Mixing in massive stellar mergers

Gaburov, Evghenii; Lombardi, James C.; Zwart, Simon Portegies

doi:10.1111/j.1745-3933.2007.00399.x

Cited by 67 publications

(70 citation statements)

References 15 publications

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“…In our simulations, contact results in merging of the stars as this is the most likely outcome (see also discussion by de Mink et al 2014). The simulations of Gaburov et al (2008) and Glebbeek et al (2013) suggest that the merger product that forms will initially be a puffed up and red object (Tylenda et al 2011;Pejcha et al 2016), but as it radiates away the excess energy, it will recover a thermal equilibrium structure. The core of the primary is thought to sink to the center of the new object with the core of the less evolved secondary settling above (Glebbeek et al 2013).…”

Section: Ms⇒msmentioning

confidence: 99%

Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction

Zapartas

Mink

Izzard

et al. 2017

A&A

159

152

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Most massive stars, the progenitors of core-collapse supernovae, are in close binary systems and may interact with their companion through mass transfer or merging. We undertake a population synthesis study to compute the delay-time distribution of core-collapse supernovae, that is, the supernova rate versus time following a starburst, taking into account binary interactions. We test the systematic robustness of our results by running various simulations to account for the uncertainties in our standard assumptions. We find that a significant fraction, 15 +9 −8 %, of core-collapse supernovae are 'late', that is, they occur 50-200 Myrs after birth, when all massive single stars have already exploded. These late events originate predominantly from binary systems with at least one, or, in most cases, with both stars initially being of intermediate mass (4 − 8M ). The main evolutionary channels that contribute often involve either the merging of the initially more massive primary star with its companion or the engulfment of the remaining core of the primary by the expanding secondary that has accreted mass at an earlier evolutionary stage. Also, the total number of core-collapse supernovae increases by 14 +15 −14 % because of binarity for the same initial stellar mass. The high rate implies that we should have already observed such late core-collapse supernovae, but have not recognized them as such. We argue that φ Persei is a likely progenitor and that eccentric neutron star -white dwarf systems are likely descendants. Late events can help explain the discrepancy in the delay-time distributions derived from supernova remnants in the Magellanic Clouds and extragalactic type Ia events, lowering the contribution of prompt Ia events. We discuss ways to test these predictions and speculate on the implications for supernova feedback in simulations of galaxy evolution.

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Section: Ms⇒msmentioning

confidence: 99%

Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction

Zapartas

Mink

Izzard

et al. 2017

A&A

159

152

View full text Add to dashboard Cite

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“…This simulates the results of detailed stellar evolution models of low-mass merged stars by the use of molecular weight as a proxy for entropy (Gaburov et al 2008;Sills & Glebbeek 2010;Ivanova et al 2013). When a binary star enters a common envelope phase both stellar envelopes are homogenized in the process under the assumption that the orbital energy and angular momentum deposited in the common envelope mixes it completely prior to ejection or merging.…”

Section: Stellar Mass Loss and Gain In _mentioning

confidence: 99%

Binary stars in the Galactic thick disc

Izzard

Preece

Jofré

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The combination of asteroseismologically-measured masses with abundances from detailed analyses of stellar atmospheres challenges our fundamental knowledge of stars and our ability to model them. Ancient red-giant stars in the Galactic thick disc are proving to be most troublesome in this regard. They are older than 5 Gyr, a lifetime corresponding to an initial stellar mass of about 1.2 M . So why do the masses of a sizeable fraction of thick-disc stars exceed 1.3 M , with some as massive as 2.3 M ? We answer this question by considering duplicity in the thick-disc stellar population using a binary population-nucleosynthesis model. We examine how mass transfer and merging affect the stellar mass distribution and surface abundances of carbon and nitrogen. We show that a few per cent of thick-disc stars can interact in binary star systems and become more massive than 1.3 M . Of these stars, most are single because they are merged binaries. Some stars more massive than 1.3 M form in binaries by wind mass transfer. We compare our results to a sample of the APOKASC data set and find reasonable agreement except in the number of these thick-disc stars more massive than 1.3 M . This problem is resolved by the use of a logarithmically-flat orbital-period distribution and a large binary fraction.

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“…Since material that has a higher mean molecular weight has a lower entropy, any material that is helium-rich will fall to the centre of the collision product. This "sort by entropy" prescription is the basis for the codes Make Me A Star (MMAS) [29] and Make Me A Massive Star (MMAMS) [12], which provide detailed stellar structure profiles of collision products for collisions between low mass and high mass stars respectively.…”

Section: Collisional Modelsmentioning

confidence: 99%

Models of Individual Blue Stragglers

Sills

2014

Ecology of Blue Straggler Stars

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As we have seen in previous chapters, blue stragglers are thought to form in both of two broad classes of formation mechanisms: through collisions or through binary mass transfer. Both processes transform two stars into a blue straggler on reasonably short timescales compared to the main sequence lifetimes of low mass stars: a headon collision can take a few days, while stable mass transfer from main sequence stars can take much longer, up to the nuclear timescale of the stars. However, it is not enough to follow the hydrodynamic phases of either process. We must determine the structure of the proto-blue straggler at the moment when the remnant is in hydrostatic equilibrium, and then follow its evolution using a stellar evolution code for the next few billion years in order to make direct comparisons to the observed properties of blue stragglers. Those stellar evolution models are the subject of this chapter.In the context of stellar models, it makes sense to try to define these two formation mechanisms a little more clearly. For our purposes, a collision is a short-lived and strong interaction between two stars. The situation where two previously unrelated stars move through a cluster and find themselves close enough that their radii overlap is obviously a collision, and those could be either head-on or off-axis. A similar situation during a resonant encounter involving binaries or triples can also be modelled using the same techniques as a collision. In this case the two stars might have originally been a binary, but the event that made the blue straggler was not a slow spiral-in of the two stars, but a more dramatic event caused by the overall interaction of the systems. In the literature, these kinds of collisions are often called "binary-mediated". The key distinction that I would like to make is that the event which triggered the hydrodynamic phase of a collision is very short-lived, and de-

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Mixing in massive stellar mergers

Cited by 67 publications

References 15 publications

Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction

Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction

Binary stars in the Galactic thick disc

Models of Individual Blue Stragglers

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