COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2455 Konkoly Observatory Budapest 30 December 1983 HU ISSN 0374-0676 Halpha VARIABILITY IN ALPHA LYRAE Suspected variability is a valuable clue in finding new emission stars. Halpha observations of bright stars with no history of line emission can lead to the discovery of hydrogen-emission stars. alpha Lyrae had been a well known standard star with spectral type A0V. Johnson and Wisniewski (1978) have reported violet shifted emission features associated with the OI lambda 7774 A and lambda 8446 A, as well as the infrared Ca II triplet lines in the infrared spectra of Vega. These features, however, could not be confirmed during later observations by Barker et al. (1978), Griffin (1978) and Bord and Messina (1980). Weak hydrogen-emission superimposed on absorption were noticed by us on 8, 18 and 20 September 1982. In confirmation with that we again observed alpha Lyrae for several nights. On 12 October 1983 the star alpha Lyrae again showed hydrogen- emission. We present Halpha observations of alpha Lyrae showing variable Halpha profile. During our spectrophotometric programme of Be stars, the star alpha Lyrae, used as a standard, was surprisingly found to have Halpha in emission. We obtained 18 spectrophotometric scans of alpha Lyrae on 12 October 1983. Observations were obtained with a Hilger and Watts monochromator on the Cassegrain focus of the 1.0 m telescope at Uttar Pradesh State Observatory on one night. The dispersion at the exit slit of the monochromator was 70 A/mm. The scans were obtained with an exit slit of 0.7 mm, admitting 50 A of the spectrum. The enlarged dispersion at the original tracings was 7.8 A/mm. Figure 1 shows a series of spectrum scans of alpha Lyrae. The emission at Halpha is obvious. alpha Lyrae showed variation in the depth and shape of Halpha over time scales of about 1.5 hours. First three scans show a normal absorption feature at Halpha. The next four scans show peculiar type of Halpha profiles with one component in emission and another in absorption. Later on centrally reversed emission was seen at Halpha in about six scans. In last few scans the emission disappeared and alpha Lyrae showed a normal absorption feature at Halpha again as it was at the beginning. The activity persisted for about 1.5 hours. We also observed xi^2 Cet(B9III) as the comparison star. The Halpha scans of xi^2 Cet are shown in Figure 2. It is evident from Figure 2 that xi^2 Cet showed a normal [FIGURE 1] Figure 1 Original spectrophotometric scans of Vega at Halpha line region. [FIGURE 2] Figure 2 Original spectrophotometric scans of xi^2 Cet at Halpha line region. absorption feature at Halpha. Hydrogen-emission in single early-type stars whose luminosities place them on or near the main sequence may be associated with mass ejection produced by rapid rotation. The projected rotational velocity of alpha Lyrae is very small, i.e., 15km/sec (Hoffleit, 1982). Suspected variability in early-type stars, plus rapid rotation, is a strong indication that the star has been, is, or will be, a hydrogen-emission star. Since the presence of emission depends on the intrinsic and not on the projected rotational velocity, suspected variability in some of the apparently slowly rotating stars is probably also connected with line emission, e.g., alpha Lyrae. From this type of Halpha variability we suggest that alpha Lyrae would be an excellent candidate for becoming Be star, as was proposed by Irvine (1975) for the star alpha Leo. We also suggest that alpha Lyrae may have a thin variable envelope. We are thankful to Drs. H.S. Mahra and C.D. Kandpal for helpful discussions and suggestions. P.S. GORAYA and MAHENDRA SINGH Uttar Pradesh State Observatory Manora Peak, Naini Tal-263 129, India References: Barker, E.S., Lambert, D.L. Tomkin, J. and Africano, J.: 1978, Publ.Astron. Soc. Pacific, 90, 514 [BIBCODE 1978PASP...90..514B ] Bord, D.J. and Messina, R.J.: 1980, Bull. American Astron.Soc., 12, 439 [BIBCODE 1980BAAS...12..439B ] Griffin, R. and R.: 1978, Publ.Astron.Soc. Pacific, 90, 518 [BIBCODE 1978PASP...90..518G ] Hoffleit, D.: 1982, The Bright Star Catalogue, Yale University Observatory Irvine, N.J.: 1975, Astrophys.J., 196, 773 [BIBCODE 1975ApJ...196..773I ] Johnson, H.L. and Wisniewski, W.Z.: 1978, Publ.Astron.Soc. Pacific, 90, 139 [BIBCODE 1978PASP...90..139J ]