bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two-Frequency VLA Monitoring of LSI+61°303 during a Full Radio Period
Authors: Paredes J. M. , Peracaula M. , Ribó M. , Martí J. , Tavani M. , Kniffen D. A. , Mattox J. R. 
Published: July 2016

AbstractWe report observations of the radio periodic Be X-ray binary LSI+61°303, obtained with the VLA at 3.6 and 2.0 cm during a full 26.5 d cycle. These observations were carried out in coordination with CGRO monitoring of its possible γ-ray counterpart 2CG 135+1.
First EVN Maps of 6-GHz OH Lines in Star Forming Regions
Authors: Desmurs J.-F. , Baudry A. 
Published: July 2016

AbstractWe have used 3 antennas of the EVN to observe in 6 star-forming regions simultaneously, and for the first time, the 2 main lines of the J=5/2 state of OH with right and left circularly polarized feeds. Maser features and Zeeman pairs are identified by searching for emission over adjacent channels, and adjacent positions (within one synthesized beam) in both polarizations after we had mapped and used one selected simple channel as a reference. The magnetic field strength is thus estimated from the Zeeman pairs identified in our OH maps. We briefly present results obtained for W3(OH), ON1, and W51.
VLBA Imaging of 12.2 GHz Methanol Masers
Authors: Ellingsen S. P. , McCulloch P.M. , Diamond P. J. , Norris R. P. 
Published: July 2016

AbstractWe have used the VLBA to image the 12.2 GHz (20-3−1 E) masing transition of methanol toward the massive star formation region G345.01+1.79. The maser spots are distributed in a curved structure with a near monotonic velocity distribution along the curve. The cluster of maser emission covers an area of approximately 200 milli-arcseconds in right ascension and 70 milli-arcseconds in declination.Comparison of the positions of the 12.2 GHz methanol maser spots in G345.01+1.79 as determined from the 1995 VLBA observations with 1988 Parkes-Tidbinbilla Interferometer observations shows that the relative positions of the maser spots detected in both epochs has changed by less than 5 milli-arcseconds during that interval. Assuming a distance of 2.3 kpc to G345.01+1.79 implies an upper limit on the relative tangential velocities of the maser spots of 7 km s−1.
0″.4 BIMA Array Mapping of the 107 GHz Methanol Maser in W3(OH)
Authors: Slysh V. I. , Val’tts I. E. , Kalenskii S. V. , Larionov G. M. , Mundy L. G. 
Published: July 2016

AbstractUsing A-configuration of the BIMA-array with 0″.4 angular resolution maps were obtained of the 107 GHz methanol line in W3(OH). The 107 GHz masers have their counterparts in another methanol transition at 6.7 GHz. The strongest maser spots are unresolved with the BIMA-array and are less than , which corresponds to the lower limit of the brightness temperature 5×105 K. A model of Class II methanol masers emitted in the extended atmosphere of icy planets orbiting around the O-star which excites H ɪɪ region is proposed.
Link of the Hipparcos Stellar Reference Frame to the Distant Quasars
Authors: Lestrade J.-F. , Preston R.A. , Jones D.L. , Phillips R.B. , Rogers A.E.E. , Titus M.A. , Reynolds J.E. , Jauncey D.J. , Gabuzda D.C. , Rioja M.J. , Guirado J.C. , McCulloch P.M. 
Published: July 2016

AbstractThe link of the Hipparcos and VLBI extragalactic reference frames has been achieved with a precision of 0.0005″ in global orientation at the epoch of the catalogue (1991.25) and of 0.0003″/yr in rate of rotation by VLBI observations of 12 radio-emitting stars.
High Precision Astrometry with Closure Constraints
Authors: Ros E. , Marcaide J. M. , Guirado J. C. , Ratner M. I. , Shapiro I. I. , Krichbaum T. P. , Witzel A. , Preston R. A. 
Published: July 2016

AbstractWe determine the relative separations of the sources in the triangle 1803+784/1928+738/2007+777 with submilliarcsecond accuracy from global 8.4 GHz VLBI observations. We remove the ionospheric contribution to the phase-delay observable using ionospheric total electron content estimates obtained from Global Positioning System (GPS) data. The triangular geometry provides a consistency check through sky closure.
Giga-bit VLBI Data Recorder, New Concept of Formatter Independent
Authors: Nakajima J. , Koyama Y. , Sekido M. , Kiuchi H. , Hama S. , Kondo T. , Takahashi Y. , Kawaguchi N. , Chikada Y. , Miyoshi M. 
Published: July 2016

