Title: Blue stragglers and other stellar population mysteries beyond the Milky Way

Time：10:30 a.m., April 16(Tuesday)

Location：Middle Conference Room, 3rd floor

Speaker: Richard de Grijs (Macquarie University, Sydney, Australia)

Abstract: We have analyzed populations of blue straggler stars (BSSs) in 24 Magellanic Cloud star clusters using multi-passband Hubble Space Telescope images. We uncovered a correlation between the number of BSSs in the cluster cores and the clusters' core masses, characterized by a power-law index of 0.51±0.07. For low stellar collision rates, the mass-normalized number of BSSs depends only weakly (or perhaps not at all) on the collision rate, implying that the binary-driven BSS formation channel dominates. Comparison with simulations suggests that stellar collisions contribute less than 20% to the total number of BSSs formed. Further tests, including analysis of the BSS specific frequencies and their population numbers at larger cluster radii, suggest that binary interactions may be their main formation channel, hinting at an anti-correlation between a cluster's binary fraction and its core mass. This study forms part of our group's overall approach to understanding the complexities of star cluster stellar populations. We have been making significant progress in recent years towards a better understanding, of which I will present a number of recent and hot-off-the-press highlights.