GCN Circular 8045
Subject
GRB 080727B: GROND redshift limit
Date
2008-07-28T21:21:10Z (16 years ago)
From
Jochen Greiner at MPI <jcg@mpe.mpg.de>
T. Kruehler, J. Greiner, F. Schrey, C. Clemens, A. Yoldas (all MPE Garching),
A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on
behalf of the GROND team:
Since telescope pointing constraints did not allow a prompt observation of
GRB 080727B (Swift trigger 318101, Immler et al. 2008, GCN #8022), GROND
(Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope
at La Silla Observatory (Chile), started observations in g'r'i'z'JHK only
on Jul 27, 23:08 UT, nearly 15 hrs after the burst. Under mediocre conditions
a total of 90 min effective exposure in g'r'i'z' and 76 min in JHK was
collected. Correcting for foreground extinction of A_V = 6.15 (Schlegel et al.
1998), we measure the following AB magnitudes/limits:
g'>17.7, r'>19.7, i'>19.9, z'=19.8+-0.1, J=19.45+-0.15, H=19.2+-0.1,
K=19.0+-0.15.
The corresponding SED is well fit by a single power law with slope 0.85,
with no evidence of additional (intrinsic) extinction, and with the
i'-limit being consistent with that power law. Our SED power law has an
extinction-corrected R-H=1.0. The best fit Hyper-z redshift to our data
gives z=5.5-6.5, with a firm upper limit of 6.7. Given the non-constraining
upper limits at i' and bluer, no lower limit can be placed. If the color
R-H = 3.24 mag from the combination of KAIT (Li et al. 2008, GCN #8024)
and REM data (D'Avanzo et al. 2008, GCN #8037) is correct, then the redshift
of GRB 080727B would be larger than 5.8.