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A Sun-like star orbiting a boson star: The high-precision astrometric mission GAIA recently reported the remarkable discovery of a Sun-like star closely orbiting a dark object, with a semi-major axis and period of $1.4\, \rm{AU}$ and $187.8$ days respectively. While the plausible expectation for the central dark object...
astro-ph_SR
Multi-scale magnetic field investigation of the M-dwarf eclipsing binary CU Cancri: We aim to characterise the magnetic field of the eclipsing binary CU Cnc. The determination of magnetic field parameters of this target enables comparisons with both observations of similar stars and theoretical predictions of the mag...
astro-ph_SR
ALMA and VLA observations of the outflows in IRAS 16293-2422: We present ALMA and VLA observations of the molecular and ionized gas at 0.1-0.3 arcsec resolution in the Class 0 protostellar system IRAS 16293-2422. These data clarify the origins of the protostellar outflows from the deeply embedded sources in this comple...
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The Anatomy of an Unusual Edge-on Protoplanetary Disk I. Dust Settling in a Cold Disk: As the earliest stage of planet formation, massive, optically thick, and gas rich protoplanetary disks provide key insights into the physics of star and planet formation. When viewed edge-on, high resolution images offer a unique o...
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Science with the ngVLA: Planetary Nebulae: Planetary nebulae (PNe) represent the near endpoints of evolution for stars of initial mass $\sim$1-8 $M_\odot$, wherein the envelope of an asymptotic giant branch (AGB) star becomes photodissociated and ionized by high-energy radiation from a newly emerging white dwarf that w...
astro-ph_SR
A Separable Solution for the Oscillatory Structure of Plasma in Accretion Disks: We provide a new analysis of the system of partial differential equations describing the radial and vertical equilibria of the plasma in accretion disks. In particular, we show that the partial differential system can be separated once a...
astro-ph_SR
Signature of Collision of Magnetic Flux Tubes in the Quiet Solar Photosphere: Collision of the magnetic flux tubes in the Quiet Sun was proposed as one of the possible sources for the heating of the solar atmosphere (Furusawa and Sakai, 2000). The solar photosphere was observed using the New Solar Telescope ad Big Be...
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A Kepler Study of Starspot Lifetimes with Respect to Light Curve Amplitude and Spectral Type: Wide-field high precision photometric surveys such as Kepler have produced reams of data suitable for investigating stellar magnetic activity of cooler stars. Starspot activity produces quasi-sinusoidal light curves whose ph...
astro-ph_SR
Seismic detection of acoustic sharp features in the CoRoT target HD49933: The technique of determining the acoustic location of layers of sharp changes in the sound speed inside a star from the oscillatory signal in its frequencies is applied on a solar-type star, the CoRoT target, HD49933. We are able to determine the...
astro-ph_SR
The Origin of Major Solar Activity - Collisional Shearing Between Nonconjugated Polarities of Multiple Bipoles Emerging Within Active Regions: Active Regions (ARs) that exhibit compact Polarity Inversion Lines (PILs) are known to be very flare-productive. However, the physical mechanisms behind this statistical infer...
astro-ph_SR
Carbon, nitrogen and $α$-element abundances determine the formation sequence of the Galactic thick and thin disks: Using the DR12 public release of APOGEE data, we show that thin and thick disk separate very well in the space defined by [$\alpha$/Fe], [Fe/H] and [C/N]. Thick disk giants have both higher [C/N] and hig...
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On the photometric signature of fast rotators: Rapidly rotating stars have been recently recognized as having a major role in the interpretation of colour-magnitude diagrams of young and intermediate-age star clusters in the Magellanic Clouds and in the Milky Way. In this work, we evaluate the distinctive spectra and d...
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Predictive Capabilities of Avalanche Models for Solar Flares: We assess the predictive capabilities of various classes of avalanche models for solar flares. We demonstrate that avalanche models cannot generally be used to predict specific events due to their high sensitivity to their embedded stochastic process. We sho...
astro-ph_SR
Kepler observations of the beaming binary KPD 1946+4340: The Kepler Mission has acquired 33.5d of continuous one-minute photometry of KPD 1946+4340, a short-period binary system that consists of an sdB and a white dwarf. In the light curve, eclipses are clearly seen, with the deepest occurring when the compact white dw...
