bluuebunny/crossref_metadata_2025 huggingface dataset:
CP violating vacuum transition and Big Bang Nucleosynthesis
Authors: Duorah H. L. , Das R. K.
Published: June 2019

An analysis of primordial nucleosynthesis is made in the perspective of transition in the early universe from quark gluon to a hadronic phase in a CP violating vacuum. The universe opaque to color, quarks and anti quarks binds into globally colorless hadrons. u, d and s quarks are considered in a sea of degenerate neutrinos for the case of μve = μvμ = μvτ. The nn/np ratio is calculated for a transition temperature ˜ 100 − 200MeV for various values of neutrino degeneracy ξve = μve/T, μve being the chemical potential of electron type neutrino. The limiting value of ξve is found to be 2.38, if the upper bound of fractional helium abundance Yp is 0.26.
RATAN-600 as Multibeam Radio Telescope for CMBA Observations
Authors: Khaikin V. , Majorova E.
Published: June 2019

The characteristics of the RATAN-600 radio telescope in multi-beam mode for CMBA observations are presented. First results of 8-element MMIC focal array testing are given.
Surveying the foreground sources for the Very Small Array, with the Ryle Telescope at 15 GHz
Authors: Waldram E. M. , Pooley G. G.
Published: June 2019

The three fields chosen for the first observations with the Very Small Array (VSA), a total area of ˜ 200 deg2, are being surveyed with the Ryle Telescope at 15 GHz. This is the only wide-field survey at a comparable radio frequency; its purpose is to investigate the source population and to define a catalogue of the foreground sources which must be monitored by the VSA during its observations. We present preliminary source counts.
VLBI observations of H2O masers in the LkHα 234 star-forming region
Authors: Umemoto Tomofumi , Imai Hiroshi , Furuya Ray S. , Kitamura Yoshimi , Kawabe Ryouhei
Published: June 2019

We made observations of H2O masers in the LkHα 234 star forming region using the Japanese domestic VLBI network (J-Net). We first present spatial and velocity structures of the maser sources of C1 and C3 which are detected by Tofani et al.(1995). The distribution of H2O maser components in C1 shows an extent of 300×150 AU. On the other hand, it shows a compact and linear extent of 15×3 AU in C3, and its position angle (RA.=232 °) roughly agrees with that of the H2 jet (PA.=226 °). Moreover, the most blue-shifted and red-shifted maser components are located at both ends of the linear extent, indicating that this might be a very small jet ejected from the deeply embedded protostar. However, it is difficult to explain the distribution of intermediate velocity components by a simple jet model. We will discuss whether the H2O masers originate in a jet or a disk.
mm-VLBI observations of SiO masers: Further support for radiative pumping and rotation of the inner shell
Authors: Desmurs Jean-François , Bujarrabal Valentín , Colomer Francisco , Alcolea Javier
Published: June 2019

We have performed VLBA observations of the SiO v = 1 and v = 2 J = 1-0 masers in two AGB stars, TX Cam and IRC +10011. We confirm the ring-like spatial distribution, previously found in several AGB objects, as well as the tangential polarization pattern, already reported for TX Cam. Both properties, that seem to be systematic in this kind of objects, are characteristic of radiatively pumped SiO masers. On the contrary, we do not confirm the previous report on the spatial coincidence between the J = 1-0 v = 1 and 2 masers, a result that would have argued in favor of collisional pumping. We find that both lines sometimes arise from nearby spots, typically separated by 1-2 mas, but are rarely coincident. The discrepancy with previous results is explained by the very high spatial resolution of our observations, ∼ 0.5 mas, an order of magnitude better than in the relevant previously published experiment. Moreover, we have been able to measure a probable rotation of the inner shell of a few km/s. Rotation of circumstellar shells is assumed by the most convincing models explaining the drastic change of symmetry between the AGB envelopes (spherical symmetry) and Proto Planetary Nebulae (axial symmetry).
Interferometric observations of OH and H2O masers in protoplanetary nebulae imaged with HST - A unique diagnostic of their spatial-kinematic structure
Authors: Sahai Raghvendra , Claussen Mark J. , Morris Mark
Published: June 2019

One of the most exciting challenge facing theories of post-main sequence evolution today is to understand how Asymptotic Giant Branch (AGB) stars transform themselves into aspherical planetary nebulae (PNe). Recently, high-resolution imaging surveys of young planetary nebulae and protoplanetary nebulae (PPNe: objects in transition between the AGB and PN phases) have revealed that the majority of these objects are characterised by multipolar bubbles distributed roughly point-symmetrically around the central star. These data strongly suggest that the current model for the shaping of PNe is no longer adequate. High angular-resolution kinematic information is sorely needed to complement the imaging data in order to test new hypotheses, such as our proposal that episodic high-speed jet-like outflows, operating during the protoplanetary or very late-AGB phase, are the primary agent.

