Present Observational Status of the Intermediate Mass Stars: δ Sct Stars, γ Dor Stars and roAp Stars

The present observational status of the Sct stars, Dor stars and roAp stars is discussed. The Sct stars are the most intensively observed of the three groups, but it has become clear that there are severe problems in extracting asteroseismic information from them. Dozens of frequencies are observed, but hundreds of frequencies are predicted from the models; unique matches of observation and theory still elude us. The Sct stars are observationally complex – some recent `best case' campaigns are discussed. It is possible that substantial observational advances for Sct stars may need to await upcoming satellite missions. New Dor stars are beingdiscovered frequently, and new behaviour is being found for them. They constitutean observationally young field. Their pulsational frequency range is being expanded, their position in the HR diagram is becoming better known (but is yet to be fully constrained), and the possibility exists of hybrid Dor – Sct stars that have greatasteroseismic promise, although it is clear such stars are rare, if they do exist. It has been observationally challenging to extract more than a fewfrequencies for any Dor star so far. Exciting spectroscopic discoveries of new behaviour in roAp stars promise unprecedented information about the structure of the peculiar atmospheres ofthose stars – pulsation amplitude and phase in 3D, magnetic field structurein 3D, abundance stratification in 3D, realistic T- for the most peculiarstars – as well as entirely new information about the interaction of pulsation,rotation and magnetic fields. Recent theoretical work has led to new understandingof the previously inexplicable frequency spacing of HR 1217 with new Whole Earth Telescope observations supporting this theory. An `improved oblique pulsator model' has been developed in which the pulsationaxis is not the magnetic axis; this model has passed several observationaltests and new ones are being devised to examine it further.     

The Age of Beta Pic Type Stars: Vega, Fomalhaut, β Pic and HR4796

We have established that several prominent β Pic stars are associated to moving groups. Based on this fact, we have estimated their ages. Our estimates are 200±100 Myr for Castor (which contains Vega and Fomalhaut), the same age for β Pic, and 8±2 Myr for HR4796 A. This revised version was published online in July 2006 with corrections to the Cover Date.     

Type II–IV radio bursts and compact and diffuse white-light clouds in the outer corona of December 14, 1971

The radio observations of type II–IV bursts on December 14, 1971 are analyzed. These radio events were associated with a H-spray or eruptive prominence, and later followed by several compact moving clouds observed with the NRL white-light coronagraph aboard OSO-7. There was also observed a diffuse expanding cloud behind the compact moving clouds.From the comparison of the interferometer observation of the bursts with the optical observation, it is strongly suggested that the compact moving clouds were likely to be the optical counterparts of the sources of moving type IV radio emission. This fact suggests that the magnetic bubbles were really produced in the flare process. The frequency-drift of the first group of type II bursts was so rapid, that we could neither identify the type II shock with the leading edge of the diffuse expanding cloud nor interpret it as the piston-driven shock of the latter. Because of the uncertainty of the velocities of the compact clouds due to the projection effect, the possibility that the type II shock was the piston-driven shock of the compact clouds cannot be excluded. Nevertheless we suggest that the type II shock was a blast type MHD shock and had no direct physical relation to the flare-associated mass-ejection processes. The relation between the type II–IV bursts and the interplanetary shock is also discussed.     

The Greenwich Photo-heliographic Results (1874 – 1976): Summary of the Observations, Applications, Datasets, Definitions and Errors

The measurements of sunspot positions and areas that were published initially by the Royal Observatory, Greenwich, and subsequently by the Royal Greenwich Observatory (RGO), as the Greenwich Photo-heliographic Results (GPR), 1874?–?1976, exist in both printed and digital forms. These printed and digital sunspot datasets have been archived in various libraries and data centres. Unfortunately, however, typographic, systematic and isolated errors can be found in the various datasets. The purpose of the present paper is to begin the task of identifying and correcting these errors. In particular, the intention is to provide in one foundational paper all the necessary background information on the original solar observations, their various applications in scientific research, the format of the different digital datasets, the necessary definitions of the quantities measured, and the initial identification of errors in both the printed publications and the digital datasets. Two companion papers address the question of specific identifiable errors; namely, typographic errors in the printed publications, and both isolated and systematic errors in the digital datasets. The existence of two independently prepared digital datasets, which both contain information on sunspot positions and areas, makes it possible to outline a preliminary strategy for the development of an even more accurate digital dataset. Further work is in progress to generate an extremely reliable sunspot digital dataset, based on the programme of solar observations supported for more than a century by the Royal Observatory, Greenwich, and the Royal Greenwich Observatory. This improved dataset should be of value in many future scientific investigations.     

High fluences of low energy (10–25 MeV/amu) C,N, O and heavier ions at 450 km altitude; results from the skylab experiment

High fluences (i.e. the integrated fluxes) of C, N, O group of nuclei and some of the heavier ones, in the energy interval 10–25 MeV/amu, have been identified in a Lexan polycarbonate detector assembly exposed on the exterior of the Skylab for 73 days. The existence of large flux of low energy nuclei in the Skylab orbit is surprising since the minimum geomagnetic cut-off energy for fully stripped nuclei (A/Z=2) is 50 MeV/amu at the orbit of the satellite, and the period of exposure was a quiet one, free from significant solar particle events. We have considered two sources for these particles: (i) partly ionized interplanetary ions accelerated within the magnetosphere and (ii) heavy nuclei trapped in the Earth's radiation belt. The flux and composition of the nuclei observed by us seem to be significantly different from those in the trapped radiation as known at present; hence it seems likely that the major part of the observed flux may be interpreted, in terms of partly ionized interplanetary ions that are further accelerated in the magnetosphere.     

