A search for thermal gyro-synchrotron emission from hot stellar coronae

Autor(en)

Walter W. Golay, Robert L. Mutel, Dani Lipman, Manuel Güdel

Abstrakt

We searched for thermal gyro-synchrotron radio emission from a sample of five radio-loud stars whose X-ray coronae contain a hot (K) thermal component. We used the JVLA to measure Stokes I and V/I spectral energy distributions (SEDs) over 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-law index, 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 discovered low-latitude poloidal magnetic field, respectively.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

University of Iowa, University of Connecticut

Journal

Monthly Notices of the Royal Astronomical Society

Band

522

Seiten

1394-1410

Anzahl der Seiten

17

ISSN

0035-8711

DOI

https://doi.org/10.1093/mnras/stad980

Publikationsdatum

06-2023

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie, 103004 Astrophysik

Schlagwörter

ASJC Scopus Sachgebiete

Astronomy and Astrophysics, Space and Planetary Science

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/1a1108bf-e236-4a7c-9abd-ad08cbedb0b9