GRB 241206B

SVOM/ECLAIRs Commissioning Team: Andrea Saccardi, Dylan Adrien, Nicolas Dagoneau, Stéphane Schanne, Frédéric Chateau, Hervé Le Provost (CEA), Jean-Luc Atteia, Laurent Bouchet, Marius Brunet, Sebastien Guillot, Juliette Alaux, Hui Yang (IRAP), Wenjin Xie, Donghua Zhao (NAOC), Alexis Coleiro (APC), Tais Maiolino (LUPM), Karine Mercier, Marie-Claire Charmeau, Stefano Crepaldi (CNES)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Olivier Godet (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, the SVOM/ECLAIRs telescope triggered and located the long duration soft transient called GRB 241206B (sb24120602) at 2024-12-06T15:08:48 UT (Tb).

The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network.

The burst was detected by the Image Trigger (IMT) only and 2 alerts were received. The best detection is obtained with a signal-to-noise ratio of 9.3 in the 5-8 keV energy band over a time window of 1310.72 s starting at Tb.

The localization of the best Alert is RA, Dec = 300.202, 65.182 (J2000).

The statistical uncertainty on this position is 9.1 arcminutes, to which we recommend adding 2 arcminutes of systematic uncertainty in quadrature.

SVOM did not slew on this burst.

We notice that QSO B1959+650 is within the error box.

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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP.

The SVOM point of contact for this burst is: andrea.saccardi@cea.fr

SVOM/GWAC-F50A team：L.P.Xin(NAOC), Y.G.Yang(HNU), C.WU(NAOC), Y.L.Qiu(NAOC), J.Wang(NAOC), H.L.Li(NAOC), E.W.Liang(GXU), X.H.Han (NAOC), X.M.Lu(NAOC), R.S.Zhang(NAOC), Y.Xu(NAOC), L. Huang(NAOC), H.B.Cai(NAOC), Y.J.Xiao(NAOC), P.P.Zhang(NAOC), L.Lan(NAOC), W.J.Xie(NAOC), Z.H.Yao(NAOC), X.G.Wang (GXU), J.Y.Wei(NAOC)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Olivier Godet (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:

We began to observe GRB 241206B (Saccardi et al., GCN 38450
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 ), with 50cm telescope (GWAC-F50A) at Xinglong station, China, at 2024-12-06T15:38:26.8 (UT), about 19.7 min after the burst. 

With the initial observation with exposure time of 50 sec, no any uncatalogued source was detected in our image down to a limit magnitude of 17.0 mag in R band comparing to several nearby USNO B1.0 stars.

We acknowledge the excellent support from observation assistant Yangtong Zheng and Winlong Dong.

D. Götz (CEA/Irfu), N. Leroy (IJClab), M. Moita, H. Goto, C. Plasse (CEA Irfu), F. Robinet, C. Van Hove (IJCLab), P. Maggi (ObAS) report on behalf of the SVOM MXT Team.

SVOM/MXT observed the SVOM/ECLAIRs error box (Saccardi et al. GCN 38450
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 ) as a TOO starting at 16:50 UT on December 6th 2024, i.e. 52 minutes after the ECLAIRs trigger.

The on-board software clearly detects a single persistent X-ray source at

RA = 300.013, 
DEC = 65.1563

with a R90 error of about 35 arc sec (90% c.l.).

This position is compatible with the one of the QSO 1ES 1959+650. We hence suggest that the ECLAIRs trigger is related to an outburst of this source and it is not a real GRB.