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The Araucaria Project: High-precision orbital parallax and masses of the eclipsing binary TZ~Fornacis: Context: Independent distance estimates are particularly useful to check the precision of other distance indicators, while accurate and precise masses are necessary to constrain evolution models. Aim: The goal is to...
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Multi-wavelength Spectral Analysis of Ellerman Bombs Observed by FISS and IRIS: Ellerman bombs (EBs) are a kind of solar activities that is suggested to occur in the lower atmosphere. Recent observations using the Interface Region Imaging Spectrograph (IRIS) show connections of EBs and IRIS bombs (IBs), implying that...
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Multi-epoch spectropolarimetry of SN 2009ip: direct evidence for aspherical circumstellar material: We present spectropolarimetry of SN 2009ip throughout the evolution of its 2012 explosion. During the initial 2012a phase, when the source spectrum exhibits broad P-Cygni lines, we measure a V-band polarization of P~0....
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Heavy Elements Nucleosynthesis On Accreting White Dwarfs: building seeds for the p-process: The origin of the proton-rich trans-iron isotopes in the solar system is still uncertain. Single-degenerate thermonuclear supernovae (SNIa) with n-capture nucleosynthesis seeds assembled in the external layers of the progenito...
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An empirical clock to measure the dynamical age of stellar systems: Blue Straggler Stars (BSS) are among the brightest and more massive stars in globular clusters (GCs). For this reason they represent an ideal tool to probe the dynamical evolution of these stellar systems. Here I show, following the results by Ferraro ...
astro-ph_SR
Faint warm debris disks around nearby bright stars explored by AKARI and IRSF: Context: Debris disks are important observational clues for understanding planetary-system formation process. In particular, faint warm debris disks may be related to late planet formation near 1 AU. A systematic search of faint warm debri...
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The IACOB spectroscopic database of Northern Galactic OB stars: We present the IACOB spectroscopic database, an homogeneous set of high quality, high resolution spectra of Galactic O- and B-type stars obtained with the FIES spectrograph attached to the Nordic Optical Telescope. We also present some results from ongoing...
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Absolute Properties of the Eclipsing $γ$ Dor Star V404 Lyrae: We present the first high-resolution spectra for the eclipsing binary V404 Lyr showing $\gamma$ Dor pulsations, which we use to study its absolute properties. By fitting models to the disentangling spectrum of the primary star, we found that it has an effect...
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STiC -- A multi-atom non-LTE PRD inversion code for full-Stokes solar observations: The inference of the underlying state of the plasma in the solar chromosphere remains extremely challenging because of the nonlocal character of the observed radiation and plasma conditions in this layer. Inversion methods allow us to...
astro-ph_SR
On the nature of massive helium star winds and Wolf-Rayet-type mass loss: The mass-loss rates of massive helium stars are one of the major uncertainties in modern astrophysics. Regardless of whether they were stripped by a binary companion or managed to peel off their outer layers by themselves, the influence and final...
astro-ph_SR
Photoionization and electron-ion recombination in astrophysical plasmas: Photoionization and its inverse, electron-ion recombination, are key processes that influence many astrophysical plasmas (and gasses), and the diagnostics that we use to analyse the plasmas. In this review we provide a brief overview of the import...
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Evidence of a Plasmoid-Looptop Interaction and Magnetic Inflows During a Solar Flare/CME Eruptive Event: Observational evidence is presented for the merging of a downward-propagating plasmoid with a looptop kernel during an occulted limb event on 2007 January 25. RHESSI lightcurves in the 9-18 keV energy range, as we...
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On the Distribution of Orbital Eccentricities for Very Low-Mass Binaries: We have compiled a sample of 16 orbits for very low-mass stellar (<0.1 Msun) and brown dwarf binaries, enabling the first comprehensive study of the eccentricity distribution for such objects. We find that very low-mass binaries span a broad rang...
