Spectroscopic and photometric observations of a five-magnitude flare event on UV Ceti

Eason, E. L. E.; Giampapa, M. S.; Radick, R. R.; Worden, S. P.; Hege, E. K.

doi:10.1086/116305

Cited by 57 publications

(84 citation statements)

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“…There are only few observations of such giant flares, but even these few examples show very different timescales and lightcurve characteristics. While the CN Leo flare lasted about 50 min, a 5-mag flare in the U-Band on UV Cet lasted only 12 min (Eason et al 1992), while the large flare on AD Leo from 1985 lasted more than 4 h (Hawley & Pettersen 1991). Compared to somewhat smaller (but nevertheless very large) flares, these can be of the same duration or even longer than the CN Leo flare.…”

Section: Discussionmentioning

confidence: 90%

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Multiwavelength observations of a giant flare on CN Leonis

Fuhrmeister¹,

Liefke²,

Schmitt³

et al. 2008

A&A

122

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Section: Discussionmentioning

confidence: 90%

“…Güdel et al 2002Güdel et al , 2004, and even greater magnitude increases have occasionally been reported in the optical (e.g. Eason et al 1992;Hawley & Pettersen 1991).…”

Section: Introductionmentioning

confidence: 90%

Multiwavelength observations of a giant flare on CN Leonis

Fuhrmeister¹,

Liefke²,

Schmitt³

et al. 2008

A&A

122

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“…Hawley & Pettersen 1991). Along with their blue spectra, (Eason et al 1992) obtained data with a different instrument at lower time resolution showing that the Hα line, being already very optically thick, does not respond strongly during a large flare in accord with models (Allred et al 2006). Figure 8 illustrates the line flux normalized to the bolometric luminosity for several lines (top), as well as Balmer decrements for four flares (bottom; two rise-and two decayphase).…”

Section: The Balmer Decrements Of Rise and Decay Flaresmentioning

confidence: 98%

M Dwarf Flares from Time-Resolved SDSS Spectra

Hilton¹,

Hawley²,

West³

et al. 2009

AIP Conference Proceedings

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We have identified 63 flares on M dwarfs from the individual component spectra in the Sloan Digital Sky Survey using a novel measurement of emission line strength called the Flare Line Index. Each of the ∼38,000 M dwarfs in the SDSS low mass star spectroscopic sample of West et al. was observed several times (usually 3-5) in exposures that were typically 9-25 minutes in duration. Our criteria allowed us to identify flares that exhibit very strong Hα and Hβ emission line strength and/or significant variability in those lines throughout the course of the exposures. The flares we identified have characteristics consistent with flares observed by classical spectroscopic monitoring. The flare duty cycle for the objects in our sample is found to increase from 0.02% for early M dwarfs to 3% for late M dwarfs. We find that the flare duty cycle is larger in the population near the Galactic plane and that the flare stars are more spatially restricted than the magnetically active but non-flaring stars. This suggests that flare frequency may be related to stellar age (younger stars are more likely to flare) and that the flare stars are younger than the mean active population.

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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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Spectroscopic and photometric observations of a five-magnitude flare event on UV Ceti

Cited by 57 publications

References 0 publications

Multiwavelength observations of a giant flare on CN Leonis

Multiwavelength observations of a giant flare on CN Leonis

M Dwarf Flares from Time-Resolved SDSS Spectra

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

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