COMMISSION 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3831 Konkoly Observatory Budapest 18 January 1993 HU ISSN 0374 - 0676 THE RATES OF PERIOD CHANGE IN BS Aqr AND DY Her The rate of change in the pulsational period is in fact a measurement of stellar evolution rate. So, it is important to record the times of light maximum and to study the rates of period change of pulsating variable stars. Percy et al. (1980) collected forty-three times of light maximum occurred in the variable BS Aqr from 1935 to 1973 and five times of light maximum of BS Aqr in 1983 was observed by Meylan (1986). We observed the variable too in 1984, and obtained one moment of light maximum. These times, altogether forty-nine, are listed in Table 1. Mahdy et al. (1980) collected sixty times of light maximum occurred in the variable DY Her from 1938 to 1979, including their own observational results. We obtained three times of light maximum of the variable in 1981. These moments, altogether sixty-three, are listed in Table 2. We not only collected aforecited observational data, but also redetermined certain times of light maximum of BS Aqr and DY Her using the original data, and drew the O-C diagrams of them (Figures 1 and 2), computed their rates of period change. If the linear fitting formula of the times of light maximum T_max with cycle number E is: T_max=T_01+P_01*E, the quadratic fitting formula is: T_max=T_02+P_02*E+0.5BetaE^2 then T_01, P_01, T_02, P_02 and Beta of the variable stars are listed below: star T_01(HJD) P_01(days) T_02(HJD) P_02(days) Beta(day/cycle) BS Aqr 2428095.3350 0.197822604 2428095.3303 0.197822854 -5x10^-12 +-9 +-16 +-13 +-56 +-1x10^-12 DY Her 2433439.4876 0.148631221 2433439.4868 0.148631303 -2.11 x 10^-12 +-1 +-4 +-1 +-10 +-0.25x10^-8 [FIGURE 1] Figure 1. The O-C Diagram of BS Aqr Table 1 Time of Light Maximum and O-C Residuals of BS Aqr for Linear and Quadratic Fits No: T_max E (O-C)_L (O-C)_Q W. Ref. 1 28095.338 0.0 0.0030 0.0077 1.0 An 2 29111.745 5138.0 -0.0025 0.0009 1.0 As 3 29899.266 9119.0 -0.0133 -0.0107 1.0 Sa 4 30187.304 10575.0 -0.0050 -0.0027 1.0 Sa 5 33027.446 24932.0 -0.0021 -0.0022 1.0 Sa 6 33862.460 29153.0 0.0026 0.0022 1.0 Sa 7 33888.365 29284.0 -0.0071 -0.0076 1.0 Sa 8 34211.422 30917.0 0.0056 0.0049 1.0 Sa 9 34400.335 31872.0 -0.0020 -0.0028 1.0 Sa 10 34961.366 34708.0 0.0041 0.0031 1.0 Sa 11 35631.392 38095.0 0.0049 0.0037 1.0 Sa 12 35696.472 38424.0 0.0013 0.0000 1.0 Sa 13 36040.0771 40161.0 -0.0115 -0.0128 0.1 Ki 14 36300.426 41477.0 0.0029 0.0015 1.0 Sa 15 36458.0904 42274.0 0.0027 0.0012 1.0 Sp 16 36460.854 42288.0 -0.0033 -0.0047 0.3 Sp 17 36461.8475 42293.0 0.0011 -0.0003 0.5 Sp 18 36874.112 44377.0 0.0033 0.0018 0.5 Ki 19 37561.3491 47851.0 0.0047 0.0031 0.5 TS 20 37561.5445 