TITLE:   GCN CIRCULAR
NUMBER:  23959
SUBJECT: GRB190311A: OAO observations
DATE:    19/03/12 15:13:24 GMT
FROM:    Alberto Fernandez-Soto at IFCA (CSIC/UC,Santander)  <fsoto@ifca.unican.es>

V. Peris (OAUV-Valencia) and A. Fernandez-Soto (IFCA-Santander) report:

We have observed the field of GRB190311A (Troja et al., GCN 23946) with
the OAUV-0.5m telescope at the Observatorio de Aras de los Olmos (OAO)
in Aras de los Olmos (Valencia, Spain). Observations began after local
midnight on March 12 (UT 01:03, (t-t0) ~ 10.7 hours ~ 0.444 days).

We took 23 ten-minute exposures using a Johnson R filter, out of which 
15 have been selected based on best quality. The afterglow reported in 
GCN23946 and confirmed by Pozanenko et al. (GCN 23947) is
clearly detected in our combined image, with the following magnitude 
and timestamp:

UT(middle)    (t-t0)  Exposure    R    Error
----------   -------  --------  -----  -----
  03:41:46   0.4443d  15x10min  21.45   0.15

The image has been calibrated using 100 stars in the field, the
APASS catalog (r and i mags) and the conversion equations in Lupton 
(2005) as given in the SDSS pages. The calibration zeropoint error is
not significant in comparison with the flux uncertainty (Delta(ZP)~0.03).

Our results confirm the fading of the afterglow and extend the time 
baseline from previous observations. We cannot at the present stage
measure the fading rate within our observations.

OAO is operated by the Observatori Astronomic de la Universitat de
Valencia (OAUV).