GRB 070427
GCN Circular 6352
Subject
GRB 070427: Swift detection of a burst
Date
2007-04-27T08:48:05Z (18 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
G. Sato (GSFC/ISAS), S. Campana (INAF-OAB), P. A. Evans (U Leicester),
C. Guidorzi (Univ Bicocca&INAF-OAB), C. B. Markwardt (GSFC/UMD),
P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
R. L. C. Starling (U Leicester) and H. Ziaeepour (UCL-MSSL) report on
behalf of the Swift Team:
At 08:31:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070427 (trigger=277356). This burst was too close to
the Sun (42 degrees) for Swift to slew to it.
The BAT on-board calculated location is
RA, Dec 28.862, -27.633 which is
RA(J2000) = 01h 55m 27s
Dec(J2000) = -27d 37' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a multiple-peaked
structure with a duration of about 15 sec. The peak count rate
was ~3500 counts/sec (15-350 keV), at ~5 sec after the trigger.
The GRB will become observable by the XRT and UVOT on May 5.
GCN Circular 6354
Subject
GRB 070427, Swift-BAT Refined Analysis
Date
2007-04-27T18:56:04Z (18 years ago)
From
Michael Stamatikos at GSFC <michael@milkyway.gsfc.nasa.gov>
G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings
(GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C.
Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto
(GSFC/ORAU), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the
Swift-BAT team:
Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 070427
(trigger #277356) (Sato, et al., GCN Circ. 6352). The BAT
ground-calculated position is RA, Dec = 28.871, -27.603 deg which is
RA(J2000) = 1h 55m 29.1s
Dec(J2000) = -27d 36' 11.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 100%.
The mask weighted light curve steeply rises at ~ T+0 sec, exhibiting some
multi-peak sub structure, falling more gradually until ~T+20 sec, with
trivial emission above 100 keV. T90 (15-350 keV) is 11 +- 1 sec (estimated
error including systematics).
The time-averaged spectrum from T-0.2 to T+13.7 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is 2.08
+- 0.10. The fluence in the 15-150 keV band is 7.2 +- 0.4 x 10^-07 erg/cm^2.
The 1-sec peak photon flux measured from T+6.79 sec in the 15-150 keV band
is 1.3 +- 0.1 ph/cm^2/sec. All the quoted errors are at the 90%
confidence level.