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GCN Circular 6346

Subject
GRB 070411, deep LBT photometry
Date
2007-04-23T18:37:00Z (17 years ago)
From
Peter Garnavich at U of Notre Dame <pgarnavi@nd.edu>
J. Prieto (Ohio State), P. Garnavich (Notre Dame), J. Hill (LBTO/UAz),
X. Fan, J. Harris (U Ariz), X. Dai,  P. Martini, K. Z. Stanek (Ohio State),
R. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State),
S. Herbert-Fort (UAz) report:

The Large Binocular Telescope (LBT) imaged the position of the GRB 070411
afterglow (Moretti et al, GCN 6267; Kann et al. GCN 6268) with the
LBC-blue CCD camera (http//lbc.mporzio.astro.it) and 8.4-m SX mirror on
2007 April 15.145 (UT). Ten dithered, 200 second exposures were obtained
with the Sloan-r filter in 0.7" seeing. A point source within 0.1" of
the Swift/UVOT position is clearly detected in each image.

In the combined image we find the afterglow to be 5.431 magnitudes
fainter than the unsaturated star at RA=7:09:23.35 DEC=1:04:09.98
and listed in the USNO-B catalog at R2=18.52 mag. An out-of-focus
image shows that this star is 0.916 mag fainter than the star
used by Berger, Modjaz & Garg et al. (GCN 6278) implying the two
calibrations are consistent. So we find the afterglow brightness to
be r=23.95+/-0.05 mag. 3.30 days after the burst.

Image subtraction of individual frames shows no significant
variability (<0.10 mag) on time-scale between 4 minutes and
an 40 minutes.

The fading between the Berger et al. observation and the LBT
image is consistent with a power-law decay index of 1.0, but
note the possibility of a break reported by Malesani et al.
(GCN 6343).

The LBT image can be found at:
http://www.nd.edu/~pgarnavi/grb070411/grb070411_LBT.jpg

The LBT is an international collaboration among institutions in the
United States, Italy and Germany. The LBT Corporation partners are:
*  The University of Arizona on behalf of the Arizona university system
*  Istituto Nazionale di Astrofisica, Italy
*  LBT Beteiligungsgesellschaft, Germany, representing the Max Planck
Society, the Astrophysical Institute Potsdam, and Heidelberg University
*  The Ohio State University
*  The Research Corporation, on behalf of The University of Notre Dame,
University of Minnesota and University of Virginia


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