Latest in astro-ph.sr

total 38352took 0.15s
Discovery of tidally-perturbed pulsations in the eclipsing binary U Gru: a pioneering system for tidal asteroseismologyAug 22 2019The interior physics of stars is currently not well constrained for early-type stars. This is particularly pertinent for multiple systems as binary interaction becomes more prevalent for more massive stars, which strongly affects their evolution. High-precision ... More
Validating time-distance helioseismic inversions for non-separable subsurface profiles of an average supergranuleAug 22 2019Supergranules are divergent 30-Mm sized cellular flows observed everywhere at the solar photosphere. Their place in the hierarchy of convective structures and their origin remain poorly understood (Rincon et al., 2018). Estimating supergranular depth ... More
On the recent parametric determination of an asteroseismological model for the DBV star KIC 08626021Aug 22 2019Asteroseismology of white dwarf (WD) stars is a powerful tool that allows to reveal the hidden chemical structure of WD and infer details about their evolution by comparing the observed periods with those obtained from stellar models. A recent asteroseismological ... More
Discovery of weak magnetic fields in four DZ white dwarfs in the local 20pc volume. Implications for the frequency of magnetic fields with cooling ageAug 22 2019We report the discovery of weak magnetic fields in three white dwarfs within the local 20pc volume (WD 0816-310, WD 1009-184, and WD 1532+129), and we confirm the magnetic nature of a fourth star (WD 2138-332) in which we had previously detected a field ... More
Short Duration Stellar Flares in GALEX DataAug 22 2019We report on a population of short duration near-ultraviolet (NUV) flares in stars observed by the Kepler and GALEX missions. We analyzed NUV light curves of 34,276 stars observed from 2009-2013 by both the GALEX (NUV) and Kepler (optical) space missions ... More
First search for GeV neutrinos from bright gamma-ray solar flares using the IceCube Neutrino ObservatoryAug 22 2019In response to a reported increase in the total neutrino flux in the Homestake experiment in coincidence with solar flares at the end of the eighties, solar neutrino detectors have searched for solar flare signals. Solar flares convert magnetic energy ... More
A Sparkler in the Fireworks Galaxy: Discovery of an Ultraluminous X-ray Transient with a Strong Oxygen Line in NGC 6946Aug 22 2019We discovered and studied an ultraluminous X-ray source (CXOU J203451.1+601043) that appeared in the spiral galaxy NGC 6946 at some point between 2008 February and 2012 May, and has remained at luminosities $\approx$2-4 $\times 10^{39}$ erg s$^{-1}$ in ... More
Into the Darkness: Classical and Type II Cepheids in the Zona Galactica IncognitaAug 22 2019The far side of the Milky Way's disk is one of the most concealed parts of the known Universe due to extremely high interstellar extinction and point source density toward low Galactic latitudes. Large time-domain photometric surveys operating in the ... More
Discovery of an Outbursting 12.8 Minute Ultracompact X-Ray BinaryAug 22 2019We report the discovery of OGLE-UCXB-01, a 12.8 minute variable object located in the central field of Galactic bulge globular cluster Djorg 2. The presence of frequent, short-duration brightenings at such an ultrashort period in long-term OGLE photometry ... More
Not so different after all: Properties and Spatial Structure of Column Density Peaks in the Pipe and Orion A CloudsAug 22 2019We present a comparative study of the physical properties and the spatial distribution of column density peaks in two Giant Molecular Clouds (GMC), the Pipe Nebula and Orion A, which exemplify opposite cases of star cluster formation stages. The density ... More
Laboratory Calibrations of Fe XII-XIV Line-Intensity Ratios for Electron Density DiagnosticsAug 21 2019We have used an electron beam ion trap to measure electron-density-diagnostic line-intensity ratios for extreme ultraviolet lines from F XII, XIII, and XIV at wavelengths of 185-205 255-276 Angstroms. These ratios can be used as density diagnostics for ... More
FIRTEZ-dz: A Forward and Inverse solver of the polarized Radiative Transfer Equation under Zeeman regime in geometrical scaleAug 21 2019We present a numerical code that solves the forward and inverse problem of the polarized radiative transfer equation in geometrical scale under the Zeeman regime. The code is fully parallelized, making it able to easily handle large observational and ... More
Impact of Cosmic-Ray Feedback on Accretion and Chemistry in Circumstellar DisksAug 21 2019We use the gas-grain chemistry code UCLCHEM to explore the impact of cosmic-ray feedback on the chemistry of circumstellar disks. We model the attenuation and energy losses of the cosmic-rays as they propagate outwards from the star and also consider ... More
The Progenitors of Calcium-Strong TransientsAug 21 2019A new class of faint, spectroscopically peculiar transients has emerged in the last decade. We term these events "calcium-strong transients" (CaSTs) because of their atypically high calcium-to-oxygen nebular line ratios. Previous studies have struggled ... More
The case of NGC 6302: The impact of shocks in the derivation of Nitrogen abundancesAug 21 2019High nitrogen abundance is characteristic of Type I planetary nebulae as well as their highly filamentary structure. In the present work we test the hypothesis of shocks as a relevant excitation mechanism for a Type-I nebula, NGC 6302, using recently ... More
Tidal circularization of gaseous planets orbiting white dwarfsAug 21 2019A gas giant planet which survives the giant branch stages of evolution at a distance of many au and then is subsequently perturbed sufficiently close to a white dwarf will experience orbital shrinkage and circularization due to star-planet tides. The ... More
Interpretation and diversity of exoplanetary material orbiting white dwarfsAug 21 2019Nine metal-polluted white dwarfs are observed with medium-resolution optical spectroscopy,where photospheric abundances are determined and interpreted through comparison against solar system objects. An improved method of making such comparisons is presented ... More
Modeling Time Dependent Water Chemistry Due to Powerful X-ray Flares from T-Tauri StarsAug 21 2019Young stars emit strong flares of X-ray radiation that penetrate the surface layers of their associated protoplanetary disks. It is still an open question as to whether flares create significant changes in disk chemical composition. We present models ... More
Variability of Ha emission in young stellar objects in the cluster IC 348Aug 21 2019The aim of this work is to identify and study the stellar objects with variable EW(Ha) in the young stellar cluster IC 348. We performed photometric and slit-less observations at several epochs in order to reveal the variable objects. Significant variability ... More
An atlas of coronal electron density at 5Rs II: A spherical harmonic method for density reconstructionAug 21 2019This is the second of a series of three papers that present a methodology with the aim of creating a set of maps of the coronal density over a period of many years. This paper describes a method for reconstructing the coronal electron density based on ... More
SN 2018hna: 1987A-like supernova with a signature of shock breakoutAug 21 2019High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission ... More
Rotational spectroscopy of methyl mercaptan CH$_3$$^{32}$SH at millimeter and submillimeter wavelengthsAug 21 2019We present a new global study of the millimeter (mm) wave, submillimeter (sub-mm) wave, and terahertz (THz) spectra of the lowest three torsional states of methyl mercaptan (CH$_3$SH). New measurements have been carried out between 50 and 510 GHz using ... More
Stellar population astrophysics (SPA) with the TNG. GIANO-B spectroscopy of red supergiants in Alicante 7 and Alicante 10Aug 21 2019The Scutum complex in the inner disk of the Galaxy hosts a number of young clusters and associations of red supergiant stars that are heavily obscured by dust extinction. These stars are important tracers of the recent star formation and chemical enrichment ... More
SITES: Solar Iterative Temperature Emission Solver for differential emission measure inversion of EUV observationsAug 21 2019Extreme UltraViolet (EUV) images of the optically-thin solar corona in multiple spectral channels give information on the emission as a function of temperature through differential emission measure (DEM) inversions. The aim of this paper is to describe, ... More
Supernova lightCURVE POPulation Synthesis II: Validation against supernovae with an observed progenitorAug 21 2019We use the results of a supernova light-curve population synthesis to predict the range of possible supernova light curves arising from a population of single-star progenitors that lead to type IIP supernovae. We calculate multiple models varying the ... More
