We have carried out a high-sensitivity search for circumstellar disks around Herbig Be stars in the continuum at 1.4mm and 2.7mm using the IRAM interferometer at the Plateau de Bure ( PdBI ) .
In this letter , we report data on three well studied B0 stars , MWC 1080 , MWC 137 and R Mon .
The two latter have also been observed in the continuum at 0.7 cm and 1.3 cm using the NRAO Very Large Array ( VLA ) .
We report the detection of circumstellar disks around MWC 1080 and R Mon with masses of M _ { d } \sim 0.003 and 0.01 M _ { \odot } , respectively , while for MWC 137 we estimate a disk mass upper limit of 0.007 M _ { \odot } .
Our results show that the ratio M _ { d } /M _ { * } is at least an order of magnitude lower in Herbig Be stars than in Herbig Ae and T Tauri stars .