{
  "bibcode": "2006GCN..5821....1M",
  "body": "D. Malesani (SISSA/ISAS & NBI-DARK), S. Covino (INAF/OABr), S. \nPiranomonte (INAF/OAR), L.A. Antonelli (INAF/OAR), G. Chincarini (Univ. \nMilano-Bicocca & INAF-OABr), P. D'Avanzo (INAF/OABr), L. Stella \n(INAF/OAR), and G. Tagliaferri (INAF/OABr), report on behalf of the \nMISTICI collaboration:\n\nWe observed the field of one-year-old GRB 050915B (Falcone et al., GCNs \n3987, 389) with the ESO-VLT UT2 equipped with FORS1. Observations \nstarted on 2005 Sep 16.01065 UT (2.87 hr after the GRB) and consisted in \na series of 24 R-band images lasting 1 minute each. The field was \nobserved again, in the R band, with the ESO-NTT equipped with the SuSI2 \nimager, with mean time 2005 Oct 1.0261 UT (15.13 days after the GRB). \nThe field is very crowded and reddened due to the low Galactic latitude \n(b = -6.6 deg).\n\nInside the XRT error circle (Moretti et al. 2006, A&A, 448, L9) there \nare three sources, but only two are consistent with the \nboresight-corrected position (Butler 2006, astro-ph/0611031 + priv. \ncomm.), which has a 90% error radius of 1.4\". One of them is clearly \nfading between the VLT and NTT exposures, being undetectable in the NTT \nimages. Its coordinates (J2000) are:\n\nalpha = 14:36:26.17\ndelta = -67:24:32.5\n\nIt is remarkable, however, that no fading is seen for this source over \nthe course of the VLT observation (2.87-3.66 hr after the GRB). \nPSF-matched profile photometry revealed that the source was constant \n(<R> = 21.68 +- 0.03) to within ~0.1 mag, with no trend for decline. In \nthe SuSI2 image (15 days after the burst), it has R > 23.4 (3-sigma \nupper limit).\n\nThe other object consistent with the X-ray position has coordinates\n\nalpha = 14:36:26.39\ndelta = -67:24:31.6\n\nand is constant between the FORS1 and SuSI2 exposures at R = 21.2. This \nsource, which is just 1.5\" away from the afterglow, might be consistent \nwith source \"B\" reported by Cobb & Bailyn. (GCN 3994).\n\nThis message can be cited.",
  "circularId": 5821,
  "createdOn": 1163458234000,
  "email": "malesani@astro.ku.dk",
  "subject": "GRB 050915B: optical afterglow",
  "submitter": "Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center  <malesani@astro.ku.dk>",
  "eventId": "GRB 050915B"
}