The first photometric solution and period variation of BG Vul binary star

New Astronomy 28 (2014) 79–84

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The first photometric solution and period variation of BG Vul binary star Mehmet Tanrıver ⇑ Astronomy and Space Science, Science Faculty, University of Erciyes, Kayseri 38039, Turkey

h i g h l i g h t s  We present the first photometric analysis of the BG Vul binary system.  We analysed the orbital period changing.  We get that there is mass transfer from the second component to the primary.  We demonstrated that BG Vul should be an A-type W UMa binaries.  We proposed the possible evolutionary statue.

a r t i c l e

i n f o

Article history: Received 9 September 2013 Received in revised form 25 September 2013 Accepted 29 September 2013 Available online 22 October 2013 Communicated by P.S. Conti Keywords: Stars: binaries: eclipsing Stars: late-type Stars: individual: (BG Vul) Stars: fundamental parameters

a b s t r a c t This study is focused on the photometric solution of stars of the G2V spectral type. Photometric solutions light curve analysis in V-band were applied to the sun-like star (BG Vul) located in the ASAS catalog. The light curve of BG Vul showed variation in W UMa (EW/KW) type. Absolute parameters very close to the astrophysical fundamental values of the sun were obtained as a result of the solution. Period variation of the sun-like BG Vul variable star selected from the solar analog star list of Tanriver (2012, 2013) was performed. We conducted an unspotted solution for the BG Vul binary system. The masses of the primary and secondary components for BG Vul were M1 = 1.017 M and M2 = 0.895 M, respectively, while the radius for the primary was R1 = 1.238 R, and R2 = 1.176 R for the secondary. The temperatures of the primary and secondary were T1 = 5868 K and T2 = 5520 K, respectively. We revealed that BG Vul is most likely a member of the A-type subclass of W UMa binaries. Ó 2013 Elsevier B.V. All rights reserved.

1. Introduction The BG Vul (NSVS 8746889, 2MASS J21192440+2202413, ASAS ID 211924+2202.7) binary system is classified as an eclipsing binary of W UMa type (a contact binary) in the SIMBAD database and as EC (eclipsing contact, contact or almost contact configurations) in the ASAS catalog. It is an EW/KW type of variability in GCVS classification. W UMa contact binaries are very common eclipsing variables in which the eclipsing light curves have nearly equal minima. Binnendijk (1970) classified W UMa contact binaries as A-type and W-type according to their light curves. In the A-type systems the larger component has the higher temperature, whereas in the Wtype systems the smaller component has the higher temperature. The 2MASS have J, H and K (infrared) magnitudes in binary systems. BG Vul is an eclipsing variable (binary star) with a short period according to the information in the ASAS catalog. V magnitude of BG Vul is given as 12.275 mag in the ASAS catalog and as 12.403 ⇑ Tel.: +90 3522076660; fax: +90 3524374933. E-mail address: [email protected] 1384-1076/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.newast.2013.09.010

mag (Vmin) in the SIMBAD database. B magnitude of BG Vul is also given as 12.9 mag in the SIMBAD database. There isn’t any spectral type or luminous class information about the star in the catalogs and literature. However, there are the infrared color indices of the system (J–H, H–K, J–K). Table 1 gives some photometric information about the system. The variable nature and light curve of the system were obtained by the All Sky Automated Survey (ASAS) and the light elements of the system were given in the ASAS catalog. BG Vul is located in some of the catalogs in literature (Hoffman et al., 2009; Malkov et al., 2006; Gettel et al., 2006). Photoelectric minima of BG Vul eclipsing binary have been indicated in earlier studies (Hübscher, 2011, 2010, 2006; Brat et al., 2007; Nelson, 2006; Safar and Zejda, 2002). Although a light curve has been obtained for BG Vul, no light curve analysis has been reported in the literature. There are several systems similar to BG Vul (Yakut and Eggleton, 2005; Jiang et al., 2009; Essam et al., 2010; Yıldız and Dog˘an, 2013) in the literature. In this paper, the first photometric solution of BG Vul is presented. Analyzing the orbital period variation, we adjusted the light elements of the system and derived the mass transfer rate between the components. This paper is focused on

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Table 1 Informations about the system.

ID

RA (2000)

DEC (2000)

Period [days]

To 2450000+

V [mag]

V Amp. [mag]

Class

211924 + 2202.7 (BG Vul)

21:19:24

22:02:42

0.403236

5071.3537

12.275

0.607

EC

J

H

K

V–J

V–H

V–K

J–H

H–K

J–K

11.13

10.83

10.78

1.145

1.445

1.495

0.3

0.05

0.35

period variation and the evolutionary state of the system. We analyzed the light curve of BG Vul and then obtained the solution and absolute parameters of the system. Finally, some results of BG Vul are briefly discussed in the Section 5. 2. Selection of variable star in the ASAS catalog This study used the lists of the sun-like stars (solar analog and solar twin) created by Tanriver (2012, 2013) in the ASAS catalog (Pojmanski, 1997, 1998, 2000, 2002, 2003, 2004; Pojmanski and Maciejewski, 2004, 2005; Pojmanski et al., 2005). Attention was paid to those while selecting a sun-like star in the ASAS catalog. Magnitudes in the U, B, V, R, I, J, H and K filters of the sun needed to be known. The UBVRI and infrared (J, H, K, L, M) colors and color indices of the sun were taken from the values obtained in the study by Tanriver (2012, 2013). The ASAS catalog also contains the V–J, V–H, V–H, J–H, H–R and J–K color indices together with the J, H and K magnitudes of the stars that possess any ID number. We selected the BG Vul variable star which is compatible with the V–J, V–H, V–H, J–H, H–R and J–K color indices of the sun from the ASAS solar analog and the solar twin lists of Tanriver (2012, 2013). 3. Period variation of the BG Vul system There are several photoelectric minima times of the BG Vul eclipsing binary system in the literature (Hübscher, 2011; Hübscher et al., 2010, 2006; Brat et al., 2007; Nelson, 2006; Safar and Zejda, 2002). Although there are minima times of BG Vul, no (O– C) analysis of period variation has been conducted in the literature. All the minima times reported in the literature are listed in Table 2. In this table, O is the observed minima times in the literature, while C is the calculated minima times corresponding with the observed minima times. (O  C) is the difference between the observed and the calculated minima times. When the (O  C) values were calculated according to our first T0 value in use (2453636.4302), we show that it is different to the minima time types given by Hübscher (2011) and Hübscher et al. (2010) in the literature. The minimum time reported as the primary minimum (I) is actually the secondary minimum (II) and vice versa. We used

the actual primary mimima time as the initial epoch (T0; 2455071.5551). (O  C)I values were again calculated according to this new T0 (2455071.5551). These values are given in Table 2. The variation graphic of (O  C)I according to this table is given in Fig. 1. Looking at this figure, it appears to be a parabolic variation superimposed on the linear variation. First, we corrected the linear variation in the changing graphic of (O  C)I. Later, we managed to obtain the variation of the residuals from the linear variation. This variation is a parabolic variation where its arms are upward. Using the regression method, we applied an upward parabolic curve to the variation of (O  C)II (see Table 2). As the BG Vul binary system was in a state of over-contact, we considered the most likely cause of the period change to be the transfer of mass between the components. An upward parabolic curve must be caused by possible mass transfer from the secondary component (the small mass) to the primary (the high mass) or mass loss. Therefore, the period variation was represented by the quadratic light elements which are given by Eq. (1). Min I ðHel:Þ ¼

2455071:5532 þ 0d :40323646  E þ 2:9429  1010  E2 0:0012 0:00000251 0:0002  1010 ð1Þ

The period variation according to (O  C)II (see Table 2) and its parabolic fit are given in Fig. 2. Considering the quadratic term (Q), the parameter of the period variation (dP/dt) was found to be 1.32  106yr1. The relation between the parameter of the period variation (dP/dt) and the rate of mass transfer was determined by Eq. (2) developed by Coughlin et al. (2008) and Yang and Liu (2003a,b,c).

dm Mq dP ¼ dt 3Pð1  q2 Þ dt

ð2Þ

where dm/dt is the rate of mass transfer, dP/dt is the change in period, M is the total mass of the system, q is the mass ratio and P is the revolution period. By employing M = 1.913 ± 0.09 M and q = 0.88 in this equation, the mass transfer rate of the BG Vul system from the secondary component to the primary turns out to be 8.14  106M yr1.

