- Email: [email protected]
Kottamia 74-inch telescope discovery of the new eclipsing binary 2MASS J20004638 + 0547475.: First CCD photometry and light curve analysis
New Astronomy 53 (2017) 35–38
Contents lists available at ScienceDirect
New Astronomy journal homepage: www.elsevier.com/locate/newast
Kottamia 74-inch telescope discovery of the new eclipsing binary 2MASS J20 0 04638 + 0547475.: First CCD photometry and light curve analysis M.S. Darwish a,b,∗, A. Shokry a,b, S.M. Saad a,b, M.A. El-Sadek a,b, A. Essam a, M. Ismail a,b a b
Astronomy Dept., National Research Institute of Astronomy and Geophysics, (NRIAG), 11421, Box:138, Helwan, Cairo, Egypt. Kottamia Center of Scientific Excellence in Astronomy and Space Sciences (KCScE) STDF, ASRT, Cairo, Egypt
h i g h l i g h t s • • • •
Photometric observations of a new eclipsing binary system have been obtained. The system was found to be as A-subtype of WUMa with fill-out factor of about 69%. We estimated the orbital and absolute parameters of the new discovered system. The evolution status was performed along with ZAMS and TAMS tracks.
a r t i c l e
i n f o
Article history: Received 11 October 2016 Revised 27 November 2016 Accepted 29 November 2016 Available online 30 November 2016 Keywords: 2mass j20 0 04638 + 0547475 Evolution W Uma Eclipsing binary and mass transfer
a b s t r a c t A CCD photometric study is presented for the eclipsing binary system 2MASS J20 0 04638 + 0547475. Observations of the system were obtained in the V, R and I colours with the 2Kx2K CCD attached to 1.88 m Kottamia Optical Telescope. New times of light minimum and new ephemeris were obtained. The V, R and I light curves were analyzed using the PHOEBE 0.31 program to determine geometrical and physical parameters of the system. The results show that 2MASS J20 0 04638 + 0547475, is A-Type WUMa and is an overcontact binary with high fill-out factor = 69%. The current evolutionary status of the system indicates that the primary component lies very close to the main sequence while the secondary is evolved. The asymmetric maxima were studied and a modeling of the hot spot parameters is given. © 2016 Elsevier B.V. All rights reserved.
1. Introduction
2. Observations and data reduction
2MASS J20 0 04638 + 054,7475 is a W Uma Eclipsing binary system with a period of 0.d2864 (∼7 h). Both components of such systems usually fill their critical Roche lobes. They are important for studying the dynamical evolution of the overcontact binaries and for a better understanding of binary star formation. The eclipsing binary system is registered as a new variable star by The American Association of Variable Star Observers (AAVSO): (VSX). Its details are given in: https://www.aavso.org/vsx/index.php?view= detail.top&oid=473895. It was discovered during 2 nights of a regular observing campaign of variable stars at the Kottamia Astronomical Observatory (KAO). It was not before recognized as variable star.
The observations of 2MASS J20 0 04638 + 054,7475 were carried out during 1&3 Aug 2016 at the 1.88 m KAO telescope using 2Kx2K CCD camera and obtained in three filters V, R and I. The basic data reduction was performed for bias, dark and flat fielding of each CCD image by the using MUNIWIN (Motl, 2007) program. Differential photometry was performed with respect to the comparison star (TYC-506-2313-1) and checked by the star (USNO-B1.0 0957– 050,8108). Fig. 1 illustrates the field of the star (V), the comparison (C) and the Check (K) stars. The difference in magnitude was computed and a total of 264 observations were obtained in different filters. New times of minima in different filters were derived using the method of Kwee and Van Woerden (1956), while the period was determined by using the method of Nelson (2006). Table 1 represents the times of the light minimum of the system and Eq. (1) was found to represent the VRI light curves with respect to the orbital phase. Fig. 2, represents the phase diagram for the system 2MASS J20 0 04638 + 054,7475 in the VRI filters. We determined the V mag. of 2MASS J20 0 04638 + 054,7475 using the
∗
Corresponding author. Fax: +225548020. E-mail address: [email protected] (M.S. Darwish).
http://dx.doi.org/10.1016/j.newast.2016.11.009 1384-1076/© 2016 Elsevier B.V. All rights reserved.
