Context.
In the era of gravitational wave astrophysics and with the precise astrometry of billions of stellar sources, the hunt for compact objects is more alive than ever. Rarely seen massive ...binaries with a compact object are a crucial phase in the evolution towards compact object mergers. With the upcoming third
Gaia
data release (DR3), the first
Gaia
astrometric orbital solutions for binary sources will become available, potentially revealing many such binaries.
Aims.
We investigate how many black holes (BHs) with massive main-sequence dwarf companions (OB+BH binaries) are expected to be detected as binaries in
Gaia
DR3 and at the end of the nominal 5-year mission. We estimate how many of those are identifiable as OB+BH binaries and discuss the distributions of the masses of both components as well as of their orbital periods. We also explore how different BH-formation scenarios affect these distributions.
Methods.
We apply observational constraints to tailored models for the massive star population, which assume a direct collapse and no kick upon BH formation, to estimate the fraction of OB+BH systems that will be detected as binaries by
Gaia
, and consider these the fiducial results. These OB+BH systems follow a distance distribution according to that of the second Alma Luminous Star catalogue (ALS II). We use a method based on astrometric data to identify binaries with a compact object and investigate how many of the systems detected as binaries are identifiable as OB+BH binaries. Different scenarios for BH natal kicks and supernova mechanisms are explored and compared to the fiducial results.
Results.
In the fiducial case we conservatively estimate that 77% of the OB+BH binaries in the ALS II will be detected as binaries in DR3, of which 89% will be unambiguously identifiable as OB+BH binaries. By the end of the nominal 5-year mission, the detected fraction will increase to 85%, of which 82% will be identifiable. The 99% confidence intervals on these fractions are of the order of a few percent. These fractions become smaller for different BH-formation scenarios.
Conclusions.
Assuming direct collapse and no natal kick, we expect to find around 190 OB+BH binaries in
Gaia
DR3 among the sources in the ALS II, which increases the known sample of OB+BH binaries by more than a factor of 20 and covers an uncharted parameter space of long-period binaries (10 ≲
P
≲ 1000 d). Our results further show that the size and properties of the OB+BH population that is identifiable using
Gaia
DR3 will contain crucial observational constraints that will help us improve our understanding of BH formation. An additional ∼5 OB+BH binaries could be identified at the end of the nominal 5-year mission, which are expected to have either very short (
P
≲ 10 d) or long periods (
P
≳ 1000 d).
Context.
The majority of massive stars are part of binary systems. In about a quarter of these, the companions are so close that mass transfer occurs while they undergo core hydrogen burning, first ...on the thermal and then on the nuclear timescale. The nuclear timescale mass transfer leads to observational counterparts: the semi-detached so-called massive Algol binaries. These systems may provide urgently needed tests of the physics of mass transfer. However, comprehensive model predictions for these systems are sparse.
Aims.
We use a large grid of detailed evolutionary models of short-period massive binaries and follow-up population synthesis calculations to derive probability distributions of the observable properties of massive Algols and their descendants.
Methods.
Our results are based on ∼10 000 binary model sequences calculated with the stellar evolution code MESA, using a metallicity suitable for the Large Magellanic Cloud (LMC), covering initial donor masses between 10
M
⊙
and 40
M
⊙
and initial orbital periods above 1.4 d. These models include internal differential rotation and magnetic angular momentum transport, non-conservative mass and angular momentum transfer between the binary components, and time-dependent tidal coupling.
Results.
Our models imply ∼30, or ∼3% of the ∼1000, core hydrogen burning O-star binaries in the LMC to be currently in the semi-detached phase. Our donor models are up to 25 times more luminous than single stars of an identical mass and effective temperature, which agrees with the observed Algols. A comparison of our models with the observed orbital periods and mass ratios implies rather conservative mass transfer in some systems, while a very inefficient one in others. This is generally well reproduced by our spin-dependent mass transfer algorithm, except for the lowest considered masses. The observations reflect the slow increase of the surface nitrogen enrichment of the donors during the semi-detached phase all the way to CNO equilibrium. We also investigate the properties of our models after core hydrogen depletion of the donor star, when these models correspond to Wolf-Rayet or helium+OB star binaries.
