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KV Vel is a non-eclipsing short-period (P = 0.3571 days) close binary containing a very hot subdwarf primary (77000 K) and a cool low-mass secondary star (3400 K) that is located at the center of the planetary nebula DS 1. The changes in the orbital period of the close binary were analyzed based on 262 new times of light maximum together with those compiled from the literature. It is discovered that the O-C curve shows a small-amplitude (0.0034 days) cyclic period variation with a period of 29.55 years. The explanation by the solar-type magnetic activity cycles of the cool component is ruled out because the required energies are much larger than the total radiant energy of this component in a whole cycle. Therefore, the cyclic variation was plausibly explained as the light-travel time effect via the presence of a tertiary component, which is supported by the periodic changes of the O-C curve and the rather symmetric and stable light curves obtained by TESS. The mass of the tertiary companion is determined to be M_3sini' = 0.060(7) M_sun. If the third body is coplanar with the central binary (i.e., i' = 62.5{\deg}), the mass of the tertiary component is computed as M_3 ~ 0.068 M\sun, and thus it would be below the stable hydrogen-burning limit and is a brown dwarf. The orbital separation is shorter than 9.35 astronomical units (AU). KV Vel together with its surrounding planetary nebula and the brown-dwarf companion may be formed through the common-envelope evolution after the primary filled its Roche lobe during the early asymptotic giant branch stage.

Noticing the potential relationship between the pulsation amplitude of fundamental mode RR Lyrae stars and their average effective temperatures, we derived the relation between them from observational data. Using these relationships, we present the zero-age horizontal branch lines and corresponding evolutionary tracks in the Bailey diagrams. We first find that the trends of zero-age horizontal branch lines are consistent with the distributions of Oosterhoff I RR Lyrae stars, and there is a period shift effect in relatively metal-rich samples ([Fe/H] > -1). Main results show that evolutionary effects are the direct cause of the Oosterhoff dichotomy. The vast majority of Oosterhoff I RR Lyrae stars are in the early stage of horizontal branch evolution, while most of the Oosterhoff II stars are near the end of the horizontal branch phase. Our Bailey diagrams can intuitively explain some Oosterhoff phenomena (e.g., long-period RR Lyrae stars in the metal-rich globular clusters NGC 6388 and NGC 6441), and also have the potential to become an important tool for in-depth study of RR Lyrae stars. Further research is needed on the Oosterhoff dichotomy to explore the formations and evolutionary processes of the Milky Way and its substructures., Comment: 4 figures

Noting the weakest modulation and relatively high metal abundance of the ab-type RR Lyrae star V838 Cyg, we collected the photometric data of this star from several sky surveys to carry out an in-depth analysis. The O-C diagram shows that the pulsation period of V838 Cyg increases linearly over a long timescale. In a reanalysis of the high-precision Kepler data, we confirmed the modulation with a period of 59.45\pm0.07 days found by Benko et al., (2014), and also found an additional weak modulation with a longer period (840\pm21 days). After a series of analyses, we incline to the view that the mechanisms causing the two modulations are different: the former is more similar to the typical Blazhko effect, while the mechanism leading to the latter may be an extrinsic factor. We also collected and compared the modulation and physical parameters of other Blazhko RR Lyrae stars from several works in the literature, and find that there is a potential negative correlation between the modulation amplitude (or upper limit of amplitude) and the metal abundance. We infer that the relatively high metal abundance will promote convection in the outer stellar atmosphere, and then inhibit those factors (turbulence, shock wave, etc.) that may cause Blazhko modulation. Future observations and research work can be carried out with reference to this viewpoint. We also introduce the moire effects that appear in the Kepler long-cadence light curves and their possible interference in the previous analyses., Comment: 22 pages, 12 figures

We reanalyzed the c-type RR Lyrae star BE Dor (MACHO 5.4644.8, OGLE-LMC-RRLYR-06002) that had been discovered to show cyclic period changes. The photometric data of several sky surveys (DASCH, MACHO, OGLE, ASAS-SN, and TESS) were used for analyses. The O-C diagram and pulsation period obtained from Fourier analysis show significant period modulations in BE Dor. However, different from the previous viewpoint, the changes are quasi-periodic and abrupt. Therefore, the light-travel time effect caused by the companion motion cannot explain the changes. Noting a same subtype star KIC 9453114 with similar phenomena has a high macroturbulent velocity, and the degree of O-C changes seem to be positively correlated with these velocities, we consider that the mechanism leading to period modulation should be caused by the interaction between turbulent convection and magnetic field activity in the ionization zone, i.e., the viewpoint of Stothers. It may not explain the general Blazhko effect but should explain such period modulations in BE Dor and those other c-type RR Lyrae stars. We hope our discoveries and viewpoints can provide some information and inspiration for relevant research., Comment: 11 pages, 10 figures

