Blackbody excess in persistent Be pulsars

Abstract

We report on the main results obtained thanks to an observation campaign, performed with XMM-Newton, of four persistent, low-luminosity (Lx ~ 10^34 erg/s) and long-period (P > 200 s) Be accreting pulsars. We found that all sources considered here are characterized by a spectral excess that can be described with a blackbody component of high temperature (kT > 1 keV) and small area (R < 0.5 km). We show that: 1) this feature is a common property of several low-luminosity X-ray binaries; 2) for most sources the blackbody parameters (radius and temperature) are within a narrow range of values; 3) it can be interpreted as emission from the NS polar caps.

2 pages, 2 figures, 1 table. Proceedings of the conference "X-ray Astronomy: towards the next 50 years!" (Milano, 1-5 October 2012), to be published on "Memorie della Società Astronomica Italiana"