TITLE:   GCN CIRCULAR
NUMBER:  15624
SUBJECT: GRB 131227A: Gemini-North Redshift
DATE:    13/12/27 18:44:22 GMT
FROM:    Antonino Cucchiara at NASA/GSFC  <antonino.cucchiara@nasa.gov>

A. Cucchiara (ORAU/NASA-GSFC) and S.B. Cenko (NASA-GSFC)
report on behalf of a larger collaboration:

"On December 27.42 UT (~ 5.1 hr after the Swift trigger) we
began observing the afterglow of GRB 131227A (Oates et al.
GCN 15616, Zheng et al. GCN 15617) with the GMOS spectrograph
mounted on the Gemini-North telescope.

Under poor seeing conditions the afterglow was marginally
detected in our i’-band acquisition image.
Nevertheless, we performed a spectroscopic sequence of 2x900s
spectra with GMOS and the R400 grating, covering the 4400-8600A
wavelength range.

Clear evidence of continuum flux is detected beyond 7600A, while
no flux is present in either spectra nor in a coadded spectrum
blueward of this wavelength.
No other obvious emission or absorption features are present in
the spectrum, though the signal-to-noise ratio is not extremely
high.

If this break is due to Lyman-alpha, the implied GRB redshift
would be z~5.3.
We caution, however, that this line of sight is subject to high
galactic extinction (A_V= 2.8).

We thank the Gemini staff for performing these observations under
challenging conditions, in particular Marie Lemoine-Busserolle."