TITLE: GCN CIRCULAR NUMBER: 39729 SUBJECT: SVOM/MXT upper limit on GRB 250314A DATE: 25/03/15 07:13:31 GMT FROM: Diego Gotz at CEA diego.gotz@cea.fr
D. Götz (CEA), F. Robinet (IJCLab), H. Goto (CEA), C. Plasse (CEA), P. Maggi (ObAS), M. Moita (CEA), C. van Hove (IJCLab) on behalf of the MXT team report:
The field of GRB 250310A (Wange et al. GCN 39719, Li et al. 39728) was observed by MXT promptly after the SVOM slew starting at 12:59:55 UT, i.e. 193 s after ECLAIRs trigger. The analysis conducted on board did not reveal any significant source in the field of view of the telescope.
By analyzing the full available MXT data set, we do not detect any X-ray counterpart within the ECLAIRs error box, nor at the position of the possible J-band/X-ray afterglow (Malesani et al. GCN 39727), down to a 3 sigma upper limit of about 5.5e-11 ergs/cm^2/s in the 0.5-10 keV energy range. This upper limit likely favours a high-z scenario, rather than a nearby highly extinguished GRB.
The Space-based multi-band astronomical 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. MXT has been developed by CNES in collaboration with CEA, IJCLab, University of Leicester and MPE.
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