36
M.S. Darwish et al. / New Astronomy 53 (2017) 35–38
Fig. 3. VRI light curves of the system 2MASS J20 0 04638 + 054,7475 fitted with the synthetic spotted model (sold line). Fig. 1. Image of the observed field, where V, C and K represent the position of the variable, the comparison and the check stars, respectively.
Fig. 4. The different phases and outline of the star and the overcontact configuration.
By utilizing the obtained times of light minima, we could determine a new ephemeris for the primary minimum as:
HJD.(Min.I ) = 2457602.50010 ± 0.00023 + 0.286476 × E
Fig. 2. Phase diagram for the system 2MASS J20 0 04638 + 054,7475 with VRI filters. Table 1 Times of light minima for the system. Filter
Min. I
Min. II
V R I
2,457,602.50013 ± 0.0037 2,457,602.50010 ± 0.00027 2,457,602.50096 ± 0.00066
2,457,602.35718 ± 0.0 0 049 2,457,602.35790 ± 0.0 0 033 2,457,602.35821 ± 0.0 0 031
following formula which is a transformation formula from Infrared (IR) band filters to optical V band: (V = 0.6278∗ j-k + 0.9947∗ CMC15 r’-mag), where V(550 μm) is the optical band, while j, k and CMC15 r’ are j(1.25 μm), k (2.17 μm) in IR band and the r’ magnitude is close to the SLOAN r’ bandpass from Carlsberg Meridian Catalog 15 (CMC15), respectively. The star’s visual mag. is V = 17.4 at its maximum brightness while its minimum mag. is V = 18.04.
(1)
The observational data that represent the difference in magnitudes between the variable and comparison stars together with the corresponding Heliocentric Julian date in V, R and I filters, can be seen through this link https:// www.dropbox.com/s/5fzobper66p4mcn/Table%201.docx?dl=0. 3. Light curve analysis To analyze the light curves, we used the overcontact mode of the PHOEBE program. PHOEBE (PHysics Of Eclipsing BinariEs) is a tool for the modeling of eclipsing binary stars that is designed based on the Wilson–Devinney (W–D) code to analyze the light curve and radial velocity curve (Prsa and Zwitter, 2005). The parameters in the three bands (V,R and I) such as: orbital inclination (i), surface temperature of the secondary component (T2), surface potential of the two components (1 = 2 ), the luminosity of star 1 (L1 ), and mass ratio (q) we adjusted. Regarding the fixed parameters such as surface temperature of the primary component were calculated this from the J-H filters in 2MASS catalog. The
M.S. Darwish et al. / New Astronomy 53 (2017) 35–38
37
Fig. 5. The position of both components on the Mass–Radius (right panel) and on Mass-Luminosity (left panel) relations diagrams.
Table. 2 Results of light curve parameters using the PHOEBE program. Parameter
VRI
Error
Inclination(i˚) mass ratio(q) T1(K) T2(K) Ω1 A1,2 g1,2 L1/(L2+L1)V L1/(L2+L1)R L1/(L2+L1)I Ωinner Ωouter r1(back) r1(side) r1(pole) r2(back) r2(side) r2(pole) Fill-out Ratio Ʃ(o-c)2 spot parameter S(secondary) co-latitude co-longitude Radius Temperature factor
81.91560 0.45054 5392 5170 2.59079 0.5 0.32 0.7415 0.7426 0.7579 2.779504 2.507648 0.543560 0.498118 0.458455 0.426315 0.351130 0.329738 69% 0.04
0.210 0.006 Fixed 22.97 0.009 Assumed Assumed
110 80 13 1.3
Assumed Assumed Assumed Assumed
effective temperature was found to be 5392 K (Cox,20 0 0). Gravity brightness, g1 = g2 = 0.32 was assumed for a convective star (Lucy, 1967), and the bolometric albedo, A1 = A2 = 0.5 for a convective star (Rucinski, 1969). After several iterations, the best synthetic light curve was obtained and fitted with the observed one and a set of parameters was derived, and listed in Table. 2 We attempted modeling with a spotted model to solve for the significant maximum difference in the observed light curves. The best fit of the observed and the theoretical curves was reached for a model with a hot spot on the secondary star at latitude 110° and longitude 80° Its mean radius is about 13° and the temperature
Table 3 Absolute physical parameters of the system 2MASS J20 0 04638+ 054,7475. Element
M(M )
R(R )
T(T )
L(L )
mbol .
