long-term precision
DESCRIPTION
Satellite meeting - Designating habitable planets for follow-up study: what are the relative parameter spaces of RV and astrometry? (P2 Panel) Scientific program Radial velocities to detect habitable planets in the visible: performance and limitations (F. Pepe) - PowerPoint PPT PresentationTRANSCRIPT
Satellite meeting - Designating habitable planets for follow-up study: what are the relative parameter spaces of RV and astrometry? (P2 Panel)
Scientific program
• Radial velocities to detect habitable planets in the visible: performance and limitations (F. Pepe)
• Radial velocities to detect habitable planets in the nIR: performance and limitations (E. Martin)
• Astrometry to detect habitable planets: performance and limitations (M. Shao)
• Astrometry to detect habitable planets: future prospects (F. Malbet)
• Double blind tests (W. Traub)
P1 = 8.67 days M sini = 10.2 M
P2 = 31.6 days M sini = 11.8 M
P3 = 197 days M sini = 18.1 M
HD69830 - Lovis et al., Nature, 2006
Long-term precisionσO-C ~ 0.8 m/s rms (raw)
~ 0.3 m/s rms (time-binned)
F. Pepe
Error sourcesStellar noise (p modes, activity)
Contaminants (Earth’s atmosphere, moon, etc.)
Measurement noise
✴Photon noise
✴Instrumental errors (from calibration to measurement)
✴Calibration accuracy (any technique)
Beat the stellar limitations with• good targe selection• clever observational strategy
F. Pepe
23/01/08 - Reunión Plan Estratégico 4
• Nearby cool stars are plentiful
• HZ planets have stronger RV signal
• Current NIR RV precision ~20 m/s
• New instruments & calibration methods need to be developed to reach 1 m/s (CRIRES, CARMENES, NAHUAL, PRVS, SPIROU)
E. Martín
Impact of Star Spots on Astrometry and RV
• We find that for the Earth-Sun system, starspots – do not appreciably interfere with astrometric detection.– impose significant requirements on the number of
measurements and duration of an observing campaign needed for radial velocity detection.
Example:Spot area 10-3, Sun @ 10pc Astrometry RVSpot bias 0.25 as 1 m/sEarth @1AU amp 0.3 as 0.09 m/s
• Equiv ast noise ~0.08 as 0.3 as signature• Equiv RV noise ~0.45 m/s 0.09 m/s signature
M. Shao
• Relative to a planet in a 1yr orbit, the star spot noise for RV is ~10X larger than for Astrometry. (short periods favor RV, long periods favor Astrometry)
F. Malbet
F. Malbet
Henry 1998
Martín et al. 2004
10 pc sample
E. Martín
ConclusionsInstrumental considerations:
• RV is a time-tested technique, although no proof yet that it can get to a few cm/s (superEarths are better) but only minimum mass
• Prospects seem good (50 cm/s today)
• NIR RVs can help for planets in the HZs around cool stars ~10-20 m/s achieved so far but 1 m/s needed
• Astrometry has 2D information and it is not severely affected by inclination degeneracy
• Astrometry has not been tested at the as level (best performance 300 as)
• Expensive space mission
Astrophysical noise
• Limitation to visible RVs since only inactive stars (a few 10s within 15 pc) can be observed to the highest accuracy
• This is less stringent for NIR RVs ½ of the jitter and more stars (Ms)
• Astrometry is less affected in solar-type stars
Final considerations
• Astrometry seems better suited to carry out a census of habitable planets for follow up
• Especially so for Earth analogs (i.e., solar-like stars)
• RVs are more cost-efficient and can find some valuable systems early on (JWST?)
• NIR RVs have good potential for nearby stars
F. Malbet