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 ...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.展开更多
In this paper,CCD photometric light curves for the short-period eclipsing binary 1 SWASP J140533.33＋114639.1（hereafter J1405） in the BV R bands are presented and analyzed using the 2013 version of the Wilson-Devin...In this paper,CCD photometric light curves for the short-period eclipsing binary 1 SWASP J140533.33＋114639.1（hereafter J1405） in the BV R bands are presented and analyzed using the 2013 version of the Wilson-Devinney（W-D） code. It is discovered that J1405 is a W-subtype shallow contact binary with a contact degree of f = 7.9±0.5% and a mass ratio of q = 1.55±0.02. In order to explain the asymmetric light curves of the system,a cool starspot on the more massive component is employed. This shallow contact eclipsing binary may have been formed from a short-period detached system through orbital shrinkage due to angular momentum loss. Based on the（O-C） method,the variation of orbital period is studied using all the available times of minimum light. The（O-C） diagram reveals that the period is increasing continuously at a rate of d P/dt = ＋2.09×10^-7 d yr^-1,which can be explained by mass transfer from the less massive component to the more massive one.展开更多
Contact binaries at various stages of evolution unveil various operating mechanisms that drive them.We report the photometric and period variation analysis of two contact binaries EV Cnc and AH Cnc in open cluster M67...Contact binaries at various stages of evolution unveil various operating mechanisms that drive them.We report the photometric and period variation analysis of two contact binaries EV Cnc and AH Cnc in open cluster M67.We observed the cluster from the JCBT 1.3 m telescope and utilized TESS and Kepler observations.The photometric solutions of EV Cnc and AH Cnc revealed a mass ratio of q~0.41 and~0.15 with an inclination of i=42°and87°respectively.These solutions suggest that EV Cnc is probably a semi-detached and AH Cnc is a deep low-mass ratio contact binary.The study of O-C variation analysis indicates that for both systems,the period is increasing which suggests the mass transfer is occurring from secondary to primary.In the case of AH Cnc and based on simulations by randomly varying the time of minima to fit the LITE solution,we noted the third body orbital period to be around P_(3)=26.82±2.54 yr,which is different from earlier reported values and conclude that future observations are required to confirm this scenario.We compare these two systems with other similar contact binaries to get an estimate of the final configuration of the respective systems.展开更多
We present results of CCD photometric observations of the short-period W UMatype contact binary system, RZ Com. The light curve of the binary has changed from Wsubtype to A-subtype from 1998 to 2003, then back to W-su...We present results of CCD photometric observations of the short-period W UMatype contact binary system, RZ Com. The light curve of the binary has changed from Wsubtype to A-subtype from 1998 to 2003, then back to W-subtype in 2004. An analysis was carried out using the 2003 version of the Wilson-Devinney code. It is confirmed that RZ Com is a low-degree, overcontact f = 20.1% （±7.4%） binary system with a high inclination of i = 81.°40 （＋0.°40）, and a mass ratio q = 2.351 （＋0.031）. Combining four newly determined times of light minimum with others in the literature, the variations in orbital period is examined. A small-amplitude oscillation （A=0.0065d）, with a period of 41.5 year, is discovered superimposed on a long-term increase at rate dP/dt = ＋3.97 × 10^-8d yr^-1. The period oscillation can be explained either by the light-time effect due to the presence of an unseen third body, or by cycles of magnetic activity on the components. Combining our photometric solution with the spectroscopic elements obtained by Mclean ＆ Hilditch, the absolute dimensions ofRZ Com are： M1 = 1.14 （±0.19）M⊙, M2 = 0.50 （±0.09）M⊙, R1 = 1.12 （±0.01）R⊙, R2 = 0.78 （＋0.01）R⊙ and A = 2.41 （±0.02）R⊙.展开更多
BH Cen is a short-period early-type binary with a period of 0.792^d in the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are ana...BH Cen is a short-period early-type binary with a period of 0.792^d in the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are analyzed by using the Wilson-Devinney code. It is detected that BH Cen is a high-mass-ratio overcontact binary with a fill-out factor of 46.4% and a mass ratio of 0.89. The derived orbital inclination i is 88.9 degrees, indicating that it is a totally eclipsing binary and the photometric parameters can be determined reliably. By adding new eclipse times, the orbital period changes in the binary are analyzed. It is confirmed that the period of BH Cen shows a long-term increase while it undergoes a cyclic oscillation with an amplitude of A3 = 0.024 d and a period of P3 = 50.3 yr. The high mass ratio, overcontact configuration and long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary state after the shortest-period stage of Case A mass transfer.The continuous increase in period can be explained by mass transfer from the secondary component to the primary one at a rate of˙M2 = 2.8×10^-6 M⊙per year. The cyclic change can be plausibly explained by the presence of a third body because both components in the BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 M⊙ at an orbital separation of about 32.5 AU. Since no third light was found during the photometric solution, it is possible that the third body may be a candidate for a compact object.展开更多
