# [Mesa-users] Calculating R Parameter (t_HB/t_RGB) in GC by interpolating stellar evolutionary tracks

Iñigo Muñoz Elorza imunozelorza at gmail.com
Tue Oct 17 18:44:43 EDT 2017

```OS: macOS SIerra 10.12.5
MESA version: r9575

Dear community,

I'm trying to calculate the R parameter in GC by obtaining the evolutionary
tracks of a star of 0.82 Msolar with different eta_Reimers mass loss
factors, and then interpolating the solution at Log_T_ZAHB = 3.85, which
has been determined by different observational data for that kind of stars.

Trying to replicate the results from some previous work by Ayala, I'm
considering:
- initial_mass = 0.82
- initial_Y = 0.248
- initial_Z = 0.001
- and Reimers_scaling_factor = 0.2 (or 0.35), depending on the case.

The problem is that I obtain a value of T_ZAHB lower than 3.85 for both
cases, and it should be higher for the case of eta_Reimers = 0.35, but I'm
not sure what control parametrs I'm not taking into account.

I'm attaching the inlist for both cases, together with the Python script to
calculate R. With my current runs, those are my resuts:

*eta_Reimers = 0.2*
V_ZAHB: 0.549654103615
T_ZAHB:  3.71087121492
t_HB:  80.6521275821  My
t_RGB:  55.9783179064  My
R parameter:  1.44077440335

*eta_Reimers = 0.35*
V_ZAHB: 0.685704604046
T_ZAHB:  3.72446361968
t_HB:  82.1772995776  My
t_RGB:  61.9668190125  My
R parameter:  1.32615004106

Any ideas why the T_ZAHB are so similar? The t_RGB is also quite different,
and should be almost the same for both cases.

I have also "experimented" with the parameters modified in the test_suites
create_zahb, he_core_flash and hot_cool_wind (opacities, MLT,
photospheres), but I haven't seen any improvement on the T issue (of
course, the results were different for the different times).

Cheers,
Iñigo Muñoz
-------------- next part --------------
An HTML attachment was scrubbed...
-------------- next part --------------
A non-text attachment was scrubbed...
Name: inlist_082MReimers02
Type: application/octet-stream
Size: 1308 bytes
Desc: not available
-------------- next part --------------
A non-text attachment was scrubbed...
Name: inlist_082MReimers035
Type: application/octet-stream
Size: 1310 bytes
Desc: not available