Centrifugal breakout reconnection as the electron acceleration mechanism powering the radio magnetospheres of early-type stars

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Author(s)Owocki, S. P.
Author(s)Shultz, M. E.
Author(s)ud-Doula, A.
Author(s)Chandra, P.
Author(s)Das, B.
Author(s)Leto, P.
Date Accessioned2022-06-24T17:42:33Z
Date Available2022-06-24T17:42:33Z
Publication Date2022-04-27
DescriptionThis article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved. The version of record is available at: https://doi.org/10.1093/mnras/stac341en_US
AbstractMagnetic B-stars often exhibit circularly polarized radio emission thought to arise from gyrosynchrotron emission by energetic electrons trapped in the circumstellar magnetosphere. Recent empirical analyses show that the onset and strength of the observed radio emission scale with both the magnetic field strength and the stellar rotation rate. This challenges the existing paradigm that the energetic electrons are accelerated in the current sheet between opposite-polarity field lines in the outer regions of magnetized stellar winds, which includes no role for stellar rotation. Building on recent success in explaining a similar rotation-field dependence of H α line emission in terms of a model in which magnetospheric density is regulated by centrifugal breakout (CBO), we examine here the potential role of the associated CBO-driven magnetic reconnection in accelerating the electrons that emit the observed gyrosynchrotron radio. We show in particular that the theoretical scalings for energy production by CBO reconnection match well the empirical trends for observed radio luminosity, with a suitably small, nearly constant conversion efficiency ϵ ≈ 10−8. We summarize the distinct advantages of our CBO scalings over previous associations with an electromotive force, and discuss the potential implications of CBO processes for X-rays and other observed characteristics of rotating magnetic B-stars with centrifugal magnetospheres.en_US
SponsorMES acknowledges the financial support provided by the Annie Jump Cannon Fellowship, supported by the University of Delaware and endowed by the Mount Cuba Astronomical Observatory. AuD acknowledges support by NASA through Chandra Award 26 number TM1-22001B issued by the Chandra X-ray Observatory 27 Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. PC and BD acknowledge support of the Department of Atomic Energy, Go v ernment of India, under project no. 12-R&D-TFR-5.02-0700.en_US
CitationS P Owocki, M E Shultz, A ud-Doula, P Chandra, B Das, P Leto, Centrifugal breakout reconnection as the electron acceleration mechanism powering the radio magnetospheres of early-type stars, Monthly Notices of the Royal Astronomical Society, Volume 513, Issue 1, June 2022, Pages 1449–1458, https://doi.org/10.1093/mnras/stac341en_US
ISSN1365-2966
URLhttps://udspace.udel.edu/handle/19716/31028
Languageen_USen_US
PublisherMonthly Notices of the Royal Astronomical Societyen_US
Keywordsmagnetic reconnectionen_US
Keywordsstars: early typeen_US
Keywordsstars: magnetic fielden_US
Keywordsstars: rotationen_US
Keywordsradio continuum: starsen_US
TitleCentrifugal breakout reconnection as the electron acceleration mechanism powering the radio magnetospheres of early-type starsen_US
TypeArticleen_US
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