Report - School of Physics

4.2 Follow-Up Observations
With reference to Figure 7, over the next 5–10 years ongoing or approved survey
experiments are expected to generate:
(a) high-mass (∼ M J ) candidates: some hundreds from COROT, Kepler and Eddington;
thousands with Gaia astrometry and thousands of transiting systems with
Gaia photometry; some hundreds from ongoing and future ground-based radial velocity
surveys; and hundreds (possibly thousands) of hot Jupiters from ground-based
transit surveys;
(b) low-mass (∼ 1−3 M ⊕ ) candidates: a small number of hot terrestrial planets from
COROT around 2008; with tens to hundreds from Kepler expected to be available
to the community after about 2010.
In principle, the information required for further characterisation of a detected planetary
system is independent of the star or planet mass: as discussed elsewhere in
this report: (a) radial velocity measurements of transit detections to eliminate false
alarms due to grazing eclipsing binaries, triple stars, star spots, and false positives;
(b) transit spectroscopy from ground or space for the determination of atmospheric
properties; (c) the combination of transit or astrometry data with radial velocity
information allowing the determination of the true mass of the planet; (d) photometric
or spectroscopic information needed to characterise the parent star; (e) followup
imaging of transiting candidates with high spatial resolution adaptive optics to
minimise the possibility that the object is actually multiple, or that a foreground or
background binary system is causing the dimming of the light; (f) all the above will
provide candidates for ground-based imaging by VLT, VLTI, OWL, etc.
For microlensing candidates, no follow-up observations are generally possible. Nevertheless,
due to the relative proper motion, the lens star will increase its angular
separation to the source star and become visible after some time. One case is known:
MACHO LMC–5, in which the lens star was imaged after about 8 years or so (Alcock
et al., 2001). So in principle, there exists a possibility to study the host star
of a microlensing planet, depending on the mass/apparent brightness of the lensing
(i.e., host) star, and on the relative transverse velocity.
In practice, the problem is distinct for high-mass or low-mass planets.
4.2.1 High-Mass Planets
For high-mass objects (of order 1 M J ), ground-based follow-up transit measurements
will generally be technically feasible with the current generation of instruments.
COROT, Kepler, Eddington, Gaia, OGLE, possibly HST, and the ground-based
transit networks will supply thousands of targets which can be followed from the
ground. Small telescopes, preferably robotic, and substantial amounts of observing
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