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M dwarf flares

Statistical study of M dwarf flares in Stripe 82 is presented in Kowalski et al. 2009.

Flare example Stripe82.png
  • Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3
  • The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.
  • flares are the most pronounced in u-band
  • around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8
  • g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.
  • amplitude in u > 0.7 mag up to 5 mag.
  • large and small flares possible on the same star
  • flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare
  • Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120.
  • 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.

Ampitude distribution for Stripe82 flares.

Light curve examples

High temporal resolution observations of a flare from UV Cet star. From Bopp & Moffett 1973.
The YZ Cmi U-band flare. From Kowalski 2010
Outburst of the flare star CN Leo. From Sokolowski 2008.
High temporal resolution observations of a flare star by Pi of the Sky. From Sokolowski 2008.

Spectrum examples

Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From Kowalski 2010.
File:M flare spectrum.png
Spectrum of an M6 dwarf is extremely red. From SDSS DR8