bluuebunny/crossref_metadata_2025 huggingface dataset:
New WET Observations of the δ Scuti Star CD-24 7599: amplitude variability and discovery of 13 pulsation modes
Authors: Handler G. , O’Donoghue D. , Buckley D. A. H. , Giovannini O. , Kepler S. O. , Provencal J. L. , Wood M. A. , Clemens J. C. , O’Brien M. S. , Kleinman S. J. , Watson T. K. , Nather R. E. , Winget D. E. , Kanaan A. , Nitta A. , Montgomery M. H. , Klumpe E. , Bradley P. A. , Sullivan D. J. , Wu K. , Leibowitz E.
Published: July 2016

The variability of CD-24 7599 (V=11.48 mag) was discovered by JCC during observing run XCOV7 of the Whole Earth Telescope (WET, Nather et al. 1990) network in February, 1992. The star was observed as an additional target and 117 hours of high-quality temporal spectroscopic observations were obtained.

Our analysis of these data revealed the presence of 7 independent pulsation modes between 27.0 and 38.1 cycles per day (313 – 441 μHz) with semiamplitudes of 2.1 – 10.2 milli-modulation amplitudes (mma). We showed that peaks at linear combination frequencies detected in the power spectra were not due to eigenmodes excited to visible amplitude by resonant mode coupling.
On the Mechanism of Mode Selection in Rapidly-Oscillating Magnetic Ap-Stars
Authors: Roxburgh I. W. , Vorontsov S. V.
Published: July 2016

We address the problem of the preferential mode excitation in magnetic Ap-stars by estimating the pulsation energy losses in the atmosphere through the generation of the Alfvenic waves.
The Cape Rapidly Oscillating Ap Star Survey
Authors: Martinez Peter
Published: July 2016

The Cape rapidly oscillating Ap star survey is a systematic search for rapidly oscillating Ap stars in the southern hemisphere. To date, 12 new roAp stars have been discovered. This paper describes the current state of the survey.
The Chemical Composition of S-Cepheids and Double-Mode Cepheids
Authors: Usenko I.A. , Kovtjukh V.V. , Andrievsky S.M. , Klochkova V.G. , Galazutdinov G.A.
Published: July 2016

The main aim of this work is to consider the evolutionary status of s-Cepheids (SC), - small-amplitude Cepheids with smooth sinusoidal light, colour and radial velocity curves. The unusual character of these objects could be explained in two ways: (1) SCs are crossing the Cepheid instability strip for the first time and they are first (or high) overtone pulsators (Efremov 1970); (2) SCs have close early-type companions, which affect gravitationally the Cepheid He II zone. Such an effect can decrease the Cepheid pulsational activity (Lloyd Evans, 1968).

According to theoretical calculations, low helium abundance in Cepheid atmospheres, which are crossing the instability strip for the first time, could produce small-amplitude oscillations. On the other hand, double-mode Cepheids (DMC) show oscillations with two (or three) periods: fundamental with large-amplitude asymmetrical light, colour and radial velocity curves, and first overtone with smooth sinusoidal small-amplitude ones. Nevertheless, detailed spectral and photometric investigations permit the detection of companions for the brightest SCs, and support the second hypothesis.
Cepheids in Binary and Multiple Systems
Authors: Szabados László
Published: July 2016

Compilation of the list of Cepheids which are members in binary and multiple systems is in progress. During this project SB-nature of a number of Cepheids was revealed. The frequency of binaries among Cepheids exceeds 60 per cent.
Type II? Cepheid Radii and TX Del
Authors: Laney C.D.
Published: July 2016

There is often some dispute in the literature as to whether a particular Cepheid (S Vul, for example) belongs to Type I or Type II. JHK photometry has been used to calculate Baade-Wesselink radii for a number of stars always, sometimes or occasionally stated to be Type II Cepheids. Radial velocities have been taken from the literature.

The (K, J – K) radius of SW Tau is 8.30 ± 0.34. This is about half of the expected radius for a Type I Cepheid at this period and normal for Type II.

For V553 Cen, the relative phasing of radial velocities and infrared photometry has to be done by choosing a relative phasing where the phase shift between the radius displacement curve integrated from the radial velocities and the photometric radius displacements is minimized, and where the surface brightness coefficient A (Balona 1977) is normal for a star with the colour indices of V553 Cen. Uncertainty in the reddening has a negligible effect on the radius solution obtained in this way. I have also considered the degree to which the K, J – K and K, V – K solutions give similar answers, as the relative phasing of the optical photometry and the radial velocities was more straightforward. The (K, J 73x2013; K) radius is 11.2 ± 0.4, normal for a Type II Cepheid.
Turbulence Variations in Cepheids
Authors: Bersier David , Burki Gilbert
Published: July 2016

From radial velocity measurements obtained with a cross-correlation technique, the variation of turbulence during the pulsation cycle is studied for a sample of 40 Cepheids. We will propose a new way to separate classical and s-Cepheids. More complete results will appear in a forthcoming paper (Bersier & Burki 1995)

The radial velocities have been measured with the spectrometer CORAVEL (Baranne et al. 1979), whose cross-correlation function (CCF) is fitted with a Gaussian, giving the radial velocity Vr, the width σobs the depth H and the continuum, normalised to 1. The pulsation broadens the lines and thus also the CCF. In the Gaussian approximation one can write

where σobs is the observed width, σinst is the instrumental width, σpuls is the additional width caused by the pulsational velocity field and σres contains all the other effects (turbulence, rotation, magnetic field, etc.). To be less affected by the noise in the data, a Fourier series has been fitted to each curve of σobs. With numerical simulations, one is able to synthesise the additional Doppler width due to pulsation, with a high accuracy. The instrumental width being well known for CORAVEL, the computation of σres is then straightforward. One then has a curve in phase for σres. From this curve, we determined the maximum residual broadening σmax (observed at or very close to minimum radius), and the width σo that the star would have if it did not pulsate. As shown by Bersier & Burki (1995), σo is slightly higher than the mean value of σres.
Iron Abundances of the Cluster RR Lyrae Variables Based on Their Light Curves
Authors: Jurcsik Johanna , Kovács Géza
Published: July 2016

[Fe/H] values of cluster RRab variables were calculated from the Fourier parameters of their light curves using a recently published method. The average cluster metallicities obtained this way agree with direct observations within the error range.
Mode Switching in Red Semiregular Variable Stars?
Authors: Gál J. , Szatmáry K.
Published: July 2016

Light curve analysis of the carbon variable RY Dra and the oxygen-rich variables TX Dra and AF Cyg is summarised. In each case, two shorter periods were found (which may be connected with the radial pulsation of the stars) and also a long term variation in the mean brightness. In the case of RY Dra, the amplitudes of the shorter periods both decreased while the amplitude of the long secondary variation was found to be increasing. The light curves and frequency spectra of TX Dra and AF Cyg can be interpreted as a result of mode switching. These stars pulsate with two different periods and there are time intervals when the longer period disappears and the shorter one remains dominant, and it lasts for many cycles. We concluded that the double and multi-periodic red semiregular variables may be very important from both theoretical and observational point of view, because, based on the ratio of the periods, we can identify the pulsational modes in these variables.
Blackbody Fits of Semiregular Variables
Authors: Kerschbaum F. , Hron J.
Published: July 2016

Semiregular variables of type SRa and SRb are studied by fitting combinations of blackbodies to new near infrared and IRAS data.
Pulsations of Long-Period Variables and their Connection to Variations of Circumstellar Maser Emission
Authors: Rudnitskij G. M.
Published: July 2016

