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Astrophysics

New submissions

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New submissions for Wed, 29 Jan 20

[1]  arXiv:2001.09987 [pdf, other]
Title: Technological Challenges in Low-mass Interstellar Probe Communication
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Building on a preliminary paper design of a downlink from a swarm of low-mass interstellar probes for returning scientific data from the vicinity of Proxima Centauri, the most critical technology issues are summarized, and their significance is explained in the context of the overall system design. The primary goal is to identify major challenges or showstoppers if such a downlink were to be constructed using currently available off-the-shelf technology, and thereby provide direction and motivation to future research on the constituent design challenges and technologies. While there are not any fundamental physical limits that prevent such communication systems, currently available technologies fall significantly short in several areas and there are other major design challenges with uncertain solutions. The greatest identified challenges are in mass constraints, multiplexing simultaneous communication from multiple probes to the same target exoplanet, attitude control and pointing accuracy, and Doppler shifts due to uncertainty in probe velocity. The greatest technology challenges are electrical power, high power and wavelength-agile optical sources, very selective and wavelength-agile banks of optical bandpass filters, and single-photon detectors with extremely low dark-count rates. For a critical subset of these, we describe the nature of the difficulties we encounter and their origins in the overall system context. A receiver that limits reception to a single probe is also considered and compared to the swarm case.

[2]  arXiv:2001.09999 [pdf, other]
Title: The BUFFALO HST Survey
Comments: Accepted ApJS; MAST archive will be live concurrent with publication
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Beyond Ultra-deep Frontier Fields and Legacy Observations (BUFFALO) is a 101 orbit + 101 parallel Cycle 25 Hubble Space Telescope Treasury program taking data from 2018-2020. BUFFALO will expand existing coverage of the Hubble Frontier Fields (HFF) in WFC3/IR F105W, F125W, and F160W and ACS/WFC F606W and F814W around each of the six HFF clusters and flanking fields. This additional area has not been observed by HST but is already covered by deep multi-wavelength datasets, including Spitzer and Chandra. As with the original HFF program, BUFFALO is designed to take advantage of gravitational lensing from massive clusters to simultaneously find high-redshift galaxies which would otherwise lie below HST detection limits and model foreground clusters to study properties of dark matter and galaxy assembly. The expanded area will provide a first opportunity to study both cosmic variance at high redshift and galaxy assembly in the outskirts of the large HFF clusters. Five additional orbits are reserved for transient followup. BUFFALO data including mosaics, value-added catalogs and cluster mass distribution models will be released via MAST on a regular basis, as the observations and analysis are completed for the six individual clusters.

[3]  arXiv:2001.10000 [pdf, other]
Title: Turbulence Regulates the Rate of Planetesimal Formation via Gravitational Collapse
Comments: Submitted to ApJ, Comments welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We study how the interaction between the streaming instability and intrinsic gas-phase turbulence affects planetesimal formation via gravitational collapse. Turbulence impedes the formation of dense particle clumps by acting as an effective turbulent diffusivity, but it can also promote planetesimal formation by concentrating solids, for example in zonal flows. We quantify the effect of turbulent diffusivity using numerical simulations of the streaming instability in small local domains, forced with velocity perturbations that establish approximately Kolmogorov-like fluid turbulence. We find that planetesimal formation is strongly suppressed by turbulence once velocity fluctuations exceed a threshold value of $\delta v^2 \simeq 10^{-3.5} - 10^{-3} c_s^2$. Turbulence whose strength is just below the threshold reduces the rate of solid material being converted into bound clumps. The main effect of turbulence is to thicken the mid-plane solid layer. Our results are thus consistent with planetesimal formation requiring a mid-plane solid-to-gas ratio $\epsilon \gtrsim 0.5$. We describe a method for tracking bound clumps in our simulations, and use this method to construct a mass function of planetesimals that is measured for each clump shortly after its collapse. Adopting this definition of the initial mass, instead of measuring masses at a fixed time, reduces planetesimal masses by a factor of three. For models in which planetesimals form, we show that the initial mass function is well-described by a broken power law, whose parameters are robust to the inclusion and strength of imposed turbulence. Turbulence in protoplanetary disks is likely to substantially exceed the threshold for planetesimal formation at radii where temperatures $T \gtrsim 10^3 \ {\rm K}$ lead to thermal ionization. Fully in situ planetesimal and planet formation may therefore not be viable for the closest-in exoplanets.

[4]  arXiv:2001.10003 [pdf, other]
Title: Evolution of fractality and rotation in embedded star clusters
Comments: 12 pages, 11 figures, submitted to MNRAS. Comments welcome!
Subjects: Astrophysics of Galaxies (astro-ph.GA)

More and more observations indicate that young star clusters could retain imprints of their formation process. In particular, the degree of substructuring and rotation are possibly the direct result of the collapse of the parent molecular cloud from which these systems form. Such properties can, in principle, be washed-out, but they are also expected to have an impact on the relaxation of these systems. We ran and analyzed a set of ten hydrodynamical simulations of the formation of embedded star clusters through the collapse of turbulent massive molecular clouds. We systematically studied the fractality of our star clusters, showing that they are all extremely substructured (fractal dimension $D=1.0-1.8$). We also found that fractality is slowly reduced, with time, on small scales, while it persists on large scales on longer timescales. Signatures of rotation are found in different simulations at every time of the evolution, even for slightly supervirial substructures, proving that the parent molecular gas transfers part of its angular momentum to the new stellar systems.

[5]  arXiv:2001.10004 [pdf, other]
Title: Angular momentum profiles of Class 0 protostellar envelopes
Comments: Accepted for publication in Astronomy & Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

[abridged] Understanding how the infalling gas redistribute most of its initial angular momentum inherited from prestellar cores before reaching the stellar embryo is a key question. Disk formation has been naturally considered as a possible solution to this "angular momentum problem". However, how the initial angular momentum of protostellar cores is distributed and evolves during the main accretion phase and the beginning of disk formation has largely remained unconstrained up to now. In the framework of the IRAM CALYPSO survey, we used high dynamic range C$^{18}$O (2-1) and N$_2$H$^+$ (1-0) observations to quantify the distribution of specific angular momentum along the equatorial axis in a sample of 12 Class 0 protostellar envelopes from scales ~50 to 10000 au. The radial distributions of specific angular momentum in the CALYPSO sample suggest two distinct regimes within protostellar envelopes: the specific angular momentum decreases as $j \propto r^{1.6 \pm 0.2}$ down to ~1600 au and then tends to become relatively constant around 6 $\times$ 10$^{-4}$ km s$^{-1}$ pc down to ~50 au. The values of specific angular momentum measured in the inner Class 0 envelopes suggest that the material directly involved in the star formation process ($<$1600 au) on the same order of magnitude as what is inferred in small T-Tauri disks. Thus, disk formation appears to be a direct consequence of angular momentum conservation during the collapse. Our analysis reveals a dispersion of the directions of velocity gradients at envelope scales $>$1600 au, suggesting that they may not be related to rotational motions of the envelopes. We conclude that the specific angular momentum observed at these scales could find its origin in core-forming motions (infall, turbulence) or trace an imprint of the initial conditions for the formation of protostellar cores.

[6]  arXiv:2001.10005 [pdf, ps, other]
Title: Constraints on the density distribution of type Ia supernovae ejecta inferred from late-time light curves flattening
Authors: Doron Kushnir, Eli Waxman (WIS)
Comments: 8 pages, 5 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The finite time, $\tau_{\rm dep}$, over which positrons from $\beta^{+}$ decays of $^{56}$Co deposit energy in type Ia supernovae ejecta lead, in case the positrons are trapped, to a slower decay of the bolometric luminosity compared to an exponential decline. Significant light curve flattening is obtained when the ejecta density drops below the value for which $\tau_{\rm dep}$ equals the $^{56}$Co life-time. We provide a simple method to accurately describe this "delayed deposition" effect, which is straightforward to use for analysis of observed light curves. We find that the ejecta heating is dominated by delayed deposition typically from 600 to 1200 days, and only later by longer lived isotopes $^{57}$Co and $^{55}$Fe decay (assuming solar abundance). For the relatively narrow $^{56}$Ni velocity distributions of commonly studied explosion models, the modification of the light curve depends mainly on the $^{56}$Ni mass weighted average density, $\langle \rho \rangle t^{3}$. Accurate late-time bolometric light curves, which may be obtained with JWST far-IR measurements, will thus enable to discriminate between explosion models by determining $\langle \rho \rangle t^3$ (and the $^{57}$Co and $^{55}$Fe abundances). The flattening of light curves inferred from recent observations, which is uncertain due to the lack of far-IR data, is readily explained by delayed deposition in models with $\langle \rho\rangle t^{3} \approx 0.2\,M_{\odot}\,(10^{4}\, \textrm{km}\,\textrm{s}^{-1})^{-3}$, and does not imply super-solar $^{57}$Co and $^{55}$Fe abundances.

