INFRARED PHOTOMETRY OF BETA-PICTORIS TYPE SYSTEMS

We obtained small-aperture (4 ''-5 '' diameter) infrared (2-20 mu m) p hotometry of 10 early-type main-sequence stars with infrared excesses from circumstellar dust. These systems possibly exemplify the beta Pic toris phenomenon. We observed them with either the NASA Marshall Space Flight Center bolometer array camera (''Big Mac'') or the Infrared Te lescope Facility 2-30 mu m single-channel bolometer system. Measuremen ts were obtained in the KLMNQ filters and the narrowband (Delta lambda approximate to 1 mu m) 10 mu m ''silicate'' filters. We fitted Kurucz photospheric models to the photometric data to determine excess-emiss ion spectra. We report the nondetection of small-aperture circumstella r dust emission from HR 10 and 21 LMi. We confirmed previous nondetect ions of near-infrared or 10 mu m excess emission from 68 Oph, alpha Ps A, and HR 4796A. We did not detect prominent silicate emission from an y of the sources. The spectra of gamma Oph, sigma Her, HR 2174A, beta UMa, and zeta Lep show weak 10 mu m excesses. We fitted simple models to these data, together with IRAS excess fluxes, to determine plausibl e distributions of temperature and density of circumstellar dust grain s. Significant quantities of these grains around HR 2174A, zeta Lep, a nd beta UMa are at temperatures similar to terrestrial material in the solar system.