Asteroseismology from space and from the ground Benot

Asteroseismology, from space and from the ground Benoît Mosser September 17, 2007 Observatoire de Paris/LESIA 2 nd ARENA Conference Postdam 1

Summary 1. Space-borne asteroseismology Co. Ro. T results 2. Ground-based observations Current results 3. Future projects Space, network, Dome C 4. Comparison / complementarity and unique role of Dome C September 17, 2007 2 nd ARENA Conference Postdam 2

Asteroseismology • Age determination • Stellar radii (impact for exoplanet radii) • Composition ~ a few % • Diagnostic of convective cores • Depth of convection and of second Helium ionization zones • Excitation mechanisms (convection) • Rotation and internal structure Specification: September 17, 2007 eigenfrequency precision continuous observations long duration 2 nd ARENA Conference Postdam = 0. 2 m. Hz (h > 80 %) (T > 2. 5 months) 3

Co. Ro. T • launched on December 27 th , 2006 • by Soyuz 2, from Baikonour, Kazakhstan • low Earth polar orbit, 896 km altitude • orbital period 6184 s (~1 h 43 mn, 162 m. Hz) • high precision photometry The Co. Ro. T space mission has been developped and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany and Spain September 17, 2007 2 nd ARENA Conference Postdam 4

Co. Ro. T « Eyes » Co. Ro. T eyes: d=0, a=6 h 50 and 18 h 50 September 17, 2007 2 nd ARENA Conference Postdam 5

Co. Ro. T asteroseismology targets 7 B stars, including 1 known Beta Ceph, 3 Be, 1 ecl. bin. 4 giants (G, F) 12 A stars including 4 known pulsators, 2 Am, 2 Ap, 2 eclips. Bin. 3 (early) F stars 4 solar-like puls. cand. 5 -month long run on each target September 17, 2007 2 nd ARENA Conference Postdam 6

Co. Ro. T first observations February, March initial run, 60 days April 1 st short run May, 11 Oct. 15 1 st long run not yet completed Raw data N 0 OK 1 st corrections N 1 OK Scientific data N 2 not yet distributed Sensitivety 0. 6 ppm in 5 days, for m. V=5. 4 as expected Duty cycle 92% (6% lost in SAA) better than expected September 17, 2007 2 nd ARENA Conference Postdam 7

Example of light curves Typically 10 -4 in 30 s A 6 th mag F-type star showing daily variability below the 10 -3 level September 17, 2007 2 nd ARENA Conference Postdam 8

Light curve An 9 th magnitude suspected delta Scuti showing beat phenomena at a few 10 -3 September 17, 2007 2 nd ARENA Conference Postdam 9

Light curve An 8 th magnitude B star in an eclipsing binary September 17, 2007 2 nd ARENA Conference Postdam 10

Quiet target A 7 th magnitude giant F star showing very low dispersion of ~10 -4 September 17, 2007 2 nd ARENA Conference Postdam 11

HD 49933 1 st solar-like target, initial run, 60 days Simulations: Baudin et al. 06 Photon noise Granulation September 17, 2007 2 nd ARENA Conference Postdam 12

HD 49933, observed Mosser et al. 2005, 10 days with HARPS, duty cycle ~ 23% September 17, 2007 2 nd ARENA Conference Postdam 13

d Scuti Example of an 8 th magnitude delta Scuti observed with Co. Ro. T. The red line illustrates common lowest detection limit from the ground. September 17, 2007 2 nd ARENA Conference Postdam 14

Ground-based observations • solar-like oscillations in solar-like stars - HARPS @ ESO 3. 6 -m - UCLES @ AAT - CORALIE @ Euler telescope - SOPHIE @ OHP + instruments @ SARG, Mc. D, Okoyama, Lick Oscillation detection Mode identification 2 -sites observation Network observation Stellar structure modelling Rotation, fine structure… September 17, 2007 ٧ ٧ ٧ ~ 20 targets for ~ 12 targets 5 targets 1 target (Procyon) ~ 2 targets Observations limited to a few days insufficient precision 2 nd ARENA Conference Postdam 15

Single/multi-sites observation September 17, 2007 2 nd ARENA Conference Postdam 16

Proyon: network observations January 2007: Multi-site campaign -AAT -Okoyama -TLS -OHP -NOT -SARG -ESO -Euler -Mc. Donald -Lick • Arentoft et al. ; Bedding et al, in preparation • time series ~ 9 days September 17, 2007 2 nd ARENA Conference Postdam Procyon m. V = 0. 4 2 Gyr 1. 5 Msun 2. 0 Rsun 17

Procyon: network result • Observation duration T • Eigenfrequency precision dn ~ 1 / T 0. 5 • Modelling precision varies as dn Despite network observations, the expected gain for interior structure modelling is limited, due to a too limited observation duration From Matthews et al 2004. September 17, 2007 2 nd ARENA Conference Postdam 18

