COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2503 Konkoly Observatory Budapest 13 April 1984 HU ISSN 0374-0676 WALRAVEN VBLUW PHOTOMETRY OF FIVE SUSPECTED VARIABLE STARS* While observing pulsating variable stars with periods between one and three days with the Walraven five channel photometer attached to the Dutch 91 cm telescope at the European Southern Observatory, La Silla, Chile, five stars suspected of variability were observed occasionally in order to confirm their variability. They were selected on the grounds of the spectral information given in the "New Catalogue of Suspected Variable Stars" (Kholopov et. al, 1982). For a detailed analysis of the properties of the VBLUW system and its instrumental implementations, we refer the reader to the article by Lub and Pel (1977) and the references given therein. For the understanding of the tables in this paper it is necessary to recall the fact, that in the Walraven system all measurements are expressed in terms of log(intensity) units. All the data presented in this paper were obtained differentially in respect to nearby comparison stars whose intensities were tied into the standard Walraven system by frequent and nightly observations of a number of primary standards. The conventional transformation and extinction formulae were applied. The integration times (most of the time in the order of a few minutes) were chosen with the aim of attaining a 1% accuracy. A more detailed description of the observing procedures and their internal errors will be given in subsequent paper on the observations of known pulsating variables. Table I contains all the data on the five local standards used as comparison stars. Nights of photometric quality were only used for the determination of these values. The columns give: (1) HD number, (2) Walraven data with standard deviations, (3) number of observations and (4) V(J) magnitude as derived by the conversion formula given by Pel (1976) and NSV-number of the corresponding variable. The standard deviations listed indicate non- variability of the comparison stars at the 0.01 magnitude level. * Based on observations collected at the European Southern Observatory, La Silla, Chile Table I VBLUW-data for the five local standards used HD V V-B B-U U-W B-L n V(J) 8188 -0.3212 0.2176 0.3138 0.1933 0.2142 4 7.64 +- 48 12 32 45 45 (NSV 470) 160069 -0.4483 0.0055 0.2356 0.0594 0.0730 11 7.99 +- 49 15 16 57 39 (NSV 9246) 177681 -1.0117 0.1204 0.3161 0.1210 0.1184 7 9.38 +- 41 29 25 42 39 (NSV 11708) 189270 -0.6963 0.2278 0.2899 0.1825 0.2048 11 8.57 +- 67 33 35 62 47 (NSV 12665) 213543 -0.7870 0.1672 0.3428 0.1788 0.1922 6 8.81 +- 31 14 49 62 44 (NSV 14164) Notes on individual stars: NSV 470 = BV 637 = HD 8093 (F0): The star was discovered by Strohmeier, Knigge and Ott (1965) as variable with an amplitude of 0.3 m(pg) Table II lists our data on this suspected variable. As in Table I, for the convenience Table II VBLUW-data for NSV 470= BV 637= HD 8093 JDhel V V-B B-U U-W B-L V(J) B-V(J) 2445541.817 -0.746 0.147 0.363 0.172 0.195 8.72 0.36 .855 -0.752 0.148 0.358 0.169 0.193 8.73 0.36 542.851 -0.757 0.147 0.361 0.162 0.188 8.74 0.36 .873 -0.758 0.146 0.361 0.163 0.192 8.75 0.36 544.871 -0.748 0.144 0.358 0.160 0.190 8.72 0.36 .906 -0.755 0.150 0.360 0.163 0.196 8.74 0.37 546.858 -0.754 0.146 0.361 0.167 0.198 8.74 0.36 551.820 -0.763 0.145 0.365 0.162 0.195 8.76 0.36 of the reader, the transformation into the Johnson BV system is provided, employing Pel's formula (1976) as well as Table 7 of Walraven, Tinbergen and Walraven (1964). A slight correction term due to the changes in the V-band sensitivity as determined by Lub and Pel (1977) has been added. Our observations do not confirm the variability with the given amplitude during ten nights of monitoring. Thus, the star is not a short-period Cepheid. NSV 9246 = BV 547 = HD 159654 (F5 Ib): The variability of this star was first noted by Strohmeier, Knigge and Ott (1964). They observed an amplitude of 0.6 m(pg). Our data, covering 58 nights and listed in Table III, confirm the Table III VBLUW-data for NSV 9246 = BV 547 = HD 159659 JDhel V V-B B-U U-W B-L V(J) B-V(J) 2445540.653 -0.099 0.306 0.549 0.328 0.286 7.07 0.74 .778 -0.108 0.299 0.525 0.283: 0.278 7.10 0.72 541.646 - 0.358 0.541 0.342 0.306 - 0.86 .759 -0.226 0.375 0.557 0.384 0.352 7.38 0.89 542.666 -0.231 0.367 0.543 0.355 0.335 7.39 0.88 544.784 -0.153 0.340 0.530 0.313 0.307 7.20 0.82 545.546 -0.236 0.378 0.543 0.356 0.346 7.40 0.90 546.537 -0.175 0.336 0.540 0.338 0.310 7.26 0.81 .742 -0.146 0.323 0.546 0.334 0.302 7.19 0.78 547.491 -0.114 0.312 0.555 0.337 0.293 7.11 0.76 .642 -0.123 0.315 0.554 0.340 0.299 7.13 0.76 .683 -0.134 0.319 0.562 0.345 0.306 7.16 0.77 548.502 -0.223 0.368 0.546 0.357 0.341 7.37 0.88 551.518 -0.174 0.349 0.549 0.348 0.321 7.25 0.84 564.533 -0.120 0.317 0.556 0.327 0.305 7.12 0.77 566.499 -0.209 0.355 0.543 0.348 0.328 7.34 0.85 582.495 -0.224 0.373 0.551 0.355 0.349 7.37 0.89 583.611 - 0.342 0.546 0.338 0.319 - 0.82 585.545 -0.208 0.358 0.560 0.353 0.336 7.34 0.86 593.504 -0.218 0.359 0.542 0.328: 0.328 7.36 0.86 596.506 -0.234 0.375 0.547 0.349 0.348 7.40 0.89 597.495 -0.144 0.320 0.545 0.339 0.300 7.18 0.77 598.528 -0.134 0.326 0.555 0.343 0.309 7.16 0.79 variability both in brightness and in colour, indicating Cepheid variation. Our observation are sufficient to deduce preliminary elements using the method of Stellingwerf (1978), namely: JD(max) = 2445540.43 + 3.3825 * E +-.05 +-.015 (me) In Figure 1 the Walraven V, V-B and B-U light and colour curves are depicted, phased according to these elements. These light curves show that NSV 9246 is a small amplitude disc population Cepheid, therefore it pulsates in the first harmonic mode. NSV 11708 = SVS 994 = BD-05d4861 (F5): The first mentioning of a possible variation of this star with an amplitude of one magnitude (photographic) and [FIGURE 1] Figure 1 Light and colour curves of NSV 9246 in the Walraven system phased according to the elements JDhel = 2445540.43 + 3.3825 * E a possible EA classification was provided by Soloviev (1945). Our data as listed in Table IV might lend some support to this classification. A slight decrease of the brightness (delta V approx.