A high-resolution spectroscopy survey of β Cephei pulsations in bright stars

¹ Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain e-mail: jht@not.iac.es
² Astronomical Institute Anton Pannekoek, University of Amsterdam, and Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
³ Royal Dutch Meteorological Institute (KNMI), Wilhelminalaan 10, 3732 GK De Bilt, The Netherlands
⁴ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁵ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
⁶ Radboud Universiteit, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands

Received: 20 December 2005
Accepted: 28 February 2006

Abstract

We present a study of absorption line-profile variations in early-B type near-main-sequence stars without emission lines. We have surveyed a total of 171 bright stars using the Nordic Optical Telescope (NOTSA), William Herschel Telescope (ING) and Coudé Auxiliary Telescope (ESO). Our sample contains 75% of all O9.5-B2.5 III-V non-emission-line stars brighter than 5.5 mag. We obtained high signal-to-noise, high-resolution spectra of the SiIII λ4560 triplet – for 125 stars of our sample we obtained more than one spectrum – and examined these for pulsational-like line-profile variations and/or structure.
We conclude that about half of our sample stars show evidence for line-profile variations (LPV). We find evidence for LPV in about 65% of our sample stars brighter than . For stars with rotational broadening  km s^-1, we find evidence for LPV in about 75% of the cases. We argue that it is likely that these LPV are of pulsational origin, and that hence more than half of the solar-neighbourhood O9.5-B2.5 III-V stars is pulsating in modes that can be detected with high-resolution spectroscopy. We detected LPV in 64 stars previously unknown to be pulsators, and label these stars as new β Cep candidates. We conclude that there is no obvious difference in incidence of (pulsational) LPV for early-B type near-main-sequence stars in binaries or in OB associations, with respect to single field stars.