GCN Circular 10519
Subject
GRB 100316D: Swift XRT enhanced position and further refined analysis
Date
2010-03-17T13:42:03Z (14 years ago)
From
Rhaana Starling at U of Leicester <rlcs1@star.le.ac.uk>
R.L.C. Starling, P.A. Evans (U. Leicester) and M. Stamatikos
(OSU/NASA/GSFC) report on behalf of the Swift XRT team:
We have now analysed the first 3 orbits of Swift XRT data for GRB 100316D
(trigger=416135, Stamatikos et al. GCN Circ. 10496),
comprising 8 s of Windowed Timing (WT) settling mode data, 593 s of WT
mode data and 3.7 ks of Photon Counting (PC) mode data. The early light
curve is flat and can be modelled with a power-law decay with a decay
index of alpha=0.13+/-0.03 as described in Starling et al. (GCN Circ.
10505). This now breaks at some time after T+750 s to a steeper decay of
alpha=2.0 +0.3/-0.1.
Using 1967 s of XRT Photon Counting mode data and 1 U-band UVOT
image, we find an astrometrically corrected X-ray position (using the
XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 107.62763, -56.25547 which is equivalent to:
RA (J2000): 07h 10m 30.63s
Dec (J2000): -56d 15' 19.7"
with an uncertainty of 3.7 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
We note that this position is 1.5 arcsec from the optical/nIR candidate
'Object A' reported in the VLT/X-Shooter and Gemini/GMOS observations by
Vergani et al. (GCN Circ. 10513) and GROND observations reported by Afonso
et al. (GCN Circ. 10514