J/ApJ/881/9 EvryFlare. I. Cool stars's flares in southern sky (Howard+, 2019)
EvryFlare.
I. Long-term Evryscope monitoring of flares from the cool stars across half the
southern sky.
Howard+, Howard W.S., Corbett H., Law N.M., Ratzloff J.K., Glazier A.,
Fors O., del Ser D., Haislip J.
<Astrophys. J., 881, 9 (2019)>
=2019ApJ...881....9H 2019ApJ...881....9H
ADC_Keywords: Stars, flare; Surveys; Spectral types; Optical
Keywords: stars: flare ; stars: low-mass ; surveys ;
ultraviolet: planetary systems ; ultraviolet: stars
Abstract:
We search for superflares from 4068 cool stars in 2+yr of Evryscope
photometry, focusing on those with high-cadence data from both
Evryscope and the Transiting Exoplanet Survey Satellite (TESS). The
Evryscope array of small telescopes observed 575 flares from 284
stars, with a median energy of 1034.0erg. Since 2016, Evryscope has
enabled the detection of rare events from all stars observed by TESS
through multi-year, high-cadence continuous observing. We report
around twice the previous largest number of 1034erg high-cadence
flares from nearby cool stars. We find eight flares with amplitudes of
3+g' magnitudes, with the largest reaching 5.6mag and releasing
1036.2erg. We observe a 1034erg superflare from TOI-455 (LTT1445), a
mid-M with a rocky planet candidate. We measure the superflare rate
per flare-star and quantify the average flaring of active stars as a
function of spectral type, including superflare rates, flare frequency
distributions, and typical flare amplitudes in g'. We confirm
superflare morphology is broadly consistent with magnetic
reconnection. We estimate starspot coverage necessary to produce
superflares, and hypothesize maximum allowed superflare energies and
waiting times between flares corresponding to 100% coverage of the
stellar hemisphere. We observe decreased flaring at high Galactic
latitudes. We explore the effects of superflares on ozone loss to
planetary atmospheres: we observe one superflare with sufficient
energy to photodissociate all ozone in an Earth-like atmosphere in one
event. We find 17 stars that may deplete an Earth-like atmosphere via
repeated flaring. Of the 1822 stars around which TESS may discover
temperate rocky planets, we observe 14.6%±2% emit large flares.
Description:
The Evryscope is an array of small telescopes simultaneously imaging
8150 square degrees and 18400 square degrees in total each night on
the sky at two minute cadence in g'. The Evryscope is optimized for
bright, nearby stars, with a typical dark-sky limiting magnitude of
g'=16. The Evryscope is designed to observe the entire Southern sky
down to an airmass of two and at a resolution of 13"/pixel.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 122 575 Individual flares observed by evryscope from cool
stars in TESS sectors 1-6
table2.dat 125 284 Cool flare stars observed by evryscope in TESS
sectors 1-6
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/AJ/132/866 : New M dwarfs in solar neighborhood (Riaz+, 2006)
J/AJ/134/2340 : Member. of Praesepe & Coma Berenices clusters (Kraus+,2007)
J/AJ/136/1242 : LMC long-period variables from MACHO (Fraser+, 2008)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/ApJ/767/95 : Stellar parameters of smallest KIC stars (Dressing+, 2013)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/MNRAS/443/2561 : CONCH-SHELL catalog of nearby M dwarfs (Gaidos+, 2014)
J/AJ/147/146 : Spectroscopy of Tuc-Hor candidate members (Kraus+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJ/807/45 : Habitable planets orbiting M dwarfs (Dressing+, 2015)
J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs (Mann+, 2015)
J/ApJ/812/3 : MEarth mid-to-late M dwarfs rot. & kinematics (West+, 2015)
J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)
J/MNRAS/463/1844 : M dwarfs rotation-activity relation (Stelzer+, 2016)
