EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 469/3 Article
Free access article

Issue A&A
Volume 469, Number 3, July III 2007
Page(s) 1069 - 1076
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20065563



A&A 469, 1069-1076 (2007)
DOI: 10.1051/0004-6361:20065563

A study of the $\beta$ Cephei star $\gamma$ Pegasi: binarity, magnetic field, rotation, and pulsations

V. V. Butkovskaya1 and S. I. Plachinda1, 2

1  Crimean Astrophysical Observatory, Nauchny, Crimea, 98409, Ukraine
    e-mail: varya@crao.crimea.ua
2  Institute for Astronomy, University of Vienna, Tuerkenschanzstrasse 17, 1180 Vienna, Austria

(Received 6 May 2006 / Accepted 2 April 2007)

Abstract
Aims.We provide observational material to study the magnetic field variability of the classical $\beta$ Cep-type star $\gamma$ Peg .
Methods.The observations were carried out in the $\ion{He}{i}$ 6678 line in the course of 23 observing nights from 1997 to 2005 with using the Coudé spectrograph in spectropolarimetric mode at the Crimean 2.6 m telescope. The behavior of stellar wind was studied in the UV region using data from the IUE satellite (the INES database).
Results.It is shown that the UV stellar wind exhibits a variability. A variation of the wind due to stellar pulsations has been detected. In the $\ion{He}{i}$ 6678 line, the abnormally blueshifted radial velocities ($\gamma$ = -60.57 $\pm$ 0.29 km s-1) were detected during a single night in 2005. We do not confirm the 370.5-day orbital period. The most probable orbital period was estimated as $P_{\rm orb}$ = 6.81608 $\pm$ 0.00012 day. The ratio $P_{\rm orb}/P_{\rm puls}$ = 44.92 appeared to be very close to integer. We have detected the presence of a weak magnetic field on the star. The longitudinal component of the field varies from -10 G to 30 G with the stellar rotation. The most probable rotational period is $P_{\rm rot}$ = 6.6538 $\pm$ 0.0016 days. Both the orbital and the rotational periods are integral multiples of the difference between them: $P_{\rm orb}/\vert P_{\rm orb} - P_{\rm rot}\vert$ = 42.002, and $P_{\rm rot}/\vert P_{\rm orb} - P_{\rm rot}\vert$ = 41.002. Variation in the longitudinal magnetic field during the pulsation period with an amplitude about 7 G was detected.


Key words: stars: magnetic fields -- stars: early-type -- stars: oscillations -- stars: binaries: spectroscopic -- stars: individual: $\gamma$ Pegasi



© ESO 2007


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.