COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 2999 Konkoly Observatory Budapest 16 March 1987 HU ISSN 0374 - 0676 PHOTOELECTRIC LIGHT CURVES OF BX PEGASI The very short period eclipsing binary system BX Peg was discovered by Hughes (Shapley and Hughes, 1934). Photoelectric light curves have been published by Zhai and Zhang (1979) and Hoffman (1982). Three photoelectric times of minimum light have been recently published by BAV (1984). Leung, Zhai, and Zhang (1985) used the Wilson-Devinney code to determine a solution from Zhai's and Zhang's data which were obtained with an uncooled photomultiplier. Another solution using light curve synthesis techniques was determined by Kaluzny (1984) who used Hoffman's incomplete light curve. Both sets of data indicate that BX Peg undergoes total eclipse during primary minimum, but the depth of this minimum is somewhat different in the two curves. It is interesting to note that Chou's (1966) light elements give a primary minimum which now appears as a secondary minimum when compared to Zhai's and Hoffman's primary epochs. The present observations of BX Peg were made on the nights of September 27-30, inclusive. The 24 inch F/13.5 reflector at Lowell Observatory was used with standard V, I filters in the Kron-Cousins-Bessell system (Bessell, 1976) with a dry-ice-cooled RCA 31034B photomultiplier tube. The comparison and check stars were BD +25d4584 and BD +25d4582, respectively. Observations were halted during the last night due to instrument failure, so the light curve is incomplete. Approximately 200 observations were obtained at each effective wavelength. Four epochs of minimum light were determined from observations made during two primary and two secondary eclipses. All minima were determined by the Hertzsprung technique (1928) except for the earliest minimum which was found by the bisection-of-chords method. These are the last four epochs given in Table I. Table I JD Hel. 2440000+ Minimum Cycles (O-C) Source 44195.3771 I -5192.0 -0.0002 Hoffman, 1982 44195.2373 II -5192.5 0.0002 Hoffman, 1982 45640.2445 II -39.5 -0.0006 BAV #38, 1984 45646.2746 I -18.0 0.0005 BAV #38, 1984 45651.3219 I 0.0 0.0002 BAV #38, 1984 46701.7787 I 3746.0 0.0010 Present Observations 46703.7409 I 3753.0 0.0002 Present Observations 46703.8797 II 3753.5 -0.0011 Present Observations 46704.7227 II 3756.5 0.0006 Present Observations The times of minimum light shown in Table I were introduced with variable weights into a least squares solution to obtain the following improved ephemeris: JD Hel Min. I = 2445651.3217+ 0d.28042071E +- 2 +- 4 (p.e.) and this was used in calculating the O-C's in Table I and in determining the phases of the observations. The period is significantly different than that given by Chou (1966). [FIGURE 1] Fig. 1 - Light curves of BX Peg defined by normal points. The V and I light curves of BX Peg defined by normal points are shown in Figure 1 as delta m versus phase. The large scatter in the observations is due, at least in part, to the variable weather conditions which were present during the observing run. RONALD G. SAMEC BEVERLY B. BOOKMYER Dept. of Physics & Astronomy Clemson University Clemson, SC 29634-1911 USA References: BAV 1984, Mitt. Nr. 38, 5. Bessell, M. S. 1976, Pub. Astron. Soc. Pac. 88, 557. [BIBCODE 1976PASP...88..557B ] Chou, K. C. 1966, Rocz. Astron. Krakow 37. Hoffman, M. 1982, Acta Astron. 32(1-2), 131. [BIBCODE 1982AcA....32..131H ] Kaluzny, J. 1984, Acta Astron. 34(2), 217. [BIBCODE 1984AcA....34..217K ] Leung, K. C., Zhai, D. S. and Zhang, Y. X. 1985, Astron. Journal 90, 515. [BIBCODE 1985AJ.....90..515L ] Shapley, H. and Hughes, E. M. 1934, Harvard Ann. 90, 4. Zhai, D. S. and Zhang, Y. X. 1979, Kexue Tongbao 21, 895.