bluuebunny/crossref_metadata_2025 huggingface dataset:
AG Carinae: Variability, extinction, distance and luminosity
Authors: Lamers Henny J.G.L.M. , Hoekzema Nick , Trams Norman R. , Cassatella Angelo , Barylak Mike
Published: July 2016

AG Car is one of the few Luminous Blue Variables (LBV’s) in our galaxy. The star is a photometric variable which had a recent outburst in 1981 (Whitelock et al., 1983; Wolf and Stahl, 1982) and is surrounded by a resolved ring nebula (Thackeray, 1950; Paresce, 1989). These properties indicate that AG Car is a typical LBV. However, at its canonical distance of 2-2.5 kpc, derived from its assumed membership of the Car OBI or OB2 association, AG Car has a bolometric luminosity of Mbol⋍ −8.5 to −9.0 and is located significantly below the Humphreys-Davidson limit, and also below the upperlimit for red supergiants (RSG). This implies that AG Car might have been a RSG and that the ring might be due to the interaction of the RSG wind and the LBV wind.
Stellar Kinematics of Elliptical Galaxies in Pairs
Authors: Madejsky Rainer , Bender Ralf
Published: July 2016

Observations of elliptical galaxy pairs allow the study of different states of tidal interaction between galaxies. The comparison with normal elliptical galaxies directly reveals the disturbed morphological and kinematical properties. Numerical simulations have shown that with the known initial luminosity profile, the time elapsed since closest approach between two galaxies can be estimated from the radial position of the disturbances (Aguilar and White, 1986).

The two galaxy pairs Arp 166 (NGC 750/1) and 3C 278 (NGC 4782/3) considered here exhibit distorted and nonconcentric isophotes (cf. Madejsky, 1989). In Arp 166 the major relative shift of the centers of the isophotes occurs in the outer parts while in 3C 278 the nonconcentric isophotes are more pronounced in the inner parts of the galaxies, suggesting that more time ha&elapsed since the moment of closest approach in Arp 166 than in 3C 278. Furthermore, in Arp 166, both galaxies have the same radial velocity, implying that their orbital plane is perpendicular to the line of sight. In turn, the galaxies NGC 4782 and NGC 4783 are moving with a very high radial velocity difference of 680kms-1. Taking into account the location of both galaxies, which are the dominant members of a small group of about 25 galaxies (De Souza and Quintana, 1990), the true velocity difference probably is not much higher than the observed radial velocity difference. Therefore it is very likely that we are viewing at high inclination onto (i.e. nearly parallel to) the orbital plane of the galaxies NGC 4782 and 4783.
An Atlas of Mixed-Morphology Pairs
Authors: Sharp N. A.
Published: July 2016

Current theories of galaxy formation imply that environment is the most important factor in deciding whether a collapsing region becomes a spiral galaxy or an elliptical galaxy. If this is the case, then isolated pairs comprising a galaxy of each morphology provide an especially interesting test, since, strictly speaking, they should not exist.

The first phase of studying E-S pairs is to define a sample which is genuinely isolated and genuinely E-S. The catalog compiled by Karachentsev is the most useful northern hemisphere starting point, containing 603 pairs which obeyed certain well-defined angular isolation criteria. All of these pairs now have velocities, enabling further removal of at least some of the non-physical binaries. The conventional cutoff at 500 km s−1 was used for this purpose.
The cD Galaxy in Abell Cluster 1775
Authors: Hayes J. J. E. , Bhattacharya B.
Published: July 2016

Over the last 20 years, a number of workers have studied the multiple nuclei cD galaxy in the rich Abell cluster 1775, trying to discover its nature. In all the cases though, very little has been published concerning its morphology. The majority of arguments about the nature of the this object have been based on the relative radial velocities of the 2 components with each other and with the other galaxies in the cluster, or its radio morphology. Very little work has been done on the optical morphology. To rectify that lack of data, we have obtained BVRI CCD images of the cD. We find from our CCD data that the cD is unlikely to be a bound object and that there is strong evidence for an collision.
Dumb-Bell Galaxies in Southern Clusters: Catalog and Preliminary Statistical Results
Authors: Vettolani G. , Gregorini L. , Parma P. , de Ruiter H.R.
Published: July 2016

The dominant galaxy of a rich cluster is often an object whose formation and evolution is closely connected to the dynamics of the cluster itself. Hoessel (1980) and Schneider et al. (1983) estimate that 50 % of the dominant galaxies are either of the dumb-bell type or have companions at projected distances less than 20 kpc, which is far in excess of the number expected from chance projection (see also Rood and Leir 1979).

