arXiv subjects

J. P. Sánchez Arias

Publications and source records attributed to J. P. Sánchez Arias.

5 recordsLinked to original sources

arXiv2026

Photometric variability of blue supergiants: Constraints on stellar masses and evolutionary stages

Blue supergiants (BSGs) are crucial to understanding the evolution of massive stars. Although distinguishing between pre- and post-red supergiant (RSG) phases is challenging, stellar pulsations provide valuable constraints on their masses and evolutionary status. This study analyzes TESS light curves of six BSGs with high L/M to identify periodicities. We performed theoretical modeling of the radial unstable modes to characterize the strange modes. We aim to estimate asteroseismic masses, compare them with spectroscopic and evolutionary mass estimates, and assess the evolutionary stage of the stars. We employed the Lomb-Scargle periodogram and the weighted wavelet Z-transform to address quasiperiodic behavior and time-varying signals. A linear nonadiabatic stability analysis was performed to test for radial perturbations, generating eigenfrequencies that enable stellar mass estimation. In addition, we characterized the stochastic low-frequency variability (SLFV). We derive a first guess at the asteroseismic masses. We find that HD 74371 and HD 79186 are evolving blueward following the RSG phase, while the evolutionary stage of HD 115842 cannot be uniquely determined with the available mass estimates. We also find that HD 52382 and HD 99953 are likely in the post-RSG phase; however, their low masses are difficult to reconcile with the available evolutionary models. The extreme supergiant HD 80077 shows the largest mass discrepancy in the sample, suggesting a more complex evolutionary history. The SLFV properties do not provide a clear diagnostic of the evolutionary stage. These results highlight the potential of asteroseismology as a complementary tool for constraining the evolutionary status of BSGs. However, the mass discrepancies found for some objects indicate that additional observational and theoretical efforts are required.

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arXiv2020

Asteroseismology of the heartbeat star KIC 5006817

This paper summarizes the project work on asteroseismology at the ERASMUS+ GATE 2020 Summer school on space satellite data. The aim was to do a global asteroseismic analysis of KIC 5006817 and quantify its stellar properties using the high-quality, state of the art space missions data. We employed the aperture photometry to analyze the data from the Kepler space telescope and the Transiting Exoplanet Survey Satellite (TESS). Using the lightkurve Python package, we have derived the asteroseismic parameters and calculated the stellar parameters using the scaling relations. Our analysis of KIC 5006817 confirmed its classification as a heartbeat binary. The rich oscillation spectrum facilitate estimating power excess ($ν_{\rm max}$) at 145.50$\pm$0.50 $μ$Hz and large frequency separation ($Δν$) to be 11.63$\pm$0.10 $μ$Hz. Our results showed that the primary component is a low-luminosity, red-giant branch star with a mass, radius, surface gravity, and luminosity of 1.53$\pm$0.07 M$_\odot$, 5.91$\pm$0.12 R$_\odot$, 3.08$\pm$0.01 dex, and 19.66$\pm$0.73 L$_\odot$, respectively. The orbital period of the system is 94.83$\pm$0.05 d.

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arXiv2019

The first view of $δ$ Scuti and $γ$ Doradus stars with the TESS mission

We present the first asteroseismic results for $δ$ Scuti and $γ$ Doradus stars observed in Sectors 1 and 2 of the TESS mission. We utilise the 2-min cadence TESS data for a sample of 117 stars to classify their behaviour regarding variability and place them in the Hertzsprung-Russell diagram using Gaia DR2 data. Included within our sample are the eponymous members of two pulsator classes, $γ$ Doradus and SX Phoenicis. Our sample of pulsating intermediate-mass stars observed by TESS also allows us to confront theoretical models of pulsation driving in the classical instability strip for the first time and show that mixing processes in the outer envelope play an important role. We derive an empirical estimate of 74% for the relative amplitude suppression factor as a result of the redder TESS passband compared to the Kepler mission using a pulsating eclipsing binary system. Furthermore, our sample contains many high-frequency pulsators, allowing us to probe the frequency variability of hot young $δ$ Scuti stars, which were lacking in the Kepler mission data set, and identify promising targets for future asteroseismic modelling. The TESS data also allow us to refine the stellar parameters of SX Phoenicis, which is believed to be a blue straggler.

astro-ph.SR↗

arXiv2016

Asteroseismology of hybrid $δ$ Scuti--$γ$ Doradus pulsating stars

Hybrid $δ$ Scuti-$γ$ Doradus pulsating stars show acoustic ($p$) oscillation modes typical of $δ$ Scuti variable stars, and gravity ($g$) pulsation modes characteristic of $γ$ Doradus variable stars simultaneously excited. Observations from space missions like MOST, CoRoT, and \emph{Kepler} have revealed a large number of hybrid $δ$ Scuti-$γ$ Doradus pulsators, thus paving the way for a exciting new channel for asteroseismic studies. We perform a detailed asteroseismological modeling of five hybrid $δ$ Scuti-$γ$ Doradus stars. We employ a grid-based modeling approach to sound the internal structure of the target stars by employing a huge grid of stellar models from the zero-age main sequence to the terminal-age main sequence, varying parameters like stellar mass, effective temperature, metallicity and core overshooting. We compute their adiabatic radial ($\ell= 0$) and non-radial ($\ell= 1, 2, 3$) $p$ and $g$ mode periods. We employ two model-fitting procedures to searching for the models that best reproduce the observed pulsation spectra of each target star, that is, the asteroseismological models. We derive the fundamental parameters and the evolutionary status of five hybrid $δ$ Scuti-$γ$ Doradus variable stars recently observed with the CoRoT and \emph{Kepler} space missions: CoRoT 105733033, CoRoT 100866999, KIC 11145123, KIC 9244992, and HD 49434. The asteroseismological model for each star results from different criteria of model selection, in which we take full advantage of the richness of periods that characterizes the pulsation spectra of this kind of stars.

astro-ph.SR↗

arXiv2016

Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*

Context. The discovery of pulsations in low-mass stars opens an opportunity for probing their interiors and to determine their evolution, by employing the tools of asteroseismology. Aims. We aim to analyze high-speed photometry of SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25 and discover brightness variabilities. In order to locate these stars in the $T_{\rm eff} - \log g$ diagram we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods. To carry out this study, we used the photometric data obtained by us for these stars with the 2.15m telescope at CASLEO, Argentina. We analyzed their light curves and we apply the Discrete Fourier Transform to determine the pulsation frequencies. Finally, we compare both stars in the $T_{\rm eff} - \log g$ diagram, with known two pre-white dwarfs, seven pulsating pre-ELM white dwarf stars, $δ$ Scuti and SX Phe stars. Results. We report the discovery of pulsations in SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25. We determine their effective temperature and surface gravity to be $T_{\rm eff}$ = 7 972 $\pm$ 200 K, $\log g$ = 4.25 $\pm$ 0.5 and $T_{\rm eff}$ = 7 925 $\pm$ 200 K, $\log g$ = 4.25 $\pm$ 0.5, respectively. With these parameters these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ~ 0.17 Mo) or more massive SX Phe stars. We identified pulsation periods of 3 278.7 and 1 633.9 s for SDSSJ145847.02$+$070754.46 and a pulsation period of 3 367.1 s for SDSSJ173001.94$+$070600.25. These two new objects together with those of Maxted et al. (2013, 2014) indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded.

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