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New submissions for Tue, 25 Feb 20
- [1] arXiv:2002.09490 [pdf, other]
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Title: A Possible Distance Bias for Type Ia Supernovae with Different Ejecta VelocitiesComments: 14 pages, 15 figures. Accepted for publication in MNRAS. Repository at this https URL , database and composite spectra at this https URL , and our documentation at this https URLSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
After correcting for their light-curve shape and color, Type Ia supernovae (SNe Ia) are precise cosmological distance indicators. However, there remains a non-zero intrinsic scatter in the differences between measured distance and that inferred from a cosmological model (i.e., Hubble residuals or HRs), indicating that SN Ia distances can potentially be further improved. We use the open-source relational database kaepora to generate composite spectra with desired average properties of phase, light-curve shape, and HR. At many phases, the composite spectra from two subsamples with positive and negative average HRs are significantly different. In particular, in all spectra from 9 days before to 15 days after peak brightness, we find that SNe with negative HRs have, on average, higher ejecta velocities (as seen in nearly every optical spectral feature) than SNe with positive HRs. At +4 days relative to B-band maximum, using a sample of 62 SNe Ia, we measure a 0.091 +/- 0.035 mag HR step between SNe with Si II 6355 line velocities higher/lower than -11,000 km/s (the median velocity). After light-curve shape and color correction, SNe with higher velocities tend to have underestimated distance moduli relative to a cosmological model. The intrinsic scatter in our sample reduces from 0.094 mag to 0.082 mag after making this correction. Using the Si II 6355 velocity evolution of 115 SNe Ia, we estimate that a velocity difference > 500 km/s exists at each epoch between the positive-HR and negative-HR samples with 99.4% confidence. Finally at epochs later than +37 days, we observe that negative-HR composite spectra tend to have weaker spectral features in comparison to positive-HR composite spectra.
- [2] arXiv:2002.09491 [pdf, other]
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Title: Gravitational wave population inference with deep flow-based generative networkComments: 11 pages, 3 figuresSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
We combine hierarchical Bayesian modeling with a flow-based deep generative network, in order to demonstrate that one can efficiently constraint numerical gravitational wave (GW) population models at a previously intractable complexity. Existing techniques for comparing data to simulation,such as discrete model selection and Gaussian process regression, can only be applied efficiently to moderate-dimension data. This limits the number of observable (e.g. chirp mass, spins.) and hyper-parameters (e.g. common envelope efficiency) one can use in a population inference. In this study, we train a network to emulate a phenomenological model with 6 observables and 4 hyper-parameters, use it to infer the properties of a simulated catalogue and compare the results to the phenomenological model. We find that a 10-layer network can emulate the phenomenological model accurately and efficiently. Our machine enables simulation-based GW population inferences to take on data at a new complexity level.
- [3] arXiv:2002.09493 [pdf, other]
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Title: Orbital evidences for dark-matter free Milky-Way dwarf-spheroidal galaxiesAuthors: Francois Hammer, Yanbin Yang, Frederic Arenou, Jianling Wang, Hefan Li, Piercarlo Bonifacio, Carine BabusiauxComments: 16 pages, 6 Figures, accepted for publication in The Astrophysical JournalSubjects: Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
The nature of Milky Way dwarf spheroidals (MW dSphs) has been questioned, in particular whether they are dominated by dark matter (DM). Here we investigate an alternative scenario, for which tidal shocks are exerted by the MW to DM-free dSphs after a first infall of their gas-rich progenitors, and for which theoretical calculations have been verified by pure N-body simulations. Whether or not the dSphs are on their first infall cannot be resolved on the sole basis of their star formation history. In fact, near pericenter passages can give rise to complex gas removal causing gravitational instabilities and tidal disruptive processes. Advanced precision with the Gaia satellite in determining both their past orbital motions and the MW velocity curve is however providing crucial results.
First, tidal shocks explain why DM-free dSphs are found preferentially near their pericenter where they are in a destructive process, while their chance to be long-lived satellites is associated to a very low probability P$\sim$ 2 $10^{-7}$, which is at odds with the current DM-dominated dSph scenario. Second, most dSph binding energies are consistent with a first infall. Third, the MW tidal shocks that predict the observed dSph velocity dispersions, are themselves predicted in amplitude by the most accurate MW velocity curve. Fourth, tidal shocks accurately predict the forces or accelerations exerted at half light radius of dSphs, including the MW and the Magellanic System gravitational attractions. The above is suggestive of dSphs that are DM-free and tidally-shocked near their pericenters, which may provoke a significant quake in our understanding of near-field cosmology. - [4] arXiv:2002.09494 [pdf, other]
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Title: Understanding the large inferred Einstein radii of observed low-mass galaxy clustersComments: 7 pages, 3 figures, submitted to MNRASSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
We assess a claim that observed galaxy clusters with mass ~10^14 Msun are more centrally concentrated than predicted in LCDM. We generate mock strong gravitational lensing observations, taking the lenses from a cosmological hydrodynamical simulation, and analyse them in the same way as the real Universe. The observed and simulated lensing arcs are consistent with one another, with three main effects responsible for the previously claimed inconsistency. First, galaxy clusters containing baryonic matter have higher central densities than their counterparts simulated with only dark matter. Second, a sample of clusters selected because of the presence of pronounced gravitational lensing arcs preferentially finds centrally concentrated clusters with large Einstein radii. Third, lensed arcs are usually straighter than critical curves, and the chosen image analysis method (fitting circles through the arcs) overestimates the Einstein radii. After accounting for these three effects, LCDM predicts that galaxy clusters should produce giant lensing arcs that match those in the observed Universe.
- [5] arXiv:2002.09495 [pdf, other]
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Title: The Stars in M15 Were Born with the r-processAuthors: Evan N. Kirby (1), Gina Duggan (1), Enrico Ramirez-Ruiz (2,3), Phillip Macias (2) ((1) Caltech, (2) UC Santa Cruz, (3) Niels Bohr Institute, University of Copenhagen)Comments: 10 pages, 2 figures, accepted to ApJLSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
High-resolution spectroscopy of stars on the red giant branch (RGB) of the globular cluster M15 has revealed a large (~1 dex) dispersion in the abundances of r-process elements, like Ba and Eu. Neutron star mergers (NSMs) have been proposed as a major source of the r-process. However, most NSM models predict a delay time longer than the timescale for cluster formation. One possibility is that a NSM polluted the surfaces of stars in M15 long after the cluster finished forming. In this case, the abundances of the polluting elements would decrease in the first dredge-up as stars turn on to the RGB. We present Keck/DEIMOS abundances of Ba in 66 stars along the entire RGB and the top of the main sequence. The Ba abundances have no trend with stellar luminosity (evolutionary phase). Therefore, the stars were born with the Ba they have today, and Ba did not originate in a source with a delay time longer than the timescale for cluster formation. In particular, if the source of Ba was a neutron star merger, it would have had a very short delay time. Alternatively, if Ba enrichment took place before the formation of the cluster, an inhomogeneity of a factor of 30 in Ba abundance needs to be able to persist over the length scale of the gas cloud that formed M15, which is unlikely.
- [6] arXiv:2002.09496 [pdf, other]
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Title: From birth associations to field stars: mapping the small-scale orbit distribution in the Galactic discAuthors: Johanna Coronado, Hans-Walter Rix, Wilma H. Trick, Kareem El-Badry, Jan Rybizki, Maosheng XiangComments: 16 pages, 13 figures. Submitted to MNRASSubjects: Astrophysics of Galaxies (astro-ph.GA)
Stars born at the same time in the same place should have formed from gas of the same element composition. But most stars subsequently disperse from their birth siblings, in orbit and orbital phase, becoming 'field stars'. Here we explore and provide direct observational evidence for this process in the Milky Way disc, by quantifying the probability that orbit-similarity among stars implies indistinguishable metallicity. We define the orbit similarity among stars through their distance in action-angle space, $\Delta (J,\theta)$, and their abundance similarity simply by $\Delta$[Fe/H]. Analyzing a sample of main sequence stars from Gaia DR2 and LAMOST, we find an excess of pairs with the same metallicity ($\Delta\mathrm{[Fe/H]}<0.1$) that extends to remarkably large separations in $\Delta (J,\theta)$ that correspond to nearly 1 kpc distances. We assess the significance of this effect through a mock sample, drawn from a smooth and phase-mixed orbit distribution. Through grouping such star pairs into associations with a friend-of-friends algorithm linked by $\Delta (J,\theta)$, we find 100s of mono-abundance groups with $\ge 3$ (to $\gtrsim 20$) members; these groups -- some clusters, some spread across the sky -- are over an order-of-magnitude more abundant than expected for a smooth phase-space distribution, suggesting that we are witnessing the 'dissolution' of stellar birth associations into the field.
- [7] arXiv:2002.09497 [pdf, ps, other]
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Title: The Edge of the GalaxyAuthors: Alis J. Deason (Durham), Azadeh Fattahi (Durham), Carlos S. Frenk (Durham), Robert J. J. Grand (MPA), Kyle A. Oman (Durham), Shea Garrison-Kimmel (Factual), Christine M. Simpson (Chicago), Julio F. Navarro (UVic)Comments: 14 pages, 11 figures. Submitted to MNRASSubjects: Astrophysics of Galaxies (astro-ph.GA)
We use cosmological simulations of isolated Milky Way-mass galaxies, as well as Local Group analogues, to define the "edge'' --- a caustic manifested in a drop in density or radial velocity --- of Galactic-sized haloes, both in dark matter and in stars. In the dark matter, we typically identify two caustics: the outermost caustic located at ~1.4r_200m corresponding to the "splashback'' radius, and a second caustic located at ~0.6r_200m which likely corresponds to the edge of the virialized material which has completed at least two pericentric passages. The splashback radius is ill defined in Local Group type environments where the halos of the two galaxies overlap. However, the second caustic is less affected by the presence of a companion, and seems a more natural definition for the boundary of the Milky Way halo. Curiously, the stellar distribution also has a clearly defined caustic, which, in most cases, coincides with the second caustic of the dark matter. This can be identified in both radial density and radial velocity profiles, and should be measurable in future observational programmes. Finally, we show that the second caustic can also be identified in the phase-space distribution of dwarf galaxies in the Local Group. Using the current dwarf galaxy population, we predict the edge of the Milky Way halo to be 292 +/- 61 kpc.
- [8] arXiv:2002.09498 [pdf, other]
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Title: ALMA Observations of the Molecular Clouds in NGC 625Subjects: Astrophysics of Galaxies (astro-ph.GA)
We present the highest resolution (1") $^{12}$CO(1-0) observations of molecular gas in the dwarf starburst galaxy NGC 625, to date, obtained with ALMA. Molecular gas is distributed in discrete clouds within an area of $0.4$ kpc$^2$ and does not have well-ordered large-scale motions. We measure a total molecular mass in NGC 625 of $5.3\times 10^6 M_\odot$, assuming a Milky Way CO-to-H$_2$ conversion factor. We use the CPROPS package to identify molecular clouds and measure their properties. The 19 resolved CO clouds have a median radius of 20 pc, a median line width 2.5 km s$^{-1}$, and a median surface density of 169 $M_\odot$pc$^{-2}$. Larson scaling relations suggest that molecular clouds in NGC 625 are mostly in virial equilibrium. Comparison of our high-resolution CO observations with a star formation rate map, inferred from ancillary optical observations observations, suggests that about 40% of the molecular clouds coincide with the brightest HII regions. These bright HII regions have a range of molecular gas depletion timescales, all within a factor of $\sim 3$ of the global depletion time in NGC 625 of 106-134 Myr. The highest surface density molecular clouds towards the southwest of the galaxy, in a region we call the Butterfly, do not show strong star formation activity and suggest a depletion time scale longer than 5 Gyr.
- [9] arXiv:2002.09499 [pdf, other]
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Title: The regulation of galaxy growth along the size-mass relation by star-formation, as traced by H$α$ in KMOS$^{3D}$ galaxies at 0.7 < z < 2.7Authors: D.J. Wilman (1), M. Fossati (1) (2), J.T. Mendel, R. Saglia, E. Wisnioski, S. Wuyts, N. Förster Schreiber, A. Beifiori, R. Bender, S. Belli, H. Übler, P. Lang, J.C.C. Chan, R.L. Davies, E. J. Nelson, R. Genzel, L.J. Tacconi, A. Galametz, R. I. Davies, D. Lutz, S. Price, A. Burkert, K. Tadaki, R. Herrera-Camus, G. Brammer, I. Momcheva, P. van Dokkum ((1) USM/MPE, Munich (2) Durham University)Comments: 29 pages, 18 figures, accepted for publication in ApJ. Table C1 will be available in machine readable format with the final published version of the paperSubjects: Astrophysics of Galaxies (astro-ph.GA)
We present half-light sizes measured from H${\alpha}$ emission tracing star-formation in 281 star-forming galaxies from the KMOS3D survey at 0.7 < z < 2.7. Sizes are derived by fitting 2D exponential disk models, with bootstrap errors averaging 20%. H${\alpha}$ sizes are a median (mean) of 1.19 (1.26) times larger than those of the stellar continuum, which due to radial dust gradients places an upper limit on the growth in stellar size via star formation, with just 43% intrinsic scatter. At fixed continuum size the H${\alpha}$ size shows no residual trend with stellar mass, star formation rate, redshift or morphology. The only significant residual trend is with the excess obscuration of H${\alpha}$ by dust, at fixed continuum obscuration. The scatter in continuum size at fixed stellar mass is likely driven by the scatter in halo spin parameters. The stability of the ratio of H${\alpha}$ size to continuum size demonstrates a high degree of stability in halo spin and in the transfer of angular momentum to the disk over a wide range of physical conditions and cosmic time. This may require local regulation by feedback processes. The implication of our results, as we demonstrate using a toy model, is that our upper limit on star-formation driven growth is sufficient only to evolve star-forming galaxies approximately along the observed size-mass relation, consistent with the size growth of galaxies at constant cumulative co-moving number density. To explain the observed evolution of the size-mass relation of star-forming disk galaxies other processes, such as the preferential quenching of compact galaxies or galaxy mergers, may be required.
- [10] arXiv:2002.09502 [pdf, other]
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Title: Illuminating black hole cusp populations in young star clustersComments: 13 pages, 6 figures. Submitted to ApJSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
There is increasing evidence that globular clusters retain sizeable black hole populations at present day. This is supported by dynamical simulations of cluster evolution, which have unveiled the spatial distribution and mass spectrum of black holes in clusters across cosmic age. However, the black hole populations of young, high metallicity clusters remain unconstrained. The black holes hosted by these clusters are expected to rapidly mass segregate early in their evolutionary history, forming central cusps of hundreds to thousands of black holes. Here, we argue that the host young cluster can accumulate gas from its dense surroundings, from which the black hole cusp members can accrete at highly enhanced rates. Their collective accretion luminosity can be substantial and provides a novel observational constraint for nearby young massive clusters. We test this hypothesis by performing 3D hydrodynamic simulations where we embed discretized potentials, representing our black holes, within the core potential of a massive cluster. This system moves supersonically with respect to a gaseous medium from which it accretes. We study the accretion of this black hole cusp for different cusp populations and determine the integrated accretion luminosity of the black hole cusp. We apply our results to the young massive clusters of the Antennae Galaxies and find that a typical cusp accretion luminosity should be in excess of $\approx 10^{40}\,{\rm ergs\,\,s^{-1}}$. We argue that no strong candidates of this luminous signal have been observed, and constrain the cusp population of a typical cluster in the Antennae Galaxies to $\lesssim10-2\times10^2$ $10\,M_\odot$ black holes. This is in conflict with predictions of dynamical simulations, which suggest that these systems should harbor several hundred to thousands of black holes, and we explore the reasons for this discrepancy in our conclusions.
