Estimation of plasma parameters in an accretion column near the surface of accreting white dwarfs from their flux variability

Семена, А. Н.; Revnivtsev, M.

doi:10.1134/s1063773712050076

Cited by 9 publications

(5 citation statements)

References 24 publications

(11 reference statements)

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“…Basko & Sunyaev 1976;Ghosh & Lamb 1978, 1979Campbell 1992;Shu et al 1994;Lovelace et al 1995) the width of the transition region remains uncertain, and until recently could not be estimated observationally. A method to estimate the thickness of the transition region based on measurements of the cooling time of matter in the accretion column has been proposed for magnetic white dwarfs (Semena & Revnivtsev 2012;Semena et al 2014). The inferred plasma penetration depth at the boundary of the magnetosphere is in general agreement with earlier theoretical (Shu et al 1994;Lovelace et al 1995).…”

Section: Interaction Between Ns Magnetosphere and Accretion Flowsupporting

confidence: 63%

Magnetic Fields of Neutron Stars in X-Ray Binaries

Revnivtsev

Mereghetti

2016

The Strongest Magnetic Fields in the Universe

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A substantial fraction of the known neutron stars resides in X-ray binaries -systems in which one compact object accretes matter from a companion star. Neutron stars in X-ray binaries have magnetic fields among the highest found in the Universe, spanning at least the range from ∼ 10 8 to several 10 13 G. The magnetospheres around these neutron stars have a strong influence on the accretion process, which powers most of their emission. The magnetic field intensity and geometry, are among the main factors responsible for the large variety of spectral and timing properties observed in the X-ray energy range, making these objects unique laboratories to study the matter behavior and the radiation processes in magnetic fields unaccessible on Earth. In this paper we review the main observational aspects related to the presence of magnetic fields in neutron star X-ray binaries and some methods that are used to estimate their strength.

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Section: Interaction Between Ns Magnetosphere and Accretion Flowsupporting

confidence: 63%

Magnetic Fields of Neutron Stars in X-Ray Binaries

Revnivtsev

Mereghetti

2016

The Strongest Magnetic Fields in the Universe

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“…The innermost and densest parts of the flow penetrate through the magnetic field and form the innermost parts of the magnetosphere. However, all these separate streams should merge near the magnetic poles and form the accretion columns or curtains at the surface of the white dwarf [41]. This scenario for the formation of hierarchial magnetospheres in polars differs appreciably from the classical picture; taking this into account can affect the results of analyses and the interpretation of observations.…”

Section: Discussionmentioning

confidence: 99%

Features of the Flow Structure in the Vicinity of the Inner Lagrangian Point in Polars

2018

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The structures of plasma flows in close binary systems whose accretors have strong intrinsic magnetic fields are studied. A close binary system with the parameters of a typical polar is considered. The results of three dimensional numerical simulations of the material flow from the donor into the accretor Roche lobe are presented. Special attention is given to the flow structure in the vicinity of the inner Lagrangian point, where the accretion flow is formed. The interaction of the accretion flow material from the envelope of the donor with the magnetic field of the accretor results in the formation of a hierarchical structure of the magnetosphere, because less dense areas of the accretion flow are captured by the magnetic field of the white dwarf earlier than more dense regions. Taking into account this kind of magnetosphere structure can affect analysis results and interpretation of the observations. * isakovapb@inasan.ru

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“…1). Our simulations also show that the smearing of the variability take place exactly on the plasma cooling time scale, which is proportional to the specific accretion rate in the accretion columnṀ/A, where A is accretion column footprint area andṀ is accretion rate on to the WD surface (Semena & Revnivtsev, 2012). Thus the specific accretion rate for IPs can be measured by the analysis of a variability of their luminosity.…”

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confidence: 84%

Assessment the area of accretion curtains from fast aperiodic time variability of Intermediate Polars

Семена¹,

Revnivtsev²,

Buckley³

2017

Proceedings of the Golden Age of Cataclysmic Variables and Related Objects - III — PoS(Golden2015)

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Results of a study of the fast timing variability of the magnetic cataclysmic variable (mCV) EX Hya are presented. It was shown that one may expect the rapid flux variability of mCVs to be smeared out at timescales shorter than the cooling time of hot plasma in the post shock region of the accretion curtain near the WD surface. Estimates of the cooling time and the mass accretion rate, thus provide us with a tool to measure the density of the post-shock plasma and the crosssectional area of the accretion funnel at the WD surface. We have probed the high frequencies in the aperiodic noise of one of the brightest mCV EX Hya with the help of optical telescopes, namely SALT and the SAAO 1.9m telescope. We place upper limits on the plasma cooling timescale τ < 0.3 sec, on the fractional area of the accretion curtain footprint f < 1.6 × 10 −4 , and a lower limit on the specific mass accretion rateṀ/A > 3 g sec −1 cm −2 . We show that measurements of accretion column footprints via eclipse mapping highly overestimate their areas. From the measurements we estimate an upper limit to the penetration depth of the accretion disk plasma at the magnetosphere boundary δ r/r < 10 3

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Estimation of plasma parameters in an accretion column near the surface of accreting white dwarfs from their flux variability

Cited by 9 publications

References 24 publications

Magnetic Fields of Neutron Stars in X-Ray Binaries

Magnetic Fields of Neutron Stars in X-Ray Binaries

Features of the Flow Structure in the Vicinity of the Inner Lagrangian Point in Polars

Assessment the area of accretion curtains from fast aperiodic time variability of Intermediate Polars

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