GCN Circular 19155

S. D. Barthelmy (GSFC), H. A. Krimm (CRESST/GSFC/USRA) and
K. L. Page (U Leicester) report on behalf of the Swift Team:

At 09:41:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located IGRJ17091-3624 (trigger=677981).  Swift slewed immediately to the source,
although Swift was already looking at this source at the time of the trigger. 
The BAT on-board calculated location is 
RA, Dec 257.250, -36.448, which is 
   RA(J2000)  =  17h 09m 00s
   Dec(J2000) = -36d 26' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers (10 min in this case),
there is nothing significant in the real-time light curve. 

No source was detected in the 2.5-s image taken 676 seconds after the trigger. 
The X-ray source was, however, bright enough to force the XRT to 
remain in WT mode. 

This source is a black hole candidate, which has been reported 
to be in outburst by Miller et al (ATel #8742) and is being 
observed as a Swift ToO.  The BAT transient monitor shows it 
to be brightening, reaching ~65 mCrab for the average of 
6 March 2016.