Issue |
A&A
Volume 422, Number 3, August II 2004
|
|
---|---|---|
Page(s) | 1053 - 1058 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20040264 | |
Published online | 16 July 2004 |
Detection of a companion to the pulsating sdB Feige 48 *,**
1
Dr Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstr. 7, Bamberg 96049, Germany e-mail: otoole@sternwarte.uni-erlangen.de
2
Department of Physics, University of Wisconsin-Whitewater, Whitewater, WI 53190, USA
Received:
13
February
2004
Accepted:
30
April
2004
We present the discovery of a binary companion to the pulsating sdB Feige 48. Using HST/STIS and archival FUSE spectra, we measure a period of
d and a velocity semi-amplitude of
km s-1. This implies that the companion star must either
be of very low mass, or the orbit is at low inclination. Combining
2MASS fluxes, the lack of a reflection effect, results from
asteroseismology and a measurement of the rotation velocity of Feige 48, we
show that the orbital inclination must be ≤11.4° and that the
unseen companion is a white dwarf with mass ≥0.46
.
The implications of this discovery, and of
binarity amongst sdB pulsators, is then discussed in the context of recent
theoretical work on sdB formation. In particular we suggest that radial
velocity studies focus on sdB pulsators with no known companion, and that
asteroseismological studies of sdBs investigate a larger mass range than
previously considered in order to test formation models.
Key words: stars: individual: Feige 48 / stars: binaries: close / stars: oscillations
© ESO, 2004
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