COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1895 Konkoly Observatory Budapest 1980 December 22 HU ISSN 0374-0676 NEW PERIOD INCREASE IN THE CEPHEID S Vul The aim of this paper is twofold: 1. To emphasize that S Vul is a Cepheid variable not a semiregular star as classified in the General Catalogue of Variable Stars (Kukarkin et al. 1969-1970). 2. To call attention to a new period increase that occurred quite recently. The stability of the light curve can clearly be seen when comparing Fernie's (1970) observations with the recent photoelectric light curve. Fernie also suggested that S Vul should be classified as a Cepheid. As a matter of fact, the only evidence which seems to support its belonging to the semiregular stars is the shape of the light curve during two or three cycles in the visual series of observations made by Schonfeld (Valentiner, 1900). The overwhelming majority of Schonfeld's light curves are typical of a Cepheid variable as are all the other visual, photographic and photoelectric light curves. The variable star S Vul was observed photoelectrically in the B and V colours of the Johnson system at Konkoly Observatory. The telescope used was the 24 inch reflector equipped with an unrefrigerated EMI 9502B photomultiplier. The star BD +26d3672 was used as the comparison star. Its magnitudes V = 10.10m and B-V = 0.68m were adopted from Fernie's (1969) paper. The observations (made in 1979 and 1980) are listed in Table 1 and shown plotted in Fig. 1. Systematic differences both in V and B-V between the average magnitudes determined by Fernie and on the basis of the present photometry can be pointed out; these differences are partly due to close companions of the comparison and of the variable stars as well as to the possibly different diameters of the diaphragm used in the two photometries. Table 1 J.D.Hel. V B-V J.D.Hel. V B-V 2444000+ 2444000+ 049.484 9.27m 1.73m 150.313 8.98m 1.47 054.422 9.41 1.74 157.291 9.00 1.57 066.424 9.19 1.68 159.290 8.97 1.66 100.526 9.08 1.65 166.253 9.09 1.68 108.407 9.17 1.78 167.26? 9.06 1.69 111.431 9.24 1.78 173.241 9.19 1.77 113.367 9.32 1.81 372.478 9.08 1.64 129.376 9.42 1.71 455.406 9.21 1.75 140.380 9.05 1.51 486.396 8.93 1.53 143.375 8.92 1.48 495.409 8.93 1.50 147.334 8.87 1.56 [FIGURE 1] Although there are several papers dealing with the period changes in S Vul (Ahnert, 1948, Makarenko, 1978; Wachmann, 1966) a new O-C diagram has been constructed. In constructing this, newly determined maximum times based on the original observations of the individual observers have been used instead of the published normal maxima. When only the moments of the normal maxima were published the yearly average normal maxima were