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Pulsating Stars in the ASAS-3 Database. I. β Cephei Stars

Piguslki A.

Acta Astronomica

2005

Vol. 55, No. 2

219--236

We present results of an analysis of the ASAS-3 data for short-period variables from the recently published catalog of over 38 000 stars. Using the data available in the literature we verify the results of the automatic classification related to β Cep pulsators. In particular, we find that 14 stars in the catalog can be classified unambiguously as new β Cep stars. By means of periodogram analysis we derive the frequencies and amplitudes of the excited modes. The main modes in the new β Cep stars have large semi-amplitudes, between 35 and 80 mmag. Up to four modes were found in some stars. Two (maybe three) new β Cep stars are members of southern young open clusters: ASAS 164409-4719.1 belongs to NGC 6200, ASAS 164630-4701.2 is a member of Hogg 22, and ASAS 164939-4431.7 could be a member of NGC 6216. We also analyze the photometry of four known β Cep stars in the ASAS-3 catalog, namely IL Vel, NSV 24078, V1449 Aql and SY Equ. Finally, we discuss the distribution of β Cep stars in the Galaxy.

Empirical Luminosities and Radii of Early-Type Stars after Hipparcos

Jerzykiewicz M., Molenda-Żakowicz J.

Acta Astronomica

2000

Vol. 50, No. 3

369--380

Using Hipparcos parallaxes we derive empirical luminosities and radii of the early-type stars for which the effective temperatures are known from directly measured angular diameters and total absolute fluxes. The empirical luminosities allow a direct comparison of the position of these stars in the fundamental HR diagram with evolutionary tracks. The comparison shows an overall agreement with the Y=0.30 and Z=0.02 tracks computed with OPAL opacities and moderate amount of overshooting from the convective core. In addition, we present evidence that systematic errors of the masses read off the evolutionary tracks are below 10%. Consequently, the surface gravities obtained from these "evolutionary" masses and the empirical radii are very nearly model-independent. Spectrographic and photometric observations of these stars can therefore be used for verifying model atmospheres and calibrating photometric log g indices.