A comprehensive study of supernovae modeling (original) (raw)
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Monthly Notices of the Royal Astronomical Society, 2010
We discuss a new one-dimensional (1D) non-local thermodynamic equilibrium (non-LTE) time-dependent radiative-transfer technique for the simulation of supernova (SN) spectra and light curves. Starting from a hydrodynamical input characterizing the homologously expanding ejecta at a chosen post-explosion time, we model the evolution of the entire ejecta, including gas and radiation. The boundary constraints for this time-, frequency-, space-and angle-dependent problem are the adopted initial ejecta, a zero-flux inner boundary and a free-streaming outer boundary. This relaxes the often unsuitable assumption of a diffusive inner boundary, but will also allow for a smooth transition from photospheric to nebular conditions. Non-LTE, which holds in all regions at and above the photosphere, is accounted for. The effects of line blanketing on the radiation field are explicitly included, using complex model atoms and solving for all ion level populations appearing in the statistical-equilibrium equations. Here, we present results for SN1987A, evolving the model 'lm18a7Ad' of Woosley from 0.27 to 20.8 d. The fastest evolution occurs prior to day 1, with a spectral energy distribution peaking in the range ∼300-2000 Å, subject to line blanketing from highly ionized metal and CNO species. After day 1, our synthetic multiband light curve and spectra reproduce the observations to within 10-20 per cent in flux in the optical, with a greater mismatch for the faint UV flux. We do not encounter any of the former discrepancies associated with He I and H I optical lines, which can be fitted well with a standard blue-supergiant-star surface composition and no contribution from radioactive decay. The effects of time dependence on the ionization structure, discussed in Dessart & Hillier, are recovered, and thus nicely integrated in this new scheme. Despite the 1D nature of our approach, its high physical consistency and accuracy will allow reliable inferences to be made on explosion properties and pre-SN star evolution.
The Astrophysical Journal, 2011
We have developed a relativistic, radiation-hydrodynamics Lagrangian code, specifically tailored to simulate the evolution of the main observables (light curve and the evolution of photospheric velocity and temperature) in core-collapse supernova (CC-SN) events. The distinctive features of the code are an accurate treatment of radiative transfer coupled to relativistic hydrodynamics, a self-consistent treatment of the evolution of the innermost ejecta taking into account the gravitational effects of the central compact remnant, and a fully implicit Lagrangian approach to the solution of the coupled nonlinear finite difference system of equations. Our aim is to use it as a numerical tool to perform calculations of a grid of models to be compared with observations of CC-SNe. In this paper, we present some testcase simulations and a comparison with observations of SN 1987A, as well as with the results obtained with other numerical codes. We also briefly discuss the influence of the main physical parameters (ejected mass, progenitor radius, explosion energy, amount of 56 Ni) on the evolution of the ejecta, and the implications of our results in connection with the possibility to "standardize" hydrogen-rich CC-SNe for using them as candles to measure cosmological distances.
Analytic solutions for the evolution of radiative supernova remnants
Astronomy & Astrophysics, 2004
We present the general analytic solution for the evolution of radiative supernova remnants in a uniform interstellar medium, under thin-shell approximation. This approximation is shown to be very accurate approach to this task. For a given set of parameters, our solution closely matches the results of numerical models, showing a transient in which the deceleration parameter reaches a maximum value of 0.33, followed by a slow convergence to the asymptotic value 2/7. Oort (1951) and McKee and Ostriker (1977) analytic solutions are discussed, as special cases of the general solution we have found.
A Comparative Modeling of Supernova 1993J
The Astrophysical Journal, 1998
The light curve of Supernova (SN) 1993J is calculated using two approaches to radiation transport as exemplified by the two computer codes, STELLA and EDDINGTON. Particular attention is paid to shock breakout and the photometry in the U , B, and V bands during the first 120 days. The hydrodynamical model, the explosion of a 13 M ⊙ star which had lost most of its hydrogenic envelope to a companion, is the same in each calculation. The comparison elucidates differences between the approaches and also serves to validate the results of both. STELLA includes implicit hydrodynamics and is able to model supernova evolution at early times, before the expansion is homologous. STELLA also employs multi-group photonics and is able to follow the radiation as it decouples from the matter. EDDINGTON uses a different algorithm for integrating the transport equation, assumes homologous expansion, and uses a finer frequency resolution. Good agreement is achieved between the two codes only when compatible physical assumptions are made about the opacity. In particular the line opacity near the principal (second) peak of the light curve must be treated primarily as absorptive even though the electron density is too small for collisional deexcitation to be a dominant photon destruction mechanism. Justification is given for this assumption and involves the degradation of photon energy by "line splitting", i.e. fluorescence. The fact that absorption versus scattering matters to the light curve is indicative of the fact that departures from equilibrium radiative diffusion are important. A new result for SN 1993J is a prediction of the continuum spectrum near the shock breakout (calculated by STELLA) which is superior to the results of other standard single energy group hydrocodes such as VISPHOT or TITAN. Based on the results
Dynamics and radiation of young type-Ia supernova remnants: Important physical processes
Astronomy Letters, 2004
We examine and analyze the physical processes that should be taken into account when modeling young type-Ia supernova remnants (SNRs) with ages of several hundred years, in which there are forward (propagating into an interstellar medium) and reverse (propagating into ejecta) shock waves. It is shown, that the energy losses in the metalrich ejecta can be essential for remnants already at this stage of evolution. The influence of electron thermal conduction and the rate of the energy exchange between electrons and ions on the temperature distribution and the X-radiation from such remnants is studied. The data for Tycho SNR from the XMM-Newton space X-ray telescope have been employed for the comparison of calculations with observations. ⋆ sorokina@sai.msu.su Numerical simulations of supernova remnants (SNRs) have been conducted already long ago. However, since the physics of these objects is very complex, it has not yet been completely included in any computer program in the world. Moreover, different physical processes can be essential at different stages of evolution.