Presently there is no complete sample of these objects, with the exception of the listing of dumb-bell galaxies in BM type I and I-II clusters in the Abell statistical sample of Rood and Leir (1979).
A Multiwavelength Survey of Interacting Galaxies
Authors: Bushouse H. , Lamb S. , Lo K.-Y. , Lord S. , Werner M.
Published: July 2016

Galaxy-galaxy collisions are known to produce drastic changes in morphology and, in many cases, enhance the level of star formation activity in galaxies. In order to better quantify the effects that interactions have on the star formation characteristics of galaxies we have undertaken a multiwavelength survey of a large sample of interacting disk-type galaxies. The sample is optically-selected, the inclusion of systems having been based upon the presence of unusual morphological features—such as tidal tails, plumes, rings, warped disks—suggestive of tidal interaction. The sample is composed of about 115 systems, most of which are spiral-spiral pairs, with a few spiral-elliptical pairs and a few merging systems (see Bushouse 1986 for more details of the sample selection). This sample has now been studied in the optical, infrared, and radio regimes, including optical spectra and Ha images, near-infrared photometry and imaging, far-infrared photometry, HI 21cm emission-line measurements, VLA 20cm maps, and CO emission-line measurements. This paper presents an overview and comparison of the results of the optical, infrared and CO surveys. With these data we can compare the far-infrared and CO properties of the galaxies with the classic optical and radio indicators of star formation activity and thereby determine what, if any, relationships exist between star formation activity and the far-infrared and CO properties of the galaxies.
Quantifying the Fir Interaction Enhancement in Paired Galaxies
Authors: Xu Cong , Sulentic Jack W.
Published: July 2016

We study the “Catalogue of Isolated Pairs of Galaxies in the Northern Hemisphere” (CPG hereafter) by Karachentsev (1972), and a well matched comparison sample taken from the “Catalog of Isolated Galaxies” (Karachentseva 1973, CIG hereafter), in order to quantify the enhanced FIR emission properties of interacting galaxies (see Sulentic 1989 for details of the samples). The isolation criterion used in compiling the CPG and the CIG means that both the pairs and single galaxies have been Httle influenced by their environment for a long time (t ≳ 109 yrs: Stocke et al 1978).
Observational Effects of Interaction in the Seyfert galaxy NGC 7469
Authors: Pronik I. , Metik L.
Published: July 2016

Some pecularities of the circummucleus of the Seyfert galaxy NGC 7469 were revealed, plausibly caused by interaction with the satellite IC 5283 and a starlike detail, situated on the edge of the west spiral branch 14” from the nucleus. Shock excited HII regions were noted in the part of NGC 7469 turned toward the satellite IC 5283. The galaxy’s central radio structure (λ ~ 6 cm) stretches in the direction toward the satellite IC 5283 and the starlike detail. The spectum and color index of the starlike detail suggest that it is a cluster of early type stars (Mv = -19m) and dust clouds (Av = 3m), in NGC 7469.
Galaxy Interactions and the Stimulation of Nuclear Activity
Authors: Heckman Timothy M.
Published: July 2016

The idea that interactions between galaxies can lead to enhanced galactic activity has a long and noble lineage. Since the early days of Baade and Minkowski (1954), through the seminal paper of Toomre and Toomre (1977) with its “stoking the furnace” imagery, to the similarly colorful and influential “feeding the monster” paper of Gunn (1979), and the landmark work by Larson and Tinsley (1978), this idea was elaborated upon and generalized. The pace of development of this hypothesis has accelerated greatly on both the observational and theoretical fronts during the 1980’s, due in part to a growing perception that the AGN phenomenon could only be understood when the role of the environment in triggering or nurturing the activity was understood (cf. Balick and Heckman 1982). In recent years, the impact of the extragalactic IRAS database (on the observational side) and of the new generation of supercomputers and innovative software (on the numerical side) have led to an almost explosive growth in the number of papers written about this subject.
Dust and Ionized Gas in Active Radio Elliptical Galaxies
Authors: Forbes D.A. , Sparks W.B. , Macchetto F.D.
Published: July 2016

We present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large Hα + [Nil] luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and we a currently investigating possible excitation mechanisms (Sparks et al. 1990).
Correlations between Environmental Parameters and Nuclear Activity
Authors: Kollatschny W. , Fricke K.J.
Published: July 2016

The occurrence and quantitative properties of Seyfert 1 and Seyfert 2 galaxies as a function of the galaxy environment have been studied in a systematic way. For this investigation we have selected from the Catalogue of Quasars and Active Nuclei (Veron & Veron, 1989) all Seyfert galaxies with the following properties:

(i) mV ≤ 15,

(ii) listed classification as Sey 1, Sey 2, or Sey 3,

(iii) vrad ≤ 20000 km s-1.

This results in a sample size of 242 Seyfert galaxies. For all these objects their galaxy environment has been inspected on POSS and ESO/SRC plates.

The vicinity of each sample Seyfert galaxy was searched for companion galaxies out to at least 0.5 Mpc. Lacking redshift information we adopted as a companion galaxy any galaxy in this area having a size between 20 and 200 percent of the Seyfert galaxy size.
The Role of Shocks in NGC 6240
Authors: Keel William C.
Published: July 2016

One of the most notable results of the IRAS mission was the recognition of a class of galaxies with large bolometric luminosities, most of whose radiation emerges in the far-infrared (typically 50-100μ). The space density of these “IRAS galaxies” approaches that of QSOs for comparable luminosities, so that these are a significant component of the population of galaxies. The frequent occurrence of interacting and merging galaxies among these infrared-bright systems has underscored the importance of understanding how various energetic processes (active nuclei, starbursts) are related to the disturbances produced during galaxy encounters. The same material directly responsible for the signature infrared excess of these systems degrades many of the diagnostics normally useful for probing the nature of he observed activity, so that in many systems it remains unclear just what kinds of phenomena are being observed.
IC5063: A Merger with A Hidden Luminous Active Nucleus
Authors: Colina L. , Sparks W. , Macchetto F.
Published: July 2016

Despite intense theoretical and observational effort during the past few years, two important questions in the field of active galaxies remain open and are the subject of vigorous debate.

