Predicting the time variation of radio emission from MHD simulations of a flaring T-Tauri star
Date Issued
2020
Author(s)
Abstract
We model the time dependent radio emission from a disk accretion event in a
T-Tauri star using 3D, ideal magnetohydrodynamic simulations combined with a
gyrosynchrotron emission and radiative transfer model. We predict for the first
time, the multi-frequency (1$-$1000 GHz) intensity and circular polarisation
from a flaring T-Tauri star. A flux tube, connecting the star with its
circumstellar disk, is populated with a distribution of non-thermal electrons
which is allowed to decay exponentially after a heating event in the disk and
the system is allowed to evolve. The energy distribution of the electrons, as
well as the non-thermal power law index and loss rate, are varied to see their
effect on the overall flux. Spectra are generated from different lines of
sight, giving different views of the flux tube and disk. The peak flux
typically occurs around 20$-$30 GHz and the radio luminosity is consistent with
that observed from T-Tauri stars. For all simulations, the peak flux is found
to decrease and move to lower frequencies with elapsing time. The
frequency-dependent circular polarisation can reach 10$-$30$\%$ but has a
complex structure which evolves as the flare evolves. Our models show that
observations of the evolution of the spectrum and its polarisation can provide
important constraints on physical properties of the flaring environment and
associated accretion event.
Volume
496
Issue
3
Start page
2715
Issn Identifier
0035-8711
Rights
open.access
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