AbstractA high performance VLBI recorder project using advanced digital technology started in 1995. TOSHIBA GBR 1000 and VLBI interface define 32 parallel, 32 MHz clock standard digital interface and support transparent recording/play-back to extremely high-speed digital bit stream. This is the formatter independent scientific recording bind the UTC to observed data. This highly reliable, low-bit-error-rate (10−16) recording system is also expected to be used in other scientific field. For the first example to examine the recorder performance in VLBI, we had been prepared 1024 Mbps sampler (256/512/1024 MSps, 2 bit, 4/2/1 ch). And here, an experimental giga-bit correlator specification for these VLBI acquisition system is introduced.
Gigabits XF Type Correlator
Authors: Hashimoto T. , Ozeki K. , Natori K. 
Published: July 2016

AbstractThe National Astronomical Observatory of Japan (NAO), has an Optical Linked VLBI Experiment Project named OLIVE that directly connects a correlation site wit h some other VLBI observation stations in network by optical fiber, and correlates in real time. 2 Gbps (1 Gsps 2-bit or 2 Gsps 1-bit) or 8 Gbps (4 Gsps 2-bit) VLBI correlator is necessary in OLIVE. We are developing Gigabits correlators (XF type) using special-purpose correlation chips developed by NAO. We have already completed the Ultra Wideband Correlator named UWBC (2 Gsps 2-bit 256 lags) of 15 baselines for the Nobeyama Millimater Array (NMA). The Nobeyama Radio Observatory (NRO) offered the common use of a new wide-band observation system to astronomers since March 1997. We consider that the 2-Gbps VLBI correlator, which is needed in the OLIVE project, is possible to manufacture. It is also possible to manufacture a 8 Gbps-VLBI correlator using the UWBC chip.
Operating a Telescope Larger than the Earth: How to Schedule the HALCA Space VLBI Mission
Authors: Meier D. L. 
Published: July 2016

AbstractWe outline the HALCA Space VLBI mission scheduling process, with special emphasis placed on software that decides when to observe the proposed sources and how to ensure that the highest quality science is obtained. This information will be useful to the many principal investigators whose very high resolution VLBI observations are being supported by the mission.
Comet and Asteroid Ephemerides for Spacecraft Encounters
Authors: Yeomans Donald K. 
Published: July 2016

AbstractTo a significant degree, the success of spacecraft missions to comets and asteroids depends upon the accuracy of the target body ephemerides. In turn, accurate ephemerides depend upon the quality of the astrometric data set used in determining the object’s orbit and the accuracy with which the target body’s motion can be modelled. Using error analyses studies of the target bodies for the NEAR, Muses-C, Clementine 2, Stardust, and Rosetta missions, conclusions are drawn as to how to minimize target body position uncertainties at the times of encounter. In general, these uncertainties will be minimized when the object has a good number of optical observations spread over several orbital periods. If a target body lacks a lengthy data interval, its ephemeris uncertainties can be dramatically reduced with the use of radar Doppler and delay data taken when the body is relatively close to the Earth. The combination of radar and optical angle data taken at close Earth distances just before a spacecraft encounter can result in surprisingly small target body ephemeris uncertainties.
The Galactic Disk Tidal Force: Simulating the Observed Oort Cloud Comets
Authors: Dybczyński P. A. , Prȩtka H. 
Published: July 2016

In previous papers (Prȩtka and Dybczyński, 1994; Dybczyński and Prȩtka, 1996) we presented detailed analysis of selected examples of the long-term evolution of the orbit of Oort cloud comets under the influence of the galactic disk tidal force, as well as some statistical characteristics of the simulated observable comet population. This paper presents further improvements in our Monte Carlo simulation programme which allow us to represent in a better way the real processes of production of observable comets due to galactic perturbations.In our second paper (Dybczyński and Prȩtka, 1996), following some other authors (see for example Matese and Whitman, 1989), we treated a comet as observable when its osculating perihelion distance decreased below some adopted observability limit (5 AU in our case). Limiting the investigation to the evolution of osculating elements allowed us to use very fast and efficient averaged Hamiltonian equations of motion in our simulation. However, further detailed analysis of the problem showed that the adopted observability definition was insufficient: what makes a comet observable is not its osculating perihelion distance but its true distance from the Sun, smaller than some adopted threshold value. It may happen that when the osculating perihelion distance is at its smallest, the comet is around its aphelion distance.
Evolution of the Rotational Motion of a Planet with a Liquid core
Authors: Sidorenko V. V. 
Published: July 2016

