bluuebunny/crossref_metadata_2025 huggingface dataset:
IUE and Optical Spectra of RZ LMI and ER UMa Throughout their 19 and 43 Day Cycles
Authors: Szkody Paula , Silber Andrew , Honeycutt R. K. , Robertson J. W. , Hoard D. W. , Pastwick Lora
Published: July 2016

IUE and optical data were obtained throughout the supercycles of RZ LMi and ER UMa during 1993/94. While most of the spectral and photometric characteristics are consistent with disk changes in systems with a relatively high accretion rate and low inclination, the cause of the high accretion rate in this subset of SU UMa stars is not known.
Population Studies of Cataclysmic Variables
Authors: Ringwald F. A.
Published: July 2016

Cataclysmic variables (CVs) are idiosyncratic objects, but progress can be made by studying groups of them. To do this, one must identify samples that are representative of their true properties. Because of the wide variety of physics that occurs in CVs, they have a complex phenomenology in which effects are still being discovered (e.g. permanent superhumps: Patterson & Richman 1991). CV outbursts have their own complex phenomenology (but see Osaki 1995a,b and this volume, for ideas on unification for dwarf novae), so it is unwise to rely on outburst properties to give unbiased samples.

One wants to identify CVs by some property common to all of them. One such property is flickering; another is color excess. CVs are very blue, especially in the ultraviolet, with U – B < −0.46 for 95% of CVs (Bruch & Engel 1994). This color index also defines inclusion in the Palomar-Green (PG) survey (Green, Schmidt & Liebert 1986), and a preliminary list of PG CVs was given by Green et al. (1982). My Ph.D. thesis (Ringwald 1993) completed this work, being the first optically selected complete sample of CVs at high latitude. At the same time, Andy Silber was writing his Ph.D. thesis on an X-ray-selected sample of CVs, from the HEAO-A1 MC-LASS survey (Silber 1992). One might say I was Andy’s optical counterpart.
Dynamo Driven Accretion Discs and Dwarf Nova Eruptions
Authors: Armitage P.J. , Livio M. , Pringle J.E.
Published: July 2016

A magnetic dynamo whose crucial ingredient is the Balbus-Hawley instability (Balbus & Hawley 1991) is a promising candidate for generating accretion disc viscosity. Both semi-quantitative analyses (Tout & Pringle 1992) and simulations (e.g. Brandenberg et al. 1995) suggest that such dynamos can operate in a disc environment. Here we aim to apply simple dynamo ideas to models of dwarf novae, and in particular investigate how dynamo driven discs can produce different values for α in quiescence and in outburst.
The Rise and Fall of α-Model Viscosity
Authors: Hessman F. V. , Obach C.
Published: July 2016

For nearly two decades, our only useful model for the viscosity in accretion disks has been the so-called ‘α-model’. However, it has become clear that the simplest models –in which α is constant – are inadequate to explain the range of behaviours seen in real disks. We show that the properties of steady-state, vertically-averaged models can be determined without any assumptions other than that the disks obey the classical Navier-Stokes equation. These solutions have derived values of α which vary with radius by many orders of magnitude even in small CV disks.
Physical Parameter Mapping of Accretion Disks
Authors: Vrielmann S. , Hessman F. V. , Horne K. , Baptista R.
Published: July 2016

We present a further development of the classical eclipse mapping method, which reconstructs the spatial distribution of physical parameters in the accretion disks of cataclysmic variables.
The Flares of AE Aqr
Authors: Eracleous M. , Horne K. , Livio M. , Welsh W. F.
Published: July 2016

The enigmatic flaring activity of AE Aqr, which extends from the radio to the X-ray bands, may be the exotic outcome of a relatively feeble accretion flow onto the rapidly spinning white dwarf. We summarize and interpret the results of recent observations by HST and ROSAT of the aperiodic flares. Optical and UV flares are tightly correlated and are clearly involved in powering the emission lines. The spectrum of a flare consists of a Balmer continuum, and a plethora of emission lines, which vary synchronously. The large optical/UV flares are not accompanied by large X-ray outbursts. The radial velocity curves of the UV lines, and of Hα, suggest that they originate in the accretion stream. The observational results dis-favor scenarios invoking coronal activity on the secondary star or instabilities at the disk/magnetosphere interface. Rather, they support a recently proposed scenario in which the accretion flow consists of blobs which are shocked upon encountering the white dwarf magnetosphere.
The Magnetic Field of the Intermediate Polar RE 0751+14
Authors: Väth H.
Published: July 2016

Piirola, Hakala & Coyne (1993) modeled the optical/IR light curve of RE 0751+14 assuming a uniform shock structure and neglecting the hard X-ray emission. In this paper, we model the light curves at optical/IR and hard X-ray wavelengths and include the effects of the shock structure.