- [11] arXiv:2002.09503 [pdf, other]
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Title: Multiple Chemodynamic Stellar Populations of the Ursa Minor Dwarf Spheroidal GalaxyAuthors: Andrew B. Pace (CMU), Manoj Kaplinghat (UCI), Evan Kirby (Caltech), Joshua D. Simon (Carnegie Obs), Erik Tollerud (STSci), Ricardo R. Muñoz (U. Chile), Patrick Côté (NRC), S. G. Djorgovski (Caltech), Marla Geha (Yale)Comments: 19 pages, 11 figures, data included. Comments welcome. Submitted to MNRASSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
We present a Bayesian method to identify multiple (chemodynamic) stellar populations in dwarf spheroidal galaxies (dSphs) using velocity, metallicity, and positional stellar data without the assumption of spherical symmetry, building on the work of Walker and Pe{\~n}arrubia (2011). We apply this method to a new Keck/DEIMOS spectroscopic survey of the Ursa Minor (UMi) dSph. We identify 892 likely members, making this the largest UMi sample with line-of-sight velocity and metallicity measurements. Our Bayesian method detects two distinct chemodynamic populations with high significance ($\ln{B}\sim32$). The metal-rich ($[{\rm Fe/H}]=-2.05_{-0.03}^{+0.03}$) population is kinematically colder ($\sigma_v=4.7_{-1.1}^{+0.8}km/s$) and more centrally concentrated than the metal-poor ($[{\rm Fe/H}]=-2.27_{-0.06}^{+0.05}$) and kinematically hotter population ($\sigma_v =11.4_{-0.7}^{+0.9}km/s$). Furthermore, we apply the same analysis to the independent MMT/Hectochelle data set with 413 members from Spencer et al. (2018) and confirm the existence of two chemodynamic populations in UMi. In both data sets, the metal-rich population is significantly flattened ($\epsilon=0.74\pm0.04$) and the metal-poor population is closer to spherical ($\epsilon=0.33_{-0.11}^{+0.09}$). Despite the presence of two populations, we are unable to robustly estimate the slope of the dynamical mass profile. We found hints for prolate rotation of order $\sim 2 km/s$ in the MMT data set, but further observations are required to verify this. The flattened metal-rich population invalidates assumptions built into simple dynamical mass estimators, so we computed new astrophysical dark matter annihilation (J) and decay profiles based on the rounder, hotter metal-poor population and inferred $\log{J}\sim19.1$ for the Keck data set. Our results paint a more complex picture of the evolution of Ursa Minor than previously discussed.
- [12] arXiv:2002.09506 [pdf, other]
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Title: Modelling the 3D Climate of Venus with OASISComments: Submitted to MNRAS, revised version after first referee reportSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
Flexible 3D models to explore the vast diversity of terrestrial planets and interpret observational data are still in their early stages. In this work, we present OASIS: a novel and flexible 3D virtual planet laboratory. With OASIS we envision a platform that couples self-consistently seven individual modules representing the main physical and chemical processes that shape planetary environments. Additionally, OASIS is capable of producing simulated spectra from different instruments and observational techniques. In this work we focus on the benchmark test of coupling four of the physical modules: fluid dynamics, radiation, turbulence and surface/soil. To test the OASIS platform, we produced 3D simulations of the Venus climate and its atmospheric circulation and study how the modeled atmosphere changes with various cloud covers, atmospheric heat capacity, and surface friction. 3D simulations of Venus are challenging because they require long integration times with a computationally expensive radiative transfer code. By comparing OASIS results with observational data, we verify that the new model is able to successfully simulate Venus. With simulated spectra produced directly from the 3D simulations, we explore the capabilities of future missions, like LUVOIR, to observe Venus analogs located at a distance of 10 pc. With OASIS, we have taken the first steps to build a sophisticated and very flexible platform capable of studying the environment of terrestrial planets, which will be an essential tool to characterize observed terrestrial planets and plan future observations.
- [13] arXiv:2002.09508 [pdf, other]
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Title: The Pre-Explosion Mass Distribution of Hydrogen-Poor Superluminous Supernova Progenitors and New Evidence for a Mass-Spin CorrelationAuthors: Peter K. Blanchard (1), Edo Berger (2), Matt Nicholl (3 and 4), V. Ashley Villar (2) ((1) Northwestern/CIERA, (2) Harvard/CfA, (3) University of Birmingham, (4) University of Edinburgh)Comments: 18 pages, 11 figures, Submitted to ApJSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Despite indications that superluminous supernovae (SLSNe) originate from massive progenitors, the lack of a uniformly analyzed statistical sample has so far prevented a detailed view of the progenitor mass distribution. Here we present and analyze the pre-explosion mass distribution of hydrogen-poor SLSN progenitors as determined from uniformly modelled light curves of 62 events. We construct the distribution by summing the ejecta mass posteriors of each event, using magnetar light curve models presented in our previous works (and using a nominal neutron star remnant mass). The resulting distribution spans $3.6-40$ M$_{\odot}$, with a sharp decline at lower masses, and is best fit by a broken power law described by ${\rm d}N/{\rm dlog}M \propto M^{-0.41 \pm 0.06}$ at $3.6-8.6$ M$_{\odot}$ and $\propto M^{-1.26 \pm 0.06}$ at $8.6-40$ M$_{\odot}$. We find that observational selection effects cannot account for the shape of the distribution. Relative to Type Ib/c SNe, the SLSN mass distribution extends to much larger masses and has a different power-law shape, likely indicating that the formation of a magnetar allows more massive stars to explode as some of the rotational energy accelerates the ejecta. Comparing the SLSN distribution with predictions from single and binary star evolution models, we find that binary models for a metallicity of $Z\lesssim 1/3$ Z$_{\odot}$ are best able to reproduce its broad shape, in agreement with the preference of SLSNe for low metallicity environments. Finally, we uncover a correlation between the pre-explosion mass and the magnetar initial spin period, where SLSNe with low masses have slower spins, a trend broadly consistent with the effects of angular momentum transport evident in models of rapidly-rotating carbon-oxygen stars.
- [14] arXiv:2002.09517 [pdf, other]
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Title: The Blue Compact Dwarf Galaxy VCC848 Formed by Dwarf-Dwarf MergingAuthors: Hong-Xin Zhang (USTC), Sanjaya Paudel (Yonsei Univ), Rory Smith (KASI), Pierre-Alain Duc (Univ of Strasburg), Thomas H. Puzia (PUC), Eric W. Peng (PKU), Patrick Cote (NRC-HIA), Laura Ferrarese (NRC-HIA), Alessandro Boselli (Aix Marseille Univ), Kaixiang Wang (PKU), Se-Heon Oh (Sejong Univ)Comments: 10 pages, 5 figures, accepted by ApJLSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
It has long been speculated that many starburst or compact dwarf galaxies are resulted from dwarf-dwarf galaxy merging, but unequivocal evidence for this possibility has rarely been reported in the literature. We present the first study of deep optical broadband images of a gas-dominated blue compact dwarf galaxy (BCD) VCC848 (Mstar=2e8Msun) which hosts extended stellar shells and thus is confirmed to be a dwarf-dwarf merger. VCC848 is located in the outskirts of the Virgo Cluster. By analyzing the stellar light distribution, we found that VCC848 is the result of a merging between two dwarf galaxies with a primary-to-secondary mass ratio < ~ 5 for the stellar components and < ~ 2 for the presumed dark matter halos. The secondary progenitor galaxy has been almost entirely disrupted. The age-mass distribution of photometrically selected star cluster candidates in VCC848 implies that the cluster formation rate (CFR, proportional to star formation rate) was enhanced by a factor of ~ 7 - 10 during the past 1 Gyr. The merging-induced enhancement of CFR peaked near the galactic center a few hundred Myr ago and has started declining in the last few tens of Myr. The current star formation activities, as traced by the youngest clusters, mainly occur at large galactocentric distances (> ~ 1 kpc). The fact that VCC848 is still (atomic) gas-dominated after the period of most violent collision suggests that gas-rich dwarf galaxy merging can result in BCD-like remnants with extended atomic gas distribution surrounding a blue compact center, in general agreement with previous numerical simulations.
- [15] arXiv:2002.09540 [pdf]
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Title: Aphelion Cloud Belt Phase Function Investigations with Mars Color Imager (MARCI)Authors: Brittney A. Cooper, John E. Moores, Joseph M. Battalio, Scott D. Guzewich, Christina L. Smith, Rachel C. N. Modestino, Michael V. TabascioComments: 45 pages, 12 figures, preprint for the Journal of Planetary and Space ScienceSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
This paper constrains the scattering phase function of water ice clouds (WICs) found within Mars' Aphelion Cloud Belt (ACB), determined from orbit by processing publicly available raw Mars Color Imager (MARCI) data spanning solar longitudes (Ls) 42-170 during Mars Years (MYs) 28 and 29. MARCI visible wavelength data were calibrated and then pipeline-processed to select the pixels most likely to possess clouds. Mean phase function curves for the MARCI blue filter data were derived, and for all seasons investigated, modeled aggregates, plates, solid and hollow columns, bullet rosettes, and droxtals were all found to be plausible habits. Spheres were found to be the least plausible, but still possible. Additionally, this work probed the opposition surge to examine the slope of the linear relationship between column ice water content and cloud opacity on Mars, and found a significant dependence on particle radius. The half-width-half-maxima (HWHM) of the visible 180 degree peak of five MARCI images were found to agree better with modeled HWHM for WICs than with modeled HWHM for dust.
- [16] arXiv:2002.09550 [pdf, ps, other]
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Title: Iron Line Tomography of General Relativistic Hydrodynamic Accretion around Kerr Black HolesComments: accepted to ApJ, 6 figsSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
We consider a temporal response of relativistically broadened line spectrum of iron from black hole accretion irradiated by an X-ray echo under strong gravity. The physical condition of accreting gas is numerically calculated in the context of general relativistic hydrodynamics under steady-state, axisymmetry in Kerr geometry. With the onset of a point-like X-ray flare of a short finite duration just above the accretion surface, the gas is assumed to be ionized to produce a neutral iron fluorescent line. Using a fully relativistic ray-tracing approach, the response of line photons due to the X-ray illumination is traced as a function of time and energy for different source configurations around \sw and Kerr black holes. Our calculations show that the X-ray echo on the accretion surface clearly imprints a characteristic time-variability in the line spectral features depending on those parameters. Simulated line profiles, aimed for the future microcalorimeter missions of large collecting area such as {\it Athena}/X-IFU for typical radio-quiet Seyfert galaxies, are presented to demonstrate that state-of-the-art new observations could differentiate various source parameters by such an X-ray tomographic line reverberation.
- [17] arXiv:2002.09552 [pdf, other]
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Title: Visible and near-infrared spectro-interferometric analysis of the edge-on Be star $ο$ AquariiAuthors: E. S. G. de Almeida, A. Meilland, A. Domiciano de Souza, P. Stee, D. Mourard, N. Nardetto, R. Ligi, I. Tallon-Bosc, D. M. Faes, A. C. Carciofi, D. Bednarski, B. C. Mota, N. Turner, T. A. ten BrummelaarComments: 24 pages, 17 figures, accepted for publication in Astronomy & Astrophysics on 06/02/2020. Abstract shortened to fit within arXiv character limitSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
We present a detailed visible and near-IR spectro-interferometric analysis of the Be-shell star $\omicron$ Aquarii from quasi-contemporaneous CHARA/VEGA and VLTI/AMBER observations. We measured the stellar radius of $\omicron$ Aquarii as 4.0 $\pm$ 0.3 $\mathrm{R_{\odot}}$. We constrained the disk geometry and kinematics using a kinematic model and a MCMC fitting procedure. The disk sizes in H$\alpha$ and Br$\gamma$ were found to be similar, at $\sim$10-12 $\mathrm{D_{\star}}$, which is uncommon since most results for Be stars show a larger extension in H$\alpha$ than in Br$\gamma$. We found that the inclination angle $i$ derived from H$\alpha$ is significantly lower ($\sim$15 deg) than the one derived from Br$\gamma$. The disk kinematics were found to be near to the Keplerian rotation in Br$\gamma$, but not in H$\alpha$. After analyzing all our data using a grid of HDUST models (BeAtlas), we found a common physical description for the disk in both lines: $\Sigma_{0}$ = 0.12 g cm\textsuperscript{-2} and $m$ = 3.0. The stellar rotational rate was found to be very close ($\sim$96\%) to the critical value. Our analysis of multi-epoch H$\alpha$ profiles and imaging polarimetry indicates that the disk has been stable for at least 20 years. Compared to Br$\gamma$, the data in H$\alpha$ shows a substantially different picture that cannot fully be understood using the current physical models of Be star disks. $\omicron$ Aquarii presents a stable disk, but the measured $m$ is lower than the standard value in the VDD model for steady-state. Such long-term stability can be understood in terms of the high rotational rate for this star, the rate being a main source for the mass injection in the disk. Our results on the stellar rotation and disk stability are consistent with results in the literature showing that late-type Be stars are more likely to be fast rotators and have stable disks.
- [18] arXiv:2002.09593 [pdf, other]
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Title: Strange Quark Matter Objects Excited in Stellar SystemsComments: 5pages, 2figuresSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
It is shown that strange quark matter (SQM) objects, stars and planets, can very efficiently convert the mechanical energy into hadronic energy when they oscillate. This is because the mass density at the edge of SQM objects, $\rho_0{=}4.7{\times}10^{14}\frac{\mathrm{g}}{\mathrm{cm}^3}$, is the critical density below which strange quark matter is unstable with respect to decay into photons, leptons. We consider here radial oscillations of SQM objects that could be induced in stellar or planetary systems where tidal interactions are ubiquitous. Already oscillations of $0.1\%$ radius amplitude result in $1\,$keV per unit baryon number excitation near the surface of SQM stars. The excitation energy is converted into electromagnetic energy in a short time of 1 msec, during a few oscillations. Higher amplitude oscillations result in faster energy release that could lead to fragmentation or dissolution of SQM stars. This would have significant consequences for hypothetical SQM star binaries and planetary systems of SQM planets with regard to gravitational wave emission.
- [19] arXiv:2002.09618 [pdf, ps, other]
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Title: Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G-K DwarfsComments: Accepted for publication in Astronomical Journal, 38 pages (including 14 figures and 2 tables), with supplementary online materialSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
It has been occasionally suggested that Fe abundances of K dwarfs derived from Fe I and Fe II lines show considerable discrepancies and oxygen abundances determined from high-excitation O I 7771-5 triplet lines are appreciably overestimated (the problem becoming more serious towards lower Teff), which however has not yet been widely confirmed. With an aim to clarify this issue, we spectroscopically determined the atmospheric parameters of 148 G-K dwarfs (Hyades cluster stars and field stars) by assuming the classical Fe I/Fe II ionization equilibrium as usual, and determined their oxygen abundances by applying the non-LTE spectrum fitting analysis to O I 7771-5 lines. It turned out that the resulting parameters did not show any significant inconsistency with those determined by other methods (for example, the mean differences in Teff and log g from the well-determined solutions of Hyades dwarfs are mostly <~100K and <~0.1dex). Likewise, the oxygen abundances of Hyades stars are around [O/H]~+0.2dex (consistent with the metallicity of this cluster) without exhibiting any systematic Teff-dependence. Accordingly, we conclude that parameters can be spectroscopically evaluated to a sufficient precision in the conventional manner (based on the Saha-Boltzmann equation for Fe I/Fe II) and oxygen abundances can be reliably determined from the O I 7771-5 triplet for K dwarfs as far as stars of Teff>~4500K are concerned. We suspect that previously reported strongly Teff-dependent discrepancies may have stemmed mainly from overestimation of weak-line strengths and/or improper Teff scale.
- [20] arXiv:2002.09638 [pdf, other]
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Title: Synchrotron radiation in $γ$-ray burst prompt emissionAuthors: Bing ZhangComments: published in Comment | Nature AstronomySubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Growing evidence suggests that synchrotron radiation plays a significant role in shaping the spectra of most $\gamma$-ray bursts. The relativistic jets producing them likely carry a significant fraction of energy in the form of a Poynting flux.
