The Astronomical Journal, 142:124 (8pp), 2011 October C 2011.
doi:10.1088/0004-6256/142/4/124
The American Astronomical Society. All rights reserved. Printed in the U.S.A.
DEEP, LOW MASS RATIO OVERCONTACT BINARY SYSTEMS. XI. V1191 CYGNI L. Y. Zhu1,2 , S. B. Qian1,2 , B. Soonthornthum3 , J. J. He1,2 , and L. Liu1,2 1
National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, 650011 Kunming, China;
[email protected] 2 Key Laboratory for the Structure and Evolution of Celestial Bodies, Chinese Academy of Sciences, 650011 Kunming, China 3 National Astronomical Research Institute of Thailand/Ministry of Science and Technology, Bangkok, Thailand Received 2010 September 25; accepted 2011 August 17; published 2011 September 13
ABSTRACT Complete CCD photometric light curves in BV(RI)c bands obtained on one night in 2009 for the short-period closebinary system V1191 Cygni are presented. A new photometric analysis with the 2003 version of the Wilson–Van Hamme code shows that V1191 Cyg is a W-type overcontact binary system and suggests that it has a high degree of overcontact (f = 68.6%) with very low mass ratio, implying that it is at the late stage of overcontact evolution. The absolute parameters of V1191 Cyg are derived using spectroscopic and photometric solutions. Combining new determined times of light minimum with others published in the literature, the period change of the binary star is investigated. A periodic variation, with a period of 26.7 years and an amplitude of 0.023 days, was discovered to be superimposed on a long-term period increase (dP/dt = +4.5(±0.1) × 10−7 days yr−1 ). The cyclic period oscillation may be caused by the magnetic activity cycles of either of the components or the light-time effect due to the presence of a third body with a mass of m3 = 0.77 M and an orbital radius of a3 = 7.6 AU, when this body is coplanar to the orbit of the eclipsing pair. The secular orbital period increase can be interpreted as a mass transfer from the less massive component to the more massive one. With the period increases, V1191 Cyg will evolve from its present low mass ratio, high filled overcontact state to a rapidly rotating single star when its orbital angular momentum is less than three times the total spin angular momentum. V1191 Cyg is too blue for its orbital period and it is an unusual W-type overcontact system with such a low mass ratio and high fill-out overcontact configuration, which is worth monitoring continuously in the future. Key words: binaries: close – binaries: eclipsing – stars: evolution – stars: individual (V1191 Cygni)
observations. In the present paper, the combined results of the period investigation, photometric and spectroscopic solutions, structure, and evolutionary state of this binary star are discussed.
1. INTRODUCTION The light variability of V1191 Cyg (=GSC 03159-01512) was discovered by Mayer (1965). He identified this star as an eclipsing variable of the W UMa type and published the earliest photoelectric minima of this system. He also derived the first ephemeris as MinI = 2438634.5471 + 0.313377E. After that, V1191 Cyg was neglected until 2005 when Pribulla et al. (2005b) analyzed their CCD observations obtained from the 50 cm Newton telescope of Star´a Lesn´a Observatory. They found that this system is a W-type contact binary with i (inclination) = 80.◦ 4, q (mass ratio) = 0.094, and f (the degree of overcontact) = 46%. During their investigation of the period variation of V1191 Cyg, they noticed that there was a large gap in the data because the first data recorded after the discovery observations by Mayer (1965) did not appear until 1993. Considering that this would cause ambiguity regarding the number of cycles that had elapsed in between, they did not use the minima from Mayer in their analysis and suggested an unusually fast period increase with ΔP /P = 4.216 × 10−6 yr−1 . Most recently, Rucinski et al. (2008) published the first spectroscopic study of the system. They confirmed that V1191 Cyg is a W-type system and they derived the spectroscopic mass ratio as 0.107 ± 0.005. In addition, they corrected the spectral type of this system to F6V. Following the investigation by Pribulla et al. (2005b), many CCD times of light minima for V1191 Cyg were published, its spectral type was corrected, and a more precise mass ratio was available. In order to understand the evolutionary state of the system, the photometric solutions and the study of the orbital period changes of this binary star need to be improved. Therefore, we included this binary star in our
2. NEW CCD PHOTOMETRIC OBSERVATIONS FOR V1191 CYGNI Complete CCD BV(RI)c light curves of V1191 Cyg were observed with the PI 1024 × 1024 CCD photometric system attached to the 60 cm telescope at Xinglong Station of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) on 2009 August 27. During the observation, the integration times were set as 30 s, 30 s, 20 s, and 20 s for the BV(RI)c wavelengths, respectively. N2HV000438 (αJ2000 = 20h 16m 18.s 55, δJ2000 = 41◦ 58 53. 11) and N2HV000483 (αJ2000 = 20h 16m 40.s 68, δJ2000 = 41◦ 55 57. 63), which are near the target, were chosen as comparison and check stars, respectively. The observations are plotted in Figure 1 with open circles and are listed in Tables 1–4. With these observed data, one primary eclipsing timing (HJD2455071.1339 (1)) and one secondary timing (HJD2455071.2922 (4)) are determined by using parabola fitting. From Figure 1, we can see that our one-night light curves are symmetrical, which is different from the light curves published by Pribulla et al. (2005b), who found a systematic deviation around primary minimum in the R band. In addition, we observed this target in the (RI )c bands on 2008 April 15, May 20, November 8, and 10 with the DW436 2048 × 2048 CCD attached to the 1.0 m Cassegrain reflecting telescope of the Yunnan Astronomical Observatory (YNAO), in the R band on 2011 May 28 with the DW436 2048 × 2048 CCD attached to the 60 cm Cassegrain reflecting telescope of YNAO, and in the BV(RI)c bands on 2009 August 23, and the 1
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al. Table 1 B-band CCD Observations of V1191 Cyg
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD(Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
70.9922 71.0107 71.0227 71.0340 71.0455 71.0567 71.0676 71.0785 71.0894 71.1003 71.1113 71.1222 71.1331 71.1440 71.1550 71.1659 71.1769 71.1878 71.1993 71.2112 71.2223 71.2333 71.2444 71.2559 71.2670 71.2784 71.2897 71.3008 71.3119
1.565 1.437 1.359 1.319 1.283 1.266 1.274 1.305 1.357 1.420 1.513 1.581 1.597 1.575 1.538 1.436 1.359 1.304 1.270 1.261 1.279 1.310 1.350 1.422 1.505 1.568 1.563 1.539 1.530
70.9945 71.0130 71.0243 71.0356 71.0471 71.0583 71.0691 71.0801 71.0910 71.1019 71.1129 71.1238 71.1347 71.1456 71.1565 71.1675 71.1784 71.1894 71.2011 71.2128 71.2239 71.2349 71.2459 71.2575 71.2686 71.2802 71.2913 71.3024 71.3135
1.558 1.426 1.347 1.304 1.281 1.265 1.283 1.308 1.367 1.438 1.531 1.594 1.593 1.571 1.525 1.417 1.348 1.299 1.269 1.265 1.282 1.315 1.363 1.425 1.517 1.568 1.555 1.583 1.521
70.9972 71.0146 71.0259 71.0373 71.0488 71.0598 71.0707 71.0817 71.0925 71.1035 71.1144 71.1253 71.1362 71.1472 71.1581 71.1690 71.1800 71.1910 71.2027 71.2144 71.2255 71.2365 71.2476 71.2590 71.2702 71.2818 71.2929 71.3040
1.554 1.402 1.345 1.304 1.272 1.271 1.282 1.321 1.370 1.451 1.548 1.588 1.590 1.574 1.506 1.404 1.344 1.293 1.268 1.255 1.286 1.314 1.363 1.436 1.532 1.557 1.578 1.569
70.9999 71.0162 71.0275 71.0390 71.0504 71.0614 71.0723 71.0832 71.0941 71.1051 71.1160 71.1269 71.1378 71.1487 71.1597 71.1706 71.1816 71.1926 71.2044 71.2160 71.2270 71.2380 71.2492 71.2606 71.2717 71.2834 71.2945 71.3055
1.539 1.394 1.332 1.300 1.274 1.263 1.293 1.328 1.379 1.471 1.565 1.596 1.589 1.564 1.500 1.394 1.333 1.282 1.254 1.268 1.296 1.326 1.374 1.447 1.542 1.565 1.569 1.566
71.0026 71.0178 71.0292 71.0406 71.0520 71.0629 71.0738 71.0848 71.0956 71.1066 71.1175 71.1284 71.1394 71.1503 71.1612 71.1722 71.1831 71.1942 71.2061 71.2176 71.2286 71.2396 71.2508 71.2622 71.2733 71.2850 71.2960 71.3071
1.516 1.381 1.328 1.298 1.268 1.270 1.285 1.331 1.396 1.474 1.565 1.593 1.583 1.563 1.484 1.383 1.324 1.286 1.255 1.268 1.295 1.335 1.379 1.453 1.560 1.568 1.552 1.575
71.0054 71.0195 71.0308 71.0422 71.0536 71.0645 71.0754 71.0863 71.0972 71.1082 71.1191 71.1300 71.1409 71.1519 71.1628 71.1737 71.1847 71.1959 71.2078 71.2192 71.2302 71.2412 71.2526 71.2638 71.2749 71.2865 71.2976 71.3087
1.488 1.374 1.331 1.284 1.271 1.275 1.294 1.340 1.402 1.489 1.575 1.596 1.580 1.553 1.456 1.377 1.315 1.278 1.262 1.269 1.301 1.339 1.399 1.475 1.557 1.566 1.553 1.535
71.0080 71.0211 71.0324 71.0439 71.0552 71.0660 71.0769 71.0879 71.0988 71.1097 71.1206 71.1316 71.1425 71.1534 71.1644 71.1753 71.1863 71.1975 71.2096 71.2207 71.2317 71.2428 71.2543 71.2654 71.2765 71.2881 71.2992 71.3103
1.465 1.370 1.329 1.286 1.262 1.271 1.303 1.342 1.412 1.507 1.584 1.599 1.583 1.543 1.449 1.368 1.311 1.276 1.264 1.275 1.305 1.341 1.400 1.494 1.557 1.566 1.556 1.571
N2HV000483, N2HV000459 (αJ2000 = 20h 17m 05.s 52, δJ2000 = 41◦ 57 46. 98), N2HV000497 (αJ2000 = 20h 17m 03.s 14, δJ2000 = 41◦ 54 47. 88), and N2HV000468 (αJ2000 = 20h 17m 16.s 33, δJ2000 = 41◦ 57 13. 26) were chosen as interactive comparison and check stars. 3. LIGHT CURVE ANALYSIS OF V1191 CYGNI BV RI c light curves of V1191 Cyg observed on one night (August 27) were analyzed with the 2003 version of the Wilson–Van Hamme code (Wilson & Devinney 1971; Wilson 1979, 1990, 1994; Wilson & Van Hamme 2003). In accordance with a spectral type of F6 for V1191 Cyg (Rucinski et al. 2008), we assumed an effective temperature of T1 =6500 K for the primary component (the star eclipsed at primary minimum). The gravity-darkening coefficients g1 = g2 = 0.32 (Lucy 1967) and the bolometric albedo A1 = A2 = 0.5 were used, corresponding to the convective envelope of this binary system. The mass ratio was fixed at 0.107 according to the radial velocity result published by Rucinski et al. (2008). Bolometric and bandpass square-root limb-darkening parameters taken from Van Hamme’s (1993) paper are reported in Table 5. The adjustable parameters in our fit to the light curve were the inclination, i, the mean temperature of star 2, T2 , the monochromatic luminosity of star 1 (L1B , L1V , L1R , L1I ), and the dimensionless potentials of star 1, Ω1 . The final converged photometric solutions are listed in Table 5 and the corresponding synthetic light curves are shown in Figure 1 with solid lines. Figure 2 shows the configuration of this system at phases of 0.0, 0.25, 0.50, and 0.75. Our solutions show that V1191 Cyg is a Wtype overcontact binary system with a high degree of overcontact
Figure 1. Observed and theoretical BV(IR)c light curves of V1191 Cyg. Open circles represent the observations obtained with the 60 cm telescope on 2009 August 27. The solid lines indicate the theoretical calculated light curves of V1191 Cyg.
R band on 2011 June 17 with the PI 1024×1024 CCD attached to the 85 cm telescope (Zhou et al. 2009) at the Xinglong Station of NAOC. Eight new minima (HJD2454572.3725 (±0.0006), HJD2454607.3168 (±0.0004), HJD2454608.2605 (±0.0005), HJD2454779.0565 (±0.0002), HJD2454781.0921 (±0.0002), HJD2455067.0595 (±0.0001), HJD2455710.2961 (±0.0004), HJD2455730.1953 (±0.0003)) were derived with observations obtained by using these three telescopes. N2HV000438, 2
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al. Table 2 V-band CCD Observations of V1191 Cyg
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD(Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
70.9929 71.0115 71.0231 71.0345 71.0459 71.0572 71.0681 71.0789 71.0899 71.1008 71.1118 71.1227 71.1336 71.1445 71.1554 71.1664 71.1773 71.1883 71.1998 71.2117 71.2228 71.2338 71.2448 71.2563 71.2675 71.2788 71.2902 71.3013 71.3124
1.090 .973 .892 .854 .824 .811 .824 .849 .899 .967 1.052 1.113 1.121 1.100 1.069 .975 .897 .847 .824 .813 .827 .858 .898 .965 1.057 1.095 1.111 1.091 1.119
70.9952 71.0135 71.0248 71.0361 71.0476 71.0587 71.0696 71.0806 71.0914 71.1024 71.1133 71.1242 71.1351 71.1461 71.1570 71.1679 71.1789 71.1899 71.2015 71.2133 71.2243 71.2354 71.2464 71.2579 71.2691 71.2807 71.2918 71.3028 71.3140
1.088 .954 .884 .852 .814 .807 .817 .862 .901 .982 1.070 1.111 1.120 1.101 1.060 .960 .891 .847 .816 .806 .827 .864 .910 .972 1.067 1.110 1.100 1.122 1.082
70.9980 71.0151 71.0264 71.0377 71.0492 71.0603 71.0712 71.0821 71.0930 71.1040 71.1149 71.1258 71.1367 71.1476 71.1586 71.1695 71.1805 71.1914 71.2031 71.2149 71.2259 71.2369 71.2480 71.2595 71.2706 71.2823 71.2933 71.3044 71.3156
1.080 .945 .884 .851 .815 .810 .828 .863 .921 .989 1.080 1.120 1.120 1.092 1.041 .948 .886 .846 .809 .808 .827 .866 .915 .984 1.082 1.105 1.081 1.097 1.072
71.0007 71.0167 71.0280 71.0394 71.0508 71.0619 71.0727 71.0837 71.0945 71.1055 71.1164 71.1273 71.1383 71.1492 71.1601 71.1711 71.1820 71.1931 71.2049 71.2165 71.2275 71.2385 71.2497 71.2611 71.2722 71.2839 71.2949 71.3060
1.054 .928 .877 .829 .815 .817 .835 .873 .929 .998 1.096 1.113 1.124 1.098 1.023 .939 .873 .837 .817 .813 .836 .873 .918 1.000 1.091 1.096 1.104 1.108
71.0034 71.0183 71.0296 71.0411 71.0525 71.0634 71.0743 71.0852 71.0961 71.1071 71.1180 71.1289 71.1398 71.1508 71.1617 71.1726 71.1836 71.1947 71.2066 71.2181 71.2291 71.2401 71.2513 71.2627 71.2738 71.2854 71.2965 71.3076
1.046 .918 .872 .835 .814 .818 .831 .876 .929 1.019 1.099 1.122 1.115 1.098 1.007 .923 .867 .831 .813 .819 .836 .880 .931 1.009 1.107 1.100 1.127 1.067
71.0061 71.0199 71.0312 71.0427 71.0541 71.0650 71.0758 71.0868 71.0977 71.1086 71.1196 71.1305 71.1414 71.1523 71.1633 71.1742 71.1852 71.1964 71.2084 71.2196 71.2306 71.2417 71.2530 71.2643 71.2754 71.2870 71.2981 71.3092
1.020 .916 .868 .834 .812 .817 .843 .882 .945 1.027 1.105 1.118 1.113 1.083 .997 .913 .863 .825 .808 .819 .846 .884 .932 1.032 1.096 1.109 1.124 1.062
71.0088 71.0215 71.0329 71.0443 71.0556 71.0665 71.0774 71.0883 71.0992 71.1102 71.1211 71.1320 71.1429 71.1539 71.1648 71.1758 71.1867 71.1980 71.2101 71.2212 71.2322 71.2432 71.2548 71.2659 71.2770 71.2886 71.2997 71.3108
.993 .901 .862 .829 .813 .814 .851 .892 .954 1.037 1.106 1.116 1.107 1.079 .987 .909 .860 .819 .808 .818 .850 .887 .947 1.048 1.110 1.091 1.105 1.092
Table 3 Rc -band CCD Observations of V1191 Cyg JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD(Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
70.9935 71.0121 71.0236 71.0349 71.0463 71.0576 71.0685 71.0793 71.0903 71.1012 71.1122 71.1231 71.1340 71.1449 71.1558 71.1668 71.1777 71.1887 71.2003 71.2121 71.2232 71.2342 71.2452 71.2567 71.2679 71.2793 71.2922 71.3033 71.3144
.749 .622 .552 .513 .487 .478 .487 .513 .560 .627 .718 .770 .763 .759 .725 .632 .555 .512 .490 .472 .491 .518 .555 .620 .706 .757 .754 .759 .712
70.9959 71.0139 71.0252 71.0365 71.0480 71.0592 71.0700 71.0810 71.0918 71.1028 71.1137 71.1246 71.1355 71.1465 71.1574 71.1683 71.1793 71.1903 71.2020 71.2137 71.2248 71.2358 71.2468 71.2583 71.2695 71.2811 71.2938 71.3048 71.3160
.744 .607 .550 .514 .492 .479 .497 .530 .572 .632 .724 .770 .767 .764 .714 .617 .554 .513 .480 .482 .486 .524 .560 .637 .728 .756 .788 .734 .713
70.9986 71.0155 71.0268 71.0381 71.0496 71.0607 71.0716 71.0825 71.0934 71.1044 71.1153 71.1262 71.1371 71.1480 71.1590 71.1699 71.1809 71.1918 71.2036 71.2153 71.2263 71.2373 71.2484 71.2599 71.2710 71.2843 71.2953 71.3064
.736 .600 .543 .509 .476 .478 .508 .527 .578 .647 .741 .767 .762 .759 .698 .602 .543 .502 .474 .482 .497 .534 .577 .636 .726 .773 .772 .752
71.0014 71.0171 71.0284 71.0398 71.0512 71.0623 71.0731 71.0841 71.0950 71.1059 71.1168 71.1277 71.1387 71.1496 71.1605 71.1715 71.1824 71.1935 71.2053 71.2169 71.2279 71.2389 71.2501 71.2615 71.2726 71.2858 71.2969 71.3080
.719 .590 .541 .509 .484 .481 .502 .533 .584 .660 .754 .772 .770 .763 .686 .596 .535 .499 .480 .482 .497 .538 .589 .652 .748 .763 .740 .726
71.0041 71.0187 71.0300 71.0415 71.0529 71.0638 71.0747 71.0856 71.0965 71.1075 71.1184 71.1293 71.1402 71.1512 71.1621 71.1730 71.1840 71.1951 71.2070 71.2185 71.2295 71.2405 71.2517 71.2631 71.2742 71.2874 71.2985 71.3096
.697 .578 .536 .504 .480 .479 .515 .544 .592 .675 .760 .775 .770 .744 .668 .584 .535 .491 .478 .479 .501 .542 .593 .682 .752 .766 .746 .713
71.0068 71.0203 71.0316 71.0431 71.0545 71.0654 71.0762 71.0872 71.0981 71.1090 71.1200 71.1309 71.1418 71.1527 71.1637 71.1746 71.1856 71.1968 71.2088 71.2200 71.2310 71.2421 71.2535 71.2647 71.2758 71.2890 71.3001 71.3112
.669 .578 .524 .494 .478 .489 .516 .546 .607 .686 .758 .777 .756 .742 .641 .579 .528 .490 .475 .485 .513 .551 .596 .693 .764 .773 .768 .754
71.0095 71.0219 71.0333 71.0447 71.0560 71.0669 71.0778 71.0887 71.0996 71.1106 71.1215 71.1324 71.1433 71.1543 71.1652 71.1762 71.1871 71.1985 71.2105 71.2216 71.2326 71.2437 71.2552 71.2663 71.2775 71.2906 71.3017 71.3128
.639 .574 .522 .496 .471 .486 .513 .557 .618 .707 .755 .774 .761 .735 .644 .562 .520 .488 .486 .488 .522 .556 .613 .693 .758 .756 .732 .742
3
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al. Table 4 Ic -band CCD Observations of V1191 Cyg
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD(Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
JD (Hel.) 2455000+
Δ(m)
70.9939 71.0126 71.0239 71.0352 71.0467 71.0579 71.0688 71.0797 71.0906 71.1015 71.1125 71.1234 71.1343 71.1452 71.1562 71.1671 71.1780 71.1890 71.2007 71.2124 71.2235 71.2345 71.2455 71.2571 71.2682 71.2797 71.2909 71.3036 71.3163
.376 .256 .206 .156 .124 .119 .134 .168 .210 .270 .351 .398 .402 .402 .350 .265 .201 .152 .132 .120 .137 .159 .204 .263 .337 .377 .421 .381 .321
70.9965 71.0142 71.0255 71.0368 71.0483 71.0595 71.0703 71.0813 71.0922 71.1031 71.1140 71.1249 71.1359 71.1468 71.1577 71.1687 71.1796 71.1906 71.2023 71.2140 71.2251 71.2361 71.2472 71.2587 71.2698 71.2814 71.2925 71.3052
.374 .256 .193 .145 .121 .124 .136 .172 .213 .280 .381 .399 .398 .376 .347 .244 .202 .154 .131 .127 .140 .171 .204 .280 .370 .400 .383 .407
70.9992 71.0158 71.0271 71.0385 71.0500 71.0610 71.0719 71.0828 71.0937 71.1047 71.1156 71.1265 71.1374 71.1483 71.1593 71.1702 71.1812 71.1922 71.2039 71.2156 71.2266 71.2377 71.2488 71.2602 71.2714 71.2830 71.2941 71.3083
.367 .238 .178 .147 .120 .123 .137 .192 .231 .303 .384 .404 .403 .381 .329 .251 .181 .146 .110 .122 .130 .178 .210 .296 .385 .390 .383 .404
71.0019 71.0174 71.0287 71.0402 71.0516 71.0626 71.0734 71.0844 71.0953 71.1062 71.1172 71.1281 71.1390 71.1499 71.1608 71.1718 71.1827 71.1938 71.2057 71.2172 71.2282 71.2392 71.2504 71.2618 71.2729 71.2846 71.2957 71.3099
.339 .235 .182 .138 .119 .122 .140 .188 .231 .311 .389 .393 .396 .377 .314 .238 .185 .127 .124 .123 .144 .175 .208 .290 .380 .377 .398 .419
71.0047 71.0190 71.0304 71.0418 71.0532 71.0641 71.0750 71.0859 71.0968 71.1078 71.1187 71.1296 71.1405 71.1515 71.1624 71.1734 71.1843 71.1955 71.2073 71.2188 71.2298 71.2408 71.2521 71.2634 71.2745 71.2862 71.2972 71.3115
.318 .223 .177 .132 .110 .116 .160 .189 .231 .321 .393 .402 .393 .382 .308 .220 .168 .130 .122 .119 .146 .185 .225 .299 .378 .384 .390 .364
71.0074 71.0207 71.0320 71.0434 71.0548 71.0657 71.0765 71.0875 71.0984 71.1094 71.1203 71.1312 71.1421 71.1530 71.1640 71.1749 71.1859 71.1971 71.2092 71.2204 71.2314 71.2424 71.2538 71.2650 71.2761 71.2877 71.2988 71.3131
.299 .213 .165 .132 .116 .121 .156 .200 .256 .343 .398 .409 .393 .364 .252 .218 .157 .134 .118 .125 .165 .197 .242 .316 .394 .401 .400 .354
71.0100 71.0223 71.0336 71.0451 71.0564 71.0672 71.0781 71.0890 71.0999 71.1109 71.1218 71.1327 71.1437 71.1546 71.1655 71.1765 71.1874 71.1989 71.2108 71.2219 71.2329 71.2440 71.2555 71.2666 71.2779 71.2893 71.3004 71.3147
.275 .214 .154 .132 .118 .124 .162 .203 .258 .354 .402 .407 .387 .368 .273 .206 .161 .121 .116 .130 .148 .191 .257 .339 .395 .409 .388 .353
Table 5 Photometric Solutions for V1191 Cyg Parameter
Values
Parameter
Values
g1 = g2 A1 = A2 T1 (K)
0.32 0.5 6 500
T2 (K) Ω1 = Ω2
6 626(30) 1.933(1) 0.8566(2)
