COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 1281 Konkoly Observatory Budapest 1977 May 24 Veroffentlichungen der Remeis-Sternwarte Bamberg Astronomisches Institut der Universitat Erlangen - Nurnberg Band XII, Nr. 126 THE VARIABILITY OF PQ NORMAE = BV 1556 = HD 148013 The variability of PQ Nor = BV 1556 has been discovered by Strohmeier and Knigge (1973). They claimed a period of 0.931 days and EW light curve with amplitude of 0.3 mag. in the photographic region. The star has been observed photoelectrically in UBV with the 50 cm photometric telescope at the European Southern Observatory (ESO) on La Silla, Chile in May-June 1974. The results are given in the Table. Corrections for extinction have been applied, The primary comparison star was HD 147670 (V = 7.84m, B-V = .00m, U-B = -.44m; B5), check star was HD 148028 (V = 8.76m, B-V = -.09m, U-B = -.26m; B5). No variability of these two stars larger than the observing errors was found. The period and the type of variability given by Strohmeier and Knigge could not be confirmed, and the amplitude was found considerably smaller than 0.3 mag. Best fit of the data is obtained with a period of 5.58 days. The light curve is shown in the Figure, JD 2442180.0000 was chosen arbitrarily as starting epoch. The amplitude in V is found as 0.045 mag., the amplitude in B is about 0.065 mag. The light curve seems slightly asymmetric with a steeper increasing branch. J.M. Vreux very kindly has taken a spectrogram of the star with dispersion 12.3 A/mm at the 1.5 m spectrographic telescope of the European Southern Observatory. The spectrogram shows only strong Balmer lines and a sharp but weak Calcium K line, The latter very probably is of interstellar origin since its radial velocity differs by about 35 km/s from the radial velocities derived from the Balmer lines. From the appearence of the spectrum the star is classified as A0. No metal lines are discernible, The colour index B-V = +.26m for mean light is considerably redder than for normal A0 stars, indicating an interstellar reddening of about E_B-V = 0.25m. Since E_U-B = E_B-V*(.72+.05*E_B-V) the unreddened U-B colour index must be close to (U-B)_0 =-.35m. The reddening is in agreement with the galactic position at (1950) l = 329.13 deg, b = -5.83 deg, Since the total interstellar absorption A_V in visual is about three times as large as the selective reddening in B-V we have A_V = 0.8m. The corrected visual appearent brightness is therefore m_0 = 6.9m. Since the Spectrum shows no metal lines the variability probably is not connected with the observed A0 star. The simplest explanation is the assumption of a possibly physical companion which exhibits a normal Cepheid light curve of period 5.58 days, Assuming a visual amplitude of about 0.8m this Cepheid must be fainter than the A0 star by about 2.8m. The period-luminosity relation of Cepheids gives an absolute visual magnitude of M_CV = -3.6m. If the two stars are at the same distance the absolute visual magnitude of the A0 star is M_AV = -6.4m according to luminosity class I_ab which also would be in good agreement with the unreddened ultraviolet colour index (U-B)_0 = -.35m. The distance of the two stars is then about 4.5 kpc. Further observations of the object, especially the determination of radial velocities, are needed to confirm the proposed nature of the variability of PQ Nor = BV 1556. The author wishes to express his sincere thanks to J.M. Vreux who very kindly took the spectrogram of PQ Nor. Gratefully acknowledged is the allocation of observing time by the European Southern Observatory. EBERHARD SCHOEFFEL References: Strohmeier, W, and Knigge, R, Veroff. Remeis-Obs, Bamberg Bd X, Nr. 106 (1973) [BIBCODE 1973BamVe..10..106S ] Landoldt-Bornstein, Neue Serie Bd I, Astronomie und Astrophysik (ed. H.H. Voigt), Springer Berlin (1965) Photoelectric observations of BV 1556 = PQ Normae Jul.date V B-V U-B Jul.date V B-V U-B 2442000+ 2442000+ 185.7541 7.682 .253 -.134 193.8317 7.738 .268 -.151 185.7568 7.685 .256 -.139 193.8343 7.720 .273 -.137 185.7594 7.692 .255 -.140 193.8372 7.725 .264 -.130 185.7618 7.694 .252 -.141 193.8396 7.729 .260 -.141 185.7652 7.703 .248 -.146 193.8438 7.735 .259 -.150 185.7677 7.697 .254 -.145 193.8461 7.735 .261 -.144 185.7702 7.693 .263 -.147 193.8483 7.739 .257 -.141 185.7729 7.688 .249 -.160 193.8577 7.735 .260 -.146 185.7754 7.690 .245 -.156 193.8603 7.738 .262 -.147 185.7782 7.694 .248 -.142 193.8644 7.735 .256 -.134 185.7837 7.697 .248 -.147 193.8668 7.729 .264 -.142 185.7860 7.694 .255 -.149 193.8697 7.732 .263 -.149 185.7953 7.701 .248 -.143 193.8722 7.726 .271 -.150 185.7982 7.678 .256 -.138 193.8832 7.736 .263 -.155 185.8009 7.675 .254 -.141 193.8870 7.734 .268 -.156 185.8037 7.696 .245 -.142 193.9020 7.724 .269 -.158 185.8037 7.696 .245 -.142 194.7730 7.736 .269 -.134 185.8062 7.695 .251 -.150 194.7754 7.738 .268 -.139 185.8087 7.697 .248 -.144 194.7792 7.731 .274 -.138 185.8145 7.701 .244 -.146 194.7816 7.732 .275 -.142 185.8196 7.696 .250 -.151 194.7868 7.731 .274 -.137 185.8221 7.692 .251 -.142 194.7900 7.734 .271 -.134 185.8247 7.699 .247 -.148 194.7923 7.736 .269 -.131 185.8309 7.704 .243 -.144 194.7950 7.728 .274 -.134 185.8333 7.706 .249 -.150 194.7976 7.731 .273 -.137 185.8361 7.700 .255 -.158 194.8007 7.733 .268 -.134 185.8422 7.693 .243 -.132 194.8254 7.737 .265 -.134 185.8448 7.694 .242 -.136 194.8287 7.735 .266 -.138 185.8474 7.696 .240 -.138 194.8376 7.737 .270 -.143 185.8501 7.697 .243 -.139 194.8408 7.730 .275 -.138 185.8527 7.698 .254 -.155 194.8443 7.736 .267 -.138 188.7973 7.731 .262 -.130 194.8574 7.744 .263 -.144 188.8010 7.731 .264 -.133 194.8612 7.729 .277 -.148 188.8044 7.734 .274 -.137 195.4755 7.730 .275 -.151 188.8258 7.728 .272 -.141 195.4792 7.730 .265 -.133 188.8304 7.742 .263 -.144 195.6258 7.724 .257 -.128 188.8331 7.736 .261 -.139 195.6281 7.729 .255 -.128 188.8358 7.728 .268 -.141 195.7682 7.719 .259 -.133 188.8385 7.717 .275 -.146 195.8391 7.717 .256 -.141 188.8413 7.729 .271 -.157 195.8414 7.716 .256 -.137 188.8441 7.729 .264 -.158 195.9017 7.720 .256 -.151 188.8565 7.737 .270 -.145 196.4615 7.706 .243 -.156 188.8608 7.734 .270 -.145 196.6777 7.697 .249 -.139 188.8658 7.740 .257 -.140 196.6799 7.695 .250 -.143 188.9028 7.737 .263 -.145 196.7988 7.695 .245 -.136 188.9069 7.728 .260 -.147 196.8010 7.702 .238 -.144 188.9094 7.733 .249 -.156 196.8823 7.696 .241 -.160 188.9151 7.721 .263 -.156 196.8848 7.691 .246 -.153 188.9176 7.717 .272 -.170 197.4958 7.708 .233 -.146 188.9203 7.738 .247 -.152 197.4986 7.701 .244 -.163 188.9229 7.738 .258 -.161 197.7766 7.698 .244 -.145 188.9257 7.728 .271 -.158 198.7773 7.725 .266 -.121 189.8052 7.729 .270 -.145 198.7797 7.722 .258 -.131 189.8085 7.733 .267 -.143 199.6790 7.728 .259 -.126 189.8127 7.730 .265 -.136 199.7550 