TALLINNA TÄHETORN TALLINN OBSERVATORY III. Number 1

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1 Tallinna Tehnikaülikooli Füüsikainstituut TALLINNA TÄHETORN TALLINN OBSERVATORY III Number

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3 Tallinna Tähetorn Tallinn Observatory

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5 TALLINNA TEHNIKAÜLIKOOL FÜÜSIKAINSTITUUT TALLINNA TÄHETORN TALLINN TECHNICAL UNIVERSITY INSTITUTE OF PHYSICS TALLINN OBSERVATORY TALLINNA TÄHETORN TALLINN OBSERVATORY III Number 1 TALLINN 2004

6 Koostanud ja toimetanud T. Aas, V. Harvig c Tallinna Tähetorn ISSN

7 Contents UU Cnc

8 Sisukord UU Cnc

9 2004 Tallinn Observatory III No.1 Observations of UU Cancri P. Kalv Tallinn Technical University, Institute of Physics, Tallinn Observatory Tähetorni 2, Tallinn, Estonia T.Oja Astronomical Observatory, Box 515, SE Uppsala, Sweden V. Harvig Tallinn Technical University, Institute of Physics, Tallinn Observatory Tähetorni 2, Tallinn, Estonia Introduction The main problem of UU Cancri was brought forth in the first spectroscopic studies (Popper [(1956), (1977)] and Eggen [(1973)]) : the component whose lines were measured for velocity is eclipsed at phase zero and must be the hotter component, but its hydrogen lines are too strong for a K4 III star. Furthermore, the hydrogen lines strengthen considerably during primary minimum, i.e. the invisible companion star seems to be earlier than K4. Popper also suggests the component stars to be of nearly equal masses and radii. High-dispersion spectra at H α obtained by [Eaton(1990)] and [Eaton et al.(1991)] as well as IUE spectra only magnified the amount of contradictions: no variations greater than 0 ṃ 3 in the ultraviolet continuum; the uv flux is lower than expected from a star as massive as the unseen component; the rotational velocity near conjunction requires the optically undetected companion star to be more massive than the K4 giant. The phasedependent Balmer absorption seemingly implies a semidetached accreting system, but a strong chromosphere or wind from the secondary of a contact system is possible as well. Photoelectric V light curves were published by Winiarski and Zola[(1987)], [Lee(1988)], and B, V light curves by [Eaton et al.(1991)]. From these observations three light curve solutions were presented in which the system is a contact binary with both components overfilling their Roche lobes Winiarski and Zola[(1987)], [Barone et al.(1989)], and three semidetached models Winiarski and Zola[(1987)], [Eaton(1990)], [Eaton et al.(1991)]. The most important physical parameters are quite different in these models, e.g. the mass ratio was derived from 0.3 to 1.5. Thereafter [Zola et al.(1994)] rediscussed earlier results and presented an accretion disk model for the system. Observations UU Cnc was observed with the Tallinn 50 cm telescope (BV from 1972, UBV R from 1980), the Kvistaberg 40 cm telescope (UBV from 1985), the 60 cm telescope of the Royal Swedish Academy of Sciences at Observatorio Astrofisico del Roque de los Muchachos, La Palma Canary Islands(U BV from 1991) and 2.5 m Nordic Optical Telescope (U BV RI and polarization on seven nights from 1990). Up to 1994 in total 234 observations (one normal point per night, Fig. 1) have been obtained. The brightness of the comparison 9

