bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass-to-light ratio of intermediate and old clusters in the Magellanic Clouds
Authors: Seitzer Patrick
Published: July 2016

The observed central velocity dispersion of a stellar system is dependent on the mass distribution and the velocity distribution function. For the past several years a program has been undertaken to determine central velocity dispersions of LMC and SMC clusters for comparison with galactic clusters. The mass-to-light ratio (M/L) estimates so obtained should be considerably more accurate than those obtained by tidal arguments (Chun 1978, Elson & Freeman 1985).

Accurate radial velocities (mean error = 1.3 km s−1) have been obtained for a sample of K-type giants with the CTIO 4m telescope and échelle spectrograph with CCD detector. All of the stars observed were within two core radii of the cluster centre. Multiple observations at several epochs (1984 and 1989) were used to determine the velocity errors.

The central M/L in solar units has been estimated from single component isotropic King models (King 1966), with the assumption that the distribution of mass follows that of the light. Observed values for the total integrated light and core radius were taken from the literature (in particular, from Chun 1978, van den Bergh 1981, Mateo 1987).
Faint HII regions in the Magellanic Clouds
Authors: Wilcots Eric M. , Hodge Paul
Published: July 2016

We present CCD observations of several faint regions of active star formation in the Magellanic Clouds. For the five regions for which we were able to obtain photometric data we have extended the luminosity function (LF) two orders of magnitude below the previous faint limit of 1037 erg s−1 (1). Our preliminary results indicate that the LF turns over at 1036 erg s−1 for the LMC and 1036.5 erg s−1 for the SMC. It is also apparent that much of the Ha emission fainter than 1036 erg s−1 is diffuse or filamentary in nature.
A 22-GHz map of the 30-Doradus region
Authors: Sabalisck N. S. , Abraham Z.
Published: July 2016

We present a preliminary map of the 30-Doradus region at 22 GHz with a HPBW of 4'.6 arc. The results are compared with those from maps at lower frequencies and at similar resolution. Three supernova remnants were detected: N157b, MC 78 and MC 89.
Cepheids in the Magellanic Clouds
Authors: Caldwell John A.R. , David Laney C.
Published: July 2016

Cepheid variables provide a key to understanding the structure and distance of the Magellanic Clouds, as well as providing accurate reddenings there. Recent major observing programs have continually expanded the data base of photometry and velocities. It is important to try to reconcile the plethora of Cepheid data into a consonant picture of the three-dimensional spatial structure of the Clouds and to compare in a consistent manner the bulk Cloud distance moduli found by several photometric methods.
Long-period variables in the Magellanic Clouds
Authors: Wood P.R. , Moore G.K.G. , Hughes S.M.G.
Published: July 2016

Until recently, surveys for variable stars in the Magellanic Clouds were carried out in blue and visual passbands, but these passbands are not ideal for finding very cool stars such as long-period variables (LPVs). Consequently, the early surveys generally found only the brightest LPVs in the Magellanic Clouds. The most extensive surveys were the Harvard surveys whose results are summarized by Payne-Gaposhkin and Gaposhkin 1966 (SMC) and Payne-Gaposhkin 1971 (LMC), with some supplementary data in Hodge and Wright (1969) and Wright and Hodge (1971). LPVs were also found during other smaller surveys such as those of Dessy (1959), Butler (1972, 1978) and Lloyd Evans (1971, see also Glass and Lloyd Evans 1981, Lloyd Evans 1978,1985 and Lloyd Evans et al. 1988).
Binary X-ray sources in the LMC
Authors: Hutchings J. B. , Cowley A. P.
Published: July 2016

We report new results on the X-ray binaries in the LMC since IAU Symposium 108 (see review by Hutchings 1984). These include an update of the point source identifications after further optical observations and a reprocessing of the Einstein database. We report major new results on several specific systems. Among low-mass systems (LMXB), we report periods and orbital determinations for LMC X-2 (long period), CAL 83, and CAL 87 (eclipsing black-hole binary). For the high-mass X-ray binaries (MXRB), we announce an ˜ 99 day (precession?) period in LMC X-3 and discuss orbital determinations for LMC X-1 and 0538–66.
Studies of SNRS in the Magellanic Clouds
Authors: Turtle A. J.
Published: July 2016

In the Magellanic Clouds about 60 confirmed supernova remnants (SNRs) or candidates are known. They have been detected by a combination of X-ray, optical and radio observations. Various statistical aspects of these SNRs will be considered including the implied supernova rate, the spatial distribution, the implications of the radio luminosity/diameter distribution for SNR evolution, and the relation to the extended non-thermal emission.
Supernova explosions in stellar wind bubbles
Authors: Jane Arthur S.
Published: July 2016

Type II supernovae play a major role in the dynamics of the interstellar medium. The interstellar medium in which such supernovae evolve is often considerably modified by the strong stellar winds both from the progenitor and other nearby stars. The result is that the appearance and energetics of the remnants can be very different from that of remnants in a uniform medium. In this paper we will consider the evolution of supernova remnants in stellar wind bubbles including the effect of departures from spherical symmetry. The aim is to understand both the appearance of such remnants and their effect on the overall energetics of the interstellar medium.
Properties of fast winds in hot stars in the Magellanic Clouds
Authors: Patriarchi P. , Perinotto M.
Published: July 2016

