Orbital Motion Research Articles

Three Years of High-contrast Imaging of the PDS 70 b and c Exoplanets at Hα with MagAO-X: Evidence of Strong Protoplanet Hα Variability and Circumplanetary Dust

We present 3 yr of high-contrast imaging of the PDS 70 b and c accreting protoplanets with the new extreme AO system MagAO-X as part of the MaxProtoPlanetS survey of Hα protoplanets. In 2023 and 2024, our sharp (25–27 mas FWHM), well-AO-corrected (20%–26% Strehl), deep (2–3.6 hr) images detected compact (r ∼ 30 mas; r ∼ 3 au) circumplanetary disks (CPDs) surrounding both protoplanets. Starlight scattering off the front edge of these dusty CPDs is the likely source of the bright compact continuum light detected within ∼30 mas of both planets in our simultaneously obtained continuum 668 nm filter images. After subtraction of contaminating continuum and point-spread function residuals with pyKLIP angular differential imaging and spectral differential imaging, we obtained high-contrast ASDI Hα images of both planets in 2022, 2023, and 2024. We find the Hα line flux of planet b fell by (8.1 ± 1.6) × 10−16 erg s−1 cm−2, a factor of 4.6 drop in flux from 2022 to 2023. In 2024 March, planet b continued to be faint with just a slight 1.6× rise to an Hα line flux of (3.64 ± 0.87) × 10−16 erg s−1 cm−2. For c, we measure a significant increase of (2.74 ± 0.51) × 10−16 erg s−1 cm−2 from 2023 to 2024, which is a factor of 2.3 increase. So both protoplanets have recently experienced significant Hα variability with ∼1 yr sampling. In 2024, planet c is brighter than b: as c is brightening and b generally fading. We also tentatively detect one new point source “CC3” inside the inner disk (∼49 mas; at PA ∼ 295°; 2024) with orbital motion roughly consistent with a ∼5.6 au orbit.

Enhancing System Capacity Through Joint Space‐Ground Multi‐Beam Coordination for LEO Satellite Systems

ABSTRACTDue to the long transmission distance of the constellation network represented by the low‐orbit satellite system, the satellite‐to‐ground link is subject to large path loss and limited communication performance. This paper uses multi‐satellite and multi‐beam joint transmission technology to form a virtual multiplex network with ground multi‐antenna terminals (Multiple‐Input Multiple‐Output [MIMO] system). However, due to the high‐speed movement of satellites, the topology of the MIMO system is unstable, which in turn affects the stability of the system throughput. This article proposes two inter‐satellite cooperation modes to improve the stability of MIMO system capacity. The first method is to optimize the channel capacity by rationally allocating the beam power of the gateway station so that the gateway station can achieve transparent forwarding through satellites. The second method rotates the angle of the user's receiving antenna to combat channel changes caused by changes in satellite position. Simulation results show that both methods can effectively improve the minimum channel capacity. Transparent forwarding can increase the capacity by about 22.7%, while the rotating antenna can still improve the performance gain by at least 36.3% even with a limited rotation angle. This research contributes to the development of stable and efficient communication systems in satellite‐ground cooperative networks.

ESPRESSO reveals a single but perturbed broad-line region in the supermassive black hole binary candidate PG 1302-102

In this work, we present a new, fully Bayesian analysis of the highest-resolution optical spectrum of the supermassive black hole (SMBH) binary candidate PG 1302-102, obtained with ESPRESSO at the VLT ( R ). Our methodology, based on robust Bayesian model selection, reveals the presence of multiple narrow emission lines at the expected redshift of the source and confirms (for Hbeta ) and detects (for Hgamma ) the clear presence of redshifted broad components. Additionally, we have discovered a ``very broad'' and, if it is associated with the Hbeta , ``very redshifted'' component at $ We evaluate two scenarios for explaining the observed broad emission line (BEL) features in PG 1302-102. In the case in which the redshifted BEL asymmetry arises from the orbital motion of a putative binary, our measurements coupled with simple estimates of the broad-line region (BLR) sizes suggest that the individual black hole BLRs are either settled in a single BLR or in the process of merging and, therefore truncated and highly disturbed. Alternatively, in the scenario of a single SMBH, we explain the distorted emission of the BELs with a nonsymmetric distribution of the BLR clouds; namely, a thin disk with a spiral perturbation. This BLR configuration is statistically preferred over any empirical multi-Gaussian fit and simultaneously explains the asymmetric emission of the Hbeta and Hgamma close to the bulk of the line and any additional excess (or the lack of it, in the case of the Hgamma ) at much longer wavelengths. The physical origins of the perturbation are still unclear and a connection with the possible presence of a black hole binary cannot be ruled out. Given the growing evidence from theoretical and observational works demonstrating the common presence of disturbed BLRs in active galactic nuclei, we argue that an origin related to self-gravitating instabilities may be more plausible.

