bluuebunny/crossref_metadata_2025 huggingface dataset:
Galaxy Harassment—Interactions for the 90s
Authors: Lake George , Moore Ben
Published: July 2016

The origin of the Hubble sequence remains a long-standing puzzle in astronomy. Giant galaxies range from slowly-rotating dense ellipticals to thin late-type spiral disks. At the faint end, there are two distinct classes of “ellipticals/spheroids” that are easily separated in plots of nearly any two of their properties, such as central surface brightness versus luminosity (Ferguson and Binggeli 1994; Kormendy 1985). The elliptical class includes the bright giants and extends to the rare high surface brightness “dwarf ellipticals”, M32 being the prototype. The “spheroidal” galaxies have low surface brightnesses and are all ≳3 magnitudes fainter than L∗, the characteristic break in the luminosity function. The dwarf spheroidal galaxies (dSph) in our Local Group of galaxies with magnitudes in the range −8≳MB≳ - 12 are often considered to be the low luminosity extreme of this sequence, but nearly all other known galaxies in this class reside in clusters.
Environmental Effects: The Molecular Gas in Spiral Galaxies
Authors: de Mello D.F. , Wiklind T. , Maia M.
Published: July 2016

We have started a survey of the molecular gas content of spiral galaxies in high and low density regions (HDS and CS), selected according to well-defined criteria (Maia et al. 1994, ApJS, 93, 425). The HDS sample is formed by galaxies that are in groups of three or more members. The groups are defined such that they have a density contrast δρ/ρ ≥ 500. This is equivalent to densities larger than 18 galaxies/Mpc3. The CS sample is made up of galaxies which are not members of any group and which are situated in a region with a density contrast δρ/ρ ≤ 0.01, i.e. less than 0.0004 galaxies/Mpc3.
Large Scale Gradient in the Velocity Field of the Coma Cluster and a Study of the Spin Orientation of Galaxies in the Virgo Cluster
Authors: Iye M. , Ozawa T.
Published: July 2016

This paper reports two studies on the distribution of the spin angular momenta of galaxies in physical clusters of galaxies.
A Deep, Large-Area K-Band Survey for Highly Redshifted Hα Emission
Authors: van der Werf P.P.
Published: July 2016

The most significant unknown in searches for high-z starburst galaxies is the role and importance of absorption by dust. Emission line searches have mostly targeted the Lyα line, which, due to resonant scattering, will be strongly suppressed even if only small amounts of dust are present. Indeed, most of the high redshift starburst galaxies identified by Steidel et al. (1996) have no Lyα emission. The U-band and V-band dropout techniques developed by these authors and by Madau et al. (1996) are likewise sensitive to dust absorption, both because of absorption of the observed ultraviolet (UV) radiation and because UV-obscured galaxies will not be accounted for in these dropout studies.
The Effects of Spatial Correlations on Merger Trees of Dark Matter Halos
Authors: Nagashima Masahiro , Gouda Naoteru
Published: July 2016

The effects of spatial correlations of density fluctuations on merger histories of dark matter halos (so-called ‘merger trees’) are analyzed (Nagashima & Gouda 1997). We compare the mass functions of dark haloes derived by a new method for calculating merger trees, that proposed by Rodrigues & Thomas (1996), with those given by other methods such as the Block model, the Press-Schechter formula and our own formula in which the mass functions are analytically expressed in a way that takes into consideration the spatial correlations (Yano et al. 1996). It is found that the mass functions given by the new method are well fit by those given by our formula. We believe that the new method naturally and correctly takes into account the spatial correlations of the density fluctuations due to a calculated, grid-based realization of the density fluctuations, and so is very useful for estimating the merger tree accurately in a way that takes into consideration spatial correlations.
On the Angular Correlation Functions of the Hubble Deep Field
Authors: Roukema Boudewijn F.
Published: July 2016

Roukema & Valls-Gabaud (1997) reinforce the conclusion of Colley et al. (1996, 1997) that the Hubble Deep Field (HDF) “galaxies” are probably star-forming regions, not “building-blocks”.
Far-IR Galaxy Counts Expected in the Iris Survey
Authors: Takeuchi T.T. , Hirashita H. , Hattori T. G. , Ohta K. , Shibai H.
Published: July 2016

Infrared Imaging Surveyor (IRIS, officially Astro-F) is a satellite which will be launched in the winter of 2003. The main purpose of the IRIS mission is an all sky survey in the mid- and far-IR with a flux limit much deeper than that of IRAS. In order to examine the performance of the survey and to find a suitable set of bandpasses for tracing galaxy evolution and picking up protogalaxy candidates as effective as possible using IRIS, we estimated the FIR galaxy counts based on a simple model with various sets of cosmological parameters and evolution types.
Clustering of Red Galaxies Near a Radio-Loud Quasar at z = 1.086
Authors: Tanaka I. , Yamada T. , Aragón-Salamanca A. , Kodama T. , Ohta K. , Arimoto N.
Published: July 2016

