RAS_WEB (Page 4,426)

A Hot Ultraviolet Flare on the M Dwarf Star GJ 674. (arXiv:1901.08647v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Froning_C/0/1/0/all/0/1">C.S. Froning</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kowalski_A/0/1/0/all/0/1">A. Kowalski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+France_K/0/1/0/all/0/1">K. France</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Loyd_R/0/1/0/all/0/1">R.O. Parke Loyd</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schneider_P/0/1/0/all/0/1">P. Christian Schneider</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Youngblood_A/0/1/0/all/0/1">A. Youngblood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wilson_D/0/1/0/all/0/1">D. Wilson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brown_A/0/1/0/all/0/1">A. Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berta_Thompson_Z/0/1/0/all/0/1">Z. Berta-Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pineda_J/0/1/0/all/0/1">J. Sebastian Pineda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Linsky_J/0/1/0/all/0/1">J. Linsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rugheimer_S/0/1/0/all/0/1">S. Rugheimer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miguel_Y/0/1/0/all/0/1">Y. Miguel</a> As part of the Mega MUSCLES Hubble Space Telescope (HST) Treasury program, we obtained time-series ultraviolet spectroscopy of the M2.5V star, GJ~674. During the FUV monitoring observations, the target exhibited several small flares and one large flare (E_FUV = 10^{30.75} ergs) that persisted over the entirety of a HST orbitRead More →

ALMA Autocorrelation Spectroscopy of Comets: The HCN/H^13CN ratio in C/2012 S1 (ISON). (arXiv:1901.08676v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Cordiner_M/0/1/0/all/0/1">M. A. Cordiner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Palmer_M/0/1/0/all/0/1">M. Y. Palmer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Val_Borro_M/0/1/0/all/0/1">M. de Val-Borro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charnley_S/0/1/0/all/0/1">S. B. Charnley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paganini_L/0/1/0/all/0/1">L. Paganini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Villanueva_G/0/1/0/all/0/1">G. Villanueva</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bockelee_Morvan_D/0/1/0/all/0/1">D. Bockel&#xe9;e-Morvan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Biver_N/0/1/0/all/0/1">N. Biver</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Remijan_A/0/1/0/all/0/1">A. J. Remijan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuan_Y/0/1/0/all/0/1">Y.-J. Kuan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Milam_S/0/1/0/all/0/1">S. N. Milam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Crovisier_J/0/1/0/all/0/1">J. Crovisier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lis_D/0/1/0/all/0/1">D. C. Lis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mumma_M/0/1/0/all/0/1">M. J. Mumma</a> The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful tool for high-resolution mapping of comets, but the main interferometer (comprised of 50×12-m antennas) is insensitive to the largest coma scales due to a lack of very short baselines. In this work,Read More →

Investigation of the Mode-Switching Phenomenon in Pulsar B0329+54 Through Polarimetric Analysis. (arXiv:1901.08677v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Brinkman_C/0/1/0/all/0/1">Casey Brinkman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mitra_D/0/1/0/all/0/1">Dipanjan Mitra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rankin_J/0/1/0/all/0/1">Joanna Rankin</a> The phenomenon of profile mode switching in pulsars, where the stable average pulse profile changes to another stable state on the timescale of a pulsar’s period, remains poorly understood. We sought to understand how pulsars undergo profile mode switching through a comparative analysis of the polarization and geometry of the two different profile modes of PSR B0329+54. The polarization behavior and fitted parameters of the rotation-vector model remain constant between modes, and the emission height remains constant as well. These similarities lend supportRead More →

Fourier series expansion of the dark energy equation of state. (arXiv:1901.08679v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Tamayo_D/0/1/0/all/0/1">David Tamayo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vazquez_J/0/1/0/all/0/1">J. Alberto Vazquez</a> The dark energy component of the universe still remains as a mystery, however, several papers based on observational data have shown that its equation of state may have an oscillatory behaviour. In this paper, we provide a general description for the dark-energy equation-of-state $w(z)$ in the form of Fourier series. This description generalises some previous dynamical dark energy models and is in agreement with the $w(z)$ reconstructions. We make use of a modified version of a simple and fast Markov Chain Monte Carlo code to constraintRead More →

The Local Perspective on the Hubble Tension: Local Structure Does Not Impact Measurement of the Hubble Constant. (arXiv:1901.08681v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Kenworthy_W/0/1/0/all/0/1">W. D&#x27;Arcy Kenworthy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scolnic_D/0/1/0/all/0/1">Dan Scolnic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riess_A/0/1/0/all/0/1">Adam Riess</a> We use the largest sample to date of spectroscopic SN Ia distances and redshifts to look for evidence in the Hubble diagram of large scale outflows caused by local voids suggested to exist at zRead More →

