bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy Density of the Relic Radiation
Authors: Blair A. G.
Published: June 2019

Experimental measurements of the intensity of the submillimeter background are reviewed. The latest results all indicate a low background; it is not yet possible to say whether or not the spectrum in this range is blackbody.
Whirl Theory of the Origin of Galaxies and Clusters of Galaxies
Authors: Ozernoy L. M.
Published: June 2019

This paper reviews the present state of the theory of primaeval whirls which may be responsible for the origin of galaxies and galaxy systems. The main problems on which the author will concentrate are concerned with the pre-recombination evolution of the whirls. Special attention is given to new results, obtained by Kurskov and the author, concerning the dissipation of cosmological turbulence and the constraints which follow on the parameters of primaeval whirls. In contrast to some assertions in the literature, there is not contradiction between the whirl concept and observations. Moreover, the fact that the final spectrum of motions and corresponding inhomogeneities does not depend essentially upon the details of the initial whirl spectrum makes the theory very attractive.

The formation of galaxy systems (groups, clusters etc.) is discussed, and alternatives for the formation of galaxies themselves are briefly outlined. Many aspects of the whirl theory are suitable for further observational and theoretical development.
Low Frequency Gravitational Waves in Cosmology
Authors: Dautcourt G.
Published: June 2019

An intense non-thermal background of cosmic gravitational radiation in the Megaparsec wave band could be detected by its influence on many astrophysical processes. In particular, it may give an explanation of the so-called redshift anomalies.
An Upper Limit to the Mass Loss from the Centre of the Galaxy
Authors: Poveda Arcadio , Allen Christine
Published: June 2019

A mass loss of 200 M⊙ per year, as conservatively suggested if Weber is detecting gravitational waves from an isotropic source at the galactic centre, is shown to be incompatible with the existence of (a) globular clusters, (b) old wide binaries, if this loss rate has been constant over the past 1010 yr.

From the orbit of ω Centauri in the galactic field and its observed mass distribution and tidal radius an upper limit to the mass loss from the galactic centre is found to be 1 M⊙ yr-1 over the past 1010 yr.
The Use of Cryogenic Techniques to Achieve High Sensitivity in Gravitational Wave Detectors
Authors: Boughn S. P. , Fairbank W. M. , McASHAN M. S. , Paik H. J. , Taber R. C. , Bernat T. P. , Blair D. G. , Hamilton W. O.
Published: June 2019

Cryogenic detectors for gravitational wave astronomy promise greatly improved sensitivity over room temperature detectors. The 3 mK detector which we have under construction should give an improvement of 106 over existing detectors. The cryogenic antennae are described and the calculated low temperature performance is detailed. New superconducting instrumentation is described.
Analysis of Gravitational-Wave Detection Experiments
Authors: Eardley Douglas M. , Lee David L. , Lightman Alan P. , Wagoner R. V. , Will Clifford M.
Published: June 2019

The structure of weak, plane, null gravitational waves is obtained for any metric theory of gravity. In general, six polarization states are present, which reduce to three (spin 0, ±2) if the theory is to be quantizable. Schemes for obtaining the polarization amplitudes, as well as the direction and velocity of a wave, are presented.
On the Problem of Detection of Isolated Black Holes
Authors: Shvartsman V. F.
Published: June 2019

The interstellar plasma accreted by isolated black holes should be heated during the infall process and radiate in the magnetic fields connected with the infalling material. A portion of the radiation in the optical range is likely to have a luminosity of order 1027–1030 erg s-1. In SAO U.S.S.R. AS an experiment is being carried out to observe isolated black holes as faint optical stars without spectral lines. So far the results of the experiment are negative.
Infrared Emission at High Galactic Latitude
Authors: Boulanger F.
Published: June 2019

Results obtained with the Infrared Astronomy Satellite (IRAS) on the IR emission at high galactic latitude are reviewed. We present evidence for the detection of galactic emission at 12, 25, 60, and 100 μm. We describe the morphology of this emission and summarize work on the correlation of IR cirrus with H I, CO, and optical emission. We discuss the contribution of the neutral atomic, ionized, and molecular gas to the total IR emission and the contribution of different components of interstellar dust to the emission seen at different wavelengths.
Optical Characteristics of Galactic 100 μm Cirrus
Authors: Guhathakurta P. , Tyson J. A.
Published: June 2019

Variations in the optical surface brightness of the night sky on angular scales of arcseconds to degrees are contributed to by phenomena ranging from geophysics to cosmology. Known time-independent (over years) sources include (1) fluctuations in the distant galaxy distribution and (2) scattered disk light off dust in the plane of our galaxy and at high latitudes (IRAS cirrus; Low et al. 1984). Sandage (1976) found optical “cirrus” on photographic plates, which were later correlated with bright 100 μm cirrus (de Vries and Le Poole 1985). We describe here a systematic investigation of fainter and more widespread high-latitude IRAS cirrus using deep multicolor charge-coupled device (CCD) imaging photometry (Guhathakurta and Tyson 1989).
Extragalactic Backgrounds: Common Features and New Work on Intracluster Light
Authors: Partridge R. B.
Published: June 2019

I examine some common features of several extragalactic backgrounds, beginning with the best studied of all backgrounds, the 3 K microwave radiation, then continuing on to the newly discovered submillimeter flux and the near infrared (IR) background. Both the total surface brightness and fluctuations (or anisotropies) in the brightness of these backgrounds are considered. Some implications for cosmology and for astrophysics are mentioned.
Optical Background from Galaxies
Authors: Kalinkov M. , Kuneva I.
Published: June 2019

The optical brightness of the sky due to galaxies is determined up to 15.7 Zwicky magnitude and to B = 15m.
Infrared Dust Emission in Galaxies and Spectral Distortion of Microwave Background
Authors: Khersonskii V. K. , Voshchinnikov N. V.
Published: June 2019

Recent observations (Matsumoto et al., 1988) indicate that at submillimeter wavelengths the spectrum of the cosmic background radiation (CBR) deviates from that of Planckian blackbody with a temperature T0R = 2.76 K. The relative excess of the flux ζ(v) = [F(v) – F0(v)] / F0(v) (where F(v) and F0(v) are the registered flux and the flux of the blackbody radiation at the frequency of the observations) are 0.6 at a frequency v1 = 380 GHz (λ = 709 μm) and 3.4 at a frequency v2 = 624 GHz (λ = 481 μm).
Cosmic Background Radiation Anisotropies in the Far Infrared
Authors: de Bernardis P. , De Petris M. , Epifani M. , Gervasi M. , Guarini G. , Masi S.
Published: June 2019

The motion of the earth with respect to the distant matter frame produces a spectral distortion in the observed background radiation given by
1

The second-order approximation in β gives (de Bernardis et al., 1989) 2 where α≅(dlnI/dln v) = (v/I)(dI/dv). The first term in cosθ of equation (2) is the usual dipole anisotropy, the second constant term is the equivalent of the transverse Doppler effect in special relativity, and the third term is the quadrupole anisotropy. It is interesting to note that the quadrupole term is zero in the Rayleigh-Jeans region of the blackbody spectrum: Q ≈ 1/2(3–α)(2–α)β2cos2θ.
The X-Ray Background from Star-Forming Galaxies
Authors: Griffiths Richard E.
Published: June 2019

It has been established observationally that at least 30% of the all-sky X-ray background (XRB) in the energy range of 1–3 keV comes from active galactic nuclei (AGN) in the redshift interval of 0.4 to 1.2 (Griffiths et al. 1983, 1988); it is also quite plausible that AGN contribute half of the XRB in the 1–3 keV range (Morisawa and Takahara 1989). However, analysis of spatial fluctuations in the Einstein deep survey counts (Hamilton and Helfand 1987; Barcons and Fabian 1989) has indicated the presence of a relatively smooth component of the XRB with a corresponding surface density of discrete sources of at least several thousand per square degree.
Behaviour of Point Masses Against the Background Radiation with Dissipation in an Expanding Universe
Authors: Kozhanov Toktasyn S.
Published: June 2019

One of the most important cosmological problems is the question of the properties of systems of particles in a regular field of homogeneous and isotropically expanding two-component Metagalactic substratum. Within the framework of the Newtonian cosmology, we consider the behaviour of the ensemble of point masses embedded in a homogeneous expanding medium having two different equations of the state. Dissipation phenomena caused by the chaotic motion of the background matter are taken into account.
Can Very Large-Scale Structures Exist in the Universe?
Authors: Martǐn-Mirones J. M. , Goicoechea L. J.
Published: June 2019

The controversy about the position of the matter accumulation that causes our peculiar motion with respect to the cosmic background radiation (CBR) has very recently acquired great interest. So, the very local attractor suggested by Lynden-Bell et al. (1988) and Dressler (1988) begins to be questioned. The histogram done by Melnick and Moles (1987) shows that the dominant structure may be at ~140 h−1 Mpc. Similar results have been obtained by Scaramella et al. (1989). On the other hand, the analysis of the very local candidate in the X-ray band shows that this does not have rich clusters of galaxies (Jahoda and Mushotzky 1989). Moreover, Lahav et al. (1989) have studied a sample of 53 clusters emitting X-rays (E ≈ 2–20 keV, LX ≈ 5 × 1042–7 × 1044h−2 erg s−1); they have observed a great concentration of clusters in the direction of the attractor suggested by Lynden-Bell et al., but at a distance of ~100 h−1–150 h−1 Mpc. The detections of nonlocal structures (further than 300 h−1 Mpc) are very few. However, the study done by Shaver (1987) using catalogs of quasars showed that a superstructure with a radius of ~200 h−1 Mpc and with a density in excess of δ ≈ 1 may exist at a distance of ~800 h−1 Mpc.
III.—The Temple of Aphrodite: its Architectural History and Remains
Authors: Smith R. Elsey
Published: June 2019

The history of the temple, as far as it can be ascertained from literary records from the study of ancient coins and from any similar sources, is elsewhere fully discussed; it remains to examine the actual ruins of the fabric, in order to extract from them what internal evidence there may be as to the date of the various portions from the style of workmanship and the methods of construction therein employed.

