Science topics: Space ScienceStellar Astrophysics
Science topic
Stellar Astrophysics - Science topic
Stellar Astrophysics is the study of stars by means of theoretical physics and observational astronomy. Astronomy was turned into an active field of Physics by explaining stellar structure and evolution through natural laws of Physics. One novel example of such explanations is the famous Chandrashekhar limit discovered by one of the most famous astrophysicists of all time Subrahmanyan Chandrasekhar.
Publications related to Stellar Astrophysics (10,000)
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Background: Type I X-Ray bursts (XRBs) are energetic stellar explosions that occur on the surface of a neutron star in an accreting binary system with a low-mass H/He-rich companion. The rate of the $^{34}$Ar($\alpha,p$)$^{37}$K reaction may influence features of the light curve that results from the underlying thermonuclear runaway, as shown in re...
Contact binaries challenge contemporary stellar astrophysics with respect to their incidence, structure, and evolution. We explore these issues through a detailed study of two bright examples: S Ant and $\varepsilon$ CrA, that permit high-resolution spectroscopy at a relatively good S/N ratio. The availability of high-quality photometry, including...
Sirius is the brightest star in the night sky and, despite its proximity, this binary system still imposes intriguing questions about its current characteristics and past evolution. Bond et. al. (arXiv:1703.10625) published decades of astrometric measurements of the Sirius system, determining the dynamical masses for Sirius A and B, and the orbital...
Asteroseismology of dwarf stars cooler than the Sun is very challenging owing to the low amplitudes and rapid timescales of oscillations. Here we present the asteroseismic detection of solar-like oscillations at 4-minute timescales ( ν max ∼ 4300 μ Hz) in the nearby K dwarf σ Draconis using extreme-precision Doppler velocity observations from the K...
Context. Blue large-amplitude pulsators (BLAPs) are a recently discovered group of hot stars pulsating in radial modes. Their origin needs to be explained, and several scenarios for their formation have already been proposed.
Aims. We investigate whether BLAPs can originate as the product of a merger of two low-mass white dwarfs (WDs) and estimate...
Asteroseismology is the study of the interior physics and structure of stars using their pulsations. It is applicable to stars across the Hertzsprung-Russell (HR) diagram and a powerful technique to measure masses, radii and ages, but also directly constrain interior rotation, chemical mixing, and magnetism. This is because a star's self-excited pu...
Contact binaries challenge contemporary stellar astrophysics with respect to their incidence, structure and evolution. We explore these issues through a detailed study of two bright examples: S Ant and Eps CrA, that permit high-resolution spectroscopy at a relatively good S/N ratio. The availability of high-quality photometry, including data from t...
Helium-burning stars, in particular Cepheids, are especially difficult to model, as the choice of free parameters can greatly impact the shape of the blue loops—the part of the evolutionary track at which the instability strip is crossed. Contemporary one-dimensional stellar evolution codes, like Modules for Experiments in Stellar Astrophysics ( ME...
The solar atmosphere is a complex environment with diverse species and varying ionization states, especially in the chromosphere, where significant ionization variations occur. This region transitions from highly collisional to weakly collisional states, leading to complex plasma state transitions influenced by magnetic strengths and collisional pr...
Context. A central challenge in the field of stellar astrophysics lies in accurately determining the mass of stars, particularly when dealing with isolated ones. However, for pulsating white dwarf stars, the task becomes more tractable due to the availability of multiple approaches such as spectroscopy, asteroseismology, astrometry, and photometry,...
This study applied machine learning models to estimate stellar rotation periods from corrected light curve data obtained by the NASA Kepler mission. Traditional methods often struggle to estimate rotation periods accurately due to noise and variability in the light curve data. The workflow involved using initial period estimates from the LS-Periodo...
A central challenge in the field of stellar astrophysics lies in accurately determining the mass of isolated stars. However, for pulsating white dwarf (WD) stars, the task becomes more tractable due to the availability of multiple approaches such as spectroscopy, asteroseismology, astrometry, and photometry. The objective of this work is to compare...
Supersoft X-ray sources (SSSs) have been proposed as one of the progenitors for Type Ia supernovae. However, the exact origin of the quasi-periodic variability in the optical light curve remains a mystery.In this work, our goal is to investigate the effect of the feedback of an evolved main-sequence companion star on X-ray irradiation and find whet...
