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Astron. Astrophys. 358, 600-604 (2000)

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A newly-discovered cataclysmic binary near the ROSAT galactic plane source RX J1910.8+2856

J.R. Thorstensen 1 and F. Haberl 2

1 Department of Physics and Astronomy, 6127 Wilder Laboratory, Dartmouth College, Hanover, NH 03755-3528, USA
2 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany

Received 21 December 1999 / Accepted 23 February 2000


We report the discovery of a new cataclysmic binary star from the ROSAT Galactic Plane Survey. The star has [FORMULA] at minimum light and we have measured it as bright as [FORMULA]. Spectroscopy shows broad hydrogen and helium emission lines; HeII [FORMULA] is not detected. H[FORMULA] radial velocities yield an orbital period of [FORMULA] d ([FORMULA] h). Time-series photometry covering one orbital cycle near maximum light shows irregular variability, but no evidence of an eclipse. The system appears to be a new dwarf nova of the U Gem or Z Cam type, and is unlikely to be a magnetic system. Its period is unusually short for a U Gem star.

Curiously, the new cataclysmic binary is 83" from the original ROSAT PSPC survey position, which puts it outside the PSPC positional uncertainty. Follow-up observations with the HRI reveal that the PSPC source is the superposition of two sources, and the cataclysmic is much the weaker of the two in X-rays. Its discovery in this survey is therefore essentially accidental. A [FORMULA] mag star is located 1.2" from the stronger source's HRI position.

Key words: stars: binaries: close – stars: individual: RX J1910.8+2856 – stars: individual: RX J191059.6+285639 – stars: novae, cataclysmic variables – X-rays: stars

Send offprint requests to: J.R. Thorstensen (thorstensen@dartmouth.edu)

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© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000