TITLE:   GCN CIRCULAR
NUMBER:  19119
SUBJECT: GRB 160228A: RATIR Optical and NIR Observations
DATE:    16/02/29 18:20:16 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC),
José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM),
Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC),
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 160228A (Malesani et al., GCN Circular 19107)
with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org)
on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico
Nacional on Sierra San Pedro Mártir from 2016/02 29.12 to 2016/02 29.38 UTC
(9.23 to 15.50 hours after the BAT trigger), obtaining a total of 4.27
hours exposure in the r and i bands and 1.79 hours exposure in the Z, Y, J,
and H bands.

For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper limits:

  r > 24.46
  i > 24.39
  Z > 23.21
  Y > 22.76
  J > 22.43
  H > 22.10

These magnitudes are in the AB system and are not corrected for
Galactic extinction in the direction of the GRB.

We do not detect the candidate afterglow seen by Delvaux et al. (GCN Circ
19114) with GROND.  Our upper-limits in rZJH are above their detections.
However, there is weak evidence for fading in i, since GROND detected i =
23.8 ± 0.2 at about 7.5 hours and we obtain i > 24.4 at 12.4 hours.

We see suggestions of the "extended bluish object” mentioned by Delvaux et
al. in our r-band image. We also clearly detect the "larger, brighter
galaxy” at 07:09:15.89 +26:55:59.3 (±0.5”) with:

  r = 22.64 ± 0.07
  i = 22.17 ± 0.05
  Z = 22.07 ± 0.13
  Y = 21.69 ± 0.14
  J = 21.60 ± 0.17
  H = 21.64 ± 0.24

We thank the staff of the Observatorio Astronómico Nacional in San
Pedro Mártir.