COMMISSION 27 OF THE I. A. U.
     INFORMATION BULLETIN ON VARIABLE STARS
                  NUMBER 697

                                        Konkoly Observatory
                                        Budapest
                                        1972 July 14


          RADIAL VELOCITY OF RR LYRAE VARIABLE - RW Ari


RW Ari is a well known RR Lyrae type variable star. On the basis of
photoelectric observations, Wisniewski (1971 A.A. 21. 3. 307) suggested that the
star is a component of an eclipsing system, with a primary minima depth of 0.8
mag. after correction for the pulsation effect. To test that hypothesis, we have
undertaken a spectroscopic study of this star.

Two spectrograms were obtained with the Kitt Peak Cassegrain spectrograph of
the 84-inch (210 cm) telescope. Since at the pulsation maximum the stellar
brightness is 12.1 mag., the dispersion of 103 A/mm and the projected slit
width of 15 micron were used. The spectrograms were measured with a Grant
comparator using five lines of HI and CaII, and the digitized output was
reduced on the observatory's CDC 6400 computer. Below we give the individual
velocities and their internal probable errors:

Helio. J.D.      Radial            Internal
2400000+         velocity            p.e.
                           km*s^-1
41348.678        -46.5              +-1.9
41375.619        -11.7                3.5

Both observations were obtained at the same pulsational phase (0.03 phase
apart) of decreasing light when radial velocities are expected to change
slowly, particularly for Baily type "c" variables. Despite that, our observed
radial velocities differ by 35 km/sec! If the radial velocity variation is
caused by pulsation only, the observed difference should be a few km/sec. We
belive, therefore, that such a large observed difference in radial velocity is
due to orbital motion. Additional spectroscopic and photoelectric observations
are planned.


HELMUT A. ABT
Kitt Peak National Observatory

WIESLAW Z. WISNIEWSKI
Lunar and Planetary Laboratory
The University of Arizona