Are the magnetic fields of millisecond pulsars ∼108 G?

It is generally assumed that the magnetic fields of millisecond pulsars (MSPs) are ～10⁸ G. We argue that this may not be true and the fields may be appreciably greater. We present six evidences for this: (1) The ～10⁸G field estimate is based on magnetic dipole emission losses which is shown to be questionable; (2) The MSPs in low mass X-ray binaries (LMXBs) are claimed to have <10¹¹ G on the basis of a Rayleygh-Taylor instability accretion argument. We show that the accretion argument is questionable and the upper limit 10¹¹ G may be much higher; (3) Low magnetic field neutron stars have difficulty being produced in LMXBs; (4) MSPs may still be accreting indicating a much higher magnetic field; (5) The data that predict ～10⁸ G for MSPs also predict ages on the order of, and greater than, ten billion years, which is much greater than normal pulsars. If the predicted ages are wrong, most likely the predicted ～10⁸ G fields of MSPs are wrong; (6) When magnetic fields are measured directly with cyclotron lines in X-ray binaries, fields ?10⁸ G are indicated. Other scenarios should be investigated. One such scenario is the following. Over 85% of MSPs are confirmed members of a binary. It is possible that all MSPs are in large separation binaries having magnetic fields >10⁸ G with their magnetic dipole emission being balanced by low level accretion from their companions.     

Identification of absorption lines of rare-earth elements in the region of the spectrum λλ 610.25–610.57 nm roAp stars,HD 101065, HD 134214, HD 137949, and HD 24712

In the spectral region λλ = 610.25−610.57 nm of the roAp star HD 101065, we performed the identification of the rare-earth element absorption lines absent from the atomic spectral line databases VALD and DREAM. The identified lines were used for calculating the synthetic spectra of the roAp stars HD 137949, HD 134214, and HD 24712. The upper limit of the identified line estimates was determined. The rotation/pulsation parameter νsini and magnetic field modulus were determined using the lines Nd III 669.083 nm and Ca I 616.217 nm. The element abundance in the roAp stars HD 134214 and HD 24712 was determined for the first time using Nd III lines. Calculations were carried out with the help of the code SynthM developed by S.A. Khan.     

Polar magnetic fields – Filaments and the zero-flux contour

We investigate the reliability with which magnetograph observations of the large-scale polar fields establish the zero-flux contour by comparing magnetic maps from various sources with one another and with the locations of filament structures seen on the disk in H filtergrams. The daily MWO and NSOKP magnetograms smoothed over 120 arc sec provide consistent large-scale zero-flux contours which align with the filaments out to heliocentric angles of about 75°. Synoptic maps match in regions where the locations of the zero-flux contour and of the filaments are maintained for several days. Attention is drawn to regions at the tips of unipolar `plumes' and the polar crown gap where the contours are variable from day to day; these are tentatively identified as regions of active reorganization of large-scale flux.     

Statistical interrelation of 22-yr-long variations in the data on parameters of the Earth’s rotation and magnetic fields of the Earth and the Sun

By means of spectral analysis, oscillations have been detected in many-year time series of deviations in the duration of days from the standard that cannot be explained within the framework of existing gravitational theory. The solution of the problem of the origin and structure of these oscillations is associated with the essence of the phenomena taking place inside the Earth and the mechanisms of energy transfer by external fields and the Sun. The effect of the Sun on the Earth’s rotation also leads to the formation of a unified cyclic background, resulting in correlated oscillations in all shells of the Earth, as well as in its atmosphere and its nucleus. Ground magnetic fields of the Earth and the Sun play the leading role in the abovementioned unified cyclic process. The results of spectral autoregressive and wavelet analyses of experimental data concerning deviations in the duration of days from the standard in the years 1832–2006, ground geomagnetic field intensities in 1832–2006, and the mean magnetic field of the Sun during the period from 1975 to 2005 have been discussed in this paper to reveal and compare correlating oscillations. To analyze a short-period (31-yr-long) series of daily data on the mean magnetic field of the Sun, the results of wavelet transformations (the Morlet wavelet) of the detected amplitude of a burst envelope with a carrier frequency of 13 cycles/yr have been obtained.     

