GRB 241002D

SVOM/GRM team: Wen-Jun Tan, Shi-Jie Zheng, Yong-Wei Dong, Jiang-Tao Liu, Jian-Chao Sun, Yue Huang, Jiang He, Min Gao, Hao-Xuan Guo, Lu Li, Yong-Ye Li, Hong-Wei Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, You-Li Tuo, Chen-Wei Wang, 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, Yan-Qiu 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), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC),Olivier Godet (IRAP),  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),  Shao-Lin Xiong (IHEP), Bing Zhang  (UNLV)

report on behalf of the SVOM team:

During the commissioning phase, the SVOM/GRM was triggered in-flight by a long GRB 241002D (SVOM trigger reference: sb 24100205) at 2024-10-02T22:08:07.000 UT (T0).

The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. The light curve shows that this burst consists of a single pulse with a T90 of 4.8 +/- 2.8s.

The GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb241002D.png

At the time of the burst ECLAIRs was not in operational mode.

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: Wen-Jun Tan (IHEP)(tanwj@ihep.ac.cn)

O.J. Roberts (USRA/NASA-MSFC), E. Burns (LSU), A. Goldstein (USRA/NASA-MSFC), J. Wood (NASA-MSFC) report on behalf of the Fermi-GBM Team:

SVOM detected GRB 241002D on 2024-10-02 at 22:08:07.000 UTC (Tan et al., GCN #37693
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 ). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no candidates. 

The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, identified an unambiguous transient starting -0.128 s before the SVOM trigger time most significantly on the 1.024 s timescale, with a LogLR = 297. Fermi-GBM did not trigger on-board due to intentional suppression of soft transients. The Fermi-MET of the start time of this transient is 749599691.872 s. Using the standard search protocol, the Targeted Search localized the signal to an RA=24.6 deg., Dec.= 20.3 deg., with an error of 11.4 deg. (90 % confidence level, includes the systematic error), at a SNR of 24.0. 

Additionally, the GBM Targeted Search event was found with the highest significance using a "soft" spectrum (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB. The duration is about 5s, consistent with the T90 reported previous by Tan et al.

The Targeted Search data release product for this event can be found here: https://zenodo.org/uploads/13886511

[1] Goldstein et al. 2019 arXiv:1903.12597
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