bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral Changes of Pleione - Start of a New Cycle?
Authors: Iliev L.
Published: July 2016

This is a preliminary report on spectral variability of Pleione during the present Be phase. The spectral activity of the star confirms the observed photometrical trend.
59 Cygni: A Tilted ϕ Persei like System
Authors: Rivinius Th. , Štefl S.
Published: July 2016

The binarity of 59 Cygni was confirmed and orbital parameters from the radial velocity curve of the primary derived. The observed emission variability resembles the one of ɸ Per in quite some detail, suggesting a similar nature of the companion: a hot, compact star.
Selfconsistent Models of Winds from Rotating Early-Type Stars – Application to B[e] star winds
Authors: Petrenz P. , Puls J.
Published: July 2016

We present results of 2.5-D radiation hydrodynamical simulations of winds from rapidly rotating stars. For the first time, we consider the dependence of the line statistics on local density and radiation temperature implying a spatial variation of the force-multiplier parameters k, α and δ which control the dynamics of the flow.

We apply our models to the problem of disk formation in B[e]-star winds.
He I Line Profiles Obtained From a Be Wind Model
Authors: Rohrmann R.
Published: July 2016

We undertook a non-LTE radiative transfer calculation to find out the possible conditions under which observed H and He I line profiles arise from some Be stars.
Be stars in X-ray binary systems
Authors: Coe M.J.
Published: July 2016

This paper will review the status of our observations and understanding of Be stars in X-ray binary systems. In virtually all cases the binary partner to the Be star is a neutron star. The circumstellar disk provides the accretion fuel and hence stimulates the X-ray emission, whilst the neutron star provides a valuable probe of the environment around the Be star. The results coming from studies of such systems are helping in our understanding of the Be phenomenon.
New JHK Photometry of LS I +61 303
Authors: Martínez-Núñez S. , Fabregat J.
Published: July 2016

We present new JHK photometry of the Be/X-ray binary L SI +61 303, obtained during the period 1994-1998. The IR light curves do not show the modulation with the orbital period apparently present in the smaller photometry set analyzed by Paredes et al. (1994).

The reddening-corrected standard photometric values indicate that the circumstellar envelope is optically thick at infrared wavelengths, and much denser than those of isolated Be stars. It is argued that this higher density is produced by disk truncation due to the presence of the compact object in a close orbit.
Searching for FAST Pulsars
Authors: McLaughlin M. , Cordes J. M. , Arzoumanian Z.
Published: July 2016

We outline the pulsar search capabilities of the AOFTM, describe results from recent searches, and discuss future plans.
High-Precision NBPP Timing Measurements at Nançay
Authors: Cognard I. , Lestrade J.-F. , Backer D.C. , Ray P.S. , Foster R.S. , Cadwell B.J.
Published: July 2016

The Nançay radiotelescope in France is a large collecting area (7000m2) with receivers around 1.4, 1.7 and 3.5GHz. At this observatory, we are conducting frequent high-precision timing observations of 5 millisecond pulsars (PSR B1937+21, B1821-24 since 1988; J1643-1224, J1713+0747 and B1620-26 since 1996) with a swept frequency oscilllator based on a DDS as a dedisperser.

The most interesting result from these dense series of observations is the detection of several Extreme Scattering Events in direction of B1937+21 and possibly in direction of B1821-24 (Cognard, 1993,Nature,366, 320; Cognard & Lestrade, 1996, in ASP Conf. Ser. Vol 105, Pulsars: Problems and Progress (San Francisco: ASP), 469; Lestrade, Rickett & Cognard 1998, A&A,334, 1068). The flux density variations and TOA fluctuations observed have been used to estimate the size (several AU) and electron density (a few hundreds electrons cm−3) of the discrete ionised clouds localized in the interstellar medium that are thought to be responsible for this phenomena. The number of events recorded at Nançay in direction of B1937+21 yields the space density 105– 106pc−3for these clouds. This density is very large and is about 100 times higher than the density estimated from Extreme Scattering Events observed in direction of extragalactic radio sources (Fiedler et al., 1994,ApJ,430, 581). This might mean that the line of sight to B1937+21 is peculiar. This is being investigated with additional observations of a larger array of pulsars at Nançay with the Navy-Berkeley-Pulsar Processor (Figure 1) This processor NBPP (Foster et al., in ASP Conf. Ser. Vol 105, Pulsars: Problems and Progress (San Francisco: ASP), 25) has been used to acquire pulsar search data for 2 years at Nancay and we are now using its real-time folding capability.
Timing of the young pulsar J1907+0918
Authors: Xilouris K. , Lorimer D.R. , Dowd A.
Published: July 2016

We have extensively searched for periodic signals in the area of the soft gamma-ray repeater SGR 1900+14, at 430 and 1410 MHz with the Arecibo telescope. Our observations did not reveal the 5.16-s periodicity reported for the magnetar down to a 430-MHz flux density limit of 150μJy. During the search we discovered a 226-ms radio pulsar, PSR J1907+0918. The period derivative implies the characteristic age for this pulsar is only 38 kyr. Independent evidence in support of this apparent youth are the unusually high degree of circular polarization and its relatively flat radio spectrum. The close proximity of PSR J1907+0918 to SGR 1900+14 suggests that they may have evolved from a massive binary system. Regardless of this possibility, it is presently not clear to us that SGR 1900+14 is associated with the supernova remnant G42.8+0.6.
Periodicities in Rotation and Pulse Shape in PSR B1828–11
Authors: Lyne A. G. , Stairs I. H. , Shemar S. L.
Published: July 2016

