Periodic Variation Studies of the Two Short Period W UMa-type Eclipsing Binaries: LX Lyn and V0853 Aur

In this paper,new light curves(LCs) of contact eclipsing binary(CEB) systems LX Lyn and V0853 Aur are presented and analyzed by using the 2015 version of the Wilson-Devinney(W-D) code.In order to explain their asymmetric LCs,cool starspots on the components were employed.It is suggested that their fill-out degrees are f=12.0%(LX Lyn) and f=26.3%(V0853 Aur).At the same time,we found that LX Lyn is a W-type eclipsing binary(EB) with an orbital inclination of i=84°.88 and a mass ratio of q=2.31.V0853 Aur is also a W-type CEB with a mass ratio of q=2.77 and an orbital inclination of i= 79°.26.Based on all available times of light minimum,their orbital period changes are studied by using the O-C method.The O-C diagram of LX Lyn reveals a cyclic oscillation with a period of about 14.84 yr and an amplitude of 0.0019 days,which can be explained by the light-travel time effect(LTTE) due to the presence of a third body with a minimum mass of0.06M_⊙.For V0853 Aur,it is discovered that the O-C diagram of the system also shows a cyclic oscillation with a period of 9.64 yr and an amplitude of 0.03365 days.The cyclic oscillation of V0853 Aur can be attributed to the LTTE by means of a third body with a mass no less than 3.77M_⊙.The third body may play an important role in the formation and evolution of these systems.

Period Investigation on Two W UMa Binaries HH UMa and V1175 Her

HH UMa and V1175 Her are two W UMa contact binary systems whose periods were reported as undergoing secular increase.In this paper,we improved their period analyses with a more extensive database of eclipse timings,finding that both periods show cyclic variation.The cyclic variation could be attributed to a Light Travel Time Effect induced by a third body.Both circular orbit and eccentric orbit cases were considered.For HH UMa,the cyclic variation with a period of around 20 yr has been detected,which may be caused by a third body with the mass larger than 0.23 M_(⊙).However,no parabolic variation was detected in its O−C curve,implying the balance of the mass transfer between the two components and the angular momentum loss from the binary system.As to V1175 Her,a long-term period increase superposed on a periodic oscillation was detected.The period increase with a rate of about dP/dt=2×10^(-7)day yr^(−1)indicates the mass transfer from the less massive component to its companion.The cyclic variation of about 7.5 yr could be caused by a hierarchical third body with a minimal mass exceeding 0.46M_(⊙)orbiting around the central binary.This mass is larger than that of the less massive component of the binary,which means that the secondary component was not replaced by the third body during early stellar interactions,implying that it keeps original dynamical information.By removing angular momentum from the central binary system,the tertiary component has played a significant role in the formation of contact binaries.

Physical Parameters of W UMa Type Contact Binaries and Their Stability of Mass Transfer

In this study,we determined the physical parameters of W UMa type contact binaries and their stability of mass transfer with different stellar mass ranges over a broad space by applying the basic dynamical evolution equations of the W UMa type contact binaries using accretor and donor masses between 0.079 and 2.79 M_(⊙).In these systems,we have studied the three subclasses of W UMa systems of A-,B-and W-type contact binaries using the initial and final mass ranges and we investigated different stellar and orbital parameters for the subclasses of W UMa systems.We examined the stability of the W UMa type contact binaries using the orbital parameters such as critical mass ratio,Roche lobe radius of the donor star and mass ratio of these systems.Thus,we computed the observed and calculated physical parameters of A-,B-and W-type W UMa systems.Moreover,we determined the combined and color temperatures to classify the three subclasses of the systems.Also,we presented the result of the internal stellar structure and evolution of W UMa type contact binaries by using the polytropic model.

Formation and Destiny of White Dwarf and Be Star Binaries

The binary systems consisting of a Be star and a white dwarf(Be WDs) are very interesting.They can originate from the binaries composed of a Be star and a subdwarf O or B star(Besd OBs),and they can merge into red giants via luminous red nova or can evolve into double WD potentially detected by the LISA mission.Using the method of population synthesis,we investigate the formation and the destiny of Be WDs,and discuss the effects of the metallicity(Z) and the common envelope evolution parameters.We find that Besd OBs are significant progenitors of Be WDs.About 30%(Z = 0.0001)-50%(Z = 0.02) of Be WDs come from Besd OBs.About 60%(Z = 0.0001)-70%(Z = 0.02) of Be WDs turn into red giants via a merger between a WD and a non-degenerated star.About 30%(Z = 0.0001)-40%(Z = 0.02) of Be WDs evolve into double WDs which are potential gravitational waves of the LISA mission at a frequency band between about 3 × 10^(-3)and 3 × 10^(-2)Hz.The common envelope evolution parameter introduces an uncertainty with a factor of about 1.3 on Be WD populations in our simulations.

The Width-Flux Relation of the Broad Iron KαLine during the State Transitions of the Black Hole X-Ray Binaries

The observations of varying broad iron lines during the state transition of the black hole X-ray binaries have been accumulating.In this work,the relation between the normalized intensity and the width of iron lines is investigated,in order to understand better the variation of iron lines and possibly its connection to state transition.Considering the uncertainties due to ionization and illuminating X-rays,only the effects of geometry and gravity are taken into account.Three scenarios were studied,i.e.,the continuous disk model,the innermost annulus model,and the cloud model.As shown by our calculations,at given iron width,the line flux of the cloud model is smaller than that of the continuous disk model;while for the innermost annulus model,the width is almost unrelated with the flux.The range of the line strength depends on both the BH spin and the inclination of the disk.We then apply to the observation of MAXI J1631-479 by Nuclear Spectroscopic Telescope Array during its decay from the soft state to the intermediate state.We estimated the relative line strength and width according to the spectral fitting results in Xu et al.,and then compared with our theoretical width-flux relation.It was found that the cloud model was more favored.We further modeled the iron line profiles,and found that the cloud model can explain both the line profile and its variation with reasonable parameters.

NuSTAR View of the R-ΓCorrelation in the Hard State of Black Hole Lowmass X-Ray Binaries

The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from these two types of sources.The relevant parameters describing the shape of both components and the potential correlation between these parameters can provide important clues on the geometric and physical properties of the disk and the corona in these sources.In this work,we present a positive correlation between the photon indexΓand the reflection strength R for the low-mass BHXRBs in the hard state by modeling NuSTAR data,which is qualitatively consistent with the previous studies.We compare our results with the predictions from different theoretical disk-corona models.We show that the RIT correlation found in this work seems to favor the moving corona model proposed by Beloborodov.Our results indicate that the coronal geometry varies significantly among BHXRBs.We further compare our results with that of AGNs.We find that the reflection strength R is smaller than unity in the hard state of BHXRBs,while it can be as large as~5 in AGNs,which implies that the variations of the disk-coronal geometry of AGNs are more vigorous than that of the BHXRBs in the hard state.

Fractions of Compact Object Binaries in Star Clusters:Theoretical Predictions

The binary population in field stars and star clusters contributes to the formation of gravitational wave(GW)sources.However,the fraction of compact-object binaries(CBs),which is an important feature parameter of binary populations,is still difficult to measure and very uncertain.This paper predicts the fractions of important CBs and semi-compact object binaries(SCBs) making use of an advanced stellar population synthesis technique.A comparison with the result of N-body simulation is also presented.It is found that most CBs are formed within about 500 Myr after the starburst.The fractions of CBs and SCBs are demonstrated to correlate with stellar metallicity.The higher the metallicity becomes,the smaller the fraction of black hole binaries(BHBs),neutron star binaries(NSBs) and SCBs.This suggests that the GW sources of BHBs and NSBs are more likely to form in metal-poor environments.However,the fraction of black hole-neutron star binaries is shown to be larger for metalrich populations on average.

