Effects Of Orbital Motion Research Articles

X-ray confirmation of the intermediate polar IGR J16547-1916

Using X-ray observations from the NuSTAR and Swift satellites, we present temporal and spectral properties of an intermediate polar (IP) IGR J16547-1916. A persistent X-ray period at ∼546 s confirming the optical spin period obtained from previous observations is detected. The detection of a strong X-ray spin pulse reinforces the classification of this system as an intermediate polar. The lack of orbital or side-band periodicities in the X-rays implies that the system is accreting predominantly via a disk. A variable covering absorber appears to be responsible for the spin pulsations in the low energy range. In the high energy band, the pulsations are likely due to the self occultation of tall shocks above the white dwarf surface. The observed double-humped X-ray spin pulse profile indicates two-pole accretion geometry with tall accretion regions in short rotating IP IGR J16547-1916. We present the variation of the spin pulse profile over an orbital phase to account for the effects of orbital motion on the spin pulsation. X-ray spectra obtained from the contemporaneous observations of Swift and NuSTAR in the 0.5–78.0 keV energy band are modeled with a maximum temperature of 31 keV and a blackbody temperature of 64 eV, along with a common column density of 1.8 × 1023 cm−2 and a power-law index of −0.22 for the covering fraction. An additional Gaussian component and a reflection component are needed to account for a fluorescent emission line at 6.4 keV and the occurrence of X-ray reflection in the system. We also present the spin phase-resolved spectral variations of IGR J16547-1916 in the 0.5–78.0 keV energy band and find dependencies in the X-ray spectral parameters during the rotation of the white dwarf.

Relativistic fluid modelling of gamma-ray binaries

Context.Gamma-ray binaries are systems that radiate the dominant part of their non-thermal emission in the gamma-ray band. In a wind-driven scenario, these binaries are thought to consist of a pulsar orbiting a massive star, accelerating particles in the shock arising in the wind collision.Aims.We develop a comprehensive numerical model for the non-thermal emission of shock-accelerated particles including the dynamical effects of fluid instabilities and orbital motion. We demonstrate the model on a generic binary system.Methods.The model was built on a dedicated three-dimensional particle transport simulation for the accelerated particles that were dynamically coupled to a simultaneous relativistic hydrodynamic simulation of the wind interaction. In a post-processing step, a leptonic emission model involving synchrotron and inverse-Compton emission was evaluated based on resulting particle distributions and fluid solutions, consistently accounting for relativistic boosting andγγ-absorption in the stellar radiation field. The model was implemented as an extension to the CRONOScode.Results.In the generic binary, the wind interaction leads to the formation of an extended, asymmetric wind-collision region distorted by the effects of orbital motion, mixing, and turbulence. This gives rise to strong shocks terminating the pulsar wind and secondary shocks in the turbulent fluid flow. With our approach it is possible for the first time to consistently account for the dynamical shock structure in particle transport processes, which yields a complex distribution of accelerated particles. The predicted emission extends over a broad energy range, with significant orbital modulation in all bands.

Relativistic Effects in Orbital Motion of the S-Stars at the Galactic Center

The Galactic Center star cluster, known as S-stars, is a perfect source of relativistic phenomena observations. The stars are located in the strong field of relativistic compact object Sgr A* and are moving with very high velocities at pericenters of their orbits. In this work we consider motion of several S-stars by using the Parameterized Post-Newtonian (PPN) formalism of General Relativity (GR) and Post-Newtonian (PN) equations of motion of the Feynman’s quantum-field gravity theory, where the positive energy density of the gravity field can be measured via the relativistic pericenter shift. The PPN parameters β and γ are constrained using the S-stars data. The positive value of the Tg00 component of the gravity energy–momentum tensor is confirmed for condition of S-stars motion.

