2009/08/31 by Edward M. Cackett, E. M. Cackett, J. M. Mïller +12 · 5 citations
Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black-body radiation #Emission spectrum #High-pressure geophysics and materials #Neutron star #Nuclear physics #Physics #Pulsar #Pulsars and Gravitational Waves Research #Radiation #Spectral line #X-ray binary #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/720/1/205
Accepted to ApJ
arxiv created 2010/07/06 · openalex publication_date 2010/08/06 · arxiv updated 2015/05/13 · openalex created_date 2020/11/23 · openalex updated_date 2026/08/06
A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can broaden emission lines. We present a comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10 neutron star LMXBs, all of which display broad Fe K emission lines. Of the 10 sources, 4 are Z sources, 4 are atolls, and 2 are accreting millisecond X-ray pulsars (also atolls). The Fe K lines are fit well by a relativistic line model for a Schwarzschild metric, and imply a narrow range of inner disk radii (6–15 GM / c 2 ) in most cases. This implies that the accretion disk extends close to the neutron star surface over a range of luminosities. Continuum modeling shows that for the majority of observations, a blackbody component (plausibly associated with the boundary layer) dominates the X-ray emission from 8 to 20 keV. Thus it appears likely that this spectral component produces the majority of the ionizing flux that illuminates the accretion disk. Therefore, we also fit the spectra with a blurred reflection model, wherein a blackbody component illuminates the disk. This model fits well in most cases, supporting the idea that the boundary layer illuminates a geometrically thin disk.