Infrared studies of circumstellar matter around Herbig Ae/Be and related stars

• Published in: The Astrophysical journal Vol. 406; no. 2; pp. 674 - 691
• Main Authors: Natta, Antonella, Palla, Francesco, Butner, Harold M., Evans, Neal J., II, Harvey, Paul M.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 01.04.1993
• Subjects: Astronomy; Astrophysics; Circumstellar shells, clouds, and expanding envelopes. Circumstellar masers; Earth, ocean, space; Exact sciences and technology; Pre-main sequence objects, young stellar objects (yso's) and protostars (t tauri stars, orion population, herbig-haro objects, bok globules, bipolar outflows, cometary nebulae, etc.); Stars; Stellar characteristics and properties; Circumstellar dust; Premain sequence star; Circumstellar shells; Images; Infrared radiation; Circumstellar disks; Infrared star; Herbig Ae/Be star; Photometry
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/172478

The study presents high spatial resolution data at 50 and 100 microns for seven young intermediate-mass stars with flat or rising spectral energy distributions. Five stars, namely, LkH-alpha 198, R Mon, CD -42 deg 11721, R CrA, and V645 Cyg, are resolved at 100 microns. The emission comes from spatially extended envelopes, with sizes varying between 0.025 and 0.4 pc. The wavelengths are optically thin at mid-IR and FIR wavelengths but become optically thick in the visual where the extinction amounts to 5-10 mag. In two cases, R CrA and V 645 Cyg, dust density distributions with steep density gradients are obtained, alpha is approximately equal to 2, while for LkH-alpha, R Mon, and CD -42 deg 11721, alpha is approximately equal to 0.5. Model fitting to the spectral energy distributions, combined with the constraints on the size of the emitting regions, indicates that inside the circumstellar envelopes a large fraction of the stellar radiation is already degraded to longer wavelengths.