TITLE:   GCN CIRCULAR
NUMBER:  9563
SUBJECT: PAIRITEL observations of GRB 090618
DATE:    09/06/23 01:00:35 GMT
FROM:    Adam Morgan at U.C. Berkeley  <qmorgan@gmail.com>

A. N. Morgan,  C. R. Klein,  J. S. Bloom,  (UC Berkeley), report:

We observed the location of the optical afterglow of GRB 090618
(Schady et al., GCN 9512) with the 1.3m PAIRITEL located at Mt.
Hopkins, Arizona. Observations began at 2009-06-18 08:29:40 UT, 71
seconds after the Swift Trigger, under non-ideal sky conditions. In
the initial images, we detect a variable infrared source (identified
as the IR afterglow) in individual frames of 7.8 second simultaneous
exposures in the J, H, and Ks bands.

The preliminary photometry on selected stacks of images yield the
following photometry:

time
post burst exp.   filt  mag   m_err
[s]        [s]

210        93.6   J     12.7  0.1
210        93.6   H     12.1  0.1
210        93.6   Ks    11.4  0.2

2818       327    J     15.1  0.1
2818       327    H     14.6  0.1
2818       327    Ks    13.7  0.1

10636      585    J     16.2  0.2
10636      585    H     15.7  0.2
10636      585    Ks    >14.8 3-sigma

Intermittent clouds led to highly variable transmission and sky
brightnesses during the PAIRITEL observations. All magnitudes are
given in the Vega system, calibrated to 2MASS. No correction for
Galactic extinction has been made to the above reported values.
Further analysis is ongoing.