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GCN Circular 18190

Subject
GRB 150821A: Fermi GBM detection
Date
2015-08-21T15:43:49Z (9 years ago)
From
Oliver Roberts at UCD/Fermi <oliver.roberts@ucd.ie>
O.J. Roberts (UCD) reports on behalf of the Fermi GBM team:

"At 09:44:20.33 UT on August 21st 2015, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 150821A (trigger
461843064/150821406), which was also detected by Swift
(Troja et al. 2015, GCN 18186).

The trigger resulted in an Autonomous Repoint Request (ARR)
due to the high peak flux of the GRB. This ARR was accepted
and the spacecraft slewed to the GBM in-flight location. Both
the GBM in-flight and on-ground locations are consistent with
the Swift position.

The angle of the burst direction to the Fermi LAT boresight
is 57 degrees.

The GBM light curve consists of a FRED-like burst, with two
unresolved peaks and a duration of about 103 s (50-300 keV).
The time-averaged spectrum from T0-2.0s to T0+101.4s is well
fit by a Band function with Epeak = 322 +/- 18 keV,
Alpha =-1.21 +/- 0.01 and Beta = -2.27 +/- 0.10.

The event fluence (10-1000 keV) in this time interval is
(6.87 +/- 0.08)E-05 erg/cm^2. The 1.024 s peak photon flux
measured starting from T0+17.1s in the 10-1000 keV band
is 11.1 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
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