We present multi-color photometric observations and a one-dimensional spectrum, acquired from March 2016 to May 2017, for the short-period eclipsing binary PS Vir, by using the 2.16-m, 85-cm and 60-cm telescopes at Xi...We present multi-color photometric observations and a one-dimensional spectrum, acquired from March 2016 to May 2017, for the short-period eclipsing binary PS Vir, by using the 2.16-m, 85-cm and 60-cm telescopes at Xinglong station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. The spectral type was determined as G2V from the one-dimensional spectrum. The photometric solution was reduced from BVRc light curves. The results imply that PS Vir is a W-subtype contact binary with a mass ratio of q - 0.305（zk0.008） and a fill-out factor of f = 14.4（＋1.8）%. The orbital period may be undergoing a cyclic oscillation with an ampli-tude of A = 0.0027（~0.0001）d and a modulated period of 11.7（4-0.2） yr, which may result from the light-time effect due to a third body. The lower limit on mass for the assumed component is 0.12 Me. Moreover, the more massive component of PS Vir may be a bit more evolved star as determined from the mass-luminosity diagram.展开更多
Orbital period changes of the W UMa-type binary YY Eri are analyzed by using all photoelectric and ccd times of light minimum. The results show that its orbital period is undergo- ing a secular increase superposed on ...Orbital period changes of the W UMa-type binary YY Eri are analyzed by using all photoelectric and ccd times of light minimum. The results show that its orbital period is undergo- ing a secular increase superposed on two cyclic oscillations. The continuous increase at the rate of dP/dt = 6.3806 × 10^-8 d yr^-1 may be accounted for by mass transfer from the less massive com- panion to the more massive one. Two periodic variations with periods of 38.6192 and 22.3573 yr may be attributed to the light-time effect of a faint third star and the cyclic magnetic activity of the system, respectively.展开更多
We report the results from our analysis of Fermi Large Area Telescope （LAT） data for the transitional millisecond pulsar binary PSR J1023＋0038. The time period of the data is nearly 9 yr, and that after the source...We report the results from our analysis of Fermi Large Area Telescope （LAT） data for the transitional millisecond pulsar binary PSR J1023＋0038. The time period of the data is nearly 9 yr, and that after the source＇s transition, in June 2013 from the disk-free state to the active state of having an accretion disk, is approximately 4 yr. We identify a high-energy 〉5.5 GeV component in the source＇s spectrum in the active state, and find this component is only significantly detected in half of the orbital phase centered at the descending node （when the pulsar is moving towards the Earth）. Considering the pulsar scenario proposed for multi-frequency emission from the source, in which the pulsar is still active and a cold-relativistic pulsar wind inverse-Compton scatters the photons from the accretion disk, we discuss the origin of the high-energy component. In order to explain the observed spectrum, a power-law distribution of particles, with an index of ~3, in the pulsar wind is required, while the orbital variations are possibly due to changes in power-law index as a function of orbital phase.展开更多
A photometric analysis and evolutionary stages of the contact binary V2790 Ori are presented.The BV RC observations were carried out at the Thai National Observatory. The photometric light curves were fitted to provid...A photometric analysis and evolutionary stages of the contact binary V2790 Ori are presented.The BV RC observations were carried out at the Thai National Observatory. The photometric light curves were fitted to provide fundamental parameters, required to examine evolutionary stages of the binary. The results indicate that V2790 Ori is a W-type contact system with a mass ratio of q = 2.932. The orbital period increase is found at a rate of d P/dt = 1.03×10^-7 d yr^-1. This implies that a rate of mass transfer from the secondary component to the primary one is dm2/dt =6.31×10^-8 M⊙yr^-1. Furthermore, we find that from the detached phase to the contact phase, the amount of mass that the evolved secondary component has lost is 1.188±0.110 M⊙, i.e., mass lost by the system is 0.789±0.073 M⊙and mass transfer to the primary is0.399±0.037 M⊙. Since the time of the first overflow, the angular momentum loss is found to be 72.2% of JFOF, causing the orbit and Roche surface to shrink until the present time.展开更多
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 ...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.展开更多
