bluuebunny/crossref_metadata_2025_split huggingface dataset:
Different Types of Photometric and Polarimetric Behaviour of AM Her in 1989–1994
Authors: Shakhovskoy N. M. , Andronov I. L. , Kolesnikov S. V. 
Published: July 2016

AbstractVariations in UBVRI are classified as: luminosity– and wavelength– dependent phase variations with differences from cycle-to-cycle; flares caused by accretion events; UV Cet-type flares from the secondary.
Comptel Observations of X-Ray Binaries
Authors: Iyudin A. F. 
Published: July 2016

The COMPTEL experiment on the Compton Gamma-Ray Observatory measures γ–radiation in the energy range from 0.75 to 30 MeV [10]. X-ray binaries form one category of potential γ-ray sources. Up to now only two X-ray binaries, Cyg X-l and Nova Per, have been seen by COMPTEL.Cyg X-l. Preliminary results were reported by [6] and indicate that (i) there was no evidence for any hardening of the spectrum near lMeV, (ii) the plasma temperature suggested by a Wien spectral model was much higher than that implied by hard X-ray observations. This latter conclusion seems to require a revision in the standard spectral model for Cyg X-l.The α–ray flux from Cyg X-l is constant up to several MeV. The time history of the flux in the 0.75… 2.0 MeV energy range shows that there are no significant variations near 1 MeV. The average photon spectrum derived from all observations up to 1994 July shows evidence for significant emission extending well above 2 MeV, with a data point in the 2…5 MeV range at 4.3 σ significance. However, the observed flux near 1 MeV is significantly below that reported by HEAO-3 and several other balloon observations [6]. The COMPTEL spectral data show a broad line-like feature around ~ 4 MeV with the best fit of a single power law plus Gaussian. If we assume that the Gaussian represents a single broadened nuclear line of 12C*, then the width of 1.38 MeV demands a temperature of ~ 2 1012 K [7].
The Nature of GQ Mus As Depicted From Photoionization Models of the Shell
Authors: Péquignot D. , Morisset C. 
Published: July 2016

Consequences of a detailed photoionization model study of the shell ejected by Nova Mus 1983 (GQ Mus) are presented for the period from early 1983 to 1990 (Morisset & Péquignot 1996).The drastic time variation of the emission line spectrum, including the transition from a nebular to a coronal stage in 1986, can be quantitatively understood in terms of a smooth evolution of both the expanding shell and the hot thermal source. This transition is due to a decrease of the shell density with time, and not to an increase of the source effective temperature.The model shell comprises two components so that not all directions become optically thin to ionizing radiation simultaneously. The range of density and geometrical thickness of the emitting material is of the order of a factor 2.
Ultraviolet Spectropolarimetry of Classical Novae in Outburst: Evidence for Aspherical Ejecta
Authors: Johnson J.J. , Anderson C.M. , Bjorkman K.S. , Code A.D. , Fox G.K. , Weitenbeck A.J. , Wood K. , Edgar R.J. , Sanders W.T. , Babler B. , Meade M. , Zellner N.E.B. , Clayton G.C. , Schulte-Ladbeck R. , Lupie O.L. 
Published: July 2016

AbstractWe used the Wisconsin Ultraviolet Photo-Polarimeter Experiment during the Astro-2 mission aboard the Space Shuttle Endeavour, to obtain ultraviolet spectropolarimetry of three classical novae that had recently gone into outburst. All three novae appear to have intrinsic polarization, with polarization changes across emission lines. This result indicates that, geometrically, the ejecta were quite aspherical.
V1016 Cyg: Proper Motion of Radio Emission
Authors: Eyres S. P. S. , Dougherty S. M. , Davis R. J. , Bode M. F. , Lloyd H. M. , Kenny H. T. 
Published: July 2016

AbstractWe present MERLIN maps of V1016 Cyg at 6 cm, observed on 1992 July 21 and 1995 March 23. Previously discovered bipolar structure is resolved into three distinct peaks. Evolution and proper motion of these peaks has been measured.
A unique symbiotic-like/cataclysmic triple star 4 Dra (=CQ Dra): six years of UBV monitoring
Authors: Urban Z. , Hric L. , Leedjärv L. 
Published: July 2016

The bright (mv ≈ 5) M3III star 4 Dra (HD108907, HR4765, CQ Dra) is a unique triple system combining in itself the basic structural properties of a symbiotic-like binary and of a cataclysmic one. The red giant 4 Dra A forms a wide binary (Porb ≈ 1703 d) with a hot companion 4 Dra B which seems to be a compact cataclysmic binary system (4 Dra BC, probable Porb of about 4 h).We have monitored the 4 Dra system in UBV at the Skalnaté Pleso and Starà Lesna Observatories and at the Tartu Astrophysical Observatory during a total of 205 nights between 1989 March 12 and 1995 June 20; a few additional data points were obtained at the Bucharest Observatory.
Observations of Low Mass X-Ray Binaries
Authors: Smale Alan P. 
Published: July 2016

AbstractIn this paper I review the properties and behavior of low-mass X-ray binary systems (LMXBs) that contain neutron stars (NS), concentrating on the Galactic bulge sources and bursters. I describe the observed characteristics of LMXBs including their light curves, spectra, eclipses, dips, bursts, flares, pulsations, QPO, long-term periodicities and orbital period changes, and explain how fast timing results and the distinction between ‘Z’ and ‘atoll’-type sources provide the key to a unified model of LMXB behavior.
Merlin Observations of Extended Emission Around GRS 1915+105
Authors: Newell S. J. , Spencer R. E. , Jowett F. H. 
Published: July 2016

AbstractWe present MERLIN observations of the exciting X-ray transient GRS 1915+105. Previous radio observations of GRS 1915 have shown that it is a source of superluminal radio jets. The emission of anti-parallel radio knots has led to this being described as a ‘microquasar’. MERLIN observations presented here show further details of the structure. The two main features observed are a bright extension in the direction of the superluminal jet and also, an extended region of low brightness which is elongated almost at right angles to the jet. This latter feature could either be an associated nebulosity or the remains of a jet which has undergone a radical change in direction.
The X-Ray Nova GRO J0422+32 in Decline and Quiescence
Authors: Garcia M. R. , Callanan P. J. , McClintock J. E. , Zhao P. 
Published: July 2016

We have followed the X-ray nova GRO J0422+32, spectroscopically and photometrically, throughout the decline to quiescence.In the final stages of decay (days 430…880 after the outburst, see Callanan et al. (1995) for the epoch 1995), the equivalent width (EW) of the Hα emission increases monotonically and the R magnitude decreases monotonically. This suggests that the flux in the Hα line is constant, while the continuum fades. The Hα flux is the product of the R band flux (F(R), arbitrarily scaled to 100 at R = 19 mag) and the EW, and is shown in the last column of the table below. The Hα flux varies by only ~ 30% while the continuum fades by a factor of eight (from R = 19 mag to R = 21.3 mag). So, to first order, the Hα luminosity is constant in the final stages of decay. While it is generally the case that the emission line EWs in individual dwarf novae also increase during the decay, the exact behavior seen in GRO J0422+32 is not what is seen for dwarf novae (on average). Using the relation between EW[Hβ] and Mv given in figure 6 of Patterson (1984), we would expect a factor of ~ 5 variation in the Hα flux during days 430…880. The stability of the Hα flux implies that somehow the emission line region is ‘disconnected’ from the continuum (R–band) emission region.
A Model for the Galactic Population of Supersoft X-Ray Sources
Authors: Yungelson L. , Tutukov A. , Fedorova A. , Livio M. , Truran J. W. 
Published: July 2016

AbstractThree major sub-populations of Galactic supersoft X-ray sources may exist: semi-detached binaries with main sequence or subgiant donors, and symbiotic binaries (~550, ~460, and ~600 objects, respectively). Each group contains both permanent and transient sources. The intrinsic and interstellar absorptions reduce the number of observable sources to ~25. We derive the distributions of the sources over orbital periods, masses of the components, and ‘on’-times. The rate at which white dwarfs in Galactic binaries reach MCh is ~ 3 10−5 yr−1. The rate of He-shell detonations which may lead to supernovae may be up to 3 10−4 yr−1.
The Supersoft X-Ray Source RXJ0537.6–7033
Authors: Orio M. , Valle M. Della , Massone G. , Ögelman H. 
Published: July 2016

AbstractWe present new X-ray data with an improved position for the supersoft X-ray source RXJ0537.6–7033, and propose a candidate for the optical identification.The source was initially designated as RXJ0537.7–7034 because there was a high uncertainty in the position, at the edge of the field of the ROSAT PSPC (Orio & Ögelman 1993). It was later observed three more times by the ROSAT PSPC at intervals of approximately 6 months, from the beginning of 1992 to the end of 1993. The change of the name is due to the new, more precise position obtained in these observations. The count rate was 0.021 ± 0.005 count s−1 in the first 1992 observation and remained at the same level in the second 1992 observation. The source was not detected in the first half of 1993, with an upper limit of 0.002 count s−1; finally in 1993 December it was detected with only 0.0035±0.0007 count s−1. It seems therefore to be very variable.
Simulations of Angular Momentum Evolution in Wind-Fed CV Precursors
Authors: Pearson K.J. , Wynn G.A. , King A.R. 
Published: July 2016

It is thought that the secondary stars in cataclysmic variables (CVs) may undergo a period of mass loss in the form of a wind during the evolution of the system (Mullan et al. 1992). This wind is thought to magnetically brake the secondary star with a time-scale ~ 108 yr (e.g. van Paradijs 1986). When the secondary’s spin has been brought close to synchronism with the orbit it is possible for tidal torques to lock the secondary in synchronous rotation.We have modelled this process by adapting a method that has proved successful in explaining the properties of the intermediate polars (Wynn & King 1995). We model the secondary magnetic field as a pure dipole which drags on the wind material as it crosses field lines. This has the effect of trying to force material to move along field lines. This does not model the magnetic interaction completely since it does not allow for the back reaction of the material on the field structure. However, this will only become significant in regions where the field is weak and hence where material is not exerting a large torque on the star.
Evolutionary Scenarios for Double Degenerate Systems
Authors: Marks P. B. , Sarna M. J. , Smith R. C. 
Published: July 2016

There are presently eight double degenerate systems with well determined orbital parameters, their periods being either a few hours or a few days (Marsh, Dhillon & Duck 1995; Marsh 1995). The masses of the primaries and secondaries lie in the range 0.15… 0.45M⊙.We calculate two evolutionary scenarios (Sarna, Marks & Smith 1996); the first is Algol-type evolution with two phases of stable mass transfer, and the second involves first a stage of common envelope (CE) evolution followed by a stage of stable mass transfer. In both calculations we assume non-conservative mass transfer by which we mean that the total mass and angular momentum of the system are not conserved. For both scenarios we start our calculations after the first stage of mass transfer has finished. In all calculations the primary is the initially more massive star that filled its Roche lobe and transferred material to the secondary during the first phase of mass transfer, hence the secondary is the star that fills its Roche lobe in our calculations. The system’s orbital period decreases and then increases until the system detaches; we are left with a detached white dwarf/white dwarf binary with an orbital period of the order of hours or of days (see Table 1). There must exist some bifurcation period below which the systems evolve towards orbital periods of the order of hours and above which the systems evolve to periods of the order of several days.
Line and Continuum Emission from the Outer Regions of a Self-Gravitating, Magnetized Accretion Disk
Authors: Lu Ye , Yang Lantian , Wu Shaoping 
Published: July 2016

AbstractWe determine the variation with radius of the physical parameters (scale height, central density, and central temperature) of a stationary self-gravitating, magnetized accretion disk at radii larger than 102RG. Our results are relevant in the context of line and continuum emission from the outer region of the disk. We have also studied the influence of self-gravitation and magnetic fields over typical radii, and have shown that the value of RBB is larger than that computed by Collin- Souffrin & Dumont by a factor of about 4.7.
Emission Lines in the Far-UV and Extreme-UV Region
Authors: Zheng W. 
Published: July 2016

AbstractRecent observations with HST and HUT have been made of the spectral region shortward of Lyα in AGN. Emission lines in this region, such as O VIλ1035 and Ne VIIIλ774, are mainly produced by collisional excitation. Their strengths and the lack of other significant emission lines of higher excitation energy indicate a temperature of ~ 6 × 104 K for the highly ionized gas in line-emitting clouds. Model calculations suggest that the strength of O VI and Ne vIII emission is correlated to the intensity of the high-energy photons above 100 eV. Therefore, these lines are useful diagnostics of the continuum shape in the soft X-ray range. The luminosity dependence of emission-line equivalent widths is more prominent for lines of higher ionization level, suggesting that the UV bump in AGN spectra may be weaker at higher luminosities.
Velocity-Resolved Line Response of the Emission Lines in the High-Luminosity (Mv ≈ −24) Seyfert 1 Galaxy Fairall 9
Authors: Wamsteker W. , Recondo-González M.C. , Rodríguez-Pascual P.M. , Vio R. , Makino F. 
Published: July 2016

AbstractA detailed emission-line decomposition has been made from 15 years of observations with the IUE satellite of the highly variable Seyfert 1 galaxy Fairall 9, allowing us to study the line variability as a function of velocity and continuum brightness. The variability over the different velocity domains of the broad lines has been related to the continuum variability over a large wavelength domain from the X-rays to the infrared. Clear delays were established between the redshifted and blueshifted parts of the lines in Lyα and C IV, with the red sides of the lines responding faster with no delay and the blue sides responding with a delay of some 230 days. The observed spectral variability behavior of the continuum has been used as input for photoionization model calculations and the combined constraints from the models and differences for gas at different velocities define the structure and motions in the BLR.
Keck High-Resolution Spectroscopy of Mrk 335: Constraints on the Number of Emitting Clouds in the BLR
Authors: Arav Nahun , Barlow Tom A. , Blandford Roger D. , Laor Ari 
Published: July 2016

AbstractBy applying cross-correlation (CC) techniques to high-resolution (~ 6km s−1), high S/N (~ 400 at Hα line center) spectra of Mrk 335, we are able to put a lower limit of ~ 3 × 106 on the number of emitting clouds in this objects. This limit is applicable for clouds with T = 2 × 104 K and an optical depth of a few hundred in their Hα line. Current BEL models based on stellar atmospheres of bloated stars can be ruled out based on this lower limit.
The Evolving XUV Absorber in NGC 3516
Authors: Mathur Smita , Wilkes Belinda , Aldcroft Thomas 
Published: July 2016

AbstractFor NGC 3516 we find that the X-ray warm absorption and the broad UV associated absorption features can be produced by the same absorbing material. We argue that the evolution of the XUV absorber from pre-1992 to 1995 is consistent with expectation for an expanding, outflowing material.
The Narrow-Line Regions of Seyfert and Radio Galaxies
Authors: Wilson Andrew S. 
Published: July 2016

AbstractThis paper reviews the morphology, excitation, and ionization of the gas in the narrow and extended narrow line regions (NLRs and ENLRs) in AGNs. Many high-resolution images of the NLRs of Seyfert galaxies are now available from HST. In some galaxies, these images reveal straight, sharp-edged V-shaped structures (believed to be the projections of 3-dimensional cones), while in others there is a close association between the ionized gas and the radio components. The latter effect arises through radiative shocks driven into the surrounding interstellar gas by the outwardly moving radio components or jets. Photoionization models of ionization-bounded clouds are quite successful in reproducing the line intensity ratios, but a number of problems remain. These problems may be resolved if matter-bounded clouds are also present. Differences between the excitation levels of different NLRs and ENLRs may reflect variations in the fraction of matter-bounded clouds as well as variations in the ionization parameter. I discuss the issue of whether the radiation responsible for photoionizing the gas in Seyfert 2 galaxies originates from a hidden, compact type 1 Seyfert nucleus or from photoionizing shocks within the NLR. These two scenarios are hard to distinguish between. The photoionizing-shock model requires surprisingly high pre-shock densities, raising the question of whether the shocks are sufficiently energetic to power the observed line emission.
Coronal Lines in Active Galactic Nuclei
Authors: Oliva E. 
Published: July 2016

AbstractRecent observations show that the CLR is small (a few tens of parsecs), has large column densities (N ≈ 1022 cm−2), and lies close to and is probably photoionized by the AGN. Coronal lines give information on Ne, Mg, Si, S, Ca, and Fe abundances, on the dust content and dynamics of the CLR, and can be used to trace hidden AGN. If they are powered by photoionization, coronal lines could be used to reconstruct the AGN spectrum at 100-400 eV. However, a proper understanding of the results requires careful use of photoionization codes, since the ionization parameter at the inner face is probably meaningless for CLR models, and a reliable convergence of the ‘highly variable’ atomic parameters for coronal lines. A shock model for the CLR in NGC 1068 requires collisional ionization of ≥ 600 M⊙ yr−1 of dense (n > 104 cm −3) gas within a region no larger than 30 pc. Maintaining a shock-excited CLR for a reasonable time requires > 1010M⊙ of fuel, which must be continuously supplied to the CLR.
Mid-Infrared Forbidden Lines of NGC 1068, NGC 4151, and NGC 5506
Authors: Greenhouse M.A. , Hayward T.L. , Satyapal S. , Wooden D.H. , Miles J.W. , Witteborn F.C. , Bregman J.D. , Woodward C.E. , Malkan M.A. , Fischer J. , Smith H.A. 
Published: July 2016

