GRB 180923B
GCN Circular 23263
Subject
GRB 180923B: Fermi GBM detection
Date
2018-09-24T19:51:56Z (7 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA) and C. Meegan (UAH) and report
on behalf of the Fermi GBM Team:
"At 22:20:30.53 UT on 23 September 2018, the Fermi
Gamma-Ray Burst Monitor triggered and located
GRB 180923B (trigger 559434035 / 180923931).
The on-ground calculated location, using the GBM trigger
data, is
RA, Dec = 310.6, -0.7 (J2000 degrees)
with an uncertainty of 1.0 degree (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 initial angle from the Fermi LAT boresight to
the best location is 86 degrees.
The GBM light curve shows/consists of two bright peaks
with a duration (T90) of about 8.2 s (50-300 keV).
The time-averaged spectrum from T0+0 s to T0+8.9 s is
best fit by a Band function with Epeak = 44.5 +/- 0.5,
alpha index = -0.77 +/- 0.03 and beta index = -3.02 +/- 0.05.
The event fluence (10-1000 keV) in this time interval is
(1.880 +/- 0.003)E-05 erg/cm^2. The 1s peak photon flux
measured starting from T0+4.0 s in the 10-1000 keV band
is 53 +/- 1 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
[GCN OPS NOTE(24sep18): Based on CIrcular 23265, the name
of the GRB used in this circular (23263) was changed
from "180923A" to "180923B".]
GCN Circular 23265
Subject
GRB 180923B - GBM Correction to GCN 23263
Date
2018-09-24T20:46:13Z (7 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA) reports on behalf of the GBM Team:
In GCN 23263, the incorrect GRB ID was used.
All references to GRB 180923A in this GCN are incorrect and should read as 180923B.
GRB 180923A was already detected by MAXI earlier that day (GCN 23257),
and used in subsequent GCNs (23258 and 23259).
My apologies for any confusion this error may have caused.