bluuebunny/crossref_metadata_2025 huggingface dataset:
Inference of the Hard X-Ray Source Dimensions in the 1972, August 7 White Light Flare
Authors: Rust David M.
Published: July 2016

Broadband photographs and spectra of the white light flare of 1972, August 7 have been compared with hard X-ray spectra from the same event. There is a very close temporal correspondence between the hard X-ray and white light emission curves, and these emissions come from layers that are separated by a height of less than 2000 km. The flare shows at least two distinct particle acceleration phases: the first, occurring at a stationary source, gave very bluish continuum emission from 4 bright stationary knots while the X-ray (E > 60 keV) spectrum hardened and reached peak intensity. This phase occurred between 1520 and 1523 UT. In the second phase (1524–1537 UT) the bright knots dissolved and a faint wave moved out from the flare center at 40 km s–1. The spectrum of the wave was nearly flat in the range 4950–5900 Å and analysis of the spectrum indicates that the emission was probably due to heating and ionization by 20–100 keV electrons. The X-ray spectrum, as derived from Interkosmos 7 and ESRO TD-1A satellite data, becomes softer during the wave phase. The close correspondence between the X-ray and continuum emission events shows that, in effect, the hard X-ray source has been resolved. It consists of several changing patches approximately 3″ × 5″ in area, consistent with the upper limit of 1′ from balloon observations (Takakura et al., 1971).
Relation of Microwave Emission to X-Ray Emission from Solar Flares
Authors: Takakura Tatsuo
Published: July 2016

Recent observations of impulsive microwave and hard X-ray emissions during the early phase of the flares are briefly reviewed in order to deduce the dynamics of energetic electrons consistently from two view points of the microwaves and X-rays. An emphasis is put on the necessity of distinction between temporal and spatial variations so far confused in the interpretation of the time histories of the X-ray and radio emissions. The role of plasma turbulence on the dynamics of the energetic electrons is shown to be important in deducing the model of X-ray and radio sources.
Nonthermal Processes in Large Solar Flares
Authors: Hudson H. S. , Jones T. W. , Lin R. P.
Published: July 2016

In many small solar flares the ∼10–100 keV electrons accelerated during the flash phase contain the bulk of the total flare energy output. In large flares, such as those in the period 1972, August 2–7, the flash phase electrons are present in substantially greater numbers. These electrons can explosively heat the chromosphere-lower corona and eject flare material. The ejected matter can produce a shock wave which will then accelerate nucleons and electrons to relativistic energies. We analyze energetic particle, radio, X-ray, gamma ray and interplanetary shock observations of the 1972 August flares to obtain quantitative estimates of the energy contained in each facet of these large flares. In general these observations are consistent with the above hypothesis. In particular:

(1)

From the X-ray emission (van Beek et al., 1973) the energy contained in >25 keV electrons is calculated to be 2 × 1032 erg for the 1972, August 4 event. Since the lower energy cutoff to the electron spectrum is known to be below 25 keV and possibly below 10 keV, the electrons contain enough energy to produce the following interplanetary shock wave, which has by far the bulk of the energy dissipated in the flare. Similar numbers are obtained for the large August 7 flare event.

(2)

From the γ-ray emission (Chupp et al., 1973) the energy in protons dumped at the same level of the atmosphere, assuming a thick target situation, is at least a factor of three smaller than the electrons. Moreover the γ-ray emission indicates that the bulk of the protons are accelerated at least several minutes after the electrons. Thus it is more likely that the electrons are responsible for the flare optical (Hα and white light) emissions which occur in the chromosphere.

(3)

Approximately 5% of the electrons and 99% of the protons escape into the interplanetary medium to be observed by spacecraft. This situation is consistent with the hypothesis of shock acceleration of the protons high in the solar corona.

(4)

The four most intense X-ray bursts observed during the period July 31–August 11 are the only bursts followed by an interplanetary shock wave and a new injection of energetic protons into the interplanetary medium.
Long Carbon Chain Molecules in the Laboratory and in Space
Authors: Winnewisser G. , Toelle F. , Ungerechts H. , Walmsley C. M.
Published: July 2016

The unsaturated long carbon chain molecules of the type HC2n+1N (with n=1,2..) have the remarkable property of being very stable under a wide variety of different laboratory and interstellar conditions. In fact, they can be synthesized in the laboratory under the action of a radio frequency discharge in a mixture of acetylene, HCCH, and hydrogen cyanide, HCN (Creswell et al. 1977, Winnewisser et al. 1978). Once they are formed they are for example very stable towards temperature changes as well as saturation of the carbon bonds due to hydrogen addition. In the laboratory their chief cause of destruction is polymerization. These experiments were triggered by our observation that in the course of producing hydrogen isocyanide, HNC, (Creswell et al. 1976) by reacting CH3I with N2in a gas discharge, also small amounts of HC3N were present which clearly requires the joining together of four heavy atoms from different starting molecules.
Cloud-to-Cloud Variations in H2Co-to-H2 Ratios
Authors: Sherwood W. A.
Published: July 2016

The ratio H2CO/H2 has been determined for Heiles Cloud 2 (HC2) (Sherwood and Wilson, 1980, and references therein). Rather surprisingly, the ratio was much larger than that found by Kutner (1973) in a cloud KC only 3 degrees away. In both ratios the H2 density was determined from a relation between star counts and dust column density (see Sherwood and Wilson, 1980). Two other clouds have been studied in a similar manner: Khavtassi 3 (K3) (Myers, 1975) and ρ Oph (Myers et al., 1978). The ratio H2CO/H2 varies among the four clouds as does the minimum visual extinction apparently required before H2CO can form. The data are summarized in the Table. In all cases linear fits were used to determine H2CO/H2.
CO (J=2-1) Observations of the Carina Nebula and G 333.6-0.2 and a Search for CO in LMC and SMC
Authors: de Graauw T. , Lidholm S. , Fitton B. , Israel F. P. , Beckman J. , Nieuwenhuyzen H. , Vermue J.
Published: July 2016

We used the ESO 3.6 m telescope at La Silla (Chile) in conjunction with the Estec heterodyne receiver to observe CO (J=2-1) emission from southern sources. The telescope HPBW was 2.2 arcmin, the beam efficiency 43 per cent. The receiver used backward-wave oscillators and Schottky barrier diode mixers. It had a single-sideband noise temperature of 4000 K at 230 GHz. The backend was a 256 channel filterbank of 1 MHz (1.3 km s−1) bandwidth per channel. Calibration was done in the usual way.
High Rate of Destruction of Molecular Clouds by Hot Stars
Authors: Heydari-Malayeri M. , Lortet M. C. , Deharveng L.
Published: July 2016

Tenorio-Tagle (1979) first proposed the idea of a third dynamical phase, the champagne phase, following the formation and expansion phases of an HII region; the idea was further explored by Bodenheimer et al. (1979) and Tenorio-Tagle et al. (1979). The champagne phase begins when the high pressure gas of an HII region formed inside a molecular cloud reaches the edge of the cloud and bursts into the lower pressure, low density, intercloud medium. One important implication of the model is the prediction of an enormous enhancement of the rate of erosion of the molecular cloud by the ionising radiation of hot stars, which begins as soon as the process of the decrease of the gas density between the star and the cloud is started. The proportion of hydrogen molecules eroded by ionising photons may reach about 10-2. The mass eroded may exceed the mass of the ionised gas in the case where the ionisation front reaching the edge of the cloud is of D-type. Additional mechanisms (for instance stellar winds), if at work, may even increase the efficiency of the mechanism.
Hydrostatic Models of Molecular Clouds
Authors: De Jong T. , Dalgarno A. , Boland W.
Published: July 2016

It is customary to convert observed brightness temperatures of molecular lines to molecular column densities by assuming some excitation temperature to describe the population of the energy levels of the molecule. Observers often speak about “abundances” after dividing these column densities by the dimension of the cloud that is being studied. This procedure can be misleading because the level populations are usually not well characterized by one single excitation temperature and because clouds are probably quite centrally condensed. Some molecules are formed preferentially at high densities in the opaque cores of clouds, others reach their maximum abundance in the moderately shielded much less dense outer regions of clouds.
Contagious B Star Formation in the Rho Ophiuchi Dark Cloud
Authors: Falgarone E.
Published: July 2016

Three young stars are still embedded in the small (0.7 pc wide) and densest region of the Rho Ophiuchi dark cloud. One of these stars coincides with the continuum source Oph 4 (Brown and Zuckerman, 1975). Their existence is indicated by the following: i) thermal continuum sources detected at 21 cm and 6 cm with the Westerbork Synthesis Radiotelescope (Netherlands) which display the presence of compact HII regions surrounding each of three stars; ii) peaks of CO emission (J = 1 → 0 transition) detected with the MWO antenna of MacDonald (Texas) which are associated with asymmetrically shaped lines; iii) C 158α (and S 158α for Oph 4) line emission mapped with the Nancay Radiotelescope. All these observations imply that the three stars have B3 - B2 spectral types.
The Hydrogen Molecule as a Collision Partner
Authors: Oka Takeshi
Published: July 2016

Because of its abundance in molecular clouds, the hydrogen molecule is the most important collision partner in a discussion of thermal equilibrium or non-equilibrium in most interstellar molecules. The purpose of this talk is to summarize the properties of the H2 molecule as a collision partner based on laboratory experiments on NH3-H2 collisions.
Laboratory Measurements of Oscillator Strengths of Ultraviolet Molecular Lines of HC1 and H2O and Column Densities of These Molecules in the Zeta Ophiuchi Cloud
Authors: Smith Peter L. , Yoshino K. , Parkinson W. H.
Published: July 2016

The oscillator strengths of two ultraviolet molecular lines expected to be seen in diffuse interstellar clouds have been measured. For the 1290.257 A° line of HC1, f=0.16±0.06. For the 1114.225 A° line of H2O, f=(5.0±2.0)x10−3. These results have been used in conjunction with observational data to compare measured and predicted column densities of these molecules in the ζ Óphiuchi cloud.
Chlorine Chemistry in Diffuse Interstellar Clouds
Authors: Black John H. , Smith Peter L.
Published: July 2016

The results of recent observations of the column densities of chlorine species in diffuse interstellar clouds are inconsistent with the column densities predicted by model calculations. The use of new atomic and molecular data fails to decrease the discrepancy. We speculate that the exothermic reaction C1++H2→HC1++H may not be rapid at the low temperatures prevailing in diffuse interstellar clouds.
Experimental Measurements of Ion-Molecule Reactions
Authors: Fehsenfeld F. C.
Published: July 2016

The applicability of ion-molecule reaction rate constants measured at room temperature to simulation of interstellar cloud chemistry is discussed. Three-body association-rate constants of C+ and NH+3 have been measured between 100 K and 300 K. These results give information about the same associations by radiative processes. Possible implications for interstellar molecule production by radiative association and free radical reaction are discussed.
An ICR Study of an Association Reaction at Low Pressure
Authors: Mcewan M.J. , Anicich V. G. , Huntress W.T. , Kemperer P. R. , Bowers M. T.
Published: July 2016

