- Email: [email protected]
First photometric study of the W UMa system GSC 1042-2191
New Astronomy 44 (2016) 35–39
Contents lists available at ScienceDirect
New Astronomy journal homepage: www.elsevier.com/locate/newast
First photometric study of the W UMa system GSC 1042-2191 A. Bulut a,c,∗, I.˙ Bulut b,c, O. Demircan b,c a
Department of Physics, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Terzio˘glu Kampüsü, TR-17020 Çanakkale, Turkey Department of Space Sciences and Technologies, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Terzio˘glu Kampüsü, TR-17020 Çanakkale, Turkey c Astrophysics Research Centre and Observatory, Çanakkale Onsekiz Mart University, Terzio˘glu Kampüsü, TR-17020 Çanakkale, Turkey b
h i g h l i g h t s •
The first analysis of the light curve of the W UMa system GSC 1042–2191 were made. The orbital and physical parameters of the system were obtained. • The system was found a low mass ratio, A-type over-contact binary with a fill out parameter of f 65.01%. •
a r t i c l e
i n f o
Article history: Received 4 September 2015 Accepted 16 September 2015 Available online 9 October 2015 Communicated by P. S. Conti Keywords: Stars: binaries: close Binaries: eclipsing Stars: individual: GSC 1042-2191
a b s t r a c t We present new photometric observations covering eight minima times for the eclipsing binary GSC 10422191. The light curves in BVRI colors were analyzed by using WD-code for the system parameters. Eight minima times were obtained from the new observations. The system is found a low mass ratio (q = 0.148), A-type over-contact binary with a fill out parameter of f = 65.01 ± 12.18%. The preliminary absolute dimensions (M1 = 1.26 ± 0.06 M , M2 = 0.18 ± 0.06 M , R1 = 1.54 ± 0.20 R , R2 = 0.69 ± 0.01 R , L1 =3.30 ± 0.30 L and L2 = 0.59 ± 0.20 L ) indicate the very much oversized and over-luminous secondary component, by assuming the present luminosity of the secondary is its main sequence luminosity, we predict the original mass is about 0.8 M , this means the present secondary could be transferred and/or lost 77% of its original mass and only its core is left. © 2015 Elsevier B.V. All rights reserved.
1. Introduction
2. Photometric CCD observations
GSC 1042-2191, TYC 1042-2191-1, 2MASS J19234908+0818254, HD 182314, SAO 124582, R.A. = 19h 23m 49s .0854, DEC = +08◦ 18 25 .516) belongs to the list of “New Eclipsing Binaries Found in the NSVS Database I” published by Otero et al. (2004). The photometric observations of the system show an eclipsing W UMa-type binary light curve. The orbital period of the system P = 0d .423796 was obtained by Otero et al. (2004). The V magnitude of the binary in the Tycho Catalogue is about 9m .31 (Hog et al., 2000). There is no complete photometric and spectroscopic study of the system in the literature. In this paper, we present the results of the first photometric solution obtained from the first multi-band CCD light curves of GSC 1042-2191.
We observed GSC 1042-2191 three nights, on July 2, 6 and 10 in 2014. and three nights on July 11–13 in 2015 with the 40-cm Schmidt– Cassegrain telescope equipped with the Apogee Alta U47 CCD camera at Ulupinar Observatory (UPO) of Çanakkale Onsekiz Mart University (Turkey). This camera gives image scales of 0.65 arcseconds per pixel and provides an observed field of view (FOV) of 12 arcmin × 12 arcmin. Several bias, dark and flat frames were taken during the night of each observation to take into account pixel-to-pixel variations on the frame. Relevant data for eclipsing system and the adopted comparison stars are summarized in Table 1. The observational log of the system is listed in Table 2. The reduction of the CCD frames has been made by C-MUNIPACK software (http://integral.sci.muni.cz/cmunipack). All frames have been calibrated by dark frame and flat-field corrections. Differential aperture photometry has been also performed in C-MUNIPACK. The new observations contributed eight times of minimum light in four filters. The minimum times determined by using the Kwee and van Woerden (1956) method are listed in Table 3. A linear least squares method appication to the minima times yielded the light elements of
∗ Corresponding author at: Department of Physics, Faculty of Arts and Sciences, Canakkale Onsekiz Mart University, Terzioglu Kampusu, TR-17020 Canakkale, Turkey. Tel.: +90 2862180018; fax: +90 2862180533. E-mail address: [email protected] (A. Bulut).
http://dx.doi.org/10.1016/j.newast.2015.09.003 1384-1076/© 2015 Elsevier B.V. All rights reserved.
36
A. Bulut et al. / New Astronomy 44 (2016) 35–39
Fig. 1. The observational and theoretical light and color curves of GSC 1042-2191.
Table 1 The coordinates and V magnitudes of GSC 1042-2191 and two comparison stars.
Table 3 New times of minima and residuals for GSC 1042-2191.
Star
R.A. (2000)
DEC. (2000)
V (mag)
Hel.JD
GSC 1042-2191 C1= TYC 1042 2112 C2= TYC 1042 2113
19h 23m 49s .0854 19h 23m 56s .0867 19h 23m 34s .8523
+08◦ 18 25 .516 +08◦ 20 10 .698 +08◦ 20 06 .646
9.310 ± 0.020 11.167 ± 0.116 11.312 ± 0.122
the system as
HJD (Min I) = 2456841.3245(58) + 0d .4238006(5) × E.
(1)
which was used in phase calculation in forming the light and color curves. The B, V, R and I light curves and the B–V, V–R and R–I color curves are plotted in Fig. 1. The light curves in Fig. 1 show that the secondary eclipse is total; i.e, the eclipsing component in the secondary eclipse is larger and hotter component. It is clear in this case before analysis that the system is an A-type W UMa system. The variation of the color curves in Fig. 1. especially in B–V up to 0.1 magnitude indicate the temperature variation on the surfaces of the larger component. Since no spot effect is observable on the light curves such variations can be atributed to mass motions on or arround the larger primary component.
2400000 (days)
Error (days)
Min.
Filter
56841.3276 56841.5356 56845.3502 56845.5608 56849.3763 57215.5391 57216.3875 57217.4492
±0.0004 ±0.0005 ±0.0006 ±0.0004 ±0.0006 ±0.0011 ±0.0005 ±0.0007
I II II I II I I II
BVRI BVRI BVRI BVRI BVRI BVRI BVRI BVRI
3. Analysis of the light curves The analysis of four light curves of GSC 1042-2191 were made by using the PHOEBE program (ver. 0.31, Prsa and Zwitter, 2005), based on the Wilson–Devinney (W–D) program (Wilson and Devinney, 1971). The program computes the light curves as a function of following main parameters: surface potentials (1, 2 ), mass ratio (q), luminosities of the components (L1, 2 ), orbital eccentricity (e), inclination (i), argument of periastron (ω), limb-darkening coefficients
Table 2 Observational log for photometric observations. Star
Hel.JD 2450000
Filter
N
Sigma (B)
Sigma (V)
Sigma (R)
Sigma (I)
GSC 1042-2191
7215-7217
BVRI
410
0.012
0.012
0.011
0.010
A. Bulut et al. / New Astronomy 44 (2016) 35–39
37
0.1010
0.1005
0.1000
0.0995
0.0990
0.0985
0.0980 0.135
0.140
0.145
0.150
0.155
0.160
0.165
q Fig. 2. Sum of the squared residuals as a function of the mass ratio for GSC 1042-2191. Table 4 Photometric indices and inferred mean effective temperature of GSC 1042-2191. Photometric index
Value
Johnson V 2MASS J 2MASS H 2MASS Ks Johnson B–V Tycho-2 BT –VT Johnson/2MASS V–J Johnson/2MASS V–H Johnson/2MASS V–Ks 2MASS J–Ks
9.310 8.355 8.275 8.154 0.437 0.465 0.955 1.035 1.156 0.201
± ± ± ± ± ± ± ± ± ±
0.020 0.024 0.047 0.022 0.030 0.025 0.022 0.034 0.021 0.023
T (K)
References
– – – – 6499 ± 446 6559 ± 952 6280 ± 145 6490 ± 210 6406 ± 116 5650 ± 647
Hog et al. (2000) Cutri et al. (2003) Cutri et al. (2003) Cutri et al. (2003) Hog et al. (2000) Hog et al. (2000) Hog et al. (2000) and Cutri et al. (2003) Hog et al. (2000) and Cutri et al. (2003) Hog et al. (2000) and Cutri et al. (2003) Cutri et al. (2003)
