2011A&A...536L...4E

We present Herschel PACS 100 and 160µm observations of the solar-type stars α Men, HD 88230 and HD 210277, which form part of the FGK stars sample of the Herschel open time key programme (OTKP) DUNES (DUst around NEarby Stars). Our observations show small infrared excesses at 160µm for all three stars. HD 210277 also shows a small excess at 100µm, while the 100µm fluxes of α Men and HD 88230 agree with the stellar photospheric predictions. We attribute these infrared excesses to a new class of cold, faint debris discs. Both α Men and HD 88230 are spatially resolved in the PACS 160 µm images, while HD 210277 is point-like at that wavelength. The projected linear sizes of the extended emission lie in the range from ∼115 to ≤250AU. The estimated black body temperatures from the 100 and 160µm fluxes are ≲22K, and the fractional luminosity of the cold dust is L_dust/L_*∼10^–6, close to the luminosity of the solar-system's Kuiper belt. These debris discs are the coldest and faintest discs discovered so far around mature stars, so they cannot be explained easily invoking ``classical'' debris disc models.