Abstract

λ Boo stars are Population I, A0-F3 stars with strongly depleted Fe peak elements abundances but relatively normal solar abundances of C, N, O, and S. Since they are only 1% of field stars and exhibit a variety of ages, transient mechanisms external to the photosphere have been proposed to explain the abnormal surface abundances. These include ISM interactions or accretion from a debris disk. In these external mechanisms the gas and dust are deferentially accreted, such that the surface will appear depleted in Fe-peak metals but rich in gases. With Herschel observations it was found that 8/8 of λ Boo stars observed show an excess emission at 100 to 160 microns. λ Boo, ρ Vir, and HD31295 are resolved and well modeled by a cold debris disk. Other unresolved sources are consistent with the presence of a cold debris disk due to the fact that 0.1 micron dust grains typical of the ISM would reach the equilibrium temperature observed at much larger scales in a bow shock than a debris disk. We compare stellar abundances from high-resolution spectroscopy and disk properties inferred by sub-mm emission to determine if there is any correlation that would further support debris disks as the cause of the λ Boo phenomenon.

Presentation

Poster