[vsnet-grb-info 19637] GRB 170728B: I-band detection from 1.5m OSN

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21381
SUBJECT: GRB 170728B: I-band detection from 1.5m OSN 
DATE:    17/07/29 14:31:54 GMT
FROM:    Luca Izzo at IAA-CSIC  <Luca.Izzo at ICRA.it>

L. Izzo, D.A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene (HETH/IAA-CSIC) and A. Sota (IAA-CSIC) report on behalf of a larger collaboration:

We observed the field of GRB 170728B (Cenko et al., GCN 21371) with the 1.5m OSN telescope of the Sierra Nevada Observatory (Granada, Spain). Observation consisted of a series of 300 s Ic-band exposures, starting at 00:06:02.7 UT (1.05 hr after the burst). The afterglow is detected at a position consistent with the one reported by D’Avanzo et
al., (GCN 21373).

In the combination of the first 7x300s exposures we measure a magnitude of Ic(Vega) = 19.8+/- 0.2 as compared to USNO-B1 stars.