A Debris Disk around the Central Star of the Helix Nebula?

Abstract

Excess emission from a point-like source coincident with the central star of the Helix Nebula is detected with Spitzer at 8, 24, and 70 µm. At 24 µm, the central source is superposed on an extended diffuse emission region. While the [O IV] 25.89 µm line contributes to the diffuse emission, a 1035 µm spectrum of the central source shows a strong thermal continuum. The excess emission from the star most likely originates from a dust disk with blackbody temperatures of 90–130 K. Assuming a simple optically thin debris disk model, the dust is distributed in a ring between �35 and �150 AU from the central star, possibly arising from collisions of Kuiper-Belt-like Objects or the break-up of comets from an Oort-like cloud that have survived from the post-main-sequence evolution of the central star. Subject headings: infrared: stars – stars: individual (WD 2226 210) – white dwarfs