COMMUNICATIONS             MITTEILUNGEN
                     FROM THE                     DER
                KONKOLY OBSERVATORY            STERNWARTE
                      OF THE            DER UNGARISCHEN AKADEMIE
          HUNGARIAN ACADEMY OF SCIENCES    DER WISSENSCHAFTEN

                            BUDAPEST - SZABADSAGHEGY



                                   No. 75.



                      B. SZEIDL and HAMID A. MAHDY

                   PERIOD CHANGES IN DWARF CEPHEIDS, II 
                   YZ BOOTIS, XX CYGNI AND DY HERCULIS




                                BUDAPEST, 1981


PERIOD CHANGES IN DWARF CEPHEIDS, II YZ BOOTIS, XX CYGNI AND DY HERCULIS ABSTRACT The period changes in the dwarf cepheids YZ Boo, XX Cyg and DY Her are discussed and O-C diagrams of these stars are constructed. The period of XX Cyg changed abruptly in 1942 (Delta P = +87x10^-9 day = +0.0075 sec). Besides the sudden increase of the period, it has also shown small fluctuations. With regard to YZ Boo there may be a slight continuous increase (at a rate beta = +10.6x10^-13 day cycle^-1 = +3.2x10^-2 sec century^-1) in its period. The period of DY Her has shown a definite continuous decrease at a rate beta = -37.2x10^-13 day cycle^-1 = -7.9x10^-2 sec century^-1 during the time interval covered by photoelectric observations (1951-1979). INTRODUCTION As a continuation of our previous work (Mahdy and Szeidl, 1980) we publish here our results on the period changes in the dwarf cepheids YZ Boo, XX Cyg and DY Her. A description of the equipment used both for our photographic and our photoelectric observations can be found in several publications of the Konkoly Observatory (see e.g. Olah and Szeidl, 1978). The observations presented here represent the work of the staff of Konkoly Observatory. The photographic plates were obtained by Dr. Julia Balazs (2 plates, 40 exp.), Mr. D. Elter (2 plates, 36 exp.), Mr. K. Gefferth (1 plate, 11 exp.) and Mr. S. Horvath (1 plate, 17 exp.). The table below summarizes the photoelectric observations of all observers concerned. Table 1 Observer YZ Boo XX Cyg DY Her Total L. Csank 427 126 - 553 L. Detre 60 175 - 235 M. Lovas 24 - - 24 K. Olah 95 - - 95 G. Paal 233 36 - 269 P. Sarkany 71 - - 71 L. Szabados 101 - - 101 B. Szeidl 261 349 224 834 Total 1272 686 224 2182 All the available observations on each star are discussed separately. We constructed the O-C diagrams using only photographic and photoelectric observations, and then by making use of the diagrams we studied the period changes of YZ Boo, XX Cyg and DY Her. YZ BOOTIS The variability of the star YZ Boo = BD +37 2635 = S 4768 = CSV 2335 was discovered by Hoffmeister (1949) at Sonneberg Observatory. He reported a light variation of one magnitude by estimating the Sonneberg sky-patrol plates. Eggen (1955) observed the star photoelectrically at Lick Observatory in 1955 and found it to vary in light with a period near 2 1/2 hours. He obtained 32 photoelectric observations without filters but did not give any epoch of maximum. Nevertheless two epochs could be determined in his figure. Tsesevich (1958, 1966), using old Moscow and Odessa sky-patrol plates, determined two photographic epochs for the years 1939 and 1954. He also made some visual observations in 1957. In his book (Tsesevich, 1966) he also published some visual epochs of maximum observed by Migach and Sacharov. Broglia and Masani (1957) carried out extensive photoelectric photometry of the star. During five nights in 1956 they obtained 95 blue and 97 yellow observations. They deduced 6 epochs of maximum and arrived at a period of 0.1041138 day. They found some evidence of the variations of the light curve from cycle to cycle even though their data cover only about 6 cycles out of a possible 105 in an 11 day interval. In the fifties Spinrad (1959) made a detailed investigation of RR Lyrae stars. YZ Boo was also included in the programme and he collected 32 yellow and 31 blue photoelectric observations of this star during three nights. Spinrad also found some evidence for light curve variation, but the amplitude variation was less than 0.1 mag in blue. Ahnert (1959) and Strelkova (1960, 1964) observed the star visually and obtained six maxima in 1959 and one maximum in 1958, respectively. The first systematic photographic photometry of the star was carried out by Tremko and Antal (1959) at Skalnate Pleso Observatory in 1959. Based on their 162 photographic magnitudes they gave five epochs of maximum light and determined a period of 0.104 001 91 day. In 1960 Broglia (1961) secured 189 blue observations of the variable at Merate Observatory and obtained six new epochs of maximum. Combining these new maxima with the old ones he was able to determine a highly accurate value of the period of YZ Boo: 0.104091543 day. Heiser and Hardie (1964) obtained a total of 216 photoelectric observations on the UBV system. They found that the ascending branches of the light curve and the amplitudes were relatively repetitive but the descending branch might be subject to small changes from cycle to cycle. Near the 0.2 phase they detected undoubtedly real variations among various cycles. They also carried out a detailed investigation of the colour variation of the variable at different phases of light variation. Fitch et al. (1966) obtained 48 UBV observations in 1964; these observations also provided an opportunity to determine the accurate photometric characteristics of the star and a new epoch of maximum. Gieren et al. (1974) carried out photoelectric UBV photometry of the star on one night in 1974. They observed three consecutive cycles and found distinct changes in shape and amplitude of the light curve and mean luminosity of the variable. Since Gieren et al. did not investigate the constancy of the comparison star they used, some doubts arise in connection with the light curve changes (especially with the change in mean luminosity). They used all available photoelectric data and found the improved period: 0.10409156 day. At Konkoly Observatory we commenced to observe YZ Boo in two colours in 1959. Since that time we have obtained 628 yellow and 644 blue observations. These are transformed to the international UBV system and are given in Tables 8 and 9, respectively, in the sense variable minus comparison. As comparison star we used BD +37 2634 (9.0). On two fairly poor nights we made tie-in observations of this star into the UBV system and obtained the magnitude and colour: V = 10.14m and B-V = 0.60m. The comparison star mostly used by others was BD +37 2639 for which Spinrad (1959) determined the following visual brightness and colour: V = 9.02m and B-V = 1.38m. The light curves obtained at Konkoly Observatory in the years 1954, 1973, 1974, 1975 and 1979 show slight differences which can be ascribed to the observational errors and uncertainties in the transformation to the international system. The fairly large scatter of the observations in 1959, however, indicates that some real light curve variation may be present among the different cycles. It may well be worth trying to subject the homogeneous 1959 data to a careful period analysis in order to search for a beat period. In Figure 1 we plotted the 1959 data according to phase. In Table 2 we have gathered all reliable data available to us pertaining to times of maximum brightness except the visual observations. Because of the large errors in the visual epochs of maximum we have simply ignored them. We used only the yearly means of those photoelectric maxima that are certain when carrying out a least-squares solution for the period. The resulting linear ephemeris is: Max. hel. = J.D. 2442146.3544 + 0.104091551*E +-.0003 +-6 or if we take into account the quadratic term, as well: Max. hel. = J.D. 2442146.3543 + 0.104091580d*E + 5.3dx10^-13 E^2. +-.0002 +-14 +-2.6 Figure 1: Delta V and Delta B observations of YZ Boo made in the year 1959, plotted against phase It appears from the photoelectric works of Eggen (1955), Broglia and Masani (1957), Spinrad (1959), Broglia (1961), Heiser and Hardie (1964), Fitch et al. (1966), Gieren et al. (1974) and ourselves that the times of maximum recur periodically within the accuracy of measurements (about +-0.0015 day). Nevertheless, a slight continuous increase of the period (10.6x10^-13 day/cycle) may have taken place in the interval 1955-1979. Further photoelectric observations will enable a decision to be made on the constancy of or the increase in the period. Figure 2: O-C diagram of YZ Boo Table 2 Photographic and photoelectric maxima of YZ Boo year J.D.max.hel. Remarks O-C E mean(O-C) mean(E) n 1939 2429403.3603 pg Ts -0.0023 -122421 -0.0023 -122421 1 1954 (34926.3665: pg Ts +0.0103: - 69362) 1955 35282.766 pe Eg^1 +0.0003 - 65938 +0.0002 - 65937 2 .870 pe Eg^1 +0.0002 - 65937 1956 35688.4090 pe BM -0.0015 - 62041 -0.0001 - 61993 5 35689.4497 pe BM -0.0017 - 62031 35695.3862 pe BM +0.0016 - 61974 .4900 pe BM +0.0013 - 61973 35698.4032 pe BM -0.0001 - 