We have therefore begun a program of using interferometric mapping of OH (and H2O, when feasible) maser emission in order to trace the kinematics of the structures discovered in protoplanetary nebulae with HST. These masers provide a unique and crucial probe of the kinematics of the circumstellar material in PPNe, because of the lack of other emission-line diagnostics. Although our work is still in its infancy (only two objects have been studied in detail), we find that the OH masers indicate the presence of multiple low-latitude outflows and an increase of outflow velocity with latitude. This paper summarises our progress so far, the state of current studies, and future prospects.
The Globular Clusters of the Fornax Dwarf Spheroidal Galaxy: Properties, Environment
Authors: Hardy Eduardo
Published: June 2019

The power of HST to resolve dense stellar aggregates is such that most of the relevant information on the stellar populations of Fornax was obtained only recently. These results are presented here both for the globular clusters and for the field. But Fornax has probably been the most often studied dSph galaxy, partly on account of its abundant system of globular clusters. A brief retrospective is presented, not only for its historical interest but also because it reveals the striking improvement in observational tools and analysis techniques that has taken place over the last twenty years.
Age as the Second Parameter in NGC 288/NGC 362?
Authors: Catelan M. , Bellazzini M. , Ferraro F. R. , Pecci F. Fusi , Galleti S. , Landsman W. B.
Published: June 2019

We derive the age difference between NGC 288 and NGC 362 using the bimodal horizontal branch (HB) of NGC 1851 as a “bridge” in the CMD analysis. Our results suggest that NGC 288 is older than both NGC 362 and NGC 1851 by ⋍ 2 ± 1 Gyr. A new grid of synthetic HBs discloses that age may be the second parameter (2ndP) for this pair provided that the Carretta & Gratton (1997) metallicity scale is to be preferred over the Zinn & West (1984) scale. In addition, the dispersion in ZAHB mass is found to be about twice as large in NGC 362 as in NGC 288, probably due to the much higher central density of the former.
Cluster Distances using δ Sct Stars; Oscillating Blue Stragglers in ω Cen
Authors: Freyhammer L.M. , Petersen Jørgen Otzen
Published: June 2019

The complicated star formation history of the most massive globular cluster in our Galaxy — ω Centauri — is seen as a presence of an asymmetric spatial distribution of two stellar populations having different ages and metallicities. The cluster hosts the largest known sample of Population II δ Sct variables, or SX Phœnicis stars, which are valuable Galactic and extragalactic distance estimators. We discuss the applicability of these variables for estimating distances to the cluster, and compare different techniques for the critical identifications of oscillation modes.
M31 Globular Clusters in the Near-Infrared
Authors: Brandner Wolfgang , Tully R. Brent , N. Heasley James
Published: June 2019

We have observed the M31 globular clusters with the University of Hawaii Adaptive Optics System Hokupa'a at the Gemini North 8m telescope on Mauna Kea. This is part of a project which aims at spatially resolving intermediate-age and old-age stellar populations in the Local Volume and beyond - possibly out to distances of the Virgo and Fornax clusters. The sparse M31 globular cluster G27 (Hubble 6) is for the first time resolved into individual stars. The tip of the red giant branch (TRGB) at K≈18.8mag yields a metallicity of Z around 0.001 solar for G27.
The Globular Cluster Systems of Ellipticals and Spirals
Authors: Forbes Duncan A.
Published: June 2019

In this overview of the key properties of globular cluster (GC) systems I show that the GCs in elliptical and spiral host galaxies have more in common than previously thought. After contrasting these properties I briefly comment on GC formation.
The Outer Halo Cluster System of NGC 1399
Authors: Dirsch B. , Geisler D. , Richtler T. , Forte J.C.
Published: June 2019

We investigate the outer halo globular cluster population of NGC 1399. This study uses wide-field imaging of this cluster system, which covers the largest area studied with CCD photometry until now. The cluster system of NGC 1399 is found to extend further than 100 kpc from the galaxy. A population of metal-rich, as well as metal-poor clusters has been identified at these large radii. At radii smaller than 55 kpc the specific frequency of the red cluster system remains constant, while that of the blue clusters increases proportional tor0.8±0.2. For larger radii, the uncertainty of the galaxy light profile does not permit any reliable statement.
The Infrared Luminosity Function in the 30 Dor Cluster
Authors: Zinnecker Hans , Andersen Morten , Brandl Bernhard , Brandner Wolfgang , Hunter Deidre , Larson Richard , McCaughrean Mark , Meylan Georges , Moneti Andrea
Published: June 2019

We present the first infrared luminosity function in the 30 Doradus star cluster obtained with the HST NIC1 camera (0.043″ pixel−1) in the F160W (H-band) filter. Despite diffraction limited resolution (0.15″), crowding and blending is so severe that the cluster centre R136 cannot be studied. Instead a neighbouring NIC1 field (about 15″ away from the centre), for which an empirical PSF could be obtained, was analysed. We obtained photometry for some 750 stars in the range H = 14 to 22 mag. The luminosity function continues rising up to H = 2.1 mag (1 M⊙ at an age of 2 Myr) after which incompleteness corrections become dramatic (exceeding 50%). Contrary to recent optical studies based on a V vs. V—I diagram (Sirianni et al. 2000), we do not infer a flattening or turnover of the implied IMF slope near 2 M⊙.
Dwarf Galaxies and Star Clusters in Tidal Tails
Authors: Weilbacher Peter M. , Fritze-von Alvensleben Uta , Duc Pierre-Alain
Published: June 2019

