COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3657 Konkoly Observatory Budapest 9 September 1991 HU ISSN 0374 - 0676 SOME ADDITIONAL DATA ON THE NEW SHORT-PERIOD VARIABLE IN NGC 7142 Recently, Crinklaw & Talbert (1991; =CT) reported on results of a survey for short-period variables in the open cluster NGC 7142. Due to its apparent similarity in both age and morphology to NGC 188, NGC 7142 might have turned out to be a rewarding objective particularly with respect to W UMa stars, since NGC 188 is overabundant in such variables. However, out of 432 stars with V <=18.0, only one was found to be variable. Unfortunately, there were insufficient observations of this star to classify its variable type, although the data presented appeared to be consistent with those of an eclipse. The above authors suggested further observations of this star. For some time past, we are engaged in research work in the neighborhood of NGC 7142 and have 5 V and 4 B Tautenburg Schmidt plates at our disposal. From these plates, by iris photometry, we determined the brightness of the star using standards close to it taken from CT. The accuracy of our data is about +-0.05m in B and V; they are listed in Table 1 together with CT's values. The light curve, again with inclusion of CT's data, is presented in Figure 1. On the basis of our graphical and tabular material, we can confirm that the star in question obviously is a short-period variable. See Figure 2 for a finding chart and coordinates. [FIGURE 1] Figure 1. Light curve for the variable star. Circles indicate V-magnitude measurements, squares are B-magnitude values. Filled symbols are our data; open symbols are data taken from Crinklaw and Talbert (1991) Table 1. Photometry of the variable star. Above dashed line: Our data. Below: data from Crinklaw & Talbert (1991) H.J.D. V H.J.D. B 5466.5487 16.16 5464.5570 17.40 6650.4841 16.59 5466.5043 17.42 6650.5022 16.36 5466.5865 17.17 6650.5216 16.11 6679.4169 17.04 6679.4946 16.11 -------------------------------------- 7442.8104 16.463 7469.6625 17.408 7469.6410 16.472 7469.7410 17.036 7469.7354 16.172 7469.7910 17.040 7469.7861 16.111 7469.8438 17.039 7469.8382 16.123 7470.7410 17.034 7470.7361 16.130 7470.7938 17.067 7470.7888 16.130 [FIGURE 2] Figure 2: Finding chart for the variable (1950: 21h43m44s, +65d30'08"; +-10"), reproduced from a red-sensitive Kiso plate In particular, we note: I) our maximum brightnesses fit well with those of CT in both B and V (17.04m and 16.11m, respectively); II) the faintest value is V = 16.59m, lower by 0.12m than CT's minimum; III) there are two sets consisting of three consecutive exposures respectively. With the - somewhat realistic - assumption that V = 16.6m represents the actual (main?) minimum value, the full duration of the minimum would be about 1.5 to 2 hours. Obviously, some further information on variability is hidden in the paper by VandenBerg and Heeringa (1970): based on 3 V and 4 B plates, they presented the following averaged brightness data for the star (no. 127): V = 16.24m, B = 17.02m. Therefore, in V a minimum seems to be partly included. Apart from the reasoning above, on a low-dispersion (2600 angstrom at H_gamma) Tautenburg Schmidt objective prism plate of moderate quality, the star appears to be of intermediate spectral type. In short, we note that the variable might well be of W UMa type as originally suspected by CT, but a final conclusion can not be drawn unless further monitoring observations are available. R.S. and R.W. want to express their thanks for allocation of observing time at the Karl Schwarzschild Observatorium. R. SEEBERGER, R. WEINBERGER R. ZIENER Inst. fur Astronomie, Technikerstr. 25 Karl Schwarzschild Observatorium A-6020 Innsbruck, AUSTRIA O-6901 Tautenburg, GERMANY References: Crinklaw, G., & Talbert, F. D. 1991, PASP, 103, 536 [BIBCODE 1991PASP..103..536C ] VandenBergh, S., & Heeringa, R. 1970, A&A, 9, 209 [BIBCODE 1970A&A.....9..209V ]