TITLE:   GCN CIRCULAR
NUMBER:  39372
SUBJECT: SVOM/sb25021804: QSO variability in Liverpool Telescope observations
DATE:    25/02/19 11:37:18 GMT
FROM:    Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>

R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report on behalf of a larger collaboration:
 
We observed the field of the SVOM/ECLAIRs transient sb25021804 (Wang et al., GCN 39363) in four pointings covering ~87% of the error area using the IO:O on the 2m Liverpool Telescope. We obtained 4x150s exposures per pointing in the SDSS g’ filter starting at 2025-02-19 04:59:09 UT, approximately 21.7 hours after the SVOM/ECLAIRs detection.
 
We performed image subtraction on the stacked images using reference images from Pan-STARRS. We identify a residual at RA, Dec 195.044, 28.130 which corresponds to the X-ray bright QSO WISEA J130010.60+280749.7, about 3.4 arcmin from the SVOM ECLAIRs position reported by Wang et al., GCN 39363. We performed PSF photometry on the stacked image and find g’ = 20.09 +/- 0.11 calibrated to Pan-STARRS and not corrected for Galactic extinction. This is ~0.5 mag brighter than the magnitude catalogued in Pan-STARRS DR2 and we suggest sb25021804 is related to this variability.

We find no other obvious residuals in the subtracted images to a 3-sigma limiting magnitude of ~21.5.