Swift/BAT detects a new outburst likely from RX J0059.2-7138
ATel #5756; H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC), R. H. D. Corbet (UMBC/GSFC), J. Cummings (CRESST/GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. Palmer (LANL), T. Sakamoto (Aoyama Gakuin Univ.), M. Stamatikos (OSU/GSFC), T. Ukwatta (MSU)
on 11 Jan 2014; 03:41 UT
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)
Subjects: X-ray, Binary, Transient, Pulsar
The Be/X-ray binary and transient pulsar RX J0059.2-7138 (also known as SXP 2.76) in the Small Magellanic Cloud has been detected in the 15-50 keV band in the Swift/BAT hard X-ray transient monitor. The source was detected in the BAT monitor starting on 2013 December 26 (MJD 56652) with a count rate of 0.002 +/- 0.0006 ct/s/cm^2 (~10 mCrab). The source has remained detectable since that time with a slowly rising flux, reaching 0.005 +/- 0.001 ct/s/cm^2 (~25 mCrab) on 2014 January 9.
RX J0059.2-7138 was discovered by ROSAT (Hughes, ApJ 427, L25, 1994) and confirmed as a Be/X-ray binary by Southwell & Charles (MNRAS 281, L63, 1996). Spectral analysis from ASCA and ROSAT by Kohno, Yokogawa & Koyama (PASJ 52, 299, 2000) confirmed the pulsar nature of the source and showed that it had a soft excess in addition to a power-law spectral component.
The source RX J0059.2-7138 is ~2 arc minutes from the best BAT position, so within positional uncertainty. However, since there have been, as far as we can tell from the literature, no other reported outbursts or hard X-ray detections, we cannot rule out this being a previously unknown transient source positionally coincident with RX J0059.2-7138. An observation with a telescope with finer angular resolution will be required to determine the true location of the BAT source. We will request a Swift target of opportunity observation for this purpose.
Swift/BAT transient monitor light curve for RX J00059.2-7138