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Function: mc_chirp()

void mc_chirp(float time, float latitude, float orientation, long *seed,
	      float *invMpc, float *c0, float *c1)

This routine makes a random chirp from a hypothetical distribution of Galactic binary neutron stars. The arguments are:

time: Input. The time of arrival of the chirp in sidereal seconds.
latitude: Input. The latitude of the detector in radians North.
orientation: Input. The orientation of the arm of the detector in radians counter clockwise from North.
seed: Input/Output. A random number seed for use in the Numerical Recipes random number generator ran1().
invMpc: Output. The effective distance of the chirp, i.e., the distance of the binary system if it were optimally oriented.
c0: Output. The cosine of the random phase of the chirp.
c1: Output. The sine of the random phase of the chirp.
The resulting chirp waveform is $h(t)=\texttt{invMpc}\times[\texttt{c0}\times h_c(t)+\texttt{c1}\times h_s(t)]$ where $h_c (t)$ is the cosine-phase chirp waveform and $h_s(t)$ is the sine-phase chirp waveform normalized to one megaparsec.

The hypothetical number of Galactic binary neutron star systems between the Galactocentric radii $R$ and $R+dR$, and between disk heights $z$ and $z+dz$, is taken to be

\begin{displaymath}
dN \propto R\,dR\,dz\,e^{-R^2/2R_0^2}\,e^{-\vert z\vert/h_z}
\end{displaymath} (12.7.286)

with $R_0=4.8\:\mbox{kpc}$ and $h_z=1\:\mbox{kpc}$. Only the disk population is considered in this calculation. The Galactocentric radius of the Sun is taken to be $R_\odot=8.5\:\mbox{kpc}$.

Author: Jolien Creighton, jolien@tapir.caltech.edu
Comments: The hypothetical distribution was adapted from the distribution used by S. J. Curran and D. R. Lorimer, Mon. Not. R. Astron. Soc. 276 347 (1995). The scale height is a guestimate. Very little is known about the actual distribution of Galactic neutron star binaries! The routine assumes that the arms of the detector are perpendicular; it is not suitable for the GEO-600 site because the opening angle is approximately $94^\circ$.


next up previous contents
Next: Example: inject program Up: Galactic Modelling Previous: Function: beam_pattern()   Contents
Bruce Allen 2000-11-19