An ICR investigation of the association reaction

CH3+ + HCN CH3.HCN+

has shown the reaction follows second order kinetics over the pressure range 1 × 10-6 to 3 × 10-4 Torr with a rate coefficient of 2 × 10-10 cm3s-1. These results can be interpreted in terms of a saturated 3-body or radiative association mechanism.
Reproduction of the Interstellar Ice Band by Grain Mantle Analogs
Authors: Hagen W. , Tielens A.G.G.M. , Greenberg J. M.
Published: July 2016

The near-infrared spectrum of many sources associated with molecular clouds shows a broad absorption feature at 3.08 μm (e.g. Merrill et al., 1976; Harris et al., 1978). This feature has usually been attributed to absorption by H2O ice frozen on grains, but it has been impossible to satisfactorily reproduce the observed band shape (Merrill et al., 1976; Mukai et al., 1978). We have been able to obtain a complete fit of this absorption feature in the laboratory using very low temperature mixtures of H2O with other polar molecules. The preparation of these interstellar dust grain-mantle analogs has been described elsewhere (Greenberg, 1979; Hagen et al., 1979). They are prepared by allowing a gas mixture of simple molecules (e.g. CO, H2O, NH3, CH4 etc.) to condense on a low temperature (10 K) substrate. This frozen mixture can be heated and recooled. The samples are analyzed with an infrared spectrometer.
Correlations for Interstellar Molecules and Diffuse Bands
Authors: Somerville W. B.
Published: July 2016

Results are presented from a programme of optical spectroscopy and related studies which has the double purpose of investigating the structure of diffuse molecular clouds and of establishing tighter correlations for the unidentified interstellar diffuse bands.
Observations of the V=0 S(2) Line of Molecular Hydrogen at 12.28μm in the Orion Molecular Cloud
Authors: Geballe T. R. , Beck S. C. , Lacy J. H.
Published: July 2016

The 12.28μm pure rotational line of molecular hydrogen has been detected in emission from the region of vibration-rotation line emission in Orion. The line shapes, widths, and velocities are similar to those observed in the V=1 → 0 transition at 2.12μm. Constraints imposed by these new results on models of the emitting region are discussed.
Spectra of the 2.12μm Quadrupole Line of H2 in the Orion Molecular Cloud
Authors: Nadeau D. , Neugebauer G. , Geballe T. R.
Published: July 2016

New spectra of the 2.12μm line of H2 in Orion have been obtained during 1979 February at the Mount Wilson 2.5m and Palomar 5m telescopes. These data provide wider spatial coverage and higher spatial resolution than the observations reported earlier by Nadeau and Geballe (1979). The complete data, displayed here in two maps, are consistent with the earlier interpretation, which is summarized below.
Infrared Heterodyne Spectroscopy of Circumstellar Molecules
Authors: Betz A. L. , McLaren R.A.
Published: July 2016

Ammonia has been detected in the circumstellar envelopes of IRC+10216, VY CMa, VX Sgr, and IRC+10420. A number of absorption lines of 14NH3 in the ν2 vibration-rotation band around 28 THz (950 cm-1) have been observed at a velocity resolution of 0.2 km/s. Typical linewidths are 1 to 4 km/s, and the details of the line profiles provide additional insights on the process of mass loss in these stars.
Spectroscopic Studies of IRC+10216 and Similar Objects
Authors: Ridgway Stephen T. , Hall Donald N. B.
Published: July 2016

Spectroscopy of circumstellar molecular species in the 2-14μm range provides evidence for a range of shell optical depths in the +10216 class of stars. In some cases a photospheric spectrum is present. The spectrum of +10216 shows absorption over a range of velocities including two distinct velocities of different excitation temperature. The occurrence of multiple velocities may be common in similar objects.
Time Variation of SiO Maser Emissions
Authors: Ukita Nobuharu , Kaifu Norio
Published: July 2016

We report a series of observations of the v=1, J=2-1 transition of SiO (86243.28 MHz) toward four Mira variables (o Cet, R Leo, W Hya, and R Cas) and Orion A over the period September 1976 - February 1978. Observations were made with the 6-m mm-wave telescope of the Tokyo Astronomical Observatory. Most of the spectra were taken with an acousto-optical spectrometer with an effective resolution of about 57 kHz.
Time Variability of the Orion A, R Leo and o Ceti SiO (V=1, J=2-1) Masers
Authors: Hjalmarson Å. , Olofsson H.
Published: July 2016

We here report on observations of 86 GHz SiO (v=1, J=2-1) maser emission from the Mira variables R Leo and o Ceti and from Orion A, made between December 1977 and June 1979 with the new Onsala 20 m millimeter wave telescope equipped with a room temperature mixer. The SiO fluxes from R Leo and o Ceti appear to be correlated with their near infrared intensities, and to have a distinct phase lag with respect to the visual light curve. An irregular behaviour of the R Leo maser, at a time when the star approached an unusually bright maximum, is very probably a manifestation of the extreme sensitivity of the maser process to any disturbances. Definite intensity variations on a time scale of a day have been observed. The total integrated flux of the Orion A SiO maser is relatively stable but there are considerable relative intensity variations between the two main components, and weak emission appears to be present in the entire interval between the two strong features. Pumping considerations indicate that a very efficient, probably radiative pump is needed.
Observations of Masers in Regions of Star Formation
Authors: Downes D. , Genzel R.
Published: July 2016

This review covers recent progress in observations of masers in regions of star formation, especially in the years since the reviews by Burke (1975) and Lequeux (1977). Four regions of special interest are described in more detail: Orion, W51, W49 and W3.
Future Possibilities for Ultraviolet Observations of Interstellar Molecules
Authors: Carruthers George R.
Published: July 2016

Ultraviolet observations of interstellar molecules are currently being obtained primarily with two astronomical satellites, Copernicus (OAO-3) and International Ultraviolet Explorer (IUE). The former covers the wavelength range down to 900 Å with 0.05 or 0.2 Å resolution. IUE can observe fainter or more highly reddened stars than Copernicus, with 0.1 Å resolution, but its wavelength range does not include the resonance absorptions of the important interstellar molecules H2, HD, and N2.
New Experimental Possibilities and the Future at Far IR Wavelengths
Authors: Townes C. H.
Published: July 2016

The observation of molecular phenomena in interstellar clouds by spectroscopy in the longer wavelength region of the infrared is discussed. This is a region where sensitivity is almost universally affected by background continua, appropriate techniques may be either coherent or incoherent, and work above most of the atmosphere is required for much of the spectral range. So far, only a very limited amount of molecular work has been done in the far-infrared, but one can expect fairly rapid growth and important results.
On the Structure and Evolution of Massive Interstellar Clouds
Authors: Kimura H. , Cai-pin Liu
Published: July 2016

The evolution of massive clouds is discussed with emphasis on inhomogeneous and heterogeneous nature of the system. We start from the two-phase model of interstellar medium and choose initial conditions of the clouds as being in the vicinity of critical state for gravitational instability. The equilibrium and stability problem for clouds is formulated in terms of polytropic models. Combining this with the thermal and chemical balance problem, we find that, even before the commencement of gravitational collapse, the fragmentation due to thermal instability can occur. The system begins to contract at a rate much slower than free fall, and thereafter, its evolution is governed mainly by collisions between fragments. The collision dynamics of the N-fragment system should be examined carefully by numerical experiments. The general trend to be expected is that the system tends to develop into a core-halo structure, accompanying by sporadic local events of star formation. The core or a clustering of massive fragments near the center could grow up into a favourable formation site of star clusters.
Pre-Main-Sequence Stellar Evolution
Authors: Bisnovatyi-Kogan G.S.
Published: July 2016

The problems of the stellar evolution to the main sequence are reviewed, taking into account the effects of mass loss, rotation and binarity. Properties of T Tauri stars are discussed which are connected with the recent observations of these stars in ultraviolet and X-ray regions. FU Ori phenomen is considered briefly.
Formation of the Planets
Authors: Hayashi Chushiro
Published: July 2016

A timetable for an evolutionary sequence of processes, which begins with the formation of the solar nebula being nearly in equilibrium and ends with the planetary formation, is presented. Basic features of the processes and grounds for the estimation of time-scales are explained for each of the processes.
Dissipation of the Primordial Terrestrial Atmosphere Due to Irradiation of Solar EUV
Authors: Sekiya Minoru , Nakazawa Kiyoshi , Hayashi Chushiro
Published: July 2016

When the Earth had grown to the present mass through accretion of the planetesimals in the solar nebula, the Earth was surrounded by a dense primordial atmosphere which was mainly composed of hydrogen and helium (Hayashi et al. 1979). Mass of the atmosphere was about 1×1026 g. We investigate the dissipation of this atmosphere due to the irradiation of solar EUV. The effect of solar wind is neglected. We assume that the flow of the escaping gas is spherically symmetric and steady. We impose the boundary condition that the flow velocity go through a sonic point. The results show that the primordial atmosphere is dissipated within a period of 5 × 108 yrs, which is the upper limit imposed from the theory of the origin of the present terrestrial atmosphere (Hamano and Ozima 1978), as far as the solar EUV flux is more than two hundred times as large as the present one. In this case, the rare gases contained in the promordial atmosphere are also dissipated owing to the drag effect (Sekiya et al. 1980).
The Formation of Compact Objects in Binary Systems
Authors: van den Heuvel E.P.J.
Published: July 2016

The various ways in which compact objects (neutron stars and black holes) can be formed in interacting binary systems are qualitatively outlined on the basis of the three major modes of binary interaction identified by Webbink (1980). Massive interacting binary systems (M1 ≳ 10–12 M⊙) are, after the first phase of mass transfer expected to leave as remnants:

(i) compact stars in massive binary systems (mass ≳ 10 M⊙) with a wide range of orbital periods, as remnants of quasi-conservative mass transfer; these systems later evolve into massive X-ray binaries.

(ii) short-period compact star binaries (P ~ 1–2 days) in which the companion may be more massive or less massive than the compact object; these systems have high runaway velocities (≳ 100 km/sec) and start out with highly eccentric orbits, which are rapidly circularized by tidal forces; they may later evolve into low-mass X-ray binaries;

(iii) single runaway compact objects with space velocities of ~ 102 to 4.102 km/sec; these are expected to be the most numerous compact remnants.

