Instantaneous Starburst of the Massive Clusters Westerlund 1 and NGC 3603 Yc

Kudryavtseva, N.; Brandner, W.; Gennaro, Mario; Rochau, Boyke; Stolte, A.; Andersen, M.; Rio, Nicola Da; Henning, Thomas; Tognelli, E.; Hogg, David W.; Clark, S.; Waters, Rens

doi:10.1088/2041-8205/750/2/l44

Cited by 84 publications

(122 citation statements)

References 41 publications

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“…Beccari et al (2010) show CMDs from the cluster and surrounding area implying age spreads of more than 20 Myr. However, from a much smaller "core" region where extinction is uniform and disks may have photoevaporated, and with a proper-motion selected sample, Kudryavtseva et al (2012) claim that star formation is "instantaneous". This cautions that one must consider the size of the region being observed, ensure that membership of the cluster is secure and carefully assess the observational uncertainties.…”

Section: Observed Age Spreads and Observational Uncertaintiesmentioning

confidence: 99%

Ages of Young Stars

Soderblom¹,

Hillenbrand²,

Jeffries³

et al. 2014

Protostars and Planets VI

107

132

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Determining the sequence of events in the formation of stars and planetary systems and their time-scales is essential for understanding those processes, yet establishing ages is fundamentally difficult because we lack direct indicators. In this review we discuss the age challenge for young stars, specifically those less than ∼100 Myr old. Most age determination methods that we discuss are primarily applicable to groups of stars but can be used to estimate the age of individual objects. A reliable age scale is established above 20 Myr from measurement of the Lithium Depletion Boundary (LDB) in young clusters, and consistency is shown between these ages and those from the upper main sequence and the main sequence turn-off -if modest core convection and rotation is included in the models of higher-mass stars. Other available methods for age estimation include the kinematics of young groups, placing stars in Hertzsprung-Russell diagrams, pulsations and seismology, surface gravity measurement, rotation and activity, and lithium abundance. We review each of these methods and present known strengths and weaknesses. Below ∼ 20 Myr, both model-dependent and observational uncertainties grow, the situation is confused by the possibility of age spreads, and no reliable absolute ages yet exist. The lack of absolute age calibration below 20 Myr should be borne in mind when considering the lifetimes of protostellar phases and circumstellar material.

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Section: Observed Age Spreads and Observational Uncertaintiesmentioning

confidence: 99%

Ages of Young Stars

Soderblom¹,

Hillenbrand²,

Jeffries³

et al. 2014

Protostars and Planets VI

107

132

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show abstract

“…2). All three stars are expected to share the same natal metalicity and evolutionary pathway (since Wd-1 appears essentially co-eval; Negeuruela et al 2010;Kudryavtseva et al 2012) and so it is difficult to account for this observational finding unless Wd1-5 has a greater C-abundance than these objects.…”

Section: Comparison To Related Objectsmentioning

confidence: 99%

A VLT/FLAMES survey for massive binaries in Westerlund 1

Clark

Ritchie

Najarro

et al. 2014

A&A

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Context. The first soft gamma-ray repeater was discovered over three decades ago, and was subsequently identified as a magnetar, a class of highly magnetised neutron star. It has been hypothesised that these stars power some of the brightest supernovae known, and that they may form the central engines of some long duration gamma-ray bursts. However there is currently no consenus on the formation channel(s) of these objects. Aims. The presence of a magnetar in the starburst cluster Westerlund 1 implies a progenitor with a mass ≥40 M , which favours its formation in a binary that was disrupted at supernova. To test this hypothesis we conducted a search for the putative pre-SN companion.Methods. This was accomplished via a radial velocity survey to identify high-velocity runaways, with subsequent non-LTE model atmosphere analysis of the resultant candidate, Wd1-5. Results. Wd1-5 closely resembles the primaries in the short-period binaries, Wd1-13 and 44, suggesting a similar evolutionary history, although it currently appears single. It is overluminous for its spectroscopic mass and we find evidence of He-and N-enrichement, O-depletion, and critically C-enrichment, a combination of properties that is difficult to explain under single star evolutionary paradigms. We infer a pre-SN history for Wd1-5 which supposes an initial close binary comprising two stars of comparable (∼41 M + 35 M ) masses. Efficient mass transfer from the initially more massive component leads to the mass-gainer evolving more rapidly, initiating luminous blue variable/common envelope evolution. Reverse, wind-driven mass transfer during its subsequent WC Wolf-Rayet phase leads to the carbon pollution of Wd1-5, before a type Ibc supernova disrupts the binary system. Under the assumption of a physical association between Wd1-5 and J1647-45, the secondary is identified as the magnetar progenitor; its common envelope evolutionary phase prevents spin-down of its core prior to SN and the seed magnetic field for the magnetar forms either in this phase or during the earlier episode of mass transfer in which it was spun-up. Conclusions. Our results suggest that binarity is a key ingredient in the formation of at least a subset of magnetars by preventing spin-down via core-coupling and potentially generating a seed magnetic field. The apparent formation of a magnetar in a Type Ibc supernova is consistent with recent suggestions that superluminous Type Ibc supernovae are powered by the rapid spin-down of these objects.

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“…Since the half-life time t 1/2 leaves an imprint onto the FWHM of the observed star age distribution of a young gas-free cluster, it may be doable to infer the mean volume density of the cluster progenitor from its observed star age distribution (Parmentier, Pfalzner & Grebel 2014). One expects denser molecular clumps to give rise to clusters with narrower stellar age distributions, an effect which seems to have been unveiled recently (Kudryavtseva et al 2012). Note that the mean volume density of young clusters differs from that of their parent clumps because of the post-gas-expulsion 1 It should be noted that, to avoid a singularity at the centre of our model clumps, a power-law density profile with a central flat core has been adopted (here rc = 0.01 pc).…”

Section: Star Age Spreads In Young Clustersmentioning

confidence: 99%

Local‐density driven clustered star formation: Model and (some) implications

Parmentier

2014

Astron Nachr

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A positive power-law trend between the local surface densities of molecular gas, Σgas, and young stellar objects, Σstars, in molecular clouds of the solar neighbourhood has recently been identified. How it relates to the properties of embedded clusters has so far not been investigated. To that purpose, we model the development of the stellar component of molecular clumps as a function of time and local volume density. Specifically, we associate the observed volume density gradient of molecular clumps to the density-dependent free-fall time and we obtain the molecular clump star formation history by applying a constant star formation efficiency per free-fall time, ff . The model reproduces naturally the observed (Σgas, Σstars) relation quoted above. The consequences of our model in terms of cluster survivability after residual star-forming gas expulsion and in terms of star age distribution in young gas-free clusters are discussed.

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Instantaneous Starburst of the Massive Clusters Westerlund 1 and NGC 3603 Yc

Cited by 84 publications

References 41 publications

Ages of Young Stars

Ages of Young Stars

A VLT/FLAMES survey for massive binaries in Westerlund 1

Local‐density driven clustered star formation: Model and (some) implications

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