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Detection of a 36.3 day orbital period from the HMXB system IGR J01054-7253 with RXTE

ATel #2202; L. J. Townsend (Southampton), R. H.D. Corbet (NASA/GSFC), M. J. Coe (Southampton), V. A. McBride (Southampton), A. B.Hill (LAOG), A. J. Bird (Southampton)
on 18 Sep 2009; 16:01 UT
Credential Certification: Malcolm Coe (mjcoe@soton.ac.uk)

Subjects: X-ray, Binary, Neutron Star, Pulsar

The Be/X-ray binary IGR J01054-7253 has been frequently observed with RXTE since 2009-06-19 (ATel #2092). From the subsequent analysis of these data, a clear Doppler modulation of the 11.48s pulse period can be seen as well as an accretion driven spin-up. Model fitting to these data has allowed us to distinguish the spin-up rate from the orbital modulation. The best fit to the data reveals an orbital period of 36.3 +/- 0.4 days and an average spin-up rate of (4.7 +/- 0.3) E-10 s/s. Using a circular orbit in the model fitting gave a poor fit, indicating the need for an eccentric orbit. The best fit solution gives an eccentricity of 0.28 +/- 0.03. The orbital and spin periods place this system nicely onto the Be/X-ray binary region of the Corbet diagram of binary pulsars. Pdot is also consistent with what has previously been observed in other Be/X-ray binary pulsars in the Magellanic Clouds (see Figure 2 of Coe et al. 2009, arXiv:0908.4332v1).