Volume 374, Number 3, August II 2001
|Page(s)||1003 - 1008|
|Section||Interstellar and circumstellar matter|
|Published online||15 August 2001|
The white dwarf revealed in the intermediate polar V709 Cassiopeiae*
Service d'Astrophysique, DSM/DAPNIA/SAp, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
2 DAEC et UMR 8631 du CNRS, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France
3 Université Denis Diderot, Place Jussieu, 75005 Paris, France e-mail: firstname.lastname@example.org
4 Osservatorio Astronomico di Capodimonte, 80131 Napoli, Italy e-mail: email@example.com
5 Dipartimento di Fisica, Universita Roma Tre, 00146 Roma, Italy e-mail: firstname.lastname@example.org
6 CNRS, Observatoire de Strasbourg, 67000 Strasbourg, France e-mail: email@example.com
Corresponding author: J. M. Bonnet-Bidaud, firstname.lastname@example.org
Accepted: 23 May 2001
Results are presented from the first detailed spectroscopic observations of the recently identified intermediate polar RX J0028.8+5917/V709 Cas. The study of the emission line radial velocities allows us to remove the uncertainties on the different aliases of the orbital period and a best value is found at (0.22250.0002) day. It is also found that the system shows significant (2-4) Åbroad absorptions affecting the Balmer lines from H to H. These broad absorptions are interpreted as the contribution of an underlying white dwarf atmosphere. The characteristics of the absorptions are found to be consistent with a DA log g = 8 white dwarf at a temperature of ~23 000 K, contributing ~17% (at 4500 Å) to the overall flux. This is the first direct detection of a white dwarf in an intermediate polar system. The absence of significant Zeeman splitting indicates a magnetic field lower than 10 MG, confirming that, at least in some cases, intermediate polars have weaker fields than polars. Different possibilities are discussed to explain the substantial contribution of the white dwarf to the overall flux.
Key words: stars: white dwarfs / stars: novae, cataclysmic variables / stars: magnetic fields / X-rays stars: V709 cas
© ESO, 2001
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