(x1, 2 ), gravity-darkening exponents (g1, 2 ) and bolometric albedo coefficients (A1, 2 ). The contact binary mode (in W–D mode 3) was used with several assumptions. Some parameters of the components should be fixed during the light-curve modeling. The linear limb-darkening coefficients of each star were automatically interpolated by the PHOEBE program from van Hamme (1993) tables. The values of gravitydarkening exponents (g1, 2 = 0.32) and bolometric albedo coefficients (A1, 2 = 0.5) were set at their suggested values for the convective atmospheres (Lucy, 1968). The grid size was set to N = 20 for both stars. A blackbody approximation was selected to both stars (IFAT = 0) The mass ratio (q = M2 /M1 ) is an important parameter because the W–D method is based on the Roche geometry of the system, which is sensitive to the mass ratio. For the present system, since there is no spectroscopically determined values for the mass ratio, trial values of the mass ratio were used in the photometric solutions. A series of solutions were obtained for the trial values of the mass ratio from 0.2 to 1.0 with a step of 0.05. The R light curves were used in this process. The sum of the squared residuals, W(O − C )2 , are displayed as a function of the trial values in Fig. 2. In this way, we achieved the minimum at mass ratio of 0.148. This value was used later as the initial value of the mass ratio in a differential-corrections stage of the program. Absolute photometry of the stars is available in the literature from several sources, and color indices can be used to estimate a mean effective temperature for the combined light of the systems (assuming no interstellar reddening). The results were collected in Tables 4. We used the color/temperature calibrations of Casagrande et al. (2010), Ramírez and Meléndez (2005) for the dwarf stars. In all cases, we assumed solar metallicity ([Fe/H] = 0.0 dex). The weighted average of
the seven estimates is 6315 ± 419 for the average temperature of GSC 1042-2191. These values is adopted the mean of the effective temperature of the larger primary star in the analyses. The temperature of the primary component was fixed at 6315 K for GSC 1042-2191. The temperature of the secondary component was left to converge to T2 . CCD observations in B, V, R and I bands were simultaneously used to obtain the light curve solutions. The free parameters in the light curve fitting were (T2 ), (1 ) and (2 ), (L1 ), and (i). The results of the light curves solution can be found in Table 5. For the parameters in the light curve fitting, the standard deviations of the differential corrections supplied by the WD program were used as error. The theoretical light and color curves calculated by using the parameters obtained from simultaneous modeling of the B, V, R and I light curves are shown in Fig. 1. The Roche lobes related to the system are given in Fig. 3. The mass ratio and fill-out factor are found as q = 0.1464 ± 0.0017 and f = 65.01 ± 12.18% , respectively. 4. Conclusions and remarks The first photometric observations of the short-period binary, GSC 1042-2191 in four colors have been presented, and the new light curves were analyzed by using W–D program. The solutions suggest that GSC 1042-2191 is an A type W UMa system with a mass ratio of 0.1464 ± 0.0017. The observed light curves of GSC 1042-2191 are almost symmetric, no spots were introduced on its components. The absolute parameters of the system cannot be determined directly because no spectroscopic observations were available. Assuming that the more massive component is a normal, main-sequence star, its mass can be estimated to be 1.26 ± 0.06 M (Eker et al., 2015). The preliminary values of other absolute parameters of the components
