Implementing the Shikauchi+ (2024) core mass prescription for main sequence stars

compas_python_utils/preprocessing/compasConfigDefault.yaml

@@ -236,6 +236,7 @@ stringChoices:
 #    --initial-mass-function: 'KROUPA'                                     # Default: 'KROUPA'                      # Options: ['KROUPA','UNIFORM','POWERLAW','SALPETER']
 #    --LBV-mass-loss-prescription: 'HURLEY_ADD'                            # Default: 'HURLEY_ADD'                  # Options: ['BELCZYNSKI','HURLEY','HURLEY_ADD','ZERO','NONE']
 #    --luminous-blue-variable-prescription: 'HURLEY_ADD'                   # Default: 'HURLEY_ADD'                  # Options: ['BELCZYNSKI','HURLEY','HURLEY_ADD','ZERO','NONE']
+#    --main-sequence-core-mass-prescription: 'MANDEL'                      # Default: 'MANDEL'                      # Options: ['SHIKAUCHI','MANDEL','ZERO']
 #    --mass-loss-prescription: 'MERRITT2024'                               # Default: 'MERRITT2024'                 # Options: ['MERRITT2024','BELCZYNSKI2010','HURLEY','ZERO','NONE']
 #    --OB-mass-loss: 'VINK2021'                                            # Default: 'VINK2021'                    # Options: ['KRTICKA2018','BJORKLUND2022','VINK2021','VINK2001','ZERO','NONE']
 #    --OB-mass-loss-prescription: 'VINK2021'                               # Default: 'VINK2021'                    # Options: ['KRTICKA2018','BJORKLUND2022','VINK2021','VINK2001','ZERO','NONE']

online-docs/pages/User guide/Program options/program-options-list-defaults.rst

@@ -795,6 +795,15 @@ Default = 4.2
 
 :ref:`Back to Top <options-props-top>`
 
+**--main-sequence-core-mass-prescription** |br|
+Main sequence core mass prescription. |br|
+Options: {ZERO, MANDEL, SHIKAUCHI} |br|
+``ZERO``      : No core mass treatment, set to zero |br|
+``MANDEL``    : The core following case A mass transfer is set equal to the expected core mass of a newly formed HG star
+ with mass equal to that of the donor, scaled by the fraction of the donor's MS lifetime at mass transfer |br|
+``SHIKAUCHI`` : Core mass according to Shikauchi et al. (2024) |br|
+Default = MANDEL |br|
+
 **--mass-change-fraction** |br|
 Approximate desired fractional change in stellar mass on phase when setting SSE and BSE timesteps (applied before ``--timestep--multiplier``). |br|
 Recommended value is 0.005. |br|
@@ -1161,7 +1170,8 @@ Default = MULLERMANDEL
 If TRUE, preserve a larger donor core mass following case A mass transfer. |br|
 The core is set equal to the expected core mass of a newly formed HG star with mass equal to that of the donor,
 scaled by the fraction of the donor's MS lifetime at mass transfer. |br|
-Default = TRUE
+Default = TRUE |br|
+DEPRECATION NOTICE: this option has been deprecated and will soon be removed. Please use ``--main-sequence-core-mass-prescription MANDEL`` in future.
 
 **--revised-energy-formalism-nandez-ivanova** |br|
 Enable revised energy formalism of Nandez & Ivanova. |br|
@@ -1418,7 +1428,7 @@ Go to :ref:`the top of this page <options-props-top>` for the full alphabetical
 **Stellar evolution and winds**
 
 --use-mass-loss, --check-photon-tiring-limit, --cool-wind-mass-loss-multiplier, --luminous-blue-variable-prescription, --LBV-mass-loss-prescription
---luminous-blue-variable-multiplier, --mass-loss-prescription, --overall-wind-mass-loss-multiplier, --wolf-rayet-multiplier, 
+--luminous-blue-variable-multiplier, --main-sequence-core-mass-prescription, --mass-loss-prescription, --overall-wind-mass-loss-multiplier, --wolf-rayet-multiplier, 
 --expel-convective-envelope-above-luminosity-threshold, --luminosity-to-mass-threshold,
 --OB-mass-loss, --OB-mass-loss-prescription, --RSG-mass-loss, --RSG-mass-loss-prescription, --VMS-mass-loss, --vms-mass-loss-prescription, --WR-mass-loss, --WR-mass-loss-prescription
 

online-docs/pages/whats-new.rst

@@ -3,6 +3,12 @@ What's new
 
 Following is a brief list of important updates to the COMPAS code.  A complete record of changes can be found in the file ``changelog.h``.
 