[7]  arXiv:2001.10012 [pdf, other]
Title: An all-sky proper motion map of the Sagittarius stream using Gaia DR2
Comments: Accepted for publication in A&A Letters. See additional material at this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We aim to measure the proper motion along the Sagittarius stream that is the missing piece to determine its full 6D phase space coordinates. We conduct a blind search of over-densities in proper motion from Gaia DR2 in a broad region around the Sagittarius stream by applying wavelet transform techniques. We find that for most of the sky patches, the highest intensity peaks delineate the path of the Sagittarius stream. The 1500 peaks identified depict a continuous sequence spanning almost $2\pi$ in the sky, only obscured when the stream crosses the Galactic disk. Altogether, around $100\,000$ stars potentially belong to the stream as indicated by a coarse inspection of the colour-magnitude diagrams. From these stars, we determine the proper motion along the Sagittarius stream, making it the proper motion sequence with the largest span and continuity ever measured for a stream. A first comparison with existing N-body models of the stream reveals some discrepancies, especially near the pericentre of the trailing arm and an overestimation of the total proper motion for the leading arm. Our study can be the starting point for determining the variation of the population of stars along the stream, the distance to the stream with red clump stars, and the solar motion. It will also allow a much better measurement of the Milky Way potential.

[8]  arXiv:2001.10018 [pdf, other]
Title: Probing the thermal state of the intergalactic medium at $z>5$ with the transmission spikes in high-resolution Ly$α$ forest spectra
Comments: 20 pages (+10 pages appendices), 12 figures (+14 figures appendices); submitted to MNRAS; Main results are summarized in Fig. 10, Fig. 12 and Table 3
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

We compare a sample of five high-resolution, high S/N Ly$\alpha$ forest spectra of bright $6<z \lesssim 6.5$ QSOs aimed at spectrally resolving the last remaining transmission spikes at $z>5$ with those obtained from mock absorption spectra from the Sherwood and Sherwood-Relics suites of hydrodynamical simulations of the intergalactic medium (IGM). We use a profile fitting procedure for the inverted transmitted flux, $1-F$, similar to the widely used Voigt profile fitting of the transmitted flux $F$ at lower redshifts, to characterise the transmission spikes that probe predominately underdense regions of the IGM. We are able to reproduce the width and height distributions of the transmission spikes, both with optically thin simulations of the post-reionization Universe using a homogeneous UV background and full radiative transfer simulations of a late reionization model. We find that the width of the fitted components of the simulated transmission spikes is very sensitive to the instantaneous temperature of the reionized IGM. The internal structures of the spikes are more prominant in low temeperature models of the IGM. The width distribution of the observed transmission spikes, which require high spectral resolution ($\leq $ 8 \kmps) to be resolved, is reproduced for optically thin simulations with a temperature at mean density of $T_0= (11000 \pm 1600,10500\pm 2100,12000 \pm 2200)$ K at $z= (5.4,5.6,5.8)$. This is weakly dependent on the slope of the temperature-density relation, which is favoured to be moderately steeper than isothermal. In the inhomogeneous, late reionization, full radiative transfer simulations where islands of neutral hydrogen persist to $z\sim5.3$, the width distribution of the observed transmission spikes is consistent with the range of $T_0$ caused by spatial fluctuations in the temperature-density relation.

[9]  arXiv:2001.10023 [pdf, other]
Title: Hot atmospheres of galaxies, groups, and clusters of galaxies
Comments: Accepted for publication in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-035562
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

Most of the ordinary matter in the local Universe has not been converted into stars but resides in a largely unexplored diffuse, hot, X-ray emitting plasma. It pervades the gravitational potentials of massive galaxies, groups and clusters of galaxies, as well as the filaments of the cosmic web. The physics of this hot medium, such as its dynamics, thermodynamics and chemical composition can be studied using X-ray spectroscopy in great detail. Here, we present an overview of the basic properties and discuss the self similarity of the hot "atmospheres" permeating the gravitational halos from the scale of galaxies, through groups, to massive clusters. Hot atmospheres are stabilised by the activity of supermassive black holes and, in many ways, they are of key importance for the evolution of their host galaxies. The hot plasma has been significantly enriched in heavy elements by supernovae during the period of maximum star formation activity, probably more than 10 billion years ago. High resolution X-ray spectroscopy just started to be able to probe the dynamics of atmospheric gas and future space observatories will determine the properties of the currently unseen hot diffuse medium throughout the cosmic web.

[10]  arXiv:2001.10031 [pdf, other]
Title: Globular Clusters in Coma Cluster Ultra Diffuse Galaxies (UDGs): Evidence for Two Types of UDG?
Comments: 11 pages, 11 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Ultra diffuse galaxies (UDGs) reveal extreme properties. Here we compile the largest study to date of 85 globular cluster (GC) systems around UDGs in the Coma cluster, using new deep ground-based imaging of the known UDGs and existing imaging from the Hubble Space Telescope of their GC systems. We find that the richness of GC systems in UDGs generally exceeds that found in normal dwarf galaxies of the same stellar mass. These GC-rich UDGs imply halos more massive than expected from the standard stellar mass-halo mass relation. The presence of such overly massive halos presents a significant challenge to the latest simulations of UDGs in cluster environments. In some exceptional cases, the mass in the GC system is a significant fraction of the stellar content of the host galaxy. We find that rich GC systems tend to be hosted in UDGs of lower luminosity, smaller size and fainter surface brightness. Similar trends are seen for normal dwarf galaxies in the Coma cluster. A toy model is presented in which the GC-rich UDGs are assumed to be `failed' galaxies within massive halos that have largely old, metal-poor, alpha-element enhanced stellar populations. On the other hand, GC-poor UDGs are more akin to normal, low surface brightness dwarfs that occupy less massive dark matter halos. Additional data on the stellar populations of UDGs with GC systems will help to further refine and test this simplistic model.

[11]  arXiv:2001.10062 [pdf, other]
Title: Planet formation around M dwarfs via disc instability: Fragmentation conditions and protoplanet properties
Comments: 26 pages, A&A accepted
Journal-ref: A&A, 633 (2020), A116
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

Context: Around 30 per cent of the observed exoplanets that orbit M dwarf stars are gas giants that are more massive than Jupiter. These planets are prime candidates for formation by disc instability. Aims: We want to determine the conditions for disc fragmentation around M dwarfs and the properties of the planets that are formed by disc instability. Methods: We performed hydrodynamic simulations of M dwarf protostellar discs in order to determine the minimum disc mass required for gravitational fragmentation to occur. Different stellar masses, disc radii, and metallicities were considered. The mass of each protostellar disc was steadily increased until the disc fragmented and a protoplanet was formed. Results: We find that a disc-to-star mass ratio between $\sim 0.3$ and $\sim 0.6$ is required for fragmentation to happen. The minimum mass at which a disc fragments increases with the stellar mass and the disc size. Metallicity does not significantly affect the minimum disc fragmentation mass but high metallicity may suppress fragmentation. Protoplanets form quickly (within a few thousand years) at distances around $\sim50$ AU from the host star, and they are initially very hot; their centres have temperatures similar to the ones expected at the accretion shocks around planets formed by core accretion (up to 12,000K). The final properties of these planets (e.g. mass and orbital radius) are determined through long-term disc-planet or planet-planet interactions. Conclusions: Disc instability is a plausible way to form gas giant planets around M dwarfs provided that discs have at least 30% the mass of their host stars during the initial stages of their formation. Future observations of massive M dwarf discs or planets around very young M dwarfs are required to establish the importance of disc instability for planet formation around low-mass stars.

