Transcript GAIA and astrometry of giant planets

Gaia and astrometry of giants planets
M. G. Lattanzi
INAF – Osservatorio Astronomico di Torino
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MLA agreement (ESA
+ National Agencies)
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Now Spring 2012
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But…..
A factor of 2 better errors for M (red) stars of same
magnitude (fainter than V~13)
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Looking at the Galaxy...
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Gaia and Extrasolar planets - I
What will Gaia “see”?
• Because of its mode of operation (magnitude limited survey, or
better, S/N threshold –limited survey, uneven coverage geometry scanning law), there has “never” been any optimization of the
mission to the case of extrasolar planets with the exception of
requiring, at the time of establishing the science case, sufficient
astrometric accuracy at bright magnitudes (V<=13).
>>>>> Since little can be done with the photometric and
spectroscopic capabilities aboard the satellite: what can be done
with just the astrometry!
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Gaia and Extrasolar planets - II
Large Double Blind Test campaign on more than 160,000 systems for
detection and characterization of planets utilizing only astrometric
observations (Casertano, Lattanzi, Sozzetti et al., AA, 2008). Different teams
for systems simulation, fitting (especially) , and evaluation.
Characterization primarily “targeting” Jupiter-size “first” planets with periods
just exceeding the mission operational time (6 yr compared to 5 yr).
Sample included multi-planet systems (Co-planarity)
Unbiased survey across all spectral types with constant astrometric
sensitivity up to <=200 pc
Because the data volume expected, set FAP to conservative values (1%)
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Gaia and Extrasolar planets - III
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Astrometric Orbits
• Astrometry measures stellar positions and uses them to
determine a binary orbit projected onto the plane of the sky
• measures all 7 parameters of the orbit, in multiple systems it
derives the relative inclination angles between pairs of orbits,
regardless of the actual geometry. Mass is derived given a guess
for the primary’s.
• In analysis, one has to take the proper motion and the stellar
parallax into account
• The measured amplitude of the orbital motion (in mas) is:
S/N =  / 
( error of epoch astrometry)
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How Many Planets will Gaia find?
Star counts (V<13),
Fp(Mp,P),
Gaia completeness
limit
Casertano, Lattanzi, Sozzetti et al. 2008
How Many Multiple-Planet Systems will Gaia find?
Star counts (V<13),
Fp,mult,
Gaia detection
limit
Unbiased, magnitude-limited census of hundreds of thousands stars
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How do Planet Properties and Frequencies Depend Upon the Characteristics of the
Parent Stars (also, What is the Preferred Mechanism of Gas Giant Planet Formation?)?
Johnson 2007
?
The Gaia Legacy (1)
Sozzetti et al. 2009
Gaia will test the fine structure of giant planet
parameters distributions and frequencies, and
investigate their possible changes as a function
of stellar mass, metallicity, and age with
unprecedented resolution
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Casertano et al. 2008
104 stars per 0.1 MSun bin!
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The Gaia Legacy (2)
How Do Dynamical Interactions Affect the Architecture of Planetary Systems?
E.g., coplanarity tests will allow to determine
the relative importance of many proposed
mechanisms for eccentricity excitation in a
statistical sense, not just on a star-by-star basis.
a) Interactions between a planet and the
gaseous/planetesimal disk?
b) Planet-planet resonant interactions?
c) Close encounters between planets?
d) Secular interactions with a companion star?
Thommes & Lissauer 2003
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The Gaia Legacy (3)
What Are the Phase Functions and Light Curves of Gas Giant Planets?
Burrows et al. 2005
Gaia could provide important supplementary data
to aid in the interpretation of direct detections
of giant exoplanets both by helping to characterize
their thermo-physical conditions and by determining
the epoch and location of their maximum brightness.
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Where Are the Earth-Like Planets, and What Are Their Characteristics?
Nearby stars:
THE targets.
The Gaia Legacy (4)
They must be studied
as best as one can
Gaia will provide important supplementary data for
the optimization of the characterization of targets,
e.g., by screening all stars within ~25 pc (including
the large numbers of M dwarfs) for Jupiter- and
Saturn-sized planets out to several AUs.
Kaltenegger et al. 2007
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Conclusions
• The largest compilation of astrometric orbits of,
largely, massive planets (in many cases sign posts of
more interesting systems!) unbiased across all
spectral types up to <=200 pc
• This contribution will be crucial to several aspects
of planetary systems astrophysics (formation
theories, dynamical evolution), in combination with
present-day and future extrasolar planet search
programs
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