Previous abstract Next abstract
Changes in the UV extinction and IR emission were searched for in four stars with circumstellar dust envelopes by comparing observations made approximately 10 years apart. The stars in this project were: the Herbig Ae/Be stars HD259431 and NGC2264/Walker90, the suspected Ae/Be star HD45677, and the Red Rectangle central star HD44179. Only HD45677 varied significantly, becoming more than 50 percent brighter than it was a decade ago. A comparison of the observations between epochs indicates that if the variations are due to changes in dust obscuration, the dust acts as a gray absorber into the near IR and must be depleted in grains smaller than one micron. This is similar to the results obtained on the circumstellar disks of stars like Vega and Beta Pictoris, and suggests that radiation pressure may be responsible for the small-grain depletion. In addition, the total infrared flux seems to have declined, indicating a decrease in the total mass of the dust envelope.
Thursday program listing