TITLE:   GCN CIRCULAR
NUMBER:  14453
SUBJECT: GRB 130427A: PAIRITEL NIR Detections
DATE:    13/04/27 09:47:41 GMT
FROM:    Adam Morgan at U.C. Berkeley  <qmorgan@gmail.com>

A. N. Morgan (UC Berkeley) reports:

We observed the field of GRB 130427A (Maselli et al., GCN 14448) with the
1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at
2013-Apr-27 07h59m24s UT, 11.45 minutes after the Swift Trigger.  In
preliminary mosaics (consisting of 75 ~8 second images for a total
effective exposure time of 9.75 minutes) taken simultaneously in the J, H,
and Ks filters, we detect the optical afterglow (Elenin et al., GCN 14450;
Perley, GCN 14451; Melandri et al., GCN 14452).

The preliminary photometry yields:

post burst
t_mid (hr) exp.(m)   filt  mag   m_err
0.36       9.75      J     12.13  0.03
0.36       9.75      H     11.75  0.04
0.36       9.75      Ks    11.02  0.08

Observations continued until the source passed beyond telescope limits. All
magnitudes are given in the Vega system, calibrated to 2MASS. No correction
for Galactic extinction has been made to the above reported values.