rhotheta: Calculate the separation and position angle of a binary star

In astrolibR: Astronomy Users Library

Description

Calculate the separation and position angle of a binary star

Usage

rhotheta(p, t, e, a, i, omega, omega2, t2)

Arguments

p	period (scalar, year)
t	time of periastron passage (scalar, year)
e	orbit eccentricity (scalar between 0 and 1)
a	semi-major axis (scalar, arc second)
i	scalar, inclination
omega	node (scalar, degree)
omega2	longitude of periastron (scalar, degree)
t2	epoch of observation (scalar, year)

Details

This function will return the separation rho and position angle theta of a visual binary star derived from its orbital elements. The algorithm is from Meuss (1992; also 1998).

Value

An R list with two scalar elements: \

rho	separation (arcsec)
theta	position angle measured east of north (degree)

In case of errors, rho and theta are returned as -1.

Author(s)

Written, Sebastian Kohl, 2012.

R adaptation by Arnab Chakraborty June 2013

References

Meeus J., 1992, Astronomische Algorithmen, Barth. Meeus, J., 1998, “Astronomical Algorithms”, 2nd ed.

Examples

#  Find the position of Eta Coronae Borealis at the epoch 1980.0
#  Result:   rho=     0.411014    theta=       318.42307
rhotheta(41.623, 1934.008, 0.2763, 0.907, 59.025, 23.717, 219.907, 1980.0)

Example output

$rho
[1] 0.4110178

$theta
[1] 318.4243

astrolibR documentation built on May 2, 2019, 3:26 a.m.