Discovery of X-ray pulsations in the Be/X-ray binary IGR J21343+4738

Abstract

We report on the discovery of X-ray pulsations in the Be/X-ray binary IGR J21343+4738 during an XMM-Newton observation. We obtained a barycentric corrected pulse period of 320.35 ± 0.06 s. The pulse profile displays a peak at low energy that flattens at high energy. The pulse fraction is 45 ± 3 per cent and independent of energy within the statistical uncertainties. The 0.2-12 keV spectrum is well fitted by a two-component model consisting of a blackbody with kT = 0.11 ± 0.01 keV and a power law with photon index G{cyrillic} = 1.02 ± 0.07. Both components are affected by photoelectric absorption with an equivalent hydrogen column density NH = (1.08 ± 0.15) × 1022 cm-2. The observed unabsorbed flux is 1.4 × 10-11erg cm-2s-1in the 0.2-12 keV energy band. Despite the fact that the Be star's circumstellar disc has almost vanished, accretion continues to be the main source of high-energy radiation. We argue that the observed X-ray luminosity (LX ~ 1035erg s-1) may result from accretion via a low-velocity equatorial wind from the optical companion. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.