# Spectroscopic Orbits of Subsystems in Multiple Stars. X (Summary)

**Authors:** Andrei Tokovinin  
**arXiv:** [2304.02706](https://arxiv.org/abs/2304.02706)  
**Date:** 2023-04-05  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.02706v1/

## Key points

- This paper summarizes a program of spectroscopic monitoring of nearby solar-type stellar hierarchical systems using the CHIRON echelle spectrograph at the 1.5 m telescope since 2015.
- The program has resulted in ten papers containing 102 spectroscopic orbits, which contribute significantly to our understanding of periods and eccentricities in these systems.
- The results provide valuable input for studying their formation and early evolution.
- In addition to the published orbits, this paper presents radial velocities of an additional 91 targets without CHIRON orbits, which are members of wide physical pairs.
- Ground-based monitoring gives a more accurate and complete picture of nearby hierarchies than Gaia as some NSS orbits have reduced velocity amplitudes or other problems.
- The distribution of inner periods in hierarchical systems is non-monotonic with a shallow minimum in the 30-100 days bin and a strong excess at shorter periods compared to simple binaries in the field.
- The period-eccentricity diagram updated by this survey, recent literature, and Gaia displays an interesting structure.
- Monitoring selected objects from the ground remains a classical approach for finding periods, mass ratios, and orbital eccentricities; it is now complemented by large spectroscopic surveys such as GALAH and LAMOST as well as space missions like Gaia.
- Current NSS suffers from incompleteness and selection bias resulting in a non-negligible fraction of wrong orbits.

## Summary

This paper provides a summary of a large program of spectroscopic monitoring of nearby solar-type stellar hierarchical systems using the CHIRON echelle spectrograph at the 1.5 m telescope. The program has been ongoing since 2015 and has resulted in ten papers containing 102 spectroscopic orbits, which significantly contribute to our understanding of periods and eccentricities in these systems. The results also provide valuable input for studying their formation and early evolution. In addition to the published orbits, this paper presents radial velocities of an additional 91 targets without CHIRON orbits, which are members of wide physical pairs. The authors compare their results to the recent Gaia Non-Single Star (NSS) catalog, which provides orbital periods for about one third of the CHIRON sample. They find that ground-based monitoring gives a more accurate and complete picture of nearby hierarchies than Gaia, as some NSS orbits have reduced velocity amplitudes or other problems. The distribution of inner periods in hierarchical systems is non-monotonic, with a shallow minimum in the 30-100 days bin and a strong excess at shorter periods compared to simple binaries in the field. The period-eccentricity diagram updated by this survey, recent literature, and Gaia displays an interesting structure. The authors note that while monitoring selected objects from the ground remains a classical approach for finding periods, mass ratios, and orbital eccentricities; it is now complemented by large spectroscopic surveys such as GALAH and LAMOST as well as space missions like Gaia. However, they highlight that current NSS suffers from incompleteness and selection bias resulting in a non-negligible fraction of wrong orbits. Overall, this paper provides valuable insights into our understanding of multiple star systems' dynamics through long-term ground-based monitoring programs such as CHIRON. It highlights both strengths and weaknesses associated with different approaches to studying these systems and emphasizes the importance of continued efforts towards improving our understanding of their formation and evolution.