+**03.12.00 Jan 16, 2025**
+* Added convective core mass prescription for main sequence stars from Shikauchi+ (2024), describing how the core mass evolves under mass loss and mass gain.
+* New command line option ``--main-sequence-core-mass-prescription`` with arguments ``SHIKAUCHI`` (new prescription), ``MANDEL`` (replaces the functionality of ``--retain-core-mass-during-caseA-mass-transfer``), and ``ZERO`` (core mass set to zero, no treatment).
+* Added new luminosity prescription for main sequence stars from Shikauchi+ (2024).
+* Added treatment for rejuvenation of main sequence accretors when the new prescription is used.
+
 **03.10.00 Nov 29, 2024**
 
 Added functionality to log stellar mergers in the BSE switchlog file.

src/BaseBinaryStar.cpp

@@ -1736,8 +1736,22 @@ void BaseBinaryStar::ResolveMainSequenceMerger() {
 
     double finalMass               = (1.0 - phi) * (mass1 + mass2);
     double initialHydrogenFraction = m_Star1->InitialHydrogenAbundance();
-    double finalHydrogenMass       = finalMass * initialHydrogenFraction - tau1 * TAMSCoreMass1 * initialHydrogenFraction - tau2 * TAMSCoreMass2 * initialHydrogenFraction;
 
+    double finalHydrogenMass;
+    if ((OPTIONS->MainSequenceCoreMassPrescription() == CORE_MASS_PRESCRIPTION::SHIKAUCHI) &&
+        (utils::Compare(m_Star1->MZAMS(), SHIKAUCHI_LOWER_MASS_LIMIT) >= 0)                &&
+        (utils::Compare(m_Star2->MZAMS(), SHIKAUCHI_LOWER_MASS_LIMIT) >= 0)) {
+
+        double coreMass1       = m_Star1->MainSequenceCoreMass();
+        double coreMass2       = m_Star2->MainSequenceCoreMass();
+
+        double coreHeliumMass1 = m_Star1->HeliumAbundanceCore() * coreMass1;
+        double coreHeliumMass2 = m_Star2->HeliumAbundanceCore() * coreMass2;
+
+        finalHydrogenMass      = finalMass * initialHydrogenFraction - coreHeliumMass1 - coreHeliumMass2;
+    }
+    else finalHydrogenMass     = finalMass * initialHydrogenFraction - tau1 * TAMSCoreMass1 * initialHydrogenFraction - tau2 * TAMSCoreMass2 * initialHydrogenFraction;
+
     m_SemiMajorAxis = std::numeric_limits<float>::infinity();                                   // set separation to infinity to avoid subsequent fake interactions with a massless companion (RLOF, CE, etc.)
 
     m_Star1->UpdateAfterMerger(finalMass, finalHydrogenMass);
@@ -2088,22 +2102,25 @@ void BaseBinaryStar::CalculateMassTransfer(const double p_Dt) {
             }
             else {                                                                                                              // have required mass loss
                 massDiffDonor = -massDiffDonor;                                                                                 // set mass difference
-                m_Donor->UpdateMinimumCoreMass();                                                                               // reset the minimum core mass following case A
+                m_Donor->UpdateTotalMassLossRate(massDiffDonor / (p_Dt * MYR_TO_YEAR));                                         // update mass loss rate for MS donor
+                m_Donor->UpdateMainSequenceCoreMass(p_Dt, massDiffDonor / (p_Dt * MYR_TO_YEAR));                                // update core mass for MS donor
             }
         }
 
         if (!m_CEDetails.CEEnow) {                                                                                              // CE flagged?
                                                                                                                                 // no
-            m_MassTransferTrackerHistory = m_Donor == m_Star1 ? MT_TRACKING::STABLE_1_TO_2_SURV : MT_TRACKING::STABLE_2_TO_1_SURV;  // record what happened - for later printing
-            double massGainAccretor = -massDiffDonor * m_FractionAccreted;                                                      // set accretor mass gain to mass loss * conservativeness
-
+            m_MassTransferTrackerHistory = m_Donor == m_Star1 ? MT_TRACKING::STABLE_1_TO_2_SURV : MT_TRACKING::STABLE_2_TO_1_SURV; // record what happened - for later printing
+
+            double massGainAccretor  = -massDiffDonor * m_FractionAccreted;                                                     // set accretor mass gain to mass loss * conservativeness
             double omegaDonor_pre_MT = m_Donor->Omega();                                                                        // used if full donor envelope is removed
 
