New upper limits on deviation from the inverse-square law of gravity in the solar system:a Yukawa parameterization

New physics beyond the standard model of particles might cause deviation from the inverse-square law of gravity.In many theoretical models of modified gravity,it is parameterized by the Yukawa correction to the Newtonian gravitational force in terms of two parameters α and λ.Here α is a dimensionless strength parameter and λ is a length scale.Using the supplementary advances in perihelia provided by INPOP10a and EPM2011 ephemerides,we obtain new upper limits on the deviation from the inverse-square law when the uncertainty of the Sun's quadrupole moment is taken into account.We find that INPOP10a yields the upper limits as α = 3.1 × 10-11and λ = 0.15 au,and EPM2011 gives α = 5.2 × 10-11and λ = 0.21 au.In both of them,α is at least 10 times less than the previous results.     

New upper limits on deviation from the inverse-square law of gravity in the solar system： a Yukawa parameterization

New physics beyond the standard model of particles might cause deviation from the inverse-square law of gravity. In many theoretical models of modified gravity, it is parameterized by the Yukawa correction to the Newtonian gravitational force in terms of two parameters α and λ. Here α is a dimensionless strength parameter and A is a length scale. Using the supplementary advances in perihelia provided by INPOP10a and EPM2011 ephemerides, we obtain new upper limits on the deviation from the inverse-square law when the uncertainty of the Sun＇s quadrupole moment is taken into account. We find that INPOP10a yields the upper limits as α =- 3.1× 10-11 and λ= 0.15 au, and EPM2011 gives α = 5.2 × 10-11 and λ=- 0.21 au. In both of them, α is at least 10 times less than the previous results.     

Preliminary limits on deviation from the inverse-square law of gravity in the solar system:a power-law parameterization

New physics beyond the standard model of particles might cause a deviation from the inverse-square law of gravity. In some theories,it is parameterized by a power-law correction to the Newtonian gravitational force,which might originate from the simultaneous exchange of particles or modified and extended theories of gravity. Using the supplementary advances of the perihelia provided by INPOP10a(IMCCE,France) and EPM2011(IAA RAS,Russia) ephemerides,we obtain preliminary limits on this correction. In our estimation,we take the Lense-Thirring effect due to the Sun's angular momentum into account. The parameters of the power-law correction and the uncertainty of the Sun's quadrupole moment are simultaneously estimated with the method of minimizing χ2. From INPOP10 a,we find N = 0.605 for the exponent of the power-law correction. However,from EPM2011,we find that,although it yields N = 3.001,the estimated uncertainty in the Sun's quadrupole moment is much larger than the value given by current observations. This might be caused by the intrinsic nonlinearity in the power-law correction,which makes the estimation very sensitive to the supplementary advances of the perihelia.     

Precession effects on a liquid planetary core

Motivated by the desire to understand the rich dynamics of precessionally driven flow in a liquid planetary core, we investigate, through numerical simulations, the precessing fluid motion in a rotating cylindrical annulus, which simultaneously possesses slow precession. The same problem has been studied extensively in cylinders, where the precessing flow is characterized by three key parameters: the Ekman number E, the Poincar′e number P o and the radius-height aspect ratio Γ. While in an annulus,there is another parameter, the inner-radius-height aspect ratio Υ, which also plays an important role in controlling the structure and evolution of the flow. By decomposing the nonlinear solution into a set of inertial modes, we demonstrate the properties of both weakly and moderately precessing flows. It is found that, when the precessional force is weak, the flow is stable with a constant amplitude of kinetic energy. As the precessional force increases, our simulation suggests that the nonlinear interaction between the boundary effects and the inertial modes can trigger more turbulence, introducing a transitional regime of rich dynamics to disordered flow. The inertial mode u_(111), followed by u_(113) or u_(112), always dominates the precessing flow when 0.001 ≤ Po ≤ 0.05, ranging from weak to moderate precession.Moreover, the precessing flow in an annulus shows more stability than in a cylinder which is likely to be caused by the effect of the inner boundary that restricts the growth of resonant and non-resonant inertial modes. Furthermore, the mechanism of triadic resonance is not found in the transitional regime from a laminar to disordered flow.     

A long time span relativistic precession model of the Earth

A numerical solution to the Earth’s precession in a relativistic framework for a long time span is presented here.We obtain the motion of the solar system in the Barycentric Celestial Reference System by numerical integration with a symplectic integrator.Special Newtonian corrections accounting for tidal dissipation are included in the force model.The part representing Earth’s rotation is calculated in the Geocentric Celestial Reference System by integrating the post-Newtonian equations of motion published by Klioner et al.All the main relativistic effects are included following Klioner et al.In particular,we consider several relativistic reference systems with corresponding time scales,scaled constants and parameters.Approximate expressions for Earth’s precession in the interval±1 Myr around J2000.0 are provided.In the interval±2000 years around J2000.0,the difference compared to the P03 precession theory is only several arcseconds and the results are consistent with other long-term precession theories.     

