A&A 447, 1049-1092 (2006)

DOI: 10.1051/0004-6361:20053783

## Two-dimensional hydrodynamic core-collapse supernova simulations with spectral neutrino transport

##### I. Numerical method and results for a 15 *M* star

**R. Buras**

^{1, 2}, M. Rampp^{1}, H.-Th. Janka^{1}and K. Kifonidis^{1}^{1}Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany

e-mail: thj@mpa-garching.mpg.de

^{2}Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany

(Received 6 July 2005 / Accepted 18 October 2005 )

** Abstract **

Supernova models with a full spectral treatment of the neutrino
transport are presented, employing the PROMETHEUS/VERTEX
neutrino-hydrodynamics code with a variable Eddington factor closure
of the
moments equations of neutrino number, energy,
and momentum. Our "ray-by-ray plus" approximation developed for
two- (or three-) dimensional problems assumes that the local neutrino
distribution function is azimuthally symmetric around the radial
direction, which implies that the nonradial flux components
disappear. Other terms containing the angular velocity components are
retained in the moments equations and establish a coupling of the
transport at different latitudes by lateral derivatives. Also lateral
components of the neutrino pressure gradients are included in the
hydrodynamics equations. This approximative approach for neutrino
transport in multi-dimensional environments is motivated and
critically assessed with respect to its capabilities, limitations, and
inaccuracies in the context of supernova simulations.
In this first paper of a series, one- (1D) and two-dimensional (2D)
core-collapse calculations for a (nonrotating)
star are
discussed, uncertainties in the treatment of the equation of
state - numerical and physical - are tested, Newtonian results are
compared with simulations using a general relativistic potential,
bremsstrahlung and interactions of neutrinos of different flavors are
investigated, and the standard approximation in neutrino-nucleon
interactions with zero energy transfer is replaced by rates that
include corrections due to nucleon recoil, thermal motions, weak
magnetism, and nucleon correlations.
Models with the full implementation of the "ray-by-ray plus"
spectral transport were found not to explode, neither in spherical
symmetry nor in 2D when the computational grid is constrained to a
lateral wedge (<) around the equator. The success
of previous two-dimensional simulations with grey, flux-limited
neutrino diffusion can therefore not be confirmed. An explosion is
obtained in 2D for the considered
progenitor, when the
radial velocity terms in the neutrino momentum equation are
omitted. This manipulation increases the neutrino energy density in
the convective gain layer by about 20-30% and thus the integral
neutrino energy deposition in this region by about a factor of two
compared to the non-exploding 2D model with the full transport. The
spectral treatment of the transport and detailed description of
charged-current processes leads to proton-rich neutrino-heated ejecta,
removing the problem that previous explosion models with approximate
neutrino treatment overproduced *N*=50 closed neutron shell nuclei by
large factors.

**Key words:**supernovae: general

**--**neutrinos

**--**radiative transfer

**--**hydrodynamics

SIMBAD Objects

**©**

*ESO 2006*