Physical Properties of an Eclipsing Binary System, YY Eridani

Photometric observations of an eclipsing binary system, YY Eridani were done in blue (B) and yellow (V) wavelength bands and, finally, the light curve in each wavelength band was constructed. Orbital elements and physical properties of YY Eridani have been calculated using observational data of Binnendijk (1965) and authors have developed Wilson Devinney technique in analyzing the best solution of this eclipsing binary system. More physical parameters eg: orbital inclination, gravity darkening exponent, effective temperature, gravitational potential etc. of each component were calculated in this research for the best solution of YY Eridani. Synthetic light curves which were constructed from the best solution are in good correspondence with observational light curves of Binnendijk. When comparing with observational light curves obtained from this research, it was found that there exist the phase shift of 0 1. It is possible that physical properties of YY Eridani have been changed due to the rotation of its major axis or mass transfer mechanism of the system.

NSVS 1908107, an EB-type eclipsing binary in the open cluster NGC 869

We present a time-series BV CCD photometry for an EB-type eclipsing binary NSVS 1908107, a member of the young open cluster NGC 869. The photometric solution was obtained by using the 2003 version of the Wilson-Devinney code. It reveals that the system is a semi-detached binary with the secondary component filling its Roche lobe. The mass ratio was determined to be 0.059±0.001. With the physical parameters of the cluster, the masses, radii and luminosities of the two components of NSVS 1908107 are estimated to be M1 = 10.34±2.29 M⊙, R1 = 4.65re±0.34 Rspectivel⊙, L1 = 8076 y. The results s±371 L = 2.40 how tha⊙and M2 = 0.61 t the secondary co±0.13M⊙, R2±0.17 R⊙, L2 = 1054±48 L⊙mponent could be a giant or subgiant star with the outer envelope being stripped.

Photometric investigation of the eclipsing binary TX Herculis observed by LUT

The lander of China’s Chang’E-3 spacecraft is equipped with a 15-cm telescope that is very useful for monitoring celestial objects in the ultraviolet(UV) band(245–340 nm).The Lunar-based Ultraviolet Telescope(LUT) is the first long-term lunar-based astronomical observatory,that can make uninterrupted observations of a target from the Moon.Here we present the continuous complete UV light curve of the eclipsing binary TX Herculis(TX Her).The analysis of the light curve suggests that TX Her is a detached binary.The dip in the light curve was explained by the emergence of a stellar dark spot on the less massive F0 type component.The cyclic change of arrival eclipse times for the system reveals that it contains an additional stellar companion with a minimal mass of 0.35 M⊙ and a period of 48.92 yr,which is supported by the detected light contribution of the third body from light curve analysis.This third body may play an important role in the formation of the present short-period system TX Her.

Spot and Facula Activity Variations of the Eccentric Detached Eclipsing Binary KIC 8098300 Based on the Time-series Orbital Solutions

The LAMOST spectra and Kepler light curves are combined to investigate the detached eclipsing binary KIC 8098300,which shows the O’Connell effect caused by spot/facula modulation.The radial velocity(RV)measurements are derived by using the tomographic spectra disentangling technology.The mass ratio q=K1/K2=0.812±0.007,and the orbital semimajor axis a sin i=14.984±0.048 R_(⊙)are obtained by fitting the RV curves.We optimize the binary model concerning the spot/facula activity with the code PHOEBE and obtain precise parameters of the orbit including the eccentricity e=0.0217±0.0008,the inclination i=87°.71±0°.04,and the angle of periastronω=284°.1±0°.5.The masses and radii of the primary and secondary star are determined as M_(1)=1.3467±0.0001 M_(⊙),R_(1)=1.569±0.003 R_(⊙),and M_(2)=1.0940±0.0001 M_(⊙),R_(2)=1.078±0.002 R_(⊙),respectively.The ratio of temperatures of the two component stars is r_(teff)=0.924±0.001.We also obtain the periastron precession speed of 0.000024±0.000001 day cycle-l.The residuals of out-of-eclipse are analyzed using the auto-correlation function and the discrete Fourier transform.The spot/facula activity is relatively weaker,but the lifetime is longer than that of most single main sequence stars in the same temperature range.The average rotation period of the spots P_(rot)=4.32 days is slightly longer than the orbital period,which may be caused by either the migration of spots/faculae along the longitude or the latitudinal differential rotation.The activity may be spot-dominated for the secondary star and facula-dominated for the primary star.The method of this work can be used to analyze more eclipsing binaries with the O’Connell effect in the Kepler field to obtain the precise parameters and investigate the difference of spot behavior between binaries and single stars.It is helpful for a deeper understanding of the stellar magnetic activity and dynamo theory.