[12]  arXiv:2001.10085 [pdf, other]
Title: Asymmetric expansion of coronal mass ejections in the low corona
Comments: 11 pages, 10 figures, accepted for publication in Astronomy and Astrophysics on January 5, 2020
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

Aims. The study of the morphology of coronal mass ejections (CMEs) is an auspicious approach to understanding how magnetic fields are structured within CMEs. Although earlier studies have suggested an asymmetry in the width of CMEs in orthogonal directions, this has not been inspected using multi-viewpoint observations. Methods. We inspect the early evolution (below ten solar radii) of the morphology of a dozen CMEs occurring under specific conditions of observing spacecraft location and CME trajectory, favorable to reduce uncertainties typically involved in the 3D reconstruction used here. These events are carefully reconstructed by means of a forward modeling tool using simultaneous observations of STEREO EUVI and SDO/AIA as input when originating low in the corona, and followed up in the outer fields of view of the STEREO and the SOHO coronagraphs. We then examine the height evolution of the morphological parameters arising from the reconstructions. Results. The multi-viewpoint analysis of this set of CMEs revealed that their initial expansion --below three solar radii-- is considerably asymmetric and non-self-similar. Both angular widths, namely along the main axes of CMEs ($AW_L$) and in the orthogonal direction ($AW_D$, representative of the flux rope diameter), exhibit much steeper change rates below this height, with the growth rate of $AW_L$ found to be larger than that of $AW_D$, also below that height. Angular widths along the main axes of CMEs are on average $\approx$1.8 times larger than widths in the orthogonal direction $AW_D$. The ratios of the two expansion speeds, namely in the directions of CMEs main axes and in their orthogonal, are nearly constant in time after $\sim$4 solar radii, with an average ratio $\approx$1.6. Heights at which the width change rate is defined to stabilize are greater for $AW_L$ than for $AW_D$.

[13]  arXiv:2001.10103 [pdf, ps, other]
Title: Torsional Alfvénic Oscillations Discovered in the Magnetic Free Energy During Solar Flares
Comments: 21 pages and 8 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report the discovery of torsional Alfv\'enic oscillations in solar flares, which modulate the time evolution of the magnetic free energy $E_f(t)$, while the magnetic potential energy $E_p(t)$ is uncorrelated, and the nonpotential energy varies as $E_{np}(t) = E_p + E_f(t)$. The mean observed time period of the torsional oscillations is $P_{obs}=15.1 \pm 3.9$ min, the mean field line length is $L=135\pm35$ Mm, and the mean phase speed is $v_{phase} =315 \pm 120$ km s$^{-1}$, which we interpret as torsional Alfv\'enic waves in flare loops with enhanced electron densities. Most of the torsional oscillations are found to be decay-less, but exhibit a positive or negative trend in the evolution of the free energy, indicating new emerging flux (if positive), magnetic cancellation, or flare energy dissipation (if negative). The time evolution of the free energy has been calculated in this study with the {\sl Vertical-Current Approximation (Version 4) Nonlinear Force-Free Field (VCA4-NLFFF)} code, which incorporates automatically detected coronal loops in the solution and bypasses the non-forcefreeness of the photospheric boundary condition, in contrast to traditional NLFFF codes.

[14]  arXiv:2001.10113 [pdf, other]
Title: Candidate LBV stars in galaxy NGC 7793 found via HST photometry + MUSE spectroscopy
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Only about 19 Galactic and 25 extra-galactic bona-fide Luminous Blue Variables (LBVs) are known to date. This incomplete census prevents our understanding of this crucial phase of massive star evolution which leads to the formation of heavy binary black holes via the classical channel. With large samples of LBVs one could better determine the duration and maximum stellar luminosity which characterize this phase. We search for candidate LBVs (cLBVs) in a new galaxy, NGC 7793. For this purpose, we combine high spatial resolution images from two Hubble Space Telescope (HST) programs with optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE). By combining PSF-fitting photometry measured on F547M, F657N, and F814W images, with restrictions on point-like appearance (at HST resolution) and H{\alpha} luminosity, we find 100 potential cLBVs, 36 of which fall in the MUSE fields. Five of the latter 36 sources are promising cLBVs which have M(V) less than or equal to -7 and a combination of: H{\alpha} with a P-Cygni profile; no [O I] 6300 emission; weak or no [O III] 5007 emission; large [N II]/H{\alpha} relative to H II regions; and [S II] 6716 / [S II] 6731 similar to 1. It is not clear if these five cLBVs are isolated from O-type stars, which would favor the binary formation scenario of LBVs. Our study, which approximately covers one fourth of the optical disc of NGC 7793, demonstrates how by combining the above HST surveys with multi-object spectroscopy from 8-m class telescopes, one can efficiently find large samples of cLBVs in nearby galaxies.

[15]  arXiv:2001.10129 [pdf, ps, other]
Title: SPI Analysis and Abundance Calculations of DEM L71, and Comparison to SN explosion Models
Authors: Jared Siegel, Vikram V. Dwarkadas (Univ of Chicago), Kari Frank (CIERA, Northwestern Univ), David N. Burrows (PSU), Aldo Panfichi (Univ of Chicago)
Comments: 6 pages, 7 Figures. Accepted for publication in Astronomische Nachrichten. To appear as part of the Proceedings of the XMM-Newton 2019 Workshop on "Astrophysics of Hot Plasma in Extended X-Ray Sources"
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We analyze the X-Ray emission from the supernova remnant DEM L71 using the Smoothed Particle Inference (SPI) technique. The high Fe abundance found appears to confirm the Type Ia origin. Our method allows us to separate the material ejected in the supernova explosion from the material swept-up by the supernova shock wave. We are able to calculate the total mass of this swept-up material to be about 228 $\pm$ 23 M$_{\odot}$. We plot the posterior distribution for the number density parameter, and create a map of the density structure within the remnant. While the observed density shows substantial variations, we find our results are generally consistent with a two-dimensional hydrodynamical model of the remnant that we have run. Assuming the ejected material arises from a Type Ia explosion, with no hydrogen present, we use the predicted yields from Type Ia models available in the literature to characterize the emitting gas. We find that the abundance of various elements match those predicted by deflagration to detonation transition (DDT) models. Our results, compatible with the Type Ia scenario, highlight the complexity of the remnant and the nature of the surrounding medium.

[16]  arXiv:2001.10135 [pdf, other]
Title: Tracing the high energy theory of gravity: an introduction to Palatini inflation
Authors: Tommi Tenkanen
Comments: 23 pages, no figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

We present an introduction to cosmic inflation in the context of Palatini gravity, which is an interesting alternative to the usual metric theory of gravity. In the latter case only the metric $g_{\mu\nu}$ determines the geometry of space-time, whereas in the former case both the metric and the space-time connection $\Gamma^\lambda_{\mu\nu}$ are a priori independent variables - a choice which can lead to a theory of gravity different from the metric one. In scenarios where the field(s) responsible for cosmic inflation are coupled non-minimally to gravity or the gravitational sector is otherwise extended, assumptions of the underlying gravitational degrees of freedom can have a big impact on the observational consequences of inflation. We demonstrate this explicitly by reviewing several interesting and well-motivated scenarios including Higgs inflation, $R^2$ inflation, and $\xi$-attractor models. We also discuss some prospects for future research and argue why $r=10^{-3}$ is a particularly important goal for future missions that search for signatures of primordial gravitational waves.

[17]  arXiv:2001.10139 [pdf, other]
Title: The cosmic-ray content of the Orion-Eridanus superbubble
Comments: 20 pages, 17 figures, accepted for publication in Astronomy & Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The nearby Orion-Eridanus superbubble, which was blown by multiple supernovae several Myr ago, has likely produced cosmic rays. Its turbulent medium, still energised by massive stars, can impact cosmic-ray transport locally. The gamma rays produced in cosmic-ray interactions with interstellar gas were used to compare the GeV to TeV cosmic-ray spectrum in the superbubble and in other regions near the Sun. We used ten years of Fermi-LAT data in the 0.25-63 GeV energy range to study the closer (Eridanus) end of the superbubble. We modelled the spatial and spectral distributions of the gamma rays produced in the different gas phases of the clouds found in this direction. We found that the gamma-ray emissivity spectrum of the gas along the outer rim and in a shell inside the superbubble is consistent with the average spectrum measured in the solar neighbourhood. This result calls for a detailed assessment of the recent supernova rate and census of massive stellar winds in the superbubble in order to estimate the epoch and rate of cosmic-ray production and to constrain the transport conditions that can lead to such homogeneity and little re-acceleration. We also found significant evidence that a diffuse cloud lying outside the superbubble, at a height of 200-250 pc below the Galactic plane, is pervaded by a 34\% lower cosmic-ray flux, but with the same particle energy distribution as the local one. Super-GeV cosmic rays should freely cross such a diffuse atomic cloud without significant loss or spectral distorsion. We tentatively propose that the cosmic-ray loss relates to the orientation of the magnetic field lines threading the cirrus, which point towards the halo according to the dust polarisation data. We gathered past and present emissivity measurements near the Sun to show how the local cosmic-ray flux decreases with Galactic height and to compare this trend with model predictions.

