GCN Circular 40707

Subject

sb25061207: SVOM/VT optical counterpart

Event

sb25061207

Date

2025-06-12T15:40:31Z (6 months ago)

Edited On

2025-06-12T21:00:37Z (6 months ago)

From

Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>

Edited By

Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>

Via

Web form

H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), L. Zhang (IHEP), Y.-D. Hu (GXU), X.-L. Chen (YNU) report on behalf of the SVOM mission team

SVOM performed an automatic slew on the burst (sb25061207) triggered by SVOM/ECLAIRs (Zhang et al., GCN 40697Loading...
 
 ). SVOM/VT began observing the field at 2025-06-12T10:30:44  UTC,  202 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.

A candidate is found using VT X-band data, compared to Legacy survey, within the error box of SVOM/Eclairs (Zhang et al., GCN 40697Loading...
 
 ) at R.A., Dec 198.09415,  +0.07508  degrees:

RA (J2000) = 13:12:22.597
Dec (J2000) =  +00:04:30.28

with an uncertainty of 0.5 arcsec.
 
The source is detected in both VT_R and VT_B bands. With the data available, the light curve shows that this source was fading at first time, and then rebrightening to the peak of VT_R ~ 18.0 mag at around 1000 seconds after the trigger time, and then decayed.  

 mid-time    |  exposure time   | band | mag (AB) 
------------ |----------------- |-------------------
 1.79 hour   |  50 sec          | VT_B |  21.6+/-0.2        
 1.79 hour   |  50 sec          | VT_R |  20.8+/-0.1    

Given the VT colour of the candidate, it might be a low redshift transient.

More followups are encouraged. 

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the   Chinese National Space Administration (CNSA, China), National Centre 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.
 
The Burst Advocate (BA) on shift for this alert is Y.-D. Hu : hyd@gxu.edu.cn.