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, t...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.展开更多
We present a long-term time-resolved photometry of the short-period eclipsing binary IU Per. It confirms the intrinsic 6 Scuti-like pulsation of the system reported by Kim et al.. With the obtained data, an orbital pe...We present a long-term time-resolved photometry of the short-period eclipsing binary IU Per. It confirms the intrinsic 6 Scuti-like pulsation of the system reported by Kim et al.. With the obtained data, an orbital period study and an eclipsing light curve synthesis based on the Wilson-Devinney method were carded out. The photometric solution reveals a semi-detached configuration with the less-massive component filling its own Roche-lobe. By subtracting the eclipsing light changes from the data, we obtained the pure pulsating light curve of the mass-accreting primary component. A Fourier analysis reveals four pulsation modes with confidence larger than 99%. A mode identification based on the results of the photometric solution was made. It suggests that the star may be in radial pulsation with a fundamental period of about 0.0628 d. A brief discussion concerning the evolutionary status and the pulsation nature is finally given.展开更多
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 wer...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.展开更多
About 786.4 thousand stars were observed by LAMOST twice or more during the first stage of its spectroscopic survey. The radial velocity differences for about 256 thousand targets are larger than10 km s^(-1) and they ...About 786.4 thousand stars were observed by LAMOST twice or more during the first stage of its spectroscopic survey. The radial velocity differences for about 256 thousand targets are larger than10 km s^(-1) and they are possible spectroscopic binary or variable candidates(SBVCs). It is shown that most SBVCs are slightly metal poorer than the Sun. There are two peaks in the temperature distribution of SBVCs around 5760 K and 4870 K, while there are three peaks in the distribution of the gravitational acceleration at 2.461, 4.171 and 4.621 cm s^(-2). The locations of SBVCs on the [Fe/H]-T, [Fe/H]-log g, log g-T and H-R diagrams are investigated. It is found that the detected SBVCs could be classified into four groups. The first group has higher log g～4.621 and lower T ～ 4870 K which are mainly cool red dwarf binaries. The second group of SBVCs has logg around 4.171 cm s^(-2) that includes binaries and pulsating stars such as δSet and γ Dor variables. The gravitational accelerations of the third group of SBVCs are higher and some of them are below the zero-age main sequence. They may be contact binaries in which the primary components are losing energy to the secondaries in the common envelopes and are at a special stellar evolutionary stage.The last group is composed of giants or supergiants with log g around 2.461 cm s^(-2) that may be evolved pulsating stars. One target(C134624.29+333921.2) is confirmed as an eclipsing binary with a period of 0.65 days. A preliminary analysis suggests that it is a detached binary with a mass ratio of 0.46. The primary fills its critical Roche lobe by about 89%, indicating that mass transfer will occur between the two components.展开更多
New photometric observations of NS VS 01286630 were performed and two sets of fourcolor（B, V, Rc, Ic） light curves（LCs） were obtained. Using the 2013 version of the Wilson-Devinney（W-D） code, we analyzed these d...New photometric observations of NS VS 01286630 were performed and two sets of fourcolor（B, V, Rc, Ic） light curves（LCs） were obtained. Using the 2013 version of the Wilson-Devinney（W-D） code, we analyzed these data. The photometric solutions reveal that NS VS 01286630 is an active detached eclipsing binary（EB） with a high orbital inclination（nearly 90°）. Remarkably, the temperature of the primary component（the hotter star） is higher than the secondary one, but the value of mass ratio q（M2/M1）for NS VS 0128663 is more than 1, which can be explained in that the surface of the secondary component of NSVS 01286630 is covered with big cool starspots. Based on our new CCD mid-eclipse times and the data published until now, variations in the mid-eclipse times were reanalyzed in detail using a weighted least-squares method. It is discovered that the（O-C） diagram of the system shows a cyclic oscillation with a period of 3.61 yr and an amplitude of 0.001 d. The cyclic variation may be caused by the light-travel time effect（LTTE） due to the presence of a third companion, whose mass we calculated as M3 sin（i3） =0.11 M（⊙）. The third body may affect the orbital evolution of the central binary system by transferring angular momentum.展开更多
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 perio...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.展开更多
ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS survey.However,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational insta...ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS survey.However,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g-T diagram ofδScuti pulsating stars.To understand the physical properties of the variable star,we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan Observatories.Multi-color light curves in B,V,R_c and I_c bands were obtained and are analyzed by using the W-D program.It is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 d rather than aδScuti star.It is a W-subtype contact binary with a mass ratio of 1.135(±0.019)and a fill-out factor of 10.4%(±5.6)%.The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn,ⅡPer and GW Tau.All of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation theory.The linear ephemeris was corrected by using 303 new determined times of light minimum.It is detected that the O-C curve shows a sinusoidal variation that could be explained by the light-travel-time effect via the presence of a cool red dwarf.The present investigation reveals that some of theδScuti-type stars beyond the red edge of pulsating instability strip on the log g-T diagram are misclassified eclipsing binaries.To understand their structures and evolutionary states,more studies are required in the future.展开更多
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 ...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.展开更多
IO Cnc was classified to be a new G-type(G0)W UMa-type eclipsing binary system.Our first multicolor photometric solutions show that IO Cnc is a new W-subtype shallow contact binary with a fill-out factor of f=16.1%and...IO Cnc was classified to be a new G-type(G0)W UMa-type eclipsing binary system.Our first multicolor photometric solutions show that IO Cnc is a new W-subtype shallow contact binary with a fill-out factor of f=16.1%and a low mass ratio of q=3.12(or 1/q=0.32).During orbital period investigations,a cyclic variation and a downward parabolic variation with a rate of(-1.28±0.43)×10^(-7) d yr^(-1) was discovered in the observed–calculated(O-C)curve.The cyclic variation was analyzed by the light travel time effect(LTTE)via a potential red dwarf companion star,an orbital semi-major axis shorter than 4.88±0.82 AU was obtained.Finally,we collect physical parameters of a sample of 50 G-type shallow contact binaries(f≤20%),it is suggested that most of the G-type shallow contact binaries are undergoing a longterm and periodic orbital period changes,especially more systems show long-term decreases.The long-term orbital period decrease indicates that IO Cnc is in a mass transferring from the more massive component to the less massive one.With the long-term decrease of the orbital period,this shallow contact binary will evolve into a deeper contact one.展开更多
We presented photometry for an EB-type totally eclipsing binary,1SWASP J010313.78+352903.7,observed with the Xinglong 85 cm telescope on 2021 October 22.Light curves in five bands(including the TESS data)were analyzed...We presented photometry for an EB-type totally eclipsing binary,1SWASP J010313.78+352903.7,observed with the Xinglong 85 cm telescope on 2021 October 22.Light curves in five bands(including the TESS data)were analyzed by employing the Wilson-Devinney method.The photometric solutions show that it is a contact binary with a relatively low mass ratio(q≌0.28),relatively large fill-out factor(f≌40%)and large temperature difference(ΔT≌1700 K).Max.I-Max.II is up to about 9%of variable light amplitude of the asymmetric light curves.It is well described by double-hot spots model on the surface of the cooler secondary.The two hot spots are both in growing and evolving.They may be caused by two different mechanics,i.e.,magnetic stellar activity and mass transfer.The large temperature difference between the two contact components indicates that they share a non-thermal equilibrium common envelope.展开更多
基金supported by the National Natural Science Foundation of China (No. 11325315)National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission
文摘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.
基金partly supported by the National Natural Science Foundation of China (Nos.11133007 and 11573063)the Science Foundation of Yunnan Province (Grant No.2012HC011)
文摘In this paper,CCD photometric light curves for the short-period eclipsing binary 1 SWASP J140533.33＋114639.1（hereafter J1405） in the BV R bands are presented and analyzed using the 2013 version of the Wilson-Devinney（W-D） code. It is discovered that J1405 is a W-subtype shallow contact binary with a contact degree of f = 7.9±0.5% and a mass ratio of q = 1.55±0.02. In order to explain the asymmetric light curves of the system,a cool starspot on the more massive component is employed. This shallow contact eclipsing binary may have been formed from a short-period detached system through orbital shrinkage due to angular momentum loss. Based on the（O-C） method,the variation of orbital period is studied using all the available times of minimum light. The（O-C） diagram reveals that the period is increasing continuously at a rate of d P/dt = ＋2.09×10^-7 d yr^-1,which can be explained by mass transfer from the less massive component to the more massive one.
基金support from the SRF INSPIRE(IF 170314)fellowship program,Government of Indiafinancial support from the SERB Core Research Grant project,the Government of India。
文摘Contact binaries at various stages of evolution unveil various operating mechanisms that drive them.We report the photometric and period variation analysis of two contact binaries EV Cnc and AH Cnc in open cluster M67.We observed the cluster from the JCBT 1.3 m telescope and utilized TESS and Kepler observations.The photometric solutions of EV Cnc and AH Cnc revealed a mass ratio of q~0.41 and~0.15 with an inclination of i=42°and87°respectively.These solutions suggest that EV Cnc is probably a semi-detached and AH Cnc is a deep low-mass ratio contact binary.The study of O-C variation analysis indicates that for both systems,the period is increasing which suggests the mass transfer is occurring from secondary to primary.In the case of AH Cnc and based on simulations by randomly varying the time of minima to fit the LITE solution,we noted the third body orbital period to be around P_(3)=26.82±2.54 yr,which is different from earlier reported values and conclude that future observations are required to confirm this scenario.We compare these two systems with other similar contact binaries to get an estimate of the final configuration of the respective systems.
基金the NSFC(Nos.10573032,10433030 and 10573013)the Yunnan Natural Science Foundation(No.2005A0059M)
文摘We present results of CCD photometric observations of the short-period W UMatype contact binary system, RZ Com. The light curve of the binary has changed from Wsubtype to A-subtype from 1998 to 2003, then back to W-subtype in 2004. An analysis was carried out using the 2003 version of the Wilson-Devinney code. It is confirmed that RZ Com is a low-degree, overcontact f = 20.1% （±7.4%） binary system with a high inclination of i = 81.°40 （＋0.°40）, and a mass ratio q = 2.351 （＋0.031）. Combining four newly determined times of light minimum with others in the literature, the variations in orbital period is examined. A small-amplitude oscillation （A=0.0065d）, with a period of 41.5 year, is discovered superimposed on a long-term increase at rate dP/dt = ＋3.97 × 10^-8d yr^-1. The period oscillation can be explained either by the light-time effect due to the presence of an unseen third body, or by cycles of magnetic activity on the components. Combining our photometric solution with the spectroscopic elements obtained by Mclean ＆ Hilditch, the absolute dimensions ofRZ Com are： M1 = 1.14 （±0.19）M⊙, M2 = 0.50 （±0.09）M⊙, R1 = 1.12 （±0.01）R⊙, R2 = 0.78 （＋0.01）R⊙ and A = 2.41 （±0.02）R⊙.
基金supported by the National Natural Science Foundation of China(Grant No.11325315)
文摘BH Cen is a short-period early-type binary with a period of 0.792^d in the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are analyzed by using the Wilson-Devinney code. It is detected that BH Cen is a high-mass-ratio overcontact binary with a fill-out factor of 46.4% and a mass ratio of 0.89. The derived orbital inclination i is 88.9 degrees, indicating that it is a totally eclipsing binary and the photometric parameters can be determined reliably. By adding new eclipse times, the orbital period changes in the binary are analyzed. It is confirmed that the period of BH Cen shows a long-term increase while it undergoes a cyclic oscillation with an amplitude of A3 = 0.024 d and a period of P3 = 50.3 yr. The high mass ratio, overcontact configuration and long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary state after the shortest-period stage of Case A mass transfer.The continuous increase in period can be explained by mass transfer from the secondary component to the primary one at a rate of˙M2 = 2.8×10^-6 M⊙per year. The cyclic change can be plausibly explained by the presence of a third body because both components in the BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 M⊙ at an orbital separation of about 32.5 AU. Since no third light was found during the photometric solution, it is possible that the third body may be a candidate for a compact object.
