Volume 465, Number 2, April II 2007
|Page(s)||541 - 547|
|Section||Stellar structure and evolution|
|Published online||22 January 2007|
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland, UK e-mail: firstname.lastname@example.org
2 Dept. of Physics, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, Nebraska 68182-0266, USA
Accepted: 8 January 2007
Aims. The aim of this study is to understand the nature and origin of a chemically peculiar star JL 87 by measuring its physical parameters and chemical abundances.
Methods. Physical parameters – effective temperature, surface gravity and helium abundance were measured from a moderate resolution optical spectrum using fully line-blanketed LTE model atmospheres. The effective temperature and extinction were verified by comparing FUSE, IUE spectrophotometry and optical/IR broadband photometry with theoretical flux distributions from LTE model atmospheres. The photospheric chemical abundances were measured from a high-resolution optical spectrum using LTE model atmospheres and spectral synthesis.
Results. On the basis of its physical parameters and chemical abundances, we confirm that JL 87 is a chemically peculiar subluminous B star. It is significantly cooler, has a lower surface gravity and is more helium-rich than previously believed. It is moderately enriched in carbon and nitrogen, but its overall metallicity is slightly subsolar.
Conclusions. The shallow-mixing model of a late core-flash on a white-dwarf cooling track currently provides the most consistent agreement with the observable properties of JL 87.
Key words: stars: chemically peculiar / stars: early-type / subdwarfs / stars: individual: JL 87 / stars: abundances / stars: fundamental parameters
© ESO, 2007
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