Effect of Coriolis force on the shapes of rotating stars and stars in binary systems

In this paper an attempt has been made to determine the effect of Coriolis force on the shapes of Roche equipotential surfaces of rotating stars and stars in binary systems. Equations of Roche equipotential surfaces have been obtained for rotating and binary stars which take into account the effects of Coriolis force besides the centrifugal and gravitational forces. Shapes of Roche equipotentials and values of Roche limits are obtained for different values of angular velocity of rotation for rotating stars and for different values of mass ratios for the binary stars. The obtained results have been compared with the corresponding results in which the effect of Coriolis force has not been considered.     

Comparison of the magnetic fields in active prominences measured from the He I D3 and Hα lines

We present the results of magnetic field measurements in three active prominences, July 24, 1981, July 24, 1999, and July 12, 2004, obtained from observations with the echelle spectrograph of the horizontal solar telescope at the Astronomical Observatory of the Taras Shevchenko Kiev National University. The magnetic fields were measured from the Zeeman splitting of the I ± V profiles in the He I D₃ and H?? lines in the atmosphere at heights from 3 to 14 Mm. Our measurements of the effective magnetic fields B _eff from the shift of the profile centroids have shown that the magnetic fields averaged over the entrance slit area were within the range from ?600 to +1500 G. The amplitude values of the local fields have been estimated from the splitting of the bisectors of the central parts of the line profiles at 0.9 of the peak intensity. The corresponding fields B _0.9 have turned out to be approximately twice B _eff and reached 4000 G in absolute value. Narrow (1?C2 Mm) height peaks at heights of 6?C11 Mm have been found in the height distributions of the magnetic field. We have found an interesting effect in two prominences-an anticorrelation between the magnetic field strengths measured from the D₃ and H?? lines.     

Can the turbulent galactic dynamo generate large-scale magnetic fields?

Large-scale magnetic fields in galaxies are thought to be generated by a turbulent dynamo. However, the same turbulence also leads to a small-scale dynamo which generates magnetic noise at a more rapid rate. The efficiency of the large-scale dynamo depends on how this noise saturates. We examine this issue, taking into account ambipolar drift, which obtains in a galaxy with significant neutral gas. We argue as follows.
(i) The small-scale dynamo generated field does not fill the volume, but is concentrated into intermittent rope-like structures. The flux ropes are curved on the turbulent eddy scales. Their thickness is set by the diffusive scale determined by the effective ambipolar diffusion.
(ii) For a largely neutral galactic gas, the small-scale dynamo saturates, as a result of inefficient random stretching, when the peak field in a flux rope has grown to a few times the equipartition value.
(iii) The average energy density in the saturated small-scale field is subequipartition, since it does not fill the volume.
(iv) Such fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale into wave-like motion. The diffusive effects needed for the large-scale dynamo operation are then preserved until the large-scale field itself grows to near equipartition levels.     

Chromospheric and coronal Alfvénic oscillations in non-vertical magnetic fields

We generalize previous studies of Alfvénic oscillations in the solar atmosphere to geometries in which the background magnetic field is not parallel to the gravitational acceleration. A uniform but inclined field produces only subtle changes in the mathematics, and virtually no changes to the coronal energy flux, over previous vertical field studies. We show that simple, two-layer models agree remarkably well with more sophisticated, multi-layer calculations. In addition, we derive several useful and accurate analytic results with which we highlight many features and parameter dependences. We also study a model with a spreading field geometry. For low magnetic fields (- 10 G) the corona still appears WKB to the oscillations and we do not find any significant deviations from the uniform field calculations. This is not the case for higher magnetic fields in active regions (- 3000 G) where we confirm previous results which suggest an order of magnitude increase in the coronal flux. Again, we derive useful analytic approximations.Now at: Mathematics Department, Monash University, Clayton, Victoria, Australia.     

Variations of the λ525.02 nm FeI line profile over the solar disk and observations of large-scale magnetic fields

This paper examines the question of the influence of the 525.02 nm Fei line profile (slope of its wings) variations over the solar disk upon observations of large-scale magnetic fields (LSMF) made in this line. The study has shown that depending on the position on the disk (center-limb effect) and magnetic field parameters at the place of the observation, values of magnetic field strengths determined with proper account of the real line profile and in the usual way (by calibration using the line profile at the center of the solar disk only) can differ by 25% or more, which is of crucial importance. Observations at the Solar Telescope for Operative Predictions (STOP) of the Sayan Observatory have been used to accomplish this work.     

The influence of magnetic fields on the Sunyaev–Zel’dovich effect in clusters of galaxies

We study the influence of intracluster large scale magnetic fields on the thermal Sunyaev–Zel’dovich (SZ) effect. In a macroscopic approach we complete the hydrostatic equilibrium equation with the magnetic field pressure component. Comparing the resulting mass distribution with a standard one, we derive a new electron density profile. For a spherically symmetric cluster model, this new profile can be written as the product of a standard (β-) profile and a radius dependent function, close to unity, which takes into account the magnetic field strength. For non-cooling flow clusters we find that the observed magnetic field values can reduce the SZ signal by ∼10% with respect to the value estimated from X-ray observations and the β-model. If a cluster harbours a cooling flow, magnetic fields tend to weaken the cooling flow influence on the SZ-effect.     

What can we hope to know about the symmetry properties of stellar magnetic fields?

We summarize evidence that neither dynamo theory nor the observational data give strong support to the idea that stellar magnetic fields must have dipolar rather than quadrupolar symmetry with respect to the stellar equator. We demonstrate that even the most basic model for magnetic stellar activity, i.e. the Parker migratory dynamo, provides many possibilities for the excitation of large-scale stellar magnetic fields of non-dipolar symmetry. We demonstrate the spontaneous transition of the dynamo-excited magnetic field from one symmetry type to another. We explore observational tests to distinguish between the two types of magnetic field symmetry, and thus detect the presence of quadrupolar magnetic symmetry in stars. Complete absence of quadrupolar symmetry would present a distinct challenge for contemporary stellar dynamo theory. We revisit some observations which, depending on further clarification, may already be revealing some properties of the quadrupolar component of the magnetic fields generated by stellar dynamos.     

Solar chromospheric magnetic fields in active regions inferred by monochromatic images of the Stokes' parameterV of the Hβ line

A series of H chromospheric magnetograms was obtained at various wavelengths near the line center with the vector video magnetograph at Huairou Solar Observing Station as a diagnostic of chromospheric magnetic structures. The two-dimensional distribution of the circular polarization light of the H line with its blended lines at various wavelength in active regions was obtained, which consists of the analyses of Stokes' profileV of this line. Due to the disturbance of the photospheric blended line Fei 4860.98 for the measurement of the chromospheric magnetic field, a reversal in the chromospheric magnetograms relative to the photospheric ones occurs in the sunspot umbrae. But in the quiet, plage regions, even penumbrae, the influence of the photospheric blended Fei 4860.98 line is not obvious. As regards the observation of the H chromospheric magnetograms, we can select the working wavelength between -0.20 and -0.24 from the line core of H to avoid the wavelengths of the photospheric blended lines in the wing of H.After the spectral analysis of chromospheric magnetograms, we conclude that the distribution of the chromospheric magnetic field is similar to the photospheric field, especially in the umbrae of the sunspots. The chromospheric magnetic field is the result of the extension of the photospheric field.     

