  We present Herschel PACS 100 and 160 micron observations of the solar-type
stars alpha 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
S tars). Our observations show small infrared excesses at 160 micron for all
three stars. HD 210277 also shows a small excess at 100 micron, while the 100
micron fluxes of alpha Men and HD 88230 agree with the stellar photospheric
predictions. We attribute these infrared excesses to a new class of cold, faint
debris discs. alpha Men and HD 88230 are spatially resolved in the PACS 160
micron 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 ~ 250 AU.
The estimated black body temperatures from the 100 and 160 micron fluxes are
$\lesssim$ 22 K, while the fractional luminosity of the cold dust is
Ldust/Lstar ~ 10E-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 and cannot easily be explained by invoking "classical" debris disc
models.

Solar and Stellar Astrophysics