Physical and geometrical parameters of CVBS X: the spectroscopic binary Gliese 762.1

We present the physical and geometrical parameters of the individual components of the close visual double-lined spectroscopic binary system Gliese 762.1, which were estimated using Al-Wardat's complex method for analyzing close visual binary systems. The estimated parameters of the individual components of the system are as follows: radius RA= 0.845±0.09R⊙, RB= 0.795±0.10R⊙, effective temperature TA eff= 5300luminosity±50 K, TB eff= 5150 L±50 K, surface gravity log gA= 4.52±0.10, log gB=4.54±0.15 and A= 0.51 with a semi-major axis of 0.0865±0.08L⊙, LB= 0.40±0.07L⊙. New orbital elements are presented±0.010 arcsec using the Hippracos parallax π = 58.96 ndividual masses of the system are determined as M = 1.±0.65 mas, and an accurate total mass and i72±0.60 M⊙,MA= 0.89±0.08 M⊙and MB= 0.83 K0 V and±0.07 M⊙. Finally, the spectral types and luminosity classes of both components are assigned as K1.5V for the primary and secondary components respectively,and their positions on the H-R diagram and evolutionary tracks are given.     

Physical and geometrical parameters of VCBS XIII: HIP 105947

The best physical and geometrical parameters of the main sequence close visual binary system(CVBS), HIP 105947, are presented. These parameters have been constructed conclusively using Al-Wardat's complex method for analyzing CVBSs, which is a method for constructing a synthetic spectral energy distribution(SED) for the entire binary system using individual SEDs for each component star. The model atmospheres are in its turn built using the Kurucz(ATLAS9) line-blanketed plane-parallel models. At the same time, the orbital parameters for the system are calculated using Tokovinin's dynamical method for constructing the best orbits of an interferometric binary system. Moreover, the mass-sum of the components, as well as the ?θ and ?ρ residuals for the system, is introduced. The combination of Al-Wardat's and Tokovinin's methods yields the best estimations of the physical and geometrical parameters. The positions of the components in the system on the evolutionary tracks and isochrones are plotted and the formation and evolution of the system are discussed.     

Photometric studies of two W UMa type variables in the field of distant open cluster NGC 6866

We present photometric analysis of the two W UMa type binaries identified in the field of distant open star cluster NGC 6866. Although these systems, namely ID487 and ID494, were reported by Joshi et al., a detailed study of these stars has not been carried out before. The orbital periods of these stars are found to be 0.415110±0.000001 day and 0.366709±0.000004 day, respectively. Based on the photometric and infrared colors, we find their respective spectral types to be K0 and K3. The photometric light variations of both stars show the O'Connell effect which can be explained by employing a dark spot on the secondary components. The V and I band light curves are analyzed using the Wilson-Devinney(WD) code and relations given by Gazeas which yield radii and masses for the binary components of star ID487 of R_1= 1.24 ± 0.01R⊙, R_2 = 1.11 ± 0.02R⊙, and M_1 = 1.24 ± 0.02M⊙, M_2 = 0.96 ± 0.05M⊙and for star ID494 of R_1 = 1.22 ± 0.02R⊙, R_2 = 0.81 ± 0.01 R0 ⊙, and M_1 = 1.2± 0.06 M⊙, M_2 = 0.47 ± 0.01M⊙.     

Investigation of near-contact semi-detached binary W UMi through observations and evolutionary models

