Does z stad for the mass fraction of all the remaining chemical elements except helium and hydrogen, please?

Source: https://github.com/chrysante87/pyterpol/wiki

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1 Answer 1


Welcome to the world of software developed by scientists for their own use. There are not many clues.

The top-level README cites Nemravová et al. 2016. That paper mentions PYTERPOL briefly in section 3.4 and says "solar metallicity was assumed" for the components of ξ Tauri.

pyterpol/fitting/parameter.py has this code:

    teff=dict(name='teff', value=10000., vmin=6000., vmax=50000., unit='K', fitted=False, group=0, typedef=(float)),
    logg=dict(name='logg', value=3.5, vmin=0.0, vmax=5.0, unit='log(g.cm^-2)', fitted=False, group=0, typedef=(float)),
    vrot=dict(name='vrot', value=0.0, vmin=0.0, vmax=500., unit='km.s^-1', fitted=False, group=0, typedef=(float)),
    rv=dict(name='rv', value=0.0, vmin=-1000., vmax=1000., unit='km.s^-1', fitted=False, group=0, typedef=(float)),
    lr=dict(name='lr', value=1.0, vmin=0.0, vmax=1.0, unit='relative', fitted=False, group=0, typedef=(float)),
    z=dict(name='z', value=1.0, vmin=0.0, vmax=2.0, unit='Z_solar', fitted=False, group=0, typedef=(float)),

I think z=1.0 means the metallic mass fraction is the same as in the Sun, and other z values between 0 and 2 would be relative to that.

  • $\begingroup$ Thank you very much. $\endgroup$
    – Anna-Kat
    Aug 30, 2021 at 17:24

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