Be Stars are rapidly rotating massive stars that eject gas into a circumstellar disk.  Long baseline optical/infrared interferometry can spatially resolve the disks around Be stars.

 

Model images of the Be stars Gam Cas (left) and Zet Tau (right) fit to interferometric data collected at the CHARA Array.  Image credit:  Gies, D. R., et al. 2007, ApJ, 654, 527

 

Image reconstruction of the Be star Phi Per. The disk contributes about 29% of the total flux in the near-infrared H-band. The location of the faint, subdwarf companion is shown with the best fit circular orbit with a period of 126.7 days. The companion contributes only 1.5% of the total light. Image credit: Mourard, D., et al. 2015, A&A, 577, 51

 

Sequence of intensity maps of the Be star Phi Per (6.4 × 6.4 mas) as a function of wavelength with north up and east left as imaged by VEGA (upper sequence), as computed from the kinematic model (middle sequence), and as imaged through a simulated observation of the above model (lower sequence). Image credit: Mourard, D., et al. 2015, A&A, 577, 51

 

Cartoon depicting the disk precession variations of zeta Taurus as seen in the sky. The Be star is shown as a black circle, the circumstellar disk as a gray ellipsoid, and the mean position angle of the long axis of the disk (aligned with the stellar equator) as dotted lines extending from the disk. The panels show the change in the precession of the disk tilt and of the one-armed spiral density maximum (small gray dot) for eight steps in the precession cycle. Image credit: Schaefer, G. H., et al. 2010, AJ, 140, 1838

 

References:

Gies, D. R., et al. 2007, ApJ, 654, 527

Mourard, D., et al. 2015, A&A, 577, 51

Schaefer, G. H., et al. 2010, AJ, 140, 1838

Touhami, Y., et al. 2013, ApJ, 768, 128