It is a pleasure for me to present, on behalf of the international consortium of scientist and engineers who built the instrument, some interim results from the Long-Wavelength Spectrometer (LWS). I shall briefly review the scientific capabilities of the instrument before describing some of the highlights of its scientific programme.

A model of internal structure and evolution of the peculiar binary system v Sgr is presented. The model corresponds well to the observed chemical composition of the main component atmosphere (10-4 H, 0.844 He, 0.013 C, 0.042 N by mass). It is supposed that about 5 million years ago the main component passed the stage of hydrogen nuclear burning in the shell over the helium core where the helium-carbon reactions took place. Because of convective mixing, the synthesized carbon diffusing into the hydrogen burning zone was catalyzing the reactions of the CN - cycle. This has resulted in anomalies in the chemical composition, particularly high nitrogen abundance in the layer observed now as the atmosphere of the main component since external layers were thrown off during the evolution. Following the calculated results, the quantitative restrictions of temperature and density in the layers and values of mixing parameters are obtained. It is shown that the best agreement with observations exists if the mass of the matter penetrating from the zone of helium-carbon reactions into the helium layer is 0.25 of the helium-carbon core mass. Moreover, the ratio of mass concentration He/C in this matter should equal 2, and the mass share diffusing into the layer of hydrogen burning should be in the range 0.25 - 0.30 of the layer mass.

Surveys with ISO (Kessler et al 1996), in particular with the CAM (Cesarsky et al 1996) and PHOT (Lemke et al 1996) instruments, will greatly extend our understanding of extra-galactic populations and their cosmological evolution. The main advantages that ISO surveys have over e.g IRAS are increased sensitivity/depth and wavelength coverage. Within the Guaranteed and Open Time programmes there are many field surveys which will efficiently map the limits in these parameters. In this talk I will briefly overview those surveys before concentrating in more detail on one survey in particular, the ISO survey of the Hubble Deep Field (HDF), to illustrate the kind of results that can be expected.

On the basis of the analysis of the observed equivalent line widths of FeI, FeII, and TiII in the spectra of Sirius A and Omicron Peg and calculation of abundances of these elements, the oscillator strengths of the lines used are refined. With the improved oscillator strengths, the iron and titanium abundances in the atmosphere of Sirius A are obtained with a higher accuracy than previously:

lgN(FeI) = 7.899 ±0.011,

lgN(FeII) = 7.908±0.010,

lgN(TiII) =5.30±0.02.

The improved accuracy allowed one to conclude that the surface magnetic field is absent in the atmosphere of Sirius A: H =3D 0±100 Gs. The equivalent widths of 7 helium lines of the red region of the spectrum are measured. The calculations of these lines (with allowance for their blending with lines of other elements) show normal helium abundance. Following a comparison of features of Sirius A and Omicron Peg, a suggestion is advanced on possible reasons for the existence of Am stars.

Photometry of AU Ser, a contact binary in poor thermal contact, was made using the 1-meter reflector of the Yunnan Observatory, China, in 1991, 1992and 1995. Our observations, together with Binnendijk’s (1972), show variations in light curves similar to ones of VW Cep:

1. 1) Changes in sign and value of O’Connell effect. According to Binnendijk(1972), the maximum following primary minimum was higher than the other maximum, i.e., the O’Connell effect was positive. In our 1991 and 1992 light curves it became negative. After three years, however, the situation has reversed again.

2. 2) Variations of the difference between minimum depths.The difference in 1991 was smaller than that in 1969 and 1970. It got smallest in 1992 and largest in 1995. The difference increases by about 0.3 mag in three years, which is hard to explained.

3. 3) The phase shift. The observed minimum phase in 1991, 1992 and 1995 have progressively displaced forward with respect to computed minimum phase according to Binnendijk’s ephemeris. The O-C diagram seems to indicate a sudden decrease of orbital period after 1970. Also, short period oscillations have been found at frequencies of 0.0003, 0.005 and 0.0075 Hz. Flickering. with an average amplitude of about 0.05 mag, can be seen in the light curves. The power spectral analysis suggest the existence of oscillations. It is unusual that such oscillations exist in a contact binary.

