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Astronomy & Astrophysics manuscript no. H4669 October 9, 2003 (DOI: will be inserted by hand later)

Summary: Astronomy & Astrophysics manuscript no. H4669 October 9, 2003
(DOI: will be inserted by hand later)
Physical parameters of helium­rich subdwarf B stars from
spectral energy distributions #
A. Ahmad and C. S. Je#ery
Armagh Observatory, College Hill, Armagh BT61 9DG. N. Ireland. UK
Received 15 July 2003 / Accepted 02 October 2003
Abstract. We present e#ective temperatures and angular radii for eleven helium­rich subdwarf B stars. These are measured
using spectral energy distributions from archival IUE spectra and existing optical and infrared photometry. The data have been
analysed using a grid of high­gravity helium­rich LTE model atmospheres and a # 2 ­minimization procedure. The parameters
derived here allow for independent verification of the parameters derived from the analysis of optical spectra.
Key words. stars: chemically peculiar ­ stars: early­type ­ subdwarfs ­ stars: atmospheres ­ stars: fundamental parameters
1. Introduction
Helium­rich subdwarf B stars (He­sdB) stars are rare faint blue
stars first identified as sdOD stars in the Palomar­Green (PG)
survey of faint blue objects (Green et al. 1986). They are found
both in our Galaxy (PG survey) as well as in globular clus­
ters (Moehler et al. 1997; 2002). The optical spectra of He­sdB
stars, by definition show strong He# and in some cases He## ab­
sorption lines. Some of them also show strong carbon lines.


Source: Armagh Observatory


Collections: Physics