We could find a new 5 year periodicity in the occurrences of peaks in sunspot activity and inferred deviations of annual Indian monsoon rainfall variations from the normal during the Maunder minimum (MM) period. This result is explained in terms of solar dynamo functioning in a different mode from normal during the MM where quadrupole field (first harmonic, 5-5.5 years) dominate over dipole field (fundamental, 11 years) causing extreme north south asymmetry in sunspot activity.

In the present paper, we stress the importance of the magnetic field in the problem of acceleration and collimation of astrophysical jets, and discuss our proposed generic picture for such “central gravitator + jets + lobes” systems and inherent interpretations of the various observational characteristics of such systems: Mechanisms are proposed for (1) the enhanced liberation of gravitational energy at the central object, (2) the transfer of a part of the liberated energy along the large-scale magnetic field by large-amplitude, torsional Alfvén wave trains that form collimated jets (we call this a sweeping pinch process), (3) the dumping of the transferred energy at the end of the jets when they impinge on the denser region outside the border of the “cavity” from which the mass contracted to the central condensation (central gravitator + accretion disk, as well as the larger-scale condensation surrounding them), and (4) the formation of wiggled jets and lobes as helical kinks and the tucked-up magnetic field produced in the sweeping pinch process, respectively.

After neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations—under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients—similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 Å by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.

Increasing spatial resolution and contrast capabilities will make possible new direct detections of exoplanets, exozodis, and circumstellar disks. The Large Binocular Telescope Interferometer (LBTI) has been engineered to sit at the combined focus of the Large Binocular Telescope's two 8.4m apertures. Both apertures are equipped with 672-actuator deformable secondary mirrors, the first of the next generation of “extreme” adaptive optics (AO) systems. We present an overview of the LBTI AO instrument suite and detail current on-sky performance.

X-ray spectra of stellar X-ray sources taken with high, moderate and low spectral resolution are discussed. Only low resolution spectra are available for a sufficiently large number of late-type stars. It is shown that high temperature plasmas (log T > 7) produce the dominant emission component in the coronae of red dwarfs as well as yellow giants, while the coronae of F stars – usually – have X-ray temperatures similar to those found in the quiet Sun. The need for density diagnostics of stellar coronae is stressed and it is argued that the waveband region between 90 – 140 Å is particularly well suited for this purpose.

The scientific goals for the TMT (Thirty Meter Telescope) are consistent with all the objectives outlined by the top level astronomy review committees in both Canada and the United States. In addition to powerful seeing-limited instruments, TMT will include instruments that will take advantage of the full diffraction-limited performance of a 30m telescope at wavelengths $\gt 1 \mu {\rm m}$. This will enable TMT to meet the challenges presented by the scientific requirements and will provide full complementarity with future project like JWST and ALMA. This paper presents a brief review of the status of TMT and an overview of the instruments and their adaptive optic systems.

In Chinese ancient times the Sun worship was in vogue. Mainly there were two sorts of the worship rites: 1) for rising and setting Sun; 2) for solar eclipses. Many evidences for Sun worship have been found in Chinese ancient books and bone inscriptions (Xu Zhentao et al.1985).

The everyday worship to the Sun certainly caused spontaneous observations for solar phenomena. Since the ancients only had a limited knowledge they could not understand what were these phenomena and they, however, created many wonderful myths to describe them. These myths about Solar phenomena have vividly been expressed in the works of art of the Han Dynasty recently unearthed. So analysing the works of art we may trace the original phenomena of solar activity.

Cultural astronomy is the study of the astronomy of ancient cultures and is sometimes called the anthropology of astronomy. The many ways that astronomy was used by ancient cultures are fascinating and this can be used to inspire interest in all astronomy, as well as astronomy in culture. Archaeoastronomy is interdisciplinary and among its practitioners are not only astronomers and astrophysicists, but also anthropologists, archaeologists, and Indigenous scholars. Much can be learned about ancient cultures though examination of how and why they used astronomy. This paper will highlight several examples that can capture public attention.

Here we summarize the discussion that took place after the presentation of papers discussing measurement of abundances from emission lines in H II regions. A cosmological test using 4He is harder than those using the other light elements due to the small dynamic range over which He/H varies for cosmologically interesting parameters. A precision of much better than 1% is needed. This precision challenges both observations and theory. Several of the major uncertainties were identified and methods of improving the accuracy were described.

The 3 micron spectrum of the galactic center source IRS 7 is compared to a spectrum obtained on the deuterium-rich organic polymer extracted from the Orgueil carbonaceous meteorite. The almost perfect match between the two spectra in the 3.4 μm region suggests that the chemical composition of the interstellar organic matter resembles that of the meteoritic macromolecule.

The Extreme Ultraviolet Explorer data archive has been used to study flare energy distributions and infer the role of flares in coronal heating. We have constructed flare number distributions as a function of observed EUV and X-ray emitted thermal energy. We find cumulative flare distributions of the form N(> E) ∝ E−α+1 with α ≍ 1.5–2.6. We present results in the context of spectral type classification.

The paper emphasizes the connection between observations and theory in the Lower Instability Strip. It is argued that the $\delta$ Scuti and $\gamma$ Doradus pulsators are very close relatives in the sense that the $\gamma$ Doradus phenomenon can also be seen in the slightly hotter $\delta$ Scuti variables.

