Mutual Phenomena Research Articles

Differential aperture photometry and digital coronagraphy with PRAIA

PRAIA – Package for the Reduction of Astronomical Images Automatically – is a suite of photometric and astrometric tasks designed to cope with huge amounts of heterogeneous observations with fast processing, no human intervention, minimum parametrization and yet maximum possible accuracy and precision. It is the main tool used to analyse astronomical observations by an international collaboration involving Brazilian, French and Spanish researchers under the Lucky Star umbrella for Solar System studies. Here, we focus on the concepts of differential aperture photometry and digital coronagraphy underneath PRAIA, used in the reduction of stellar occultations, rotational light curves, mutual phenomena and natural satellite observations. We highlight novelties developed by us and never before reported in the literature, which significantly enhance the precision and automation of photometry and digital coronagraphy, such as: (a) PRAIA’s pixelized aperture photometry (PCAP), which avoids pixel sub-sampling or fractioning; (b) fully automatic object detection and aperture determination (BOIA), which abolishes the use of arbitrary sky background sigma factors, and finds better apertures than by using subjective FWHM factors; (c) better astrometry improving the aperture and coronagraphy centres, including the new Photogravity Center Method besides circular and elliptical Gaussian and Lorentzian generalized profiles; (d) coronagraphy of faint objects close to bright ones and vice-versa; e) use of elliptical rings for the coronagraphy of elongated profiles; (f) refined quartile ring statistics; (g) multiprocessing image capabilities for faster computation speed. We give examples showing the photometry performance, discuss the advantages of PRAIA over other popular packages for Solar System differential photometric observations, point out the uniqueness of its digital coronagraphy in comparison with other coronagraphy tools and methods, and comment about future planed implementations. Besides Solar System works, PRAIA can also be used in the differential photometry of variable and cataclysmic stars and transient phenomena like exoplanet transits and microlensing, and in the digital coronagraphy of astrophysical observations. PRAIA codes and input files are publicly available for the first time at: https://ov.ufrj.br/en/PRAIA/.

The 2021 mutual phenomena involving the Galilean satellites of Jupiter and the inner satellite Thebe

ABSTRACT Astrometric studies and orbital modelling of planetary moons have contributed significantly to advancing our understanding of their orbital dynamics. These studies require precise positions measured over extended periods. In this paper, we present the results of the 2021 Brazilian Jovian mutual phenomena campaign. The data correspond to eight events between Galilean satellites, in addition to a rare eclipse of Thebe, an inner satellite, totalling nine events. A geometric model along with the DE440/JUP365 ephemerides was used to reproduce the events and simulate the light curves. A Monte Carlo method and chi-squared statistics were used to fit the simulated light curves to the observations. The reflectance model adopted for our simulations was the complete version of the Oren–Nayer model. The average uncertainty of the relative positions of the Galilean satellites was 5 mas (15 km) and for the inner Thebe satellite 32 mas (96 km). The seven mutual events (nine independent observations) here analysed represent an addition of 17 per cent events (10 per cent light curves) with respect to the 2021 international mutual phenomena campaign. Furthermore, our result of Thebe eclipse is only the second measurement published to date. Our results contribute to the ephemeris data base, being fundamental to improving satellite orbits and thus minimizing their uncertainties.

