[vsnet-grb-info 15903] GRB 141121A: Keck observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17191
SUBJECT: GRB 141121A: Keck observations
DATE:    14/12/18 12:15:16 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

D. A. Perley (Caltech) reports:

I observed the location of GRB 141121A (Lien et al., GCN
17075) using the imaging mode of the Low-Resolution Imaging
Spectrometer (LRIS) on the Keck I 10-meter telescope between 10:55 and 
11:16 UT on 2014-12-18.  A short sequence of exposures in g, R, and 
i-bands was acquired.

The optical counterpart (Tanga et al., GCN 17078) is clearly detected in 
all filters. Calibrating relative to SDSS, the magnitude is:

i = 23.96 +/- 0.07  (t = 27.3 days)

This measurement is significantly fainter than that reported by Toy et 
al. based on DCT observations on 2014-12-07, and the counterpart appears 
point-like in 0.8-arcsecond seeing.  This suggests that the light is 
still dominated by the afterglow.