Published standards

Published standards fall into two distinct classes; they are similar, but differ sufficiently that Figaro provides different sets of functions for dealing with them.

Older, brighter, standards such as those in Oke & Gunn⁴ are published as tables giving wavelengths and the corresponding flux densities calculated by measuring the observed flux over a range of wavelength centred on the tabulated wavelength. (This is the significance of the .Z.BANDWIDTH value shown in the section on standard files.) These tabulated values therefore correspond exactly to what the observed spectrum should look like, even in the presence of absorption features.

More recently, Filippenko & Greenstein⁵ have published tables for fainter stars where they fit a continuum to the observed data and tabulate the value of this continuum at various wavelength values. These values will not therefore represent the actual observed data in regions where there is absorption, and the concept of a `bandwidth' does not apply.