RAS_WEB (Page 4,387)

Recent VLBI Results on SN 1986J and the Possibility of FRBs Originating from Inside the Expanding Ejecta of Supernovae. (arXiv:1905.06690v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Bietenholz_M/0/1/0/all/0/1">Michael F. Bietenholz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bartel_N/0/1/0/all/0/1">Norbert Bartel</a> We discuss our VLA and VLBI observations of supernova 1986J, which is characterized by a compact radio-bright component within the expanding shell of ejecta. No other supernova (SN) has such a central component at cm wavelengths. The central component therefore provides a unique probe of the propagation of radio signals at cm wavelengths through the ejecta of a young SN. Such a probe is important in the context of Fast Radio Bursts (FRB), which, in many models,Read More →

Satellite monitoring of atmospheric temperature profiles and cloud cover over the Yakutsk EAS array and the TAIGA observatory. (arXiv:1905.06694v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Lagutin_A/0/1/0/all/0/1">Anatoly A. Lagutin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Volkov_N/0/1/0/all/0/1">Nikolay V. Volkov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhukov_A/0/1/0/all/0/1">Andrey P. Zhukov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Makushev_K/0/1/0/all/0/1">Konstantin M. Makushev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maslov_A/0/1/0/all/0/1">Alexander A. Maslov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mordvin_E/0/1/0/all/0/1">Egor Yu. Mordvin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raikin_R/0/1/0/all/0/1">Roman I. Raikin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Serebryakova_T/0/1/0/all/0/1">Tatyana L. Serebryakova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sinitsin_V/0/1/0/all/0/1">Vladimir V. Sinitsin</a> We consider the problem of night-time atmosphere monitoring at the locations of the Yakutsk EAS array and the TAIGA observatory for the annual October-April period of observations at these facilities. It is shown that the use of data from instruments aboard Terra, Aqua, Suomi-NPP and NOAA-20 satellites, received byRead More →

Origin of hardening and universality of cosmic rays spectra in GV-PV rigidity region. (arXiv:1905.06699v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Lagutin_A/0/1/0/all/0/1">A A Lagutin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Volkov_N/0/1/0/all/0/1">N V Volkov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raikin_R/0/1/0/all/0/1">R I Raikin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tyumentsev_A/0/1/0/all/0/1">A G Tyumentsev</a> Recent balloon-borne and satellite experiments have established new features in the behavior of the spectra of cosmic rays. An analysis of all the data showed that hardening of most abundant primary cosmic ray nuclei spectra with increasing rigidity is observed in $>200$ GV region. At the same time, rigidity dependencies of secondary cosmic rays are distinctly different. The AMS-02 data show that above 200 GV the secondary cosmic rays Li, Be, B harden moreRead More →

Hot UV-bright stars of galactic globular clusters. (arXiv:1905.06718v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Moehler_S/0/1/0/all/0/1">S. Moehler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Landsman_W/0/1/0/all/0/1">W. B. Landsman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lanz_T/0/1/0/all/0/1">T. Lanz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bertolami_M/0/1/0/all/0/1">M. M. Miller Bertolami</a> We have performed a census of the UV-bright population in 78 globular clusters using wide-field UV telescopes. This population includes a variety of phases of post-horizontal branch (HB) evolution, including hot post-asymptotic giant branch (AGB) stars, and post-early AGB stars. There are indications that old stellar systems like globular clusters produce fewer post-(early) AGB stars than currently predicted by evolutionary models, but observations are still scarce. We obtained FORS2 spectroscopy of eleven of these UV-selected objects (covering a range of -2.3Read More →

K2 rotation periods for low-mass Hyads and a quantitative comparison of the distribution of slow rotators in the Hyades and Praesepe. (arXiv:1905.06736v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Douglas_S/0/1/0/all/0/1">S. T. Douglas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Curtis_J/0/1/0/all/0/1">J. L. Curtis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Agueros_M/0/1/0/all/0/1">M. A. Ag&#xfc;eros</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cargile_P/0/1/0/all/0/1">P. A. Cargile</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brewer_J/0/1/0/all/0/1">J. M. Brewer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Meibom_S/0/1/0/all/0/1">S. Meibom</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jansen_T/0/1/0/all/0/1">T. Jansen</a> We analyze K2 light curves for 132 low-mass ($1 gtrsim M_* gtrsim 0.1$~${M_{odot}}$) members of the 600–800~Myr-old Hyades cluster and measure rotation periods ($P_{rot}$) for 116 of these stars. These include 93 stars with no prior $P_{rot}$ measurement; the total number of Hyads with known $P_{rot}$ is now 232. We then combine literature binary data withRead More →

Average shape of longitudinal shower profiles measured at the Pierre Auger Observatory. (arXiv:1905.06752v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Andringa_S/0/1/0/all/0/1">Sofia Andringa</a> (on behalf of the Pierre Auger Collaboration) The average profiles of cosmic ray shower development as a function of atmospheric depth are measured for the first time with the Fluorescence Detectors at the Pierre Auger Observatory. The profile shapes are well reproduced by the Gaisser-Hillas parametrization at the 1% level in a 500 g/cm2 interval around the shower maximum, for cosmic rays with log(E/eV) > 17.8. The results are quantified with two shape parameters, measured as a function of energy. The average profiles carry information on the primaryRead More →

ALMA detection of dark chromospheric holes in the quiet Sun. (arXiv:1905.06763v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Loukitcheva_M/0/1/0/all/0/1">Maria A. Loukitcheva</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+White_S/0/1/0/all/0/1">Stephen M. White</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Solanki_S/0/1/0/all/0/1">Sami K. Solanki</a> We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of a quiet-Sun region at a wavelength of 3 mm, obtained during the first solar ALMA cycle on April 27, 2017, and compare them with available chromospheric observations in the UV and visible as well as with photospheric magnetograms. ALMA images clearly reveal the presence of distinct particularly dark/cool areas in the millimeter maps having temperatures as low as 60% of the normal quiet Sun at 3 mm, which are not seen inRead More →

Extension of the HCOOH and CO2 solid-state reaction network during the CO freeze-out stage: inclusion of H2CO. (arXiv:1905.06767v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Qasim_D/0/1/0/all/0/1">D. Qasim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lamberts_T/0/1/0/all/0/1">T. Lamberts</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chuang_K/0/1/0/all/0/1">K.-J. Chuang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fedoseev_G/0/1/0/all/0/1">G. Fedoseev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ioppolo_S/0/1/0/all/0/1">S. Ioppolo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boogert_A/0/1/0/all/0/1">A.C.A. Boogert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Linnartz_H/0/1/0/all/0/1">H. Linnartz</a> Formic acid (HCOOH) and carbon dioxide (CO2) are simple species that have been detected in the interstellar medium. The solid-state formation pathways of these species under experimental conditions relevant to prestellar cores are primarily based off of weak infrared transitions of the HOCO complex and usually pertain to the H2O-rich ice phase, and therefore more experimental data are desired. In this article, we present aRead More →

Osculating Versus Intersecting Circles in Space-Based Microlens Parallax Degeneracies. (arXiv:1905.06770v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gould_A/0/1/0/all/0/1">Andrew Gould</a> (MPIA, OSU) I investigate the origin of arc degeneracies in satellite microlens parallax pi_E measurements with only late time data, e.g., t > t0 + t_E as seen from the satellite. I show that these are due to partial overlap of a series of osculating, exactly circular, degeneracies in the pi_E plane, each from a single measurement. In events with somewhat earlier data, these long arcs break up into two arclets, or (with even earlier data) two points, because these earlier measurmeents give rise to intersecting rather than osculating circles. TheRead More →

Dark sector evolution in Horndeski models. (arXiv:1905.06795v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Pace_F/0/1/0/all/0/1">Francesco Pace</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Battye_R/0/1/0/all/0/1">Richard A. Battye</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bolliet_B/0/1/0/all/0/1">Boris Bolliet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trinh_D/0/1/0/all/0/1">Damien Trinh</a> We use the Equation of State (EoS) approach to study the evolution of the dark sector in Horndeski models, the most general scalar-tensor theories with second order equations of motion. By including the effects of the dark sector into our code EoS_class, we demonstrate the numerical stability of the formalism and excellent agreement with results from other publicly available codes for a range of parameters describing the evolution of the function characterising the perturbations for Horndeski models, $alpha_{rm x}$, with ${rm x}={{rm K}, {rmRead More →

