Modelling RXTE/ASM observations of the 35-d cycle in Her X-1

Leahy, D. A.

doi:10.1046/j.1365-8711.2002.05547.x

Cited by 45 publications

(86 citation statements)

References 16 publications

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“…In the X-ray band, the eclipse of the NS in Her X-1 lasts for about 0.15 P orb (e.g., Leahy 2002). In the ASM/RXTE data, the periodicity of these eclipses creates a scatter uniformly distributed in time.…”

Section: Discussionmentioning

confidence: 99%

“…Her X-1 usually resides in the so-called active state when it displays strong variations of X-ray intensity with a superorbital cycle length P C of approximately 35 days (about 20 times longer than its P orb ). In the active state, the X-ray light curve of Her X-1 contains only two segments of the On state (Main-On and Short-On) during a single epoch of the superorbital cycle (e.g., Tananbaum et al 1972;Giacconi et al 1973;Leahy 2002;Staubert et al 2013). The durations of the Main-On and ShortOn states are about ∼10 and 5 days, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…According to Scott et al (2000), this body consists of the composite pencil beam and fan beam emission from the accretion column. Leahy (2002) showed that the inner disk region also contributes. Evolution of the 35 day cycle, measured by the turn-on times of the Main-On state, is correlated with that of the spin period P spin of the NS.…”

Section: Introductionmentioning

confidence: 99%

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Long-Term Evolution of the Main-on States in Hercules X-1

Šimon

2015

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Rossi X-ray Timing Explorer All-sky Monitor (RXTE ASM) observations and American Association of Variable Star Observers (AAVSO) optical data were used for a time-series analysis of the long-term activity of Her X-1. The problem of measuring the long-term evolution of the X-ray intensity in the light curve which consists only of separated intense spikes was addressed. For this purpose, the fluence of each Main-On state was determined. The fluences vary generally (not only in the transitions into/from anomalous low states (ALSs)) by tens of percent on timescales of at least several epochs of the cycle length of the superorbital cycle (but without any stable cycle) while irradiation of the donor producing the optical modulation remains considerably more stable. ALS1 and ALS2 are extensions of the tail in the statistical distribution of these fluences. In this interpretation, the variations of the fluences are caused by the changes of the structure of the inner disk region, which produces variable obscuration of the beams (emitting in the ASM band) at the neutron star. A small change of obscuration of these beams by the inner disk region suffices to change the fluences largely. However, the irradiation of the donor is changed significantly less because this inner disk region (which emits beyond the ASM band and acts as the occulting region of the beams) also irradiates the donor.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long-Term Evolution of the Main-on States in Hercules X-1

Šimon

2015

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“…[28,14]). On and Off-states do not form a clear profile of the long-term light curve in the ASM/RXTE data; only two anomalous low states ALS1 and ALS2 in which I sum was below the detection limit can be resolved.…”

Section: Activity In Her X-1mentioning

confidence: 99%

The X-Ray Binary KS 1731{260: Possible Analogy with Her X-1

Šimon

2014

APP

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The X-ray binary with the neutron star (NS), KS 1731-260, displays superorbital cycle similar to that in Her X-1. The accretion disk had the memory of the cycle-length even when this modulation sometimes disappeared in the main outburst of KS 1731-260, and during anomalous low state in Her X-1. The disk still existed during such seasons. Although irradiation of the disk by X-rays is a viable explanation for the disk precession and warping (see model of Foulkes et al.), the mechanisms which give rise to the observed X-ray modulation are quite different for each of these systems. Variable absorption can explain this cycle only in Her X-1. We propose a variable mass accretion rate onto the NS in KS 1731-260 due to a highly variable impact of the inflowing mass stream with the changing phase of the cycle.

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“…The twisted-tilted disk model put forward by Petterson(1975), had its geometry determined in detail by Leahy(2002) curve. This same disk also gives the changes of the X-ray pulse profile over 35-day cycle as shown by Scott et al(2000).…”

Section: -Day Cycle and Accretion Diskmentioning

confidence: 99%

Accretion disk and stream origin of the dip phenomenon in Hercules X-1

Leahy

Igna²

2012

Proc. IAU

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Abstract. The Rossi X-ray Timing Explorer has observed Hercules X-1 over a period of about 13 years, allowing detailed measurement of the properties of the dip phenomenon. We construct a model for the dips based on the impact between the accretion stream and the disk, including the geometry and dynamics of the stream and disk. We also consider the case where the stream penetrates the outer parts of the disk, where its density is low, and proceeds to a second impact at smaller radius in the disk. The results from the model are discussed and compared to the observed properties of the dips.

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Modelling RXTE/ASM observations of the 35-d cycle in Her X-1

Cited by 45 publications

References 16 publications

Long-Term Evolution of the Main-on States in Hercules X-1

Long-Term Evolution of the Main-on States in Hercules X-1

The X-Ray Binary KS 1731{260: Possible Analogy with Her X-1

Accretion disk and stream origin of the dip phenomenon in Hercules X-1

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