bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Stellar Flares and Their Characteristics
Authors: Pettersen B. R.
Published: July 2016

We review the flaring activity of stars across the HR-diagram. Brightenings have been reported along the entire Main Sequence and in many stars off the Main Sequence. Some stars are decidedly young, others are in advanced stages of stellar evolution. Flares are common on stars with outer convection zones and outbursts have been reported also on other types of stars, although confirmations are needed for some of them.

Analyses of flare occurrence sometimes find flares to be randomly distributed in time, and sometimes indicate a tendency for flares to come in groups. Preferred active longitudes have been suggested. Recent solar results, where the occurrence rate for flares is found to exhibit a periodicity of 152 days, suggest that stellar flare data should be reanalyzed over long time baselines to see if the present confusing situation can be resolved.

The radiation from stellar flares is dominated by continuum emission and about equal amounts of energy have been recorded in the optical, UV, and X-ray regions of the spectrum. In solar flares strong continuum emission is rarely recorded and a large collection of bright emission lines takes prominence. Small flares occur more frequently than large ones and the latter have longer time-scales. Flare energies can exceed 1037 erg. The most productive flare stars are those where the convective envelopes occupy large volumes. Slow stellar rotation rates are believed to reduce the level when the star has been braked significantly from its young rotation rate.
A Digital Computer as Process Controller of a 2.2 m Ritchey-Chrétien Telescope
Authors: Bahner K. , Solf J.
Published: July 2016

In 1969 a new astronomical institution was founded in the Federal Republicof Germany. This “Max-Planck-Institut für Astronomie” will consist of a central institute at Heidelberg and two observatories, one in the South-East of Spain and one in the Southern hemisphere (possibly in South-West Africa). Each observatory will be equipped with a 2.2-metre Ritchey-Chrétien telescope; these instruments are now under construction at Carl Zeiss, Oberkochen, Western Germany. In addition, a 3.5-metre telescope will be built. A smaller Ritchey-Chrétien telescope of 1.2 m will go into operation next year in Spain. The mirror disks of the 3.5-metre and 2.2-metre telescopes have been ordered from Schott & Gen. at Mainz; they are made of glass ceramic “Zerodur”, a zero-expansion material similar to CerVit. In the operation of the 2.2-metre telescopes and their peripherals, small, general purpose digital computers will be employed.
Some Applications of Small Computers to Optical Spectroscopy
Authors: Robinson Lloyd B.
Published: July 2016

At Lick Observatory we have begun to use small computers as a basic element of some electronic instrumentation systems. It is felt that computer technology has advanced to the point where the results are likely to repay the investment. In our approach and choice of machine, we have tried to benefit by the experience gained over the past several years by nuclear physicists in nuclear spectroscopy applications.

The major factor involved in choosing a small computer is probably one of economics. The initial cost is important, but, equally important, the costs of maintenance, programming, and the connection of peripheral equipment must be considered. A computer is sufficiently complex to require at least one person in an organization to spend considerable time familiarizing himself with the details of the machine. These extra costs, required to realize the potential of any computer system, are likely to exceed the initial purchase price of the system! It is important to take such factors into account when choosing a machine.
Period and Period Changes of RR Lyrae Variables in M15
Authors: Wesselink A. J.
Published: July 2016

New observations of the variables in M15 have been made with the Yale 40-in. reflector for the study of periods and period changes.

Since the counting of cycles from the time of Bailey’s observations to the present day cannot always be made unambiguously, there is a corresponding uncertainty in the nature and amount of the period changes. Good lightcurves are obtained even when the periods used for their reduction are incorrect because the number of cycles in a day, or in a month, or in a year, is wrong by one. When this happens, however, period changes are likely to be indicated, and these will be spurious.

Nevertheless, it can be shown that the periods of most variables have not been constant during the interval 1900–1970.

The situation could be improved if a relatively small number of plates were to be obtained each year for several decades, preferably with the same instrument. Individual accuracy could be improved by the use of the electronic camera.

The full contents of this paper will be published elsewhere.
The program of observation of minor planets and comets at the Bucharest Observatory
Authors: Cristescu Cornelia
Published: July 2016

The observation of minor planets and comets began at the Bucharest Observatory in 1930, using the refracting telescope Merz—Prin (D = 38 cm, F = 600 cm). The observations were interrupted during the Second World War, and only in 1951 the department of photographic astrometry, much more developed, resumed the work.

The program was devoted to the observation of comets and minor planets, the maximum magnitude obtained being 12 for minor planets and 9 for comets. Beginning from 1954 the Bucharest Observatory participates in the observation of the 10 minor planets, selected for the Catalogue of Faint Stars, and up to the end of 1970 about 4000 precise positions were obtained. At the request of the Institute of Theoretical Astronomy from Leningrad, these observations are continued. Besides these, about 1000 precise positions for other minor planets were obtained in the interval 1951—1963.
Optical Flares: Observations and Interpretations
Authors: Mirzoyan L.V.
Published: July 2016

Observational results on flare stars in the Galaxy and their interpretation, based on the observational approach to early stages of stellar evolution at Byurakan, are considered. The evolutionary path of red flare stars is determined. Stellar flare activity is explained as an internal phenomenon of stars. The significance of photographic observations of stellar flares in star clusters and associations is emphasized.
Short-Time Flare Events of EV Lac
Authors: Zhilyaev B.E. , Verlyuk I.A.
Published: July 2016

Moffett (1972) pointed out the existence of short-time outbursts in flare stars as long ago as 1972. Gershberg & Petrov (1986) had registered a flare in EV Lac with a duration of 28.4 and an amplitude of 38.4 in 1984 with ASTRON. In recent years, a few reports appeared about observations of short-time outbursts in EV Lac with a duration in the range from 08.1 to several seconds. These results were summarized briefly by Zhilyaev (1993). Our observations confirm the existence of short-time flare activity on EV Lac.

