# Absorption of Gravitational Waves from Distant Sources

## TL;DR

This paper calculates how gravitational waves are absorbed by ionized gas, finding that absorption decreases at lower frequencies and is negligible for nanohertz waves detectable via pulsar timing.

## Contribution

It provides a detailed calculation of gravitational wave absorption through inverse bremsstrahlung and shows that ionized gas does not significantly block low-frequency gravitational waves.

## Key findings

- Absorption increases as frequency decreases, following a $
u^{-3}$ trend.
- Stimulated emission nearly cancels absorption, reducing overall attenuation.
- Ionized gas in galaxy clusters does not hinder detection of nanohertz gravitational waves.

## Abstract

The rate of gravitational wave absorption by inverse bremsstrahlung is calculated. It increases with decreasing frequency $\nu$ as $\nu^{-3}$. Nevertheless, because of the near cancellation of absorption by stimulated emission, the ionized gas in galaxy clusters does not block gravitational waves at the nanohertz frequencies that may be detected by the use of pulsar timing observations.