We analyse star cluster properties in the nearby spiral galaxy M33, combining our extensive HST WFPC2 photometry and ground-based follow up spectroscopy. These data show that cluster velocity dispersion increases with age. Simulations comparing synthetic disk and halo populations with observations indicate a composite disk/halo system for the old M33 clusters. The best fit fraction of 85 ± 5% halo plus 15 ± 5% disk differs from that found in the Milky Way, where ∼ 30% of the globular clusters are metal rich objects associated with the bulge and/or thick disk. Spectroscopic line indices for a halo subsample (17 objects) reveal an age spread of ∼ 5 — 7 Gyr, and little progression in metal abundance with age. This is consistent with a chaotic formation for a substantial portion of the M33 halo, and also consistent with an accretion origin for a large number of the halo clusters.

We are finally on the threshold of obtaining a coherent morphological and physical picture for the local interstellar medium (LISM), especially the region within 300 pc of the Sun. The EUVE is playing a special role in revealing this picture. This instrument can provide direct measurements of the the radiation field that photoionizes both hydrogen and helium. It also can yield direct measurements of the column densities of hydrogen, but especially He I and He II toward nearby white dwarfs. These observations suggest that the ionization in the Local Cloud, the cloud in which the Sun is embedded, is not in equilibrium, but in a recombination phase. Heuristic calculations imply that the the present ionization is due to the passage of shocks, at times greater than 3 × 106 years ago. The origin of these shocks are probably linked to the supernova which was responsible for the expanding nebular complex of clouds know as the Loop I supernova remnant, of which the Local Cloud is a part, extreme- UV radiation field, that which ionizes both hydrogen and helium in the LISM. Of the ISM within 300 pc, the volume appears to be predominantly filled by hot (106 K) coronal gas. This gas is laced with six largescale shell structures with diameters ~100−150 pc including the long-recognized radio loops, Loop I−IV, as well as the Orion-Eridanus and Gum Nebulae are identified. An idea that has evolved in the literature for over two decades is that the kinematically-linked OB associations representing Gould’s Belt, plus the gas and dust of Lindblad’s Ring, require that previous supernova activity and stellar winds carved out a 400–600 pc diameter cavity some 3 to 6 × 107 yr ago. This activity produced a pre-existing low density region, into which the present young loop structures have expanded. The outer boundaries of the identified expanding loop structures, inside this preexisting cavity, delineate the periphery of the the mis-named “local interstellar bubble.” Thus, this picture naturally explains some of the problems often associated with the presence of this low density region exterior to Loop I.

Ultraviolet and optical observations of seven very low excitation nebulae (He 2-131, He 2-138, TC 1, M 1-11, M 1-12, M 1-26, H 2-1) and of two low-excitation nebulae (IC 418 and He 2-108) are discussed.

RR Lyrae stars being distance indicators and tracers of old population serve as excellent probes of the structure, formation, and evolution of our Galaxy. Thousands of them are being discovered in ongoing wide-field surveys. The OGLE project conducts the Galaxy Variability Survey with the aim to detect and analyze variable stars, in particular of RRab type, toward the Galactic bulge and disk, covering a total area of 3000 deg2. Observations in these directions also allow detecting background halo variables and unique studies of their properties and distribution at distances from the Galactic Center to even 40 kpc. In this contribution, we present the first results on the spatial distribution of the observed RRab stars, their metallicity distribution, the presence of multiple populations, and relations with the old bulge. We also show the most recent results from the analysis of RR Lyrae stars of the Sgr dwarf spheroidal galaxy, including its center, the globular cluster M54.

This summary reports new emission lines of Fe XVII observed in two coronal active regions (McMath regions 12624, 12628). The lines were recorded by a Bragg plane crystal spectrometer collimated to 3′ FWHM, with a gypsum crystal scanning the wavelength range 8–14 Å. This spectrometer, part of a three spectrometer package previously used by Parkinson (1972, 1973), was mounted aboard a Skylark rocket (SL 1206) launched from Woomera at 0535 UT on 26th November 1973. One of the active regions studied (12624) was observed about 60 minutes after the peak of an importance – N class CO flare.

We present the most extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN), NGC 7026. Ten spectra were acquired using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the 3-dimensional visualization and kinematic program, Shape, and using HST images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. Knowledge of the 3-D structure of this nebula is relevant to understand the physics behind the extended X-ray emission in this object.

High resolution imaging with HST-wfpc2 of seven of the most luminous evolved cool stars shows that the three OH/IR stars NML Cyg, VX Sgr and S Per have circumstellar nebulae while no ejecta was detected for the M-type supergiant μ Cep and the yellow hypergiants ρ Cas, HR 8752 and HR 5171a.

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

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.