We report on the observation of highly-periodic, correlated variations in the rotation and pulse shape of PSR B1828–11. Three harmonically-related periodicities of 100, 500 and 250 days are seen in both the rotation rate and profile shape. The 0.7% modulation in period derivative is apparently related to oscillatory changes in the magnetospheric configuration. The origin of the periodic effects most likely lies in the free precession of the neutron star.
Geodetic Precession in PSR B1534+12
Authors: Stairs I. H. , Thorsett S. E. , Taylor J. H. , Arzoumanian Z.
Published: July 2016

We present Arecibo observations of PSR B1534+12 which confirm previous suggestions that the pulse profile is evolving secularly. This effect is similar to that seen in PSR B1913+16, and is almost certainly due to general relativistic precession of the pulsar’s spin axis.
General Relativistic Precession of the Spin Axis of Binary Pulsar B1913+16: First Two Dimensional Maps of the Emission Beam
Authors: Weisberg Joel M. , Taylor Joseph H.
Published: July 2016

Relativistic spin-orbit coupling should cause the spin axis of Binary Pulsar B1913+16 to precess at a rate of about 1 deg / yr. As a result, the pulse profile is expected to exhibit secular evolution. Weisberg, Romani, & Taylor (1989), and Weisberg & Taylor (1992) found that the intensity ratio of the two conal components changed at a one percent per year rate from 1981 to 1989, but that their spacing did not measurably change. They attributed these observations to our line of sight passing across the middle of a patchy cone of emission. Recently Kramer (1998) found that the intensity ratio continued its secular change for another decade, and also detected a narrowing of the conal component separation.

We present our analysis of eighteen years of 21 cm pulse profile data. We confirm that the profile is narrowing as precession finally carries our line of sight away from the emission beam axis, and we map the beam in two dimensions. The beam is elongated in the latitude direction, and the degree of elongation grows with radius.
Astrometry of Southern Pulsars
Authors: Legge David
Published: July 2016

A preliminary determination of the proper motion and parallax of the Vela pulsar was made using phase-referencing VLBI. The measured proper motion in right ascension and declination are respectively,µα= −49.8 ± 0.2 mas yr−1andµδ= 30.5 ± 0.1 mas yr−1. The parallax of Vela was calculated to beπveia= 3.16 ± 0.33 mas, which corresponds to a distance ofpc.
Polar-Fluxtube Emission ‘Weather’ of Pulsar B0943+10: Polarisation, Modes, & Theoretical Implications
Authors: Rankin Joanna M. , Deshpande Avinash A.
Published: July 2016

Building on the analysis of the previous paper by one of us, we here turn first to a discussion of B0943+ 10’s chaotic “Q” mode and then to the polarisation properties of its “B”-mode radiation. Here again, we see evidence that the plasma processes responsible for pulsar emission may be organized into a system of columns. In short, 0943+10 provides unprecedented insight into the phenomena comprising what might be termed pulsar polar-fluxtube “weather”.
Giant Pulses from the Crab Pulsar
Authors: Hankins Timothy H.
Published: July 2016

Recent observations of the “giant” radio pulses received from the Crab pulsar are reviewed. The frequency range over which they have been detected spans at least two decades, and individual pulses appear to have a frequency span of 3:1 or more. The pulse structure is dominated by scattering at frequencies below about 2 GHz; at higher frequencies the intrinsic pulse width is about 1µs with nanostructure extending down to 10 ns. The polarization structure may be contaminated by scattering at low frequencies and the polarization is weak and highly variable at high frequencies. No definitive emission mechanism with testable hypotheses for the giant pulses has been put forth. One of the most promising, based on the collapse of plasma solitons, predicts nanostructure bandwidths narrower than what is seen for the giant pulses themselves, though the observations do not show wideband correlation of the shortest resolvable intensity structure.
Single Pulse Analysis of the Core-Dominated Pulsar B0611+22
Authors: Kern Jeffrey S.
Published: July 2016

Single pulse studies of pulsar radio emission provide a window into the time dependent behavior of the radio loud region. I have analyzed a series of precision polarimetric observations of pulsar B0611+22 to determine the geometry of the emission region. The observations are consistent with a central core emission region, and a periodically present conal component. This identification leads to the surprising result that all emission is from the leading half of the polar cap.
Microstructure and other short time-scale events in millisecond pulsars
Authors: Soglasnov V. A.
Published: July 2016

MSP have much more various short time-scale phenomena than ”classical” microstructure in NP. Some of them have a long life-time and are observable not only in single pulses.
Pulsar spectra analysis
Authors: Maron Olaf , Kijak Jaroslaw , Kramer Michael , Wielebinski Richard
Published: July 2016

We have extended the database of flux density measurements of 280 pulsars made by Lorimer et al. (1995) to frequencies higher than 1.4 GHz and lower than 300 MHz. Our analysis shows that the spectral behaviour of the majority of pulsars can be well described by a simple power law (S~υαwhere= −1.8) though some pulsar spectra are described by a ”broken power law” with a break at high frequenciesυb~ 1.8 GHz.
Radio Emission Properties of Millisecond Pulsars
Authors: Kramer Michael , Xilouris Kiriaki M.
Published: July 2016

We report the most recent progress in understanding the emission properties of millisecond pulsars.
Mean, individual pulses and spectrum of Geminga radio emission
Authors: Malofeev V.M. , Malov O.I.
Published: July 2016

The measurements of profiles at 102, 87, 59 and 40 MHz are presented. Geminga shows unique character of radio emission: the most steep spectrum, the large changes of pulse widths, phases of pulse time of arrival and the presence of giant pulses.
Linear Polarization Properties of Pulsars at 35 & 327 MHz
Authors: Asgekar Ashish , Deshpande A. A.
Published: July 2016

Faraday Rotation of the plane of polarization of broad-band signals, during propagation through the intervening medium, manifests as quasi-sinusoidal spectral modulations when observed with a telescope sensitive to a single linear polarization. Such a modulation can be exploited to study linear polarization characteristics of pulsars (Suleimanova, Volodin, & Shitov, 1988; Smirnova & Boriakoff 1997, Ramkumar & Deshpande 1999 (RD99)). We have used our data on a few bright pulsars at 35 MHz (Asgekar & Deshpande 1999, elsewhere in this volume) and data obtained at 327 MHz using Ooty Radio Telescope (see RD99 for details), to study average linear polarization properties using this technique. The data obtained over 256 frequency channels were re-sampled in the spectral domain to make the Faraday modulation appear periodic, and then a simple Fourier analysis was performed to look for (ACF) features associated with the possible spectral modulation (see RD99 for the analysis details).
Signatures of Polar-cap Current Flow in Polarization Angle Sweeps
Authors: Hibschman Johann A. , Arons Jonathan
Published: July 2016

Upon re-examining the characteristic polarization angle sweep of rotation-powered pulsars, we find that the sweep is perceptibly shifted by aberrational effects and by polar-cap current flow. In addition to the previously known phase shift of the entire sweep by ΔΦ = −4r/RL, aberration shifts the polarization angle itself by ΔΨ = −(10/3)(r/RL) cos α. Similarly, current flow above the polar cap shifts the polarization sweep by ΔΨ = (10/3)(r/RL)(J/JGJ) COSα, potentially providing a method of directly measuring the magnitude of the current. The competition between these two effects produces a potentially observable signature in the polarization angle sweep.
An Arithmetic Method for Mean Pulse Profile De-disperse of pulsars
Authors: Wu X.J. , Liu X.F.
Published: July 2016

In this paper we discuss an arithmetic method for mean pulse profile de-disperse. We proceed from the principle of dispersion measure, and invert the de-dispersion problem as to refutations of solving integral equations. Under idealization condition, the refutations results fit very well with the given theoretical curvature.
Search for an Optical Counterpart of PSR J0537–6910
Authors: Gouiffès Christian , Ögelman Hakki
Published: July 2016

We have conducted an optical study of the recently discovered very fast (P∼16msec) X-ray pulsar PSR J0537-6910 in the supernova remnant N157B. Broad band imaging has been obtained to study the field around the X-ray position and a high speed photometry programme was carried out in an attempt to detect optical pulses.
OPTIMA An Optical Pulsar Timing Analyser
Authors: Straubmeier Christian , Kanbach Gottfried
Published: July 2016

OPTIMA is a small and mobile highspeed photometer which is primarily intended for the observation of young high energy pulsars at optical wavelengths. The detector system consists of a fiber fed photon counter based on avalanche photodiodes, a GPS timing receiver and an integrating CCD camera to ensure the correct positioning of the targeted object. In January 1999, OPTIMA proved its functionality by measuring the lightcurve of the Crab pulsar.
X-ray observations of the high magnetic field radio pulsar PSR J1814–1744
Authors: Pivovaroff M. J. , Kaspi V. M. , Camilo F.
Published: July 2016

We present X-ray observations of PSR J1814–1744, a 4 s radio pulsar with inferred surface dipole magnetic field strength 5.5 × 1013G recently discovered in the on-going Parkes multibeam survey. This pulsar’s spin parameters are very similar to those of anomalous X-ray pulsars (AXPs). X-ray emission is not detected from the position of the radio pulsar in observations withROSATandASCA. The derived upper flux limit implies an X-ray luminosity significantly smaller than those of all known AXPs. These results argue that magnetar mechanism invoked to explain X-ray emission from AXPs must depend on more than merely the inferred surface magnetic field strength as estimated fromPand.
Likely detection of pulsed high-energy γ-rays from millisecond pulsar PSR J0218+4232
Authors: Kuiper L. , Hermsen W. , Verbunt F. , Lyne A. , Stairs I. , Thompson D.J. , Cusumano G.
Published: July 2016

We report on the likely detection of pulsed high-energyγ-rays from the binary millisecond pulsar PSR J0218+4232 in 100–1000 MeV data from CGRO EGRET. Imaging analysis demonstrates that the highly significantγ-ray source 2EG J0220+4228 (∼ 10σ) is for energies > 100 MeV positionally consistent with both PSR J0218+4232 and the BL Lac 3C66A. However, above 1 GeV 3C66A is the evident counterpart, whereas between 100 and 300 MeV PSR J0218+4232 is the most likely one. Timing analysis using one ephemeris valid for all EGRET observations yields in the 100-1000 MeV range a double-pulse profile at a ∼ 3.5σsignificance level. The phase separation is similar to the component separation of ∼ 0.47 observed at X-rays. A comparison of theγ-ray profile with the 610 MHz radio profile in absolute phase shows that the twoγ- ray pulses coincide with two of the three emission features in the complex radio profile.
Propagation of radio waves in pulsar magnetospheres
Authors: Petrova S.A. , Lyubarskii Yu.E.
Published: July 2016