I consider maser emission in the H2O spectral line λ = 1.35 cm from long-period variable stars. Some models for H2O maser variability are suggested.
Pulsations in the Nucleus of Planetary Nebula IC 418?
Authors: Kuczawska E. , Zola S.
Published: July 2016

IC 418 belongs to the group of about a dozen planetary nebulae with central stars that show irregular spectroscopic and photometric variations. Recent theoretical results provide arguments that this group may constitute a new class of pulsators. We present new photometric observations of the nucleus of IC 418 showing variations with a timescale of about 1/4 day. We discuss two possible explanations of the observed phenomena: pulsational instability and an unstable wind.
Decomposing Interacting Binary Light Curves: The Eclipses of the Mean Light, Secular Variability and Flickering in RW Tri
Authors: Bennie Paul J. , Hilditch R. W. , Horne Keith
Published: July 2016

We describe a new method of orbital light curve decomposition which is applicable to long-term photometry of interacting binaries. This method determines the orbital dependence (including eclipses) of the mean light, secular variability and RMS flickering. We identify the true line of centres of RW Tri and find that the accretion disc is a location of secular variability and a source of flickering.
The Place of Origin of the Flickering in Z Cha
Authors: Bruch Albert
Published: July 2016

The variability in the observable light curve of a CV can be attributed to (i) orbital and long-term variations; (ii) flickering, (iii) photon noise, (iv) scintillation (negligible) and (v) any residual noise. Calculating the rms-scatter of the count rates in a light curve as a function of orbital phase, ϕ, through accretion disk eclipse of high inclination CVs – after subtraction of a smoothed light curve to remove orbital and long-term variations, and applying a correction for photon noise – permits one to confine the place of origin of the flickering if its visibility is phase dependent or if eclipses take place (assuming any residual source of noise to be constant in time). The rms-scatter curve is then defined as the function where is the variance due to flickering and the variance due to residual noise.
The Temperatures of White Dwarfs in Dwarf Novae
Authors: Hassall B. J. M. , La Dous C.
Published: July 2016

We attempt to measure the temperature of all the quiescent dwarf novae that have been observed with IUE, by fitting the observed flux distribution of white dwarfs (WDs) with known temperatures. This approach gives results similar to those using much more sophisticated modelling, but allows us to investigate the relationship with system parameters and subclasses.
Inner Edge Drag by an Asynchronous Primary and Accretion Disc Structure in Close Binaries
Authors: Lanzafame G. , Belvedere G. , Molteni D.
Published: July 2016

In this work a 3–D ‘Smoothed Particle Hydrodynamics’ ([1]; [4]; [5]) accretion disc is simulated where particles at its inner edge are dragged by a fast spinning compact central star, as in the case of the intermediate polars. The angular velocity of the central star is twice the orbital angular velocity ωo. This drag can be attributed mainly to viscous interaction in the dense compact star atmosphere, although magnetic coupling may also play a role.

Our simulations have been performed for a system with a primary (a white dwarf) mass M1 = 1.3 M⊙, a secondary mass M2 = 2.2 M⊙, a separation between the components (centre to centre) d12 = 6.33 1011 cm and an orbital period = 1.7 d, the integration time being as long as ≃ 75 d. As in [2] and [3], we have considered quasi-polytropic structures with γ = 1.01. We adopt the term quasi-polytropic since we have in fact solved also an energy equation.
Thermal-Tidal Instability Model of Dwarf Novae Below the Period Gap: A Unification Theory
Authors: Osaki Y.
Published: July 2016

A unification theory is proposed in which almost all of outburst behavior in dwarf novae may be understood in a unified way within the basic framework of the disk instability model. In particular, a rich variety of outburst behavior of cataclysmic variables below the period gap may be understood by the thermal-tidal instability model in which the coupling of the two intrinsic instabilities in the accretion disk plays a unique role.
Model Spectra for the Helium Cataclysmic Variable: AM CVn
Authors: Bard S.
Published: July 2016