A dynamical and radiation semi-analytical model of pulsar-star colliding winds along the orbit: Application to LS 5039

Context.Gamma-ray binaries are systems that emit nonthermal radiation peaking at energies above 1 MeV. One proposed scenario to explain their emission consists of a pulsar orbiting a massive star, with particle acceleration taking place in shocks produced by the interaction of the stellar and pulsar winds.Aims.We develop a semi-analytical model of the nonthermal emission of the colliding-wind structure, which includes the dynamical effects of orbital motion. We apply the model to a general case and to LS 5039.Methods.The model consists of a one-dimensional emitter, the geometry of which is affected by Coriolis forces owing to orbital motion. Two particle accelerators are considered: one at the two-wind standoff location and the other one at the turnover produced by the Coriolis force. Synchrotron and inverse Compton emission is studied taking into account Doppler boosting and absorption processes associated to the massive star.Results.If both accelerators are provided with the same energy budget, most of the radiation comes from the region of the Coriolis turnover and beyond, up to a few orbital separations from the binary system. Significant orbital changes of the nonthermal emission are predicted in all energy bands. The model allows us to reproduce some of the LS 5039 emission features, but not all of them. In particular, the MeV radiation is probably too high to be explained by our model alone, the GeV flux is recovered but not its modulation, and the radio emission beyond the Coriolis turnover is too low. The predicted system inclination is consistent with the presence of a pulsar in the binary.Conclusions.The model is quite successful in reproducing the overall nonthermal behavior of LS 5039. Some improvements are suggested to better explain the phenomenology observed in this source, such as accounting for particle reacceleration beyond the Coriolis turnover, unshocked pulsar wind emission, and the three-dimensional extension of the emitter.

CFD Simulations of Self-Propulsion and Turning Circle Maneuver up to 90º of Ship in Waves

In the present work, a Reynolds-Averaged Navier-Stokes (RANS)-overset method is used to numerically investigate self-propulsion and turning circle maneuver in waves for a container ship. A computational fluid dynamics (CFD) solver naoe-FOAM-SJTU is used for the numerical computations of the fully appended Duisburg Test Case ship model. Overset grids are used to handle the motions of the ship hull appended with the propeller and the rudder. Open source toolbox waves2Foam is used to prevent wave reflection in the computational domain. The current numerical method is validated by comparing the ship speed in the self-propulsion case between CFD and Experimental Fluid Dynamics (EFD). Predicted ship 6-DOF motions, hydrodynamic forces, free surfaces, and inflow of the propeller are presented. The propulsion characteristic is mainly studied. Assuming the thrust identification method works even in unsteady conditions, the wake fraction and propulsion efficiency are discussed. The effect of orbital motion of water particle and ship motion on the propulsion performance are identified. In conclusion, the present RANS-overset method is a reliable approach to directly simulate self-propulsion and turning circle maneuver in waves.

The effect of orbital motion and eccentricity of drill pipe on pressure gradient in eccentric annulus flow with Newtonian and non-Newtonian fluids

The correct prediction of the pressure gradient is the fundamental parameter to establish an effective hydraulics program, which enables an optimised drilling process. In the present work, the effect of the orbital motion of the drill pipe on the pressure drop in an eccentric annulus flow with Newtonian and non-Newtonian fluids is studied numerically for both laminar and turbulent regimes using finite volume method (FVM). Furthermore, the effect of eccentricity when the inner pipe makes an orbital motion is evaluated. Different behaviours are observed in laminar and turbulent regimes. In the laminar regime, the simulation results showed that an increase of the orbital motion speed causes a considerable increment of the pressure gradient for the Newtonian fluid. For the power-law, non-Newtonian fluid in the laminar regime, on the contrary, a decrease of the pressure gradient is observed due to the shear-thinning effect. In the turbulent regime the mentioned trends are predicted to be much weaker. As eccentricity increases, the pressure drop of the non-Newtonian fluid decreases with a more pronounced diminish in pressure drop when the drill pipe is in orbital motion for both laminar and turbulent flow regimes.

