bluuebunny/crossref_metadata_2025 huggingface dataset:
IRAS 03158+4227 - a ULIRG in a Widely Separated Pair of Galaxies
Authors: Meusinger Helmut , Stecklum Bringfried , Brunzendorf Jens
Published: July 2016

We present new deep optical images, optical spectroscopy, and high-resolution NIR images of IRAS 03158+4227, one of the most luminous ULIRGs from the IRAS 2 Jy sample. The data are best explained either by a multiple merger or by the assumption of a ULIRG triggered in an early phase of galaxy interaction.
The Obscured AGN Population Probed by X-ray Observations
Authors: Iwasawa K.
Published: July 2016

X-ray properties of obscured AGN are reviewd and recent results obtained from ASCA, BeppoSAX, and Chandra are presented. There is a population of AGN that can only be revealed by hard X-ray observations. Studies of the X-ray background suggest that obscured AGN should significantly outnumber their unobscured counterparts.
Optical Identification of X-ray Sources in a High X-ray Flux Sensitivity Area from the RASS
Authors: Mújica Raúl , Zickgraf Franz-Josef , Chavushyan V. , Juárez Y. , Serrano A. , Appenzeller I. , Krautter J.
Published: July 2016

We have optically identified a complete sub-sample of ROSAT All-Sky Survey (RASS) X-ray sources contained in 6 study areas. Of the original 12° × 12° area near the NEP, only one-quarter was observed until now in order to keep the number of sources to a manageable size. This area is of particular interest because the RASS integration time is about a factor of ten longer than in the other areas and therefore a factor of 3-4 deeper in flux. We have started to observe the RASS sources in the remaining 3/4 of this area. First results are presented.
AGN Search from Multicolor Photometric Observations of Faint ROSAT X-ray Sources in a One Square Degree Field
Authors: Xue Suijian , Zhou Xu , Zhang Haotong
Published: July 2016

We report that a volume-limited, X-ray selected AGN sample, including 49 QSO like and starburst galaxies (SBs) at the 0.1-2.4 keV flux level of ≳ 5.3 × 10−14 ergs cm−2 s−1 was formed with photometric redshifts.
Decametric AGNs: FIRST and NVSS Maps and Radio Spectra
Authors: Verkhodanov O.V. , Verkhodanova N.V. , Andernach H.
Published: July 2016

Radio sources from the decametric UTR-2 catalog were cross-identified with other radiocatalogs at higher frequencies. We used the CATS database to extract all sources within the UTR beam size (~40’) to find candidate radio identifications. Using the least squares method, we fitted the spectrum of each source with one of a set of curves. We extracted NVSS and FIRST radio images for the radio-identified sources, and looked for a possible relation between size and spectral index.
Using the NASA/IPAC Extragalactic Database (NED) and Federated Virtual Observatory Archives for Multiwavelength Studies of AGNs
Authors: Mazzarella Joseph M. ,   the NED Team_a1
Published: July 2016

We live in an exciting era that offers increasing opportunities for people all over the world to make discoveries about the Universe using interconnected archives on the Internet as a primary research tool. We review how NED (http://ned.ipac.caltech.edu) can be used in concert with globally distributed online archives to perform multi-wavelength, crosscorrelated studies of AGNs and other galaxy types. The present status and planned evolution of NED capabilities are discussed.
Conference Summary
Authors: Sanders D. B.
Published: July 2016

This conference on AGN Surveys has proved to be a significant milestone in our understanding of the redshift distribution of optically selected QSOs, and in our initial understanding of the cosmic distribution of AGN from the first far-infrared and X-ray deep fields. It has also set the stage for continuing debates concerning the multiwave-length properties of AGN, the cosmological distribution of “obscured” AGN, and the “orientation versus evolution” debate on the nature of the sources discovered at different wavelengths. Much of this debate could have been anticipated from previous studies of the complete samples of optically-selected AGN provided to us by the pioneering work carried out by the staff of the Byurakan Astronomical Observatory over the past 40 years.
Numerical simulations of the accretion of Uranus and Neptune. II. Effect of low velocity encounters
Authors: Brunini A. , Fernández J.A.
Published: July 2016

New numerical simulations of the accretion of the outer solar system were carried out by means of a symplectic integration code developed by the authors. By contrast with our previous numerical experiments, we now pay special attention to the treatment of low relative velocity encounters between planetesimals. Our new results corroborate, in general, a marked radial drift of the accreting outer planets, and that less than 50% of the solid material originally present in the system contributes to the accretion process. The results confirm that mean motion resonances play a major role during the accretion of the outer solar system.
Šumava meteoroid − was it a small comet?
Authors: Nemtchinov I.V. , Kuzmicheva M.Yu. , Shuvalov V.V. , Golub' A.P. , Popova O.P. , Kosarev I.B. , Borovička J.
Published: July 2016

Šumava event was one of the brightest bolides detected by the European Network. At the altitudes from 75 to 59 km its light curve shows four major maxima. Low strength appears the evidence of its cometary origin, while spectrum is consistent with a chondritic composition. The velocity of impactor lateral expansion is higher than that caused by simple aerodynamics. We consider some probable models of meteoroid disruption.
Collisional frequency in the inner part of the Solar system
Authors: Galád A.
Published: July 2016

Numbered asteroids were used to study their close encounters in time period from December 3, 1939 to February 25, 2023. Encounter velocities were computed only for very close approaches. The lower limit of collisional frequency is derived.
Detection of a high density meteoroid on cometary orbit
Authors: Spurný P. , Borovička J.
Published: July 2016

We report a detection of a unique fireball photographed at three Czech stations of the European Fireball Network on June 1, 1997. The main exceptionality of this fireball is given by its retrograde heliocentric orbit (i= 138°) typical for comets and, at the same time, a behavior in the Earth’s atmosphere typical for the hardest component of the interplanetary matter. The spectrum of the fireball is unique by the absence of the sodium line. With the entry velocity of 65 km s−1, the meteoroid of an estimated initial mass of 0.2 kg (diameter of several centimeters) penetrated down the altitude 65 km, i.e. significantly deeper (about 25 km) than cometary meteoroids of a comparable velocity and mass. A comparison with a typical cometary meteoroid is demonstrated on anηAquarid fireball photographed one month before.

The event reported is unique in decades-long records of the fireball networks. The origin of the meteoroid in the asteroid belt is highly improbable owing to the orbit. The possibility that comets contain centimeter sized compact stones is therefore suggested.
The O–C diagrams of minor planets − a new approach to modelling the rotation
Authors: Szabó Gy. , Sárneczky K. , Kiss L.L.
Published: July 2016

A widely used tool in studying quasi-monoperiodic processes is the O–C diagram. This paper deals with the application of this diagram in minor planet studies. The main difference between our approach and the classical O–C diagram is that we transform the epoch (=time) dependence into the geocentric longitude domain. We outline a rotation modelling using this modified O–C and illustrate the abilities with detailed error analysis. The primary assumption, that the monotonity and the shape of this diagram is (almost) independent of the geometry of the asteroids is discussed and tested. The monotonity enables an unambiguous distinction between the prograde and retrograde rotation, thus the four-fold (or in some cases the two-fold) ambiguities can be avoided. This turned out to be the main advantage of the O–C examination. As an extension to the theoretical work, we present some preliminary results on 1727 Mette based on new CCD observations.
Are there two populations of comets based on polarimetric properties of dust particles?
Authors: Kiselev N.N.
Published: July 2016

A critical analysis of attempts to classify comets on the basis of their polarimetric properties is given. It was shown that a degree of polarization depends strongly on the gas-to-dust ratio of comets and bandpass of filters. At present, there are no rigorous polarimetric evidences for two taxonomic classes of comets.
CCD photometry of high inclination faint asteroids and Kuiper belt objects
Authors: Ivanova A. , Ivanova V. , Tsvetkova A.
Published: July 2016

A new program for CCD photometric observations of Kuiper belt objects and high inclination faint asteroids with the 2m RC telescope of Rozhen National Observatory, Bulgaria, started at the beginning of 1998. We present our observations andV-composite lightcurve of 863 Benkoela.
Approaches of stars to the Sun
Authors: Dybczyński P.A. , Kankiewicz P.
Published: July 2016

Close approaches of stars to the Solar System perturb comets from the Oort cloud so that they pass into the planetary system − the gravitational impulse changes the distribution of observable comets. This paper presents the results of calculations of the motion of stars in the solar neighbourhood in the past and future. The main results for each star are: the time of the encounter and the minimum distance between the Sun and the star. They are calculated using three different methods: a straight line motion model, a model with a Sun − star Keplerian interaction, and the numerical integration of the equations of motion with galactic perturbations included. In the last case, two models of the Galactic potential are used: a simplified potential of the Galactic disk and the more complex potential of the Galaxy by Dauphole and Colin. Coordinates and velocities of nearby stars are taken from several different catalogues: the Gliese catalogue, the Hipparcos catalogue, and the Barbier-Brossat catalogue of Radial Velocities.
From Jupiter-family comets to objects in Encke-like orbits
Authors: Valsecchi G.B.
Published: July 2016

Numerical integrations of the orbital evolution of objects in orbits resembling the peculiar cometary orbit of 2P/Encke have allowed the identification of the dynamical paths connecting these orbits to the possible source regions and to the possible end states. A certain degree of concentration of the longitudes of perihelion of objects in Encke-like orbits has led to the idea that 2P/Encke and the asteroidal objects in nearby orbits all come from the recent fragmentation of a giant progenitor. However, the fact that the majority of Earth-crossing asteroids are discovered when passing near the Earth induces a correlation between the date of discovery and a range of possible longitudes of perihelion. By combining this correlation with the variable rate of asteroid discoveries over the year, it is possible to show that the discovery of asteroids on orbits of given semimajor axis and eccentricity is favoured if their longitudes of perihelion fall within certain intervals. A question still open is the efficiency of the dynamical path linking the Jupiter family to Encke-like orbits; nongravitational forces seem to play an important rôle in this respect.
Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body
Authors: Ibadinov Kh.I.
Published: July 2016

From the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.
Solar Flare Spectral Diagnosis: Present and Future
Authors: Antonucci Ester
Published: July 2016

New perspectives in solar diagnosis have been opened in recent years with the advent of high-resolution soft X-ray spectroscopy for plasmas forming at temperatures above 107K. The spectra obtained with the soft X-ray spectrometers flown during the last solar maximum on the major space missions dedicated to flares have allowed detailed studies of the hydrodynamic response of coronal loops to impulsive energy deposition and of the formation of the high-temperature plasma as a consequence of such dynamic effects. These studies are possible since high-resolution spectrometers give an accurate measure of both line intensities and profiles in important spectral regions, covering the emission of highly ionized heavy ions, which allow a direct determination of most of the crucial plasma parameters in the flare region. In response to the impulsive energy release in the flare region, while the intensity of soft X-ray lines increases, line profiles show large non-thermal broadenings and strong blue-asymmetries.

There have been important contributions in the understanding of the formation of the flare high-temperature plasma, as an effect of the hydrodynamic response of the solar atmosphere to impulsive chromospheric heating. On the other hand, the attempts to investigate the primary energy release and transport, on the basis of the soft X-ray spectral data, have not yet been entirely successful. Significant differences in the emitted spectra are expected at the very onset of flares for different energy deposition and transport processes, but the sensitivity of the present experiments is still insufficient to detect with good statistics the early stage of flares and, therefore, to allow a reliable discrimination. It is expected that future experiments with higher sensitivity will be of great importance for relating with less ambiguity the observed flare evolution in soft X-rays to the primary energy deposition in the flaring coronal loops.
Solar Flares: The Impulsive Phase
Authors: Dennis Brian R. , Schwartz Richard A.
Published: July 2016

Only during the previous solar cycle have systematic observations begun to be made with the sensitivity and time resolution, and the continuous coverage required to catch the impulsive phase and measure the rapid variations present in many wavelength ranges. Observations in X-rays, gamma-rays, UV, Ha, and radio wavelengths all reveal rapid variations during the impulsive phase and have contributed to our understanding of the different phenomena involved. Results have been obtained from several spacecraft, from rocket and balloon flights, and from ground-based observations. These are reviewed in the context of a simple single loop flare model with a view to showing what results are consistent with this model and what the major problems are in our understanding of the impulsive phase. New instrumentation planned for observations during the present Cycle 22 will provide a concerted attack on the impulsive phase as part of the Max'91 program.
Preflare Activity
Authors: Gaizauskas V.
Published: July 2016

Magnetic reconnection at current sheets or in current-bearing arches in the solar atmosphere is generally accepted as the mechanism responsible for the sudden energy release in solar flares. Attempts have so far been unsuccessful to isolate from the observations some unique preconditions which would be necessary and sufficient to ensure rapid conversion of energy by this process. Here we survey recent multi-wavelength observations which illustrate the variety of preflare activity. Multiple structures are now believed to participate in the energy release. Dynamic global coupling of the magnetic fields between a flaring site and the rest of an activity complex is seen from the data to be an important aspect of preflare activity.
Simultaneous Multi-Frequency Imaging Observations of Solar Microwave Bursts
Authors: Kundu M. R. , White S. M. , Schmahl E. J.
Published: July 2016

We review the results of simultaneous two-frequency imaging observations of solar microwave bursts with the Very Large Array. Simultaneous 2 and 6 cm observations have been made of bursts which are optically thin at both frequencies, or optically thick at the lower frequency. In the latter case the source structure may differ at the two frequencies, but the two sources usually seem to be related. However, this is not always true of simultaneous 6 and 20 cm observations. The results have implications for the analysis of non-imaging radio data of solar and stellar flares.
Solar and Stellar Magnetic Fields and Structures: Observations
Authors: Linsky Jeffrey L.
Published: July 2016

This review of stellar magnetic field measurements is both a critique of recent spectral diagnostic techniques and a summary of important trends now appearing in the data. I will discuss both the Zeeman broadening techniques that have evolved from Robinson's original approach and techniques based on circular and linear polarization data. I conclude with an ambitious agenda for developing self-consistent models of the magnetic atmospheres of active stars.
Mass Motions Associated with Solar Flares
Authors: Martin Sara F.
Published: July 2016

Mass motions are a principal means by which components of solar flares can be distinguished. Typical patterns of mass motions in Ha are described for chromospheric flare ribbons, remote chromo-spheric flare patches, flare loops, flaring arches, surges, erupting filaments and some expanding coronal features. Interrelationships between these phenomena are discussed and illustrations of each are presented.
The Importance of Solar White-Light Flares
Authors: Neidig Donald F.
Published: July 2016

The basic results of white-light flare (WLF) photometric and spectrographic observations are reviewed. WLFs represent the most extreme density conditions in solar optical flares and are similar to stellar flares in many respects. It is shown that WLFs originate in the low chromosphere and upper photosphere, and that their huge radiative losses remain difficult to explain within the context of known mechanisms of energy transport.
Long-Duration Solar and Stellar Flares
Authors: Poletto Giannina
Published: July 2016

According to one of the most popular classifications, solar flares may be assigned either to the category of small short-lived events, or to the category of large, long-duration two-ribbon (2-R) flares. Even if such a broad division oversimplifies the flare phenomenon, our knowledge of the characteristics of stellar flares is so poor, that it is worthwhile to investigate the possibility of adopting this classification scheme for stellar flares as well. In particular we will analyze Einstein observations of a long duration flare on EQ Peg to establish whether it might be considered as a stellar analogy of 2-R solar events. To this end we apply to EQ Peg data a reconnection model, developed originally for solar 2-R flares, and conclude that stellar observations are consistent with model predictions, although additional information is required to identify uniquely the physical parameters of the flare region. Application of the model to integrated observations of a 2-R solar flare, for which high spatial resolution data are also available, shows, however, that future integrated observations may allow us to solve the ambiguities of the model and use it as a diagnostic tool for a better understanding of stellar flares.
Polarimetry of Stellar Active Regions and Flares
Authors: Tuominen I. , Huovelin J. , Efimov Yu. S. , Shakhovskoy N. M. , Shcherbakov A. G.
Published: July 2016

Observations of regular and irregular polarimetric variability in late-type stars are reviewed, and the related physical and geometrical effects are discussed. There are indications that the irregular part of the variability could be caused by transient events, possibly associated with flares. Polarimetric observations during flares are reviewed, and preliminary results of new observations of a well-known flare star, YY Geminorum, are presented. The results show that the small flare in YY Gem did not cause any significant variations in linear polarization, while the binary eclipse evidently causes an enhancement in the polarization. The reasons for the difficulties in stellar flare polarimetry are discussed. Finally, future prospects for the observations of flaring stars and for the utilization of linear polarimetry as a complementary method to other techniques of surface imaging of stellar activity and flares are presented.
The 6-metre Altazimuth Telescope
Authors: Mihel’son N. N.
Published: July 2016

Dr. B. K. Ioannisiani was unable to give his scheduled paper on this subject, but Dr. N. N. Mihel’son kindly agreed to answer questions in its place.
Telescope Interface Compatibility
Authors: Breda I. G. Van
Published: July 2016

Recently an automatic UBVRI photometer has been under construction at the University Observatory, St Andrews, for use on the 1.02-metre telescope at the Royal Observatory, Cape Town. Two problems have been encountered which would seem to be of general relevance. Firstly a Cassegrain focus acquisition head, specific to the photometer, was required, and secondly a large rack of electronics must be shipped to South Africa. Clearly these problems have occurred to other guest observers, and it is suggested that they would be greatly reduced by the adoption of international standards, preferably through the IAU, relating to mechanical and electronic interfaces.
The Kitt Peak Magnetograph III. Automation and the 40-Channel Probe
Authors: Livingston W. , Harvey J. , Slaughter C.
Published: July 2016

In this paper we describe the 40-channel magnetograph primarily as an example of the automated data system at the McMath Solar Telescope. The principles of the magnetograph itself have been recently given in paper I (Livingston and Harvey, 1970), while the reduction and interpretation of data is covered in paper II (Harvey and Livingston, 1970).
Computer Controlled Pulse Counting Photometry
Authors: Nielsen R. Florentin
Published: July 2016

I wish to present some aspects of a computer controlled pulse counting system for general photoelectric photometry.

The pulse counting technique applied in astronomical photoelectric photometry has yielded significant improvements as to telescope efficiency, especially in connection with the measurement of very faint light sources. This is achieved through the advantages inherent in the pulse counting technique over the conventional charge technique, that is:
The Cambridge Automatic Plate-Measuring Project
Authors: Kibblewhite Edward J.
Published: July 2016

The Cambridge automatic plate measuring project is an attempt to develop a reasonably cheap system capable of measuring photographic images to sub-micron accuracies at high speed, typically 10 images/sec.
A Digitized Microphotometer and Some Applications
Authors: Gratton L. , Martini A. , Martino E. , Natali G. , Viotti R.
Published: July 2016

Despite the great progress which is being continuously made towards direct photoelectric recording, it is almost certain that for many years to come photographic plates will remain the most common means for detecting images of stars and stellar spectra, whether directly or through the intermediary of an image intensifier.

The photographic image of the spectrum of a star contains an enormous wealth of information whose utilization is one of the most important tasks of observational astrophysics. To achieve this task many difficult problems must be solved, the first being to express the information in a form which lends itself to further processing.

This is usually done by means of two different kinds of instruments.
Coherence Problems in High-Resolution Microdensitometry
Authors: Parrent G. B.
Published: July 2016

My background is neither astronomy nor instrumentation but rather image analysis. Hence, I am not going to describe new equipment nor new astronomical findings, but rather some difficulties which have arisen in other fields where images must be interpreted and manipulated, and which are sure to arise in astronomy as well.

I shall limit my attention to problems arising from coherence of the radiation in the analysing instrument and attempt to isolate their source and give guidance on how to recognize them and avoid them.
Calculation of Equivalent Widths via an Interactive Display Device
Authors: Klinglesmith Daniel A.
Published: July 2016

This paper describes a computer program used to compute equivalent widths via an IBM 2250 attached to an IBM 360/75J.

The measurement of stellar equivalent widths is a long tedious procedure and the final results depend to a large extent on where the stellar continuum is drawn. Therefore, a method which permits the continuum to be redrawn and the equivalent width remeasured quickly is desirable. An interactive CRT display device is an ideal instrument for allowing an astronomer to adjust the continuum level and the other parameters that are involved in equivalent width measurements. The display device discussed in this paper is an IBM model 2250 used in conjunction with a IBM 360/75J.

The “2250” consists of a 12 inch (30 cm) square CRT display tube plus a 32 function key box, an alphanumeric keyboard and a light pen which can be pointed at any illuminated spot on the screen. Thus, there are 34 interrupts that can be sensed by the program controlling the “2250”. The program that has been used communicates with the astronomer via messages and questions displayed on the CRT screen. The main program remains in a wait state until one of the 34 possible interrupts occurs, whereupon it branches to the designated subroutine and executes the procedures necessary to satisfy the interrupt.
Spectral Changes in the Grygar Variable HBV 475
Authors: Mammano A. , Righini G. M.
Published: July 2016

Photovisual and spectroscopic observations of HBV 475 in the range λλ 3800–11 000 Å by means of S-20 and S-1 Carnegie Intensifies and prismatic cameras (dispersion 60 A/mm at Hγ), made in 1969 through 1971, have revealed the simultaneous presence of hot and cold sources of radiation, both variable.

In 1969 when the magnitudes were B = 12.45, V = 12.05, U = 11.40 the hot source gave origin to a quite strong ultraviolet continuum and to emission lines among which the most intense are due to: HI (H16 to Hα and P14 to P7); OI 8446; Fell (mult. 27, 37, 38, 42, 48, 49); [NII] 5755; Hel (4471, 5876, 6678, 7065, 10 830 very strong); [OIII] (5007, 4959, 4363); [NeIII] (3869, 3968); Hell 4686 weak.
Some Observations of the Flare Star YZ CMi
Authors: Bhatt T. R. , Sinvhal S. D.
Published: July 2016

YZ CMi (mv = 11ṃ28; B-V = + 1.60; π = 0.̎182 was observed photoelectrically through the B filter of the Johnson and Morgan system on 8 nights during December 1970 to January 1971. The total monitoring time was 22ḥ8 and 3 flares exceeding Oṃ4 in brightness were detected.
High-Frequency Stellar Oscillations. The Cerro Tololo Search for Luminosity-Variable White Dwarfs
Authors: Hesser James E. , Lasker Barry M. , Kunkel W.
Published: July 2016

The techniques and procedures of time-series monitoring and Fourier analysis which are used at Cerro Tololo to search for luminosity variations in white dwarfs are summarized. Further null results from this program, which are applicable to the problem of defining the region of white-dwarf variability in the HR-diagram, are considered; and the properties of the four known variables are reviewed as possible archetypes of a group.
Rapid Spectral Variations in Be Stars — New Techniques and Results
Authors: Hutchings J. B. , Walker G. A. H. , Auman J. R.
Published: July 2016

High resolution spectral scans of some Be stars, taken with an Isocon television camera, show changes in the Ha line profile in times of the order of a minute or less.
The Evolution of a Contact Binary
Authors: Hazlehurst J. , Meyer-Hofmeister E.
Published: July 2016

Test calculations have been made to study the effects of central hydrogen depletion, luminosity exchange and mass exchange on the evolution of a contact binary. The Munich Henyey programme was adapted to allow the study of both components in a time-dependent way.

The first model considered was that of LUCY (Ap. J. 151, 1126) in which entropy is assumed to be at all times uniform throughout the adiabatic portion of a common convective envelope. This model was found to be unstable, in the sense that mass flows from the primary to the secondary in a time short compared with the nuclear time-scale.
Variability due to Contact Configurations
Authors: Mauder Horst
Published: July 2016

The question of whether W UMa stars are contact binaries or not is still a problem. It is promising to see that the theoretical investigators are on the way to explain that and how contact binaries can really exist, even at age zero and with different masses. Let us assume — as is generally done — that the surfaces of the two components of a W UMa star can be set identical to the equipotential surfaces of the Roche model of two mass points. If these surfaces coincide with the limiting Roche lobe or even exceed it for a little amount, than we are justified to call the figure a contact system. However, it may well be that one star fills its critical lobe and the other one is a little bit below it, or even both components may be below their limiting lobes by a small amount. The uncertainty of the elements that can be derived from W UMa light curves for the time being does not allow for a definite decision. We have to look, therefore, for the possible differences between the light-curves of very close, not contact binaries and the variability of contact pairs.
Variations of the Period of AH Virginis
Authors: Bakos Gustav A.
Published: July 2016

AH Virginis was discovered by GUTHNICK and PRAGER (1929) and since that time the system was observed photographically, visually and, more recently, photoelectrically. The variable belongs to the class of eclipsing binaries of the W UMa type. It has a period of 0.41 days and spectrographic as well as photometric elements have been derived by CHANG (1948) and BINNENDIJK (1960), respectively. The most interesting result of discussions by KWEE (1958), BINNENDIJK (1960), HERCZEG (1962), and PURGATHOFER and PROCHAZKA (1967) is the fact that the residuals between the observed and the computed epochs of minima cannot be represented by a linear relation and show the tendency of producing sudden variations in the period of the system.
Observations of Faint Globular Clusters
Authors: Rosino L. , Pinto G.
Published: July 2016

The present communication reports some results of observations made at Asiago on three faint globular clusters discovered on Palomar Sky Survey plates (Abell 1955).

Palomar 2 (4h43.m1, + 31 °23’, 1950; l= 170°, b= -9°). This cluster was studied some years ago by McCarthy and Treanor (1964) on infrared plates taken with the Schmidt telescope of the Vatican Observatory. After an extensive discussion the authors concluded that the object was either a peculiar globular cluster at an estimated distance of 63 kpc or an old galactic cluster at a distance of the order of 16 kpc.
Planetary Nebulae, Globular Clusters and the Galactic Halo
Authors: Bergh Sidney Van Den
Published: July 2016

Planetary nebulae are used as a tracer for halo Population II stars. A comparison of the number of planetary nebulae in the galactic pole caps (|b| ≥ 45°) with the number of planetaries in globular clusters suggests that (to within a factor of 2 or 3) the galactic halo has a luminosity LB ⋍ 2 × 108L⊙. From the work of Oort it is estimated that the galactic halo has a mass of at least so that for the galactic halo.
Variable Stars In NGC 4590
Authors: Terzan A. , Rutily B. , Ounnas CH.
Published: July 2016

The globular cluster NGC 4590 has been observed at Haute Provence Observatory (photographic photometry, 80-cm reflector, F/6) and at the European Southern Observatory (image-tube, 152-cm reflector, F/15).

– A sequence of red magnitudes, mr (λett ≅ 6400 Å) has been established around the cluster. It comprises 28 stars with magnitudes between 11.66 and 16.50.

– Five new variable stars were discovered in a one square degree field, centered on the cluster.

– Four other variable stars (No. 39, 40, 41, and 42) were discovered in the cluster.
Intermediate Band Photometry of RR Lyrae Variables in ω Cen and 47 Tuc
Authors: Jones D.H.P.
Published: July 2016

I have recently prepared for publication a study of 100 field RR Lyraes which were measured on the u, k, b, y, β system described by Jones (1971). It is shown that the following indices

β1 = β − 0.125(k − b) + 0.103(b−y)

(u − b)3 = (u − b) − 0.93(b − y) − 0.62(k − b) − 1.95(β − 2.75)

(k − b)2 = (k − b) − 0.826(b − y) + 0.25(β − 2.75)

correlate strongly with θeff, logg and [Fe/H] respectively. Figures in that paper show the tightness of the correlations.
The RR Lyrae Stars in the Magellanic Clouds
Authors: Graham J. A.
Published: July 2016

The characteristics of the RR Lyrae stars in the Magellanic Clouds are discussed. The existence of numerous RR Lyrae variables in the Large Magellanic Cloud (LMC) cluster NGC 1835 is noted. The variables indicate that this cluster is of Oosterhoff type I. No cluster of Oosterhoff type II has yet been recognized in the Clouds. Some new results of a study of the RRLyrae variables in an LMC field 1° x 1.°3 are discussed. Periods have been determined for 50 out of 72 probable RR lyraes in this field. RR Lyrae ab stars with periods less than 0.d46 are absent. The time averaged and are 19.m56 and 19.m20 with surprisingly small dispersion. First impressions of results for a similar field in the Small Magellanic Cloud (SMC) suggest that the old stellar population of the SMC may have a slightly lower metal abundance than that of the LMC. The best available distance moduli for the Magellanic Clouds indicate a mean absolute visual magnitude M of +0.m5 ±0.2 for the RR Lyrae stars in these systems.
Observational Aspects of Slow Variables in Globular Clusters
Authors: Feast M. W.
Published: July 2016

There are up to 14 known Mira variables in seven globular clusters, though several have not yet been confirmed as radial velocity members. The periods of only 5 are known, all near 200 days. The clusters seem to form a compact group of relatively metal rich clusters. In 3 or 4 cases spectroscopy shows that the giant branches of these clusters penetrate into the M types. The Mira-containing clusters also contain red variables of shorter period and smaller amplitude which are generally also M type stars. Stars apparently evolve to the red of the giant tip as variables of increasing amplitude and period. Effects of TiO blanketing on the (B — V) colours may be anticipated in these clusters.

Besides variables at the red giant tip the metal poor globular cluster ω Cen contains variables with strong TiO bands. Photometry, including recent J, H, K, L photometry by Glass shows that these stars are very cool objects. They indicate an extension of the giant branch considerably cooler than previously considered for metal poor clusters.

V1, NGC 121 in the Small Magellanic Cloud has a spectrum indicative of an SRd variable. It is not yet clear whether galactic stars similar to this star exist or not.
Narrow-Band Photometry of Red Variables in Globular Clusters
Authors: Wing Robert F.
Published: July 2016

Fourteen red variables in the southern globular clusters 47 Tuc, ω Cen, and NGC 362 have been observed on an eight-color system of narrow-band photometry in the near infrared. Temperatures are derived from blackbody fits to the calibrated fluxes, and spectral types are given for the M stars. The types observed for the three Mira variables in 47 Tuc range from M3.1 to M7.5; two small-range variables in the same cluster are later than M4. The variables in ω Cen are mostly earlier than K5, but spectra of types M3 and MO were also encountered among radial-velocity members. In both the metal-rich 47 Tuc and the metal-poor ω Cen, the relation between TiO band strength and temperature is approximately normal. Several of these stars fall well above or below the red giant branches of their clusters in diagrams of infrared magnitude against temperature. Comparisons are made with recent results obtained at Radcliffe Observatory on some of the same stars.
The Period-Luminosity Relation for Cepheids in Globular Clusters
Authors: Kukarkin B. V. , Rastorgouev A. S.
Published: July 2016

The period-luminosity relation for Cepheids in globular clusters has been investigated many times (e.g. Fernie, 1964; Kwee, 1968; Frolov, 1970; Demers, 1971).

The method of determination of the apparent distance moduli was recently revised by Kukarkin and Russev (1972). Instead of using a single absolute magnitude for RR Lyrae variables, the magnitudes according to pulsation theory (Christy, 1966, 1971) were adopted. The inhomogeneity of the absolute magnitudes of the RR Lyrae variables had already been established long ago (Pavlovskaya, 1953), but it attracted attention only recently. The different methods for determining the distance moduli of globular clusters were calibrated according to the new absolute magnitudes of the RR Lyrae variables. The problem consisted in the determination of the absolute magnitudes of the Cepheids in globular clusters according to the apparent distance moduli.
Variable Stars and Evolution in Globular Clusters
Authors: Demarque Pierre
Published: July 2016

Traditionally, cluster variables have been used as distance indicators and have in this sense played an important role in our understanding of stellar evolution. In particular, the determination of the distance moduli of globular clusters and of the absolute magnitude of the main sequence turnoff, thus yielding the ages of the cluster, have relied heavily in the past on observations of RR Lyrae stars.
On the Interpretation of RR Lyrae Properties in Globular Clusters and in Other Population II Systems
Authors: Castellani V. , Giannone P. , Renzini A.
Published: July 2016

The differences in observational parameters of the RR Lyrae variables and horizontal branch stars of globular clusters and other population II systems are considered. A discontinuous behaviour of some parameters is outlined. The Oosterhoff dichotomy and the HB morphology are discussed with regard to a conjecture of mass loss in the pre-HB phase.
Semiconvection and the RR Lyrae Variables
Authors: Sweigart A. V. , Demarque P.
Published: July 2016

Theoretical computations (Hoyle and Schwarzschild, 1955; Faulkner, 1966; Iben and Rood, 1970; Demarque and Mengel, 1971a, b) have identified the horizontal-branch stars in globular clusters with the evolution phase in which helium burns within a convective core and hydrogen burns in a shell outside the convective core. Most computations for such double-energy-source models have indicated that the evolution proceeds smoothly on a nuclear time scale during the horizontal-branch phase, leading to small predicted rates of change in the RR Lyrae pulsation period (Iben and Rood, 1970). Sweigart and Demarque (1972) have recently considered the effects of semiconvection on the horizontal-branch evolution of typical Population II stars and have suggested that changes in the composition distribution within the core may occur on a time scale considerably shorter than the nuclear time scale during the phase immediately preceding core-helium exhaustion. It has been found that the composition distribution generated by the growth of a semiconvective zone in the layers surrounding the convective core can become unstable when Yc, the helium abundance within the convective core, decreases below roughly 0.12. The changes in the internal structure caused by this instability result in relatively rapid movement of the models in the HR diagram and consequently produce large predicted rates of change in the RR Lyrae pulsation period. The possibility that RR Lyrae period changes may be associated with the behavior of the semiconvective zone has been previously suggested by Schwarzschild (1970). A similar instability may occur in the late core-hydrogen burning phase for stars around 10 M⊙. Percy (1970) has noted the coincidence of β Cephei stars with stellar models containing semiconvective zones. It is tempting to suggest that such an instability in the semiconvective zone could also be related to the β Cephei phenomenon.
The comet and minor planet program at Lowell Observatory
Authors: Giclas H. L.
Published: July 2016

The Lowell Observatory has traditionally been involved with the planets, at its inception in 1894 with the bright planet Mars and culminating in 1930 with the discovery of a 15th. magnitude one, Pluto. In the interim and following, many thousands of minor planets and comets have been observed from five separate series of sky surveys and special observing programs.

The first program in search of a trans-Neptunian planet, initiated by Percival Lowell, was begun in 1905 and completed in 1907. The entire ecliptic was photographed, using a 5-inch Brashear lens of 35 inches focal length which covered a good usable field of 5 degrees. Many of the 250 plates made in this series were three-hour exposures, in order to reach the 16th. magnitude. The shorter exposures reached the 14th. magnitude. Cramer Iso-Instant and Seed’s 27 plates were used. Each plate pair of this series was laboriously examined by hand magnifier comparing star for star.
The program of observations of minor planets at the Goethe Link Observatory
Authors: Edmondson Frank K.
Published: July 2016

The Indiana program was started in response to an appeal in 1947 from Dirk Brouwer, President of Commission 20 of the IAU, for cooperation to help overcome the effects of the war-time gap in asteroid observations. The 10-inch Cooke triplet lens which we have used is the property of the Cincinnati Observatory. The scale is 120.̎15/mm. Observations were started in 1948 and continued until the retirement of Mrs. Beryl H. Potter in June 1966. Nearly 6300 plates were taken during this period.

A micrometer eyepiece on the guide telescope was used to produce a round image of the asteroid and trailed images of the stars. Prior to 1961 a one hour exposure on Eastman 103a—0 plates would show objects almost to the 18th magnitude. After 1961 the plates were slower and the sky brightness increased with the growth of Indianapolis, 10 miles to the northeast. The plates were taken in pairs in immediate succession, and were blinked by Mrs. Potter. She also did a large part of the measuring and supervised the student assistants who participated in the measuring. By the time Mrs. Potter retired, she had found nearly all of the “critical list” objects which could be reached with our equipment.
Le programme des observations des astéroïdes et des comètes à l’Observatoire de Nice
Authors: Milet B.
Published: July 2016

Depuis 1966, après la remise eh état de l’Astrographe Double ZEISS (40 cm X 200 cm), les observations photographiques des astéroïdes et des comètes ont été faites régulièrement en vue de déterminer leurs positions précises. La transformation des chassis porte-plaques en 30 × 30 cm, au lieu de leur dimension d’origine (24 × 30), permet d’utiliser un champ de 8° × 8°. On emploie couramment des plaques Kodak II a O et la magnitude limite que l’on peut espérer est d’environ la 18ème s’il s’agit d’images stellaires. C’est pourquoi chaque fois que cela est nécessaire, on utilise la méthode Trépied-Metcalf; toutefois, lorsque le déplacement de l’objet est trop rapide, il n’est plus possible d’envisager un décalage micrométrique manuel. L’une des chambres de l’instrument a été équipée d’un système automatique de glissement du chassis en vitesse et en direction, ces deux données étant calculées en fonction de l’éphéméride.
On the improvement of star positions from minor planet observations
Authors: Orelskaya V. I.
Published: July 2016

The idea of improving star positions from observations of the minor planets was put forward in the first half of our century. In 1928 F. Dyson (1928) suggested using the meridian observations of minor planet Vesta for checking the position of the equator. Then, in 1932 N. I. Dneprovsky investigated the problem concerned with the improvement of fundamental star declinations utilizing the motions of asteroids. At the same time M. F. Subbotin (1932) suggested that a correction to the equinox position could be determined from observations of the minor planets. Theoretical aspects relating to obtaining the solution were set forth by B. V. Numerov (1933, 1936) as well as by D. Brouwer (1935, 1941) and G. Clemence (1948).
Méthode des moindres carrés (erreurs) L’écart sur un point de référence consécutif à une erreur sur sa position, dans la réduction des clichés astrométriques par formules polynomials, peut ne pas être minimum au centre
Authors: Debehogne Henri
Published: July 2016

Une meilleure compréhension du «méchanisme» de réduction des clichés se trouve assurée par la connaissance des effets d’une erreur sur un point de référence.

En ce qui concerne l’effet sur l’ensemble du cliché, nous avons établi graphiquement (Debehogne, 1972), comment

1° le degré du polynôme de transformation,

2° le nombre d’étoiles de référence,

3° la position du point d’application de l’erreur déterminent le nombre et la valeur des extrema.
Monte Carlo simulation of asteroid collisions
Authors: Napier W. McD. , Dodd R. J.
Published: July 2016

Derivation of the mass distribution resulting from the fragmentation of mutually colliding bodies is a problem of some analytical-complexity, even in the asymptotic case (see, for example, Safronov, 1963, Hellyer 1970). A related question is that of the mass distributionn(m) expected at any time if small bodies stick on impact, so coagulating into large ones. This latter problem might be relevant to the growth of planetesimals in the early stages of Solar System evolution. At Edinburgh, a Monte Carlo technique is being used to simulate these collision processes directly. Numerical simulation has advantages over and above the avoidance of analytical complexities. For example the physical assumptions can be easily changed, and the random variations which occur in reality are automatically incorporated, that is, the problem is treated stochastically rather than deterministically.
Total asteroid mass from comet perturbations
Authors: van Flandern T. C.
Published: July 2016

Deviations of Halley’s Comet from its predicted orbit more closely approximate perturbations caused by a gravitational ring of matter, rather than a point source or the usual nongravitational force model for comets. This is especially evident from the perturbations on the perihelion, node, and inclination for this comet. It is hypothesized that the gravitating ring was the asteroid belt. The observed deviations were used to solve for the total mass of the asteroids, giving the result of fifty times the mass of the Earth. Such a large mass can be ruled out by the absence of corresponding secular perturbations on the orbit of Mars, provided that the mean plane and shape of the asteroid belt do not correspond exactly with the orbit of Mars.

A mean set of elements for the asteroid belt was determined by averaging the elements of the numbered minor planets, and three short-period comets were then tested with the same hypothesis. It is concluded that there is no correlations between perturbations due to the mean asteroid belt and those exhibited by the three short-period comets.

The upper limit for the total mass of the asteroids, set by Mars, is 0.1 Earth mass. The source of the out-of-plane perturbations and of the cause of the secular increase in perihelion distance for Halley’s Comet is still an open question, since these cannot be explained by the usual nongravitational force model for comets.