基金funding from the National Natural Science Foundation of China(Nos.11473009 and U1231102)the Outstanding Young Talents Program of the Education Department of Anhui Province (No.gxyq2018161)supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences
文摘We present multi-color photometric observations and a one-dimensional spectrum, acquired from March 2016 to May 2017, for the short-period eclipsing binary PS Vir, by using the 2.16-m, 85-cm and 60-cm telescopes at Xinglong station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. The spectral type was determined as G2V from the one-dimensional spectrum. The photometric solution was reduced from BVRc light curves. The results imply that PS Vir is a W-subtype contact binary with a mass ratio of q - 0.305（zk0.008） and a fill-out factor of f = 14.4（＋1.8）%. The orbital period may be undergoing a cyclic oscillation with an ampli-tude of A = 0.0027（~0.0001）d and a modulated period of 11.7（4-0.2） yr, which may result from the light-time effect due to a third body. The lower limit on mass for the assumed component is 0.12 Me. Moreover, the more massive component of PS Vir may be a bit more evolved star as determined from the mass-luminosity diagram.
基金supported by the Joint Research Funds in Astronomy (U1531108, U1731106 and U1731110)the National Natural Science Foundation of China and Chinese Academy of Sciencespartially supported by the National Natural Science Foundation of China (11703020)
文摘Orbital period changes of the W UMa-type binary YY Eri are analyzed by using all photoelectric and ccd times of light minimum. The results show that its orbital period is undergo- ing a secular increase superposed on two cyclic oscillations. The continuous increase at the rate of dP/dt = 6.3806 × 10^-8 d yr^-1 may be accounted for by mass transfer from the less massive com- panion to the more massive one. Two periodic variations with periods of 38.6192 and 22.3573 yr may be attributed to the light-time effect of a faint third star and the cyclic magnetic activity of the system, respectively.
基金supported by the National Program on Key Research and Development Project (Grant No.2016YFA0400804)the National Natural Science Foundation of China (NSFC) (Nos.11373055,11633007 and U1738131)+1 种基金the CAS/SAFEA International Partnership Program for Creative Research Teamsthe NSFC (Nos.11573010,U1631103 and 11661161010)
文摘We report the results from our analysis of Fermi Large Area Telescope （LAT） data for the transitional millisecond pulsar binary PSR J1023＋0038. The time period of the data is nearly 9 yr, and that after the source＇s transition, in June 2013 from the disk-free state to the active state of having an accretion disk, is approximately 4 yr. We identify a high-energy 〉5.5 GeV component in the source＇s spectrum in the active state, and find this component is only significantly detected in half of the orbital phase centered at the descending node （when the pulsar is moving towards the Earth）. Considering the pulsar scenario proposed for multi-frequency emission from the source, in which the pulsar is still active and a cold-relativistic pulsar wind inverse-Compton scatters the photons from the accretion disk, we discuss the origin of the high-energy component. In order to explain the observed spectrum, a power-law distribution of particles, with an index of ~3, in the pulsar wind is required, while the orbital variations are possibly due to changes in power-law index as a function of orbital phase.
文摘A photometric analysis and evolutionary stages of the contact binary V2790 Ori are presented.The BV RC observations were carried out at the Thai National Observatory. The photometric light curves were fitted to provide fundamental parameters, required to examine evolutionary stages of the binary. The results indicate that V2790 Ori is a W-type contact system with a mass ratio of q = 2.932. The orbital period increase is found at a rate of d P/dt = 1.03×10^-7 d yr^-1. This implies that a rate of mass transfer from the secondary component to the primary one is dm2/dt =6.31×10^-8 M⊙yr^-1. Furthermore, we find that from the detached phase to the contact phase, the amount of mass that the evolved secondary component has lost is 1.188±0.110 M⊙, i.e., mass lost by the system is 0.789±0.073 M⊙and mass transfer to the primary is0.399±0.037 M⊙. Since the time of the first overflow, the angular momentum loss is found to be 72.2% of JFOF, causing the orbit and Roche surface to shrink until the present time.
基金supported by the National Natural Science Foundation of China (No. 11703016)the Joint Research Fund in Astronomy (No. U1431105) under cooperative agreement between the National Natural Science Foundation of China and the Chinese Academy of Sciences+5 种基金the program of the Light in China’s Western Region (No. 2015-XBQNA-02)the Natural Science Foundation of Shandong Province (Nos. ZR2014AQ019 and JQ201702)the Young Scholars Program of Shandong University, Weihai (Nos. 20820162003 and 20820171006)the program of Tianshan Youth (No. 2017Q091)the Open Research Program of Key Laboratory for the Structure and Evolution of Celestial Objects (No. OP201704)partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences
文摘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.