Table 2 (O  C)I and (O  C)II residuals according to 2455071.5551 epoch and the minima times (in the seventh column, the actual minimum times are given as italic). After corrected the linear variation, (O  C)II represents the residuals from the linear variation. O (2400000+)

E’

E00

E

(O  C)I

(O  C)II

Min. type

Mthd

Refs.

55481.4461 55071.5551 55071.3537 53636.4302 53595.9052 53236.41925 51782.3557 51404.5246 51394.4404

1016.5040 0.0000 0.4995 3559.0198 3659.5192 4551.0219 8157.0083 9094.0057 9119.0139

1016.5075 0.0047 0.4947 3559.0110 3659.5104 4551.0120 8156.9944 9093.9908 9118.9989

1016.5 0.0 0.5 3559.0 3659.5 4551.0 8157.0 9094.0 9119.0

0.00161 0.00000 0.00022 0.00798 0.00776 0.00881 0.00335 0.00232 0.00562

0.00304 0.00190 0.00212 0.00446 0.00419 0.00484 0.00227 0.00372 0.00044

II* I** II* I II I I I I

Ir Ir Ir Ir R CCD CCD

(1) (2) (2) (3) (4) (5) (5) (6) (6)

Method: Ir: Infrared, I: primary min., II: secondary min. Refs: (1): Hübscher (2011), (2): Hübscher et al. (2010), (3): Hübscher et al. (2006), (4): Nelson (2006), (5): Brat et al. (2007), (6): Safar and Zejda (2002). * It is expressed as the primary minimum (I) in the literature. ** It is expressed as the secondary minimum (II) in the literature.

M. Tanrıver / New Astronomy 28 (2014) 79–84

Fig. 1. The variation graphic of (O  C)I according to epoch numbers(E0 ). It is a parabolic variation superimposed on the linear variation (see Table 2).

Fig. 2. The variation graphic of (O  C)II according to epoch numbers (E00 ) (see Table 2).

4. Observational data and photometric solution The light curve in the V filter of the ASAS ID 211924+2202.7 (BG Vul) variable star was selected for the study. The observational data in the V filter and the magnitude values versus HJD were taken from the ASAS database. The phase values of the variable star were calculated using the epoch time (T0; 2455071.3537) and the period (0.403236 days) of the binary star. The phases between 0 and 0.2 were passed onto phases greater than 1 for a stronger appearance of the two minima. The light curve of the phase of the binary star is given as follows in Fig. 3. Afterwards, the averages of the phase and magnitude were calculated in every 3 points. The light curve of the binary star after calculating the averages is given as follows in Fig. 4. We achieved the photometric solution of the BG Vul binary star (ASAS ID 211924+2202.7) using the phase and mag-

Fig. 3. The V-band light curve of the BG Vul binary system according to the phase.

