NICMOS Imaging of HD 179821 and AFGL 4106

Abstract

Near-infared images from a NICMOS survey revealed the circumstellar matter around several proto-planetary nebulae (PPNe), including IRAS 18184–1623, AFGL 4106, and HD 179821 (=IRAS 19114+0002). The IRAS 18184 data was previously analyzed by O'Hara et al. (2003). Here we present the data on the other two objects.

The true nature of HD 179821 is still a subject of some debate. It could be a yellow hypergiant or a post-AGB star. Regardless, the NICMOS images show that it is surrounded by a nebula with a diameter of $\sim12^{\prime\prime}$. Until 1600 years ago, it was losing mass at a rate of 3 $\times 10^{-4}$ M$_{\odot}$ yr$^{-1}$. It now exhibits multiple concentric shells with small bipolar outer protuberances.

AFGL 4106 was known previously as a spectroscopic binary, consisting of a luminous F-type post-red-supergiant and an M-type red supergiant. It is surrounded by a faint nebula with a diameter of $\sim3^{\prime\prime}$. Here we present the first image that shows not only the nebula but also the binary companion. It appears at a position angle of $\sim270^{\circ}$ and a separation of 0.$^{\prime\prime}$3.