W UMi is a near contact, semi-detached, double-lined eclipsing binary star with an orbital period of 1.7 d. Simultaneous analysis of new BV R multi-color light curves and radial velocity data yields the main astrophysical parameters of the binary and its component stars. We determined mass and radius to be M_1 = 3.22 ± 0.08 M_⊙, R_1 = 3.63 ± 0.04 R_⊙ for the primary star and M_2 = 1.44 ± 0.05 M_⊙,R_2 = 3.09 ± 0.03 R_⊙ for the secondary star. Based on analysis of mid-eclipse times, variation in the orbital period is represented by a cyclic term and a downward parabola. Mass loss from the system is suggested for a secular decrease(-0.02 s yr~(-1)) in the period. Both the mechanisms of a hypothetical tertiary star orbiting around W UMi and the surface magnetic activity of the less massive cooler companion were used to interpret periodic changes. Observational parameters were found to be consistent with binary stellar evolution models produced in the non-conservative approach of MESA at a higher metallicity than the Sun and an age of about 400 Myr for the system. Evidence that the system is rich in metal was obtained from spectral and kinematic analysis as well as evolution models. W UMi, a high mass ratio system compared to classical semi-detached binaries, is an important example since it is estimated from binary evolutionary models that the system may reach its contact phase in a short time interval.     

Long-term photometric study of a faint W UMa binary in the direction of M31

We carry out a re-analysis of the photometric data in R_cI_c bands which were taken during the Nainital Microlensing Survey from 1998 to 2002 with the aim to detect gravitational microlensing events in the direction of M31. Here, we do photometric analysis of a faint W UMa binary CSS_J004259.3 +410629 identified in the target field. The orbital period of this star is found to be 0.266402±0.000018 d.The photometric mass ratio, q,is found to be 0.28 ± 0.01. The photometric light curves are investigated using the Wilson-Devinney(WD) code and absolute parameters are determined using empirical relations which provide masses and radii of the binary as M_1 = 1.19 ± 0.09 M_☉,M_2 = 0.33 ± 0.02 M_⊙ and R_1=1.02±0.04 R_⊙,R_2 = 0.58 ±0.08 R_⊙ respectively based on R_c band data. Quite similar values are found by analyzing I_c band data. From the photometric light curve examination, the star is understood to be a low mass-ratio overcontact binary of A-subtype with a high fill-out factor of about 47%. The binary system is found to be located approximately at a distance of 2.64 ± 0.03 kpc having a separation of 2.01 ± 0.05 R_⊙ between the two components.     

NSVS 2569022:a peculiar binary among W UMa stars with extremely small mass ratios

Photometric observations of the W UMa binary NSVS 2569022 are presented. The light curve solution reveals that both components are of F spectral type(temperatures T_1= T_2= 6100 K). NSVS2569022 undergoes a total eclipse of W subtype and the mass ratio is well-determined. Its extremely small value of only 0.077 implies that the target will probably experience instability and a possible merger. This value ranks NSVS 2569022 in sixth place among binaries with the smallest mass ratio.Based on an empirical relation of "period – total mass" for low mass-ratio binaries, we estimate the global parameters of NSVS 2569022: masses M_1= 1.17 M⊙and M_2= 0.09 M⊙; radii R_1= 1.19 R⊙and R_2= 0.38 R⊙; luminosities L_1= 1.73 L⊙and L_2= 0.17 L⊙. An analysis of the characteristics of binaries with extremely low-mass ratios is made. NSVS 2569022 turns out to be a peculiar binary among W UMa stars with extremely small mass ratios due to its unexpectedly small fill-out factor of only 0.014(slightly overcontact configuration).     

Spectroscopic and photometric studies of a candidate pulsating star in an eclipsing binary:V948 Her

Eclipsing binary stars with a pulsating component are powerful tools that allow us to probe the stellar interior structure and the evolutionary statuses with a good accuracy. Therefore, in this study,spectroscopic and photometric examinations of an eclipsing binary system V948 Her are presented. The primary component of the system is classified to be a candidate δ Scuti variable in the literature. The fundamental stellar, atmospheric and orbital parameters, and the surface abundance of the star were determined and the pulsation behaviour was investigated in this study. The orbital parameters were derived by the analysis of radial velocity and Super WASP light curves. The spectral classification was found to be F2V. The initial atmospheric parameters of the primary component were derived by analysis of the spectral energy distribution and hydrogen lines. The final atmospheric parameters and chemical abundances of the primary component were obtained by using the method of spectrum synthesis. As a result, the final atmospheric parameters were determined as T_(eff)= 7100±200 K, log g= 4.3±0.1 cgs and ξ = 2.2 ± 0.2 km s~(-1). The surface abundance was found to be similar to solar. The fundamental stellar parameters of both components were also obtained to be M = 1.722 ± 0.123, 0.762 ± 0.020 M⊙, R =1.655 ± 0.034, 0.689 ± 0.016 R⊙for primary and secondary components, respectively. The pulsation characteristic of the primary component was examined using Super WASP data and the pulsation period was found to be ~0.038 d. The position of the primary pulsating component was also obtained inside the instability strip of δ Sct stars. The primary component of V948 Her was defined to be a δ Sct variable.     

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 on the W-subtype contact binary V1197 Her

Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at the Thai National Observatory and the Wilson-Devinney(W-D) program was used to model the observational light curves. The photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of q = 2.61 and a fill-out factor of f = 15.7%. The temperature difference between the primary star and secondary star is only 140 K in spite of the low degree of contact, which means that V1197 Her is not only in geometrical contact configuration but is also already under thermal contact status.The orbital inclination of V1197 Her is as high as i = 82.7?, and the primary star is completely eclipsed at the primary minimum. The totally eclipsing characteristic implies that the determined physical parameters are highly reliable. The masses, radii and luminosities of the primary star(star 1) and secondary star(star2) are estimated to be M1 = 0.30(1) M_⊙, M2 = 0.77(2) M_⊙, R1 = 0.54(1) R_⊙, R2 = 0.83(1) R_⊙,L1 = 0.18(1) L_⊙and L2 = 0.38(1) L_⊙. The evolutionary statuses of the two component stars are drawn in the Hertzsprung-Russell diagram, showing that the less massive but hotter primary star is more evolved than the secondary star. The period of V1197 Her is decreasing continuously at a rate of d P/dt =-2.58 ×10-7 day · year-1, which can be explained by mass transfer from the more massive star to the less massive one at a rate of dM_2/dt=-1.61 × 10~(-7) M_⊙year~(-1). The light curves of V1197 Her are reported to show the O'Connell effect. Thus, a cool spot is added to the more massive star to model the asymmetry in the light curves.     

CN Andromedae:a shallow contact binary with a possible tertiary component

In this study, new photometric observations of shallow contact binary CN Andromedae(CN And)were performed and multi-color(BV R) CCD light curves(LCs) were obtained. Simultaneous analysis of new LCs and published radial velocity(RV) data reveals that the system is an early contact binary in which both components have recently filled their inner Roche lobes. Asymmetric LCs were modeled by a dark spot on the primary component and a hot spot on the secondary component that probably resulted from magnetic activity and mass transfer, respectively. Modeling of LCs and RV data allows us to estimate the following absolute parameters: M1= 1.40 ± 0.02 M⊙, M2= 0.55 ± 0.01 M⊙, R1= 1.45 ± 0.02 R⊙and R2= 0.94 ± 0.02 R⊙. A decreasing orbital period with a rate of d P/dt =-1.5 × 10-7d yr-1can be seen as evidence that the system is evolving into a contact binary with higher contact degree. Cyclic oscillation of the O-C data was interpreted by the Applegate mechanism and light-time effect due to an unseen component around the close binary system. The hypothetical third component is probably a fully convective red dwarf star with a minimal mass of 0.1 M⊙. CN And is at the early phase of the contact stage of its evolution and is an interesting example for studying the formation and evolution of close binaries.     

Absolute parameters of the three totally-eclipsing W UMa stars NSVS 2443858, NSVS 780649 and V1098 Her

We present the first photometric analysis of three totally-eclipsing W UMa binaries,NS VS2443858,NSVS 780649 and V1098 Her.The absolute astrophysical parameters of the stellar components were determined by means of Gaia distances and light curve solutions.The results show that:(ⅰ) Two of the systems,NSVS 2443858 and V1098 Her,are of A subtype while the obtained temperature of the secondary component of NSVS 780649 indicates that it is a W-subtype system;(ⅱ) The estimated mass ratios approach the lower limit of the mass ratio assumed by researchers in recent years so our targets could be classified as extreme mass ratio binary(EMRB) systems;(ⅲ) All the systems have deep contact configurations,so they also are deep low mass ratio(DLMR) systems;(ⅳ) The components of our systems are stars of F and G spectral type and undergo total eclipses;(ⅴ) The sum 0.871 M_⊙ of the component masses of NSVS 780649 is below the mass limit of 1.0-1.2 M_⊙ assumed for the known contact binary stars.     

Physical and geometrical parameters of CVBS XIV:the two nearby systems HIP 19206 and HIP 84425

Data release 2(DR2) from the Gaia mission was of great help in precise determination of fundamental parameters of Close Visual Binary and Multiple Systems(CVBMSs), especially masses of their components, which are crucial parameters in understanding formation and evolution of stars and galaxies. This article presents the complete set of fundamental parameters for two nearby close visual binary systems(CVBSs), which are HIP 19206 and HIP 84425. We utilised a combination of two methods; the first one is Tokovinin's dynamical method to solve the orbit of the system and to estimate orbital elements and the dynamical mass sum, and the second one is Al-Wardat's method for analysing CVBMSs to estimate the physical parameters of the individual components. The latest method employs grids of Kurucz lineblanketed plane parallel model atmospheres to build synthetic Spectral Energy Distributions(SEDs) of the individual components. Trigonometric parallax measurements given by Gaia DR2 and Hipparcos catalogues are used to analyse the two systems. The difference in these measurements yielded slight discrepancies in the fundamental parameters of the individual components, especially masses. So, a new dynamical parallax is suggested in this work based on the most convenient mass sum as given by each of the two methods. The new dynamical parallax for the system HIP 19205 of 22.97±0.95 mas coincides well with the trigonometric one reported recently(in December 2020) by Gaia EDR3 of 22.3689 ± 0.4056 mas. The positions of the components of the two systems on the evolutionary tracks and isochrones are plotted, which suggest that all components are solar-type main sequence stars. Their most probable formation and evolution scenarios are also discussed.     

New photometric investigation of the low-mass-ratio contact binary star V1853 Orionis

Four-color charge-coupled device(CCD) light curves in the B, V, Rc and I c bands of the totaleclipsing binary system V1853 Orionis(V1853 Ori) are presented. By comparing our light curves with those published by previous investigators, it is determined that the O'Connell effect on the light curves has disappeared. By analyzing those multi-color light curves with the Wilson-Devinney code(W-D code),it is discovered that V1853 Ori is an A-type intermediate-contact binary with a degree of contact factor of f = 33.3%(3.7%) and a mass ratio of q = 0.1896(0.0013). Combining our 10 newly determined times of light minima together with others published in the literature, the period changes of the system are investigated. We found that the general trend of the observed minus calculated(O-C) curve shows a downward parabolic variation that corresponds to a long-term decrease in the orbital period with a rate of d P/dt =-1.96(0.46)×10~(-7) d yr~(-1). The long-term period decrease could be explained by mass transfer from the more-massive component to the less-massive one. By combining our photometric solutions with data from Gaia DR_2, absolute parameters were derived as M_1 = 1.20 M⊙, M_2 = 0.23 M⊙, R_1 = 1.36 R⊙and R_2 = 0.66 R⊙. The long-term period decrease and intermediate-contact configuration suggest that V1853 Ori will evolve into a high fill-out overcontact binary.     

