COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1575 Konkoly Observatory Budapest 1979 March 26 ASYMMETRIC PROFILES OF EW LAC As reported by Hadrava et al. (1978) and Harmanec et al. (1979), the Be and shell star EW Lac (HD 217050, B2IIIpe) has exhibited a strong change in its spectrum and colors in 1978, after a long stable shell phase. We here present our results of spectroscopic observations, which were made on November 14, 15, and 19, 1978 with the coude spectrograph attached to the 188-cm reflector at the Okayama Astrophysical Observatory. The list of our observations is as follows: ------------------------------------------------------------------------- Plate number Julian day Dispersion Exposure time Spectral region (A/mm) (minute) (A) ------------------------------------------------------------------------- C4-5464 2443827.00 10.2 49 3500-4300 C4-5465 2443827.03 10.1 29 3800-4600 C4-5466 2443827.06 10.2 36 3500-4300 C4-5467 2443827.13 10.1 166 3800-4600 C4-5471 2443827.99 9.9 54 4300-5050 C4-5488 2443831.97 20.1 128 5200-6800 ------------------------------------------------------------------------ The strong asymmetry and the strengthening of the shell lines were noticed on the whole. Figure 1 shows the H_beta-, H_gamma-, and Hdelta-line profiles normalized to the adjacent continuum, together with the CaII K and FeII lambda4233 lines. The abscissa is the heliocentric radial velocity in km/sec. It is evident that the shell-absorption profiles are very steep in their shortward sides, while distinctly winged in the longward sides. The deepest points are located at the shortward edge of the absorption cores. The violet emission components are stronger than the red ones (V/R > 1). The shell absorption profiles for some Balmer lines on the spectrogram C4-5466 are shown in figure 2, where the point-to-point normalization with [FIGURE 1] [FIGURE 2] [FIGURE 3] [FIGURE 4] respect to the photospheric line profile has been made up to H17. The steep shortward wing coincides with each other in the lower members, while the longward wing weakens rapidly as the principal quantum number increases. These behaviors could be attributed to the difference in the optical depth tau_alpha(v) of the envelope in the Halpha line and the fractional area beta(v) of the photospheric disk which is screened by the envelope, where v is the line- of-sight velocity (Kogure et al.1978). That is, the profiles of shortward wings in the lower members correspond to large tau_alpha(v), and thus represent beta(v), while those of longward wings correspond to smaller values of tau_alpha(v) with large beta(v), in each zone of the corresponding line-of-sight velocity. In the higher members like the H25 line, the optical thickness of the envelope becomes smaller even in the shortward wing. The heliocentric radial velocities of the deepest points in the pro- files of the Balmer shell lines and the CaII H and k lines are plotted in figure 3. The symbols in figure 3 are as follows: C4-5464 (o), C4-5465 (filled triangle), C4-5466 (dot), C4-5467 (triangle), C4-5471 (square), and C4-5488 (filled square). The progression phenomenon is clearly seen in between the Halpha and H15 lines in the sense that the higher members have larger velocities. The higher members than H15 show rather constant velocity of about -7 km/sec. The mean radial velocity of the metallic lines was about -5 km/sec, slightly larger than those of the higher Balmer lines. These results are in good agreement with Hadrava et al. (1978) in December 5.869, 1978. The profile of the Halpha line in November 19, 1978 is puzzling (figure 4). For comparison, the Halpha-line profile in October 23, 1974 (JD 2442344.14, Vr = -19.7 km/sec) is also shown in figure 4 (broken line). While the emission wing was similar in these two epochs, the central part was considerably filled by the emission, and the central dip was the reverse type of the other shell lines in November 19, 1978. We note that the NaI D lines on the same plate (C4-5488) with the Halpha line had the similar type profile to the CaII K line in figure 1. Because of the strong emission intensity, the profile of the Halpha line reflects essentially the emission profile and may also be influenced by the re-absorption process in the outer part. It is hard to judge at present whether this active phenomenon is a transient one as observed in Pleione or indicates the beginning of the longterm cyclic variation as in 48 Lib and zeta Tau. Further spectroscopic observations and the photoelectric monitoring are highly desirable. Finally we wish to acknowledge M. Nakagiri for his kind help in the use of the Grant-type comparator at the Tokyo Astronomical Observatory. RYUKO HIRATA and TOMOKAZU KOGURE Department of Astronomy University of Kyoto Kyoto, 606, Japan References: Hadrava, P., Harmanec, P., Koubsky, P., Krpata, J., Zdarsky, F. 1978, IAU Circular No. 3317. [BIBCODE 1978IAUC.3317....2H ] Harmanec, P., Horn, J., Koubsky, P., Zdarsky, F., Kriz, and Pavlovski, K. 1979, IBVS No. 1555. Kogure, T., Hirata, R., and Asada, Y. 1978, Publ. Astron. Soc. Japan, 30, 385. [BIBCODE 1978PASJ...30..385K ]