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\IBVShead{4113}{15 November 1994}                      % Use it with dummy or empty arguments

% Call for macro \title {Title of the paper}
\centerline{\ft A DETECTION OF MOVING BUMPS IN THE EMISSION}
\centerline{\ft PROFILES OF THE Be STAR FX Lib}
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This star has a long history of spectroscopic observations. Since 1932-35, its
shell become active. Long-term variations of the radial velocity of the shell
absorption lines and of V/R ratio of Balmer emission lines are cyclic (Faraggiana,
1971; Delplace and Chambon, 1976; Aydin and Faraggiana, 1978, Hubert-Delplace et al.,
1983). Its H$\alpha$ profile also underwent rapid changes on a time scale of
days as well as long-term changes on a time scales of years (Aydin and Faraggiana, 
1978; Slettebak and Reynolds, 1978).

A series of CCD H$\alpha$ spectra of the star were taken using the grating
spectograph of the 2.16 m telescope at the Xinglong Station of Beijing Astronomical
Observatory during 1994 April-June. The detector was a CCD with 512$\times$512 
pixels. The reciprocal linear dispersion of the spectra was 50\AA\ mm$^{-1}$
at H$\alpha$. One pixel corresponds to 1.35\AA. The observational and data reduction
techniques have already been described by Guo and Guo (1992). The following changes
can be found from these data:

1. Night-to-night changes occur in the H$\alpha$ emission profile. Figure 1 shows
three H$\alpha$ profiles which represent the mean profile obtained on 1994 April 
27, 28 and June 25 respectively. It can be seen from the figures that 1994
April 27 H$\alpha$ profile appears as a double emission, but one day later,
the H$\alpha$ profile had three emission peaks. While in the H$\alpha$ 
profiles of $\eta$ UMa and $\kappa$ Dra which were observed in same two nights,
were not found any changes. This demonstrates that the H$\alpha$ profile 
changes of 48 Lib are reliable. It is worth noting that the 1994 June 25 H$\alpha$
profile become again a double emission peak but the violet emission component 
obviously weaker than red one. The remarkable change in the H$\alpha$ profile 
observed on 1994 April 27-28 implies the possible occurrence of rapid violent 
activity in the stellar emission envelope. 

2. H$\alpha$ emission profiles of the star exhibit ultrarapid and as if cyclic
changes. 16 spectra of the star were taken on 1994 April 28 (see Figure 2a).
The H$\alpha$ displayed change with time. It is seen at a glance that, there
were two red emission components varying in intensity. The bottom profile
in Figure 2b represents the mean profile of these spectra, and the other which are
formed by subtracting the mean profile from each spectrum, are the line profile 
residuals. It is obvious that its H$\alpha$ emission undergoes the ultrarapid
changes on a time scale of minutes.

It can be seen from Figure 2b that the ultrarapid variations of the H$\alpha$
profiles resemble the moving bumps which have been observed at high-resolution
and high-signal-to-noise-ratio in the absorption lines of some Be stars (Walker
et al., 1979; Yang et al., 1990; Floquet et al., 1992, Bossi et al., 1993).
At present, there were two interpretations for these line-profile variations in Be stars: photospheric
non-radial pulsations (Vogt and Penrod, 1983), or corotating structures in the
matter above the stellar photosphere (Harmanec, 1989; Gies, 1994). Our
observations showed that the H$\alpha$ profiles had dramatic moving features but 
the phenomenon was not found in HeI $\lambda$6678. Therefore, we may infer \hfill that
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\centerline{Figure 1}
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\centerline{Figure 2}
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\centerline{3}
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{
\noindent the
H$\alpha$ line-profile variations could be due to the nonuniform distribution of
the circumstellar matter. The nonuniform distribution of the circumstellar
envelope is possibly related to the violent activity of the emission envelope
in the star during 1994 April 27-28. Unfortunately, our resolution is considerably
lower and observations are limited only to H$\alpha$ and HeI $\lambda$6678. In order
to better understand the details of the variations and throughly investigate
the nature of the variations, it is necessary to make high-resolution
and high-signal-to-noise-ratio observations of different lines of interest at
widely different wavelengths.
}

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% Call for macros \authors - \authorsrightcol - \endauthors
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YULIAN GUO
Beijing Astronomical Observatory
Chinese Academy of Sciences
Beijing, China
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\references

Aydin, C., Faraggiana, R., 1978, {\it A}\&{\it A Suppl.}, {\bf 34}, 51

Bossi, M., Guerrero, G., and Zanin, F., 1993, {\it A}\&{\it A}, {\bf 269}, 343

Delplace, A. M., Chambon, M. Th., 1976, {\it IAU Symp.},
{\bf 70}, 79, in: Slettebak A. (ed.), Be and Shell Stars. Reidel, Dordrecht 
%Changed: Tue Jun 14 15:34:33 MEST 2005

Faraggiana, R., 1971, {\it Ap. Letters}, {\bf 8}, 45

Floquet, M., Hubert, A. M., Janot-Pacheco, E., Mekkas, A., Hubert, H., and Leister,
N. V., 1992, {\it A}\&{\it A}, {\bf 264}, 177

Gies, D. R., 1994, {\it IAU Symp.}, {\bf 162}, 89, in: Balona, L. A., Henrichs,
H. F., and Le Contel, J. M., (eds.), Pulsation, Rotation and Mass Loss in 
Early-type Stars, Kluwer Academic Publishers, London
%Changed: Tue Jun 14 15:34:33 MEST 2005

Guo Yulian, Guo Xiozhen, 1992, {\it Inf. Bull. Var. Stars}, No.\,3786

Harmanec, P., 1989, {\it Bull. Astron. Inst. Czech}, {\bf 40}, 201

Hubert-Delplace, A. M., Mon, M., Ungerer, V., Hirata, R., Paterson-Beeckmans, F., 
Hubert, H., Baade, D., 1983, {\it A}\&{\it A}, {\bf 121}, 174

Slettebak, A., Reynolds, R. C., 1978, {\it Ap. J. Suppl.}, {\bf 38}, 205

Vogt, S. S., and Penrod, G. D., 1983, {\it Ap. J.}, {\bf 275}, 661

Walker, G. A. H., Yang, S., and Fahlman, G. G., 1979, {\it Ap. J.}, {\bf 233}, 199

Yang, S., Walker, G. A. H., Hill, G. M. and Harmanec, P., 1990, {\it Ap. J. Suppl.},
{\bf 74}, 595

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