{
  "bibcode": "2007GCN..6165....1G",
  "body": "P. Garnavich (Notre Dame), X. Fan, L. Jiang (U Ariz), X. Dai (Ohio State),\nO. Kuhn (LBTO), N. Bouche, P. Buschkamp (MPE), P. Smith,\nP. Milne, J. Bechtold (U Ariz), K. Z. Stanek, J. Prieto (Ohio State),\nR. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State), J. Hill (LBTO/UAz),\nA. Baruffolo, C. DeSantis, E. Diolaiti, A. DiPaola,  J. Farinato,\nA. Fontana,  S. Gallozzi, F. Gasparo, E. Giallongo, A. Grazian,\nF. Pasian, F. Pedichini, R. Ragazzoni, R. Smareglia, R. Speziali,\nV. Testa, E. Vernet (LBC Team/INAF) reprt:\n\n\nThe Large Binocular Telescope (LBT) imaged the position of the GRB 070125\nafterglow (Cenko & Fox, GCN 6028) with the LBC-blue CCD camera\n(http//lbc.mporzio.astro.it) and 8.4-m SX mirror on 2007 February 21.1 (UT).\nTen dithered, 200 second exposures were obtained with the Sloan r filter\nin 1.3\" seeing. After combining the images a faint source is detected at\nthe position of the afterglow. Using SDSS stars in the field and\n1.4\" apertures, we estimate the brightness of the source\nat r=26.3+/-0.3 mag. Since the source may be dominated by the host galaxy,\nthis observation represents a lower-limit on the magnitude of the\nafterglow 26.8 days after the GRB.\n\nThe last reported detection of the GRB afterglow was R=21.07 at 4.04 days\n(Mirabal, Halpern & Thorstensen, GCN 6096) and it was decaying with an\nindex of 1.6. Converting our observation to Johnson-Cousins R-band\n(assuming beta=-1.0 so B-V=0.34) we find that after the light curve break\nthe power-law decay index was equal to, or greater than 2.5.\n\nThis confirms the sharp steepening in the light curve four days after the\nGRB and the jet opening angle reported by Mirabal et al. (GCN 6096). We\nexpect that a supernova at z=1.5 and similar to SN 1998bw (Galama et al.\n1998, Nature, 395, 670) would have r~28 mag at the time of our observation\nso would not contribute significantly to the observed flux.\n\nThe LBT image is available at:\nhttp://www.nd.edu/~pgarnavi/grb070125/LBT_070221.jpg\n\nThe X-ray light curve is generally consistent with the optical. Both show\na break at late time and a steep decay. The x-ray light curve actually has\na strong detection at an age of 10 days suggesting a steeper post-break\ndecay and possibly a wider opening angle than the optical limits.\n\nIt has been suggested that the existence of jet breaks in Swift x-ray\nlight curves are rare (e.g. Burrows & Racusin 2007, astro-ph/0702633),\nbut here is a good example occurring at a time later than expected. This\nsuggests the lack of Swift jet breaks is a selection effect and that many\noccur beyond the Swift sensitivity limit.\n\nThe X-ray/optical light curve comparison is available at:\nhttp://www.astronomy.ohio-state.edu/~xinyu/grb/070125.jpg\n\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 provides access to The\nUniversity of Notre Dame, University of Minnesota and University of\nVirginia.\n\nThis message may be cited.",
  "circularId": 6165,
  "createdOn": 1172789233000,
  "email": "pgarnavi@nd.edu",
  "subject": "GRB 070125, deep late-time optical observation",
  "submitter": "Peter Garnavich at U of Notre Dame  <pgarnavi@nd.edu>",
  "eventId": "GRB 070125"
}