ORCID Profile
0000-0002-4858-7598
Current Organisation
University of Tokyo
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Publisher: American Astronomical Society
Date: 12-2022
Abstract: We perform intensity variability analyses (photometric analyses: the Lomb–Scargle periodogram, autocorrelation, and wavelet) and asteroseismic analysis of 92 Kepler solar-like main-sequence stars to understand the reliability of the measured stellar rotation periods. We focus on the 70 stars without reported stellar companions, and classify them into four groups according to the quarter-to-quarter variance of the Lomb–Scargle period and the precision of the asteroseismic period. We present detailed in idual comparison among photometric and asteroseismic constraints for these stars. We find that most of our targets exhibit significant quarter-to-quarter variances in the photometric periods, suggesting that the photometrically estimated period should be regarded as a simplified characterization of the true stellar rotation period, especially under the presence of the latitudinal differential rotation. On the other hand, there are a fraction of stars with a relatively small quarter-to-quarter variance in the photometric periods, most of which have consistent values for asteroseismically and photometrically estimated rotation periods. We also identify over 10 stars whose photometric and asteroseismic periods significantly disagree, which would be potentially interesting targets for further in idual investigations.
Publisher: American Astronomical Society
Date: 04-2008
DOI: 10.1086/524984
Publisher: American Astronomical Society
Date: 12-04-2019
Publisher: American Astronomical Society
Date: 18-05-2009
Publisher: American Physical Society (APS)
Date: 09-07-2007
Publisher: American Astronomical Society
Date: 07-03-0009
Publisher: American Astronomical Society
Date: 10-2007
DOI: 10.1086/518864
Publisher: American Astronomical Society
Date: 11-2022
Abstract: We examine the stability of hierarchical triple systems using direct N -body simulations without adopting a secular perturbation assumption. We estimate their disruption timescales in addition to the mere stable/unstable criterion, with particular attention to the mutual inclination between the inner and outer orbits. First, we improve the fit to the dynamical stability criterion by Mardling & Aarseth widely adopted in the previous literature. Especially, we find that that the stability boundary is very sensitive to the mutual inclination coplanar retrograde triples and orthogonal triples are much more stable and unstable, respectively, than coplanar prograde triples. Next, we estimate the disruption timescales of triples satisfying the stability condition up to 10 9 times the inner orbital period. The timescales follow the scaling predicted by Mushkin & Katz, especially at high e out where their random walk model is most valid. We obtain an improved empirical fit to the disruption timescales, which indicates that the coplanar retrograde triples are significantly more stable than the previous prediction. We furthermore find that the dependence on the mutual inclination can be explained by the energy transfer model based on a parabolic encounter approximation. We also show that the disruption timescales of triples are highly sensitive to tiny changes of the initial parameters, reflecting the genuine chaotic nature of the dynamics of those systems.
Publisher: EDP Sciences
Date: 2015
Publisher: SPIE
Date: 09-08-2016
DOI: 10.1117/12.2232103
No related grants have been discovered for Yasushi Suto.