bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Supersoft Source RXJ0019.8+2156: New Photoelectric Observations
Authors: Bartolini C. , Guarnieri A. , Piccioni A. , Solmi L. 
Published: July 2016

RXJ0019.8+2156 is a Supersoft X-ray Source (SSS) discovered by ROSAT and identified (Beuermann et al. 1995) as an object of magnitude V = 12.2, brighter than any other known SSS. The mass function and the optical spectrum are similar to CAL 83, but the X-ray luminosity seems to be lower. The main light variations are: a cyclic modulation with a 15.8 h period and a 0.3 mag amplitude, a quasi-periodic pulsation less than 0.1 mag in 2 h (Beuermann et al. 1995), variations of about 1 mag over a time-scale of 20 yr and small irregular fluctuations on a time-scale of weeks to months (Greiner & Wenzel 1995).The most promising model, at present, involves a binary system in which a hot 1 M⊙ white dwarf with an accretion disk is accreting at a mean rate of Ṁ ≈ 10−7 M⊙yr−1; sporadic hydrogen burning caused by an unstable mass transfer (Greiner & Wenzel 1995) seems to be present.
On the Origin of the Abundance Anomalies in IK Peg
Authors: Smalley B. , Smith K.C. , Wonnacott D. 
Published: July 2016

AbstractIK Peg is a binary system comprising a pulsating A-type star in orbit with a massive white dwarf. A detailed abundance analysis of IK Peg A has been performed. It is found that the Ca and Sc abundances are approximately solar, and the Fe-group elements slightly enhanced. IK Peg is not a classical Am star but the results are not inconsistent with its spectroscopic classification as a marginal Am star. An excess of Ba and Sr are found. These anomalies could be explained by radiative diffusion processes operating in the atmosphere of IK Peg A, even though it is undergoing small-amplitude pulsations. Alternatively, since the companion is a massive white dwarf, these anomalies could be the result of mass transfer during the common envelope phase of the binary system’s evolution.
UV and X-Ray Variability of 3C 390.3
Authors: Wang Ting-gui , Wamsteker Willem , Cheng Fu.-Zhen 
Published: July 2016

AbstractWe present the results of an analysis of the UV and X-ray variability of the broad-line radio galaxy 3C 390.3 over 15 years. The UV continuum of 3C 390.3 showed large variations with amplitudes of up to a factor of 10. The variations of C IV and Lyα are highly correlated with the UV continuum, and are delayed with respect to the continuum variations by 65-120 days with the red wing of both C IV and Lyα leading the blue wing, implying that the C IV and Lyα-emitting gas is infalling towards the center. The C IV/Lyα ratio is positively correlated with both the continuum flux and UV line strength. The overall UV/optical to X-ray spectrum can be described by a single power law with αuvx = 0.90. The behavior of C IV/Lyα variations might be related to this hard ionizing continuum in 3C 390.3.
The Nature and Origin of Structure in Broad Emission Line Profiles
Authors: Gaskell C. Martin , Snedden Stephanie A. 
Published: July 2016

AbstractWe postulate that all structure in broad lines can be explained by a central component (at the systemic redshift) and the addition of two ‘displaced components’, one blueshifted and the other redshifted. We have been able to successfully classify all Balmer-line profiles on this basis. 3C 390.3-type objects are merely examples where the shifts of the displaced components are unusually large. We believe that the displaced peaks are less prominent in the UV lines because the higher ionization lines are broader.
Hydromagnetic Wind Model for the Broad-Line Region of NGC 5548
Authors: Bottorff M.C. , Korista K.T. , Shlosman I. , Blandford R.D. 
Published: July 2016

AbstractA hydromagnetic wind model from a dusty molecular disk (Emmering, Blandford, & Shlosman 1992) was applied to the BLR in NGC 5548 and produced synthetic C IV line profiles as a function of time. The model C IV profiles are compared to data from the 1993 IUE/HST campaign and properties of the the BLR of NGC 5548 are inferred.
Bidimensional Spectroscopy with Optical Fibers of Spatially Resolved Emission-Line Regions Around Active Galactic Nuclei
Authors: Arribas S. , Mediavilla E. , del Burgo C. , García-Lorenzo B. 
Published: July 2016

AbstractWe summarize our experience in observing the circumnuclear regions of AGN with the optical-fiber systems that we have developed for the William Herschel and Nordic Optical Telescopes at La Palma.
The Green Bank Northern Sky Survey: Discovery of a New Neutron Star-Neutron Star Binary
Authors: Nice David J. , Sayer Ronald W. , Taylor Joseph H. 
Published: July 2016

We have surveyed 15,900 deg2of the northern sky for millisecond pulsars at 370 MHz with the Green Bank 140ft telescope. The telescope was driven along lines of constant declination such that a given point on the sky was observed for two minutes. A Fourier transform spectrometer synthesized 512-channel spectra across 40 MHz in each of two polarizations. Total intensity levels were boxcar averaged at intervals of 256μs, quantized to 1 bit, and written to tape. Data were processed with the Cray C90 of the Pittsburgh Supercomputer Center. The flux limit of the survey was 8 mJy for slow pulsars. A further 1500 deg2were observed with 20 MHz bandwidth, yielding 71% the usual sensitivity.Eighty-four slow pulsars were detected, of which six were previously unknown. Three recycled pulsars were detected: the relativistic binary B1534+12; the neutron star-white dwarf binary J1022+1001, discovered nearly simultaneously at Arecibo; and J1518+4904, a previously unknown pulsar with a 41 ms rotation period.
The Effelsberg surveys of pulse shapes
Authors: Kijak Jaroslaw , Kramer Michael , Wielebinski Richard , Jessner Axel , Seiradakis John-Hugh 
Published: July 2016

Pulse shapes of pulsars have been observed at many frequencies with the Effelsberg 100-m radiotelescope since 1972. The rationale behind these surveys was to use the great sensitivity of the 100-m telescope of the Max-Planck-Institut für Radioastronomie in particular at high radio frequencies for a complete study of pulse profiles.The recent advent of HEMT amplifiers has improved the observational sensitivity enormously. Using these new systems it was possible to obtain integrated profiles of 183 pulsars at 1.4 GHz, 46 pulsars at 4.75 GHz and 24 pulsars at 10.6 GHz (see Seiradakis et al. 1995). Furthermore eight pulsars have been studied at 9 mm wavelengths (Kramer et al. 1996).
A 60 Second Periodic Modulation in Crab Pulsar Optical Light-Curve
Authors: Čadež Andrej , Galičič Mirjam 
Published: July 2016

AbstractThe HST High Speed Photometer data and stroboscopic photometry data from the Asiago 1.82m telescope (1994) show a (0.0065±0.0015) magnitude weak modulation peak in Crab’s light-curve at 60 seconds. Hubble data also suggest a phase modulation peak at the same period with the amplitude (0.07 ± 0.02)°. New stroboscopic data from December 1995 Asiago observations suggests the modulation amplitude (0.0045±0.0015) magnitude, consistent with previous results.
The Attenuation of Hard γ-rays in Strongly-Magnetized Pulsars
Authors: Harding Alice K. , Baring Matthew G. 
Published: July 2016

AbstractWe investigate the spectral attenuation due to one-photon pair production and photon splitting in neutron star magnetospheres. The calculations are performed in a Schwarzschild metric, thereby including redshift and field enhancement effects associated with curved spacetime. We find that pair production and splitting totally inhibit emission above around 10-30 MeV in PSR1509-58, whose surface field is inferred to be as high as 3 × 1013Gauss. Model pulsar spectra of splitting cascades for high field cases, where splitting is important, are consistent with the very low cutoff energy in PSR1509-58 for a wide range of polar cap sizes.
Recent Results from the CANGAROO Project
Authors: Dazeley S.A. , Edwards P.G. , Patterson J.R. , Rowell G.P. , Sinnott M. , Thornton G.J. , Wilkinson C. , Hara T. , Hayashida N. , Katsumata H. , Kifune T. , Konishi T. , Matsubara Y. , Matsuoka T. , Mizumoto Y. , Mori M. , Muraishi M. , Muraki Y. , Oda T. , Ogio S. , Ohsaki T. , Sako T. , Sakurazawa K. , Susukita R. , Suzuki A. , Tamura T. , Tanimori T. , Yanagita S. , Yoshida T. , Yoshikoshi T. 
Published: July 2016

TheCollaboration ofAustralia andNippon for aGAmmaRayObservatory in theOutback operates two large telescopes at Woomera (South Australia), which detect the Čerenkov light images produced in the atmosphere by electronpositron cascades initiated by very high energy (~1 TeV or 1012eV) gamma rays. These gamma rays arise from a different mechanism than at EGRET energies: inverse Compton (IC) emission from relativistic electrons.The spoke-like images are recorded by a multi-pixel camera which facilitates the rejection of the large numbers of oblique and ragged cosmic ray images. A field of view ~3.5° is required. The Australian team operates a triple 4 m diameter mirror telescope, BIGRAT, with a 37 photomultiplier tube camera and energy threshold 600 GeV. The Japanese operate a single, highly accurate 3.8 m diameter f/1 telescope and high resolution 256 photomultipler tube camera. In 1998 a new 7 m telescope is planned for Woomera with a design threshold ~;200GeV.
Distances to Binary Pulsars and Implications for Tests of General Relativity
Authors: Bell J. F. , Bailes M. 
Published: July 2016

AbstractWe propose a new way to measure accurate distances and transverse velocities for some nearby binary pulsars. In many cases the distances will be more accurately determined than is possible by annual parallax, as the relative error decreases ast−5/2. We also note that tests of the general relativistic prediction of orbital period decay of nearby relativistic binary pulsars will be limited to accuracies of a few percent. Nevertheless, PSR B1534+12 observations are consistent with general relativistic predictions if the proper-motion contribution to the orbital period derivative is accounted for.
Observations of a new eclipsing binary millisecond pulsar
Authors: Stappers B. W. 
Published: July 2016

AbstractWe report on the discovery and timing observations of the new eclipsing binary millisecond pulsar J2051–0827. This 4.5ms pulsar is in a 2.4 hour binary orbit with a 0.027 M⊙companion. The companion and the pulsar are separated by only 1 R⊙. The pulsar is often, but not always, eclipsed for approximately 10% of the orbit at frequencies below 660 MHz. This indicates that the eclipse material extends well beyond the Roche lobe. During a number of observations pulses have been detected throughout the eclipse region at 1.4 GHz and 2.0 GHz. The delays measured with respect to the timing model associated with these observations indicate significant structure and variability in the electron column density in the eclipse region.
Orbital Parameters of the PSR B1620–26 Triple System
Authors: Arzoumanian Z. , Joshi K. , Rasio F. A. , Thorsett S. E. 
Published: July 2016

AbstractPrevious timing data for PSR B1620–26 were consistent with a second companion mass m2anywhere in the range ∼ 10−3– 1M⊙, i.e., from a Jupiter-type planet to a star. We present the latest timing parameters for the system, including a significant change in the projected semi-major axis of the inner binary, a marginal detection of the fourth time derivative of the pulse frequency, and the pulsar proper motion (which is in agreement with published values for the proper motion of M4), and use them to further constrain the mass m2and the orbital parameters. Using the observed value of, we obtain a one-parameter family of solutions, all with m2≲ 10−2M⊙, i.e., excluding stellar masses. Varyingwithin its formal 1σ error bar does not affect the mass range significantly. However, if we varywithin a 4σ error bar, we find that stellar-mass solutions are still possible. We also calculate the predicted rate of change of the projected semi-major axis of the inner binary and show that it agrees with the measured value.
The relation between recycled radio pulsars and wide low-mass X-ray binaries
Authors: Li Xiangdong , Wang Zhenru 
Published: July 2016

The origin and evolution of neutron star magnetic fields has been hotly debated for a long time. Spontaneous field decay was originally proposed with timescales of (5–10) × 106years, while another possible model which associates field decay with mass accretion in the evolution of binary systems has been suggested (see Bhattacharya &amp; van den Heuvel 1991 for a review). The aim of this paper is to examine whether accretion-induced field decay can reproduce the observed properties of the wide binary radio pulsars in quantitative calculations.In a binary system consisting of a neutron star and a low-mass giant companion, if the initial orbital period is longer than 1 day, mass transfer, taking the form of Roche-lobe overflow, is driven by the nuclear evolution of the giant through radius expansion (Webbink et al. 1983). We assume the mass accretion rateṀof the neutron star is limited to the Eddington accretion rateṀE≃ 10−8M⊙yr−1. If the mass transfer rate is in excess ofṀE, the rest mass is blown from the system in the forms of jets or beams.
Global, Nonaxisymmetric Instabilities in Magnetized Accretion Disks
Authors: Curry Charles , Pudritz Ralph E. 
Published: July 2016

AbstractWe investigate the global stability of a differentially rotating, ideal MHD fluid shell to linear, nonaxisymmetric perturbations. This system, which approximates an accretion disk near its midplane, is known to be unstable to both axisymmetric and nonaxisymmetric local perturbations. Keplerian disks, which are entirely stable in the hydrodynamic case, show the most rapid growth for radially extended shells.
Wind Accretion vs Roche Lobe Overflow in HMXBs
Authors: Blondin John M. , Owen Michael P. 
Published: July 2016