Physical properties and catalog of EW-type eclipsing binaries observed byLAMOST

EW-type eclipsing binaries(hereafter called EWs)are strong interacting systems in which both component stars usually fill their critical Roche lobes and share a common envelope.Numerous EWs were discovered by several deep photometric surveys and there were about 40 785 EW-type binary systems listed in the international variable star index(VSX)by 2017 March 13.7938 of them were observed with LAMOST by 2016 November 30 and their spectral types were identified.Stellar atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic observations.In the paper,those EWs are cataloged and their properties are analyzed.The distributions of orbital period(P),effective temperature(T),gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(RV)are presented for these observed EW-type systems.It is shown that about 80.6% of sample stars have metallicity below zero,indicating that EW-type systems are old stellar populations.This is in agreement with the conclusion that 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 unusually high metallicities of a few percent of EWs may be caused by contamination of material from the evolution of unseen neutron stars or black holes in the systems.The correlations between orbital period and effective temperature,gravitational acceleration and metallicity are presented and their scatters are mainly caused by(i)the presence of third bodies and(ii)sometimes wrongly determined periods.It is shown that some EWs contain evolved component stars and the physical properties of EWs mainly depend on their orbital periods.It is found that 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.

Spin Evolution of Neutron Stars in OB/X-ray Binaries

We have investigated the relation between the orbital period Porb and the spin period Ps of neutron stars in OB/X-ray binaries. By simulating the time-development of the mass loss rate and radius expansion of a 20M☉ donor star, we have calculated the detailed spin evolution of the neutron star before steady wind accretion occurs (that is, when the break spin period is reached), or when the OB star begins evolving off the main sequence or has filled its Roche lobe. Our results are compatible with the observations of OB/X-ray binaries. We find that in relatively narrow systems with orbital periods less than tens of days, neutron stars with initial magnetic field B0 stronger than about 3×1012 G can reach the break spin period to allow steady wind accretion in the main sequence time, whereas neutron stars with B0 < 3×1012 G and/or in wide systems would still be in one of the pulsar, rapid rotator or propeller phases when the companion evolves off the main sequence or fills its Roche lobe. Our results may help understand the various characteristics of the observed OB/neutron star binaries along with their distributions in the Ps-Porb diagram.

Photometric study of eclipsing binaries in the Large Magellanic Cloud--I.W UMa type binaries in the Large Magellanic Cloud

Eclipsing binaries are among the most important sources of information on stellar parameters like radii,masses,luminosities,etc.We present the analysis of six W UMa systems discovered in the Large Magellanic Cloud using the Wilson-Devinney method.

Photometric investigation and orbital period analyses of the W UMa binaries FP Lyn, FV CVn and V354 UMa

New light curves and photometric solutions of FP Lyn,FV CVn and V354 UMa are presented.We found that these three systems are W-subtype shallow contact binaries.In addition,it is obvious that the light curves of FP Lyn and V354 UMa are asymmetric.Therefore,a hot spot was added on the primary star of FP Lyn and a dark spot was added on the secondary star of V354 UMa.At the same time,we added a third light to the photometric solution of FP Lyn for the final result.The obtained mass ratios and fill-out factors are q = 1.153 and f = 13.4% for FP Lyn,q = 1.075 and f = 4.6% for FV CVn,and q = 3.623 and f = 10.7% for V354 UMa respectively.The investigations of orbital period for these three systems indicate that the periods are variable.FP Lyn and V354 UMa were discovered to have secularly increasing components with rates of dp/dt = 4.19 ×10^-7 dyr^-1 and dp/dt = 7.70 ×10^-7 dyr^-1 respectively,which are feasibly caused by conservative mass transfer from the less massive component to the more massive component.In addition,some variable components were discovered for FV CVn,including a rate of dp/dt =-1.13 ×10^-6 dyr^-1 accompanied by a cyclic oscillation with amplitude and period of 0.0069 d and 10.65 yr respectively.The most likely explanation for the long-term decrease is angular momentum loss.The existence of an additional star is the most plausible explanation for the periodic variation.

