COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                          NUMBER 63

                                          Konkoly Observatory
                                          Budapest
                                          17 August 1964


          BEATS IN THE BRIGHTNESS VARIATION OF tau' LUPI

      At his announcement in 1956 that tau' Lup was a beta CMa star,
B.E. Pagel (Monthly Notices, 116, 10, 1956.) communicated the 
following elements:
                 P = 0d.177365 +- 15
               2 K = 10.6 +- 0.8 km/sec

average (Delta m)_{(Y+B)/2} = 0m.03

      Photoelectric observations carried out at the Boyden Observatory 
on 29 nights, spread over the interval 1964 March 19/20 -
July 13/14 clearly reveal beats with a period of 8.0 days. JD 2438506
is the epoch of a well observed maximum in the amplitude.

      In the course of a beat cycle the brightness variation in the
short period cycle changes from

      m_y = 0m.025     to     m_y = 0m.035

in yellow light. The ratio of the amplitudes in yellow and in ultraviolet
light is

             m_y / m_u = 0.75.

      From the run in the epochs of maximum light there can be
concluded that the stronger oscillation corresponds to the shorter of
the two main periods, as is usually the case among beta CMa stars.
We find:
      P_0 = 0d.177353 +- 6         m_a = 0m.030
     P_02 = 0d.181374 +- 6        m_02 = 0m.005
      P_2 = 0d.089670 +- 9

Hence the ratio
           P_2/P_0 = 0.5056.

     The same ratio was found earlier for nu Eri, (A. Van Hoof,
Zeitschr. f. Astroph., 53, 124, 1961,) the main beat of which matches
that of tau' Lup.


                             A. VAN HOOF
                             W. S. PRETORIUS
                             C. PIKOOS

                            Boyden Observatory,
                            Bloemfontein, O.F.S.
                              South Africa