1. Spots and White Light Flares in an L dwarf John Gizis Department of Physics and Astronomy University of Delaware May 24, 2013 @Brown Dwarfs Come of Age

2. Collaborators and Facilities Adam Burgasser Edo Berger Peter K. G. Williams Fred Vrba and the USNO Flagstaff Infrared Parallax Team Kelle Cruz Stan Metchev NASA award No. NNX13AC18G. WISE, 2MASS, SDSS, IRTF, Kepler, VLA, Gemini, MMT, Keck 1

4. WISEP J190648.47+401106.8 The L1 dwarf W1906+40 is bright enough to be measured by Kepler.

5. W1906+40 Properties Ordinary L1 dwarf in both optical and near-infrared. SDSS g=22.4, r=20.0, i=17.4. 2MASS J=13.08 K s =11.77 USNO preliminary trigonometric parallax gives 16.35 +/- 0.35 pc. U,V,W = -6, -12, -41 km/s Luminosity is 10 -3.67 solar. W1906+40 is magnetically active. Quiscent radio emission of 23 mJy. u L u = (4.5 +/- 0.9) x 10 22 erg/s Quiescent but variable Ha emission of 1-10 Angstroms Equivalent Width Rotational velocity v sin i = 11.2 +/- 2.2 km/s 4

6. This L dwarf may be modeled by a single dark spot with P=8.9 hours, or some more complicated pattern Dark spot not unlike those seen in Kepler M dwarfs (GO 030021)

7. Five Quarters of Data 6 The phase and amplitude are largely consistent for 1.25 years Previous I-band studies reported non-periodic variations on short timescales, and inconsistencies between observing runs. W1906+40 is much different than the late-L/T “weather” variables

8. Evidence of Flares (30 minute cadence) 7

9. The Kepler filter is sensitive to blue light, enhancing flare sensitivity 8

10. Gemini spectra 29 July 2012

11. Kepler 1-minute photometry and Emission Lines 10 White Light traces heated photosphere, to ~8000K Longer Lived Heated Chromospheric Lines 1 1 2 2 3 3

12. Flare Light Curves (1 minute cadence) 11

13. Flare Frequencies 12 10 31 erg flare every ~300 hours One 10 32 erg flare in three months Long Cadence data ~3 times less frequent. Sensitivity or variability?

14. Summary Remarks This L1 dwarf shows quiescent H alpha and radio emission. Large magnetic starspots(s) seem likely. The cloud variations seen in late- L/T-dwarfs don’t stay consistent for very long. For the first time, we have seen white light flares in an L dwarf (although similar flares have been seen in M7-M9 dwarfs.) These flares require heating of both the chromosphere and the photosphere, to >6000K. Very similar to dMe flares. The frequency of these flares is much less than in M dwarfs with similar rotation period, but are as frequent as in the Sun. 13