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GCN Circular 17770

Subject
GRB 150428A: RATIR optical observations
Date
2015-04-28T06:46:58Z (9 years ago)
From
Owen Littlejohns at Az State U <olittlej@asu.edu>
Owen Littlejohns (ASU), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer
(UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC),
Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja
(GSFC), Enrico Ramirez-Ruiz (UCSC), Jos� A. de Diego (UNAM), Leonid
Georgiev (UNAM), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM),
Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report:

We observed the field of GRB 150428A (Page, et al., GCN 17765Not found
 
 
) with
the Reionization and Transients Infrared Camera (RATIR; www.ratir.org)
on the 1.5m Harold Johnson Telescope at the Observatorio Astron�mico
Nacional on Sierra San Pedro M�rtir from 2015/04 28.14 to 2015/04
28.27 UTC (1.80 to 4.88 hours after the BAT trigger), obtaining a
total of 2.49 hours exposure in the r, i and z bands.

We find no uncatalogued source within the Swift-XRT error circle
(Osborne, et al., GCN 17768Not found
 
 
). In comparison with the SDSS DR9, we
obtain the following upper limits (3-sigma):

  r     > 23.94
  i     > 23.90
  z     > 19.56

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. We note that the source detected
by GROND (Knust, et al., GCN 17767Not found
 
 
) and P60 (Perley, GCN 17769Not found
 
 
) is not
consistent with the enhanced X-ray position. For the GROND source, in
comparison with the SDSS DR9, we obtain the following detections and
upper limit (3-sigma):

  r     = 23.41 +/- 0.22
  i     = 22.75 +/- 0.14
  z     > 19.56

The RATIR observations of the GROND source, therefore, do not show
evidence of fading between the GROND and RATIR epochs of observations.
Further RATIR observations are ongoing.

We thank the staff of the Observatorio Astron�mico Nacional in San Pedro
M�rtir.