Journal article
A search for thermal gyro-synchrotron emission from hot stellar coronae
Monthly notices of the Royal Astronomical Society, Vol.522(1), pp.1394-1410
04/13/2023
DOI: 10.1093/mnras/stad980
Abstract
We searched for thermal gyro-synchrotron radio emission from a sample of five radio-loud stars whose X-ray coronae contain a hot ( T-e > 10(7) K) thermal component. We used the JVLA to measure Stokes I and V/I spectral energy distributions (SEDs) o v er the frequency range 15 - 45 GHz, determining the best-fitting model parameters using power-law and thermal gyro synchrotron emission models. The SEDs of the three chromospherically active binaries (Algol, UX Arietis, HR 1099) were well-fit by a power-law gyro-synchrotron model, with no evidence for a thermal component. However, the SEDs of the two weak-lined T Tauri stars (V410 Tau, HD 283572) had a circularly polarized enhancement above 30 GHz that was inconsistent with a pure power-law distribution. These spectra were well-fit by summing the emission from an extended coronal volume of power-law gyro-synchrotron emission and a smaller region with thermal plasma and a much stronger magnetic field emitting thermal gyro-synchrotron radiation. We used Bayesian inference to estimate the physical plasma parameters of the emission regions (characteristic size, electron density, temperature, power-la w inde x, and magnetic field strength and direction) using independently measured radio sizes, X-ray luminosities, and magnetic field strengths as priors, where available. The derived parameters were well-constrained but somewhat degenerate. The power-law and thermal volumes in the pre-main-sequence stars are probably not co-spatial, and we speculate they may arise from two distinct regions: a tangled-field magnetosphere where reconnection occurs and a recently disco v ered low-latitude poloidal magnetic field, respectively.
Details
- Title: Subtitle
- A search for thermal gyro-synchrotron emission from hot stellar coronae
- Creators
- Walter W. Golay - University of IowaRobert L. Mutel - University of Iowa, Physics and AstronomyDani Lipman - University of IowaManuel Guedel - University of Vienna
- Resource Type
- Journal article
- Publication Details
- Monthly notices of the Royal Astronomical Society, Vol.522(1), pp.1394-1410
- Publisher
- Oxford Univ Press
- DOI
- 10.1093/mnras/stad980
- ISSN
- 0035-8711
- eISSN
- 1365-2966
- Number of pages
- 17
- Language
- English
- Date published
- 04/13/2023
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984473217902771
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