qsp
0.107
x1B = x2B
0.281
y1B = y2B
0.604
x1V = x2V y1V = y2V x1R = x2R y1R = y2R x1I = x2I y1I = y2I i
0.108 0.697 0.021 0.713 −0.035 0.682 80.◦ 4(4)
L1B L1B +L2B L1V L1V +L2V L1R L1R +L2R L1I L1I +L2I
R1pole R1side R1back R2pole R2side R2back f
0.8601(2) 0.8620(1) 0.8636(1) 0.5439(3)A 0.6120(5)A 0.6343(6)A 0.2108(4)A 0.2217(5)A 0.2810(17)A 68.6%
Figure 2. Configuration of the low mass ratio, high fill-out W-type overcontact binary system V1191 Cyg at phases of 0.0, 0.25, 0.50, and 0.75.
Rucinski et al. (2008) pointed out that the B − V = 0.62 for V1191 Cyg is uncorrected for interstellar absorption, and that an F6V spectral type should be correct. According to this spectral type, we assumed a primary temperature of 6500 K and set initial parameters accordingly. Therefore, our photometric solutions may be more plausible.
Note. “A” is the separation between the components.
(f ∼ 68.6%, which is defined as f = (Ωin − Ω)/(Ωin − Ωout )). Comparing our results to those of Pribulla et al. (2005b), our degree of overcontact is deeper than their value (f ∼ 46%). This difference may come from the different light curves and the primary temperatures adopted by them and us. The light curves analyzed by Pribulla et al. (2005b) are incomplete around phase 0.25 and a systematic deviation exists around primary minimum in the R band, but our light curves are complete and obtained in one night. In addition, they assumed the temperature of the primary to be 5800 K according to B − V = 0.62. However,
4. ORBITAL PERIOD VARIATIONS FOR V1191 CYG To investigate the period variations of V1191 Cyg, we collected all available photoelectric and CCD times of minimum light for this target and listed them in Table 6 along with the timings we obtained. The observational method is indicated in the 4
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al.
Table 6 CCD and Photoelectric Times of Light Minimum for V1191 Cyg HJD 2400000+ 38634.550 38636.429 38663.375 38668.395 49099.4613 49217.4512 49587.3879 49599.4536 49608.384 49619.3527 49619.5106 49621.3904 49644.2651 49644.4228 50672.455 51165.2414 51433.4949 51797.4916 52075.4565 52413.445 52445.4067 52456.3748 52465.4622 52528.3033 52548.3544 52901.5459 52902.3257 52902.4848 52905.305 52905.4591 53156.4815 53258.4871 53340.2859
Meth.
E
(O − C)1 (days)
(O − C)2 (days)
Ref.
HJD 2400000+
Meth.
E
(O − C)1 (days)
(O − C)2 (days)
Ref.
pe pe pe pe cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
−52450 −52444 −52358 −52342 −19055.5 −18679 −17498.5 −17460 −17431.5 −17396.5 −17396 −17390 −17317 −17316.5 −14036 −12463.5 −11607.5 −10446 −9559 −8480.5 −8378.5 −8343.5 −8314.5 −8114 −8050 −6923 −6920.5 −6920 −6911 −6910.5 −6109.5 −5784 −5523
.0398 .0385 .0341 .0400 −.1172 −.1137 −.1186 −.1179 −.1187 −.1182 −.1170 −.1175 −.1193 −.1183 −.1193 −.1183 −.1155 −.1062 −.1067 −.0953 −.0980 −.0981 −.0986 −.0896 −.0946 −.0790 −.0827 −.0803 −.0805 −.0830 −.0756 −.0742 −.0668
.0146 .0133 .0098 .0159 .0016 .0043 −.0035 −.0029 −.0037 −.0033 −.0021 −.0026 −.0046 −.0036 −.0157 −.0215 −.0227 −.0194 −.0248 −.0198 −.0231 −.0234 −.0241 −.0164 −.0218 −.0135 −.0172 −.0148 −.0151 −.0176 −.0157 −.0166 −.0111
(1) (1) (1) (1) (2) (3) (4) (4) (4) (4) (4) (4) (5) (5) (6) (7) (8) (9) (9) (10) (10) (10) (10) (10) (10) (11) (12) (12) (12) (12) (12) (13) (13)
53512.4895 53612.4622 53685.642 53879.7805 53893.7283 53915.5113 53921.4649 53934.4683 54025.3548 54049.6383 54258.3604 54335.4533 54440.5940 54572.3725 54607.3168 54608.2605 54620.4785 54653.3860 54654.4816 54654.3264 54656.5204 54662.4744 54779.0565 54781.0921 54941.5475 54946.5605 55071.1339 55071.2922 55067.0595 55086.8059 55710.2961 55730.1953
cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
−4973.5 −4654.5 −4421 −3801.5 −3757 −3687.5 −3668.5 −3627 −3337 −3259.5 −2593.5 −2347.5 −2012 −1591.5 −1480 −1477 −1438 −1333 −1329.5 −1330 −1323 −1304 −932 −925.5 −413.5 −397.5 0 .5 −13 50 2039.5 2103
−.0639 −.0585 −.0522 −.0507 −.0482 −.0449 −.0455 −.0472 −.0401 −.0433 −.0303 −.0281 −.0254 −.0219 −.0191 −.0156 −.0193 −.0164 −.0176 −.0161 −.0157 −.0159 −.0100 −.0114 −.0050 −.0060 0 .0016 −.0005 .0032 .0298 .0296
−.0122 −.0092 −.0047 −.0080 −.0059 −.0031 −.0039 −.0059 −.0012 −.0050 .0025 .0026 .0025 .0023 .0042 .0076 .0036 .0056 .0043 .0058 .0062 .0058 .0084 .0069 .0087 .0075 .0098 .0114 .0094 .0125 .0197 .0188
(12) (14) (15) (16) (16) (17) (17) (17) (18) (19) (16) (16) (20) (21) (21) (21) (16) (22) (22) (22) (22) (22) (21) (21) (16) (16) (21) (21) (21) (23) (21) (21)