We base our model on accretion onto a white dwarf with a displaced magnetic dipole for a range of likely white dwarf masses. We find that the observed intensity variations of X-rays and in the I band over one spin period largely determine the position of the emission regions. Furthermore, the observed maximum X-ray flux constrains the specific accretion rate. We deduce that the magnetic field at the pole is likely to be in the range 9 .. .21 MG, which is consistent with the estimates of Piirola et al. (1993). It had been proposed previously that there must exist asynchronous rotators with sufficiently strong magnetic fields such that the binaries will evolve into AM Her binaries (Chanmugam & Ray 1984; King, Frank & Ritter 1985). With this deduced high magnetic field RE 0751+14 is the most likely example of such a system known to date.
Radiation Hydrodynamics of Accreting Magnetic White Dwarfs
Authors: Beuermann K. , Woelk U.
Published: July 2016

We solved the stationary one-dimensional two-fluid radiation hydrodynamic equations including cyclotron radiation for a wide range of mass flow rates. Here, we discuss the implications for accretion phenomena on the white dwarfs in AM Her binaries.
Long-Term Brightness Changes of Two CVs
Authors: Sokolov D. A. , Shugarov S. Yu. , Pavlenko E. P.
Published: July 2016

The long-term light curves of the AM Her type binary BY Cam and the nova-like variable PG 2133+115 are presented. The BVR observations were carried out at a 0.5 m telescope equipped with a high sensitive TV tube superisocon (Abramenko et al. 1978), the UBV photoelectric data were obtained at 0.6 and 1.25 m telescopes and the photographic estimates were made from the negatives obtained at the 0.4 m astrograph in Crimea.

Both stars show high and low brightness states. They show similar behaviour in some respects: the amplitude between high and low states was about two magnitudes in B, but the duration of a low state was approximately two months for BY Cam and 1… 2 years for PG 2133+115.
Recent Progress on the Polar QS Tel: The HST Results
Authors: Clayton K. L. , Rosen S. R. , Osborne J. P.
Published: July 2016

We report on the Hubble Space Telescope (HST) observation of the polar, QS Tel, made during 1994 June. Orbital modulation is present in both the continuum and lines. A narrow dip is observed in the continuum folded light curve. The spectrum of the occulted source during this dip is broadly consistent in shape with the Rayleigh-Jeans tail of the EUV source.
Preliminary analysis of a Hubble FOS spectrum of VW Hyi in quiescence: A DAZQ white dwarf and accretion belt/ring
Authors: Sion E. M. , Huang M. , Cheng F. H. , Hubeny I. , Szkody P.
Published: July 2016

We present a preliminary analysis of the UV spectrum of the dwarf nova VW Hyi during early quiescence, obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST). The data were obtained approximately one day after the end of a normal outburst.
The ROSAT observations of classical novae
Authors: Orio M. , Ögelman H. , Balman S.
Published: July 2016

We observed a number of classical and recurrent novae in the Galaxy and the LMC with the ROSAT X-ray telescope and searched the archival data for other serendipitous observations. Preliminary results show that only 9 out of 37 observed objects were bright enough in X-rays to be detected with ROSAT, either in outburst or at quiescence.

Three basic mechanisms can cause X-ray emission from classical or re-current novae. The first is hot hydrogen burning in a thin shell of the remnant envelope left on the white dwarf after the nova explosion. Hydrogen burning post-novae should be blackbody like emitters at nearly Eddington luminosity (as per the ‘supersoft’ X-ray sources). In our sample, only GQ Mus (Nova Mus 1983, see Ögelman et al. 1993; Shanley et al. 1995) and V1974 Cyg 1992 (Krautter et al. 1996) had these characteristics. Remarkably, among 10 LMC novae that had an outburst in the last 47 yr none was detected as a ‘supersoft’ X-ray source. The 3 σ upper limits for the black-body temperatures of the post-nova white dwarfs are mainly in the range 20… 30 eV. A post-nova can also emit X-rays because of shocks occurring in the ejected shell (e.g. O’Brien et al. 1994). Three out of four classical novae that were observed in outburst displayed a hard X-ray component in the ROSAT energy band, which might be due to a shocked shell. Finally, X-ray emission is expected from quiescent nearby novae because of accretion. Only four nearby accreting sources were detected; the ROSAT upper limits for the non-detected quiescent novae are Lx < 1031… 1032 ergs−1, assuming a thermal plasma at kT = a few keV.
TNR on Top of Accreting WDs: 2-D Simulations
Authors: Glasner S. A. , Livne E. , Truran J. W.
Published: July 2016

Spherically symmetric models for classical novae as thermonuclear run-aways (TNR) of hydrogen-rich, accreted, envelopes on top of cold white dwarfs (WD) are in very good agreement with observations (Starrfield, Sparks & Truran 1974, 1985; Prialnik, Shara & Shaviv 1978; Prialnik 1986; MacDonald 1980). Multi-dimensional investigations are needed since the burning rate is very sensitive to the temperature and small fluctuations in temperature can lead to large differences between the flash times of different points on the burning shell; these differences can be much larger than the rise time of the nova light curve. Convection is assumed to be the mechanism that couples the burning process at different points in the shell so that the overall phenomena is spherically symmetric.
UBV Photometry of V705 Cas (Nova Cas 1993) During the First Year of the Outburst
Authors: Petrík K. , Hric L. , Urban Z. , Hanžl D. , Chochol D.
Published: July 2016

Nova Cas 1993 (=V705 Cas) was discovered ten days before it reached its maximum brightness in the V colour (Vmax = 5.53 mag and Bmax = 6.14 mag) on 1993 December 17.29 (Munari et al. 1994b). The pre-nova varied around 18… 18.5 mag and 17… 17.5 mag in B and V, respectively. No more prominent light fluctuations were found (Munari et al. 1994a). The nova started to fade rapidly, entering the deep minimum typical for the transition period of the DQ Her-subclass of novae in 1994 mid-February. The time development of the UV luminosity of the nova was discussed by Hauschildt et al. (1994). In this paper, we analyze our original UBV photometric data and all the available data obtained by the other authors. We derive the basic parameters of the nova and present the results of our search for short-term periodicities.
Detection of the Irradiated Red Dwarf in WY Sge (Nova 1783)
Authors: Somers M. W. , Mukai K. , Naylor T. , Ringwald F.A.
Published: July 2016

