Properties of Radiative Shock Waves in the Atmospheres of Red Dwarf Stars

Belova, O. M.; Bychkov, K. V.

doi:10.1007/s10511-019-09577-4

Cited by 3 publications

(1 citation statement)

References 23 publications

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“…However, the beam current densities may be too large to last during the propagation from the corona to the chromosphere. Further, electron-beam-generated chromospheric condensations (e.g., Livshits et al 1981;Fisher et al 1985;Fisher 1989;Gan et al 1992) in some of these models produce hydrogen Balmer line spectra that are too broad (Kowalski 2022); other recent perspectives and arguments have been provided by Belova & Bychkov (2019) and Morchenko (2020aMorchenko ( , 2020b. Stellar flare RHD models have considered smaller electron-beam heating fluxes, but the model Balmer jumps are larger than in all known spectral observations; the photosphere is radiatively backheated by this Balmer continuum radiation, which originates at chromospheric heights (Allred et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Time-dependent Stellar Flare Models of Deep Atmospheric Heating

Kowalski,

Allred,

Carlsson

2024

ApJ

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Optical flares have been observed from magnetically active stars for many decades; unsurprisingly, the spectra and temporal evolution are complicated. For example, the shortcomings of optically thin, static slab models have long been recognized when confronted with the observations. A less incorrect—but equally simple—phenomenological T ≈ 9000 K blackbody model has instead been widely adopted in the absence of realistic (i.e., observationally tested) time-dependent, atmospheric models that are readily available. We use the RADYN code to calculate a grid of 1D radiative-hydrodynamic stellar flare models that are driven by short pulses of electron-beam heating. The flare heating rates in the low atmosphere vary over many orders of magnitude in the grid, and we show that the models with high-energy electron beams compare well to the global trends in flux ratios from impulsive-phase stellar flare, optical spectra. The models also match detailed spectral line-shape properties. We find that the pressure broadening and optical depths account for the broad components of the hydrogen Balmer γ lines in a powerful flare with echelle spectra. The self-consistent formation of the wings and nearby continuum level provides insight into how high-energy electron-beam heating evolves from the impulsive to the gradual decay phase in white-light stellar flares. The grid is publicly available, and we discuss possible applications.

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Section: Introductionmentioning

confidence: 99%

Time-dependent Stellar Flare Models of Deep Atmospheric Heating

Kowalski,

Allred,

Carlsson

2024

ApJ

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On the Origin of Optical Radiation during the Impulsive Phase of Flares on dMe Stars. I. Discussion of Gas Dynamic Models

Morchenko

2020

Astrophysics

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On the Origin of Optical Radiation During the Impulsive Phase of Flares on dMe Stars. II. Continuum and Line Radiation

Morchenko

2020

Astrophysics

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It is argued that not only the blue (at the brightness maximum) but also the red (in the slow decay phase) components of the optical continuum of powerful flares on dMe stars are formed near the photosphere. The possible appearance of HeI lines in the relaxation zones for the plasma to a state of thermal equilibrium (as a result of a rise in electron temperature owing to elastic collisions of electrons with atoms and ions) is noted (for sufficiently high speeds of a non-stationary chromospheric shock wave propagating toward the photosphere of the Sun and stars). A scheme is proposed for the positioning of the "layers" of plasma responsible for the generation of radiation in the white light continuum during the impulsive phase of powerful stellar flares.

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Properties of Radiative Shock Waves in the Atmospheres of Red Dwarf Stars

Cited by 3 publications

References 23 publications

Time-dependent Stellar Flare Models of Deep Atmospheric Heating

Time-dependent Stellar Flare Models of Deep Atmospheric Heating

On the Origin of Optical Radiation during the Impulsive Phase of Flares on dMe Stars. I. Discussion of Gas Dynamic Models

On the Origin of Optical Radiation During the Impulsive Phase of Flares on dMe Stars. II. Continuum and Line Radiation

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