bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotational Velocities of Evolved A and F Stars
Authors: Faber Sandra M. , Danziger I. J. 
Published: July 2016

AbstractMean rotational velocities are presented for stars on and above the main sequence from spectral type A5 to F9. The velocities are shown to be inconsistent with the hypothesis of stellar rotation in completely uncoupled shells for stars that have expanded in radius by less than a factor of four. They do, however, support the hypothesis of solid-body rotation for these stars. The data for the giant stars are discussed, but no firm conclusions about the mode of rotation in these stars can be drawn.
On the Effect of Rotation on Stellar Absorption Lines
Authors: Tuominen Ilkka V. , Vilhu Osmi 
Published: July 2016

AbstractThe effect of rapid uniform rotation on equivalent widths of spectral lines is studied in the case of a star seen pole-on. Contrary to the situation for the strong lines MgII 4481 and SiII 4128, the effect may be significant for the weak ones, especially those of the EuII-type. Because the mean atmospheric parameters of a rapidly rotating star seen pole-on are very similar to those of a non-rotating star of the same mass, this may cause significant errors in abundance determinations, especially for Eu-type elements. The aspect effect on the central intensity of two EuII lines of different strengths is also studied.
Observations of Stellar Rotation and Line Strengths for Ob Stars
Authors: Buscombe William 
Published: July 2016

For 121 southern stars of spectral types between 05 and A3, including 35 supergiants, equivalent widths and values of ve sini have been measured for absorption lines on direct-intensity tracings of coudé spectrograms from Mount Stromlo, with original dispersion 150 microns per angstrom. For stars of a particular temperature and luminosity class, the strength of the hydrogen lines is weaker and the triplet helium lines stronger in fast rotators than in sharp-lined objects which are rotating more slowly. Full details are in print (Monthly Notices Roy. Astron. Soc. 144 (1969), 1): subsequent papers in press present detailed profiles of the Balmer lines for 23 slowly rotating stars and details of emission features shown by several fast rotators.The investigation is being continued with spectrograms of northern B stars secured at the Dominion Astrophysical Observatory, supported in part by grant GP-13544 from the National Science Foundation.
Rotation in Close Binaries (Review Paper)
Authors: Plavec Miroslav 
Published: July 2016

When studying the axial rotation of the components of binary systems, we ask the following fundamental question: How much is axial rotation affected by the other star? In particular, is there any synchronism between the periods of axial rotation and orbital revolution?Thus in fact we are more interested here in the angular than in the linear velocity of rotation. It was pointed out by McNally (1965) that the angular velocity of rotation reaches its maximum near A5 and drops off rather rapidly on both sides so that the GOV and 05V stars have approximately the same average period of rotation. The accompanying Table I is an adaptation of McNally’s figures.
A Scanning Micrometer with On-Line Computer
Authors: Høg Erik 
Published: July 2016

AbstractA photoelectric scanning photometer is being tested at the 60 cm-refractor in Hamburg in order to measure visual binaries. The data-acquisition is accomplished by a small on-line computer PDP-8/S which samples data from three photon-counters connected to three narrow slits in the focal plane.A preliminary investigation of the image profile as it is obtained from the adding of many scans of a star on top of each other shows that about 80% of the light is concentrated in a Gaussian core with σ = 1″–2″ whereas the rest goes into non-Gaussian wings. The deviation of the profile from a single Gaussian is most pronounced in good seeing.
Photométrie des Étoiles Doubles
Authors: Muller P. 
Published: July 2016

Du point de vue de la photométrie, on peut distinguer très schématiquement trois sortes d’étoiles doubles:(1)les couples optiques(2)les couples physiques sans orbite connue(3)les couples orbitaux.Ce classement correspond à une progression parallèle dans l’intérêt et dans la difficulté d’observation des objets.
The Excess Secular Change in the Obliquity of the Ecliptic and its Relation to the Internal Motion of the Earth
Authors: Aoki Shinko , Kakuta Chuichi 
Published: July 2016

