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R. Mauersberger
, T.L. Wilson 
R.T. Rood
,
T.M. Bania
H. Hein
, A. Linhart
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69, D-53121 Bonn, Germany
Radioastronomisches Institut der Universität Bonn, Auf dem Hügel
69, D-53121 Bonn, Germany
Steward Observatory, The University of Arizona, Tucson, AZ 85721,
USA
Department of Astronomy, University of Virginia, Charlottesville, VA
22903, USA
Department of Astronomy, Boston University, Boston, MA 02215, USA
IRAM, Avenida Divina Pastora 7-9, Núcleo Central, E-18012 Granada,
Spain
Submillimeter Telescope Observatory, The University of Arizona,
Tucson, AZ 85721, USA
Institut für Weltraumsensorik, DLR, Rudower Chaussee 5, D-12489
Berlin, Germany
Abstract: A directed search for extraterrestrial intelligence (SETI) has been
carried out using the IRAM 30m telescope. Following a suggestion by
Kardashev (1979), the search was conducted at the spin-flip line of
the lightest atom, namely positronium, at 203GHz. Most of the 17
targets are mature stars with excess infrared radiation, which might
be the waste heat of a power-rich technological civilization. The
rest frame of the cosmic background radiation was chosen as the
velocity frame. The spectral resolution used was 9.7kHz. From the
noise level, which was determined by the limited telescope time and
weather conditions, the upper limit for the power of artificial
omnidirectional transmitters at the positronium line frequency is of
order 
W. The relevance of this non-detection is discussed.
Robert Lucas
Fri Jul 7 18:58:08 METDST 1995