GRB 260618A
GCN Circular 45044
Subject
GRB 260618A: Fermi GBM Observation
Date
2026-06-25T13:02:58Z (15 days ago)
From
Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>
Via
Web form
C. Malacaria (INAF-OAR) and R. Sonawane (IISER, TVM) report
on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 06:45:34.28 UT on 18 June 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260618A (trigger 803457939/260618282).
Final Real-time localization was reported in GCN 44973.
A possible afterglow is detected by EP (Yang et al., GCN 44978,
Jiang et al., GCN 44991).
The GBM light curve consists of a variable emission episode with a duration (T90)
of about 140 s (50-300 keV). The time-averaged spectrum
from T0-17 to T0+150 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.4 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 43 +/- 2 keV.
The event fluence (10-1000 keV) in this time interval is
(5.9 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+25 s in the 10-1000 keV band is 2.7 +/- 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/"
GCN Circular 44973
Subject
GRB 260618A: Fermi GBM Final Real-time Localization
Date
2026-06-18T06:56:28Z (22 days ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 06:45:34 UT on 18 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260618A (trigger 803457939.281242 / 260618282).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 281.5, Dec = 21.1 (J2000 degrees, equivalent to J2000 18h 45m, 21d 06'), with a statistical uncertainty of 6.3 degrees.
The angle from the Fermi LAT boresight is 72.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618282/quicklook/glg_skymap_all_bn260618282.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618282/quicklook/glg_healpix_all_bn260618282.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618282/quicklook/glg_lc_medres34_bn260618282.gif