A Possible Periodicity in the Radio Light Curves of 3C 454.3

During the period 1966.5–2006.2 the 15GHz and 8GHz light curves of 3C 454.3 (z = 0.859) show a quasi-periodicity of ～12.8 yr (～6.9 yr in the rest frame of the source) with a double-bump structure. This periodic behaviour is interpreted in terms of a rotating double-jet model in which the two jets are created from the black holes of a binary system and rotating with the period of the orbital motion. The periodic variations in the radio fluxes of 3C 454.3 are suggested to be mainly due to the lighthouse effects (or the variation in Doppler boosting) of the precessing jets caused by the orbital motion. In addition, variations in the rate of mass accreting onto the black holes may be also involved.     

太阳大气中的磁流体力学现象

Solar atmosphere is a rotating plasma shell filled by magnetic field. The coupling between the magnetic and the movement of plasma makes a variety of magnetohydrodynamic phenomena in the solar atmosphere. After giving a brief introduction on the basic theoretical regime of solar MHD, we describe mainly the magnetohydrodynamic aspects of solar flares, solar prominences (filaments) and flux tubes with different scales. Some future works are also discussd.     

The Binary Black Hole Scenario for the BL Lacertae Object AO 0235＋16

Recent analysis of the long term radio light curve of the extremely variable BL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outbursts with a period of ～ 5.7±0.5 yr. Periodicity analysis of the optical light curve also shows evidence for a shorter period. Here we discuss whether such a behavior can be explained by a binary black hole model where the accretion disk of one of the supermassive black holes is precessing due to the tidal effects of the companion. We estimate the mass of the accreting hole and analyze constraints on the secondary mass and the orbital parameters of the system. It is possible to provide a viable interpretation of the available multiwavelength data.     

Electromagnetic effects on the orbital motion of a charged spacecraft

This paper deals with the effects of electromagnetic forces on the orbital motion of a spacecraft.The electrostatic charge which a spacecraft generates on its surface in the Earth’s magnetic field will be subject to a perturbative Lorentz force.A model incorporating all Lorentz forces as a function of orbital elements has been developed on the basis of magnetic and electric fields.This Lorentz force can be used to modify or perturb the spacecraft’s orbits.Lagrange’s planetary equations in the Gauss variational form are derived using the Lorentz force as a perturbation to a Keplerian orbit.Our approach incorporates orbital inclination and the true anomaly.The numerical results of Lagrange’s planetary equations for some operational satellites show that the perturbation in the orbital elements of the spacecraft is a second order perturbation for a certain value of charge.The effect of the Lorentz force due to its magnetic component is three times that of the Lorentz force due to its electric component.In addition,the numerical results confirm that the strong effects are due to the Lorentz force in a polar orbit,which is consistent with realistic physical phenomena that occur in polar orbits.The results confirm that the magnitude of the Lorentz force depends on the amount of charge.This means that we can use artificial charging to create a force to control the attitude and orbital motion of a spacecraft.     

A Survey of Newtonian Core-Shell Systems with Pseudo High Order Symplectic Integrator and Fast Lyapunov Indicator

Newtonian core-shell systems, as limiting cases of relativistic core-shell models under the two conditions of weak field and slow motion, could account for massive circumstellar dust shells and rings around certain types of star remnants. Because this kind of systems have Hamiltonians that can be split into a main part and a small perturbing part, a good choice of the numerical tool is the pseudo 8th order symplectic integrator of Laskar ＆ Robutel, and, to match the symplectic calculations, a good choice of chaos indicator is the fast Lyapunov indicator （FLI） with two nearby trajectories proposed by Wu, Huang ＆ Zhang. Numerical results show that the FLI is very powerful when describing not only the transition from regular motion to chaos but also the global structure of the phase space of the system.     

