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Prospects for asteroseismology of
solar-like stars
T. Appourchaux
Institut d’Astrophysique Spatiale, Orsay
Contents
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HELAS VI: Helioseismology and applications
What is a solar-like star?
A shopping list for physics
The store: PLATO 2.0
Summary
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What is meant by a solar-like star?
Huber (2014)
Huber et al (2011)
Houdek et al (2000)
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Shopping list for physics
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Internal rotation (Subgiant stars, MS star)
Helium ionization and convection zones
Excitation and damping (mode physics)
Stellar cycle and activity
Atmosphere: surface effect, asymmetries
Stellar Radius, Mass and Age
Clusters and Binary stars
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Rotation in solar-like stars
Nielsen et al (2014)
Seismically derived rotation provides light on
differential rotation and gyrochronology
(a few stars)
HELAS VI: Helioseismology and applications
Davies et al (2014)
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Rotation in evolved stars
Deheuvels et al (2014)
g-mode like
p-mode like
Subgiant stars having mixed modes provides
the stellar rotation as a function of depth
(6 stars)
HELAS VI: Helioseismology and applications
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Second differences: in depths...
Mazumdar et al (2014)
BCZ
HeII
Signatures and depths of the base of the convection and second Helium ionization zones
(20 stars)
HELAS VI: Helioseismology and applications
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...leading to Helium abundance
Verma et al (2014)
Amplitude of the signature of the second Helium ionization
zone as a marker of helium abundance
(1 star)
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Mode physics: linewidth et al
Appourchaux et al (2014)
Different inferred background affects mode-physic parameters (and vice versa)
HELAS VI: Helioseismology and applications
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Stellar linewidths
Appourchaux et al (2014)
Linewidth depression at nmax decreases with effective temperature
(23 stars)
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Stellar activity
Garcia et al (2013)
Garcia et al (2010)
Sun
HD49933
Studies of stellar activity impact on seismic parameters
to be done on more stars than just 2!
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Departure from Lorentzian mode
profile (asymmetry)
Toutain and Kosovichev (2005)
Mode asymmetry yet to be detected in other stars than the Sun
(impact on stellar modelling)
HELAS VI: Helioseismology and applications
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Surface effects
Ball and Gizon (2014)
Understanding and proper modelling of surface effect key for stellar modelling
(8 stars)
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Stellar mass and radius
Huber et al (2012)
• Calibration of scaling laws using interferometry
• From scaling laws to stellar modelling
Lebreton and Goupil (2014)
White et al (2014)
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Stellar age
Lebreton and Goupil (2014)
No seismic proxy for stellar age (yet),
model comparison required using
frequencies and /or ratio
Metcalfe et al (2012)
Age determination on single stars
(>50 stars)
HELAS VI: Helioseismology and applications
Age calibration possible on binary stars
(3 binary stars)
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Binary stars
A "typical" seismic binary (Kepler)
"Speckle-Interferometry" binary
Chaplin et al (2014)
Appourchaux et al (2012)
Seismic binary detection 0.5% for MS
and subgiant stars to 1% for Red giants
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Clusters
Appourchaux et al (1993)
Stello et al (2011)
Improved stellar age precision and other stellar
parameters with cluster by a factor 3
(No cluster MS stars but...cluster RG stars)
HELAS VI: Helioseismology and applications
Seismic scaling relation
provides ways of identifying
cluster members
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PLATO 2.0
Credits: G. Perez Diaz, IAC (MultiMedia Service)
PLATO 2.0 in short
- Selected by ESA in February 2014
- 32 « Normal » 12cm cameras, cadence 25 s, white light
- 2 « Fast » 12cm cameras, cadence 2.5 s, 2 colours
- Dynamic range: 4 ≤ mV ≤ 16
- L2 orbit
- Nominal mission duration: 6 years launched in 2024
- 2 long pointings of 2-3 years + step-and-stare phase (2-5 months per pointing)
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PLATO 2.0 targets
4300 deg2
(long stare fields)
For the
Baseline mission
20,000 deg2
(plus step
and stare
fields)
Noise Level
(ppm/√hr)
Number of
cool stars
mV
Number of
cool stars
34
22,000
9.8-11.3
85,000
267,000
11.6-12.9
1,000,000
(Asteroseismology)
80
(Earth radius
detection)
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Summary
• Stellar physics will face a revolution with PLATO 2.0
• Stellar physics will improve in the following fields:
– Stellar evolution
– Internal structure and rotation (g modes?)
– Convection zone, HeII zone
– Stellar activity
– Seismic inversion and diagnostics (left out here...)
• Stellar physics will be calibrated with:
– Binary stars and clusters
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PLATO 2.0 observing strategy
Baseline observing strategy:
• 6 years nominal science operation
• 2 long pointings of 2-3 years + step-and-stare phase (2-5 months per pointing)
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