COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1000 Konkoly Observatory Budapest 1975 May 20 UBV AND SPECTRAL DATA ON RV PICTORIS Photoelectric UBV observations of the eclipsing binary RV Pictoris were made with one of the 16-inch (40 cm) telescopes at the Cerro Tololo Interamerican Observatory (CTIO) on four nights in November and December, 1971, using HD 31507 (CPD -52deg603) as a comparison star; suitable standards were measured to correct for atmospheric extinction and express the results in the UBV system. The uncertainty of an individual observation is estimated to be 0m.015. The mean values obtained from 17 observations of HD 31507 are: V = 8.048 B-V = 0.000 U-B = -0.019 The three light curves were used to determine the time of primary minimum, which combined with that given by Hoffmeister (1942) yielded the following ephemeris: Primary minimum = JD hel 2441286.757 + 3d.971780 E This is in good agreement with Knipe's determination (Knipe 1969). If the uncertainty in Hoffmeister's minimum is 0d.01, the uncertainty in the period is 0d.000003. The results of the UBV observations are given in Table 1. The heliocentric time corresponds to the V observation, and the phases were calculated with the ephemeris given above. Ten spectrograms of RV Pic were obtained by Virpi Niemela in November and December 1971 with the CTIO 36-inch (90 cm) and 60-inch (150 cm) telescopes, at dispersions of 125 and 80 A mm^(-1), respectively. Only the spectrum of the primary component is visible. The spectral type was determined by comparison with spectrograms of standard stars taken by O.H. Levato with the same equipment. The Balmer and metallic lines suggest a type A5 V, while the Ca II K line yields a slightly earlier type, A2 or A3; perhaps this is an indication of very mild metallicity, but a confirmation is desirable. The radial velocities were measured at La Plata Observatory with a Grant comparator, and they are represented in Figure 1. The scatter is large, but a system velocity of 20 +- 10 km s^(-1) and a semiamplitude K of 25 +- 5 km s^(-1) are suggested. TABLE 1 Photometric Observations of RV Pictoris JD hel_V phase_V V phase_B B phase_U U 2441000+ 282.599 0.9531 9.953 0.9536 10.071 0.9539 10.179 .609 .9556 9.925 .9561 10.089 .9564 10.145 .617 .9576 10.006 .9579 10.139 .9581 10.198 .627 .9602 10.059 .9604 10.199 .9607 10.263 .702 .9790 10.872 .9793 11.240 .9796 11.363 .713 .9818 11.073 .9821 11.419 .9823 11.509 .722 .9841 11.244 .9842 11.631 .9846 11.766 .729 .9858 11.345 .9863 11.833 .9866 12.014 286.585 .9567 9.963 .9572 10.089 .9577 10.151 .595 .9592 10.038 .9593 10.147 .9595 10.270 .613 .9637 10.165 .9640 10.335 .9645 10.383 .621 .9658 10.254 .9660 10.437 .9665 10.478 .630 .9680 10.333 .9683 10.492 .9685 10.608 .647 .9723 10.508 .9726 10.734 .9728 10.787 .654 .9741 10.615 .9743 10.847 .9746 10.849 .661 .9758 10.713 .9761 10.963 .9763 11.035 .678 .9801 10.949 .9804 11.290 .9809 11.392 .687 .9824 11.143 .9826 11.486 .9829 11.581 .695 .9844 11.268 .9849 11.676 .9851 11.846 .704 .9867 11.457 .9869 11.864 .9872 12.081 .713 .9889 11.565 .9894 12.135 .9897 12.404 .727 .9924 11.777 .9927 12.406 .9930 12.694 .740 .9957 11.969 .9960 12.594 .9962 12.867 .749 .9980 12.005 .9985 12.804 .9987 13.028 .771 .0035 11.983 .0038 12.673 .0039 12.911 .784 .0068 11.804 .0073 12.424 .0074 12.657 .797 .0101 11.599 .0103 12.063 .0106 12.385 .810 .0133 11.393 .0136 11.759 .0141 11.845 287.713 .2407 9.650 .2412 9.763 .2415 9.815 .722 .2430 9.645 .2435 9.787 .2436 9.813 .733 .2457 9.644 .2460 9.784 .2462 9.807 288.590 .4615 9.690 .4618 9.794 .4620 9.815 .599 .4638 9.697 .4643 9.806 .4648 9.864 .618 .4686 9.689 .4691 9.804 .4698 9.837 .632 .4721 9.680 .4723 9.794 .4728 9.834 .643 .4749 9.691 .4751 9.792 .4754 9.828 .662 .4796 9.702 .4801 9.806 .4804 9.877 .673 .4824 9.711 .4827 9.790 .4832 9.821 .683 .4849 9.713 .4852 9.791 .4857 9.846 .695 .4879 9.710 .4882 9.802 .4889 9.832 .719 .4940 9.725 .4942 9.816 .4947 9.860 .731 .4970 9.743 .4971 9.805 .4975 9.859 [FIGURE 1] RV Pictoris - Heliocentric Radial Velocities, km s^{-1} The scarcity of the observations does not permit a detailed analysis of the system; yet it is possible to make some rough calculations. Knowledge of K and the period allows us to estimate the mass function, if we assume a circular orbit; we find f(M)= 0.0064. If we adopt 2.2M_{sun} for the mass of the primary and suppose that the inclination is 90deg, we get a value of 0.35 M_{sun} for the mass of the secondary. The depths of the primary eclipse are 2m.45 in V, 3m.07 in B and 3m.24 in U (assuming constant brightness outside of eclipse). This imposes an upper limit to the depths of the secondary eclipse, even in the most favourable case of total eclipses and equal stellar radii the secondary eclipse cannot be deeper than 0m.12 in V, 0m.07 in B and 0m.06 in U. This is very near the observed values (in fact, Knipe (1969) gives 0m.15 in V for the secondary minimum); so we can safely conclude that both stars are approximately of the same size; and that the eclipses are almost total. It is thus very simple to obtain the difference in absolute visual magnitude between the components of the system as about 2m.3. Remembering the low mass of the secondary component, obtained on the assumption that the hotter star is on the main sequence, we see that we can place RV Pictoris in the selected group of Algol systems that have a subgiant component which is overluminous by more than 5 magnitudes (see e.g. Plavec 1973). I would like to thank V. Niemela for taking the spectrograms of RV Pic. The assistance and hospitality of the Director and staff of the Cerro Tololo Interamerican Observatory are gratefully acknowledged. ROBERTO H. MENDEZ Instituto de Astronomia y Fisica del Espacio Casilla de Correo 67 - Sucursal 28 Buenos Aires Argentina References: Hoffmeister, C. 1942, Astr.Nachr. 273, 88 [BIBCODE 1942AN....273...88H ] Knipe, G.F.G. 1969, Rep.Obs.Johannesburg, Circ., 7, 198 [BIBCODE 1969ROCi....7R.198K ] Plavec, M. 1973, I.A.U. Symposium No 51, p. 225 [BIBCODE 1973IAUS...51..216P ]