2. March 21, 2006SONG workshop1/27 SIAMOIS Sismomètre Interferentiel A Mesurer les Oscillations des Intérieurs Stellaires An asteroseismic network with 1 site... in Antarctica Benoît Mosser, Tristan Buey, Claude Catala Michel Auvergne, Thierry Appourchaux, Annie Baglin, Caroline Barban, François Bouchy, Stéphane Charpinet, Marc-Antoine Dupret, Marie-Jo Goupil, Jean-Pierre Maillard, Eric Michel, Reza Samadi, François-Xavier Schmider, Frédéric Thévenin, Gérard Vauclair et al. Observatoire de Paris/LESIA, IAP, IAS, UNSA/LUAN, OMP/LATT, OCA

3. March 21, 2006SONG workshop2/27 SUMMARY Which program in asterosismology after COROT ? Dome C in Antarctica SIAMOIS: principle SIAMOIS: performances (/ SONG) Project: organisation, science

4. March 21, 2006SONG workshop3/27 Ground-based observations, 2006 Ground-based asteroseismic observations remain limited by the window effect

5. March 21, 2006SONG workshop4/27 Ground-based observations, 2006 Even with bi-sites observations Continuous observations are required for precise structure modelling Kjeldsen et al 2005

6. March 21, 2006SONG workshop5/27 In 2009, end of COROT will have done a considerable work ! And after that ???

7. March 21, 2006SONG workshop6/27 Photometry / spectrometry Spectrometry less sensitive to granulation than photometry Visibility of l = 3 modes enhanced about ~ 3 times in spectometry  Small separation between modes with degrees 1 et 3 Ground-based measurements = spectrometric observations Necessarily: continuity, long duration  network or Antarctica

8. March 21, 2006SONG workshop7/27 Dome C Concordia station, Italy + France 75°06’ south, 123°21’ east Average temperatures  40°C in summer  60°C in winter Slow wind Rare precipitations: 2 to 10 cm snow/year Polar night: 3 months

9. March 21, 2006SONG workshop8/27 Duty cycle > 90 % during 3 months in winter (K. Agabi)

10. March 21, 2006SONG workshop9/27 (First) observations at Dome C Specifications for observations at Dome C integrated project - has to be fully tested before installation in Antarctica - with limited setup small size telescope - pioneering project project has to be fully automatic, ~ spatial condition - human intervention limited to routine, or survival - mass, power, telemetry: limited values scientific programme has to be - ambitious - unfeasible elsewhere - to make sense after COROT

11. March 21, 2006SONG workshop10/27 Observations at Dome C -1- dedicated asteroseismometer with a small size telescope first wintering in 2010 -2-2-m class telescope + spectropolarimeter IPEV (Institut Paul-Emile Victor) - in charge of the Concordia base; wintering since 2005 - supervises scientific projects INSU (National Institute for Astronomy)/ Antarctic group - promotes observations at Dome C - has to identify pioneering projects in astronomy PNPS (National programme for stellar physics) - promotes the rapid development of an asteroseismometer at Dome C

12. March 21, 2006SONG workshop11/27 Principle ( Bouchy et al. 2001): photon noise limited performances An asteroseismometer has to be extremely stable and efficient - quality factor Q - number of photoelectrons N e Q depends on: - the spectral type and rotation of the star - the instrument GS: grating spectrometer FS: Fourier Transform spectrometer Doppler asteroseismometry

13. March 21, 2006SONG workshop12/27 The quality factor gives a measure of the: - number - depth - width of the stellar lines Q # dln A /dln Stellar quality factor Cool stars are favored Better performances in the blue part of the visible spectrum

14. March 21, 2006SONG workshop13/27 The real quality factor depends on the resolution R of the spectrometer A high resolution requires a narrow entrance slit as well as a large spectrometer R # f / d Seismology with a GS Grating spectrometer: necessarily a large instrument

15. March 21, 2006SONG workshop14/27 Fourier transform Seismometry The Doppler signal is searched in the interferogram of part of the stellar spectrum FS: seismometry by TF

