[vsnet-grb-info 14766] GRB 140402A: Deep limit on the optical afterglow from Magellan observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16080
SUBJECT: GRB 140402A: Deep limit on the optical afterglow from Magellan observations
DATE:    14/04/04 17:26:41 GMT
FROM:    Wen-fai Fong at CFA  <wfong at cfa.harvard.edu>

W. Fong (Harvard), S. Ehlert (MIT), D. Osip (LCO/OCIW), B. Rackham
(Arizona), M. McDonald (MIT), and E. Berger (Harvard) report:

"We observed the location of the short-duration GRB 140402A, detected by
Fermi/LAT (Bissaldi et al., GCN 16069), Fermi/GBM (Jenke et al., GCN 16070)
and Swift/BAT (Cummings et al., GCN 16071) with the Inamori Magellan Areal
Camera and Spectrograph (IMACS) mounted on the Magellan/Baade 6.5-m
telescope to cover the full refined BAT position (Cummings et al., GCN
16073). We obtained 3x300-sec r-band observations on 2014 Apr 03.22 UT
(1.21 days post-burst) in 0.7" seeing at an airmass of 1.2. To check for
the presence of a fading optical source, we re-observed the field
(3x300-sec) on 2014 Apr 04.35 UT, 2.33 days post-burst and 1.12 days after
the first set of observations. Digital image subtraction of the two epochs
using the ISIS software package reveals no residuals in or around the
BAT-refined position. Therefore, calibrated to SDSS DR9 sources in the same
field, we place a 3-sigma limit of r>25.0 mag on the optical afterglow of
GRB 140402A at 1.21 days after the burst."