bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of Nonrigid-Earth Nutation Theory by Adding a Model Free Core Nutation Term
Authors: Shirai Toshimichi , Fukushima Toshio 
Published: July 2016

AbstractFrom the analysis of VLBI observational data compiled by USNO (U.S. Naval Observatory) from MJD 44089.994 to 51618.250 (McCarthy, 2000), we showed that a strong peak around –400 sidereal days in the spectrum of its differences from the IERS96 nutation theory could be explained by adding a model Free Core Nutation (FCN) term in the form of a single damped oscillation. Then we developed a new analytical theory of the nonrigid-Earth nutation including the derived FCN model. We adopted RDAN98 (Roosbeek and Dehant, 1998) as the rigid Earth nutation theory. It was convolved with a transfer function using numerical convolution in the time domain (Shirai and Fukushima, 2000). The form of the transfer function was the same as that of Herring (1995). However, its free parameters such as the complex amplitude and frequency of the FCN were readjusted by fitting to the above VLBI data. Even after truncating the forced nutation series so as to contain only 180 terms, the WRMS (Weighted Root Mean Square) of the complex residuals for the new nutation series is 0.312 mas, which is significantly smaller than 0.325 mas, that of the IERS96 nutation theory. As for the FCN term, we estimated its oscillatory period as –430.8±0.6 sidereal days, and its Q-value as 16200 ± 1600. Also we estimated the correction of the precession constants as −0.29297±0.00047”/cy in longitude and −0.02430±0.00019”/cy in obliquity, respectively.
Nonrigid-Earth Rotation Solution
Authors: Bretagnon P. , Rocher P. , Simon J.-L. 
Published: July 2016

AbstractThe accuracy of the rigid-Earth solution SMART97 is 2 μas over the time interval (1968, 2023). To obtain a nonrigid-Earth solution, we use the transfer function of Mathews (1999). The perturbations of the third component of the angular velocity vector are taken into account.
Advances in the Unified Theory of the Rotation of the Nonrigid Earth
Authors: Getino Juan , Ferrándiz José M. 
Published: July 2016

Investigations of nonrigid-Earth rotation usually rely on the convolution of a transfer function with a rigid-Earth solution. A possible alternative is to develop a unified theory to encompass in only one body both rigid and nonrigid effects. It is represented in the Hamiltonian theory by Getino and Ferrándiz (GF). This theory combines the convenience of being a really analytical theory with good practical performance, since the residuals with respect to observations are also at the same ±1 mas level as the present IERS series.We report on more recent results we obtained in the last year, not collected in the “Considerations” paper of the WGN (joint IAU/IUGG Working Group on Nutations).
Kinematical Relativistic Corrections for Earth’s Rotation Parameters
Authors: Brumberg V.A. , Bretagnon Pierre 
Published: July 2016

AbstractDynamical theories of the Earth’s rotation like SMART97 (Bretagnon et al., 1998) are to be considered in a DGRS (dynamically nonrotating geocentric reference system) (Brumberg et al., 1996). Such a theory gives the explicit expressions in terms of TCG (Geocentric Coordinate Time) of three Euler angles relating a DGRS to the ITRS (International Terrestrial Reference System). These angular quantities together with their TCG derivatives enable one to get all Earth’s rotation parameters. At the same time, the analysis of observations result in the values for slightly different angles and their TCG derivatives characterizing the relationship between the ITRS and a KGRS (kinematically nonrotating geocentric reference system). The differences between these two sets of six quantities represent kinematical relativistic corrections (due to geodesic precession, geodesic nutation and luni-planetary terms). The paper presents these differences computed by means of the VSOP87 series (Bretagnon and Francou, 1988). In particular, in analysing observations at the microarcsecond level these expressions will permit an experimental check of geodesic precession in a more direct manner than it is done nowadays (Bertotti et al., 1987).
Observational Model for Precision Astrometry with the Space Interferometry Mission
Authors: Turyshev Slava G. , Milman Mark H. 
Published: July 2016

