The IACOB project

Holgado, G.; Herrero, A.; Barbá, R. H.

doi:10.1051/0004-6361/202243851

Cited by 20 publications

(40 citation statements)

References 89 publications

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“…main sequence stars with masses in the range of ∼20-80 M ). This study was partly motivated by the necessity to provide an explanation for an empirical result already highlighted by Conti & Ebbets (1977), Wolff et al (1982) and subsequently confirmed by some other authors (see further references in Simón-Díaz & Herrero 2014;Ramírez-Agudelo et al 2013;Holgado et al 2022); namely: the spin-rate distribution of any investigated (large) sample of O-type stars (even in different metallicity environments) is characterised by a main component, including stars spinning with projected rotational velocities (v sin i) below ∼150-200 km s −1 , and a tail of fast rotators reaching values of v sin i up to 400-600 km s −1 . Such a tail of fast rotators normally comprises ∼20-25% of stars in the considered samples.…”

Section: Introductionmentioning

confidence: 73%

“…Simón-Díaz) to provide solid empirical foundations to our knowledge about the physical properties and evolution of massive OB-type stars (see e.g. Simón-Díaz & Herrero 2014;Simón-Díaz et al 2017;Holgado et al 2020Holgado et al , 2022, in this paper, we perform a complete and homogeneous search for empirical signatures of binarity in a statistically meaningful sample of several tens of fast-rotating Galactic O-type stars. Our ultimate goal is to evaluate the scenario proposed by de Mink et al ( , 2014 to explain the existence of a tail of fast rotators in this stellar domain.…”

Section: Introductionmentioning

confidence: 99%

“…Our ultimate goal is to evaluate the scenario proposed by de Mink et al ( , 2014 to explain the existence of a tail of fast rotators in this stellar domain. To this aim, we use as starting point the results presented in Holgado et al (2022), where we performed a reassessment of the empirical rotational properties of Galactic massive O-type stars using the results from a detailed analysis of ground-based multi-epoch optical spectra obtained in the framework of the IACOB & OWN surveys (see Sect. 2).…”

Section: Introductionmentioning

confidence: 99%

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The IACOB project

Britavskiy

Holgado

Burssens

et al. 2023

A&A

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Context. The empirical distribution of projected rotational velocities (v sin i) in massive O-type stars is characterised by a dominant slow velocity component and a tail of fast rotators. It has been proposed that binary interaction plays a dominant role in the formation of this tail. Aims. We perform a complete and homogeneous search for empirical signatures of binarity in a sample of 54 fast-rotating stars with the aim of evaluating this hypothesis. This working sample has been extracted from a larger sample of 415 Galactic O-type stars that covers the full range of v sin i values. Methods. We used new and archival multi-epoch spectra in order to detect spectroscopic binary systems. We complemented this information with Gaia proper motions and TESS photometric data to aid in the identification of runaway stars and eclipsing binaries, respectively. We also benefitted from additional published information to provide a more complete overview of the empirical properties of our working sample of fast-rotating O-type stars. Results. The identified fraction of single-lined spectroscopic binary (SB1) systems and apparently single stars among the fast-rotating sample is ∼18% and ∼70%, respectively. The remaining 12% correspond to four secure double-line spectroscopic binaries (SB2) with at least one of the components having a v sin i > 200 km s−1 (∼8%), along with a small sample of 2 stars (∼4%) for which the SB2 classification is doubtful: these could actually be single stars with a remarkable line-profile variability. When comparing these percentages with those corresponding to the slow-rotating sample, we find that our sample of fast rotators is characterised by a slightly larger percentage of SB1 systems (∼18% vs. ∼13%) and a considerably smaller fraction of clearly detected SB2 systems (8% vs. 33%). Overall, there seems to be a clear deficit of spectroscopic binaries (SB1+SB2) among fast-rotating O-type stars (∼26% vs. ∼46%). On the contrary, the fraction of runaway stars is significantly higher in the fast-rotating domain (∼33–50%) than among those stars with v sin i < 200 km s−1. Lastly, almost 65% of the apparently single fast-rotating stars are runaways. As a by-product, we discovered a new over-contact SB2 system (HD 165921) and two fast-rotating SB1 systems (HD 46485 and HD 152200) Also, we propose HD 94024 and HD 12323 (both SB1 systems with a v sin i < 200 km s−1) as candidates for hosting a quiescent stellar-mass black hole. Conclusions. Our empirical results seem to be in good agreement with the assumption that the tail of fast-rotating O-type stars (with v sin i > 200 km s−1) is mostly populated by post-interaction binary products. In particular, we find that the final statistics of identified spectroscopic binaries and apparent single stars are in good agreement with newly computed predictions obtained with the binary population synthesis code BPASS and earlier estimations obtained in previous studies.