16. March 21, 2006SONG workshop15/27 FT seismometry successfully tested with the FTS at CFHT Procyon Mosser et al. 1998, A&A 340, 457 Jupiter Mosser et al. 2000, Icarus 144, 104 Sismometry by TF FTS at CFHT: scan of one fringe Dedicated instrument: simultaneous scan of the fringe signal

17. March 21, 2006SONG workshop16/27 ( Mosser et al. 2003, PASP 115, 990) Q increases with - wavenumber   - working path difference  opt - fringe contrast C A high fringe contrast C requires a narrow bandwidth … in contradiction with the specification on N e FS: quality factor It is necessary to observe with a post-dispersive device avec

18. March 21, 2006SONG workshop17/27 Fourier transform seismometry with post-dispersion The Doppler signal is searched in the interferogram of each spectral element defined by the post- dispersion FS: post - dispersion

19. March 21, 2006SONG workshop18/27 FS / GS GSFS Fiberdouble scrambler ( /400) 1"~ 6 m/s simple scrambler ( /100) 1" ~ 1 cm/s Quality factor Q GS = Q(Q *, R)Q FS = Q(Q *, R pd ) Resolution Dispersion R ~ 10 5 ----- Post-dispersionPost-dispersion R pd ~1000 InterferenceGrating ~ 10 x 40 cmPath difference 1 cm CCD4k x 2k1k x 256 GS: smaller and simpler instrument, monolithic interferometer, no moving parts  possible installation and setup in Antarctica

20. March 21, 2006SONG workshop19/27 Antarctic / network ProjectsSONGSIAMOIS Equatorial networkConcordia, Dome C # sites for duty cycle > 90% At least 61  Technology; redundancy ? Site: duty cycle, altitude Site Budget N1 k€ by site; N2 sites N1 x N2 k€ 850 k€ On-site maintenanceN2 sites~ space project Complementary projects

21. March 21, 2006SONG workshop20/27 Performances: GS / FS GS: HARPS (ref = ThAr lamp) R ~ 90000 FS: SIAMOIS; post- dispersion providing a spectral resolution R~ 1000. GS > FS if reference = ThAr lamp (Mosser et al. 2003) GS ~ FS if reference = iodine cell

22. March 21, 2006SONG workshop21/27 GS: performances at Dome C Photon noise limited performances SIAMOIS, at Dome C, 40-cm telescope, 120 hours with 95% duty cycle, mV = 4 ‘‘SNR’’ on circumpolar targets

23. March 21, 2006SONG workshop22/27 Targets Observable targets with SIAMOIS and a 40-cm telescope dedicated to the project 40-cm telescope: - 7 targets, type: F, G, K class: IV & V - many red giants;  Scuti (v sin i < 20 km/s)  Scientific programme for more than 6 winterings COROT

24. March 21, 2006SONG workshop23/27 Targets 1) K, G, F, class IV & V targets

25. March 21, 2006SONG workshop24/27 Targets 1) K, G, F, class IV & V targets 2) red giants 3) delta-Scuti

26. March 21, 2006SONG workshop25/27 Instrument 40-cm telescope low cost, easy ‘antartization’, dedicated to the project Interferometer monolithic instrument no moving parts, reduced size fiber fed Post-dispersion efficiency, photon noise limited performances

27. March 21, 2006SONG workshop26/27 Planning 2004 - design 2006 - thermo-mechanical analysis 2007 - PDR - FDR 2008 - integration 2009 - tests - summer campaign: Dome C 2010 - first winterover at Dome C Laboratories: LESIA (Obs. Paris), IAS (Orsay), LUAN (Nice), LATT (Toulouse) SIAMOIS Interferometer JP Amans, GEPI, Obs Paris

28. March 21, 2006SONG workshop27/27 Dome C: a unique site for asterosismology 3-month continuous observation with duty cycle ~ 90% A specific scientific program after High performances with a 40-cm collector –Pioneering project at Dome C –FT seismometry: suitable concept for installation and setup at Dome C –Multiplex advantage of FT spectrometry Conclusion ‘‘Big science’’ at Dome C with a budget < 1 ME