Characteristics of extensive air showers around the energy threshold for ground-particle-based gamma-ray observatories. (arXiv:1905.06816v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Schoorlemmer_H/0/1/0/all/0/1">Harm Schoorlemmer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hinton_J/0/1/0/all/0/1">Jim Hinton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Coto_R/0/1/0/all/0/1">Rub&#xe9;n L&#xf3;pez-Coto</a> Very high energy gamma-ray astronomy based on the measurement of air shower particles at ground-level has only recently been established as a viable approach, complementing the well established air Cherenkov technique. This approach requires high (mountain) altitudes and very high surface coverage particle detectors. While in general the properties of air showers are well established for many decades, the extreme situation of ground-level detection of very small showers from low energy primaries has not yet been well characterised for the purposesRead More →

A Search for High-Energy Counterparts to Fast Radio Bursts. (arXiv:1905.06818v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Cunningham_V/0/1/0/all/0/1">Virginia Cunningham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cenko_S/0/1/0/all/0/1">S. Bradley Cenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burns_E/0/1/0/all/0/1">Eric Burns</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goldstein_A/0/1/0/all/0/1">Adam Goldstein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lien_A/0/1/0/all/0/1">Amy Lien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kocevski_D/0/1/0/all/0/1">Daniel Kocevski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Briggs_M/0/1/0/all/0/1">Michael Briggs</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Connaughton_V/0/1/0/all/0/1">Valerie Connaughton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miller_M/0/1/0/all/0/1">M. Coleman Miller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Racusin_J/0/1/0/all/0/1">Judith Racusin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stanbro_M/0/1/0/all/0/1">Matthew Stanbro</a> We report on a search for high-energy counterparts to fast radio bursts (FRBs) with the Fermi Gamma-ray Burst Monitor (GBM), Fermi Large Area Telescope (LAT), and the Neil Gehrels Swift Observatory Burst Alert Telescope (BAT). We find no significant associations for any of the 23 FRBs in our sample, but report upper limits to the high-energy fluence for eachRead More →

Ricci Reheating. (arXiv:1905.06823v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Opferkuch_T/0/1/0/all/0/1">Toby Opferkuch</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Schwaller_P/0/1/0/all/0/1">Pedro Schwaller</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Stefanek_B/0/1/0/all/0/1">Ben A. Stefanek</a> We present a model for viable gravitational reheating involving a scalar field directly coupled to the Ricci curvature scalar. Crucial to the model is a period of kination after inflation, which causes the Ricci scalar to change sign thus inducing a tachyonic effective mass $m^{2} propto -H^2$ for the scalar field. The resulting tachyonic growth of the scalar field provides the energy for reheating, allowing for temperatures high enough for thermal leptogenesis. Additionally, the required period of kination necessarily leads to a blue-tilted primordial gravitational wave spectrum with the potential toRead More →

A chemical kinetics code for modelling exoplanetary atmospheres. (arXiv:1905.06826v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Hobbs_R/0/1/0/all/0/1">R.Hobbs</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shorttle_O/0/1/0/all/0/1">O. Shorttle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Madhusudhan_N/0/1/0/all/0/1">N. Madhusudhan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rimmer_P/0/1/0/all/0/1">P. Rimmer</a> Chemical compositions of exoplanets can provide key insights into their physical processes, and formation and evolutionary histories. Atmospheric spectroscopy provides a direct avenue to probe exoplanetary compositions. However, whether obtained in transit or thermal emission, spectroscopic observations probe limited pressure windows of planetary atmospheres and are directly sensitive to only a limited set of spectroscopically active species. It is therefore critical to have chemical models that can relate retrieved atmospheric compositions to an atmosphere’s bulk physical and chemical state. To this end we presentRead More →

Constraining a black hole companion for M87* through imaging by the Event Horizon Telescope. (arXiv:1905.06835v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Safarzadeh_M/0/1/0/all/0/1">Mohammadtaher Safarzadeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Loeb_A/0/1/0/all/0/1">Abraham Loeb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reid_M/0/1/0/all/0/1">Mark Reid</a> The Event Horizon Telescope (EHT), a global very long baseline interferometric array observing at a wavelength of 1.3 mm, detected the first image of the M87 supermassive black hole (SMBH). M87 is a giant elliptical galaxy at the center of Virgo cluster, which is expected to have formed through merging of cluster galaxies. Consequently M87* hosted mergers of black holes through dynamical friction and could have one or multiple binary companions with a low mass ratio at large separations. WeRead More →

