TITLE:   GCN CIRCULAR
NUMBER:  39756
SUBJECT: GRB 250317B: refined SVOM/MXT analysis
DATE:    25/03/17 08:04:00 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:

We performed further analysis of the GRB 250317B (Zhao et al., GCN 39753) MXT X-ray data, using promptly downloaded photons through the VHF band. We can improve the X-ray afterglow position. The new J2000 coordinates are 

R.A. = 14h 06m 32s	
Dec. = +40d 05mm 02ss

with a 90% c.l. error radius of 48 arc seconds, including systematics.

This position supersedes the one reported in GCN 39753, which was affected by early satellite instability after the slew.

We note that this position is consistent with the SVOM/F-GFT (COLIBRÍ) position (Watson et al. GCN 39754) and the VT one (Palmeiro et al. GCN 39755).

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.