scholarly journals A numerical light curve model for interaction-powered supernovae

2020 ◽  
Vol 72 (4) ◽  
Author(s):  
Yuki Takei ◽  
Toshikazu Shigeyama
Keyword(s):  
Radiative Transfer ◽  
Light Curve ◽  
Transfer Equation ◽  
Energy Equation ◽  
Radiative Transfer Equation ◽  
Circumstellar Matter ◽  
Physical Parameters ◽  
Time Step ◽  
Curve Model ◽  
Forward Shock

Abstract We construct a numerical light curve model for interaction-powered supernovae that arise from an interaction between the ejecta and the circumstellar matter (CSM). In order to resolve the shocked region of an interaction-powered supernova, we solve the fluid equations and radiative transfer equation assuming steady states in the rest frames of the reverse and forward shocks at each time step. Then we numerically solve the radiative transfer equation and the energy equation in the CSM with the radiative flux obtained from the forward shock as a radiation source. We also compare the results of our models with observational data of two supernovae, 2005kj and 2005ip, classified as type IIn, and discuss the validity of our assumptions. We conclude that our model can predict the physical parameters associated with supernova ejecta and the CSM from the observed features of the light curve as long as the CSM is sufficiently dense. Furthermore, we found that the absorption of radiation in the CSM is an important factor in calculating the luminosity.

scholarly journals Discontinuities in numerical radiative transfer

2019 ◽  
Vol 622 ◽  
pp. A162 ◽  
Author(s):  
Gioele Janett
Keyword(s):  
Radiative Transfer ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Transfer Problem ◽  
Stellar Atmospheres ◽  
Physical Parameters ◽  
Radiative Transfer Problem ◽  
Intermittent Behavior ◽  
High Order Convergence ◽  
Magnetohydrodynamic Simulations

Observations and magnetohydrodynamic simulations of solar and stellar atmospheres reveal an intermittent behavior or steep gradients in physical parameters, such as magnetic field, temperature, and bulk velocities. The numerical solution of the stationary radiative transfer equation is particularly challenging in such situations, because standard numerical methods may perform very inefficiently in the absence of local smoothness. However, a rigorous investigation of the numerical treatment of the radiative transfer equation in discontinuous media is still lacking. The aim of this work is to expose the limitations of standard convergence analyses for this problem and to identify the relevant issues. Moreover, specific numerical tests are performed. These show that discontinuities in the atmospheric physical parameters effectively induce first-order discontinuities in the radiative transfer equation, reducing the accuracy of the solution and thwarting high-order convergence. In addition, a survey of the existing numerical schemes for discontinuous ordinary differential systems and interpolation techniques for discontinuous discrete data is given, evaluating their applicability to the radiative transfer problem.

scholarly journals FIRTEZ-dz

2019 ◽  
Vol 629 ◽  
pp. A24 ◽  
Author(s):  
A. Pastor Yabar ◽  
J. M. Borrero ◽  
B. Ruiz Cobo
Keyword(s):  
Radiative Transfer ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Three Dimensional ◽  
Direct Calculation ◽  
Momentum Equation ◽  
Gas Pressure ◽  
Numerical Code ◽  
Physical Parameters ◽  
Geometrical Scale

We present a numerical code that solves the forward and inverse problem of the polarized radiative transfer equation in geometrical scale under the Zeeman regime. The code is fully parallelized, making it able to easily handle large observational and simulated datasets. We checked the reliability of the forward and inverse modules through different examples. In particular, we show that even when properly inferring various physical parameters (temperature, magnetic field components, and line-of-sight velocity) in optical depth, their reliability in height-scale depends on the accuracy with which the gas-pressure or density are known. The code is made publicly available as a tool to solve the radiative transfer equation and perform the inverse solution treating each pixel independently. An important feature of this code, that will be exploited in the future, is that working in geometrical-scale allows for the direct calculation of spatial derivatives, which are usually required in order to estimate the gas pressure and/or density via the momentum equation in a three-dimensional volume, in particular the three-dimensional Lorenz force.

scholarly journals Spectral Line Identification and Modelling (SLIM) in the MAdrid Data CUBe Analysis (MADCUBA) package

2019 ◽  
Vol 631 ◽  
pp. A159 ◽  
Author(s):  
S. Martín ◽  
J. Martín-Pintado ◽  
C. Blanco-Sánchez ◽  
V. M. Rivilla ◽  
A. Rodríguez-Franco ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Spectral Line ◽  
Transfer Equation ◽  
Spectroscopic Data ◽  
Radiative Transfer Equation ◽  
Data Cube ◽  
Physical Parameters ◽  
Data Cubes ◽  
Line Identification ◽  
Wide Range

Context. The increase in bandwidth and sensitivity of state-of-the-art radio observatories is providing a wealth of molecular data from nearby star-forming regions up to high-z galaxies. Analysing large data sets of spectral cubes requires efficient and user-friendly tools optimised for astronomers with a wide range of backgrounds. Aims. In this paper we present the detailed formalism at the core of Spectral Line Identification and Modelling (SLIM) within the MAdrid Data CUBe Analysis (MADCUBA) package and their main data-handling functionalities. These tools have been developed to visualise, analyse, and model large spectroscopic data cubes. Methods. We present the highly interactive on-the-fly visualisation and modelling tools of MADCUBA and SLIM, which includes a stand-alone spectroscopic database. The parameters stored therein are used to solve the full radiative transfer equation under local thermodynamic equilibrium (LTE). The SLIM package provides tools to generate synthetic LTE model spectra based on input physical parameters of column density, excitation temperature, velocity, line width, and source size. It also provides an automatic fitting algorithm to obtain the physical parameters (with their associated errors) better fitting the observations. Synthetic spectra can be overlayed in the data cubes/spectra to ease the task of multi-molecular line identification and modelling. Results. We present the Java-based MADCUBA and its internal module SLIM packages which provide all the necessary tools for manipulation and analysis of spectroscopic data cubes. We describe in detail the spectroscopic fitting equations and make use of this tool to explore the breaking conditions and implicit errors of commonly used approximations in the literature. Conclusions. Easy-to-use tools like MADCUBA allow users to derive physical information from spectroscopic data without the need for simple approximations. The SLIM tool allows the full radiative transfer equation to be used, and to interactively explore the space of physical parameters and associated uncertainties from observational data.

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