Swift/BAT reports the detection of a new transient source Swift J1357.2-0933

ATel #3138; H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC), J. Cummings (CRESST/GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (GSFC), D. Palmer (LANL), T. Sakamoto (CRESTT/GSFC/UMBC), G. Skinner (CRESST/GSFC/UMD), M. Stamatikos (OSU/GSFC), J. Tueller (GSFC), T. Ukwatta (GSFC/GWU)
on 31 Jan 2011; 23:09 UT
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)

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The hard X-ray transient monitor of the Swift Burst Alert Telescope (BAT) has detected a previously unknown transient source. This source, Swift J1357.2-0933, was first detected at a daily average rate of 0.0070 ± 0.0008 counts/sec/cm2 (30 mCrab) in the 15-50 keV band on 2011 Jan 28 (MJD 55589). It appeared at a lower significance (.0073 ± 0.0035) on 2011 Jan 27 and has remained at roughly the same brightness for the past four days.

The BAT position was determined to be:

RA (J2000): 13 57 17.91 (209.325 deg)
DEC (J2000): -09 33 08.2 (-9.552 deg)
The estimated error is 3.0 arc minutes (radius, 90% confidence).
This corresponds to galactic coordinates, Glon = 328.703, Glat = +49.995.

A Swift target of opportunity observation has been approved and will be carried out starting at 04:55 UT on 2011 1 Februrary.

BAT Hard X-ray Transient light curve for Swift J1357.2-0933 Mrk 421