ObservationaObservational l Constraints Constraints on the on the Formation Formation and and Properties Properties of Giant of Giant PlanetsPlanets
Jeff Valenti
Orbital Properties of Planets
Observed Planet-Metallicity Relationship Two competing planet formation theories We measured lots of stellar abundances Higher metallicity stars have more detected planets!
Not caused by accretion of rocky debris
Timescale for Building Gas Giant Planets Our HST detection of hot H2
Characterizing Transiting Planets My HST program to observe an evaporating exosphere JWST spectra of atmospheric absorption and emission
Road Map for the Talk
Planet DiscoveryPLANET consortium
SWEEPS, XO
N2K, Ge
Planets Migrate!http://exoplanets.org/a_hist.gif
“Snow Line”
Pile-up at P=3 days
Disk is Truncated by Stellar Magnetosphere
Shu et al. (1994)
Milky Way & CookiesMonday, April 3
Two Theories of Planet Formation
Metals : 0.1 nm
Dust : 1 nm – 1 mm
Planetesimals : 1 mm – 1 km
Cores : 1 km – 1 Mm
Planets : 1 Mm – 0.1 Gm
Core-AccretionCore-Accretion
GravitationalGravitationalInstabilityInstability
crit nH
Do Metals Matter ?
Do Metals Matter ?
SME - “Spectroscopy Made Easy” Valenti & Piskunov (1996, A&AS, 118, 595) Publicly available
Radiative transfer code [with Nikolai Piskunov] LTE, Feautrier solver, Adaptive λ grid, C++ Chemical equilibrium for over 150 molecules (NextGen EOS)
Fit observed spectrum with synthetic spectrum Use precise atomic data from solar spectrum fit Interpolate Kurucz atmospheres in Teff, logg, and [M/H] Calculate synthetic intensities across the stellar surface
Integrate over stellar surface: rotation and RT macroturbulence
Non-linear least squares solver (Levenberg-Marquardt) Free parameters: log(gf), Teff, logg, [M/H], etc.
Spectroscopic Analysis Tool
Determining Spectroscopic Properties
Segment #1
Segment #2
Valenti & Fischer (2005)
Stellar Macroturbulence
Valenti & Fischer (2005)
Isochrone Analysis
1040 Stars
T, L, Fe,
M, R, age
Spectroscopic Properties of Cool Stars
Valenti & Fischer (2005, ApJS, 159, 141) 1807 observed spectra (6 CPU months) 1040 nearby dwarfs and subgiants N2K: 410 Keck + 400 Subaru + 270 Magellan spectra analyzed
Properties based on fitting spectra Effective temperature (1%) Surface gravity (15%) Rotational velocity (0.5 km/s) Abundances: Na, Si, Ti, Fe, Ni (5-10%)
Properties based on matching evolutionary models Stellar mass (15%) Radius (3%) Age constraints
Metals in Full Sample and Stars with Planets
Quadratic Dependence on Stellar Metals
p = (10 [Fe/H])
= ( N(Fe) M)
= (4.5 ± 0.8) % = (1.8 ± 0.3)
N(Fe) M
Increasing metals by 40% doubles the number of stars with planets
Fischer & Valenti (2005)
Dependence on Stellar Mass? Fischer & Valenti (2005)
Cooler Stars
Metallicity bias…
Does Accretion Cause Planet-Metallicity Relationship?
6500 6000 5500 5000TEFF (K)
0.0
-0.2
-0.4
-0.6
0.2
0.4
0.6
[M/H]
Stars withPlanets
Pinsonneault, De Poy, & Coffee (2001)
1 M
Subgiants with and without Planets
6500 6000 5500 5000TEFF (K)
4.0
6.0
8.0
2.0
0.0
M bol
Planets
Subgiants
Subgiant Test – No Diluted Enrichment
6500 6000 5500 5000TEFF (K)
4500
-0.2
-0.6
0.2
0.6
[Fe/H]
Subgiants with planets are still metal rich
[Fe/H]=0.15
Velocity Precision vs. Metallicity
Line Depths NOT Proportional to Abundance
Strong Lines are Saturated
Metals Do Not Affect Migration Stopping Point
Stars with Distant Planets Seem To Be Metal Rich
3% of Keck sample has long period
planets
Statistics are improving where giant planets form.
Next Step: Detection Limits for Each Star
Adapted from Cumming(2004, MNRAS, 354, 1165)P < 4 yr
K > 30
m/s
30 m/s
N=15
N=30
p=99%p=50%
FV05
Classical Core-Accretion Model Is Slow
Phase ICore formation
via rapid accretionof planetesimalsin “feeding zone”
Phase IIEnvelope formation viagradual gas accretion
Phase IIIGiant planet formationvia rapid gas accretion
Pollack et al. (1996)
IsolationMass
Core Only
Core +Envelope
Dust Near a Star Dissipates Quickly
Haisch, Lada, & Lada (2001)
Warm dust only lasts “a
few Myr”
How long does the gas last?
Hot Inner Edge(s) of Disks
Akeson et al. (2006)
RY TauSU Aur
Molecular Hydrogen in Accretion Disks
Herczeg et al.(2002; 2004; 2005)
Ly- Pumped Fluorescence of Hot H2Herczeg et al. (2004)
Ly- Pumped Fluorescence of Hot H2Herczeg et al. (2004)
Find planets that transit bright (V<12) stars Absorption by planetary atmosphere during transit Thermal emission in and out of secondary eclipse 1) HD209458b, 2) TrES-1, 3) HD189733b, 4) HD149026b
N2K Survey Fischer (SFSU), Laughlin (UCSC), Valenti (STScI), … Surveying the “next 2000” stars, V<10.5 (14,000 candidates)
Constructed metal-rich sample using photometric indexes
“Three strikes and you’re out!” - focus on short periods
So far: 410 Keck + 400 Subaru + 270 Magellan stars So far: 7 planets announced + 3 in press + 36 candidates
So far: 1 new transiting planet!
Comparative Planetology
“N2K” Discovers Its First Transiting Planet!
Subaru & Keck– 0.5 0.0 0.5
Orbital Phase
– 40
0
40
Velocity (m/s)
HD 149026
Sato et al. (2006)
Diversity of Planets - Formation vs. Evolution
Bouchy et al. (2005)Evaporating
Exosphere Program 10718
Evaporating Exospheres
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Vidal Madjar et al. (2003)
Planetary Transits with JWST/NIRSpec
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Brown (1991)
R=3000
Planetary Eclipses with JWST/NIRSpec
Spitzer
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R=3000
Key Results Spectroscopic Properties of Cool Stars (SPOCS)
1040 solar-type stars in Keck, Lick, AAT planet search programs
Analyzing another 2000 stars in N2K program
Quantified Planet-Metallicity Relationship Increasing metals by 40% doubles the number of stars with planets
Not due to preferential accretion of metals onto star Inconsistent with gravitational instability (migration?) Fundamental constraint on all formation models
HST and JWST will characterize disks and atmospheres Use fluoresced H2 to study gas in protoplanetary disks Measure extent of planetary exosphere during transit Obtain atmospheric absorption spectra during transit Measure thermal emission spectra in/out of secondary eclipse
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