The formation and annealing of circumstellar dust, as gauged by IRAS low-resolution spectra and the microwave maser chronology

Journal Article · Thu Feb 01 00:00:00 EST 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/185664· OSTI ID:7135464

Stencel, R E; Nuth, III, J A; Little-Marenin, I R; Little, S J ^[1]

---

1. Colorado Univ., Boulder (USA) NASA, Goddard Space Flight Center, Greenbelt, MD (USA) Whitin Observatory, Wellesley, MA (USA) Bentley College, Waltham, MA (USA)

By comparing IRAS mean colors and LRS spectral differences in a large sample of Mira variables with the chronological sequence for development of microwave maser emission among such stars, it appears possible to describe a dust grain formation and annealing sequence. The early time spectra are dominated by aluminum oxides, which are then overrun by the emergence of silicates. Rather than the growth of silicate mantles on aluminate cores, this sequence is interpreted as a simple result of the higher electron affinity of aluminum for oxygen, resulting in an initial abundance of AlO bonds in the underoxidized grains. Once all the Al becomes fully oxidized, the relative abundances of Al and Si dictate that the AlO signature will be swamped by the growth of the SiO stretching fundamental. The correlations among the proposed dust chronology, the increasingly thick circumstellar envelopes, and the light curve asymmetries of Mira variables are instructive for understanding the evolutionary changes occurring in such stars. 10 refs.

• OSTI ID: 7135464
• Journal Information: Astrophysical Journal; (USA), Vol. 350; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MASERS
MICROWAVE RADIATION
VARIABLE STARS
STAR EVOLUTION
ALUMINIUM OXIDES
COSMIC DUST
ELEMENT ABUNDANCE
INFRARED RADIATION
INTERSTELLAR SPACE
SILICATES
ABUNDANCE
ALUMINIUM COMPOUNDS
AMPLIFIERS
CHALCOGENIDES
DUSTS
ELECTROMAGNETIC RADIATION
ELECTRONIC EQUIPMENT
EQUIPMENT
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SILICON COMPOUNDS
SPACE
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources