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Astron. Astrophys. 358, L45-L48 (2000)


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Letter to the Editor

HS0922+1333: another low accretion rate polar with a pronounced cyclotron line spectrum *

D. Reimers and H.-J. Hagen

Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

Received 10 April 2000 / Accepted 9 May 2000

Abstract

We present time resolved spectroscopy of the newly discovered magnetic CV HS 0922+1333. Our observations show that it has a period of 244[FORMULA]2 min. Its optical spectra are dominated by a strong single spot cyclotron line at 5334 Å. A detailed analysis shows that further cyclotron harmonics are at 7800 Å (hidden by the M dwarf companion) and at 4034 Å which yields a field strength of 66 MG (n = 2, 3 and 4). A much weaker spot appears to be present at antiphase with [FORMULA] 81 MG (n = 2 and 3 visible). HS 0922+1333 does not show any emission lines (like Balmer, HeII) except the cyclotron harmonics. It has an extremely low accretion rate of the order of [FORMULA][FORMULA], atypical for its long period. It has not been detected by ROSAT. HS 0922+1333 is the third member of a class of strong cylotron line emitters (low accretion rates) defined by HS 1023+3900 and 1RXS J012851.9-233933, both probably in the CV period gap, while HS 0922+1333 is clearly above the period gap. At a distance of 190 pc the WD primary is rather faint ([FORMULA] = 12.6) and cool ([FORMULA] 10 000 K) implying the system is old.

Key words: stars: individual: HS0922+1333 – stars: novae, cataclysmic variables – stars: magnetic fields – stars: white dwarfs – stars: binaries: general

* Based on observations at the German - Spanish observatory (DSAZ) on Calar Alto, Spain

Send offprint requests to: D. Reimers (dreimers@hs.uni-hamburg.de)

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000

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