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.

Observations and light curve solutions of a selection of middle-contact W UMa binaries

Photometric observations in Sloan g′and i′ bands of W UMa binaries NSVS 4340949,T-Dra0–00959,GSC 03950–00707,NSVS 4665041,NSVS 4803568,MM Peg,MM Com and NSVS4751449 are presented.The light curve solutions revealed that the components of each target are of G and K spectral types.The binaries of the sample have middle-contact configurations whose fillout factors are within the range 0.2–0.4.The only exception is NSVS 4751449 which is in deeper contact（fillout factor of 0.55）.It precisely obeys the relation between mass ratio and fillout factor for deep,low mass ratio overcontact binaries.One of the eclipses of almost all targets（except MM Peg）is an occultation and their photometric mass ratios and solutions could be accepted with confidence.We found that the target components have almost equal temperatures but differ considerably in size and mass.The components of the partially-eclipsed MM Peg have close parameters.Our solutions reveal that NSVS 4340949,T-Dra0–00959,NSVS 4803568 and MM Com are of W subtype while GSC 03950–00707,NSVS 4665041,MM Peg and NSVS 4751449 are of A subtype.This subclassification is well-determined for all totallyeclipsed binaries.The targets confirm the trends in which W-subtype systems have smaller periods and lower temperatures than A subtype binaries.

Photometric investigations on two totally eclipsing contact binaries:V342 UMa and V509 Cam

By analyzing two sets of complete BV Rc Ic light curves for V342 UMa and three sets of complete BV Rc Ic light curves for V509 Cam, we determined that the two systems are both W-subtype contact binaries and that V342 UMa manifests a shallow contact configuration, while V509 Cam exhibits a medium contact configuration. Given that both of them are totally eclipsing binaries, the physical parameters derived only by the photometric light curves are reliable. Meanwhile, the period changes of the two targets were analyzed based on all available eclipsing times. We discovered that V342 UMa shows long-term period decrease with a rate of-1.02(±0.54)× 10^-7 d yr^-1 and that V509 Cam displays long-term period increase with a rate of 3.96(±0.90)× 10^-8 d yr^-1. Both the conservative mass transfer and angular momentum loss via magnetic stellar winds can be used to interpret the long-term period decrease of V342 UMa. The longterm period increase of V509 Cam can be explained by mass transfer from the less massive star to the more massive one. The absolute parameters of the two binaries were estimated according to their Gaia distances and our derived photometric solution results. This method can be extended to other contact binaries without radial velocities but with reliable photometric solutions. Their evolutionary states were investigated and we found that they reveal properties that are identical to other W-subtype contact systems.

On the possibility of disk-fed formation in supergiant high-mass X-ray binaries

We consider the existence of a neutron star magnetic field by the detected cyclotron lines. We collected data on nine sources of high-mass X-ray binaries with supergiant companions as a test case for our model, to demonstrate their distribution and evolution. The wind velocity, spin period and magnetic field strength are studied under different mass loss rates. In our model, correlations between mass-loss rate and wind velocity are found and can be tested in further observations. We examine the parameter space where wind accretion is allowed, avoiding the barrier of rotating magnetic fields, with robust data on the magnetic field of neutron stars. Our model shows that most sources(six of nine systems) can be fed by the wind with relatively slow velocity, and this result is consistent with previous predictions. In a few sources,our model cannot fit the standard wind accretion scenario. In these peculiar cases, other scenarios(disk formation, partial Roche lobe overflow) should be considered. This would provide information about the evolutionary tracks of various types of binaries, and thus exhibit a clear dichotomy behavior in wind-fed X-ray binary systems.

Observations and light curve solutions of the W UMa binaries V796 Cep,V797 Cep,CSS J015341.9+381641 and NSVS 3853195

Photometric observations in Sloan g′and i′bands of four W UMa binaries, V796 Cep,V797 Cep, CSS J015341.9＋381641 and NSVS 3853195, are presented. Our observations showed that CSS J015404.1＋382805 and NSVS 3853195 are the same star. We determined the initial epochs T_0 of all targets and found improved values for the period of NSVS 3853195. The light curve solutions of our data revealed that the components of each target are almost the same in terms of mass, temperature,radius and luminosity. The stellar components are G and K spectral types and undergo partial eclipses.All systems have barely-overcontact configurations and can be classified as H subtype W UMa binaries.We established that the relation between the luminosity ratio l_2/l_1 and mass ratio q of our targets is approximately l_2/l_1 = q^（1.5）.

