bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rosat WFC EUV Observations of Ab Dor (And other Local Group Stars)
Authors: Kellett Barry J. , Bromage Gordon E. 
Published: July 2016

The Rosat Observatory was launched on June 1st, 1990, and after a brief Performance Verification phase, performed an almost complete sky survey. One of the two main telescopes on the Observatory is the UK Wide Field Camera (WFC). The WFC is the first extreme ultraviolet (EUV) instrument to survey the whole sky, and during the survey detected several hundred active late-type stars.The WFC (Wells et al., 1990) was built by a consortium of five UK institutes, four Universities and the Rutherford Appleton Laboratory. During the all-sky survey, two filters were used. These allow broad-band photometry to be performed. The SIA filter (lexan/carbon/boron) and S2A filter (lexan/beryllium) were alternated on a one day basis. The SIA filter covers the energy range 0.085-0.180 KeV, centred on 0.124 KeV, while the softer S2A filter covers the range 0.070-0.110 KeV (centred on 0.090 KeV) (10% efficiency) [see Kent et al. (1990) for a full description of the WFC filters].
Low-Level Stellar Variability
Authors: Grenon M. 
Published: July 2016

AbstractThe capability of ground-based photometry to detect and monitor low-level stellar variations is discussed in the particular case of amplitudes in the range of few magnitudes to few percent. The technical and atmospherical constraints are briefly recalled. The variability level of the so-called constant stars is discussed as function of the spectral type, the luminosity class and the effective temperature. The photometric aspects of the Hipparcos mission are presented here since this satellite allows a systematic detection of microvariables and the obtention of light curves across the whole HR-diagram with an unprecedented efficiency.
Radial and Nonradial Mode Instability in B-Type Stars
Authors: Dziembowski W.A. , Pamyatnykh A.A. 
Published: July 2016

Recently three independent groups(Cox et al. 1992; Kiriakidis et al. 1992; Moskalik and Dziembowski, 1992), using opacity tables published by Iglesias and Rogers (1991), demonstrated that β Cep star models are pulsationally unstable. The instability is driven by the classical к- mechanism acting in the layer with temperatures near 2 × 105K where there is a bump in metal opacity. The groups reported results of calculations made for rather narrow ranges of stellar parameters and oscillation modes. We conducted an extensive search for unstable modes in complete evolutionary models of B-type stars of luminosity classes III - V. Our aim was to determine the domain of instability and examine its role not only in β Cep stars but also in variable stars located in the nearby areas of the H-R diagram.An unexpected new aspect of our calculations is the use of the improved opacity data. In a very recent work Iglesias, Rogers and Wilson (1992) showed that effects of spin-orbit interactions significantly enhance opacity in the critical region for driving the pulsations in β Cep stars. These effects and improved information about the solar metal mixture have been included in the updated opacity tables kindly provided to us via electronic mail by Dr. Rogers. The consequences of this change in opacity for stability of B-type star models are indeed quite important. Contrary to previously announced results, that only the fundamental mode is unstable, we now find the first two radial overtones to be unstable, as well. Thus, the discrepancy between the theoretical prediction and the mode identification suggested by observers has been removed. Furthermore, no longer is a high metal abundance (Z > 0.03) required to explain the occurrence of pulsation in most of the objects. In fact, the theoretical instability domain in the H-R diagram, based on the models calculated with Z = 0.02, agrees better with the observational β Cep domain than that based on the models Z = 0.03.
Stephi: A New Approach to δ Scuti Asteroseismology
Authors: Belmonte J.A. , Cortés T. Roca , Vidal I. , Schmider F.X. , Michel E. , Baglin A. , Chevreton M. , Auvergne M. , Man-Geney A. , Goupil M.J. , Massacrier G. , Serre T. , Álvarez M. , Jiang S.Y. , Liu Y.Y. , Fu J.N. , Dolez N. , Sareyan J.P. , Valtier J.C. 
Published: July 2016

The STEPHI network (STEllar PHotometry International) is a multinational cooperation stablished in order to get as perfect data as possible on several δ Scuti stars, within a reasonable period of time. STEPHI is currently integrated by nearly 15 people, belonging to the first four institutions cited above. However, astronomers of other institutions have eventually contributed to the network. The idea was born in 1986 and the network has been working to full operation since August 1989. A campaign, observing one or two δ Scuties is normally undertaken every 15 months. They are usually order of three weeks long, avoiding full-moon periods. Up to now, four campaigns have been performed, the last ending February 1992.Very good outcomes on five δScuties [63 Herculis in June 1987 (Belmonte et al, 1991), GX Pegasi in September 1989 (Michel et al, 1992a), v650 Tauri in November 1990 (Belmonte and Michel, 1991; Michel et al, 1992b) and, finally, BN Cancri and BU Cancri in February 1992] have been obtained. Indeed, some very useful aditional information on comparison stars (see e.g. Belmonte et al, 1990) and sky conditions (transparency, brightness, scintillation, etc..) has been obtained as well. Aditionally, some key information about mostly all multiperiodic (four or more periods) δ Scuti stars studied up to March 1992, with good quality data, is presented in this report.
The Berkeley-Illinois-Maryland-Association Millimeter Array
Authors: Welch Wm. J. 
Published: July 2016

AbstractThis is a general description of the BIMA millimeter wavelength array, including some recent scientific results, the status of the expansion to a larger number of antennas, and preliminary results of attempts to correct for atmospheric “seeing”. The examples of scientific results show CO images of the galaxy IC 342, emission in other spectral lines from the two regions of massive star formation SGR B2 and Orion South, and continuum emission from solar flares and the planet Mercury. There follows a brief description of the new antennas, new correlator, new receivers, and new refrigerators of the expanded array. Finally, there is a discussion of the first results from attempts to use measured fluctuations in the brightness of the atmosphere at the observing wavelength to infer the visibility phase fluctuatons due to the atmosphere. Removal of the phase fluctuations using the brightness fluctuations provides a better image of a test observation of M87.
The IRAM Interferometer on Plateau de Bure
Authors: Guilloteau S. 
Published: July 2016

AbstractIn November 1992, the IRAM interferometer on Plateau de Bure has reach two years of operation. After a review of its current technical status, with emphasis on its specificities, this paper presents an overview of its capabilities, illustrated by examples taken from the scientific program carried on during these two years. On-going upgrades and future plans are presented.
A VLBI Study of H2O Maser Spots Associated with a Molecular Outflow ρ Oph-East
Authors: Iwata Takahiro , Takaba Hiroshi , Matsumoto Kin-Ya , Kameno Seiji , Kawaguchi Noriyuki 
Published: July 2016

A molecular outflow is one of the most conspicuous active phenomena associated with protostars, and the kinetic energy of its outflowing mass is as large as that of random motions of ambient molecular cloud, which suggests that outflow has dynamically influence on ambient molecular gas. Possible observational evidence which suggests the existence of dynamical interaction between molecular outflow and ambient molecular cloud has been detected in several star forming regions (Fukui et al. 1986; Iwata et al. 1988). Recent detections of H2O maser emission associated with low-mass protostars (e.g. Comoretto et al. 1990) also suggest that there still exist active phenomena in the low-mass star forming regions.Molecular outflow ρ Oph-East, discovered toward a low-mass protostar IRAS 16293-2422 (Fukui et al. 1986), has been known as a site of dynamical interaction between molecular outflowing gas and ambient molecular cloud by CO and NH3 observation (Mizuno et al. 1990). Existence of several strong H2O maser spots (Wilking & Claussen 1987; Wotten 1989; Terebey et al. 1992) also suggests that active phenomena are occurring in this region. In this paper, we report our result of H2O maser observation for molecular outflow ρ Oph-East with milli-arcsecond resolution by VLBI.
The Submillimeter Telescope - A Status Report
Authors: Martin R. N. , Baars J. W. M. 
Published: July 2016

SummaryThe Max-Planck-Institut für Radioastronomie, Bonn and the Steward Observatory of the University of Arizona, Tucson are collaborating on the construction and operation of a dedicated submillimeter facility. The Submillimeter Telescope (SMT) is a 10 m diameter reflector surrounded by a corotating enclosure. The instrument is an alt-azimuth mounted f/13.8 Cassegrain homology telescope with two Nasmyth and bent Cassegrain foci. The SMT will have diffraction limited performance at a wavelength of 300 μm. and an operating overall figure accuracy of 15 μm rms. The primary and secondary reflector surfaces are constructed out of aluminum-core, carbon-fiber-reinforced-plastic (CFRP) face sheet sandwich panels. The primary reflector backup structure and secondary support are fabricated from CFRP structural members. This modern technology provides both the means for reaching the required precision of the SMT for both night and day operation (basically because of the low coefficient of thermal expansion and high strength-to-weight ratio of CFRP) and a potential route for the realization of lightweight telescopes of even greater accuracy in the future. The SMT will be the highest accuracy radio telescope ever built.The SMT is located at an altitude of 3180 m on Emerald Peak (Mt. Graham) 120 km northeast of Tucson in southern Arizona. Measurements indicate that atmospheric conditions allow submillimeter observations during about 40% of the time in winter months. The telescope is placed in a co-rotating enclosure of novel design. The enclosure fits tightly around the telescope, with the focus flanges extending from the elevation bearings into the receiver rooms of the enclosure. A flat tertiary mirror is used to direct the beam through either of the two elevation bearings. Thus, we are able to mount receivers directly on the telescope while maintaining laboratory type conditions in the access area surrounding the receivers. On the “facility instrument” side, several receivers can be operated simultaneously.
Statistical Comparison of CLEAN and MEM
Authors: Ishiguro M. , Ishiguro M. , Morita K.-I. , Murata Y. 
Published: July 2016

Assume that a set of visibility data{(uj, vj, zj)| j = 1, 2,...,N}is given where visibility zj observed at time j can be expressed in terms of “true visibility” defined by the brightness distribution T(x,y) and observation noise εj:where{(uj, vj)} is a given set of points in the u-v plane. It is assumed that u-v plane is gridded with the interval Δ. The dirty map obtained byis a crude estimate of the true brightness distribution. CLEAN and MEM are two typical methods to get better estimates.
Spectral Turn-Over of Radio Arc Filaments at 43 GHz: Magnetic Tubes of 4000-yr Old in the Galactic Center
Authors: Sofue Yoshiaki , Murata Yasuhiro , Reich Wolfgang 
Published: July 2016

The origin of the straight magnetic filaments in the Radio Arc near the Galactic Center is still controversial: either if they are permanent structure of constant configuration for a galactic-time scale, or they are temporary structure of short life time such as due to a sudden injection of cosmic rays or to sudden shock compression. Measurement of life time of the radio emitting cosmic ray electrons consisting the filaments is one of the crucial methods besides a time variation measurement of the fine structure of the filaments.In order to investigate possible spatial variation of spectral index at higher frequencies in the filaments, which might give information about the life time of cosmic ray electrons, we have performed high-resolution radio continuum observations at 43 GHz of the GO.18-0.04 region of the radio Arc near the galactic center using the Nobeyama Millimeter-wave Array. A detailed description of this work is given in Sofue et al. (1992).
Aperture Synthesis Obervations of The Galactic Center 50-km·s−1 Moleculer Could
Authors: Tsuboi Masato , Okumura Sachiko K. , Ishiguro Masato 
Published: July 2016

Molecular clouds in the Galactic center region are distributed mainly along the Galactic plane and have filamentary shapes with several clumps (Bally et al. 1987, Tsuboi et al. 1989). The “50-km.s−1 molecular cloud (M-0.02-0.07)”, which is located ~3’ east from Sgr A West, is one of most remarkable clumps on these molecular filaments. The intimate relation between this cloud and Sgr A East has been mentioned by many authers (e.g. Ho et al. 1986). Several compact HII regions are located toward the cloud (Ekers et al. 1983). The recombination line velocities correspond to the molecular line velocities in the cloud (Goss et al. 1987). Thus this cloud is one of active star forming regions near the Galactic center.We observed the 50-km-s−1 molecular cloud in CS J=1-0 emission line (48.991 GHz) using the Nobeyama Millimeter Array (NMA) to reveal the detailed structure of the star forming regions near the Galactic center.
Observations of Orion Molecular Cloud with NMA
Authors: Murata Y. , Kawabe R. , Ishiguro M. , Morita K.-I. , Hasegawa T. , Hayashi M. 
Published: July 2016

