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Warped Accretion Disks and Longterm X-Ray Periodicities

Published online by Cambridge University Press:  22 February 2018

W. I. Clarkson
Affiliation:
University of Southampton Open University
P. A. Charles
Affiliation:
University of Southampton
S. Laycock
Affiliation:
University of Southampton Harvard Centre for Astrophysics
M. J. Coe
Affiliation:
University of Southampton
C. Wilson-Hodge
Affiliation:
NASA/MSFC
M. D. Tout
Affiliation:
University of Southampton

Abstract

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A significant number of X-ray binaries are now known to exhibit long-term periodicities on timescales of ~10 - 100 days. Several physical mechanisms have been proposed that give rise to such periodicities, one of which is radiation-driven warping and precession of the accretion disk. Recent theoretical work predicts the stability to disk warping as a, function of the mass ratio, binary radius, viscosity and accretion efficiency. We investigate the stability of the superorbital periodicities in the neutron star X-ray binaries Cyg X-2, LMC X-4, SMC X-l and Her X-l, and thereby confront stability predictions with observation. We find that the period and nature of the superorbital variations in these sources is consistent with the predictions of warping theory.

Resumen

Resumen

En la actualidad se conoce un numero significativo de binarias de rayos X que presentan periodicidades de largo plazo en escalas do tiempo do ~10 - 100 días. Fueron propuestos varios mecanismos fisicos que dan origen a tales periodieidades, uno de los cuales es alabeo empujado por la radiación y precesión del disco de acreción. Recientes trabajos teórioos predicen la estabilidad del alabeo del disco como una función del cociente do masa, radio binario, viscosidad y eficiencia do acreción. Investigamos la estabilidad de las periodicidades superorbitales en las binarias do rayos X de estrellas do neutrones Cyg X-2, LMC X-4, SMC X-l y Her X-l, confrontando las prediccioncs do estabilidad con las observaciones. Encontramos que el período y la naturaleza de las variaciones superorbitales son consistentes en estas fuentes con las predicciones de la teoría de distorsión.

Type
The Contributed Papers
Copyright
Copyright © Instituto de astronomia/revista mexicana de astronomίa y astrofίsica 2004

References

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