[vsnet-grb-info 6674] GRB 080919: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8276
SUBJECT: GRB 080919: Swift-XRT refined analysis
DATE:    08/09/19 16:40:58 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri at asdc.asi.it>

B. Preger (ASDC), G. Stratta (ASDC), M. Perri (ASDC) report on behalf
of the Swift XRT team:

The Swift XRT started observing the field of GRB080919 (trigger=325268;
Preger et al., GCN Circ. 8270) at 00:06:23.8 UT, 70.8 seconds
after the trigger.

The position of the X-ray afterglow is: RA, Dec= 265.223958, -42.368667
which is equivalent to:

RA (J2000): 17 40 53.75
Dec (J2000): -42 22 07.2

with an uncertainty of 2.0 arcsec (90% confidence).

The X-ray light curve from T0+74 s to T0+25 ks shows a fading behavior.
At ~T0 + 200 data show a 200 s long flare peaking
at ~T0 + 240 s with peak count rate of (1.2+/-0.3) cts/s
that is about a factor of 4 above the underlying continuum.
Excluding the flare, the light curve can be well modelled with
a broken power law, with best fit first decay index
alpha_1 = 2.2+/-0.2, a temporal break at ~T0 + 891 s and second
decay index alpha_2= 0.8+/-0.2.

A 4.5 ks exposure X-ray spectrum from T0+100 s to T0+7811 s can be
fit by an absorbed power-law model with a photon index of 2.0 (+0.5 -0.4)
and a column density of 3.9 (+3.2) (-2.3) x 10^21 cm^-2 in addition to
the Galactic column density value in the direction of the burst
(2.6 x 10^21 cm^-2, Kalberla et al. 2005).

Providing the source continues to decay at the same rate, we predict an
observed flux of about 2 x 10^-14 erg cm^-2 s^-1 at T0+1 days.

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