GRB 240918A
GCN Circular 37549
Subject
GRB 240918A: Fermi GBM Final Real-time Localization
Date
2024-09-18T21:04:21Z (8 months 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 20:55:11 UT on 18 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240918A (trigger 748385716.160644 / 240918872).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 221.6, Dec = 17.0 (J2000 degrees, equivalent to J2000 14h 46m, 17d 00'), with a statistical uncertainty of 10.4 degrees.
The angle from the Fermi LAT boresight is 86.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240918872/quicklook/glg_skymap_all_bn240918872.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240918872/quicklook/glg_healpix_all_bn240918872.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240918872/quicklook/glg_lc_medres34_bn240918872.gif
GCN Circular 37550
Subject
Fermi GRB 240918A: Global MASTER-Net observations report
Date
2024-09-18T23:30:50Z (8 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 240918A ( Fermi GBM team, GCN 37549) errorbox 8469 sec after notice time and 8476 sec after trigger time at 2024-09-18 23:16:27 UT, with upper limit up to 13.1 mag. Observations started at twilight. The observations began at zenith distance = 73 deg. The sun altitude is -11.0 deg.
The galactic latitude b = 61 deg., longitude l = 18 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2607032
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
8507 | 2024-09-18 23:16:27 | MASTER-OAFA | (14h 49m 57.03s , +19d 01m 43.5s) | C | 60 | 12.0 |
8770 | 2024-09-18 23:20:50 | MASTER-OAFA | (15h 06m 05.69s , +19d 01m 26.3s) | C | 60 | 12.7 |
8990 | 2024-09-18 23:24:30 | MASTER-OAFA | (14h 48m 30.08s , +15d 13m 06.5s) | C | 60 | 13.1 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 37560
Subject
GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVE
Date
2024-09-19T23:14:33Z (8 months ago)
From
Devraj Pawar at R. J. College, Mumbai - 86, India <devrajdp@gmail.com>
Via
Web form
Devraj Pawar (R. J. College, Mumbai-86, India) on behalf of a collaboration studying transients.
GRB 240918A and GRB 240918B were reported by the Fermi GBM team in GCN 37549 and GCN 37558 respectively.
We analyzed the INTEGRAL SPI ACS data around the T0 given in GCN 37549 and detected two peaks separated by ~108 seconds in the light curve. These events occur at the times reported in GCN 37549 and GCN 37558. SPI ACS is sensitive above 80 keV : the peak of the first burst is at ~3550 counts/s and peak count rate of the second burst is 3800 counts/s. The steady count rate preceding the events is around 3350 counts/s. The count rate is affected by the instruments orientation with respect to the direction of the sources and hence the relative intensity of the two bursts cannot be compared with the analysis done so far. GRB 240918A is not visually detected with the 0.05 s resolution of the INTEGRAL SPI ACS, hence we time averaged the light curve. The light curves at various time resolutions and the burst profiles are given in the link below and any further analysis will be shared on the same link :
[GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVES](https://docs.google.com/document/d/15b887kxPSdQVyT9NLfZZzb8XMLhijewiSY8KHXPTdhI/edit?usp=sharing)
This work is based on observations with INTEGRAL, an ESA project with instruments and a science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), and with the participation of Russia and the USA. The SPI-ACS detector system has been provided by MPE Garching/Germany.