bluuebunny/crossref_metadata_2025 huggingface dataset:
Voyages Through Time: Everything Evolves
Authors: Fisher Jane , Tarter Jill , DeVore Edna , Pendleton Yvonne , O'Sullivan Kathleen , Burke Meg
Published: June 2019

The SETI Institute, the California Academy of Sciences, NASA Ames Research Center, and San Francisco State University have developed standards-based curriculum materials for a one-year high school integrated science course centered on the unifying theme of evolution. Scientists, teachers, curriculum writers, and media specialists are currently finalizing six modules that integrate astronomical, geological, and biological sciences as well as the history of science and technology. The sequence of lessons in each module is designed to promote students' understanding and skills as defined by the National Science Education Standards and Benchmarks for Science Literacy. The modules cover: Cosmic Evolution, Planetary Evolution, Origin of Life, Evolution of Life, Hominid Evolution, and the Evolution of Technology. The core lessons for all six modules are provided via CD-ROM, including instructional guidelines, science background information, and additional resources (print, audiovisual, software, WWW sites, and databases). These products will be published as a complete set for use as a yearlong science course and will also be available as individual modules for use in discipline-based courses. Evolutionary change is a powerful framework for studying our world and our place therein. It is a story of epic size, capable of inspiring awe and of expanding our sense of time and place. This story is the basis of Voyages Through Time.
Mapping the Local and Distant Universe with SUMSS
Authors: Sadler Elaine M. , Hunstead Richard W. , Mauch Thomas , Campbell-Wilson Duncan , Jackson Carole A. , De Breuck Carlos , Blake Chris
Published: June 2019

The Sydney University Molonglo Sky Survey (SUMSS) is a radio continuum imaging survey of the southern sky at 843 MHz, with similar sensitivity and resolution to the northern NRAO VLA Sky Survey (NVSS). We have combined radio data from SUMSS and NVSS with optical spectra from the 2dF Galaxy Redshift Survey and 6dF Galaxy Survey to study the space distribution and properties of both AGN and star-forming galaxies in the local universe (redshift range 0 < z < 0.3). We also discuss new results on radio-source clustering in the more distant universe (z ∼ 1) and present the first results from a search for the most distant (z > 3) southern radio galaxies.
Amplitude-Phase Analysis of Cosmic Microwave Background Maps
Authors: Novikov D. , Naselsky P. , Silk J.
Published: June 2019

We propose a novel method for the extraction of unresolved point sources from CMB maps. This method is based on the analysis of the phase distribution of the Fourier components for the observed signal and unlike most other methods of denoising does not require any significant assumptions about the expected CMB signal. The aim of our investigation is to show how, using our algorithm, the contribution from point sources can be separated from the resulting signal on all scales.
A New Radio Continuum Survey of the Sky at 1465 MHz between declinations −52° and +68°
Authors: Tello C. , Villela T. , Smoot G. F. , Torres S. , Bersanelli M.
Published: June 2019

We have mapped the total sky brightness at 1465 MHz in two adjacent 60° declination bands with the portable 5.5-m parabolic reflector of the Galactic Emission Mapping (GEM) project, an on-going international collaboration to survey the radio continuum of the sky in decimeter and centimeter wavelengths. The observations were conducted from two locations, one in the USA and the other in Brazil, using a novel instrumental approach to overcome the well-known shortcomings of survey experiments. Our strategy consists of a 1-rpm rotating dish to circularly scan the sky at 30° from Zenith. The dish uses a rim-halo to re-direct the spillover sidelobes of its backfire helical feed toward the sky and the entire assembly has been enclosed inside a wire mesh ground shield in order to minimize and level out the contamination from the ground. The diffraction characteristics of this set-up have been successfully modelled and un-desired systematic striping across the observed bands has been carefully removed by a baseline propagation method which exploits the time-forward and time-backward intersections of the circular scans. The map displays nearly 300 hours of our best quality data taken with a HPBW of 5.4° at a sensitivity of 20 mK.
(Non-)fractality on Large Scales
Authors: Martínez Vicent J.
Published: June 2019

The debate about the possible smoothness of the Universe on large scales as opposed to an unbounded fractal hierarchy has been the subject of increasing interest in recent years. The controversy arises as a consequence of different statistical analyses performed on surveys of galaxy redshifts. I review the observational evidence supporting the idea that a gradual transition occurs in the galaxy distribution: from a fractal regime at small scales to large scale homogeneity.
Observations of H2O maser and continuum emission in AFGL 2591
Authors: Trinidad Miguel A. , Curiel Salvador , Cantó Jorge , Torrelles José M. , Rodríguez Luis F. , Gómez José F. , Ho Paul T.P.
Published: June 2019

We report results of radio continuum (1.3 and 3.6 cm) and H2O maser line observations, made with the Very Large Array (A configuration), toward the star-forming region AFGL 2591. We detected 85 maser spots toward this region, which are distributed in three main groups. Two of these groups spatially coincide with the radio continuum sources VLA 2 and VLA 3. The maser spots associated with VLA 3 are distributed along a shell-like structure of 0.01 and nearly perpendicular to the CO bipolar outflow. We propose that VLA 3 is the center of the observed molecular flow in this region. Finally, we confirm that AFGL 2591 region is a cluster of B type stars, each one with its own optically thin H II region.
OH masers associated with IRAS point sources
Authors: W. Masheder M.R. , Cohen R.J. , Martin-Hernandez N.L.
Published: June 2019