Orbital motion and epicyclic oscillations around a black hole with magnetic charge

Orbital motion and epicyclic oscillations around a black hole with magnetic charge

A Spectroscopic and Interferometric Study of W Serpentis Stars. I. Circumbinary Outflow in the Interacting Binary W Serpentis

W Serpentis is an eclipsing binary system and the prototype of the Serpentid class of variable stars. These are interacting binaries experiencing intense mass transfer and mass loss. However, the identities and properties of both stars in W Ser remain a mystery. Here, we present an observational analysis of high-quality, visible-band spectroscopy made with the Apache Point Observatory 3.5 m telescope and Astrophysical Research Consortium Echelle Spectrograph spectrograph plus the first near-IR, long-baseline interferometric observations obtained with the Center for High Angular Resolution Astronomy Array. We present examples of the appearance and radial velocities of the main spectral components: prominent emission lines, strong shell absorption lines, and weak absorption lines. We show that some of the weak absorption features are associated with the cool mass donor, and we present the first radial velocity curve for the donor star. The donor’s absorption lines are rotationally broadened, and we derive a ratio of donor to gainer mass of 0.36 ± 0.09 based on the assumptions that the donor fills its Roche lobe and that it rotates synchronously with the orbit. We use a fit of the All-Sky Automated Survey light curve to determine the orbital inclination and mass estimates of 2.0M ⊙ and 5.7M ⊙ for the donor and gainer, respectively. The partially resolved interferometric measurements of orbital motion are consistent with our derived orbital properties and the distance from Gaia EDR3. Spectroscopic evidence indicates that the gainer is enshrouded in an opaque disk that channels the mass transfer stream into an outflow through the L3 region and into a circumbinary disk.

Dynamic 3D Simulation of Surface Charging on Rotating Asteroids

The surface-charging phenomenon of asteroids, mainly resulting from solar wind plasma and solar radiation, has been extensively studied. However, the influence of the asteroid’s rotation on surface charging is not yet fully understood. In this study, a neural network is established to replace numerical integration, improving the efficiency of dynamic 3D simulations. We simulate rotating asteroids and their surrounding plasma environments under various conditions, including the quiet solar wind and solar storms. Different minerals on the asteroid surface are also considered. Additionally, the effects of orbital motion and obliquity are studied for asteroids with rotation periods comparable to their orbital periods. The results show that under the typical solar wind, the maximum and minimum potentials of asteroids gradually decrease with increasing rotation periods, especially when the solar wind is obliquely incident. For asteroids with rotation periods longer than one week, this decreasing trend becomes extremely slow. During a solar storm, the solar wind plasma changes sharply, and the susceptibility of an asteroid’s surface potential to rotation is greatly pronounced. Surface minerals also play a role; plagioclase is the most sensitive mineral among those explored, while ilmenite appears indifferent to changes in rotation periods. Understanding the surface charging of asteroids under various rotation periods and angles is crucial for further research on solar wind plasma and asteroids’ surface dust motion, providing a reference for the safe landing and exploration of asteroids.

