COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3387

                                         Konkoly Observatory
                                         Budapest
                                         20 October 1989

                                         HU ISSN 0374 - 0676


 H_alpha SPECTROSCOPY OF THE Be STAR OMEGA ORIONIS DURING 1986 - 1987


Between 1 April 1986 (JD 2,446,521) and 2 January 1988 (JD 2,447,162) we
obtained 10 high-dispersion Reticon spectra of the H_alpha region in the B3
IIIe star omega Orionis (HR 1934). This star has recently been observed to
exhibit variations in visual brightness, polarization, and UV line profiles
(Sonneborn et al. 1988). While the polarization, photometric colors, and
continuum flux in the UV show variations that are correlated, the Si IV and C
IV resonance line profiles vary independently of the polarization. Both Guinan
and Hayes (1984) and Bergin et al. (1989) discuss episodes of enhanced
mass-loss in omega Ori where the star becomes dimmer and redder, and the
broad-band polarization increases.

Our H_alpha spectroscopy of omega Ori was obtained at Ritter Observatory using
the intensified Reticon system described by Bopp, Dempsey, and Maniak (1988).
The spectral data have 0.3 A resolution, and signal-to-noise ratio from
30-50:1. A log of the observations is given in Table 1.

While our data set is too small to permit us track the behavior of the H_alpha
line in any detail, it may be useful to compare our profile, intensity, and
equivalent width (EW) data with the occasional observations reported by others.
The EW measures listed in Table 1 show the emission to have varied by more than
a factor of two between April 1986 and October 1986. There was a further
enhancement in EW that took place between March 1987 and January 1988, when the
Reticon observations concluded. There also appear to be EW variations on
timescales of days as well as weeks or months: four Reticon scans obtained
during April 1986 show a variation of 50%, when the spectrophotometric
precision of the data should be no worse than +-10%. Our EW values for omega
Ori may be compared with those reported by Hanuschik et al. (1988) and
Andrillat and Fehrenbach (1982) which range from 5.7 to 7.7 A.


                             [FIGURE 1]
                             [FIGURE 2]
                             [FIGURE 3]
                             [FIGURE 4]
                             [FIGURE 5]
                             [FIGURE 6]

 Figures 1-6: Ritter Observatory Reticon scans of the Halpha region in 
              omega Ori.


We illustrate some of our H_alpha profiles of omega Ori in Figures 1-6.  The
line shows profiles qualitatively similar to those illustrated by Andrillat and
Fehrenbach (1982) and Hanuschik et al. (1988): it always shows blue and red
emission peaks of essentially equal intensity, with a separation in velocity of
150-200 kms^-1. The change in EW of the line that we observe is the result of
varying emission intensity, which is about 1.6 times the continuum level on 3
April 1986, rising to 2.2 times the continuum on 28 October 1987.

Table I H_alpha Observations of omega Ori

Date UT                JD     EW(H_alpha)
                  (2440000+)    (A)
 1 Apr.1986         6521.53    4.18
 3 Apr.1986         6523.54    4.55
19 Apr.1986         6539.57    3.70
23 Apr.1986         6543.56    5.76
11 Oct.1986         6714.88    8.34
 8 Mar.1987         6862.59    8.11
28 Oct.1987         7096.73   10.00
 4 Nov.1987         7103.72    9.01
 6 Nov.1987         7105.70    9.82
 2 Jan.1988         7162.65    9.92

It would clearly be useful to Monitor the H_alpha profile on an intensive
basis, to establish a lower limit on the timescale of EW variability and to
probe its behavior over the course of the 10 month outburst cycle suggested by
Bergin et al. (1989).


B. W. BOPP   R. C. DEMPSEY
Ritter Observatory and
Dept. of Physics and Astronomy
University of Toledo
Toledo, OH 43606, USA

References:

Andrillat, J., and Fehrenbach, C. 1982, Astron. Astrophys. Suppl. 48, 93. [BIBCODE 1982A&AS...48...93A ]
Bergin, E., Burns, J., Guinan, E., and McCook, G. 1989, 
   Inf. Bull. Var. Stars 3358.
Bopp, B. W., Dempsey, R. C., and Maniak, S. 1988, Astrophys. J. Suppl.
   68, 803. [BIBCODE 1988ApJS...68..803B ]
Guinan, E., and Hayes, D. 1984, Astrophys. J. (Lett.). 287, L39. [BIBCODE 1984ApJ...287L..39G ]
Hanuschik, R., Kozok, J., and Kaiser, D. 1988, Astron. Astrophys. 189, 147. [BIBCODE 1988A&A...189..147H ]
Sonneborn, G., Grady, C., Wu, C., Hayes, D., Guinan, E., Barker, P., and
   Heinrichs, H. 1988, Astrophys. J. 325, 784. [BIBCODE 1988ApJ...325..784S ]