We have studied with the SEI method (Sobolev approximation plus Exact Integration of the transfer equation) seven hot stars, five belonging to the Large Magellanic Cloud (LMC) and two to the Small Magellanic Cloud (SMC), which have been observed with IUE in high resolution. We present preliminary results of the work, i.e. the terminal velocities and the optical depth of the P Cygni profile. An evaluation of qiM has been done, as well as a comparison with previous work.
Asymptotic Giant Branch Stars in the Magellanic Clouds
Authors: Reid Neill , Mould J. R.
Published: July 2016

Since the pioneering objective prism surveys by Westerlund (1960) and Blanco et al. (1980), the Magellanic Clouds have proved a fruitful site for exploring the evolution of AGB stars. We have used photometric techniques to extend the prism C-star surveys to M- and S-type AGB stars, constructing luminosity functions and obtaining spectra of individual stars for comparison with theoretical predictions. We have concentrated on the Large Magellanic Cloud (LMC), but we have recently obtained observations of luminous red giants in a region of the Small Magellanic Cloud (SMC). In this paper we compare the results from these studies of the two satellite systems.
Element abundances from B stars in the Magellanic Clouds
Authors: Jüttner A. , Stahl O. , Wolf B. , Baschek B.
Published: July 2016

High resolution spectrograms of B stars in the blue globular cluster NGC 2004, located in the Large Magellanic Cloud (LMC), have been used to derive chemical abundances, differentially with respect to a galactic comparison star.
EXOSAT Medium energy observations of the binary X-ray pulsar SMC X1
Authors: Zang Zhj-Yun
Published: July 2016

The binary X-ray pulsar SMC X-1 was observed with EXOSAT in 1984. The data of all six observation periods have been through preliminary processing. Some evolution information about SMC X-1, which was obtained from the pulse-timing and spectrum study, is reported in this paper.
The interstellar medium of the Magellanic Clouds from absorption lines
Authors: De Boer Klaas S.
Published: July 2016

General aspects of ISM studies using absorption line studies are given and available data are reviewed. Topics are: galactic foreground gas, individual fields in the Magellanic Clouds (MCs) and MC coronae. Overall investigations are discussed. It is demonstrated that the metals in the gas of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are a factor of 3 and 10, respectively, in abundance below solar levels. The depletion pattern in the LMC is similar to that of the Milky Way.
Dust distribution and temperature in the Magellanic Clouds interstellar medium
Authors: Sauvage M. , Vigroux L.
Published: July 2016

This review deals with the various aspects of interstellar dust in the Magellanic Clouds (MCs). Dust properties can be traced from interstellar absorption, with an emphasis on UV properties, and from infrared emission. Thanks to IRAS, most of the recent developments in this field have been found in the infrared. The low resolution of IRAS was, in fact, well suited for MC mapping and these observations offer a unique opportunity to study the dust properties in various conditions of the Interstellar Radiation Field (ISRF) and of chemical abundances. The proximity of the MCs allows a direct study of the link between the stellar population and the dust properties via the ISRF. On the other hand, the comparison of IRAS data in the MCs and in the Galaxy allows us to study the dust composition for metallicity varying by a factor of 10. From these data and the previous results on UV absorption, it emerges that if the gas-to-dust ratio changes with metallicity, there is also a variation in the relative abundances of the dust components. In this review, we will also discuss how our knowledge of the MCs will be used to prepare for observations of more distant galaxies, with the next generation of space observatories such as the Hubble Space Telescope and the Infrared Space Observatory.
Studies of the large Magellanic Cloud using optical interstellar emission lines
Authors: Meaburn J.
Published: July 2016

Optical observations have been made of the halo of 30 Doradus, in the vicinity of SN 1987A and of giant shells in the LMC.
Studies of the ISM in the LMC using SN1987A
Authors: Pettini Max
Published: July 2016

The exceptional brightness of SN1987A provided a wealth of opportunities for probing not only the interstellar medium in our Galaxy and in the Large Magellanic Cloud (LMC), but also any intergalactic matter between the two. Spectroscopic work has been directed both towards searches for very weak absorption lines, which require data of exceptionally high signal-to-noise ratio, and towards recording spectra of known features at unprecedentedly high resolution. Both approaches have yielded exciting and unexpected results. The first detection of [FeX] absorption has revealed the presence of million-degree gas in the interstellar medium of the LMC, possibly resulting from the explosions of previous supernovae in the 30-Doradus HII region. The ultra-high-resolution observations have been successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds along the line of sight to the supernova. This implies that the clouds are at temperatures of, at most, 170 K and have internal turbulent velocities of not more than 0.2 km s−1; large-scale motions thus appear to be mainly subsonic in these clouds. Radio observations of HI emission at 21-cm with the Parkes telescope have been combined with measurements of a variety of ultraviolet absorption lines, obtained with the International Ultraviolet Explorer satellite, to give the most detailed picture yet of the chemical composition of the gas between the Galaxy and the LMC. Finally, photographic monitoring of the light echo of SN 1987A over the last two years has provided a three-dimensional view of the interstellar environment in which SN 1987A exploded, complementing vividly the information deduced from the spectroscopic results.
CO observations of Arp's interacting galaxies
Authors: Sofue Yoshiaki , Wakamatsu Ken-Ichi , Taniguchi Yoshiaki , Nakai Naomasa , Handa Toshihiro
Published: July 2016

