Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Fabry, M.; Hawcroft, C.; Frost, A. J.; Mahy, L.; Marchant, Pablo; Bouquin, J. Le; Sana, H.

doi:10.1051/0004-6361/202140452

Cited by 13 publications

(6 citation statements)

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“…(spinOS 2 , Fabry et al 2021). This code allows us to compute the orbital parameters of the different systems in our sample from a set of RV measurements.…”

Section: Starmentioning

confidence: 99%

Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries

Mahy

Sana

Shenar

et al. 2022

A&A

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Context. The quest to detect dormant stellar-mass black holes (BHs) in massive binaries (i.e. OB+BH systems) is challenging; only a few candidates have been claimed to date, all of which must still be confirmed. Aims. To search for these rare objects, we study 32 Galactic O-type stars that were reported as single-lined spectroscopic binaries (SB1s) in the literature. In our sample we include Cyg X-1, which is known to host an accreting stellar-mass BH, and HD 74194, a supergiant fast X-ray transient, in order to validate our methodology. The final goal is to characterise the nature of the unseen companions to determine if they are main-sequence (MS) stars, stripped helium stars, triples, or compact objects such as neutron stars (NSs) or stellar-mass BHs. Methods. After measuring radial velocities and deriving orbital solutions for all the systems in our sample, we performed spectral disentangling to extract putative signatures of faint secondary companions from the composite spectra. We derived stellar parameters for the visible stars and estimated the mass ranges of the secondary stars using the binary mass function. Variability observed in the photometric TESS light curves was also searched for indications of the presence of putative companions, degenerate or not. Results. In 17 of the 32 systems reported as SB1s, we extract secondary signatures, down to mass ratios of ∼ 0.15. For the 17 newly detected double-lined spectroscopic binaries (SB2s), we derive physical properties of the individual components and discuss why they have not been detected as such before. Among the remaining systems, we identify nine systems with possible NS or low-mass MS companions. For Cyg X-1 and HD 130298, we are not able to extract any signatures for the companions, and the minimum masses of their companions are estimated to be about 7 M . Our simulations show that secondaries with such a mass should be detectable from our dataset, no matter their nature: MS stars, stripped helium stars or even triples. While this is expected for Cyg X-1, confirming our methodology, our simulations also strongly suggest that HD 130298 could be another candidate to host a stellar-mass BH. Conclusions. The quest to detect dormant stellar-mass BHs in massive binaries is far from over, and many more systems need to be scrutinised. Our analysis allows us to detect good candidates, but confirming the BH nature of their companions will require further dedicated monitorings, sophisticated analysis techniques, and multi-wavelength observations.

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“…(spinOS 2 , Fabry et al 2021). This code allows us to compute the orbital parameters of the different systems in our sample from a set of RV measurements.…”

Section: Starmentioning

confidence: 99%

Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries

Mahy

Sana

Shenar

et al. 2022

A&A

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“…Of the current sample of stars, the sometimes complex multiplicities of HD 191612, Cyg OB2-9, Cyg OB2-8A, HD 206267, 15 Mon, δ Ori, V460 Mon, ζ Ori, σ Ori, θ 1 Ori C, and ι Ori were discussed by Maíz ; and those of ζ Ori, ι Ori, 15 Mon, τ CMa, HD 206267, and HD 93129A by Maíz . 9 Sgr alias HD 164794: The two Chandra HETG observations analyzed here were taken 216 and 245 days after the 2004 October periastron passage of the most recent definition of the SB2 binary orbit of the 8.9 yr period established by Fabry et al (2021). The change in MEG count rate after the gap of about a month was small at 1.5% ± 1.4%.…”

Section: Appendix a Notes On Some Individual Starsmentioning

confidence: 95%

Survey of X-Rays from Massive Stars Observed at High Spectral Resolution with Chandra