Conclusions.
A dedicated spectroscopic survey of massive Algol systems may allow to derive the dependence of the efficiency of thermal timescale mass transfer on the binary parameters, as well as the efficiency of semiconvective mixing in the stellar interior. This would be a crucial step towards reliable binary models up to the formation of supernovae and compact objects.
Context.
In the Milky Way, ∼18 Wolf-Rayet+O star (WR+O) binaries are known with estimates of their stellar and orbital parameters. Whereas black hole+O star (BH+O) binaries are thought to evolve from ...WR+O binaries, only one such system is known in the Milky Way. To resolve this disparity, it was suggested recently that upon core collapse, the WR stars receive large kicks such that most of the binaries are disrupted.
Aims.
We reassess this issue, with a particular emphasis on the uncertainty in predicting the X-ray emission from wind-accreting BHs in BH+O binaries, which is key to identifying such systems.
Methods.
BH+O systems are thought to be X-ray bright only when an accretion disk forms around the BHs. We followed the methodology of previous work and applied an improved analytic criterion for the formation of an accretion disk around wind accreting BHs. We then used stellar evolutionary models to predict the properties of the BH+O binaries which are expected to descend from the observed WR+O binaries if the WR stars would form BHs without a natal kick.
Results.
We find that disk formation sensitively depends on the O stars’ wind velocity, the amount of specific angular momentum carried by the wind, the efficiency of angular momentum accretion by the BH, and the spin of the BH. We show that whereas the assumption of a low wind velocity may lead to the prediction that most of the BH+O star binaries will have an extended X-ray bright period, this is not the case when typical wind velocities of O stars are considered. We find that a high spin of the BH can boost the duration of the X-ray active phase as well as the X-ray brightness during this phase. This produces a strong bias for detecting high mass BH binaries in X-rays with high BH spin parameters.
Conclusions.
We find that large BH formation kicks are not required to understand the sparsity of X-ray bright BH+O stars in the Milky Way. Probing for a population of X-ray silent BH+O systems with alternative methods can likely inform us about BH kicks and the necessary conditions for high energy emission from high mass BH binaries.
Digital traffic management solutions are essential for the effective management of the continuing growth of road traffic. However, technical possibilities for implementing traffic management ...strategies by Traffic Control Centres are limited to a strategic network. At the same time, modern mobility apps from routing services offer road users many options to get informed and guided. The latter usually work independently from traffic management strategies of public authorities. Thus, different route recommendations not only lead to uncertainty of road users, but ultimately to a reduction in the effectiveness of the public traffic management strategies. A direct information exchange between both systems does not yet exist. This however would be a key to more efficient traffic management.City2Navigation therefore developed a technical concept for a nationwide implementation of a digital data exchange service (C2N service) to link public traffic management with routing services of private vendors. This service fills the gap between both group of actors, thereby serving as a crucial building block for digital traffic management in response to the goals of European and national frameworks for Intelligent Transport Systems (ITS).The C2N service not only promotes the cooperation of public authorities with private routing services, it also offers a variety of opportunities to develop new business models. It is a complement to C2C and C2X communication solutions in road transport, ultimately also enabling future possibilities for municipalities to conduct efficient and sustainable traffic management.
The work of the German missionaries on South Australian languages in the first half of the nineteenth century has few contemporary parallels for thoroughness and clarity. This commentary on the ...grammatical introduction to Pastor Clamor Schürmann’s Vocabulary of the Parnkalla language of 1844 reconstructs a significant amount of Barngarla morphology, phonology and syntax. It should be seen as one of a number of starting points for language-reclamation endeavours in Barngarla, designed primarily for educators and other people who may wish to re-present its interpretations in ways more accessible to non-linguists, and more suited to pedagogical practice.
