GRB 230905B
GCN Circular 34630
Subject
GRB 230905B: GECAM-C detection of a long burst
Date
2023-09-06T13:43:51Z (2 years ago)
From
yqzhang_cl@163.com
Via
Web form
Shaolin Xiong, Wangchen Xue, Yue Huang report on behalf of the GECAM team:
GECAM-C was triggered in-flight by a long burst, GRB 230905B,
at 2023-09-05T15:49:35.850, which was also observed by INTEGRAL/SPI-ACS.
According to the realtime alert data of GECAM-C, this burst
mainly consists of a long pulse with a duration (T90) of about ~10 sec (20-1000 keV).
Using the automatic on-ground localization pipeline with the realtime alert data,
GECAM-C localized this burst to the following position (J2000):
RA: 340.1 deg
DEC: 9.2 deg
Err: 5.2 deg (1-sigma, statistical only)
The systematic error of this location is estimated to be several degrees.
The time-averaged spectrum of GECAM-C realtime data shows that it could be
adequately fit by a cut-off power-law with a fluence about 2.7E-6 erg/cm^2 in 20-1000 keV.
We note that these results are based on realtime alert data and thus very preliminary.
Refined analysis will be reported later.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B)
launched in Dec. 2020. As the third member of GECAM constellation,
GECAM-C was launched onboard SATech-01 experimental satellite in July 2022.
GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular 34635
Subject
GRB 230905B: AstroSat CZTI detection
Date
2023-09-07T08:06:48Z (2 years ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
P. K. Navaneeth (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 230905B which was also detected by GECAM-C (Xiong et al., GCN Circ. 34630), and INTEGRAL/SPI-ACS.
The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2023-09-05 15:49:37.50 UTC. The measured peak count rate associated with the burst is 186 (+46, -24) counts/s above the background in the combined data of all quadrants, with a total of 1858 (+502, -520) counts. The local mean background count rate was 447 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 45 (+14, -22) s.
The source was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 34644
Subject
Glowbug gamma-ray detection GRB 230905B
Date
2023-09-09T14:06:23Z (2 years ago)
From
matthew.kerr@gmail.com
Via
Web form
M. Kerr, C.C. Cheung, J. E. Grove, R. Woolf (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 230905B, which was also detected by GECAM-C, AstroSat/CZTI, and INTEGRAL/SPI-ACS (GCN 34630, 34635).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2023-09-05 15:49:30.096 with a duration of 12.3 s and a total significance of about 34.6 sigma. The light curve comprises a single primary peak with three distinct sub-peaks, each lasting for and separated by about two seconds.
Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission over this duration results in a photon index dN/dE~E^x of x=1.5 and a cutoff energy ("Epeak") of 189 keV. The modeled 10-10000 keV fluence is 1.7e-06 erg/cm^2.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS. The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
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