SuperNOVAS v1.5
The NOVAS C library, made better
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spectral.c File Reference

Various spectral / velocity related functions. More...

Functions

double novas_lsr_to_ssb_vel (double epoch, double ra, double dec, double vLSR)
 Returns a Solar System Baricentric (SSB) radial velocity for a radial velocity that is referenced to the Local Standard of Rest (LSR).
 
double novas_ssb_to_lsr_vel (double epoch, double ra, double dec, double vLSR)
 Returns a radial-velocity referenced to the Local Standard of Rest (LSR) for a given Solar-System Barycentric (SSB) radial velocity.
 
double novas_v2z (double vel)
 Converts a radial recession velocity to a redshift value (z = Δλ / λrest).
 
double novas_z2v (double z)
 Converts a redshift value (z = Δλ / λrest) to a radial velocity (i.e.
 
double novas_z_add (double z1, double z2)
 Compounds two redshift corrections, e.g.
 
double novas_z_inv (double z)
 Returns the inverse of a redshift value, that is the redshift for a body moving with the same velocity as the original but in the opposite direction.
 
int rad_vel (const object *restrict source, const double *restrict pos_src, const double *vel_src, const double *vel_obs, double d_obs_geo, double d_obs_sun, double d_src_sun, double *restrict rv)
 Predicts the radial velocity of the observed object as it would be measured by spectroscopic means.
 
double rad_vel2 (const object *restrict source, const double *pos_emit, const double *vel_src, const double *pos_det, const double *vel_obs, double d_obs_geo, double d_obs_sun, double d_src_sun)
 Predicts the radial velocity of the observed object as it would be measured by spectroscopic means.
 
double redshift_vrad (double vrad, double z)
 Applies an incremental redshift correction to a radial velocity.
 
double unredshift_vrad (double vrad, double z)
 Undoes an incremental redshift correction that was applied to radial velocity.
 

Detailed Description

Various spectral / velocity related functions.

SuperNOVAS velocities are always calculated with relativistic corrections for motion (both source and observer) and gravitational effects (both at the source and at the observer), so they represent spectroscopically accurate values.

As such radial velocity measures are always specroscopically precise, and follow the relation:

λobs / λrest = (1 + z) = sqrt((1 + β) / (1 - β)),

where β = vrad / c.

Date
Created on Mar 5, 2025
Author
Attila Kovacs and G. Kaplan
See also
target.c, frames.c