Journal Article

Hα long-term monitoring of the Be star β Cephei Aa

G. Catanzaro

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 2, pages 759-766
Published in print June 2008 | ISSN: 0035-8711
Published online May 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13263.x
Hα long-term monitoring of the Be star β Cephei Aa

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Papers published in recent years have contributed to resolve the enigma of the hypothetical Be nature of the hot pulsating star β Cephei. This star shows variable emission in the Hα line, typical for Be stars, but its projected rotational velocity is very much lower than the critical limit, contrary to what is expected for a typical Be star. The emission has been attributed to the secondary component of the β Cephei spectroscopic binary system.

In this paper, using both our and archived spectra, we attempt to recover the Hα profile of the secondary component and to analyse its behaviour with time for a long period. To accomplish this task, we first derive the atmospheric parameters of the primary, Teff= 24 000 ± 250 K and log g= 3.91 ± 0.10, and then we use these values to compute its synthetic Hα profile, and finally we reconstruct the secondary's profile disentangling the observed one.

The secondary's Hα profile shows the typical two-peak emission of a Be star with a strong variability. We also analysed the behaviour versus time of some linewidth parameters: equivalent width, ratio of blue to red peak intensities, full width at half-maximum, peak separation and radial velocity of the central depression.

The projected rotational velocity (v sin i) of the secondary and the dimension of the equatorial surrounding disc have also been estimated.

Keywords: binaries: spectroscopic; stars: emission-line, Be; stars: individual: β Cephei

Journal Article.  4752 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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