38
A. Bulut et al. / New Astronomy 44 (2016) 35–39 Table 5 Parameters of the light curves of GSC 1042-2191.
Parameter
GSC 1042-2191 value
T0 (HJD) P (day) i (deg) e PSHIFT T1 (K) T2 (K) 1 = 2 q x1 (B, V, R, I) x2 (B, V, R, I) A1 = A2 g1 = g2 L1 /(L1 + L2 ) (B, V, R, I) L2 /(L1 + L2 ) (B, V, R, I) r1 (pole) r1 (side) r1 (back) r2 (pole) r2 (side) r2 (back) r1, mean r2, mean f(% )
2456841.3245 0.4238006 80.49 ± 0.12 0.0 0.01219 ± 0.00711 6315 (fixed) 6114 ± 15 2.0303 ± 0.0049 0.1464 ± 0.0017 0.812 (B) 0.720 (V) 0.627 (R) 0.535 (I) 0.811 (B) 0.719 (V) 0.626 (R) 0.534 (I) 0.5 0.32 0.869 ± 0.019 (B) 0.863 ± 0.016 (V) 0.854 ± 0.015 (R) 0.847 ± 0.013 (I) 0.131 (B) 0.137 (V) 0.146 (R) 0.153 (I) 0.5273 ± 0.0014 0.5874 ± 0.0023 0.6128 ± 0.0029 0.2312 ± 0.0042 0.2434 ± 0.0053 0.3048 ± 0.0078 0.5758 ± 0.0022 0.2598 ± 0.0091 65.01 ± 12.18
Fig. 3. The Roche geometry of the system GSC 1042-2191.
Table 6 The preliminary physical parameters of GSC 1042-2191. Parameter
GSC 1042-2191
M1 (M ) M2 (M ) R1 (R ) R2 (R ) log g (cgs) log g (cgs) T1 (K) T2 (K) L1 (L ) L2 (L ) M1,bol M2,bol (BC)1 (BC)2 Mv,1 Mv,2
1.26 ± 0.18 ± 1.54 ± 0.69 ± 4.16 ± 4.01 ± 6315 ± 6114 ± 3.30 ± 0.59 ± 3.45 ± 5.32 ± −0.008 −0.030 3.46 ± 5.35 ±
0.06 0.06 0.20 0.01 0.02 0.02 419 419 0.30 0.20 0.05 0.05
0.05 0.05
are then obtained by well known formula, and the results are listed in Table 6. The bolometric corrections (BC) have been adopted from Flower (1996), together with M,bol = 4.75. As it was expected from mass transferring contact binaries the secondary component of GSC 1042-2191 turns out to be very much oversized and overluminuous, If we assume the present luminosity of the secondary is its original main sequence luminosity then we predict its original mass is about 0.8 M ; (Eker et al., 2015) thus it could be transferred and lost 77% of its mass, and only about the core of the original secondary is left. Acknowledgments This work has been supported in part by the Scientific and Technological Research Council of Turkey (TUBITAK) Grant number 114F166. We acknowledge the observing time at Ulupinar Observatory of Çanakkale Onsekiz Mart University. We also thank to Dr. Edwin Budding for his valuable comments.
A. Bulut et al. / New Astronomy 44 (2016) 35–39
References Casagrande, L., Ramírez, I., Meléndez, J., Bessell, M., Asplund, M., 2010. A&A 512, 54. Cutri, R.M., Skrutskie, M.F., van Dyk, S., Beichman, C.A., et al., 2003. VizeR Online Data II/ 2246. Eker, Z., Soydugan, F., Soydugan, E., Bilir, S., Yaz Gökçe, E., Steer, I., Tüysüz, M., Senyüz, ¸ T., Demircan, O., 2015. AJ 149, 131. Flower, P.J., 1996. ApJ 469, 355. Hog, E., Fabricius, C., Makarov, V.V., Urban, S., Corbin, T., Wycoff, G., Bastian, U., Schwekendiek, P., Wicenec, A., 2000. A&A 355, L27.
