Blue Straggler Stars beyond the Milky Way. IV. Radial Distributions and Dynamical Implications

Authors: Li, Chengyuan; Sun, Weijia; Hong, Jongsuk; Deng, Licai; de Grijs, Richard; Sills, Alison Bibcode: 2019ApJ...871..171L arXiv: 1812.07154

Blue straggler stars (BSSs) have been proposed as powerful indicators to measure the dynamical state of Galactic globular clusters (GCs). Here we examine for the first time whether this framework of BSSs as dynamical clocks, which was specifically developed for Galactic GCs, may also hold for younger GCs in the Large Magellanic Cloud (LMC).

Concentration factor (A) versus dynamical age for seven LMC clusters.

Using Hubble Space Telescope observations, we study seven LMC star clusters with ages between ~700 Myr and 7 Gyr. We confirm that our sample clusters are consistent with the empirical correlation previously derived for Galactic GCs, within a modest tolerance. We suggest that to further examine whether BSSs can measure the dynamical state of their host clusters over an extended range of dynamical ages, more studies of dynamically older Magellanic Cloud clusters are required. We discuss the physical implications of our results in terms of their central, dimensionless King potential, as well as the initial retention fraction of black holes.

Evolutionary sequences of concentration factor (A) over time.