基金partly supported by the Yunnan Natural Science Foundation(2016FB004)the Young Academic and Technology Leaders project of Yunnan Province(No.2015HB098)+1 种基金the National Natural Science Foundation of China(Nos.11773066,11403095 and 11325315)the Key Research Programme of the Chinese Academy of Sciences(Grant No.KGZD-EW-603)
文摘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.
基金Supported by the National Natural Science Foundation of China
文摘We present a long-term time-resolved photometry of the short-period eclipsing binary IU Per. It confirms the intrinsic 6 Scuti-like pulsation of the system reported by Kim et al.. With the obtained data, an orbital period study and an eclipsing light curve synthesis based on the Wilson-Devinney method were carded out. The photometric solution reveals a semi-detached configuration with the less-massive component filling its own Roche-lobe. By subtracting the eclipsing light changes from the data, we obtained the pure pulsating light curve of the mass-accreting primary component. A Fourier analysis reveals four pulsation modes with confidence larger than 99%. A mode identification based on the results of the photometric solution was made. It suggests that the star may be in radial pulsation with a fundamental period of about 0.0628 d. A brief discussion concerning the evolutionary status and the pulsation nature is finally given.
基金supported by the National Natural Science Foundation of China(Grant No. 10773015)
文摘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.
基金The Guo Shou Jing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciencesprovided by the National Development and Reform Commission
文摘About 786.4 thousand stars were observed by LAMOST twice or more during the first stage of its spectroscopic survey. The radial velocity differences for about 256 thousand targets are larger than10 km s^(-1) and they are possible spectroscopic binary or variable candidates(SBVCs). It is shown that most SBVCs are slightly metal poorer than the Sun. There are two peaks in the temperature distribution of SBVCs around 5760 K and 4870 K, while there are three peaks in the distribution of the gravitational acceleration at 2.461, 4.171 and 4.621 cm s^(-2). The locations of SBVCs on the [Fe/H]-T, [Fe/H]-log g, log g-T and H-R diagrams are investigated. It is found that the detected SBVCs could be classified into four groups. The first group has higher log g～4.621 and lower T ～ 4870 K which are mainly cool red dwarf binaries. The second group of SBVCs has logg around 4.171 cm s^(-2) that includes binaries and pulsating stars such as δSet and γ Dor variables. The gravitational accelerations of the third group of SBVCs are higher and some of them are below the zero-age main sequence. They may be contact binaries in which the primary components are losing energy to the secondaries in the common envelopes and are at a special stellar evolutionary stage.The last group is composed of giants or supergiants with log g around 2.461 cm s^(-2) that may be evolved pulsating stars. One target(C134624.29+333921.2) is confirmed as an eclipsing binary with a period of 0.65 days. A preliminary analysis suggests that it is a detached binary with a mass ratio of 0.46. The primary fills its critical Roche lobe by about 89%, indicating that mass transfer will occur between the two components.
基金supported by the National Natural Science Foundation of China(Nos.11573063,11611530685)the Key Science Foundation of Yunnan Province(No.2017FA001)+1 种基金support from the staff of the Xinglong 85 cm telescopepartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences
文摘New photometric observations of NS VS 01286630 were performed and two sets of fourcolor（B, V, Rc, Ic） light curves（LCs） were obtained. Using the 2013 version of the Wilson-Devinney（W-D） code, we analyzed these data. The photometric solutions reveal that NS VS 01286630 is an active detached eclipsing binary（EB） with a high orbital inclination（nearly 90°）. Remarkably, the temperature of the primary component（the hotter star） is higher than the secondary one, but the value of mass ratio q（M2/M1）for NS VS 0128663 is more than 1, which can be explained in that the surface of the secondary component of NSVS 01286630 is covered with big cool starspots. Based on our new CCD mid-eclipse times and the data published until now, variations in the mid-eclipse times were reanalyzed in detail using a weighted least-squares method. It is discovered that the（O-C） diagram of the system shows a cyclic oscillation with a period of 3.61 yr and an amplitude of 0.001 d. The cyclic variation may be caused by the light-travel time effect（LTTE） due to the presence of a third companion, whose mass we calculated as M3 sin（i3） =0.11 M（⊙）. The third body may affect the orbital evolution of the central binary system by transferring angular momentum.