Compact star binaries may also form from Cataclysmic binaries or wide binaries in which an O-Ne-Mg white dwarf is driven over the Chandrasekhar limit by accretion.
Rotation and the Evolution of the Mass-Accreting Component in Close Binary Systems
Authors: Packet Wim
Published: July 2016

When mass is transferred between the two components in a close binary system, the matter falling towards the secondary star can gain a considerable amount of angular momentum. Eventually a ring or disk around this star is formed. The star can increase its angular momentum by accreting part (or the whole) of this matter. We have examined the ensuing changes in rotational velocity of the mass-accreting star. A simplified calculation (assuming accretion from a ring, rigid rotation of the star, and taking the stellar radius as well as its radius of gyration constant) shows that the star reaches its break-up velocity after increasing its original mass by only a few percent.
Asymmetric Supernova Explosions: The Missing Link between Wolf-Rayet Binaries, Run-Away OB Stars and Pulsars
Authors: De Cuyper Jean-Pierre
Published: July 2016

The WR binary systems, consisting of a WR star and an O or B star companion, are supposed to be the progenitors of the massive X-ray binaries. The missing link is generally accepted to be the SN explosion of the WR star which leaves a pulsar remnant. As most pulsars originate from single stars, observations of their proper motions indicate that they receive at their birth a “kick” velocity of about 100 km s−1. We assume this velocity to be due to the asymmetry of the SN explosion. This asymmetry, together with the loss of the SN shell and its impact on the OB star, may cause to disrupt the remaining system.

For the ten best known WR binaries we evaluated the survival probability P after an instantaneous SN explosion, leaving a 1.5 M⊙ collapsar with a random orientated kick velocity of 75 kms−1 (case a) and 150 kms−1 (case b) respectively. The influence of the impact is found to be marginal. The run-away velocity of the remaining system and of the disrupted OB star are comparable and of the same order of magnitude, but smaller than the initial orbital velocity of the OB companion; which decreases for increasing values of the initial orbital period. They are found to be independent of the kick velocity.
Comptonized X-Ray Emission from the Accretion Disk Around a Massive Black Hole
Authors: Takahara F.
Published: July 2016

We report the Monte Carlo simulation of the unsaturated Comptonization to probe the phyiscal state of the accreting plasma near a compact object. We calculate the emission spectrum and the Compton cooling rate of the plane-parallel hot plasma layer with the finite optical depth to the Thomson scattering, τ. The distribution of electrons is assumed to be a relativistic Maxwellian with the temperature Te. The energy and angular distribution of the soft photons impinging on the plasma layer is taken to be Planckian with the temperature Tph. We use the Klein-Nishina formula for the scattering between a photon and an electron.
Can Stellar Atmospheres be in Quasi-Static Equilibrium in the Presence of Magnetic Fields?
Authors: Nariai Kyoji
Published: July 2016

Among the observational astronomers it is quite customary to assume potential magnetic fields in calculating the strength and the direction of the magnetic fields on the stellar surface. People use this assumption because

1.

it is easy to calculate,

2.

it is possible to fit the observations with the calculations to some extent using the parameters inherent to the model,

3.

at a first glance, there is no difficulty in assuming both potential magnetic fields and static stellar atmosphere because they do not interact each other (except at the pole).
Influence of Convection on the Pulsational Stability of Stars
Authors: Osaki Y. , Gonczi G.
Published: July 2016

Influence of convection on the pulsational stability of stars is examined based on Unno's (1967) theory of time-dependent convection. This theory is an extension of Vitense's local mixing-length theory of convection to the time-dependent problem. The equations of linear non-adiabatic pulsations, which include the thermal interaction between convection and pulsation, have been solved numerically on a series of Cepheid models. It is found that the thermal eigenfunctions (of δ T/T and δ L/L) exhibit spatial oscillations with short wavelength in cool stellar models where the energy is mostly transported by convection. This phenomenon of spatial oscillations is interpreted, and it is shown that they arise because of the phase lag of the convective flux to pulsation and they are related to the local character of the convection theory. It is found that the spatial oscillations play a determinant role in the pulsational stability in the region of the red edge of the Cepheid instability strip, as far as the thermal convection-pulsation coupling is concerned. The details of this study have been pulbished in Astronomy and Astrophysics.
Supernova Explosions in Degenerate Stars —Detonation, Deflagration, and Electron Capture—
Authors: Nomoto Ken'ichi
Published: July 2016

Presupernova evolution and the hydrodynamic behavior of supernova explosions in stars having electron-degenerate cores are summarized. Carbon deflagration supernovae in C+O cores disrupt the star completely. On the other hand, in electron capture supernovae, O+Ne+Mg cores collapse to form neutron stars despite the competing oxygen deflagration.

Also discussed are white dwarf models for Type I supernovae (SN I). Supernova explosions in accreting white dwarfs are either the detonation or deflagration type depending mainly on the accretion rate. The carbon deflagration model reproduces many of the observed features of SN I.
What can we learn about Cosmic Rays from the UV, Optical, Radio and X-Ray Observations of Supernova 1979c in M 100?
Authors: Palumbo G.G.C. , Cavallo G.
Published: July 2016

Theories on the Origin of Cosmic Rays almost invariably invoke the Supernova (SN) phenomenon in its early phases as the cause for production and acceleration of high energy particles. So far only optical information about SNe has been available and from it there is no direct evidence of Cosmic Rays. It is not surprising then that models of Cosmic Ray production are still rich in free parameters. On April 19th 1979 a very bright (~12 mag) SN, labelled 1979c, was detected in the relatively nearby galaxy (~16 Mpc) M 100 (≡NGC 4321). This galaxy, incidentally has produced 4 SNe in 78 years. Event 1979c was followed quite intensively in the optical and UV (with IUE) regions of the spectrum as well as observed at radio and X-ray frequencies. A detailed account of these observations is in press (Panagia et al. 1980). Here we summarize only very briefly the results relevant to the present discussion.
Extended Radio Sources
Authors: Fomalont Edward B.
Published: July 2016

