A Chandra observation of the bursting millisecond X-ray pulsar IGR j17511-3057

IGRJ17511-3057 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 20ks Chandra grating observation of IGRJ17511-3057, performed on 2009 September 22. We determine the most accurate X-ray position of IGRJ17511-3057, α_J2000 = 17^h51^m0866, δ _J2000 = -30°57′410 (90% uncertainty of 06). During the observation, a 54s long type-I X-ray burst is detected. The persistent (non-burst) emission has an absorbed 0.5-8keV luminosity of 1.7 × 10 ³⁶ erg s^-1 (at 6.9kpc) and can be well described by a thermal Comptonization model of soft, 0.6keV, seed photons upscattered by a hot corona. The type-I X-ray burst spectrum, with average luminosity over the 54s duration L _{0.5-8 keV} = 1.6 × 10³⁷ erg s ^-1, 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 IGRJ17511-3057.