TITLE:   GCN CIRCULAR
NUMBER:  27335
SUBJECT: GRB 200306C: OSN 1.5m afterglow detection
DATE:    20/03/07 02:51:33 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann, M. Blazek (both HETH/IAA-CSIC), A. de Ugarte Postigo 
(HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, J. F. Agui Fernandez (both 
HETH/IAA-CSIC), and V. Casanova (IAA-CSIC) report:

We observed the optical afterglow position of GRB 200306C (Lipunov et 
al., GCNs #27324, #27325; Gropp et al., GCN #27326; Jelinek et al., GCN 
#27328; Hu et al., GCN #27329; Moskvitin, GCN #27333; Izzo & Perley, GCN 
#27334) with the 1.5m telescope of the Sierra Nevada Observatory, 
Granada, Spain, in the V filter. Observations began 46 minutes after the 
GRB, and we obtained 18 x 30 s images under moonlight. We also obtained 
four Rc images before technical problems shut down the telescope, but 
stray light from a nearby bright star precludes a detection.

We detect the afterglow in a stacked image centered 0.03985 days after 
the GRB, at V = 19.38 +/- 0.14 mag (Vega mag).

The afterglow magnitude was measured against six comparison stars from 
the GSC 2.3 catalog.