COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                   Number 1590

                                Konkoly Observatory
                                Budapest
                                1979 April 27




         ALGENIB IS A SPECTROSCOPIC BINARY


	Algenib (gamma Peg, 88 Peg, HD 886) is a well-known
representative of a group of beta Cep stars. Its periodic
radial-velocity variations with a period of 0.15175 days
were discovered by McNamara (1953). Williams (1954)
closed small light variations modulated by the same period. 
Many subsequent studies led to the conclusion that
the period has remained constant. McNamara (1955) pointed.
out a possibility that the gamma-velocity of the 0.15-day
curve varies but little attention was devoted to this
fact in all subsequent investigations.
    During the night September 7/8, 1978 we obtained a
series of 18 spectrograms of the star using the coude focus 
of the Ondrejov 2-m telescope. A very detailed analysis
of all velocity and, photometric data available in literature 
was undertaken by us and the study will soon be submitted 
to Bull. Astr. Inst. Czech. However, one result
in worth mentioning right now and should be available to
astronomical community before the star will be observable
again:
    We have revealed a periodic variation of the gamma-velocity 
of Algenib, with a period, of 6.83072 days, which seems
to indicate that the star is a spectroscopic binary. Modulation 
with this period is clearly detectable also in OAO 2
photometry of Algenib, kindly communicated to us by Dr. Lesh.
In fact, the 6.83-day period is probably responsible for the
scatter in OAO 2 data mentioned by Lesh (1976). Both periods
are detectable even in more scattered photometry by 
Magalashvili and Kumsishvili (1970).
    Orbital elements of Algenib as a spectroscopic binary
are the following:

    P = 6.830713 +- 0.000169 days
    T_max RV = HJD 2434675.620 +- 0.092
    e = 0 (according to the test suggested by Lucy and.
           Sweeney 1971)
    K = 1.34 +- 0.11 km/s
    gamma = 2.50 +- 0.09 km/s
    f(m) = 1.71 x 10^-6 m_Sun   a_1 sin i = 0.181 R_sun

    This solution is illustrated by Figure. To obtain
reasonable mass for the secondary component, one is led
to conclusion that the inclination of orbit must be very
low. It means, in turn, that the visible B2 component may
be even a normal rapidly rotating B star seen almost pole-
on.
    Using all available velocities since 1899 we have
also derived the following improved ephemeris for the short
period,

     T_max RV = HJD 2414888.6733 + 0.151750125d x E
                            +-18          +-15

which allows to count unambiguously all 0.15-day cycles
covered by available data.

                      [FIGURE 1] 

    We appeal to all spectroscopists and photometrists
interested, in the field to obtain new series of data 
during the forthcoming season and to confirm (or disprove)
our finding. As to UBV photometry, it would be wise to
accept 34 Psc (used by previous observers) as  a comparison
star, and to reduce all the measurements to the international 
system.





                     P. HARMANEC, P. KOUBSKY,
                     J. KRPATA, F. ZDARSKY
                     Astronomical Institute of CSAV
                     251 65 Ondrejov, Czechoslovakia





References:

Lesh, J.R., (1976) Astrophys. J. 208, 135 [BIBCODE 1976ApJ...208..135L ]
Lucy, L.B. Sweeney, M.A., (1971) Astron. J. 76, 514 [BIBCODE 1971AJ.....76..544L ]
Magalashvili, N.L., Kumsishvili Y.I. (1960) Perem. zvezdy
   13, 37 [BIBCODE 1960PZ.....13...37M ]
McNamara, D.H., (1953) Publ. Astr. Soc. Pacific. 65, 144 [BIBCODE 1953PASP...65..144M ]
McNamara, D.H., (1955) Astrophys. J. 122, 95 [BIBCODE 1955ApJ...122...95M ]
Williams, A.D. (1954) Publ. Astr. Soc.  Pacific   66, 25 [BIBCODE 1954PASP...66...25W ]