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annihilation_polygon.py
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annihilation_polygon.py
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import numpy as np
from astropy import units as u
from astropy import constants as const
def GammaGammaAbsorption(frequency_ph, E_abs, n_abs, R):
"""
Gamma-gamma absorption due to the soft photon.
:param frequency_ph: radiative photon frequency [Hz]
:param E_abs: soft photon energy [eV]
:param n_abs: soft photon number density distribution [eV-1 cm-3]
:param R: size of the region [cm]
:return: optical depth
"""
pi = np.pi
R = R.to(u.cm).value
E_ph = (const.h.cgs*frequency_ph).to(u.eV).value
E_abs = E_abs.to(u.eV).value
n_abs = n_abs.to(u.eV**-1 * u.cm**-3).value
epsilon_ph = E_ph / (const.m_e.cgs * const.c.cgs**2).to(u.eV).value
epsilon_abs = E_abs / (const.m_e.cgs * const.c.cgs**2).to(u.eV).value
n_abs_epsilon = n_abs * (const.m_e.cgs * const.c.cgs**2).to(u.eV).value
r_e = (2.8179e-13*u.cm).value
dtau = (np.zeros(len(epsilon_ph)) * u.cm**-1).value
for i in range(len(epsilon_ph)):
temp = 0
for j in range(len(epsilon_abs)-1):
if epsilon_abs[j] < 1/epsilon_ph[i]:
continue
else:
s0 = epsilon_abs[j]*epsilon_ph[i]
phibar = np.select([s0 >= 3, s0 >= 0.1, s0 < 0.1],
[2 * s0 * (np.log(4 * s0) - 2) + np.log(4 * s0) * (np.log(4 * s0) - 2) - (
pi ** 2 - 9) / 3 + (np.log(4 * s0) + 8 / 9) / s0,
2.2151050 - 5.6254697 * s0 + 4.2940799 * s0 ** 2 - 0.98922329 * s0 ** 3 + 0.095506958 * s0 ** 4,
4 / 3 * (s0 - 1) ** (3 / 2) + 6 / 5 * (s0 - 1) ** (5 / 2) - 253 / 70 * (
s0 - 1) ** (7 / 2)])
temp += n_abs_epsilon[j] / epsilon_abs[j]**2 * phibar * (epsilon_abs[j+1] - epsilon_abs[j])
dtau[i] = pi * r_e**2 / epsilon_ph[i]**2 * temp
tau = dtau * R
return tau