The Excess Infrared Emission of Herbig Ae/Be Stars: Disks or Envelopes?
Abstract
It is suggested that the near-IR emission in many Herbig Ae/Be stars arises in surrounding dusty envelopes, rather than circumstellar disks. It is shown that disks around Ae/Be stars are likely to remain optically thick at the required accretion rates. It is proposed that the IR excesses of many Ae/Be stars originate in surrounding dust nebulae instead of circumstellar disks. It is suggested that the near-IR emission of the envelope is enhanced by the same processes that produce anomalous strong continuum emission at temperatures of about 1000 K in reflection nebulae surrounding hot stars. This near-IR emission could be due to small grains transiently heated by UV photons. The dust envelopes could be associated with the primary star or a nearby companion star. Some Ae/Be stars show evidence for the 3.3-6.3-micron emission features seen in reflection nebulae around hot stars, which lends further support to this suggestion.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1993
- DOI:
- 10.1086/172507
- Bibcode:
- 1993ApJ...407..219H
- Keywords:
-
- A Stars;
- Accretion Disks;
- B Stars;
- Infrared Astronomy;
- Stellar Envelopes;
- Stellar Models;
- Cosmic Dust;
- Near Infrared Radiation;
- Nebulae;
- Pre-Main Sequence Stars;
- Spectral Energy Distribution;
- Astrophysics;
- ACCRETION;
- ACCRETION DISKS;
- STARS: CIRCUMSTELLAR MATTER;
- STARS: EMISSION-LINE;
- BE;
- STARS: PRE--MAIN-SEQUENCE