We summarize the properties of tidal dwarf candidates in a sample of interacting galaxies and classify objects in tidal tails depending on their morphological appearance. New high-resolution dynamical models are needed to understand how the different structures seen in tidal tails are formed.
Massive Stars Ejected from R136?
Authors: Brandl Bernhard R. , Chernoff David F. , Moffat Anthony F. J.
Published: June 2019

We present the observational signature of a statistically significant number of very massive stars around the core of R136 and discuss the evidence for dynamical processes to be responsible for their apparent location. Alternative scenarios are discussed as well.
New Astrometric Instrumentation in Japan
Authors: Yoshizawa M.
Published: June 2019

The meridian circle is one of the most fundamental instrument in the field of astrometry where the astronomical objects are studied observationally for positions and their changes on the celestial sphere. At the Tokyo Astronomical Observatory (= National Astronomical Observatory since July, 1988) the Gautier Meridian Circle of 1903 was used until 1982 for various international meridian circle observations like SRS and NPZT programs, as well as for observations of OB stars, and the Moon and planets.
Scientific Contents of the Hipparcos input Catalogue
Authors: Turon C. , Gomez A.E. , Morin D.
Published: June 2019

The Hipparcos Input Catalogue -hereafter called HIC– (Turonet al.1992a, Turonet al.1994) contains the observing programme of the Hipparcos mission: 118 000 preselected stars, 48 minor planets and three satellites of major planets. These objects were selected on the grounds of more than 200 scientific programmes proposed by the world-wide astronomical community, and dealing with a large variety of astronomical and astrophysical topics. It contains the most up-to-date, comprehensive and homogeneous data and information related to these programme stars, collected during the years 1981-1990 by the INCA Consortium (Hipparcos INput CAtalogue consortium).
Fringe Interferometry in Space: The Fine Structure of R136A with the Astrometer Fine Guidance Sensor Aboard HST
Authors: Lattanzi M.G. , Burg R. , Hershey J.L. , Taff L.G. , Holfeltz S.T. , Bucciarelli B.
Published: June 2019

We report on the highest angular resolution observation to date of the bright core, R136a, of the massive star cluster R136 within the 30 Doradus complex in the LMC. This visual observation was obtained with the interferometric fringe mode of operation of Fine Guidance Sensor No. 3 (FGS3) on board HST. Crowding and strong diffuse background from nebular emission make this a challenging observation.

The giant HII region 30 Dor has provided some of the best candidates for the most massive stars, like R136al. We provide evidence for a new component, R136a1B, within the previously known R136a1-a2 system with a separation of 80 mas (or ≈ 4000 au from a1 at the distance of the LMC), and δV = 1.1 mag fainter than the brightest component a1. Estimates from current evolutionary models of massive stars based on the new FGS photometry predict, after subtraction of a1B, that the present mass of R136a1 is 30 M⊙with a main sequence progenitor of 60 M⊙. To date, this is thelowestdirect estimate of the mass of R136a1.

The success of this difficult observation adds a new, unique feature to FGS3 and gives a much expanded, astrophysically very rewarding, role to the interferometer.
The Hipparcos Extragalactic Link
Authors: Kovalevsky Jean
Published: June 2019

In conformity with the IAU resolutions on reference frames adopted in 1991, the Hipparcos catalogue will represent, in the visible spectrum, the celestial reference system defined by fixed positions of extra-galactic radio-sources. This will be realized by the strongest possible link between the IERS celestial reference frame with positions and/or proper motions of the largest possible number of Hipparcos stars determined also with respect to extragalactic objects. The data which will be used must be available before April 1995. It will include the following: positions and proper motions of radio stars observed by VLBI, VLA and MERLIN; photographic positions in fields including quasars; proper motions with respect to galaxies of the Lick, Yale, and Kiev programs, proper motions derived from pairs of photographic plates taken at large time intervals; and possibly data acquired by Hubble Space Telescope and from Earth's rotation data. The organization of the tasks within the working group is briefly described. The final accuracy of the link is expected to be of the order of, or better than, half a milliarcsecond.
Prospects for Detecting Unseen Companions of Periodic Variables
Authors: Pigulski A.
Published: June 2019

All periodic variables with stable periods such as pulsating stars, eclipsing binaries and pulsars offer the possibility of detecting unseen companion(s) by means of the light-time effect. We discuss the limitations of the method (the visibility of the effect) for different types of periodic variables. Special attention is paid to the ranges of mass ratios and orbital periods in which unseen companions can be found. We also indicate several systems with light-time effect in which hypothetical companions can be detected by speckle interferometry or precise astrometric observations. In these cases, the detection of the companions may lead to the determination of the components' masses.
Probing Non-Axisymmetry with Proper Motions
Authors: Binney James
Published: June 2019

The potential of the Milky Way is almost certainly not axisymmetric: the centre is believed to be dominated by a bar, and beyond the solar radius some non-axisymmetric feature of the potential appears to warp the disk. There are grounds for believing that the outer potential is mildly elliptical. Sub mas yr–1 proper motions of objects that lie near the plane several kiloparsecs from the Sun would play a crucial role in refining our understanding of these non-axisymmetries.
High Accuracy Astrometry Benefits for Celestial Mechanics
Authors: Seidelmann P. K.
Published: June 2019

Achieving angular accuracies at milli- and microarcsecond levels for objects within the solar system presents real challenges concerning the meaning of the observations due to the effects of phase and due to the sizes of the objects being observed. The use of retroreflectors or transmitters located on solar system objects may be the most promising technique.

