{
  "bibcode": "2009GCN.10294....1H",
  "body": "J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, R. Egger, A. Foster, J. \nMoore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. \nNysewander report:\n\nSkynet observed the Swift/BAT localization of GRB 091221 (Palmer et al., \nGCN 10283) with four of the 16\" PROMPT telescopes at CTIO beginning 4.3 \nhours after the trigger in BVRI.\n\nWe detect the afterglow (Palmer et al., GCN 10283; Zheng et al., GCN \n10284).  Stacking only images that increase the limiting magnitude yields:\n\nmean                                                       1-sig. 1-sig.\ntime                                                       sys.   stat.\nsince                                          cal.        cal.   cal.\ntrig. tel.     exp.     fil. magnitude         stars       unc.   unc.\n(h)            (# x s)                                     (mag)  (mag)\n\n4.9   PROMPT-5 44 x 80  I    > 21.1 (3 sigma)  143 USNO B1 0.338  0.000\n            + 1 x 40\n4.9   PROMPT-4 42 x 80  R    21.49 +0.27 -0.22 139 USNO B1 0.362  0.000\n4.9   PROMPT-3 41 x 80  B    > 21.5 (3 sigma)  82 USNO B1  0.154  0.000\n4.9   PROMPT-1 41 x 80  V    21.41 +0.42 -0.31 27 NOMAD    0.193  0.000\n7.3   PROMPT-3 136 x 80 B    > 22.1 (3 sigma)  79 USNO B1  0.153  0.000\n7.3   PROMPT-5 134 x 80 I    > 21.8 (3 sigma)  120 USNO B1 0.337  0.000\n7.3   PROMPT-4 139 x 80 R    22.44 +0.38 -0.28 112 USNO B1 0.392  0.000\n7.4   PROMPT-1 145 x 80 V    > 22.0 (3 sigma)  28 NOMAD    0.112  0.000",
  "circularId": 10294,
  "createdOn": 1261606260000,
  "email": "haislip@physics.unc.edu",
  "subject": "GRB 091221: Skynet/PROMPT Detections",
  "submitter": "Josh Haislip at U.North Carolina  <haislip@physics.unc.edu>",
  "eventId": "GRB 091221"
}