Gauge string in the fermion asymmetric matter

Two new effects of interaction of the gauge string with a homogeneous density of fermions are considered in a gauge model with an anomalous coupling of vector fields with fermions. First, the presence of an induced nonzero magnetic-like helicity on the straight string is demonstrated. Second, it is shown that the equation of motion of the string is modified by a nonlinear term that can be decomposed into the correction to the string tension and an additional force perpendicular to the tangent and normal vectors of the string. Static configurations are found and their stability is studied.Comment: revtex, 9 pages, to appear in Phys. Lett.

Explaining critical angular velocities of the vortex formation in a stirred Bose-Einstein condensate

The problem of explanation of the critical angular velocity $\Omega_c$ when the formation of a vortex in the stirred Bose-Einstein condensate becomes energetically possible, is considered in the framework of the variational approach. The origin of smallness of the calculated $\Omega_c$ in comparison with the measured values which takes place for pure quantum state with the unit angular momentum per condensed particle, is uncovered. The agreement with the measured $\Omega_c$ is achieved upon admitting a small admixture of the zero angular momentum state in the wave function of the one-vortex quantum state prepared after stirring. The portion of this admixture amounts to 10 - 13 % of the total condensed atoms. Possible test of this hypothesis is proposed.Comment: Latex, 5 pages including 1 ps figure, references added in v

An extensive photometric study of the recently discovered intermediate polar V647 Aur (1RXS J063631.9+353537)

We report the results of photometry of the intermediate polar V647 Aur. Observations were obtained over 42 nights in 2012 and 2013. The total duration of the observations was 246 h. We clearly detected three oscillations with periods of 932.9123+\-0.0011, 1008.30797+\-0.00038 and 1096.955+\-0.004 s, which may be the white dwarf spin period and two orbital sidebands, accordingly. The oscillation with a period of 932.9123 s has a quasi-sinusoidal pulse profile with a slightly changeable semi-amplitude from 10.9 mmag in 2012 to 12.5 mmag in 2013. The oscillation with a period of 1008.30797 s has a slightly asymmetric pulse profile with a remarkable small hump on the ascending part. The semi-amplitude of this oscillation is highly changeable both in a time-scale of days (26-77 mmag) and in a time-scale of years (47 mmag in 2012 and 34 mmag in 2013). The oscillation with a period of 1096.955 s has a highly asymmetric pulse profile with a semi-amplitude of about 6 mmag. The three detected oscillations imply an orbital period of 3.46565+\-0.00006 h. By comparing our data with the data of B. T. Gansicke et al., which were obtained 8 years ago, we discovered that the spin period of the white dwarf in V647 Aur decreases with dP/dt=(-1.36+\-0.08) X 10^-10. This important result should be confirmed by future observations. Our oscillation ephemeredes and times of maxima can be useful for this confirmation.Comment: 9 pages, 8 figures, will be published in MNRAS. arXiv admin note: text overlap with arXiv:1202.249

Extensive photometry of the intermediate polar MU Cam: detection of a spin period change

Intermediate polars with known rates of spin period changes are not numerous because such tasks require measurements performed for a long time. To measure a spin period change, MU Cam is a good candidate because it has a spin oscillation with a large amplitude enabling measurements with high precision. Fortunately, in the past the spin period of MU Cam was measured with high precision. To measure the spin period anew, in 2014-2015 we performed extensive photometric observations of MU Cam, spanning a total duration of 208 h within 46 nights. We found that the spin, sideband and orbital periods are equal to 1187.16245+/-0.00047 s, 1276.3424+/-0.0022 s and 4.71942+/-0.00016 h, respectively. Comparing the measured spin period with the spin period of MU Cam in the past, we detected the spin period change with dP/dt=-(2.17+/-0.10) X 10^(-10). This rate of the spin period change was not stable and varied in a time scale of years. During four nights in 2014 April-May MU Cam was fainter than usual by 0.8 mag, and the amplitude of the sideband oscillation was five times larger, denoting significant fraction of disc-overflow accretion. The sideband oscillation showed a double-peaked pulse profile in the normal brightness state. When the star brightness was decreased by 0.8 mag, the sideband oscillation showed a single-peaked pulse profile. In contrast, the spin pulse, which was quasi-sinusoidal, remained remarkably stable both in profile and in amplitude. Moreover, the spin pulse was also remarkably stable in a time scale of years and even decades. MU Cam is of great interest because it represents a distinctive object with a large and unstable rate of the spin period change and exhibits a distinctive behaviour of the pulse profiles.Comment: 12 pages, 10 figures, accepted for publication in Astrophysics and Space Scienc

Extensive photometry of the WZ Sge-type dwarf nova V455 And (HS2331+3905): detection of negative superhumps and coherence features of the short-period oscillations

We report the results of photometry of the WZ Sge-type dwarf nova V455 And. Observations were obtained over 19 nights in 2013 and 2014. The total duration of the observations was 96 h. We clearly detected three coherent oscillations with periods of 80.376+/-0.003 min, 40.5431+/-0.0004 min and 67.619685+/-0.000040 s. The 67.619685-s period can be the spin period of the white dwarf. The 40.5431-minute period is the first harmonic of the orbital period. The 80.376-minute oscillation can be a negative superhump because its period is 0.9% less than the orbital period. This oscillation was evident both in the data of 2013 and in the data of 2014. These results make V455 And a permanent superhump system which shows negative superhumps. This is also the first detection of persistent negative superhumps in a WZ Sge-type dwarf nova. In addition, the analysis of our data revealed incoherent oscillations with periods in the range 5-6 min, which were observed earlier and accounted for by non-radial pulsations of the white dwarf. Moreover, we clearly detected an oscillation with a period of 67.28+/-0.03 s, which was of a low degree of coherence. This oscillation conforms to the beat between the spin period of the white dwarf and the 3.5-h spectroscopic period, which was discovered earlier and accounted for by the free precession of the white dwarf. Because the 67.28-s period is shorter than the spin period and because the free precession of the white dwarf is retrograde, we account for the 67.28-s oscillation by the free precession of the white dwarf.Comment: 9 pages, 9 figures, will be published in New Astronom