We investigated the environment of the radio-loud quasar 1335.8+2834 at z = 1.086 where an excess surface number density of galaxies was reported by Huthings et al. (1993). By obtaining near-infrared and new deep optical images of the field, we found a clustering of objects with very red optical-NIR color, 4 < R - K < 6 and 3 < I - K < 5 near the quasar. The colors and magnitude of the reddest objects are consistent with those predicted for old (2–4 Gyr) passively evolving elliptical galaxies at z = 1.1.
NGST: Seeing the First Stars and Galaxies Form
Authors: Stockman H.S. , Mather John
Published: July 2016

The Next Generation Space Telescope (NGST) is a key element in NASA's Origins program. The primary goals for the NGST are observing the origins of stars, galaxies, and the elements that are necessary for life. To reach those goals, the telescope must work in the near and mid-infrared – at wavelengths where the Earth's atmosphere outshines the distant galaxies by up to 8 orders of magnitude. NASA, industry, US astronomers and international collaborators have completed the initial feasibility study and have begun the development of the technologies required to make the mission affordable and ready to launch by 2007.
Big Bang Nucleosynthesis
Authors: Schramm D.N.
Published: July 2016

Big Bang Nucleosynthesis (BBN) is on the verge of undergoing a transformation now that extragalactic deuterium is being measured. Previously, the emphasis was on demonstrating the concordance of the Big Bang Nucleosynthesis model with the abundances of the light isotopes extrapolated back to their primordial values using stellar and Galactic evolution theories. Once the primordial deuterium abundance is converged upon, the nature of the field will shift to using the much more precise primordial D/H to constrain the more flexible stellar and Galactic evolution models (although the question of potential systematic error in 4He abundance determinations remains open). The remarkable success of the theory to date in establishing the concordance has led to the very robust conclusion of BBN regarding the baryon density. The BBN constraints on the cosmological baryon density are reviewed and demonstrate that the bulk of the baryons are dark and also that the bulk of the matter in the universe is non-baryonic. Comparison of baryonic density arguments from Lyman-α clouds, x-ray gas in clusters, the Sunyaev-Zeldovich effect, and the microwave anisotropy are made and shown to be consistent with the BBN value.
Deuterium Abundance in the Local ISM
Authors: L. Linsky Jeffrey , E. Wood Brian
Published: July 2016

Excellent HST/GHRS spectra of interstellar hydrogen and deuterium Lyman-α absorption toward nearby stars allow us to identify systematic errors that have plagued earlier work and to measure accurate values of the D/H ratio in local interstellar gas. Analysis of 12 sightlines through the Local Interstellar Cloud leads to a mean value of D/H = (1.50 ± 0.10) x 10−5 with all data points lying within ±1σ of the mean. Deciding whether or not the D/H ratio has different values elsewhere in the Galaxy and beyond will be one of the major objectives of the FUSE mission.
Abundances in Halo Population Stars
Authors: Sneden Christopher
Published: July 2016

The quest to define early galactic nucleosynthesis has drawn on the efforts of many observers and theoreticians over the past few decades. Significant insights on galactic halo chemical evolution have been revealed through the use of high resolution, high S/N spectroscopy to determine abundances in stars with metallicities ranging over three orders of magnitude. In the process, many galactic nucleosynthesis ideas that were firmly established only a decade ago now are either disproved, or are currently under challenge, or are weighed down with multiple known exceptions. The galactic halo has a rich chemical history, and we are just beginning to understand just how much work still remains before we can decipher its evolution.
Abundances in a Hot Horizontal-Branch Star in the Old Open Cluster NGC/6791
Authors: Peterson R.C. , Green E.M.
Published: July 2016

The open cluster NGC 6791 is more metal-rich than any other open cluster, yet several hot blue horizontal branch (BHB) stars are probable members. We have performed an abundance analysis of the coolest such star, 2-17, which has a radial velocity and a proper motion which support cluster membership. We find parameters typical of a metal-rich BHB star, with rotational velocity = 16 ± 1 km/s, an effective temperature Teff = 7250 ± 150 K, log gravity = 3.5 ±0.5 dex, and an iron abundance more than twice solar, [Fe/H] = +0.4 ± 0.1 dex. The light even-Z elements Mg, Ca, and Si are further enhanced, ruling out A-star peculiarities. Its analysis thus establishes the cluster metallicity accurately, free from serious blending which is problematical in metal-rich giants. Abundances of C, N, and O suggest little mixing. Visual comparison of the spectra of red HB stars in the cluster with that of the field star μ Leo indicates that the spectra are indistinguishable except for stronger CN in the former.

The high iron abundance, the light-element overabundances, the spectral similarity to strong-lined field giants, and the extensive presence of hot stars all highlight the fact that this old open cluster provides an excellent template for the study of metal-rich extragalactic systems. Properties of cluster members should establish not only accurate abundances for comparison with scenarios of nucelosynthesis and star formation, but also provide a testbed for ideas of the production of hot stars in a metal-rich environment, and so for the generation of the ultraviolet upturn in elliptical galaxies.
Enrichment of Heavy Elements in Clusters of Galaxies
Authors: Ishimaru Yuhri
Published: July 2016

We study the roles of type Ia (SNIa) and type II supernovae (SNII) in enrichment of the intra-cluster medium (ICM). Considering stellar [Fe/H] of ellipticals, iron mass in ICM to luminosity ratios, and [α/Fe] of ICM, we show that ~ 53% of iron in ICM comes from SNIa. While clusters keep all of ejecta from ellipticals, we obtain the observational evidence for that groups of galaxies lose parts of the gas by supernovae-driven winds. This ‘group wind’ scenario is confirmed by an 1D hydrodynamical model.
Are Elliptical Galaxies Really Metal-Rich?
Authors: Loewenstein M. , Mushotzky R. F.
Published: July 2016

In elliptical galaxies, where most of the stars - and therefore most of the heavy elements - were formed at an early epoch, the total mass, spatial distribution, and relative abundances of metals are intimately connected to the galaxy formation process.
Chemical Evolution of Spiral Galaxies from Redshift 4 to the Present
Authors: Fritze - v. Alvensleben U. , Lindner U. , Fricke K. J.
Published: July 2016

ISM abundances in nearby spiral galaxies are well known from HII region studies (Zaritsky et al. 1994). While early type spirals, Sa, Sb, have rather uniform abundances and a narrow range of present star formation rates (SFR) the galaxy-to-galaxy variations both in HII region abundances and in present SFR increase towards late spiral types Sc, Sd (see e.g. Kennicutt & Kent 1983). ISM abundances of spiral galaxies or their progenitors up to the highest redshifts can be studied via the absorption properties imprinted in the spectra of background QSOs. While MgII- and CIV- absorption lines are produced in the low column density gas of the extended haloes around galaxies, the Damped Lyα Absorption (DLA) is believed to originate in (proto-)galactic disks. High resolution spectroscopy of a large number of metal lines associated with DLA systems reveal the redshift evolution of ISM abundances from z ≳ 4 to z ~ 0.6.
The Hot Universe: An Overview
Authors: Tanaka Y.
Published: July 2016

The universe contains an extremely wide variety of temperature structures from 3K to 1 billion K and even beyond. This symposium focuses on the hot part of the universe. The “hot universe” is by far the best place to study high-energy astrophysics. In this overview, I shall be based mainly on the results in the X-ray band that best manifests the hot universe. However, needless to say that multi-wavelength investigations, from radio, infrared through gamma-rays, are essential for comprehensive understanding.
Solar Arcade Flarings as Magnetodynamic Process of Mass and Energy Shedding from Energized Magnetic Regions
Authors: Uchida Y. , Hirose S. , Cable S. , Uemura S. , Fujisaki K. , Torii M. , Morita S.
Published: July 2016

Prototypes of magnetic actions in producing and shedding the X-ray-emitting high temperature plasmas in various astrophysical objects are witnessed in the spatially-resolved form on the Sun by the Solar X-ray Satellite “Yohkoh”. The most prominent of those are arcade flarings seen as powerful arcade flares in active regions with strong magnetic field. Larger scale fainter X-ray arcade formation observed at high latitudes, shedding a large amount of mass and energy as CME's (coronal mass ejections) also belongs to this category. Since some features found by the new observation by Yohkoh are incompatible with the so-called “classical model of arcade flarings”, we advance an alternative model based on the quadruple magnetic sources in the photosphere.
Galactic 1.8 MeV Emission from Al-26
Authors: Prantzos N.
Published: July 2016

The detection of the relatively short-lived (~106 yr) radioactive 26Al in our Galaxy, more than 12 years ago, convincingly showed that nucleosynthesis is still active today on a large scale. Still, despite considerable efforts in the past decade, the site of this nucleosynthetic activity cannot be identified from theory alone; several potential sites are still on the list, been able to provide the 2-3 M⊙ of 26Al per Myr, implied by the detected 1.8 MeV flux of ~4 10−4 cm−2 s−1 from the galactic plane (see for a review).
Search for Nonthermal X-Rays from Supernova Remnant Shells
Authors: Petre R. , Keohane J. , Hwang U. , Allen G. , Gotthelf E.
Published: July 2016

The suggestion that the shocks of supernova remnants (SNR's) are cosmic ray acceleration sites dates back more than 40 years. While observations of nonthermal radio emission from SNR shells indicate the ubiquity of GeV cosmic ray production, there is still theoretical debate about whether SNR shocks accelerate particles up to the well-known “knee” in the primary cosmic ray spectrum at ~3,000 TeV. Recent X-ray observations of SN1006 and other SNR's may have provided the missing observational link between SNR shocks and high energy cosmic ray acceleration. We discuss these observations and their interpretation, and summarize our ongoing efforts to find evidence from X-ray observations of cosmic ray acceleration in the shells of other SNR's.
X-Ray Aspects of the IRAS Galaxies
Authors: Meurs E.J.A.
Published: July 2016

Several IRAS galaxies have been detected at X-rays, with a variety of satellite observatories. About half of these are classified optically as Seyfert galaxies. Among those not (convincingly) classified as AGN, many have X-ray luminosities for which stellar evolution products offer convenient explanations. Some non-active IRAS galaxies display anomalously high levels of X-ray emission for which several conceivable origins are investigated: optical misclassification, X-ray misidentification, hidden AGN, incidental activity, starburst, environmental sources. X-ray spectral studies and temporal variations constitute important tools for further investigation, for instance to assess the strength of a starburst or to establish signatures of an active core.
High Energy Phenomena in AGN Jets
Authors: Takahara F.
Published: July 2016

BL-Lac objects and optically violent variable quasars (OVVs), called together blazars, are characterized by rapid time variability, strong optical polarization, superluminal expansion and strong gamma-ray emission. Such properties are understood in the framework of a relativistic jet emanated from the central powerhouse. Blazars are considered to be objects for which the direction of the jet is very close to the line of sight.
Hierarchical Structure in Dark Matter Distributions
Authors: Makishima K.
Published: July 2016

Galaxy observers argue for the dark halo surrounding each galaxy, while cluster investigators discuss the dominance of dark matter (DM) in the intra-cluster space. Then, what is the relation between the cluster DM and the DM associated with member galaxies of the cluster?
Resistive Processes in the Preflare Phase of Eruptive Flares
Authors: Magara T. , Shibata K.
Published: July 2016

In this study, we perform 2.5-dimensional MHD simulations and clarify the role of perpendicular magnetic fields (which are perpendicular to the 2D plane) in a preflare current sheet of solar flares. At the first stage, a current sheet formed within a coronal magnetic structure is filled with the perpendicular fields (force-free structure). Then this sheet begins to be dissipated through the tearing instability under a uniform resistivity. As the instability proceeds, the distribution of the perpendicular fields vary in such a way that most of them gather around O-point (magnetic island) instead of X-point. Therefore, the magnetic pressure of these fields weaken in the vicinity of X-point so that they no longer suppress the inflows toward this point. These flows then make the current sheet thinner and thinner, which implies that the current density around X-point becomes high enough to cause an anomalous resistivity whose value is much larger than that of the normal collisional resistivity. In this way, the transition from a uniform resistivity to a locally-enhanced one occurs, which can make the violent energy release observed in solar flares.
HgMn Stars as Apparent X-Ray Emitters
Authors: Hubrig S. , Berghöfer T. W.
Published: July 2016

In the ROSAT all-sky survey 11 HgMn stars were detected as soft X-ray emitters (Berghöfer, Schmitt & Cassinelli 1996). Prior to ROSAT, X-ray observations with the Einstein Observatory had suggested that stars in the spectral range B5-A7 are devoid of X-ray emission. Since there is no X-ray emitting mechanism available for these stars (also not for HgMn stars), the usual argument in the case of an X-ray detected star of this spectral type is the existence of an unseen low-mass companion which is responsible for the X-ray emission. However, this hypothesis is not easily testable. Based on high resolution X-ray images taken with the ROSAT HRI, Berghöfer & Schmitt (1994) showed that known visual late-type companions can be disregarded in this context. In almost all cases studied so far (including two HgMn stars in our sample) the X-ray emission is associated with the primary B star.
Flares and MHD Jets in Protostar
Authors: Hayashi Mitsuru , Shibata Kazunari , Matsumoto Ryoji
Published: July 2016

By using ASCA, Koyama et al. (1994, 1996) carried out a systematic survey of hard X-ray sources in molecular clouds and revealed that protostars are strong hard X-ray emitting sources. Some of them show flare-like activities. Protostellar flares differ from solar flares in their total energy(1035-36 erg), size(several times the radius of protostar), and higher temperature(8keV). Protostellar flares are also observed in lower energy band by ROSAT in YLW15 (Grosso et al. 1997). By extending the model of solar flares associated with footpoint shearing motion, we proposed a model of protostellar flares in which the magnetic field connecting the protostar and the disk disrupt by twist injection from the rotating disk(Hayashi et al. 1996).
The Half-Life of Titanium 44 and SN 1987A
Authors: Mochizuki Yuko S. , Kumagai Shiomi
Published: July 2016

The radioactive isotopes, such as 44Ti and 56Ni, are synthesized as a result of rapid nucleosynthesis in supernova explosions. The gamma-ray photons coming out from the decay sequence of 44Ti is now a strong candidate to explain the the late light curve of SN 1987A. It is noted here that the energy release from the 44Ti decay depends strongly on its half-life. However, the published values for 44Ti half-life display a large spread, ranging from ~ 35 to ~ 68 years. In this paper (Kumagai et al. 1997; see also Kumagai et al. 1993), we discuss the value of the half-life by comparing the theoretical light curves and the observations in SN 1987A. The unestablished half-life value is related to the ratio of the abundance of 44Ti to that of 56Ni.
ASCA Observation of the Cygnus Loop Supernova Remnant
Authors: Miyata E. , Tsunemi H.
Published: July 2016

The Cygnus Loop is the prototype shell-like supernova remnant (SNR) and one of the brighest SNRs in X-ray wavelength. We have observed the entire Cygnus Loop with the X-ray satellite, ASCA. Its large apparent size, high surface brightness, and low absorption features have made the Cygnus Loop to be an ideal target for the study of the spatially-resolved spectroscopic structure in detail. Part of this work was summarized in Miyata (1996). Here, we present the first X-ray image of the Cygnus Loop obtained with ASCA.
Generation and Implications of Post-Merger Turbulence in Clusters of Galaxies
Authors: Goldman I.
Published: July 2016

