TITLE: GCN CIRCULAR NUMBER: 38541 SUBJECT: GRB 241212A: SVOM detection of a bright long burst DATE: 24/12/12 10:40:13 GMT FROM: SVOM_group svomgroup@bao.ac.cn

Zhang Li (IHEP), Wenjin Xie (NAOC), Nicolas Dagoneau, Stéphane Schanne (CEA), Maria-Grazia Bernardini (INAF, LUPM), Clara Plasse (CEA), Shaolin Xiong (IHEP) report:

At 2024-12-12T09:21:49 (Tb) SVOM/ECLAIRs triggered on GRB 241212A (SVOM burst-id sb24121201), also detected by Fermi GBM (GCN Circular 38540).

The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. A total of 12 Alerts were received from Count-Rate Trigger (CRT) and Image Trigger (IMT). The best Alert was produced by CRT with a signal-to-noise ratio of 35.5 in the 8-120 keV energy band over a time window of 20.48 s starting at Tb. The light curve shows a single broad peak of duration of about 40 s.

The localization of the best Alert is RA, Dec = 45.119, 6.701 (J2000) with a 90% C.L. radius of 2.9 arcmin (including a systematic error of 2 arcmin added in quadrature).

GRM light curve showed a broad peak structure with a T90 duration of about 40 s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb241212A.png

SVOM slewed automatically to the burst.

MXT began observing the field at 2024-12-12T09:24:05, 133 seconds after Tb, during an exposure of 6 seconds, before SAA entry.

Using onboard processed data we found one uncatalogued X-ray source located at RA, Dec 45.087, 6.719 degrees with a 90% C.L. radius of 70 arcseconds, corresponding to:

RA = 03h 00m 21s Dec = 06° 43' 08"

This location is 2.2 arcminutes from the ECLAIRs onboard position.

VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular on the follow-up of the SVOM optical instruments.

Burst Advocate for this burst is Zhangli (zhangli@ihep.ac.cn). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.

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