bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvements to Reference Systems and Their Relationships
Authors: Seidelmann P. K. 
Published: June 2019

Reference Systems include the reference frames and their relationships, time arguments, ephemerides, and the standard constants and algorithms.The extragalactic, or radio, reference frame will be the basic frame. Achieving milli to microarcsecond accuracies at optical wavelengths will reduce the disparity between optical, radar, and radio reference frame determinations. Thus, the relationships and identifications of common sources should be much more accurate. Another significant change should be the ability to determine distances, and thus space motions on a three-dimensional basis, rather than the current two-dimensional basis of proper motions.Improvements in ephemerides provide the opportunity to investigate the difference between atomic and dynamical time, the relationship between the dynamical and extragalactic reference frame and the values of precession and nutation.Also, the relationships between the bright and faint optical catalogs, the infrared, and extragalactic reference frames should be better determined. Reference frames at other wavelengths will become determinable.
The Project OSI
Authors: Shao M. 
Published: June 2019

The OSI project at JPL is a study of a series of concepts for space based astrometric interferometry. The various concepts are designed for slightly different types of astrometry. The original concept OSI was designed for wide angle/global astrometry by look at stars about 30 degrees apart. A derivative of OSI, called SONATA was designed for narrow angle astrometry (10 arcmin) at sub-microarcsec levels for exo-planet searches. This paper describes optical concepts of theses instruments with regard to metrology and systematic error. In addition to conceptual designs, system error budgets and covariance analysis the OSI project has a technology development program in place to investigate the most difficult problems.Technology is being persued in three areas. One is laser metrology at the picometer level where sub-picometer accuracy for null metrology has been achieved and < 2 picometer accuracy has been achieved for relative metrology. A second area is the control of vibration on a large space structure. A 5 m truss structure has been built at JPL with an interferometer on the structure to test vibration isolation and control technologies. Tests with this structure will begin in winter of 1994. The key to vibration control for OSI will be the delay lines. The third technology project is a shuttle flight experiment, Stellar Interferometer Technology Experiment (SITE), currently in a phase A study, (part of NASA's INSTEP program). The goal is to fly the experiment on the Shuttle in 1997-1998.
New Measurements of Positions for the Astrographic Catalogue Stars
Authors: Ivanov G.A. , Kislyuk V.S. , Pakulyak L.K. , Sergeev A.V. , Sergeeva T.P. , Yatsenko A.I. 
Published: June 2019

Six observatories of the former USSR carry out photographic observations within the FON project (the fourfold coverage of the northern sky) since 1982. The same type wide-angle Zeiss astrographs (D=400 mm, F=2000 and 3000 mm) are used. At present Golosiiv Observatory almost finished the Kiev observational part of the project and the measurements of onefold coverage plates have been started. The special measuring machine PARSEC (Programming Automatic Radial-Scanning Coordinatometer) has recently been constructed for this purpose.We intend to apply the measurements of the FON project plates to the determination of new positions and proper motions of all stars in the Astrographic Catalogue (AC) using the last one as the first epoch of observations. AC is applied also as input catalogue for PARSEC. About 500 plates have been measured at the moment and proper motions for more than 500000 stars in different areas of the northern sky have been obtained.The accuracy of the FON positions and proper motions of stars from the measurements of onefold coverage plates is estimated to be 0.35 arcsec and 0.006 arcsec/yr, respectively.Futher investigations will be carried out in cooperation with Sternberg Astronomical Institute (Moscow, Russia) and Astronomisches Rechen-Institut (Heidelberg, Germany).The above-described reasearches became possible partly by Grant N V41000 from the International Science Foundation.
Intergalactic Gas
Authors: Field George B. 
Published: June 2019

Evidence that rich clusters of galaxies contain hot (T = 108 K) intracluster gas is reviewed. Such gas contributes little to Ω (0.003) but it has been argued that Ω must be less than 0.05 for true intergalactic gas, if accretion of more gas than is observed in rich clusters is to be avoided. This argument is reviewed.If the de Vaucouleurs' groups are bound by intracluster gas, T is expected to be 105 to 107 K and the contribution to Ω is ≃ 1. Since the clumping factor C is estimated to be ≃ 7, the resulting value of Ω2C is ≃ 7. This does not violate the observed diffuse soft X-ray background intensity. Gas should be sought in such groups. Smoothly distributed gas with 107 < T < 3 × 108 K and Ω = 1 is not ruled out by direct observations.
The Stability of Relativistic Systems
Authors: Chandrasekhar S. 
Published: June 2019

