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GCN Circular 9161

GRB 090419: Swift detection of a burst
2009-04-19T13:59:53Z (15 years ago)
David Burrows at PSU/Swift <>
G. Stratta (ASDC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), N. P. M. Kuin (MSSL),
V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),
R. Margutti (Univ Bicocca&OAB), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Perri (ASDC),
P. Romano (INAF-IASFPA) and B. Sbarufatti (INAF-IASFPA) report on
behalf of the Swift Team:

At 13:43:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090419 (trigger=349592).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 196.976, -75.609 which is 
   RA(J2000) = 13h 07m 54s
   Dec(J2000) = -75d 36' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a slow single
peak taking 30 seconds to rise to a maximum with a duration of
at least 90 seconds, and an additional peak at T+320.  The peak
count rate was ~800 counts/sec  (15-350 keV), at ~30 sec after 
the trigger. 

The XRT began observing the field at 13:45:31.0 UT, 119.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 196.92907,
-75.60534 which is equivalent to:
   RA(J2000)  = 13h 07m 42.98s
   Dec(J2000) = -75d 36' 19.2"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 44 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 in excess of the Galactic value (1.2e+21
cm^-2, Kalberla et al. 2005), with an excess column of 1.1
(+0.85/-0.64) x 10^22 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 5.55e-10 erg cm^-2 s^-1 (0.2-10

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 126 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The coverage of the XRT error circle by the 8'x8' region for the list of
sources generated on-board is uncertain because the large number of sources
filled the available telemetry. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.30. 

Burst Advocate for this burst is G. Stratta (giulia.stratta 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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