Cycle lengths of active stars are derived from long-term photometric monitoring of their secular light variability. With the help of photographic data archives the lengths of the datasets are extended for HK Lac and V833 Tau. Using time-frequency analysis it is shown that the cycles are continuously changing in time. Thus, the reported cycle lengths derived by simple Fourier analysis are mean values that are valid only for a given time interval.

The recent calculations of atomic data for ions of astrophysical interest are reviewed with a focus on work performed in Cambridge. The calculations have been benchmarked against high-resolution laboratory and astrophysical spectra. A framework for assessing uncertainties in atomic data has also been developed. Long-standing discrepancies in predicted spectral line intensities have been resolved, and a significant number of levels in coronal ions have finally been identified, improving the modelling of the extreme-ultraviolet and soft X-ray spectral regions. Recent improvements based on collisional-radiative modelling are presented. They are relevant for the modelling of satellite lines in the X-rays and for solving the long-standing problems in the chromosphere-corona transition in stellar atmospheres.

Exoplanet search programs need to study how to disentangle radial-velocity (RV) variations due to Doppler motion and the noise induced by stellar activity. We monitored the active K2V HD 189733 with the high-resolution SOPHIE spectrograph (OHP, France). We refined the orbital parameters of HD 189733b and put limitations on the eccentricity and on a long-term velocity gradient. We subtracted the orbital motion of the planet and compared the variability of activity spectroscopic indices (HeI, Hα, Ca II H&K lines) to the evolution of the RV residuals and the shape of spectral lines. All are in agreement with an active stellar surface in rotation. We used such correlations to correct for the RV jitter due to stellar activity. This results in achieving a high precision on the orbital parameters, with a semi-amplitude: K=200.56±0.88m⋅s−1 and a derived planet mass of MP=1.13±0.03 MJup.

The Infrared Space Observatory (ISO), a fully approved and funded project of the European Space Agency (ESA), is an astronomical satellite, which will operate at wavelengths from 3–200 μm. ISO will provide astronomers with a unique facility of unprecedented sensitivity for a detailed exploration of the universe ranging from objects in the solar system right out to distant extragalactic sources. The satellite essentially consists of a large cryostat containing at launch about 2300 litres of superfluid helium to maintain the Ritchey-Chrétien telescope, the scientific instruments and the optical baffles at temperatures between 2K and 8K. The telescope has a 60-cm diameter primary mirror and is diffraction-limited at a wavelength of 5μm. A pointing accuracy of a few arc seconds is provided by a three-axis-stabilisation system consisting of reaction wheels, gyros and optical sensors. ISO’s instrument complement consists of four instruments, namely: a photo-polarimeter (3–200μm), a camera (3–17μm), a short wavelength spectrometer (3–45μm) and a long wavelength spectrometer (45–180μm). These instruments are being built by international consortia of scientific institutes and will be delivered to ESA for in-orbit operations. ISO will be launched in 1993 by an Ariane 4 into an elliptical orbit (apogee 70000km and perigee 1000km) and will be operational for at least 18 months. In keeping with ISO’s role as an observatory, two-thirds of its observing time will be made available to the european and american astronomical community.

Although Einstein's general relativity has passed all the tests so far, alternative theories are still required for deeper understanding of the nature of gravity. Double pulsars provide us a significant opportunity to test them. In order to probe some modified gravities which try to explain some astrophysical phenomena without dark matter, we use periastron advance $\dot{\omega}$ of four binary pulsars (PSR B1913+16, PSR B1534+12, PSR J0737-3039 and PSR B2127+11C) to constrain their Yukawa parameters: λ = (3.97 ± 0.01) × 108m and α = (2.40 ± 0.02) × 10−8. It might help us to distinguish different gravity theories and get closer to the new physics.

We report on the discovery of a supermassive binary black-hole (SBBH) system in the radio galaxy 0402+379, with a projected separation between the two black holes of just 7.3 pc. This is the most compact SBBH pair yet imaged by more than two orders of magnitude. These results are based upon multi-frequency imaging using the Very Long Baseline Array (VLBA) which reveal two compact, variable, flat-spectrum, active nuclei within the elliptical host galaxy of 0402+379. Multi-epoch observations from the VLBA also provide constraints on the total mass and dynamics of the system. The two nuclei appear stationary while the jets emanating from the weaker of the two nuclei appear to move out and terminate in bright hot spots. The discovery of this system has implications for the number of compact binary black holes that might be sources of gravitational radiation. The VLBI Imaging and Polarimetry Survey (VIPS) currently underway should discover several more SBBHs.

