What is New in SPECTRUM v2.76?

There are four major improvements in v2.76 compared with the last major release, v2.75d. These improvements are:

1

The addition of AlH and AlO to the list of molecules that can be computed with SPECTRUM. Note that this has required a revision of stdatom.dat, which is now incompatible with earlier versions.

2

The addition of a facility to compute autoionizing lines (see § ).

3

The addition of a facility to input a ``fixed abundance'' file containing elemental abundances that will not be scaled by the [M/H] of the model.

4

A significant improvement in the calculation of the ``computation radius'' for spectral lines (see § ). Earlier versions used a rough and ready empirical estimate for the computation radius, which occasionally resulted in line wings being truncated. Various work arounds were used in these earlier versions to avoid these truncations, but in this version, the line profile is calculated until the depth falls below 0.0001 continuum units. Weak lines with central depths less than 0.0001 continuum units are thus not computed. This strategy has negligible effects on the line blanketing and thus the flux, and has the advantage that the computational speed is greatly enhanced. In regions of high line density, such as the ultraviolet, speed increases up to factors of 2.5 and more can be seen.