J/A+A/678/A24 New rotation periods of 67163 Kepler stars (Reinhold+, 2023)
New rotation period measurements of 67,163 Kepler stars.
Reinhold T., Shapiro A.I., Solanki S.K. and Basri G.
<Astron. Astrophys. 678, A24 (2023)>
=2023A&A...678A..24R 2023A&A...678A..24R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Optical
Keywords: stars: rotation
Abstract:
The Kepler space telescope leaves a legacy of tens of thousands of
stellar rotation period measurements. While many of these stars show
strong periodicity, there exists an even bigger fraction of stars with
irregular variability for which rotation periods are rarely visible or
in most cases unknown. As a consequence, many stellar activity studies
might be strongly biased toward the behavior of more active stars, for
which rotation periods have been determined.
To at least partially lift this bias, we apply a new method capable of
determining rotation periods of stars with irregular light curve
variability. This effort greatly increases the number of stars with
well-determined periods, especially for stars with small variabilities
similar to that of the Sun.
To achieve this goal, we employ a novel method based on the Gradient
of the Power Spectrum (GPS). The maximum of the gradient corresponds
to the position of the inflection point (IP), i.e., the point where
the curvature of the high-frequency tail of the power spectrum changes
its sign. It was shown previously that the stellar rotation period
Prot is linked to the inflection point period PIP) by the simple
equation Prot=PIP/alpha, where alpha is a calibration factor. The
GPS method is superior to classical methods (such as auto-correlation
functions (ACF)) because it does not require a repeatable variability
pattern in the time series, making it an ideal tool for detecting
periods of stars with very short-lived spots.
From the initial sample of 142168 stars with effective temperatures
Teff≤6500K and logg≥4.0 in the Kepler archive, we could measure
rotation periods for 67163 stars by combining the GPS and the ACF
method. We further report the first determination of a rotation period
for 20,397 stars. The GPS periods show good agreement with previous
period measurements using classical methods, where these are
available. Furthermore, we show that the scaling factor alpha
increases for very cool stars with effective temperatures below 4000K,
which we interpret as spots located at higher latitudes.
We conclude that new techniques (such as the GPS method) must be
applied to detect rotation periods of stars with small and more
irregular variabilities. Ignoring these stars will distort the overall
picture of stellar activity and, in particular, solar-stellar
comparison studies.
Description:
The data are released in 'quarters' with lengths of ∼90 days,
with exceptions for quarters Q0, Q1, and Q17, which have shorter
observing times of 10-33 days. In the following, we use all
available quarters except for Q0, Q1, and Q17 because these are
significantly shorter than the other quarters, which becomes important
in the period analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 84 67515 Periods measured with the ACF and the GPS
methods, including a final rotation period
tableb1.dat 40 4808 Up to 8 bad quarters removed from the analysis
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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)
J/ApJS/255/17 : Kepler stars surface rotation + activity. II. (Santos+, 2021)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC KIC number
11- 15 F5.2 d ProtACF ACF rotation period
18- 21 F4.2 --- LPH Local ACF peak height
24- 28 F5.2 d ProtGPS GPS rotation period
31- 34 F4.2 --- hIP Inflection point peak height
37- 43 F7.1 --- SNR Signal-to-noise ratio
46- 52 F7.3 % Rvar6h Median 6-hours smoothed variability range
55- 57 F3.1 --- points Point metric
60- 64 F5.2 d ProtFin Final rotation period
67- 69 A3 --- Method ACF or GPS method used
72- 76 F5.2 d ProtMcQ14 McQuillan et al. (2014ApJS..211...24M 2014ApJS..211...24M,
Cat. J/ApJS/211/24) rotation period
79- 84 F6.2 d ProtS21 Santos et al (2021ApJS..255...17S 2021ApJS..255...17S,
Cat. J/ApJS/255/17) rotation period
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 I8 --- KIC KIC number
11- 12 I2 --- Quarter1 Bad quarter removed
15- 16 I2 --- Quarter2 ? Bad quarter removed
19- 20 I2 --- Quarter3 ? Bad quarter removed
23- 24 I2 --- Quarter4 ? Bad quarter removed
27- 28 I2 --- Quarter5 ? Bad quarter removed
31- 32 I2 --- Quarter6 ? Bad quarter removed
35- 36 I2 --- Quarter7 ? Bad quarter removed
39- 40 I2 --- Quarter8 ? Bad quarter removed
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Acknowledgements:
Timo Reinhold, reinhold(at)mps.mpg.de
(End) Patricia Vannier [CDS] 02-Aug-2023