Rotation and differential rotation of active Kepler stars

By T. Reinhold, A. Reiners, G. Basri. 2013

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We present rotation periods for thousands of active stars in the Kepler field derived from Q3 data. In most cases a second period close to the rotation period was detected, which we interpreted as surface differential rotation (DR). Active stars were selected from the whole sample using the range of the variability amplitude. To detect different periods in the light curves we used the Lomb-Scargle periodogram in a pre-whitening approach to achieve parameters for a global sine fit. The most dominant periods from the fit were ascribed to different surface rotation periods, but spot evolution could also play a role. Due to the large number of stars the period errors were estimated in a statistical way. We thus cannot exclude the existence of false positives among our periods. In our sample of 40.661 active stars we found 24.124 rotation periods $P_1$ between 0.5-45 days. The distribution of stars with 0.5 < B-V < 1.0 and ages derived from angular momentum evolution that are younger than 300 Myr is consistent with a constant star-formation rate. A second period $P_2$ within $\pm30$% of the rotation period $P_1$ was found in 18.619 stars (77.2%). Attributing these two periods to DR we found that the relative shear $\alpha=\Delta\Omega/\Omega$ increases with rotation period, and slightly decreases with effective temperature. The absolute shear $\Delta\Omega$ slightly increases between $T_{eff}=3500-6000$ K. Above 6000 K $\Delta\Omega$ shows much larger scatter. We found weak dependence of $\Delta\Omega$ on rotation period. Latitudinal differential rotation measured for the first time in more than 18.000 stars provides a comprehensive picture of stellar surface shear, consistent with major predictions from mean-field theory. To what extent our observations are prone to false positives and selection bias is not fully explored, and needs to be addressed using more Kepler data.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/67e3768ac3fa54037f55856b2c898a2c73ea5e5c

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Citations in the corpus

THE KEPLER CATALOG OF STELLAR FLARES (2016, background): “(5) Using this iteratively smoothed light curve segment, which should have most large amplitude flares removed, I search for periodic signals in the data that are typically due to starspot modulations (e.g. Reinhold et al. 2013; Davenport et al. 2015).”
ROTATION PERIODS OF 34,030 KEPLER MAIN-SEQUENCE STARS: THE FULL AUTOCORRELATION SAMPLE (2014, methodology): “To directly compare our periods with those detected by Reinhold et al. (2013) and Nielsen et al. (2013), for the stars where both methods report periods, we plotted their periods versus ours in Figure 7.”
Rotation and magnetism of Kepler pulsating solar-like stars : Towards asteroseismically calibrated age-rotation relations (2014, methodology): “Reinhold et al. (2013) also studied the low-frequency part of the periodogram – computed using only Q3 data – to extract rotation periods and differential rotation for almost 20 000 targets in a wider range of periods from 0.5 to 45 days.”
K2 Variable Catalogue: Variable Stars and Eclipsing Binaries in K2 Campaigns 1 and 0 (2015, methodology): “…Kepler space telescope was primarily aimed at the detection and study of exoplanets, its high precision lightcurves were used for studies with astroseismology (e.g. Chaplin et al. 2013), stellar rotation (e.g. Reinhold et al. 2013) and eclipsing binaries (e.g. Prsa et al. 2011), to name just a few.”
Rotation, differential rotation, and gyrochronology of active Kepler stars (2015, methodology): “To detect periodic signals in the data we use the LombScargle periodogram in a prewhitening approach as described in Reinhold et al. (2013).”