Measurements of visual double stars with PISCO2 at the Nice 76-cm refractor in 2013–2014 (new data) and in 2015

We present relative astrometric and photometric measurements of visual double stars made in 2013–2015, with PISCO2 installed at the 76-cm refractor of Côte d'Azur Observatory in Nice (France). Our observing list contains orbital couples as well as double stars whose motion is still uncertain. Most of the observations were done in 2015, but some other observations of wide couples were done in 2013–2014 (0.3% of the total of the observations). Three different techniques were used for obtaining measurements: lucky imaging, speckle interferometry and the direct vector autocorrelation method. From our observations of 2837 multiple stars, we obtained 5182 new measurements with angular separations in the range of 0 ${}^{″}$.1–32 ${}^{″}$ and an average accuracy of $0^{″}.018$. The mean error on the position angles is 0°.8. Most of the position angles were determined without the usual 180° ambiguity with the application of the direct vector autocorrelation technique and/or by inspection of the Lucky images or the long integration files. We managed to routinely monitor faint systems ( $m_V\approx 9-11$) with large magnitude difference (up to $\mathrm{\Delta }{m}_V\approx 4.5$). We have thus been able to measure 21 systems containing red dwarf stars that had been poorly monitored since their discovery, from which we estimated the stellar masses thanks to Gaia measurements. We also measured the magnitude difference of the two components of 1079 double stars with an estimated error of 0.2 mag. Except for a few objects that are discussed, our measurements are in good agreement with the ephemerides computed with published orbital elements, even for the double stars whose separation is smaller than the diffraction limit. Thanks to good seeing images and with the use of high-contrast numerical filters, we have also been able to obtain 196 measurements with an angular separation smaller than the diffraction limit of our instrumentation, and consistent with those obtained with larger telescopes. We also report measurements of the 164 new double stars that we found in the files obtained during the observations. Finally, from a study of the DR3 Gaia release, it is shown that all the objects of the Tycho Double Star Catalog that we did not resolve in 2015 are probably false detections by Tycho.     

HD 45583—a chemically peculiar star with an unusual curve of longitudinal magnetic field variations

The results of a complex study of the chemically peculiar star HD 45583 are reported. Observations were made using the Main Stellar Spectrograph equipped with a circular polarization analyzer and NES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. Our measurements of Zeeman spectra show that the star exhibits unusual variations of the longitudinal component of magnetic field with a secondary minimum. The period of spectral and magnetic variability coincides with the rotation period, which is equal to 1.^d177000. Two possible causes of the secondary minimum are discussed: spots with higher than ambient content of some chemical elements on the star’s surface or complex structure of the stellar magnetic field. The parameters of the star’s atmosphere are determined (T _eff = 13000 K, log g = 4.0), as well as the abundances of some elements: the star shows a 1–2 dex overabundance of Fe, Si, and Cr, helium is underabundant by about 2 dex with respect to the Sun.     

Does the large-scale solar magnetic field distribution really reflect the convective velocity fields?

We have tried to decide whether the typical circular cellular-like features, which are striking during some intervals in the large-scale distribution of weak magnetic fields measured with low resolution, are related to large-scale convective motions. Two scales of such patterns were found and their morphological, kinematical and evolutionary behaviour was estimated. Their slower and overall rotation is also demonstrated in comparison with the rotation of highly averaged sunspot and magnetic fields. It is difficult to explain all the observed characteristics as random, or due to the method of field measurement and map construction used. We also discuss the change of their magnetic field polarities with the solar polar field reversal.     

On the cyclicity of solar magnetic fields during cycles 21–23

The cyclicity of weak local and strong large-scale components of the low-latitude solar magnetic field during the last three cycles of solar activity is studied using the average monthly values for the total area of sunspots and general magnetic field of the sun as a star. A local decrease in the value of magnetic flux is found for both components of the magnetic field in the phase of growing solar activity. This decrease coincides in time with the intervals of monopolarity for the polar magnetic field of the sun.     

The height stratification of solar magnetic fields in cycles 21–23

The radial component of the solar magnetic field, Br, was calculated in the potential approximation in the height range from 1 to 2.5 solar radii, Ro. According to these data, synoptic maps of the magnetic field for solar cycles 21–23 were constructed. For each 10-degree latitudinal zone, the proportion of its area, S _+field, that was occupied by the “+” field in each rotation was found. In the entire latitudinal zone, the radial component of the field is assumed to be positive if S_+field ≥ 80% and negative if S _+field ≤ 20%. The field proved to be virtually unipolar at the level of the photosphere (R = Ro) during most of the cycle, from the poles to the north and south latitude ≈60°. In the vicinity of minimums between cycles 21 and 22, as well as cycles 22 and 23, for a few rotations of the Sun, the field was almost unipolar within the range of latitudes (?40°)-90°. At R = 2.5 Ro, for most of each cycle, the field was unipolar in the range of latitudes (?20°-(-90°)) and (20°–90°). According to our interpretation, the shift of the polar-field boundary to the equator with height reflects superradial expansion of open magnetic flux tubes from the polar coronal holes. It was found that the reversal of the polar fields began with 1–2 rotations and ended from 2 to 14 solar rotations earlier at great heights than at the surface of the Sun. This indicates that the reversal of the large-scale field occurs first and then that of the small-scale one. In the study of the sectoral structure of the magnetic field at different heights it was found that the boundaries that rotate with a period of less than the Carrington revolution extend to greater heights than the boundaries with a Carrington or longer period. We assume that the boundaries of the first type are formed by the large-scale structures of the magnetic field and the boundaries of the second type are determined by the active regions.     

Possible presence of magnetic fields and iron content of atmospheres of “Metallic” Am-stars

Measurements with a CCD camera were made of two Fell lines at =6747.7 Å and 6149.2 Å in the spectra of 12 Am stars. The greater line strength of Fell 6147.7 Å relative to that of 6149.2 Å can be taken as evidence of a magnetic field in the atmosphere of the classical Am-star 15 Vul. Our observations support the conclusion of Mathys and Lanz [1] that a magnetic field is present in the atmosphere of yet another Am star, o Peg. For the rest of the stars studied the differences in the equivalent widths of the Fell lines can be explained by blending of the Fell line 6147.7 Å. Using the Fell line 6149.2 Å, which is free of blending, we estimate the iron content of the atmospheres of 12 Am stars with effective temperatures ranging from 7400 K to 9800 K. Our results indicate a star-to-star variation in log (Fe) of no less than 0.5 dex, a value greater than the measurement accuracy.Translated from Astrofizika, Vol. 37, No. 2, pp. 187–195, April–June, 1994.     

Mode and period changes in pulsating stars near the main sequence: δ Scuti stars

Reported mode changes in δ Scuti stars can usually be explained by data insufficient to obtain multiperiodic solutions and by the effect of time-variable amplitudes. The extensive data on 4 CVn obtained by the Delta Scuti Network are used to illustrate that the large changes in the appearance of the power spectra over the years from 1966 to 1996 can be ascribed to amplitude variability. The period changes of δ Scuti stars have been collected or redetermined from the available observations and are compared with values computed from evolutionary models. For the radial pulsators of Pop. I, the observations indicate (1/P)(dP/dt) values around 10⁻⁷ yr⁻¹ with equal distribution between period increases and decreases. The evolutionary models, on the other hand, predict that the vast majority should show increasing periods a factor of about ten smaller than observed. Arguments are given why the rate of evolution for these relatively unevolved stars cannot yet be deduced from the observed period changes.     

On the behavior of the Cii 4267.261, 6578.052 and 6582.882 Å lines in chemically peculiar and standard stars

With the aim of investigating the possible particular behavior of carbon in a sample of chemically peculiar stars of the main sequence without turning to modeling, we performed spectroscopic observations of three important and usually prominent single ionized carbon lines: 4267.261, 6578.052 and 6582.882 Å. In addition, we observed a large number of standard stars in order to define a kind of normality strip, useful for comparing the observed trend for the peculiar stars. We paid particular attention to the problem of the determination of fundamental atmospheric parameters, especially for the chemically peculiar stars for which the abundance anomalies change the flux distribution in such a way that the classical photometric methods to infer effective temperatures and gravities parameter cannot be applied. Regarding CP stars, we found a normal carbon abundance in Hg–Mn, Si (with some exceptions) and He strong stars. He weak stars are normal too, but with a large spread out of the data around the mean value. A more complicated behavior has been noted in the group of SrCrEu stars: four out of seven show a strong overabundance, being the others normal.