Light curve solutions of six eclipsing binaries at the lower limit of periods for W UMa stars

Photometric observations are presented in V and I bands of six eclipsing binaries at the lower limit of the orbital periods for W UMa stars. Three of them are newly discovered eclipsing systems. The light curve solutions reveal that all shortperiod targets are contact or overcontact binaries and six new binaries are added to the family of short-period systems with estimated parameters. Four binaries have com- ponents that are equal in size and a mass ratio near 1. The phase variability shown by the V-I colors of all targets may be explained by lower temperatures on their back surfaces than those on their side surfaces. Five systems exhibit the O＇Connell effect that can be modeled by cool spots on the side surfaces of their primary components. The light curves of V1067 Her in 2011 and 2012 are fitted by diametrically opposite spots. Applying the criteria for subdivision of W UMa stars to our targets leads to ambiguous results.

New photometric studies for two deep,low-mass ratio overcontact binaries:Y Sex and V1363Ori

We present new photometry for two contact binaries,Y Sex and V1363 Ori,which were observed by three small telescopes in China.By using the W-D method,the absolute parameters are updated from new BVR light curves and previous radial velocity curves.Results identify that two binaries are deep,lowmass ratio(DLMR)overcontact binaries with q≤0.25 and f≥50%.From the temperature-luminosity diagram,the primary components are slightly evolved main-sequence stars,whose evolutionary ages are~2.51 Gyr for Y Sex and~3.56 Gyr for V 1363 Ori,respectively.From the(O-C)curves,it is found that the orbital periods may be undergoing secular increase with cyclic variations,which may be interpreted either by magnetic activity cycles or by the light-time orbit effect.With period increasing,this kind of DLMR overcontact binaries,such as Y Sex and V1363 Ori,will evolve into the rapid-rotating single stars.

New Apsidal Motion in Four Eccentric Eclipsing Binaries:V610 Car,V944 Cep,V2815 Ori and V1260 Tau

This paper presents an apsidal motion analysis.The apsidal motion analysis of the eccentric eclipsing binaries V610 Car(P=4.84 days),V944 Cep(P=6.56 days),V2815 Ori(P=2.13 days),and V1260 Tau(P=5.43 days)was performed using minima times from the O-C Gateway database,ASAS-3,ASAS-SN,and TESS,following Lacy’s approach.The rates of change of periastron longitude were found to be 0.0253±0.0041,0.0347±0.0015,0.0288±0.0010 and0.0294±0°.0079 cycle^(-1),respectively.From the light curve study,the first photometric mass ratio of V944 Cep was found to be q=1.4994±0.0012.A new light curve of V944 Cep was obtained using TESS data.The first absolute dimensions of V944 Cep were M_(1)=1.10±0.01 M_(⊙),M_(2)=1.64±0.02 M_(⊙),R_(1)=2.04±0.37 R_(⊙),R_(2)=3.77±0.67 R_(⊙)for the hotter primary component(T_(1)=4925 K),and M_(1)=1.04±0.01 M_(⊙),M_(2)=1.57±0.02 M_(⊙),R_(1)=2.26±0.36 R_(⊙),R_(2)=3.74±0.59 R_(⊙)for the cooler primary component(T_(1)=4475 K).For V610 Car,V944 Cep,V2815 Ori and V1260 Tau,the apsidal motion periods were found to be 188±26 yr,186±8 yr,73±3 yr and 182±38 yr,respectively.For V944 Cep,the internal structural constants of the component stars log_(k2,obs)=-2.05±0.01 and log_(k2,theo)=-1.83 for hotter primary component and log_(k2,obs)=-1.97±0.01 and log_(k2,theo)=-1.89 for cooler primary component were calculated.

