Kuiper belts around nearby stars

摘要

Context. The existence of dusty debris disks arounda large fraction of solar type main-sequence stars, inferred fromexcess far-IR and submillimetre emission compared to that expected fromstellar photospheres, suggests that leftover planetesimal beltsanalogous to the asteroid- and comet reservoirs of the solar system arecommon. Aims. Sensitive submillimetre observations areessential to detect and characterise cold extended dust originatingfrom collisions of small bodies in disks, belts, or rings atKuiper-belt distances (30-50AU or beyond). Measurements ofthe flux densities at these wavelengths will extend existing IRphotometry and permit more detailed modelling of the Rayleigh-Jeanstail of the disks spectral energy distribution (SED), effectivelyconstraining dust properties and disk extensions. By observing starsspanning from a few up to several hundred Myr, the evolution of debrisdisks during crucial phases of planet formation can be studied. Methods. We observed 22 exo-Kuiper-belt candidatesat 870m,as part of a large programme with the LABOCA bolometer at the APEXtelescope. Dust masses (or upper limits) were calculated fromintegrated 870mfluxes, and fits to the SED of detected sources revealed the fractionaldust luminosities ,dust temperatures ,and power-law exponents of the opacity law. Results. A total of 10 detections with at least 3significance were made, out of which five (HD95086,HD131835, HD161868, HD170773, andHD207129) have previously never been detected atsubmillimetre wavelengths. Three additional sources are marginallydetected with >2.5significance. The best-fit parameters all lie between 0.1 and 0.8, in agreement with previousresults indicating the presence of significantly larger grains thanthose in the ISM. From our relatively small sample we estimate,with ,and identify an evolution of the characteristic radial dust distancethat is consistent with the t1/3increase predicted from models of self-stirred collisions in debrisdisks. Key words: circumstellar matter -planetary systems - planets and satellites: formation - Kuiper belt:general - submillimeter: planetary systems