TITLE:   GCN CIRCULAR
NUMBER:  21180
SUBJECT: GRB 170531A: Swift-XRT refined Analysis
DATE:    17/06/01 11:33:02 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), S. J. LaPorte (PSU),
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), B. Mingo (U. Leicester), V.
D'Elia (ASDC) and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.2 ks of XRT data for GRB 170531A (Evans et al. GCN
Circ. 21170), from 254 s to 44.6 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The best available XRT
position  (using the promptly downlinked event data, the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue) is
RA, Dec = 121.2524, -14.0227 which is equivalent to:

RA (J2000): 08 05 00.57
Dec(J2000): -14 01 21.8

with an uncertainty of 3.5 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.62 (+0.20, -0.16).

If the light curve continues to decay with a power-law decay index of
0.62, the count rate at T+24 hours will be 1.3 x 10^-3 count s^-1

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00755343.

This circular is an official product of the Swift-XRT team.