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| Paper: |
Asteroseismology of Cool Dwarfs and Giants with Kepler |
| Volume: |
448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun |
| Page: |
167 |
| Authors: |
Gilliland, R. L. |
| Abstract: |
The primary science goal of the Kepler Mission is to detect planets
in the habitable zones of their host stars where liquid water could exist
on the planet surface, and to determine the intrinsic frequency of these
and other exoplanets. The technique employed by Kepler is to search
for shallow transits, that in the case of a true Earth analog would be
85 parts per million deep, lasting an average of 10 hours, and happening
once per year. This combination of small, short, and rare events drives
mission development and operations to support ultra-high precision
photometry on one field of 150,000 largely solar-like stars with nearly
continuous exposures covering at least 3.5 years. Since the transit depth
returns only the size of a candidate planet relative to the size of its
host star, fulfillment of an additional Kepler science goal of
determining physical properties of the discovered planets requires us to
also determine stellar properties, with stellar radius being the most
important. For the latter asteroseismology is a particularly important
tool that allows stellar radii to be determined to ∼1% in favorable
cases.
The Kepler asteroseismology program is organized into a large
international collaboration – the Kepler Asteroseismic Science
Consortium consisting of a dozen working groups and some 300 members.
The observations to date in the area of cool giant stars consist of
30 minute integrations for some 1,200 stars spanning a full year.
For cool dwarfs the observations to date using 1 minute integrations aimed at asteroseismology
consist of three types: (1) A few thousand stars observed for one month
each in a “survey” mode to identify the best prospects for lengthier
observations. (2) About 200 stars hosting planet candidates observed for periods now reaching
up to a year for which asteroseismology is
desired whenever possible. (3) A set of about 100 stars for which much
more extended observations are possible that have been selected purely
on the basis of asteroseismic interest.
The red giants have typical magnitudes of about 12th, with a couple
of hundred selected at brighter magnitudes. In nearly all cases the
astrophysical signatures of oscillations and granulation dominate
noise sources.
Cool dwarfs studied for asteroseismology range from 16 Cyg A and B
near 6th magnitude, to planet host stars of 13th magnitude for which
extensive observations may allow detection of at least the
asteroseismic large separation to constrain the stellar mean density
and hence radius.
I review the target selections, the instrumental capabilities
relevant for cool-star asteroseismology, and the basic approaches
and promises of asteroseismology. Emphasis is given to
reviewing the extensive new returns from the Kepler Mission
that are providing new insights into cool dwarfs and giants from
asteroseismic analyses. |
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