Photometric study of an eclipsing binary in Praesepe

We present CCD photometric observations of an eclipsing binary in the direction of the open cluster Praesepe using the 2 m telescope at IUCAA Girawali Observatory, India. Though the system was classified as an eclipsing binary by Pepper et al., detailed investigations have been lacking. The photometric solutions using the Wilson-Devinney code suggest that it is a W-type W UMa system and, interestingly, the system parameters are similar to another contact binary system SW Lac.

Multi-color light curves and orbital period research of eclipsing binary V1073 Cyg

New multi-color BVRcIc photometric observations are presented for the W UMa type eclips- ing binary V1073 Cyg. The multi-color light curve analysis with the Wilson-Devinney procedure yielded the absolute parameters of this system, showing that V 1073 Cyg is a shallow contact binary system with a fill-out factor f = 0.124（±0.011）. We collected all available times of light minima spanning 119yr, including CCD data to construct the O - C curve, and performed detailed O - C analysis. The O - C diagram shows that the period change is complex. A long-term continuous decrease and a cyclic vari- ation exist. The period is decreasing at a rate ofP = -1.04（±0.18） × 10-10 d cycle-land, with the period decrease, V1073 Cyg will evolve to the deep contact stage. The cyclic variation with a period of P3 = 82.7（±3.6） yr and an amplitude of A = 0.028（±0.002） d may be explained by magnetic activ- ity of one or both components or the light travel time effect caused by a distant third companion with M3（i1 = 90°） = 0.511 M⊙.

Absolute parameters and observed flares in the M-type detached eclipsing binary 2MASS J04100497+2931023

The eclipsing binary 2 MASS J04100497+2931023(J04100497+2931023) is classified its spectral type of M0±2 V on basis of a low-resolution spectral survey by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST). The low-resolution spectra exhibit strong single-peak emission in the Hα line. We obtained the radial velocities of this binary by means of the Cross-Correlation Function method from the LAMOST medium-resolution spectra. Both components of J04100497+2931023 indicate strong emissions in the Hα line. We performed follow-up photometric observations of J04100497+2931023 using the Xinglong 85 cm telescope of National Astronomical Observatories, Chinese Academy of Sciences. We obtained its full light curve in V RI filters. We first determined their absolute parameters from simultaneously radial velocity and light curves by the Wilson-Devinney program. From our new light curves, we detected three flares for the first time, including one convective flare. The amplitudes,durations, energies, and spectral indices of three flares were also determined. J04100497+2931023 was monitored for approximately 29 h, which indicates that the flare rate is 0.1 flare per hour. We conclude that J04100497+2931023 is a low-mass detached eclipsing binary with strong magnetic activity.

Eclipsing binary XZ CMi in a hierarchical quadruple system

The new complete BV Rc Ic light curves and spectra of the short-period eclipsing binary XZ CMi are presented.The results from the combined analysis based on the photometric and spectroscopic data show that XZ CMi is a near contact binary with the secondary component filling its critical Roche lobe while the primary filling 91%of its Roche lobe.The investigation of the O-C diagram reveals that its orbital period is continuously increasing,which is consistent with the derived configuration and caused by the mass transfer from the less massive star to the more massive one.In addition,an obvious periodic modulation with the amplitude of0.0187(±0.0016)d and a high eccentric of 0.86(±0.04)is detected,which could be the results of the light time effect as a third star with the mass no less than 0.42(±0.09)M⊙orbiting around the central eclipsing binary once every 95.7(±2.1)yr.Furthermore,we found a visual companion star at 2.4′′east by south of this system at a much greater distance by direct image.The large third light contribution found from the light curve analysis could be well explained by the existence of the third star and the fourth visual one.The similar parallax and proper motion imply that the components of this hierarchical quadruple system might be bounded by gravitation.Spectroscopic observations for two visual components were carried out by the LAMOST and 2.16 m telescopes,respectively.Their different values of[Fe/H]suggest that they were not born from the same origin.Thus,XZ CMi system is an interesting and important target to study the formation of the multiple stars.

