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Astrophysics

New submissions

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New submissions for Tue, 20 Mar 18

[1]  arXiv:1803.06343 [pdf, other]
Title: Forward Modeling of Spectroscopic Galaxy Surveys: Application to SDSS
Comments: 28 pages, 13 figures, submitted to JCAP
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Galaxy spectra are essential to probe the spatial distribution of galaxies in our Universe. To better interpret current and future spectroscopic galaxy redshift surveys, it is important to be able to simulate these data sets. We describe Uspec, a forward modeling tool to generate galaxy spectra taking into account intrinsic galaxy properties as well as instrumental responses of a given telescope. The model for the intrinsic properties of the galaxy population was developed in an earlier work for broad-band imaging surveys [1]. We apply Uspec to the SDSS/CMASS sample of Luminous Red Galaxies (LRGs). We construct selection cuts that match those used to build this LRG sample, which we then apply to data and simulations in the same way. The resulting real and simulated average spectra show a very good agreement overall, with the simulated one showing a slightly bluer galaxy population. For a quantitative comparison, we perform Principal Component Analysis (PCA) of the sets of spectra. By comparing the PCs constructed from simulations and data, we find very good agreement for the first four components, and moderate for the fifth. The distributions of the eigencoefficients also show an appreciable overlap. We are therefore able to properly simulate the LRG sample taking into account the SDSS/BOSS instrumental responses. The small residual differences between the two samples can be ascribed to the intrinsic properties of the simulated galaxy population, which can be reduced by adjusting the model parameters in the future. This provides good prospects for the forward modeling of upcoming large spectroscopic surveys.

[2]  arXiv:1803.06345 [pdf, other]
Title: The Role of Cosmic Ray Transport in Shaping the Simulated Circumgalactic Medium
Comments: 20 pages, 14 figures, submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The majority of galactic baryons reside outside of the galactic disk in the diffuse gas known as the circumgalactic medium (CGM). The physical processes that govern the galactic inflows and outflows that shape the complex multiphase structure of the CGM place rigid constraints on theories of galactic evolution. While state-of-the art simulations excel at reproducing galactic disk properties, many struggle to drive strong galactic winds or to match the observed ionization structure of the CGM using only thermal supernova feedback. To remedy this, recent studies have invoked non-thermal cosmic ray (CR) stellar feedback prescriptions. However, numerical schemes of CR transport are still poorly constrained. We explore how the choice of CR transport affects the multiphase structure of the simulated CGM. We implement anisotropic CR diffusion and streaming in the astrophysical simulation code, Enzo and simulate a suite of isolated disk galaxies with varying prescriptions for CR transport: isotropic diffusion, anisotropic diffusion, and streaming. We find that all three transport mechanisms result in strong, metal-rich outflows but differ in the temperature and ionization structure of their CGM. Isotropic diffusion results in a spatially uniform, warm CGM that underpredicts the column densities of low-ions. Anisotropic diffusion develops a reservoir of cool gas that extends further from the galactic center, but disperses rapidly with distance. CR streaming projects cool gas out to radii of 200 kpc, supporting a truly multiphase medium. In addition, we find that streaming is less sensitive to changes in constant parameter values like the CR injection fraction, transport velocity, and resolution than diffusion. We conclude that CR streaming is a more robust implementation of CR transport and motivate the need for detailed parameter studies of this mode of CR transport.

[3]  arXiv:1803.06348 [pdf, other]
Title: Likelihood Non-Gaussianity in Large-Scale Structure Analyses
Comments: 33 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Standard present day large-scale structure (LSS) analyses make a major assumption in their Bayesian parameter inference --- that the likelihood has a Gaussian form. For summary statistics currently used in LSS, this assumption, even if the underlying density field is Gaussian, cannot be correct in detail. We investigate the impact of this assumption on two recent LSS analyses: the Beutler et al. (2017) power spectrum multipole ($P_\ell$) analysis and the Sinha et al. (2017) group multiplicity function ($\zeta$) analysis. Using non-parametric divergence estimators on mock catalogs originally constructed for covariance matrix estimation, we identify significant non-Gaussianity in both the $P_\ell$ and $\zeta$ likelihoods. We then use Gaussian mixture density estimation and Independent Component Analysis on the same mocks to construct likelihood estimates that approximate the true likelihood better than the Gaussian $pseudo$-likelihood. Using these likelihood estimates, we accurately estimate the true posterior probability distribution of the Beutler et al. (2017) and Sinha et al. (2017) parameters. Likelihood non-Gaussianity shifts the $f\sigma_8$ constraint by $-0.44\sigma$, but otherwise, does not significantly impact the overall parameter constraints of Beutler et al. (2017). For the $\zeta$ analysis, using the pseudo-likelihood significantly underestimates the uncertainties and biases the constraints of Sinha et al. (2017) halo occupation parameters. For $\log M_1$ and $\alpha$, the posteriors are shifted by $+0.43\sigma$ and $-0.51\sigma$ and broadened by $42\%$ and $66\%$, respectively. The divergence and likelihood estimation methods we present provide a straightforward framework for quantifying the impact of likelihood non-Gaussianity and deriving more accurate parameter constraints.

[4]  arXiv:1803.06352 [pdf, other]
Title: Age-resolved chemistry of red giants in the solar neighbourhood
Comments: 26 pages, 20 figures, accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

In the age of high-resolution spectroscopic stellar surveys of the Milky Way, the number of stars with detailed abundances of multiple elements is rapidly increasing. These elemental abundances are directly influenced by the evolutionary history of the Galaxy, but this can be difficult to interpret without an absolute timeline of the abundance enrichment. We present age-abundance trends for [M/H], [{\alpha}/M], and 17 individual elements using a sample of 721 solar neighbourhood Hipparcos red giant stars observed by APOGEE. These age trends are determined through a Bayesian hierarchical modelling method presented by Feuillet et al. (2016). We confirm that the [{\alpha}/M]- age relation in the solar neighbourhood is steep and relatively narrow (0.20 dex age dispersion), as are the [O/M]- and [Mg/M]-age relations. The age trend of [C/N] is steep and smooth, consistent with stellar evolution. The [M/H]-age relation has a mean age dispersion of 0.28 dex and a complex overall structure. The oldest stars in our sample are those with the lowest and highest metallicities, while the youngest stars are those with solar metallicity. These results provide strong constraints on theoretical models of Galactic chemical evolution (GCE). We compare them to the predictions of one-zone GCE mod- els and multi-zone mixtures, both analytic and numerical. These comparisons support the hypothesis that the solar neighbourhood is composed of stars born at a range of Galactocentric radii, and that the most metal-rich stars likely migrated from a region with earlier and more rapid star formation such as the inner Galaxy.

[5]  arXiv:1803.06356 [pdf, ps, other]
Title: The Spitzer-IRAC/MIPS Extragalactic Survey (SIMES): II enhanced nuclear accretion rate in galaxy groups at z$\sim$0.2
Comments: 31 pages, 23 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

For a sample of star forming galaxies in the redshift interval 0.15$<$z$<$0.3, we study how both the relative strength of the AGN infra-red emission, compared to that due to the star formation (SF), and the numerical fraction of AGNs, change as a function of the total stellar mass of the hosting galaxy group (M$^{*}_{\mathrm{group}}$), between $10^{10.25}$ and $10^{11.9}$M$_{\odot}$. Using a multi-component SED fitting analysis, we separate the contribution of stars, AGN torus and star formation to the total emission at different wavelengths. This technique is applied to a new multi-wavelength data-set in the SIMES field (23 not redundant photometric bands), spanning the wavelength range from the UV (GALEX) to the far-IR (Herschel) and including crucial AKARI and WISE mid-IR observations (4.5 \mu m$<\lambda<$24 \mu m), where the BH thermal emission is stronger. This new photometric catalog, that includes our best photo-z estimates, is released through the NASA/IPAC Infrared Science Archive (IRSA). Groups are identified through a friends of friends algorithm ($\sim$62% purity, $\sim$51% completeness). We identified a total of 45 galaxies requiring an AGN emission component, 35 of which in groups and 10 in the field. We find BHAR$\propto ($M$^{*}_{\mathrm{group}})^{1.21\pm0.27}$ and (BHAR/SFR)$\propto ($M$^{*}_{\mathrm{group}})^{1.04\pm0.24}$ while, in the same range of M$^{*}_{\mathrm{group}}$, we do not observe any sensible change in the numerical fraction of AGNs. Our results indicate that the nuclear activity (i.e. the BHAR and the BHAR/SFR ratio) is enhanced when galaxies are located in more massive and richer groups.

[6]  arXiv:1803.06359 [pdf, ps, other]
Title: SMSS J130522.47-293113.0: a high-latitude stellar X-ray source with pc-scale outflow relics?
Comments: 15 pages, 8 figures. Accepted by MNRAS on 2018 March 13
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report the discovery of an unusual stellar system, SMSS J130522.47-293113.0. The optical spectrum is dominated by a blue continuum together with emission lines of hydrogen, neutral and ionized helium, and the N III, C III blend at around 4640-4650 Angstrom. The emission line profiles vary in strength and position on timescales as short as 1 day, while optical photometry reveals fluctuations of as much as ~0.2 mag in g on timescales as short as 10-15 min. The system is a weak X-ray source (f_{0.3-10} = (1.2 +/- 0.1) x 10^{-13} ergs cm^{-2} s^{-1} in the 0.3-10 keV band) but is not detected at radio wavelengths (3-sigma upper limit of 50 microJy at 5.5 GHz). The most intriguing property of the system, however, is the existence of two "blobs", a few arcsec in size, that are symmetrically located 3.8 arcmin (2.2 pc for our preferred system distance of ~2 kpc) each side of the central object. The blobs are detected in optical and near-IR broadband images but do not show any excess emission in Halpha images. We discuss the interpretation of the system, suggesting that the central object is most likely a nova-like CV, and that the blobs are relics of a pc-scale accretion-powered collimated outflow.

[7]  arXiv:1803.06362 [pdf, ps, other]
Title: A Candidate Tidal Disruption Event in a Quasar at z=2.359 from Abundance Ratio Variability
Authors: Xin Liu (UIUC), Alexander Dittmann (UIUC), Yue Shen (UIUC), Linhua Jiang (KIAA/PKU)
Comments: 14 pages, 11 figures, ApJ resubmitted addressing referee report; comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

A small fraction of quasars show unusually high nitrogen-to-carbon ratio (N/C) in their spectra. These "nitrogen-rich" (N-rich) quasars are a long-standing puzzle because their interstellar medium implies stellar populations with abnormally high metallicities. It has recently been proposed that N-rich quasars may result from tidal disruption events (TDEs) of stars by supermassive black holes. The rapid enhancement of nitrogen and the depletion of carbon due to the carbon-nitrogen-oxygen cycle in supersolar mass stars could naturally produce high N/C. However, the TDE hypothesis predicts that the N/C should change with time, which has never hitherto been observed. Here we report discovery of the first N-rich quasar with rapid N/C variability that could be caused by a TDE. Two spectra separated by 1.7 yr (rest-frame) show that the N III]\lambda 1750/C III]\lambda 1909 intensity ratio decayed by ~86%+/-14% (1 \sigma). Optical (rest-frame UV) light curve and X-ray observations are qualitatively consistent with the TDE hypothesis, although the time baseline falls short for a definitive proof. Putting the single-object discovery into context, statistical analyses of the ~80 known N-rich quasars with high-quality archival spectra show evidence (at a 5-\sigma\ significance level) of a decrease in N/C on timescales of >1 yr (rest-frame) and a constant level of ionization (indicated by the C III]\lambda 1909/C IV\lambda 1549 intensity ratio). If confirmed, our results demonstrate the method of identifying TDE candidates in quasars via abundance ratio variability, opening a new window of TDE observations at high redshift (z>2) with upcoming large-scale time-domain spectroscopic surveys.

[8]  arXiv:1803.06367 [pdf, other]
Title: The supernova remnant population in the very-high-energy sky: prospects for CTA
Comments: 4 pages, 1 figure
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The detection of very-high-energy gamma rays from supernova remnant shells testifies of the acceleration of particles at strong shocks. Many aspects of the particle acceleration remain however unclear. The study of individual objects is very helpful, but the study of the entire population of SNRs detected in this range and its characteristics can also bring valuable science. Using Monte-Carlo simulations, the population of shells bright in the TeV and multi-TeV range can be simulated. The results of these simulations aim at being compared with observations of in struments operating in these ranges, such as the Cherenkov Telescope Array (CTA). Our results suggest that CTA should be able to effectively constrain the slope of particles accelerated at SNRs and the electron-to-proton ratio.

