P. Goldoni — Page 8

arXiv1995

Multiwavelength Phenomenology of Isolated Neutron Stars

After reviewing the multifrequency behaviour of the Isolated Neutron Stars detected so far, we analyze for each object the efficiency of conversion of the star's rotational energy loss into optical, X and gamma radiation. Although the number of pulsars detected at different wavelengths is rather limited, a pattern is seen to emerge from our analysis pointing towards the period derivative as the leading parameter to describe the multifrequency emission of INS. One object in particular, PSR 1509-58, stands out as archetypal for the Pdot-dependence of its luminosity at different wavelengths.

astro-ph↗

arXiv1995

X-ray observations of the peculiar Be star LSI +61 303

We present the results of a ROSAT Position Sensitive Proportional Counter observation of the variable radio star \ls. The source has a power law spectrum with photon index 1.1 +/- 0.3 and a luminosity of 5.9 x 10^{33} erg/s in the 0.1 -2.4 keV range. Variability 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 difficult to explain in the context of the models involving super Eddington 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 variability and the rather hard spectrum are more suggestive of non thermal emission. This might originate in a shocked region produced by a young pulsar in orbit around the Be star.

astro-ph↗