SLA_PM

Proper Motion

ACTION:
Apply corrections for proper motion to a star [α, δ].
CALL:
CALL sla_PM (R0, D0, PR, PD, PX, RV, EP0, EP1, R1, D1)
GIVEN:

R0,D0

D

[α, δ] at epoch EP0 (radians)

PR,PD

D

proper motions: rate of change of [α, δ] (radians per year)

PX

D

parallax (arcsec)

RV

D

radial velocity (km s−1, +ve if receding)

EP0

D

start epoch in years (e.g. Julian epoch)

EP1

D

end epoch in years (same system as EP0)


RETURNED:

R1,D1

D

[α, δ] at epoch EP1 (radians)


NOTES:
(1)
The α proper motions are α̇ rather than α̇ cos δ, and are in the same coordinate system as R0,D0.
(2)
If the available proper motions are pre-FK5 they will be per tropical year rather than per Julian year, and so the epochs must both be Besselian rather than Julian. In such cases, a scaling factor of 365.2422D0/365.25D0 should be applied to the radial velocity before use also.
REFERENCES:
(1)
1984 Astronomical Almanac, pp B39-B41.
(2)
Lederle & Schwan, 1984. Astr. Astrophys. 134, 1-6.