Identifying Hierarchically Triple Star Systems with Gaia DR3 and LAMOST

TL;DR

This study identifies 23 hierarchical triple star systems using Gaia DR3 and LAMOST data, with detailed orbital analysis for two triples, highlighting spectroscopic methods' effectiveness for short-period triples.

Contribution

The paper presents the first large sample of spectroscopically confirmed hierarchical triples from Gaia and LAMOST, including detailed orbital parameters for two systems.

Findings

23 triple systems identified, 18 are new discoveries.

Detection efficiency is highest for inner periods under 10 days.

Spectroscopic methods are effective for short-period triple detection.

Abstract

Triple star systems are critical for understanding stellar dynamics and compact objects in astrophysics, yet confirmed hierarchical triples identified via spectroscopy remain limited. In this study, we identified 23 triple systems by cross-matching the Gaia DR3 non-single star catalog with LAMOST DR10 spectroscopic data; 18 of them are new discoveries. For two well-observed triples, we performed radial velocity curve fitting and light curve analysis to determine their orbital parameters, with inner and outer periods of 1.26 days and 656 days for one triple, and 3.42 days and 422 days for the other. We compared the results with other studies. We also analyzed the radial velocities (RVs) of these 23 triples, revealing a range of $V$ from approximately 40~km~s$^{-1}$ to 210~km~s$^{-1}$. Due to spectral resolution and detection limitations, velocity differences below 45~km~s$^{-1}$ in binaries and below 90~km~s$^{-1}$ in the inner binaries of triple systems are challenging to detect. Consequently, our detection range for inner orbital periods is restricted to 0.2--20 days, with the highest efficiency for periods under 10 days. These findings underscore the advantage of spectroscopic observations for identifying triple systems with short inner orbital periods.