GRB 241217A : SVOM/ECLAIRs,GRM,MXT detection of a long burst with a bright X-ray afterglow candidate

During the commissioning phase, the SVOM/ECLAIRs telescope triggered and located the long duration GRB 241217A (sb24121704) starting at 2024-12-17T16:57:13 UTC (Tb). The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 9 alerts were received. The best detection is obtained by IMT with a signal-to-noise ratio of 11.9 in the 8-120 keV energy band over a time window of 82 s starting at Tb. The light light curve shows multiple broad peaks in 5-50 keV in ECLAIRs and below 550 keV in GRM. The localization of the best Alert is RA, Dec = 84.160, -25.324 (J2000). The statistical uncertainty on this position is 6.8 arcminutes, which includes a systematic uncertainty of 2 arcminutes in quadrature. SVOM slewed automatically on this burst. MXT began observing the field at 2024-17-12T17:01:36, 263 seconds after Tb. Using onboard processed data we found one very bright uncatalogued X-ray source located at RA, Dec 84.152, -25.295 degrees with a 90% C.L. radius of 25 arcsec (statistic + systematic), corresponding to: R.A. = 05h 36m 36s Dec = -25° 17' 42'' This location is 1.8 arcminutes from the ECLAIRs onboard position. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The SVOM point of contact for this burst is: Brunet Marius (marius.brunet@irap.omp.eu)