The first concerns the connection between the interaction/merger of galaxies and the generation of starburst and/or active nuclei. A large fraction of high luminosity radio galaxies (Baum et al. 1988), quasars (Hutchinga, 1987) and IRAS galaxies (Sanders et al. 1988), show the presence of a large companion or have a peculiar optical morphology which is offen interpreted as evidence of a recent merger or interaction. In Seyferts, there are also several examples of individual galaxies with clear evidence of interaction/merger (Colina et al. 1987; Fricke and Kollatschny, 1989; Macchetto et al. 1990). Also a significant fraction of low luminosity radio galaxies are associated with a system of two elliptical galaxies in interaction (Colina and Pérez-Fournon, 1990a,b).
Selection Effects and Binary Galaxy Velocity Differences
Authors: Schneider Stephen E. , Salpeter Edwin E.
Published: July 2016

Measurements of the velocity differences (Δυ’s) in pairs of galaxies from large statistical samples have often been used to estimate the average masses of binary galaxies. A basic prediction of these models is that the Δυ distribution ought to decline monotonically. However, some peculiar aspects of the kinematics have been uncovered, with an anomalous preference for Δυ ≈ 72 km s-1 appearing to be present in the data.
A Classification of the Galaxy Groups
Authors: Anosova Joanna P.
Published: July 2016

A statistical criterion has been proposed to reveal the random and physical clusterings among stars, galaxies and other objects. This criterion has been applied to the galaxy triples of the list by Karachentseva, Karaschentsev and Scherbanovsky, and the double galaxies of the list by Dahari where the primary components are the Seyfert galaxies. The confident physical, probable physical, probable optical and confident optical groups have been identified. The limit difference of radial velocities of components for the confident physical multiple galaxies has also been estimated.
A Survey of Young Stars in Taurus for Multiplicity
Authors: Leinert Ch. , Weitzel N. , Haas M. , Lenzen R. , Zinnecker H. , Christou J. , Ridgway S.T. , Jameson R. , Richichi A.
Published: July 2016

We surveyed all stars in Taurus (3h 45m < α < 4h 15m, 15° < δ < 35°) for multiplicity which are contained in the Herbig-Bell catalogue of young stars and have a 2 micron brightness of K ≤ 9.5 mag. This sample consists of 106 stellar systems (single or multiple), of which 43 are double or multiple according to the criteria of our survey, i.e. with separations of ≈0″.2 ≤ d ≤ 10″. Of these, 23 binaries are new detections found in this survey. The resulting degree of multiplicity, 43/106 = 41±6%, is higher than found for main-sequence stars. Provided that the period distribution is the same for young stars as on the main sequence, our result implies that the vast majority of stars are born in binary or multiple systems.
A Comparative Study of Lithium Abundances, Radial Velocities, and Emission Lines in Pre-Main Sequence Visual Binaries
Authors: Martín Eduardo L. , Rebolo Rafael , Magazzù Antonio
Published: July 2016

High resolution (R ~ 20000) spectroscopic observations of visual pairs of T Tauri stars (TTS) in the spectral range 655-675 nm, and 385-405 nm for some systems, are reported. Good seeing allows us to resolve pairs with minimum angular separation of ~ 2″. The radial velocities, overall spectral properties and detection of the Li I line are used to decide whether the components of the binaries are likely to be gravitationally bounded. In this paper we present first results on a subset of our sample: 3 visual companions are not TTS, namely DL Tau/c, GG Tau/c(SW) and NTTS 45251+3016/c. The star GG Tau/c(S) is confirmed as a T Tauri star. The system UZ Tau is probably composed of at least 4 components. The star 1E0255.3+2018 (Fleming et al. 1989), previously thought to be single, is found to be a close visual binary. Finally, lithium abundances for the PMS components of 6 binaries are presented and their consistency with theoretical expectations is briefly discussed.
Duplicity Among Solar-Type Stars
Authors: Abt Helmut A. , Willmarth Daryl W.
Published: July 2016

From a new study of 113 F8-G1 IV or V primaries in an apparent-magnitude limited sample, measured with a CCD for about 20 radial velocities of accuracy 0.2-0.5 km s−1 each, we collected data for 28 binary orbits and 39 visual systems. We again found a flat distribution (or slightly decreasing toward lower masses) of secondary masses, unlike the Salpeter distribution for B2-B5 stars. But we find that the different distributions for these field stars and for open clusters of various ages can all be explained by a capture mechanism of binary formation.
Star-Disc Interactions and Binary Formation
Authors: Clarke Cathie
Published: July 2016

By the time a binary arrives on the main sequence, its dynamics have essentially become those of a simple two-body system, so that its orbital parameters are constants of the motion thereafter. This statement of course needs to be modified under several circumstances, such as where tidal effects, mass exchange or interactions with field stars come into play. For the majority of binaries, however, orbital evolution is all but over by the main sequence. Therefore, in order to explain the distribution of binary orbital parameters one has to look to earlier times (prior to 107 years) when the more complicated dynamics can drive the orbital evolution that establishes these parameters.
Searching for Optical Visual Double Stars
Authors: Sinachopoulos D. , Mouzourakis P.
Published: July 2016

We study a sample of 123 wide visual double stars for which astrophysical parameters are at least partly available from uvby Hβ photometry. All of these have components brighter than 10 mags and a component angular separation between 10 and 20 arcseconds.

