ExoZodical Emission and ExoPlanets: Ground-based Challenges C. Beichman (NASA Exoplanet Science Institute) With lots of help from A. Tanner (Georgia State), G. Bryden (JPL), S. Lawler (Wesleyan/UBC) R. Akeson (NExScI), D. Ciardi (NExScI), C. Lisse (JHU), Mark Wyatt (Cambridge)
13
Embed
ExoZodical Emission and ExoPlanets: Ground-based Challenges C. Beichman (NASA Exoplanet Science Institute) With lots of help from A. Tanner (Georgia State),
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
ExoZodical Emission and ExoPlanets:
Ground-based Challenges
C. Beichman (NASA Exoplanet Science Institute)
With lots of help from A. Tanner (Georgia State), G. Bryden (JPL), S. Lawler (Wesleyan/UBC)
R. Akeson (NExScI), D. Ciardi (NExScI), C. Lisse (JHU), Mark Wyatt (Cambridge)
Stars are a billion times brighter…
…than the planet
…hidden in the glare.
Like this firefly.
Near-IR Interferometry
Results• PTI and CHARA indicate
Vega, Leo and Lep have a 1-2% near-infrared excess
• Companions (none known), dust scattering or emission– Scattering produces too much mid-infrared flux emission from host
dust is the most likely explanation
• 2 to 10 m flux ratio requires small, hot, non-silicate grains– Dust needs to be near sublimation radius– Grain size below radiation pressure blowout radius lifetime problem?
• Transient event (comet sublimation, recent asteroid collision)– Minimum mass ~ breakup of single 10 km radius body
• Generated by collisions in planetesimal belt at < 1 AU
Fit to both baselinediam = 1.32 ± 0.013 masflux = 2.4 ± 1.3%
Keck Nulling Key Project
• In 2007, NASA HQ allocated the majority of the NASA Keck time to exozodi survey of nearby stars
Keck Interferometer
• 3 teams were competitively selected – Phil Hinz, Univ of Arizona– Marc Kuchner, Goddard Space Flight Center– Gene Serabyn, Jet Propulsion Laboratory
• Observational programs cover known debris disk systems and nearby main sequence stars
Observing Summary• 8 runs Feb. ‘08 – Jan. ‘09: 32 interferometer nights• 44/46 targets observed• No excess for 40 targets (F/F<0.1-1%)• 3-5× improvement over Spitzer photometry (0.5-2%)
Colavita et al (2009, PASP in press)
MIDI
Keck Nuller
Spitzer51 Ophiuchus:A PictorisAnalog Measuredwith the KeckInterferometer Nuller
Stark et al. 2009, ApJ
Simultaneous fit to Spitzer, MIDI, andKeck Nuller data
10 parameter modelwith 2 dust clouds:
1) inner ring of large grains (“birth ring”)
2) small particles (maybe meteoroids)
Stark et al. 200951 Ophiuchus
HD 69830 from Ground & Space
• Spitzer IRS shows disk small, hot grains at 1 AU (outside of outermost planet) at 1,400x zodi– NO evidence for variability
• Unresolved with Gemini @ 11 m (0.3” 4 AU)
• MIDI resolves emission, but exact distribution ambiguous, 0.25 -1 AU (Smith, Wyatt and Haniff 2009)
LBTI ExoZodi Science• MMT nulling experiments
indicate detection of disks with an uncertainty of 25-75 zodi
• The larger apertures and faster correction of the LBT will improve this limit by a factor of 6
• LBTI could characterize debris disks with an uncertainty of ~3-10 zodi around nearby stars.
• Planned survey of 60 stars once LBTI becomes operational
Detection of a 390±70 zody dust disk around β Leo and a non-detection around o Leo with an uncertainty of 50 zodi.
Nulling observations with the MMT(Phil Hinz)
Origin of Hot Dust Disks• Wyatt et al (2006) suggest hot disks rare (<1-2%)• Long term decline due to dissipation at few AU implies mature systems may be clean (few Zodi)• Hot dust disk in mature stars may be LHB analogs