Skip to main content
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 9301

GRB 090427B: Fermi GBM detection
2009-04-29T20:24:39Z (15 years ago)
Michael S. Briggs at UAH and MSFC <>
M. S. Briggs (UAH) reports on behalf of the Fermi GBM Team:

"At 15:27:00.86  UT on 27 April 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090427B (trigger 262538822 / 090427644).

The on-ground calculated location, using the GBM trigger
data, is RA = 210.0, DEC = -45.7 (J2000 degrees,
equivalent to 14 h 00 m, -45 d 42'), with an uncertainty
of 11.8 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
The angle from the Fermi LAT boresight is 14 degrees.

The GBM light curve consists of a single peak
with a duration about 7 s (8-1000 keV).
The time-averaged spectrum from T0-4.096 s to T0+2.048 s is
well fit by a simple power law function with
index -1.1 +/- 0.1.

The event fluence (8-1000 keV) in this time interval is
(8.0 +/- 0.5)E-7 erg/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
Looking for U.S. government information and services? Visit