Infrared photometry of β Pictoris type systems

We obtained small-aperture (4 "-5 " diameter) infrared (2-20 mu m) photometry of 10 early-type main-sequence stars with infrared excesses from circumstellar dust. These systems possibly exemplify the beta Pictoris phenomenon. We observed them with either the NASA Marshall Space Flight Center bolometer array camera ("Big Mac") or the Infrared Telescope Facility 2-30 mu m single-channel bolometer system. Measurements 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-emission spectra. We report the nondetection of small-aperture circumstellar dust emission from HR 10 and 21 LMi. We confirmed previous nondetections of near-infrared or 10 mu m excess emission from 68 Oph, alpha PsA, and HR 4796A. We did not detect prominent silicate emission from any 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 plausible distributions of temperature and density of circumstellar dust grains. Significant quantities of these grains around HR 2174A, zeta Lep, and beta UMa are at temperatures similar to terrestrial material in the solar system.