The response of chromospheric emission lines to flares on YZ Canis Minoris

Worden, S. P.; Schneeberger, T. J.; Giampapa, M. S.; DeLuca, E. E.; Cram, L. E.

doi:10.1086/161611

Cited by 22 publications

(24 citation statements)

References 8 publications

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“…For a notable Stark broadening of helium lines, very high densities of at least 10 16 cm −3 would have to be reached (Ben Chaouacha et al 2007), which is not expected for this rather small flare. Therefore we argue that the broadening We note that Stark broadening should affect higher members of the Balmer series more strongly (Švestka 1972;Worden et al 1984). While Hβ is as broad as or even broader than Hα, this is not found for the Hδ line.…”

Section: Stark Broadening Versus Turbulent Broadeningmentioning

confidence: 72%

A multi-wavelength view of AB Doradus outer atmosphere

Lalitha

Fuhrmeister

Wolter

et al. 2013

A&A

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Aims. We study the chromosphere and corona of the ultra-fast rotator AB Dor A at high temporal and spectral resolution using simultaneous observations with XMM-Newton in the X-rays, VLT/UVES in the optical, and the ATCA in the radio. Our optical spectra have a resolving power of ∼50 000 with a time cadence of ∼1 min. Our observations continuously cover more than one rotational period and include both quiescent periods and three flaring events of different strengths. Methods. From the X-ray observations we investigated the variations in coronal temperature, emission measure, densities, and abundance. We interpreted our data in terms of a loop model. From the optical data we characterised the flaring chromospheric material using numerous emission lines that appear in the course of the flares. A detailed analysis of the line shapes and line centres allowed us to infer physical characteristics of the flaring chromosphere and to coarsely localise the flare event on the star. Results. We specifically used the optical high-cadence spectra to demonstrate that both turbulent and Stark broadening are present during the first ten minutes of the first flare. Also, in the first few minutes of this flare, we find short-lived (one to several minutes) emission subcomponents in the Hα and Ca ii K lines, which we interpret as flare-connected shocks owing to their high intrinsic velocities. Combining the space-based data with the results of our optical spectroscopy, we derive flare-filling factors. Finally, comparing X-ray, optical broadband, and line emission, we find a correlation for two of the three flaring events, while there is no clear correlation for one event. Also, we do not find any correlation of the radio data to any other observed data.

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Section: Stark Broadening Versus Turbulent Broadeningmentioning

confidence: 72%

A multi-wavelength view of AB Doradus outer atmosphere

Lalitha

Fuhrmeister

Wolter

et al. 2013

A&A

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“…Stark broadening is thought to be an important symmetric broadening mechanism of the hydrogen Balmer lines during solar and stellar flares (Svestka, 1963;Worden et al, 1984;Hawley and Pettersen, 1991;Johns-Krull et al, 1997;Paulson et al, 2006;Allred et al, 2006), in addition to possible turbulent (Eason et al, 1992;Doyle et al, 1988) and thermal contributions. The linear (first order) Stark effect is the splitting of the degenerate orbital angular momentum (l) states of each principal quantum state (n) of hydrogen, due to a net electric microfield from the surrounding distribution of charges.…”

Section: Stark Broadening At the Balmer Edgementioning

confidence: 99%

New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation

et al. 2015

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The heating mechanism at high densities during M-dwarf flares is poorly understood. Spectra of M-dwarf flares in the optical and near-ultraviolet wavelength regimes have revealed three continuum components during the impulsive phase: 1) an energetically dominant blackbody component with a color temperature of T ≈ 10 4 K in the blue-optical, 2) a smaller amount of Balmer continuum emission in the near-ultraviolet at λ ≤ 3646Å and 3) an apparent pseudo-continuum of blended high-order Balmer lines between λ = 3646Å and λ ≈ 3900Å. These properties are not reproduced by models that employ a typical solar-type flare heating level of ≤ 10 11 erg cm −2 s −1 in non-thermal electrons, and therefore our understanding of these spectra is limited to a phenomenological three-component interpretation. We present a new 1D radiative-hydrodynamic model of an M-dwarf flare from precipitating non-thermal electrons with a large energy flux of 10 13 erg cm −2 s −1 . The simulation produces bright nearultraviolet and optical continuum emission from a dense (n >10 15 cm −3 ), hot (T ≈ 12 000 − 13 500 K) chromospheric condensation. For the first time, the observed color temperature and Balmer jump ratio are produced self-consistently in a radiative-hydrodynamic flare model. We find that a T ≈ 10 4 K blackbodylike continuum component and a small Balmer jump ratio result from optically thick Balmer (∞ → n = 2) and Paschen recombination (∞ → n = 3) radiation, and thus the properties of the flux spectrum are caused by blue (λ ≈ 4300Å) light escaping over a larger physical depth range compared to red (λ ≈ 6700Å) and near-ultraviolet (λ ≈ 3500Å) light. To model the near-ultraviolet pseudocontinuum previously attributed to overlapping Balmer lines, we include the extra Balmer continuum opacity from Landau-Zener transitions that result from merged, high order energy levels of hydrogen in a dense, partially ionized atmosphere. This reveals a new diagnostic of ambient charge density in the densest regions of the atmosphere that are heated during dMe and solar flares.

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“…Optical flares on flare stars are now generally recognized to be qualitatively similar to those on the Sun (Worden et al, 1984). The important difference is the relative importance of line to continuum emission and, as a consequence, the total energy liberated during the course of a flare event -as much as two to three orders of magnitude greater than the largest solar flares.…”

Section: Overview Of Optical Uv and X-ray Observationsmentioning

confidence: 99%

“…For the stellar case, the line to continuum ratio is of order a few percent during the rise phase and flare maximum and is only a few tens of percent during the decay phase; in contrast, line emission completely dominates in most solar flares. Even so, Worden (1983) and Worden et aL (1984) conclude that Balmer line behavior in stellar flares is essentially the same as in solar flares. Until relatively recently, solar flares that possessed a significant continuum component (white light flares) were regarded as a rare and separate class.…”

Section: Overview Of Optical Uv and X-ray Observationsmentioning

confidence: 99%

Radio emission from flare stars

Bastian

1990

Sol Phys

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Observations of radio emission from flare stars are reviewed, including surveys of flare stars in the solar neighborhood and in stellar associations, studies of quiescent emission, and continuum and spectral studies of radio burst emission. The radio observations are placed in an observational context provided by soft X-ray, UV, and optical observations. It is stressed that, as is the case for the latter wavelength regimes, observations ofrado bursts on flare stars are qualitatively similar to those on the Sun, albeit in a dramatically scaled-up fashion.

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The response of chromospheric emission lines to flares on YZ Canis Minoris

Cited by 22 publications

References 8 publications

A multi-wavelength view of AB Doradus outer atmosphere

A multi-wavelength view of AB Doradus outer atmosphere

New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation

Radio emission from flare stars

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