315 research outputs found
The Kepler Smear Campaign: Light curves for 102 Very Bright Stars
We present the first data release of the Kepler Smear Campaign, using
collateral 'smear' data obtained in the Kepler four-year mission to reconstruct
light curves of 102 stars too bright to have been otherwise targeted. We
describe the pipeline developed to extract and calibrate these light curves,
and show that we attain photometric precision comparable to stars analyzed by
the standard pipeline in the nominal Kepler mission. In this paper, aside from
publishing the light curves of these stars, we focus on 66 red giants for which
we detect solar-like oscillations, characterizing 33 of these in detail with
spectroscopic chemical abundances and asteroseismic masses as benchmark stars.
We also classify the whole sample, finding nearly all to be variable, with
classical pulsations and binary effects. All source code, light curves, TRES
spectra, and asteroseismic and stellar parameters are publicly available as a
Kepler legacy sample.Comment: 35 pages, accepted ApJ
An asteroseismic age estimate of the open cluster NGC 6866 using Kepler and Gaia
Asteroseismology of solar-like oscillations in giant stars allow the
derivation of their masses and radii. For members of open clusters this allows
an age estimate of the cluster which should be identical to the age estimate
from the colour-magnitude diagram, but independent of the uncertainties that
are present for that type of analysis. Thus, a more precise and accurate age
estimate can be obtained. We aim to measure asteroseismic properties of
oscillating giant members of the open cluster NGC 6866 and utilise these for a
cluster age estimate. Model comparisons allow constraints on the stellar
physics, and here we investigate the efficiency of convective-core overshoot
and effects of rotation during the main-sequence, which has a significant
influence on the age for these relatively massive giants. We identify six giant
members of NGC 6866 and derive asteroseismic measurements for five of them.
This constrains the convective-core overshoot and enables a more precise and
accurate age estimate than previously possible. Asteroseismology establishes
the helium-core burning evolutionary phase for the giants, which have a mean
mass of 2.8 . Their radii are significantly smaller than predicted
by current 1D stellar models unless the amount of convective-core overshoot on
the main sequence is reduced to in the
step-overshoot description. Our measurements also suggest that rotation has
affected the evolution of the stars in NGC 6866 in a way that is consistent
with 3D simulations but not with current 1D stellar models. The cluster age is
estimated to be 0.43 0.05 Gyr, significantly younger and more precise
than most previous estimates. We derive a precise cluster age while
constraining convective-core overshooting and effects of rotation in the
models. We uncover potential biases for automated age estimates of helium-core
burning stars.Comment: Accepted on 21/08/2023 for publication in Section 7. Stellar
structure and evolution of Astronomy & Astrophysics. 20 Pages, 11 Figures +
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