- [21] arXiv:2002.09691 [pdf, other]
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Title: The Soft State of the Black Hole Transient Source MAXI J1820+070: Emission from the Edge of the Plunge Region?Authors: A.C. Fabian, D.J Buisson, P. Kosec, C.S. Reynolds, D.R. Wilkins, J.A. Tomsick, D.J. Walton, P. Gandhi, D. Altamirano, Z. Arzoumanian, E.M. Cackett, S. Dyda, J.A. Garcia, K.C. Gendreau, B.W Grefenstette, F.A. Harrison, J. Homan, E. Kara, R.M. Ludlam, J.M. Miller, J.F. SteinerComments: 8 pages, 10 figures, accepted for publication in MNRASSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
The Galactic black hole X-ray binary MAXI J1820+070 had a bright outburst in 2018 when it became the second brightest X-ray source in the Sky. It was too bright for X-ray CCD instruments such as XMM-Newton and Chandra, but was well observed by photon-counting instruments such as NICER and NuSTAR. We report here on the discovery of an excess emission component during the soft state. It is best modelled with a blackbody spectrum in addition to the regular disk emission, modelled either as diskbb or kerrbb. Its temperature varies from about 0.9 to 1.1 keV which is about 30 to 80 per cent higher than the inner disc temperature of diskbb. Its flux varies between 4 and 12 percent of the disc flux. Simulations of magnetised accretion discs have predicted the possibility of excess emission associated with a non-zero torque at the Innermost Stable Circular Orbit (ISCO) about the black hole, which from other NuSTAR studies lies at about 5 gravitational radii or about 60 km (for a black hole mass is 8 M). In this case the emitting region at the ISCO has a width varying between 1.3 and 4.6 km and would encompass the start of the plunge region where matter begins to fall freely into the black hole.
- [22] arXiv:2002.09714 [pdf, other]
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Title: The bursty star formation history of the Fornax dwarf spheroidal galaxy revealed with the HSTSubjects: Astrophysics of Galaxies (astro-ph.GA)
We present a new star formation history (SFH) of the dwarf spheroidal galaxy Fornax characterized by unprecedented high precision and age resolution. It reveals that star formation has proceeded in sharp bursts separated by periods of low-level or quiescent activity. The SFH was derived by applying the well-tested technique of colour-magnitude diagram fitting to two extremely deep colour magnitude diagrams obtained with data from the Hubble Space Telescope, and sampling stellar populations at the centre and at one core radius. The attained age resolution at different epochs not only allowed us to observe the major bursts of star formation at $10.6\pm2.4$ (centre) and $10.9\pm1.3$ Gyr ago (core radius), but also a strong burst at $4.6\pm0.4$ Gyr ago and recent intermittent episodes of activity during the period $\sim2-0.2$ Gyr ago. Detailed testing using mock stellar populations allowed us to estimate the duration of the main bursts and to study the occurrence of low-level star formation between bursts. The two regions in Fornax were observed to have many common features in their SFH, with activity at the same epochs and similar age-metallicity relationship. However, clear indications of a spatial population gradient were also found, with mean stellar ages increasing with radius and star formation episodes being more prolonged in the centre. We calculated an orbit of Fornax relative to the closest dwarfs and Milky Way and observed a correspondence between the main intermediate-age and young SFH events and pericentric passages of Fornax around the Milky Way, possibly indicating tidally induced star formation.
- [23] arXiv:2002.09816 [pdf, ps, other]
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Title: Estimating red noise in quasi-periodic signals with MCMC-based BayesianComments: 7 pages, 5 figuresJournal-ref: Astrophys Space Sci 365, 40 (2020)Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Multi-parameter Bayesian inferences based on Markov chain Monte Carlo (MCMC) samples have been widely used to estimate red noise in solar period-periodic signals. To MCMC, proper priors and sufficient iterations are prerequisites ensuring the accuracy of red noise estimation. We used MCMC-based Bayesian inferences to estimate 100 groups of red noise synthesized randomly for evaluating its accuracy. At the same time, the Brooks-Gelman algorithm was employed to precisely diagnose the convergence of the Markov chains generated by MCMC. The root-mean-square error of parameter inferences to the synthetic data is only 1.14. Furthermore, we applied the algorithm to analyze the oscillation modes in a sunspot and a flare. A 70 s period is detected in the sunspot umbra in addition to 3- and 5-minute periods, and a 40 s period is detected in the flare. The results prove that estimating red noise with MCMC-based Bayesian has more high accuracy in the case of proper priors and convergence. We also find that the number of iterations increases dramatically to achieve convergence as the number of parameters grows. Therefore, we strongly recommend that when estimating red noise with MCMC-based Bayesian, different initial values must be selected to ensure that the entire posterior distribution is covered.
- [24] arXiv:2002.09826 [pdf, other]
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Title: Unveiling the Intrinsic Alignment of Galaxies with Self-Calibration and DECaLS DR3 dataComments: Submitted to ApJSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
Galaxy intrinsic alignment (IA) is both a source of systematic contamination to cosmic shear measurement and its cosmological applications, and a source of valuable information on the large scale structure of the universe and galaxy formation. The self-calibration (SC) method \citep{SC2008} was designed to separate IA from cosmic shear, free of IA modeling. It was first successfully applied to the KiDS450 and KV450 data \citep{Yao2019}. We apply the SC method to the DECaLS DR3 shear + photo-z catalog and significantly improve the IA detection to $\sim 20\sigma$. We find a strong dependence of IA on galaxy color, with strong IA signal for red galaxies, and weak/vanishing IA signal for blue galaxies. The detected IA for red galaxies is in reasonable agreement with the non-linear tidal alignment model and the inferred IA amplitude increases with redshift. We discuss various caveats and possible improvements in the measurement, theory and parameter fitting that will be addressed in future works.
- [25] arXiv:2002.09829 [pdf, ps, other]
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Title: A Small-Scale Investigation of Molecular Emission toward the Tip of the Western Lobe of W50/SS433Comments: 33 pages, 12 figures, 3 tables. Accepted to the Astrophysical JournalSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
We perform a molecular (CO and CN) line observation using IRAM 30m telescope toward two small regions near the western edge of supernova remnant (SNR) W50/SS433. CO observation reveals spatial correspondence of two molecular clumps at the local-standard-of-rest (LSR) velocity around +53 km s$^{-1}$ with multiwavelength local features of W50/SS433 system. One of the two clumps appears to be embedded in a void of diffuse radio and X-ray emission. Toward the two clumps, asymmetric broad line profiles of the $^{12}$CO lines are obtained, which provide kinematic evidence of the association between the clumps and the jet-related gas. The $^{12}$CO $J=2-1$/$J=1-0$ line ratios ($> 0.9$) and the kinetic temperatures ($\sim 30$ K) of the clumps are distinctively higher than all those of the clumps at other LSR velocities along the same line of sight, which may be physical signatures of the association. We show that the clump coincident with the void can survive the thermal heating if it is surrounded by hot gas, with an evaporation timescale much larger than the age of SNR W50. We also show that the thermal equilibrium in the high temperature clumps can be maintained by the heating of the penetrating environmental CRs. CN ($J=3/1-1/2$) line emission is detected in the two clumps, and the CN abundances derived are much higher than that in the interstellar molecular clouds (MCs) and that in the SNR-interacting MCs.
- [26] arXiv:2002.09837 [pdf]
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Title: Sunward propagating whistler waves collocated with localized magnetic field holes in the solar wind: Parker Solar Probe observations at 35.7 Sun radiiAuthors: O.V. Agapitov, T. Dudok de Wit, F.S. Mozer, J. W. Bonnell, J. F. Drake, D. Malaspina, V. Krasnoselskikh, S. Bale, P. L. Whittlesey, A. W. Case, C. Chaston, C. Froment, K. Goetz, K. A. Goodrich, P. R. Harvey, J. C. Kasper, K. E. Korreck, D.E. Larson, R. Livi, R. J. MacDowall, M. Pulupa, C. Revillet, M. Stevens, J. R. WygantSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)
Observations by the Parker Solar Probe mission of the solar wind at about 35.7 solar radii reveal the existence of whistler wave packets with frequencies below 0.1 f/fce (20-80 Hz in the spacecraft frame). These waves often coincide with local minima of the magnetic field magnitude or with sudden deflections of the magnetic field that are called switchbacks. Their sunward propagation leads to a significant Doppler frequency downshift from 200-300 Hz to 20-80 Hz (from 0.2 f/fce to 0.5 f/fce). The polarization of these waves varies from quasi-parallel to significantly oblique with wave normal angles that are close to the resonance cone. Their peak amplitude can be as large as 2 to 4 nT. Such values represent approximately 10% of the background magnetic field, which is considerably more than what is observed at 1 a.u. Recent numerical studies show that such waves may potentially play a key role in breaking the heat flux and scattering the Strahl population of suprathermal electrons into a halo population.
- [27] arXiv:2002.09839 [pdf, ps, other]
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Title: Resolving Power of Asteroseismic Inversion of the Kepler Legacy SampleComments: 9 pages, 5 figuresSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
The Kepler Asteroseismic Legacy Project provided frequencies, separation ratios, error estimates, and covariance matrices for 66 Kepler main sequence targets. Most of the previous analysis of these data was focused on fitting standard stellar models. We present results of direct asteroseismic inversions using the method of optimally localized averages (OLA), which effectively eliminates the surface effects and attempts to resolve the stellar core structure. The inversions are presented for various structure properties, including the density stratification and sound speed. The results show that the mixed modes observed in post-main sequence F-type stars allow us to resolve the stellar core structure and reveal significant deviations from the evolutionary models obtained by the grid-fitting procedure to match the observed oscillation frequencies.
- [28] arXiv:2002.09842 [pdf]
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Title: Magnetic Activity of F-, G-, and K-type Stars in the LAMOST-Kepler FieldAuthors: Jinghua Zhang, Shaolan Bi, Yaguang Li, Jie Jiang, Tanda Li, Han He, Jie Yu, Shourya Khanna, Zhishuai Ge, Kang Liu, Zhijia Tian, Yaqian Wu, Xianfei ZhangComments: 8 pages,7 figuresJournal-ref: ApJS,247,2020,9Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and Rhk+, for 59,816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with log Rhk+. We estimate the power-law indexes between Reff and Rhk+ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca II H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
- [29] arXiv:2002.09904 [pdf, other]
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Title: What Can We Learn by Combining the Skew Spectrum and the Power Spectrum?Comments: 18 pages, 8 figures, submitted to JCAPSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Clustering of the large scale structure provides complementary information to the measurements of the cosmic microwave background anisotropies through power spectrum and bispectrum of density perturbations. Extracting the bispectrum information, however, is more challenging than it is from the power spectrum due to the complex models and the computational cost to measure the signal and its covariance. To overcome these problems, we adopt a proxy statistic, skew spectrum which is a cross-spectrum of the density field and its quadratic field. By applying a large smoothing filter to the density field, we show our theory fits the simulations very well. With the spectra and their covariance form $N$-body simulations as our "mock" Universe, we perform a global fits on the cosmological parameters. The results show a slight sub-Poisson shot noise, and by adding skew spectrum to power spectrum, the $1\sigma$ marginalized errors for $ b_1^2A_s, n_s$ and $f_{\rm NL}^{\rm loc}$ are reduced by $34\%, 22\%, 46\%$, respectively. The skew spectrum will be an effective method to study the complementary information to those from the power spectrum measurements, especially with the forthcoming generation of wide-field galaxy surveys.
- [30] arXiv:2002.09909 [pdf, ps, other]
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Title: Multiple measurements of quasars acing as standard probes: exploring the cosmic distance duality relation at higher redshiftComments: 8 pages, 6 figures, 1 table, Accepted for publication in ApJSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
General relativity reproduces main current cosmological observations, assuming the validity of cosmic distance duality relation (CDDR) at all scales and epochs. However, CDDR is poorly tested in the redshift interval between the farthest observed Type Ia supernovae (SN Ia) and that of the Cosmic Microwave background (CMB). We present a new idea of testing the validity of CDDR, through the multiple measurements of high-redshift quasars. Luminosity distances are derived from the relation between the UV and X-ray luminosities of quasars, while angular diameter distances are obtained from the compact structure in radio quasars. This will create a valuable opportunity where two different cosmological distances from the same kind of objects at high redshifts are compared. Our constraints are more stringent than other currently available results based on different observational data and show no evidence for the deviation from CDDR at $z\sim 3$. Such accurate model-independent test of fundamental cosmological principles can become a milestone in precision cosmology.
- [31] arXiv:2002.09918 [pdf, other]
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Title: Hydrogen recombination line luminosities and -variability from forming planetsComments: Submitted. 13 pages, 7 figures, 4 tablesSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
We calculated hydrogen recombination line luminosities (H-$\alpha$, Paschen-$\beta$ and Brackett-$\gamma$) from three dimensional thermo-hydrodynamical simulations of forming planets from 1 to 10 Jupiter-masses. We explored various opacities to estimate the line emissions with extinction in each cases. When realistic opacities are considered, only lines from planets $\ge$10 Jupiter-mass can be detected with current instrumentation, highlighting that from most planets one cannot expect detectable emission. This might explain the very low detection rate of H-$\alpha$ from forming planets from observations. While the line emission comes from both the forming planet and its circumplanetary disk, we found that only the disk component could be detected due to extinction. We examined the line variability as well, and found that it is higher for higher mass planets. Furthermore, we determine for the first time, the parametric relationship between the mass of the planet and the luminosity of the hydrogen recombination lines, as well as the equation between the accretion luminosity and hydrogen recombination line luminosities. These relationships for planets appear to be steeper than the analogous relation for young stars, suggesting that the accretion process around planets proceeds differently than around stars.
- [32] arXiv:2002.09948 [pdf, other]
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Title: Magnetic Field Morphology in Interstellar Clouds with the Velocity Gradient TechniqueAuthors: Yue Hu, Ka Ho Yuen, Victor Lazarian, Ka Wai Ho, Robert A. Benjamin, Alex S. Hill, Felix J. Lockman, Paul F. Goldsmith, Alex LazarianComments: 14 pages, 8 figuresJournal-ref: 2019NatAs...3..776HSubjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Magnetic fields, while ubiquitous in many astrophysical environments, are challenging to measure observationally. Based on the properties of anisotropy of eddies in magnetized turbulence, the Velocity Gradient Technique is a method synergistic to dust polarimetry that is capable of tracing plane-of-the-sky magnetic field, measuring the magnetization of interstellar media and estimating the fraction of gravitational collapsing gas in molecular clouds using spectral line observations. In this paper, we apply this technique to five low-mass star-forming molecular clouds in the Gould Belt and compare the results to the magnetic-field orientation obtained from polarized dust emission. We find the estimates of magnetic field orientations and magnetization for both methods are statistically similar. We estimate the fraction of collapsing gas in the selected clouds. By means of the Velocity Gradient Technique, we also present the plane-of-the-sky magnetic field orientation and magnetization of the Smith cloud, for which dust polarimetry data are unavailable.
- [33] arXiv:2002.09950 [pdf]
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Title: Mineralogy of a Sulfate-rich Inverted Channel in the Atacama Desert, Chile: Clues to its Formation and PreservationAuthors: E. Z. Noe Dobrea, R. M. E. Williams, W. E. Dietrich, A. D. Howard, J. C. Cawley, R. P. Irwin IIIComments: Submitted to Icarus Feb 22, 2020; 19 pages, 1 Table, 19 FiguresSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
We have performed a stratigraphic and mineralogical analysis of a vertical transect across a ridge located at the distal end of a system of eroded alluvial deposits in the northern Atacama Desert of Chile. The ridge, which is interpreted to be an inverted channel, exhibits a history of sedimentary, evaporitic, and diagenetic origin that includes groundwater mobilization and precipitation of anhydrite cements throughout the volume of the ridge. The ridge consists of two units: a lower one exhibiting a sedimentary and diagenetic history, and an upper one exhibiting an evaporitic history. Interbedded in the section are also anhydritic and gypsic paleosols. Two mechanisms that contribute to channel preservation and inversion are identified in this case. The first mechanism is the cementation of the volume by anhydrite cements during early diagenesis, and the second newly identified mechanism is the armoring of the lateral slopes of the ridge by halite-rich cement. The slope-conforming armor formed by this second mechanism developed subsequent to the formation of the ridge as a consequence of the remobilization of soluble salts. Finally, we identify a series of Ca-sulfate-rich plates on the surface of the ridge, which we interpret here to form by fracturing and subsequent erosion of an evaporitic deposit. The plates exhibit a reticulated surface texture, which we interpret as the result of periodic deliquescence and reprecipitation of a thin surface film of the evaporite deposits in response to thick morning fogs that occur in this part of the Atacama. The cross section of the plates exhibits a thin portion of biological material, which we ascribe to bacterial mats that take advantage of the deliquescence of the substrate to obtain their water. This later has important implications in the search for extant or extinct life on Mars.
