TITLE:   GCN CIRCULAR
NUMBER:  11116
SUBJECT: GRB 100816A: Gemini-N spectroscopy
DATE:    10/08/16 22:32:01 GMT
FROM:    Nial Tanvir at U.Leicester  <nrt3@star.le.ac.uk>

N. R. Tanvir, K. Wiersema (U. Leicester), J. P. U. Fynbo (DARK)
A. J. Levan (U. Warwick) & D. Perley (UC Berkeley) report on
behalf of a larger collaboration:

We obtained medium resolution, long-slit spectroscopy of GRB 100816A
(Oates et al. GCN 11102) with Gemini-N/GMOS following the imaging
reported in Tanvir et al. (GCN 11109).  The afterglow was centred in the
slit, and the nearby candidate host galaxy (see also Im et al. GCN 11108)
was also partially in the slit.  The spectrum covers a wavelength range
from about 4000A to 6700A.

Our analysis of the galaxy trace provides a tentative detection of the OIII
(5007A/4959A) doublet and Hbeta (4863A) at a redshift of z~0.245, although
we caution that all these features are low S/N.  No other lines are clearly seen
even though OII 3727A would be within the spectral range (but we note the
galaxy continuum is not apparent below about 4700A, in part due to declining
detector quantum efficiency in the blue).  Neither have we identified so far
any significant features in the afterglow spectrum.

This is a similar redshift to a number of Swift short-duration burst hosts,
but further observations are encouraged to confirm the result.

We thank the Gemini observers, particularly Alexander
Fritz, for their assistance in obtaining these observations.