COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2052 Konkoly Observatory Budapest 1981 December 8 HU ISSN 0374-0676 LIGHT ELEMENTS OF GG Vel The variability of GG Vel = BV 1201 = HD 79459 = SAO 220955 = = CoD-42d5065 = CPD-42d3467 was discovered by Strohmeier and Patterson (1967) on Sky Patrol plates taken from Mt. John Observatory. They published a list of times of minimum light, gave the first light elements, an Algol-like variability, a weak secondary minimum and an amplitude of 0.45 mag. These elements were also listed by Strohmeier and Knigge (1969). This variable was named by Kukarkin et al. (1972) and mentioned in a report of the Rosemary Hill Observatory as part of a VRI photoelectric photometry observing program (see Bull.Am.Astr. Soc. Vol.10, pg 107, 1978). In this note I present six photoelectric times of minimum light for each pass-band in the UBV system and the derived light elements. Observations were made between 1979 and 1980 from CTIO* in Chile, and from Bosque Alegre (Cordoba) and El Leoncito (San Juan) Observatories, both in Argentina, with apertures of 40, 152, and 76 cm, respectively. Individual minima are listed in Table I with the standard deviation given in parenthesis. They were determined from the light curve on each pass-band. The color average of these minima are listed in Table II (standard deviations in parenthesis) together with the photographic minima given by Strohmeier and Patterson (1967). Table I Individual times of minima ------------------------------------------- HJD 2440000+ V B U ------------------------------------------- 3899.8150(13) 3899.8180(06) 3899.8161(12) 3902.7628(06) 3902.7610(13) 3902.7623(08) 3908.6737(10) 3908.6721(17) 3908.6744(11) 3973.5714(12) 3973.5706(11) 3973.5725(07) 4302.5533(09) 4302.5513(23) 4302.5533(13) 4306.9765(08) 4306.9798(07) 4306.9778(09) ------------------------------------------- Table II Minima of GG Vel -------------------------------------------------------------- Meth. HJD w E (O-C) (O-C)' (O-C)" 2440000+ -------------------------------------------------------------- Pg 38379.542 1 -2000 -0.0154 -0.014 Pg 38382.545 1 -1998 0.0371 0.039 Pg 38385.543 1 -1996 0.0847 0.087 Pg 38441.399 1 -1958 -0.1175 -0.116 Pg 38490.272 1 -1925 0.0734 0.075 Pg 38841.292 1 -1687 -0.0080 -0.007 Pg 38844.293 1 -1685 0.0425 0.044 Pg 38869.233 1 -1668 -0.0962 -0.095 Pg 38872.227 1 -1666 -0.0526 -0.052 Pg 39118.543 1 -1499 -0.0977 -0.097 Pg 39198.313 1 -1445 0.0107 0.011 Pg 39201.311 1 -1443 0.0582 0.059 Pg 39232.237 1 -1422 0.0047 0.005 Pg 39235.230 1 -1420 0.0473 0.048 Pg 39862.101 1 - 995 -0.0485 -0.049 Pg 39907.964 1 - 964 0.0828 0.082 UBV 43899.8164(15) 1 1742 0.0007 0.0023 UBV 43902.7620(09) 3 1744 -0.0041 -0.0026 UBV 43908.6734(12) 2 1748 0.0064 0.0079 UBV 43973.5715(10) 3 1792 -0.0050 -0.0041 UBV 44302.5526(12) 2 2015 0.0029 0.0008 UBV 44306.9780(17) 1 2018 0.0027 0.0005 --------------------------------------------------------------- A least squares solution for the 16 photographic minima give the following linear light elements: Min I = HJD 2443973.556d + 1.475218d E" +-0.026 +-0.000047 m.e. (1) while for the present 6 photoelectric minima the light elements are: Min I = HJD 2443973.5756d + 1.475230d E" +-0.0014 +-0.000012 m.e. (2) These results show the period to be constant within the errors. Finally, a least squares linear fit was performed with all the minima giving the following elements: Min I = HJD 2441329.98944d + 1.4752160d E +-0.0096 +- 0.0000056 m.e. which comprise about 4000 cycles of the "history" of this system. The cycles E and the residuals (O-C) from the latter ephemeris are listed in columns 4 and 5 of Table II, while (O-C)' and (O-C)" from (1 ) and (2) are in columns 6 and 7. The light curve is not completely observed yet. The present observations show partial eclipses, a primary minimum of amplitude 0.5 mag and no evidence of a secondary eclipse. GG Vel has a visual companion (Delta_alpha=0, Delta_delta=6") of magnitude V=11.2. The effect of the light of this star on the combined light of the components at maxima is about 0.01 mag. Therefore, one component of the system would be a faint star with a luminosity beyond the accuracy of photoelectric magnitudes, only detected due to a pronounced reflection effect as seen in the observations. On the other hand, if the period were twice that considered above, then the system would be composed by two similar stars in temperature and luminosity. This is also supported by the observations because the colors are almost constant during the whole period and the amplitudes of all measured minima are of the same order. Then also the orbit would be circular, as shown by the behaviour of the residuals (O-C) of odd cycles. A spectrographic study of GG Vel could decide between the two possibilities. Observations of this system are planned in the next season. 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 NSF (USA). References: Strohmeier, W., and Patterson, I., 1967. Bamberg Veroff., Band VIII, 82=1969, IBVS No. 330. Strohmeier, W., and Knigge, R., 1969, MNASSA Vol 28, 75. [BIBCODE 1969MNSSA..28...75S ] Kukarkin, et al., 1972, IBVS No. 717.