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nitude values belonging to the light curve of the variable star in PHOBE V.0.31a software (Prša and Zwitter, 2005) based on the 2003 version of the Wilson–Devinney code (Wilson and Devinney, 1971 and Wilson, 1990) which is widely used as a standard tool for the solution of photometric light curves of eclipsing binaries. We attempted to analyze the light curves in mode = 3, including the ‘‘over-contact binary’’. Our initial analyses demonstrated that an astrophysically reasonable solution was obtainable only in this mode. We accepted that the hot component was the sun-like star during the photometric solution. The other component was detected as the cold component star. First, we maintained constant physical parameters of the hot component compatible with the sun during our solution. Thus, the effective temperature, mass and radius values of the primary star were taken as the initial values of 5800 K, 1 M and 1 R which are close to the effective temperature, mass and radius of the sun and we kept them constant during solution. As for the mass of the other component, we selected a mass suitable for the revolution period (0.403236 days) using Newton’s law of universal gravitation and Kepler’s third law in the binary system with the eclipsing contact (EC) type so that the secondary component could be combined together with the primary component. We measured the mass of the secondary component as 0.9 M. Therefore, the mass ratio (q = M2/M1) of the system is given as 0.9. We accepted this value as the initial mass ratio. The surface potential belonging to the primary component was kept constant during our solution. The surface potential of the secondary component was given in accordance with a potential value suitable for the eclipsing contact (EC) binary system. The albedo value of the primary and secondary components was taken as 0.5 and the gravity darkening value for both components was taken as 0.32. We utilized the tables of van Hamme (1993) for the limb-darkening coefficients. We changed the orbital inclination angle, the temperature of the secondary component and the surface potentials of the primary and secondary component during our solution. By ‘‘q searching’’, we found the best q value. The ‘‘q-search’’ process was performed to find a feasible photometric mass ratio. A series of tried solutions was used for several assumed values of q. The resulting q  R curve is displayed in Fig. 5, where a minimum value of R is achieved at q = 0.88. The mass ratio was then considered as an initial parameter for the final iteration. We fixed this value (0.88) during solution. First, provided that we didn’t move away from the sun parameters, we revised the free parameters and repeated them until the best agreement was achieved in the solution. The iterations were carried out automatically until convergence, and a solution was defined as the set of parameters for which the differential corrections were smaller than the probable errors. The parameters obtained as a result of the photometric solution are given in Table 3. The uncertainties

Fig. 4. The V-band light curve of binary star with the average of the phase and magnitude.

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Fig. 5. The relation R(res)2 – mass ratio q in Mode 3 for BG Vul.

Fig. 6. The V-band theoretical and observational light curves of BG Vul.

Table 3 The solution parameters of the variable star (BG Vul). Zero point of orbital ephemeris – T0 (HJD) Period of binary orbit – P (days) Phase shift Semi-major axis (SMA) Mass ratio (q) Binary orbit inclination (i) Binary orbit eccentricity (e) Mean surface effective temperature (K) of star1 (T1) Mean surface effective temperature (K) of star2 (T2) Surface potential of the components star1. 2 (X1 = X2) Bolometric albedo of star 1 (A1) Bolometric albedo of star 2 (A2) Exponent in gravity brightening of star1 (g1) Exponent in gravity brightening of star1 (g2) Third light (l3) Bolometric limb darkening coefficient of star1 (x1, y1) Bolometric limb darkening coefficient of star2 (x2, y2) Linear limb darkening coefficient of star1 (x1, y1) Linear limb darkening coefficient of star2 (x2, y2)

2455071.3537 0.403236 0.01629 2.848 ± 0.041 R 0.880 ± 0.005 74.48 ± 0.23 0.0 5868 ± 13 K 5520 ± 15 K 3.33062 ± 0.0031 0.5 0.5 0.32 0.32 0.0 0.64682 0.64679 0.752786 0.775258

0.21261 0.21261 0.243355 0.205364

assigned to the adjusted parameters are the internal errors provided directly by the code. The absolute parameters from this solution are given as follows in Table 4. The theoretical and observational light curves according to these solution parameters are given as follows (see Fig. 6). The 3D binary system configuration of BG Vul is represented in Fig. 7 for the 0.00, 0.25, 0.50 and 0.75 phases. The Roche lobes related to the system are given in Fig. 8. The fill factor (f) of the eclipsing binaries with contact class is the range of 0 < f < 1, that of semi-detached binaries is f = 0, and that of detached binaries is f < 0. The fill-out factor (f) is given by

f ¼

Xin  X1;2 Xin  Xout

ð3Þ

where Oin and Oout and O1,2 are the inner and outer Lagrangian surface potentials, and surface potentials of star 1 and 2, respectively. In cases of contact binaries, the surface potentials of primary and

Fig. 7. The geometric configurations of BG Vul in the 0.00, 0.25, 0.50 and 0.75 phases.

