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Title: Orbital and Physical Properties of the Pleiades Binary 27 Tau (Atlas)
Abstract We report new spectroscopic and interferometric observations of the Pleiades binary star Atlas, which played an important role nearly 3 decades ago in settling the debate over the distance to the cluster from ground-based and space-based determinations. We use the new measurements, together with other published and archival astrometric observations, to improve the determination of the 291 day orbit and the distance to Atlas (136.2 ± 1.4 pc). We also derive the main properties of the components, including their absolute masses (5.04 ± 0.17M⊙and 3.64 ± 0.12M⊙), sizes, effective temperatures, projected rotational velocities, and chemical compositions. We find that the more evolved primary star is rotationally distorted, and we are able to estimate its oblateness and the approximate orientation of its spin axis from the interferometric observations. The spin axis may well be aligned with the orbital axis. Models of stellar evolution from the Modules for Experiments in Stellar Astrophysics (or MESA) that account for rotation provide a good match to all of the primary’s global properties, and point to an initial angular rotation rate on the zero-age main sequence of about 55% of the breakup velocity. The current location of the star in the Hertzsprung–Russell diagram is near the very end of the hydrogen-burning main sequence, at an age of about 105 Myr, according to these models. Our spectroscopic analysis of the more slowly rotating secondary indicates that it is a helium-weak star, with other chemical anomalies.  more » « less
Award ID(s):
2407956 2034336
PAR ID:
10659332
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
American Astronomical Society / IOP
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
990
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
107
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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