When and how did galaxies form? In order to understand this important problem in astrophysics, many observational studies have been conducted so far. Deep survey observations in the optical are powerful for detecting very faint sources in the high-z universe The observed surface density of such high-z star forming galaxies may, however, be smaller than the value expected from the local density of luminous galaxies (e.g., Lanzetta et al. 1996; Steidel et al. 1996) and it is possible that we are missing classes of objects with substantial reddening and have not yet sampled fully the high-z counterparts of typical nearby galaxies. Since the nearby, well evolved galaxies consist of old low-mass stars, it is important to find galaxies with numerous low-mass stars. These stars emit their energy from the optical to near infrared (NIR) mostly, implying that they are more luminous in the NIR and MIR (mid-infrared) than in the optical if they were present at high redshifts.

In the paper we report the discovery of X-ray emission differences in SNR MSH14-63 based on the ROSAT PSPC observation. The structures of MSH14-63 are different in different energy bands. These images along with the radial brightness distributions in these energy bands show the existence of a region which only emit X-ray photons harder than l.OkeV. Though weak, there actually exist large scale X-ray emissions beyond the bright rim in many parts of the northeast remnant component, which is in conflict with the Sedov phase assumption used in previous research. These new soft X-ray features provide astronomers more information to study its physical characteristics.

The evolution of galaxy clusters from their formation due to the merging of sub structures, the bulk of star formation and subsequent chemical enrichment of the intra-cluster medium, is expected to be quite recent (z<l-2) in the hierarchical clustering scenario (White & Frenk 1991).

All the ISO instruments are contributing to the study of activity in galaxies of essentially all types. Although AGN's as such are pointlike, the beautiful CAM image of CenA shown by Catherine Cesarsky has given us the clearest view so far of its visually obscured nucleus and surrounding spiral disc embedded in an elliptical galaxy. The CAM CVF is also providing spectral images of the PAH features and important diagnostic ionic lines (e.g [NeII] and [NeIII]) in the circumnuclar regions of AGN and merging starburst systems (Vigroux et al., 1996). PHT is providing detailed spectral energy distributions over the complete 2.5-240µm range and PHTS is proving invaluable for assembling a catalogue of low resolution (R ⋍ 90) galaxy spectra covering the 6-12µm PAH features. SWS and LWS are generating higher resolution (R ⋍ 2000-200) spectra over the range 2.5-200µm such as that shown in Fig. 1. of the Circinus galaxy which exhibits both AGN and starburst activity and well illustrates the wide range of diagnostic features, many seen for the first time, accessible to ISO studies of galaxies. It shows the overall continuum with a peak around 100µm; PAH features and Si absorption which dominate the spectrum around 10µm; H recombination lines; H2 pure rotational emission lines; low ionization potential ionic lines excited by starburst activity and high excitation lines (up to ⋍ 300eV) excited by the visually obscured AGN.

New CCD observations of the eclipsing binary VW Cephei were made on the 9th and 10th of October 1996 and on the 11th of Nov. 1996. The light curves and short time-scale variations are discussed. Photometric elements were determined from analyses of the light curves. These new solutions are also discussed.

A systematic near-infrared survey was made for globular clusters in the Magellanic Clouds. Two infrared stars were discovered in NGC419 (SMC) and NGC1783 (LMC). NGC419 and NGC1783 are well-studied rich globular clusters whose turn-off masses and ages are estimated MTO ~ 2.0 Mʘ and т ~1.2 Gyr for NGC419, and MT0 ~ 2.0 Mʘ and т ʘ 0.9 Gyr for NGC1783, respectively.

The periods of the infrared light variations were determined to be 540 dfor NGC419IR1 and to be 480 d for NGC1783IR1, respectively. Comparison of the measurements with the period—if magnitude relation for carbon Miras in the LMC by Groenewegen and Whitelock(1996) revealed that the Kmagnitudes of the infrared stars were fainter by about 0.3 — 0.8 magnitude than those predicted by the P — K relation. This deviation can be explained if the infrared stars are surrounded by thick dust shells and are obscured even in the K band. The positions of NGC419IR1and NGC1783IR1 on the P — K diagram suggest that AGB stars with the main sequence masses of about 2 Mʘ start their heavy mass-loss when P ʘ 500 d.

