{
  "bibcode": "2000GCN...715....1H",
  "body": "Stephen Holland, Johan Fynbo, Bjarne Thomsen (University of Aarhus),\nMichael Andersen (University of Oulu),\nGunnlaugur Bjornsson (University of Iceland),\nJens Hjorth (University of Copenhagen),\nAndreas Jaunsen (University of Oslo),\nPriya Natarajan (Universities of Cambridge, & Yale), and\nNial Tanvir (University of Hertfordshire)\n\n\tWe have obtained 8224 seconds of STIS images with the F28X50LP\n(long pass) aperture of the host galaxy of GRB 990123.  This data was\ntaken as part of the Survey of the Host Galaxies of Gamma-Ray Bursts\n(Holland et al. GCN 698) approximately 509 days after the burst.\nCombined images are now available at\n\"http://www.ifa.au.dk/~hst/grb_hosts/data/index.html\".\n\n\tUsing the light curve fits of Holland et al. (2000, submitted\nto A&A) we predict that the optical afterglow will have R = 31.6 on 15\nJune 2000, and thus will not be visible in the STIS images.\nTherefore, we used aperture photometry to determine the AB magnitudes,\nin the long pass filter, of the three knots found by Holland & Hjorth\n(1999, A&A, 344, L67).  We find the following colours for the three\nextended knots where CL is the AB magnitude in the STIS clear\naperture, LP is the AB magnitude in the STIS long pass aperture, and\nbeta is the corresponding spectral index, f = k*nu^beta.\n\nKnot   CL     LP         CL-LP       beta\n  1   28.3   28.2    +0.1 +/- 0.4    -0.4\n  2   28.1   27.5    +0.6 +/- 0.4    -2.6\n  3   28.0   27.5    +0.5 +/- 0.4    -2.2\n\n       The GRB occurred on the southeast edge of Knot 1.  This knot is\napproximately one sigma bluer than the other two knots, and two sigma\nbluer than the overall colour of the galaxy (V-R = 0.43 +/- 0.18;\nCastro-Tirado et al., 1999, Science 283, 2069).  This suggests that\nKnot 1 might be undergoing stronger star formation than the rest of\nthe galaxy.",
  "circularId": 715,
  "createdOn": 961348520000,
  "email": "holland@ifa.au.dk",
  "subject": "GRB990123, HST/STIS observations of the host galaxy",
  "submitter": "Stephen Holland at IFA, U of Aarhus  <holland@ifa.au.dk>",
  "eventId": "GRB 990123"
}