[18]  arXiv:2001.10144 [pdf, other]
Title: A Deep Search for Binary TNOs
Comments: 9 pages, 3 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Latitude Density Search utilized Hyper Suprime-Cam on Subaru Telescope to discover 60 moving objects in the outer Solar System, 54 of which have semi-major axes beyond 30 AU. The two night orbit arcs are insufficient for tracking, but the images were acquired in exceptional seeing (0.4") and reached a detection limit of m_r~=25.2. We searched the detections for binary sources, and identified one binary object with a separation of 0.34", the previously known object 2010 HE79 (471165). Although we would have been able to identify binaries with the same separation and relative brightness for 18% of the 54 trans-Neptunian objects in the search, or 88% of objects with a brighter secondary, only one binary was found in the sample. This detection rate is lower than expected based on previous work, particularly for the cold classical objects, and implies that the prevalence of binary trans-Neptunian objects with 7.5~< H_r ~<9 may be significantly lower than for larger objects.

[19]  arXiv:2001.10147 [pdf, ps, other]
Title: Magnetic fields in isolated and interacting white dwarfs
Comments: Invited, refereed review paper to appear in the COSPAR 2018 special issue of Advances in Space Research (Elsevier) entitled Nova Eruptions, Cataclysmic Variables and related systems: Observational vs. theoretical challenges in the 2020 era, 98 pages, 30 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The magnetic white dwarfs (MWDs) are found either isolated or in interacting binaries. They divide into two groups: a high field group (0.1-1,000MegaGauss) comprising some 13% of all white dwarfs (WDs), and a low field group (B<0.1MG) whose incidence is currently under investigation. The situation may be similar in magnetic binaries because the bright accretion discs in low field systems hide the photosphere of their WDs thus preventing the study of their magnetic fields' strength and structure. Considerable research has been devoted to the vexed question on the origin of magnetic fields. One hypothesis is that WD magnetic fields are of fossil origin. The other is that magnetic fields arise from binary interaction, through differential rotation, during common envelope evolution. The recently discovered population of hot, carbon-rich WDs exhibiting an incidence of magnetism of up to about 70% and a variability from a few minutes to a couple of days may support the merging binary hypothesis. Several studies have raised the possibility of the detection of planets around MWDs. Rocky planets may be discovered by the detection of anomalous atmospheric heating of the MWD. Planetary remains have recently revealed themselves in the atmospheres of about 25% of WDs that are polluted by elements such as Ca, Si, and often also Mg, Fe, Na. This pollution has been explained by ongoing accretion of planetary debris. The study of isolated and accreting MWDs is likely to continue to yield exciting discoveries for many years to come.

[20]  arXiv:2001.10203 [pdf, other]
Title: Solar Total Eclipse of 21 August 2017: Study of the Inner Corona Dynamical Events Leading to a CME
Comments: 25 pages, 11 figures, the paper has been accepted for publication in Solar Phys
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Total solar eclipse (TSE) coronal large and small scale events were reported in the historical literature but a definite synoptic coverage was missing for studying a relationship with the more general magnetic context of the solar-disk. We here analyze temporal changes in the solar corona before, during, and after the total solar eclipse on 21 August 2017 from a set of ground-based and of space-borne observations. High-quality ground-based white-light (W-L) observations and a deep image processing allow us to reveal these changes for the first time with a fraction of a one-minute time resolution. Displacements of a number of fine coronal features were measured for the first time at these small radial distances, using a diffraction limited instrument at a single site. The comparison with space-based observations, including observations from the {\it Solar Terrestrial Relations Observatory} (STEREO) mission, showed that the features belong to a slow coronal mass ejection (CME) propagating through the corona with the nearly constant speed of 250 km/s. Our TSE images provide the same typical velocity as measured at a distance of one solar radius from the surface. The event was initiated by coronal dynamics manifested by a prominence eruption that started just before the eclipse observations and an ascent of a U-shaped structure visible in the AIA 171 A channel, which we assume as the lower part of a coronal cavity. The prominence material was observed draining down towards the chromosphere along the prominence arch. While the prominence disappears in the STEREO-A field-of-view at the height of about 6$^{\prime}$ above the limb, the corresponding flux rope seems to continue towards the outer corona and produces the slow CME with turbulent motion. The overall mass of the moving features is evaluated based on absolute photometrical data extracted from our best W-L eclipse image.

[21]  arXiv:2001.10211 [pdf, ps, other]
Title: Simulating the JUNO Neutrino Detectors
Authors: Srikanta Sinha
Comments: 11 pages, 4 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)

The JUNO neutrino detector system is simulated using Monte-Carlo and analytical methods. A large number of proton decay events are also simulated. Preliminary results from this endeavor are presented in the present article.

[22]  arXiv:2001.10232 [pdf, other]
Title: Patterns in the multi-wavelength behavior of candidate neutrino blazars
Comments: submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Motivated by the identification of the blazar TXS 0506+056 as the first promising high-energy neutrino counterpart candidate, we search for additional neutrino blazars candidates among the Fermi-LAT detected blazars. We investigate the multi-wavelength behavior from radio to GeV gamma rays of blazars found to be in spatial coincidence with single high-energy neutrinos and lower-energy neutrino flare candidates. In addition, we compare the average gamma-ray emission of the potential neutrino-emitting sources to the entire sample of gamma-ray blazars. We find that blazars found in spatial correlation with high-energy single neutrinos tend to have high gamma-ray energy flux, which is in mild tension (p-value of 4%) with the hypothesis of no correlation between neutrino and gamma-ray energy flux. The distribution instead matches the expectation of a linear correlation between the two fluxes. Candidate neutrino-flare emitting blazars are compatible with chance coincidences.

[23]  arXiv:2001.10241 [pdf, other]
Title: Collimated outflows from long-lived binary neutron star merger remnants
Authors: Riccardo Ciolfi
Comments: 8 pages, 4 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)

The connection between short gamma-ray bursts (SGRBs) and binary neutron star (BNS) mergers was recently confirmed by the association of GRB 170817A with the merger event GW170817. However, no conclusive indications were obtained on whether the merger remnant that powered the SGRB jet was an accreting black hole (BH) or a long-lived massive neutron star (NS). Here, we explore the latter case via BNS merger simulations covering up to 250 ms after merger. We report, for the first time in a full BNS merger simulation, the formation of a magnetically-driven collimated outflow along the spin axis of the NS remnant. For the system at hand, the properties of such an outflow are found largely incompatible with a SGRB jet. With due consideration of the limitations and caveats of our present investigation, our results favour a BH origin for GRB 170817A and SGRBs in general. Even though this conclusion needs to be confirmed by exploring a larger variety of physical conditions, we briefly discuss possible consequences of all SGRB jets being powered by accreting BHs.

[24]  arXiv:2001.10243 [pdf, ps, other]
Title: Quantifying the Redshift Space Distortion of the Bispectrum I: Primordial Non-Gaussianity
Comments: 10 pages, 10 figures, accepted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The anisotropy of the redshift space bispectrum contains a wealth of cosmological information. This anisotropy depends on the orientation of three vectors ${\bf k_1,k_2,k_3}$ with respect to the line of sight. Here we have decomposed the redshift space bispectrum in spherical harmonics which completely quantify this anisotropy. To illustrate this we consider linear redshift space distortion of the bispectrum arising from primordial non-Gaussianity. In the plane parallel approximation only the first four even $\ell$ multipoles have non-zero values, and we present explicit analytical expressions for all the non-zero multipoles {\it i.e.} upto $\ell=6,m=4$. The ratio of the different multipole moments to the real space bispectrum depends only on $\beta_1$ the linear redshift distortion parameter and the shape of the triangle. Considering triangles of all possible shapes, we have studied how this ratio depends on the shape of the triangle for $\beta_1=1$. We have also studied the $\beta_1$ dependence for some of the extreme triangle shapes. If measured in future, these multipole moments hold the potential of constraining $\beta_1$. The results presented here are also important if one wishes to constrain $f_{\text{NL}}$ using redshift surveys.

