GRB 240812B

A. Dasgupta (BITS Pilani, Hyderabad), S. Srijan (IITB), G. Waratkar (IITB), J. Joshi (IUCAA), 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-duration GRB 240812B which was also detected by INTEGRAL/SPI-ACS (Trigger 10849).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-08-12 09:05:55 UTC. The measured peak count rate associated with the burst is 111 (+43, -10) counts/s above the background in the combined data of all quadrants, with a total of 833 (+183, -176) counts. The local mean background count rate was 338 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 11 (+3, -3) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-08-12 09:05:55 UTC. The measured peak count rate is 352 (+74, -49) counts/s above the background in the combined Veto data of all quadrants, with a total of 1890 (+472, -502) counts. The local mean background count rate was 1570 (+8, -9) counts/s. We measure a T90 of 9 (+4, -3) s from the cumulative Veto light curve.

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

SVOM/GRM team: Jian-Chao Sun, Yue Huang, Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, Jiang He, Chen-Wei Wang, Wen-Jun tan, Min Gao, Hao-Xuan Guo, Lu Li, Yong-Ye Li, Hong-Wei Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, You-Li Tuo, Hao-Xi Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Rui-Jie Wang, Yu-Xi Wang, Bo-Bing Wu, Shao-Lin Xiong, Jian-Ying Ye, Yi-Tao Yin, Wen-Hui Yu, Fan Zhang, Li Zhang, Peng Zhang, Shuang-Nan Zhang, Wen-Long Zhang, Yan-Ting Zhang, Shu-Min Zhao, Xiao-Yun Zhao, Chao Zheng (IHEP), Maria-Grazia Bernardini (LUPM/INAF-OAB), Laurent Bouchet (IRAP), David Corre (CEA), Tais Maiolino (LUPM), Frédéric Piron (LUPM) , Stéphane Schanne (CEA), Jingwei Wang (IAP)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), JeanLuc Attéia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)

report on behalf of the SVOM team:

During the commissioning phase, the SVOM/GRM was triggered in-flight by GRB 240812B (SVOM trigger reference: sb24081211) at 2024-08-12T09:05:54.000 UT (T0), which was also observed by INTEGRAL/SPI-ACS (Trigger 10848) and AstroSat/CZTI (GCN 37152
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 ).

The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. The GRM light curve shows that the T90 of this burst is about 13.2 s +-0.8 s.

The GRM light curve can be found here:
https://www.bursthub.cn/admin/static/svgrb240812B.png

At the time of this burst, SVOM/ECLAIRs was in operation. However the lack of detection suggests that the GRB was outside the SVOM/ECLAIRs FoV.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.

The SVOM point of contact for this burst is: Jian-Chao Sun (IHEP)(sunjc@ihep.ac.cn)