def calculatefx(fov=1000.0, plam=7.7e4, dlam=0.0):
# fov: diameter of field-of-view [km]
# plam: Molecular lifetime of parent [km], if molecule is parent use plam = 0
# dlam: Molecular lifetime of daughter [km]
if fov == 0 or plam == 0.0: return 0.0
x = 0.5 * fov / plam
if dlam == 0.0:
# Parent molecule
gx = 1.0 / x
gx += -special.k1(x)
gx += np.pi / 2.0 - special.iti0k0(x)[1]
fx = x * gx
else:
# Daughter molecule
u2 = plam / dlam
if u2 == 1.0: u2 = 1.001
gx = 1.0 / (u2 * x) - 1.0 / x
gx += -special.k1(u2 * x) + special.k1(x)
gx += -special.iti0k0(u2 * x)[1] + special.iti0k0(x)[1]
fx = (u2 * x / (1.0 - u2)) * gx
#Endelse
return fx
def _iK0(self, x):
"""Integral of the modified Bessel function of 2nd kind, 0th order."""
if not scipy:
raise AstropyWarning('scipy is not present, cannot continue.')
return special.iti0k0(x.decompose().value)[1]
def _iK0(self, x):
"""Integral of the modified Bessel function of 2nd kind, 0th order."""
if not scipy:
raise RequiredPackageUnavailable('scipy')
return special.iti0k0(x)[1]
def i_frac_0(x, su):
# x = np.array([vals])
return 0.5 / su * iti0k0(x * su)[1]