[25]  arXiv:2001.10252 [pdf, other]
Title: Constraints on the Spacetime Dynamics of an Early Dark Energy Component
Comments: 23 pages, 12 figures, 4 tables. To be submitted to JCAP. Comments are welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We consider an Early Dark Energy (EDE) cosmological model, and perform an analysis which takes into account both background and perturbation effects via the parameters $c^{2}_{\rm eff}$ and $c^{2}_{\rm vis}$, representing effective sound speed and viscosity, respectively. By using the latest available data we derive constraints on the amount of dark energy at early times and the present value of the equation of state. Our focus is on the effect that early dark energy has on the Cosmic Microwave Background (CMB) data, including polarization and lensing, in a generalized parameter space including a varying total neutrino mass, and tensor to scalar ratio, besides the 6 standard parameters of the minimal cosmological model. We find that the inclusion of Baryonic Acoustic Oscillations (BAO) data and CMB lensing significantly improves the constraints on the EDE parameters, while other high redshift data like the Quasar Hubble diagram and the Lyman-$\alpha$ forest BAO have instead a negligible impact. We find $\Omega_{\rm eDE} < 0.00391 $ and $w_{0} < -0.9500 $ at the $95 \%$ C.L. for EDE accounting for its clustering through the inclusion of perturbation dynamics. This limit becomes weaker $\Omega_{\rm eDE} < 0.00337$ if perturbations are neglected. The constraints on the EDE parameters are remarkably stable even when $\Sigma m_{\nu}$, and $r$ parameters are varied, with weak degeneracies between $\Omega_{\rm eDE}$ and $r$ or $\Sigma m_{\nu}$. Perturbation parameters are not constrained with current data sets, and tensions between the CMB derived $H_0$ and $\sigma_8$ values and those measured with local probes are not eased. This work demonstrates the capability of CMB probes to constrain the total amount of EDE well below the percent level.

[26]  arXiv:2001.10267 [pdf, other]
Title: Pushing Point spread function reconstruction to the next level. Application to SPHERE/ZIMPOL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Point spread function (PSF) reconstruction (PSF-R) is a well established technique to determine reliably and accurately the PSF from Adaptive Optics (AO) control loop data. We have successfully applied this technique to improve the precision on photometry and astrometry to observation of NGC6121 obtained with SPHERE/ZIMPOL as it will be presented in a forthcoming letter. Firstly, we present the methodology we followed to reconstruct the PSF combining pupil-plane and focal-plane measurements using using our PSF-R method PRIME (Beltramo-Martin et al. 2019), with upgrade of both the model and best-fitting steps compared to previous papers. Secondly, we highlight that PRIME allows to maintain the PSF fitting residual below 0.2% over 2 hours of observation and using only 30 s of AO telemetry, which may have important consequences for telemetry storage for PSF-R purpose on future 30-40 m class telescopes. Finally, we deploy PRIME in a more realistic regime using faint stars so as to identify the precision needed on the initial guess parameters to ensure the convergence towards the optimal solution.

[27]  arXiv:2001.10271 [pdf, other]
Title: Modelling the asymmetries of the Sun's radial $p$-mode line profiles
Comments: 26 pages (19 without appendices), 14 figures. Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In this paper, we aim to develop a predictive model for solar radial $p$-mode line profiles in the velocity spectrum. Unlike the approach favoured by prior studies, this model is not described by free parameters and we do not use fitting procedures to match the observations. Instead, we use an analytical turbulence model coupled with constraints extracted from a 3D hydrodynamic simulation of the solar atmosphere. We then compare the resulting asymmetries with their observationally derived counterpart.
We find that stochastic excitation localised beneath the mode upper turning point generates negative asymmetry for $\nu < \nu_\text{max}$ and positive asymmetry for $\nu > \nu_\text{max}$. On the other hand, stochastic excitation localised above this limit generates negative asymmetry throughout the $p$-mode spectrum. As a result of the spatial extent of the source of excitation, both cases play a role in the total observed asymmetries. By taking this spatial extent into account and using a realistic description of the spectrum of turbulent kinetic energy, both a qualitative and quantitative agreement can be found with solar observations perfoemed by the GONG network. We also find that the impact of the correlation between acoustic noise and oscillation is negligible for mode asymmetry in the velocity spectrum.

[28]  arXiv:2001.10272 [pdf, other]
Title: QUBIC: the Q & U Bolometric Interferometer for Cosmology
Comments: Accepted for publication in the Journal of Low Temperature Physics
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The Q & U Bolometric Interferometer for Cosmology, QUBIC, is an innovative experiment designed to measure the polarization of the Cosmic Microwave Background and in particular the signature left therein by the inflationary expansion of the Universe. The expected signal is extremely faint, thus extreme sensitivity and systematic control are necessary in order to attempt this measurement. QUBIC addresses these requirements using an innovative approach combining the sensitivity of Transition Edge Sensor cryogenic bolometers, with the deep control of systematics characteristic of interferometers. This makes QUBIC unique with respect to others classical imagers experiments devoted to the CMB polarization. In this contribution we report a description of the QUBIC instrument including recent achievements and the demonstration of the bolometric interferometry performed in lab. QUBIC will be deployed at the observation site in Alto Chorrillos, in Argentina at the end of 2019.

[29]  arXiv:2001.10275 [pdf, other]
Title: Periodic activity from a fast radio burst source
Comments: Submitted to Nature. Subject to press embargo until date TBA
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Fast radio bursts (FRBs) are bright, millisecond-duration radio transients originating from extragalactic distances. Their origin is unknown. Some FRB sources emit repeat bursts, ruling out cataclysmic origins for those events. Despite searches for periodicity in repeat burst arrival times on time scales from milliseconds to many days, these bursts have hitherto been observed to appear sporadically, and though clustered, without a regular pattern. Here we report the detection of a $16.35\pm0.18$ day periodicity from a repeating FRB 180916.J0158+65 detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB). In 28 bursts recorded from 16th September 2018 through 30th October 2019, we find that bursts arrive in a 4.0-day phase window, with some cycles showing no bursts, and some showing multiple bursts, within CHIME's limited daily exposure. Our results suggest a mechanism for periodic modulation either of the burst emission itself, or through external amplification or absorption, and disfavour models invoking purely sporadic processes.

[30]  arXiv:2001.10319 [pdf, other]
Title: Efficient modeling of correlated noise I. Statistical significance of periodogram peaks
Comments: Accepted in A&A
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Periodograms are common tools used to search for periodic signals in unevenly spaced time series. The significance of periodogram peaks is often assessed using false alarm probability (FAP), which in most studies assumes uncorrelated noise and is computed using numerical methods such as bootstrapping or Monte Carlo. These methods have a high computational cost, especially for low FAP levels, which are of most interest. We present an analytical estimate of the FAP of the periodogram in the presence of correlated noise, which is fundamental to analyze astronomical time series correctly. The analytical estimate that we derive provides a very good approximation of the FAP at a much lower cost than numerical methods. We validate our analytical approach by comparing it with Monte Carlo simulations. Finally, we discuss the sensitivity of the method to different assumptions in the modeling of the noise.

[31]  arXiv:2001.10368 [pdf, other]
Title: Extreme quasars as distance indicators in cosmology
Comments: 21 pages, 3 figures
Journal-ref: Front. Astron. Space Sci. 6:80 (2020)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

Quasars accreting matter at very high rates (known as extreme Population A [xA] quasars, possibly associated with super-Eddington accreting massive black holes) may provide a new class of distance indicators covering cosmic epochs from present day up to less than 1 Gyr from the Big Bang. At a more fundamental level, xA quasars are of special interest in studies of the physics of AGNs and host galaxy evolution. However, their observational properties are largely unknown. xA quasars can be identified in relatively large numbers from major optical surveys over a broad range of redshifts, thanks to selection criteria defined from the systematic changes along the quasars main sequence. It has been possible to build a sample of about 250 quasars at low and intermediate redshift, and larger samples can be easily selected from the latest data releases of the Sloan Digital Sky Survey. A large sample can clarify the main properties of xA quasars which are expected - unlike the general population of quasars - to radiate at an extreme, well defined Eddington ratio with small scatter. As a result of the small scatter in Eddington ratio shown by xA quasars, we propose a method to derive the main cosmological parameters based on redshift-independent "virial luminosity" estimates from measurements of emission line widths, roughly equivalent to the luminosity estimates based from line width in early and late type galaxies. A major issue related to the cosmological application of the xA quasar luminosity estimates from line widths is the identification of proper emission lines whose broadening is predominantly virial over a wide range of redshift and luminosity. We report on preliminary developments using the AlIII 1860 intermediate ionization line and the Hydrogen Balmer line H-beta as virial broadening estimators, and we briefly discuss the perspective of the method based on xA quasars.

[32]  arXiv:2001.10404 [pdf, other]
Title: The Impact of Metallicity on the Evolution of Rotation and Magnetic Activity of Sun-Like Stars
Authors: L. Amard, S. P. Matt
Comments: 14 pages, 6 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

The rotation rates and magnetic activity of Sun-like and low-mass (< 1.4 Msun) main-sequence stars are known to decline with time, and there now exist several models for the evolution of rotation and activity. However, the role that chemical composition plays during stellar spin-down has not yet been explored. In this work, we use a structural evolution code to compute the rotational evolution of stars with three different masses (0.7, 1.0, and 1.3Msun and six different metallicities, ranging from [Fe/H]=-1.0 to [Fe/H]=+0.5. We also implement three different wind-braking formulations from the literature (two modern and one classical) and compare their predictions for rotational evolution. The effect that metallicity has on stellar structural properties, and in particular the convective turnover timescale, leads the two modern wind-braking formulations to predict a strong dependence of the torque on metallicity. Consequently, they predict that metal rich stars spin-down more effectively at late ages (> 1 Gyr) than metal poor stars, and the effect is large enough to be detectable with current observing facilities. For example, the formulations predict that a Sun-like (solar-mass and solar-aged) star with [Fe/H]=-0.3 will have a rotation period of less than 20 days. Even though old, metal poor stars are predicted to rotate more rapidly at a given age, they have larger Rossby numbers and are thus expected to have lower magnetic activity levels. Finally, the different wind-braking formulations predict quantitative differences in the metallicity-dependence of stellar rotation, which may be used to test them.

[33]  arXiv:2001.10417 [pdf, other]
Title: Power spectrum response of large-scale structure in 1D and in 3D: tests of prescriptions for post-collapse dynamics
Comments: 18 pages, 8 figures, submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The power spectrum response function of the large-scale structure of the Universe describes how the evolved power spectrum is modified by a small change in initial power through non-linear mode coupling of gravitational evolution. It was previously found that the response function for the coupling from small to large scales is strongly suppressed in amplitude, especially at late times, compared to predictions from perturbation theory (PT) based on the single-stream approximation. One obvious explanation for this is that PT fails to describe the dynamics beyond shell-crossing. We test this idea by comparing measurements in $N$-body simulations to prescriptions based on PT but augmented with adaptive smoothing to account for the formation of non-linear structures of various sizes in the multi-stream regime. We first start with one-dimensional (1D) cosmology, where the Zel'dovich approximation provides the exact solution in the single stream regime. Similarly to the 3D case, the response function of the large-scale modes exhibits a strong suppression in amplitude at small scales which cannot be explained by the Zel'dovich solution alone. However, by performing adaptive smoothing of initial conditions to identify haloes of different sizes and solving approximately post-collapse dynamics in the 3-streams regime, agreement between theory and simulations drastically improves. We extend our analyses to the 3D case using PINOCCHIO algorithm, in which similar adaptive smoothing is implemented on the Lagrangian PT fields to identify haloes and is combined with a spherical halo prescription to account for post-collapse dynamics. Again, a suppression is found in the coupling between small- and large-scale modes and the agreement with simulations is improved.

[34]  arXiv:2001.10434 [pdf, other]
Title: Equation of State and Progenitor Dependence of Stellar-Mass Black-Hole Formation
Comments: 22 pages, 13 figures, 3 tables
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)

The core collapse of a massive star results in the formation of a proto-neutron star (PNS). If enough material is accreted onto a PNS it will become gravitationally unstable and further collapse into a black-hole (BH). We perform a systematic study of failing core-collapse supernovae in spherical symmetry for a wide range of presupernova progenitor stars and equations of state (EOSs) of nuclear matter. We analyze how variations in progenitor structure and the EOS of dense matter above nuclear saturation density affect the PNS evolution and subsequent BH formation. Comparisons of core-collapse for a given progenitor star and different EOSs show that the path traced by the PNS in mass-entropy phase space $M_{\mathrm{grav}}^{\mathrm{PNS}}-\tilde{s}$ is well correlated with the progenitor compactness and almost EOS independent, apart from the final endpoint. Furthermore, BH formation occurs, to a very good approximation, soon after the PNS overcomes the maximum \textit{gravitational} mass supported by a hot NS with constant entropy equal to $\tilde{s}$. These results show a path to constraining the temperature dependence of the EOS through the detection of neutrinos from a failed galactic supernova.

[35]  arXiv:2001.10454 [pdf, other]
Title: Stimulated-emission based model of fast radio bursts
Comments: submitted on January 13th, 2020 to MNRAS. After the referee comments
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Fast radio bursts (FRBs) are bright, short-duration radio transients with very high brightness temperatures implying highly coherent emission. We suggest that the FRBs are caused by the self-focusing of an electron beam interacting with an ambient plasma right beyond the light cylinder radius of a neutron star. The magnetic field at the light cylinder radius is relatively high which can accommodate both young Crab-like systems and old millisecond pulsars addressing the diverse environments of FRBs. At the first stage, the intense pulsed-beam passing through the background plasma causes instabilities such that the trapped particles in local Buneman-type cavitons saturate the local field. The beam is then radially self-focused due to the circular electric field developed by the two-stream instability which leads to Weibel instability in the transverse direction. Finally, the non-linear saturation of the Weibel instability results in the self-modulational formation of solitons due to plasmoid instability. The resonant solitary waves are the breather-type solitons hosting relativistic particles with self-excited oscillations. The analytical solutions obtained for non-linear dispersion and solitons suggest that, near the current sheets, the relativistic bunches are accelerated/amplified by klystron-like structures due to self-excited oscillations by the induced local electric field. Boosted coherent radio emission propagates through a narrow cone with strong focusing due to radial electric field and magnetic pinching. The non-linear evolution of solitons and the stimulated emission are associated with the Buneman instability and the possibility of the presence of nanosecond shots in FRBs are investigated.

[36]  arXiv:2001.10456 [pdf, other]
Title: A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating III. 3D Simulations and Atmospheric Response
Comments: 17 pages, 13 figures, to appear in The Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Inspired by recent observations suggesting that photospheric magnetic flux cancellation occurs much more frequently than previously thought, we analytically estimated the energy released from reconnection driven by photospheric flux cancellation, and proposed that it can act as a mechanism for chromospheric and coronal heating (Priest et al., 2018). Using two-dimensional simulations we validated the analytical estimates and studied the resulting atmospheric response (Syntelis et al. 2019). In the present work, we set up three-dimensional resistive MHD simulations of two cancelling polarities in a stratified atmosphere with a horizontal external field to further validate and improve upon the analytical estimates. The computational evaluation of the parameters associated with the energy release are in good qualitative agreement with the analytical estimates. The computational Poynting energy flux into the current sheet is in good qualitative agreement with the analytical estimates, after correcting the analytical expression to better account for the horizontal extent of the current sheet. The atmospheric response to the cancellation is the formation of hot ejections, cool ejections, or a combination of both hot and cool ejections, which can appear with a time difference and/or be spatially offset, depending on the properties of the cancelling region and the resulting height of the reconnection. Therefore, during the cancellation, a wide spectrum of ejections can be formed, which can account for the variety of multi-thermal ejections associated with Ellerman bombs, UV bursts and IRIS bombs, and also other ejections associated with small-scale cancelling regions and spicules.

[37]  arXiv:2001.10458 [pdf, other]
Title: The K Dwarf Advantage for Biosignatures on Directly Imaged Exoplanets
Authors: Giada N. Arney
Comments: Published in Astrophysical Journal Letters in March 2019
Journal-ref: The Astrophysical Journal Letters, 873(1), L7 (2019)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Oxygen and methane are considered to be the canonical biosignatures of modern Earth, and the simultaneous detection of these gases in a planetary atmosphere is an especially strong biosignature. However, these gases may be challenging to detect together in the planetary atmospheres because photochemical oxygen radicals destroy methane. Previous work has shown that the photochemical lifetime of methane in oxygenated atmospheres is longer around M dwarfs, but M dwarf planet habitability may be hindered by extreme stellar activity and evolution. Here, we use a 1-D photochemical-climate model to show that K dwarf stars also offer a longer photochemical lifetime of methane in the presence of oxygen compared to G dwarfs. For example, we show that a planet orbiting a K6V star can support about an order of magnitude more methane in its atmosphere compared to an equivalent planet orbiting a G2V star. In the reflected light spectra of worlds orbiting K dwarf stars, strong oxygen and methane features could be observed at visible and near-infrared wavelengths. Because K dwarfs are dimmer than G dwarfs, they offer a better planet-star contrast ratio, enhancing the signal-to-noise (SNR) possible in a given observation. For instance, a 50 hour observation of a planet at 7 pc with a 15-m telescope yields SNR = 9.2 near 1 um for a planet orbiting a solar-type G2V star, and SNR = 20 for the same planet orbiting a K6V star. In particular, nearby mid-late K dwarfs such as 61 Cyg A/B, Epsilon Indi, Groombridge 1618, and HD 156026 may be excellent targets for future biosignature searches.

