[vsnet-grb-info 4617] GRB 070412, deep LBT imaging

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6374
SUBJECT: GRB 070412, deep LBT imaging
DATE:    07/05/04 23:39:44 GMT
FROM:    Peter Garnavich at U of Notre Dame  <pgarnavi at nd.edu>

J. Prieto (Ohio State), P. Garnavich (Notre Dame), J. Hill (LBTO/UAz),
X. Fan, J. Harris, J. Bechtold (U Ariz), X. Dai,  P. Martini,
K. Z. Stanek (Ohio State), R. M. Wagner (LBTO/OSU),
J. Rhoads (Ariz State), E. Pian (INAF) report:

The Large Binocular Telescope (LBT) imaged the position of the GRB 070412
afterglow (Romano et al, GCN 6273; Romano et al. GCN 6282) with the
LBC-blue CCD camera (http//lbc.mporzio.astro.it) and 8.4-m SX mirror on
2007 April 12.18 (UT) and again on April 20.31 (UT). These are 2.8 hours
and 8.2 days after the burst respectively.  On the first visit,
ten dithered, 200 second exposures were obtained
with the Sloan-r filter in 1.7" seeing while on the second visit, five
exposures were obtained in 1.0" seeing.

Image matching, PSF correction and subtraction of the two images shows
no variable sources within 30" of the corrected XRT position
(Romano et al. GCN 6282). We place a 3-sigma upper-limit on any
optical afterglow at R>25.2 around 2.8 hours post-burst.

No new source is detected in our second epoch image
(also see Rol et al. GCN 6353) and we place a similar detection
upper-limit as our April 12 image. If the burst is associated
with the bright elliptical galaxy near the XRT position (Ofek &
Berger GCN 6275), then we find any supernova or other GRB progenitor
would have an absolute magnitude fainter than -11 mag eight days
after the burst.

A comparison of the two images after unsharp masking to
reduce the elliptical galaxy light variations can be found at:
http://www.nd.edu/~pgarnavi/grb070412/grb070412_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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