High precision optical interferometry and application to Be stars.
Published: 2004
Language: eng
Number of pages: 149
Description: A new technique for calibrating optical long-baseline interferometric observations is developed where both the calibration corrections and the source characteristics are obtained from the observations of a program star. This calibration technique can only be applied to certain classes of objects, such as emission line sources or binary systems, where the parameters describing the characteristics of the source have different functional dependence than the calibration parameters. To demonstrate its effectiveness, the technique is applied to observations of four different Be stars obtained with the Navy Prototype Optical Interferometer. The interferometric observations utilize measurements obtained simultaneously in many spectral channels covering a wide spectral range, where only two channels contain a strong signal due to the circumstellar envelope in the Halpha emission line. The calibrated observations in Halpha allow modeling of the circumstellar envelopes of all four stars with circularly symmetric and elliptical Gaussian models. The best-fit model parameters are then combined with similar results for other Be stars, already published in the literature, to study the relationship between the Ha emission and the physical extent of the Halpha-emitting circumstellar region. For the first time, a clear dependence of the net Halpha emission on the extent of the circumstellar region is demonstrated. These results are consistent with an optically thick line emission that is directly proportional to the effective area of the emitting disk. Within the small sample of stars considered in this analysis, no clear dependence on the spectral type or stellar rotation is established, although the results do suggest that hotter stars might have more extended circumstellar regions.
Notes: Adviser:  J. B. Lester.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5192.