X-RAY OBSERVATIONS OF THE PECULIAR BE STAR LSI-DEGREES-303(61)

We present the results of a ROSAT Position Sensitive Proportional Coun ter observation of the variable radio star LS I +61 degrees 303. The s ource has a power law spectrum with photon index 1.1 +/- 0.3 and a lum inosity of 5.9 x 10(33) erg s(-1) in the 0.1 -2.4 keV range. Variabili ty on a timescale of days is clearly visible in the ROSAT data, but no periodic pulsations have been detected. The low X-ray luminosity is d ifficult to explain in the context of the models involving super Eddin gton accretion which have been proposed to account for the non thermal radio outbursts. Though the weak X-ray flux is marginally compatible with the levels expected from normal B and Be star winds, the variabil ity and the rather hard spectrum are more suggestive of non thermal em ission. This might originate in a shocked region produced by a young p ulsar in orbit around the Be star.