Magnetic vortex, as one of the most interesting magnetic solitons, has attracted great interests in the past two decades. A fast and reliable method to switch vortex polarity and chirality is one of the key issues for various applications. Based on micromagnetic simulation, here we report a fast, low energy cost and deterministic switching of vortex core, through the designing of a notch structure in disks and the use of out-of-plane current geometry. We demonstrate that with such design, the multiple switching problems found in notch disk system can be avoided. Furthermore, the switching time can be reduced by more than 50% compared with disks without notch.

Magnetic vortices are characterized by the senses of in-plane magnetization chirality and by the polarity of the vortex core. The electrical control of vortex polarity and chirality is highly demanded not only for fundamental understanding on spin dynamics in nano-disks under different circumstances, but also for technological applications, such as magnetic non-volatile memories and spin torque oscillators for neuromorphic computing. Here we report a novel approach that enables one to electrically control both the vortex chirality and polarity with low energy consumption. Thorough micromagnetic simulations, we show that in thin nano-disks of diameter larger than 160 nm, with the presence of current-induced Oersted field, the dynamic transformation of the edge solitons is able to efficiently switch both vortex chirality and polarity with low current under certain circumstances. We then developed an approach to directly write any of the four vortex states by electrical current pulses from a random state. We further investigated the switching phase diagram as a function of disk diameters. The results show that the switching process is highly size-dependent. As disk diameter is smaller than 160 nm, the switch of VC chirality and polarity always takes place at the same time, resulting in an unchanged handedness before and after switch. Furthermore, the critical switch current can be as low as 3 x 10^6 A/cm^2 , indicating a possible way for low current switch of vortex chirality in small disks.

We present a timing analysis of the eclipsing post-common envelope binary (PCEB) DE CVn. Based on new CCD photometric observations and the published data, we found that the orbital period in DE CVn has a cyclic period oscillation with an amplitude of $28.08$ s and a period of $11.22$ years plus a rapid period decrease at a rate of $\dot{P}=-3.35\times10^{-11}ss^{-1}$. According to the evolutionary theory, secular period decreases in PCEBs arise from angular momentum losses (AMLs) driven by gravitational radiation (GR) and magnetic braking (MB). However, the observed orbital decay is too fast to be produced by AMLs via GR and MB, indicating that there could be other AML mechanism. We suggest that a circumbinary disk around DE CVn may be responsible for the additional AML. The disk mass was derived as a few$\times$$10^{-4}$-$10^{-3}$$M_{\odot}$ , which is in agreement with that inferred from previous studies in the order of magnitude. The cyclic change is most likely result of the gravitational perturbation by a circumbinary object due to the Applegate's mechanism fails to explain such a large period oscillation. The mass of the potential third body is calculated as $M_{3}\sin{i'}=0.011(\pm0.003)M_{\odot}$. Supposing the circumbinary companion and the eclipsing binary is coplanar, its mass would correspond to a giant planet. This hypothetical giant planet is moving in a circular orbit of radius $\sim5.75(\pm2.02)$ AU around its host star., Comment: 19 pages, 5 figures

About 3196 EA-type binaries (EAs) were observed by LAMOST by June 16, 2017 and their spectral types were derived. Meanwhile stellar atmospheric parameters of 2020 EAs were determined. In the paper, those EAs are catalogued and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EWs indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs (0.4 < P < 1 days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may be formed through the combination of aforementioned mechanisms., Comment: 32 pages, 12 figures, accepted for publication in ApJS

1SWASP\,J162117.36$+$441254.2 was originally classified as an EW-type binary with a period of 0.20785\,days. However, it was detected to have undergone a stellar outburst on June 3, 2016. Although the system was latter classified as a cataclysmic variable (CV) and the event was attributed as a dwarf-nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since April 19, 2016 and many light curves were obtained before, during and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from April 19 to September 14, 2016, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the $L_1$ region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion., Comment: 16 pages, 6 figures, accepted for publication in ApJ