7.732 .272 -.145 189.8154 7.732 .262 -.129 199.7595 7.717 .279 -.142 189.8175 7.730 .265 -.137 199.7618 7.731 .267 -.132 189.8206 7.729 .265 -.141 199.7640 7.733 .262 -.141 189.8238 7.727 .261 -.131 199.7775 7.730 .269 -.138 189.8261 7.722 .270 -.133 199.7953 7.734 .265 -.146 189.8300 7.725 .269 -.134 199.8325 7.725 .274 -.146 189.8323 7.722 .270 -.138 200.4681 7.739 .267 -.145 189.8396 7.732 .264 -.139 200.4705 7.745 .270 -.154 189.8423 7.728 .261 -.136 200.4997 7.731 .278 -.143 189.8445 7.735 .257 -.140 200.5836 7.745 .260 -.135 189.8485 7.728 .265 -.136 200.5864 7.733 .274 -.141 189.8512 7.726 .267 -.131 200.7889 7.739 .271 -.154 189.8544 7.728 .269 -.143 201.4772 7.714 .259 -.143 189.8577 7.734 .264 -.142 201.4798 7.714 .254 -.135 189.8615 7.727 .265 -.133 201.7555 7.703 .249 -.140 189.8649 7.728 .262 -.145 201.7578 7.701 .250 -.138 189.8713 7.732 .258 -.135 201.7948 7.695 .256 -.146 189.8753 7.735 .258 -.136 201.7970 7.700 .248 -.139 189.8780 7.737 .256 -.132 201.7994 7.698 .253 -.142 189.8832 7.732 .257 -.146 201.8031 7.696 .257 -.147 189.8866 7.731 .260 -.143 201.8052 7.698 .253 -.147 189.8902 7.741 .253 -.138 201.8078 7.697 .256 -.148 189.8949 7.734 .257 -.136 201.8308 7.703 .246 -.153 189.8984 7.735 .259 -.141 201.8480 7.704 .250 -.150 189.9019 7.727 .268 -.155 201.8503 7.703 .255 -.153 189.9073 7.728 .258 -.136 201.8815 7.695 .257 -.162 191.7957 7.686 .254 -.146 201.8838 7.697 .256 -.162 191.7972 7.690 .244 -.142 202.4652 7.697 .240 -.134 191.8007 7.691 .246 -.142 202.4675 7.692 .247 -.141 191.8028 7.686 .245 -.143 202.7384 7.692 .246 -.148 191.8063 7.686 .245 -.143 202.7409 7.689 .246 -.150 191.8104 7.685 .250 -.147 202.8036 7.695 .243 -.155 191.8125 7.682 .253 -.149 202.8058 7.687 .248 -.145 191.8146 7.689 .247 -.151 202.8270 7.687 .251 -.154 191.8198 7.687 .244 -.136 202.8295 7.693 .245 -.148 191.8219 7.692 .245 -.747 202.8429 7.686 .251 -.151 191.8260 7.684 .250 -.143 203.4707 7.709 .254 -.146 191.8285 7.686 .255 -.151 203.7388 7.716 .248 -.135 191.8305 7.691 .244 -.147 204.4707 7.731 .267 -.156 191.8330 7.690 .241 -.139 204.7526 7.735 .264 -.145 191.8349 7.690 .244 -.141 204.7550 7.733 .266 -.146 191.8372 7.687 .247 -.151 204.8471 7.731 .262 -.152 191.8410 7.685 .253 -.147 204.8879 7.746 .254 -.168 191.8438 7.697 .249 -.147 204.8908 7.738 .265 -.166 191.8460 7.682 .246 -.142 204.8935 7.741 .260 -.163 193.5895 7.714 .283 -.142 204.8956 7.742 .256 -.161 193.6005 7.732 .267 -.137 204.8999 7.749 .250 -.158 193.6029 7.729 .271 -.131 204.9028 7.748 .253 -.174 193.7811 7.734 .261 -.127 204.9072 7.748 .250 -.172 193.7833 7.731 .269 -.141 204.9096 7.742 .249 -.171 193.7854 7.731 .265 -.137 205.5386 7.737 .260 -.128 193.7895 7.731 .265 -.142 205.6326 7.731 .269 -.134 193.7917 7.730 .265 -.133 205.6349 7.733 .270 -.135 193.7944 7.730 .268 -.144 205.7449 7.730 .271 -.136 193.7968 7.729 .265 -.143 205.7472 7.728 .273 -.137 193.8005 7.724 .272 -.140 205.9161 7.752 .267 -.180 193.8038 7.728 .274 -.138 205.9183 7.716 .284 -.159 193.8059 7.729 .269 -.145 206.4643 7.733 .257 -.140 193.8083 7.725 .273 -.148 206.4765 7.736 .254 -.141 193.8125 7.730 .265 -.133 206.4727 7.708 .241 -.152 193.8149 7.735 .257 -.133 208.4742 7.706 .246 -.154 193.8173 7.735 .258 -.142 208.4764 7.703 .240 -.148 193.8248 7.728 .262 -.137 209.4758 7.726 .251 -.139 193.8270 7.724 .270 -.139 210.4927 7.731 .266 -.131 193.8295 7.734 .258 -.142 210.4950 7.725 .272 -.132 [FIGURE 1]