However, if these accurate observations can be achieved, this provides the opportunity for significant improvements in the orbits of the planets, satellites, and minor planets, and will provide, or require, improvements in the models for the tidal interactions, secular accelerations, and masses. The observations will provide a test, or improvement, of the ties between radar, optical, and radio observations. This should provide an opportunity for improving the reductions of pulsar timing observations and improve our determination of the solar system reference system. This will also test the accuracy of the equivalence between Atomic Time and Dynamical Time. These accuracy levels should permit the discovery of other solar systems and the resulting increase in our knowledge, based on more than a single solar system.

Improvements in the accuracy level of observations provide increases in our knowledge and raises new challenges to explain the signatures detected by the observations.
Newcomb Astrometric Satellite
Authors: Johnston K. J. , Seidelmann P. K. , Reasenberg R. D. , Babcock R. , Phillips J. D.
Published: June 2019

Newcomb is a design concept for an astrometric optical interferometer satellite with a nominal single measurement accuracy of 100 microarcseconds. In a 30-month mission life, it will make scientifically interesting measurements of O stars, RR Lyrae and Cepheid distances, probe dark matter in our Galaxy via parallax measurements of K giants in the disk, establish a reference grid with internal consistency better than 50 microarcseconds, and lay the groundwork for the larger optical interferometers that are expected to produce a profusion of scientific results during the next century.
Astronomy from a Lunar Base
Authors: Volonte S.
Published: June 2019

The Moon is generally considered to be an ideal site for astronomy, offering excellent observing conditions and access to the entire electromagnetic and particle spectrum. A wide range of astronomical observations can be carried out from the Moon, but, as concluded in a recent ESA study (Mission to the Moon 1992), only a restricted number could be better implemented from a lunar site rather than from any other location. Very low frequency (VLF) astronomy, astrometry and interferometry fall into this category, as well as a transit telescope to map dark matter in the Universe. Whilst VLF and astrometric telescopes should be automatic, long baseline interferometers will probably require human intervention and will thus benefit from a manned lunar base.
Schmidt Plate Astrometry: Subplate Software
Authors: Zarate N. , Bucciarelli B. , Taff. L.G.
Published: June 2019

A portable computer program called SUBPLATE was developed to implement the sub-plate overlap technique proposed by Taff (1989 AJ 358, 359). The main point of the technique is to divide the plate into smaller pieces and then to overlap them, each with a minimum number of reference stars to solve for a linear solution.
Accurate Proper Motions as Probes of Distance and Dynamical Structure: The Case of M13
Authors: Wybo M. , Dejonghe H.
Published: June 2019

We explore the proper motion distributions of anisotropic Plummer models, and show that accurate measurements on the proper motions and radial velocity of individual stars can lead to information on the distance of a stellar system. We consider a one-parameter family of models, which all have the same Plummer law in the mass density, but have different anisotropic 2-integral distribution functions F(E, L), and hence different orbital structure (Dejonghe 1986). The input data for M13 are the photometry and the radial velocities as measured by Lupton, Gunn & Griffin (1987, AJ, 91, 1114), and the proper motion data as measured by Cudworth (1979, AJ, 84, 774). We represent the distribution function as a power series expansion in Fricke-type form. The Quadratic Programming (QP)-algorithm (Dejonghe 1989, Ap.J., 343, 113) determines the coefficients in the expansion by minimising a χ2-type variable, subject to the constraints that the distribution function must be positive in phase space. From the photometry we calculate the spatial mass density (the well-known Abel inversion) and the potential. The total mass is accounted for by applying a suitable scaling on the kinematical data. All models have a constant M/L. We use surface luminosities and the 3 (anisotropic) pressures, which depend on the three velocity dispersions. By re-iterating the procedure for various distances (and masses), the best distance estimate can be obtained.
The Thermal History of the Universe and the Spectrum of Relic Radiation
Authors: Sunyaev R. A.
Published: June 2019

Many of the cosmological models currently under discussion and theories of the origin of galaxies which involve antimatter, strong turbulence and so on result in significant energy release during the evolution of the Universe. It is evident that significant energy production should lead to distortions of the spectrum of the relic radiation. The absence of noticeable deviations from the Planckian spectrum enables us to set limits to the energy release in the early Universe (102<z< 108). But in order to have a clear picture of possible distortions, let us first review the idealized situation.
Gravitational Radiation Detector Magnetic Tapes from Rochester and Maryland
Authors: Lee M. , Weber J.
Published: June 2019

The Maryland Univac 1108 computer has analyzed magnetic tapes, one set having outputs of a 1661 Hz gravitational radiation detector at the University of Maryland and another set having outputs of a 710 Hz gravitational radiation detector at the University of Rochester. For a seven day period beginning August 23, 1973, 391 coincidences were found. Time delay experiments performed by the computer observed 338 accidental coincides. The zero delay excess is therefore 53 coincidences.