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The intimate relation between the low T/W instability and the co-rotation point: We study the low T/W instability associated with the f-mode of differentially rotating stars. Our stellar models are described by a polytropic equation of state and the rotation profile is given by the standard j-constant law. The proper...
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Flux emergence and coronal eruption: Our aim is to study the photospheric flux distribution of a twisted flux tube that emerges from the solar interior. We also report on the eruption of a new flux rope when the emerging tube rises into a pre-existing magnetic field in the corona. To study the evolution, we use 3D nume...
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Exploring Bistability in the Cycles of the Solar Dynamo through Global Simulations: The calling card of solar magnetism is the sunspot cycle, during which sunspots regularly reverse their polarity sense every 11 years. However, a number of more complicated time-dependent behaviors have also been identified. In partic...
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High spatial resolution imaging of SO and H2CO in AB Auriga: the first SO image in a transitional disk: Transitional disks are structures of dust and gas around young stars with large inner cavities in which planet formation may occur. Lopsided dust distributions are observed in the dust continuum emission at millime...
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Driving solar coronal MHD simulations on high-performance computers: The quality of today's research is often tightly limited to the available computing power and scalability of codes to many processors. For example, tackling the problem of heating the solar corona requires a most realistic description of the plasma dy...
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Hydrogen Balmer Line Broadening in Solar and Stellar Flares: The broadening of the hydrogen lines during flares is thought to result from increased charge (electron, proton) density in the flare chromosphere. However, disagreements between theory and modeling prescriptions have precluded an accurate diagnostic of the d...
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An AMR Study of the Common Envelope Phase of Binary Evolution: The hydrodynamic evolution of the common envelope phase of a low mass binary composed of a 1.05 Msun red giant and a 0.6 Msun companion has been followed for five orbits of the system using a high resolution method in three spatial dimensions. During the ra...
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Physical and chemical properties of Wolf-Rayet planetary nebulae: Wolf-Rayet ([WR]) and weak emission-line ($wels$) central stars of planetary nebulae (PNe) have hydrogen-deficient atmospheres, whose origins are not well understood. In the present study, we have conducted plasma diagnostics and abundance analyses of 18...
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Submillimeter continuum observations of Sagittarius B2 at subarcsecond spatial resolution: We report the first high spatial resolution submillimeter continuum observations of the Sagittarius B2 cloud complex using the Submillimeter Array (SMA). With the subarcsecond resolution provided by the SMA, the two massive sta...
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Collision strengths for FIR and UV transtions in PIII and the phosphorus abundance: Phosphorus abundance is crucial for DNA-based extraterrestrial life in exoplanets. Atomic data for observed spectral lines of P-ions are needed for its accurate determination. We present the first calculations for collision strengths ...
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MAVKA: Software for Statistically Optimal Determination of Extrema: We introduce the program MAVKA for determination of characteristics of extrema using observations in the adjacent data intervals, with intended applications to variable stars, but it may be used for signals of arbitrary nature. We have used a dozen of ...
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Inferring properties of small convective cores in main-sequence solar-like pulsators: This work concerns the study of the properties of convective cores in main-sequence models of solar-like pulsators and what information they may hold about stellar ages. We verified that the maximum absolute frequency derivative of ...
astro-ph_SR
Primordial triples and collisions of massive stars: Massive stars are known to have a high multiplicity, with examples of higher order multiples among the nearest and best studied objects. In this paper we study hierarchical multiple systems (an inner binary as a component of a wider binary) of massive stars in a clust...
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Epicyclic frequencies of spheroidal stars with non-uniform density: We consider the gravitational potential of a rotating star with non-uniform density to derive the orbital and epicyclic frequencies of the particles orbiting the star. We assume that the star is composed of concentric spheroids of constant density, wit...
astro-ph_SR
Images of unclassified and supergiant B[e] stars disks with interferometry: B[e] stars are among the most peculiar objects in the sky. This spectral type, characterised by allowed and forbidden emission lines, and a large infrared excess, does not represent an homogenous class of objects, but instead, a mix of stella...
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The kinematic characteristics of magnetic O-type stars: Although magnetic fields have been discovered in ten massive O-type stars during the last years, the origin of their magnetic fields remains unknown. Among the magnetic O-type stars, two stars, HD36879 and HD57682, were identified as candidate runaway stars in the...
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Dynamical investigation of the multiple star ADS 9173 AB: Star ADS 9173=WDS 14135+5147=Hip 69483 is a complex system. The B component has a spectroscopic companion, whose orbit with a period of 4.9 years has been known since 1986. The Gaia telescope has detected a distant faint pair over 100 arcsec away from the bright...
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EUV Emission and Scattered Light Diagnostics of Equatorial Coronal Holes as Seen by Hinode/EIS: Spectroscopic diagnostics of solar coronal plasmas critically depends on the uncertainty in the measured line intensities. One of the main sources of uncertainty is instrumental scattered light, which is potentially most i...
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Achieving Fast Reconnection in Resistive MHD Models via Turbulent Means: Astrophysical fluids are generally turbulent and this preexisting turbulence must be taken into account for the models of magnetic reconnection which are attepmted to be applied to astrophysical, solar or heliospheric environments. In addition, re...
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Characterization of solar-cycle induced frequency shift of medium- and high-degree acoustic modes: Although it is well known that the solar acoustic mode frequency increases as the solar activity increases, the mechanism behind it is still unknown. Mode frequencies with 20 < l < 900 obtained by applying spherical har...
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Effect of latitudinal differential rotation on solar Rossby waves: Critical layers, eigenfunctions, and momentum fluxes in the equatorial $β$ plane: Retrograde-propagating waves of vertical vorticity with longitudinal wavenumbers between 3 and 15 have been observed on the Sun with a dispersion relation close to tha...
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Calibration of the mixing-length parameter $α$ for the MLT and FST models by matching with CO$^5$BOLD models: The CoRoT and Kepler missions provided a wealth of high-quality data for solar-like oscillations. To make the best of such data for seismic inferences, we need theoretical models with precise near-surface str...
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The nonisothermal stage of magnetic star formation. II. Results: In a previous paper we formulated the problem of the formation and evolution of fragments (or cores) in magnetically-supported, self-gravitating molecular clouds in axisymmetric geometry, accounting for the effects of ambipolar diffusion and Ohmic dissipa...
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Multiscale statistical analysis of coronal solar activity: Multi-filter images from the solar corona are used to obtain temperature maps which are analyzed using techniques based on proper orthogonal decomposition (POD) in order to extract dynamical and structural information at various scales. Exploring active regions...
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The orbital and superhump periods of the dwarf nova SDSS J093249.57+472523.0: We report unfiltered CCD photometry of the eclipsing dwarf nova SDSS J093249.57+472523.0 obtained during its first confirmed outburst in 2011 March. The outburst amplitude was at least 3.0 magnitudes above mean quiescence and it lasted at l...
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The Progress of Solar Cycle 24 at High Latitudes: The "extended" solar cycle 24 began in 1999 near 70 degrees latitude, similarly to cycle 23 in 1989 and cycle 22 in 1979. The extended cycle is manifested by persistent Fe XIV coronal emission appearing near 70 degrees latitude and slowly migrating towards the equator, ...
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Bipolar jets produced by a spectroscopic binary: We present evidence that the spectroscopically identified bipolar jets of the pre-main sequence binary KH 15D are a common product of the whole binary system, rather than being launched from either star individually. They may be launched from the innermost part of the ci...
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The Massive Binary System 9 Sgr Revisited: New Insights into Disentangling Methods: Disentangling techniques are often needed to obtain the spectra of the individual components of binary or multiple systems. A thorough analysis of the shift-and-add algorithm of Marchenko, Moffat, & Eenens (1998) reveals that in many ...
astro-ph_SR
Magnetohydrodynamic Turbulent Cascade of Coronal Loop Magnetic Fields: The Parker model for coronal heating is investigated through a high resolution simulation. An inertial range is resolved where fluctuating magnetic energy E_M (k_perp) \propto k_\perp^{-2.7} exceeds kinetic energy E_K (k_\perp) \propto k_\perp^{-0.6...
