bluuebunny/crossref_metadata_2025 huggingface dataset:
QQ Vul Revisited
Authors: Catalán M.S. , Davey S. D. , Smith R. C. , Jones D. H. P.
Published: July 2016

With simultaneous blue (λλ4200–5000 Å) and far-red (λλ7950–8380 Å) phase-resolved, high resolution spectrophotometry, we re-examine the magnetic CV QQ Vul. A thorough radial velocity and flux analysis of all the observable features is carried out. We derive a complete set of system parameters and classify the donor star to be a spectral type M4.5 V. In addition to the Balmer, He I and He II emission lines in the blue range, arising from the accretion regions, we detect various emission features which solely follow the movement of the secondary star. The lines, which we interpret as reprocessed light from the illuminated hemisphere of the donor star, are Mg II at λ4481 Å, He II at λ8236 Å and C I at λ8335 Å. Intensity maps based on the line flux and radial velocity variations of the Na I absorption near λ8190 Å and Mg II emission feature were also made. These show that the line distribution on the surface of the donor is consistent with being symmetric. As a result of our analysis the position of the real zero phase was found to be at ϕ = 0.42 of the linear polarisation ephemeris.
RX J1015.5+0904: A New Polar at the Lower Period Limit
Authors: Burwitz V. , Reinsch K. , Schwope A. D. , Beuermann K. , Mengel S. , Notni P. , Van Teeseling A. , Thomas H.-C.
Published: July 2016

We present X-ray and optical observations of the ROSAT discovered polar (AM Her binary) RX J1015.5+0904 and first results of our analysis of the X-ray and optical data. These results indicate a one-pole accretion geometry and an orbital period of P = 79.88 m for this V ~ 17 mag system.
Accretion Disk Winds in Cataclysmic Variables
Authors: Knigge Christian , Drew Janet E. , Mason Keith O.
Published: July 2016

We present preliminary results of a modelling campaign based on HST eclipse observations of the wind-formed C IV resonance line in the eclipsing nova-like variable UX UMa. Within the framework of a simple kinematic accretion disk wind model, we are currently able to reproduce the shapes (but not the strengths) of the observed line profiles away from and during eclipse, as well as the behaviour of the integrated line flux light curve. The most important aspect of our modelling is that it suggests the presence of a vertically extended, relatively dense and slow moving transition region between the disk photosphere and the fast wind.
ROSAT observations of non-magnetic CVs
Authors: van Teeseling A. , Verbunt F. , Beuermann K.
Published: July 2016

In non-magnetic cataclysmic variables the accreted matter forms an accretion disk around the white dwarf. In the boundary layer between the white dwarf and the accretion disk the accreted matter decelerates from Keplerian velocities to the rotation velocity of the white dwarf. If the accretion rate is high the boundary layer would be optically thick and cool (T ~ 105K), and if the accretion rate is low the boundary layer would be optically thin and hot (T ~ 108K) (Pringle & Savonije 1979).

There are several observational problems with this simple picture: a soft X-ray component could only be detected so far in 5 dwarf novae in outburst and not in any nova-like variable. Also in high-accretion-rate systems there is a hot optically thin X-ray source, which has, however, an X-ray luminosity which is much less than the UV luminosity of the system (van Teeseling & Verbunt 1994). Finally, there is evidence for orbital modulation in the X-rays from some systems (e.g. van Teeseling et al. 1995).
V1974 Cyg (Nova Cyg 1992) - A Possible Link to SU Uma Stars
Authors: Retter A. , Leibowitz E. M. , Ofek E. O.
Published: July 2016

V1974 Cyg erupted on 1992 February 19, and was the brightest nova since V1500 Cyg. It soon became an object of massive international multiwavelength observational study.

Some major photometric features of the nova were investigated by DeYoung & Schmidt (1994), and Semeniuk et al. (1994,1995). They found two periodicities in the nova light curve. While the shorter 0.081263 d period was present during the 1993 and 1994 observations, the longer 0.0850 d period was only observed from 1994 July. Semeniuk et al. (1995) interpreted the shorter period as the orbital period of the binary system, and the longer one as caused by the rotation of the white dwarf due to a magnetic field.
The Spectrum of the old Nova V603 Aql observed with the HST
Authors: Friedjung M. , Selvelli P. L. , Cassatella A.
Published: July 2016

Spectra of the old nova V603 Aql taken with the HST-GHRS did not reveal resonance doublet absorption components arising in material ejected in the 1918 outburst. However absorption components, probably produced by a disk wind, were observed, though most line emission probably comes from regions associated with an accretion disk. Most strikingly, dramatic line profile variations on time-scales of not much more than 10 m were seen.
A New Type of Asymmetric Outflow in the Recurrent Nova RS Oph in Quiescence
Authors: Iijima T.
Published: July 2016

H I emission lines in the spectrum of the recurrent nova and symbiotic star RS Oph in quiescence are sometimes accompanied by blue- or red-shifted broad emission components. The displacements of the broad components from the narrow lines change from −1300 to +1200 km s−1, but possibly not continuously. The broad components seem to appear in some restricted regions on the spectra. An asymmetry between the blue- and red-shifts is noticed.
The peculiar symbiotic star CH Cyg – a bright counterpart of cataclysmic variables?
Authors: Leedjärv Laurits
Published: July 2016

CH Cyg has begun to show symbiotic features only since 1963. Up to now four outbursts of CH Cyg have been recorded, the fifth going on at the present time. CH Cyg reveals a lot of peculiarities as compared to ‘normal’ symbiotic stars (extended inactive periods between the ‘symbiotic’ periods; the most extended active period in 1977–1986 including the ejection of bipolar radio jets; a stage of increased activity since 1992, with peculiar profiles of the Balmer emission lines etc.); see Mikolajewski, Mikolajewska & Khudyakova (1990) for further references.

