COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3188 Konkoly Observatory Budapest 18 May 1988 HU ISSN 0374-0676 BD+0 3566, A NEW SHORT PERIOD VARIABLE STAR A new variable star was found during a photometric study of the W UMa type star V502 Oph. The comparison stars were chosen according to the standard criteria: they must be of approximately the same magnitude and less than two degrees from the program star. The characteristics of the observed stars are shown in Table I. The observations were made with the 0.84m reflector at the Observatorio Astronomico Nacional, San Pedro Martir, Mexico during the nights of 13/14 and 14/15 June 1987. A Lowell photon counting system was utilized with Johnson's V filter. Each observation is the result of one 40 s integration on each star. The sequence C1, C2, V was followed except at the time of the eclipse of V502 Oph when a continuous monitoring of the eclipsing star was undertaken. This explains the gaps in the photometry of this new variable star. The photometric values reported in Table II and shown schematically in Figure 1 are the magnitude differences between BD+0 3566 (C2) and BD+0 3569 (C1). On each night the average of the points has been subtracted to establish the zero baseline. The data points are accurate to 0.005 mag. the average time span between successive points is 0.01 d and the accuracy in time is 0.0014 d. From Figure 1 it can be seen that the amplitude of the variation is 0m04, although it is changing from one day to another. If the star is pulsating, this suggests the existence of several simultaneously interacting modes. The Fourier transform of the two nights confirms this result. Table I Characteristics of the observed stars BD V Sp. RA (1950) D Type SAO V502 Oph +0 3562 8.4-8.98 G2V+F9V 16h38m48s +0 36'8"5 W UMa 121784 C1 +0 3569 8.5 GO 16 40 19 +0 10 6.9 Comp. 121805 C2 +0 3566 8.45 A3 16 40 07 +0 37 11.3 New 121803 [FIGURE 1] Figure 1. Light curve of the new variable star BD +0d 3566. On top, night HJD 2446961; bottom, night HJD 2446962. Table II Photoelectric photometry of BD +0 3566 HJD Delta V HJD Delta V 2446960+ 2446960+ 1.6221 -0.049 1.8103 0.000 1.6304 0.000 1.8179 0.000 1.6373 0.000 1.8262 -0.040 1.6450 0.010 1.8346 0.000 1.6485 0.010 2.6367 -0.018 1.6561 0.020 2.6512 0.002 1.6686 0.010 2.6644 0.022 1.6797 0.010 2.6728 0.022 1.6894 0.010 2.6818 0.022 1.6978 0.000 2.6915 0.022 1.7061 -0.010 2.7436 -0.038 1.7151 -0.020 2.7492 -0.048 1.7318 0.010 2.7554 -0.048 1.7387 0.020 2.7610 -0.018 1.7471 0.020 2.7665 -0.018 1.7554 0.020 2.7714 -0.008 1.7623 0.020 2.7776 0.012 1.7693 0.010 2.7832 0.022 1.7762 0.010 2.7887 0.022 1.7853 -0.010 2.7978 0.032 1.7929 0.000 2.8054 0.022 1.8012 -0.030 [FIGURE 2] Figure 2a. Power spectrum of the two nights. Figure 2b. Window function Figure 2b represents the window function, whereas Figure 2a the power spectrum of the two nights, with peaks at 9.70 and 18.45 c/d or, corresponding, periods at 0.103 and 0.05. Since the spectral class of the newly found variable has been reported in the SAO Catalogue as A3, one might speculate from the observational characteristics, that it might be a pulsating star of Delta Scuti type, especially since it shows a relatively small and changing amplitude, two close and short periods of pulsation and a spectral type of A3. More detailed observations are needed to univocally decide on its nature. We would like to acknowledge the assistance of the staff of the Observatorio Astronomico Nacional. Fruitful discussions with R. Peniche are also acknowledged. Proofreading was done by J. A. Miller and typing by D. A. Ramos. T. GOMEZ Instituto de Astronomia-UNAM Apdo. Postal 70-264 C.P. 04510 Mexico, D.F. J.H. PENA(1) and M. A. HOBART(2) Instituto Nacional de Astrofisica, Optica y Electronica Apdo. Postal 51 y 216 ZC 72000 Puebla, Pue 1 On leave from Instituto de Astronomia-UNAM Apdo. Postal 70-264 C.P. 04510 Mexico, D.F. 2 On sabbatical from University Veracruzana Facultad de Fisica Apdo. Postal 270 Xalapa, Veracruz