Report - School of Physics

4.4 Astrophysical Characterisation of Host Stars
Several thousand planetary systems should be discovered by a combination of COROT,
Kepler, Eddington, SIM and Gaia over the years 2006–2015. There will be a need
for detailed astrophysical characterisation of large numbers of stars (some tens of
thousands), in both the northern and southern hemispheres. Specifically:
(a) physical characteristics of the host star via photometry: it will be important
to characterise, homogeneously, luminosity (T eff , log g), metallicity, and microvariability.
Large-scale multi-colour, multi-epoch photometry for this purpose may
be available from Pan-STARRS (Panoramic Survey Telescope and Rapid Response
System) or LSST (Large Synoptic Survey Telescope) and from Gaia’s 11-band multicolour
photometry, although not before 2012;
(b) physical characteristics of the host star via spectroscopy: the goal is again
to determine the spectroscopic parameters of the central star: T eff , log g, [Fe/H].
Medium-high spectral resolving power is needed (20 000–60 000) in the visible range;
(c) spatial distribution and kinematics: Gaia will provide highly-accurate distances
essential for luminosity calibration (e.g., 1% at 1 kpc at 15 mag), characterised
as a function of the local environment (e.g., for stars within the core or halo of
open clusters), and kinematic motions (e.g., with respect to the Local Standard of
Rest, velocity with respect to the Galactic mid-plane, etc.). This characterisation is
important because of possible links with habitability (as discussed in Section 1.2).
(d) kinematic radial velocities for fainter stars. Hipparcos would have greatly benefited
from a coordinated acquisition of radial velocities from the ground. Key
programmes went part way towards this, but only for half the sky, for a subset
of spectral types, and on a schedule out of phase with the Hipparcos Catalogue
publication in 1997—the Geneva-Copenhagen survey of 14 000 F and G dwarfs has
just been published (Nordström et al., 2004). Gaia partly addresses the problem
by acquiring radial velocities on-board, but higher precision and a fainter limiting
magnitude would demand a concerted and coordinated campaign on the ground.
With the caveats on the time-scales of data availability, planned surveys (Gaia, if
not others) should generally provide detailed astrophysical characterisation of the
host stars of all detected systems, with the possible exception of kinematic radial
velocities for faint stars (> 20 mag), and a dedicated spectral survey.
4.4.1 A Dedicated Spectral Survey
ESO has capabilities to perform a full spectral characterisation of all F–K type stars
in the southern hemisphere within a radius of say 50 pc. Facilities at ESO could be
used to obtain a complete spectrum of the stars from the atmospheric cut-off to 5 µm.
By combining the Echelle spectrographs FEROS (2.2-m), UVES, and CRIRES the
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