Analysis of TESS Field Eclipsing Binary Star V948 Her: A Pulsating or Non-pulsating Star?

Pulsating stars occupy a significant place in the H-R diagram and it was thought that all stars inside the classical instability strip should pulsate. However, recent studies showed that there are many non-pulsating stars located inside the classical instability strip. The existence of these non-pulsating stars is still a mystery. To deeply understand the properties of these non-pulsating and pulsating stars, one needs precise fundamental stellar parameters(e.g. mass).For this purpose, the eclipsing binaries are unique systems. Hence, in this study, we present the TESS data analysis of one candidate pulsating eclipsing binary system, V948 Her. TESS data were used for the binary modeling with the literature radial velocity measurements, and the precise fundamental parameters of the system were obtained. The system’s age was derived as 1 ± 0.24 Gyr. The positions of the binary components in the H-R diagram were examined and the primary component was found inside the δ Scuti instability strip. However, in the frequency analysis of TESS data, we found no significant pulsation frequencies. Only the harmonics of the orbital periods were obtained in the analysis. Therefore, the system was classified as a non-pulsator. V948 Her is an important object to understand the nature of non-pulsating stars inside the δ Scuti instability strip.

Candidate Eclipsing Binary Systems with aδScuti Star in Northern TESS Field

The existence of pulsating stars in eclipsing binaries has been known for decades.These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipse and pulsation variations.The eclipsing binaries are the only way to directly measure the mass and radius of stars with a good accuracy(≤1%),while the pulsations are a unique way to probe the stellar interior via oscillation frequencies.There are different types of pulsating stars existing in eclipsing binaries.One of them is theδScuti variables.Currently,the known number ofδScuti stars in eclipsing binaries is around 90 according to the latest catalog of these variables.An increasing number of these kinds of variables is important to understand the stellar structure,evolution and the effect of binarity on the pulsations.Therefore,in this study,we focus on discovering new eclipsing binaries withδScuti component(s).We searched within the northern Transiting Exoplanet Survey Satellite(TESS)field with a visual inspection by following some criteria such as light curve shape,the existence of pulsation like variations in the out-of-eclipse light curve and the T_(eff) values of the targets.As a result of these criteria,we discovered some targets.The orbital variations were first removed from the TESS light curves and frequency analysis was performed on the residuals.The luminosity,and absolute and bolometric magnitudes of the targets were calculated as well.To find how much of these parameters represent the primary(more luminous)binary component,we also computed the flux density ratio of the systems by utilizing the area of the eclipses.In addition,the positions of the systems in the H-R diagram were examined considering the flux density ratios.As a consequence of the investigation,we defined 38 candidateδScuti stars and also one Maia variable in eclipsing binary systems.

Investigation of the shortest period Am type eclipsing binary TYC 6408–989–1

The first BV bands photometric observations and the low-resolution spectrum of the shortest period Am type eclipsing binary TYC 6408-989-1 have been obtained.The stellar atmospheric parameters of the primary star were obtained through the spectral fitting as follows:Teff=6990±117 K,log g=4.25±0.26 cm s^(-2),[Fe/H]=-0.45±0.03 dex.The original spectra obtained by European Southern Observatory(ESO)were processed with an IRAF package by us.Based on the ESO blue-violet spectra,TYC 6408-989-1 was concluded as a marginal Am(Am:)star with a spectral type of kA3 hF1 mA5Ⅳ-Ⅴidentified through the MKCLASS program.The observed light curves were analyzed through the WilsonDevinney code.The final photometric solutions show that TYC 6408-989-1 is a marginal contact binary with a low mass ratio(q=0.27).The temperature of the secondary component derived through the light curve analysis is significantly higher than main sequence stars.In addition,TYC 6408-989-1 is a poor thermal contact binary.The temperature differences between the two components is about 1800 K.TYC6408-989-1 should be located in the oscillation stage predicted by the thermal relaxation oscillations theory(TRO)and will evolve into the shallow contact stage eventually.The very short period(less than one day),marginal Am peculiarity and quite large rotational velocity(v sin i■160 km s^(-1))make TYC 6408-989-1 become a challenge to the cut-off of rotation velocities and periods of Am stars.We have collected the well known eclipsing Am binaries with absolute parameters from the literature.