The effect of orbital motion and eccentricity of drill pipe on pressure gradient in eccentric annulus flow with Newtonian and non-Newtonian fluids

The correct prediction of the pressure gradient is the fundamental parameter to establish an effective hydraulics program, which enables an optimised drilling process. In the present work, the effect of the orbital motion of the drill pipe on the pressure drop in an eccentric annulus flow with Newtonian and non-Newtonian fluids is studied numerically for both laminar and turbulent regimes using finite volume method (FVM). Furthermore, the effect of eccentricity when the inner pipe makes an orbital motion is evaluated. Different behaviours are observed in laminar and turbulent regimes. In the laminar regime, the simulation results showed that an increase of the orbital motion speed causes a considerable increment of the pressure gradient for the Newtonian fluid. For the power-law, non-Newtonian fluid in the laminar regime, on the contrary, a decrease of the pressure gradient is observed due to the shear-thinning effect. In the turbulent regime the mentioned trends are predicted to be much weaker. As eccentricity increases, the pressure drop of the non-Newtonian fluid decreases with a more pronounced diminish in pressure drop when the drill pipe is in orbital motion for both laminar and turbulent flow regimes.

Effect of orbital motion of drill pipe on the transport of non-Newtonian fluid-cuttings mixture in horizontal drilling annulus

The effect of orbital motion of drill pipe on the transport of non-Newtonian fluid and cuttings is simulated by means of the two-fluid model in combination with the kinetic theory of granular flow in the horizontal wellbore annulus. The drill pipe self-rotates around its own axis while pursuing a circular orbit around the axis of the wellbore annulus, in which the orbital radius is the eccentric distance of the drill pipe from the axis of the wellbore. The embedded sliding mesh method is adopted to achieve the effect of the orbital movement of the drill pipe wall on the liquid-solid mixture. The cuttings transport ratio (CTR) which is defined as the ratio of the concentration of injected cuttings to the concentration of cuttings retained in the annulus is chosen as the measurement to evaluate hole cleaning. Cuttings transport behaviors in the annuli with the four motion states of drill pipe are investigated respectively. Simulations indicate that if the drill pipe is not concentric, there must be the fluid force that causes the lateral movement of drill pipe when it rotates. The orbital motion of drill pipe improves cuttings transport ratio in the annulus due to the periodical stirring and entrainment effect on cutting particles. The tangential flow within the annulus is dominated by the orbital motion of drill pipe rather than the self-rotation. The secondary flow appears especially when the self-rotation and orbital motion of drill pipe are in the opposite direction. With the increase of the orbital radius, the cuttings transport ratio is improved and the pressure drop is reduced because of the agitation of the drill string against the flow field. Increasing the rotating speed of the drill pipe contributes to a better wellbore cleaning, while an excessive rotating speed causes a higher pressure drop. Although the orbital motion of the drill pipe improves the hole cleaning, it also greatly increases the resistance and resultant moment exerted by the liquid-solid mixture, especially at high rotation speeds and eccentricity ratios.

Dynamic nuclear polarization at high Landau levels in a quantum point contact

We demonstrate a way to polarize and detect nuclear spin in a gate-defined quantum point contact operating at high Landau levels. Resistively-detected Nuclear Magnetic Resonance (RDNMR) can be achieved up to the $5$th Landau level and at a magnetic field lower than $1$ T. We are able to retain the RDNMR signals in a condition where the spin degeneracy of the first 1D subband is still preserved. Furthermore, the effects of orbital motion on the first 1D subband can be made smaller than those due to electrostatic confinement. This developed RDNMR technique is a promising means to study electronic states in a quantum point contact near zero magnetic field.