[38]  arXiv:2001.10465 [pdf, ps, other]
Title: The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence
Comments: 17 pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)

We present new constraints on anisotropic birefringence of the cosmic microwave background polarization using two seasons of data from the Atacama Cosmology Telescope covering $456$ square degrees of sky. The birefringence power spectrum, measured using a curved-sky quadratic estimator, is consistent with zero. Our results provide the tightest current constraint on birefringence over a range of angular scales between $5$ arcminutes and $9$ degrees. We improve previous upper limits on the amplitude of a scale-invariant birefringence power spectrum by a factor of between $2$ and $3$. Assuming a nearly-massless axion field during inflation, our result is equivalent to a $2\sigma$ upper limit on the Chern-Simons coupling constant between axions and photons of $g_{\alpha\gamma}<4.0\times 10^{-2}/H_I$ where $H_I$ is the inflationary Hubble scale.

[39]  arXiv:2001.10492 [pdf, other]
Title: The Birth Function for Black Holes and Neutron Stars in Binaries
Comments: submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

The mass function for black holes at birth in close binary systems is explored. The effects of varying the mass-loss rate and metallicity are calculated using a simple semi-analytic approach to stellar evolution that is tuned to reproduce detailed numerical calculations. Though the total fraction of black holes made in stellar collapse events varies considerably with metallicity, mass-loss rate, and mass cutoff, from 5$\%$ to 30$\%$, the shapes of their birth functions are very similar for all reasonable variations in these quantities. Median neutron star masses are in the range 1.32 -- 1.37 $M_\odot$ regardless of metallicity. The median black hole mass for solar metallicity is typically 8 to 9 $M_\odot$ if only initial helium cores below 40 $M_\odot$ (ZAMS mass less than 80 $M_\odot$) contribute, and 9 -- 13 $M_\odot$, in most cases, if helium cores up to 150 $M_\odot$ (ZAMS mass less than 300 $M_\odot$) contribute. As long as the mass-loss rate as a function of mass exhibits no strong non--linearities, the black hole birth function from 15 to 35 $M_\odot$ has a slope that depends mostly on the initial mass function for main sequence stars. These findings imply the possibility of constraining the initial mass function and the properties of mass loss in close binaries using ongoing measurements of gravitational wave radiation. The expected rotation rates of the black holes are discussed.

Cross-lists for Wed, 29 Jan 20

[40]  arXiv:2001.10011 (cross-list from gr-qc) [pdf, other]
Title: LISA parameter estimation and source localization with higher harmonics of the ringdown
Comments: 19 pages, 15 figures, 2 tables
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

LISA can detect higher harmonics of the ringdown gravitational-wave signal from massive black-hole binary mergers with large signal-to-noise ratio. The most massive black-hole binaries are more likely to have electromagnetic counterparts, and the inspiral will contribute little to their signal-to-noise ratio. Here we address the following question: can we extract the binary parameters and localize the source using LISA observations of the ringdown only? Modulations of the amplitude and phase due to LISA's motion around the Sun can be used to disentangle the source location and orientation when we detect the long-lived inspiral signal, but they can not be used for ringdown-dominated signals, which are very short-lived. We show that (i) we can still measure the mass ratio and inclination of high-mass binaries by carefully combining multiple ringdown harmonics, and (ii) we can constrain the sky location and luminosity distance by relying on the relative amplitudes and phases of various harmonics, as measured in different LISA channels.

[41]  arXiv:2001.10132 (cross-list from physics.ins-det) [pdf, other]
Title: An analysis and visualization of the output mode-matching requirements for squeezing in Advanced LIGO and future gravitational wave detectors
Comments: Submitted to PRD
Subjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The sensitivity of ground-based gravitational wave (GW) detectors will be improved in the future via the injection of frequency-dependent squeezed vacuum. The achievable improvement is ultimately limited by losses of the interferometer electromagnetic field that carries the GW signal. The analysis and reduction of optical loss in the GW signal chain will be critical for optimal squeezed light-enhanced interferometry. In this work we analyze a strategy for reducing output-side losses due to spatial mode mismatch between optical cavities with the use of adaptive optics. Our goal is not to design a detector from the top down, but rather to minimize losses within the current design. Accordingly, we consider actuation on optics already present and one transmissive optic to be added between the signal recycling mirror and the output mode cleaner. The results of our calculation show that adaptive mode-matching with the current Advanced LIGO design is a suitable strategy for loss reduction that provides less than 2% mean output mode-matching loss. The range of actuation required is +47 uD on SR3, +140 mD on OM1 and OM2, +50 mD on the SRM substrate, and -50 mD on the added new transmissive optic. These requirements are within the demonstrated ranges of real actuators in similar or identical configurations to the proposed implementation. We also present a novel technique that graphically illustrates the matching of interferometer modes and allows for a quantitative comparison of different combinations of actuators.

[42]  arXiv:2001.10143 (cross-list from nucl-th) [pdf, ps, other]
Title: Effects of symmetry energy on equation of state for simulations of core-collapse supernovae and neutron-star mergers
Comments: 13 pages, 11 figures
Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)

We construct a new equation of state (EOS) for numerical simulations of core-collapse supernovae and neutron-star mergers based on an extended relativistic mean-field model with a small symmetry energy slope $L$, which is compatible with both experimental nuclear data and recent observations of neutron stars. The new EOS table (EOS4) based on the extended TM1 (TM1e) model with $L=40$ MeV is designed in the same tabular form and compared with the commonly used Shen EOS (EOS2) based on the original TM1 model with $L=110.8$ MeV. This is convenient and useful for performing numerical simulations and examining the influences of symmetry energy and its density dependence on astrophysical phenomena. In comparison with the TM1 model used in EOS2, the TM1e model provides a similar maximum neutron-star mass but smaller radius and tidal deformability for a $1.4 M_\odot$ neutron star, which is more consistent with current constraints. By comparing the phase diagram and thermodynamic quantities between EOS4 and EOS2, it is found that the TM1e model predicts relatively larger region of nonuniform matter and softer EOS for neutron-rich matter. Significant differences between EOS4 and EOS2 are observed in the case with low proton fraction, while the properties of symmetric matter remain unchanged.

[43]  arXiv:2001.10200 (cross-list from stat.ME) [pdf, other]
Title: The n-dimensional Extension of the Lomb-Scargle Method
Comments: to be published
Subjects: Methodology (stat.ME); Instrumentation and Methods for Astrophysics (astro-ph.IM)

The common methods of spectral analysis for n-dimensional time series investigate Fourier transform (FT) to decompose discrete data into a set of trigonometric components, i. e. amplitude and phase. Due to the limitations of discrete FT, the data set is restricted to equidistant sampling. However, in the general situation of non-equidistant sampling FT based methods will cause significant errors in the parameter estimation. Therefore, the classical Lomb-Scargle method (LSM) was developed for one dimensional data to circumvent the incorrect behaviour of FT in case of fragmented and irregularly sampled data. The present work deduces LSM for n-dimensional (multivariate) data sets by a redefinition of the shifting parameter $\tau$. An analytical derivation shows, that nD LSM extents the traditional 1D case preserving all the statistical features. Applications with ideal test data and experimental data will illustrate the derived method.

[44]  arXiv:2001.10307 (cross-list from gr-qc) [pdf, other]
Title: Effects of magnetic field on the radiation pressure dominated discs around neutron stars
Comments: 14 pages, 9 figures, accepted in Modern Physics Letters A
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

We supplement the analytic solution obtained by Matthews O. M., et. al., 2005, MNRAS, \textbf{356}, 66 to investigate the steady-state structure of radiation pressure dominated disc under the influence of a stellar magnetic field which deploys a torque. The solutions converge to the non-magnetic Shakura N. I., Sunyaev R. A., 1973, A\& A, \textbf{24}, 337 form when magnetic field of the star tends to zero and also at large radii. Effects of varying the mass accretion rates and the spin period of a typical neutron star on the disc parameters are presented. We further report that the presence of a magnetic correction term $k$ reduces the radial extent upto which radiation pressure and electron scattering continue to be the major source of pressure and opacity respectively. We also report that magnetic effects amplify the viscous timescale several times in the inner disc.