+            m_Accretor->UpdateTotalMassLossRate(massGainAccretor / (p_Dt * MYR_TO_YEAR));                                       // update mass gain rate for MS accretor
+            m_Accretor->UpdateMainSequenceCoreMass(p_Dt, massGainAccretor / (p_Dt * MYR_TO_YEAR));                              // update core mass for MS accretor
+
             m_Donor->SetMassTransferDiffAndResolveWDShellChange(massDiffDonor);                                                 // set new mass of donor
             m_Accretor->SetMassTransferDiffAndResolveWDShellChange(massGainAccretor);                                           // set new mass of accretor
 
             aFinal              = CalculateMassTransferOrbit(m_Donor->Mass(), massDiffDonor, *m_Accretor, m_FractionAccreted);  // calculate new orbit
-
             m_aMassTransferDiff = aFinal - aInitial;                                                                            // set change in orbit (semi-major axis)
 
             STELLAR_TYPE stellarTypeDonor = m_Donor->StellarType();                                                             // donor stellar type before resolving envelope loss

src/BaseStar.cpp

@@ -129,12 +129,13 @@ BaseStar::BaseStar(const unsigned long int p_RandomSeed,
     m_Dt                                       = DEFAULT_INITIAL_DOUBLE_VALUE;
     m_Tau                                      = DEFAULT_INITIAL_DOUBLE_VALUE;
     m_Age                                      = 0.0;                                               // ensure age = 0.0 at construction (rather than default initial value)
+    m_MainSequenceCoreMass                     = DEFAULT_INITIAL_DOUBLE_VALUE;
     m_Mass                                     = m_MZAMS;
     m_Mass0                                    = m_MZAMS;
-    m_MinimumCoreMass                          = 0.0;
     m_Luminosity                               = m_LZAMS;
     m_Radius                                   = m_RZAMS;
     m_Temperature                              = m_TZAMS;
+    m_TotalMassLossRate                        = DEFAULT_INITIAL_DOUBLE_VALUE;
 	m_ComponentVelocity						   = Vector3d();
 
     m_OmegaCHE                                 = CalculateOmegaCHE(m_MZAMS, m_Metallicity);
@@ -2709,7 +2710,9 @@ double BaseStar::CalculateMassLossRate() {
 
         mDot = mDot * OPTIONS->OverallWindMassLossMultiplier();                                                     // apply overall wind mass loss multiplier
     }
-
+
+    UpdateTotalMassLossRate(-mDot);                                                                                 // update total mass loss rate
+
     return mDot;
 }
 
@@ -4571,12 +4574,15 @@ STELLAR_TYPE BaseStar::EvolveOnPhase(const double p_DeltaTime) {
     STELLAR_TYPE stellarType = m_StellarType;
 
     if (ShouldEvolveOnPhase()) {                                                    // evolve timestep on phase
+
+        UpdateMainSequenceCoreMass(p_DeltaTime, -m_Mdot);                           // update core mass, relevant for MS stars
+
         m_Tau        = CalculateTauOnPhase();
 
         m_COCoreMass = CalculateCOCoreMassOnPhase();
         m_CoreMass   = CalculateCoreMassOnPhase();
         m_HeCoreMass = CalculateHeCoreMassOnPhase();
-        
+
         m_Luminosity = CalculateLuminosityOnPhase();
 
         // Calculate abundances
@@ -4627,7 +4633,7 @@ STELLAR_TYPE BaseStar::ResolveEndOfPhase(const bool p_ResolveEnvelopeLoss) {
         if (p_ResolveEnvelopeLoss) stellarType = ResolveEnvelopeLoss();         // if required, resolve envelope loss if it occurs
 
         if (stellarType == m_StellarType) {                                     // staying on phase?
-
+            
             m_Tau         = CalculateTauAtPhaseEnd();
 
             m_COCoreMass  = CalculateCOCoreMassAtPhaseEnd();