{
  "bibcode": "1999GCN...189....1D",
  "body": "GRB 980613:  Spectroscopy of the host galaxy\n\nS. G. Djorgovski, S. R. Kulkarni, J. S. Bloom (Caltech), D. Frail (NRAO),\nF. Chaffee and R. Goodrich (CARA/WMKO), on behalf of the Caltech-NRAO-CARA\nGRB collaboration, report:\n\nWe obtained spectra of the host galaxy of GRB 980613 (see GCN Circ. 114 and\n117) at the Keck-I telescope, on 17 Dec 1998 UT.  The reduced spectrum shows\na single strong emission line at 7814 Angstroms, which we interpret as the \n[O II] 3727 line at z = 1.0964 +- 0.0003, a probable 4000-A break just to\nthe red of it, and a very blue, featureless continuum blueward of the line.  \nOther plausible spectroscopic identifications of this line (e.g., Ly alpha,\nBalmer lines, [O III], etc.) would predict appearance of other strong \nemission lines or continuum breaks, which are clearly not seen in our data.  \nWe thus consider our redshift interpretation to be secure.  The spectrum is \ntypical of star forming galaxies at comparable redshifts.\n\nBoth the continuum and the line emission are clearly extended.  The images\nof the galaxy (which is coincident with the OT discovered by Hjorth et al.,\n1998, GCN Circ. 109), show a patchy or asymmetric morphology, suggestive of\nan interacting system.\n\nIn what follows, we assume the Galactic foreground extinction A(V) = 0.27 mag\nfrom Schlegel et al. (1998, ApJ 500, 525), and a simple Friedman model \ncosmology with H_0 = 65 km/s/Mpc, Omega_0 = 0.2, and Lambda_0 = 0.  At this \nredshift, the luminosity distance is 2.256e28 cm.\n\nThe extinction-corrected spectroscopic magnitudes of the host are: B = 24.4, \nV = 24.1, and R = 23.85 mag, with the zero-point uncertain by at least 0.2 \nmag.  This is in an excellent agreement with the R-band magnitude in a \ncomparable aperture, derived from direct images obtained at the Keck-II \ntelescope on 28 Nov 1998 UT, and consistent with our earlier estimate (GCN \nCirc. 117).  \n\nFrom the BATSE fluence of 1.71e-6 erg/cm2 (Woods et al. 1998, GCN Circ. 112) \nthe implied isotropic gamma-ray energy of the burst was 5.2e51 erg.\n\nThe extinction-corrected [O II] line flux is 4.4e-17 erg/cm2/s, giving the\nline luminosity of 2.8e41 erg/s.  The implied unobscured SFR, using the\nconversion from Kennicutt (1998, ARAA 36) is 3.9 Msun/yr.  The observed, \nextinction-corrected monochromatic flux at the rest wavelength of 2800 A is \n0.9 microJy, corresponding to the restframe power of 2.76e28 erg/s/Hz.  The \nimplied unobscured SFR, using the estimator from Madau et al. (1998, ApJ 498,\n106) is 3.5 Msun/yr, in an excellent agreement with the [O II] line estimate, \nalthough both may be uncertain by as much as 20-50%.  This agreement suggests \nthat the host galaxy as a whole is not heavily obscured.  We note that this \nSFR is rather moderate, despite the very blue color of the host galaxy.\n\nFurther observations and analysis are in progress.  This report may be cited.",
  "circularId": 189,
  "createdOn": 915401904000,
  "email": "george@oracle.caltech.edu",
  "subject": "GRB 980613:  Spectroscopy of the host galaxy",
  "submitter": "George Djorgovski at Caltech/Palomar  <george@oracle.caltech.edu>",
  "eventId": "GRB 980613"
}