It will be easier to follow this examination in connection with the plan if we systematically pursue it from the south-west corner northwards. There are two great divisions into which the work may be separated—pre-Roman and Roman. In the first of these there are certainly three subdivisions, and the Roman work shows two main divisions denoting two great periods of restorative work; but the work of all these five distinct periods is so interwoven that it is not possible to separate and make them clear on a small scale plan. The two main divisions are indicated by differences in shading on the plan opposite, and the position of the more minute subdivisions will be referred to in order as they occur.
Presidential Address
Authors: Powickk F. M.
Published: June 2019

On previous occasions I have chosen as the subject of my address at the annual meeting of this Society a historical theme suggested by my studies. Three historical addresses, each of which involved careful preparation, are, I venture to think, as many as a President of the Society need feel it his duty to deliver. Yet I think that I should have inflicted a fourth upon the Society if some special considerations had not combined to divert me from what is certainly the safer, and is perhaps the more profitable course. Moreover, it so happens that the period of my presidency has been a time of significant development in the organisation of historical study in this country. The history of this Society has been affected by the general movement. We have tried deliberately to adjust ourselves to it, and to take a leading part in it. I decided, therefore, to make my last appearance in the chair an occasion for a review of current developments and for some reflections upon them.
Perception and Action
Authors: Ayers M. R.
Published: June 2019

There is an ancient and ambiguous philosophical doctrine that perception is passive. This can mean that the mind contributes nothing to the content of our sensory experience: its power of perception is a mere receptivity. In this sense the principle has often been questioned, and is indeed doubtful on empirical grounds, given one reasonable interpretation of what it would be for the mind to make such a contribution.
Freedom, Knowledge, Belief and Causality
Authors: Wiggins David
Published: June 2019

When we try to think about the causal nexus and the physical nature of the world as a whole we may be struck by two quite different difficulties in finding room in it to accommodate together (a) knowledge or reasoned belief and (b) causal determinism. (a) may seem to us to exclude (b) and (b) may seem to us to exclude (a). Taking it as a fact that there is knowledge and that knowledge seems to be indefinitely extensible, it has been felt by some philosophers that we can disprove total determinism by showing that if there were laws of nature which purported to govern all movements of matter in the universe there would still be something which even an ‘all-knowing’ predicter could not predict, viz. his own predictions or his own actions; and that given enough knowledge any agent could refute anybody else's predictions of his actions. So it has been thought that the phenomenon of knowledge somehow shows there cannot be laws to govern all movements of matter in the universe. This comfortably anodyne reflection is examined in the second part of the lecture. It elevates human minds and even confers a sort of cosmic importance on them. The other difficulty in making room for both (a) and (b) is in some loose sense the dual of this. Instead of taking knowledge for granted and questioning total determinism, it merely takes causality for granted but then deduces the total impossibility of knowledge. It simply asks: ‘How can we take a belief seriously, or consider it seriously as a candidate to be knowledge, if it is no better than a simple physical effect?’ This is a more pessimistic reflection and I shall begin with it.
Discourse about the Future
Authors: Clark Michael
Published: June 2019

While philosophers feel relatively comfortable about talking of the present and the past, some of them feel uncomfortable about talking in just the same way of future events. They feel that, in general, discourse about the future differs significantly from discourse about the past and present, and that these differences reflect a logical asymmetry between the past and future beyond the merely defining fact that the future succeeds, and the past precedes, the present time. The problem is: how can we talk about events which have not yet happened, or at any rate are not yet bound to happen, or whose participants do not yet exist? The effect of these worries has led them to claim to recognise restrictions on our talk about the future which do not govern talk about the past and present. The most famous of these views is Aristotle's. According to one familiar interpretation, he holds that a statement about a future event which is not yet settled, a contingent event in the future, is neither true nor false, even though the statement that the event either will or will not happen is necessarily true. Proponents of this view felt that if a future-tensed statement were already true then the fact that it stated would already be settled. I do not propose to discuss this well-known and muchdiscussed doctrine of Aristotle's, but I do want to consider some allied views which have been aired recently, and to look at their philosophical significance. Before I look at these, however, it will be convenient to recall three of the main reasons why the Aristotelian doctrine is unpopular. In the first place it is paradoxical to accept that a statement of the form p v ∼ p is (necessarily) true while claiming that neither of its disjuncts is true. Then there are misgivings about the notion of truth involved: many feel that truth is essentially an attribute of timeless propositions and that it is nonsense to talk of a statement's becoming true as you would of Aristotle's views if the event described became inevitable. There is also the difficulty of accounting for the meaning of a future-tensed sentence which may express a statement that is neither true nor false simply because what it states is not yet settled. It could not be said of the sentence expressing such a statement that you know what it means if you know what it is for the sentence to express a true statement. I know the meaning of the present-tensed sentence ‘A sea-battle is now being waged’ if I know that it can normally be used to make a true statement precisely in the event of there being a sea-battle being waged at present. But I do not know the meaning of the future-tensed sentence ‘A sea-battle will be waged tomorrow’ simply by knowing that the sentence expresses a true statement if it is already settled that there is going to be a battle: the statement doesn't mean that the battle is already settled, otherwise it would not lack a truth-value when the matter was still open – it would be false.
The Bias
Authors: Jennings Jesse D.
Published: June 2019

Now against a regional and local environmental background, I should like to present in simple narrative the Great Basin chapter of the story of man in the western hemisphere as I conceive it.