AbstractThe basic astrometric observable of the Space Interferometry Mission (SIM) instrument is the pathlength delay. This measurement is made by a combination of internal metrology measurements that determine the distance the starlight travels through the two arms of the interferometer and a measurement of the white light stellar fringe to find the point of equal pathlength. Because this operation requires a non-negligible integration time, the interferometer baseline vector is not stationary over this time period, as its absolute length and orientation are time-varying. This paper addresses how the time-varying baseline can be “regularized” so that it may act as a single baseline vector for multiple stars, as required for the solution of the astrometric equations.
SIM Grid Star Observations: Astrometry with a New High Dynamic Range Imaging Device
Authors: Winter L. 
Published: July 2016

AbstractFirst astrometric and photometric applications of the logarithmically scaled HDRC4 imager (developed by the Institut für Mikroelektronik Stuttgart, IMS, Germany) are presented. To test the HDRC4 imager at the telescope, a cooled camera had to be constructed by modifying a camera designed by IMS. First observations were performed with various telescopes at Hamburg Observatory, Germany. These showed the dynamic range to exceed 14 mag and the sensitivity to be comparable to that of the Kodak KAF 4200 CCD at a chip temperature of –35°C.
The Galactic Distribution of Electron Density Microstructure Inferred from Radio Scattering Observations
Authors: Cordes James 
Published: July 2016

AbstractI first review the observables and optics of interstellar seeing associated with radio wave scattering in the interstellar medium. I then describe the Galactic distribution of electron density and its fluctuations, as inferred from a number of observables, including angular and pulse broadening, diffractive scintillations, and dispersion measures. Propects for improving the Galactic model are outlined.
On Post-SKA Radio Astronomy
Authors: Parijskij Yuri , Chernenkov Vladimir 
Published: July 2016

AbstractIt is suggested that the development of the SKA will drastically change the face of radio astronomy in the 21 st Century. A FAST-style SKA would admit observations of low contrast features, and would be the best design for studying the ‘dark ages’ of the Universe (x » 1) where sub-arcmin total power instruments can usefully be employed. To date there have been no proposals for post-SKA, billion square-metra instruments; we speculate that mobile communication systems can be used. In the very distant future, SKA multi-beam systems could be used to collect signals reflected by Solar system bodies such as the asteroid belt.
Modelling, Simulation and Testing of an Optomechatronics Design of a Large Radio Telescope
Authors: Duan B.Y. , Qiu Y.Y. , Su Y.X. , Wang W.L. , Nan R.D. , Peng B. 
Published: July 2016

AbstractAn innovative design for a feed support structure for the next generation large radio telescope, based on the idea of integrating mechanical, electronic and optical technologies (Optomechatronics), is considered. Theoretical analyses and simulations are carried out. A 5 m experimental model is built to demonstrate the idea.
The Gamma-ray Large Area Space Telescope (GLAST)
Authors: Kotani Taro 
Published: July 2016

AbstractGLAST, the next U.S. general gamma-ray astrophysics mission scheduled to be launched into low Earth orbit in April, 2006, for 5–10 years of operation, is described. A product of a NASA/DOE and international collaboration, the Large Area Telescope (LAT) is the primary instrument that covers the < 20 MeV to > 300 GeV band with an effective area > 8000 cm2. The angular resolution ranges from < 3.5° at 100 MeV to < 0.15° at 10 GeV. The GLAST Burst Monitor (GBM) consists of a group of NaI and BGO detectors to extend GLAST’s sensitivity to gamma-ray bursts to the < 10 keV to > 25 MeV band. GLAST’s localizations enables us to identify the X-ray, optical and radio counterparts of thousands of gamma-ray sources and to determine their nature.
Multiple Probes of the AS Cam Dynamical Problem
Authors: Van Hamme W. , Wilson R.E. , Branly R.M. 
Published: July 2016