[45]  arXiv:2001.10506 (cross-list from physics.space-ph) [pdf]
Title: On the properties of solar energetic particle events associated with metric type II radio bursts
Comments: 24 pages, 5 figures, accepted for publication in Sun and Geosphere, a special issue devoted to the ISWI Workshop, Trieste, Italy, 20 - 24 May, 2019
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

Metric type II solar radio bursts and solar energetic particles (SEPs) are both associated with shock fronts driven by coronal mass ejections (CMEs) in the solar corona. Recent studies of ground level enhancements (GLEs), regular large solar energetic particle (SEP) events and filament eruption (FE) associated large SEP events have shown that SEP events are organized by spectral index of proton fluence spectra and by the average starting frequencies of the associated type II radio bursts. Both these results indicate a hierarchical relationship between CME kinematics and SEP event properties. In this study, we expand the investigations to fluence spectra and the longitudinal extent of metric type II associated SEP events including low-intensity SEP events. We utilize SEP measurements of particle instruments on the Solar and Heliospheric Observatory (SOHO) and Solar Terrestrial Relations Observatory (STEREO) spacecraft together with radio bursts observations by ground-based radio observatories during solar cycle 24. Our results show that low-intensity SEP events follow the hierarchy of spectral index or the hierarchy of the starting frequency of type II radio bursts. We also find indications of a trend between the onset frequency of metric type II bursts and the estimated longitudinal extent of the SEP events although the scatter of data points is quite large. These two results strongly support the idea of SEP acceleration by shocks. Stronger shocks develop closer to the Sun.

[46]  arXiv:2001.10527 (cross-list from physics.ed-ph) [pdf]
Title: A New Lecture-Tutorial for Teaching Interferometry to Astro 101 Students
Comments: 12 pages, 7 figures, 1 table, submitted to The Physics Teacher
Subjects: Physics Education (physics.ed-ph); Astrophysics of Galaxies (astro-ph.GA)

The ground-breaking image of a black hole's event horizon, which captured the public's attention and imagination in April 2019, was captured using the power of interferometry: many separate telescopes working together to observe the cosmos in incredible detail. Many recent astrophysical discoveries that have revolutionized the scientific community's understanding of the cosmos were made by interferometers such as LIGO, ALMA, and the Event Horizon Telescope. Astro 101 instructors who want their students to learn the science behind these discoveries must teach about interferometry. Decades of research show that using active learning strategies can significantly increase students' learning and reduces achievement gaps between different demographic groups over what is achieved from traditional lecture-based instruction. As part of an effort to create active learning materials on interferometry, we developed and tested a new Lecture-Tutorial to help Astro 101 students learn about key properties of astronomical interferometers. This paper describes this new Lecture-Tutorial and presents evidence for its effectiveness from a study conducted with 266 Astro 101 students at the University of North Carolina at Chapel Hill.

Replacements for Wed, 29 Jan 20

[47]  arXiv:1611.08279 (replaced) [pdf, ps, other]
Title: Goldstone models of modified gravity
Comments: 38 pages
Journal-ref: Phys. Rev. D 95, 043515 (2017)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[48]  arXiv:1802.00024 (replaced) [pdf, other]
Title: Advancing the Velocity Gradient Technique: Using Gradient Amplitudes and handling thermal broadening
Comments: 18 pages, 8 figures, 1 extra figure in the appendix, submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[49]  arXiv:1902.07719 (replaced) [pdf, other]
Title: Shot noise in the astrophysical gravitational-wave background
Comments: 7 pages, 1 figure, version published in PRD
Journal-ref: Phys. Rev. D 100, 063508 (2019)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[50]  arXiv:1903.00013 (replaced) [pdf, other]
Title: Boosting the dark matter signal with Coulomb resonances
Comments: 29 pages, 9 figures. v2: published version. Few typos corrected and added comment on perturbative unitarity
Journal-ref: JCAP 1909 (2019) no.09, 056
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)
[51]  arXiv:1903.12191 (replaced) [pdf, other]
Title: Comment on the paper "Calorimetric Dark Matter Detection with Galactic Center Gas Clouds"
Comments: 2 pages, 1 figure. Version appearing in Phys. Rev. Lett
Journal-ref: Phys. Rev. Lett. 124, 029001 (2020)
Subjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics of Galaxies (astro-ph.GA)
[52]  arXiv:1904.12854 (replaced) [pdf, other]
Title: Collisional formation of massive exomoons of super-terrestrial exoplanets
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[53]  arXiv:1907.06642 (replaced) [pdf, other]
Title: Estimating the angular power spectrum of the gravitational-wave background in the presence of shot noise
Comments: 11 pages, 3 figures, version published in PRD
Journal-ref: Phys. Rev. D 100, 083501 (2019)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)
[54]  arXiv:1908.02508 (replaced) [pdf, other]
Title: The Core-Cusp Problem Revisited: ULDM vs. CDM
Comments: 15 pages, accepted for publication in PASA
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[55]  arXiv:1908.03084 (replaced) [pdf, other]
Title: On the impact of magnetic-field models in galaxy clusters on constraints on axion-like particles from the lack of irregularities in high-energy spectra of astrophysical sources
Comments: 8 pages, 4 figures, elsarticle.sty. V2: extended explanations, corrected figures (including the would-be exclusion plot) - conclusions unchanged. Version accepted by Phys. Lett. B. V3: A misprint corrected
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[56]  arXiv:1908.04740 (replaced) [pdf, other]
Title: First-order phase transition from hypernuclear matter to deconfined quark matter obeying new constraints from compact star observations
Comments: 37 pages, 13 figures, 1 table, references added, text and figures revised, version accepted for publication in Phys. Rev. C
Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[57]  arXiv:1909.00568 (replaced) [pdf, ps, other]
Title: B-mode Power Spectrum of CMB via Polarized Compton Scattering
Comments: 20 pages,3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
[58]  arXiv:1909.01395 (replaced) [pdf, other]
Title: Modelling the AGN broad line region using single-epoch spectra II. Nearby AGN
Comments: Accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[59]  arXiv:1909.13814 (replaced) [pdf, other]
Title: Binary Pulsars as probes for Spin-2 Ultralight Dark Matter
Journal-ref: JCAP 01(2020)053
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[60]  arXiv:1910.12785 (replaced) [pdf, other]
Title: Detection of a Water Tracer in Interstellar Comet 2I/Borisov
Comments: 8 pages, 2 figures, 1 table, Accepted in ApJ Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[61]  arXiv:1910.12896 (replaced) [pdf, other]
Title: Milky Way Analogues in MaNGA: Multi-Parameter Homogeneity and Comparison to the Milky Way
Comments: 33 pages, 28 figures. Accepted by MNRAS. Definition of "old stars" from Hasselquist et al. 2019 corrected from 10 Gyr to 9 Gyr; results and discussion unchanged
Journal-ref: MNRAS, Volume 491, p.3672-3701 (2020)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[62]  arXiv:1912.04312 (replaced) [pdf, other]
Title: Galactic Archaeology with asteroseismic ages. II. Confirmation of a delayed gas infall using Bayesian analysis based on MCMC methods
Comments: Accepted for publication in Astronomy and Astrophysics (A&A), 12 pages, 13 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[63]  arXiv:1912.06663 (replaced) [pdf, other]
Title: An analysis of galaxy cluster mis-centring using cosmological hydrodynamic simulations
Comments: 12 pages, 9 Figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[64]  arXiv:1912.07007 (replaced) [pdf, other]
Title: The influence of NLTE effects in Fe I lines on an inverted atmosphere I. 6301 A and 6302 A lines formed in 1D NLTE
Comments: Includes language corrections
Journal-ref: A&A 633, A157 (2020)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[65]  arXiv:1912.08235 (replaced) [pdf, other]
Title: Dim Prospects for Transmission Spectra of Ocean Earths Around M Stars
Comments: Accepted to the Astrophysical Journal. 25 pages, 10 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[66]  arXiv:1912.12217 (replaced) [pdf, other]
[67]  arXiv:2001.03135 (replaced) [pdf, other]
Title: X-ray Detected AGN in SDSS Dwarf Galaxies
Comments: 19 pages, 12 figures, 1 table. Accepted for publication in MNRAS
Journal-ref: MNRAS, Volume 492, Issue 2, February 2020, Pages 2268 to 2284
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[68]  arXiv:2001.03425 (replaced) [pdf, other]
Title: Mass limits for stationary protoplanetary accretion disks
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
[69]  arXiv:2001.05469 (replaced) [pdf, other]
Title: Cosmological constraints on dark energy in light of gravitational wave bounds
Authors: Johannes Noller
Comments: 16 pages, 4 figures, 1 table; v2 minor clarifications added and typos corrected, results/equations/conclusions unchanged
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[70]  arXiv:2001.08751 (replaced) [pdf, other]
Title: Semi-analytic forecasts for JWST -- IV. Implications for cosmic reionization and LyC escape fraction
Comments: 21 pages, 15 figures, submitted to MNRAS, all comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
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