Log g
Sp.type
Primary Secondary
0.968 0.441
1.048 0.972
0.933 0.894
0.834 0.606
4.888 5.235
4.382 4.414
G7 K0
factor is 1.3 which indicates that the spot is 30% hotter than its surrounding photosphere. The analyses of the light curves show that the primary component is more massive and hotter than the secondary one, where the difference in the temperature between the components is about 222 K. Fig. 3 shows the best fit of the model to the observed V RI light curves of the system. According to the accepted orbital solution, the components of the system are of spectral type G7 and K0, respectively, following Covey et al. (2007). Fig. 4 shows the geometric configuration of the binary system. The absolute physical parameters of the components were calculated using the empirical relation adopted by Harmanec (1988) and listed in Table 3. 4. Evolutionary status of 2MASS J20 0 04638 + 054,7475 The most popular evolutionary scenario for W UMa type binary stars is that they are formed from initially detached systems by angular momentum loss (Eggen and Iben 1989). Both the shrinking of the Roche lobe and the expanding of the components due to evolution will result in a massive component star that fills the critical Roche lobe and the system evolves into an overcontact binary through a primary to secondary mass transfer. The overcontact configuration of 2MASS J20 0 04638 + 054,7475, in Fig. 4 shows that both of the binary components fill their Roche lobes and they are evolved to that stage of common envelope and transfere of primary matter to secondary component. Using the calculated physical parameters listed in Table 3 we investigated the current evolutionary status of the system. Fig. 5, shows the components of the system on the Mass–Radius (M–R) relation (right panel) and Mass- Luminosity (M-L) relation (left panel) along with the evolutionary models computed by Mowlavi et al. (2012) for both Zero Age Main Sequence (ZAMS), the
38
M.S. Darwish et al. / New Astronomy 53 (2017) 35–38
Fig. 6. Location of both components on Teff –Luminosity diagram (left panel), and on the empirical Mass–Teff relation for intermediate mass stars by Malkov (2007), (right panel).
Terminal Age Main Sequence (TAMS) with metallicity z = 0. 014. Fig. 6 shows the location of the system components on the Teff – Luminosity diagram from Girardi et al. (20 0 0) (left panel) and the position of the components of the system on the empirical Mass– Teff relation for intermediate mass stars by Malkov (2007) (right panel). As it’s clear from figures, 5 and 6 the primary component follows closely the relation for main sequence stars, while the secondary component is over-luminous with temperature and radius larger than that expected for main-sequence stars. This may be related to the transfer of mass from the primary to the secondary star. 5. Conclusion We presented new light curves obtained by multicolor CCD photometry of a new short period WUMa eclipsing binary. We obtained its first ephemeris using the times of its minimum light. The first photometric solution of the system was obtained using the PHOEBE 0.31 software and can be summarized as follows: •
•
•
•
•
•
The fitted synthetic model suggests a hot spot on its secondary component The system is an overcontact with a relatively high fill-out factor = 69%. The system is an A-Subtype WUMa with mass ratio of about 0.45 The spectral types of the primary and secondary components are G7 and K0, respectively. The primary component of 2MASS J20 0 04638 + 054,7475 is the more massive one. The evolution study of the binary system revealed that the primary component is a main sequence star while the secondary is an evolved component which is considerably oversized and over-luminous if compared to main-sequence stars of the same mass.
As the system is a newly discovered one, for better determinations of the system parameters, further photometric and spectroscopic observations are strongly requested. Acknowledgments Many thanks are given to the anonymous referee for constructive remarks and suggestions. This research has made use of NASA’s Astrophysics Data System, the 2MASS All-Sky Survey and (AAVSO): (VSX). The research granted by Science and Technology Development Fund (STDF) N5217. We are very grateful the teams of KCScE and the team of Kottamia Astronomical Observatory, Dr. F. I. El-Nagahy, M. Ismail, Doaa El-Sayed I. Helmy. We would like to give thanks to Dr. M. Hassan, Dr. M. M.Elkhateeb, Dr. N. M. Ahmed, I. Zaid, A. Shokry D. Fouda and M. H. El-Depsy for their fruitful discussions and help. References ´ Ž., Schlegel, D., Finkbeiner, D., Padmanabhan, N., Lupton, R.H., Covey, K.R., Ivezic, Agüeros, M.A., Bochanski, J.J., Hawley, S.L., West, A.A., Seth, A., Kimball, A., Gogarten, S.M., Claire, M., Haggard, D., Kaib, N., Schneider, D.P., Sesar, B., 2007. AJ 134, 2398. Cox, A.N., 20 0 0. Allen’s Astrophysical Quantities, 4th ed. Springer, NewYork. Eggen, O.J., Iben Jr., I., 1989. AJ. 97, 431. Girardi, L., Bressan, A., Bretelli, G., Chiosi, C., 20 0 0. AAS 141, 371. Harmanec, P., 1988. Bull. Astron. Inst. Czechosl. 39, 329. Kwee, K., Van Woerden, H., 1956. BAN 12, 327K. Lucy, L., 1967. Z. Astrophys 65, 89. Malkov, O.Yu., 2007. MNRAS 382, 1073. Motl, D., 2007 C-Munipack Project v1.2.32 http://sourceforge.net/projects/ c-munipack/files. Mowlavi, N., Eggenberger, P., Meynet, G., Ekström, S., Georgy, C., Maeder, A., Chrnel, C., Eyer, L., 2012. A&A 541, 41. Nelson, R.H., 2006 MinimaV2.3., available from: http://members.shaw.ca/bob.nelson/ software1.htm. Prša, A., Zwitter, T., 2005. ApJ 628, 426. Rucinski, S., 1969. Acta Astron. 19, 156.
Contents lists available at ScienceDirect
New Astronomy journal homepage: www.elsevier.com/locate/newast
Kottamia 74-inch telescope discovery of the new eclipsing binary 2MASS J20 0 04638 + 0547475.: First CCD photometry and light curve analysis M.S. Darwish a,b,∗, A. Shokry a,b, S.M. Saad a,b, M.A. El-Sadek a,b, A. Essam a, M. Ismail a,b a b
Astronomy Dept., National Research Institute of Astronomy and Geophysics, (NRIAG), 11421, Box:138, Helwan, Cairo, Egypt. Kottamia Center of Scientific Excellence in Astronomy and Space Sciences (KCScE) STDF, ASRT, Cairo, Egypt
h i g h l i g h t s • • • •
Photometric observations of a new eclipsing binary system have been obtained. The system was found to be as A-subtype of WUMa with fill-out factor of about 69%. We estimated the orbital and absolute parameters of the new discovered system. The evolution status was performed along with ZAMS and TAMS tracks.
a r t i c l e
i n f o
Article history: Received 11 October 2016 Revised 27 November 2016 Accepted 29 November 2016 Available online 30 November 2016 Keywords: 2mass j20 0 04638 + 0547475 Evolution W Uma Eclipsing binary and mass transfer
a b s t r a c t A CCD photometric study is presented for the eclipsing binary system 2MASS J20 0 04638 + 0547475. Observations of the system were obtained in the V, R and I colours with the 2Kx2K CCD attached to 1.88 m Kottamia Optical Telescope. New times of light minimum and new ephemeris were obtained. The V, R and I light curves were analyzed using the PHOEBE 0.31 program to determine geometrical and physical parameters of the system. The results show that 2MASS J20 0 04638 + 0547475, is A-Type WUMa and is an overcontact binary with high fill-out factor = 69%. The current evolutionary status of the system indicates that the primary component lies very close to the main sequence while the secondary is evolved. The asymmetric maxima were studied and a modeling of the hot spot parameters is given. © 2016 Elsevier B.V. All rights reserved.
