K2 Ultracool Dwarfs Survey I: Photometry of an L Dwarf Superflare

Abstract

We report on K2 Campaign 8 measurements of a huge white light flare on the L1 dwarf SDSSp J005406.55-003101.8 (EPIC 220186653). The source is a typical L1 dwarf at a distance of $\sim 50$ pc, probably an old hydrogen-burning star rather than a young brown dwarf. In the long (30-minute) cadence photometry, the flare peak is 21 times the flux of the stellar photosphere in the broad optical Kepler filter, which we estimate corresponds to $\Delta V\approx -7.1$. The total equivalent duration of the flare is 15.4 hr. We estimate the total bolometric energy of the flare was $4\times 10^{33}$ erg, more powerful than the previously reported Kepler white light flares for the L1 dwarf WISEP J190648.47+401106.8, but weaker than the $\Delta V=-11$ L0 dwarf superflare ASASSN-16ae. The initial (impulsive) cooling phase is too rapid to resolve with our 30-minute cadence data, but after one hour the gradual cooling phase has an exponential time constant of 1.8 hours. We use template fitting to estimate that the full-time-width-at-half-amplitude of the light curve is $<10$ minutes and that the true flare maximum reached $\sim 70$ times the stellar photosphere, or $\Delta V\approx -8$. This flare is comparable to the most powerful Kepler flares observed on the active M4 dwarf GJ 1243.

arXiv commentAccepted to ApJ

References in corpus (42)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The K2 Mission: Characterization and Early results
• The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
• First Results from the Catalina Real-time Transient Survey
• Kepler Mission Design, Realized Photometric Performance, and Early Science
• Kepler Input Catalog: Photometric Calibration and Stellar Classification
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence
• Characterization of M,L and T dwarfs in the Sloan Digital Sky Survey
• Kepler Flares I. Active and Inactive M dwarfs
• Initial Characteristics of Kepler Long Cadence Data For Detecting Transiting Planets
• The Kepler Catalog of Stellar Flares
• The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8
• Kepler Flares II: The Temporal Morphology of White-Light Flares on GJ 1243
• Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs
• Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra
• Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• The standard flare model in three dimensions. II. Upper limit on solar flare energy
• White-light flares on cool stars in the Kepler Quarter 1 Data
• Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. III. X-ray, Radio, and H-alpha Activity Trends in M and L Dwarfs
• The Solar Neighborhood XXXII. The Hydrogen Burning Limit
• SpeX Spectroscopy of Unresolved Very Low Mass Binaries. II. Identification of Fourteen Candidate Binaries with Late-M/Early-L and T Dwarf Components
• Precise time-series photometry for the Kepler-2.0 mission
• BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
• A path towards understanding the rotation-activity relation of M dwarfs with K2 mission, X-ray and UV data
• Superflare occurrence and energies on G-, K- and M-type dwarfs
• K2P${}^2$ $-$ A photometry pipeline for the K2 mission
• Kepler Monitoring of an L Dwarf I. The Photometric Period and White Light Flares
• A Survey for H-alpha Emission from Late L dwarfs and T dwarfs
• A PSF-based approach to Kepler/K2 data. I. Variability within the K2 Campaign 0 star clusters M 35 and NGC 2158
• ASASSN-16ae: A Powerful White-Light Flare on an Early-L Dwarf
• L Dwarfs Found in Sloan Digital Sky Survey Commissioning Data II. Hobby-Eberly Telescope Observations
• Trends in Ultracool Dwarf Magnetism. II. The Inverse Correlation Between X-ray Activity and Rotation as Evidence for a Bimodal Dynamo
• Kepler Flares IV: A Comprehensive Analysis of the Activity of the dM4e Star GJ 1243
• Short duration high amplitude flares detected on the M dwarf star KIC 5474065
• The view from K2: Questioning the traditional view of flaring on early dM stars
• Searching for I band variability in stars in the M/L spectral transition region

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• K2 Ultracool Dwarfs Survey II: The White Light Flare Rate of Young Brown Dwarfs
• A Catalog of M-dwarf Flares with ASAS-SN
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• Do long-cadence data of {\it Kepler} satellite capture the basic properties of flares ?
• A Study of Flares in the Ultra-Cool Regime from SPECULOOS-South
• $K2$ Ultracool Dwarfs Survey. VI. White light superflares observed on an L5 dwarf and flare rates of L dwarfs
• K2 Ultracool Dwarfs Survey. IV. Monster flares observed on the young brown dwarf CFHT-BD-Tau 4
• Hubble Space Telescope astrometry of the closest brown dwarf binary system -- I. Overview and improved orbit
• Detection of a giant white-light flare on an L2.5 dwarf with the Next Generation Transit Survey
• Minute-cadence Observations of the LAMOST Fields with the TMTS: III. Statistic Study of the Flare Stars from the First Two Years
• The Puzzling Story of Flare Inactive Ultra Fast Rotating M dwarfs. II. Searching for radial velocity variations
• Fast Photometric Variability of Very Low Mass Stars in IC 348: Detection of Superflare in an M-dwarf
• 2MASS J10274572+0629104: The very short period young M6 Dwarf Binary System identified in K2 data
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