Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 21520

GRB 170817A: Fermi GBM detection
2017-08-17T20:00:07Z (7 years ago)
Andreas von Kienlin at MPE <>
A. von Kienlin (MPE), C. Meegan (UAH) and A. Goldstein (USRA)
report on behalf of the Fermi GBM Team:

"At 12:41:06.47 UT on 17 August 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170817A (trigger 524666471 / 170817529).

The on-ground calculated location, using the GBM trigger
data, is RA = 176.8, DEC = -39.8 (J2000 degrees,
equivalent to 12 h 47 m, -39 d 48'), with an uncertainty
of 11.6 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 91 degrees.

The GRB light curve shows a weak short pulse
with a duration (T90) of about 2 s (50-300 keV).
The time-averaged spectrum from T0-0.512 s to 2.048 s is
well fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.89 +/- 0.5 and
the cutoff energy, parameterized as Epeak, is 82 +/- 21 keV

The event fluence (10-1000 keV) in this time interval is
(2.3 +/- 0.4)E-07 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0-0.32 s in the 8-1000 keV band
is 1.9 +/- 0.2 ph/s/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