Влияние бара на хаотическую динамику шаровых скоплений в центральной области Галактики

The paper is devoted to the analysis of the influence of the galactic bar on the nature of the orbital motion (chaotic or regular) of globular clusters in the central region of the Galaxy with a radius of 3.5 kpc, which are subject to the greatest influence of the bar. The sample includes 45 globular clusters. To form the 6D phase space required for integrating the orbits, the most accurate astrometric data to date from the Gaia satellite (Vasiliev, Baumgardt, 2021) were used, as well as new refined average distances (Baumgardt, Vasiliev, 2021). The orbits of the globular clusters were obtained both in an axisymmetric potential and in a potential including the bar. The following, most realistic, bar parameters were adopted: mass 1010M⊙, semi-major axis length 5 kpc, bar axis rotation angle 25o, angular otation velocity 40 km/s/kpc. The analysis of the chaoticity/regularity of the orbital motion in both potentials was carried out using one of the most effective methods, namely, the frequency method, which consists in calculating the drift of fundamental frequencies. As a result, the influence of the bar on the dynamics of each GC of the sample was assessed. We ectablished that 8 GCs changed regular dynamics to chaotic under the influence of the bar, and 9 GCs changed chaotic dynamics to regular.

The overflowing atmosphere of WASP-121 b. High-resolution transmission spectroscopy with VLT/CRIRES+

Transmission spectroscopy is a prime method to study the atmospheres of extrasolar planets. We obtained a high-resolution spectral transit time series of the hot Jupiter with CRIRES$^+$ to study its atmosphere via transmission spectroscopy of the triplet lines. Our analysis shows a prominent absorption feature moving along with the planetary orbital motion, which shows an observed, transit-averaged equivalent width of approximately 30\,m a slight redshift, and a depth of about 2\,<!PCT!>, which can only be explained by an atmosphere overflowing its Roche lobe. We carried out 3D hydrodynamic modeling to reproduce the observations, which favors asymmetric mass loss with a more pronounced leading tidal tail, possibly also explaining observational evidence for additional absorption stationary in the stellar rest frame. A trailing tail is not detectable. From our modeling, we derived estimates of $ for the stellar and $5.4 for the planetary mass loss rate, which is consistent with X-ray and extreme-ultraviolet (XUV) driven mass loss in

Radio frequency interference from radio navigation satellite systems: simulations and comparison to MeerKAT single-dish data

Abstract Radio Frequency Interference (RFI) is emitted from various sources, terrestrial or orbital, and creates a nuisance for ground-based 21-cm experiments. In particular, single-dish observations will be highly susceptible to RFI due to their wide primary beam and sensitivity. This work aimed to simulate the contamination effects from the Radio Navigational Satellite System (RNSS) within the 1100-1350 (MHz) frequency band. The simulation can be divided into two parts: i) satellite positioning, emission power, and the beam response on the telescope, and ii) calibration of the satellite signals to data to improve the original model. We utilise previously observed single-dish L-band data from the Meer-Karoo Array Telescope (MeerKAT), which requires special calibration to account for regions contaminated by satellite-based RFI. We find that we can recreate the satellite contamination with high accuracy around its peak frequencies provided the satellite is not too close to the telescope’s pointing direction. The simulation can predict satellite movements and signals for past and future observations, aiding in RFI avoidance and testing novel cleaning methods. The predicted signal sits below the noise in the target cosmology window in the L-band (970 - 1015 MHz) making it difficult to confirm any out-of-band emission from satellites. However, in our simulations, this contamination still overwhelmed the 21-cm auto-power spectrum. Nevertheless it is possible to detect the signal in cross-correlations after mild foreground cleaning. Whether such out of band contamination does exist will require further characterisation of the satellite signals far away from their peak frequencies.

Exploring implications of elephant movements between land use types in an arid savannah landscape

