set 'logg@primary' value manually

[aliyyanurr]

hello, I am trying to set log g for primary stars manually from spectroscopic data. I tried b.set_valuae('logg@primary', ...) and it shows an error, that logg@primary is constrained by mass@primary and requiv@primary. I checked print(b.filter(context='constraint')) and I found that mass and requiv is also constrained by another parameters. I tried b.flip_constraint('logg@primary', solve_for='mass@primary' (or 'requiv@primary')) and it doesn't work since both of them are constrained by another parameters. Is there any way for me to set logg@primary manually? What are and how many constrained parameters I should flip to set logg@primary?

[kecnry]

By default, requiv@primary should not be constrained (unless you have a contact or semidetached system, or have manually flipped requivsumfrac or requivratio), and you should be able to flip the logg constraint to solve for requiv.

For example:

import phoebe

b = phoebe.default_binary()
print(b.filter(qualifier=['logg', 'mass', 'requiv'], component='primary'))

ParameterSet: 5 parameters
         requiv@primary@component: 1.0 solRad
C          logg@primary@component: 4.437551877570185
C          mass@primary@component: 0.9988131358058301 solMass
          logg@primary@constraint: log10((({mass@primary@component} / ({requiv@primary@component} ** 2.000000)) * 2942.206218) * 9.319541)
          mass@primary@constraint: (39.478418 * ({sma@binary@component} ** 3.000000)) / ((({period@binary@component} ** 2.000000) * ({q@binary@component} + 1.000000)) * 2942.206217504419328179210424423218)

b.flip_constraint('logg@primary', solve_for='requiv@primary')
print(b.filter(qualifier=['logg', 'mass', 'requiv'], component='primary'))

print(b.filter(qualifier=['logg', 'mass', 'requiv'], component='primary'))
print(b.filter(qualifier=['logg', 'mass', 'requiv'], component='primary'))
ParameterSet: 5 parameters
C        requiv@primary@component: 1.0000000000000004 solRad
           logg@primary@component: 4.437551877570185
C          mass@primary@component: 0.9988131358058301 solMass
                requiv@constraint: sqrt((({mass@primary@component} * 2942.206218) * 9.319541) / (10.000000 ** {logg@primary@component}))
          mass@primary@constraint: (39.478418 * ({sma@binary@component} ** 3.000000)) / ((({period@binary@component} ** 2.000000) * ({q@binary@component} + 1.000000)) * 2942.206217504419328179210424423218)

If requiv is constrained already, then you'll first need to flip the requiv constraint so that requiv is a free parameter (and one of the other parameters in the requiv constraint will become constrained in its place).

If you want to instead have mass computed based on your provided logg, then you need to first flip the mass constraint to solve for something else in Kepler's third law (sma, period, or q), and then should be able to flip the logg parameter.

print(b.filter(['logg@secondary', 'mass@secondary', 'requiv@secondary', 'sma@binary', 'q@binary']))

ParameterSet: 7 parameters
C        logg@secondary@component: 4.437551877570185
                  logg@constraint: log10((({mass@secondary@component} / ({requiv@secondary@component} ** 2.000000)) * 2942.206218) * 9.319541)
C        mass@secondary@component: 0.9988131358058301 solMass
        mass@secondary@constraint: (39.478418 * ({sma@binary@component} ** 3.000000)) / ((({period@binary@component} ** 2.000000) * ((1.000000 / {q@binary@component}) + 1.000000)) * 2942.206217504419328179210424423218)
       requiv@secondary@component: 1.0 solRad
             sma@binary@component: 5.3 solRad
               q@binary@component: 1.0

b.flip_constraint('mass@secondary', solve_for='sma@binary')
b.flip_constraint('logg@secondary', solve_for='mass@secondary')
print(b.filter(['logg@secondary', 'mass@secondary', 'requiv@secondary', 'sma@binary', 'q@binary']))

ParameterSet: 7 parameters
         logg@secondary@component: 4.437551877570185
C        mass@secondary@component: 0.9988131472111608 solMass
        mass@secondary@constraint: (({requiv@secondary@component} ** 2.000000) * (10.000000 ** {logg@secondary@component})) / 27420.011166
       requiv@secondary@component: 1.0 solRad
C            sma@binary@component: 5.30000002017336 solRad
            sma@binary@constraint: (((({mass@secondary@component} * ({period@binary@component} ** 2.000000)) * ((1.000000 / {q@binary@component}) + 1.000000)) * 2942.206217504419328179210424423218) / 39.478418) ** (1./3)
               q@binary@component: 1.0