Based on results from the first half of its mission, ISO (Kessler et al. 1996) is contributing to our understanding of normal galaxies by offering effective gauges of the physical conditions within the interstellar medium (ISM) of galaxies. ISO data permit a more precise and detailed characterization of the radiation, dust and gas deep within many more galaxies than had been previously possible. This in turn yields new insight into the regulation mechanisms of star formation and galaxy evolution. Apart from these ISM diagnostics, ISO also contributes a vastly improved empirical description of galaxies at all infrared wavelengths, which will be critical in guiding the search for the origins and early life of galaxies.

We study the short-time evolutionary history of the well-known contact binary VW Cep. Our analysis is based partly on the numerous UBV lightcurves obtained at Tartu Observatory, IUE spectra, and samples from the published data. Special attention is given to the effects of asymmetry of the light curves. A higher degree of asymmetry outside the eclipses along with the significant displacements of the brightness maxima in respect to the elongation phase is interpreted as evidence that a considerable portion of the flaring source is concentrated close to the neck connecting the components. We discuss the nature of asymmetry in terms of possible mass exchange and the flare activity and compare the results of our model computations with the record of orbital period variations over the last 60 years.

With all its instruments, ISO is sensitive to temperatures in the range ~ 30 – 2000 K. This range is particularly adapted to studies of dense interstellar matter (gas and dust) in cold clouds, and to material associated with very early stages of stellar evolution: circumstellar matter around low-mass stars (disks, envelopes), outflows generated by them and interactions with the surrounding medium.

Interstellar abundances studies can provide answers to some questions about stellar processes, and they can lead to new questions about others. We will discuss some recent interstellar abundance determinations and their implications for stellar studies.

Although Cd and Sn are chemically similar to elements which are moderately to heavily depleted from the gas-phase interstellar medium (ISM), they appear to have solar-like abundances in inter-stellar clouds. This is likelythe result of these elements being depleted from an ISM which has been enriched with Cd and Sn since the formation of the sun. These two elements are mainly produced by s-process neutron capture in intermediate to low mass AGB stars. The present ISM abundances of Cd and Sn can therefore provide information about s-process yields and the cumulative injection of this material into the ISM over the past 4.5 Gy.

Recent studies of C and O abundances in the ISM have shown that the C/H and O/H are constant out to approximately 1500pc from the sun. Local B star abundance studies, however, find that C/O is not constant, thereby indicating that the ISM is not well mixed or homogeneous. We currently do not have an explanation for this apparent inconsistency between stars and the ISM.

Circumstellar matter is found almost exclusively around young stars that have not yet reached the main sequence and around old stars that have left this sequence. Some main sequence stars still carry the remnants of a disk of dustlike material as a remnant of their time of formation.

Propagation of the surface waves of the lobe-filing components of close binary systems is investigated theoretically. Such waves are considered to be analogous to the gravity waves of water on the earth. As a result, the equations of the surface wave in the rotating frame of reference are reduced to the so-called Kortewegde Vries (KdV) equation and non-linear Schroedinger (NLS) equation according to its ”depth”. Each of these equations is known to have the solution of soliton. When this soliton is sent to the other component of the binary system through the Lagrangian point, it can give rise to the flare activity observed in some kinds of close binary systems.

Among the important contributions of ISO to the physics of the interstellar medium, this paper concentrates only on the emission from the solid phase (the interstellar grains) and the small atom clusters which are the bridge between the grains and the small molecules with less than about 10 atoms.

From 1994 to 1997, we observed the star HD229221 several times spectroscopically by using the Beijing Astronomical Observatory 2.16 m telescope and the spectrograph Universal.

From the spectra we clearly see that the H-α spectral feature of this star underwent a peculiar variation, from a single emission line to one composed of three components, i.e. emission+absorption+filled emission. In our paper, based on an analysis of its spectral line variation and some physical parameters (e.g. luminosity, age, etc.), we discuss the possible reasons that might cause this peculiar variation.

Among the important contributions of ISO to the physics of the interstellar medium, this paper concentrates only on the emission from the solid phase (the interstellar grains) and the small atom clusters which are the bridge between the grains and the small molecules with less than about 10 atoms.