AbstractWe present a series of time-dependent 2D and 3D numerical simulations illustrating the evolutionary sequence between high mass X-ray binaries fed by wind accretion (where the primary star sits well within its critical tidal lobe) and those fed by Roche lobe overflow (where the primary star extends out to its tidal lobe). When the primary lies well within its critical surface we find negligible tidal mass loss enhancement, and a system that is characterized by wind accretion with the development of a photoionization zone around the compact object. As the surface of the primary nears the critical surface, we observe tidally enhanced mass loss via a thin tidal stream, resulting in higher accretion wake densities. For full RLOF we observe the development of a steady accretion disk characterized by a total shadowing of the X-rays in the orbital plane.
Cylindrically-Collimated, Self-Similar MHD Disk Outflows
Authors: Ostriker Eve C. 
Published: July 2016

AbstractWe describe the dynamics of a class of MHD winds from Keplerian-rotating disks. In this model, all flow velocities are assumed to vary self-similarly with spherical radius r as υ(r, θ) ∝ r−1/2, with density varying as ρ(r, θ) ∝ r−q for arbitrary q. At large distances from the disk, the wind is explicitly required to become cylindrically collimated. We find that the asymptotic wind solution has power-law scalings of all flow variables in the cylindrical radius R = r sin θ, and q < 1 is necessary. We describe how the Alfvén criticality condition limits the space of energy and angular momentum parameters defining these wind solutions. We present an example of the run of density, velocity, and magnetic field for a full solution of the wind equations, and compare the properties of these cylindrically-collimated wind solutions to previous work.
Three-Dimensional Global MHD Simulations of Magnetised Accretion Disks and Jets
Authors: Matsumoto R. , Shibata K. 
Published: July 2016

AbstractWe carried out three-dimensional global MHD simulations of jet formation from an accretion disk threaded by large-scale magnetic fields. Numerical results show that bipolar jets with maximum speed υjet ~ υKepler are created. The surface layer of the disk accretes faster than the equatorial part because magnetic braking most effectively affects that layer. Accretion proceeds along spiral channels which correspond to the surface avalanche flow appearing in previous axisymmetric simulations. Spirally shaped low β (= Pgas/Pmag < 1) regions appear in the innermost part of accretion disks where toroidal magnetic fields become dominant.
HST Spatially Resolved Spectra Of Accretion Discs In CVs
Authors: Baptista Raymundo 
Published: July 2016

AbstractTime-resolved eclipse spectroscopy of the novalike variable UX UMa obtained with the HST/FOS is analized with eclipse mapping techniques to produce spatially resolved spectra of its accretion disk and gas stream as a function of distance from disk center. The results reveal a noticeable asymmetry in the disk emission, with the disk side closest to the secondary star showing pronounced absorption bands in the UV and a Balmer jump in absorption. The spectrum of the infalling gas stream is noticeably different from the disk spectrum at the same radius suggesting that gas overflows through the impact point at disk rim and continues along the stream trajectory, producing distinct emission down to 0.1 RL1.
Polarization Properties of Active Galactic Nuclei
Authors: Hough J. H. 
Published: July 2016

AbstractOne of the main uses of polarimetry over the last decade, has been to identify the nature of AGN that are normally hidden from direct view by an optically and geometrically thick torus, and thereby to unify different classes of AGN. Of growing importance is the role that polarimetry can play in our understanding of the properties and structure of AGN on a size scale which cannot be resolved directly. We review the progress being made in understanding the role of disks, extended scattering regions, and the obscuring torus in AGN.
High-Velocity Maser Emission From Shocks Along Spiral Waves In The Circumnuclear Disk Of NGC 4258
Authors: Maoz Eyal 
Published: July 2016

AbstractVLBI observations of H2O maser line emission from the central sub-parsec region of the galaxy NGC 4258 have recently revealed a remarkably well-defined, rapidly rotating molecular disk which is viewed nearly edge–on. We show that the peculiar clustering of the maser sources into several distinct clumps which are almost equally spaced apart from one another, and the striking asymmetry in the high-velocity maser spectrum can be naturally explained by spiral activity in the disk.
Compact Radio Cores in the Galactic Center and Elsewhere
Authors: Falcke Heino 
Published: July 2016