AbstractSecular changes in the rotational motion of a planet due to dissipation of energy in its core are investigated. It is assumed that the effect of a liquid core is equivalent to the action on a “frozen” planet of a special type of nonconservative torque. The Bogoliuboff-Mitropolsky method is used to explain the secular effects. The following qualitative features of the evolution of the motion are established: the fast rotation of a planet gradually becomes slower and the inclination of its equator to the orbital plane gradually increases.
Agreements and Disagreements between Theories of Rigid Earth Nutation
Authors: Souchay J. 
Published: July 2016

AbstractThe necessity to elaborate a theory of nutation and precession matching the accuracy of very modern techniques as Very Long Baseline Interferometry and Lunar Laser Ranging led recently to various works. We discuss here the good agreement between those related to the nutation when considering the Earth as a solid body. In comparison we show the uncertainty concerning the modelisation of the transfer function leading to theoretical determination of the nutation coefficients when including dominant geophysical characteristics.
On the Problem of post-Newtonian Rotational Motion
Authors: Klioner Sergei A. 
Published: July 2016

AbstractThe problems of modeling of the rotational motion of the Earth are considered in the framework of general relativity. Both, rigid and deformable bodies are discussed. Rigorous definitions of the tensor of inertia, Tisserand-like axes and the angular velocity of rotation of an extended deformable body moving and rotating in external gravitational fields are proposed in the first post-Newtonian approximation. The implications of these post-Newtonian definitions on modeling of Earth rotation are analyzed.
First Year of Observations with SOHO/EIT of the “Quiet” Sun Corona
Authors: Portier-Fozzani F. , Maucherat A.J. , EIT Team  
Published: July 2016

AbstractSince January 1996 (EIT first light) the Extreme Ultraviolet Telescope aboard SOHO has produced about 20,000 wide-field images of the corona and transition regions. Four different emission lines (He II, Fe IX/X, Fe XII, Fe XV) were selected to detail morphologies of magnetic structures in the corona. They show the different structures present in the corona with information about their topologies (Neupert et al. 1998). They provide the global temperature distribution in the quiet corona in the range 0.5 to 3 × 106 K.The evolution of the corona during the first year of the SOHO mission revealed its nonuniform aspect and the nonregularity of the appearance of new active regions. Changes observed in active regions and coronal holes (e.g., August–September 1996) showed the complex role of magnetic fields including magnetic interactions and possible reconnections needed to explain some loop morphology evolution.
NLTE Model of a Quiescent Filament
Authors: Kononovich E.V. , Gorshkov A.B. , Smirnova O.B. , Kotrč P. 
Published: July 2016

AbstractThe Sacramento Peak Observatory VTT Echelle Spectrograph was used to obtain high resolution spectrograms of the filament at W06° S27° observed on April 9, 1991 in hydrogen Hα, Hβ, and CaII H and λ 8498 lines. The line profiles were measured and digitized. A numerical code based on the MALI approach with partial frequency redistribution (PRD) in resonance lines was applied to obtain theoretical profiles of hydrogen and CaII lines. As a result of fitting the observed and calculated profiles, the physical parameters of the filament plasma were obtained. They include temperature, gas pressure, electron density and turbulent velocity.
Prominence Emission Lines Observed With SUMER and Two Ground-based Telescopes
Authors: de Boer C.R. , Stellmacher G. , Wiehr E. 
Published: July 2016

AbstractTwo sets of H, He, and Ca+ emission lines were observed in a quiescent prominence simultaneously with the VTT and the Gregory telescope on Tenerife. At the same time, SUMER took two scans of low-ionized EUV emission lines.The emission ratios of Ca+–to–Balmer lines from ground vary little in the prominence, indicating a largely constant gas-pressure. In contrast, the ratio of He–to–Balmer from the ground shows the (known) increase toward the prominence borders, indicating higher temperature there. Similarly, the two-dimensional distributions of the ratios S IV/N II and C III/He I show pronounced bright prominence rims.The reduced He 537Å and He 584Å line widths are 2.6 and 3.6 times larger, respectively, than those of He D3 and He 3888Å. Explaining this by the optical thickness yields τ0 = 104 and τ0 = 2 · 105 for the two EUV lines. The total He 584 emission amounts to 13 watt/m2 ster in the main prominence body where the D3 line yields 4 watt/m2 ster; existing models, however, predict a factor 0.18.The widths of simultaneously observed optical lines with different atomic weights yield thermal and non-thermal broadening parameters of Tkin ≈ 8000 K and 2.5 < ξ < 6.5 km/s. The EUV lines, however, show line widths which correspond to much higher temperatures and non-thermal velocities. Assuming for each ion the corresponding ionization temperature, the line widths require non-thermal velocities of 15–40 km/s which is similar to values for the quiet corona.
Modelling of Non-Uniform Prominence Slabs
Authors: Heinzel P. , Anzer U. 
Published: July 2016

