We report on Bayesian parameter estimation of the mass and equatorial radius of the millisecond pulsar PSR J0030+0451, conditional on pulse-profile modeling of Neutron Star Interior Composition ...Explorer X-ray spectral-timing event data. We perform relativistic ray-tracing of thermal emission from hot regions of the pulsar's surface. We assume two distinct hot regions based on two clear pulsed components in the phase-folded pulse-profile data; we explore a number of forms (morphologies and topologies) for each hot region, inferring their parameters in addition to the stellar mass and radius. For the family of models considered, the evidence (prior predictive probability of the data) strongly favors a model that permits both hot regions to be located in the same rotational hemisphere. Models wherein both hot regions are assumed to be simply connected circular single-temperature spots, in particular those where the spots are assumed to be reflection-symmetric with respect to the stellar origin, are strongly disfavored. For the inferred configuration, one hot region subtends an angular extent of only a few degrees (in spherical coordinates with origin at the stellar center) and we are insensitive to other structural details; the second hot region is far more azimuthally extended in the form of a narrow arc, thus requiring a larger number of parameters to describe. The inferred mass M and equatorial radius Req are, respectively, 1.34 − 0.16 + 0.15 M and 12.71 − 1.19 + 1.14 km , while the compactness GM R eq c 2 = 0.156 − 0.010 + 0.008 is more tightly constrained; the credible interval bounds reported here are approximately the 16% and 84% quantiles in marginal posterior mass.
The high-precision observational data on water temperature obtained during seven winters in a small boreal lake are considered. The spectral analysis revealed that the oscillations with a period of ...about 27 min prevailed in a water column. This period is close to the theoretical estimate of the first mode of the longitudinal barotropic seiche. The variability of temperature oscillations, vertical velocity, and displacement of isotherms suggest the presence of short internal waves along with seiches. The amplitude of the internal waves is an order of magnitude greater than that of seiches, and the length of internal waves is two orders of magnitude less than the linear extent of the lake.
The effect of isothermal annealing at 1100°C on the kinetics of phase transitions in the coatings system Ni-Al, obtained by the complex technology, is studied. The cyclic heat resistance of the ...coating is investigated at 1100°C.
The PP2PP experiment is one of five experiments at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory, Long Island, New York. It is designed to measure the elastic ...scattering of protons at
s
= 50–500
GeV. The detector consists of silicon strip detectors mounted in Roman Pots and installed in the RHIC ring 60
m from the interaction region. During the engineering run of 2002 and physics run of 2003 the detectors were inserted as close as 15 mm from the proton beam. An overview of the experiment and details of the detector design and performance will be presented.
The paper is devoted to the substantiation and further development of the approach to the analysis of the mesoscopic and integral structure of binary metal nanoparticles from the radial distributions ...of the local density of the components. As an example, the local density distributions of Ni and Al obtained using the results of molecular dynamics modeling of binary Ni-Al nanoparticles with an initial uniform distribution of components and Ni@Al core-shell icosahedral nanostructures are considered. Both patterns demonstrate the surface segregation of Al atoms during relaxation and subsequent quenching of the initial configurations containing 5000 atoms in 1:1 ratio (nanoparticle radius 3 nm). During cooling, the temperature of the nanoparticles decreased from 1000 K to 0,01 K with a low for atomistic simulation cooling rate. Experimentally binary Ni-Al nanoparticles with a radius of about 100 nm (76Ni:24Al at.%) were synthesized by the wire electric explosion. The experimental intensity distributions obtained from the data of energy-dispersive analysis under the action of an electron beam are presented and analyzed. These distributions correspond to a greater extent to the initial configurations in our molecular dynamics experiments, i.e., they are obviously nonequilibrium. At the same time, it was concluded that the final molecular dynamic configurations are also not entirely equilibrium.
The processes of structure formation in Co-Au and Ti-V metal nanoparticles as well as factors affecting the crystallization process are considered. The objects of the study were Co-Au and Ti-V binary ...nanoparticles containing N = 400, 800, 1520 and 5000 atoms with the equiatomic composition. The computer experiment was carried out using method of molecular dynamics. The interatomic interaction was described by the tight-binding potential. According to the results of a series of computer experiments, it was found that the main factors influencing the possibility of obtaining crystalline phases are: the cooling rate of binary nanoparticles, their size and the size mismatch of atoms included in the composition, as well as the nature of the interaction of metal atoms. The manifestation of stability/instability in binary nanoparticles may be due to patterns of formation of crystalline phases. Moreover, the tendency to segregate one of the components in a binary system may not be the main factor determining the stability/instability of such a system.
The article presents the results of application of Implicit Large Eddy Simulation method to numerical simulation of under-ice radiatively driven convection, developing in ice-covered water bodies in ...the moderate zone at the end of freeze-up period. Studies of the radiatively driven convection are of importance because of the role it plays in the temperature regime of lakes and the functioning of lake ecosystems at the end of freeze-up period. The simulation was carried out with the use of the finite-volume software code SINF/Flag-S, developed in SPbPU. The SIMPLEC algorithm with second-order accuracy was used for advancing in time. The discretization of the convective terms was made with the use of QUICK scheme. The results of calculations were used to study variations in the temperature and pulsation velocity components with periodically varying intensity of external energy pumping during the daily cycle. The dissipation of the kinetic energy, background potential energy, and buoyancy flux were evaluated, and changes in these variables during a daily cycle of radiation impact were calculated. The efficiency mixing of water column was evaluated for the period of development of radiatively driven convection in a model domain simulating a small lake covered by ice.
Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in ...their cores. One of the most informative approaches for determining the equation of state (EoS) of this dense matter is to measure both a star's equatorial circumferential radius Re and its gravitational mass M. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are km and (68%). The independent analysis reported in the companion paper by Riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of Re and M that are consistent with those found in this work. We show that our measurements of Re and M for PSR J0030+0451 improve the astrophysical constraints on the EoS of cold, catalyzed matter above nuclear saturation density.
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