J/ApJ/902/115 EvryFlare. III. Superflares from Evryscope & TESS (Howard+, 2020)
EvryFlare.
III. Temperature evolution and habitability impacts of dozens of
superflares observed simultaneously by Evryscope and TESS.
Howard W.S., Corbett H., Law N.M., Ratzloff J.K., Galliher N.,
Glazier A. L, Gonzalez R., Vasquez Soto A., Fors O., del Ser D., Haislip J.
<Astrophys. J., 902, 115 (2020)>
=2020ApJ...902..115H 2020ApJ...902..115H
ADC_Keywords: Stars, flare; Stars, M-type; Colors; Effective temperatures;
Stars, masses; Optical
Keywords: Exoplanet atmospheres ; Ultraviolet astronomy ; Astrobiology ;
Stellar flares ; Optical flares
Abstract:
Superflares may provide the dominant source of biologically relevant
UV radiation to rocky habitable-zone M-dwarf planets (M-Earths),
altering planetary atmospheres and conditions for surface life. The
combined line and continuum flare emission has usually been
approximated by a 9000K blackbody. If superflares are hotter, then the
UV emission may be 10 times higher than predicted from the optical.
However, it is unknown for how long M-dwarf superflares reach
temperatures above 9000K. Only a handful of M-dwarf superflares have
been recorded with multiwavelength high-cadence observations. We
double the total number of events in the literature using simultaneous
Evryscope and Transiting Exoplanet Survey Satellite observations to
provide the first systematic exploration of the temperature evolution
of M-dwarf superflares. We also increase the number of superflaring
M-dwarfs with published time-resolved blackbody evolution by ∼10x. We
measure temperatures at 2 minutes cadence for 42 superflares from
27 K5-M5 dwarfs. We find superflare peak temperatures (defined as the
mean of temperatures corresponding to flare FWHM) increase with flare
energy and impulse. We find the amount of time flares emit at
temperatures above 14000K depends on energy. We discover that 43% of
the flares emit above 14000K, 23% emit above 20000K and 5% emit above
30000K. The largest and hottest flare briefly reached 42000K. Some do
not reach 14000 K. During superflares, we estimate M-Earths orbiting
<200 Myr stars typically receive a top-of-atmosphere UV-C flux of
∼120W/m2 and up to 103W/m2, 100-1000 times the time-averaged
X-ray and UV flux from Proxima Cen.
Description:
Evryscope-South is located at Cerro Tololo Inter-American Observatory
in Chile, and Evryscope-North is located at Mount Laguna Observatory
in California, USA. Each Evryscope is an all-sky array of small
telescopes that continuously and simultaneously images 8150deg2 and
18400deg2 in total each night at a resolution of 13"/pixel and down
to an airmass of two. Evryscope-South observes at 2 minute cadence in
g'.
The TESS mission is looking for transiting exoplanets across the
entire sky, split into 26 sectors. TESS observes each sector
continuously with four 10.5cm optical telescopes in a red (600-1000nm)
bandpass for 28 days at 21"/pixel.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 121 44 Temperatures of simultaneous flares observed
during TESS Cycle 1
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See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)
J/AJ/132/866 : New M dwarfs in solar neighborhood (Riaz+, 2006)
J/A+A/460/695 : Search for Associations Containing Young stars (Torres+, 2006)
J/AJ/134/2340 : Membership of Praesepe & Coma Berenices (Kraus+, 2007)
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/788/81 : BANYAN III. RVel and rotation of low-mass stars (Malo+, 2014)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS) (Sullivan+, 2015)
J/A+A/600/A13 : HARPS M dwarfs magnetic activity (Astudillo-Defru+, 2017)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
J/ApJ/840/87 : Young star systems observed with SALT (Riedel+, 2017)
J/ApJ/856/23 : BANYAN. XI. The BANYAN Σ algorithm (Gagne+, 2018)
J/A+A/615/A172 : alpha Cen A and B chemical composition (Morel, 2018)
J/ApJ/867/105 : ATLAS all-sky stellar ref. cat., ATLAS-REFCAT2 (Tonry+, 2018)
J/ApJ/883/88 : Short-duration flares from GALEX & Kepler (Brasseur+, 2019)
J/ApJ/881/9 : EvryFlare. I. Cool stars's flares (Howard+, 2019)
J/A+A/622/A133 : M45, M44 and M67 flare stars (Ilin+, 2019)
J/AJ/159/60 : Flares from 1228 stars in TESS sectors 1 & 2 (Gunther+, 2020)
J/ApJ/895/140 : EvryFlare. II. Param. of 122 cool flare stars (Howard+, 2020)
J/ApJ/890/23 : NUV and FUV measurements of planet host stars (Loyd+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- TIC [5796048/441398770] TESS Input catalog ID
11- 26 A16 "datime" Date Observation date and time (ISO 8601, UTC) (1)
28- 32 F5.2 [10-7J] logEg' [31.2/35.1] Evryscope flare energy (erg)
34- 38 F5.2 [10-7J] logET [31.25/35] TESS flare energy (erg)
40- 43 F4.2 --- g'Amp [0.08/7.3] Evryscope amplitude
in normalized flux, Ag' (ΔF/F)
45- 48 F4.2 --- TAmp [0.01/0.65] TESS amplitude
in normalized flux, AT (ΔF/F
50- 53 F4.2 mag Color [0.07/6.6] Flare color between
normalized-flux amplitudes (Ag'-AT)
55- 59 F5.3 mag e_Color [0.003/0.6] Uncertainty in Color
61- 65 I5 K TeffPk [2700/43200] Peak temperature,
avg. temperature in FWHM
67- 70 I4 K e_TeffPk [300/3300] Uncertainty in TeffPk
72- 76 I5 K TeffTot [2600/50000] Total temperature
78- 82 I5 K e_TeffTot [200/13400]?=0 Lower uncertainty in TeffTot
84- 88 I5 K E_TeffTot [200/17100]?=0 Upper uncertainty in TeffTot
90- 93 F4.1 min tAbv [0/19.2] Time spent above 14000K
95- 99 F5.3 --- Impulse [0.003/1.3] Impulse, normalized Everyscope
flux amplitude Ag' / minute (2)
101-105 F5.3 --- e_Impulse [0/0.6] Uncertainty in Impulse
107-115 F9.6 d Prot [0.11/83]? Stellar rotation period
117-121 F5.3 Msun Mass [0.13/0.7] Stellar mass
-------------------------------------------------------------------------------
Note (1): UT observation identifiers are approximated from barycentric TESS
epochs and may differ by up to 10min from the exact flare peak time.
Note (2): The power-law fit for each flare observable Ofl versus
flare impulse I is of the form log10Ofl=αIlog10I+βI.
Table 2: relationships between flare temperature observables and
flare energy and impulse
----------------------------------------------------------------------------
Ofl αE βE αI βI
----------------------------------------------------------------------------
Peak Teff 0.128 -0.193 0.115 4.193
Entire flare Teff 0.064 1.811 0.114 4.07
Time above 14000K 0.285 -8.969
Peak color --- --- 0.792 0.507
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See Section 6.3.
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History:
From electronic version of the journal
References:
Howard et al. Paper I. 2019ApJ...881....9H 2019ApJ...881....9H Cat. J/ApJ/881/9
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 This Catalog
Howard et al. Paper IV. 2021ApJ...920...42H 2021ApJ...920...42H
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Apr-2022