Classical models for explaining the outbursts of symbiotic stars (e.g. Mikolajewska & Kenyon 1992) are unable to account for the behaviour of CH Cyg. The magnetic rotator model has been proposed and developed by Mikolajewski & Mikolajewska (1988, 1996). The model includes a wind accreting, magnetic (B ~ 107 G), rapidly rotating (P ~ 8 m) white dwarf (WD) as the hot component of the symbiotic system. A strong magnetic field prevents matter from the red giant’s wind being accreted onto the WD surface in the usual way. Instead, three stages of accretion could be considered: inactive, propeller and accretor state.
A close look at the outburst of the very slow symbiotic nova PU Vul – a triple system
Authors: Chochol D. , Tamura S. , Kanamitsu O. , Pribulla T. , Tajitsu A.
Published: July 2016

The very slow nova PU Vul was discovered by Honda and Kuwano in 1979 after the rise from B ~ 15…16 mag to a maximum B ~ 9 mag. The object has been studied by many authors (for references see Belyakina et al. 1989; Vogel & Nussbaumer 1992) but a clear picture of the system was not given. Two minima of different duration were observed in the system in the active stage, in 1980-81 and 1993-94 (Kolotilov et al. 1995). Nussbaumer & Vogel (1996) ascribed the minima to eclipses of the hot component by the cool M giant in a binary with orbital period of 4900±100 d. Our period analysis of the preoutburst B data (Liller & Liller 1979) by Stellingwerf’s (1978) method revealed a period of 4858 d. We found the third minimum in 1926-28 (lasting for 500…630 d) in these data.
The 35 Day Cycle of Her X-1
Authors: Schandl S. , Meyer F.
Published: July 2016

The 35 d period in the observed X-ray and optical light curves of Her X-1 can be understood in terms of a warped accretion disk precessing in the tidal field of the companion. We propose that repulsive forces of the X-ray driven coronal wind acting on the disk causes and maintains the warp of the disk (Fig. 1). The resulting shape of the precessing disk reproduces the main features of the observed X-ray light curve [1]. Based on the calculated disk shape we model the dip structure in the X-ray observations as caused by the interaction between the accretion stream and the warped disk.
Investigation of the Optical Variability of GRO J0422+32
Authors: Popova M. , Beskin G. , Mitronova S. , Neizvestny S. , Panferova I. , Plokhotnichenko V. , Bartolini C. , Guarniero A. , Minarini R. , Piccioni A.
Published: July 2016

Nova Per 1992 was observed in 1992–94 on the 6 m and 1 m telescopes at the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciencies and on the 1.5 m telescope at the Bologna Astronomical Observatory (Italy). The apparatuses used were a TV spectrum scanner with the hard/software photometrical system MANIA (Multichannel Analysis of Nanoseconds Intensity Alterations) complex with a time resolution of 10−7 s [3] (on the 6m telescope), a CCD photometer (on the lm telescope) and a double head fast photometer (on the 1.5 m telescope) [5].
Understanding the Long-Term Evolution of CVs and LMXBs: Principles and Problems
Authors: Kolb U.
Published: July 2016

We introduce the standard model for formation and evolution of CVs, and show how observed collective properties compare with theoretically predicted population models. A short overview relates LMXBs to CVs.
Secular Evolution of Cataclysmic Variables with Irradiation-Induced Mass Transfer
Authors: Ritter H. , Zhang Z. , Hameury J. M.
Published: July 2016

The possible importance of the reaction of a low-mass star to external irradiation for the long-term evolution of compact binaries has been noted only rather recently; first in the context of the evolution of low-mass X-ray binaries (e.g. Podsiadlowski 1991; Harpaz & Rappaport 1991; Frank, King & Lasota 1992; Hameury et al. 1993) and subsequently by Ritter, Zhang & Kolb (1995a,b, hereafter RZK) also for the evolution of cataclysmic variables (CVs). Based on a simple model for describing the reaction of a low-mass star to irradiation RZK showed that CVs can be dynamically unstable against irradiation-induced mass transfer and that, as a consequence of this, mass transfer could occur via cycles in which phases of high, irradiation-enhanced mass transfer alternate with phases of little or no mass transfer. The occurrence of such mass transfer cycles in CVs was subsequently discussed from a more general point of view by King (1995) and King et al. (1995). Whereas the possibility of mass transfer cycles in CVs is now fully recognised, the question as to which systems can undergo such cycles and which cannot has not yet been addressed in detail. It is the purpose of this contribution to provide at least a partial answer to this question.
ASCA Observations of LINERs
Authors: Terashima Y. , Kunieda H. , Iyomoto N. , Makishima K. , Serlemitsos P. J.
Published: July 2016

ASCA observations have revealed the presence of low-luminosity AGN in ~10 LINERs as a hard point sources at the nucleus. The X-ray continuum shapes (photon indices Γ ≈ 1.8) are very similar to those of Seyfert galaxies (Makishima et al. 1997, Serlemitsos et al. 1996). An iron emission line is observed from heavily absorbed low-luminosity AGNs (Makishima et al. 1997), while M81 is the only object among those with small intrinsic absorption from which an iron line detected (Ishisaki et al. 1996) on account of limited photon statistics for other objects.