A number of starburst galaxies are included in the Atlas of Peculiar Galaxies (Arp 1966) which is the collection of peculiar-morphology galaxies showing mutual tidal interaction. A scenario of starburst can be summarized as follows (e.g. Sofue 1987, Noguchi 1988). Tidal interaction between galaxies causes an oval disturbance in the gravitational potential of a galaxy. The oval disturbance causes a bar in the innermost region of the galaxy. By this bar a galactic shock wave is excited, which results in rapid accretion of gas toward the central region. The accreted gas produces a dense ring or a core of molecular gas in the central region, from which massive stars are born. Intense UV radiation from the stars heats dust in the dense molecular gas core/ring, and the dust emits strong FIR emission.
Special purpose computer for N-body problems
Authors: Sugimoto D. , Ebisuzaki T. , Ito T. , Marino J.
Published: July 2016

Backend processors for use in gravitational N-body problems were constructed. They are as cheap as a personal computer, yet their speed is comparable to a supercomputer. As an example we show some results of simulations which were done for the dynamical evolution of galaxies in a compact group.
The AGB-star Phenomenon: Setting the Stage
Authors: Olofsson Hans
Published: July 2016

The asymptotic giant branch (AGB) evolution of stars is interesting from many points of view. It is the final evolutionary phase for the large majority of all stars in the Universe that have left the main sequence. During this stage they contribute to the chemical evolution of galaxies, contribute to the integrated starlight of many galaxies, may provide the only interstellar matter there is in some galaxies, and can, due to their high luminosities and ages, be used as important probes of galactic structure and dynamics. It is also the final evolutionary stage of our own star, the Sun, and hence touches on aspects beyond the immediate astronomical interest. Furthermore, these stars provide us with fascinating systems, where intricate interplays between physical and chemical processes take place, that we simply would like to understand. In this introductory outline our present knowledge of the AGB-star phenomenon is reviewed.
The modelling of M-giant spectra
Authors: Plez Bertrand
Published: July 2016

I review the current status of cool O-rich giant star spectral modelling, stressing some specific problems like line profiles and molecular data completeness. I discuss recent progress in molecular line lists (TiO, VO) and describe recent attempts in modelling normal M-giants as well as AGB star spectra, using static and hydrodynamic models. I anticipate further advances in the near future, with better radiative transfer in hydrodynamic models, that will allow detailed comparisons of models and observations, opening the possibility of deriving stellar parameters from spectroscopic and interferometric observations.
Infrared spectra of C-type variables with ISO
Authors: Hron J. , Loidl R. , Höfner S. , Jørgensen U.G. , Aringer B. , Kerschbaum F. , Windsteig W.
Published: July 2016

We present ISO-SWS spectra for several representative AGB carbon stars obtained at several phases of the pulsational cycle. For stars with significant mass loss we correct the spectra for the dust emission by using DUSTY models. We then compare these corrected data to synthetic spectra based on hydrostatic and dynamical model atmospheres. We also discuss the influence of the fundamental model parameters on the resulting synthetic spectra.
Dynamical Modeling of Circumstellar Outflows
Authors: Fleischer Axel J. , Winters Jan Martin , Sedlmayr Erwin
Published: July 2016

We review dynamical models of circumstellar dust shells around long-period variables which include time-dependent hydrodynamics and a detailed treatment of dust formation, growth and evaporation. Important effects caused by the complex interaction between the dynamics of the pulsating atmosphere and the dust complex which only can be revealed in the dynamical approach are summarized. Special emphasis is given to the treatment of the dust and gas opacity.
Making movies of stars: VLBA monitoring of the SiO masers around the Mira variable TX Cam
Authors: Diamond P. J. , Kemball A. J.
Published: July 2016

We have produced a movie of the time evolution of the v=1, J=1−0 43 GHz SiO masers in the inner circumstellar envelope of the isolated Mira variable TX Cam. Our observations, taken every two weeks with the VLBA, currently cover about 60% of the stellar cycle from ϕ ∼ 0.6 → ϕ ∼ 1.2. They show that, in contrast to previous observations and theoretical models, the gas in which the masers are embedded is undergoing expansion during this period with a typical velocity of 3.65 ± 0.15 km/s. Some isolated features are seen to start falling back towards the star at around ϕ ∼ 1.0. We suggest that the 5 → 10 G magnetic fields we have previously detected at the position of the SiO masers may explain the departure from the expected behaviour.
Formation of crystalline silicate around oxygen–rich AGB stars
Authors: Kozasa Takashi , Sogawa Hisato
Published: July 2016

Crystallization of silicate has been investigated within the framework of dust formation in steady state gas outflows around oxygen–rich AGB stars, where silicates are locked not only into homogeneous silicate grains but also into the mantles of heterogeneous grains. Based on the thermal history of dust grains after their formation, the crystallization calculation results in no crystalline silicate for the mass loss rate Ṁ ≤ 2 × 10−5M⊙ yr−1. Only silicate in the mantles of heterogeneous grains can be crystallized for Ṁ ≥ 3 × 10−5M⊙ yr−1, while homogeneous silicate grains remain amorphous. The mass fraction of crystalline silicate increases with increasing Ṁ. The radiation transfer calculations confirm the appearance of an emission feature around 33.5 μm, taking olivine as a representative of crystalline silicates. On the other hand, the 10μm feature appears in absorption, being dominated by homogeneous silicate grains. These trends are consistent with the observations. Thus the crystalline silicate is a diagnostics of high mass loss rate at the late stage of AGB stellar evolution, reflecting the formation process of dust grains.
Diffraction-limited 76 mas speckle-masking interferometry of the carbon star IRC+10 216 and related AGB objects with the SAO 6 m telescope
Authors: Weigelt G. , Blöcker T. , Hofmann K.-H. , Osterbart R. , Balega Y.Y. , Fleischer A. J. , Winters J. M.
Published: July 2016

We present high-resolution J–, H–, and K–band observations of the carbon star IRC+10 216. The images were reconstructed from 6 m telescope speckle interferograms using the speckle masking bispectrum method. The H image has the unprecedented resolution of 70 mas. The H and K images consist of at least five dominant components within a 0.21 arcsec radius and a fainter asymmetric nebula. The J-, H-, and K—band images seem to have an X-shaped bipolar structure. A comparison of our images from 1995, 1996, 1997, and 1998 shows that the separation of the two brightest components A and B increased from ∼ 193 mas in 1995 to ∼ 246 mas in 1998.

