TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  322
SUBJECT: GRB 990510: BATSE Observations
DATE:    99/05/12 22:10:44 GMT
FROM:    R. Marc Kippen at BATSE/UAH/MSFC  <marc.kippen@msfc.nasa.gov>

R. M. Kippen (University of Alabama in Huntsville) reports on behalf
of the BATSE GRB team:

GRB 990510 was detected by BATSE on 1999 May 10.367434 as trigger
number 7560.  The event was strong and consisted of a complex series
of pulses with two major episodes lasting >100 s, with significant
spectral evolution.  The T50 and T90 durations are 32.64 (-/+ 0.45) s
and 67.58 (-/+ 1.86) s, respectively.  The burst's peak flux (50-300
keV; integrated over 1.024 s) and fluence (>20 keV) are 8.16 (-/+
0.08) photons cmE-2 sE-1 and 2.56 (-/+ 0.09) x 10E-5 erg cmE-2,
respectively---ranking it in the top 4% (9%) of the BATSE burst flux
(fluence) distribution.  The average spectral hardness of the burst,
as estimated by the ratio of 100-300 keV counts to those in the 50-100
keV range, is H32 = 0.764 (-/+ 0.008), which is average among BATSE
bursts of this duration.  The BATSE burst location is consistent with
those measured by BeppoSAX (GCN 304,311) and the IPN (BATSE/Ulysses;
GCN 309), and with the proposed optical transient counterpart (GCN
310, 313-321).  A location sky-map and lightcurve for this event (and
other notable bursts) are available at the BATSE Rapid Burst Response
world-wide-web site:

          http://www.batse.msfc.nasa.gov/~kippen/batserbr/

This notice is citeable.

-eof-