Effects of rotation on stellar spectra

Abstract

Models have been produced to study the spectral energy distributions (SEDs) and absorption lines for rapidly rotating B stars. A fully implicit 2D stellar structure and evolution code was used to generate the rotating structure models. The code PHOENIX was then used to generate non-LTE stellar atmospheres and spectra. An integrator code, CLIC, then created SEDs and absorption lines as viewed from 10 inclination angles. The SEDs were used to create a series of inclination curves, defining a rotating star's possible positions on an HR diagram. It was found that uniform rotation creates a relatively straight line parallel to the main sequence. The line extends in length and moves away from the main sequence as the rate of rotation increases. Differential rotation creates a more extended and complex inclination curve. The effects of differential rotation on line profiles was explored. It was found that differential rotation creates a very different profile from uniform rotation, especially when viewed closer to the pole. Both the SEDs and line profiles were used to test the limits of von Zeipel's theorem against more realistic models. The SEDs produced appreciably different inclination curves for rotation rates greater than around 0.76 of critical rotation. The difference in the line profiles produced by von Zeipel's models and the more realistic models were small.