Observations in X-ray and optical suggest that mergers of sub-clusters with galaxy clusters are quite common (for Coma see e.g., White et al. 1993; Colless & Dunn 1996; Ishizaka & Mineshige 1996). A merger leads to violent relaxation of the dissipationless dark matter resulting in a time-dependent gravitational potential. This in turn generates large-scale flows and shocks in the collisional baryonic intracluster gas (Takizawa & Mineshige 1997). Both the large scale flows and the shocks will excite turbulence in the gas. We focus here on turbulence generated by shocks, which is less dependent on the specifics of the merger. This paper is based on a more detailed work (Goldman 1997).
ASCA Study of Shaplay Supercluster
Authors: Hanami H.
Published: July 2016

We observed five clusters of galaxies in Shapley supercluster with ASCA; A3562, SC13290-313, SC1327-312, A3558 and A3556, which are candidates for interacting clusters since their separation and relative velocities are only 1Mpc and 700-1000km/s (e.g. Raychaudhury et al. '91, Breen et al. '94, Scaramella et al. '89). Main purpose of mapping observations is to make clear the formation and evolution process of the clusters of galaxies in a supercluster. ASCA gives essential informations of ICM like the temperature distribution related to the dynamics; the interactions due to the infalling and merging events. They are important tests for observational cosmology (e.g. Hanami '93).
Temperature Structure in Merging Coma Cluster of Galaxies
Authors: Honda H. , Hirayama M. , Ezawa H. , Kikuchi K. , Ohashi T. , Watanabe M. , Kunieda H. , Yamahita K.
Published: July 2016

The Coma cluster has been recognized as an archetype of rich and relaxed clusters, until recent ROSAT observations reveal that the intracluster medium (ICM) has a complex distribution (Briel et al. 1992; White et al. 1993). The X-ray surface brightness distribution shows a secondary peak around the galaxy NGC 4839, at 40' SW from the cluster center.
ASCA Observations of Three Gravitational Lensing Clusters of Galaxies; CL0500-24, CL2244-02, and A370
Authors: Ota Naomi , Mitsuda Kazuhisa , Fukazawa Yasushi
Published: July 2016

We determined the X-ray temperatures of three gravitational lensing clusters, CL0500-24, CL2244-02, and A370, and obtained significant constraints on the surface brightness profile assuming the β-model and the King model profiles. The mass of the cluster estimated from these X-ray data is by a factor of two to three smaller than the mass estimated from lens models for two of the clusters.
Final Performances of the X-Ray Mirrors of the Jet-X Telescope
Authors: Poretti E. , Campana S. , Citterio O. , Conconi P. , Ghigo M. , Mazzoleni F. , Tagliaferri G. , Cusumano G. , La Rosa G. , Bräuninger W. , Burkert W. , Castelli C.M. , Willingale R.
Published: July 2016

The Joint European X-ray Telescope (JET-X) is one of the core scientific instruments of the SPECTRUM RONTGEN-γ astrophysics mission. The project is a collaboration of British, Italian and Russian consortia, with the participation of the Max Planck Institut (Germany). JET-X was designed to study the emission from X-ray sources in the band of 0.3-10 keV. Citterio et al. (1996 and references therein) describe its structure, composed by two identical and coaligned Wolter I telescopes. Focal plane imaging is provided by cooled X-ray sensitive CCD detectors which combine high spatial resolution with good spectral resolution, including coverage of the iron line complex around 7 keV at a resolution of ΔE/E ~ 2%.
Radiative Winds from Accretion Disks in CVS
Authors: Hachiya M. , Tajima Y. , Fukue J.
Published: July 2016

P Cyg profiles observed in CVs strongly suggest the existence of accretion disk winds in CVs. Recently, X-ray observations revealed bipolar outflows in supersoft X-ray sources. The wind velocity measured in these observations is about 3000-5000 km s−1, which is of the order of the escape velocity of white dwarfs. Hence, it is supposed that the winds would originate from the inner disk and/or the boundary layers between the disk and white dwarf. We examine radiatively-acclerated accretion-disk winds, and found that the terminal speed of the wind emanated from the inner region becomes ~ 0.6GM/rin, where M is the white dwarf mass and rin the inner radius of the disk.
Rapid X-Ray Variability of Cyg X-1
Authors: Agrawal P. C. , Paul B. , Rao A. R. , Vahia M. N. , Yadav J. S. , Marar T. M. K. , Seetha S. , Kasturirangan K.
Published: July 2016

We have made observations of the black hole binary Cyg X-1 with the Indian X-ray Astronomy Experiment (IXAE). Observations made with time resolution ranging from 0.4 ms to 1 s showed variations and flaring activity on sub-sec and longer time scales. Results on time variability on different time scales and flaring characteristics in the two states of Cyg X-1 are presented.
Two-Temperature Transonic Accretion Disks
Authors: Nakamura K.E. , Kusunose M. , Matsumoto R. , Kato S.
Published: July 2016

The optically thin, advection-dominated accretion flows are thermally stable against global perturbations. In addition, they have high temperatures because of inefficient radiative cooling. They are thus promising candidates of models to explain the high energy emission of X-ray stars and AGNs. So far, models, however, take no account of the advective heat transport in determining the thermal structure of the electron system. The validly of this neglect, however, must be checked by integrating the electron energy equation globally as well as the ion energy one.
Enhancement of Turbulent Viscosity by Global Magnetic Fields in Accretion Disks
Authors: Nakao Yasushi
Published: July 2016

