{
  "bibcode": "2013GCN.14608....1T",
  "body": "A. Trotter, D. Reichart, J. Haislip, A. LaCluyze, K. McLin, L. Cominsky, \nT. Berger, H. T. Cromartie, R. Egger, A. Foster, N. Frank, K. Ivarsen, \nM. Maples, J. Moore, M. Nysewander, E. Speckhard, and J. A. Crain report:\n\nSkynet continued observing the Swift/XRT localization of GRB 130427A \n(Maselli et al., GCN 14448, Swift trigger #554620) with four 16\" \ntelescopes of the PROMPT array at CTIO, Chile (BVRI bands), and with the \n14\" GLAST Optical Robotic Telescope (GORT) at the Hume Observatory in \nCalifornia (RcIc bands). Our observations span 10 nights, from t=0.65 to \n10.8 days post-trigger. Skynet has taken 2684 160-second exposures on \nthe 4 PROMPT telescopes, and 360 160-second exposures on GORT, or a \ntotal of over 135 hours on source. We performed photometry on each \nexposure, calibrated to two SDSS stars in the field. We stacked \nexposures to improve sensitivity, in groups ranging from 3 exposures on \nnight 1, to 60 exposures on night 10.\n\nWe detect a fading afterglow in BVRI at the position reported by Elenin \net al. (GCN 14450), which is ~50\" south of the initial XRT localization. \nFrom night 2 onwards, the light curves fade with an approximate power \nlaw index alpha=-1 (with no corrections for the known host galaxy flux). \nWe see some evidence for flattening of the I-band light curve beginning \nat t~8 days, and of the R-band curve at t~10 days, though it is not \nclear whether this is due to host galaxy contamination or to an \nintrinsic re-brightening.\n\nA preliminary light curve including all Skynet observations through \nt=10.8 days is at:\nhttp://skynet.unc.edu/grb/grb130427a_10.png\n\nSee Trotter et al. (GCN 14497, GCN 14510) for descriptions and light \ncurves of the first and second nights' observations. Further Skynet \nobservations are ongoing.",
  "circularId": 14608,
  "createdOn": 1368040483000,
  "email": "atrotter@physics.unc.edu",
  "subject": "GRB 130427A: Ten nights of Skynet/PROMPT/GORT observations",
  "submitter": "Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter@physics.unc.edu>",
  "eventId": "GRB 130427A"
}