Accretion through Roche lobe overflow in the helium cataclysmic binary AM CVn is considered and its emitted spectrum is computed using model stellar atmospheres. The accretion disc in AM CVn is helium-rich and such discs have hitherto not been constructed. We have computed the models by numerically solving the radiative transfer equation for helium opacities. The method adopted is that of treating the accretion disc as a set of optically thick and geometrically thin concentric annuli. Each annulus is treated individually as a blackbody or as a stellar atmosphere. We find that our description of AM CVn is consistent with both photometric and spectroscopic measurements of the system which have been made using the Nordic Optical Telescope (NOT) and the International Ultraviolet Explorer (IUE). We find that the stellar model synthetic spectrum provides a better fit to the observed spectrum than the Planckian disc spectrum. Also, for a given accretion rate, the synthetic spectrum composed of the sum of a series of stellar atmospheres is flatter than the corresponding blackbody sum.
The Accretion Disk Model for the First Hundred Days of the Outburst Evolution in the Black Hole X-Ray Novae
Authors: Kim S.-W. , Wheeler J. C. , Mineshige S.
Published: July 2016

We present time-dependent, irradiated, accretion disk models for the black hole X-ray novae in the first hundred days of the dwarf nova-like outbursts, including the rise, precursor, maximum and the secondary re-flare. This work is based on the disk instability model (Kim, Mineshige & Wheeler 1996, Kim, Wheeler & Mineshige 1996). The model is reasonably consistent with the observed optical light curves. The irradiators are the central hot region around the black hole, and the corona or chromosphere above the accretion disk. In addition, we include the time-dependent shadowing effect and consequent blocking of the outer portions of the disk from the central irradiator. We find the stagnation phenomenon whereby the disk stays in the intermediate temperature stage between the hot and cool state. This can explain the recently discovered optical precursor rise prior to the maximum light in Nova Sco 1994 (Bailyn et al. 1995: see Fig. 1). We suggest the secondary re-flare after the maximum is due to the coupled effects of the irradiation and stagnation. In the model, the stagnation phenomenon during the rise results from the partial ionization and molecular opacity. In addition, we find irradiation-induced stagnation during the decay phase, which is consistent with the observed secondary re-flare in X-ray novae (see Fig. 1). In the overall evolution of model outbursts in the first hundred days, the outer disk is blocked from the irradiation and, in turn, the companion star may not be strongly irradiated. This suggests that there is no appreciable increase of mass transfer rate during the decay prior to the secondary re-flare, unlike the behaviour in the mass transfer burst models.
Accretion Disc Formation in Intermediate Polars
Authors: Wynn G. A. , King A. R.
Published: July 2016

The large-scale accretion flow in the intermediate polars (IPs) is still a matter of vigorous debate. It is known that the magnetic field of the white dwarf (WD) controls the accretion flow close to the surface, channeling the plasma onto the polecaps and giving rise to X-ray emission modulated at the WD spin period (Pspin). After their discovery it was assumed that IPs were the WD analogues of the pulsing X-ray binaries, where a magnetic neutron star accretes from a disrupted accretion disc. However, a number of authors have pointed out that the criteria for disc formation in IPs are less certain than those for the X-ray binaries.

The simplest possible criterion for disc formation in a binary is that the accretion flow should be able to orbit freely about the primary star (see Frank, King & Raine 1991 for a review). In non-magnetic systems this is merely the condition that the minimum approach distance of the free stream (Rmin) should exceed the radius of the primary. The situation in magnetic systems is more complex, as the magnetic field of the primary presents an obstacle to the infalling accretion stream. In many treatments of IPs it is assumed that the plasma stream is able to orbit freely about the WD until the ram pressure of the stream is of the same order as the magnetic pressureρv2~B2/8π, whereρis the stream density,vthe stream velocity andBthe local magnetic field strength. This condition fixes the magnetospheric radius,Rmag, inside which the magnetic field is assumed to thread the stream material and direct the accretion flow along the fieldlines.
Triggering the Radio Emission from AE Aqr
Authors: Steeghs D. , Kuijpers J. , Fletcher L. , Abada-Simon M. , Horne K. , Ramsay G.
Published: July 2016