Asteroids,comets, meteoric matter: Proceedings of the IAU Colloquium No. 22, held at the University of Nice,France, April 4–6, 1972. Edited by C. Cristescu,W. J. Klepczynski,and B. Milet. Acad. Rep. Soc. Romania,Bucharest, 1974. 333 pp., 27 L

A model is proposed for single close encounters between two small masses, m₁and m₂, which orbit a much larger mass, M. The main new feature of the model is the assumption of conic motion of the center of mass of m₁and m₂ in the gravitational field of M. Comparisons of the model with the three-body equations of motion indicate that the model is a useful approximation for m₁, m₂ ? 10^?5M. The model is therefore applicable for encounters between bodies of the order of an earth mass or smaller in the presence of the sun. Comparisons are also made of outcomes obtained by the model with outcomes of numerical integration for a large variety of close encounters. The above comparisons reveal that for many purposes the model is an adequate approximation for those encounters with ? ≥ 4, where ? is the eccentricity of the hyperbolic orbit of m₁about m₂.     

Far infrared photometry of planets: Saturn and Venus: Volume 38, Number 3 (1979), in the article,by R. Courtin,P. Léna,M. De Muizon,D. Rouan,C. Nicollier,and J. Wijnbergen,pp. 411–419

The global distribution of existing lunar topography suffers from a lack of measurements of far-side radii because of the sparsity of data types in the nonequatorial regions. This paper presents determinations of far-side lunar radii based on the reduction of photogrammetric measurements derived from selected Apollo 16 trans-Earth phase photographs. The regions covered in this analysis lie west of Mare Moscoviense between longitudes 90 and 130°E and latitudes 10 and 60°N. The determinations are made using control points appearing on both NASA topographic orthophoto maps and the Apollo 16 photographs. The estimated lunar radii are referred to these control points and determined with a relative accuracy of 500 m. The new lunar radii are used to generate a topographic map covering the area investigated. The map shows that, with the given spatial density of surface festures measured, basin-sized features can be resolved. In particular, the far-side craters Fabry, Riemann, and Szilard comprise a topographically depressed region about 500 km in diameter centered at 120°E and 38.5°N. The floor of this basin is 2.4 to 3.4 km below the reference sphere of 1738.0 km and 4.8 to 5.8 km below the northern rim of the basin. A comparison of the depth of the unfilled basin with the depths of maria-filled front-side basins leads to the conclusion that basalt fill of the near-side maria may be 2 km deep. The topographic map shows good correlation with geologic provinces of young plains and cratered terra in the far-side highland region investigated. Lack of correlation between sampled values of the state-of-the-art 16th-order and 16th-degree harmonic gravity field model and corresponding topographical values leads to the conclusion that the far-side region investigated is isostatically compensated.     

<Emphasis Type="Italic">Wind</Emphasis> Magnetic Clouds for the Period 2013 – 2015: Model Fitting,Types, Associated Shock Waves,and Comparisons to Other Periods

We give the results of parameter fitting of the magnetic clouds (MCs) observed by the Wind spacecraft for the three-year period 2013 to the end of 2015 (called the “Present” period) using the MC model of Lepping, Jones, and Burlaga (J. Geophys. Res.95, 11957, 1990). The Present period is almost coincident with the solar maximum of the sunspot number, which has a broad peak starting in about 2012 and extending to almost 2015. There were 49 MCs identified in the Present period. The modeling gives MC quantities such as size, axial attitude, field handedness, axial magnetic-field strength, center time, and closest-approach vector. Derived quantities are also estimated, such as axial magnetic flux, axial current density, and total axial current. Quality estimates are assigned representing excellent, fair/good, and poor. We provide error estimates on the specific fit parameters for the individual MCs, where the poor cases are excluded. Model-fitting results that are based on the Present period are compared to the results of the full Wind mission from 1995 to the end of 2015 (Long-term period), and compared to the results of two other recent studies that encompassed the periods 2007?–?2009 and 2010?–?2012, inclusive. We see that during the Present period, the MCs are, on average, slightly slower, slightly weaker in axial magnetic field (by 8.7%), and larger in diameter (by 6.5%) than those in the Long-term period. However, in most respects, the MCs in the Present period are significantly closer in characteristics to those of the Long-term period than to those of the two recent three-year periods. However, the rate of occurrence of MCs for the Long-term period is \(10.3~\mbox{year}^{-1}\), whereas this rate for the Present period is \(16.3~\mbox{year}^{-1}\), similar to that of the period 2010?–?2012. Hence, the MC occurrence rate has increased appreciably in the last six years. MC Type (N–S, S–N, All N, All S, etc.) is assigned to each MC; there is an inordinately large percentage of All S, by about a factor of two compared to that of the Long-term period, indicating many strongly tipped MCs. In 2005, there was a distinct change in variability and average value (viewed at \(1/2\) year averages) of the duration, MC speed, axial magnetic field strength, axial magnetic flux, and total current to lower values. In the Present period, upstream shocks occur for 43% of the 49 cases; for comparison, the Long-term rate is 56%.