Turbulence vs. fire hose instabilities: 3-D hybrid expanding box simulationsAug 21 2019The relationship between a decaying plasma turbulence and proton fire hose instabilities in a slowly expanding plasma is investigated using three-dimensional (3-D) hybrid expanding box simulations. We impose an initial ambient magnetic field along the ... More
Planetary systems in a star cluster I: the Solar system scenarioAug 21 2019Young stars are mostly found in dense stellar environments, and even our own Solar system may have formed in a star cluster. Here, we numerically explore the evolution of planetary systems similar to our own Solar system in star clusters. We investigate ... More
First clear detection of the CCS Zeeman splitting toward the pre-stellar core, Taurus Molecular Cloud-1Aug 21 2019We report a first clear detection of the Zeeman splitting of a CCS emission line at 45 GHz toward a nearby prestellar dense filament, Taurus Molecular Cloud-1. We observed HC$_3$N non-Zeeman line simultaneously as the CCS line, and did not detect any ... More
Photospheric nitrogen abundances and carbon 12C/13C ratios of red giant starsAug 21 2019Nitrogen abundances and carbon isotope ratios (12C/13C) in the atmospheres of red giants are known to be influenced by dredge-up of H-burning products and serve as useful probes to study the nature of evolution-induced envelope mixing. We determined the ... More
Precise Radial Velocities of Cool Low Mass Stars With iSHELLAug 20 2019The coolest dwarf stars are intrinsically faint at visible wavelengths and exhibit rotationally modulated stellar activity from spots and plages. It is advantageous to observe these stars at near infrared (NIR) wavelengths (1-2.5 microns) where they emit ... More
Runaway Young Stars in the Orion NebulaAug 20 2019The star forming region of the Orion Nebula (ONC) is ideal to study the stellar dynamics of young stars in a clustered environment. Using Gaia DR2 we search for the pre-main sequence stars with unusually high proper motions that may be representative ... More
Towards precise stellar ages: combining isochrone fitting with empirical gyrochronologyAug 20 2019We present a new age-dating technique that combines gyrochronology with isochrone fitting to infer ages for FGKM main-sequence and subgiant field stars. Gyrochronology and isochrone fitting are each capable of providing relatively precise ages for field ... More
Linear spectropolarimetry of 35 Type Ia Supernovae with VLT/FORS: An analysis of the Si II line polarizationAug 20 2019Spectropolarimetry enables us to measure the geometry and chemical structure of the ejecta in supernova explosions, which is fundamental for the understanding of their explosion mechanism(s) and progenitor systems. We collected archival data of 35 Type ... More
Galactic Cosmic Ray Sun Shadow during the declining phase of cycle 24 observed by HAWCAug 20 2019The High Altitude Water Cherenkov (HAWC) array is sensitive to high energy Cosmic Rays (CR) in the $\sim 10$ to $\sim 200$ TeV energy range, making it possible to construct maps of the so called "Sun Shadow" ($SS$), i. e. of the deficit of CR coming from ... More
A comparison between solar plage and network propertiesAug 20 2019We compare the properties of kG magnetic structures in the solar network and in active region plage at high spatial resolution. Our analysis used six SP scans of the solar disc centre aboard Hinode SOT and inverted the obtained spectra of the photospheric ... More
New Spatially Resolved Imaging of the SR 21 Transition Disk and Constraints on the Small-Grain Disk GeometryAug 20 2019We present new 0.6 - 4 $\mu$m imaging of the SR 21 transition disk from Keck/NIRC2 and Magellan/MagAO. The protoplanetary disk around SR 21 has a large (~ 30 - 40 AU) clearing first inferred from its spectral energy distribution and later detected in ... More
The origin of R CrA variability: A complex triple system hosting a diskAug 20 2019R~CrA is the brightest member of the Coronet star forming region and it is the closest Herbig AeBe star with a spectrum dominated by emission lines. Its luminosity has been monitored since the end of the 19th century, but the origin of its variability, ... More
The census of non-radial pulsation in first-overtone RR Lyrae stars of the OGLE Galactic bulge collectionAug 20 2019We analyzed photometry for the up-to-date collection of the first-overtone RR Lyrae stars (RRc; 11415 stars) and double-mode RR Lyrae stars (RRd; 148 stars) towards the Galactic bulge from the Optical Gravitational Lensing Experiment. We analyzed frequency ... More
