OBSERVATIONS OF R-CORONAE-BOREALIS STARS IN DECLINE - EMPIRICAL ARGUMENTS FOR DUST FORMATION NEAR THE STELLAR SURFACE

被引:47
作者
CLAYTON, GC
WHITNEY, BA
STANFORD, SA
DRILLING, JS
机构
[1] HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138
[2] UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720
[3] LOUISIANA STATE UNIV,DEPT PHYS & ASTRON,BATON ROUGE,LA 70803
关键词
CIRCUMSTELLAR MATTER; DUST; EXTINCTION; STARS; VARIABLES; OTHER (R-CORONAE BOREALIS); ULTRAVIOLET;
D O I
10.1086/171821
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present new IUE observations which monitor the spectroscopic evolution of RY Sgr through a deep decline. These data, along with other IUE, visible, and infrared observations of declines in RY Sgr, R CrB, and V854 Cen, are considered in an attempt to understand the dust formation process and the source of the narrow- and broad-line emission seen during declines. Spectroscopic, photometric, and polarimetric data covering 10 declines of these stars have been analyzed. The evolution of the UV emission spectrum is similar to that found in the visible. Previous models of dust formation assume that dust forms around 20 stellar radii, where gas ejected from the star is cool enough to condense. However, the spectral evolution, and the dispersal times of dust implied by the light curve are consistent with dust forming within a few stellar radii and moving outward due to radiation pressure. The expanding dust cloud eclipses the photosphere and parts of the emission line region, causing the observed spectral evolution.
引用
收藏
页码:652 / 663
页数:12
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