TITLE:   GCN CIRCULAR
NUMBER:  41143
SUBJECT: SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
DATE:    25/07/23 14:57:46 GMT
FROM:    Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>

R. A. J. Eyles-Ferris and N. Habeeb (U of Leicester) report on behalf of a larger collaboration:

We observed the field of the SVOM transient SVOM J195836+32283 / sb25072103 (Götz et al., GCN 41131) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS g’, r’, i’ and z’ filters starting at 23:43:39 UT on 2025-07-22, approximately 41 hours after the ECLAIRs trigger.

No sources consistent with the SVOM/VT position are identified in the g’ or r’ images and we obtain 3-sigma upper limits of g’ > 22.7 and r’ > 22.9 calibrated to Pan-STARRS and not corrected for Galactic extinction.

In the i’ and z’ images, we do identify a source, the morphology of which is inconsistent with a single point source. Instead, it appears to be extended, consistent with the suggestion of Mo et al. (GCN 41138), or may be a combination of several components. We measure i’ = 22.9 +/- 0.3 and z’ = 21.9 +/- 0.2 for the source, again calibrated to Pan-STARRS and not corrected for Galactic extinction. The relative contributions of the transient and possible host to this flux are currently unknown and we encourage further observations of this source.