MAXI J0057-720: Swift observations, SXP 46.6 in outburst
ATel #5930; J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), P. A. Evans (U Leicester), P. Romano (INAF-IASF PA), V. Mangano (PSU), P. Curran (Curtin), K. Yamaoka (Nagoya U) and H. Negoro (Nihon U.)
on 28 Feb 2014; 07:06 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)
Subjects: X-ray, Transient
Referred to by ATel #: 9348
Swift has performed two target of opportunity observations of the MAXI error circle of MAXI J0057-720 (Suzuki et al., ATEL #5925). The first began at 16:44UT on February 27th, 2013, for 2ks with the Swift X-ray telescope (XRT) configured in Photon Counting (PC) mode. No bright X-ray sources were detected in this observation, despite covering the error region quoted in ATEL #5925. In order to search for possible counterparts outside of the MAXI error radius, at 02:17 UT on February 28th, 2014, Swift took a series of seven 200s long exposure tiling observations in PC mode, covering approximately 0.5 degrees radius around the center of the MAXI error circle.
Based on preliminary data, we find 3 previously known moderately bright X-ray sources in this region, the supernova remnant EO102, and two known Be/X-ray binary systems: SXP 46.6 (e.g. Sturm et al., ATEL #2876) and RX J0059.2-7138, which has recently been in outburst (e.g. Krimm et al., ATELs #5756 and #5773, Coe et al., ATEL #5766). SXP 46.6 lies 30 degrees from the center of the MAXI error circle, and RX J0059.2-7138 lies 24 arc-minutes from the center of the MAXI error circle.
At this time it would appear that there is no new SMC transient, we suggest that MAXI J0057-720 may be related to SXP 46.6, although we cannot rule out also a possibility of a contribution from RX J0059.2-7138.
SXP 46.6 appears to be in outburst again. We note that in the most recent previous Swift observations of SXP 46.6, taken on December 3rd, 2012, XRT did not detect the source. In the current observation SXP 46.6 is detected at a level of approximately 0.3 XRT count/s, compared with 0.14 XRT count/s reported for the first Swift observation of the September 2010 outburst (Sturm et al., ATEL #2876). However, this brightness is much lower than the reported 15 mCrab brightness of the MAXI transient.
