Herschel imaging of 61 Vir: implications for the prevalence of debris in low-mass planetary systems

摘要: This paper describes Herschel observations of the nearby (8.5pc) G5V multi-exoplanet host star 61Vir at 70, 100, 160, 250, 350 and 500m carried out as part DEBRIS survey. These reveal emission that is significantly extended to a distance >15arcsec with morphology can be fitted by nearly edge-on (77° inclination) radially broad (from 30au least 100au) debris disc fractional luminosity 2.7 × 10 -5, two additional (presumably unrelated) sources become more prominent longer wavelengths. Chance alignment background object seen 1.4GHz provides potential for confusion, however, star's 1.4arcsecyr -1 proper motion allows archival Spitzer 70m images confirm what we are interpreting really circumstellar. Although exact shape disc's inner edge not well constrained, region inside must depleted in planetesimals. readily explained if there planets outside those already known (i.e. 0.5-30au region), but also consistent collisional erosion. We find tentative evidence presence detectable around stars correlates lowest mass current radial velocity surveys. Out an unbiased sample nearest 60G stars, 11 have planets, which six (including 61Vir) all less massive than Saturn, four these debris. The towards one planet hosts (HD20794) reported here first time. fraction (4/6) higher expected field (15per cent), implies systems form low-mass able retain bright discs. suggest this correlation could arise because such planetary dynamically stable include regions populated planetesimals formation process where remain unperturbed over Gyr time-scales.