AbstractCompact radio cores are not only common in radio galaxies and quasars but also in many nearby galaxies with low-active, supermassive black holes. One famous example is the Galactic Center source Sgr A*. Recent studies of proper motions and radial velocities of stars in the inner parsec of the Galaxy convincingly demonstrate the presence of a compact dark mass of 2.5 · 106M⊙in the nucleus of the Milky Way. Millimeter VLBI and submm observations of Sgr A*thus probe a region of only a few Schwarzschild radii in diameter. In this paper I will review our current theoretical and observational knowledge of this source and compare it to some famous LINER galaxies like NGC 4258, NGC 3079, and NGC 6500. In all cases these radio cores can be well explained by a standard AGN jet model, and, with the exception of Sgr A*, large scale outflows are observed that have powers comparable to those inferred from the radio cores. Recent VLBI observations of radio-weak quasars and HST observations of Seyfert galaxies indicate that these AGN also produce powerful jets which, however, have relatively less luminous radio cores than radio-loud quasars and the LINERs discussed here. Therefore, jets and compact radio cores appear to be natural constituents of an AGN, but the reason why apparently some jets are radio-loud and others not remains a mystery.
Accretion in the Center of the Milky Way
Authors: Duschl Wolfgang J. , von Linden Susanne 
Published: July 2016

AbstractWe have analyzed the distribution of giant molecular clouds and their radial velocities in the inner ~ 300 pc of the Milky Way in order to deduce the characteristic properties of its large scale motion. We find radial inflow of matter towards the Galactic Center of ~ 10−2 M⊙/yr. Moreover, we have determined the position of individual clouds along the line of sight.
Lifetimes of Circumstellar Disks in Lynds 1641
Authors: Allen Lori E. , Strom Karen M. 
Published: July 2016

AbstractIt is by now evident that most young stars have associated disks and/or envelopes, which may be active (accreting) or passive (reprocessing stellar photons), or both. Knowing how such disks evolve is crucial to our understanding of how stars form, and may be relevant to other questions, such as the time available for the formation of planets in solar nebulae. In this poster we discuss the properties of pre-main sequence circumstellar disks in Lynds 1641 in Orion, the nearest giant molecular cloud complex.
Spectropolarimetry of Double Peaked Broad Hα Lines in Radio Galaxies
Authors: Corbett E.A. , Robinson A. , Young S. , Axon D.J. 
Published: July 2016

AbstractSpectropolarimetric observations of 3 broad line radio galaxies exhibiting double peaked broad Hα lines, show that two of the sources (Arpl02B and 3C390.3) have single peaked line profiles in polarized flux with a position angle aligned with the jet axis. The third source (3C382) exhibits no polarized line emission at all. The consequences of these observations for the relativistic accretion disk and other BLR models are discussed.
Binary Star Formation in Disc-Disc Encounters
Authors: Watkins S.J. , Bhattal A.S. , Francis N. , Whitworth A.P. 
Published: July 2016

AbstractWe present results of 3-D self-gravitating hydrodynamical calculations of the encounter between two protostellar discs. We find that the interaction leads to fragmentation of the discs and the formation of new stars and multiple systems.
A New Physical Mechanism to Account for the “Anomalous Viscosity” in Accretion Disks
Authors: Zhang X. 
Published: July 2016

AbstractA new physical mechanism responsible for producing significant radial mass accretion in the inner disk of spiral galaxies has recently been found (Zhang 1996, ApJ, 457, 125). Since this mechanism depends only on the skewness of the global patterns (one-armed or two-armed spiral patterns, as well as skewed central bars) in the underlying disks, and since this process is collective in nature and produces an effective viscosity many orders of magnitude larger than that due to the microscopic processes, it is likely to be an important candidate for the long soughtafter “anomalous viscosity” in many types of astrophysical accretion disks which admit nonaxisymmetric instabilities.
The Caltech-Jodrell Bank VLBI Surveys
Authors: Pearson T.J. , Browne I.W.A. , Henstock D.R. , Polatidis A.G. , Readhead A.C.S. , Taylor G.B. , Thakkar D.D. , Vermeulen R.C. , Wilkinson P.N. , Xu W. 
Published: July 2016

AbstractThe Caltech-Jodrell Bank VLBI surveys of bright extragalactic radio sources north of declination 35° were carried out between 1990 and 1995 using the Mark-II system, achieving images with a resolution of about 1 mas at 5 GHz. The CJl survey (together with the older “PR” survey) includes 200 objects with 5 GHz flux density greater than 0.7 Jy; the CJ2 survey includes 193 flat-spectrum sources with 5 GHz flux density greater than 0.35 Jy; and we have defined a complete flux-density limited sample, CJF, of 293 flat-spectrum sources stronger than 0.35 Jy. We summarize the definition of the samples and the VLBI, VLA, MERLIN, and optical observations, and present some highlights of the astrophysical results. These include: (1) superluminal motion and cosmology; (2) morphology and evolution of the “compact symmetric objects” (CSOs); (3) two-sided motion in some CSOs; (4) the angular-size-redshift diagram; (5) misalignment of parsec-scale and kiloparsec-scale jets.