TITLE:   GCN CIRCULAR
NUMBER:  11845
SUBJECT: GRB 110328A / Swift J164449.3+573451: PAIRITEL NIR Detection in 2nd Epoch
DATE:    11/03/30 21:28:44 GMT
FROM:    Adam Morgan at U.C. Berkeley  <qmorgan@gmail.com>

A. N. Morgan, J. S. Bloom (UC Berkeley), A.J. Levan (U. Warwick), and
N.R. Tanvir (U. Leicester), report:

We continued to observe the field of GRB 110328A / Swift
J164449.3+573451 (Cummings et al., GCN 11823, Barthelmy et al., GCN
11824) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona for a
second epoch beginning at 2011-03-30 08:22:23 UT, ~43.4 hours after
the first Swift Trigger.  In  mosaics (effective exposure time of 1.9
hours) taken simultaneously in the J, H, and Ks filters, we detect a
source in all 3 filters at the optical/radio position (Cenko et al.,
GCN 11827, Leloudas et al., GCN 11830, Zauderer et al., GCN 11836,
Volnova et al., GCN 11837, Im et al. GCN 11839, Kelemen et al. 11840,
Zauderer et al. GCN 11841).

The preliminary photometry yields:

post burst
t_mid (hr) exp.(hr) filt  mag    m_err
44.9       1.90     J     19.1   0.3
44.9       1.90     H     18.9   0.5
44.9       1.90     Ks    17.3   0.4

Compared to our first epoch upper limits at ~20 hours post-burst
(Morgan et al., GCN 11838), these values suggest either a constant
source or re-brightening in J.

All magnitudes are given in the Vega system, calibrated to 2MASS. No
correction for Galactic extinction has been made to the above reported
values.