INTEGRAL, XMM-Newton and Rossi-XTE Observations of the State Transition of the X-ray Transient and Black Hole Candidate XTE J1720-318

Marion Cadolle Bel (1) , Andrea Goldwurm (1) , Jerome Rodriguez (1) , Paolo Goldoni (1) , Stephane Corbel (1) , Patrick Sizun (1) , Arvind Parmar (2) , Eric Kuulkers (2) , Fiamma Capitanio (3) , Melania Del Santo (3) , Antonella Tarana (3) , Pietro Ubertini (3) , Jean-Pierre Roques (4) , Laurent Bouchet (4) , Ruben Farinelli (5) , Filippo Frontera (5) , Niels Westergaard (6)

1 DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
2 ESTEC - Research and Scientific Support Department
3 IASF - Instituto di Astrofisica
4 CESR - Centre d'étude spatiale des rayonnements
5 Dipartimento di Fisica [Ferrara]
6 DSRI - Danish Space Research Institute

We report the results of extensive high-energy observations of the X-ray transient and black hole candidate XTE J1720-318 performed with INTEGRAL, XMM-Newton and RXTE. The source, which underwent an outburst in January 2003, was observed in February in a spectral state dominated by a soft component with a weak high-energy tail. The XMM-Newton data provided a high column density Nh of 1.2*e22 cm^{-2} which suggests that the source lies at the Galactic Center distance. The simultaneous RXTE and INTEGRAL Target of Opportunity observations allowed us to measure the weak and steep tail, typical of a black-hole binary in the so-called High/Soft State. We could follow the evolution of the source outburst over several months using the INTEGRAL Galactic Center survey observations. The source regained activity at the end of March: it showed a clear transition towards a much harder state, and then decayed to a quiescent state in summer. In the hard state, the source was detected up to 200 keV with a typical power law index of 1.8 and a peak luminosity of 7.5*e36 ergs s^{-1} in the 2-100 keV band, for an assumed distance of 8 kpc. We conclude that XTE J1720-318 is indeed representative of the class of the black hole X-ray novae which populate our Galactic bulge and we discuss its properties in the frame of the spectral models used for transient black hole binaries.

Mots clés: Black hole physics; accretion; X-rays binaries; gamma-rays: observations; stars: individual: XTE J1720-318

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

Marion Cadolle Bel, Andrea Goldwurm, Jerome Rodriguez, Paolo Goldoni, Stephane Corbel, et al.. INTEGRAL, XMM-Newton and Rossi-XTE Observations of the State Transition of the X-ray Transient and Black Hole Candidate XTE J1720-318. The 5th INTEGRAL Workshop: "The INTEGRAL Universe", February 16-20, 2004, 2004, Munich, Germany. ⟨hal-00002221⟩