A VLT/FLAMES survey for massive binaries in Westerlund 1 V. the X-ray selected blue stragglers Wd1-27 and -30a

Abstract

Observational studies suggest that many OB stars are found within binary systems which may be expected to interact during their lifetimes. Significant mass transfer or merger of both components will modify evolutionary pathways, facilitating the production of exceptionally massive stars which will present as blue stragglers. Identification and characterisation of such objects is crucial if the outcomes of binary evolutionary channels are to be quantified. The massive cluster Westerlund 1 hosts a rich population of X-ray bright stars where the emission is thought to derive from the wind collision zones of massive binaries. Selected on this basis, we present the results of a multiwavelength analysis of the X-ray luminous O stars Wd1-27 and -30a. We find both to be early/mid-O hypergiants with luminosities, temperatures and masses significantly in excess of other early stars within Wd1, hence qualifying as massive blue stragglers. The nature of Wd1-27 remains uncertain but the detection of radial velocity changes and the X-ray properties of Wd1-30a suggest that it is a binary. Analysis of Gaia proper motion and parallactic data indicates that both are cluster members; we also provide a membership list for Wd1 based on this analysis. The presence of hypergiants of spectral types O to M within Wd1 cannot be understood via single-star evolution. We suppose that the early-B and mid-O hypergiants formed via binary-induced mass-stripping of the primary and mass-transfer to the secondary, respectively. This implies that for a subset of objects massive star-formation may be regarded as a two-stage process, with binary-driven mass-transfer or merger yielding stars with masses significantly in excess of their initial birth mass (Abridged).

arXiv comment19 pages, 9 figures, accepted for publication in Astronomy and Astrophysics

