Refraction-dependent kinematic shift of spectral lines

W T Chyla

doi:10.1140/epjp/i2015-15078-4

Abstract

If a luminous source moves with respect to the medium in which it is embedded, the kinematic shift of spectral lines depends both on the relative velocity and on the (relativistic) index of refraction of the medium. This effect is frequency-dependent, which makes it distinguishable from the cosmological redshift, the gravitational redshift and the regular Doppler shift in vacuum, which are all achromatic. The refraction-dependent shift of spectral lines is considered in more detail in the case of Ia supernovae, where the thermally generated electron-positron plasma ball, which expands with relativistic speeds, constitutes the refractive medium; it turns out that the discussed effect is relatively small at the UV and visible frequencies, but it can be significantly larger at longer wavelengths (the IR band). Other examples are given in optics and in other situations, where the refraction-dependent kinematic shift of frequency can be of significance.

Highlights

Spectral shifts of luminous astronomical objects can be affected by a number of phenomena
These include the cosmological redshift, gravity and the Doppler shift due to relative motion of the source of radiation and the observer: orbital motion of the terrestrial observer, peculiar motion of stars, orbital motion of stars in a galaxy, relative motion of galaxies, relativistic motion of luminous baryonic clouds ejected in stellar explosions
The magnitude of the refraction-dependent contribution zm to the value of zobs in the crucial region of zobs > 0.1 in the visible band is relatively small, similar to the uncertainty associated with the peculiar motion of the luminous source; the refraction-dependent correction can be significant for spectral lines in the IR band

Summary

Introduction

Spectral shifts of luminous astronomical objects can be affected by a number of phenomena These include the cosmological redshift, gravity and the Doppler shift due to relative motion of the source of radiation and the observer: orbital motion of the terrestrial observer, peculiar (random) motion of stars, orbital motion of stars in a galaxy, relative motion of galaxies, relativistic motion of luminous baryonic clouds ejected in stellar explosions. We consider the kinematic shift of spectral lines due to relative motion of the source of radiation and the refractive medium in which it is embedded. One example of such a situation is the light wave that escapes from the plasma ball spreading with relativistic speeds due to explosion of a supernova. A brief summary and a discussion of other situations, where the refraction-dependent kinematic shift of frequency can be of significance, conclude this paper

Refraction-dependent kinematic shift of frequency

Summary and discussion