Pradhan,

Huenemoerder,

Ignace

et al. 2023

ApJ

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Identifying trends between observational data and the range of physical parameters of massive stars is a critical step to the still-elusive full understanding of the source, structure, and evolution of X-ray emission from the stellar winds, requiring a substantial sample size and systematic analysis methods. As of 2022, the Chandra data archive contains 37 high-resolution spectra of O, B, and WR stars, observed with the Chandra/HETGS, and of sufficient quality to fit the continua and emission-line profiles. Using a systematic approach to the data analysis, we explore morphological trends in the line profiles (i.e., O, Ne, Mg, and Si) and find that the centroid offsets of resolved lines versus wavelength can be separated in three empirically defined groups based on the amount of line broadening and centroid offset. Using Fe xvii (15.01, 17.05 Å) and Ne x α (12.13 Å) lines, which are prevalent among the sample stars, we find a well-correlated linear trend of increasing Full Width Half Maximum with faster wind terminal velocity. The H-like/He-like total line flux ratio for strong lines displays different trends with spectral class depending on ion species. Some of the sources in our sample have peculiar properties (e.g., magnetic and γ Cas-analog stars) and we find that these sources stand out as outliers from more regular trends. Finally, our spectral analysis is presented summarily in terms of X-ray spectral energy distributions in specific luminosity for each source, including tables of line identifications and fluxes.

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“…Since the multidimensional disentangling fit fails to recover the secondary signal, we fixed the orbital period (P), eccentricity (e), longitude of the periastron passage (ω), the time of reference (T 0 ), and the RV semi-amplitude K 1 of the primary star, only allowing to K 2 to vary. This grid-based disentangling approach (Fabry et al 2021) is similar to that successfully applied to detect spectral signatures of faint companions with optical brightness contributions below 1% (Shenar et al 2020;Bodensteiner et al 2020). While we were able to extract the spectra of the putative companions and characterise their main features, retrieving their semi-amplitude K 2 with accuracy was more challenging -typical uncertainties on the values of K2 tended to be around 50 km s −1 .…”

Section: Spectral Disentanglingmentioning

confidence: 99%

Searching for compact objects in the single-lined spectroscopic binaries of the young Galactic cluster NGC 6231

G.¹,

Mahy²,

H.³

et al. 2023

A&A

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Context. Recent evolutionary computations predict that a few percent of massive O-or early-B stars in binary systems should have a dormant BH as a companion. However, despite several reported candidate X-ray quiet OB+BH systems over the last couple of years, finding them with certainty remains challenging. Yet these have great importance as they as they can be gravitational wave (GW) source progenitors, and are landmark systems in constraining supernova kick physics. Aims. This work aims to characterise the hidden companions to the single-lined spectroscopic binaries (SB1s) identified in the B star population of the young open Galactic cluster NGC 6231 to find candidate systems for harbouring compact object companions. Methods. With the orbital solutions for each SB1 constrained in a previous study, we applied Fourier spectral disentangling to multi-epoch optical VLT/FLAMES spectra of each target to extract a potential signature of a faint companion, and to identify newly disentangled double-lined spectroscopic binaries (SB2s). For targets where the disentangling does not reveal any spectral signature of a stellar companion, we performed atmospheric and evolutionary modelling on the primary (visible) star to obtain constraints on the mass and nature of the unseen companion. Results. For 7 of the 15 apparent SB1 systems, we extracted the spectral signature of a faint companion, resulting in seven newly classified SB2 systems with mass ratios down to near 0.1. From the remaining targets, for which no faint companion could be extracted from the spectra, four are found to have companion masses that lie in the predicted mass ranges of neutron stars (NSes) and BHes. Two of these targets have companion masses between 1 and 3.5 M , making them potential hosts of NSes (or lower mass main sequence stars). The other two have mass ranges between 2.5 to 8 M and 1.6 and 26 M , respectively, and so are identified as candidates for harbouring BH companions. Conclusions. We present four SB1 systems in NGC 6231 that are candidates for harbouring compact objects. However, unambiguous identification of these systems as X-ray quiet compact object harbouring binaries will only result from photometric and interferometric follow-up observations of these objects.

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Resolving the dynamical mass tension of the massive binary 9 Sagittarii

Cited by 13 publications

References 50 publications

Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries

Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries

Survey of X-Rays from Massive Stars Observed at High Spectral Resolution with Chandra

Searching for compact objects in the single-lined spectroscopic binaries of the young Galactic cluster NGC 6231

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