References in corpus (85)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Correcting for the Effects of Interstellar Extinction
• Binary interaction dominates the evolution of massive stars
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Toward Understanding Massive Star Formation
• Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones
• Gaia Data Release 2: using Gaia parallaxes
• Competitive accretion in embedded stellar cluster
• On the Formation of Massive Stars
• The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
• The rotation rates of massive stars: the role of binary interaction through tides, mass transfer and mergers
• The incidence of stellar mergers and mass gainers among massive stars
• Physical Parameters and Wind Properties of Galactic Early B Supergiants
• On the massive stellar population of the Super Star Cluster Westerlund 1
• A Neutron Star with a Massive Progenitor in Westerlund 1
• Three-dimensional mapping of the local interstellar medium with composite data
• The VLT-FLAMES survey of massive stars: constraints on stellar evolution from the chemical compositions of rapidly rotating Galactic and Magellanic Cloud B-type stars
• The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of HeII 1640 in young star clusters
• A census of the Wolf-Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy
• The VLT-FLAMES survey of massive stars: rotation and nitrogen enrichment as the key to understanding massive star evolution
• The most massive stars in the Arches cluster
• Constraining the mass transfer in massive binaries through progenitor evolution models of Wolf-Rayet+O binaries
• Stellar and wind properties of massive stars in the central parsec of the Galaxy
• A Medium Resolution Near-Infrared Spectral Atlas of O and Early B Stars
• BONNSAI: a Bayesian tool for comparing stars with stellar evolution models
• Physical parameters of the high-mass X-ray binary 4U1700-37
• The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turn-offs. II. Results from 12 Galactic Clusters and OB Associations
• The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turn-offs. I. Results from 19 OB Associations in the Magellanic Clouds
• The ages of young star clusters, massive blue stragglers and the upper mass limit of stars: analysing age dependent stellar mass functions
• The evolution of massive stars and their spectra I. A non-rotating 60 Msun star from the zero-age main sequence to the pre-supernova stage
• Statistical Confirmation of a Stellar Upper Mass Limit
• The Massive Star Population of Cygnus OB2
• The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars
• L-band spectroscopy of Galactic OB-stars
• The Star Formation History and Mass Function of the Double Cluster h and Chi Persei
• Metallicity in the Galactic Center: The Quintuplet cluster
• Metallicity in the Galactic Center: The Arches cluster
• The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars
• The population of OB supergiants in the starburst cluster Westerlund 1
• Evolution of Mass Functions of Coeval Stars through Wind Mass Loss and Binary Interactions
• The Stellar Population of h and chi Persei: Cluster Properties, Membership, and the Intrinsic Colors and Temperatures of Stars
• On the nature of the galactic early-B hypergiants
• Instantaneous starburst of the massive clusters Westerlund 1 and NGC 3603 YC
• Runaway massive stars from R136: VFTS 682 is very likely a "slow runaway"
• Cygnus OB2 DANCe: A high precision proper motion study of the Cygnus OB2 association
• Massive binaries in the vicinity of Sgr A*
• Detection of white dwarf companions to blue stragglers in the open cluster NGC 188: direct evidence for recent mass transfer
• The G305 star-forming complex: the central star clusters Danks 1 and Danks 2
• Mid-infrared imaging and spectroscopy of the enigmatic cocoon stars in the Quintuplet Cluster
• The emergence of super-canonical stars in R136-type star-burst clusters
• New very massive stars in Cygnus OB2
• Optical-NIR dust extinction towards Galactic O stars
• The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation
• A VLT/FLAMES survey for massive binaries in Westerlund 1. IV. Wd1-5 - binary product and a pre-supernova companion for the magnetar CXOU J1647-45?
• Bolometric luminosity variations in the Luminous Blue Variable AFGL2298
• A serendipitous survey for variability amongst the massive stellar population of Westerlund 1
• The Quintuplet Cluster I. A K-band spectral catalog of stellar sources
• On the sensitivity of HeI singlet lines to the FeIV model atom in O stars
• Extinction law in the range 0.4-4.8 $\mu$m and the 8620 $\mathring{A}$ DIB towards the stellar cluster Westerlund 1
• A VLT/FLAMES survey for massive binaries in Westerlund 1: I. first observations of luminous evolved stars
• Spectroscopic monitoring of the luminous blue variable Westerlund1-243 from 2002 to 2009
• A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti
• Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1
• A Fast Chi-squared Technique For Period Search of Irregularly Sampled Data
• Radio emission from the massive stars in the Galactic Super Star Cluster Westerlund 1
• The Arches cluster revisited: I. Data presentation and stellar census
• The Quintuplet Cluster III. Hertzsprung-Russell diagram and cluster age
• The circumstellar environment and evolutionary state of the supergiant B[e] star Wd1-9
• The Formation of Very Massive Stars
• An updated stellar census of the Quintuplet cluster
• History and modes of star formation in the most active region of the Small Magellanic Cloud, NGC 346
• The Optical/Near-Infrared Extinction Law In Highly Reddened Regions
• Further Wolf-Rayet stars in the starburst cluster Westerlund 1
• The K-band Spectrum of The Hot Star in IRS~8: An Outsider in the Galactic Center?
• A VLT/FLAMES survey for massive binaries in Westerlund 1. III. The WC9d binary W239 and implications for massive stellar evolution
• The Arches cluster revisited: II. A massive eclipsing spectroscopic binary in the Arches cluster
• The X-ray catalog of spectroscopically identified Galactic O stars: Investigating the dependence of X-ray luminosity on stellar and wind parameters
• An ALMA 3mm continuum census of Westerlund 1
• The eclipsing, double-lined, Of supergiant binary Cyg OB2-B17
• The Ionized Nebula surrounding the Red Supergiant W26 in Westerlund 1
• The VLT-FLAMES survey of massive stars: NGC346-013 as a test case for massive close binary evolution
• ALMA observations of the supergiant B[e] star Wd1-9
• Asymmetric Ejecta of Cool Supergiants and Hypergiants in the Massive Cluster Westerlund 1
• Blue Stragglers in Globular Clusters: Observations, Statistics and Physics

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