While the numbers and distribution of African savannah elephants (Loxodonta africana) have declined in most African range States, they have been steadily increasing in much of southern Africa. In Namibia’s arid north-west, elephants are expanding beyond Protected areas (PA) into multiple types of land use, leading to socio-economic implications, both positive and negative. Our study aimed to quantify cross-land use movements and fence breaches and explore the institutional, legislative and policy implications of fencing, and a new conservation paradigm for the area. We used satellite movements of eight collared elephant herds in multiple types of land use to the south and west of Etosha National Park for one year. Of these herds, seven had home ranges spanning multiple PA/communal/commercial landscapes, often crossing fences with management or disease significance. The implications of the movements between land uses are assessed in the context of relevant policy regarding management and economics. We conclude that despite challenges to livestock disease control and fencing damage, the expansion of elephant range has resulted in economic benefits to landowners and communal conservancies through tourism and possible consumptive use opportunities, as well as an improvement in general wildlife conservation practices in the area. Regardless of these benefits and the growing interest among rural residents in supporting the establishment of elephant corridors and the removal of fences, Namibia’s legal and policy framework creates numerous implications for landowners and managers when considering fence breaches by elephants. We conclude with recommendations for holistic situational analysis of policy, law and practice and the consideration of amendments to outdated fencing requirements, thereby unlocking the economic and conservation benefits of elephant range expansion in the area.

Effect of an incoming Gaussian wave packet on underlying turbulence

We present a simulation-based study of the effect of a passing wave packet on underlying fully developed turbulence. We propose a novel wave-phase-resolved simulation method inspired by Helmholtz decomposition to directly couple the turbulence simulation with instantaneous wave orbital motions without wave-phase averaging. We also introduce a boundary condition treatment for the turbulence at the wave surface, which allows the turbulence simulation to be conducted in a rectangular domain while retaining the wave-phase effect. The results obtained from the proposed method reveal considerable variations in turbulence statistics, including the enstrophy and Reynolds normal stresses, during wave packet passage. Most changes occur rapidly when the narrow bandwidth around the wave packet core passes. Further analyses of the energy spectra indicate that the enhancement of turbulence occurs across a wide range of scales, with the near-surface small-scale motions experiencing the most significant intensification. Meanwhile, large-scale motions with scales comparable to the boundary layer depth are also enhanced. The mechanisms underlying the Reynolds normal stress variation at different length scales are related to the energy transfer from the wave orbital straining to turbulence through production, the pressure–strain effect, the pressure diffusion and the wave advection. By assessing the turbulence statistics and dynamics impacted by a wave packet in detail, this study provides an improved understanding of the response of a developed turbulent flow to a transient wave field. The proposed simulation method also proves to be a promising phase-resolved approach for efficiently modelling the wave effect on turbulence.

Orbital motion and QPOs testing around rotating Hairy black holes in Horndeski gravity

We investigate the orbital and oscillatory motion of test particles around a rotating hairy black hole in the context of Horndeski gravity. This black hole consists of three parameters, namely, the mass M of the black hole, spin parameter a of the black hole, and the hairy parameter q that results from the Horndeski theory of gravity. Analytical solutions are obtained for the radial profiles of specific energy and angular momentum corresponding to equatorial stable circular orbits, in terms of the model parameters. Using the effective potential method, we also examine the stability of these orbits. Additionally, we derive the analytical expressions for frequencies of radial and latitudinal harmonic oscillations, as a function of the black hole’s mass, charge, and spin of the black hole, for both local and distant observers. The key characteristics of quasi-periodic oscillations near stable circular orbits in the equatorial plane are explored. Furthermore, we analyze the precession of periastron and the Lense-Thirring effect. Our findings reveal that the particle motion around the black hole is significantly shaped by the parameters of the model.

Orbital motion control of an electrically charged spacecraft

In this paper, the orbital motion of an electrically charged spacecraft in the gravitational and magnetic fields of the Earth is investigated. The “direct magnetic dipole” is considered as a model of the geomagnetic field. The nonlinear non-autonomous system of differential equations of motion of the spacecraft center of mass in the Cartesian and spherical coordinate systems is derived. The analytical study of the influence of the Lorentz force on the orbital motion of a charged spacecraft is carried out. The approximate solution of the differential system is found. The results of numerical simulation of the spacecraft orbital motion based on the derived system of differential equations are presented. The analytical and numerical solutions are compared. The problem of stabilizing the spacecraft’s center of mass in the orbital plane is considered. Feedback control methods based on the use of jet engines are proposed. The technical justification of the proposed control methods is carried out. As a result, stabilization of an electrically charged spacecraft in a small neighborhood of the plane of the initial orbit is achieved. The motion of a spacecraft with a variable electric charge is considered. Methods of controlling orbital motion due to low thrust as a result of the Lorentz force effect are proposed.

