bluuebunny/crossref_metadata_2025 huggingface dataset:
Massive Stars in the MCs: What They Tell Us about the IMF, Stellar Evolution, and Upper Mass “Cutoffs”
Authors: Massey Philip
Published: July 2016

Studies over the past decade have shown that the initial mass function (IMF) is the same for massive stars born in the OB associations of the LMC and SMC as in the associations of the Milky Way: the slope of the IMF is essentially Salpeter (Γ ~ −1.3), despite the factor of 4 difference in metallicity between these systems, and despite a factor of several hundred in stellar density between the sparsest and richest OB associations. However, there does appear to be a number of massive stars that are born in relative isolation, and the IMF of this mixed-age, field population is quite different than that of OB associations, with Γ ~ −4 in all three galaxies. The distribution of stars in the HR diagram is in excellent agreement with the Geneva group's evolutionary models for stars with masses with no “main-sequence widening problem” left to be solved. The massive stars born in clusters are formed quite coevally (Δτ < 1–2Myr), which allows us to use the “turn-off masses” to determine what mass objects become Wolf-Rayet stars of various types, and new results are briefly described. For the LMC, WNEs come from a wide range of masses, WCs come only from the highest mass stars, and Ofpe/WN9 “slash” stars come from lower mass OBs. Recent work on the R136a cluster (described in Hunter's review talk) suggest that there is no such thing as an upper mass cutoff to the IMF, at least not one that has been found observationally: for the youngest clusters (2 Myr and younger), the mass of the highest mass star present is simply dependent upon how populous the cluster is; i.e., the IMF is truncated by statistics, not physics.
Massive Binary Stars in the Magellanic Clouds
Authors: Niemela V. S. , Morrell N. I.
Published: July 2016

We discuss the present status of knowledge for massive binary stars in the Magellanic Clouds. New data for known binaries, and radial velocity orbits for new binaries are reported.
Ultraviolet Imaging Telescope Observations of the Magellanic Clouds
Authors: Parker Joel Wm. , Hill Jesse K. , Cornett Robert , Hollis Joan , Zamkoff Emily , Bohlin Ralph C. , O'Connell Robert W. , Neff Susan G. , Smith Andrew M. , Stecher Theodore P. , Roberts Morton S.
Published: July 2016

We present an analysis of wide-field, far-ultraviolet images of the LMC and SMC obtained by the Ultraviolet Imaging Telescope. The photometric catalog of over 37,000 stars allows us to make large-scale, statistical studies of massive star formation in OB associations and in the field population. Our results show that: (1) the most probable slope for the initial mass function (IMF) of field stars is Γ = −1.80, slightly steeper than the Salpeter slope; and (2) there doesn't seem to be a single, unique IMF slope for stars in OB associations, with a range of values from Γ = −1.0 to −2.0. We also analyze the stellar vs. diffuse UV flux, and the population of OB star candidates in the field.
Comparison of Six Supersoft X-ray Binaries
Authors: Cowley A. P. , Schmidtke P. C. , Hutchings J. B. , Crampton D.
Published: July 2016

The supersoft X-ray sources are a distinct class of X-ray sources identified by ROSAT. They are characterized by very high luminosities (Lbol ~ 1038 ergs s−1) and black body temperatures of kT~ 30–60 eV. These sources are easily detected in the LMC and SMC because of the low column density of absorbing H gas. Thus, the samples found there are complete. They are much more difficult to find in the Galaxy due to soft X-ray absorption in the galactic plane.
A Photometric Survey of Field Stars in the Large Magellanic Cloud: Probing its Star-Formation History
Authors: Smecker-Hane T. A. , Gallagher J. S. , Cole Andrew , Stetson P. B. , Tolstoy E.
Published: July 2016

The Large Magellanic Cloud (LMC) is unique among galaxies in the Local Group in that it is the most massive non-spiral, is relatively gas-rich, and is actively forming stars. Determining its star-formation rate (SFR) as a function of time will be a cornerstone in our understanding of galaxy evolution. The best method of deriving a galaxy's past SFR is to compare the densities of stars in a color-magnitude diagram (CMD), a Hess diagram, with model Hess diagrams. The LMC has a complex stellar population with ages ranging from 0 to ~ 14 Gyr and metallicities from −2 ≲ [Fe/H] ≲ −0.4, and deriving its SFR and simultaneously constraining model input parameters (distance, age-metallicity relation, reddening, and stellar models) requires well-populated CMDs that span the magnitude range 15 ≤ V ≤ 24. Although existing CMDs of field stars in the LMC show tantalizing evidence for a significant burst of star formation that occurred ~ 3 Gyr ago (for examples, see Westerlund et al. 1995; Vallenari et al. 1996; Elson, et al. 1997; Gallagher et al. 1999, and references therein), estimates of the enhancement in the SFR vary from factors of 3 to 50. This uncertainty is caused by the relatively large photometric errors that plague crowded ground-based images, and the small number statistics that plague CMDs created from single Wide Field Planetary Camera 2 (WFPC2) images.
The Initial/Final Mass Relation for Stars with Different Initial Chemical Compositions
Authors: Frantsman Ju.
Published: July 2016

The initial/final mass relation (Mi–Mf) for small and intermediate mass stars depends strongly on the initial chemical composition (Z). Two factors play an important role in this effect: the dependence on Z of mass loss rates and the carbon-oxygen core initial mass. For heavy element abundances Z = 0.001 and Z = 0.02 the greatest differences of Mf and Mi are found between 1.5 < Mi/M⊙ < 4 and may be as great as 0.1 M⊙.
Expected Differences between AGB Stars in the LMC and the SMC Due to Differences in Chemical Composition
Authors: Frantsman Ju.
Published: July 2016

