ALMA observations of the supergiant B[e] star Wd1-9

Fenech, Danielle; Clark, J. S.; Prinja, R. K.; Morford, J. C.; Dougherty, S. M.; Blomme, R.

doi:10.1093/mnrasl/slw183

Cited by 13 publications

(19 citation statements)

References 32 publications

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“…Recently, the LHA 120-S 35 membership to the cluster SL 482 has been discussed by Bitsakis et al (2017), who were able to determine the members of the star cluster using a robust decontamination technique, providing a probability of more than 92% that LHA 120-S 35 is member of the cluster. The previously reported B[e]SGs associated to open clusters are: LHA 120-S 111, which belongs to the compact cluster NGC 1994 of the LMC (Melgarejo et al 2001;Lortet & Testor 1988) and Wd1-9, which is a member of the massive Galactic stellar cluster Westerlund 1 (Clark et al 2013b;Fenech et al 2017). The small number of B[e]SGs found in stellar clusters is reasonable taking into account that their lifetime in this post-main-sequence phase is relatively short.…”

Section: Discussionmentioning

confidence: 72%

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Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35

Torres

Cidale

Kraus

et al. 2018

A&A

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Context. B[e] supergiants are massive post-main-sequence stars, surrounded by a complex circumstellar environment where molecules and dust can survive. The shape in which the material is distributed around these objects and its dynamics as well as the mechanisms that give rise to these structures are not well understood. Aims. The aim of this work is to deepen our knowledge of the structure and kinematics of the circumstellar disc of the B[e] supergiant LHA 120-S 35. Methods. High-resolution optical spectra were obtained in three different years. Forbidden emission lines, that contribute to trace the disc at different distances from the star, are modelled in order to determine the kinematical properties of their line-forming regions, assuming Keplerian rotation. In addition, we used low-resolution near-infrared spectra to explore the variability of molecular emission. Results. LHA 120-S 35 displays an evident spectral variability in both optical and infrared regions. The P-Cygni line profiles of H i, as well as those of Fe ii and O i, suggest the presence of a strong bipolar clumped wind. We distinguish density enhancements in the P-Cygni absorption component of the first Balmer lines, which show variations in both velocity and strength. The P-Cygni profile emission component is double-peaked, indicating the presence of a rotating circumstellar disc surrounding the star. We also observe line-profile variations in the permitted and forbidden features of Fe ii and O i. In the infrared, we detect variations in the intensity of the H i emission lines as well as in the emission of the CO band-heads. Moreover, we find that the profiles of each [Ca ii] and [O i] emission lines contain contributions from spatially different (complete or partial) rings. Globally, we find evidence of detached multiring structures, revealing density variations along the disc. We identify an inner ring, with sharp edge, where [Ca ii] and [O i] lines share their forming region with the CO molecular bands. The outermost regions show a complex structure, outlined by fragmented clumps or partial-ring features of Ca ii and O i. Additionally, we observe variations in the profiles of the only visible absorption features, the He i lines. Conclusions. We suggest that LHA 120-S 35 has passed through the red-supergiant (RSG) phase and evolves back bluewards in the Hertzsprung-Russell diagram. In this scenario, the formation of the complex circumstellar structure could be the result of the windwind interactions of the post-RSG wind with the previously ejected material from the RSG. The accumulation of material in the circumstellar environment could be attributed to enhanced mass-loss, probably triggered by stellar pulsations. However, the presence of a binary companion can not be excluded. Finally, we find that LHA 120-S 35 is the third B[e] supergiant belonging to a young stellar cluster.

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Section: Discussionmentioning

confidence: 72%

“…A similar global structure composed by an equatorial disc perpendicular to a bipolar flow has been proposed to interpret the observations at millimeter and radio wavelengths for the B[e]SGs MWC 349 (Danchi et al 2001; Table 1). Tafoya et al 2004) and Wd1-9 (Fenech et al 2017) and the optical and infrared observations of MWC 137 .…”

Section: Discussionmentioning

confidence: 94%

Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35

Torres

Cidale

Kraus

et al. 2018

A&A

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“…Lastly, while X-ray observations and our RV studies suggest that a number of (colliding wind) binaries are found within the cluster (Wang et al 2006, Papers II and III), the Arches appears to lack any systems in which rapid case-A mass-transfer is ongoing. Several examples of such systems have been proposed -Wd1-9 (Clark et al 2013b;Fenech et al 2017), RY Scuti (Gehrz et al 1995(Gehrz et al , 2001Grundstrom et al 2007), NaSt1 (Mauerhan et al 2015), and LHA 115-S 18 (Clark et al 2013a) -and appear to manifest as (supergiant) B[e] stars (cf. discussion in Kastner et al 2010), supporting a combination of a rich low excitation emission line spectrum and bright X-ray, IR, and sub-mm/radio continuum emission (due to colliding winds, the presence of hot dust and a highly elevated mass-loss rate, respectively).…”