New developments and recent progress are reviewed. Arguments are given why all (or almost all) stars in the Lower Instability Strip are pulsators. Furthermore, the question of the so-called missing modes is answered as very extensive photometry campaigns have revealed a large number of pulsation modes with amplitudes less than one millimag. Arguments are given that the 500+ $\ell$ = 0 to 2 modes predicted for $\delta$ Scuti stars are actually present.

The progress made in developing reliable methods of pulsation mode identification is briefly discussed. The discovery of many close modes with small amplitudes sets severe requirements concerning the length of future studies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The rotational energy transfer of NH3, OH and D2CO in inelastic collisions with He and H2 is studied in a crossed molecular beam experiment. The molecules are prepared in a single initial state by rotational cooling in an adiabatic expansion followed by electrostatic state selection. Relative state-to-state cross sections are determined by measuring the collision induced redistribution of the population of the initial state by using state selective laser detection techniques. The results for NH3 and OH are compared to theoretical values obtained from quantum calculations. Except for NH3 — He where theory predicts a parity selection rule for transitions to the 33 and 43 states, which is not observed in the experiment, good agreement between experiment and theory is obtained.

For several of the rapidly oscillating Ap stars the best luminosity estimates available come from the asteroseismological interpretation of their pulsational frequency spectra. We give a list of the 23 currently known roAp stars along with their Strömgren photometric indices, Teff estimated from the Hβ index, and luminosity estimated asteroseismologically. In one case, ϒ Equ, we have an asteroseismological luminosity and a parallax luminosity which are in good agreement. Some of the roAp stars pulsate with frequencies greater than the critical frequency calculated for standard A-star models. This plus multi-colour high-speed photometry of HR 3831 indicate that the temperature gradients in the atmospheres of these stars are substantially steeper than in standard A-star models. We advocate a fine analysis of HR 3831 to see if there is consistency with the pulsational conclusions about T-τ in this star. Further fine analyses and multi-colour pulsational analyses on other roAp stars are then called for. The pulsation mode in HR 3831 can be decomposed into primarily an axisymmetric dipole mode with small radial, quadrupole and octupole perturbations. If the magnetic field is governing the distortion of this mode from a purely dipole mode, then the pulsation can be used to infer the magnetic field geometry. Comments on our current knowledge of all 23 roAp stars are made.

We present a study of the emission line profiles of a sample of 12 single-peaked Active Galactic Nuclei (AGNs- Sy 1 and QSOs). The narrow [OIII] lines seem to be related to two components; NLR1, which has dispersion velocities from 200 to 500 km s−1 and is blueshifted with respect to the systemic by about 20 to 350 km s−1; and NLR2, with smaller dispersion velocities (∼100-200 km s−1) and a redshift corresponding to the cosmological one. The broad lines have complex structure and a two-component model has been applied.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Galaxies undergoing ram pressure stripping in clusters are an excellent opportunity to study the effects of environment on both the AGN and the star formation activity. We report here on the most recent results from the GASP survey. We discuss the AGN-ram pressure stripping connection and some evidence for AGN feedback in stripped galaxies. We then focus on the star formation activity, both in the disks and the tails of these galaxies, and conclude drawing a picture of the relation between multi-phase gas and star formation.

The National Observatory of Brazil was established in 1827 to study the problems of latitude and time. Time and latitude programs are still an important part of its work, but are now accompanied by increasing activity in the fields of geophysics, astrophysics and radio astronomy.

The Hubble Space Telescope Wide Field Planetary Camera 2 imaging data provide the highest spatial resolution of individual Shoemaker-Levy 9 impact sites. Analysis of images obtained with the F410M filter yielded horizontal translation rates of tropospheric cloud structures and the east-west components have been interpreted as zonal winds which vary with latitude. When the tropospheric zonal winds between —60° and —30°, which were derived from the SL9 images, are compared with Voyager data there are no discernible changes in the magnitude or latitudinal positions of wind minima and maxima. This result provides additional evidence of the long-term stability of the zonal winds. Changes in individual sites during a two week period in July 1994 have been mapped. Their evolution is consistent with zonal winds decreasing with height and it provides evidence that local circulation associated with isolated weather systems perturbs the lower stratosphere.

. Hercules X-1 (Her X-1) was observed extensively by the Rossi X-ray Timing Explorer (RXTE) over its 17 year lifetime. Here, the archival RXTE/PCA observations of Her X-1 are analyzed with emphasis on the 35-day cycle dependence. Spectral fits are carried out and the 35-day phase dependences are characterized. The regular behaviours of the changes are interpreted in terms of the precessing accretion disk. We find that the most important variation is caused by the changing illumination of the inner edge of the disk, but other variations with different causes are also seen.

The software for the reduction of the VLBI observations of the Main Astronomical Observatory of the Ukrainian Academy of Science is described.

Our program complex has three parts:

1) calculation of geometrical delay τ,

2) calculation of required corrections to values of τ,

3) data analysis procedures.

This software has been tested using the NGS VLBI data for the obtaining of corrections to the ERP. The parameters of the clock were derived. Our results were compared with similar results, which were published by Shanghai observatory (China) and IRIS bulletin.

The differences between our results and the data given in the IRIS bulletin are within 5 mas, and for UT are within 0.1 ms.