arXiv:1909.10817 (replaced) [pdf, other]
[88]  arXiv:1910.04591 (replaced) [pdf, other]
Title: A relativistic particle pusher for ultra-strong electromagnetic fields
Authors: J. Pétri
Comments: New version with 1D PIC code tests and new references
Subjects: Computational Physics (physics.comp-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[89]  arXiv:1910.07536 (replaced) [pdf, other]
Title: The dark matter component of the Gaia radially anisotropic substructure
Comments: 29 pages, 14 figures, 6 tables; JCAP accepted version
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
[90]  arXiv:1910.13370 (replaced) [pdf, other]
Title: Particle acceleration in kink-unstable jets
Comments: 9 pages, 5 figures, accepted for publication in ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph)
[91]  arXiv:1911.06605 (replaced) [pdf, other]
Title: Modeling bias in supermassive black hole spin measurements
Comments: 22 pages, 14 figures. v2: refereed version
Journal-ref: Astrophys.J. 895: 61 (2020)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[92]  arXiv:1912.01622 (replaced) [pdf, other]
Title: Testing gamma-ray models of blazars in the extragalactic sky
Comments: Matches the published version; extended discussion on detection efficiency, 4FGL fit improved, comments added. Main results and conclusions unchanged
Journal-ref: Phys. Rev. D 101, 103026 (2020)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[93]  arXiv:1912.10243 (replaced) [pdf, other]
Title: The MOSDEF-LRIS Survey: The Interplay Between Massive Stars and Ionized Gas in High-Redshift Star-Forming Galaxies
Comments: 16 pages, 12 figures. Accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[94]  arXiv:1912.11489 (replaced) [pdf, other]
Title: Time of Flight and Supernova Progenitor Effects on the Neutrino Halo
Comments: 7 pages, 3 figures and 1 table
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[95]  arXiv:1912.13128 (replaced) [pdf, ps, other]
Title: Unifying Inflation with Early and Late-time Dark Energy in $F(R)$ Gravity
Comments: Revised Version, PDU Accepted
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[96]  arXiv:2002.00979 (replaced) [pdf, other]
Title: The ALPINE-ALMA [CII] survey. Little to no evolution in the [CII]-SFR relation over the last 13 Gyr
Comments: 11 pages, 7 figures. Accepted for publication in Astronomy & Astrophysics. Minor revisions, see e.g. Table A.1
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[97]  arXiv:2002.07740 (replaced) [pdf, other]
Title: Hunting distant BL Lacs with the photometric technique using Swift and SARA
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
[98]  arXiv:2002.10771 (replaced) [pdf, other]
Title: Cosmic microwave background bounds on primordial black holes including dark matter halo accretion
Comments: 14 pages, 7 figures. v2: Minor clarifications added and extra references. Matches published version
Journal-ref: Phys. Rev. Research 2, 023204 (2020)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
[99]  arXiv:2003.05220 (replaced) [pdf, other]
Title: Tidal disruption events around spherically symmetric compact boson stars
Comments: Submitted to IJMPD for consideration
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[100]  arXiv:2003.07306 (replaced) [pdf, other]
Title: On-sky calibration of a SKA1-low station in the presence of mutual coupling
Journal-ref: Borg, Josef, et al. "On-sky calibration of a SKA1-low station in the presence of mutual coupling." Monthly Notices of the Royal Astronomical Society (2020)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)
[101]  arXiv:2003.08244 (replaced) [pdf, ps, other]
Title: A comment on "Lense-Thirring frame dragging induced by a fast-rotating white dwarf in a binary pulsar system" by V. Venkatraman Krishnan et al
Authors: Lorenzo Iorio
Comments: LaTex2e, 20 pages, 3 figures, no tables. Due to arXiv's space limitations, low-resolution pictures have been upoloaded. Version at press in Monthly Notices of the Royal Astronomical Society (MNRAS)
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Space Physics (physics.space-ph)
[102]  arXiv:2003.10498 (replaced) [pdf, other]
Title: Analytic I-Love-C relations for realistic neutron stars
Authors: Nan Jiang, Kent Yagi
Comments: A new section on interpretation of the possible origin of the I-C and Love-C universality is added(accepted to PRD)
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
[103]  arXiv:2003.12152 (replaced) [pdf, other]
Title: Shouts and Murmurs: Combining Individual Gravitational-Wave Sources with the Stochastic Background to Measure the History of Binary Black Hole Mergers
Comments: Submitted to ApJL, minor updates in response to referee comments
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[104]  arXiv:2003.13349 (replaced) [pdf, other]
Title: Constraints on compact dark matter with fast radio burst observations
Comments: 6 pages, 5 figures; Accepted for publication in ApJ Letters
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
[105]  arXiv:2004.00037 (replaced) [pdf, other]
Title: Giant Planet Influence on the Collective Gravity of a Primordial Scattered Disk
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[106]  arXiv:2004.01440 (replaced) [pdf, other]
Title: Rotating black holes without $\mathbb{Z}_2$ symmetry and their shadow images
Authors: Che-Yu Chen
Comments: 22 pages, 9 figures. Updated to match the published version
Journal-ref: JCAP 05 (2020) 040
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
[107]  arXiv:2004.11366 (replaced) [pdf, other]
Title: Hypercompact stellar clusters: morphological renditions and spectro-photometric models
Comments: Accepted for publication on MNRAS, 17 pages, 7 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[108]  arXiv:2005.03735 (replaced) [pdf, other]
Title: The role of environment on quenching, star formation and AGN activity
Comments: Proceedings of the IAU Symposium 359 "Galaxy evolution and feedback across different environments", editors T. Storchi-Bergmann, R. Overzier, W. Forman & R. Riffel - final version
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[109]  arXiv:2005.04807 (replaced) [pdf, other]
Title: Basis function expansions for galactic dynamics: Spherical versus cylindrical coordinates
Comments: 14 pages, 17 figures, Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[110]  arXiv:2005.05977 (replaced) [pdf, other]
Title: High-eccentricity migration of planetesimals around polluted white dwarfs
Comments: 17 pages, 13 figures, 2 appendices; submitted to MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[111]  arXiv:2005.10133 (replaced) [pdf, ps, other]
Title: Generalization of cosmological attractor approach to Einstein-Gauss-Bonnet gravity
Authors: E.O. Pozdeeva
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[112]  arXiv:2005.10601 (replaced) [pdf, ps, other]
Title: Optical properties and dust temperatures in clumpy diffuse medium
Comments: 13 pages, 7 figures, accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[113]  arXiv:2005.11109 (replaced) [pdf, ps, other]
Title: On the Distance of SGR 1935+2154 Associated with FRB 200428
Comments: 7 pages in emulateapj format, 3 figures, a few typos corrected
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[114]  arXiv:2005.12080 (replaced) [pdf, other]
Title: ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- II. Compact objects in ACA observations and star formation scaling relations
Comments: Accepted to be published in MNRAS. The full tables are included in Tables.pdf or Tables.tex files, which can be downloaded from source files
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
[115]  arXiv:2005.12114 (replaced) [pdf, other]
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