Certain aspects of the AGB population, such as the relative number of M and N stars, the mass loss rates, and the initial masses of carbon-oxygen cores, depend on the initial heavy element abundance Z. I have calculated synthetic populations of AGB stars for different initial Z values taking into consideration the evolution of single and close binary stars. I present the results of population syntheses of AGB stars in clusters as a function of different initial chemical compositions. The relation for the tip luminosity of AGB stars versus cluster age as a function of Z is presented and is used to determine the ages for a number of clusters in the LMC and the SMC, including clusters with no previous age determinations.
Star Clusters in the Magellanic Clouds
Authors: Da Costa G. S.
Published: July 2016

Recent results for the old and intermediate-age star clusters of the Magellanic Clouds are reviewed. Highlights include new evidence that the LMC old clusters are as old the Galaxy's halo globular clusters and the persistence of the LMC cluster “Age Gap” despite field star evidence for significant star formation during the cluster age gap epoch. For the SMC new data confirm the lack of significant change in cluster abundances with age prior to ~4 Gyr ago.
Numerical Simulation of the Global Star Formation Pattern in the LMC
Authors: Gardiner L. T. , Turfus C.
Published: July 2016

We have constructed a dynamical model of the LMC to examine the effects of an off-center bar perturbation on the global distribution of the gas and star formation activity. We find that a weak rotating bar potential, whose center is displaced by 0.6 kpc from the disk center, gives rise to an asymmetric spiral structure which mimics the observed chains of recent star formation as well as activity in the bar region.
New accuracy levels for solar system ephemerides
Authors: Standish E. M. , Newhall X X
Published: July 2016

DE403/LE403 is the latest JPL Planetary and Lunar Ephemeris. It represents a number of changes and improvements to previous JPL ephemerides: the reference frame is now that of the IERS, newer and more accurate observations are used in the adjustment process, some of the data reduction techniques have been refined, and improved dynamical modeling has been incorporated into the equations of motion. As a result, the internal accuracy of the inner four planets has been improved. Further, various measurements accurately tie Jupiter onto the IERS Reference Frame. In the future, use of CCD measurements and the Hipparcos Catalogue should improve the ephemerides of the outermost four planets.

DE403/LE403 has been integrated over 6000 years, from 3000 BC to 3000 AD. A more condensed representation has been made from this, named DE404/LE404. It replaces DE102 as the new JPL “Long Ephemeris”.
On the secular motion of the jovian planets
Authors: Ghil M. , Varadi F. , Kaula W. M.
Published: July 2016

The motion of the Jovian planets is investigated using Hamiltonian perturbation theory and numerical integrations. Experiments varying the mass of Neptune exhibit 1:1 secular resonance between the perihelion motions of Jupiter and Uranus.
The motion of Pluto over the age of the solar system
Authors: Kinoshita Hiroshi , Nakai Hiroshi
Published: July 2016

Pluto's motion is chaotic in the sense that the maximum Lyapunov exponent is positive and the Lyapunov time (the inverse of the Lyapunov exponent) is about 20 million years (Myr). We have carried out the numerical integration of Pluto over the age of the solar system (5.7 billion years towards the past and 5.5 billion years towards the future), which is about 280 times of the Lyapunov time. Our integration does not show any indication of gross instability in the motion of Pluto. The time evolution of Keplerian elements of a nearby trajectory of Pluto at first grow linearly with the time and then start to increase exponentially. These exponential divergences stop at about 420 Myr and saturate. The exponential divergences are suppressed by the following three resonances that Pluto has:

(1)

Pluto is in the 3:2 mean motion resonance with Neptune and the libration period of the critical argument is about 20000 years.

(2)

The argument of perihelion librates around 90 degrees and its period is 3.8 Myr.

(3)

The motion of the Pluto's orbital plane referred to the Neptune's orbital plane is synchronized with the libration of the argument of perihelion (a secondary resonance). The libration period associated with the second resonance is 34.5 Myr.

We briefly discuss the motions of Kuiper belt objects in a 3:2 mean motion resonance with Neptune and several possible scenarios how Pluto evolves to the present stable state.
Pluto's Lyapunov numbers in different dynamical models
Authors: Dvorak R. , Lohinger E.
Published: July 2016

We present the results of numerical integrations of Pluto and some fictitious Plutos in three different models (the circular and the elliptic restricted three body problem and the outer solar system). We determined the “extension” of the stable region in these models by means of the Lyapunov Characteristic Numbers and by an analysis of the orbital elements.
Theory compression with elliptic functions
Authors: Brumberg Victor A.
Published: July 2016

Introduction of Jacobi elliptic functions in planetary, satellite and cometary problems of celestial mechanics is a transformation of variables to present the analytical theories of motion in the more compact form as compared with the traditional series in multiples of mean longitudes or mean anomalies.
Pulsars and solar-system ephemerides
Authors: Chandler J.F.
Published: July 2016

The analysis of pulsar time-of-arrival data is intimately bound up with planetary ephemerides. Highly accurate ephemerides are required for Earth and Moon and, to a lesser degree, for the other planets, in order to make full use of the timing data for millisecond-class pulsars. These data, in turn, present an opportunity for improving planetary ephemerides in a variety of ways. Fitting the Earth and Moon orbital parameters to the timing data is the obvious first step, though it is less valuable in the short term for many applications than using the current accumulation of spacecraft-tracking and lunar laser ranging data. By themselves, the pulsar timing data convey no information on the orientation of Earth's orbit, since each pulsar's position on the sky must be determined from those same data. However, independent pulsar position measurements by VLBI, in combination with the timing-derived positions, can serve to fix the orientation of Earth's orbit with respect to the radio reference frame and thereby link the planetary and radio frames. In the long run, the acquisition of timing data over increasing time spans and with improving precision should prove to be an important factor in determining the shape, as well as the orientation, of Earth's orbit. In addition, pulsar timing over a sufficiently long span can directly measure a planet mass through the reaction of the rest of the solar system. The effect must be observed for a major fraction of the orbital period of the planet in question so that the signature can be separated from that of the ordinary spin-down of each pulsar. Finally, pulsar timing can be used to probe gravitational physics, a field with far-reaching consequences and a basic part of the framework for constructing the ephemerides.
Reviewing the theories of motion of the satellites of Saturn
Authors: Duriez L.
Published: July 2016

The state of knowledge of the motions of all Saturn's satellites is presented (excluding however the rings and their relating shepherding satellites). In particular, it appears that the theory of motion of the major satellites is now more precise than the available Earth-based observations, allowing to expect new progress with the next observations from mutual events and then with those from the Cassini mission.
Dynamics and orbital evolution of Oort cloud comets
Authors: Zheng J.Q. , Valtonen M.J. , Mikkola S. , Rickman H.
Published: July 2016

Investigators generally conjecture a steady flux of new comets from the Oort cloud through the inner Solar system. Due to gravitational perturbations by major planets these objects may escape, become long period comets (LPCs) if their orbital periods P are larger than 200yr or become short period comets (SPCs) when their period is less than 200yr. SPCs are further divided in two types: the Halley type comets (HT, for P > 20yr) and the Jupiter family comets (JF, for P < 20yr).
Dynamical screening of interactions in gravitating systems and the ephemeris time
Authors: Vityazev A.V. , Bashkirov A.G.
Published: July 2016

The concept of the screening of interparticle interactions has its origin in electrolyte and plasma theories. The most known example is the Debye-Hückel screening of the potential of the resting test charge provided with the availability of charges of the opposite sign and the total electroneutrality of the plasma. When this charge is moving, the static Debye screening decreases and an anisotropic dynamic screening develops due to excitation of waves of charge density. As a result, an effective potential of the positive moving ion becomes alternating with a characteristic length of space oscillations of order of the Debye length (Peter, 1990). Such dynamic screening is due to perturbations of charges of both signs by the varying field of moving test charge. This effect does not call for an electroneutrality of the system and is associated with the long-range character of the Coulomb interaction potential only.
Controlling the observational data on minor planets with the “CERES” software package
Authors: Chernetenko Yu. , L'vov V. , Shor V. , Smekhacheva R. , Tsekmejster S.
Published: July 2016

CERES is a powerful software package for calculating the ephemerides of the major planets, minor planets and comets and for executing related tasks.
Radar Astrometry of Asteroids, Comets and Planetary Satellites
Authors: Ostro Steven J.
Published: July 2016

Groundbased radar has considerable astrometric potential for asteroids, comets and natural satellites that enter the detectability windows of available telescopes. For very closely approaching asteroids and comets, measurements of the distribution of echo power in time delay (range) and Doppler frequency (radial velocity) can achieve a fractional precision between 10−5 and 10−9, and consequently are invaluable for refining orbits and prediction ephemerides. Even for mainbelt asteroids and the more readily detectable planetary satellites whose orbits are very well known, radar can collapse range uncertainties from a few target radii to a few percent of a target radius, with direct implications for the navigation of spacecraft on flyby or rendezvous trajectories.
Astrometry by asteroid occultations
Authors: Kristensen L. Kahl
Published: July 2016

For the determination of the dynamical equinox in fundamental star catalogues observed by astrometric satellites it is proposed to observe occultations of stars by selected asteroids. Being a long term programme now is the time for planning. Quadrature observations and photometric back-up are essential.
Hipparcos minor planets: Towards an improvement of the model analysis by detecting influence factors
Authors: Bougeard M. L. , Bange J.-F. , Mahfouz M. , Bec-Borsenberger A.
Published: July 2016

In order to evaluate a possible rotation between the Hipparcos and the dynamical reference frames, Hipparcos minor planets preliminary data are analysed. The resolution of the problem is very sensitive to correlations induced by the short length of the interval of observation. Several statistical methods are performed to appreciate the factors of bad conditioning. A procedure for variable selection and model building is given.
Indirect linking of the Hipparcos catalog to extragalactic reference frame via Earth orientation parameters
Authors: Vondrák J.
Published: July 2016

The indirect method of linking the Hipparcos reference frame to the frame defined by extragalactic sources is described. To this end, two independent time series of Earth orientation parameters observed by two different techniques with respect to the two reference frames are used: a) Optical astrometry observations (referred to Hipparcos stars), b) VLBI observations (referred to extragalactic objects). The parallel use of both techniques during the last decade enables to determine the orientation of the two reference frames at a fixed epoch and their mutual slow rotation with precision of at least 1mas and 1mas/year, respectively. In order not to raise confusion, the potentiality of the method is demonstrated on the example based on the star catalogues originally used at the participating observatories, not on any of the existing preliminary versions of the Hipparcos catalog.
The Prospects of Large Surveys in Astronomy
Authors: Harwit M.
Published: July 2016

