  Population III stars are believed to be rapidly-rotating sources with a mass
range of hundreds to thousand of solar masses. Masses larger than 260 M$_\odot$
are expected to collapse resulting in central rotating Kerr black holes with
large rotation parameter a. Due to particle-antiparticle asymmetry is small, we
use the neutrino effective potential up to order $1/M_W^4$ in a magnetized
plasma at the base of the ejecta to constrain the rotation parameter by means
of neutrino oscillations. Additionally, we investigate the implications in the
magnetic field, temperature and electron asymmetry.
