J/ApJ/895/140 EvryFlare. II. Parameters of 122 cool flare stars (Howard+, 2020)
EvryFlare.
II. Rotation Periods of the Cool Flare Stars in TESS across Half the Southern
Sky.
Howard W.S., Corbett H., Law N.M., Ratzloff J.K., Galliher N., Glazier A.,
Fors O., del Ser D., Haislip J.
<Astrophys. J., 895, 140 (2020)>
=2020ApJ...895..140H 2020ApJ...895..140H
ADC_Keywords: Stars, flare; Stars, masses; Stars, diameters; Spectral types;
Effective temperatures; Optical
Keywords: Starspots ; Optical flares ; Sky surveys ; Stellar rotation ;
Time series analysis
Abstract:
We measure rotation periods and sinusoidal amplitudes in Evryscope
light curves for 122 two-minute K5-M4 TESS targets selected for strong
flaring. The Evryscope array of telescopes has observed all bright
nearby stars in the south, producing 2-minute cadence light curves
since 2016. Long-term, high-cadence observations of rotating flare
stars probe the complex relationship between stellar rotation,
starspots, and superflares. We detect periods from 0.3487 to 104days
and observe amplitudes from 0.008 to 0.216 g'mag. We find that the
Evryscope amplitudes are larger than those in TESS with the effect
correlated to stellar mass (p-value=0.01). We compute the Rossby
number (Ro) and find that our sample selected for flaring has twice as
many intermediate rotators (0.04<Ro<0.4) as fast (Ro<0.04) or slow
(Ro>0.44) rotators; this may be astrophysical or a result of period
detection sensitivity. We discover 30 fast, 59 intermediate, and 33
slow rotators. We measure a median starspot coverage of 13% of the
stellar hemisphere and constrain the minimum magnetic field strength
consistent with our flare energies and spot coverage to be 500G, with
later-type stars exhibiting lower values than earlier-type stars. We
observe a possible change in superflare rates at intermediate periods.
However, we do not conclusively confirm the increased activity of
intermediate rotators seen in previous studies. We split all rotators
at Ro∼0.2 into bins of PRot<10days and PRot>10 days to confirm that
short-period rotators exhibit higher superflare rates, larger flare
energies, and higher starspot coverage than do long-period rotators,
at p-values of 3.2x10-5, 1.0x10-5, and 0.01, respectively.
Description:
The Transiting Exoplanets Survey Satellite (TESS) mission is searching
for transiting exoplanets across the entire sky, split into 26
sectors. TESS observes each sector continuously in the red with four
10.5cm optical telescopes for 28days at 21"/pixel.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 129 122 Rotation periods and starspots on cool flare stars
observed by Evryscope in TESS Sectors 1-6
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
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)
V/128 : Chromospherically Active Binaries. Third version (Eker+, 2008)
J/ApJ/457/L99 : 25yr CaII-HK observations of F-K nearby stars (Baliunas+,1996)
J/AJ/134/2340 : Membership of Praesepe & Coma Berenices clusters (Kraus+,2007)
J/AJ/141/166 : HATNet variability survey of K and M dwarfs (Hartman+, 2011)
J/ApJ/743/48 : Stars with Prot and X-ray luminosities (Wright+, 2011)
J/MNRAS/424/11 : Rotation of field stars from CoRoT data (Affer+, 2012)
J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs (Mann+, 2015)
J/ApJ/821/93 : Rotation & Galactic kinematics of mid M dwarfs (Newton+, 2016)
J/A+A/600/A13 : HARPS M dwarf sample magnetic activity (Astudillo-Defru+,2017)
J/MNRAS/472/1618 : Kepler study of starspot lifetimes (Giles+, 2017)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
J/ApJ/849/36 : Flaring activity of M dwarfs in the Kepler field (Yang+, 2017)
J/AJ/156/217 : Stellar properties for M dwarfs in MEarth-South (Newton+,2018)
J/AJ/155/39 : Variability properties TIC sources with KELT (Oelkers+, 2018)
J/ApJ/881/9 : EvryFlare. I. Cool stars's flares southern sky (Howard+, 2019)
J/A+A/622/A133 : M45, M44 and M67 flare stars (Ilin+, 2019)
J/AJ/159/60 : 8695 flares 1228 stars in TESS sectors 1 & 2 (Gunther+, 2020)
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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 identifier
11- 15 A5 --- Sectors TESS sectors (1)
17- 25 F9.5 deg RAdeg [3.69/360] Right Ascension (J2000) (2)
27- 34 F8.4 deg DEdeg [-84.4/2.51] Declination (J2000) (2)
36- 44 F9.5 d Prot [0.34/104] Stellar rotation period
46- 52 F7.5 d e_Prot [1e-05/9.5] Uncertainty in Prot
54- 57 F4.2 --- Ro [0.01/3.21] Rossby number
59- 60 I2 --- LSSN [6/71] Lomb-Scargle peak, signal-to-noise,
σ
62- 70 F9.3 d MJD [57398/58293] Modified Julian date of peak
phase; MJD=JD-2400000.5 (3)
72- 76 F5.3 mag dM-EVR [0.008/0.22] Amplitude, Evryscope g' band (4)
78- 82 F5.3 % dF-EVR [0.015/0.438] Fractional light blocked,
ΔF/F, Evryscope (4)
84- 87 A4 --- Rot? Evryscope rotation in TESS data? (5)
89- 93 F5.3 mag dM-TESS [0.004/0.06]? Amplitude, Evryscope g' band (6)
95- 99 F5.3 % dF-TESS [0.007/0.2]? Fractional light blocked,
ΔF/F, TESS (6)
101-104 I4 K Tspot [2800/3400] Estimated spot temperature
106-109 F4.2 % Fspot [0.03/1.04] Evryscope-measured starspot coverage
fraction
111-114 F4.2 Msun Mass [0.2/0.7] Mass, star
116-119 F4.2 Rsun Rad [0.23/0.63] Radius, star
121-124 I4 K Teff [3200/4400] Stellar surface temperature
126-129 A4 --- SpT Estimated spectral type
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Note (1): The TESS sectors of the star was observed; if observed for more than
3 but less than six of the sectors, 'most' is recorded.
Note (2): The current Evryscope-measured position of the star, epoch 2018
Note (3): Time of peak rotational brightness in the phase-folded Evryscope
light curve in Modified Julian Date.
Note (4): Evryscope-measured sinusoidal amplitude of rotation in ΔMg',
and the Evryscope-measured double amplitude of rotation in fractional-flux,
i.e., the fraction of starlight blocked by spots.
Note (5): Note as follows:
yes = The rotation period observed by Evryscope is also visible in the
TESS light curve (75 occurrences)
no = The rotation period observed by Evryscope isn't visible in the
TESS light curve (29 occurrences)
harm = a harmonic period (4 occurrences)
beat = a beat frequency of 1 d and the TESS period (4 occurrences)
prob = a likely but noisy match (7 occurrences)
long = period too long to observe in TESS (3 occurrences)
Note (6): The TESS-measured amplitude of rotation in ΔM_TESS, and the
TESS-measured double-amplitude of rotation in fractional-flux, i.e. the
fraction of starlight blocked by spots.
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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 This catalog
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], 23-Sep-2021