Eclipsing binary XZ CMi in a hierarchical quadruple system

The new complete BV Rc Ic light curves and spectra of the short-period eclipsing binary XZ CMi are presented. The results from the combined analysis based on the photometric and spectroscopic data show that XZ CMi is a near contact binary with the secondary component filling its critical Roche lobe while the primary filling 91% of its Roche lobe. The investigation of the O-C diagram reveals that its orbital period is continuously increasing, which is consistent with the derived configuration and caused by the mass transfer from the less massive star to the more massive one. In addition, an obvious periodic modulation with the amplitude of0.0187(±0.0016) d and a high eccentric of 0.86(±0.04) is detected, which could be the results of the light time effect as a third star with the mass no less than 0.42(±0.09) M⊙orbiting around the central eclipsing binary once every 95.7(±2.1) yr. Furthermore, we found a visual companion star at 2.4′′ east by south of this system at a much greater distance by direct image. The large third light contribution found from the light curve analysis could be well explained by the existence of the third star and the fourth visual one.The similar parallax and proper motion imply that the components of this hierarchical quadruple system might be bounded by gravitation. Spectroscopic observations for two visual components were carried out by the LAMOST and 2.16 m telescopes, respectively. Their different values of [Fe/H] suggest that they were not born from the same origin. Thus, XZ CMi system is an interesting and important target to study the formation of the multiple stars.     

A low-mass-ratio and deep contact binary as the progenitor of the merger V1309 Sco

Nova Sco 2008(=V1309 Sco) is an example of a V838 Mon type eruption rather than a typical classical nova. This enigmatic object was recently shown to have resulted from the merger of two stars in a contact binary. It is the first stellar merger that was identified to be undergoing a common envelope transient. To understand the properties of its binary progenitor, the pre-outburst light curves were analyzed by using the W-D method. The photometric solution of the 2002 light curve shows that it is a deep contact binary(f = 89.5(±40.5)%) with a mass ratio of 0.094. The asymmetry of the light curve is explained by the presence of a dark spot on the more massive component. The extremely high fill-out factor suggests that the merging of the contact binary is driven by dynamical mass loss from the outer Lagrange point. However,the analysis of the 2004 light curve indicates that no solutions were obtained even at an extremely low mass ratio of q = 0.03. This suggests that the common convective envelope of the binary system disappeared and the secondary component spiraled into the envelope of the primary in 2004. Finally, the ejection of the envelope of the primary produced the outburst.     

Modeling the high-energy emission from the gamma-ray binary 1FGL J1018.6–5856

1FGL J1018.6–5856 is a high mass gamma-ray binary containing a compact object orbiting around a massive star with a period of 16.544 d. If the compact object is a pulsar, non-thermal emissions are likely produced by electrons accelerated at the termination shock, and may also originate from the magnetosphere and the un-shocked wind of the pulsar. In this paper, we investigate the non-thermal emissions from the wind and the shock with different viewing geometries and study the multi-wavelength emissions from 1FGL J1018.6–5856. We present the analysis results of the Fermi/LAT using nearly 10 years of data. The phase-resolved spectra indicate that the Ge V emissions comprise a rather steady component that does not vary with orbital motion and a modulated component that shows flux maximum around inferior conjunction. The ke V/Te V light curves of 1FGL J1018.6–5856 also exhibit a sharp peak around inferior conjunction, which are attributed to the boosted emission from the shock, while the broad sinusoidal modulations could be originating from the deflected shock tail at a larger distance. The modulations of Ge V flux are likely caused by the boosted synchrotron emission from the shock and the IC emission from the unshocked pulsar wind, while the steady component comes from the outer gap of the pulsar magnetosphere.Finally, we discuss the similarities and differences of 1FGL J1018.6–5856 with other binaries, like LS 5039.     

Optical and near-infrared photometric study of NGC 6724

BVRI CCD photometry of the poorly studied open cluster NGC 6724 has been carried out down to a limiting magnitude of V ～20 mag. The stars of the cluster have been observed using the Newtonian focus(f/4.84) of the 74-inch telescope at Kottamia Astronomical Observatory in Egypt.Also, the 2 MASS-JHK system is used to confirm the results we obtained. The main photometric parameters have been estimated for the present object; the diameter is found to be 6 arcmin, the distance is 1530±60 pc from the Sun and the age is 900±50 Myr. The optical reddening E(B-V) = 0.65 mag,while the infrared reddening is E(J-H) = 0.20 mag. The slope of the mass function distribution and the relaxation time estimations indicate that cluster NGC 6724 is dynamically relaxed.     

Re-Identification of the ''''Enigmatic'''' X-ray Source 1RXS J114003.0+124112

The ROSAT X-ray source 1RXS J114003.0 124112 was identified as a starburst galaxy at redshift 0.177 by He et al. The authors also noted that the source is almost two orders of magnitude brighter in X-ray than the X-ray-brightest starburst galaxy and it seems to be in a merging system, making this source an enigmatic system demanding further observations. Here we report a re-identification of 1RXS J114003.0 124112 using observations on the 2.6m telescope at Byurakan Astrophysical Observatory, Armenia and the SDSS data. The results indicate that the starburst activity is associated with the brighter object of the system, while the fainter object is a typical Seyfert 1 galaxy at a different redshift (0.282). Therefore, the two objects are not in a merging system, and the Seyfert 1 galaxy naturally accounts for the high X-ray flux. Three more objects reside in the vicinity, but they are all too faint to be responsible for the high X-ray flux.     