The observations reported here were obtained at the 60 cm telescope at the Peak Terskol high-altitude Observatory (3 100 m above sea level) with a highspeed two-channel photometer (Zhilyaev et al. 1992) in B as well as simultaneously in both, U and V bands, with a time resolution down to 08.1. A new prefiltering technique (Zhilyaev 1995) has been used for the detection of smallscale activity of the flare star EV Lac.
Flare Activity in Algol-type Binaries
Authors: Pustylnik Izold
Published: July 2016

Two sites of flare activity have been identified in Algol-type binaiies. One is associated with the shock region from the accretion on B-A type primary, another, predominant one is apparently connected with coronal mass ejections (CME) from the late-type, Roche lobe filling secondary. The relative contribution from both sources of activity is still to be found. According to Peters & Polidan (1984), a moderately hot (105 K) and low density ne ≃ 109 cm−3 high turbulent accretion region (HTAR) surrounding the hot component has been discovered. Typical dimensions of HTAR agree with the scale height of the X-ray source HX ≃ 1.2 · 1011 · T7 cm (Harnden et al 1977), where T7 is the temperature in units of 107 K. But the decay time of the HTAR, comparable to the orbital period, more favourably agrees with the idea of CME as deduced from Ginga observations of X-ray flares on Algol (Stern et al. 1992). One solution of the controversy as to the contribution from HTAR would be to concentrate on X-ray observations of systems like u Her and U CrB, where the secondary is possibly earlier than FO (thus, is not expected to possess an extensive convection zone) and on the other hand on systems like U Cep, where during periods of high activity Ṁ ≃ 10−6M⊙ per year. Thus, the accretion luminosity must be at least by two orders of magnitude higher than in Algol. At present the analysis of X-ray flares is based upon the solar type CME assuming different scenarios of radiative and/or conductive cooling (see Stern et al. 1992). However, the current models of CME do not take into account the binary nature of the flaring object.
The Odessa Sky Patrol Plate Collection
Authors: Karetnikov V.G. , Markina A.K. , Sotnikov V.P.
Published: July 2016

The Odessa Astronomical Observatory has three collections of Sky Patrol negatives, which have been exposed since the beginning of the 20th century. Altogether, there are about 100,000 negatives of the stellar sky, covering a declination range from −15 to +90°. The limiting stellar magnitudes are 15 (photographic - pg) and 12 (photovisual - pv), respectively.
Flares And Flashes: The Future
Authors: Vanderspek R. , Duerbeck H.W. , Fishman G.J. , Greiner J. , Hudec R. , Merck M. , Poveda A. , Samus N.N. , Seitter W.C. , Vanderspek R. , van Paradijs J. , Zinnecker H.
Published: July 2016

The goal of this round-table discussion is to bring up issues which may be of mutual interest to those working on specific flare and variable stars and those performing wide-field searches for, among other things, counterparts to gamma-ray bursts (GRBs). Admittedly, however, trying to unify the interests of the flare people and the GRB people will be an interesting task. Many of the presentations this week have been devoted to future instrumentation and future modes of observations, but there have been also interesting discussions of specific questions regarding flare stars, variable stars and GRBs. Certainly, wide-field observations of the night sky will continue for the foreseeable future: there are a lot of instruments running now, and there are many instruments being planned. Most of these observations cover many square degrees of sky for long periods with a reasonable magnitude limit. How could these observations could be modified or improved to also allow useful data on on variable stars or flare stars to be taken? What sort of information, statistics, periodicities could be gleaned from wide-field searches that will be happening in the future and searches that are going on today? Are there methods in common use by one group of observers that may be useful to the other?

The speakers in this session have volunteered to give a short presentation on issues which may benefit from discussion within this group.
Results from the Second EUVE Source Catalog
Authors: Lampton M. , Bowyer S. , Lewis J. , Wu X. , Jelinsky P. , Lieu R. , Malina R.F.
Published: July 2016

We present the results of the Second EUVE Source Catalog, including all detections from the EUVE all-sky survey, the EUVE deep survey, and sources detected during dedicated instrument pointings. Where available, we furnish identifications of these objects and statistics with regard to type of stellar or extragalactic object.
The FIP Effect and Abundance Anomalies in Late-Type Stellar Coronae
Authors: Drake J.J. , Laming J.M. , Widing K.G.
Published: July 2016

“Yes, it will be a long time before people know what I know. How much of iron and other metal there is in the sun and the stars is easy to find out, but anything which exposes our swinishness is difficult, terribly difficult” (Tolstoy 1889).

In the solar corona, the abundances of elements appear to differ from the photospheric values in a manner related to the element first ionization potential (FIP): species with FIP ≤ 10 eV are observed to be enhanced relative to the photosphere by factors of ~3−4. The first studies of stellar coronal composition with EUVE suggest that some stars exhibit a solar-like FIP effect, whereas others do not. We briefly review the latest results, and we argue that element abundance anomalies, such as the FIP effect, can provide potentially powerful new coronal diagnostics. Moreover, knowledge of the composition of a stellar corona is crucial for interpreting its spectrum—for understanding its structure and energy balance, and for testing its possible heating mechanisms: We must begin to understand coronal abundance anomalies and the compositions of active stars in order to begin to understand their coronal physics.
EUV/Soft X-ray Emission from Classical Novae
Authors: MacDonald James
Published: July 2016

Multiwavelength observations have shown that, after optical decline, the stellar remnants of classical nova outbursts evolve at constant, near-Eddington, bolometric luminosity to high effective temperature (> 2 105 K), before turning off. Here we briefly review the observations of classical novae in this phase of evolution and show that, in principle, EUV and soft X-ray observations can be used to determine the mass of the underlying white dwarf and place limits on the rate of mass loss by stellar winds and the rate of mass gain due to accretion from the stellar companion. We also describe our model atmosphere calculations of EUV/Soft X-ray emission from hot, high gravity stars and their application to the EUVE all-sky survey detection of Nova Cygni 1992 (V1974 Cyg).
Novae and Helium Novae As Bright EUV Sources
Authors: Kato Mariko
Published: July 2016

I present theoretical light curves of novae and helium novae in EUV and visible bands derived from optically thick wind theory. The EUV light curves are very useful in determining the white dwarf mass and the distance to the star. Helium novae are bright EUV sources but much less luminous in the optical. Identification of helium novae will be observational evidence for the growth of the white dwarf, which will eventually become a Type la supernova. A semi-detached system may be a new progenitor model of Type la supernovae, which is a very bright EUV source with a faint optical counterpart.
TheEUVEOptical Identification Campaign II: Late-Type and White Dwarf Stars
Authors: Craig N. , Fruscione A. , Dupuis J. , Mathioudakis M. , Drake J.J. , Abbott M. , Christian C. , Green R. , Boroson T. , Howell S.B.
Published: July 2016

We present optical identifications of nine previously unidentified extreme ultraviolet (EUV) sources discovered during theExtreme Ultraviolet Explorer(EUVE) satellite surveys. The all-sky survey detected four of the sources and the more sensitive deep survey detected the other five sources. Three of the four all-sky survey sources, EUVE_J1918+59.9, EUVE_J2249+58.5, and EUVE_J2329+41.4, are listed in present catalogs as having possible associations with optical counterparts but without spectral class. The first two of these sources are hot DA white dwarfs showing an optical spectrum with broad Balmer lines. The source EUVE_J2329+41.4 is listed as having a possible association with an unclassified M star. We show that a pair of dMe stars are actually optical counterparts located within the error circle of theEUVEsource position. The EUVE_J2114+503 remains unidentified even though all the possible candidates have been studied. Based on the count rates we predict a fainter white dwarf or a cataclysmic variable counterpart for this candidate. All five sources discovered with theEUVEdeep survey, EUVE_J0318+184, EUVE_J0419+217, EUVE_J2053−175, EUVE_J2056−171 and EUVE_J2233−096, have been identified as late-type stars. The spectral classes, distances, visual magnitudes, and estimated hydrogen column densities for theseEUVEsources are presented.
The Sun in Time: Evolution of Coronae of Solar-Type Stars
Authors: Güdel Manuel , Guinan Edward F.
Published: July 2016

We report on the results of a multi-frequency program to study coronal X-ray, EUV, and microwave activity of solar-type (G0-5 V) stars of greatly different ages. These stars are of interest as proxies for the Sun for ages from 50 Myr to 10 Gyr. Coronal temperatures decrease with X-ray/EUV luminosity and with increasing age and rotation period according to power-law relations. The young Sun had an extremely luminous corona with LEUV,X = 100 − 600LEUV,X (present Sun) and temperatures up to 10 MK; this information is pivotal for the study of the young planetary atmospheres. The findings further suggest an intimate connection between the presence of very hot coronal plasma and non-thermal radio-emitting particles.
Population II Stellar Structure and Evolution: A Few Selected Topics
Authors: Chiosi Cesare
Published: July 2016

In this review we discuss in some detail the evolution of low mass stars, and other related topics, limiting ourselves to the class of stars with solar and super-solar metal content that likely constitute the basic component of elliptical galaxies and bulges. In particular, we deal with the stars responsible of the UV flux observed in elliptical galaxies and the role played by the chemical composition and mass loss by stellar wind in producing hot progenies with effective temperatures in the range indicated by the UV data. In this context, we briefly report on recent chemo - spectro - photometric models for elliptical galaxies. In addition to this, we discuss the subject of galaxy ages by means of the ultraviolet properties and narrow band indices. Finally, we briefly report on a new formulation of diffusive mixing in stellar interiors and its effects on the structure and evolution of intermediate- and high-mass stars.
Precision Asteroseismology of DAV (ZZ Ceti) White Dwarf Stars
Authors: Bradley Paul A.
Published: July 2016

Recently, Clemens suggested that the similarity in period structure of the hotter DAV (ZZ Ceti) stars could be explained if they pulsated in a common set of modes. Here, I use theoretical pulsation periods from a new grid of evolutionary DA white dwarf models to determine the internal structure of G 117–B15A and R 548. Both stars have hydrogen layer masses of × 1.5 × 10−4M* and oxygen-rich cores with a composition gradient starting near 0.75M*.
Analysis of the Asteroseismological Data of Six δ Scuti Stars in the Open Cluster NGC 6134
Authors: Audard Nathalie , Kjeldsen Hans , Frandsen Søren
Published: July 2016