Mutual approximations between the five main moons of Uranus

ABSTRACT Doing high-precision astrometry on Uranus’ moons is currently quite challenging. No probes will orbit the system before 2040. New high-precision mutual phenomena measurements will only occur in 2050. Besides, Uranus is slowly passing through a sky region without many stars, which makes it difficult to map field of view (FOV) distortions below 50 mas. In this context, the new astrometric technique of mutual approximations comes in handy. It measures central instants at the closest approach between two moving satellites in the sky plane. Measurements are made on small portions of the FOV, benefiting from the so-called precision premium. Approximations and mutual phenomena share geometric principles and parameters, with similar precision in the central instant as indicated by first applications to the Jovian moons. However, mutual phenomena can only be observed at the planet’s equinoxes, while approximations always occur. Central instants do not depend on reference stars and are useful in orbit and ephemeris fittings. Here, we present results for 23 mutual approximations between the five main Uranus satellites observed in Brazil during 2015–2018 with a 1.6 m aperture telescope. Digital coronagraphy mitigated Uranus’ scattered light, improving measurements for Miranda, Ariel and Umbriel. We measured the impact parameter and relative velocity in milliarcseconds for the first time by using a variant of the method. Relative position errors, including Miranda, were 45 mas per coordinate, twice as good as in classical CCD astrometry for this satellite, and comparable to mutual phenomena. This shows the potential of mutual approximations for improving the current orbits and ephemerides of Uranus’ moons.

The 2014–2015 Brazilian mutual phenomena campaign for the Jovian satellites and improved results for the 2009 events

Progress in astrometry and orbital modelling of planetary moons in the last decade enabled better determinations of their orbits. These studies need accurate positions spread over extended periods. We present the results of the 2014–2015 Brazilian campaign for 40 mutual events from 47 observed light curves by the Galilean satellites plus one eclipse of Amalthea by Ganymede. We also reanalysed and updated results for 25 mutual events observed in the 2009 campaign.All telescopes were equipped with narrow-band filters centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The albedos’ ratio was determined using images before and after each event. We simulated images of moons, umbra, and penumbra in the sky plane, and integrated their fluxes to compute albedos, simulate light curves and fit them to the observed ones using a chi-square fitting procedure. For that, we used the complete version of the Oren-Nayer reflectance model. The relative satellite positions mean uncertainty was 11.2 mas (~35 km) and 10.1 mas (~31 km) for the 2014–2015 and 2009 campaigns respectively. The simulated and observed ascii light curve files are freely available in electronic form at the Natural Satellites DataBase (NSDB).The 40/25 mutual events from our 2014–2015/2009 campaigns represent a significant contribution of 17%/15% in comparison with the PHEMU campaigns lead by the IMCCE. Besides that, our result for the eclipse of Amalthea is only the 4th such measurement ever published after the three ones observed by the 2014–2015 international PHEMU campaign. Our results are suitable for new orbital/ephemeris determinations for the Galilean moons and Amalthea.

Results of the investigation of the asteroid (2121) Sevastopol based on photometric observations of mutual phenomena

The asteroid (2121) Sevastopol is a binary asteroid from the main belt. The duplicity of the asteroid was discovered based on photometric observations of mutual phenomena (eclipses and occultations) that were detected in its light curves (Higgins et al., 2010).We organized a photometrical observational campaign for the observations of mutual phenomena in binary system of the asteroid (2121) Sevastopol and an investigation of the properties of the asteroid's satellite. The observations allowed us to define mass, density, taxonomical class and preliminary orbit of the satellite of the asteroid (2121) Sevastopol.

Natural satellites mutual phenomena observations: Achievements and future

Astrometry of Solar system objects needs to perform observations regularly since the motions are fast and the dynamical models need sample of data on long intervals of time.The goal of this paper is to show that some phenomena occurring during the equinox on the giant planets are worth to be observed. Past experience has shown the interest of such observations which should be continued in the future due to their relevant contribution to improve the dynamical models.Using the best ephemerides of the natural planetary satellites, we calculate the next phenomena to occur in order to prepare the future observational campaigns.We provide in this paper the tables of the dates of the next phenomena as their observational conditions which depends on the opposition and the declination of the planet.Past observations provided particularly accurate data, better than all the other ground based observations and we encourage observations in the next future especially for planetary systems for which no space mission is planned.

