{
  "bibcode": "2005GCN..3064....1D",
  "body": "P. D'Avanzo, D. Fugazza, S. Covino, G. Tagliaferri, D. Malesani, L.A. \nAntonelli, S. Campana, G. Chincarini, M. Della Valle, F. Fiore, L. \nStella, F.M. Zerbi, on behalf of the MISTICI collaboration report :\n\n\nOptical and near-infrared monitoring of the field of GRB050219b \n(Cummings et al., GCN 3044) was performed at the ESO-VLT, with the FORS2 \nand ISAAC instruments respectively. Observations were carried out under \na clear sky, starting 0.18 days after the GRB. The log is reported below.\n\nMean date (UT) t-t0 (days)  filter  seeing (\")\n----------------------------------------------\nFeb 20.062     0.18         R       1.0\nFeb 21.062     1.18         R       1.0\nFeb 21.088     1.21         Ks      0.5\nFeb 24.024     4.14         Ks      0.5\n----------------------------------------------\nt0 = Feb 19.879 UT (GRB trigger).\n\nIn the refined XRT position and error circle (Burrows et al., GCNs 3043; \nRacusin et al., GCN 3049) we detect three sources in the Ks images:\n\n\n1. RA: 05:25:15.99  Dec: -57:45:28.7\n2. RA: 05:25:16.13  Dec: -57:45:30.5\n3. RA: 05:25:15.59  Dec: -57:45:25.4\n\nSource #2 and #3 do not exhibit significant variations (the latter being \nalso present in the 2MASS catalogue).\nSource #1 is pointlike and is fading by 1.09 +- 0.19 mag in the Ks band \nbetween 1.21 and 4.15 days after the burst. We therefore identify this \nis the NIR afterglow of GRB050219b. The flux decay index (F = \nK*t^-delta) is delta = 0.81 +- 0.14.\n\nThe candidate afterglow has a magnitude Ks = 21.47 +- 0.18 on Feb 24.02, \nbased upon field calibration with standard stars. We caution that we get \nKs = 16.45 +- 0.04 for the 2MASS star quoted above (source #3), which \nhas a tabulated magnitude K=15.345 in the 2MASS catalog.\n\nIn the R band, no source is detected at the position of the candidate \nafterglow, down to a limiting magnitude R~23, based on calibration \nagainst the USNO catalog.\n\nFurther observations are planned at the VLT.\n\nThis message can be cited.",
  "circularId": 3064,
  "createdOn": 1109284048000,
  "email": "davanzo@merate.mi.astro.it",
  "subject": "GRB 050219b: candidate NIR afterglow",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <davanzo@merate.mi.astro.it>",
  "eventId": "GRB 050219B"
}