10 Table 1: The comparison and ckeck star for UU Cancri. Star V U B B V V R R I Comparison star SAO ±0.003 ±0.004 ±0.002 ±0.001 ±0.006 Check star SAO ±0.004 ±0.002 ±0.002 ±0.002 ±0.010 and the check star (also used as extinction stars) given in Table 1 are from measurements with the Nordic Optical Telescope. The mean-square-root errors of the normal points, as calculated from the measurements of comparison and the check stars, are less than 0 ṃ 01 for V, B V and V R. In the ultraviolet UU Cnc was too faint for the Tallinn and Kvistaberg telescopes. Often the sky background was bright from full or nearly full Moon and we have tried to observe also at relatively poor atmospheric conditions. Therefore in many nights the error in U may reach up to 0 ṃ 04. On the other hand, some observations made on the same nights at La Palma and Tallinn convince us that it has not happened too often and irregular variations up to 0 ṃ 2 in the ultraviolet are real. The observations are given in Table 4, Table 5a and Table 5b. Period The times of minimum were determined with the aid of Pogson s tracing paper method in differential mode [Albo(1964)], computerized by [Kalv(1979)]. We have used all available times of minima beginning from Huth s[(1963)] photographic determinations from the beginning of last century. The results are given in Table 2 and Fig.2. The quadratic term of the light elements derived from the same data is of the same order of magnitude as its error. Therefore we have used linear light elements derived by the least-squares-method: Min = J.D ḍ 6760 E ±0.4 ± The determination of the weights of the normal minima given in Table 2 was arbitrary in some respects. The weights corresponding to square-root errors σ of normal minima were calculated according to their dispersion in a preliminary nonweighted solution and were adopted as follows: ±3 ḍ 6 for visual, ±2 ḍ 2 for photographic and ±0 ḍ 3 days for photoelectric times of minima. Striving not to be unjust to modern visual observers, whose observations seem to be as accurate as those of earlier photographic measurements, we adopt ±2 ḍ 2 days for them also. The number of the first photoelectric observations (Eggen [(1973)]) is too small for determining the accurate moment of minimum. Therefore we have merged Eggen s data with the data of our first series (minimum E=166). We also have determined two minima from the measurements by HIP P ARCOS. The photoelectric mimimum E=220, with O C > 3σ did not take part in the final levelling off procedure with weights. 10

11 U -0.2 B V R Phase Fig.1 All our observations. 11

12 UU Cnc JD Hel ±σ E O C Observer H H H H H H H H H H H H H L L H H H H H H H H H B H H B H, S B H H, S B H, S H, S B H H H, S H, S B S H H H 12

13 UU Cnc: continued JD Hel ±σ E O C Observer H B B B H H H B H H H B H B H H B H H B H B H B B B E + KO T KO W Z W Z T Br KO KO I KCL KCL KO EHH KO E + KO KO KO KO KCL KCL 13

14 UU Cnc: continued JD Hel ±σ E O C Observer KO KO Observers: B - Beyer 1964, Br - Brelstaff 1985, E - Eggen 1973, EHH - Eaton, Hall, Honeycutt 1991, H - Huth 1963, I - Isles 1986, KCL - Kim, Chun, Lee 1988, KO - this paper, L - Lause 1938, S - Schachowskoi 1956, T - Taylor 1984, 1985, WZ - Winiarski, Zola Light curves It is obvious from Fig. 1 that the dispersion around a mean curve is consisiderably higher that the errors of observation. Fig. 3 shows the residuals as a function of time. It appears that the orbital light-variations are modulated with a wave lasting at least 8000 days. These intrinsic variations are colour-dependent with an amplitude of about 0 ṃ 10 in B and 0 ṃ 06 in V. In U the amplitude is probably greater than 0 ṃ 11 whereas in R these variations are imperceptible. Evidently the same variations were mentioned already by Eaton et al (1991) as a difference between Winiarski s and Zola s[(1987)] lightcurve (observed at around the maximum of the 8000 day cycle) and that measured with Vanderbilt-Tennessee State APT near the minimum of the cycle. The long-period changes were approximated with polynomial (except R) and for further use deviations from the polynomial were taken. We have combined all available observations. Thereafter the observations were joined to normal points and normalized by max II of the orbital light curve. The normalized light curves are showing contradictory behaviour of depths of minima. From Table 3 it appears that from R to U in every light curve the depth of both minima is increasing. For this phenomenon the only explanation we could imagine is some kind of third light in the system. Table 3: Depths of minima from orbital light-curves, corrected for intrinsic variations and normalized by max II. Flux Band min I min II U B V R 0.645: We hope to publish the results of the investigation in near future. The autors are grateful to Toomas Aas for his persistent help. 14

