The binary mass transfer origin of the red blue straggler sequence in M30

Abstract

Two separated sequences of blue straggler stars (BSSs) have been revealed by Ferraro et al. (2009) in the color-magnitude diagram (CMD) of the Milky Way globular cluster M30. Their presence has been suggested to be related to the two BSS formation channels (namely, collisions and mass-transfer in close binaries) operating within the same stellar system. The blue sequence was indeed found to be well reproduced by collisional BSS models. In contrast, no specific models for mass transfer BSSs were available for an old stellar system like M30. Here we present binary evolution models, including case-B mass transfer and binary merging, specifically calculated for this cluster. We discuss in detail the evolutionary track of a $0.9+0.5M_{\odot }$ binary, which spends approximately 4 Gyr in the BSS region of the CMD of a 13 Gyr old cluster. We also run Monte-Carlo simulations to study the distribution of mass transfer BSSs in the CMD and to compare it with the observational data. Our results show that: (1) the color and magnitude distribution of synthetic mass transfer BSSs defines a strip in the CMD that nicely matches the observed red BSS sequence, thus providing strong support to the mass transfer origin for these stars; (2) the CMD distribution of synthetic BSSs never attains the observed location of the blue BSS sequence, thus reinforcing the hypothesis that the latter formed through a different channel (likely collisions); (3) most ($\sim 60\%$) of the synthetic BSSs are produced by mass-transfer models, while the remaining $<40\%$ requires the contribution from merger models.

8 pages, 5 figures, accepted to ApJ

References in corpus (14)

• Dynamical age differences among coeval star clusters as revealed by blue stragglers
• A Binary Origin for Blue Stragglers in Globular Clusters
• Discovery of Carbon/Oxygen depleted Blue Straggler Stars in 47 Tucanae: the chemical signature of a mass-transfer formation process
• Another Non-segregated Blue Straggler Population in a Globular Cluster: the Case of NGC 2419
• A Panchromatic Study of the Globular Cluster NGC 1904. I: The Blue Straggler Population
• Blue Straggler Stars in the Unusual Globular Cluster NGC 6388
• A Correlation between Blue Straggler and Binary Fractions in the core of Galactic Globular Clusters
• The blue stragglers formed via mass transfer in old open clusters
• Evolution of stellar collision products in open clusters. I. Blue stragglers in N-body models of M67
• Primordial Binary Evolution and Blue Stragglers
• The surprising external upturn of the Blue Straggler radial distribution in M55
• The Blue Straggler Star Population in NGC 1261: Evidence for a Post-Core-Collapse Bounce State
• Dynamical friction in multi-component evolving globular clusters
• Spinning like a Blue Straggler: the population of fast rotating Blue Straggler stars in Omega Centauri

Cited by in corpus (12)

• The "dynamical clock": dating the internal dynamical evolution of star clusters with Blue Straggler Stars
• Discovery of a double Blue Straggler sequence in M15: new insight into the core-collapse process
• Spectral Energy Distribution of Blue Stragglers in the core of 47 Tucanae
• Formation and Evolution of Blue Stragglers in 47 Tucanae
• Contribution of primordial binary evolution to the two blue-straggler sequences in globular cluster M30
• A Deep Search for Faint Chandra X-ray Sources, Radio Sources, and Optical Counterparts in NGC 6752
• Blue Stragglers and Friends: Initial Evolutionary Pathways in Close Low-Mass Binaries: Literature Review
• Discovery of double BSS sequences in the old Galactic open cluster Berkeley 17
• Rotational velocities of Blue Straggler Stars in the Globular Cluster M55
• Far-ultraviolet investigation into the galactic globular cluster M30 (NGC 7099): I. Photometry and radial distributions
• Unveiling Bifurcated Blue Straggler Sequences in NGC 2173: Insights from Binary Evolution
• Fast Rotating Blue Straggler Stars in the globular cluster NGC 1851