We report the first near infrared ( NIR ) imaging of a circumstellar annular disk around the young ( \sim 8 Myr ) , Vega-like star , HR 4796A .
NICMOS coronagraph observations at 1.1 and 1.6 \mu m reveal a ring-like symmetrical structure peaking in reflected intensity 1.05 \arcsec  \pm 0.02 \arcsec  ( \sim 70 AU ) from the central A0V star .
The ring geometry , with an inclination of 73.1 ^ { \circ } Â \pm 1.2 ^ { \circ } Â and a major axis PA of 26.8 ^ { \circ } Â \pm 0.6 ^ { \circ } is in good agreement with recent 12.5 and 20.8 \mu m observations of a truncated disk ( Koerner , et al .
1998 ) .
The ring is resolved with a characteristic width of less than 0.26 \arcsec  ( 17 AU ) and appears abruptly truncated at both the inner and outer edges .
The region of the disk-plane inward of \sim 60 AU appears to be relatively free of scattering material .
The integrated flux density of the part of the disk that is visible ( greater than 0.65 \arcsec  from the star ) is found to be 7.5 \pm 0.5 mJy and 7.4 \pm 1.2 mJy at 1.1 and 1.6 \mu m , respectively .
Correcting for the unseen area of the ring yields total flux densities of 12.8 \pm 1.0 mJy and 12.5 \pm 2.0 mJy , respectively ( Vega magnitudes = 12.92 \pm 0.08 and 12.35 \pm 0.18 ) .
The NIR luminosity ratio is evaluated from these results and ground-based photometry of the star .
At these wavelengths L _ { disk } ( \lambda ) / L _ { * } ( \lambda ) = 1.4 \pm 0.2 \times 10 ^ { -3 } and 2.4 \pm 0.5 \times 10 ^ { -3 } , giving reasonable agreement between the stellar flux scattered in the NIR and that which is absorbed in the visible and re-radiated in the thermal infrared .
The somewhat red reflectance of the disk at these wavelengths implies mean particle sizes in excess of several microns , larger than typical interstellar grains .
The confinement of material to a relatively narrow annular zone implies dynamical constraints on the disk particles by one or more as yet unseen bodies .