Six δ Scuti stars have been detected in the open cluster NGC 6134 (Frandsen et al. 1995). A first mode identification attempt shows that several radial modes of radial order n = 0, 1, 2 or 3 might have been observed. We may also be dealing with g-modes and/or modes split by rotation.
Baade-Wesselink Analysis of a Sample of Equal Period SMC Cepheids A progress report
Authors: Storm Jesper , Carney Bruce W. , Freedman Wendy , Madore Barry F.
Published: July 2016

We present a progress report on a project to investigate the differences in absolute physical parameters for a sample of five equal period SMC Cepheids from a Baade-Wesselink analysis of the stars.
The Distribution of the RR Lyrae Variables in ω Centauri and Background Light
Authors: Petersen J. O. , Andersen M.
Published: July 2016

The distribution of the RR Lyrae stars in the globular cluster ω Centauri is studied, using the data published by Martin in 1938. Comparing the accumulated numbers of variables within the angular distance, r, from the centre of the cluster, it is shown that the known RRc variables seem to be less concentrated towards the centre than the RRab stars. 6-10 RRc stars are missing within r = 2–3 arcmin, if the two distributions are actually identical, as expected from evolution models. We conclude that the central region may contain several RRc stars that have not yet been discovered. This could be due to their relatively low amplitude, since it is very difficult to find low-amplitude variables by means of photographic photometry in the crowded, central region of ω Cen with large and varying corrections due to unresolved background light.
The Temperature of the Supergiant α Per
Authors: Evans Nancy Remage , Teays Terry J. , Taylor Lyla L. , Lester John B. , Hindsley Robert B.
Published: July 2016

We compare observed fluxes from the ultraviolet (IUE) through J and K with recent Kurucz model atmospheres to determine a temperature for the F5 lb supergiant α Per. The two most important advances in this study as compared with previous work are the use of well calibrated ultraviolet fluxes and the use of models with an appropriate microturbulence.
The Mass Loss and Pulsation Activity in Supernova Progenitors
Authors: Tsiopa O. A.
Published: July 2016

The wind-formed regular structures revealed in early supernova (SN) spectra can be a result of the radial pulsation of the precursor.
Infrared Radial Velocity Results for Long Period Variables
Authors: Hinkle Kenneth H.
Published: July 2016

High-resolution time-series infrared spectra have been observed for a total of 20 Long Period Variables. The stars can be placed in four groups with distinct kinematic behaviour.
Studies of Small-Amplitude Red Variables
Authors: Percy John R. , Au Winnie , Desjardins Adrien , Yu Lawrence ,   AAVSO Photoelectric Photometry Program
Published: July 2016

We describe a survey of suspected small-amplitude red variables, and long-term (up to 10 years) monitoring of about two dozen such variables.
A New, Systematic Search at 1612 MHz for OH/IR Stars in the Inner Galaxy
Authors: Sevenster M.N. , Habing H.J. , Chapman J.M. , Killeen N.E.B.
Published: July 2016

We have surveyed the inner part of the Galaxy for OH 1612 MHz maser emission from OH/IR stars. The full survey is expected to give around 2000 detections. Here we report initial results for the Bulge region between |l| < 10° and |b| < 3°.

The observations discussed here were taken with the Australia Telescope Compact Array in Oct-Nov 1993. For each field we used a total integration time of 8 min. spread over an hour-angle range of 12 hours in intervals of an hour. Interference in the 1612 MHz band is a major concern in this program - it is ubiquitous for the shorter baselines. Another concern is the beam-pattern resulting from taking short cuts spread over 12 hours, with a one dimensional array. This causes sidelobe patterns which can easily lead to spurious detections. In addition to these problems, the size of the data set calls for special reduction techniques. We have developed a non-interactive method that is not I/O intensive and is well suited for use on supercomputers. To identify the OH/IR stars, all fields are ‘skimmed’ at successively weaker levels, subtracting point sources at the positions of the highest peaks in the fields, until we reach the (known) 3 σ level. Our method reduces the data reduction time by a factor of eight whilst giving comparable results to conventional cleaning methods. The disk space required is reduced by a factor of 100.
On the Formation of Hydrogen Emission Lines in Miras
Authors: de Laverny Patrick , Magnan Christian
Published: July 2016

We investigate non-LTE effects in the hydrogen recombination zone of Long-Period Variables of Mira type. We propose that the Balmer hydrogen emission lines could be formed in this deep layer. We show how the spectral cyclic variations of Miras could be mimicked with this interpretation. As a result the radius of a Mira in the Balmer transitions could be much smaller than its radius in the molecular absorptions, which are formed in higher layers.
A Nonlinear Pulsation Model for V652 Her
Authors: Fadeyev Yu. A. , Lynas-Gray A. E.
Published: July 2016

When compared with observation, stellar pulsation model predictions provide a test of stellar envelope opacities. Of specific interest, is the radially pulsating extreme helium star V652 Her for which luminosity and radial velocity observations are published. Nonlinear pulsation models of V652 Her, calculated using Opacity Project (OP) opacities, predict luminosity and radial velocity variations in close agreement with observation.
The Pulsating White Dwarf L19-2
Authors: Sullivan Denis J.
Published: July 2016

Previous studies of the southern DAV white dwarf L19-2 have revealed that it pulsates non-radially in at least five modes with periods ~ 102 s and amplitudes less than 10 mmag. All of these modes showed fine structure splitting, but the one-day aliases resulting from the gaps in the single-site data made identification of the various frequencies, at best, difficult. Recent observations of L19-2 obtained from Mt. John (NZ) are presented, along with a discussion of the prospects for a Whole Earth Telescope run on this object scheduled for 1995.
Visibility Functions of Solar and Stellar Irradiance Variations
Authors: Staude Jürgen , Bartling Günter , Zhugzhda Yuzef D. , Dzhalilov Namig S.
Published: July 2016

We calculated visibility functions of intensity fluctuations due to adiabatic waves in a realistic model of a non-grey, stratified atmosphere in LTE. The results for different optical wavelengths λ and their angular dependence are discussed; moreover, a method for selecting various low-degree p-modes from observations of spectral irradiance fluctuations at different λ including the UV is suggested.
The Nova-Likes AC Cnc, RW Tri, UX UMa and the Nova DQ Her: Common and Different Properties
Authors: Dmitrienko E. S.
Published: July 2016

An analysis of the main photometric properties of the nova-like variables AC Cnc, RW Tri and UX UMa, and Nova Her 1934 (DQ Her) is presented. The analysis is based on simultaneous high-speed UBVRI photometry, covering several dozens of orbital cycles evenly distributed over 14 years (1982 ... 1995) for DQ Her, and over 11 years (1985 ... 1995) for the other three stars. All data have been obtained with the 1.25 m telescope at the Crimean Astrophysical Observatory.
Roche Tomography of the Cool Star in IP Peg
Authors: Rutten R. G. M. , Dhillon V. S.
Published: July 2016

We analyse orbitally-resolved spectra of the Na I doublet in the dwarf nova IP Peg, using the newly developed technique of Roche tomography. We show that Roche tomography can be successfully employed to image the secondary stars in CVs, and that it also serves as an independent aid for determining binary system parameters. Our preliminary results suggest that the mass of the white-dwarf primary is 1.2 M⊙, significantly higher than previous estimates.
TT ARI–94: A Study of 1.6…60 Minute Variability
Authors: Andronov I. L. , Arai K. , Chinarova L. L. , Dorokhov N. I. , Dorokhov T. A. , Dumitrescu A. , Nogami D. , Lepardo A. , Mason P. A. , Matumoto K. , Oprescu G. , Pajdosz G. , Passuelo R. , Patkos L. , Sostero G. , Tremko J. , Zola S.
Published: July 2016

We report photometric results from 44 runs at 11 observatories during the international campaign ‘TT Ari–94’. No coherent oscillations in the frequency range 10… 900 cycle d−1 are found. The highest peaks in the power spectrum cover the wide range of 28… 139 cycle d−1. Variations occur at a few preferred time-scales rather than at one cycle length, with a possible secular decrease. In the frequency range 90… 900 cycle d−1 the power spectrum obeys a power law with slope γ ranging from 0.8 to 2.6 for different runs.

TT Ari is one of the brightest cataclysmic variables and remains one of the most interesting objects of this class. It exhibits a variety of phenomena observed at time-scales from seconds to months. A recent detailed photometric study of this object and a bibliographical overview may be found in Tremko et al. (1996). Tremko et al. (1992, 1993, 1994) discuss aspects of the TT Ari–88 campaign. Our campaign TT Ari–94 was unprecedented, as the observations were longitude-dispersed, from Japan through Turkmenia, to Europe and the American continent. Moreover, our optical data on October 7 partially overlap with the HST observations obtained by Home & Welsh (1995, private communication). The numerical results of observations obtained during these nights are shown in Table 1.
Outburst Activity Data on Selected Cataclysmic Variables
Authors: Vanmunster T. , Howell S. B
Published: July 2016

We have created a database with outburst activity for 269 selected cataclysmic variables. It includes nearly 1000 outburst measurements discovered through 1995 June. The database and a complete paper describing the observations and the sources of information that were consulted are accessible over the Internet.
Results of Optical Monitoring of the Dwarf Nova SS Cyg During the 1993 Campaign of co-ordinated Observations with the Asca Satellite
Authors: Voloshina Irina
Published: July 2016

SS Cyg is the brightest known and therefore best studied classical dwarf nova and it was the first one from which X-ray radiation was discovered. SS Cyg is unique because it has been detected at very wide range of energies, from a few eV up to ~ 10 keV (Jones & Watson 1992). It was chosen as the first cataclysmic variable for X-ray observations with the Japanese satellite ASCA. Simultaneous optical photometric and spectroscopic observations were also provided for completeness of the study.
Observation of the WZ Sge-Type Dwarf Nova AL Com
Authors: Kato T. , Nogami D. , Baba H. , Matsumoto K. , Arimoto J. , Tanabe K. , Ishikawa K.
Published: July 2016

Although presently classified as a SU UMa-type dwarf nova, WZ Sge is well known as one of the most peculiar objects in that it shows only superoutbursts with exceptional duration and amplitude, and no normal outbursts. Furthermore, on its decline from the 1978 outburst, WZ Sge showed a deep temporal dip. All of these characteristics have puzzled both theoreticians and observers.

The dwarf nova AL Com was photometrically observed during the outburst in 1995 April, which occurred for the first time since 1975. The striking similarity of AL Com to WZ Sge, as demonstrated by the present observation (Fig. 1), provides plenty of material in interpreting the enigmatic nature of WZ Sge-type dwarf novae.
Non Circular Disks in am CVn Systems?
Authors: Solheim J.-E.
Published: July 2016

The AM CVn stars are mass transferring, interacting binary, white dwarf systems with orbital periods of 15…45 minutes. Hydrogen is completely lost from these systems, and we observe small helium disks which may show thermal and tidal instabilities if the mass transfer rate is large enough (Osaki 1995). A tidal instability brings the disk into a superoutburst state, and in the light curve we may observe superhumps. Based on the observed periods and mass transfer rates we can divide the AM CVn stars into three groups:

A: In permanent superoutburst: AM CVn and EC 15330-1403

B: Regular superoutbursts: CR Boo, V803 Cen and CP Eri

C: Not yet observed superoutburst: GP Com

Group A consists of systems with disks which are too hot to decline into a low state. These disks are in a constant superoutburst state, analogous to nova-like CVs which show no outbursts, but still exhibit permanent superhumps (Skillman & Patterson 1993). Group B shows normal outbursts which can trigger superoutbursts, analogous to the VY Scl dwarf novae. The group C object may also be a superhumper, but with very infrequent outbursts analogous to the SU UMa stars (Warner 1995). In the following we will discuss evidence for superoutbursts in these systems, and the likelihood for these systems to develop elliptical disks.
The 71-Second Oscillation of DQ Her at 2180 Å
Authors: Robinson E. L. , Zhang E. , Bless R. C. , Dolan J. F. , Elliot J. L. , van Citters G. W.
Published: July 2016

The 71-s modulation in the light curve of the old nova DQ Her has a mean semi-amplitude of 1.8% at 2180 Å, although the amplitude varies by at least a factor of two from orbit to orbit. The disturbance in the amplitude and phase of the modulation during eclipses is similar to that observed at visual wavelengths. We conclude that at 2180 Å, as at visual wavelengths, the modulated flux is reprocessed and comes from the accretion disk.
On the Long-Term Light Curve Behaviour of the Intermediate Polar TX Col
Authors: Buckley D. A. H.
Published: July 2016

TX Col (1H0547–407; Porb = 5.72 h) is an intermediate polar (IP) with spin and synodic (beat) periods of 1911s and 2106 s respectively (Buckley & Tuohy 1989). EXOSAT observations (Tuohy et al. 1986) showed the beat period dominated at higher energies (ME; 1… 9keV), while the spin period was stronger in softer X-rays (LE1; 0.1… IkeV). The high flux level, and pulse fraction (>70%), of the soft X-rays were unique in an IP at that time. Now three other IPs, recently discovered from the ROSAT survey, have been found to show a true separate soft X-ray component, similar to the polars (Motch & Haberl 1994).

The strength of the synodic X-ray period in TX Col was, until the recent discovery of the variable polarised IP, RX J1712.6–2414 (Buckley et al. 1995), unique. This was taken as evidence for direct accretion onto the magnetosphere (e.g. Mason, Rosen & Hellier 1988), through a component of the accretion stream overflowing the disc (Hellier 1992).
X-ray and optical observations of BY Cam
Authors: Ramsay Gavin , Mason Paul A.
Published: July 2016

We present preliminary results of an analysis of X-ray and optical data of the asynchronous AM Her star BY Cam [1]. We use X-ray data from EXOSAT (0.1… 50 keV), Ginga (1.5… 50 keV) and ROSAT (0.1…2.0 keV) and optical data obtained during a 45-day campaign in 1994.

There are 4 known periods: the orbital period (201.30 m), the spin period of the white dwarf (199.3303 m), a spin-orbit beat period (14.15 d) and a side-band period (197.4 m). The detection of this side-band period lends credence to the theory of [2], who suggest that for a stream accreting, diskless, magnetic CV a frequency, f = 2ωspin − Ωorb (=197.399 m), will appear as a strong spike in the power spectrum for certain systems. Wu & Mason (this volume) discuss a competing model where Pspin = 197.4 m.
Observations of Novae in M51, M87, and M101: A Preliminary Report
Authors: Shafter A. W. , Ciardullo R. , Pritchet C. J.
Published: July 2016

We report preliminary results from a new program of observations of novae in nearby galaxies. The principal goal of the program is to explore the population of nova progenitors through observations of galaxies having a wide range of Hubble types. Here we present preliminary results from observations of the spiral systems M51 and M101, and the giant elliptical, M87. Based on available data, we find no evidence that the luminosity specific nova rate varies across the Hubble sequence.
The Gamma-Ray Spectrum of Classical Novae
Authors: Hernanz M. , José J. , Gómez J.
Published: July 2016

We report on preliminary hydrodynamic simulations of thermonuclear runaways in the hydrogen-rich envelopes of accreting white dwarfs, leading to nova outbursts. A one-dimensional, Lagrangian, implicit, hydrodynamic code (Kutter & Sparks 1972) has been used to reproduce the gross features of a classical nova, from the onset of accretion, through the progress of the outburst up to the expansion stage, where significant mass loss takes place. Special interest is focused on the synthesis of 22Na and 26Al, for their interest in γ-ray line astrophysics. The γ-ray spectrum is built by means of a Monte Carlo simulation.
A Unified Model for the Radio and Optical Images and Spectra of Nova V1974 Cyg 1992
Authors: Hjellming R. M.
Published: July 2016

A model for nova shells which is a combination of wind model and spherically symmetric, Hubble flow shell model, fits the light curve, image, and nebular line shape data for Nova V1974 Cyg 1992. The results show that after outburst the shell is ejected by a wind-like outflow with a linear velocity gradient, and that after 180 d this outflow stops. The shape of the elliptical inner boundary at this time determines the subsequent emission measure structure seen in images, light curves, and nebular line profiles.
Nova Outbursts and the Secular Evolution of Cataclysmic Variables
Authors: Schenker K. , Kolb U. , Ritter H.
Published: July 2016

We present calculations of the long-term evolution of CVs which include the influence of nova outbursts. In particular we investigate the consequences of the discontinuous mass loss due to recurring outburst events and the effects of frictional angular momentum loss (FAML), i.e. the interaction of the expanding nova envelope with the secondary. We show that a description assuming continuous mass loss – averaged over a complete nova cycle – is applicable for determining the mean mass transfer rate and the secular evolution both with and without FAML. Between two subsequent outbursts, deviations from the mean evolution depend on the strength of FAML and on the mass ejected during the outburst. Formally FAML is a consequential angular momentum loss [1] and therefore increases the mean mass transfer rate by pushing the systems closer to mass transfer instability. Depending on the actual strenghth of FAML the long-term evolution of CVs could be significantly different from the standard model predictions.
ASCA Observations of Narrow-Line Seyfert 1 Galaxies
Authors: Hayashida K.
Published: July 2016

ASCA observations of four narrow-line Seyfert 1 galaxies are presented. Among the four sources, two show X-ray spectra consisting of soft and hard components. Rapid X-ray variability is observed in all four sources. We estimate the central black-hole mass of these sources and find indications that the apparent luminosities exceed the Eddington limit under some assumptions.
A Multicolor Study of AGNs and BL Lacs
Authors: Sun W.-H. , Su Yu-Ya , Tang Hsiao-Feng , Malkan Matthew A. , Stone Remington P. S.
Published: July 2016

We present preliminary results of two monitoring projects on AGNs and BL Lacs with four intermediate-band optical filters at Lick Observatory, South African Astronomical Observatory, and Siding Spring Observatory. We applied differential photometry between the target and non-variable field stars to derive the variability amplitudes. All the AGNs varied in all wavebands, with amplitudes from 30% to 90%. The variations in shorter wavelength filters are always larger than in longer wavelength filters. We did not observe significant continuum slope changes. Continuum variations of BL Lacs up to 0.2 mag in 20 minutes were observed. Interestingly, we found a time lag of 6–8 minutes between two seemingly correlated variations observed in the intermediate U band with the 1-m telescope and in broad V band with the 24-in. telescope at SSO.
The Diversity of Broad Emission-Line Profiles
Authors: Stirpe Giovanna M. , Robinson Andrew , Axon David J.
Published: July 2016

We present preliminary results from a study of broad-line profiles in active galaxies. A simple model in which the emissivity is a broken power-law function of radius, and the BLR clouds emit anisotropically, yields very good fits to almost all the Ha profiles in our data base.
Broad-Line Profiles and Time Lags of Bloated Stars
Authors: Alexander Tal
Published: July 2016

The bloated stars model for AGN broad-line emission proposes that this emission originates in the mass-loss envelopes or winds of giant stars. I present here a version of the model that simultaneously reproduces typical AGN broad emission-line ratios, line profiles, and linereverberation time lags without excessive stellar collisions. This can be achieved if (1) the bloated star envelope is about 10 times denser than that of normal supergiants, (2) the fraction of the bloated stars within the stellar population falls off as r−2, and (3) the size of the envelope is limited by the black-hole tidal forces.
The Relationship Between the Emission-Line Spectra and X-Ray/UV Continuum
Authors: Lu Youjun , Wang Tinggui
Published: July 2016

According to photoionization calculations, the broad emission-line (BEL) spectrum depends not only on the physical conditions of line-emitting gas, but also on the spectral shape of incident ionizing continuum, especially from the UV to X-ray. Analysis of emission-line spectra and their correlations with the continuum, therefore, provide a way of probing the anisotropy of ionizing continuum on the BLR scale, which is predicted by current models. Previous works have concentrated on explaining the Baldwin effect, an inverse correlation between equivalent width and continuum luminosity. In this contribution, we present the results of an analysis of 75 AGNs which have well-determined soft X-ray spectral parameters from ROSAT and UV line and continuum measurements.
A Survey of Spectral Features in ISO SWS Spectra of AGNs
Authors: Sturm E. , Lutz D. , Genzel R.
Published: July 2016

Various AGNs, starburst galaxies, and ultraluminous infrared galaxies (ULIRGs) are observed as part of the ISO-SWS central program of mid-infrared spectroscopy on bright galactic nuclei. Prototypical template sources are scanned over the full spectral range of SWS (2.5–45µm) in order to get a complete census of spectral features in this wavelength domain. As an example we present the spectrum of the Seyfert 2 galaxy Circinus. The application of results from this survey to the study of the nature and evolution of other galaxies can be demonstrated by an analysis of the ultraluminous infrared galaxy Arp 220.
The Kyoto 3-D Spectrograph and an Imaging Fabry-Perot Observation of the Nuclear Region of NGC 4151
Authors: Ohtani H. , Ishigaki T. , Hayashi T. , Ozaki S. , Hattori T. , Sasaki M. , Aoki K. , Yoshida M. , Watanabe E.
Published: July 2016

