Hardness Ratio Estimation in Low Counting X-ray Photometry

Abstract

Hardness ratios are commonly used in X-ray photometry to indicate spectral properties roughly. It is usually defined as the ratio of counts in two different wavebands. This definition, however, is problematic when the counts are very limited. Here we instead define hardness ratio using the $\lambda$ parameter of Poisson processes, and develop an estimation method via Bayesian statistics. Our Monte Carlo simulations show the validity of our method. Based on this new definition, we can estimate the hydrogen column density for the photoelectric absorption of X-ray spectra in the case of low counting statistics.

12 pages, 4 figures, 1 table. Originally submitted on 29-03-2006, and accepted on 24-08-2006 for publication in The Astrophysical Journal

References in corpus (4)

• Bayesian Estimation of Hardness Ratios: Modeling and Computations
• Analysis of Energy Spectra with Low Photon Counts via Bayesian Posterior Simulation
• Properties of the Chandra Sources in M81
• Chandra Observations of Diffuse Gas and Luminous X-ray Sources Around the X-ray Bright Elliptical NGC 1600

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