Dynamical friction in rotating ultralight dark matter galactic cores

Abstract Dynamical friction and stellar orbital motion in spiral galaxies with dark matter composed of ultralight bosons in the state of rotating Bose–Einstein condensate (BEC) are studied. It is found that the dynamical friction force is significantly affected by the topological charge of the vortex structure of the BEC core with the strongest effect at distances near the galactic center. It is also shown that the ultralight dark matter self-interaction plays an important role in studying the dynamical friction.

Optical aspects of Born-Infeld BTZ black holes in massive gravity

We explore the dynamics of thin accretion disks, the radius of black hole shadows, observed intensities, and the visual characteristics of Born-Infeld BTZ black holes in massive gravity. We find out the relations for angular velocity, specific energy, and angular momentum of particles around the black hole. We observe that intense Born-Infeld electromagnetic effects lead to a reduction in the rotational motion of particles within the accretion disk, and the massive gravity slows down the orbital motion of these particles. We reveal that the influence of massive gravity parameter correlates with a reduction in the black hole’s shadow size, which suggests that massive gravity effects intensify the gravitational fields, thereby reducing the angular diameter of the shadows. On the other hand, a higher Born-Infeld parameter enlarges the black hole’s shadow, which manifests a visual relationship between the black hole’s physical dimensions and its gravitational influence. Moreover, we also uncover the optical characteristics of Born-Infeld BTZ black holes, which show that the Born-Infeld parameter greatly influences the electromagnetic field around the black hole, which affects energy distribution in the space. Finally, we observe that massive gravity significantly influences the spacetime structure near black holes, which is crucial for grasping gravitational lensing and the dynamics of accretion disks under such extreme conditions.

The twisted jets and magnetic fields of the extended radio galaxy 4C 70.19

Context. The appearance of the jets and lobes of some radio galaxies makes it difficult to assign them to a known class of objects. This is often due to the activity of the central engine and/or interactions with the environment, as well as projection effects. Aims. We analyse the radio data for an apparently asymmetric radio source 4C 70.19, which is associated with the giant elliptical galaxy NGC 6048. The source shows distorted radio jets and lobes, one of which bends by 180°. The aim of our study is to explain the nature of the observed distortions. Methods. We used LOFAR, Effelsberg, and VLA radio data in a wide range of frequencies. At high frequencies, we also used radio polarimetry to study the properties of the magnetic fields. Additionally, we made use of optical, infra-red, and X-ray data. Results. Polarisation data suggest shearing of the magnetic fields at points where the jets bend. The low-frequency LOFAR map at 145 MHz, as well as the sensitive single-dish Effelsberg map at 8.35 GHz, reveal previously undetected diffuse emission around the source. The rotation measure (RM) derived from the polarimetric data allowed us to estimate the density of the medium surrounding the source, which agrees with typical densities of the intergalactic medium or the outer parts of insterstellar halos. Conclusions. We propose that the southern jet is bent in the same manner as the northern one, but that it is inclined to the sky plane. Both these bends are likely caused by the orbital motion within the galaxy group, as well as interactions with the intergalactic medium. Our analyses suggest that, despite its complex morphology, 4C 70.19 seems to be intrinsically symmetric with a physical extent of up to 600 kpc, and that the diffuse emission detected in our high-sensitivity maps is related to radio plumes that are expanding behind the source.

A Novel Ephemeris Model for Martian Moons Incorporating Their Free Rotation

High-precision ephemerides not only support space missions, but can also be used to study the origin and future of celestial bodies. In this paper, a coupled orbit-rotation dynamics model that fully takes into account the rotation of the Martian moons is developed. Phobos and Deimos’ rotations are first described by Eulerian rotational equations, and integrated simultaneously with the orbital motion equations. Orbital and orientational parameters of Mars satellites were simultaneously obtained by numerical integration for the first time. In order to compare the differences between our newly developed model and the one now used in the ephemerides, we first reproduced and simulated the current model using our own parameters, and then fit it to the Institut de Mécanique Céleste et de Calcul des Éphémérides ephemerides using least-square procedures. The adjustment test simulations show Phobos and Deimos’ orbital differences between the refined model and the current model are no more than 300 m and 125 m, respectively. The orientation parameters are confirmed and the results are in good agreement with the International Astronomical Union results. Moreover, we simulated two perturbations (main asteroids and mutual torques) which were not included in our refined model, and find that their effects on the orbits are completely negligible. As for the effect on rotation, we propose to take care of the role of mutual attraction in future models.

