bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ground-Based Observations of Mars and Venus Water Vapor during 1972 and 1973
Authors: Barker E. S. 
Published: July 2016

The Venus water vapor line at 8197.71 Å has been monitored at several positions on the disk of Venus and at phase angles between 22° and 91°. Variations in the abundance have been found with both position and time. The total two-way transmission has varied from less than 5 to 77 μ of water vapor. Comparisons will be made between the water vapor abundances, presence of UV features, and the CO2 abundances determined from near simultaneous observations of CO2 bands at the same positions on the disk of Venus.The amount of Martian atmospheric water vapor has been monitored during the past two years at McDonald Observatory using the échelle coudé scanner of the 272 cm reflector. Two periods of the Martian year have been monitored. The first period was during and after the great 1971 dust storm (L8 = 280° to 20° or summer in the southern hemisphere). The results obtained will be compared to the Mariner 9 IRIS and Mars 3 observations made during the same period.During the second period (L8 = 124° to 266°) observations were made to follow the seasonal latitudinal and diurnal changes in the water vapor abundance in the Martian atmosphere. The water vapor abundance declines from a maximum of 20–35 μm at L8 = 125° to the 5–15 μm level at L8 = 180°. Then it remained relatively constant until L8 = 250° when the increase to 20–25 μm occurred in the southern latitudes. Studies of the latitudinal and diurnal water vapor distributions indicate the location of maximum and minimum abundances for this season are positively correlated with surface temperature variations.
Results of the Beta Scorpii Occultation by Jupiter on May 13, 1971
Authors: Vapillon L. 
Published: July 2016

The aim of this paper is to present results of temperature and density profiles of the upper atmosphere of Jupiter as deduced from observation of the occultation of β Sco on May 13, 1971.The occultation light curve of β Sco is shown. The analysis of data is based on the Abelian integral inversion. Jovian refractivity profiles and typical temperature and density profiles are also shown.The extent of the atmospheric zone where results are significant is discussed.It is shown that no valid information about the thermosphere has been obtained.
Kinematics of Molecules at the Galactic Centre
Authors: Robinson B. J. 
Published: July 2016

Dense gas clouds containing OH, CO, NH3 and H2CO are found in the inner part of the H1 nuclear disk. The molecular spectral lines allow direct observations of the kinematics of the gas near the galactic centre. Strong absorption of the thermal continuum sources by OH and H2CO shows that much of the gas on the near side of the centre can be located in a massive ‘ring’ expanding at 130 km s-1 which may have originated close to the nucleus about 106yr ago. Observations of CO emission from beyond the centre show that the far side of the ‘ring’ is expanding at a lower velocity, less than 90 km s-1. Observations of CO and NH3 emission with positive velocities for l < 360° are needed to establish whether the ‘ring’ is a continuous structure.OH and H2CO are also observed to be falling towards the centre. There is no agreement as to the location of this infalling matter.The nuclear regions of the Galaxy are compared with those of NGC 253, particularly in regard to expansional velocities, IR and radio emission, and OH absorption.
Extended Structure in High-Redshift Radio Sources
Authors: Duffett-Smith P. J. , Purvis A. 
Published: July 2016

We have compared measurements of several hundred 3C and 4C radio sources at large redshifts to investigate how radio-source structure changes over a factor of 5–10 in luminosity. Our results show that for z ≳ 0.6:
(i)most sources (both 3C and 4C) have hotspots about 3.5 kpc in size (Ho = 50 km s−1 Mpc−1, Ω = 1);(ii)lower-luminosity sources (bottom of 4C) have less-extended outer lobes.
Hot-Spots in Luminous Extragalactic Radio Sources
Authors: Laing R. A. 
Published: July 2016

Compact hot-spots in luminous extragalactic radio sources are often double on the scale of a few kpc (Laing 1981a). Examples are shown in Figures 1–3; the maps were made with the A and B configurations of the VLA. The general features are as follows:
(a)It is usually possible to recognize a compact, “active” subcomponent within a radio lobe. This has a size of <1 kpc and may only contain a small fraction of the total flux of the hot-spot. It need not be at the leading edge.(b)More diffuse regions are often grossly offset from the source axis (e.g. 3C 196). In some cases, there is apparent inversion symmetry about the optical identification.(c)The characteristic morphology of a diffuse subcomponent is best illustrated by the eastern hot-spot of 3C 20, which is limb-brightened, with a circumferential magnetic field. The bright edge is on the side furthest away from the compact subcomponent.(d)The polarization structure in the diffuse subcomponents, like that in most extended radio lobes, can be explained if the magnetic field has been sheared so as to be tangential to the surface, but is otherwise random (Laing 1980; 1981b).(e)The most obvious explanation for the multiple structure is that the compact subcomponents represent the points of impact on the surrounding gas of twin beams from the associated galactic nucleus; if these alter their direction, then diffuse remnants may be formed. This idea would be consistent with the inversion symmetry seen, for example, in 3C 196.(f)A problem with this model is posed by the detailed morphology of the diffuse subcomponents: why should the bright limb be opposite the compact subcomponent, rather than at the leading edge of the source? An alternative picture, in which the diffuse subcomponents are formed by material escaping from the active regions, should also be considered.
The Wolf-Rayet Stars in 30 Doradus
Authors: Melnick Jorge 
Published: July 2016

Giant HII regions as sites of massive star formation.Giant HII regions are the brightest extragalactic emission line objects that can be studied in detail. With diameters of several hundreds of parsecs, these nebulae can be easily resolved out to distances of a few Mpc. Typically 100 or more 0 stars are required to account for the observed ionization of the nebular gas and this implies that the cores of giant HII regions contain populous young star clusters. The stars in these clusters have essentially the same age and chemical composition. Thus, giant HII region cores provide excellent sites where theories of the formation and evolution of massive stars and, in particular, of Wolf-Rayet (WR) stars can be tested.
First Solar Radar Observations in Microwaves
Authors: Benz A. O. , Fitze H. R. 
Published: July 2016

(Paper to be submitted to The Astrophysical Journal)A first solar radar experiment in microwaves has been carried out with the 300 m dish in Arecibo. *The goal was to scatter the radio waves at 2380 MHz on coronal Langmuir waves in the range from 170 to 270 MHz. The nonlinear interaction of these two wave modes produce a radio signal in backward direction at the beat frequencies
Receiption was at 2600 MHz with a bandwidth of 100 MHz. The transmitter of 250 kW power was pulsed in periods between 0.5 and 1.5 s. The received flux was Fourier analysed and searched for the transmitter period.
Observation of a Coronal Impulsive X-ray Burst and its Implications Regarding the Associated Microwave Source
Authors: Kane Sharad R. 
Published: July 2016

SummaryRadial structure of impulsive hard X-ray and microwave sources in solar flares is not well known at the present time. Measurements of near-the-limb flares with a high spatial and temporal resolution is, of course, the best way to determine the radial structure of these sources. In absence of such measurements, particularly for the hard X-ray emission, behind-the-limb flares provide (through occultation) a means of observing the coronal part of the impulsive source. Here we summarize the characteristics of the impulsive coronal X-ray source deduced from multi-spacecraft observations of a behind-the-limb flare and their implications with respect to impulsive microwave source.
Light Variations in Several Broad-Lined B Stars
Authors: Jerzykiewicz M. , Sterken C. 
Published: July 2016

In our photoelectric searches for the β Cephei variables (JS77, JS79, and J82) several early B stars with nebulous lines were included. A summary of their photometric behaviour is presented in Table 1, columns four to six. Two of the stars, HR 2963 and HR 3476, areapparently constant in light, HR 3213 is a short-period β Cephei star, HR 3462 shews ellipsoidal variations with a period of Od.563, which implies an orbital period twice that long (cf. also Shobbrook 1981), and HR 8854 is an eclipsing binary with P = 2d.3913.
The Strongly Polarized P Cygni Star with Infrared Excess CPD −52° 9243
Authors: Swings J. P. 
Published: July 2016

The visible spectrum of the point-like source with infrared excess CPD-52°9243 is identified; emission and absorption line strengths are given together with various ion velocities of P Cygni profiles; a strong polarization is detected: P ≃ 5 %, θ ≃ 36°. From stellar and interstellar features, a spectral type around B8Ia and a distance of about 3.1 kpcs are derived.A detailed publication is presently in press in Astronomy and Astrophysics.
Density of Meteoroids and Their Mass Influx on the Earth
Authors: Babadzhanov Pulat B. 
Published: July 2016

According to the investigation technique it is customary to divide meteoroids into three groups: 1) micrometeorites, with masses between 10–13 g and 10–6 g, and densities between 0.4 and 4 g/cm3; 2) meteorites, for which the chemical composition is studied in detail, and having densities from 2 to 8 g/cm3; 3) meteoroids proper, with masses larger than 10–6 g, which produce meteoric phenomena in the Earth's atmosphere detected by optical and radar means.On the basis of available photographic and radar observations in Dushanbe the influx M(m) of meteoroids with mass equal or greater than m is determined as log in kg to the Earth per day. This formula is applicable to a mass range from 10–6 g to 102 g.The phenomenon of meteoroid fragmentation in the atmosphere was observed repeatedly by means of different methods and especially using the photographic technique of instantaneous exposure. Among four principal forms of fragmentation, the quasi-continuous fragmentation, i.e. a gradual release of smallest fragments from the surface of a parent meteoroid and their subsequent evaporation, is most common. The analysis of photographic observations shows that about 30% of meteoroids display this type of fragmentation. According to the theory of quasi-continuous fragmentation and on the basis of lightcurves of meteors, the densities of 85 meteoroids have been determined, which vary in the range from 0.1 to 8 g/cm3. Not only porous and crumbly meteoroids but more dense stony and stony-iron meteoroids are also the subjects of fragmentation as well.
A new radio telescope of high resolving power
Authors: Khaĭkin S. E. , Kaĭdanovskiĭ N. L. 
Published: July 2016

Attempts to construct large parabolic reflectors for microwaves have met with the following difficulty. For normal operation of radio telescopes, the form of the reflecting surface must not deviate from the theoretical by more than 0.1λ; therefore, the larger its size the higher the requirements for relative accuracy (i.e., the ratio of the largest permissible deviation to the cross-section of the reflector). So far, a relative accuracy better than 10–4 has not been attained in any of the existing radio telescopes, and there are no grounds for supposing that it can be increased considerably.Since the deviation from the theoretical form of the surface should not be more than 0.1λ, then for a relative accuracy of 10–4, the diameter of the reflector D cannot be much larger than 1000λ, and the beamwidth cannot be less than 3 minutes of arc (the beam angle is equal to about λ/D at half-power width).
Some problems on the classification of M, S and C-type stars
Authors: Fujita Y. , Yamashita Y. , Kamijo F. , Tsuji T. , Utsumi K. 
Published: July 2016

Sixty spectrograms of 25 M-, S- and C-type stars obtained with the spectrographs attached to the 72-inch reflector of the Dominion Astrophysical Observatory, Victoria, have been analysed and the equivalent widths of some atomic lines and molecular bands have been measured.The relation of C2Swan band and SiC2Merrill-Sanford band intensities with the C classification and of TiO, ScO, VO and YO band intensities with the M and S classification were investigated. The correlation between the temperature sequence of the spectral type M, S and C and corresponding sub-classification was discussed and the assignment of the C subtype equivalent to the M subtype with respect to the excitation temperature was tentatively tried. The relation of absolute intensities with the spectral type was also discussed.
The Surprising Constancy of Relative Chemical Abundances in Different Regions of Interstellar Space – Particularly for Formaldehyde
Authors: Heiles Carl , Gordon M. A. 
Published: July 2016

Many of the places in which radio astronomers search for molecules are located in exotic regions lying near the galactic center, near H II regions or other continuum sources, or in high density regions. Such regions have wide variations in their physical environment. Here we wish to compare two types of region whose environments are thought to be well-understood. One of these is dust clouds; the other is unshielded (from UV) cold clouds in front of bright radio sources. For the sake of interest, we include without comment results for molecular regions near the Galactic center and near Orion A.Comparison of dust clouds and unshielded clouds is of interest because the volume density differs by a factor of 104 or more and the extinction differs by 8 mag. or more. Neither type of cloud lies near H II regions or other sources of intense radiation. Even though their properties differ widely, we will see that the abundances of OH and H2CO relative to hydrogen are approximately the same in the two. Although this is understandable for OH, no current theory would predict this situation for H2CO.
Disks and Outflows as seen from the IRAM Interferometer
Authors: Guilloteau S. , Dutrey A. , Gueth F. 
Published: July 2016

The IRAM interferometer has been used to map 3 high velocity outflows from Class 0 sources in SiO and CO rotational lines. The images show that such outflows are driven by highly collimated, dense, but optically invisible jets, through large travelling bow shocks. Precession is important in explaining some morphological and kinematic aspects. A significant part of the SiO emission is directly associated with the jet. Images of the molecular core surrounding L 1157 in CO isotopic lines show direct evidence for infall in a large, flattened disk.For more evolved objects, “surveys” of mm emission from T Tauri stars provide evidence for circumstellar dust disks with relatively flat surface density distribution and typical radii 100 to 200 AU. Much larger gas disks (radii 800 to 1000 AU) have been detected and imaged in a few objects (2 singles and 2 binaries) through CO isotopomers, but in most sources 13CO is difficult to detect. The spectral line images provide unambiguous evidence for Keplerian rotation. In two cases (GG Tau and DM Tau), direct measurements of the gas mass (independently of the dust) has been made thanks to the detection of 7 molecular species. The molecules are found to be depleted by factors between 5 (for CO) to 100 (for H2CO). These results suggest that circumstellar disks consist in a small, dense, inner disk of outer radius ≃ 150AU (traced by the dust emission), surrounded by a much larger, less massive, outer disk (traced by the gas emission).
Close Binaries Before and After Mass Exchange: A Comparison of Observations through Theoretical Computations
Authors: De Grève J. P. , Vanbeveren D. 
Published: July 2016

From a search through the literature 174 close binaries with completely known absolute dimensions are sampled. Distinction is made between systems before and after mass exchange, giving resp. 100 and 40 systems (a third group contains the systems not definitely belonging to these two). Mass, period and mass ratio distributions and relations of the group of “unevolved” binaries (i.e. prior to mass exchange) are transformed into corresponding distributions and relations of evolved binaries. The transformations are based upon the M1 f = g (M1 i) relation derived from an extended set of published theoretical computations on the evolution of close binaries. Final masses resulting from the same initial mass are averaged. Equations are derived for the cases A (for all masses), B1 (M1 i/Mo < 2.8), B2 (2.8 < M1 i/Mo < 9) and B3 (M1 i/Mo > 9). For the changes of the period due to angular momentum loss the formalism of Vanbeveren et al. (1979) was adopted. The following characteristics of the system after mass exchange are computed: M1 f, M2 f (and qf), Pf. Three different modes were applied for the mass loss from the system:a) conservative case (mass and angular momentum of the system remain constant), called C.b) non conservative case with 50% of the transferred mass leaving the system with a small or a large angular momentum loss (resp. called NC51 and NC53).c) non conservative case with 100% of the transferred mass leaving the system with a small or a large angular momentum loss (resp. called NC101 and NC103).
Results from an absolute test of the NPL dispersometer over 4 km
Authors: Williams D. C. 
Published: July 2016

