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New submissions for Wed, 15 Jan 20

[1]  arXiv:2001.04467 [pdf, other]

Title: Mass ejection from disks surrounding a low-mass black hole: Viscous neutrino-radiation hydrodynamics simulation in full general relativity

Authors: Sho Fujibayashi, Masaru Shibata, Shinya Wanajo, Kenta Kiuchi, Koutarou Kyutoku, Yuichiro Sekiguchi

Comments: 26 pages, 15 figures, to be submitted to PRD

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

New viscous neutrino-radiation hydrodynamics simulations are performed for accretion disks surrounding a spinning black hole with low mass $3M_\odot$ and dimensionless spin 0.8 or 0.6 in full general relativity, aiming at modeling the evolution of a merger remnant of massive binary neutron stars or low-mass black hole-neutron star binaries. We reconfirm the following results found by previous studies of other groups: 15-30% of the disk mass is ejected from the system with the average velocity of $\sim $5-10% of the speed of light for the plausible profile of the disk as merger remnants. In addition, we find that for the not extremely high viscous coefficient case, the neutron richness of the ejecta does not become very high, because weak interaction processes enhance the electron fraction during the viscous expansion of the disk before the onset of the mass ejection, resulting in the suppression of the lanthanide synthesis. For high-mass disks, the viscous expansion timescale is increased by a longer-term neutrino emission, and hence, the electron fraction of the ejecta becomes even higher. We also confirm that the mass distribution of the electron fraction depends strongly on the magnitude of the given viscous coefficient. This demonstrates that a first-principle magnetohydrodynamics simulation is necessary for black hole-disk systems with sufficient grid resolution and with sufficiently long timescale (longer than seconds) to clarify the nucleosynthesis and electromagnetic signals from them.

[2]  arXiv:2001.04468 [pdf, other]

Title: The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. A Statistical Characterization of Class 0 and I Protostellar Disks

Authors: John J. Tobin (NRAO), Patrick Sheehan (NRAO/Northwestern), S. Thomas Megeath (U. Toledo), Ana Karla Diaz-Rodriguez (IAA), Stella S. R. Offner (Texas), Nadia M. Murillo (Leiden), Merel van 't Hoff (Leiden), Ewine F. van Dishoeck (Leiden), Mayra Osorio (IAA), Guillem Anglada (IAA), Elise Furlan (IPAC), Amelia M. Stutz (U. Concepcion), Nickalas Reynolds (Oklahoma), Nicole Karnath (U. Toledo), William J. Fischer (STSci), Magnus Persson (Chalmers), Leslie W. Looney (Illinois), Zhi-Yun Li (Virginia), Ian Stephens (CfA), Claire J. Chandler (NRAO), Erin Cox (Northwestern), Michael M. Dunham (SUNY-Fredonia), Lukasz Tychoniec (Leiden), Mihkel Kama (Cambridge), Kaitlin Kratter (Arizona), Marina Kounkel (U. Western Washington), Brian Mazur (U. Toledo), Luke Maud (ESO), Lisa Patel (Oklahoma), Laura Perez (U. Chile), et al. (6 additional authors not shown)

Comments: 107 pages, 21 Figures, 11 Tables, accepted to ApJ. Version with all source figures: this https URL Reduced data available from this https URL

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We have conducted a survey of 328 protostars in the Orion molecular clouds with ALMA at 0.87 mm at a resolution of $\sim$0.1" (40 au), including observations with the VLA at 9 mm toward 148 protostars at a resolution of $\sim$0.08" (32 au). This is the largest multi-wavelength survey of protostars at this resolution by an order of magnitude. We use the dust continuum emission at 0.87 mm and 9 mm to measure the dust disk radii and masses toward the Class 0, Class I, and Flat Spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The mean dust disk radii for the Class 0, Class I, and Flat Spectrum protostars are 44.9$^{+5.8}_{-3.4}$, 37.0$^{+4.9}_{-3.0}$, and 28.5$^{+3.7}_{-2.3}$ au, respectively, and the mean protostellar dust disk masses are 25.9$^{+7.7}_{-4.0}$, 14.9$^{+3.8}_{-2.2}$, 11.6$^{+3.5}_{-1.9}$ Earth masses, respectively. The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. At least 146 protostellar disks (35% out of 379 detected 0.87 mm continuum sources plus 42 non-detections) have disk radii greater than 50 au in our sample. These properties are not found to vary significantly between different regions within Orion. The protostellar dust disk mass distributions are systematically larger than that of Class II disks by a factor of $>$4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase.

[3]  arXiv:2001.04469 [pdf, other]

Title: The Surprisingly Small Impact of Magnetic Fields On The Inner Accretion Flow of Sagittarius A* Fueled By Stellar Winds

Authors: Sean M. Ressler, Eliot Quataert, James M. Stone

Comments: Accepted by MNRAS; 22 pages; 24 figures, comments welcome

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study the flow structure in 3D magnetohydrodynamic (MHD) simulations of accretion onto Sagittarius A* via the magnetized winds of the orbiting Wolf-Rayet stars. These simulations cover over 3 orders of magnitude in radius to reach $\approx$ 300 gravitational radii, with only one poorly constrained parameter (the magnetic field in the stellar winds). Even for winds with relatively weak magnetic fields (e.g., plasma $\beta$ $\sim$ $10^6$), flux freezing/compression in the inflowing gas amplifies the field to $\beta$ $\sim$ few well before it reaches the event horizon. Overall, the dynamics, accretion rate, and spherically averaged flow profiles (e.g., density, velocity) in our MHD simulations are remarkably similar to analogous hydrodynamic simulations. We attribute this to the broad distribution of angular momentum provided by the stellar winds, which sources accretion even absent much angular momentum transport. We find that the magneto-rotational instability is not important because of i) strong magnetic fields that are amplified by flux freezing/compression, and ii) the rapid inflow/outflow times of the gas and inefficient radiative cooling preclude circularization. The primary effect of magnetic fields is that they drive a polar outflow that is absent in hydrodynamics. The dynamical state of the accretion flow found in our simulations is unlike the rotationally supported tori used as initial conditions in horizon scale simulations, which could have implications for models being used to interpret Event Horizon Telescope and GRAVITY observations of Sgr A*.

[4]  arXiv:2001.04471 [pdf, other]

Title: Nonstationarity of AGN variability: The only way to go is down!

Authors: Neven Caplar, Theodore Pena, Sean D. Johnson, Jenny E. Greene

Comments: 8 pages, 5 figures, accepted to ApJL; The associated data and code are available at this https URL

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

To gain insights into long-term Active Galactic Nuclei (AGN) variability, we analyze an AGN sample from the Sloan Digital Sky Survey (SDSS) and compare their photometry with observations from the Hyper Suprime-Cam survey (HSC) observed $\langle 14.85 \rangle$ years after SDSS. On average, the AGN are fainter in HSC than SDSS. We demonstrate that the difference is not due to subtle differences in the SDSS versus HSC filters or photometry. The decrease in mean brightness is redshift dependent, consistent with expectations for a change that is a function of the rest-frame time separation between observations. At a given redshift, the mean decrease in brightness is stronger for more luminous AGN and for objects with longer time separation between measurements. The mean decrease in brightness with time violates the stationarity assumption often invoked in AGN variability studies. We demonstrate that the dependence on redshift and luminosity of measured mean brightness decrease is consistent with simple models of Eddington ratio variability in AGN on long (Myr, Gyr) timescales. We show how our results can be used to constrain the variability and demographic properties of AGN populations.

[5]  arXiv:2001.04472 [pdf, other]

Title: Interacting galaxies in the IllustrisTNG simulations -- II: Star formation in the post-merger stage

Authors: Maan H. Hani, Hayman Gosain, Sara L. Ellison, David R. Patton, Paul Torrey

Comments: submitted to MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Galaxy mergers are a major evolutionary transformation whose effects are borne out by a plethora of observations and numerical simulations. However, most previous simulations have used idealised, isolated, binary mergers and there has not been significant progress on studying statistical samples of galaxy mergers in large cosmological simulations. We present a sample of 27,691 post-merger (PM) galaxies ($0\le z \le 1$) identified from IllustrisTNG: a cosmological, large box, magneto-hydrodynamical simulation suite. The PM sample spans a wide range of merger and galaxy properties ($M_\star$, $\mu$, $f_\mathrm{gas}$). We demonstrate that star forming (SF) PMs exhibit enhanced star formation rates (SFRs) on average by a factor of $\sim 2$, while the passive PMs show no statistical enhancement. We find that the SFR enhancements: (1) show no dependence on redshift, (2) anti-correlate with the PM's stellar mass, and (3) correlate with the gas fraction of the PM's progenitors. However, SF PMs show stronger enhancements which may indicate other processes being at play (e.g., gas phase, feedback efficiency). Although the SFR enhancement correlates mildly with the merger mass ratio, the more abundant minor mergers ($0.1 \le \mu < 0.3 $) still contribute $\sim 50\%$ of the total SFR enhancement. By tracing the PM sample forward in time, we find that galaxy mergers can drive significant SFR enhancements which decay over $\sim 0.5$ Gyr independent of the merger mass ratio, although the decay timescale is dependent on the simulation resolution. The strongest merger-driven starburst galaxies evolve to be passive/quenched on faster timescales than their controls.

[6]  arXiv:2001.04473 [pdf, other]

Title: High-redshift cosmology with oxygen lines from H$α$ surveys

Authors: José Fonseca, Stefano Camera

Comments: 9 pages, 6 figures, 2 tables; comments welcome

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

A new generation of cosmological experiments will spectroscopically detect the H$\alpha$ line from emission-line galaxies (ELGs) at optical/near-infrared frequencies. Other emission lines will also be present, which may come from the same H$\alpha$ sample or constitute a new galaxy sample altogether. Our goal is to assess the value, for cosmological investigation, of galaxies at $z\gtrsim2$ present in H$\alpha$ galaxy surveys and identifiable by the highly redshifted ultra-violet and optical lines - namely the OII line and the OIII doublet in combination with the H$\beta$ line. We use state-of-the-art models of luminosity functions of astrophysical spectral lines to estimate the volumetric number density of OIII+H$\beta$ and OII ELGs. We focus on a wavelength range which will be covered by planned cosmological surveys. We study the constraining power of these high-redshift galaxy samples on cosmological parameters such as the amplitude of baryon acoustic oscillations, $H(z)$, $D_A(z)$, $f\sigma_8(z)$, and $b\sigma_8(z)$ for different survey designs. We present a strong science case for extracting the OIII+H$\beta$ sample, which we consider as an independent probe of the Universe in the redshift range 2 to 3. Moreover, we show that the OII sample can be used to measure the baryon acoustic oscillations and the growth of structures above $z=3$; albeit it may be shot-noise dominated, it will nonetheless provide valuable tomographic information. Summarising, we discuss the scientific potential of a sample of galaxies which, so far, has been mainly considered as a contaminant in H$\alpha$ galaxy surveys. Our findings indicate that planed H$\alpha$ surveys should include the extraction of these oxygen-line samples in their pipeline, to enhance their scientific impact on cosmology.

[7]  arXiv:2001.04474 [pdf, other]

Title: On the possibility of GW190425 being a black hole--neutron star binary merger

Authors: Koutarou Kyutoku, Sho Fujibayashi, Kota Hayashi, Kyohei Kawaguchi, Kenta Kiuchi, Masaru Shibata, Masaomi Tanaka

Comments: 8 pages, 1 figure

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

We argue that the kilonova/macronova associated with a gravitational-wave event GW190425 could have been bright enough to be detected if it was caused by the merger of a low-mass black hole and a neutron star. Although tidal disruption occurs for such a low-mass black hole as is generally expected, the masses of the dynamical ejecta are limited to <~10^{-3}M_sun, consistently with previous work in the literature. The remnant disk could be as massive as 0.05--0.1M_sun, and the disk outflow of ~0.01--0.03M_sun is likely to be driven by the viscous or magnetohydrodynamic effects. The disk outflow may not be neutron rich enough to synthesize abundance of lanthanide elements even in the absence of strong neutrino emitter if the ejection is driven on the viscous time scale of >~0.3s. If this is the case, the opacity of the disk outflow is kept moderate and the kilonova/macronova at the distance of GW190425 reaches detectable 20--21mag at 1day after merger for most viewing angles. If some disk activity ejects the mass within ~0.1s, instead, lanthanide-rich outflows would be launched and the detection of emission becomes challenging. Future possible detections of kilonovae/macronovae from GW190425-like systems will disfavor prompt collapse of binary neutron stars and a non-disruptive low-mass black hole--neutron star binary associated with a neutron-star small radius, whose mass ejection is negligible. The host-galaxy distance will constrain the viewing angle and deliver further information about the mass ejection.

[8]  arXiv:2001.04475 [pdf, ps, other]

Title: Black widow evolution: magnetic braking by an ablated wind

Authors: Sivan Ginzburg, Eliot Quataert

Comments: Submitted to MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Black widows are close binary systems in which a millisecond pulsar is orbited by a companion a few per cent the mass of the sun. It has been suggested that the pulsar's rotationally powered $\gamma$-ray luminosity gradually evaporates the companion, eventually leaving behind an isolated millisecond pulsar. The evaporation efficiency is determined by the temperature $T_{\rm ch}\propto F^{2/3}$ to which the outflow is heated by the flux $F$ on a dynamical time-scale. Evaporation is most efficient for companions that fill their Roche lobes. In this case, the outflow is dominated by a cap around the L1 point with an angle $\theta_g\sim (T_{\rm ch}/T_g)^{1/2}$, and the evaporation time is $t_{\rm evap}=0.46(T_{\rm ch}/T_g)^{-2}\textrm{ Gyr}$, where $T_g>T_{\rm ch}$ is the companion's virial temperature. We apply our model to the observed black widow population, which has increased substantially over the last decade, considering each system's orbital period, companion mass, and pulsar spin-down power. While the original (Fruchter et al. 1988) black widow evaporates its companion on a few Gyr time-scale, direct evaporation on its own is too weak to explain the overall population. We propose instead that the evaporative wind couples to the companion's magnetic field, removes angular momentum from the binary, and maintains stable Roche-lobe overflow. While a stronger wind carries more mass, it also reduces the Alfv\'en radius, making this indirect magnetic braking mechanism less dependent on the flux $t_{\rm mag}\propto t_{\rm evap}^{1/3}$. This reduces the scatter in evolution times of observed systems, thus better explaining the combined black widow and isolated millisecond pulsar populations.

[9]  arXiv:2001.04476 [pdf, other]

Title: Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

Authors: T. Shenar, A. Gilkis, J. S. Vink, H. Sana, A. A. C. Sander

Comments: 10 pages, 5 figures, accepted to A&A on the 12.01.2020. Comments welcome!