About 766 $\delta$ Scuti stars were observed by LAMOST by June 16, 2017. Stellar atmospheric parameters of 525 variables were determined, while spectral types were obtained for all samples. In the paper, those spectroscopic data are catalogued. We detect a group of 131 unusual and cool variable stars (UCVs) that are distinguished from the normal $\delta$ Scuti stars (NDSTs). On the H-R diagram and the $\log g-T$ diagram, the UCVs are far beyond the red edge of pulsational instability trip. Their effective temperatures are lower than 6700\,K with periods in the range from 0.09 to 0.22\,days. NDSTs have metallicity close to that of the Sun as expected, while UCVs are slightly metal poor than NDSTs. The two peaks on the distributions of the period and stellar atmospheric parameters are all caused by the existence of UCVs. When those UCVs are excluded, it is discovered that the effective temperature, the gravitational acceleration and the metallicity all are correlated with the pulsating period for NDSTs and their physical properties and evolutionary states are discussed. The detecting of those UCVs indicates that about 25\% of the known $\delta$ Scuti stars may be misclassified. However, if some of them are confirmed to be pulsating stars, they will be a new-type pulsator and their investigations will shed light on theoretical instability domains and on the theories of interacting between the pulsation and the convection of solar-type stars. Meanwhile, 88 $\delta$ Scuti stars are detected to be the candidates of binary or multiple systems., Comment: 15 pages, 16 figures, accepted for publication in MNRAS

Numerous EWs were discovered by several deep photometric survey and there are about 40785 EW-type binary systems listed in the international variable star index (VSX) by March 13, 2017. 7938 of them were observed by LAMOST by November 30, 2016 and their spectral types were given. Stellar atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic observations. In the paper, those EWs were catalogued and their properties are analyzed. The distributions of the orbital period (P), the effect temperature (T), the gravitational acceleration (Log(g)), the metallicity ([Fe/H]) and the radial velocity (RV) are presented for those observed EW-type systems. It is shown that about 80.6\% sample stars have metallicity below zero indicating that EW-type systems are old stellar population. This is in agreement with the the conclusion that the EW binaries are formed from moderately close binaries through angular momentum loss via magnetic braking that takes a few hundred million to a few billion years. The unusual high metallicities of a few percent of EWs may be caused by contaminating of material from the evolution of unseen neutron stars and black holes in the systems. The correlations between the orbital period and the effect temperature, the gravitational acceleration and the metallicity are presented and their scatters are mainly caused by (i) the presence of the third bodies and (ii) the wrong determined periods sometimes. It is shown that some EW contain evolved component stars and the physical properties of EWs are mainly depending on their orbital periods. It is found that the extremely short-period EWs may be older than their long-period cousins because they have lower metallicities. This reveals that they have a longer timescale of pre-contact evolution and their formation and evolution are mainly driven by angular momentum loss via magnetic braking., Comment: 20 pages, 16 figures; Accepted for publication in Research in Astronomy and Astrophysics (RAA)

We present the photometric results of the eclipsing cataclysmic variable (CV) WZ Sge near the period minimum ($P_{min}$). Eight new mid-eclipse times were determined and the orbital ephemeris was updated. Our result shows that the orbital period of WZ Sge is decreasing at a rate of $\dot{P}=-2.72(\pm0.23)\times{10^{-13}}\,s s^{-1}$. This secular decrease, coupled with previous detection of its donor, suggest that WZ Sge is a pre-bounce system. Further analysis indicates that the observed period decrease rate is about $1.53$ times higher than pure gravitational radiation (GR) driving. We constructed the evolutionary track of WZ Sge, which predicts that $P_{min}$ of WZ Sge is $\sim77.98 (\pm0.90)$ min. If the orbital period decreases at the current rate, WZ Sge will evolve past its $P_{min}$ after $\sim25.3$ Myr. Based on the period evolution equation we find $\dot{M}_{2}\simeq4.04(\pm0.10)\times10^{-11}M_{\odot}yr^{-1}$, which is compatible with the current concept of CV evolution at ultrashort orbital periods., Comment: 8 pages, 5 figures

DV UMa is an eclipsing dwarf nova with an orbital period of $\sim2.06$ h, which lies just at the bottom edge of the period gap. To detect its orbital period changes we present 12 new mid-eclipse times by using our CCD photometric data and archival data. Combining with the published mid-eclipse times in quiescence, spanning $\sim30$ yr, the latest version of the $O-C$ diagram was obtained and analyzed. The best fit to those available eclipse timings shows that the orbital period of DV UMa is undergoing a cyclic oscillation with a period of $17.58(\pm0.52)$ yr and an amplitude of $71.1(\pm6.7)$ s. The periodic variation most likely arises from the light-travel-time effect via the presence of a circumbinary object because the required energy to drive the Applegate mechanism is too high in this system. The mass of the unseen companion was derived as $M_{3}\sin{i'}=0.025(\pm0.004)M_{\odot}$. If the third body is in the orbital plane (i.e. $i'=i=82.9^{\circ}$) of the eclipsing pair, it would match to a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of $\sim8.6$ AU in an eccentric orbit ($e=0.44$)., Comment: 16 pages, 6 figures

The MINERvA experiment is designed to perform precision studies of neutrino-nucleus scattering using $\nu_\mu$ and ${\bar\nu}_\mu$ neutrinos incident at 1-20 GeV in the NuMI beam at Fermilab. This article presents a detailed description of the \minerva detector and describes the {\em ex situ} and {\em in situ} techniques employed to characterize the detector and monitor its performance. The detector is comprised of a finely-segmented scintillator-based inner tracking region surrounded by electromagnetic and hadronic sampling calorimetry. The upstream portion of the detector includes planes of graphite, iron and lead interleaved between tracking planes to facilitate the study of nuclear effects in neutrino interactions. Observations concerning the detector response over sustained periods of running are reported. The detector design and methods of operation have relevance to future neutrino experiments in which segmented scintillator tracking is utilized.

We report a study of muon neutrino charged-current quasi-elastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a {\mu}^- and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross-section, d{\sigma}/dQ^2, and study the low energy particle content of the final state. Deviations are found between the measured d{\sigma}/dQ^2 and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state., Comment: 7 pages, 5 figures. Added correlation between neutrino and anti-neutrino result in ancillary files (CSV)

We have isolated muon anti-neutrino charged-current quasi-elastic interactions occurring in the segmented scintillator tracking region of the MINERvA detector running in the NuMI neutrino beam at Fermilab. We measure the flux-averaged differential cross-section, d{\sigma}/dQ^2, and compare to several theoretical models of quasi-elastic scattering. Good agreement is obtained with a model where the nucleon axial mass, M_A, is set to 0.99 GeV/c^2 but the nucleon vector form factors are modified to account for the observed enhancement, relative to the free nucleon case, of the cross-section for the exchange of transversely polarized photons in electron-nucleus scattering. Our data at higher Q^2 favor this interpretation over an alternative in which the axial mass is increased., Comment: 8 pages, 5 figures. Added correlation between neutrino and anti-neutrino results in ancillary text files (CSV)

Magnetization noncollinearity in ferromagnet-superconductor (F/S) heterostructures is expected to enhance the superconducting transition temperature (Tc) according to the domain-wall superconductivity theory, or to suppress Tc when spin-triplet Cooper pairs are explicitly considered. We study the proximity effect in F/S structures where the F layer is a Sm-Co/Py exchange-spring bilayer and the S layer is Nb. The exchange-spring contains a single, controllable and quantifiable domain wall in the Py layer. We observe an enhancement of superconductivity that is nonmonotonic as the Py domain wall is increasingly twisted via rotating a magnetic field, different from theoretical predictions. We have excluded magnetic fields and vortex motion as the source of the nonmonotonic behavior. This unanticipated proximity behavior suggests that new physics is yet to be captured in the theoretical treatments of F/S systems containing noncollinear magnetization., Comment: 17 pages, 4 figures. Physical Review Letters in press

We report a comprehensive study of dc susceptibility, specific heat, neutron diffraction, and inelastic neutron scattering measurements on polycrystalline Ba3(Cr1-xVx)2O8 samples, where x=0, 0.06, 0.15, and 0.53. A Jahn-Teller structure transition occurs for x=0, 0.06, and 0.15 samples and the transition temperature is reduced upon vanadium substitution from 70(2) K at x=0 to 60(2) K at x=0.06 and 0.15. The structure becomes less distorted as x increases and such transition disappears at x=0.53. The observed magnetic excitation spectrum indicates that the singlet ground state remains unaltered and spin gap energy \Delta=1.3(1) meV is identical within the instrument resolution for all x. In addition, the dispersion bandwidth W decreases with increase of x. At x=0.53, W is reduced to 1.4(1) meV from 2.0(1) meV at x=0., Comment: 11 pages, 7 figures, some typos are corrected

