| 1 | #include "slalib.h"
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| 2 | #include "slamac.h"
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| 3 | float slaRvlsrk ( float r2000, float d2000 )
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| 4 | /*
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| 5 | ** - - - - - - - - - -
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| 6 | ** s l a R v l s r k
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| 7 | ** - - - - - - - - - -
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| 8 | **
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| 9 | ** Velocity component in a given direction due to the Sun's motion
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| 10 | ** with respect to an adopted kinematic Local Standard of Rest.
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| 11 | **
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| 12 | ** (single precision)
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| 13 | **
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| 14 | ** Given:
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| 15 | ** r2000,d2000 float J2000.0 mean RA,Dec (radians)
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| 16 | **
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| 17 | ** Result:
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| 18 | ** Component of "standard" solar motion in direction R2000,D2000 (km/s)
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| 19 | **
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| 20 | ** Sign convention:
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| 21 | ** The result is +ve when the Sun is receding from the given point on
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| 22 | ** the sky.
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| 23 | **
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| 24 | ** Note: The Local Standard of Rest used here is one of several
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| 25 | ** "kinematical" LSRs in common use. A kinematical LSR is the
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| 26 | ** mean standard of rest of specified star catalogues or stellar
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| 27 | ** populations. The Sun's motion with respect to a kinematical
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| 28 | ** LSR is known as the "standard" solar motion.
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| 29 | **
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| 30 | ** There is another sort of LSR, the "dynamical" LSR, which is a
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| 31 | ** point in the vicinity of the Sun which is in a circular orbit
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| 32 | ** around the Galactic centre. The Sun's motion with respect to
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| 33 | ** the dynamical LSR is called the "peculiar" solar motion. To
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| 34 | ** obtain a radial velocity correction with respect to the
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| 35 | ** dynamical LSR use the routine slaRvlsrd.
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| 36 | **
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| 37 | ** Reference: Delhaye (1965), in "Stars and Stellar Systems", vol 5, p73.
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| 38 | **
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| 39 | ** Called: slaCs2c, slaVdv
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| 40 | **
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| 41 | ** Last revision: 27 November 1994
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| 42 | **
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| 43 | ** Copyright P.T.Wallace. All rights reserved.
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| 44 | */
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| 45 | {
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| 46 | /*
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| 47 | **
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| 48 | ** Standard solar motion (from Methods of Experimental Physics, ed Meeks,
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| 49 | ** vol 12, part C, sec 6.1.5.2, p281):
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| 50 | **
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| 51 | ** 20 km/s towards RA 18h Dec +30d (1900).
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| 52 | **
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| 53 | ** The solar motion is expressed here in the form of a J2000.0
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| 54 | ** equatorial Cartesian vector:
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| 55 | **
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| 56 | ** va(1) = x = -speed*cos(ra)*cos(dec)
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| 57 | ** va(2) = y = -speed*sin(ra)*cos(dec)
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| 58 | ** va(3) = z = -speed*sin(dec)
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| 59 | */
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| 60 | static float va[3] = { -0.29000f, 17.31726f, -10.00141f };
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| 61 | float vb[3];
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| 62 |
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| 63 | /* Convert given J2000 RA,dec to x,y,z */
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| 64 | slaCs2c ( r2000, d2000, vb );
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| 65 |
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| 66 | /* Compute dot product with solar motion vector */
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| 67 | return slaVdv ( va, vb );
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| 68 | }
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