The understanding of the nature of strong radio emission associated with galaxies and quasars has significantly increased in the last five years. A large contribution to this increase has been obtained from the arcsec and milli-arcsec mapping of radio sources which show remarkable features. Because of the recent, extremely good review articles concerning extended extragalactic radio sources (Miley 1980 and Willis 1978), I shall emphasize some new, mostly unpublished works, stemming from VLA observations. This is not to slight European experimental and theoretical work which have led in the formulation of our current thinking, but to try to bridge the inevitable communication gap caused by the Atlantic Ocean and ever higher airfares.
Particle Acceleration by Pulsars
Authors: Arons Jonathan
Published: July 2016

The evidence that pulsars accelerate relativistic particles is reviewed, with emphasis on the γ-ray observations. The current state of knowledge of acceleration in strong waves is summarized, with emphasis on the inability of consistent theories to accelerate very high energy particles without converting too much energy into high energy photons. The state of viable models for pair creation by pulsars is summarized, with the conclusion that pulsars very likely lose rotational energy in winds instead of in superluminous strong waves. The relation of the pair creation models to γ-ray observations and to soft X-ray observations of pulsars is outlined, with the conclusion that energetically viable models may exist, but none have yet yielded useful agreement with the extant data. Some paths for overcoming present problems are discussed.
Rayleigh Taylor Instabilities in the Interstellar Medium
Authors: Lachièze-Rey Marc
Published: July 2016

Parker (1966, 1969) proposed that the interstellar medium could be subjected to instabilities, able to destroy its structure in a time shorter than the galactic evolution time. He emitted the idea that this phenomenon could lead to halo formation, escape of magnetic field and cosmic rays from the galaxy, via some sort of interstellar “bubbles”, and also to cloud formation. He showed then that if the interstellar medium was well represented by a simple horizontal stratified equilibrium model, perturbations would effectively grow and destroy the structure.
Cosmic Ray Antiprotons 5–12 GeV
Authors: Gaisser T. K. , Owens A. J. , Steigman Gary
Published: July 2016

Secondary antiprotons are a potentially interesting probe of cosmic ray propagation because their production cross section is strongly energy-dependent, increasing by more than two orders of magnitude between 10 and 1000 GeV/c. This is quite unlike the case for fragmentation cross sections of complex nuclei, which are virtually constant with energy. Moreover, the flux depends primarily on the environment seen by protons which need not be identical to that probed by other nuclei.
Gamma Rays from Galaxy Clusters
Authors: Giler M. , Wdowczyk J. , Wolfendale A. W.
Published: July 2016

In our recent work we have shown that a good model for the highest energy cosmic rays is one where they are generated in clusters of galaxies with a relatively flat production spectrum and then propagate with an energy dependent diffusion coefficient. There is evidence for a similar flat production spectrum (γ ≃ 2.1) for both protons and electrons in our own Galaxy. Here we assume that the spectrum for clusters (specifically the VIRGO cluster) is independent of energy and an evaluation is made of the likely flux of γ-rays.
Search for X-Ray Sources in the COS-B Gamma-Ray Error Boxes
Authors: Bignami Giovanni F.
Published: July 2016

The publication of the first and preliminary second catalogue of the COS-B sources, has brought to the attention of the astronomical community the new reality of the high-energy Galactic Gamma-Ray Sources (GGRS). It is worth recalling here the definition of such objects, in the COS-B sense: “A GRS is a significant excess of photon counts, compatible with the instrument's angular resolution, or, more clearly, with the instrument's Point Spread Function”. This definition of an unresolved (as it is the case for the vast majority of the GGRS) GRS is, to some extent, dependent on the shape of the source spectrum; however a general shape of the PSF for the case of the source associated with 3C273 can be found in Bignami et al, 1980. Naturally, the absolute flux (i.e. the total number of photons) from a source is also important in determining the positional error, especially when usage is made of the cross-correlation method. Typical photon numbers (100 Mev) for GGRS range from 50 to few hundreds. The COS-B catalogue error boxes are defined taking into account both the PSF and the photon statistics; it is then apparent that the search for candidate counterparts of the GGRS should be carried out inside such boxes, or in their immediate vicinity, and that, for examples, such loose positional coincidences as obtainable by increasing a quoted error radius by 50%, let alone doubling it, are totally unacceptable. Systematic searches for counterparts at other wavelengths have not yet been carried out, except for a few cases of X-ray and radio observations, as for example in the case of CG 135+1 (the only COS-B GRS erbox compatible with a 4U erbox) which led to the discovery of a new X-ray QSO by Apparao et al, 1978.
Cosmic-Ray Injection into Shock-Waves
Authors: Cesarsky Catherine J. , Bibring Jean-Pierre
Published: July 2016

When corrected for the effects of propagation in the interstellar medium (i.s.m.), the observed composition of galactic cosmic rays can give us some clues as to the origin of these particles. It is noteworthy that the main pecularities of the cosmic ray source composition (CRS), as compared to normal i.s.m. abundances, bear some resemblance to that of i.s. grains, as inferred from i.s. absorption line measurements (e.g. York 1976): (1) the refractory elements Al, Si, Mg, Ni, Fe and Ca, which in i.s. clouds are almost completely locked into grains, are present with normal abundance ratios in the CRS. (2) normalized to Si, the volatile and reactive elements C, N, O, S and Zn are underabundant in CRS by factors of 2.5 to 6; these elements are only partially depleted in the i.s.m. (3) at a given rigidity the ratios H/Si and He/Si are lower than in the i.s.m. by a factor of ~ 25; while H and He atoms are virtually absent in i.s. grains. (1) implies that cosmic rays originate in astrophysical sites where the grains have either not condensated as yet, or where they have been (at least partially) destroyed. Then, to account for (2) and (3), one might consider that an unspecified mechanism selects the particles to be accelerated, possibly according to their first ionization potential (Cassé 1979 and references there-in).
Magnetospheric Processes Possibly Related to the Origin of Cosmic Rays
Authors: Haerendel Gerhard
Published: July 2016

