BAT99 126: A multiple Wolf-Rayet system in the Large Magellanic Cloud with a massive near-contact binary

Janssens, S.; Shenar, T.; Mahy, L.; Marchant, Pablo; Sana, H.; Bodensteiner, J.

doi:10.1051/0004-6361/202039305

Cited by 10 publications

(9 citation statements)

References 72 publications

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“…We conclude that the system has a tight OB + OB binary and a WR star whose connection to the OB binary is yet to be established. This is similar to BAT99 126, the WR star in the Large Magellanic Cloud that was found to be a quadruple system (Janssens et al 2021).…”

Section: Discussionsupporting

confidence: 77%

A spectroscopic multiplicity survey of Galactic Wolf-Rayet stars

Dsilva

Shenar

Sana

et al. 2022

A&A

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Context. Most massive stars reside in multiple systems that will interact over the course of their lifetime. This has important consequences on their future evolution and their end-of-life products. Classical Wolf-Rayet (WR) stars represent the final end stages of stellar evolution at the upper-mass end. While their observed multiplicity fraction is reported to be ∼0.4 in the Galaxy, their intrinsic multiplicity properties and the distributions of their orbital parameters remain insufficiently constrained to provide a reliable anchor to compare to evolutionary predictions. Aims. As part of a homogeneous, magnitude-limited (V ≤ 12) spectroscopic survey of northern Galactic WR stars, this paper aims to establish the observed and intrinsic multiplicity properties of the early-type nitrogen-rich WR population (WNE), including estimates of the multiplicity fraction and the shape of their orbital period distribution. Additionally, we compare these with the properties of the carbon-rich WR population (WC) stars obtained in the first paper of this series. Methods. We obtained high-resolution spectroscopic time series of the complete magnitude-limited sample of 16 WNE stars observable with the 1.2 m Mercator telescope at La Palma, typically providing a time base of about two to eight years. We measured relative radial velocities (RVs) using cross-correlation and used RV variations to flag binary candidates. Using an updated Monte Carlo method with a Bayesian framework, we calculated the three-dimensional likelihood for the intrinsic binary fraction ( f WNE int ), the maximum period (log P max ), and the power-law index for the period distribution (π) for the WNE population with P min fixed at 1 d. We also used this updated method to re-derive multiplicity parameters for the Galactic WC population. Results. Adopting a peak-to-peak RV variability threshold of 50 km s −1 as a criterion, we classify 7 of the 16 targets as binaries. This results in an observed multiplicity fraction ( f WNE obs ) of 0.44 ± 0.12. Assuming flat priors, we derive the best-fit multiplicity properties f WNE int = 0.56 +0.20 −0.15 , log P max = 4.60 +0.40 −0.77 , and π = −0.30 +0.55 −0.53 for the parent WNE population. We explored different mass-ratio distributions and note that they did not change our results significantly. For the Galactic WC population from Paper 1, we re-derive f WC int = 0.96 +0.04 −0.22 , log P min = 0.75 +0.26 −0.60 , log P max = 4.00 +0.42 −0.34 , and π = 1.90 +1.26 −1.25 . Conclusions. The derived multiplicity parameters for the WNE population are quite similar to those derived for main-sequence O binaries but differ from those of the WC population. The significant shift in the WC period distribution towards longer periods is too large to be explained via expansion of the orbit due to stellar winds, and we discuss possible implications of our results. Analysis of the WNL population and further investigation of various evolutionary scenarios is required to connect the different evolutionary phases of stars at the upper-ma...

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Section: Discussionsupporting

confidence: 77%

A spectroscopic multiplicity survey of Galactic Wolf-Rayet stars

Dsilva

Shenar

Sana

et al. 2022

A&A

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“…We then measured K 3 and K 4 by disentangling the strong He ii and He i λ4471 lines, whose weighted mean yields K 3 = 282 ± 36 km s −1 , K 4 = 323 ± 33 km s −1 , yielding in turn K 2 = 41 ± 13. This unique system could be a prototypical progenitor of the triple/quadruple WR system BAT99 126, which was also found to host a contact binary (Janssens et al 2021).…”