The morphological classification of pulsar profiles is interpreted within the frame of the primordial hollow-cone emission model taking into account wave propagation in the magnetosphere. In this context the frequency evolution of the profiles as well as the difference in polarization properties of core and conal components can be explained naturally.
Recent developments of inverse Compton scattering model of pulsar radio emission
Authors: Qiao G. J. , Xu R. X. , Liu J. F. , Zhang B. , Han J. L.
Published: July 2016

Many theoretical efforts were made to understand the core and conal emission identified from observations by Rankin (1983) and Lyne and Manchester (1988). One of them, named as inverse Compton scattering (ICS) model (Qiao & Lin 1998), has been proposed. It is found in the model that: there are central or ‘core’ emission beam, and one or two hollow conical emission beams; the different emission components are emitted at different heights; owing to different radiation components emitted from different height, the observed emission beams can be shifted from each other due to retardation and aberration effects; the sizes of emission components change with frequencies. Recent developments of the model include: simulations of pulse profiles at different frequencies; studying the basic polarization properties of inverse Compton scattering in strong magnetic fields; computing the polarizations and spectrum of core and cones. A new classification system was also proposed. The main results calculated from the model are consistent with the observations.
High Energy Radiation from Pulsars
Authors: Cheng K.S.
Published: July 2016

We propose a three dimensional pulsar magnetosphere model in which the vertical size of the outer gap is first determined by a self-consistent model in which the outer gap is limited by the pair production from collisions of thermal photons produced by polar cap heating of backflow outer gap current and the curvature photons emitted by the gap accelerated charged particles. The transverse size of the outer gap is determined by local pair production condition. In principle, there are two topologically disconnected outer gaps existing in the magnetosphere of a pulsar and both incoming and outgoing particle flows are allowed. And yet double-peak light curves with strong bridges are most common. Using this model and its local properties, we compare the model results with phase-resolved spectra of the Crab pulsar and Geminga.
A model for the energetic emission from pulsars
Authors: Lyubarskii Yu.E.
Published: July 2016

A current sheet separates, beyond the closed part of the pulsar magnetosphere, two half-spaces with oppositely directed magnetic fields. It is shown that reconnection in this sheet may provide a source for high-energy emission.
Pulsar Magnetospheres: Classical, Quasi-Classical and Quantum Descriptions
Authors: Costa A. A. da
Published: July 2016

The plasma motion in pulsar magnetospheres is no longer classical, but quasi-classical, following stochastic trajectories, when random curvature radiation of high energetic gamma-ray photons takes place. This implies an extension to the relativistic kinetic theory of plasmas. But with high energies involved other quantum radiative processes become important, in the context of vacuum (quantum) electrodynamics. The consequences for pulsar radiation mechanisms will be outlined.
Neutron Star/Supernova Remnant Associations
Authors: Kaspi Victoria M.
Published: July 2016

The evidence for associations between neutron stars and supernova remnants is reviewed. After summarizing the situation for young radio pulsars, I consider the evidence from associations that young neutron stars can have properties very different from those of radio pulsars. This, though still controversial, shakes our simple perception of the Crab pulsar as prototypical of the young neutron star population.
Predictions of inverse Compton radiation from PSR B1259–63
Authors: Kirk J. G. , Ball Lewis , Skjæraasen O.
Published: July 2016

Unpulsed high energy (TeV) emission has been detected from several isolated pulsars (Aharonian 1999) and presumably results from relativistic electrons accelerated at the termination shock of an MHD wind driven by the pulsar itself. These electrons inverse Compton scatter target photons from either the cosmic microwave background, or from their own synchrotron radiation.

The rotation-powered binary pulsar PSR B1259–63 (Johnston et al. 1996) is also thought to drive an MHD wind, and the synchrotron radiation of electrons accelerated at its termination shock is probably the source of the unpulsed X-rays seen from this object by ROSAT, OSSE and ASCA (Tavani & Arons 1997). Compared to the isolated pulsars, however, the the pulsar’s Be-star companion provides an energy density of target photons available for inverse Compton scattering which is some 11 orders of magnitude larger. Using delta-function approximations to the emissivities and a monochromatic approximation to the spectrum of the target photons, we modelled the observed X-ray synchrotron emission and predicted the TeV emission in a recent paper (Kirk et al. 1999). In this contribution we improve these calculations in two respects – by treating the target spectrum more precisely, as described in the companion paper (Ball & Kirk 1999), and by relaxing the approximations made in the emissivities.
On the Nature of Radio Eclipsing
Authors: Istomin Ya. N.
Published: July 2016

It is shown that the phenomena of radio eclipsing can be explained by the linear mechanism of transformation of the transverse electromagnetic wave, propagating in the pulsar wind, into the plasma waves in the region of interaction of wind with a companion star atmosphere. The coefficient of the passingηdepends on the wave frequencyωby the exponential mannerη= exp{–const ·ω−1}. The estimated scale for the pulsar wind and star’s atmosphere density gradients are of the order of 100 meters. Such gradient can be obtained in the bow shock forming when the pulsar wind enters into the companion star atmosphere. Annihilation of the part of the wind’s positrons with the star’s electrons produces the electric current. This current generates the magnetic field from which the pulsar wind’s particles are reflected. The magnitude of the magnetic field in this shock of about several Gauss.
Pulsar Scintillation Studies and Structure of the Local Interstellar Medium
Authors: Bhat N. D. Ramesh , Gupta Yashwant , Rao A. Pramesh , Preethi P. B.
Published: July 2016