The cometary shapes of component A in the H and J images and the 0.79 μm and 1.06 μm HST images suggest that the core of A is not the central star, but the southern (nearer) lobe of the bipolar structure. The position of the central star is probably at or near the position of component B, where the H—K color has its largest value of H—K = 4.2.

If the star is located at or near B, then the components A, C, and D are located close to the inner boundary of the dust shell at separations of ∼200 mas ∼30 AU (projected distance) ∼6 stellar radii for a distance of ∼ 150 pc, in agreement with our 2-dimensional radiative transfer modelling.

In addition to IRC+ 10 216 we studied the stellar disks and the dust shells of several related objects. Angular resolutions of 24 mas at 700 nm or 57 mas 1.6 μm were achieved.
Extended Dust Shells Surrounding AGB Stars Revealed with ISO
Authors: Izumiura H. , Hashimoto O.
Published: July 2016

We obtained high resolution far-infrared images of the circumstellar dust shells of several AGB carbon stars using ISOPHOT on board the ISO. We used the C-100 and C-200 detector arrays in PHT32 oversampling mode at 90 μm and 160 μm except for U Ant, which was observed at 60 μm and 90 μm. AFGL 3068 is very compact in both bands. R Scl is marginally resolved at 90 μm. U Ant shows a double shell structure, a compact but well resolved shell surrounded by a very extended envelope. Y CVn exhibits a very extended, hollow dust shell. We analyse the structure of the dust shells using a simple dust shell model and discuss the mass-loss behaviors, particularly in conjunction with the thermal pulses on the AGB.
High-resolution, near-IR spectroscopy and imaging of the Egg and Rotten Egg nebulae (AFGL 2688 and OH 231.8+4.2)
Authors: Kastner Joel H. , Henn LeeAnn , Weintraub David A. , Gatley Ian
Published: July 2016

Velocity-resolved 2.12 μm H2 maps of the Egg Nebula (AFGL 2688), obtained with the NOAO Phoenix spectrometer, elaborate on previous observations of large velocity gradients in molecular emission both along and perpendicular to the polar axis of the system. The measured gradients along the polar axis support the notion that the polar H2 emission regions are formed in shocks as fast, collimated winds collide with material ejected while the central star was still on the AGB. The kinematics of H2 emission along the equatorial plane, meanwhile, are consistent with a model combining spherical expansion with rotation about the polar axis, although a model invoking multiple outflow axes cannot be ruled out.

We also obtained the first direct near-infrared images of QX Pup, a Mira variable embedded within the evolved bipolar nebula OH 231.8+4.2. The inferred absolute K magnitude of the central Mira appears “normal” given its ∼ 700 day period, which is remarkable in light of its position at the heart of such an unusual object.
AGB stars in binaries and their progeny
Authors: Jorissen A.
Published: July 2016

An AGB star in a binary system is likely to pollute its companion with carbon- and s-process-rich matter. After the AGB star has faded into an unconspicuous white dwarf, the polluted companion enters the zoo of stars with chemical peculiarities. In this paper, the progeny of AGB stars in binary systems are identified among existing spectroscopic classes (Abell 35-like, binary post-AGB, WIRRing, dwarf Ba and C, subgiant CH, Ba, CH, S, yellow symbiotics) and their filiation is discussed from the properties of their eccentricity – period diagrams.
The Nature of RV Tauri Stars
Authors: Evans T. Lloyd
Published: July 2016

The infrared colours of the RV Tauri stars fall in a well-defined and thinly-populated region of the IRAS [12] – [25], [25] – [60] diagram. This provides an alternative method of searching for such stars. Stars with these IRAS colours as well as the K and L excesses which are also typical of RV Tauri stars have spectral types from B to M. The characteristic variability of RV Tauri-type has been found for several stars with spectral types typical of known RV Tauri stars, while stars of different spectral types do not vary in this way. RV Tauri stars are the stars with these colours, probably indicative of a dusty circumstellar disk, which lie within the Cepheid instability strip.
RV Tauri stars and Type II Cepheids in the LMC
Authors: Pollard Karen R. , Evans T. Lloyd
Published: July 2016

A review of the main results from the MACHO project for RV Tauri stars and Type II Cepheids in the LMC is presented. In light and colour curve behaviour, the RV Tauri stars appear to be a direct extension of the Type II Cepheids to longer periods. A single period–luminosity–colour relationship is seen to describe both the Type II Cepheids and RV Tauri stars in the LMC.