We propose a model for the acceleration of particles by magnetic pumping to drive the radio emission from AE Aqr.
HST FOS Observations of YY Dra
Authors: Haswell Carole A. , Patterson Joseph
Published: July 2016

The UV continuum of YY Dra exhibits a sinusoidal modulation with 15.5% semi-amplitude and period 264.7 s, commensurate with one half the white dwarf spin period. The Civ line profile varies with spin phase, implying accretion onto, and visibility of, both magnetic poles. The line width is greatest at the phases of continuum pulsation maximum, when the wings extend out to ±3000 km s−1. This implies a minimum white dwarf mass of 0.62 M⊙, and constrains the angle between the line of sight and the magnetic axis.
Magnetic Fields and Accretion Streams in Polars
Authors: Schwope Axel D.
Published: July 2016

The flow of matter, the accretion geometry and the energy release in polars (AM Her binaries) are to a large extent dominated by the strong magnetic field of the accreting white dwarf. In this review I summarize the main tools used to investigate the magnetic fields and the accretion streams, using optical and X-ray spectroscopy and photometry.
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

Variations 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.
The Transient EUV Sky as Observed by Alexis
Authors: Roussel-Dupré Diane , Bloch Jeffery J.
Published: July 2016

Los Alamos National Laboratory’s ALEXIS satellite, containing six wide field of view EUV telescopes was launched 1993 April 25. ALEXIS is a sky monitor/survey experiment, and with each 50 s rotation, the satellite’s six telescopes (three energy bands 130, 178 and 186 Å) scan nearly half of the sky. Due to the damage sustained at launch by the satellite, the ALEXIS project team has had to spend over a year devising new methods to determine spacecraft attitude knowledge, essential for putting photons back on the sky correctly. These efforts have been successful. A recent review of the ALEXIS point source effort can be found in the Proceedings of IAU Colloquium 152, 1995. This paper reviews the transient systems that have been observed by ALEXIS which fall into two types: cataclysmic variables and unknown, short duration transients.
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].
Nova Ejecta Abundances Resulting from Multi-Cycle Evolutionary Calculations
Authors: Prialnik Dina , Kovetz Attay
Published: July 2016

The theory of nova outbursts invokes accretion of hydrogen-rich material by a white dwarf (WD) in a close binary system, due to Roche lobe overflow of a red dwarf companion, leading to periodic outbursts — powered by thermonuclear runaways — that result in mass ejection. Observed characteristics of novae are reproduced by varying the values of three basic and independent parameters: the accreting white dwarf’s mass, its core temperature, and the mass transfer rate. In a recent study (Prialnik & Kovetz 1995) we have carried out a systematic investigation of nova outbursts on WD progenitors composed of C and O in equal mass fractions, concluding that the entire range of observed nova characteristics could be accounted for. A subset of 34 out of 64 evolutionary sequences (obtained with different parameter combinations) reproduced classical novae, and here we focus on the break-up of the heavy element abundances in the ejecta of these models, in comparison with observations, based on a recent analysis of observed nova abundances by Livio & Truran (1994).
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

We 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

We 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

In 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

We 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

Three 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

We 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.
A Core-Envelope Decoupling Dynamo Model for Cataclysmic Variables
Authors: Zangrilli L. , Tout C. A. , Bianchini A.
Published: July 2016