We report here the discovery of an optical flare observed in R band from the red-dwarf eclipsing binary CU Cnc whose component stars are at the upper boundary of full convection (M1=0.43 and M2=0.4M0, M0 is the solar mass). The amplitude of the flare is the largest among those detected in R band (~0.52mag) and the duration time is about 73 minutes. As those observed on the Sun, quasi-periodic oscillations were seen during and after the flare. Three more R-band flares were found by follow up monitoring. In total, this binary was monitored photometrically by using R filter for 79.9 hours, which reveals a R-band flare rate about 0.05 flares per hour. These detections together with other strong chromospheric and coronal activities, i.e., very strong H_alpha and H_beta emission features and an EUV and X-ray source, indicate that it has very strong magnetic activity. Therefore, the apparent faintness (~1.4 magnitude in V) of CU Cnc compared with other single red dwarfs of the same mass can be plausibly explained by the high coverage of the dark spots., Comment: It will be published in MNRAS

Beams of neutrinos have been proposed as a vehicle for communications under unusual circumstances, such as direct point-to-point global communication, communication with submarines, secure communications and interstellar communication. We report on the performance of a low-rate communications link established using the NuMI beam line and the MINERvA detector at Fermilab. The link achieved a decoded data rate of 0.1 bits/sec with a bit error rate of 1% over a distance of 1.035 km, including 240 m of earth., Comment: 10 pages, 7 figures, updated with final figures used in Modern Physics Letters A publication

By using six new determined mid-eclipse times together with those collected from the literature, we found that the Observed-Calculated (O-C) curve of RR Cae shows a cyclic change with a period of 11.9 years and an amplitude of 14.3s, while it undergoes an upward parabolic variation (revealing a long-term period increase at a rate of dP/dt =+4.18(+-0.20)x10^(-12). The cyclic change was analyzed for the light-travel time effect that arises from the gravitational influence of a third companion. The mass of the third body was determined to be M_3*sin i' = 4.2(+-0.4) M_{Jup} suggesting that it is a circumbinary giant planet when its orbital inclination is larger than 17.6 degree. The orbital separation of the circumbinary planet from the central eclipsing binary is about 5.3(+-0.6)AU. The period increase is opposite to the changes caused by angular momentum loss via magnetic braking or/and gravitational radiation, nor can it be explained by the mass transfer between both components because of its detached configuration. These indicate that the observed upward parabolic change is only a part of a long-period (longer than 26.3 years) cyclic variation, which may reveal the presence of another giant circumbinary planet in a wide orbit., Comment: It will be published in the MNRAS

We examine the anomalous inverse spin switch behavior in La$_{0.7}$Ca$_{0.3}$MnO$_3$ (LCMO)/YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO)/LCMO trilayers by combined transport studies and polarized neutron reflectometry. Measuring magnetization profiles and magnetoresistance in an in-plane rotating magnetic field, we prove that, contrary to many accepted theoretical scenarios, the relative orientation between the two LCMO's magnetizations is not sufficient to determine the magnetoresistance. Rather the field dependence of magnetoresistance is explained by the interplay between the applied magnetic field and the (exponential tail of the) induced exchange field in YBCO, the latter originating from the electronic reconstruction at the LCMO/YBCO interfaces., Comment: Total 7 pages,with Supplemental Material. Accepted for publication in Physical Review Letters

We report here the tentative discovery of a Jovian planet in orbit around the rapidly pulsating subdwarf B-type (sdB-type) eclipsing binary NY Vir. By using new determined eclipse times together with those collected from the literature, we detect that the observed-calculated (O-C) curve of NY Vir shows a small-amplitude cyclic variation with a period of 7.9\,years and a semiamplitude of 6.1\,s, while it undergoes a downward parabolic change (revealing a period decrease at a rate of $\dot{P}=-9.2\times{10^{-12}}$). The periodic variation was analyzed for the light-travel time effect via the presence of a third body. The mass of the tertiary companion was determined to be $M_3\sin{i^{\prime}}=2.3(\pm0.3)$\,$M_{Jupiter}$ when a total mass of 0.60\,$M_{\odot}$ for NY Vir is adopted. This suggests that it is most probably a giant circumbinary planet orbiting NY Vir at a distance of about 3.3 astronomical units (AU). Since the rate of period decrease can not be explained by true angular momentum loss caused by gravitational radiation or/and magnetic braking, the observed downward parabolic change in the O-C diagram may be only a part of a long-period (longer than 15 years) cyclic variation, which may reveal the presence of another Jovian planet ($\sim2.5$$M_{Jupiter}$) in the system., Comment: 12 pages, 3 figures, accepted by ApJ Letters

