GCN Circular 5157
Subject
XMM-Newton observation of GRB060510b
Date
2006-05-23T14:45:56Z (19 years ago)
From
Sergio Campana at INAF-OAB <sergio.campana@brera.inaf.it>
Sergio Campana (INAF/OAB) and Andrea DeLuca (INAF/IASF
Milano) report:
We have analyzed the XMM-Newton observation of the field
of GRB060510B, discovered by Swift/BAT on May 10 2006,
08:22:14 UT (Krimm et al., GCN 5096).
The XMM-Newton observation started ~5 hours after the
GRB trigger and lasted for ~40 ks. The observation is
affected by a high particle background, resulting in
about 17 ks of usable data.
We report here on data collected by the EPIC/pn camera.
The afterglow of GRB060510B is detected at the following
coordinates:
RA(J2000): 15h 56m 29s.2,
Dec(J2000): +78d 34' 12.0",
with an uncertainty of 1.5 arcsec (1sigma), fully
consistent with the reported Swift/XRT (Krimm et al.)
and optical (Mirabal et al. GCN5097) positions.
Extracting source events from a circle of 30 arcsec
radius, the pn time-averaged, background-subtracted count
rate in the 0.5-8 keV range is of 0.11+/-0.003 cts/s.
The source is clearly fading with a power law decay
with alpha=-0.7+/-0.1 (error at 90% c.l. for a single
parameter) with reduced chi2=1.3, 16 d.o.f.
The time-integrated X-ray spectrum is well fit (reduced
chi2=1.0, 72 d.o.f.) by a power law absorbed by a column
NH=(9.4+/-3.5)x10^20 cm^-2 (error at 90% confidence level),
slightly larger than the Galactic value of NH_gal=3.8x10^20
cm^-2 (Dickey & Lockman 1990), and with a photon index
Gamma=2.7+/-0.3.
Since the redshift of the GRB afterglow is known we consider
also an intrinsic absorption at z=4.9 (Price, GCN5104). The
fit is similarly good (reduced chi2=0.99, 72 d.o.f.) with
NH_z=(2.1+/-1.2)x10^22 cm^-2 and Gamma=2.5+/-0.2.
The observed flux (0.5-10 keV) is of 1.4x10^-13 erg
cm^-2 s^-1, corresponding to an unabsorbed flux of
1.8x10^-13 erg cm^-2 s^-1.
No spectral evolution as a function of time
(first 16 ks vs. remaining 22 ks of data) has been observed.