Mysteries of the geometrization of gravitation

As we now know, there are at least two major difficulties with general rel- ativity （GR）. The first one is related to its incompatibility with quantum mechanics, in the absence of a consistent, widely accepted theory that combines the two theo- ries. The second problem is related to the requirement of the dark sectors-inflaton, dark matter and dark energy by the energy-stress tensor, which are needed to explain a variety of astronomical and cosmological observations. Research has indicated that the dark sectors themselves do not have any non-gravitational or laboratory evidence. Moreover, the dark energy poses, in addition, a serious confrontation between funda- mental physics and cosmology. Guided by theoretical and observational evidences, we are led to an idea that the source of gravitation and its manifestation in GR should be modified. The result is in striking agreement with not only the theory, but also the ob- servations, without requiring the dark sectors of the standard approach. Additionally, it provides natural explanations to some unexplained puzzles.     

A modified TreePM code

We discuss the performance characteristics of using the modification of the tree code suggested by Barnes in the context of the TreePM code. The optimization involves identifying groups of particles and using only one tree walk to compute the force for all the particles in the group. This modification has been in use in our implementation of the TreePM code for some time, and has also been used by others in codes that make use of tree structures. We present the first detailed study of the performance characteristics of this optimization. We show that the modification, if tuned properly, can speed up the TreePM code by a significant amount. We also combine this modification with the use of individual time steps and indicate how to combine these two schemes in an optimal fashion. We find that the combination is at least a factor of two faster than the modified TreePM without individual time steps. Overall performance is often faster by a larger factor because the scheme for the groups optimizes the use of cache for large simulations.     

Disks and outflows in the S255IR area of high mass star formation from ALMA observations

We describe the general structure of the well known S255 IR high mass star forming region,as revealed by our recent ALMA observations. The data indicate a physical relation exists between the major clumps SMA1 and SMA2. The driving source of the extended high velocity, well collimated bipolar outflow, is not the most pronounced disk-like SMA1 clump harboring a 20 M_⊙young star(S255 NIRS3), as was assumed earlier. Apparently, it is the less evolved SMA2 clump, which drives the outflow and contains a compact rotating structure(probably a disk). At the same time, the SMA1 clump drives another outflow, with a larger opening angle. The molecular line data do not show an outflow from the SMA3 clump(NIRS1), which was suggested by IR studies of this region.     

Preliminary limits of a logarithmic correction to the Newtonian gravitational potential in binary pulsars

We obtain preliminary limits on a logarithmic correction to the Newtonian gravitational potential by using five binary pulsars:PSR J0737-3039,PSR B1534+12,PSR J1756-2251,PSR B1913+16 and PSR B2127+11C.This kind of correction may originate from fundamental frameworks,like string theories,effective models of gravity due to quantum effects and the non-local gravity scheme.We estimate the upper limit of the Tohline-Kuhn-Kruglyak parameter λ and the lower limit of the FabrisCampos parameter a,which parameterize the correction and are connected to each other by αλ=—1.By analyzing the advances of periastron of these binary pulsars,we find that the preliminary upper limit of α is 0.19±0.14 kpc~(-1) and the preliminary lower limit of λ is-5.2±3.8 kpc.They are compatible with the bounds based on dynamics of spiral galaxies but quite different from those given by solar system dynamics.These results indicate that this logarithmic correction might be more observable in current timings of binary pulsars than in motions of the solar system.     

A survey of weak stability boundaries in the Sun-Mars system

We investigate the weak stability boundary(WSB) for a new primary, Mars,in the framework of the planar circular restricted 3-body problem, and also in the planar bicircular restricted 4-body problem by including a perturbation due to Jupiter. For the sake of a simple stability/instability criterion, our computations have been done using the equations of motion in polar coordinates. It is found that the relative size of the weakly stable sets around Mars is much larger than that of the Earth-Moon and the Sun-Jupiter systems, as the mass ratio of the Sun-Mars system is significantly smaller.We propose that this difference could be scaled by the Hill radius. In an enlarged view of the domain close to Mars, the geometry of the WSB has been presented for various parameters and compared to previous works. Our results also show that Jupiter’s gravitational force would strongly affect the Martian stable regions and should be taken into account to design a ballistic capture trajectory.