We use local and global magnetometry measurements to study the influence of magnetic domain width w on the domain-induced vortex pinning in superconducting/ferromagnetic bilayers, built of a Nb film and a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy, with an insulating layer to eliminate proximity effect. The quasi-periodic domain patterns with different and systematically adjustable width w, as acquired by a special demagnetization procedure, exert tunable vortex pinning on a superconducting layer. The largest enhancement of vortex pinning, by a factor of more than 10, occurs when w ~ 310 nm is close to the magnetic penetration depth., Comment: 5 pages, 3 figures, accepted to Phys. Rev. B, Rapid Communications

The new discovered short-period close binary star, XY LMi, was monitored photometrically since 2006. It is shown that the light curves are typical EW-type and show complete eclipses with an eclipse duration of about 80 minutes. By analyzing the complete B, V, R, and I light curves with the 2003 version of the W-D code, photometric solutions were determined. It is discovered that XY LMi is a high fill-out, extreme mass ratio overcontact binary system with a mass ratio of q=0.148 and a fill-out factor of f=74.1%, suggesting that it is on the late evolutionary stage of late-type tidal-locked binary stars. As observed in other overcontact binary stars, evidence for the presence of two dark spots on both components are given. Based on our 19 epoches of eclipse times, it is found that the orbital period of the overcontact binary is decreasing continuously at a rate of dP/dt=-1.67\times10^{-7}\,days/year, which may be caused by the mass transfer from the primary to the secondary or/and angular momentum loss via magnetic stellar wind. The decrease of the orbital period may result in the increase of the fill-out, and finally, it will evolve into a single rapid-rotation star when the fluid surface reaching the outer critical Roche Lobe., Comment: 19 pages, 4 figures, 9 tables

Using the precise times of mid-egress of the eclipsing polar HU Aqr, we discovered that this polar is orbited by two or more giant planets. The two planets detected so far have masses of at least 5.9 and 4.5\,M_{Jup}. Their respective distances from the polar are 3.6 AU and 5.4 AU with periods of 6.54 and 11.96 years, respectively. The observed rate of period decrease derived from the downward parabolic change in O-C curve is a factor 15 larger than the value expected for gravitational radiation. This indicates that it may be only a part of a long-period cyclic variation, revealing the presence of one more planet. It is interesting to note that the two detected circumbinary planets follow the Titus-Bode law of solar planets with n=5 and 6. We estimate that another 10 years of observations will reveal the presence of the predicted third planet., Comment: 13 pages, 4 figures, 2 tables

We have observed the evolution of phase diagram and vortex pinning using a single ferromagnet/superconductor bilayer of [Co/Pt]8/Nb through a special demagnetization procedure. It induces a continuous and reversible change of the domain width with equal positive/negative domains enabling the observation of the predicted tunable phase diagram. The tunable domain pattern also systematically affects vortex pinning. We have determined the dependence of the activation energy of vortex pinning on domain width, temperature, and magnetic field., Comment: 17 pages, 4 figures

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range $4.5 < m_{\mu \mu} < 15$ GeV/c$^2$ (excluding the $\Upsilon$ resonance region), $0 < p_T < 4 $ GeV/c, and $0 < x_F < 0.8$. The $p+p$ angular distributions are similar to those of $p+d$, and both data sets are compared with models which attribute the $\cos 2 \phi$ distribution either to the presence of the transverse-momentum-dependent Boer-Mulders structure function $h_1^\perp$ or to QCD effects. The data indicate the presence of both mechanisms. The validity of the Lam-Tung relation in $p+p$ Drell-Yan is also tested., Comment: 4 pages, 3 figures

