[vsnet-grb-info 10759] GRB 110719A: z-band upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12181
SUBJECT: GRB 110719A: z-band upper limit
DATE:    11/07/19 18:51:56 GMT
FROM:    Stefano Covino at Brera Astronomical Observatory  <stefano.covino at gmail.com>

Andrew J. Levan (Univ. Warwick), Stefano Covino, Andrea Melandri (INAF/ 
OABr), Daniele Malesani, Antonio de Ugarte Postigo, Johan P.U.
Fynbo (DARK/NBI), report on behalf of the X-shooter GRB GTO  
collaboration:

We observed the field of GRB 110719A (Sakamoto et al., GCN 12173) with  
the ESO VLT equipped with X-shooter. We could only take a short
acquisition image, with mean time 2011 July 19.42 UT (3.95 hr after  
the GRB). No new object is detected within the refined XRT error circle
(Goad et al., GCN 12176), down to a limiting magnitude z > 22.5 (AB),  
calibrated against SDSS stars in the field.

We note that the inferred limit on the broad-band spectral slope is  
beta_OX < 0.64 (computed between the z band and 1 keV). Given the hard
X-ray spectral slope beta_X = 0.58 (Pagani et al., GCN 12178), our non  
detection is consistent with the extrapolation of the X-ray spectrum.
Our data do not allow to classify GRB 110719A as dark.