6,572 research outputs found
Long-term EXOTIME photometry and follow-up spectroscopy of the sdB pulsator HS 0702+6043
Pulsating subdwarf B (sdB) stars oscillate in short-period p-modes or
long-period g-modes. HS0702+6043 (DW Lyn) is one of a few objects to show
characteristics of both types and is hence classified as hybrid pulsator. It is
one of our targets in the EXOTIME program to search for planetary companions
around extreme horizontal branch objects. In addition to the standard exercise
in asteroseismology to probe the instantaneous inner structure of a star,
measured changes in the pulsation frequencies as derived from an O-C diagram
can be compared to theoretical evolutionary timescales. Based on the
photometric data available so far, we are able to derive a high-resolution
frequency spectrum and to report on our efforts to construct a multi-season O-C
diagram. Additionally, we have gathered time-resolved spectroscopic data in
order to constrain stellar parameters and to derive mode parameters as well as
radial and rotational velocities.Comment: 2 pages, JENAM 2008 proceedings, to be published in 'Communications
in Asteroseismology', 15
Asteroseismology and evolution of EHB stars
The properties of the Extreme Horizontal Branch stars are quite well
understood, but much uncertainty surrounds the many paths that bring a star to
this peculiar configuration. Asteroseismology of pulsating EHB stars has been
performed on a number of objects, bringing us to the stage where comparisons of
the inferred properties with evolutionary models becomes feasible. In this
review I outline our current understanding of the formation and evolution of
these stars, with emphasis on recent progress. The aim is to show how the
physical parameters derived by asteroseismology can enable the discrimination
between different evolutionary models.Comment: 13 pages, 6 figures, invited review to appear in Communications in
Asteroseismology vol.159, "Proceedings of the JENAM 2008 Symposium No 4:
Asteroseismology and Stellar Evolution
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