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Astron. Astrophys. 331, 612-618 (1998)

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The short-time variability of the supersoft X-ray source RX J0019.8+2156

E. Meyer-Hofmeister 1, S. Schandl 2, B. Deufel 3, H. Barwig 3 and F. Meyer 1

1 Max-Planck-Institut für Astrophysik, Karl Schwarzschildstr. 1, D-85740 Garching, Germany
2 Institut für Astronomie und Astrophysik, Universität Tübingen, Waldhäuserstr. 64, D-72076 Tübingen, Germany
3 Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München, Germany

Received 4 August 1997 / Accepted 10 November 1997


Optical observations of the galactic supersoft X-ray source RX J0019.8+2156 reveal essential changes of the lightcurve from night to night. From October to December 1996 time resolved UBVRI photometry was performed with the high speed multichannel multicolour photometer MCCP at the 80 cm telescope of the Wendelstein Observatory of the Universitäts-Sternwarte München. To model these observations we compute lightcurves using a code which includes as sources of radiation the irradiated disk with an elevated outer rim and the irradiated secondary star in a consistent way. As found earlier the accretion disk rim is an important feature. We show in our investigation, that the variability of the optical flux can be understood as resulting from changes of the rim height, either from night to night or even within hours.

Key words: stars: individual: RX J0019.8, CAL 87 – accretion, accretion disks – binaries: close – binaries: eclipsing – X-rays: stars

Send offprint requests to: Emmi Meyer-Hofmeister

© European Southern Observatory (ESO) 1998

Online publication: February 16, 1998