EUV Flare Activity in Late-Type Stars
By M. Audard, M. Güdel, J. J. Drake, Vinay L. Kashyap. 2000
187 citations recorded by the source corpus.
\textit{Extreme Ultraviolet Explorer} Deep Survey observations of cool stars (spectral type F to M) have been used to investigate the distribution of coronal flare rates in energy and its relation to activity indicators and rotation parameters. Cumulative and differential flare rate distributions were constructed and fitted with different methods. Power laws are found to approximately describe the distributions. A trend toward flatter distributions for later-type stars is suggested in our sample. Assuming that the power laws continue below the detection limit, we have estimated that the superposition of flares with radiated energies of about $10^{29}-10^{31}$ergs could explain the observed radiative power loss of these coronae, while the detected flares are contributing only $\approx 10$%. While the power-law index is not correlated with rotation parameters (rotation period, projected rotational velocity, Rossby number) and only marginally with the X-ray luminosity, the flare occurrence rate is correlated with all of them. The occurrence rate of flares with energies larger than $10^{32}$ergs is found to be proportional to the average total stellar X-ray luminosity. Thus, energetic flares occur more often in X-ray bright stars than in X-ray faint stars. The normalized occurrence rate of flares with energies larger than $10^{32}$ergs increases with increasing \lxlbol and stays constant for saturated stars. A similar saturation is found below a critical Rossby number. The findings are discussed in terms of simple statistical flare models in an attempt to explain the previously observed trend for higher average coronal temperatures in more active stars. It is concluded that flares can contribute a significant amount of energy to coronal heating in active stars.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/2cafd173dc7ade79e57768f14338deee90796520
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In Astronomy and Astrophysics
Citations in the corpus
- The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, methodology): “The flare distribution of Proxima can be crudely approximated using the analysis of Audard et al. (2000) for CN Leo, which has similar X-ray luminosity and spectral type.”
- The Sun in Time: Activity and Environment (2007, methodology): “To avoid bias with regard to detection limits at lower energies, new methods have been devised by Audard et al. (1999), Audard et al. (2000), Kashyap et al. (2002), Güdel et al. (2003b), and Arzner and Güdel (2004), the latter three using Monte Carlo forward methods and analytical inversion.”
- KEPLER FLARES. I. ACTIVE AND INACTIVE M DWARFS (2014, methodology): “…that the field 7 This diagram is similar to those shown in LME but with the energy as the independent variable, following more recent studies (Audard et al. 2000; Hilton 2011; Ramsay et al. 2013). is weaker and/or less organized into substantial active regions where magnetic heating can…”
- Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records (2012, background): “Figure 3 shows stellar flare data for five G and K main sequence stars [from Audard et al., 2000] in soft X-ray and EUV bands (0.01 − 10 keV, or 1.2 − 1200 Å), scaled to approximate bolometric fluences by assuming the same ratio between bolometric and coronal fluences holds as for solar EUV…”