bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonthermal Processes in Large Solar Flares
Authors: Hudson H. S. , Jones T. W. , Lin R. P. 
Published: July 2016

SummaryIn 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.
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 reactionCH3+ + 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.
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.
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.
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).
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.
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.
A Possible Fundamental Difference Between Radio Loud and Radio Quiet AGN
Authors: Calvani M. , Sulentic J.W. , Marziani P. , Dultzin-Hacyan D. , Moles M. 
Published: July 2016

We report on some striking differences between radio loud and quiet emitters that we found in a comparative analysis of the high and low ionization lines for 52 low redshift AGN (31 loud; 21 quiet).The broad components of Civλ1549 and Hβ were chosen as representative of the high and low ionization lines respectively. CIVλ1549 observations were obtained with the Faint Object Spectrograph on the HST. They were retrieved from the HST data archive and matching optical spectra for the region of Hβ were obtained at several ground based observatories. Details on observations, narrow/broad component deconvolution and profile cleaning from satellite lines (especially FeII) can be found in Marziani et al. (1995). The rest frame for each quasar was determined from the radial velocity of strong narrow lines, typically [Oiii]λλ4959,5007.
Radio-Optical Alignments in Nearby Cooling Flow Cluster Central Galaxies
Authors: Mcnamara B.R. 
Published: July 2016

The centers of dominant cluster galaxies in cooling flows are often unusually blue, they have spatially extended nebular line emission and bright, FR I radio sources (Fabian 1994). As a class, they are the most rapidly evolving giant elliptical galaxies known. Among the most interesting of these objects, the Abell 1795 (z = 0.06) and Abell 2597 (z = 0.08) central cluster galaxies have very blue, lobe-like structures that are located along their FR I radio lobes (McNamara & O'Connell 1993). This discovery was surprising because correlations between the radio source and blue optical continuum were thought to occur exclusively in powerful, FR II radio galaxies at redshifts z > 0.6 that show the alignment effect. By analogy with the distant radio galaxies, the blue lobes are thought to be regions of star formation that were triggered by the passage of the radio source (De Young 1995), or scattered light from an obscured, anisotropically radiating active nucleus that is beaming its light obliquely to the line of sight (Sarazin & Wise 1993; Crawford & Fabian 1993; Sarazin et al. 1995). Scattered light is usually polarized. Therefore, polarization measurements of the aligned optical continuum should provide a strong test of the scattering hypothesis.McNamara et al. (1995) have obtained U-band polarimetry of the blue lobes in the Abell 1795 cluster central galaxy. They found an upper limit to the degree of polarization of the light emitted from the lobes of < 7%. The accuracy of this measurement is limited by the presence of diluting background starlight. This limit is inconsistent with the lobes being scattered light that originated in an obscured, anisotropically radiating nucleus, unless the radiation is beamed and is viewed at an angle < 22° to the line of sight, which is unlikely. The absence of a detailed correspondence between the radio lobes and optical lobes and the absence of a polarized signal is also inconsistent with synchrotron light.The blue optical lobes are probably regions of vigorous star formation. If a burst of star formation were triggered by the expanding radio lobes, the age of the burst population should be ≃ 107 yr. The star formation rate in both lobes, assuming the Local IMF, would then be ≃ 20 M⊙ yr–1 and the stellar mass of the lobes would be ≃ 108 M⊙. The large cooling flow in A1795 may be fueling the star formation and the radio source or the fuel may have originated from one or more gaseous cluster galaxies that recently fell into the cluster's core. This result strongly suggests that the radio sources in central cluster galaxies may be a significant factor driving the evolution of their stellar populations.
Comptonization as Blazar High Energy Emission
Authors: Dreissigacker Oliver 
Published: July 2016

We explain the overall continuous Grazar (Gamma Ray Blazar) spectrum from the synchrotron turnover to the EGRET GeV detections by means of Comptonization in the parsec scale jet's substructures.While making use of the constraints on the synchrotron spectrum and other measurable quantities, no exotic particle acceleration is needed to achieve the high energy output.We show, that the “Lighthouse Model” of blobs of relativistic electrons, travelling with the jet plasma at relativistic speeds, produce both, correct timescales and shapes for the lightcurve, and correct ratios and slopes of the synchrotron, X-ray and γ-ray branches.
MHD Self-Similar Solutions for Collimated Jets
Authors: Trussoni E. , Sauty C. , Tsinganos K. 
Published: July 2016

