ISOPHOT Observations of Dust Disks around Main Sequence (Vega-Like) Stars

Abstract The photometer (ISOPHOT) on the Infrared Space Observatory (ISO) has proved to be invaluable for investigating the dust around main sequence stars (both prototypes and candidate Vega-like stars). The long wavelength camera (at 60 and 90 μm) has been used to map the area around the stars to establish whether the dust disk is extended. Low-resolution spectra between 5.8 and 11.6 μm show whether the dust is composed of silicate grains, and whether molecular features are present. The four prototype Vega-like stars (Vega, β Pic, Fomalhaut, ϵ Eri) are studied, as well as eight other stars, which are main sequence stars with cool dust associated with them. We find that the spectra of β Pic, 49 Cet, HD98800, and HD135344 show excess emission from the cool dust around the star, HD144432 and HD139614 show silicate dust emission, HD169142 and HD34700 show emission features from carbon-rich molecules (possibly PAHs, polycyclic aromatic hydrocarbon molecules), and HD142666 shows emission features from both carbon-rich molecules and silicate dust. Up to 11.6 μm, the emission from Vega, Fomalhaut, and ϵ Eri is dominated by the stellar photosphere. At 60 and 90 μm, the extended dust emission is mapped, and the disk resolved in eight cases. The dust mass in the disks is found to range from around 10 −9 to 10 −4 M ⊙ . Since several of the stars are younger than the Sun, and the disks have sufficient material of the type found in the Solar System, these disks could be in the early stages of planet formation.