New nearby white dwarfs from Gaia DR1 TGAS and UCAC5/URAT

Aims. Using an accurate Tycho-Gaia Astrometric Solution (TGAS) 25 pc sample that is nearly complete for GK stars and selecting common proper motion (CPM) candidates from the 5th United States Naval Observatory CCD Astrograph Catalog (UCAC5), we search for new white dwarf (WD) companions around nearby stars with relatively small proper motions. Methods. To investigate known CPM systems in TGAS and to select CPM candidates in TGAS+UCAC5, we took into account the expected effect of orbital motion on the proper motion and proper motion catalogue errors. Colour-magnitude diagrams (CMDs) MJ ∕J − Ks and MG ∕G − J were used to verify CPM candidates from UCAC5. Assuming their common distance with a given TGAS star, we searched for candidates that occupied similar regions in the CMDs as the few known nearby WDs (four in TGAS) and WD companions (three in TGAS+UCAC5). The CPM candidates with colours and absolute magnitudes corresponding neither to the main sequence nor to the WD sequence were considered as doubtful or subdwarf candidates. Results. With a minimum proper motion of 60 mas yr−1, we selected three WD companion candidates; two of which are also confirmed by their significant parallaxes measured in URAT data, whereas the third may also be a chance alignment of a distant halo star with a nearby TGAS star that has an angular separation of about 465 arcsec. One additional nearby WD candidate was found from its URAT parallax and GJKs photometry. With HD 166435 B orbiting a well-known G1 star at ≈24.6 pc with a projected physical separation of ≈700 AU, we discovered one of the hottest WDs, classified by us as DA2.0 ± 0.2, in the solar neighbourhood. We also found TYC 3980-1081-1 B, a strong cool WD companion candidate around a recently identified new solar neighbour with a TGAS parallax corresponding to a distance of ≈8.3 pc and our photometric classification as ≈M2 dwarf. This raises the question of whether previous assumptions on the completeness of the WD sample to a distance of 13 pc were correct.

Astrometric detectability of systems with unseen companions: effects of the Earth orbital motion

Astrometric detection of an unseen companion is based on analysis of apparent motion of its host star around the system's barycentre. Systems with orbital period close to one year may escape detection if orbital motion of their host stars are observationally indistinguishable from parallax effect. Additionally, the astrometric solution may produce a biased parallax estimation for such systems. We examine effects of orbital motion of the Earth on astrometric detectability in terms of correlation between the Earth's orbital position and position of the star relative to its system barycentre. The $\chi^2$ statistic for parallax estimation is calculated analytically, leading to expressions that relate the decrease in detectability and accompanying parallax bias to the position correlation function. The impact of the Earth's motion critically depends on the exoplanet's orbital period, diminishing rapidly as the period deviates from one year. Selection effects against one-year period systems is therefore expected. Statistical estimation shows that the corresponding loss of sensitivity results in a typical 10 per cent increase in detection threshold. Consideration of eccentric orbits shows that the Earth's motion has no effect on detectability for $e\ge0.5$. Dependence of detectability on other parameters, such as orbital phases and inclination of the orbit plane to the ecliptic, are smooth and monotonic because they are described by simple trigonometric functions.

Effects of Orbital Motion on the Velocity Field of Boundary Layer Flow over a Rotating Disk

The purpose of this study is to investigate experimentally the effects of orbital motion on the velocity field of boundary layer flow over a rotating disk. The characteristics of velocity field at a fixed orbital angular section measured by a hot-wire anemometer show that the structure of the 3-dimensional boundary layer flow is deformed elliptically and displaced in a certain direction that is not in the orbital radial direction, but the direction of deformation depends on the combination of orbital and rotational directions. For coincide orbital and rotational directions, there are regions where the intensity of low-frequency disturbances increases rapidly in a certain central region (laminar region under pure rotation). The transient vortices, which form streaks on the coating film, are considered to be destroyed by low-frequency disturbances. However, for opposite orbital and rotational directions, the low-frequency disturbances are not observed in any section. As the adding orbital speed increases, the intensity of velocity fluctuations in the turbulence region becomes larger in the expected except in a certain region. This location of the region also depends on the direction of deformation or the combination of orbital and rotational directions.