AbstractCriticisms of the senior author’s paper (1967) are examined, and it is found that there still seems to be a possibility that the cause of the excess secular change is in the mantle-core coupling. Part II is devoted to an improvement of the previous result (Aoki, 1969) using a model of the elastic mantle and fluid core. In order to give the observed value of excess secular change of the obliquity, a value of the coupling coefficient of the Earth’s rotation is 3.5 times larger than Rochester’s (1968) value is required. This is not impossible from the geophysical view-point. In fact, if we take into account Hide’s argument (1969), then the coupling coefficient will be much larger than the present geophysical value.
Correction to the Mass of Jupiter Derived from the Motion of (153) Hilda, (279) Thule, and (334) Chicago
Authors: Scholl H. 
Published: July 2016

AbstractAn analysis of the observations of the minor planets (153) Hilda, (279) Thule and (334) Chicago yields the following values for the reciprocal mass of Jupiter: (153) Hilda 1047.378 ±0.019, (279) Thule 1047.347 ±0.023, (334) Chicago 1047.325 ± 0.010. A possible error in the mass of Saturn that might affect these results is discussed.
Direct Integration Methods of theN-Body Problem
Authors: Aarseth S. J. 
Published: July 2016

AbstractA fourth-order polynomial method for the integration ofN-body systems is described in detail together with the computational algorithm. Most particles are treated efficiently by an individual time-step scheme but the calculation of close encounters and persistent binary orbits is rather time-consuming and is best performed by special techniques. A discussion is given of the Kustaanheimo-Stiefel regularization procedure which is used to integrate dominant two-body encounters as well as close binaries. Suitable decision-making parameters are introduced and a simple method is developed for regularizing an arbitrary number of simultaneous two-body encounters.
Contribution to the Background Rate of a Satellite X-Ray Detector by Spallation Products in a Caesium Iodide Crystal
Authors: Dyer C. S. , Morfill G. E. 
Published: July 2016

AbstractThe energy spectra observed in a CsI crystal in the 20 keV–2 MeV range, due to the decay of radioactive isotopes produced in the crystal by bombardment with 155 MeV protons, are presented as a function of time after irradiation.It is shown that the large number of decay products produced by spallation can account for these spectra and that these spectra are in quantitative agreement with the predictions of a semi-empirical formula due to Rudstam, which gives the numbers of different isotopes produced. This formula is used to predict the spallation that would occur in such a crystal on board a satellite due to cosmic rays and passages through the South Atlantic Anomaly. Inspection shows that the spallation produced in the latter case is well approximated by that at 155 MeV. Hence the experimental results are used to explain previously observed background rates and to predict the background rates that would occur in the U.K.5 X-ray telescope of Imperial College. Using the Rudstam formula an estimate of cosmic ray induced background is also made.The relative importance of activity resulting from neutron interactions (atmospheric albedo and spacecraft secondaries) is considered.It is suggested that the Rudstam formula provides a general method of predicting induced radioactivity in satellite materials and that observed breaks in the diffuse cosmic X-ray spectrum could be due to inadequate allowance for this source of background.
Small-Scale Magnetic Structures and Supergranulation Flows
Authors: Yi Zhang , Jensen Eberhart , Engvold Oddbjørn 
Published: July 2016

AbstractRelations between horizontal flow and filigree structure obtained from high-resolution observations (~1/4) are discussed. The magnetic flux elements move with the horizontal flow in the supergranulation network, and as downdrafts are approached both magnetic flux and intensity gradually decrease. Reasons for this disappearance are discussed. If the photosphere actually is a turbulent magneto-plasma, as suggested by the good coupling between the magnetic flux elements and the flow field, the integrated magnetic flux in the background field will exceed the flux in the discrete kilogauss structures.
Relation of Magnetic Fields with Solar Activity Indexes in a Descending Phase of Solar Cycle
Authors: Choe Won Chol 
Published: July 2016

AbstractWe examine the solar activity indexes (relative intensity of sunspots and faculae) of an active region #83137 during 1983 June 21–26. The results are compared with daily variation of magnetic fields of the region to find a characteristic of solar activity variation in the descending phase of solar cycle.
The Development of Sunspot Groups
Authors: Howard Robert F. 
Published: July 2016

AbstractIt is shown that the growth and decay rates of sunspot groups are both a function of the axial tilt angles of the groups. Both of these rates reach a maximum near the average tilt angle, which is around +5°, not 0°. (A positive tilt angle represents the situation where the leading spots are equatorward of the following spots). The fact that this peak angle is close to the average tilt and not 0° suggests that this may be the orientation of the subsurface toroidal flux tube(s) from which the sunspot groups form. In general, spot groups with positive tilt angles show faster average percentage growth rates for greater positive tilt angles. For negative tilt angles (following spots equatorward of leading spots) the situation is quite different. Within certain well-defined ranges of tilt angles the average group percentage area growth rates are quite high and the dispersion in this quantity is large. In other well-defined tilt angle ranges the percentage growth rates are uniformly (relatively) small. The difference between these average growth rates is more than a factor two. The reality of this result can be demonstrated by selecting for analysis various subsets of the data. It may be hypothesized that in general the dispersion measured in group tilt angles results from the random action of large-scale convection on the rising magnetic flux loops. Both growth and decay are facilitated in the case of flux loops that have a minimum twist. The percentage growth and decay rates are affected by the fact that groups with tilt angles near the average value tend to be larger than groups with different tilt angles. The ‘quantized’ behavior of the percentage growth rates for negative tilt angles is difficult to fit into any rough model of flux emergence. The more or less ‘quantized’ nature of the growth-tilt angle relationship for negative tilt angles is quite puzzling and may reflect some characteristic of the subsurface flux orientation or development which is at present unknown.
MHD Numerical Simulations of Magnetic Reconnection Associated with Emerging Flux
Authors: Shibata K. , Nozawa S. , Matsumoto R. 
Published: July 2016

AbstractTwo-dimensional (2D) magnetohydrodynamic (MHD) numerical simulations have been performed to study magnetic reconnection between emerging flux and the overlying coronal magnetic field, taking into account of gravity. It is found that (1) reconnection starts when most of chromospheric mass in the current sheet between the emerging flux and the coronal field has drained down along the loop because of gravity, (2) multiple magnetic islands, which confine cool, dense chromospheric plasma, are created in the sheet; the islands coalesce dynamically and are ejected along the sheet, together with the ambient hot plasma, at Alfven speed. The coexistence of hot and cool plasmas in the mass ejection (jet) associated with the reconnection seems to explain those X-ray jets observed by Yohkoh, which are identified with Hα surges.
Structure in the Solar Corona from Radio Scintillation Measurements
Authors: Woo Richard 
Published: July 2016

AbstractSince the 1950s, a wide variety of radio observations based on scattering by electron density fluctuations in the solar wind has provided much of our information on density fluctuations and solar wind speed near the source region of the solar wind. This paper reviews recent progress in the understanding of the nature of these density fluctuations and their relationship to features on the Sun. The results include the first measurements of fine-scale structure within coronal streamers and evidence for structure in solar wind speed in the inner corona.
Coronal Hole Flux Tubes and the Problem of Relating Interplanetary and Solar Features
Authors: Bravo S. 
Published: July 2016

AbstractCoronal flux tubes have in general very large divergence, and the properties of their flow vary greatly inside the flux tube. We present here a general description of the evolution and the characteristics of coronal holes and discuss how these characteristics may lead to erroneous associations between interplanetary and solar structures.
Acceleration Phenomena Observed by Interplanetary Scintillation at 0.1–0.3 AU
Authors: Kojima M. , Misawa H. , Watanabe H. , Yamauchi Y. 
Published: July 2016

