[vsnet-grb-info 16834] GRB 150728A: TNG optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18115
SUBJECT: GRB 150728A: TNG optical observations
DATE:    15/08/05 20:10:52 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo at brera.inaf.it>

P. D'Avanzo, D. Fugazza (INAF/OABr), V. D'Elia (INAF/OAR and ASI/ASDC), V. Lorenzi, H. Stoev (INAF/TNG) report on behalf of the CIBO collaboration:
We observed the field of the short GRB 150728A (Krimm et al., GCN 18087; Ukwatta et al. GCN 18091) with the 3.6m TNG telescope equipped with the DOLoRes camera. Observations consisted of 12 images in the r-sdss band for a total of 48 min exposure. The seeing was ~1.2".

No object is detected within the enhanced XRT position (Beardmore et al., GCN 18088), down to a limiting magnitude r > 24.5 (calibrated against nearby USNO-B1 stars). The mean time of the observation was 2015 Jul 30.9439 UT (2.41 days after the GRB). In particular, we find no evidence for fading for the object reported by Dichiara et al. in GCN 18090 (which appears to be point-like in our images), by measuring in our dataset a magnitute of r = 21.4 +/- 0.1 for this source (calibrated against nearby USNO-B1 stars).