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. Strawman sites
Izaña: proposed for prototype

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 = , 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: 12e read-out noise, 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 with Iodine
Men meget svært fra under atmosfæren  dedikerede satellitter!!!

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. Zoom of previous figure – agreement with Butler et al. (2004)
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. Example: sharp features in stellar models
HeII ionization
No overshoot
With overshoot

22. Oscillatory signals Houdek & Gough (2007; MNRAS 375, 861)
Fit
He II
BCZ
He I
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
10 days
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
(Ulrich et al. 2000)
(Garcia et al. 2005)
GOLF

26. Velocity background
From GOLF data

27. Velocity detection of planets

29. 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

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

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

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

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

36. 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.

37. SUMMARY SONG is singing ! Workshop in Aarhus, Last half of March, 2009
High-resolution spectrograph ( ), 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