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Classical Wolf-Rayet (WR) stars are massive, hydrogen depleted, post main-sequence stars that exhibit emission-line dominated spectra. For a given metallicity Z, stars exceeding a certain initial mass M_single(Z) can reach the WR phase through intrinsic mass-loss (single-star channel). Stars of lower masses can reach the WR phase via binary mass transfer (binary channel). It is commonly assumed that the binary channel dominates the formation of WR stars in environments with low Z such as the SMC and LMC. However, their reported WR binary fractions of 30-40% are comparable to that of the Galaxy. Here, we explain this apparent contradiction by considering the minimum initial mass M_spec(Z) needed for the stripped product to appear as a WR star. We calibrate M_spec(Z) using the lowest-luminosity WR stars in the Clouds and the Galaxy. A range of M_single(Z) values are explored using various evolution codes. We estimate the additional contribution of the binary channel by considering the interval [M_spec(Z), M_single(Z)], which characterises the initial-mass range in which binaries can form additional WR stars.
Results: The WR-phenomenon ceases below luminosities of logL = 4.9, 5.25, and 5.6 [Lsun] in the Galaxy, LMC, and SMC, which translates to He-star masses of 7.5, 11, 17 Msun and initial masses of M_spec = 18, 23, 37 Msun. Stripped stars with lower initial masses in the respective galaxies would tend to not appear as WR stars. M_single lies in the range 20-30, 30-60, and > 40 Msun for the Galaxy, LMC, and SMC. We find that that the additional contribution of the binary channel is a non-trivial function of Z that cannot be conclusively claimed to be monotonically increasing with decreasing Z. Hence, one should not a-priori expect that binary interactions become increasingly important in forming WR stars at low Z, or that the WR binary fraction grows with decreasing Z.

[10]  arXiv:2001.04478 [pdf, other]

Title: LoCuSS: exploring the connection between local environment, star formation and dust mass in Abell 1758

Authors: Matteo Bianconi, Graham P. Smith, Chris P. Haines, Sean L. McGee, Alexis Finoguenov, Eiichi Egami

Comments: 16 pages, 11 figures. Accepted for publication in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We explore the connection between dust and star formation, in the context of environmental effects on galaxy evolution. In particular, we exploit the susceptibility of dust to external processes to assess the influence of dense environment on star-forming galaxies. We have selected cluster Abell 1758 from the Local Cluster Substructure Survey (LoCuSS). Its complex dynamical state is an ideal test-bench to track dust removal and destruction in galaxies due to merger and accretion shocks. We present a systematic panchromatic study (from 0.15 $\rm \mu$m with GALEX to 500 $\rm \mu$m with Herschel) of spectroscopically confirmed star-forming cluster galaxies at intermediate redshift. We observe that the main subclusters (A1758N and A1758S) belong to two separate large-scale structures, with no overlapping galaxy members. Star-forming cluster members are distributed preferentially outside cluster central regions, and are not grouped in substructures. Rather, these galaxies are being funneled towards the main subclusters along separate accretion filaments. Additionally, we present the first study of dust-to-stellar (DTS) mass ratio used as indicator for local environmental influence on galaxy evolution. Star-forming cluster members show lower mean values (32% at 2.4$\rm \sigma$) of DTS mass ratio and lower levels of infrared emission from birth clouds with respect to coeval star-forming field galaxies. This picture is consistent with the majority of star-forming cluster members infalling in isolation. Upon accretion, star-formation is observed to decrease and warm dust is destroyed due to heating from the intracluster medium radiation, ram-pressure stripping and merger shocks.

[11]  arXiv:2001.04479 [pdf, other]

Title: A panchromatic spatially-resolved analysis of nearby galaxies: sub-kpc scale Main Sequence in grand-design spirals

Authors: A. Enia, G. Rodighiero, L. Morselli, V. Casasola, S. Bianchi, L. Rodriguez-Munoz, C. Mancini, A. Renzini, P. Popesso, P. Cassata, M. Negrello, A. Franceschini

Comments: 21 pages, 15 figures. Submitted to MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We analyse the spatially resolved relation between stellar mass (M$_{\star}$) and star formation rate (SFR) in disk galaxies (i.e. the Main Sequence, MS). The studied sample includes eight nearby face-on grand-design spirals, e.g. the descendant of high-redshift, rotationally-supported star-forming galaxies. We exploit photometric information over 23 bands, from the UV to the far-IR, from the publicly available DustPedia database to build spatially resolved maps of stellar mass and star formation rates on sub-galactic scales of 0.5-1.5 kpc, by performing a spectral energy distribution fitting procedure that accounts for both the observed and the obscured star formation processes, over a wide range of internal galaxy environments (bulges, spiral arms, outskirts). With more than 30 thousands physical cells, we have derived a conservative definition of the local spatially resolved MS per unit area for disks, $\log(\Sigma_{SFR})$=0.82log$(\Sigma_{*})$-8.69. This is consistent with the bulk of recent results based on optical IFU, using the H$\alpha$ line emission as a SFR tracer. Our work extends the analysis at lower sensitivities in both M$_{\star}$ and SFR surface densities, up to a factor $\sim$ 10. The self consistency of the MS relation over different spatial scales, from sub-galactic to galactic, as well as with a rescaled correlation obtained for high redshift galaxies, clearly proves its universality.

[12]  arXiv:2001.04480 [pdf, other]

Title: Cradles of the first stars: self-shielding, halo masses, and multiplicity

Authors: Danielle Skinner, John H. Wise

Comments: Accepted in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

The formation of Population III (Pop III) stars is a critical step in the evolution of the early universe. To understand how these stars affected their metal-enriched descendants, the details of how, why and where Pop III formation takes place needs to be determined. One of the processes that is assumed to greatly affect the formation of Pop III stars is the presence of a Lyman-Werner (LW) radiation background, that destroys H$_2$, a necessary coolant in the creation of Pop III stars. Self-shielding can alleviate the effect the LW background has on the H$_2$ within haloes. In this work, we perform a cosmological simulation to study the birthplaces of Pop III stars, using the adaptive mesh refinement code Enzo. We investigate the distribution of host halo masses and its relationship to the LW background intensity. Compared to previous work, haloes form Pop III stars at much lower masses, up to a factor of a few, due to the inclusion of H$_2$ self-shielding. We see no relationship between the LW intensity and host halo mass. Most haloes form multiple Pop III stars, with a median number of four, up to a maximum of 16, at the instance of Pop III formation. Our results suggest that Pop III star formation may be less affected by LW radiation feedback than previously thought and that Pop III multiple systems are common.

[13]  arXiv:2001.04482 [pdf, other]

Title: Wind morphology around cool evolved stars in binaries: the case of slowly accelerating oxygen-rich outflows

Authors: I. El Mellah, J. Bolte, L. Decin, W. Homan, R. Keppens

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The late stellar evolutionary phases of low and intermediate-mass stars are strongly constrained by their mass-loss rates. The wind surrounding cool evolved stars frequently shows non-spherical features, thought to be due to an unseen companion orbiting the donor star. We study the morphology of the circumbinary envelope, in particular around oxygen-rich asymptotic giant branch (AGB) stars. We run a grid of 70 3D hydrodynamics simulations of a progressively accelerating wind propagating in the Roche potential formed by a mass-loosing evolved star in orbit with a main sequence companion. We resolve the flow structure both in the immediate vicinity of the secondary, where bow shocks, outflows and wind-captured disks form, and up to 40 orbital separations, where spiral arms, arcs and equatorial density enhancements develop. When the companion is deeply engulfed in the wind, the lower terminal wind speeds and more progressive wind acceleration around oxygen-rich AGB stars make them more prone than carbon-rich AGB stars to display more disturbed outflows, a disk-like structure around the companion and a wind concentrated in the orbital plane. In these configurations, a large fraction of the wind is captured by the companion which leads to a significant shrinking of the orbit over the mass-loss timescale, if the donor star is at least a few times more massive than its companion. Provided the companion has a mass of at least a tenth of the mass of the donor star, it can compress the wind in the orbital plane up to large distances. Our grid of models covers a wide scope of configurations function of the dust chemical content, the terminal wind speed relative to the orbital speed, the extension of the dust condensation region around the cool evolved star and the mass ratio. It provides a frame of reference to interpret high-resolution maps of the outflows surrounding cool evolved stars.

[14]  arXiv:2001.04483 [pdf, other]

Title: Two delays in white dwarf evolution revealed by Gaia

Authors: Sihao Cheng

Comments: 4 pages, 2 figures; contributed to the Proceedings of IAU Symposium No. 357, "White Dwarfs as Probes of Fundamental Physics and Tracers of Planetary, Stellar, and Galactic Evolution," held in Hilo, Hawaii, 21-25 October 2019

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

By comparing two age indicators of high-mass white dwarfs derived from Gaia data, two discoveries have been made recently: one is the existence of a cooling anomaly that produces the Q branch structure on the Hertzsprung--Russell diagram, the other is the existence of double-white-dwarf merger products. The former poses a challenge for white dwarf cooling models, and the latter has implications on binary evolution and type-Ia supernovae.

[15]  arXiv:2001.04493 [pdf, ps, other]

Title: Broadband variability and correlation study of 3C 279 during flare of 2017-2018

Authors: Raj Prince

Comments: 13 pages, 10 figures, Accepted in ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

A multiwavelength temporal and spectral analysis of flares of 3C 279 during November 2017--July 2018 are presented in this work. Three bright gamma-ray flares were observed simultaneously in X-ray and Optical/UV along with a prolonged quiescent state. A "harder-when-brighter" trend is observed in both gamma-rays and X-rays during the flaring period. The gamma-ray light curve for all the flares are binned in one-day time bins and a day scale variability is observed. Variability time constrains the size and location of the emission region to 2.1$\times$10$^{16}$ cm and 4.4$\times$10$^{17}$ cm, respectively. The fractional variability reveals that the source is more than 100\% variable in gamma-rays and it decreases towards the lower energy. A cross-correlation study of the emission from different wavebands is done using the \textit{DCF} method, which shows a strong correlation between them without any time lags. The zero time lag between different wavebands suggest their co-spatial origin. This is the first time 3C 279 has shown a strong correlation between gamma-rays and X-rays emission with zero time lag. A single zone emission model was adopted to model the multiwavelength SEDs by using the publicly available code GAMERA. The study reveals that a higher jet power in electrons is required to explain the gamma-ray flux during the flaring state, as much as, ten times of that required for the quiescent state. However, more jet power in magnetic field has been observed during the quiescent state compared to the flaring state.

[16]  arXiv:2001.04497 [pdf, ps, other]

Title: Pulsation among TESS A and B stars reveals unexpected results

Authors: Luis A Balona, Dogus Ozuyar

Comments: 9 pages, 7 figures, 3 tables

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Classification of over 50000 TESS stars in sectors 1-18 has resulted in the detection of 766 pulsating main sequence B stars as well as over 5000 $\delta$ Scuti, 2300 $\gamma$ Doradus and 114 roAp candidates. It is found that a distinct group of $\beta$ Cephei stars, defined as B stars with frequencies greater than 2.5 d$^{-1}$ and predicted by models, does not exist. Instead, high frequencies are to be found over the whole B-star range, eventually merging with $\delta$ Scuti stars. The cool B stars pulsating in high frequencies are the Maia variables. It is shown that Maia variables are not rapidly-rotating $\beta$ Cephei or SPB stars. In the region where $\beta$ Cephei variables are found, the proportion of pulsating stars is larger and amplitudes are higher and a considerable fraction pulsate in a single mode and low rotation rate. There is no distinct SPB instability region. Stars pulsating sole in low frequencies are found among all B stars. At most, only one-third of B stars appear to pulsate. These results, as well as the fact that a large fraction of A and B stars show rotational modulation, indicate a need for a revision of current ideas regarding stars with radiative envelopes.

[17]  arXiv:2001.04499 [pdf, ps, other]

Title: Are exoplanetesimals differentiated?

Authors: Amy Bonsor, Philip J. Carter, Mark Hollands, Boris T. Gaensicke, Zoe Leinhardt, John H. D. Harrison

Comments: 18 pages, MNRAS, accepted

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Metals observed in the atmospheres of white dwarfs suggest that many have recently accreted planetary bodies. In some cases, the compositions observed suggest the accretion of material dominantly from the core (or the mantle) of a differentiated planetary body. Collisions between differentiated exoplanetesimals produce such fragments. In this work, we take advantage of the large numbers of white dwarfs where at least one siderophile (core-loving) and one lithophile (rock-loving) species have been detected to assess how commonly exoplanetesimals differentiate. We utilise N-body simulations that track the fate of core and mantle material during the collisional evolution of planetary systems to show that most remnants of differentiated planetesimals retain core fractions similar to their parents, whilst some are extremely core-rich or mantle-rich. Comparison with the white dwarf data for calcium and iron indicates that the data are consistent with a model in which $66^{+4}_{-6}\%$ have accreted the remnants of differentiated planetesimals, whilst $31^{+5}_{-5}\%$ have Ca/Fe abundances altered by the effects of heating (although the former can be as high as $100\%$, if heating is ignored). These conclusions assume pollution by a single body and that collisional evolution retains similar features across diverse planetary systems. These results imply that both collisions and differentiation are key processes in exoplanetary systems. We highlight the need for a larger sample of polluted white dwarfs with precisely determined metal abundances to better understand the process of differentiation in exoplanetary systems.

[18]  arXiv:2001.04502 [pdf, other]

Title: GW190425 is inconsistent with being a binary neutron star born from a fast merging channel

Authors: Mohammadtaher Safarzadeh, Enrico Ramirez-Ruiz, Edo Berger

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

The LIGO/Virgo Scientific Collaboration (LSC) recently announced the detection of a compact object binary merger, GW190425, with a total mass of $3.4^{+0.3}_{-0.1}$ M$_{\odot}$, and individual component masses in range of about 1.1 to 2.5 $M_{\odot}$. If the constituent compact objects are neutron stars, then the total mass is five standard deviations higher than the mean of $2.66\pm 0.12$ M$_{\odot}$ for Galactic binary neutron stars. The non-detection of such massive BNS systems in the Galaxy indicates a potential bias against their detection, which can arise if such massive BNS systems are born with short orbital periods and hence inspiral times of $\sim 10$ Myr. However, we show that the reported merger rate, $\mathcal{R}_{\rm GW190425}=460^{+1050}_{-390}$ yr$^{-1}$ Gpc$^{-3}$, requires extremely high formation efficiency for such systems of $\lambda_{\rm f,BNS}= 2\times10^{-4}-5\times10^{-3}$ M$_{\odot}^{-1}$, orders of magnitude larger than the formation efficiency of fast merging BNS systems from population synthesis models, $\lambda_{\rm f,BNS}\approx (2-5)\times10^{-6} M_{\odot}^{-1}$. Moreover, the comparable merger rates inferred from GW190425 and GW170817 is problematic for two reasons: (i) more massive systems are expected to have a lower formation rate, and (ii) fast merging channels should constitute $\lesssim 10\%$ of the total BNS systems if case BB unstable mass transfer is permitted to take place as a formation pathway. We argue that to account for the high merger rate of GW190425 as a BNS system requires: (i) a change in our understanding NS formation in supernova explosions, or (ii): that more massive NSs need to be preferentially born with weaker magnetic fields so that they would be undetectable in the radio surveys. Whether such an explanation is plausible would require detailed modeling of BNS population with careful treatment of their magnetic fields evolution.