AbstractAS Camelopardalis is notorious for its apparent disregard for the theory of apsidal motion. The orbit of this 3.43-day double-lined eclipsing binary (B8V + B9.5V) rotates approximately 15° per century, which is only 0.3 to 0.4 as fast as predicted (classical + relativistic). Our dynamical program explores, as have others, the suggestion that a third star perturbs the orbit of the eclipsing pair and slows its apsidal motion, dω/dt. On the observational side, we unify the process of extracting apsidal motion and light-time effect parameters from eclipse minima by directly including a third body light-time effect along with the usual ephemeris parameters. By numerical experiment we identify third body parameters consistent with the eclipse timings and with the dynamics of third body perturbations. Results include the minimum third body mass required to produce the given retrograde apsidal rate. Finally, we use a general binary star light curve program that includes a light-time effect to solve for dω/dt and ephemeris parameters together with other quantities, combining 21 years of radial velocities and light curves within one coherent analysis. The program has an improved stellar atmosphere routine based on Legendre polynomials that have been fitted to Kurucz atmosphere models. By analyzing whole light curves, the program has access to more information than only times of minima. Results agree well with those from eclipse timings over 100 years and attain smaller standard errors despite utilizing only one-fifth of the traditional method’s baseline in time.
Strange Among the Strange: The B-emission Star γ Cassiopeiæ
Authors: Harmanec P. 
Published: July 2016

Abstractγ Cas (HD 5394) is an important representative of Be stars, hot B stars exhibiting Balmer and other emission lines in their spectra at certain epochs. Its emission spectrum was observed as early as in 1863 and has undergone spectacular changes since then. γ Cas is also extremely interesting because it qualifies for several phenomenologically defined groups: it is a light and colour variable, long-term radial-velocity variable, X-ray source, IRAS source, rapid line-profile variable, a single-line spectroscopic binary and a central star of a reflection nebula.A critical compilation of the wealth of observational data on the star, with emphasis on its time variability on several time scales, as well as an estimate of the most probable values of all basic physical properties of the object is presented. It is pointed out that in spite of a large quantity of data, systematic and well-calibrated observations are still rather rare. The present understanding of the object is put into perspective of the more general – and as yet unsolved – problem of the formation of Be envelopes.
Maser Emission from Icy Planets Orbiting Young Stars
Authors: Slysh Viacheslav 
Published: July 2016

AbstractA model of maser emission spots as icy planets orbiting young massive stars is proposed. It is argued that the interstellar gas phase abundance of methanol, H2O and OH is much too low to produce maser emission from small gas clumps. The interstellar grains, on the other hand, consisting mainly of water ice and several per cent of methanol, can produce a favorable environment for the maser emission when evaporated. Big comets or planets covered by the water/methanol ice orbiting young massive stars can be the sites of the maser emission. The ice evaporates under stellar radiation, and water and methanol molecules emit corresponding maser lines, while OH molecules are produced from dissociation of water by the stellar radiation. VLBI observations of masers in W 3(OH), W 75N and V645 Cyg show that proposed planets are found in disks, and are moving on Keplerian orbits around O, B-stars. In the case of the O-star in W 3(OH) the planets are located beyond the compact HII region of the star. Extended envelopes of the icy planets provide molecular abundance, gas temperature and density adequate for the maser emission.
Be Binaries with Warm Dust and Exotic High-Luminosity A–F Emission-Line Stars
Authors: Miroshnichenko Anatoly S. , Bjorkman Karen S. , Klochkova Valentina G. , Chentsov Eugene L. 
Published: July 2016

AbstractWe present the results of photometric and high-resolution spectroscopic studies of a group of B[e] stars (Be stars with warm dust or B[e]Ds) and of two cooler objects with extremely high luminosities (HDE 331319 and IRC+10420). The B[e]Ds is a growing group of objects with very strong emission-line spectra, some of which show direct evidence of the presence of a hot and a cool star in the system. Their basic properties and connection to other groups of binaries are discussed, and a new list of members is presented. Fundamental parameters and chemical composition of an unusual F-supergiant HDE 331319 and recent results on a fast evolving object IRC+10420 are also reported.
The β Pictoris Disk: Peculiar or Just Young?
Authors: Lissauer Jack J. , Backman Dana E. 
Published: July 2016

AbstractThe star β Pictoris is not in itself very remarkable; however, it is surrounded by a dust disk that is much more prominent than any other main sequence star’s disk. The proximity of β Pic and the nearly edge-on viewing geometry of the disk enhance its appearance, but do not fully account for the disk’s prominence. While it is possible that β Pic’s disk is intrinsically unusual, a more likely explanation is that β Pic is simply a very young (~ 20 Myr old) main sequence star with a consequently denser second-generation debris disk remnant of its protostellar disk than possessed by older main sequence A stars.
Light Curve Changes in AH Cancri
Authors: Branly R.M. , Van Hamme W. 
Published: July 2016

