{
  "bibcode": "2000GCN...605....1C",
  "body": "GRB 000301C:  A Precise Redshift Determination\n\nS. M. Castro, A. Diercks, S. G. Djorgovski, S. R. Kulkarni, T. J. Galama,\nJ. S. Bloom, F. A. Harrison (Caltech), and D. A. Frail (NRAO), report on\nbehalf of the Caltech-CARA-NRAO GRB collaboration:\n\nModerately high resolution spectra (FWHM ~ 1 Ang) of the optical transient\n(OT) associted with GRB 000301C (Fynbo et al., GCN 570) were obtained on UT \n2000 March 04, by W. L. W. Sargent, A. Boksenberg, and M. Rauch, using the \nESI Echelle spectrograph on the Keck-II 10-m telescope on Mauna Kea, Hawaii.\nTwo exposures of 1800 sec each were obtained, over an effective wavelength \nrange from ~3800 Ang, to ~10800 Ang.  The OT continuum is well detected.\n\nNo strong absorption systems were found in the spectrum.  However, a number\nof possible weak lines are present.  We identify a subset of them with the\nfollowing lines: Fe II 2260, 2344, 2374, 2382, 2586, and 2600, and Mg II 2796 \nand 2803; and a less reliable set of O I 1302, C II 1334, Si IV 1393, \nSi II 1526, C IV 1550, Fe II 1608, Al II 1670.  The weighted mean absorption \nredshift of this 16-line system is z = 2.0335 +- 0.0003.\n\nThis is fully consistent with the redshift estimate from the HST spectroscopy, \nz = 1.95 +- 0.1 (Smette et al., GCN 603), based on the ostensible Lyman break.\nWe thus consider our redshift determination to be secure, and interpret it as \nthe redshift of the GRB host galaxy, with no intervening foreground systems.\n\nThe restframe equivalent widths of the absorption lines are in the range of\ninterstellar medium in the host galaxy.\n\nAssuming z = 2.0335, and a simple Friedmann cosmology with H_0 = 65 km/s/Mpc, \nOmega_0 = 0.2, and Lambda_0 = 0, the luminosity distance is D_L = 5.11e28 cm, \nthe distance modulus is (m-M) = 49.1 mag, and the relativistic (1+z)**4 \nsurface brightness dimming factor is 4.8 mag.  This may account for the lack \nof a detection of the host galaxy in the HST images (Fruchter et al., GCN 602).\n\nThis note can be cited.",
  "circularId": 605,
  "createdOn": 952681277000,
  "email": "george@oracle.caltech.edu",
  "subject": "GRB 000301C:  A Precise Redshift Determination",
  "submitter": "George Djorgovski at Caltech/Palomar  <george@oracle.caltech.edu>",
  "eventId": "GRB 000301C"
}