MUSE Observations of NGC330 in the Small Magellanic Cloud: Helium Abundance of Bright Main-sequence Stars*

Carini, R.; Biazzo, K.; Brocato, E.; Pulone, L.; Pasquini, L.

doi:10.3847/1538-3881/ab7334

Cited by 10 publications

(4 citation statements)

References 79 publications

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“…However, this additional mixing does not significantly affect the distribution of early mergers in the CMD, as the long-lasting later evolution of the merger product after it has been created washes out this small natal difference. Whereas potential surface He enhancement may also impact the distribution of the merger products, it is not found in both theoretical simulations or spectroscopic observations [82,74,83].…”

Section: E: Merger Models and Merger Historymentioning

confidence: 90%

Stellar mergers as the origin of the blue main-sequence band in young star clusters

et al. 2022

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Section: E: Merger Models and Merger Historymentioning

confidence: 90%

Stellar mergers as the origin of the blue main-sequence band in young star clusters

et al. 2022

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“…The significant surface He en-hancement in the SYCLIST fast-rotating models near the cluster turnoff explains their higher temperature. Despite a scarcity of detailed measurements of He abundance of the stars in young star clusters, Carini et al (2020) found similar surface He abundances for the red and blue MS stars in the turn-off area of the young SMC star cluster NGC 330, which may argue against efficient rotational mixing. Nevertheless, their results should be taken with a grain of salt, given their low S/N, resolution and small sample size.…”

Section: Surface Chemical Compositionmentioning

confidence: 80%

The initial spin distribution of B-type stars revealed by the split main sequences of young star clusters

Wang¹,

Hastings²,

Schootemeijer³

2023

A&A

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Spectroscopic observations of stars in young open clusters have revealed evidence for a dichotomous distribution of stellar rotational velocities, with 10−30% of stars rotating slowly and the remaining 70−90% rotating fairly rapidly. At the same time, high-precision multiband photometry of young star clusters shows a split main sequence band, which is again interpreted as due to a spin dichotomy. Recent papers suggest that extreme rotation is required to retrieve the photometric split. Our new grids of MESA models and the prevalent SYCLIST models show, however, that initial slow (0−35% of the linear Keplerian rotation velocities) and intermediate (50−65% of the Keplerian rotation velocities) rotation are adequate to explain the photometric split. These values are consistent with the recent spectroscopic measurements of cluster and field stars, and are likely to reflect the birth spin distributions of upper main-sequence stars. A fraction of the initially faster-rotating stars may be able to reach near-critical rotation at the end of their main-sequence evolution and produce Be stars in the turn-off region of young star clusters. However, we find that the presence of Be stars up to two magnitudes below the cluster turnoff advocates for a crucial role of binary interaction in creating Be stars. We argue that surface chemical composition measurements may help distinguish these two Be star formation channels. While only the most rapidly rotating, and therefore nitrogen-enriched, single stars can evolve into Be stars, slow pre-mass-transfer rotation and inefficient accretion allows for mild or no enrichment even in critically rotating accretion-induced Be stars. Our results shed new light on the origin of the spin distribution of young and evolved B-type main sequence stars.

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“…Ages reported for NGC 1866 inferred from isochrone modeling range from 140 to 220 Myr (Milone et al 2017) and those inferred from Cepheids range from 176 to 288 Myr (Costa et al 2019). Ther ages of NGC 2164 and NGC 330 are ∼80-100 Myr (e.g., Mucciarelli et al 2006;Milone et al 2018) and ∼20-50 Myr (e.g., Keller et al 2000;Sirianni et al 2002;McLaughlin & van der Marel 2005;Li et al 2017b;Bodensteiner et al 2020;Carini et al 2020), respectively.…”

Section: Isochrone Fittingmentioning

confidence: 95%

The spatial distributions of blue main-sequence stars in Magellanic Cloud star clusters

Yang,

Li,

de Grijs

et al. 2021

Preprint

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The color-magnitude diagrams (CMDs) of young star clusters show that, particularly at ultraviolet wavelengths, their upper main sequences (MSs) bifurcate into a sequence comprising the bulk population and a blue periphery. The spatial distribution of stars is crucial to understand the reasons for these distinct stellar populations. This study uses high-resolution photometric data obtained with the Hubble Space Telescope to study the spatial distributions of the stellar populations in seven Magellanic Cloud star clusters. The cumulative radial number fractions of blue stars within four clusters are strongly anti-correlated with those of the high-mass-ratio binaries in the bifurcated region, with negative Pearson coefficients < −0.7. Those clusters generally are young or in an early dynamical evolutionary stage. In addition, a supporting N -body simulation suggests the increasing percentage of blue-MS stars from the cluster centers to their outskirts may be associated with the dissolution of soft binaries. This study provides a different perspective to explore the MS bimodalities in young clusters and adds extra puzzles. A more comprehensive study combined with detailed simulations is needed in the future.

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MUSE Observations of NGC330 in the Small Magellanic Cloud: Helium Abundance of Bright Main-sequence Stars*

Cited by 10 publications

References 79 publications

Stellar mergers as the origin of the blue main-sequence band in young star clusters

Stellar mergers as the origin of the blue main-sequence band in young star clusters

The initial spin distribution of B-type stars revealed by the split main sequences of young star clusters

The spatial distributions of blue main-sequence stars in Magellanic Cloud star clusters

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