I outline some of the main processes that shape planetary rings. Then I focus on two outstanding issues, the role of self-gravity in the precession of narrow rings and the dynamics of Neptune's arcs. By airing these well-defined but unsolved problems, I hope to encourage others to join me in the quest for their solutions.

Imaging of active regions in continuum around 1.6 μm shows that many facular regions are less bright than the photosphere when observed nearer to disk center than μ = cos θ ~ 0.75. The contrast of these dark faculae increases with magnetic flux above a threshold of approximately 2 × 1018 Mx. This explains why not all faculae are dark at 1.6 μm, since the magnetic flux density in many regions of bright Ca K plage emission falls below this threshold. After correction for blurring, the typical contrast value is about 4-5%, so the brightness temperature deficit is about 130 K. Faculae are brighter than the photosphere at 1.63 μm nearer to the limb than μ ~ 0.5. The negative contrast of dark faculae may arise from cooling of the surrounding photosphere, or from increased visibility of cool layers of the facular flux tube itself. Quantitative comparison of these IR data with MHD models awaits calculation of flux tube contrasts at realistic angular resolution.

This paper examines the distribution of pulsars in the Galaxy and compares it with the distribution of supernova remnants. The dispersion measure has been used as a distance indicator to obtain the distribution in luminosity, z-distance and period of the pulsars. The z-distance distribution is similar within the uncertainties to that of the supernova remnants. An estimate of the total number of pulsars in the Galaxy with a peak luminosity ≥ 1 fu(dm)2 gives 5 × 105 within a factor of 10. The data is consistent with the hypothesis that pulsars are formed at the same rate as supernovae, if the pulsars are assumed to have a timescale of 107yr.

The period–luminosity (PL) relation of the Cepheid variable stars is the most reliable primary distance indicator for nearby galaxies, and serves as the foundation of the extragalactic distance scale, providing the firm calibration for various secondary distance indicators. However, a major disadvantage of the Cepheid distance scale is that it can only be applied to late–type systems with recent or current star formation. An alternative distance indicator is a Pop II, tip of the red giant branch (TRGB) method, which is extremely attractive because of its applicability to all morphological types of galaxies. As long as a metal–poor RGB stars are present in abundant numbers, the distance can be estimated with an accuracy that is as good as that of the Cepheid PL relation.

Improved observing and data analysis strategies have initiated a considerable expansion of the empirical knowledge about the pulsations of OB stars. Possible correlations between physical parameters and associated pulsation characteristics are becoming more clearly perceivable. This starts to include the asteroseismologically fundamental areas of g-modes and rapid rotation. The β Cephei instability strip continues to be the only locus where radial pulsations occur (but apparently not in all stars located in that strip). Except for spectral types B8/B9 near the main sequence, where pulsations are hardly detected even at low amplitudes, any major group of stars in the Galaxy that are obviously not candidate pulsators still remains to be identified. However, the incidence and amplitudes of OB star pulsations decrease steeply with metallicity. The behaviour of high-luminosity stars is less often dominated by very few modes. In broad-lined stars the moving-bump phenomenon is more common than low-order line-profile variability. But its relation to nonradial pulsation is not clear. The beating of low-ℓ nonradial pulsation modes that have identical angular mode indices may be the clockwork of the outbursts of at least some Be stars. The physics of this episodic mass loss process remains to be identified.

The Sun drives most events of space weather in the vicinity of the Earth. Because the activities of the Sun are complicated, a visualized chart with key objects of solar activities is needed for space weather forecast. This work investigates the key objects in research during the past forty years and surveys a variety of solar observational data. We design the solar synoptic chart (SSC) that covers the key objects of solar activities, i.e., active regions, coronal holes, filaments/prominences, flares and coronal mass ejections, and synthesizes images from different heights and temperatures of solar atmosphere. The SSC is used to analyze the condition of the Sun in March 2012 and October 2014 as examples. The result shows that the SSC is timely, comprehensive, concise and easy to understand. It has the potentiality for space weather forecast and can help in improving the public education.