The NPL instrument to correct for angular refraction in geodesy measures the small dispersion between images of red (633 nm) and blue (442 nm) laser sources formed by a telescope. It uses a rotating chopper disc in association with an optical compensator plate and a phase null meter. The instrument and some early field tests have been described in detail elsewhere (Williams, D.C., 1978).Absolute tests of the prototype have recently been made over a 4 km suburban range at an average height of 30 m. The apparent elevation of the red laser was observed with a T3 theodolite and corrected for refraction, the laser and theodolite being referred to local bench marks with a known height difference determined by spirit levelling.On an occasion in late May 1978, the effects of turbulence were particularly small. The refraction-corrected theodolite readings then agreed with the expected value to within one sexagesimal second. Other results obtained during the preceding two months indicate that increasing turbulence causes the dispersion angle to appear too large, the greatest error observed being about 3 seconds of refraction. It is thought that most of the turbulence was due to effluent from chimneys, and that the apparent error may be due to an instrumental effect which has not yet been identified.The performance of the instrument has also been evaluated on a 20 km range near Uppsala during the present Symposium, by kind invitation of Prof. E. Tengström. The principal difference from the 4 km range was that the intensity scintillations of the red and blue signals were no longer correlated when the refraction was large. Independent compensation of red and blue signals for this effect should enable good results to be obtained over this distance.The author wishes to acknowledge the help of S-G. Mårtensson and S. Eklund (University of Uppsala) and A.J. Griffiths (NPL) in performing the tests.
Experiences from IDM measurements at the test base of the Geodetic Institute of Uppsala University
Authors: Mårtensson S-G. 
Published: July 2016

IDM measurements carried out in Uppsala sometimes show violent changes in refraction over short periods of time.The explanation for these changes might be found if the dynamics of atmospheric turbulence is taken into consideration.It is too early to make scientific conclusions from the material collected so far, but observations show the way this particular problem can be handled in the future.The paper presented, reflects some of the turbulence effects achieved by the IDM instrument constructed by prof. E. Tengström.
Solar and Interplanetary Dynamics (Symposium Summary)
Authors: Kuperus M. 
Published: July 2016

Solar and interplanetary dynamics comprises dynamic and plasma-physical phenomena in the solar atmosphere, the corona and the interplanetary medium in the broadest sense. In this symposium, however, one has essentially tried to restrict the subject matter to the study of the propagation of a disturbance, produced in the solar atmosphere, through the corona and the interplanetary medium. In studying solar and interplanetary dynamical phenomena we find ourselves in the unique position, with respect to other astrophysical disciplines, to be able to relate solar observations obtained with the highest possible spectral, spatial and time resolution with in situ measurements made in the interplanetary medium. It has now turned out that the two fundamental questions to be answered are:a) How does the medium in between the sun and the earth and beyond the earth's orbit, the socalled heliosphere, look like? Does a basic undisturbed heliosphere actually exist, and is one able to model its observed magnetic structures and plasma motions with their spatial and temporal variations?b) How and where in the solar atmosphere are the disturbances generated and what are the characteristic time scales, geometries and energies involved?
Potentialities of Yale Astrometric Materials
Authors: Hoffleit E. D. 
Published: July 2016

A brief summary is given of the plate materials and results obtained at Yale since the advent of photographic astrometry. The distributions of plates not yet measured or reduced are indicated and possible supplementary programmes for their effective utilization are discussed. Interest centres chiefly in the following areas:(1) The unmeasured parallax plates.(2) Reduction of the −60° to −70° zone catalogue.(3) The El Leoncito programmes for the determination of both positions and proper motions relative to faint galaxies.(4) The feasibility of a search for intrinsically faint nearby stars with the Yale 40-in. at Cerro Tololo and the 20-in. double astrograph at El Leoncito.
Proper Motion and Parallax Programmes for Large Telescopes
Authors: Murray C. A. 
Published: July 2016

Proper motion work at the present time relies on the availability of plates taken in the past, for which the magnitude limit is generally not fainter than about mpg = 16, apart from Luyten's survey with the Palomar Schmidt. It is very important for future studies to fainter magnitudes in, for example, star clusters, that sufficient time is made available on large telescopes so that plates can be taken now. Consideration should also be given to an extension of proper motion work in Selected Areas.Ideally, trigonometric parallax observations are best carried out on a dedicated telescope, such as the USNO 61-in. reflector, with a large amount of time available; but if sufficient observational material is to be obtained on faint stars, time must also be taken on other medium sized and large reflectors. With the severe limitation of time available on these telescopes, the criteria for selection of stars for such programmes become of prime importance. Large Schmidt telescopes, with fast automatic plate measurement, may possibly be used for surveys of nearby stars, unbiased by any kinematic or photometric selection effects.