Submillimeter observations of evolved stars
Broad-band submillimeter observations of the thermal emission from evolved stars have been obtained with the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. These observations, at an effective wavelength of 400 ..mu..m, provide the most direct method for estimating the mass loss rate in dust from these stars and also help to define the long-wavelength thermal spectrum of the dust envelopes. The mass loss rates in dust that we derive range from 10/sup -9/ to 10/sup -6/ M/sub sun/ yr/sup -1/ and are compared with mass loss rates derived from molecular line observations to estimate gas-to-dust ratios in outflowing envelopes. These values are found to be generally compatible with the interstellar gas-to-dust ratio of approx.100 if submillimeter emissivities appropriate to amorphous grain structures are assumed. Our analysis of the spectrum of IRC+10216 confirms previous suggestions that the grain emissivity varies as lambda/sup -1.2/ rather than as lambda/sup -2/ for 10<1000 ..mu..m. The overall properties of the model that we use in the analysis of IRC+10216 are found to be applicable to the similar carbon-rich object CRL 3068. Similar analysis of the spectra of oxygen-rich objects indicates that our submillimeter fluxes for IRC+10011 and NML Cyg are greater than those predicted by previous modeling. This, we argue, is the result of a slower decline in grain emissivity with wavelength than is seen in published silicate grain models. We are not able to distinguish a systematic difference in the dust masses of carbon-rich and oxygen-rich envelopes. We find the largest mass loss rates in dust in the bipolar objects OH 231.8+4.2, CRL 2688, and CRL 618 and in NGC 7027 and VY CMa.
- Research Organization:
- University of Maryland and Catonsville Community College
- OSTI ID:
- 5308697
- Journal Information:
- Astrophys. J.; (United States), Vol. 294:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
CRL 2688 and CRL 618: Proto--planetary nebulae
A MOLECULAR LINE SURVEY OF THE EXTREME CARBON STAR CRL 3068 AT MILLIMETER WAVELENGTHS
Related Subjects
GENERAL PHYSICS
INTERSTELLAR GRAINS
EMISSIVITY
STAR EVOLUTION
MASS TRANSFER
STARS
CARBON
COSMIC DUST
COSMIC GASES
INFRARED RADIATION
OXYGEN
SILICATES
DUSTS
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
GASES
NONMETALS
OPTICAL PROPERTIES
OXYGEN COMPOUNDS
PARTICLES
PHYSICAL PROPERTIES
RADIATIONS
SILICON COMPOUNDS
SURFACE PROPERTIES
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources