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 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 This message may be cited