Photometric and Spectroscopic Studies for Two Magnetic-activity Contact Binaries:V724 And and QR Com

We presented new CCD photometry for two contact binaries,V724 And and QR Com,which were observed during the 2020–2022 observing seasons.By using the Wilson–Devinney method,the photometric solutions were deduced from new observed data and TESS ones.Their asymmetric light curves were modeled by a dark spot on the more massive component.Results indicate that the starspot may immigrate or disappear on the surface of the active component.From the TESS observations of QR Com,it is discovered that the difference between light maxima exhibits a 29.5 day oscillation,which implies the continuous evolution of spot feathers on the timescale of several weeks.Their mass ratio and fill-out factor are q=2.308 and f=11.55% for V724 And,and q=0.624 and f=12.77% for QR Com,respectively.From the(O-C)curve,the orbital period secularly decrease at a rate of d P/dt=-1.66×10^(-7)day yr^(-1)for V724 And and d P/dt=-3.98×10^(-7)day yr^(-1)for QR Com,which was interpreted by mass transfer from the more massive component to the less massive one.With period decreasing,this kind of shallow-contact binaries,V724 And and QR Com,will evolve into the deep-contact configurations.

Muslim Fundamentalism: Psychological Orientations and Counter-Narratives

The current study attempted to formulate a conceptualization of Muslim fundamentalism as well as its counter-narratives as grounded in religious experience of Pakistani Muslims.Open ended interviews were conducted with 133 Pakistani Muslim men and women of prominent local religious affiliations.Analysis revealed a grounded theory model of Muslim fundamentalism highlighting cognitive,and social psychological processes involved.Participants saw their religion as a complete code of conduct and inferred various meanings from completeness of Islam as finalized,closed to inquiry as well as rejecting of other cultures and religious traditions.The major inter-related themes of the model were totalitarianism,closed mindedness,binary thinking,hyper-exotericism,ambiguity intolerance,authoritarianism,punitive approach,violent tendencies,labelling,diversity intolerance and paranoia or threat perceiving attitude.The interplay of these factors is discussed in the light of earlier research on fundamentalism.The research also revealed strong counter narratives to fundamentalist stance which formulated the major themes of esoteric religiosity,open mindedness,pluralism,and Islam and civil society.The study carries implications for religious education of Muslims and their socialization with believers of other religious traditions.

A Photometric Study of Two Contact Binaries: CRTS J025408.1+265957 and CRTS J012111.1+272933

We performed new photometric observations for two contact binaries(i.e., CRTS J025408.1+265957 and CRTS J012111.1+272933), which were observed by the 1.0 m telescope at Xingjiang Astronomical Observatory. From our light curves and several survey data, we derived several sets of photometric solutions. We found that CRTS J025408.1+265957 and CRTS J012111.1+272933 were A-and W-type W UMa, respectively. The results imply that the spot migrates or disappears in the two contact binaries, which were identified by chromospheric activity emissions(e.g., Hαemission) from LAMOST spectra. From the O-C curves, the orbital periods of the two contact binaries may be increasing, which is interpreted by the mass transfer from the less massive component to the more massive one. With mass transferring, the two contact binaries may evolve from the contact configurations to semi-detached ones as predicted by the theory of thermal relaxation oscillation.

Absolute parameters and physical nature of two W-UMa type binaries:V1123 Tau and V1128 Tau

We present high-precision, multi-band CCD photometry of two less-studied close binaries V1123 Tau and V1128 Tau. Complete covered light curves and a number of new times of light minima of the two eclipsing systems were obtained, based on which, revised orbital elements and new ephemerides were given. By adopting the Wilson-Devinney method, the light curves were analyzed. The photometric solutions confirm the W UMa-type nature of the binary systems. With the less-massive secondary slightly cooler than the primary, V1123 Tau could be classified as an A- type contact system. While V1128 Tau is typically considered a W-type W UMa star, the surface temperature of its secondary component is determined to be absolutely higher than the primary by about 270 K. Combining with the results of radial-velocity solutions, we determined absolute parameters of the two systems. The mass, radius and luminosity for each component of V1123 Tau were derived as： 1.36 ±0.05M⊙, 1.37 ± 0.02R⊙, and 2.01± O.07L⊙ and 0.40±0.02M⊙, 0.80±0.01R⊙, and 0.67±0.04L⊙, respectively. For V1128 Tau, the absolute parameters were computed to be 1.09±0.03M⊙, 1.01±0.01R⊙, and 1.34±0.06Le and 0.58 ± 0.01M⊙, 0.76±0.01R⊙, and 0.91±0.05L⊙, respectively. Based on these results, the evolutionary status and the physical nature of the two binary systems are discussed, while also connecting with the theoretical models.