calculated. These points in the O-C diagram (see Fig. 2 and Table 2) have lower weight. The O-C diagram has a cyclic structure. The presence of a 25 year long cycle was revealed by Makarenko (1978). The new photoelectric observations support this value of the cycle [FIGURE 2] Table 2 The O-C residuals J.D.Hel. E O-C Type Weight Reference 2401353.129 -630 +45d876 vis 0.5 Turner, Blagg1 (1917) 2401827.161 -623 +43.908 vis 0.5 Turner, Blagg1 (1917) 2402103.238 -619 +47.985 vis 1 Turner, Blagg1 (1917) 2402440.436 -614 +45.183 vis 1 Turner, Blagg1 (1917) 2402510.712 -613 +47.459 vis 1 Valentiner2(1900) 2402784.518 -609 +49.265 vis 1 Valentiner2 (1900) 2402846.258 -608 +43.005 vis 1 Turner, Blagg1 (1917) 2403182.080 -603 +38.827 vis 1 Valentiner2(1900) 2403256.691 -602 +45.438 vis 0.5 Turner, Blagg1 (1917) 2403522.788 -598 +39.535 vis 1 Valentiner2(1900) 2403527.262 -598 +44.009 vis 1 Turner, Blagg1 (1917) 2403995.650 -591 +36.397 vis 1 Valentiner2(1900) 2404333.399 -586 +34.146 vis 1 Valentiner2 (1900) 2404667.087 -581 +27.834 vis 1 Valentiner2 (1900) 2405072.289 -575 +25.036 vis 1 Valentiner2 (1900) 2405478.180 -569 +22.927 vis 1 Valentiner2(1900) 2405741.661 -565 +14.408 vis 1 Valentiner2(1900) 2406009.754 -561 +10.501 vis 1 Valentiner2(1900) 2406150.9 -559 +15.6 vis 0.5 Chandler (1877) 2406213.078 -558 +9.825 vis 1 Beljawsky3(1910) 2406416.470 -555 +9.217 vis 1 Zinner4(193.2) 2406829.175 -549 +13.922 vis 1 Zinner4(1932) 2408021.035 -531 -18.218 vis 0.5 Turner, Blagg1 (1917) 2408379.984 -526 +0.731 vis 1 Wilsing (1897) 2408716.424 -521 -2.829 vis 1 Wilsing (1897) Table 2 (cont.) J.D.Hel. E O-C Type Weight Reference 2409059.145 -516 -5d108 vis 0.5 Wilsing (1897) 2409122.246 -515 -5.007 vis 1 Hagen (1891) 2409393.161 -511 -6.092 vis 1 Hagen (1891) 2409457.036 -510 -10.217 vis 1 Turner, Blagg1 (1917) 2409799.989 -505 -8.064 vis 1 Turner, Blagg1 (1917) 2409804.214 -505 -3.039 vis 1 Hagen (1891) 2410138.708 -500 -9.145 vis 0.5 Turner, Blagg1 (1917) 2410888.287 -489 -6.966 vis 1 Hagen (1891) 2412774.986 -469 -24.267 vis 1 Parkhurst (1894) 2412784.9 -461 -14.4 vis 0.5 Hisgen (1896) 2413532 -450 -15 vis 0.5 Hisgen (1896) 2414881 -430 -26 pg 0.5 Hufnagel (1929) 2415768.4 -417 -22.9 pg 0.5 Hufnagel (1929) 2416174.4 -411 -24.9 pg 0.5 Hufnagel (1929) 2416441.9 -407 -29.4 pg 0.5 Hufnagel (1929) 2416648.9 -404 -26.4 pg 0.5 Hufnagel (1929) 2416926.6 -400 -20.7 pg 0.5 Hufnagel (1929) 2417129.9 -397 -21.4 pg 0.5 Hufnagel (1929) 2417472.4 -392 -18.9 pg 0.5 Hufnagel (1929) 2417813 -387 -18 vis 0.5 Sperra (1909) 2417815 -387 -16 pg 0.5 Hufnagel (1929) 2418150.3 -382 -21.0 vis 0.5 Sperra (1913) 2418223.9 -381 -15.4 pg 0.5 Hufnagel (1929) 2418560.0 -376 -19.3 pg 0.5 Hufnagel (1929) 2418832.6 -372 -18.7 pg 0.5 Hufnagel (1929) 2418959.843 -370 -27.310 vis 0.5 Jost (1913) 2419308.4 -365 -18.9 pg 0.5 Hufnagel (1929) 2419648.4 -360 -18.9 pg 0.5 Hufnagel (1929) 2419994.9 -355 -12.4 pg 0.5 Hufnagel (1929) 2420407.5 -349 -7.8 pg 0.5 Hufnagel (1929) 2420407.820 -349 -7.433 vis 1 Doberck (1919) 2420748.4 -344 -6.9 pg 0.5 Hufnagel (1929) 2420750.593 -344 -4.660 vis 1 Doberck (1919) 2421026 -340 -1 pg 0.5 Hufnagel (1929) 2421155.864 -338 -7.389 vis 1 Doberck (1919) 2421427.123 -334 -8.130 vis 1 Leiner (1922) 2421433.731 -334 -1.522 vis 1 Doberck (1919) 2421566.9 -332 -4.4 pg 0.5 Hufnagel (1929) 2421768.038 -329 -7.215 vis 1 Leiner (1922) 2421842 -328 -1 pg 0.5 Hufnagel (1929) 2421842.925 -328 -0.328 vis 1 Doberck (1919) 2422109.848 -324 -5.405 vis 1 Leiner (1922) 2422247.852 -322 -3.401 vis 1 Leiner (1923) 2422447.253 -319 -8.000 vis 1 Leiner (1923) 2422650 -316 -9 pg 0.5 Hufnagel (1929) 2422990.390 -317 -8.863 vis 1 Leiner (1923) 2423257.038 -307 -14.215 vis 1 Leiner (1923) 2423666.163 -301 -13.090 vis 1 Ahnert (1931) 2423736.714 -300 -10.539 vis 1 Beyer (1930) 2423739 -300 -8 pg 0.5 Hufnagel (1929) 2423941.070 -297 -10.183 vis 1 Beyer (1930) 2424071.709 -295 -15.544 vis 1 Ahnert (1931) 2424075.977 -295 -11.276 vis 1 Beyer (1930) 2424279.301 -292 -11.952 vis 1 Beyer (1930) Table 2 (cont.) J.D.Hel. E O-C Type Weight Reference 2424360 -391 +1d pg 0.5 Hufnagel (1929) 2424414.689 -290 -12.564 vis 1 Beyer (1930) 2424495.584 -290 -11.669 vis 1 Ahnert (1931) 2424683.746 -286 -15.507 vis 1 Beyer (1930) 2424755.467 -285 -11.786 vis 1 Ahnert (1931) 2425092.458 -280 -14.795 vis 9 Beyer (1930) 2425156.608 -279 -18.645 vis 1 Nielsen5 (1932) 2425159.361 -279 -15.892 vis 1 Ahnert (1931) 2425498.968 -274 -16.285 vis 9 Beyer (1930) 2425701.879 -271 -17.374 vis 1 Beyer (1930) 2425834.996 -269 -20.257 vis 1 Ahnert (1931) 2426170.4 -264 -24.9 vis 0.5 Ahnert (1948) 2426170.73 -264 -24.52 pg 0.5 Nassau, Townson (1932) 2426249.4 -263 -21.9 vis 0.5 Kukarkin (1931) 2426241.782 -263 -21.471 vis 1 Nielsen5 (1932) 2426244.260 -263 -18.993 vis 1 Terkan (1935) 2426307.9 -262 -23.4 vis 0.5 Ahnert (1948) 2426514.4 -259 -20.9 vis 0.5 Ahnert (1948) 2426580.425 -258 -22.828 vis 1 Nielsen5 (1932) 2426584.899 -258 -18.354 vis 1 Terkan (1935) 2426654.4 -257 -16.9 vis 0.5 Ahnert (1948) 2426858.3 -254 -17.0 vis 0.5 Ahnert (1948) 2426993.6 -252 -17.7 vis 0.5 Ahnert (1948) 2427331.7 -247 -19.6 pg 0.5 Nassau, Ashbrook (1943) 2427544.802 -244 -10.451 pvis 1 Azhusenis (1956) 2429672.9 -242 -18.9 pg 0.5 Nassau, Ashbrook (1943) 2428017.3 -237 -14.0 pg 0.5 Nassau, Ashbrook (1943) 2428363.673 -232 -7.580 pg 1 Azhusenis (1956) 2428429.9 -231 -9.4 pg 0.5 Nassau, Ashbrook (1943) 2428432.3 -231 -6.9 pg 0.5 Ahnert (1948) 