The Galactic Center: An Improved Astrometric Reference Frame for Stellar Orbits around the Supermassive Black Hole. (arXiv:1901.08685v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Sakai_S/0/1/0/all/0/1">Shoko Sakai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_J/0/1/0/all/0/1">Jessica R. Lu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ghez_A/0/1/0/all/0/1">Andrea Ghez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jia_S/0/1/0/all/0/1">Siyao Jia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Do_T/0/1/0/all/0/1">Tuan Do</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Witzel_G/0/1/0/all/0/1">Gunther Witzel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gautam_A/0/1/0/all/0/1">Abhimat K. Gautam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hees_A/0/1/0/all/0/1">Aurelien Hees</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Becklin_E/0/1/0/all/0/1">E. Becklin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matthews_K/0/1/0/all/0/1">K. Matthews</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hosek_M/0/1/0/all/0/1">M.W.Hosek Jr</a> Precision measurements of the stars in short-period orbits around the supermassive black hole at the Galactic Center are now being used to constrain general relativistic effects, such as the gravitational redshift and periapse precession. One of the largest systematic uncertainties in the measured orbits has been errors in the astrometric reference frame,Read More →

Selected topics in scalar-tensor theories and beyond. (arXiv:1901.08690v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Quiros_I/0/1/0/all/0/1">Israel Quiros</a> Scalar fields have played an important role in the development of the fundamental theories of physics as well as in other branches of physics such as gravitation and cosmology. For a long time these escaped detection until 2012 year when the Higgs boson was observed for the first time. Since then alternatives to the general theory of relativity like the Brans-Dicke theory, scalar-tensor theories of gravity and their higher derivative generalizations — collectively known as Horndeski theories — have acquired renewed interest. In the present review we discuss on several selected topics regardingRead More →

Astrophysics with core-collapse supernova gravitational wave signals in the next generation of gravitational wave detectors. (arXiv:1901.08692v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Roma_V/0/1/0/all/0/1">Vincent Roma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Powell_J/0/1/0/all/0/1">Jade Powell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heng_I/0/1/0/all/0/1">Ik Siong Heng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frey_R/0/1/0/all/0/1">Ray Frey</a> The next generation of gravitational wave detectors will improve the detection prospects for gravitational waves from core-collapse supernovae. The complex astrophysics involved in core-collapse supernovae pose a significant challenge to modeling such phenomena. The Supernova Model Evidence Extractor (SMEE) attempts to capture the main features of gravitational wave signals from core-collapse supernovae by using numerical relativity waveforms to create approximate models. These models can then be used to perform Bayesian model selection to determine ifRead More →

1I/`Oumuamua As Debris of Dwarf Interstellar Comet That Disintegrated Before Perihelion. (arXiv:1901.08704v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Sekanina_Z/0/1/0/all/0/1">Zdenek Sekanina</a> Intrinsically faint comets in nearly-parabolic orbits with perihelion distances much smaller than 1 AU exhibit strong propensity for suddenly disintegrating at a time not long before perihelion, as shown by Bortle (1991). Evidence from available observations of such comets suggests that the disintegration event usually begins with an outburst and that the debris is typically a massive cloud of dust grains that survives over a limited period of time. Recent CCD observations revealed, however, that also surviving could be a sizable fragment, resembling a devolatilized aggregate of loosely-bound dustRead More →

Searching for Super-Fast Rotators Using the Pan-STARRS 1. (arXiv:1901.08719v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Chang_C/0/1/0/all/0/1">Chan-Kao Chang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lin_H/0/1/0/all/0/1">Hsing-Wen Lin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ip_W/0/1/0/all/0/1">Wing-Huen Ip</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_W/0/1/0/all/0/1">Wen-Ping Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yeh_T/0/1/0/all/0/1">Ting-Shuo Yeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chambers_K/0/1/0/all/0/1">K. C. Chambers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Magnier_E/0/1/0/all/0/1">E. A. Magnier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huber_M/0/1/0/all/0/1">M. E. Huber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Flewelling_H/0/1/0/all/0/1">H. A. Flewelling</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Waters_C/0/1/0/all/0/1">C. Z. Waters</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wainscoat_R/0/1/0/all/0/1">R. J. Wainscoat</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schultz_A/0/1/0/all/0/1">A.S.B. Schultz</a> A class of asteroids, called large super-fast rotators (large SFRs), have rotation periods shorter than 2 hours and diameters larger than ~ 0.3 km. They pose challenges to the usual interior rubble-pile structure unless a relatively high bulk density is assumed. So far, only six large SFRs have been found. Therefore, we presentRead More →

Model dispersion with PRISM; an alternative to MCMC for rapid analysis of models. (arXiv:1901.08725v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Velden_E/0/1/0/all/0/1">Ellert van der Velden</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duffy_A/0/1/0/all/0/1">Alan R. Duffy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Croton_D/0/1/0/all/0/1">Darren Croton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mutch_S/0/1/0/all/0/1">Simon J. Mutch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sinha_M/0/1/0/all/0/1">Manodeep Sinha</a> We have built PRISM, a “Probabilistic Regression Instrument for Simulating Models”. PRISM uses the Bayes linear approach and history matching to construct an approximation (’emulator’) of any given model, by combining limited model evaluations with advanced regression techniques, covariances and probability calculations. It is designed to easily facilitate and enhance existing Markov chain Monte Carlo (MCMC) methods by restricting plausible regions and exploring parameter space efficiently. However, PRISM can additionally beRead More →