APPROX – mutual approximations between the Galilean moons: the 2016–2018 observational campaign

The technique of mutual approximations accurately gives the central instant at the maximum apparent approximation of two moving natural satellites in the sky plane. This can be used in ephemeris fitting to infer the relative positions between satellites with high precision. Only the mutual phenomena -- occultations and eclipses -- may achieve better results. However, mutual phenomena only occur every six years in the case of Jupiter. Mutual approximations do not have this restriction and can be observed at any time along the year as long as the satellites are visible. In this work, we present 104 central instants determined from the observations of 66 mutual approximations between the Galilean moons carried out at different sites in Brazil and France during the period 2016--2018. For 28 events we have at least two independent observations. All telescopes were equipped with a narrow-band filter centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The telescope apertures ranged between 25--120 cm. For comparison, the precision of the positions obtained with classical CCD astrometry is about 100 mas, for mutual phenomena it can achieve 10 mas or less and the average internal precision obtained with mutual approximations was 11.3 mas. This new kind of simple, yet accurate observations can significantly improve the orbits and ephemeris of Galilean satellites and thus be very useful for the planning of future space missions aiming at the Jovian system.

Parallel Groups: Simultaneous Dynamic Groups—Mutual Influences and Unique Phenomena

Parallel Groups: Simultaneous Dynamic Groups—Mutual Influences and Unique Phenomena

Using Galilean satellites’ mutual orbital events as an educational tool for studies of orbital dynamics

We present a methodology to analyse and interpret a set of telescopic observations of the mutual orbital phenomena between Jupiter’s Galilean satellites (occultation and eclipses) as a practical teaching tool for photometry and astrodynamic studies in astronomy courses. The mutual phenomena we describe took place in 2014 and 2015 and the observations were obtained using a 28 cm aperture telescope and a video camera. We introduce simple models to explain occultation and eclipses of the events, and offer the data and the software for their analysis.

Astrometry of mutual approximations between natural satellites. Application to the Galilean moons

Typically we can deliver astrometric positions of natural satellites with errors in the 50-150 mas range. Apparent distances from mutual phenomena, have much smaller errors, less than 10 mas. However, this method can only be applied during the equinox of the planets. We developed a method that can provide accurate astrometric data for natural satellites -- the mutual approximations. The method can be applied when any two satellites pass close by each other in the apparent sky plane. The fundamental parameter is the central instant $t_0$ of the passage when the distances reach a minimum. We applied the method for the Galilean moons. All observations were made with a 0.6 m telescope with a narrow-band filter centred at 889 nm with width of 15 nm which attenuated Jupiter's scattered light. We obtained central instants for 14 mutual approximations observed in 2014-2015. We determined $t_0$ with an average precision of 3.42 mas (10.43 km). For comparison, we also applied the method for 5 occultations in the 2009 mutual phenomena campaign and for 22 occultations in the 2014-2015 campaign. The comparisons of $t_0$ determined by our method with the results from mutual phenomena show an agreement by less than 1-sigma error in $t_0$, typically less than 10 mas. This new method is particularly suitable for observations by small telescopes.

A novel roll-bonding methodology for the cross-scale analysis of phase properties and interactions in multiphase structural materials

Abstract We introduce a new thermo-mechanical approach for producing layered bulk samples built-up from the constituent phases of structural materials for the analysis of multiphase co-deformation phenomena. Following a thermo-mechanically controlled roll-bonding procedure, the intrinsic properties of the microstructural components as well as their mutual mechanical interaction and interfacial phenomena can be systematically investigated in highly controlled model microstructures of reduced complexity. The effectiveness of the approach is demonstrated on two examples where austenite or martensite layers, respectively, are introduced in a bulk ferritic matrix, representing in either case components of high strength steels. Special emphasis is laid on how the plasticity of martensite within ferrite, as a key parameter required for understanding and optimising dual phase steels, can be investigated following the proposed approach.

A new solution for biomedical experiments

This article discusses mutual interactions phenomena especially in the case of Transverse ElectroMagnetic (TEM) cell applications as an exposure system in technical and biomedical studies. Problem of mutual interactions between tested objects placed in the electromagnetic field (EMF) is described. A new device for exposure system is presented. Its role is elimination of mentioned harmful phenomenon that leads to falsifications of results.

