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Astron. Astrophys. 332, 984-998 (1998)

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A comprehensive study of multi-emission sites in IP Peg *

Sebastian Wolf 1, Heinz Barwig 1, Andreas Bobinger 1, Karl-Heinz Mantel 1 and Damir imi 2

1 Universitäts-Sternwarte, Scheinerstr.1, D-81679 München, Germany
2 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr. 1, D-85740 Garching, Germany

Received 22 October 1997 / Accepted 12 December 1997


We present a comprehensive study of the eclipsing binary IP Peg during quiescence by analysing phase-resolved spectroscopy and simultaneously recorded high-speed-spectrophotometry. By combining both data sets we obtained photometric data of IP Peg with high spectral (1.3Å) resolution. Trailed spectrograms show in unprecedented clearness the well-known Doppler broadened Balmer emission line profiles as well as TiO absorption bands and KI and NaI absorption doublets. By means of Doppler tomography the origin of the s-wave in the H [FORMULA], H [FORMULA] emission lines can be located on the irradiated surface of the secondary star. This indicates an irradiation of the red dwarf during quiescence by an extended accretion disk. Two bright emitting regions superposed to the typical ring-shaped emission of the accretion disk could also be detected. It was possible to analyse separately the eclipse behaviour of the emission lines and of the respective continua. The decomposed continuum light-curves show a second weaker hump phase shifted by 0.5 to the well known orbital hump created by the hot spot. The emission line light curves are dominated by radiation from the accretion disk, showing a slight asymmetry in the V-like eclipse. It is shown, by applying the eclipse mapping method to the emission line light curves, that the bright regions in our high resolution Doppler maps are corresponding to distinct regions in the eclipse maps. In order to compare the two bright emission regions with our spectral data set we reconstructed trailed spectra from the eclipse maps dominated by these multi-emission sites. The following tomographic analysis was in good agreement with our high-resolution Doppler maps. The results obtained from this method are, that IP Peg has a mainly Keplerian accretion disk and that the deviation from the Keplerian field in the hot spot region can be measured by comparing the different Doppler maps with each other. Two theoretical models are discussed to explain the nature and origin of these multi-emission sites, namely a second bright spot model created by a gas stream overflow or by spiral shock waves originating from the interaction of tidal forces of the secondary star with outer regions of an extended accretion disk.

Key words: stars: individual: IP Peg – binaries: eclipsing – novae, cataclysmic variables – accretion, accretion disks – shock waves

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

Send offprint requests to: Sebastian Wolf (wolf@usm.uni-muenchen.de)

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© European Southern Observatory (ESO) 1998

Online publication: March 30, 1998