# New millimeter CO observations of the gas-rich debris disks 49 Cet and HD 32297

**Authors:** Attila Moór, Quentin Kral, Péter Ábrahám, Ágnes Kóspál, Anne Dutrey, Emmanuel di Folco, A. Meredith Hughes, Attila Juhász, Ilaria Pascucci, Nicole Pawellek  
**arXiv:** [1908.09685](https://arxiv.org/abs/1908.09685)  
**Date:** 2019-08-26  
**Summary page:** https://www.summarizepaper.com/en/paper/1908.09685v1/

## Key points

- Recent study by Attila Moór et al. reveals new insights into CO gas presence at protoplanetary levels in gas-rich debris disks surrounding 49 Cet and HD 32297.
- High levels of $^{13}$CO and C$^{18}$O emissions detected using ALMA 7m-array, indicating CO content exceeding 0.01M$_\oplus$ in both systems.
- Efficient shielding mechanism protects CO molecules from stellar and interstellar ultraviolet photons.
- Researchers adapted secondary gas disk model to explain observed CO levels by considering carbon atom shielding and self-shielding of CO.
- Derived gas densities suggest coupling between dust and gas in HD 32297 disk, impacting dynamics of small grains due to gaseous component.
- Further investigation needed for 49 Cet to determine if coupling exists.
- Findings establish these objects as the first known representatives of shielded debris disks around young A-type stars, shedding light on complex interactions between gas and dust components, providing insights into formation and evolution processes.

## Summary

A recent study by Attila Moór et al. has revealed new insights into the presence of CO gas at protoplanetary levels in the gas-rich debris disks surrounding 49 Cet and HD 32297. Using the ALMA 7m-array, high levels of $^{13}$CO and C$^{18}$O emissions were detected in both systems, indicating a significant amount of CO content exceeding 0.01M$_\oplus$. This suggests a highly efficient shielding mechanism that protects CO molecules from stellar and interstellar ultraviolet photons. The researchers adapted a secondary gas disk model to consider carbon atom shielding and self-shielding of CO, successfully explaining the observed CO levels in both systems. The derived gas densities led to the conclusion that there is coupling between dust and gas in the HD 32297 disk, impacting the dynamics of small grains due to the gaseous component. Further investigation is needed for 49 Cet to determine if coupling exists. These findings align with previously identified debris disks with high CO content and establish these objects as the first known representatives of shielded debris disks. This study sheds light on complex interactions between gas and dust components within debris disks around young A-type stars, providing valuable insights into their formation and evolution processes.