WIYN Open Cluster Study. XXXVI. Spectroscopic Binary Orbits in NGC 188

TL;DR

This study provides detailed spectroscopic binary orbits for 98 stars in the old open cluster NGC 188, revealing the properties and dynamics of binary systems that influence cluster evolution.

Contribution

It presents the first comprehensive set of binary orbits in NGC 188, including new orbital solutions and identification of notable binary systems, expanding understanding of binary populations in old clusters.

Findings

98 binary orbits determined, mostly cluster members

Binary periods range from days to thousands of days

Identification of special binaries like blue straggler pairs

Abstract

We present 98 spectroscopic binary orbits resulting from our ongoing radial-velocity survey of the old (7 Gyr) open cluster NGC 188. All but 13 are high-probability cluster members based on both radial-velocity and proper-motion membership analyses. Fifteen of these member binaries are double lined. Our stellar sample spans a magnitude range of 10.8 <=V<= 16.5 (1.14-0.92 Msun) and extends spatially to 17 pc (~13 core radii). All of our binary orbits have periods ranging from a few days to on the order of 10^3 days, and thus are hard binaries that dynamically power the cluster. For each binary, we present the orbital solutions and place constraints on the component masses. Additionally, we discuss a few binaries of note from our sample, identifying a likely blue straggler-blue straggler binary system (7782), a double-lined binary with a secondary star which is under-luminous for its mass (5080), two potential eclipsing binaries (4705 and 5762), and two binaries which are likely members of a quadruple system (5015a and 5015b).