Context. Supersoft X-ray sources (SSSs) have been proposed as one of the progenitors for Type Ia supernovae. However, the exact origin of the quasi-periodic variability in the optical light curve remains a mystery.
Aims. In this work, our goal is to investigate the effect of the feedback of an evolved main-sequence companion star on X-ray irradiati...
Spectral lines of hot massive stars are known to exhibit large excess broadening in addition to rotational broadening. This excess broadening is often attributed to macroturbulence whose physical origin is a matter of active debate in the stellar astrophysics community. By looking into the statistical properties of a large sample of O- and B-type s...
We used synthetic photometry from DR3 BP and RP spectra for a large selected sample of stars in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) to derive the magnitude of the red giant branch (RGB) tip for these two galaxies in several passbands across a range of widely used optical photometric systems, including those of space mi...
Context . The estimation of rotation periods of stars is a key challenge in stellar astrophysics. Given the large amount of data available from ground-based and space-based telescopes, there is a growing interest in finding reliable methods to quickly and automatically estimate stellar rotation periods with a high level of accuracy and precision.
A...
Helium-burning stars, in particular Cepheids, are especially difficult to model, as the choice of free parameters can greatly impact the shape of the blue loops - the part of the evolutionary track at which instability strip is crossed. Contemporary one-dimensional stellar evolution codes, like MESA (Modules for Experiments in Stellar Astrophysics)...
The source of the Galactic lithium (Li) has long been a puzzle. With the discovery of Li in novae, extensive research has been conducted. However, there still exists a significant disparity between the observed abundance of Li in novae and the existing theoretical predictions. Using the Modules for Experiments in Stellar Astrophysics, we simulate t...
We present optical follow-up of IGR J16194-2810, a hard X-ray source discovered by the INTEGRAL mission. The optical counterpart is a ∼500 L ⊙ red giant at a distance of 2.1 kpc. We measured 17 radial velocities (RVs) of the giant over a period of 271 days. Fitting these RVs with a Keplerian model, we find an orbital period of P orb = 192.73 ± 0.01...
Recent James Webb Space Telescope data analyses have shown that massive red galaxies existed at redshifts z ≳ 6, a discovery that is difficult to understand in the context of standard cosmology (ΛCDM). Here, we analyze these observations more deeply, by fitting a stellar population model to the optical and near-infrared photometric data. These fits...
We present a comprehensive evaluation of proprietary and open-weights large language models using the first astronomy-specific benchmarking dataset. This dataset comprises 4,425 multiple-choice questions curated from the Annual Review of Astronomy and Astrophysics, covering a broad range of astrophysical topics. Our analysis examines model performa...
The source of the Galactic Lithium (Li) has long been a puzzle. With the discovery of Li in novae, extensive research has been conducted. However, there still exists a significant disparity between the observed abundance of lithium in novae and the existing theoretical predictions. Using the Modules for Experiments in Stellar Astrophysics (MESA), w...
Carbon fusion is important to understand the late stages in the evolution of a massive star. Astronomically interesting energy ranges for the 12C+12C reactions have been, however, poorly constrained by experiments. Theoretical studies on stellar evolution have relied on reaction rates that are extrapolated from those measured in higher energies. In...
Large samples of Am and Ap stars are helpful in studying the interplay between phenomena like atomic diffusion, magnetic fields, and stellar rotation in stellar astrophysics. Existing samples of Am and Ap stars, mostly obtained from spectral data with a signal-to-noise ratio in the g band (S/Ng) greater than 50, can benefit from expansion by explor...
Accurately characterizing the intrinsic stellar photometric noise induced by stellar astrophysics, such as stellar activity, granulation, and oscillations, is of crucial importance for detecting transiting exoplanets. In this study, we investigate the relation between the intrinsic stellar photometric noise, quantified by the Kepler combined differ...
Recent James Webb Space Telescope (JWST) data analyses have shown that massive red galaxies existed at redshifts $z>6$, a discovery that is difficult to understand in the context of standard cosmology ($\Lambda $CDM). Here we analyze these observations more deeply by fitting a stellar population model to the optical and near-infrared photometric da...
A number of stellar astrophysical phenomena, such as tidal novae and planetary engulfment, involve sudden injection of subbinding energy in a thin layer within the star, leading to mass ejection of the stellar envelope. We use a 1D hydrodynamical model to survey the stellar response and mass loss for various amounts ( E dep ) and locations of the e...
