The massive binary system 9 Sgr revisited: New insights into disentangling methods

Quintero, Edwin A.; Rauw, Grégor

doi:10.1002/asna.202013696

Cited by 10 publications

(13 citation statements)

References 20 publications

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“…), we update the classi- to O3V((f + )), and narrow down the subtype of the secondary from O5-5.5V((f)) to O5V((f)). This is in excellent agreement with the recent work of Quintero et al (2020), who used an updated version of the shift-and-add disentangling technique in wavelength space and also obtained spectral types of O3V((f + )) and O5V((f)).…”

Section: Spectral Disentanglingsupporting

confidence: 91%

Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Fabry

Hawcroft

Frost

et al. 2021

A&A

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Context. Direct dynamical mass measurements of stars with masses above 30 M⊙ are rare. This is the result of the low yield of the upper initial mass function and the limited number of such systems in eclipsing binaries. Long-period, double-lined spectroscopic binaries that are also resolved astrometrically offer an alternative to eclipsing binaries for obtaining absolute masses of stellar objects. 9 Sgr (HD 164794) is one such long-period, high-mass binary. Unfortunately, a large amount of tension exists between its total dynamical mass inferred spectroscopically from radial velocity measurements and that from astrometric data. Aims. Our goal is to resolve the mass tension of 9 Sgr that exists in literature, to characterize the fundamental parameters and surface abundances of both stars, and to determine the evolutionary status of the binary system, henceforth providing a reference calibration point to confront evolutionary models at high masses. Methods. We obtained the astrometric orbit from existing and new multi-epoch VLTI/PIONIER and VLTI/GRAVITY interferometric measurements. Using archival and new spectroscopy, we performed a grid-based spectral disentangling search to constrain the semi-amplitudes of the radial velocity curves. We computed atmospheric parameters and surface abundances by adjusting FASTWIND atmosphere models and we compared our results with evolutionary tracks computed with the Bonn Evolutionary Code (BEC). Results. Grid spectral disentangling of 9 Sgr supports the presence of a 53 M⊙ primary and a 39 M⊙ secondary, which is in excellent agreement with their observed spectral types. In combination with the size of the apparent orbit, this puts 9 Sgr at a distance of 1.31 ± 0.06 kpc. Our best-fit models reveal a large mass discrepancy between the dynamical and spectroscopic masses, which we attribute to artifacts from repeated spectral normalization before and after the disentangling process. Comparison with BEC evolutionary tracks shows the components of 9 Sgr are most likely coeval with an age of roughly 1 Myr. Conclusions. Our analysis clears up the contradiction between mass and orbital inclination estimates reported in previous studies. We detect the presence of significant CNO-processed material at the surface of the primary, suggesting enhanced internal mixing compared to currently implemented in the BEC models. The present measurements provide a high-quality high-mass anchor to validate stellar evolution models and to test the efficiency of internal mixing processes.

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Section: Spectral Disentanglingsupporting

confidence: 91%

Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Fabry

Hawcroft

Frost

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…Columns 3, 4 and 5 give the MC median and 1σ confidence intervals.Semi-amplitudes Data MC median σ − σ + K 1 (km s −1 primary byRauw et al (2012) from O3.5V((f + )) to O3V((f + )), and narrow down the subtype of the secondary from O5-5.5V((f)) to O5V((f)). This is in excellent agreement with the recent work ofQuintero et al (2020), who used an updated version of the shift-and-add disentangling technique in wavelength space and also obtained spectral types of O3V((f + )) and O5V((f)).…”

supporting

confidence: 91%

Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Fabry,

Hawcroft,

Frost

et al. 2021

Preprint

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Context. Direct dynamical mass measurements of stars with masses above 30 M are rare. This is the result of the low yield of the upper initial mass function and the limited number of such systems in eclipsing binaries. Long-period, double-lined spectroscopic binaries that are also resolved astrometrically offer an alternative to eclipsing binaries for obtaining absolute masses of stellar objects. 9 Sgr (HD 164794) is one such long-period, high-mass binary. Unfortunately, a large amount of tension exists between its total dynamical mass inferred spectroscopically from radial velocity measurements and that from astrometric data. Aims. Our goal is to resolve the mass tension of 9 Sgr that exists in literature, to characterize the fundamental parameters and surface abundances of both stars, and to determine the evolutionary status of the binary system, henceforth providing a reference calibration point to confront evolutionary models at high masses. Methods. We obtained the astrometric orbit from existing and new multi-epoch VLTI/PIONIER and VLTI/GRAVITY interferometric measurements. Using archival and new spectroscopy, we performed a grid-based spectral disentangling search to constrain the semi-amplitudes of the radial velocity curves. We computed atmospheric parameters and surface abundances by adjusting fastwind atmosphere models and we compared our results with evolutionary tracks computed with the Bonn Evolutionary Code (BEC). Results. Grid spectral disentangling of 9 Sgr supports the presence of a 53 M primary and a 39 M secondary, which is in excellent agreement with their observed spectral types. In combination with the size of the apparent orbit, this puts 9 Sgr at a distance of 1.31 ± 0.06 kpc. Our best-fit models reveal a large mass discrepancy between the dynamical and spectroscopic masses, which we attribute to artifacts from repeated spectral normalization before and after the disentangling process. Comparison with BEC evolutionary tracks shows the components of 9 Sgr are most likely coeval with an age of roughly 1 Myr. Conclusions. Our analysis clears up the contradiction between mass and orbital inclination estimates reported in previous studies. We detect the presence of significant CNO-processed material at the surface of the primary, suggesting enhanced internal mixing compared to currently implemented in the BEC models. The present measurements provide a high-quality high-mass anchor to validate stellar evolution models and to test the efficiency of internal mixing processes.

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“…It is well known that the shift-and-add technique often results in apparent "emission wings" in the disentangled spectra, which are not of astrophysical origin, but are intrinsic to the method (Quintero et al 2020). Removing these features typically requires very large number of iterations, making the disentangling procedure inefficient.…”

Section: Spectral Disentanglingmentioning

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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The massive binary system 9 Sgr revisited: New insights into disentangling methods

Cited by 10 publications

References 20 publications

Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Resolving the dynamical mass tension of the massive binary 9 Sagittarii

The Tarantula Massive Binary Monitoring

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