Non-thermal emission from cosmic rays accelerated in HII regionsAug 20 2019Aug 21 2019Radio observations at metre-centimetre wavelengths shed light on the nature of the emission of HII regions. Usually this category of objects is dominated by thermal radiation produced by ionised hydrogen, namely protons and electrons. However, a number ... More
Non-thermal emission from cosmic rays accelerated in HII regionsAug 20 2019Radio observations at metre-centimetre wavelengths shed light on the nature of the emission of HII regions. Usually this category of objects is dominated by thermal radiation produced by ionised hydrogen, namely protons and electrons. However, a number ... More
When does the onset of multiple stellar populations in star clusters occur-II: No evidence of multiple stellar populations in Lindsay 113Aug 20 2019The presence of multiple populations (MPs) in almost all globular clusters (GCs) older than ~10 Gyr, has caught lots of attention. Recently, cumulative evidence indicates that extragalactic GCs that are older than 2 Gyr, seem to also harbor MPs, however, ... More
Damping Mechanisms of the Solar Filament Longitudinal Oscillations in Weak Magnetic FieldAug 20 2019Longitudinal oscillations of solar filament have been investigated via numerical simulations continuously, but mainly in one dimension (1D), where the magnetic field line is treated as a rigid flux tube. Whereas those one-dimensional simulations can roughly ... More
The Dust Particle Radial Distribution in the HL Tau Disk from ALMA and VLA ObservationsAug 20 2019Understanding planet formation requires to discern how dust grows in protoplanetary disks. An important parameter to measure in disks is the maximum dust grain size present. This is usually estimated through measurements of the dust opacity at different ... More
Synthetic Extreme-ultraviolet Emissions Modulated by Leaky Fast Sausage Modes in Solar Active Region LoopsAug 20 2019We study the extreme-ultraviolet (EUV) emissions modulated by leaky fast sausage modes (FSMs) in solar active region loops and examine their observational signatures via spectrometers like EIS. After computing fluid variables of leaky FSMs with MHD simulations, ... More
Nonlinear Rossby wave-wave and wave-mean flow theory for long term Solar cycle modulationsAug 19 2019The Schwabe cycle of solar activity exhibits modulations and frequency fluctuations on slow time scales of centuries and millennia. Plausible physical explanations for the cause of these long-term variations of the solar cycle are still elusive, with ... More
Hot Jupiters are Destroyed by Tides While Their Host Stars are on the Main SequenceAug 19 2019While cooler giant planets are often observed with non-zero eccentricities, the short-period circular orbits of hot Jupiters suggest that they lose orbital energy and angular momentum due to tidal interactions with their host stars. However, orbital decay ... More
Infrared interferometric three-dimensional diagnosis of the atmospheric dynamics of the AGB star R Dor with VLTI/AMBERAug 19 2019The mechanism of mass loss in late evolutionary stages of low- and intermediate-mass stars is not yet well understood. Therefore, it is crucial to study the dynamics of the region within a few stellar radii, where the wind acceleration is considered to ... More
WISE J072003.20-084651.2B Is A Massive T DwarfAug 19 2019We present individual dynamical masses for the nearby M9.5+T5.5 binary WISE J072003.20$-$084651.2AB, a.k.a. Scholz's star. Combining high-precision CFHT/WIRCam photocenter astrometry and Keck adaptive optics resolved imaging, we measure the first high-quality ... More
Super-Earth ingestion can explain the anomalously high metal abundances of M67 Y2235Aug 19 2019We investigate the hypothesis that ingestion of a terrestrial or super-Earth planet could cause the anomalously high metal abundances seen in a turn-off star in the open cluster M67, when compared to other turn-off stars in the same cluster. We show that ... More
The K2 Bright Star Survey I: Methodology and Data ReleaseAug 19 2019While the Kepler Mission was designed to look at tens of thousands of faint stars (V > 12), brighter stars that saturated the detector are important because they can be and have been observed very accurately by other instruments. By analyzing the unsaturated ... More