We report a search for masers from the A-doublet of the ground-state of OH at 18cm, carried out with the Jodrell Bank Lovell Telescope and with the 25m Dwingeloo telescope. All objects north of δ = −20° which appear in the IRAS Point Source Catalog with fluxes > 1000 Jy at 60μm and 100μm were observed in all four lines and both circular polarisations over the required velocity range. Preliminary results of 52 maser sources are reported here.
The H2O maser proper motions of RT Vir and VX Sgr
Authors: Yates Jeremy , Richards Anita , Gray Malcolm
Published: June 2019

We have measured significant proper motions using the water maser clouds in the outflows from RT Vir (6 epochs) and VX Sgr (2 epochs). In both cases proper motions are measured in the bright emission found perpendicular to the OH emission. This strongly suggests latitude dependent mass-loss with the water masers tracing a dense equatorial outflow and the OH emission tracing a less dense polar outflow. In both cases the rotational velocities are < 1 km s−1 thus ruling out a strongly rotating circumstellar envelope. This suggests the outflow is not shaped by an orbiting companion. In the case of VX Sgr the proper motions are contained in a wedge perpendicular to the measured magnetic field axis, thus strongly suggesting that the magnetic field is helping to shape the mass outflow.

The proper motion results have thrown up a puzzle. For VX Sgr the material is being radially accelerated and material enters the water maser zone at 4 km s−1. This is consistent with the mass loss model of Bowen (1988). However the RT Vir proper motion results show no such radial acceleration. The masers have already received their acceleration before they reach the water maser zone at 3-AU (our numerical models seem to support the small radius). This was probably done in the pulsation zone. The acceleration mechanism is unclear for this source.
Masers, from protostars to black holes: conference summary
Authors: Reid Mark J.
Published: June 2019

Astronomical sources of maser emission have now been studied for more than 30 years, and research related to masers spans a very wide range of topics in astrophysics. Over this period great progress has been made in many areas of maser research. This summary will put maser research into an historical perspective and focus on highlights from this conference.
The Globular Cluster System of M31
Authors: Jablonka P.
Published: June 2019

This review presents the current status of our knowledge of M31 star clusters. Given the broadness of the subject, I chose to focus on some of its aspects which are not covered by the other participants in this conference.
M31 Globular Cluster Metallicities and Ages
Authors: Barmby Pauline
Published: June 2019

Globular cluster ages are more than just lower limits to the age of the universe; the distribution of ages constraints the timescales for galaxy formation and chemical evolution. Globular cluster populations with different metallicities have now been detected in many galaxies, and understanding how these populations formed requires knowing their relative ages. We examined the relative ages of the two M31 globular cluster populations using their color and luminosity distributions and found that the metal-rich clusters could be up to 50% younger than the metal-poor clusters. While a small delay in the formation of metal-rich clusters might be imposed by chemical enrichment timescales, a large age gap demands a more detailed explanation. I outline several possibilities and their promises and problems.
A Survey of M31 Globular Clusters Using WFPC2 on board HST
Authors: Rich R.M. , Corsi C.E. , Bellazzini M. , Federici L. , Cacciari C. , Pecci F. Fusi
Published: June 2019

We report new, as yet unpublished HST/WFPC2 V, I photometry of 9 globular clusters in M31. These are part of a total sample of 19 clusters on M31 with well observed CMDs from HST. The clusters have the full range of horizontal branch morphologies from blue HB to red clump, but none are found with an extreme (blue only) horizontal branch. Plots of HB type vs [Fe/H] are similar to those of Galactic clusters, including a hint of second parameter clusters. Sixteen halo fields adjacent to the observed clusters included in our images have been analysed. The M31 halo metallicity distribution peaks at [Fe/H]=-0.7 dex with a tail toward low metallicity, resembling the halo of NGC 5128; metal-rich giants appear to be centrally concentrated.
Kinematics of Star Clusters in M33: Distinct Populations
Authors: Chandar Rupali , Bianchi Luciana , C. Ford Holland , Sarajedini Ata
Published: June 2019

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.
Globular Clusters and Planetary Nebula Kinematics in NGC 5128 (Cen A)
Authors: Peng Eric W. , Ford Holland C. , Freeman Kenneth C.
Published: June 2019

We have conducted a wide-field optical survey of NGC 5128 (Cen A), the nearest large elliptical galaxy (3.5 Mpc). From UBVRI imaging and spectroscopic follow-up, we have identified and obtained kinematics for 125 new globular clusters out to a projected radius of 40 kpc. We also extend our survey of field star kinematics in NGC 5128, and now possess a total of 736 radial velocities for planetary nebulae out to a projected radius of 80 kpc.

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The PNe sample along the photometric major axis shows significant rotational support out to 80 kpc.