These data have not been verified by the Rochester group and any errors in this report are solely the responsibility of the Maryland authors.
On the Evaluation of the Munich-Frascati Weber-Type Experiment
Authors: Kafka Peter
Published: June 2019

Both the theory of optimal evaluation, developed in Munich, and tests with artificial pulses suggest that the Munich-Frascati experiment was more sensitive to short gravitational pulses than the Maryland-Argonne experiment. This was the case even in April 1973, before the Munich sensitivity was increased by another factor of 5. Nevertheless, the coincidences between Munich and Frascati did not show any surplus number for zero time delay.

It is concluded that Weber's events very likely were not due to gravitational radiation. However, a tape with four days of data from Maryland and Argonne (June 1973), which Weber kindly sent to us, does show a peak at approximately zero time delay, about 0.3 s wide and centered at 0.1 s time delay. The significance is not quite 2 standard deviations for the zero delay bin, but higher when the bins are chosen 0.3 s wide. No explanation can be offered at the moment.
Gravitational Collapse
Authors: Penrose R.
Published: June 2019

In the standard picture of gravitational collapse to a black hole, a key role is played by the hypothesis of cosmic censorship – according to which no naked space-time singularities can result from any collapse. A precise definition of a naked singularity is given here which leads to a strong ‘local’ version of the cosmic censorship hypothesis. This is equivalent to the proposition that a Cauchy hypersurface exits for the space-time. The principle that the surface area of a black hole can never decrease with time is presented in a new and simplified form which generalizes the earlier statements. A discussion of the relevance of recent work to the naked singularity problem is also given.
Alternative Approach to Infinity
Authors: Bergmann Peter G.
Published: June 2019

Following Penrose's construction of space-time infinity by means of a conformal construction, in which null-infinity is a three-dimensional domain, whereas time- and space-infinities are points, Geroch has recently endowed space-infinity with a somewhat richer structure. An approach that might work with a large class of pseudo-Riemannian manifolds is to induce a topology on the set of all geodesics (whether complete or incomplete) by subjecting their Cauchy data to (small) displacements in space-time and Lorentz rotations, and to group the geodesics all of whose neighborhoods intersect into equivalence classes. The quotient space of geodesics over equivalence classes is to represent infinity. In the case of Minkowski, null-infinity has the usual structure, but I0, I+, and I- each become three-dimensional as well.
Properties of Black Holes Relevant to their Observation
Authors: Bardeen James M.
Published: June 2019

Black holes are very small objects by astronomical standards, so in many circumstances they interact with their surroundings like a Newtonian mass point. However, if black holes are present in X-ray binary systems, the X-rays emitted in the inner part of the accretion disk probe the highly curved spacetime geometry near the horizon, particularly if the black hole is rapidly rotating. Some of the properties of circular orbits near the black hole are quite sensitive to the amount of angular momentum. The relativistic corrections remove a Newtonian degeneracy between several of the characteristic frequencies associated with perturbations of the circular orbits.

Hot spots in the inner part of the disk can produce dramatic fluctuations in intensity, since the frequency shifts of photons emitted by a given point on the disk are strongly time-dependent. The bending of the photon trajectories by the strong gravitational field can drastically affect the energy balance of the disk; much of the radiation emitted by the inner part of the disk is reabsorbed. The dragging of inertial frames by the angular momentum of the black hole can have striking consequences for the structure of the disk at quite large radii if the angular momentum of the accreting matter is not in the same direction as the angular momentum of the black hole.

Dynamic perturbations of black holes are now being intensively studied to see if there are any surprising physical effects associated with the rotation of the black hole. Unfortunately, though quite interesting methods of extracting energy from the black hole exist in principle most of them are unlikely to be realized to an important extent in the real astrophysical world.
Quantum Aspects of Accretion onto Black Holes in the Early Universe
Authors: Hawking S. W. , Gibbons G. W.
Published: June 2019

It is argued that for black holes of mass less than roughly 1017 g formed in the early Universe, the accretion process must be calculated using quantum mechanics. It is also argued that primordial black holes must be more massive than 1017 g if they are to possess charge.
Surface Composition of Neutron Stars that are Accreting Matter
Authors: Tsuruta S. , Ramaty R. , Börner G.
Published: June 2019

Surface composition of a neutron star in the absence of accretion is pure iron (Tsuruta, 1964). We considered two cases of accretion. (a) The accretion of inter-stellar matter: Here we expect the presence of a significant amount of various elements between proton and iron, though iron is still the most dominant. (b) The accretion as the energy source of an X-ray source in a binary system. Here it is most likely that the incoming flux is sufficiently high (non-steady state) and protons accumulate on the accreting region of the surface.
New Solutions of Einstein Equations Representing Spinning Masses
Authors: Sato Humitaka , Tomimatsu Akira
Published: June 2019

We found new, stationary axisymmetric, asymptotically flat exact solutions to Einstein's vacuum field equations, which are classified by an integer δ and Kerr metric is the solution of δ = 1. The number of ring singularity on the equatorial plane is δ. The odd δ metrices contain the surfaces of event horizon but the even δ metrices do not. Except the Kerr metric, however, the space-time becomes singular at the poles on these surfaces.
Accretion onto Relativistic Objects
Authors: Rees M. J.
Published: June 2019

