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X-Ray Variability Coherence: How to Compute It, What It Means, and How It Constrains Models of GX 339-4 and Cygnus X-1

Vaughan, Brian A. and Nowak, Michael A. (1997) X-Ray Variability Coherence: How to Compute It, What It Means, and How It Constrains Models of GX 339-4 and Cygnus X-1. Astrophysical Journal Letters, 474 (1). L43-L46. ISSN 2041-8205. http://resolver.caltech.edu/CaltechAUTHORS:20141203-111905220

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Abstract

We describe how the coherence function—a Fourier frequency–dependent measure of the linear correlation between time series measured simultaneously in two energy channels—can be used in conjunction with energy spectra, power spectra, and time delays between energy channels to constrain models of the spectrum and variability of X-ray binaries. Here we present a procedure for estimating the coherence function in the presence of counting noise. We apply this method to the black hole candidates Cyg X-1 and GX 33924 and find that the near-perfect coherence between low- and high-energy X-ray photons rules out a wide range of models that postulate spatially extended fluctuating emission, thermal flares, and overlapping shot noise.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1086/310430DOIArticle
http://adsabs.harvard.edu/abs/1997ApJ...474L..43VADSArticle
Additional Information:Copyright 1997. American Astronomical Society. The authors would like to acknowledge useful conversations with Peter Michelson, Michiel van der Klis, Mitch Begelman, James Dove, and John Wilms, as well as generous support from NASA grants NAG 5-3239 (B. A. V.) and NAG 5-3225 (M. A. N.) and the Netherlands Organization for Scientific Research (NWO) under grant PGS 78-277.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANAG5-3239
NASANAG5-3225
Non-Subject Keywords:BLACK HOLE PHYSICS, METHODS: STATISTICAL, X-RAYS: STARS, Black Hole Physics, Methods: Statistical, X-Rays: Stars
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1997-54
Record Number:CaltechAUTHORS:20141203-111905220
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141203-111905220
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52330
Collection:CaltechAUTHORS
Deposited By: Deborah Miles
Deposited On:08 Dec 2014 02:49
Last Modified:08 Dec 2014 02:49

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