Asteroseismology depends absolutely on the detection of authentic pulsation signatures in stars. A variety of mathematical and statistical tools have been developed to extract such signatures from photometric and spectroscopic time series. The earliest tools were developed on the platform of Fourier analysis, and Fourier-based methodology still plays a major part in the detection of pulsation signatures in the present day. Alternative approaches have been gaining ground in recent years. This article offers a brief but broad review of the various methodologies for detecting authentic periodic signals that have been developed over the past few decades, including examples of their pitfalls and successes.

The effect of tidal friction in the lunar orbit is one of the classic examples of ad hoc modelling of an unknown physical phenomenon. The two basic calculational approaches in current use are developed in some detail, and numerical tests and comparisons are presented. Although attention is normally concentrated on the acceleration in orbital longitude produced as a result of terrestrial dissipation, it is shown that the variation in Earth-Moon distance due to Earth tides is far from negligible. A significant, though minor, fraction of this variation is supplied by the radial component of the acceleration, which would exist even in the absence of tidal friction. In fact, this represents almost all the difference in the predictions of the two models.

How can teachers and researchers contribute to a new world-wide way to teach astronomy? The Hands-On-Universe group proposes multi-media tools, from remote telescopes to image processing, inspired by the most recent research activities in astronomy and astrophysics. Teachers and students can learn, in a quantitative way, to analyse images and spectra using free data sets and softwares available at the website www.eu-hou.org.

Observational results of radio bursts at 35 GHz by the sixteen-element fanbeam interferometer in Nagoya are briefly discussed.

Although originally conceived as primarily an extragalactic survey, the Sloan Digital Sky Survey (SDSS-I), and its extensions SDSS-II and SDSS-III, continue to have a major impact on our understanding of the formation and evolution of our host galaxy, the Milky Way. The sub-survey SEGUE: Sloan Extension for Galactic Exploration and Understanding, excuted as part of SDSS-II, obtained some 3500 square degrees of additional ugriz imaging, mostly at lower Galactic latitudes, in order to better sample the disk systems of the Galaxy. Most importantly, it obtained over 240,000 medium-resolution spectra for stars selected to sample Galactocentric distances from 0.5 to 100 kpc. In combination with stellar targets from SDSS-I, and the recently completed SEGUE-2 program, executed as part of SDSS-III, the total sample of SDSS spectroscopy for Galactic stars comprises some 500,000 objects.

The development of the SEGUE Stellar Parameter Pipeline has enabled the determination of accurate atmospheric parameter estimates for a large fraction of these stars. Many of the stars in this data set within 5 kpc of the Sun have sufficiently well-measured proper motions to determine their full space motions, permitting examination of the nature of much more distant populations represented by members that are presently passing through the solar neighborhood. Ongoing analyses of these data are being used to draw a much clearer picture of the nature of our galaxy, and to supply targets for detailed high-resolution spectrscopic follow-up with the world's largest telescopes. Here we discuss a few highlights of recently completed and ongoing investigations with these data.

In this paper, the availability, applicability and deviation of nonlinear force-free (NLFF) fields extrapolated by Approximate Vertical Integration (AVI), Boundary Integral Equation (BIE) and Optimization (Opt.) methods are studied based on the comparison with two semi-analytical fields (Low & Lou 1990). These NLFF extrapolations based on the observational vector magnetograms are used to study the spatial magnetic field in the quiet Sun.

We consider how positions of unresolved pre-main-sequence binaries in the HR diagram compare with the positions of their corresponding primaries and secondaries. As one might expect from simple considerations, the composites appear younger than their components, and have masses intermediate between those of the two stars. However, the amount of the age difference between the composite and its components ranges from nearly zero to as much as an order of magnitude depending upon the specifics of the system such as the reddening and relative spectral types of the objects. We present four examples that illustrate these issues.

Work in progress at Steward Observatory covering three aspects of magnetism in degenerate dwarfs is reviewed. First, the identification of the Minkowski bands in Grw + 70° 8247 with Zeeman transitions in hydrogen. Second, a determination of field strengths in the more strongly magnetic white dwarfs. Third, some observations and speculations concerning the origin of white dwarf and neutron star magnetic fields.