{
  "bibcode": "2007GCN..6219....1D",
  "body": "X. Dai (Ohio State), P. Garnavich (Notre Dame), R. Pogge (Ohio State),\nJ. Hill (LBTO/UAz), X. Fan (U Ariz), J. Prieto, K. Z. Stanek (Ohio State),\nR. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State), E. Egami, J. Bechtold,\nS. Herbert-Fort (UAz) report:\n\nThe Large Binocular Telescope (LBT) imaged the position of the GRB 070311\nafterglow (Mereghetti et al, GCN 6189; Covino et al. GCN 6190) with the\nLBC-blue CCD camera (http//lbc.mporzio.astro.it) and 8.4-m SX mirror on\n2007 March 17.14 (UT). Ten dithered, 200 second exposures were obtained\nwith the Sloan-r filter in 0.65\" seeing. After combining the images, the\nafterglow is clearly detected. No obvious GRB host galaxy is visible. The\nfield is filled with clouds of faint emission due to the low Galactic\nlatitude of the region.\n\nThe comparison star used by Halpern & Armstrong (GCN 6195; star \"A\"\nwith USNO-B1.0 R2=16.67 mag) is heavily saturated in the LBT data,\nso we obtained short exposure images of the field with LBC-blue to\ncalibrate a fainter star (\"B\") at 5:50:10.341, 03:23:02.58 (J2000).\nThe difference in brightness between star A and B is 2.62+/-0.01 mag.\nin Sloan-r and this is confirmed with R-band images taken at MDM\n(E. Armstrong, private communication). From point-spread-function fitting\nphotometry, the afterglow is 5.44+/-0.06 mag fainter than comparison\nstar B or at a brightness of R2=16.67+2.62+5.44= 24.73+/-0.06 mag.\n\nThe brightness of the afterglow 6.0 days after the GRB suggests that it\nhas continued a very steep decline after its optical flare\n(Halpern & Armstrong GCN 6203). The afterglow has not resumed the shallow\ndecay it followed on the first day after the GRB. A late flare\noccurring just before the break resembles GRB 000301c (Garnavich, Loeb &\nStanek 2000, ApJ, 544, 11; Rhoads & Fruchter 2001, ApJ 546, 117)\nand GRB 060526 (Dai et al. 2006, astro-ph/0609269).\n\nThe light curve of 070311 is available at:\nhttp://www.astronomy.ohio-state.edu/~xinyu/grb/070311.jpg\nand uses photometry from GCNs 6198 (Wren et al. 2007), 6195\n(Halpern & Armstrong 2007), 6199 (Halpern & Armstrong 2007), 6203 (Halpern\n& Armstrong 2007), 6204 (Greco et al. 2007), 6206 (Kann et al. 2007), 6208\n(Halpern & Armstrong 2007).\n\nThe LBT image is available at:\nhttp://www.nd.edu/~pgarnavi/grb070311/LBT_grb070311.jpg\nand a wide-field view is at:\nhttp://www.nd.edu/~pgarnavi/grb070311/LBT_grb070311_clr.jpg\n\nWe thank Eve Armstrong for providing MDM images to calibrate\nfainter comparison stars.\n\nThe LBT is an international collaboration between institutions in the\nU.S.A., Italy and Germany. LBT Corporation partners are The Universities\nof Arizona; Italy's Istituto Nazionale di Astrofisica; Germany's LBT\nBeteiligungsgesellschaft representing the Max-Planck Society, the\nAstrophysical Institute Potsdam, and Heidelberg University; The Ohio State\nUniversity and The Research Corporation, which represents The\nUniversity of Notre Dame, University of Minnesota and University of\nVirginia.\n\nThis message may be cited.",
  "circularId": 6219,
  "createdOn": 1174417221000,
  "email": "pgarnavi@nd.edu",
  "subject": "GRB 070311, deep optical photometry",
  "submitter": "Peter Garnavich at U of Notre Dame  <pgarnavi@nd.edu>",
  "eventId": "GRB 070311"
}