COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2803

                                           Konkoly Observatory
                                           Budapest
                                           2 October 1985

                                           HU ISSN 0374 - 0676


        FAR ULTRAVIOLET PHOTOMETRIC VARIABILITY IN alpha Eri


         The Be star Alpha Eri has been observed with the ultraviolet 
spectrometers on board the Voyager 1 and 2 spacecraft. These spectrometers are
sensitive in the 500 - 1700 A wavelength region and have an 
effective resolution of 20 A. The instruments and their calibration and 
performance have been described in Broadfoot et al. (1977) and Holberg et al. 
(1982).
         Extensive observations of Alpha Eri were obtained with the Voyager 
spectrometers in 1979 and 1980 with additional isolated observations obtained 
in 1983 and 1984. Figure 1 shows the integrated 950-1150 flux with 1 sigma 
error bars for the 1979-1980 epoch. As can be seen from Figure 1 the Far-UV 
flux from Alpha Eri was statistically constant until approximately JD 2444325 
(Mar. 25, 1980). After that date significant variations in the UV flux level 
was observed. The 1983 and 1984 data have flux levels consistent with the mean
of the pre-"out-burst" 1979/80 data.
         Spectroscopic observations of Halpha obtained by de Freitas Pacheco 
(1982) on JD2444243 (Jan. 2, 1980) show a "rotationally broadened photospheric
profile with a slight central emission and a small central absorption". 
Slettebak (1982) reports an observation obtained in Oct, 1980 that shows 
Hbeta to be "weak-relative to standard star spectra, and filling in by 
emission likely".
         Additional spectroscopic and/or photometric observations of Alpha Eri
during 1979-1981 would be appreciated. Voyager observations of this star are 
continuing.

 
                              [FIGURE 1]

 Fig. 1. Far-UV (1050 A +- 100 A) integrated flux measurements with +-1 
 sigma errors in alpha Eri for 1979/80. The logarithm of the weighed 
 far-UV flux for the six observations prior to JD 2444325 is -5.273 +- 
 0.004. Observations of alpha Eri in 1983 (JD 2445579.2) and 1984 (JD 
 2445894.2) yield log F_1050 values of -5.252 +- 0.009 and -5.270 +- 0.013 
 respectively.




    
   R.S. POLIDAN               G.J. PETERS                    R. STALIO

Lunar and Planetary Lab.    Space Sciences Ctr.        Departimento di Astron.
University of Arizona       and Dept. of Astronomy     Universita' di Trieste
3625 E. Ajo Way             Univ. of So. California    Trieste
Tucson, Arizona 85713       Los Angeles, CA 90089      Italy
USA                         USA



References:

Broadfoot, A. L., 1977, Space Sci. Rev., 21, 183. [BIBCODE 1977SSRv...21..183B ]
de Freitas Pacheco, J. A., 1982, Mon. Not. R. Astr. Soc., 199, 591, [BIBCODE 1982MNRAS.199..591D ]
Holberg, J. B., 1982, Ap. J., 257, 656. [BIBCODE 1982ApJ...257..656H ]
Slettebak, A., 1982, Ap. J. Supp., 50, 55. [BIBCODE 1982ApJS...50...55S ]