COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2627 Konkoly Observatory Budapest 15 November 1984 HU ISSN 0374 - 0676 PHOTOMETRIC OBSERVATIONS OF ACTIVE CHROMOSPHERE STARS: II Peg, HD 175 742, HD 199 178 Photometric observations of three active chromosphere stars were carried out between August 17 and September 4, 1984 at the Ostrowik Station of the Warsaw University Observatory. Single channel photometer equipped with an uncooled EMI 6256A photomultiplier, attached to the 60cm reflector, was used. Differential observations were reduced to the standard UBV system. 1) II Peg This often observed object belongs to RS CVn group. BD +28d4667 served as a comparison star. It was measured four times relative to BD +27d4648. Assuming for this star V=9.39 and B-V=1.02 (Bohusz and Udalski 1981) I obtained for BD +28d4667 V=8.24 +- 0.01 and B-V=0.76+- 0.01. The differential observations, in the sense II Peg minus comparison star, are listed in Table I. The Table I --------------------------------------- JD 2445+ Phase DeltaV Delta(B-V) --------------------------------------- 935.5688 0.590 -0.780 -0.269 935.5736 0.591 -0.757 -0.268 936.4611 0.723 -0.711 -0.268 936.4632 0.723 -0.696 -0.276 935.5396 0.735 -0.683 -0.287 937.4826 0.875 -0.636 -0.266 937.4875 0.876 -0.631 -0.269 937.5653 0.887 -0.649 -0.244 939.4590 0.169 -0.682 -0.321 939.5736 0.186 -0.683 -0.285 939.5771 0.186 -0.681 -0.293 940.3882 0.307 -0.688 -0.284 940.3951 0.308 -0.691 -0.286 940.3139 0.296 -0.696 -0.271 941.4701 0.468 -0.749 -0.260 941.4750 0.469 -0.755 -0.273 941.5514 0.480 -0.764 -0.233 948.5549 0.521 -0.757 -0.262 948.5618 0.523 -0.759 -0.249 948.5667 0.523 -0.761 -0.277 948.5701 0.524 -0.762 -0.256 [FIGURE 1] phases were calculated with the spectroscopic ephemeris (Vogt 1980): phi =JD 244 3033.47 +6.72422E. 7 nightly means in V are plotted in Figure 1. Although the light curve is not well covered, it is visible that the amplitude is about 0.12 mag. and the minimum is roughly near the phase 0.0. 2) HD 175 742 This star is classified as a BY Dra variable. It exhibits pronounced variations of light curve on a time scale of weeks ( Bopp et al. 1984). The differential observations made relative to BD +24d3586 are given in Table II. The phases were calculated according to the ephemeris (Bopp et al. 1984): phi =JD 244 4338.94+2.900E. 6 nightly normal points are plotted in Figure 2. Table II ------------------------------------- JD 2445+ Phase DeltaV Delta(B-V) ------------------------------------- 932.3424 0.449 -0.752 -0.193 932.3514 0.452 -0.759 -0.186 936.3271 0.823 -0.636 -0.175 937.3326 0.170 -0.682 -0.219 937.3431 0.173 -0.688 -0.208 939.3340 0.860 -0.618 -0.205 939.3424 0.863 -0.622 -0.211 940.3 49 0.195 -0.698 -0.203 940.3104 0.197 -0.702 -0.210 941.3208 0.545 -0.741 -0.181 941.3250 0.547 -0.733 -0.188 [FIGURE 2] 3) HD 199 178 According to Bopp and Stencel (1981) this star is a member of FK Comae class. Its photometric and spectroscopic observations were recently published by Bopp et al. (1984). The differential observations made relative to BD+43d3780 are given in Table III., The accuracy of individual observations is about 0.006, 0.008 and 0.018 mag. in V, B-V and B-U, respectively. These estimates are based on 7 observations of secondary comparison star, BD+42d3913. The U-B colour can be slightly affected by read leak which was not taken into account. The phases were calculated with the ephemeris (Bopp at al. 1984): phi =JD 244 4395. 