prospects for asteroseismology of solar-like stars t. appourchaux institut d’astrophysique...
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Prospects for asteroseismology of solar-like stars
T. Appourchaux
Institut d’Astrophysique Spatiale, Orsay
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Contents
• What is a solar-like star?• A shopping list for physics• The store: PLATO 2.0• Summary
HELAS VI: Helioseismology and applications
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What is meant by a solar-like star?
HELAS VI: Helioseismology and applications
Houdek et al (2000)
Huber (2014)
Huber et al (2011)
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Shopping list for physics
• 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
HELAS VI: Helioseismology and applications
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Rotation in solar-like stars
HELAS VI: Helioseismology and applications
Nielsen et al (2014)
Davies et al (2014)
Seismically derived rotation provides light on differential rotation and gyrochronology
(a few stars)
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Rotation in evolved stars
HELAS VI: Helioseismology and applications
Deheuvels et al (2014)
Subgiant stars having mixed modes provides the stellar rotation as a function of depth
(6 stars)
g-mode like
p-mode like
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Second differences: in depths...
HELAS VI: Helioseismology and applications
Mazumdar et al (2014)
BCZ
HeII
Signatures and depths of the base of the convection and second Helium ionization zones(20 stars)
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...leading to Helium abundance
HELAS VI: Helioseismology and applications
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
HELAS VI: Helioseismology and applications
Appourchaux et al (2014)
Different inferred background affects mode-physic parameters (and vice versa)
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Stellar linewidths
HELAS VI: Helioseismology and applications
Appourchaux et al (2014)
Linewidth depression at nmax decreases with effective temperature(23 stars)
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Stellar activity
HELAS VI: Helioseismology and applications
Garcia et al (2010)
Garcia et al (2013)
Studies of stellar activity impact on seismic parameters to be done on more stars than just 2!
Sun HD49933
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Departure from Lorentzian mode profile (asymmetry)
HELAS VI: Helioseismology and applications
Toutain and Kosovichev (2005)
Mode asymmetry yet to be detected in other stars than the Sun (impact on stellar modelling)
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Surface effects
HELAS VI: Helioseismology and applications
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
HELAS VI: Helioseismology and applications
Huber et al (2012)
White et al (2014)
Lebreton and Goupil (2014)
• Calibration of scaling laws using interferometry• From scaling laws to stellar modelling
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Stellar age
HELAS VI: Helioseismology and applications
Lebreton and Goupil (2014)
Metcalfe et al (2012)
Age calibration possible on binary stars(3 binary stars)
Age determination on single stars(>50 stars)
No seismic proxy for stellar age (yet), model comparison required using
frequencies and /or ratio
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Binary stars
HELAS VI: Helioseismology and applications
Chaplin et al (2014)
Seismic binary detection 0.5% for MS and subgiant stars to 1% for Red giants
A "typical" seismic binary (Kepler)
Appourchaux et al (2012)
"Speckle-Interferometry" binary
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Clusters
HELAS VI: Helioseismology and applications
Seismic scaling relation provides ways of
identifying cluster members
Stello et al (2011)
Appourchaux et al (1993)
Improved stellar age precision and other stellar parameters with cluster by a factor 3
(No cluster MS stars but...cluster RG stars)
Credits: G. Perez Diaz, IAC (MultiMedia Service)
PLATO 2.0
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PLATO 2.0 in short
HELAS VI: Helioseismology and applications
- 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
HELAS VI: Helioseismology and applications
4300 deg2 (long stare fields)
20,000 deg2 (plus step and stare
fields)
Noise Level (ppm/√hr)
Number of cool stars
mV Number of cool stars
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(Asteroseismology)
22,000 9.8-11.3 85,000
80(Earth radius detection)
267,000 11.6-12.9 1,000,000
For the Baseline mission
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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
HELAS VI: Helioseismology and applications
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PLATO 2.0 observing strategy
HELAS VI: Helioseismology and applications
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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