Constraining Circumstellar Environments: High-resolution Far-Infrared Observations of Herbig Ae/Be Stars
Session 34 -- Airbourne Astronomy
Display presentation, Tuesday, 9:30-6:30, Pauley Room

## [34.17] Constraining Circumstellar Environments: High-resolution Far-Infrared Observations of Herbig Ae/Be Stars

J. Di Francesco, N.J.Evans II, P.M.Harvey (Univ. of Texas), L.G.Mundy (Univ. of Maryland), H.M.Butner (NASA/Ames Research Center)

Observations of 6 Herbig Ae/Be stars (AB Aur, MWC 137, LkH$\alpha$ 215, MWC 297, LkH$\alpha$ 234, and MWC 1080) have been made at 50 and 100 $\mu$m with the Kuiper Airborne Observatory in an attempt to constrain their circumstellar environments. All sources examined were previously classified as Group I by Hillenbrand et al. 1992, indicating that their far-infrared spectral energy distributions could be specified solely by a model of a circumstellar disk. This model implies that they should be unresolved with our instrument's $\sim$30 arcsecond beam at 100 $\mu$m, regardless of the sizes of their disks. In contrast, we find that 5 out of 6 sources are clearly resolved with our beam suggesting that the far-infrared emission must arise in another component, possibly a circumstellar envelope. Only AB Aur was found to be unresolved. Since envelopes have been also observed around Group II Herbig Ae/Be stars, the presence of envelopes around the other 5 sources suggests that these two groups of Herbig Ae/Be stars are less distinct than previously thought. In addition, since a circumstellar envelope can affect the actual temperature distribution of a disk inside the envelope, more consistent models of these objects, including disks and envelopes, are needed.