We present infrared (IR) photometry and optical spectroscopy of the eclipsing old nova WY Sge. According to hibernation theorists the disc in a system a few centuries after outburst should be significantly fainter than in other, more recent, old novae but similar to the discs of dwarf novae in quiescence. Despite the apparent faintness of the late type star we have sufficient information to infer that the face closest to the white dwarf (WD) is irradiated.
Possible Periodic Components in the Flickering of CH Cyg and MWC 560
Authors: Mikołajewski M. , Tomov T. , Dapergolas A. , Bellas-Velidis Y.
Published: July 2016

CH Cyg and MWC 560 are very peculiar symbiotic binaries consisting of an M giant and a white dwarf companion. The systems have many features in common. In particular, both show occasional eruptions with sub-Eddington luminosity, followed by the appearance of high-velocity jets. Recently, Mikołajewski, Mikołajewska & Tomov (1995) have proposed a model of activity for these systems with a rapidly rotating magnetic white dwarf accreting from the M giant’s wind. Two states of activity are possible: propeller and accretor. Although, both stars spend most time in the propeller state, occasional propeller-accretor (and vice versa) transitions may give rise to bipolar outflows and rapid jet formations. Mikołajewski et al. (1995) also proposed to distinguish a new subclass of interacting binaries – propeller stars – with CH Cyg and MWC 560 being the prototypes.
Generation of X-Ray Fluctuations in X-Ray Binaries
Authors: Mineshige S. , Takeuchi M. , Negoro H.
Published: July 2016

Short-term aperiodic fluctuations with 1/f-like power spectral density (PSD), where f is the frequency, are characteristics of X-ray radiation from X-ray binaries. To investigate a mechanism creating fluctuations, we construct a cellular-automaton model for accretion disks based on the concept of self organized criticality (SOC). In this model, mass accretion takes place either by an avalanche triggered when the local mass density exceeds some critical value, or by a gradual diffusion occurring regardless of the critical condition. With this model, we can reproduce the observational PSD, the distributions of peak intensities of X-ray shots, and non-random temporal distribution of the shots. Possible accretion disk models producing l/f-like X-ray fluctuations are discussed. We conclude that such disks are likely to be advection dominated.
Cyg X-2: Its Recurrent X-Ray Behaviour
Authors: Kuulkers E. , van Der Klis M.
Published: July 2016

We find evidence for the occurrence of three different types of behaviour which as their basic distinction have different X-ray brightness levels. They are found to be recurrent.
Models of Soft X-Ray Transients and Dwarf Novae
Authors: Lasota J. P.
Published: July 2016

Models of Soft X-ray Transients are presented and compared with observations. The importance of inner advection-dominated flows in quiescent transient sources is discussed, as well as the problem of global stability of the standard outer accretion disc. A comparison is made with similar problems in dwarf nova models.
From Common Envelope to Pre-Cataclysmic Variables: An Observational Test of Common Envelope Evolution
Authors: Sarna M. J.
Published: July 2016

The generally accepted evolutionary scenario for cataclysmic variables (CVs) is common envelope (CE) evolution (Iben & Livio 1993) proposed by Paczyñski (1976). The secondary spirals towards the giant’s compact core converting orbital energy into kinetic energy of the giant’s envelope and the envelope is ejected. The dynamics of the red dwarf and red giant envelope interaction have been studied by several groups (Livio & Soker 1988; Taam & Bodenheimer 1991). After the ejection of the red giant envelope the post common envelope detached binaries (PCEBs) are formed. These can be divided into three groups:

• Hot subdwarf with a red dwarf star inside a planetary nebula.

• Hot subdwarf with a red dwarf star without a planetary nebula.

• Hot white dwarf with a red dwarf star without a planetary nebula. Next, due to angular momentum loss by magnetic braking and/or gravitational radiation, the red dwarf component fills its Roche lobe and a cataclysmic variable is formed.
The 12C/13C Ratio as a Tracer of the Evolution of Post Common Envelope Systems and Cataclysmic Variables
Authors: Sarna M. J. , Marks P. B. , Smith R. C.
Published: July 2016

To provide a direct test of common envelope (CE) evolution which can be easily confirmed by observations, we (Sarna et al. 1995) recently modelled the change in the abundance ratio of 12C/13C on the surface of the lower mass star of a binary during the CE phase. The model is based on the fact that it is probable that the dwarf star accretes material during the CE phase. Since, during the CE phase, the dwarf secondary effectively exists within the atmosphere/envelope of the giant or supergiant primary, the accreted material has the abundances/composition of a giant/supergiant star. The 12C/13C ratio is known to decrease from approximately 90 in dwarf stars (in which the 13CO band at 2.3448 microns is barely visible) to approximately 10 in giants (in which the 13CO band at 2.3448 microns is fairly prominent). Hence, by measuring the 12C/13C ratio in post common envelope binaries (PCEBs) and comparing it to our models we would be able not only to confirm the CE theory but also to determine the amount of mass accreted during the CE phase and hence the initial mass of the dwarf component prior to the CE phase. We also propose an evolutionary scenario in which PCEBs with secondary component mass near 1.0 M⊙ start semi-detached evolution almost immediately after the CE phase. The progenitor system is a wide binary consisting of a 3 M⊙ primary with a 1.0 M⊙ secondary star. The primary evolves to fill its Roche lobe when it has a 0.6 M⊙ C–O core, with two shell burning regions. Such a star has a thick convective envelope, mass transfer is dynamically unstable and a common envelope forms. After the CE phase we are left with a close detached binary consisting of the primary’s core (0.6 M⊙) and the secondary (1.0 M⊙) main sequence star. Shortly afterwards the secondary fills its Roche lobe and mass transfer occurs (Sarna, Marks & Smith 1995). The system now evolves as a semi-detached binary (CV), transferring material to the white dwarf which undergoes nova outbursts. Figs. 1 and 2 show the isotopic ratios of 12C/13C and 16O/17O during the semi-detached evolution. In Fig. 1 the secondary did not accrete any material during CE evolution whilst in Fig. 2 the secondary accreted 0.2M⊙ during the CE stage.
The Eclipses of the Close Binary Star BE UMa
Authors: Wood Janet H. , Robinson E. L. , Zhang E.-H.
Published: July 2016

