Photometric Colours from Spectra of Single Stars
and of Stellar Populations
Joachim Köppen Kiel Jan.2019
Some brief explanations
- This utility shows the spectrum (blue) of single stars or of a stellar population
composed of a mixture of main sequence and red giant stars, specified by their
contributions, and the resultant photometric colours. For comparison, the
spectrum (green) and the colours of a blackbody with specified temperature
are given.
- Hit the Enter key after entering a new value to display the new results.
- The transmission curves of the photometric filters are shown for the
- Johnson-Cousins-Glass UBVRIJHKL system (from Landoldt-Börnstein and
Bessell(2005), magenta).
- blue-green-red (KB-KG-KR) 'system' of our practice telescope at
the Astrophysics Institute in Kiel (blue-green-red). The colours are
computed with these filter curves, but also weighted with the quantum
efficiency curve of the CCD camera.
[KW is the 'white' setting, i.e. with the clear filter].
- The magenta and red vertical lines delimit the visible wavelength region.
- All spectra (from PEGASE) are normalized to the same bolometric absolute magnitude
Mbol = 4.74 mag. Thus to compute the spectral contribution one has to take
into account the number of stars as well as the luminosity (i.e. the radius)
of a single star.