Binarity as the solution to the stellar evolution enigma posed by NGC 6791

Abstract

Binary evolution is investigated as the source for the extreme horizontal branch (EHB) stars in the old and metal rich open cluster NGC~6791. Employing an updated version of our binary stellar evolution code we demonstrate that EHB stars naturally emerge from the common envelope phase. In sum, the binary model reproduces the observed ($T_{\mathrm{eff}}$, $\log g$) and temporal properties of the EHB over-density tied to NGC 6971, without needing an ad-hoc and anomalous mass-loss prescription.

9 pages, 5 eps figures, accepted for publication in the Astrophysical Journal Letters

References in corpus (5)

• The Puzzling White Dwarf Cooling Sequence in NGC6791: A Simple Solution
• Searching for Chemical Signatures of Multiple Stellar Populations in the Old, Massive Open Cluster NGC 6791
• Rapidly rotating second-generation progenitors for the blue hook stars of ω Cen
• Spitzer Space Telescope evidence in NGC 6791: no super-mass-loss at super-solar metallicity to explain helium white dwarfs?
• Is a binary fraction-age relation responsible for the lack of EHB binaries in globular clusters?

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• Photometric Identification of Unresolved Binary Stars in Nearby Open Star Clusters