BE UMa is a close binary star, not transferring mass, with an extremely hot primary star irradiating the inner face of the cool secondary star. The light curve shows a large-amplitude, sinusoidal variation with a period of 2.29 d, and an eclipse that is centered on the minimum of the variation [1], [3]. According to [1], the eclipse is partial, not total. However, it has been argued [2] that the eclipse was really flat bottomed and thus total. This has important repercussions for the deduced model of the system. To resolve this issue we obtained simultaneous UBVR photometry of BE UMa using the Stiening 4-channel, high-speed photometer on the 82-inch telescope at McDonald Observatory. The mean light curves are shown in Fig. 1. The eclipse in all colours is round bottomed and partial. The different depths are caused by the different contribution from the red secondary star in each bandpass.
An Evolutionary Scenario for Short Period (≤10 Days) Millisecond Binary Pulsars
Authors: Ergma E. , Sarna M. J. , Antipova J.
Published: July 2016

We present numerical calculations that simulate the evolution of a low mass (1M⊙) star transfering mass to a compact object (Muslimov & Sarna 1993; Ergma & Sarna 1996). Mass transfer starts when the secondary turns off the main sequence (having a small helium core). We have calculated 14 evolutionary sequences with the assumption of non-conservative or conservative evolution. We can conclude that near the bifurcation point the evolution is very sensitive to: (i) the assumption of conservative or non-conservative evolution, (ii) the structure of the mass losing star. Small changes in the initial period when the secondary fills its Roche lobe will lead to large changes in the final period and final mass of the remnant. Presently there are 40 known low-mass binary pulsars (LMBP). The evolutionary scenario for the wider systems (10 < Porb(d) < 1000) is connected with that of wide low-mass X-ray binaries (LMXB) in which the donor star will fill its Roche lobe after helium core formation.
X-Ray Emission Lines: Present and Future Experiments
Authors: Kunieda H.
Published: July 2016

After 34 years of X-ray astronomical observations, we approach the time when we will be able to explore AGN using line spectroscopy with newly developed technology and methods. In the beginning, X-rays from AGN were observed using proportional counters in a sort of photometric way, allowing us to determine that the continuum is a power law. This result suggested a predominance of non-thermal emission mechanisms in AGN. Rapid variability on time scales as short as 1000 seconds implied a small size for the X-ray emitting region, of order 1014cm, which is 3 orders of magnitude smaller than the optical emission-line regions.

The first detection of line emission from AGN was the Fe-K line by the GINGA satellite. The line energy was 6.4 keV and its equivalent width was about 150 eV in Seyfert 1 galaxies. Detection became possible by use of large-area, low-noise proportional counters. The Fe-K line emission is important in X-ray astronomy because iron is rather abundant and this line is isolated in energy from neighboring lines.

The Fe-K line profile has been examined with the CCD detectors on board ASCA. Many Seyfert 1 galaxies exhibit a broad-line profile of more than 1 keV width with an asymmetric tail on the low-energy side. This is explained as the fluorescence line from a relativistic accretion disk around a black hole, which is broadened by the Doppler motion and distorted by the strong gravitational field. The CCD detectors also revealed the absorption edges of warm material in the line of sight, which is ionized by the strong emission from AGN.

In the next decade, new spectrometers will be launched which can perform spectroscopy with E/dE > 100: AXAF in 1998, XMM in 1999, and Astro-E in 2000. Dispersive spectrometers on board AXAF and XMM will be powerful tools for low-energy lines, while the calorimeter on board Astro-E will examine the Fe-K line profile. Spectral resolution E/dE of several hundred will reveal the intensity ratio of satellite and resonance lines. This will give us physical parameters, such as the density and absolute size of surrounding matter. We hope that the structure of the nucleus will be more deeply understood using X-ray spectroscopy with new instruments, and we will come close to the level of optical spectroscopy, which has worked well in the study of the outskirts of AGN.
High-Energy Lines in Active Galactic Nuclei
Authors: Netzer Hagai
Published: July 2016

The recent observations of a highly ionized, X-ray absorbing gas in active galactic nuclei (AGN) suggest a new nuclear component, the so-called ‘warm absorber’. This gas is likely to be at a temperature of ~ 1–2 × 105 K and is most easily detected in the 0.5–10keV range, where several oxygen absorption edges are often observed.

This review describes the properties of warm absorbers and the relation
to other nuclear components, such as the broad-line emitting gas. The stability of the gas is a key issue and analysis shows that it is likely to be thermally stable, at the above mentioned temperature. When successful models are compared to the data, they can be used to infer the column density, composition and level of ionization of the X-ray absorbing gas. They also show that, on top of the strong continuum absorption, the gas must emit X-ray lines that are at the limit of detection by present day X-ray instruments.

