RELATIVISTIC LINES AND REFLECTION FROM THE INNER ACCRETION DISKS AROUND NEUTRON STARS

Journal Article · Wed Sep 01 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/720/1/205· OSTI ID:21460150

Cackett, Edward M; Miller, Jon M ^[1]; Ballantyne, David R ^[2]; Barret, Didier; Boutelier, Martin ^[3]; Bhattacharyya, Sudip ^[4]; Miller, M Coleman ^[5]; Strohmayer, Tod E ^[6]; Wijnands, Rudy ^[7]

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1. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
2. Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)
3. Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, 9 Avenue du Colonel Roche, 31028 Toulouse Cedex04 (France)
4. Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai 400005 (India)
5. Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)
6. Astrophysics Science Division, NASA/GSFC, Greenbelt, MD 20771 (United States)
7. Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH, Amsterdam (Netherlands)

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 {sup 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.

• OSTI ID: 21460150
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 720; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ASYMMETRY
BOUNDARY LAYERS
COSMIC RADIO SOURCES
ENERGY RANGE
LAYERS
LUMINOSITY
METRICS
NEUTRON STARS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PULSARS
RELATIVISTIC RANGE
SCHWARZSCHILD METRIC
SIMULATION
SPECTRA
STARS
X-RAY SPECTRA