[19]  arXiv:2001.04503 [pdf, other]

Title: Detection of VHE gamma-ray transients with monitoring facilities

Authors: G. La Mura, G. Chiaro, R. Conceiçao, A. De Angelis, M. Pimenta, B. Tomé

Comments: 10 pages, 7 figures. Submitted to MNRAS

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

The study of the sky in Very High Energy gamma rays (VHE, E > 100 GeV) has led to the identification of a wealth of processes that are responsible for the acceleration of particles at the highest observed energies within the Milky Way and beyond. Observations with VHE facilities, like the Cherenkov Telescope Array (CTA), will be fundamental to investigate the characteristics of these processes. Still, the transient and unpredictable nature of the most powerful sources requires that effective monitoring strategies should be adopted to track them. With this study, we focus on the type of VHE transients that can be effectively detected with monitoring facilities. Using the data collected by Fermi-LAT during its observing campaign, we investigate the frequency, luminosity and timescales of different VHE transients, focusing on blazar flares and Gamma-Ray Bursts. We compare their properties with the performance of existing and future instruments. We show that pursuing an enhanced spectral coverage in the sub-TeV range with a large field-of-view instrument, operating in the Southern hemisphere, will effectively contribute to the investigation of different types of transients, both by providing prompt alerts to activate follow-up observations of the most energetic events, as well as by collecting critical information on their temporal and spectral evolution.

[20]  arXiv:2001.04506 [pdf, other]

Title: Application of Convolutional Neural Networks to Identify Stellar Feedback Bubbles in CO Emission

Authors: Duo Xu, Stella S. R. Offner, Robert Gutermuth, Colin Van Oort

Comments: ApJ Accepted

Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We adopt the deep learning method CASI (Convolutional Approach to Shell Identification) and extend it to 3D (CASI-3D) to identify signatures of stellar feedback in molecular line spectra, such as 13CO. We adopt magneto-hydrodynamics simulations that study the impact of stellar winds in a turbulent molecular cloud as an input to generate synthetic observations. We apply the 3D radiation transfer code radmc-3d to model 13CO (J=1-0) line emission from the simulated clouds. We train two CASI-3d models: ME1 predicts only the position of feedback, while MF predicts the fraction of the mass coming from feedback in each voxel. We adopt 75% of the synthetic observations as the training set and assess the accuracy of the two models with the remaining data. We demonstrate that model ME1 identifies bubbles in simulated data with 95% accuracy, and model MF predicts the bubble mass within 4% of the true value. We use bubbles previously visually identified in Taurus in 13CO to validate the models and show both perform well on the highest confidence bubbles. We apply our two models on the full 98 deg2 FCRAO 13CO survey of the Taurus cloud. Models ME1 and MF predict feedback gas mass of 2894 M and 302 M, respectively. When including a correction factor for missing energy due to the limited velocity range of the 13CO data cube, model ME1 predicts feedback kinetic energies of 4.0*1e46 ergs and 1.5*1e47 ergs with/without subtracting the cloud velocity gradient. Model MF predicts feedback kinetic energy of 9.6*1e45 ergs and 2.8*1e46 ergs with/without subtracting the cloud velocity gradient. Model ME1 predicts bubble locations and properties consistent with previous visually identified bubbles. However, model MF demonstrates that feedback properties computed based on visual identifications are significantly overestimated due to line of sight confusion and contamination from background and foreground gas.

[21]  arXiv:2001.04510 [pdf, other]

Title: A NECTAr-based upgrade for the Cherenkov cameras of the H.E.S.S. 12-meter telescopes

Authors: Terry Ashton, Michael Backes, Arnim Balzer, David Berge, Julien Bolmont, Simon Bonnefoy, Francois Brun, Thomas Chaminade, Eric Delagnes, Gerard Fontaine, Matthias Füßling, Gianluca Giavitto, Berrie Giebels, Jean-Francois Glicenstein, Tobias Gräber, Jim Hinton, Albert Jahnke, Stefan Klepser, Marko Kossatz, Axel Kretzschmann, Valentin Lefranc, Holger Leich, Jean-Philippe Lenain, Hartmut Lüdecke, Iryna Lypova, Pascal Manigot, Vincent Marandon, Emmanuel Moulin, Thomas Murach, Mathieu de Naurois, Patrick Nayman, Stefan Ohm, Marek Penno, Duncan Ross, David Salek, Markus Schade, Thomas Schwab, Kleopas Shiningayamwe, Christian Stegmann, Constantin Steppa, Jean-Paul Tavernet, Julian Thornhill, Francois Toussnel, Pascal Vincent

Comments: 35 pages, 14 figures, accepted for publication in "Astroparticle physics"

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The High Energy Stereoscopic System (H.E.S.S.) is one of the three arrays of imaging atmospheric Cherenkov telescopes (IACTs) currently in operation. It is composed of four 12-meter telescopes and a 28-meter one, and is sensitive to gamma rays in the energy range ~30 GeV - 100 TeV. The cameras of the 12-m telescopes recently underwent a substantial upgrade, with the goal of improving their performance and robustness. The upgrade involved replacing all camera components except for the photomultiplier tubes (PMTs). This meant developing new hardware for the trigger, readout, power, cooling and mechanical systems, and new software for camera control and data acquisition. Several novel technologies were employed in the cameras: the readout is built around the new NECTAr digitizer chip, developed for the next generation of IACTs; the camera electronics is fully controlled and read out via Ethernet using a combination of FPGA and embedded ARM computers; the software uses modern libraries such as Apache Thrift, ZMQ and Protocol buffers. This work describes in detail the design and the performance of the upgraded cameras.

[22]  arXiv:2001.04532 [pdf, other]

Title: The high-energy environment and atmospheric escape of the mini-Neptune K2-18 b

Authors: Leonardo A. dos Santos, David Ehrenreich, Vincent Bourrier, Nicola Astudillo-Defru, Xavier Bonfils, François Forget, Christophe Lovis, Francesco Pepe, Stéphane Udry

Comments: 5 pages, 4 figures, accepted for publication in A&A Letters

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

K2-18 b is a transiting mini-Neptune that orbits a nearby (38 pc) cool M3 dwarf and is located inside its region of temperate irradiation. We report on the search for hydrogen escape from the atmosphere K2-18 b using Lyman-$\alpha$ transit spectroscopy with the Space Telescope Imaging Spectrograph (STIS) instrument installed on the Hubble Space Telescope (HST). We analyzed the time-series of the fluxes of the stellar Lyman-$\alpha$ emission of K2-18 in both its blue- and redshifted wings. We found that the average blueshifted emission of K2-18 decreases by $67\% \pm 18\%$ during the transit of the planet compared to the pre-transit emission, tentatively indicating the presence of H atoms escaping vigorously and being blown away by radiation pressure. This interpretation is not definitive because it relies on one partial transit. Based on the reconstructed Lyman-$\alpha$ emission of K2-18, we estimate an EUV irradiation between $10^1-10^2$ erg s$^{-1}$ cm$^{-2}$ and a total escape rate in the order of $10^8$ g s$^{-1}$. The inferred escape rate suggests that the planet will lose only a small fraction (< 1%) of its mass and retain its volatile-rich atmosphere during its lifetime. More observations are needed to rule out stellar variability effects, confirm the in-transit absorption and better assess the atmospheric escape and high-energy environment of K2-18 b.

[23]  arXiv:2001.04534 [pdf, other]

Title: MOBSTER: Identifying Candidate Magnetic O Stars through Rotational Modulation of TESS Photometry

Authors: James Barron, Gregg A. Wade, Dominic M. Bowman, Alexandre David-Uraz, Melissa S. Munoz, Herbert Pablo, Sergio Simón-Díaz

Comments: 9 pages, 4 figures, Conference proceedings: "Stellar Magnetic Fields - A workshop in honour of the career and contributions of John Landstreet", London, Canada, July 2019 (to be published in the Proceedings of the Polish Astronomical Society)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Being relatively rare, the properties of magnetic O stars are not fully understood. To date fewer than a dozen of these stars have been confirmed, making any inference of their global properties uncertain due to small number statistics. To better understand these objects it is necessary to increase the known sample. The MOBSTER collaboration aims to do this by identifying candidate magnetic O, B, and A stars from the identification of rotational modulation in high-precision photometry from the Transiting Exoplanet Survey Satellite (TESS). Here we discuss the collaboration's efforts to detect rotational modulation in TESS targets to identify candidate magnetic O stars for future spectropolarimetric observations.

[24]  arXiv:2001.04548 [pdf, other]

Title: Tidal Disruption Flares from Stars on Marginally Bound and Unbound Orbits

Authors: Gwanwoo Park, Kimitake Hayasaki

Comments: 37 pages, 11 figures, 2 tables, comments welcome

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study the mass fallback rate of tidal disruption of a star on marginally bound and unbound orbits by a supermassive black hole (SMBH) by performing a three-dimensional smoothed particle hydrodynamic simulations with three key parameters: the star is modeled by a polytrope with two different indexes ($n=1.5$ and $3$). The stellar orbital properties are characterized by five various orbital eccentricities ranging from $e=0.98$ to $1.02$ and five different penetration factors ranging from $\beta=1$ to $3$, where $\beta$ represents the ratio of the tidal disruption to pericenter distance radii. We analytically derive the formulae of the differential mass distributions and corresponding mass fallback rates by taking account of the three key parameters. Moreover, two critical eccentricities ($e_{\rm crit,1}$ and $e_{\rm crit,2}$) to classify tidal disruption events (TDEs) into five different types by the stellar orbit are reevaluated based on the assumption that the spread in debris energy is proportional to $\beta^k$, where $k$ is presumed to range for $0<k<2$. We confirm by our simulations that it ranges for $0<k\lesssim2$. We find that the peak of mass fallback rates is higher and its slope is steeper in the early time as the penetration factor increases for all TDE types. When the stars on marginally bound orbits with $e_{\rm crit,1}\lesssim{e}<1$ are tidally disrupted, the peak of mass fallback rates can be about one order of magnitude larger than that of parabolic TDE ($e=1$) case. For marginally hyperbolic TDEs ($1<e\lesssim{e}_{\rm crit,2}$), the mass fallback rates can be much lower than the Eddington accretion rate, which can lead to the formation of a radiatively inefficient accretion flow, while stars on hyperbolic orbits with $e\gtrsim{e_{\rm crit,2}}$ leads to a failed TDE. Marginally unbound TDEs could be an origin of a very low density gas disk around a dormant SMBH.

[25]  arXiv:2001.04550 [pdf, other]

Title: ExoMol molecular line lists -- XXXVII: spectra of acetylene

Authors: Katy L. Chubb, Jonathan Tennyson, Sergey N. Yurchenko

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

A new ro-vibrational line list for the ground electronic state of the main isotopologue of acetylene, $^{12}$C$_2$H$_2$, is computed as part of the ExoMol project. The aCeTY line list covers the transition wavenumbers up to 10,000 cm$^{-1}$ ($ \lambda >1$ $\mu$m), with lower and upper energy levels up to 12,000 cm$^{-1}$ and 22,000 cm$^{-1}$ considered, respectively. The calculations are performed up to a maximum value for the vibrational angular momentum, $K_{\rm max}=L_{\rm max}$ = 16, and maximum rotational angular momentum, $J$ = 99. Higher values of $J$ were not within the specified wavenumber window. The aCeTY line list is considered to be complete up to 2200 K, making it suitable for use in characterising high-temperature exoplanet or cool stellar atmospheres. Einstein-A coefficients, which can directly be used to calculate intensities at a particular temperature, are computed for 4.3 billion (4,347,381,911) transitions between 5 million (5,160,803) energy levels. We make comparisons against other available data for $^{12}$C$_2$H$_2$, and demonstrate this to be the most complete line list available. The line list is available in electronic form from the online CDS and ExoMol databases.

[26]  arXiv:2001.04558 [pdf, other]

Title: Modelling Stochastic Signatures in Classical Pulsators

Authors: P. P. Avelino, M. S. Cunha, W. J. Chaplin

Comments: 7 pages, 5 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We consider the impact of stochastic perturbations on otherwise coherent oscillations of classical pulsators. The resulting dynamics are modelled by a driven damped harmonic oscillator subject to either an external or an internal forcing and white noise velocity fluctuations. We characterize the phase and relative amplitude variations using analytical and numerical tools. When the forcing is internal the phase variation displays a random walk behaviour and a red noise power spectrum with a ragged erratic appearance. We determine the dependence of the root mean square phase and relative amplitude variations ($\sigma_{\Delta \varphi}$ and $\sigma_{\Delta A/A}$, respectively) on the amplitude of the stochastic perturbations, the damping constant $\eta$, and the total observation time $t_{\rm obs}$ for this case, under the assumption that the relative amplitude variations remain small, showing that $\sigma_{\Delta \varphi}$ increases with $t_{\rm obs}^{1/2}$ becoming much larger than $\sigma_{\Delta A/A}$ for $t_{\rm obs} \gg \eta^{-1}$. In the case of an external forcing the phase and relative amplitude variations remain of the same order, independent of the observing time. In the case of an internal forcing, we find that $\sigma_{\Delta \varphi}$ does not depend on $\eta$. Hence, the damping time cannot be inferred from fitting the power of the signal, as done for solar-like pulsators, but the amplitude of the stochastic perturbations may be constrained from the observations. Our results imply that, given sufficient time, the variation of the phase associated to the stochastic perturbations in internally driven classical pulsators will become sufficiently large to be probed observationally.

[27]  arXiv:2001.04575 [pdf]

Title: The Extreme Space Weather Event in 1903 October/November: An Outburst from the Quiet Sun

Authors: Hisashi Hayakawa, Paulo Ribeiro, José M. Vaquero, María Cruz Gallego, Delores J. Knipp, Florian Mekhaldi, Ankush Bhaskar, Denny M. Oliveira, Yuta Notsu, Víctor M. S. Carrasco, Ana Caccavari, Bhaskara Veenadhari, Shyamoli Mukherjee, Yusuke Ebihara

Comments: 20 pages, 5 figures, 1 table, and accepted for publication in the ApJL

Journal-ref: The Astrophysical Journal Letters, 2020

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

While the Sun is generally more eruptive during its maximum and declining phases, observational evidence shows certain cases of powerful solar eruptions during the quiet phase of the solar activity. Occurring in the weak Solar Cycle 14 just after its minimum, the extreme space weather event in 1903 October -- November was one of these cases. Here, we reconstruct the time series of geomagnetic activity based on contemporary observational records. With the mid-latitude magnetograms, the 1903 magnetic storm is thought to be caused by a fast coronal mass ejection (~1500 km/s) and is regarded as an intense event with an estimated minimum Dst' of ~-513 nT The reconstructed time series has been compared with the equatorward extension of auroral oval (~44.1{\deg} in invariant latitude) and the time series of telegraphic disturbances. This case study shows that potential threats posed by extreme space weather events exist even during weak solar cycles or near their minima.