Analysis of 25 mutual eclipses and occultations between the Galilean satellites observed from Brazil in 2009★

The light curves of mutual eclipses and occultations between the natural satellites of a planet allow us to obtain high-precision position and relative motion from differential photometry, enough to detect weak orbital disturbing forces, such as tidal forces. The observations are made during the equinoxes of the planet. We studied 25 light curves observed in Brazil during the 2009 campaign of the Galilean satellites’ mutual phenomena. A narrow-band filter centred at 890 nm was used, strongly attenuating the Jupiter's scattered light. We fitted the occultation and eclipse light curves using semi-analytical models that take into account the gradual decrease of light over the shadow, the solar limb darkening and the solar phase angle. The Oren–Nayar reflexive model was used to map the inhomogeneous light scattering on the surface of the satellites. For the first time it is used in a work about mutual events. Here, we include the study that made us decide for this model. We measured the impact parameter, relative velocity and central instant with average precisions of 7.46 km (2.2 mas), 0.08 km s−1 (0.02 mas s−1) and 0.42 s (6.13 km), respectively. The fit precision of the normalized light-curve fluxes ranged between 0.4 and 4.4 per cent.

Calciothermic co-reduction of TiO2-Cr2O3 oxides in molten CaCl2: Effect of particle size of starting materials

In this research, the effect of particle size of starting materials (TiO2 and Cr2O3) was investigated on calciothermic co-reduction of oxides and in-situ dissolution of the CaO by-product in molten CaCl2. The particle size of starting oxides, molar ratio of molten salt and holding time of reaction at elevated temperature affected the progress of reduction reactions and the remaining oxygen. In the best optimized condition, the remaining oxygen in the obtained TiCr2 was 1020 and 802 ppm using 388 and 120 nm particle sizes of starting oxides, respectively. The formation of TiCr2 in calciothermic co-reduction process was considered to be mutual diffusion phenomena. Also, the kinetics of hydrogen adsorption for the co-reduced sample was better than that of the arc-melted sample. Particle sizes of the obtained products decreased with-the decrease of the particle sizes of the starting oxides.

Observations of mutual phenomena of Galilean's satellites at Catania

AbstractThe mutual phenomena between Jupiter and Saturn's satellites occur every half orbital period of these planets, when the Earth and the Sun cross their equatorial plane. At Physics and Astronomy Department of Catania University the events between Jupiter's satellites have been observed during the 1973, 1979, 1985/86, 1991, 1997 and 2009 campaigns and the ones between Saturn's satellites during the 1980/81 and 1995 campaigns. An overview of the main results obtained since 1973 is presented.

Study of mutual occultation phenomena of the Galilean satellites at radio wavelengths

AbstractWe present preliminary results for our study of mutual phenomena of the Galilean satellites performed at radio wavelengths with the Medicina and Noto antennas of the Istituto di Radioastronomia - INAF, and with the Effelsberg 100-m radio telescope of the Max-Planck-Institute for Radioastronomy, Bonn. Measurements of the radio flux density variation during the mutual occultations of Io by Europa and Ganymede were carried out during the PHEMU09 campaign at 22 GHz and 43 GHz. Flux density variations observed at radio wavelengths are consistent with the typical optical patterns measured when partial occultations occur.

Geometrodynamics of polarized light: Berry phase and spin Hall effect in a gradient-index medium

We review the geometrical-optics evolution of an electromagnetic wave propagating along a curved ray trajectory in a gradient-index dielectric medium. A Coriolis-type term appears in Maxwell equations under transition to the rotating coordinate system accompanying the ray. This term describes the spin–orbit coupling of light which consists of (i) the Berry phase responsible for trajectory-dependent polarization variations and (ii) the spin Hall effect representing polarization-dependent trajectory perturbations. These mutual phenomena are described within universal geometrical structures underlying the problem and are explained by the dynamics of the intrinsic angular momentum carried by the wave. Such close geometrodynamical interrelations illuminate a dual physical nature of the phenomena.

