COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3201 Konkoly Observatory Budapest 10 June 1988 HU ISSN 0374-0676 THE SHORT-PERIOD ECLIPSING BINARY V728 HERCULIS 1 This short-period W UMa system was discovered along with dozens of others by N. E. Kurochkin (1977) from 100 x 100 astrographic plates taken for a study of M92. In Kurochkin's work it is identified as SP 2086. The photographic light curve presented by Kurochkin suggests a contact system and we elected to attempt to obtain photoelectric light curves of this relatively bright system. The system has been observed at the Rothney Astrophysical Observatory with the Rapid Alternate Detection System (RADS) for the past two seasons. The photometry system is a chopping, gated pulse-counting two-star-and-sky device and has been described by Milone et al. (1982) and by Milone and Robb (1983). Partial BVI light curves were obtained during 1986 and complete BVI light curves were obtained in 1987. Because the ephemeris provided by Kurochkin and cited in Kholopov (1985) failed to successfully reproduce the light curve, we applied a modified version of the period-finding program of Jurkevich (1971) to the 1987 season data to obtain a preliminary period: P = 0.471302 d. The epoch used was E0 = HJD 2441571.273, from Kurochkin. The evidence, however, is that the same period can not fit adequately the data from both seasons and the large uncertainty obtaining from the early photographic data is too great to permit a significant q (dP/dt) term to be found. With the above elements, the O-C phases of minima were obtained for each of the wavelengths and weighted means were found. The results are: O-C 2446612.868 0.1635 +- 0.0013 613.809 0.1604 +- 0.0018 949.835 0.1357 +- 0.0008 The system will be observed again this season with special attention to observing phases of minima in order to determine if abrupt or continuous changes of the period are involved. We have also observed the system spectroscopically with the 1.8-m telescope of the Dominion Astrophysical Observatory in Victoria for radial velocity studies. This work has also provided the spectral type of the system: F3 with an estimated uncertainty of 1/10 class. Complete analyses of the system will be published elsewhere. Student observers who helped to gather the data during the 1 Publications of the Rothney Astrophysical Observatory Series B No. 12 past two seasons included J. van Leeuwen and D. Thistlethwaite. This work was supported by grants from the Canadian Natural Sciences and Engineering Research Council to EFM, by Student Temporary Employment Programme Grants from the Goverment of Alberta to EFM and JEP and by the Department of Physics of the University of Calgary, all of which are gratefully acknowledged. R. NELSON E.F. MILONE The College of New Caledonia Physics Department 3330-22nd Avenue The University of Calgary Prince George, B. C. V2N 1P8 2500 University Dr., N. W. Calgary, Alberta T2N 1N4 J.E. PENFOLD Department of Mathematics, Physics, and Engineering Mt. Royal College 4825 Richard Road, S. W. Calgary, Alberta T3E 6K6 References: Jurkevich, I., 1971, Ap and Sp Sci. 13, 154. [BIBCODE 1971Ap&SS..13..154J ] Kholopov, P. N.(ed.-in-chief), 1985, General Catalogue of Variable Stars II.(Moscow: NAUKA Publishing House). Kurochkin, N. E., 1977, Variable Stars, Supplement 3, No. 15. 201. [BIBCODE 1977PZP.....3..201K ] Milone, E. F. and Robb, R. M., 1983, PASP 95, 666. [BIBCODE 1983PASP...95..666M ] Milone, E. F., Robb, R. M., Babott, F. M., and Hansen, C. H., 1982, Appl.Optics 21, 2992. [BIBCODE 1982ApOpt..21.2992M ]