Follow-up low resolution spectroscopy of the LMC RV Tauri stars has been undertaken. The spectra of the longest period RV Tauri star in the MACHO sample show that this star has strong C2 bands with a pronounced phase dependence, their strength being greater at minimum light. This and other spectral features are similar to those observed in proto-planetary nebulae. This LMC star therefore appears to combine the main spectral anomaly of the proto-planetary nebulae with RV Tauri-like photometric variability. This is an intriguing result which indicates a possible link between RV Tauri stars and proto-planetary nebulae, and strengthens the post-AGB interpretation of the RV Tauri stars.
Born-again AGB stars: Starting point of the H-deficient post-AGB evolutionary sequence?
Authors: Werner K. , Dreizler S. , Rauch T. , Koesterke L. , Heber U.
Published: July 2016

We discuss the origin of hot hydrogen-deficient post-AGB stars. Evidence is growing that the “born-again AGB star scenario” as a consequence of a late He shell flash cannot explain the diverse observations. Analyses of the stars and their associated planetary nebulae suggest that the H-deficiency is not formed during the second post-AGB phase but already while the star is still on the AGB. There are even hints that the H-deficiency can occur before the first departure from the AGB.
Long-period Variable Stars Near the Galactic Centre
Authors: Glass I.S. , Matsumoto S. , Carter B.S. , Sekiguchi K.
Published: July 2016

A second report on our 4-year survey for long-period variables (LPVs) in the central 24 × 24 arcmin2 of the Galactic Bulge is presented. All four seasons of data have now been reduced and ∼ 350 variables have been found. Preliminary periods have been obtained for most of them. Fifty-five out of 103 known OH/IR stars in the field have been recovered in the K-band.
Iron Abundances in AGB Stars and M Supergiant Stars at the Galactic Center
Authors: Ramírez S. V. , Sellgren K. , Terndrup D. M. , Carr J. S. , Balachandran S. , Blum R. D.
Published: July 2016

We are measuring Fe abundances of cool, luminous stars within 30 pc of the center of the Milky Way. Our sample contains both AGB stars and M supergiants. Low-resolution (λ/Δλ = 500) H and K band spectra are used to estimate temperatures and gravities. Stellar Fe abundances are determined from high-resolution (λ/Δλ = 40 000) K band spectra obtained on the IRTF using CSHELL. We find that Fe abundances of stars in the Galactic Center are consistent with the solar Fe abundance.
AGB Theory — A Retrospective
Authors: Iben Icko
Published: July 2016

My assignment was to listen to all of the talks at the symposium and to discover and summarize results that have appeared since the last conference on AGB stars. Since the entire meeting was devoted to new results, discovery was a simple task. Because of the large volume of new results, an adequate summary is impossible. I therefore do not attempt to provide a comprehensive survey, but confine my remarks to a small subset of the discoveries and advances which have enriched and modified our understanding of AGB stars over the past decade.
Stellar Clusters in the Outermost Milky Way Galaxy
Authors: Hesser J. E. , Stetson P. B. , van den Bergh S. , Bolte M. , Johnson J. A. , Harris W. E. , VandenBerg D.A. , Bell R. A. , Bond H. E. , Fullton L. E. , Fahlman G. G. , Richer H. B.
Published: July 2016

HST V, I color-magnitude diagrams (CMDs) of four outer-halo clusters, NGC 2419, Pa13, Pal4 and Eridanus, provide insight into the relative ages of old star clusters throughout the 200 kpc diameter volume sampled, and thus into the formation epoch of the Milky Way galaxy.
A Survey of X-ray Point Sources in the Magellanic Clouds
Authors: Cowley A. P. , Schmidtke P. C. , Taylor V. A. , McGrath T.K. , Hutchings J. B. , Crampton D.
Published: July 2016

In this study we compare the global populations of stellar X-ray sources in the LMC, SMC, and the Galaxy. After removing foreground stars and background AGN from the samples, the relative numbers of the various types of X-ray point sources within the LMC and SMC are similar, but differ markedly from those in the Galaxy. The Magellanic Clouds are rich in high-mass X-ray binaries (HMXB), especially those containing rapidly rotating Be stars. However, the LMC and SMC both lack the large number of low-mass X-ray binaries (LMXB) found in the Milky Way, which are known to represent a very old stellar population based on their kinematics, chemical composition, and spatial distribution.
The Sagittarius Dwarf Galaxy Survey (SDGS): Constraints on the Star Formation History of the Sgr dSph
Authors: Bellazzini M. , Ferraro F. R. , Buonanno R.
Published: July 2016

The main characteristics of a wide photometric survey of the Sgr dwarf spheroidal galaxy are briefly presented. V and I photometry has been obtained for ~90000 stars toward Sgr and for ~9000 stars in a region devoid of Sgr stars (for decontamination purposes).

The full potential of this large database is far from being completely explored. Here we present only preliminary results from the analysis of statistically decontaminated Color Magnitude Diagrams, trying to set a scheme of the Star Formation History of the Sgr Galaxy. A scenario is proposed in which star formation in Sgr began very early and lasted for several Gyr, with progressive chemical enrichment of the Inter-Stellar Medium (ISM). Nearly 8 Gyr ago the star formation rate abruptly decreased, perhaps in coincidence with the event that led to the gas depletion of the galaxy. A very small rate of star formation continued until relatively recent times (~ 1 Gyr ago).
A Search for RR Lyrae Variables and Anomalous Cepheids in the Fornax Dwarf Galaxy
Authors: Bersier David , Wood Peter R.
Published: July 2016

We have started a search for variable stars in Fornax, covering a area of 40′ x 40′. We have ~ 30 data points in both V and I. To detect variable stars, we use the variability index defined by Welch & Stetson (1993). We present here our first results.
Star Formation History in the Fornax Dwarf Galaxy from HST data
Authors: Marconi G. , Buonanno R. , Castellani M. , Corsi C. E. , Zinn R.
Published: July 2016

Using observations from the Hubble Space Telescope archive, color-magnitude diagrams have been constructed for globular Cluster 4 in the Fornax dSph galaxy and its surrounding field. These diagrams extend below the main-sequence turnoffs and have yielded measurements of the ages of the populations. In particular, from our analysis Cluster 4 shows [Fe/H] ≃ 2.0, a value significantly lower than that derived for the Fornax field ([Fe/H] ≃ −1.40). Putting our results in the frame of the findings of Buonanno et al. (1998) for the Fornax clusters 1, 2, 3 and 5, a global analysis of the properties of Fornax stellar populations has been performed.
Detailed Star-Formation Histories of Nearby Dwarf Irregular Galaxies using HST
Authors: Tolstoy Eline
Published: July 2016

Unless the nearby universe is subtly anomalous, it should contain a relatively normal selection of galaxies whose histories are representative of field galaxies in general throughout the Universe. We can therefore take advantage of our ability to resolve the nearby galaxies into individual stars to directly, and accurately, measure star formation histories. The star formation histories are determined from model-fitting analysis, based on stellar evolution tracks, of colour-magnitude diagrams. The most accurate information on star formation rates extending back to the earliest epochs can be obtained from the structure of the main sequence. However, the oldest main sequence turnoffs are very faint, and it is often necessary to use the more evolved stars to infer the star formation history. These can then be compared with the properties of galaxies seen over a large range of lookback times at moderate to high redshifts. There is considerable evidence that the faint blue galaxies seen in large numbers in cosmological redshift surveys are the progenitors of the small late-type irregular galaxies seen in copious numbers in the Local Group, and we concentrate on these here.
HST Color-Magnitude Diagrams of Globular Clusters in NGC 185 and NGC 205
Authors: Geisler Doug , Armandroff Taft , Da Costa Gary , Lee Myung Gyoon , Sarajedini Ata
Published: July 2016

We present a progress report on our ongoing HST WFPC2 study of globular clusters in NGC 185 and NGC 205. Most of the cluster candidates studied previously only from the ground are indeed globular clusters; however, several candidates turn out to be either foreground stars or background galaxies. In addition, we have discovered one new, previously unsuspected cluster. A complete knowledge of the globular cluster systems in even these nearby galaxies requires high spatial resolution data. We then derive preliminary I, (V – I) color-magnitude diagrams for some of the clusters, as well as for their surrounding fields. The clusters show the blue horizontal branches expected for the low metallicities we derive, which are in agreement with those derived from ground-based integrated spectra. The fields appear generally more metal-rich than indicated by previous ground-based studies. The field blue horizontal branch in NGC 185 is only a very minor component, while that in NGC 205 is even smaller. After all of our observations have been acquired, these data will allow a very accurate knowledge of the individual and composite properties of the globular cluster systems of these 2 galaxies, as well as those of their field stars.
The Young Stars in IC 1613
Authors: Borissova J. , Georgiev L. , Rosado M. , Koenigsberger G. , Kurtev R. , Ivanov G.
Published: July 2016

Deep UBV and JHK photometry of the stars in IC 1613 was used to investigate the stellar content in the H II regions of the northeast sector of the galaxy. The ages of nine of the associations outlined by Hodge (1978) were determined. A10 and A14 were found to be the youngest associations with ages of approximately 5 Myr, while A12, A18 and A19 were the oldest ones found, having a common age of approx. 20 Myr. Analysis of theoretical HR diagrams shows the presence of young massive stars in the associations, which have been born almost coeval. We have also found evidence of a difference between the slopes of the IMFs and differential LFs, between the group of associations embedded in gas and the group containing A12, A18 and A19, which are not affected by nebulosity.
Synthesis of Lick Spectral Indices With Overshooting and No-Overshooting Model Atmospheres
Authors: Gulati R. K. , Chavez M.
Published: July 2016

Using Lester's version of the Kurucz codes, we have computed a set of models with and without “approximate overshooting”. Based on the new models, we have synthesized the spectra in the wavelength range 4800–5400 Å in order to investigate the role of overshooting and no-overshooting models on the Lick indices. Preliminary results show that the differences between the indices are significant in the case of Hβ and Mgb. We need to investigate further the importance of this convection parameter, by comparing model spectra with observed spectra.
New Grids of Synthetic Spectra for Abundance Derivation and Population Synthesis
Authors: Barbuy B. , Perrin M.-N. , Cayrel R. , Katz D. , Van't Veer C. , Schiavon R. P.
Published: July 2016

We have built a new grid of synthetic spectra in the wavelength range λλ 4600-5600 Å for [α-elements/Fe] = 0.0, +0.2, +0.4 and +0.6. The Lick indices Mg2, Mgb, Fe5270 and Fe5335 are measured in all grid spectra, and their behaviour with stellar parameters is studied.