J/A+A/600/A13 : HARPS M dwarf magnetic activity (Astudillo-Defru+, 2017)
J/AJ/154/67 : HAZMAT II Low-mass stars GALEX UV obs. (Miles+, 2017)
J/ApJ/851/91 : Statistical studies solar whitelight flares (Namekata+,2017)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
J/ApJS/232/26 : Catalog of Kepler flare stars (Van Doorsselaere+, 2017)
J/ApJ/849/36 : Flaring activity of M dwarfs in Kepler field (Yang+, 2017)
J/A+A/613/A25 : Radial velocity for Ross 128 (Bonfils+, 2018)
J/AJ/155/180 : Catalog of cool dwarf targets for the TESS (Muirhead+, 2018)
J/AJ/156/259 : Robo-AO detected close binaries in Gaia DR2 (Ziegler+, 2018)
J/AJ/157/113 : TESS M-dwarf exoplanetary systems (Ballard, 2019)
J/A+A/622/A133 : M45, M44 and M67 flare stars (Ilin+, 2019)
J/ApJ/874/L8 : The TESS Habitable Zone Star Catalog (Kaltenegger+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- TIC TESS Input Catalog identifier
11- 19 A9 --- Sector TESS sector
21- 29 F9.3 d MJDs [57399/58293] MJD of flare start
31- 39 F9.3 d MJDp [57399/58293] MDJ of flare peak
41- 49 F9.3 d MJDe [57399/58293] MDJ of flare end
51- 54 F4.1 [10-7J] logE [31/36.1] log bolometric flare energy; erg
56- 59 F4.1 [10-7J] e_logE [29.4/35.4] Uncertainty in logE
61- 63 F3.1 mag Con [0.1/5.6] Flare amplitude (contrast) in g'
magnitudes
65- 68 F4.2 mag e_Con [0/0.19] Uncertainty in Con
70- 73 F4.1 --- Amp [0/84.3] Flare amplitude in fractional flux
units
75- 78 F4.2 --- e_Amp [0/0.16] Uncertainty in Amp
80- 83 F4.1 [10-7W] logL [29.3/31.8] log stellar quiescent luminosity
in g'; erg/s
85- 90 I6 s ED [0/100000] Equivalent duration in g'
92- 96 I5 s e_ED [0/18240] Uncertainty in ED
98-102 F5.1 min FWHM [2/143] Flare Full Width at Half Maximum
104-104 I1 min e_FWHM [2] Uncertainty in FWHM
106-109 F4.2 min-1 Imp [0/8.26] Flare impulse; Amp/FWHM
111-114 F4.2 min-1 e_Imp [0/6.18] Uncertainty in Imp
116-119 F4.1 mag gMAG [8/14.3] Absolute stellar g' band magnitude
121-122 A2 --- SpT Estimated photometric spectral type
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- TIC TESS Input Catalog identifier
11- 19 F9.5 deg RAdeg [0.35/360] Right Ascension in decimal degrees
(J2018)
21- 29 F9.5 deg DEdeg [-85/8.9] Declination in decimal degrees (J2018)
31- 39 A9 --- Sector TESS sector
41- 42 I2 --- Flares [1/24] Number of flares observed by Evryscope
44- 48 F5.1 d NObs [5.2/100] Total continuous Evryscope observation
time over 2 years
50- 54 F5.1 yr-1 SFlares [0/288] Annual superflare rate
56- 60 F5.2 yr-1 e_SFlares [0/99] Lower uncertainty in SFlare
62- 66 F5.2 yr-1 E_SFlares [3.5/91] Upper uncertainty in SFlare
68- 72 F5.2 --- alpha [-0.86/-0.24]? The FFD parameter α
74- 77 F4.1 --- beta [6.6/27.8]? The FFD parameter β
79- 82 F4.1 [10-7J] logE [31.6/35.7] mean bolometric flare energy; erg
84- 87 F4.1 [10-7J] logEmax [31.6/36.1] maximum bolometric flare energy; erg
89- 91 F3.1 mag Con [0.1/3.6] Mean flare amplitude (contrast) (1)
93- 95 F3.1 mag Conmax [0.1/5.6] Maximum flare amplitude (contrast) (1)
97-102 F6.2 deg GLAT [-82.55/-7.03] Galactic latitude
104-107 F4.1 mag Tmag [7/18.4] TESS apparent magnitude
109-112 F4.1 mag gmag [9.4/15] The g' band apparent magnitude
114-117 F4.1 [10-7W] logL [29.4/31.8] stellar quiescent luminosity in g';
erg/s
119-122 F4.1 mag gMAG [8.1/14] Absolute stellar g' band magnitude
124-125 A2 --- SpT Estimated photometric spectral type
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Note (1): In Delta g' magnitudes.
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History:
From electronic version of the journal
References:
Howard et al. Paper II. 2020ApJ...895..140H 2020ApJ...895..140H Cat. J/ApJ/895/140
Howard et al. Paper III. 2020ApJ...902..115H 2020ApJ...902..115H Cat. J/ApJ/902/115
Howard et al. Paper IV. 2021ApJ...920...42H 2021ApJ...920...42H
(End) Prepared by [AAS], Coralie Fix [CDS], 21-Dec-2020