References. (1) Mayer 1965; (2) H¨ubscher et al. 1993; (3) H¨ubscher et al. 1994; (4) Agerer & H¨ubscher 1995; (5) Agerer & H¨ubscher 1996; (6) Agerer & H¨ubscher 1998; (7) Agerer & H¨ubscher 1999; (8) Agerer & H¨ubscher 2001; (9) Agerer & H¨ubscher 2002; (10) Pribulla et al. 2002; (11) H¨ubscher 2005; (12) Pribulla et al. 2005a; (13) H¨ubscher et al. 2005; (14) H¨ubscher et al. 2006; (15) Nelson 2006; (16) Parimucha et al. 2009; (17) Parimucha et al. 2007; (18) H¨ubscher 2007; (19) Nelson 2007; (20) Nelson 2008; (21) the present paper; (22) Yilmaz et al. 2009; (23) Nelson 2010.
second and eighth columns, where “pe” indicates photoelectric data and “cc” denotes CCD observations. The corresponding O − C values and circles E were calculated with the following ephemeris and are plotted in the upper panel of Figure 3: MinI = HJD2455071.1339 + 0.313377 days × E.
best fit of a quadratic ephemeris, indicating that there is a periodic variation superposed on the increase of the orbital period. The sinusoidal term in Equation (2) reveals a periodic change with an amplitude of 0.023 days and a period of 26.7 years, easily seen in the middle panel of Figure 3. The solid line in this figure represents the fit by the sinusoidal term. As shown in the upper panel of Figure 3, the combination of the increase and the periodic oscillation give the best description (solid line) of the (O − C)1 values. The residuals based on the ephemeris (Equation (2)) are plotted in the lower panel of Figure 3, where no significant systematic variation can be traced. As one can see from the upper panel of Figure 3, there is an observational gap between HJD 2438668.395 and HJD 2449099.4613. The O − C analysis strongly depends on the minimum times of light of Mayer (1965). For a short-period close-binary system, the accumulation of any period error can lead to O − C values larger or smaller than P /2 or more times. For this reason, the correct choice of cycle, E, for the four earliest minima is unclear. If we subtract the period (0.313377 days) from the times of the four earliest minima and construct a new O − C curve (plotted in Figure 4, where crosses indicate the revised data), we can then use the same method as before to
(1)
As one can see from this figure, the O − C curve suggests a trend of upward quadratic variation, and another change may exist besides the increasing trend. By means of a least-squares method, the following equation was obtained: (O − C)1 = −0.0098(±0.0019) − 9.37(±0.30) days × 10−6 × E + 1.91(±0.05) × 10−10 × E 2 + 0.023(±0.001) days sin [0.◦ 012 × E − 31.◦ 2(±4.◦ 0)].
(2)
According to the quadratic term of this ephemeris, a continuous period increase, at a rate of dP/dt = +4.5(±0.1) × 10−7 days yr−1 , was determined. The dashed line plotted in the upper panel of Figure 3 shows the increase of the orbital period. The (O − C)2 residuals from the parabolic fit are displayed in the middle panel of Figure 3. The (O − C)2 residuals show a sinusoidal variation that cannot be removed by the 5
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al.
Figure 3. O − C diagram of V1191 Cyg. The dots refer to photoelectric and CCD observations. The upper panel: (O − C)1 diagram computed with Equation (1). The general trend of the (O − C)1 curve reveals a long-term period increase (dashed line). The solid line shows the fit of Equation (2). The middle panel: the (O − C)2 curve from the parabolic fit and its description by a sinusoidal equation (solid line). The bottom panel: residuals from Equation (2).
Figure 4. Revised O − C diagram of V1191 Cyg. Crosses indicate the revised data. Other symbols and lines represent the same meaning as that of Figure 3, but for Equation (3).
dP/dt = +0.67(±0.13) × 10−7 days yr−1 . The corresponding fit curves and residuals are plotted in Figure 4.
obtain the following equation: (O − C)1 = −0.0191(±0.0024) − 9.1(±3.7) days × 10−7 × E + 0.286(±0.054) × 10−10 × E 2 + 0.043(±0.001) days sin [0.◦ 010 × E − 9.◦ 2(±3.◦ 0)].
5. DISCUSSION AND CONCLUSIONS (3)
Based on our one-night BV(IR)c symmetric light curves, the photometric solutions for V1191 Cyg were derived. We found that V1191 Cyg is a W-type low mass ratio overcontact binary system with a high degree of overcontact (f = 68.6%). The
From this fit, we can conclude that there is a periodic variation with an amplitude of 0.043 days and a period of 31.9 years, superposed on the long-term period increase at a rate of 6
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al.
