Are Coronae of Magnetically Active Stars Heated by Flares? III. Analytical Distribution of Superimposed Flares

Abstract

(abridged) We study the hypothesis that observed X-ray/extreme ultraviolet emission from coronae of magnetically active stars is entirely (or to a large part) due to the superposition of flares, using an analytic approach to determine the amplitude distribution of flares in light curves. The flare-heating hypothesis is motivated by time series that show continuous variability suggesting the presence of a large number of superimposed flares with similar rise and decay time scales. We rigorously relate the amplitude distribution of stellar flares to the observed histograms of binned counts and photon waiting times, under the assumption that the flares occur at random and have similar shapes. Applying these results to EUVE/DS observations of the flaring star AD Leo, we find that the flare amplitude distribution can be represented by a truncated power law with a power law index of 2.3 +/- 0.1. Our analytical results agree with existing Monte Carlo results of Kashyap et al. (2002) and Guedel et al. (2003). The method is applicable to a wide range of further stochastically bursting astrophysical sources such as cataclysmic variables, Gamma Ray Burst substructures, X-ray binaries, and spatially resolved observations of solar flares.

accepted for publication in ApJ

References in corpus (4)

• Are Coronae of Magnetically Active Stars Heated by Flares? II. EUV and X-Ray Flare Statistics and the Differential Emission Measure Distribution
• X-Ray Evidence for Flare Density Variations and Continual Chromospheric Evaporation in Proxima Centauri
• Flare Heating in Stellar Coronae
• Separating the X-Ray Emissions of UV Ceti A and B with Chandra

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• GALEX high time-resolution ultraviolet observations of dMe flare events
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• A common stochastic process rules gamma-ray burst prompt emission and X-ray flares
• Statistical Signatures of Nanoflare Activity. I. Monte Carlo Simulations and Parameter-space Exploration
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