# Extreme radio-wave scattering associated with hot stars

## TL;DR

This study links extreme radio-wave scattering to hot stars, revealing ionized gas structures around them, similar to cometary knots in planetary nebulae, with implications for circumstellar matter and star evolution.

## Contribution

It demonstrates the association between radio scintillation and hot stars, identifying ionized gas structures at specific distances and velocities, and suggests molecular clumps are common around stars regardless of their evolutionary stage.

## Key findings

- Ionized gas responsible for scattering is up to 1.75pc from stars.
- Plasma structures exhibit azimuthal velocities up to 9.7 km/s.
- Molecular clumps are ubiquitous and contain mass comparable to the star.

## Abstract

We use data on extreme radio scintillation to demonstrate that this phenomenon is associated with hot stars in the solar neighbourhood. The ionized gas responsible for the scattering is found at distances up to 1.75pc from the host star, and on average must comprise 1.E5 distinct structures per star. We detect azimuthal velocities of the plasma, relative to the host star, up to 9.7 km/s, consistent with warm gas expanding at the sound speed. The circumstellar plasma structures that we infer are similar in several respects to the cometary knots seen in the Helix, and in other planetary nebulae. There the ionized gas appears as a skin around tiny molecular clumps. Our analysis suggests that molecular clumps are ubiquitous circumstellar features, unrelated to the evolutionary state of the star. The total mass in such clumps is comparable to the stellar mass.