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Astron. Astrophys. 329, 115-130 (1998)


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Spectroscopic and spectrophotometric studies of V2301 Oph

I. The high accretion state *

Damir imi, Heinz Barwig, Andreas Bobinger, Karl-Heinz Mantel and Sebastian Wolf

Universitäts-Sternwarte, Scheinerstr. 1, D-81679 München, Germany

Received 14 April 1997 / Accepted 8 August 1997

Abstract

An approach is made to clarify the two different classifications of V2301 Oph (formerly: 1H1752+081) as a low field intermediate polar or an AM Her candidate, by analysing phase-resolved spectroscopy and simultaneously recorded high-speed-spectrophotometry. By combining both data sets we obtained for the first time photometric data of V2301 Oph with high spectral (1.3Å) resolution during an enhanced accretion state. The trailed spectrograms show in unprecedented clearness the well-known complex emission line profiles which are characterized by a broad and a narrow component shifted in phase by [FORMULA]. By means of Doppler tomography the origin of the narrow component can be located on the irradiated face of the secondary star, whereas the broad component can be traced back to the coupling region where the accreting material is connected to the field lines.

It was also possible to analyse separately the eclipse behaviour of the emission lines and of the respective continua. The decomposed continuum light curves clearly reveal that the pre-eclipse hump cannot be explained with a hot spot on an accretion disk. It can be rather assigned to cyclotron radiation from a shock-region on the white dwarf. Furthermore, it is shown from the eclipse features, that the acccretion stream is distorted due to a weak magnetic field. An investigation of the superimposed flickering did not reveal any short-periodic variation, which would be an evidence for a non-synchronously rotating primary star. Therefore, we can classify V2301 Oph as an AM Her system, where the dipole axis of the white dwarf is inclined to its rotational axis.

Key words: stars: individual: V2301 Oph – cataclysmic variables – eclipsing binaries – stars: magnetic fields

* Based on observations obtained at the German-Spanish Astronomical Center, Calar Alto, Spain.

Send offprint requests to: D. imi (e-mail: simicusm.uni-muenchen.de)

© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997
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