INTEGRAL and BeppoSAX observations of the transient atoll source 4U 1608-522: from quiescent to hard spectral state

Abstract

In this paper we report on the spectral evolution of 4U 1608-522 performed as part of the long Galactic Bulge monitoring with INTEGRAL. The data set include the April 2005 outburst. BeppoSAX archival data (two observations, in 1998 and 2000) have been also analysed and compared with the INTEGRAL ones. Three different spectral states have been identified from the hard Color-Intensity diagram derived from INTEGRAL: the canonical Hard and Soft as well as an Intermediate state. The hard state spectrum is well described by a weak black body component plus a Comptonised plasma component with high electron temperature (kTe~60 keV) extending up to 200 keV without any additional cut-off. The soft spectra are characterized by a cold Comptonised plasma (kTe= 2-3 keV, and 7 keV for the intermediate state) and a strong disk black body component. A reflection component, indicating reflection of the X-ray radiation from the accretion disc, is also present in the soft state revealed by BeppoSAX in 1998. The 2000 BeppoSAX observation revealed the source in quiescent state modelled by a neutron star atmosphere (assuming a neutron star with radius 10 km and mass 1.4 Msun) with an effective temperature, kTeff of 0.1 keV plus a power law component with Gamma~3 detected for the first time for this source. This spectrum can also be modelled with a simple black body compatible with emission originating from a small fraction of the NS surface of radius of 0.4 km.

arXiv comment8 pages, 6 figures, to be published in ApJ

References in corpus (23)

• Modelling the behaviour of accretion flows in X-ray binaries
• The Two-Phase Pair Corona Model for Active Galactic Nuclei and X-ray Binaries: How to Obtain Exact Solutions
• The INTEGRAL Science Data Centre (ISDC)
• Jets in neutron star X-ray binaries: a comparison with black holes
• Radiative Processes, Spectral States and Variability of Black-Hole Binaries
• The INTEGRAL/IBIS Scientific Data Analysis
• The Neutron Stars of Soft X-Ray Transients
• Theory of high-energy emission from the pulsar/Be-star system PSR 1259$-$63 I: radiation mechanisms and interaction geometry
• Hard X-ray Emission From Low Mass X-ray Binaries
• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• Crustal Emission and the Quiescent Spectrum of the Neutron Star in KS 1731-260
• The Thermal X-ray Spectra of Cen X-4, Aql X-1, and 4U 1608-522 in Quiescence
• Spectra of the spreading layers on the neutron star surface and constraints on the neutron star equation of state
• The X-ray spectrum of the atoll source 4U 1608-52
• Boundary layer emission and Z-track in the color-color diagram of luminous LMXBs
• A Method for Distinguishing Between Transiently Accreting Neutron Stars and Black Holes, in Quiescence
• X-ray and gamma-ray spectra and variability of the black-hole candidate GX 339-4
• Spitzer Reveals Infrared Optically-Thin Synchrotron Emission from the Compact Jet of the Neutron Star X-Ray Binary 4U 0614+091
• The Low Quiescent X-Ray Luminosity of the Neutron Star Transient XTE J2123-058
• BeppoSAX observation of 4U 1705-44: detection of hard X-ray emission in the soft state
• INTEGRAL spectral variability study of the atoll 4U 1820-30: first detection of hard X-ray emission
• The first detection of Compton Reflection in the Low-Mass X-ray Binary 4U1705-44 with INTEGRAL and BeppoSAX
• A BeppoSAX view of transient black hole candidates in quiescence

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