COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3638 Konkoly Observatory Budapest 16 July 1991 HU ISSN 0374 - 0676 B, V, R, I LIGHT CURVES OF V803 AQUILAE The very short period eclipsing binary system V803 Aquilae was discovered by Bakos (1950). He correctly classified this system as a W UMa-type. He gave 29 epochs of minimum light and presented a photographic light curve. A finder chart was also included. Later, Harwood (1962) observed V803 Aql and noted that the finder chart by Bakos failed to show a bright star about 0.5' northward of the variable. This object was used as our check star. Also, Locher (1978) found an error in Bakos' elements. He used 26 minimum timings of his own to determine the following ephemeris: JD Hel Min. I = 2448780.357 + 0.2634254d * E Moreover, Locher pointed out that V 803 Aql was not observed at all between 1937 and 1973. The BBSAG Bulletin has since published well over 100 times of minimum light for this system. The present observations were made on 1-7 June, 1989 at Kitt Peak National Observatory in Tucson, Arizona using the 0.9m #2 reflector which housed a dry-ice-cooled RCA 31034a Ga-As photometer tube. More than 500 observations were taken at each effective wavelength. The coordinates of the check, comparison and the variable star are given in Table I. TABLE I Star R.A.(1950) Dec.(1950) V803 Aql 18h 58m 04s -7d 33.5' Comparison 18h 58m 11s -7d 35.1' Check 18h 58m 02s -7d 33.2' Six epochs of minimum light were determined from observations made during three primary and three secondary eclipses. The first four epochs of minimum light were determined by an iterative technique based on the Hertzsprung method (1928), while the last two were determined with the bisection-of-chords method. These epochs are given in Table II. The probable errors are indicated in parentheses. [FIGURE 1] Fig. 1 - Light curves of V803 Aql as defined by the individual observations. TABLE II JD HEL. 2440000 Cycles O-C 7678.8756(1) -22.5 - 0.0012 7680.8523(2) -15.0 - 0.0002 7681.9052(1) -11.0 - 0.0010 7683.8806(1) -3.5 - 0.0013 7684.8043(3) 0.0 - 0.0004 7684.9351(6) 0.5 - 0.0004 These times of minimum light along with BBASG minima following JD 2444500 were introduced into a least squares solution to obtain the following improved linear ephemeris: JD Hel Min. I = 2447684.8038 + 0.263422299d * E. +- 3 11 This ephemeris when used in conjunction with all previous times of minimum light indicates that there have been at least two distinct period changes: an increase followed by a recent decrease. The light curves of V803 Aquilae defined by the individual observations are shown in Figure 1 as delta m versus phase. The analysis of the observations is underway. WEN SU ^b RONALD G. SAMEC ^a,b,c Dept. of Physics & Astronomy J. I. Holcomb Observatory Butler University Indianapolis, IN 46208 USA a^ Visiting Astronomer, Kitt Peak National Observatory National Optical Astronomy Observatories which are operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation b^ This research was supported partially by 1988-89 Butler Faculty and 1991-92 Student Fellowship Academic Grants. c^ This research was partially supported by a grant from NASA administered by the American Astronomical Society. References: Bakos G. A. 1950, Leiden Ann 20, 177. [BIBCODE 1950AnLei..20..177B ] Harwood, M. 1962, Leiden Ann 21, 387. [BIBCODE 1960AnLei..21..387H ] Hertzsprung E. 1928, Bull. Astron. Inst. Neth. 4,179. [BIBCODE 1928BAN.....4..178H ] Locher, K. 1978, BBSAG Bull. #38, 6. [BIBCODE 1978BBSAG..38....6L ]