Given a pair of masses (or other equivalent parameters) compute related chirp parameters. More...

Prototypes
void	LALInspiralParameterCalc (LALStatus status, InspiralTemplate params)

int	XLALInspiralParameterCalc (InspiralTemplate *params)

Detailed Description

Given a pair of masses (or other equivalent parameters) compute related chirp parameters.

Author: Sathyaprakash, B. S.

Prototypes

XLALInspiralParameterCalc()

params: Input/Output, given a pair of binary parameters and a lower frequency cutoff, other equivalent parameters are computed by this function.

Description

The code takes as its input params->fLower in Hz and a pair of masses (in units of \(M_\odot\)) or chirptimes (in seconds measured from params->fLower) and computes all the other {mass} parameters in the params structure. Users choice of input pair of {masses} should be specified by appropriately setting the variable params->massChoice as described in the Table below:

Table I. For a given `params->massChoice` in column 1 the user should specify the parameters as in column 2, in units as in column 3. Column 4 gives the conventional meaning of the parameters. Chirp times are measured from a lower frequency cutoff given in `params->fLower.`
`params->massChoice`	User should set	in units	which means
m1Andm2	(`mass1, mass2`)	\((M_\odot, M_\odot)\)	\((m_1,m_2)\)
totalMassAndEta	(`totalmass, eta`)	\((M_\odot, 0 < \eta \le 1/4)\)	\((m, \eta)\)
totalMassAndMu	(`totalmass, mu`)	\((M_\odot, M_\odot)\)	\((m, \mu)\)
t02	(`t0, t2`)	(sec, sec)	\((\tau_0, \tau_2)\)
t03	(`t0, t3`)	(sec, sec)	\((\tau_0, \tau_3)\)
t04	(`t0, t4`)	(sec, sec)	\((\tau_0, \tau_4)\)

If massChoice is not set properly an error condition will occur and the function is aborted with status code defined by LALINSPIRALH_EMASSCHOICE in LALInspiral.h. In the above list \(m_{1}\) and \(m_{2}\) are the masses of the two compact objects, \(m=m_{1}+m_{2}\) is the total mass, \(\eta=m_{1}m_{2}/(m_{1}+m_{2})^{2}\) is the symmetric mass ratio, \(\mu=m_{1}m_{2}/(m_{1}+m_{2})\) is the reduced mass and \(\tau\)'s are the chirptimes defined in terms of \(f_{a}\)=fLower by:

\begin{eqnarray} \tau_{0} = \frac{5}{256 \eta m^{5/3} (\pi f_{a})^{8/3}}, \ \ \ \tau_{2} = \frac{(3715 + 4620 \eta)}{64512 \eta m (\pi f_{a})^{2}}, \ \ \ \tau_{3} = \frac{\pi}{8 \eta m^{2/3} (\pi f_{a})^{5/3}} \\ \tau_{4} = \frac{5}{128 \eta m^{1/3} (\pi f_{a})^{4/3}} \left[ \frac{3058673}{1016064} + \frac{5429}{1008} \eta + \frac{617}{144} \eta^{2} \right],\ \ \ \tau_5 = \frac {5}{256\eta f_a} \left (\frac {7729}{252} + \eta \right ). \end{eqnarray}

%% Beyond 2.5 PN order, chirp times do not have an %% explicit expression in terms of the masses and \(f_a.\) Whichever pair of parameters is given to the function as an input, the function calculates the rest. Apart from the various masses and chirptimes the function also calculates the chirp mass \(\mathcal{M}=(\mu^{3} m^{2})^{1/5}\) and the total chirp time \(\tau_C\) consistent with the approximation chosen:

Table II: \(t_C\) will be set according to the PN order chosen in `params->approximant.`
	Newtonian	onePN	onePointFivePN	twoPN	twoPointFivePN
\(\tau_C\)	\(\tau_0\)	\(\tau_0 + \tau_2\)	\(\tau_0 + \tau_2-\tau_3\)	\(\tau_0 + \tau_2-\tau_3 + \tau_4\)	\(\tau_0 + \tau_2-\tau_3 + \tau_4 - \tau_5\)

Algorithm

Root finding by bisection method is used to solve for mass ratio \(\eta\) when chirptimes \((\tau_0,\, \tau_2)\) or \((\tau_0,\, \tau_4)\) is input.

Uses

When appropriate this function calls: XLALDBisectionFindRoot() XLALEtaTau02() XLALEtaTau04()

Notes

Definition in file LALInspiralParameterCalc.c.

Go to the source code of this file.

Function Documentation

◆ LALInspiralParameterCalc()

void LALInspiralParameterCalc	(	LALStatus *	status,
		InspiralTemplate *	params
	)

Definition at line 117 of file LALInspiralParameterCalc.c.

◆ XLALInspiralParameterCalc()

int XLALInspiralParameterCalc ( InspiralTemplate * params )

Definition at line 136 of file LALInspiralParameterCalc.c.