[9]  arXiv:1803.06384 [pdf, other]
Title: Star formation toward the H~II region IRAS 10427-6032
Comments: 12 pages, 9 figures, 2 tables, Accepted for publication in New Astronomy
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The formation and properties of star clusters formed at the edges of H II regions are poorly known. We study stellar content, physical conditions, and star formation processes around a relatively unknown young H II region IRAS 10427-6032, located in the southern outskirts of the Carina Nebula. We make use of near-IR data from VISTA, mid-IR from Spitzer and WISE, far-IR from Herschel, sub-mm from ATLASGAL, and 843 MHz radio-continuum data. Using multi-band photometry, we find a total of 5 Class I and 29 Class II young stellar object (YSO) candidates, most of which newly identified, in the 5'$\times$5' region centered on the IRAS source position. Modeling of the spectral energy distribution for selected YSO candidates using radiative transfer models shows that most of these candidates are intermediate mass YSOs in their early evolutionary stages. A majority of the YSO candidates are found to be coincident with the cold dense clump at the western rim of the H II region. Lyman continuum luminosity calculation using radio emission indicates the spectral type of the ionizing source to be earlier than B0.5-B1. We identified a candidate massive star possibly responsible for the H II region with an estimated spectral type B0-B0.5. The temperature and column density maps of the region constructed by performing pixel-wise modified blackbody fits to the thermal dust emission using the far-IR data show a high column density shell-like morphology around the H II region, and low column density (0.6 $\times$ 10$^{22}$ cm$^{-2}$) and high temperature ($\sim$21 K) matter within the H II region. Based on the morphology of the region in the ionized and the molecular gas, and the comparison between the estimated timescales of the H II region and the YSO candidates in the clump, we argue that the enhanced star-formation at the western rim of the H II region is likely due to compression by the ionized gas.

[10]  arXiv:1803.06391 [pdf, ps, other]
Title: The route to massive black hole formation via merger-driven direct collapse: a review
Comments: Invited Review submitted to Reports of Progress in Physics, version revised after referee reports. Comments are welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA)

In this paper we review a new scenario for the formation of massive black hole seeds that relies on multi-scale gas inflows initiated by the merger of massive gas-rich galaxies at $z > 6$, where gas has already achieved solar composition. Hydrodynamical simulations undertaken to explore our scenario show that supermassive, gravitationally bound gaseous disks, weighing a billion solar masses and of a few pc in size, form in the nuclei of merger remnants in less than $10^5$ yr. These could later produce a supermassive protostar or supermassive star at their center via various mechanisms. Moreover, we present a new analytical model, based on angular momentum transport in mass-loaded gravitoturbulent disks. This naturally predicts that a nuclear disk accreting at rates exceeding $1000 M_{\odot}$/yr, as seen in the simulations, is stable against fragmentation irrespective of its metallicity. This is at variance with conventional direct collapse scenarios, which require the suppression of gas cooling in metal-free protogalaxies for gas collapse to take place. Such high accretion rates reflect the high free-fall velocities in massive halos appearing at $z < 10$, and occur naturally as a result of the efficient angular momentum loss provided by mergers. We discuss the implications of our scenario on the observed population of high-z quasars and on its evolution to lower redshifts using a semi-analytical galaxy formation model. Finally, we consider the intriguing possibility that the secondary gas inflows in the unstable disks might drive gas to collapse into a supermassive black hole directly via the General Relativistic radial instability. Such {\it dark collapse} route could generate gravitational wave emission detectable via the future Laser Interferometer Space Antenna (LISA). [Abridged]

[11]  arXiv:1803.06392 [pdf, other]
Title: MESA Models of the Evolutionary State of the Interacting Binary epsilon Aurigae
Comments: 6 pages, 2 figures, accepted by MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Using MESA code (Modules for Experiments in Stellar Astrophysics, version 9575), an evaluation was made of the evolutionary state of the epsilon Aurigae binary system (HD 31964, F0Iap + disk). We sought to satisfy several observational constraints: 1) requiring evolutionary tracks to pass close to the current temperature and luminosity of the primary star; 2) obtaining a period near the observed value of 27.1 years; 3) matching a mass function of 3.0; 4) concurrent Roche lobe overflow and mass transfer; 5) an isotopic ratio 12 C/ 13 C = 5 and, (6) matching the interferometrically determined angular diameter. A MESA model starting with binary masses of 9.85 + 4.5 Msun , with a 100 day initial period, produces a 1.2 + 10.6 Msun result having a 547 day period, and a single digit 12 C/ 13 C ratio. These values were reached near an age of 20 Myr, when the donor star comes close to the observed luminosity and temperature for epsilon Aurigae A, as a post-RGB/pre-AGB star. Contemporaneously, the accretor then appears as an upper main sequence, early B-type star. This benchmark model can provide a basis for further exploration of this interacting binary, and other long period binary stars.

[12]  arXiv:1803.06403 [pdf, other]
Title: Characterizing Earth Analogs in Reflected Light: Atmospheric Retrieval Studies for Future Space Telescopes
Comments: Resubmitted to AAS Journals after incorporating reviewer feedback. 26 pages, 18 figure, 9 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Space-based high contrast imaging mission concepts for studying rocky exoplanets in reflected light are currently under community study. We develop an inverse modeling framework to estimate the science return of such missions given different instrument design considerations. By combining an exoplanet albedo model, an instrument noise model, and an ensemble Markov chain Monte Carlo sampler, we explore retrievals of atmospheric and planetary properties for Earth twins as a function of signal-to-noise ratio (SNR) and resolution ($R$). Our forward model includes Rayleigh scattering, single-layer water clouds with patchy coverage, and pressure-dependent absorption due to water vapor, oxygen, and ozone. We simulate data at $R = 70$ and $R = 140$ from 0.4-1.0 $\mu$m with SNR $ = 5, 10, 15, 20$ at 550 nm (i.e., for HabEx/LUVOIR-type instruments). At these same SNR, we simulate data for WFIRST paired with a starshade, which includes two photometric points between 0.48-0.6 $\mu$m and $R = 50$ spectroscopy from 0.6-0.97 $\mu$m. Given our noise model for WFIRST-type detectors, we find that weak detections of water vapor, ozone, and oxygen can be achieved with observations with at least $R = 70$ / SNR$\ = 15$, or $R = 140$ / SNR$\ = 10$ for improved detections. Meaningful constraints are only achieved with $R = 140$ / SNR$\ = 20$ data. The WFIRST data offer limited diagnostic information, needing at least SNR = 20 to weakly detect gases. Most scenarios place limits on planetary radius, but cannot constrain surface gravity and, thus, planetary mass.

[13]  arXiv:1803.06413 [pdf, other]
Title: Thermal kinetic inductance detectors for ground-based millimeter-wave cosmology
Comments: 8 pages, 4 figures. Submitted to Journal of Low Temperature Physics
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We show measurements of thermal kinetic inductance detectors (TKID) intended for millimeter wave cosmology in the 200-300 GHz atmospheric window. The TKID is a type of bolometer which uses the kinetic inductance of a superconducting resonator to measure the temperature of the thermally isolated bolometer island. We measure bolometer thermal conductance, time constant and noise equivalent power. We also measure the quality factor of our resonators as the bath temperature

[14]  arXiv:1803.06423 [pdf, other]
Title: Relativistic Viscous Radiation Hydrodynamic Simulations of Geometrically Thin Disks: I. Thermal and Other Instabilities
Comments: 16 pages, 15 figures, accepted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present results from two-dimensional, general relativistic, viscous, radiation hydrodynamic numerical simulations of Shakura-Sunyaev thin disks accreting onto stellar mass Schwarzschild black holes. We consider cases on both the gas- and radiation-pressure-dominated branches of the thermal equilibrium curve, with mass accretion rates spanning the range from $\dot{M} = 0.01 L_\mathrm{Edd}/c^2$ to $10 L_\mathrm{Edd}/c^2$. The simulations directly test the stability of this standard disk model on the different branches. We find clear evidence of thermal instability for all radiation-pressure-dominated disks, resulting universally in the vertical collapse of the disks, which in some cases then settle onto the stable, gas-pressure-dominated branch. Although these results are consistent with decades-old theoretical predictions, they appear to be in conflict with available observational data from black hole X-ray binaries. We also find evidence for a radiation-pressure-driven instability that breaks the unstable disks up into alternating rings of high and low surface density on a timescale comparable to the thermal collapse. Since radiation is included self-consistently in the simulations, we are able to calculate lightcurves and power density spectra (PDS). For the most part, we measure radiative efficiencies (ratio of luminosity to mass accretion rate) close to 6%, as expected for a non-rotating black hole. The PDS appear as broken power laws, with a break typically around 100 Hz. There is no evidence of significant excess power at any frequencies, i.e. no quasi-periodic oscillations are observed.

[15]  arXiv:1803.06430 [pdf, other]
Title: The effects of metallicity and cooling physics on fragmentation: implications on direct-collapse black hole formation
Comments: 5 pages, 4 figures, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

A promising supermassive black hole seed formation channel is that of direct collapse from primordial gas clouds. We perform a suite of 3D hydrodynamics simulations of an isolated turbulent gas cloud to investigate conditions conducive to forming massive black hole seeds via direct collapse, probing the impact of cloud metallicity, gas temperature floor and cooling physics on cloud fragmentation. We find there is no threshold in metallicity which produces a sharp drop in fragmentation. When molecular cooling is not present, metallicity has little effect on fragmentation. When molecular cooling is present, fragmentation is suppressed by at most $\sim 25\%$, with the greatest suppression seen at metallicities below $2\%$ solar. A gas temperature floor $\sim 10^{4}$K produces the largest drop in fragmentation of any parameter choice, reducing fragmentation by $\sim 60\%$. At metallicities below $2\%$ solar or at temperatures $\sim 10^{3}$K we see a reduction in fragmentation $\sim 20-25 \%$. For a cloud of metallicity $2\%$ solar above and a temperature below $10^3$K, the detailed choices of temperature floor, metallicity, and cooling physics have little impact on fragmentation.

[16]  arXiv:1803.06436 [pdf, other]
Title: The Kepler Light Curves of AGN: A Detailed Analysis
Comments: 39 pages including 2 appendices. Accepted for Publication in the Astrophysical Journal, with higher resolution figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present a comprehensive analysis of 21 light curves of Type 1 AGN from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales which roughly correlate with black hole mass. These timescales are consistent with orbital timescales or freefall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms-flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1-10% level.

[17]  arXiv:1803.06473 [pdf, other]
Title: Variational Inference as an alternative to MCMC for parameter estimation and model selection
Comments: 12 pages, 3 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an)

Many problems in Astrophysics involve using Bayesian Inference to deal with problems of parameter estimation and model selection. In this paper, we introduce Variational Inference to solve these problems and compare how the results hold up to Markov Chain Monte Carlo which is the most common method. Variational Inference converts the inference problem into an optimization problem by approximating the posterior from a known family of distributions and using Kullback-Leibler divergence to measure closeness. Variational Inference takes advantage of fast optimization techniques which make it ideal to deal with large datasets and also makes it trivial to parallelize. As a proof of principle, we apply Variational Inference for parameter estimation and model comparison to four different problems in astrophysics where MCMC techniques were previously used: measuring exoplanet orbital parameters from radial velocity data, tests of periodicities in measurements of $G$, significance of a turnover in the spectral lag data of GRB 160625B , and estimating the mass of a galaxy cluster using weak lensing. We find that Variational Inference is much faster than MCMC for these problems.

[18]  arXiv:1803.06487 [pdf]
Title: Magnetic Fields of Extrasolar Planets: Planetary Interiors and Habitability
Authors: J. Lazio (JPL, CIT), G. Hallinan (Caltech), V. Airapetian (NASA/GSFC), D. A. Brain (Univ. Colorado, Boulder), C. F. Dong (Princeton), P. E. Driscoll (Carnegie), J.-M. Griessmeier (LPC2E-Universitè d'Orlèans/CNRS, Station de Radioastronomie de Nançay, Observatoire de Paris), W. M. Farrell (NASA/GSFC), J. C. Kasper (Univ. Michigan), T. Murphy (Univ. Sydney), L. A. Rogers (Univ. Chicago), A. Wolszczan (Penn State), P. Zarka (Observatoire de Paris, CNRS, PSL), M. Knapp (MIT EAPS), C. R. Lynch (Univ. Sydney), J.D. Turner (Univ. Virginia)
Comments: A white paper submitted to the National Academy of Science Committee on Exoplanet Science Strategy; 6 pages
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Jupiter's radio emission has been linked to its planetary-scale magnetic field, and spacecraft investigations have revealed that most planets, and some moons, have or had a global magnetic field. Generated by internal dynamos, magnetic fields are one of the few remote sensing means of constraining the properties of planetary interiors. For the Earth, its magnetic field has been speculated to be partially responsible for its habitability, and knowledge of an extrasolar planet's magnetic field may be necessary to assess its habitability. The radio emission from Jupiter and other solar system planets is produced by an electron cyclotron maser, and detections of extrasolar planetary electron cyclotron masers will enable measurements of extrasolar planetary magnetic fields.
This white paper draws heavily on the W. M. Keck Institute for Space Studies report Planetary Magnetic Fields: Planetary Interiors and Habitability (Lazio, Shkolnik, Hallinan, et al.), it incorporates topics discussed at the American Astronomical Society Topical Conference "Radio Exploration of Planetary Habitability," it complements the Astrobiology Science Strategy white paper "Life Beyond the Solar System: Space Weather and Its Impact on Habitable Worlds" (Airapetian et al.), and it addresses aspects of planetary magnetic fields discussed in the NASA Astrobiology Strategy.