The structure of ceftazidime pentahydrate, a third generation cephalosporin antibiotic, is reported. Data collection was carried out in a remarkably short time with synchrotron radiation and the ...latest detector technology, illustrating that single‐crystal X‐ray diffraction can be used as a technique for screening hundreds of compounds in a short amount of time. Structure refinement made use of invarioms, namely non‐spherical scattering factors, which allow more information to be derived from a diffraction experiment. Properties that can be screened are bond‐topological parameters, empirical hydrogen‐bond energies, molecular dipole moments and electrostatic potentials.
We present life history data on wild Sumatran orangutans gleaned from a 32-year and a 5.5-year study. Estimated age at first reproduction was 15.4 years. At 9.3 years, the average interbirth interval ...for this population is the longest ever recorded for any great ape population, significantly longer than that of a Bornean orangutan population. We find that age-specific mortality of Sumatran orangutans does not differ between sexes and is significantly lower than that of wild chimpanzees. We conclude that orangutan life history is the slowest among extant great apes. In accordance with their slow life history, longevity in the wild is estimated to be at least 58 years for males and at least 53 for females. We find no evidence for menopause. These data suggest that compared to the ancestral state, humans have undergone less of an increase in longevity than commonly assumed, and have experienced selection on earlier cessation of reproduction.
The early Universe, together with many nearby dwarf galaxies, is deficient in heavy elements. The evolution of massive stars in such environments is thought to be affected by rotation. Extreme ...rotators among them tend to form decretion disks and manifest themselves as OBe stars. We use a combination of
U
B
,
Gaia
,
Spitzer
, and
Hubble
Space Telescope photometry to identify the complete populations of massive OBe stars – from one hundred to thousands in number – in five nearby dwarf galaxies. This allows us to derive the galaxy-wide fraction of main sequence stars that are OBe stars (
f
OBe
), and how it depends on absolute magnitude, mass, and metallicity (
Z
). We find
f
OBe
= 0.22 in the Large Magellanic Cloud (0.5
Z
⊙
), increasing to
f
OBe
= 0.31 in the Small Magellanic Cloud (0.2
Z
⊙
). In the thus-far unexplored metallicity regime below 0.2
Z
⊙
, in Holmberg I, Holmberg II, and Sextans A, we also obtain high OBe star fractions of 0.27, 0.27, and 0.27, respectively. These high OBe star fractions and the strong contribution in the stellar mass range – which dominates the production of supernovae–, shed new light on the formation channel of OBe stars, as well as on the tendency for long-duration gamma-ray bursts and superluminous supernovae to occur in metal-poor galaxies.
In order to predict the spins of stellar remnants we need to understand the evolution of the internal rotation of stars, and to identify at which stage the rotation of the contracting cores of ...evolved stars decouples from their expanding envelopes. The donor stars of mass transferring binaries lose almost their entire envelope and may thus offer a direct view on their core rotation. After the mass transfer event they contract and fade rapidly, although they are well observable when caught in the short-lived B-star phase. The B-type primary of the galactic binary system
LB-1
, which was originally suggested to contain a massive black hole, is nicely explained as a stripped star accompanied by a fainter Be star. The narrow absorption lines in the primary’s spectrum signify extremely slow rotation, atypical of B-type main-sequence stars. Here we investigate the evolution of mass donors in generic grids of detailed binary evolution models, where both stars include differential rotation, internal angular momentum transport, and spin-orbit coupling. Whereas the mass gainers are typically spun-up during the mass transfer, we find that the spins of the stripped donor models depend sensitively on the employed mechanism for internal angular momentum transport. Purely hydrodynamic transport cannot explain the observed slow rotation, while models including magnetic angular momentum transport are able to reproduce the observed rotation of LB-1 and similar stars, independent of the initial rotation rate. In such models the spin of the white dwarfs that emerge at the end of the evolution is independent of the mass stripping. We find evidence that the mass transfer in LB-1 was moderately non-conservative.
PDF