Section: The Absence Of H-free Wrs Lbvs and Interacting Binariesmentioning

confidence: 99%

The Arches cluster revisited

Clark

Lohr

Najarro

et al. 2018

A&A

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Context. Located within the central region of the Galaxy, the Arches cluster appears to be one of the youngest, densest, and most massive stellar aggregates within the Milky Way. As such, it has the potential to be uniquely instructive laboratory for the study of star formation in extreme environments and the physics of very massive stars. Aims. To realise this possibility, the fundamental physical properties of both cluster and constituent stars need to be robustly determined; tasks we attempt here. Methods. In order to accomplish these goals we provide and analyse new multi-epoch near-IR spectroscopic data obtained with the VLT/SINFONI and photometry from the HST/WFC3. We are able to stack multiple epochs of spectroscopy for individual stars in order to obtain the deepest view of the cluster members ever obtained. Results. We present spectral classifications for 88 cluster members, all of which are WNLh or O stars: a factor of three increase over previous studies. We find no further examples of Wolf–Rayet stars within the cluster; importantly no H-free examples were identified. The smooth and continuous progression in spectral morphologies from O super/hypergiants through to the WNLh cohort implies a direct evolutionary connection. We identify candidate giant and main sequence O stars spectroscopically for the first time. No products of binary evolution may be unambiguously identified despite the presence of massive binaries within the Arches. Conclusions. Notwithstanding difficulties imposed by the highly uncertain (differential) reddening to the Arches, we infer a main sequence/luminosity class V turn-off mass of ~30−38 M⊙ via the distribution of spectral types. Analysis of the eclipsing binary F2 suggests current masses of ~80 M⊙ and ~60 M⊙ for the WNLh and O hypergiant cohorts, respectively; we conclude that all classified stars have masses >20 M⊙. An age of ~2.0−3.3 Myr is suggested by the turn-off between ~O4-5 V; constraints imposed by the supergiant population and the lack of H-free WRs are consistent with this estimate. While the absence of highly evolved WC stars strongly argues against the prior occurrence of SNe within the Arches, the derived age does accommodate such events for exceptionally massive stars. Further progress will require quantitative analysis of multiple individual cluster members in addition to further spectroscopic observations to better constrain the binary and main sequence populations; nevertheless it is abundantly clear that the Arches offers an unprecedented insight into the formation, evolution and death of the most massive stars nature allows to form.

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“…Ritchie et al 2009aRitchie et al , 2010 have revealed a rich binary population comprising pre-interaction (e.g. Wd1-43a; Ritchie et al 2011), interacting (Wd1-9;Clark et al 2013, Fenech et al 2017) and post-interaction binaries (Wd1-13 and -239; Ritchie et al 2010.…”

Section: The Ymc Westerlundmentioning

confidence: 99%

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

Clark,

Najarro,

Negueruela

et al. 2018

Preprint

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Context. Recent observational studies indicate that a large number of OB stars are found within binary systems which may be expected to interact during their lifetimes. Significant mass transfer or indeed merger of both components is expected to 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 efficiency of mass transfer is to be established; a critical parameter in determining the outcomes of binary evolutionary channels. Aims. The young and coeval massive cluster Westerlund 1 hosts a rich population of X-ray bright OB and Wolf-Rayet stars where the emission is attributed to shocks in the wind collision zones of massive binaries. Motivated by this, we instigated a study of the extremely X-ray luminous O supergiants Wd1-27 and -30a. Methods. We subjected a multi-wavelength and -epoch photometric and spectroscopic dataset to quantitative non-LTE model atmosphere and time-series analysis in order to determine fundamental stellar parameters and search for evidence of binarity. A detailed examination of the second Gaia data release was undertaken to establish cluster membership. Results. Both stars were found 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 binary 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 with an orbital period ≤ 10 days. Analysis of Gaia proper motion and parallactic data indicates that both stars are cluster members; we also provide a membership list for Wd1 based on this analysis. Conclusions. The presence of hypergiants of spectral types O to M within Wd1 cannot be understood solely 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.

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ALMA observations of the supergiant B[e] star Wd1-9

Cited by 13 publications

References 32 publications

Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35

Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35

The Arches cluster revisited

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

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