47852.0 0.0023 0.0007 0.5 TS 21 37562.5345 47857.0 0.0032 0.0016 0.5 TS 22 37563.5242 47862.0 0.0038 0.0022 0.5 TS 23 37564.5156 47867.0 0.0060 0.0045 0.5 TS 24 37582.5180 47958.0 0.0066 0.0050 0.5 TS 25 37583.3105 47962.0 0.0078 0.0062 0.5 TS 26 37584.2934 47967.0 0.0016 0.0000 0.5 TS 27 37584.4924 47968.0 0.0028 0.0012 0.5 TS 28 37911.4916 49621.0 0.0012 -0.0004 0.5 TS 29 37932.4617 49727.0 0.0021 0.0005 0.5 TS 30 37933.4552 49732.0 0.0065 0.0049 0.5 TS 31 37934.4383 49737.0 0.0005 -0.0011 0.5 TS 32 37946.3083 49797.0 0.0011 -0.0005 0.5 TS 33 37947.2960 49802.0 -0.0003 -0.0019 0.1 TS 34 39087.1561 55564.0 0.0060 0.0044 0.5 HP 35 41946.6714 70019.0 -0.0045 -0.0051 0.6 El 36 41946.8693 70020.0 -0.0044 -0.0050 0.5 El 37 41947.6620 70024.0 -0.0030 -0.0036 1.0 El 38 41947.8603 70025.0 -0.0025 -0.0031 0.5 El 39 41948.6500 70029.0 -0.0041 -0.0047 0.5 El 40 41948.8489 70030.0 -0.0030 -0.0036 0.5 El 41 41949.6400 70034.0 -0.0032 -0.0038 0.5 El 42 41950.6300 70039.0 -0.0023 -0.0029 1.0 El 43 41950.8295 70040.0 -0.0007 -0.0013 0.5 El 44 45612.7240 88551.0 -0.0004 0.0017 1.0 Me 45 45620.6380 88591.0 0.0007 0.0028 1.0 Me 46 45625.5830 88616.0 0.0002 0.0023 1.0 Me 47 45637.6470 88677.0 -0.0030 -0.0009 1.0 Me 48 45644.5720 88712.0 -0.0018 0.0003 1.0 Me 49 45997.0920 90494.0 -0.0017 0.0008 1.0 Pp An=Andrews (1936) As=Ashbrook (1943) El=Elst (1976) HP=Harding and Penston (1966) Ki=Kinman (1961) Me=Meylan et al.(1986) Pp=Present paper Sa=Satanova (1961) Sp=Spinrad (1959) TS=Tremko and Sajtak (1964) Table 2 Time of Light Maximum and O-C Residuals of DY Her for Linear and Quadratic Fits No: T_max E (O-C)_L (O-C))Q W. Ref. 1 29068.390 -29409.0 -0.0020 0.0021 0.1 MS 2 33366.807 -489.0 0.0001 0.0009 0.1 As 3 33371.857 -455.0 -0.0034 -0.0026 0.1 As 4 33442.607 21.0 -0.0019 -0.0011 0.1 As 5 33501.614 418.0 -0.0014 -0.0007 0.1 As 6 33506.671 452.0 0.0021 0.0028 0.1 As 7 33507.563 458.0 0.0023 0.0030 0.1 As 8 33509.640 472.0 -0.0015 -0.0008 0.1 As 9 33767.5172 2207.0 0.0005 0.0011 0.5 BM 10 33775.837 2263.0 -0.0031 -0.0025 0.5 Sm 11 33815.5243 2530.0 -0.0003 0.0003 0.5 Sm 12 34068.940 4235.0 -0.0008 -0.0004 0.5 Sm 13 34097.923 4430.0 -0.0009 -0.0005 0.5 Sm 14 34118.881 4571.0 0.0001 0.0005 0.5 Sm 15 34119.771 4577.0 -0.0017 -0.0013 0.5 Sm 16 34123.785 4604.0 -0.0007 -0.0003 0.5 Sm 17 34133.744 4671.0 0.0000 0.0004 0.5 Sm 18 34134.785 4678.0 0.0005 0.0009 0.5 Sm 19 34137.755 4698.0 -0.0021 -0.0017 0.5 Sm 20 34139.689 4711.0 -0.0003 0.0001 0.5 Sm 21 34149.794 4779.0 -0.0022 -0.0018 0.5 Sm 22 34159.4570 4844.0 -0.0002 0.0002 0.5 LD 23 34162.4295 4864.0 -0.0004 0.0000 0.5 LD 24 34178.4818 4972.0 -0.0002 0.0001 0.5 LD 25 34180.4140 4985.0 -0.0002 0.0001 0.5 LD 26 34182.4950 4999.0 -0.0001 0.0003 0.5 LD 27 34184.4277 5012.0 0.0004 0.0008 