J/A+A/635/A43 Stellar rotation periods from K2 Campaigns 0-18 (Reinhold+, 2020)
Stellar rotation periods from K2 Campaigns 0-18.
Evidence for rotation period bimodality and simultaneous variability decrease.
Reinhold T., Hekker S.
<Astron. Astrophys. 635, A43 (2020)>
=2020A&A...635A..43R 2020A&A...635A..43R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Magnitudes
Keywords: stars: activity - stars: rotation
Abstract:
Rotation period measurements of stars observed with the Kepler mission
have revealed a lack of stars at intermediate rotation periods,
accompanied by a decrease of photometric variability. Whether this
so-called dearth region is a peculiarity of stars in the Kepler field,
or reflects a general manifestation of stellar magnetic activity, is
still under debate. The K2 mission has the potential to unravel this
mystery by measuring stellar rotation and photometric variability
along different fields in the sky.
Our goal is to measure stellar rotation periods and photometric
variabilities for tens of thousands of K2 stars, located in different
fields along the ecliptic plane, to shed light on the relation between
stellar rotation and photometric variability.
We use Lomb-Scargle periodograms, auto-correlation and wavelet
functions to determine consistent rotation periods. Stellar brightness
variability is assessed by computing the variability range, Rvar,
from the light curve. We further apply Gaussian mixture models to
search for bimodality in the rotation period distribution.
Combining measurements from all K2 campaigns, we detect rotation
periods in 29860 stars. The reliability of these periods was
estimated from stars observed more than once. We find that 75-90% of
the stars show period deviation smaller than 20% between different
campaigns, depending on the peak height threshold in the periodograms.
For effective temperatures below 6000K, the variability range shows a
local minimum at different periods, consistent with an isochrone age
of ∼750Myr. Additionally, the rotation period distribution shows
evidence for bimodality, although the dearth region in the K2 data is
less pronounced compared to the Kepler field. The period at the dip of
the bimodal distribution shows good agreement with the period at the
local variability minimum.
We conclude that the rotation period bimodality is present in
different fields of the sky, and is hence a general manifestation of
stellar magnetic activity. The reduced variability in the dearth
region is interpreted as a cancelation between dark spots and bright
faculae. Our results strongly advocate that the role of faculae has
been underestimated so far, suggesting a more complex dependence of
the brightness variability on the rotation period.
Description:
The table contains the measured rotation periods and fundamental
parameters of the stars in our sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 56 32387 Parameter table
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See also:
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC Unique identifier in the K2 input catalog
11- 12 I2 --- Campaign K2 observing campaign
14- 17 I4 K Teff Effective temperature
19- 22 F4.2 [cm2/s] logg Surface gravity
24- 28 F5.2 d Prot Rotation period
30- 34 F5.2 d e_Prot Rotation period uncertainty
36- 39 F4.2 --- HPeak Normalized peak height
41- 44 F4.2 % Rvar ? Variability range
46- 50 F5.2 mag Kpmag Kepler magnitude
52- 56 F5.2 mag GMAG ? Gaia absolute magnitude
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Acknowledgements:
Timo Reinhold, reinhold(at)mps.mpg.de,
Max Planck Institute for Solar System Research
(End) Timo Reinhold [Max Planck Inst.], Patricia Vannier [CDS] 27-Jan-2020