TITLE:   GCN CIRCULAR
NUMBER:  20685
SUBJECT: GRB170214A: RATIR Optical and NIR Afterglow Confirmation
DATE:    17/02/16 15:00:45 GMT
FROM:    Eleonora Troja at GSFC  <eleonora.troja@nasa.gov>

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

We observed the field of GRB 170214A (Mailyan, et al., GCN 20675;
Racusin, et al., GCN 20676) 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 2017/02 16.46 to 2017/02 16.54 UTC (43.4
to 45.4 hours after the GBM trigger), obtaining a total of 1.42
hours exposure in the r and i bands and 0.60 hours exposure in the
Z and Y bands.

Source 1 (Beardmore, et al., GCN 20679; Troja, et al., GCN 20681) is
still detected in our observations at a position consistent with the
NOT source (Malesani, et al., GCN 20683). In comparison with the
SDSS DR9 and 2MASS catalogs, we obtain the following detections:

   r    22.78 +/- 0.08
   i    22.40 +/- 0.15
   Z    21.54 +/- 0.17
   Y    21.22 +/- 0.17

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

Compared to our first night of observations (Troja, et al., GCN 20681)
the source significantly faded in all filters, confirming that it is the
optical (Malesani, et al., GCN 20683) and NIR afterglow of GRB170214A.

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