J/ApJ/893/67 Smoothed amplitudes from Kepler, K2 and TESS phot. (Morris, 2020)
A relationship between stellar age and spot coverage.
Morris B.M.
<Astrophys. J., 893, 67-67 (2020)>
=2020ApJ...893...67M 2020ApJ...893...67M (SIMBAD/NED BibCode)
ADC_Keywords: Photometry; Optical; Associations, stellar; Stars, variable
Keywords: Stellar photospheres; Starspots; Stellar rotation; Bayesian statistics
Abstract:
We investigate starspot distributions consistent with space-based
photometry of F, G, and K stars in six stellar associations ranging in
age from 10Myr to 4Gyr. We show that a simple light-curve statistic
called the "smoothed amplitude" is proportional to stellar age as
t-1/2, following a Skumanich-like spin-down relation. We marginalize
over the unknown stellar inclinations by forward modeling the ensemble
of light curves for direct comparison with the Kepler, K2, and TESS
photometry. We sample the posterior distributions for spot coverage
with approximate Bayesian computation. We find typical spot coverages
in the range 1%-10%, which decrease with increasing stellar age. The
spot coverage is proportional to tn where n=-0.37±0.16, also
statistically consistent with a Skumanich-like t-1/2 decay of
starspot coverage with age. We apply two techniques to estimate the
spot coverage of young exoplanet-hosting stars likely to be targeted
for transmission spectroscopy with the James Webb Space Telescope, and
estimate the bias in exoplanet radius measurements due to varying
starspot coverage.
Description:
We devise a method for inverting an ensemble of light curves to
measure spot coverage as a function of stellar age. In Section 2, we
describe several samples of stars in six stellar associations sourced
from Kepler, K2, and TESS photometry.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 525 Smoothed amplitudes and rotation periods
for all targets considered in this work
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
J/ApJS/101/117 : UBVRIJHKLMNQ photometry in Taurus-Auriga (Kenyon+ 1995)
J/ApJ/733/L9 : Stellar rotation for 71 NGC 6811 members (Meibom+, 2011)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/PASP/124/1279 : Q3 Kepler's combined photometry (Christiansen+, 2012)
J/A+A/549/A134 : 4 new WASP transiting close-in giant planets (Hebrard+, 2013)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/ApJ/795/167 : Transits of PH3b, c & d through January, 2019 (Schmitt+, 2014)
J/MNRAS/452/2127 : Fundamental param. of Kepler stars (Silva Aguirre+, 2015)
J/MNRAS/459/1060 : M67 var. stars from Kepler/K2-Campaign-5 (Gonzalez, 2016)
J/MNRAS/461/794 : Scorpius-Centaurus K-Type Stars (Pecaut+, 2016)
J/MNRAS/463/3513 : M67 Kepler/K2-Campaign-5 variable stars (Gonzalez, 2016)
J/ApJ/842/83 : Praesepe members rot. periods from K2 LCs (Douglas+, 2017)
J/MNRAS/472/1618 : Kepler study of starspot lifetimes (Giles+, 2017)
J/ApJ/856/23 : BANYAN. XI. The BANYAN Σ algorithm (Gagne+, 2018)
J/A+A/612/L2 : Compilation of stellar rotation data (Kovacs, 2018)
J/AJ/156/18 : APOGEE DR14:Bin. comp. of evolved stars (Price-Whelan+, 2018)
J/A+A/622/L13 : Stellar stream in Gaia DR2 discovery (Meingast+, 2019)
J/A+A/624/A15 : Kepler-411 mid-transit times (Sun+, 2019)
J/ApJ/879/49 : Rot. periods for 171 Gaia members of NGC 6811 (Curtis+, 2019)
J/AJ/158/77 : Cand. & members of the Pisces-Eridanus stream (Curtis+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- Name Source identifier
30- 38 A9 --- Assoc Association identifier (1)
40- 44 F5.2 d Per [0.19/39.2] Period
46- 51 F6.4 --- SAmp [0.0001/0.15] Smoothed amplitude (2)
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Note (1): Stellar association as follows:
M67 = M67 (4Gyr; 90 occurrences). See Section 2.7.
NGC 6811 = NGC 6811 (1Gyr; 62 occurrences). See Section 2.6.
Praesepe = Praesepe (650Myr; 220 occurrences). See Section 2.5.
Psc-Eri = The Pisces-Eridanus stream (120Myr; 100 occurrences).
See Section 2.4.
UCL = The Upper Centaurus Lupus association (16Myr; 34 occurrences).
See Section 2.3.
Upper Sco = Upper Scorpius (10Myr; 19 occurrences). See Section 2.2.
Note (2): The smoothed amplitude is the difference between the maximum and
minimum flux after the light curve has been phase folded and smoothed
with a Gaussian kernel. See Section 2.1.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Sep-2021