New calculations of X-ray emission lines emitted by ionized X-ray absorbers are shown and discussed. Various line equivalent widths are defined and examples are shown over a large range of column density and ionization parameter. The equivalent width of the strongest 0.5-5 keV lines is only a few tens of eV, but in cases of obscured X-ray source, like in Seyfert 2s, the lines are measured against the scattered and diffuse radiation with much larger equivalent widths. The X-ray absorbing and emitting gas is responsible also for a fraction of the observed flux of some UV emission lines. It is also the cause of the detection of several UV absorption lines. The calculations predict that some of those absorption lines, in particular 0 VI λ1035, are very sensitive warm-absorber tracers. Thus, analysis of the combined X-ray and UV properties is the best way to identify the location and properties of this gas.

Understanding the origin and properties of warm X-ray absorbers is a major challenge of AGN research. Several new ideas are briefly discussed, trying to relate the location, mass, and motion of this gas to what is known about other observed nuclear components.
ASCA Observations of Seyfert 2 Galaxies
Authors: Awaki H.
Published: July 2016

We have observed a sample of Seyfert 2 galaxies with ASCA. The targets were selected based on their [O III] λ5007 flux, the existence of polarized broad lines, and previous X-ray detection. The nuclear luminosities of these galaxies range from 1042 to 1044 ergs s−1 in the 2–10 keV band. Obscured nuclei were found in all galaxies in our sample, with absorption column densities distributed around a value of 1023.5 cm−2.

The cold iron Kα line was clearly detected in half of our sample, and emission from He-like and H-like Fe Kα was detected from two galaxies. These lines are explained by fluorescent lines from thick cold matter and warm/hot thin matter. Highly ionized lines originating in starburst activity were also detected from NGC 1068.
X-Ray Observations of Low-Luminosity Active Galactic Nuclei
Authors: Makishima K. , Iyomoto N. , Ishisaki Y. , Terashima Y.
Published: July 2016

Through X-ray observations with ASCA, low-luminosity active galactic nuclei have been found in at least seven near-by spiral galaxies. Some of them exhibit very intense, and possibly broad, Fe-K emission lines. Their time variability is relatively insignificant, in contrast to lowluminosity Seyfert galaxies.
Broad Emission Lines in Active Galactic Nuclei
Authors: Baldwin J. A.
Published: July 2016

This paper assesses what we have learned about the structure of AGN broad-line region (BLR), with emphasis on the work other than reverberation studies in order to complement other recent reviews. Basic photoionization models are briefly described. Current models of the BLR and some of the observations that might distinguish among them are discussed.
IR Spectroscopy of High-Redshift Quasars
Authors: Bechtold Jill , Shields Joseph , Rieke Marcia , Ji Peiwen , Scott Jennifer , Kuhn Olga , Elvis Martin , Elston Richard
Published: July 2016

We have obtained near-IR, optical, and soft X-ray spectrophotometry for a number of bright quasars with 2 ≲ z ≲ 4. The observed ratios of Lyα/Hβ in this sample are smaller than Case B, and span a similar range to those seen at lower redshift. A correlation between the line width of Hβ and X-ray spectral index found for low-redshift PG quasars is also seen for the high-redshift objects.
Velocity Diagnostics of the Broad Emission-Line Region of Active Galactic Nuclei
Authors: Espey Brian
Published: July 2016

We present a brief review of emission-line velocity differences, and describe an ongoing project to determine the driving mechanisms responsible. We conclude with a brief outline of the use of velocity differences as probes of the conditions in the nuclear region of AGNs.
Broad-Line Profile Variability
Authors: Wanders Ignaz
Published: July 2016

Many years of monitoring a sample of 10 AGNs with a median sampling rate of about one spectrum per week yields strong evidence that broad-line profile variations are not induced by reverberation effects, but rather signify real changes in the structure of the continuum-source and broad-line region complex, contrary to line flux variations, which do respond to continuum variations. If the profile variations indeed trace internal changes in the BLR, then the BLR cannot consist of the billions of small clouds as the standard model of the BLR prescribes. Rather, small-number statistics are necessary. The sample of AGNs also indicates there are three preferred ‘components’ in the line profiles. These can be explained as geometrical projection effects due to an anisotropic continuum irradiating an otherwise spherical BLR.
Inconsistency of Photoionization Models for NGC 5548: Proof of Mechanical Heating?
Authors: Collin-Souffrin S. , Dumont A.-M. , Nazarova L.
Published: July 2016

It is shown that, in the case of NGC 5548, photoionization models cannot account for line fluxes, line ratios, and line variations. The assumption that a fraction of the broad-line region is mechanically heated can solve the problem.
The Contribution of Čerenkov Line Radiation to the Broad Lines in AGNs
Authors: Wu Hao , Shi Jian-rong , You Jun-han
Published: July 2016

In 1980, You & Cheng (1980) suggested that in a dense gas medium, relativistic electrons will produce Čerenkov atomic or molecular emission lines of widths Δλ ≈ 1 – 10Å. The Čerenkov line is broader than a normal emission line and has small redshift (ΔZc≡ Δλp/λlu≈ 10–3), so the apparent velocity is about a few hundred km s−1. We refer to this as the ‘Čerenkov redshift’. In 1986, You & Cheng gave simplified formulae for Čerenkov line emission and the mechanism was confirmed by a series of elegant experiments (Xu et al. 1988, 1989). Recent progress in studies of AGNs, both in theory and observation, provide support for the Čerenkov line-emission model of the BLR of AGNs. In this paper, we prove that for a dense gas, if there are enough relativistic electrons, the Čerenkov line emission is strong enough to compare with the observations, and the Čerenkov line emission dominates over the spontaneous emission lines in the optically thick case.
Near-IR Spectroscopy of High-z QSOs: Relating the Broad and Narrow-Line Regions
Authors: Brotherton M.S.
Published: July 2016