The MHD modelling of jets in axisymmetric geometry requires the treatment of the Bernoulli and the transfield equations, that can be treated following a self-similar approach. This technique is based on two main assumptions: i) the physical variables are factorized; ii) a suitable scaling law in one direction is prescribed. Solutions self-similar in the r direction (in a spherical frame of reference) have been studied to model collimated winds from disks (Blandford and Payne 1982). Here we present solutions self-similar in the θ direction, suitable to study the collimated wind around the polar axis of a rotating object (Tsinganos and Trussoni 1991, Sauty and Tsinganos 1994). Our basic assumptions are:
–The magnetic flux function, that describes the poloidal components of velocity and magnetic field, is expressed as A(r, θ) ∝ f(r)sin2θ.–The density and the pressure of the plasma are assumed to scale linearly with A: ρ(r, θ) ∝ 1 + δA and P(r, θ) ∝ Po(r) (1 + KfA). Accordingly, the surfaces with equal poloidal Alfvén number M are spherical.
Doppler imaging of eclipsing binaries
Authors: Piskunov N. 
Published: July 2016

We describe the extension of our Doppler imaging technique to the case of eclipsing binary systems. Using numerical experiments, we show that the simultaneous imaging of both components breaks the north-south ambiguity that occurs for single stars with high inclination. Characteristic map distortions can be used to correct errors in the orbital parameters of the binary.We apply this technique to ER Vul – an active RS CVn type binary. Our preliminary results show the presence of the hot spots on the substellar sides of both components, perhaps due to the reflection effect.We also discuss application of the same technique to contact binaries, where non-sphericity is significant.
Positional Observations of Components of Triple Stars for the Hipparcos and HST Missions
Authors: Anosova J. P. , Orlov V. V. 
Published: July 2016

This work has been made in accordance with the plan of the International Working Group “Double Stars: HIPPARCOS Input Catalogue Consortium.” The precise coordinates for the components of the triple stars from the programs of the Astronomical Observatory (AO) of Leningrad State University (LSU) and the Uccle zone (declination from +30° to +50°) are determined. The work has been made by two methods: (1) special astrometrical observations for about 70 triple stars; some colleagues from the observatories in Pulkovo, Nikolaev, and Goloseevo (USSR), as well as from Belgrade (Yugoslavia) have taken part in this work; (2) statistical treatment for about 200 triple stars, using the data of the catalogues ADS and WDS—all available positional observations of the relative coordinates of the components.Also, the special observations of the triple stars in Pulkovo and Belgrade have been used, as well as the data from the catalogue by Ch. Worley from 1820 to 1988. The old observations by W. Struve in 1820-1830 play an important role. The data obtained are used for the compilation of the observational programs of the AO of LSU by the HIPPARCOS and HST.
Problem of Using Lunar Positional Observations for Determination of Zero-Points of Fundamental Star Catalogues
Authors: Fomin V. A. 
Published: July 2016

The long series of meridian observations of the Moon can be used for the precise determination of the equinox- and equator-corrections of a star catalogue. Systematic errors of different charts of the lunar marginal zone used for the reduction of the lunar limb observations have no influence on the determination of the secular variations of the zero-points of the fundamental coordinate system.From meridian observations of the lunar limb made during the interval 1923-1977 in Washington, Greenwich, Cape and Tokyo the following estimate is found for the correction to the right ascension system of the FK4 catalogue:

which is in disagreement with the values used for the compilation of the FK5 catalogue.
The SRS Catalog of 20,488 Star Positions Culmination of an International Cooperative Effort
Authors: Smith C. A. , Corbin T. E. , Hughes J. A. , Jackson E. S. , Khrutskaya E. V. , Polozhentsev A. D. , Polozhentsev D. D. , Yagudin L. I. , Zverev M. S. 
Published: July 2016

A major international effort to observe and compile the results of observations from many transit circle programs into a single catalog of positions referred to the FK4 system came to a conclusion with the completion and distribution of the Southern Reference Star (SRS) catalog of 20,488 stars. Previous discussions focussed on the adjustments to the observational material to refer it to the FK4 system and on the random errors as estimated from residual differences. In the present discussion, we give the results of internal comparisons which have been made between the individual contributing catalogs and the final combined SRS catalog. Also, results of a comparison between the SRS catalog and the AGK3R catalog are given where they overlap in the declination zone from +5 to −5 degrees. The possibility of magnitude equation and color error in the SRS catalog is discussed.The reduction procedure used to transform the version of the SRS catalog based on the FK4/B1950.0 system to the version based on the FK5/J2000.0 system is given.
The Second Cape Photographic Catalogue: CPC2
Authors: Murray C. A. , Penston M. J. , Zacharias N. , de Vegt Chr. 
Published: July 2016

