Mutual Occultations and Eclipses of Galilean Satellites of Jupiter in 2002–2003

Information on the approach of a new epoch of mutual occultations and eclipses in the system of Galilean satellites of Jupiter is presented. The importance of observations of such phenomena is highly emphasized.     

The 1997 Campaign of Observations of Mutual Occultations and Eclipses in the System of Jupiter's Galilean Satellites: Final Results

This paper presents the final results of the campaign of photometric observations of the Galilean satellites of Jupiter at the time of their mutual occultations and eclipses at the epoch of 1997 at observatories of Kazakhstan, Russia, and Ukraine. These results essentially contribute to the worldwide database of this type. They will help to refine the models of motion of the Galilean satellites of Jupiter. A comparison is made of the obtained data with the results of the worldwide campaign of observations of mutual occultations and eclipses in 1997. From the results of these observations, the differences of planetocentric coordinates of two satellites are calculated for a sequence of instants of time. Processing is based on the theory and the model of mutual occultations and eclipses of natural planetary satellites, which were developed by one of the authors in previous papers (Emel'yanov, 1999, 2000). In this paper, some new elements of the technique were used. We estimated the accuracy of observations. The paper contains information on the observing conditions and describes briefly the instruments employed.     

Eclipses and Occultations of Galilean Satellites Observed at Yunnan Observatory in 2003

We describe and analyze observations of mutual events of Galilean satellites made at the Yunnan Observatory in February 2003 from CCD imaging for the first time in China. Astrometric positions were deduced from these photometric observations by modelling the relative motion and the photometry of the involved satellites during each event.     

木星卫星掩食观测与初步分析

2009年7月在上海天文台江南天池观测站对木星伽利略卫星的相互掩食现象进行了观测。通过对此次观测获得的CCD图像进行测光处理和数据分析,确定了7月25日观测到的木卫一食木卫三的开始与结束时刻,以及被食星（木卫三）的光流量处于最小值的时刻。     

Searching for Planetary Eclipses in Open Clusters: NGC 7086

In an attempt to discover planetary eclipses, we observed the open cluster NGC 7086. On one night we observed the cluster and standard stars through the B and V filters, enabling us to make a colour-magnitude diagram. Plots of the differential magnitudes were inspected for variability, but no planetary eclipses were found. New variable stars were discovered and their light curves show some of them to be eclipsing binary stars. The location on the colour-magnitude diagram of some of the variable stars is consistent with cluster membership.     

Studies of Planetary Atmospheres by Stellar Occultations: Application to Mars and Venus

We consider the application of the stellar occultation method to the studies of planetary atmospheres and its history and briefly describe the instruments designed for such measurements (SPICAM/Mars-96, GOMOS/ENVISAT). In comparison with solar occultations, this method allows the profiles to be measured almost at any time of the day and at any location of the planet, irrespective of the orbit of the spacecraft from which observations are carried out. Based on the measuring characteristics of the SPICAM-Light UV spectrometer for the spectral range 118–320 nm with a resolution of 0.9 nm (for the ESA Mars Express Mission; launched in June 2003), we simulate the capabilities of the method to study the Martian atmosphere. In stellar occultation measurements, the stellar spectrum changes because of the absorption by CO₂ and O₃, other gases, and aerosols. The profiles of the CO₂ and O₃ density (and, hence, the temperature) and the aerosol content can be restored by solving the inverse problem. Observations of bright stars (no fewer than 30) three to five times in a turn allow us to measure the atmospheric density at altitudes 10–150 km with an accuracy of about 2% and the temperature at altitudes 20–130 km with an accuracy of 3 K. Ozone is measured with an accuracy of several percent at altitudes 25–40 km or lower, depending on the conditions. Optically thin clouds and hazes, particularly on the nightside where no measurements are possible in reflected light, can be studied. The SPICAV experiment, which is similar to SPICAM-Light, is part of the Venus Express (to be launched in 2005) scientific payload. On Venus, stellar occultations can be used to measure the atmospheric temperature and density above clouds at altitudes up to 130–150 km and to study the SO₂ profile. The results of our simulations can be easily extended to instruments with different measuring characteristics.     