The Kyoto 3-D Spectrograph was commissioned successfully at the 188-cm telescope of the Okayama Astrophysical Observatory in the spring of 1996. This instrument has four distinct modes (Ohtani et al. 1994): (1) narrow-band imager, which is an ordinary focal-reducer camera; (2) Spectro-NebulaGraph (long-slit spectrograph; Kosugi et al. 1995); (3) imaging Fabry-Perot interferometer, using either of two Fabry-Perot etalons from Queensgate Instruments (a tunable filter with R = 300 and another with R = 7000 for velocity-field observations. Broad-band (400–700 nm) coatings are deposited on both etalons. During observations, the etalon temperature is stabilized within 0.5°C); and (4) integral-field spectrograph of the TIGER-type (Bacon et al. 1995). In this mode, the spectra of 7 × 11 objects can be recorded simultaneously, along with 7 × 2 spectra of the sky 4′ away. The spatial resolution is 1″.3 and the field of view is 9″ × 14″.
3-D TIGER Observations of Radio Galaxies
Authors: Adam G. , Rocca-Volmerange B. , Ferruit P. , Bacon R.
Published: July 2016

The cosmological evolution of stellar populations can be studied by observing, e.g,, high-z radio galaxies, and comparing their SEDs to those of local objects. But in such objects, the nuclear activity strongly influences the optical properties; to disentangle the superposition of spatial and spectral effects, complete 3-D data cubes are needed, such as those that can be obtained with the pioneering 3-D instrument TIGER.
One-Armed Oscillations of Accretion Disks in AGN: Application to the Warped Maser Disk of NGC 4258
Authors: Okazaki Atsuo T.
Published: July 2016

We present a numerical example of a warping mode in the maser disk of NGC 4258. We find that the characteristics of the mode agree with the observed position and velocity distribution of the maser sources.
Clumpy Scattering Regions in Active Galactic Nuclei
Authors: Kishimoto Makoto
Published: July 2016

Simple unified models predict that many Seyfert 2s should be highly polarized ( ≳ 50%), but such highly polarized Seyfert 2s are not observed. As one of the possibilities to explain this problem, the existence of clumpy scattering clouds with optically thick condensations in the nuclear regions is discussed.
The investigations of pulsar integral radio luminosities
Authors: Malov Igor’ F. , Malov Oleg I. , Malofeev Valerij M.
Published: July 2016

We have calculated accurate integral radio luminositiesLfor 232 pulsars (Malov et al., 1994) using new average spectra of these objects. Histogram ofL-distribution is characterized by the mean value < logL>= 28.45 and by the mean-square-root deviationS= 1.0. We have analysed also data for short-periodic pulsars (P < 0.1 s) and long-periodic ones (P > 1 s) separately.The main goal of such separation was to test the hypothesis on two types of pulsars (Malov, 1987): i) for the first group of objects radiation is emitted from the neighbourhood of the light cylinder (r=rLC=cP/2π, P is the pulsar period), ii) for the second one emission is generated at distancesr≪rLC. In the second case the main mechanism of radiation is curvature radiation. For the first group of pulsars the radiation is connected with the cyclotron mechanism. The difference between two basic mechanisms and the locations of the emission generation regions must cause some differences in the observable features for these two classes of pulsars.
Neutron stars and strange stars
Authors: Gondek Dorota
Published: July 2016

If strange quark plasma is the real ground state of baryonic matter (Witten 1984), then some of neutron stars (NS) could actually be strange stars (SS). It is difficult to distinguish SS from NS observationally. They have similar radii and masses and their crusts are built of the same matter. It seems that a good method for testing the existence of SS would be the studies of phenomena related to the stellar pulsations. In 1976 Boriakoff proposed that radial oscillations of NS could be observed within radio subpulses of pulsars. While various modes of pulsations of NS were studied by a number of authors, little attention was paid to seismological signatures of SS. The radial oscilations of bare SS were studied by Väth & Chanmugam (1992). Recently Weber (this volume) studied properties of stars made of matter described by BPS equation of state (EOS) (Baym et al. 1971) with a ball of strange matter inside, but they mainly concentrated on stability of white-dwarf-like SS. In this work I present fully relativistic calculations of the radial oscillation frequencies of SS. I determined the fundamental frequency for bare SS and SS with two different types of crusts depending on origin (Alcock et al. 1986) of SS and showed differences between them.
Nonlinear Propagation of Pulsar Radiation
Authors: Shukla P. K. , Stenflo L.
Published: July 2016

The nonlinear propagation of pulsar radiation in an electronpositron plasma is considered. Accounting for the pulsar radiation ponderomotive force, the relativistic mass variation, and the plasma magnetization, we obtain a pair of nonlinear equations which exhibit coupling of pulsar radiation with the background plasma slow motions in magnetized plasmas. The modulational/filamentation instability as well as the localization of pulsar radiation are investigated. We conclude that our investigation is relevant to the microstructures in the pulsar magnetosphere.