The physics of spherically symmetrical accretion onto a compact object is briefly reviewed. Neither neutron stars nor stellar-mass black holes are likely to be readily detectable if they are isolated and accreting from the interstellar medium. Supermassive black holes in intergalactic space may however be detectable. The effects of accretion onto compact objects in binary systems are then discussed, with reference to the phenomena observed in variable X-ray sources.
Improvements in the IRAS Calibration by Separation of the Different Infrared Surface Brightness Components
Authors: Kester D. J. M. , Wesselius P. R. , Price S. D.
Published: June 2019

A new calibration has been developed for GEISHA (Groningen Exportable Infrared System for High-Resolution Analysis) employing the zodiacal emission that is clearly present in each long scan. We have assumed, because of several other fundamental IRAS studies, that the zodiacal emission as a whole (ZEM) can be approximated by the emission of a tilted oblate ellipsoid emitting at a certain effective brightness. Besides this zodiacal emission, there is always a contribution of the galactic emission (GEM). As a standard candle, we take the sum of ZEM and GEM. We allow the electronic baseline to change linearly over a scan. We assume that the slow exponential decay that occurs will be sufficiently approximated by a straight line. The nonlinear behavior of the gain is corrected by a model developed in Groningen.
The Galactic Far-UV Background: Correlations with Gas and Dust at High Galactic Latitudes
Authors: Lequeux James
Published: June 2019

The correlations between the UV galactic background (after subtraction of direct starlight), the neutral hydrogen HI, the extinction and the 100 μm emission are discussed for high galactic latitudes mainly based on a new analysis of the D2B satellite data. While clear correlations exist between UV and the other quantities, indicating that most of the UV galactic background is starlight scattered by interstellar dust, these correlations are less tight than the correlation between HI and the 100 μm emission. Localized UV excesses are shown to exist and are due in some cases to 2-photon emission by ionized gas. The quantitative interpretation of the UV galactic background in terms of dust properties is discussed, and it is shown that both the galactic model and the clumpiness of interstellar radiation may affect the results considerably.
Spectroscopic Observations of the Far Ultraviolet Background
Authors: Martin Christopher , Hurwitz Mark , Bowyer Stuart
Published: June 2019

We report on results from the Berkeley Ultraviolet Experiment (UVX), which performed 15 ± 2 Å resolution spectroscopy of the diffuse far ultraviolet background in eight directions. We have used the spectrum obtained in the direction of low H I column density to derive constraints on any extragalactic background. We find evidence that a hitherto unidentified dust component is present that accounts for most of the background in directions of low neutral hydrogen column density.
CCD Observation of Diffuse Light in the Rich Cluster A2029
Authors: Boughn S. P. , Uson J. M. , Kuhn J. R.
Published: June 2019

By mosaicking many CCD frames together, we have constructed a large-scale (~ 1/2°) R-band map of the cD cluster Abell 2029. The map was flat from one edge to the other to about 0.05% of the night sky, which corresponds to vR ~30 mag arcsec2. Using a novel technique involving the pixel distribution function, we measured diffuse light in the cluster out to 450″ (500 h−1 Kpc) along the minor axis of the cluster. In the elliptical region from minor radius 100″ to minor radius 300″, the diffuse light corresponds to roughly 8% of the total cluster light. Data in other optical bands and on other clusters are in the process of being reduced. The applicability of the above technique to measurements of the fluctuations in the extragalactic background light (EBL) is discussed.
High Latitude Galactic Emission and the Search for Anisotropies in the CBR
Authors: Masi S. , Calisse P. , de Bernardis P. , De Petris M. , Epifani M. , Gervasi M. , Guarini G. , Melchiorri F. , Moreno G. , Temi P.
Published: June 2019

The study of the anisotropies of the submillimeter relict radiation (RR) can provide important arguments to select among different theoretical scenarios (Panek and Rudak 1988). However, interstellar dust (ISD) emission is present in this spectral region and its patchy distribution can heavily contaminate anisotropy measurements. For example, the most sensitive measurement of CBR anisotropies has been reported so far in a broad band around 1 mm (Melchiorri et al. 1981): the detection of anisotropy is statistically very significant, but its cosmological origin is questionable.
Cosmic Microwave Background Fluctuation Searches On 5° to 10° Scales
Authors: Davies R. D. , Watson R. A. , Rebolo R. , Beckman J. , Lasenby A. N.
Published: June 2019

Deep observations of the cosmic microwave background (CMB) have been made at 10 GHz with beamwidths of 5° and 8° using a triple-beam technique, which greatly reduces atmospheric effects. Significant signals are detected with an rms of ΔT/T ~ 4×10−5. These signals could be intrinsic to the CMB and are providing fundamental information about galaxy formation in the early universe. A component of this 10 GHz emission may be coming from galactic synchrotron features. This galactic contribution will be elucidated in forthcoming 15 and 30 GHz observations.
Statistics of Radio-X-Ray Emission and Magnetic Fields in the Intergalactic Medium
Authors: Hanami Hitoshi
Published: June 2019

