http://arxiv.org/abs/2204.09414
Westerlund 1 (Wd 1) is one of the most massive young star clusters in the Milky Way. Although relevant for star formation and evolution, its fundamental parameters are not yet very well constrained. Our goal is to derive an accurate distance and provide constraints on the cluster age. We used the photometric and astrometric information available in the Gaia Early Data Release 3 (Gaia-EDR3) to infer its distance of 4.06$^{+0.36}{-0.34}$ kpc. Modelling of the eclipsing binary system W36 reported in Paper II led to the distance of 4.34$\pm$0.25 kpc, in agreement with the Gaia-EDR3 distance and, therefore, validating the parallax zero-point correction approach appropriate for red objects. By taking advantage of another two recent distance determinations using the Gaia-EDR3, we obtained a weighted mean distance for the cluster as d${\rm wd1}$=4.23$^{+0.15}{-0.13}$ kpc ($m-M$=13.13$^{+0.08}{-0.07}$ mag), which has an unprecedented accuracy of 4\%. We adopted recent Geneva evolutionary tracks for supra-solar metallicity objects to infer the age of the faintest RSG source from Wd 1, leading to a cluster age of 11.0$\pm$0.5 Myr, in excellent agreement with recent work by Beasor \& Davies (10.4$^{+1.3}_{-1.2}$ Myr) based on MIST evolutionary models. The age of W36 was reported to be 3.5$\pm$0.5 Myr in Paper II, supporting recent claims of a temporal spread of several Myr for the star-forming process within Wd 1 instead of a monolithic starburst scenario.
F. Navarete, A. Damineli, A. Ramirez, et. al.
Thu, 21 Apr 22
43/73
Comments: 16 pages, 9 figures, revised version submitted to MNRAS on April 20th, 2022
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