- [34] arXiv:2002.10005 [pdf, ps, other]
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Title: Surprising Variability of the Planetary Nebula IC 4997 = QV SgeAuthors: V.P. Arkhipova, M.A. Burlak, N.P. Ikonnikova, G.V. Komissarova, V.F. Esipov, V.I. ShenavrinComments: 28 pages, 6 tables, 10 figuresSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
We present the results of a new epoch of a long-term photometric monitoring of the variable planetary nebula IC~4997. The integral $UBV$ light curves display a continuing brightening of 0.$^{m}15$ in $V$, a slight rise (<0.$^{m}1$) in $B$, and constancy in $U$. The $B-V$ color has got redder from 0.$^{m}4$ in 2000 to 0.$^{m}7$ in 2019, whereas the $U-B$ color has not changed significantly. New $JHKL$ photometry was obtained in 2019. We found the source to be fainter by 0.$^{m}4$ in $L$ and bluer by 0.$^{m}2$ in the $K-L$ color if compared to the data of 1999-2006. The long-term brightness variations are due mostly to the changing input of emission lines to the integral light. Low-dispersion spectroscopic observations carried out in 2010-2019 revealed a continuing decrease in the $\lambda4363/\lambda4340$ ratio: it decreased by a factor of $\sim3$ in 30 years and reached the level of 1960-1970. The absolute intensities of [OIII] nebualr lines increased by a factor of $>2$ from 1990 to 2019, whereas the [OIII] $\lambda$4363 line had weakened by a factor of 2 comparing to the maximum value observed in 2000. The variation of H$\beta$ absolute intensity in 1960-2019 was shown to be similar to that of [OIII] nebular lines, but of smaller amplitude. The electron density in the outer part of the nebula was estimated from the [SII] and [ClIII] lines. Basing on the data on absolute intensities we propose a possible scenario describing the change of $N_e,T_e$ in 1970-2019. The spectral variability of IC~4997 could be explained by a variation of electron temperature in the nebula caused by not so much the change in ionizing flux from the central star as the variable stellar wind and related processes. The photometric and spectral changes observed for IC~4997 in 1960-2019 may be interpreted as an observable consequence of a single episode of enhanced mass loss from the variable central star.
- [35] arXiv:2002.10017 [pdf, other]
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Title: EDEN: Sensitivity Analysis and Transiting Planet Detection Limits for Nearby Late Red DwarfsAuthors: Aidan Gibbs, Alex Bixel, Benjamin Rackham, Daniel Apai, Martin Schlecker, Nestor Espinoza, Luigi Mancini, Wen-Ping Chen, Thomas Henning, Paul Gabor, Richard Boyle, Jose Perez Chavez, Allie Mousseau, Jeremy Dietrich, Quentin Jay Socia, Wing Ip, Chow-Choong Ngeow, Anli Tsai, Asmita Bhandare, Victor Marian, Hans Baehr, Samantha Brown, Maximilian Haberle, Miriam Keppler, Karan Molaverdikhani, Paula SarkisComments: Accepted to AJSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
Small planets are common around late-M dwarfs and can be detected through highly precise photometry by the transit method. Planets orbiting nearby stars are particularly important as they are often the best-suited for future follow-up studies. We present observations of three nearby M-dwarfs referred to as EIC-1, EIC-2, and EIC-3, and use them to search for transits and set limits on the presence of planets. On most nights our observations are sensitive to Earth-sized transiting planets, and photometric precision is similar to or better than TESS for faint late-M dwarfs of the same magnitude (I=15 mag). We present our photometry and transit search pipeline, which utilizes simple median detrending in combination with transit least squares based transit detection (Hippke & Heller 2019).For these targets, and transiting planets between one and two Earth radii, we achieve an average transit detection probability of 60% between periods of 0.5 and 2 days, 30% between 2 and 5 days,and 10% between 5 and 10 days. These sensitivities are conservative compared to visual searches.
- [36] arXiv:2002.10024 [pdf]
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Title: Spacecraft Tracking Applications of the Square Kilometre ArrayComments: 9 pages, 5 tables, 2 figuresJournal-ref: Proceedings of the 3rd International Workshop on Tracking, Telemetry and Command Systems for Space Applications, ESA-ESOC, Darmstadt, Germany, 2004Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Detectors (physics.ins-det)
The Square Kilometre Array (SKA) is the next generation radio telescope distinguished by a superb sensitivity due to its large aperture (about one square kilometre) and advanced instrumentation. It will cover a broad range of observing bands including those used for tracking of and communications to deep space missions. While spacecraft tracking is not a main application defining the technical specifications of the SKA, this facility might play a role in tracking deep space probes as a backup to the ``dedicated'' deep space tracking networks. This paper presents possible applications of the SKA as a deep space tracking facility and major related technical specifications of various concepts of the SKA. It was presented at the 3rd International Workshop on Tracking, Telemetry and Command Systems for Space Applications, ESA-ESOC, Darmstadt, Germany, 7-9 September 2004. Over the past years, the SKA concept has developed to a much higher level of detalisation and is currently at the implementation phase. A number of specific considerations in this presentation no longer correspond to the actual status of the SKA project. However, the overall concept of the SKA applications for communication and tracking of interplanetary spacecraft remain topical, and some approaches presented here remain of interest for prospective deep space missions.
- [37] arXiv:2002.10076 [pdf, other]
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Title: MCG+07-20-052: Interacting dwarf pair in a group environmentComments: Accepted for publication in AJSubjects: Astrophysics of Galaxies (astro-ph.GA)
We present an observational study of the interacting pair of dwarf galaxies, MCG+07-20-052, in the vicinity of Milky Way mass spiral galaxy NGC 2998. MCG+07-20-052 is located at a sky-projected distance of 105 kpc from NGC 2998 and the two have a relative line-of-sight velocity of 60 kms. We observed tidal tail-like extensions on both members (D1 and D2) of the interacting pair MCG+07-20-052. The interacting dwarf galaxies, D1 and D2, have B-band absolute magnitudes of $-$17.17 and $-$17.14 mag, respectively, and D2 is significantly bluer than D1. We obtained HI 21 cm line data of the NGC 2998 system using the Giant Metrewave Radio Telescope (GMRT) to get a more detailed view of the neutral hydrogen (HI) emission in the interacting dwarf galaxies and in the galaxy members of the NGC 2998 group. Evidence of a merger between the dwarf galaxies in the MCG+07-20-052 is also present in the HI kinematics and morphology where we find that the HI is mostly concentrated around D2, which also shows a higher level of star-forming activity and bluer $g-r$ color index compared to D1. In addition, we detect extended tenuous HI emission around another member galaxy, NGC 3006, located close to the MCG+07-20-052-pair at a sky-projected distance of 41 kpc. We compare here our results from the MCG+07-20-052 pair-NGC 2998 system with other known LMC-SMC-Milky Way type systems and discuss the possible origin of the dwarf-dwarf interaction.
- [38] arXiv:2002.10115 [pdf, other]
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Title: Three-dimensional core-collapse supernova simulations of massive and rotating progenitorsSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
We present three-dimensional simulations of the core-collapse of massive rotating and non-rotating progenitors performed with the general relativistic neutrino hydrodynamics code CoCoNuT-FMT and analyse their explosion properties and gravitational-wave signals. The progenitor models include Wolf-Rayet stars with initial helium star masses of $39\,M_{\odot}$ and $20\,M_{\odot}$, and an $18\,M_{\odot}$ red supergiant. The $39\,M_{\odot}$ model is a rapid rotator, whereas the two other progenitors are non-rotating. Both Wolf-Rayet models produce healthy neutrino-driven explosions, whereas the red supergiant model fails to explode. By the end of the simulations, the explosion energies have already reached $1.1\times 10^{51}\,\mathrm{erg}$ and $0.6\times 10^{51}\,\mathrm{erg}$ for the $39\,M_{\odot}$ and $20\,M_{\odot}$ model, respectively. The explosions produce neutron stars of relatively high mass, but with modest kicks. Due to the alignment of the bipolar explosion geometry with the rotation axis, there is a relatively small misalignment of $30^\circ$ between the spin and the kick in the $39\,M_{\odot}$ model. In terms of gravitational-wave signals, the massive and rapidly rotating $39\,M_{\odot}$ progenitor stands out by large gravitational-wave amplitudes that would make it detectable out to almost 2 Mpc by the Einstein Telescope. For this model, we find that rotation significantly changes the dependence of the characteristic gravitational-wave frequency of the f-mode on the proto-neutron star parameters compared to the non-rotating case. The other two progenitors have considerably smaller detection distances, despite significant low-frequency emission in the most sensitive frequency band of current gravitational-wave detectors due to the standing accretion shock instability in the $18\,M_{\odot}$ model.
- [39] arXiv:2002.10154 [pdf, other]
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Title: Adversarial training applied to Convolutional Neural Network for photometric redshift predictionsAuthors: Jean-Eric CampagneComments: 12 pages, 6 figuresSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Image and Video Processing (eess.IV)
The use of Convolutional Neural Networks (CNN) to estimate the galaxy photometric redshift probability distribution by analysing the images in different wavelength bands has been developed in the recent years thanks to the rapid development of the Machine Learning (ML) ecosystem. Authors have set-up CNN architectures and studied their performances and some sources of systematics using standard methods of training and testing to ensure the generalisation power of their models. So far so good, but one piece was missing : does the model generalisation power is well measured? The present article shows clearly that very small image perturbations can fool the model completely and opens the Pandora's box of \textit{adversarial} attack. Among the different techniques and scenarios, we have chosen to use the Fast Sign Gradient one-step Method and its Projected Gradient Descent iterative extension as adversarial generator tool kit. However, as unlikely as it may seem these adversarial samples which fool not only a single model, reveal a weakness both of the model and the classical training. A revisited algorithm is shown and applied by injecting a fraction of adversarial samples during the training phase. Numerical experiments have been conducted using a specific CNN model for illustration although our study could be applied to other models - not only CNN ones - and in other contexts - not only redshift measurements - as it deals with the complexity of the boundary decision surface.
- [40] arXiv:2002.10170 [pdf, ps, other]
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Title: New white dwarf envelope models and diffusion. Application to DQ white dwarfsComments: accepted by Astronomy & AstrophysicsSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
Recent studies of the atmospheres of carbon-rich (DQ) white dwarfs have demonstrated the existence of two different populations that are distinguished by the temperature range, but more importantly, by the extremely high masses of the hotter group. The classical DQ below 10000 K are well understood as the result of dredge-up of carbon by the expanding helium convection zone. The high-mass group poses several problems regarding their origin and also an unexpected correlation of effective temperature with mass. We propose to study the envelopes of these objects to determine the total hydrogen and helium masses as possible clues to their evolution. We developed new codes for envelope integration and diffusive equilibrium that are adapted to the unusual chemical composition, which is not necessarily dominated by hydrogen and helium. Using the new results for the atmospheric parameters, in particular, the masses obtained using Gaia parallaxes, we confirm that the narrow sequence of carbon abundances with Teff in the cool classical DQ is indeed caused by an almost constant helium to total mass fraction, as found in earlier studies. This mass fraction is smaller than predicted by stellar evolution calculations. For the warm DQ above 10000 K, which are thought to originate from double white dwarf mergers, we obtain extremely low hydrogen and helium masses. The correlation of mass with Teff remains unexplained, but another possible correlation of helium layer masses with Teff as well as the gravitational redshifts casts doubt on the reality of both and suggests possible shortcomings of current models.
- [41] arXiv:2002.10189 [pdf, ps, other]
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Title: Reconstructing the Fraction of Baryons in the Intergalactic Medium with Fast Radio Bursts via Gaussian ProcessesComments: 13 pages, 6 figures, revtex4Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
Nowadays, fast radio bursts (FRBs) are promising new probe for astronomy and cosmology. Due to their extragalactic and cosmological origin, FRBs could be used to study the intergalactic medium (IGM) and the cosmic expansion. It is expected that numerous FRBs with identified redshifts will be available in the future. $\rm DM_{IGM}$, the contribution from IGM to the observed dispersion measure (DM) of FRB, carries the key information about IGM and the cosmic expansion history. We can study the evolution of the universe by using FRBs with identified redshifts. In the present work, we are interested in the fraction of baryon mass in IGM, $f_{\rm IGM}$, which is useful to study the cosmic expansion and the problem of "missing baryons". We propose to reconstruct the evolution of $f_{\rm IGM}$ as a function of redshift $z$ with FRBs via a completely model-independent method, namely Gaussian processes. Since there is no a large sample of FRBs with identified redshifts by now, we use the simulated FRBs instead. Through various simulations, we show that this methodology works well.
- [42] arXiv:2002.10193 [pdf, other]
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Title: When the disc's away, the stars will play: dynamical masses in the nova-like variable KR Aur with a pinch of accretionAuthors: P. Rodríguez-Gil, T. Shahbaz, M. A. P. Torres, B. T. Gänsicke, P. Izquierdo, O. Toloza, A. Álvarez-Hernández, D. Steeghs, L. van Spaandonk, D. Koester, D. RodríguezComments: 18 pages, 17 figures, 6 tables, accepted for publication in MNRAS (2020 Feb 19)Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)
We obtained time-resolved optical photometry and spectroscopy of the nova-like variable KR Aurigae in the low state. The spectrum reveals a DAB white dwarf and a mid-M dwarf companion. Using the companion star's $i$-band ellipsoidal modulation we refine the binary orbital period to be $P = 3.906519 \pm 0.000001$ h. The light curve and the spectra show flaring activity due to episodic accretion. One of these events produced brightness oscillations at a period of 27.4 min, that we suggest to be related with the rotation period of a possibly magnetic white dwarf at either 27.4 or 54.8 min. Spectral modelling provided a spectral type of M4-5 for the companion star and $T_{1}=27148 \pm 496$ K, $\log g=8.90 \pm 0.07$, and $\log (\mathrm{He/H})= -0.79^{+0.07}_{-0.08}~~$ for the white dwarf. By simultaneously fitting absorption- and emission-line radial velocity curves and the ellipsoidal light curve, we determined the stellar masses to be $M_1 = 0.94^{+0.15}_{-0.11}~$ $M_\odot$ and $M_2 = 0.37^{+0.07}_{-0.07}~$ $M_\odot$ for the white dwarf and the M-dwarf, respectively, and an orbital inclination of $47^{+1^{\rm o}}_{-2^{\rm o}}$. Finally, we analyse time-resolved spectroscopy acquired when the system was at an $i$-band magnitude of 17.1, about 1.3 mag brighter than it was in the low state. In this intermediate state the line profiles contain an emission S-wave delayed by $\simeq 0.2$ orbital cycle relative to the motion of the white dwarf, similar to what is observed in SW Sextantis stars in the high state.
