COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 983 Konkoly Observatory Budapest 1973 April 1 PHOTOMETRIC OBSERVATIONS OF SUSPECTED SMALL-AMPLITUDE CEPHEIDS In the course of a search for stable stars in the Cepheid instability strip, Fernie and Hube (1971) found several stars which were slightly variable in brightness. Since these stars lay in or near the instability strip, they were good candidates for small- amplitude Cepheid variables, but Fernie and Hube's observations were too scattered in time to confirm the nature of the variability. This paper reports on photometric observations of these stars, obtained during a one-week run at Kitt Peak National Observatory. The five stars on the program are listed in Table I. The spectral types and magnitudes are taken either from Fernie and Hube (1971) or from the Catalog of Bright Stars. Table I Program and Comparison Stars Comparison Stars Visual Program Star Name (Sp.T.,m_v or V) Spectrum Magnitude Variability epsilon Leo mu Leo (K2 III, 3.94) G0 II 2.96 variable ? HD 191010 HD 190788 (K5, 8.26) G3 Ib 8.6 constant ? HD 213482 HD 213419 (A0, 8.6) F8 Ib 8.6 constant ? HD 239994 HD 214259 (A0, 8.6) F8 Ib 9.0 Cepheid variable HD 214847 HD 215177 (A0, 8.7) G0 Ib 8.1 constant Observations Photometric observations were obtained with the 41 cm telescope number 3 at Kitt Peak National Observatory during December 9-16, 1973. The photometric system consisted of a refrigerated 1P21 photomultiplier tube, a charge-integrating amplifier, and a chart recorder. Measurements were made through KPNO standard UBV filter set number 2, relative to the comparison stars listed in Table I. These measurements were corrected for differential extinction and reduced to the sun, but were left on the instrumental magnitude system. The measurements of epsilon Leo are slightly less accurate than those of the other stars, because the comparison star is not quite as suitable. The observations are listed in Table II and are plotted in Figure 1. Table II Photometric Observations of Suspected Small-Amplitude Cepheid Variables epsilon Leo - mu Leo HD 191010 - HD 190788 JD 2440000+ Delta(m) (V) Delta(m) (B) JD 2440000+ Delta(m) (V) Delta(m) (B) 2026.862 -0.908 -1.307 2027.609 +0.270 +1.033 2027.038 -0.914 -1.313 2028.580 +0.25: +1.055 2027.991 -0.848 -1.276 2029.570 +0.255 +1.032 2029.949 -0.906 -1.31: 2030.567 +0.237 +1.019 2030.922 -0.902 -1.317 2031.576 +0.249 +1.015 2031.900 -0.920 -1.329 2032.571 +0.26: +1.018 2032.903 -0.927 -1.331 HD 213482 - HD 213419 HD 239994 - HD 214259 JD 2440000+ Delta(m) (V) Delta(m) (B) JD 2440000+ Delta(m) (V) Delta(m) (B) 2027.628 -0.684 +0.178 2027.664 +0.689 +1.412 2028.602 -0.686 +0.168 2028.611 +0.626 +1.375 2029.594 -0.692 +0.166 2029.602 +0.872 +1.709 2030.583 -0.700 +0.163 2030.590 +0.667 +1.394 2031.591 -0.697 +0.168 2031.598 +0.660 +1.410 2032.594 -0.688 +0.175 2032.600 +0.873 +1.739 HD 214847- HD 215177 JD 2440000+ Delta(m) (V) Delta(m) (B) 2028.591 -0.541 +0.485 2029.586 -0.531 +0.482 2030.578 -0.537 +0.485 2031.586 -0.528 +0.495 2032.587 -0.534 +0.488 Discussion of Individual Stars epsilon Leo: Fernie and Hube (1971) found that this star was variable with a range of 0.m1 or more. Significant variations occurred on a time scale of one day. The present observations give similar results, with a time scale of variation of a few days. epsilon Leo does not lie in the instability strip if the luminosity class (II) is correct, but may do so if the luminosity class is actually (II-Ib). In this case a pulsation period of a few days would be reasonable. There is no evidence, amid the vast amount of radial velocity data for this star, that epsilon Leo varies in radial velocity by more than about 2 km.s^{-1}. Furthermore, the rotational period of a giant star would be much greater than a few days, so that it is unlikely that the variations are due to a rotational phenomenon. The variations may possibly be similar to the irregular variations which are frequently found in K and M giants. HD 191010: There is no significant variation in brightness during the period of observation, though the scatter is rather larger than might be expected. HD 213482: The variation in B and V during one week is only 0m.015, but may possibly be systematic. If the total range is as great as 0m.06, as found by Fernie and Hube (1971), then the "period" would be several weeks. The expected period of a Cepheid variable of spectral type F8Ib would be a week or less. [FIGURE 1] Photometric observations of epsilon Leo and HDE 239994. The comparison stars are indicated on the figure. The scale on the left applies to the blue magnitude differences (filled circles) and that on the right applies to the visual magnitude differences (open circles). The dashed lines represent the presumed trend of the observations. HD 239994: This star is a Cepheid variable with a period of 3 days and ranges in B and V of 0m.4 and 0m.3, respectively. Fernie and Hube (1971) found a total range of 0m.2 in four observations. HD 214847: The variation, on five consecutive nights, is no more than 0m.01 in B or V. Fernie and Hube (1971) found a total range of 0m.05 in four observations. The period of a Cepheid variable of spectral type G0Ib would be about ten days; the present observations do not support the conclusion that this star is a Cepheid variable. Acknowledgement I wish to thank Dr. J.D. Fernie for suggesting this project, and for making the individual observations by Fernie and Hube (1971) available to me. I also thank the Director of Kitt Peak National Observatory for the use of facilities there. Mrs. D.L. Harmer, Royal Greenwich Observatory, and Mr. G.C. Aikman, Dominion Astrophysical Observatory, provided unpublished data on the velocity of epsilon Leo. This project was supported by an operating grant from the National Research Council of Canada. JOHN R. PERCY David Dunlap Observatory University of Toronto Toronto, Canada M5S 1A7 Reference: Fernie, J.D., and Hube, J.O. (1971), Astrophys.J. 168, 437 [BIBCODE 1971ApJ...168..437F ]