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Radio spectral index analysis of southern hemisphere symbiotic stars

Dickey, JM ORCID: 0000-0002-6300-7459, Weston, JHS, Sokoloski, JL, Vrtilek, SD and McCollough, M 2021 , 'Radio spectral index analysis of southern hemisphere symbiotic stars' , Astrophysical Journal, vol. 911, no. 1 , pp. 1-10 , doi: 10.3847/1538-4357/abe774.

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Symbiotic stars show emission across the electromagnetic spectrum from a wide array of physical processes. At centimeter waves, both synchrotron and thermal emissions are seen, often highly variable and associated with outbursts in the optical and X-rays. Most models of the radio emission include an ionized region within the dense wind of the red giant star that is kept ionized by activity on the white dwarf companion or its accretion disk. In some cases, there is ongoing shell burning on the white dwarf due to its high mass accretion rate or a prior nova eruption; in other cases, nuclear fusion occurs only occasionally as recurrent nova events. In this study, we measure the spectral indices of a sample of symbiotic systems in the Southern Hemisphere using the Australia Telescope Compact Array. Putting our data together with results from other surveys, we derive the optical depths and brightness temperatures of some well-known symbiotic stars. Using parallax distances from Gaia Data Release 3, we determine the sizes and characteristic electron densities in the radio emission regions. The results show a range of a factor of 10(4) in radio luminosity and a factor of 100 in linear size. These numbers are consistent with a picture where the rate of shell burning on the white dwarf determines the radio luminosity. Therefore, our findings also suggest that radio luminosity can be used to determine whether a symbiotic star is powered by accretion alone or also by shell burning.

Item Type: Article
Authors/Creators:Dickey, JM and Weston, JHS and Sokoloski, JL and Vrtilek, SD and McCollough, M
Keywords: Symbiotic binary stars, stellar accretion disks, white dwarf stars, interacting binary stars
Journal or Publication Title: Astrophysical Journal
Publisher: Institute of Physics Publishing, Inc
ISSN: 0004-637X
DOI / ID Number: 10.3847/1538-4357/abe774
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© 2021. The American Astronomical Society. All rights reserved.

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