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The blue globular clusters seem to possess little or no angular momentum.

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The kinematics of the red globular cluster sample show some evidence for rotation around an axis common to that of the field stars.
The Disruption Time of Clusters in Different Galaxies
Authors: Boutloukos Stratos G. , Lamers Henny J.G.L.M.
Published: June 2019

If the cluster formation rate is constant and the disruption time of clusters depends only on their initial mass as tdis = t4 × (Mcl/104M⊙)γ, the values of t4 and γ can be derived in a very simple way from the age and mass histograms of observed clusters. We derived these values from cluster samples in fields of five galaxies: M51, M33, LMC, SMC and the solar neighbourhood. The values of γ are the same in the five galaxies with < γ > = 0.62 ± 0.03. However the disruption time t4 of clusters of 104M⊙ is very different in the different locations.
Possible Mechanisms of Single and Multiple Star Formation
Authors: Odgers G. J. , Stewart R. W.
Published: June 2019

If we suppose that at least some stars are the result of the gravitational collapse of HI clouds, it seems necessary to consider Jeans' criterion. This can be derived by a number of arguments, but for our purpose it is sufficient to consider it a result of dimensional analysis, and we get where G is the gravitational constant, M is a typical dimension, and V is a characteristic velocity comprising all velocities interior to the region of gas being considered.
On the Propagation and Structure of Ionization Fronts
Authors: Goldsworthy F. A.
Published: June 2019

The problem discussed here is that of determining the motion of a cloud of neutral atomic hydrogen gas, when it is subjected to ionizing radiation from a star embedded in it. Initially the gas is in gravitational equilibrium at a constant temperature of about 100°K. It is supposed that at time t=0 the star suddenly begins to radiate with a certain intensity, which remains constant thereafter. Part of the surrounding gas will be ionized and an ionization front (separating the ionized gas from the neutral gas) will move outwards into the neutral gas. A shock wave may also propagate ahead of the ionization front into the neutral gas. There will therefore be two regions to consider—a region of ionized gas (HII region) and a region of neutral gas (HI region) in which there may be a shock.
Collision of Two Highly Ionized Clouds of Gas
Authors: Kahn F. D.
Published: June 2019

If two rarefied masses of gas collide at a sufficiently high speed, their relative motion will be stopped by a collective plasma instability, rather than by collisions of individual particles. This is true even if the gases are initially non-ionized. In the present note, the possible influence of magnetic fields is ignored for the most part, but a criterion is found to decide under what conditions the collective interaction remains dominant even when they cannot be ignored. It seems that the neglect of magnetic effects may be justified, for example, in the case of two galaxies in collision at a relative speed of 1000 km/sec. The magnetic energy density here is (1/8π)H2∼4X10−12 erg/cm3 (with H∼10−5 gauss), which is much less than the kinetic energy density 1/2NmU2∼8X10−9 erg/cm3 (with N∼1 particle per cm3).
Distortion of a Toroidal Field by Convection
Authors: Allan D. W. , Bullard E. C.
Published: June 2019

In a perfectly conducting body the lines of magnetic force move with the material; the total number crossing the surface in either direction is therefore constant, and cannot be changed by motions of the material forming the body. Both in terrestrial magnetism and in sunspots, large changes in the external field are observed which do involve a change in the total number of lines and cannot be explained by a mere crowding together of lines of force that already cross the surface. In these phenomena loops of field must emerge through the surface, and the theory must involve the finite conductivity of the material.
Observational Foundations of Inhomogeneous Universe
Authors: Flin P. , Machalski J. , Maslowski J. , Urbanik M. , Zieba A. , Zieba S.
Published: June 2019

Using new observational data at optical (Jagiellonian Field) and radio (GB region) frequencies, the distributions of galaxies and radio sources are analysed.

The results of the analysis show that there is a significant non-random surface distribution of galaxies irrespective of the scale of the field investigated. The observed clumpiness does not allow us to introduce discrete hierarchical structures. The distribution of galaxies shows rather a continuous hierarchical structure and for the description of the distribution of galaxies, some density indices should be used instead of imprecisely defined clusters of galaxies.

In the radio domain, the distribution of radio sources in the GB region and the number-flux density relations which come from the different sub-regions are investigated. The results of our investigation show that the surface density of radio sources at several flux density levels and the number-flux density relations vary from place to place in the GB region and the significance level of the observed variations is at least 1%.

The most important conclusion which can be drawn from the GB data is that results obtained from the observations of a single selected region of the sky cannot be generalized to obtain information about the whole population of radio sources in a given flux density range, and in addition the region itself – even chosen at random – ought not to be considered as a typical one.
uvby Colours of Cepheid Variables
Authors: Bell R. A.
Published: June 2019

Synthetic stellar spectra have been computed for Cepheids and supergiant F and G stars, using flux constant model atmospheres. These spectra have been used to compute theoretical uvby and UBV colours which may be compared with the observed colours. The supergiant α Per is used to establish the zero points of the theoretical colours. The colour comparison can be used to determine the temperatures, gravities and metal abundances of the stars as well as an estimate of the interstellar reddening. The reddening determinations are carried out by arguing that the temperature and gravity values obtained from U – B and B – V must match those obtained from c1 and b – y.

A more detailed account of this work will be given elsewhere.
Multiple Periodicities in δ Scuti Stars
Authors: Shobbrook R. R. , Stobie R. S.
Published: June 2019

Four δ Scuti stars (θ Tuc, ϱ Phe, 1 Mon and 21 Mon) have been observed intensively in an effort to understand the periodicities present in these stars. The stars selected were known to be of variable amplitude and relatively large light range. The data of each star was Fourier analysed. In no case did the period ratios have values consistent with the period ratios of low order radial modes. The most interesting result appears in the analysis of 1 Mon. The three principal periodicities present occur at P1 = 0.13612, P2 = 0.13378 and P3 = 0.13855 days. To within the errors these periods form an equal frequency split, i.e. 1/P2 −1/P1 = 1/P1 −1/P3.
Explosive and Eruptive Stars
Authors: Schatzman E.
Published: June 2019

A summary of the main results and problems concerning explosive and eruptive stars is given. The way in which the observations are related to the internal structure problems is briefly explained. Suggestions for further work are made: (1) dynamo theory, supersonic turbulence, stability of the envelope of T Tau stars; (2) rate of exchange of matter in close binary as the final clue to the thermal runaway theory of novae.
The Oscillations and the Stability of Rotating Masses With Magnetic Fields
Authors: Kochhar R. K. , Trehan S. K.
Published: June 2019

It is shown that when a magnetic field is present along the axis of rotation, the point of bifurcation, where the Jacobi ellipsoids branch off from the Maclaurin spheroids, occurs at a value of eccentricity higher than the value e = 0.81267 that obtains in the absence of a magnetic field. This is in contrast with the effect of a toroidal magnetic field which, as has been shown earlier, leaves the point of bifurcation unaffected.
Internal Rotation, Mixing and Lithium Abundances
Authors: Chaboyer Brian
Published: June 2019

Lithium is an excellent tracer of mixing in stars as it is destroyed (by nuclear reactions) at a temperature around ~ 2.5 × 106 K. The lithium destruction zone is typically located in the radiative region of a star. If the radiative regions are stable, the observed surface value of lithium should remain constant with time. However, comparison of the meteoritic and photospheric Li abundances in the Sun indicate that the surface abundance of Li in the Sun has been depleted by more than two orders of magnitude. This is not predicted by solar models and is a long standing problem. Observations of Li in open clusters indicate that Li depletion is occurring on the main sequence. Furthermore, there is now compelling observational evidence that a spread of lithium abundances is present in nearly identical stars. This suggests that some transport process is occurring in stellar radiative regions. Helioseismic inversions support this conclusion, for they suggest that standard solar models need to be modified below the base of the convection zone. There are a number of possible theoretical explanations for this transport process. The relation between Li abundances, rotation rates and the presence of a tidally locked companion along with the observed internal rotation in the Sun indicate that the mixing is most likely induced by rotation. The current status of non-standard (particularly rotational) stellar models which attempt to account for the lithium observations are reviewed.
Large Scale Convection - Observations: How Does the Energy Flow?
Authors: Ulrich R.K.
Published: June 2019

Although the rate of production of nuclear energy in the sun's core almost certainly increases smoothly on time scales shorter than and comparable to the solar age, the mechanisms transporting this energy to the photosphere may be subject to more erratic fluctuations. Indeed space observations establish that the total solar irradiance in the direction of the earth is variable on time scales of days to years. I discuss energy transport by convection and magnetic fields with consideration of the possibility of energy storage through changes in the solar radius. Convection is the primary means of energy transport below the solar surface and must be involved in any modulation of energy flow. The large scale and long duration properties of solar convection arising from zones below the solar surface can be well studied using the Michelson-Doppler Imager instrument on SOHO. New evidence of long duration convective structures based on the MDI data is presented. These patterns appear to be related to the torsional oscillations observed at the Mt. Wilson Observatory.
Stellar Convective Cores
Authors: Roxburgh I.W.
Published: June 2019

The internal structure of stars is governed by hydrostatic support, the distribution of the chemical elements, the transport of energy by radiation and convection, and the liberation of energy by nuclear reactions. The evolution of stars is primarily determined by the changing composition due to the nuclear burning of elements in the central parts of the star, and the redistribution of the products of these reactions by mixing processes. The dominant mixing process is convection: it governs the extent of the mixed cores in moderate and large mass main sequence stars and their subsequent evolution, it mixes nuclear processed material into the envelopes of giants affecting the composition of material ejected into the interstellar medium, thereby affecting the chemical (and luminosity) evolution of galaxies. Understanding convection is essential if one is to understand the evolution of stars. Here I am concerned with convection in stellar cores and in particular with the extension of these cores by the penetration of convective motions into the surrounding stable layers affecting the internal structure and enlarging the chemically mixed region, which in turn affects the subsequent evolution. I briefly discuss a number of approaches to this problem: isochrone fitting of clusters and binary stars; simple theoretical models, the integral constraint, numerical simulation and what we can hope to get from asteroseismological observations of individual stars and of clusters and stellar groups.
Excitation and Damping of P-Modes
Authors: Nordlund Åke , Stein Robert F.
Published: June 2019

Millions of seismic eigenmodes are excited to low amplitudes in the Sun, with an amplitude spectrum that grows approximately as a power of the frequency until it reaches a maximum at 3 mHz, and then drops off again towards higher frequencies (Libbrecht, 1988; Libbrecht & Woodard, 1991).
Raman Spectroscopy of Solar P-Modes
Authors: Ryutova M.P. , Tarbell T.D.
Published: June 2019

According to observational data some regions of quiet sun show an excess, or the “emission” of acoustic waves. We propose a mechanism to explain the excess of the emission of acoustic waves based on nonlinear coupling of magnetic flux tube oscillations and the acoustic waves. We also suggest a new approach in the data analysis, which can be called “Raman spectroscopy of p-modes”. This new idea is based on the fact that oscillating flux tubes constructively interfere with the acoustic wave which results in the generation of beat waves with combinational frequencies: the power spectra of scattered waves in addition to main peak will have Stokes and anti-Stokes satellites. Their amplitude and frequency shift reflect the properties and the structure of the observed region.
On the Formation of Line Profiles of Solar P Modes
Authors: Roxburgh I.W. , Vorontsov S.V.
Published: June 2019

We address the problem of the opposite asymmetry of low-frequency p-mode line profiles observed in intensity and velocity measurements (Duvall et al. 1993). We use a simple model to illustrate that this feature can be explained by including a contribution from the stochastic excitation velocity field to the non-resonant background in the doppler measurements.
Results from the Hipparcos Mission on Stellar Seismology
Authors: Eyer L. , Grenon M.
Published: June 2019

Photometric results from the HIPPARCOS mission are of interest to stellar seismology. HIPPARCOS provides a general description of the HR diagram in terms of stability, microvariability and variability. The satellite has detected systematically variables with amplitudes exceeding a threshold, strongly magnitude dependent but as small as a few mmag for bright stars. When the signal is periodic, periods and amplitudes are determined. Because of the peculiar time sampling of HIPPARCOS only first modes and associated amplitudes are generally obtained. This information is particularly relevant to seismology in the case of pulsating stars as δ Scuti stars, slowly pulsating B stars and β Cephei stars.
Pulsations of Ob-Stars: New Observations
Authors: Baade Dietrich
Published: June 2019

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.
Asteroseismology from Equivalent Widths: A Test of the Sun
Authors: Keller C.U. , Harvey J.W. , Barden S.C. , Giampapa M.S. , Hill F. , Pilachowski C.A.
Published: June 2019

Kjeldsen et al. (1995) reported a probable detection of solar-like, low-amplitude p-mode oscillations in η Bootes using equivalent width measurements from low-resolution spectra of hydrogen Balmer lines. However, this detection has not been confirmed so far. Indeed, there is no confirmed detection of p-mode oscillations in a solar-like star using the equivalent width technique or any other approach (Bedding 1998).
Asteroseismology of the β Cephei Star 12 (DD) Lacertae
Authors: Dziembowski W.A. , Jerzykiewicz M.
Published: June 2019

The frequency spectrum in Fig. 1 shows that at least five pulsation modes are excited in DD Lac. Three frequencies, f1, f4, and f3, form an equidistant triplet. In addition to the value of the central frequency, f4, the triplet can be characterized by the mean separation, S = (f3 − f1)/2, and the asymmetry, Δf = f4 − (f1 + f3)/2. Taking the values of the frequencies from a recent analysis of all available data (Pigulski 1994), we get S = 0.15544 ± 0.00021 and Δf = −0.00014 ± 0.00029 d−1.
Line Profile Variations in the Spectra of the γ Dor Star HR 2740
Authors: Poretti E. , Mantegazza L. , Koen C. , Martinez P. , Breuer F. , De Alwis D. , Haupt H.
Published: June 2019

HR 2740 was a target for a photometric campaign carried out at La Silla (ESO) and Sutherland (SAAO) from 1997 January 14 to 1997 February 11 (Poretti et al., 1997). The campaign revealed that HR 2740 is one of the brightest γ Dor stars, a class of variable stars located near the cool border of the instability strip, and in which gravity pulsation modes are excited. Four frequencies were identified (f1=1.0434, f2=0.9951, f3=1.1088, f4=0.9019 c d−1), which together yield a satisfactory solution to the observed light curve. The frequency analysis was not simple, but thanks to the large coverage in longitude we could separate the effect of aliasing on the two terms f3=1.1088 c d−1 and f4=0.9019 c d−1, linked by the relationship f4 = 2 - f3. Moreover, only the long time baseline allowed us to resolve the two close terms f1=1.0434 c d−1 and f2=0.9951 c d−1. See Poretti et al. (1997) for a detailed discussion.
The Light Curves of Double-Mode Cepheids: The CO Aur Case
Authors: Poretti E. , Pardo I.
Published: June 2019