There are numerous archeologic stations in the west and in the Plains where deep layers of earth, one upon the other, have yielded collections of considerable age. Man’s tools are found, particularly in the Plains, in some of these layers in direct association with animals now extinct. Taken singly these locations tell very little — they are mere paragraphs in a long chapter — about man's history as the western hemisphere was peopled. In the aggregate, however, the findings from these several sites permit a coherent if sometimes skimpy account to be built up.
Statistical Properties of Solar-Type Close Binaries
Authors: Halbwachs J.-L. , Mayor M. , Udry S. , Arenou F.
Published: June 2019

Two Coravel radial velocity surveys dedicated to F7-K field dwarfs and to open clusters are merged in order to investigate the statistical properties of binaries with periods up to 10 years. Thanks to the accurate trigonometric parallaxes provided by Hipparcos, an unbiased sample of spectroscopic binaries (SB) is selected. After correction for the uncertainties of the measurements, the following results are obtained: 1. The distribution of mass ratios exhibits a peak for equal-mass binaries (twins), which is higher for short-period binaries than for long-period binaries. 2. Apart from the twins, the distribution of mass ratios exhibits a broad peak from 0.2 to 0.6. 3. The orbital eccentricities of twins are slightly smaller than those of other binaries. 4. An excess of SB is observed with periods shorter than about 50 days in comparison with the Duquennoy and Mayor log-normal distribution of periods. These features suggest that close binary stars are generated by two different processes. A possible difference could come from the accretion onto the binary, for instance from a common envelope or from a circumbinary disk. Alternatively, twins could come from dynamic evolution of multiple systems. It is not clear whether the formation models are already sufficiently elaborated to reproduce our statistics.
Infrared Differential Photometry of Selected Orbital Binaries
Authors: Lampens Patricia , Prieur Jean-Louis , Argyle Robert
Published: June 2019

High-angular resolution observations were acquired for a sample of F-G and K nearby orbital binaries, making use of the ADONIS instrument mounted at the 3.6m ESO telescope from La Silla observatory. The aim is to derive broad-band near-infrared colours for the individual components of those binaries which do not fit well the mean mass-luminosity relation, but which have accurate parallaxes (from the Hipparcos satellite) and high-quality orbits, thanks to many previous efforts. Such colour determinations allow component temperatures and photometric mass ratios to be derived.
Addressing Confusion in Double Star Nomenclature: The Washington Multiplicity Catalog
Authors: Hartkopf William I. , Mason Brian D.
Published: June 2019

Advances in instrumentation and reduction methods are blurring the historical distinctions between various classes of double stars. One result of this is increasing confusion in double star nomenclature, as the conventions followed by different observers are sometimes incompatible. The Washington Multiplicity Catalog is presented as a means of developing a single nomenclature scheme for all types of doubles, as well as a comprehensive database for all duplicity information.
VLA Observations of Disks and Jets in Young Close Binaries
Authors: Anglada G.
Published: June 2019

We show high-angular resolution results from VLA observations of the sources SVS 13, NGC 1333 VLA 2, and L723 VLA 2. Our results suggest that these sources are very young close (25-75 AU separation) binary systems and that the development of disks and jets can proceed in a different way for each component of the binary system.
VLA Observations of Orbital Motions in YLW 15
Authors: Curiel S. , Girart J.M. , Rodríguez L.F. , Cantó J.
Published: June 2019

Using high angular resolution (~ 03) Very Large Array (VLA) observations made at 3.6 cm during the period 1990 to 2002, we report the detection of proper motions in the components of the binary source YLW 15. We find absolute proper motions of the order of 15 km s-1. In addition, the relative astrometry between the two components reveals orbital proper motions that suggest that the total mass of this binary system is ~ 1.7 M⊙, and that VLA 1 is more massive than VLA 2.
Binary Star Formation and Mass Outflows: MHD Nested Grid Simulation
Authors: Machida M.N. , Tomisaka K. , Matsumoto T.
Published: June 2019

We study the binary star formation process from a rotating magnetized molecular cloud. We assume an isothermal cylindrical cloud in hydrostatic balance whose rotation axis and the direction of global magnetic field lines are both identical, and parallel to the cylinder axis. We added axisymmetric and non-axisymmetric density perturbations to the initial state and followed the subsequent evolutions. The evolution is characterized by three parameters: the amplitude of the non-axisymmetric perturbations, the rotation speed, and the magnetic field strength. As a result, it is found that non-axisymmetry hardly evolves in the early phase, but begins to grow after the gas contracts and forms a thin disk. There are two types of fragmentation: fragmentation from a ring and that from a bar. Thin adiabatic cores fragments if a thickness is smaller than 1/4 of the radius. For the fragments to survive, they should be formed in a heavily elongated barred core or a flat round disk. In the models showing fragmentation, outflows from respective fragments are found as well as those driven by the rotating bar or the disk.
Multiple Protostars, Jets, and the Origin of Brown Dwarfs
Authors: Clarke Cathie , Reipurth Bo , Delgado-Donate Eduardo
Published: June 2019

