Improved determination of the atmospheric parameters of the pulsating sdB star Feige 48

Abstract

As part of a multifaceted effort to exploit better the asteroseismological potential of the pulsating sdB star Feige 48, we present an improved spectroscopic analysis of that star based on new grids of NLTE, fully line-blanketed model atmospheres. To that end, we gathered four high S/N time-averaged optical spectra of varying spectral resolution from 1.0 Å to 8.7 Å, and we made use of the results of four independent studies to fix the abundances of the most important metals in the atmosphere of Feige 48. The mean atmospheric parameters we obtained from our four spectra of Feige 48 are : Teff= 29,850 $\pm$ 60 K, log $g$ = 5.46 $\pm$ 0.01, and log N(He)/N(H) = $-$2.88 $\pm$ 0.02. We also modeled for the first time the He II line at 1640 Å from the STIS archive spectrum of the star and we found with this line an effective temperature and a surface gravity that match well the values obtained with the optical data. With some fine tuning of the abundances of the metals visible in the optical domain we were able to achieve a very good agreement between our best available spectrum and our best-fitting synthetic one. Our derived atmospheric parameters for Feige 48 are in rather good agreement with previous estimates based on less sophisticated models. This underlines the relatively small effects of the NLTE approach combined with line blanketing in the atmosphere of this particular star, implying that the current estimates of the atmospheric parameters of Feige 48 are reliable and secure.

arXiv commentAccepted for publication in ApJ, April 2014

References in corpus (12)

• The chemical composition of the Sun
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• The Potential of Asteroseismology for Hot, Subdwarf B Stars: A New Class of Pulsating Stars?
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
• Structural Parameters of the Hot Pulsating B Subdwarf PG 1219+534 from Asteroseismology
• Hot subdwarf stars in close-up view - III. Metal abundances of subdwarf B stars
• The Potential of Multi-Colour Photometry for Pulsating Subdwarf B Stars
• Observations of the pulsating subdwarf B star Feige 48: Constraints on evolution and companions
• Detection of a companion to the pulsating sdB Feige 48
• A NLTE analysis of the hot subdwarf O star Bd+28 4211. I. The UV spectrum

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• A NLTE analysis of the hot subdwarf O star BD+28 4211. II. The optical spectrum