The default mode of operation of SPECTRUM calculates the normalized
integrated-intensity spectrum using the abundances in the atomic and
molecular data file, stdatom.dat. In this default mode, SPECTRUM prints to the screen the wavelength currently being computed along
with two other numbers. The actual synthetic spectrum is printed
to an ascii file. The two numbers printed to the screen refer to
the number of spectral lines under computation at the current
wavelength and the number of spectral
lines in a ``look-ahead'' list. See § 3.8 for more
details. The mode of operation of SPECTRUM can be changed by using one
or more of the following ``switches''.
- Prompts the user to supply the name of a custom atomic and
molecular data file. This is useful if the user needs to compute a
spectrum with a
non-standard set of abundances. Without this switch, SPECTRUM will
read in the default file stdatom.dat. The custom file should
have exactly the same format as the
supplied file stdatom.dat. While stdatom.dat must
be in your working directory, this switch gives the user the
opportunity to specify the path to the custom data file. The full
path must be given. See § 3.3 for details
on the information contained in stdatom.dat.
- This switch will cause SPECTRUM to output the synthetic
spectrum in a binary format. The advantage of this is that the size
of the output file will be about 5 times smaller than the standard
ascii output. The disadvantage is that it is much more difficult to
work with than the normal ascii output file. This mode cannot
be used in under Windows, and if used under Linux/UNIX the output
file permissions must be altered with chmod to make it
readable by the SPECTRUM auxiliary programs BSMOOTH2 and VSINI. This
switch was introduced ``in the old days'' when disk space was at a
premium. I don't recommend using this switch at present.
- Ignores all spectral lines and outputs only the continuum.
- This switch causes SPECTRUM to compute the disk integrated
absolute flux (in erg/cm/s/Å as measured at the stellar
- An experimental mode that allows the user to input a
``velocity gradient'' file to study the effects of non-zero
velocities on the line profiles. The format is an ascii file with a
single column of velocities, one line corresponding to each layer in
the stellar atmosphere. This switch should only be used in
conjunction with the specific intensity modes (switches m and M) and
only for center of disk calculations.
- Isotope mode. SPECTRUM fully supports the calculation of both
atomic and molecular isotopic spectra, but this requires the use of
a special format for the linelist file. In addition, in this mode
SPECTRUM will prompt the user for an isotope file. The default
isotope file is isotope.iso. See § 3.6 for
- Both switches invoke the specific intensity mode. This
allows the user to calculate, for instance, the center-of-disk solar
spectrum, or the emergent specific intensity spectrum at any other
point on the disk. The ``m'' switch causes SPECTRUM to output the
normalized specific intensity (i.e. the continuum is normalized to
1.0); the ``M'' switch outputs the true, non-normalized specific
intensity. This mode could be used to build up a spectrum for a
star with a non-uniform surface, such as a rapidly rotating star
with and which vary from point to point on
the surface, or a spotted star, or even the emergent spectrum from a
- Silent mode. In this mode, SPECTRUM prints out only a few
lines of information and then runs silently. It will not even
prompt the user for the various inputs, and thus in this mode SPECTRUM must be used with a response file. See § 3.9 for
more details. The advantage of running in this mode is that SPECTRUM will run much faster if it doesn't have to print wavelength
information to the screen.
- This switch will cause SPECTRUM to print out number densities
of selected species (such as atoms, ions and molecules) at each
depth in the atmosphere.
- This switch signals SPECTRUM that the input stellar
atmosphere model is in the ATLAS9/12 format. See
§ 3.2 for more details.
- An experimental mode that allows the user to compute a
spectrum with a microturbulent velocity that varies with depth. The
program will read the microturbulent velocity from the seventh
column of the stellar atmosphere model.
Switches are used on the command line. For example, if we
want SPECTRUM to operate in the isotope
mode, to read in a stellar atmosphere model in the ATLAS9 format, and
to output the absolute flux, we would use the command line:
Or, if we wish to operate SPECTRUM in the silent mode with a response
spectrum n < spec.rsp
Notice that the ``switch string'' should be separated from the spectrum command by at least one space, and that the string itself
should not contain any spaces. For instance, the following is
illegal and will not produce the desired result:
spectrum ni tf < spec.rsp
Using a Response File with SPECTRUM
As mentioned in the above paragraph, SPECTRUM may be run from the command
line using a response file. This file contains the responses to all
the prompts SPECTRUM prints to the screen. Thus, the file vega.rsp
(included in the distribution) may be used to run the test example in
§ 2.3 simply by using the command line:
spectrum n < vega.rsp
The contents of vega.rsp are as follows:
This assumes that the linelist file luke.lst is in the working
directory. If it is not, that line should include the full path.
Note that the last line of the response file must end in a carriage return.
By using response files, shell batch files can be set up that will run
multiple SPECTRUM sessions successively.