COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1830 Konkoly Observatory Budapest 1980 August 19 HU ISSN 0374-0676 LIGHT ELEMENTS OF AG PHOENICIS The variability of AG Phe=BV 1488=SAO 215098=HD 2320 (A3) was discovered by Strohmeier (I.B.V.S. No. 610, 1972) on sky patrol plates. He describes the star as an EB-type variable showing an amplitude of 0.5m and a deep secondary minimum. From 14 times of minimum light he obtained a period of 1.510653d. The variable (BV 1488) was listed as AG Phe by Kukarkin et al. (GCVS, 2nd Suppl., 1974). Eggen (A.J. 83, 288, 1978) obtained u,v,b,y,beta observations of the system, showing constant light of V_E=8.9m at maximum, in disagreement with EB characteristics. Also, he found a midsecondary minimum of V_E= 9.4m suggesting a shift from phase 0.5, or a slightly incorrect period. In this note I present 7 photoelectric times of minimum light covering 524 cycles derived from about 1000 UBV observations made between September 1978 and August 1979. Of these observations 200 were made with the 154 and 76 cm reflecting telescopes of Bosque Alegre and El Leoncito, respectively in Argentina; and the rest with a 40 cm telescope of Cerro Tololo Observatory in Chile*. The present photoelectric observations show the existence of a shallow secondary minimum, instead of a deep one, and that therefore the period is half of the value previously derived by Strohmeier. Individual minima are listed in Table I. The standard errors given in parentheses were determined from the light curves on each pass-band. A least squares linear ephemeris using the mean values of the minima in the UBV bands, gives Min I = JDHel 2444170.79481+ 0.75533809d E +-.00018 +-.00000059 (1) Table I. Individual times of Minima JDHel 2440000+ V U B 3778.7749(04) 3778.7745(03) 3778,7756(03) 3781.7957(03) 3781.7954(04) 3781.7956(09) 3902.6494(03) 3902.6487(03) 3902.6483(10) 4170.7951(08) 4170.7949(04) 4170.7948(03) 4171.5509(03) 4171.5507(07) 4171.5501(03) 4173.8161(04) 4173.8157(04) 4173.8144(09) 4174.5715(04) 4174.5717(03) 4174.5721(08) Table II . Photographic and Photoelectric times of Minima. JDHel w cycles (O-C) (O-C)' 2400000+ 38309.365 0.5 -7760.0 0.030 38315.369 0.5 -7752.0 -0.008 38318.369 0.5 -7748.0 -0.030 38340.292 0.5 -7719.0 -0.012 38614.528 0.5 -7356.0 0.035 38642.446 0.5 -7319.0 0.005 38670.374 0.5 -7282.0 -0.015 38695.340 0.5 -7249.0 0.025 39053.350 0.5 -6775.0 0.003 39361.490 0.5 -6367.0 -0.073 39383.418 0.5 -6338.0 -0.014 40415.233 0.5 -4972,0 0.002 40526.302 0.5 -4825.0 0.036 40823.093 0.5 -4432.0 -0.023 43778.77502(49) 1.5 - 519.0 0.0024 0.0007 43781.79559(14) 1.8 - 515.0 0.0015 -0.0001 43902.64902(37) 1.6 - 355.0 0.0001 -0.0008 44170.79486(09) 1.9 0.0 -0.0008 0.0000 44171.55052(39) 2.6 1.0 -0.0005 0.0004 44173.81577(47) 1.5 4.0 -0.0012 -0.0004 44171.57167(16) 1.7 5.0 -0.0007 0.0002 The photographic minima given by Strohmeier and the present observations lead to the following ephemeris: Min I = JDHel 2444170.7956d+0.7553429d E +-.0045 +-.0000011 (2) The data for both ephemeris are listed in Table II; weights w=0.5 are given to photographic minima, while w=0.1 ln(1/sigma) to the colour-averaged photoelectric values; (O-C) and (O-C)' are the residuals from 1) and (2), respectively. It is seen that the error of the photoelectric elements are smaller than the photographic ones. The period including all observations over 16 years is slightly larger than the present value determined from photoelectric data alone. This would indicate that the period [FIGURE 1] FIGURE 1: Mean light and colour curves of AG Phe. is decreasing at a ratio of about 2.6x10^{-2}sec/year. However photographic residuals are very large, therefore more photoelectric observations are needed in order to establish the period-decrease. The light curves (Figure 1) show partial eclipses with minima fairly different in depth, the amplitude of the symmetrical primary minimum is 0.49m, while that of the secondary is 0.08m, displaying its descending branch steeper than the ascending one. The secondary eclipse is centered around phase 0.5, but due to its asymmetry and shallowness small eccentricities are not excluded. The light and colours outside eclipses are almost constant. MIGUEL ANGEL CERRUTI ** Instituto de Astronomia y Fisica del Espacio CC 67 - Suc 28 1428 Buenos Aires,Argentina *Cerro Tololo Interamerican Observatory is operated by AURA, Inc., under contract with the NFS (U.S.A.). **Fellow of CONICET, Argentina. [DATAFILE 3]