The blue supergiant (BSG) problem, namely, the overabundance of BSGs inconsistent with classical stellar evolution theory, remains an open question in stellar astrophysics. Several theoretical explanations have been proposed, which may be tested by their predictions for the characteristic time variability. In this work, we analyze the light curves...
Applications of Functional and Asymptotic Analysis are presented for an approximation scheme commonly used in stellar astrophysics - the Cowling approximation. Self-adjointness and symmetric integral operators are exploited to develop error estimates involved in the scheme. Asymptotic estimates are also employed to assure appropriate two-point boun...
We conduct an asteroseismological analysis on the non-Blazhko ab-type RR Lyrae star EPIC 248846335, employing the Radial Stellar Pulsations module of the Modules for Experiments in Stellar Astrophysics based on the set of stellar parameters. The atmospheric parameters T eff = 6933 ± 70 K, log g = 3.35 ± 0.50, and [Fe/H] = −1.18 ± 0.14 are estimated...
![Surface lithium (Li) abundance as a function of [Fe/H] for Milky Way...](publication/379834862/figure/fig1/AS:11431281237689829@1713664914156/Surface-lithium-Li-abundance-as-a-function-of-Fe-H-for-Milky-Way-dwarf-stars-blue_Q320.jpg)
The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is the optical and near-infrared high-resolution echelle spectrograph envisioned for the Extremely Large Telescope (ELT). We present a selection of science cases, supported by new calculations and simulations, where ANDES could enable major advances in the fields of stars and stellar popula...
Thanks to the recent advancement in producing rare isotopes and measuring their masses with unprecedented precision, the updated nuclear masses around the waiting-point nucleus 64Ge in the rapid-proton capture process have led to a significant revision of the surface gravitational redshift of the neutron star (NS) in GS 1826-24 by re-fitting its X-...
The Majorana transformation makes it possible to reduce the Thomas–Fermi equation to a first-order differential equation. This reduction is possible due to the special scaling property of the Thomas–Fermi equation under homology transformations. Such reductions are well known in the context of stellar astrophysics, where the use of homology-invaria...
Blue supergiants are the brightest stars in their host galaxies, and yet their evolutionary status has been a long-standing problem in stellar astrophysics. In this pioneering work, we present a large sample of 59 early B-type supergiants in the Large Magellanic Cloud with newly derived stellar parameters and identify the signatures of stars born f...
El presente proyecto de investigación surge a partir de la necesidad de introducir una enseñanza contextualizada de la física, para lo cual se vale de la astrofísica y utiliza las habilidades de pensamiento computacional (PC) como insumo didáctico. Para abordar esta cuestión, se llevó a cabo una revisión sistemática en la base de datos Scopus, con...
![Figure 8. The time of small dip of luminosity for both stars' vs Mass[M⊙]](publication/382927364/figure/fig5/AS:11431281270345827@1723042456251/The-time-of-small-dip-of-luminosity-for-both-stars-vs-MassM_Q320.jpg)
We explore how the main sequence evolution of 1-2 stars depend on the different nuclear reactions that occur in its core. We employ MESA (Modules for Experiments in Stellar Astrophysics) to analyze the effects of adding or removing reactions. The simulations showed counter-intuitive results where the PP chain stars lasted longer on the main sequenc...
Astrometry from the Gaia mission was recently used to discover the two nearest known stellar-mass black holes (BHs), Gaia BH1 and Gaia BH2. These objects are among the first stellar-mass BHs not discovered via X-rays or gravitational waves. Both systems contain ∼1 M ⊙ stars in wide orbits ( a ≈ 1.4 au, 4.96 au) around ∼9 M ⊙ BHs, with both stars (s...
We interpret the peculiar supersolar nitrogen abundance recently reported by the James Webb Space Telescope observations for GN-z11 ( z = 10.6) using our state-of-the-art chemical evolution models. The observed CNO ratios can be successfully reproduced—independently of the adopted initial mass function, nucleosynthesis yields, and presence of super...
The Transiting Exoplanet Survey Satellite (TESS) mission delivers time-series photometry for millions of stars across the sky, offering a probe into stellar astrophysics, including rotation, on a population scale. However, light-curve systematics related to the satellite’s 13.7 day orbit have prevented stellar rotation searches for periods longer t...
