TITLE:   GCN CIRCULAR
NUMBER:  34491
SUBJECT: GRB 230818A: Tautenburg observations
DATE:    23/08/19 16:59:54 GMT
FROM:    Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>

S. Klose, S. Melnikov, B. Stecklum, A. Nicuesa Guelbenzu, F. Ludwig (all TLS Tautenburg) report:

We observed the field of GRB 230818A (Fermi GBM team, GCN 34478; Tohuvavohu et al., GCN 34479) with the Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD camera and using the Sloan filter set.

For the optical transient discovered by Lipunov et al. (GCN 34476) we measure the following magnitudes:

g = 19.98 +/- 0.02  (midtime: August 19, 2023,  00:03:14 UT),
r = 19.76 +/- 0.02  (midtime: August 19, 2023,  00:14:43 UT),
i = 19.79 +/- 0.03  (midtime: August 19, 2023,  00:26:00 UT),

and

g = 21.35 +/- 0.12  (midtime: August 19, 2023,  01:57:48 UT),
r = 20.97 +/- 0.10  (midtime: August 19, 2023,  02:08:35 UT),
i = 20.86 +/- 0.10  (midtime: August 19, 2023,  02:19:32 UT),

calibrated against the Pan-STARRS catalog.