[19]  arXiv:1803.06529 [pdf, other]
Title: Connecting Coronal Mass Ejections to their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects
Comments: Accepted for publication in Solar Physics. 31 pages, 15 figures, 4 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments alongside models, however this can be challenging for automated operational systems. The EU Framework Package 7 HELCATS project provides catalogues of CME observations and properties from the Helio- spheric Imagers onboard the two NASA/STEREO spacecraft in order to track the evolution of CMEs in the inner heliosphere. From the main HICAT catalogue of over 2,000 CME detections, an automated algorithm has been developed to connect the CMEs observed by STEREO to any corresponding solar flares and active region (AR) sources on the solar surface. CME kinematic properties, such as speed and angular width, are compared with AR magnetic field properties, such as magnetic flux, area, and neutral line characteristics. The resulting LOWCAT catalogue is also compared to the extensive AR property database created by the EU Horizon 2020 FLARECAST project, which provides more complex magnetic field parameters derived from vector magnetograms. Initial statistical analysis has been undertaken on the new data to provide insight into the link between flare and CME events, and characteristics of eruptive ARs. Warning thresholds determined from analysis of the evolution of these parameters is shown to be a useful output for operational space weather purposes. Parameters of particular interest for further analysis include total unsigned flux, vertical current, and current helicity. The automated method developed to create the LOWCAT catalogue may also be useful for future efforts to develop operational CME forecasting.

[20]  arXiv:1803.06614 [pdf, ps, other]
Title: On existence of out-of-plane equilibrium points in restricted three-body problem with oblateness
Comments: Some results in Section 2.3 will appear in A&A as a comment paper (DOI: 10.1051/0004-6361/201832575). 11 papges
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We analyze in this paper the existence of the "out-of-plane" equilibrium points in the restricted three-body problem with oblateness. From the series expansion of the potential function of an oblate asteroid, we show analytically all equilibrium points locate on the orbital plane of primaries and how artificial equilibrium points may arise due to an inappropriate application of the potential function. Using the closed form of the potential of a triaxial ellipsoid, we analytically demonstrate that the gravitational acceleration in $z$-direction is always pointing toward the equatorial plane, thus it could not be balanced out at any value of $z\neq 0$ and the out-of-plane equilibrium points cannot exist. The out-of-plane equilibrium points appear only when additional acceleration other than the gravitation from primaries is taken into account. We suggest that special attention must be paid to the application of the spherical harmonics expansion of potential to find the equilibrium points, especially when these points may be very close to the celestial body.

[21]  arXiv:1803.06621 [pdf, ps, other]
Title: Future of Pulsar Research and Facilities
Authors: Matthew Bailes
Comments: 6 pages, no figures, Presented at Pulsar Astrophysics - The Next 50 Years, IAU Symposium 337, held at Jodrell Bank Observatory, September 2017. Accepted, Cambridge University Press
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Radio pulsars have been responsible for many astonishing astrophysical and fundamental physics breakthroughs since their discovery 50 years ago. In this review I will discuss many of the highlights, most of which were only possible because of the provision of large-scale observing facilities. The next 50 years of pulsar astronomy can be very bright, but only if our governments properly plan and fund the infrastructure necessary to enable future discoveries. Being a small sub-field of astronomy places an onus on the pulsar community to have an open-source/open access approach to data, software, and major observing facilities to enable new groups to emerge to keep the field vibrant.

[22]  arXiv:1803.06628 [pdf, ps, other]
Title: A machine learning method to separate cosmic ray electrons from protons from 10 to 100 GeV using DAMPE data
Comments: 11 pages, 8 figures, accepted for publication in RAA
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)

DArk Matter Particle Explorer (DAMPE) is a general purpose high energy cosmic ray and gamma ray observatory, aiming to detect high energy electrons and gammas in the energy range 5 GeV to 10 TeV and hundreds of TeV for nuclei. This paper provides a method using machine learning to identify electrons and separate them from gammas,protons,helium and heavy nuclei with the DAMPE data from 2016 January 1 to 2017 June 30, in energy range from 10 to 100 GeV.

[23]  arXiv:1803.06630 [pdf, other]
Title: Stellar Yields of Rotating First Stars. II. Pair Instability Supernovae and Comparison with Observations
Comments: Accepted for publication in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Recent theory predicts that a first star is born with a massive initial mass of $\gtrsim$ 100 $M_\odot$. Pair instability supernova (PISN) is a common fate for such a massive star. Our final goal is to prove the existence of PISN and thus the high mass nature of the initial mass function in the early universe by conducting {\it abundance profiling}, in which properties of a hypothetical first star is constrained by metal-poor star abundances. In order to determine reliable and useful abundances, we investigate the PISN nucleosynthesis taking both rotating and non-rotating progenitors for the first time. We show that the initial and CO core mass ranges for PISNe depend on the envelope structures: non-magnetic rotating models developing inflated envelopes have a lower-shifted CO mass range of $\sim$ 70--125 $M_\odot$, while non-rotating and magnetic rotating models with deflated envelopes have a range of $\sim$ 80--135 $M_\odot$. However, we find no significant difference in explosive yields from rotating and non-rotating progenitors, except for large nitrogen production in non-magnetic rotating models. Furthermore, we conduct the first systematic comparison between theoretical yields and a large sample of metal-poor star abundances. We find that the predicted low [Na/Mg] $\sim$ $-1.5$ and high [Ca/Mg] $\sim$ $0.5$--$1.3$ abundance ratios are the most important to discriminate PISN signatures from normal metal-poor star abundances, and confirm that no currently observed metal-poor star matches with the PISN abundance. Extensive discussion on the non-detection is finally made.

[24]  arXiv:1803.06634 [pdf, other]
Title: Detection of a Double Relic in the Torpedo Cluster: SPT-CL J0245-5302
Comments: 18 pages, 12 figures, submitted to MNRAS, this version after application of the referee's comments
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Torpedo cluster, SPT-CL J0245-5302 (S0295) is a massive, merging cluster at a redshift of z = 0.300, which exhibits a strikingly similar morphology to the Bullet cluster 1E 0657-55.8 (z = 0.296), including a classic bow shock in the cluster's intra-cluster medium revealed by Chandra X-ray observations. We present Australia Telescope Compact Array data centred at 2.1 GHz and Murchison Widefield Array data at frequencies between 72 MHz and 231 MHz which we use to study the properties of the cluster. We characterise a number of discrete and diffuse radio sources in the cluster, including the detection of two previously unknown radio relics on the cluster periphery. The average spectral index of the diffuse emission between 70 MHz and 3.1 GHz is $\alpha=-1.63_{-0.10}^{+0.10}$ and a radio-derived Mach number for the shock in the west of the cluster is calculated as M = 2.04. The Torpedo cluster is thus as a double relic system at moderate redshift.

[25]  arXiv:1803.06650 [pdf, other]
Title: A large and pristine sample of standard candles across the Milky Way: ~100,000 red clump stars with 3% contamination
Comments: 7 pages, 4 figures, 1 table, submitted to ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Core helium-burning red clump (RC) stars are excellent standard candles in the Milky Way: beyond 3 kpc, RC stars may have more precise distance estimates from spectrophotometry than from Gaia parallaxes. However, RC stars have $T_{\rm eff}$ and $\log g$ very similar to some red giant branch (RGB) stars. Especially for low-resolution R=2000 spectroscopic studies with $T_{\rm eff}$, $\log g$, and [Fe/H] estimated of limited precision, separating RC stars from RGB through established method can incur ~20% contamination. Recently, Hawkins et al. (2018) demonstrated that the additional information in single-epoch spectra, such as the C/N ratio, can be exploited to cleanly differentiate RC and RGB stars. In this second paper of the series, we establish a data-driven mapping from spectral flux space to independently determined asteroseismic parameters, the frequency and the period separations. From this, we identify 210,371 RC stars from the publicly available LAMOST DR3 and APOGEE DR14 data, with ~9% of contamination. We provide an RC sample of 92,249 stars with a contamination of only ~3%, by restricting the combined analysis to LAMOST stars with${\rm S/N}_{\rm pix} \ge 75$. This demonstrates that high-S/N, low-resolution spectra covering a broad wavelength range can identify RC samples at least as pristine as their high-resolution counterparts. As coming and ongoing surveys such as TESS, DESI, and LAMOST will continue to improve the overlapping training spectroscopic-asteroseismic sample, the method presented in this study provides an efficient and straightforward way to derive a vast yet pristine RC stars to reveal the 3D structure of the Milky Way.

[26]  arXiv:1803.06652 [pdf, other]
Title: Hesperos: A geophysical mission to Venus
Comments: The article was submitted to Advances in Space Research in November 2016. It was accepted with major revisions. Due to unavailability of the team after the end of the project, the paper wasn't fully revised and the submission was withdrawn. The current version includes most of the revisions
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The Hesperos mission proposed in this paper is a mission to Venus to investigate the interior structure and the current level of activity. The main questions to be answered with this mission are whether Venus has an internal structure and composition similar to Earth and if Venus is still tectonically active. To do so the mission will consist of two elements: an orbiter to investigate the interior and changes over longer periods of time and a balloon floating at an altitude between 40 and 60\~km to investigate the composition of the atmosphere. The mission will start with the deployment of the balloon which will operate for about 25 days. During this time the orbiter acts as a relay station for data communication with Earth. Once the balloon phase is finished the orbiter will perform surface and gravity gradient mapping over the course of 7 Venus days. This mission proposal is the result of the Alpbach Summer School and the post-Alpbach week.

[27]  arXiv:1803.06678 [pdf, ps, other]
Title: The Implications of 3D Thermal Structure on 1D Atmospheric Retrieval
Comments: 23 pages
Journal-ref: The Astrophysical Journal, 848:127 (24pp), 2017 October 20
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Using the atmospheric structure from a 3D global radiation-hydrodynamic simulation of HD 189733b and the open-source BART code, we investigate the difference between the secondary-eclipse temperature structure produced with a 3D simulation and the best-fit 1D retrieved model. Synthetic data are generated by integrating the 3D models over the Spitzer, HST, and JWST bandpasses, covering the wavelength range between 1 and 11 um. Using the data from different observing instruments, we present detailed comparisons between the temperature-pressure profiles recovered by BART and those from the 3D simulations. We calculate several averages of the 3D thermal structure and implement two temperature parameterizations to investigate different thermal profile shapes. To assess which part of the thermal structure is best constrained by the data, we generate contribution functions for both our theoretical model and each of our retrieved models. Our conclusions are strongly affected by the spectral resolution of the instruments included, their wavelength coverage, and the number of data points combined. We also see some limitations in each of the temperature parametrizations. The results show that our 1D retrieval is recovering a temperature and pressure profile that most closely matches the arithmetic average of the 3D thermal structure. When we use a higher resolution, more data points, and a parametrized temperature profile that allows more flexibility in the middle part of the atmosphere, we find a better match between the retrieved temperature and pressure profile and the arithmetic average.

[28]  arXiv:1803.06698 [pdf, ps, other]
Title: Possible interaction between baryons and dark-matter particles revealed by the first stars
Authors: Rennan Barkana (Tel Aviv University)
Comments: 26 pages, 3 figures. The version here is old, before peer review. The version published in Nature can be seen at this http URL
Journal-ref: Nature 555 (2018) 71-74
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from Lyman-alpha radiation from some of the earliest stars. By observing this 21-centimetre signal - either its sky-averaged spectrum or maps of its fluctuations, obtained using radio interferometers - we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. The recent detection of the global 21-centimetre spectrum reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3.8 standard deviations. Here we report that this absorption can be explained by the combination of radiation from the first stars and excess cooling of the cosmic gas induced by its interaction with dark matter. Our analysis indicates that the spatial fluctuations of the 21-centimetre signal at cosmic dawn could be an order of magnitude larger than previously expected and that the dark-matter particle is no heavier than several proton masses, well below the commonly predicted mass of weakly interacting massive particles. Our analysis also confirms that dark matter is highly non-relativistic and at least moderately cold, and primordial velocities predicted by models of warm dark matter are potentially detectable. These results indicate that 21-centimetre cosmology can be used as a dark-matter probe.