61945 (35699.341: pe BM +0.0009: - 61936) 1958 36428.8140 pe Sp +0.0003 - 54928 +0.0009 - 54923 2 36429.7520 pe Sp +0.0015 - 54919 1959 36603.4867 pg TA +0.0074 - 53250 +0.0030 - 53210 5 36606.4985 pg TA +0.0005 - 53221 36607.4397 pg TA +0.0049 - 53212 .5403 pg TA +0.0014 - 53211 36613.4727 pg TA +0.0006 - 53154 36709.5510 pe Pp +0.0024 - 52231 -0.0005 - 52148 13 36712.4634 pe Pp +0.0002 - 52203 36713.3985 pe Pp -0.0015 - 52194 .5031 pe Pp -0.0010 - 52193 36714.4389 pe Pp -0.0020 - 52184 36716.4174 pe Pp -0.0012 - 52165 .5222 pe Pp -0.0005 - 52164 36717.3545 pe Pp -0.0010 - 52156 36723.4963 pe Pp -0.0006 - 52097 36724.4332 pe Pp -0.0005 - 52088 .5380 pe Pp +0.0002 - 52087 36725.3701 pe Pp -0.0004 - 52079 .4733 pe Pp -0.0013 - 52078 1960 37077.5112 pe Br -0.0010 - 48696 -0.0005 - 48376 5 37098.4340 pe Br -0.0006 - 48495 37120.3975 pe Br -0.0005 - 48284 .5010 pe Br -0.0010 - 48283 37137.3654 pe Br +0.0005 - 48121 (37168.385: pe Br +0.0008: - 47823) 1963 38206.6955 pe HH -0.0019 - 37848 -0.0009 - 37785 4 38209.8200 pe HH -0.0001 - 37818 38214.7130 pe HH +0.0006 - 37771 38221.6845 pe HH -0.0021 - 37704 1964 38466.9260 pe FA -0.0003 - 35348 -0.0003 - 35348 1 1973 41860.4151 pe Pp +0.0002 - 2747 +0.0002 - 2747 1 1974 42146.3546 pe GA +0.0002 0 -0.0002 + 197 2 (42183.4164 pg Bu +0.0054 + 356) 42187.4700 pe Pp -0.0006 + 395 1975 42464.5624 pe Pp +0.0001 + 3057 -0.0001 + 3338 4 .6666 pe Pp +0.0002 + 3058 42522.4374 pe Pp +0.0002 + 3613 42523.4772 pe Pp -0.0009 + 3623 1979 43936.6255 pe Pp +0.0005 + 17199 +0.0005 + 17199 1 Remarks to Table 2: pg = photographic; pe = photoelectric; Ts = Tsesevich (1958, 1966); Eg = Eggen (1955); BM = Broglia and Masani (1957); Sp = Spinrad (1959); TA = Tremko and Antal (1959); Br = Broglia (1961); HH = Heiser and Hardie (1964); FA = Fitch et al. (1966); GA = Gieren et al. (1974); Bu = Busch (1976); Pp = Present paper; ^1 = epoch determined by us Unfortunately, not only do the visual observations usually have large errors but the photographic ones, too. Tremko's and Antal' s (1959) careful photographic work shows that the accuracy of the photographic maximum is, at best, about 0.005 day. It may, however, exceed 0.01 day in an average case (see, for example, the maximum determined by Tsesevich, 1958, from the Odessa photographic, material for the year 1954). In view of this, we should not attribute too much weight to the early photographic maximum obtained from the Moscow plate material. We cannot, however, preclude the possibility of a sine wave-like O-C diagram, i.e. a long-term periodic change in the period of YZ Boo. XX CYGNI The variability of this star was announced by Ceraski (1904) who stated that the range of light variation was from 10.7 to 11.6 magnitude, the period about 3.2 hours, and the light curve resembled the "cluster variables". The star received the preliminary designation 14.1904. Shortly after the discovery of the light variation of XX Cygni its visual observations were commenced. Between 1904 and 1911 more than 2600 visual estimations had been obtained and almost 150 visual epochs of light maximum were deduced from these observations. Schwab (1906) gave a period of 0.134859 day and found the light maximum and minimum to be fairly constant. Graff (1906) obtained a slightly shorter period: 0.134 846 day. Blazhko (1906) using his own visual observations of the years 1904, 1905 and 1906 arrived at the elements: Max. hel. = J.D. 2416563.411 + 0.1348643d*E. He found that light curve variation was present. Luizet (1908) and Nijland (1911) made further visual observations and gave the values of the period: 0.1348645 day and 0.1348650 day, respectively. The first photographic observations were made by Parkhurst and Jordan (1906). Their 48 observations were obtained with 6 minute exposure time. The light variation was confirmed but their period was too short. A comprehensive study of the light variation of XX Cyg was carried out by Kron (1912). He reduced all the visual observations obtained up to 1911 to the Potsdam visual system and critically discussed the data. He derived 140 epochs of maximum light and gave the elements with a quadratic term: Max. hel. = J.D. 2416563.41065 + 0.13486522d*E - 0.1578dx10^-10 * E^2. According to Kron there exists a secondary maximum on the descending branch of the light curve about half a period from the main maximum, and this secondary maximum oscillates in the way given by the formula: 0.0625d - 0.0160d sin [2pi/7.2(E/1000+0.8)] Shapley and Shapley (1915) observed the star at Mt. Wilson in 1914 and 1915 and obtained 40 photographic observations with 1 minute exposure time and 37 photovisual observations with 2 minute exposure time. They argued against the existence of a secular term introduced by Kron (1912) but they found that neither the shape of the light curve nor the range was constant for successive periods and suspected a short-period oscillation in the time of maximum. Shapley and Shapley gave three epochs of maximum light for 1914 and one epoch for 1915. Two of the epochs of 1914 were, however, very uncertain and therefore we omitted them from our list of photographic and photoelectric maxima (Table 3). A further 265 visual observations were obtained by Blazhko (1922) in 1919 and 1921. Supplementing the list of maxima by his 7 and 8 visual maxima from the years 1919 and 1921, respectively, Blazhko also questioned the secular variation of the period but he stated that periodic variations were present and gave the new elements: Max.hel. = J.D. 2416563.4098 + 0.134865027d*E + 0.00175d sin(0.0103deg*E + 22.6deg) Nijland (1923) published his 227 original visual observations which had already been discussed by Kron (1912). A rediscussion of these data definitely showed that no secondary wave was present, and that the period of XX Cyg was sensibly constant: P = 0.13486527 day. Nijland also doubted Kron's quadratic term. Important photographic observations were made by Jordan (1929) in the years 1915 and 1921. He obtained 17 plates (containing 74 exposures) on six different nights. Exposures were in general 10 minutes in length. Jordan did not find any definite difference in the shape of the light curve or the phase of maximum at different cycles. He gave the period as P = 0.134864907 day. Blazhko (1936) continued his visual observations and obtained a further 576 visual estimates from 1923 to 1934. Curiously enough, in contrast with Jordan (1929), Blazhko again found a periodic variation in the phase of light maxima: Max. hel. = J.D. 2416563.410 + 0.134865014d + 0.0019d sin(0.01deg*E + 20deg). Table 3 Photographic and photoelectric maxima of XX Cyg year J.D.max.hel. Remarks O-C E mean O-C mean E n 1905 2417172.596 pg PJ^1 +0.0050 -100089 +0.0043 -100072 3 17175.564 pg PJ^1 +0.0060 -100067 17176.504 pg PJ^1 +0.0019 -100060 1914 20366.8729 pg SS +0.0027 - 76404 +0.0027 - 76404 1 1915 20574.9729 pg SS +0.0059 - 74861 +0.0041 - 74221 4 20687.716 pg Jo^1 +0.0018 - 74025 20689.742 pg Jo^1 +0.0048 - 74010 20692.708 pg Jo^1 +0.0038 - 73988 1921 22963.699 pg Jo^1 +0.0019 - 57149 +0.0019 - 57149 1 1933 27189.560 pg Kl +0.0008 - 25815 +0.0008 - 25815 1 1935 27961.392 pg De 0.0000 - 20092 +0.0006 - 19854 7 27962.471 pg De +0.0001 - 20084 27979.465 pg De +0.0011 - 19958 27980.410 pg De +0.0020 - 19951 27983.511 pg De +0.0011 - 19928 27993.490 pg De +0.0001 - 19854 28093.290 pg De -0.0001 - 19114 1937 28694.520 pg Kl +0.0015 - 14656 +0.0015 - 14656 1 1950 33538.468 pg Pp +0.0007 + 21261 +0.0007 + 21261 1 1952 34150.486 pg Pp +0.0011 + 25799 +0.0011 + 25799 1 1953 34576.390 pg Pp +0.0012 + 28957 +0.0012 + 28957 1 (34630.213 pg Al +0.0130 + 29356) 1954 35035.336 pg Pp +0.0013 + 32360 +0.0013 + 32360 1 1955 35258.5370 pe De^2 +0.0006 + 34015 +0.0010 + 34518 2 35394.3468 pe De^2 +0.0013 + 35022 1957 36077.4395 pe De^2 +0.0024 + 40087 +0.0017 + 40320 7 .5734 pe De^2 +0.0015 + 46088 36080.4055 pe De^2 +0.0014 + 40109 36081.4852 pe De^2 +0.0022 + 40117 36136.2395 pe De^2 +0.0013 + 40523 36143.2538 pe De^2 +0.0026 + 40575 36165.2350 pe De^2 +0.0008 + 40738 1958 36403.4079 pe Pp +0.0020 + 42504 +0.0020 + 42635 3 .5430 pe Pp +0.0022 + 42505 36456.4096 pe Pp +0.0017 + 42897 1959 36815.4216 pe Pp +0.0029 + 45559 +0.0023 + 45666 4 .5565 pe Pp +0.0029 + 45560 36844.2818 pe Pp +0.0020 + 45773 .4160 pe Pp +0.0013 + 45774 1965 38886.9495 pe FA^3 +0.0033 + 60919 +0.0033 + 60919 1 1972 41538.5311 pe Pp +0.0028 + 80580 +0.0028 + 80580 1 1974 42278.4010 pe Pp +0.0029 + 86066 +0.0030 + 86400 4 42335.7191 pe MF^3 +0.0033 + 86491 42338.6860 pe MF^3 +0.0032 + 86513 42340.7085 pe MF^3 +0.0027 + 86528 1975 42655.7548 pe MF^3 +0.0042 + 88864 +0.0042 + 88864 1 1976 42973.7675 pe MF^3 +0.0051 + 91222 +0.0045 + 91276 5 .9020 pe MF^3 +0.0047 + 91223 42980.7795 pe MF^3 +0.0041 + 91274 .9146 pe MF^3 +0.0043 + 91275 42995.7495 pe MF^3 +0.0041 + 91385 1980 44455.3944 pe Pp +0.0043 +102208 +0.0043 +102208 1 Remarks to Table 3: PJ = Parkhurst and Jordan (1906); SS = Shapley and Shapley (1915); Jo = Jordan (1929); Kl = Kleissen (1938); De = Detre (1936); Pp = Present paper; Al = Alania (1954); FA = Fitch et al. (1966); ME = McNamara and Feltz (1980); ^1 = determined by Detre (1936); ^2 = from Detre's early unpublished photoelectric observations; ^3 = determined by us In order to disentangle the question of periodic variation Detre (1936) made a thorough investigation of XX Cyg. He made 316 photographic observations on 9 nights in 1935 between 6 June and 17 October. He discussed all the data on the star published up to 1935 and redetermined the epochs of maximum lights observed by different authors. He found no definite light curve variation and gave the linear elements: Max. hel. = J.D. 2416564.4897 + 0.134865016 2d*E. Kleissen (1938) also carried out photographic photometry on XX Cyg at Hamburg Observatory and obtained 44 observations in 1933 and 12 observations in 1937. Two maxima were covered and a secondary wave was found at phase 0.557 day. Further visual observations were published by Hacar (1951), Domke and Pohl (1952) and Oskanjan (1953). Later on, Alania (1954) made some photographic observations and gave an epoch of light maximum which has turned out to be very uncertain. Detre was the first who observed this star photoelectrically. He obtained 401 observations without filter on ten nights between 30 May 1955 and 23 November 1957. From these data nine photoelectric maxima could be determined. We give these maxima in Table 3. Fitch et al. (1966) also observed this star and secured 30 UBV measures with the 36 inch telescope at Kitt Peak observing station of Steward Observatory on one night in 1965. We redetermined the time of maximum of their light curve using our mean light curve. McNamara and Feltz (1980) obtained almost 1500 photometric uvby beta observations of XX Cyg with the 24 inch telescope at Brigham Young University on eight nights in the time interval 1974-1976. They did not publish epochs of maximum light, but their data allowed us to determine nine times of maximum. Like Fitch et al., McNamara and Feltz also found the total light range of this star to be about 0.8 mag in V, which is the largest amplitude observed for any RRs variable. They also secured two single-trail spectrograms with the 200 inch telescope at a reciprocal dispersion of 18 A mm^-1. The total velocity range of XX Cyg is about 34 km sec^-1 which is small compared with the large light amplitude. Since 1950 a great number of unpublished photographic and photoelectric observations have been collected at the Konkoly Observatory, Budapest, in order to study the stability of the period of XX Cyg, The 87 photographic observations obtained on four nights in 1950, 1952, 1953 and 1954 are given in Table 10. In measuring the photographic plates we used the comparison stars of Detre (1936). These observations allowed us to determine 4 epochs of photographic maxima, one for each year. The two colour (B,V) photoelectric investigation of this star was commenced at Konkoly Observatory in 1958. In all, 378 yellow and 308 blue observations have been obtained with the 24 inch reflector at Budapest with the exception of the 1974 and the 1980 observations. These were made with the 20 inch and 40 inch reflectors, respectively, at the Mountain Station of Konkoly Observatory. The differential photoelectric yellow and blue observations are given in Tables 11 and 12, and plotted against phase in Figure 3. Figure 3: Delta V and Delta B observations of XX Cyg plotted against phase The differential magnitudes (in the sense variable minus comparison) were corrected for transformation to the standard system and for differential extinction. As a comparison star we used star No, 7 of Kron's list. Our photoelectric data gave a further 10 epochs of maximum light. All the available times of photographic and photoelectric maxima of XX Cyg are collected in Table 3. The O-C values were calculated by the formula: C(J.D. max.hel.) = 2430671.1010 + 0.134865070d*E. We formed yearly means of the epoch numbers and O-C values and then we calculated the mean epochs. These are given in Table 4. The O-C diagram of XX Cyg (Figure 4) was constructed by using the mean O-C values. Table 4 Mean photographic and photoelectric maxima of XX Cyg year Mean Hel.Max. W E O-C O-C_1 O-C_2 1905 2417174.8880 pg 2 -100072 +0.0043 -0.0001 - 1914 20366.8729 pg 1 - 76404 +0.0027 -0.0007 - 1915 20661.2847 pg 2 - 74221 +0.0041 +0.0008 - 1921 22963.6990 pg 1 - 57149 +0.0019 -0.0006 - 1933 27189.5600 pg 1 - 25815 +0.0008 -0.0004 - 1935 27993.4905 pg 2 - 19854 +0.0006 -0.0003 - 1937 28964.5200 pg 1 - 14656 +0.0015 +0.0008 - 1950 33538.4680 pg 1 + 21261 +0.0007 - -0.0002 1952 34150.4860 pg 1 + 25799 +0.0011 - 0.0000 1953 34576.3900 pg 1 + 28957 +0.0012 - -0.0001 1954 35035.3360 pg 1 + 32360 +0.0013 - -0.0001 1955 35326.3745 pe 1 + 34518 +0.0010 - -0.0005 1957 36108.8623 pe 2 + 40320 +0.0017 - -0.0001 1958 36421.0753 pe 2 + 42635 +0.0020 - +0.0002 1959 36829.8516 pe 2 + 45666 +0.0023 - +0.0003 1965 38886.9495 pe 1 + 60919 +0.0033 - +0.0007 1972 41538.5311 pe 1 + 80580 +0.0028 - -0.0007 1974 42323.4461 pe 2 + 86400 +0.0030 - -0.0007 1975 42655.7548 pe 1 + 88864 +0.0042 - +0.0004 1976 42981.0496 pe 2 + 91276 +0.0045 - +0.0005 1980 44455.3944 pe 1 +102208 +0.0043 - -0.0001 Figure 4: O-C diagram of XX Cyg The O-C diagram of XX Cyg can be interpreted by two straight lines. This means that the period of this star has been constant, only it changed abruptly around 1942. Least-squares solutions give the following ephemerides before and after 1942: C_1(J.D. max. hel.) = 2430671.1010 + 0.134865026d*E, before 1942, +-.0004 +-7 C_2(J.D. max. hel.) = 2430671.1010 + 0.134865113d*E, after 1942. +-.0003 +-4 In Table 4 the O-C_1 and O-C_2 values are also given; these clearly show that the period has indeed been constant during the past 75 years, apart from one sudden change by 87x10^-9 day = 75x10^-4 sec. DY HERCULIS DY Her = BD +12 3028 (9.5) was discovered to be variable by Hoffmeister (1935, 1936), who gave the temporary designation 62.1935 Oph to the star and remarked that it was a short periodic variable star. Soloviev (1935) at first suspected the star to be a W UMa type variable, but shortly after (Soloviev, 1936, 1937) he determined the proper type of its variability and the preliminary and approximate value of its period (0.14858 day) from his 1936-37 visual observations. Later on he rediscussed his 240 visual observations made in the years 1936-1938, but he used a wrong period (Soloviev, 1952). Tsesevich (1949) also observed the star visually in 1944 and 1947 and derived a new period: 0.148 586 65 day which, however, could not satisfactorily represent the observed maxima. Both Soloviev and Tsesevich claimed to notice light curve variation which has not been confirmed by modern photoelectric measurements. Kuhn (1951), and Sauer (1955) also made some visual estimates. They found some strange waves on the light curve which are not present either on the photographic or on the photoelectric light curves. There is little doubt that their observations were not sufficiently accurate. From estimates on 1392 Harvard patrol plates Gaposchkin (1952) gave a period of 0.14857964 day. Oddly enough, his normal points formed with this period trace out a light curve with an amplitude of only some hundredth of magnitude. Thence it follows that his period is wrong. In addition to that, as Gaposchkin remarks, DY Her is an unsatisfactory object for the patrol plates because the average exposure time is about an hour, one third of the period. It is hardly surprising that he was unable to determine any epoch of maximum light from his observations. With the help of 239 photographic observations secured between 23 March 1950 and 15 August Ashbrook (1954) succeeded in determining the correct period of DY Her. The new elements given by him are: Max. hel. = J.D. 2433439.4878 + O.14863081d*E His observations yielded 7 maxima. In his paper Ashbrook also listed Harlan Smith's unpublished photoelectric maxima. Alania (1954) gave an epoch of photographic maximum. Because his observations were fairly poor, little weight should be ascribed to his value. The first photoelectric measurements of this star were made by Broglia and Masani (1955) in 1951. They continued the observation in 1954 and obtained more than 450 photoelectric measurements in four colours. In determining the times of maximum we used only the blue and yellow observations and have ignored the ultraviolet and orange observations because the scatter of the observations in those colours was larger than in blue and yellow. Discussing the times of maximum available to them Broglia and Masani suspected a change in the period around 1952. Lenouvel and Daguillon (1954) observed the variable photoelectrically on 9 nights in 1951. They obtained some 997 observations in two colours. As comparison star they used BD +12 3027 and as check star BD +12 3033. Although Lenouvel and Daguillon gave only two times of maximum five further epochs could be