KEPLER • NASA; launch = nov 2008 • High precision photometry • a few fields reserved for asteroseismology Co. Ro. T Kepler : tel. 27 cm 95 cm orbit polar L 2 + duty cycle in L 2 - sensitivety (m. V > 9), radiations in L 2 ? exact scientific case for asteroseismology? 29 -31 October 2007: First KASC workshop, Paris. The Kepler Asteroseismic Science Consortium (KASC) is an international consortium of researchers dedicated to the asteroseismic analysis of Kepler data. September 17, 2007 2 nd ARENA Conference Postdam 19

MOST • Microsatellite for asteroseismology • Operated by the Canadian Space Agency since 2004 • High precision photometry • Best performance ~ 20 ppm Many results on pulsators with large amplitudes Not sensitive enough for asteroseismology of solar-like stars with solar-like oscillations (Procyon’s oscillations not detected) September 17, 2007 2 nd ARENA Conference Postdam 20

SONG • Project currently in phase 0 • Danish asteroseismology centre, Aarhus University • Network of 6 to 8 small telescopes (60 80 cm) • Echelle spectrometer + iodine cell • Expected schedule: 1 prototype for 2012 >> 2012 September 17, 2007 2 nd ARENA Conference Postdam 21

• Fourier Tachometer • to be installed at Dome C • Phase A completed • Scientific Committee Th Appourchaux (France, pdt), C Catala (inst. scientist), S Charpinet (France), D Kurz (UK), Ph Mathias (France), A Noels (Belgium), E Poretti (Italy), • 40 -cm telescope: - solar-like oscillations in solar-like targets (type: F, G, K; class: IV & V) - red giants; d Scuti; g Dor; PMS (with vsin i < 20 km/s) Scientific program: September 17, 2007 for more than 6 winters complementary to Co. Ro. T 2 nd ARENA Conference Postdam 22

SIAMOIS • 40 -cm telescope • Interferometer • Data small size, low cost, easy ‘antarctization’, dedicated to the projet fiber fed Fourier Tachometer, operated at room temperature, monolithic interferometer, photon noise limited performance automatic pipeline reduction, telemetry: limited flow < 100 kb/day Phase A completed, April 2007 September 17, 2007 2 nd ARENA Conference Postdam 23

Space / Ground Main differences between space-borne and ground-based observations space ground Observation photometry spectrometry Max. degree 2 3 Targets magnitude dim bright September 17, 2007 2 nd ARENA Conference Postdam 24

Doppler / photometry Solar granulation noise September 17, 2007 2 nd ARENA Conference Postdam 25

Granulation noise September 17, 2007 2 nd ARENA Conference Postdam 26

l=3 modes visible in spectroscopy Small separation September 17, 2007 2 nd ARENA Conference Postdam 27

Doppler / photometry September 17, 2007 2 nd ARENA Conference Postdam Gabriel et al 1998 low frequency noise + l=3 modes Inversion 4 times more precise with Doppler data 28

Complementary observations Complementary ground-based observations are necessary - to measure fundamental parameters - to improve the modelling Strömgren photometry Teff , log g, metallicity High resolution spectrometry Teff , log g, abundances Interferometry angular diameter Astrometry distance Stellar radius determined with enough precision only for bright stars September 17, 2007 2 nd ARENA Conference Postdam 29

Comparison Co. Ro. T Kepler SONG SIAMOIS 2 eyes diam = 12° 10° x 10° (Cygnus-Lyra) |d| < 30° d < - 45° Duty cycle 92 % ~ Co. Ro. T ~ 85 % ~ 90 % 5 -day perf. 0. 6 ppm > 1. 2 ppm 5 months 4 years Magnitude >6 >9 <7 # targets 28 Up to 40 : 4 yr Up to 160 : 1 yr Up to 1000 : 90 d > 30 # solar-like 4 Max obs. Status Instrument cost September 17, 2007 In operation 65 M€ 2 -20 cm/s 3 months 7 Launch = 11/ 2008 Phase 0 Prototype > 2012 Phase A is OK 2012 at Dome C > 6 M€ (6 tel) 0. 86 M€ (1 tel) 1. 02 M€ (2 tel) 2 nd ARENA Conference Postdam 30

Clear sky fraction at Dome C Clear sky fraction measured by Eric Aristidi (2006 winter) Clear sky fraction > 90% during 84% of the time Average number of consecutive clear days: 6. 8 days September 17, 2007 2 nd ARENA Conference Postdam 31

Duty cycle Better performance at Dome C compared to a 6 -site network (Mosser & Aristidi 2007, PASP) September 17, 2007 2 nd ARENA Conference Postdam 32

