J/ApJ/871/187 Spot parameters on KIC solar-type stars (Namekata+, 2019)
Lifetimes and emergence/decay rates of star spots on solar-type stars estimated
by Kepler data in comparison with those of sunspots.
Namekata K., Maehara H., Notsu Y., Toriumi S., Hayakawa H., Ikuta K.,
Notsu S., Honda S., Nogami D., Shibata K.
<Astrophys. J., 871, 187 (2019)>
=2019ApJ...871..187N 2019ApJ...871..187N
ADC_Keywords: Stars, G-type; Stars, diameters; Magnetic fields;
Effective temperatures
Keywords: stars: activity ; starspots ; stars: solar-type ; sunspots
Abstract:
Active solar-type stars show large quasi-periodic brightness
variations caused by stellar rotation with star spots, and the
amplitude changes as the spots emerge and decay. The Kepler data are
suitable for investigations of the emergence and decay processes of
star spots, which are important to understand the underlying stellar
dynamo and stellar flares. In this study, we measured the temporal
evolution of the star-spot area with Kepler data by tracing the local
minima of the light curves. In this analysis, we extracted the
temporal evolution of star spots showing clear emergence and decay
without being disturbed by stellar differential rotation. We applied
this method to 5356 active solar-type stars observed by Kepler and
obtained temporal evolution of 56 individual star spots. We calculated
the lifetimes and emergence/decay rates of the star spots from the
obtained temporal evolution of the spot area. As a result, we found
that the lifetimes (T) of star spots range from 10 to 350days when the
spot areas (A) are 0.1%-2.3% of the solar hemisphere. We also compared
them with sunspot lifetimes and found that the lifetimes of star spots
are much shorter than those extrapolated from an empirical relation of
sunspots (T∝A), while being consistent with other research on
star-spot lifetimes. The emergence and decay rates of star spots are
typically 5x1020Mx/hr (8MSH/hr) with an area of 0.1%-2.3% of the
solar hemisphere and mostly consistent with those expected from
sunspots, which may indicate the same underlying processes.
Description:
In order to assess the diversity and similarity of the star spots by
comparing them with the sunspots, we selected solar-type stars as
target stars from the Kepler data set on the basis of the stellar
effective temperature (Teff) and surface gravity (logg) listed in the
Kepler Input Catalog (see DR25; Mathur+, 2017, J/ApJS/229/30).
In this study, we defined solar-type stars with a criterion of
5000K<Teff<6000K and logg>4.0. For each star, we used all of the
available Kepler pre-search data conditioning long-cadence (30min)
data in which instrumental effects are removed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 111 56 Physical parameters of star spots and the host
stars
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/other/A+ARV/17.251 : Stars observed with Doppler imaging (Strassmeier, 2009)
J/ApJS/197/2 : Transit timing observations from Kepler. I. (Ford+, 2011)
J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)
J/ApJS/209/5 : Superflares of Kepler stars. I. (Shibayama+, 2013)
J/ApJ/783/123 : Surface gravity for 220 Kepler stars (Campante+, 2014)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/ApJ/833/170 : Spots parameters for LCs of the EB star KIC 6048106 (Lee, 2016)
J/AJ/152/158 : Final Kepler transiting planet search (DR25) (Twicken+, 2016)
J/A+A/601/A67 : Kepler solar-type stars modeling (Creevey+, 2017)
J/ApJ/851/91 : Statistical studies solar white-light flares (Namekata+, 2017)
J/ApJS/229/30 : Revised stellar properties Q1-17 Kepler targets (Mathur+, 2017)
J/ApJ/866/99 : Revised radii of KIC stars & planets, Gaia DR2 (Berger+, 2018)
J/ApJS/235/38 : Kepler planetary cand. VIII. DR25 reliability (Thompson+, 2018)
J/ApJS/241/29 : Flare catalog through LC data of Kepler DR25 (Yang+, 2019)
J/AJ/158/109 : Occurrence rates of planets orbiting FGK stars (Hsu+, 2019)
J/AJ/159/24 : Spectroscopy & Kepler data of the EB star V404 Lyr (Lee+, 2020)
http://archive.stsci.edu/kepler/ : Kepler on MAST home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/56] Sequential running number
of the spot candidates
4- 11 I8 --- KIC [2158548/12783364] Kepler Input Catalog
identifier of the host star
13- 13 I1 --- f_KIC [1/2]? Source flag on KIC (1)
15- 18 I4 K Teff [5026/6000] Stellar effective temperature
(2)
20- 23 F4.2 [cm/s2] logg [4.28/4.69] Stellar surface gravity (2)
25- 28 F4.2 Rsun R* [0.7/2.7]? Corrected stellar radii (3)
30- 33 F4.1 d Prot [1/17] Stellar rotational period
35- 39 F5.1 d dT [13/351] Lifetimes of star spots
41- 45 F5.1 d e_dT [0.6/104] Uncertainty in dT
47- 50 F4.1 --- Amax [1.6/68]? Maximum star spot area;
in 10e+3MSH units (4)
52- 56 F5.1 --- e_Amax [-12/-0.3]? Lower uncertainty for Amax (4)
58- 61 F4.1 --- E_Amax [0.4/15]? Upper uncertainty for Amax (4)
63- 66 F4.1 10+23G.cm2 Imax [0.5/73]? Maximum magnetic flux
(Φmax) in 1023Mx units (5)
68- 72 F5.1 10+23G.cm2 e_Imax [-28/-0.2]? Lower uncertainty for Imax (5)
74- 77 F4.1 10+23G.cm2 E_Imax [0.3/45]? Upper uncertainty for Imax (5)
79- 82 F4.1 10+20G.cm2/h dI-e [0.3/87]? Emergence rates of star spots
(dΦe/dt) in 1020Mx/h units (5)
84- 88 F5.1 10+20G.cm2/h e_dI-e [-39/-0.1]? Lower uncertainty for dI-e (5)
90- 93 F4.1 10+20G.cm2/h E_dI-e [0.2/68]? Upper uncertainty for dI-e (5)
95- 99 F5.1 10+20G.cm2/h dI-d [0.4/184]? decay rates of star spots
(dΦd/dt) in 1020Mx/h units (5)
101-105 F5.1 10+20G.cm2/h e_dI-d [-74/-0.2]? Lower uncertainty for dI-d (5)
107-111 F5.1 10+20G.cm2/h E_dI-d [0.3/112]? Upper uncertainty for dI-d (5)
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Note (1): Source flags as follows:
1 = subgiant or main-sequence binary candidates (Berger+, 2018, J/ApJ/866/99)
2 = cool main-sequence binary candidates (Berger+ 2018, J/ApJ/866/99)
Note (2): Stellar values taken from Kepler Input Catalog DR25;
see Mathur+, 2017, J/ApJS/229/30
Note (3): Corrected stellar radii by Berger+ 2018, J/ApJ/866/99
Note (4): Sunspot area units, millions of solar hemisphere (MSH),
2πxRsun2=3.1x1022cm2 (Maehara+ 2017PASJ...69...41M 2017PASJ...69...41M)
Note (5): Sunspot flux units, Mx=G*cm2, e.g., Norton+ 2017ApJ...842....3N 2017ApJ...842....3N
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 06-Apr-2020