Figure 5. Relations between the mass and the orbital inclination for an assumed third body in V1191 Cyg. The left panel is derived from the fit of Equation (2) and the right panel is derived from the fit of Equation (3).
of a third body or by magnetic activity cycles in the component. For V1191 Cyg, it has an F6 spectral-type primary and a late M spectral-type secondary according to Allen’s table (Cox 2000) for a mass of 0.139 M . If the components have strong magnetic activity, the light curves usually display asymmetrically with different degrees as in the case of WZ Cep (Zhu & Qian 2009). However, our light curves show quite good symmetrical shapes, which may indicate that V1191 Cyg is in a weak-activity stage at present. Assuming the period oscillation is a consequence of magnetic cycles in the primary component, then by inserting the absolute parameters in the following equation (Lanza & Rodon`o 2002): ΔP ΔQ = −9 , (5) P Ma 2
Table 7 Absolute Parameters for V1191 Cyg Parameters Mass (M ) Radius (R ) Luminosity (L ) Semimajor axis (R )
Primary
Secondary
1.306 ± 0.022 0.139 ± 0.08 1.307 ± 0.007 0.518 ± 0.003 2.731 ± 0.029 0.463 ± 0.006 2.194 ± 0.012
effective temperature of the more massive component of this system is cooler than the less massive one. Combining our photometric solutions and spectroscopic elements with those from Rucinski et al. (2008), the absolute physical parameters were obtained. Assuming an eccentricity of e = 0, the mass of the components was derived from the expression (Kopal 1959, p. 471) M1,2 sin3 i = 1.0385 × 10−7 (K1 + K2 )2 K2,1 P ,
where Q is the quadrupole moment, and M is the mass of the active star and the semimajor axis of the orbit, the required variation of the quadrupole moment ΔQ in order to reproduce the period oscillation ΔP = 4.64 × 10−6 days is calculated to be ΔQ = 2.5 × 1049 g cm2 for the primary component. For the revised case, the corresponding quadrupole moment ΔQ is calculated to be 3.9 × 1049 g cm2 . On the other hand, if the cyclic period variation is caused by the light-time effect via the presence of a third body, with a semi-amplitude of the O − C oscillation, the value a12 sin i is calculated to be a12 sin i = 3.99 AU. Then by using the following equation:
(4)
where the orbital period is in days and semi-amplitudes are in km s−1 . The separation between the components can be given using Kepler’s third law. All absolute parameters for V1191 Cyg were calculated and are listed in Table 7. By combining our 10 determinations of minimum light with those compiled from the literature, we found that the orbital period of V1191 Cyg shows a cyclic period variation with a period of 26.7 years and an amplitude of 0.023 days, while it undergoes a secular period increase at the rate of dP/dt = +4.5(±0.1) × 10−7 days yr−1 . However, there is a large observational gap between HJD 2438668.395 and HJD 2449099.4613, so we tried subtracting one period from the minima of Mayer (1965) and reanalyzed the new data set. In this revised case, a periodic variation still exists superposed on the long-term period increase. A period oscillation superimposed on the secular term is usually encountered for such deep, low mass ratio overcontact binary systems, such as GR Vir (Qian & Yang 2004), IK Per (Zhu et al. 2005), TV Mus (Qian et al. 2005a), AH Cnc (Qian et al. 2006), EM Psc (Qian et al. 2008), and V345 Gem (Yang et al. 2009). The periodic changes are usually explained either by the light-time effect via the presence
f (m) =
(M3 sin i )3 4π 2 = × (a12 sin i )3 , 2 (M1 + M2 + M3 ) GT32
(6)
a mass function of f (m) = 0.089 M is determined for the assumed third body. The masses of the third body for many values of the orbital inclination (i ) are computed and are shown in the left panel of Figure 5. We can estimate the minimum mass of the additional body to be m3 = 0.76 M . If we assume that the third body is coplanar to the orbit of the eclipsing pair (i.e., i = 80.◦ 4), the values of the mass and the orbital radius of the third body would be m3 = 0.77 M and a3 = 7.6 AU, respectively. To verify the presence of a third body, during the photometric solution, we added a third light (i.e., we made l3 7
The Astronomical Journal, 142:124 (8pp), 2011 October
Zhu et al.
10903026, and 11133007), Yunnan Natural Science Foundation (2008CD157), and the National Key Fundamental Research Project through grant 2007CB815406.
an adjustable parameter), but l3 is usually negative, indicating that the third body may be too faint relative to the eclipsing pair to contribute to the whole system. However, by analyzing the phase-averaged spectrum, D’Angelo et al. (2006) pointed out that tertiaries within mass ratios 0.28 M3 /M12 0.75 could be detected. Thus, the spectroscopic observations are important to test the tertiary we suggested in V1191 Cyg due to its M3 /M12 = 0.53. For the revised case, we also plotted the m3 –i relation in the right panel of Figure 5. If we assume i = 80.◦ 4, the mass and the orbital radius of the third body would be m3 = 1.56 M and a3 = 6.9 AU, respectively. If this additional body is a main-sequence star, it will be brighter than the center pair so that it can be easily detected. However, in the spectroscopic study of Rucinski et al. (2008) and our l3 test in the light curve analysis, there are no signs of such a brighter target. Therefore, the former case is more plausible. When the oscillating part of the orbital period change is removed, the increasing part may be caused by mass transfer from the less massive component to the more massive one. If such an orbital period increase results from a conservative mass transfer, then according to the well-known equation, P˙ /P = 3(M1 /M2 − 1)ΔM1 /M1 ,