MOA-2011-BLG-028Lb: A NEPTUNE-MASS MICROLENSING PLANET IN THE GALACTIC BULGE*

ABSTRACT We present the discovery of a Neptune-mass planet orbiting a 0.8 ± 0.3 M ⊙ star in the Galactic bulge. The planet manifested itself during the microlensing event MOA-2011-BLG-028/OGLE-2011-BLG-0203 as a low-mass companion to the lens star. The analysis of the light curve provides the measurement of the mass ratio ( 1.2 ± 0.2 ) × 10 − 4 , which indicates that the mass of the planet is 12–60 Earth masses. The lensing system is located at 7.3 ± 0.7 kpc away from the Earth near the direction of Baade’s Window. The projected separation of the planet at the time of the microlensing event was 3.1–5.2 au. Although the microlens parallax effect is not detected in the light curve of this event, preventing the actual mass measurement, the uncertainties of mass and distance estimation are narrowed by the measurement of the source star proper motion on the OGLE-III images spanning eight years, and by the low amount of blended light seen, proving that the host star cannot be too bright and massive. We also discuss the inclusion of undetected parallax and orbital motion effects into the models and their influence onto the final physical parameters estimates.

Orbital motion effects in astrometric microlensing

We investigate lens orbital motion in astrometric microlensing and its detectability. In microlensing events, the light centroid shift in the source trajectory (the astrometric trajectory) falls off much more slowly than the light amplification as the source distance from the lens position increases. As a result, perturbations developed with time such as lens orbital motion can make considerable deviations in astrometric trajectories. The rotation of the source trajectory due to lens orbital motion produces a more detectable astrometric deviation because the astrometric cross-section is much larger than the photometric one. Among binary microlensing events with detectable astrometric trajectories, those with stellar-mass black holes have most likely detectable astrometric signatures of orbital motion. Detecting lens orbital motion in their astrometric trajectories helps to discover further secondary components around the primary even without any photometric binarity signature as well as resolve close/wide degeneracy. For these binary microlensing events, we evaluate the efficiency of detecting orbital motion in astrometric trajectories and photometric light curves by performing Monte Carlo simulation. We conclude that astrometric efficiency is 87.3 per cent whereas the photometric efficiency is 48.2 per cent.

Characteristics of transient vortices in the boundary layer on a rotating disk under orbital motion

The objective of this study is to experimentally examine the characteristics of transient vortices in the boundary layer on a disk undergoing both rotation and orbital motion. The velocity fluctuations on a rotating, orbiting disk (disk radius equal to orbital radius) are measured by the hot-wire method, and the effects of orbital motion on the transient vortices in the boundary layer are examined. When the ratio of the orbital speed to the speed of rotation is ±0.025, the interval of transient vortices depends on only the orbital radius, regardless of the directions of rotation and orbital motion. The rate of low-frequency disturbances increases as the orbital speed increases, and the vortices induced by these low-frequency disturbances travel over the disk and then develop in the region of increased velocity. Consequently, no vortices generated on a rotating disk under orbital motion are stationary relative to the disk.

ORBITAL-PHASE-RESOLVED SPECTROSCOPY OF THE INTERMEDIATE POLAR FO AQR USINGXMM-NEWTONOBSERVATORY DATA

We present the orbital-phase-resolved analysis of an archival FO Aqr observation obtained using the X-ray Multi-Mirror Mission, European Photon Imaging Camera (pn instrument). We investigate the variation of the spin pulse amplitudes over the orbital period in order to account for the effects of orbital motion on spin modulation. The semi-amplitude variations are in phase with the orbital modulation, changing from (38.0 {+-} 1.8)% at the orbital maximum to (13.3 {+-} 3.7)% at the orbital minimum. The spectral parameters also show changes over the orbital period. One of the absorption components increase by a factor of five between the orbital minimum and maximum. We interpret that this absorption arises from the bulge where accretion stream from the secondary impacts the disk. The spectrum extracted from the orbital minima and maxima can be fitted with a warm absorber model yielding values N{sub H} = 2.09{sup +0.98}{sub -1.09} Multiplication-Sign 10{sup 22} and 0.56{sup +0.26}{sub -0.15} Multiplication-Sign 10{sup 22} cm{sup -2}; and log({xi}) = 0.23{sup +0.37}{sub -0.26} and <0.30 erg cm s{sup -1}, respectively, indicating the existence of ionized absorption from the bulge at the impact zone which is spread out on the disk. The absorption due to accretion curtain and/or column whichmore » causes the spin modulation can be distinguished from the disk absorption via spectral modeling.« less

