The Annals of Applied Statistics

Detecting abrupt changes in the spectra of high-energy astrophysical sources

Raymond K. W. Wong, Vinay L. Kashyap, Thomas C. M. Lee, and David A. van Dyk

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Variable-intensity astronomical sources are the result of complex and often extreme physical processes. Abrupt changes in source intensity are typically accompanied by equally sudden spectral shifts, that is, sudden changes in the wavelength distribution of the emission. This article develops a method for modeling photon counts collected from observation of such sources. We embed change points into a marked Poisson process, where photon wavelengths are regarded as marks and both the Poisson intensity parameter and the distribution of the marks are allowed to change. To the best of our knowledge, this is the first effort to embed change points into a marked Poisson process. Between the change points, the spectrum is modeled nonparametrically using a mixture of a smooth radial basis expansion and a number of local deviations from the smooth term representing spectral emission lines. Because the model is over-parameterized, we employ an $\ell_{1}$ penalty. The tuning parameter in the penalty and the number of change points are determined via the minimum description length principle. Our method is validated via a series of simulation studies and its practical utility is illustrated in the analysis of the ultra-fast rotating yellow giant star known as FK Com.

Article information

Ann. Appl. Stat., Volume 10, Number 2 (2016), 1107-1134.

Received: August 2015
Revised: December 2015
First available in Project Euclid: 22 July 2016

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Astronomy change point estimation FK Comae Berenices marked poisson process minimum description length principle semi-parametric modeling stars stellar coronae stellar flare X-ray astronomy


Wong, Raymond K. W.; Kashyap, Vinay L.; Lee, Thomas C. M.; van Dyk, David A. Detecting abrupt changes in the spectra of high-energy astrophysical sources. Ann. Appl. Stat. 10 (2016), no. 2, 1107--1134. doi:10.1214/16-AOAS933.

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