Kwee, K.K., van Woerden, H., 1956. Bull. Astron. Inst. Netherlands 12, 327. Lucy, L.B., 1968. ApJ 151, 1123. Otero, S.A., Wils, P., Dubovsky, P.A., 2004. IBVS 5570, 1. Prsa, A., Zwitter, T., 2005. ApJ 628, 426. Ramírez, I., Meléndez, J., 2005. ApJ 626, 465. van Hamme, W., 1993. AJ 106, 2096. Wilson, R.E., Devinney, R.J., 1971. ApJ 166, 605.
39
Contents lists available at ScienceDirect
New Astronomy journal homepage: www.elsevier.com/locate/newast
First photometric study of the W UMa system GSC 1042-2191 A. Bulut a,c,∗, I.˙ Bulut b,c, O. Demircan b,c a
Department of Physics, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Terzio˘glu Kampüsü, TR-17020 Çanakkale, Turkey Department of Space Sciences and Technologies, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Terzio˘glu Kampüsü, TR-17020 Çanakkale, Turkey c Astrophysics Research Centre and Observatory, Çanakkale Onsekiz Mart University, Terzio˘glu Kampüsü, TR-17020 Çanakkale, Turkey b
h i g h l i g h t s •
The first analysis of the light curve of the W UMa system GSC 1042–2191 were made. The orbital and physical parameters of the system were obtained. • The system was found a low mass ratio, A-type over-contact binary with a fill out parameter of f 65.01%. •
a r t i c l e
i n f o
Article history: Received 4 September 2015 Accepted 16 September 2015 Available online 9 October 2015 Communicated by P. S. Conti Keywords: Stars: binaries: close Binaries: eclipsing Stars: individual: GSC 1042-2191
a b s t r a c t We present new photometric observations covering eight minima times for the eclipsing binary GSC 10422191. The light curves in BVRI colors were analyzed by using WD-code for the system parameters. Eight minima times were obtained from the new observations. The system is found a low mass ratio (q = 0.148), A-type over-contact binary with a fill out parameter of f = 65.01 ± 12.18%. The preliminary absolute dimensions (M1 = 1.26 ± 0.06 M , M2 = 0.18 ± 0.06 M , R1 = 1.54 ± 0.20 R , R2 = 0.69 ± 0.01 R , L1 =3.30 ± 0.30 L and L2 = 0.59 ± 0.20 L ) indicate the very much oversized and over-luminous secondary component, by assuming the present luminosity of the secondary is its main sequence luminosity, we predict the original mass is about 0.8 M , this means the present secondary could be transferred and/or lost 77% of its original mass and only its core is left. © 2015 Elsevier B.V. All rights reserved.
1. Introduction
2. Photometric CCD observations
GSC 1042-2191, TYC 1042-2191-1, 2MASS J19234908+0818254, HD 182314, SAO 124582, R.A. = 19h 23m 49s .0854, DEC = +08◦ 18 25 .516) belongs to the list of “New Eclipsing Binaries Found in the NSVS Database I” published by Otero et al. (2004). The photometric observations of the system show an eclipsing W UMa-type binary light curve. The orbital period of the system P = 0d .423796 was obtained by Otero et al. (2004). The V magnitude of the binary in the Tycho Catalogue is about 9m .31 (Hog et al., 2000). There is no complete photometric and spectroscopic study of the system in the literature. In this paper, we present the results of the first photometric solution obtained from the first multi-band CCD light curves of GSC 1042-2191.