The progenitors of cataclysmic variables (CVs) undergo a common envelope phase, during which their initial orbital period is reduced to a few hours. After this phase the radiative core of the secondary might rotate at a lower rate than the tidally coupled envelope. A shear is then generated at the core-envelope interface which can give rise to a boundary layer dynamo and, consequently, to the magnetic braking of the binary system. The temporal variation of the shear energy content can be obtained by comparing the rate of magnetic energy production with the input rate of orbital energy in the convective envelope. We assume for the flux tubes a filling factor, fV, owing to the expected size of the tubes and the fact that the dynamo action may be concentrated inside an equatorial belt of the boundary layer shell. We also assume that the production of toroidal field is efficient only inside the boundary layer, while the poloidal component of the field can be enhanced also across the outer convective envelope (see also Zangrilli & Bianchini 1995). We find that the decrease in the shear energy, caused by the continuous production of magnetic field and by the progressive reduction of the core moment of inertia, leads the core coupling with the envelope, thus switching off the dynamo at the core-envelope boundary. Further details of this core-envelope decoupling dynamo model will be given in a forthcoming paper (Zangrilli, Tout & Bianchini 1996).
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

We 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

Recent 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.
Reverberation Mapping and Broad-Line Region Models
Authors: Maoz D.
Published: July 2016

I review what we have learned about the BLR from reverberation mapping, point to some problems and complications that have emerged, and outline some future directions.
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

A 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.
Line-Profile Variations in AGN
Authors: Kollatschny W. , Dietrich M.
Published: July 2016

Line-profile variations in the Seyfert galaxies NGC 5548 and NGC 4593 are discussed. The variations of individual line segments are different from line to line and from outburst to outburst.
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

By 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

For 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

This 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

Recent 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

The 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.
Tri-dimensional Spectroscopy of the Seyfert Galaxy NGC 1275: Kinematics and Excitation of the Cooling-Flow Gas
Authors: Yoshida M. , Kosugi G. , Aoki K.
Published: July 2016

NGC 1275, the Perseus cluster cD galaxy, is a well-known Seyfert 1 galaxy and also one of the strongest extragalactic radio sources (3C84). Although many studies have been done on the extended optical emission-line region of NGC 1275, which is thought to be associated with the X-ray cooling-flow phenomenon (e.g., Heckman et al. 1989, Ferruit and Pecontal 1994), the excitation mechanism of the emission-line gas and two-dimensional gas kinematics are still unclear. We made tri-dimensional spectroscopy of NGC 1275 in order to reveal two-dimensional kinematics and- the relation between the gas motion and the excitation of the emission lines.
High-Velocity Outflow in the Extended Emission-Line Region of the Seyfert Galaxy NGC 7319
Authors: Aoki Kentaro
Published: July 2016

NGC 7319 is a member of the compact group of galaxies known as Stephan’s Quintet. The systemic velocity 6740 km s−1 gives a distance of 90Mpc (H0= 75 kms−1 Mpc−1) for NGC 7319. This galaxy has a tail and/or ring which suggests interaction with a neighboring pair of galaxies, NGC 7318A and B (e.g., Arp 1973). Durret & Warrin (1990) and Durret (1994) performed optical long-slit spectroscopy and found an extended emission-line region (EELR) in NGC 7319. They detected highly excited gas over along PA = 61° and 10″ along PA – 151°. Apart from these works, there have not been any studies on the velocity field and excitation of the gas in the EELR of NGC 7319. More details were published by Aoki et al. (1996).
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.
Masers in Active Galactic Nuclei
Authors: Greenhill L.J.
Published: July 2016

Studies of OH and H2O masers contribute to our understanding of the dynamics and physical conditions in the innermost few parsecs of AGN. Angular and velocity resolutions that may be routinely achieved with radio interferometry are substantially better than those possible with traditional observational techniques in the optical and ultraviolet.
A Study of the Spectrum of the OH Megamaser in III Zw 35
Authors: Yu Zhi-yao
Published: July 2016

III Zw 35 is an OH megamaser galaxy which is of great interest. In this paper, the spectrum has been fitted and the position map has been studied. A new model of multiple and distinct rotating and expanding rings in a thin disk is proposed in this paper.
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

The 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

A 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.