307 research outputs found
Modelling the components of binaries in Hyades: The dependence of the mixing-length parameter on stellar mass
We present our findings based on a detailed analysis for the binaries of the
Hyades, in which the masses of the components are well known. We fit the models
of components of a binary system to the observations so as to give the observed
total V and B-V of that system and the observed slope of the main-sequence in
the corresponding parts. According to our findings, there is a very definite
relationship between the mixing-length parameter and the stellar mass. The
fitting formula for this relationship can be given as , which is valid for stellar masses greater than
0.77 M_sun. While no strict information is gathered for the chemical
composition of the cluster, as a result of degeneracy in the colour-magnitude
diagram, by adopting Z=0.033 and using models for the components of 70 Tau and
theta^2 Tau we find the hydrogen abundance to be X=0.676 and the age to be 670
Myr. If we assume that Z=0.024, then X=0.718 and the age is 720 Myr. Our
findings concerning the mixing length parameter are valid for both sets of the
solution. For both components of the active binary system V818 Tau, the
differences between radii of the models with Z=0.024 and the observed radii are
only about 4 percent. More generally, the effective temperatures of the models
of low mass stars in the binary systems studied are in good agreement with
those determined by spectroscopic methods.Comment: 11 pages, 7 figures, accepted for publication in MNRA
Angular Momentum Loss by Magnetic Braking and Gravitational Radiation in Relativistic Binary Stars
Angular momentum loss (AML) mechanisms and dynamical evolution owing to
magnetic braking and gravitational radiation in relativistic binary stars (RBS)
are studied with use of physical parameters collected from the literature. We
have calculated and compared AML time scales for the RBS with non-degenerate
components and double degenerate (DD) systems.Comment: 6 pages, 3 figure
General Relativistic Simulations of High-Mass Binary Neutron Star Mergers: rapid formation of low-mass stellar black holes
Almost 100 compact binary mergers have been detected via gravitational waves
by the LIGO-Virgo-KAGRA collaboration in the past few years providing us with a
significant amount of new information on black holes and neutron stars. In
addition to observations, numerical simulations using newly developed modern
codes in the field of gravitational wave physics will guide us to understand
the nature of single and binary degenerate systems and highly energetic
astrophysical processes. We here present a set of new fully general
relativistic hydrodynamic simulations of high-mass binary neutron star systems
performed with the publicly available Einstein Toolkit and LORENE codes. We
considered systems with a total baryonic mass between 2.8 and 4.0
and we adopted the SLy equation of state. For all models we analyzed
the gravitational wave signal and we report potential indicators of the systems
undergoing rapid collapse into a black hole that may be observed by
future-planned detectors such as the Einstein Telescope and the Cosmic
Explorer. We also extracted the properties of the post-merger black hole, the
disk and ejecta masses and their dependence on the binary parameters. We also
compare our numerical results with recent analytical fits presented in the
literature and we also provide parameter-dependent semi-analytical relations
between the total mass and mass ratio of the systems and the resulting black
hole masses and spins, coalescence time scale, mass loss, and gravitational
wave energy.Comment: 13 pages, 5 figure, 4 tables, submitted for publicatio
Close Binary System GO Cyg
In this study, we present long term photometric variations of the close
binary system \astrobj{GO Cyg}. Modelling of the system shows that the primary
is filling Roche lobe and the secondary of the system is almost filling its
Roche lobe. The physical parameters of the system are , , , , , , and . Our results show that \astrobj{GO
Cyg} is the most massive system near contact binary (NCB). Analysis of times of
the minima shows a sinusoidal variation with a period of years due
to a third body whose mass is less than 2.3. Finally a period
variation rate of d/yr has been determined using all
available light curves.Comment: Accepted for publication in New Astronomy, 18 pages, 4 figures, 7
table
Recommended from our members
School Counselor Knowledge, Beliefs, and Practices Related to the Implementation of Standards-Based Comprehensive School Counseling in the United States
As school counselors have adapted to changing policy and social structures, their beliefs, knowledge, and practices have evolved. Over the past two decades, a body of survey research has examined school counselors’ beliefs, knowledge, and practices, though no systematic review exists. In this review, we synthesize and evaluate survey research on the knowledge, beliefs, and practices relevant to the implementation of a standards-based comprehensive school counseling model in the United States. We identify the most salient findings, evaluate the research, identify the most rigorous studies, discuss their findings, and provide recommendations for future research. Considering the recent changes to how funding is distributed to states and schools within the Every Student Succeeds Act of 2015, such research is both timely and necessary to help clarify and increase the role school counselors play in helping schools achieve the goals of legislation
Analysis of MERCATOR data Part I: variable B stars
We re-classified 31 variable B stars which were observed more than 50 times
in the Geneva photometric system with the P7 photometer attached to the
MERCATOR telescope (La Palma) during its first 3 years of scientific
observations. HD89688 is a possible beta Cephei/slowly pulsating B star hybrid
and the main mode of the COROT target HD180642 shows non-linear effects. The
Maia candidates are re-classified as either ellipsoidal variables or spotted
stars. Although the mode identification is still ongoing, all the
well-identified modes so far have a degree l = 0, 1 or 2.Comment: 4 pages, 3 figures. To appear in: Proceedings of JENAM 2005 'Distant
worlds', Communications in Asteroseismolog
Total and regional body fat status among children and young people with cerebral palsy: A scoping review
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151256/1/cob12327_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151256/2/cob12327.pd
Spectral characterizations and antibacterial effect of 2-(5-R-1H-benzimidazol-2-YL)-4-methyl/bromo-phenols and some metal complexes
2-(5-H/Cl/Me/NO2-1H-benzimidazol-2-yl)-4-Me/Br-phenols (HL1–HL5) were synthesized. HL1 complexes with Cu(NO3)2, AgNO3, Zn(ClO4)2 and; HL4, HL5 complexes with Zn(ClO4)2 were prepared. The structures of the compounds were confirmed on the basis of elemental analysis, molar conductivity, magnetic moment, FT-IR, 1H- and 13C-NMR. Antibacterial activity of the ligands and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against nine bacteria, and the results were compared with penicillin–G and oxytetracycline. While HL1 ligand has considerable antibacterial activity on B. cereus only; it’s Ag(I) complex show antibacterial effect toward almost all the bacteria. It is highly interesting that HL5 and [Zn(HL5)(L5)]ClO4 exhibit considerable high antibacterial activity toward K. pneumoniae, B. cereus, S. epidermidis and B. subtilis. KEY WORDS: Benzimidazole, Phenol, Metal complexes, Antibacterial activity Bull. Chem. Soc. Ethiop. 2010, 24(3), 391-400
- …