XMM-Newton observations of High Mass X-ray Binaries in the SMC

Abstract

Based on XMM-Newton EPIC data of four pointings towards the Small Magellanic Cloud (SMC), results on timing and spectral analyses of 16 known high mass X-ray binaries (HMXBs) and HMXB candidates in the SMC are presented. We confirm the pulse periods of four sources which were known to show pulsations. In addition, two new X-ray pulsars are discovered: XMMU J005605.2-722200 with P_pulse = 140.1 +/- 0.3 s and RX J0057.8-7207 with P_pulse = 152.34 +/- 0.05 s. Due to the low Galactic foreground absorption, X-ray binary systems in the Magellanic Clouds are well suited for studies of the soft component in their X-ray spectrum. Spectral analysis reveals soft emission besides a power law component in the spectra of three sources. The existence of emission lines in at least one of them corroborates the thermal nature of this emission with temperatures of 0.2 - 0.3 keV and heavy element abundances lower than solar. For the HMXB SMC X-2 which was in a low luminosity state, we determine a flux upper limit of 1.5 x 10^-14 erg cm^-2 s^-1 (0.3 - 10.0 keV). Furthermore, two new sources (XMMU J005735.7-721932 and XMMU J010030.2-722035) with hard spectrum and emission line objects as likely optical counterparts are proposed as new X-ray binary candidates.