TITLE:   GCN CIRCULAR
NUMBER:  13084
SUBJECT: GRB 120229A: Magellan observations and limit on an optical afterglow
DATE:    12/03/21 13:41:19 GMT
FROM:    Wen-fai Fong at CFA  <wfong@cfa.harvard.edu>

W. Fong, E. Berger, N. Sanders (Harvard), K. Cooksey, A. Zangari (MIT) and
N. Morrell (LCO) report:

"We observed the location of the short-duration GRB 120229A (GCN 12997)
with the Low Dispersion Survey Spectrograph 3 (LDSS3) mounted on the
Magellan/Clay 6.5-meter telescope. We obtained 3x180-sec
r-band observations on 2012 March 01.01 UT (9.6 hours post-burst) at
high airmass in mediocre seeing conditions (1.3"). To check for the
presence of a fading optical source, we re-observed the field (6x180-sec)
on 2012 March 02.01 UT (33.6 hours post-burst and 24.0 hours after
the first observations) at similar airmass. Digital image subtraction
of the two epochs using the ISIS software package reveals no
residuals within the BAT-refined position (GCN 12998). Therefore,
calculating the zeropoint from a standard star field at similar
airmass based on several stars, we place a 3-sigma limit of r>22.4 mag on
the optical afterglow of GRB 120229A at 9.6 hours after the burst."