Discovery of 1323 s pulsations from RX J0103.6–7201: The longest period X-ray pulsar in the SMC
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: firstname.lastname@example.org
Accepted: 16 March 2005
XMM-Newton archival observations of the Be/X-ray binary candidate revealed pulsations with a period of ~1323 s. This makes the X-ray pulsar with the longest period known in the Small Magellanic Cloud (SMC). More than 150 X-ray observations of by ROSAT, Chandra and XMM-Newton show flux variations by a factor of 50 on time scales of days to years. Using the accurate positions obtained from ACIS-I images, the optical counterpart is identified as a V = 14.6 mag emission line star. EPIC spectra of above 1 keV are consistent with an absorbed power-law with column density between (6-9) 1021 cm-2, except during one observation when an extraordinary high value of 1.1 1023 cm-2 was measured which strongly attenuated the power-law emission below 3 keV. A soft excess between 0.5 and 1.0 keV is evident in the spectra which becomes best visible in the highly absorbed spectrum. The soft component can be reproduced by a thermal plasma emission model with its luminosity strongly correlated with the total intrinsic source luminosity. Including results from three other SMC Be/X-ray binaries extends the linear correlation over three orders of magnitude in source intensity, strongly suggesting that the same mechanism is responsible for the generation of the soft emission.
Key words: galaxies: individual: small Magellanic Cloud / stars: neutron / X-rays: binaries / X-rays: galaxies / X-rays: individual: / stars: emission-line, Be
© ESO, 2005