Photometric study and period analysis of the W UM-type binary system QW Gem

New multi-color photometric observations of the previously unstudied contact binary QW Gem are presented. Completely covered BVRI band light curves were obtained, including four new times of light minima. The light curves were simultaneously analyzed with the 2013 version of the Wilson-Devinney method, assuming a third light. The photometric solutions confirm that QW Gem is a W-type W UMa system with a fill-out factor of f~17%. The absolute parameters of the components were determined to be M_p= 1.33 ± 0.03 M_☉,M_s = 0.44 ± 0.01 M_☉,R_p = 1.25 ± 0.01 R_☉,R_s = 0.77 ± 0.01 R_☉,Lp= 1.68 ± 0.03 L_☉ and L_s = 0.68 ± 0.01 L_☉. The orbital period change of QW Gem was investigated by the O-C method using all available data. The results show that this binary system could have undergone a continuous orbital period decrease during the past two decades at a rate of about dP/dt =-2.55 × 10~(-7) d yr~(-1). In addition, a small-amplitude oscillation was detected to be superimposed on a long-term decrease.     

LO And: an A-subtype contact binary with a very cool third component

Despite the intensive investigations since the discovery of LO And approximately 60 yr ago, its evolutionary status and subtype are still a matter of controversy. By simultaneously modeling the radialvelocity curves and new light curves with the Wilson-Devinney code, we present new geometric,photometric and absolute parameters for this system. The simultaneous solution suggests that LO And is an A-subtype contact binary with a contact degree of 32.4%. The absolute parameters are modified to become M_1= 1.409 M⊙, M_2= 0.449 M⊙, R_1= 1.36 R⊙and R_2= 0.83 R⊙. From our observations and data from surveys, we determined 334 eclipse timings. The O-C diagram, constructed from the new eclipse timings and those reported in the literature, reveals a secular increase and a cyclic variation in its orbital period. The former is caused by conservative mass transfer from the secondary component with less mass to the primary one with more mass. The latter may be explained by either the cyclic magnetic activity on the two components or the light-time effect due to a third body. With the absolute physical parameters,we investigated its evolutionary status, and find that LO And is an unevolved contact binary undergoing thermal relaxation oscillation, which will eventually coalesce into a single star with rapid rotation.     

Period investigation of Algol systems TZ Eri and TU Her

TZ Eri and TU Her are both classic Algol-type systems(Algols). By observing and collecting times of minimum light, we constructed the O-C curves for the two systems. The long-time upward and downward parabolas shown in these diagrams are considered to be the result of the combination of mass transfer and angular momentum loss. The secular orbital period change rates are d P/dt = 4.74(±0.12) ×10~(-7) d yr~(-1) and d P/dt =-2.33(±0.01) × 10~(-6) d yr~(-1), respectively. There are also cyclic variations in their O-C curves which might be caused by the light-travel time effect(LTTE). A circumbinary star may exist in the TZ Eri system with a mass of at least 1.34 M_⊙, while there are possibly two celestial bodies that almost follow a 2 : 1 resonance orbit around the TU Her binary pair. Their masses are at least 2.43 M_⊙and 1.27 M_⊙.     

Evolutions of CH_3CN abundance in molecular clumps

To investigate the effects of massive star evolution on surrounding molecules,we select nine massive clumps previously observed with the Atacama Pathfinder Experiment(APEX) telescope and the Submillimeter Array(SMA) telescope.Based on the observations of APEX,we obtain luminosity to mass ratios L_(clump)/M_(clump) that range from 10 to 154 L_⊙/M_⊙,where some of them embedded ultra compact(UC) H Ⅱ region.Using the SMA,CH_3CN(12_K-11_K) transitions were observed toward nine massive starforming regions.We derive the CH_3CN rotational temperature and column density using the XCLASS program,and calculate its fractional abundance.We find that CH_3CN temperature seems to increase with the increase of L_(clump)/M_(clump) when the ratio is between 10 to 40 L_⊙/M_⊙,then decrease when L_(clump)/M_(clump)≥ 40 L_⊙/M_⊙.Assuming that the CH_3CN gas is heated by radiation from the central star,the effective distance of CH_3CN relative to the central star is estimated.The distance ranges from ～ 0.003 to ～ 0.083 pc,which accounts for ～ 1/100 to ～ 1/1000 of clump size.The effective distance increases slightly as L_(clump)/M_(clump) increases(R_(eff)～(L_(clump)/M_(clump))~(0.5±0.2)).Overall,the CH_3 CN abundance is found to decrease as the clumps evolve,e.g.,X_(CH_3CN) ～(L_(clump)/M_(clump))~(-1.0±0.7).The steady decline of CH_3CN abundance as the clumps evolution can be interpreted as a result of photodissociation.     