We report on the design and commissioning of two silica aerogel Cherenkov detectors with different refractive indices. In particular, extraordinary performance in terms of the number of detected photoelectrons was achieved through an appropriate choice of PMT type and reflector, along with some design considerations. After four years of operation, the number of detected photoelectrons was found to be noticeably reduced in both detectors as a result of contamination, yellowing, of the aerogel material. Along with the details of the set-up, we illustrate the characteristics of the detectors during different time periods and the probable causes of the contamination. In particular we show that the replacement of the contaminated aerogel and parts of the reflecting material has almost restored the initial performance of the detectors., Comment: 18 pages, 9 Figures, 4 Tables, 44 References

We report a high statistics measurement of Upsilon production with an 800 GeV/c proton beam on hydrogen and deuterium targets. The dominance of the gluon-gluon fusion process for Upsilon production at this energy implies that the cross section ratio, $\sigma (p + d \to \Upsilon) / 2\sigma (p + p\to \Upsilon)$, is sensitive to the gluon content in the neutron relative to that in the proton. Over the kinematic region 0 < x_F < 0.6, this ratio is found to be consistent with unity, in striking contrast to the behavior of the Drell-Yan cross section ratio $\sigma(p+d)_{DY}/2\sigma(p+p)_{DY}$. This result shows that the gluon distributions in the proton and neutron are very similar. The Upsilon production cross sections are also compared with the p+d and p+Cu cross sections from earlier measurements., Comment: 4 pages, 5 figures. Submitted for journal publication

Recent experiments introducing controlled disorder into optimally doped cuprate superconductors by both electron irradiation and chemical substitution have found unusual behavior in the rate of suppression of the critical temperature Tc vs. increase in residual resistivity. We show here that the unexpected discovery that the rate of Tc suppression vs. resistivity is stronger for out-of-plane than for in-plane impurities may be explained by consistent calculation of both Tc and resistivity if the potential scattering is assumed to be nearly forward in nature. For realistic models of impurity potentials, we further show that significant deviations from the universal Abrikosov-Gor'kov Tc suppression behavior may be expected for out of plane impurities., Comment: 6 pages, 5 figures

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a deuterium target. The muon angular distributions in polar angle $\theta$ and azimuthal angle $\phi$ have been measured over the kinematic range $4.5 < m_{\mu \mu} < 15$ GeV/c$^2$, $0 < p_T < 4 $ GeV/c, and $0 < x_F < 0.8$. No significant cos$2\phi$ dependence is found in these proton-induced Drell-Yan data, in contrast to the situation for pion-induced Drell-Yan. The data are compared with expectations from models which attribute the cos$2\phi$ distribution to a QCD vacuum effect or to the presence of the transverse-momentum-dependent Boer-Mulders structure function $h_1^\perp$. Constraints on the magnitude of the sea-quark $h_1^\perp$ structure functions are obtained., Comment: 4 pages, 3 figures

The differential cross section for the gamma +n --> pi- + p and the gamma + p --> pi+ n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The pi- and pi+ photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi+ data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams., Comment: 18 pages, 19 figures

We present analytical and numerical results for the electronic spectra of wires of a d-wave superconductor on a square lattice. The spectra of Andreev and other quasiparticle states, as well as the spatial and particle-hole structures of their wave functions, depend on interference effects caused by the presence of the surfaces and are qualitatively different for half-filled wires with even or odd number of chains. For half-filled wires with an odd number of chains N at (110) orientation, spectra consist of N doubly degenerate branches. By contrast, for even N wires, these levels are split, and all quasiparticle states, even the ones lying above the maximal gap, have the characteristic properties of Andreev bound states. These Andreev states above the gap can be interpreted as a consequence of an infinite sequence of Andreev reflections experienced by quasiparticles along their trajectories bounded by the surfaces of the wire. Our microscopic results for the local density of states display atomic-scale Friedel oscillations due to the presence of the surfaces, which should be observable by scanning tunneling microscopy. For narrow wires the self-consistent treatment of the order parameter is found to play a crucial role. In particular, we find that for small wire widths the finite geometry may drive strong fluctuations or even stablilize exotic quasi-1D pair states with spin triplet character., Comment: 21 pages, 20 figures. Slightly modified version as published in PRB

We have measured the differential cross section for the gamma n --> pi- p and gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon energies greater than 3.3 GeV exhibit a global scaling behavior for both pi- and pi+ photoproduction, consistent with the constituent counting rule and the existing pi+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi- to pi+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.