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Context. The homogenization of the stellar parameters is an important goal for large observational spectroscopic surveys, but it is very difficult to achieve it because of the diversity of the spectroscopic analysis methods used within a…

Reliable predictions of mass-loss rates are important for massive-star evolution computations. We aim to provide predictions for mass-loss rates and wind-momentum rates of O-type stars, carefully studying the behaviour of these winds as…

Solar and Stellar Astrophysics · Physics 2021-04-14 R. Björklund , J. O. Sundqvist , J. Puls , F. Najarro

I present here a review of past and present multi-disciplinary research of the Pittsburgh Computational AstroStatistics (PiCA) group. This group is dedicated to developing fast and efficient statistical algorithms for analysing huge…

Context. The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely…

Solar and Stellar Astrophysics · Physics 2011-08-15 R. S. Schnerr , H. F. Henrichs , C. Neiner , E. Verdugo , J. de Jong , V. C. Geers , K. Wiersema , B. van Dalen , A. Tijani , B. Plaggenborg , K. L. J. Rygl

Photometric redshifts are estimated on the basis of template scenarios with the help of the code ZPEG, an extension of the galaxy evolution model PEGASE.2 and available on the PEGASE web site. The spectral energy distribution (SED)…

Astrophysics · Physics 2009-11-07 Damien Le Borgne , Brigitte Rocca-Volmerange

Analyzing the spectra from Wolf-Rayet stars requires adequate non-LTE modeling of their expanding atmosphere. The numerical schemes for solving the radiative transfer in the co-moving frame of reference have been developed by Mihalas and…

Solar and Stellar Astrophysics · Physics 2014-11-20 W. -R. Hamann , G. Graefener , L. M. Oskinova , A. Feldmeier

Automated method of full spectrum fitting gives reliable estimates of stellar atmospheric parameters (Teff, logg and [Fe/H]) for late A, F, G and early K type stars. Recently, the technique was further improved in the cooler regime and the…

Solar and Stellar Astrophysics · Physics 2018-07-24 Kaushal Sharma , Santosh Joshi , H. P. Singh

Recently, machine learning methods presented a viable solution for automated classification of image-based data in various research fields and business applications. Scientists require a fast and reliable solution to be able to handle the…

Solar and Stellar Astrophysics · Physics 2020-07-07 T. Szklenár , A. Bódi , D. Tarczay-Nehéz , K. Vida , G. Marton , Gy. Mező , A. Forró , R. Szabó

(abridged) Mass loss is a key parameter in the evolution of massive stars, with discrepancies between theory and observations and with unknown importance of the episodic mass loss. To address this we need increased numbers of classified…

Solar and Stellar Astrophysics · Physics 2022-10-19 Grigoris Maravelias , Alceste Z. Bonanos , Frank Tramper , Stephan de Wit , Ming Yang , Paolo Bonfini

Recent advances in the modelling of stellar winds driven by radiation pressure make it possible to fit many wind-sensitive features in the UV spectra of hot stars, opening the way for a hydrodynamically consistent determination of stellar…

Astrophysics · Physics 2007-05-23 A. W. A. Pauldrach , T. L. Hoffmann , R. H. Méndez

We present analysis of both the resolved X-ray emission line profiles and the broadband X-ray spectrum of the O2 If* star HD 93129A, measured with the Chandra HETGS. This star is among the earliest and most massive stars in the Galaxy, and…

We provide an extensive set of theoretical spectral energy distributions of massive stars derived from our "combined stellar structure and atmosphere models". The calculations covering the entire main sequence evolution for initial masses…

Astrophysics · Physics 2016-08-30 Daniel Schaerer , Alex de Koter

The properties of exoplanet host stars are traditionally characterized through a detailed forward-modeling analysis of high-resolution spectra. However, many exoplanet radial velocity surveys employ iodine-cell-calibrated spectrographs,…

Earth and Planetary Astrophysics · Physics 2024-01-17 Jude Gussman , Malena Rice

X-rays/EUV radiation emitted from wind-embedded shocks in hot, massive stars can affect the ionization balance in their outer atmospheres, and can be the mechanism responsible for the production of highly ionized species. To allow for these…

Solar and Stellar Astrophysics · Physics 2016-05-18 Luiz P. Carneiro , J. Puls , J. O. Sundqvist , T. L. Hoffmann

Innovation in the ground and space-based instruments has taken us into a new age of spectroscopy, in which a large amount of stellar content is becoming available. So, automatic classification of stellar spectra became subjective in recent…

Solar and Stellar Astrophysics · Physics 2020-06-26 Y. A. Azzam , M. I. Nouh , A. A. Shaker

Over the last decades, evolutionary population synthesis models have powered an unmatched leap forward in our understanding of galaxies. From dating the age of the first galaxies in the Universe to detailed measurements of the chemical…

Astrophysics of Galaxies · Physics 2024-11-13 I. Martín-Navarro , A. Vazdekis

In this paper, we explore the feasibility of using machine learning regression as a method of extracting basic stellar parameters and line-of-sight extinctions from spectro-photometric data. We built a stable gradient-boosted random-forest…

Intermediate-mass stars are often fast rotators, and hence are centrifugally flattened and affected by gravity darkening. To analyse this kind of stars properly, one must turn to 2D models to compute the visible radiative flux and to take…

Solar and Stellar Astrophysics · Physics 2024-02-28 Axel Lazzarotto , Alain Hui-Bon-Hoa , Michel Rieutord

Libraries of stellar spectra, such as ELODIE (Prugniel & Soubiran 2001), CFLIB (Valdes et al. 2004), or MILES (S\'anchez-Bl\'azquez et al. 2006), are used for a variety of applications, and especially in modelling stellar populations (e. g.…

Solar and Stellar Astrophysics · Physics 2018-07-24 Kaushal Sharma , H. P. Singh , A. Kashyap , P. Prugniel

The Sloan Digital Sky Survey has recently initiated its 5th survey generation (SDSS-V), with a central focus on stellar spectroscopy. In particular, SDSS-V Milky Way Mapper program will deliver multi-epoch optical and near-infrared spectra…