We summed up the ASCA spectra of 5 LINERs which host low-luminosity AGN of low intrinsic absorption to search for an iron emission line. We used 7 observations of 5 objects (NGC 1097, NGC 3310, NGC 3998, NGC 4450, and NGC 4594) to make a composite spectrum. All the objects have very similar X-ray characteristics (spectral slope, intrinsic absorption, no short time-scale variability; Iyomoto et al. 1996, Serlemitsos et al. 1996).
Parameter Space of Shock Formation in Adiabatic Flows
Authors: Lu Ju-Fu , Yu K.N. , Yuan F. , Young E. C. M.
Published: July 2016

We study shock formation in a stationary, axisymmetric, adiabatic flow of a perfect fluid in the equatorial plane of a Kerr geometry. For such a flow, there exist two intrinsic constants of motion along a fluid world line, namely the specific total energy, E = −hut, and the specific angular momentum, l = −uφ/ut, where the uμ’s are the four velocity components, h is the specific enthalpy, i.e., h = (P + ε)/ρ, with P, ε, and ρ being the pressure, the mass-energy density, and the rest-mass density, respectively.

As shown in Fig. 1 (Fig. la is for a Schwarzschild black hole, i.e. the hole’s specific angular momentum a = 0; Fig. lb is for a rapid Kerr hole, i.e. a = 0.99M, where M is the black-hole mass, and prograde flows: and Fig. 1c is for a = 0.99M and retrograde flows), in the parameter space spanned by E and l there is a strictly defined region bounded by four lines: three characteristic functional curves lk(E), lmax(E), and lmin(E), and the vertical line E = 1. Only such a flow with parameters located within this region can have two physically realizable sonic points, the inner one rin, and the outer one rout. In between there is still one more, but unrealizable, sonic point, rmid. The region is divided by another characteristic functional curve lc(E) into two parts: in region I (= Ia + Ib) only τout is realized in a shock-free global solution (i.e., that joining the black-hole horizon to large distances), while in region II (= IIa + IIb) only rin is realized.
Metal Abundances and Ionization in QSO Broad Emission-Line Regions
Authors: Hamann F. , Shields J.C. , Cohen R. D. , Junkkarinen V.T. , Burbidge E.M.
Published: July 2016

We describe two ongoing studies of QSO broad emissionline regions (BELRs). The first employs the N V λ1240/He II λ1640 and N V/C IV λ1549 line ratios as diagnostics of QSO metallicities. Hamann & Ferland and Ferland et al. showed that many observed N V ratios require enhanced N abundances and Z > Z⊙. Here we present new measurements of large line ratios at redshifts z > 4, which indicate super-solar abundances within ~1 Gyr of the Big Bang (for q0 ≈ 0.5). We also note that the N V line is relatively stronger in more luminous QSOs, in contrast to the well-known Baldwin effect in Lyα, C IV, and O VI λ1034. This unusual behavior in N V could be due to a luminosity-metallicity correlation among QSOs that is coupled to a mass-metallicity relation in their host galaxies.

Our second study involves Ne VIII λ774 as a probe of highly ionized gas. We show that a broad emission feature near 774 Å is common in QSOs. Photoionization models indicate that Ne VIII is the most likely identification for this feature. The models also indicate that the Ne VIII emitting gas covers > 40% of the continuum source, has a total hydrogen column density of NH > 1022 cm−2 (for solar abundances) and an ionization parameter of U > 5 (for a nominal QSO continuum shape). This gas would be an X-ray “warm73x201D; absorber — with O VII–O VIII bound-free edges — if it lies along our line-of-sight to the X-ray continuum source.
Emission-Line Properties of z ≥ 4 QSOs
Authors: Shields J.C. , Hamann F. , Foltz C.B. , Chaffee F.H.
Published: July 2016

We report on preliminary results of a program of rest-frame UV spectroscopy of z ≥ 4 QSOs. Despite their high luminosity and inherent youth, these objects exhibit spectra that are generally very similar to those of AGNs at lower z. We find some evidence that the z ≥ 4 systems are described by unusually strong O Iλ1304 emission, which may be a result of elevated metallicity or unusual prominence of the ‘intermediate-line region’. High metallicities are also signaled by strong N Vλ1240 emission, consistent with quasar behavior at z ≈ 2–3.
Emission Lines and the Spectral Energy Distributions of Quasars
Authors: Wilkes B.J. , Green P.J. , Mathur S. , McDowell J.C.
Published: July 2016

Many years of study have failed to establish conclusively relationships between a quasar’s spectral energy distribution (SED) and the emission lines it is thought to produce. This is at least partially due to the lack of well-observed SEDs. We present initial results from a line–SED study for a sample of 43 quasars and active galaxies for which we have optical and ultraviolet spectra and far-infrared–X-ray SEDs. We present the results of tests for correlations between line equivalent widths and SED luminosity and slope parameters and compare these results to those from earlier studies. We find that the Baldwin effect is weaker when the luminosity is defined close to the ionizing continuum of that line and conclude that the detailed SED is likely to be important in making further progress.
The Spectra of Dusty Quasars
Authors: Francis Paul J. , Webster Rachel L. , Masci Frank J. , Drinkwater Michael J. , Peterson Bruce A.
Published: July 2016

Flat radio spectrum quasars from the Parkes half-Jansky survey show an enormous range of optical to near-IR colors. The spectra of these quasars suggest that this diversity is probably due to variable amounts of dust somewhere along the line of sight.
Results from Five Years of Spectrophotometric Monitoring of 28 Palomar-Green Quasars
Authors: Kaspi Shai
Published: July 2016

