The B-type binaries characterization programme I. Orbital solutions for the 30 Doradus population

Villaseñor, J. I.; Taylor, W. D.; Evans, C. J.; Ramírez-Agudelo, O. H.; Sana, H.; Almeida, L. A.; Mink, S. E. de; Dufton, P. L.; Langer, N.

doi:10.1093/mnras/stab2197

Cited by 21 publications

(21 citation statements)

References 73 publications

(116 reference statements)

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“…The spectroscopic binary fraction reaches ∼50% for B stars and up to ∼70% for O stars, meaning that long-period massive binaries also exist. Indeed, the period distribution of massive binaries with ages of a few megayears follows a well-defined power law, ranging from about 1 d to at least 10 years (Fryer et al 2012;Sana et al 2012Sana et al , 2014Kobulnicky et al 2014;Almeida et al 2015;Banyard et al 2021;Villaseñor et al 2021). A migration affecting about half to two-thirds of all OB stars is therefore probably sufficient to explain the wide variety of separation observed.…”

Section: Connection With Star Formation Modelsmentioning

confidence: 98%

The origin of close massive binaries in the M17 star-forming region

Bordier

Frost

Sana

et al. 2022

A&A

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Context. Spectroscopic multiplicity surveys of O stars in young clusters and OB associations have revealed that a large portion (∼70%) of these massive stars (Mi > 15 M⊙) belong to close and short-period binaries (with a physical separation of less than a few astronomical units). Follow-up VLT(I) high-angular-resolution observations led to the detection of wider companions (up to d ∼ 500 au), increasing the average companion fraction to > 2. Despite the recent and significant progress, the formation mechanisms leading to such close massive multiple systems remain to be elucidated. As a result, young massive close binaries (or higher-order multiple systems) are unique laboratories for determining the pairing mechanism of high-mass stars. Aims. We present the first VLTI/GRAVITY observations of six young O stars in the M17 star-forming region (≲1 Myr) and two additional foreground stars. VLTI/GRAVITY provides the K-band high-angular-resolution observations needed to explore the close environment of young O-type stars, and, as such, offers an excellent opportunity to characterise the multiplicity properties of the immediate outcome of the massive star formation process. Methods. From the interferometric model fitting of visibility amplitudes and closure phases, we search for companions and measure their positions and flux ratios. Combining the resulting magnitude difference with atmosphere models and evolutionary tracks, we further constrain the masses of the individual components. Results. All six high-mass stars are in multiple systems, leading to a multiplicity fraction of 100% and yielding a 68% confidence interval of 94–100%. We detect a total of nine companions with separations of up to 120 au. Including previously identified spectroscopic companions, the companion fraction of the young O stars in our sample reaches 2.3 ± 0.6. The derived masses span a wide range, from 2.5 to 50 M⊙, with a great tendency towards high-mass companions. However, we do not find a significant correlation between the mass of the companions and their separation. Conclusions. While based on a modest sample, our results clearly indicate that the origin of the high degree of multiplicity is rooted in the star formation mechanism of the sample stars. No clear evidence for one of the competing concepts of massive star formation (core accretion or competitive accretion) could be found. However, given that we find all of the companions within ∼120 au, our results are compatible with migration as a scenario for the formation of close massive binaries.

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Section: Connection With Star Formation Modelsmentioning

confidence: 98%

The origin of close massive binaries in the M17 star-forming region

Bordier

Frost

Sana

et al. 2022

A&A

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“…Armed with extensive binary properties of early-type stars in the Tarantula from VFTS (Sana et al 2013;Walborn et al 2014), TMBM (Almeida et al 2017, Shenar et al, in prep) and BBC (Villaseñor et al 2021) we have been able to separate T-ReX sources into single, SB1 and SB2. In general, we confirm previous X-ray studies of Galactic OB stars that binaries possess similar X-ray properties to single stars (Oskinova 2005).…”

Section: Discussionmentioning

confidence: 99%

“…Fortunately, 76 T-ReX sources were included in VFTS, with spectroscopy across a range of cadences and whose spectroscopic binary status has been summarised in Walborn et al (2014) and Evans et al (2015). A subset of VFTS sources identified as spectroscopic binaries have been followed up with the Tarantula Massive Binary Monitoring (TMBM, Almeida et al 2017, Shenar et al in prep) and B-stars binaries characterization (BBC, Villaseñor et al 2021) surveys in order to establish orbital properties. Excluding complex systems in R136a, 41 sources are confirmed spectroscopic binaries, of which 24 are double-lined spectroscopic binaries (SB2).…”