Fig. 8. The Roche lobes related to the system.

secondary components are equal to the surface potential (O) of the common envelope for the binary system (i.e. O1 = O2 = O). The fill-out factor for the BG Vul was obtained to be 0.454 and was in

Table 4 The absolute parameters of the variable star (BG Vul). Potential of Lagrangian point L1 – X(L1)

3.552238

Bolometric absolute magnitude of star1 – M bol 1

4.25

Potential of Lagrangian point L2 – X(L2)

3.063984

4.63

Mass of star1 (solar mass M) – M1 Mass of star2 (solar mass M) – M2 Radius of star1 (solar radius R) – R1 Radius of star2 (solar radius R) – R2

1.01 ± 0.04 0.89 ± 0.09 1.23 ± 0.03 1.17 ± 0.04

Bolometric absolute magnitude of star2 – M bol 2 Surface gravity of star1 (logarithmic) Log(g1) Surface gravity of star2 (logarithmic) Log(g2) Luminosity of star1 L1 (solar unit L) Luminosity of star2 L2 (solar unit L)

4.26 ± 0.05 4.25 ± 0.08 1.632 ± 0.015 1.151 ± 0.018

M. Tanrıver / New Astronomy 28 (2014) 79–84

the range of contact binaries. The absolute parameters of BG Vul, as reported in Table 4, were used to estimate the evolutionary status of the system by means of the mass-radius, mass-luminosity, and luminosity-effective temperature diagram shown in Figs. 9–12. At the same time, in order to test whether or not the absolute parameters were generally acceptable in the astrophysical sense, we used these diagrams to compare the components of the BG Vul binary system with other systems of W UMa type. In these plots, the solid line represents the zero age main sequence (ZAMS) theoretical model developed for the stars with Z = 0.02 by Girardi et al. (2000) and the dashed lines represent the TAMS theoretical model. The position of components on the mass-radius diagram is obviously outside the zero age main sequence and they are located to the left on the zero age main sequence (ZAMS). The primary component of the BG Vul binary system approach to the terminal age main sequence (TAMS) and the secondary component are also on the terminal age main sequence (TAMS). Figs. 9–11 show that the mass-radius, the massluminosity and effective temperature-luminosity relations of both components are different from those of the ZAMS. Both components are clearly separated away from the ZAMS due to the mass transfer from the secondary component to the primary and while it made the secondary component small-sized and less luminous than the primary, it made the primary component over-sized and more luminous than the secondary. The filled labels represent the primary components, while the open labels represent the secondary ones. The components of BG Vul are located together with some samples of its analogs. The sample systems were taken from Yakut and Eggleton (2005), Jiang et al. (2009), Essam et al. (2010) and Yıldız and Dog˘an (2013) and they are shown in black, while BG Vul is shown in red in Figs. 9–12. The locations and evolutionary status in the HR diagram (effective temperature–luminosity) of the component stars composing the system are given in Fig. 12.

5. Conclusion and discussion

83

Fig. 10. The places of the components of BG Vul on the planes of the massluminosity (logM/M–logL/L). The symbols are the same as Fig. 8 and these curves are derived from the assumptions (see the text).

Fig. 11. The places of the components of BG Vul on the planes of the effective temperature-luminosity (logTeff–logL/L). The symbols are the same as Fig. 8 and these curves are derived from the assumptions (see the text).

In this study, we have tried to determine the nature of the eclipsing binary system BG Vul. Our analysis of the orbital period variation indicated it to be mass transfer from the secondary to the primary component and/or to be mass loss from the system. From our analysis, BG Vul is a WUMa-type eclipsing binary star, in which both components fill their Roche lobes. The mass ratio is q = 0.88 (±0.005). According to its color indices, the mass of the primary component is M1 = 1.017 M (Popper, 1980). With Kelper’s

Fig. 9. The places of the components of BG Vul on the planes of the mass-radius (logM/M–logR/R). In the panels, the continuous and dashed lines represent the ZAMS and TAMS theoretical models developed by Girardi et al. (2000), respectively. The filled circles represent the primary components of other contact binaries with the A-type subclass, and the open circles represent the secondary ones. The red diamonds represent the BG Vul components.

