BBODY-Calculate a black body spectrum.

Usage:

bbody temp in=? xstart=? xstep=? xend=? xlabel=? xunit=? out=?

Description:

This routine calculates for a given (vacuum) wavelength or frequency axis the intensity of a black body at given temperature. The intensity is the energy per unit time, per unit area, per unit solid angle, and per unit frequency (and for all polarisations):

2 h nu^3 1 B_nu = ----- --------- c^2 exp(h nu/kT) - 1

where c is the velocity of light, and h and k are the Planck and Boltzmann constants.

Parameters:

LOGAR

LOGAR = LOGICAL (Read) True if the common logarithm of intensity is to be written rather than the intensity itself. [NO]

TEMP

TEMP = REAL (Read) The black body temperature in Kelvin.

ERRTEMP

ERRTEMP = REAL (Read) The error in the black body temperature in Kelvin.

IN

IN = NDF (Read) The file holding axis data to be used. Enter the null value (!) to read axis data parameters from keyboard.

XSTART

XSTART = REAL (Read) The spectroscopic value (pixel centre) for the first output pixel.

XSTEP

XSTEP = REAL (Read) The spectroscopic step (pixel distance) for the output pixels.

XEND

XEND = REAL (Read) The spectroscopic value (pixel centre) for the last output pixel.

XLABEL

XLABEL = CHARACTER (Read) The label for the spectroscopic axis. Allowed values are "wavelength" and "frequency". [wavelength]

XUNIT

XUNIT = CHARACTER (Read) The unit for the spectroscopic axis. If the label is "wavelength" then the unit can basically be "m" for metre, "micron" for micrometre, or "Angstrom" for Angstroem. If the label is "frequency" then the unit must be basically "Hz" for Hertz. Any of these units may be preceded by a power of ten, so it could be "10**1*Angstrom" if you want to use nanometre as unit, or "10**-9*m" to the same effect. The power must be an integer. You can achieve a logarithmic axis by specifying something like "log10(10**-3*micron)". In this example the axis values will be the common logarithms of the wavelength in nanometres.

OUT

OUT = NDF (Read) The output file.

Examples:

bbody 5500 in=in out=out
   This calculates the black-body spectrum for 5500 K. The
   spectrum is written to file OUT. The routine tries to find all
   necessary information for the 1st (and only) axis in OUT from
   the spectroscopic axis of the file IN. Since LOGAR is left at
   its default value of FALSE, the data are intensity in Jy/sr.

bbody 2.7 logar=true in=! xstart=0 xstep=0.05 xend=6

xlabel=wavelength xunit=log(micron) out=out
   This calculates the black-body spectrum for 2.7 K. The spectrum
   is written to OUT. No input file is specified. The axis
   contains the logarithms of wavelengths in micron, which run
   from 0 (1 micron) to 6 (1 metre). Since LOGAR=TRUE, the data
   are the logarithms of intensity in Jy/sr.

bbody 1e6 logar=true in=! xstart=-1 xstep=0.05 xend=2

xlabel=frequency xunit=log10(10**15*Hz) out=out
   This calculates the black-body spectrum for 1 million K. This
   time the axis is logarithms of frequency, the units used are
   10^15 Hz. The frequency range covered is from 10^14 Hz to
   10^17 Hz.

Notes:

This routine recognises the Specdre Extension v. 0.7.

References:

Lang, K.R., 1980, Astrophysical Formulae, Springer, Heidelberg, Berlin, New York, p. 21