A Broadband X-Ray Investigation of Fast-spinning Intermediate Polar CTCV J2056–3014

We report on XMM-Newton, NuSTAR, and NICER X-ray observations of CTCV J2056–3014, a cataclysmic variable (CV) with one of the fastest-spinning white dwarfs (WDs) at P = 29.6 s. While previously classified as an intermediate polar, CJ2056 also exhibits the properties of WZ Sge–type CVs, such as dwarf novae and superoutbursts. With XMM-Newton and NICER, we detected the spin period up to ∼2 keV with 7σ significance. We constrained its derivative to |Ṗ|<1.8×10−12 s s−1 after correcting for binary orbital motion. The pulse profile is characterized by a single broad peak with ∼25% modulation. NuSTAR detected a fourfold increase in unabsorbed X-ray flux coincident with an optical flare, in 2022 November. The XMM-Newton and NICER X-ray spectra at 0.310 keV are best characterized by an absorbed, optically thin three-temperature thermal plasma model (kT = 0.3, 1.0, and 4.9 keV), while the NuSTAR spectra at 3–30 keV are best fit by a single-temperature thermal plasma model (kT = 8.4 keV), both with Fe abundance Z Fe/Z ⊙ = 0.3. CJ2056 exhibits similarities to other fast-spinning CVs, such as low plasma temperatures and no significant X-ray absorption at low energies. As the WD’s magnetic field strength is unknown, we applied both nonmagnetic and magnetic CV spectral models (MKCFLOW and MCVSPEC) to determine the WD mass. The derived WD mass range (M = 0.7–1.0 M ⊙) is above the centrifugal breakup mass limit of 0.56 M ⊙ and consistent with the mean WD mass of local CVs (M ≈ 0.8–0.9 M ⊙).

Circular motion and particle collisions in ergoregion of rotating and twisting charged black holes

The presence of clouds of strings, quintessential fields, and NUT charges has significant consequences for spacetime geometry, and their study is much more important from an observational and theoretical perspective. Hence, in this article, we aim to explore the rotating and twisting charged black holes with the cloud of strings and quintessential field through horizons, ergoregions, photon regions, circular motion, and energy efficiency. First, we derive the equation of motion and the expressions for studying the photon region. To investigate circular motion, we derive the mathematical expressions of energy and angular momentum. The cloud of stings reduces the stability of angular momentum and energy in prograde particle motions and shifts their minima from the black hole’s center to the right. Static black holes with clouds of strings have the greatest angular momentum in prograde orbital motion, while rotating ones without clouds of strings have the least. Furthermore, we examine the efficiency of energy extraction through the Penrose process. The known energy extraction efficiency of the Penrose process for an extreme Kerr black hole is about 21%, but in the presence of clouds of strings, it exceeds 100%.

Modeling of the leader-follower satellite formation for long baseline

Abstract Interferometric Synthetic Aperture Radar (InSAR) represents a crucial component of synthetic aperture radar technologies, with the accuracy of measurements significantly improving as the baseline length increases. In comparison with the traditional Hill-Clohessy-Wiltshire (HCW) equations, the application of curvilinear coordinate systems for modeling satellite formations in circular orbits has demonstrated enhanced precision, especially when the formations span larger distances. However, these improvements were initially limited to circular orbits. Addressing this limitation, this study introduces a novel approach by incorporating elliptical orbits into the model, thereby refining the state transition matrix through the incorporation of eccentricity factors and maintaining the direct correlation with the temporal dynamics of satellite motion in three dimensions. Through rigorous numerical simulations, it has been established that this refined model substantially improves accuracy in leader-follower satellite formations.