Prsentation PowerPoint

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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
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SUMMARY

• Which program in asterosismology after COROT
  ?
• Dome C in Antarctica
• SIAMOIS principle
• SIAMOIS performances (/ SONG)
• Project organisation, science

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Ground-based observations, 2006
Ground-based asteroseismic observations remain
limited by the window effect
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Ground-based observations, 2006
Even with bi-sites observations
Kjeldsen et al 2005
Continuous observations are required for precise
structure modelling
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In 2009, end of COROT
will have done a considerable work
!
And after that ???
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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
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Dome C

• Concordia station, Italy France
• 7506 south, 12321 east
• Average temperatures
• - 40C in summer
• - 60C in winter
• Slow wind
• Rare precipitations
• 2 to 10 cm snow/year
• Polar night 3 months

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Duty cycle gt 90 during 3 months in winter (K.
Agabi)
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(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

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Observations at Dome C

• 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

-1- dedicated asteroseismometer with a small
size telescope first wintering in 2010 -2- 2-m
class telescope spectropolarimeter
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Doppler asteroseismometry

• Principle (Bouchy et al. 2001) photon noise
  limited performances
• An asteroseismometer has to be extremely stable
  and efficient
• - quality factor Q
• - number of photoelectrons Ne
• Q depends on
• - the spectral type and rotation of the star
• the instrument
• GS grating spectrometer
• FS Fourier Transform spectrometer

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Stellar quality factor

• The quality factor gives a measure of the
• number
• depth
• width
• of the stellar lines
• Q dln A /dln l

Cool stars are favored Better performances in the
blue part of the visible spectrum
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Seismology with a GS
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
Grating spectrometer necessarily a large
instrument
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FS seismometry by TF
Fourier transform Seismometry The Doppler signal
is searched in the interferogram of part of the
stellar spectrum
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Sismometry by TF
FT seismometry successfully tested with the FTS
at CFHT Procyon Mosser et al. 1998, AA 340,
457 Jupiter Mosser et al. 2000, Icarus 144, 104

• FTS at CFHT scan of one fringe
• Dedicated instrument simultaneous scan of the
  fringe signal

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FS quality factor
avec

• (Mosser et al. 2003, PASP 115, 990)
• Q increases with
• wavenumber s0
• working path difference dopt
• fringe contrast C
• A high fringe contrast C requires a narrow
  bandwidth
• in contradiction with the specification on Ne

It is necessary to observe with a post-dispersive
device
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FS post - dispersion
Fourier transform seismometry with
post-dispersion The Doppler signal is searched
in the interferogram of each spectral element
defined by the post-dispersion
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FS / GS
GS smaller and simpler instrument, monolithic
interferometer, no moving parts ? possible
installation and setup in Antarctica
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Antarctic / network
Complementary projects
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Performances GS / FS
GS HARPS (ref ThAr lamp) R 90000 FS
SIAMOIS post-dispersion providing a spectral
resolution R 1000.
GS gt FS if reference ThAr lamp (Mosser et al.
2003) GS FS if reference iodine cell
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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
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Targets
Observable targets with SIAMOIS and a 40-cm
telescope dedicated to the project
COROT

• 40-cm telescope
• - 7 targets, type F, G, K class IV V
• - many red giants d Scuti (v sin i lt 20 km/s)
• ? Scientific programme for more than 6 winterings

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Targets
1) K, G, F, class IV V targets
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Targets
3) delta-Scuti
1) K, G, F, class IV V targets 2) red giants
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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

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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
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Conclusion

• 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

siamois
Big science  at Dome C with a budget lt 1 ME