2428633.142 -228 -10.111 pg 1 Azhusenis (1956) 2428703.4 -227 -7.9 pg 0.5 Ahnert (1948) 2428840.4 -225 -6.9 pg 0.5 Ahnert (1948) 2428842.592 -225 -4.661 pg 1 Azhusenis (1956) 2428974.8 -223 -8.5 pg 0.5 Nassau, Ashbrook (1943) 2429114.4 -221 -4.9 pg 0.5 Ahnert (1948) 2429115.985 -221 -3.268 pg 1 Azhusenis (1956) 2429247.4 -219 -7.9 pg 0.5 Ahnert (1948) 2429455.0 -216 -4.3 pg 0.5 Ahnert (1948) 2429522.4 -215 -4.9 pg 0.5 Nassau, Ashbrook (1943) 2429793.9 -211 -5.4 pg 0.5 Ahnert (1948) 2429934.0 -209 -1.3 pg 0.5 Ahnert (1948) 2430135 -206 -4 pg 0.5 Nassau, Ashbrook (1943) 2430205.3 -205 -2.0 pg 0.5 Ahnert (1948) 2430544.9 -200 -2.4 pg 0.5 Ahnert (1948) 2430678.9 -198 -4.4 pg 0.5 Ahnert (1948) 2430819 -196 0 pg 0.5 Ahnert (1948) 2431026.9 -193 +3.6 pg 0.5 Ahnert (1948) 2431291 -189 -4 pg 0.5 Ahnert (1948) 2431635.4 -184 +0.1 pg 0.5 Ahnert (1948) 2431772.4 -182 +1.1 pg 0.5 Ahnert (1948) 2432048.4 -178 +5.1 pg 0.5 Ahnert (1948) 2432178.0 -176 -1.3 pg 0.5 Ahnert (1948) 2432844.0 -166 -15.3 pg 0.5 Wachmann (1966) Table 2 (cont.) J.D.Hel. E O-C Type Weight Reference 2433523 -156 -16d pg 0.5 Wachmann (1966) 2433928 -150 -19 pg 0.5 Wachmann (1966) 2434204.4 -146 -14.9 pg 0.5 Wachmann (1966) 2434675.4 -139 -19.9 pg 0.5 Wachmann (1966) 2435098.9 -134 -16.4 pg 0.5 Wachmann (1966) 2435155.9 -132 -15.4 pg 0.5 Wachmann (1966) 2435.358.7 -129 -16.6 pg 0.5 Wachmann (1966) 2436119.506 -118 -3.747 pg 1 Chuprina (1968) 2436464.413 -113 +1.160 pg 1 Chuprina (1968) 2436808 -108 +5 pg 0.5 Wachmann (1966) 2436819.936 -108 +8.683 pg 1 Chuprina (1968) 2437150 -103 +7 pg 0.5 Wachmann (1966) 2437152.576 -103 +9.323 pg 1 Chuprina (1968) 2437493.422 -98 +10.169 pg 1 Chuprina (1968) 2437906 -92 +15 pg 0.5 Wachmann (1966) 2437906.746 -92 +15.493 pg 1 Chuprina (1968) 2438249.795 -87 +18.542 pg 1 Chuprina (1968) 2438652.244 -81 +12.991 pvis 1 Chuprina (1968) 2439006.9 -76 +26.6 pvis 0.5 Makarenko (1978) 2439345.7 -71 +26.4 pvis 0.5 Makarenko (1978) 2439755.9 -65 +28.6 pvis 0.5 Makarenko (1978) 2440097.349 -61 +18.096 pe 3 Fernie (1970) 2440093.5 -60 +26.2 pvis 0.5 Makarenko (1978) 2440495.4 -54 +20.1 pvis 0.5 Makarenko (1978) 2440906.4 -48 +23.1 pvis 0.5 Makarenko (1978) 2441235.4 -43 +12.1 pvis 0.5 Makarenko (1978) 2441506.6 -39 +11.3 pvis 0.5 Makarenko (1978) 2449906 -33 +3 pvis 0.5 Makarenko (1978) 2442256 -28 +13 pvis 0.5 Makarenko (1978) 2442655.4 -22 +4.1 pvis 0.5 Makarenko (1978) 2442980 -1.7 -11 pvis 0.5 Makarenko (1978) 2443738.161 -6 -1.092 pe 1 Turner (1980) 2444147.253 0 0.000 pe 3 present paper 2444422.573 +4 +3.320 pe 2 present paper Remarks: 1 Observer: Baxendell, 2 Obs.: Schonfeld, 3 Obs.: Glasenapp, 4 Obs.: Hartwig, 5 Obs.: Moller Nicolaisen and Pedersen Table 3 Interval P E<-532 67d379 -532