Section: Appendix B: Comments On Individual Targetsmentioning

confidence: 99%

The Tarantula Massive Binary Monitoring

Shenar

Sana

Mahy

et al. 2022

A&A

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Context. Massive binaries hosting a black hole (OB+BH) represent a critical phase in the production of BH mergers in the context of binary evolution. In spite of this, such systems have so far largely avoided detection. Single-lined spectroscopic (SB1) O-type binaries are ideal objects to search for elusive BH companions. Moreover, SB1 binaries hosting two main sequence stars probe a regime of more extreme mass ratios and longer periods compared to double-lined binaries (SB2), and are thus valuable for establishing the natal mass ratio distribution of massive stars. Aims. We characterise the hidden companions in 51 SB1 O-type and evolved B-type binaries identified in the Large Magellanic Cloud (LMC) in the framework of the VLT-FLAMES Tarantula Survey (VFTS) and its follow-up, the Tarantula Massive Binary Monitoring (TMBM). The binaries cover periods between few days to years (0 < log P < 3 [d]). Goals are to hunt for BHs and sample the low-mass end of the mass-ratio distribution. Methods. To uncover the hidden companions, we implement the shift-and-add grid disentangling algorithm on 32 epochs of spectroscopy acquired in the framework of TMBM with the FLAMES spectrograph, allowing us to detect companions contributing as little as ≈ 1 − 2% to the visual flux. We further analyse OGLE photometric data for the presence of eclipses or ellipsoidal variations. Results. Out of the 51 SB1 systems, 43 (84%) are found to have non-degenerate stellar companions, of which 28 are confident detections, and 15 are less certain (SB1: or SB2:). Of these 43 targets, one is found to be a triple (VFTS 64), and two are found to be quadruples (VFTS 120, 702). Our sample includes a total of eight eclipsing binaries. The remaining 8 targets (16%) retain an SB1 classification. We model the mass-ratio distribution as f (q) ∝ q κ , and derive κ through a Bayesian approach. We use massratio constraints from previously known SB2 binaries, newly uncovered SB2 binaries, and SB1 binaries, while accounting for binary detection bias. We find κ = 0.2 ± 0.2 for the entire sample and κ = −0.2 ± 0.2 when excluding binaries with periods shorter than 10 d. In contrast, κ = 1.2 ± 0.5 is retrieved for tight binaries (P < 10 d), proposed here to be a consequence of binary interaction. Aside from the unambiguous O+BH binary VFTS 243, analysed in detail in a separate paper, we identify two additional OB+BH candidates: VFTS 514 and 779. Conclusions. Our study firmly establishes a virtually flat natal mass-ratio distribution (κ = 0) for O-type stars at LMC metallicity, covering the entire mass-ratio range (0.05 < q < 1) and periods in the range 0 < log P < 3 [d]. The nature of the OB+BH candidates should be verified through future monitoring, but the frequency of OB+BH candidates is generally in line with recent predictions at LMC metallicity.

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“…Furthermore, it has a known triple companion on a relatively close orbit (Zasche et al 2017). BAT 99-126 is a higher order system that contains an O-type contact system; however the orbital configuration of the system is not known so it is rejected (Janssens et al 2021). HD 64315 is a quadruple system containing two pairs of close binaries, one of which is in a contact configuration.…”

Section: Rejected Systemsmentioning

confidence: 99%

“…Throughout their lives, it is expected that approximately 70% of massive stars will interact with a companion (e.g., Sana et al 2012) and of those that do, 40% (24% of all massive stars) will evolve through an overcontact phase (e.g., Pols 1994;Wellstein et al 2001;de Mink et al 2007). Nevertheless, very few massive overcontact systems are known (see, e.g., Leung & Schneider 1978;Popper 1978;Hilditch et al 2005;Penny et al 2008;Lorenzo et al 2014Lorenzo et al , 2017Almeida et al 2015;Martins et al 2017;Mahy et al 2020a;Janssens et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Constraining the overcontact phase in massive binary evolution

Abdul-Masih

Escorza

Menon

et al. 2022

A&A

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Context. Given that mergers are often invoked to explain many exotic phenomena in massive star evolution, understanding the evolutionary phase directly preceding a merger, the overcontact phase, is of crucial importance. Despite this, large uncertainties exist in our understanding of the evolution of massive overcontact binaries. Aims. We aim to provide robust observational constraints on the future dynamical evolution of massive overcontact systems by measuring the rate at which the periods change for a sample of six such objects. Furthermore, we aim to investigate whether the periods of unequal mass systems show higher rates of change than their equal mass counterparts, as theoretical models predict. Methods. Using archival photometric data from various ground-and space-based missions covering up to ∼40 years, we measure the periods of each system over several smaller time spans. We then fit a linear regression through the measured periods to determine the rate at which the period is changing over the entire data set. Results. We find that all of the stars in our sample have very small period changes and that there does not seem to be a correlation with the mass ratio. This implies that the orbital periods for these systems are stable on the nuclear timescale, and that the unequal mass systems may not equalize as expected. Conclusions. When comparing our results with population synthesis distributions, we find large discrepancies between the expected mass ratios and period stabilities. We find that these discrepancies can be mitigated to a degree by removing systems with shorter initial periods, suggesting that the observed sample of overcontact systems may originate from binary systems with longer initial orbital periods.

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BAT99 126: A multiple Wolf-Rayet system in the Large Magellanic Cloud with a massive near-contact binary

Cited by 10 publications

References 72 publications

A spectroscopic multiplicity survey of Galactic Wolf-Rayet stars

A spectroscopic multiplicity survey of Galactic Wolf-Rayet stars

The Tarantula Massive Binary Monitoring

Constraining the overcontact phase in massive binary evolution

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