We find that at least one third of them are optical; for relative proper motion (RPM) pairs this fraction is 60% or even more. These results are in fair agreement with the predictions we formulated in an earlier paper on the basis of a statistical criterion.
An Impression from Programmes Performed at ESO about the Interest of European Astronomers in Visual Double and Multiple Star Research
Authors: Van Dessel E.L.
Published: July 2016

The European Southern Observatory gives opportunity to the European astronomical community to use a large variety of instruments. In this paper we try to make an assessment about the proposals that show an interest in visual binary and multiple star research. The material is based on projects proposed and performed in the last 3 years. Main streams of research are: speckle measurements, radial velocities, photometry (completion of catalogues), and astrometric positions.
Survey for Duplicity Frequencies: Status and Prospects
Authors: Couteau Paul
Published: July 2016

I.

We recall the main surveys: J. Herschel (1826), W. Struve (1825), A.W. Burnham and G.W. Hough (1880), R.G. Aitken and W.J. Hussey (1910), R. Jonckeere and T.E. Espin (1910), W.H. van den Bos (1925), R.A. Rossiter (1950). Presently the classical surveys are continuing with P. Muller, W.D. Heintz, and P. Couteau. The interferometric survey with large telescopes is carried out at CHARA.

II.

The results of old surveys, up to 1950, amount to 700 known orbits out of more than 35000 found binaries. The new surveys since 1965, both visual and interferometric, had checked 4000 new binaries giving already about 30 orbits. The periods are shorter and shorter: the mean period is 200 years for Struve (1825) binaries, 75 years for Aitken’s (1910), 25 years for Couteau and Muller’s (1970), and 7 years for CHARA’s. The number of known orbits increases exponentially with time.

III.

The “classical” surveys will have to be performed again within fifty years with refractors.

The interferometric and aperture syntheses surveys will be able to observe every binary, even those in contact with each other. With HIPPARCOS’ results, astronomers will dispose of a complete set of data for new theories of stellar evolution.
A Study of the Motion of the Nearby Red Dwarf Lalande 21185
Authors: Shakht Natalia A.
Published: July 2016

A series of photographic observations spanning the interval 1962 – 1991 have been examined in a study of Lalande 21185, suspected to be a double or multiple object. The observed value of secular acceleration corresponds to the radial velocity of this star. The perturbations in proper motion with suspected period of 8 years have not been confirmed.
A Study of ADS 5983 (δ Geminorum)
Authors: Shakht Natalia A. , Kiyaeva Olga V.
Published: July 2016

Regular photographic observations of ADS 5983 (δ Gem) with the Pulkovo 26-in refractor have been made since 1972. The series of observations over the time interval 1972-1990 are considered. New orbital elements of the binary are obtained by the AMP–method. Some wave with a period about 5 years in the orbital motion of this star is found.
The Analysis of HST Fine Guidance Sensor Transfer Functions
Authors: Lattanzi M.G. , Bucciarelli B. , Holfeltz S.T. , Taff L.G.
Published: July 2016

We present an overview of the ST ScI calibration program and the reduction, smoothing, and analysis capabilities we have developed to deal with Transfer Functions. The Transfer Function (TF) is the name for the fringe visibility curve produced by the Koesters prism interferometer in the Fine Guidance Sensors (FGSs). The TF for a single, point, monochromatic source becomes modified — in different ways — when we observe a real source with a typical stellar energy spectrum, a finite disc, or a double system. Thus, we have constructed an in depth calibration program and designed and developed a comprehensive set of TF analysis algorithms. The ST ScI calibration program includes the acquisition of reference TFs at 19 different places in the astrometer FGS (there are field–dependent aberrations beyond the well–publicized spherical aberration of the primary mirror). In addition, for Cycle 2, both stars with finite angular diameters and minor planets will be observed. The software to implement our correlation–based analysis techniques has been extensively tested on artificial binary stars created by combining real TFs and re-introducing photon noise. A wide variety of synthetic binaries — with separations from 10 to 135 milli-arcseconds and magnitude differences from 0 to 4.2 mag — were used so that we can objectively and quantitatively characterize the capability of both the software and the instrument to resolve close pairs and to detect faint companions. Separations to a few milli-arcseconds, position angles to , and magnitude differences to are attainable for primaries brighter than V = 13 mag and Δm < 3 mag. The software is being incorporated into IRAF/STSDAS at the ST ScI.
Searching for X-ray Binaries in the LMC: The Optical Counterparts of CAL 9 and CAL E
Authors: Schmidtke Paul C. , Cowley Anne P.
Published: July 2016

