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multabs

Multabs tries to account for line broadening by absorption by multiple discrete components rather than by turbulence or bulk flow. This model is essentially identical to warmabs in that it uses the warm absorber spectrum generated by warmabs, but initially assuming that the lines are broadened only by thermal gas motions. It then replicates these lines a fixed number of times and spreads the components over a given velocity width. The input parameters include the same parameters as warmabs: ionization parameter, column, and abundances. These control the properties of the individual absorbing components, in the same way as for warmabs. In addition, the user specifies the velocity spread of the components, still called vturb, and the covering fraction, cfrac. This covering fraction can be interpreted as a covering fraction in velocity space. The number of discrete components is given by cfrac*vturb/vtherm, where vturb is input by the user and vtherm is the thermal line width which is determined by the equilibrium temperature (calculated by xstar). The optical depth of each component is divided by the number of components, so that the total optical depth summed over the components is independent of their number. The number of components cannot be less than 1. If it is 1 then the component will be placed at the redshifted energy of the line. If it is greater than 1, then the components will be spaced uniformly in velocity from -vturb to +vturb relative to the rest energy of the line. There is no restriction on the value of cfrac, so it is possible to set cfrac to some large number and thereby fill a uniform trough in velocity with the line.


next up previous contents
Next: hotabs Up: WARMABS Previous: windabs   Contents
Tim Kallman 2014-09-12