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SONG – Stellar Observations Network Group PowerPoint Presentation
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SONG – Stellar Observations Network Group

SONG – Stellar Observations Network Group

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SONG – Stellar Observations Network Group

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  1. SONG – Stellar Observations Network Group J. Christensen-Dalsgaard1, F. Grundahl1, U. G. Jørgensen2, H. Kjeldsen1, T. Arentoft1, S. Frandsen1 and P. Kjærgaard2 1) Danish AsteroSeismology Centre, University of Aarhus 2) Niels Bohr Institute, Copenhagen University

  2. Torben Arentoft talk: Procyon campaign

  3. Torben Arentoft talk: Procyon campaign • Overlapping data from 3 observatories:

  4. SONG Goals Do for stars what GONG does for the Sun well, almost...... (BiSON, IRIS)‏ - Asteroseismology (Doppler; also daytime solar observations)‏ Main focus on solar-like oscillators - Exoplanets (microlensing, Doppler)‏ Microlensing can potentially detect very small planets Set limits on occurrence of planets Use Lucky-Imaging (photometry)

  5. SONG asteroseismology – overview • Seismology targets: solar-like stars with V < 6 • Long, continuous periods • Bright, nearby targets, hence well-characterized; can get R from interferometry • Relatively few but well studied targets • Complementary to the space missions

  6. Doppler velocity – the optimal tool for solar-like asteroseismology

  7. Solar-type star at V=10, 4 years with Kepler Solar-type star at V=2, 2 × 4 months with SONG l = 3 can be detected

  8. How will these goals be reached? SONG baseline configuration: • 8 network nodes (4S / 4N) at already existing sites • 1.0m telescopes at each node • Instruments: spectrograph + lucky imager • Optimized for main science goals • Automatic operations The first step is the construction of a full prototype node

  9. Izaña: proposed for prototype Strawman sites

  10. Telescope • Aperture: 1m • Focal-length: 36m • Coudé focus • 10” rms. pointing precision • No instruments in dome • Telescope pier next to instrument container

  11. Focal plane • Atmospheric dispersion correction (lucky-imaging)‏ • Field de-rotation • Tip/tilt correction (spectroscopy)‏ • Calibration light for spectrograph (ThAr, FF)‏ • Iodine cell temperature controlled • Auxiliary port for other instrumentation

  12. Focal plane layout for SONG (not to exact scale)‏ Spectrograph slit Tip-tilt mirror AUX. port

  13. Spectrograph: Characteristics and capabilities • R = 100 000, 1.”3 × 10” slit, 2.5pixel sampling, R4 echelle, 75mm x 300mm • Throughput: 55% (slit to CCD camera)‏ • Possibility to change slits (resolution). • Wavelength range: 4800 – 6800Å with gaps, no Hα or Li on detector. BUT... • Good order separation (7-25 pixels), very small line tilt. • 2048 × 2048 pixel detector, back. illuminated. Andor. • Readout rate: 3MHz @ 12e read-out noise, 5MHz @ 30e RON)‏ • Low level of stray-light • Iodine cell for velocity reference • Very good image quality (80% encircled energy : ø = 5-7µm over detector). • Temperature controlled • Compact design ( 50 × 90cm)‏ Spectrograph design and analysis:Paolo Spanò, INAF, Brera

  14. Velocity precision of SONG spectrograph 55s. exposure

  15. Stellar spectrum without iodine Stellar spectrum with Iodine

  16. Data reduction for an iodine cell SONG employs an iodine cell as velocity reference. We have started the development of the SONG iodine cell software Code is based on IDL – publicly available when developed. Basic version is working. Flat-fielding and extraction of spectra using REDUCE (Piskunov & Valenti, 2002). Strategy: Develop and test software on existing (RAW) UVES data from previous asteroseismology observing campaigns which allows a comparison of results. The adopted procedure is close to that described in papers by Butler and Marcy. The SONG spectrograph is very similar in layout, resolution and sampling to UVES. The results presented here represent the first attempt of this on the data obtained by Butler et al. (2004).

  17. (d)‏ Enlarge this section

  18. from previous figure (d)‏ Zoom of previous figure – agreement with Butler et al. (2004) is excellent. Grundahl errors are approximately 25% larger.

  19. Amplitude and power spectra for αCen A, 688 UVES spectra, high-pass filtered. 76cm/s 76 cm/s 70 cm/s

  20. 4 months of SONG observations

  21. HeII ionization Example: sharp features in stellar models No overshoot With overshoot

  22. He I Fit He II BCZ Oscillatory signals Houdek & Gough (2007; MNRAS 375, 861) Simulated SONG data

  23. Full-disk helioseismology with SONG BiSON HARPS Kjeldsen et al. (2008; ApJ 682, 1370)

  24. Beyond asteroseismology • Stellar activity • Planet search with Doppler velocity • Planet search with microlensing

  25. Torben Arentoft talk: Procyon campaign Constraining inclination: corresponding to the rotation period or half the period (Clarke 2003) With the known radius and vsin(i) = 3.16 km s-1 we find: or 10 days (Ulrich et al. 2000) (Garcia et al. 2005) GOLF

  26. Velocity background From GOLF data

  27. Velocity detection of planets

  28. Microlensing observations • Follow up of high-amplification events discovered by OGLE or MOA (and LSST etc.) • Only a small field of view needed (46" × 46")‏ • Planetary events have durations less than 24h • Continuous coverage for entire duration of event is desirable • Microlensing has already produced several planet discoveries as well as limits on the occurrence of planetary systems. • However, more events with better coverage are desirable and the fields are very crowded - good image quality is a big advantage

  29. FOV 2' x 2' The field of the recent 5.5 Earth mass Planet discovered by microlensing. Beaulieu et al. (2006; Nature 439, 437)

  30. Lucky-Imaging • Camera f.o.v: ~46" x 46", 0."09 pixels, from Andor. • only for 4500Å and longwards • 2-colors simultaneous (split @ 700nm). • filter mechanism • possibly simultaneous 2 color photometry + spectroscopy • provide signal for tip/tilt correction

  31. Planned schedule • 2006 – 2007: Conceptual design • 2008: Prototype Phase A • 2009 – 2011: Prototype design, construction and test • 2012 – 2014: Network construction • 2014 – ????: Network operation

  32. Current status of SONG • Funding situation • Major funding from: • Villum Kann-Rasmussen Fondet (Velux) • Danish Natural Sciences Research Council • This is sufficient for the full prototype phase • Prototype schedule

  33. Current status of SONG • Funding situation • Prototype schedule • - 2008: finish optical design/layout, ordering • - 2009: mechanical design, building of instruments • - 2010: assembly, integration, test (instr, tel)‏ • - 2011: assembly (Tenerife) – live test on sky.

  34. SUMMARY • SONG is singing ! • High-resolution spectrograph (4800-6800), accurate velocities • Dual-colour imaging with high duty-cycle (small field)‏ • Dual-colour imaging AND spectroscopy (probably)‏ • First light for telescope: late 2010 • On-site testing 2011 Workshop in Aarhus, Last half of March, 2009 http://astro.phys.au.dk/SONG