[29]  arXiv:1803.06703 [pdf, other]
Title: The X-ray modulation of PSR J2032+4127/MT91 213 during the Periastron Passage in 2017
Comments: 6 pages, including 2 figures. Accepted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present the Neil Gehrels Swift Observatory (Swift), Fermi Large Area Telescope (Fermi-LAT), and Karl G. Jansky Very Large Array (VLA) observations of the gamma-ray binary PSR J2032+4127/MT91 213, of which the periastron passage has just occurred in November 2017. In the Swift X-ray light curve, the flux was steadily increasing before mid-October 2017, however, a sharp X-ray dip on a weekly time-scale is seen during the periastron passage, followed by a post-periastron X-ray flare lasting for ~20 days. We suggest that the X-ray dip is caused by (i) an increase of the magnetization parameter at the shock, and (ii) the suppression due to the Doppler boosting effect. The 20-day post-periastron flare could be a consequence of the Be stellar disk passage by the pulsar. An orbital GeV modulation is also expected in our model, however, no significant variability is seen in the Fermi-LAT light curve. We suspect that the GeV emission resulted from the interaction between the binary's members is hidden behind the bright magnetospheric emission of the pulsar. Pulsar gating technique would be useful to remove the magnetospheric emission and recover the predicted GeV modulation, if an accurate radio timing solution over the periastron passage is provided in the future.

[30]  arXiv:1803.06704 [pdf, other]
Title: Dynamical Evolution of Planetary Systems
Comments: Review to appear as a chapter in the "Handbook of Exoplanets", ed. H. Deeg & J.A. Belmonte
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Planetary systems can evolve dynamically even after the full growth of the planets themselves. There is actually circumstantial evidence that most planetary systems become unstable after the disappearance of gas from the protoplanetary disk. These instabilities can be due to the original system being too crowded and too closely packed or to external perturbations such as tides, planetesimal scattering, or torques from distant stellar companions. The Solar System was not exceptional in this sense. In its inner part, a crowded system of planetary embryos became unstable, leading to a series of mutual impacts that built the terrestrial planets on a timescale of ~100 My. In its outer part, the giant planets became temporarily unstable and their orbital configuration expanded under the effect of mutual encounters. A planet might have been ejected in this phase. Thus, the orbital distributions of planetary systems that we observe today, both solar and extrasolar ones, can be different from the those emerging from the formation process and it is important to consider possible long-term evolutionary effects to connect the two.

[31]  arXiv:1803.06708 [pdf]
Title: Accretion Processes
Comments: Review to appear as a chapter in the "Oxford Encyclopedia"
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

In planetary science, accretion is the process in which solids agglomerate to form larger and larger objects and eventually planets are produced. The initial conditions are a disc of gas and microscopic solid particles, with a total mass of about 1% of the gas mass. Accretion has to be effective and fast. Effective, because the original total mass in solids in the solar protoplanetary disk was probably of the order of ~ 300 Earth masses, and the mass incorporated into the planets is ~100 Earth masses. Fast, because the cores of the giant planets had to grow to tens of Earth masses in order to capture massive doses of hydrogen and helium from the disc before the dispersal of the latter, i.e. in a few millions of years. There is probably not one accretion process but several, depending on the scale at which accretion operates. A first process is the sticking of microscopic dust into larger grains and pebbles. A second process is the formation of an intermediate class of objects called planetesimals. A third accretion process has to lead from planetesimals to planets. Actually, several processes can be involved in this step, from collisional coagulation among planetesimals to the accretion of small particles under the effect of gas drag, to giant impacts between protoplanets. This chapter will detail all these processes, adopting a historical perspective: i.e. from the classic processes investigated in the past decades to those unveiled in the last years.

[32]  arXiv:1803.06776 [pdf, other]
Title: A Decade of MWC 758 Disk Images: Where Are the Spiral-Arm-Driving Planets?
Comments: 9 pages, 4 figures, Accepted by ApJ Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Large-scale spiral arms have been revealed in scattered light images of a few protoplanetary disks. Theoretical models suggest that such arms may be driven by and co-rotate with giant planets, which has called for remarkable observational efforts to look for them. By examining the rotation of the spiral arms for the MWC 758 system over a 10-yr timescale, we are able to provide dynamical constraints on the locations of their perturbers. We present reprocessed {\it Hubble Space Telescope} ({\it HST})/NICMOS F110W observations of the target in 2005, and the new {\it Keck}/NIRC2 $L'$-band observations in 2017. MWC~758's two well-known spiral arms are revealed in the NICMOS archive at the earliest observational epoch. With additional {\it Very Large Telescope} ({\it VLT})/SPHERE data, our joint analysis leads to a pattern speed of ${0.6^\circ}^{+3.3^\circ}_{-0.6^\circ}\, \mathrm{yr}^{-1}$ at $3\sigma$ for the two major spiral arms. If the two arms are induced by a perturber on a near-circular orbit, its best fit orbit is at $89$ au ($0.59''$), with a $3\sigma$ lower limit of 30 au ($0.20''$). This finding is consistent with the simulation prediction of the location of an arm-driving planet for the two major arms in the system.

[33]  arXiv:1803.06781 [pdf]
Title: Orbital Stability Close to Asteroid 624 Hektor using the Polyhedral Model
Comments: 35 pages, 8 figures, Advance in Space Research 2018
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid s mass center when the density increases, and the inner equilibrium point moves close to the asteroid s mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary s equatorial plane of this binary Trojan asteroid, the results indicate that the orbit remains stable after 28.8375 d.

[34]  arXiv:1803.06787 [pdf, ps, other]
Title: Depletion of heavy nitrogen in the cold gas of star-forming regions
Comments: 12 pages, 5 figures, 1 table, Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP)

We investigate nitrogen isotope fractionation in forming and evolving molecular clouds using gas-ice astrochemical simulations. We find that the bulk gas can become depleted in heavy nitrogen (15N) due to the formation of 15N-enriched ices. Around the chemical transition from atomic nitrogen to N2, N15N is selectively photodissociated, which results in the enrichment of 15N in atomic nitrogen. As 15N-enriched atomic nitrogen is converted to ammonia ice via grain surface reactions, the bulk gas is depleted in 15N. The level of 15N depletion in the bulk gas can be up to a factor of two compared to the elemental nitrogen isotope ratio, depending on the photodesorption yield of ammonia ice. Once the nitrogen isotopes are differentially partitioned between gas and solids in a molecular cloud, it should remain in the later stages of star formation (e.g., prestellar core) as long as the sublimation of ammonia ice is inefficient. Our model suggests that all the N-bearing molecules in the cold gas of star-forming regions can be depleted in 15N, which is at least qualitatively consistent with the observations toward prestellar core L1544. In our models, icy species show both 15N and deuterium fractionation. The fractionation pattern within ice mantles is different between 15N and deuterium, reflecting their fractionation mechanisms; while the concentration of deuterium almost monotonically increases from the lower layers of the ice mantles to the upper layers, the concentration of 15N reaches the maximum at a certain depth and declines towards the surface.

[35]  arXiv:1803.06792 [pdf, other]
Title: Zenith angle distribution of cosmic ray showers measured with the Yakutsk array and its application to analysis of arrival directions in equatorial coordinates
Authors: A.A. Ivanov
Comments: 9 pages, 9 figures, 3 tables, submitted to PRD
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The Yakutsk array dataset in the energy interval $(10^{17},10^{19})$ eV is revisited in order to interpret the zenith angle distribution of an extensive air shower event rate of ultra-high energy cosmic rays. The close relation of the distribution to the attenuation of the main measurable parameter of showers, $S_{600}$, is examined. Measured and expected distributions are used to analyze the arrival directions of cosmic rays on an equatorial map including the energy range below $10^{18}$ eV, which was previously avoided due to the reduced trigger efficiency of the array in the range. While the null hypothesis cannot be rejected with data from the Yakutsk array, an upper limit on the fraction of cosmic rays from a separable source in the uniform background is derived as a function of declination and energy.

[36]  arXiv:1803.06830 [pdf, ps, other]
Title: IRAS 22150+6109 - a young B-type star with a large disc
Comments: 7 pages, 7 figures, accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We present the results of a spectroscopic analysis and spectral energy distribution (SED) modelling of the optical counterpart of the infrared source IRAS 22150+6109. The source was suggested to be as a Herbig Be star located in the star forming region L 1188. Absorption lines in the optical spectrum indicate a spectral type B3, while weak Balmer emission lines reflect the presence of a circumstellar gaseous disc. The star shows no excess radiation in the near-infrared spectral region and a strong excess in the far-infrared that we interpret as radiation from a large disc, whose inner edge is located very far from the star (550 au) and does not attenuate its radiation. We conclude that IRAS 22150+6109 is an intermediate-mass star that is currently undergoing a short pre-main-sequence evolutionary stage.

[37]  arXiv:1803.06848 [pdf]
Title: Period Increase and Amplitude Distribution of Kink Oscillation of Coronal Loop
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Coronal loops exist ubiquitously in the solar atmosphere. These loops puzzle astronomers over half a century. Solar magneto-seismology (SMS) provides a unique way to constrain the physical parameters of coronal loops. Here, we study the evolution of oscillations of a coronal loop observed by the Atmospheric Imaging Assembly (AIA). We measure geometric and physical parameters of the loop oscillations. In particular, we find that the mean period of the oscillations increased from 1048 to 1264 s during three oscillatory cycles. We employ the differential emission measure method and apply the tools of SMS. The evolution of densities inside and outside the loop is analyzed. We found that an increase of density inside the loop and decrease of the magnetic field strength along the loop are the main reasons for the increase in the period during the oscillations. Besides, we also found that the amplitude profile of the loop is different from a profile would it be a homogeneous loop. It is proposed that the distribution of magnetic strength along the loop rather than density stratification is responsible for this deviation. The variation in period and distribution of amplitude provide, in terms of SMS, a new and unprecedented insight into coronal loop diagnostics.

[38]  arXiv:1803.06851 [pdf, ps, other]
Title: Cosmological Tests With Strong Gravitational Lenses using Gaussian Processes
Comments: 8 pages, 12 figures, 6 tables. Accepted for publication in the European Physical Journal C
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

Strong gravitational lenses provide source/lens distance ratios D_obs useful in cosmological tests. Previously, a catalog of 69 such systems was used in a one-on-one comparison between the standard model, LCDM, and the R_h=ct universe, which has thus far been favored by the application of model selection tools to many other kinds of data. But in that work, the use of model parametric fits to the observations could not easily distinguish between these two cosmologies, in part due to the limited measurement precision. Here, we instead use recently developed methods based on Gaussian Processes (GP), in which D_obs may be reconstructed directly from the data without assuming any parametric form. This approach not only smooths out the reconstructed function representing the data, but also reduces the size of the 1-sigma confidence regions, thereby providing greater power to discern between different models. With the current sample size, we show that analyzing strong lenses with a GP approach can definitely improve the model comparisons, producing probability differences in the range ~10-30%. These results are still marginal, however, given the relatively small sample. Nonetheless, we conclude that the probability of R_h=ct being the correct cosmology is somewhat higher than that of LCDM, with a degree of significance that grows with the number of sources in the subsamples we consider. Future surveys will significantly grow the catalog of strong lenses and will therefore benefit considerably from the GP method we describe here. In addition, we point out that if the R_h=ct universe is eventually shown to be the correct cosmology, the lack of free parameters in the study of strong lenses should provide a remarkably powerful tool for uncovering the mass structure in lensing galaxies.

[39]  arXiv:1803.06853 [pdf, other]
Title: A turnover in the radio lightcurve of GW170817
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present 2--9~GHz radio observations of \object{GW170817} covering the period 125--200 days post-merger, taken with the Australia Telescope Compact Array and the Karl G. Jansky Very Large Array. We see no evidence for evolution in the radio-only spectral index, which remains consistent with optically-thin synchrotron emission connecting the radio, optical, and X-ray regimes. Our observations demonstrate that the radio afterglow peaked at $149\pm2$ days post-merger and is now declining in flux density. The peak implies a total energy in the synchrotron-emitting component of a ${\rm few}\times 10^{50}$ erg. The temporal decay rate is most consistent with mildly- or non-relativistic material and we do not see evidence for a very energetic off-axis jet, but we cannot distinguish between a lower-energy jet and more isotropic emission.