We report near-infrared spectroscopy of three Seyfert galaxies. Velocity resolved spectra covering low excitation-potential transitions of [Ar III] 8.991 µm, [S IV] 10.514 µm, and [Ne II] 12.813 µm were obtained using the facility mid-infrared array spectrometer (SpectroCam) of the Palomar Observatory Hale 5-m Telescope, and low-resolution spectra covering [Mg V] 5.608 µm, [Ar II] 6.985 µm, and [Ne VI] 7.642 µm were obtained using the faint-object spectrograph (HIFOGS) of the Kuiper Airborne Observatory (KAO).We find high contrast [Ar III] and [S IV] in each galaxy, and [Ne II] in NGC 1068 and NGC 4151 (12.8 µm data were not obtained on NGC 5506). The line profiles are well resolved. In NGC 1068 and NGC 4151, they are fit by singlecomponent Gaussians. However, in NGC 5506, evidence for a broad pedestal is seen in the [Ar III] and [S IV] spectra, similar to the broad Paβ component reported by Blanco et al. (1990) and Rix et al. (1990).
Integral Field Spectrography of Active Galaxies with TIGER
Authors: Ferruit P. , Pécontal E. , Adam G. , Bacon R. 
Published: July 2016

AbstractThe TIGER integral field spectrograph has been used to study nearby and distant active galaxies. We first present new TIGER observations of the Seyfert galaxy NGC 1275. In this very complex object, TIGER allows us to disentangle the contributions of the numerous components. We present the first very promising results on NGC 5252 obtained with the 3-D data-cube deconvolution techniques developed by our team in Lyon.
Excitation Mechanisms in Seyfert Galaxies
Authors: Allen M.G. , Dopita M.A. , Tsvetanov Z. I. 
Published: July 2016

The excitation mechanism of the extended emission-line regions (EELRs) in Seyfert galaxies is commonly thought to be nuclear photoionization. However, some Seyfert galaxies have EELRs with disturbed kinematics, outflows, and morphology which is indicative of interaction between radio plasma and the ISM of the host galaxy. In these cases shock excitation must also be considered (BickneU 1993).To investigate the importance of shocks and photoionization, we have taken two approaches: mapping the spatial dependence of the line ratios, and using UV line ratios which are sensitive discriminants between shocks and photoionization.
New AGNs Discovered with the 2.16-m Telescope at Xinglong Station of Beijing Astronomical Observatory
Authors: Zou Z. L. , Li Q. B. 
Published: July 2016

AbstractThe preliminary results of several on-going AGN programs using the 2.16-m telescope at Xinglong Station of Beijing Astronomical Observatory are described. About 150 new AGNs including QSOs, BL Lac objects, and Seyferts have been discovered in the last two years.
Discovery of Five Bright Low-Redshift Quasars from ROSAT PSPC Sources
Authors: Wei Jianyan , Cao Li , Hu Jiangyao , Li Qibin 
Published: July 2016

AbstractA program to identify bright ROSAT sources is being carried out with the 216-cm and 60-cm telescopes at Xinglong station. As the result of the first run, five bright low-redshift quasars have been discovered.
Luminous IR Galaxies: Evolution and Molecular Gas
Authors: Gao Yu 
Published: July 2016

Luminous infrared galaxies (LIRGs), denned by the criterion LIR ≳ 2 × 1011L⊙ (for H0=75 kms−1 Mpc−1), are the most powerful IR sources in the Universe, with most of their emission (~ 90%) in the far-IR. Most LIRGs are interacting/merging galaxies with large amounts of molecular gas as revealed by CO surveys (Sanders et al. 1991; Solomon et al. 1996). However, whether starbursts or dust-enshrouded AGNs/QSOs dominate the IR luminosity is not resolved.CO may not trace the active star-forming regions where gas density is more than one order of magnitude higher than the average. Dense molecular gas is better traced by high dipole-moment molecules like HCN and CS (e.g., Nguyen-Q-Rieu et al. 1992; Gao & Solomon 1996). Therefore, it is essential to survey HCN emission in a large sample of LIRGs to better reveal the nature of LIRGs. We here study IR and molecular gas properties vs. galaxy-galaxy interactions in LIRGs over various merging phases to trace their evolution and explore some links among interactions, starbursts, and AGN phenomena.
The Unification of Active Galaxies: Observations
Authors: Goodrich R.W. 
Published: July 2016

AbstractUnification theories have been central to much of our recent progress in the study of active galactic nuclei (AGN). These theories often explain the differences between some observationally defined classes of objects as due to what might be considered ‘uninteresting’ or nonfundamental parameters, such as viewing angle. In this presentation, I discuss not only such orientation-dependent unification theories, but also expand the concept to unification through other means, such as evolutionary effects.