Results from new observations of pulsars using the Ooty Radio Telescope (ORT) are used for investigating the structure of the Local Interstellar Medium (LISM). The observations show anomalous scintillation effects towards several nearby pulsars, and these are modeled in terms of large-scale spatial inhomogeneities in the distribution of plasma density fluctuations in the LISM. A 3-component model, where the Solar neighbourhood is surrounded by a shell of enhanced plasma turbulence, is proposed for the LISM. The inferred scattering structure is strikingly similar to the Local Bubble. Further, analysis based on recent scintillation measurements show evidence for enhanced scattering towards pulsars located in the general direction of the Loop I Superbubble. The model for the LISM has been further extended by incorporating the scattering due to turbulent plasma associated with Loop I.
A (new) Phenomenon in Pulsar Dynamic Spectra
Authors: Stinebring D. R. , Becker K. M. , Goodman J. E. Espinoza , Kramer M. A. , Sheckard J. L. , Cordes J. M. , Lazio T. J.
Published: July 2016

Several studies in the last decade have explored dramatic instances of refractive fringing in dynamic spectra. We draw attention to a subtler but more widespread refractive effect: wisp-like structures extending (either linearly or with curvature) outward from the origin in the secondary spectrum plane. We have employed a simple pinhole screen simulation to investigate this phenomenon. It appears that the presence of one or more wisps in a secondary spectrum indicates a clump of scattering material that is significantly offset from the optical axis. Unlike the dramatic fringing events that have been investigated in the past, however, the interference that gives rise to a wisp is interference between rays within a scattering clump rather than between two major ray bundles. Furthermore, the scattering clump must be significantly elongated along the direction of pulsar motion. The range of fringe spacings that this produces, all with a similar slope in the secondary spectrum, gives rise to the linear extent of the wisp in the secondary spectrum.
Close Binaries with Two Compact Objects
Authors: Kalogera V.
Published: July 2016

The coalescence of close binary systems with two compact objects (neutron stars and black holes) are considered to be promising sources of gravitational waves for the currently built laser interferometers. Here, I review the current Galactic coalescence estimates derived both theoretically and empirically. I discuss the uncertainties involved as well as ways of obtaining an upper limit to the coalescence rate of two neutron stars.
Partially ionized layers of accreted envelopes of weakly and strongly magnetized neutron stars
Authors: Potekhin Alexander , Chabrier Gilles , Shibanov Yuri
Published: July 2016

We study equilibrium properties of partially ionized hydrogen atmospheres and subphotospheric layers of weakly (with magnetic fieldB≪ 109G) and strongly (B≫ 1010G) magnetized neutron stars. In both weak- and strong-field cases, the ionization degree, atomic occupation numbers, and equation of state are calculated. These results are used to calculate opacities of neutron-star atmospheres.
Helium white dwarf cooling in PSR J0751+1807 and PSR J1012+5307
Authors: Ergma Ene , Antipova J. , Sarna M. J.
Published: July 2016

It is accepted that formation of a binary millisecond (or recycled) pulsar with a low–mass companion may be explained as the end–point of close binary evolution in which an old pulsar is spun–up by accretion from the secondary (Alpar et al., 1982). After detachment from the Roche lobe, the pulsar spin period starts to change due to magneto–dipole radiation and the white dwarf begins to cool down. In this paper we shall discuss the cooling history of helium core low–mass white dwarfs in the short orbital period millisecond binary pulsars PSR J0751+1807 and PSR J1012+5307 (Ergma, Sarna, & Antipova 1999).
Kilohertz QPOs and general-relativistic orbital motion—a maximum likelihood test
Authors: Bulik Tomasz
Published: July 2016

Using the maximum likelihood method we show that the observed distribution of maximum frequencies of kilohertz quasi periodic oscillations (QPOs) in LMXBs agrees with the frequencies of orbital motion in the marginally stable orbit around compact objects with masses chosen randomly from some interval, which we find to be (1.55M⊙, 2.40M⊙) at the 99% confidence level. As this remarkable agreement with the expected mass range of neutron stars in LMXBs demonstrates, the assumption that the maximum-frequency QPOs occur in the marginally stable orbit is consistent with the current data set.
Effect of Photon Rocket in X-ray Binaries
Authors: Pal’shin V. D. , Tsygan A. I.
Published: July 2016

It is shown that X-ray binaries can be accelerated by their own radiation. It is possible if the magnetic field of a neutron star in a binary differs from the dipolar field. Asymmetric X-ray emission generated due to accretion of matter onto a neutron star surface creates an accelerating force. Its magnitude can be comparable or even larger than gravitational attraction of the binary to the Galaxy.
A microscopic study of neutron stars’ structure
Authors: Bombaci I. , Baldo M. , Burgio G.F.
Published: July 2016

Starting from the nuclear interactions which are used to calculate the properties of atomic nuclei, we derive a new equation of state (EOS) for neutron star matter. With this realistic EOS, we calculate the structure of non-rotating neutron stars.
Are Pulsars Bare Strange Stars?
Authors: Xu R. X. , Qiao G. J. , Zhang B.
Published: July 2016