Linear unstable whistler eigenmodes excited by a finite electron beamAug 19 2019Electron beam-generated whistler waves are widely found in the Earth's space plasma environment and are intricately involved in a number of phenomena. Here we study the linear growth of whistler eigenmodes excited by a finite gyrating electron beam, to ... More
Resonant excitation of whistler waves by a helical electron beamAug 19 2019Chorus-like whistler-mode waves that are known to play a fundamental role in driving radiation-belt dynamics are excited on the Large Plasma Device by the injection of a helical electron beam into a cold plasma. The mode structure of the excited whistler ... More
Spectroscopic studies of stellar populations in globular clusters and field stars: implications for globular cluster and Milky Way halo formationAug 19 2019We review spectroscopic results concerning multiple stellar populations in globularclusters. The cluster initial mass is the most important parameter determining the fraction of second generation stars. The threshold for the onset of the multiple population ... More
Effects of Radiation in Accretion Regions of Classical T Tauri Stars: Pre-heating of accretion column in non-LTE regimeAug 19 2019Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns, in which optically thin and thick plasma components coexist. Thus an accurate description of these ... More
Effects of Radiation in Accretion Regions of Classical T Tauri Stars: Pre-heating of accretion column in non-LTE regimeAug 19 2019Aug 20 2019Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns, in which optically thin and thick plasma components coexist. Thus an accurate description of these ... More
Systematic search for stellar pulsators in the eclipsing binaries observed by KeplerAug 19 2019Eclipsing binaries (EBs) are unique targets for measuring precise stellar properties and constrain stellar evolution models. In particular, it is possible to measure at the percent level masses and radii of both components of a double-lined spectroscopic ... More
Erosion of an exoplanetary atmosphere caused by stellar windsAug 19 2019We present a formalism for a first-order estimation of the magnetosphere radius of exoplanets orbiting stars in the range from 0.08 to 1.3 Mo. With this radius, we estimate the atmospheric surface that is not protected from stellar winds. We have analyzed ... More
Multiple Stellar Populations of Globular Clusters from Homogeneous Ca--CN--CH Photometry. V. $cn^\prime_{\rm JWL}$ as a Surrogate $cn_{\rm JWL}$ Index and NGC 6723Aug 19 2019We introduce new color indices $cn^\prime_{\rm JWL}$ (= $Ca_{\rm CTIO} - Ca_{\rm JWL}$) and $ch_{\rm JWL}$ [=$(JWL43 - b) - (b-y)$], accurate photometric measures of the CN band at $\lambda$3883 and the CH G band, respectively, in the study of the multiple ... More
Particle-in-cell simulations of the whistler heat-flux instability in the solar wind conditionsAug 19 2019In collision-poor plasmas from space, e.g., solar wind or stellar outflows, the heat-flux carried by the strahl or beaming electrons is expected to be regulated by the self-generated instabilities. Recently, simultaneous field and particle observations ... More
Stellar rotation bifurcation caused by tidal locking in the open cluster NGC 2287?Aug 18 2019We present a detailed analysis of the projected stellar rotational velocities of the well-separated double main sequence (MS) in the young, $\sim200$Myr-old Milky Way open cluster NGC 2287 and suggest that stellar rotation may drive the split MSs in NGC ... More
Tidal-locking-induced stellar rotation dichotomy in the open cluster NGC 2287?Aug 18 2019Stars spend most of their lifetimes on the `main sequence' (MS) in the Hertzsprung--Russell diagram. The obvious double MSs seen in the equivalent color--magnitude diagrams characteristic of Milky Way open clusters pose a fundamental challenge to our ... More
The Traditional Approximation of Rotation including the centrifugal acceleration for slightly deformed starsAug 18 2019The Traditional Approximation of Rotation (TAR) is a treatment of the dynamical equations of rotating stably stratified fluids where the action of the Coriolis acceleration along the direction of the entropy (and chemicals) stratification is neglected ... More
Scattering of energetic electrons by heat-flux-driven whistlers in flaresAug 18 2019The scattering of electrons by heat-flux-driven whistler waves is explored with particle-in-cell (PIC) simulations relevant to the transport of energetic electrons in flares and the solar wind. The simulations are initiated with a large heat flux that ... More