Major astronomical discoveries of the past have been closely linked with the implementation of strikingly powerful new observational techniques in astronomy. Surveys, in general, were not as likely to lead to the discovery of new phenomena. In recent years, however, many far-reaching instrumental advances have been incorporated into observatories in space, whose mission, in part, was to conduct unbiased surveys. Here, we provide a review of some of the successes of earlier surveys, with the purpose of identifying the relative extent to which increased instrumental capabilities, as contrasted to increased sky coverage or numbers of sources observed, may be expected to lead to the discovery of new phenomena. A similar comparison can be made of the extent to which these two approaches—emphasis on instrumental capabilities, as contrasted to emphasis on sky coverage— also contribute to an increase in astrophysical understanding. Here, the distinction needs to be made between discovering a new phenomenon and understanding its underlying processes.
The Miyun 232 MHz General Catalogue: A Reliability and Positional Uncertainties Study
Authors: Peng B. , Yuan W. , Nan R. , Yan Y.
Published: July 2016

A meter-wave sky survey of the region north of declination +30°, excluding only four fields straddling the Galactic plane (each 8° × 8° in angular size), has been conducted with the Miyun Synthesis Radio Telescope operating at 232 MHz. The reduced Miyun General Catalogue contains 34,426 radio sources in total. To distinguish which sources were not observed by other sky surveys, we first identify sources in the MGC with those in the 6C (151 MHz) catalogue, using a matching radius of 100 arcseconds. The remaining MGC objects were then matched with the B2/B3 (408 MHz), 4C (178 MHz), Texas (365 MHz, 1400 MHz) and 87GB (4.85 GHz) catalogues. 6850 MGC sources were found to lack any radio counterpart in these reference catalogues. It means 19.9% of sources listed in the MGC are probably new.
The UTR-2 Very Low Frequency Sky Survey and Its Main Results
Authors: Sokolov K.P.
Published: July 2016

During the past decade there has been a dramatic increase in the amount of high-frequency (v > 1000 MHz) data currently underlying the studies of bright compact sources (Tb ∼ 1011–12K, l ≤ 1 kpc) with flat spectra. But in order to determine physical conditions inside extragalactic radio sources at different stages of their evolution the studies of old extended (l ∼ 100 kpc) sources with low surface brightness and steep spectra which constitute the dominant radio source population at very low frequencies (v ≪ 100 MHz) are also needed. These sources are known to represent the final stage in the evolution of extragalactic objects.
Lamost Project
Authors: Chu Y. , Zhao Y.-H.
Published: July 2016

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project is a Chinese National Big Scientific Project. It has been recently been approved by The National Committee of Science and National Committee of Planning. LAMOST will get funds from our government and will start at the end of 1996. We expect to finish this project within 7 years. Here we describe the LAMOST project briefly.
Arops : The ASIAGO Red Objective-Prism Survey
Authors: Munari U. , Passuello R.
Published: July 2016

AROPS is an objective-prism survey conducted at high galactic latitudes with the 67/92 cm (f=205 cm) Schmidt telescope of the Asiago Astrophysical Observatory (Italy). The basic technical data are:

– TP4415 high resolution plates, 20×20 cm, treated in forming gas (H2+N2) and covering 24 deg2 on sky

– 4° UBK7 objective prism, for a dispersion of 1490 Åmm−1 at NaI D

– blue side cut-off at 4980 Å using a 2mm GG14 filter, for a recorded λ range 5000–7000 Å

– untrailed spectra to record V ∼ 16.5 mag stars with 40 min exposures
Tracing the Interstellar Medium in Ophiuchus Across 14 Orders of Magnitude in Frequency
Authors: Digel S.W. , Hunter S.D. , Snowden S.L.
Published: July 2016

The spectral range of ground and space-based observations has expanded rapidly in recent years. Essentially complete sky coverage is available in bands spanning more than 14 orders of magnitude in frequency, with varying sensitivities and resolutions. Remarkably, extended emission (and absorption) associated with the interstellar medium can be seen across this range. This poster illustrated the range of information now at hand for just a single interstellar cloud complex, that in Ophiuchus. This complex, well known for its abundant on-going star formation, is relatively nearby (∼125 pc), and well removed from the plane, offering the advantages of large angular size and little confusion in most bands from background Galactic emission.
A Large-Scale CO Imaging of the Galactic Center
Authors: Oka T. , Hasegawa T. , Sato F. , Yamasaki H. , Tsuboi M. , Miyazaki A.
Published: July 2016

Molecular gas in the Galactic center region is spatially and kinematically complex, and its physical conditions are distinctively different from those of molecular gas in the Galactic disk (e.g., Morris 1996). Relative paucity of current star formation activity, despite the abundance of dense molecular gas in this region, is one of the problem at issue.
Survey of Fine-Scale Structure in the Far-Infrared Milky Way
Authors: Waller W.H. , Varosi F. , Boulanger F. , Digel S.W.
Published: July 2016

What is the general morphology of the diffuse interstellar medium? Is it mostly uniform or clumpy? Are the clumps mostly in the form of spheroidal clouds, sinuous filaments, extended sheets, or discrete shells? And do the clumps or the voids better define the overall structure? By addressing these morphological questions, one can better constrain the dynamical processes that are most responsible for shaping and energizing the ISM.
Multiwavelength Milky Way: An Educational Poster
Authors: Leisawitz D. , Digel S.W. , Geitz S.
Published: July 2016