We observed GSC 1042-2191 three nights, on July 2, 6 and 10 in 2014. and three nights on July 11–13 in 2015 with the 40-cm Schmidt– Cassegrain telescope equipped with the Apogee Alta U47 CCD camera at Ulupinar Observatory (UPO) of Çanakkale Onsekiz Mart University (Turkey). This camera gives image scales of 0.65 arcseconds per pixel and provides an observed field of view (FOV) of 12 arcmin × 12 arcmin. Several bias, dark and flat frames were taken during the night of each observation to take into account pixel-to-pixel variations on the frame. Relevant data for eclipsing system and the adopted comparison stars are summarized in Table 1. The observational log of the system is listed in Table 2. The reduction of the CCD frames has been made by C-MUNIPACK software (http://integral.sci.muni.cz/cmunipack). All frames have been calibrated by dark frame and flat-field corrections. Differential aperture photometry has been also performed in C-MUNIPACK. The new observations contributed eight times of minimum light in four filters. The minimum times determined by using the Kwee and van Woerden (1956) method are listed in Table 3. A linear least squares method appication to the minima times yielded the light elements of
∗ Corresponding author at: Department of Physics, Faculty of Arts and Sciences, Canakkale Onsekiz Mart University, Terzioglu Kampusu, TR-17020 Canakkale, Turkey. Tel.: +90 2862180018; fax: +90 2862180533. E-mail address: [email protected] (A. Bulut).
http://dx.doi.org/10.1016/j.newast.2015.09.003 1384-1076/© 2015 Elsevier B.V. All rights reserved.
36
A. Bulut et al. / New Astronomy 44 (2016) 35–39
Fig. 1. The observational and theoretical light and color curves of GSC 1042-2191.
Table 1 The coordinates and V magnitudes of GSC 1042-2191 and two comparison stars.
Table 3 New times of minima and residuals for GSC 1042-2191.
Star
R.A. (2000)
DEC. (2000)
V (mag)
Hel.JD
GSC 1042-2191 C1= TYC 1042 2112 C2= TYC 1042 2113
19h 23m 49s .0854 19h 23m 56s .0867 19h 23m 34s .8523
+08◦ 18 25 .516 +08◦ 20 10 .698 +08◦ 20 06 .646
9.310 ± 0.020 11.167 ± 0.116 11.312 ± 0.122
the system as
HJD (Min I) = 2456841.3245(58) + 0d .4238006(5) × E.
(1)
which was used in phase calculation in forming the light and color curves. The B, V, R and I light curves and the B–V, V–R and R–I color curves are plotted in Fig. 1. The light curves in Fig. 1 show that the secondary eclipse is total; i.e, the eclipsing component in the secondary eclipse is larger and hotter component. It is clear in this case before analysis that the system is an A-type W UMa system. The variation of the color curves in Fig. 1. especially in B–V up to 0.1 magnitude indicate the temperature variation on the surfaces of the larger component. Since no spot effect is observable on the light curves such variations can be atributed to mass motions on or arround the larger primary component.
2400000 (days)
Error (days)
Min.
Filter
56841.3276 56841.5356 56845.3502 56845.5608 56849.3763 57215.5391 57216.3875 57217.4492
±0.0004 ±0.0005 ±0.0006 ±0.0004 ±0.0006 ±0.0011 ±0.0005 ±0.0007
I II II I II I I II
BVRI BVRI BVRI BVRI BVRI BVRI BVRI BVRI
3. Analysis of the light curves The analysis of four light curves of GSC 1042-2191 were made by using the PHOEBE program (ver. 0.31, Prsa and Zwitter, 2005), based on the Wilson–Devinney (W–D) program (Wilson and Devinney, 1971). The program computes the light curves as a function of following main parameters: surface potentials (1, 2 ), mass ratio (q), luminosities of the components (L1, 2 ), orbital eccentricity (e), inclination (i), argument of periastron (ω), limb-darkening coefficients
Table 2 Observational log for photometric observations. Star
Hel.JD 2450000
Filter
N
Sigma (B)
Sigma (V)
Sigma (R)
Sigma (I)
GSC 1042-2191
7215-7217
BVRI
410
0.012
0.012
0.011
0.010
A. Bulut et al. / New Astronomy 44 (2016) 35–39
37
0.1010
0.1005
0.1000
0.0995
0.0990
0.0985
0.0980 0.135
0.140
0.145
0.150
0.155
0.160
0.165
q Fig. 2. Sum of the squared residuals as a function of the mass ratio for GSC 1042-2191. Table 4 Photometric indices and inferred mean effective temperature of GSC 1042-2191. Photometric index
Value
Johnson V 2MASS J 2MASS H 2MASS Ks Johnson B–V Tycho-2 BT –VT Johnson/2MASS V–J Johnson/2MASS V–H Johnson/2MASS V–Ks 2MASS J–Ks