=0.1m) was observed on JD 2445541 during a two and a half hour timespan. The period is probably rather long. Table IV VBLUW-data for NSV 11708 = SVS 994 = BD -05d4861 JDhel V V-B B-U U-W B-L V(J) B-V(J) 2445540.701 -1.324 0.259 0.403 0.263 0.240 10.14 0.63 541.670 -1.330 0.263 0.407 0.269 0.235 10.16 0.64 .767 -1.362 0.252 0.423 0.288 0.248 10.24 0.62 542.740 -1.325: 0.265 0.413 - 0.235 10.14: 0.64 544.791 -1.336 0.258 0.414 0.250 0.245 10.17 0.63 546.725 -1.338 0.261 0.412 0.229 0.230 10.18 0.64 547.562 -1.331 0.254 0.421 0.238 0.236 10.16 0.62 551.686 -1.344 0.251 0.416 0.237 0.235 10.19 0.62 NSV 12665 = BV 1477 = HD 189306 (F2): The star was reported to be variable with an amplitude of 0.3 m(pg) by Strohmeier (1971). Our observations listed in Table V indicate a slight variability by only a few hundredths of a magnitude in V, Table V VBLUW-data for NSV 12665 = BV 1477 = HD 189306 JDhel V V-B B-U U-W B-L V(J) B-V(J) 2445540.771 -0.526 0.190 0.358 0.189 0.212 8.16 0.47 .854 -0.490: 0.187 0.362 0.202 0.212 8.07: 0.46 541.707 -0.524 0.187 0.351 0.190 0.211 8.15 0.46 .773 -0.530 0.194 0.350 0.196 0.213 8.17 0.48 .839 -0.540 0.199 0.369 0.220 0.228 8.19 0.49 542.746 -0.527 0.188 0.352 0.196 0.209 8.16 0.46 .864 -0.524 0.191 0.351 0.194 0.211 8.15 0.47 544.821 -0.524 0.190 0.348 0.200 0.212 8.15 0.47 546.749 -0.524 0.189 0.349 0.194 0.211 8.15 0.47 547.676 -0.523 0.189 0.350 0.194 0.208 8.15 0.47 551.808 -0.533 0.191 0.350 0.192 0.212 8.18 0.47 NSV 14164 =BV 793 = HD 212936 (F5): The last star in our sample was found by Strohmeier Fischer and Ott (1966) to be variable with an amplitude of 0.4 m(pg). The nine observations collected in Table VI show no variability exceeding the internal errors of the measurements. If the star is variable at all, it is probably an eclipsing binary. Table VI VBLUW-data for NSV 14164= BV 793= HD 212936 JDhel V V-D B-U U-W B-L V(J) B-V(J) 2445541.749 -1.066 0.176 0.350 0.183 0.206 9.51 0.44 .814 -1.070 0.170 0.342 0.178 0.208 9.52 0.42 .863 -1.064 0.169 0.350 0.175 0.207 9.51 0.42 542.753 -1.059 0.168 0.344 0.170 0.201 9.49 0.42 .869 -1.061 0.170 0.338 0.182 0.195 9.50 0.42 544.867 -1.060 0.165 0.334 0.164: 0.194 9.50 0.41 .912 -1.066 0.172 0.338 0.180 0.196 9.51 0.43 546.853 -1.070 0.173 0.346 0.188 0.208 9.52 0.43 We would like to express our gratitude towards the directorate of the European Southern Observatory for the allotment of observing time on the Dutch telescope at La Silla, Chile. Furthermore it is a pleasure to thank Drs. J. Pel and C. Trefzger for their assistance concerning the operation of the telescope and the handling of the Walraven photometer. R. DIETHELM Astronomisches Institut der Universitaet Basel, Venusstrasse 7 CH-4102 Binningen/Switzerland. S. TJEMKES Sterrenkundig Instituut "Anton Pannekoek", Roeterstraat 15, 1018 wb Amsterdam, The Netherlands References: Kholopov, P.N. et al.: 1982, New Catalogue of Suspected Variable Stars, Publishing Office "Nauka", Moscow [BIBCODE 1982ncss.book.....K ] Lub, J., Pel, J.W.: 1977, Astron.Astrophys. 54, 137 [BIBCODE 1977A&A....54..137L ] Pel, J.W.: 1976, Astron.Astrophys.Suppl.Ser. 24, 413 [BIBCODE 1976A&AS...24..413P ] Soloviev, A.V.: 1945 Astr.Tsirk. USSR, No. 40 Stellingwerf, R.F.: 1978, Astrophys. J., 224, 953 [BIBCODE 1978ApJ...224..953S ] Strohmeier, W.: 1971, Inf.Bull.Var. Stars No. 562 Strohmeier, W., Fischer, H., Ott, H.: 1966, Inf.Bull.Var. Stars No. 120 Strohmeier, W., Knigge, R., Ott, H.: 1964, Inf.Bull.Var. Stars No. 74 Strohmeier, W., Knigge, R., Ott, H.: 1965, Inf.Bull.Var. Stars No. 107 Walraven, J.H., Tinbergen, J., Walraven, Th.: 1964, Bull.Astron.Inst. Neth., 17, 520 [BIBCODE 1964BAN....17..520W ]