[40]  arXiv:1803.06855 [pdf]
Title: Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar
Comments: 12 pages, 5 figures, published in Science Advances
Journal-ref: 2018, Science Advances, 4, eaao7228
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.

[41]  arXiv:1803.06862 [pdf, other]
Title: Reconstruction of cosmic ray air showers with Tunka-Rex using template fitting
Comments: to be submitted in PRD
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

We present an improved method for the precise reconstruction of cosmic ray air showers above $10^{17}$ eV with sparse radio arrays. The method is based on the comparison of predictions for radio pulse shapes by CoREAS simulations to measured pulses. We applied our method to the data of Tunka-Rex, a 1 km$^2$ radio array in Siberia operating in the frequency band of 30-80 MHz. Tunka-Rex is triggered by the air-Cherenkov detector Tunka-133 and by scintillators (Tunka-Grande). The instrument collects air-shower data since 2012. The present paper describes updated data and signal analyses of Tunka-Rex and details of a new method applied. After efficiency cuts, when Tunka-Rex reaches its full efficiency, the energy resolution of about 10% given by the new method has reached the limit of systematic uncertainties due to the calibration uncertainty and shower-to-shower fluctuations. At the same time the shower maximum reconstruction is significantly improved up to an accuracy of 35 g/cm$^2$ compared to the previous method based on the slope of the lateral distribution. We also define and now achieved conditions of the measurements, at which the shower maximum resolution of Tunka-Rex reaches a value of 25 g/cm$^2$ and becomes competitive to optical detectors. To check and validate our reconstruction and efficiency cuts we compare individual events to the reconstruction of Tunka-133. Furthermore, we compare the mean of shower maximum as a function of primary energy to the measurements of other experiments.

[42]  arXiv:1803.06877 [pdf, other]
Title: The mm-wave compact component of AGN
Authors: Ehud Behar (1), Stuart Vogel (2), Ranieri D. Baldi (3), Krista L. Smith (4), Richard F. Mushotzky (2) ((1), Technion, (2) University of Maryland, (3) University of Southampton, (4) Stanford University)
Comments: submitted to MNRAS, revised by the referee, comments welcome (9 pages, 4 figures)
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

mm-wave emission from Active Galactic Nuclei (AGN) may hold the key to understanding the physical origin of their radio cores. The correlation between radio/mm and X-ray luminosity may suggest a similar physical origin of the two sources. Since synchrotron self absorption decreases with frequency, mm-waves probe smaller length scales than cm-waves. We report on 100 GHz (3 mm) observations with CARMA of 26 AGNs selected from the hard X-ray Swift/BAT survey. 20/26 targets were detected at 100 GHz down to the 1 mJy (3 $\sigma$) sensitivity, which corresponds to optically thick synchrotron source sizes of 10$^{-4}$ - 10$^{-3}$ pc). Most sources show a 100 GHz flux excess with respect to the spectral slope extrapolated from low frequencies. This mm spectral component likely originates from smaller scales than the few-GHz emission. The measured mm sources lie roughly around the L$_{mm}$ (100 GHz) $\sim$ 10$^{-1}$ L$_{X}$ (2-10 keV) relation, similar to a few previously published X-ray selected sources, and hinting perhaps at a common coronal origin.

[43]  arXiv:1803.06888 [pdf, other]
Title: Gamma-Ray Observations of Nova Sgr 2015 No. 2 with INTEGRAL
Comments: 11 pages, 7 figures, 1 table, accepted by A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

INTEGRAL observed the nova V5668 Sgr around the time of its optical maximum on March 21, 2015. Studies at UV wavelengths showed spectral lines of freshly produced Be-7. This could be measurable also in gamma-rays at 478 keV from the decay to Li-7. Novae are also expected to synthesise Na-22 which decays to Ne-22, emitting a 1275 keV photon. About one week before the optical maximum, a strong gamma-ray flash on time-scales of hours is expected from short-lived radioactive nuclei, such as N-13 and F-18. These beta-plus-unstable nuclei should yield emission up to 511 keV, but which has never been observed. The spectrometer SPI aboard INTEGRAL pointed towards V5668 by chance. We use these observations to search for possible gamma-ray emission of decaying Be-7, and to directly measure the synthesised mass during explosive burning. We also aim to constrain possible burst-like emission days to weeks before the optical maximum using the SPI anticoincidence shield (ACS). We extract spectral and temporal information to determine the fluxes of gamma-ray lines at 478 keV, 511 keV, and 1275 keV. A measured flux value directly converts into abundances produced by the nova. The SPI-ACS rates are analysed for burst-like emission using a nova model light-curve. For the obtained nova flash candidate events, we discuss possible origins. No significant excess for the expected gamma-ray lines is found. Our upper limits on the synthesised Be-7 and Na-22 mass depend on the uncertainties of the distance to the nova: The Be-7 mass is constrained to less than $4.8\times10^{-9}\,(d/kpc)^2$, and Na-22 to less than $2.4\times10^{-8}\,(d/kpc)^2$ solar masses. For the Be-7 mass estimate from UV studies, the distance to V5668 Sgr must be larger than 1.2 kpc. During three weeks before the optical maximum, we find 23 burst-like events in the ACS rate, of which six could possibly be associated with V5668 Sgr.

[44]  arXiv:1803.06890 [pdf, other]
Title: Frequency and mode identification of γ Doradus from photometric and spectroscopic observations
Comments: Accepted for Publication in Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 3, p.3813-3822
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The prototype star for the {\gamma} Doradus class of pulsating variables was studied em- ploying photometric and spectroscopic observations to determine the frequencies and modes of pulsation. The four frequencies found were self-consistent between the obser- vation types and almost identical to those found in previous studies (1.3641 d-1 ,1.8783 d-1 , 1.4742 d-1 and 1.3209 d-1). Three of the frequencies are classified as l, m = (1, 1) pulsations and the other is ambiguous between l = 2 modes. Two frequencies are shown to be stable over twenty years since their first identification. The agreement in ground-based work makes this star an excellent calibrator for the upcoming TESS observations and a standard for continued asteroseismic modelling.

[45]  arXiv:1803.06891 [pdf, other]
Title: Correlations between X-ray properties and Black Hole Mass in AGN: towards a new method to estimate black hole mass from short exposure X-ray observations
Comments: 19 pages, 20 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

Several investigations of the X-ray variability of active galactic nuclei (AGN) using the normalised excess variance (${\sigma^2_{\rm NXS}}$) parameter have shown that variability has a strong anti-correlation with black hole mass ($M_{\rm BH}$) and X-ray luminosity ($L_{\rm X}$). In this study we confirm these previous correlations and find no evidence of a redshift evolution. Using observations from XMM-Newton, we determine the ${\sigma^2_{\rm NXS}}$ and $L_{\rm X}$ for a sample of 1091 AGN drawn from the XMM-Newton Cluster Survey (XCS) - making this the largest study of X-ray spectral properties of AGNs. We created light-curves in three time-scales; 10 ks, 20 ks and 40 ks and used these to derive scaling relations between ${\sigma^2_{\rm NXS}}$, $L_{\rm X}$ (2.0-10 keV range) and literature estimates of $M_{\rm BH}$ from reverberation mapping. We confirm the anti-correlation between $M_{\rm BH}$ and ${\sigma^2_{\rm NXS}}$ and find a positive correlation between $M_{\rm BH}$ and $L_{\rm X}$. The use of ${\sigma^2_{\rm NXS}}$ is practical only for pointed observations where the observation time is tens of kiloseconds. For much shorter observations one cannot accurately quantify variability to estimate $M_{\rm BH}$. Here we describe a method to derive $L_{\rm X}$ from short duration observations and used these results as an estimate for $M_{\rm BH}$. We find that it is possible to estimate $L_{\rm X}$ from observations of just a few hundred seconds and that when correlated with $M_{\rm BH}$, the relation is statistically similar to the relation of $M_{\rm BH}$-$L_{\rm X}$ derived from a spectroscopic analysis of full XMM observations. This method may be particularly useful to the eROSITA mission, an all-sky survey, which will detect $>$10$^{6}$ AGN.

[46]  arXiv:1803.06896 [pdf]
Title: Prehistory of Transit Searches
Authors: Danielle Briot (Paris Observatory), Jean Schneider (Paris Obsevatory)
Comments: Submiited to Handbook of Exoplanets (Springer)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Nowadays the more powerful method to detect extrasolar planets is the transit method. We review the planet transits which were anticipated, searched, and the first ones which were observed all through history. Indeed transits of planets in front of their star were first investigated and studied in the solar system. The first observations of sunspots were sometimes mistaken for transits of unknown planets. The first scientific observation and study of a transit in the solar system was the observation of Mercury transit by Pierre Gassendi in 1631. Because observations of Venus transits could give a way to determine the distance Sun-Earth, transits of Venus were overwhelmingly observed. Some objects which actually do not exist were searched by their hypothetical transits on the Sun, as some examples a Venus satellite and an infra-mercurial planet. We evoke the possibly first use of the hypothesis of an exoplanet transit to explain some periodic variations of the luminosity of a star, namely the star Algol, during the eighteen century. Then we review the predictions of detection of exoplanets by their transits, those predictions being sometimes ancient, and made by astronomers as well as popular science writers. However, these very interesting predictions were never published in peer-reviewed journals specialized in astronomical discoveries and results. A possible transit of the planet beta Pic b was observed in 1981. Shall we see another transit expected for the same planet during 2018? Today, some studies of transits which are connected to hypothetical extraterrestrial civilisations are published in astronomical refereed journals. Some studies which would be classified not long ago as science fiction are now considered as scientific ones.

[47]  arXiv:1803.06910 [pdf, other]
Title: Exploring neutrino mass and mass hierarchy in the scenario of vacuum energy interacting with cold dark matter
Comments: 11 pages, 4 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

We investigate the constraints on the total neutrino mass in the scenario of vacuum energy interacting with cold dark matter. We focus on two typical interaction forms, i.e., $Q=\beta H\rho_{\rm c}$ and $Q=\beta H\rho_{\Lambda}$. To avoid the occurrence of large-scale instability in interacting dark energy cosmology, we adopt the parameterized post-Friedmann approach to calculate the perturbation evolution of dark energy. We employ the observational data including the Planck cosmic microwave background temperature and polarization data, the baryon acoustic oscillation data, the JLA sample of type Ia supernovae observation, the direct measurement of the Hubble constant, and the redshift space distortions data. We find that, compared with those in the $\Lambda$CDM model, much looser constraints on $\sum m_{\nu}$ are obtained in the $Q=\beta H\rho_{\rm c}$ model, while slightly tighter constraints are obtained in the $Q=\beta H\rho_{\Lambda}$ model. After considering the mass hierarchies of neutrinos, the smallest upper limit results of $\sum m_{\nu}$ are given in the degenerate hierarchy case. By comparing the values of $\chi^2_{\rm min}$, we find that the normal hierarchy case is more favored than the inverted one. In particular, we find that the difference $\Delta \chi^2_{\rm min} \equiv \chi^2_{\rm IH; min}-\chi^2_{\rm NH; min}> 2$ in the $Q=\beta H\rho_{\rm c}$ model. In addition, we find that $\beta=0$ is consistent with the current observations in the $Q=\beta H\rho_{\rm c}$ model, and $\beta < 0$ is favored at the more than $1\sigma$ level in the $Q=\beta H\rho_{\Lambda}$ model.

[48]  arXiv:1803.06927 [pdf, ps, other]
Title: Ultra Diffuse Galaxies are a Subset of Cluster Dwarf Elliptical/Spheroidal Galaxies
Comments: Accepted for publication the Research Notes of the AAS (RNAAS)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Since 2015 there has been a great deal of interest in a supposed new class of galaxy called Ultra Diffuse Galaxies (UDGs). These are large systems with sizes $> 1.5$ kpc and have surface brightness values which are $\mu > 25$ mag arcsec$^{-2}$. Because of their low-surface brightness they are proposed to be `failed' Milky Way type galaxies given their similar size, but much lower stellar masses. As such, these systems are considered by some as a new type of galaxy, yet we show that they are a subset of a well-established and well studied population of low-surface brightness galaxies found mostly in dense areas of the universe - clusters of galaxies. We argue based on previous literature that the most likely method for forming these galaxies is through cluster processes such as `Galaxy Harassment', where through multiple high speed encounters an infalling galaxy is gradually removed of its mass, until it resembles a dwarf elliptical. Future studies of UDGs should consider the above and their more general connection to previously studied populations.