It is believed that pulsars are neutron stars or strange stars with crusts. However we suggest here that pulsars may bebare strange stars(i.e., strange stars without crust). Due to rapid rotation and strong emission, young strange stars produced in supernova explosions should be bare when they act as radio pulsars. Because of strong magnetic field,twopolar-crusts would shield the polar caps of an accreting strange star. Such a suggestion can be checked by further observations.
Magneto–rotational and Thermal Evolution of Magnetars with Crustal Magnetic Fields
Authors: Geppert U. , Page D. , Colpi M. , Zannias T.
Published: July 2016

The interpretation of Soft–Gamma–Repeaters (SGRs) and Anomalous X–Ray Pulsars (AXPs) as Magnetars (Thompson & Duncan 1996) raises again the issue of the generation of the ultra–strong magnetic fields (MFs) in neutron stars (NSs) and the related question of where these fields are anchored: in the core, penetrating the whole star, or confined to the crust. Recently, Heyl & Kulkarni (1998) considered the magneto–thermal evolution of magnetars with a core field. Since the assumption of a crustal field is at least not in disagreement with the observations of isolated pulsars (Urpin & Konenkov 1997) and of NSs in binary systems (Urpin, Geppert & Konenkov 1998, Urpin, Konenkov & Geppert 1998), here we would like to address the question whether the observations of SGRs and AXPs can be interpreted as magnetars having a crustal MF. Given the strength of the MF in magnetars we take into account, in an approximate manner, the strongly non–linear Hall effect on its decay. We intend to provide a contribution to an unified picture of NS MF evolution based on the crustal field hypothesis.
Anomalous X-ray pulsars and soft gamma-ray repeaters in supernova remnants
Authors: Gaensler B. M.
Published: July 2016

I consider the state of play regarding associations of supernova remnants (SNRs) with anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs). The three AXP/SNR associations are convincing, and are consistent with AXPs being young, low-velocity neutron stars. The three SGR/SNR associations are far more likely to be chance superpositions, and rely on SGRs being high velocity (>1000 km s−1) objects. These results imply either that AXPs evolve into SGRs, or that SGRs and AXPs represent different populations of object.
The Status of Pulsar Emission Theory
Authors: Melrose D.B.
Published: July 2016

It is argued that there is now a preferred pulsar radio emission mechanism, involving beam-driven Langmuir turbulence. A testable prediction is that, at least in a statistical sense, features in the spectra of pulsars should scale with the plasma frequency,υGJ, implied by the Goldreich-Julian number density.
Romanian Contribution to the Study of Polar Motion
Authors: Stavinschi Magda
Published: July 2016

Romanian astronomy has an old tradition, which is rather less well-known abroad. More known perhaps are the Dacian sanctuary of Sarmizegetusa Regia, very similar to that of Stonehenge, or the contribution of the monk Dionysius Exiguus (born at Tomis, in Dobrogea) to the initiation of the Christian Era. But one of the most important applications of the astronomical knowledge was coordinate determination. It is interesting to remark that the development of astronomy since the 16th century followed closely the advances of accuracy in estimating the coordinates of the main localities.
Küstner’s Observations of 1884–85: the Turning Point in the Empirical Establishment of Polar Motion
Authors: Brosche P.
Published: July 2016

Since Euler in 1765 predicted the possibility of polar motion, the search for an observational confirmation went on. While some indications were found before, the proof without doubt is generally attributed to Küstner. Ironically, the aim of Küstner’s precise observations of 1884–1885 in Berlin was another one, namely an improved value of the constant of aberration. Using the Horrebow-Talcott method, he could conclude that the latitude of Berlin had decreased significantly by 02 in about one year. His findings promoted the start of international cooperation to observe the polar motion. Measurements from Honolulu in 1891 exhibited the effect in counterphase, thus omitting the last chance for a local explanation.
Seth Carlo Chandler Jr.: The Discovery of Variation of Latitude
Authors: Carter M.S. , Carter W.E.
Published: July 2016

It took Seth Carlo Chandler Jr. just one year to discover the 14 month and annual components of the variation of latitude (polar motion) that had eluded the most talented astronomers for more than a century. He succeeded where those before him had failed because: he used a global set of observations that had been painstakingly collected by astronomers of many nationalities over more than 150 years; he ignored the common wisdom that unexpected annual variations in astronomical observations were always caused by temperature effects on instruments or atmospheric refraction anomalies; and he was not misled by the theory, which predicted that the Eulerian wobble must have a period of approximately 10 months. Chandler was a true amateur only in the sense that he pursued astronomy out of love, while making his living as an actuary. He began his scientific training at the youthful age of 15 under the tutelage of Benjamin Pierce, perhaps the greatest American mathematician of that time. He then became: a private assistant to Benjamin Apthorp Gould, Jr., an aide to Gould while employed by the US Coast Survey, and Assistant Editor to Gould for the Astronomical Journal. It would be impossible to understand and appreciate Chandler’s achievements without recognizing his relationship with Gould, his brilliant mentor and lifelong colleague — the man he once described as his “Magnus Apollo.”

