[vsnet-grb-info 15940] GRB 141221A: Keck spectroscopy

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17228
SUBJECT: GRB 141221A: Keck spectroscopy
DATE:    14/12/25 13:26:00 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

D. A. Perley, Y. Cao (Caltech), and S. B. Cenko (GSFC) report:

We observed the optical afterglow of GRB 141221A (Sonbas et al., GCN 
17206) with the DEIMOS spectrograph on the Keck II telescope between 
12:48 and 13:10 UT on 2014-12-21.  Two 900-second exposures were 
acquired at high airmass.

We detect significant continuum flux across the entire spectral range 
between 4490-9660 Angstroms.  Inspection of the 1D spectrum shows two 
apparent absorption features at 6854 and 6873 Angstroms which we 
tentatively associate with the Mg II doublet at z=1.452. 
Lower-significance probable absorption lines are also seen at the 
wavelengths of the Fe II 2599, 2585, 2383, 2374, and 2344 lines at 
similar redshift, lending additional credence to this association. 
However, due to a failure of the blue arc calibration lamps, we note 
that our wavelength solution is preliminary and this result should be 
considered tentative.