IGR J17511-3057 is a low mass X-ray binary hosting a neutron star and is one
of the few accreting millisecond X-ray pulsars with X-ray bursts. We report on
a 20ksec Chandra grating observation of IGR J17511-3057, performed on 2009
September 22. We determine the most accurate X-ray position of IGR J17511-3057,
alpha(J2000) = 17h 51m 08.66s, delta(J2000) = -30deg 57' 41.0" (90% uncertainty
of 0.6"). During the observation, a ~54sec long type-I X-ray burst is detected.
The persistent (non-burst) emission has an absorbed 0.5-8keV luminosity of 1.7
x 10^36 erg/sec (at 6.9kpc) and can be well described by a thermal
Comptonization model of soft, ~0.6keV, seed photons up-scattered by a hot
corona. The type-I X-ray burst spectrum, with average luminosity over the 54sec
duration L(0.5-8keV)=1.6 x 10^37 erg/sec, can be well described by a blackbody
with kT_(bb)~1.6keV and R_(bb)~5km. While an evolution in temperature of the
blackbody can be appreciated throughout the burst (average peak
kT_(bb)=2.5(+0.8/-0.4)keV to tail kT_(bb)=1.3(+0.2/-0.1)keV), the relative
emitting surface shows no evolution. The overall persistent and type-I burst
properties observed during the Chandra observation are consistent with what was
previously reported during the 2009 outburst of IGR J17511-3057.Comment: 6 pages, 4 figures, accepted for publication in ApJ (2012-06-08