IMPACT OF TYPE Ia SUPERNOVA EJECTA ON BINARY COMPANIONS IN THE SINGLE-DEGENERATE SCENARIO

Type Ia supernovae are thought to be caused by thermonuclear explosions of a carbon-oxygen white dwarf in close binary systems. In the single-degenerate scenario (SDS), the companion star is non-degenerate and can be significantly affected by the explosion. We explore this interaction by means of multi-dimensional adaptive mesh refinement simulations using the FLASH code. We consider several different companion types, including main-sequence-like stars (MS), red giants (RG), and helium stars (He). In addition, we include the symmetry-breaking effects of orbital motion, rotation of the non-degenerate star, and Roche-lobe overflow. A detailed study of a sub-grid model for Type Ia supernovae is also presented. We find that the dependence of the unbound stellar mass and kick velocity on the initial binary separation can be fitted by power-law relations. By using the tracer particles in FLASH, the process leading to the unbinding of matter is dominated by ablation, which has usually been neglected in past analytical studies. The level of Ni/Fe contamination of the companion that results from the passage of the supernova ejecta is found to be a $\sim 10^{-5} M_{\odot}$ for the MS star, $\sim 10^{-4} M_{\odot}$ for the He star, and $\sim 10^{-8} M_{\odot}$ for the RG. The spinning MS companion star loses about half of its initial angular momentum during the impact, causing the rotational velocity to drop to a quarter of the original rotational velocity, suggesting that the Tycho G star is a promising progenitor candidate in the SDS.

Escape rates and variability constraints for high‐energy sodium sources at Mercury

We present a 3‐D time‐dependent modeling of Mercury's extended sodium exosphere in the region of the distant tail. Recent simulations in support of the MESSENGER and BepiColombo missions have shown spatial distributions in Mercury's exosphere can be linked to specific source processes. Our model builds upon these efforts by concentrating on the escaping component of Mercury's surface‐bound exosphere to assess the wide‐field (7°) data described in the studies by Baumgardner et al. (2008) and Schmidt et al. (2010). Escape rates of several source processes in Mercury's exosphere are determined, and the effects of orbital motion, surface‐gas interactions, variable source rates, and spatially heterogeneous sources are explored. Our simulations demonstrate that both photon‐stimulated desorption and micrometeoroid impacts can result in a ∼20% loss of Mercury's sodium atmosphere, depending on orbital phase, and are jointly responsible for the observed comet‐like tail as driven by solar radiation pressure. For a constant supply of both these sources into the exosphere, the modeled average column density over Mercury's disc decreases by ∼1/3 at 70° true anomaly (the orbital position for peak escape), consistent with observations over many orbits.

Effects of Orbital Motion on the Boundary Layer Flow on a Spinning Disk

Effects of Orbital Motion on the Boundary Layer Flow on a Spinning Disk

Effects of Orbital Motion on the Boundary Layer Flow on a Spinning Disk

The objective of this study is to experimentally examine the effects of orbital motion on the boundary layer flow on a spinning disk. The boundary layer flow on the disk is visualized by the oil flow method, and velocity in the boundary layer is measured by the hot-wire method. For the oil flow pattern in the case of spinning motion only, streaks are clearly observed on the disk as transient vortices, but by adding orbital motion to the spinning motion, we find that streaks are not observed in a certain range of orbital conditions. With increasing orbital motion speed, the laminar re- gion becomes narrower and transition is promoted from the inward region of the disk, regardless of the direction of ro- tation. Also, with the addition of orbital motion, the velocity profile in the boundary layer becomes more asymmetric with respect to the spin axis of the disk. Furthermore, stationary vortices do not appear on the disk when the orbital speed is beyond a certain critical value. Therefore, the lack of streaks in the oil film pattern when orbital motion is added is due to the spatiotemporal unsteadiness of the flow field on the disk.