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Astronomy and Astrophysics 464 (2007) 1069-1074
Simultaneous INTEGRAL and RXTE observations of the accreting millisecond pulsar HETE J1900.1-2455
M. Falanga1, 2, J. Poutanen, E. W. Bonning3, L. Kuiper, J.M. Bonnet-Bidaud2, A. Goldwurm1, 2, W. Hermsen, L. Stella
INTEGRAL Collaboration(s)

Aims: Hete J1900.1-2455 is the seventh known X-ray transient accreting millisecond pulsar and has been in outburst for more than one year. We compared the data on Hete J1900.1-2455 with other similar objects and made an attempt at deriving constraints on the physical processes responsible for a spectral formation. Methods: The broad-band spectrum of the persistent emission in the 2-300 keV energy band and the timing properties were studied using simultaneous INTEGRAL and the publicly available RXTE data obtained in October 2005. The properties of the X-ray bursts observed from Hete J1900.1-2455 were also investigated. Results: The spectrum is well described by a two-component model consisting of a blackbody-like soft X-ray emission at 0.8 keV temperature and a thermal Comptonized spectrum with the electron temperature of 30 keV and Thomson optical depth tau_T ~ 2 for the slab geometry. The source is detected by INTEGRAL up to 200 keV at the luminosity of 5E36 erg/s (assuming a distance of 5 kpc) in the 0.1-200 keV energy band. We have also detected one type I X-ray burst which shows the photospheric radius expansion. The burst occurred at an inferred persistent emission level of ~ 3-4% of the Eddington luminosity. Using the data for all X-ray bursts observed to date from Hete J1900.1-2455, the burst recurrence time is estimated to be about 2 days. No pulsations have been detected either in the RXTE or in the INTEGRAL data which puts interesting constraints on theories of the magnetic field evolution in neutron star low-mass X-ray binaries.
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
2 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
3 :  LUTH - Laboratoire Univers et Théories
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique
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