[Mesa-users] calculation clarification

[Biswas, Anwesha [PHYSA]]

Okay So using profile.T_face instead of profile.T solves the issue(I could match the calculation with the output shown) (outer location vs. midpoint in the cell). However now, A new question is why the profile.log_P_face = 0 for all the cells in a single profile?  (it means that pressure at the surface of each cell is 1) while the pressure at the midpoints of the same cells (profile.pressure) outputs are different?

Anwesha
​

________________________________________
From: Biswas, Anwesha [PHYSA] <anwesha at iastate.edu>
Sent: Wednesday, September 13, 2023 19:57
To: mesa-users at lists.mesastar.org
Subject: calculation clarification

Hi,

I need a little help with clarification of some calculations

Using Eddington Grey atmosphere, varying opacity controls, when I am reading the profile of interest using mesa reader in python (loading it as profile say)

so,
profile.Teff --> gives me the effective temperature of that profile which is Teff = 10813.33 [K]

tau_factor = 37.5 --> tau_surface = (2/3)*37.5 = 25
sets my outermost grid of the stellar model to an optical depth of tau_surface =  25 (I can match this calculation from output profile.logtau[0]~1.4)

so, the temperature of the surface of this model is calculated by the relation --> T^4 = (3/4)(Teff^4) (tau_surface +2/3) = (3/4)(10813.33^4)(25+2/3)
giving me T_surface = 22649.94 [K] which means Temperature at tau=25 is 22649.94 [K]

when I read the temperature from profile file at grid 0 (since it is surface to center)
profile.temperature[0] = 33247.17 [K]
which means temperature at tau=25 is showing as 33247.17[K]

can someone explain to me why is the difference?


Anwesha