1SWASP J034439.97+030425.5:a short-period eclipsing binary system with a close-in stellar companion

First multi-wavelength photometric light curves(LCs)of the short-period eclipsing binary(EB)1 SWASP J034439.97+030425.5(hereafter J0344)are presented and analyzed by using the 2013 version of the Wilson-Devinney(W-D)code.To explain the asymmetric LCs of J0344,a cool star-spot on the less massive component was employed.The photometric solutions suggest that J0344 is a W-subtype shallow contact EB with a contact degree of f=4.9%±3.0%and a mass ratio of q=2.456±0.013.Moreover,an obvious third light was detected in our analysis.We calculated the average luminosity contribution of the third light to the total light,and that value reaches up to 49.78%.Based on the O-C method,the variations of the orbital period were studied for the first time.Our O-C diagram reveals a secular decrease superimposed on a cyclic oscillation.The orbital period decreases at a rate of d P/dt=-6.07×10-7 d yr-1,which can be explained by the mass transfer from the more massive component to the less massive one.Besides,its O-C diagram also shows a cyclic oscillation with an amplitude of 0.0030 d and a period about 7.08 yr,which can be explained by the presence of a third body with a minimum mass of M3 min=0.15±0.02 M⊙.The third component may play an important role in the formation and evolution of J0344 by drawing angular momentum from the central system.

Photometric study of an eclipsing binary in the field of M37

CCD photometric observations with B and V passbands were performed on the contact binary V3 in the field of open cluster M37. The solutions were obtained for data from both B and V passbands along with R passband given by Hartman et al. using the Wilson-Devinney code. The positive O＇Connell effect was observed in all the three passbands and its associated cool spot parameters were derived. The results indicate that the spot parameters have not shown any significant variability during the last four years. The spot radius was found to be 40° and located close to the equator of the secondary component. The absolute parameters of the system were derived using the empirical relations given by Gazeas et al.

Four New Eclipsing Binary Systems in the TESS field:CD-3413220,HD 295082,TYC 6484–426–1 and TYC 6527–2310–1

We present the first evidence for the binarity of four targets in the TESS field.The temperatures are estimated by SED analysis and the orbital periods are determined.The TESS light curves of the systems are analyzed and the orbital and the absolute parameters are derived.The targets are also compared to wellstudied binary systems with the same morphological type and their evolutionary states are discussed.Our results indicate that the stars belong to the class of eclipsing detached binary systems.

TZ Lyrae:an Algol-type Eclipsing Binary with Mass Transfer

We present a detailed investigation of the Algol-type binary TZ Lyrae, based on 55 light minimum timings spanning 90 years. It is found that the orbital period shows a long-term increase with a cyclic variation superimposed. The rate of the secular increase is dP/dt = ＋7.18 × 10^-8d yr^-1, indicating that a mass transfer from the less massive component to the more massive one at a rate of dra = ＋2.21 × 10^-8M⊙ yr^-1. The cyclic component, with a period of P3 = 45.5 yr and an amplitude of A = 0.^d0040, may be interpreted as either the light-time effect in the presence of a third body or magnetic activity cycles in the components. Using the latest version Wilson-Devinney code, a revised photometric solution was deduced from B and V observations. The results show that TZ Lyr is an Algol-type eclipsing binary with a mass ratio of q = 0.297±0.003）. The semidetached configuration with a lobe-filling secondary suggests a mass transfer from the secondary to the primary, which is in agreement with the long-term period increase of the binary system.

