COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2805 Konkoly Observatory Budapest 7 October 1985 HU ISSN 0374 - 0676 NEW EPHEMERIDES FOR FOUR SOUTHERN HEMISPHERE ECLIPSING BINARIES Times of minimum light were obtained for four southern hemisphere eclipsing binaries, and these enabled us to obtain new ephemerides for these stars. The observations were made during 1984 with the 40 cm reflector of the Black Birch Station of the Carter Observatory, which is located near Blenheim, New Zealand. A d. c. amplifier was used, and usually the observations were made in only one bandpass. All times quoted in this paper are heliocentric. The ephemerides were obtained from least squares solutions, and unless otherwise noted, all times of minimum light were given unit weight. V535 ARAE V535 Arae (formerly BV 419) was previously observed by Chambliss (1967) and by Schoffel (1970). Both of these investigators calculated ephemerides and orbital elements for this system. The observations of Chambliss were made in 1966, while those of Schoffel were made in the following year. An additional time of minimum light observed in 1980 was reported by Wolf et al. (1982), but this time was of lower precision than that of the earlier ones or the two obtained in this investigation, and consequently it was given a lower weight (one-tenth instead of unit weight) in the least squares solution. A least squares solution using all available photoelectronic times of minimum light for V535 Arae yields the following ephemeris: JD 2439292.9351 + 0.62930098d E +- 3 +- 9 p.e. The times of minimum light together with their residuals are as follows : JD Hel. E O-C Observer 2439292.9332 0 -0.0019d Chambliss 293.2508 0.5 +0.0011 " 296.0828 5 +0.0012 " 315.9076 36.5 +0.0030 " 319.0525 41.5 +0.0014 " 328.1751 56 -0.0008 " 329.1191 57.5 -0.0008 " 2439608.5313 501.5 +0.0018 Schoffel 610.4180 504.5 +0.0006 " 611.3619 506 +0.0005 " 619.5416 519 -0.0007 " 620.4857 520.5 -0.0005 " 625.5208 528.5 +0.0002 " 626.4639 530 -0.0007 " 627.4075 531.5 -0.0011 " 628.3522 533 -0.0003 " 629.6105 535 -0.0006 " 630.5541 536.5 -0.0010 " 643.4545 557 -0.0012 " 2444458.533 8208.5 -0.0192 Wolf 2445908.1485 10512 +0.0015 this paper 920.1039 10531 +0.0002 " The residuals show no systematic trends, and thus there is no evidence for a variation of period over the interval in which this system has been observed photoelectrically. The period given above falls within the range implied by the mean error given by Schoffel, but this period is now much more precisely known, since the time baseline is now very much longer than was previously the case. RR CENTAURI RR Centauri has been known to be variable for many years, but the first photoelectric investigation of this system was made by Knipe (1965). This was followed by an investigation by Chambliss (1971). RR Centauri has long been known to have a variable period, and both Knipe and Chambliss discussed this fact in their respective papers. Knipe's observations were obtained in 1960, while those of Chambliss were made in 1969. Sistero (1970) also reported times of minimum light for RR Centauri, and two times of minimum light were obtained in the present investigation. A linear least squares solution for all eight photoelectric times of minimum light yields the following ephemeris: JD 2437092.3206 + 0.60569243d E +- 22 +- 26 p.e. The times of minimum light together with their residuals are as follows: JD Hel. E O-C Observer 2437092.326 0 +0.0054d Knipe 7132.301 66 +0.0047 " 2440410.6002 5478.5 -0.0064 Chambliss 417.5652 5490 -0.0069 " 2440761.6003 6058 -0.0051 Sistero 762.5158 6059.5 +0.0019 " 2445914.8376 14566 +0.0010 this paper 917.8703 14571 +0.0053 " The residuals for this solution are not random, and thus they indicate that a systematic change of period has taken place for this system. A quadratic least squares solution yields the following ephemeris: JD 