COMMISSION 27 OF THE I. A. U.
                   INFORMATION BULLETIN ON VARIABLE STARS
                                Number 2472

                                                       Konkoly Observatory
                                                       Budapest
                                                       8 February 1984

                                                       HU ISSN 0374-0676


      LACK OF DETECTION OF A 1.77h-PERIODICITY IN THE CP STAR HD 32633


  The CP2 star, HD 32633 (HZ Aur, BD +33d954, SAO 57631, m_v = 6.94, sp=B8)
was first noted to have a possible photometric variability of 1h46m by Rakos
(1963), but neither the details nor light curves are given. Evidence for
radial velocity variations with this period were presented by Preston and
Stepien (1968), but it is not conclusive. Percy (1973) found no systematic
variations greater than 0.010m in B, while Stepien and Romaniuk (1973) claim
some evidence exists for short-period variability. Weiss (1983) discusses


                               [FIGURE 1]




HD 32633 as a possible member of the small group of CP stars showing delta Sct
characteristics, but points out the marginal evidence. Consequently, additional
photoelectric observations were secured at Lowell Observatory.
  Photometry was obtained on three nights using Lowell's 1.1 m telescope with
a dual-channel photometer and electronically cooled EMI tubes. As a comparison 
star, either BD +33d949 (m_v = 8.5) or BD +34d948 (m_v = 7.8) was used.
Differential photometry was performed using the average of three 15-second
integrations on the program star and the comparison star. Johnson U,B and V
filters were utilized. The resulting differential magnitudes are plotted in
the Figure, no corrections to heliocentric time have been applied.
  No period is evident on the time scale of 1h46m in any of these data sets.
If the periodicity is to be explained as a delta Sct-like pulsation, the amplitude
in B should be about 0.03m (Weiss 1983, op. cit.). The data presented here
speak against any such periodicity, but if the situation is similar to the
lack of an observed 1h29m period in HD 10088 (Kreidl 1984), it certainly
cannot be ruled out that such a period may be present on occasion.
  Both HD 10088 and HD 32633 seem to cease delta Sct-like pulsational activity
over longer periods of time than one would expect. If only these two and not
the other known members (HD 3326, HD 4849 and HD 108945) show stages of 
inactivity, then an explanation is certainly needed to account for such a
major difference among the group members.





                 TOBIAS J. KREIDL
                 Lowell Observatory
                 P.O. Box 1269
                 Flagstaff, AZ 86002
                 U.S.A.





References:

Kreidl, T.J., 1984, I.B.V.S. No. 2460
Percy, J.R., 1973, Astron.Astrophys. 22, 381 [BIBCODE 1973A&A....22..381P ]
Preston, G.W. and Stepien, K., 1968, Ap.J. 151, 577 [BIBCODE 1968ApJ...151..577P ]
Rakos, K.D., 1963, Lowell Obs. Bull. 6, No. 2, 91 [BIBCODE 1963LowOB...6...91R ]
Stepien, K. and Romaniuk, M., 1973, Acta Astron. 23, 257 [BIBCODE 1973AcA....23..257S ]
Weiss, W.W., 1983, Astron.Astrophys. 128, 152 [BIBCODE 1983A&A...128..152W ]