We present 5 years of results from a spectrophotometric monitoring program of 28 quasars. The typical sampling intervals are several months. We show the light curves obtained for two quasars, PG 0804+762 and PG 0953+414. Both sources show Balmer emissionline variations which follow those of the continuum with a time lag of order 100 days. This is the first reliable measurement of such a lag in active galactic nuclei with luminosity L > 1045 erg s−1. The broad-line region (BLR) size that is implied is almost an order of magnitude larger than that measured in several Seyfert 1 galaxies and is consistent with the hypothesis that the BLR size grows as L0.5.
IUE Monitoring of the Bright Seyfert 1 Galaxy Fairall 9
Authors: Rodríguez-Pascual P. M.
Published: July 2016

An eight-month spectrscopic monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been carried out with the International Ultraviolet Explorer (IUE) in order to measure continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). The results are consistent with those of previous campaigns on lower luminosity AGNs: (i) there is no measurable time lag between different ultraviolet continuum bands, (ii) the measured time lags for the emission lines are relatively short, and (iii) the more rapid and stronger response to continuum changes of He II, as compared to C IV, is consistent with a stratified broad-line region (BLR) structure.
Long-Term Variability of AGN
Authors: Bischoff K. , Kollatschny W. , Dietrich M.
Published: July 2016

We present a long-term variability study of the Seyfert 1 galaxies Mkn 110 and NGC 7603. Both objects show strong variations over a period of several years.
Line Profiles Radiated by Orbiting Matter Around Black Holes
Authors: Østgaard E. , Bao G. , Hadrava P.
Published: July 2016

Emission-line profiles from both narrow eccentric rings and an extended disk around a black hole are presented. In both cases, a black-hole signature appears when the inclination of the emitting orbit is larger than 80°.
Is the Broad-Line Region Expanding?
Authors: Liang Kan , He Xiang-Tao , Wang Zhong-min , You Jun-Han
Published: July 2016

We suggest that the broad-line regions (BLRs) of QSOs with broad emissionlines (BALs) are expanding, i.e., the clouds are undergoing radial outflow, as illustrated simply in Fig. 1. At least the following observational facts can be explained:

1.

Optical observations show that some moderate and high-redshift QSOs have BALs. The number of these QSOs is about 3–10% of all QSOs (Foltz et al. 1990). One can see in Fig. 2 that very low-redshift QSOs have no BALs.

2.

Almost all BAL QSOs exhibit zabs < zem.

3.

High-resolution observations reveal that the widths of the broad absorption lines are narrower than that of the corresponding emission line for all BAL QSOs, i.e. Δλ ab < Δλ em.
Iron Lines, X-Rays, and Outflowing Winds
Authors: Lawrence A.
Published: July 2016

The strength of optical Fe II lines seems to be connected to both X-ray spectral slope and X-ray loudness, as well as other interesting properties such as emission-line width and the presence of a low-ionization broad absorber. The reason for this cluster of correlations is far from clear.
Intrinsic Absorption and Emission Lines in Seyfert Galaxies
Authors: Crenshaw D.M.
Published: July 2016

RecentHSTspectra indicate that a large fraction of Seyfert 1 galaxies have UV absorption lines that are intrinsic to the active nucleus or its environment.IUEmonitoring or multipleHSTobservations of several sources show that many absorption lines are variable, either as a result of mass motion across the line-of-sight or of changing ionization within the gas in response to variations in the ionizing continuum. The UV absorbers may be related to the warm absorbers seen in the X-ray spectra of many Seyfert galaxies, but a direct connection between the two has not been made. Some of the absorption lines may arise in the emission-line regions in the nucleus or host galaxy, providing valuable clues to their nature.
Properties of Warm Absorbers and Constraints from their Optical and UV Line Emission
Authors: Komossa Stefanie , Fink Henner
Published: July 2016

We have studied the warm absorbers in several Seyfert galaxies using both PI and archival ROSAT data. The parameters that govern the emissivity of the ionized material, ionization parameter U, warm-absorber column density Nwa, and the source intrinsic power-law photon index Γx, are determined from X-ray spectral fits. These are then used to predict the expected IR to UV line emission of the ionized material in the individual objects. In particular, the possibility of a warm-absorber origin of one of the known emission-line regions in AGN is assessed. Good ‘candidate components’ are, e.g., the coronal-line region, and/or the high-ionization component of the NLR, or the component responsible for broad wings in the Balmer lines. All calculations have been carried out using the code CLOUDY (Ferland 1993).
A Correlation Analysis for Emission Lines in 52 AGN
Authors: Dultzin-Hacyan D. , Sulentic J. , Marziani P. , Calvani M. , Moles M.
Published: July 2016

We recently completed the first comparison of high- and low-ionization broad lines in a sample of 52 AGN. We summarize here the principal results of a correlation analysis for this sample. We then briefly outline a model for the broad-line structure in radio-quiet AGN that is suggested by the correlation analysis.
A Correlated Optical-Infrared Outburst of Mrk 744: Strong Evidence for Thermal Dust Reverberation
Authors: Nelson B.
Published: July 2016

Simultaneous optical and infrared monitoring of a sample of 50 Seyfert 1 galaxies and quasars has revealed an outburst of the active galaxy Markarian 744. Cross-correlation analysis indicates that the IR lags the optical light curve by roughly one month. A simple model developed by the author can fully explain the IR variability of this object in terms of thermal dust reverberation.
Near-Infrared View of the Nuclear Region of NGC 1808
Authors: Kotilainen J. K.
Published: July 2016

We discuss NIR imaging of the starburst galaxy NGC 1808. The circumnuclear continuum emission shows no morphological change with wavelength and most of it is produced by an evolved bulge population, not by red supergiants or dust. The line emission arises from distinct hot spots. From comparison of Brγ and Hα fluxes, we derive extinction Av = 3–5 toward the hot spots. From modeling of the line and continuum luminosities, we derive a star-formation rate of 0.1–0.6 M⊙ yr–1 and SN rate ~ 0.4–11 × 10–3 yr–1 per hot spot. The age of the burst is 8–17 Myr for the hot spots and ~ 40 Myr for the nucleus. Finally, evidence for and against hidden Seyfert activity in NGC 1808 is discussed.
Excitation Mechanism of Extended Emission-Line Regions in Active Galaxies
Authors: Evans Ian , Koratkar Anuradha , Allen Mark , Tsvetanov Zlatan , Dopita Michael
Published: July 2016

Photoionization and shock models of the extended emissionline regions (EELRs) in active galaxies demonstrate that the optical emission lines alone are a poor discriminant of the excitation mechanism. Combining optical and UV data provides a discriminant between nuclear photoionization and autoionizing shock models. Hubble Space Telescope UV spectrophotometry of two Seyferts suggests that the EELRs in these objects are probably photoionized by the nucleus.
An Ultraluminous IRAS Galaxy with an Extremely Soft X-Ray Spectrum
Authors: Xia X.Y. , Boiler Th. , Deng Z.G.
Published: July 2016

Redshift surveys of the extragalactic IRAS sources have revealed a class of galaxies, ultraluminous infrared galaxies (ULIRGs), that radiate an enormous amount of energy in the far-infrared (Soifer et al. 1986), typically LIR ≥ 1012L⊙, which is comparable to the luminosities of quasars. The energy source for most ULIRGs is believed to be massive nuclear starbursts triggered by galaxy interactions or mergers (Rigopoulou et al. 1996, Crawford et al. 1996). There is much debate about the evolution of ULIRGs. Sanders et al. (1988) suggested that ULIRGs are forming QSOs. However, it is not clear how merging galaxies evolve to QSOs. Meanwhile, observations and N-body simulations show that mergers between disk galaxies can form ellipticals. Some ULIRGs, such as Arp 220 and NGC 6240, do have elliptical characteristics. What is the evolutionary connection between QSOs and elliptical galaxies? About 10% of ULIRGs are IR QSOs or Seyfert 1 galaxies, on the basis of their optical spectra and appearance. Some of them are hosted in ellipticals (Hutchings et al. 1988, Lipari et al. 1994). Also, most of them are strong Fen emitters. Studying this subsample of ULIRGs in detail may give some clues to understanding the evolutionary process mentioned above.
The Westerbork Flexible Filterbank Backend
Authors: Kouwenhoven Marco , Voûte Lodie , Klis Michiel van der , Weggemans Hans , Deich Will , Vasisht Gautam , Kulkarni Shri
Published: July 2016

The Westerbork Synthesis Radio Telescope (WSRT) has recently been fitted with a new backend designed for pulsar detection. This backend is a filterbank with 32 channels, for both the X and Y polarised signals. A novel feature is that the channel bandwidths are digitally tunable between 6.25 kHz and 2.8 MHz (Vasisht et al. in preparation). The time constant of the integration which follows detection can be digitally set at values between circa 50 ms and 10μS. For each observing frequency and each pulsar (with a known dispersion measure) we can choose an optimal bandwidth and signal smoothing.
The S2 Baseband Processing System for Phase-coherent Pulsar Observations
Authors: Wietfeldt R. , Straten W. Van , Rizzo D. Del , Bartel N. , Cannon W. , Bailes M. , Reynolds J. , Wilson W.
Published: July 2016

The phase-coherent recording of pulsar data and subsequent software dispersion removal provide a flexible way to reach the limits of high time resolution, useful for more precise pulse timing and the study of fast signal fluctuations within a pulse. Because of the huge data rate and lack of adequate recording and computing capabilities, this technique has been used mostly only for small pulsar data sets. In recent years, however, the development of very capable, reasonably inexpensive high-speed recording systems and computers has made feasible the notion of pulsar baseband recording and subsequent processing with a workstation/computer. In this paper we discuss the development of a phase-coherent baseband processing system for radio pulsar observations. This system is based on the S2 VLBI recorder developed at ISTS/York University in Toronto, Canada. We present preliminary first results for data from the Vela pulsar, obtained at Parkes, Australia, and processed at ISTS/York University, and discuss plans for future developments.
Pulsar Velocities – Revisions & Ramifications
Authors: Lorimer D. R.
Published: July 2016

The recent shift of opinion concerning the distribution of pulsar velocities at birth with a mean value of 400-500 km/s has several ramifications for our understanding of the origin and evolution of pulsars. From the present data, there is no convincing evidence for a causal correlation between velocity and magnetic field, any magnetic field evolution in neutron stars or that galactic neutron stars once active as radio pulsars are the sources ofγ-ray bursts. Asymmetric kicks seem the most plausible origin for the high velocities.
Pulsar Period and Magnetic Field Evolution
Authors: Camilo F.
Published: July 2016

One of the important unsolved problems in pulsar astrophysics concerns the formation and evolution of their magnetic fields. We summarize measurements of braking indices and their implications for the spin and magnetic field evolution of young pulsars. An analysis of the period-period derivative diagram suggests one or more of the following: (a) a substantial population of young pulsars remains undiscovered; (b) a large fraction of all slow pulsars may be recycled; (c) magnetic fields in isolated pulsars decay by a factor of a few in the first few million years. We also note that the observed P-Ṗ distribution of millisecond pulsars may be shaped by luminosity evolution.
The velocity distribution of young radio pulsars: simulating the observations
Authors: Hartman J.W.
Published: July 2016

Lyne & Lorimer (1994) argue that the velocities of young pulsars are much higher than was previously thought. However, recent radio pulsar population synthesis work by Hartman et al. (1996, these proceedings) shows that simulations that use a birth velocity distribution with more pulsars at low velocities, Phinney’s modification of the Paczyński (1990) distribution

describes the observed magnetic field, period and luminosity distribution equally well as simulations that use the Lyne & Lorimer distribution.