X-ray observations have demonstrated that the intergalactic medium in many clusters (cf. Coma, Perseus) contains a thin, hot plasma that may be produced by the accretion process in the gravitational potential of clusters with radiative cooling; this is usually called “cooling flows” (Fabian, Nulsen, and Canizares 1984; Sarazin 1986). On the other hand, the existence of radio halos in some clusters has been reported (Coma: Jaffe, Perola, and Valentijn 1976; A401: Roland et al. 1981). In addition, many elliptical galaxies in the center of clusters are also strong synchrotron radio sources. These radio emissions provide evidence for large amounts of relativistic electrons associated with the active phenomena in or around these galaxies and clusters. We can estimate the values or limits on the magnetic field in the cluster from the limits on the inverse Compton X-ray emission with the synchrotron radio emission (cf. Jaffe 1980). The intracluster field strength Bo is roughly 1 μG. It has been suggested that the influence of cosmic rays and magnetic fields is important for the properties and dynamics of the intercluster medium (Böhringer and Morfill 1988; Soker and Sarazin 1989). If cooling flows are real, this inward flow can impede the escape of the cosmic rays from the central galaxies in clusters and enhance the magnetic field. The confinement of the cosmic rays and the magnetic field in the center of clusters affects the gas of the intracluster medium.
The Far Ultraviolet Imaging Spectrograph on Spartan-281
Authors: Carruthers George R. , Heckathorn Harry M. , Raymond John C. , Dufour Reginald J. , Witt Adolf N. , Opal Chet B.
Published: June 2019

The study of diffuse celestial sources in the ground-inaccessible ultraviolet spectral range is less advanced than UV studies of point and compact sources. The main reason is that the characteristics of instrumentation optimized for the two types of objects are quite different. Studies of diffuse objects are best made with fast focal ratio optics with wide fields of view, whereas studies of point and compact objects are best made with large telescope aperture and high angular resolution. As a result, most space ultraviolet instruments to date (such as the International Ultraviolet Explorer and the forthcoming Hubble Space Telescope) are not well suited to the study of faint, extended diffuse objects in the ultraviolet.
Perceptual Consciousness
Authors: Yolton John W.
Published: June 2019

In his contribution to Human Senses and Perception, R. J. Hirst has made a number of important suggestions about perceptual consciousness, (i) He has emphasised the need to describe ‘what the percipient is or may be conscious of’ from the percipient's own point of view (p. 294). This mode of description is contrasted with stimulus or neurological description. Perceptual consciousness of one object is distinguished from perceptual consciousness of another object ‘only by or on the evidence of, the person concerned’ (p. 295). The method of obtaining descriptions of perceptual consciousness is either to question a percipient or to reflect on our own experience, (ii) The second important point stressed by Hirst is that the end product of perceiving is ‘the conscious experience of external objects’ (p. 303). Such an obvious point is often lost sight of in behavioural, dispositional, or neurophysiological analyses, (iii) The third and final suggestion made by Hirst to which I want to call attention is the usefulness of a genetic hypothesis to explain and account for perceptual consciousness. Hirst feels that perceptual consciousness is ‘unanalysable at the conscious level’, meaning (a) that it is ‘a unitary awareness of objects or scenes’ and (b) that the ‘various interacting unconscious activities’ which coexist with awareness ‘cannot be brought forward into consciousness’ (p. 305). The various analytical theories of perception (e.g. the traditional empiricist, the sense-datum) have been designed to break perceptual consciousness into its components. This has resulted in their being false to perceptual consciousness. A genetic explanation of awareness has several advantages, prime among them being its ability to explain the complexity and development of awareness.
Thinking and Performance
Authors: Palmer A.
Published: June 2019

The explanation of change or movement has always been a central concern of philosophers. Some, like Aristotle, have taken the movement of living things as their paradigm, and tried to explain all movement or change in that way. Others, after the fashion of Descartes, concentrate on the movement of inanimate things and generalise explanations of this to encompass all movement or change. For Aristotle, things have a principle of growth, organisation and movement in their own right. The movement or change of a natural thing is explained by its tendency to move in that way. The line he draws is not, as the line which we would perhaps like to draw is, between organic and inorganic things, but between these grouped together as subject to the same kind of explanation and, on the other hand, artificial things. A problem that results from this division is that while it might seem plausible to explain changes which occur in a baby when it grows into a man by saying that babies naturally tend to grow into men, and if they do not then something has interfered with their natural development, it seems odd to treat inorganic things in this way. Restricted to the contrast between the natural and the artificial, the explanation of stones falling when unsupported is clearly going to provide some difficulty. Although it is true that Aristotle does not think that because in the case of man the form with which matter is formed to make that substance is called a soul, that therefore any kind of form joined with matter to make a substance is called a soul, nevertheless the explanation of things which are a combination, a natural combination, of form and matter is the same for both man and other substances. Confronted with the explanation of falling bodies in this way, it first of all seems implausible and then suggests that things should happen which in fact do not. If it is assumed that the principle of movement is in the stone, ought it not to be assumed that the principle of stopping is in it too? Babies grow into men because it is in their nature to do so perhaps, but that stones fall downwards because it is in their nature to do so has, as Molière noticed in the case of a similar explanation of why opium puts you to sleep, a hollow ring.
Physical Determinism
Authors: Swinburne R. G.
Published: June 2019

The object of this paper is to examine what evidence we can have for or against the truth of determinism, a doctrine often set forward by the proposition ‘every event has a cause’. I understand in this context by the cause of an event a set of prior conditions jointly sufficient for the occurrence of the event. Since the determinist is concerned with all physical states and not merely with changes of states, which are most naturally termed events, we may phrase this claim more precisely as follows: There is for every physical state at some earlier instant a set of conditions jointly sufficient for its occurrence.
Memory, Memories and Me
Authors: Locke Don
Published: June 2019

In this paper I want to discuss two separate problems about memory, connected in that they both have to do with memory as a source or ground of knowledge.
The Setting
Authors: Jennings Jesse D.
Published: June 2019

The pages which follow are a report of the findings from a series of archeological excavations in western Utah. The archeological sites were Danger (42To13), Juke Box (42To20), and Raven (24EK2) caves. Of these three Danger Cave was the most informative and lends its name to the report. Juke Box and Raven provided interesting problems in excavation, but their evidence as to cultural events was meager.

