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Planets of young stars: the TLS radial velocity survey

Planets of young stars: the TLS radial velocity survey. Massimiliano Esposito Eike Guenther Artie P. Hatzes Michael Hartmann. Scientific motivations: lack of close-in giant planets. Planets in binaries. BD.

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Planets of young stars: the TLS radial velocity survey

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  1. Planets of young stars: the TLS radial velocity survey Massimiliano Esposito Eike Guenther Artie P. Hatzes Michael Hartmann

  2. Scientific motivations: lack of close-in giant planets Planets in binaries BD There is a lack of massive planets (m sin i 2 MJup) on short-period orbits (P  100 days). (Udry, Mayor & Santos 2003) This can possibly give us insight in the formation and evolution of planetary systems.

  3. Scientific motivations: lack of close-in giant planets Very massive planets form in the outer regions, then: HYPOTHESES • They stay there: Type II migration is less effective for higher masses. • (Trilling, Lunine & Benz, 2002) 2)They migrate inward: The rate (da/dt)of type I migration is a linear function of the planetary mass. (Ward, 1997) Then: 2a) They fall into the parent star (timescale t ~ 1 Gyr). (Pätzold & Rauer, 2002) 2b) They experience a strong evaporation losing most of their mass (t ~ 1 Gyr). (Baraffe et al ,2004) (Not) To find close-in giant planets around young stars can indicate that 2 (1) is more likely .

  4. Scientific motivations: close-in eccentric orbits Very short period (P < 3 days) planets have all zero eccentricity : did they form on circular orbits or tidal interaction damped their initial eccentricity? Let’s have a look to young planets.

  5. Scientific motivations: detection of planetary light (Burrows et al. 1997, ApJ 491, 856) Young planets will be optimal candidates for direct detection: infrared interferometry and/or high resolution spectroscopy.

  6. The TLS observing facilities The 2m TLS “Alfred Jensch Teleskop” at the Thüringer Landessternwarte (TLS) in Tautenburg Spectral coverage: λ  4660 ÷ 7410 Å Wslit = 0.52mm (  1.2’’) Resolving power: R  67000 The spectrograph is equipped with a iodine cell.

  7. Hipparcos distances Visual magnitudes The TLS sample: 46 nearby bright stars

  8. The TLS sample: young stars (30  300 Myr) Tautenburg sample (Zuckerman & Song, 2004 ARAA 42, 685)

  9. The TLS radial velocity survey Observations started already in 2001. Presently ~1500 spectra have been acquired.

  10. The TLS radial velocity survey RV-scatter vs vsin(i) Internal RV-error vs vsin(i) For vsin(i) < 10 km/s the RV-signal of a Jupiter-massplanet would emerge from the RV-jitter noise !

  11. A TLS young planet candidate P=4.040 days Orbital parameters P = 4.040 days e = 0.16 K = 37.8 m/s MP sin(i) = 0.28 MJ Stellar parameters SpT = G5 v sin(i) = 6 km/s M = 0.92 MSun

  12. A TLS young planet candidate: photometry We have scheduled more photometry for our three best candidates.

  13. Detection limits: a few examples σRV= 14.4 m/s Np = 48 σRV= 139 m/s Np = 68 10% 50% 100% 10% 100% 50% σRV= 11.3 m/s Np = 20 σRV= 10.5 m/s Np = 10

  14. Detection limits:results Percentage of stars without companions

  15. Conclusions In spite of their activity, detecting planets orbiting young stars is possible. In the TLS sample (46 stars) we have (possibly) found 3 planets . For 80% of the stars we can exclude planets with P<10 days and M>2MJ (95% for M>7MJ). The frequency of planets of young stars is probably not much higher than for old stars … but the sample has to be increased. A similar survey began in 2004 for young stars in the southern hemisphere with HARPS. Have a look at the poster by Eike Guenther.

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