COMMISSION 27 OF THE I. A. U.
	   INFORMATION BULLETIN ON VARIABLE STARS
			Number 2357

							Konkoly Observatory
							Budapest
							22 June 1983

							HU ISSN 0374-0676
		
		PHOTOELECTRIC PHOTOMETRY OF UX ARIETIS 


  The non-eclipsing RS CVn binary UX Ari (HD 21242) was observed by us
during 1976, 1982 and 1983 using the 38-cm Grubb refractor of the Nizamiah.
Observatory with an uncooled EMI 9502B photomultiplier, GR 1230A DC amplifier
and Honeywell Brown strip-chart recorder. Standard Johnson B, V filters were
used. 62 Ari and HR 999 were used as comparison and check stars, respectively.
  Figure 1 gives the observed light curves in the instrumental yellow system.

                           [FIGURE 1]

  Figure 1  Plot of Delta m (normal points) versus phase in instrumental
  yellow. The phases are calculated using the ephemeris HJD = 2440133.75 =
  6.43791d E

The phases were computed using the following ephemeris given by Landis et
al. (1978):

           HJD = 2440133.75 + 6.43791d E

 The individual observations (about 200) in each year were Fourier analysed
with the equation

         l = A_0 + A_1 cos Theta + A_2 cos 2Theta + B_1 sin Theta

  The amplitude and the phase of minimum light (average of yellow and blue)
for each year are given below:


Observing Epoch   Phase      Amplitude
(year)                       (mag)
1976.0               0.0064     0.02
                  -+ 0.004   -+ 0.003
1982.0               0.004      0.15
                  -+ 0.002   -+ 0.004
1983.0               0.001      0.15
                  -+ 0.002   -+ 0.004


  Zeilik et al. (1982) have reported that their observations of this system
during fall-winter of 1981 give a value of 0.97 as the minimum phase and an
amplitude of 0.21m in yellow.

                           [FIGURE 2]

  Figure 2 Plot of phase of light minimum versus year of observation. The
  bracketed number near each point indicates the amplitude of the wave during
  that year.

  The phase and amplitude of the distortion wave in UX Ari has been reported
to be undergoing an erratic behaviour during the past 10 years (Zeilik et
al., 1982). Using the values of the epoch, phase of light minimum and amplitude 
published by Guinan et al. (1981), Zeilik et al. (1982) and our own
values given above, a plot, the year of observation versus phase of light
minimum, is shown in Figure 2. From this figure, it appears that the spot or
spots on UX Ari which form first above the co-latitude, have a direct motion
for sometime and then move in a retrograde direction after they migrate below
the co-latitude and arrive near the star's equator. They disappear after 
sometime and a new spot cycle starts with the spots forming above the co-latitude
again. We suggest a period of 5-6 years for one cycle. If this model is
correct, the spots before 1975, between 1975-80 and 1981 onwards form three
distinct cycles. There appears to be not much variation in the amplitude of
a wave during a cycle suggesting that the nature of the spot or spots does
not vary much in a cycle but differs from cycle to cycle.
  We suggest that the behaviour of the distortion wave in UX Ari is not
erratic but systematic. At present, the spot or spots seem to lie near the
co-latitude and will migrate towards the equator thus leading to retrograde
motion in the coming years. Further observations will shed more light on the
above model.




                M.B.K. SARMA,
                B.V.N.S. PRAKASA RAO,
                B.D. AUSEKAR

           Centre of Advanced Study in Astronomy,
           Nizamiah Observatory,
           Osmania University,
           Hyderabad - 500 007
           India





References:
Guinan, E.F., McCook, G.P., Pragola, J.L., O'Donnell, W.C., Weisenbergen,
  A.C., 1981, P.A.S.P. 93, 495 [BIBCODE 1981PASP...93..495G ]
Landis, R.J., Lovell, L.P., Hall, D.S., Henry, G.W., Renner, T.R., 1978,
  A.J., 83, 176 [BIBCODE 1978AJ.....83..176L ]
Zeilik, M., Elston, R., Henson, G., Smith, P., 1982, I.B.V.S. No. 2168