TITLE:   GCN CIRCULAR
NUMBER:  27582
SUBJECT: GRB 200412B: continued Tautenburg observations 
DATE:    20/04/15 09:30:32 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

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

We continued observing the field of GRB 200412B (Fermi GBM team, GCN 
27547) with the Tautenburg 1.34m Schmidt telescope equipped with the 
TAUKAM 6k x 6k CCD camera and the wide V-band filter (VB; Stecklum et al., 
GCN 27567; Klose et al., GCN 27575).

For the optical transient (Lipunov et al., GCN 27555, 27556) at a mean 
time of 2.521 days post burst we measure VB = 21.38 +/- 0.06. This is 
about 0.2 mag fainter than expected for a decay slope of alpha = 1.582 +/- 
0.004 based on our previous VB-band data (see also Xin et al., GCN 27571; 
Belkin et al., GCN 27574), suggesting that the light curve decay is 
steepening. Additional data are required to confirm (or reject) this 
conclusion.

We note that in our images there is still no evidence for an underlying 
host galaxy.