A model of magnetohydrodynamic (MHD) turbulence in accretion disks with global magnetic fields is constructed using a second-order closure modeling of turbulence. The transport equations of the Reynolds stress tensor, the Maxwell stress tensor, and the cross-helicity tensor (the correlation of velocity fluctuation and magnetic fluctuation) are closed by second-order quantities using atwo-scale direct interaction approximation(TSDIA). The quantities appearing these equations are considered to be those averaged in the vertical direction of the disks. The turbulence is assumed to be stationary. We are interested only in the effects of the global magnetic fields on the turbulence in the disks, i.e., no dynamo processes are considered, and the global magnetic fields are supposed to be embedded in the diska priori.
Numerical Simulation of Relativistic Jet Formation in Black Hole Magnetosphere
Authors: Koide Shinji , Shibata Kazunari , Kudoh Takahiro
Published: July 2016

The radio jets ejected from active galactic nuclei (AGNs) sometimes show proper motions with apparent velocity exceeding the speed of light. This phenomenon, called superluminal motion, is explained as relativistic jets propagating in a direction almost toward us, and has been thought to be ejected from the close vicinity of hypothetical supermassive black holes powering AGNs (Rees 1996). The magnetic mechanism has been proposed not only for AGN jets (Lovelace 1976; Blandford & Payne 1983) but also for protostellar jets (Pudritz & Norman 1986; Uchida & Shibata 1985; Shibata & Uchida 1986), although no one has yet performed nonsteady general relativistic magnetohydrodynamic (GRMHD) numerical simulations on the formation of jets from the accretion disk around a black hole.
Radiation from Advection-Dominated Flows
Authors: Manmoto T.
Published: July 2016

Advection-dominated accretion flow (hereafter ADAF) is the only self-consistent solution to describe the optically thin accretion flows around compact objects. The main feature of ADAF is that the dynamics of the flow is dominated by accretion process rather than radiation process. As a result of advection domination, the luminosity of ADAFs is very low. Coupled with the existence of the event horizon, ADAF has been successfully applied to the dim accretion black holes such as central core of our Galaxy: Sgr A*. In this issue, we calculate the spectrum radiated from the optically thin ADAFs and show that the observed spectrum of Sgr A* is explained with the accretion massive black hole.
Black-Hole Accretion Corona Immersed in the Disk Radiation Fields
Authors: Miwa T. , Watanabe Y. , Fukue J.
Published: July 2016

We examined an accretion-disk corona around a black hole immersed in the disk radiation fields (cf. Watanabe, Fukue 1996a, b). The corona is supposed to be initially at rest far from the center. During infall above and below the disk, the corona is suffered from the disk radiation fields. As a disk model, we adopted the standard α-disk, and in order to mimic the general relativisitic effects, we use the pseudo-Newtonian force proposed by Artemova et al. (1996). Moreover, we assume that the corona is geometrically thin and optically thin, and ignored any motion such as wind. We consider the cold case, where the pressure-gradient force is ignored. Under these assumptions, we calculated the motion of the corona gas and found that the infall of corona is supressed due to disk radiation fields.
ROSAT X-Ray Observations of the Radio Galaxy 4C46.09
Authors: Leahy D.A.
Published: July 2016

4C46.09 is the radio source that shows up as a point-like x-ray source inside the supernova remnant HB9 (Leahy, 1987). Leahy, 1987 found a 0.2-4 keV Einstein IPC flux of approximately 1.5 × 10−12erg cm−2s−1 and a significantly higher hardness ratio than the rest of HB9. Too few counts were available for any spectral analysis. Seward et al, 1991, found 4C46.09 to be a large radio galaxy at redshift 0.195 and distance 1280 Mpc (Ho = 50 km s−1Mpc−1). 4C46.09 is of further interest due to the observation of a high energy component in the spectrum of HB9 observed by GINGA (Yamauchi and Koyama, 1993). Whether this was due to HB9 or to 4C46.09 could not be determined.
Dynamical Evolution of Accretion Flow onto a Black Hole
Authors: Yokosawa M.
Published: July 2016

Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.
Stellar radii
Authors: Scholz M.
Published: July 2016

Observing a stellar radius basically means observing a center-to-limb intensity variation. The significance and properties of center-to-limb variations, common approximations, the correlation with optical-depth radii in extended-photophere stars, and direct measurements of angular (interferometry, lunar occultation) and absolute diameters (binary eclipses) are discussed. Spectrophotometric and doppler techniques of diameter determination are also briefly outlined.
The visual and infrared flux calibrations
Authors: Megessier C.
Published: July 2016

We present a critical review of the available visible and near infrared flux calibrations. In the visible, the accuracy and the good consistency of three independent determinations of Vega monochromatic flux allow one to recommend with confidence f5556-Vega = 3.46 10−11Wm−2nm−1 within 0.7%. In the near infrared, the possible flux excess of Vega, as compared to that derived from the atmosphere models fitting the visible, does not allow such a good accuracy. The agreement between the calibrations, either from a comparison of Vega to blackbodies or from solar analog stars, would question the calibrations relying on models. More work is necessary to conclude with confidence and then to reduce the uncertainty on the near infrared calibrations.
Review of abundances for mid-Teff range stars
Authors: Nissen P.E.
Published: July 2016

