[Mesa-users] Inconsistency between Omega/Omega_crit reported by MESA and that computed with Paxton et al. (2019) equations

Larry Molnar lmolnar at calvin.edu
Mon Jul 13 14:20:45 EDT 2020


I am running the latest MESA based on the revisions described in Paxton et al. (2019): MESA R12778, SDK 20.3.2, on a Linux operating system.

I am interested in rotation of main sequence stars with intermediate mass, so I ran a case with 1.0 Msun and default (solar) abundances with several initial values of the frequency ratio omega := Omega_Psi/Omega_crit [p. 28 of Paxton et al. (2019)]. I attach the inlist used and copy the first few lines of output from profile39.data (at which age = 6.79 Gy).

The run completed fine and the results largely look sensible. The left side of Equation 39 of section 4 of Paxton et al. (2019) contains j_rot, m_Psi, and r_Psi, the quantities needed to determine omega for a given zone (and hence the quantities r_e and i_rot which are found on the right side of the equation). As a consistency check I computed both sides separately for a number of zones and found significant disagreement (up to several percent, depending on the zone). So I used Equation B30 to implicitly find the value of omega that is consistent (and the values for other things like r_e, r_p, etc.). I found a slightly larger value of omega that was consistent with everything. Using this revised omega, I checked separately and found the profile values of Omega_Psi, r_e, r_p, and i_rot are all consistent with the left side of Eqn. 39 while omega, v_rot, and Omega_crit are not. I repeated this for different zones and for two initial values of omega (0.3 and 0.4). I find the omega reported by the profile is approximately equal to the following function of the omega from the equation: omega_Eqn*(1 - 0.25*omega_Eqn^2).

For the example below, omega of zone 1 is reported to be 0.32961 when it should be 0.33906, a difference of 2.8%.

In summary, the correct omega ratio seems to be computed and used for some things (like r_e, r_p, i_rot, Omega_Psi), but something else is being reported (and being used to compute v_rot and Omega_crit).

Prof. Larry Molnar
Department of Physics and Astronomy
Calvin University
1734 Knollcrest Circle SE
Grand Rapids, MI 49546-4403 USA

E-mail: lmolnar at calvin.edu
Phone: 616-526-6341

Profile39.data: first three zones plus header

                                       1                                        2                                        3                                        4                                        5                                        6                                        7                                        8                                        9                                       10                                       11                                       12                                       13                                       14                                       15                                       16                                       17                                       18                                       19                                       20                                       21                                       22                                       23                                       24                                       25                                       26                                       27                                       28                                       29                                       30                                       31                                       32                                       33                                       34                                       35                                       36                                       37                                       38                                       39                                       40                                       41                                       42                                       43                                       44                                       45                                       46                                       47                                       48                                       49                                       50                                       51                                       52
                            model_number                                num_zones                             initial_mass                                initial_z                                 star_age                                time_step                                     Teff                            photosphere_L                            photosphere_r                               center_eta                                center_h1                               center_he3                               center_he4                               center_c12                               center_n14                               center_o16                              center_ne20                                star_mass                                star_mdot                             star_mass_h1                            star_mass_he3                            star_mass_he4                            star_mass_c12                            star_mass_n14                            star_mass_o16                           star_mass_ne20                             he_core_mass                              c_core_mass                              o_core_mass                             si_core_mass                             fe_core_mass                   neutron_rich_core_mass                               tau10_mass                             tau10_radius                              tau100_mass                            tau100_radius                             dynamic_time                             kh_timescale                            nuc_timescale                           power_nuc_burn                             power_h_burn                            power_he_burn                                power_neu                                burn_min1                                burn_min2                             time_seconds                           version_number                                 compiler                                    build                         MESA_SDK_version                             math_backend                                     date
                                     840                                      788                  1.0000000000000000E+000                  2.0000000000000000E-002                  6.7862319465169029E+009                  1.0974467458049601E+008                  5.6913137780955512E+003                  1.1106458896908029E+000                  1.0854793927473201E+000                 -1.4234108223730109E+000                  1.7892625342288088E-001                  1.2875481967828730E-006                  8.0076368174195711E-001                  3.0901329101104673E-005                  6.8050315038511392E-003                  7.2830595800253044E-003                  2.0994604783340942E-003                  1.0000000000000000E+000                  0.0000000000000000E+000                  6.4251076451589306E-001                  9.1978547547992594E-004                  3.3638630678708026E-001                  2.3204305753635767E-003                  2.3422350540312545E-003                  9.3306927181358093E-003                  2.0994604783340300E-003                  0.0000000000000000E+000                  0.0000000000000000E+000                  0.0000000000000000E+000                  0.0000000000000000E+000                  0.0000000000000000E+000                  0.0000000000000000E+000                  9.9999999986641774E-001                  1.0852251060789109E+000                  9.9999999977220166E-001                  1.0850847080353851E+000                  1.1323115727543849E+004                  1.9470734833037574E+007                  9.0037698719471607E+009                  1.1106109430736193E+000                  1.1106109430736197E+000                  1.9379726463585424E-041                  3.1117358618271040E-002                  5.0000000000000000E+001                  1.0000000000000000E+003                  2.1416092559439270E+017                                  "12778"                               "gfortran"                                  "9.2.0"                    "x86_64-linux-20.3.2"                                 "CRMATH"                               "20200707"

