Characterizing X-ray binary long-term variability

Abstract

Long-term ("superorbital") periods or modulations have been detected in a wide variety of both low and high-mass X-ray binaries at X-ray and optical wavelengths. A variety of mechanisms have been proposed to account for the variability properties, such as precessing and/or warped accretion discs, amongst others. The All Sky Monitor on board the Rossi X-ray Timing Explorer provides the most extensive (~15 years) and sensitive X-ray archive for studying such behaviour. It is also clear that such variations can be intermittent and/or a function of X-ray spectral state. Consequently, we use a time-dependent Dynamic Power Spectrum method to examine how these modulations vary with time in 25 X-ray binaries for which superorbital periodicities have been previously reported. Our aim is to characterize these periodicities in a completely systematic way. Some (such as Her X-1 and LMC X-4) are remarkably stable, but others show a range of properties, from even longer variability time-scales to quite chaotic behaviour.Comment: 17 pages, 26 figures, 4 tables, Accepted for publication in MNRAS on 4 November 201

A systematic search for periodicities of X-ray binaries in the Swift BAT data

“…Several orbital periods are detected, confirming the detections by [7] in BAT data and by [4], [6] in…”

“…1), confirming the suggestions by [4], [6] -The Rapid Burster (X1730-333) is a neutron star system in the globular cluster Liller 1. It shows outburst with a variable recurrence time, about 200 days or 100 days.…”

“…in both archives confirms the detection by [7] in the BAT data and by [4], [6] in the ASM data -SS 433 is a peculiar source, showing two jets in opposite directions with a β factor of 0.26 and precessing with a period of about 164 days [4]; the orbital period is about 13 days; the analysis of the present paper detects both periodicities in BAT data -During the INTEGRAL scans of the Galactic plane, several highly absorbed HMXB systems have been discovered, after the detection of the first system IGR J16318-4848 [13]: IGR J16320-4751 (AX J1631.9-4752), IGR J16393-4641, IGR J16465-4507, IGR J16479-4514, IGR J16493-4348, IGR J 18027-2016 [14]. The physical characteristics of these system are more easily investigated at higher energies.…”

“…-SMC X-1 shows the orbital periods in both data sets, as in [4]; in addition, there is a superorbital quasi periodicity peaked at about 56 days, confirming the suggestion by [4], [6] PoS(SWIFT 10)157…”

“…The initial searches for periodicities in the X-ray time series have been involving a few sources at a time. Recently, extensive investigations have been presented by [4], [5], [6] using the RXTE ASM data. Some X-ray binaries observed with Swift BAT have been investigated by [7].…”