- [43] arXiv:2002.10195 [pdf, other]
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Title: ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT): I. CO, CS, CN, and H2CO around DG Tau BAuthors: Antonio Garufi, Linda Podio, Claudio Codella, Kazi Rygl, Francesca Bacciotti, Stefano Facchini, Davide Fedele, Anna Miotello, Richard Teague, Leonardo TestiComments: 13 pages, 6 figures, accepted by A&ASubjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
The chemical composition of planets is inherited by the distribution of the various molecular species in the protoplanetary disk at thetime of their formation. As of today, only a handful of disks has been imaged in multiple spectral lines with high spatial resolution. As part of a small campaign devoted to the chemical characterization of disk-outflow sources in Taurus, we report on new ALMA Band 6 observations with 20 au resolution toward the embedded young star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm. The disk, as well as the prominent outflow cavities, are detected in CO, H2CO, CS, and CN while they remain undetected in SO2, HDO, and CH3OH. From the absorption of the back-side outflow, we inferred that the disk emission is optically thick in the inner 50 au. This morphology explains why no line emission is detected from this inner region and poses some limitations toward the calculation of the dust mass and the characterization of the inner gaseous disk. The H2CO and CS emission from the inner 200 au is mostly from the disk and their morphology is very similar. The CN emission significantly differs from the other two molecules as it is observed only beyond 150 au. This ring-like morphology is consistent with previous observations and the predictions of thermochemical disk models. Finally, we constrained the disk-integrated column density of all molecules. In particular, we found that the CH3OH/H2CO ratio must be smaller than 2, making the methanol non-detection still consistent with the only such a ratio available from the literature (1.27 in TW Hya).
- [44] arXiv:2002.10204 [pdf, ps, other]
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Title: Fast-rotating galaxies do not depart from the MOND mass-asymptotic-speed relationAuthors: Mordehai MilgromComments: 4 pagesSubjects: Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
Ogle et al. have fallaciously argued recently that fast-rotating disc galaxies break with the predictions of MOND: the 6 fastest rotators of the 23 galaxies in their sample appear to have higher rotational speeds than is consistent with the MOND relation between the baryonic mass of a galaxy, $M$, and its `rotational speed', $V$. They interpret this departure as a break in the observed $M-V$ relation from a logarithmic slope near the MOND-predicted $4$, to a shallow slope of $\approx 0$. However, Ogle et al. use the MAXIMAL rotational speed of the galaxies, $V_{max}$, not the ASYMPTOTIC one, $V_\infty$, which appears in the MOND prediction, $V_\infty^4=MGa_0$. Plotting their $M$ vs. $V_{max}$ pairs on an $M$ vs. $V_\infty$ plot from Lelli et al. (2016), they arrive erroneously at the above tension with MOND. The $H_\alpha$ rotation curves used by Ogle et al. are far too short reaching to probe the asymptotic regime, and determine $V_\infty$. However, it is well documented for fast rotators with observed, extended, HI rotation curves, that they can have $V_{max}$ considerably larger than the MOND-relevant $V_\infty$ [Noordermeer and Verheijen (NV) (2007) and others]. E.g., the fastest rotator in the NV sample has $V_{max}\approx 490{\rm ~km/s}$, but $V_\infty\approx 250{\rm ~km/s}$. NV also show that in a (MOND-irrelevant) $M-V_{max}$ plot the high-speed galaxies fall off the power-law line defined by the lower-speed ones, creating a break in the $M$ vs. $V$ relation, in just the way claimed by Ogle et al. But, when plotting the MOND-relevant $M$ vs. $V_\infty$ all galaxies fall near the same power-law relation, without a break.
- [45] arXiv:2002.10209 [pdf, other]
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Title: Over-sized gas clumps in an extremely-metal-poor molecular cloud revealed by ALMA's pc-scale mapsAuthors: Yong Shi (NJU), Junzhi Wang (SHAO), Zhi-Yu Zhang (NJU), Qizhou Zhang (CfA), Yu Gao (XMU), Luwenjia Zhou (NJU), Qiusheng Gu (NJU), Keping Qiu (NJU), Xiao-Yang Xia (TJNU), Cai-Na Hao (TJNU), Yanmei Chen (NJU)Comments: ApJ in press, 8 figuresSubjects: Astrophysics of Galaxies (astro-ph.GA)
Metals are thought to have profound effects on the internal structures of molecular clouds in which stars are born. The absence of metals is expected to prevent gas from efficient cooling and fragmentation in theory. However, this effect has not yet been observed at low metallicity environments, such as in the early Universe and local dwarf galaxies, because of the lack of high spatial resolution maps of gas. We carried out ALMA observations of the carbon monoxide (CO) J=2-1 emission line at 1.4-parsec resolutions of a molecular cloud in DDO 70 at 7% solar metallicity, the most metal-poor galaxy currently known with a CO detection. In total, five clumps have been identified and they are found to follow more or less the Larson's law. Since the CO emission exists in regions with visual extinction A_V around 1.0, we converted this A_V to the gas mass surface density using a gas-to-dust ratio of 4,594+-2,848 for DDO 70. We found that the CO clumps in DDO 70 exhibit significantly larger (on average four times) sizes than those at the same gas mass surface densities in massive star-formation regions of the Milky Way. The existence of such large clumps appears to be consistent with theoretical expectations that gas fragmentation in low metallicity clouds is suppressed. While our observation is only for one cloud in the galaxy, if it is representative, the above result implies suppressed gas fragmentation during the cloud collapse and star formation in the early Universe.
- [46] arXiv:2002.10218 [pdf, other]
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Title: Baryon acoustic oscillations reconstruction using convolutional neural networksAuthors: Tian-Xiang Mao, Jie Wang, Baojiu Li, Yan-Chuan Cai, Bridget Falck, Mark Neyrinck, Alex SzalaySubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Machine Learning (cs.LG)
Here we propose a new scheme to reconstruct the baryon acoustic oscillations (BAO) signal, with key cosmological information, based on deep convolutional neural networks. After training the network with almost no fine-tuning, in the test set, the network recovers large-scale modes accurately: the correlation coefficient between the ground truth and recovered initial conditions still reach $90\%$ at $k \leq 0.2~ h\mathrm{Mpc}^{-1}$, which significantly improves the BAO signal-to-noise ratio until the scale $k=0.4~ h\mathrm{Mpc}^{-1}$. Furthermore, our scheme is independent of the survey boundary since it reconstructs initial condition based on local density distribution in configuration space, which means that we can gain more information from the whole survey space. Finally, we found our trained network is not sensitive to the cosmological parameters and works very well in those cosmologies close to that of our training set. This new scheme will possibly help us dig out more information from the current, on-going and future galaxy surveys.
- [47] arXiv:2002.10223 [pdf, ps, other]
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Title: Photometric study of selected X-ray binariesComments: 5 pages, 8 figures, accepted for publication in the CAOSPSubjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)
We present results of a long-term photometric multicolor optical monitoring project of selected low-mass and high-mass X-ray binaries carried out at the T\"UB\.ITAK National Observatory (TUG). New long-term $VRI$ multicolor observations of three selected X-ray binaries with neutron star components (HZ Her, ScoX-1, SAX J2103.5+4545) were observed between 2015 and 2019 with the TUG 60-cm telescope. The light variations of the systems are presented and discussed.
- [48] arXiv:2002.10225 [pdf, other]
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Title: An Updated Galactic Double Neutron Star Merger Rate Based on Radio Pulsar PopulationsComments: Published in Research Notes of the AAS. The data for figure 1 is available with the RNAAS publicationSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Following the procedure described in Pol et al., we update the Galactic double neutron star (DNS) merger rate by including the new, highly eccentric DNS system J0509+3801 (Lynch et al.). This leads to a new Galactic DNS merger rate of $\mathcal{R}_{\rm MW} = 37^{+24}_{-11}$ Myr$^{-1}$, where the errors represent 90% confidence intervals. The corresponding DNS merger detection rate for Advanced LIGO is $\mathcal{R} = 1.9^{+1.2}_{-0.6} \times \left( D_{\rm r} / 100 \ \rm Mpc \right)^3 \rm yr^{-1},$ where $D_{\rm r}$ is the range distance. Using the LIGO O3 range distance of 130 Mpc (Abbott et al.), we predict that LIGO will detect anywhere between three and seven DNS mergers per year of observing at O3 sensitivity.
- [49] arXiv:2002.10250 [pdf, other]
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Title: The Thousand-Pulsar-Array programme on MeerKAT I: Science objectives and first resultsAuthors: Simon Johnston, A. Karastergiou, M. J. Keith, X. Song, P. Weltevrede, F. Abbate, M. Bailes, S. Buchner, F. Camilo, M. Geyer, B. Hugo, A. Jameson. M. Kramer, A. Parthasarathy, D. J. Reardon, A. Ridolfi, M. Serylak, R. M. Shannon, R. Spiewak, W. van Straten, V. Venkatraman Krishnan, F. Jankowski, B. W. Meyers, L. Oswald, B. Posselt, C. Sobey, A. Szary, J. van LeeuwenComments: Accepted by MNRASSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
We report here on initial results from the Thousand Pulsar Array (TPA) programme, part of the Large Survey Project "MeerTime" on the MeerKAT telescope. The interferometer is used in tied-array mode in the band from 856 to 1712~MHz, and the wide band coupled with the large collecting area and low receiver temperature make it an excellent telescope for the study of radio pulsars. The TPA is a 5 year project which aims to observe (a) more than 1000 pulsars to obtain high-fidelity pulse profiles, (b) some 500 of these pulsars over multiple epochs, (c) long sequences of single-pulse trains from several hundred pulsars. The scientific outcomes from the programme will include determination of pulsar geometries, the location of the radio emission within the pulsar magnetosphere, the connection between the magnetosphere and the crust and core of the star, tighter constraints on the nature of the radio emission itself as well as interstellar medium studies. First results presented here include updated dispersion measures, 26 pulsars with Faraday rotation measures derived for the first time and a description of interesting emission phenomena observed thus far.
- [50] arXiv:2002.10256 [pdf, other]
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Title: Classification of Blazar Candidates of Uncertain Type from the Fermi LAT 8-Year Source Catalog with an Artificial Neural NetworkComments: Accepted for publication in MNRAS. 10 pages, 11 figures, 1 large online tableSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)
The Fermi Large Area Telescope (LAT) has detected more than 5000 gamma-ray sources in its first 8 years of operation. More than 3000 of them are blazars. About 60 per cent of the Fermi-LAT blazars are classified as BL Lacertae objects (BL Lacs) or Flat Spectrum Radio Quasars (FSRQs), while the rest remain of uncertain type. The goal of this study was to classify those blazars of uncertain type, using a supervised machine learning method based on an artificial neural network, by comparing their properties to those of known gamma-ray sources. Probabilities for each of 1329 uncertain blazars to be a BL Lac or FSRQ are obtained. Using 90 per cent precision metric, 801 can be classified as BL Lacs and 406 as FSRQs while 122 still remain unclassified. This approach is of interest because it gives a fast preliminary classification of uncertain blazars. We also explored how different selections of training and testing samples affect the classification and discuss the meaning of network outputs.
- [51] arXiv:2002.10265 [pdf, ps, other]
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Title: Periodicity in fast radio bursts due to forced precession by a fallback diskComments: 6 pages, submittedSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Recently, a 16-day periodicity in one fast radio burst is reported. We propose that this 16-day periodicity may due to forced precession of the neutron star by a fallback disk. When the rotation axis is misaligned with the normal direction of the disk plane, the neutron star will precess. The eccentricity of the neutron star may due to rotation or strong magnetic field etc. We found that the 16-day period may be understood using typical masses of the fallback disk. Polarization observations and information about the neutron star rotation period may help to discriminate different models. The possible precession observations in pulsars, magnetars, and fast radio bursts may be understood together using forced precession by a fallback disk.
- [52] arXiv:2002.10282 [pdf, other]
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Title: Impact of low-energy cosmic rays on star formationAuthors: Marco Padovani (1), Alexei V. Ivlev (2), Daniele Galli (1), Stella S. R. Offner (3), Nick Indriolo (4), Donna Rodgers-Lee (5), Alexandre Marcowith (6), Philipp Girichidis (7), Andrei M. Bykov (8), J. M. Diederik Kruijssen (9) ((1) INAF-OAA - Italy, (2) MPE - Germany, (3) U. Texas - USA, (4) ALMA-NAOJ-NINS - Japan, (5) U. Dublin - Ireland, (6) LUPM - France, (7) AIP - Germany, (8) Ioffe Institute - Russian Federation, (9) ARI-ZAH - Germany)Comments: Submitted to Space Science Reviews topical collection Star formationSubjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
In recent years, exciting developments have taken place in the identification of the role of cosmic rays in star-forming environments. Observations from radio to infrared wavelengths and theoretical modelling have shown that low-energy cosmic rays (<1 TeV) play a fundamental role in shaping the chemical richness of the interstellar medium, determining the dynamical evolution of molecular clouds. In this review we summarise in a coherent picture the main results obtained by observations and by theoretical models of propagation and generation of cosmic rays, from the smallest scales of protostars and circumstellar discs, to young stellar clusters, up to Galactic and extragalactic scales. We also discuss the new fields that will be explored in the near future thanks to new generation instruments, such as: CTA, for the $\gamma$-ray emission from high-mass protostars; SKA and precursors, for the synchrotron emission at different scales; and ELT/HIRES, JWST, and ARIEL, for the impact of cosmic rays on exoplanetary atmospheres and habitability.
- [53] arXiv:2002.10287 [pdf, other]
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Title: Inequalities in access to permanent positions in astronomy in FranceComments: Comments welcomeSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
We investigate inequalities in access to permanent positions in professional astronomy in France, focusing on the hiring stage. We use results from a national survey conducted on behalf of the French society of astronomy and astrophysics (SF2A) aimed at young astronomers holding a PhD obtained in France, and answered by over 300 researchers. We find that women are nearly two times less likely than men to be selected by the (national or local) committees attributing permanent positions ($p=0.06$). We also find that applicants who did their undergraduate studies in an elite school ("Grande \'Ecole"), where women are largely under-represented, rather than in a university, are nearly three times more likely to succeed in obtaining a position ($p=0.0026$). Our analysis suggests the existence of two biases in committees attributing permanent positions in astronomy in France: a gender bias, and a form of elitism. These biases against women in their professional life impacts their personal life as our survey shows that a larger fraction of them declare that having children can have a negative effect on their careers. They are half as many as men having children in the sample.
- [54] arXiv:2002.10307 [pdf, ps, other]
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Title: Signal Processing Firmware for the Low Frequency Aperture ArrayAuthors: Gianni Comoretto, Riccardo Chiello, Matt Roberts, Rob Halsall, Kristian Zarb Adami, Monica Alderighi, Amin Aminaei, Jeremy Baker, Carolina Belli, Simone Chiarucci, Sergio D'Angelo, Andrea De Marco, Gabriele Dalle Mura, Alessio Magro, Andrea Mattana, Jader Monari, Giovanni Naldi, Sandro Pastore, Federico Perini, Marco Poloni, Giuseppe Pupillo, Simone Rusticelli, Marco Schiaffino, Francesco Schillirò, Emanuele ZaccaroComments: 19 pagesJournal-ref: Journal of Astronomical Instrumentation, Vol. 06, No. 01, 1641015 (2017)Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)
The signal processing firmware that has been developed for the Low Frequency Aperture Array component of the Square Kilometre Array is described. The firmware is implemented on a dual FPGA board, that is capable of processing the streams from 16 dual polarization antennas. Data processing includes channelization of the sampled data for each antenna, correction for instrumental response and for geometric delays and formation of one or more beams by combining the aligned streams. The channelizer uses an oversampling polyphase filterbank architecture, allowing a frequency continuous processing of the input signal without discontinuities between spectral channels. Each board processes the streams from 16 antennas, as part of larger beamforming system, linked by standard Ethernet interconnections. There are envisaged to be 8192 of these signal processing platforms in the first phase of the Square Kilometre array so particular attention has been devoted to ensure the design is low cost and low power.
