GCN Circular 21283

A. Cholden-Brown (PSU), A. A. Breeveld (UCL-MSSL),
S. W. K Emery (UCL-MSSL), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 12:53:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170629A (trigger=759159).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 130.016, -46.587 which is 
   RA(J2000) = 08h 40m 04s
   Dec(J2000) = -46d 35' 11"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve is incomplete at this
time due to lost telemetry, but was still rising at 8 sec after 
the trigger with a count rate of ~1500 counts/sec. 

The XRT began observing the field at 12:54:56.0 UT, 82.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 129.98653, -46.57155 which
is equivalent to:
   RA(J2000)  = 08h 39m 56.77s
   Dec(J2000) = -46d 34' 17.6"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 91 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 5.16e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of  90 seconds with the UVW2 filter
 starting  86 seconds after the BAT trigger. No credible afterglow 
candidate has been  found in the initial data products. Analysis is
complicated because of a nearby bright star (b Vel). Full  results
will have to await the full dataset. 

Burst Advocate for this burst is A. Cholden-Brown (aaronb AT swift.psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)