1. Introduction
2. Observations and data reduction
2MASS J20 0 04638 + 054,7475 is a W Uma Eclipsing binary system with a period of 0.d2864 (∼7 h). Both components of such systems usually fill their critical Roche lobes. They are important for studying the dynamical evolution of the overcontact binaries and for a better understanding of binary star formation. The eclipsing binary system is registered as a new variable star by The American Association of Variable Star Observers (AAVSO): (VSX). Its details are given in: https://www.aavso.org/vsx/index.php?view= detail.top&oid=473895. It was discovered during 2 nights of a regular observing campaign of variable stars at the Kottamia Astronomical Observatory (KAO). It was not before recognized as variable star.
The observations of 2MASS J20 0 04638 + 054,7475 were carried out during 1&3 Aug 2016 at the 1.88 m KAO telescope using 2Kx2K CCD camera and obtained in three filters V, R and I. The basic data reduction was performed for bias, dark and flat fielding of each CCD image by the using MUNIWIN (Motl, 2007) program. Differential photometry was performed with respect to the comparison star (TYC-506-2313-1) and checked by the star (USNO-B1.0 0957– 050,8108). Fig. 1 illustrates the field of the star (V), the comparison (C) and the Check (K) stars. The difference in magnitude was computed and a total of 264 observations were obtained in different filters. New times of minima in different filters were derived using the method of Kwee and Van Woerden (1956), while the period was determined by using the method of Nelson (2006). Table 1 represents the times of the light minimum of the system and Eq. (1) was found to represent the VRI light curves with respect to the orbital phase. Fig. 2, represents the phase diagram for the system 2MASS J20 0 04638 + 054,7475 in the VRI filters. We determined the V mag. of 2MASS J20 0 04638 + 054,7475 using the
∗
Corresponding author. Fax: +225548020. E-mail address: [email protected] (M.S. Darwish).
http://dx.doi.org/10.1016/j.newast.2016.11.009 1384-1076/© 2016 Elsevier B.V. All rights reserved.
36
M.S. Darwish et al. / New Astronomy 53 (2017) 35–38
Fig. 3. VRI light curves of the system 2MASS J20 0 04638 + 054,7475 fitted with the synthetic spotted model (sold line). Fig. 1. Image of the observed field, where V, C and K represent the position of the variable, the comparison and the check stars, respectively.
Fig. 4. The different phases and outline of the star and the overcontact configuration.
By utilizing the obtained times of light minima, we could determine a new ephemeris for the primary minimum as:
HJD.(Min.I ) = 2457602.50010 ± 0.00023 + 0.286476 × E
Fig. 2. Phase diagram for the system 2MASS J20 0 04638 + 054,7475 with VRI filters. Table 1 Times of light minima for the system. Filter
Min. I
Min. II
V R I
2,457,602.50013 ± 0.0037 2,457,602.50010 ± 0.00027 2,457,602.50096 ± 0.00066
2,457,602.35718 ± 0.0 0 049 2,457,602.35790 ± 0.0 0 033 2,457,602.35821 ± 0.0 0 031
following formula which is a transformation formula from Infrared (IR) band filters to optical V band: (V = 0.6278∗ j-k + 0.9947∗ CMC15 r’-mag), where V(550 μm) is the optical band, while j, k and CMC15 r’ are j(1.25 μm), k (2.17 μm) in IR band and the r’ magnitude is close to the SLOAN r’ bandpass from Carlsberg Meridian Catalog 15 (CMC15), respectively. The star’s visual mag. is V = 17.4 at its maximum brightness while its minimum mag. is V = 18.04.
