The observed multiplicity properties of B-type stars in the Galactic young open cluster NGC 6231

Banyard, G.; Sana, H.; Mahy, L.; Bodensteiner, J.; Villaseñor, J. I.; Evans, C. J.

doi:10.1051/0004-6361/202141037

Cited by 46 publications

(39 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This unfortunate alignment of cadence and orbital phase explains why our data do not reveal its multiplicity. Including these two literature binaries would raise the raw (uncorrected for line profile variability contamination) multiplicity fraction of our GOSC sample to 16 out of 25 sources-64%-comparable to multiplicity fractions of other OB star samples (Kobulnicky et al 2014;Banyard et al 2022). Our data reinforce the conclusion that multiple-star systems are common, not just among OB stars in general, but among high-velocity runaways as well.…”

Section: Multiplicity Fraction Of Runaway Gosc Starssupporting

confidence: 74%

“…These results show that both the full OB-star SBN sample and O-star SBN sample are consistent with the runaway GOSC O-star multiplicity fraction within 1σ. The apparent multiplicity fraction of the GOSC and SBN samples are formally consistent, despite the fact that early B stars dominate the SBN sample , and B stars have been shown to exhibit a lower multiplicity fraction than O stars (Kobulnicky et al 2014;Banyard et al 2022). This bias should augment the disparity in spectral type between the samples.…”

Section: Multiplicity Fraction Of Runaway Gosc Starsmentioning

confidence: 65%

“…Furthermore, the GOSC contains exclusively O stars while the SBN sample contains both O and early B stars-predominantly the latter. If the kinematic properties of O and early B stars differ systematically (e.g., as suggested by Kobulnicky et al (2016) and Banyard et al (2022) with regard to O stars having a higher multiplicity fraction than B stars), then the comparisons between the SBN and GOSC samples may be regarded as approximate but imperfect.…”

Section: Goals Of This Investigationmentioning

confidence: 99%

See 2 more Smart Citations

Kinematics of the Central Stars Powering Bowshock Nebulae and the Large Multiplicity Fraction of Runaway OB Stars

Kobulnicky,

Chick

2022

Preprint

View full text Add to dashboard Cite

OB stars powering stellar bowshock nebulae (SBNe) have been presumed to have large peculiar velocities. We measured peculiar velocities of SBN central stars to assess their kinematics relative to the general O star population using Gaia EDR3 data for 267 SBN central stars and a sample of 455 Galactic O stars to derive projected velocities v 2D . For a subset of each sample we obtained new optical spectroscopy to measure radial velocities and identify multiple-star systems. We find a minimum multiplicity fraction of 36±6% among SBN central stars, consistent with >28% among runaway Galactic O stars. The large multiplicity fraction among runaways implicates very efficient dynamical ejection rather than binary-supernova origins. The median v 2D of SBN central stars is v 2D =14.6 km s −1 , larger than the median v 2D =11.4 km s −1 for non-bowshock O stars. Central stars of SBNe have a runaway (v 2D >25 km s −1 ) fraction of 24 +9 −7 %, consistent with the 22 +3 −3 % for controlsample O stars. Most (76%) of SBNe central stars are not runaways. Our analysis of alignment (∆ PA ) between the nebular morphological and v 2D kinematic position angles reveals two populations: a highly aligned (σ P A =25 • ) population that includes stars with the largest v 2D (31% of the sample) and a random (non-aligned) population (69%). SBNe that lie within or near H II regions comprise a larger fraction of this latter component than SBNe in isolated environments, implicating localized ISM flows as a factor shaping their orientations and morphologies. We outline a new conceptual approach to computing the Solar LSR motion, yielding [U , V , W ]= [5.5, 7.5, 4.5] km s −1 .

show abstract

Section: Multiplicity Fraction Of Runaway Gosc Starssupporting

confidence: 74%

Section: Multiplicity Fraction Of Runaway Gosc Starsmentioning

confidence: 65%

Section: Goals Of This Investigationmentioning

confidence: 99%

See 1 more Smart Citation

Kinematics of the Central Stars Powering Bowshock Nebulae and the Large Multiplicity Fraction of Runaway OB Stars

Kobulnicky,

Chick

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…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

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…Geller et al ( 2021 ) summarized their observations of o v er 45 yr for the old OC M67 and reported an o v erall α = 34 ± 3 per cent and 70 ± 17 per cent for the cluster centre. On the other hand, Banyard et al ( 2022 ) estimated α to be 52 ± 8 per cent for the B-type stars of the OC NGC 6231.…”

mentioning

confidence: 96%

The young Galactic cluster NGC 225: binary stars’ content and total mass estimate

Yalyalieva

Carraro

Glushkova

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Galactic star clusters are known to harbour a significant amount of binary stars, yet their role in the dynamical evolution of the cluster as a whole is not comprehensively understood. We investigated the influence of binary stars on the total mass estimate for the case of the moderately populated Galactic star cluster NGC 225. The analysis of multi-epoch radial velocities of the 29 brightest cluster members, obtained over two observational campaigns, in 1990-1991 and in 2019-2020, yields a value of binary fraction of α = 0.52 (15 stars out of 29). Using theoretical isochrones and Monte Carlo simulations we found that the cluster mass increases at least 1.23 times when binaries are properly taken into account. By combining Gaia EDR3 photometric data with our spectroscopic observations, we derived estimates of NGC 225 fundamental parameters foras follows: mean radial velocity <Vr > = − 9.8 ± 0.7 km s−1, log (τ)=8.0-8.2 dex, distance D = 676 ± 22 pc, and colour excess E(B − V) = 0.29 ± 0.01 mag.

show abstract

The observed multiplicity properties of B-type stars in the Galactic young open cluster NGC 6231

Cited by 46 publications

References 63 publications

Kinematics of the Central Stars Powering Bowshock Nebulae and the Large Multiplicity Fraction of Runaway OB Stars

Kinematics of the Central Stars Powering Bowshock Nebulae and the Large Multiplicity Fraction of Runaway OB Stars

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

The young Galactic cluster NGC 225: binary stars’ content and total mass estimate

Contact Info

Product

Resources

About