Two O2 If*/WN6 stars possibly ejected from the massive young Galactic cluster Westerlund 2

Roman-Lopes, Alexandre; Barbá, R. H.; Morrell, N.

doi:10.1111/j.1365-2966.2011.19062.x

Cited by 32 publications

(40 citation statements)

References 42 publications

(53 reference statements)

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“…WR20aa and WR20c appear to be members of Westerlund 2 as well, although whether they are runaway cluster members (Roman-Lopes et al 2011) or simply members of the cluster corona is left for future study. The cluster color-magnitude diagram (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Their inferred luminosities are consistent with results for other late-type WN stars in open clusters. Roman-Lopes et al (2011) suggest that they are runaway stars from the cluster. The case for WR21a is much more interesting.…”

Section: Wolf-rayet Membersmentioning

confidence: 99%

“…The parameters of the Wolf-Rayet stars near Westerlund 2 are summarized in Table 6, where the broad-band magnitudes and colors are from the present study, Roman-Lopes et al (2011), and Simbad, and the spectral types are from Roman-Lopes et al (2011). The inferred broad-band luminosities are based upon the assumption of membership in Westerlund 2.…”

Section: Wolf-rayet Membersmentioning

confidence: 99%

“…The anomaly for this star defies a simple explanation. Roman-Lopes et al (2011) summarized the case for this star as uncertain.…”

Section: Wolf-rayet Membersmentioning

confidence: 99%

“…Several Wolf-Rayet stars in the cluster and surroundings Roman-Lopes et al 2011) are potential sources of highenergy radiation, as is the case, for example, for the northern hemisphere cluster Berkeley 87 (Manchanda et al 1996;Tluczykont 2001;Abdo et al 2009). Berkeley 87 is spatially coincident with the strongest northern hemisphere source of γ-rays and contains the WO2 Wolf-Rayet star WR 142 as well as several unusual high-mass objects (Turner & Forbes 1982).…”

Section: Introductionmentioning

confidence: 99%

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The distance to the young open cluster Westerlund 2

Carraro

Turner

Majaess

et al. 2013

A&A

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A new X-ray, UBVRI c , and JHKs study of the young cluster Westerlund 2 was undertaken to resolve discrepancies tied to the cluster's distance. Existing spectroscopic observations for bright cluster members and new multi-band photometry imply a reddening relation toward Westerlund 2 described by E U−B /E B−V = 0.63 + 0.02 E B−V . Variable-extinction analyses for Westerlund 2 and nearby IC 2581 based upon spectroscopic distance moduli and ZAMS fitting yield values of R V = A V /E B−V = 3.88±0.18 and 3.77±0.19, respectively, and confirm prior assertions that anomalous interstellar extinction is widespread throughout Carina. The results were confirmed by applying the color-difference method to UBVRI c JHK s data for 19 spectroscopically observed cluster members, yielding R V = 3.85 ± 0.07. The derived distance to Westerlund 2 of d = 2.85 ± 0.43 kpc places the cluster on the far side of the Carina spiral arm. The cluster's age is no more than τ ∼ 2 × 10 6 yr as inferred from the cluster's brightest stars and an X-ray (Chandra) cleaned analysis of its pre-main-sequence demographic. Four Wolf-Rayet stars in the cluster core and surrounding corona (WR20a, WR20b, WR20c, and WR20aa) are very likely cluster members, and their inferred luminosities are consistent with those of other late-WN stars in open clusters. The color-magnitude diagram for Westerlund 2 also displays a gap at spectral type B0.5 V with associated color spread at higher and lower absolute magnitudes that might be linked to close binary mergers. These features, in conjunction with the evidence for mass loss from the WR stars, may help to explain the high flux of γ-rays, cosmic rays, and X-rays from the direction toward Westerlund 2.

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Section: Discussionmentioning

confidence: 99%

Section: Wolf-rayet Membersmentioning

confidence: 99%

Section: Wolf-rayet Membersmentioning

confidence: 99%

“…The anomaly for this star defies a simple explanation. Roman-Lopes et al (2011) summarized the case for this star as uncertain.…”

Section: Wolf-rayet Membersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The distance to the young open cluster Westerlund 2

Carraro

Turner

Majaess

et al. 2013

A&A

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Fundamental parameters of four massive eclipsing binaries in Westerlund 1

Koumpia

Bonanos

2012

A&A

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Context. Only a small number of high mass stars (>30 M ) have fundamental parameters (i.e. masses and radii) measured with high enough accuracy from eclipsing binaries to constrain formation and evolutionary models of massive stars. Aims. This work aims to increase this limited sample, by studying the four massive eclipsing binary candidates discovered by Bonanos in the young massive cluster Westerlund 1. Methods. We present new follow-up echelle spectroscopy of these binaries and models of their light and radial velocity curves. Results. We obtain fundamental parameters for the eight component stars, finding masses that span a range of 10−40 M , and contributing accurate fundamental parameters for one additional very massive star, the 33 M component of W13. WR77o is found to have a ∼40 M companion, which provides a second dynamical constraint on the mass of the progenitor of the magnetar known in the cluster. We also use W13 to estimate the first, direct, eclipsing binary distance to Westerlund 1 and therefore the magnetar and find it to be at 3.7 ± 0.6 kpc. Conclusions. Our results confirm previous evidence for a high mass for the progenitor of the magnetar. In addition, the availability of eclipsing binaries with accurate parameters opens the way for direct, independent, high precision eclipsing binary distance measurements to Westerlund 1.

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The VLT-FLAMES Tarantula Survey

Walborn

Sana

Simón‐Díaz

et al. 2014

A&A

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Detailed spectral classifications are presented for 352 O-B0 stars in the VLT-FLAMES Tarantula Survey ESO Large Programme, of which 213 O-type are judged of sufficiently high quality for further morphological analysis. Among them, six subcategories of special interest are distinguished. (1) Several new examples of the earliest spectral types O2-O3 have been found, while a previously known example has been determined to belong to the nitrogen-rich ON2 class. (2) A group of extremely rapidly rotating main-sequence objects has been isolated, including the largest v sin i values known, the spatial and radial-velocity distributions of which suggest ejection from the two principal ionizing clusters NGC 2070 and NGC 2060. (3) Several new examples of the evolved, rapidly rotating Onfp class show similar evidence, although at least some of them are spectroscopic binaries. (4) No fewer than 48 members of the Vz category, hypothesized to be on or near the zero-age main sequence, are found in this sample; in contrast to the rapid rotators, they are strongly concentrated to the ionizing clusters and a newly recognized region of current and recent star formation to the north, supporting their interpretation as very young objects, as do their relatively faint absolute magnitudes. (5) A surprisingly large fraction of the main-sequence spectra belong to the recently recognized V((fc)) class, with C iii emission lines of similar strength to the usual N iii in V((f)) spectra, although a comparable number of the latter are also present, as well as six objects with very high-quality data but no trace of either emission feature, presenting new challenges to physical interpretations. (6) Two mid-O Vz and three late-O giant/supergiant spectra with morphologically enhanced nitrogen lines have been detected. Absolute visual magnitudes have been derived for each star with individual extinction laws, and composite Hertzsprung-Russell diagrams provide evidence of the multiple generations present in this field. Spectroscopic binaries, resolved visual multiples, and possible associations with X-ray sources are noted. Astrophysical and dynamical analyses of this unique dataset underway will provide new insights into the evolution of massive stars and starburst clusters.

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Two O2 If*/WN6 stars possibly ejected from the massive young Galactic cluster Westerlund 2

Cited by 32 publications

References 42 publications

The distance to the young open cluster Westerlund 2

The distance to the young open cluster Westerlund 2

Fundamental parameters of four massive eclipsing binaries in Westerlund 1

The VLT-FLAMES Tarantula Survey

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