To better define the global properties of X-ray binaries in the Large Magellanic Cloud, a program of optical identification has been initiated, combining improved X-ray positions from ROSAT with photometry and spectroscopy obtained at CTIO. This initiative is an extension of work by Cowley et al. (1984) and Crampton et al. (1985), who attempted to identify the optical counterparts of “CAL” X-ray point sources found in the Einstein IPC survey of the LMC conducted by Columbia Astrophysical Laboratory (Long et al. 1981). A key element in our investigation of the remaining unidentified sources is the use of significantly more accurate coordinates (typically ±5″ from ROSAT HRI data versus ±30″ for the older IPC positions), thereby greatly reducing the number of stars needing examination. Likely candidates are selected using multicolor photometry (by location in color–color plots or through variability) prior to spectroscopic observing. Although the identifications for CAL 9 and CAL E were reasonably secure (in particular the latter since it had an Einstein HRI position, see Crampton et al.), these sources have been re-observed to test our procedures and to verify the previous results.
Raw Data from HIPPARCOS Double and Multiple Stars
Authors: Bernacca P.L. , Donati F. , Mignard F.
Published: July 2016

The HIPPARCOS Input Catalogue comprises about 118,000 entries of which 16,000 are flagged as related to double or multiple stars. Data analysis begins by fitting Fourier model signals to the observations: the intensity coefficients and the phases at several locations on the spatial modulator are estimated and a first rough recognition of possibly unknown non-single stars is performed. After calibration corrections, a normal point is produced at every transit of a star across the field of view of the telescope and the improved parameters are stored for extensive multiplicity testing and relative astrometry when enough scans are accumulated.
HIPPARCOS First Results in the Double Star Photometry
Authors: Mignard F. , Falin J.L. , Froeschlé M.
Published: July 2016

In addition to its astrometric capabilities the HIPPARCOS main detector proves to be a good phototometer. The main features of the photometric reduction applied to double stars are outlined. We show how it is possible to discriminate single stars from multiple stars from the photometric signal. Results presented are based on about 16000 stars recognized as non-single, of which 8000 were not known to be double in the HIPPARCOS Input Catalogue. Magnitudes for multiple systems as a whole are derived with a precision usually better than 0.005 mag while the magnitude of each component is recovered up to magnitude difference of 3 mag, but with less accuracy and precision.
First Double Star Observations in the HIPPARCOS Tycho Project
Authors: Halbwachs Jean–Louis
Published: July 2016

The Tycho project will provide positions and (B, V) magnitudes for about 1 million stars, and will be complete for stars brighter than magnitude (B + V)/2 = 10.5. The components of double stars will obtain individual measurements when the separations are wider than 3″.
The Potential of Long–Baseline Optical Interferometry of Binary Stars
Authors: McAlister H.A.
Published: July 2016

Interferometric arrays possessing sub-milliarcsecond resolution are either about to be fully scientifically productive, as in the case of the Sydney University Stellar Interferometer, or are under various stages of planning and development. The 1990’s will thus witness a hundred–fold gain in resolution over speckle interferometry at the largest telescopes and 5,000 times the resolution of classical direct imaging. Where speckle interferometry can now resolve binary stars with periods of 1 to 2 years, interferometric arrays with baselines of hundreds of meters will resolve binaries with periods of a few hours. Arrays will resolve the majority of the known spectroscopic binaries, providing a substantial increase in the quantity and quality of stellar mass determinations. Surveys for new binaries among the field stars and other restricted samples will be accomplished with unprecedented completeness. The remarkable enhancement in resolution we are about to witness from facilities like SUSI and our own proposed CHARA Array will quite literally revolutionize the field of double and multiple star research.
Prospects for Rapid, Routine Speckle Photometry
Authors: Barry D.J. , Bagnuolo W.G. , Mason B.D. , McAlister H.A. , Turner N.H.
Published: July 2016

Image reconstruction techniques have rapidly matured over the last decade, and increasing reference to full–aperture and masked aperture results appear in the literature. Although anomalies in morphology are understood, most work uses nonlinear iterative refinements of questionable photometric robustness. Recent development of linear least–squares phase reconstruction techniques from the bispectrum (Glindemann et al. 1991) offers hope for a robust technique using a computational tour de force. However, the field cannot be considered mature until routine photometry of a large number of speckle–resolved objects is performed and demonstrated to be repeatable. We review our work and our expectations for use of both computationally intensive and simple techniques in our routine speckle reductions.
Binary Orbits from Interferometric Data
Authors: Hummel C.A. , Armstrong J.T.
Published: July 2016

Using the variable baseline of the Mark III Optical Interferometer (Shao et al. 1988) with lengths ranging from 3 to 31.5 m, we measured the fringe visibility of stars in three 25 nm bandpass filters, at wavelengths between 800 nm and 450 nm. This setup gives fringe spacings ranging from 55 mas to 3 mas.

255 stars brighter than fifth magnitude and north of –10° declination were selected from the Batten et al. (1989) catalog of spectroscopic binaries. We compiled values for the orbital axes from the McAlister & Hartkopf (1988) catalog. If unknown (in the majority of cases), they were estimated from the masses predicted from the spectral types, the periods (if known), and the distances to the binaries. Priority was given to the binaries with orbital axes between 3 mas and 40 mas. Observational procedures and the calibration of the data are described by Armstrong et al. (1992). Statistical and calibration uncertainties are in the range of 1% (red channel) to 10% (blue channel).
Speckle Observations of Triple Stars
Authors: Isobe Syuzo , Baba Naoshi
Published: July 2016

