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GCN Circular 23238

Subject
GRB 180914B: RATIR Optical and NIR Observations
Date
2018-09-16T05:48:12Z (5 years ago)
From
Eleonora Troja at GSFC <eleonora.troja@nasa.gov>
Eleonora Troja (GSFC), 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 (UVI), , Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jesus Gonzalez (UNAM), Carlos Roman-Zuniga (UNAM),
Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.),
and Vicki Toy (UMD) report:

We observed the field of GRB 180914B, detected by AGILE/MCAL (Ursi,
et al., GCN 23226) AGILE/GRID (Verrecchia, et al., GCN 23231), and
Fermi/LAT (Bissaldi, et al., GCN 23232) with the Reionization and
Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold
Johnson Telescope at the Observatorio Astronomico Nacional on Sierra
San Pedro Martir from 2018/09 16.14 to 2018/09 16.16 UTC (32.90 to
33.43 hours after the burst), obtaining 0.36 hours exposure in the
r and i bands and 0.15 hours exposure in the Z, Y, J, and H bands.

Within the Swift-XRT error circle (D'Ai, et al., GCN 23236),
we detect the object reported by Zheng & Filippenko (GCN 23237).
In comparison with the SDSS DR9 and 2MASS catalogs, we obtain
the following detections:

r = 19.51 +/- 0.01
i = 19.20 +/- 0.01
z = 18.93 +/- 0.03
Y = 18.75 +/- 0.03
J = 18.60 +/- 0.05
H = 18.28 +/- 0.04

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

The source position is consistent with a catalogued SDSS galaxy with
photometric redshift z~0.58. However, its brightness is significantly
higher than the values reported in the catalogue,suggesting that the
emission may be dominated by the GRB afterglow and that the SDSS
object may be the GRB host galaxy.

Further observations to establish the source variability are planned.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.
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