COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3691 Konkoly Observatory Budapest 11 December 1991 HU ISSN 0374 - 0676 PHOTOELECTRIC PHOTOMETRY OF TWO SMALL-AMPLITUDE RED VARIABLES D. H. Kaiser reported the photographic discovery of two 7th-magnitude red variables, which were designated DHK 12 and DHK 15 in his discovery lists (Kaiser et al. 1990, Kaiser 1990). These stars were thought to be SR type, but the periods were undetermined. To confirm the type and define the periods, I have made differential photoelectric observations of these stars during the past two seasons using a 28-cm Schmidt-Cassegrain telescope, Optec SSP-3 solid-state photometer, and V filter. The observations have been corrected for differential extinction and transformed to V of the UBV system. DHK 12 - BD +29 3730, HD 186860, SAO 68801, IRC +30391, NSV 12387 Six photoelectric observations from the 1989 season were reported earlier (Williams 1990). Table I presents 13 additional observations made on 12 nights in 1990. Figure 1 shows the 1990 light curve. [FIGURE 1] Figure 1. DHK 12 TABLE I. DHK 12 HJD 2440000+ (n) Delta V s.d. HJD (n) Delta V s.d. 8111.598 (3) +2.924 +0.006 8170.599 (3) +2.817 +0.018 8118.603 (3) 2.848 0.005 8176.605 (3) 2.850 0.019 8129.614 (3) 2.737 0.008 .633 (3) 2.864 0.009 8134.597 (3) 2.799 0.013 8177.593 (3) 2.868 0.006 8136.642 (3) 2.846 0.005 8184.609 (3) 2.911 0.010 8151.579 (3) 2.982 0.004 8191.627 (3) 3.018 0.013 8159.549 (3) 3.003 0.008 The comparison star was Phi Cygni. Single measures of the check star HR 7505 on 12 nights show a constant difference, the standard deviation of a single observation from the mean being +-0.007m. Based on Phi Cyg's magnitude, 4.69 V in The Bright Star Catalogue (Hoffleit and Jaschek 1982), the variable's observed range during the two seasons was 7.43 - 7.83 V. A Discrete Fourier Transform analysis of all the observations indicates a period of 43.0 days. DHK 15 - BD +10 2067, HD 85720, SAO 98835 Table II presents 17 observations from the 1989-90 and 1990-91 seasons. Figure 2 is the 1990-91 light curve. The comparison star was 31 Leonis. Twenty measures of the check star SAO 118138 on 17 nights have a standard deviation of a single observation from the mean of +-0.019m. Based on 31 Leo's magnitude, 4.37 V, in the Bright Star Catalogue, the variable's observed range was 7.78 - 8.13 V. DFT analysis yields a primary peak at P = 62.3 days and a secondary peak near 52 days. The second peak may [FIGURE 2] Figure 2. DHK 15 TABLE II. DHK 15 HJD 2440000+ (n) Delta V s.d. 7869.847 (4) +3.583 +-0.009 7953.697 (3) 3.527 0.011 7954.675 (4) 3.486 0.005 7971.635 (3) 3.552 0.028 7977.674 (4) 3.587 0.011 8000.643 (3) 3.535 0.021 8019.663 (4) 3.473 0.005 8041.601 (3) 3.609 0.006 8043.612 (3) 3.636 0.012 HJD (n) Delta V s.d. 8309.684 (6) +3.682 +-0.017 8323.631 (3) 3.459 0.005 8330.607 (3) 3.410 0.004 8353.593 (5) 3.671 0.007 8357.692 (3) 3.735 0.003 8362.632 (3) 3.762 0.001 8371.625 (3) 3.662 0.010 8377.609 (3) 3.460 0.018 represent a difference in the semiregular variable's actual period during the two brief seasons of observation or a 1-cycle per year alias. DAVID B. WILLIAMS 9270-A Racquetball Way Indianapolis, IN 46260 U.S.A. REFERENCES Hoffleit, D., and Jaschek, C., 1982, The Bright Star Catalogue, Yale University Observatory, New Haven. [BIBCODE 1982bscf.book.....H ] Kaiser, D. H., 1990, Inform. Bull. Var. Stars No. 3480. Kaiser, D. H., Baldwin, M. E., and Williams, D. B., 1990, Inform. Bull. Var. Stars No. 3442. Williams, D. B., 1990, Inform. Bull. Var. Stars No. 3443.