TITLE: GCN CIRCULAR NUMBER: 36633 SUBJECT: GRB 240606B: GECAM-B detection a long burst DATE: 24/06/07 04:49:43 GMT FROM: Yue Wang m18509381757@163.com

Yue Wang, Shao-Lin Xiong, Chen-Wei Wang report on behalf of the GECAM team:

GECAM-B was triggered both in-flight and on-ground by a long burst, GRB 240606B, at 2024-06-06T13:33:06.050 UTC (T0), which initialized Swift/BAT-GUANO observation (GCN # 36628).

According to the realtime alert data, the GECAM-B light curve shows a long pulse with a duration about ~10 sec (15-1020 keV).

The time-averaged spectrum of GECAM-B realtime data from T0-2 to T0+2 s could be adequately fit by a cut-off power-law with a flux about 6.67E-7 erg/cm^2/s in 20-1000 keV.

The GECAM light curve could be found here: https://twikinew.ihep.ac.cn/pubgecam/Sandbox/GRB/GRB240606B_lightcurve.png

The GECAM-B localization is consistent with the Swift/BAT localization within the error. 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).

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