2437092.3256 + 0.60568992d E + 1.64 x 10^(-10) E^2 +- 17 +- 54 +- 0.34 p.e. The sum of the squares of the residuals for the linear solution is 1.97 x 10^(-4); for the quadratic solution it is 0.63 x 10^(-4), implying a better fit to the data. The latter solution indicates that the period of RR Centauri has increased by about 0.2s during the 24 years in which this system has been under photoelectric investigation. V716 CENTAURI Despite its brightness (V = 5.96 at maximum) the eclipsing binary V716 Centauri (formerly BV 516) has received very little attention from astronomers. In 1966 Chambliss (1969) obtained four photoelectric times of minimum light for this system, and an additional time of minimum light was obtained in this investigation. These seem to be the only photoelectric times of minimum light reported for this star. A least squares solution for the five times of minimum light yields the following ephemeris: JD 2439262.0045 + 1.49009305d E +- 34 +- 55 p.e. The times of minimum light together with their residuals are as follows: JD Hel. E O-C Observer 2439262.0070 0 +0d0025 Chambliss 264.9801 2 -0.0046 " 282.8659 14 +0.0001 " 291.8084 20 +0.0020 " 2445907.8195 4460 0.0000 this paper The period given above falls within the range implied by the mean error previously given by Chambliss, and thus there is no evidence for any change of period over the interval in which this system has been observed photoelectrically. V701 SCORPII V701 Scorpii was observed photoelectrically in 1966 by Leung (1974), and one time of minimum light was obtained in the present investigation. The ephemeris quoted by Leung was based on his own observations as well as on the earlier photographic observations of Plaut, which were made between 1934 and 1937. The time of minimum light observed in this investigation was 1.5 hours later than it would be according to Leung's ephemeris. This implies a significant increase in the period of V701 Scorpii over the interval in which this system has been observed photoelectrically. A least squares solution for all photoelectronic times of minimum light yields the following ephemeris: JD 2439329.6674 + 0.76187804d E +- 25 +- 55 p.e. The times of minimum light together with their residuals are as follows: JD Hel. E O-C Observer 2439330.0455 0.5 -0.0029d Leung 331.9516 3 -0.0015 " 341.8572 16 -0.0003 " 2445918.0107 8647.5 +0.0029 this paper The period quoted in this paper is about 0s6 longer than that quoted by Leung, and thus it appears that the period of V701 Scorpii has increased by that amount over the past 18 years. Wilson and Leung (1977) consider V701 Scorpii to be an overcontact system. Such systems have considerable amounts of material flowing between the two components, and consequently significant changes of period are to be expected. We would like to express our sincere thanks to Dr. Edwin Budding of the Carter Observatory, Wellington, New Zealand, for providing us with observing time, accommodations, and advice at the Black Birch Station of Carter Observatory. JAMES R. BRUTON CARLSON R. CHAMBLISS Dyer Observatory Kutztown University Vanderbilt University Kutztown, Pennsylvania Nashville, Tennessee USA 19530 USA 37235 References: Chambliss, C. R.: 1967, Astron. J. 72, 512 [BIBCODE 1971AJ.....76...64C ] Chambliss, C. R.: 1969, Inf. Bull. Var. Stars No. 408 Chambliss, C. R.: 1971, Astron. J. 76, 64 [BIBCODE 1967AJ.....72..512C ] Knipe, G. F. G.: 1965, Astrophys. J. 142, 1068 [BIBCODE 1965ApJ...142.1068K ] Leung, K. C.: 1974, Astron. Astrophys. Suppl. Ser. 13, 315 [BIBCODE 1974A&AS...13..315L ] Schoffel, E.: 1970, Veroeff. der Remeis-Sternwarte Bamberg 8, No. 88 [BIBCODE 1970VeBam..88.....S ] Sistero, R. F. and Castore de Sistero, M. E.: 1970, Inf. Bull. Var. Stars No. 453 Wilson, R. E. and Leung, K. C.: 1977, Astron. Astrophys. 61, 137 [BIBCODE 1977A&A....61..137W ] Wolf, G. W. et al.: 1982, Inf. Bull. Var. Stars No. 2185