The human story inferred in this report was set in one of the most remarkable of North American environments—the desert West. The natural subsistence resources of this land are today quite sparse; the balance between success and failure in survival has always been delicate. The fact that human groups survived in this environment deserves serious ecological note. Although no intensive study of this aspect of the problem is being undertaken here, the cultural data cannot be appreciated or evaluated without a modicum of information regarding the terrain and the biotic resources of the region.
Modeling Eclipsing Binaries in Globular Clusters
Authors: Milone E.F. , Kallrath J. , Stagg C.R. , Williams M.D.
Published: June 2019

We describe the use of eclipsing binaries to derive fundamental properties of the binary star components in a cluster. The method requires the use of reliable isochrones and accurate properties of stars that lie along them.
Fe II Fluorescence in Symbiotic Stars
Authors: Eriksson M. , Veenhuizen H. , Wahlgren G.M. , Johansson S.
Published: June 2019

Fe II fluorescence by PAR has been investigated in eight symbiotic stars having a wide range in temperature of the hot component and orbital period. The data used are spectra obtained from the IUE archive. All pumping lines investigated in this work are in the short wavelength region of IUE (1200-2000 Å), except for He ɪɪ λ1084.942 and O VI λ1032.041. The resulting Fe ɪɪ fluorescence lines are mainly in the long wavelength region (2000-3300 Å), but a few fall in the same region as the pumping lines. The aim is to understand the optimal conditions for formation of Fe ɪɪ fluorescence lines caused by PAR. Three of the selected systems, RR Tel, AG Peg and V1016 Cyg, have 10-30 active Fe ɪɪ channels. Two conditions connect those systems to each other: The hot component is a white dwarf of extreme temperature (80·103-150·103 K) and all three systems are so called symbiotic novae and have had outbursts during the last 150 years. Three systems, AG Dra, RW Hya and R Aqr, have only 2-3 active Fe ɪɪ channels. In the two remaining systems, CI Cyg and T CrB, Fe ɪɪ fluorescence lines were totally absent. These two systems have two features in common: The emission strength of highly ionized elements is less than in most symbiotic systems, and the hot component is suspected to be an accreting main sequence star rather than a white dwarf.
The Primordial Binary Population in OB Associations
Authors: Kouwenhoven M.B.N. , Brown A.G.A. , Gualandris A. , Kaper L. , Portegies Zwart S.F. , Zinnecker H.
Published: June 2019

We present the first results of our adaptive optics survey of 200 (mainly) A-type stars in the nearby OB association Sco OB2, which we will use, together with literature data and detailed simulations of young star clusters, to determine the primordial binary population.
Three-Body Problem and Multiple Stellar Systems
Authors: Valtonen M.
Published: June 2019

Three-body processes go on in star clusters where binary stars meet single stars and frequently form temporary triple systems. The triples are typically unstable and break up into a new binary and a single star. Also a simple scattering of a single star from a binary may take place. Both processes can be handled by the statistical theories of three-body break-up and scattering. Here we apply the theory to binary stars, assuming that binaries have been involved in the three-body process. The distributions of binary periods, eccentricities and mass ratios are discussed from this point of view and compared with observational samples.
X-ray Spectra of Young Supernovae
Authors: Pooley David
Published: June 2019

X-ray spectra of young supernovae (SNe) can provide information on the progenitor star and the interaction of the supernova ejecta and the circumstellar material. I will discuss some examples, with particular emphasis on SN 1998S, whose X-ray spectrum revealed for the first time in a young supernova a wealth of heavy element emission features (Ne, Al, Si, S, Ar, and Fe). By comparison with detailed calculations of supernova explosion elemental yields, these data can be used to constrain the progenitor mass. With increasingly sophisticated models and additional high quality data, application of this technique could result in many more reliable progenitor mass determinations. In addition, high resolution X-ray spectra allow us to measure the temperature evolution of a supernova and can give us a detailed picture of the progenitor’s pre-supernova evolution. As we build up additional examples from the great diversity of core collapse supernovae, we hope to come to a better understanding of the last stages of massive star evolution.
56Ni Mass in Type IIP SNe: Light Curves and Hα Luminosity Diagnostics
Authors: Elmhamdi A. , Chugai N.N. , Danziger I.J.
Published: June 2019

We analyze late-time observations, available photometry and spectra, of a sample of type II plateau supernovae (SNe IIP). The possibility of using Hα luminosity at the nebular epoch as a tracer of 56Ni mass in this class of objects is investigated, yielding a consistency with the photometry-based estimates within 20%. Interesting correlations are found and their impacts on our present understanding of the physics of core collapse SNe are discussed.