Correlated timing and spectral behavior of 4U 1705-44

Abstract

We follow the timing properties of the neutron star low-mass X-ray binary system 4U 1705-44 in different spectral states, as monitored by the Rossi X-ray Timing Explorer over about a month. We fit the power density spectra using multiple Lorentzians. We show that the characteristic frequencies of these Lorentzians, when properly identified, fit within the correlations previously reported. The time evolution of these frequencies and their relation with the parameters of the energy spectra reported in Barret & Olive (2002) are used to constrain the accretion geometry changes. The spectral data were fitted by the sum of a blackbody and a Comptonized component and were interpreted in the framework of a truncated accretion disk geometry, with a varying truncation radius. If one assumes that the characteristic frequencies of the Lorentzians are some measure of this truncation radius, as in most theoretical models, then the timing data presented here strengthen the above interpretation. The soft to hard and hard to soft transitions are clearly associated with the disk receding from and approaching the neutron star respectively. During the transitions, correlations are found between the Lorentzian frequencies and the flux and temperature of the blackbody, which is thus likely to be coming from the disk. On the other hand, in the hard state, the characteristic Lorentzians frequencies which are at the lowest, remained nearly constant despite significant evolution of the spectra parameters. The disk no longer contributes to the X-ray emission, and the blackbody is now likely to be emitted by the neutron star surface which is providing the seed photons for the Comptonization.

arXiv comment20 pages, 8 figures, 2 tables, to appear in the Astrophysical Journal (see also astro-ph/0205184)

References in corpus (16)

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• A peculiar spectral state transition of 4U1705--44: when an Atoll looks like a Z
• Two-phase radiative/conductive equilibrium in AGN and GBH
• A comment on the colour-colour diagrams of Low Mass X-ray Binaries
• Energy Spectra and High Frequency Oscillations in 4U 0614+091
• Quasi-periodic variability and the inner radii of thin accretion disks in galactic black-hole systems
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Cited by in corpus (26)

• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• The atoll source states of 4U 1608-52
• An abrupt drop in the coherence of the lower kilohertz QPO in 4U 1636-536
• Relations Between Timing Features and Colors in Accreting Millisecond Pulsars
• A relativistically smeared spectrum in the neutron star X-ray Binary 4U 1705-44: Looking at the inner accretion disc with X-ray spectroscopy
• RossiXTE monitoring of 4U 1636-53: I. Long-term evolution and kHz Quasi-Periodic Oscillations
• A self-consistent approach to the hard and soft states of 4U 1705-44
• Testing reflection features in 4U 1705-44 with XMM-Newton, BeppoSAX and RXTE in the hard and soft state
• Suzaku broad-band spectrum of 4U 1705-44: Probing the Reflection component in the hard state
• Suzaku and BeppoSAX X-ray Spectra of the Persistently Accreting Neutron-Star Binary 4U 1705-44
• Spectral state transitions in low-mass X-ray binaries - the effect of hard and soft irradiation
• Rapid spectral and timing variability of Be/X-ray binaries during type II outbursts
• Spectral and Timing Properties of Atoll Source 4U 1705-44 : LAXPC/AstroSat Results
• Peak Luminosities of the Hard States of GX 339-4: Implications for the Accretion Geometry, Disk Mass, and Black Hole Mass
• Hard X-ray Flares Preceding Soft X-ray Outbursts in Aquila X-1: A Link between Neutron Star and Black Hole State Transitions
• Reversal of the amplitude difference of kHz QPOs in six atoll sources
• Correlated optical/X-ray variability in the high-mass X-ray binary SAX J2103.5+4545
• Relativistically broadened iron line in the SUZAKU observation of the neutron star X-ray binary 4U 1705-44
• Timing properties of XB 1254-690
• The first detection of Compton Reflection in the Low-Mass X-ray Binary 4U1705-44 with INTEGRAL and BeppoSAX
• Simultaneous BeppoSAX and Rossi X-ray Timing Explorer observations of 4U1812-12
• A variable near-infrared counterpart to the neutron-star low-mass X-ray binary 4U 1705-440
• The Chaotic Long-term X-ray Variability of 4U 1705--44
• The 17 min orbital period in the Ultra Compact X-ray Binary 4U 0513-40
• Timing and spectral study of XB 1254-690 using new RXTE PCA data
• Investigating the coronal structure by studying time lags in the Atoll source 4U 1705-44 using AstroSat