Modelling the disk atmosphere of the low mass X-ray binary EXO 0748-676

Abstract

Low mass X-ray binaries exhibit ionized emission from an extended disk atmosphere that surrounds the accretion disk. However, its nature and geometry is still unclear. In this work we present a spectral analysis of the extended atmosphere of EXO 0748-676 using high-resolution spectra from archival XMM-Newton observations. We model the RGS spectrum that is obtained during the eclipses. This enables us to model the emission lines that come only from the extended atmosphere of the source, and study its physical structure and properties. The RGS spectrum reveals a series of emission lines consistent with transitions of O VIII, O VII, Ne IX and N VII. We perform both Gaussian line fitting and photoionization modelling. Our results suggest that there are two photoionization gas components, out of pressure equilibrium with respect to each other. One with ionization parameter of 2.5 and a large opening angle, and one with 1.3. The second component is possibly covering a smaller fraction of the source. From the density diagnostics of the O vii triplet using photoionization modelling, we detect a rather high density plasma of > 10^13 cm^-3 for the lower ionization component. This latter component also displays an inflow velocity. We propose a scenario where the high ionization component constitutes an extended upper atmosphere of the accretion disk. The lower ionization component may instead be a clumpy gas created from the impact of the accretion stream with the disk.

arXiv commentA&A accepted, 10 pages, 9 figures

References in corpus (20)

• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• The Formation and Structure of a Strongly Magnetized Corona above Weakly Magnetized Accretion Disks
• X-ray photoionized plasma diagnostics with Helium-like ions. Application to Warm Absorber-Emitter in Active Galactic Nuclei
• Resolved atomic lines reveal outflows in two ultraluminous X-ray sources
• On the use of C-stat in testing models for X-ray spectra
• Spectral changes during dipping in low-mass X-ray binaries due to highly-ionized absorbers
• Systematic comparison of photoionised plasma codes with application to spectroscopic studies of AGN in X-rays
• The Structure and X-ray Recombination Emission of a Centrally Illuminated Accretion Disk Atmosphere and Corona
• An XMM-Newton study of the X-ray binary MXB1659-298 and the discovery of narrow X-ray absorption lines
• High-Resolution spectroscopy of the low-mass X-ray binary EXO 0748-67
• Identification of an Extended Accretion Disk Corona in the Hercules X-1 Low State: Moderate Optical Depth, Precise Density Determination, and Verification of CNO Abundances
• Chandra and XMM Observations of the ADC Source 0921-630
• Discrete X-ray Signatures of a Photoionized Plasma Above the Accretion Disk of the Neutron Star EXO 0748-676
• High-Resolution X-Ray Spectroscopy of the Accretion Disk Corona Source 4U 1822-37
• A Strong X-Ray Burst from the Low Mass X-Ray Binary EXO0748-676
• Properties of the ionised plasma in the vicinity of the neutron-star X-ray binary EXO 0748-676
• Anatomy of the AGN in NGC 5548 IX. Photoionized emission features in the soft X-ray spectra
• The broad-band X-ray spectrum of the dipping Low Mass X-ray Binary EXO0748--676
• High efficiency of soft X-ray radiation reprocessing in supersoft X-ray sources due to multiple scattering

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