[28]  arXiv:2001.04576 [pdf, other]

Title: High-resolution radio astronomy: an outlook for Africa

Authors: Leonid I. Gurvits, Robert Beswick, Melvin Hoare, Ann Njeri, Jay Blanchard, Carla Sharpe, Adrian Tiplady, Aletha de Witt

Comments: Presentation at the IAU Symposium. No. 356, Addis Ababa, Ethiopia, Oct 2020; 5 pages, 4 figures

Journal-ref: Proceedings of the IAU Symp. No. 356, 2020, M. Povic, J. Masegosa, H. Netzer, P. Marziani, P. Shastri, S.B. Tessema and S.H. Negu, eds

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Very Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the IAU Symposium No. 356, the Active Galactic Nuclei (AGN) of all types, constitute the major observing sample of modern VLBI networks. At present, the largest in the world in terms of the number of telescopes and geographical coverage is the European VLBI Network (EVN), which operates under the open sky policy via peer-reviewed observing proposals. Recent EVN observations cover a broad range of science themes from high-sensitivity monitoring of structural changes in inner AGN areas to observations of tidal eruptions in AGN cores and investigation of redshift-dependent properties of parsec-scale radio structures of AGN. All the topics above should be considered as potentially rewarding scientific activities of the prospective African VLBI Network (AVN), a natural scientific ally of EVN. This contribution briefly describes the status and near-term strategy for the AVN development as a southern extension of the EVN-AVN alliance and as an eventual bridge to the Square Kilometre Array (SKA) with its mid-frequency core in South Africa.

[29]  arXiv:2001.04581 [pdf, other]

Title: The Megamaser Cosmology Project. XI. A geometric distance to CGCG 074-064

Authors: D. W. Pesce, J. A. Braatz, M. J. Reid, J. J. Condon, F. Gao, C. Henkel, C. Y. Kuo, K. Y. Lo, W. Zhao

Comments: 22 pages, 6 figures, accepted for publication in ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA)

As part of the survey component of the Megamaser Cosmology Project, we have discovered a disk megamaser system in the galaxy CGCG 074-064. Using the GBT and the VLA, we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years. We find that the systemic maser features display line-of-sight accelerations of ~4.4 km s$^{-1}$ yr$^{-1}$ that are nearly constant with velocity, while the high-velocity maser features show accelerations that are consistent with zero. We have also used the HSA to make a high-sensitivity VLBI map of the maser system in CGCG 074-064, which reveals that the masers reside in a thin, edge-on disk with a diameter of ~1.5 mas (0.6 pc). Fitting a three-dimensional warped disk model to the data, we measure a black hole mass of $2.42^{+0.22}_{-0.20} \times 10^7$ M$_{\odot}$ and a geometric distance to the system of $87.6^{+7.9}_{-7.2}$ Mpc. Assuming a CMB-frame recession velocity of $7308 \pm 150$ km s$^{-1}$, we constrain the Hubble constant to $H_0 = 81.0^{+7.4}_{-6.9}$ (stat.) $\pm 1.4$ (sys.) km s$^{-1}$ Mpc$^{-1}$.

[30]  arXiv:2001.04587 [pdf, other]

Title: A Merged Search-Coil and Fluxgate Magnetometer Data Product for Parker Solar Probe FIELDS

Authors: Trevor A. Bowen, Stuart D. Bale John W. Bonnell, Thierry Dudok de Wit, Keith Goetz, Katherine Goodrich, Jacob Gruesbeck, Peter R. Harvey, Guillaume Jannet, Andriy Koval Robert J. MacDowall, David M. Malaspina, Marc Pulupa, Claire Revillet, David Sheppard, Adam Szabo

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Detectors (physics.ins-det); Space Physics (physics.space-ph)

NASA's Parker Solar Probe (PSP) mission is currently investigating the local plasma environment of the inner-heliosphere ($< $0.25$R_\odot$) using both {\em{in-situ}} and remote sensing instrumentation. Connecting signatures of microphysical particle heating and acceleration processes to macro-scale heliospheric structure requires sensitive measurements of electromagnetic fields over a large range of physical scales. The FIELDS instrument, which provides PSP with {\em{in-situ}} measurements of electromagnetic fields of the inner heliosphere and corona, includes a set of three vector magnetometers: two fluxgate magnetometers (MAGs), and a single inductively coupled search-coil magnetometer (SCM). Together, the three FIELDS magnetometers enable measurements of the local magnetic field with a bandwidth ranging from DC to 1 MHz. This manuscript reports on the development of a merged data set combining SCM and MAG (SCaM) measurements, enabling the highest fidelity data product with an optimal signal to noise ratio. On-ground characterization tests of complex instrumental responses and noise floors are discussed as well as application to the in-flight calibration of FIELDS data. The algorithm used on PSP/FIELDS to merge waveform observations from multiple sensors with optimal signal to noise characteristics is presented. In-flight analysis of calibrations and merging algorithm performance demonstrates a timing accuracy to well within the survey rate sample period of $\sim340 \mu s$.

[31]  arXiv:2001.04588 [pdf, ps, other]

Title: Determination of Potassium Abundances for Giant and Dwarf Stars in the Galactic Disk

Authors: Yoichi Takeda

Comments: 16 pages with online material, published in Stars and Galaxies (2019, Vol.2, id.1)

Journal-ref: Stars and Galaxies (2019), Vol.2, id.1 (http://www.nhao.jp/research/starsandgalaxies/02.html#2019J-1)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

An extensive study on the potassium abundances of late-type stars was carried out by applying the non-LTE spectrum-fitting analysis to the K I resonance line at 7698.96A to a large sample of 160 FGK dwarfs and 328 late-G /early-K giants (including 89 giants in the Kepler field with seismologically known ages) belonging to the disk population (-1 < [Fe/H] < 0.5), which may provide important observational constraint on the nucleosynthesis history of K in the galactic disk. Special attention was paid to clarifying the observed behaviors of [K/Fe] in terms of [Fe/H] along with stellar age, and to checking whether giants and dwarfs yield consistent results with each other. The following results were obtained. (1) A slightly increasing tendency of [K/Fe] with a decrease in [Fe/H] (d[K/Fe]/d[Fe/H] ~ -0.1 to -0.15; a shallower slope than reported by previous studies) was confirmed for FGK dwarfs, though thick-disk stars tend to show larger [K/Fe] deviating from this gradient. (2) Almost similar characteristics was observed also for apparently bright field giants locating in the solar neighborhood (such as like dwarfs). (3) However, the [K/Fe] vs. [Fe/H] relation for more distant {\it Kepler} giants shows larger scatter and is systematically higher (by <~0.1dex) than that of dwarfs, implying that chemical evolution of K is rather diversified depending on the position in the Galaxy. (4) Regarding the age-dependence, a marginal trend of increasing [K/Fe] with age is recognized for dwarfs, while any systematic tendency is not observed for Kepler giants. These consequences may suggest that evolution of [K/Fe] with time in the galactic disk does exist but proceeded more gradually than previously thought, and its condition is appreciably location-dependent.

[32]  arXiv:2001.04590 [pdf, ps, other]

Title: Spectrum variability of the active solar-type star Xi Bootis A

Authors: Yoichi Takeda, Satoshi Honda, Hikaru Taguchi, Osamu Hashimoto

Comments: 22 pages with online material, accepted for publication in Publ. Astron. Soc. Japan (2020)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

An extensive spectroscopic study on \xi Boo A (chromospherically active solar-type star) was conducted based on the spectra obtained in 2008 December though 2010 May, with an aim to detect any spectrum variability and to understand its physical origin. For each spectrum, the atmospheric parameters were spectroscopically determined based on Fe lines, and the equivalent widths (along with the line-broadening parameters) of selected 99 lines were measured. We could detect meaningful small fluctuations in the equivalent widths of medium-strength lines. This variation was found to correlate with the effective temperature (T_eff) consistently with the T-sensitivity of each line, which indicates that the difference in the mean temperature averaged over the disk of inhomogeneous condition is mainly responsible for this variability. It was also found that the macrobroadening widths of medium-strength lines and the equivalent widths dispersion of saturated lines tend to increase with the effective Lande factor, suggesting an influence of magnetic field. Our power spectrum analysis applied to the time-sequence data of V I/Fe II line-strength ratio and T_eff could not confirm the 6.4 d period reported by previous studies. We suspect that surface inhomogeneities of \xi Boo A at the time of our observations were not so much simple (such as single star patch) as rather complex (e.g., intricate aggregate of spots and faculae).

[33]  arXiv:2001.04606 [pdf, other]

Title: Fundamental limits from chaos on instability time predictions in compact planetary systems

Authors: Naireen Hussain, Daniel Tamayo

Comments: 10 pages, 7 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Instabilities in compact planetary systems are generically driven by chaotic dynamics. This implies that an instability time measured through direct N-body integration is not exact, but rather represents a single draw from a distribution of equally valid chaotic trajectories. In order to characterize the "errors" on reported instability times from direct N-body integrations, we investigate the shape and parameters of the instability time distributions (ITDs) for ensembles of shadow trajectories that are initially perturbed from one another near machine precision. We find that in the limit where instability times are long compared to the Lyapunov (chaotic) timescale, ITDs approach remarkably similar lognormal distributions with standard deviations ~0.43 $\pm$ 0.16 dex, despite the instability times varying across our sample from $10^4-10^8$ orbits. We find excellent agreement between these predictions, derived from ~450 closely packed configurations of three planets, and a much wider validation set of ~10,000 integrations, as well as on ~20,000 previously published integrations of tightly packed five-planet systems, and a seven-planet resonant chain based on TRAPPIST-1, despite their instability timescales extending beyond our analyzed timescale. We also test the boundary of applicability of our results on dynamically excited versions of our Solar System. These distributions define the fundamental limit imposed by chaos on the predictability of instability times in such planetary systems. It provides a quantitative estimate of the intrinsic error on an N-body instability time imprinted by chaos, approximately a factor of 3 in either direction.

[34]  arXiv:2001.04632 [pdf, ps, other]

Title: Study of the Dynamics of Convective Turbulence in the Solar Granulation by Spectral Line Broadening and Asymmetry

Authors: Ryohtaroh T. Ishikawa, Yukio Katsukawa, Takayoshi Oba, Motoki Nakata, Kenichi Nagaoka, Tatsuya Kobayashi

Comments: Accepted for publication in ApJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In the quiet regions on the solar surface, turbulent convective motions of granulation play an important role in creating small-scale magnetic structures, as well as in energy injection into the upper atmosphere. The turbulent nature of granulation can be studied using spectral line profiles, especially line broadening, which contains information on the flow field smaller than the spatial resolution of an instrument. Moreover, the Doppler velocity gradient along a line-of-sight (LOS) causes line broadening as well. However, the quantitative relationship between velocity gradient and line broadening has not been understood well. In this study, we perform bisector analyses using the spectral profiles obtained using the Spectro-Polarimeter of the Hinode/Solar Optical Telescope to investigate the relationship of line broadening and bisector velocities with the granulation flows. The results indicate that line broadening has a positive correlation with the Doppler velocity gradients along the LOS. We found excessive line broadening in fading granules, that cannot be explained only by the LOS velocity gradient, although the velocity gradient is enhanced in the process of fading. If this excessive line broadening is attributed to small-scale turbulent motions, the averaged turbulent velocity is obtained as 0.9 km/s.

[35]  arXiv:2001.04633 [pdf, other]

Title: Continuous Null-Point Magnetic Reconnection Builds Up a Torus Unstable Magnetic Flux Rope Triggering the X9.3 Flare in Solar Active Region~12673

Authors: Peng Zou, Chaowei Jiang, Fengsi Wei, Xueshang Feng, Pingbing Zuo, Yi Wang

Comments: 11 pages, 5 figures, accepted by ApJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Two X-class solar flares occurred on 2017 September 6 from active region NOAA 12673: the first one is a confined X2.2 flare, and it is followed only $\sim 3$ hours later by the second one, which is the strongest flare in solar cycle 24, reaching X9.3 class and accompanied with a coronal mass ejection. Why these two X-class flares occurred in the same position with similar magnetic configurations, but one is eruptive while the other is not? Here we track the coronal magnetic field evolution via nonlinear force-free field extrapolations from a time sequence of vector magnetograms with high cadence. A detailed analysis of the magnetic field shows that a magnetic flux rope (MFR) forms and grows gradually before the first flare, and shortly afterwards, the MFR's growth is significantly enhanced with a much faster rise in height, from far below the threshold of torus instability to above it, while the magnetic twist only increases mildly. Combining EUV observations and the magnetic field extrapolation, we found that overlying the MFR is a null-point magnetic topology, where recurrent brightening is seen after the first flare. We thus suggest a scenario to interpret the occurrence of the two flares. The first flare occurred since the MFR reached a high enough height to activate the null point, and its continuous expansion forces the null-point reconnection recurrently. Such reconnection weakens the overlying field, allowing the MFR to rise faster, which eventually crosses the threshold of torus instability and triggers the second, eruptive flare.

[36]  arXiv:2001.04634 [pdf, other]

Title: Unsupervised Distribution Learning for Lunar Surface Anomaly Detection

Authors: Adam Lesnikowski, Valentin T. Bickel, Daniel Angerhausen

Comments: Second Workshop on Machine Learning and the Physical Sciences, NeurIPS 2019. Five pages, three figures

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Machine Learning (cs.LG)

In this work we show that modern data-driven machine learning techniques can be successfully applied on lunar surface remote sensing data to learn, in an unsupervised way, sufficiently good representations of the data distribution to enable lunar technosignature and anomaly detection. In particular we train an unsupervised distribution learning neural network model to find the Apollo 15 landing module in a testing dataset, with no dataset specific model or hyperparameter tuning. Sufficiently good unsupervised data density estimation has the promise of enabling myriad useful downstream tasks, including locating lunar resources for future space flight and colonization, finding new impact craters or lunar surface reshaping, and algorithmically deciding the importance of unlabeled samples to send back from power- and bandwidth-constrained missions. We show in this work that such unsupervised learning can be successfully done in the lunar remote sensing and space science contexts.

