TITLE:   GCN CIRCULAR
NUMBER:  46145
SUBJECT: EP261103a: SVOM/VT optical observation
DATE:    26/11/04 07:06:59 GMT
FROM:    Yinuo Ma <mayn@bao.ac.cn>

Y. N. Ma, H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, J. R. Xu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. 

SVOM/VT performed a Target of Opportunity observation of EP261103a detected by EP/WXT (Ren et al., GCN 46142). SVOM/VT began observing the field at 2026-11-03T21:22:47 UTC, 1.07 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. 

With X-band data available, the NOT counterpart candidate (Jiang et al., GCN 46143) was only detected in VT_R band. The photometric measurements in AB magnitudes are:

mid time (h) | exposure time (s) | band |  mag (AB) 
-------------|-------------------|------|---------------
     2.19    |      89*50        | VT_B |  >23.6 (3-sigma)
     2.19    |      89*50        | VT_R |  23.4+/-0.3 

Our photometry was not corrected for Galactic extinction.

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.