- [55] arXiv:2002.10332 [pdf, ps, other]
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Title: New data on young and old black holes and other unexpected creaturesAuthors: A.D. DolgovComments: 16 pages, talk presented at 8th International Conference on New Frontiers in Physics 21-30 August, 2019 Conference Center of the Orthodox Academy of Creta, Crete, Greece. arXiv admin note: substantial text overlap with arXiv:1911.02382Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
A review on recent astronomical observations indicating to unexpectedly abundant population of the contemporary and $ z \sim 10 $ universe by massive black holes in all mass ranges are is presented. It is argued that these black holes are mostly primordial. The data on some other stellar-kind objects which are also may be primordial are discussed.
- [56] arXiv:2002.10337 [pdf, ps, other]
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Title: The FAST discovery of an Eclipsing Binary Millisecond Pulsar in the Globular Cluster M92 (NGC 6341)Authors: Zhichen Pan, Scott M. Ransom, Duncan R. Lorimer, William Fiore, Lei Qian, Lin Wang, Benjamin W. Stappers, George Hobbs, Weiwei Zhu, Youling Yue, Pei Wang, Jiguang Lu, Kuo Liu, Bo Peng, Lei Zhang, Di LiComments: 9 pages, 2 figures, submitted to ApJL, comments are welcomed!Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
We report the discovery of an eclipsing binary millisecond pulsar in the globular cluster M92 (NGC6341) with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). PSR J1717+4308A, or M92A, has a pulse frequency of 316.5~Hz (3.16~ms) and a dispersion measure of 35.45 pc cm$^{-3}$. The pulsar is a member of a binary system with an orbital period of 0.20~days around a low-mass companion which has a median mass of $\sim$0.18~\Ms. From observations so far, at least two eclipsing events have been observed in each orbit. The longer one lasted for ~5000~s in the orbital phase range 0.1--0.5. The other lasted for ~500~s and occurred between 1000--2000~s before or after the longer eclipsing event. The lengths of these two eclipsing events also change. These properties suggest that J1717+4308A is a ``red-back'' system with a low-mass main sequence or sub-giant companion. Timing observations of the pulsar and further searches of the data for additional pulsars are ongoing.
- [57] arXiv:2002.10357 [pdf, other]
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Title: Magnetic field configurations in neutron stars from MHD simulationsComments: Submitted to Monthly Notices of the Royal Astronomical SocietySubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)
We have studied numerically the evolution of magnetic fields in barotropic neutron stars, by performing nonlinear magnetohydrodynamical simulations with the code PLUTO. For both initially predominantly poloidal and toroidal fields, with varying strengths, we find that the field settles down to a mixed poloidal-toroidal configuration, where the toroidal component contributes between 10% and 20% of the total magnetic energy. This is, however, not a strict equilibrium, as the instability leads to the development of turbulence, which in turn gives rise to an inverse helicity cascade, which determines the final 'twisted torus' setup. The final field configuration is thus dictated by the non-linear saturation of the instability, and not stationary. The average energy of the poloidal and toroidal components, however, is approximately stable in our simulations, and a complex multipolar structure emerges at the surface, while the magnetic field is dipolar at the exterior boundary, outside the star.
- [58] arXiv:2002.10368 [pdf, other]
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Title: Distinguishing multicellular life on exoplanets by testing Earth as an exoplanetAuthors: Christopher E. Doughty, Andrew Abraham, James Windsor, Michael Mommert, Michael Gowenlock, Tyler Robinson, David TrillingComments: 7 pages, 8 figures, 1 tableSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
Can multicellular life be distinguished from single cellular life on an exoplanet? We hypothesize that abundant upright photosynthetic multicellular life (trees) will cast shadows at high sun angles that will distinguish them from single cellular life and test this using Earth as an exoplanet. We first test the concept using Unmanned Arial Vehicles (UAVs) at a replica moon landing site near Flagstaff, Arizona and show trees have both a distinctive reflectance signature (red edge) and geometric signature (shadows at high sun angles) that can distinguish them from replica moon craters. Next, we calculate reflectance signatures for Earth at several phase angles with POLDER (Polarization and Directionality of Earth's reflectance) satellite directional reflectance measurements and then reduce Earth to a single pixel. We compare Earth to other planetary bodies (Mars, the Moon, Venus, and Uranus) and hypothesize that Earths directional reflectance will be between strongly backscattering rocky bodies with no weathering (like Mars and the Moon) and cloudy bodies with more isotropic scattering (like Venus and Uranus). Our modelling results put Earth in line with strongly backscattering Mars, while our empirical results put Earth in line with more isotropic scattering Venus. We identify potential weaknesses in both the modeled and empirical results and suggest additional steps to determine whether this technique could distinguish upright multicellular life on exoplanets.
- [59] arXiv:2002.10370 [pdf, other]
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Title: Extrasolar enigmas: from disintegrating exoplanets to exoasteroidsComments: 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-KA203-035562Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Thousands of transiting exoplanets have been discovered to date, thanks in great part to the {\em Kepler} space mission. As in all populations, and certainly in the case of exoplanets, one finds unique objects with distinct characteristics. Here we will describe the properties and behaviour of a small group of `disintegrating' exoplanets discovered over the last few years (KIC 12557548b, K2-22b, and others). They evaporate, lose mass unraveling their naked cores, produce spectacular dusty comet-like tails, and feature highly variable asymmetric transits. Apart from these exoplanets, there is observational evidence for even smaller `exo-'objects orbiting other stars: exoasteroids and exocomets. Most probably, such objects are also behind the mystery of Boyajian's star. Ongoing and upcoming space missions such as {\em TESS} and PLATO will hopefully discover more objects of this kind, and a new era of the exploration of small extrasolar systems bodies will be upon us.
- [60] arXiv:2002.10379 [pdf, other]
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Title: The effect of internal gravity waves on cloud evolution in sub-stellar atmospheresComments: 10 pages, 6 figures. Accepted for publication in Astronomy & AstrophysicsSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Sub-stellar objects exhibit photometric variability which is believed to be caused by a number of processes such as magnetically-driven spots or inhomogeneous cloud coverage. Recent sub-stellar models have shown that turbulent flows and waves, including internal gravity waves, may play an important role in cloud evolution.
The aim of this paper is to investigate the effect of internal gravity waves on dust cloud nucleation and dust growth, and whether observations of the resulting cloud structures could be used to recover atmospheric density information.
For a simplified atmosphere in two dimensions, we numerically solve the governing fluid equations to simulate the effect on dust nucleation and mantle growth as a result of the passage of an internal gravity wave. Furthermore, we derive an expression that relates the properties of the wave-induced cloud structures to observable parameters in order to deduce the atmospheric density.
Numerical simulations show that the density, pressure and temperature variations caused by gravity waves lead to an increase of dust nucleation by up to a factor 20, and dust mantle growth rate by up to a factor 1.6, compared to their equilibrium values. Through an exploration of the wider sub-stellar parameter space, we show that in absolute terms, the increase in dust nucleation due to internal gravity waves is stronger in cooler (T dwarfs) and $\text{TiO}_2$-rich sub-stellar atmospheres. The relative increase however is greater in warm (L dwarf) and $\text{TiO}_2$-poor atmospheres due to conditions less suited for efficient nucleation at equilibrium. These variations lead to banded areas in which dust formation is much more pronounced, and lead to banded cloud structures similar to those observed on Earth.
Using the proposed method, potential observations of banded clouds could be used to estimate the atmospheric density of sub-stellar objects. - [61] arXiv:2002.10409 [pdf, other]
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Title: A Modified Spheromak Model Suitable for Coronal Mass Ejection SimulationsSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)
Coronal Mass Ejections (CMEs) are one of the primary drivers of extreme space weather. They are large eruptions of mass and magnetic field from the solar corona and can travel the distance between Sun and Earth in half a day to a few days. Predictions of CMEs at 1 Astronomical Unit (AU), in terms of both its arrival time and magnetic field configuration, are very important for predicting space weather. Magnetohydrodynamic (MHD) modeling of CMEs, using flux-rope-based models is a promising tool for achieving this goal. In this study, we present one such model for CME simulations, based on spheromak magnetic field configuration. We have modified the spheromak solution to allow for independent input of poloidal and toroidal fluxes. The motivation for this is a possibility to estimate these fluxes from solar magnetograms and extreme ultraviolet (EUV) data from a number of different approaches. We estimate the poloidal flux of CME using post eruption arcades (PEAs) and toroidal flux from the coronal dimming. In this modified spheromak, we also have an option to control the helicity sign of flux ropes, which can be derived from the solar disk magnetograms using the magnetic tongue approach. We demonstate the applicability of this model by simulating the 12 July 2012 CME in the solar corona.
- [62] arXiv:2002.10431 [pdf, other]
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Title: Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequenciesAuthors: F. de Gasperin, J. Vink, J.P. McKean, A. Asgekar, M.J. Bentum, R. Blaauw, A. Bonafede, M. Bruggen, F. Breitling, W.N. Brouw, H.R. Butcher, B. Ciardi, V. Cuciti, M. de Vos, S. Duscha, J. Eisloffel, D. Engels, R.A. Fallows, T.M.O. Franzen, M.A. Garrett, A.W. Gunst, J. Horandel, G. Heald, L.V.E. Koopmans, A. Krankowski, P. Maat, G. Mann, M. Mevius, G. Miley, A. Nelles, M.J. Norden, A.R. Offringa, E. Orru, H. Paas, M. Pandey-Pommier, R. Pizzo, W. Reich, A. Rowlinson, D.J. Schwarz, A. Shulevski, O. Smirnov, M. Soida, M. Tagger, M.C. Toribio, A. van Ardenne, A.J. van der Horst, M.P. van Haarlem, R. J. van Weeren, C. Vocks, O. Wucknitz, P. Zarka, P. ZuccaComments: 7 pages, 2 figures, accepted A&A, online data on A&A websiteSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)
The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (<100 MHz) can reach several thousands of janskys, and they often contaminate observations of the low-frequency sky by interfering with image processing. Furthermore, these sources are foreground objects for all-sky observations hampering the study of faint signals, such as the cosmological 21 cm line from the epoch of reionisation.
We aim to produce robust models for the surface brightness emission as a function of frequency for the A-team sources at ultra-low frequencies. These models are needed for the calibration and imaging of wide-area surveys of the sky with low-frequency interferometers. This requires obtaining images at an angular resolution better than 15 arcsec with a high dynamic range and good image fidelity.
We observed the A-team with the Low Frequency Array (LOFAR) at frequencies between 30 MHz and 77 MHz using the Low Band Antenna (LBA) system. We reduced the datasets and obtained an image for each A-team source.
The paper presents the best models to date for the sources Cassiopeia A, Cygnus A, Taurus A, and Virgo A between 30 MHz and 77 MHz. We were able to obtain the aimed resolution and dynamic range in all cases. Owing to its compactness and complexity, observations with the long baselines of the International LOFAR Telescope will be required to improve the source model for Cygnus A further. - [63] arXiv:2002.10440 [pdf, other]
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Title: Modeling Aerial Gamma-Ray Backgrounds using Non-negative Matrix FactorizationComments: 14 pages, 12 figures, accepted for publication in IEEE Transactions on Nuclear ScienceSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Applied Physics (physics.app-ph); Data Analysis, Statistics and Probability (physics.data-an)
Airborne gamma-ray surveys are useful for many applications, ranging from geology and mining to public health and nuclear security. In all these contexts, the ability to decompose a measured spectrum into a linear combination of background source terms can provide useful insights into the data and lead to improvements over techniques that use spectral energy windows. Multiple methods for the linear decomposition of spectra exist but are subject to various drawbacks, such as allowing negative photon fluxes or requiring detailed Monte Carlo modeling. We propose using Non-negative Matrix Factorization (NMF) as a data-driven approach to spectral decomposition. Using aerial surveys that include flights over water, we demonstrate that the mathematical approach of NMF finds physically relevant structure in aerial gamma-ray background, namely that measured spectra can be expressed as the sum of nearby terrestrial emission, distant terrestrial emission, and radon and cosmic emission. These NMF background components are compared to the background components obtained using Noise-Adjusted Singular Value Decomposition (NASVD), which contain negative photon fluxes and thus do not represent emission spectra in as straightforward a way. Finally, we comment on potential areas of research that are enabled by NMF decompositions, such as new approaches to spectral anomaly detection and data fusion.
- [64] arXiv:2002.10449 [pdf, other]
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Title: Latest evidence for a late time vacuum -- geodesic CDM interactionComments: 18 pages, 7 figuresSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
We perform a reconstruction of the coupling function between vacuum energy and geodesic cold dark matter using the latest observational data. We bin the interaction in seventeen redshift bins but use a correlation prior to prevent rapid, unphysical oscillations in the coupling function. This prior also serves to eliminate any dependence of the reconstruction on the binning method. We use two different forms of the correlation prior, finding that both give similar results for the reconstruction of the dark matter -- dark energy interaction. Calculating the Bayes factor for each case, we find no meaningful evidence for deviation from the null interacting case, i.e. $\Lambda$CDM, in our reconstruction.
Cross-lists for Tue, 25 Feb 20
- [65] arXiv:2002.09483 (cross-list from gr-qc) [pdf, ps, other]
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Title: A reliable description of the radial oscillations of compact starsComments: 13 pages, 8 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
We develop a numerical algorithm for the solution of the Sturm-Liouville differential equation governing the stationary radial oscillations of nonrotating compact stars. Our method is based on the Numerov's method that turns the Sturm-Liouville differential equation in an eigenvalue problem. In our development we provide a strategy to correctly deal with the star boundaries and the interfaces between layers with different mechanical properties. Assuming that the fluctuations obey the same equation of state of the background, we analyze various different stellar models and we precisely determine hundreds of eigenfrequencies and of eigenmodes. If the equation of state does not present an interface discontinuity, the fundamental radial eigenmode becomes unstable exactly at the critical central energy density corresponding to the largest gravitational mass. However, in the presence of an interface discontinuity, there exist stable configurations with a central density exceeding the critical one and with a smaller gravitational mass.
- [66] arXiv:2002.09501 (cross-list from physics.plasm-ph) [pdf, other]
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Title: Generation of chiral asymmetry via helical magnetic fieldsComments: 16 pages, 11 figures, submitted to PRDSubjects: Plasma Physics (physics.plasm-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); Soft Condensed Matter (cond-mat.soft); High Energy Physics - Phenomenology (hep-ph)
It is well known that helical magnetic fields undergo a so-called inverse cascade by which their correlation length grows due to the conservation of magnetic helicity in classical ideal magnetohydrodynamics (MHD). At high energies above approximately $10$ MeV, however, classical MHD is necessarily extended to chiral MHD and then the conserved quantity is $\langle\mathcal{H}\rangle + 2 \langle\mu_5\rangle / \lambda$ with $\langle\mathcal{H}\rangle$ being the mean magnetic helicity and $\langle\mu_5\rangle$ being the mean chiral chemical potential of charged fermions. Here, $\lambda$ is a (phenomenological) chiral feedback parameter. In this paper, we study the evolution of the chiral MHD system with the initial condition of nonzero $\langle\mathcal{H}\rangle$ and vanishing $\mu_5$. We present analytic derivations for the time evolution of $\langle\mathcal{H}\rangle$ and $\langle\mu_5\rangle$ that we compare to a series of laminar and turbulent three-dimensional direct numerical simulations. We find that the late-time evolution of $\langle\mathcal{H}\rangle$ depends on the magnetic and kinetic Reynolds numbers ${\rm Re}_{_\mathrm{M}}$ and ${\rm Re}_{_\mathrm{K}}$. For a high ${\rm Re}_{_\mathrm{M}}$ and ${\rm Re}_{_\mathrm{K}}$ where turbulence occurs, $\langle\mathcal{H}\rangle$ eventually evolves in the same way as in classical ideal MHD where the inverse correlation length of the helical magnetic field scales with time $t$ as $k_\mathrm{p} \propto t^{-2/3}$. For a low Reynolds numbers where the velocity field is negligible, the scaling is changed to $k_\mathrm{p} \propto t^{-1/2}\mathrm{ln}\left(t/t_\mathrm{log}\right)$. After being rapidly generated, $\langle\mu_5\rangle$ always decays together with $k_\mathrm{p}$, i.e. $\langle\mu_5\rangle \approx k_\mathrm{p}$, with a time evolution that depends on whether the system is in the limit of low or high Reynolds numbers.