We use this radio pulsar population synthesis model to obtain the proper motion distribution of the simulated sample, and from that we calculate the transverse velocity distribution to compare it with the observed transverse velocity distribution. A full report of this work will be given in Hartman (1996).
Rotational Instabilities in Pulsars
Authors: Lyne A. G.
Published: July 2016

In general, radio pulsars are superb clocks. However a few years after their discovery, it became clear that some pulsars show significant departures from their regular slow-down which make their rotation unpredictable. Two main forms of irregularities have been identified – glitches and timing noise – which are most marked in, but not confined to, young pulsars. Both are probably related to the internal structure of the neutron star and the properties of the internal neutron superfluid which prevent the smooth outward flow of angular momentum as the star slows down. In this review, the observational status and statistical aspects of the phenomena are described. We do not discuss in any detail their implications for neutron star structure. Rather, we consider them in so far as they limit studies in which the rotational stability is paramount and may limit the use of pulsars as astronomical chronometers. Glitch activity, the amount of post-glitch relaxation and the amplitude of timing noise all depend roughly linearly on the frequency derivative, implying that even the millisecond pulsars are prone to these effects.
Millisecond Pulsar Timing in Effelsberg
Authors: Kramer M. , Doroshenko O. , Jessner A. , Wielebinski R. , Wolszczan A. , Camilo F. , Taylor J.H. , Xilouris K.M.
Published: July 2016

Millisecond pulsar as clocks are excellent tools for studying a variety of phenomena in physics and astrophysics (e.g. Foster & Backer 1990). We have been observing millisecond pulsars with the 100–m Effelsberg radiotelescope since April 1994. Initially, the goal of this program was to help continuing the timing of Arecibo pulsars during the upgrade–related shutdown period of the 305–m radiotelescope. Gradually, the program has evolved to time and study the emission physics of all short period pulsars detectable from Effelsberg. In particular, polarization measurements are used to make inferences about the emission physics of millisecond pulsars (cf. Xilouris & Kramer, this proceeding). At present, the programme involves approximately monthly observations of a set of 22 sources.
Twelve years of Glitches in the Vela Pulsar
Authors: Flanagan Claire S.
Published: July 2016

The Vela pulsar (PSR B0833–45) has been observed from Hartebeesthoek RAO since 1984, as part of an ongoing monitoring project. During this time, the pulsar has undergone five sudden and relatively large spin-ups (“glitches”). Good observational coverage was obtained for the four most recent of these events.

The post-glitch behaviour of(t) is modelled by:
On the timing histories of the crab, PSR1509-58 and PSR0540-69
Authors: Carramiñana Alberto , Alvarez César
Published: July 2016

A simple model of a combined magnetic dipole, gravitational and/or magnetic quadrupole and particle accelerator is applied to simulate the time behaviour of the timing parameters of PSR 0531+21, PSR 1509-58 and PSR0540-69, as well as their energy budget. The model restricts the allowed values for the second braking index and is therefore testable through measurements of.
Orbital Parallaxes of Wide Orbit Binary Pulsars and their implications
Authors: Kopeikin Sergei M.
Published: July 2016

A complete theoretical description of the parallactic terms in the timing formula for a wide orbit binary pulsar is presented. It is shown that the terms depend not only on the annual motion of Earth but also on the orbital motion of the binary pulsar as well. It is proved that measurements of the effect of orbital parallax open a new way in determination of pulsar distances, and can be used for measurement of companion masses as well. Estimates of expected magnitudes of the corresponding timing signals for the most appropriate binary pulsar candidates are tabulated, and prospects for the measurement of orbital parallaxes are discussed.
Testing the Strong Equivalence Principle in strong field regimes
Authors: Wex Norbert
Published: July 2016

A possible functional dependence of the ratio of ‘gravitational’ massmGand ‘inertial’ massmIon the gravitational self-energyEG,

is called aviolation of the Strong Equivalence Principle (SEP).

Weakly self-gravitating bodies are found in the solar system where lunarlaser-ranging data restrict the Nordtvedt parameter η to absolute values smaller than 0.001, (Dickey et al. 1994, Müller et al. 1995). To test higher order contributions one needs to consider strongly self-gravitating bodies such as neutron-stars.