AbstractLight curves of the W Ursae Majoris binary AH Cancri obtained in 1973 and 1988 show a remarkable change in shape. Earlier curves have rounded minima and eclipses appear to be partial; later curves have flat-bottomed minima indicating total eclipses. The 1973 curves are consistent with a system in overcontact with an orbital inclination of approximately 65°. Such a low inclination, however, is incompatible with the -duration flat-bottomed eclipse seen in the more recent light curves. Intrigued by this puzzle we decided to make new photometric observations. We present CCD photometry in V and R obtained with the Southeastern Association for Research in Astronomy (SARA) 0.9-m and Buehler Observatory 0.4-m telescopes. We solve the new light curves and find a high-inclination (i ≈ 84°), low-mass-ratio (q ≈ 0.145) model fits the observations reasonably well. In the post-1988 light curves, limb darkening causes eclipses of the cooler star to be deeper than those of the hotter star. Times of minima suggest a possible third body interaction.
Looking for Twins of Przybylski’s Star
Authors: Hubrig S. , Cowley C.R. , Bagnulo S. , Mathys G. , Ritter A. , Wahlgren G.M. 
Published: July 2016

AbstractThe examination of high resolution spectra of two Ap stars, HD 965 and HD 217522, discloses a spectral appearance similar to Przybylski’s star. Here we present the preliminary results of a comparative study of all three stars. Further, we discuss the possibility of having a good spectroscopic indicator of magnetic fields in Ap stars. In all three studied stars the strong Lu II line at λ 5984 Å is present and very likely not affected by significant blends. Its hyperfine structure has been recently measured and we show the results of a model that accounts for the Paschen-Back effect on hyperfine structure.
Simultaneous Stokes Imaging and Doppler tomography of MCVs
Authors: Potter Stephen , Romero-Colmenero Encarni , Buckley David , Wood Derren 
Published: July 2016

AbstractStokes imaging uses polarimetric observations in order to image indirectly the accretion region on the surface of the white dwarf in magnetic cataclysmic variables (MCVs). Doppler tomography uses spectroscopic observations in order to gain insights into the velocity dynamics of the secondary star, and the ballistic and magnetically confined parts of the accretion stream. Until now, both of these techniques have been applied separately. We present and compare the results of applying both techniques to simultaneous spectroscopic and polarimetric observations of MCVs.
Dwarf Nova Oscillations and Quasi-Periodic Oscillations: Extension of the Two-QPO Diagram of X-Ray Binaries, and a new kind of DNO
Authors: Warner Brian , Woudt Patrick A. 
Published: July 2016

AbstractSeventeen examples are given of Cataclysmic Variable (CV) stars possessing both Dwarf Nova Oscillations (DNOs) and Quasi-Periodic Oscillations (QPOs). These form an extension of the X-Ray Two-QPO correlation to frequencies three orders of magnitude lower. We draw attention to the existence of a second type of DNO in CVs, which is probably caused by magnetically channelled accretion onto the white dwarf.
RX J0524+42: A New Asynchronous Magnetic CV
Authors: Schwarz Robert , Schwope A. D. , Staude A. , Urrutia T. , Rau A. , Hasinger G. 
Published: July 2016

AbstractExtensive optical photometry of the canditate magnetic CV RX J0524+42 has uncovered three persistent periods at 157, 146 and 136 minutes, which are the manifestation of the orbital motion of the system, the white dwarf spin and a possible side-band period of the latter. Depending on the interpretation of the 146 or the 136 minute period as the spin period, the system is an asynchronous by 7% or 14% (1 – PSpin/Porb), and therefore intermediate between the near-synchronous polars (< 2%) and the two DQ Her stars with long spin periods (EX Hya and V1025 Cen). Sampling the data over the beat period of 1.4 or 0.7 days reveals a prominent double-humped modulation on the spin period for certain fractions of the beat cycle. The phasing of this modulation strongly suggests that either pole switching onto two diametrically opposed accretion sites, or pole migration is operating in this system. With a period right within the period gap, RX J0524+42 is a key object for MCV evolution: it might be the first transition object between the DQ and AM Her subclasses where the white dwarf is currently in the process of synchronisation.
Fireballs, Flares and Flickering
Authors: Pearson K. J. , Horne Keith , Skidmore Warren 
Published: July 2016