Detailed chemical composition of stars is of prime interest for a range of topics in modern stellar astrophysics, such as the chemical evolution of the Galaxy or the formation, composition, and structure of exoplanets. In this work, we derive the C and O abundances and update Sc, V, Mn, and Co abundances considering hyperfine structure effects (HFS...
The possibility of transparent stars remains a subject of ongoing research. While there is no direct evidence for their existence, theoretical models suggest that they could form under certain conditions. If discovered, transparent stars would represent a significant departure from our current understanding of stellar evolution and emission spectra...
The vast majority of stars in the nearby stellar neighborhood are M dwarfs. Their low masses and luminosities result in slow rates of nuclear evolution and minimal changes to the stars’ observable properties, even along astronomical timescales. However, they possess relatively powerful magnetic dynamos and resulting X-ray to UV (X–UV) activity, com...
The post-main sequence evolution in massive star evolution is a complex process that depends on various stellar model parameters. One of these numerous parameters is stellar mass loss. This study aims to analyze the lifetime of stars in the Red Supergiant (RSG) phase, their evolutionary tracks on the Hertzsprung-Russell (HR) diagram, and several ot...
Regular, automated testing is a foundational principle of modern software development. Numerous widely used continuous integration systems exist, but they are often not suitable for the unique needs of scientific simulation software. Here we describe the testing infrastructure developed for and used by the Modules for Experiments in Stellar Astroph...
We study a system of equations, involving a large parameter, arising from stellar astrophysics for which a combination of procedures are used to approximate a fundamental solution. This work may be of broad interest for its demonstration of combined applications of singular and non-singular perturbation methods aided by symbolic computation as well...
Low energy imprints of modifications to general relativity are often found in pressure balance equations inside stars. These modifications are then amenable to tests via astrophysical phenomena, using observational effects in stellar astrophysics that crucially depend on such equations. One such effect is tidal disruption of stars in the vicinity o...
The solar neighborhood is a unique stellar astrophysical laboratory formed by a variety of stars from different origins. In particular, two of the most notable populations known are the thick and thin disk stars, each characterized by distinct chemical compositions, ages, kinematics, and origins. Based on Tsallis nonextensive statistics, we investi...
Context. The origin of the initial rotation rates of stars, and how a star’s surface rotational velocity changes during the evolution, either by internal angular momentum transport or due to interactions with a binary companion, remain open questions in stellar astrophysics.
Aims. Here, we aim to derive the physical parameters and study the distrib...
Age is a fundamental stellar property, yet for many stars, it is difficult to reliably determine. For M dwarfs, it has been notoriously so. Due to their lower masses, core hydrogen fusion proceeds at a much slower rate in M dwarfs than it does in more massive stars like the Sun. As a consequence, more customary age determination methods (e.g., isoc...
We interpret the peculiar super-solar nitrogen abundance recently reported by the James Webb Space Telescope observations for GN-z11 (z=10.6) using our state-of-the-art chemical evolution models. The observed CNO ratios can be successfully reproduced -- independently of the adopted initial mass function, nucleosynthesis yields and presence of super...
The origin of initial rotation rates of stars, and how a star's surface rotational velocity changes during the evolution, either by internal angular momentum transport or due to interactions with a binary companion, remain open questions in stellar astrophysics. Here, we aim to derive the physical parameters and study the distribution of (projected...
The disc instability mechanism (DIM) is widely accepted to account for the transient behaviour of dwarf novae (DNe), which experience short outbursts separated by long quiescence. The duty cycle (the ratio between the outburst duration and the recurrence time) determines the amount of accreted mass by the white dwarf (WDs) during outbursts, thus pl...
In 1604, the last of the supernovae seen with the naked eye in the Milky Way had a great impact on the history of astronomy and cosmology. Scientists with different conceptions of the Universe - among them Galilei and Kepler but also Arab and Chinese astronomers - competed and collaborated to explain its nature, its origin and its astrological mean...
The launch of NASA’s Kepler space telescope in 2009 revolutionized the quality and quantity of observational data available for asteroseismic analysis. While Kepler was able to detect solar-like oscillations in hundreds of main-sequence and subgiant stars, the Transiting Exoplanet Survey Satellite is now making similar observations for thousands of...
