rate22_cse_code

The UDfA Rate22 circumstellar chemical kinetics model describes the gas-phase chemistry in an AGB outflow with a constant mass-loss rate and outflow velocity. This release includes the effects of

• A clumpy outflow using the porosity formalism (Van de Sande et al. 2018)
• Stellar UV photons (Van de Sande & Millar 2019)
• Close-by stellar companion UV photons (Van de Sande & Millar 2022)

Contents

• The FORTRAN77 code, located in the folder code/.

• A makefile, my_makefile.

• .rates files, containing the chemical reaction network.

  Pick either one of:

  • rate22_revised.rates is the latest UDfA release.
  • rate22_G_revised.rates excludes the reactions identified by Tinnaci et al. (2021) as endothermic (done by putting their rates to zero)

  Optional:

  • IP.rates lists the photoreaction rates caused by UV photons from the central AGB star (with an effective temperature of 2330 K, like IRC+10216)
  • AP_4000K.rates, AP_6000K.rates, and AP_10000K.rates list the photoreaction rates caused by UV photons from a closeby stellar companion (with an effective temperature of 4000, 6000, or 10000 K).

• A .specs file, containing all species and parent abundances: rate22_revised.specs.

• A perl script to compile new ODEs: rate12cse.pl.

• A test input file, test_input.txt.

• A file listing dipole moments, rate22_dipole.specs.

Compiling the model

Running ./my_makefile compiles the code to the executable csmodel. Note that a fortran compiler (e.g., gfortran) is necessary to do so. Note that the standard ODEs (code/acodes.f) do not include any internal photons!

Running a model

The model takes input from an input file. The command ./csmodel (inputfile) calculates your desired model.

Adding inner photoreactions

The photoreactions from an internal stellar and companion UV source are listed in IP.rates (AGB star) and AP_4000K.rates, AP_6000K.rates, and AP_10000K.rates (stellar companion). If you want to include these, please follow these steps:

1. Add the desired reactions to rate22_revised.rates, creating a new .rates file
2. Write a new ODE file using ./rate12cse.pl (name of your new rates file) -o acodes.f
3. Move acodes.f to the code/ folder and recompile the model
4. The perl script also writes a new .specs file. It works in mysterious ways, more likely than not the order of the species is changed. Make sure to use this .specs file!

Input parameters

The input parameters and their units are listed in test_input.txt. It's essential that you keep the basic format of the input file.

Special care needs to be taken with

1. The clumping parameters

• CLUMPMODE should be either SMOOTH for a smooth outflow (classical CSE model) or POROSITY for a clumpy (porous) model.
• FVOL is the clump volume filling factor, setting raction of the total volume occupied by the clumps. Therefore, 0 < FVOL < 1. FVOL = 0 will result in an error, FVOL = 1 is equivalent to a smooth outflow.
• FIC is the interclump density contrast between the interclump component and the mean density. Again, 0 < FIC < 1. FIC = 0 will result in an error, FIC = 1 is equivalent to a smooth outflow.
• L is the size of the clumps at the stellar surface. Therefore, L should be smaller than the stellar radius.

The porosity formalism implemented in the model assumes a constant FVOL, which results in uniformly expanding clumps. More information can be found in Van de Sande et al. 2018

2. The inner photon parameters

• ISTELLAR and IBIN turn stellar and companion UV photons on and off.
• When turning on IBIN, the type of stellar companion needs to be specified. Make sure to match the companion's radius to its temperature:
  • Red dwarf companion: RBIN = 1.53e10 cm, TBIN = 4000 K
  • Solar-like companion: RBIN = 8.14e10 cm, TBIN = 6000 K
  • White dwarf companion: RBIN = 6.96e8 cm, TBIN = 10000 K
• RDUST is the dust condensation radius. Dust formation isn't included in the model, this is the radius where the dust is assumed to have fully formed. The starting radius R_INNER_CHEM cannot be smaller or equal to RDUST. For best results, choose the initial radius as close to RDUST as possible.

Parent species

The parent species are listed at the bottom of the .specs file. Their units are fractional abundance relative to H.

Contact

If you have any comments or isues, please contact Marie Van de Sande at "mvdsande at strw.leidenuniv.nl".

Acknowledgements

The code is free to use. Please cite the Rate22 paper.

When including the effects of a clumpy outflow or internal photons, please also cite the relevant papers.

• Clumping: Van de Sande et al., 2018, A&A, 631, A106
• Stellar UV photons: Van de Sande & Millar, 2019, ApJ, 873, 36
• Companion UV photons Van de Sande & Millar, 2022, MNRAS, 510, 1204