AbstractWe have made aperture synthesis multifield observations of Orion Molecular Cloud-1 (OMC-1) in the CS (J=1-0) line using the Nobeyama Millimeter Array (NMA), and obtained 9” resolution maps over 10’ length. The OMC-1 ridge shows a wiggled structure. The position angle of whole the ridge is ~ 0° - 10°, but ~ 20° - 30°around the clumps. It is possible to make this structure by the magnetic field with a position angle of ~ 150°. We also found filamentary structures in the northwest of Orion-KL, with a length-width ratio of more than 25, which are made by the gas flow from Orion-KL.
Probing Molecular Shocks with Millimeter and Near-IR Interferometric Imaging
Authors: Wang Zhong , Burton Michael G. 
Published: July 2016

AbstractWe make detailed comparison between the high resolution CO (J=2-l, 1-0) maps obtained with the OVRO Millimeter Array and the 2.12 µm H2(v=1-0) S(1) multi-channel images obtained using a Fabry-Perot system with the UKIRT Infrared Array Camera. Both datasets cover an interstellar shockfront region in the vicinity of the Galactic supernova remnant IC 443, and provide complementary information of the strongly shocked molecular gas on scales of 0.01 pc and a few km s−1. Combining our data with other atomic/molecular line probes, we find that a combination of bow-shock and cloud internal shock can best describe the interface between the supernova blast wave and pre-existing molecular clouds.
Numerical Simulations of Collapse of a Magnetized Rotating Molecular Cloud
Authors: Ohta Kanji , Habe Asao 
Published: July 2016

Recent observations reveal the velocity structure of star forming regions and the magnetic field in molecular clouds. It is known from observations that the molecular clouds rotate. It is suggested that the magnetic field have a important roll of the star formation process (e.g. Myers and Goodman 1988) and rotation of cloud have effects for evolution of molecular cloud. However it is not cleared how the magnetic field plays a roll of the star formation process in a rotating cloud.In the previous theoretical studies, most of simulations are performed for collapse process of a rotating cloud without magnetic field (e.g. Miyama et al. 1984, Boss 1990) or collapse process of a magnetized cloud without rotation (e.g. Scott and Black 1980). Dorfi (1982) studied collapse of a magnetized, rotating cloud. However he did not calculate those with high resolutions, since he performed 3-dimensional calculations of about 6000 grid points.Since observation instruments have been developed, it is possible to observe the star forming regions with good resolution. We study the collapse of the rotating, magnetized, isothermal cloud by mean of the axisymmetric numerical simulations with high resolution.
CO (2-1) in IC 342
Authors: Turner Jean L. , Hudson David , Hurt Robert L. 
Published: July 2016

AbstractWe present aperture synthesis maps of the CO J=2-1 emission in the central region of the spiral galaxy IC 342. The 4” resolution maps reveal emission that is a factor of two brighter than the CO (1-0) emission mapped at the same resolution. Since the CO (2-1) emission is likely to be optically thick, the high ratio is probably due to the fact that the two transitions sample different cloud layers in externally heated clouds. The high signal to noise of the maps indicates that CO (2-1) will be a powerful tool in the study of gas in galaxies.
The Polar Ring Starburst Galaxy NGC 660
Authors: van Driel W. , Combes F. , Nakai N. , Yoshida S. 
Published: July 2016

NGC 660 is a gas-rich, peculiar polar ring RSBa-type starburst galaxy with two distinct morphological and kinematic components: an inner disc, seen almost edge-on, with a major axis position angle of 45° and a diameter of ~11 kpc [D=13 Mpc, Ho=75 kms−1 Mpc−1], and an outer polar ring (p.a. 170°) with a diameter of 31 kpc, inclined on average about 55° with respect to the major axis of the inner disc.We obtained deep, 30 min. exposure CCD images of NGC 660 with the 105 cm Schmidt telescope of Kiso Observatory in the B, V, R, and I bands. A preliminary reduction shows that the inner disc is clearly redder than the polar ring and the nucleus.Optical spectra indicate that the galaxy has a LINER-type spectrum, suggesting intense massive star formation in the nucleus. We obtained a long-slit Ha spectrum along the major axis of the inner disc at ESO, which shows a very steep gradient near the nucleus. Assuming an inclination of 80°, it implies a rotational velocity of about 150 km s−1 for the inner disc.
A Basic Step Toward the CO-Line Tully-Fisher Relation
Authors: Sofue Yoshiaki , Schöniger Franz 
Published: July 2016

The Tully-Fisher relation makes use of the correlation between the HI linewidth and the luminosity of a galaxy and is one of the most powerful tools to estimate distances of galaxies. Because of the smaller beam the CO line might be an alternative to HI for distant galaxies which so far can not be examined even by the largest telescopes (Dickey and Kazes 1992).In order to consider the question whether the CO lineprofile could be used as an alternative or a supplement for HI in the Tullly-Fisher relation, we compared the total CO (J=2-1) line profiles of ten galaxies with the corresponding HI profiles. Four almost perfect edge-on galaxies (NGC 891, NGC 4565, NGC 4631 and NGC 3079) and the Seyfert galaxy NGC 1808 have been observed in CO using the Nobeyama 45-m telescope. The HI profiles and the data of the other galaxies has been taken from the literature.
12CO(J = 1-0) Mapping of the Merging Galaxy NGC 3310
Authors: Kikumoto T. , Taniguchi Y. , Suzuki M. , Tomisaka K. 
Published: July 2016

Since molecular gas clouds in nuclear regions play important roles on both the intense star formation and fueling active galactic nuclei, a large number of molecular-line observations have been made for starburst, Seyfert, and merging galaxies. Recently, millimeter-wave arrays have been used to study circumnuclear molecular gas in merging galaxies. Most of them, however, have been devoted to the observations of more luminous objects such as ultra-luminous merging galaxies (ULMGs) discovered by IRAS (Sanders et al. 1988). In order to obtain a comprehensive understanding, it is necessary to study less-luminous merging galaxies. With this motivation, we present results of CO mapping of NGC 3310 which is one of less luminous merger candidates (LFIR = 2.5 × 1010Lʘ).The central region (5.1 kpc in diameter) of NGC 3310 was observed in CO(J = 1 − 0) using the Nobeyama Millimeter Array. The synthesized beam size was 6″.3 × 6″.1, which corresponds to 500 × 480 pc at the distance 16.3 Mpc. Our main results and conclusions are summarized as follows.
CO(3-2) Observations of IRAS F10214+4724 at NMA
Authors: Kazushi Sakamoto , Ryohei Kawabe , Sumio Ishizuki , Masato Ishiguro 
Published: July 2016

AbstractWe have observed CO(J=3-2) emission of the z=2.286 galaxy IRAS F10214+4724 using the Nobeyama Millimeter Array.
N and Fe-Peak Elemental Abundances from IUE Co-Added Spectra of Hg-Mn and Normal Stars
Authors: Roby Scott W. , Adelman Saul J. , Leckrone David S. , Cowley Charles , Wahlgren Glenn M. 
Published: July 2016

AbstractLeckrone and Adelman have established an IUE observing strategy that has yielded co-added spectra with enhanced S/N ratios for several A and B stars. New observations by Roby and Adelman using the same technique have added two new Hg-Mn stars into this sample. We have begun a long-term study of elemental abundances in this uniform, high-quality set of IUE spectra for 13 stars. We report on the first stages of this project: abundances for N, Cr, Mn, Fe, Co, and Ni. The study of the Fe- peak elements show that our data set can provide accurate abundances and that abundances obtained from UV and optical spectra often are in good agreement. This study provides the groundwork for self-consistent abundance analyses of more exotic elements in our long term project.
Estimation of Stellar Magnetic Fields from Line-Strengths: Refined Hensberge-De Loore Method
Authors: Takeda Yoichi 
Published: July 2016

AbstractA method for determining the strength of a stellar magnetic field is presented, which is based on the requirement that the scatter of abundances from various lines should be minimized on the best choice of the field strength and the microturbulence. This procedure is applied to o Peg and cool Ap stars, showing that the resulting solutions are consistent with those derived from other methods.
Radio and X-Ray Emissions from Chemically Peculiar B- and A-Type Stars: Observations and a Model
Authors: Linsky Jeffrey L. 
Published: July 2016

AbstractConventional wisdom holds that early-type and late-type stars have very different outer atmospheres, because the early-type stars lack deep convective zones. I argue that the magnetic chemically peculiar (CP) stars hotter than about spectral type A2 display many of the activity phenomena seen in the most active late-type stars. In particular, many CP stars are luminous nonthermal radio and coronal x-ray sources like the RS CVn systems. A wind-fed magnetosphere model has been proposed to explain both the nonthermal radio and the x-ray emission. In this model the stellar wind plays the role of a mechanical energy source analogous to the role played by convection in the active late-type stars.