{
  "bibcode": "2007GCN..6486....1H",
  "body": "J. Hill (LBTO/UAz), P. Garnavich (Notre Dame), O. Kuhn (LBTO/UAz),\nN. Bouche, P. Buschkamp (MPE), X. Fan, (U Ariz), X. Dai, J. Prieto,\nK. Z. Stanek (Ohio State), P. Milne, J. Bechtold (U Ariz),\nR. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State) report:\n\nThe Large Binocular Telescope (LBT) continued to image the position of the\nGRB 070419A afterglow (Stamatikos et al, GCN 6302; Chornock et al. GCN 6304;\nGarnavich et al. GCN 6406) with the LBC-blue CCD camera\n(http//lbc.mporzio.astro.it) and 8.4-m SX mirror. Data were obtained\n2007 May 10.18 (UT) and May 20.22 (UT) which are 20.8 and 30.8\ndays after the burst. Using the calibration assumed by Garnavich et al.\n(GCN 6406), we estimate the brightness of the source at the\nposition of the afterglow using point-spread-function fitting\nphotometry as follows:\n\n UT Date   Age (days)  Exposures   Seeing    r mag  Error\n-----------------------------------------------------------\nApr 23.15    3.7        10x200s     1.2\"     24.75   0.18 (GCN 6406)\nMay 10.18   20.8        25x200s     0.96\"    25.29   0.05\nMay 20.22   30.8        15x200s     0.73\"    25.71   0.13\n\nThe decay between 4 days (LBT observation from GCN 6406) and 20 days\nafter the burst is very slow and corresponds to a power-law index of\n0.3. This could indicate host galaxy contamination, but the\nimages remain unresolved. Extrapolating the decline to 30 days\npost-burst predicts the afterglow should be 30% brighter than\nthe actual observed magnitude. This increased fading rate is\ninconsistent with a host galaxy dominating the flux and\nsuggests light from a GRB progenitor supernova may be powering\nthe late-time light curve.\n\nThe Sloan-r filter has an effective wavelength of 623 nm which\nmaps to a rest-frame UV wavelength near 316 nm at a redshift\nof 0.97 (Cenko et al. GCN 6322). The U-band light curve\nof SN 1998bw peaked 13 to 15 days after GRB 980425 (Galama\net al. 1998, Nature, 395, 670) and possibly earlier at short\nwavelengths.  Some supernovae associated with GRB such as\nSN 2001dh/011121 (Garnavich et al. 2003, ApJ, 582, 924) and\n2006aj/060218 (Modjaz et al. 2006, ApJ, 645, 21) have peaked\nearlier than SN 1998bw, so the decay seen at 16 rest-frame days\nis consistent with a supernova interpretation.\n\nExtrapolating the spectrum of SN 1998bw near maximum (Patat et al.\n2001, ApJ, 555, 900) out to UV wavelengths, we estimate a peak\nbrightness of R=25.4 when viewed at z=0.97, which is also consistent\nwith the LBT observations.\n\nA plot of the light curve can be found at:\nhttp://www.nd.edu/~pgarnavi/grb070419a/grb070419a_lc.jpg\n\nThe LBT is an international collaboration among institutions in the\nUnited States, Italy and Germany. The LBT Corporation partners are:\n*  The University of Arizona on behalf of the Arizona university system\n*  Istituto Nazionale di Astrofisica, Italy\n*  LBT Beteiligungsgesellschaft, Germany, representing the Max Planck\nSociety, the Astrophysical Institute Potsdam, and Heidelberg University\n*  The Ohio State University\n*  The Research Corporation, on behalf of The University of Notre Dame,\nUniversity of Minnesota and University of Virginia\n\n\nThis message may be cited",
  "circularId": 6486,
  "createdOn": 1180982189000,
  "email": "pgarnavi@nd.edu",
  "subject": "GRB 070419A, deep LBT photometry and possible supernova detection",
  "submitter": "Peter Garnavich at U of Notre Dame  <pgarnavi@nd.edu>",
  "eventId": "GRB 070419A"
}