Iron-line and continuum variations in the XMM-Newton and Suzaku spectra of the neutron-star low-mass X-ray binary 4U 1636-53

Abstract

We used six simultaneous XMM-Newton and Rossi X-ray Timing Explorer plus five Suzaku observations to study the continuum spectrum and the iron emission line in the neutron-star low-mass X-ray binary 4U 1636-53. We modelled the spectra with two thermal components (representing the accretion disc and boundary layer), a Comptonised component (representing a hot corona), and either a Gaussian or a relativistic line component to model an iron emission line at about 6.5 keV. For the relativistic line component we used either the diskline, laor or kyrline model, the latter for three different values of the spin parameter. The fitting results for the continuum are consistent with the standard truncated disc scenario. We also find that the flux and equivalent width of the iron line first increase and then decrease as the flux of the Comptonised component increases. This could be explained either by changes in the ionisation state of the accretion disc where the line is produced by reflection, or by light bending of the emission from the Comptonised component if the height at which this component is produced changes with mass accretion rate.

Accepted for publication in MNRAS, 16 pages, 10 figures, 5 tables

References in corpus (14)

• Modelling the behaviour of accretion flows in X-ray binaries
• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• RXTE observations of the first transient Z source XTE J1701-462: shedding new light on mass accretion in luminous neutron star LMXBs
• X-ray time variability across the atoll source states of 4U 1636--53
• The coherence of kHz quasi-periodic oscillations in the X-rays from accreting neutron stars
• Average hard X-ray emission from NS LMXBs: Observational evidence of different spectral states in NS LMXBs
• Evidence of a Broad Relativistic Iron Line from the Neutron Star Low-Mass X-ray Binary Serpens X-1
• Constraints on the Neutron Star and Inner Accretion Flow in Serpens X-1 Using NuSTAR
• On the maximum amplitude and coherence of the kilohertz quasi-periodic oscillations in low-mass X-ray binaries
• RossiXTE monitoring of 4U 1636-53: I. Long-term evolution and kHz Quasi-Periodic Oscillations
• BeppoSAX observation of 4U 1705-44: detection of hard X-ray emission in the soft state
• Suzaku Wide Band Analysis of the X-ray Variability of TeV Blazar Mrk 421 in 2006
• Disc-Jet coupling in the LMXB 4U1636-53 from INTEGRAL

Cited by in corpus (6)

• Thermonuclear X-ray bursts
• Spectral and timing analysis of the mHz QPOs in the neutron-star low-mass X-ray binary 4U 1636-53
• Suzaku Observation of the High-Inclination Binary EXO 0748-676 in the Hard State
• Broadband X-ray emission and the reality of the broad iron line from the Neutron Star - White Dwarf X-ray binary 4U 1820-30
• X-ray variability with spectral state transitions in NS-LMXBs observed with MAXI/GSC and Swift/BAT
• Neutron Star Radius-to-mass Ratio from Partial Accretion Disc Occultation as Measured through Fe K$\alpha$ Line Profiles