Our speckle observations were started in 1987 using a 212-cm telescope at San Pedro Martir Observatory in Mexico. A D-IMOSS camera was used until 1990 and an I-CCD camera was introduced in 1991. The old camera has only 0″.20 angular resolution because of an aging effect in its intensifier, while the new camera has 0″.06 angular resolution, which is nearly equal to the diffraction limit of the telescope. 128 visual binary stars and 755 spectroscopic binary stars have been observed. The numbers of stars and observations each year are shown in Table 1 and all the observed data are given in a series of papers by Isobe et al. (1990a, 1990b, 1992a) and Miura et al. (1992).
The Spectroscopic-Speckle Triple System HR 6469
Authors: Scarfe C. , Barlow D. , McAlister H. , Hartkopf W. , Fekel F. , Rees R. , Lyons R. , Bolton C.
Published: July 2016

HR 6469 consists of an evolved G5 star and a close pair of fainter stars, probably both on the main sequence. The period of the close pair is just over two days, and shallow eclipses have been detected (Boyd et al. 1985), although no analysis of the light curve has been published. The wide system has a period of about 5.5 years, and has been resolved by speckle interferometry (McAlister et al. 1983). The G5 star and the primary of the close pair are detectable in the spectrum, with the latter showing modest rotational broadening. Spectral types and rotational velocities for the evolved star and the brighter component of the close pair have been published by Strassmeier & Fekel (1990).
Photoelectric Photometry — The First Fifty Years
Authors: Hearnshaw J.B.
Published: July 2016

This historical review covers the first fifty years of the electrical measurement of starlight, which saw its beginnings in August 1892 when William Monck used a Minchin photovoltaic cell on his refractor in Dublin. The work of Stebbins using photoconductive cells from 1907 and of Guthnick, Stebbins and others using photoelectric cells from 1912 is also discussed. The advances brought about by thermionic amplification and the red-sensitive Cs-O-Ag photocathode in the early 1930s by respectively Whitford and Hall enabled new astrophysical problems to be tackled. Although many observers attempted photoelectric photometry, relatively few were successful during the 1920s and ‘30s. It was not until the introduction of the 1P21 photomultiplier tube that astronomers had a reliable and sensitive detector for photometric observations.
Atmospheric Intensity Scintillation of Stars on Milli- and Microsecond Time Scales
Authors: Dravins D. , Lindegren L. , Mezey E.
Published: July 2016

Stellar intensity scintillation on short and very short time scales (≃ 100 ms - 100 ns) was studied using an optical telescope on La Palma (Canary Islands). Photon counting detectors and real-time signal processing equipment were used to study atmospheric scintillation as function of telescope aperture size, degree of apodization, for single and double apertures, in different optical colors, at different zenith distances, times of night, and seasons of year. The statistics of temporal intensity variations can be adequately described by log-normal distributions, varying with time. The scintillation timescale (≃10 ms) decreases for smaller telescope apertures until ≃5 cm, where the atmospheric ‘shadow bands’ apparently are resolved. Some astrophysical sources may undergo very rapid intrinsic fluctuations. To detect such phenomena through the turbulent atmosphere requires optimized observing strategies.
Photometric and Spectrophotometric Data Required for the SUSI Programme
Authors: Shobbrook R.R.
Published: July 2016

The Sydney University Stellar Interferometer, SUSI, a modern version of a Michelson stellar interferometer, will be capable of measuring the angular diameters of stars down to V ≈ 8.0, for all spectral types. The resolution of the 640 m baseline — <0.1 milliarcsec at optical wavelengths — includes reasonable sample sizes of all spectral types and luminosity classes to this magnitude limit.

The angular diameter data require complementary photometric, spectrophotometric and also spectroscopic data for the determination of fundamental parameters of single and multiple stars. This paper discusses the accuracy required of these data for some of the main problems to be tackled by SUSI. A selection of the programmes planned for this unique instrument is listed below, where the need for complementary data is also indicated.

• The measurement of the changes of angular diameters of Cepheids and other pulsating stars such as Mira variables. Comparison with the linear changes determined from radial velocity curves will enable their distances and luminosities to be determined by an essentially geometric method.

• The measurement of the angular sizes of the orbits and of one or both components of spectroscopic binary stars. This effectively makes them ‘visual’ binaries so that the orbital inclination, i, may be determined. When these data are combined with the velocity curve solutions which include (mass)sin3i and (semi – majoraxis)sin i, we may determine masses and linear radii of one or both components and also the distances to the systems. Also, the light curve of an eclipsing binary provides information on the ellipticities and radii of the components and on the eccentricity of the orbit — information which may be used to aid the analysis of the SUSI data. In addition, the determination of the light curve (some bright systems have not been observed for up to one or two decades) is the quickest method of finding the current phase of its orbit.

• The establishment of the total-flux-based temperature scale of all spectral types and luminosity classes from O to M. This requires accurate photometry and spectrophotometry over as wide a wavelength range as possible; it therefore also requires observations from space observatories, as was also necessary for the analysis using the Narrabri intensity interferometer data (Code et al., 1976).