The Astrophysics Data Facility at NASA Goddard Space Flight Center supports the processing, management, and dissemination of data obtained by past, current, and future NASA and international astrophysics missions, and promotes the effective use of those data by the astrophysics community, educators, and the public. Our Multiwavelength Milky Way poster was printed for broad distribution. It depicts the Galaxy at radio, infrared, optical, X-ray, and gamma-ray wavelengths. In particular, the poster contains images of the Galactic 21-cm and CO (J = 1 → 0) line emission, and IRAS 12, 60, and 100 μm, COBE/DIRBE 1.25, 2.2, and 3.5 μm, Digitized Sky Survey optical wavelength, ROSAT/PSPC 0.25, 0.75, and 1.5 keV X-ray, and CGRO/EGRET E > 100 MeV gamma ray broadband emission. All of the data sets are publicly available. Captions describe the Milky Way and what can be learned about the Galaxy from measurements made in each segment of the electromagnetic spectrum. The poster is intended to be an educational tool, one that will stimulate heightened awareness by laypersons of NASA's contribution to modern astronomy.

Through an interface available on the World Wide Web at http://adf.gsfc.nasa.gov/adf/adf.html one may view the images that appear on the poster, read the poster captions, and locate the archived data and references.
The Evolution of Quasars and Their Clustering
Authors: Osmer P.S.
Published: July 2016

George Djorgovski's message to me on behalf of the organizing committee suggested that I discuss 1) Evolution of the Quasar Luminosity Function; 2) Possible Differences among Radio-Loud, Radio-Quiet, and X-Ray Selected Samples; 3) Quasars as Probes of Clustering and Large-Scale Structure at High Redshift; 4) Searches for Extremely Distant Quasars; 5) Theoretical Implications; 6) Major Surveys in Progress and Planned; and 7) What Surveys Should We Do in the Future. To cover all these topics in a 25-minute talk and 7-page article is a challenge, but I am happy to try.
Towards a Better Understanding of Active Galactic Nuclei
Authors: Padovani P.
Published: July 2016

Active Galactic Nuclei (AGN) are ideal sources for multi-wavelength studies as their emission can cover almost 20 orders of magnitude in frequency from the radio to the γ-ray band. After reviewing their basic properties, I will assess how well we know the multifrequency spectra of AGN as a class. I will then briefly illustrate how currently available and forthcoming sky surveys will help in addressing some of the open questions of AGN studies. Finally, an analysis of the problem of the missing Type 2 QSO will exemplify the dangers of monochromatic sky surveys for AGN.
The Scaling Relations for Clusters of Galaxies
Authors: Annis J.
Published: July 2016

The dominant baryonic component of clusters of galaxies is their X-ray emitting atmosphere. X-ray surveys have made it possible to examine this component in large samples of clusters. David et al. (1993) provided a catalog of X-ray temperatures. I have measured 79 clusters from that list using Einstein IPC data (Harris et al. 1990), determining several measures of the radius. The most useful turns out to be the Petrosian radius. Given a radius, one can measure the surface brightness at that position.
The K-Band Luminosity Function of Galaxies
Authors: Gardner J. P. , Sharples R. M. , Frenk C. S. , Carrasco B. E.
Published: July 2016

The luminosity function of galaxies is central to many problems in cosmology, including the interpretation of faint number counts. The near-infrared provides several advantages over the optical for statistical studies of galaxies, including smooth and well-understood K-corrections and expected luminosity evolution. The K–band is dominated by near-solar mass stars which make up the bulk of the galaxy. The absolute K magnitude is a measure of the visible mass in a galaxy, and thus the K–band luminosity function is an observational counterpart of the mass function of galaxies.
Kiss: A New Digital Survey for Emission-Line Objects
Authors: Kniazev A. , Salzer J. , Lipovetsky V. , Boroson T. , Moody J. , Thuan T. , Izotov Yu. , Herrero J. , Frattare L.
Published: July 2016

We have initiated a major new survey for emission-line galaxies (ELGs) which we call the KPNO International Spectroscopic Survey (KISS). Survey observations began in March 1994 with the 0.61-m Burrell Schmidt telescope. The technique we employ combines the benefits of a traditional photographic objective-prism survey with the advantages of using a CCD detector. The field of view of our CCD is 1.1° square, and the prism employed provides a dispersion of 19 Å/pixel at 5000 Å. The spectral range covered (4800-5500 Å) is restricted by a specially designed filter that transmits from rest-frame Hβ to just shortward of the strong night-sky line at 5577 Å; this greatly reduces the sky background. We expect KISS to be sensitive to galaxies with magnitudes as faint as B = 20m–21m, much deeper than existing photographic surveys. Our initial pilot project covers 100 square degrees (Salzer et al. 1994) and overlaps the CfA/Dartmouth Century Redshift Survey (α = 8h30m–16h45m and δ = 29°–30°) in the North Galactic cap.
The Warps X-Ray Survey of Galaxies, Groups, and Clusters
Authors: Horner D. , Scharf C.A. , Jones L.R. , Ebeling H. , Perlman E. , Malkan M. , Wegner G.
Published: July 2016