Opposite polarity magnetic field and convective downflows in a simulated sunspot penumbraAug 18 2019Recent numerical simulations and observations of sunspots show a significant amount of opposite polarity magnetic field within the sunspot penumbra. Most of the opposite polarity field is associated with convective downflows. We present an analysis of ... More
Formation of a Magnetic Flux Rope in the Early Emergence Phase of NOAA Active Region 12673Aug 18 2019In this work, we investigate the formation of a magnetic flux rope (MFR) above the central polarity inversion line (PIL) of NOAA Active Region 12673 during its early emergence phase. Through analyzing the photospheric vector magnetic field, extreme ultraviolet ... More
Interaction of Stars Hosting Planets with Sgr A* Black holeAug 17 2019We present some preliminary results of our ongoing project about planetary systems around S-stars in the vicinity of Sgr A* black hole. Since S-stars might have migrated in the Galactic Centre (GC) from elsewhere, they probably still keep their planetary ... More
The Wolf-Rayet Content of the Galaxies of the Local Group and BeyondAug 17 2019Wolf-Rayet stars (WRs) represent the end of a massive star's life as it is about to turn into a supernova. Obtaining complete samples of such stars across a large range of metallicities poses observational challenges, but presents us with an exacting ... More
How Drag Force Evolves in Global Common Envelope SimulationsAug 16 2019We compute the forces, torque and rate of work on the companion-core binary due to drag in global simulations of common envelope (CE) evolution for three different companion masses. Our simulations help to delineate regimes when conventional analytic ... More
Modeling subgrid combustion processes in simulations of thermonuclear supernovaeAug 16 2019Supernovae of type Ia are thought to arise from the thermonuclear incineration of a carbon-oxygen white dwarf stellar remnant. However, the detailed explosion scenario and stellar evolutionary origin scenario -- or scenarios -- which lead to observed ... More
On the optimal calibration of VVV photometryAug 16 2019Prompted by some inconsistencies in the photometry of the VISTA Variables in the V\'ia L\'actea (VVV) survey, we conduct a revision of the standard calibration procedure of VISTA data in the $J$, $H$, and $K_S$ passbands. Two independent sources of bias ... More
S and VV Corona Australis: Spectroscopic Variability in Two Young Binary Star SystemsAug 16 2019We used high-resolution near-infrared spectroscopy from the NIRSPEC instrument on the Keck II telescope, taken over multiple epochs spanning five years, to examine two young binary T Tauri star systems, S Corona Australis and VV Corona Australis. The ... More
Abundance ratios in GALAH DR2 and their implications for nucleosynthesisAug 16 2019Using a sample of 70 924 stars from the second data release of the GALAH optical spectroscopic survey, we construct median sequences of [X/Mg] vs. [Mg/H] for 21 elements, separating the low-Ia (high-$\alpha$) and high-Ia (low-$\alpha$) stellar populations ... More
Driving white dwarf metal pollution through unstable eccentric periodic orbitsAug 16 2019Planetary debris is observed in the atmospheres of over 1,000 white dwarfs, and two white dwarfs are now observed to contain orbiting minor planets. Exoasteroids and planetary core fragments achieve orbits close to the white dwarf through scattering with ... More
The isolation of Luminous Blue Variables resembles aging B-type supergiants, not the most massive unevolved starsAug 16 2019Luminous blue variables (LBVs) are suprisingly isolated from the massive O-type stars that are their putative progenitors in single-star evolution, implicating LBVs as binary evolution products. Aadland et al. (A19) found that LBVs are, however, only ... More
The impact of stars stripped in binaries on the integrated spectra of stellar populationsAug 16 2019Stars stripped of their envelopes from interaction with a binary companion emit a significant fraction of their radiation as ionizing photons. They are potentially important stellar sources of ionizing radiation, however, they are still often neglected ... More