Revealing A Head-on Major Merger in the Nearby NGC 6338 Group with Chandra and VLA observations. (arXiv:1901.08769v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_Y/0/1/0/all/0/1">Yu Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lui_F/0/1/0/all/0/1">Fuyao Lui</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shen_Z/0/1/0/all/0/1">Zhiqiang Shen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_J/0/1/0/all/0/1">Jingying Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hu_D/0/1/0/all/0/1">Dan Hu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_H/0/1/0/all/0/1">Hai-Guang Xu</a> By analyzing the Chandra archival data of the nearby NGC 6338 galaxy group, we identify two X-ray bright clumps (N-clump and S-clump) within the central 100 kpc, and detect an arc-like X-ray brightness discontinuity at the south boundary of the N-clump, which is defined as a cold front with a gas flow Mach number of MRead More →

Sectoral r modes and periodic RV variations of Sun-like stars. (arXiv:1901.08777v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Lanza_A/0/1/0/all/0/1">A. F. Lanza</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gizon_L/0/1/0/all/0/1">L. Gizon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zaqarashvili_T/0/1/0/all/0/1">T. V. Zaqarashvili</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liang_Z/0/1/0/all/0/1">Z.-C. Liang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodenbeck_K/0/1/0/all/0/1">K. Rodenbeck</a> Radial velocity (RV) measurements are used to search for planets orbiting late-type main-sequence stars and confirm the transiting planets. The most advanced spectrometers are approaching a precision of $sim 10$ cm/s that implies the need to identify and correct for all possible sources of RV oscillations intrinsic to the star down to this level and possibly beyond. The recent discovery of global-scale equatorial Rossby waves in the Sun, also called r modes, prompted us to investigateRead More →

Spacetime Instability and the Problems with Quantum Gravity. (arXiv:1901.08785v1 [hep-th]) <a href="http://arxiv.org/find/hep-th/1/au:+Matsui_H/0/1/0/all/0/1">Hiroki Matsui</a> In this paper we discuss spacetime instability problems in effective field theories of the quantum gravity (QG). The effective action of the gravity requires higher-derivative curvature terms $R^{2}, { R }_{ mu nu }{ R }^{ mu nu }, R_{munukappalambda} R^{munukappalambda}dots$ and they are leading quantum gravitational corrections. Although these higher-curvature terms are indispensable for the construction of the semiclassical or quantum gravity theories, they lead to many pathologies. We clearly show that even if they are Planck-suppressed operators they lead to serious consequences of the spacetime stability and, de Sitter spacetimeRead More →

On the connection of radio and $gamma$-ray emission in blazars. (arXiv:1901.08793v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Boula_S/0/1/0/all/0/1">Stella Boula</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petropoulou_M/0/1/0/all/0/1">Maria Petropoulou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mastichiadis_A/0/1/0/all/0/1">Apostolos Mastichiadis</a> Blazars are a sub-category of radio-loud active galactic nuclei with relativistic jets pointing towards to the observer. They are well-known for their non-thermal variable emission, which practically extends over the whole electromagnetic spectrum. Despite the plethora of multi-wavelength observations, the issue about the origin of the $gamma$-ray and radio emission in blazar jets remains unsettled. Here, we construct a parametric leptonic model for studying the connection between the $gamma$-ray and radio emission in both steady-state and flaring states of blazars. Assuming that relativistic electronsRead More →

Current problems in stellar pulsation theory. (arXiv:1901.08809v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Dupret_M/0/1/0/all/0/1">Marc-Antoine Dupret</a> The last decade lead to major progress in asteroseismology and stellar physics with the advent of space missions. Thanks to the richness and precision of current oscillation spectra, sophisticated seismic probing techniques allow us now to pinpoint the limits of our current models of stellar structure and evolution. However, the accuracy of the seismic diagnosis depends on the accuracy of the pulsation models. In solar-like oscillations, the main source of inaccuracy comes from the near-surface layers where the oscillations are non-adiabatic and strongly coupled with turbulent convection. Some pulsating stars rotate fast and thisRead More →

The EUV spectrum of the Sun: quiet and active Sun irradiances and chemical composition. (arXiv:1901.08841v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Zanna_G/0/1/0/all/0/1">G. Del Zanna</a> We benchmark new atomic data against a selection of irradiances obtained from medium-resolution quiet Sun spectra in the EUV, from 60 to 1040 AA. We use as a baseline the irradiances measured during solar minimum on 2008 April 14 by the prototype (PEVE) of the Solar Dynamics Observatory Extreme ultraviolet Variability Experiment (EVE). We take into account some inconsistencies in the PEVE data, using flight EVE data and irradiances we obtained from Solar & Heliospheric Observatory (SoHO) Coronal Diagnostics Spectrometer (CDS) data. We perform aRead More →