AAS 207th Meeting, 8-12 January 2006
Session 82 Ground Based Optical Interferometry
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[82.05] Narrowband H\alpha Interferometry with the NPOI

C. Tycner (USNO), G. C. Gilbreath, J. T. Armstrong (NRL), J. A. Benson, A. R. Hajian, D. J. Hutter (USNO), C. E. Jones (UWO), T. A. Pauls (NRL), N. M. White (Lowell Observatory), R. T. Zavala (USNO)

We report on the first results from the narrowband H\alpha observations using the Navy Prototype Optical Interferometer at baselines of up to 64.4~m. We demonstrate how a custom-made filter that isolates the H\alpha emission line can be used to increase the contrast between the interferometric signature due to the central star and its H\alpha-emitting circumstellar material. The narrowband filter isolates the H\alpha emission line from the nearby continuum flux, but it does not significantly attenuate the continuum radiation in spectral regions 50~nm or more away from the line. This allows for the calibration of the interferometric signal in the H\alpha channel with respect to the continuum channels. To test the performance of the narrowband interferometric setup we observed two well known Be stars, \gamma~Cas and \phi~Per. The observations presented in this paper represent the highest spatial resolution measurements of the H\alpha-emitting regions of Be stars obtained to date. These observations allow us to demonstrate for the first time that the intensity distribution in the circumstellar region of a Be star cannot be represented by uniform disk or ring-like structures, whereas a Gaussian intensity distribution appears to be fully consistent with our observations.

This work was performed in part under a contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology.

The author(s) of this abstract have provided an email address for comments about the abstract: tycner@nofs.navy.mil

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