Recent investigations of the broad UV lines in luminous QSOs identified strong correlations involving emission-line widths, shifts, equivalent widths, and ratios (Francis et al. 1992; Wills et al. 1993; Brotherton et al. 1994a, b). A simple model developed to explain these trends approximates UV broad lines as emission from two regions, an intermediate-line region (ILR), and a very broad-line region (VBLR), together comprising the traditional broad-line region (BLR). The observed and derived properties for the ILR and VBLR are summarized in Table 1, along with typical values for the narrow-line region (NLR).
Gas Outflow in the Seyfert Galaxy IC 5063
Authors: Morganti R. , Oosterloo T. , Tsvetanov Z.
Published: July 2016

IC 5063 (PKS 2048–572) is a nearby (z = 0.0110) early-type galaxy hosting a Seyfert 2 nucleus. In broad-band optical images, it shows a complex dust lane, while the ionized gas extends up to ~ 20 kpc and has an unusual X-shaped structure (Danziger et al. 1981, Colina et al. 1990). A faint, very broad emissionline component has been detected (Bergeron et al. 1983, Colina et al. 1991) together with an off-nuclear broad emission-line region (Wagner & Appenzeller 1989). Broad Hα emission was also detected in polarized light (Inglis et al. 1993). Thus, it is likely that this galaxy has a broad-line region which is obscured from our direct view (while the broad-line radiation is scattered into our line of sight by scatterers outside the obscuring regions). The radio luminosity of IC 5063 is nearly two orders of magnitude larger than typical values for nearby Seyferts (Ulvestad & Wilson 1984), making it one of the strongest radio sources found in Seyfert galaxies (1.3 Jy at 1.4 GHz, i.e., 2 × 1023W Hz−1 for H0 = 50 km s−1 Mpc−1). Its H I content is also very high: Danziger et al. (1981) found 1.0 × 1010M⊙, which gives MHI/LB = 0.4, quite anomalous for this type of object.
AGN Spectra as Seen by the Infrared Space Observatory: First Results
Authors: Lutz D. , Genzel R. , Sturm E. , Moorwood A.F.M. , Oliva E. , Marconi A. , Netzer H.
Published: July 2016

We discuss 2.5–45 µm spectra of the Circinus galaxy and of Cen A, obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory. The large number of detected ionic fine structure lines, observable also in visually obscured sources, provides strong constraints on the shape of the ionizing spectrum, which is found to exhibit a UV bump peaking at ~ 70 eV in the case of Circinus. Pure rotational emission of molecular hydrogen, directly probing warm molecular gas, can for the first time be detected in external galaxies.
Cospatial Line Emission and Accelerated Outflow in the Spatially Resolved Narrow-Line Region of NGC 4151: Confirming Model Predictions
Authors: Moore D. , Cohen R.D. , De Robertis M.M.
Published: July 2016

We present results of high S/N, high spatial and spectral resolution (0″.65 and 0.8Å FWHM, respectively) spectrophotometry of the NLR of NGC 4151 using the Keck 10-m Telescope. The observations are the first in a series that test unambiguously several specific predictions that are based on earlier modeling of spatially unresolved emissionline spectra. Importantly, we partially resolve the source of most of the emission-line flux. Thus, the observations suitably complement analyses of spatially unresolved NLR spectra.
A Critical Test for Photoionization of Seyfert NLRs
Authors: Metz S.K. , Tadhunter C.N. , Robinson A. , Axon D.J.
Published: July 2016

We present measurements of the central ionizing photon flux q across three spatially resolved Seyfert NLRs, with implications for the ionization mechanisms.
Millisecond Pulsar Surveys
Authors: Bailes M.
Published: July 2016

There are now more than 30 millisecond pulsars known to be associated with the Galactic disk. The majority of these have been discovered in just the last few years as the result of large-scale all-sky surveys. The properties of the population vary tremendously. One unique object hosts a planetary system, more than half of those discovered possess white dwarf companions, two have extremely low-mass companions that are undergoing mass-loss and several others appear to be solitary. In this review I discuss the methods employed to find these millisecond pulsars, the parallels with early surveys for “normal” pulsars, and possible strategies for future searches.
Velocity-Magnetic Field Correlation of Pulsars
Authors: Itoh Naoki , Kotouda Takemi
Published: July 2016

Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.
The Origin of Millisecond Pulsar Velocities
Authors: Tauris Thomas M.
Published: July 2016

We have developed a computer code (Tauris & Bailes 1996) to follow the evolution of a binary system from the zero-age main sequence to its “final” state as a binary millisecond pulsar (BMSP), at all stages keeping careful track of the mass and orbital separation of the two stars.

