bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Orbital Period of the Galactic Z Source Sco X-2
Authors: Southwell K. A. , Casares J. , Charles P. A. 
Published: July 2016

AbstractSco X-2 is a bright Galactic bulge Z source, whose optical counterpart was discovered in 1990 [?], and observed to exhibit strong Hα emission. We have therefore obtained spectroscopic data in order to determine the orbital period and investigate the nature of the companion star. From an analysis of the Hα emission line velocities, we find a most likely orbital period of 13.94 d. This implies an evolved companion, and is consistent with the currently known orbital periods in other Z sources.
Optical Counterpart of the LMXB GX 13+1
Authors: Groot P. J. , van Der Klis M. , van Paradijs J. , Augusteijn T. , Berger M. 
Published: July 2016

We have observed the IR counterpart of the Atoll type LMXB GX 13+1, (Naylor, Charles & Longmore 1991), from 1993 July 11…30, with the Dutch 90 cm telescope at ESO using a Gunn z (0.9–1.0 μm) filter. Over this period 110 usable images (integration time 12 m) were obtained. The data were reduced using the ESO-MIDAS/DAPHOT reduction package. A Lomb-Scargle period search was performed with the PERIOD package.Fig. 1 shows our Gunn z band image with stars labeled as in Naylor et al. (1991). They propose their star 101 as the IR counterpart. Fig. 2 shows the light curve we obtained for this star. The star is clearly variable on a time-scale of ~ 10 d. To estimate any period more accurately we have made a Lomb-Scargle statistics periodigram (see Fig. 3); maximum power is at 12.6 d. We estimate the error to be ~ 1 day.
Detection of the Secondary Star in X1822–371
Authors: Harlaftis E. T. , Charles P. A. , Horne K. 
Published: July 2016

AbstractWe have detected He I absorption from the companion star to X1822–371 and find a lower limit to its K–velocity of 230±50km s−1. We interpret the He I as arising on the X-ray heated inner face of the companion star.
Hot Subdwarfs in Binaries: Multiwavelength Observations and Evolutionary Implications
Authors: Ulla A. , Thejll P. , Vennes S. , Hansen-Ruiz C. S. , Rasilla J. L. 
Published: July 2016

AbstactWe are looking for stellar companions to very hot helium-rich subluminous (sdO) stars by using infrared photometry, optical CCD imaging and spectroscopy. The work is complemented with a comprehensive bibliographic and space-mission databanks search for the objects in our sample (Thejll, Ulla & MacDonald 1995). Companions can be used to indirectly measure the distance to the hot subdwarfs, and give clues about possible binary evolution scenarios. We have therefore gathered and analysed data for 57 hot subdwarfs in a search for IR excesses and companions. 43 of the stars are observed for the first time in the JHK bands and 28 objects are found to have larger IR fluxes than expected from a single sdO.
On the Orbital Period Distribution of Recycled Pulsars
Authors: Nelson L. A. , Rappaport S. 
Published: July 2016

AbstractUsing population synthesis techniques, we investigate the orbital period distribution of ‘recycled’ pulsars. We find that the relative distribution of systems with periods between approximately one and fifty days are reasonably well reproduced. However, the existence of binary pulsars with periods between 70 and ~ 1000 d cannot be explained within the evolutionary framework considered here.
The Relativistic Beaming Model and Superluminal Motions
Authors: Fan J. H. , Xie G.Z. , Zhang Y.H. , Qin Y.P. 
Published: July 2016

In this paper, we consider a compilation of 55 objects with known superluminal motions (SM), and whose flux density (X-ray, optical, radio), core dominance parameter (R), superluminal velocity, and radio Doppler factor (δR) are known. Our study shows that SM is consistent with the beaming model, and the relationis reasonable. The statistical correlation between superluminal velocity and redshift is a result of selection and the statistical correlation between R and brightness temperature (Tob) is actually a reflection of the correlations between δ, R, and Tob for objects with SM. Up to now, 59 objects have been reported to have SM, but for reasons discussed elsewhere (Vermeulen & Cohen 1994), only 55 are considered here.
The HST Spectrum of I Zw 1: Implications of the C III* λ1176 Emission Line
Authors: Laor Ari , Jannuzi Buell T. , Green Richard F. , Boroson Todd A. 
Published: July 2016

AbstractI Zw 1 is a well-known narrow-line quasar with very strong Fe II emission. High S/N spectra obtained with the HST FOS show a remarkably rich emission-line spectrum. The C III*λ1176 line is clearly detected in emission for the first time in AGNs. This line arises from radiative decay to the 2s2p3Pº0,1,2 metastable levels of C III. The observed flux is ~ 50 times larger than expected from collisional excitation or dielectronic recombination in photoionized gas. The most plausible mechanism for the large enhancement in the C III* λ1176 flux is resonance scattering of continuum photons by C III* ions. This mechanism requires large velocity gradients (~ 1000 km s−1) within each emitting cloud in the BLR. Such large velocity gradients can be induced by forces external to the gas in the BLR clouds, such as tidal disruption, or radiation pressure.
Velocity-Resolved Echo Mapping
Authors: Horne K. 
Published: July 2016

AbstractWe probe the structure and kinematics of Seyfert broad-line regions by using a velocity-delay map to fit simultaneously the observed variations in the continuum and the emission-line profiles. The velocity-delay map of C IVλ1550 emission constructed from 44 IUE spectra of NGC 4151 suggests virial motions, with 107M⊙ inside two light days. Pure inflow and outflow kinematics are ruled out by the approximate symmetry of the map. A stronger redshifted response at small delays suggests either a component with free-fall kinematics, or an outflow with CIV being emitted inward by optically thick gas clouds.
Line Shifts in the Two-Phase Broad-Line Region with Radial Kinematics
Authors: Xue Sui-Jian , Cheng Fu-Zhen 
Published: July 2016

AbstractWe consider in detail the two-phase BLR model with radial infall kinematics. Numerical calculations show that Lyα and C IVλ1549 profiles are blueshifted from their systemic rest-frame velocity, and their profiles are in qualitative agreement with the observations. It seems that the observed velocity differences between the high and low-ionization lines in the spectra of quasars can be understood in such a simple, physical, self-consistent model.
An Analysis of Broad Emission-Line Profiles from HST Data
Authors: Snedden Stephanie A. , Gaskell C. Martin 
Published: July 2016

AbstractWe have analyzed the HST FOS spectra of all quasars in the Stirpe (1990) high S/N line-profile sample and studied line-profile ratios as a function of radial velocity. Some quasars show no sign at all of NLR Lyα. We confirm that Hα is narrower than Lyα (after allowance for NLR contributions). The Lyα/Hα ratios in the cores of the broad lines are all close to or slightly less than case B and values predicted by single-cloud photoionization models. The Lyα/Hα ratio is surprisingly high in the blue wing. With only one exception, the ratios are equal to or greater than the case B value. Intrinsic reddening must be very small in most cases. We also briefly discuss other ratios.
Unusual Balmer-Line Variations in the Radio-Loud AGN 4C 37.43
Authors: Romano P. , Sulentic J. , Marziani P. , Calvani M. , Moles M. , Zwitter T. 
Published: July 2016

AbstractWe present new observations of the quasar 4C 37.43 in the course of a more general study of broad-line profiles in radio-loud AGN. During the most recent observations it became obvious that the broad profile Hβ had changed significantly. Difference spectra show that a new blue component has appeared on the Hβ profile. The centroid of this new component is displaced about 2500 km s−1 from the rest frame [O III] λ5007. A corresponding blueshifted He IIλ4686 component may have also appeared.
Reprocessing Models and the ASCA Spectrum of Mkn 290
Authors: Turner T. J. , George I. M. , Kallman T. , Yaqoob T. , Życki P.T. 
Published: July 2016

AbstractWe describe a warm absorber/emitter model that is used to model the complex X-ray spectrum of Mkn 290. The best fit to the data also includes a contribution from an ionized reflector.
Correlation Between the FWHM of the Broad Emission Lines and the Soft X-Ray Photon Index in the PG Quasars
Authors: Gondhalekar P.M. , Rouillon-Foley C. , Kellettl B.J. 
Published: July 2016

AbstractThe correlation between the FWHM of Lyα, C IV and Hβ lines and the photon index of the soft X-ray continuum is investigated for a sample of PG quasars. Only the FWHM of Hβ line is correlated with the photon index and this correlation depends on the sample of the AGNs considered.
Are Radio-Loud Quasars Rebellious or are Radio-Quiets Just Plain Untalented?
Authors: Vestergaard M. , Wilkes B.J. , Barthel P.D. 
Published: July 2016

AbstractWe present some of the results of a preliminary statistical study of 20 QSOs. We compare equivalent widths and widths at 40–80% of flux maximum of the Lyα, Si IVλ1400, C IV λ1549, and C III] λ1909 lines between radio-loud and radio-quiet QSO subsamples and with previously reported findings.
Infrared Emission-Line Signatures of Tori in the Nuclei of Seyferts
Authors: Storchi-Bergmann Thaisa , Winge Cláudia , Ward Martin J. , Wilson Andrew S. 
Published: July 2016

AbstractWe present infrared (IR) long-slit spectroscopy of two galaxies with Seyfert 2 nuclei, NGC 2110 and the Circinus galaxy, both known from previous studies to exhibit anisotropic high-excitation gaseous emission. In the “unified models” for Seyferts, this anisotropy is due to collimation of the ionizing nuclear radiation by an optically thick molecular torus which surrounds the nucleus. We have looked for signatures of this torus and its collimating effect in the IR (J and K bands), taking advantage of the reduced relative attenuation at these wavelengths. The two galaxies are found to show extended emission in the lines [Fe II] λl.257 µm, Paβ, H2λ2.12 °m, and Brγ, both along the collimation axis as well as perpendicular to it. The [Fe II] line is found to trace the high-excitation emission, and, in the case of NGC 2110, is more extended along the collimation axis. The H2 emission, although consistent with the presence of a molecular torus, extends for hundreds of parsecs and the derived kinematics is consistent with circular rotation in the plane of the galaxies. The emission-line ratios [Fe II]/Paβ and H2/Brγ are much smaller in Circinus (respectively ~ 0.5 and 1) than in NGC 2110 (~ 7 and ≥ 4, respectively), and indicate the presence of a nuclear starburst in the former galaxy. IR rotation curves were determined for both galaxies. In the case of NGC 2110, the IR rotation curve shows different behavior than the rotation curve determined from optical lines, which shows the importance of obscuration effects in the study of the gas kinematics.
Infrared to Millimeter Spectroscopy and Imaging of Active Galactic Nuclei
Authors: Genzel R. , Lutz D. , Sturm E. , Tacconi L. , Thatte N. , Sternberg A. 
Published: July 2016

AbstractObservations in the 1 µm to 1 cm wavelength band give important information on the physical processes occurring in and immediately around active galactic nuclei. Concentrating on recent results on ionic, atomic, and molecular emission lines, we discuss as examples the first ISO results on the nature of ultra-luminous infrared galaxies, and near-infrared and millimeter measurements of the central 100 parsecs of the Seyfert 2 galaxy NGC 1068.
Narrow Lines and Continuum Emission in Seyfert 2 Galaxies
Authors: Polletta M. , Bassani L. , Caroli E. , Malaguti G. , Malizia A. , Palumbo G.G.C. 
Published: July 2016

AbstractA statistical analysis of the relationship between the continuum and the narrow emission lines of a sample of Seyfert 2 galaxies strongly suggests the presence of a starburst emitting at all wavelengths from radio to soft X-rays as well as in the narrow lines.
Shocks and Photoionization in the Narrow-Line Region
Authors: Viegas Sueli M. , Contini Marcella 
Published: July 2016

AbstractThe presence of shocked regions in the narrow-line region (NLR) of active galactic nuclei (AGN) is discussed. Their effect on the physical conditions, in addition to photoionization from the central radiation source, is analyzed. We show that composite models, accounting for both shocks and photoionization, provide a consistent picture of the NLR which accounts for the observed emission-line and continuum spectra and is in agreement with the AGN unified model. The study of a particular object, NGC 5252, strengthens these results. It also shows that, besides explaining the observational data, the models make predictions that can be tested by infrared, optical, and X-ray imaging.
Dynamical Models of the Maser in NGC 4258
Authors: Moran J.M. 
Published: July 2016

The presence of two quasars symmetrically displaced from the nucleus of the galaxy NGC 4258 (Pietsch et al. 1994) has given rise to some speculation that they might have some dynamical connection with the high-velocity maser emission seen in the nucleus (Burbidge 1996; Ozernoy 1996). The case that the masers define a simple Keplerian disk is very compelling; nonetheless, it is instructive to investigate whether any other dynamical models could fit the available data.The evidence that the masers define a thin Keplerian disk can be found in Miyoshi et al. (1995) and Moran et al. (1995). Some of the relevant data are shown elsewhere in this volume (Fig. 2 of Greenhill’s paper). The basic analysis is as follows. The features near the systemic velocity of 470km s−1 show a linear dependence of line-of-sight velocity versus distance along the major axis, while the redshifted and blueshifted high-velocity features show a nearly Keplerian dependence with distance.
A Survey of X-ray–Emitting IRAS Galaxies: A New Class of Objects or Hidden AGNs?
Authors: Dennefeld M. 
Published: July 2016

A cross-correlation between the IRAS PSC and the ROSAT All-Sky Survey has provided 242 sources detected in both surveys (Boiler et al. 1992). About half of these have redshifts in the literature and a spectral classification. An unexpected result was the discovery of many galaxies with X-ray luminosities up to a few 1043 ergs s−1, yet without Seyfert characteristics in their optical spectra (e.g., Boiler et al. 1993). To investigate this problem further and evaluate the frequency of occurrence of these peculiar objects, a spectroscopic follow-up has been undertaken to:• Determine velocities and luminosities for all the unclassified objects.• Reevaluate the classification of high X-ray luminosity objects previously not recognized as Seyferts. In particular, spectral resolution or coverage and variability are important parameters to consider if one wants to detect faint signs of Seyfert activity.
Optical Identification of the ROSAT All-Sky Survey Sources in Two 2° × 2° Fields
Authors: Zhao Y. , Zhong J. , Wei J. , Hu J. , Li Q. 
Published: July 2016

AbstractWe used the CCD camera and spectrograph of the 2.16-m telescope of Beijing Astronomical Observatory to identify the ROSAT All-Sky survey sources in two 2° Ü 2° fields. Of a total of 16 X-ray sources, we identified 13 of them as follows: two QSOs, two Seyfert galaxies, two active galaxies, two clusters of galaxies, and five late-type stars. Three X-ray sources remained unidentified.
The Spectra of Very Luminous IRAS Galaxies
Authors: Wu Hong , Zou Zhenlong , Xia Xiaoyang , Deng Zugan 
Published: July 2016

AbstractWe discuss new optical spectra and DSS images of a complete sample of very luminous IRAS galaxies. The statistics of classification of spectral types and interactions show that interaction can account for the nuclear activity (AGN and starburst) of ultraluminous infrared galaxies.
A Unified View of How the Study of Emission Lines Furthers Our Knowledge of AGN
Authors: Krolik Julian H. 
Published: July 2016

AbstractA global view is given of how emission lines have been, and may in the future, be used to enhance our understanding of AGN. Lines from the microwave to the X-ray bands all contribute. Although we have a deep understanding of the physical processes by which line photons are generated, when the circumstances of line emission are complicated, models become too unreliable to provide strong inferences about the rest of the AGN system. At present, the lines which appear the most promising for helping answer the most important questions about AGN are the 22 GHz H2O rotational transition and the 6.4keV FeKα fluorescence.
Periodic Changes in Intensity and Arrival Time of Pulses from the Vela Pulsar: Evidence for Free Precession?
Authors: Deshpande A.A. , McCulloch P.M. 
Published: July 2016

We present dual-frequency measurements on the Vela pulsar with a view to study the slow variations in the pulsed flux and the apparent differences in the pulse arrival times. We examine the data for correlated variations between the pulse intensities and arrival times at the two frequencies and discuss two main possibilities in order to explain the observed behaviour.The data presented here consists of a) Pulse intensities, S635&amp; S950, at S635&amp; S950MHz respectively and b) the ‘residual’ differences in the time of arrival of the pulse at the lower frequency, ΔTOA, with respect to that at the higher frequency. These data, over a span of ~1300 days (during 1988-92), were obtained as a part of the routine monitoring of the Vela pulsar from Mt. Pleasant Observatory of University of Tasmania, Hobart (see McCullochet al. 1990).
Expectancy of large pulsar glitches
Authors: Baykal Altan , Alpar Ali 
Published: July 2016

AbstractWe study the expectancy of large glitches (ΔΩ/Ω &gt; 10−7) from a sample of 472 pulsars other than the Vela pulsar. The pulsars in this sample have exhibited 20 large glitches. In the sample the total observation span is larger than 2000 pulsar years. We assume that all pulsars experience such glitches, with rates that depend on the pulsars’ rotation rate and spin-down rate, and on the glitch model. The superfluid vortex unpinning model gives good agreement with the observed distribution of glitches and with the parameter values deduced for the Vela pulsar glitches.
Microlensing of pulsar-radiation
Authors: Wex Norbert , Gil Janusz , Sendyk Marek 
Published: July 2016