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Statistical Study and Live Catalogue of Multi-Spacecraft 3He-Rich Time Periods over Solar Cycles 23, 24, and 25: Using ion measurements from Ultra-Low-Energy Isotope Spectrometer (ULEIS) observations onboard Advanced Composition Explorer (ACE) and Solar Isotope Spectrometer (SIS) observations onboard the Solar Terres...
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Spiral arms and instability within the AFGL 4176 mm1 disc: We present high-resolution (30 mas or 130 au at 4.2 kpc) Atacama Large Millimeter/submillimeter Array observations at 1.2 mm of the disc around the forming O-type star AFGL 4176 mm1. The disc (AFGL 4176 mm1-main) has a radius of ~1000 au and contains significan...
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Multi-Channel Three-Dimensional SOLA Inversion for Local Helioseismology: Inversions for local helioseismology are an important and necessary step for obtaining three-dimensional maps of various physical quantities in the solar interior. Frequently, the full inverse problems that one would like to solve prove intractab...
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GW Librae: Still Hot Eight Years Post-Outburst: We report continued Hubble Space Telescope (HST) ultraviolet spectra and ground-based optical photometry and spectroscopy of GW Librae eight years after its largest known dwarf nova outburst in 2007. This represents the longest cooling timescale measured for any dwarf nov...
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Analytical expressions for the envelope binding energy of giants as a function of basic stellar parameters: The common-envelope (CE) phase is an important stage in the evolution of binary stellar populations. The most common way to compute the change in orbital period during a CE is to relate the binding energy of th...
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Predicting convective blueshift and radial-velocity dispersion due to granulation for FGK stars: To detect Earth-mass planets using the Doppler method, a major obstacle is to differentiate the planetary signal from intrinsic stellar variability (e.g., pulsations, granulation, spots and plages). Convective blueshift, ...
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The dependence of the evolution of SN type Ia progenitors on the C burning rate uncertainty and parameters of convective boundary mixing: Evolution of a supernova type Ia progenitor requires formation of a CO white dwarf, which implies a dependence on the C burning rate (CBR). It can also be affected by the recently ...
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A resolved debris disk around the candidate planet-hosting star HD95086: Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD95086. The strong infrared excess of the system indicates that, similarly to HR8799, {\ss} Pic, and Fomalhaut, the star harbors a circumste...
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Exploring the RCrA environment with SPHERE: Discovery of a new stellar companion: Aims. R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. It has very red colors, probably due to dust absorption and it is strongly variable. High contrast instrume...
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Intense bipolar structures from stratified helical dynamos: We perform direct numerical simulations of the equations of magnetohydrodynamics with external random forcing and in the presence of gravity. The domain is divided into two parts: a lower layer where the forcing is helical and an upper layer where the helicity...
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Molecules with ALMA at Planet-forming Scales (MAPS) XIII: HCO$^+$ and disk ionization structure: We observed HCO$^+$ $J=1-0$ and H$^{13}$CO$^+$ $J=1-0$ emission towards the five protoplanetary disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480 as part of the MAPS project. HCO$^+$ is detected and mapped at 0....
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The diversity of light curve variations of Blazhko stars: The ground-based Konkoly Blazhko Survey I and II aim to collect accurate, extended, multicolour light curves of galactic field RRab stars in order to determine the incidence rate of the modulation in the sample, to study the modulation in details, to study long-...
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The single-sided pulsator CO~Camelopardalis: CO~Cam (TIC 160268882) is the second ``single-sided pulsator'' to be discovered. These are stars where one hemisphere pulsates with a significantly higher amplitude than the other side of the star. CO~Cam is a binary star comprised of an Am $\delta$~Sct primary star with $T_...
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Temporal and Spatial Evolutions of a Large Sunspot Group and Great Auroral Storms around the Carrington Event in 1859: The Carrington event is considered to be one of the most extreme space weather events in observational history within a series of magnetic storms caused by extreme interplanetary coronal mass ejectio...
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Gaps in the Main-Sequence of Star Cluster Hertzsprung Russell Diagrams: The presence of gaps or regions of small numbers of stars in the main sequence of the Hertzsprung Russell Diagram (HRD) of star clusters has been reported in literature. This is interesting and significant as it could be related to star formation a...
