Simulation of the visual light curve of CAL 87

Schandl, S.; Meyer-Hofmeister, E.; Meyer, F.

doi:10.1007/bfb0102246

Cited by 115 publications

(197 citation statements)

References 18 publications

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“…For details of such models and corresponding parameters see e.g. Schandl & Meyer (1994); Wijers & Pringle (1999); Scott et al (2000); Leahy (2002). It is then natural to assume that the disk is also responsible for the changing pulse profile shape, with the inner edge, precessing with the same period as the outer edge (and all other rings), being the prime candidate.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to initial conditions (e.g. the relative orientation of neutron star spin and orbital angular momentum at birth of the X-ray binary), the existence of internal forces on the accretion disk, like coronal winds (Schandl & Meyer 1994), radiation pressure (Pringle 1996;Wijers & Pringle 1999), or the impact of the accretion stream (Shakura et al 1999) have been proposed to produce and maintain the observed configuration. 2.…”

Section: Discussionmentioning

confidence: 99%

“…The 35-day modulation of the X-ray flux is generally explained by the precession of the accretion disk, which quasiregularly blocks the line of sight to the X-ray emitting regions near the magnetic poles of the neutron star (Gerend & Boynton 1976;Schandl & Meyer 1994). The resulting clock, however, is irregular, showing deviations from regularity of up to ±10 d. This is generally demonstrated by the (O-C) (observed-minuscalculated) diagram (see Fig.…”

Section: Introductionmentioning

confidence: 94%

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Variable pulse profiles of Hercules X-1 repeating with the same irregular 35 d clock as the turn-ons

Staubert¹,

Klochkov²,

Vasco³

et al. 2013

A&A

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The accreting X-ray pulsar Her X-1 shows two types of long-term variations, both with periods of ∼35 days: 1) turn-on cycles, a modulation of the flux, with a ten-day long main-on and a five-day long short-on, separated by two off-states, and 2) a systematic variation in the shape of the 1.24 s pulse profile. While there is general consensus that the flux modulation is due to variable shading of the X-ray emitting regions on the surface of the neutron star by the precessing accretion disk, the physical reason for the variation in the pulse profiles has remained controversial. Following the suggestion that free precession of the neutron star may be responsible for the variation in the pulse profiles, we developed a physical model of strong feedback interaction between the neutron star and the accretion disk in order to explain the seemingly identical values for the periods of the two types of variations, which were found to be in basic synchronization. In a deep analysis of pulse profiles observed by several different satellites over the last three decades we now find that the clock behind the pulse profile variations shows exactly the same erratic behavior as the turn-on clock, even on short time scales (a few 35 d cycles), suggesting that there may in fact be only one 35 d clock in the system. If this is true, it raises serious questions with respect to the idea of free precession of the neutron star, namely how the neutron star can change its precessional period every few years by up to 2.5% and how the feedback can be so strong, such that these changes can be transmitted to the accretion disk on rather short time scales.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

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Variable pulse profiles of Hercules X-1 repeating with the same irregular 35 d clock as the turn-ons

Staubert¹,

Klochkov²,

Vasco³

et al. 2013

A&A

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“…This modulation is the best evidence for an inclined, precessing, and warped accretion disk in an X-ray binary system. The origin of the warping is not yet fully understood, but may be caused either by radiation driven accretion disk winds (Schandl & Meyer 1994) or by radiation pressure (Maloney & Begelman 1997). The precessing motion of the disk can be understood in the context of tidal interaction and/or as a consequence of non vanishing torques acting on the disk, e.g.…”

Section: Introductionmentioning

confidence: 99%

Probing the outer edge of an accretion disk: a Her X-1 turn-on observed withRXTE

Kuster

Wilms

Staubert

et al. 2005

A&A

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We present the analysis of Rossi X-ray Timing Explorer (RXTE) observations of the turn-on phase of a 35 day cycle of the X-ray binary Her X-1. During the early phases of the turn-on, the energy spectrum is composed of X-rays scattered into the line of sight plus heavily absorbed X-rays. The energy spectra in the 3-17 keV range can be described by a partial covering model, where one of the components is influenced by photoelectric absorption and Thomson scattering in cold material plus an iron emission line at 6.5 keV. In this paper we show the evolution of spectral parameters as well as the evolution of the pulse profile during the turn-on. We describe this evolution using Monte Carlo simulations which self-consistently describe the evolution of the X-ray pulse profile and of the energy spectrum.

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“…Crosa & Boynton (1980) found that the average mass transfer rate to the outer rim of the accretion disk is somewhat larger than that required to maintain the observed X-ray luminosity. In the model of Schandl & Meyer (1994), the disk wind results from irradiation of the disk by the central source. Vrtilek et al (2001) and Boroson et al (2001) found signatures of outflowing gas in the UV spectrum of the system.…”

Section: Evidence For the Coronal Mass Ejectionmentioning

confidence: 99%

Continuous monitoring of pulse period variations in Hercules X-1 usingSwift/BAT

Klochkov¹,

Staubert²,

Постнов³

et al. 2009

A&A

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Context. Monitoring of pulse period variations in accreting binary pulsars is an important tool to study the interaction between the magnetosphere of the neutron star and the accretion disk. While the X-ray flux of the brightest X-ray pulsars have been successfully monitored over many years (e.g. with RXTE/ASM, CGRO/BATSE, Swift/BAT), the possibility to monitor their pulse timing properties continuously has so far been very limited. Aims. In our work we show that the Swift/BAT observations can be used to monitor coherent pulsations of bright X-ray sources and use Swift archival data to study one of the most enigmatic X-ray pulsars, Hercules X-1. A quasi-continuous monitoring of the pulse period and the pulse period derivative of an X-ray pulsar, here Her X-1, is achieved over a long time ( 4 yr). We compare our observational results with predictions of accretion theory and use them to test different aspects of the physical model of the system. Methods. In our analysis we use the data accumulated with Swift/BAT starting from the beginning of 2005 (shortly after launch) until the present time. To search for pulsations and for their subsequent analysis we used the count rate measured by the BAT detector in the entire field of view. Results. The slope of the correlation between the locally determined spin-up rate and the X-ray luminosity is measured for Her X-1 and found to be in agreement with predictions of basic accretion torque theory. The observed behaviour of the pulse period together with the previously measured secular decrease of the system's orbital period is discussed in the framework of a model assuming ejection of matter close to the inner boundary of the accretion disk.

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Simulation of the visual light curve of CAL 87

Cited by 115 publications

References 18 publications

Variable pulse profiles of Hercules X-1 repeating with the same irregular 35 d clock as the turn-ons

Variable pulse profiles of Hercules X-1 repeating with the same irregular 35 d clock as the turn-ons

Probing the outer edge of an accretion disk: a Her X-1 turn-on observed withRXTE

Continuous monitoring of pulse period variations in Hercules X-1 usingSwift/BAT

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