In 1901 Chandler announced that the 14 month motion was not a simple oscillation but was in itself a compound motion consisting of the previously discovered 428 day component, and a much smaller 436 day component, whose reality was “beyond reasonable doubt.” The beating of two such components would result in a rapid change in the phase and amplitude of the Chandler motion at intervals of about 80 years. If Chandler was correct, in about 2010, give or take perhaps five years, we should see the next occurrence of this phenomenon. With the International Earth Rotation Service in operation there should be no difficulty in detecting and quantifying such an event, very nearly one century after Chandler’s death.
Polar Motion — An Overview
Authors: McCarthy Dennis D.
Published: July 2016

After one hundred years of intensive study, some aspects of polar motion remain poorly understood. This motion of the Earth’s axis of rotation with respect to its mantle and crust has been observed and studied since the creation of the International Latitude Service. Research has shown that the motion of the pole is quite complicated and distinguished by components over all time scales. Observationally, the secular, Chandler and annual components of polar motion are well documented, and various geophysical processes have been suggested as likely causes. Other components such as the approximately thirty-year motion, the high-frequency motion and the daily/sub-daily motion remain as subjects of extensive research.
IGS Combined and Contributed Earth Rotation Parameter Solutions
Authors: Kouba Jan , Beutler Gerhard , Rothacher Markus
Published: July 2016

Since January 1995 the International GPS Service (IGS) has been combining and analyzing daily polar motion (PM) series, produced and submitted by seven IGS analysis centers (ACs) for the IGS Final orbit/clock combinations. Since June 30, 1996 the IGS Earth Rotation Parameter (ERP) series that accompany the IGS combined orbits, also include combined PM rates. Furthermore, since March 1997, the IGS LOD (Length of Day) solutions are based on separate combinations of AC LOD solutions calibrated and weighted according to the IERS Bulletin A definite values. Similar to AC orbit solutions, the PM solutions have improved considerably since 1995, so that currently the IGS combined and the best AC PM solutions are at or below the 0.1 mas precision level, although PM biases may exceed .1 mas. Comparisons of AC ERP and PM rate solutions with the IGS Final combined ERP series revealed signals with 7 and 14-day periods for some AC solutions.

During 1998, the IGS Final and the best AC PM rate solutions compared with Atmospheric Angular Momentum (AAM) at 0.3 mas/day (rms) with an average correlation of about 0.8 and 0.6 for the PM x and PM y rate components. The correlation varied considerably with time and frequency, though significant correlation already started from 6-day periods and reaching maxima within 10 to 50 day period bands. Most of the remaining signal in the PM rate solutions could likely be accounted for by Ocean Angular Momentum (OAM) as seen from the comparisons of combined OAM and AAM with the IGS PM series during 1995 and early 1996 when also OAM data were made available. During this period the IGS PM rates agreed with the combined OAM + AAM series with 0.3 and 0.2 mas/day (rms) for the PM x and y components and with an average correlation of about 0.8 for both PM components.
A Mechanism of Variations of the Earth Rotation at Different Timescales
Authors: Barkin Yu. V.
Published: July 2016

To explain the observed effects in the Earth’s polar motion, a mechanism of the relative motion of the lower mantle and upper mantle with a boundary at 670 km of depth is proposed. According to the new approach, the Earth’s layers (including separate plates) are considered as nonspherical, heterogeneous celestial bodies, interacting with each other, with the Moon and the Sun and executing a wide spectrum of relative motions in different timescales. The small displacements of the centers of masses of the lower and upper mantles and their relative rotations have here a primary importance. These displacements display themselves at various time scales (from a few months to millions of years), and their manifestations are readily detected in the regularities of the distribution of geological structures as well as in many geodynamical processes. Important regularities of the ordered positions of the plate centers, of their triple junctions, hot spots, systems of fractures and cracks, geographic structures, fields of fossils, etc., are observed as consequences of certain displacements and inclined rotations (Barkin, 1999). At geological time intervals, the slow motion of the layers causes mutually correlated variations of the processes of rifting, spreading, subduction, regressions and transgressions of the sea, of the plate motion, formation and breakdown of super continents, etc. The motions and the accompanying tectonic mass redistribution cause variations of the components of the Earth’s inertia tensor and geopotential, which lead to variations of its diurnal rotation and polar motion. Explanation of the main properties of the perturbed Chandler polar motion has been done.
Chandler Motion Observations
Authors: Yatskiv Ya. S.
Published: July 2016

The history of observations of the Chandler motion is presented in brief and the importance of the ninety years of the ILS data is stressed. Essential features and different empirical models of the Chandler motion are discussed.
Excitation of the Chandler Wobble
Authors: Sidorenkov N.S.
Published: July 2016

The redistribution of air and water masses between the Pacific and Indian oceans during the El Niño/Southern oscillation (ENSO) changes the components of the Earth’s inertia tensor and shifts the position of the pole of the Earth’s rotation. The spectrum of the ENSO has components with periods of about 6, 3.6, 2.8, and 2.4 years. These periods are all the multiples of the Chandler period T = 1.2 yr. and the principal period of nutation 18.6 yr. A nonlinear model for the Chandler polar motion has been constructed based on this empirical fact. In this model, the ENSO excites the Chandler polar motion by acting on the Earth at the frequencies of combinative resonance. At the same time, the Chandler polar motion induces a polar tide in the atmosphere and the World Ocean, which orders the ENSO. As a result, the dominant components in the noise spectrum of the ENSO are those with the periods indicated above.
Dissipation and Ellipticity of the Chandler Wobble
Authors: Zhu Yaozhong , Gao Buxi
Published: July 2016