Small-eccentricity binary-star systems consisting of a neutron star (|EG|/mc2~ 0.15) and a white dwarf (|EG|/mc2~ 10−4) are excellent ‘laboratories’ to test the SEP in a strong-field regime. As shown by Damour and Schäfer (1991) a violation of the SEP would lead to a periodic change in the eccentricity of the orbit of the binary pulsar caused by the galactic acceleration. Thus the observation of old small-eccentricity long-orbital-period neutron-star white-dwarf binary systems put (with a certain confidence level) a limit on the violation of the SEP.
Limits on a stochastic background of gravitational waves
Authors: McHugh M. P. , Zalamansky G. , Vernotte F. , Lantz E.
Published: July 2016

A gravitational wave background (GWB) of sufficient strength, characterized by Ω, the energy density per logarithmic frequency interval in units of the closure density, would introduce timing residuals in the most stable millisecond pulsars. For a description pertaining to the observations of PSR’s 1937+21 and 1855+09 see Kaspi, Taylor and Ryba (1994), hereafter KTR, and references therein. Thorsett and Dewey (1996, see also this volume) present a method for placing a statistical upper limit on Ω. Their method however, cannot correctly account for the presence of a known level of white measurement noise in the timing residuals. We use a Bayesian approach which can best account for this white noise along with our lack of previous knowledge on the parameter Ω (McHugh, Zalamansky, Vernotte and Lantz, submitted).
Pulsar Timing Limits on Very Low Frequency Stochastic Gravitational Radiation
Authors: Dewey Rachel J. , Thorsett Stephen E.
Published: July 2016

A low-frequency, stochastic gravitational radiation background can be detected through the irregularities it induces in pulsar arrival times. In this poster we re-examine pulsar timing data presented in Kaspi, Taylor and Ryba (1994) [Ap.J.,428, p. 713] and present an optimal statistical framework for using timing data from a single pulsar to constrain the energy density in a gravitational wave background. Observations of PSRB1855+09 yield an upper limit (95% confidence) 1.0 × 10−8or (90% confidence) 4.8 × 10−9of the closure density at frequency 4.4 × 10−9Hz. This result probably rules out cosmological models that use cosmic strings as seeds for galaxy formation. Using combined observations of the orbital decay of four binary pulsars we also derive weaker limits at frequencies as low as 10−12Hz.
Whence the pulses?
Authors: Melrose D.B.
Published: July 2016

Radio emission mechanisms for pulsars are reviewed with emphasis on five possible sites for the emission: the pair production front (PPF), two regions in the relativistically outflowing plasma (denoted ROP1 and ROP2) between the PPF and the light cylinder (LC), and two sited near the LC. Several maser emission mechanism are viable for ROP1, where radius-to-frequency mapping applies. Suggested Schott radiation from outside the LC is discussed critically.
Physics of the Radio Emission Region
Authors: Eilek Jean A.
Published: July 2016

The radio emission process in pulsars is still a mystery. It will help us all if the “theorist’s freedom” in allowed models can be reduced. In order to do this, high quality data must be considered carefully in the light of existing or new theories, and the theories must be extended to address the data.
Are Giant Pulses Evidence of Self-Organized Criticality?
Authors: Young Matthew D. T. , Kenny Brian G.
Published: July 2016

The statistical distributions of certain giant pulse (GP) properties appear to be well described by power laws. This suggests that the emission mechanism that produces giant pulses is a scale-invariant one. In turn this may indicate that the source of the GPs is in a state of self-organized criticality (SOC). For a recent discussion of SOC see Sornetteet al. (1995).

Prior to this conference, the only pulsars reported to exhibit GPs were the Crab pulsar, PSR B0531+21 (Lundgrenet al. 1995), and the millisecond pulsar PSR B1937+21 (Cognardet al. 1996). However, at the conference it was reported that giantmicropulseshad recently been observed from PSR J0437–4715 (Ables and McConnell, this volume). In all cases the statistical distributions of observed GP heights and/or fluxes are found to be well described by simple power laws. The arguments in this note apply to all these pulsars.
Mosaic structure of the emission region of pulsar PSR 0329+54
Authors: Kuzmin A.D. , Izvekova V.A.
Published: July 2016

We performed the multifrequency time aligned measurements and the component structure analysis of the integrated profile of PSR 0329+54 in frequency range from 0.1 to 10 GHz. The result is that a commonly adopted five-component structure of the integrated profile does not provide a good match to the observed profiles. Only a six-component structure fits observations well. This result calls into question the validity of the two conal and core zones emission model. We suggest that the emission region inside of the cone of the open magnetic field lines represents a mosaic bunch of the discrete outflows of relativistic charges along magnetic field lines, injected by mosaic group of localized sparks in the polar cap. Our suggestion is based on the Rutherman and Sutherland belief that the polar gap discharges through a group of localized sparks, spaced at distances nearly equal to the height of the polar gap.

Mode changing may be produced by the change of an activity of some sparks pattern without rearranging the structure of the emission region.
Single pulse profiles and the Lorentz factor of emitting particles in pulsar magnetospheres
Authors: Rathnasree N.
Published: July 2016

If each significant component in a single pulse from a radio pulsar represents emission from a single site and the intensity at longitudes other than the peak arises from the forward beaming of this emission, the angular distribution of intensity within a component is given by (Zheleznyakov, & Shaposhnikov 1972),

Here,, with ν the velocity of the emitting particles at the emission site, α is the spectral index of emission in the rest frame of the emitting particles, and is also the spectral index as seen by the observer, ν is the observed frequency of the radiation.Kναis the intensity in the rest frame of the emitting particles. ϕ0is the angular co-ordinate corresponding to the direction of motion of the emitting particles, and ϕ is the angular co-ordinate at different regions in a single component.
Individual Pulse Polarization of Pulsars at Low Frequencies
Authors: Suleymanova S.A. , Izvekova V.A. , Pugachev V.D.
Published: July 2016

This paper presents the results of the measurements of linear polarization characteristics of individual pulses at frequencies 40, 60 and 103 MHz for 10 strong pulsars. We have measured total intensity, linear polarization percentage and angle along the pulse window and obtained distribution displays for these data.

