SIMBAD references

We observed the mid- and far-infrared spectral energy distributions of 9 A-type stars from the 300Myrs 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 0.05M_moon 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.