[AAVSO-HEN] GRB 090118: KPNO 4m 2nd Epoch Observations

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  8831
SUBJECT: GRB 090118: KPNO 4m 2nd Epoch Observations
DATE:    09/01/20 07:40:24 GMT
FROM:    Adria C. Updike at Clemson U  <aupdike at clemson.edu>

Adria C. Updike and Dieter H. Hartmann (Clemson University) report:

We observed the field of GRB 090118 (GCN 8825, Copete et al.) for a second
epoch beginning 36.7 hours after the burst.  Our observations consisted of
80 min of J band exposures.  In the stacked image, we still detect the
candidate (GCN 8829, Updike & Hartmann).  We re-analyzed our first epoch
image relative to 17 2MASS field stars, as well as our second epoch image.
 The brightness of the candidate source appears to be constant within
photometric uncertainties. While slow fading can't be ruled out, the
two-epoch results suggest that most likely the candidate source is
not the afterglow of GRB 090118. Third epoch observations are planned.


Time after burst     Band     Magnitude       Exp time
------------------------------------------------------
11.6 hours            J       21.2 +/- 0.6     40 min
36.7 hours            J       21.4 +/- 0.6     80 min


The images have been placed on the following site.

http://www.ces.clemson.edu/~aupdike/GRB090118/090118_J.jpg