Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Beyond OCCAM: Measuring Optical Neutron Capture Abundances of Open Cluster Stars

Natalie Myers, Sarah Loebman, Henrique Reggiani, Peter Frinchaboy

TL;DR

This study addresses calibrating Milky Way age-dating through neutron-capture abundances in open clusters. It employs high-resolution optical spectroscopy from Keck I/HIRES on cluster members identified by the OCCAM survey, extending chemical clocks beyond light elements by measuring s-process elements (Ba, Ce, La, Y, Mo, Zr) across seven distant clusters and planning r-process measurements (e.g., Eu). The findings reveal a non-linear increase of neutron-capture abundances with metallicity, with Mo and Zr showing shallower trends, demonstrating the feasibility and value of incorporating heavy elements into Galactic chemical evolution studies. The work enhances age-dating capabilities for stellar populations and informs models of Galactic enrichment by providing a broader, optically-derived element census complementary to infrared data.

Abstract

Open clusters have long been used to determine ages of stars, as well as calibrate stellar evolution models and other methods of age-dating stellar groups, e.g., gyrochronology, asteroseismology, and chemical clocks. In this work, we have obtained new high-resolution (R $\ge$ 50,000), high-S/N, optical data for 3+ stellar members in open clusters, using Keck/HIRES, with membership derived from the Open Cluster Chemical Abundances and Mapping (OCCAM) survey. From these new Keck/HIRES data, we have derived neutron capture abundances for stars in seven distant outer Galaxy open cluster

Beyond OCCAM: Measuring Optical Neutron Capture Abundances of Open Cluster Stars

TL;DR

This study addresses calibrating Milky Way age-dating through neutron-capture abundances in open clusters. It employs high-resolution optical spectroscopy from Keck I/HIRES on cluster members identified by the OCCAM survey, extending chemical clocks beyond light elements by measuring s-process elements (Ba, Ce, La, Y, Mo, Zr) across seven distant clusters and planning r-process measurements (e.g., Eu). The findings reveal a non-linear increase of neutron-capture abundances with metallicity, with Mo and Zr showing shallower trends, demonstrating the feasibility and value of incorporating heavy elements into Galactic chemical evolution studies. The work enhances age-dating capabilities for stellar populations and informs models of Galactic enrichment by providing a broader, optically-derived element census complementary to infrared data.

Abstract

Open clusters have long been used to determine ages of stars, as well as calibrate stellar evolution models and other methods of age-dating stellar groups, e.g., gyrochronology, asteroseismology, and chemical clocks. In this work, we have obtained new high-resolution (R 50,000), high-S/N, optical data for 3+ stellar members in open clusters, using Keck/HIRES, with membership derived from the Open Cluster Chemical Abundances and Mapping (OCCAM) survey. From these new Keck/HIRES data, we have derived neutron capture abundances for stars in seven distant outer Galaxy open cluster
Paper Structure (4 sections, 2 figures)

This paper contains 4 sections, 2 figures.

Table of Contents

  1. Introduction
  2. Methods
  3. Results
  4. Acknowledgments

Figures (2)

  • Figure 1: The OCCAM metallicity gradient from OCCAM_Myers with follow-up clusters identified. All OCCAM high-quality clusters are shown as colored triangles with color indicating cluster age, saturating at 1 Gyr (the maximum age in this sample is 9 Gyr). The clusters marked with stars represent those which we have re-observed with Keck HIRES in the optical regime, presented in this work. The circled cluster in the solar neighborhood is our calibrator, M67. The metallicity gradient fit is shown in blue with the slopes of the fit in the upper right. We specifically targeted old open clusters at large Galactic radii to extend the neutron capture trends.
  • Figure 2: The neutron-capture elements Ba, Ce, La, Mo, Zr, and Y for the stars of our eight clusters plotted with metallicity on the x-axis. The colors correspond to the cluster the stars belong to. In this analysis, not all stars have well-measured abundances for all elements.