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efac2.f
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1  FUNCTION efac2(ZETA,ICASE)
2 *
3 *
4 * Tidal capture efficiency factor (l = 2).
5 * ----------------------------------------
6 *
7 * Fitting functions for the second spherical harmonic index based on
8 * Ray et. al. (A & A 184, 164) and Lee & Ostriker (Ap. J. 310, 176).
9 * Developed at IOA by S. Portegies Zwart & T. Meinen (A & A 280, 174).
10 *
11  REAL*8 zeta,coeff(6),efac2
12 *
13 *
14 * Select coefficients for a given polytropic index (ICASE = 1, 2, 3).
15  IF (icase.EQ.1) THEN
16 * Polytropic index 1.5.
17  coeff(1) =-0.397
18  coeff(2) = 1.678
19  coeff(3) = 1.277
20  coeff(4) =-12.42
21  coeff(5) = 9.446
22  coeff(6) =-5.550
23  ELSE
24  IF (icase.EQ.2) THEN
25 * Polytropic index 2.
26  coeff(1) =-0.517
27  coeff(2) =-0.906
28  coeff(3) = 23.88
29  coeff(4) =-93.49
30  coeff(5) = 112.3
31  coeff(6) =-44.15
32  ELSE
33 * Polytropic index 3.
34  coeff(1) =-1.124
35  coeff(2) = 0.877
36  coeff(3) =-13.37
37  coeff(4) = 21.55
38  coeff(5) =-16.48
39  coeff(6) = 4.124
40  END IF
41  END IF
42 *
43 * Obtain the tidal energy factor from fifth-order polynomial fit.
44  y = log10(zeta)
45  efac2 = ((((coeff(6)*y + coeff(5))*y + coeff(4))*y + coeff(3))*y
46  & + coeff(2))*y + coeff(1)
47  efac2 = 10.0**efac2
48 *
49  RETURN
50 *
51  END