The evolution of eccentricity in the eclipsing binary system AS Camelopardalis

In 2002,2004 and 2017 we conducted high precision CCD photometry observations of the eclipsing binary system AS Cam.By analysis of the light curves from 1967 to 2017（our data ＋ data from the literature） we obtained photometric elements of the system and found a change in the system＇s orbital eccentricity of ？e = 0.03 ± 0.01.This change can indicate that there is a third companion in the system in a highly inclined orbit with respect to the orbital plane of the central binary,and its gravitational influence may cause the discrepancy between observed and theoretical apsidal motion rates of AS Cam.

First photometric study of the eclipsing binary PS Persei

CCD photometric observations of the eclipsing binary PS Persei （PS Per） were obtained on two consecutive days in 2009.The 2003 version of the WilsonDevinney code was used to analyze the first complete light curves in the V and R bands.It is found that PS Per is a short-period Algol-type binary with the less massive component completely filling its inner critical Roche lobe.The mass ratio of q=0.518 and the orbital inclination of i=89.86° are obtained.In addition,based on all available times of primary light minima,including two new ones,the orbital period has been improved.

Photometric analysis of a blue straggler eclipsing binary in the old open cluster NGC 2141

To understand the formation mechanism of blue stragglers in open clusters, we conducted a photometric analysis for a blue straggler eclipsing binary in the old open cluster NGC 2141. By using the least square fitting of times of minima, we derived the ephemeris and redetermined the orbital period of this system to be 0.6227 d. We have also done a photometric analysis for light curve with the Wilson-Devinney Code （2003）. The photometric solutions reveal a semi-detached binary with the second- ary component filling its Roche lobe. The photometric mass ratio MJMI （secondary/primary） was determined to be 0.190_＋0.002 and the ratio of V-band luminosity L2/LI（V） is about 0.033_＋0.001, which indicates the secondary component is overluminous. Thus, this blue straggler likely results from a substantial mass exchange between these two components.

A close-in substellar object orbiting the sd OB-type eclipsing-binary system NSVS 14256825

NSVS 14256825 is the second discovered sdOB+dM eclipsing-binary system with an orbital period of 2.65 h. This special binary was reported to contain circumbinary planets or brown dwarfs by using the timing method. However, different results were derived by different authors because of the insufficient coverage of eclipse timings. Since 2008, we have monitored this binary for about 10 yr using several telescopes and 84 new times of light minimum were obtained with high precision. It is found that the O-C curve has been increasing recently and it shows a cyclic variation with a period of 8.83 yr and an amplitude of 46.31 seconds. The cyclic change cannot be explained by magnetic activity cycles of the red dwarf component because the required energy is much larger than that radiated by this component in one whole period. This cyclic change detected in NSVS 14256825 could be explained by the light-travel time effect via the presence of a third body. The lowest mass of the third body is determined to be 14.15 Mjupwhich is in the transition range between planets and brown dwarfs. The substellar object is orbiting around this evolved binary at an orbital separation of around 3 AU with an eccentricity of 0.12. These results indicate that NSVS 14256825 is the first sdOB-type eclipsing binary consisting of a hierarchical substellar object.The detection of a close-in substellar companion to NSVS 14256825 will provide some insights on the formation and evolution of sdOB-type binaries and their companions.

The first photometric analysis of the totally eclipsing contact binary V811 Cep

The first photometric analysis of V811 Cep was carried out.The first complete light curves of V,R and I bands are given.The analysis was carried out by the Wilson-Devinney(W-D)program,and the results show that V811 Cep is a median-contact binary(f=33.9(±4.9)%)with a mass ratio of 0.285.It is a W-subtype contact binary,that is,the component with less mass is hotter than the component with more mass,and the light curves are asymmetric(O’Connell effect),which can be explained by the existence of a hot spot on the component with less mass.The orbital inclination is i=88.3°,indicating that it is a totally eclipsing binary,so the parameters obtained are reliable.Through the O-C analyzing,it is found that the orbital period decreases at the rate of P=-3.90(±0.06)×10^(-7)d yr^(-1),which indicates that the mass transfer occurs from the more massive component to the less massive one.