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`star_utils:get_phot_info` should raise non-zero `ierr` if L < 0
The various code paths in star_utils:get_phot_info currently avoid dealing with a negative luminosity (which causes problems in e.g. set_phot_info when trying to evaluate Teff ~ (L/4πR²σ)⁰·²⁵) by limiting the output luminosity to max(1, L). As @adamjermyn suggested in PR 278, we should probably rather have the various routines raise a non-zero ierr rather than make up a value of L and pretend everything is OK.
I suppose the counterargument would be that maybe the solver learns something by evaluating with a small but non-negative L, and we'd be cutting off that iteration prematurely by raising an error. I don't find that argument terribly convincing but it is at least in principle an empirical case someone could make...
Yeah, I figured step one here would be to try raising ierr /= 0 and see what happens.
Hmmm actually thinking more, can't there be physical setups where L < 0(temporarily) at the surface? I'm thinking of irradiated stars...
Like in that case the radiation field doesn't become strictly outward-facing at infinity, and I think you need that to define a photosphere?
That's what I'm thinking too. But in that case you might not want to call a subroutine who's name implies you want information at the photosphere.
That said, I'm not sure that isn't what we're doing anyway when using the 'irradiated' atmosphere option. I just had a quick look in atm and it looks like even that assumes a positive luminosity, since it computes some sort of temperature using the Stefan–Boltzman law. So all this possibly deserves a rethink but at a higher level than get_phot_info.
Agreed. I don't think get_phot_info is the right place for this change.
-Adam
On Mon, Jun 21, 2021 at 11:31 AM, Warrick Ball @.***> wrote:
That's what I'm thinking too. But in that case you might not want to call a subroutine who's name implies you want information at the photosphere.
That said, I'm not sure that isn't what we're doing anyway when using the 'irradiated' atmosphere option. I just had a quick look in atm and it looks like even that assumes a positive luminosity, since it computes some sort of temperature using the Stefan–Boltzman law. So all this possibly deserves a rethink but at a higher level than get_phot_info.
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