J/ApJ/890/46 Superflares on solar-type stars from TESS first year (Tu+, 2020)
Superflares on solar-type stars from the first year observation of TESS.
Tu Z.-L., Yang M., Zhang Z.J., Wang F.Y.
<Astrophys. J., 890, 46-46 (2020)>
=2020ApJ...890...46T 2020ApJ...890...46T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, G-type; Stars, flare
Keywords: Stellar flares; G stars
Abstract:
Superflares, which are strong explosions on stars, have been well
studied with the progress of spacetime-domain astronomy. In this work,
we present the study of superflares on solar-type stars using
Transiting Exoplanet Survey Satellite (TESS) data. Thirteen sectors of
observations during the first year of the TESS mission covered the
southern hemisphere of the sky, containing 25734 solar-type stars. We
verified 1216 superflares on 400 solar-type stars through automatic
search and visual inspection with 2 minute cadence data. Our result
suggests a higher superflare frequency distribution than the result
from Kepler. This may be because the majority of TESS solar-type stars
in our data set are rapidly rotating stars. The power-law index
γ of the superflare frequency distribution
(dN/dE∝E-γ) is constrained to be γ=2.16±0.10,
which is a little larger than that of solar flares but consistent with
the results from Kepler. Because only seven superflares of Sun-like
stars are detected, we cannot give a robust superflare occurrence
frequency. Four stars were accompanied by unconfirmed hot planet
candidates. Therefore, superflares may possibly be caused by stellar
magnetic activities instead of planet-star interactions. We also find
an extraordinary star, TIC43472154, which exhibits about
200 superflares per year. In addition, the correlation between the
energy and duration of superflares (Tduration∝Eβ) is
analyzed. We derive the power-law index to be β=0.42±0.01,
which is a little larger than β = 1/3 from the prediction
according to magnetic reconnection theory.
Description:
The Transiting Exoplanet Survey Satellite (TESS) was launched on
2018 April 18, and carries four identical cameras. During its first
year of observations, TESS has scanned the southern hemisphere of the
sky and obtained data products for 13 segments (sector 1-sector 13).
Each segment covers about 27 days. In this work, we adopt the
presearch data conditioned (PDC) light curves.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 49 400 Flare stars
table2.dat 46 1216 Superflares
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See also:
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/AJ/141/50 : White-light flares on cool stars from Kepler (Walkowicz+, 2011)
J/AJ/143/93 : Rotational velocities in early-M stars (Reiners+, 2012)
J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)
J/ApJS/209/5 : Superflares of Kepler stars. I. (Shibayama+, 2013)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/ApJ/849/36 : Flaring activity of M dwarfs in the Kepler field (Yang+, 2017)
J/ApJ/851/91 : Stat. studies of solar white-light flares (Namekata+, 2017)
J/A+A/614/A76 : CARMENES input catalogue of M dwarfs. III. (Jeffers+, 2018)
J/ApJ/866/99 : Radii of KIC stars & planets using Gaia DR2 (Berger+, 2018)
J/ApJS/241/29 : Flare catalog through LC data of Kepler DR25 (Yang+, 2019)
J/ApJ/883/88 : Short-duration flares from GALEX & Kepler (Brasseur+, 2019)
J/AJ/159/60 : Flares from 1228 stars in TESS sectors 1 & 2 (Gunther+, 2020)
J/other/CoSka/51.78 : Flare stars in nearby Gal. open clusters (Maryeva+ 2021)
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 [737327/468899939] TESS identifier
11- 14 I4 K Teff [5103/5998] Effective temperature
16- 19 F4.2 [cm/s2] logg [4/4.71] log surface gravity
21- 24 F4.2 Rsun Rad [0.69/1.7] Stellar radius
26- 30 F5.2 d Per [0.14/25.5] Stellar rotational period
32- 33 I2 --- Nfl [1/63] Number of flares (1)
35- 36 I2 --- Nset [1/13] Number of Set-n (2)
38- 43 F6.2 yr-1 Freq [1.19/233.2] Flare frequency, f*, deduced
by Equ. 9 (N*flares/τ*) (3)
45- 49 A5 --- Flag Flare star flag (4)
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Note (1): Same as N*flares of Equation 9.
Note (2): The observation mode of TESS, unlike Kepler, causes various observing
spans for different targets. It is not suitable for calculating the
occurrence frequency of superflares directly using the unequal
observing spans. We therefore improve the method suggested by
Maehara+ (2012, J/other/Nat/485.478). First of all, we subdivided all
the solar-type stars into different sets based on how many sectors the
star was observed in. For example, Set-1 means that the stars were
observed in only one sector. Similarly, Set-13 covers the stars
observed in all 13 sectors. See Section 3.1.
Note (3): The flare frequency for an individual star is described by Equ. (9):
f*=N*flares/τ* where τ* is the continuous observation length of
each flare star, and N*flares denotes the number of flares from an
individual star.
Note (4): Flag as follows:
GM = star may possess M dwarfs candidates nearby (42" from the main target).
GB = star brighter than the main stars, and 21 to 42" from the main targets.
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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 [737327/468899939] TESS identifier
11- 19 F9.4 d DatePk [1325.58/1681.99] Date of superflares' peak
21- 28 E8.2 10-7W FluxPk [1.29e+31/7.9e+33] Peak Flux (1)
30- 37 E8.2 10-7J Energy [4.75e+33/1.8e+37] Superflare energy
39- 46 F8.2 s Duration [480/15960] Superflare duration
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Note (1): Calculated by L* x Fflare(t), when t equals to the peak time.
L* is defined in Equ. 2 as L*=4πR*2σsbT*4 where
R* and T* are the stellar radius and effective temperature given by
TIC v8, and σsb is the Stefan-Boltzmann constant.
Fflare(t) is the normalized flux above the fitted quadratic function
(see Section 2.2), defined in Equ. 4 as Fflare(t)=F(t)-Fq(t).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 29-Jul-2021