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