Wavelet Denoising and Flare Detection in X-Ray All-Sky Monitor Data

Recent techniques in wavelet analysis are applied to X-ray all-sky monitor data from the Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM) and the Swift Burst Alert Telescope (BAT) in order to characterize flaring activity and variability of potential neutrino sources. A flexible technique has been developed based on wavelet outlier detection methods and a Poisson burst model thresholding prescription. Outliers can be detected by correlating the highest level of a thresholded multi-resolution wavelet decomposition with the time series data points represented. This method can be used to determine flare duration and timing for use with a neutrino multi-messenger analysis, but could also be applied to a variety of astronomical time series problems.

The denoising process is used to remove background noise from an ASM data set to simplify variability studies. Results from an example source are presented to show the effectiveness of the wavelet methods. The results of a future flare detection analysis will be applied to neutrino candidates from the Antarctic Muon and Neutrino Detector Array (AMANDA) and IceCube telescopes to reduce background and to investigate time correlations in order to search for neutrino point sources. Objects of interest for future study include BL Lac objects, flat-spectrum radio quasars, and microquasars.