Catania 09/08SIAMOIS1/26 Benoît Mosser, for the SIAMOIS team Ground-based Doppler asteroseismology after CoRoT and Kepler

Catania 09/08SIAMOIS2/26 Asteroseismology What do we need after CoRoT, that Kepler, and hopefully PLATO, will not provide? Doppler velocity (Space-borne observations are photometric) Provide additional information More precise for structure inversion Ground-based High duty cycle, continuous measurements Dome C in Antarctica provide excellent observation conditions Scientific objectives require the observation of a few bright targets for convergence of very precise measurements observed with a small collector Asteroseismic program at Dome C simple, robust, with an easy setup

Catania 09/08SIAMOIS3/26 Spectrometry / Photometry

Catania 09/08SIAMOIS4/26 Granulation noise

Catania 09/08SIAMOIS5/26 HD CoRoT/HARPS data Mosser et al 2005 Appourchaux et al 2008, in press

Catania 09/08SIAMOIS6/26 Additional Information l =3 modes not visible in photometry Granulation noise at low frequency

Catania 09/08SIAMOIS7/26 Large and small separations Small separation  1-3

Catania 09/08SIAMOIS8/26 Doppler / photometry on the Sun Inversion 4 times more precise with Doppler data Low low-frequency noise + l=3 modes  Courtesy Thierry Appourchaux

Catania 09/08SIAMOIS9/26 High duty cycle, long duration time series

Catania 09/08SIAMOIS10/26 Clear sky fraction at Dome C Clear sky fraction > 90% during 84% of the time Average number of consecutive clear days: 6.8 days Clear sky fraction (naked eye, Eric Aristidi, 2006 winter)

Catania 09/08SIAMOIS11/26 Duty cycle: h_sun = -4° Bad weather Operations: telescope derotation… Sky brightness Resulting duty cycle (bright targets) > 90% during 90 days Mosser & Aristidi 2007

Catania 09/08SIAMOIS12/26 Duty cycle: h_sun = -8°

Catania 09/08SIAMOIS13/26 Duty cycle: h_sun = -13°

Catania 09/08SIAMOIS14/26 Duty cycle at Dome C Performance at Dome C compared to a 6-site network as GONG (Mosser & Aristidi 2007, PASP) [GONG data]

Catania 09/08SIAMOIS15/26 Scientific program

Catania 09/08SIAMOIS16/26 Scientific program High-precision determination of the interior structure of nearby stars Age determination~ a few % Stellar radii (impact for exoplanet radii)~ a few % Composition Comparative study: photometry / Doppler Convection, damping, excitation mechanisms Diagnostic of convective cores; depth of convection and of second Helium ionization zones Classical pulsators Non-linear physics, saturation effects, mode coupling Stochastically excited modes Slowly rotating targets Rotation

Catania 09/08SIAMOIS17/26 Simulations F6V star, mV = 4, vsini = 5 km/s, 90-day long run Modelling: stochastic excitation + intrinsic damping + SIAMOIS characteristics and performance l =

Catania 09/08SIAMOIS18/26 Simulations F6V star, mV = 4.5, vsini = 5 km/s, 90-day long run Precision on the eigenfrequency measurement: 0.10 – 0.25  Hz (Libbrecht 1992) l = Longer lifetimes at low frequency  clear multiplets

Catania 09/08SIAMOIS19/26 Targets with a 40-cm telescope Observable solar-like stars with p-mode oscillations for a dedicated 40-cm telescope 40-cm telescope: - 7 bright targets, type: F, G, K class: IV & V - many red giants;  Scuti (v sin i < 20 km/s)  Enough targets for completing the scientific program in 3 to 6 winterings [for all selected targets SNR > 6 in 5 nights]

Catania 09/08SIAMOIS20/26 Targets with a 40-cm telescope Long duration observation  dedicated collector Observable targets (solar- like stars with solar-like oscillations) with SIAMOIS and a 40-cm telescope dedicated to the project