For the calculation of this new grid, the set of atomic and molecular constants was revised and model atmospheres with overshooting and mixing length parameters appropriate to reproduce the wings of the Hβ line (suitable to indicate temperatures) were computed. We also present a grid in the wavelength range λλ 6000 – 10200 Å. A computation of a high-resolution grid of spectra in the range λλ 3800–7000 Å, as well as a full grid in the range λλ 3000–10200 Å, to be further used in conjunction with evolutionary population synthesis models, are also underway.
Hot Horizontal-Branch Stars in the Galactic Bulge
Authors: Terndrup D. M. , Peterson R. C. , Sadler E. M. , Walker A. R.
Published: July 2016

We report the discovery of hot horizontal branch stars in the nuclear bulge of the Milky Way. Spectra from the 2dF instrument of the Anglo-Australian Telescope allow us to confirm their membership in the bulge through radial velocities. We also review the current observational information on hot horizontal branch stars in Milky Way clusters and the Local Group, and discuss the relevance of star-by-star studies in the bulge for the ultraviolet-excess phenomenon seen in large ellipticals.
The Dynamics of the Substructures and the Bulk Flow of the Local Group
Authors: Gurzadyan V. G. , Rauzy S.
Published: July 2016

The S-tree method is used to reveal the substructures of the Local Group, namely the membership of each individual galaxy in the Milky Way and M31 subgroups; the method is determining the degree of mutual influence of the galaxies. Once the main physical subgroups of the Local Group are defined, we use a general method of reconstruction of their bulk flow using the radial velocity distribution of the member galaxies. The results particularly indicate the essential mutual bulk flow of the Milky Way and M31 subgroups which does not simply coincide with the radial approaching velocity (blueshift) of M31. Finally, having obtained the 3D velocity vectors of both the subgroups, we determine the 3D bulk flow of the Local Group itself, which in the Cosmic Microwave Background rest frame is equal to VLG→CMB = 668 kms−1 towards l = 265 and b = 42.
A New Look at Poor Groups of Galaxies
Authors: Zabludoff Ann I.
Published: July 2016

We use a new fiber spectroscopic survey of 12 nearby, poor groups of galaxies to examine the dynamics and evolution of galaxies in these common, but poorly studied, environments. Some of our conclusions are: (1) The nine groups in our sample with diffuse X-ray emission are in fact bound systems with at least 20-50 group members with absolute magnitudes as faint as MB ~ −14 + 5 log10h. (2) Galaxies in each X-ray-detected group have not all merged together because a significant fraction of the group mass lies outside of the galaxies and in a common halo, thereby reducing the rate of galaxy-galaxy interactions. (3) The similarity of the recent star formation histories and the fraction of early type galaxies in some poor groups to those in rich clusters suggest that cluster-specific environmental effects may not play a dominant role in the recent evolution of cluster galaxies. The evolution of group and cluster members may be driven instead by galaxy-galaxy interactions, which are likely to occur with equal frequency in field groups and in groups that have recently fallen into clusters (i.e., subclusters).
Comparative Morphology of the HST Color-Magnitude Diagram of the Nearby Blue Compact Dwarf Galaxy VII Zw 403 with that of Local Group Dwarfs
Authors: Schulte-Ladbeck R.E. , Hopp U. , Crone M. M.
Published: July 2016

There are no examples of Blue Compact Dwarf (BCD) galaxies known within the Local Group (LG). Multicolor HST/WFPC2 observations of the nearby BCD VII Zw 403 (= UGC 6456) now resolve single stars with the quality (in terms of limiting magnitude and completeness) previously achieved for LG dwarfs from the ground. We use the MI, V - I color-magnitude diagrams (CMDs) of several LG dwarfs as templates to assess the stellar content and star-formation history (SFH) of the BCD VII Zw 403. This is the first BCD for which a clear spatial segregation of the resolved stellar content into a “core-halo” structure is detected: active star formation is observed in the central region of VII Zw 403, while in “Baade's red sheet”, this young population is strikingly absent. If BCD halos are home to dominant ancient stellar populations, then the fossil record conflicts with delayed-format ion scenarios for dwarfs. We present a sketch of the SFH in the core and halo of VII Zw 403.
Application of SALT to the Local Group
Authors: Stobie R. S.
Published: July 2016

In collaboration with international partners, South Africa plans to construct a 9-m class telescope for optical/infrared astronomy. This Southern African Large Telescope (SALT) will be a southern hemisphere equivalent of the Hobby-Eberly Telescope at McDonald Observatory, Texas. By limiting the scientific mission to primarily spectroscopic survey studies, with some reduced imaging capability, it is possible to construct SALT for about one-fifth of the cost of a general-purpose telescope of similar aperture. The telescope will be operated in queue-scheduled mode which opens up new applications in the time-dependent domain. A description of SALT, its capabilities, and samples of the science programme are presented.
Compact Binaries as Tracers of Star Formation Histories: the XMM Survey of M31
Authors: Kolb U. , Osborne J. , Watson M. G.
Published: July 2016

X-ray binaries (XBs) dominate the X-ray emission of normal galaxies. The new X-ray satellite XMM will study the XB population of M31 in detail. The resulting M31 sample will significantly advance our understanding of the evolutionary history of XBs, and ultimately allow us to probe the star formation history of stellar populations by X-ray observations.
The IVth Catalogue of LMC Wolf-Rayet stars
Authors: Breysacher Jacques , Azzopardi Marc , Testor Gérard
Published: July 2016

A number of 134 WR stars is currently known in the Large Magellanic Cloud. A summary of the content and format of the new, Fourth, LMC Wolf-Rayet Catalogue is presented.
Binary interaction effects: predictions and observations
Authors: Koenigsberger Gloria , Moreno Edmundo , Cantó Jorge , Raga Alejandro C.
Published: July 2016

Observations and predictions of interactions in close and massive binary systems are summarized. Tidal interactions are analyzed using a model which predicts the response of the stellar surface to the external gravitational force of the companion. The possible role of tidal interactions in determining the peculiar behavior of systems like HD 5980 and η Carinae is discussed.
Eclipses in V444 Cygni: analysis of the continuum λ 4244 Å light-curve on a class of non-negative monotonically decreasing concaved/convex functions
Authors: Antokhin Igor I. , Cherepashchuk Anatol M.
Published: July 2016

