Document Type

Article

Publication Date

9-4-2018

Publication Title

Monthly Notices of the Royal Astronomical Society

Volume

481

Issue

2

First page number:

2628

Last page number:

2645

Abstract

Magnetic, radiation pressure, and thermal driving are the three mechanisms capable of launching accretion disc winds. In X-ray binaries, radiation pressure is often not significant, as in many systems the luminosity is too low for driving due to continuum transitions yet too high for driving due to line transitions. This leaves thermal and magnetic driving as the contender launching mechanisms in these systems. Using ATHENA++, we perform axisymmetric ideal MHD simulations that include radiative heating and cooling processes appropriate for Compton heated winds to show that the inclusion of magnetic fields into a thermally driven wind has the opposite effect of what one might expect: rather than provide a velocity boost, the thermal wind is suppressed in low-plasma beta regions where the field lines are strong enough to reshape the direction of the flow. Our analysis reveals that magneto-centrifugal launching is present but weak, while the reduction in wind velocity is not due to the change in gravitational potential through the magnetically imposed streamline geometry, but rather due to the increased flow tube area just above the surface of the disc, which is less conducive to acceleration. Our results suggest that for magnetothermal wind models to be successful at producing fast dense outflows in low-mass X-ray binaries, the winds must be magnetically launched well within the Compton radius.

Keywords

MHD; Stars: Winds, outflow; X-rays: Binaries

Disciplines

Astrophysics and Astronomy

File Format

PDF

File Size

11.789 Kb

Language

English

Permissions

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society©: 2018 [owner as specified on the article] Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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