Polarimetry of Binary Systems: Polars, Magnetic CVs, XRBs

Shahbaz, T.

doi:10.1007/978-3-030-19715-5_10

“…There is also a population of cataclysmic variables where approximately 25% of the WDs are magnetic (Ferrario et al 2015). It has long been known that a magnetic field on a WD (or other accreting body) can have a dramatic effect on accretion dynamics (e.g : Cropper 1990;Collier Cameron and Campbell 1993;King 1993;Wynn and King 1995;Schmidt et al 1999;Li and Wilson 1999;Wu 2000;Alecian et al 2007;Bouvier et al 2007;Gregory and Donati 2011;Zhilkin et al 2012;Hussain and Alecian 2014;Wickramasinghe 2014;Isakova et al 2017;Van Box Som et al 2018;Ablimit and Maeda 2019;Shahbaz 2019). Farihi et al (2017) use a model where dust is trapped in the magnetosphere of a WD to explain the observational anomaly in WD1145+017.…”

Section: Introductionmentioning

confidence: 99%

The Effect of a Magnetic Field on the Dynamics of Debris Discs Around White Dwarfs

Hogg,

Cutter,

Wynn

2020

Preprint

0

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Observational estimates of the lifetimes and inferred accretion rates from debris discs around polluted white dwarfs are often inconsistent with the predictions of models of shielded Poynting-Robertson drag on the dust particles in the discs. Moreover, many cool polluted white dwarfs do not show any observational evidence of accompanying discs. This may be explained, in part, if the debris discs had shorter lifetimes and higher accretion rates than predicted by Poynting-Robertson drag alone. We consider the role of a magnetic field on tidally disrupted diamagnetic debris and its subsequent effect on the formation, evolution, and accretion rate of a debris disc. We estimate that magnetic field strengths greater than ∼10kG may decrease the time needed for circularisation and the disc lifetimes by several orders of magnitude and increase the associated accretion rates by a similar factor, relative to Poynting-Robertson drag. We suggest some polluted white dwarfs may host magnetic fields below the typical detectable limit and that these fields may account for a proportion of polluted white dwarfs with missing debris discs. We also suggest that diamagnetic drag may account for the higher accretion rate estimates among polluted white dwarfs that cannot be predicted solely by Poynting-Robertson drag and find a dependence on magnetic field strength, orbital pericentre distance, and particle size on predicated disc lifetimes and accretion rates.

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Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038

Baglio¹,

Zelati²,

Campana³

et al. 2023

A&A

4

0

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Transitional millisecond pulsars are an emerging class of sources that link low-mass X-ray binaries to millisecond radio pulsars in binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray to optical pulsations are observed only during the high mode. The root cause of this puzzling behaviour remains elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar prototype, PSR J1023+0038, covering from the radio to X-rays. The campaign was carried out over two nights in June 2021 and involved 12 different telescopes and instruments, including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA, and FAST. By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with ALMA at the high-to-low mode switch. The pulsar is subsequently re-enshrouded, completing our picture of the mode switches.

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The effect of a magnetic field on the dynamics of debris discs around white dwarfs

Hogg

¹

,

Cutter

²

,

Wynn

³

2020

Monthly Notices of the Royal Astronomical Society

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Observational estimates of the lifetimes and inferred accretion rates from debris discs around polluted white dwarfs are often inconsistent with the predictions of models of shielded Poynting-Robertson drag on the dust particles in the discs. Moreover, many cool polluted white dwarfs do not show any observational evidence of accompanying discs. This may be explained, in part, if the debris discs had shorter lifetimes and higher accretion rates than predicted by Poynting-Robertson drag alone. We consider the role of a magnetic field on tidally disrupted diamagnetic debris and its subsequent effect on the formation, evolution, and accretion rate of a debris disc. We estimate that magnetic field strengths greater than ∼10kG may decrease the time needed for circularisation and the disc lifetimes by several orders of magnitude and increase the associated accretion rates by a similar factor, relative to Poynting-Robertson drag. We suggest some polluted white dwarfs may host magnetic fields below the typical detectable limit and that these fields may account for a proportion of polluted white dwarfs with missing debris discs. We also suggest that diamagnetic drag may account for the higher accretion rate estimates among polluted white dwarfs that cannot be predicted solely by Poynting-Robertson drag and find a dependence on magnetic field strength, orbital pericentre distance, and particle size on predicted disc lifetimes and accretion rates.

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Polarimetry of Binary Systems: Polars, Magnetic CVs, XRBs

Cited by 6 publications

References 145 publications

The Effect of a Magnetic Field on the Dynamics of Debris Discs Around White Dwarfs

The Effect of a Magnetic Field on the Dynamics of Debris Discs Around White Dwarfs

Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038

The effect of a magnetic field on the dynamics of debris discs around white dwarfs

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