[AAVSO-HEN] GRB 091117: Gemini-North spectroscopy of DSS galaxy

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
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TITLE:   GCN CIRCULAR
NUMBER:  10176
SUBJECT: GRB 091117: Gemini-North spectroscopy of DSS galaxy
DATE:    09/11/19 11:01:41 GMT
FROM:    Ryan Chornock at UC Berkeley  <chornock at astro.berkeley.edu>

R. Chornock and E. Berger (Harvard) report:

We obtained spectra of the DSS galaxy coincident with the XRT source (GCN 10173)
seen in the Swift observations of the short GRB 091117 (GCN 10171) using GMOS on
Gemini-North.  A pair of 1800s exposures using the R400 grating were taken
starting at 07:27 UT on Nov. 19.  Numerous emission lines are present at
z=0.096.  The slit was aligned through both the nucleus and the point source on
the spiral arm (GCN 10174).  The off-nuclear point source exhibits the
high-equivalent-width nebular emission lines expected of an H II region and is
therefore unlikely to be related to the afterglow of GRB 091117.  In addition,
the nuclear spectrum shows a broad component to the H-alpha line (FWHM ~ 1670
km/sec), indicative of an AGN.  The AGN could also be responsible for the
observed X-ray emission.