Report - School of Physics

complete wavelength range can be observed at R ∼ 50 000. A cursory study shows
that such a project could be undertaken at the level of a (very) large programme, of
the order of 100 nights in total. Selecting stars within 50 pc (Hipparcos distances)
and at declination south of 30 degrees North, a total of about 2500 stars would have
to be observed. 75% of these have V magnitudes between 5 and 9 making them
ideal targets for FEROS, while the remaining fainter ones would be observed with
UVES. Using the ESO exposure time estimators for the respective instruments we
found that a S/N of about 100 will be achieved within minutes. Using about 110 hr
of time on FEROS and about 40 hr on UVES per period to obtain the spectra from
350–980 nm the optical survey could be completed within two years with existing
facilities, assuming an ESO ‘Large Programme’ using only late twilight and periods
of bright moon and/or poor seeing. CRIRES is being assembled at this point,
therefore no estimate of the time required for the infrared observation is given here.
Because the majority of stars are rather bright a very substantial fraction (30–50%)
of the stars can be observed during twilight while the remainder can be observed
during bright time. It is evident that a high degree of homogeneity of spectral data
needs to be achieved across the full set of stars in order to achieve the scientific goals
of the project. In particular the combination of spectra calls for excellent calibration
across instruments. To this end the ECF’s Instrument Physical Modelling Group
which is involved in the calibration of instruments on HST and at ESO is prepared
to make major contributions thereby ensuring maximum quality of the data and the
resulting high level products.
A comparable ‘Nearby Stars’ project (PI: R.E. Luck) is being conducted in the
northern hemisphere (http://astrwww.cwru.edu/adam/) using the McDonald 2.1-
m Struve reflector and the Sandiford Echelle Spectrograph.
A dedicated survey would provide data useful for other applications in astrophysics.
Results would include a very fine spectral library which, combined with e.g. Gaia
information on the luminosity function and kinematics, would be very powerful.
4.5 Potential Overlap and Competition
Eddington and Kepler
The arguments for undertaking the Eddington mission are unchanged from the time
that the ESA Astronomy Working Group placed it at the top of the list of astronomy
projects to be undertaken if financing can be made available. Essentially, Kepler is
designed to study a single low-latitude target field and thus a single population of
stars, in a limited mass range. In the same way that the star formation history of the
Galaxy cannot be ascertained by observing a single field, the acceptance of Kepler
results as being of general applicability to the complete Galaxy is questionable. This
is exemplified by the absence of planets in 47 Tuc, and is a question that can only
be resolved by further observations.
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