TITLE:   GCN CIRCULAR
NUMBER:  35868
SUBJECT: Swift Trigger 1218701: Yes, we triggered on Swift J151857.0-572147 again
DATE:    24/03/05 04:23:22 GMT
FROM:    Jamie Kennea at Penn State <jak51@psu.edu>


J. A. Kennea (PSU) and A. Y. Lien (U Tampa) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 04:13:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located Swift J151857.0-572147 (trigger=1218701).  
Swift slewed immediately to the source. 
The BAT on-board calculated location is 
RA, Dec 229.705, -57.343 which is 
   RA(J2000) = 15h 18m 49s
   Dec(J2000) = -57d 20' 32"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with an image trigger, the BAT light curve
does not show anything significant. 

The XRT began observing the field at 04:16:16.1 UT, 153.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 229.7317, -57.3641 which is equivalent to:
   RA(J2000)  = 15h 18m 55.61s
   Dec(J2000) = -57d 21' 50.8"
with an uncertainty of 5.9 arcseconds (radius, 90% containment). This
location is 91 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.