ATA: A computer code for calculation of model stellar atmospheres

The computer code ATA solves the model stellar atmosphere (generally NLTE) for given effective temperature, log g (gravitational acceleration at the stellar surface), and stellar radius. The atmosphere is represented with ND depth points.

Basic methods used in the code:

• radiative transfer: accelerated lambda iteration in the linearization step; standard Feautrier scheme for the formal solution, NF frequency points possible
• energy equilibrium: at large optical depths differential form (flux correction), at lower optical depths either radiative equilibrium or thermal balance of electrons
• hydrostatic equilibrium: standard
• statistical equilibrium: NL levels possible, many atomic species; occupation probability formalism; arbitrary reference atom

Basic options:

• model atmosphere calculation
• NLTE line formation problem
• synthetic spectrum
• irradiated atmospheres
• shells (irradiated from the bottom)

Input files

• Debugging options file DEBUG.DAT (obsolete, useless for users; sorry)
• Basic input file FT05.DAT
• Input of the model atmosphere
• Optional input:
• Input of the incident flux at the upper boundary RTEUBC.DAT
• Input of the incident flux at the lower boundary RTELBC.DAT

Output files

• Output file of the model atmosphere MODELO.DAT
• Basic output file report.lst
• Output file of the current maximum relative change iter.lst
• Output file of the relative changes relch.lst
• Output file of the errors errors.lst
• Optional output:
• Output of the transitions data: transit.lst
• Cross sections: cross.lst

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• Approximate lambda operator: aprlam.lst
• Output of the mean intensities, variable Eddington factors, and Eddington flux: intensit.lst
• Output of the angle dependence of the emergent specific intensity: limb.lst
• Auxilliary output from the formal solution: formal.lst
• Emergent flux for all frequency points, equivalent widths: emflux.lst
• Flux for all frequency points at tau_R~2/3: formflux.lst
• Flux for all frequency points at the lower boundary: ndflux.lst
• Total flux for all depth points: flux.lst
• Output of the relative changes of b-factors during the formal solution step: relbf.lst

---

• Convective gradients and other convective variables: convec.lst
• Energy (radiative and thermal) balance: enbal.lst
• All LTE populations, b-factors, ion populations: popul.lst
• All rates (both collisional and radiative) for all depth points: rates.lst
• Stability tests: stabil.lst
• Detailed output of the LTE populations, ionization fractions, etc.: lte.lst
• Extensive output of all relative changes: relal.lst
• Output during the depth integration: depint.lst

References:

• Kubát J.: 1994, Astron. Astrophys. 287, 179
• Kubát J.: 1996, Astron. Astrophys. 305, 255
• Kubát J.: 1997, Astron. Astrophys. 326, 277
• Kubát J.: 2001, Astron. Astrophys. 366, 210
• Kubát J.: 2003, in Stellar Atmosphere Modelling, I. Hubeny, D. Mihalas & K. Werner eds., ASP Conf. Ser. Vol. 288, p. 87
• Kubát J.: 2003, in Modelling of Stellar Atmospheres, IAU Symp. 210, N. E. Piskunov, W. W. Weiss & D. F. Gray eds., ASP, A8

Program is available upon request.

Last update: 19.1.2006