[37]  arXiv:2001.04638 [pdf, ps, other]

Title: A non-corotating gas component in an extreme starburst at z=4.3

Authors: Ken-ichi Tadaki, Daisuke Iono, Min S. Yun, Itziar Aretxaga, Bunyo Hatsukade, Minju M. Lee, Tomonari Michiyama, Kouichiro Nakanishi, Toshiki Saito, Junko Ueda, Hideki Umehata

Comments: 10 pages, 8 figures. Accepted for publication in ApJ. GIF images of [CII] line emission are available at this https URL

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We report the detection of a non-corotating gas component in a bright unlensed submillimeter galaxy at z=4.3, COSMOS-AzTEC-1, hosting a compact starburst. ALMA 0.17 and 0.09 arcsec resolution observations of [CII] emission clearly demonstrate that the gas kinematics is characterized by an ordered rotation. After subtracting the best-fit model of a rotating disk, we kinematically identify two residual components in the channel maps. Both observing simulations and analysis of dirty images confirm that these two subcomponents are not artificially created by noise fluctuations and beam deconvolution. One of the two has a velocity offset of 200 km/s and a physical separation of 2 kpc from the primary disk and is located along the kinematic minor axis of disk rotation. We conclude that this gas component is falling into the galaxy from a direction perpendicular to the disk rotation. The accretion of such small non-corotating gas components could stimulate violent disk instability, driving radial gas inflows into the center of galaxies and leading to formation of in-situ clumps such as identified in dust continuum and CO. We require more theoretical studies on high gas fraction mergers with mass ratio of 1:>10 to verify this process.

[38]  arXiv:2001.04645 [pdf, other]

Title: Observational constraints on the non-flat $ΛCDM$ model and a null test using the transition redshift

Authors: Velasquez-Toribio, A.M, Magnago, A. dos R

Comments: 11 pages, 7 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

A natural extension of the standard cosmological model are models that include curvature as a free parameter. In this work we study in detail the observational constraints on the non-flat $\Lambda CDM$ model using the two main geometric tests: SNIa and Hubble parameter measurements. In general we show that the observational constraints on the parameters of the $\Lambda CDM$ model strongly depend on the curvature parameter. In particular, we study the constraints on the transition redshift ($z_{t}$) of a universe dominated by matter for a universe dominated by the cosmological constant. Using this observable we construct a new null test defining $\zeta = z_{t, flat}-z_{t, non flat}$. This test depends only on the data of the Hubble parameter, the Hubble constant and the matter density parameter. However, it does not depend on derivative of an observable as generally many tests in the literature. To reconstruct this test, we use the Gaussian process method. When we use the best-fit parameters values of $PLANCK/2018$, we find no evidence of a disagreement between the data and the standard model (flat $\Lambda CDM$), but if we use the value $H_{0}$ from $RIESS/2018$ we found a disagreement with respect at the standard model. However, it is important to note that the Hubble parameter data has large errors for a solid statistical analysis.

[39]  arXiv:2001.04649 [pdf, ps, other]

Title: Synchrotron Gamma-Ray Emission Model of the Giant Outburst of Quasar 3C 279 in 2015 June: Fast Reconnection or Stochastic Acceleration with Electromagnetic Cascade?

Authors: Katsuaki Asano, Masaaki Hayashida

Comments: 7 pages, 5 figures, accepted for publication in ApJ

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We test the synchrotron emission scenario for the very bright gamma-ray flare of blazar 3C 279 observed in 2015 June using time-dependent numerical simulations. A bulk Lorentz factor as high as 100 can bring the synchrotron maximum energy above the GeV energy range. We find two possible solutions for the X-ray to gamma-ray spectrum. One is a prompt electron injection model with a hard power-law index as magnetic reconnection models suggest. A too strong magnetic field yields a too bright synchrotron X-ray flux due to secondary electron--positron pairs. Even in the prompt electron injection model, the Poynting flux luminosity is at most comparable to the gamma-ray or electron luminosity. Another model is the stochastic acceleration model, which leads to a very unique picture accompanying the electromagnetic cascade and re-acceleration of the secondary electron--positron pairs. In this model, the energy budget of the magnetic field is very low compared to gamma rays and electrons.

[40]  arXiv:2001.04653 [pdf, other]

Title: Age dating of an early Milky Way merger via asteroseismology of the naked-eye star $ν$ Indi

Authors: William J. Chaplin, Aldo M. Serenelli, Andrea Miglio, Thierry Morel, J. Ted Mackereth, Fiorenzo Vincenzo, Hans Kjeldsen Sarbani Basu, Warrick H. Ball, Amalie Stokholm, Kuldeep Verma, Jakob Rørsted Mosumgaard, Victor Silva Aguirre, Anwesh Mazumdar, Pritesh Ranadive, H. M. Antia, Yveline Lebreton, Joel Ong, Thierry Appourchaux, Timothy R. Bedding, Jørgen Christensen-Dalsgaard, Orlagh Creevey, Rafael A. García, Rasmus Handberg, Daniel Huber, Steven D. Kawaler, Mikkel N. Lund, Travis S. Metcalfe, Keivan G. Stassun, Michäel Bazot, Paul Beck, Keaton J. Bell, Maria Bergemann, Derek L. Buzasi, Othman Benomar, Diego Bossini, Lisa Bugnet, Tiago L. Campante, Zeynep Çelik Orhan, Enrico Corsaro, Lucía González-Cuesta, Guy R. Davies, Maria Pia Di Mauro, Ricky Egeland, et al. (41 additional authors not shown)

Comments: Accepted for publication as a Letter in Nature Astronomy (26 pages, 7 figures, including main article and methods section)

Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. While these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to precisely date the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called \textit{Gaia}-Enceladus, leading to a substantial pollution of the chemical and dynamical properties of the Milky Way. Here, we identify the very bright, naked-eye star $\nu$\,Indi as a probe of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric, and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be $11.0 \pm 0.7$ (stat) $\pm 0.8$ (sys)$\,\rm Gyr$. The star bears hallmarks consistent with it having been kinematically heated by the \textit{Gaia}-Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 Gyr ago at 68 and 95% confidence, respectively. Input from computations based on hierarchical cosmological models tightens (i.e. reduces) slightly the above limits.

[41]  arXiv:2001.04681 [pdf, other]

Title: Revisiting old (AGN) friends -- what's changed in their spectral looks

Authors: Hartmut Winkler

Comments: accepted for publication in the Proceedings of IAU Symposium 356, Nuclear Activity in Galaxies across Cosmic Time, Addis Ababa, Ethiopia, Oct 2019

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Active Galactic Nuclei (AGN) have long been known to be variable, but the amplitude, timescale and nature of these changes can often differ dramatically from object to object. The richest source of information about the properties of AGN and the physical processes driving these remains the optical spectrum. While this spectrum has remained remarkably steady over decades for some AGN, other objects, referred to as Changing Look AGN, have experienced a comprehensive spectral transformation. Developments in the detection technology have enabled detailed probing in other wavebands, highlighting for example often quite different variability patterns for high energy emission. This paper explores the current characteristics of some long-known (and almost forgotten) Seyfert galaxies. It compares their present optical spectral properties, determined from recent observations at the South African Astronomical Observatory, with those from much earlier epochs. It furthermore considers the implication of the changes that have taken place, alternatively the endurance of specific spectral features, on our understanding of the mechanisms of the observed targets in particular, and on AGN models in general.

[42]  arXiv:2001.04707 [pdf, ps, other]

Title: A spectroscopic survey of Abell 1703: is it a rare relaxed cluster hosting a radio halo or a usual merging system?

Authors: Walter Boschin, Marisa Girardi, Fabio Gastaldello

Comments: 15 pages, 13 figures, 5 tables. In press on MNRAS

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

We present the study of the internal dynamics of the intriguing galaxy cluster Abell 1703, a system hosting a probable giant radio halo whose dynamical status is still controversial. Our analysis is based on unpublished spectroscopic data acquired at the Italian Telescopio Nazionale Galileo and data publicly available in the literature. We also use photometric data from the Sloan Digital Sky Survey. We select 147 cluster members and compute the cluster redshift $\left<z\right>\sim 0.277$ and the global line-of-sight velocity dispersion $\sigma_{\rm v}\sim 1300$ km/s. We infer that Abell 1703 is a massive cluster: $M_{200}\sim 1-2\times 10^{15}$ $M_{\odot}$. The results of our study disagree with the picture of an unimodal, relaxed cluster as suggested by previous studies based on the gravitational lensing analysis and support the view of a perturbed dynamics proposed by recent works based on Chandra X-ray data. The first strong evidence of a dynamically disturbed cluster comes from the peculiarity of the BCG velocity with respect to the first moment of the velocity distribution of member galaxies. Moreover, several statistical tests employed to study the cluster galaxies kinematics find significant evidence of substructure, being Abell 1703 composed by at least two or three subclumps probably caught after the core-core passage. In this observational scenario, the suspected existence of a radio halo in the centre of this cluster is not surprising and well agrees with the theoretical models describing diffuse radio sources in clusters.

[43]  arXiv:2001.04720 [pdf, other]

Title: Qwind code release. A non-hydrodynamical approach to modelling line-driven winds in active galactic nuclei

Authors: Arnau Quera-Bofarull, Chris Done, Cedric Lacey, Jonathan C. McDowell, Guido Risaliti, Martin Elvis

Comments: 11 pages, 14 figures, for Qwind code see this https URL , submitted to MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

UV line driven winds may be an important part of the AGN feedback process, but understanding their impact is hindered by the complex nature of the radiation hydrodynamics. Instead, we have taken the approach pioneered by Risaliti & Elvis, calculating only ballistic trajectories from radiation forces and gravity, but neglecting gas pressure. We have completely re-written their QWIND code using more robust algorithms, and can now quickly model the acceleration phase of these winds for any AGN spectral energy distribution spanning UV and X-ray wavebands. We demonstrate the code using an AGN with black hole mass $10^8\, M_\odot$ emitting at half the Eddington rate and show that this can effectively eject a wind with velocities $\simeq (0.1-0.2)\, c$. The mass loss rates can be up to $\simeq 0.3 M_\odot$ per year, consistent with more computationally expensive hydrodynamical simulations, though we highlight the importance of future improvements in radiation transfer along the multiple different lines of sight illuminating the wind. The code is fully public, and can be used to quickly explore the conditions under which AGN feedback can be dominated by accretion disc winds.

[44]  arXiv:2001.04722 [pdf, other]

Title: Stellar cores in the Sh 2-305 H II region

Authors: Rakesh Pandey, Saurabh Sharma, Neelam Panwar, Lokesh K. Dewangan, Devendra K. Ojha, D. P. Bisen, Tirthendu Sinha, Arpan Ghosh, Anil K. Pandey

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Using our deep optical and near-infrared photometry along with multiwavelength archival data, we here present a detailed study of the Galactic H II region Sh 2-305, to understand the star/star-cluster formation. On the basis of excess infra-red emission, we have identified 116 young stellar objects (YSOs) within a field of view of ~ 18.5 arcminute x 18.5 arcminute, around Sh 2-305. The average age, mass and extinction (A_V) for this sample of YSOs are 1.8 Myr, 2.9 solar mass and 7.1 mag, respectively. The density distribution of stellar sources along with minimal spanning tree calculations on the location of YSOs reveals at least three stellar sub-clusterings in Sh 2-305. One cluster is seen toward the center (i.e., Mayer 3), while the other two are distributed toward the north and south directions. Two massive O-type stars (VM2 and VM4; ages ~ 5 Myr) are located at the center of the Sh 2-305 H II region. The analysis of the infrared and radio maps traces the photon dominant regions (PDRs) in the Sh 2-305. Association of younger generation of stars with the PDRs is also investigated in the Sh 2-305. This result suggests that these two massive stars might have influenced the star formation history in the Sh 2-305. This argument is also supported with the calculation of various pressures driven by massive stars, slope of mass function/K-band luminosity function, star formation efficiency, fraction of Class I sources, and mass of the dense gas toward the sub-clusterings in the Sh 2-305.

[45]  arXiv:2001.04725 [pdf, other]

Title: The discovery of radio halos in the Frontier Fields clusters Abell S1063 and Abell 370

Authors: C. Xie, R. J. van Weeren, L. Lovisari, F. Andrade-Santos, A. Botteon, M. Brüggen, E. Bulbul, E. Churazov, T. E. Clarke, W. R. Forman, H. T. Intema, C. Jones, R. P. Kraft, D. V. Lal, T. Mroczkowski, A. Zitrin

Comments: 12 pages, 13 figures, 4 tables; resubmitted to A&A after incorporating reviewer's comments

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

Massive merging galaxy clusters often host diffuse Mpc-scale radio synchrotron emission. This emission originates from relativistic electrons in the ionized intracluster medium (ICM). An important question is how these synchrotron emitting relativistic electrons are accelerated. Our aim is to search for diffuse emission in the Frontier Fields clusters Abell S1063 and Abell 370 and characterize its properties. While these clusters are very massive and well studied at some other wavelengths, no diffuse emission has been reported for these clusters so far. We obtained 325 MHz Giant Metrewave Radio Telescope (GMRT) and 1--4 GHz Jansky Very Large Array (VLA) observations of Abell S1063 and Abell 370. We complement these data with Chandra and XMM-Newton X-ray observations. In our sensitive images, we discover radio halos in both clusters. In Abell S1063, a giant radio halo is found with a size of $\sim 1.2$ Mpc. The integrated spectral index between 325 MHz and 1.5 GHz is $-0.94\pm0.08$ and it steepens to $-1.77 \pm 0.20$ between 1.5 and 3.0 GHz. This spectral steepening provides support for the turbulent re-acceleration model for radio halo formation. Abell 370 hosts a faint radio halo mostly centred on the southern part of this binary merging cluster, with a size of $\sim 500-700$ kpc. The spectral index between 325 MHz and 1.5 GHz is $-1.10\pm0.09$. Both radio halos follow the known scaling relation between the cluster mass proxy $Y_{500}$ and radio power, consistent with the idea that they are related to ongoing cluster merger events.

