[vsnet-grb-info 5207] GRB 071010B correction to GCN 6892 optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6903
SUBJECT: GRB 071010B correction to GCN 6892 optical observations
DATE:    07/10/12 17:58:30 GMT
FROM:    AAVSO GRB Network at AAVSO  <matthewt at aavso.org>

M. Templeton (AAVSO), D.A. Kann (TLS Tautenburg), A. Oksanen (Hankasalmi
Observatory, Hankasalmi, Finland) and A. Henden (AAVSO) report the
following correction to the decay rate for unfiltered optical photometry
of GRB 071010B given in Oksanen et al. (GCN #6892):

Due to a software error, the decay rate originally given in GCN #6892
(-1.14) is incorrect.  The correct power-law for the optical decay is
-0.482 +/- 0.064.  This is consistent with an independent measure of
-0.464 +/- 0.016 performed by D.A. Kann using additional data from the
TLS Tautenburg 2-meter telescope.

We also note the original data were obtained by A. Oksanen with the
Hankasalmi Observatory 0.4-meter, rather than at Nyrola Observatory,
and have corrected his affiliation accordingly.

The corrected version of GCN #6892 follows:

A. Oksanen (Hankasalmi Observatory, Hankasalmi, Finland), M. Templeton
(AAVSO) and A. Henden (AAVSO) report further details on optical
observations of GRB071010B (GCN #6871, Markwardt et al.; GCN #6873
Oksanen; GCN #6878 Kennea et al.; GCN #6884 Kann et al.):

Further to the initial report given in GCN #6873, Arto Oksanen reports
unfiltered photometry of the GRB 071010B afterglow spanning 2007 Oct 10
21:02:33 UT to 2007 Oct 11 03:24:27 UT (T0 + 17 minutes to T0 + 6 hours
39 minutes post-burst).  The data are reasonably well fit by a single
power law with index -0.482 +/- 0.064.  The measured unfiltered
magnitudes are approximately 0.3 magnitudes fainter than the Rc
magnitudes reported by Kann et al (GCN #6884) taken at the same time,
which is consistent with differences in zero-point calibration and
bandpass.  It should be noted that this field is covered by the SDSS,
and that the AAVSO will obtain a BVRI calibration with the Sonoita
Research Observatory, weather permitting.

Oksanen also reports additional preliminary Ic and V-band magnitudes:

2007 Oct 10, 21:32 UT   Ic = 17.64 +/- 0.05
2007 Oct 10, 21:52 UT   V  = 18.30 +/- 0.05

Both magnitudes are calibrated relative to the transformed SDSS ugriz
magnitudes for the object at RA 10:01:54.62, Dec +45:40:29.0 (J2000).

Further details of these observations, light curves, and analyses are in
preparation for publication in the electronic Journal of the AAVSO.

Full details of the observations are available at the following URL:
ftp://ftp.aavso.org/grb/ArtoOksanen_GRB071010B_2454384.45422_.txt

The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.