AbstractInterplanetary scintillation has observed high-latitude streams which show low speeds (≤400 km/s) within 0.3 AU and high speeds (≥700 km/s) beyond 0.3 AU. The foot points of these streams were located in the Hel coronal holes or at their boundaries. Since the IPS measurement is biased by one or several mechanisms, we investigated whether this acceleration phenomena could be caused by bias effects or not. Speed increase of more than 100 km/s is left without being explained by the bias effects.
Solar Radio Burst (Type III)
Authors: Om Vats Hari , Deshpande M.R. , Iyer K.N. , Kondo Tetsuro , Isobe Takeshi 
Published: July 2016

AbstractThis article describes the observations of a type III radio burst observed at 103 MHz simultaneously by the two radio telescopes situated at Rajkot (22.3°N, 70.7°E) and Thaltej (23°N, 72.4°E). This event occurred on September 30, 1993 at about 0430 UT and lasted for only half a minute. The event consisted of several sharp spikes in a group. The rise and fall time of these are comparable, however the peaks of individual spikes varied by a factor of four. The comparison of these observations with the data of solar radio spectrograph HiRAS indicates that this was a metric radio burst giving highest emission at about 103 MHz.
The US and Other Optically Selected Bright QSO Samples
Authors: Mitchell Kenneth J. , Usher Peter D. 
Published: July 2016

AbstractThe US Bright Quasar Sample (UBQS) is a color-selected sample of quasars with B < 17 that has been constructed with an eye towards completeness within well-defined selection limits. The redshift distribution of the UBQS shows an interesting spike at z ~ 0.55. The significance of this enhancement increases when the UBQS is combined with other bright quasar samples which also show evidence of high levels of completeness. Reconstitution of this combined bright quasar sample after removal of the emission-line flux from the B magnitudes indicates that the z ~ 0.55 spike is not caused by an emission-line selection bias. Rather, the largest effect of these sample corrections would be to depress the high end of the optical luminosity function that is derivable from this combined sample.
The 2MASS Red AGN Survey
Authors: Cutri R.M. , Nelson B.O. , Francis Paul J. , Smith Paul S. 
Published: July 2016

AbstractThe Two Micron All Sky Survey (2MASS) provides an unprecedented, uniform photometric data set for large samples of AGN discovered at other wavelengths, and also forms the basis to search for previously unknown, obscured AGN. We present the results of a highly efficient near infrared color-based AGN survey using 2MASS that has already discovered 485 new, red AGN and QSOs. The extrapolated surface density of the 2MASS red AGN is ~0.57 deg~−2 for Ks≤15.5 mag. The ratio of Type 1 to Type 2 AGN among the newly discovered objects is 4:1, similar to proportions found in X-ray and deep ISO surveys, but the inverse of that found in IRAS surveys. The median redshift of the the new 2MASS red AGN sample is z<0.22, and all but three have z<0.7. The color distribution, polarization and X-ray properties data suggest that most of the 2MASS-discovered AGN are red because of obscuration by dust in and around their nuclei.
Compact Jets in 100 AGNs with the Strongest Broad-Band Variability of 1-22 GHz Spectra in 1997-2001
Authors: Kovalev Yu. A. , Kovalev Y. Y. , Nizhelsky N. A. , Bogdantsov A. V. 
Published: July 2016

AbstractResults of monitoring observations at the radio telescope RATAN-600 and a model interpretation of instantaneous 1-22 GHz spectra at six frequencies for 100 selected AGNs are presented. The index of variability at these frequencies is shown for 550 sources monitored in 1997-2001 at 11 epochs. The spectra of the selected sources exhibit flux density variations of about 50% and up. The type of spectral evolution is similar for all the selected objects, favoring the same basic physical model. Model analysis shows that the nature of the radio sources and the observed variability behavior of the spectra can be explained by a model with a relativistic jet of parsec scale in a longitudinal magnetic field.
System to Estimate Ages and Redshifts for Radio Galaxies
Authors: Verkhodanov O. V. , Kopylov A.I. , Verkhodanova N.V. , Zhelenkova O.P. , Chernenkov V.N. , Parijskij Yu. N. , Soboleva N.S. , Temirova A.V. 
Published: July 2016

