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《中国天文和天体物理学报(英文版)》 1987-01
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Variations in the Shell Spectra of the Be Star EW Lac

Guo Yulian Cao Huilai Gao Weishi(Beijing Obtcrvatory, Academia Sinica)  
We have observed EW Lac with the grating spectrograph attached to the 60/90 cm Schmidt telescope at Beijing Observatory from 1982 to 1984. The Balmer shell absorption lines of the star showed especially interesting variation. These lines were with sharp and deep single cores on Dec. 16, 1983 but displayed double absorption cores on Dec. 18, 1983, with the two components of nearly equal intensity. Several days later, the R component of double absorption cores became much weaker than the V component. On a spectrogram taken in Sep., 1984, these lines showed again sharp and deep single absorption core (Figure 1). As the Balmer shell absorption lines changed from single to double core structure, they became'markedly shallower and wider (Figure 2). In our observation we failed to see any double cores of the Hβ line similar with that of the Hα line shown up on a spectrogram taken on Dec. 26, 1983 (Figure 3).We measured the radial velocities of the shell absorption lines. The results show: (1) There is no obvious Balmer progression; (2) When the Balmer shell obsorption lines start to show double structure, the R component velocities remain nearly the same as those of the sing-le absorption lines; (3) the redial velocities of the V and R components change with time (Figure 4).We consider that the shell absorption line changes may be caused by some violent activities in the shell of the star.Since 1978, many authors reported that the shell of EW Lac has started a new stage of activity. Further observation and consideration of the star should be very rewarding.
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【References】
Chinese Journal Full-text Database 1 Hits
1 Shen Liangzhao (Beijing Astronomical Observatory, Academia Stnica);Radial Velocity Studies of Spectroscopic Binaries[J];Progress In Astronomy;1990-02
【Co-references】
Chinese Journal Full-text Database 5 Hits
1 Liu Xuefu (Astronomy Department, Beijing Normal University)Tan Hnisong (Yunnan Observatory, Academia Sinica);Observation and Study for H_α Emission of 33 RS CVn Stars[J];中国天文和天体物理学报(英文版);1986-02
2 Lu Wenxian(Shanghai Observatory, Academic Sinica);Spectroscopic Orbits of Eclipsing Binaries: AA UMa[J];中国天文和天体物理学报(英文版);1988-01
3 Lu Wenxian(Shanghai Observatory, Academia Sinica)Shen Liangzhao Jiang Zhaoji(Beijing Observatory, Academia Sinica);A Spectroscopic Orbit for Theta Draconis from Photoelectric Radial Velocities[J];中国天文和天体物理学报(英文版);1988-02
4 Zhai Di-sheng (Beijing Observatory, Acadcmia Sinica) Lu Wen-xian (Shanghai Observatory, Academia Sinica);SIMULTANEOUS LIGHT AND VELOCITY CURVE SOLUTIONS OF U PEGASI[J];Acta Astronomica Sinica;1988-01
5 Li Zong-yun (Department of Astronomy, Nanjing University) Leung Kam-ching (Behlen Observatory, University of Nebraska, USA) Ding Yue-rong (Department of Astronomy, Nanjing University);LONG-PERIOD CONTACT OR SEMIDETACHED SYSTEMS: 5 CETI, CoD-30°5135 AND HD104901B[J];Acta Astronomica Sinica;1988-04
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