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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 v_SSB)
| 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