Morphological Assessment of the Small Intestine of Broilers Fed Dietary Natural Zeolite Including Plant Extract

Many kinds of feed additives （e.g., probiotics, prebiotics, antibiotics, etc.） can be used in chicken diets to stimulate intestinal morphological maturation and, consequently, intestinal function. The aim of this trial was to investigate the possibility that natural zeolite including plant extract （ZEM） could encourage the hypertrophy of intestinal villi and the absorptive function of epithelial cells in broiler chickens. At 7 days old, 64 male Marshall Chunky broilers were divided into four groups, each with four replicates of four chickens. The birds were fed a basal mash diet supplemented with ZEM at 0% （control）, 0.05%, 0.1%, and 0.2% for 42 days. At 49 days old, four chickens from each treatment were killed to obtain intestinal samples. Morphological intestinal assessment was conducted using both a light and a scanning electron microscope. A tendency to increased villus height and cell area could be observed throughout the intestinal segments of the broilers fed ZEM. Particularly, the villus height in the duodenum was significantly increased （P 〈 0.05） in the 0.05% ZEM group when compared with the control group. The area of the villus cells tended to be higher in the ZEM groups in all intestinal regions and showed a significant increase （P 〈 0.05） in the ileal part of the 0.2% ZEM group. Also, the assessment of cells mitosis in the intestinal crypts showed significantly higher numbers （P 〈 0.05） in all levels of ZEM groups in the duodenum and a tendency to increase in value in the jejunum and ileum, as compared with the control group. More protuberated cells and multi-cell clusters were found in the ZEM groups than in the control group, resulting in a rough cellular surface. In conclusion, the present study might suggest that the intestinal villi and epithelial cells on the villus apical surface are hypertrophied in the ZEM groups, and that intestinal villi adapt to enhance their absorption capacity by increasing the absorptive surface area. These results are indicated that ZEM can provide effective nutritive value when used as a feed additive.

The W UMa binaries USNO-A2.0 1350-17365531,V471 Cas,V479 Lac and V560 Lac:light curve solutions and global parameters based on Gaia distances

We present photometric observations in Sloan filters g′, i′of the eclipsing W UMa stars USNOA2.0 1350-17365531, V471 Cas, V479 Lac and V560 Lac. The sinusoidal-like O-C diagram of V471 Cas indicates the presence of a third body with mass 0.12 M_⊙(a red dwarf) at distance 897 R_⊙. The O-C diagram of V479 Lac reveals a period decrease of d P/dt =-1.69 × 10-6d yr-1. The results of the light curve solutions are:(i) the targets are overcontact binaries with small fill-out factors;(ii) their components are F–K stars, comparable in size, whose temperature differences are below 80 K;(iii) all targets undergo partial eclipses and to limit the possible mass ratios we carried out two-step q-search analysis. The target global parameters(luminosities, radii, masses) were obtained on the basis of their Gaia distances and the results of our light curve solutions. The obtained total mass of V560 Lac turns out to be smaller than the lower mass limit for presently known W UMa binaries of 1.0-1.2 M_⊙, i.e. this target is a peculiar overcontact system.

Chaos in Compact Binaries with Frequency Map Analysis

The dynamics of compact binaries is very complicated because of spin-orbit cou- pling and spin-spin coupling. With Laskar＇s frequency map analysis （FMA） and frequency diffusion as an indicator, we found that misalignment of the spins and orbital angular momentum has a great effect on the dynamics, and for systems with different mass ratios β = m2/ml chaos occurs at different spin-orbit configurations. For equal-mass binaries （β = 1）, chaos occurs when the spins nearly cancel each other out. For some other systems （for exampleβ - 1/2）, the binaries are irregular, even chaotic, when the spins are perpendicular to the orbital angular momentum. For the case where gravitational radiation is taken into account, we give an analytic estimation for the frequency diffusion based on the decay of the orbit, which is roughly consistent with our simulations. This means the FMA is not suitable as a chaos indicator for weak chaotic cases with dissipative terms.

