chirptime.py: Fix the overestimate of the final black hole spin PR 2023

gstlal-inspiral/python/chirptime.py

@@ -116,11 +116,8 @@ def mergetime(M):
 def overestimate_j_from_chi(chi):
 	"""
 	Overestimate final black hole spin
-	formula is roughly based on
-	Tichy and Marronetti Physical Review D 78 081501 (2008)
-	(don't allow j >= 1 ... truncate at 0.998)
 	"""
-	return max(0.686 + 0.15 * chi, chi, 0.998)
+	return min(max(lalsim.SimIMREOBFinalMassSpin(1, 1, [0, 0, chi], [0, 0, chi], lalsim.GetApproximantFromString('SEOBNRv2'))[2], abs(chi)), 0.998)
 
 def imr_time(f, m1, m2, j1, j2, f_max = None):
 	"""