15 U B V R JD Fig.3 All our residuals. 15

16 All our observation data of the UU Cancri JD Hel U B V R I

17 All our observation data of the UU Cancri: continued JD Hel U B V R I

18 All our observation data of the UU Cancri: continued JD Hel U B V R I

19 All our observation data of the UU Cancri: continued JD Hel U B V R I

20 All our observation data of the UU Cancri: continued JD Hel U B V R I

21 All our observation data of the UU Cancri: continued JD Hel U B V R I Instrumental polarization at NOT (March 1990) fil PX EPX PY EPY POL EPOL NOBS Polarization data of UU Cancri at NOT Star f d JD Pq Pu Err1 Err2 mag smag emag

22 Polarization data of UU Cancri at NOT: continued Star f d JD Pq Pu Err1 Err2 mag smag emag

23 Polarization data of UU Cancri at NOT: continued Star f d JD Pq Pu Err1 Err2 mag smag emag UU Cancri = BD 15*1733 comparison star = BD 16*1614 check/extinction star = BD 15*1731 UU Cancri vaatlused. UU Cnc vaadeldi Tallinna 50 cm teleskoobiga alates aastast, Kvistabergi 40 cm teleskoobiga alates aastast, Rootsi Kuningliku Teaduste Akadeemia Kanaari saarte 60 cm teleskoobiga alates aastast ja 2.5 m Põhjamaade Optilise Teleskoobiga (NOT) seitsmel ööl alates aastast. Kokku vaadeldi 234 ööl. 23

24 Reference [Albo(1964)] Albo, H., 1964, Tartu Publ., 34, 169 [Barone et al.(1989)] Barone, F., Milano, L., Russo, G., Sarna, M.J., 1989, Ap&SS, 159, 67 [Beyer(1964)] Beyer, M., 1964, Mitt. Hamburg. Sternw. Bergedorf, No.122, 87 [(1993)] Bradstreet, D.H., 1993, Binary Maker 2.0, Contact Software [Brelstaff(1985)] Brelstaff, T., 1985, BAAVS Circ., No. 60, 19 [Eaton(1990)] Eaton, J.A., 1990, MNRAS, 247, 62 [Eaton et al.(1991)] Eaton, J.A., Hall, D.S., Honeycutt, R.K., 1991, ApJ, 376, 289 [(1973)] Eggen, O. J. 1973, PASP, 85, 42 [Hipparcos()] Hipparcos Catalogue Epoch P hotometry Data, HIP [(1963)] Huth, H., 1963, Mitt. Verand. Sterne, No [Isles(1986)] Isles, J., 1986, BAAVS Circ., No. 63, 19 [Kalv(1979)] Kalv, P., 1979, Tartu AO Teated, No. 58, 64 [Kim et al.(1988)] Kim, H.I., Chun, Y.W., Lee, Y.S., 1988, Vistas in Astron., 31, 343 [Lause(1938)] Lause, F., 1938, Astron. Nachrichten., 266, 237 [Lee(1988)] Lee, Y-S., 1988, Vistas Astron., 31, 323 [(1956)] Popper, D. M. 1956, PASP, 68, 131 [(1977)] Popper, D. M. 1977, PASP, 89, 315 [Schachowskoi(1956)] Schachowskoi, N.M., 1956, Bull. AO Stalinabad, No.17, 35 [Taylor(1984)] Taylor, M.D., 1984, BAAVS Circ., No. 58, 11 [Taylor(1985)] Taylor, M.D., 1985, BAAVS Circ., No. 60, 19 [(1987)] Winiarski, M., Zola, S., 1987, Acta Astronomica, 37, 375 [Zola et al.(1994)] Zola, S., Hall, D.S., Henry, G.W., 1994, A&A, 285, 531 [Zola(1995)] Zola, S., 1995, A&A, 294, 525 [Zola(1998)] Zola, S., 1998, Acta Astronomica, 48,