A5048516609- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Gamma-ray bursts and supernovae
- Geomagnetism and Paleomagnetism Studies
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Inertial Sensor and Navigation
- Field-Flow Fractionation Techniques
- Scientific Research and Discoveries
- Nonlinear Dynamics and Pattern Formation
- Opinion Dynamics and Social Influence
- Advanced Measurement and Metrology Techniques
- Geological and Geophysical Studies
- Phase Equilibria and Thermodynamics
- nanoparticles nucleation surface interactions
- Complex Systems and Time Series Analysis
Universidad de Granada
2022-2024
Instituto de Astrofísica de Andalucía
2024
University of Surrey
2018-2023
The University of Tokyo
2023
Scuola Internazionale Superiore di Studi Avanzati
2018
Max Planck Institute for Astrophysics
2018
Université Toulouse III - Paul Sabatier
2013-2016
Institut de Recherche en Astrophysique et Planétologie
2013-2016
Centre National de la Recherche Scientifique
2013-2016
Université de Toulouse
2013-2016
The process referred to as "semi-convection" in astrophysics and "double-diffusive convection the diffusive regime" Earth planetary sciences, occurs stellar interiors regions which are stable according Ledoux criterion but unstable Schwarzschild criterion. In this series of papers, we analyze results an extensive suite 3D numerical simulations process, ultimately propose a new 1D prescription for heat compositional transport regime can be used or structure evolution models. preliminary study...
Light curves and periodograms of 160 B stars observed by the TESS space mission 29 main-sequence from Kepler K2 were used to classify variability type. There are 114 in sample, which 45 classified as possible rotational variables. This confirms previous findings that a large fraction (about 40 percent) A may exhibit modulation. Gaia DR2 parallaxes estimate luminosities, radii equatorial velocities can be deduced. It is shown values projected lower than estimated for nearly all stars, they...
Properties of the first generation stars (Pop III), such as their initial mass function (IMF), are poorly constrained by observations and have yet to converge between simulations. The cosmological 21-cm signal neutral hydrogen is predicted be sensitive Lyman-band photons produced these stars, thus providing a unique way probe stellar population. In this paper, we investigate impacts Pop III IMF on cosmic dawn via Wouthuysen-Field effect, Lyman-Werner feedback, Ly-alpha heating, CMB heating....
ABSTRACT The first population of X-ray binaries (XRBs) is expected to affect the thermal and ionization states gas in early Universe. Although these sources are predicted have important implications for high-redshift observable signals, such as hydrogen 21-cm signal from cosmic dawn background, their properties poorly explored, leaving theoretical models largely uninformed. In this paper we model a arising zero metallicity stars. We explore how depend on adopted initial mass function (IMF)...
ABSTRACT We present the first asteroseismic results for δ Scuti and γ Doradus stars observed in Sectors 1 2 of TESS mission. utilize 2-min cadence data a sample 117 to classify their behaviour regarding variability place them Hertzsprung–Russell diagram using Gaia DR2 data. Included within our are eponymous members two pulsator classes, SX Phoenicis. Our pulsating intermediate-mass by also allows us confront theoretical models pulsation driving classical instability strip time show that...
Uncertainties in stellar structure and evolution theory are largest for stars undergoing core convection on the main sequence. A powerful way to calibrate free parameters used of interiors is asteroseismology, which provides direct measurements angular momentum element transport. We report detection classification new variable O B using high-precision short-cadence (2-min) photometric observations assembled by Transiting Exoplanet Survey Satellite (TESS). In our sample 154 stars, we detect a...
Context. The theoretically studied impact of rapid rotation on stellar evolution needs to be compared with these results high-resolution spectroscopy-velocimetry observations. Early-type stars present a perfect laboratory for studies. prototype A0 star Vega has been extensively monitored in recent years spectropolarimetry. A weak surface magnetic field was detected, implying that there might (still undetected) structured surface. First indications the presence small amplitude radial velocity...
The gravito-inertial waves propagating over a shellular baroclinic flow inside rotating spherical shell are analysed using the Boussinesq approximation. wave properties examined by computing paths of characteristics in non-dissipative limit, and solving full dissipative eigenvalue problem high-resolution spectral method. Gravito-inertial found to obey mixed-type second-order operator be often focused around short-period attractors or trapped wedge formed turning surfaces boundaries. We also...
We report an analysis of the first known Beta Cep pulsator observed by TESS mission, runaway star PHL 346 = HN Aqr. The star, previously as a singly-periodic pulsator, has at least 34 oscillation modes excited, 12 those in g-mode domain and 22 p modes. Analysis archival data implies that amplitude frequency dominant mode stellar radial velocity were variable over time. A binary nature would be inconsistent with inferred ejection from Galactic disc 420 km/s, which is too large to survivable...
