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Detection of Extrasolar Giant Planets

Detection of Extrasolar Giant Planets. Hwihyun Kim 03/30/06. PAPER. G. W. Marcy & R. P. Butler, “Detection of Extrasolar Giant Planets”, ARAA, 1998, 36:57-97. HISTORY OF DETECTION. 4 th century : Aristotle and Epicurus argued about the uniqueness of the Earth

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Detection of Extrasolar Giant Planets

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  1. Detection of Extrasolar Giant Planets Hwihyun Kim 03/30/06

  2. PAPER • G. W. Marcy & R. P. Butler, “Detection of Extrasolar Giant Planets”, ARAA, 1998, 36:57-97

  3. HISTORY OF DETECTION • 4th century : Aristotle and Epicurus argued about the uniqueness of the Earth • Late 1500s : Copernicus(con), G. Bruno(pro) • Early-1900s : • some “spiral nebulae” such as M51 misinterpreted as planetary systems • Jeans-Jeffreys’ model for planet formation • Aitken(1938) : direct detection or by the wobble

  4. HISTORY OF DETECTION • Wolszczan & Frail (1992) : 1st planetary system, PSR1257+12 (post-SN recapture of material) by pulsar-timing method • Mayor & Queloz (1995) : 51 Pegasi by Doppler periodicity • Butler & Marcy (1996) : 1st detections of Jupiter-mass planets to solar-type star, 47 UMa and 70 Vir • 2000s : HST-NICMOS, Spitzer, Kepler Space Mission(2007 ?), Space Interferometry Mission(SIM), Terrestrial Planet Finder(TPF) and so on....

  5. DETECTION TECHNIQUES • Direct Detections • Astrometric Detections • Photometric Technique • Doppler Technique • Pulsar Timing • Gravitational Microlensing

  6. DIRECT DETECTIONS • Direct Imaging • Small fluxes from the planets • Competing wings of the stellar PSF • Solar-type star with MJ-planet at 5AU (Benchmark model) • Visible : ~10-9 (Vs = 5 and Vp = 27, 0.5”) • IR : improved to ~10-4 but low-resolution(>1”) • Noise in PSF wings : seeing, microroughness of the mirror, and diffraction

  7. DIRECT DETECTIONS • Minimum aperture D (diffraction alone) • Remedy • Adaptive optics, Dark-speckle camera(JWST ?) • Ground-based interferometry, Keck, VLT, Spitzer....

  8. ASTROMETRIC DETECTIONS • Stellar (proper) motion by its companion • Determine Mp and i of a planet • Detect sub-MJ planets with future precision below 0.1 milliarcsec (mas) • Confirm planets detected by other means • Angular wobble • Proportional to Mp and r • Inversely proportional to d • Benchmark model : 0.5 mas • Palomar 5-m (~250 μas, 1997), Keck (20 μas), & SIM (4 μas)

  9. PHOTOMETRIC TECHNIQUE • Transit method : reduction in light • aligned from astronomers’ vantage point • 1% dimming by the Jupiter size planet • Probability :

  10. PHOTOMETRIC TECHNIQUE • Marcy & Butler(1997) : 0.19% of solar-type star exhibit transits • Determination of • existence rate • occurrence rate • Planet radius

  11. DOPPLER TECHNIQUE • Our Sun • wobbles around the barycenter with ~13m/s by Jupiter(12.5 m/s) and Saturn(2.7m/s) • Semi-amplitude K of the stellar radial velocity

  12. Detectability of companions by the reflex velocity Intrinsic velocity scatter(σ) vs. rotational period(P) for F(∆), G(⊙) and K(■) dwarfs (Saar et al, 1997) DOPPLER TECHNIQUE

  13. OBSERVATIONS OF EXTRASOLAR PLANETS • Walker et al (1995) : 21 dwarfs for 12 yrs with 13m/s • Mayor & Queloz (1995) : 140 MS stars for 3 yrs • Cochran & Hatzes (1994) : 33 stars for 10 yrs • Marcy & Butler (1997) : 107 FGKM dwarfs with ~10m/s (8yrs) and 3m/s (4yrs)

  14. DISTRIBUTION OF PLANETARY MASSES • Histogram of M sini for all companions known around solar-type stars • Tallest peak is at the lowest, least detectable masses(0-10 MJ)

  15. 47 Ursae Majoris • By Butler & Marcy (1996) with Doppler measurement • P = 3.0 yrs, e = 0.09 ± 0.04, a = 2.1 ± 0.1 AU and companion mass = (2.4 ± 0.1)/sini

  16. 55 Cancri and ρ Corona Borealis • Mp ~ 1.0 MJ/sini (true masses < 3MJ) • Orbital radii : 0.11 AU (55 Cnc) and 0.24 AU (ρ CrB) placing them inward of the ice-condensation point (~3AU) • Low eccentricities (e= 0.04 and 0.11) • ρ CrB : too large orbit for tidal effects to cause low-e • 55 Cnc : tidal circulation and period of 14.7 days

  17. a) 55 Cnc • b) ρ CrB by Noyes et al (1997) • Both appear to have MJ-companions in nearly circular orbits.

  18. 70 Vir & 16 Cygni B : non-sinusoidal velocities • Very eccentric Keplerian curves • e = 0.4 (70 Vir) and 0.687 (16 Cygni B) • Well fit by a simple Keplerian model 70 Vir ( Mp = 6.7 MJ/sini ) 16 Cygni - Lick(∆) & McDonald(x) - Mp = 1.67 ± 0.1 MJ/sini

  19. GIANTS PLANETS ORBITING WITHIN 0.1AU • MJ-companions with the orbital radii <0.1 AU • Proximity to the star enhances the detectability (Fig. 1) • 51 Peg : active corona and high X-ray flux • Tau Boo : higher mass companion (3.7 MJ/sini ) • Upsilon And : short-term scatter (25m/s) by the rapid rotation of the star

  20. SUMMARY • 8 extrasolar planet candidates have been identified by Keplerian Doppler shifts(1998). • Masses are between 0.5-7 MJ and semi-major axes are less than 2.1 AU. • Detections imply that ~6% of solar-type stars have giant planets within 2 AU.

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