Like many radio-selected blazars, 0716+714 shows a high level of variability on different time scales, as short as a few days (e.g. Wagner et al 1996, Ghisellini et al. 1997). The mechanism of the emission in the optical band, in the general scheme of a relativistic plasma jet highy collimated toward the observer, is generally believed to be synchrotron radiation from electrons in a strong magnetic field. Our monitoring of S5 0716+714 is aimed to clarify whether the flux variations are chromatic or achromatic. In the first case, one could guess that variations in the spectrum of the injected electrons are responsible for the flux variations; in the second case, geometrical effects like small changes in the angle between the jet and the line of sight could be more likely (Wagner et al. 1993).

We present an ISOCAM-CVF map of the ρ Oph A region, covering 3′ × 3′. For each 6 arcsec2 pixel, we extract the spectrum from 5–15 μm. We determine the fluxes of the main PAH features by fitting Lorentzian profiles to the spectrum. The peaks of the various PAH components correspond well with the known positions of the PDRs in this vicinity. The spectrum in several pixels exhibits strong rotational lines of molecular hydrogen which can be used to derive the physical properties of the cloud. The H2 emission traces the hot gas of the bipolar CO outflow from VLA1623.

Using the IUE satellite we obtained high resolution UV spectrograms (1200 < λ < 3200 Å) of the S Dor type variable R 71 in the LMC. The IUE observations were supplemented by coordinated groundbased high dispersion spectroscopy and by photometric observations. From these observations we derive for the minimum state of R 71 the following stellar parameters: L = 2.0 × 105 L⊙, R ≈ 81 R⊙, Teff ≈ 13 600 K. For the expanding envelope we find a surprisingly low temperature of only about 6000 K and an apparently decelerated velocity field with a maximum outflow velocity of ~ 127 km s−1. The minimum state mass loss rate is in the order of 3 × 10−7 M⊙ y−1. Our results support the suggestion that the visual light variations of the S Dor type variables are produced by strong density variations of the expanding envelopes of these objects. A detailed study is forthcoming in Astronomy & Astrophysics.

Wandering in the wilderness (1) of search space and (2) among the stars.

My summary will certainly leave out much fine work but will stress a few of the points that impressed me.

First, I note remarkable progress since 1967 when I last worried about the interplanetary complex, particularly the new observations from space and of very small particles. I am delighted to see the ground based Zodiacal Light observers, like Weinberg and Dumont, converging on their observations both of polarization and of intensity. The larger particles are clearly the major contributors particularly away from the Sun. This forces the theoreticians and the laboratory people to find out how these larger particles produce the observed polarization including the negative polarization. Theoreticians always can prove the answer when it is known.

A new software to handle the large expressions involved in high accuracy analytical theories has been developped by H. Claes, M. Moons, J.M. Zune and J. Henrard. The main ideas on which this software is based are described here.

We present a preliminary analysis of a number of spectrophotometric scans of reddened and unreddened early-type stars obtained with the OAO-A2 satellite. The principal findings are: (1) all the extinction curves show a ‘bump’ at 1/λ ≈ 4.5; (2) most extinction curves show a minimum at 1/λ ≈ 5.5–6.0; (3) all the extinction curves show a rapid rise in the far ultraviolet; and (4) there appear to be real differences in the far ultraviolet extinction. A brief comparison of our observed extinction curves is made with theoretical particle models.

We investigate the magnetic sensitivity of molecular lines observed in sunspot umbrae and briefly discuss their major differences compared to atomic lines.

The study of the nongravitational effects on comets began slightly more than a century and a half ago. As is well known, Encke (1819) demonstrated that comet 1819 I had a revolution period of not more than a few years and that the same comet had also been observed in 1786, 1795 and 1805. The observations clearly required that the revolution period be about 3.3 years, and Encke went on to remark that, after approximate allowance had been made for the perturbations by the planets, the average revolution period seemed to be 1207.9 days between 1795 and 1805, but only 1207.3 days between 1805 and 1819. As a result of a more refined computation of the planetary perturbations, the following year he (Encke 1820) was able to confirm these figures and find in addition that the average period between 1786 and 1795 was as much as 1208.1 days.

Heavy element abundances, in particular those of oxygen, obtained from recent spectroscopic surveys of Magellanic Cloud planetary nebulae (PN), are reviewed and compared with those derived for H regions and objects in our own galaxy. These abundances have been based on collisionally excited lines and are very sensitive to the adopted electron temperature. There is increasing evidence that temperature or density fluctuations within nebulae lead to the electron temperatures being overestimated, with the corollary that the heavy element abundances have been underestimated.