[49]  arXiv:1803.06944 [pdf, ps, other]
Title: Interacting Dark Energy: Possible Explanation for 21-cm Absorption at Cosmic Dawn
Comments: 4 pages, 2 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

A recent observation points to an excess in the expected 21-cm brightness temperature from cosmic dawn. In this paper, we present an alternative explanation of this phenomenon, an interaction in the dark sector. Interacting dark energy models have been extensively studied recently and there is a whole variety of such in the literature. Here we particularize to a specific model in order to make explicit the effect of an interaction.

[50]  arXiv:1803.06995 [pdf, other]
Title: Combined dynamical effects of the bar and spiral arms in a Galaxy model. Application to the solar neighbourhood
Comments: 17 pages, 16 figures. Submitted to A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Observational data indicate that the Milky Way is a barred spiral galaxy. Computation facilities and availability of data from Galactic surveys stimulate the appearance of models of the Galactic structure. More efforts to build dynamical models containing both spiral arms and the central bar/bulge are needed.
We expand the study of the stellar dynamics in the Galaxy by adding the bar/bulge component to a model with spiral arms introduced in our previous paper. The model is tested by applying it to the solar neighborhood, where observational data are more precise.
We model analytically the potential of the Galaxy to derive the force field in its equatorial plane. The model comprises an axisymmetric disc derived from the observable rotation curve, four arms with Gaussian-shaped groove profiles, and a classical elongated/oblate ellipsoidal bar/bulge structure. The parameters describing the bar/bulge are constrained by observations and the stellar dynamics, and their possible limits are determined.
A basic model of the bar results in length 2.9 kpc and mass with order of a few 10$^9M_\odot$. The size and orientation of the bar are also restricted by the position of masers with VLBI distances. The bar's rotation speed is constrained to $\Omega_{\rm bar}<50$ km s$^{-1}$ kpc$^{-1}$ taking into account the allowed mass range.
We conclude that our basic model is compatible with observations and with the dynamical constraints. The model explains simultaneously the bulk of the main moving groups, associated here with the spiral corotation resonance, and the Hercules stream, associated with the inner spiral 8/1 resonance. From the dynamical constraints on the bar's angular speed, it is unlikely that the bar's OLR lies near the solar circle, since it would compromise the stability of the Local Arm structure.

[51]  arXiv:1803.07006 [pdf, other]
Title: Observations of one young and three middle-aged $γ$-ray pulsars with the Gran Telescopio Canarias
Authors: R. P. Mignani (INAF/IASF - Milan, Janusz Gil Institute of Astronomy), V. Testa (INAF/OAR), N. Rea (ICE, CSIC, Anton Pannekoek Institute for Astronomy, IEEC), M. Marelli, D. Salvetti (INAF/IASF Milan), D. Torres (ICE, CSIC, IEEC, ICREA), E. de Ona Wilhelmi (ICE, CSIC, IEEC)
Comments: 10 pages, 11 figures, submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We used the 10.4m Gran Telescopio Canarias to search for the optical counterparts to four isolated $\gamma$-ray pulsars, all detected in the X-rays by either \xmm\ or \chan\ but not yet in the optical. Three of them are middle-aged pulsars -- PSR\, J1846+0919 (0.36 Myr), PSR\, J2055+2539 (1.2 Myr), PSR\, J2043+2740 (1.2 Myr) -- and one, PSR\, J1907+0602, is a young pulsar (19.5 kyr). For both PSR\, J1907+0602 and PSR\, J2055+2539 we found one object close to the pulsar position. However, in both cases such an object cannot be a viable candidate counterpart to the pulsar. For PSR\, J1907+0602, because it would imply an anomalously red spectrum for the pulsar and for PSR\, J2055+2539 because the pulsar would be unrealistically bright ($r'=20.34\pm0.04$) for the assumed distance and interstellar extinction. For PSR\, J1846+0919, we found no object sufficiently close to the expected position to claim a possible association, whereas for PSR\, J2043+2740 we confirm our previous findings that the object nearest to the pulsar position is an unrelated field star. We used our brightness limits ($g' \approx 27$), the first obtained with a large-aperture telescope for both PSR\, J1846+0919 and PSR\, J2055+2539, to constrain the optical emission properties of these pulsars and investigate the presence of spectral turnovers at low energies in their multi-wavelength spectra.

[52]  arXiv:1803.07008 [pdf, other]
Title: Asymmetric Ejecta of Cool Supergiants and Hypergiants in the Massive Cluster Westerlund 1
Comments: 5 pages, 2 figures, Acccepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We report new 5.5 GHz radio observations of the massive star cluster Westerlund 1, taken by the Australia Telescope Compact Array, detecting nine of the ten yellow hypergiants (YHGs) and red supergiants (RSGs) within the cluster. Eight of nine sources are spatially resolved. The nebulae associated with the YHGs Wd1-4a, -12a and -265 demonstrate a cometary morphology - the first time this phenomenon has been observed for such stars. This structure is also echoed in the ejecta of the RSGs Wd1-20 and -26; in each case the cometary tails are directed away from the cluster core. The nebular emission around the RSG Wd1-237 is less collimated than these systems but once again appears more prominent in the hemisphere facing the cluster. Considered as a whole, the nebular morphologies provide compelling evidence for sculpting via a physical agent associated with Westerlund 1, such as a cluster wind.

[53]  arXiv:1803.07022 [pdf, other]
Title: The Feasibility and Benefits of In Situ Exploration of `Oumuamua-like objects
Comments: Accepted to AJ, 13 pages, 8 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

A rapid accumulation of observations and interpretation have followed in the wake of 1I `Oumuamua's passage through the inner Solar System. We briefly outline the consequences that this first detection of an interstellar asteroid implies for the planet-forming process, and we assess the near-term prospects for detecting and observing (both remotely and in situ) future Solar System visitors of this type. Drawing on detailed heat-transfer calculations that take both `Oumuamua's unusual shape and its chaotic tumbling into account, we affirm that the lack of a detectable coma in deep images of the object very likely arises from the presence of a radiation-modified coating of high molecular weight material (rather than a refractory bulk composition). Assuming that `Oumuamua is a typical representative of a larger population with a kinematic distribution similar to Population I stars in the local galactic neighborhood, we calculate expected arrival rates, impact parameters and velocities of similar objects and assess their prospects for detection using operational and forthcoming facilities. Using `Oumuamua as a proof-of-concept, we assess the prospects for missions that intercept interstellar objects (ISOs) using conventional chemical propulsion. Using a "launch on detection" paradigm, we estimate wait times of order 10 years between favorable mission opportunities with the detection capabilities of the Large-Scale Synoptic Survey Telescope (LSST), a figure that will be refined as the population of interstellar asteroids becomes observationally better constrained.

[54]  arXiv:1803.07035 [pdf, other]
Title: Prandtl-Number Effects in High-Rayleigh-Number Spherical Convection
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Fluid Dynamics (physics.flu-dyn)

Convection is the predominant mechanism by which energy and angular momentum are transported in the outer portion of the Sun. The resulting overturning motions are also the primary energy source for the solar magnetic field. An accurate solar dynamo model therefore requires a complete description of the convective motions, but these motions remain poorly understood. Studying stellar convection numerically remains challenging; it occurs within a parameter regime that is extreme by computational standards. The fluid properties of the convection zone are characterized in part by the Prandtl number $\mathrm{Pr}=\nu/\kappa$, where $\nu$ is the kinematic viscosity and $\kappa$ is the thermal diffusion; in stars, $\mathrm{Pr}$ is extremely low, $\mathrm{Pr}\approx 10^{-7}$. The influence of $\mathrm{Pr}$ on the convective motions at the heart of the dynamo is not well understood since most numerical studies are limited to using $\mathrm{Pr}\approx1$. We systematically vary $\mathrm{Pr}$ and the degree of thermal forcing, characterized through a Rayleigh number, to explore its influence on the convective dynamics. For sufficiently large thermal driving, the simulations reach a so-called convective free-fall state where diffusion no longer plays an important role in the interior dynamics. Simulations with a lower $\mathrm{Pr}$ generate faster convective flows and broader ranges of scales for equivalent levels of thermal forcing. Characteristics of the spectral distribution of the velocity remain largely insensitive to changes in $\mathrm{Pr}$. Importantly, we find that $\mathrm{Pr}$ plays a key role in determining when the free-fall regime is reached by controlling the thickness of the thermal boundary layer.

[55]  arXiv:1803.07036 [pdf, other]
Title: Characterizing the Epoch of Reionization with the small-scale CMB: constraints on the optical depth and physical parameters
Comments: 8 pages, 3 figures. Comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Patchy reionization leaves a number of imprints on the small-scale cosmic microwave background (CMB) temperature fluctuations, the largest of which is the kinematic Sunyaev-Zel'dovich (kSZ), the Doppler shift of CMB photons scattering off moving electrons in ionized bubbles. It has long been known that in the CMB power spectrum, this imprint of reionization is largely degenerate with the kSZ signal produced by late-time galaxies and clusters, thus limiting our ability to constrain reionization. Following Smith & Ferraro (2017), it is possible to isolate the reionization contribution in a model independent way, by looking at the large scale modulation of the small scale CMB power spectrum. In this paper we extend the formalism to use the full shape information of the small scale power spectrum (rather than just its broadband average), and argue that this is necessary to break the degeneracy between the optical depth $\tau$ and parameters setting the duration of reionization. In particular, we show that the next generation of CMB experiments could achieve up to a factor of 3 improvement on the optical depth $\tau$ and at the same time, constrain the duration of reionization to $\sim$ 25 %. This can help tighten the constrains on neutrino masses, which will be limited by our knowledge of $\tau$, and shed light on the physical processes responsible for reionization.

[56]  arXiv:1803.07040 [pdf, ps, other]
Title: Habitability from Tidally-Induced Tectonics
Comments: 14 pages, 10 figures, Accepted in Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The stability of Earth's climate on geological timescales is enabled by the carbon-silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and outgas of atmospheric carbon. On Earth, this thermostat is enabled by plate tectonics that sequesters outgassed CO2 back into the mantle via weathering and subduction at convergent margins. Here we propose a separate tectonic mechanism -- vertical recycling -- that can serve as the vehicle for CO2 outgassing and sequestration over long timescales. The mechanism requires continuous tidal heating, which makes it particularly relevant to planets in the habitable zone of M stars. Dynamical models of this vertical recycling scenario and stability analysis show that temperate climates stable over Gy timescales are realized for a variety of initial conditions, even as the M star dims over time. The magnitude of equilibrium surface temperatures depends on the interplay of sea weathering and outgassing, which in turn depends on planetary carbon content, so that planets with lower carbon budgets are favoured for temperate conditions. Habitability of planets such as found in the Trappist-1 may be rooted in tidally-driven tectonics.

[57]  arXiv:1803.07051 [pdf, ps, other]
Title: Stripped-envelope supernova SN 2004dk is now interacting with hydrogen-rich circumstellar material
Comments: Submitted to MNRAS on 2018 March 16; 6 pages, 5 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

The dominant mechanism and time scales over which stripped-envelope supernovae (SNe) progenitor stars shed their hydrogen envelopes are uncertain. Observations of Type Ib and Ic SNe at late phases could reveal the optical signatures of interaction with distant circumstellar material (CSM) providing important clues on the origin of the necessary pre-SN mass loss. We report deep late-time optical spectroscopy of the Type Ib explosion SN 2004dk 4684 days (13 years) after discovery. Prominent intermediate-width H-alpha emission is detected, signaling that the SN blast wave has caught up with the hydrogen-rich CSM lost by the progenitor system. The line luminosity is the highest ever reported for a SN at this late stage. Prominent emission features of He, Fe, and Ca are also detected. The spectral characteristics are consistent with CSM energized by the forward shock, and resemble the late-time spectra of the persistently interacting Type IIn SNe 2005ip and 1988Z. We suggest that the onset of interaction with H-rich CSM was associated with a previously reported radio rebrightening at ~1700 days. The data indicate that the mode of pre-SN mass loss was a relatively slow dense wind that persisted millennia before the SN, followed by a short-lived Wolf-Rayet phase that preceded core-collapse and created a cavity within an extended distribution of CSM. We also present new spectra of SNe 2014C, PTF11iqb, and 2009ip, all of which also exhibit continued interaction with extended CSM distributions.