REFERENCES Agerer, F., & H¨ubscher, J. 1995, IBVS, 4222, 1 Agerer, F., & H¨ubscher, J. 1996, IBVS, 4383, 1 Agerer, F., & H¨ubscher, J. 1998, IBVS, 4606, 1 Agerer, F., & H¨ubscher, J. 1999, IBVS, 4711, 1 Agerer, F., & H¨ubscher, J. 2001, IBVS, 5016, 1 Agerer, F., & H¨ubscher, J. 2002, IBVS, 5296, 1 Cox, A. N. 2000, Allen’s Astrophysical Quantities (4th ed.; New York: Springer) D’Angelo, C., van Kerkwijk, M. H., & Rucinski, S. M. 2006, AJ, 132, 650 Hilditch, R. W., King, D. J., & McFarlane, T. M. 1988, MNRAS, 231, 341 H¨ubscher, J. 2005, IBVS, 5643, 1 H¨ubscher, J. 2007, IBVS, 5802, 1 H¨ubscher, J., Agerer, F., & Wunder, E. 1993, Bundesdeutsche Arbeitsgemeinschaft f¨ur Ver¨anderliche Sterne e.V., 62, www.bav-astro.de/sfs/mitteilungen. php H¨ubscher, J., Agerer, F., & Wunder, E. 1994, Bundesdeutsche Arbeitsgemeinschaft f¨ur Ver¨anderliche Sterne e.V., 68, www.bav-astro.de/sfs/mitteilungen. php H¨ubscher, J., Paschke, A., & Walter, F. 2005, IBVS, 5657, 1 H¨ubscher, J., Paschke, A., & Walter, F. 2006, IBVS, 5731, 1 Hut, P. 1980, A&A, 92, 167 Kopal, Z. 1959, Close Binary Systems (London: Chapman & Hall) Lanza, A. F., & Rodon`o, M. 2002, Astron. Nachr., 323, 424 Lucy, L. B. 1967, Z. Astrophys., 65, 89 Maceroni, C., Milano, L., & Russo, G. 1985, MNRAS, 217, 843 Mayer, P. 1965, Bull. Astron. Inst. Czech., 16, 255 Mochnacki, S. W. 1981, ApJ, 245, 650 Nelson, R. H. 2006, IBVS, 5672, 1 Nelson, R. H. 2007, IBVS, 5760, 1 Nelson, R. H. 2008, IBVS, 5820, 1 Nelson, R. H. 2010, IBVS, 5929, 1 Parimucha, S., Dubovsky, P., Baludansky, D., et al. 2009, IBVS, 5898, 1 Parimucha, S., Vanko, M., Pribulla, T., et al. 2007, IBVS, 5777, 1 Pribulla, T., Baludansky, D., Chochol, D., et al. 2005a, IBVS, 5668, 1 ˇ & Balud’ansk´y, D. Pribulla, T., Vaˇnko, M., Chochol, D., Parimucha, S, 2005b, Ap&SS, 296, 281 ˇ & Chochol, D. 2002, IBVS, 5341, 1 Pribulla, T., Vaˇnko, M., Parimucha, S, Qian, S. B., He, J. J., Soonthornthum, B., et al. 2008, AJ, 136, 1940 Qian, S. B., Liu, L., Soonthornthum, B., Zhu, L. Y., & He, J. J. 2006, AJ, 131, 3028 Qian, S. B., Liu, L., Soonthornthum, B., Zhu, L. Y., & He, J. J. 2007, AJ, 134, 1475 Qian, S. B., & Yang, Y. G. 2004, AJ, 128, 2430 Qian, S. B., & Yang, Y. G. 2005, MNRAS, 356, 765 Qian, S. B., Yang, Y. G., Soonthornthum, B., et al. 2005a, AJ, 130, 224 Qian, S. B., Zhu, L. Y., Soonthornthum, B., et al. 2005b, AJ, 130, 1206 Rucinski, S. M., Pribulla, T., Mochnacki, S. W., et al. 2008, AJ, 136, 586 Van Hamme, W. 1993, AJ, 106, 2096 Wilson, R. E. 1979, ApJ, 234, 1054 Wilson, R. E. 1990, ApJ, 356, 613 Wilson, R. E. 1994, PASP, 106, 921 Wilson, R. E., & Devinney, E. J. 1971, ApJ, 166, 605 Wilson, R. E., & Van Hamme, W. 2003, Computing Binary Stars Observables, the 4th edition of the W-D Program, ftp://ftp.astro.ufl.edu/pub/wilson/ lcdc2003 Yang, Y. G., Qian, S. B., & Zhu, L. Y. 2005, AJ, 130, 2252 Yang, Y. G., Qian, S. B., Zhu, L. Y., & He, J. J. 2009, AJ, 138, 540 Yilmaz, M., Basturk, O., Alan, N., et al. 2009, IBVS, 5887, 1 Zhou, A. Y., Jiang, X. J., Zhang, Y. P., & Wei, J. Y. 2009, Res. Astron. Astrophys., 9, 349 Zhu, L. Y., & Qian, S. B. 2009, AJ, 138, 2002 Zhu, L. Y., Qian, S. B., Soonthornthum, B., & Yang, Y. G. 2005, AJ, 129, 2806
(7)
the mass transfer rate is determined to be dm/dt = 7.45 × 10−8 M yr−1 . With an increasing period, the mass ratio of the binary system will decrease. The case of V1191 Cyg resembles those of XY Boo, V410 Aur (Yang et al. 2005), V857 Her (Qian et al. 2005b), AH Cnc (Qian et al. 2006), QX And (Qian et al. 2007), and EM Psc (Qian et al. 2008); both the high degree of overcontact configuration and the long-term period increase suggest that it is in the late evolutionary stage of late-type tidallocked binaries and may evolve from the present low mass ratio, high fill-out stage into a rapidly rotating single star after its orbital angular momentum becomes less than three times the total spin angular momentum, i.e., Jorb < 3Jrot (Hut 1980). Furthermore, according to the statistics of W UMa systems in Mochnacki (1981), Maceroni et al. (1985), and Hilditch et al. (1988), W-type systems have some characteristics with high mass ratios and a shallow degree of overcontact relative to A-type systems. V1191 Cyg is a rarity among deep, low mass ratio overcontact binary systems, which belongs to a W-type overcontact system, just like the systems FG Hya (Qian & Yang 2005), AH Cnc (Qian et al. 2006), and EM Psc (Qian et al. 2008). The light curves of FG Hya, AH Cnc, and EM Psc, all show the exchange between A-type and W-type, but until now, all published light curves of V1191 Cyg displayed a W-type shape. In addition, V1191 Cyg has the shortest orbital period compared with the contact binaries with spectral types earlier than F6V. It is too blue for its orbital period. Therefore, this target is a special system and worth monitoring continuously in the future. This work was partly supported by the Special Foundation of the President of The Chinese Academy of Sciences and West Light Foundation of the Chinese Academy of Sciences, Chinese Natural Science Foundation (Nos. 10973037,
8