Three-dimensional modeling of type Ia supernovae – The power of late time spectra
Astronomy and Astrophysics, 2005
Late time synthetic spectra of Type Ia supernovae, based on three-dimensional deflagration models, are presented. We mainly focus on one model, "c3 3d 256 10s", for which the hydrodynamics (Röpke 2005) and nucleosynthesis was calculated up to the homologous phase of the explosion. Other models with different ignition conditions and different resolution are also briefly discussed. The synthetic spectra are compared to observed late time spectra. We find that while the model spectra after 300 to 500 days show a good agreement with the observed Fe II-III features, they also show too strong O I and C I lines compared to the observed late time spectra. The oxygen and carbon emission originates from the low-velocity unburned material in the central regions of these models. To get agreement between the models and observations we find that only a small mass of unburned material may be left in the center after the explosion. This may be a problem for pure deflagration models, although improved initial conditions, as well as higher resolution decrease the discrepancy. The relative intensity from the different ionization stages of iron is sensitive to the density of the emitting iron-rich material. We find that clumping, with the presence of low density regions, is needed to reproduce the observed iron emission, especially in the range between 4000 and 6000Å. Both temperature and ionization depend sensitively on density, abundances and radioactive content. This work therefore illustrates the importance of including the inhomogeneous nature of realistic three-dimensional explosion models. We briefly discuss the implications of the spectral modeling for the nature of the explosion.
Numerical Modeling of Type Ia Supernovae Explosions
Astrophysics and Space Science Proceedings, 2010
A better knowledge of the mechanism behind the explosion of Type Ia supernovae (SNIa) is necessary to use these events in cosmological applications such as to study the large scale geometry of the universe or to find its equation of state. We review the present status of the subject with special emphasis in the so-called pulsating models which reproduce the gross features of the explosions without using free parameters.
Physical Review D, 2002
This is the second in a series of papers on the construction and validation of a three-dimensional code for the solution of the coupled system of the Einstein equations and of the general relativistic hydrodynamic equations, and on the application of this code to problems in general relativistic astrophysics. In particular, we report on the accuracy of our code in the long-term dynamical evolution of relativistic stars and on some new physics results obtained in the process of code testing. The tests involve single non-rotating stars in stable equilibrium, non-rotating stars undergoing radial and quadrupolar oscillations, non-rotating stars on the unstable branch of the equilibrium configurations migrating to the stable branch, non-rotating stars undergoing gravitational collapse to a black hole, and rapidly rotating stars in stable equilibrium and undergoing quasi-radial oscillations. The numerical evolutions have been carried out in full general relativity using different types of polytropic equations of state using either the rest-mass density only, or the rest-mass density and the internal energy as independent variables. New variants of the spacetime evolution and new high resolution shock capturing (HRSC) treatments based on Riemann solvers and slope limiters have been implemented and the results compared with those obtained from previous methods. Finally, we have obtained the first eigenfrequencies of rotating stars in full general relativity and rapid rotation. A long standing problem, such frequencies have not been obtained by other methods. Overall, and to the best of our knowledge, the results presented in this paper represent the most accurate long-term three-dimensional evolutions of relativistic stars available to date.
The Relativistic Three-Dimensional Evolution of SN 1987A
The high velocities observed in supernovae require a relativistic treatment for the equation of motion in the presence of gradients in the density of the interstellar medium. The adopted theory is that of the thin layer approximation. The chosen medium is auto-gravitating with respect to an equatorial plane. The differential equation which governs the relativistic conservation of momentum is solved numerically and by recursion. The asymmetric field of relativistic velocities as well the time dilation is plotted at the age of 1 yr for SN 1987A.