Thermomagnetic Ettingshausen-Nernst effect in tachocline, magnetic reconnection phenomenon in lower layers, axion mechanism of solar luminosity variations, coronal heating problem solution and mechanism of DM spike variations around BHAug 16 2019It is shown that the holographic principle of quantum gravity (in the hologram of the Universe, and therefore in our Galaxy, and of course on the Sun!), in which the conflict between the theory of gravitation and quantum mechanics disappears, gives rise ... More
Multi-waveband detection of quasi-periodic pulsations in a stellar flare on EK Draconis observed by XMM-NewtonAug 16 2019Context. Quasi-periodic pulsations (QPPs) are time variations in the energy emission during a flare that are observed on both the Sun and other stars and thus have the potential to link the physics of solar and stellar flares. Aims. To characterise the ... More
Electron Impact Excitation of S III: an AssessmentAug 16 2019In a recent paper, Tayal et al. [{\em Astrophys. J. Suppl.} {\bf 2019}, {\emph 242}, 9] have reported results for energy levels, radiative rates (A-values) and effective collision strengths ($\Upsilon$) for transitions among the 198 levels of Si-like ... More
Evaluation of nearby young moving groups based on unsupervised machine learningAug 16 2019Nearby young stellar moving groups have been identified by many research groups with different methods and criteria giving rise to cautions on the reality of some groups. We aim to utilise moving groups in an unbiased way to create a list of unambiguously ... More
The aromatic UniverseAug 16 2019The rich molecular structures of polycyclic aromatic hydrocarbons -- essentially planar flakes of fused benzene rings -- and their fullerene cousins are revealed through their vibrational and electronic spectra.
Properties of solar Rossby waves from normal mode coupling and characterizing its systematicsAug 16 2019Rossby waves play an important role in mediating the angular momentum of rotating spherical fluids, creating weather on Earth and tuning exoplanet orbits in distant stellar systems (Ogilvie 2014). Their recent discovery in the solar convection zone provides ... More
IRC+10216 mass loss properties through the study of $λ$3mm emission: Large spatial scale distribution of SiO, SiS, and CSAug 15 2019The study of the gas in the envelopes surrounding asymptotic giant branch (AGB) stars through observations in the millimetre wavelength range provides information about the history and nature of these molecular factories. Here we present ALMA observations ... More
A VLT/FLAMES survey for massive binaries in Westerlund 1: VII. Cluster censusAug 15 2019The formation, properties, and evolution of massive stars remain subject to considerable uncertainty; impacting on fields as diverse as galactic feedback and the nature of the progenitors of both electromagnetic and gravitational wave transients. The ... More
Delving into the Historical Ca II K Archive from the Kodaikanal Observatory: the Potential of the Most Recent Digitised SeriesAug 15 2019Full-disc Ca II K photographic observations of the Sun carry direct information about the evolution of solar-plage regions for more than a century and are therefore a unique dataset for solar-activity studies. For a long time Ca II K observations were ... More
Molecular envelope around the HII region RCW 120Aug 15 2019The H II region RCW120 is a well-known object, which is often considered as a target to verify theoretical models of gas and dust dynamics in the interstellar medium. However, the exact geometry of RCW120 is still a matter of debate. In this work, we ... More
Properties of the Interstellar Medium along Sight Lines to Nearby Planet Hosting StarsAug 15 2019We analyze high-resolution ultraviolet spectra of three nearby exoplanet host stars (HD 192310, HD 9826, and HD 206860) to study interstellar properties along their lines of sight and to search for the presence of astrospheric absorption. Using HST/STIS ... More
Measuring the ionisation fraction in a jet from a massive protostarAug 14 2019It is important to determine if massive stars form via disc accretion, like their low-mass counterparts. Theory and observation indicate that protostellar jets are a natural consequence of accretion discs and are likely to be crucial for removing angular ... More
Modelling Mg II During Solar Flares, I: Partial Frequency Redistribution, Opacity, and Coronal IrradiationAug 14 2019The Interface Region Imaging Spectrograph (IRIS) has routinely observed the flaring Mg II NUV spectrum, offering excellent diagnostic potential and a window into the location of energy deposition. A number of studies have forward modelled both the general ... More
