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Accepted manuscript

VAST-MeMeS: Characterising non-thermal radio emission from magnetic massive stars using the Australian SKA Pathfinder

Published online by Cambridge University Press:  09 October 2025

Barnali Das*
Affiliation:
CSIRO, Space and Astronomy, P.O. Box 1130, Bentley WA 6102, Australia
Laura N. Driessen
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney, New South Wales 2006, Australia
Matt E. Shultz
Affiliation:
Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, Delaware, 19716, USA
Joshua Pritchard
Affiliation:
Australian Telescope National Facility, CSIRO, Space and Astronomy, PO Box 76, Epping, 1710, NSW, Australia
Kovi Rose
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney, New South Wales 2006, Australia Australian Telescope National Facility, CSIRO, Space and Astronomy, PO Box 76, Epping, 1710, NSW, Australia
Yuanming Wang
Affiliation:
Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria, 3122, Australia
Yu Wing Joshua Lee
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney, New South Wales 2006, Australia Australian Telescope National Facility, CSIRO, Space and Astronomy, PO Box 76, Epping, 1710, NSW, Australia ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), Hawthorn, 3122, Victoria, Australia
Gregory Sivakoff
Affiliation:
Department of Physics, University of Alberta, CCIS 4-181, Edmonton AB T6G 2E1, Canada
Andrew Zic
Affiliation:
Australian Telescope National Facility, CSIRO, Space and Astronomy, PO Box 76, Epping, 1710, NSW, Australia
Tara Murphy
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney, New South Wales 2006, Australia
*
Author for correspondence: Barnali Das, Email: Barnali.Das@csiro.au.
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Abstract

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Magnetic massive stars are stars of spectral types O, B and A that harbour ∼ kG strength (mostly dipolar) surface magnetic fields. Their non-thermal radio emission has been demonstrated to be an important magnetospheric probe, provided the emission is fully characterised. A necessary step for that is to build a statistically significant sample of radio-bright magnetic massive stars. In this paper, we present the ‘VAST project to study Magnetic Massive Stars’ or VAST-MeMeS that aims to achieve that by taking advantage of survey data acquired with the Australian SKA Pathfinder telescope. VAST-MeMeS is defined under the ‘Variables and Slow Transients’ (VAST) survey, although it also uses data from other ASKAP surveys. We found radio detections from 48 magnetic massive stars, out of which, 14 do not have any prior radio detections. We also identified 9 ‘Main-sequence Radio Pulse Emitter’ candidates based on variability and circular polarisation of flux densities. The expanded sample suggests a slightly lower efficiency in the radio production than that reported in earlier work. In addition to significantly expanding the sample of radio-bright magnetic massive stars, the addition of flux density measurements at ≲ 1 GHz revealed that the spectra of incoherent radio emission can extend to much lower frequencies than that assumed in the past. In the future, radio observations spanning wide frequency and rotational phase ranges should be conducted so as to reduce the uncertainties in the incoherent radio luminosities. The results from these campaigns, supplemented with precise estimations of stellar parameters, will allow us to fully understand particle acceleration and non-thermal radio production in large-scale stellar magnetospheres.

Information

Type
Research Article
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia