A systematic periodicity and time-variable modulation search in RXTE ASM data : methods, findings, and implications for astrophysical X-ray sources

Abstract

In this work, we present the results of a general search for periodicities and for time-variable modulation strength in X-ray sources using data from the All-Sky Monitor onboard the Rossi X-ray Timing Explorer. New findings, including a sharp increase in the modulation of the X-ray flux from the Galactic bulge low-mass X-ray binary GX 9+9 and the recent spin-down event of the pulsar in the high-mass X-ray binary X0114+650, are reported. These searches employed new methods of periodicity detection that employed an algorithm to reduce the effects of low frequency noise from X-ray sources. We discuss these methods and show how they can be used to enhance the signal-to-noise ratio in the Fourier domain for many sources.