70 3.337E. The normal points in V based on two or more (with one exception) Table III ---------------------------------------------- JD 2445+ Phase DeltaV Delta(B-V) Delta(U-B) ---------------------------------------------- 930.3563 0.891 0.540 -0.306 931.4285 0.212 0.620 -0.292 931.4340 0.214 0.604 -0.274 -0.610 931.4458 0.217 0.604 -0.295 -0.577 932.3167 0.478 0.589 -0.290 -0.603 932.3264 0.481 0.565 -0.273 -0.621 935.3062 0.374 0.627 -0.289 -0.601 935.3125 0.376 0.607 -0.287 -0.606 935.3208 0.380 0.605 -0.288 -0.586 935.3868 0.398 0.602 -0.292 -0.596 935.3951 0.401 0.607 -0.305 -0.595 935.4007 0.403 0.579 -0.291 -0.618 935.5514 0.448 0.584 -0.297 -0.628 935.5590 0.450 0.618 -0.298 -0.606 Table III /cont./ ---------------------------------------------- J.D.2445+ Phase Delta V Delta(B-V) Delta(U-B) ---------------------------------------------- 937.3236 0.979 0.577 -0.301 -0.571 937.4646 0.021 0.581 -0.281 -0.616 937.5535 0.048 0.576 -0.286 -0.572 936.3090 0.675 0.600 -0.307 -0.600 936.3167 0.677 0.577 -0.277 -0.619 936.4264 0.710 0.584 -0.291 -0.617 936.4903 0.730 0.573 -0.299 -0.614 939.3132 0.574 0.595 -0.290 -0.596 939.3222 0.578 0.588 -0.283 -0.607 939.4174 0.606 0.607 -0.304 -0.601 939.4910 0.628 0.591 -0.292 -0.593 940.3160 0.876 0.566 -0.305 -0.607 940.3236 0.878 0.560 -0.297 -0.580 940.4951 0.929 0.541 -0.288 -0.597 941.4479 0.215 0.605 -0.286 941.5368 0.241 0.603 -0.286 941.5403 0.243 0.593 -0.268 941.5431 0.244 0.600 -0.279 [FIGURE 3] individual measurements are plotted in Figure 3. The upper panel of this figure shows the individual differential observations of the secondary comparison in the sense c2-c1. One can see that V light curve of HD 119 178 has an amplitude about 0.06 mag.. The minimum is wide and seems to be located between phases 0.1 and 0.5. Inspection of Table III reveals that colour B-V is, on the average, bluer by about 0.02 mag. in the phase interval 0.5-1.1 than in the phase interval 0.1-0.5. Several authors reported flares of FK Com itself, best visible in U filter ( Rucinski 1981; Morris and Milone 1983; Holtzman and Nations 1984). It seems that no flare with an amplitude larger than about 0.02 mag., was detected during the present observing run. T. KALUZNY Warsaw University Observatory Al. Ujazdowskie 4 00-478 Warszawa Poland References: Bohusz, E., and Udalski, A. 1982, Acta Astron., 31, 185. [BIBCODE 1981AcA....31..185B ] Bopp, B.W., and Stencel, R.E. 1981, Ap.J., 247, L131. [BIBCODE 1981ApJ...247L.131B ] Bopp, B.W., Noah, P.V., Klimke, A., and Africano, J. 1981, Ap.J., 249, 210. [BIBCODE 1981ApJ...249..210B ] Bopp, B.W., Africano, J.L., Stencel, R.E., Noah, P.V., Klimke, A. 1984, preprint. [BIBCODE 1983ApJ...275..691B ] Holtzman, J.A., and Nations, H.L. 1984, A.J., 89, 391. [BIBCODE 1984AJ.....89..391H ] Morris, S.L., and Milone, E.F., 1983 Publ.A.S.P., 95, 376. [BIBCODE 1983PASP...95..376M ] Rucinski, S.M. 1981 Astron. Astrophys., 104, 260. [BIBCODE 1981A&A...104..260R ] Vogt, S.S. 1980, Ap.J., 240, 567. [BIBCODE 1980ApJ...240..567V ]