A code for the chemistry of CircumStellar ENVelopes

by Gary Mamon and Al Glassgold (send comments and bug reports to

Description References Download CSENV (238943 bytes)
CSENV (pronounced See-Senv) is a code that computes the chemical abundances for a desired set of species as a function of radius in a stationary, non-clumpy, CircumStellar ENVelope.

The chemical species can be atoms, molecules, ions, radicals, molecular ions, and/or their specific quantum states.

Collisional ionization or excitation can be incorporated through the proper chemical channels.

The chemical species interact with one another and can are subject to photo-processes (dissociation of molecules, radicals, and molecular ions as well as ionization of all species). Cosmic ray ionization can be included.

Chemical reaction rates are specified with possible activation temperatures and additional power-law dependences.

Photo-absorption cross-sections vs. wavelength, with appropriate thresholds, can be specified for each species, while for H2+ a photoabsorption cross-section is provided as a function of wavelength and temperature.

The photons originate from both the star and the external interstellar medium. The chemical species are shielded from the photons by circumstellar dust, by other species and by themselves (self-shielding).

Shielding of continuum-absorbing species by these species (self and mutual shielding), line-absorbing species, and dust varies with radial optical depth:

Shielding of line-absorbing species (e.g. CO, H2) can be incorporated:

The stellar and insterstellar radiation fields are respectively black-body and a good match to Draine's (1978) fit, by default, but can be altered.

The envelope is spherical by default, but can be made bipolar with an opening solid-angle that varies with radius. In the non-spherical case, no provision is made for photons penetrating the envelope from the sides.

The envelope is subject to a radial outflow (or wind), constant velocity by default, but the wind velocity can be made to vary with radius.

The temperature of the envelope is specified (and thus not computed self-consistently).

The data from all input files is fit to cubic splines (log X vs log radius, or log wavelength, except for species cross-sections which are fit to linear cubic splines and dust selective extinction). Internal wavelength integrations for photo-rates and mean cross-sections are obtained by cubic spline fit to the linear relations.

The code starts out at the base of the wind, and integrates outwards the (photo-)chemical orindary differential equations, using Gear's stiff method, along steps of log (radial distance), with much smaller internal steps of log (radial distance).

The integration is repeated in the case of shielding of interstellar radiation, so as to use the ith order estimate of the column density N(r) for the (i+1)th order photo-chemical integration. Convergence is based upon the absolute variations from one iteration to the next of the column densities of all continuum photo-absorbing species as well as the total column density.



CSENV works on most UNIX platforms (SunOS 4.1.3, OSF 4.0, Linux, and perhaps others). To install, run:

UNIX% cd installdir

where UNIX% is the UNIX prompt and installdir is the name of the directory under which you wish to place the csenv/ directory, and then:

UNIX% gtar zxvf csenv.tar.gz

where csenv.tar.gz is the name under which you saved the file, or alternatively:

UNIX% gunzip csenv.tar.gz
UNIX% tar xvf csenv.tar


UNIX% cd csenv

Finally, read the README file and type: