KEPLER FLARES. I. ACTIVE AND INACTIVE M DWARFS

By S. Hawley, James R. A. Davenport, A. Kowalski, J. Wisniewski, L. Hebb, R. Deitrick, E. Hilton. 2014

173 citations recorded by the source corpus.

We analyzed Kepler short-cadence M dwarf observations. Spectra from the Astrophysical Research Consortium 3.5 m telescope identify magnetically active (Hα in emission) stars. The active stars are of mid-M spectral type, have numerous flares, and have well-defined rotational modulation due to starspots. The inactive stars are of early M type, exhibit less starspot signature, and have fewer flares. A Kepler to U-band energy scaling allows comparison of the Kepler flare frequency distributions with previous ground-based data. M dwarfs span a large range of flare frequency and energy, blurring the distinction between active and inactive stars designated solely by the presence of Hα. We analyzed classical and complex (multiple peak) flares on GJ 1243, finding strong correlations between flare energy, amplitude, duration, and decay time, with only a weak dependence on rise time. Complex flares last longer and have higher energy at the same amplitude, and higher energy flares are more likely to be complex. A power law fits the energy distribution for flares with log 31 erg, but the predicted number of low-energy flares far exceeds the number observed, at energies where flares are still easily detectable, indicating that the power-law distribution may flatten at low energy. There is no correlation of flare occurrence or energy with starspot phase, the flare waiting time distribution is consistent with flares occurring randomly in time, and the energies of consecutive flares are uncorrelated. These observations support a scenario where many independent active regions on the stellar surface are contributing to the observed flare rate.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/1e39f1dff4a971329fb2e4d1ac19d0e79fefd3bc

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In Astronomy and Astrophysics

Citations in the corpus

The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “Indeed, assuming flare characteristics similar to those of an active M dwarf such as GJ1243 (Hawley et al., 2014) and an Earth-like planet orbiting in the habitable zone, the flare activity and associated energetic proton events could strongly impact the ability of the planet’s atmosphere to shield ”
THE Hα EMISSION OF NEARBY M DWARFS AND ITS RELATION TO STELLAR ROTATION (2016, unknown): “High-quality M dwarf light curves are available from space-based data and offer unique opportunities for studying M dwarf stellar physics (e.g. Hawley et al. 2014; Stelzer et al. 2016), but the disadvantage is that the sample is dominated by early M dwarfs and stars that are typically more distant…”
A UNIFIED COMPUTATIONAL MODEL FOR SOLAR AND STELLAR FLARES (2015, background): “These joel.c.allred@nasa.gov stars spin faster and generate much larger magnetic fields (Hawley et al. 2014, and references therein) resulting in flares some 103 times more energetic than typical solar flares (e.g., Hawley & Pettersen 1991; Hawley et al. 2003; Kowalski et al. 2010).”
Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, methodology): “This is commonly denoted as the flare frequency distribution (FFD; e.g. Gershberg 1972; Lacy et al. 1976; Hawley et al. 2014).”
THE KEPLER CATALOG OF STELLAR FLARES (2016, methodology): “However the accuracy of this fit flare rate is limited due to the possible presence of significant breaks in the FFD power-law shape as shown in Figure 6 at the high energy end, or by Hawley et al. (2014) at lower flare energies.”
Frequent Flaring in the TRAPPIST-1 System—Unsuited for Life? (2017, background): “The best fit yields α = 1.59, suggesting that TRAPPIST-1 flare energies are mostly nonthermal (cf. Aschwanden et al. 2016), similarly to other very active M dwarfs in the Hawley et al. (2014) sample.”
THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, background): “In addition, Hawley et al. (2014) have shown that inactive M dwarfs display flares in their Kepler light curves, confirming that chromospheric activity is present on MUSCLES-type stars.”
The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up (2017, background): “26 Lower-energy flares occur more frequently but emit substantially less UV radiationand are likely also shorter in duration (cf. the study of Hawley et al. 2014 for GJ 1243).”