SIMBAD references

2021A&A...645L..10R - Astronomy and Astrophysics, volume 645, L10-10 (2021/1-1)

A relation between the radial velocity dispersion of young clusters and their age. Evidence for hardening as the formation scenario of massive close binaries.

RAMIREZ-TANNUS M.C., BACKS F., DE KOTER A., SANA H., BEUTHER H., BIK A., BRANDNER W., KAPER L., LINZ H., HENNING T. and POORTA J.

Abstract (from CDS):

The majority of massive stars (>8M) in OB associations are found in close binary systems. Nonetheless, the formation mechanism of these close massive binaries is not understood yet. Using literature data, we measured the radial-velocity dispersion (σ1D) as a proxy for the close binary fraction in ten OB associations in the Galaxy and the Large Magellanic Cloud, spanning an age range from 1 to 6Myr. We find a positive trend of this dispersion with the cluster's age, which is consistent with binary hardening. Assuming a universal binary fraction of fbin=0.7, we converted the σ1D behavior to an evolution of the minimum orbital period Pcutoff from ∼9.5-years at 1Myr to ∼1.4-days for the oldest clusters in our sample at ∼6Myr. Our results suggest that binaries are formed at larger separations, and they harden in around 1 to 2Myr to produce the period distribution observed in few million year-old OB binaries. Such an inward migration may either be driven by an interaction with a remnant accretion disk or with other young stellar objects present in the system. Our findings constitute the first empirical evidence in favor of migration as a scenario for the formation of massive close binaries.

Abstract Copyright: © M. C. Ramírez-Tannus et al. 2021

Journal keyword(s): binaries: close - stars: formation - stars: early-type - open clusters and associations: general - binaries: general

Simbad objects: 14

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2021.07.28-16:32:41

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