9.310 8.355 8.275 8.154 0.437 0.465 0.955 1.035 1.156 0.201
± ± ± ± ± ± ± ± ± ±
0.020 0.024 0.047 0.022 0.030 0.025 0.022 0.034 0.021 0.023
T (K)
References
– – – – 6499 ± 446 6559 ± 952 6280 ± 145 6490 ± 210 6406 ± 116 5650 ± 647
Hog et al. (2000) Cutri et al. (2003) Cutri et al. (2003) Cutri et al. (2003) Hog et al. (2000) Hog et al. (2000) Hog et al. (2000) and Cutri et al. (2003) Hog et al. (2000) and Cutri et al. (2003) Hog et al. (2000) and Cutri et al. (2003) Cutri et al. (2003)
(x1, 2 ), gravity-darkening exponents (g1, 2 ) and bolometric albedo coefficients (A1, 2 ). The contact binary mode (in W–D mode 3) was used with several assumptions. Some parameters of the components should be fixed during the light-curve modeling. The linear limb-darkening coefficients of each star were automatically interpolated by the PHOEBE program from van Hamme (1993) tables. The values of gravitydarkening exponents (g1, 2 = 0.32) and bolometric albedo coefficients (A1, 2 = 0.5) were set at their suggested values for the convective atmospheres (Lucy, 1968). The grid size was set to N = 20 for both stars. A blackbody approximation was selected to both stars (IFAT = 0) The mass ratio (q = M2 /M1 ) is an important parameter because the W–D method is based on the Roche geometry of the system, which is sensitive to the mass ratio. For the present system, since there is no spectroscopically determined values for the mass ratio, trial values of the mass ratio were used in the photometric solutions. A series of solutions were obtained for the trial values of the mass ratio from 0.2 to 1.0 with a step of 0.05. The R light curves were used in this process. The sum of the squared residuals, W(O − C )2 , are displayed as a function of the trial values in Fig. 2. In this way, we achieved the minimum at mass ratio of 0.148. This value was used later as the initial value of the mass ratio in a differential-corrections stage of the program. Absolute photometry of the stars is available in the literature from several sources, and color indices can be used to estimate a mean effective temperature for the combined light of the systems (assuming no interstellar reddening). The results were collected in Tables 4. We used the color/temperature calibrations of Casagrande et al. (2010), Ramírez and Meléndez (2005) for the dwarf stars. In all cases, we assumed solar metallicity ([Fe/H] = 0.0 dex). The weighted average of
the seven estimates is 6315 ± 419 for the average temperature of GSC 1042-2191. These values is adopted the mean of the effective temperature of the larger primary star in the analyses. The temperature of the primary component was fixed at 6315 K for GSC 1042-2191. The temperature of the secondary component was left to converge to T2 . CCD observations in B, V, R and I bands were simultaneously used to obtain the light curve solutions. The free parameters in the light curve fitting were (T2 ), (1 ) and (2 ), (L1 ), and (i). The results of the light curves solution can be found in Table 5. For the parameters in the light curve fitting, the standard deviations of the differential corrections supplied by the WD program were used as error. The theoretical light and color curves calculated by using the parameters obtained from simultaneous modeling of the B, V, R and I light curves are shown in Fig. 1. The Roche lobes related to the system are given in Fig. 3. The mass ratio and fill-out factor are found as q = 0.1464 ± 0.0017 and f = 65.01 ± 12.18% , respectively. 4. Conclusions and remarks The first photometric observations of the short-period binary, GSC 1042-2191 in four colors have been presented, and the new light curves were analyzed by using W–D program. The solutions suggest that GSC 1042-2191 is an A type W UMa system with a mass ratio of 0.1464 ± 0.0017. The observed light curves of GSC 1042-2191 are almost symmetric, no spots were introduced on its components. The absolute parameters of the system cannot be determined directly because no spectroscopic observations were available. Assuming that the more massive component is a normal, main-sequence star, its mass can be estimated to be 1.26 ± 0.06 M (Eker et al., 2015). The preliminary values of other absolute parameters of the components