Fig. 12. Locations and evolutionary status in the HR diagram (logTeff–logL/L) of the component stars. We used a theoretical HR diagram of the evolution track and isochrones computed by Girardi et al. (2000).

third law of M1  (1 + q) = a3/P2, the separation between both components is a = 2.8481 R. For the first time in the literature, we analyzed the light curves of the system. The inclination (i) of the

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system was found to be 74°.48983 ± 0°.23, while the temperature of the secondary component was found to be 5520 ± 15 K from the analysis. Using the photometric elements, other absolute parameters of the system assumed two components which were as follows: M2 = 0.895 M, R2 = 1.176 R and R1 = 1.238 R respectively. The O–C analysis indicated the orbital period to be 0d.4032365. In addition, the temperature of the primary component was 5868 K, while the secondary one was 5520 K. Although some W UMa type binaries have components with some different surface temperatures, they generally have the same surface temperature. Here, the primary component of BG Vul was slightly hotter than the secondary one. The results in Tables 3 and 4 indicate that the primary component of the system was the more massive and hotter component, while the secondary component was the less massive and cooler one. Our analysis indicates that the star BG Vul showed most of the characteristics of the so-called over-contact binaries. The sum of fractional radii of r1 + r2  0.8 was in agreement with Kopal (1956) criteria for over-contact systems. Considering the fundamental characteristics of the system such as the short orbital period, mass ratio, hotter primary component and etc., BG Vul seems to be in agreement with the members of the A-type subclass of WUMa binaries (Berdyugina, 2005; Rucinski, 1985). The degree of over-contact with a fill-out ratio (f) of BG Vul is 0.45. This fillout ratio (f = 0.45) is in agreement with those of A-type W UMa binaries (Rucinski, 1985). Based on the computed absolute parameters of BG Vul, we compared the positions of the components of BG Vul and compared BG Vul with the samples of W UMa binary systems in some diagrams, such as logM/M–logR/R, logM/M–logL/L and logTeff–logL/L planes with the evolutionary tracks and isochrones given by Girardi et al. (2000), as seen from Figs. 9–12. We estimated the evolutionary status of the system using evolutionary tracks and isochrones. The components of BG Vul and selected A-type W UMa’s were plotted on mass–luminosity, mass–radius and effective temperature–luminosity (HR diagrams) (see Figs. 9–12). We demonstrated that the components of the system are in agreement with their analogs. If the absolute parameters of the primary star are considered, they are in agreement with the evolutionary track of a 1 M single star with solar abundance. Comparing stellar evolutionary models for the mass of the components, we find that the locations of both the components in the HR diagram are suitable with their masses. As is clear from the figures, the primary component of the system is located near the TAMS. The secondary component is located on the TAMS. These situations indicate that both components are an evolved star. On the other hand, both components were seen to be closer to each other in the figures. If the result obtained from the O–C analysis is taken into account, it is possible that the secondary component will continue to lose its mass, while the primary component will gather. Therefore, both components will have been separated from each other on the planes shown in Figs. 9–12. Comparing stellar evolutionary models for the mass of the components, we find that the location of the primary and secondary stars in the HR diagram is suitable with their masses. The primary star came out as a typical sun-like star according to the absolute parameters obtained by the photometric solution, as is seen from the figures. The absolute solution parameters of the primary star are very consistent with those of the sun.