Among the mid-Teff (5000–7000 K) range stars, those on or near the main sequence are particularly important, because they provide much information on Galactic evolution and nucleosynthesis of the elements. This is due to the fact that these stars represent an age range from 0 to 15 Gyr, and a metallicity range from [Fe/H] ⋍ −4.0 to +0.3. Furthermore, it is likely that the present composition of elements in their atmospheres is similar to the composition of the interstellar gas from which they were formed, and that the present kinematics of the stars give information about their birthplaces. Hence, by observing selected samples of nearby F and G main sequence and subgiant stars one has the possibility to study the chemical and dynamical history of our Galaxy. Due to space limitation the present review is limited to these F and G stars. Supergiants are not discussed, but it should be emphasized, that their abundances are important for studies of advanced stellar evolutionary phases and determinations of the chemical composition of nearby galaxies. e.g. the Magellanic Clouds (Hill et al. 1995).
Abundances of the elements in the halo stars, interaction between observation and theory
Authors: Spite M.
Published: July 2016

The halo stars are very old stars formed at the beginning of the evolution of the Galaxy. Their main characteristic is that their atmosphere is very metal-poor since at the time of their birth, the matter of the Galaxy had been enriched by only a few number of supernovae. The first very metal deficient stars have been studied in the sixties: Baschek (1959), Aller and Greenstein(1960) Wallerstein et al. (1963). The stellar models used in these first studies were rather crude: the atmosphere of the stars was represented by only one layer with a mean temperature and a mean electronic pressure, the continuum opacity was supposed to be due to H− and included in addition only the contribution by Rayleigh scattering. Later rescaled solar models were used and finally, at the end of the seventies, grids of theoretical models more and more sophisticated became available.
Chromospheres, activity and magnetic fields
Authors: Gnedin Yu. N.
Published: July 2016

This brief review presents the current state of observations of stellar activity effects including the fluxes of chromospheric emission lines: CaII H+K, MgII h+k, SiII 1812 Å multiplet, CIV, as well as radio and X-ray fluxes versus B-V colours and luminosity classes, rotation periods, Rossby number and especially versus the mean magnetic flux density 〈fB〉. Results of stellar magnetic field measurements are presented.
Constraints on stellar interior physics from helioseismology
Authors: Christensen-Dalsgaard J.
Published: July 2016

Traditional observations of the properties of stars generally provide tests of only the gross aspects of stellar structure and evolution. The limitation lies in the amount and precision of the available data of relevance to the structure of the stellar interior, i.e., the determination of stellar effective temperatures, surface composition, luminosities and, in a few cases, masses. Additional constraints on the observed stars, such as the common age and composition normally assumed for stars in clusters or multiple systems, clearly increase the information. However, detailed information on the physics and processes of stellar interiors requires more extensive data, with a dependence on stellar structure sufficiently simple to allow unambiguous interpretation. Such data are offered by observations of stellar pulsation frequencies: they can be observed with great accuracy and their dependence of stellar structure is generally well understood. In particular, the richness and precision of the observed frequencies of solar oscillation are now offering a detailed view on the interior properties of a star.
Hipparcos subdwarfs and globular cluster ages: towards reliable absolute ages
Authors: Pont F. , Mayor M. , Turon C.
Published: July 2016

The maximum age of galactic globular clusters provides the best observational constraint on the minimum age of the Universe. One of the main “missing link” in the globular cluster age determination has been the lack of a precise calibration, with local subdwarfs, of the position of the subdwarf sequence at different [Fe/H].

Hipparcos data may change this situation. As many precise parallaxes become available for local subdwarfs, the distance to globular clusters can be estimated directly from ZAMS fitting to the subdwarf locus. The ages can then be inferred from the turnoff luminosity (a robust prediction of stellar evolution models), rather than using secondary indicators such as Horizontal-Branch position, or indicators depending on the uncertain colour scale such as turnoff colour.

Combining Hipparcos parallaxes with [Fe/H] values determined with the CORAVEL spectrometer, we are studying the position of the subdwarfs in the Colour-Magnitude Diagram from a sample of more than 900 subdwarf candidates. Preliminary results are presented here. It is shown that the distances of many subdwarfs had been underestimated in previous studies, mainly because a large fraction of them is in fact evolved off the main sequence into the turnoff or the subgiant branch.
SMC 1 or What's in a Name?
Authors: Dickel Hélène R.
Published: July 2016

What's in a name? Everything! SMC 1 is a planetary nebula in the Large Magellanic Cloud! URLs of Web documents are given to aid astronomers in designating their astronomical sources so as to avoid confusion in the literature.
Neutral Hydrogen in the Magellanic Clouds
Authors: Staveley-Smith L. , Kim S. , Stanimirović S.
Published: July 2016