AbstractWe review our understanding of the prototype “Propeller” system AE Aqr and we examine its flaring behaviour in detail. The flares are thought to arise from collisions between high density regions in the material expelled from the system after interaction with the rapidly rotating magnetosphere of the white dwarf. We show calculations of the time-dependent emergent optical spectra from the resulting hot, expanding ball of gas and derive values for the mass, lengthscale and temperature of the material involved. We see that the fits suggest that the secondary star in this system has reduced metal abundances and that, counter-intuitively, the evolution of the fireballs is best modelled as isothermal.
Earth Rotation in the Erold Framework
Authors: Calame O. 
Published: July 2016

The project EROLD (Earth Rotation from Lunar Distances) was conceived in 1974, in the COSPAR framework, with the goal of demonstrating that the lunar distances technique might be an efficient candidate in a new-generation service for the determination of Earth orientation.Two years later, it was decided that the computations of the observational residuals and partial derivatives, as well as the analyses themselves, would be done at C.E.R.G.A. on a regular basis, for all the participating stations. Indeed, it was recognized to be important that all the observations be reduced in an homogeneous process. The target chosen for this program was that of Apollo XV which is the easiest to observe. Unfortunately, the operations could not start quickly due to a lack of observations and each station was encouraged to press the completion of the equipment, but many problems slowed the integration of these stations. Still now, only McDonald Observatory transmits observations regularly, and Orroral is operating, but with scattered results; presently this latter station is in course of modifications for improvement of accuracy.
On the Absolute Orientation of the Selenodetic Reference Frame
Authors: Kislyuk V. S. 
Published: July 2016

The selection of selenodetic reference coordinate system is an important problem in astronomy and selenodesy. For the purposes of reduction of observations, planning and executing space missions to the Moon, it is necessary, in any case, to know the orientation of the adopted selenodetic reference system in respect to the inertial coordinate system.Let us introduce the following coordinate systems:
C(ξc, ηc, ζc), the Cassini system which is defined by the Cassini laws of the Moon rotation;D(ξd, ηd, ζd), the dynamical coordinate system, whose axes coincide with the principal axes of inertia of the Moon;Q(ξq, ηq, ζq), the quasi-dynamical coordinate system connected with the mean direction to the Earth, which is shifted by 254" West and 75" North from the longest axis of the dynamical system (Williams et al., 1973);S(ξs, ηs, ζs), the selenodetic coordinate system, which is practically realized by the positions of the points on the Moon surface given in Catalogues;I(X,Y,Z), the space-fixed (inertial) coordinate system. All the systems are selenocentric with the exception of S(ξs, ηs, ζs On the whole, the origin of this system does not coincide with the center of mass of the Moon.
Preprint Databases at NRAO and STScI
Authors: Bouton Ellen , Stevens-Rayburn Sarah 
Published: July 2016

A couple of different facts coalesced in the mid-70s that forced us to try to come up with a manageable scheme for handling preprints. First, as librarians at the National Radio Astronomy Observatory, we were charged with tracking papers by NRAO staff and by visitors using Nrao telescopes to provide an annual listing of staff and visitor publications and to aid in compiling statistics on telescope use.Second, staff and visitors kept asking for preprints — by series and/or by author, subject, or cover color — and the number of preprint series being received had increased to the point where we could no longer always pull that information off the tops of our heads. So, after consulting with colleagues who had similar concerns, we put together a database in 1978, modestly based on the highly successful Preprint/Antipreprint lists produced by the Stanford Linear Accelerator Center. We decided to produce a biweekly list of new papers received and an as-needed list of recently published papers. The scientific staff were very enthusiastic from the beginning, seeing that our efforts would make their efforts to keep up with the literature that much easier.