High Mass X-ray Binary Pulsars in the Small Magellanic Cloud

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  • 1 December 2003
Abstract
We report two additions to the class of accreting X-ray pulsars from the direction of the Small Magellanic Cloud with periods of 263 and 202 s. (Recently Haberl & Pietsch (2004) reported the 263 s pulsar.) The source positions of these two pulsars are consistent with early B stars in the SMC and therefore we identify them as high mass X-ray binaries (HMXBs). Properties of an ensemble of 24 optically identified HMXB pulsar from the SMC are investigated. The locations of the pulsars and an additional 14 X-ray pulsars not yet identified as having high mass companions are located predominately in the young (ages less than 3x10^{7} years) star forming regions of the SMC as expected on the basis of binary evolution models. We find no significant difference between the distribution of spin periods for the HMXB pulsars of the SMC compared with that of the Milky Way. For those HMXB pulsars which have Be companions we note an inverse correlation between spin period and maximum X-ray flux density. This correlation may be a reflection of the fact that the spin periods and orbital periods of Be HMXBs are correlated. We note a similar correlation between X-ray luminosity and spin period for the Be HMXB pulsars of the Milky Way. We have also established the pulse period of the possible AXP CXOU J010043.1-721134 to be 8.0 s. This corrects an earlier report (Lamb et al. 2002b) of a 5.4 s period for this object

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