[vsnet-grb-info 13278] GRB 130427A: Keck/LRIS Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14615
SUBJECT: GRB 130427A: Keck/LRIS Observations
DATE:    13/05/09 15:39:04 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

D. A. Perley and S. Tang (Caltech) report:

On the night of 2013-05-09 UT we observed the location of GRB 130427A 
with the Low Resolution Imaging Spectrometer (LRIS) on the Keck I 10m 
telescope, during excellent weather conditions (clear skies and 0.7 
arcsecond seeing).

In a pair of 90 second g-band images we clearly detect the transient 
superimposed on a faint, extended source that we identify as the host 
galaxy.  While blended with the light of the transient, the diameter of 
this extended emission is approximately 3 arcseconds, corresponding to a 
physical size of ~14 kpc at a redshift of z=0.34.  The magnitude of the 
transient at this time (within a 1" aperture centered on the optical 
position) is:

  g = 21.23 +/- 0.04 mag  (t = 12.00 days)

This is consistent (within uncertainties) with the rate of decay seen in 
recent P60 observations between 1-8 days post-GRB after subtraction of 
the host galaxy.

We also acquired a deep sequence of spectroscopic observations (2000 sec 
total integration) with LRIS, covering a wavelength range from 
approximately 3250 to 10300 Angstroms.   We observe no broad features or 
other evidence of contribution of a supernova to the spectrum at this 
time, similar to as reported from LBT observations two nights previously 
(Garnavich et al., GCN 14605.)

We thank and S. R. Kulkarni and the PTF collaboration for these 
observations.