Section: T-rex Point Source Cataloguementioning

confidence: 99%

X-ray properties of early-type stars in the Tarantula Nebula from T-ReX

Crowther¹,

Broos²,

Townsley³

et al. 2022

Preprint

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We reassess the historical 𝐿 X /𝐿 Bol relation for early-type stars from a comparison between T-ReX, the Chandra ACIS X-ray survey of the Tarantula Nebula in the LMC, and contemporary spectroscopic analysis of massive stars obtained primarily from VLT/FLAMES, VLT/MUSE and HST/STIS surveys. For 107 sources in common (some host to multiple stars), the majority of which are bolometrically luminous (40% exceed 10 6 𝐿 ), we find an average log 𝐿 X /𝐿 Bol = −6.90 ± 0.65. Excluding extreme systems Mk 34 (WN5h+WN5h), R140a (WC4+WN6+) and VFTS 399 (O9 IIIn+?), plus four WR sources with anomalously hard X-ray components (R130, R134, R135, Mk 53) and 10 multiple sources within the spatially crowded core of R136a, log 𝐿 X /𝐿 Bol = −7.00 ± 0.49, in good agreement with Galactic OB stars. No difference is found between single and binary systems, nor between O, Of/WN and WR stars, although there does appear to be a trend towards harder X-ray emission from O dwarfs, through O (super)giants, Of/WN stars and WR stars. The majority of known OB stars in the Tarantula are not detected in the T-ReX point source catalogue, so we have derived upper limits for all undetected OB stars for which log 𝐿 Bol /𝐿 ≥ 5.0. A survival analysis using detected and upper-limit log 𝐿 X /𝐿 Bol values indicates no significant difference between luminous O stars in the LMC and the Carina Nebula. This analysis suggests that metallicity does not strongly influence 𝐿 X /𝐿 Bol . Plasma temperatures for single, luminous O stars in the Tarantula (𝑘𝑇 𝑚 = 1.0 keV) are higher than counterparts in Carina (𝑘𝑇 𝑚 = 0.5 keV).

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“…Inspection of Fig. 7 also shows that their estimated semiamplitudes are all relatively low, with 𝐾 1 < 40 km s −1 ; by contrast Villaseñor et al (2021) found 29 VFTS B-type systems (that have not been classified as supergiants), which had 𝐾 1 > 40 km s −1 . The number of VFTS targets classified (Evans et al 2015) as Be-type and B-type (excluding supergiants) were 69 and 310 respectively.…”

Section: Binaritymentioning

confidence: 91%

“…3.2. Spectral types and sub-cluster membership (H: Hodge 301, S: SLS 639) are taken from Evans et al (2015), whilst systems identified as SB1 binaries by Dunstall et al (2015); Villaseñor et al (2021) are marked by asterisks. As discussed by Evans et al (2006), the "Be+" classification is on based on the identification of Fe emission features.…”

Section: Systematic Errors In 𝑣 E Sin 𝑖-Estimatesmentioning

confidence: 99%

Properties of the Be-type stars in 30 Doradus

Dufton,

Lennon,

Villasenor

et al. 2022

Preprint

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The evolutionary status of Be-type stars remains unclear, with both single-star and binary pathways having been proposed. Here, VFTS spectroscopy of 73 Be-type stars, in the spectral-type range, B0-B3, is analysed to estimate projected rotational velocities, radial velocities and stellar parameters. They are found to be rotating faster than the corresponding VFTS B-type sample but simulations imply that their projected rotational velocities are inconsistent with them all rotating at near critical velocities. The de-convolution of the projected rotational velocities estimates leads to a mean rotational velocity estimate of 320-350 km s −1 , approximately 100 km s −1 larger than that for the corresponding B-type sample. There is a dearth of targets with rotational velocities less than 0.4 of the critical velocity, with a broad distribution reaching up to critical rotation. Our best estimate for the mean or median of the rotational velocitiy is 0.68 of the critical velocity. Rapidly-rotating B-type stars are more numerous than their Be-type counterparts, whilst the observed frequency of Be-type stars identified as binary systems is significantly lower than that for normal B-type stars, consistent with their respective radial-velocity dispersions. The semi-amplitudes for the Be-type binaries are also smaller. Similar results are found for a SMC Be-type sample centred on NGC 346 with no significant differences being found between the two samples. These results are compared with the predictions of single and binary stellar evolutionary models for Be-type stars. Assuming that a single mechanism dominated the production of classical Be-type stars, our comparison would favour a binary evolutionary history.

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The B-type binaries characterization programme I. Orbital solutions for the 30 Doradus population

Cited by 21 publications

References 73 publications

The origin of close massive binaries in the M17 star-forming region

The origin of close massive binaries in the M17 star-forming region

X-ray properties of early-type stars in the Tarantula Nebula from T-ReX

Properties of the Be-type stars in 30 Doradus

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