[Mesa-users] Caveats to implementing time- and space-varying gravitational constant to MESA RSP Cepheid

[Øyvind Christiansen]

Dear Mesa users,


I am working on a project where we intend to study the effect of temporally and possibly spatially varying gravitational constant on Cepheids using the radially pulsating stellar library, basing it on the test_suite rsp_Cepheid working folder. We are updating the gravitational constant every time step according to our model, and the results seem well-behaved and reasonable. However, I wanted to ask if anyone with more experience in working with Mesa are aware of possible caveats to doing so?


Possible difficulties that I see are

1) Energy conservation constraints and termination criterion, if the time varying G transfers energy into or out of the system.

2) External libraries like gyre, and whether they are using the updated value for G at every time step

3) Equations such as the hydrostatic equilibrium where the gravitational pressure is calculated assuming constant G.


The variations that we intend to look at for now are around percentage and below, so possibly we will be able argue that these effects are negligible.


Any input is appreciated!


Best wishes,

Øyvind Christiansen

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