Discovery of the spin period and a new bright outburst of RXJ0520.5-6932

ATel #5673; G. Vasilopoulos, R. Sturm, P. Maggi, F. Haberl (MPE)
on 19 Dec 2013; 10:46 UT
Credential Certification: Richard Sturm (rsturm@mpe.mpg.de)

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RX J0520.5-6932 is a recently confirmed Be/X-ray binary system in the LMC (see ATel #4748).

With a triggered XMM-Newton observation on 2013 Jan 22 a modulation in the X-ray flux was discovered with a period of 8.03533(3) s.

Ongoing Swift monitoring revealed a new strong outburst reaching a luminosity of L_x~7×10³⁷erg s^-1 (0.3-10 keV band). With a Swift/XRT observation in timing mode performed on 2013 Dec 18, the period is confirmed independently to be 8.034(5) s.

The periodic pulses should be attributed to the spin period of the neutron star, making the system a classical Be/X-ray binary with a neutron star primary. This spin period together with the 24.43 d optical period (Coe et al. 2001, MNRAS, 324, 623) places the source in the region expected by the Corbet diagram for Be/X-ray binaries.

The complete results of the Swift monitoring and the XMM-Newton observation are going to be presented in Vasilopoulos et al. (in preparation). Further Swift monitoring will reveal if the currently ongoing outburst is of type II.

We thank the Swift team for accepting and scheduling the target of opportunity observations.