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Abstract M35 is a young open cluster and home to an extensive binary population. Using Gaia Data Release 3, Pan-STARRS, and Two Micron All Sky Survey photometry with the Bayesian statistical software, BASE-9, we derive precise cluster parameters, identify single and binary cluster members, and extract their masses. We identify 571 binaries down to GaiaG= 20.3 and a lower limit on the binary frequency offb= 0.41 ± 0.02. We extend the binary demographics by many magnitudes faint-ward of previous (radial-velocity) studies of this cluster and further away from the cluster center (1.°78, roughly 10 core radii). We find the binary stars to be more centrally concentrated than the single stars in the cluster. Furthermore, we find strong evidence for mass segregation within the binary population itself, with progressively more-massive binary samples becoming more and more centrally concentrated. For the single stars, we find weaker evidence for mass segregation; only the most massive single stars (>2.5M⊙) appear more centrally concentrated. Given the cluster age of ∼200 Myr, and our derived half-mass relaxation time for the cluster of 230 ± 84 Myr, we estimate ∼47% of the binary stars and ∼12% of single stars in the cluster have had time to become dynamically mass segregated. Importantly, when we investigate only stars with mass segregation timescales greater than the cluster age, we still find the binaries to be more centrally concentrated than the singles, suggesting the binaries may have formed with a primordially different spatial distribution from that of the single stars.
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This content will become publicly available on July 17, 2026
Precise Age for the Binary HD 21278 in the Young α Persei Cluster
Abstract We present a study of the double-lined spectroscopic binary HD 21278 that contains one of the brightest main-sequence stars in the youngαPersei open cluster. We analyzed new spectra and reanalyzed archived spectra to measure precise new radial velocity curves for the binary. We also obtained interferometric data using the CHARA Array at Mount Wilson to measure the sky positions of the two stars and the inclination of the ∼2 mas orbit. We determine that the two stars have masses of 5.381 ± 0.084M⊙and 3.353 ± 0.064M⊙. From isochrone fits, we find the cluster’s age to be 49 ± 7 Myr (using PARSEC models) or 49.5 ± 6 Myr (MIST models). Finally, we revisit the massive white dwarfs that are candidate escapees from theαPersei cluster to try to better characterize the massive end of the white dwarf initial–final mass relation. The implied progenitor masses challenge the idea that Chandrasekhar-mass white dwarfs are made by single stars with masses near 8M⊙.
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- PAR ID:
- 10624004
- Publisher / Repository:
- American Astronomical Society / IOP Publishing
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 988
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 113
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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