J/MNRAS/472/1618 Kepler study of starspot lifetimes (Giles+, 2017)
A Kepler study of starspot lifetimes with respect to light-curve amplitude
and spectral type.
Giles H.A.C., Collier Cameron A., Haywood R.D.
<Mon. Not. R. Astron. Soc., 472, 1618-1627 (2017)>
=2017MNRAS.472.1618G 2017MNRAS.472.1618G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable
Keywords: techniques: photometric - stars: activity -
stars: rotation, starspots
Abstract:
Wide-field high-precision photometric surveys such as Kepler have
produced reams of data suitable for investigating stellar magnetic
activity of cooler stars. Starspot activity produces quasi-sinusoidal
light curves whose phase and amplitude vary as active regions grow and
decay over time. Here we investigate, first, whether there is a
correlation between the size of starspots - assumed to be related to
the amplitude of the sinusoid - and their decay time-scale and,
secondly, whether any such correlation depends on the stellar
effective temperature. To determine this, we computed the
auto-correlation functions of the light curves of samples of stars
from Kepler and fitted them with apodised periodic functions. The
light-curve amplitudes, representing spot size, were measured from the
root-mean-squared scatter of the normalized light curves. We used a
Monte Carlo Markov Chain to measure the periods and decay time-scales
of the light curves. The results show a correlation between the decay
time of starspots and their inferred size. The decay time also depends
strongly on the temperature of the star. Cooler stars have spots that
last much longer, in particular for stars with longer rotational
periods. This is consistent with current theories of diffusive
mechanisms causing starspot decay. We also find that the Sun is not
unusually quiet for its spectral type - stars with solar-type rotation
periods and temperatures tend to have (comparatively) smaller
starspots than stars with mid-G or later spectral types.
Description:
Our samples are drawn from the sample of stars analysed by McQ14
(McQuillan et al, 2014, Cat. J/ApJS/211/24). They analysed over
34000 main-sequence stars taken from the Kepler mission stellar
archive at the NASA Exoplanet Archive (Akeson et al.,
2013PASP..125..989A 2013PASP..125..989A). All of the stars in McQ14 were less than
6500K in temperature and excluded known eclipsing binaries (EBs)
and Kepler Objects of Interest (KOIs). McQ14 utilized Teff-logg and
colour-colour cuts used by Ciardi et al. (2011AJ....141..108C 2011AJ....141..108C) to
select only main-sequence stars. The boundary of 6500K was selected by
McQ14 to ensure that only stars with convective envelopes, which spin
down during their lifetime, were included.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 97 1774 Full results
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC KIC number
10- 15 F6.3 --- PMCMC MCMC period
17- 21 F5.3 --- e_PMCMC rms uncertainty on PMCMC
23- 28 F6.3 --- PMCQ14 MCQ14 period
30- 34 F5.3 --- e_PMCQ14 rms uncertainty on PMCQ14
36- 42 F7.3 d tau Resultant decay lifetime
44- 49 F6.3 d e_tau rms uncertainty on tau
51- 57 F7.5 --- rms Root mean square scatter of individual
Kepler light curves which were normalized
to a mean flux of unity
59- 65 F7.5 --- F8 F8 parameter
67- 71 F5.3 [cm/s2] logg Surface gravity
73- 76 I4 K Teff Effective temperature
78- 85 F8.5 --- Pe1/Pe2 Pe1/Pe2 ratio
88- 97 F10.5 --- Pe2/Pe3 Pe2/Pe3 ratio
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 17-Jun-2020