THE FATE OF THE SOLID MATTER ORBITING HR 4796A

We have obtained optical spectra, 2 mu m speckle images, and an upper limit to the 800 mu m flux for HR 4796A, and optical spectra for its p hysical companion separated by 7 ''.7, HR 4796B. We detect H beta, H g amma, and the calcium H and K lines in emission from HR 4796B; these d ata are consistent with the hypothesis that it is later than spectral type M2 and lies substantially above the main-sequence. From the locat ion of HR 4796B on the H-R diagram, the estimated age of this star is 3 x 10(6) yr, and assuming this age for the entire system, we find fro m our 2 mu m speckle data that there is no close stellar companion to HR 4796A (M > 0.125 M.) between 11 and 120 AU from the star. From the IRAS and ground-based photometry, it seems that there is a hole in the dust distribution around HR 4796A with an inner radius of between sim ilar to 40 and similar to 200 AU. The observed circumstellar dust grai ns, which lie at D > 40 AU from the star, are likely to be at least 3 mu m in radius in order to be gravitationally bound to HR 4796A, if th e circumstellar dust cloud is optically thin. Since they are larger th an almost all interstellar grains, the circumstellar dust grains proba bly grew by coalescence. Because the existing grains at D > 40 AU have undergone measurable coalescence, it is possible that particles that presumably once existed at D < 40 AU, where the collision times were s horter than at D > 40 AU, grew into macroscopic objects. A likely expl anation for the dust hole is that there is a companion located at abou t half the inner radius of the dust hole, or between 20 and 100 AU fro m the star. If such a companion exists, it must have a mass less than 0.125 M.. Since grain coalescence has occurred, this putative companio n possibly could be a planet.