Pushing the Limits of the Coronagraphic Occulters on HST/STIS. (arXiv:1905.06838v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Debes_J/0/1/0/all/0/1">J. H. Debes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ren_B/0/1/0/all/0/1">B. Ren</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schneider_G/0/1/0/all/0/1">G. Schneider</a> The Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) contains the only currently operating coronagraph in space that is not trained on the Sun. In an era of extreme–adaptive-optics–fed coronagraphs, and with the possibility of future space-based coronagraphs, we re-evaluate the contrast performance of the STIS CCD camera. The 50CORON aperture consists of a series of occulting wedges and bars, including the recently commissioned BAR5 occulter. We discuss the latest procedures in obtaining high contrast imaging of circumstellar disks and faint point sources withRead More →

Observations of Ultrafast Kelvin Wave Breaking in the Mars Thermosphere. (arXiv:1905.06849v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Thiemann_E/0/1/0/all/0/1">Edward M.B. Thiemann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Entin_N/0/1/0/all/0/1">Nicholas D. Entin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bougher_S/0/1/0/all/0/1">Stephen Bougher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yigit_E/0/1/0/all/0/1">Erdal Yigit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pawlowski_D/0/1/0/all/0/1">David Pawlowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eparvier_F/0/1/0/all/0/1">Francis Eparvier</a> Ultrafast Kelvin Waves (UFKWs) have been recently discovered at Mars using measurements by the Mars Atmosphere and Evolution (MAVEN) Accelerometer (ACC) instrument and the Mars Reconnaissance Orbiter (MRO) Mars Climate Sound (MCS) instrument [1]. UFKWs are eastward propagating, have a 2-3 sol period with sufficiently long vertical wavelengths to propagate into the thermosphere, and are predicted by classical wave theory to be equatorially trapped. These prior measurements characterized UFKWs at two relatively narrowRead More →

New Chandra observations of PG 1116+215 to investigate an extragalactic OVIII WHIM absorption line. (arXiv:1905.06862v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Bonamente_M/0/1/0/all/0/1">Massimiliano Bonamente</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ahoranta_J/0/1/0/all/0/1">Jussi Ahoranta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nevalainen_J/0/1/0/all/0/1">Jukka Nevalainen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Holt_P/0/1/0/all/0/1">Patrick Holt</a> This is a short AAS Research Note on the analysis of new Chandra observations of PG 1116+215, for which an extragalactic OVIII WHIM line was reported by Bonamente et al. (2016). The new observations occurred at a time when the source flux was three times lower, and the background was three times higher, than in the earlier observations. The analysis described in this research note show that the new observations are consistent with the old one atRead More →

Solar flare forecasting using morphological properties of sunspot groups. (arXiv:1905.05759v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Falco_M/0/1/0/all/0/1">M. Falco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Costa_P/0/1/0/all/0/1">P. Costa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Romano_P/0/1/0/all/0/1">P. Romano</a> We describe a new tool developed for solar flare forecasting on the base of some sunspot group properties. Assuming that the flare frequency follows the Poisson statistics, this tool uses a database containing the morphological characteristics of the suspot groups daily observed by the Equatorial Spar of INAF $-$ Catania Astrophysical Observatory since January 2002 up today. By means of a linear combination of the flare rates computed on the base of some properties of the sunspot groups, like area, number of pores and sunspots,Read More →

An Inflationary Probe of Cosmic Higgs Switching. (arXiv:1905.05764v1 [hep-th]) <a href="http://arxiv.org/find/hep-th/1/au:+Fan_J/0/1/0/all/0/1">JiJi Fan</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Reece_M/0/1/0/all/0/1">Matthew Reece</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Wang_Y/0/1/0/all/0/1">Yi Wang</a> A scalar Higgs field can be repeatedly switched on and off when it couples to a classically oscillating scalar modulus field. The modulus flips the Higgs mass term between stable and tachyonic values. We study a cosmological scenario in which such repeated phase transitions occur during inflation. An irrelevant operator coupling the Higgs field to the inflaton can then imprint the pattern of phase transitions in the correlation functions of the inflaton. Using both numerical and analytic studies, we show that the inflaton 2-point function carries characteristicRead More →