The observation that young stars are clustered in few body non-hierarchical multiple systems at very young ages has profound consequences for our understanding of the formation of stars, binaries and the disks and planets that may surround them. In this chapter we review theoretical progress made over the last decade in modeling the break up of these natal clusters and discuss a range of observational predictions that arise from these models, relating to the kinematics, binary statistics and possession of disks of both stars and brown dwarfs. We also argue that one of the most spectacular manifestations of dynamical interactions in young multiple systems should be the formation of giant Herbig-Haro flows, and present observational evidence that may be interpreted in this light.
On The Formation of Brown Dwarfs
Authors: Jiang Ing-Guey , Laughlin G. , Lin D.N.C.
Published: June 2019

The observational properties of brown dwarfs pose challenges to the theory of star formation. Because their masses are much smaller than the typical Jeans mass of interstellar clouds, brown dwarfs are most likely formed through secondary fragmentation processes, rather than through the direct collapse of a molecular cloud core. In order to prevent substantial post-formation mass accretion, young brown dwarfs must leave the high-density formation regions in which they form. We propose here that brown dwarfs are formed in the optically thin outer regions of circumbinary disks. Through post-formation dynamical interaction with their host binary stars, young brown dwarfs are either scattered to large distance or removed, with modest speed, from their cradles.
Summary of IAU Colloquium 191: The Environment and Evolution Binary and Multiple Stars
Authors: Guinan Edward F.
Published: June 2019

A summary is given of the IAU Colloquium No 191 “The Environment and Evolution of Binary and Multiple Stars.” This conference was held in Mérida, Mexico during February 2003 and dedicated to Dr. Arcadio Poveda for his major contributions to binary- and multiple-star systems and dynamics. The conference was organized to discuss the major developments that are occurring in the fields of binary- and multiple-star formation, evolution, dynamics, and the environments where they form and evolve.
A Decade of Radio and X-ray Observations of SN 1993J
Authors: Van Dyk Schuyler D. , Weiler Kurt W. , Sramek Richard A. , Panagia Nino , Stockdale Christopher , Lacey Christina , Montes Marcos , Rupen Michael
Published: June 2019

We review ten years of radio continuum and X-ray monitoring of the Type IIb SN 1993J in M81. The supernova (SN) has been observed continuously, since only a few days after explosion, by our group with the Very Large Array at a number of radio frequencies, as well as by other groups. As a result, it is among the best-studied radio supernovae. The observed synchrotron radio emission is thought to arise from the interaction of the SN shock with the pre-SN wind-established circumstellar medium around the progenitor star. We describe the properties of the circumstellar interaction, based on the more fully-developed dataset, and compare this to our earlier characterization made in 1994. SN 1993J has also been a target of X-ray satellites, and we briefly discuss the nature of the X-ray emission and, together with the radio emission, describe the implications for the nature of the SN’s progenitor.
Imaging of SN 1993J
Authors: Alberdi A. , Marcaide J.M.
Published: June 2019

SN 1993J has been imaged with VLBI, and its angular expansion monitored, for almost ten years. The images show shell-like radio structures with almost circular symmetry. SN 1993J expands according to models of shock excited emission. The angular expansion has a changing deceleration rate and is best modeled with two different slopes. The swept-up mass estimate at an age of 3159 days (∼0.4 M⊙), comparable to the low-mass envelope, favors a binary scenario. The observed spectral index of SN 1993J has slowly flattened since age 1000 days onward (α has changed from −1 to −0.67 at an age of 2820 days).
Modeling the Radio and X-ray Emission of SN 1993J and SN 2002ap
Authors: Fransson Claes , Björnsson Claes-Ingvar
Published: June 2019

Modeling of radio and X-ray observations of supernovae interacting with their circumstellar media are discussed, with special application to SN 1993J and SN 2002ap. We emphasize the importance of including all relevant physical mechanisms, especially for the modeling of the radio light curves. The different conclusions for the absorption mechanism (free-free or synchrotron self-absorption), as well as departures from an ρ ∝ r−2 CSM, as inferred by some authors, are discussed in detail. We conclude that the evidence for a variation in the mass loss rate with time is very weak. The results regarding the efficiencies of magnetic field generation and relativistic particle acceleration are summarized.
Detection of the Binary Companion to the Progenitor of SN 1993J
Authors: Smartt S.J. , Maund J.R. , Kudritzki R.P. , Podsiadlowski P. , Gilmore G.
Published: June 2019

We present a detailed late-time photometric and spectroscopic study of SN1993J with HST/ACS and Keck LRIS-B. We find a clear signature of a hot star component in the spectra of SN1993J which cannot be explained by the surrounding faint blue stars. This is the first detection of the expected massive binary companion to the red supergiant progenitor and confirms that SN1993J did indeed arise in an interacting binary system.
Supernova 1987A: The Birth of a Supernova Remnant
Authors: McCray Richard
Published: June 2019

I describe and interpret observations of the rapidly developing impact of the debris of SN1987A with its circumstellar ring.
Supernova Spectra
Authors: Turatto Massimo
Published: June 2019

In this paper are summarized the main advances of the last years in the field of SN spectra . The arguments against a monodimensional sequence for SNIa are discussed as well as the efforts to improve the temporal and spectral coverage of this kind of SNe, with the aim to understand the physics of the explosions for their use as cosmological distance indicators. Although variety is the main character of core-collapse SNe, we have been recently surprised by both exceptionally under and over-energetic explosions. The main properties of these two extreme subclasses are here reviewed.
Nucleosynthesis in Black-Hole-Forming Supernovae
Authors: Nomoto K. , Maeda K. , Umeda H. , Tominaga N. , Ohkubo T. , Deng J. , Mazzali P.A.
Published: June 2019

Stars more massive than ~ 20 − 25 M⊙ form a black hole at the end of their evolution. Stars with non-rotating black holes are likely to collapse “quietly” ejecting a small amount of heavy elements (faint supernovae). In contrast, stars with rotating black holes are likely to give rise to very energetic supernovae (hypernovae). We present distinct nucleosynthesis features of these two types of “black-hole-forming” supernovae. Nucleosynthesis in hypernovae is characterized by larger abundance ratios (Zn, Co, V, Ti)/Fe and smaller (Mn, Cr)/Fe than normal supernovae, which can explain the observed trend of these ratios in extremely metal-poor stars. Nucleosynthesis in faint supernovae is characterized by a large amount of fall-back. We show that the abundance pattern of the recently discovered most Fe-poor star, HE0107-5240, and other extremely metal-poor carbon-rich stars are in good accord with those of black-hole-forming supernovae, but not pair-instability supernovae. This suggests that black-hole-forming supernovae made important contributions to the early Galactic (and cosmic) chemical evolution. Finally we discuss the nature of first (Pop III) Stars.
Synthetic Spectra for Type Ia Supernovae at Early Epochs
Authors: Sauer D.N. , Pauldrach A.W.A. , Hoffmann T. , Hillebrandt W.
Published: June 2019

We present the current status of our construction of synthetic spectra for type Ia supernovae. These properly take into account the effects of NLTE and an adequate representation of line blocking and blanketing. The models are based on a sophisticated atomic database. We show that the synthetic spectrum reproduces the observed spectrum of ‘normal’ SN-Ia near maximum light from the UV to the near-IR. However, further improvements are necessary before truly quantitative analyses of observed SN-Ia spectra can be performed. In particular, the inner boundary condition has to be fundamentally modified. This is due to the dominance of electron scattering over true absorption processes coupled with the flat density structure in these objects.
Optical and Near-IR Observations of SN 1998bw
Authors: Patat Ferdinando
Published: June 2019

Thus, the observation of gamma-ray line emission from a young supernova seems very promising in the near future. The observation, or even a null observation at a low threshold, will give significance in the fields of nuclear astrophysics and supernova theory. The scientific importance of a positive measurement would be analogous with and comparable to the importance of successful detection of neutrinos from the Sun.

Clayton, Colgate, and Fishman [2].
SN 1998bw and Other Hyperenergetic Type Ic Supernovae
Authors: Mazzali Paolo A. , Nomoto Ken’ichi , Deng Jinsong , Maeda Keiichi , Iwamoto Koichi , Filippenko Alexei V. , Foley Ryan T.
Published: June 2019

The properties of the best-observed peculiar, SN 1998bw-like Type Ic supernovae (sometimes called “hypernovae” ) are reviewed, starting from SN 1998bw itself and including SNe 1997ef and 2002ap. Analysis of the light curves and the spectra shows that, while these SNe display a range of properties (kinetic energy, mass of the ejecta, mass of 56Ni synthesized in the explosion), they have in common a larger-than-normal explosion kinetic energy, giving rise to the characteristic broad-lined spectra. Also, they all come from the collapse of bare CO cores of massive ( ≳ 20M⊙) progenitor stars. Some of the properties of these SNe, such as kinetic energy and mass of 56Ni, are probably correlated with the mass of the progenitor. Evidence that these powerful events are intrinsically asymmetric, suggesting that a correlation with at least some gamma-ray bursts can be expected, is also discussed.
How Common are Engines in Ib/c Supernovae?
Authors: Berger Edo
Published: June 2019

The association of γ-ray bursts (GRBs) and core-collapse supernovae (SNe) of Type Ib and Ic was motivated by the detection of SN 1998bw in the error box of GRB 980425 and the now-secure identification of a SN 1998bw-like event in the cosmological GRB 030329. The bright radio emission from SN 1998bw indicated that it possessed some of the unique attributes expected of GRBs, namely a large reservoir of energy in (mildly) relativistic ejecta and variable energy input. Here we discuss the results of a systematic program of radio observations of most reported Type Ib/c SNe accessible to the Very Large Array, designed to determine the fraction of Type Ib/c SNe driven by an engine. We conclude that: (i) the incidence of such events is low, < 3%, and (ii) there appears to be a clear dichotomy between the majority of hydrodynamic explosions (SNe) and engine-driven explosions (GRBs).
The Radio Afterglows of Gamma-Ray Bursts
Authors: Frail Dale A.
Published: June 2019