Contact binaries at different evolutionary stages

Contact binaries consist of two strongly interacting component stars where they are filling their critical Roche lobes and sharing a common envelope.Most of them are main-sequence stars,but some of them are post main-sequence systems.They are good astrophysical laboratories for studying several problems such as the merging of binary stars,evolution of the common envelope,the origin of luminous red nova outbursts and the formation of rapidly rotating single stars with possible planetary systems.A large number of contact binary candidates were detected by several photometric surveys around the world and many of them were observed by the LAMOST spectroscopic survey.Based on follow-up observations,the evolutionary states and geometrical structures of some systems were understood well.In this review,we will introduce and catalog new stellar atmospheric parameters(i.e.,the effective temperature(Teff),the gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(Vr))for 9149 EW-type contact binaries that were obtained based on low-and medium-resolution spectroscopic surveys of LAMOST.Then we will focus on several groups of contact binary stars,i.e.,marginal contact binary systems,deep and low-mass ratio contact binary stars,binary systems below the short-period limit of contact binaries and evolved contact binaries.Marginal contact binaries are at the beginning of the contact stage,while deep and low-mass ratio contact binary stars are at the final evolutionary stage of tidally locked binaries.Several statistical relations including the period-temperature relation are determined well by applying LAMOST data and their formation and evolutionary states are reviewed.The period-color relation of M-type binaries reveals that there are contact binaries below the short-period limit.Searching for and investigating contact binaries near and below this limit will help us to understand the formation of contact binary systems and a new prediction for the short-period limit is about 0.15 d.Some evolved contact binaries were detected by the LAMOST survey where both components are sub-giants or giants.They provide a good opportunity to investigate evolution of the common envelope and are the progenitors of luminous red novae like V1309 Sco.

Gravitational Radiation of Binaries Coalescence into Intermediate Mass Black Holes

This paper discusses the gravitation waveforms of binaries coalescence into intermediate mass black holes(about 30 times of the solar mass).We focus on the non-spinning intermediate mass black hole located less than 100 Mpc from earth.By comparing two simulation waveforms(effective one body numerical relativity waveform(EOBNR),phenomenological waveform),we discuss the relationship between the effective distance and frequency;and through analyzing large amounts of data in event,we find that the phenomenological waveform is much smoother than EOBNR waveform,and has higher accuracy at the same effective distance.

Anterior transhepatic approach for total caudate lobectomy including spigelian lobe,paracaval portion and caudate process:A Brazilian experience

To the Editor:Nowadays,because of the infiltration of cholangiocarcinoma to the parenchyma and/or bile ducts of the caudate lobe,the inclusion of caudate lobe combined with a major hepatectomy remains the gold standard approach for a resectable hilar cholangiocarcinoma.Since the last years of the 20th century,some authors have begun to report isolated caudate lobe resection for hepatocellular

Photometric study of W UMa type binaries in the old open cluster Berkeley 39

The study of W UMa binary systems gives a wealth of information about their nature as well as their parent bodies （if any）, like clusters. In this paper, we present the I passband photometric solutions of four W UMa binaries in the open cluster Berkeley 39 using the latest version of the W-D program. The result shows that two binary systems are W-subtype W UMa binary systems and the other two systems are H-subtype W UMa binary systems. No third body has been found in any of the four systems. We found a correlation between the period and mass-ratio as well as temperature and mass-ratio for the respective variables, which is similar to the relationship between mass ratio and total mass of the contact binaries as shown by van＇t Veer and Li et al.

Investigations into the thermal non-equilibrium of W UMa-type contact binaries

Traditionally, some physical details（e.g., magnetic braking, energy transfer, angular momentum loss, etc.） have to be taken into consideration during investigations into the evolution of contact binaries. However, the real evolutionary processes which usually contain several of these physical mechanisms are very complicated as a result of strong interaction between components. To avoid dealing with these factors, a linear relationship is applied to the temperatures of components. It is found that the higher the mass ratio（M2/M1） of a contact system, the weaker the deviation from thermal equilibrium.On this basis, a variation trend of fill-out factor（f） changing with mass ratio can be inferred, which is consistent with observations. Moreover, if we stick to this point of view, it should be natural that the number of semi-detached binaries in the predicted broken-contact phase of relaxation oscillations is less than the number in the contact phase.

A Precise Description of the Electronic Structures and Spin-Allowed Transition Properties of PF and Its Cation:All-Electron Configuration-Interaction Investigations Including Relativistic Effect

The electronic structures of PF and PF＋ are calculated with the high-level configuration interaction method. To improve the precision of calculations, the spin-orbit coupling effect, the scalar relativistic effect, and the Davidson correction（q-Q） are also considered. The spectroscopic parameters of bound states are derived by the electronic structures of PF and PF＋, which are in good accordance with the measurements. The transition dipole moments of spin-allowed transitions are evaluated, and the radiative lifetimes of several A S states of PF and PF＋ are obtained.