[46]  arXiv:2001.04759 [pdf, other]

Title: Global Chemistry and Thermal Structure Models for the Hot Jupiter WASP-43b and Predictions for JWST

Authors: Olivia Venot, Vivien Parmentier, Jasmina Blecic, Patricio E. Cubillos, Ingo P. Waldmann, Quentin Changeat, Julianne I. Moses, Pascal Tremblin, Nicolas Crouzet, Peter Gao, Diana Powell, Pierre-Olivier Lagage, Ian Dobbs-Dixon, Maria E. Steinrueck, Laura Kreidberg, Natalie Batalha, Jacob L. Bean, Kevin B. Stevenson, Sarah Casewell, Ludmila Carone

Comments: 26 pages, 16 figures, accepted in The Astrophysical Journal

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The James Webb Space Telescope (JWST) is expected to revolutionize the field of exoplanets. The broad wavelength coverage and the high sensitivity of its instruments will allow characterization of exoplanetary atmospheres with unprecedented precision. Following the Call for the Cycle 1 Early Release Science Program, the Transiting Exoplanet Community was awarded time to observe several targets, including WASP-43b. The atmosphere of this hot Jupiter has been intensively observed but still harbors some mysteries, especially concerning the day-night temperature gradient, the efficiency of the atmospheric circulation, and the presence of nightside clouds. We will constrain these properties by observing a full orbit of the planet and extracting its spectroscopic phase curve in the 5--12 $\mu$m range with JWST/MIRI. To prepare for these observations, we performed an extensive modeling work with various codes: radiative transfer, chemical kinetics, cloud microphysics, global circulation models, JWST simulators, and spectral retrieval. Our JWST simulations show that we should achieve a precision of 210 ppm per 0.1 $\mu$m spectral bin on average, which will allow us to measure the variations of the spectrum in longitude and measure the night-side emission spectrum for the first time. If the atmosphere of WASP-43b is clear, our observations will permit us to determine if its atmosphere has an equilibrium or disequilibrium chemical composition, providing eventually the first conclusive evidence of chemical quenching in a hot Jupiter atmosphere. If the atmosphere is cloudy, a careful retrieval analysis will allow us to identify the cloud composition.

[47]  arXiv:2001.04762 [pdf, other]

Title: Towards early-type eclipsing binaries as extragalactic milestones: II. NLTE spectral analysis and stellar parameters of the detached O-type system OGLE-LMC-ECL-06782 in the LMC

Authors: Mónica Taormina, Rolf-Peter Kudritzki, Joachim Puls, Bogumił Pilecki, Eva Sextl, G. Pietrzyński, Miguel A. Urbaneja, Wolfgang Gieren

Comments: 18 pages, 16 figures, 3 tables, Accepted for publication in ApJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We combine the NLTE spectral analysis of the detached O-type eclipsing binary OGLE-LMC-ECL-06782 with the analysis of the radial velocity curve and light curve to measure an independent distance to the LMC. In our spectral analysis we study composite spectra of the system at quadrature and use the information from radial velocity and light curve about stellar gravities, radii and component flux ratio to derive effective temperature, reddening, extinction and intrinsic surface brightness. We obtain a distance modulus to the LMC of m - M = 18.53 +/- 0.04 mag. This value is 0.05 mag larger than the precision distance obtained recently from the analysis of a large sample of detached, long period late spectral type eclipsing binaries but agrees within the margin of the uncertainties. We also determine the surface brightnesses of the system components and find good agreement with the published surface brightness color relationship. A comparison of the observed stellar parameters with the prediction of stellar evolution based on the MESA stellar evolution code shows reasonable agreement, but requires a reduction of the internal angular momentum transport to match the observed rotational velocities.

[48]  arXiv:2001.04778 [pdf, other]

Title: Concluding Remarks at the Multifrequency Behaviour of High Energy Cosmic Sources -- XIII Workshop -- II

Authors: Paolo Padovani (ESO)

Comments: Invited talk at Multifrequency Behaviour of High Energy Cosmic Sources - XIII - June 3-8 , 2019, Palermo, Italy. 10 pages, 3 figures. To appear in Proceedings of Science

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

I summarise the concluding remarks I gave at the Multifrequency Behaviour of High Energy Cosmic Sources - XIII Workshop. That was not a summary talk and was meant to be provocative. I first give what I think the main message of the workshop was, then provide some (biased) highlights, touch upon the upcoming new facilities and the issues of "quantity vs. quality" and productivity in astronomy, and finally conclude with a look to the future. Astronomers who did not attend the workshop might still find the first two topics appealing and the last two thought-provoking.

[49]  arXiv:2001.04853 [pdf, other]

Title: A modern guide to quantitative spectroscopy of massive OB stars

Authors: S. Simón-Díaz

Comments: Accepted for publication in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-035562

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Quantitative spectroscopy is a powerful technique from which we can extract information about the physical properties and surface chemical composition of stars. In this chapter, I guide the reader through the main ideas required to get initiated in the learning process to become an expert in the application of state-of-the-art quantitative spectroscopic techniques to the study of massive OB stars.
NB: This chapter is intended to serve to young students as a first approach to a field which has attracted my attention during the last 20 years. I should note that, despite its importance, at present, the number of real experts in the field around the world is limited to less than 50 people, and about one third of them are close to retirement. Hence, I consider that this is a good moment to write a summary text on the subject to serve as guideline for the next generations of students interested in joining the massive star crew. If you are one of them, please, use this chapter as a first working notebook. Do not stop here. Dig also, for further details, into the literature I quote along the text. And, once there, dig even deeper to find all the original sources explaining in more detail the physical and technical concepts that are presently incorporated into our modern (almost) automatized tools.

[50]  arXiv:2001.04865 [pdf, other]

Title: Water production rates and activity of interstellar comet 2I/Borisov

Authors: Zexi Xing, Dennis Bodewits, John Noonan, Michele T. Bannister

Comments: 11 pages, 3 figures, 2 tables, submitted to ApJL

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We observed the interstellar comet 2I/Borisov using the Neil Gehrels-Swift Observatory's Ultraviolet/Optical Telescope. We obtained images of the OH gas and dust surrounding the nucleus at four epochs spaced before and just after perihelion (-2.56 AU to 2.03 AU). Water production rates increased steadily before perihelion from $(7.0\pm1.5)\times10^{26}$ molecules s$^{-1}$ on Nov. 1, 2019 to $(10.7\pm1.2)\times10^{26}$ molecules s$^{-1}$ on Dec. 1. This rate of increase in water production rate is slower than that of most Jupiter-family comets and quicker than most dynamically new comets. After perihelion, the water production rate decreased rapidly to $(4.9\pm0.9)\times10^{26}$ molecules s$^{-1}$ on Dec. 21. Our sublimation model constrains the minimum radius of the nucleus to 0.37 km, and indicates an active fraction of at least 55% of the surface. $A(0)f\rho$ calculations show variation between 90 and 106 cm with a slight trend peaking before the perihelion, lower than previous and concurrent published values. The observations confirm that 2I/Borisov is carbon-chain depleted and enriched in NH$_2$ relative to water.

[51]  arXiv:2001.04876 [pdf, other]

Title: Collective Oscillations of Majorana Neutrinos in Strong Magnetic Fields and Self-induced Flavor Equilibrium

Authors: Sajad Abbar

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We study collective oscillations of Majorana neutrinos in some of the most extreme astrophysical sites such as neutron star merger remnants and magneto-rotational core-collapse supernovae which include dense neutrino media in the presence of strong magnetic fields. We show that neutrinos can reach flavor equilibrium if neutrino transition magnetic moment $\mu_\nu$ is strong enough, namely when $\mu_\nu/\mu_{\rm{B}} \gtrsim 10^{-14}-10^{-15}$ with $\mu_{\rm{B}}$ being the Bohr magneton. This sort of flavor equilibrium, which is not necessarily flavor equipartition, can occur on (short) scales determined by the strength of the magnetic term. Our findings can have interesting implications for the physics of such violent astrophysical environments.

[52]  arXiv:2001.04895 [pdf, other]

Title: Formation of COMs through CO hydrogenation on interstellar grains

Authors: M.A.J. Simons, T. Lamberts, H.M. Cuppen

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Glycoaldehyde, ethylene glycol, and methyl formate are complex organic molecules that have been observed in dark molecular clouds. Because there is no efficient gas-phase route to produce these species, it is expected that a low-temperature surface route existst that does not require energetic processing. CO hydrogenation experiments at low temperatures showed that this is indeed the case. Glyoxal can form through recombination of two HCO radicals and is then further hydrogenated. Here we aim to constrain the methyl formate, glycolaldehyde, and ethylene glycol formation on the surface of interstellar dust grains through this cold and dark formation route. We also probe the dependence of the grain mantle composition on the initial gas-phase composition and the dust temperature. A full CO hydrogenation reaction network was built based on quantum chemical calculations for the rate constants and branching ratios. This network was used in combination with a microscopic kinetic Monte Carlo simulation to simulate ice chemistry, taking into account all positional information. After benchmarking the model against CO-hydrogenation experiments, simulations under molecular cloud conditions were performed. COMs are formed in all interstellar conditions we studied, even at temperatures as low as 8 K. This is because the HCO + HCO reaction can occur when HCO radicals are formed close to each other and do not require to diffuse. Relatively low abundances of methyl formate are formed. The final COM abundances depend more on the H-to-CO ratio and less on temperature. Only above 16 K, where CO build-up is less efficient, does temperature start to play a role. Molecular hydrogen is predominantly formed through abstraction reactions on the surface. Our simulations are in agreement with observed COM ratios for mantles that have been formed at low temperatures.

[53]  arXiv:2001.04912 [pdf, other]

Title: The BRITE-SONG of Aldebaran -- Stellar Music in three voices

Authors: P. G. Beck, R. Kuschnig, G. Houdek, T. Kallinger, W. W. Weiss, P. L. Palle, F. Grundahl, A. Hatzes, H. Parviainen, C. Allende Prieto, H. J. Deeg, A. Jiménez, S. Mathur, R. A. Garcia, T. R. White, T. R. Bedding, D. H. Grossmann, S. Janisch, T. Zaqarashvili, A. Hanslmeier, K. Zwintz, the BRITE, SONG teams

Comments: Proceedings paper for an oral contribution at the 'Stars and their Variability' conference in August 2019, in Vienna Austria. Five pages, two colored figures

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Solar-like oscillations in red-giant stars are now commonly detected in thousands of stars with space telescopes such as the NASA Kepler mission. Parallel radial velocity and photometric measurements would help to better understand the physics governing the amplitudes of solar-like oscillators. Yet, most target stars for space photometry are too faint for light-demanding ground-based spectroscopy. The BRITE Constellation satellites provide a unique opportunity of two-color monitoring of the flux variations of bright luminous red giants. Those targets are also bright enough to be monitored with high-resolution spectrographs on small telescopes, such as the SONG Network. In these proceedings, we provide a first overview of our comprehensive, multi-year campaign utilizing both BRITE and SONG to seismically characterize Aldebaran, one of the brightest red giants in the sky. Because luminous red giants can be seen at large distances, such well-characterized objects will serve as benchmark stars for galactic archeology.

[54]  arXiv:2001.04962 [pdf, other]

Title: Temperatures and Metallicities of M dwarfs in the APOGEE Survey

Authors: Jessica Birky, David W. Hogg, Andrew W. Mann, Adam Burgasser

Comments: 26 pages, 37 figures, ApJ under review

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

M dwarfs have enormous potential for understanding structure and formation on both Galactic and exoplanetary scales through their properties and compositions. However, current atmosphere models have limited ability to reproduce spectral features in stars at the coolest temperatures ($T_{\rm eff} < 4200$K) and to fully exploit the information content of current and upcoming large-scale spectroscopic surveys. Here we present a catalog of spectroscopic temperatures, metallicities, and spectral types for 5,875 M dwarfs in the APOGEE + Gaia DR2 surveys using The Cannon: a flexible, data-driven spectral-modeling and parameter-inference framework demonstrated to estimate stellar-parameter labels ($T_{\rm eff}$, logg, [Fe/H], and detailed abundances) to high precision. Using a training sample of 87 M dwarfs with optically derived labels spanning $2860 < T_{\rm eff} < 4130$K calibrated with bolometric temperatures, and $-0.5 < [Fe/H] < 0.5$dex calibrated with FGK binary metallicities, we train a two-parameter model with predictive accuracy (in cross-validation) to 77K and 0.09dex respectively. We also train a one-dimensional spectral classification model using 51 M dwarfs with SDSS optical spectral types ranging from M0 to M6, to predictive accuracy of 0.7 types. We find Cannon temperatures to be in agreement to within 60K compared to a subsample of 1,702 sources with color-derived temperatures, and Cannon metallicites to be in agreement to within 0.08dex metallicity compared to a subsample of 15 FGK+M or M+M binaries. Finally, our comparison between Cannon and APOGEE pipeline (ASPCAP) labels finds that ASPCAP is systematically biased towards reporting higher temperatures and lower metallicities for M dwarfs.

[55]  arXiv:2001.04965 [pdf, other]

Title: Interpreting Observations of Absorption Lines in the Circumgalactic Medium with a Turbulent Medium

Authors: Edward Buie II, Michele Fumagalli, Evan Scannapieco

Comments: 19 pages, 13 figures, accepted in ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Single-phase photoionization equilibrium (PIE) models are often used to infer the underlying physical properties of galaxy halos probed in absorption with ions at different ionization potentials. To incorporate the effects of turbulence, we use the MAIHEM code to model an isotropic turbulent medium exposed to a redshift zero metagalactic UV background, while tracking the ionizations, recombinations, and species-by-species radiative cooling for a wide range of ions. By comparing observations and simulations over a wide range of turbulent velocities, densities, and metallicity with a Markov chain Monte Carlo technique, we find that MAIHEM models provide an equally good fit to the observed low-ionization species compared to PIE models, while reproducing at the same time high-ionization species such as \ion{Si}{4} and \ion{O}{6}. By including multiple phases, MAIHEM models favor a higher metallicity ($Z/Z_\odot \approx 40\%$) for the circumgalactic medium compared to PIE models. Furthermore, all of the solutions require some amount of turbulence ($\sigma_{\rm 3D} \geqslant 26\ {\rm km}\ {\rm s}^{-1}$). Correlations between turbulence, metallicity, column density, and impact parameter are discussed alongside mechanisms that drive turbulence within the halo.

[56]  arXiv:2001.04966 [pdf, ps, other]

Title: The Large Scale Behaviour in the Disk of $δ$ Scorpii from 2000-2018

Authors: M.W. Suffak, C.E. Jones, C. Tycner, G.W. Henry, A.C. Carciofi, B.C. Mota, A.C. Rubio

Comments: 16 pages, 12 figures, 4 tables, accepted for publishing in ApJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We model the circumstellar disk of $\delta$ Sco using the 3-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large scale changes in the disk through the years 2000 to 2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models through matching simulated observations to actual H$\rm \alpha$ spectroscopy and V-band photometric observations. Our modelling results confirm previous findings that the disk of $\delta$ Sco was forming early in the century. We also find a period of disk dissipation when the companion is at apastron, as well as a significant growth of the disk between 2009 and 2011, prior to the periastron of 2011. Due to the steady-state nature of the disk after 2011, it is difficult to say whether the variations seen are due to the effect of the close passage of the binary companion.

[57]  arXiv:2001.04973 [pdf, other]

Title: On the Inference of a Star's Inclination Angle from its Rotation Velocity and Projected Rotation Velocity

Authors: Kento Masuda (IAS), Joshua N. Winn (Princeton)

Comments: accepted for publication in AJ [7 pages]

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

It is possible to learn about the orientation of a star's rotation axis by combining measurements of the star's rotation velocity ($v$) and its projection onto our line of sight ($v\sin i$). This idea has found many applications, including the investigation of the obliquities of stars with transiting planets. Here, we present a method for the probabilistic inference of the inclination of the star's rotation axis based on independent data sets that constrain $v$ and $v\sin i$. We also correct several errors and misconceptions that appear in the literature.

