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Title: CHARACTERIZING A DRAMATIC ΔV ∼ –9 FLARE ON AN ULTRACOOL DWARF FOUND BY THE ASAS-SN SURVEY

We analyze a ΔV ∼ –9 magnitude flare on the newly identified M8 dwarf SDSS J022116.84+194020.4 (hereafter SDSSJ0221) detected as part of the All-Sky Automated Survey for Supernovae. Using infrared and optical spectra, we confirm that SDSSJ0221 is a relatively nearby (d ∼ 76 pc) M8 dwarf with strong quiescent Hα emission. Based on kinematics and the absence of features consistent with low-gravity (young) ultracool dwarfs, we place a lower limit of 200 Myr on the age of SDSSJ0221. When modeled with a simple, classical flare light curve, this flare is consistent with a total U-band flare energy E{sub U} ∼ 10{sup 34} erg, confirming that the most dramatic flares are not limited to warmer, more massive stars. Scaled to include a rough estimate of the emission line contribution to the V band, we estimate a blackbody filling factor of ∼10%-30% during the flare peak and ∼0.5%-1.6% during the flare decay phase. These filling factors correspond to flare areas that are an order of magnitude larger than those measured for most mid-M dwarf flares.
Authors:
; ; ; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ; ;  [5] ;  [6] ; ; ; ; ; ;  [7] more »; « less
  1. Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
  2. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States)
  3. Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile)
  4. Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States)
  5. Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warsaw (Poland)
  6. Coral Towers Observatory, Cairns, Queensland 4870 (Australia)
  7. Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Santa Barbara, CA 93117 (United States)
Publication Date:
OSTI Identifier:
22364017
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 781; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DIAGRAMS; DWARF STARS; EMISSION; EMISSION SPECTRA; GRAVITATION; HYDROGEN; MASS; STELLAR FLARES; SUPERNOVAE; VISIBLE RADIATION