A continuum λ 4244 Å light-curve of the eclipsing binary V444 Cyg (WN5+O6) is solved. The results generally agree with the previous ones obtained by Antokhin et al. (1997), with the exception that the conclusion on the slowness of the acceleration in the extended atmosphere of the WR component must be ‘softened’.
Neon abundances in three Wolf-Rayet stars observed with the ISO Short Wavelength Spectrometer
Authors: Morris Patrick W. , van der Hucht Karel A. , Willis Allan J. , Dessart Luc , Crowther Paul A. , Williams Peredur M.
Published: July 2016

We are motivated to study the Ne/He abundance ratio at the surfaces of Wolf-Rayet stars by evolutionary models, which have predicted enhancements by more than an order of magnitude over cosmic levels during the WC stage (e.g., Maeder 1991). This should occur early in the WC phase, as core-hydrogen is exhausted and the CNO bi-cycle gives way to the following chain of reactions for the Galactic stars:

The latest evolutionary models, which include the effects of interior mixing due to stellar rotation, indicate that the enhancement may be somewhat more gradual, but that the Ne/He ratio is essentially unchanged in its peak value, coinciding with complete H-depletion (e.g., Meynet, these Proceedings).
Wolf-Rayet stars in OB associations
Authors: Niedzielski Andrzej , Strobel A.
Published: July 2016

We present first results of our search for Wolf-Rayet members of OB associations, aiming in determination of distances and absolute magnitudes for WR stars.
Clumping-corrected mass-loss rates of Wolf-Rayet stars: comparison with the optically thick wind model
Authors: Nugis Tiit
Published: July 2016

Clumping-corrected mass-loss rates of Wolf-Rayet stars lie in the range 0.2–10 x 10−5 M⊙ yr−1. It was found that optically thick wind models can lead to the observed mass-loss rates of WR stars at certain energy supply conditions in the subsonic zone.
Ionization-stratification in Wolf-Rayet atmospheres
Authors: Rochowicz Krzysztof
Published: July 2016

We summarize an analysis of low-resolution IUE archival data for galactic and LMC Wolf-Rayet stars. We examine the correlation between ionization potential with line-width (FWHM) constituting a sample of stars showing a well-defined UV ionization structure.
WSRT 21-cm continuum field in Cygnus OB2: in search of more Wolf-Rayet stars
Authors: Setia Gunawan Diah Y.A. , van der Hucht Karel A. , Ger de Bruyn A. , Williams Peredur M.
Published: July 2016

We present a deep look into the Cygnus OB2 region using the WSRT. A 2° x 2° map of the optically highly-obscured region was obtained at 1400 MHz, with a noise level down to 0.2 mJy and an angular resolution of 1″. We will compare the resulting radio point source list with optical and near-IR catalogues, in order to identify stellar wind sources like WR and OB stars.
Galactic Wolf-Rayet stars in the mid-infrared
Authors: Smith John D. , Houck Jim R.
Published: July 2016

We present the results of observations of a sample of Galactic WR stars with SCORE, the SIRTF Cornell Echelle spectrograph. Spectra with resolution R ≃ 600 and wavelength coverage from 7.5–15 μm were obtained for a variety of WR subtypes.
Science opportunities with the Space Infrared Telescope Facility (SIRTF)
Authors: Thaller Michelle
Published: July 2016

After a quarter century of dreams and designs, the Space Infrared Telescope Facility (SIRTF) has begun formal development, with a planned launch date of December 2001. SIRTF consists of a 85 cm telescope and three cryogenically-cooled science instruments capable of performing imaging, photometry, and spectroscopy in the 3–180 μm wavelength range. Incorporating the latest in large-format infrared detector arrays, SIRTF offers orders-of-magnitude improvements in capability over existing programs. One of the many innovative aspects of this observatory is the Legacy Science program, in which hundreds, perhaps thousands of hours of observing time will be allocated to coherent groups of scientists to carry out programs whose scientific data, upon archiving, are of general and lasting importance to the broad community. The capabilities of this telesope, and the possibiltiy of participating in a Legacy Science proposal, offer the community of hot stellar astronomers an unprecedented scientific opportunity.
HST-WFPC2 observations of Galactic Wolf-Rayet stars, preliminary results
Authors: Wallace Debra J. , Shara Michael M. , Moffat Anthony F.J. , Niemela Virpi S.
Published: July 2016

We present preliminary results of our HST-WFPC2 pc-survey of Wolf-Rayet stars. Initiated in 1996, the goal was to discover new companions to, and cluster/association memberships of, known Galactic WR stars. From these results, Niemela et al. (1998) have already established a firm link between non-thermal radio emission and the location of binary wind-collision zones for WR 146 (confirming radio data of Dougherty et al. 1996) and WR 147 (confirming radio and IR data of Williams et al. 1997; see also Williams, these Proceedings), and confirmed the presence of a binary companion for WR 86 (listed by Jeffers et al. 1963). Here, for the first time, we present new information on WR38, WR38a, and WR 104.
Non-thermal high-energy emission from Galactic Wolf-Rayet stars?
Authors: Wessolowski Ulf
Published: July 2016

We have updated the list of promising candidates for observations of non-thermal high-energy emission from Galactic Wolf-Rayet stars with present and future X/γ-ray instruments.