- [67] arXiv:2002.09584 (cross-list from physics.atom-ph) [pdf]
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Title: Cavity ring-down spectroscopy of CO$_2$ near $λ$ = 2.06 $μ$m: Accurate transition intensities for the Orbiting Carbon Observatory-2 (OCO-2) "strong band"Comments: 30 pages, 9 figures, 4 tablesSubjects: Atomic Physics (physics.atom-ph); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Atmospheric and Oceanic Physics (physics.ao-ph); Chemical Physics (physics.chem-ph); Instrumentation and Detectors (physics.ins-det)
The $\lambda$ = 2.06 $\mu$m absorption band of $^{12}$C$^{16}$O$_2$ is widely used for the remote sensing of atmospheric carbon dioxide, making it relevant to many important top-down measurements of carbon flux. The forward models used in the retrieval algorithms employed in these measurements require increasingly accurate line intensity and line shape data from which absorption cross-sections can be computed. To overcome accuracy limitations of existing line lists, we used frequency-stabilized cavity ring-down spectroscopy to measure 39 transitions in the $^{12}$C$^{16}$O$_2$ absorption band. We estimate the relative combined standard uncertainty for the measured intensities to be $u_r$ = 0.09 %, which is dominated by several type B (systematic) contributions each with $u_r$ = 0.04 %. We predicted the $J$-dependence of the measured intensities using two theoretical models: a one-dimensional quantum mechanical model with Herman-Wallis rotation-vibration corrections, and a line-by-line ab initio model [Zak et al. JQSRT 2016;177:31-42]. For the second approach, we fit only a single factor to rescale the theoretical integrated band intensity to be consistent with the measured intensities. We find that the latter approach yields an equally adequate representation of the fitted $J$-dependent intensity data and provides the most physically general representation of the results. Our recommended value for the integrated band intensity equal to 7.180$\times$10$^{-21}$ cm molecule$^{-1}$ $\pm$ 6$\times$10$^{-24}$ cm molecule$^{-1}$ is based on the rescaled ab initio model and corresponds to a fitted scale factor of 1.0065 $\pm$ 0.0002. Comparisons of literature intensity values to our results reveal systematic deviations ranging from $-$1.1 % to 0.4 %.
- [68] arXiv:2002.09613 (cross-list from physics.comp-ph) [pdf, other]
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Title: General Relativistic Hydrodynamics on a Moving-mesh I: Static SpacetimesComments: 10 pages, 4 figures, submitted to MNRASSubjects: Computational Physics (physics.comp-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)
We present the first-ever moving-mesh general relativistic hydrodynamics solver for static spacetimes as implemented in the code, MANGA. Our implementation builds on the architectures of MANGA and the numerical relativity Python package NRPy+. We review the general algorithm to solve these equations and, in particular, detail the time stepping; Riemann solution across moving faces; conversion between primitive and conservative variables; validation and correction of hydrodynamic variables; and mapping of the metric to a Voronoi moving-mesh grid.
We present test results for the numerical integration of an unmagnetized Tolman-Oppenheimer-Volkoff star for 24 dynamical times. We demonstrate that at a resolution of $10^6$ mesh generating points, the star is stable and its central density drifts downward by 2% over this timescale. At a lower resolution the central density drift increases in a manner consistent with the adopted second order spatial reconstruction scheme. These results agree well with the exact solutions, and we find the error behavior to be similar to Eulerian codes with second-order spatial reconstruction. We also demonstrate that the new code recovers the fundamental mode frequency for the same TOV star but with its initial pressure depleted by 10% - [69] arXiv:2002.09771 (cross-list from hep-th) [pdf, other]
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Title: Creating Spatial Flatness by Combining String Gas Cosmology and Power Law InflationComments: 9 pages, 2 figuresSubjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
We show that it is possible to combine an early phase of String Gas Cosmology which can explain the origin of the observed structures on cosmological scales with a short later period of power law inflation which creates spatial flatness. The resulting model is consistent with the ``swampland criteria'' and the constraints coming from the {\it Trans-Planckian Censorship Conjecture}. Such a construction is not possible using only canonical slow-roll inflation, but it can emerge in the warm inflation scenario or in cold inflation with an exponential potential. The resulting cosmology is non-singular. We discuss the spectrum of cosmological perturbations resulting in our scenario. On large scales (scales which remain larger than the Hubble radius after the initial string gas phase) the spectrum is determined by the thermal string gas fluctuations set up in the primordial phase, and it is almost scale-invariant with a slight red tilt. On small scales, the perturbations produced during the inflationary phase dominate. On these scales, the spectrum is once again nearly scale-invariant. There is an intermediate range (scales which enter the Hubble radius during the period of inflation) where the string gas fluctuations are damped but continue to dominate over those produced during the period of inflation. On these scales the spectrum has a sharp red spectral index of $n_s - 1 \sim -2$.
- [70] arXiv:2002.09955 (cross-list from hep-ph) [pdf, other]
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Title: Observational constraints on dark matter decaying via gravity portalsSubjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Global symmetry can guarantee the stability of dark matter particles (DMP). However, nonminimal coupling between dark matter (DM) and gravity can destroy the global symmetry of DMP, which in turn leads to their decay. Under the framework of nonminimal coupling between DM and gravity, it is worth exploring to what extent the symmetry of DMP is broken. It is suggested that the total amount of decay products of DMP cannot exceed current observational constraints. Along these lines, the data obtained with satellites such as Fermi-LAT and AMS-02 can limit the strength of the global symmetry breaking of DMP. Since the mass of the DMP may be in the GeV--TeV range, we determine a reasonable parameter range for the coupling strength between DM and gravity in this range. We find that when the mass of the DMP is around the electroweak scale (246 GeV), we can exclude values of the nonminimal coupling parameter $\xi$ greater than $1.5\times10^{-10}$. We also show that the larger the mass of the DMP, the stronger this restriction. Our results give the strongest constraints to date of the possible coupling strength under current observations.
- [71] arXiv:2002.09994 (cross-list from physics.chem-ph) [pdf, other]
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Title: Spectroscopy of YO from first principlesJournal-ref: Phys. Chem. Chem. Phys., 21:22794-22810, 2019Subjects: Chemical Physics (physics.chem-ph); Solar and Stellar Astrophysics (astro-ph.SR)
We report an ab initio study on the spectroscopy of the open-shell diatomic molecule yttrium oxide, YO. The study considers the six lowest doublet states, $X\,{}^{2}\Sigma^{+}$, $A\,{}^{2}\Pi$, $C\,{}^{2}\Pi$, $A'\,{}^{2}\Delta$, $B\,{}^{2}\Sigma^{+}$, $D\,{}^{2}\Sigma^{+}$ and a few higher-lying quartet states using high levels of electronic structure theory and accurate nuclear motion calculations. The coupled cluster singles, doubles, and perturbative triples, CCSD(T), and multireference configuration interaction (MRCI) methods are employed in conjunction with a relativistic pseudopotential on the yttrium atom and a series of correlation-consistent basis sets ranging in size from triple-$\zeta$ to quintuple-$\zeta$ quality. Core-valence correlation effects are taken into account and complete basis set limit extrapolation is performed for CCSD(T). Spin-orbit coupling is included through the use of both MRCI state-interaction with spin-orbit (SI-SO) approach and four-component relativistic equation-of-motion CCSD calculations. Using the ab initio data for bond lengths ranging from 1.0 to 2.5 A, we compute 6 potential energy, 12 spin-orbit, 8 electronic angular momentum, 6 electric dipole moment and 12 transition dipole moment (4 parallel and 8 perpendicular) curves which provide a complete description of the spectroscopy of the system of six lowest doublet states. The Duo nuclear motion program is used to solve the coupled nuclear motion Schr\"{o}dinger equation for these six electronic states. The spectra of $^{89}$Y$^{16}$O simulated for different temperatures are compared with several available high resolution experimental studies; good agreement is found once minor adjustments are made to the electronic excitation energies.
- [72] arXiv:2002.10155 (cross-list from gr-qc) [pdf, ps, other]
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Title: Non-Euclidean Newtonian CosmologyAuthors: John D. BarrowComments: 11 pages, no figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); History and Philosophy of Physics (physics.hist-ph)
We formulate and solve the problem of Newtonian cosmology under the assumption that the absolute space of Newton is non-Euclidean. In particular, we focus on the negatively-curved hyperbolic space, H3. We point out the inequivalence between the curvature term that arises in the Friedmann equation in Newtonian cosmology in Euclidean space and the role of curvature in the H3 space. We find the generalisation of the inverse-square law and the solutions of the Newtonian cosmology that follow from it. We find the generalisations of the Euclidean Michell 'black hole' in H3 and show that it leads to different maximum force and area results to those we have found in general relativity. We show how to add the counterpart of the cosmological constant to the gravitational potential in H3 and explore the solutions and asymptotes of the cosmological models that result. We also discuss the problems of introducing compact topologies in Newtonian cosmologies with non-negative spatial curvature.
- [73] arXiv:2002.10262 (cross-list from gr-qc) [pdf, ps, other]
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Title: Electromagnetic phenomena around black holesAuthors: A.D. DolgovComments: 6 pages, talk presented at 8th International Conference on New Frontiers in Physics, 21-30 August, 2019, Conference Center of the Orthodox Academy of Creta Crete, GreeceSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Transition of gravitational waves, produced in the process of coalescence of black hole binaries, into electromagnetic radiation in magnetic field is discussed. The magnetic field is assumed to be created by rotating electrically charged black holes. The process of electric charging of black holes due to different mobilities of protons and electrons in the surrounding plasma is described.
- [74] arXiv:2002.10264 (cross-list from gr-qc) [pdf, ps, other]
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Title: An exact solution for a force-free field electrodynamics accretion disk surrounding a perturbed charged black holeAuthors: Haidar SheikhahmadiComments: I appreciate any constructive comments and enlightening criticisms. 4 pagesSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
Recently the first real image of the supermassive black hole at the heart of the galaxy M87 successfully has been captured. To explain the behavior of both the observed powerful jets and the electromagnetic accretion disk the Blandford Znajek mechanism, by the Event Horizon Telescope collaboration, has been considered. To justify these phenomena we are seeking an exact solution for a perturbed Rissner-Nordstrom black hole surrounded by a force-free field electrodynamics accretion disk. Although a charged black hole is a toy model, by tending the charge to zero one can obtain the results for a perturbed, rotating, Schwarzschild one immediately. Finding an exact solution in regards to the force-free field electrodynamics as a source for perturbations in different classes of the black holes is may one of the open problems yet. Here to find the solution, different Maxwell's scalars besides the energy-momentum tensor in both tangent and bend backgrounds are calculated. In doing so, the well known Newman-Penrose formalism is considered.
- [75] arXiv:2002.10331 (cross-list from hep-th) [pdf, ps, other]
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Title: Black Hole as a Quantum Field ConfigurationSubjects: High Energy Physics - Theory (hep-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
We describe 4D evaporating black holes as quantum field configurations by solving the semi-classical Einstein equation $G_{\mu\nu}=8\pi G \langle \psi|T_{\mu\nu}|\psi \rangle$ and quantum matter fields in a self-consistent manner. As the matter fields we consider $N$ massless free scalar fields ($N$ is large). We find a spherically symmetric self-consistent solution of the metric $g_{\mu\nu}$ and state $|\psi\rangle$. Here, $g_{\mu\nu}$ is locally $AdS_2\times S^2$ geometry, and $|\psi\rangle$ provides $\langle \psi|T_{\mu\nu}|\psi \rangle=\langle0|T_{\mu\nu}|0 \rangle+T_{\mu\nu}^{(\psi)}$, where $|0\rangle$ is the ground state of the matter fields in the metric and $T_{\mu\nu}^{(\psi)}$ consists of the excitation of s-waves that describe the collapsing matter and Hawking radiation with the ingoing negative energy flow. This object is supported by a large tangential pressure $\langle0|T^\theta{}_\theta|0 \rangle$ due to the vacuum fluctuation of the bound modes with large angular momenta. This describes the interior of the black hole when the back reaction of the evaporation is considered. The black hole is a compact object with a surface (instead of horizon) that looks like a conventional black hole from the outside and eventually evaporates without a singularity. If we count the number of self-consistent configurations $\{|\psi\rangle\}$, we reproduce the area law of the entropy. This tells that the information is carried by the s-waves inside the black hole. $|\psi\rangle$ also describes the process that the negative ingoing energy flow created with Hawking radiation is superposed on the collapsing matter to decrease the total energy while the total energy density remains positive. As a special case, we consider conformal matter and show that the interior metric is determined by the matter content of the theory, which leads to a new weak-gravity conjecture.
- [76] arXiv:2002.10364 (cross-list from gr-qc) [pdf, ps, other]
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Title: Revisiting the 2PN pericentre precession in view of possible future measurements of itAuthors: Lorenzo IorioComments: Latex2e, 24 pages, 2 figures, no tablesSubjects: General Relativity and Quantum Cosmology (gr-qc); Earth and Planetary Astrophysics (astro-ph.EP); Space Physics (physics.space-ph)
At the second post-Newtonian (2PN) order, the secular pericentre precession $\dot\omega^\mathrm{2PN}$ of either a full two-body system made of well detached non-rotating monopole masses of comparable size and a restricted two-body system composed of a point particle orbiting a fixed central mass have been analytically computed so far with a variety of approaches. We offer our contribution by analytically computing $\dot\omega^\mathrm{2PN}$ in a perturbative way with the method of variation of elliptical elements by explicitly calculating both the direct contribution due to the 2PN acceleration ${\boldsymbol A}^\mathrm{2PN}$, and also an indirect part arising from the self-interaction of the 1PN acceleration ${\boldsymbol A}^\mathrm{1PN}$ in the orbital average accounting for the instantaneous shifts induced by ${\boldsymbol A}^\mathrm{1PN}$ itself. Explicit formulas are straightforwardly obtained for both the point particle and full two-body cases without recurring to simplifying assumptions on the eccentricity $e$. Two different numerical integrations of the equations of motion confirm our analytical results for both the direct and indirect precessions. The values of the resulting effects for Mercury and some binary pulsars are confronted with the present-day level of experimental accuracies in measuring/constraining their pericentre precessions. The supermassive binary black hole in the BL Lac object OJ 287 is considered as well. A comparison with some of the results appeared in the literature is made.
