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GCN Circular 9536

Subject
GRB090618: OAA-OAUV Optical observations
Date
2009-06-19T23:05:06Z (16 years ago)
From
Alberto Fernandez-Soto at IFCA (CSIC/UC,Santander) <fsoto@ifca.unican.es>
A. Fernandez-Soto (IFCA-Santander), V. Peris (OAUV-Valencia), and
J. Alonso-Lorite (OAUV-Valencia) report:

We have observed the field of GRB090618 (Schady et al., GCN 9512) with
the OAUV-0.4m telescope at the Observatorio Astronomico de Aras (OAA)
in Aras de Alpuente (Valencia, Spain). Observations began after local
sunset on June 18 (UT 19:32, (t-t0)~11.1 hours).

We took 23 four-minute exposures using a Johnson R filter. The
individual frames have been combined in five groups. The afterglow
reported in GCN9512 and confirmed by Cenko et al. (GCN 9513) is
clearly detected in all five images, with magnitudes and times:

UT(middle)   Exposure    R    Error
----------   --------  -----  -----
  21:30:03     5x4min   18.67   0.14
  21:50:51     5x4min   18.57   0.09
  22:42:14     4x4min   18.62   0.09
  23:21:44     5x4min   18.92   0.13
  23:45:19     2x4min   18.96   0.13

All magnitudes have been calibrated using stars in the field and the
USNO-B1 catalog (R1 mags).

Our results agree with those reported by Cano et al. (GCN 9531), and
support the presence of a break in the R-band decay, which happened at
(t-t0) ~ 14.6 hours.

A lightcurve combining our data and previous GCNs is posted at
http://ayalga.uv.es/~fsoto/grb090618

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