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NIKA2 observations around LBV stars: emission from stars and circumstellar material: Luminous Blue Variable (LBV) stars are evolved massive objects, previous to core-collapse supernova. LBVs are characterized by photometric and spectroscopic variability, produced by strong and dense winds, mass-loss events and very i...
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On WD-WD Mergers in Triple Systems: The Role of Kozai Resonance with Tidal Friction: White dwarf-white dwarf (WD-WD) mergers may lead to type Ia supernovae events. Thompson (2011) suggested that many such binaries are produced in hierarchical triple systems. The tertiary induces eccentricity oscillations in the inner...
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Variable stars in Palomar 13; an evaporating globular cluster: We present new CCD $VI$ photometry of the distant globular cluster Pal 13. Fourier decomposition of the light curves of the three cluster member RRab stars lead to estimations of [Fe/H]=-1.65, and a distance of 23.67$\pm$0.57 kpc. Light and colour near mini...
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The Outburst of the Young Star Gaia19bey: We report photometry and spectroscopy of the outburst of the young stellar object Gaia19bey. We have established the outburst light curve with archival Gaia G, ATLAS Orange, ZTF r-band and Pan-STARRS rizy-filter photometry, showing an outburst of approximately 4 years duration,...
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The Sun Remains Relatively Refractory Depleted: Elemental Abundances for 17,412 Gaia RVS Solar Analogs and 50 Planet Hosts: The elemental abundances of stars, particularly the refractory elements (e.g., Fe, Si, Mg), play an important role in connecting stars to their planets. Most Sun-like stars do not have refractor...
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Origin of the CEMP-no Group Morphology in the Milky Way: The elemental-abundance signatures of the very first stars are imprinted on the atmospheres of CEMP-no stars, as various evidence suggests they are bona-fide second-generation stars. It has recently been recognized that the CEMP-no stars can be sub-divided into a...
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Chemical Compositions of a sample of candidate post-AGB stars: We have derived elemental abundances for a sample of nine IRAS sources with colours similar to those of post-AGB stars. For IRAS 01259+6823, IRAS 05208-2035, IRAS 04535+3747 and IRAS 08187-1905 this is the first detailed abundance analysis based upon high r...
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Ensemble Learning for CME Arrival Time Prediction: The Sun constantly releases radiation and plasma into the heliosphere. Sporadically, the Sun launches solar eruptions such as flares and coronal mass ejections (CMEs). CMEs carry away a huge amount of mass and magnetic flux with them. An Earth-directed CME can cause se...
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Shape-based Feature Engineering for Solar Flare Prediction: Solar flares are caused by magnetic eruptions in active regions (ARs) on the surface of the sun. These events can have significant impacts on human activity, many of which can be mitigated with enough advance warning from good forecasts. To date, machine learn...
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A new way to infer variations of the seismic solar radius: We show that the mean phase of waves propagating all the way from the far side of the Sun to the front side, as measured by seismic holography, varies with time. The change is highly anticorrelated with solar cycle activity and is consistent with other recent r...
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Multiple Star Systems in the Orion Nebula: This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium Cluster with the recently comissioned GRAVITY instrument. We observe a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for $\theta ^1$ Or...
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Measuring stellar rotation periods with Kepler: We measure rotation periods for 12151 stars in the Kepler field, based on the photometric variability caused by stellar activity. Our analysis returns stable rotation periods over at least six out of eight quarters of Kepler data. This large sample of stars enables us to ...
astro-ph_SR
Rotational Splitting of Pulsational Modes: Mode splittings produced by uniform rotation and a particular form of differential rotation are computed for two-dimensional rotating 10 Mo ZAMS stellar models. The change in the character of the mode splitting is traced as a function of uniform rotation rate, and it is found ...
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The HST Large Programme on NGC6752. II. Multiple populations at the bottom of the main sequence probed in NIR: Historically, multiple populations in Globular Clusters (GCs) have been mostly studied from ultraviolet and optical filters down to stars that are more massive than ~0.6 solar masses. Here we exploit deep ne...