[58]  arXiv:1803.07052 [pdf, other]
Title: The Knee and the Second Knee of the Cosmic-Ray Energy Spectrum
Comments: 10 pages, 5 figures, submitted to Astroparticle physics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The cosmic ray flux measured by the Telescope Array Low Energy Extension (TALE) exhibits three spectral features: the knee, the dip in the $10^{16}$ eV decade, and the second knee. Here the spectrum has been measured for the first time using fluorescence telescopes, which provide a calorimetric, model-independent result. The spectrum appears to be a rigidity-dependent cutoff sequence, where the knee is made by the hydrogen and helium portions of the composition, the dip comes from the reduction in composition from helium to metals, the rise to the second knee occurs due to intermediate range nuclei, and the second knee is the iron knee.

[59]  arXiv:1803.07057 [pdf, ps, other]
Title: A radial velocity survey of the Carina Nebula's O-type stars
Comments: 20 pages, 16 figures, accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We have obtained multi-epoch observations of 31 O-type stars in the Carina Nebula using the CHIRON spectrograph on the CTIO/SMARTS 1.5-m telescope. We measure their radial velocities to 1--2 km s$^{-1}$ precision and present new or updated orbital solutions for the binary systems HD 92607, HD 93576, HDE 303312, and HDE 305536. We also compile radial velocities from the literature for 32 additional O-type and evolved massive stars in the region. The combined data set shows a mean heliocentric radial velocity of 0.6 km s$^{-1}$. We calculate a velocity dispersion of $\le9.1$ km s$^{-1}$, consistent with an unbound, substructured OB association. The Tr 14 cluster shows a marginally significant 5 km s$^{-1}$ radial velocity offset from its neighbor Tr 16, but there are otherwise no correlations between stellar position and velocity. The O-type stars in Cr 228 and the South Pillars region have a lower velocity dispersion than the region as a whole, supporting a model of distributed massive-star formation rather than migration from the central clusters. We compare our stellar velocities to the Carina Nebula's molecular gas and find that Tr 14 shows a close kinematic association with the Northern Cloud. In contrast, Tr 16 has accelerated the Southern Cloud by 10--15 km s$^{-1}$, possibly triggering further massive-star formation. The expansion of the surrounding H II region is not symmetric about the O-type stars in radial velocity space, indicating that the ionized gas is constrained by denser material on the far side.

[60]  arXiv:1803.07058 [pdf, other]
Title: Overshooting calibration and age determination from evolved binary system
Comments: Accepted for publication in A&A. Abstract shortened
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We evaluated the bias and variability on the fitted age and convective core overshooting parameter for evolved binary stars accounting for observational and internal uncertainties. We considered a binary system composed of a 2.50 $M_{\sun}$ primary star coupled with a 2.38 $M_{\sun}$ secondary in three evolutionary stages (primary at the end of the central helium burning; at the bottom of the RGB; and in the helium core burning). The simulations have been carried out for two values of accuracy on the mass determination (1% and 0.1%). We found that the fitted age and overshooting efficiency are always biased towards low values. The underestimation is relevant for a primary in the central helium burning stage, reaching -8.5% in age and -0.04 (-25% relative error) in the overshooting parameter $\beta$. In the other scenarios, an undervaluation of the age by about 4% occurs. A large variability in the fitted values between simulations was found: for an individual system calibration, the value of $\beta$ can vary from 0.0 to 0.26. For an error of 0.1% on the masses the global variability is suppressed by a factor of two. We accounted for a systematic offset in the effective temperature of the stars by $\pm 150$ K. For a mass error of 1% $\beta$ is largely biased towards the edges of the explored range, while for the lower mass uncertainty it is basically unconstrained from 0.0 to 0.2. We evaluated the possibility of individually recovering the $\beta$ value for both stars. We found that this is impossible for a primary near to central hydrogen exhaustion, while in the other cases the fitted $\beta$ are consistent, but always biased. Finally, the possibility to distinguish between models computed with mild overshooting from models with no overshooting resulted in a reassuring power of 80%. However, the scenario with a primary in the central helium burning showed a power lower than 5%.

[61]  arXiv:1803.07064 [pdf, ps, other]
Title: Far-ultraviolet Spectroscopy of Recent Comets with the Cosmic Origins Spectrograph on the Hubble Space Telescope
Authors: Paul D. Feldman (1), Harold A. Weaver (2), Michael F. A'Hearn (3), Michael R. Combi (4), Neil Dello Russo (2), ((1) JHU, (2) JHU/APL,(3) UMd, (4) UMi)
Comments: 10 pages, 6 figures, accepted for publication in the Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Since its launch in 1990, the Hubble Space Telescope (HST) has served as a platform with unique capabilities for remote observations of comets in the far-ultraviolet region of the spectrum. Successive generations of imagers and spectrographs have seen large advances in sensitivity and spectral resolution enabling observations of the diverse properties of a representative number of comets during the past 25 years. To date, four comets have been observed in the far-ultraviolet by the Cosmic Origins Spectrograph (COS), the last spectrograph to be installed in HST, in 2009: 103P/Hartley 2, C/2009 P1 (Garradd), C/2012 S1 (ISON), and C/2014 Q2 (Lovejoy). COS has unprecedented sensitivity, but limited spatial information in its 2.5 arcsec diameter circular aperture, and our objective was to determine the CO production rates from measurements of the CO Fourth Positive system in the spectral range of 1400 to 1700 A. In the two brightest comets, nineteen bands of this system were clearly identified. The water production rates were derived from nearly concurrent observations of the OH (0,0) band at 3085 A by the Space Telescope Imaging Spectrograph (STIS). The derived CO/H2O production rate ratio ranged from ~0.3% for Hartley 2 to ~22% for Garradd. In addition, strong partially resolved emission features due to multiplets of S I, centered at 1429 A and 1479 A, and of C I at 1561 A and 1657 A, were observed in all four comets. Weak emission from several lines of the H2 Lyman band system, excited by solar Lyman-alpha and Lyman-beta pumped fluorescence, were detected in comet Lovejoy.

Cross-lists for Tue, 20 Mar 18

[62]  arXiv:1803.06350 (cross-list from physics.flu-dyn) [pdf, other]
Title: Magnetic Prandtl number dependence of turbulence generated by chiral MHD dynamos
Comments: 18 pages, 10 figures, submitted to GAFD for the special issue "Recent Developments in Natural Dynamos"
Subjects: Fluid Dynamics (physics.flu-dyn); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph)

An asymmetry in the number density of left- and right-handed fermions is known to give rise to a new term in the induction equation that can result in a small-scale instability. This is a microphysical effect characterised by a chiral chemical potential and is mathematically similar to the alpha effect, which is a turbulent or macrophysical effect. At high temperatures, when a chiral asymmetry can survive for long enough, these chiral MHD dynamos can amplify magnetic fields efficiently, which in turn drive turbulence via the Lorentz force. While it has been demonstrated in numerical simulations that chiral magnetically driven turbulence exists and modifies the evolution of the plasma, the details of this process remain unclear. The goal of this paper is to shed new light on the properties of chiral magnetically driven turbulence using numerical simulations with the Pencil Code. We explore the generation of turbulence for different initial conditions, including a variation of the initial chiral chemical potential and the magnetic Prandtl number, Pm. In particular, we determine the ratio of kinetic to magnetic energy, Upsilon^2, that can be reached in chiral magnetically driven turbulence. Within the parameter space explored in this study, Upsilon reaches a value of approximately 0.24-0.29 - independently of the initial chiral asymmetry and for Pm=1. Our simulations suggest, that Upsilon decreases as a power law when increasing Pm. While the exact scaling depends on the details of the fitting criteria and the Reynolds number regime, an approximate result of Upsilon(Pm)=0.3*Pm^{-0.2} is reported. Using the findings from our numerical simulations, we estimate the properties of chiral magnetically driven turbulence in the early Universe.

[63]  arXiv:1803.06633 (cross-list from nucl-th) [pdf, ps, other]
Title: Constraints on the inner boundary of a neutron star crust with applications on slow rotating neutron stars
Comments: 23 pages, 7 figures, 5 tables
Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)

We systematically study the symmetry energy effects of the transition density $n_{\rm t}$ and the transition pressure $P_{\rm t}$ around the crust-core interface of a neutron star in the framework of the dynamical and the thermodynamical method respectively. We employ both the parabolic approximation and the full expansion, for the definition of the symmetry energy. We use various theoretical nuclear models, which are suitable for reproducing the bulk properties of nuclear matter at low densities, close to saturation density as well as the maximum observational neutron star mass. Firstly we derive and present an approximation for the transition pressure $P_{\rm t}$ and crustal mass $M_{\rm crust}$. Secondly, we explore the effects of the Equation of State (EoS) on a few astrophysical applications which are sensitive to the values of $n_{\rm t}$ and $P_{\rm t}$ including neutron star oscillation frequencies, thermal relaxation of the crust, crustal fraction of the moment of inertia and the r-mode instability window of a rotating neutron star. We found that the above quantities are sensitive mainly on the applied approximation for the symmetry energy (confirming previous results). Furthermore, an additional sensitivity also exists, depending on the used method (dynamical or thermodynamical). The above findings lead us to claim that the determination of the $n_{\rm t}$ and $P_{\rm t}$ must be reliable and accurate before they are used to constrain relevant neutron star properties.

[64]  arXiv:1803.06758 (cross-list from nucl-th) [pdf, ps, other]
Title: Impact of the $^7$Be($α, γ$)$^{11}$C reaction on the primordial abundance of $^7$Li
Comments: 15 pages and 2 figures
Subjects: Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Experiment (nucl-ex)

We calculate the radiative capture cross section for $^7$Be($\alpha, \gamma$)$^{11}$C and its reaction rate for the big bang nucleosynthesis. The impact of this reaction on the primordial $^7$Li abundance is revised with the assumption of a narrow resonance in the low energy region. We show that such a resonance is unlikely to emerge within a two-body potential model. Taking the existence of this resonance for granted, we show that a small shift of its energy to a location right below the previously suggested value of $E_r=270$ KeV, with a narrow width of 160 eV, can modify substantially the $^7$Li abundance and solve the cosmological lithium puzzle.

[65]  arXiv:1803.06761 (cross-list from nucl-th) [pdf, other]
Title: Hadron-Quark Combustion as a Nonlinear, Dynamical System
Comments: 8 pages, 2 figures
Journal-ref: Universe, 4(3), 51 (2018)
Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)

The hadron-quark combustion front is a system that couples various processes, such as chemical reactions, hydrodynamics, diffusion, and neutrino transport. Previous numerical work has shown that this system is very nonlinear, and can be very sensitive to some of these processes. In these proceedings, we contextualize the hadron-quark combustion as a nonlinear system, subject to dramatic feedback triggered by leptonic weak decays and neutrino transport.

[66]  arXiv:1803.06793 (cross-list from hep-ph) [pdf, ps, other]
Title: $Z^\prime$ portal dark matter in the minimal $B-L$ model
Authors: Satomi Okada
Comments: 10 pages, 5 figures, Review article to be published in Advances in High Energy Physics
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex)

In this article, we consider a dark matter scenario in the context of the minimal extension of the Standard Model (SM) with a $B-L$ (baryon number minus lepton number) gauge symmetry, where three right-handed neutrinos with a $B-L$ charge $-1$ and a $B-L$ Higgs field with a $B-L$ charge $+2$ are introduced to make the model anomaly-free and to break the $B-L$ gauge symmetry, respectively. The $B-L$ gauge symmetry breaking generates the Majorana masses for the right-handed neutrinos. We introduce a Z$_2$ symmetry to the model and assign an odd parity only for one right-handed neutrino, and hence the Z$_2$-odd right-handed neutrino is stable and the unique dark matter candidate in the model. The so-called minimal seesaw works with the other two right-handed neutrinos and reproduces the current neutrino oscillation data. We consider the case that the dark matter particle communicates with the SM particles through the $B-L$ gauge boson ($Z^{\prime}_{B-L}$ boson), and obtain a lower bound on the $B-L$ gauge coupling ($\alpha_{B-L}$) as a function of the $Z^{\prime}_{B-L}$ boson mass ($m_{Z^{\prime}}$) from the observed dark matter relic density. On the other hand, we interpret the recent LHC Run-2 results on the search for a $Z^{\prime}$ boson resonance to an upper bound on $\alpha_{B-L}$ as a function of $m_{Z^{\prime}}$. These two constraints are complementary to narrow down an allowed parameter region for this "$Z^{\prime}$ portal" dark matter scenario, leading to a lower mass bound of $m_{Z^{\prime}} \geq 3.9$ TeV.

