Eva Meyer25.03.2007MPIA-Student-Workshop, Italy Various information from different detection methods

25.03.2007 MPIA-Student-Workshop, Italy Eva Meyer

Various information from different detection methods


Outline• Introduction• Indirect detection techniques

– Radial Velocity – Astrometry– Transit– Microlensing

• Direct detection techniques– Reflected starlight– Imaging

André


Introduction• so far 215 planets are detected (23.03.2007)

• 21 multiple systems• first announcements: Peter van de Kamp (18.04.1963) Astrometric study of Barnard‘s star from plates taken with the 24-inch Sproul refractor (AJ, vol. 68, 515)• BUT: 1952 by Otto Struve: Proposal for a project of high-precision stellar radial velocity work (The Observatory, No. 870)• first detections:

• 1995 by Mayor & Queloz: 0.5 MJupiter P = 4.2 days around 51 Peg


Orbital parameters

Period PSemi-mayor axis aEccentricity eInclination iArgument of perihelion ωLongitude of the acsending node ΩTrue anomaly TTime of periapsis τ


Indirect techniques - radial velocity measurements

• 203 planets

175 Planetary systems, 20 systems with > 1 planet

94,4%• Doppler Wobble• Hot Jupiters mostly


Requirements

• High measurement precision ~ 1m - 20 cm/s

• Stability over ~ 10 years• Derived orbital

parameters– P, e, a, T, ω

Msini

Kürster et al. 2000, A&A 353, L33

RV time series of the young G0V star ι Hor


- Astrometry

• So far 8 planets:– Gl 876: 2 planets– 55 Cnc: 4 planets– ε Eri

• Wobble around center of mass due to planet• Law of the lever: Θs = mp/ms . ap/d

• Limits: 1-2 mas (ground based) 0.1 mas (HST FGS)• need for interferometrie for high precision

PRIMA• Constraints: nearby stars, not too close to the star• can derive inclination and mass of planetary

companion


What do I observe?

• I see the overlay of three different motions:– Proper motion

2007

2008


What do I observe?

• I see the overlay of three different motions:– Proper motion– Parallax

2008

2007

2008


What do I observe?

• I see the overlay of three different motions:– Proper motion– Parallax– Planetary signal

• need to measure all 3 motions accuratly

• Derived parameters:

α, i, Ω, μ, π, T

true mass of companion

2007

2008

20


Jupiter as an exampleFor a star at 10 pc distance:

Source Displacement (mas)

Jupiter at 1 AU 100

Jupiter at 5 AU 500

Jupiter at 0.05 AU 5

Neptune at 1 AU 6

Earth at 1 AU 0.33

Parallax ~100

Proper motion (yr-1) ?


And what about AO effects?

• maybe there remains a residual defocus or other distortions• one need a reference pattern of background-stars to determine the platescale and changes due to instrumental effects


And what about AO effects?

• maybe there remains a residual defocus or other distortions• one need a reference pattern of background-stars to determine the platescale and changes due to instrumental effects• but the background-stars can have their own pm and parallax


TransitsVenustransitJune 2004


Transits

• Photometric detection

• Depth of lightcurve yields planet-radius (~ 1% for Jupiter)

l

dc

w

l

dc

w

Tres-1

HD209458


Transit

• Parameters derived: P, T0, i ~ 90°, Rp/RS

• Together with the mass of the planet from RV measurements one can derive the density of the planet


Microlensing

• Principle:


Microlensing

• Principle:• Magnification due to

Star and planet acting as lenses

D. Bennett


Microlensing

• Principle:• Magnification due to

Star and planet acting as lenses

• First planet: Bond et al. (04.2004)


BUT:

• No way of confirmation• Single event• Short timescale: hours - days• Results: 4 detections as of today


Documents

Eva Meyer25.03.2007MPIA-Student-Workshop, Italy Various information from different detection methods