GAIA Photometric System: Simulation of Photometric Observations

We present a software package developed for modelling of the GAIA photometric observations. The modelling procedure is very flexible and fully controlled via the parameter file. Therefore, configuration of the GAIA telescopes and photometric systems, as well as the object samples under investigation, can be adjusted easily. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamics of Planetary Satellites in the Solar System

After the discovery of a huge number of satellites around Jupiter, Saturn, and Uranus, it is necessary to collect together information about all of the planetary satellite systems and to define the possible classification of objects and types of their motion. We give physical parameters of the satellites: their masses, sizes, apparent magnitudes in opposition, and geometrical albedos. We present some of the orbital quantities that characterize the orbits, their shapes and orientation in space, as well as data on the rotation of satellites. The emphasis is on the peculiarities of their motion—the forces acting on them, the main orbital perturbations, and the influence of commensurabilities in the mean motions of satellites. We list references to the main theories of their motion.     

Photometric Observations of LO Peg in 2017

New observations of the ultrafast rotator of the K3 spectral type, the star LO Peg, were carried out using a robotic wide-angle observation system in the Zvenigorod observatory of INASAN in 2017. Temperature-inhomogeneity maps on the LO Peg surface were reconstructed using the light curves, and the longitudes corresponding to the position of active regions were determined. The ongoing evolution of moving active regions and the phenomenon of switching positions of active longitudes in 2017 were established. The area of the star covered with spots has stopped decreasing and by now reach 17% of the area of its total visible surface. We defined more accurately the cycles of the long-period variability of LO Peg and noticed considerable changes in the shape of the power spectrum. Among cycles of the longterm variability greater than five years, only two cycles of 5.55 and 9.25 yrs began to appear. Based on analyzing the diagrams illustrating the relationship of the spot parameter with rotation, age, and Rossby numbers for LO Peg, 1570 M-dwarf stars, and eight objects from the Pleiades cluster with masses corresponding to the mass estimate for LO Peg (0.75 M_⊙), the conclusion was drawn about the increased activity (spottedness) of LO Peg in comparison with similar objects.     

超新星1993J的UBVRI多色测光

利用北京天文台兴隆站60/90cm施密特望远镜上的2048×2048CCD照相机对超新星1993J爆发的第二次极大进行了UBVRI五色测光.     

行星状星云NGC2346核星的食光变现象的消失

本文给出了对行星状星云NGC2346核星AGK3—0°695从1981年到1987年这段期间内所做的照相观测结果。从中我们看到该天体自1981年底开始出现的大变幅食光变现象持续数年之后,从1986年开始其光变幅度迅速减小,由85年的Δm～4~m减小到86年的Δm～1~m.1。而且到1987年其光变曲线仅存Δm～0~m.4的不规则亮度起伏,已无明显的周期性光变现象,文中对此现象做了初步分析讨论。     

Orientation of Figures of Small Planetary Satellites During Chaotic Rotation

Solar System Research - The effect of the preferred orientation of the largest axis of the satellite’s figure toward the planet during chaotic rotation is considered by means of numerical...     

Polarimetric and Photometric Observations of the Star CH Cygni

The results of photometric and polarimetric observations of the star CH Cygni in the B, V, and R filters are presented. Variations of brightness and color indices are given as functions of the time of observation. A fairly irregular character was found, both in the brightness variations and in the variations of color indices. The polarization observations showed that the light of CH Cygni is intrinsically polarized.     

Photometric Observations and Light Curves Analysis of Go Cygni

Photoelectric observations, in U, B and V, of the system GO Cygni were obtained during 1995 at the Birouni Observatory, Shiraz, Iran, and the corresponding light curves analysed with the use of Wilson-Devinney;'s techniques. New photoelectric and absolute elements for the system are given. The period of the system, a reverse Algol type semi-detached binary was found to continue its increasing. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photometric and Polarimetric Observations of the Star SAO 124414

In the present work we give the results of photometric and polarimetric observations of the star SAO 124414 simultaneously in the BVR ranges of the spectrum. The observations were made over three years at Byurakan Astrophysical Observatory. Strong variations in the degree of light polarization in all three spectral ranges were recorded while the star's brightness was constant during the observations. It is confirmed that the recorded polarization has a stellar character. An analysis of the polarimetric measurements did not reveal periodicity in the variations of the degree of polarization.     

Analysis of Multicolor Photometric Observations of SS 433

Observations of the rapid photometric variability of SS 433 in the BVR bands, obtained on Mt. Maidanak during 12 nights in 1989-90, are presented. The behavior of the U - B, B - V, and V - R color indices is analyzed on the basis of multicolor photoelectric observations. It is found that, both for rapid variability during a night and for variability on the scale of the orbital period, color-brightness relations exist for U-(U - B) and B-(B - V), analogous to the well-known V-(V - R) relation, with a characteristic property: the color indices decrease with increasing brightness. It is shown that the object's reddening upon a brightness decrease is not due only to eclipses. The behavior of the color characteristics can be explained by the interaction of the relativistic jets with the atmosphere around the accretion disk.     

Optical Photometric Observations of 7-Ray Loud Blazars

We report results of our optical photometric observations of ten gamma-ray loud blazers, namely: 0219+428 (3C66A), PKS 0420-014 (OA 129), S5 0716+714, 0754+100 (OI 090.4), 0827+243 (OJ248), 1652+398 (Mrk 501), 2200+420 (BL Lacertae), 2230+114 (CTA 102), 2251+158 (3C 454.3) and 2344+514. The observations were carried out in September-October, 2000 using the 70 cm optical telescope at Abstumani Observatory, Georgia. We found intra-day variations in 0420-014, S5 0716+714, BL Lacertae and CTA 102. A variation of 0.3 magnitude over a time scale of about 3 hours was observed in the R passband in BL Lacertae on JD 2451827. We did not detect any variation in 3C 66A, Mrk 501, or 3C 454.3 during our observations. Nor did we detect any clear evidence of variation in 1ES 2344+514 during our two weeks' observing run of the TeV gamma-ray source.     

Rotational Dynamics and Evolution of Planetary Satellites in the Solar and Exoplanetary Systems

Solar System Research - In this review we consider the main rotation regimes that are inherent for planetary satellites of the Solar System, satellites of trans-Neptunian objects, and potential...     

Effects of Planetary Migration on Natural Satellites of the Outer Planets

Numerous studies in the past few years have analyzed possible effects of planetary migration on the small bodies of the Solar System (mainly asteroids and KBOs), with the double aim of explaining certain dynamical structures in these systems, as well as placing limits on the magnitude of the radial migration of the planets. Here we undertake a similar aim, only this time concentrating on the dynamical stability of planetary satellites in a migration scenario. However, different from previous works, the strongest perturbations on satellite systems are not due to the secular variation of the semimajor axes of the planets, but from the planetesimals themselves. These perturbations result from close approaches between the planetesimals and satellites.We present results of several numerical simulations of the dynamical evolution of real and fictitious satellite systems around the outer planets, under the effects of multiple passages of a population of planetesimals representing the large-body component of a residual rocky disk. Assuming that this component dominated the total mass of the disk, our results show that the present systems of satellites of Uranus and Neptune do not seem to be compatible with a planetary migration larger than even one quarter that suggested by previous studies, unless these bodies were originated during the late stage of evaporation of the planetesimal disk. For larger variations of the semimajor axes of the planets, most of the satellites would either be ejected from the system or suffer mutual collisions due to excitation in their eccentricities. For the systems of Jupiter and Saturn, these perturbations are not so severe, and even large migrations do not introduce large instabilities.Nevertheless, even a small number of 1000-km planetesimals in the region may introduce significant excitation in the eccentricities and inclinations of satellites. Adequate values of this component may help explain the present dynamical distribution of distant satellites, including the highly peculiar orbit of Nereid.