108 research outputs found
Galactic Archaeology with TESS: Prospects for Testing the Star Formation History in the Solar Neighbourhood
A period of quenching between the formation of the thick and thin disks of
the Milky Way has been recently proposed to explain the observed
age-[{\alpha}/Fe] distribution of stars in the solar neighbourhood. However,
robust constraints on stellar ages are currently available for only a limited
number of stars. The all-sky survey TESS (Transiting Exoplanet Survey
Satellite) will observe the brightest stars in the sky and thus can be used to
investigate the age distributions of stars in these components of the Galaxy
via asteroseismology, where previously this has been difficult using other
techniques. The aim of this preliminary study was to determine whether TESS
will be able to provide evidence for quenching periods during the star
formation history of the Milky Way. Using a population synthesis code, we
produced populations based on various stellar formation history models and
limited the analysis to red-giant-branch stars. We investigated the
mass-Galactic-disk-height distributions, where stellar mass was used as an age
proxy, to test for whether periods of quenching can be observed by TESS. We
found that even with the addition of 15% noise to the inferred masses, it will
be possible for TESS to find evidence for/against quenching periods suggested
in the literature (e.g. between 7 and 9 Gyr ago), therefore providing stringent
constraints on the formation and evolution of the Milky Way.Comment: 4 pages, 3 figures, proceedings of "Seismology of the Sun and the
Distant Stars 2016", Mario J. P. F. G. Monteiro, Margarida S. Cunha, Joao
Miguel T. Ferreira editor
KOI-3890: A high mass-ratio asteroseismic red-giantM-dwarf eclipsing binary undergoing heartbeat tidal interactions
KOI-3890 is a highly eccentric, 153-day period eclipsing, single-lined
spectroscopic binary system containing a red-giant star showing solar-like
oscillations alongside tidal interactions. The combination of transit
photometry, radial velocity observations, and asteroseismology have enabled the
detailed characterisation of both the red-giant primary and the M-dwarf
companion, along with the tidal interaction and the geometry of the system. The
stellar parameters of the red-giant primary are determined through the use of
asteroseismology and grid-based modelling to give a mass and radius of
and
respectively. When combined with
transit photometry the M-dwarf companion is found to have a mass and radius of
and
. Moreover, through
asteroseismology we constrain the age of the system through the red-giant
primary to be . This provides a constraint on
the age of the M-dwarf secondary, which is difficult to do for other M-dwarf
binary systems. In addition, the asteroseismic analysis yields an estimate of
the inclination angle of the rotation axis of the red-giant star of
degrees. The obliquity of the system\textemdash the
angle between the stellar rotation axis and the angle normal to the orbital
plane\textemdash is also derived to give degrees
showing that the system is consistent with alignment. We observe no radius
inflation in the M-dwarf companion when compared to current low-mass stellar
models.Comment: 11 pages, 5 figures, accepted for publication in MNRA
What asteroseismology can do for exoplanets
We describe three useful applications of asteroseismology in the context of
exoplanet science: (1) the detailed characterisation of exoplanet host stars;
(2) the measurement of stellar inclinations; and (3) the determination of
orbital eccentricity from transit duration making use of asteroseismic stellar
densities. We do so using the example system Kepler-410 (Van Eylen et al.
2014). This is one of the brightest (V = 9.4) Kepler exoplanet host stars,
containing a small (2.8 Rearth) transiting planet in a long orbit (17.8 days),
and one or more additional non-transiting planets as indicated by transit
timing variations. The validation of Kepler-410 (KOI-42) was complicated due to
the presence of a companion star, and the planetary nature of the system was
confirmed after analyzing a Spitzer transit observation as well as ground-based
follow-up observations.Comment: 4 pages, Proceedings of the CoRoT Symposium 3 / Kepler KASC-7 joint
meeting, Toulouse, 7-11 July 2014. To be published by EPJ Web of Conference
Bayesian hierarchical inference of asteroseismic inclination angles
The stellar inclination angle-the angle between the rotation axis of a star
and our line of sight-provides valuable information in many different areas,
from the characterisation of the geometry of exoplanetary and eclipsing binary
systems, to the formation and evolution of those systems. We propose a method
based on asteroseismology and a Bayesian hierarchical scheme for extracting the
inclination angle of a single star. This hierarchical method therefore provides
a means to both accurately and robustly extract inclination angles from red
giant stars. We successfully apply this technique to an artificial dataset with
an underlying isotropic inclination angle distribution to verify the method. We
also apply this technique to 123 red giant stars observed with
. We also show the need for a selection function to account
for possible population-level biases, that are not present in individual
star-by-star cases, in order to extend the hierarchical method towards
inferring underlying population inclination angle distributions.Comment: 20 pages, 12 figures, accepted for publication in MNRA
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