We have imaged more than thirty early-type galaxies in the K-band to investigate their stellar populations. Our surface brightness fluctuations (SBF) measurements for the nearest 14 galaxies produce a mean fluctuations magnitude in the K-band of The scatter in the Virgo cluster is small at 0.18 mag, which implies that infrared SBF is potentially a good distance indicator (Pahre & Mould 1994). Inspection of the simple stellar population tracks of Worthey (1994) suggests that a plot of the fluctuation color against broadband color (V – I) might be useful in discriminating between age and metallicity effects in elliptical galaxies. We have measured (r – K) color gradients for the entire sample utilizing three methods, two of them independent of sky-subtraction errors, as found in Sparks & Jørgensen (1993). Our color gradients are consistent with a mean metallicity gradient of 0.14 mag dex−1, which is somewhat smaller than that implied by optical color and line gradients alone, suggesting that age gradients may also be important. Finally, we have constructed an infrared Fundamental Plane (FP) which is consistent with its optical counterpart; continued work will determine if there is a significant change in the tilt of the FP between the optical and infrared.

The cosmic infrared background (CIB) radiation was a long-sought fossil of energetic processes associated with structure formation and chemical evolution since the Big Bang. The COBE Diffuse Infrared Background Experiment (DIRBE) and Far Infrared Absolute Spectrophotometer (FIRAS) were specifically designed to search for this background from 1.25 μm to millimeter wavelengths. These two instruments provided high quality, absolutely calibrated all-sky maps which have enabled the first detections of the CIB, initially at far infrared and submillimeter wavelengths, and more recently in the near infrared as well. The aim of this paper is to review the status of determinations of the CIB based upon COBE measurements. The results show that the energy in the CIB from far infrared to millimeter wavelengths is comparable to that in the integrated light of galaxies from UV to near infrared wavelengths: the universe had a luminous but dusty past. On the assumption that nucleosynthesis in stars is the energy source for most of this light, the results also imply that 1–8% of cosmic baryons has been converted to helium and heavier elements in stars. The integrated background light from UV to millimeter wavelengths, 60–120 nW m−2 sr−1, is about 10% of that in the cosmic microwave background. Current knowledge of the CIB provides significant new constraints on models of the history of star formation and galaxy evolution.

The problem of calculating the mass distribution of meteorites and their influx rate can be resolved into three sections; (a) the flux of meteorites hitting the surface of the Earth must be calculated (b) the mass distribution of these meteorites must be assessed, care being taken to include the effect of fragmentation in the atmosphere and (c) atmospheric ablation, which is a function of mass, velocity, composition and zenith angle must be taken into account. The final result will give the meteoritic influx to the Earth's upper atmosphere and its mass distribution.

X-ray emission from spiral galaxies without activity is thought to consist of low-mass X-ray binaries (LMXBs), and the Einstein observations established the relation between X-ray (0.2-4 keV) and optical luminosities as log(LX/LB) ~ −4 (Fabbiano, 1992). This relation has been used when discussing the activity other than LMXBs (Iyomoto, 1996). However, spectral information of Einstein Observatory was rather poor above 3 keV, where LMXBs would emit significant energy flux. Therefore we performed ASCA observations of two normal spirals, NGC2903 and NGC628, in order to better calibrate the LX - LB relation.

We give here a brief report on the status of the IRAM Interferometer which is now in operation on Plateau de Bure.

The asymmetric rotor molecule methanol (CH3OH) has hundreds of transitions at centimeter-, millimeter-, and submillimeter wavelengths. Many of these are excited in the hot (T ≳ 150 K), dense (n ≳ 106 cm−3) molecular cloud cores surrounding newly formed massive stars or protostars. The high temperatures in these cores cause evaporation of icy grain mantles, releasing copious amounts of complex molecules, such as methanol, in the gas phase, which in hot cores has abundances (up to 10−6 relative to H2) that are two or more orders of magnitude higher than in cold dark clouds.

The magnetosphere of a planet, as the name implies, is the region surrounding the planet in which the planetary magnetic field plays a dominant role in determining the behaviour of the medium. The inner boundary of a magnetosphere is the surface of the planet if it has no significant atmosphere (as in the case of Mercury), or the lower ionosphere in the case of planets with atmospheres. The outer boundary, usually termed the “magnetopause”, is shaped by stresses exerted by the solar wind, being blunt on the upstream side, with normal stresses playing a dominant role, and extending in a comet-like “magnetotail” on the downstream side away from the Sun largely as a result of the action of shear stresses. The characteristic size of a magnetosphere, namely the distance Lm (in planetary radii) to the subsolar point is determined approximately by balancing solar wind ram pressure and the magnetic pressure:

where n is the ion number density and Vs the speed of the solar wind, m is the average ion mass, Bo the (dipole) field strength at the surface of the planet and C is a constant of order unity.

A review is given of continuing efforts to generate laboratory spectra at photon energies above 1 keV from highly ionized atoms. Emphasis is placed on the most easily-interpreted highest ion stages such as the hydrogenic, helium-like and lithium-like species. The close similarities to solar flare observations of certain signatures, such as the line and continuum X-ray spectra and microwave emission as well as their sequence of occurrence, are pointed out and scaling factors are given.