• The measurement of diameters of stars with shells or extended atmospheres, such as Be and Wolf Rayet stars, at different wavelengths — in particular, in the emission lines.
Robotic Observatories: Past, Present and Future
Authors: Genet Russell M. , Genet David R.
Published: July 2016

We briefly describe the history of robotic observatories, give details on an example of the current state-of-the-art in robotic observatories, and suggest several key areas for future development.
Transformations and Modern Technology
Authors: Tinbergen Jaap
Published: July 2016

Transformations are a central issue in making a global network do more than simple monitoring of low-amplitude variability. I explore the approach of observing at a much narrower instrumental bandwidth than is required for the scientific problem; such an approach would have the following advantages:

•

transformations can be handled in standard fashion at the instrumental level; at the scientific level, they can be avoided entirely,

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users have almost complete freedom in specifying the shape of the scientific passbands, hence comparison of observational data with stellar atmosphere models can be maximally effective,

•

standard star observations can be used repeatedly, for programmes running concurrently in different scientific photometric systems,

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an observer can use existing standard-star observations to create his own specially-tailored photometric system from scratch,

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all-sky homogeneity of the instrumental system can be tested against space photometry such as that provided by HIPPARCOS; this will benefit other scientific systems synthesized from the same instrumental system.

Key components in the hardware will be array detectors with low readout noise and a calibration lamp system designed specifically for this application. A data base provides the link between the observations (in the instrumental system) and the results (with scientific passbands defined by the end user).
Further Progress in CCD Photometry
Authors: Stetson Peter B.
Published: July 2016

I comment on some of the steps required to convert raw instrumental magnitudes, derived by profile-fitting or synthetic-aperture photometry from CCD images, to final calibrated photometry on a standard system. The status of the DAO program to obtain homogeneous BV photometry for star clusters and nearby galaxies will also be discussed.
CCD Time-Series Photometry of Faint Astronomical Sources
Authors: Howell Steve B.
Published: July 2016

Using CCDs to obtain time-series light curve information is an increasing area of interest in astronomy. For brighter, high signal-to-noise sources, the data collection and reduction procedures are very robust and easy to use. However, for fainter, low signal-to-noise objects we must resort to new methods. These include the use of optimum data extraction techniques, a fuller understanding of the CCD itself, and a more complete error model. This paper will provide a brief introduction to CCD time-series photometry and then explore the above new methods in relation to real observational situations.
Faint Photometry with the HST Wide Field Camera
Authors: Hughes S.M.G.
Published: July 2016

A series of 40 HST WFC exposures in v (F555W) and i (F785LP) have been obtained of two fields in M81, in order to search for Cepheid variables. This has provided an ideal opportunity to compare how the photometry programs DoPHOT and DAOPHOT cope with undersampled images, and present our ‘best solution’ to the problem of reducing WFC photometry for faint stars in crowded fields.
Supernova Rates
Authors: Van Den Bergh Sidney
Published: July 2016

Extragalactic supernova rates are reviewed. The main uncertainties in calculated rates are due to (1) the influence of the (still poorly known) luminosity function of supernova of a given type on “control times”, to (2) uncertain corrections for possible inclination - dependent bias in supernova discovery probabilities, and (3) interstellar absorption. The total supernova rate in late-type galaxies is found to be ∼ 2(H0/75)2 supernovae (SNe) per century per 1010LB(ʘ) This is consistent with the rate of 3 SNe per century that is derived from the historical data on Galactic supernovae. It is, however, a source of some concern that none of the three Galactic SNe expected to have occurred during the last century was actually observed!

The expansion velocities of SNe Ia are found to correlate strongly with parent galaxy Hubble type. This relation is in the sense that low expansion velocities are only observed for those SNe Ia that occur in early-type galaxies. This suggests that V(exp) correlates with the ages of SNe Ia progenitors. It is speculated that the progenitors of a few SNe Ia with high V(exp) values in E and S0 galaxies were formed during recent starbursts.

SNe Ia rates appear to be enhanced in post-starburst galaxies. It is suggested that supernova rates might be quite high in the recently discovered population of faint blue galaxies at intermediate redshifts.
Supernovae and the Cosmic Distance Scale
Authors: P. Kirshner Robert
Published: July 2016

Knowledge of the size and age of the Universe depends on understanding supernovae. The direct geometric measurement of the circumstellar ring of SN 1987A using IUE spectra and HST images provides an independent test of the Cepheid distance scale to the Large Magellanic Cloud. Understanding the details of the mass distribution in the circumstellar matter is important to improving the precision of this distance. Type la supernovae have a narrow distribution in absolute magnitude, and new Cepheid distances to IC 4182 (the site of SN 1937C) and to NGC 5253 (the site of SN 1972E) obtained with HST by Sandage and his collaborators allow that absolute magnitude to be calibrated. Comparison with more distant SNIa gives H0 = 56 ± 8 km s-1 Mpc-1. Recent work in supernova spectroscopy and photometry shows that the apparent homogeneity of SNIa is not quite what it seems, and a deeper understanding of these variations is needed to use the SNIa to best advantage. The Expanding Photosphere Method (EPM) allows direct measurement to each Type II supernova that has adequate photometry and spectroscopy. There are now 18 such objects. The sample of EPM distances from 4.5 Mpc to 180 Mpc indicates H0 = 73±6 (statistical) ±7 (systematic) km s-1 Mpc-1. Better understanding of supernova atmospheres can reduce the systematic error in this approach, which is completely independent of all other astronomical distances.
Towards the Cosmic Distance Scale through Nebular SNe
Ia
Authors: Ruiz-Lapuente P. , Filippenko A. V.
Published: July 2016