[58]  arXiv:2001.04975 [pdf, ps, other]

Title: Central molecular zones in galaxies: 12CO-to-13CO ratios, carbon budget, and X factors

Authors: F.P. Israel (Sterrewacht Leiden, Leiden University (NL))

Comments: Main paper 23 pages including 17 figures, appendices 18 pages

Subjects: Astrophysics of Galaxies (astro-ph.GA)

This paper presents ground-based 12CO and 13CO measurements of 126 nearby galaxy centers in various J transitions. More than 60 galaxies were measured in at least four lines. The average relative intensities of the first four 12CO transitions are 1.00 : 0.92 : 0.70 : 0.57. The average 12CO-to-13CO ratios are 13.0, 11.6, and 12.8 for the first three transitiions. The sizes of central CO concentrations are well defined in maps, but poorly determined by multi-aperture photometry. Using radiative transfer models (RADEX), we derived model gas parameters, where the assumed carbon elemental abundances and carbon gas depletion onto dust are the main causes of uncertainty. The new CO data and published [CI] and [CII] data imply that CO, Co, and C+ each represent about one-third of the gas-phase carbon in the molecular interstellar medium in galaxy centers Their mean beam-averaged central molecular hydrogen column density is N(H2) = (1.5+/-0.2) x 10^(21) cm^(2) and CO-to-H2 conversion factors are typically ten times lower than the `standard' Milky Way disk value, with a mean X(CO) = (1.9+/-0.2) x 10^(19) cm^(2)/K km/s. The corresponding [CI]-to-H2 factor is five times higher than X(CO), with X[CI] = (9+/-2) x 10^(19) cm^(2)/K km/s. No unique conversion factor can be determined for [CII]. The low molecular gas content of galaxy centers relative to their CO intensities is explained in roughly equal parts by higher central gas-phase carbon abundances, elevated gas temperatures, and larger gas velocity dispersions than found in galaxy disks.

Cross-lists for Wed, 15 Jan 20

[59]  arXiv:2001.04466 (cross-list from hep-ph) [pdf, other]

Title: Precision Early Universe Thermodynamics made simple: $N_{\rm eff}$ and Neutrino Decoupling in the Standard Model and beyond

Authors: Miguel Escudero

Comments: 23 pages, 7 figures, 2 tables, 6 appendices. Comments are welcome! NUDEC_BSM code can be found at this https URL . Ancillary file contains the SM evolution as relevant for BBN

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Precision measurements of the number of effective relativistic neutrino species and the primordial element abundances require accurate theoretical predictions for early Universe observables in the Standard Model and beyond. Given the complexity of accurately modelling the thermal history of the early Universe; in this work, we extend a previous method presented by the author to obtain simple, fast and accurate early Universe thermodynamics. The method is based upon the approximation that all relevant species can be described by thermal equilibrium distribution functions characterized by a temperature and a chemical potential. We apply the method to neutrino decoupling in the Standard Model and find $N_{\rm eff}^{\rm SM} = 3.045$ -- a result in excellent agreement with previous state-of-the-art calculations. We apply the method to study the thermal history of the Universe in the presence of a very light ($1\,\text{eV}<m_\phi < 1\,\text{MeV}$) and weakly coupled ($\lambda \lesssim 10^{-9}$) neutrinophilic scalar. We find our results to be in excellent agreement with the solution to the exact Liouville equation. Finally, we release a code: NUDEC_BSM (available in both Mathematica and Python formats), with which neutrino decoupling can be accurately and efficiently solved in the Standard Model and beyond: https://github.com/MiguelEA/nudec_BSM .

[60]  arXiv:2001.04492 (cross-list from hep-ph) [pdf, other]

Title: On dark atoms, massive dark photons and millicharged sub-components

Authors: Felix Kahlhoefer, Einar Urdshals

Comments: 10 pages, 3 figures

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a simple model of two dark matter species with opposite millicharge that can form electrically neutral bound states via the exchange of a massive dark photon. If bound state formation is suppressed at low temperatures, a sub-dominant fraction of millicharged particles remains at late times, which can give rise to interesting features in the 21 cm absorption profile at cosmic dawn. The dominant neutral component, on the other hand, can have dipole interactions with ordinary matter, leading to non-standard signals in direct detection experiments. We identify the parameter regions predicting a percent-level ionisation fraction and study constraints from laboratory searches for dark matter scattering and dark photon decays.

[61]  arXiv:2001.04494 (cross-list from gr-qc) [pdf, other]

Title: Scalar correlation functions for a double-well potential in de Sitter space

Authors: Tommi Markkanen, Arttu Rajantie

Comments: 21 pages, 12 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

We use the spectral representation of the stochastic Starobinsky-Yokoyama approach to compute correlation functions in de Sitter space for a scalar field with a symmetric or asymmetric double-well potential. The terms in the spectral expansion are determined by the eigenvalues and eigenfunctions of the time-independent Fokker-Planck differential operator, and we solve them numerically. The long-distance asymptotic behaviour is given by the lowest state in the spectrum, but we demonstrate that the magnitude of the coeffients of different terms can be very different, and the correlator can be dominated by different terms at different distances. This can give rise to potentially observable cosmological signatures. In many cases the dominant states in the expansion do not correspond to small fluctuations around a minimum of the potential and are therefore not visible in perturbation theory. We discuss the physical interpretation these states, which can be present even when the potential has only one minimum.

[62]  arXiv:2001.04741 (cross-list from hep-ph) [pdf, other]

Title: Gravitational Waves from first-order phase transition and domain wall

Authors: Ruiyu Zhou, Jing Yang, Ligong Bian

Comments: 21 pages, 8 figures, comments welcome

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In many particle physics models, domain wall can form during the phase transition process after discrete symmetry breaking. We study the scenario within a complex singlet extended Standard Model framework, where a strongly first order phase transition can occur depending on the hidden scalar mass and the mixing between the extra heavy Higgs and the SM Higgs mass. The gravitational wave spectrum is of a typical two-peak shape, the amplitude and the peak from the strongly first order phase transition is able to be probed by the future gravitational wave detectors, and the one locates around the peak from the domain wall decay is far beyond the capability of the projected IPTA, and SKA.

[63]  arXiv:2001.04864 (cross-list from nucl-th) [pdf, other]

Title: QED2 boson description of the X17 particle and dark matter

Authors: Cheuk-Yin Wong

Comments: 9 pages, 1 figure

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)

The oscillations of the color charges and electric charges of the quark and antiquarks of the underlying vacuum in a flux tube generate QCD2 bosons (mesons) and QED2 bosons (Phys.Rev.C81,064903(2010)). The predicted mass of the isoscalar QED2 boson in the flux tube environment is close to the X17 mass, leading to the suggestion that the X17 particle may be the isoscalar $I(J^\pi)$=0(0$^-$) QED2 boson arising from the oscillation of the electric charges of the quarks and antiquarks of the vacuum in the flux tube that mediates the meson-exchange interaction between the nucleon and the nuclear core in the excited 0(0$^-$) state of $^4$He. The isoscalar 0(0$^-$) QED2 boson can decay into an electron-positron pair or two photons in free space but the decays will be inhibited if the gravitational binding energy of the QED2 boson bound in a QED2 boson assembly exceeds its rest mass. Consequently, a self-gravitating isoscalar QED2 boson assembly whose mass $M$ and radius $R$ satisfy $(M/M_\odot)/(R/R_\odot) \gtrsim 4.71 \times 10^5$ will not produce electron-positron pairs or photons and may be a good candidate for a primordial dark matter.

[64]  arXiv:2001.04868 (cross-list from hep-ph) [pdf, other]

Title: Lightening Gravity-Mediated Dark Matter

Authors: Yoo-Jin Kang, Hyun Min Lee

Comments: 37 pages, 8 figures

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

We revisit the scenario of a massive spin-2 particle as the mediator for communicating between dark matter of arbitrary spin and the Standard Model. Taking the general couplings of the spin-2 particle in the effective theory, we discuss the thermal production mechanisms for dark matter with various channels and the dark matter self-scattering. For WIMP and light dark matter cases, we impose the relic density condition and various experimental constraints from direct and indirect detections, precision measurements as well as collider experiments. We show that it is important to include the annihilation of dark matter into a pair of spin-2 particles in both allowed and forbidden regimes, thus opening up the consistent parameter space for dark matter. The UV complete models of the spin-2 mediator are presented in the context of the warped extra dimension and compared to the simplified models.

[65]  arXiv:2001.04902 (cross-list from hep-th) [pdf, other]

Title: Yang-Mills Classical and Quantum Mechanics and Maximally Chaotic Dynamical Systems

Authors: George Savvidy

Comments: 13 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:2001.01785

Subjects: High Energy Physics - Theory (hep-th); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Lattice (hep-lat); Chaotic Dynamics (nlin.CD)

The maximally chaotic dynamical systems (DS) are the systems which have nonzero Kolmogorov entropy. The Anosov C-condition defines a reach class of hyperbolic dynamical systems that have exponential instability of the phase trajectories and positive Kolmogorov entropy and are therefore maximally chaotic. The interest in Anosov-Kolmogorov systems is associated with the attempts to understand the relaxation phenomena, the foundation of the statistical mechanics, the appearance of turbulence in fluid dynamics, the non-linear dynamics of the Yang-Mills field, the N-body system in Newtonian gravity and the relaxation phenomena in stellar systems and the Black hole thermodynamics. The classical- and quantum-mechanical properties of maximally chaotic dynamical systems, the application of the C-K theory to the investigation of the Yang-Mills dynamics and gravitational systems as well as their application in the Monte Carlo method will be presented.

[66]  arXiv:2001.04946 (cross-list from hep-ph) [pdf, other]

Title: Gamma-Ray Lines Generated from One-Step Cascade Annihilations of Secluded (Vector) Dark Matter via the Higgs Portal

Authors: Kwei-Chou Yang

Comments: 36, pages, 8 figures, 1 table

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

We consider a Higgs portal (vector) dark matter (DM) model where the hidden scalar, nearly degenerate with DM in mass, mediates the interaction of the secluded DM with Standard Model (SM) due to its mixing with the SM Higgs. We find that the parameter region $m_X\in[60, 132] \text{GeV}$ can provide a good fit to the Fermi Galactic center gamma-ray excess spectrum, appearing a prominent gamma-ray line with the energy $\in [30, 66]$ GeV. The best fit gives $m_X\simeq m_S \simeq 86$ GeV with a $p$-value$\, =0.42$, so that the resultant gamma-ray line, arising from the decay of the scalar mediator into $\gamma\gamma$, peaks at 43 GeV. We derive constraints on the annihilation cross section from the Fermi-LAT gamma-ray line search, gamma-ray observations of the Fermi-LAT dwarf spheroidal galaxies, and Planck cosmic microwave background measurement. For the secluded vector DM model, the parameter space constrained by the current XENON1T and future LUX-ZEPLIN is shown. Finally, for the mixing angle between the Higgs sectors, we discuss its lower bound, which is required by the big bang nucleosynthesis constraint and relevant to the hidden sector decoupling temperature.

Replacements for Wed, 15 Jan 20

[67]  arXiv:1708.05513 (replaced) [pdf, other]

Title: Yarkovsky Drift Detections for 247 Near-Earth Asteroids

Authors: Adam H. Greenberg, Jean-Luc Margot, Ashok K. Verma, Patrick A. Taylor, Susan E. Hodge

Comments: 27 pages, 9 figures, in press at the Astronomical Journal

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[68]  arXiv:1710.11072 (replaced) [pdf, other]

Title: Thermodynamic potential for quark-gluon plasma with finite quark masses and chemical potential

Authors: Mayukh R. Gangopadhyay, Grant J. Mathews, J. Pocahontas Olson

Comments: 16 pages, 6 figures

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[69]  arXiv:1809.08542 (replaced) [pdf, other]

Title: Modelling strains and stresses in continuously stratified rotating neutron stars

Authors: Elia Giliberti, Gabriele Cambiotti, Marco Antonelli, Pierre Pizzochero

Comments: 16 pages, 12 figures

Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 1, January 2020, Pages 1064-1078

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[70]  arXiv:1811.00050 (replaced) [pdf, other]

Title: Linking gravitational waves and X-ray phenomena with joint LISA and Athena observations

Authors: Sean McGee, Alberto Sesana, Alberto Vecchio

Comments: Published in Nature Astronomy

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

[71]  arXiv:1812.08141 (replaced) [pdf, other]

Title: Study in the noncanonical domain of Goldstone inflation

Authors: Sukannya Bhattacharya, Mayukh R. Gangopadhyay

Comments: 19 pages, 8 figures, PRD accepted version

Journal-ref: Phys. Rev. D 101, 023509 (2020)

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

[72]  arXiv:1812.09488 (replaced) [pdf, ps, other]

Title: The role of some collisional processes in AGNs: rate coefficients needed for modeling

Authors: M. S. Dimitrijevic, V. A. Sreckovic, Lj. M. Ignjatovic, B. P. Marinkovic

Comments: 17 pages, 3 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[73]  arXiv:1901.05792 (replaced) [pdf, other]

Title: A comparison between short GRB afterglows and AT2017gfo: shedding light on kilonovae properties

Authors: A. Rossi, G. Stratta, E. Maiorano, D. Spighi, N. Masetti, E. Palazzi, A. Gardini, A. Melandri, L. Nicastro, E. Pian, M. Branchesi, M. Dadina, V. Testa, S. Brocato, S. Benetti, R. Ciolfi, S. Covino, V. D'Elia, A. Grado, L. Izzo, A. Perego, S. Piranomonte, R. Salvaterra, J. Selsing, L. Tomasella, S. Yang, D. Vergani, L. Amati, J. B. Stephen

Comments: 41 pages, 14 figures, submitted to MNRAS. Includes a table with updated short GRB optical/NIR photometry and one with AT2017gfo light curves in UBVRIgrizJHK filters. Updated constraints on luminosity of AT2017gfo-like kilonovae. Updated sample of kilonova candidates

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[74]  arXiv:1902.00181 (replaced) [pdf, other]

Title: Using tours to visually investigate properties of new projection pursuit indexes with application to problems in physics

Authors: Ursula Laa, Dianne Cook

Comments: 39 pages, 13 figures

Subjects: Methodology (stat.ME); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph); Data Analysis, Statistics and Probability (physics.data-an)

[75]  arXiv:1903.06679 (replaced) [pdf, other]

Title: Anisotropic massive Brans-Dicke gravity extension of the standard $Λ$CDM model

Authors: Ozgur Akarsu, Nihan Katirci, Nese Ozdemir, J. Alberto Vazquez

Comments: 27 pages, 6 figures, 1 table

Journal-ref: Eur. Phys. J. C 80 (2020) 32

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[76]  arXiv:1904.03201 (replaced) [pdf, other]

Title: Halo Spin from Primordial Inner Motions

Authors: Mark C. Neyrinck, Miguel A. Aragon-Calvo, Bridget Falck, Jie Wang, Alexander S. Szalay

Comments: Revisions, updated references. 3 movies at this https URL Comments welcome!