38
A. Bulut et al. / New Astronomy 44 (2016) 35–39 Table 5 Parameters of the light curves of GSC 1042-2191.
Parameter
GSC 1042-2191 value
T0 (HJD) P (day) i (deg) e PSHIFT T1 (K) T2 (K) 1 = 2 q x1 (B, V, R, I) x2 (B, V, R, I) A1 = A2 g1 = g2 L1 /(L1 + L2 ) (B, V, R, I) L2 /(L1 + L2 ) (B, V, R, I) r1 (pole) r1 (side) r1 (back) r2 (pole) r2 (side) r2 (back) r1, mean r2, mean f(% )
2456841.3245 0.4238006 80.49 ± 0.12 0.0 0.01219 ± 0.00711 6315 (fixed) 6114 ± 15 2.0303 ± 0.0049 0.1464 ± 0.0017 0.812 (B) 0.720 (V) 0.627 (R) 0.535 (I) 0.811 (B) 0.719 (V) 0.626 (R) 0.534 (I) 0.5 0.32 0.869 ± 0.019 (B) 0.863 ± 0.016 (V) 0.854 ± 0.015 (R) 0.847 ± 0.013 (I) 0.131 (B) 0.137 (V) 0.146 (R) 0.153 (I) 0.5273 ± 0.0014 0.5874 ± 0.0023 0.6128 ± 0.0029 0.2312 ± 0.0042 0.2434 ± 0.0053 0.3048 ± 0.0078 0.5758 ± 0.0022 0.2598 ± 0.0091 65.01 ± 12.18
Fig. 3. The Roche geometry of the system GSC 1042-2191.
Table 6 The preliminary physical parameters of GSC 1042-2191. Parameter
GSC 1042-2191
M1 (M ) M2 (M ) R1 (R ) R2 (R ) log g (cgs) log g (cgs) T1 (K) T2 (K) L1 (L ) L2 (L ) M1,bol M2,bol (BC)1 (BC)2 Mv,1 Mv,2
1.26 ± 0.18 ± 1.54 ± 0.69 ± 4.16 ± 4.01 ± 6315 ± 6114 ± 3.30 ± 0.59 ± 3.45 ± 5.32 ± −0.008 −0.030 3.46 ± 5.35 ±
0.06 0.06 0.20 0.01 0.02 0.02 419 419 0.30 0.20 0.05 0.05
0.05 0.05
are then obtained by well known formula, and the results are listed in Table 6. The bolometric corrections (BC) have been adopted from Flower (1996), together with M,bol = 4.75. As it was expected from mass transferring contact binaries the secondary component of GSC 1042-2191 turns out to be very much oversized and overluminuous, If we assume the present luminosity of the secondary is its original main sequence luminosity then we predict its original mass is about 0.8 M ; (Eker et al., 2015) thus it could be transferred and lost 77% of its mass, and only about the core of the original secondary is left. Acknowledgments This work has been supported in part by the Scientific and Technological Research Council of Turkey (TUBITAK) Grant number 114F166. We acknowledge the observing time at Ulupinar Observatory of Çanakkale Onsekiz Mart University. We also thank to Dr. Edwin Budding for his valuable comments.
A. Bulut et al. / New Astronomy 44 (2016) 35–39
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