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E. Polomski, C. M. Telesco (U. Florida)
The infrared excesses of pre-main-sequence stars have long been attributed to emission from dust within a circumstellar disk. However, this assumption was based upon indirect evidence, and until recently few instruments have had the sensitivity or resolution to reveal the details of the circumstellar environments of pre-main-sequence stars. Knowledge of the properties of these environments bears directly on our understanding of the early evolution of stars. Since circumstellar disks are believed to be the birthplaces of planets, the precise nature and origin of the IR excess is also critical to understanding planet formation in pre-main-sequence stars.
We have conducted a high spatial resolution (0.183-0.223 arcseconds/pixel) mid-infrared survey of a group of intermediate mass pre-main-sequence stars, the Herbig stars. This survey was performed using the new University of Florida mid-IR imager/spectrometer, OSCIR, and the IRTF 3-meter telescope and CTIO 4-meter telescope. Our observations reveal for the first time the structure of the near-star (100-10000 A.U.) environments of Herbig stars. We find that companion stars and complex diffuse emission from dust can account for a great deal of the IR excess detected in previous low resolution observations. Although we cannot completely rule out the presence of planet-forming disks in our sample, our observations dramatically illustrate that circumstellar disks are not the only phenomenon that can account for the IR excesses. Here we present mid-IR images and spectral energy distributions of several Herbig stars and their environments. We have also determined temperature and optical depth distributions.
The author(s) of this abstract have provided an email address for comments about the abstract: elwood@astro.ufl.edu