bluuebunny/crossref_metadata_2025_split huggingface dataset:
β Cas: Simultaneous Stromgren Photometry
Authors: Rodriguez E. , Rolland A. , De Coca P. Lopez , Garrido R. , Gonzalez-Bedolla S.F. 
Published: July 2016

The observations were carried out in August, 1983 using the 75 cm telescope at Sierra Nevada Observatory in Spain. This telescope is equipped with a six-channel uvbyβ photometer for simultaneous measurements in uvby and the narrow and wide Hβ channels, respectively. The observations were collected during four nights in the four uvby filters and one more night was devoted to measuring β Cas in the n and w bands of the Hβ Crawford system. In all cases, a calibrated neutral filter was used for β Cas. The comparison star was Cl=HR 9085 (V=5.m55, F0III).The analysis of frequencies was carried out using the Discrete Fourier Transform method, as described in López de Coca et al. (1984), to the observational uvby points collected. The periodograms showed a principal peak at v=9.91 cd−l. After prewhitening for this frequency, the resulting periodograms did not show any trace of another peak, suggesting the monoperiodic nature of this star, in agreement with Antonello et al. (1986). Under the assumption of monoperiodicity of β Cas, the classical O-C method can easily be applied. Nine times of maxima were obtained for the four nights by using the method described in Rodriguez et al. (1990), where each light maximum has been derived as an average over the four uvby bands. When the O-C method was applied, the least squares fit converged to a linear ephemeris with the following elements: To=2445568.d5097 (±0.d0007) and Po=0.d10091 (±0.d00002). This linear ephemeris satisfactorily reproduces our data of β Cas.
Methodological Aspects in the Frequency Analysis of Multiperiodic δ Scuti Stars
Authors: Mantegazza L. , Poretti E. , Antonello E. , Riboni E. 
Published: July 2016

At Merate Observatory the study of δ Sct stars began in the sixties and spectroscopie and photometric campaigns were continuously undertaken in order to clarify the controversial points. As an obvious extension of the research, the observation of δ Sct stars was proposed for telescope-time allocation at European Southern Observatory, in order to take advantage of the ESO facilities and of the considerably better sky of La Silla. We put in our observing programme δ Sct stars showing cycle-to-cycle variations and, possibly, an amplitude larger than 0.05 mag in order to have a better signal-to-noise ratio; they are listed in the table. It is important to notice that we always tried to collect a number of measurements as large as possible (from 1988 we collected more than 1000 measurements per star), because it is a well-established fact that periodicities withan amplitude of a few thousandths of magnitude can be present in δ Sct stars. Moreover, when several modes are excited, an adequate frequency resolution becomes necessary and, therefore, a sufficient time baseline is requested (Poretti and Mantegazza 1992). A poor data sampling also gives an apparent good fitting for several solutions, all leaving a small residual rms, and there is no possibility to choose among them: different authors can pick up different solutions, generating the conflicting interpretations often found in δ Sct star literature.
Asteroseismology of the DBV White Dwarf GD 358 with the Whole Earth Telescope
Authors: Winget D.E. , Nather R.E. , Clemens J.C. , Provencal J. , Kleinman S.J. , Bradley P.A. , Claver C.F. , Dixson J.S. , Wood M.A. , Grauer A.D. , Hine B.P. , Hansen C.J. , Bergeron P. , Birch P. , Candy M. , Leibowitz E. , Marar T.M.K. , Seetha S. , Ashoka B.N. , O’Donoghue D. , Warner B. , Buckleys D.A. , Tripe P. , Vauclair G. , Doleza N. , Chevreton M. , Kanaan A. , Kepler S.O. , Augusteijn T. 
Published: July 2016

AbstractWe report the analysis of 154 hours of nearly continuous high-speed photometric data on the pulsating DB white dwarf (DBV) GD 358 obtained during the Whole Earth Telescope (WET) run of May 1990. The Fourier transform (FT) of the light curve is dominated by power in the range from 1200 – 1700μHz with more than 180 significant peaks in the total transform. We also see significant power at the sums and differences of the dominant frequencies, indicating the importance of nonlinear behavior. We can use this data to obtain an accurate total stellar mass, and surface He layer mass. The implied surface He layer mass, if correct, provides a significant and surprising challenge to stellar evolution theory, as well as the theory of chemical mixing.
Star Formation and the Origin of Stellar Masses
Authors: Podsiadlowski Ph. , Price N.M. 
Published: July 2016

AbstractWe present a new model to explain stellar mass distributions in different stellar environments. In our model, the protostar phase is terminated, when the protostellar core embedded in a molecular clump experiences a collision with another star or protostellar clump, which ejects the protostellar core from its parent clump. Such dynamical interactions are necessarily important, if stars preferentially form in dense clusters. We show that, in a simple model, the initial mass function approaches a simple, asymptotic form, which strongly resembles observed mass functions. The model has important consequences for star formation in different environments. We also discuss the implications of the model for our understanding of pre-main-sequence stellar evolution.
The Effect of Electron Beams on the Hydrogen Emission in Impulsive Flares on the Sun and Stars
Authors: Zharkova V.V. , Kobylinsky V.A. 
Published: July 2016

Flares are very frequent phenomena on the sun and on other stars and are actively investigated with precise observational techniques. These studies are particularly stimulated by recent X-ray and UV observations on spacecraft (Skylab, SMM). From all these observations the flares on the sun and stars seem to be of the same physical nature but of different energetic power. A number of investigations devoted to comparison between the solar and stellar flares led to the conclusion that they have the similar mechanisms for the energy release and transport and for their manifestations in different ranges of electromagnetic radiation.The hydrogen emission is easy to observe in these events, and thus it is convenient for diagnostic analysis of physical conditions in the flares. However, the impulsive events were considered to be observed in X-rays so only. Zharkova & Kobylinsky (1992, 1993) have recently shown that the hydrogen continuous radiation of the solar flares is sensitive to the electron beam parameters. We also develop an approach to detection of the flares of non-thermal or thermal origin by observing the hydrogen Balmer and Pashen continuum emissions with high temporal resolution.
Prisma: A New Space Mission For Stellar Physics
Authors: Appourchaux T. , Gough D. , Hyoyng P. , Catala C. , Frandsen S. , Fröhlich C. , Jones A. , Lemaire P. , Tondello G. , Weiss W.W. 
Published: July 2016

PRISMA (Probing Rotation and Interior of Stars: Microvariability and Activity) is a new space mission of the European Space Agency. PRISMA is currently in a Phase A study with 3 other competitors. PRISMA is the only ESA-only mission amongst those four and only one mission will be selected in Spring 1993 to become a real space mission.The goal of the Phase A study is to determine whether the payload of PRISMA can be accommodated on a second unit of the X-ray Multi-Mirror (XMM) bus; and whether the budget of the PRISMA mission can be kept below 265 MAU (’88 Economic conditions). The XMM mission is an approved cornerstone and is in a Phase A together with PRISMA.
A New Violent Activity in 3C273
Authors: Botti L.C.L. 
Published: July 2016

AbstractIn the present paper we report a sharp rise in the flux density of the quasar 3C273 observed with the Itapetinga radiotelescope in 1991. The intensity increased by factor 2, reaching a maximum value in May and July 1991 at 43 and 22 GHz, respectively.
Millimeter-Wave VLBI Observations of Compact Steep-Spectrum Radio Sources
Authors: Kameno S. , Inoue M. , Takaba H. , Iwata T. , Takahashi Y. , Nan R. , Schilizzi R. T. 
Published: July 2016

AbstractWe report the observations of compact steep-spectrum radio sources (CSSs) by VLBI at 22 and 43 GHz and single dich at 22, 43, and 92 GHz. Our results show that CSS also has an active core as well as other AGNs.
Imaging Molecular Envelopes of Evolved Stars
Authors: Bieging John H. 
Published: July 2016

AbstractResolved images of molecular emission lines from the envelopes of cool evolved stars reveal much about the physical processes by which such stars lose mass, about the chemical processes which occur in the outflowing gas, and about the evolution of the star to the planetary nebula stage. This paper reviews observational work on molecular line imaging at mm-wavelengths of carbon stars, Miras, proto-planetary nebulae, and planetary nebulae. The impact of these observations on our understanding of the late stages of stellar evolution as it affects the circumstellar environment is emphasized.
Detection of Magnetohydrodynamic Shocks in the L1551 Outflow
Authors: Barsony M. , Scoville N. Z. , Chandler C. J. 
Published: July 2016

AbstractWe report the results of CO J=l—+0 mapping of portions of the blue outflow lobe of L1551 with ~ 7” (N-S) × 4” (E-W) resolution, obtained with the 3-element OVRO millimeter array. Comparison of our interferometer mosaic with lower resolution single-dish data shows that we resolve the strongest single-dish emission regions into filamentary structures, such as are characteristic of shock fronts mapped via their near-infrared H2 emission in other outflow sources.
THE CO(J=2-1)/CO(J=1-0) Luminosity Ratio in the Orion Giant Molecular Clouds
Authors: Sakamoto Seiichi , Hasegawa Tetsuo , Hayashi Masahiko , Handa Toshihiro , Oka Tomoharu 
Published: July 2016

AbstractThe first results of large-area mapping observations of nearby giant molecular clouds in the CO(J=2-1) emission are presented. The CO(J=2-1)/CO(J=1-0) luminosity ratio is 0.75 and 0.62 for the Orion A and B clouds, respectively. These values are consistent with those observed typically in disks of galaxies (−0.6), and are significantly lower than large values (≳1) often observed in active star-forming regions in galaxies. Active star-forming regions in galaxies cannot be explained by ensemble of Orion-like GMCs; they may contain a different population of molecular clouds with high J-2-1/J=1-0 luminosity ratio.
Large Scale Structure and Kinematics of the Orion Ridge
Authors: Wiseman J. J. , Ho P. T. P. 
Published: July 2016

Clumps and filamentary structures have previously been observed in the extended molecular ridge of OMC-1 (see below). The region is affected by multiple outflow components, shock emission that extends 0.5 pc from the BN/KL core, and a foreground HII region expanding into the cloud. The region also displays a complex kinematical character, with a large scale shift in radial velocity along the ridge, multiple cloud velocity components (Womack et al. 1993), and fast gradients across constituent cores (Harris et al. 1983, Wiseman and Ho 1993).To clarify the structure and kinematics of the region, we have used the VLA to observe with high (0.3 km s−1) velocity resolution and high (8”) angular resolution the NH3 (1,1) and (2,2) rotation-inversion lines over 20 adjacent fields covering a 3’ by 8’ region encompassing the KL region.
Expanding Hemisphere in Orion-KL Hot Core — CS(2–1) Observation with NMA —
Authors: Murata Y. , Kawabe R. , Ishiguro M. , Morita K.-I. , Hasegawa T. , Hayashi M. 
Published: July 2016

AbstractWe have made aperture synthesis observations of CS(2-1) emission using the Nobeyama Millimeter Array (NMA), and obtained ~ 2” × 3” (0.005 × 0.008 pc) resolution image to investigate the velocity structures of Orion-KL. We found not only well-known expanding doughnut but the expanding hemisphere in the Orion-KL hot core.
SiO (J=2-1) Observations of W49A with NMA: Evidence of Infall Motion toward Massive Core
Authors: Miyawaki Ryosuke , Hayashi Masahiko , Hasegawa Tetsuo 
Published: July 2016

AbstractWe observed W49A with NMA. We found rotational infall motion toward massive core. The rotational velocity and the infall velocity are 2±1 km s−1 /pc and 5±2 km s−1, respectively.
An Interferometric Observation of the NGC 7538 Molecular Cloud Core
Authors: Kameya Osamu , Kawabe Ryohei , Morita Koh-Ichiro , Ishiguro Masato , Hirano Naomi 
Published: July 2016

A high-spatial-resolution observation of the NGC 7538 molecular cloud core has been performed with the Nobeyama Millimeter Array. We report on the detailed structure of the region including IRS1-3 complex and IRS11 based on the CS J = 1−0 line observational results.The observation was done in December, 1988. The field center was at R.A. (1950)=23h11m36.8s, Dec (1950)=61° 11′ 10″ which is between IRS1-3 complex and IRS11. The primary beam, 2.5’(FWHM), was large enough to cover both IRS1-3 complex and IRS11. We used 18 baselines, and the synthesized beam became 10.6″×10.4″ (natural weight).
Preliminary Results on the Molecular Emission from the T Tauri Circumstellar Disk
Authors: Van Langevelde Huib Jan , Van Dishoeck Ewine F. , Blake Geoffrey A. 
Published: July 2016

AbstractWe report the initial results of a study of the chemical composition of the T Tauri circumstellar disk. The excitation and distribution of CS and HCO+ are discussed. These two molecules behave quite differently in the YSO environment.
IRAS Galaxies
Authors: Scoville N. 
Published: July 2016

AbstractApproximately thirty of the luminous infrared galaxies highlighted by the IRAS survey have now been mapped at high resolution using the millimeter arrays. In virtually all cases, extremely high gas concentrations are found in their nuclei (≤2 kpc) and in several cases, the gas mass fraction is extremely high (25-100%). Optical and near infrared imaging of the most luminous infrared galaxies shows significant distortions, double nuclei, and/or tidal tails indicating that these galaxies have probably undergone a recent galactic interaction. The dense molecular gas probably plays a pivotal role in the evolution of such dynamically disturbed systems: being dissipative the gas readily sinks to the central regions where it may fuel a nuclear starburst and possibly build up and fuel a central active galactic nucleus. In this picture, the IRAS galaxies may be crudely characterized by three parameters: the initial mass of ISM in the progenitor galaxies, the time since the interaction, and the fraction of the total luminosity attributed to young stars versus an active nucleus. In this scenario, systems such as the antennae (NGC 4038/39) may represent the early stages of a merger before the gas has been deposited in the nucleus; Arp 220 the phase in which a large nuclear gas concentration is presently fueling a starburst/AGN, and NGC 1068 the later phase in which much of the central gas concentration has been consumed and the residual gas exists in a circumnuclear ring or arms.
IRAS and Distant Galaxies
Authors: Ryohei  , Kawabe  
Published: July 2016

AbstractRecent millimeter-wave observations of CO from the protogalaxy candidate IRAS F10214+4724 with single dishes and interferometers indicated that the huge amount of molecular gas is associated with the high-z galaxy with huge infrared luminosity. An overview of the results of recent observations of IRAS F10214 +4724 is shown. The implications of the results based on aperture synthesis CO observations and origin of the huge infrared luminosity (starburst or dust- enshrouded QSO) are discussed by comparing them with the “nearby” ultraluminous IRAS Galaxies.
Outflowing Molecular Gas in NGC 3079
Authors: Irwin J. A. , Sofue Y. 
Published: July 2016

AbstractNMA 12CO(J=1-0) observations of the radio lobe spiral galaxy, NGC 3079, reveal a dense, rigidly rotating ring of molecular gas with a radius of about 750 pc. In addition, a tilted CO component as well as several molecular gas “spurs” are interpreted as linear features which are accelerated outwards by the nuclear outflow.
H2/CO Conversion Factor for M31 Molecular Clouds
Authors: Sofue Yoahiaki , Takabayashi Mikio , Murata Yasuhiro 
Published: July 2016

The conversion factor from the CO line intensity to column density of molecular hydrogen, X = NH2/ICO is one of the most important parameters in mm-wave study of galaxies and their molecular gas (e.g., Maloney 1990). Although the same value as that obtained for our Galactic clouds (e.g. Sanders et al. 1984; Bloemen et al. 1985) has been widely applied to galaxies, it is far from trivial that the conversion factor is universal among various types of galaxies. There have been few attempts to derive the value for galaxies, and the value is still controversial if it is applicable to other galaxies or not: Approximately the same value as that for the Galaxy has been derived for M33 (Wilson and Scoville 1990, 1992), while an order of magnitude larger value is obtained for the LMC and SMC (Cohen et al. 1988; Rubin et al. 1991).In order to obtain the conversion factor in nearby galaxies, in which individual molecular clouds can be resolved, we are conducting CO-line mapping of M31. In this paper we report a preliminary results from mapping of a north-eastern spiral arm of M31 in the 12CO(J =1 − 0) line emission using the NMA.
The Smithsonian Submillimeter Array
Authors: Ho P. T. P. 
Published: July 2016

SummaryThe Smithsonian Astrophysical Observatory is currently designing and constructing the Submillimeter Array (SMA). This instrument will consist of six 6-m telescopes, which can be moved and reconfigured in four concentric ring-like arrangements with maximum baselines of 500 m. Pending negotiations, the SMA will be sited on Mauna Kea at the 4000 m plateau, adjacent to the existing CSO and JCMT submillimeter telescopes. The goal of the SMA is to provide imaging at sub-arcsecond resolution for the wavelength range of 1.3 mm to 0.35 mm. This instrument will therefore improve the angular resolution achieved with present submillimeter telescopes by more than an order of magnitude. As the cool (10-100 K) dust and gas in the Milky Way and other external systems will radiate principally in the submillimeter wavelengths, we expect the SMA to provide unprecedented resolution and to make fundamental contributions to many different problems including the studies of our solar system, star formation and circumstellar disks, galaxies and molecular cloud structures, quasars and active galactic nuclei, and perhaps even galaxy formation in the early universe.
Recent Results on Abundance Determinations
Authors: Adelman Saul J. 
Published: July 2016

AbstractI review abundance determinations of normal B5-F4 and peculiar stars published since 1984. Several analyses performed with photographic spectrograms indicate interesting stars which should be analyzed with high signal-to-noise data. Studies of stars of known ages which belong to clusters, associations, and moving groups should led to the most direct confrontations with theory. The increase in signal-to-noise ratio provided by electronic detectors with respect to photographic plates should allow accurate analyses of moderating rotating stars. High resolution, high signal-to-noise ratio studies have revealed crucial information about the line profiles of Sirius, Vega, and other A stars. It would aid comparison of analyses if we could agree on a standard set of gf-values and line damping constants. A computer bulletin board would be a useful means to provide and maintain such data as well as model atmosphere codes.
Modeling A-Type Atmospheres: NLTE Models
Authors: Hubeny Ivan , Lanz Thierry 
Published: July 2016

AbstractA brief review on NLTE models of normal and chemically peculiar stars of spectral types A and late B is presented. We will concentrate on three basic question about NLTE modeling, namely i) Why (calculate NLTE models)? ii) How (to calculate NLTE models efficiently)? and iii) What (we learn from NLTE models already calculated)?
Atomic Data: Needs and Progress
Authors: Artru Marie-Christine 
Published: July 2016

AbstractWe summarize the newly available results which improve both the accuracy and the completeness of atomic data to be used for analysis and modelization of A stars. A major progress is obtained from the large amount of theoretical work that has been performed through the recent revision of stellar opacities. Extensive lists of accurate line data are available and we present their general characteristics. Detailed photoionization cross-sections are now available for many initial states of different atomic ions. They currently show deep resonance structures and strongly depart from the hydrogenic shapes which were often assumed. Their importance is illustrated by the example of the Si II ultra-violet features. Further implications about computation of radiative forces are pointed out.
On Stark Broadening of Heavy Element Lines in A-Type Star Spectra: Bi II Lines
Authors: Dimitrijević M. S. , Popović L. Č. 
Published: July 2016

AbstractWe report here results of Bi II spectral lines Stark broadening research within the modified semiempirical approach. The strong absorption Bi II lines observed in Hg – Mn star atmospheres have been investigated as well as the influence of the departure from LS – coupling and the correct knowledge of ionization potential. The obtained results have been compared with other estimations and with experimental results.
Line Identification of Schneider’s Star (BD+24°3675) Around Hβ
Authors: Kroll Reinhold 
Published: July 2016

AbstractThe line spectrum of BD +24°3675 is investigated from 4730 to 4990 Å. I discuss the presence of individual elements, including Rare Earths. The equivalent widths of all strong lines are given. Estimates of Teff and logg indicate that the star might be evolved with a low surface gravity. Indications for spectral line variability have been found.
Spectral Characteristics of A-Type Stars in the Galactic Halo
Authors: Corbally C.J. , Gray R.O. 
Published: July 2016

AbstractAmong 67 early A-type stars at high galactic latitudes, selected to have both small m1 and large c1 Strömgren photometric indices, we find about one third to have quite normal dwarf or subgiant spectra at MK classification dispersion. Those stars with peculiarities included 10 new λ Bootis stars, though none of these appeared significantly evolved. We wonder whether some of the metal-weak dwarf stars in our set may be field horizontal-branch equivalents of the blue, downward-curving, low-luminosity end of the blue horizontal-branch stars.
A Theoretical Period-Luminosity Relation of Dwarf Cepheids
Authors: McNamara D.H. , Powell John M. 
Published: July 2016

Dwarf Cepheids (large-amplitude δ Sct variables and SXPhe variables in the GCVS) are late A-type stars near light maximum and early-F stars near light minimum. In the lower part of the instability strip where these stars are found the pulsation constant Q varies only slightly. As pointed out by Andreasen, Hejlesen, and Petersen (1983) this makes it easy to transform a theoretical HR or alternatively a (logTe, logg) diagram to a theoretical logTe, logP0) diagram by the use of the relation. This follows from the equations:where P0 is the fundamental period of pulsation. The periods, of course, can be determined with very high accuracy.