Testing the Consistency of Age Indicators in Understudied Open Clusters

Ella Roselli

Abstract: Gaia has revolutionized our ability to identify members of nearby co-moving, co-eval structures. These are critical to deepening our understanding of the main-sequence evolution of low-mass stars, which in turn dictates the evolution and therefore habitability of exoplanets. We have identified three understudied open clusters, ASCC 41, Turner 5, and Mamajek 4, whose membership has been solidified and expanded with Gaia. With distances between 300 and 450 pc and literature ages between 200 and 400 Myr, the three are intriguing targets for follow-up investigations, as we lack accessible stellar populations at these ages. We use three different approaches to improve the still-uncertain age estimates for the clusters. First, we apply rigorous cuts to their Gaia-based membership catalogs to identify the most likely single-star members, which we then fit with PARSEC isochrones. Second, we use light curves from TESS to measure rotation periods for those single-star members, and compare the resulting color-period distributions to those of well-studied clusters. Finally, we combine data from GALAH with our GRACES spectra to measure the strength of the lithium absorption in stars in all three clusters. We find consistent ages across all three age indicators: ASCC 41 has an age of ≈400 Myr, Turner 5 of ≈450 Myr, and Mamajek 4 of ≈650 Myr. Furthermore, our analysis suggests that the extended structures found with Gaia for Mamajek 4 and Turner 5 are likely real, in that the stars in these appear to be both co-moving and co-eval with stars in the cluster cores. This work represents the first step in establishing these three clusters as benchmarks for studying the time-dependent properties of low-mass stars, and is representative of the investigations that LSST astrometry and light-curves will enable for even fainter members of these and other stellar clusters.


This poster will be displayed on Monday and Tuesday.


Career Stage: 
Undergrad Student