Catania 09/08SIAMOIS21/26 With a 2-m telescope dimmer solar-like targets (e.g. star with exoplanets; Sylvie Vauclair’s cancelled talk) ro Ap+ any target with  doradusvsini < 20 km/s  scutimV< 10.5 red giants Out of the scope of SIAMOIS: white dwarfs and subdwarf B stars (too faint magnitude (13  19), with a limited number of too broad spectral lines) Don Kurtz ’ talk; Gerard Vauclair ’ s cancelled presentation  For bright targets, dedicated small telescope  For dimmer targets, shared larger telescope

Catania 09/08SIAMOIS22/26 Conclusion

Catania 09/08SIAMOIS23/26 Space / Ground spaceground Observationphotometryspectrometry Max. degree2 3 Targets magnitudefaint bright v sin i  < 20 km/s Inversion4 times more precise Precise Doppler measurements on nearby bright targets + convergent measurements (interferometry, high resolution spectrometry…)  Determination of a sample of stellar standards  Insights into the physical laws governing stellar interiors Photometry on faint targets, without any other precise measurements  Statistical approach

Catania 09/08SIAMOIS24/26 Comparison CoRoTKeplerPLATOSONGSIAMOIS 2 eyes diam = 12° 10° x 10° (Cygnus-Lyra) 20° x 20°|  | < 30° 4 sites full sky  <  45° Duty cycle 92%~ 100%~ 100% (L2)~ 85%~ 90% 5-day perf. 0.6 ppm~ ppm 2-20 cm/s Max obs. 5 months < 4 years> 4 years3 months Magnitude > 6> 9< 13<7 # targets 28Up to 40 : 4 yr Up to 160 : 1 yr Up to 1000 : 90 d >100> 30 # solar-like 4~ few 1007 Status In operationLaunch = 04/ 2009 Assessment study at ESA Phase A funded Prototype > 2011 Network > 2014 Phase A is OK 2013 at Dome C Instrument cost 65 M€Class M project> 12 M€ (6 tel)0.86 M€ (1 tel) 1.02 M€ (2 tel)

Catania 09/08SIAMOIS25/26Granada: /04/ 08 Doppler asteroseismology Space-borne observations = photometric observations MOST, CoRoT, Kepler, Brite, PLATO… Ground-based observations = Doppler observations - less noise at low frequency - measurement of modes up to degree l= 3 - observation of bright stars  very precise inversion and modelling - looking in great detail into nearby stars - identifying the physical processes Dome C= unique site for asteroseismology 3-month continuous observation with duty cycle ~ 90% * High performance with a 40-cm collector * Scientific program with 40-cm and 2-m collectors Next talk

Catania 09/08SIAMOIS26/26 Additional material

Catania 09/08SIAMOIS27/26 Perspectives Asteroseismology requires uninterrupted long-duration time series! 1 dedicated 40-cm telescope: - first season observation - fiber FOV = 5’’ (>> seeing)  stellar magnitude < 5 for solar-like oscillations < 7 for classical pulsators 2 or 3 dedicated small telescopes - next step  simultaneous observations of 2 or 3 stars 2-m class telescope? -stellar magnitude < 8.5 for solar-like oscillations - increase of the number of reachable targets  possibility to achieve specific observations in selected targets However, a dedicated telescope would be required

Catania 09/08SIAMOIS28/26 Fourier transform Seismometry: The Doppler signal is retrieved from the interferogram of the stellar spectrum Fourier Transform Seismometry

Catania 09/08SIAMOIS29/26 Photometry / activity

Catania 09/08SIAMOIS30/26 Bright targets Solar-like targets with solar-like oscillations [A scaled to (L/M) 0.7 ] -  Scuti-  Dor- PMS - Red giants

Catania 09/08SIAMOIS31/26 An example HD , F8V, mV = 4.2 Observations with HARPS: - 5 nights - duty cycle ~ 40 % - SNR = 5  Precision of interior structure parameters improved by a factor 3 to 10 Mosser et al 2008