AbstractWe present new slab models for quiescent prominences in which both the condition of magnetohydrostatic equilibrium as well as NLTE are fulfilled. Using the Kippenhahn-Schlüter model, a unique relation between the components of the magnetic field on one hand and the gas pressure and width on the other is established for a given uniform temperature. We construct a grid of such NLTE models and compare them with the set of isothermal-isobaric models of Gouttebroze et al. (1993).
Spectroscopic Study of a Quiescent Prominence
Authors: Park Y.D. , Yun H.S. , Ichimoto K. , Sim K.J. , Moon Y-J. 
Published: July 2016

AbstractWe have analyzed a set of spectra of Hα and CaII H & K lines taken from a quiescent prominence with the G1 CCD camera attached to a 25 cm coronagraph at the Norikura Coronal Station, the National Astronomical Observatory of Japan. From these lines we have determined temperature, turbulent velocity and electron density at various locations on the prominence. The final analysis shows that the averaged temperature of the prominence is about 8600K with mean turbulent velocity of 7.5 km/s and with a mean electron density of < ne > = 2.4×1010cm−3.
Analysis of Hα Observations of High Altitude Coronal Condensations
Authors: Allen U.A. , Bagenal F. , Hundhausen A.J. 
Published: July 2016

AbstractPreliminary analysis of Hα images of high-altitude coronal condensation known as “coronal spiders” is presented. The kinematics of material seen draining from the coronal spiders are also studied. An estimate of the mass of the object for a range of electron temperatures and electron densities is obtained.
Hα Observations of the Dual Eruptive Prominences of June 29, 1994
Authors: Lenža L. 
Published: July 2016

AbstractOur results in the field of observing prominences at our observatory show dual eruptive prominences on June 29, 1994 obtained by a coronograph at our observatory at Valašské Meziříčí. We tracked the evolution of these eruptive prominences in time and morphology.
On the Eruption of Prominences and Disappearance of Quiescent Filaments
Authors: Gupta S.S. , Singh Jagdev 
Published: July 2016

AbstractThe analysis of an eruptive prominence and disappearing quiescent filaments indicates that the prominence height on the limb increases after the filament develops a twist as seen in the Hα on the disc. The increase in prominence height, large change in the shear angle, and the appearance of filament as a U-shaped structure before the disappearance of the filament or prominence eruption can be explained by assuming that the middle portion of the filament rises above the solar surface with its edges anchored in the chromosphere. Further, the loop-like structure of the filament splits into two parts 2–3 days prior to its disappearance and the gap between the two increases with time. The increasing gap and simultaneous disappearance of both parts of the filament suggests that heating of the top of the loop-like structure begins about 2 days before its disappearance. The cause for this portion of the filament not being visible in Hα may be that it is heated to a high temperature.
On a Possible Mechanism of Quiescent Prominence Destabilization
Authors: Nenovski P. , Dermendjiev V.N. , Madjarska M.S. , Vial J.-C. 
Published: July 2016

AbstractThe possibility of multiple reflections generating standing surface wave modes carrying field-aligned current (FAC) in an arch-like prominence structure is studied. The conditions for enhancement of FAC leading to observable destabilising effects are specified.
Filament Disparition Brusque and CME – September 25–26, 1996 Event
Authors: van Driel-Gesztelyi L. , Schmieder B. , Aulanier G. , Démoulin P. , Martens P.C.H. , Zarro D. , DeForest C. , Thompson B. , Cyr C.St. , Kucera T. , Burkepile J.T. , White O.R. , Hanaoka Y. , Nitta N. 
Published: July 2016

AbstractDuring the September 1996 campaign of multi-wavelength observations with the SOHO (SUMER, CDS, EIT, MDI, LASCO) and Yohkoh (SXT) spacecraft, the HAO Mauna Loa Solar Observatory Chromospheric Helium Imaging Photometer and the Nobeyama radioheliograph, a filament disparition brusque (DB) associated with a Coronal Mass Ejection (CME) was observed. The timeline of this complex event, which lasted for tens of hours, shows that the CME had started before the DB of a filament, while the main “bubble” of the CME was probably launched hours after the DB from the so-called “zipper” region. All these suggest that a general reorganization of large-scale fields was taking place on the Sun, and both the DB and the CME were symptoms of this.
Soft X-Ray Observations of Eruptive Prominences
Authors: Watanabe T. , Yamamoto M. , Hudson H. , Irie M. , Ichimoto K. , Kurokawa H. , Yatagai H. 
Published: July 2016

AbstractEvolution of magnetic structures in the region around an eruptive prominence of August 28, 1992 are examined using soft X-ray images obtained by Yohkoh. The eruption was preceded by the appearance of a large-scale soft X-ray jet which was ejected from near the root of the southern end of the prominence. Changes of magnetic geometry at the southern end of the prominence appeared to trigger the eruption. In the course of prominence eruption, helically twisted soft X-ray loops were observed around the prominence. This indicates that magnetic reconnection of a sheared arcade took place underneath the erupting prominence.
New Evidence of Chromospheric Evaporation
Authors: Kašparová J. , Kotrč P. , Heinzel P. , Nikulin I.F. , Rudawy P. 
Published: July 2016

AbstractHα spectra obtained at Sternberg Astronomical Institute in Moscow during the gradual phase of the flare on May 16, 1981 are analysed. The flare-ribbon profiles show a red asymmetry of the emission peaks, and we interpret this as an absorption in the blue wing of the profile due to expected upflows. We demonstrate a good correlation between the observed Hα profiles and those computed with the flare model Fl and upflows reaching 10 km s−1.
The Present and Future of the Prominence Observations at Valašské Meziříčí Astronomical Observatory
Authors: Lenža L. , Dokoupilová D. 
Published: July 2016

AbstractThis observatory is not a large institution, though we do carry out long term photographic monitoring of prominences. Our intention is to inform everybody about our observation programmes, the quality of our observations, our archive and the possibilities for its use.We present examples of our photographic observations, an electronic archive of observation intervals and events, a prominence catalogue, and we discuss possible future co-operation.
Development of an Instrument Based on a Fibre-Bonded CCD Camera for Prominence Observations
Authors: Verma V. K. , Uddin Wahab , Gaur V.P. 
Published: July 2016

AbstractWe have devloped and tested an instrument based on a fibrebonded CCD camera for observations of solar prominences. To record faint prominences we have used a solid aluminized glass cone which reflects bright solar disc light outside the telescope tube. The prominence monitor is installed at the back end of a 15-cm f/15 coude refractor telescope after the H-alpha filter. This prominence monitor is capable of recording prominence images at an interval of 5 sec, but during prominence eruptions it can record images at an interval of 2 sec.
Doppler Detection of Extrasolar Planets
Authors: Marcy G. W. , Butler R. Paul , Fischer D. A. 
Published: July 2016

AbstractWe have measured the radial velocities of 540 G and K main sequence stars with a precision of 3−10 ms−1 using the Lick and Keck échelle spectrometers. We had detected 6 companions that have m sin i < 7 MJup. We announce here the discovery of a new planet around Gliese 876, found in our Doppler measurements from both Lick and Keck. This is the first planet found around an M dwarf, which indicates that planets occur around low-mass stars, in addition to solar-type stars. We combine our entire stellar sample with that of Mayor et al. to derive general properties of giant planets within a few AU of these stars. Less than 1% of G and K main sequence stars harbor brown dwarf companions with masses between 5 and 70 MJup. Including Gliese 876b, 8 companions exhibit m sin i < 5 MJup which constitute the best planet candidates to date. Apparently, 4% of stars have planetary companions within the range m sin i = 0.5 to 5 MJup. Planets are distinguished from brown dwarfs by the discontinuous jump in the mass function at 5 MJup. About 2/3 of the planets orbit within just 0.3 AU due in part to their favorable detectability, but also possibly due to a real “pile up” of planets near the star. Inward orbital migration after formation may explain this, but the mechanism to stop the migration remains unclear. Five of eight planets have orbital eccentricities greater than that of our Jupiter, eJup = 0.048, and tidal circularization may explain most of the circular orbits. Thus, eccentric orbits are common and may arise from gravitational interactions with other planets, stars, or the protoplanetary disk. The planet-bearing stars are systematically metal-rich, as is the Sun, compared to the solar neighborhood.