Orbital period correction and light curve modeling of the W-subtype shallow contact binary OW Leo

Orbital period and multi-color light curves’investigation of OW Leo are presented for the first time.The orbital period of OW Leo is corrected from P=0.325545 days to P=0.32554052 days in our work,and the observational data from the All-Sky Automated Survey for Super Novae(ASAS-SN)are used to test the newly determined orbital period.Then,the phased light curves are calculated with the new period and the Wilson-Devinney program is applied to model the light curves,which reveal that OW Leo is a W-subtype shallow contact binary system(q=3.05,f=12.8%).The absolute physical parameters of the two component stars are estimated to be M₁=0.31(1)M_⊙,M₂=0.95(3)M_⊙,R₁=0.63(1)R⊙,R₂=1.04(1)R_⊙,L₁=0.43(1)L_⊙and L₂=1.01(2)L_⊙.The evolutionary status shows that the more massive star is less evolved than the less massive star.OW Leo has very low metal abundance,which means its formation and evolution are hardly influenced by any additional component.It is formed from an initially detached binary system through nuclear evolution and angular momentum loss via magnetic braking,and has passed a very long time of main sequence evolution.     

Photometric solution and period analysis of the contact binary system AH Cnc

Photometric observations of AH Cnc,a W UMa-type system in the open cluster M67,were carried out by using the 50 BiN telescope.About 100 h of time-series B- and V-band data were taken,based on which eight new times of light minima were determined.By applying the Wilson-Devinney method,the light curves were modeled and a revised photometric solution of the binary system was derived.We confirmed that AH Cnc is a deep contact(f= 51%),low mass-ratio(q = 0.156) system.Adopting the distance modulus derived from study of the host cluster,we have re-calculated the physical parameters of the binary system,namely the masses and radii.The masses and radii of the two components were estimated to be respectively 1.188(±0.061) M_☉,1.332(±0.063) R_☉ for the primary component and 0.185(±0.032) M_☉,0.592(±0.051) R_☉ for the secondary.By adding the newly derived minimum timings to all the available data,the period variations of AH Cnc were studied.This shows that the orbital period of the binary is continuously increasing at a rate of dp/dt = 4.29×10~(-10)dyr~(-1).In addition to the long-term period increase,a cyclic variation with a period of 35.26 yr was determined,which could be attributed to an unresolved tertiary component of the system.     

The stellar system HIP 101227: is it a binary,a triple or a quadruple system?

In this paper, we present the analysis of the stellar system HIP 101227 to determine the actual number of components in the system, and their properties. We use dynamical modeling and complex spectrophotometric(involving atmospheric modeling) techniques with recent data, to determine the physical properties and orbital solution for the system, respectively, with better accuracy than past studies. Based on our analysis, we found that the system is more consistent with being a quadruple rather than a binary or a triple system as suggested by previous studies. The total mass of the system determined from our SED analysis is 3.42 ± 0.20 M, which is distributed almost equally between the four stars. The stars are found to be zero-age main sequence stars; i.e., at the last stage of pre-main sequence, with age less than 200 Myr and spectral types K0. All four stars have very similar physical characteristics, suggesting that the fragmentation process is the most likely theory for the formation and evolution of the system.