We have embarked on a survey of ROSAT PSPC archival data searching for all detected surface brightness enhancements due to sources in the innermost R ≤ 15′ of the PSPC field of view in the energy band 0.5–2.0 keV. This project is part of the Wide Angle ROSAT Pointed Survey (WARPS) and is designed primarily to measure the low luminosity, high redshift, X-ray luminosity function of galaxy clusters and groups. Accurate measurements of the high redshift XLF would allow the form of the XLF evolution to be determined via the position of the Schechter function break. This would help discriminate between luminosity and density evolution, and discriminate between different hierarchical models, e.g., those including a different mix of fundamental particles, a flat power spectrum of the initial fluctuations, and reheating of the intracluster gas at high redshifts.
The ESO Slice Project (ESP) Redshift Survey
Authors: Vettolani G. , Zucca E. , Cappi A. , Merighi R. , Mignoli M. , Stirpe G. , Zamorani G. , MacGillivray H. , Collins C. , Balkowski C. , Cayatte V. , Maurogordato S. , Proust D. , Chincarini G. , Guzzo L. , MacCagni D. , Scaramella R. , Blanchard A. , Ramella M.
Published: July 2016

The ESO Slice Project (ESP) is a galaxy redshift survey we have recently completed as an ESO Key-Project over about 30 square degrees, in a region near the South Galactic Pole (Vettolani et al., submitted to A&A). The survey is nearly complete to the limiting magnitude bJ = 19.4 and consists of more than three thousands galaxies with reliable redshift determination.
Exposing New Components of the X-Ray Background with Multi-Wavelength Sky Surveys
Authors: Moran E.C.
Published: July 2016

The evolving class of objects responsible for the majority of the cosmic X-ray background (XRB) remains at large nearly three and a half decades after the discovery of the XRB. Surveys of sources selected on the basis of their X-ray properties alone provide an unbiased picture of the X-ray sky, but to date they have not been ideal for the discovery of rare types of X-ray sources at faint fluxes: large-area X-ray surveys have been restricted to bright sources, while deep X-ray surveys have been limited to very small patches of sky. X-ray selection coupled with another selection criterion, e.g., a radio or infrared detection, complements “pure” X-ray surveys by (1) permitting the exploration of large areas of sky to faint flux limits for types of extragalactic X-ray sources not well represented in other surveys, and (2) assisting the location of the optical counterparts of these X-ray sources. Using this approach, I have searched for new components of the XRB among the faintest X-ray sources detected by the Einstein Observatory.
Wading Through the Quagmire of Schmidt-Plate Coordinate Systematics
Authors: Lu C.-L , Platais I. , Girard T.M. , Kozhurina-Platais V. , Van Altena W.F. , López C.E. , Monet D.G.
Published: July 2016

We attempted to quantify the magnitude-dependent systematics in a sample of Schmidt plates by comparison to positions from the Yale/San Juan Southern Proper Motion program which offers star positions and absolute proper motions down to B = 18 with a mean density of about 50 stars per square degree and a positional accuracy of 0.1″ (Platais et al. 1995).
The Rosat All-Sky Survey Bright Source Catalog
Authors: Voges W. , Aschenbach B. , Boller Th. , Bräuninger H. , Briel U. , Burkert W. , Dennerl K. , Englhauser J. , Gruber R. , Haberl F. , Hartner G. , Hasinger G. , Kürster M. , Pfeffermann E. , Pietsch W. , Predehl P. , Rosso C. , Schmitt J.H.M.M. , Trümper J. , Zimmermann U.
Published: July 2016

In order to ensure the quality of the source catalogue derived from the SASS processing an automatic as well as a visual screening procedure was applied to 1378 survey fields. Most (94%) of the 18,811 sources were confirmed by this screening process. The rest is flagged for various reasons. Broad band images are available for a subset of the flagged sources. Details of the screening process can be found at www.rosat.mpe-garching.mpg.de/survey/rass-bsc/doc.html.
Cross-Correlation of Large Scale Surveys: Radio-Loud Objects in the Rosat All Sky Survey
Authors: Brinkmann W. , Yuan W. , Siebert J.
Published: July 2016

There are basically two different approaches to study the physical conditions and the energy transfer processes operating in astronomical objects:

– the detailed observations of a few prominent objects over a wide wavelength range.

– the study of the broad band properties of suitably choosen samples
The Aladin Interactive Sky Atlas
Authors: Bonnarel F. , Ziaeepour H. , Bartlett J.G. , Bienaymé O. , Crézé M. , Egret D. , Florsch J. , Genova F. , Ochsenbein F. , Raclot V. , Louys M. , Paillou P.
Published: July 2016

The subject of this symposium, Multi-Wavelength Sky Surveys naturally invokes a discussion of methods of astronomical object identification and classification: Given a set of objects detected at a certain waveband, how does one integrate the new sources with previous data? The ALADIN system (Paillou et al. 1994) of the CDS is a software package designed to tackle this problem: It provides simultaneous access to digitized sky photographs, catalogs and databases to facilitate direct, visual comparison of user data with previously classified data, as well as automatic source extraction and calibration tools.
Surveys in the ADC Archive
Authors: Roman N.G.
Published: July 2016

The ADC archive contains more than 800 catalogs and extensive tables from more than 750 journal articles. The archive is increasing steadily at the rate of about 20 data sets per month. This archive can be accessed either by anonymous FTP or by a World Wide Web (WWW) browser at http://adc.gsfc.nasa.gov/
Southern emission line flux standards
Authors: Dopita M. A. , Hua C. T.
Published: July 2016

Absolute emission line imaging photometry is often made difficult by the absence of good flux standards. Even bright PN often show as much as 25between different authors, reflecting the varying techniques of observation. In order to correct this situation, we have made slitless absolute spectrophotometric observations at high dispersion of compact (!5 arc sec. diameter) PN drawn from the Acker al. (1992) Catalogue. The complete results will appear in the Astrophysical Journal Supplement Series in early 1997. This paper gives absolute Hα, Hβ line fluxes, equivalent widths, accurate radial velocities, and relative fluxes of a number of other emission lines for some 50 PN in the southern sky between 7hr and 17hr in R.A.
Extinction distances: partly new access to an old problem
Authors: Kerber F. , Kienel C. , Weinberger R. , Danner R.
Published: July 2016