(1)
The observational data that represent the difference in magnitudes between the variable and comparison stars together with the corresponding Heliocentric Julian date in V, R and I filters, can be seen through this link https:// www.dropbox.com/s/5fzobper66p4mcn/Table%201.docx?dl=0. 3. Light curve analysis To analyze the light curves, we used the overcontact mode of the PHOEBE program. PHOEBE (PHysics Of Eclipsing BinariEs) is a tool for the modeling of eclipsing binary stars that is designed based on the Wilson–Devinney (W–D) code to analyze the light curve and radial velocity curve (Prsa and Zwitter, 2005). The parameters in the three bands (V,R and I) such as: orbital inclination (i), surface temperature of the secondary component (T2), surface potential of the two components (1 = 2 ), the luminosity of star 1 (L1 ), and mass ratio (q) we adjusted. Regarding the fixed parameters such as surface temperature of the primary component were calculated this from the J-H filters in 2MASS catalog. The
M.S. Darwish et al. / New Astronomy 53 (2017) 35–38
37
Fig. 5. The position of both components on the Mass–Radius (right panel) and on Mass-Luminosity (left panel) relations diagrams.
Table. 2 Results of light curve parameters using the PHOEBE program. Parameter
VRI
Error
Inclination(i˚) mass ratio(q) T1(K) T2(K) Ω1 A1,2 g1,2 L1/(L2+L1)V L1/(L2+L1)R L1/(L2+L1)I Ωinner Ωouter r1(back) r1(side) r1(pole) r2(back) r2(side) r2(pole) Fill-out Ratio Ʃ(o-c)2 spot parameter S(secondary) co-latitude co-longitude Radius Temperature factor
81.91560 0.45054 5392 5170 2.59079 0.5 0.32 0.7415 0.7426 0.7579 2.779504 2.507648 0.543560 0.498118 0.458455 0.426315 0.351130 0.329738 69% 0.04
0.210 0.006 Fixed 22.97 0.009 Assumed Assumed
110 80 13 1.3
Assumed Assumed Assumed Assumed
effective temperature was found to be 5392 K (Cox,20 0 0). Gravity brightness, g1 = g2 = 0.32 was assumed for a convective star (Lucy, 1967), and the bolometric albedo, A1 = A2 = 0.5 for a convective star (Rucinski, 1969). After several iterations, the best synthetic light curve was obtained and fitted with the observed one and a set of parameters was derived, and listed in Table. 2 We attempted modeling with a spotted model to solve for the significant maximum difference in the observed light curves. The best fit of the observed and the theoretical curves was reached for a model with a hot spot on the secondary star at latitude 110° and longitude 80° Its mean radius is about 13° and the temperature
Table 3 Absolute physical parameters of the system 2MASS J20 0 04638+ 054,7475. Element
M(M )
R(R )
T(T )
L(L )
mbol .
Log g
Sp.type
Primary Secondary
0.968 0.441
1.048 0.972
0.933 0.894
0.834 0.606
4.888 5.235
4.382 4.414
G7 K0
factor is 1.3 which indicates that the spot is 30% hotter than its surrounding photosphere. The analyses of the light curves show that the primary component is more massive and hotter than the secondary one, where the difference in the temperature between the components is about 222 K. Fig. 3 shows the best fit of the model to the observed V RI light curves of the system. According to the accepted orbital solution, the components of the system are of spectral type G7 and K0, respectively, following Covey et al. (2007). Fig. 4 shows the geometric configuration of the binary system. The absolute physical parameters of the components were calculated using the empirical relation adopted by Harmanec (1988) and listed in Table 3. 4. Evolutionary status of 2MASS J20 0 04638 + 054,7475 The most popular evolutionary scenario for W UMa type binary stars is that they are formed from initially detached systems by angular momentum loss (Eggen and Iben 1989). Both the shrinking of the Roche lobe and the expanding of the components due to evolution will result in a massive component star that fills the critical Roche lobe and the system evolves into an overcontact binary through a primary to secondary mass transfer. The overcontact configuration of 2MASS J20 0 04638 + 054,7475, in Fig. 4 shows that both of the binary components fill their Roche lobes and they are evolved to that stage of common envelope and transfere of primary matter to secondary component. Using the calculated physical parameters listed in Table 3 we investigated the current evolutionary status of the system. Fig. 5, shows the components of the system on the Mass–Radius (M–R) relation (right panel) and Mass- Luminosity (M-L) relation (left panel) along with the evolutionary models computed by Mowlavi et al. (2012) for both Zero Age Main Sequence (ZAMS), the
38
M.S. Darwish et al. / New Astronomy 53 (2017) 35–38
Fig. 6. Location of both components on Teff –Luminosity diagram (left panel), and on the empirical Mass–Teff relation for intermediate mass stars by Malkov (2007), (right panel).
