Multi-wavelength observations of a giant flare on CN Leonis

Fuhrmeister, B.; Schmitt, J. H. M. M.; Hauschildt, P. H.

doi:10.1051/0004-6361/200810224

Cited by 23 publications

(27 citation statements)

References 26 publications

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“…Subtracting the quiescent photospheric spectrum, we also identify emission lines from neutral K and Na which fill in the core of the photospheric absorption features. These spectra are similar to red M dwarf flare spectra (Fuhrmeister et al 2008), and are understood as the result of the increase in electron density and heating of the chromosphere (Fuhrmeister et al 2010). The much longer duration of the emission lines is not surprising, and is consistent with solar flares (Zirin 1988) and the statistics of SDSS spectra of M dwarf flares (Kruse et al 2010;Hilton et al 2010).…”

Section: Spectroscopy and Photometry Of The 2012 July 29 Flaressupporting

confidence: 73%

KEPLERMONITORING OF AN L DWARF I. THE PHOTOMETRIC PERIOD AND WHITE LIGHT FLARES

Gizis

Burgasser

Berger

et al. 2013

ApJ

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We report on the results of 15 months of monitoring the nearby field L1 dwarf WISEP J190648.47+401106.8 (W1906+40) with the Kepler mission. Supporting observations with the Karl G. Jansky Very Large Array and Gemini North Telescope reveal that the L dwarf is magnetically active, with quiescent radio and variable Hα emission. A preliminary trigonometric parallax shows that W1906+40 is at a distance of 16.35 +0.36 −0.34 pc, and all observations are consistent with W1906+40 being an old disk star just above the hydrogen-burning limit. The star shows photometric variability with a period of 8.9 hr and an amplitude of 1.5%, with a consistent phase throughout the year. We infer a radius of 0.92±0.07R J and sin i > 0.57 from the observed period, luminosity (10 −3.67±0.03 L ), effective temperature (2300 ± 75 K), and v sin i (11.2 ± 2.2 km s −1 ). The light curve may be modeled with a single large, high latitude dark spot. Unlike many L-type brown dwarfs, there is no evidence of other variations at the 2% level, either non-periodic or transient periodic, that mask the underlying rotation period. We suggest that the long-lived surface features may be due to starspots, but the possibility of cloud variations cannot be ruled out without further multi-wavelength observations. During the Gemini spectroscopy, we observed the most powerful flare ever seen on an L dwarf, with an estimated energy of ∼1.6 × 10 32 erg in white light emission. Using the Kepler data, we identify similar flares and estimate that white light flares with optical/ultraviolet energies of 10 31 erg or more occur on W1906+40 as often as 1-2 times per month.

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Section: Spectroscopy and Photometry Of The 2012 July 29 Flaressupporting

confidence: 73%

KEPLERMONITORING OF AN L DWARF I. THE PHOTOMETRIC PERIOD AND WHITE LIGHT FLARES

Gizis

Burgasser

Berger

et al. 2013

ApJ

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“…However, it cannot be explained by chromospheric models alone, which have a temperature minimum well above a temperature allowing for CO. Such studies normally use linear combinations of a photospheric (or inactive chromospheric) and an active chromospheric model and have also been used for flare A136, page 11 of 21 A&A 623, A136 (2019) modeling (Fuhrmeister et al 2010). Classically this treatment is also known as 1.5D modeling, since it tries to account for the inhomogeneity of the stellar atmospheres (Ayres et al 2006).…”

Section: Linear-combination Fitsmentioning

confidence: 99%

The CARMENES search for exoplanets around M dwarfs

Hintz

Fuhrmeister

Czesla

et al. 2019

A&A

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Chromospheric modeling of observed differences in stellar activity lines is imperative to fully understand the upper atmospheres of late-type stars. We present one-dimensional parametrized chromosphere models computed with the atmosphere code PHOENIX using an underlying photosphere of 3500 K. The aim of this work is to model chromospheric lines of a sample of 50 M2–3 dwarfs observed in the framework of the CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs, exoplanet survey. The spectral comparison between observed data and models is performed in the chromospheric lines of Na I D2, Hα, and the bluest Ca II infrared triplet line to obtain best-fit models for each star in the sample. We find that for inactive stars a single model with a VAL C-like temperature structure is sufficient to describe simultaneously all three lines adequately. Active stars are rather modeled by a combination of an inactive and an active model, also giving the filling factors of inactive and active regions. Moreover, the fitting of linear combinations on variable stars yields relationships between filling factors and activity states, indicating that more active phases are coupled to a larger portion of active regions on the surface of the star.

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“…These spectra were originally computed to fit the mega-flare on CN Leo (Fuhrmeister et al 2010). The stars CN Leo and Proxima Centauri have similar photospheric properties.…”

Section: Theoretical Modelling Of the Flare With Phoenixmentioning

confidence: 99%

“…Since we use a photosphere with a lower T eff than is realistic, we should infer a too high column mass for the onset of the transition region and the temperature minimum. Details about the model construction can be found in Fuhrmeister et al (2010). In this paper, we constructed the flaring model as a linear combination of a quiescent spectrum observed directly before the flare and a flaring model spectrum.…”

Section: Theoretical Modelling Of the Flare With Phoenixmentioning

confidence: 99%

Multi-wavelength observations of Proxima Centauri

Fuhrmeister

Lalitha

Poppenhaeger

et al. 2011

A&A

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117

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Aims. We report simultaneous observations of the nearby flare star Proxima Centauri with VLT/UVES and XMM-Newton over three nights in March 2009. Our optical and X-ray observations cover the star's quiescent state, as well as its flaring activity and allow us to probe the stellar atmospheric conditions from the photosphere into the chromosphere, and then the corona during its different activity stages. Methods. Using the X-ray data, we investigate variations in coronal densities and abundances and infer loop properties for an intermediate-sized flare. The optical data are used to investigate the magnetic field and its possible variability, to construct an emission line list for the chromosphere, and use certain emission lines to construct physical models of Proxima Centauri's chromosphere. Results. We report the discovery of a weak optical forbidden Fe xiii line at 3388 Å during the more active states of Proxima Centauri. For the intermediate flare, we find two secondary flare events that may originate in neighbouring loops, and discuss the line asymmetries observed during this flare in H i, He i, and Ca ii lines. The high time-resolution in the Hα line highlights strong temporal variations in the observed line asymmetries, which re-appear during a secondary flare event. We also present theoretical modelling with the stellar atmosphere code PHOENIX to construct flaring chromospheric models.

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Multi-wavelength observations of a giant flare on CN Leonis

Cited by 23 publications

References 26 publications

KEPLERMONITORING OF AN L DWARF I. THE PHOTOMETRIC PERIOD AND WHITE LIGHT FLARES

KEPLERMONITORING OF AN L DWARF I. THE PHOTOMETRIC PERIOD AND WHITE LIGHT FLARES

The CARMENES search for exoplanets around M dwarfs

Multi-wavelength observations of Proxima Centauri

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