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We demonstrate that the angle between star's rotation axis and the observer'sline-of-sight, usually called the inclination angle, can be reliably determinedfor Be stars via H$\alpha$ emission-line profile fitting. We test our method ona sample of 11 Be stars with available long-baseline interferometric data fromthe Navy Precision Optical Interferometer~(NPOI). We fit the H$\alpha$ emissionline profile of each star to obtain a spectroscopic inclination angle $i_{\rmH\alpha}$. We then obtain an independent inclination angle estimate, $i_{\rmV^2}$, by fitting the observed interferometric visibilities with modelvisibilities based on a purely geometric representation of the lightdistribution on the sky. The sample differences, $\Delta i \equiv i_{\rmH\alpha} - i_{\rm V^2}$, are normally distributed with a mean of zero and astandard deviation of $6.7$ degrees, and the linear correlation coefficientbetween $i_{\rm H\alpha}$ and $i_{\rm V^2}$ is $r=0.93$. As Be stars compriseupwards of one fifth of all main-sequence B-type stars, this H$\alpha$ lineprofile fitting technique has the potential to provide an efficient method fordetecting correlated stellar spin axes in young open clusters. Furthermore, ifthe orientation of the Be star circumstellar disk on the plane of the sky canbe constrained by polarization measurements, it is possible to determine thefull 3D stellar rotation vector of each Be star.

Stellar Inclination Angles from Be Star H$\alpha$ Emission-Line Profiles