                                       1                                        2                                        3                                        4                                        5                                        6                                        7                                        8                                        9                                       10                                       11                                       12                                       13                                       14                                       15                                       16                                       17                                       18                                       19                                       20                                       21                                       22                                       23
                                    zone                                     mass                                     logR                                     logT                                   logRho                                     logP                        x_mass_fraction_H                       y_mass_fraction_He                   z_mass_fraction_metals                                        x                               luminosity                             conv_L_div_L                                    omega                                log_omega                             log_J_inside                                    i_rot                                    j_rot                                    v_rot                                  r_polar                             r_equatorial                              r_e_div_r_p                               omega_crit                     omega_div_omega_crit
                                       1                  1.0000000000000000E+000                  3.5621583017451837E-002                  3.7553873899760544E+000                 -6.8226384760895904E+000                  4.7364521258960668E+000                  6.9837283051018251E-001                  2.8162185819852292E-001                  2.0005311291294570E-002                  6.9837283051018251E-001                  1.1106458896908029E+000                  0.0000000000000000E+000                  1.8289678787990470E-004                 -3.7377939217421856E+000                  5.0141558734190070E+001                  4.0452322195411635E+021                  7.3985997918237632E+017                  1.3817339257946193E+002                  1.0466378035378214E+000                  1.1061445120438380E+000                  1.0568551110086730E+000                  5.5489221113985861E-004                  3.2960777644400241E-001
                                       2                  9.9999999999949996E-001                  3.5621053101314769E-002                  3.7558294668053462E+000                 -6.8198510069919314E+000                  4.7396826558142946E+000                  6.9837283051018251E-001                  2.8162185819852292E-001                  2.0005311291294570E-002                  6.9837283051018251E-001                  1.1106458896908031E+000                  0.0000000000000000E+000                  1.8289678787990470E-004                 -3.7377939217421856E+000                  5.0141558734187761E+001                  4.0452210785591907E+021                  7.3985794153255962E+017                  1.3817322398356947E+002                  1.0466367126293932E+000                  1.1061430561848453E+000                  1.0568548215798377E+000                  5.5489322674071766E-004                  3.2960717317489624E-001
                                       3                  9.9999999999862488E-001                  3.5620131676504144E-002                  3.7563968080601273E+000                 -6.8163424224394999E+000                  4.7437598235062506E+000                  6.9837283051018240E-001                  2.8162185819852292E-001                  2.0005311291294681E-002                  6.9837283051018240E-001                  1.1106458896908031E+000                  0.0000000000000000E+000                  1.8289678787990470E-004                 -3.7377939217421856E+000                  5.0141558734183725E+001                  4.0452026442495694E+021                  7.3985456995654310E+017                  1.3817293082741162E+002                  1.0466346781989255E+000                  1.1061406031617111E+000                  1.0568545321517389E+000                  5.5489490448713092E-004                  3.2960617659473646E-001



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