A Minimal Timescale for the Continuum in 4U 1608-52 and Aql X-1

TL;DR

This paper identifies a minimal timescale for state transitions in neutron-star X-ray binaries 4U 1608-52 and Aql X-1 using wavelet analysis, revealing a strong correlation with spectral timescales, aiding understanding of accretion processes.

Contribution

It introduces a novel wavelet-based method to determine minimal transition timescales in neutron-star X-ray binaries and demonstrates their correlation with spectral timescales.

Findings

Strong positive correlation between minimal timescale and spectral timescale

Wavelet analysis effectively captures transition dynamics

Provides a new quantitative measure for state transition timescales

Abstract

Similar to black-hole X-ray binary (BHXRB) transients, hysteresis-like state transitions are also seen in some neutron-star X-ray binaries (NSXRBs). Using a method based on wavelets and lightcurves constructed from archival RXTE observations, we extract a minimal timescale over the complete range of transitions for 4U 1608-52 during the 2002 and 2007 outbursts and the 1999 and 2000 outbursts for Aql X-1. We present evidence for a strong positive correlation between this minimal timescale and a similar timescale extracted from the corresponding power spectra of these sources.