The O–C analysis indicates possible mass transfer from the second component to the primary component. This case should be the reason for the hotter primary component. That the components of the system were near the TAMS and evolved according to ZAMS is the result of mass transfer from the secondary to the primary component. The size of mass transfer or mass loss was computed as 8.14  106 M per year, causing an increase in the orbital period. In fact, the period variation was found to be 1.32  106 yr1.We adjusted the orbital period to 0d.40323646. It is well known that several binaries of W UMa type such as YY CrB (Essam et al., 2010), BS Cas (Yang et al., 2008) and VZ Tri (Yang, 2010) exhibit a large period variation due to the large mass transfer. From the present results with Mbol(system) = 3m.674 and BC = 0.07 (interpolated from Flower, 1996) and using this property and assuming that it is a main-sequence star and considering the interstellar extinction (Av  2.15, Fresneau and Monier, 1999), we determined its distance to be 188.829 ± 4.348 pc. References Berdyugina, S.V., 2005. LRSP 2, 8. Binnendijk, L., 1970. Vistas Astron. 12, 217. Brat, L., Zejda, M., Svoboda, P., 2007. OEJV 74, 1. Coughlin, J.L., Dale III, H.A., Williamon, R.M., 2008. AJ 136, 1089. Essam, A., Saad, S.M., Nouh, M.I., Dumitrescu, A., El-Khateeb, M.M., Haroon, A., 2010. NewA 15, 227. Flower, P.J., 1996. ApJ 469, 355. Fresneau, A., Monier, R., 1999. AJ 118, 421. Gettel, S.J., Geske, M.T., McKay, T.A., 2006. AJ 131, 621. Girardi, L., Bressan, A., Bertelli, G., Chiosi, C., 2000. A&AS 141, 371. Hoffman, D.I., Harrison, T.E., McNamara, B.J., 2009. AJ 138, 466. Hübscher, J., 2011. BAVSM 215, 1. Hübscher, J., Lehmann, P.B., Monnınger, G., Steinbach, H.M., Walter, F., 2010. IBVS 5941, 1. Hübscher, J., Paschke, A., Walter, F., 2006. IBVS 5731, 1. Jiang, D., Han, Z., Jiang, T., Li, L., 2009. MNRAS 396, 2176. Kopal, Z., 1956. AnAp 19, 298. Malkov, O.Y., Oblak, E., Snegireva, E.A., Torra, J., 2006. AA 446, 785. Nelson, R.H., 2006. IBVS 5672, 1. Pojmanski, G., 1997. AcA 47, 467. Pojmanski, G., 1998. AcA 48, 35. Pojmanski, G., 2000. AcA 50, 177. Pojmanski, G., 2002. AcA 52, 397. Pojmanski, G., 2003. AcA 53, 341. Pojmanski, G., 2004. AN 325, 553. Pojmanski, G., Maciejewski, G., 2004. AcA 54, 153. Pojmanski, G., Maciejewski, G., 2005. AcA 55, 97. Pojmanski, G., Pilecki, B., Szczygiel, D., 2005. AcA 55, 275. Popper, D.M., 1980. ARA&A 18, 115. Prša, A., Zwitter, T., 2005. ApJ 628, 426. Rucinski, S., 1985. In: Pringle, J.E., Wade, R.A. (Eds.), Interacting Binary Stars. Cambridge University Press, Cambridge, p. 1. Safar, J., Zejda, M., 2002. IBVS 5263, 1. SIMBAD database, http://simbad.u-strasbg.fr/simbad/. Tanrıver, M., 2012. 18th Congress of the National Astronomy and Space Sciences, Turkey, 253–265. Tanrıver, M., 2013. NewAR (unpublished results). Van Hamme, W., 1993. AJ 106, 2096. Wilson, R.E., Devinney, E.J., 1971. ApJ 166, 605. Wilson, R.E., 1990. ApJ 356, 613. Yakut, K., Eggleton, P.P., 2005. ApJ 629, 1055. Yang, Y., Liu, Q., 2003a. AJ 126, 1960. Yang, Y., Liu, Q., 2003b. NewA 8, 465. Yang, Y., Liu, Q., 2003c. PASP 115, 748. Yang, Y.G., Wei, J.Y., He, J.J., 2008. AJ 136, 594. Yang, Y.G., 2010. Ap&SS 326, 125. Yıldız, M., Dog˘an, T., 2013. MNRAS 430, 2029.