We give an update of current research on the use of nebular spectra of SNe la as distance indicators. Results of the application of the method to a group of SNe la are reported. We describe the status of the research including theoretical and observational requirements of the method. Our results point toward a shorter distance scale than methods based on the “standard candle” hypothesis for Type la SNe.
2D Simulations of Supernovae
Authors: Arnett David
Published: July 2016

Several multidimensional computations of hydrodynamics related to supernovae have been completed, and are summarized here. More detail may be found in Arnett 1994a,b, Arnett & Livne 1994a,b, and Livne & Arnett 1993. The hydro code PROMETHEUS is based upon an implementation of the piecewise-parabolic method (PPM) of Colella & Woodward 1984, as described in Fryxell et al. 1991. A detailed comparison of PPM with other schemes is given in Woodward & Colella 1984. The method constructs the physics of the flow between grid points by a nonlinear solution of the equations of continuity of mass, momentum and energy (the Riemann problem) rather than the usual mathematical approach of a Taylor expansion about the grid points. This gives it better resolution per grid point, which is highly desirable for multidimensional problems. Although the effort required per grid point is greater, the number of such points is less (often much less) for a given level of accuracy. Because the computational load per grid point is greater, more realistic physics (reactions, radiation, gravity, etc.) may be added before affecting the runtime significantly. Thus PPM is well suited for multidimensional problems with significant physics beyond the bare hydrodynamics.
Recent Advances in Supernova Theory
Authors: Burrows Adam
Published: July 2016

In this paper, I summarize two new developments in the theory of core-collapse supernovae. The first is the recent establishment of an analytic context for understanding neutrino-driven explosions. Converting the supernova problem into an eigenvalue problem, Burrows & Goshy (1993) have derived a critical condition on neutrino luminosity and mass accretion rate through a stalled bounce shock for instability and explosion. The second development is the recent calculation of Burrows & Pryxell (1993) of the boost in the neutrino luminosities by the Rayleigh-Taylor-like overturn of the shocked mantle of a protoneutron star. This boost may turn duds into explosions and may be the missing ingredient of supernova theory.
Instabilities and Mixing in Type II-P and II-b Supernovae
Authors: Shigeyama T. , Iwamoto K. , Hachisu I. , Nomoto K. , Saio H.
Published: July 2016

We calculate a nonlinear growth of the Rayleigh-Taylor instability in the exploding red supergiant stars with a two-dimensional hydrodynamical code, and examine how the extent of mixing depends on the progenitor's core mass and the envelope mass. The results are compared with the observations of type II-P supernovae and the recent type Il-b supernova 1993J.
Supernova Nucleosynthesis in Massive Stars
Authors: Hashimoto M. , Nomoto K. , Tsujimoto T. , Thielemann F.-K.
Published: July 2016

Presupernova evolution and explosive nucleosynthesis in massive stars for main-sequence masses from 13 Mʘ to 70 Mʘ are calculated. We examine the dependence of the supernova yields on the stellar mass, 12C(α, γ)16O rate, and explosion energy. The supernova yields integrated over the initial mass function are compared with the solar abundances.
X-Rays and γ-Rays from SN 1987A
Authors: Kumagai S.
Published: July 2016

Theoretical light curves and spectra of X-rays and γ-rays from SN 1987A are calculated by the Monte Carlo method, based on a model built up from the early observations of neutrinos and optical light. Comparison of the predicted radiation with observational results obtained later confirms the radiation mechanism of supernovae: γ-rays are emitted in the decays of radioactive 56Co and X-rays are generated by the Compton degradation of these γ-rays. It also suggests that large scale mixing occurred and clumpy structure was formed inside the ejecta. These findings lead us to construct the model with a new distribution of elements, which is determined through comparisons of observations of X-rays and γ-rays with numerical simulations based on the assumed distribution. Using this model, the subsequent X-ray and γ-ray emission is predicted: the light curves of X-rays and γ-rays as well as their spectral evolution are in very good agreement with that expected from the radioactive decays of 56Co and 57Co. The mass of newly synthesized 44Ti and the emission from the neutron star will be determined by future satellite and balloon-borne observations.
Supernova Remnants in Nearby Spiral Galaxies
Authors: Long Knox S.
Published: July 2016

Large samples of supernova remnants are needed in order to study the global distribution of supernovae in galaxies, for determining how the environment in which a SN explodes affects the appearance of a SNR, for studying abundances and abundance gradients in galaxies, for estimating SN rates, and in order to determine the energetics of SNRs and their expansion. Here we describe techniques which are currently being used to expand SNR samples in nearby spirals.
Observational Techniques and Results for Visual Double Stars
Authors: Worley Charles E.
Published: July 2016

A little more than a century and a half has passed since F.G.W. Struve began to provide the astronomical world with visual double star measures of both quantity and quality. Since that time, nearly a million individual measures have been made by all techniques, and most of these are now available in machine-readable form in the punch-card Observation Catalog maintained at the Naval Observatory. As of 1 March 1981, this Catalog contained 877242 measures grouped into 398818 means. The data file is now virtually complete for all 20th century observations, and perhaps 80% complete for the 19th century material. Additions are being made steadily and we can look forward to having a complete set of observations for every known double star in a few more years.