Issue |
A&A
Volume 555, July 2013
|
|
---|---|---|
Article Number | L9 | |
Number of page(s) | 4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361/201321774 | |
Published online | 11 July 2013 |
HD 45314: a new γ Cassiopeiae analog among Oe stars⋆
1 Groupe d’Astrophysique des Hautes Énergies, Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, Bât B5c, 4000 Liège, Belgium
e-mail: rauw@astro.ulg.ac.be
2 Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
3 Penn State Worthington Scranton, Dunmore, PA 18512, USA
Received: 26 April 2013
Accepted: 26 June 2013
Context. Oe stars possibly form an extension to higher temperatures of the Be phenomenon, but it is still unclear whether these stars have disks.
Aims. X-ray spectra could provide hints for interactions of the star with a putative surrounding disk.
Methods. We obtained XMM-Newton observations of two Oe stars, HD 45314 and HD 60848. Spectra and light curves were extracted and analysed. Optical spectra were also obtained to support the X-ray observations.
Results. We find that both stars display very different X-ray properties. Whilst HD 60848 has an X-ray spectrum and emission level typical for its spectral type, HD 45314 displays a very hard X-ray emission, dominated by a thermal plasma with kT ~ 21 keV. Furthermore, HD 45314 displays count rate variations by a factor 2 on timescales of ~ 103 s and a high log (LX/Lbol) = -6.10 ± 0.03.
Conclusions. The X-ray properties of HD 45314 indicate that this star is a new member of the class of γ Cas analogs, the first one among the original category of Oe stars.
Key words: stars: emission-line, Be / stars: individual: HD 45314 / stars: individual: HD60848 / X-rays: stars
© ESO, 2013
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