[vsnet-grb-info 3304] GRB 060515: Swift/XRT Team refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5139
SUBJECT: GRB 060515: Swift/XRT Team refined analysis 
DATE:    06/05/15 13:50:58 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page, J.P. Osborne (U. Leicester), J.A. Kennea, A. Cucchiara (PSU) &
J.R. Cummings (NASA/ORAU) report on behalf of the Swift/XRT team:

We have analysed the first 4 orbits of Swift/XRT data of GRB 060515
(trigger number 210084; Cummings et al., GCN 5132), which equates to 9.6
ks between 3.4 ks and 23.2 ks after the trigger.

The source tentatively identified by Page & Kennea in GCN 5137 is found to
be fading, and so is the best candidate for the afterglow. The refined
position is:

RA(J2000)  =  08 29 09.5 
Dec(J2000) = +73 34 02.82

with an estimated uncertainty of 4.5 arcsec (90% uncertainty). This is 1.3
arcsec from the preliminary XRT given in GCN 5137, but 68.3 arcsec from
the possible optical candidate suggested by TAROT (GCN 5314, Klotz et
al.).

The source is only detected in the first 2 individual orbits of data,
giving a decay slope of alpha = 1.2 +/- 0.6. However, between the 2nd and
3rd orbits, the slope must steepen, since the 3-sigma upper limit on the
count rate (1.4e-3 count s^-1) is well below the extrapolation of alpha =
1.2. Thus, we cannot sensibly predict the flux at 24 hours. However,
between 3.4 ks - 5.9 ks, the 0.3-10 keV observed (unabsorbed) flux was
1.45e-12 (1.51e-12) erg cm^-2 s^-1.

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