S-CUBED detection of SXP 756 in outburst

ATel #12334; J. A. Kennea (PSU), M. J. Coe (Southhampton), P. A. Evans (Leicester)
on 27 Dec 2018; 18:26 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

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S-CUBED (Kennea et al., 2018, ApJ, 868, 47) is a weekly survey of the SMC in X-ray, performed by the Neil Gehrels Swift Observatory, consisting of 142 tilings each with a 60s exposure time.

Starting on Dec 27th, the Be/XRB SXP 756, which had previously been detected sporadically by S-CUBED at fluxes around 2.4 x 10^-12 erg/s/cm² (0.5 - 10 keV), showed a significant brightening, and rose to a flux level of 5.7 x 10^-11 erg/s/cm², an XRT count rate of 0.55 +/- 0.08 count/s. Assuming an SMC distance of 62 kpc, this is equivalent to a luminosity of 1.1 × 10³⁷ erg/s.

This outburst is the first by SXP 756 detected by S-CUBED since observations began in June 2016. Follow-up observations of this outburst have been requested by Swift.