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GCN Circular 13105

GRB 120326A: Swift detection of a burst
2012-03-26T01:32:31Z (12 years ago)
David Palmer at LANL <>
M. H. Siegel (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), D. Grupe (PSU), E. A. Hoversten (PSU),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-OAB/PSU) and
C. A. Swenson (PSU) report on behalf of the Swift Team:

At 01:20:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120326A (trigger=518626).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 273.925, +69.278 which is 
   RA(J2000) = 18h 15m 42s
   Dec(J2000) = +69d 16' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single FRED
structure with a duration of about 40 sec.  The peak count rate
was ~8000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 01:21:28.8 UT, 59.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 273.90195,
69.26028 which is equivalent to:
   RA(J2000)  = 18h 15m 36.47s
   Dec(J2000) = +69d 15' 37.0"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This
location is 70 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 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 5.24
x 10^20 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 2.01e-09 erg cm^-2 s^-1 (0.2-10

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 67 seconds after the BAT trigger. No credible
afterglow candidate has  been found in the initial data products. No
afterglow is seen in the 2.7'x2.7' sub-image. The 8'x8' region for the
list of sources generated on-board  covers 100% of the XRT error
circle. The list of sources is typically complete  to about 18 mag. No
correction has been made for the expected extinction  corresponding to
E(B-V) of 0.05. 

Burst Advocate for this burst is M. H. Siegel (siegel AT 
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:
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