A relativistically smeared spectrum in the neutron star X-ray Binary 4U 1705-44: Looking at the inner accretion disc with X-ray spectroscopy

Abstract

Iron emission lines at 6.4-6.97 keV, identified with fluorescent Kalpha transitions, are among the strongest discrete features in the X-ray band. These are therefore one of the most powerful probes to infer the properties of the plasma in the innermost part of the accretion disc around a compact object. In this paper we present a recent XMM observation of the X-ray burster 4U 1705-44, where we clearly detect a relativistically smeared iron line at about 6.7 keV, testifying with high statistical significance that the line profile is distorted by high velocity motion in the accretion disc. As expected from disc reflection models, we also find a significant absorption edge at about 8.3 keV; this feature appears to be smeared, and is compatible with being produced in the same region where the iron line is produced. From the line profile we derive the physical parameters of the inner accretion disc with large precision. The line is identified with the Kalpha transition of highly ionised iron, Fe XXV, the inner disc radius is Rin = (14 \pm 2) R_g (where R_g is the Gravitational radius, GM/c^2), the emissivity dependence from the disc radius is r^{-2.27 \pm 0.08}, the inclination angle with respect to the line of sight is i = (39 \pm 1) degrees. Finally, the XMM spectrum shows evidences of other low-energy emission lines, which again appear broad and their profiles are compatible with being produced in the same region where the iron line is produced.

6 pages, including 3 figures. Final version, including proof corrections, as it will appear in MNRAS

References in corpus (8)

• An absorption origin for the X-ray spectral variability of MCG-6-30-15
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• Broad relativistic iron emission line observed in SAX J1808.4-3658
• XMM-Newton detects a relativistically broadened iron line in the spectrum of the ms X-ray pulsar SAX J1808.4-3658
• Evidence of a Broad Relativistic Iron Line from the Neutron Star Low-Mass X-ray Binary Serpens X-1
• Effects of Downscattering on the Continuum and Line Spectra in Powerful Wind Environment. Monte Carlo Simulations, Analytical Results and Data Analysis
• Disk reflection signatures in the spectrum of the bright Z-source GX 340+0
• BeppoSAX observation of 4U 1705-44: detection of hard X-ray emission in the soft state

Cited by in corpus (25)

• Black hole-like hysteresis and accretion states in neutron star low mass X-ray binaries
• A Hard Look at the Neutron Stars and Accretion Disks in 4U 1636-53, GX 17+2, and 4U 1705-44 with $\text{NuSTAR}$
• Relativistic X-ray Reflection Models for Accreting Neutron Stars
• Suzaku broad-band spectrum of 4U 1705-44: Probing the Reflection component in the hard state
• X-ray polarimetry and spectroscopy of the neutron star low-mass X-ray binary GX 9+9: an in-depth study with IXPE and NuSTAR
• Chandra X-ray spectroscopy of a clear dip in GX 13+1
• Study of the reflection spectrum of the accreting neutron star GX 3+1 using XMM-Newton and INTEGRAL
• Truncation of the Accretion Disk at One Third of the Eddington Limit in the Neutron Star Low-Mass X-ray Binary Aquila X-1
• Study of the reflection spectrum of the LMXB 4U 1702-429
• A re-analysis of the NuSTAR and XMM-Newton broad-band spectrum of Ser~X-1
• On the illumination of neutron star accretion discs
• Simultaneous NICER and NuSTAR Observations of the Ultra-compact X-ray Binary 4U 1543-624
• High-frequency variability in neutron-star low-mass X-ray binaries
• Spectral analysis of the dipping LMXB system XB 1916-053
• Broad iron emission line and kilohertz quasi-periodic oscillations in the neutron star system 4U 1636-53
• Constraining the geometry of the dipping atoll 4U 1624-49 with X-ray spectroscopy and polarimetry
• Rotational parameters of strange stars in comparison with neutron stars
• Fe K$\alpha$ and Fe K$\beta$ line detection in the NuSTAR spectrum of the ultra-bright Z-source Scorpius X-1
• AstroSat view of `Clocked` burster GS 1826-238:broad-band spectral nature of persistent and burst emission during soft state
• Disk reflection and energetics from the accreting millisecond pulsar SRGA J144459.2-604207
• Investigating the coronal structure by studying time lags in the Atoll source 4U 1705-44 using AstroSat
• Relativistic disc line: a tool to constrain neutron star equation of state models
• X-ray view of emission lines in optical spectra: Spectral analysis of the two low-mass X-ray binary systems Swift J1357.2-0933 and MAXI J1305-704
• Spectral study of neutron star low mass X-ray binary source 1A 1744-361
• X-ray views of neutron star low-mass X-ray binaries