Infrared mapping of the dust around main sequence stars

The photopolarimeter on ISO (ESOPHOT) has been used to investigate the dust discs around the four prototype Vega-like stars (Vega (alpha Lyr), beta Pic, alpha PsA and epsilon Eri) and several main sequence stars with excess infrared emission from IRAS data. Mapping at 60 and 90 mu m showed that the four prototypes were resolved, as were several candidates. High resolution linear scans were made across the discs of Vega (A0V), beta Pic (A5V), HD169142 (A5Ve) and HD142666 (A8Ve). Deconvolved disc sizes, at 60 mu m are given for Vega, beta Pic, and HD142666; the disc around HD169142 was not resolved at the position angle scanned. The results confirm the cool, tenuous discs around the prototypes, and show that the younger candidate stars have larger, more massive discs. Using a distance estimate of 288 pc for HD142666, the disc was calculated to have a radius of about 1100 AU, and a mass of possibly 0.01 M. from the scan and map data.