# The REASONS Survey: Resolved Millimeter Observations of a Large Debris Disk Around the Nearby F Star HD 170773

**Authors:** Aldo G. Sepulveda, Luca Matra, Grant M. Kennedy, Carlos del Burgo, Karin I. Oberg, David J. Wilner, Sebastian Marino, Mark Booth, John M. Carpenter, Claire L. Davies, William R. F. Dent, Steve Ertel, Jean-Francois Lestrade, Jonathan P. Marshall, Julien Milli, Mark C. Wyatt, Meredith A. MacGregor, Brenda C. Matthews  
**arXiv:** [1906.08797](https://arxiv.org/abs/1906.08797)  
**Date:** 2019-06-20  
**Summary page:** https://www.summarizepaper.com/en/paper/1906.08797v1/

## Key points

- Debris disks are extrasolar analogs to our own Kuiper Belt
- Detected around at least 17% of nearby Sun-like stars
- Using ALMA, the team obtained 1.3 mm observations of the debris disk around HD 170773
- Relatively large radius compared to most other millimeter-resolved belts around late A / early F type stars, with a width of 71 ± 4 au and a radius of 193+2−3 au
- HD 170773 is part of a group of four disks around A and F stars with radii larger than expected from the recently reported planetesimal belt radius - stellar luminosity relation.
- Two systems in this group are known to host directly imaged giant planets, which may point to a connection between large belts and the presence of long-period giant planets.
- Upper limits were set on the presence of CO and CN gas in the system, implying that exocomets that constitute this belt have CO and HCN ice mass fractions consistent with Solar System comets and other exocometary belts.
- These findings provide valuable insights into how planetary systems form and evolve over time, shedding light on our understanding of our own Solar System's history.

## Summary

The REASONS survey has revealed new insights into the morphology and dynamics of debris disks, which are extrasolar analogs to our own Kuiper Belt. These disks are detected around at least 17% of nearby Sun-like stars and encode information about their history, as well as that of any exoplanets within the system. Using ALMA, the team obtained 1.3 mm observations of the debris disk around the nearby F5V star HD 170773. They imaged the face-on ring and determined its fundamental parameters by forward-modeling the interferometric visibilities through a Markov Chain Monte Carlo approach. Their findings reveal a relatively large radius compared to most other millimeter-resolved belts around late A / early F type stars, with a width of 71 $\pm$ 4 au and a radius of 193$^{+2}_{-3}$ au. This makes HD 170773 part of a group of four disks around A and F stars with radii larger than expected from the recently reported planetesimal belt radius - stellar luminosity relation. Two of these systems are known to host directly imaged giant planets, which may point to a connection between large belts and the presence of long-period giant planets. In addition, upper limits were set on the presence of CO and CN gas in the system, implying that exocomets that constitute this belt have CO and HCN ice mass fractions consistent with Solar System comets and other exocometary belts. These findings provide valuable insights into how planetary systems form and evolve over time, shedding light on our understanding of our own Solar System's history.