Open AccessCluster Ages Experiment (CASE): SX Phe stars from the globular cluster ω Centauri
Author(s) -
Olech A.,
Dziembowski W. A.,
Pamyatnykh A. A.,
Kaluzny J.,
Pych W.,
SchwarzenbergCzerny A.,
Thompson I. B.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09382.x
Subject(s) - physics , astrophysics , stars , globular cluster , blue straggler , rr lyrae variable , amplitude , excited state , oscillation (cell signaling) , radial velocity , cluster (spacecraft) , astronomy , spectral line , atomic physics , quantum mechanics , biology , computer science , genetics , programming language
We present an analysis and interpretation of oscillation spectra for all 69 SX Phoenicis stars discovered in the field of the cluster. For most of the stars we have reliable absolute magnitudes and colours. Except for one or perhaps two objects, the stars are cluster members. Their pulsational behaviour is very diverse. Multiperiodic variability with at least part of the excited modes being non‐radial is most common but there are also many cases of high‐amplitude, presumably radial mode, pulsators. In a number of such cases we have evidence for two radial modes being excited. Parameters of radial mode pulsators are in most cases consistent with standard evolutionary models for stars in the mass range 0.9–1.15 M ⊙ . However, in four cases we have evidence that the masses are significantly lower than expected. Three objects show frequency triplets that may be interpreted in terms of rotational frequency splitting of ℓ= 1 modes. Implied equatorial velocities of rotation are from 10 to over 100 km s −1 . Nearly all measured frequencies fall in the ranges predicted for unstable modes. Two cases of low‐frequency variability are interpreted as being caused by tidal distortion induced by close companions.