# HI emission from the red giant Y CVn with the VLA and FAST

## TL;DR

This study uses VLA and FAST observations to analyze the HI emission from the circumstellar shell of the red giant Y CVn, revealing a detached shell structure influenced by stellar motion and interstellar interaction.

## Contribution

It presents a detailed spectral map of Y CVn's HI emission and demonstrates how FAST can enhance understanding of circumstellar shell structures.

## Key findings

- HI emission consistent with a detached shell model
- Distortion aligned with star's motion improves spectral fit
- Simulations show FAST's potential for detailed shell studies

## Abstract

Imaging studies with the VLA have revealed HI emission associated with the extended circumstellar shells of red giants. We analyse the spectral map obtained on Y CVn, a J-type carbon star on the AGB. The HI line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium. We reproduce the spectral map by introducing a distortion along a direction corresponding to the star's motion in space. We then use this fitting to simulate observations expected from the FAST radiotelescope, and discuss its potential for improving ourdescription of the outer regions of circumstellar shells.