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2M17091769+3127589: a mass-transfer binary with an extreme mass ratio: We present the orbital solution of a peculiar double-lined spectroscopic and eclipsing binary system, 2M17091769+3127589. This solution was obtained by a simultaneous fit of both APOGEE radial velocities and TESS and ASAS-SN light curves to determin...
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Physical conditions around 6.7 GHz methanol masers-I: Ammonia: Methanol masers at 6.7 GHz are known to be tracers of high-mass star formation in our Galaxy. In this paper, we study the large scale physical conditions in the star forming clumps/cores associated with 6.7 GHz methanol masers using observations of the (1,1...
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A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona: We present a comprehensive radiative magnetohydrodynamic simulation of the quiet Sun and large solar active regions. The 197 Mm wide simulation domain spans from 18 (10) Mm beneath t...
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The Joint Milli-Arcsecond Pathfinder Survey (JMAPS): Mission Overview and Attitude Sensing Applications: The Joint Milliarcsecond Pathfinder Survey (JMAPS) is a Department of Navy bright star astrometric all-sky survey scheduled for launch in the 2012 timeframe. Mission objectives include a complete update of star po...
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Differential photometry of delta Scorpii during 2011 periastron: Hundred observations of Delta Scorpii over 200 days, from April 2 to October 16, 2011, have been made for AAVSO visually and digitally from Rio de Janeiro, Rome and Paris. The three most luminous pixels either of the target star and the two reference star...
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Optical flare activity in the low-mass eclipsing binary GJ~3236: We present our observations of the low-mass eclipsing binary GJ~3236. We have analyzed a phased $R_C$ light-curve and confirmed previously determined fundamental parameters of the components. We detected evolution of the spot(s) and found that there exist...
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A first eROSITA view of ultracool dwarfs: We present the first X-ray detections of ultracool dwarfs (UCDs) from the first all-sky survey of the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Russian Spektrum-Roentgen-Gamma (SRG) mission. We use three publicly available input catalogs of ...
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Temporal and latitudinal variations of Ca-K plage and network area: An implication to meridional flows: The Ca-K spectroheliograms obtained at the Kodaikanal observatory (KO) are used to generate a uniform time series using the equal contrast technique (ECT) to study the long and short-term variation in the solar chr...
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Discovery of possible molecular counterparts to the infrared Double Helix Nebula in the Galactic center: We have discovered two molecular features at radial velocities of -35 km/s and 0 km/s toward the infrared Double Helix Nebula (DHN) in the Galactic center with NANTEN2. The two features show good spatial correspon...
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Transients Obscured by Dusty Disks: Dust absorption is invoked in a number of contexts for hiding a star that has survived some sort of transient event from view. Dust formed in a transient is expanding away from the star and, in spherical models, the mass and energy budgets implied by a high optical depth at late time...
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Principle of Minimum Energy in Magnetic Reconnection in a Self-Organized Critical Model for Solar Flares: Solar flares are an abrupt release of magnetic energy in the Sun's atmosphere due to reconnection of the coronal magnetic field. This occurs in response to turbulent flows at the photosphere which twist the coron...
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The 1600 Angstrom Emission Bump in Protoplanetary Disks: A Spectral Signature of H$_{2}$O Dissociation: The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that addition...
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Discovery of periodic class II methanol masers associated with G339.986-0.425 region: Ten new class II methanol masers from the 6.7-GHz Methanol Multibeam survey catalogues III and IV were selected for a monitoring programme at both 6.7 and 12.2 GHz with the 26m Hartebeesthoek Radio Astronomy Observatory (HartRAO) ra...
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The Chromospheric Response to the Sunquake generated by the X9.3 Flare of NOAA 12673: Active region NOAA 12673 was extremely volatile in 2017 September, producing many solar flares, including the largest of solar cycle 24, an X9.3 flare of 06 September 2017. It has been reported that this flare produced a number of s...
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Chemical Yields from Supernovae and Hypernovae: We review the final stages of stellar evolution, supernova properties, and chemical yields as a function of the progenitor's mass M. (1) 8 - 10 Ms stars are super-AGB stars when the O+Ne+Mg core collapses due to electron capture. These AGB-supernovae may constitute an SN ...
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