COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2299 Konkoly Observatory Budapest 1983 March 21 HU ISSN 0374-0676 IMPROVED LIGHT ELEMENTS OF W GRUIS The purpose of this note is to present five new times of minimum light of the southern eclipsing binary W Gru, to give an improved (4 years baselined) photoelectric linear ephemeris and to recalculate the parabolic ephemeris given by Cerruti and De Laurenti (1981). History of this object is also given in the latter reference. The observations were made during 1981 and 1982 at CTIO* in the U, B, V bands. Individual minima together with that determined by Cerruti and De Laurenti (1981) are listed in Table I. The standard errors are given in brackets, they were determined from the light curves on each pass-band. A least squares linear ephemeris gives: Min I = HJD 2444517.6963d + 2.9685249d E, +/-.0006 +/-.0000034 m.e. (1) In Table I we also list the cycles E with their weights and the residuals (O-C) from the above ephemeris. The minimum defined by (1) together with those determined by Pickering (1913), Payne-Gaposchkin (1947) and Imbert (1974) gives the following least squares parabolic ephemeris: Min I = HJD 2430132.153d + 2.9685021d E + 7.52d 10^-9 E^2 +/-.017 +/-.0000026 +/-0.69 10^-9 m.e. (2) Residuals from the parabolic ephemeris are presented in Table II, labelled as Table I. The (O-C) residuals and the resulting increase of the period at a constant rate of 0.080 sec/y confirm our previous results (Cerruti and De Laurenti, 1981). Figure 1 depicts the (O-C) residuals from (2). *CTIO is operated by AURA under contract with the NSF (USA). Table I Times of minima and residuals for linear ephemeris HJD(sigma) Min. Band E(w) (O-C) 2400000+ I V 43778.5326(2) -249.0(7.1) -0.0010 I B 43778.5309(3) -249.0(5.8) -0.0027 I U 43778.5263(11) -249.0(3.0) -0.0073 I V 43781.4987(3) -248.0(5.8) -0.0034 I B 43781.4992(2) -248.0(7.1) -0.0029 I U 43781.4970(5) -248.0(4.5) -0.0051 II V 43818.6125(5) -235.5(4.5) 0.0038 II B 43818.6144(2) -235.5(7.1) 0.0057 II U 43818.6153(10) -235.5(3.2) 0.0066 II V 44177.8042(2) -114.5(7.1) 0.0040 II B 44177.8046(4) -114.5(5.0) 0.0044 II U 44177.8030(3) -114.5(5.8) 0.0028 I V 44517.6947(4) 0.0(5.0) -0.0016 I B 44517.6947(7) 0.0(3.8) -0.0016 I U 44517.6935(15) 0.0(2.6) -0.0028 II V 44830.8771(7) 105.5(3.8) 0.0014 II B 44830.8764(6) 105.5(4.1) 0.0007 II U 44830.8758(8) 105.5(3.5) 0.0001 II V 44833.8435(4) 106.5(5.0) -0.0007 II B 44833.8438(6) 106.5(4.1) -0.0004 II U 44833.8436(6) 106.5(4.1) -0.0006 II V 44839.7774(8) 108.5(3.5) -0.0038 II B 44839.7790(9) 108.5(3.3) -0.0022 II U 44839.7770(4) 108.5(5.0) -0.0042 II V 44842.7510(6) 109.5(4.1) 0.0012 II B 44842.7514(4) 109.5(5.0) 0.0016 II U 44842.7493(4) 109.5(5.0) -0.0005 II V 45228.6577(7) 239.5(3.8) -0.0003 II B 45228.6599(3) 239.5(5.8) 0.0019 II U 45228.6585(6) 239.5(4.1) 0.0005 Table II Times of minima and residuals for parabolic ephemeris HJD(sigma) Min. Meth. E(w) (O-C) 2400000+ II vis. 10001.6 -6781.5(1.0) -0.0015 I ph. 30132.156 0.0(3.0) 0.0033 I ep. 41569.88(55) 3853.0(1.3) -0.0231 I UBV 44517.6963(06) 4846.0(4.1) 0.0056 [FIGURE 1] The light curve constructed with 2500 individual observations and a classical orbital analysis will be published elsewhere. MIGUEL ANGEL CERRUTI Instituto de Astronomia y Fisica del Espacio CC 67 Suc 28 1428 Buenos Aires Argentina References: Cerruti, M.A. and De Laurenti, M.A., 1981, Inf. Bull. Var. Stars No. 2012 Imbert, E.C., 1974, Astr. and Astrophys. 32, 429 [BIBCODE 1974A&A....32..429I ] Payne-Gaposchkin, C., 1947, Harv. Ann. 115, (110), 127 Pickering, E.C., 1913, Harv. Circ. 179, 2