The Incompatibility of Rapid Rotation with Narrow Photospheric X-ray Lines in EXO 0748-676
arXiv:1007.1451 · doi:10.1088/0004-637X/723/2/1053
Abstract
X-ray observations of EXO 0748-676 during thermonuclear bursts revealed a set of narrow absorption lines that potentially originate from the stellar photosphere. The identification of these lines with particular atomic transitions led to the measurement of the surface gravitational redshift of the neutron star and to constraints on its mass and radius. However, the recent detection of 552 Hz oscillations at 15% rms amplitude revealed the spin frequency of the neutron star and brought into question the consistency of such a rapid spin with the narrow width of the absorption lines. Here, we calculate the amplitudes of burst oscillations and the width of absorption lines emerging from the surface of a rapidly rotating neutron star for a wide range of model parameters. We show that no combination of neutron-star and geometric parameters can simultaneously reproduce the narrowness of the absorption lines, the high amplitude of the oscillations, and the observed flux at the time the oscillations were detected. We, therefore, conclude that the observed absorption lines are unlikely to originate from the surface of this neutron star.
arXiv commentemulateapj style, accepted by ApJ. 4 pages, 4 figures
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Cited by in corpus (16)
- Equations of state for supernovae and compact stars
- Astrophysical Measurement of the Equation of State of Neutron Star Matter
- Constraining the Neutron Star Mass-Radius Relation and Dense Matter Equation of State with NICER. I. The Millisecond Pulsar X-ray Data Set
- Surface Emission from Neutron Stars and Implications for the Physics of their Interiors
- Accretion disks and coronae in the X-ray flashlight
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- Constraints on physics of neutron stars from X-ray observations
- Gemini/GMOS Spectroscopy of EXO 0748-676 (=UY Vol) in Outburst
- On the impact of an intermediate duration X-ray burst on the accretion environment in IGR J17062-6143
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