Function: make_filters()

0 void make_filters(float m1, float m2, float *ch1, float *ch2, float fstart, int n, float srate, int *filled, float *t_coal, int err_cd_sprs, int order)
This function is an even more stripped down chirp generator, which fills a pair of arrays with waveforms for an inspiraling binary. The two chirps differ in phase by $\pi/2$ radians and are given by Eqs.() and (). This routine assumes spinless masses, and computes a chirp with phase corrections up to a specified post-Newtonian order.

The arguments are:

m1: Input. The mass of body-1 in solar masses.

m2: Input. The mass of body-2 in solar masses.

ch1: Output. Upon return, ch1[0..filled-1] contains the 0-phase chirp. The remaining array elements ch1[filled..n-1] are set to zero.

ch2: Output. Upon return, ch2[0..filled-1] contains the $\pi/2$-phase chirp. The remaining array elements ch2[filled..n-1] are set to zero.

fstart: Input. The starting gravity-wave frequency of the chirp in Hz. Note: this is twice the orbital frequency!

n: Input. The length of the arrays ch1[] and ch2[].

srate: Input. The sample rate, in Hz. This is $1/\Delta t$ where $\Delta t$ is the time interval between successive entries in the ch1[] and ch2[] arrays.

filled: Output. The number of of time steps actually computed, before the chirp calculation was terminated, or until the arrays were filled (hence ${\tt filled} \le {\tt n}$). Thus, on return, only the array elements ch1[0..filled-1] and ch2[0..filled-1] are contain the chirp; the remaining array elements are zero-padded.

t_coal: Output. The time to coalescence measured from the first point output, in ch*[0].

err_cd_sprs: Input. Error code suppression. This integer specifies the level of disaster encountered in the computation of the chirp for which the user will be explicitly warned with a printed message. Set to 0: prints all the termination messages. Set to 4000: suppresses all but a few messages which are harbingers of true disaster. (See identical argument in chirp_filters().

order: Input. The order of the post-Newtonian approximation. This ranges from 0 (quadrupole approximation) up to 5 (2.5 post-Newtonian order). Setting order=4 gives second post-Newtonian chirps. Technicaly, order is the power in $(v/c)$ past the quadrupole approximation to which the post-Newtonian expansion is taken.

This routine assumes that you have already allocated storage arrays for the chirps. Note that the coalescence time may be much later than the last non-zero entry written into the ch1[] and ch2[] arrays.

Author: Bruce Allen, ballen@dirac.phys.uwm.edu

Comments: None.