The Chandler wobble, one of the main feature of the Earth’s polar motion, is related to the properties of the mantle and liquid core as well as the mobility of the oceans. The equilibrium pole tide and mantle anelasticity both lengthen the Chandler period, moreover, the former imposes a slight ellipticity on the pole path, and the latter is responsible for the wobble energy dissipation. On the basis of the perturbation principles, we derive the theoretical Qω of the Chandler wobble, assuming that the wobble energy is totally dissipated within the mantle. The theoretical ellipticity and orientation of the semimajor axis of the Chandler wobble path for an anelastic Earth are given. Compared with the results for the elastic Earth, the effect of mantle anelasticity does not change the wobble ellipticity significantly, but slightly changes the orientation of the semimajor axis in the opposite direction. This paper has also proved that the effect of the Earth’s 3-axis feature on the wobble ellipticity is only about 19% of that of the equilibrium pole tide. Analysis of the polar motion data obtained by using modern geodetic techniques shows that the observed ellipticity and orientation of the semimajor axis agree with the theoretical results. We can deduce that the pole tide in the globe should be close to equilibrium.
Atmospheric Angular Momentum Variations and Diurnal Polar Motion
Authors: Zharov V.E. , Pasynok S.L.
Published: July 2016

The atmospheric effective angular momentum functions were used to study the excitation of the diurnal polar motion and nutation. The main effect on polar motion at the frequency of the S1 tide is up to 10 µas, and on the annual prograde nutation term is up to 0.1 mas. The atmosphere and viscosity of the outer core of the Earth were taken into account in calculating the transfer function.

The atmosphere treated as a thin rotating layer gives two new eigen-modes or two new resonance frequencies in the Earth’s transfer function, and one of them is in the diurnal frequency band. Viscosity of the fluid outer core and choice of the Earth’s model change the nearly diurnal frequencies of the normal modes.
On Excitation Mechanisms of Pulsation in β Cephei Stars
Authors: Kato Shoji
Published: July 2016

The present state of our knowledge concerning the excitation mechanisms of β Cephei pulsation is reviewed. First we shall discuss whether or not oscillations of β Cephei stars can be explained by the conventional pulsation theory. After showing that the explanation by the conventional theory might be impossible, we shall discuss other specific excitation mechanisms suggested so far.
Theory Of Multiperiodic RR Lyrae Stars
Authors: Stellingwerf R. F.
Published: July 2016

The subject “Multiperiodic RR Lyrae Stars” encompasses two entirely different types of phenomena: 1) long-term modulation of amplitude known as the Blazhko-effect and 2) simultaneous excitation of several radial modes. In the first category the observational material is now quite extensive, but very little theoretical analysis has been undertaken. In the second case the results of pulsation theory are applicable, but only one such object has been found. Much progress in our understanding of RR Lyrae stars has been made in recent years, however, and many results do have a bearing on the present problem. Several excellent reviews of current pulsation theory are available (see Iben 1971c, or Cox 1974a,b). I will therefore restrict my comments to those results bearing directly on choice of mode for RR Lyrae stars.
δ Scuti and RRs Type Variables: Theoretical Aspects
Authors: Petersen J. Otzen
Published: July 2016

Theoretical problems in connection with δ Sct and RRs type variables are reviewed. All evidence shows that δ Sct stars are normal main-sequence or early post main-sequence stars. Results of linear stability analyses of δ Sct models agree well with observations, the presence of non-variables in the strip being understandable in terms of helium diffusion. Excitation of non-radial modes may also occur; comparison of observed multiple periodicities with the theoretically derived period patterns for radial and non-radial modes is discussed as a means to distinguish between these possibilities.

It is not known whether RRs variables are of the same nature as δ Sct stars or in a late evolutionary state with low mass. RRs variables pulsate in radial modes, and recent linear stability analyses seem to agree well with observations for both normal and low masses. The reason for the difference in amplitude between RRs and δ Sct stars is not known. Non-linear investigations may provide important information in the near future. The observed period ratios of RRs variables indicate for most of the double mode pulsators a slight deficiency in heavy elements and a normal mass; but more detailed investigations of this problem are needed.
Contribution A L’etude Des Perturbations Planetaires De La Lune
Authors: Abu el Ata N.
Published: July 2016

L’étude des perturbations planétaires de la Lune soulève un problème fondamental provenant de la différence de caractère entre la théorie de la Lune et la théorie des planètes. Si, les deux théories sont des cas particuliers du problème de trois corps, la distinction entre elles résulte d’une analyse classique basée sur les résultats de l’observation et de plusieurs études théoriques.
A Theory of the Trojan Asteroids
Authors: Garfinkel B.
Published: July 2016

The paper constructs a long-periodic solution for the case of 1:1 resonance in the restricted problem of three bodies. The polar coordinates r and 0 appear in the form

Here λ is the mean synodic longitude, m is the small mass-parameter, k is the integer nearest to the ratio ω2/ω1 of the fundamental angular frequencies of the motion, and ck is a Fourier coefficient of a certain periodic function. Only elementary functions enter r(λ) and θ(λ), while the calculation of λ(t) requires the inversion of a hyper-elliptic integral t(λ).

The internal resonant terms, carrying the critical divisor D, impart to the orbit an epicyclic character, in qualitative accord with the results of the numerical integration by Deprit and Henrard (1970). Our solution is valid except in the vicinity of the singularities at D = 0 and λ = 0.

The presence of the resonant terms invalidates the Brown conjecture (1911) regarding the termination of the family of the tadpoleshaped orbits at the Lagrangian point L3. However, this conjecture holds for the mean orbits defined by r = r(λ), θ = θ(λ), and it also holds in the limit as m → 0.