derived from their observations. It is rather curious that they could not determine the correct period although their observations were of excellent quality. These observations do not reveal any significant cycle-to-cycle change of the light curve. Fitch (1957) observed the star in the photoelectric UBV system a total of 5.1 cycles on 5 nights in 1955 and 1956 and added five further epochs of maximum light to the list of observed maxima. According to his observations the light curve of DY Her appeared regular and he found no evidence of non-repetitive or extremely peculiar behaviour of the star near maximum light as reported by visual observers (Tsesevich, 1949; Kuhn, 1951; Soloviev, 1952 and Sauer, 1955). Their misinterpretation can easily be explained by the underestimated errors of visual observations and by their use of an erroneous period. Fitch rediscussed all the available maxima and assuming a uniform increase in the period he gave the elements: Max. Hel. = J.D. 2433439.4872 + 0.14863113d*E + 11^dx10^-12*E^2. +-.0004 +-.00000005 +-2 Among other RR Lyrae stars Spinrad (1959) observed DY Her on 4 nights in 1958 and obtained 74 yellow and 72 blue photoelectric observations. As comparison he used BD +12 3027. He found some changes in the shape of maximum and the rise to maximum light from cycle-to-cycle, but he also remarked that the amplitude of the light variation was fairly stable. However, it should also be noted that Spinrad's observations are somewhat poorer than other photoelectric photometries. In the course of his programme on dwarf cepheids Broglia (1961) observed DY Her, too During 1958-1960 he obtained 37 blue and 124 yellow photoelectric observations. Discussing 52 epochs of maximum spread over 24 years or 59000 cycles Broglia found the period of DY Her variable and derived a new ephemeris with quadratic term: Max. hel. = J.D. 2433439.4875 + 0.14863118d*E + 53^dx10^-13*E2. +-.0003 +-.00000002 +- 10 Hardie and Lott (1961) secured over one thousand UBV observations on 11 nights in the spring and summer of 1959. According to their observations the light variations of this star appeared to be quite regular and repetitive and they also did not find any confirmation for the irregularities suggested by Sauer (1955) or the non-repetitive behaviour reported by Tsesevich (1949), Soloviev (1952) and Spinrad (1959). Having discussed all available data Hardie and Lott suggested that the period of DY Her had been essentially constant from 1950 to 1959, and all observations in that interval could adequately be described by the relation: Max. hel. = J.D. 2433439.4871 + 0.14863127d*E. They also investigated the serious departures of Soloviev's and Tsesevich's earlier observations from this relation and they found that "the data seemed insufficient to clarify whether the period had been different between 1936- 1950, whether their times were in error, or whether the period was subject to continual change". Assuming the last possibility they derived from a second-degree solution the following ephemeris: Max. hel. = J.D. 2433439.4879 + 0114863110*E + 5.9dx10-12*E^2. In the course of their photoelectric observations of RR Lyrae stars Fitch et al. (1966) obtained 120 measurements of DY Her in UBV on three nights in 1964. Using our mean light curve we determined a new epoch different from that given by them. In order to find interstellar absorption corrections Epstein (1969) observed a number of RR Lyrae and AI Velorum type stars in the uvby intermediate band photoelectric system. DY Her was also on the programme and was observed on six nights in 1966. From the 34 photoelectric V measurements we were able to determine a normal maximum. Geyer and Hoffmann (1974) published one time of maximum light with a mean error of 0.001 day. Engaging in a long-term programme to investigate the evolutionary status of the dwarf cepheid variables on a star-by-star basis Breger and his colleagues (Breger et al. 1978) studied DY Her in detail in the uvby beta photometric system during 17 nights in May and July 1977. These observations are of high precision and make it possible to determine an accurate normal maximum. The maximum light was observed on seven nights (J.D. 2443280, 283, 285, 286, 341, 342, 343) and no light curve variations could be noticed. At Konkoly Observatory this variable was observed photoelectrically on two nights: 9/10 July, 1972 and 25/26 June, 1979 and 182 and 42 observations were secured, respectively. As comparison star BD +12 3030 and as check star BD +12 3031 were used. The magnitudes and colours for these stars have been adopted from Hardie and Lott (1961). Table 5 gives the photometric data of the comparison stars used by different authors. Table 5 star V B-V U-B References BD +12 3027 10.35 +0.37 -0.10 Fitch (1957) 10.28 +0.39 Spinrad (1959) BD +12 3030 9.34 +0.56 +0.11 Hardie and Lott (1961) BD +12 3031 8.52 +0.72 +0.33 Hardie and Lott (1961) Our photoelectric observations are given in Tables 14 and 15 and are plotted against phase in Figure 5. Almost all the photoelectric observations confirm the stable and repetitive character of this variable. Therefore we have the well-grounded suspicion that the large fluctuations in the shape of the light curve of DY Her found by visual observers are not real. Figure 5: Delta V and Delta B observations of DY Her plotted against phase In the plate collection of Konkoly Observatory we found a plate of DY Her with 17 multiple exposures made on 18 June, 1938. The measurements (Table 13) were made using Ashbrook's (1954) comparison stars. Utilizing Ashbrook's mean light curve we were able to determine a photographic epoch of maximum light. This epoch is very important because only visual observations of low accuracy existed before 1950. All the photographic and photoelectric epochs available to us are gathered in Table 6. The O-C values were calculated by the ephemeris: C = J.D. 2433439.4865 + 0.148631201d*E. Table 6 Photographic and photoelectric maxima of DY Her year J.D.max.hel. Remarks O-C E mean O-C mean E n 1938 2429068.393 pg Pp +0.0015 - 29409 +0.0015 - 29409 1 1950 33366.807 pg As +0.0012 - 489 +0.0006 + 125 7 33371.857 pg As -0.0023 - 455 33442.607 pg As -0.0008 + 21 33501.614 pg As -0.0003 + 418 33506.671 pg As +0.0032 + 452 33507.563 pg As +0.0034 + 458 33509.640 pg As -0.0004 + 472 1951 33767.5172 pe BM +0.0016 + 2207 +0.0002 + 2333 3 33775.837 pe Sm^1 -0.0019 + 2263 33815.5243 pe BM +0.0009 + 2530 1952 34068.940 pe Sm^1 +0.0004 + 4235 +0.0006 + 4745 17 34097.923 pe Sm^1 +0.0003 + 4430 34118.881 pe Sm^1 +0.0013 + 4571 34119.771 pe Sm^1 -0.0005 + 4577 34123.785 pe Sm^1 +0.0005 + 4604 34133.744 pe Sm^1 +0.0012 + 4671 34134.785 pe SM^1 +0.0017 + 4678 34137.755 pe Sm^1 -0.0009 + 4698 34139.689 pe Sm^1 +0.0009 + 4711 34149.794 pe SM^1 -0.0010 + 4779 34159.4570 pe LD +0.0010 + 4844 34162.4295 pe LD^2 +0.0008 + 4864 34178.4818 pe LD^2 +0.0010 + 4972 34180.4140 pe LD^2 +0.0010 + 4985 34182.4950 pe LD^2 +0.0011 + 4999 34184.4277 pe LD +0.0016 + 5012 34188.4390 pe LD^2 -0.0001 + 5039 1953 (34568.346 pg Al +0.0055 + 7595) 1954 34875.5633 pe BM +0.0021 + 9662 +0.0016 + 9996 5 34888.4937 pe BM +0.0016 + 9749 34945.4190 pe BM +0.0012 + 10132 34956.4177 pe BM +0.0012 + 10206 34960.4316 pe BM +0.0020 + 10233 1955 35241.799 pe Fi +0.0006 + 12126 +0.0017 + 12144 3 .939 pe Fi +0.0019 + 12127 35249.817 pe Fi +0.0025 + 12180 1956 35622.881 pe Fi +0.0022 + 14690 +0.0022 + 14720 2 35631.799 pe Fi +0.0023 + 14750 1958 36336.757 pe Sp^2 +0.0025 + 19493 +0.0024 + 19590 5 36337.799 pe Sp^2 +0.0041 + 19500 .947 pe Sp^2 +0.0034 + 19501 36338.834 pe Sp^2 -0.0013 + 19507 36404.3850 pe Br +0.0033 + 19948 1959 36681.8780 pe HL^2 +0.0019 + 21815 +0.0020 + 22053 10 36694.8097 pe HL^2 +0.0026 + 21902 36695.7010 pe HL +0.0021 + 21908 36696.7410 pe HL +0.0017 + 21915 36703.7267 pe HL^2 +0.0018 + 21962 36704.7676 pe HL^2 +0.0022 + 21969 36730.4806 pe Br +0.0020 + 22142 36733.7500 pe HL +0.0016 + 22164 36747.7226 pe HL^2 +0.0028 + 22258 36782.6496 pe HL^2 +0.0015 + 22493 1960 37075.4538 pe Br +0.0022 + 24463 +0.0022 + 24463 1 1964 38476.0061 pe FA^2 +0.0027 + 33886 +0.0027 + 33886 1 1966 39252.9024 pe Ep^2 +0.0037 + 39113 +0.0037 + 39113 1 1972 41508.3797 pe Pp +0.0026 + 54288 +0.0026 + 54288 1 1973 41840.4222 pe GH +0.0030 + 56522 +0.0030 + 56522 1 1977 43341.7445 pe BE +0.0015 + 66623 +0.0015 + 66623 1 1979 44050.4181 pe Pp +0.0015 + 71391 +0.0015 + 71391 1 Remarks to Table 6: Pp = Present paper; As = Ashbrook (1954); BM = Broglia and Masani (1955); Sm = Smith (Ashbrook, 1954); LD = Lenouvel and Daguillon (1954); Al = Alania (1954); Fi = Fitch (1957); Sp = Spinrad (1959); Br = Broglia (1961); HL = Hardie and Lott (1961); FA = Fitch et al. (1966); Ep = Epstein (1969); GH = Geyer and Hoffmann (1974); BE = Breger et al. (1978); ^1 = given by Ashbrook (1954); ^2 = determined by us Mean O-C value and mean epoch number were formed for each observing season separately; these are given in Table 6 under the headings mean O-C and mean E and