Between 1962 and 1972 the southern hemisphere has been covered by a 4-fold overlap pattern on 5820 plates, taken with a scale of 100 arcsec/mm and using a visual bandpass. More than 2 million pairs of x,y coordinates of the 2 exposures from 276259 stars have been measured at RGO with the GALAXY machine. The conventional plate adjustment, carried out at Hamburg Observatory, is now complete. About 150 000 primary stars will achieve a catalogue accuracy of about 0.06 arcsec at epoch of observation.The rigorous FK4 and FK5 versions, using the SRS catalogue (C. Smith 1988), will be supplemented by preliminary new proper motions for those stars common with the SAOC. Finally, a rigorous block adjustment will be performed within the next year.
Magnetic Reconnection on the Sun
Authors: Priest E R 
Published: July 2016

Magnetic reconnection is a fundamental process in astrophysics which plays many different roles on the Sun. The classical theory of fast steady reconnection due to Sweet, Parker, Petschek and Sonnerup has been unified in a theory which possesses many new regimes that depend on the boundary conditions at large distances. For example, the flux pile-up regime possesses diverging flows, a long central diffusion region and a reconnection rate that is much larger than the Petschek value. Recent numerical experiments however, often possess three features that are not present in the earlier theoretical models, namely highly curved inflow field lines, separatrix jets and reversed current spikes, and so an attempt is described to include these features in a new theoretical model.Several solar phenomena where reconnection is believed to be operating are described. Cancelling magnetic features in photospheric magnetograms are probably evidence of reconnection submergence. Most prominences are of inverse polarity and have upflows driven by reconnection below them. Coronal heating may well be due to reconnection in many small current sheets. In solar flares reconnection may be driven below an eruptiing active-region prominence and hence power the high-temperature flare loops and chromospheric ribbons.
Evolution of Close Binaries and the Formation of Pulsars
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 outlined. It is argued that most of the remnants of massive stars (M1 ≳ 10 M⊙) will be runaway pulsars, with space velocities ≳ 100 km/s, i.e.:
(i)semi-conservatively evolving massive close binaries (~ 1/3 of all massive stars) after the first SN explosion consist of a massive star and a neutron star; subsequently, after a stage of common-envelope evolution and spiral-in most of these systems are disrupted in the second SN, producing two runaway pulsars, one young and one old.(ii)highly non-conservatively evolving systems (with initial mass ratio q0 ≲ 0.5 and binary periods up to several decades; ≳ 1/3 of all massive stars) will spiral-in during the first phase of mass transfer and are disrupted in the first SN explosion, producing one young runaway pulsar, together with a runaway star of low or moderate mass.
New Determination of the Polar Motion from 1890 to 1969
Authors: Fedorov E. P. , Rorsun A. A. , Major S. P. , Panchenko N. T. , Tarady V. K. , Yatskiv Ya. A. 
Published: July 2016

To obtain the coordinates of the Earth's pole almost all series of systematic latitude observations that continued for more than two years have been utilized. They are listed in Table I which comprises 92 series of observation at 72 observatories.Computation was made by the following stages. As initial data we used normal values of latitude φ1, φ2, ……. φn, i.e. the means of instantaneous latitudes over successive intervals of time. These values were smoothed using Whittaker's numerical method which is capable of giving the most probable curve of latitude variation. The smoothed values φ′ satisfy the following condition
where
hi is a measure of precision, λ2 an arbitrary number by means of which the degree of smoothing is set, and Δ3 designates the third difference of φ′. Whittaker's method was applied in different modifications according to whether or not the normal values of φ′i had an equal weight and were given at equidistant moments of time.For the origin of the system of coordinates we adopted the mean pole of the epoch of observation. Because of this the data given in Table II represent only the periodic part of the polar motion in the region of frequency from 0.77 to 2 cycles per year. In this connection the sequence of φ′ was subjected to filtration in order to eliminate variation of the mean latitude.Coordinates of the pole were computed in two approximations. First, it was assumed that all the series are of the same accuracy and so they were taken with an equal weight.The polar coordinates obtained on this assumption are denoted by x1, y1 and shown in the second and third columns of Table II. The divergences of the smoothed values φ′i from the latitudes computed with x1, y1 were denoted by zκi where the index κ designates the number of a series. Then for the second approximation each series of observation was taken with the weight inversely proportional to the mean value of for this series. The polar coordinates obtained in the second approximation are denoted by x2, y2 and given in the last two columns of Table II.The full paper with the tables will be published by the Ukrainian Academy of Sciences as a separate book.