Two processes are discussed which violate the frozen-in condition in a highly conducting plasma, reconnection and the auroral acceleration process. The first applies to situations in which . It plays an important role in the interaction of the solar wind with the Earth's magnetic field and controls energy input into as well as energetic particle release from the magnetosphere. Detailed in situ studies of the process on the dayside magnetopause reveal its transient and small-scale nature. The auroral acceleration process occurs in the low magnetosphere (β « 1) and accompanies sudden releases of magnetic shear stresses which exist in large-scale magnetospheric-ionospheric current circuits. The process is interpreted as a kind of breaking. The movements of the magnetospheric plasma which lead to a relief of the magnetic tensions occur in thin sheets and are decoupled along the magnetic field lines by parallel electric potential drops. It is this voltage that accelerates the primary auroral particles. The visible arcs are then traces of the magnetic breaking process at several 1000 km altitude.
THERMAL STUDIES OF PLANETARY SURFACES
Authors: Morrison David
Published: July 2016

Ground-based and spacecraft observations of planets, satellites, and asteroids in the thermal infrared have provided a wealth of information on planetary temperatures, dimensions, and surface properties. Internal heat sources have been revealed for Jupiter, Saturn, and Neptune, and active volcanism on Io has been discovered and monitored. The thermophysical properties of Mars have been mapped for nearly all the surface by spacecraft, and ground-based observations have given similar information for the Galilean satellites of Jupiter. Infrared radiometry thus sheds important light on significant problems of dynamics, interiors, and surfaces of solar system bodies.
THE IMPLICATIONS OF MOLECULAR HYDROGEN EMISSION
Authors: Beckwith Steven
Published: July 2016

Emission from vibrationally excited molecular hydrogen has been discovered in a variety of objects of widely differing ages and environs including molecular clouds, planetary nebulae, and a Seyfert galaxy. The observations of the H2 spectra indicate this emission arises in hot, nearly thermalized gas. While there is still some disagreement between detailed predictions of hydrodynamic calculations and recent observations, it is generally believed that energy supplied to the interstellar gas in the form of shock waves is responsible for the observed H2 emission.

Several of the H2 sources are molecular clouds associated with ongoing star formation, most notably the Orion Molecular Cloud. From the intensity, strength, temperature, and velocity of the molecular hydrogen emission, it is estimated that at least 1048 ergs has been deposited in the cloud over the last thousand years or so in the form of bulk kinetic energy. There is no clear explanation for this process, since the energy is large and the timescale short, and it appears unlikely that we should observe such events unless they occur frequently. Among the other H2 sources in molecular clouds, NGC 7538, DR 21, and W3 are of similar spatial extent and apparent luminosity as the Orion emission.
CONTINUUM OBSERVATIONS OF THE INFRARED SOURCES IN THE ORION MOLECULAR CLOUD
Authors: Grasdalen G. L. , Gehrz R. D. , Hackwell J. A.
Published: July 2016

The details of the processes which result in the formation of new stars are still virtually entirely obscure. Surprisingly little can be said with any assurance beyond the general view that the interstellar medium collects in large clouds, involving at least tens of solar masses, which then fragment into smaller pieces which proceed to collapse into individual stars. Numerous highly detailed theoretical predictions have been generated for the sequence of events expected in the fragmentation and collapse processes. However, the meager observational evidence we have on suspected young objects is fascinatingly at variance with these predictions.
VLBI Observations of Southern EGRET Identifications
Authors: Lovell J.E.J. , Tingay S.J. , Edwards P.G. , Jauncey D.L. , Preston R.A.
Published: July 2016

We present high resolution VLBI images of three southern radio sources: PKS 0208–512, PKS 0521–365 and PKS 0537–441. These sources have been identified as > 100 MeV gamma-ray sources with the Energetic Gamma-Ray Telescope (EGRET) on board the Compton Gamma-Ray Observatory (Thompson et al. 1995). These are the first results in a continuing program of VLBI observations of southern EGRET identifications with the Southern Hemisphere VLBI Experiment (SHEVE) array of telescopes (Jauncey et al., 1994).
A Counterjet in the Nucleus of Centaurus A
Authors: Jones D.L. , Tingay S.J. , Preston R.A. , Jauncey D.L. , Reynolds J.E. , Lovell J.E.J. , Mcculloch P.M. , Tzioumis A.K. , Costa M.E. , Murphy D.W. , Meier D.L. , Clay R.W. , Edwards P.G. , Ellingsen S.P. , Ferris R.H. , Gough R.G. , Harbison P. , Jones P.A. , King E.A. , Kemball A.J. , Migenes V. , Nicolson G.D. , Sinclair M.W. , Van OMMEN T.D. , Wark R.M. , White G.L.
Published: July 2016

