Proc. Neutrino Astrophysics - MPP Theory Group

58
a b
Figure 1: Panel a shows the absolute values of the convective velocity for a non-rotating
PNS model 0.7 s after the start of the simulation in units of 10 8 cm/s. The computation
was performed in an angular wedge of 180 ◦ assuming axisymmetry. Panel b displays the
relative deviations of the lepton fraction Ylep from the angular means 〈Ylep〉 at each radius for
t = 0.7 s. The maximum deviations are of the order of 50%. Lepton-rich matter rises while
deleptonized material sinks in.
Since convective activity continues for more than 1 s in a large region of the PNS, convective
ν transport shortens the cooling and deleptonization timescales of the PNS compared to
results of 1D simulations and enhances the calculated ν luminosities of the star by up to 65%.
The latter can have important influence on the interpretation of the measured ν signal from
SN 1987A and might change limits of various quantities in nuclear and elementary particle
physics which have been derived from these measurements. Moreover, the enhancement of the
ν fluxes can also have important consequences for the explosion mechanism of the supernova,
because it aids ν-driven explosions. The faster deleptonization modifies the luminosity ratio
of νe and ¯νe in such a way that the electron fraction Y ej
e in the ν-heated SN ejecta will be
raised during the first few 100 ms after core bounce, but it will be lowered for t > ∼ 1 s compared
to 1D simulations. This might help to solve the severe problems of the nucleosynthesis
in current models of Type-II supernovae which disregard long-lasting convective activities in
the PNS. Finally, convection in the PNS causes stochastical asymmetries of the ν flux. In
our calculation the resulting recoil accelerates the PNS to ∼ 9 km/s during 1.2 s (Fig. 2a).
This is too small to explain measured proper motions of pulsars of a few 100 km/s. Both
convective mass motions and anisotropic ν emission are a source of gravitational waves for