TITLE:   GCN CIRCULAR
NUMBER:  44919
SUBJECT: GRB 260610B: IAC-80 Optical observations
DATE:    26/06/12 07:06:28 GMT
FROM:    Daniel Perley at Liverpool JMU <d.a.perley@ljmu.ac.uk>

Dominic Jackson-Horne (UOL/LJMU), Danny McDonnell (UOL/LJMU), Esme Williams (UOL/LJMU), Daffyd Thomas (UOL/LJMU), Ruby Keeling-Roberston (UOL/LMJU), Farhan Qamar Salmo (UOL/LJMU), Oliver King (UOL/LJMU), Daniel Perley (LJMU), H.-M. S. Grabham (LJMU), and Daniel Harman (LJMU) report:


We observed the optical afterglow (D. O'Neill, et al., GCN 44903) of GRB 260610B (The Fermi GBM team, GCN 44901) using the 0.82m IAC80 telescope of Teide Observatory, equipped with the CAMELOT2 optical imager.  Our first set of observations commenced at 21:41 UT and concluded at 22:20 UT on June 11; a second set of observations was then taken between 01:20 UT and 02:05 UT on June 12.

We report the following photometry:

| Date       | UTstart  | t-T0 (d) | Exp (n*s) | Filter | Mag   | Err  |
|------------|----------|----------|-----------|--------|-------|------|
| 2026-06-11 | 21:41:52 | 0.913    | 3*180     | SDSS-r | 20.04 | 0.06 |
| 2026-06-11 | 22:03:58 | 0.928    | 3*180     | Rc     | 19.85 | 0.06 |
| 2026-06-11 | 22:17:05 | 0.938    | 3*180     | Ic     | 19.23 | 0.05 |
| 2026-06-11 | 22:25:33 | 0.943    | 3*180     | B      | 20.94 | 0.13 |
| 2026-06-12 | 01:20:48 | 1.065    | 3*120     | B      | 21.47 | 0.26 |
| 2026-06-12 | 01:27:40 | 1.070    | 3*120     | V      | 20.35 | 0.09 |
| 2026-06-12 | 01:34:33 | 1.075    | 3*120     | Ic     | 19.40 | 0.08 |
| 2026-06-12 | 01:41:26 | 1.080    | 3*120     | SDSS-r | 20.26 | 0.09 |

This preliminary photometry is calibrated relative to the SDSS star J143237.88+270028.3 (using the Lupton 2005 transformation equations) and not corrected for Galactic extinction.