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Spots and White Light Flares in an L dwarf

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. Collaborators and Facilities. Adam Burgasser Edo Berger Peter K. G. Williams

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Spots and White Light Flares in an L dwarf

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  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 Vrbaand the USNO Flagstaff Infrared Parallax Team • Kelle Cruz • Stan Metchev • NASA award No. NNX13AC18G. • WISE, 2MASS, SDSS, IRTF, Kepler, VLA, Gemini, MMT, Keck

  3. Kepler Mission

  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 Ks=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. • Quiscentradio emission of 23 mJy. • u Lu= (4.5 +/- 0.9) x 1022 erg/s • Quiescent but variable Ha emission of 1-10 Angstroms Equivalent Width • Rotational velocity v sin i = 11.2 +/- 2.2 km/s

  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 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)

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

  10. Gemini spectra 29 July 2012

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

  12. Flare Light Curves (1 minute cadence)

  13. Flare Frequencies One 1032 erg flare in three months 1031 erg flare every ~300 hours 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.

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