COMMISSION 27 OF THE I. A. U INFORMATION BULLETIN ON VARIABLE STARS NUMBER 233 Konkoly Observatory Budapest 1967 November 4 TWO PULSATING VARIABLES WITH PERIODS CLOSE TO ONE DAY The stars were found and estimated on plates taken mainly by the writer with the 10" Metcalf telescope of the Boyden Observatory. They both provide classical examples of spurious periods brought in by making the observations near the meridian. 1.- The first variable is a new one, discovered with the Zeiss-blinkmicroscope of the Astronomical Institute of the University of Louvain. Its position is R.A.(1875)=12h59m29.4s D.(1875)=-68d13.3' [FIGURE 1] Var. No.1 The square measures about 1/2deg x 1/2deg Further identification is made easy by the environment chart Figure 1. [FIGURE 2] Abscissae=J.D. -2437000 Figure 2 shows the "observed" changes in brightness, which would suggest a long period variation of P~355d were it not that the difference in slope between the ascending and descending branches had the wrong sign. This is indicative of a period slightly longer than one day and of a lightcurve with the normal skewness, which has been scanned backward by observations made at one day intervals. The apparent period is then the "beat" period P_b between the real period P of the variation and the one day period of the observations. The three are related by the formula | 1/P - 1/1 | = 1/Pb (1) In this way the correct period was found to be P=1.00282d+-0.00003d. Control plates taken afterwards over a seven hours run have shown a variation in agreement with a period of this order. [FIGURE 3] The corresponding lightcurve is given in numerical form in Table 1 and shown graphically in Figure 3. Phases were reckoned from JD 2436000.000d and magnitudes heve been derived from star counts and their comparison with the Tables in Groningen Publication No 43. Using our mean epoch the times of maximum brightness can be predicted from the ephemeris t (max.light) hel = JD 2438156.063d + 1.002282d E Table 1 n phase m n phase m n phase m 10 0.011p 13.58 10 0.218p 12.56 10 0.447p 13.02 10 .026 13.56 10 .231 12.56 10 .483 13.05 10 .040 13.54 10 .241 12.56 5 .514 13.01 10 .055 13.48 10 .255 12.49 4 .535 13.20 10 .071 13.32 10 .271 12.56 3 .558 13.24 10 .081 13.13 10 .293 12.56 1 .682 13.83 10 .093 13.21 10 .318 12.70 3 .725 13.83 10 .104 12.98 10 .341 12.73 3 .790 13.83 10 .126 12.77 10 .361 12.83 2 .876 14.33 10 .154 12.59 10 .376 12.85 3 .931 13.98 10 .174 12.49 10 .390 13.02 10 .950 13.88 10 .191 12.58 10 .406 12.93 10 .980 13.79 10 .206 12.61 10 .423 13.11 6 - - 2.- The other star proved to be the already named variable CE Oph, with coordinates R.A.(1900)=16h47m28s, D.(1900)= -26d07.4' according to Kukarkin and Paranago's GCVS, but of unknown type and period. [FIGURE 4] Var. No. 2 The square is about 1/2deg - 1/2deg Here a treatment by least squares of the 12 best observed minima led to a period P=15.3873d with no more than normal scatter of the observations around the resulting mean lightcurve. But that lightcurve very similar to the one represented in Figure 5, is of a quite uncommon shape for the period in question. For periods around 16.d one expects indeed to find, not a fairly symmetric lightcurve of rather small amplitude, but a lightcurve with a hump on its ascending branch, followed by a very steep rise to a sharp maximum and then a slow descent. For this reason the period found was again believed to represent but the "beat" period between the real period of the star and the one day period of the observations. By applying again formula (1) and by treating by least squares the 19 minima listed in Table 2, we found the final period P=1.067159d +-0.000032d (m.e.). [FIGURE 5] Table 2 JD_min E O-C JD_min E O-C 2437144.333 0 +0.093d 2437526.219d 358 -0.063d 145.312 1 + .005 527.247 359 - .103 146.297 2 - .077 8178.416 969 + .099 162.284 17 - .098 195.401 985 + .010 462.321 298 + .068 257.263 1043 - .023 464.374 300 - .014 529.486 1298 + .074 493.355 327 + .155 941.406 1684 + .071 494.342 328 + .075 989.275 1729 - .082 495.303 329 - .032 9020.220 1758 - .085 496.331 330 - .071 Table 3 n Phase m n Phase m n Phase m 10 0.022p 13.26 10 0.359p 13.90 10 0.708 13.27 10 .074 13.54 10 .387 13.93 10 .750 13.17 10 .109 13.53 10 .430 13.84 10 .779 13.19 10 .157 13.70 10 .467 13.80 10 .813 13.17 10 .203 13.73 10 .495 13.67 10 .861 13.17 10 .231 13.87 10 .530 13.56 10 .920 13.20 10 .258 13.90 10 .569 13.56 11 .977 13.21 10 .288 13.90 10 .602 13.45 10 .313 13.89 10 .626 13.36 10 .338 13.90 10 .661 13.32 Table 3 and Figure 5 give the corresponding lightcurve resp. in numerical and in graphical form. Just as in the case of the first variable phases were reckoned from JD 2436000.000d and magnitudes derived from star counts. The final ephemeris proposed is t (max. light) hel.=JD 2437794.802+1.067159d E The pronounced difference in shape between the lightcurves of stars having so nearly the same period deserves a mention. A. VAN HOOF Astron. Institute University of Louvain Belgium