Terminal Age Main Sequence (TAMS) with metallicity z = 0. 014. Fig. 6 shows the location of the system components on the Teff – Luminosity diagram from Girardi et al. (20 0 0) (left panel) and the position of the components of the system on the empirical Mass– Teff relation for intermediate mass stars by Malkov (2007) (right panel). As it’s clear from figures, 5 and 6 the primary component follows closely the relation for main sequence stars, while the secondary component is over-luminous with temperature and radius larger than that expected for main-sequence stars. This may be related to the transfer of mass from the primary to the secondary star. 5. Conclusion We presented new light curves obtained by multicolor CCD photometry of a new short period WUMa eclipsing binary. We obtained its first ephemeris using the times of its minimum light. The first photometric solution of the system was obtained using the PHOEBE 0.31 software and can be summarized as follows: •
•
•
•
•
•
The fitted synthetic model suggests a hot spot on its secondary component The system is an overcontact with a relatively high fill-out factor = 69%. The system is an A-Subtype WUMa with mass ratio of about 0.45 The spectral types of the primary and secondary components are G7 and K0, respectively. The primary component of 2MASS J20 0 04638 + 054,7475 is the more massive one. The evolution study of the binary system revealed that the primary component is a main sequence star while the secondary is an evolved component which is considerably oversized and over-luminous if compared to main-sequence stars of the same mass.
As the system is a newly discovered one, for better determinations of the system parameters, further photometric and spectroscopic observations are strongly requested. Acknowledgments Many thanks are given to the anonymous referee for constructive remarks and suggestions. This research has made use of NASA’s Astrophysics Data System, the 2MASS All-Sky Survey and (AAVSO): (VSX). The research granted by Science and Technology Development Fund (STDF) N5217. We are very grateful the teams of KCScE and the team of Kottamia Astronomical Observatory, Dr. F. I. El-Nagahy, M. Ismail, Doaa El-Sayed I. Helmy. We would like to give thanks to Dr. M. Hassan, Dr. M. M.Elkhateeb, Dr. N. M. Ahmed, I. Zaid, A. Shokry D. Fouda and M. H. El-Depsy for their fruitful discussions and help. References ´ Ž., Schlegel, D., Finkbeiner, D., Padmanabhan, N., Lupton, R.H., Covey, K.R., Ivezic, Agüeros, M.A., Bochanski, J.J., Hawley, S.L., West, A.A., Seth, A., Kimball, A., Gogarten, S.M., Claire, M., Haggard, D., Kaib, N., Schneider, D.P., Sesar, B., 2007. AJ 134, 2398. Cox, A.N., 20 0 0. Allen’s Astrophysical Quantities, 4th ed. Springer, NewYork. Eggen, O.J., Iben Jr., I., 1989. AJ. 97, 431. Girardi, L., Bressan, A., Bretelli, G., Chiosi, C., 20 0 0. AAS 141, 371. Harmanec, P., 1988. Bull. Astron. Inst. Czechosl. 39, 329. Kwee, K., Van Woerden, H., 1956. BAN 12, 327K. Lucy, L., 1967. Z. Astrophys 65, 89. Malkov, O.Yu., 2007. MNRAS 382, 1073. Motl, D., 2007 C-Munipack Project v1.2.32 http://sourceforge.net/projects/ c-munipack/files. Mowlavi, N., Eggenberger, P., Meynet, G., Ekström, S., Georgy, C., Maeder, A., Chrnel, C., Eyer, L., 2012. A&A 541, 41. Nelson, R.H., 2006 MinimaV2.3., available from: http://members.shaw.ca/bob.nelson/ software1.htm. Prša, A., Zwitter, T., 2005. ApJ 628, 426. Rucinski, S., 1969. Acta Astron. 19, 156.