# A likely flyby of binary protostar Z CMa caught in action

**Authors:** Ruobing Dong, Hauyu Baobab Liu, Nicolas Cuello, Christophe Pinte, Peter Abraham, Eduard Vorobyov, Jun Hashimoto, Agnes Kospal, Eugene Chiang, Michihiro Takami, Lei Chen, Michael Dunham, Misato Fukagawa, Joel Green, Yasuhiro Hasegawa, Thomas Henning, Yaroslav Pavlyuchenkov, Tae-Soo Pyo, Motohide Tamura  
**arXiv:** [2201.05617](https://arxiv.org/abs/2201.05617)  
**Date:** 2022-01-14  
**Summary page:** https://www.summarizepaper.com/en/paper/2201.05617v1/

## Key points

- A study reports on the discovery of a likely flyby event between young stellar objects in star-forming clusters
- The event is expected to significantly perturb circumstellar disks
- ALMA and JVLA observations towards the binary protostar Z CMa revealed a point source located ~4700 au from the binary at both millimeter and centimeter wavelengths
- This point source is situated along the extension of a ~2000 au streamer structure previously found in scattered light imaging and its counterpart in dust and gas emission was also newly identified
- Comparison with simulations showed signposts of a rare flyby event in action
- Z CMa is classified as a "double burster," as both binary components undergo accretion outbursts that may be facilitated by perturbations to the host disk caused by flybys
- The findings provide direct observational evidence for close encounters between young stellar objects that can dramatically affect their circumstellar disks, supporting previous numerical simulations of star formation.

## Summary

The study reports on the discovery of a likely flyby event between young stellar objects in star-forming clusters, which is expected to significantly perturb circumstellar disks. Sub-0".1 resolution Atacama Large Millimeter Array (ALMA) and Jansky Very Large Array (JVLA) observations towards the million-year-old binary protostar Z CMa revealed a point source located ~4700 au from the binary at both millimeter and centimeter wavelengths. This point source is situated along the extension of a ~2000 au streamer structure previously found in scattered light imaging and its counterpart in dust and gas emission was also newly identified. Comparison with simulations showed signposts of a rare flyby event in action. Z CMa is classified as a "double burster," as both binary components undergo accretion outbursts that may be facilitated by perturbations to the host disk caused by flybys. The findings provide direct observational evidence for close encounters between young stellar objects that can dramatically affect their circumstellar disks, supporting previous numerical simulations of star formation.