scholarly journals Dynamical evolution of population III stellar systems and the resulting binary statistics

2020 ◽  
Vol 501 (1) ◽  
pp. 643-663
Author(s):  
Boyuan Liu ◽  
Georges Meynet ◽  
Volker Bromm
Keyword(s):  
Initial Conditions ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Initial Mass Function ◽  
Close Binary ◽  
Close Binaries ◽  
Small Scale ◽  
Stellar Systems ◽  
X Ray ◽  
Population Iii

ABSTRACT We use N-body simulations to study the dynamical evolution of population III (Pop III) stellar systems and the resulting binary statistics. We design a physically motivated framework for the initial conditions of Pop III star clusters, based on small-scale hydrodynamic simulations and the scale-free nature of disc evolution during Pop III star formation. Our novel approach enables us to explore the dependence of binary statistics on initial conditions and arrive at more robust predictions for the signals of Pop III X-ray binaries (XRBs) and binary black hole (BBH) mergers, compared to simple extrapolations of Pop III protostar systems. We find that binary properties are highly sensitive to the initial cluster size and distribution of binary separation, while the effect of initial mass function is relatively minor. Our simulations predict less close binaries, and thus, significantly lower efficiencies (by a factor of ∼10–104) for the formation and accretion of Pop III XRBs, than found in previous studies, implying that the contribution of Pop III XRBs to the cosmic X-ray background is negligible and their feedback effects are unimportant. We estimate the efficiency of Pop III BBH mergers as $\sim 10^{-5}\!-\!10^{-4}\ \rm M_{\odot }^{-1}$, for which three-body hardening by surrounding stars in dense star clusters or close binary interactions is required to facilitate in-spirals of BBHs. All simulation data, including catalogues of Pop III binaries and multiple systems, are publicly available.

scholarly journals Young massive star clusters: achievements and challenges

2009 ◽  
Vol 5 (S266) ◽  
pp. 49-57 ◽  
Author(s):  
Richard de Grijs
Keyword(s):  
Massive Star ◽  
Initial Conditions ◽  
Cluster Formation ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Ongoing Research ◽  
Mass Segregation

AbstractIn spite of significant recent and ongoing research efforts, most of the early evolution and long-term fate of young massive star clusters remain clouded in uncertainties. Here, I discuss our understanding of the initial conditions of star cluster formation and the importance of initial substructure for the subsequent dynamical-evolution and mass-segregation timescales. I also assess our current understanding of the (initial) binary fraction in star clusters and the shape of the stellar initial mass function at the low-mass end in the low-metallicity environment of the Large Magellanic Cloud. Finally, I question the validity of our assumptions leading to dynamical cluster mass estimates. I conclude that it seems imperative that observers, modellers and theorists combine efforts and exchange ideas and data freely for the field to make a major leap forward.

scholarly journals Observed Variations in the Density Profiles of Star Clusters in the LMC

1988 ◽  
Vol 126 ◽  
pp. 571-572 ◽  
Author(s):  
M. Kontizas ◽  
D. Hatzidimitriou ◽  
M. Metaxa
Keyword(s):  
Observational Data ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Stellar Systems ◽  
Density Profiles ◽  
Valuable Source ◽  
Dynamical Properties ◽  
Source Of Information

Several dynamical theories have been developed in order to approach the dynamical evolution of stellar systems and explain the observational data. The observed density profiles of the clusters can be a valuable source of information towards the understanding of their dynamical properties. King in a series of papers has connected the established theories with the observed profiles in clusters of our own Galaxy (King, 1962, 1966; etc.). Density profiles can be obtained by means of star counts and/or by means of photometric photometry. So far the observations for clusters in our Galaxy and the MCs appear to fit well the so called King models and provide information of their tidal radii, total masses and concentration parameters (Kontizas, 1984).

scholarly journals The Dynamical Evolution of Young Clusters and Associations

1986 ◽  
Vol 7 ◽  
pp. 481-488 ◽  
Author(s):  
Robert D. Mathieu
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Initial Conditions ◽  
Dynamical Evolution ◽  
Short Review ◽  
Stellar Systems ◽  
Galactic Field ◽  
Dynamical State ◽  
Orbital Mixing ◽  
Formation Efficiency

A young cluster or association bears the imprint of the conditions at its birth for perhaps ten million years, after which the initial conditions are lost to either dilution in the galactic field or erasure by orbital mixing and stellar encounters. In its youngest years, however, the dynamical state of the system can provide valuable information concerning the structure and energetics of the parent gas, the star-formation efficiency and the star-formation process itself. This short review discusses recent theoretical and observational progress in the study of the very youngest of stellar systems.

scholarly journals Photographic Photometry With Schmidt Plates of Star Clusters in the SMC

1984 ◽  
Vol 78 ◽  
pp. 355-357
Author(s):  
M. Kontizas
Keyword(s):  
Stellar Evolution ◽  
Initial Conditions ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Large Field ◽  
Stellar Systems ◽  
Nearest Neighbour ◽  
Photographic Photometry

The star clusters have always been the most important tools of testing the stellar evolution theories and when these stellar systems belong to other galaxies, then our knowledge on stellar evolution can be extended for different initial conditions than those of our Galaxy. The Magellanic Clouds being our nearest neighbour galaxies offer ideal conditions for such studies.Since the powerful southern telescope came into operation deep plates of these two galaxies revealed a large number of new star clusters. The Schmidt plates are most useful since they have the advantage of large field where many objects can be investigated homogeneously on the same plate.

scholarly journals Radio Aspects of Stellar Activity in Close Binaries

1980 ◽  
Vol 5 ◽  
pp. 857-857 ◽  
Author(s):  
R. M. Hjellming
Keyword(s):  
Circular Polarization ◽  
Binary Systems ◽  
Close Binary ◽  
Close Binaries ◽  
Radiation Mechanisms ◽  
Dynamo Action ◽  
Stellar Activity ◽  
X Ray ◽  
Close Binary Systems ◽  
Decay Times

Excluding single stars, star systems with very strong X-ray sources, thermally radiating winds and circumstellar envelopes, marginal detections, and binary systems that are far from “normal”, there are about 21 close binary systems that show clear signs of stellar activity in the form of variable radio emission. Sixteen of these are RS CVn binaries. Typical events are smoothly varying with time scales of from a few hours to a few days. In the RS CVn binaries UX Ari and V711 Tau variable circular polarization is sometimes observed, with occasional appearence of components with only one frequency and one circular polarization, part of which shows “oscillations” with “periods” of about 4 minutes. Different stars and different events typically have inferred electron energies of about 5 MeV and inferred magnetic fields of 1 - 30 Gauss. The radiation mechanisms are usually assumed to be synchrotron or gyro-synchrotron; however, radiation from plasma processes cannot be ruled out in some cases, and it will be very important to establish or rule out this possibility. Most radio binary events show clear signs of self-absorption, so the variations appear most strongly at the higher frequencies. Typical rise times of events are about 30% of decay times. Maximum radio luminosities range from 1013 to a few times 1017 ergs s-1 Hz-1. Most radio flares are mainly at cm-wavelenghts and have observable and inferred energies 104 - 106 times those for the largest solar events, a scaling which is similar to that for X-ray emission measures of these stars when compared to solar coronal loop emission measures. Most importantly, VLBI measurements of Algol indicate that the sizes of the radio emitting regions for very strong events are of the order of 2 - 3 stellar radii. Single stars appear to be active at radio wavelengths much less commonly than close binary systems. In many cases this may be due to the way dynamo action and convection near the surface are affected by increased rotation forced by the synchronization induced by the binary system.

scholarly journals Theory of Young Clusters

2004 ◽  
Vol 221 ◽  
pp. 257-264
Author(s):  
Matthew R. Bate ◽  
Ian A. Bonnell
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Initial Conditions ◽  
Star Clusters ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Large Cluster ◽  
Close Binaries ◽  
Stellar Clusters ◽  
Small Clusters

We review recent results from hydrodynamical calculations of the formation of young stellar clusters. The calculations present a highly dynamical picture of star formation where the mass function of stars originates from competitive accretion between protostars and dynamical ejections which halt accretion. Large star clusters form hierarchically; a molecular cloud forms many small clusters that later merge into one large cluster, erasing the initial substructure. Using calculations that resolve fragmentation down to the opacity limit, we examine the implications of dynamical star formation for the IMF, the formation of brown dwarfs and close binaries, and the sizes of protoplanetary discs. Finally, we discuss the dependence of the results on the initial conditions.

scholarly journals A Candidate for the Recovered Nova of 1938 in the Globular Cluster M 14

1988 ◽  
Vol 126 ◽  
pp. 585-586
Author(s):  
Michael M. Shara ◽  
Michael Potter ◽  
Anthony F. J. Moffat ◽  
Helen Sawyer Hogg ◽  
Amelia Wehlau
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Close Binaries ◽  
Dwarf Novae ◽  
X Ray ◽  
Negative Results ◽  
Classical Nova ◽  
M 14

Although close binaries are believed to be of importance in the dynamical evolution of globular clusters, searches for such binaries have produced mostly negative results, aside from x-ray sources. Two dwarf novae which are possible cluster members are known (Margon and Downes 1983) and two classical nova candidates have been found. The crowded field around the nova observed in 1860 close to the center of M80 makes ground-based recovery of that star impossible with present techniques. Here we report on our attempt to recover the star which erupted in 1938 about 30″ (0.8 core radii) from the center of M14.

scholarly journals Black hole magnetosphere with small-scale flux tubes – II. Stability and dynamics

2019 ◽  
Vol 487 (3) ◽  
pp. 4114-4127 ◽  
Author(s):  
Yajie Yuan ◽  
Anatoly Spitkovsky ◽  
Roger D Blandford ◽  
Dan R Wilkins
Keyword(s):  
Black Hole ◽  
Compact Star ◽  
Dynamical Evolution ◽  
Compact Object ◽  
Accretion Disc ◽  
Small Scale ◽  
X Rays ◽  
Flux Tubes ◽  
X Ray ◽  
Central Object

ABSTRACT In some Seyfert galaxies, the hard X-rays that produce fluorescent emission lines are thought to be generated in a hot corona that is compact and located at only a few gravitational radii above the supermassive black hole. We consider the possibility that this X-ray source may be powered by small-scale magnetic flux tubes attached to the accretion disc near the black hole. We use three-dimensional, time-dependent, special relativistic, force-free simulations in a simplified setting to study the dynamics of such flux tubes as they get continuously twisted by the central compact star/black hole. We find that the dynamical evolution of the flux tubes connecting the central compact object and the accretion disc is strongly influenced by the confinement of the surrounding field. Although differential rotation between the central object and the disc tends to inflate the flux tubes, strong confinement from surrounding field quenches the formation of a jet-like outflow, as the inflated flux tube becomes kink unstable and dissipates most of the extracted rotational energy relatively close to the central object. Such a process may be able to heat up the plasma and produce strong X-ray emission. We estimate the energy dissipation rate and discuss its astrophysical implications.

scholarly journals The Binaries from Unstable Triples. Dynamical Processes of Formation

1989 ◽  
Vol 8 ◽  
pp. 143-144
Author(s):  
Joanna P. Anosova
Keyword(s):  
Computer Simulations ◽  
Dynamical Evolution ◽  
Close Binary ◽  
Close Binaries ◽  
State University ◽  
Dynamical Processes ◽  
Triple Systems ◽  
Gravitational Problem ◽  
Three Body

The dynamical processes of formation, evolution and disruption of binaries may be effectively studied by computer simulations in the N > 3-body gravitational problem. As a result of analysis of these investigations of diverse authors, the classification of the dynamical processes of formation of wide and close binaries may be proposed (see Table 1). This Table shows the following general processes: I-triple approaches of the single bodies; II-approaches of binaries with single bodies; Ill-escape from physical triples. The actions of these processes, and kinetics of a frequency of binaries in general field were studied at the Astronomical Observatory of the Leningrad State University (1965-1988) by computer simulations in the three-body problem. More than 3.104 orbits with negative total energy E < 0 and 5.104 with E > 0 have been run on the computers. The film “Dynamical evolution of triple systems” was produced. Part I of this movie shows the evolution of the unstable non-hierarchical triplet as well as the processes of formation, evolution, and disruption of temporary wide and final close binaries inside the physical triples. Part II of film presents in detail the trajectories of the bodies on the triple approaches of “fly-by”-and of “exchange”-types. The triple approach of “fly-by”-type results often in an escape from triple as well as the formation of final close binary. The triple approach of “exchange”-type consists as a rule of a few close double approaches of bodies and rarely results in an escape from triplet, it results in formation of temporary wide binary inside triplet. Part III of movie presents the trajectories of the different-mass bodies: an escape of the minimum-mass body, the intermediate-mass body, and the maximum-mass body as well as a formation of binaries with different-mass components.

scholarly journals The Mass Function of Young Star Clusters in our Galaxy and Nearby Galaxies: Is It Universal?

2002 ◽  
Vol 207 ◽  
pp. 515-524
Author(s):  
Ram Sagar
Keyword(s):  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Young Star ◽  
Initial Mass Function ◽  
Galactocentric Distance ◽  
Photometric Observations ◽  
Nearby Galaxies ◽  
Mass Segregation ◽  
Young Star Clusters

Mass functions (MFs) derived from photometric observations of young star clusters of our Galaxy, the Magellanic Clouds (MCs), M31 and M33 have been used to investigate the question of universality of the initial mass function and presence of mass segregation in these systems. Observational determination of the MF slope of young star clusters have an inherent uncertainty of at least ∼ 1.0 dex in the Milky Way and of ∼ 0.4 dex in the MCs. There is no obvious dependence of the MF slope on either galactocentric distance or age of the young star clusters or on the spatial concentration of the stars formed or on the galactic characteristics including metallicity. Effects of mass segregation have been observed in a good number of young stellar groups of our Galaxy and MCs. As their ages are much smaller than their dynamical evolution times, star formation processes seem to be responsible for the observed mass segregation in them.

Sign in / Sign up

Export Citation Format

Share Document