The distance determination to planetary nebulae (PNe) remains a serious problem as illustrated during the last IAU symposium in 1991 (Terzian, IAU 155, p.109). Since then the situation has not improved significantly. The number of stars for which reddening and spectral data are available, though, has increased tremendously over the last decade. Using data from the literature we have determined extinction distances for more than 50 PNe. The extinction distance method has been pioneered by Lutz (ApJ 181, 135 (1973)) and Acker (A&AS 33, 367 (1978)). The basic assumption of the extinction method is that a reddening vs distance relation (RDR) exists along the line of sight to a given object. Once this relation and the reddening of the object itself is known, a distance to the object can be derived. Gathier et al. (A&A 157, 171 (1986)) present a thorough discussion of the advantages and possible problems of the method. The most recent contributions are by Martin (A&A 281, 526 (1994)) and Saurer (A&A 297, 261 (1995)).
Self-consistent determination of distances and central star parameters for a large sample of Galactic Planetary Nebulae
Authors: Malkov Yu.F.
Published: July 2016

The distances, central star parameters Tef, log g, L∗, M∗, and optical thicknesses of the envelopes in the Lyman limits of hydrogen and helium are determined in a self-consistent way for 156 planetary nebulae (PNe) in our Galaxy (129, 22, and 5 PNe in the galactic disk, bulge, and halo respectively). For each nebula, the distance is adjusted in such a way that the theoretical evolutionary age of the central star (CS) should be equal to the dynamical age of the expanding nebular envelope (Malkov, 1994). This method combines the individual approach to each nebula with the possibility of application to a large sample of PNe. Some improvements have been introduced in the method as compared with its original version. The evolutionary tracks and time scales for CS with masses of 0.605, 0.696, 0.836, and 0.940 M⊙ were taken from Blöcker (1995). The change of the nebular expansion velocity during the evolution of a PN was roughly taken into account. The effective temperature of the CS and related parameters were found by the generalized energy balance method (Malkov et al., 1995) or, in appropriate cases, by Zanstra methods. Observational data have been collected from 93 papers published in 1975–1995.
An empirical analysis of the stellar wind and Planetary Nebulae of the [WC10] central stars CPD–56° 8032 and He 2–113
Authors: de Marco Orsola , Barlow M. J. , Storey P. J.
Published: July 2016

[WC] stars are H–deficient central stars of PN which have developed a dense, fast stellar wind. Their spectra can mimic the spectra of massive (Min∼5OM⊙) Wolf-Rayet stars of the carbon sequence. Deriving their parameters is of importance both in understanding the PN and the Wolf-Rayet phenomena. Spectra of both objects were obtained at the AAT in May 1993 with the UCL Echelle Spectrograph (3500–9200 å, R=50,0000). The reddening, determined from comparing the Hβ nebular line fluxes with radio fluxes from Purton et al. (MNRAS 128, 321, 1982), yielded E(B-V)=0.68 (CPD–56° 8032) and 1.00 (He 2–113). Distances are derived using two different methods and they agree within the relative uncertainties. They are 1.35 and 1.50 kpc for CPD–56° 8032 and He 2–113, respectively. The electron temperatures of the C ii line formation region in the wind is derived from a recombination line analysis (20,000 and 17,000 K for CPD–56° 8032 and He 2–113, respectively). From the same stellar wind recombination line analysis, we find C/He=0.12 and 0.16, together with O/He=0.19 and 0.25, for CPD–56° 8032 and He 2–113 respectively.
The companion to the central star of Abell 35
Authors: Gatti A. A. , Drew J. E. , Lumsden S. , Marsh T. , Moran C. , Stetson P.
Published: July 2016

Close binary systems may undergo the “Common Envelope” (CE) phase when the primary star expands on the red giant branch or the asymptotic giant branch. Filling its Roche Lobe, the primary transfers mass to the companion driving it out of thermal equilibrium and causing it to expand as well. The giant core and the companion star become surrounded by a CE. When sufficient energy is deposited in the circumstellar material this will be ejected and the binary orbit will shrink further (see review by Iben 1995). Planetary nebulae (PNe) with short-period binary nuclei are considered the most probable post-CE candidates. Abell 35, Lotr 1 and Lotr 5 (the Abell 35-like objects) are the only three PNe with binary nuclei known to contain a very hot UV-bright primary and a chromospherically active, rapidly rotating, G-K companion that dominates the optical spectrum. The origin of these unusual systems is unclear and hence presents a challenge to theories of binary star evolution. Identified in 1966 by Abell, Abell 35 is possibly the largest PN known (D=1.6 pc at a distance of 360 pc, Jacoby 1981) and also the oldest (the kinematical age is 185.000 years from the small expansion velocity of 4.2 km/s, Bohuski 1974). The bright giant star BD −22° 3467 (mv = 9.6mag) lies off-center within the nebula. A white dwarf was detected at the same location in 1988 in IUE spectra obtained by Grewing and Bianchi. BD − 22° 3467 has a vsin i of 90 km/s (Vilhu et al. 1991), variable Hα and Ca II emission lines associated with chromospheric activity, and a variable light curve (P=0.76 days, Jasniewicz and Acker 1988) probably produced by the rotation of the giant star. All attempts to determine the orbital period have failed, raising doubts as to whether the nucleus of Abell 35 is a close binary at all. In pursuit of this point, we have started a radial velocity study of the giant companion.
Turbulent outflows from [WC] nuclei
Authors: Grosdidier Y. , Acker A. , Moffat A.F.J. , Chesneau O. , Dimeo T.
Published: July 2016

