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GCN Circular 7088

Subject
GRB 071112C: emission lines and refined VLT redshift
Date
2007-11-14T14:18:30Z (17 years ago)
From
Pall Jakobsson at U Hertfordshire <P.Jakobsson@herts.ac.uk>
Pall Jakobsson (U. Hertfordshire), Johan P. U. Fynbo,
Daniele Malesani, Paul M. Vreeswijk, Jens Hjorth, Dong Xu
(DARK, NBI) and Jesper Sollerman (DARK, NBI;  U. Stockholm)
report on behalf of a larger collaboration:

We have flux calibrated the VLT spectrum of the GRB 071112C
optical afterglow (Jakobsson et al., GCN 7076). We clearly
detect four emission lines: [O II] 3727, [Ne III] 3869 and
[O III] 4960,5008. Using the relations by Kennicutt (1998,
ARA&A, 36, 189), the flux of the [O II] line corresponds to
a star formation rate (SFR) of approximately 0.5 M_Sun/year.
This value has not been corrected for host extinction or slit
loss, and is therefore a strict lower limit to the actual SFR.

The flux ratio of [Ne III] and [O II] is typical of GRB
host galaxies, with log([Ne III]/[O II]) ~ -0.5 (see Fig 4
in Wiersema et al., arXiv:0706.1345v1). The presence of
such strong emission lines in the OA spectrum indicates
a fairly bright host, approximately 24 < R < 25 (see also
Nugent & Bloom, GCN 7069).

Finally, using new wavelength calibration files we report
a more accurate absorption redshift (based on 8 lines):
z = 0.8230 +/- 0.0003.
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