Galaxy clusters enable unique opportunities to study cosmology, dark matter, galaxy evolution, and strongly-lensed transients. We here present a new cluster-finding algorithm, CluMPR (Clusters from Masses and Photometric Redshifts), that exploits photometric redshifts (photo-z's) as well as photometric stellar mass measurements. CluMPR uses a 2-dim...
The TESS mission delivers time-series photometry for millions of stars across the sky, offering a probe into stellar astrophysics, including rotation, on a population scale. However, light curve systematics related to the satellite's 13.7-day orbit have prevented stellar rotation searches for periods longer than 13 days, putting the majority of sta...
Age is a fundamental stellar property, yet for many stars it is difficult to reliably determine. For M dwarfs it has been notoriously so. Due to their lower masses, core hydrogen fusion proceeds at a much slower rate in M dwarfs than it does in more massive stars like the Sun. As a consequence, more customary age determination methods (e.g. isochro...
Context. The search and interpretation of non-radial pulsations from Be star light curves observed with the CoRoT satellite requires high-quality stellar astrophysical parameters.
Aims. The present work is devoted to the spectroscopic study of a sample of faint Be stars observed by CoRoT in the fourth long run (LRA02).
Methods. The astrophysical pa...
One promising way to extract information about stellar astrophysics from a gravitational-wave catalog is to compare the catalog to the outputs of stellar population synthesis modeling with varying physical assumptions. The parameter space of physical assumptions in population synthesis is high-dimensional and the choice of parameters that best repr...
This work deals with a new theoretical method proposed with the intent of improving the quality of astronomical polarimetric data. The theoretical method is applied to one of the simplest possible birefringent type polarizer device constructs, being a hybrid measurement procedure between the fixed position angles and the continuous rotation records...
Light curves are the primary observable of type-I x-ray bursts. Computational x-ray burst models must match simulations to observed light curves. Most of the error in simulated curves comes from uncertainties in $rp$ process reaction rates, which can be reduced via precision mass measurements of neutron-deficient isotopes in the $rp$ process path....
About ten percent of Sun-like (1–2 M ⊙ ) stars will engulf a 1–10 M J planet as they expand during the red giant branch (RGB) or asymptotic giant branch (AGB) phase of their evolution. Once engulfed, these planets experience a strong drag force in the star’s convective envelope and spiral inward, depositing energy and angular momentum. For these ma...
We enhance the treatment of crystallization for models of white dwarfs (WDs) in the stellar evolution software Modules for Experiments in Stellar Astrophysics (MESA) by implementing carbon–oxygen (C/O) phase separation. The phase separation process during crystallization leads to transport of oxygen toward the centers of WDs, resulting in a more co...
The technique of frequency phase transfer (FPT), enabled by multiband receivers with shared optical path (SOP), is set to become a true backbone of VLBI operations at frequencies above 22 GHz. The FPT has been successfully implemented at the Korean VLBI Network (KVN), while gaining ever more prominent attention worldwide. Over the next few years, F...
Context. The late phases of the orbital evolution of an Earth-like planet around a Sun-like star are revisited in order to consider the effect of density fluctuations associated with convective motions inside the star.
Aims. Such fluctuations produce a random perturbation of the stellar outer gravitational field that excites a small residual eccent...
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When the primary star in a close binary system evolves into a giant and engulfs its companion, its core and the companion temporarily orbit each other inside a common envelope. Drag forces transfer orbital energy and angular momentum to the envelope material. Depending on the efficiency of this process, the envelope may be ejected leaving behind a...
Stars that are over 1.6 solar masses are generally known to possess convective cores and radiative envelopes, which allows for the propagation of outwardly travelling internal gravity waves (IGWs). Here, we study the generation and propagation of IGWs in such stars using two-dimensional, fully non-linear hydrodynamical simulations with realistic st...
Context. Instrumental radial velocity (RV) precision has reached a level where the detection of planetary signals is limited by the ability to understand and simultaneously model stellar astrophysical “noise.” A common method for mitigating the effects of stellar activity is Gaussian process (GP) regression.
Aims. In this study we present an analys...
The NASA K2 mission that succeeded the nominal Kepler mission observed several hundred thousand stars during its operations. While most of the stars were observed in single campaigns of ∼80 days, some of them were targeted for more than one campaign. We perform an asteroseismic study of a sample of eight solar-like stars observed during K2 Campaign...
