Using a uniform composition

Overview

The simplest possibility for specifying an ejecta composition is to use a uniform abundance pattern in all cells specified in the density profile setup step. These constant abundances can be supplied directly in the input (YAML) file. Elemental and Isotopic abundances are set in the “abundances” subsection of the “model” section, following the “type: uniform” specifier (see example input file below). They are specified as mass fractions, e.g.

Si: 0.6
S: 0.2
Ni56: 0.2

will set the mass fraction of silicon (Z=14) to 0.6, sulphur (Z=16) to 0.2 and Nickel (Z=26, A=56) to 0.2.

Note

Suppose you specify Elemental and Isotopic abundance for the same element, e.g.

Ni: 0.8
Ni56: 0.2

Here, Ni will refer to the stable Nickel (i.e. Z=26, A=58).

Note

The mass fractions must sum to one. If mass fractions are supplied that do not sum to one, TARDIS will renormalise all the supplied abundances and print a “WARNING” message.

TARDIS input file

The following example shows the relevant section of a TARDIS input YAML file which specifies a uniform ejecta composition.

model:
    abundances:
        type: uniform
        O: 0.19
        Mg: 0.03
        Si: 0.52
        S: 0.19
        Ar: 0.02
        Ca: 0.03
        Ni56: 0.01
        Ni58: 0.01