rpmin.f

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      REAL*8 FUNCTION rpmin(M1,M2,VSTAR,H,PERI)
*
*       Minimum pericentre distance for energy change (H < 0).
*       ------------------------------------------------------
*
      IMPLICIT REAL*8 (a-h,m,o-z)
      DATA fudge /1.0d-02/
*
*       Adopt simplified eccentricity factor valid for ECC = 1.
      ge = 425.0*3.1415/(32.0*sqrt(2.0d0))
      clight = 3.0d+05/vstar
      fac = (1.0/clight)**3.5
*
*       Set mass expression for energy change in N-body units.
      fm = sqrt(m1 + m2)*m1**2*m2**2
*       Form scaled energy (without r_min).
      de = 8.0/15.0*fac*fm*clight**2*ge
*
*       Adopt a fraction of the energy (-MU*H) for determination of RPMIN.
      mu = m1*m2/(m1 + m2)
      demax = -fudge*mu*h
      rpmin = (de/demax)**(2.0/7.0)
*
*       Include some diagnostics (suppressed).
*     SEMI = -(M1 + M2)/H
*     WRITE (6,5)  SEMI, RPMIN, PERI
*   5 FORMAT (' RPMIN    A RPM PERI ',1P,3E10.2)
*
      RETURN
      END