Effects of Close Binary Evolution on the Main-sequence Morphology of Young Star Clusters

Wang, Chen; Langer, N.; Schootemeijer, A.; Castro, N.; Adscheid, Sylvia; Marchant, Pablo; Hastings, Ben

doi:10.3847/2041-8213/ab6171

Cited by 68 publications

(81 citation statements)

References 52 publications

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“…As discussed above, the single star channel, as well as various binary channels, may contribute to produce SNe Ibc. However, binary evolution predicts that the majority of SNe Ibc stem from stable Case A or Case B mass transfer, which is inevitable for roughly half of the massive binaries (with most of the other half merging to single stars; de Mink et al 2014;Wang et al 2020). This allows for a simple prediction of the metallicity dependence of the number of SNe Ibc.…”

Section: Discussionmentioning

confidence: 99%

Supernovae Ib and Ic from the explosion of helium stars

Dessart

Yoon

Aguilera-Dena

et al. 2020

A&A

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Much difficulty has so far prevented the emergence of a consistent scenario for the origin of Type Ib and Ic supernovae (SNe). Either the SN rates or the ejecta masses and composition were in tension with inferred properties from observations. Here, we follow a heuristic approach by examining the fate of helium stars in the mass range from 4 to 12 M⊙, which presumably form in interacting binaries. The helium stars were evolved using stellar wind mass loss rates that agree with observations and which reproduce the observed luminosity range of galactic Wolf-Rayet stars, leading to stellar masses at core collapse in the range from 3 to 5.5 M⊙. We then exploded these models adopting an explosion energy proportional to the ejecta mass, which is roughly consistent with theoretical predictions. We imposed a fixed 56Ni mass and strong mixing. The SN radiation from 3 to 100 d was computed self-consistently, starting from the input stellar models using the time-dependent nonlocal thermodynamic equilibrium radiative-transfer code CMFGEN. By design, our fiducial models yield very similar light curves, with a rise time of about 20 d and a peak luminosity of ~1042.2 erg s−1, which is in line with representative SNe Ibc. The less massive progenitors retain a He-rich envelope and reproduce the color, line widths, and line strengths of a representative sample of SNe Ib, while stellar winds remove most of the helium in the more massive progenitors, whose spectra match typical SNe Ic in detail. The transition between the predicted Ib-like and Ic-like spectra is continuous, but it is sharp, such that the resulting models essentially form a dichotomy. Further models computed with varying explosion energy, 56Ni mass, and long-term power injection from the remnant show that a moderate variation of these parameters can reproduce much of the diversity of SNe Ibc. We conclude that massive stars stripped by a binary companion can account for the vast majority of ordinary Type Ib and Ic SNe and that stellar wind mass loss is the key to removing the helium envelope in the progenitors of SNe Ic.

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Section: Discussionmentioning

confidence: 99%

Supernovae Ib and Ic from the explosion of helium stars

Dessart

Yoon

Aguilera-Dena

et al. 2020

A&A

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“…7 concentrates at the lowest masses and it does not offer any support for this scenario. On the other hand, the stars could be interpreted as mergers after binary interaction (de Mink et al 2014;Wang et al 2020), again corresponding to a 3-4 Myr age. In that case, helium abundances would be closer to the observed ones as a consequence of the fresh hydrogen supply, but the expected rotational velocities would be very large (although the observed one would be affected by the inclination of the rotational axis).…”

Section: Evolutionary Statusmentioning

confidence: 99%

Spectroscopic characterization of the known O-star population in Cygnus OB2

Berlanas

Herrero

Comerón³

et al. 2020

A&A

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Context. Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, an extensive spectroscopic study of the whole known O-star population in the association is still lacking. Aims. We aim to carry out a spectroscopic characterization of all the currently known O stars in Cygnus OB2, determining the distribution of rotational velocities and accurate stellar parameters to obtain an improved view of the evolutionary status of the region. Methods. Based on existing and new optical spectroscopy, we performed a detailed quantitative spectroscopic analysis of all the known O-type stars identified in the association. For this purpose, we used the user-friendly iacob-broad and iacob-gbat automatized tools, FASTWIND stellar models, and astrometry provided by the Gaia second data release. Results. We created the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing and new spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the distribution of rotational velocities, and determine the main stellar parameters for all the stars in the region that have not been detected as double-line spectroscopic binaries. We also derive radii, luminosities, and masses for those stars with reliable Gaia astrometry, in addition to creating the Hertzsprung-Russell Diagram to interpret the evolutionary status of the association. Finally, we inspect the dynamical state of the population and identify runaway candidates. Conclusions. Our spectroscopic analysis of the O-star population in Cygnus OB2 has led to the discovery of two new binary systems and the determination of the main stellar parameters, including rotational velocities, luminosities, masses, and radii for all identified stars. This work has shown the improvement reached when using accurate spectroscopic parameters and astrometry for the interpretation of the evolutionary status of a population, revealing, in the case of Cygnus OB2, at least two star-forming bursts at ~3 and ~5 Myr. We find an apparent deficit of very fast rotators in the distribution of rotational velocities. The inspection of the dynamical distribution of the sample has allowed us to identify nine O stars with peculiar proper motions and discuss a possible dynamical ejection scenario or past supernova explosions in the region.

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“…Similarly, a number of studies have explored the role of interacting binaries in causing eMSTOs, particularly at younger ages (< 100 Myr;e.g., D'Antona et al 2017;Beasor et al 2019;Wang et al 2020). These models make clear predictions as to the rate of binarity in different parts of the CMD (i.e.…”

Section: Introductionmentioning

confidence: 98%

On the origin of the bimodal rotational velocity distribution in stellar clusters: rotation on the pre-main sequence

Bastian

Kamann

Amard

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We address the origin of the observed bimodal rotational distribution of stars in massive young and intermediate age stellar clusters. This bimodality is seen as split main sequences at young ages and also has been recently directly observed in the Vsini distribution of stars within massive young and intermediate age clusters. Previous models have invoked binary interactions as the origin of this bimodality, although these models are unable to reproduce all of the observational constraints on the problem. Here, we suggest that such a bimodal rotational distribution is set-up early within a cluster’s life, i.e. within the first few Myr. Observations show that the period distribution of low-mass ($\lesssim\! 2 \, \mathrm{M}_\odot$) pre-main-sequence (PMS) stars is bimodal in many young open clusters, and we present a series of models to show that if such a bimodality exists for stars on the PMS that it is expected to manifest as a bimodal rotational velocity (at fixed mass/luminosity) on the main sequence for stars with masses in excess of ∼1.5 M⊙. Such a bimodal period distribution of PMS stars may be caused by whether stars have lost (rapid rotators) or been able to retain (slow rotators) their circumstellar discs throughout their PMS lifetimes. We conclude with a series of predictions for observables based on our model.

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Effects of Close Binary Evolution on the Main-sequence Morphology of Young Star Clusters

Cited by 68 publications

References 52 publications

Supernovae Ib and Ic from the explosion of helium stars

Supernovae Ib and Ic from the explosion of helium stars

Spectroscopic characterization of the known O-star population in Cygnus OB2

On the origin of the bimodal rotational velocity distribution in stellar clusters: rotation on the pre-main sequence

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