MESA Grid: Binary Evolution (M1=6.0, M2=4.0, Z=0.02)

The primary objective is to investigate the dependence of binary interaction on the initial orbital period. **Model Configuration:**

• **Donor Star (M1):** Fixed initial mass of 6.0 M_sun. The evolution is followed self-consistently.
• **Companion (M2):** Represented as a point mass of 4.0 M_sun.
• **Orbit:** Initially circular; the grid is constructed by varying the initial orbital period. **Physics and Assumptions:**
• **Mass Transfer:** Implemented via the *Ritter prescription* for Roche-lobe overflow (RLOF).
• **Efficiency:** Fully conservative mass transfer is assumed.
• **Angular Momentum:** Includes losses due to gravitational radiation, magnetic braking, and systemic mass loss.
• **Tides:** Tidal synchronization of the donor star is accounted for.
• **Exclusions:** Wind mass transfer and irradiation effects are not included. **Termination Criteria:** Calculations are terminated if: 1. Roche-lobe overflow occurs at the very first timestep. 2. The system undergoes overflow through the outer Lagrangian point (L2). The setup is designed to isolate the role of the initial orbital period in determining the onset of mass transfer and the subsequent evolutionary regime.