In two recent papers (Pardo & Poretti 1997; Poretti & Pardo 1997) we analyzed all the available photometry of galactic double-mode Cepheids (DMCs) with the aim of detecting in each case the importance of the harmonics and of the cross coupling terms. We found that no a priori fit can be reliably applied to the measurements of a DMC, but a careful frequency analysis must be done to evaluate the importance of each term. As a further application of this technique, we obtained very precise indications about the properties of the Fourier parameters. When discussing the generalized phase differences Gi,j we demonstrated that plotting them as a function of the order |i|+|j|, there are well-defined regions where they are confined: the second order terms have π < Gi,j < 3π/2; the third order terms have π/2 < Gi,j < π; the fourth order terms cluster around 2π.
Carbon Monoxide and the Temperature Structure of the Solar Atmosphere
Authors: Ayres T.R.
Published: June 2019

The themes woven into this review are: (1) the solar outer atmosphere is highly inhomogeneous; (2) anomalies in the behavior of particular wavelength intervals can signal key inconsistencies in an accepted model; and (3) the observations still hold surprises, particularly in the thermal infrared.
Phase Spectra Seen from Space
Authors: Straus Th. , Deubner F.-L. , Fleck B. , Marmolino C. , Severino G. , Tarbell T.
Published: June 2019

A 15 hour time series of simultaneous spectroscopic measurements of the continuum intensity, Doppler shift, and line depth in the Ni I 6768Å line at disk center of the quiet sun has been obtained during a guest investigator campaign with the Michelson Doppler Imager (MDI, see Scherrer et al. 1995). In addition, the line intensity has been calculated from the continuum intensity and the line depth data. The spatial shifts due to solar rotation have been approximately removed during the observation run by shifting the CCD read-out area by 1 pixel every 4 minutes. Small residual shifts have been removed during the data analysis. Before applying the Fourier analysis, a (temporal) low pass filtered mean velocity (line of sight component of solar rotation) and mean intensity (center-limb variation) has been removed from each frame. Finally, the continuum intensity (C), line intensity (I), and velocity (V) time series have been subjected to a 3D Fourier transform, yielding κ - ω power, cross power, phase difference, and coherence spectra. The data can now be compared to recent ground-based observations (Deubner, 1990; Deubner et al., 1992; Straus & Bonaccini, 1997).
Numerical Simulation of Twisted Solar Corona
Authors: Parhi S. , Pandey B.P. , Goossens M. , Lakhina G.S.
Published: June 2019

The solar corona supports a variety of waves generated by convective upwelling motion in the photosphere. In order to explain the observed coronal temperature profile, resonant absorption of MHD waves by coronal plasma (Goossens et al, 1995) has been proposed as a possible candidate. The physical picture is that the footpoint motion in the photosphere constantly stirs the coronal plasma leading to the MHD wave generation which is then resonantly absorbed producing the enhanced heating of the corona. Here we consider the problem of MHD wave propagation in a twisted solar corona.
Coronal Heating Mechanism in the Presence of a Flow: A Numerical Approach
Authors: Parhi S. , Tanaka T.
Published: June 2019

The solar corona is a hot, tenuous plasma permeated with the structured magnetic fields. A variety of waves is generated in the corona due to the convective upwelling motion in the photosphere. The excitation of MHD fluctuations is generated by the footpoint motion of the field lines in the photosphere. Resonant absorption of the Alfvén waves in an inhomogeneous plasma has been suggested as a means of driving current and plasma heating in the corona (Sakurai et al., 1991). We study this problem in the presence of flow.
From Clouds to Protostellar Cores
Authors: Saito Masao
Published: June 2019

Understanding the evolution of cores into protostellar envelopes is important in the star formation study. The initial condition of star formation such as density structure, kinematics, chemical composition, and magnetic field of dense cores can be derived from high resolution molecular line and continuum images at millimeter/submillimeter wavelengths. Besides, most low-mass stars are formed in clusters although the study of protoclusters is still rudimentary because of lack of observations with sufficiently high resolution to resolve individual cores/envelopes. High resolution observations with the coming SMA and ALMA will be crucial to testing and improving theoretical models of low-mass star formation.
First Results from ATCA at Millimetre Wavelengths
Authors: Minier Vincent
Published: June 2019

The newly upgraded Australia Telescope Compact Array (ATCA) at millimetre wavelengths is the first millimetre interferometer to be built in the Southern Hemisphere. The full array will be operational in 2004-2005 and will provide arcsec angular resolution at 3 mm and 12 mm. This will be a unique instrument to study at high angular resolution the interstellar chemistry and more generally the star formation process, especially in the bulk of the galactic plane and in the Magellanic Clouds. The upgraded ATCA will also be an excellent tool to detect dust emission from nearby protoplanetary disks. In this paper I will present the first results from the upgraded ATCA at 3 mm and 12 mm. The result review will cover the topics of massive star formation and hot molecular cores dust emission from star-forming regions and detection of protoplanetary disks.
High Resolution Optical and Infrared Images of Circumstellar Disks
Authors: Padgett Deborah , Stapelfeldt Karl
Published: June 2019

