[vsnet-grb-info 3275] GRB060510B: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5110
SUBJECT: GRB060510B: Swift XRT refined analysis
DATE:    06/05/10 22:07:59 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri at asdc.asi.it>

M. Perri, M. Capalbi, M.L. Conciatore, L. Vetere (ASDC),
H.A. Krimm (GSFC/USRA) and D.N. Burrows (PSU) report on behalf
of the Swift/XRT team:

We have analyzed the first four orbits of Swift XRT data on the BAT GRB
060510B (Krimm, et al., GCN 5096; Barthelmy et al., GCN 5107). A 5.3 ks
Photon Counting (PC) mode image gives a refined X-ray position of:

RA(J2000)  =  15h 56m 29.9s
Dec(J2000) = +78d 34' 09.7"

with an uncertainty of 3.6 arcsec (90% containment). This is 2 arcmin
away from the center of the refined BAT position quoted in GCN 5107, and
1.8 arcsec away from the initial XRT position reported in GCN 5096.

The early 0.3-10 keV light curve has a complex behavior. The first
orbit of data shows an initial shallow decay with slope ~ -0.3, a temporal
break at about T+350s followed by a steep decay with slope ~ -11. Three
X-ray flares at about T+200s, T+300s and T+880s are also observed during
the first orbit. The afterglow decay between the second and the fourth
orbit has a slope of ~ -0.4.

The X-ray spectrum covering the time period from T+128s to T+456s is
well fit by an absorbed power-law with a photon index of 1.42+/-0.13
and column density of (1.5+/-0.1)e21 cm**-2. We note the Galactic column
density in the direction of the source is 3.8e20 cm**-2.  The observed
(unabsorbed) 0.3-10 keV flux for this spectrum is 4.3e-9 (4.9e-9)
erg/cm**2/s. All the quoted errors are at the 90% confidence level.

If the burst continues decaying at the current rate we estimate an XRT
count rate of 6e-3 counts/s at T+24hr, which corresponds to an
unabsorbed 0.3-10.keV flux of 3e-13 ergs cm**-2 s**-1.

This circular is an official product of the Swift XRT Team.