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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The IACOB project

Britavskiy

Holgado

Burssens

et al. 2023

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“…Though these velocity choices have been inherited from investigations of lower-mass stars, they are very effective in fitting the spectral lines of hot massive stars (Simón-Díaz et al 2010Holgado et al 2022). However, because the turbulent surfaces of massive stars are significantly different to those of their low-mass counterparts (Jiang et al 2018;Schultz et al 2020Schultz et al , 2022, it is uncertain just how accurate the inferred ξ and v macro will be, based on the existing line-fitting approach.…”

Section: Introductionmentioning

confidence: 99%

Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport

Schultz

Tsang

Bildsten

et al. 2023

ApJ

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Observations indicate that turbulent motions are present on most massive star surfaces. Starting from the observed phenomena of spectral lines with widths that are much larger than their thermal broadening (e.g., micro- and macroturbulence), and considering the detection of stochastic low-frequency variability (SLFV) in the Transiting Exoplanet Survey Satellite photometry, these stars clearly have large-scale turbulent motions on their surfaces. The cause of this turbulence is debated, with near-surface convection zones, core internal gravity waves, and wind variability being proposed. Our 3D gray radiation hydrodynamic (RHD) models previously characterized the convective dynamics of the surfaces, driven by near-surface convection zones, and provided reasonable matches to the observed SLFV of the most luminous massive stars. We now explore the complex emitting surfaces of these 3D RHD models, which strongly violate the 1D assumption of a plane-parallel atmosphere. By post-processing the gray RHD models with the Monte Carlo radiation transport code Sedona, we synthesize stellar spectra and extract information from the broadening of individual photospheric lines. The use of Sedona enables the calculation of the viewing angle and temporal dependence of spectral absorption line profiles. By combining uncorrelated temporal snapshots together, we compare the turbulent broadening from the 3D RHD models to the thermal broadening of the extended emitting region, showing that our synthesized spectral lines closely resemble the observed macroturbulent broadening from similarly luminous stars. More generally, the new techniques that we have developed will allow for systematic studies of the origins of turbulent velocity broadening from any future 3D simulations.

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“…Among other massive stars, a number of weakwind O stars were investigated for the presence of magnetic fields via two large spectropolarimetric surveys, the B fields in OB stars (BOB; Morel et al 2015;Fossati et al 2015;Schöller et al 2017) and the Magnetism in Massive Stars (MiMeS) surveys (Wade et al 2016). Finally, the availability of larger samples of high-resolution spectra of O stars, in particular from the IACOB project -including many weak-wind objects -led to mass quantitative analyses, for example with respect to rotational velocities and additional line-broadening effects (Simón-Díaz & Herrero 2014) and stellar parameters (Holgado et al 2018(Holgado et al , 2022.…”

Section: Introductionmentioning

confidence: 99%

Quantitative spectroscopy of late O-type main-sequence stars with a hybrid non-LTE method

Aschenbrenner¹,

Przybilla²,

Butler³

2023

Preprint

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Context. Late O-type stars at luminosities log L/L 5.2 show weak winds with mass-loss rates lower than 10 −8 M yr −1 . This implies that, unlike their more massive and more luminous siblings, their photospheric layers are not strongly affected by the stellar wind. Aims. A hybrid non-local thermodynamic equilibrium (non-LTE) approach -line-blanketed hydrostatic model atmospheres computed under the assumption of LTE in combination with non-LTE line-formation calculations -is tested for analyses of late O-type stars with masses up to ∼25 M . A sample of 20 mostly sharp-lined Galactic O stars of spectral types O8 to O9.7 and luminosity classes V and IV, previously studied in the literature using full non-LTE model atmospheres, is investigated. Methods. Hydrostatic and plane-parallel atmospheric structures and synthetic spectra computed with Kurucz's Atlas12 code together with the non-LTE line-formation codes Detail and Surface, which account for the effects of turbulent pressure on the atmosphere, were employed. High-resolution spectra were analysed for atmospheric parameters using hydrogen lines, multiple ionisation equilibria, and elemental abundances. Fundamental stellar parameters were derived by considering stellar evolution tracks and Gaia Early Data Release 3 (EDR3) parallaxes. Interstellar reddening was characterised by fitting spectral energy distributions from the UV to the mid-IR. Results. A high precision and accuracy is achieved for all derived parameters for 16 sample stars (4 objects show composite spectra). Turbulent pressure effects turn out to be significant for the quantitative analysis. Effective temperatures are determined to 1-3% uncertainty levels, surface gravities to 0.05 to 0.10 dex, masses to better than 8%, radii to better than 10%, and luminosities to better than 20% uncertainty typically. Abundances for C, N, O, Ne, Mg, Al, and Si are derived with uncertainties of 0.05 to 0.10 dex and for helium within 0.03 to 0.05 dex (1σ standard deviations) in general. Overall, results from previous studies using unified photosphere plus wind (full) non-LTE model atmospheres are reproduced, and with higher precision. The improvements are most pronounced for elemental abundances, and smaller microturbulent velocities are found. An overall good agreement is found between our spectroscopic distances and those from Gaia. Gaia EDR3-based distances to the Lac OB1b association and to the open clusters NGC 2244, IC 1805, NGC 457, and IC 1396 are determined as a byproduct. The derived N/C versus N/O abundance ratios tightly follow the predictions from stellar evolution models. Two ON stars show a very high degree of mixing of CNO-processed material and appear to stem from binary evolution.

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The IACOB project

Cited by 20 publications

References 89 publications

The IACOB project

The IACOB project

Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport

Quantitative spectroscopy of late O-type main-sequence stars with a hybrid non-LTE method

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