When the radiation of a star passes near a massive object, its intensity is magnified due to the microlensing phenomenon. Similar effects should also apply to pulsar signals. However, because of the pulsating nature of pulsar radiation, the flux magnification will be accompanied by a time varying travel-time delay (Krauss and Small 1991, Larchenkova and Doroshenko 1995, Ohnishi et al. 1995, Wexet al. 1996).Let us denote the epoch of observation byt⊕. A travel-time delay caused by aSchwarzschild-lensis characterized by four parameters:M, the mass of the lens,q, the ratio of the transverse velocity of the lens with respect to the line of sight and the minimum impact parameter,fm, the ratio of the minimum impact parameter and the Einstein radius, andT0, the time of maximum delay. If we denote the ‘intrinsic’ frequency and its derivative with respect to time (corresponding to the barycentric arrival time t =t⊕) by ν andthen, we find for the observed phase of the pulsar at the barycentric timet:
Geometrical effects on radio pulsar profiles and spectra
Authors: Sieber Wolfgang 
Published: July 2016

AbstractConsidering the geometry of the hollow-cone model of radio pulsar emission in detail, one is led to the conclusion that several well-known observed effects may be explained quite easily purely on geometrical terms. It is shown that a steepening of the spectrum (cut-off) may be expected for certain geometrical situations as well as variations in component spectra, e.g. steeper spectra for the central component. These effects appear in addition to the already existing physical variations with frequency.
Postion angle jumps in pulsar linear polarization
Authors: Xu R.X. , Qiao G.J. , Han J.L. 
Published: July 2016

AbstractThe position angle (PA) behaviour of linear polarization of pulsar emission is simulated after considering the relative retardation between the core and conal components, which are believed to be generated from different emission altitudes. The PA will jump 90° at some points where the complete depolarization occurs.
EUV Observations of Pulsars
Authors: Edelstein Jerry , Bowyer Stuart 
Published: July 2016

AbstractThree pulsars have been detected with the Lexan (100 Å )filter of the EUVE Deep Survey telescope: the middle-aged isolated pulsars, PSR B0656+14 and Geminga, plus the aged millisecond pulsar PSR J0437–4715. The EUV detections have been used both alone and in combination with observations in other bandpasses to limit the physical state of the objects and to test theories regarding neutron star cooling and re-heating mechanisms. For Geminga, the EUVE data suggests the presence of an optical cyclotron spectral feature superimposed on the Rayleigh-Jeans continuum tail from a hot pulsar surface. We summarize EUV pulsar observations and results.
General Relativistic Electrodynamics and Pulsar Theory
Authors: Mestel L. 
Published: July 2016

AbstractMuslimov &amp; Tsygan (1986, 1990, 1991, 1992) have shown how the dragging of inertial frames modifies the Goldreich-Julian charge density. The consequences are noted for different models of the electron outflow near the neutron star’s surface.
High Energy Continuum Spectra from X-Ray Binaries
Authors: Zhang S.N. 
Published: July 2016

AbstractA variety of high energy (>1 keV) spectra have been observed in recent years from Black Hole (BH) and Neutron Star (NS) X-ray Binaries (XB). Some common physical components exist between BHXBs and NSXBs, resulting in some high energy spectral features. A common component between a BHXB and a weakly magnetized NSXB is the inner accretion disk region extending very close to the surface (for a NS) or the horizon (for a BH). The inner disk radiation can be described by a multi-color blackbody (MCB) spectral model. The surface radiation of the NS can be approximated by a Single Color Blackbody (SCB) spectrum. For a strongly magnetized NSXB, the high energy emission is from its magnetosphere, characterised by a thermal bremsstrahlung (TB) spectrum. In both BHXBs and weakly magnetized NSXBs, a hot electron cloud may exist, producing the hard X-ray power law (photon index −1.5 to −2.0) with thermal cutoff (50–200 keV). It has been recently proposed that a converging flow may be formed near the horizon of a BH, producing a softer power law (photon index about −2.5) without cutoff up to several hundred keV. Based on these concepts we also discuss possible ways to distinguish between BH and NS XBs. Finally we discuss briefly spectral state transitions in both BH and NS XBs.
Viscosity and Large-Scale Magnetic Fields from Accretion Disc Dynamos
Authors: Tout Christopher A. 
Published: July 2016

AbstractWe review those processes associated with accretion discs that are probably influenced by magnetic fields, specifically, accretiondisc viscosity, energy dissipation and jet formation. We consider how magnetic instabilities in the disc can lead to a self-sustaining dynamical dynamo and how this is manifested as magnetohydrodynamic turbulence in numerical simulations. We show that currently these models do not fit with observational constraints imposed by dwarf-nova outbursts. We also show that the drop in ionisation fraction does not lead to the apparently necessary drop in viscosity in quiescent cataclysmic variable discs. Large-scale magnetic fields are required to launch and collimate jets form discs. We describe an inverse cascade process that can construct sufficient large-scale field from small-scale field generated by a dynamo.