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 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

HISTORY OF DETECTION Wolszczan & Frail (1992) : 1 st planetary system, PSR (post-SN recapture of material) by pulsar- timing method Mayor & Queloz (1995) : 51 Pegasi by Doppler periodicity Butler & Marcy (1996) : 1 st 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....

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

DIRECT DETECTIONS Direct Imaging –Small fluxes from the planets –Competing wings of the stellar PSF Solar-type star with M J -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

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

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

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

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

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

DOPPLER TECHNIQUE 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)

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)

DISTRIBUTION OF PLANETARY MASSES Histogram of M sin i for all companions known around solar- type stars Tallest peak is at the lowest, least detectable masses(0- 10 M J )

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

55 Cancri and ρ Corona Borealis M p ~ 1.0 M J /sin i (true masses < 3M J ) 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

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

70 Vir & 16 Cygni B : non- sinusoidal velocities Very eccentric Keplerian curves –e = 0.4 (70 Vir) and (16 Cygni B) –Well fit by a simple Keplerian model 70 Vir ( M p = 6.7 M J /sin i ) 16 Cygni - Lick(∆) & McDonald(x) - M p = 1.67 ± 0.1 M J /sin i

GIANTS PLANETS ORBITING WITHIN 0.1AU M J -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 M J /sin i ) Upsilon And : short-term scatter (25m/s) by the rapid rotation of the star

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