K2 Ultracool Dwarfs Survey. II. The White Light Flare Rate of Young Brown Dwarfs
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
- Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482, Potsdam (Germany)
- Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
We use Kepler K2 Campaign 4 short-cadence (one-minute) photometry to measure white light flares in the young, moving group brown dwarfs 2MASS J03350208+2342356 (2M0335+23) and 2MASS J03552337+1133437 (2M0355+11), and report on long-cadence (thirty-minute) photometry of a superflare in the Pleiades M8 brown dwarf CFHT-PL-17. The rotation period (5.24 hr) and projected rotational velocity (45 km s{sup −1}) confirm 2M0335+23 is inflated (R⩾0.20 R{sub ⊙}) as predicted for a 0.06 M{sub ⊙}, 24 Myr old brown dwarf βPic moving group member. We detect 22 white light flares on 2M0335+23. The flare frequency distribution follows a power-law distribution with slope −α=−1.8±0.2 over the range 10{sup 31} to 10{sup 33} erg. This slope is similar to that observed in the Sun and warmer flare stars, and is consistent with lower-energy flares in previous work on M6–M8 very-low-mass stars; taking the two data sets together, the flare frequency distribution for ultracool dwarfs is a power law over 4.3 orders of magnitude. The superflare (2.6×10{sup 34} erg) on CFHT-PL-17 shows higher-energy flares are possible. We detect no flares down to a limit of 2×10{sup 30} erg in the nearby L5γ AB Dor moving group brown dwarf 2M0355+11, consistent with the view that fast magnetic reconnection is suppressed in cool atmospheres. We discuss two multi-peaked flares observed in 2M0335+23, and argue that these complex flares can be understood as sympathetic flares, in which fast-mode magnetohydrodynamic waves similar to extreme-ultraviolet waves in the Sun trigger magnetic reconnection in different active regions.
- OSTI ID:
- 22875939
- Journal Information:
- Astrophysical Journal, Vol. 845, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
STUDYING THE PHYSICAL DIVERSITY OF LATE-M DWARFS WITH DYNAMICAL MASSES
CHARACTERIZING A DRAMATIC ΔV ∼ –9 FLARE ON AN ULTRACOOL DWARF FOUND BY THE ASAS-SN SURVEY