Determination of stellar parameters of rapidly rotating massive stars

Abstract

Fast rotation directly affects the shape of the observed spectral lines. Therefore, sev- eral physical considerations must be considered when using stellar atmosphere mod- els to obtain stellar parameters. In this work, we used the code ZPEKTR, which con- siders the oblate shape of the stars due to the high rotational velocities, limb darken- ing, and gravity darkening effects. The code divides the stellar surface into a triangu- lar mesh with approximately 120000 area elements. Each one is assigned a TLUSTY model with its effective temperature, log g, and radius; the model depends on the in- clination angle of the star. We applied this code to obtain the stellar parameters of ten classical Be stars and two extremely metal-poor O stars. We create a grid of models for each star and use the chi-square test to determine the best fit to the observed HeI 4471A˚ (Be stars) and CIII 1176A˚ (O stars) spectral lines. Comparing our results of the inclination angle with data from the literature obtained using interferometry, we can conclude that with a small telescope and using spectroscopic techniques, we can find an accurate value for i. For future work, we will use the code for many fast-rotating stars and increase the number of photospheric lines used.