The stability of relativistic systems is reviewed against the background of what is known in the corresponding contexts of the Newtonian theory. In particular, the importance of determining whether Dedekind-like points of bifurcation occur along given stationary axisymmetric sequences is emphasized: the occurrence of such points of bifurcation may signal the onset of secular instability induced by radiation-reaction. (At a Dedekind-like point of bifurcation, the system can be subject, quasistationarily, to a non-axisymmetric deformation with an e2iϕ-dependence on the azimuthal angle ϕ.)A formalism is described in terms of which the normal modes of axisymmetric oscillation of axisymmetric systems can be determined. Specialized to neutral modes of oscillation the formalism provides an alternative proof of Carter's theorem and clarifies the minimal requirements for its validity. A parallel formalism is described for ascertaining whether an axisymmetric system can be subject to a quasi-stationary non-axisymmetric deformation. The possibility of applying this latter formalism to determining whether a Dedekind-like point of bifurcation occurs along the Kerr sequence is considered.
On Black and White Holes
Authors: Markov M. A. 
Published: June 2019

Various possible cases of spherically systems the matter of which is localized in a domain smaller than the corresponding gravitational radius is considered.The metic of the Friedmann closed world or of a part of it with an external continuation is suggested as a model of these systems.There can exist black holes which are described by semi-closed metrics (black holes of the second kind). The class of systems in question may be both in the state of collapse and in the state of anti-collapse (including the state of ‘white holes’).There are some grounds to suppose that collapse of celestial bodies should stop in the domain h/mvc, where mv is the mass of the vector meson, and that the pair production effect due to collapse of a charged sphere should conserve the Laplace determinism of the process.The role of the charges of sources of different fields (electromagnetic, meson vector, scalar long-range, scalar meson, various versions of neutrino fields) in the deformation of the external and internal metric of black and white holes is analysed.In this consideration a number of problems arises (the absence of horizon in the case of any small charges of scalar fields, the presence of the generalized Gauss theorem for vector meson field etc.), which provide evidence that the assertion ‘Black hole has no hair’ needs further investigations. In particular, the inverse process of formation of hair (e.g. vector-meson, scalar fields) in the process of anti-collopose has not been studied yet.For the limiting case of the Nordström-Reissner metric m = e (more correctly m → e) two essentially different possibilities of continuing to the internal metric are considered (the Papapetrou case and the case which we called ‘friedmon metric’ describing charged black holes of the second kind (friedmons)).In the case of charged holes of the second kind (friedmons) the occurance of quantum effects (pair productions) can reduce the horizon surface and violate the Hawking theorem.The notion of black holes may turn out to be essential in elementary particle theory: among the intermediate states in elementary particle theory there are states the characteristic feature of which is the localization of arbitrary large energies (masses) in a domain smaller than the gravitational radius.
The Magnetic Fields of Pulsars
Authors: Sedrakian D. M. 
Published: June 2019

Two generation mechanisms of magnetic fields in pulsars are considered.If the temperature of a star is more than 108K, the star consists of a normal fluid of neutrons, protons and electrons. Because the angular velocity of pulsars is not constant dω/dt ≠0, inertia effects can occur, and generate magnetic fields through the relative motion of charged particles with different masses. The kinematic viscosity of electrons is 30 times larger than that of protons; hence electrons move with the crust, but the proton-neutron fluid will move relative to the electrons. The magnetic momentum can be calculated by the following formula
where Meff = Mp + Mn(Nn/Np), R = radius of the star, σ = conductivity. For typical neutron stars we have dω/dt~ 10-8 s-2, R~106 cm, σ~1029 s-1 and we get a magnetic field of the order of 1010 G.
Galaxy Count Models and the Extragalactic Background Light
Authors: Shanks T. 
Published: June 2019

In this review we first discuss the various ingredients of the non-evolving models for galaxy count observations. These ingredients include the K-corrections, the galaxy luminosity function and its dependence on galaxy colour, the local space density of galaxies and the cosmological deceleration parameter. Comparing the updated count model with the most recent galaxy count observations, the conclusion is still that at B>22m the B (and the R) counts require very significant amounts of evolution to fit the observed, steep n(m) relations. We review models of galaxy luminosity evolution and also discuss the current debate as to whether B≈23m galaxies have z ≈1 or z ≈3.We also consider recent suggestions that the form of Tyson's counts at B=27m may constrain the cosmological deceleration parameter; contrary to the suggestion of Koo (1989), it is proposed here that if the turnover seen in Tyson's B counts is real then this argues for high values of qo and/or low galaxy formation redshifts. Finally, we consider the implications of these results for observations of the extragalactic background light (EBL) and conclude that in the ultraviolet (UV) and in the optical the contribution of faint galaxies to the EBL is likely to be small if the turnover in Tyson's counts is real. The galaxy count evidence gives less clear indications about the contribution of galaxies to the infrared EBL.
Binary Statistics Among Population II Stars
Authors: Zinnecker H. , Köhler R. , Jahreiß H. 
Published: June 2019

AbstractPopulation II stars are old, metal-poor, Galactic halo stars with high proper motion. We have carried out a visual binary survey of 164 halo stars in the solar neighborhood (median distance 100 pc), using infrared speckle interferometry, adaptive optics, and wide field direct imaging. The sample is based on the lists of Population II stars of Carney et al. (1994) and Norris (1986), with reliable distances from HIPPARCOS measurements.At face value, we found 33 binaries, 6 triples, and 1 quadruple system. When we limit ourselves to K-band flux ratios larger than 0.1 (to avoid background contamination), the numbers drop to 9 binaries and 1 triple, corresponding to a binary frequency of 6–7% above our angular resolution limit of about 0.1 arcsec. If we count all systems with K-band flux ratios greater than 0.01, we obtain 15 more binaries and 3 more triples, corresponding to a binary frequency for projected separations in excess of 10 AU of around 20 %. This is to be compared with the frequency of spectroscopic binaries (up to a period of 3000 days) of Population II stars of about 15 % (Latham et al. 2002). We also determined a semi-major axis distribution for our visual Population II binary and triple systems, which appears to be remarkably different from that of Population I stars. Second epoch-observations must help confirm the reality of our results.
The Mass Distribution of Secondaries to Solar-Type Stars
Authors: Abt Helmut A. , Willmarth Daryl W. 
Published: June 2019

AbstractTwo previous studies of the secondary mass function in spectroscopic binaries by Abt & Levy (1976) and by Duquennoy & Mayor (1991) are shown to be in good agreement if they are both plotted with the same abscissa scale. A new study of 271 main-sequence stars later than F6 V made with a radial-velocity accuracy of ±0.10 km s-1 yielded 10 new sets of orbital elements in addition to the 59 published ones. The resulting secondary mass function is nearly flat and shows that 2.2±1.5% of the primaries have low-mass (0.01–0.10 M⊙) companions. In contrast, the secondary mass function for visual binaries with separations >500 AU fits a van Rhijn function, as was shown previously by Abt and Levy.
Are Binary Separations Related to their System Mass?
Authors: Sterzik Michael F. , Durisen Richard H. 
Published: June 2019

AbstractWe compile most recent multiplicity fractions and binary separation distributions for different primary masses, including very low-mass and brown dwarf primaries, and compare them with dynamical decay models of small-N clusters. The model predictions are based on detailed numerical calculations of the internal cluster dynamics, as well as on Monte-Carlo methods. Both observations and models reflect the same trends: (1) The multiplicity fraction is an increasing function of the primary mass. (2) The mean binary separations are increasing with the system mass in the sense that very low-mass binaries have average separations around ≈ 4AU, while the binary separation distribution for solar-type primaries peaks at ≈ 40AU. M-type binary systems apparently preferentially populate intermediate separations. Similar specific energy at the time of cluster formation for all cluster masses can possibly explain this trend.
Observations of Hipparcos Double Stars with the WiynTelescope
Authors: Horch Elliott P. , Meyer Reed D. , van Altena William F. , MacKnight Meridith 
Published: June 2019

AbstractA program of follow-up observations of HIPPARCOS Double Stars has been started using the WIYN 3.5-m Telescope at Kitt Peak, Arizona. Observations are made with the recently-completed RYTSI speckle camera, which is capable of determining reliable magnitude differences at various wavelengths down to the diffraction limit of the telescope. Thus in addition to precise relative astrometry, component magnitudes and colors can be obtained in a survey mode for all systems observed. Preliminary results and system capabilities are described. The benefits of a sustained program of observations of the HIPPARCOS Double Stars include populating the mass-luminosity relation with many more points (once the orbital status of these stars is known and orbital parameters are determined in sufficient detail for gravitationally bound pairs), robust tests of stellar evolution calculations in cases where at least one component has evolved off the main sequence, and a more complete picture of the nearby field binary population.
Spectroscopic Binaries among a Complete Sample of Hipparcos M Giants
Authors: Jorissen A. , Famaey B. , Dedecker M. , Pourbaix D. , Mayor M. , Udry S. 
Published: June 2019

AbstractWe present the first eccentricity-period diagram for binaries among nearby field M giants, where an observed frequency of at least 8% of spectroscopic binaries is found.
High-Mass X-Ray Binaries and OB Runaway Stars
Authors: Kaper L. , Van der Meer A. , Tijani A.H. 
Published: June 2019

AbstractHigh-mass X-ray binaries (HMXBs) represent an important phase in the evolution of massive binary systems and provide fundamental information on the properties of the OB-star primaries and their compact secondaries (neutron star, black hole). Recent observations indicate that the neutron stars in some of these systems (Vela X-1, 4U 1700-37) are more massive than the canonical mass of 1.35 M⊙. These observations have important consequences for the equation of state at supranuclear densities and the formation mechanism(s) of neutron stars and black holes: supernovae and gamma-ray bursts. As a consequence of the supernova explosion that produced the compact star in these systems, HMXBs have high space velocities and thus are runaways. Alternatively, OB-runaway stars can be ejected from a cluster through dynamical interactions. Observations obtained with the Hipparcos satellite indicate that both scenarios are at work.
Spectroscopic Binaries in Southern Open Clusters
Authors: Levato H. , González J.F. , Malaroda S. , Grosso M. 
Published: June 2019

AbstractThis is a report on an ongoing program about binaries in southern open clusters. The long-term purpose of this project is to contribute to understanding the formation and evolution of spectroscopic binaries, providing observational constraints that will permit tests of some of the current theories on binary formation in open clusters.
The Possible Belts for Extrasolar Planetary Systems
Authors: Jiang Ing-Guey , Duncan M. , Lin D.N.C. 
Published: June 2019

AbstractMore than 100 extrasolar planets have been discovered since the 1990s. Unlike those of the solar system, these planets’ orbital eccentricities cover a huge range from 0 to 0.7. Incidentally, the first Kuiper belt object was discovered in 1992. Thus an interesting and important question will be whether extrasolar planetary systems could have structures like the Kuiper belt or asteroid belt. We investigate the stability of these planetary systems with different orbital eccentricities by similar procedures to Rabl & Dvorak (1988) and Holman & Wiegert (1999). We claim that most extrasolar planetary systems can have their own belts at the outer regions. However, we find that orbits with high eccentricity are very powerful in depletion of these populations.
The Impact of Large Databases on the Knowledge of Late-Type Close Binaries
Authors: Maceroni C. 
Published: June 2019

AbstractThis paper presents some results of the analysis of the eclipsing binaries samples that came out as by-products of the OGLE microlensing surveys. These experiments monitored millions of stars in the direction of the galactic bulge (OGLE-I), and of the Small Magellanic Cloud (OGLE-II). Their completeness allowed the discovery of rare and interesting systems. An example is a new group of long period binaries in the SMC with presumably a giant component in contact with the critical lobe, which dominates the systemic light variation (“β -contacts”). These systems obey a period-luminosity-color relation and could be used as an auxiliary, but independent, tool for distance determination. Another very interesting object, for its implications in the studies of angular momentum loss processes by magnetic braking and of stellar activity, is the system of shortest known period with M dwarf components, discovered by OGLE-I, BW3 V38, that is the target of a spectroscopic follow-up. The perspectives for close binary star research in view of future space missions, such as COROT and Eddington are briefly discussed.
VLBI Observations of SN 1979C and SN 1986J
Authors: Bartel N. , Bietenholz M.F. 
Published: June 2019

SummaryWe summarize our results on multi-epoch VLBI observations of SN 1979C in the galaxy M100 in Virgo, and of SN 1986 in the galaxy NGC 891. From t = 3.7 to 22 yr after the explosion, SN 1979C expands ∝ tm, almost freely, with m = 0.95 ± 0.03. For a total kinetic energy of 3 × 1051 erg, the expansion result requires a mass-loss to wind-velocity ratio for the progenitor of only 1 × 10−5 M⊙ yr−1per 10 km s−1, an order of magnitude smaller than estimated from radio light-curve fitting. We show a first image with slightly discernible structure of the supernova. For SN 1986J we present five images from 1987 to 2002 and show our result on moderately to strongly decelerated expansion with m = 0.71 ± 0.11. We comment on our result of an inversion of the radio spectrum in terms of the emergence of a possible pulsar nebula.
A Most Energetic Type Ic Supernova: SN 2003L
Authors: Soderberg Alicia M. 
Published: June 2019

SummaryWe present extensive radio observations of SN2003L, the most luminous and energetic Type Ic radio supernova with the exception of SN 1998bw. Using radio data, we are able to constrain the physical parameters of the supernova, including the velocity and energy of the fastest ejecta, the temporal evolution of the magnetic field, and the density profile of the surrounding medium. We highlight the extraordinary properties of the radio emission with respect to the supernova’s normal characteristics within optical bands. We find that although the explosion does not show evidence for a significant amount of relativistic ejecta, it produces a radio luminosity which is comparable to that seen in the unusual SN1998bw. Using SN2003L as an example, we comment briefly on the broad diversity of type Ic properties and the associated implications for progenitor models.
Synthetic Spectra of the Type Ia SN 2002bo
Authors: Stehle M. , Mazzali P.A. 
Published: June 2019

SummarySN 2002bo, a type Ia supernova in NGC 3190, is the first object of the European Supernova Collaboration (ESC). It was discovered on 09 March 2002 and is one of the earliest observed SNe. An almost complete set of spectra and photometry is available from 13 days before maximum B light until a few days after. An analysis using synthetic spectra is presented, focusing on the controversial issue of the reddening of SN 2002bo.
Optical Spectroscopy of Type Ia Supernovae
Authors: Matheson Thomas 
Published: June 2019

SummaryThe supernova (SN) group at the Harvard-Smithsonian Center for Astrophysics has been using the facilities of the F. L. Whipple Observatory to gather optical photometric and spectroscopic data on nearby supernovae for several years. The collection of spectra of Type Ia SNe is now large enough to allow a comprehensive analysis. I will present preliminary results from a study of a subsample of the CfA Type Ia spectroscopic database, with over 200 spectra of 31 Type Ia SNe. The SNe selected all have well-calibrated light curves and cover a wide scope of luminosity classes. The epochs of observation range from fourteen days before maximum to fifty days past maximum. All of the spectra were obtained with the same instrument on the same telescope, and were reduced using the same techniques. With such a large, homogeneous data set, the spectroscopic similarities and differences among Type Ia SNe become readily apparent.
Late Light Curves of Type Ia SNe
Authors: Milne Peter A. , Williams G.Grant 
Published: June 2019

SummaryAt late times, the energy deposition in the ejecta of type Ia supernovae is dominated by the slowing of energetic positrons produced in 56Co → 56Fe decays. Through comparisons of simulations of energy deposition in SN Ia models with observed light curves from supernovae, we study the positron transport and thus the magnetic fields of SNe Ia. In this paper, we summarize the current status of these investigations, emphasizing the observations made of two recent SNe Ia, 1999by and 2000cx.