COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      Number 945

                                       Konkoly Observatory
                                       Budapest
                                       1974 November 26


 1974 UBV PHOTOMETRY OF THE RADIO STAR UX ARIETIS = HD 21242

   The purpose of this short note is to announce that the light
curve of UX Arietis has changed. UX Ari is of particular interest
because it is the brightest (V ~ 6m.5) RS Canum Venaticorum-type 
binary known to date (Carlos and Popper 1971) and because it is a
radio star (Gibson et al. 1975). The last photometric observations
were made in 1972 (Montle and Hall 1972; Atkins and Hall 1972, Hall,
Montle, and Atkins 1975).
    We obtained 30 differential UBV observations with respect to
62 Arietis on 8 nights in October 1974. The constancy of 62 Ari was
again verified, via 10 differential observations with respect to
BS 999 on 7 nights in October 1974. The mean difference was consistent 
with the value found by Hall, Montle, and Atkins; and the standard 
deviation of each observation from that mean was about +-0m.013
in all three colors.
    In the Figure below we have plotted nightly normals of the V
observations. Here {delta} is in the sense UX Ari minus 62 Ari, and the
phase is reckoned with the ephemeris

            JD(hel.) = 2440133.76 + 6d.43791.E

which we derived from data in Table II of Carlos and Popper. The solid
line indicates roughly the light curve as of early 1972; the broken
line, as of late 1972.

                            [FIGURE 1]

   We can make three conclusions. (1) The overall level of the
light curve has decreased: by more than 0m.1. (2) The amplitude has
dwindled dramatically: from about 0m.14 to about 0m.04. We note that
the amplitude of the wave in RS CVn is also variable (Hall 1972),
having ranged between 0m.18 and about 0m.05. (3) There is some 
indication that minimum light still occurs where it did in 1972: 
around 0p.1. If so, then this would imply that, relative to the 
orbital motion, the wave did not migrate measurably between 1972 and
1974.
   We are continuing UBV photometry of UX Ari and encourage others 
to observe this interesting system also.



November 15, 1974


                                       CHARLES R. EVANS
                                       DOUGLAS S. HALL

                                       Dyer Observatory
                                       Vanderbilt University
                                       Nashville, Tennessee 37235
                                       U.S.A.


References:

Atkins, H.L., Hall, D.S. 1972, P.A.S.P. 84, 638. [BIBCODE 1972PASP...84..638A ]
Carlos, R.C., Popper, D.M. 1971, P.A.S.P. 83, 504. [BIBCODE 1971PASP...83..504C ]
Gibson, D.M., Hjellming, R.M., Owen, F.N. 1975, Ap.J.Letters
        (submitted). [BIBCODE 1975ApJ...200L..99G ]
Hall, D.S. 1972, P.A.S.P. 84, 323. [BIBCODE 1972PASP...84..323H ]
Hall, D.S., Montle, R.E., Atkins, H.L. 1975, Acta Astr.(submitted). [BIBCODE 1975AcA....25..125H ]
Montle, R.E., Hall, D.S. 1972, I.B.V.S. No. 646.