A systematic method to identify runaways from star clusters produced from single-binary interactions

A case study of M67

¹ Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Chile
² Department of Astrophysics, American Museum of Natural History, Central Park West and 79th Street, New York, NY 10024, USA
³ Instituto Profesional Dr. Virginio Gómez, Arturo Prat 196, 4070298 Concepción, Bío Bío, Chile
⁴ David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
⁵ Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA
⁶ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching bei München, Germany
⁷ Physics and Astronomy Department, Johns Hopkins University, Baltimore, MD 21218, USA
⁸ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy Northwestern University, 1800 Sherman Ave, Evanston, IL 60201, USA
⁹ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
¹⁰ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

^★ Corresponding author: aherrera2017@udec.cl

Received: 7 August 2024
Accepted: 24 March 2025

Abstract

Context. One hypothesis for runaway stars (RSs) is that they are ejected from star clusters with high velocities relative to the cluster center-of-mass motion. There are two competing mechanisms for their production: supernova-based ejections in binaries, where one companion explodes, leaves no remnant, and launches the other companion at the instantaneous orbital velocity, and the disintegration of triples (or higher-order multiples), which produces a recoiled runaway binary (RB) and an RS.

Aims. We search for RS candidates using data from the Gaia DR3 survey with a focus on triple disintegration since in this case the product is always a binary and a single star that should be moving in opposite directions.

Methods. We created a systematic methodology to look for candidate RS-RB runaway pairs produced from the disintegration of bound three-body systems formed from single-binary interactions based on momentum conservation and causality. The method we use is general and can be applied to any cluster with a 5D kinematic data set. We used our criteria to search for these pairs in a 150 pc circular field of view surrounding the open cluster M67, which we used as a benchmark cluster to test the robustness of our method.

Results. Our results reveal only one RS-RB pair that is consistent with all of our selection criteria out of an initial sample of 10⁸ pairs.