Nonspherical distribution of rotational velocities of Be stars via Tikhonov deconvolution
Abstract
Be stars are the fastest rotators and its nature is not completely understood. We aim to determine the probability density function (PDF) and the cumulative density function (CDF) of true rotational velocities of Be field stars, and to study whether the rotation axes are nonuniformly distributed over the unit sphere. We deconvolve the true rotational velocities ($v$) from a sample of 461 Bestar projected rotational speeds via Tikhonov regularization to obtain their PDF and CDF. For this purpose we developed a model with the apparent rotational velocity ($v \sin{i}$) and a nonuniform projection of axes given by the power law $1+\alpha$ in the Fredholm integral. The $\alpha$ parameter takes into account the nonsphericity and $i$ is the inclination angle between the star's pole and the line of sight. A nonspherical distribution ($\alpha=75.8$) of rotational velocities fits better the data than the uniform case ($\alpha=0$). This is our first theoretical model to pick out if a sample comes from a nonspherical distribution of rotational axes. In the future, we will improve our description of nonspherical distribution of axes that consider a priviledged direction of these axes. We also want to include more observations of Be stars and extend the study to rotational velocities in open clusters.
 Publication:

Boletin de la Asociacion Argentina de Astronomia La Plata Argentina
 Pub Date:
 August 2020
 Bibcode:
 2020BAAA..61C..100S
 Keywords:

 stars: emissionline;
 Be;
 stars: rotation