Stars at High Spatial ResolutionAug 14 2019We summarize some of the compelling new scientific opportunities for understanding stars and stellar systems that can be enabled by sub-milliarcsec (sub-mas) angular resolution, UV-Optical spectral imaging observations, which can reveal the details of ... More
Changes in the solar rotation over two solar cyclesAug 14 2019We use helioseismic data from ground and space-based instruments to analyze how solar rotation has changed since the beginning of solar Cycle 23 with emphasis on studying the differences between Cycles 23 and 24. We find that the nature of solar rotation ... More
Two-fluid simulations of waves in the solar chromosphere II. Propagation and damping of fast magneto-acoustic waves and shocksAug 14 2019Waves and shocks traveling through the solar chromospheric plasma are influenced by its partial ionization and weak collisional coupling, and may become susceptible to multi-fluid effects, similar to interstellar shock waves. In this study, we consider ... More
Surface rotation and photometric activity for Kepler targets I. M and K main-sequence starsAug 14 2019Brightness variations due to dark spots on the stellar surface encode information about stellar surface rotation and magnetic activity.In this work, we analyze the Kepler long-cadence data of 26,521 main-sequence stars of spectral types M and K in order ... More
Surface rotation and photometric activity for Kepler targets I. M and K main-sequence starsAug 14 2019Aug 15 2019Brightness variations due to dark spots on the stellar surface encode information about stellar surface rotation and magnetic activity. In this work, we analyze the Kepler long-cadence data of 26,521 main-sequence stars of spectral types M and K in order ... More
Regularities in the spectrum of chaotic p-modes in rapidly rotating starsAug 14 2019Interpreting the oscillations of massive and intermediate mass stars remains a challenging task. In fast rotators, the oscillation spectrum of p-modes is a superposition of sub-spectra corresponding to different types of modes. Among these modes, island ... More
Spatially resolved signatures of bi-directional flows observed in inverted-Y shaped jetsAug 14 2019Numerous apparent signatures of magnetic reconnection have been reported in the solar photosphere, including inverted-Y shaped jets. The reconnection at these sites is expected to cause localised bi-directional flows and extended shock waves; however, ... More
HAYDN -- High-precision AsteroseismologY of DeNse stellar fields (ESA Voyage 2050 White Paper)Aug 14 2019In the last decade, the Kepler and CoRoT space-photometry missions have demonstrated the potential of asteroseismology as a novel, versatile and powerful tool to perform exquisite tests of stellar physics, and to enable precise and accurate characterisations ... More
Accretion-Induced Collapse of Dark Matter Admixed White Dwarfs -- I: Formation of Low-mass Neutron StarsAug 14 2019Recently observed pulsars with masses $\sim 1.1 ~M_{\odot}$ challenge the conventional neutron star (NS) formation path by core-collapse supernova (CCSN). Using spherically symmetric hydrodynamics simulations, we follow the collapse of a massive white ... More
The First Detection of 13C17O in a Protoplanetary Disk: a Robust Tracer of Disk Gas MassAug 14 2019Measurements of the gas mass are necessary to determine the planet formation potential of protoplanetary disks. Observations of rare CO isotopologues are typically used to determine disk gas masses; however, if the line emission is optically thick this ... More
Three-dimensional Density Structure of a Solar Coronal Streamer Observed by SOHO/LASCO and STEREO/COR2 in QuadratureAug 14 2019Helmet streamers are a prominent manifestation of magnetic structures with current sheets in the solar corona. These large-scale structures are regions with high plasma density, overlying active regions and filament channels. We investigate the three-dimensional ... More
The chemical compositions of the 2 new HgMn stars HD 30085 and HD 30963. Comparison to $χ$ Lupi A, $ν$ Cap and HD 174567Aug 14 2019We report on a detailed abundance study of the fairly bright slow rotators HD 30085 (A0 IV), HD 30963 (B9 III) and HD 174567 (A0 V), hitherto reported as normal stars and the sharp-lined chi Lupi A (B9 IV HgMn). In the spectra of HD 30085, HD 30963, the ... More