Summary: Baltic Astronomy, vol. 14, XXXXXX, 2005.
SPECTRAL ANALYSIS OF sdB-He STARS FROM THE SDSS
A. Ahmad, C. Winter and C. S. Jeffery
Armagh Observatory, College Hill, Armagh BT61 9DG. N. Ireland.
Received 2005 July 28
Abstract. We present spectral classification and physical parameters of a sam-
ple of "helium-rich" sdB-He stars from spectra obtained from the SDSS archive.
The spectral classification was carried out using an automated neural network
and the physical parameters were derived using LTE model atmospheres. The
results indicate that most of these stars are not typical He-sdB stars but rather
are normal sdB stars with slight helium enrichment. This is most likely a result
of the use of a different definition of "helium-rich" in the initial SDSS classifi-
cation to that used more widely in the field.
Key words: stars: chemically peculiar - stars: early-type - subdwarfs - stars:
Subluminous B stars form the dominant population of faint blue stars in our
Galaxy down to a limiting magnitude of B 16. These so-called subdwarf B (sdB)
stars are thought to be low-mass core helium burning stars with a thin hydrogen
envelope. The surfaces of sdB stars are predominantly helium-deficient due to