0.5 LD 28 34188.4390 5039.0 -0.0013 -0.0009 0.5 LD 29 34875.5633 9662.0 0.0008 0.0009 0.5 BM 30 34888.4937 9749.0 0.0003 0.0004 0.5 BM 31 34945.4190 10132.0 -0.0001 -0.0001 0.5 BM 32 34956.4177 10206.0 -0.0001 -0.0001 0.5 BM 33 34960.4316 10233.0 0.0007 0.0007 0.5 BM 34 35241.789 12126.0 -0.0008 -0.0009 0.5 Fi 35 35241.939 12127.0 0.0006 0.0005 0.5 Fi 36 35249.817 12180.0 0.0011 0.0010 0.5 Fi 37 35622.881 14690.0 0.0008 0.0005 0.5 Fi 38 35631.799 14750.0 0.0009 0.0007 0.5 Fi 39 36336.757 19493.0 0.0010 0.0006 0.1 Sp 40 36337.797 19500.0 0.0006 0.0002 0.1 Sp 41 36337.945 19501.0 0.0000 -0.0005 0.1 Sp 42 36338.836 19507.0 -0.0008 -0.0013 0.1 Sp 43 36404.3850 19948.0 0.0018 0.0013 0.5 Br 44 36681.8780 21815.0 0.0003 -0.0002 1.0 HL 45 36694.8097 21902.0 0.0011 0.0006 1.0 HL 46 36695.7010 21908.0 0.0006 0.0001 1.0 HL 47 36696.7410 21915.0 0.0002 -0.0003 1.0 HL 48 36703.7267 21962.0 0.0002 -0.0003 1.0 HL 49 36704.7676 21969.0 0.0007 0.0002 0.5 HL 50 36730.4806 22142.0 0.0005 0.0000 0.5 Br 51 36733.7500 22164.0 0.0000 -0.0005 1.0 HL 52 36747.7226 22258.0 0.0013 0.0007 1.0 HL 53 36782.6496 22493.0 -0.0001 -0.0006 1.0 HL 54 37075.4538 24463.0 0.0006 0.0000 1.0 Br 55 38476.0061 33886.0 0.0009 0.0001 0.5 Fd 56 39252.9024 39113.0 0.0018 0.0010 0.5 Ep 57 41508.3797 54288.0 0.0004 -0.0002 1.0 MS 58 41840.4222 56522.0 0.0007 0.0002 1.0 GH 59 43341.7445 66623.0 -0.0010 -0.0009 1.0 BE 60 44050.4181 71391.0 -0.0010 -0.0007 1.0 MS 61 44755.2290 76133.0 0.0006 0.0013 0.5 Pp 62 45795.3485 83131.0 -0.0012 0.0001 1.0 Pp Al=Alania (1954) As=Ashbrook (1954) BE=Breger et al. (1978) BM=Broglia and Masani (1955) Br=Broglia (1961) Ep=Epstein (1969) FA=Fitch et al.(1966) Fi=Fitch (1957) GH=Geyer and Hoffmann (1974) HL=Hardie and Lott (1961) LD=Lenouvel and Daguillon (1954) MS=Mahdy and Szeidl (1980) Pp=Present paper Sm=Smith (Ashbrook, 1954) Sp=Spinrad (1959) [FIGURE 2] Figure 2. The O-C Diagram of DY Her For both stars the rate of period change, beta, is negative, this means that the periods of light variations are decreasing. They are respectively - -(0.9±0.2) x 10^-8 day/year and - (0.52±0.06) x 10^-8 days/year. YANG DAWEI TANG QUINQUAN Department of Physics, Department of Physics, Hebei Teachers University, Sichuan Teachers College, Shijiazhuang 050016, China Nanchong 637002, China JIANG SHIYANG WANG HONGSHENG Beijing Astronomical Observatory, Beijing Astronomical Observatory, Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100080, China Beijing 100080, China References: Mahdy, H.A. and Szeidl, B. 1980, Commun. Konkoly Obs., No. 75, 18-19. [BIBCODE 1981CoKon..75....1S ] Meylan, G. et al., 1986, A. & Ap. Suppl. Ser., 64, 39-42. [BIBCODE 1986A&AS...64...25M ] Percy, J. R. et al., 1980, A. & Ap., 82, 173. [BIBCODE 1980A&A....82..172P ]