GCN Circular 29863
Subject
GRB 210420B: Tautenburg observations
Date
2021-04-21T15:01:05Z (3 years ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
B. Stecklum, A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, and U. Laux
(all Tautenburg) report:
We observed the field of GRB 210420B (Moss et al., GCN 29844) with the
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6k x 6k CCD
camera. Observations started on April 20 at 20:13:21 UT, 99 min after the
BAT trigger (Lien et al., GCN 29854). Altogether four observing runs (5x5
min each) were performed (Sloan r'). The afterglow (Lipunov et al., GCN
29845; Oksanen, GCN 29846; Hu et al., GCN 29847; Sun et al., GCN 29848;
Leonini et al., GCN 29851; de Ugarte Postigo et al., GCNs 29852, 29853;
Watson et al., GCN 29858) was clearly detected in all frames. Magnitudes
were calibrated against SDSS.
The data show that between the first (mean time: 20:26:10 UT; r' = 18.30
+/- 0.03) and the second observing run (mean time: 21:47:07 UT; r' = 18.75
+/- 0.03) ) the light curve was steepening to a decay with alpha2 = 0.99
+/- 0.04 (break time tb = 0.091 +/- 0.017 days). Before the break the
decay index is not well constrained (alpha1 = 0.35 +/- 0.33).