{
  "bibcode": "2004GCN..2846....1S",
  "body": "M.Sasaki, Y.Aita, T.Aoki, Y.Asaoka, M.Jobashi, N.Manago, K.Noda,\nA.Okumura (ICRR,Univ.Tokyo), S.Ogawa (Toho Univ.), and H.Usami (Tohoku\nUniv.), on behalf of the Ashra collaboration, report:\n\nWe have observed the field covering the WXM error box of GRB041211 with\nthe prototype unit of All-sky Survey High Resolution Air-shower\ndetector (Ashra, http://www.icrr.u-tokyo.ac.jp/~ashra) at the Haleakala\nObservatory Site on Maui contimuously between 10:25 UT (1h7m before\nGRB041211) and 13:13 UT (1h41m after GRB041211) on 2004-12-11. The\nprototype unit utilizes a 11M-pixel CMOS sensor following a 0.4m\ndiameter image intensifier on a modified Baker-Nunn optical system with\n0.6m diameter pupil and 1.2m projected diameter spherical reflector for\nviewing a 50 degree circle region of sky. The achieved resolution is\n2arcmin. We obtained about 2000 images covering the WXM error box of\nGRB041211 every 5s with 4s exposure time respectively. The sensitive\nregion of wavelength is similar with the B-band. We detected no new\nobjects in the WXM error box. As a result of our preliminary analysis of\nfour sets of combined images, the following 3-sigma limiting magnitudes\nare derived:\n\nTime from GRB      ExpTime      Limit Mag.\n(s)                (s)\n----------------------------------------------------------------------\n-1468 ~     0      1175         11.3\n    0 ~   100        80         11.0\n  100 ~  1000       720         11.5\n 1000 ~  4035      2428         11.3\n-----------------------------------------------------------------------\n\nLimiting magnitudes were estimated by comparison with stars in Tycho-2\nCatalog. \n\nFigures of limiting magnitudes vs time and so on may be found at:\nhttp://www.icrr.u-tokyo.ac.jp/~ashra/GRB041211\n\nThis message may be cited.",
  "circularId": 2846,
  "createdOn": 1103095918000,
  "email": "nodak@icrr.u-tokyo.ac.jp",
  "subject": "GRB041211: Ashra Prototype optical observation",
  "submitter": "Koji Noda at ICRR,U of Tokyo  <nodak@icrr.u-tokyo.ac.jp>",
  "eventId": "GRB 041211"
}