Physical properties of three short period close binaries:KIC 2715417,KIC 6050116 and KIC 6287172

We present the physical parameters of three short period close binaries using data observed from the Kepler Space Telescope. All of these observations were taken in a single bandpass(which approximates the Johnson V-band). Our three systems are KIC 2715417, KIC 6050116 and KIC 6287172. The first system, KIC 2715417, is considered a semi-detached system with the secondary component filling its Roche lobe. The second system, KIC 6050116, is an overcontact system, while the third system, KIC 6287172, belongs to ellipsoidal variables as deduced from the Roche lobe geometry. For photometric analysis, we used the PHOEBE software package, which is based on the Wilson-Devinney code. Due to lack of spectroscopic data, the photometric mass ratios are determined from the analyses of light curves using the q-search method. The absolute parameters are determined using three different methods(Harmanec, Maceroni &Van'tVeer and Gazeas & Niarchos).

Absolute physical parameters of three poorly studied detached eclipsing binaries

The photometric and spectroscopic data for three double-lined detached eclipsing binaries were collected from the photometric and spectral surveys.The light and radial velocity curves of each binary system were simultaneously analyzed using Wilson-Devinney(WD)code,and the absolute physical and orbital parameters of these binaries were derived.The masses of both components of ASASSN-V J063123.82+192341.9 were found to be M1=1.088±0.016 and M20.883±0.016 M⊙;those of ASAS J011416+0426.4 were determined to be M1=0.934±0.046 and M2=0.754±0.043 M⊙;and those of MW Aur were derived to be M1=2.052±0.196 and M21.939±0.193 M⊙.Finally,the evolutionary status of these detached binaries was discussed based on their absolute parameters and the theoretical stellar models.

Photometric Study of Three Short-Period Eclipsing Binaries from the ASAS Catalogue

We present the results of our study of three previously unstudied short-period eclipsing binaries, namely: ASAS 110609 ﹣ 2045.3, ASAS105331 ﹣ 7424.7, and ASAS 130057 + 2120.3. Using the visual (V)-band data obtained from the ASAS catalogue, the orbital and physical parameters of the systems were derived for the first time using the Wilson-Divenney (WD) codes. Our investigation revealed that ASAS 110609 ﹣ 2045.3 is a near-contact binary star of the W Uma type having an angle of inclination of 80° ± 1, a mass ratio of about 0.5, an orbital period of 0.2933 ± 0.0130 days, and an effective temperature in the range of 5800 K - 6200 K, making it a G2V-F7V spectral system. ASAS 105331 ﹣ 7424.7 was established to be an over-contact binary system of the W Uma type, inclined at 86° ± 2 to the line of sight, having a mass ratio of about 0.9, a period of 0.4825 ± 0.0002, and an effective temperature in the range of 5200 K - 5300 K, making it a K2V-K0V spectral system. A third light factor of just 0.1 was established for the system, however, no evidence of starspots or discs was inferred for either component. ASAS 130,057 + 2120.3 is a W Uma binary having a mass ratio of about 0.6 in a state of marginal contact. Its orbital inclination is 55° ± 1;the effective temperature is in the range of 6200 K - 6500 K, making it a F7V-F5V stellar system. The system showed evidence of third light, with a third light factor of 0.6, however, the presence of spots or discs could not be established for either component. The deduced period was 0.8930 ± 0.0014 days. None of the systems showed any evidence of the O’Connell effect on either component.

Two-dimensional Parameter Relationships for W UMa-type Systems Revisited

Reviewing the empirical and theoretical parameter relationships between various parameters is a good way to understand more about contact binary systems.In this investigation,two-dimensional(2D)relationships for P–MV(system),P–L1,2,M1,2–L1,2,and q–Lratiowere revisited.The sample used is related to 118 contact binary systems with an orbital period shorter than 0.6 days whose absolute parameters were estimated based on the Gaia Data Release 3 parallax.We reviewed previous studies on 2D relationships and updated six parameter relationships.Therefore,Markov chain Monte Carlo and Machine Learning methods were used,and the outcomes were compared.We selected 22 contact binary systems from eight previous studies for comparison,which had light curve solutions using spectroscopic data.The results show that the systems are in good agreement with the results of this study.

Study of 26 Galactic Open Clusters with Extended Main-sequence Turnoffs

Recent studies indicate that some Galactic open clusters(OCs)exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs).However,the number of Galactic OCs with eMSTO structures detected so far is limited,and the reasons for their formation are still unclear.This work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these features.Stellar population types and fundamental parameters of cluster samples are acquired using CMD fitting methods.Among them,the results of 11 OCs are reliable as the observed CMDs are well-reproduced.We propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO morphologies.The results also show that the impact of age spread is important,as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.

Magnetic Activity and Parameters of 43 Flare Stars in the GWAC Archive

In the archive of the Ground Wide Angle Camera(GWAC),we found 43 white light flares from 43 stars,among which,three are sympathetic or homologous flares,and one of them also has a quasi-periodic pulsation with a period of 13.0±1.5 minutes.Among these 43 flare stars,there are 19 new active stars and 41 stars that have available TESS and/or K2 light curves,from which we found 931 stellar flares.We also obtained rotational or orbital periods of 34 GWAC flare stars,of which 33 are less than 5.4 days,and ephemerides of three eclipsing binaries from these light curves.Combining with low resolution spectra from LAMOST and the Xinglong 2.16 m telescope,we found that L_(Hα)/L_(bol) are in the saturation region in the rotation-activity diagram.From the LAMOST medium-resolution spectrum,we found that Star#3(HAT 178-02667)has double Hαemissions which imply it is a binary,and two components are both active stars.Thirteen stars have flare frequency distributions(FFDs)from TESS and/or K2 light curves.These FFDs show that the flares detected by GWAC can occur at a frequency of 0.5to 9.5 yr^(-1).The impact of flares on habitable planets was also studied based on these FFDs,and flares from some GWAC flare stars may produce enough energetic flares to destroy ozone layers,but none can trigger prebiotic chemistry on their habitable planets.

New Photometric Investigations of G-type Contact Binary TU Boo

Two sets of CCD photometric observations for contact binary TU Boo were obtained in 2020 and 2021.Different from its asymmetric light curves published from the literature,our BVRcIc-band curves show that the heights of maximum are almost equal.These distortions of light curves possibly indicate that the components were active in past 25 yr,but they were stable in the last two years.For total-eclipse binary TU Boo,due to some star-spots on the surface of the components,the physical structure obtained by many investigators are different.Therefore,the symmetric multi-color light curves in 2020,2021 are important for understanding configuration and evolution of this system.By using the Wilson–Devinney program,it is confirmed that TU Boo is an A-type shallow-contact binary with the temperature difference ofΔT=152 K and fill-out of f=14.67%.In the O−C diagram of orbital period analysis,a cyclic oscillation superimposed on a continuous decrease was determined.The long-term decreasing is often explained by the mass transfer from the more massive star to less massive one,this system will evolve into a deeper contact binary with time.The cyclic oscillations computed from much more CCD times of light minimum maybe result from the light-travel time effect via the presence of a third body.These characters of structure,evolution and ternary belong to typical A-type W UMa binaries with spectral G.

IP Lyn:A Totally Eclipsing Contact Binary with an Extremely Low Mass Ratio

We present the first photometric and orbital period investigations for a neglected totally eclipsing contact binary IP Lyn.The photometric solutions derived from both ground-based and several surveys'observations suggest that it is a shallow contact binary with an extremely low mass ratio of 0.055.The weak asymmetry observed in our multiple band light curves can be interpreted as a result of an active cool spot on the primary.The absolute physical parameters were determined with the Gaia-distance-based method and checked by an empirical relation.Combining the eclipse timings collected from the literature and those derived from our and variable surveys'observations,we find that IP Lyn has been undergoing a secular orbital period increase for the past two decades,implying a mass transfer from the less massive secondary to the primary.By comparing the current parameters with the critical instability ones,we infer that IP Lyn is currently stable in spite of its relatively low mass ratio and orbital angular momentum.Finally,from a catalog of 117 extremely low mass ratio contact binaries,we find that their orbital angular momenta are significantly lower than those of the contact binaries with a relatively high mass ratio,suggesting they should be at the late evolutionary stage of a contact binary.