TITLE: GCN CIRCULAR NUMBER: 6351 SUBJECT: GRB 070411, further deep LBT photometry DATE: 07/04/26 21:50:07 GMT FROM: Peter Garnavich at U of Notre Dame P. Garnavich (Notre Dame), J. Prieto (Ohio State), J. Hill (LBTO/UAz), X. Fan (U Ariz), X. Dai, K. Z. Stanek (Ohio State), R. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State), J. Bechtold (UAz), R. Gredel (MPIA), A. Grazian (Rome) 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 22.14 (UT). Ten dithered, 200 second exposures were obtained with the Sloan-r filter in poor seeing and a bright sky background. No afterglow is detected and we estimate a 3-sigma upper-limit of r>25.3 mag. Extrapolating the power-law decay found by Prieto et al. (GCN 6346) to 10.3 days after the burst, we expected an afterglow brightness of r=25.1+/-0.2 mag. Our non-detection is therefore marginal confirmation of a break in the light curve as reported by Malesani et al. (GCN 6343). The Keck observation (Perley et al GCN 6350) on day 4.4 also supports an increase in the decay rate. 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 This message may be cited