Centaurus A (NGC 5128) is the nearest giant radio galaxy. It is a Fanaroff-Riley type 1 (low luminosity) radio source, but the compact radio source in the nucleus is strong enough that VLBI imaging has been possible with both the SHEVE array and the VLBA at several frequencies. These observations have detected a sub-parsec scale counterjet. This shows that jet formation in at least some FR I sources is intrinsically two-sided over very small distances and the radio jets in Centaurus A are probably only moderately relativistic. We also find evidence that the center of activity in Centaurus A is partially obscured by a disk or torus of dense plasma.
High frequency radio observations of the nucleus of Cen A
Authors: Abraham Zulema
Published: July 2016

Cen A (NGC5128) is a giant radio galaxy that in several ways behaves like a weak active galactic nucleus. It presents three pairs of radio lobes and a compact core with a one sided jet (Jauncey et al. 1995). The compact core is highly variable in wavelengths ranging from the radio region to X and γ rays (Kinzer et al. 1995). In the radio domain, the emission from the core dominates at high frequencies and a considerable effort was made to study variability at 22 and 43 GHz for more than ten years (Botti & Abraham 1995).
Multi-Frequency VLBI observations of 3C390.3
Authors: Preuss E. , Alef W. , Kellermann K. I.
Published: July 2016

We have mapped the broad line radio galaxy 3C390.3 at 1.3, 6, and 18 cm wavelengths with resolutions ranging from 0.2 to 2.7 mas. Our new 6 cm image is consistent with a stationary bright region located 4 to 5 mas from the core and motion of the other features with apparent velocities of 0.4 to 0.7 mas/yr. Our high resolution 1.3 cm image indicates that the ‘jet’ breaks up into 5 or more distinct features.
Variability characteristics of Blazar 0J 287
Authors: Takalo L.O. , Sillanpää A. , Pursimo T. , Lehto H.J. , Nilsson K. , Teerikorpi P. , Heinämäki P. , Kidger M. , DE DIEGO J.A. , Mahoney T. , Rodríguez-Espinosa J.-M. , González-Pérez J.N. , Boltwood P. , Dultzin-Hacyan D. , Benitez E. , Turner G. , Robertson J. , Honeycut R. , Efimov Yu.S. , Shakhovskoy N. , Charles P. A. , Kühl D. , Schramm K.J. , Borgeest U. , Linde J.V. , Weneit W. , Schramm T. , Sadun A. , Grashuis R. , Heidt J. , Bock H. , Wagner S. , Kümmel M. , Heines A. , Fiorucci M. , Tosti G. , Raiteri C. , Villata M. , Latini G. , Bosio S. , Ghisellini G. , De Francesco G.
Published: July 2016

Blazar OJ 287 is one of the best observed extragalactic objects. It's historical light curve goes back to 1890′s. Based on the historical behaviour Sillanpää et al. (1988) showed that OJ 287 displays large periodic outbursts, with a period of 11.7 years. We have monitored OJ 287 intensively for two years, during the OJ-94 project. This project was created for monitoring OJ 287 during its predicted new outburst in 1994. In the data archive we have over 7000 observations on OJ 287, in the radio, infrared and optical bands. This data archive contains the best ever obtained light curves for any extragalactic object. The optical light curve shows continuous variability down to time scales of tens of minutes. The variability observed in OJ 287 can be broken down to (at least) four different categories:
The Environment of OJ 287: Nearby Galaxies and a Long Optical Jet?
Authors: Sillanpää A. , Takalo L. , Nilsson K. , Pursimo T. , Teerikorpi P. , Heidt J. , Dultzin-Hacyan D. , Benítez E.
Published: July 2016

A widely accepted model for BL Lac objects is that they are radio galaxies with a relativistic jet pointing almost directly towards us. But we need a clear trigger mechanism for these jets. One possibility is the close interaction between the BL Lac host and the closeby galaxies (e.g. Heckman et al. 1986). This interaction has been seen many times in the case of quasars (Hutchings et al. 1989) but not so much is known about the close surroundings of the BL Lac objects although there has been some pioneer work like Stickel et al. (1993). The problem has usually been that the images are not deep enough and that the seeing has not been so good. To clarify the situation we have started an observing program to get very deep images in the sub-arcsecond seeing conditions from the whole 1 Jy sample (Stickel et al. 1991) of BL Lac objects. The aims of this study are: 1. to search for very close companions to the BL Lacs, 2. to study the large scale galaxy clustering around the BL Lacs and 3. to study the BL Lac hosts themselves.
A Single Baseline VLBI Survey of Southern Peaked Spectrum Sources
Authors: King E.A. , Mcculloch P.M. , Jauncey D.L. , Reynolds J.E. , Preston R.A. , Meier D.L. , Murphy D.W. , Tzioumis A.K. , Lovell J.E.J. , Van OMMEN T.D. , Jones D.L.
Published: July 2016

A sample of 38 southern peaked-spectrum radio sources from the Parkes Catalogue have been observed using single-baseline VLBI. Thirty three objects were successfully detected on baselines of > 30Mλ at 2.3 GHz. For 21 of these sources, the flux density in the compact components contributes more than half the total flux density of the radio emission. Twenty sources showed structure more complex than a point-source.
Statistical Analysis of Observations of a Complete Sample of Compact Extragalactic Radio Sources
Authors: Kovalev Y.Y.
Published: July 2016

Here are analyzed the results of instantaneous multifrequency observations for a complete sample of 113 extragalactic radio sources (see the paper by Yu.A. Kovalev et al. in these Proceedings) with declinations −30° ÷ 43° from the VLBI–survey. It is tested the hypothesis that quasars and BL Lacs have different nature. Statistical distributions for the turnover flux, turnover frequency, spectral indexes, and other parameters are analyzed.