Radio afterglow observations continue to provide complementary and sometimes unique diagnostics on gamma-ray burst explosions, their progenitors and their environments. In this review we will first describe current search strategies and the observational properties of the detected sample. In the second part of this review we will follow the evolution of a typical radio afterglow, describe the diverse phenomenology that is observed, and interpret these observations within the framework of the fireball model.
Particle Acceleration in Gamma-Ray Bursts
Authors: Kirk J.G.
Published: June 2019

Simple kinematic theories of particle acceleration at relativistic shocks lead to the prediction of a high-energy spectral index of −1.1 for the energy flux of synchrotron photons. However, several effects can change this picture. In this paper I discuss the effect of magnetic field generation at the shock front and, by analogy with the Crab Nebula, suggest that an intrinsic break in the injection spectrum should be expected where the electron gyro radius is comparable to that of protons thermalized by the shock.
The First Steps in the Life of a GRB
Authors: Aloy Miguel A.
Published: June 2019

We present some preliminary results of relativistic hydrodynamic simulations of post-neutron star merger disks as potential candidates for progenitors of short-lasting gamma-ray bursts. We discuss some of the generic conditions under which a gamma-ray burst can be initiated in this kind of progenitor and the main characteristics of the resulting outflow.
The Standard Candle Method for Type II Supernovae and the Hubble Constant
Authors: Hamuy Mario
Published: June 2019

The “standard candle method” for Type II plateau supernovae produces a Hubble diagram with a dispersion of 0.3 mag, which implies that this technique can produce distances with a precision of 15%. Using four nearby supernovae with Cepheid distances I find H0(V)=75±7, and H0(I)=65±12.
The Host Galaxies of High-Redshift Type Ia Supernovae
Authors: Sullivan Mark , Ellis Richard ,   the Supernova Cosmology Project_a3
Published: June 2019

We present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies support earlier claims for a cosmological constant, which we demonstrate at ≃ 5σ significance, and the internal extinction implied is small even for late-type systems (AB < 0.2). Furthermore, the scatter observed in the SNe Ia Hubble diagrams correlates closely with host galaxy morphology. We find this scatter is smallest for SNe Ia occurring in early-type hosts and largest for those in late-type galaxies. Moreover, SNe residing in late-type hosts appear fainter in their light-curve-width-corrected luminosity than those in early-type hosts, as expected if a modest amount of dust extinction is a contributing factor. Thus, our data demonstrate that host galaxy extinction is unlikely to systematically dim distant SNe Ia in a manner that would produce a spurious cosmological constant.
Constraints on SN Ia Progenitors and ICM Enrichment from Field and Cluster SN Rates
Authors: Maoz D. , Gal-Yam A.
Published: June 2019

The iron mass in galaxy clusters is about 6 times larger than could have been produced by core-collapse SNe, assuming the stars in cluster galaxies formed with a standard IMF. Type-Ia SNe have been proposed as the alternative dominant iron source. We use our HST measurements of the cluster SN-Ia rate at high redshift to study the cluster iron enrichment scenario. The measurements can constrain the star-formation epoch and the SN-Ia progenitor models via the mean delay time between the formation of a stellar population and the explosion of some of its members as SNe-Ia. The low observed rate of cluster SNe-Ia at z ~ 1 pushes back the star-formation epoch in clusters to z > 2, and implies a short delay time. We also show a related analysis for high-z field SNe which implies, under some conditions, a long SN-Ia delay time. Thus, cluster enrichment by core-collapse SNe from a top-heavy IMF may remain the only viable option.
Dark Energy: Nature and Robustness
Authors: Blanchard A. , Zolnierowski Y.
Published: June 2019

Supernovae have provided the evidence for the existence of a dominant dark energy component of the Universe. The commonly accepted form of such a component is the quintessence. Here, we show that the possible nature of this component is rather well constrained by combining the various existing observational cosmological data. However, relaxing some of the various hypothesis can lead to somewhat different results.
Who are our Students — And why does it Matter?
Authors: Greenstein George
Published: June 2019

When designing courses in astronomy - or any other science - there is a tendency to assume that the students whom we are addressing are younger versions of ourselves. As undergraduates we studied astronomy and now we are practicing it: it is natural to assume that the students we teach are destined to go on to become scientists themselves. But while this was a perfectly valid assumption in the past, it is valid no longer; and if we do not adjust our teaching methods accordingly, we do our students a grave disservice.
New trends in university education in Russia: teaching Natural History for humanities
Authors: Gulyaev Sergei A.
Published: June 2019

A reform of the content of university education is taking place in Russia today. A restoration of human directed principles, the denial of strict ideological components in education and an improvement in the teaching content of the humanities, are among the most important characteristics of the on-going reforms. An important part of today's activities is the introduction of the basics of natural sciences to the process of teaching humanities. We have gained four years experience in the establishment of natural sciences in humanities at the Ural State University (Ekaterinburg, Russia).
The challenge of teaching astronomy in developing countries
Authors: Onuora Lesley
Published: June 2019

Having recently returned to England (where I am an Open University tutor) after having spent about 18 years teaching Physics and Astronomy at the University of Nigeria at Nsukka in the Eastern part of Nigeria, I find myself in an unusual position to understand the difficulties of teaching such a rapidly changing subject as astronomy in an isolated place like Nsukka. For example I have seen a great contrast between the OU Astronomy and Planetary Science course material and the few available text books at Nsukka. Although not very mathematical, the OU material includes a lot of the latest research results and theories, whereas at Nsukka the books have hardly changed in the past 20 years.
Identifying and Addressing Astronomy Misconceptions in the Classroom
Authors: Comins Neil F.
Published: June 2019

