GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A

During the commissioning phase, GECAM-B was triggered in-flight by a long burst at 2021-01-24T11:50:03.600 UTC (denoted as T0). Its alert data was promptly downlinked to the ground through the short message service of BeiDou Navigation Satellite System (BDS). The time latency of the first BeiDou message relative to the trigger time is about 1 minute. According to the BDS alert data, this burst mainly consists of a single pulse with a duration of about 60 s. The spectrum is very soft with not much emission above about 30 keV. An automatic on-ground localization was calculated using the light curves and spectrum. Although the in-flight calibration of energy response and localization has not been finalized yet, GECAM-B localized this burst to the following position (J2000): Ra: 94.9 deg Dec: 6.6 deg Galactic lon: 188.4 deg, lat: 12.1 deg Err: 2.7 deg (1-sigma, statistical only) The current systematic error of location is estimated to be several degrees which could be minimized by the ongoing calibration. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_21-22-11_65188203.png The GECAM preliminary location could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_65188203_V01.png Based on the light curve, spectral hardness and location, we suggest that this burst is likely from a galactic source. We note that 4U 0614+09 lies within the location error which could produce such an X-ray burst. However, the GRB nature could not be ruled out yet. As the detailed science data are downloaded, all analyses would be improved. Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS).