Imaging of the Jupiter system with the Solid State Imaging (SSI) camera is discussed. The results of the experiment involve three main parts: imaging of phenomena in Jupiter’s atmosphere, imaging of the Galilean satellite surfaces, and imaging of the smaller satellites and ring system.

The Crab Pulsar(PSR 0531+21) was observed by the four Narrow Field Instruments on board the Italian-Dutch satellite BeppoSAX on August and September 1996, during the Science Verificado Phase. The fine time resolution (15 μs) and the high statistic of the data provided phase histogram of very good quality, well suited for phase resolved spettroscopy over the entire energy band (0.1-300 keV) covered by BeppoSAX payload. In this contribution we present preliminary results of the spectra distribution of the peaks and the inter peak region. Moreover, we also carried out a detailed analysis of the P1 shape and the behaviour of the P2/P1 ratio with the energy.

The Galileo Near Infrared Mapping Spectrometer (NIMS) is currently obtaining spectral maps of Jupiter’s moons to determine the composition and spatial distribution of minerals on the satellite surfaces. Sulfur dioxide, as a frost or ice, covers much of Io’s surface, except in hot volcanic areas. A weak spectral feature at 3.15 μm suggests the presence of an OH containing surface compound (hydroxide, hydrate, or water) and a broad absorption above 1 μm is reasonably attributed to iron-containing minerals, such as feldspars and pyrite. Water is the dominant molecule covering Europa’s surface, occurring as ice but also as a hydrate. The trailing side shows high concentrations of these hydrous minerals, whose identifications are not yet established. Ganymede’s surface exhibits water absorption bands, largely due to ice but hydrates are also present. A dark component is present, but with a smaller proportion compared to Callisto. Some of the non-ice features seen on Ganymede are similar to those found in Callisto’s spectra (see below). Among the icy Galilean satellites, Callisto shows the least amount of water ice, covering about 10% of the surface in patchy concentrations. Most of the surface is covered with unidentified (as yet) dark minerals. The exposed ice is often associated with impact craters, implying that the darker material exists as a blanket over more pure ice. Non-ice spectral features at 3.88, 4.03, 4.25, and 4.57 μm are present in Callisto’s spectra (and some of these appear in Ganymede’s spectra), each with different spatial distributions. Laboratory spectra suggest that the 4.25-μm feature is due to carbon dioxide which is trapped in the surface grains. The band at 4.03 μm may be due to sulfur dioxide, which probably originated from Io. Molecules containing CN, SH, SiH, and perhaps deuterated constituents are candidates for the other features, some of which could be derived from shock-heated and modified material from impacts, perhaps of carbonaceous composition. There is evidence for the presence of hydrated minerals on Callisto, based on water band shifts and shapes.

We have considered a stationary outflowing envelope accelerated by the radiative force in arbitrary optical depth case. Introduced approximations provide satisfactory description of the behavior of the matter flux with partially separated radiation at arbitrary optical depths. The obtained systemof differential equations provides a continuous transition of the solution between optically thin and optically thick regions. We analytically derivedapproximate representation of the solution at the vicinity of the sonic point. Using this representation we numerically integrate the system of equations from the critical point to the infinity. Matching the boundary conditions we obtain solutions describing the problem system of differential equations. The theoretical approach advanced in this work could be useful for self-consistent simulations of massive star evolution with mass loss.

The BVR CCD observations of W UMa-type eclipsing binary SS Arietis were made for ten nights from November 1996 to December 1996 at the Sobaeksan Astronomy Observatory. From the observed light curves, nine new times of minimum lights were derived from the Kwee and van Woerden’s method. Improved light elements for this system were determined from these minimum lights with all the published minima. The analysis of the times of minima of SS Ari confirms that the orbital period of SS Ari has been suffering from a sinusoidal variation as the suggestions of other previous investigators (Kaluzny & Pojmanski 1984, Demircan & Selam 1993). The calculation shows that the cyclic period change has a period of about 56.3yrs with an amplitude of about 0.d052. The period variation has been discussed in terms of two potential mechanisms: 1) the light-time effect due to a hypothetical third body and 2) deformations in the convective envelope of a magnetically active component. The BVR light curves of SS Ari observed for about one month showed the existence of cycle to cycle light variations. Long-term light changes of SS Ari are discussed in terms of the period variation of the binary system.

The Galileo orbiter and its Solid State Imaging system have increased the photographic coverage and resolution of Europa, revealing a complex surface that has been modified by tectonic deformation, impact craters on a wide range of scales, and possible cryovolcanic activity. The morphology of many of the features suggests that the depth to either liquid water or mobile-ductile ice was relatively shallow (< few kilometers) at the time of their formation. Characteristics of the mottled terrain and impact ejecta deposits suggest the presence of a shallow (˜km) subsurface zone beneath the bright icy crust. The Galileo Europa Mission, approved to continue orbital operations through 1999, will include at least nine close flybys of Europa, enabling global and regional mapping, along with high-resolution imaging of selected areas.

A conference having the title The Three Galileos: the Man, the Spacecraft, the Telescope, was held at the University of Padova from 7-10 January 1997. The conference was jointly organized by the U.S. space agency NASA, JPL, the German space agency DARA, the University and Astronomical Observatory of Padova, and the Telescopio Nazionale Galileo, with the added support of the International Astronomical Union. The scientific committee was composed of: C. Barbieri (Chairman, University of Padova), S. Atreya (University of Michigan), E. Bellone (University of Padova), M. Belton (NOAO), P. Benvenuti (ESA), F. Bertola (University of Padova), M. Calvani (Astronomical Observatory of Padova), G. Cariolaro (University of Padova), W. Ip (Max-Planck-Institute for Aeronomy), T. Johnson (JPL), T. Owen (University of Hawaii), J. Rahe (NASA), and R. West (ESO). The purpose was to discuss the discovery of the Medicean Moons by Galileo Galilei in Padova from 7-15 January 1610, the results of the Galileo spacecraft during the cruise phase and while orbiting the Jovian system, and the construction of the 3.5-m active-optics Italian telescope Galileo (TNG) in the Canary Islands.

The post-AGB stars rapidly change their spectral energy distribution on their way from the asymptotic giant branch(AGB) to planetary nebula stage. They are generally surrounded by cool and extended dust shells emitting largely in the infrared wavelengths.

A selected sample of the post-AGB candidates were observed using the CCDand IR camera at Kiso and Nishi-Harima Astronomical Observatory. They were classified based on their broad band spectra from B to K’ band and their evolutionary stages have been discussed using the simple model of the dust shell around a star.

The light variation of some of these objects were monitored and their light curves are also presented.

The radius and temperature excesses are found to be largest for the subgiant stars in DS systems and in low-mass and long-period SD systems, being the smallest for the subgiant stars in AR systems and in low-mass and short-period SD-systems. Subgiant stars in AR and in more massive SD systems exhibit even the temperature deficiency which is the largest for the primariesof the AR systems. Necessity is shown to divide the class of SD systems into several groups according to masses and orbital periods while studying their properties.

By using of a model for the propagation of the emitted X-rays through the infalling material and the reemission of the energy deposited by photoabsorption in the optical (and UV) spectral range (Kim & Beuermann, 1995) we calculated Hϒ line spectrum of intermediate polars. Photoabsorption of X-rays by the infalling material is the dominant process in forming the observed energy-dependent rotational modulation of the X-ray flux. X-ray and optical modulations are sensitive to model parameters in different ways. In principle these dependences allow us to obtain improved insight into the geometry of intermediate polars. Some results of our calculation will be presented in this paper in comparison with the Hβ spectrum calculated by Kim & Beuermann (1996).

Our high-resolution optical spectroscopic survey of the symbiotic star CH Cyg, extending over the quiescent period 1987 - 1989 between two outbursts, shows that the spectrum did not completely lose its symbiotic character. Moreover, signs of radiation of the hot source were present, not only as remnants from the previous outburst, but also as an indication of a new one. Some of the evidences which support this idea are following:

1. • Variation of excitation and vibration temperatures of neutral metals and TiO moleculs respectively

2. • Untypical microturbulent velocity dependance of the excitation potential of the lower state for Fe I

3. • Double-peaked Balmer profiles of Ha and Hb with temporary disappearance of the central absorption

4. • Presence of forbbiden emission lines [FeII] [ SII] [NeIII] together with OIII with complex profile and variable intensity.

The Infrared Space Observatory (ISO) is a cryogenically-cooled satellite giving the astronomical community, for the first time, the capability of making detailed observations at infrared wavelengths (2.5-240 ˜m) with a sophisticated and sensitive set of observatory-class instruments for a period in excess of two years.

The proposal for ISO was made to ESA in 1979 and it was selected in 1983 to be the next new start. The instruments were chosen in 1985 and ISO’s main industrial development started in 1988. Launch took place in November 1995 and the helium coolant is expected to last until April 1998. The calibration and data analysis will be improved during the post-operations phase, which is funded to the end of 2001.

Over one year and a half after its first light in orbit, the ISOCAM camera on board the Infrared Space Observatory is bringing back very exciting results. Its spectacular infrared viewing of the Universe sheds new light on the nature of the interstellar dust, on the birth of young stars embedded in dark clouds as well as on bursts of star formation in external galaxies.

A detailed analysis of an extensive collection of primary visual, photographic and photoelectric minima of Beta Lyrae was performed. After removing the effect of the increase in orbital period we applied the Fourier analysis to the 0-C residuals. The most prominent periodicity is 283 days with amplitude about 0.05 days. It confirms the period found in the photometric light curves of Beta Lyrae [Van Hamme, Wilson and Guinan (1995)]. The 283-d quasi-variation of the period may be explained by assymetries of the light curve near the minima caused by some instabilities in disc and/or hot spot(s) brightness.

BC UMa was observed during its rare outburst in 1994. The superhumps with period 0.0619 day are clearly apparent, accompanied by secondary superhumps. This confirms the classification of BC UMa as an SU UMa type dwarf nova. The maximum brightness is 12.5 mag, which is about six magnitude brighterthan quiescence phase, and it makes BC UMa be classified as a TOAD (Tremendous Outburst Amplitude Dwarf-nova). The superoutburst’s magnitude was fainter than the preceeding normal outburst in September 1990. This faint superoutburst is uncommon among SU UMa stars and also among TOADs. The period analysis of the lightcurve taken after the end of the outburst yields the period of 0.0618 day which is shows that late superhumps is in operation.

The Short-Wavelength Spectrometer(SWS) is one of the four instruments on-board of ESA’s Infrared Space Observatory(ISO), launched on 15 Nov. 1995. It covers the wave-length range of 2.38-45.2μm with a spectral resolution ranging from 1000-2000. An overview is given of the in-orbit performance and a summary of the main scientific results and discoveries obtained in the first 18 months of operation of the ISO-SWS.

While all channels of the instrument (Lemke et al. 1996) are fully operational in the 21st month of the mission, some have turned out to be particularly productive: (1) far infrared mapping in the 200 /im range and (2) spectrophotometry in the middle infrared. The detection sensitivity of these modes is close to the preflight expectation. The photometric calibration of the instrument is a demanding task. Transient and memory effects of the low background detectors, responsivity drifts and spikes caused by the cosmic radiation as well as nonlinearities due to the preamps and the complex optical subsystems require corrections. Fortunately almost all of these effects are reproducable and correction algorithms are under development. While spectrophotometric (Klaas et al. 1997) and staring observations are already calibrated to better than ±20..30% in the pipeline data products, similar values will be achieved for all observing modes in the near future.

A Monte Carlo code is used to calculate the profiles and the polarization of Raman scattered O VI lines(λλ6827, 7088) in symbiotic stars. Various wind models around the cool giant are investigated including disk type and bipolar wind models. We obtain a large degree of polarization in the blue part and the red-asymmetric profile, which is generic to the Raman scattered feature in symbiotic stars.

We also investigate the effect of the orbital motion of the hot component around the cool giant, where the orbital velocity is comparable to the wind terminal velocity. In the case of small inclination angle of the orbitalplane, we obtain the polarization flip around the red wing of the scatteredfeature and the triple peak structure in the polarized flux, which is characteristic of many symbiotic systems including RR Tel.

Brief observational consequences are discussed and it is concluded that spectropolarimetry may provide a powerful diagnostic about the physical conditions of symbiotic stars.