Long-Term Optical∕X-ray Variability of CVs, LMXBs and BeX Sources

Charles, P. A.; Kotze, M.; Rajoelimanana, Andry

doi:10.1063/1.3536392

Cited by 3 publications

(3 citation statements)

References 18 publications

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“…Farrell, Barret & Skinner 2009). Most recently, superorbital behaviour and the various mechanisms proposed to account for it, have been summarised in Charles et al (2008Charles et al ( , 2010.…”

Section: Long-term Variationsmentioning

confidence: 99%

Characterizing X-ray binary long-term variability

Kotze

Charles

2011

Monthly Notices of the Royal Astronomical Society

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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

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Section: Long-term Variationsmentioning

confidence: 99%

Characterizing X-ray binary long-term variability

Kotze

Charles

2011

Monthly Notices of the Royal Astronomical Society

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“…As suggested by X-ray monitoring datasets on timescales of years-decades, a number of X-ray binaries are now suspected to undergo accretion disc warping, in which the accretion E-mail: kcdage@msu.edu disc warps out of the plane and may precess, giving rise to observed high/low cycles in X-ray brightness on a timescale of tens of days (e.g. Charles et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Longterm properties of accretion discs in X-ray Binaries - III. A search for spin-superorbital correlation in SMC X-1

Dage

Clarkson

Charles

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Thanks to long-term X-ray monitoring, a number of interacting binaries are now known to show X-ray periodicities on timescales of tens to hundreds of binary orbits. In some systems, precession of a warped accretion disc is the leading model to explain the superorbital modulation. The High Mass X-ray Binary SMC X-1 showed two excursions in superorbital period (from ∼60 d to ∼45 d) during the 1996-2011 interval, suggesting that some characteristic of the accretion disc is varying on a timescale of years. Because its behaviour as an X-ray pulsar has also been intensively monitored, SMC X-1 offers the rare chance to track changes in both the accretion disk and pulsar behaviours over the same interval. We have used archival X-ray observations of SMC X-1 to investigate whether the evolution of its superorbital variation and pulse period are correlated. We use the 16-year dataset afforded by the RXTE All-Sky Monitor to trace the behaviour of the warped accretion disc in this system, and use published pulse-period histories to trace the behaviour of the pulsar. While we cannot claim a strong detection of correlation, the first superorbital period excursion near MJD 50,800 does coincide with structure in SMC X-1's pulse period history. Our preferred interpretation is that the superorbital period excursion coincides with a change in the long-term spin-up rate of the SMC X-1 pulsar. In this scenario, the pulsar and the accretion disc are both responding to a change in the accretion flow, which the disc itself may regulate.

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“…Whilst the spin and orbital periods have been known for many of them ever since their discovery, it is now becoming clear that many, if not all, display so-called "super-orbital" modulations on time-scales of months to years, and that these modulations can occur for different reasons-as summarised by Charles et al (2010) in their Table 1. These will be used as examples of the kind of science that these monitoring facilities can undertake.…”

Section: Introductionmentioning

confidence: 99%

Long-term Monitoring with Small and Medium-sized Telescopes on the Ground and in Space

2011

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Abstract. The last 20 years have seen revolutionary developments of large-scale synoptic surveys of the sky, both from the ground (e.g., the MACHO and OGLE projects, which were targetted at micro-lensing studies) and in space (e.g., the X-ray All-Sky Monitor onboard RXTE). These utilised small and medium-sized telescopes to search for transient-like events, but they have now built up a huge database of long-term light-curves, thereby enabling archival research on a wide range of objects that has not been possible hitherto. This is illustrated with examples of long time-scale optical and X-ray variability studies from the field of X-ray binary research: the high-mass BeX binaries in the SMC (using MACHO and OGLE), and the bright galactic-bulge X-ray sources (mostly LMXBs, using RXTE/ASM). As such facilities develop greater capabilities in future and at other wavelengths (developments in South Africa will be described), real-time data processing will allow much more rapid follow-up studies with the new generation of queue-scheduled large telescopes such as SALT.

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Long-Term Optical∕X-ray Variability of CVs, LMXBs and BeX Sources

Cited by 3 publications

References 18 publications

Characterizing X-ray binary long-term variability

Characterizing X-ray binary long-term variability

Longterm properties of accretion discs in X-ray Binaries - III. A search for spin-superorbital correlation in SMC X-1

Long-term Monitoring with Small and Medium-sized Telescopes on the Ground and in Space

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