As the number of detected extrasolar planetary systems has steadily grown over the past five years, so too has the number of circumstellar disks with resolved images. In this contribution, we take stock of the current inventory of disk images in the optical and infrared; summarize the results of a new disk imaging survey conducted with the Hubble Space Telescope; review the major inferences that can be drawn about disk structure from the extant images; and suggest areas for future progress.
The Galactic radial gradient of velocity dispersion
Authors: Mayor Michel , Oblak Edouard
Published: June 2019

The kinematical study of the stars in the solar neighbourhood allows, via the equation of the so-called asymmetrical drift, to deduce the sum of the gradients of the density and the velocity dispersions, . In order to deduce the density gradients in the solar neighbourhood, the second term is generally supposed to be zero. This kind of hypothesis, certainly wrong, comes from the old “ellipsoidal theory”. A velocity dispersion independent of is not compatible with the Toomre's local stability. On the contrary, if we suppose negligible value compared with ∂1n (Mayor, 1974). Using Vandervoort's (1975) hydrodynamical approach, Erickson (1975) obtains a similar value for the local velocity-dispersion gradient.
The electron density in the plane of the Galaxy
Authors: Weisberg J. M. , Rankin J. M. , Boriakoff V.
Published: June 2019

Pulsars provide probably the best probes of electron density in the plane of the Galaxy. The dispersion measure, the path integral of electron density along the line of sight from the pulsar to Earth, ∫ neds, is directly measurable from multi-frequency pulse-timing observations. The distance to a pulsar, d, can be estimated from its HI absorption and emission spectra. The mean electron density along the line of sight is then just  = ∫ neds/d.
The magnetic-field structure and dynamics of NGC 253
Authors: Urbanik M. , Klein U. , Beck R. , Wielebinski R.
Published: June 2019

Total-power and polarization observations of NGC 253 at 10.7 GHz have been performed with the 100-m MPIfR radio telescope. The observed arm/interarm polarization contrasts are discussed in the context of possible field configurations in spiral arms.
A comparison of the Andromeda and Milky Way galaxies
Authors: Hodge Paul
Published: June 2019

A comparison of some of the basic properties of M31 and the Milky Way indicates that in almost every respect M31 is larger than the Galaxy. It is more luminous, redder, more massive, and of earlier Hubble type. A detailed comparison of the spiral structure, based on optical tracers, for comparable areas in the outer parts of each galaxy shows differences in the arm spacings, in density enhancement, and in pitch angle.
Large-scale maps of M31 at middle and far infrared wavelengths
Authors: Habing H. J.
Published: June 2019

The satellite IRAS (see Neugebauer et al. 1984; see also Gautier and Hauser, this volume) was in operation from January 27 until November 22, 1983. Its main goals were to carry out a survey of the sky at 12, 25, 60, and 100 micron and to make observations around selected positions achieving higher sensitivity or better angular resolution than provided in the survey. Among the very first targets of these pointed observations was the Andromeda galaxy, M31, because it was considered of prime importance and was about to leave the observing window. Here we report briefly on crude maps made from the first measurements. A more elaborate presentation may be found in Habing et al. (1984) and a publication of all the data on M31 is planned for the future.
Tidal interactions between the Galaxy and the Magellanic Clouds
Authors: Ramamani N. , Singh T. Meinya , Alladin Saleh Mohammed
Published: June 2019

The merging time and the disruption time in a binary galaxy system are analytically obtained under the Adiabatic Approximation (AA). Applications are made to the Galaxy-LMC (Large Magellanic Cloud) pair.
A barred galaxy: the inside viewpoint
Authors: Van Albada G.D.
Published: June 2019

The observed gas distribution and kinematics in the central 4 kpc of our Galaxy show many aspects reminiscent of barred spirals. In this note I describe a collection of (l,v) maps obtained from a gas flow model of a barred spiral.
Kinematical and chemical evolution of the Galactic disk
Authors: Lacey Cedric G. , Fall S. Michael
Published: June 2019

We have calculated models for the kinematical and chemical evolution of the Galactic disk that include the infall of metal-free gas and the stochastic acceleration of disk stars. Our models are similar in some respects to those of Chiosi (1980) and Vader & de Jong (1981), but the results are compared with a greater variety of observational data. A complete description of this work will appear shortly in Monthly Notices of the Royal Astronomical Society.
Secular evolution in galaxies
Authors: May A. , Norman C. A. , Van Albada T.S.
Published: June 2019

We have adapted the N-body code of Van Albada (1982) to study the secular evolution of a hot collisionless stellar component (E galaxy or galactic bulge) due to slow changes in another component of the same galaxy. Our equilibrium starting model is a non-rotating triaxial ellipsoid with axial ratios 1.3:1.4:2.0; the effects of the “other component” are then simulated by various simple means.
Gas dynamics and disk-galaxy evolution
Authors: Carlberg R. G.
Published: June 2019

Gas dynamics plays a vital role in the formation and ongoing evolution of a disk galaxy through its ability to have dissipative collisions. In this paper the simplest possible gas physics which provides a description of a gaseous component is incorporated into N-body experiments to investigate the formation of a disk galaxy.
Karian Sites and Inscriptions.—Part II
Authors: Paton W. R. , Myres J. L.
Published: June 2019

A Short journey round the north side of Mt. Latmos, undertaken in the autumn of 1896, has enabled W.R.P. to complete his investigation of the ancient sites of this neighbourhood. The purely geographical results are appended to our paper in Journ. Roy. Geogr. Soc. ix. (January, 1897), and are incorporated in the map which, by the courtesy of the Royal Geographical Society, we are able to append to this account of the archaeological results. The latter are arranged in geographical order along the actual route.

