GCN Circular 965
Subject
Redshift of the Optical Transient of GRB010222
Event
Date
2001-02-22T18:45:01Z (25 years ago)
From
Krzysztof Z. Stanek at CfA <kstanek@cfa.harvard.edu>
P. M. Garnavich (Notre Dame), M. A. Pahre, S. Jha, M. Calkins,
K. Z. Stanek, J. McDowell and R. Kilgard (Harvard-Smithsonian Center
for Astrophysics) report:
A spectrum of the optical transient (GCN 961, 962, and 963) associated
with GRB010222 (GCN 959, 960) was obtained with the F. L. Whipple
Observatory 1.5m Tillinghast telescope (+ FAST spectrograph) on 2001
February 22 beginning at UT 12:18, 4.92 hours after the burst. Two
1200s spectra were obtained with a 3 arcsec wide slit and 300 l/mm
grating, yielding 6 Angstrom resolution over the range from 3620 to
7560 A. The OT was approximately R=18.4 mag around the time of the
spectroscopy (GCN 963).
This spectrum shows a blue continuum and many narrow absorption lines
with the following preliminary identifications:
Observed Line Rest Redshift
Wavelength ID Wavelength
(angstrom) (angstrom)
6405.9 FeII 2585.4 1.477
6438.7 FeII(UV1) 2598.4,2599.4 1.477
6924.2 MgII 2796 1.476
6941.6 MgII 2803 1.476
The FeII (2585,2599) and MgII (2796,2803) doublet absorption features
are strong, absorbing approximately 50 and 80% of the continuum at
those wavelengths. These absorption lines constrain the redshift of
the optical transient associated with GRB010222 to be at >= 1.476. If
the lines come from a host galaxy associated with the GRB, then the
redshift is 1.476.
Additional unidentified absorption lines appear in the spectrum, data
analysis is continuing.
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