基金supported by the National Natural Science Foundation of China(NSFC)with grant No.12073038supported by the Joint Research Fund in Astronomy U1931133 under cooperative agreement between the National Natural Science Foundation of China(NSFC)and Chinese Academy of Sciences(CAS)+1 种基金the NSFC with grant No.61941121the Beijing Natural Science Foundation,No.1222029。
文摘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.
基金supported by the National Natural Science Foundation of China(Nos.11933008,11703080 and 11803084)the Yunnan Natural Science Foundation(No.2018FB006)。
文摘ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS survey.However,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g-T diagram ofδScuti pulsating stars.To understand the physical properties of the variable star,we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan Observatories.Multi-color light curves in B,V,R_c and I_c bands were obtained and are analyzed by using the W-D program.It is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 d rather than aδScuti star.It is a W-subtype contact binary with a mass ratio of 1.135(±0.019)and a fill-out factor of 10.4%(±5.6)%.The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn,ⅡPer and GW Tau.All of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation theory.The linear ephemeris was corrected by using 303 new determined times of light minimum.It is detected that the O-C curve shows a sinusoidal variation that could be explained by the light-travel-time effect via the presence of a cool red dwarf.The present investigation reveals that some of theδScuti-type stars beyond the red edge of pulsating instability strip on the log g-T diagram are misclassified eclipsing binaries.To understand their structures and evolutionary states,more studies are required in the future.
基金supported by the Joint Research Funds in Astronomy under a cooperative agreement between the National Natural Science Foundation of China(NSFC)and the Chinese Academy of Sciences(Nos.U1931115 and U2031114)Scientific Research Fund of Hunan Provincial Education Department grant No.22A0099+1 种基金the support of the staff of the Xinglong 85 cm telescopepartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos.11873017 and 11933008)the Science and Technology Talents and Platform Plan of Yunnan province(2018HB070)+1 种基金the Yunnan Natural Science Foundation(No.2018FB006)partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘IO Cnc was classified to be a new G-type(G0)W UMa-type eclipsing binary system.Our first multicolor photometric solutions show that IO Cnc is a new W-subtype shallow contact binary with a fill-out factor of f=16.1%and a low mass ratio of q=3.12(or 1/q=0.32).During orbital period investigations,a cyclic variation and a downward parabolic variation with a rate of(-1.28±0.43)×10^(-7) d yr^(-1) was discovered in the observed–calculated(O-C)curve.The cyclic variation was analyzed by the light travel time effect(LTTE)via a potential red dwarf companion star,an orbital semi-major axis shorter than 4.88±0.82 AU was obtained.Finally,we collect physical parameters of a sample of 50 G-type shallow contact binaries(f≤20%),it is suggested that most of the G-type shallow contact binaries are undergoing a longterm and periodic orbital period changes,especially more systems show long-term decreases.The long-term orbital period decrease indicates that IO Cnc is in a mass transferring from the more massive component to the less massive one.With the long-term decrease of the orbital period,this shallow contact binary will evolve into a deeper contact one.
基金supported by the Natural Science Foundation of Shandong Province,China(ZR2021QA082)the National Natural Science Foundation of China(No.11922306)the Doctoral Start-up Foundation of Yantai University(SX20B112)。
文摘We presented photometry for an EB-type totally eclipsing binary,1SWASP J010313.78+352903.7,observed with the Xinglong 85 cm telescope on 2021 October 22.Light curves in five bands(including the TESS data)were analyzed by employing the Wilson-Devinney method.The photometric solutions show that it is a contact binary with a relatively low mass ratio(q≌0.28),relatively large fill-out factor(f≌40%)and large temperature difference(ΔT≌1700 K).Max.I-Max.II is up to about 9%of variable light amplitude of the asymmetric light curves.It is well described by double-hot spots model on the surface of the cooler secondary.The two hot spots are both in growing and evolving.They may be caused by two different mechanics,i.e.,magnetic stellar activity and mass transfer.The large temperature difference between the two contact components indicates that they share a non-thermal equilibrium common envelope.
