# Periodic Spectral Modulations Arise from Non-random Spacing of Spectral Absorption Lines

## TL;DR

The paper explains that certain spectral modulations previously attributed to extraterrestrial signals are actually caused by the non-random spacing of spectral absorption lines, especially evident in synthetic solar spectra.

## Contribution

It demonstrates that periodic spectral modulations are due to intrinsic spectral line patterns, not extraterrestrial signals, clarifying the origin of these features.

## Key findings

- Spectral modulations are caused by non-random absorption line spacing.
- Synthetic spectra clearly show these modulations without noise.
- Previous claims of extraterrestrial signals are explained by spectral line patterns.

## Abstract

In recent publications, Borra (2013); Borra & Trottier (2016); Borra (2017) claimed the discovery of ultra-short ($10^{-12}\,$s) optical pulses originating from stars and galaxies, asserted to be sent by extraterrestrial intelligence. I show that these signals are not astrophysical or instrumental in nature, but originate from the non-random spacings of spectral absorption lines. They can be shown to arise in their clearest form in synthetic solar spectra, as these do not suffer from noise.