Radio Spectral Index Analysis of Southern Hemisphere Symbiotic Stars

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...

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Bibliographic Details
Published in:The Astrophysical journal 2021-04, Vol.911 (1), p.30
Main Authors: Dickey, John M., Weston, J. H. S., Sokoloski, J. L., Vrtilek, S. D., McCollough, Michael
Format: Article
Language:English
Subjects:
Accretion disks
Arrays
Astrophysics
Brightness temperature
Burning rate
Centimeter waves
Dwarf novae
Electron density
Emission analysis
Emissions
Giant stars
Interacting binary stars
Luminosity
Nuclear fusion
Outbursts
Parallax
Radio emission
Red giant stars
Southern Hemisphere
Stellar accretion disks
Symbiotic binary stars
Symbiotic stars
Synchrotrons
White dwarf stars
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Summary: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.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/abe774