ligo.em_bright.computeDiskMass

ligo.em_bright.computeDiskMass.compute_isco(chi_bh)

This function takes as input the aligned spin component of the BH and returns the innermost stable circular orbit radius normalized by the mass of the BH.

ligo.em_bright.computeDiskMass.max_mass_from_eosname(eosname)

ligo.em_bright.computeDiskMass.computeCompactness(M_ns, eosname='2H', max_mass=None)

Return the neutron star compactness as a function of mass and equation of state or radius

Parameters:

• M_ns (array_like) – Neutron star mass in solar masses

• eosname (str or interp1d) – Neutron star equation of state to be used

• max_mass (float) – Maximum mass of neutron star.

Returns:

Compactness, baryon mass and maximum neutron star mass in solar masses.

Return type:

[C_ns, m2_b, max_mass]

Notes

The radius and maximum mass of the neutron star is inferred based on the equation of state supplied. Max mass only needs to be supplied for EoS marginalization.

Examples

>>> computeCompactness(2.8)
[array(0.298), array(3.354), 2.834]
>>> computeDiskMass.computeCompactness(2.9, eosname='AP4')
[0.5, 0.0, 2.212]
>>> m_ns = np.array([1.1, 1.2, 1.3])
>>> computeDiskMass.computeCompactness(m_ns, eosname='AP4')
[array([0.141, 0.154, 0.167]), array([1.199, 1.318, 1.439]), 2.212]

ligo.em_bright.computeDiskMass.xi_implicit(xi, kappa, chi1, eta)

ligo.em_bright.computeDiskMass.computeDiskMass(m1, m2, chi1, chi2, eosname='2H', kerr=False, R_ns=None, max_mass=None)

This function computes the remnant disk mass after the coalescence using the equation (4) arXiv 1807.00011.

Parameters:

• m1 (array_like) – primary and secondary mass(es)

• m2 (array_like) – primary and secondary mass(es)

• chi1 (array_like) – primary and secondary spin(s)

• chi2 (array_like) – primary and secondary spin(s)

• eosname (str) – Name of the equation of state to be used. AP4 None when supplying R_ns.

• kerr (bool) – Supply to use the relativistic tidal parameter. See Fishbone (1971).

• R_ns (float) – Radius of the secondary in m, assuming it is a neutron star.

• max_mass (float) – Maximum mass of a neutron star. To be supplied if not supplying EoS.

Example

>>> computeDiskMass(5.0, 2.0, 0.99, 0.)
0.6321412881595185
>>> m1 = np.array([5., 6., 7.])
>>> m2 = np.array([1.0, 1.2, 1.6])
>>> chi1 = np.zeros(3)
>>> chi2 = np.zeros(3)
>>> computeDiskMass(m1, m2, chi1, chi2)
array([0.12833991, 0.05054819, 0.])
>>> computeDiskMass(m1, m2, chi1, chi2, eosname='AP4')
array([0.00851525, 0., 0.])
>>> max_mass = 3.0  # in m_sun
>>> r_ns = 15000.  # in meters
>>> computeDiskMass(m1, m2, chi1, chi2,
...                 R_ns=r_ns, max_mass=max_mass, eosname=None)
array([0.12265712, 0.04272054, 0.])
>>> # m1=2.0, m2=2.0 is a BNS event assuming 2H EOS
>>> # DiskMass == 1.0 is a ad hoc value assigned for BNS events
>>> masses_spins = np.array([2.0, 2.0, 0., 0.])
>>> computeDiskMass(masses_spins[0], masses_spins[1],
...                 masses_spins[2], masses_spins[3], eosname="2H")
1.0
>>> masses_spins = np.array([5.0, 2.0, 0.99, 0.])
>>> computeDiskMass(masses_spins[0], masses_spins[1],
...                 masses_spins[2], masses_spins[3], eosname="2H")
0.6321412881595185

Notes

The primary mass, by convention, is larger one. If arrays are supplied, m1, m2, chi1, chi1 should be of the same size.