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.

View this GCN Circular online at https://gcn.nasa.gov/circulars/41143. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...