In the framework of the extensive study of [WC]-type nuclei of planetary nebulae undertaken since 1993 by Acker and collaborators, we report wind fluctuations for the two brightest late-type [WC] stars in the sky, observed at Observatoire de Haute-Provence (OHP, France) and Observatoire du mont Mégantic (OMM, Canada). In particular we confirm Balick et al.'s (1996, AJ, 111, 834) CIIIλ5696 line profile variations for the [WC8] nucleus of NGC 40. Moving features seen on the top of this line are interpreted as outflowing “blobs” which are accelerated in the WR wind. Kinematic parameters have been derived and compared to those observed for massive WR stars. This will be discussed in a forthcoming paper (Grosdidier et al., 1996, in preparation). Assuming the average motion of the blobs reflects the global wind expansion and adopting the ad hoc β velocity law, we find that the exponent β must be larger than 3 in order to fit the measured radial accelerations (up to ∼ 0.08 km s–2). Evidence for clumping in the wind of the [WC9] nucleus BD+30°3639 is shown for the first time and presented in Acker et al. (1996, A&ALetters, in press). In contrast to NGC 40, the clumps in this star show very low acceleration.
The variable “hybrid” PG 1159 star HS 2324+3944
Authors: Handler G. , Kanaan A. , Montgomery M. H.
Published: July 2016

HS 2324+3944 is one of only four “hybrid” PG 1159 stars. The latter objects are a subgroup of DO white dwarfs. The spectra of “hybrids” show an He ii/C iv absorption trough similar to the “classical” PG 1159 stars, but also strong Balmer lines (Napiwotzki & Schönberner 1991).
Chemical abundances of cold stars in binary nuclei of Abell 35–type Planetary Nebulae
Authors: Jasniewicz G. , Thévenin F. , Acker A.
Published: July 2016

Jasniewicz et al. (1994) have announced and started in 1994 a program of chemical analysis of the G-stars at the centre of Abell 35-type planetary nebulae. First results concerning BD-22° 3467 and HD 112313 located respectively at the centre of Abell 35 and LoTr5 have been published by Jasniewicz et al. (1996) and Thévenin & Jasniewicz (1996).
Non-LTE model atmosphere analyses of faint PN central stars observed with Keck HIRES
Authors: McCarthy James K. , Méndez Roberto H. , Kudritzki R.-P.
Published: July 2016

We are engaged in using the HIRES echelle spectrograph (Vogt et al. 1994) on the 10 m Keck I Telescope to significantly increase the number of central stars of planetary nebulae (CSPN) studied spectroscopically at high resolution and signal-to-noise ratio. With Keck we are able to extend our previous work (Méndez et al. 1988, 1992; McCarthy 1988) to much fainter magnitudes. In short, comparisons of the observed HI Balmer, HeI, and He II line profiles to the Munich grid of plane-parallel non-LTE model atmosphere line profiles provide distance- and nebula-independent determinations of CSPN effective temperature, surface gravity, and helium abundance. For CSPN showing wind emission, the comparisons are made to new “unified” models (reviewed by Kudritzki et al., this meeting) which include radiation-driven winds. The first results of this on-going program are shown below.
On the role of evaporative wind in precataclysmic binaries (PCB)
Authors: Pustylnik I. , Pustynski V.
Published: July 2016

Recently we have started a systematic reevaluation of the existing observational methods of analysis hitherto applied to PCB-s. Here we report the first results of our investigations. The improved Napier's algorithm (Napier, 1968) to model the light curves of PCB (with the aid of the set of our computer programs in Turbo Pascal) is used. The source function is taken either from Sobieski (1965) or Strittmatter (1974). The entire luminosity received from the cool companion is calculated by integration of the emerging radiation over its disk; contributions from the illuminated and unilluminated portions of the disk are accounted for. We assume: a) the validity of the LTE in the photosphere of cool component, b) constancy of the monochromatic to mean absorption coefficient ratio within the photosphere, c) the hot star radiates as the absolutely black body, d) there are no other effects influencing the light curve except for the reflection effect. We have modelled the light curves of EC11575-1845 (Chen et al (1995). The analysis of the temperature distributions in the heated photosphere indicates the occurence of the temperature inversion. To make a rough estimate of physical conditions which can induce generation of evaporative wind we have used two criteria: i) the temperature inversion, ii) relation between radiative pressure and the effective gravitational acceleration. We assumed the density varies with the height in the atmosphere of the illuminated star as ρ ≃ exp(−Φ/RgT), Φ - being the Roche potential. The integral equation following from the definition of the mean optical depth was solved numerically to establish the relation between the mean optical depth and the distance in the atmosphere. We find the characteristic height scale for X-ray and EUV radiation is ∼ 106 − 107cm (for concentration of particles ∼ 1013cm−3). To check the validity of the ii) criterium we used a simplified model of radially expanding evaporative stellar wind and mass flux J conservation condition along the stream tube of the form J ∼ ρsvsrs2 exp −(Φ/RgT) (Pustylnik (1995)) and found M ∼ 10−12–10−11M/y. Although mass loss of such a rate cannot compete with the effects of the angular momentum loss which is responsible for a secular orbital shrinkage, the evaporative wind should significantly alter the structure of the the cool irradiated components.