We review observations of neutral atomic hydrogen (HI) in the Magellanic Clouds (MCs). Being the nearest gas-rich neighbours of the Milky Way the MCs give us an excellent opportunity to study in detail the structure and evolution of the interstellar medium (ISM) and the effect of interactions between galaxies. HI in emission provides a probe of the structure and velocity field of the Clouds, allowing the study of their velocity dispersion, 3-D structure, and large-scale total-mass distribution. Recent data from Australia Telescope Compact Array surveys reveal a morphology (for both Clouds) which is heavily dominated by the effects of local star-formation, rotational shear, fragmentation, self-gravity and turbulence. The new data, which has a spatial resolution down to 10 pc, also allows the study of the distribution functions in velocity and mass for HI clouds. We discuss the morphology, dynamics and giant shell population of the LMC and SMC.
A 12CO Survey of the LMC with NANTEN
Authors: Fukui Y. , Abe R. , Hara A. , Hayakawa T. , Kato S. , Kawamura A. , Mizuno A. , Mizuno N. , Ogawa H. , Onishi T. , Saito H. , Tachihara K. , Xiao K. C. , Yamaguchi N. , Yamaguchi R. , Yonekura Y. , Rubio M.
Published: July 2016

We have made a 12CO(J = 1−0) survey of the LMC with NANTEN. A sample of 55 giant molecular clouds has been identified and comparisons with stellar clusters, HII regions and SNRs are presented. The connection between the clouds and cluster formation is discussed.
Molecular Gas in the Magellanic Clouds
Authors: Rubio Mónica
Published: July 2016

The molecular gas content in the Magellanic Clouds has been studied, with different spatial coverage and resolution, through obervations of CO(1-0) line emission. In the LMC and the SMC the molecular gas is dominated by clouds whose properties are different from those of their Galactic counterparts. The relation between the intensity of CO emission and molecular hydrogen column density, or the conversion factor X, is different than that of molecular clouds in our Galaxy and depends on the ambient physical conditions. Studying the molecular gas through observations in the H2 emission line may prove an alternative way to determine the molecular content associated with star forming regions in the Magellanic Clouds. In particular, results obtained towards 30 Doradus in the LMC are presented.
Supernova Remnants in the Magellanic Clouds
Authors: Petre R.
Published: July 2016

Over the past decade, substantial progress has been made in understanding the properties of Magellanic Cloud supernova remnants and their role in the ISM. Among the notable results are the “typing” of progenitors via the X-ray spectra of their remnants, the use of X-ray spectra to measure ISM abundances, and the discovery of remnants with unique properties. I summarize recent studies of MC SNRs, and describe how a refined understanding of the SNR population requires consideration of the unique attributes of each remnant.
Narrow Band HI System for the Parkes Telescope Multibeam Package
Authors: Haynes Raymond , Staveley-Smith Lister , Mebold Ulrich , Kalberla Peter , Jones Keith , White Graeme , Jones Paul , Filipovic Miroslav , Dickey John , Green Anne
Published: July 2016

A narrow-band translator and filter system has been constructed for the Parkes Multibeam receiver. This brief note outlines the characteristics of the system and indicates the range of new projects that will be possible in studies of the Magellanic Clouds.
Molecular Line Observations in the Magellanic Clouds
Authors: Johansson Lars E.B. , Heikkilä Arto , Olofsson Hans
Published: July 2016

We have observed spectral line emission from a sample of clouds in the Magellanic Clouds to investigate the effects of metallicity and FUV radiation on the physical and chemical properties of the interstellar medium. The clouds were identified by CO surveys and selected to cover a wide range of environments. We present molecular line data for five clouds in the LMC and one cloud in the SMC.
Radio Properties of Magellanic Cloud SNRs
Authors: Dickel John R.
Published: July 2016

Supernova remnants in the Magellanic Clouds may have somewhat lower surface brightnesses at radio wavelengths than their counterparts in the Milky Way but otherwise they appear to be very similar. Balmer dominated SNRs have a lower radio luminosity than other shell remnants.
X-ray Spectroscopy of the Supernova Remnant N103B
Authors: Hwang U. , Petre R. , Gotthelf E. , Hughes J. , Keohane J.
Published: July 2016

We report and interpret a new, 100 ks X-ray observation of the supernova remnant N103B obtained by the ASCA Observatory.
Supernova Remnants in the Large Magellanic Cloud: A Multiwavelength Study of Energetics and Environments
Authors: Williams Rosa Murphy , Chu You-Hua , Dickel John R. , Smith R. Chris
Published: July 2016

We analyze optical, radio and X-ray data from supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) in order to make a systematic study of a full sample at a known distance. By this multiwavelength examination of SNRs from various progenitors and environments, we will build a comprehensive picture of the evolution of SNR structure and energetics.
Kinematics of the Ionized Gas in the Irregular Galaxies IC 10 and NGC 4449
Authors: Rosado M. , Bullejos A. , Valdez M. , Georgiev L. , Lacey C. , Borissova J. , Esteban C.
Published: July 2016

We have searched for supernova remnants (SNRs) in the irregular galaxies IC 10 and NGC 4449 by means of Fabry-Perot interferometry in Hα and [SII] lines, complemented by radio continuum observations. We find several new SNR candidates in each galaxy in addition to the known ones. Although these galaxies have several common properties, the distributions of SNRs in each galaxy is different. This shows that the star formation mechanisms in these galaxies act in different ways, in favor of the formation of a large nebular HII complex in IC 10, similar to 30 Dor in the Large Magellanic Cloud. We are studying the conditions over which these different star formation histories take place.