Primeros resultados del estudio observacional de estrellas masivas y centrales en cúmulos abiertos

Abstract

Theoretical models show that binary and multiple stars play an important rol in the energetics of open clusters and therefore in their dynamical evolution, particulary in poor clusters dominated by one or a few central massive stars. In this work we present the results of our spectroscopic, astrometric and photometric analysis of four young open clusters (UPK 617, Markarian 38, Alessi 19 y UPK 38), that are part of a selected sample of 43 clusters that have one or a few central stars that are at least one magnitude brighter than the rest of the members. We measure radial velocities of bright stars in spectra obtained at the Complejo Astronómico El Leoncito and we analyze photometric variability with data from TESS. Using astrometric and photometric data from Gaia DR3 we perform a membership analysis of the clusters, estimating their masses and ages. In the two youngest clusters we find that the bright central stars are massive binary systems. Specifically, the star HD 173003 in UPK 38 is a double-line binary with a period of 7.9 d, while star HD 167287 in the cluster Markarian 38 is a binary with a period of 12.1 d with a blue supergiant primary. The cluster Alessi 19 has two stars that are more massive than the rest of the members, one of which has broad spectral lines and the other presents a probable variability in radial velocity. Finally, UPK 617 is the oldest cluster analyzed whose central star (HD 139165) has a high rotation and is a slow pulsating B-type star. These massive stars could play a prominent role in the dynamical evolution of clusters, particularly in the case of poor aggregates like UPK 38, whose central binary contains about 40% of the total mass of the cluster.