Stellar far-IR fluxes: how accurate are model predictions?

Details Stellar far-IR fluxes: how accurate are model predictions? Stellar far-IR fluxes: how accurate are model predictions?

May 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...309..849v&link_type=abstract

Astronomy and Astrophysics, v.309, p.849-860

Astronomy and Astrophysics

Astrophysics

8

Stars: Atmospheres, Infrared: Stars, Stars: Fundamental Parameters

Scientific paper

We present the results of an analysis of the accuracy of predicted far infrared (FIR) fluxes of stars. Sources of errors are a) the input parameters for the model atmospheres; b) assumptions in the modelling, resulting in errors in the structure of the model atmospheres; c) the adopted IR continuous opacity, dominated by the H^-^_ff_ opacity; d) the possible presence of circumstellar (CS) dust. Stellar effective temperatures are typically determined with an accuracy of about 100K. This leads to an uncertainty in the predicted far infrared (FIR) flux of 1 to 4%, depending on the spectral type. Errors in the other two fundamental parameters of a star, the surface gravity and the metallicity, have a minor effect on the prediction of stellar FIR fluxes, less than 1%. The various assumptions made in the modelling result in errors in the temperature structure T(τ) of model atmospheres. By using the depth and shape of spectral lines, T(τ) in the outer layers of the atmosphere, where the lines are formed, can be pinned down to about 100K, resulting in uncertainties of about 1 to 2% in the FIR. Errors in the H^-^_ff_ opacity are small and as a result uncertainties in the FIR fluxes due to the continuous opacity are less than 0.1%. CS dust can have a large impact on the IR fluxes. We find that the uncertainties due to the possible presence of CS dust can be more than an order of magnitude larger than the uncertainties resulting from modelling the stellar atmosphere. Unfortunately with the present day accuracies of IR data no further constraints can be set to limit these uncertainties.

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