THE AGE OF GLIESE-879 AND FOMALHAUT

We estimate here the age of one of the prototypes of the beta Pic-like stars, Fomalhaut, based on the properties of its common proper motion companion GI 879. By combining constraints derived from the lithium a bundance, rotational velocity, H-R diagram position, and coronal activ ity we conclude that the age for GI 879, and hence the age for Fomalha ut, is 200 +/- 100 Myr. This age estimate agrees quite well with the c ompletely independent age estimate derived directly from isochrone fit ting to Fomalhaut's position in an H-R diagram, and thus confirms that circumstellar dust disks can persist in A stars for several hundred m egayears.