Replacements for Tue, 25 Feb 20
- [77] arXiv:1712.04461 (replaced) [src]
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Title: Analytic Derivation of the Halo Mass Function from the Non-Linear Cosmic Density FieldAuthors: Laila Linke, Johannes Schwinn, Matthias Bartelmann (Heidelberg University, ZAH, Institut fuer Theoretische Astrophysik)Comments: Withdrawn due to issues with the used probability distribution function and the application of the excursion-set formalismSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [78] arXiv:1804.06492 (replaced) [pdf, ps, other]
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Title: Molecular gas masses of gamma-ray burst host galaxiesAuthors: Michał J. Michałowski (AMU, Poznań), A. Karska, J. R. Rizzo, M. Baes, A. J. Castro-Tirado, J. Hjorth, L. K. Hunt, P. Kamphuis, M. P. Koprowski, M. R. Krumholz, D. Malesani, A. Nicuesa Guelbenzu, J. Rasmussen, A. Rossi, P. Schady, J. Sollerman, P. van der WerfComments: Published in A&A. 12 pages, 5 figures, 4 tablesJournal-ref: A&A 617, A143 (2018)Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
- [79] arXiv:1805.01240 (replaced) [pdf, other]
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Title: Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy colour informationSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [80] arXiv:1806.04518 (replaced) [pdf, other]
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Title: A Soliton Solution for the Central Dark Masses in 47- Tuc Globular Cluster and Implications for the AxiverseAuthors: Razieh Emami (Center for Astrophysics, Harvard-Smithsonian), Tom Broadhurst, George Smoot, Tzihong Chiueh, Hoang Nhan LuuComments: 6 Pages, 4 Figures. Accepted for publication in PRDSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
- [81] arXiv:1811.00479 (replaced) [pdf, other]
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Title: Characterizing bias on large scale CMB $B$-modes after galactic foregrounds cleaningComments: 17 pages, 10 figuresJournal-ref: Phys. Rev. D 99, 043529 (2019)Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [82] arXiv:1903.02578 (replaced) [pdf, other]
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Title: Observational signatures of the black hole Mass Distribution in the Galactic CenterAuthors: Razieh Emami (Center for Astrophysics, Harvard-Smithsonian), Abraham Loeb (Center for Astrophysics, Harvard-Smithsonian)Comments: 23 pages, 10 figures, Accepted for application in JCAPSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
- [83] arXiv:1903.02579 (replaced) [pdf, other]
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Title: Detectability of Gravitational Wave from a population of Inspiralling Black Holes in Milky Way Mass GalaxiesAuthors: Razieh Emami (Center for Astrophysics, Harvard-Smithsonian), Abraham Loeb (Center for Astrophysics, Harvard-Smithsonian)Comments: 10 ages, 7 figures. Significant improvementsSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
- [84] arXiv:1905.04592 (replaced) [pdf, other]
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Title: Atacama Cosmology Telescope: Dusty star-forming galaxies and active galactic nuclei in the equatorial surveyAuthors: Megan B. Gralla, Tobias A. Marriage, Graeme Addison, Andrew J. Baker, J. Richard Bond, Devin Crichton, Rahul Datta, Mark J. Devlin, Joanna Dunkley, Rolando Dünner, Joseph Fowler, Patricio A. Gallardo, Kirsten Hall, Mark Halpern, Matthew Hasselfield, Matt Hilton, Adam D. Hincks, Kevin M. Huffenberger, John P. Hughes, Arthur Kosowsky, Carlos H. López-Caraballo, Thibaut Louis, Danica Marsden, Kavilan Moodley, Michael D. Niemack, Lyman A. Page, Bruce Partridge, Jesus Rivera, Jonathan L. Sievers, Suzanne Staggs, Ting Su, Daniel Swetz, Edward J. WollackComments: 42 pages. Accepted version. Catalogs and maps available at this https URLSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [85] arXiv:1905.04593 (replaced) [pdf, other]
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Title: Accounting for selection bias using simulations: A general method and an application to millimeter-wavelength surveysComments: 10 pages. Accepted versionSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
- [86] arXiv:1905.05724 (replaced) [pdf, other]
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Title: On the Expected Production of Gravitational Waves During PreheatingAuthors: C. Armendariz-PiconComments: 35 pages, 6 figures. v2: Replaced with version accepted for publicationSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [87] arXiv:1907.01125 (replaced) [pdf, other]
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Title: Fitting functions on the cheap: the relative nonlinear matter power spectrumComments: 37 pages, 16 figures; v2: 40 pages, two new sections on code comparison and relation to the stable clustering ansatz, two new figures, results and conclusions unchanged, version accepted by JCAPSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [88] arXiv:1907.02573 (replaced) [pdf, ps, other]
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Title: Global characteristics of the medium produced in ultra-high energy cosmic ray collisionsAuthors: V. A. Okorokov (National Research Nuclear University MEPhI)Comments: 8 pages, 2 figures, 3 tables. II International Symposium on Cosmic Rays and Astrophysics (ISCRA'2019), Moscow, Russia, June 25 - 28, 2019Journal-ref: Phys. Atom. Nucl. 82, 838, 2019Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [89] arXiv:1908.07799 (replaced) [pdf, ps, other]
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Title: Six-dimensional Myers-Perry rotating black hole cannot be overspunComments: 10 pages, no figures, 1 TableJournal-ref: Phys. Rev. D 101, 044028 (2020)Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
- [90] arXiv:1909.00488 (replaced) [pdf, ps, other]
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Title: Bound Dark Matter (BDM) towards solving the Small Scale Structure ProblemComments: 24 pages, 10 figuesSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [91] arXiv:1909.07706 (replaced) [pdf, other]
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Title: Cosmological Relaxation from Dark Fermion ProductionComments: 40 pages, 9 figures; small modifications in the appendix: comments on the static Universe limit added, brief discussion about the shutdown of the backraction added; version accepted for publication in JHEPSubjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
- [92] arXiv:1909.09609 (replaced) [pdf, other]
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Title: The Impact of Peculiar Velocities on the Estimation of the Hubble Constant from Gravitational Wave Standard SirensComments: 8 pages, 5 figuresSubjects: 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)
- [93] arXiv:1909.10883 (replaced) [pdf, other]
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Title: Constant-roll inflation in scalar-tensor gravityComments: 15 pages, 3 figures; matches published versionJournal-ref: JCAP 11 (2019) 025Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
- [94] arXiv:1909.11672 (replaced) [pdf, other]
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Title: The X-ray and radio activity of typical and luminous Lya emitters from z~2 to z~6: evidence for a diverse, evolving populationAuthors: João Calhau, David Sobral, Sérgio Santos, Jorryt Matthee, Ana Paulino-Afonso, Andra Stroe, Brooke Simmons, Cassandra Barlow-Hall, Benjamin AdamsComments: Accepted for publication in MNRAS. 21 pages, 15 figures, 2 tables + appendices. The full SC4K catalogue of LAEs with X-ray, radio, FIR and Lya measurements is available with the MNRAS refereed version, along with tables presenting the full stacking results in X-rays and radioSubjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
- [95] arXiv:1909.12041 (replaced) [pdf, other]
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Title: Estimation of the physical parameters of a CME at high coronal heights using low frequency radio observationsSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [96] arXiv:1909.12424 (replaced) [pdf, other]
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Title: NGTS-10b: The shortest period hot Jupiter yet discoveredAuthors: James McCormac (1, 2), Edward Gillen (3, 9), James A. G. Jackman (1, 2), David J. A. Brown (1, 2), Daniel Bayliss (1, 2), Peter J. Wheatley (1, 2), Richard G. West (1, 2), David R. Anderson (1, 2), David J. Armstrong (1, 2), Francois Bouchy (4), Joshua T. Briegal (3), Matthew R. Burleigh (5), Juan Cabrera (6), Sarah L. Casewell (5), Alexander Chaushev (5, 1, 2), Bruno Chazelas (4), Paul Chote (1, 2), Benjamin F. Cooke (1, 2), Jean C. Costes (11), Szilard Csizmadia (6), Philipp Eigmuller (6), Anders Erikson (6), Emma Foxell (1, 2), Boris T. Gaensicke (1, 2), Michael R. Goad (5), Maximilian N. Gunther (8, 18), Simon T. Hodgkin (10), Matthew J. Hooton (11), James S. Jenkins (12, 13), Gregory Lambert (3), Monika Lendl (4, 17), Emma Longstaff (5), Tom Louden (1, 2), Maximiliano Moyano (14), Louise D. Nielsen (4), et al. (12 additional authors not shown)Comments: 16 pages, 19 figures and 5 tables. Submitted 27 Sept 2019. Accepted 10 Jan 2020. Published 20 Feb 2020Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
- [97] arXiv:1910.01163 (replaced) [pdf, other]
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Title: Evolution of giant molecular clouds across cosmic timeAuthors: David Guszejnov, Michael Y. Grudić, Stella S. R. Offner, Michael Boylan-Kolchin, Claude-André Faucher-Giguère, Andrew Wetzel, Samantha M. Benincasa, Sarah LoebmanComments: 15 pages, 11 figures accepted by MNRASSubjects: Astrophysics of Galaxies (astro-ph.GA)
- [98] arXiv:1910.02132 (replaced) [pdf, other]
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Title: How to measure CMB spectral distortions with an imaging telescopeComments: 13 pages, 8 figures. Published in Phys. Rev. DJournal-ref: Phys. Rev. D 100, 103508, (2019)Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
- [99] arXiv:1910.02788 (replaced) [pdf, other]
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Title: A deep learning approach to cosmological dark energy modelsComments: 22 pages, 8 figures. Version accepted for publication in JCAPSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Computational Physics (physics.comp-ph)
- [100] arXiv:1910.05463 (replaced) [pdf, other]
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Title: Large Sound Speed in Dense Matter and the Deformability of Neutron StarsComments: 5 pages, 3 figuresSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
- [101] arXiv:1911.04832 (replaced) [pdf, other]
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Title: Thermal and Resonant Emission of Dark Ages Halos in the Rotational Lines of HeH$^{+}$Comments: 13 pages, 9 figures, 9 tables; accepted for publication in Phys.Rev.DSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [102] arXiv:1911.07332 (replaced) [pdf, other]
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Title: Properties of binary components and remnant in GW170817 using equations of state in finite temperature field theory modelsComments: LaTex, 17 pages including 7 Figures; title is slightly modified and article is revisedJournal-ref: Astrophysical Journal 890 (2020) 139Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
- [103] arXiv:1911.09991 (replaced) [pdf, other]
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Title: Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1Comments: Accepted for publication in A&A, 16 pages, 7 figures, 4 tables + 1 AppendixSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [104] arXiv:1912.00378 (replaced) [pdf, ps, other]
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Title: Weakly-coupled stealth solution in scordatura degenerate theoryComments: 16 pages; matches published versionJournal-ref: JCAP 01 (2020) 030Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
- [105] arXiv:1912.00526 (replaced) [pdf, ps, other]
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Title: Are Fast Radio Bursts Made By Neutron Stars?Authors: J. I. KatzComments: 5 pp Revised with further expanded discussion of absence of Galactic micro-FRB and periodicity of FRB 180916.J0158+65Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [106] arXiv:1912.02264 (replaced) [pdf, other]
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Title: A New Likely Redback Millisecond Pulsar Binary with a Massive Neutron Star: 4FGL J2333.1--5527Authors: Samuel J. Swihart, Jay Strader, Ryan Urquhart, Jerome A. Orosz, Laura Shishkovsky, Laura Chomiuk, Ricardo Salinas, Elias Aydi, Kristen C. Dage, Adam M. KawashComments: Accepted to ApJ; 9 pages, 6 figures, 1 tableSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [107] arXiv:1912.04509 (replaced) [pdf, ps, other]
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Title: Formation rate of LB-1-like systems through dynamical interactionsComments: 10 pages, 1 figureSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [108] arXiv:1912.07657 (replaced) [pdf, other]
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Title: Time-dependence of the astrophysical stochastic gravitational wave backgroundComments: 10 pages, 5 figures. Accepted for publication in MNRAS. References addedJournal-ref: MNRAS, Volume 491, Issue 4, February 2020, Pages 4690Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
- [109] arXiv:1912.09192 (replaced) [pdf, other]
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Title: Photometric analyses of Saturn's small moons: Aegaeon, Methone and Pallene are dark; Helene and Calypso are brightAuthors: M.M. Hedman, P. Helfenstein, R.O. Chancia, P. Thomas, E. Roussos, C. Paranicas, A.J. VerbiscerComments: 93 pages, 23 figures, 28 tables. Accepted for publication in AJ. Updated to fix some typographical errors identified in the proof stageSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
- [110] arXiv:1912.11453 (replaced) [pdf, other]
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Title: Dark matter with excitable levelsAuthors: Andrew J. WrenComments: 25 pages, 11 figures, 2 tables. V3 has minor improvements to the Introduction and Discussion. Mathematica and Python code available at this https URLSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
- [111] arXiv:2001.00587 (replaced) [pdf, other]
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Title: ZTF Early Observations of Type Ia Supernovae III: Early-Time Colors as a Test for Explosion Models and Multiple PopulationsAuthors: Mattia Bulla, Adam A. Miller, Yuhan Yao, Luc Dessart, Suhail Dhawan, Semeli Papadogiannakis, Rahul Biswas, Ariel Goobar, S. R. Kulkarni, Jakob Nordin, Peter Nugent, Abigail Polin, Jesper Sollerman, Eric C. Bellm, Michael W. Coughlin, Richard Dekany, V. Zach Golkhou, Matthew J. Graham, Mansi M. Kasliwal, Thomas Kupfer, Russ R. Laher, Frank J. Masci, Michael Porter, Ben Rusholme, David L. ShupeComments: 16 pages, 9 figures, 1 table; accepted for publication in ApJ after minor revisionsSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [112] arXiv:2001.02986 (replaced) [pdf, other]
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Title: Concerns regarding the use of black hole shadows as standard rulersComments: 12 pages, 1 figure. Added references and improved discussion on weak lensing. Version accepted for publication in Class. Quant. GravSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
- [113] arXiv:2001.08036 (replaced) [pdf, other]
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Title: Relativistic hypernuclear compact stars with calibrated equations of stateComments: Open access. Supplemental Material available at this https URLJournal-ref: Phys. Rev. D 101, 034017 (2020)Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
- [114] arXiv:2002.00144 (replaced) [pdf]
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Title: Full-field modeling of heat transfer in asteroid regolith: Radiative thermal conductivity of polydisperse particulatesComments: Accepted by Journal of Geophysical Research: PlanetsSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
- [115] arXiv:2002.00335 (replaced) [pdf, ps, other]
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Title: Fast Radio Bursts from Interacting Binary Neutron Star SystemsAuthors: Bing ZhangComments: matching the version published in ApJLJournal-ref: 2020, ApJL, 890, L24Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [116] arXiv:2002.00572 (replaced) [pdf, other]
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Title: Upcoming new era of 21 cm cosmology based on SKAComments: 6 pages, 3 figures; to be published, as a paper of News & Views, in SCIENCE CHINA Physics, Mechanics & AstronomySubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
- [117] arXiv:2002.01796 (replaced) [pdf, other]
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Title: Axion and dark photon limits from Crab Nebula high energy gamma-raysComments: 7 pages, 6 figures, 1 tableSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
- [118] arXiv:2002.05178 (replaced) [pdf, other]
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Title: The first blazar observed at z>6Authors: S. Belladitta, A. Moretti, A. Caccianiga, C. Spingola, P. Severgnini, R. Della Ceca, G. Ghisellini, D. Dallacasa, T. Sbarrato, C. Cicone, L. P. Cassarà, M. PedaniComments: 7 pages, 8 figures, 3 tables, Accepted to publication in A&A Letters. Typo correctionsSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
- [119] arXiv:2002.08028 (replaced) [pdf, other]
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Title: Variability and the size-luminosity relation of the intermediate mass AGN in NGC 4395Authors: Hojin Cho, Jong-Hak Woo, Edmund Hodges-Kluck, Donghoon Son, Jaejin Shin, Elena Gallo, Hyun-Jin Bae, Thomas G. Brink, Wanjin Cho, Alexei V. Filippenko, John C. Horst, Dragana Ilić, Michael. D. Joner, Daeun Kang, Wonseok Kang, Shai Kaspi, Taewoo Kim, Andjelka B. Kovačević, Sahana Kumar, Huynh Anh N. Le, A. E. Nadzhip, Francisco Pozo Nuñez, V.G. Metlov, V. L. Oknyansky, Songyoun Park, Luka Č. Popović, Suvendu Rakshit, Malte Schramm, N. I. Shatsky, Michelle Spencer, Eon-Chang Sung, Hyun-il Sung, A. M. Tatarnikov, Oliver VinceComments: Accepted for publication in ApJ (Feb. 23rd, 2020). 18 pages, 10 figuresSubjects: Astrophysics of Galaxies (astro-ph.GA)
- [120] arXiv:2002.08319 (replaced) [pdf, other]
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Title: Spectral and atmospheric characterisation of a new benchmark brown dwarf HD13724BAuthors: E. L. Rickman, D. Ségransan, J. Hagelberg, J.-L. Beuzit, A. Cheetham, J.-B. Delisle, T. Forveille, S. UdryComments: 11 pages, Accepted to A&A, updated with language editsSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
- [121] arXiv:2002.08381 (replaced) [pdf, ps, other]
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Title: The Dark Planets of the WASP-47 Planetary SystemComments: 13 pages, 6 figures, 2 tables, accepted for publication in the Astronomical JournalSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
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