TITLE:   GCN CIRCULAR
NUMBER:  39333
SUBJECT: GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
DATE:    25/02/15 09:53:01 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

W.J. Xie (NAOC), Y.H. Cheng (SWIFAR, YNU), B.-T.Wang (YNAO, CAS), L.P. Xin, Y.L. Qiu, H.L. Li, C. Wu, Z.H. Yao, Y.N. Ma, X.H. Han, H.B. Cai, J. Wang, J.Y. Wei (NAOC), report on behalf of the SVOM team:

The SVOM/VT conducted a ToO follow-up observations of the GRB 250215A / EP250215a  (Fermi GBM Team, GCN 39327, Wang et al., GCN 39329) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. 

With the X band downlinked data, an uncatalogued optical source was clearly detected within the errorbox of EP/FXT (Wang et al., GCN 39329) in VT_R and VT_B single images, compared to the PanSTARRS and DESI catalogues. The position of source is consistent with the candidate reported (Liu et al., GCN 39300).

The brightness of the source was estimated to be 19.3+/-0.1 mag in AB magnitude in VT_R, 22.2+/-0.2 mag in AB magnitude in VT_B, at the mid time of 1.07 hours post the burst, with an exposure time of 100 seconds for each frame. 

Considering the red color of the source based on the VT data, it is likely a high redshift or highly extincted burst. More deep follow-ups are encouraged. 

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.