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Asteroseismology, from space and from the ground Benoît Mosser September 17, 2007 Observatoire de Paris/LESIA 2nd ARENA Conference Postdam 1 Summary 1. Space-borne asteroseismology CoRoT 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 2nd ARENA Conference Postdam 2 Asteroseismology • Age determination • Stellar radii (impact for exoplanet radii) • Composition ~ a few % ~ 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 = 0.2 mHz continuous observations (h > 80 %) long duration (T > 2.5 months) 2nd ARENA Conference Postdam 3 CoRoT • launched on December 27th , 2006 • by Soyuz 2, from Baikonour, Kazakhstan • low Earth polar orbit, 896 km altitude • orbital period 6184 s (~1h43mn, 162 mHz) • high precision photometry The CoRoT space mission has been developped and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany and Spain September 17, 2007 2nd ARENA Conference Postdam 4 CoRoT « Eyes » CoRoT eyes: d=0, a=6h50 and 18h50 12 0° 15 0° 90 ° 18 0° 60 ° 21 0° 22 h 20 h 18 h 16 h 14 h 12 h 10 h 8h 6h 4h 2h 0h 30 ° 24 0° 0° 27 0° 33 0° 30 0° September 17, 2007 2nd ARENA Conference Postdam 5 CoRoT 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 2nd ARENA Conference Postdam 6 CoRoT first observations February, March initial run, 60 days April 1st short run May, 11 Oct. 15 1st long run not yet completed Raw data N0 OK 1st corrections N1 OK Scientific data N2 not yet distributed Sensitivety 0.6 ppm in 5 days, for mV=5.4 as expected Duty cycle 92% (6% lost in SAA) better than expected September 17, 2007 2nd ARENA Conference Postdam 7 Example of light curves Typically 10-4 in 30 s A 6th mag F-type star showing daily variability below the 10-3 level September 17, 2007 2nd ARENA Conference Postdam 8 Light curve An 9th magnitude suspected delta Scuti showing beat phenomena at a few 10-3 September 17, 2007 2nd ARENA Conference Postdam 9 Light curve An 8th magnitude B star in an eclipsing binary September 17, 2007 2nd ARENA Conference Postdam 10 Quiet target A 7th magnitude giant F star showing very low dispersion of ~10-4 September 17, 2007 2nd ARENA Conference Postdam 11 HD 49933 1st solar-like target, initial run, 60 days Simulations: Baudin et al. 06 Photon noise Granulation September 17, 2007 2nd ARENA Conference Postdam 12 HD 49933, observed Mosser et al. 2005, 10 days with HARPS, duty cycle ~ 23% September 17, 2007 2nd ARENA Conference Postdam 13 d Scuti Example of an 8th magnitude delta Scuti observed with CoRoT. The red line illustrates common lowest detection limit from the ground. September 17, 2007 2nd 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, McD, Okoyama, Lick Oscillation detection Mode identification 2-sites observation Network observation Stellar structure modelling Rotation, fine structure… September 17, 2007 ٧ ٧ ٧ ٧ ٧ ٧ ~ 20 targets for ~ 12 targets 5 targets 1 target (Procyon) ~ 2 targets Observations limited to a few days insufficient precision 2nd ARENA Conference Postdam 15 Single/multi-sites observation September 17, 2007 2nd ARENA Conference Postdam 16 Proyon: network observations January 2007: Multi-site campaign -AAT -Okoyama -TLS -OHP -NOT -SARG -ESO -Euler -McDonald -Lick • Arentoft et al.; Bedding et al, in preparation • time series ~ 9 days September 17, 2007 2nd ARENA Conference Postdam Procyon mV = 0.4 2 Gyr 1.5 Msun 2.0 Rsun 17 Procyon:network result • Observation duration T • Eigenfrequency precision dn ~ 1 / T0.5 • 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 2nd ARENA Conference Postdam 18 KEPLER • NASA; launch = nov 2008 • High precision photometry • a few fields reserved for asteroseismology CoRoT Kepler : tel. 27 cm 95 cm orbit polar L2 + duty cycle in L2 - sensitivety (mV > 9), radiations in L2 ? 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 2nd 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 2nd ARENA Conference Postdam 20 SONG • Project currently in phase 0 • Danish asteroseismology centre, Aarhus University • Network of 6 to 8 small telescopes (6080 cm) • Echelle spectrometer + iodine cell • Expected schedule: 1 prototype for 2012 >> 2012 September 17, 2007 2nd 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 CoRoT 2nd 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 2nd 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 2nd ARENA Conference Postdam 24 Doppler / photometry Solar granulation noise September 17, 2007 2nd ARENA Conference Postdam 25 Granulation noise September 17, 2007 2nd ARENA Conference Postdam 26 l=3 modes l=3 modes visible in spectroscopy Small separation September 17, 2007 2nd ARENA Conference Postdam 27 Doppler / photometry September 17, 2007 2nd 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 2nd ARENA Conference Postdam 29 Comparison CoRoT Kepler SONG SIAMOIS 2 eyes diam = 12° 10° x 10° (Cygnus-Lyra) |d| < 30° d < - 45° Duty cycle 92 % ~ CoRoT ~ 85 % ~ 90 % 5-day perf. 0.6 ppm > 1.2 ppm Max obs. 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 Status Instrument cost September 17, 2007 In operation 65 M€ 2-20 cm/s 3 months 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) 2nd 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 2nd ARENA Conference Postdam 31 Duty cycle Better performance at Dome C compared to a 6-site network (Mosser & Aristidi 2007, PASP) September 17, 2007 2nd ARENA Conference Postdam 32 Simulations F6V star, mV = 4.5, vsini = 5 km/s, 90-day long run Modelling: stochastic excitation + intrinsic damping (Anderson et al 1990) September 17, 2007 2nd ARENA Conference Postdam 33 Simulations F6V star, mV = 4.5, vsini = 5 km/s, 90-day long run Precision on the eigenfrequency measurement: 0.10 – 0.25 mHz (Libbrecht 1992) September 17, 2007 2nd ARENA Conference Postdam 34 Conclusion Space-borne observations = photometric observations CoRot 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 2nd ARENA Conference Postdam 35 Everything is OK for SIAMOIS Risk Cost Logistics ٧ - CFHT/FTS; GONG helioseismic network - Scientific program ٧ - Construction < 1 M€ - Running cost << network ٧ - Automatic instrument; simple setup - Limited operations; low data flow ٧ September 17, 2007 - Phase A completed - Scientists, engineers, SC at work! http://siamois.obspm.fr 2nd ARENA Conference Postdam 36 Budget Site SIAMOIS Network 1 site At least 6 sites for similar performance ~ 6 ME Construction 860 ME Running cost for 3 months Observation September 17, 2007 ~ 750 kE / 600 kE (according to number of GONG, WET networks) projects 5 months / year 12 months / year 2nd 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 SoHO 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 2nd 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 SoHO) - 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 2nd 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 2nd 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 2nd 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, mV = 4 SNR on circumpolar targets September 17, 2007 2nd 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 2nd 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 2nd 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 = 0.2 mHz continuous observations (h > 80 %) long duration (T > 2.5 months) 2nd ARENA Conference Postdam 45 SIAMOIS September 17, 2007 2nd ARENA Conference Postdam 46