To help determine the origin of millisecond pulsars, we compute the space velocities predicted by various models of their formation. It is difficult to produce a millisecond pulsar velocity greater than 270 km s−1with any model, unless the formation of the neutron star is accompanied by some form of asymmetric kick. We obtain average 3-D system velocities of 〈vrecoil〉= 99.6, 137.6 and 160.7 km s−1using Gaussian kicks of 〈vkick〉=0, 200 and 450 km s−1(σ=0, 100 and 200 km s - 1, respectively). Our computations show that, in general, we expect those systems with shorter orbital periods to have larger velocities than those with longer periods, but any relation between the final orbital period and space velocity is fairly weak, especially if asymmetries are involved.
The Cluster Analysis of Pulsar Parameters
Authors: Malov Igor’ F. , Malov Oleg I.
Published: July 2016

We have used the catalogue of (Taylor et al., 1993) to investigate the problem of a classification of pulsars. Five samples have been analysed by the main components method and by methods of the cluster analysis.

i)

15 pulsars with 14 known parameters P, Ṗ, W50,L(Malov et al., 1994),B,z,spectral indexa, frequencies of maximumVMand minimumVcin a spectrum (Malofeev et al., 1994), an angle between magnetic moment and rotation axisβ(Malov, 1994), the transformation coefficientη=L/Ė, magnetic field near the light cylinderBlcand a maximum derivative of a position angleC= (dψ/dφ)max(Malov, 1990).

ii)

130 objects with 10 parameters (the spectral characteristicsα,VM,VCand the parameter C were excluded from the consideration).

iii)

218 pulsars with 4 known parameters P, Ṗ, L andz. These parameters can be considered as independent variables.

iv)

89 sources with the same 4 parameters. This sample consists of two subsamples: 65 pulsars withP> 1 s and 24 ones withP< 0.1 s.

v)

24 pulsars withP< 0.1 s from the previous sample.
An International Pulsar Data Archive
Authors: Matsakis Demetrios N. , Josties Frederick J. , Foster Roger S.
Published: July 2016

We have organized a system to provide pulsar profiles and time-of-arrivals (TOAs) via anonymous ftp and the World Wide Web (WWW) at the address http://orion.usno.navy.mil/archive.html.
Pulsar Astrometry and Improved Terrestrial Clocks
Authors: Matsakis Demetrios N. , Josties Frederick J. , Foster Roger S.
Published: July 2016

Recent improvements in cesium and hydrogen terrestrial frequency standards have brought the frequency precision of International Atomic Time (TAI) to a value of 2.5E-15 s/s over an averaging time of a month. In this paper we illustrate the improvement graphically, and discuss the state of the art for frame ties between the radio, dynamical, and optical frames. In a larger paper, available via the World Wide Web, we illustrate the measured accuracy curves of the frequency standards, show their effect on the ensemble time scales, explain the reasons for the confusing array of available time scales, and discuss the inverse problem of using pulsar data to correct the terrestrial time scale.
Phase-referenced VLBA Observations of PSRs B1937+21 and B0329+54
Authors: Dewey Rachel J. , Beasley Anthony J.
Published: July 2016

In this paper we present the preliminary results of phase-referenced VLBA observations of two pulsars PSRB1937+21 and PSRB0329+54. Since pulsar observations usually require a lower observing frequency than that used for other astrometric applications, ionospheric delays are a significant source of systematic error. For the observations presented here we used total-electron-content (TEC) measurements derived from dual-frequency GPS observations (Wilson, Mannucci & Edwards, 1995) to calibrate ionospheric delays.

Using this calibration technique were able to obtain positions for these two pulsars which we believe to be accurate to approximately 2 mas in each coordinate. With this level of accuracy we expect astrometric pulsar observations to be able to address a variety of interesting issues ranging from reference frame alignment and fundamental astrometry to the origin of pulsar velocities.
Pulsar VLBI Experiment with Kashima(Japan)-Kalyazin(Russia) Baseline
Authors: Sekido M. , Imae M. , Hanado Y. , Takahashi Y. , Koyama Y. , Ilyasov Y.P. , Rodin A.E. , Avramenko A.E. , Oreshko V.V. , Poperechenko B.A.
Published: July 2016

Interferometric measurement of a pulsar is one of the most effective techniques to measure accurate source position. Precise measurement of pulsar position will give us the information of proper motion and parallax. Interferometric measurements on pulsars have been carried out, but the number of the pulsars whose position were measured is still smaller than the total number of pulsars. Because newly discovered pulsars are rapidly increasing due to recent intensive systematic surveys. We have started measuring their position by using VLBI between Kashima and Kalyazin. This report shows the results of the first experiment.
Inverse Compton Scattering in pulsar physics
Authors: Qiao G.J.
Published: July 2016

Inverse Compton Scattering (ICS) is a very important process not only in inner gap physics, but also for radio emission. ICS of high energy particles with thermal photons is the dominant and a very efficient mechanism of the particle energy loss above the neutron star surface, and is an important process in causing gap breakdown. The pulsar distribution in theP−Pdiagram and the observed mode changing phenomenon of some pulsars can be expained by the sparking conditions due to ICS. ICS of the secondary particles with the low frequency wave from the inner gap sparking can be responsible for radio emission. In this ICS model, many observational features of pulsar radio emission can be explained, such as: one core and two conal emission components, their different emission altitudes and relative time delay effects; spectral behavior of pulse profiles; the behavior of the linear polarization and position angle.
Microstructure and patterns of coherent radiation
Authors: Ables J. G. , McConnell D.
Published: July 2016

We present data which indicates that micropulses from the bright millisecond pulsar PSR J0437–4715 are observed at equally-spaced preferred phases within the pulse window. We find the pattern similar to that expected if each micropulse is radiated from a source with a coherence scale of ~ 100 m.
Compton scattering effect on polar gap formation: Self-sustained polar cap heating
Authors: Luo Qinghuan
Published: July 2016

