Extended Main Sequences in Star Clusters
arXiv:2401.08062 · doi:10.1016/j.fmre.2023.12.007
Abstract
Extended main sequences (eMSs) and extended main-sequence turnoffs (eMSTOs) are fascinating phenomena that are routinely observed in star clusters. These phenomena strongly challenge the current canonical "simple stellar population" picture of star clusters, which postulates that star clusters are coeval and chemically homogeneous and can thus be described by a single, unique isochrone. Detections of eMSs and eMSTOs provide valuable insights into stellar physics and the evolution of star clusters. This comprehensive review delves into the observational characteristics, underlying mechanisms, and astrophysical implications of the eMSs and eMSTOs observed in young (less than 600 million years) and intermediate-age (600 to 2000 million years) star clusters. Several scenarios or hypotheses have been proposed to explain these phenomena, including the presence of an age spread, binary interactions, variable stars, and differences in stellar rotation rates. This review discusses the advantages and limitations of current models. Among contemporary models and hypotheses, stellar rotation has been demonstrated as the most plausible mechanism to explain the occurrence of eMSs and eMSTOs. Research on stellar rotation and its connection to eMSs has opened up a myriad of fascinating avenues, such as investigations of the magnetic braking mechanism in stars, searches for tidally locked binary systems in star clusters, and investigations as to whether binary mergers can give rise to massive magnetars. These endeavors have yielded valuable insights and significantly enriched our understanding of stellar astrophysics.
37 pages, 7 figures. Fundamental Research (invited review)
References in corpus (40)
- Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3
- How mergers magnetise massive stars
- Fast and inefficient star formation due to short-lived molecular clouds and rapid feedback
- A double main sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud
- PARSEC V2.0: Stellar tracks and isochrones of low and intermediate mass stars with rotation
- Multiple stellar populations in three rich Large Magellanic Cloud star clusters
- Studying the YMC population of M83: how long clusters remain embedded, their interaction with the ISM and implications for GC formation theories
- Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: A Correlation Between Turnoff Width and Early Escape Velocity
- Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
- Disruption of giant molecular clouds and formation of bound star clusters under the influence of momentum stellar feedback
- Multiple stellar populations in Magellanic Cloud clusters. III. The first evidence of an extended main sequence turn-off in a young cluster: NGC1856
- Spin alignment of stars in old open clusters
- Stellar mergers as the origin of the blue main-sequence band in young star clusters
- A high fraction of Be stars in young massive clusters: evidence for a large population of near-critically rotating stars
- Multiple stellar populations in Magellanic Cloud clusters. V. The split main sequence of the young cluster NGC1866
- No evidence of chemical anomalies in the bimodal turnoff cluster NGC 1806 in the LMC
- Searching for Chemical Signatures of Multiple Stellar Populations in the Old, Massive Open Cluster NGC 6791
- The exclusion of a significant range of ages in a massive star cluster
- How stellar rotation shapes the colour magnitude diagram of the massive intermediate-age star cluster NGC 1846
- Constraining globular cluster formation through studies of young massive clusters - III. A lack of gas and dust in massive stellar clusters in the LMC and SMC
- Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: Stellar Rotation diminishes, but does not eliminate, Age Spreads
- Photometric binaries, mass functions, and structural parameters of 78 Galactic open clusters
- On the origin of double main-sequence turn-offs in star clusters of the Magellanic Clouds
- Discovery of Extended Main Sequence Turn-offs in Four Young Massive Clusters in the Magellanic Clouds
- Extended main-sequence turnoffs in the double cluster and Persei: The complex role of stellar rotation
- On the Origin of the Bimodal Rotational Velocity Distribution in Stellar Clusters: Rotation on the Pre-Main Sequence
- The Morphology of the Sub-Giant Branch and Red Clump Reveal No Sign of Age Spreads in Intermediate Age Clusters
- Isochrone-cloud fitting of the extended Main-Sequence Turn-Off of young clusters
- Exploring the role of binarity in the origin of the bimodal rotational velocity distribution in stellar clusters
- Expanding the time domain of multiple populations: evidences of nitrogen variations in the ~1.5 Gyr old star cluster NGC 1783
- The radial distributions of the two main-sequence components in the young massive star cluster NGC 1856
- On the role of dust and mass loss in the extended main sequence turnoff of star clusters: the case of NGC 1783
- The role of binarity and stellar rotation in the split main sequence of NGC 2422
- First Observational Signature of Rotational Deceleration in a Massive, Intermediate-age Star Cluster in the Magellanic Clouds
- The overlooked role of stellar variability in the extended main sequence of LMC intermediate-age clusters
- On the origin of UV-dim stars: a population of rapidly rotating shell stars?
- Hubble Space Telescope survey of Magellanic Cloud star clusters. UV-dim stars in young clusters
- Stellar populations in star clusters
- On the origin of the split main sequences of the young massive cluster NGC 1856
- Searching for globular cluster chemical anomalies on the main sequence of a young massive cluster