Accretion Phenomena in Accreting Neutron Stars -From Atoll to Z-Sources
Abstract
Accreting neutron stars provide the bulk of high luminosity X-ray sources. Decade long studies of low-mass X-ray binaries have provided a wealth of information about the various nature of X-ray emissions and proposed emission sites include the neutron star surface, an immediate boundary layer, the inner disk region, a possible compact corona, atmospheric disk layers, or extended coronae. And even though a coherent picture of accretion models has yet to evolve, broad band timing and spectral variability studies so far favor a rough classification of sub-Eddington atoll-sources and near Eddington Z-sources. High resolution X-ray spectra now provide new evidence that accretion disks in neutron star bi-naries exhibit emissions from plasmas with large variety of ionization levels allowing to diagnose accretion geometry and feed back processes. Our analysis of line and edge properties reveal the outer disk of the ultra-compact binary 4U 0614+091, a thin accretion disk atmosphere in 4U 1822-37, an an extended accretion disk corona in Cyg X-2, and many other distinct accretion disk emission and absorber properties in atoll and Z-sources, In a very recent survey of narrow line Fe K shell fluorescence in X-ray binaries we demonstrate that these line emissions originate from mostly spherically distributed material surrounding the accreting system and are rare in low-mass X-ray binaries. In conjunction with X-ray continuum properties these results provide a vital diagnostic of proposed emission models and accreted plasma properties and allow us to draw a more coherent picture of mass accretion in these sources.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.2410S