A VLT/FLAMES survey for massive binaries in Westerlund 1

Clark, J. S.; Ritchie, B. W.; Negueruela, I.; Crowther, P. A.; Damineli, A.; Jablonski, F.; Langer, N.

doi:10.1051/0004-6361/201116990

Cited by 28 publications

(37 citation statements)

References 84 publications

(97 reference statements)

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“…) and evidence for distinct binary evolutionary channels (e.g. Clark et al 2011b) confirming the predictions of previous theoretical studies (e.g. Petrovic et al 2005).…”

Section: Introductionsupporting

confidence: 87%

On the nature of candidate luminous blue variables in M 33

Clark

Castro

García

et al. 2012

A&A

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Context. Luminous blue variables (LBVs) are a class of highly unstable stars that have been proposed to play a critical role in massive stellar evolution as well as being the progenitors of some of the most luminous supernovae known. However the physical processes underlying their characteristic instabilities are currently unknown. Aims. In order to provide observational constraints on this behaviour we have initiated a pilot study of the population of (candidate) LBVs in the Local Group galaxy M 33. Methods. To accomplish this we have obtained new spectra of 18 examples within M 33. These provide a baseline of ≥4 yr with respect to previous observations, which is well suited to identifying LBV outbursts. We also employed existing multi-epoch optical and mid-IR surveys of M 33 to further constrain the variability of the sample and search for the presence of dusty ejecta. Results. Combining the datasets reveals that spectroscopic and photometric variability appears common, although in the majority of cases further observations will be needed to distinguish between an origin for this behavour in short lived stochastic wind structure and low level photospheric pulsations or coherent long term LBV excursions. Of the known LBVs we report a hitherto unidentified excursion of M 33 Var C between 2001-5, while the transition of the WNLh star B517 to a cooler B supergiant phase between 1993−2010 implies an LBV classification. Proof-of-concept quantitative model atmosphere analysis is provided for Romano's star; the resultant stellar parameters being consistent with the finding that the LBV excursions of this star are accompanied by changes in bolometric luminosity. The combination of temperature and luminosity of two stars, the BHG [HS80] 110A and the cool hypergiant B324, appear to be in violation of the empirical Humphreys-Davidson limit. Mid-IR observations demonstrate that a number of candidates appear associated with hot circumstellar dust, although no objects as extreme as η Car are identified. The combined dataset suggests that the criteria employed to identify candidate LBVs results in a heterogeneous sample, also containing stars demonstrating the B[e] phenomenon. Of these, a subset of optically faint, low luminosity stars associated with hot dust are of particular interest since they appear similar to the likely progenitor of SN 2008S and the 2008 NGC 300 transient (albeit suffering less intrinsic extinction). Conclusions. The results of such a multiwavelength observational approach, employing multiplexing spectrographs and supplemented with quantitative model atmosphere analysis, appears to show considerable promise in both identifying and characterising the physical properties of LBVs as well as other short lived phases of massive stellar evolution.

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“…) and evidence for distinct binary evolutionary channels (e.g. Clark et al 2011b) confirming the predictions of previous theoretical studies (e.g. Petrovic et al 2005).…”

Section: Introductionsupporting

confidence: 87%

On the nature of candidate luminous blue variables in M 33

Clark

Castro

García

et al. 2012

A&A

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“…Building on the evolutionary schemes delineated in Clark et al (2011) we might suppose an additional pathway for close binaries comprising two stars of comparable masses, such that for stars within Wd1 current evolving from the MS (M init ∼ 35−50 M ):…”

Section: Evolutionary Pathways For Massive Stars In Wd1mentioning

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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“…From an observational perspective, after decades of slow progress we have now more than tripled the number of known close binary central stars to more than 40 postcommon envelope systems (Miszalski et al 2011a); we have independently refined the close binary fraction of Bond (2000) to be at least 17±5 % (Miszalski et al 2009a); identified strong tendencies for close binaries to be associated with equatorial rings and fast collimated polar outflows (Miszalski et al 2009b(Miszalski et al , 2011bCorradi et al 2011) and we have identified the binary as the shaping agent in at least 6 systems where the nebula inclination matches the orbital inclination (Jones et al 2011). In addition several efforts are underway to detect binaries of wider separation to finally determine the total binary fraction of PNe, predicted to be higher than expected from the main-sequence binary fraction (Moe & De Marco 2006.…”

Section: And References Therein)mentioning

confidence: 99%

“…Studies of individual massive binary systems are now providing us with ever more accurate parameters of the most massive stars, enabling critical tests for evolutionary models in the upper parts of the HR diagram (Pavlovski & Southworth 2009;Ritchie et al 2009;Ritchie et al 2010;Clark 2011). Record holders include R136, host of the most massive O supergiants , and R145 (Schnurr et al 2009) hosting a hydrogen-rich Wolf-Rayet star for which minimum masses near 100 M have been derived.…”

Section: Massive Binary Evolution (S De Mink)mentioning

confidence: 99%

Commission 35: Stellar Constitution

Charbonnel¹,

Limongi²,

D’Antona³

et al. 2011

Proc. IAU

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Commission 35 consists of members of the International Astronomical Union whose research is concerned with the structure and evolution of stars in all parts of the H-R diagram. Their interests range from various aspects of stellar interior physics, such as convection, diffusion, rotation, magnetic fields, to asteroseismology and the prediction of the evolutionary and nucleosynthetic histories of stars that are of vital importance for our understanding of stellar populations and galactic chemical evolution.

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A VLT/FLAMES survey for massive binaries in Westerlund 1

Cited by 28 publications

References 84 publications

On the nature of candidate luminous blue variables in M 33

On the nature of candidate luminous blue variables in M 33

A VLT/FLAMES survey for massive binaries in Westerlund 1

Commission 35: Stellar Constitution

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