Simulations F 6 V star, m. V = 4. 5, vsini = 5 km/s, 90 -day long run Modelling: stochastic excitation + intrinsic damping (Anderson et al 1990) September 17, 2007 2 nd ARENA Conference Postdam 33

Simulations F 6 V star, m. V = 4. 5, vsini = 5 km/s, 90 -day long run Precision on the eigenfrequency measurement: 0. 10 – 0. 25 m. Hz (Libbrecht 1992) September 17, 2007 2 nd ARENA Conference Postdam 34

Conclusion Space-borne observations = photometric observations Co. Rot unique results Kepler not primilarly specified for asteroseismology sensitivity for solar-like oscillations? very dim targets uncertainty on fundamental parameters Ground-based observations = Doppler observations measurement of modes with degree l = 3 much less low frequency noise much better inversion and modelling & observation of low mass stars Network very late schedule, complex organization Dome C = unique site for asteroseismology 3 -month continuous observation with duty cycle ~ 90% High performance with a 40 -cm collector Better performance than a 6 -site network http: //siamois. obspm. fr September 17, 2007 2 nd ARENA Conference Postdam 35

Everything is OK for SIAMOIS Risk Cost Logistics ٧ ٧ - CFHT/FTS; GONG helioseismic network - Scientific program ٧ - Automatic instrument; simple setup - Limited operations; low data flow ٧ September 17, 2007 - Construction < 1 M€ - Running cost << network - Phase A completed - Scientists, engineers, SC at work! http: //siamois. obspm. fr 2 nd ARENA Conference Postdam 36

Budget Site SIAMOIS Network 1 site At least 6 sites for similar performance Construction 860 ME ~ 6 ME Running cost ~ 750 k. E / 600 k. E (according to for 3 months number of GONG, WET networks) projects Observation 5 months / year 12 months / year September 17, 2007 2 nd ARENA Conference Postdam 37

SIAMOIS at Dome C Demanding site ? Project ~ spatial-like organization (but with human presence) Quasi automatic, simple setup Reduced mass, low power, very low telemetry Seeing ? Fibre = 5" on the sky No big telescope at Dome C ? Key science with a 40 -cm telescope (or 2 telescopes) Only circumpolar targets ? Scientific program for more than 6 winterings Fourier tachometer ? As the helioseismic network GONG, as onboard So. HO and SDO Duty cycle ~ 90% ! Polar night = 3 months September 17, 2007 Scientific specification #1 : duty cycle > 85% Scientific specification #2 : 100 -day long runs 2 nd ARENA Conference Postdam 38

Fourier tachometer • Why a FT instead of an échelle spectrometer? • Fourier Tachometer = best solution for - GONG (network helioseismology) - MDI (helioseismology onboard So. HO) - Velocity and Magnetic Imager, SDO Current telescope at Dome C / Telescope available in the near future for long duration observation = dedicated small telescopes tel Echelle spectrometer (as HARPS) FT FT: simple installation and setup at Dome C September 17, 2007 2 nd ARENA Conference Postdam 39

Possible targets Observable targets (solar-like stars with solar-like oscillations) with SIAMOIS and a 40 cm telescope dedicated to the project September 17, 2007 2 nd ARENA Conference Postdam 40

Planning & budget < 2006 principle: monolithic Fourier Tachometer • 2007 thermo-mechanical analysis phase A • 2008 -2010 PDR FDR integration • 2010 -2011 tests summer campaign: Dome C • 2012 First winterover at Dome C LESIA (Obs. Paris), IAS (Orsay), LUAN (Nice), OMP (Toulouse) + SESO Budget ~ 860 k€ << budget for an equivalent 6 -site network September 17, 2007 2 nd ARENA Conference Postdam 41

Mosser et al 2003 Performance Photon noise limited performance, SIAMOIS at Dome C, 40 -cm telescope, 120 hours with 90 % duty cycle, m. V = 4 SNR on circumpolar targets September 17, 2007 2 nd ARENA Conference Postdam 42

Fourier tachometer • Another advantage: multiplex advantage simultaneous observations of several targets First step: small telescope + FT Then: multi-targets observation = small telescopes + 1 FT September 17, 2007 2 nd ARENA Conference Postdam 43

Duty cycle at Dome C Polar night = 100 nights Resulting duty cycle (bright targets) > 90% during 90 days September 17, 2007 2 nd ARENA Conference Postdam 44

Asteroseismology after COROT 1 - single-site runs, short runs 2 - photometry, space-borne observations, MOST, 3 - spectrometry, ground-based observations Ground-based observations • Bright stars • Low mass stars • Doppler signal reduced granulation noise modes l=3 for small separation Specification: September 17, 2007 eigenfrequency precision continuous observations long duration 2 nd ARENA Conference Postdam = 0. 2 m. Hz (h > 80 %) (T > 2. 5 months) 45

SIAMOIS September 17, 2007 2 nd ARENA Conference Postdam 46