GCN Circular 1108
Subject
GRB010921: Spectroscopy of the Host Galaxy
Date
2001-10-19T16:50:57Z (23 years ago)
From
George Djorgovski at Caltech/Palomar <george@astro.caltech.edu>
GRB010921: Spectroscopy of the Host Galaxy
S.G. Djorgovski, A. Mahabal, P.A. Price, J.S. Bloom, D.E. Reichart, E. Berger,
D.W. Fox, S.R. Kulkarni, D.A. Frail, R. Sari, T. Galama, F. Harrison, and
S. Yost report on behalf of the Caltech-NRAO-CARA GRB collaboration:
"We obtained a spectrum of the host galaxy of the proposed afterglow of
GRB010921 (Price et al., GCN 1107) using the Double Spectrograph at the
Palomar 200-inch telescope, on 17 October 2001 UT. Preliminary reductions
of the spectrum indicate a redshift of z = 0.450 +- 0.005, on the basis of
4 emission lines, [O II] 3727, H-beta, [O III] 5007, and H-alpha. The
spectrum is typical for an actively star-forming galaxy, with no sign of
an active nucleus. Further analysis is in progress.
Assuming an H_0 = 65 km/s/Mpc, Omega_m = 0.3, Omega_lambda = 0.7 cosmology,
we derive the luminosity distance of 8.30e+27 cm. Using the fluence of
1.0e-6 erg/cm2 (Ricker et al. GCN #1096), the total energy release in the
restframe range 12-123 keV (redshifted bandpass of the HETE band at 8-85 keV)
is 6.0e+50 erg. Though no spectral information was reported, we estimate that
the isotropic equivalent energy release in the 20-2000 keV range (see Bloom
et al. 2001, AJ, 121, 2879) was E_iso(gamma) = (2.65 +- 1.45)e+51 erg.
To conform with the constant energy of E_gamma = 5e+50 erg (Frail et al.
2001, ApJ Letters, accepted; astro-ph/0102282), the time of the jet break
would be t_jet ~ 130 days after the GRB. However, a possible supernova
associated with this event may be detectable now."
This note can be cited.