[vsnet-grb-info 19890] GRB 171004A: Correction to RATIR Astrometry and Photometry

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21972
SUBJECT: GRB 171004A: Correction to RATIR Astrometry and Photometry 
DATE:    17/10/04 20:04:21 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

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),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:

The position and magnitudes of the uncataloged source reported by Watson
et al. (GCN Circ. 21968) are incorrect. We thank David Alexander Kann
for drawing our attention to this error.

The correct position is RA, Dec = 139.169462 52.693080 (J2000) or
09:16:40.67 +52:41:35.1. This position lies 0.4 arcsec from the enhanced
XRT position (Osborne et al., GCN Circ. 21970).

The correct magnitudes are

 r	= 21.17 +/- 0.06
 i	= 20.87 +/- 0.05
 Z	= 20.72 +/- 0.10
 Y	= 20.59 +/- 0.13
 J	= 20.36 +/- 0.14
 H	= 20.17 +/- 0.17

A fit to the i-band light curve of the source shows that the flux
behaves as t^(-0.9+/-0.4). That is, it is fading at the 2-sigma level.

The positional coincidence combined with the weak evidence for fading
suggest that this source might well be the afterglow of the GRB.