TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5376
SUBJECT: GRB 060218 / SN 2006aj Nebular Spectrum
DATE:    06/08/01 03:39:43 GMT
FROM:    Ryan Foley at UC Berkeley  <rfoley@astro.berkeley.edu>

Spectroscopic Detection of the Late Nebular Phase of
SN 2006aj (associated with GRB 060218)

R. J. Foley, J. S. Bloom, D. A. Perley, and N. R. Butler
(UC Berkeley) report:

"We obtained 2x600 sec spectra of GRB 060218 / SN 2006aj
(GCN 4775) on 20060726 UT, 153 rest-frame days past the
GRB trigger, with Keck I (+ LRIS).  The spectrum shows
prominent nebular emission lines attributed to [O I]
6300, 6364, Na D, and the Ca II IR triplet.  The spectrum
resembles the nebular spectrum of GRB 980425 / SN 1998bw
at a similar epoch.  With a redshift of z = 0.033
(Mirabal & Halpern, GCN 4792), this is the most distant
GRB-SN with a observed nebular spectrum.

The [O I] line has a velocity width of 10700 km/s, which
is quantitatively similar to SN 1998bw 157 rest-frame
days past the GRB trigger.  The line has one strong peak,
with a slight shoulder, attributed to [O I] 6364.  There
is no obvious asymmetry in this spectrum, consistent with
the models of Mazzali et al. (2005, Science, 308, 1284).
Further spectroscopic observations are encouraged.

A comparison of our spectrum of GRB 060218 / SN 2006aj to
a spectrum of GRB 980425 / SN 1998bw can be found at
http://astro.berkeley.edu/~rfoley/foley_etal-grb060218.jpg