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Astron. Astrophys. 338, 91-96 (1998)

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Search for cool circumstellar matter in the Ursae Majoris group with ISO *

Péter Ábrahám 1, 2, Christoph Leinert 1, Alfons Burkert 3, Dietrich Lemke 1 and Thomas Henning 3

1 Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
2 Konkoly Observatory of the Hungarian Academy of Sciences, P.O.Box 67, H-1525 Budapest, Hungary
3 Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergäßchen 3, D-07745 Jena, Germany

Received 2 June 1998 / Accepted 16 July 1998


We observed the mid- and far-infrared spectral energy distributions of 9 A-type stars from the 300 Myrs old Ursae Majoris group using the ISO satellite and the UKIRT telescope. We found that only 1 out of the 9 stars shows clear signature of circumstellar dust, and we derived an upper limit of 0.05 [FORMULA] for the dust mass around the other stars. Our results suggest that the relatively high incidence of Vega-like disks observed among A-type field stars in the solar neighbourhood by IRAS cannot be extrapolated to the rest of the Milky Way. The Vega phenomenon appears to be the exception rather than the rule.

Key words: circumstellar matter – stars: individual: fi UMa – infrared: stars

* Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the P/I countries France, Germany, the Netherlands and the United Kingdom) with participation of ISAS and NASA.

© European Southern Observatory (ESO) 1998

Online publication: September 8, 1998