are plotted in Figure 6. Then the yearly mean epochs of the observed photographic and photoelectric light maxima were calculated (Table 7). The photoelectric data were used only to carry out a second order least-squares solution which resulted in the ephemeris: C_qr = J.D. 2433439.4865 + 0.148631353d*E - 18.6dx10^-13*E^2. +-.0002 +-14 +-1.9 Figure 6: O-C diagram of DY Her Table 7 Mean photographic and photoelectric maxima of DY Her year J.D.max.hel. W E O-C O-C_qr 1938 2429068.3930 pg 0 - 29409 +0.0015 - 1950 33458.0660 pg 0 + 125 +0.0006 +0.0006 1951 33786.2433 pe 2 + 2333 +0.0002 -0.0001 1952 34144.7421 pe 2 + 4745 +0.0006 -0.0001 1954 34925.2056 pe 2 + 9996 +0.0016 +0.0003 1955 35244.4655 pe 2 + 12144 +0.0017 +0.0001 1956 35627.3400 pe 1 + 14720 +0.0022 +0.0004 1958 36351.1741 pe 2 + 19590 +0.0024 +0.0001 1959 36717.2524 pe 2 + 22053 +0.0020 -0.0004 1960 37075.4538 pe 1 + 24463 +0.0022 -0.0004 1964 38476.0061 pe 1 + 33886 +0.0027 -0.0003 1966 39252.9024 pe 1 + 39113 +0.0037 +0.0006 1972 41508.3797 pe 1 + 54288 +0.0026 -0.0002 1973 41840.4222 pe 1 + 56522 +0.0030 +0.0003 1977 43341.7445 pe 1 + 66623 +0.0015 -0.0004 1979 44050.4181 pe 1 + 71391 +0.0015 +0.0002 The deviations O-C_qr are within the observational errors therefore the continuous decrease of the period in the time interval covered by photoelectric observations (1951-1979) can be taken for certain, and the rate of period decrease is -37.2x10^-13 day cycle^-1. In this context we are reminded of Fitch's (1957), Broglia's (1861) and Hardie's and Lott's (1961) result. They found a period increase if they took into account the visual observations. These contradictory results also prove clearly that the visual observations of dwarf cepheids are of inadequate precision and useless in a more refined period analysis. Our photographic observations of the year 1938 show that the period of DY Her behaved in a different way before 1951 than after it. Our single photographic maximum (the only one before 1950) is not sufficient to trace the behaviour of the period of this variable up to 1950. GENERAL REMARKS The O-C diagram of both metal rich variables YZ Boo (Delta s = 0, Preston, 1959) and DY Her (McNamara, 1978) indicates that the periods of these stars are changing continuously at a constant rate. The period of YZ Boo has been increasing, whereas the period of DY Her has shown a definite continuous decrease during the time interval covered by photoelectric observations. EH Lib, the third metal rich variable (investigated in our previous paper) has a constant period. Although the sample of stars investigated is too small, the following statement seems to be reasonable. The continuous change in or the constancy of the period may be characteristic of the population I dwarf cepheids. It may also be interesting to note that the scatter of the points on the O-C diagram of these three stars does not exceed the observational error. XX Cyg, the third star studied in this paper is metal poor (McNamara and Feltz, 1980). The abrupt change in its period is conspicuous. The other metal poor dwarf cepheids, CY Aqr and DY Peg were studied in our previous paper. CY Aqr also exhibited and DY Peg seemed to show abrupt change in their respective periods. It is also remarkable that the periods are not stable, they show small fluctuations, too. The abrupt changes in the period of metal poor dwarf cepheids may be due to mixing in the semiconvective zone as suggested by Sweigart and Renzini (1979). In this context it is also interesting to note, that the period noise of the three investigated metal poor variables is larger than that of the metal rich dwarf cepheids. Acknowledgements: We should like to express our sincere thanks to all our colleagues who took part in the observations. We are especially grateful to Dr. Katalin Olah for her continuous help in the course of this work. Budapest - Szabadsaghegy, 8 March 1981 REFERENCES Ahnert, P., 1959, Mitt. Verand. Sterne Nos 425-427 Alania, I.F., 1954, Astr. Circ. 146.14 Ashbrook, J., 1954, Astron. Journ. 59.6 Blazhko, S., 1906, Astron. Nachr. 172.57 1922, ibid. 216.103 1936, Per. Zvezdy 5.29 Bonsack, W., 1957, Astrophys. Journ. 126.291 Breger, M., Campos, A.J. and Roby, S.W., 1978, Publ. Astr. Soc. Pacific 90.754 Broglia, P., 1961, Mem. Soc. astr. It. 32.7 Broglia, P. and Masani, A., 1955, Mem. Soc. astr. It. 26.379 = Contr. Oss. Astr. Milano-Merate No. 66 1957, Mem. Soc. astr. It. 28.1 = Contr. Oss. Astr. Milano-Merate No. 102 Busch, H., 1976, Mitt. Verand. Sterne 7.149 Ceraski, W., 1904, Astron. Nachr. 165.61 Detre, L., 1936, Astron. Nachr. 258.329 Domke, K. and Pohl, E., 1952, Astron. Nachr. 281.113 Eggen, O.J., 1955, Publ.Astr. Soc. Pacific 67.354 Epstein, I., 1969, Astron. Journ. 74.1131 Fitch, W.S., 1957, Astron. Journ. 62.108 Fitch, W.S., Wisniewski, W.Z. and Johnson, H.L., 1966, Comm. Lunar and Planetary Laboratory vol. 5. Part 2. No. 71 Gaposchkin, S., 1952, Harvard Ann. 115.257 Geyer, E.H. and Hoffmann, M., 1974, Inf. Bull. Var. Stars No. 936 (IBVS N°.936) Gieren, W., Gieseking, F, and Hoffmann, M., 1974, Astron. and Astrophys. 37.444 Graff, K., 1906, Astron. Nachr. 171.55 Hacar, B., 1951, Prace Moravsk. Akad. ved. Prirodnich XXIII. (fasc. 17) 339 Hardie, R.H. and Lott, S.H., 1961, Astrophys. Journ. 133.71 Heiser, A.M. and Hardie, R.H., 1964, Astrophys. Journ. 140.694 Hoffmeister, C., 1935, Astron. Nachr. 255.401 1936, ibid. 260.393 1949, Erg. Astron. Nachr. 12. No. 1. 22 Jordan, F.C., 1929, Allegh. Publ. 7.1 Joy, A.H., 1950, Publ. Astr. Soc. Pacific 62.60 Kleissen, E., 1938, Astron. Nachr. 267.137 Kron, E., 1912, Potsd. Publ. 22. Nr. 65. Part III. 52 Kuhn, R., 1951, Astron. Nachr 279.241 Lenouvel, F. and Daguillon, J., 1954, Journal des Observateurs 37.137 Luizet, M., 1908, Bull.Astron. 25.251 Mahdy, H.A. and Szeidl, B., 1980, Mitt. Sternw. Budapest Nr. 74 (CoKon 74) McNamara, D.H., 1978, Publ. Astr. Soc. Pacific 90.759 McNamara, D.H. and Feltz, K.A. Jr., 1976, Publ. Astr. Soc. Pacific 88.164 1980, ibid. 92.195 Nijland, A.A., 1911, Astron. Nachr. 188.149 1923, Utrecht Rech. Astr. 8.144 Olah, K. and Szeidl, B., 1978, Mitt. Sternw. Budapest Nr. 71 (CoKon 71) Oskanjan, V., 1953, Bull Obs. Astr. Beograd 18. No. 3 - 4., 12 Parkhurst, J.A. and Jordan, F.C., 1906, Astrophys. Journ. 23.79 Preston, G.W., 1959, Astrophys. Journ. 130.507 Sauer, M., 1955, Astron. Nachr. 282.178 Schwab, F., 1906, Astron. Nachr. 170.369 Shapley, H. and Shapley, M.B., 1915, Astrophys. Journ. 42.148 Soloviev, A.V., 1935, Tadjik Circ. No. 11 1936, Beobachtungs - Zirk. 18. Nr. 27; Tadjik Circ. Nos 17 and 20 1937, Tadjik Circ. No. 30.4 1952, Per. Zvezdy 9.94 Spinrad, H., 1959, Astrophys. Journ. 130.539 Strelkova, E.P., 1960, Astr. Circ. No. 209.29 1964, Per. Zvezdy 15.89 Sweigart, A.V. and Renzini, A., 1979, Astron. and Astrophys. 71.66 Tremko, J. and Antal, M., 1959, Bull. astr. Czechs. 10.195 Tsesevich, V.P., 1949, Per. Zvezdy 7.7 1958, Astr. Circ. No. 188.24 1966, RR Lyrae-Type Variable Stars, Izd. Nauka-Dumka, Kiev, pp. 382 - 388 Table 8 Photoelectric yellow observations of YZ Boo J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2436709 2436712 2436713 2436714 .4952 +0.568 .4194 +0.634 .3799 +0.549 .4465 +0.286 .4973 .566 .4215 .650 .3815 .544 .4509 .347 .4994 .579 .4257 .642 .3849 .464 .4530 .357 .5039 .590 .4278 .661 .3866 .426 .4550 .379 .5059 .624 .4298 .647 .3881 .387 .4614 .411 .5080 .621 .4350 .649 .3915 .342 .4635 .426 .5132 .627 .4371 .637 .3932 .289 .4677 .442 .5153 .632 .4392 .635 .3948 .257 .4697 .439 .5191 .642 .4441 .595 .3967 .218 .4718 .456 .5233 .641 .4517 .431 .3987 .204 .4760 .490 .5254 .625 .4559 .318 .4029 .248 .4781 .496 .5275 .598 .4580 .270 .4049 .276 .4802 .512 .5320 .576 .4600 .237 .4066 .287 .4854 .569 .5341 .533 .4642 .209 .4105 .316 .4875 .590 .5362 .497 .4663 .234 .4165 .340 .4895 .619 .5431 .354 .4684 .242 .4179 .360 .4937 .627 .5452 .300 .4725 .282 .4202 .358 .4958 .651 .5494 .246 .4746 .300 .4248 .397 .4979 .650 .5514 .232 .4767 .338 .4267 .409 .5020 .657 .5535 .239 .4809 .371 .4290 .446 .5041 .655 .5577 .270 .4833 .386 .4336 .471 .5062 .660 .5598 .298 .4854 .413 .4359 .482 .5125 .659 .5619 .309 .4909 .434 .4378 .539 .5145 .665 .5660 .363 .4937 .446 .4420 .551 .5187 .661 .5681 +0.398 .4965 .476 .4443 .558 .5208 .652 .5026 .512 .4461 .588 .5229 .657 2436712 .5050 .537 .4528 .633 .5281 .584 .3493 +0.322 .5078 .541 .4547 .638 .5302 .506 .3534 .229 .5149 .595 .4563 .644 .5322 .465 .3597 .208 .5174 .632 .4820 .637 .5353 .401 .3618 .241 .5202 .639 .4864 .563 .5366 .382 .3639 .248 .5264 .641 .4885 .468 .5380 .334 .3680 .271 .5291 .641 .4900 .450 .5408 .281 .3701 .276 .5320 .659 .4937 .369 .5422 .262 .3722 .296 .5381 .646 .4954 .298 .5436 +0.237 .3764 .335 .5408 .638 .4970 .278 .3784 .351 .5507 .514 .5002 .231 2436716 .3805 .391 .5530 .458 .5019 .212 .3269 +0.333 .3847 .411 .5581 .322 .5037 .205 .3293 .365 .3868 .467 .5602 .291 .5053 .215 .3344 .397 .3889 .483 .5623 +0.257 .5070 +0.233 .3366 .408 .3930 .500 .3387 .422 .3951 .493 2436713 2436714 .3436 .454 .3972 .526 .3494 +0.587 .4221 +0.540 .3456 .487 .4014 .559 .3542 .593 .4255 .470 .3477 .501 .4028 .560 .3561 .604 .4272 .459 .3519 .529 .4048 .581 .3637 .628 .4311 .348 .3540 .544 .4090 .574 .3667 .636 .4336 .277 .3561 .568 .4111 .575 .3711 .635 .4365 .230 .3602 .603 .4132 .593 .3751 .622 .4418 .234 .3623 .625 .4173 +0.613 .3783 +0.582 .4444 +0.262 .3644 +0.637 Table 8 (cont.) Photoelectric yellow observations of YZ Boo J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2436716 2436717 2436724 2436725 .3717 +0.664 .3455 +0.351 .4244 +0.327 .3473 +0.546 .3741 .666 .3488 .282 .4275 .277 .3509 .514 .4012 .562 .3506 .248 .4293 .257 .3529 .467 .4043 .459 .3525 .231 .4312 .231 .3545 .450 .4064 .416 .3567 .225 .4344 .212 .3578 .399 .4106 .314 .3588 .227 .4358 .206 .3591 .383 .4127 .297 .3609 .266 .4372 .225 .3612 .318 .4147 .244 .3650 .292 .4404 .263 .3642 .287 .4189 .223 .3665 .307 .4454 .309 .3656 .269 .4210 .227 .3685 .323 .4475 .331 .3670 .223 .4231 .258 .3727 .374 .4513 .357 .3698 .222 .4272 .300 .3748 +0.425 .4534 .383 .3712 .223 .4293 .307 .4555 .412 .3726 .220 .4314 .318 2436723 .4603 .450 .3754 .235 .4363 .356 .4444 +0.570 .4624 .479 .3767 .239 .4383 .375 .4486 .585 .4645 .499 .3784 .247 .4404 .387 .4507 .623 .4694 .503 .3814 .311 .4446 .435 .4548 .636 .4714 .522 .3828 .329 .4522 .502 .4569 .634 .4735 .520 .3841 .346 .4543 .518 .4590 .631 .4784 .554 .3869 .360 .4585 .574 .4632 .636 .4805 .563 .3883 .389 .4606 .582 .4652 .631 .4825 .571 .3954 .455 .4627 .594 .4673 .639 .4874 .589 .3981 .458 .4668 .627 .4715 .625 .4895 .595 .4002 .461 .4689 .640 .4736 .599 .4916 .607 .4044 .508 .4710 .652 .4757 .584 .4964 .623 .4065 .532 .4752 .668 .4798 .510 .4985 .634 .4086 .535 .4772 .677 .4819 .465 .5006 .636 .4127 .538 .4793 .681 .4840 .430 .5051 .638 .4148 .550 .4835 .694 .4882 .312 .5072 .639 .4169 .578 .4856 .697 .4902 .282 .5093 .637 .4211 .600 .4943 .701 .4923 .264 .5147 .625 .4231 .613 .4988 .692 .4968 .239 .5161 .593 .4252 .622 .5006 .681 .4989 .223 .5175 .573 .4294 .621 .5025 .638 .5010 .226 .5203 .543 .4315 .624 .5055 .588 .5100 .334 .5217 .531 .4336 .635 .5069 .538 .5142 .355 .5231 .491 .4377 .644 .5082 .504 .5166 +0.353 .5258 .424 .4398 .652 .5115 .439 .5272 .398 .4416 .648 .5129 .396 2436724 .5286 .376 .4457 .641 .5143 .341 .4006 +0.610 .5314 .298 .4478 .620 .5170 .291 .4043 .603 .5328 .264 .4499 .610 .5184 .256 .4057 .594 .5342 .237 .4529 .586 .5198 .239 .4089 .588 .5369 .232 .4543 .572 .5240 .229 .4106 .578 .5383 .227 .4557 .555 .5282 .243 .4119 .564 .5397 .235 .4585 .505 .5295 .262 .4154 .536 .5425 .248 .4598 .477 .5309 .271 .4168 .500 .5439 .253 .4612 .458 .5337 .330 .4184 .461 .5453 .272 .4647 .400 .5351 .367 .4217 .397 .5481 .295 .4661 .354 .5365 +0.388 .4231 +0.364 .5503 +0.309 .4675 +0.312 Table 8 (cont.) Photoelectric yellow observations of YZ Boo J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2436725 2442187 2442464 2442523 .4703 +0.246 .4613 +0.320 .6662 +0.186 .4822 +0.211 .4716 .241 .4623 .294 .6683 .206 .4838 .233 .4730 .231 .4630 .279 .6693 .198 .4875 .297 .4758 .253 .4638 .266 .6724 .229 .4918 .312 .4779 .272 .4646 .250 .6734 .238 .4942 .336 .4793 .283 .4654 .238 .6764 .276 .4952 +0.348 .4828 .306 .4662 .209 .6778 .311 .4841 .319 .4672 .196 .6797 .335 2442524 .4855 .324 .4681 .195 .6811 +0.344 .4190 +0.181 .4883 +0.365 .4692 .190 .4204 .189 .4700 .198 2442522 .4228 .243 2441860 .4707 .207 .4057 +0.624 .4276 .309 .3875 +0.625 .4753 .235 .4067 .619 .4290 .318 .3882 .615 .4761 .235 .4091 .625 .4321 .343 .3899 .622 .4769 .238 .4100 .598 .4336 .370 .3906 .607 .4778 .243 .4141 .584 .4378 .393 .3924 .605 .4913 .337 .4182 .564 .4392 .411 .3938 .598 .4929 .340 .4215 .511 .4422 .434 .3951 .579 .4940 .349 .4225 .487 .4434 .436 .3965 .563 .5021 .426 .4249 .422 .4474 .452 .3982 .518 .5029 .442 .4288 .352 .4488 .458 .4010 .457 .5038 .446 .4344 .224 .4522 +0.480 .4021 .439 .5047 .453 .4372 .193 .4038 .404 .5057 +0.477 .4386 .212 2443936 .4066 .334 .4467 .281 .5305 +0.233 .4077 .314 2442464 .4477 .294 .5315 .235 .4093 .281 .5606 +0.206 .4638 .448 .5333 .286 .4100 .264 .5620 .195 .4648 .453 .5343 .287 .4118 .239 .5648 .198 .4675 .483 .5364 .319 .4128 .218 .5662 .214 .4691 +0.506 .5371 .330 .4146 .206 .5711 .270 .5392 .339 .4153 .211 .5738 .295 2442523 .5399 .339 .4174 .208 .5749 .316 .4132 +0.469 .5420 .370 .4181 .211 .6190 .598 .4169 .519 .5427 .383 .4204 .233 .6207 .600 .4184 .534 .5440 .390 .4215 .247 .6238 .601 .4214 .542 .5475 .440 .4239 .270 .6248 .593 .4259 .568 .5486 .448 .4264 .307 .6280 .621 .4314 .599 .5503 .450 .4271 .318 .6294 .605 .4348 .599 .5513 .471 .4292 .343 .6322 .603 .4419 .660 .5534 .466 .4302 .362 .6377 .608 .4447 .631 .5541 .461 .4319 .387 .6408 .595 .4460 .647 .5562 .476 .4329 +0.403 .6440 .595 .4493 .669 .5572 .491 .6481 .540 .4506 .663 .5593 .483 2442187 .6502 .512 .4538 .622 .5604 .484 .4478 +0.593 .6544 .429 .4548 .622 .5621 .503 .4496 .550 .6572 .351 .4617 .518 .5628 .513 .4545 .477 .6582 .322 .4629 .458 .5649 .517 .4559 .460 .6606 .278 .4655 .400 .5656 .520 .4568 .431 .6620 .245 .4668 .374 .5677 .521 .4577 +0.413 .6648 +0.200 .4789 +0.186 .5683 +0.540 Table 8 (cont.) Photoelectric yellow observations of YZ Boo J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2443936 2443936 2443936 2443936 .5704 +0.562 .5878 +0.634 .6128 +0.418 .6274 +0.173 .5711 .571 .5888 .639 .6145 .368 .6288 .174 .5729 .582 .5906 .655 .6152 .344 .6295 .187 .5739 .581 .5920 .650 .6190 .265 .6326 .233 .5760 .600 .5933 .642 .6197 .222 .6374 .290 .5784 .605 .5947 .633 .6211 .202 .6381 .297 .5795 .603 .6038 .632 .6222 .186 .6399 .307 .5815 .605 .6055 .592 .6236 .183 .6409 .325 .5829 .612 .6062 .568 .6246 .160 .6433 .342 .5847 .607 .6090 .513 .6263 +0.168 .6444 +0.360 .5857 +0.617 .6114 +0.453 Table 9 Photoelectric blue observations of YZ Boo J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2436709 2436712 2436712 2436713 .4962 +0.244 .3607 -0.203 .4548 -0.075 .3484 +0.226 .4983 .240 .3670 .161 .4569 .143 .3533 .255 .5004 .246 .3691 .150 .4590 .171 .3552 .271 .5049 .266 .3712 .139 .4632 .202 .3596 .296 .5070 .268 .3753 .059 .4653 .214 .3703 .280 .5091 .269 .3774 .018 .4673 .195 .3722 .276 .5143 .278 .3795 -0.003 .4715 .173 .3743 .261 .5181 .290 .3837 +0.055 .4736 .160 .3774 .229 .5202 .291 .3857 .067 .4757 .147 .3791 .183 .5244 .249 .3878 .075 .4819 -0.013 .3807 .167 .5264 .224 .3920 .134 .4843 0.000 .3842 .099 .5285 .200 .3941 .159 .4896 +0.034 .3857 .057 .5330 .158 .3962 .180 .4923 .058 .3874 +0.014 .5351 .122 .4003 .221 .4951 .092 .3908 -0.081 .5372 +0.086 .4017 .226 .5012 .139 .3923 .098 .5421 -0.036 .4038 .237 .5034 .165 .3940 .149 .5441 .119 .4080 .241 .5063 .179 .3958 .172 .5462 .178 .4100 .235 .5161 .248 .3977 .191 .5504 .215 .4121 .240 .5190 .298 .4017 .176 .5525 .208 .4163 .263 .5251 .314 .4039 .160 .5546 .187 .4184 .298 .5278 .306 .4057 .147 .5587 .169 .4205 .307 .5305 .288 .4096 .113 .5608 .147 .4246 .308 .5367 .298 .4144 .074 .5629 .090 .4267 .315 .5394 .277 .4172 -0.059 .5671 .048 .4288 .331 .5420 .265 .4234 +0.017 .5691 -0.015 .4340 .316 .5495 .129 .4258 .039 .4361 .290 .5520 +0.068 .4276 .061 2436712 .4382 .289 .5570 -0.065 .4325 .123 .3503 -0.092 .4430 .219 .5592 .150 .4350 .130 .3545 .203 .4486 .098 .5612 -0.189 .4369 .138 .3587 -0.226 .4507 +0.046 .4408 +0.154 Table 9 (cont.) Photoelectric blue observations of YZ Boo J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2436713 2436714 2436716 2436723 .4434 +0.180 .5197 +0.276 .4658 +0.236 .4559 +0.291 .4450 .180 .5218 .279 .4679 .248 .4579 .294 .4538 .271 .5270 .212 .4699 .261 .4621 .291 .4593 .288 .5291 .148 .4741 .282 .4642 .281 .4851 .178 .5312 .101 .4762 .291 .4663 .290 .4876 .136 .5346 +0.019 .4783 .294 .4704 .270 .4893 +0.091 .5359 -0.015 .4824 .303 .4725 .256 .4928 0.000 .5373 .060 .4845 .306 .4746 .233 .4945 -0.084 .5401 .116 .4932 .320 .4788 .139 .4962 .114 .5415 .140 .4977 .313 .4809 .097 .4993 .197 .5429 -0.164 .4997 .282 .4829 +0.063 .5011 .221 .5015 .251 .4871 -0.066 .5028 .213 2436716 .5048 .185 .4892 .116 .5045 .219 .3258 -0.120 .5062 .150 .4913 .167 .5062 -0.211 .3281 .095 .5076 .109 .4954 .206 .3331 .051 .5108 +0.025 .4979 .209 2436714 .3356 -0.022 .5122 -0.017 .5000 .212 .4211 +0.225 .3377 +0.016 .5136 .079 .5045 .169 .4245 .129 .3422 .056 .5164 .139 .5069 .129 .4263 +0.083 .3446 .062 .5177 .183 .5090 .099 .4301 -0.038 .3467 .079 .5191 .206 .5132 .064 .4324 .134 .3508 .136 .5219 .211 .5152 -0.032 .4347 .186 .3529 .152 .5233 .210 .4409 .203 .3550 .155 .5247 .206 2436724 .4432 .189 .3592 .228 .5275 .183 .3996 +0.284 .4456 .152 .3613 .249 .5302 .169 .4036 .264 .4500 .136 .3633 .249 .5330 .142 .4050 .257 .4520 .119 .3675 .276 .5344 .131 .4082 .248 .4540 .077 .3699 .301 .5358 -0.097 .4099 .236 .4586 .045 .3731 .297 .4113 .230 .4604 -0.020 .4002 .198 2436717 .4147 .186 .4625 +0.006 .4033 .091 .3434 +0.046 .4161 .164 .4666 .050 .4054 +0.040 .3448 0.000 .4175 .112 .4687 .061 .4095 -0.094 .3478 -0.132 .4210 +0.035 .4708 .077 .4116 .139 .3497 .167 .4224 -0.018 .4750 .125 .4137 .186 .3515 .216 .4238 .050 .4770 .134 .4179 .204 .3555 .216 .4268 .106 .4791 .157 .4199 .203 .3578 .214 .4286 .163 .4843 .222 .4220 .177 .3599 .191 .4302 .190 .4864 .229 .4262 .153 .3640 .159 .4337 .206 .4885 .236 .4283 .110 .3656 .139 .4351 .210 .4927 .268 .4304 .097 .3675 .119 .4365 .210 .4947 .284 .4352 .057 .3719 .044 .4397 .180 .4968 .301 .4373 .047 .3738 -0.027 .4446 .125 .5010 .302 .4394 -0.035 .3758 +0.022 .4464 .109 .5031 .304 .4436 +0.019 .4503 .062 .5052 .307 .4512 .095 2436723 .4523 -0.026 .5093 .287 .4533 .107 .4434 +0.263 .4544 +0.007 .5114 .286 .4574 .142 .4475 .263 .4593 .038 .5135 .290 .4595 .155 .4496 .279 .4614 .065 .5177 +0.285 .4616 +0.170 .4538 +0.270 .4634 +0.092 Table 9 (cont.) Photoelectric blue observations of YZ Boo J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2436724 2436725 2441860 2442187 .4683 +0.126 .3774 -0.171 .3920 +0.244 .4934 -0.013 .4704 .160 .3791 .128 .3931 .230 .4943 -0.011 .4725 .179 .3821 .074 .3947 .214 .4953 +0.002 .4773 .216 .3835 .070 .3958 .196 .5025 .077 .4794 .219 .3848 .056 .3979 .137 .5033 .092 .4815 .232 .3876 -0.012 .4007 .082 .5042 .097 .4864 .251 .3968 +0.067 .4035 +0.013 .5051 .097 .4884 .260 .3992 .082 .4042 -0.014 .5064 +0.111 .4905 .275 .4034 .125 .4063 .081 .4954 .290 .4054 .151 .4070 .096 2442464 .4975 .305 .4075 .165 .4090 .156 .5599 -0.222 .4996 .319 .4117 .170 .4097 .167 .5613 .234 .5041 .322 .4138 .176 .4114 .208 .5655 .215 .5062 .321 .4159 .206 .4125 .212 .5690 .182 .5082 .320 .4200 .231 .4139 .218 .5704 -0.181 .5140 .296 .4221 .244 .4149 .222 .6183 +0.265 .5154 .264 .4242 .254 .4167 .213 .6200 .268 .5168 .238 .4284 .258 .4177 .212 .6231 .285 .5196 .179 .4304 .268 .4201 .202 .6241 .295 .5210 .168 .4325 .280 .4208 .195 .6273 .276 .5224 .132 .4367 .289 .4229 .179 .6287 .275 .5251 .076 .4388 .299 .4236 .173 .6315 .288 .5265 +0.013 .4409 .291 .4257 .147 .6329 .283 .5279 -0.009 .4447 .276 .4267 .137 .6356 .281 .5307 .071 .4468 .266 .4299 .093 .6370 .281 .5321 .119 .4488 .243 .4316 .069 .6391 .269 .5335 .157 .4522 .234 .4326 -0.060 .6401 .255 .5363 .203 .4536 .217 .6433 .238 .5376 .206 .4550 .190 2442187 .6495 .120 .5390 .213 .4578 .130 .4483 +0.261 .6537 +0.029 .5418 .198 .4591 .102 .4501 .240 .6565 -0.034 .5432 .189 .4605 +0.088 .4554 .117 .6575 .077 .5446 .160 .4640 -0.017 .4563 .092 .6599 .159 .5474 .132 .4654 .045 .4573 .061 .6613 .173 .5489 -0.104 .4668 .098 .4580 +0.033 .6641 .213 .4696 .188 .4618 -0.086 .6655 .223 2436725 .4710 .205 .4626 .111 .6676 .227 .3482 +0.216 .4723 .209 .4635 .134 .6690 .226 .3519 .155 .4758 .212 .4642 .160 .6717 .195 .3536 .118 .4772 .186 .4651 .186 .6731 .185 .3554 .081 .4786 .162 .4658 .208 .6759 .149 .3585 +0.010 .4821 .130 .4666 .219 .6771 .146 .3598 -0.040 .4835 .127 .4676 .221 .6794 .109 .3619 .084 .4848 .125 .4686 .240 .6804 -0.098 .3649 .136 .4876 -0.087 .4704 .230 .3663 .181 .4710 .216 2442522 .3677 .208 2441860 .4756 .169 .4050 +0.262 .3705 .219 .3871 +0.280 .4766 .164 .4062 .253 .3719 .208 .3878 .267 .4773 .162 .4087 .252 .3733 .222 .3896 .256 .4781 .155 .4096 .248 .3760 -0.199 .3903 +0.251 .4925 -0.027 .4135 +0.233 Table 9 (cont.) Photoelectric blue observations of YZ Boo J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2442522 2442523 2443936 2443936 .4187 +0.171 .4455 +0.269 .5302 -0.189 .5864 +0.270 .4210 .127 .4485 .258 .5308 .192 .5885 .257 .4220 .103 .4533 .229 .5329 .177 .5892 .263 .4244 +0.055 .4542 .247 .5367 .135 .5913 .279 .4283 -0.048 .4567 .178 .5388 .087 .5923 .271 .4292 .100 .4579 .166 .5395 .079 .5940 .273 .4323 .176 .4611 .105 .5413 .051 .6017 .238 .4336 .208 .4649 +0.027 .5423 .052 .6052 .193 .4366 .240 .4698 -0.107 .5440 .027 .6058 .186 .4410 .220 .4730 .201 .5447 -0.009 .6086 .118 .4420 .198 .4744 .245 .5468 +0.034 .6107 .062 .4507 .126 .4769 .251 .5482 .045 .6121 +0.034 .4556 .061 .4782 .232 .5531 .085 .6149 -0.031 .4566 .040 .4812 .228 .5538 .082 .6163 .081 .4598 -0.009 .4830 .207 .5558 .094 .6170 .111 .4607 +0.012 .4859 .184 .5565 .102 .6183 .152 .4631 .027 .4910 .138 .5586 .113 .6194 .201 .4643 .051 .4936 .085 .5600 .131 .6208 .230 .4667 .058 .4948 -0.075 .5614 .159 .6218 .237 .4681 +0.076 .5624 .159 .6232 .245 2442524 .5645 .167 .6239 .241 2442523 .4183 -0.252 .5652 .162 .6260 .249 .4097 +0.119 .4197 .232 .5670 .166 .6267 .251 .4126 .126 .4266 .161 .5680 .174 .6284 .241 .4137 .148 .4283 .125 .5701 .200 .6291 .249 .4163 .149 .4313 .120 .5708 .206 .6315 .233 .4176 .177 .4329 .082 .5725 .212 .6322 .219 .4222 .184 .4364 -0.014 .5732 .212 .6340 .207 .4252 .220 .4385 +0.009 .5753 .227 .6350 .207 .4265 .238 .4412 .033 .5767 .250 .6371 .179 .4296 .236 .4429 .025 .5788 .253 .6378 .167 .4308 .242 .4464 .064 .5798 .255 .6392 .134 .4341 .237 .4482 .091 .5822 .270 .6406 .121 .4398 .235 .4530 +0.138 .5833 .271 .6427 .097 .4412 +0.259 .5850 +0.272 .6440 -0.075 Table 10 Photographic observations of XX Cyg J.D. m_pg J.D. m_pg J.D. m_pg J.D. m_pg 2433538 2433538 2433538 2433538 .3369 11.61 .3619 11.82 .3932 12.28 .4265 12.43 .3397 11.61 .3702 12.06 .3959 12.14 .4293 12.47 .3425 11.48 .3730 12.01 .3987 12.21 .4320 12.46 .3480 11.63 .3758 12.12 .4098 12.29 .4376 12.37 .3536 11.84 .3814 12.06 .4154 12.28 .4404 12.33 .3564 11.74 .3876 12.16 .4182 12.38 .4439 12.32 .3591 11.80 .3904 12.10 .4209 12.33 .4466 12.28 Table 10 (cont.) Photographic observations of XX Cyg J.D. m_pg J.D. m_pg J.D. m_pg J.D. m_pg 2433538 2434150 2434576 2434576 .4494 12.15 .4626 12.32 .3562 12.54 .4006 11.58 .4522 12.17 .4675 12.23 .3589 12.40 .4034 11.68 .4550 12.15 .4702 12.16 .3617 12.43 .4578 12.03 .4730 11.98 .3645 12.35 2435035 .4605 11.90 .4758 11.97 .3673 12.39 .3236 12.16 .4633 11.60 .4786 11.70 .3700 12.30 .3264 11.93 .4661 11.55 .4814 11.56 .3728 12.22 .3292 11.65 .4689 11.47 .4841 11.47 .3756 12.10 .3319 11.52 .4723 11.52 .4869 11.48 .3784 12.03 .3347 11.51 .4751 11.54 .4897 11.48 .3812 11.92 .3375 11.47 .4779 11.63 .4925 11.45 .3839 11.71 .3431 11.48 .4807 11.55 .4952 11.53 .3867 11.48 .3458 11.55 .4980 11.63 .3895 11.46 .3486 11.57 2434150 .5008 11.63 .3923 11.45 .3514 11.60 .4571 12.39 .5064 11.75 .3950 11.44 .3545 11.68 .4598 12.30 .5091 11.80 .3978 11.49 Table 11 Photoelectric yellow observations of XX Cyg J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2436403 2436403 2436456 2436815 .3936 +0.219 .5030 +0.351 .4001 +0.004 .4216 -0.441 .3964 +0.039 .5065 .333 .4032 -0.232 .4232 .439 .3989 -0.073 .5089 .367 .4050 .377 .4271 .405 .4013 .252 .5114 .421 .4069 .416 .4293 .419 .4051 .356 .5144 .343 .4103 .435 .4311 .370 .4077 .484 .5235 .267 .4117 .430 .4345 .319 .4107 .464 .5258 .158 .4136 .423 .4387 .294 .4151 .376 .5294 +0.028 .4173 .408 .4405 .266 .4184 .354 .5319 -0.048 .4210 .350 .4443 .189 .4260 .252 .5343 .164 .4247 .284 .4460 .163 .4284 .192 .5365 .285 .4265 .235 .4479 .079 .4312 .149 .5397 .379 .4284 .199 .4522 .056 .4334 .114 .5420 .498 .4341 .137 .4542 -0.003 .4366 .060 .5443 .516 .4360 .115 .4563 +0.012 .4388 .014 .5475 .448 .4379 .098 .4604 .054 .4409 -0.025 .5495 .371 .4418 .088 .4625 .023 .4445 +0.020 .5519 .327 .4437 .075 .4646 .056 .4488 .072 .5544 -0.309 .4455 .053 .4698 .099 .4509 .078 .4492 .045 .4722 .155 .4546 .116 2436456 .4511 -0.024 .4743 .151 .4568 .174 .3865 +0.334 .4529 +0.026 .4792 .192 .4595 .178 .3902 .227 .4813 .181 .4639 .207 .3920 .231 2436815 .4833 .207 .4690 .214 .3939 .196 .4165 -0.345 .4875 .231 .4717 .225 .3972 .153 .4189 .392 .4896 .226 .4815 +0.267 .3987 +0.036 .4200 -0.415 .4917 +0.199 Table 11 (cont.) Photoelectric yellow observations of XX Cyg J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2436815 2436844 2441538 2441538 .4958 +0.233 .2750 -0.241 .4150 -0.331 .5340 -0.446 .4979 .232 .2765 .334 .4164 .310 .5361 .443 .5000 .226 .2771 .367 .4192 .203 .5368 .422 .5046 .315 .2777 .413 .4206 .192 .5385 .417 .5099 .312 .2783 .399 .4247 .091 .5392 .421 .5129 .297 .2790 .415 .4317 .054 .5421 .398 .5144 .319 .2796 .432 .4331 .037 .5435 .387 .5158 .340 .2802 .430 .4358 .026 .5463 .336 .5172 .341 .2816 .427 .4372 -0.015 .5477 -0.320 .5202 .403 .2822 .435 .4400 +0.036 .5215 .397 .2828 .417 .4414 .044 2442278 .5229 .328 .2835 .429 .4442 .049 .3692 +0.370 .5260 .318 .2841 .424 .4456 .087 .3703 .373 .5274 .357 .2849 .417 .4483 .099 .3724 .394 .5289 .392 .2871 .429 .4539 .126 .3779 .381 .5318 .328 .2877 .420 .4567 .136 .3791 .362 .5333 .270 .2882 .408 .4581 .140 .3803 .335 .5347 .260 .2888 .404 .4608 .141 .3814 .301 .5377 .204 .2893 -0.397 .4622 .172 .3823 .299 .5392 .133 .3990 +0.282 .4650 .152 .3885 .166 .5407 .107 .4009 .185 .4692 .207 .3896 .146 .5435 +0.049 .4022 .145 .4706 .195 .3905 .104 .5448 -0.055 .4029 .139 .4733 .189 .3916 +0.047 .5463 .095 .4034 .136 .4747 .247 .3926 -0.030 .5490 .242 .4040 .113 .4775 .235 .3936 .144 .5503 .330 .4045 .105 .4789 .253 .3948 .233 .5516 .394 .4051 .069 .4817 .263 .3959 .291 .5528 .456 .4056 +0.060 .4831 .257 .3979 .376 .5556 .503 .4069 -0.014 .4858 .263 .3990 .401 .5572 .516 .4073 .025 .4872 .281 .4000 .434 .5603 .492 .4078 .038 .4914 .266 .4009 .431 .5636 .452 .4083 .100 .4942 .291 .4020 .425 .5654 -0.382 .4087 .149 .4956 .315 .4031 .412 .4093 .172 .4982 .278 .4044 .414 2436844 .4101 .237 .4996 .283 .4091 .333 .2640 +0.216 .4115 .328 .5039 .276 .4101 .318 .2645 .203 .4120 .344 .5067 .300 .4114 .312 .2652 .206 .4126 .370 .5108 .250 .4126 .314 .2658 .178 .4132 .415 .5146 .182 .4137 .293 .2664 .151 .4137 .427 .5178 .153 .4214 .199 .2676 .131 .4142 .453 .5205 +0.070 .4223 .174 .2685 .092 .4148 .456 .5212 -0.014 .4233 .147 .2693 .085 .4161 .461 .5229 .078 .4244 -0.139 .2699 .075 .4167 .468 .5236 .105 .2705 +0.039 .4173 .447 .5254 .353 2444454 .2719 -0.011 .4179 .450 .5261 .367 .4141 +0.386 .2725 .056 .4184 .455 .5278 .428 .4153 .401 .2730 .069 .4189 .444 .5285 .444 .4165 .385 .2736 .144 .4194 .433 .5306 .463 .4177 .395 .2740 .166 .4207 .431 .5313 .473 .4189 .369 .2745 -0.193 .4212 -0.415 .5330 -0.469 .4202 +0.363 Table 11 (cont.) Photoelectric yellow observations of XX Cyg J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2444454 2444454 2444455 2444455 .4214 +0.361 .4673 -0.280 .3793 +0.187 .4136 -0.252 .4226 .361 .4698 .194 .3805 +0.161 .4148 .241 .4238 .348 .4710 .175 .3867 -0.184 .4211 .121 .4255 .341 .4735 .110 .3879 .300 .4223 .089 .4365 .193 .4813 .034 .3892 .371 .4235 .098 .4377 .126 .4825 .038 .3904 .428 .4248 .066 .4389 .081 .4837 .011 .3916 .459 .4260 .041 .4401 +0.003 .4849 -0.008 .3928 .478 .4272 .047 .4413 -0.043 .4874 +0.022 .3941 .487 .4284 .041 .4425 .147 .4886 .037 .3953 .476 .4309 .023 .4438 .241 .4898 +0.053 .3965 .480 .4321 -0.005 .4450 .346 .3977 .468 .4380 +0.060 .4518 .460 2444455 .4039 .394 .4391 .074 .4530 .461 .3695 +0.336 .4050 .377 .4404 .107 .4542 .452 .3707 .340 .4063 .367 .4416 .117 .4555 .435 .3719 .340 .4075 .356 .4441 .114 .4567 .426 .3732 .329 .4087 .352 .4453 .112 .4579 .411 .3745 .323 .4100 .321 .4465 .119 .4592 .389 .3756 .278 .4112 .317 .4477 .141 .4604 .394 .3768 .260 .4124 -0.296 .4489 +0.150 .4661 -0.294 .3781 +0.225 Table 12 Photoelectric blue observations of XX Cyg J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2436403 2436403 2436403 2436456 .3923 +0.027 .4558 -0.033 .5431 -0.784 .4201 -0.594 .3950 -0.099 .4579 +0.010 .5455 .721 .4238 .565 .3977 .198 .4607 .026 .5485 .671 .4256 .542 .4001 .345 .4655 .035 .5506 .638 .4275 .514 .4026 .614 .4829 .196 .5532 -0.629 .4327 .383 .4063 .709 .4860 .209 .4351 .308 .4091 .741 .4883 .199 2436456 .4370 .300 .4122 .710 .4916 .239 .3856 +0.206 .4409 .264 .4167 .643 .4956 .222 .3893 .148 .4427 .244 .4200 .583 .4986 .253 .3911 .133 .4446 .222 .4234 .500 .5015 .271 .3930 .102 .4483 .190 .4273 .398 .5076 .274 .3965 +0.071 .4502 .178 .4298 .411 .5129 .292 .3980 -0.039 .4520 -0.152 .4324 .355 .5224 .143 .3994 .134 .4355 .261 .5246 .130 .4022 .403 2436815 .4388 .195 .5268 +0.018 .4041 .497 .4160 -0.676 .4421 .166 .5306 -0.120 .4059 .649 .4183 .725 .4456 .138 .5329 .199 .4096 .708 .4194 .740 .4478 .131 .5355 .397 .4110 .720 .4208 .747 .4499 .078 .5386 .664 .4127 .699 .4224 .743 .4533 -0.051 .5406 -0.733 .4163 -0.656 .4262 -0.700 Table 12 (cont.) Photoelectric blue observations of XX Cyg J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2436815 2436815 2441538 2444454 .4285 -0.674 .5549 -0.758 .5275 -0.717 .4193 +0.261 .4302 .634 .5564 .781 .5282 .752 .4218 .216 .4336 .534 .5580 .781 .5303 .778 .4250 .217 .4380 .480 .5598 .758 .5310 .787 .4259 +0.211 .4396 .429 .5629 .705 .5327 .782 .4369 -0.017 .4435 .383 .5646 -0.672 .5337 .770 .4381 .079 .4451 .351 .5354 .755 .4393 .175 .4470 .313 2441538 .5364 .728 .4405 .239 .4511 .233 .4143 -0.596 .5382 .727 .4417 .364 .4532 .200 .4157 .571 .5389 .707 .4429 .456 .4553 .194 .4185 .485 .5414 .672 .4442 .551 .4594 .170 .4199 .476 .5428 .659 .4454 .680 .4615 .135 .4226 .416 .5456 .615 .4522 .803 .4636 .126 .4240 .370 .5470 -0.587 .4534 .791 .4685 .088 .4268 .338 .4546 .799 .4712 .070 .4310 .264 2442278 .4559 .785 .4733 -0.018 .4324 .240 .3697 +0.271 .4571 .748 .4782 +0.012 .4393 .161 .3719 .277 .4583 .724 .4803 .024 .4435 .135 .3730 .273 .4596 .713 .4823 .031 .4449 .094 .3809 .262 .4608 .679 .4865 .019 .4476 .085 .3818 .219 .4665 .565 .4886 .047 .4532 -0.043 .3829 +0.132 .4677 .524 .4907 .068 .4560 +0.007 .3890 -0.001 .4689 .474 .4948 .125 .4574 +0.022 .3901 .068 .4702 .452 .4969 .159 .4601 0.000 .3911 .153 .4714 .392 .4990 .176 .4615 +0.031 .3921 .220 .4739 .366 .5032 .237 .4643 .059 .3931 .295 .4817 .230 .5089 .231 .4657 .051 .3942 .450 .4829 .231 .5122 .238 .4699 .098 .3953 .585 .4853 .224 .5136 .227 .4726 .122 .3964 .649 .4865 .181 .5151 .244 .4740 .106 .3974 .707 .4878 .167 .5165 .216 .4768 .133 .3995 .780 .4890 .172 .5195 .220 .4782 .145 .4004 .795 .4902 -0.145 .5209 .235 .4824 .163 .4015 .809 .5222 .225 .4865 .153 .4026 .786 2444455 .5252 .189 .4893 .176 .4038 .796 .3699 +0.232 .5267 .206 .4949 .166 .4049 .773 .3711 .215 .5282 .202 .4975 .186 .4096 .658 .3724 .205 .5310 .176 .5018 .184 .4120 .645 .3736 .208 .5325 .144 .5032 .211 .4131 .626 .3748 .162 .5340 .129 .5060 .193 .4143 .603 .3760 .142 .5369 .080 .5074 .134 .4218 .440 .3773 .092 .5384 .072 .5101 .088 .4228 .429 .3785 .074 .5400 +0.050 .5115 .075 .4238 .403 .3797 +0.013 .5429 -0.086 .5143 +0.050 .4249 -0.411 .3809 -0.031 .5442 .134 .5171 -0.025 .3871 .459 .5456 .252 .5198 .058 2444454 .3884 .588 .5484 .489 .5208 .181 .4145 +0.276 .3896 .688 .5496 .568 .5226 .313 .4157 .280 .3908 .728 .5510 .662 .5233 .372 .4169 .267 .3920 .773 .5522 -0.731 .5257 -0.637 .4181 +0.284 .3933 -0.778 Table 12 (cont.) Photoelectric blue observations of XX Cyg J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2444455 2444455 2444455 2444455 .3945 -0.767 .4091 -0.624 .4240 -0.260 .4383 -0.083 .3957 .784 .4104 .612 .4252 .248 .4408 .068 .3969 .755 .4116 .568 .4264 .220 .4420 .063 .3982 .756 .4128 .539 .4276 .191 .4432 .062 .4042 .683 .4141 .523 .4289 .198 .4445 .061 .4055 .663 .4153 .506 .4301 .191 .4457 .027 .4067 .662 .4215 .329 .4313 .161 .4469 .023 .4079 -0.646 .4227 -0.277 .4325 -0.145 .4481 -0.015 Table 13 Photographic observations of DY Her J.D. m_pg J.D. m_pg J.D. m_pg J.D. m_pg 2429068 2429068 2429068 2429068 .3843 10.24 .3975 10.20 .4107 10.35 .4211 10.39 .3864 10.13 .4003 10.21 .4149 10.32 .4232 10.29 .3885 10.15 .4045 10.26 .4170 10.34 .4253 10.41 .3906 10.19 .4086 10.30 .4191 10.30 .4302 10.44 .3954 10.17 Table 14 Photoelectric yellow observations of DY Her J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2441508 2441508 2441508 2441508 .3723 +0.899 .4147 +1.083 .4522 +1.246 .4879 +1.285 .3737 .880 .4161 .095 .4550 .251 .4890 .297 .3761 .845 .4203 .117 .4564 .250 .4904 .280 .3772 .847 .4220 .129 .4585 .255 .4911 .278 .3789 .840 .4227 .142 .4599 .255 .4932 .267 .3800 .824 .4244 .150 .4619 .261 .4939 .266 .3828 .853 .4254 .149 .4626 .246 .4953 .260 .3855 .874 .4279 .149 .4654 .269 .4964 .270 .3893 .906 .4286 .166 .4689 .259 .4976 .258 .3904 .909 .4314 .154 .4713 .273 .4983 .251 .3987 .980 .4321 .166 .4720 .288 .5001 .231 .4001 0.990 .4342 .173 .4744 .283 .5011 .226 .4029 1.006 .4348 .167 .4754 .263 .5025 .214 .4036 .002 .4365 .182 .4782 .292 .5032 .210 .4057 .022 .4372 .202 .4800 .302 .5050 .191 .4067 .038 .4396 .192 .4810 .297 .5061 .189 .4085 .038 .4417 .215 .4828 .280 .5075 .159 .4092 .048 .4446 .212 .4838 .286 .5081 .159 .4112 .070 .4473 .242 .4855 .292 .5098 .130 .4126 +1.079 .4508 +1.257 .4862 +1.289 .5108 +1.124 Table 14 (cont.) Photoelectric yellow observations of DY Her J.D. Delta V J.D. Delta V J.D. Delta V J.D. Delta V 2441508 2441508 2444050 2444050 .5126 +1.074 .5233 +0.860 .3995 +1.150 .4189 +0.855 .5133 1.048 .5240 +0.848 .4023 .119 .4203 .841 .5150 0.995 .4064 1.006 .4231 .869 .5157 .981 2444050 .4078 0.976 .4245 .874 .5171 .939 .3856 +1.259 .4106 .919 .4273 .891 .5182 .934 .3870 .284 .4120 .884 .4287 .902 .5203 .877 .3939 .227 .4148 .851 .4314 .938 .5213 +0.871 .3981 +1.177 .4162 +0.848 .4328 +0.951 Table 15 Photoelectric blue observations of DY Her J.D. Delta B J.D. Delta B J.D. Delta B J.D. Delta B 2441508 2441508 2441508 2441508 .3717 +0.622 .4282 +0.936 .4796 +1.131 .5175 +0.706 .3730 .629 .4307 .950 .4807 .149 .5196 .647 .3758 .569 .4317 .960 .4821 .136 .5210 .623 .3765 .551 .4335 .979 .4835 .132 .5230 .574 .3786 .538 .4362 0.997 .4848 .122 .5237 +0.579 .3793 .536 .4369 1.004 .4858 .128 .3814 .550 .4386 0.992 .4876 .119 2444050 .3821 .556 .4393 0.995 .4883 .119 .3849 +1.114 .3848 .574 .4410 1.018 .4901 .130 .3863 .112 .3862 .585 .4420 .025 .4908 .130 .3891 .083 .3890 .606 .4442 .023 .4925 .111 .3905 .080 .3897 .605 .4449 .031 .4935 .108 .3932 .079 .3980 .710 .4470 .051 .4950 .100 .3946 .055 .3994 .717 .4501 .058 .4960 .097 .3974 .000 .4022 .756 .4543 .086 .4973 .100 .3988 1.001 .4032 .758 .4557 .088 .4980 .083 .4016 0.906 .4064 .787 .4581 .094 .4998 .087 .4030 .872 .4078 .796 .4592 .099 .5008 .064 .4057 .780 .4088 .795 .4616 .096 .5022 .061 .4071 .742 .4109 .843 .4623 .112 .5047 .030 .4099 .661 .4119 .844 .4647 .120 .5057 .020 .4113 .642 .4140 .858 .4661 .118 .5071 1.004 .4141 .583 .4154 .868 .4678 .127 .5078 0.985 .4196 .538 .4182 .886 .4685 .130 .5094 .951 .4224 .546 .4196 .899 .4710 .134 .5105 .911 .4238 .564 .4217 .910 .4717 .120 .5119 .852 .4266 .595 .4223 .909 .4751 .121 .5129 .816 .4280 .609 .4241 .923 .4765 .118 .5147 .760 .4307 .646 .4272 +0.941 .4779 +1.130 .5154 +0.743 .4321 +0.664