TITLE: GCN CIRCULAR NUMBER: 36805 SUBJECT: The first three GRBs detected by SVOM: GRB 240627B, GRB 240629A and GRB 240702A DATE: 24/07/03 03:46:41 GMT FROM: Shaolin Xiong at IHEP xiongsl@ihep.ac.cn

SVOM/GRM team: Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, Wen-Jun Tan, Jian-Chao Sun, Chen-Wei Wang, Jiang He, Min Gao, Hao-Xuan Guo, Yue Huang, 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), Patrick Maeght (LUPM), Frédéric Piron (LUPM), 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 of SVOM which was launched on June 22, 2024 from the Xichang Satellite Launching Center, China, the Gamma-Ray burst Monitor (GRM), as one of the four multi-wavelength telescopes on-board SVOM, detected three long gamma-ray bursts (GRBs), GRB 240627B at 2024-06-27T20:08:11.750 UTC (T0), GRB 240629A at 2024-06-29T16:53:53.000 UTC (T0) and GRB 240702A at 2024-07-02T21:14:50.700 UTC (T0), with on-ground blind search using event-by-event data downloaded through the X-band ground station. The light curves of GRB 240627B were also successfully downloaded through the VHF system with low latency owing to an in-flight trigger just about 50 s after this burst. Although the calibration is ongoing, the preliminary GRM light curves are well consistent with the Fermi/GBM and GECAM-C observations. The automatic in-flight trigger strategy of GRM is under commissioning.

The GRB 240627B light curves can be found here: http://www.bursthub.cn//admin/static/svgrb240627B.png

The GRB 240629A light curves can be found here: http://www.bursthub.cn//admin/static/svgrb240629A.png

The GRB 240702A light curves can be found here: http://www.bursthub.cn//admin/static/svgrb240702A.png

We note that these are the first three GRBs detected by SVOM. More GRBs are expected to be detected by SVOM as other instruments are gradually turned on according to the operation plans.

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 these bursts is: Shao-Lin Xiong (IHEP)(xiongsl@ihep.ac.cn)

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