At Sirgin Kishla on the Deniz Liman (Latmic Gulf) the fortified site or ‘kastron’ turns out to be a late mediaeval settlement.
VIII.—An Analytical Theory of the Equilibrium of an Isotropic Elastic Plate
Authors: Dougall John
Published: June 2019

The following paper contains a purely analytical discussion of the problem of the deformation of an isotropic elastic plate under given forces. The problem is an unusually interesting one. It was the first to be attacked (by Lamé and Clapeyron in 1828) after the establishment of the general equations by Navier. The solution of the problem of normal traction given by these authors, when reduced to its simplest form, involves double integrals of simple harmonic functions of the coordinates. The integrals are of complicated form, and practically impossible to interpret, a fact which, without doubt, has had much to do with the neglect of the problem in later times, and the almost complete absence of attempts to establish the approximate theory on the basis of an exact solution. An even more serious defect of Lamé and Clapeyron's solution is that the integrals, as they stand, do not converge. A flaw of this sort has often been treated lightly by physical writers, the non-convergence of an integral being regarded as due to the inclusion of an infinite but unimportant constant. In the present case, however, the infinite terms are not constant, but functions of the coordinates, and the modifications necessary to secure convergence, so far from being unimportant, lead directly to the most significant terms of the solution.
VIII / Mogollon Subsistence
Authors: Wheat Joe Ben
Published: June 2019

Of the basic elements of the Mogollon subsistence pattern there can be little doubt. Hunting, gathering, and agriculture each played its part. However, the question of relative importance of each in the total pattern has never been satisfactorily answered. There is ample evidence that each was practised; but only for one small area do we have the quantitative data necessary to assess their status.

A rich fauna recovered at Harris and Mogollon villages led Haury to postulate heavy reliance on hunting as well as on agriculture (Haury 1936b:92-93). A similar situation prevailed at Forestdale Ruin during Mogollon 3, where the number of deer bones recovered makes it seem likely that as much reliance was placed on hunting as on agriculture (Haury 1941).
XI / Bases for Comparison
Authors: Wheat Joe Ben
Published: June 2019

In the preceding part of this study I have tried to determine the functional trait constellation and cultural orientation of the Mog oil on people. In the following pages I shall attempt to trace the relationships of this group to other Southwestern groups, both prior and contemporaneous. In this paper I am not concerned with the relative taxonomic status of the various groups. Haury, Colton, Reed, Martin, Rinaldo, Nesbitt, Brew, and others have discussed various aspects of this problem at some length. Much of the Mogollon controversy has been philosophical and semantic in orientation and it does not seem necessary to review the various arguments here. Clearly there were temporal and cultural differences, as well as similarities, between these groups, and it is the examination of the nature and extent of these aspects that I propose.
New Powerful Methods for Photometry of CCD Images in Crowded Fields
Authors: Alard C.
Published: June 2019

Image subtraction is an interesting new alternative to the classical profile fitting method (DAOPHOT or DoPHOT) for finding variable stars and producing their light curves. In crowded fields this new method can lead to large improvements in the photometric accuracy. The method is based on finding the best kernel solution in order to match two images as closely as possible. This approach leads to simple mathematical equations. It is possible to find a general solution to these equations which require very reasonable computing times. It is also shown that even in the case of a spatially variable kernel an optimal solution can be found with minimum computing time. Constant flux scaling can be imposed in this case without changing the basis of the algorithm. The method is illustrated using a set of images of the central region of the globular cluster M5. Only 26 variables were found by processing this data set with DoPHOT, while 61 were found with image subtraction. A large photometric improvement was also found for the 26 variables in common. The maximum improvement achieved by using image subtraction was a factor of 20 with respect to DoPHOT. The accuracy achieved with image subtraction is comparable to what was achieved with HST in a small region around the M5 center. One consequence of this photometric improvement was the discovery of an RR Lyrae star pulsating in a nonradial mode in M5. Finally, it is concluded that image subtraction is a technique of choice when dealing with variability, and that it is important to use it when the field is crowded. It is also important to note that image subtraction may open new possibilities in the investigation of very crowded fields, even with relatively small telescope from the ground.
Large-Scale Surveys and the GCVS
Authors: Samus N. N. , Kazarovets E. V. , Durlevich O. V.
Published: June 2019

We briefly discuss changes in the work on the General Catalogue of Variable Stars (GCVS) necessary in the era of automatic variability discoveries and large-scale surveys.