TITLE:   GCN CIRCULAR
NUMBER:  6566
SUBJECT: Observations of GRB070612A at Calar Alto
DATE:    07/06/22 08:24:34 GMT
FROM:    Elena Pian at ITESRE-CNR,Bologna  <pian@iasfbo.inaf.it>

S. Taubenberger (MPA), P. Mazzali (MPA & INAF - OATs), W. Hillebrandt
(MPA), J. Alves (CAHA), U. Thiele (CAHA), S. Pedraz (CAHA),
A. Guijarro (CAHA), M. Alises (CAHA) and E. Pian (INAF - OATs) report:

We observed the afterglow (Updike et al., GCN 6515; Cenko et al., GCN
6525) of GRB 070612A (Grupe et al., GCN 6509) with the Calar Alto 2.2m
Telescope equipped with CAFOS on 2007 Jun 13.86, 14.86 and 15.87 UT.
In all three nights images were taken in the BVRI bands, at high
airmass (~ 3), and under variable seeing and transparency conditions
(2.0" - 5.6" fwhm, clear - thin clouds).

The afterglow was detected on Jun 13.86 at V = 20.40+-0.23 and
R = 19.79+-0.10 (calibrated against the Landolt field PG1633 under
photometric conditions; only measurement errors reported). In R up
to 25% of contamination from the underlying galaxy can be expected
(D'Avanzo et al., GCN 6558).
From the rest of the images only limits could be derived, in
particular V > 20.0 / 19.8 and R > 18.9 / 19.6 on Jun 14.86 / 15.87,
respectively.

Our Jun 13.86 R-band magnitude is consistent with the afterglow's
steep power-law decay suggested by observations with other telescopes
(cf. Malesani et al., GCN 6555, and references therein).