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efac3.f
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1  FUNCTION efac3(ZETA,ICASE)
2 *
3 *
4 * Tidal capture efficiency factor (l = 3).
5 * ----------------------------------------
6 *
7 * Fitting functions for the third 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),efac3
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) = -0.909
18  coeff(2) = 1.574
19  coeff(3) = 12.37
20  coeff(4) =-57.40
21  coeff(5) = 80.10
22  coeff(6) =-46.43
23  ELSE
24  IF (icase.EQ.2) THEN
25 * Polytropic index 2.
26  coeff(1) = -1.040
27  coeff(2) = -1.354
28  coeff(3) = 37.64
29  coeff(4) =-139.9
30  coeff(5) = 168.2
31  coeff(6) = -66.53
32  ELSE
33 * Polytropic index 3.
34  coeff(1) = -1.703
35  coeff(2) = 2.653
36  coeff(3) =-14.34
37  coeff(4) = 12.85
38  coeff(5) = -0.492
39  coeff(6) = -3.600
40  END IF
41  END IF
42 *
43 * Obtain the tidal energy factor from fourth-order polynomial fit.
44  y = log10(zeta)
45  efac3 = ((((coeff(6)*y + coeff(5))*y + coeff(4))*y + coeff(3))*y
46  & + coeff(2))*y + coeff(1)
47  efac3 = 10.0**efac3
48 *
49  RETURN
50 *
51  END