helio_rv {astrolibR} | R Documentation |
Calculate the heliocentric radial velocity of a spectroscopic binary
helio_rv(hjd, t, p, v0, k, e, omega, maxiter=100)
hjd |
time of observation |
t |
time of periastron passage (maximum positive velocity for circular orbits), same time system as hjd |
p |
orbital period, same time system as hjd |
v0 |
systemic velocity |
k |
velocity semi-amplitude, same units as v0 |
e |
orbital eccentricity (default=0.0) |
omega |
longitude of periastron, in degrees (default=0.0, but must be specified for eccentric orbits |
maxiter |
maximum number of iterations to achieve 1e-8 convergence |
The user should ensure consistency with time and velocity systems being used (e.g. days and km/s). Generally, users should reduce large time values by subtracting a large constant offset, which may improve numerical accuracy.
status |
Iterations needed for convergence |
rv |
predicted heliocentric radial velocity for the date(s) specified by hjd, same units as v0 |
Written by Pierre Maxted ()CUOBS) 1994
R adaptation by Arnab Chakraborty June 2013
# What was the heliocentric radial velocity of the primary component of HU Tau # at 1730 UT 25 Oct 1994? # Result: -63.66 km/s jd <- juldate(c(94,10,25,17,30)) # obtain Geocentric julian date hjd <- helio_jd(jd, ten(04,38,16)*15., ten(20,41,05)) # convert to HJD helio_rv(hjd, 46487.5303, 2.0563056, -6.0, 59.3) # Plot two cycles of an eccentric orbit, e=0.6, omega=45 for both # components of a binary star phase <- seq(0.0,2.0,length=100) # generate 100 phase points plot(phase, helio_rv(phase, 0, 1, 0, 100, 0.6, 45)$rv, ylim=c(-100,150), pch=20) lines(phase, helio_rv(phase, 0, 1, 0, 50, 0.6, 45+180)$rv)