GRB 230421A
GCN Circular 33668
Subject
GRB 230421A: Fermi GBM Final Real-time Localization
Date
2023-04-21T13:54:39Z (2 years ago)
From
William Cleveland at NASA-MSFC <william.cleveland@nasa.gov>
The Fermi GBM team reports the detection of a likely LONG GRB
At 09:42:46 UT on 21 Apr 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230421A (trigger 703762971.373066 / 230421405).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 44.5, Dec = 6.0 (J2000 degrees, equivalent to J2000 02h 58m, 6d 00'), with a statistical uncertainty of 5.5 degrees.
The angle from the Fermi LAT boresight is 99.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_skymap_all_bn230421405.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_healpix_all_bn230421405.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif
GCN Circular 33675
Subject
GRB 230421A: Fermi GBM observation
Date
2023-04-22T18:20:58Z (2 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 09:42:46.37 UT on 21 April 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230421A (trigger 703762971 / 230421405),
which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 33672).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight
at the GBM trigger time is 104 degrees.
The GBM light curve consists of a single emission episode
with a duration (T90) of about 10 s (50-300 keV).
The time-averaged spectrum from T0-1 s to T0+4 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.1 +/- 0.2 and
the cutoff energy, parameterized as Epeak, is 360 +/- 160 keV.
The event fluence (10-1000 keV) in this time interval is
(1.3 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.3 s in the 10-1000 keV band
is 3.2 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"