[67]  arXiv:1803.06994 (cross-list from hep-th) [pdf, other]
Title: Inertial Symmetry Breaking
Comments: 12 pages, 1 figure, Invited talk delivered at: "The Great Solar Eclipse Conference,"Aug. 20, 2017, Columbia, MO, USA, "Collider Physics and the Cosmos," Galileo Galilei Institute, Oct. 9, 2017, Arcetri, Florence, Italy, Physics Colloquium, Departamento de Fisica Teoricam Universidad de Valencia, Oct. 18, 2017, Burjassot, Valencia, Spain, Fermilab Seminar, Winter 2017
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We review and expand upon recent work demonstrating that Weyl invariant theories can be broken "inertially," which does not depend upon a potential. This can be understood in a general way by the "current algebra" of these theories, independently of specific Lagrangians. Maintaining the exact Weyl invariance in a renormalized quantum theory can be accomplished by renormalization conditions that refer back to the VEV's of fields in the action. We illustrate the computation of a Weyl invariant Coleman-Weinberg potential that breaks a U(1) symmetry together,with scale invariance.

[68]  arXiv:1803.07048 (cross-list from hep-ph) [pdf, other]
Title: New Physics in the Rayleigh-Jeans Tail of the CMB
Comments: 6 pages, 4 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We show that despite stringent constraints on the shape of the main part of the CMB spectrum, there is considerable room for its modification within its Rayleigh-Jeans (RJ) end, $\omega \ll T_{\rm CMB}$. We construct explicit New Physics models that give an order one (or larger) increase of power in the RJ tail, which can be tested by existing and upcoming experiments aiming to detect the cosmological 21 cm emission/absorption signal. This class of models stipulates the decay of unstable particles to dark photons, $A'$, that have a small mass, $m_{A'} \sim 10^{-14} - 10^{-9}$ eV, non-vanishing mixing angle $\epsilon$ with electromagnetism, and energies much smaller than $T_{\rm CMB}$. The non-thermal number density of dark photons can be many orders of magnitude above the number density of CMB photons, and even a small probability of $A'\to A$ oscillations, going down to values of the mixing as small as $\epsilon \sim 10^{-9}$, can significantly increase the number of RJ photons. In particular, we show that resonant oscillations of dark photons into regular photons in the interval of redshifts $20 < z < 1700$ can be invoked as an explanation of the recent tentative observation of a stronger-than-expected absorption signal of 21 cm photons. We present a realistic model that realizes this possibility, where micro-eV mass dark matter decays to dark photons, with a lifetime longer than the age of the Universe.

Replacements for Tue, 20 Mar 18

[69]  arXiv:1701.02034 (replaced) [pdf, ps, other]
Title: Can black hole superradiance be induced by galactic plasmas?
Comments: 5 pages; v2. accepted version
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[70]  arXiv:1702.03905 (replaced) [pdf, ps, other]
Title: Quantum principle of sensing gravitational waves: From the zero-point fluctuations to the cosmological stochastic background of spacetime
Comments: 14 pages, 4 figures, with typo corrections
Journal-ref: Phys. Rev. D 96, 044018 (2017)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Quantum Physics (quant-ph)
[71]  arXiv:1702.04916 (replaced) [pdf, ps, other]
Title: Constraints on a generalized deceleration parameter from cosmic chronometers
Authors: Abdulla Al Mamon
Comments: 9 pages, 5 figures, minor change in title, new references added, revised version accepted for publication in MPLA
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[72]  arXiv:1703.05371 (replaced) [pdf, other]
Title: Directional Sensitivity In Light-Mass Dark Matter Searches With Single-Electron Resolution Ionization Detectors
Comments: Most recent version
Subjects: Instrumentation and Detectors (physics.ins-det); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Materials Science (cond-mat.mtrl-sci); High Energy Physics - Experiment (hep-ex); Computational Physics (physics.comp-ph)
[73]  arXiv:1704.05413 (replaced) [pdf, other]
Title: A population study of gaseous exoplanets
Comments: 14 pages, 12 figures, 3 tables, published in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[74]  arXiv:1706.01246 (replaced) [pdf, other]
[75]  arXiv:1707.04001 (replaced) [pdf, other]
Title: Updating the (Supermassive Black Hole Mass) - (Spiral Arm Pitch Angle) Relation: A Strong Correlation for Galaxies with Pseudobulges
Comments: 18 pages, 9 figures, and 4 tables. Accepted July 13. Received 2017 July 13; in original form 2017 May 24
Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 471, Issue 2, 21 October 2017, Pages 2187-2203
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[76]  arXiv:1707.04262 (replaced) [pdf, other]
Title: MASCARA-1 b: A hot Jupiter transiting a bright $m_V=8.3$ A-star in a misaligned orbit
Comments: 7 pages, 5 figures, Published in A&A. A typo in the value of the spectroscopic impact parameter was corrected
Journal-ref: A&A 606, A73 (2017)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[77]  arXiv:1707.07681 (replaced) [pdf, ps, other]
Title: The flat-spectrum radio quasar 3C 345 from the high to the low emission state
Comments: 14 pages, 14 figures, 4 tables, accepted for publication in Astronomy & Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[78]  arXiv:1708.00204 (replaced) [pdf, ps, other]
Title: The extended Einstein-Maxwell-aether-axion model: Exact solutions for axionically controlled pp-wave aether modes
Comments: 8 pages, 0 figures. Replaced by the revised version published in Modern Physics Letters A; Introduction is extended, Remark, additional explanations and references are added
Journal-ref: Modern Physics Letters A, 33 (2018), 1850050
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[79]  arXiv:1708.01253 (replaced) [pdf, other]
Title: Gravitational waves from first-order phase transitions: Towards model separation by bubble nucleation rate
Comments: 36 pages, 13 figures, 1 figure from arXiv:1605.01403
Journal-ref: JCAP 1711 (2017) no.11, 050
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
[80]  arXiv:1709.00415 (replaced) [pdf, other]
Title: Neutrino masses, leptogenesis and dark matter from small lepton number violation?
Comments: 35 pages plus appendices, 23 figures. v2: references added, typos corrected
Journal-ref: JCAP 1712 (2017) no.12, 024
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[81]  arXiv:1709.01102 (replaced) [pdf, other]
Title: Supernova remnants in the very-high-energy gamma-ray domain: the role of the Cherenkov telescope array
Comments: 10 pages, 3 Figures, 3 Tables
Journal-ref: MNRAS 471, 201-209 (2017)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[82]  arXiv:1710.00834 (replaced) [pdf, other]
Title: Empirical Modeling of the Redshift Evolution of the [NII]/H$α$-ratio for Galaxy Redshift Surveys
Comments: 18 pages, 11 figures, 1 table, accepted for publication in ApJ
Journal-ref: 2018, ApJ, 855, 2
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[83]  arXiv:1710.05369 (replaced) [pdf, other]
Title: Near Infrared spectroscopic observations of high redshift C~{\sc i} absorbers
Comments: 26 pages, 49 figures, 3 tables, accepted by Astronomy & Astrophysics (A&A)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[84]  arXiv:1710.06102 (replaced) [pdf, other]
Title: Exploring Short-GRB afterglow parameter space for observations in coincidence with gravitational waves
Comments: Published in MNRAS
Journal-ref: Monthly Notices of the Royal Astronomical Society, 474(4), 5340-5350 (2018)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[85]  arXiv:1710.06111 (replaced) [pdf, other]
Title: Rates of Short-GRB afterglows in association with Binary Neutron Star mergers
Comments: Published in MNRAS
Journal-ref: Monthly Notices of the Royal Astronomical Society 475(1), 699-707, (2018)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[86]  arXiv:1711.01265 (replaced) [pdf, other]
Title: Science with e-ASTROGAM (A space mission for MeV-GeV gamma-ray astrophysics)
Comments: White Book, submitted to Journal of High Energy Astrophysics (Elsevier)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics - Experiment (hep-ex)
[87]  arXiv:1711.11063 (replaced) [pdf, other]
Title: Reconciling optical and radio observations of the binary millisecond pulsar PSR J1640+2224
Comments: 6 pages, 5 figures
Journal-ref: Astrophys. J. 855:122 (2018)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)
[88]  arXiv:1712.03444 (replaced) [pdf, other]
Title: The dipole anisotropy of AllWISE galaxies
Comments: Accepted for publication in MNRAS; Minor changes and clarifications, References added; 11 pages, 9 figures, 3 tables
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[89]  arXiv:1712.07241 (replaced) [pdf, other]
Title: The Herschel-ATLAS Data Release 2 Paper II: Catalogues of far-infrared and submillimetre sources in the fields at the south and north Galactic Poles
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[90]  arXiv:1712.08094 (replaced) [pdf, ps, other]
Title: Hybrid stars in the light of GW170817
Comments: version accepted by ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[91]  arXiv:1801.02600 (replaced) [pdf, other]
Title: Non-perturbative $δN$
Comments: 12 pages, 7 figures, V2 has minor amendments to the text
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[92]  arXiv:1801.04221 (replaced) [pdf, other]
Title: Radiation- and pair-loaded shocks
Authors: Maxim Lyutikov (Purdue University)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[93]  arXiv:1801.05442 (replaced) [pdf, other]
Title: Discovery of a dual AGN at z~3.3 with 20kpc separation
Comments: 4 pages, 2 figures, published in A&A, version after language editing
Journal-ref: A&A 610, L7 (2018)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[94]  arXiv:1801.09365 (replaced) [pdf, other]
Title: Positron Transport And Annihilation In The Galactic Bulge
Authors: Fiona H. Panther
Comments: 8 pages, accepted for publication in MDPI Galaxies special edition: Searching for Connections among the Fermi Bubbles, the Galactic Center GeV Excess, and Loop I
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[95]  arXiv:1802.00778 (replaced) [pdf, ps, other]
Title: Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies
Comments: 5 pages, 4 figures. Revised to match version published in MNRAS: Letters (2018 May 1, volume 476, issue 1, pages L1-L5)
Journal-ref: Monthly Notices of the Royal Astronomical Society Letters 2018, 476 (1): L1-L5 (May 1, 2018)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[96]  arXiv:1802.06561 (replaced) [pdf, other]
Title: Star formation across cosmic time with radio surveys. The promise of the SKA
Comments: 28 pages, 3 figures, to be published in the Proceedings of the 3rd Cosmology School in Cracow, July 2017
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[97]  arXiv:1803.00570 (replaced) [pdf, other]
Title: Evolution of the anti-truncated stellar profiles of S0 galaxies since $z=0.6$ in the SHARDS survey: II - Structural and photometric evolution
Comments: Accepted for publishing in Astronomy & Astrophysics. 28 pages, 27 figures. Language editor corrections applied
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[98]  arXiv:1803.03269 (replaced) [pdf, other]
Title: Exploring the Dust Content of Galactic Winds With Herschel. II. Nearby Dwarf Galaxies
Comments: 39 pages, 10 figures, Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[99]  arXiv:1803.04335 (replaced) [pdf, other]
Title: A unified accretion-ejection paradigm for black hole X-ray binaries. II. Observational signatures of jet-emitting disks
Comments: Accepted for publication in A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[100]  arXiv:1803.05005 (replaced) [pdf, ps, other]
Title: PyMUSE: a Python package for VLT/MUSE data
Comments: Proceedings of Astronomical Data Analysis Software and Systems XXVII conference
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[101]  arXiv:1803.05329 (replaced) [pdf, other]
Title: Revealing neutral bremsstrahlung in two-phase argon electroluminescence
Comments: 12 pages, 20 figures. Version2: Introduction slightly improved
Subjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)
[102]  arXiv:1803.05623 (replaced) [pdf]
Title: Long-Term Cyclicities in Phanerozoic Sea-Level Sedimentary Record and their Potential Drivers (Does the Phanerozoic sea level encode the motion of solar system in the Milky Way ?)
Comments: 47 pages, 19 figures, Accepted for publication in Global and Planetary Change
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
[103]  arXiv:1803.05803 (replaced) [pdf, ps, other]
Title: The contributions of dark matter annihilation to the global 21cm spectrum observed by the EDGES experiment
Authors: Yupeng Yang
Comments: 5 pages, 1 figure. comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[104]  arXiv:1803.05927 (replaced) [pdf, ps, other]
Title: Galactic Local Circular Velocity from Gaia DR1 Cepheids and Effects of Non-Axisymmetry
Authors: Daisuke Kawata (1), Jo Bovy (2), Noriyuki Matsunaga (3), Junichi Baba (4) ((1) MSSL, UCL, (2) Toronto, (3) Tokyo, (4) NAOJ)
Comments: 13 pages, 8 figures, 2 tables. v1 was a wrong version of draft. Replaced to match version submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[105]  arXiv:1803.06036 (replaced) [pdf, other]
Title: A Role for Turbulence in Circumgalactic Precipitation
Authors: G. M. Voit
Comments: Submitted to ApJ on 6 Oct 2017, revision resubmitted 19 Mar 2019, 20 pages, 9 figures (some typos in v1 corrected)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
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