AbstractThe system allowing a user to operate at the server sed.sao.ru with simulated curves of spectral energy distributions (SED) and to estimate ages and redshifts from photometric data is described.
Quasar Variability: New Surveys and New Models
Authors: Hawkins M.R.S. 
Published: July 2016

AbstractIn this paper results from a monitoring programme of a large sample of quasars comprising regular yearly observations over a period of 23 years are presented. Structure functions of the light curves are calculated and compared with predictions for models of quasar variability of current interest. These include recently published models of varibility from accretion disk instability, variability from starbursts or supernovae, and variations caused by the microlensing effect of compact bodies along the line of sight. The analysis favours the accretion disk model for low luminosity AGN, but suggests that the variations of more luminous quasars are dominated by microlensing.
Intermediate Resolution Hβ Spectroscopy and Photometric Monitoring of 3C 390.3. I. Further Evidence of a Nuclear Accretion Disk
Authors: Shapovalova A.I. , Burenkov A.N. , Spiridonova O.I. , Vlasuyk V.V. , Mikhailov V.P. , Carrasco L. , Chavushyan V.H. , Valdes J.R. , Legrand F. , Doroshenko V.T. , Lyuty V.M. , Bochkarev N.G. , Dumont A-M. , Collin S. , Kurtanidze O. , Nikolashvili M.G. 
Published: July 2016

AbstractThe variations of the Hβ broad emission line and continuum flux in 3C 390.3 are investigated. Our results favor the formation of the broad Hβ line of 3C 390.3 n an accretion disk.
Dynamical transport mechanisms of planet-crossing bodies
Authors: Froeschlé Ch. , Michel P. , Froeschlé C. 
Published: July 2016

AbstractIn this paper we review the most important dynamical mechanisms for transporting material from the asteroid belt to the vicinity of the inner planets. Most of these mechanisms are associated with secular or/and mean motion resonances. From numerical integrations on timescales of hundreds Myr, new quantitative results on the dynamical lifetimes of bodies injected in the main resonances have been obtained. These new results are not consistent with the observed population of Earth-crossers of large diameter. At the light of these results a new scenario for the origin of large Earth-crossers has recently been proposed.
Some selection effects in the discovery of AAA's and their influences on their q and Ω distributions
Authors: Kostolanský E. 
Published: July 2016

AbstractTheqand Ω distributions of the Amor–Apollo–Aten (AAA) asteroids indicate the existence of some selection effects of their discoveries. In the case of theqdistribution the problem of persistence of an asteroid near the Earth is decisive. The persistence of asteroids withq&lt; 1 AU anda&gt; 1 AU near the Earth is roughly ∼vg−1(vgis the geocentric velocity of an asteroid near the Earth). Functionvg−1(q) is discussed for orbits withi= 0° anda =1.1, 1.5, 2.0 and 2.5 AU, which are typical values ofafor the AAA asteroids. For asteroids withq&gt; 1 AU the problem of persistence of an asteroid near opposition is decisive. The optimum orbits (the longest persistance of an asteroid near the opposition) withq[AU] = (1 +e)⅓,i= 0° are discussed. The Ω distribution is probably influenced by a large amount of minor selection effects. One of them might be based on fact that on vernal or autumnal equinox all asteroids with Ω ≈ 180° andi≈ 23.5° have declinationδ≈ 0°, hence it is easy to observe them in these periods of the year. This selection effect is discussed in detail also with its observational consequences.
From the Oort cloud to Halley-type comets
Authors: Fernández J.A. , Gallardo T. 
Published: July 2016

AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods &lt; 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq &lt;2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods &lt; 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.