Currently, the number of known planets around intermediate-mass stars (1.5 M_⊙ < M_⋆ 3.5 M_⊙) is rather low. As a consequence, models planet formation derive their strongest observational evidence from chemical signature mostly low-mass (FGK) main-sequence (MS) with planets. We aim to test whether well-known correlation between metallicity star and presence gas-giant found for MS still holds stars. In particular, we understand or not planet-metallicity relation changes as evolve pre-MS...
ABSTRACT Binary stars evolve into chemically peculiar objects and are a major driver of the galactic enrichment heavy elements. During their evolution they undergo interactions, including tides, that circularize orbits synchronize stellar spins, impacting both individual systems populations. Using Zahn’s tidal theory mesa main-sequence model grids, we derive governing parameters λlm E2, implement them in new mint library population code binary_c. Our equilibrium tides two to five times more...
Oscillation modes in fast-rotating stars can be split into several subclasses, each with their own properties. To date, seismology of these cannot rely on regular pattern analysis and scaling relations. However, recently there has been the promising discovery large separations observed spectra $\delta$ Scuti stars: they were attributed to island-mode subclass, linked stellar mean density through a law. In this work, we investigate relevance relation by computing models oscillation spectra....
Recent numerical and theoretical considerations have shown that low-degree acoustic modes in rapidly rotating stars follow an asymptotic formula recent observations of pulsations delta Scuti seem to match these expectations. However, a key question is whether strong gradients or discontinuities can adversely affect this pattern the point hindering its identification. Other important questions are how rotational splittings affected by 2D rotation profiles expected from baroclinic effects it...
Aims. The main goal of this work is to date young open clusters using $\delta$ Sct stars. Seismic indices such as the large separation and frequency at maximum power can help constrain models better characterise We propose a reliable method identify some radial modes, which gives us greater confidence in constrained models. Methods. extract content sample stars belonging same cluster. estimate low-order by means different techniques for each member sample. use grid built with typical...
Context . Over the last few years, δ Scuti stars have been at center of attention asteroseismology community thanks to derivation seismic indices connected stellar parameters. The statistical analysis wealth data offered by a large space survey such as Transiting Exoplanet Survey Satellite (TESS), identification new stars, and correlation between asteroseismic parameters in resulting sample are therefore utmost interest. Aims goal our study is analyze properties characterize observed TESS...
Context: Rapid rotation is a common feature of early-type stars but which remains challenge for the models. The understanding its effect on stellar evolution however imperative to interpret observed properties numerous stars. Aims: We wish bring more observational constraints fast rotating stars, especially their oscillation modes. Methods: focus nearby star Altair known as very rapidly with an equatorial velocity estimated recently at 313 km/s. this high-resolution spectropolarimeter...
As the global magnetic field of Sun has an activity cycle, one expects to observe some variation dynamical properties flows visible in photosphere. We investigate flow during solar cycle by analysing SDO/HMI observations continuum intensity, Doppler velocity and longitudinal field. first picked data at disk center 6 years along with a 48-hour time step order study overall evolution intensity Then we focused on thirty 6-hour sequences quiet regions without any remnant separated months, summer...
Asteroseismology has opened a window on the internal physics of thousands stars, by relating oscillation spectra properties to stars. Mode identification, namely process associating measured frequency corresponding mode geometry and properties, is cornerstone this analysis seismic spectra. In rapidly rotating stars identification challenging task that remains incomplete, as modes assume complex geometries regular patterns in frequencies get scrambled under influence Coriolis force...
While many intermediate- and high-mass main sequence stars are rapidly differentially rotating, the effects of rotation on oscillation modes poorly known. In this communication we present a first study axisymmetric gravito-inertial in radiative zone rotating star. We consider simplified model where star is linearly stratified fluid within spherical shell, with differential due to baroclinic effects. solve eigenvalue problem high-resolution spectral computations determine propagation domain...
Many early-type stars have been measured with high angular velocities. In such stars, mode identification is difficult as the effects of fast and differential rotation are not well known. Using fundamental parameters by interferometry, ESTER structure code TOP oscillation code, we investigate spectrum Rasalhague (alpha Ophiuchi), for which observations MOST satellite found 57 oscillations frequencies. Results do show a clear modes highlight difficulties asteroseismology very complex spectrum.
Abstract The presence of low-amplitude peaks over the noise in power spectra δ Scuti stars is frequently disregarded. These seemingly insignificant peaks, collectively referred to as grass, might contain valuable information about origin these and reasons behind occurrence or absence a plateau. It crucial systematically parameterize grass phenomenon throughout comprehensive sample that covers entire star parameter range. Thus, we conduct quantitative study long-duration, high-duty-cycle TESS...