COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 2953 Konkoly Observatory Budapest 10 November 1986 HU ISSN 0374 - 0676 PHOTOELECTRIC PHOTOMETRY OF UZ Dra The period of the eclipsing binary UZ Dra=BD+68d1065 was investigated by Dugan and Wright (1939), Koch and Koch (1962), and Dueball (1964). UZ Dra is being observed spectroscopically by Lacy (1989) who suggested us to observe it photoelectrically. The system has been observed at the Ege University Observatory on 35 nights during the summer seasons of 1984 and 1985. This is going to be the first photoelectric light curve since it is neglected photometrically. The observations were made with the 48 cm Cassegrain reflector equipped with an unrefrigerated EMI 9781A photomultiplier tube and Johnson's standard B, V filters. A total of 522 and 515 individual points were obtained in B and V colours, respectively. The comparison star, BD +68d1061 showed no significant variations against the check star, BD +68d1066. The atmospheric extinction coefficients in each colour for every night were calculated from the observations of the comparison star using conventional methods. Then, all the differential observations (variable minus comparison) were corrected for differential extinction. Primary and secondary times of minima have been obtained three times of each. They are given in Table I. The other times of minima which can be found in literature are also included. The O-C residuals in the Table were calculated with the following light elements: JD Hel Min I = 2496227.4238 + 3.2613024dxE. Table I. Times of minima of UZ Dra. JD Hel. Min Method E (O-C) Ref. 2433570.300 I vis -3881 -0.009 1 751.325 II vis -3825.5 0.014 1 759.468 I vis -3823 0.003 1 34121.466 I vis -3712 -0.003 2 134.512 I vis -3708 -0.003 2 152.456 II vis -3702.5 0.004 2 439.443 II vis -3614.5 -0.003 2 488.358 II vis -3599.5 -0.008 2 530.751 II pg -3586.5 -0.012 3 35380.337 I vis -3326 0.005 4 551.552 II vis -3273.5 0.002 4 36231.531 I vis -3065 -0.001 S 859.334 II vis -2872.5 0.001 5 40363.607 I vis -1798 0.005 6 376.650 I vis -1794 0.003 6 513.632 I vis -1752 0.010 6 557.650 II vis -1738.5 0.000 5 41570.2834 I pe(B) -1428 -0.0006 7 570.2829 I pe(V) -1428 -0.0011 7 44461.428 II vis -541.5 -0.001 8 510.353 II vis -526.5 0.005 9 854.406 I vis -421 -0.009 10 929.428 I pe -398 0.003 11 45172.399 II vis -323.5 0.006 12 534.398 II vis -212.5 0.001 13 718.660 I vis -156 -0.001 14 821.379 II vis -124.5 -0.013 15 878.4650 I pe(B) -107 0.0005 16 878.4643 I pe(V) -107 -0.0001 16 914.3391 I pe(B,V) -96 0.0003 16 958.3660 II pe(B,V) -82.5 -0.0004 16 971.4105 II pe(B,V) -78.5 -0.0011 16 46191.550 I vis -11 0.001 17 227.4238 I pe(B,V) 0 0.0000 16 245.3608 II pe(B) 5.5 -0.0002 16 245.3601 II pe(V) 5.5 -0.0009 16 271.437 II vis 13.5 -0.014 17 References to Table I. 1. Domke,K., Pohl,E.: 1953, Astron. Nachr. 281, 113. [BIBCODE 1953AN....281..113D ] 2. Pohl,E.: 1955, Astron. Nachr. 282, 235. [BIBCODE 1955AN....282..235P ] 3. Koch, J.C., Koch, R.H.: 1962, Astron. J. 67, 462, [BIBCODE 1962AJ.....67..462K ] 4. Rudolph R.: 1960, Astron. Nachr. 285, 161. [BIBCODE 1960AN....285..161R ] 5. Braune, W., Quester,W.: 1962, Astron. Nachr. 286, 209. [BIBCODE 1962AN....286..209B ] 6. Baldvin, M.E.: 1973 Inf.Bull.Var.Stars, No. 795. 7. Kizilirmak, A., Pohl, E.: 1979, Inf.Bull.Var.Stars, No. 937. 8. BBSAG, 1980, No.49. 9. BBSAG, 1980, No.50. 10. BBSAG, 1981, No.56. 11. BBSAG, 1981, No.57. 12. BBSAG, 1982, No.61. 13. BBSAG, 1983, No.67. 14. BBSAG, 1984, No.70, 15. BBSAG, 1984, No.72. 16. This paper. 17. BBSAG, 1985, No.77. [FIGURE 1] Figure 1 : O-C diagram of UZ Dra. The dots, circles and crosses denote photoelectric, photographic and visual observations, respectively. [FIGURE 2] Figure 2 : The light and colour curves of UZ Dra. The period is taken from GCVS (1969,1985) which seems to fit observations fairly good. Therefore, we didn't attempt to improve it. Also the existing photoelectric times of minima are inadequate for such an attempt. Moreover, the better fit is obtained with the above new epoch which we believe more accurate one in our times of minima. The O-C diagram is shown in Figure 1. The light and colour curves of UZ Dra are shown in Figure 2 where the phases have been calculated with the above light elements. The shape of the light curve is typical of Algol type. The observed duration of eclipses are about D=4h40m which is interestingly short for this period. The amplitudes are about 0.795m and 0.765m at the primary, 0.515m and 0.530m at the secondary minimum in blue and yellow light, respectively. The system is slightly redder at the primary and bluer at the secondary minimum which implies the spectral type of the secondary component is later than that of primary. The photometric analysis of the light curves is in progress and will be published elsewhere. This work has been partly supported by the Research Foundation of Ege University with the project number 1985/036. O. GULMEN, N. GUDUR and C. SEZER Ege University Observatory Campus P.K. 21 Bornova, Izmir-Turkey References: Dueball, J.: 1969, Die Sterne, 40, Heft 5-6, 108. Dugan, R.S., Wright, F.W.: 1939, Contr. Princeton Univ. Obs. No.19. [BIBCODE 1939CoPri..19....1D ] Koch, J.C., Koch, R.H.: 1962, Astron. J. 67, 462. [BIBCODE 1962AJ.....67..462K ] Lacy, C.H.: 1984, private communication.