An A0 Search For Extrasolar Planets

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An A0 Search For Extrasolar Planets

• Denise Kaisler, UCLA
• i) Recent Findings
• ii) Planet Search Techniques
• iii)The Lure of Adaptive Optics
• iv) UCLA's AO Program
• v) Newest Results

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Planets or Brown Dwarfs?

• the distinction is given in terms of mass
• MBD 10 - 80 MJ , MP
• but formation process (rather than mass)is
  thought to be the key to telling them apart
• many search techniques are sensitive to both
• the generic term "substellar companions" is often
  used to discuss both

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Discoveries As of Today (May 18)

• 42 exoplanets
• 1 triple system
• 3 planets of M
• three classes of planets
• e (56)
• p (36)
• c (9)
• 1 unambiguous measurement of MP

• Americans are narrowly leading the Swiss in the
  planet detection game
• It's now possible to detect a planet of Jupiter's
  mass and orbital radius around a sun-like star

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Planet Search Techniques

• Radial Velocity Measurements
• Pulsar timing
• Astrometry
• Photometry
• Gravitational Microlensing
• Interferometry
• Adaptive Optics (AO)

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Radial Velocity Measurements
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Eccentricity of EGPs
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Pulsar Timing

• Companions perturb a pulsar's extremely regular
  beats.
• In 1991, a 3 objects ME were detected around a
  pulsar in Virgo.
• Many astronomers remain skeptical that these are
  in fact planets

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Gravitational Microlensing
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The Lure of AO

• sensitive to the planets that vrad searches are
  unlikely to detect
• higher resolution than unaided observations
• (diffraction-limited ? 1.22?/D)
• allows imaging
• technology more mature than interferometry

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Why Planetologists Should Get Excited

• Keck AO shows Neptune's methane clouds and allows
  a calculation of the optical depth of the
  atmosphere. High reflectance consistent w/
  hydrocarbons or large ice grains.

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The Essence of AO Systems

• AO systems remove distortions introduced by the
  Earth's turbulent atmosphere
• real-time corrections are done by a wavefront
  sensor (WFS) connected to a deformable mirror(DM)
• actuators shape the DM so that the reflected
  wavefront is planar

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The Visible Difference
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Schematic of the Visible Difference
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A Typical AO System
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Measuring AO Performance

• the critical quantity is the Strehl Ratio
• typical Strehls vary from system to system
• Lick (3m, ?1.6µm) S 0.40
• Keck (10m, ? 1.6µm) S 0.25

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UCLA AO Companion Search

• Zuckerman, Macintosh, Becklin, Kaisler
• search the environs of young (t (d
• distance fairly easy to determine
• but no single dependable diagnostic for stellar
  ages (use Li, X-ray flux, chromospheric emission,
  rotation rate, UV emission, and kinematics)

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UC AO Facilities

• Shane 3-m (Lick Obs.)
• DM 127 actuators
• Detector 256x256
• Diff. Limit 0.1"
• Guide Star Brightness
• V

• Keck 10-m Telescope
• DM 319 actuators
• Detector 1024x1024
• Diff. Limit 0.04"
• Guide Star Brightness
• V

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Sensitivity to Separation

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Sensitivity To Mass/Age
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First Results From Lick GJ 808.2
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Hottest Results from Keck A0

• HD 171488
• M dwarf companion
• HD 57821
• M dwarf companion
• GL 559.1
• M/L dwarf companion with a mass near the H-fusion
  limit possible brown dwarf

• TWA 5ABC
• brown dwarf confirmed spectroscopic binary
  resolved for the first time
• TWA 6B
• confirmed NICMOS detection of sub-stellar mass
  possible planet

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TWA 5ABC Imaged With Keck AO

• H-band (?1.6 µm), 1x60s, and 10x0.62s, ?AB 2",
  ?H AB 4 mag

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To Do List for This Weekend

• fly out to Keck
• observe remaining TWA stars
• observe new list of specially selected stars from
  Hipparcos catalogue, ones with good space motions
  (-20youth indicators
• talk with Bruce about how best to tackle the
  unreduced data from previous Lick/Keck runs