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

[77]  arXiv:1907.02018 (replaced) [pdf, other]

Title: The peculiar acceleration of stellar-origin black hole binaries: measurement and biases with LISA

Authors: Nicola Tamanini, Antoine Klein, Camille Bonvin, Enrico Barausse, Chiara Caprini

Comments: 21 pages, 2 figures, 3 tables; v2 matches published version

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)

[78]  arXiv:1907.02417 (replaced) [pdf, other]

Title: Simple Gradient Flow Equation for the Bounce Solution

Authors: Ryosuke Sato

Comments: 6 pages, 8 figures; the version published in PRD

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)

[79]  arXiv:1907.09621 (replaced) [pdf, other]

Title: Galaxy Clusters Selected via the Sunyaev-Zel'dovich Effect in the SPTpol 100-Square-Degree Survey

Authors: N. Huang, L. E. Bleem, B. Stalder, P. A. R. Ade, S. W. Allen, A. J. Anderson, J. E. Austermann, J. S. Avva, J. A. Beall, A. N. Bender, B. A. Benson, F. Bianchini, S. Bocquet, M. Brodwin, J. E. Carlstrom, C. L. Chang, H. C. Chiang, R. Citron, C. Corbett Moran, T. M. Crawford, A. T. Crites, T. de Haan, M. A. Dobbs, W. Everett, B. Floyd, J. Gallicchio, E. M. George, A. Gilbert, M. D. Gladders, S. Guns, N. Gupta, N. W. Halverson, N. Harrington, J. W. Henning, G. C. Hilton, G. P. Holder, W. L. Holzapfel, J. D. Hrubes, J. Hubmayr, K. D. Irwin, G. Khullar, L. Knox, A. T. Lee, D. Li, A. Lowitz, M. McDonald, J. J. McMahon, S. S. Meyer, L. M. Mocanu, J. Montgomery, A. Nadolski, T. Natoli, J. P. Nibarger, G. Noble, V. Novosad, S. Padin, S. Patil, C. Pryke, C. L. Reichardt, J. E. Ruhl, B. R. Saliwanchik, et al. (16 additional authors not shown)

Comments: 21 pages, 7 figures, associated data available at this http URL V2 was accepted to the AJ, and includes minor changes requested by the reviewer

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[80]  arXiv:1908.08952 (replaced) [pdf, other]

Title: Gravity and the Nonlinear Growth of Structure in the Carnegie-Spitzer-IMACS Redshift Survey

Authors: Daniel D. Kelson, Louis E. Abramson, Andrew J. Benson, Shannon G. Patel, Stephen A. Shectman, Alan Dressler, Patrick J. McCarthy, John S. Mulchaey, Rik J. Williams

Comments: 13 pages, 12 figures, submitted to Monthly Notices of the Royal Astronomical Society, 23 August 2019, and accepted for publication, 9 January 2020

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

[81]  arXiv:1909.03072 (replaced) [pdf, ps, other]

Title: On Reverberation Mapping Lag Uncertainties

Authors: Zhefu Yu, C. S. Kochanek, B. M. Peterson, Y. Zu, W. N. Brandt, E. M. Cackett, M. M. Fausnaugh, I. M. McHardy

Comments: 22 pages, 17 figures

Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 4, February 2020, Pages 6045-6064

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[82]  arXiv:1909.04624 (replaced) [pdf, other]

Title: Statistical Analysis of Stochastic Magnetic Fields

Authors: Amir Jafari, Ethan Vishniac, Vignesh Vaikundaraman

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[83]  arXiv:1909.04684 (replaced) [pdf, other]

Title: Dark Shards: velocity substructure from Gaia and direct searches for dark matter

Authors: Ciaran A. J. O'Hare, N. Wyn Evans, Christopher McCabe, GyuChul Myeong, Vasily Belokurov

Comments: 27 pages, 14 figures, code available at this https URL

Journal-ref: Phys. Rev. D 101, 023006 (2020)

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)

[84]  arXiv:1909.07548 (replaced) [pdf, ps, other]

Title: Age Dating the Galactic Bar with the Nuclear Stellar Disc

Authors: Junichi Baba (NAOJ), Daisuke Kawata (MSSL, UCL)

Comments: accepted for publication in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[85]  arXiv:1909.09094 (replaced) [pdf, other]

Title: Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit

Authors: N. L. Eisner, O. Barragán, S. Aigrain, C. Lintott, G. Miller, N. Zicher, T. S. Boyajian, C. Briceño, E. M. Bryant, J. L. Christiansen, A. D. Feinstein, L. M. Flor-Torres, M. Fridlund, D. Gandolfi, J. Gilbert, N. Guerrero, J. M. Jenkins, K. Jones, M. H. Kristiansen, A. Vanderburg, N. Law, A. R. López-Sánchez, A. W. Mann, E. J. Safron, M. E. Schwamb, K. G. Stassun, H. P. Osborn, J. Wang, A. Zic, C. Ziegler, F. Barnet, S. J. Bean, D. M. Bundy, Z. Chetnik, J. L. Dawson, J. Garstone, A. G. Stenner, M. Huten, S. Larish, L. D. Melanson, T. Mitchell, C. Moore, K. Peltsch, D. J. Rogers, C. Schuster, D. S. Smith, D. J. Simister, C. Tanner, I. Terentev, A. Tsymbal

Comments: Accepted for publication in MNRAS (16 pages, 10 figures, 3 tables)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[86]  arXiv:1909.09210 (replaced) [pdf, other]

Title: ELMAG 3.01: A three-dimensional Monte Carlo simulation of electromagnetic cascades on the extragalactic background light and in magnetic fields

Authors: M. Blytt, M. Kachelriess, S. Ostapchenko

Comments: 9 pages, 5 figures. v2: minor changes, to appear in CPC; arxiv version contains an addendum describing version 3.02 which includes plasma energy losses; program available at this http URL

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[87]  arXiv:1909.10524 (replaced) [pdf, other]

Title: Weak lensing Analysis of X-ray-selected XXL Galaxy Groups and Clusters with Subaru HSC Data

Authors: Keiichi Umetsu (ASIAA), Mauro Sereno, Maggie Lieu, Hironao Miyatake, Elinor Medezinski, Atsushi J. Nishizawa, Paul Giles, Fabio Gastaldello, Ian G. McCarthy, Martin Kilbinger, Mark Birkinshaw, Stefano Ettori, Nobuhiro Okabe, I-Non Chiu, Jean Coupon, Dominique Eckert, Yutaka Fujita, Yuichi Higuchi, Elias Koulouridis, Ben Maughan, Satoshi Miyazaki, Masamune Oguri, Florian Pacaud, Marguerite Pierre, David Rapetti, Graham P. Smith

Comments: Version accepted by ApJ; a complete version of the weak-lensing mass table (Table 2) included, text expanded and improved. We recommend to use statistically corrected mass estimates (M200MT, M500MT) of Table 2 for a given individual cluster. One of two companion papers presenting initial HSC-XXL results (Mauro Sereno et al., arXiv:1912.02827)

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

[88]  arXiv:1909.11385 (replaced) [pdf, other]

Title: Super Hot Cores in NGC 253: Witnessing the formation and early evolution of Super Star Clusters

Authors: Fernando Rico-Villas, Jesus Martin-Pintado, Eduardo Gonzalez-Alfonso, Sergio Martin, Victor M. Rivilla

Comments: typos corrected, references added

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[89]  arXiv:1910.05049 (replaced) [pdf, other]

Title: Searching for Super-Eddington Quasars using a Photon Trapping Accretion Disc Model

Authors: Quentin Pognan, Benny Trakhtenbrot, Tullia Sbarrato, Kevin Schawinski, Caroline Bertemes

Comments: 24 pages, 13 figures, accepted by MNRAS 07/01/2020

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

[90]  arXiv:1910.07841 (replaced) [pdf, other]

Title: Tidal heating as a discriminator for horizons in extreme mass ratio inspirals

Authors: Sayak Datta, Richard Brito, Sukanta Bose, Paolo Pani, Scott A. Hughes

Comments: v2: 8+4 pages, 5 figures, one new plot. Version to appear in PRD

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

[91]  arXiv:1910.08708 (replaced) [pdf, other]

Title: Ringdown overtones, black hole spectroscopy, and no-hair theorem tests

Authors: Swetha Bhagwat, Xisco Jimenez Forteza, Paolo Pani, Valeria Ferrari

Comments: 19 pages, 18 figures (updated to the version in PRD)

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

[92]  arXiv:1910.10156 (replaced) [pdf, other]

Title: Reality or Mirage? Observational Test and Implications for the Claimed Extremely Magnified Quasar at $z = 6.3$

Authors: Fabio Pacucci, Abraham Loeb

Comments: Published in ApJ: 8 pages, 4 figures. This is the final, published version

Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

[93]  arXiv:1910.10157 (replaced) [pdf, other]

Title: Lessons from a blind study of simulated lenses: image reconstructions do not always reproduce true convergence

Authors: Philipp Denzel, Sampath Mukherjee, Jonathan P. Coles, Prasenjit Saha

Comments: 20 pages, 12 figures. Accepted for publication in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[94]  arXiv:1910.10979 (replaced) [pdf, other]

Title: Quantum transport and the phase space structure of the Wightman functions

Authors: Henri Jukkala, Kimmo Kainulainen, Olli Koskivaara

Comments: 27 pages, 9 figures; (v2) minor changes, results unchanged

Journal-ref: J. High Energ. Phys. (2020) 2020: 12

Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

[95]  arXiv:1910.11873 (replaced) [pdf, other]

Title: Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Authors: D. Moździerski, A. Pigulski, Z. Kołaczkowski, G. Michalska, G. Kopacki, F. Carrier, P. Walczak, A. Narwid, M. Stęślicki, J.-N. Fu, X.-J. Jiang, Ch. Zhang, J. Jackiewicz, J. Telting, T. Morel, S. Saesen, E. Zahajkiewicz, P. Bruś, P. Śródka, M. Vučković, T. Verhoelst, V. Van Helshoecht, K. Lefever, C. Gielen, L. Decin, J. Vanautgaerden, C. Aerts

Comments: 22 pages, 24 figures. Caution: arXiv abstract is shorter than in the article

Journal-ref: A&A 632, A95 (2019)

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

[96]  arXiv:1912.01851 (replaced) [pdf, other]

Title: A Variant Stellar-to-nebular Dust Attenuation Ratio on Subgalactic and Galactic Scales

Authors: Zesen Lin, Xu Kong (USTC)

Comments: Accepted for publication in ApJ, updated to match the final version

Journal-ref: ApJ, 888, 88 (2020)

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[97]  arXiv:1912.05884 (replaced) [pdf, other]

Title: Hot Super-Earths with Hydrogen Atmospheres: A Model Explaining Their Paradoxical Existence

Authors: Darius Modirrousta-Galian, Daniele Locci, Giovanna Tinetti, Giuseppina Micela

Comments: 20 pages, 15 figures

Journal-ref: The Astrophysical Journal, 888:87 (14pp), 2020

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[98]  arXiv:1912.06161 (replaced) [pdf, ps, other]

Title: Detection of Diatomic Carbon in 2I/Borisov

Authors: Hsing Wen Lin, Chien-Hsiu Lee, David W. Gerdes, Fred C. Adams, Juliette Becker, Kevin Napier, Larissa Markwardt

Comments: 8 pages, 3 figures, accepted for publication in Astrophysical Journal Letters

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[99]  arXiv:1912.07674 (replaced) [pdf]

Title: The Legacy of Einstein's Eclipse, Gravitational Lensing

Authors: Jorge L. Cervantes-Cota, Salvador Galindo-Uribarri, George F. Smoot

Comments: 45 pages, 26 figures, Feature Papers 2019 - Gravitational Physics

Journal-ref: Universe 2020, 6(1), 9

Subjects: History and Philosophy of Physics (physics.hist-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[100]  arXiv:2001.02242 (replaced) [pdf, other]

Title: KASHz: No evidence for ionised outflows instantaneously suppressing star formation in moderate luminosity AGN at $z$$\sim$$1.4$-$2.6$

Authors: J. Scholtz, C.M. Harrison, D.J. Rosario, D.M. Alexander, C-C. Chen, D. Kakkad, V. Mainieri, A.L. Tiley, O. Turner, M. Cirasuolo, R.M. Sharples, S. Stach

Comments: Accepted for publication by MNRAS, 24 pages, 12 Figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[101]  arXiv:2001.02947 (replaced) [pdf, ps, other]

Title: Type Ia Supernova Sub-classes and Progenitor Origin

Authors: Ashley J. Ruiter

Comments: v2: a few references added. 12 pages text + references (total 15 pages); 3 figures, 1 table. Proceedings article based on invited review talk for the IAU Symposium 357, "White Dwarfs as Probes of Fundamental Physics and Tracers of Planetary, Stellar, and Galactic Evolution," held in Hilo, Hawaii, 21-25 October 2019

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

[102]  arXiv:2001.03116 (replaced) [pdf, other]

Title: Deep learning for clustering of continuous gravitational wave candidates

Authors: Banafsheh Beheshtipour, Maria Alessandra Papa

Subjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an)

[103]  arXiv:2001.03177 (replaced) [pdf, other]

Title: The Chemical Compositions of Accreted and {\it in situ} Galactic Globular Clusters According to SDSS/APOGEE

Authors: Danny Horta, Ricardo P. Schiavon, J. Ted Mackereth, Timothy C. Beers, José G. Fernández-Trincado, Peter M. Frinchaboy, D.A. García-Hernández, Doug Geisler, Sten Hasselquist, Henrik Jönsson, Richard R. Lane, Steven R. Majewski, Szabolcs Mészáros, Christian Moni Bidin, David M. Nataf, Alexandre Roman-Lopes, Christian Nitschelm, Gail Zasowski

Comments: 18 pages, 10 figures, 3 tables. Re-submitted to MNRAS following moderate revisions

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[104]  arXiv:2001.03683 (replaced) [pdf, other]

Title: The Swift Bulge Survey: optical and near-IR follow-up featuring a likely symbiotic X-ray binary & a focused wind CV

Authors: A. W. Shaw, C. O. Heinke, T. J. Maccarone, G. R. Sivakoff, J. Strader, A. Bahramian, N. Degenaar, J. A. Kennea, E. Kuulkers, A. Rau, L. E. Rivera Sandoval, L. Shishkovsky, S. J. Swihart, A. J. Tetarenko, R. Wijnands, J. J. M. in 't Zand

Comments: 18 pages, 11 figures, accepted for publication in MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

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