Research Information System
ASTRONOMY & ASTROPHYSICS, vol.465, no.2, pp.541-553, 2007 (SCI-Expanded)
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.