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Precise Ages for the Binary Star System 12 Com in the Coma Berenices Cluster

Presentation #205.09 in the session Binary Stellar System - iPoster Session.

Published onJun 29, 2022
Precise Ages for the Binary Star System 12 Com in the Coma Berenices Cluster

We present the most precise study thus far of the bright giant-dwarf binary system 12 Com in the nearby star cluster Coma Berenices. Using interferometric measurements from PTI and CHARA (CLIMB and MIRC-X beam combiners) to resolve the binary orbit alongside radial velocities from ELODIE spectra and Griffin & Griffin (2011), we fitted a joint orbital solution. The masses were found to be 2.73 ± 0.10 M and 2.14 ± 0.04 M for the primary and secondary stars, respectively. MIST isochrones and MESA evolutionary tracks are used alongside GAIA photometric data of the cluster to fit for the age of the cluster. By knowing the giant’s mass, the color-magnitude position of the binary greatly constrains the age of the giant and the cluster to be 473 ± 40 Myr. Interferometric data allows us to cleanly resolve the giant (0.9757 ± 0.0004 mas), giving a physical size of 9.12 ± 0.02 R with a GAIA distance. Mass-radius isochrones then constrain the age of the giant to be 455 ± 15 Myr. With the precision of measurements, the giant is likely the most evolved star in the cluster and in the red giant phase, too small to have helium core burning. We gratefully acknowledge support from the National Science Foundation under grant AST-1817217.

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