Some specific features of light curves of (39) Laetitia, (87) Sylvia, (90) Antiopa, and 2006 VV2 asteroids

The results of photometric observations of (87) Sylvia, 2006 VV2, (90) Antiopa, and (39) Laetitia asteroids in 2006–2008 are presented. The specific features of light curves are considered for each object. In particular, for asteroid (87) Sylvia, possible mutual phenomena in this triple system are identified. Asteroid 2006 VV2 manifests a strong dependence of the light curve on the filter color, which testifies to the presence of inhomogeneities on its surface. The previously unknown brightness variation period with a duration of about three days was obtained for this asteroid. For binary asteroid (90) Antiopa, the strong dependence of its brightness on the phase angle was noticed; this may testify to the very flattened shape of its components. Considerable time variations of the shape of the light curve for asteroid (39) Laetitia may testify either to its complex shape or to its binary character.

Astrometric and photometric observations of solar system bodies with Pulkovo Observatory’s automatic mirror astrograph ZA-320M

A brief description of the process of astrometric and photometric observations and their processing by an automatic complex, based on Pulkovo Observatory’s ZA-320M telescope, is presented. The basic results of astrometric and photometric observations of Solar System bodies obtained during 1997–2007 are given. They include, in particular, the results of astrometric observations of dangerous objects ( Near Earth Objects — NEOs), as well as the results of astrometric observations of the Pluto-Charon system. In addition, the paper presents the results of photometric observations of planetary satellites, the mutual phenomena in the system of Jupiter’s satellites, and the 2559 star occultation by the (111) Ate asteroid from the HIPPARCOS catalogue.

Spin-orbit interaction of light

Spin-orbit interaction is a weak coupling between intrinsic (spin) and extrinsic (orbital motion) degrees of freedom of spinning particles. It implies mutual conversion between a particle’s spin and orbital angular momenta. Classical polarized light also carries spin and reveals spin-orbit coupling when propagating along a curved trajectory.1 This manifests itself in two mutual phenomena. First, the curved trajectory affects the evolution of the light’s polarization state, which is described by the Berry phase and parallel-transport law: see Figure 1(a). Second, the light trajectory also experiences a reaction from the spin, i.e., a polarization-dependent perturbation of the trajectory occurs. This can also be described in terms of the Berry phase and represents a topological spin transport of photons also known as the spin-Hall effect of light or the optical Magnus effect: see Figure 1(b). We recently reported the first direct observation of this effect.2 Remarkably, the spin-orbit coupling phenomena have a dual, geometro-dynamical nature. On the one hand, the parallel transport of the polarization and the spin-Hall effect can be attributed to the inertia of the wave field and the Coriolis effect. On the other, the spin-orbit interaction of light has an inherent geometrical origin that is described by the Berry-phase topological monopole in momentum space. Two decades ago, the Berry phase brought a geometrical beauty to the description of quantum-adiabatic evolution.3, 4 Physicists started to realize that seemingly ‘passive’ geometrical concepts, such as Berry curvature, also manifest themselves dynamically, producing a real action on physical objects. As a result, geometry-induced forces appear that affect the dynamics of quantum particles with some internal properties.5 In particular, they describe the Magnus effect of quantum vortices6 and spinHall effect of spinning particles.7, 8 This offers a novel type of quantum transport that is robust against the details of the system and is determined solely by the geometry and intrinsic properties of the particles. Figure 1. Spin-orbit interaction of light. (a) Evolution of the polarization vector (e → e′ → e′′) along a helical trajectory according to the Berry phase and parallel-transport law. Θ: Polarization rotation angle for each helix. (b) Topological spin transport of photons: Reaction of spin to the trajectory causes splitting of rightand left-hand circularly polarized beams. ∆: Splitting for each helix. (Reproduced with permission from Nature Photonics.2)