The activities and some research progress of IAU Commission 19 (C19) - Rotation of the Earth - in the past triennial term (2012-2015) is reported in this paper, including the scientific session and business meeting of C19, as well as a business meeting of the IAU/IAG Joint Working Group of “Theory of Earth Rotation” (JWG_ThER) during the XXIX IAU General Assembly in Hawaii, USA. Three reports of JWG_ThER progress, IERS and IAG, eleven reports of national projects and individual institutions, a short summary of the history and heritage of C19, and an Overview of the status and outlook of new Commission A2 are also presented.

The thermodynamics of condensation from a cooling neutral gas of solar composition, have now been explored in great detail. Theories based on equilibrium condensation have had some striking successes, but there is still much to learn. There seems good reason to explore the condensation process experimentally, so far as it is possible to simulate the conditions usually assumed, to compare the results with what we see in the meteorites, and with the calculations. Preliminary results of this experimental investigation are being reported here.

Recently derived bolometric absolute magnitudes are used to investigate the pulsational properties of some classes of red variables. The Mira variables with periods over 200 days have pulsation constants appropriate to overtone pulsatore but the shorter period 135 day Miras seem to be hotter and less luminous and may be fundamental pulsators. The large amplitude Shapley-Nail variables in the SMC are probably fundamental pulsators with masses in the 5-10 solar range. Bright supergiant red variables in the LMC show evidence of the period-luminosity relation expected if they are in the early stages of core helium burning.

Observing supernova remnants provides important clues to the nature of supernova explosions. Conversely, the late stages of stellar evolution and the mechanism of supernova explosions affect supernova remnants through circumstellar matter, stellar remnants, and nucleosynthesis. The elements of supernova classification and the connection between supernova type and remnant properties are explored. A special emphasis is placed on SN 1987a which provides a unique opportunity to learn the connection between the star that exploded (whose name we know) and the remnant that will develop in our lifetimes.

Synthesis maps of HI in three SO galaxies are discussed. In one case several companions are observed. An evolutionary sequence based on accretion is suggested.

Magnetic fields are anchored in gas clouds. Field lines are tangled in spiral arms, but highly regular between the arms. The similarity of pitch angles between gaseous and magnetic arms suggests a coupling between the density wave and the magnetic wave. Observations of large-scale patterns in Faraday rotation favour a dynamo origin of the regular fields. Fields in barred galaxies do not reveal the strong shearing shocks observed in the cold gas, but swing smoothly from the upstream region into the bar. Magnetic fields are important for the dynamics of gas clouds, for the formation of spiral structures, bars and halos, and for mass and angular momentum transport in central regions.

We present the first sub-kpc (∼ 0.7 ≈ 0.8 kpc) resolution 12CO(1–0) observations of the ISM in the host galaxy of the QSO I Zw 1 which were obtained with the BIMA mm-interferometer in its A configuration. The measurements, which are part of a multi-wavelength study of I Zw 1, will allow comparison of the ISM properties of a QSO host with those of nearby galaxies and place constraints on galaxy formation/evolution models. Our maps of the 12CO(1–0) line emission from the host galaxy of a QSO show a ring-like structure in the circumnuclear molecular gas distribution with a radius of about 900 pc. The presence of such a molecular gas ring was already predicted from earlier lower angular resolution PdBI observations (Schinnerer, Eckart, & Tacconi 1998). A first comparison of the BIMA data with new PdBI 12CO(2–1) observations with 0.9 angular resolution shows variations in the excitation conditions of the molecular gas in the innermost 3 comprising the nuclear region of I Zw 1.

The current evidence concerning the nature of comet nuclei suggests that comets may be sizeable aggregations of interstellar grains. This is a progress report on an effort to find circumstances and processes whereby such aggregations might be formed in the solar system at distances far beyond the proto-planets during the early stages of solar-system development. Under investigation are interactions between the early solar “gale” and the surrounding interstellar gas and dust—the so-called “snowplow effect.” Compression of the gas and resultant motions of the dust coupled with the pressure radiation from the Sun and nearby new stars may, under certain idealized circumstances, produce a high enough concentration of dust for gravitational instability to occur in the dust, thereby producing km-sized coherent bodies. The likelihood or probability of actual comet formation by such processes remain to be determined.

During the 25 years that the author has been involved in astrometry, the quality of ground-based parallaxes has increased by about a factor of 10 (from 3 mas to 0.3 mas), but the quantity has increased by only a few hundred. When asked, the average astronomer will cite the $H^2$ space missions (Hubble and Hipparcos) as the great advances in astrometry even thought the ground-based work has played a critical role in the understanding classes of stars such as the L- and T-dwarfs. The next decade promises stunning advances in both the quality and quantity of parallax measurements, and both ground- and space-based projects will play significant roles. The Gaia space mission and the various ground-based telescopes with large etendue (DMT, LSST, Pan-STARRS, etc.) will improve the quality or quantity (or both) by factors of a thousand or more. The situation will be discussed, and the author will express his hope that he might live long enough to see the fruits of these labors.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

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