Students come into our classrooms with many misconceptions about science in general and astronomy in particular (see numerous papers and references in Novak, 1993 and Pfundt & Duit 1993). These beliefs evolve from a variety of sources throughout childhood and adolescence (Comins, 1993a, 1993b, 1995). I have found that directly addressing these incorrect beliefs in the context of their origins helps my students replace them with correct knowledge. By understanding the origins of their misconceptions students can screen information more effectively, i.e., they learn to think more critically. My purpose in this paper is to briefly identify origins of misconceptions and classroom techniques for replacing them.
Public Education: the ultimatum for the profession
Authors: Othman M.
Published: June 2019

The impact of public education is without question in the ‘public good’ domain and hence there is really no need to justify the demand for it. However, some professionals and scientists remain unconvinced about the necessity for it. This paper will lay out the benefits it holds for the scientists, categorise the target groups and identify the methods of approach for each target group and finally outline some strategies that can be adopted to achieve the educational aims.
Astronomy Education in Latvia - problems and development
Authors: Vilks I.
Published: June 2019

School education in Latvia, as in many other countries, is divided into two stages: primary and secondary education. Primary education is compulsory. Every year 30 000 new school children start attending primary school. This is a potential audience that can study astronomy fundamentals. During first grade studies school children learn the basics of natural science which include some elements of astronomy. These lessons are given once a week. At this stage children's interest in the Universe is great; therefore the most active teachers use some out of curriculum activities to give the schoolchildren an idea about the stars, planets and other celestial bodies. The science curriculum itself contains very few elements of astronomy (Karule, 1995). Even more many teachers have problems teaching science at the elementary school, because they are afraid that it is too sophisticated. This situation should be corrected, but at the moment no teacher training in science is planned.
Desktop Space Exploration
Authors: Martin-Smith M. , Buckland R.
Published: June 2019

The Humble Space Telescope project aims to launch a small space telescope for educational and recreational purposes, in time for the New Millennium.

The arrival of the 3rd Millennium, accompanied in the United Kingdom by a Millennium Commission distributing 250 million per year of National Lottery funds for good causes and imaginative projects which would otherwise require direct funding by the taxpayer, provides a unique opportunity to design, build and operate a small but capable version of the pioneering Hubble Space Telescope.

In July 1994, a leading British newspaper with a long history of covering developments in science, launched a competition for members of the public to propose science projects to be funded by the Millennium Commission.
New Trends in Astronomy Teaching
Authors: Abati L.E.
Published: June 2019

We are all aware of the fact that Astronomy teaching is not an easy task for many different reasons which we are going to examine during this Colloquium. The present contribution focuses on one of these reasons we consider of major importance for Astronomy in the school: Teacher Training.

Teacher training has been debated extensively for a long time and discussion is being presently livened up.
Measuring the Eccentricity of the Terrestrial Orbit: An Experiment in the Classroom
Authors: Szostak R.
Published: June 2019

Most textbooks of physics present the terrestrial orbit by a drawing which shows an ellipse of substantial eccentricity. This suggests a remarkable variation of the distance between Sun and Earth during the year up to a value of about 3:1 and more. Imagine the dramatic variation in size of the radiating area of the Sun seen by the terrestrial inhabitants with all the terrible consequences for temperature. All this is not true. There is no obvious change in size of the solar disc.
Classroom Activity: Kepler's Laws of Planetary Motion
Authors: Tsubota Y.
Published: June 2019

This activity was originally developed by a group of teachers in Japan during 1960s under the influence of the American Curriculum-Reform Movement. This was used in Earth Sciences in order to develop the students’ cognitive skill. Kepler had been trying to analyze Tycho's observations of Mars, fitting them into the Copernican orbital system. It simply would not work. The problem is with the circular orbit that the Copernican system still used. Mars obviously did not have a circular orbit about the Sun. So Kepler tried a variety of other geometrical shapes, until he finally found the ellipse.
Collaboration As a Viable Approach for Making Astrophysics Research Accessible to the K-12 Community Through the Internet and the World Wide Web
Authors: Hawkins Isabel , Battle Robyn , Wilson Marlene
Published: June 2019

We describe a partnership approach in place at UC Berkeley's Center for Extreme Ultraviolet Astrophysics (CEA) that: (a) facilitates the adaptation of astrophysics data and information from NASA and other sources for use in the K-12 classroom, (b) facilitates scientists’ participation in astronomy education, and (c) engages a sustained collaboration typically including personnel from research institutions, centers of informal science teaching such as museums and planetaria, university-based schools of education, and K-12 schools. We are investigating several ways of engaging scientists in partnerships for the purpose of making their research results accessible in appropriate ways to the K-12 community via Internet and World Wide Web technologies. Our investigation addresses the hypothesis that the transition of scientific data and research results from the workplace to the classroom can be facilitated by the joint creation of curriculum materials by teams of cognitive experts, subject-matter experts, and teachers.