50 research outputs found
Radiative, magnetic and numerical feedbacks on small-scale fragmentation
Radiative feedback and magnetic field are understood to have a strong impact
on the protostellar collapse. We present high resolution numerical calculations
of the collapse of a 1 solar mass dense core in solid body rotation, including
both radiative transfer and magnetic field. Using typical parameters for
low-mass cores, we study thoroughly the effect of radiative transfer and
magnetic field on the first core formation and fragmentation. We show that
including the two aforementioned physical processes does not correspond to the
simple picture of adding them separately. The interplay between the two is
extremely strong, via the magnetic braking and the radiation from the accretion
shock.Comment: 4 pages, 2 figures ; to appear in "IAU Symposium 270: Computational
Star formation", Eds. J. Alves, B. Elmegreen, J. Girart, V. Trimbl
A Godunov-Type Solver for the Numerical Approximation of Gravitational Flows
International audienceWe present a new numerical method to approximate the solutions of an Euler-Poisson model, which is inherent to astrophysical flows where gravity plays an important role. We propose a discretization of gravity which ensures adequate coupling of the Poisson and Euler equations, paying particular attention to the gravity source term involved in the latter equations. In order to approximate this source term, its discretization is introduced into the approximate Riemann solver used for the Euler equations. A relaxation scheme is involved and its robustness is established. The method has been implemented in the software HERACLES and several numerical experiments involving gravitational flows for astrophysics highlight the scheme
Measure of precursor electron density profiles of laser launched radiative shocks
We have studied the dynamics of strong radiative shocks generated with the
high-energy subnanosecond iodine laser at Prague Asterix Laser System facilityComment: with small correction in Fig.1
Experimental study of radiative shocks at PALS facility
We report on the investigation of strong radiative shocks generated with the
high energy, sub-nanosecond iodine laser at PALS. These shock waves are
characterized by a developed radiative precursor and their dynamics is analyzed
over long time scales (~50 ns), approaching a quasi-stationary limit. We
present the first preliminary results on the rear side XUV spectroscopy. These
studies are relevant to the understanding of the spectroscopic signatures of
accretion shocks in Classical T Tauri Stars.Comment: 21 pages, 1 table, 7 figure
Numerical simulations of super-luminous supernovae of type IIn
We present numerical simulations that include 1-D Eulerian multi-group
radiation-hydrodynamics, 1-D non-LTE radiative transfer, and 2-D polarised
radiative transfer for super-luminous interacting supernovae (SNe). Our
reference model is a ~10Msun inner shell with 10^51erg ramming into a ~3Msun
cold outer shell (the circumstellar-medium, or CSM) that extends from 10^15cm
to 2x10^16cm and moves at 100km/s. We discuss the light curve evolution, which
cannot be captured adequately with a grey approach. In these interactions, the
shock-crossing time through the optically-thick CSM is much longer than the
photon diffusion time. Radiation is thus continuously leaking from the shock
through the CSM, in disagreement with the shell-shocked model that is often
invoked. Our spectra redden with time, with a peak distribution in the near-UV
during the first month gradually shifting to the optical range over the
following year. Initially Balmer lines exhibit a narrow line core and the broad
line wings that are characteristic of electron scattering in the SNe IIn
atmospheres (CSM). At later times they also exhibit a broad blue shifted
component which arises from the cold dense shell. Our model results are broadly
consistent with the bolometric light curve and spectral evolution observed for
SN2010jl. Invoking a prolate pole-to-equator density ratio in the CSM, we can
also reproduce the ~2% continuum polarisation, and line depolarisation,
observed in SN2010jl. By varying the inner shell kinetic energy and the mass
and extent of the outer shell, a large range of peak luminosities and
durations, broadly compatible with super-luminous SNe IIn like 2010jl or
2006gy, can be produced.Comment: paper accepted to MNRA