Multiband photometric detection of a huge flare on the M9 dwarf 2MASSW J1707183+643933 |
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Authors: | Boris Rockenfeller Coryn A L Bailer-Jones Reinhard Mundt Mansur A Ibrahimov |
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Institution: | Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany;Ulugh Beg Astronomical Institute, 33 Astronomical Str., Tashkent 700052, Uzbekistan |
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Abstract: | We present simultaneous UV , G , R and I monitoring of 19 M dwarfs that reveal a huge flare on the M9 dwarf with an amplitude in the UV of at least 6 mag. This is one of the strongest detections ever of an optical flare in an M star and one of the first in an ultracool dwarf (spectral types later than about M7). Four intermediate-strength flares (Δ m UV < 4 mag) were found in this and three other targets. For the whole sample we deduce a flare probability of 0.013 (rate of 0.022 h?1 ), and 0.049 (0.090 h?1) for 2M1707+64 alone. Deviations of the flare emission from a blackbody is consistent with strong Hα line emission. We also confirm our previously found rotation period for 2M1707+64 and determine it more precisely to be 3.619 ± 0.015 h . |
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Keywords: | methods: data analysis techniques: photometric stars: activity stars: flare stars: late-type stars: rotation |
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