One of the essential ingredients in existing polar gap models (e.g. Ruderman & Sutherland 1975; Arons & Scharlemann 1979, hereafter AS) is a pair cascade above polar caps. In these models, pair cascade is initiated by curvature photons radiated by primary particles and produced pairs screen out the electric field, forming a pair-production-limited acceleration zone (called the polar gap). For pulsars with strong magnetic fields (B≳ 1012G) and hot polar caps, resonant inverse Compton scattering (RICS) can be important (e.g. Dermer 1990; Sturner 1995, and references therein). The gap height is significantly reduced by the RICS effect (Luo 1996), and this may reduce the energetics of the polar gap as the maximum energy of primary particles is constrained by the gap height. The minimum temperature for RICS to be important is (Luo 1996)
Radio emission from polar caps in pulsars
Authors: Kuijpers Jan , Volwerk Martin
Published: July 2016

Radiation from a charge accelerated along its path or Linear Acceleration Emission (LAE) involves a number of subtleties (Pauli 1921; Ginzburg 1970, 1989). Potential interest of the mechanism for astrophysics has been pointed out by Wagoner (1969). Melrose (1978) and Rowe (1995) have studied amplified LAE from time-varying electric fields for radio pulsars. In contrast with the latter work our calculations are for static electric field structures or double layers (DLs) as are thought to occur in magnetospheres of neutron stars. In ordinary stellar atmospheres a LAE maser can operate in non-relativistic DLs (Kuijpers 1990) at a frequencyω≈kDLυ≈ 2π/ttr, and a wave vectorwithkDL= 2π/L(Lis the DL length,υis the particle speed, andttris the transit time of the DL by the particle). The emission process can be considered as scattering of the electrostatic electric field on fast electrons into electromagnetic radiation satisfying the resonance condition:, when the frequency of the radiated mode in the frame of the emitting electron equals the Doppler shifted frequency of the electric field of the DL (DL wave frequencyωDL≈ 0). For relativistic DLs, as are applicable to pulsar magnetospheres, the emission is expected to be beamed under an angleθ≈γ−1and the frequency of emission boosted (ω≈kDLυ(1 −υcosθ/c)−1≈γ2kDLυ).
Giant Micropulses from PSR J0437–4715
Authors: Anderson S. B. , Jenet F. A. , Kaspi V. M. , Prince T. A. , Sandhu J. S. , Unwin S. C. , Navarro José
Published: July 2016

Although individual radio pulses from pulsars vary in amplitude from pulse to pulse, their height distribution in general does not extend to amplitudes more than 10 times the mean. Two notable exceptions are the Crab pulsar and PSR B1937+21 (Lundgren 1995, Cognard et al. 1996 and references therein) which occasionally emit single radio pulses that have amplitudes more than 100 times the mean. Here we report on the detection of short time-scale, extremely large amplitude radio pulses from the nearby millisecond pulsar PSR J0437–4715. The events we have observed are distinguished by having peak flux densities in excess of 10 times the average pulse amplitude, and occur only within a very narrow (80 µs) window centered on the main pulse.
A model for PSR J0437-4715
Authors: Gil Janusz , Krawczyk Agnieszka
Published: July 2016

We present the modelling results of full polarization data of the PSR J0437-4715, recently published by Manchester & Johnston (1995). This pulsar presents a real challenge for pulsar modelling because of seven clear components in its mean profile. In terms of the conal model of pulsar emission this is the first case indicating three distinct cones surrounding the central core beam. We have attempted to model this pulsar and obtained a very satisfactory fit to the data. We succeded to reproduce the complexities of the multiple component profile and polarization properties.

To model the radiation from PSR J0437-4715 we use the method presented in Gil et al. (1995 and references therein). We assume that subpulses in single pulses correspond to the subpulse-associated plasma columns distributed within the overall pulsar beam. Each column represents a gaussian intensity distribution. These columns rotate more or less regularly around the magnetic axis. The exception is the central column directed almost along the magnetic axis defined by the local surface magnetic pole. This column corresponds to the core beam and consequently to the core component in our model. Outer columns rotating at some distances from the core axis will form a number of coaxial conal beams corresponding to the conal profile components. Figure 1a represents a projection of the subpulse-associated columns onto the polar cap while Fig. lb represents schematically a corresponding multiconal structure of the average beam. The initial positions, the characteristic dimensions and the relative amplitudes of the subpulse spots (Fig. 1a) have been estimated from the mean profile (Fig. 2b). We assume that the subpulse spots are separated from each other by distances comparable with their sizes (Fig. 1a). The very large polar cap with the radiusrp= 1.4 · 104P−1/2cm ≈ 1900 m as compared with the characteristic subpulse spot dimensionD≈ 300 m allows three conal rings surrounding the central core beam (Fig. 1b).
Properties of individual and integrated pulses drawn into mode changing phenomenon in PSR 0943+10 at 40, 103 and 430 MHz
Authors: Suleymanova S.A. , Izvekova V.A. , Rankin J.M.
Published: July 2016

Pulsar 0943+10 demonstrates very obviously that the mode switching phenomenon includes simultaneous and dramatic alterations of all principal properties of radioemission, i.e. intensity, polarization (both linear and circular) and drifting behaviour of individual pulses over a broad frequency range. On the basis of observations of PSR 0943+10 at the frequencies 40 and 430 MHz, a complete scenario of the transition process between two modes of radiation has been revealed. The ‘pre-switching transition process’ is found which manifests itself as attenuation of the pulse intensity of the current mode during hundreds of the pulse periods preceding a switch.