Two orthogonal polarization modes are common features in the radiation of pulsars at low frequency. The energy ratio of these two modes can change significantly between different frequencies. The linear polarisation percentage has a general tendency to increase at low frequencies, but by very different factors for different components of the integrated intensity profile. The relationship between the polarization properties of PSR 0943+10 and its mode changing behaviour was studied. It is shown that the energy ratio and the frequency of occurence of two polarization modes change simultaneously with changes in the integrated intensity profile.
Recent Gamma-Ray Observations
Authors: Thompson D.J.
Published: July 2016

With the results from the Compton Gamma Ray Observatory, multiwavelength pulsar studies have taken on new importance.
Pulsar Electrodynamics — Pulsars and Puzzlers —
Authors: Shibata Shinpei
Published: July 2016

A gedanken experiment presented here provides basic understanding of how the pulsar magnetosphere operates. We discuss current issues about the electric-field acceleration along magnetic field lines and subsequent pair creation, and also about the pulsar wind problem. It is stressed that any local model, such as the inner gap model, the outer gap model and the pulsar wind model, must have free parameters to link it to other part of the magnetosphere.
Wave Propagation in Pulsar Magnetospheres and Interstellar Interferometric Observations
Authors: Gallant Yves A.
Published: July 2016

Using a refractive scintillation event of PSR 1237+25, Wolszczan & Cordes (1987) inferred a projected displacement of the emission region of order 108cm across the pulse. Gupta (these proceedings) inferred a lower separation limit of a few times 107cm from a similar event for PSR 1133+16. In both cases the projected displacement was also a nonmonotonic function of pulse phase.

Neither these large separations nor the nonmonotonic behavior can be explained in a simple model which assumes that the emission originates parallel to the field lines of a magnetic dipole, at a fixed altitude across the open field zone, and propagates in a straight line to the observer. There is considerable circumstantial evidence for dipolar fields from polarization sweep and pulse morphological studies. Time delays due to different emission altitudes could produce asymmetries in pulse profiles and projected displacements, but cannot explain the large separations if the emission originates well within the light cylinder.
Magnetic field amplification in newly-born neutron stars
Authors: Wiebicke H.-J. , Geppert U.
Published: July 2016

We present a scenario of magnetic field (MF) evolution of newly-born neutron stars (NSs). Numerical calculations show that in the hot phase of young NSs the MF can be amplified by thermoelectric effects, starting from a moderately strong seed-field. Therefore, there is no need to assume a 1012G dipole field immediately after the gravitational collapse of the supernova (SN) event. The widely accepted scenario for such a field to be produced by flux conservation during the collapse is critically discussed. Instead, it can be generated by amplification and selection effects in the first 104yrs, and by the subsequent fast ohmic decay of higher multipole components, when the NS cools down.
An AU-Aperture Lens to Resolve the Vela Pulsar’s Radio Emission Region
Authors: Gwinn C.R. , Ojeda M.J. , Britton M.C. , Reynolds J.E. , Jauncey D.L. , King E.A. , Flanagan C.S. , Smits D.P. , Preston R.A. , Jones D.L.
Published: July 2016

We use radio-wave scattering in the Vela supernova remnant, surrounding the Vela pulsar, as an AU-scale lens to study the Vela pulsar’s emission region.
Characterization of Multiple Refractive Scintillation Events in the Directions of Two Millisecond Pulsars
Authors: Cognard I. , Lestrade J.-F.
Published: July 2016

High-precision timing of the millisecond pulsars PSR B1937+21 and PSR B1821-24 are conducted at 1.4 and 1.7 GHz with the high rate of observations of 10-15 times per month at Nançay. Time Of Arrival (TOA) and pulsar flux density are both measured. The rms of the daily post-fit TOA residuals are at the level of 0.5μs and 3.0μs, respectively. A characterization of refractive scintillation events produced by the Ionized Interstellar Medium (IISM) both in the TOA residuals and flux density variations is discussed.

Timing at Nan^ay is conducted with a pre-detection dedispersion system. The analysis of the TOAs was done with our software AnTiOPE solving for the classical pulsar parameters. The flux densities of the pulsars are averaged over ~30 or ~70 minutes. Calibration of the system temperature and efficiency of the telescope is good at the 10% level and diffrative scintillation limits this calibration to a comparable level (~35 scintels for PSR B1937+21 over 30 minutes and 7.5 MHz).
The White Dwarf Companions of Recycled Pulsars
Authors: van Kerkwijk M. H.
Published: July 2016

I review what properties of the white-dwarf companions of recycled pulsars can be inferred from optical observations, and discuss how these can help us understand the characteristics and evolution of these binaries. I focus on spectroscopic observations, describing results obtained recently, and looking forward to what may come.
Hubble Space Telescope Observations of Millisecond Pulsar Companions: Constraints on Evolution
Authors: Lundgren S. C. , Foster R. S. , Camilo F.
Published: July 2016

In observations of six binary millisecond pulsars with the Hubble Space Telescope, we have discovered white dwarf companions to PSRs J0034-0534, J1022+1001, J1713+0747, and J2019+2425 and improved photometry on PSRs J1640+2224 and J2145-0750. Three of the white dwarfs are among the coolest and oldest known. We have determined that the masses for the helium companions are consistent with the expectation based on the core mass of a progenitor that filled its Roche lobe. The cooling times for many of the white dwarfs are much less than the characteristic spin-down times, implying that the spin period at the end of the accretion stage was close to the current period. The initial spin periods calculated are used to place limits on the accretion rate at the end of the low-mass X-ray binary phase. The accretion rates are found to be over an order of magnitude less than the Eddington rate.