TITLE: GCN CIRCULAR NUMBER: 6346 SUBJECT: GRB 070411, deep LBT photometry DATE: 07/04/23 18:37:00 GMT FROM: Peter Garnavich at U of Notre Dame 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 This message may be cited