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arXiv · 1611.07080

K2 Ultracool Dwarfs Survey I: Photometry of an L Dwarf Superflare

John E. Gizis·Rishi R. Paudel·Sarah J. Schmidt·Peter K. G. Williams·Adam J. Burgasser
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Abstract

We report on K2 Campaign 8 measurements of a huge white light flare on the L1 dwarf SDSSp J005406.55-003101.8 (EPIC 220186653). The source is a typical L1 dwarf at a distance of $\sim50$ pc, probably an old hydrogen-burning star rather than a young brown dwarf. In the long (30-minute) cadence photometry, the flare peak is 21 times the flux of the stellar photosphere in the broad optical Kepler filter, which we estimate corresponds to $ΔV \approx -7.1$. The total equivalent duration of the flare is 15.4 hr. We estimate the total bolometric energy of the flare was $4 \times 10^{33}$ erg, more powerful than the previously reported Kepler white light flares for the L1 dwarf WISEP J190648.47+401106.8, but weaker than the $ΔV = -11$ L0 dwarf superflare ASASSN-16ae. The initial (impulsive) cooling phase is too rapid to resolve with our 30-minute cadence data, but after one hour the gradual cooling phase has an exponential time constant of 1.8 hours. We use template fitting to estimate that the full-time-width-at-half-amplitude of the light curve is $<10$ minutes and that the true flare maximum reached $\sim70$ times the stellar photosphere, or $ΔV \approx -8$. This flare is comparable to the most powerful Kepler flares observed on the active M4 dwarf GJ 1243.

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John E. Gizis, Rishi R. Paudel, Sarah J. Schmidt, Peter K. G. Williams, Adam J. Burgasser. 2017-02-19. K2 Ultracool Dwarfs Survey I: Photometry of an L Dwarf Superflare. https://doi.org/10.3847/1538-4357%2Faa6197

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