COMMISSIONS 27 AND 42 OF THE IAU
                  INFORMATION BULLETIN ON VARIABLE STARS
                              Number 3886

                                              Konkoly Observatory
                                              Budapest
                                              27 May 1993

                                              HU ISSN 0374 - 0676


                   ON THE PERIOD OF THE CEPHEID CI Per


Variability of CI Per was discovered by Hoffmeister (1944), who later published
(Hoffmeister, 1947) the elements:

  Max JD hel=2429230.5+3.3779d*E

Schmidt (1991) pointed out that the period 3.3779d is wrong, and derived 
a new one as 3.767d.  However, Berdnikov (1992a) found that the current 
period was 3.2963d.

For investigation of the period of CI Per we have analysed all published
observations, which are photoelectric ones only, with Hertzsprung's method.
The computer version of this method (Berdnikov, 1992b) was used, as Berdnikov's
(1992a) light curve served as the standard one.  Normal maxima in filter V
together with their errors and numbers (N) of observations utilized are listed
in Table 1.  These data were analysed with the least squares method (with
weight being inversely proportional to error squares) and the following new
ephemeris used for computing the O-C residuals listed in Table 1 was obtained:

  Max JD hel=2446298.815 + 3.297224d * E
                 +-0.045 +-0.000068

The plot of the residuals in Figure 1, however, shows that the period may
undergo periodic and/or sudden changes.  In the latter case the following
values of the pulsation period can be derived from the existing data:

  before JD 2447800  P=3.297525d+-0.000061d;
  after JD 2447800   P=3.297074d+-0.000099d.


                           [FIGURE 1]


                           Table 1

Max JD hel    Error    N      E           O-C            Reference
2446298.734  +-0.016   15     0    0.081d    -0.024d    Berdnikov, 1987
2447419.873    0.012   27   340    0.003      0.001     Berdnikov, 1992c
2447769.428    0.011   19   446    0.051      0.015     Berdnikov, 1992d
2448115.622    0.015   20   551    0.037      0.011     Berdnikov, 1992e
2448514.548    0.004   75   672   -0.001      0.000     Berdnikov, 1992a
2448877.252    0.010   26   782    0.008      0.002     Berdnikov, 1993

Obviously, more observations are needed to verify or to reject these results.



  L. N. BERDNIKOV
  Sternberg Astronomical Institute,
  13, University Avenue,
  Moscow 119899
  Russia
  Saratov University,
  Saratov,
  Russia

References:

Berdnikov, L. N., 1987, Perem Zvezdy, 22, 530 [BIBCODE 1987PZ.....22..530B ]
Berdnikov, L. N., 1992a, Pisma v Astron. Zh., 18, 325 [BIBCODE 1992SvAL...18..130B ]
Berdnikov, L. N., 1992b, Pisma v Astron. Zh., 18, 519 [BIBCODE 1992SvAL...18..207B ]
Berdnikov, L. N., 1992c, Astron. and Astrophys. Transactions, 2, 43 [BIBCODE 1992A&AT....2...43B ]
Berdnikov, L. N., 1992d, Astron. and Astrophys. Transactions, 2, 107 [BIBCODE 1992A&AT....2..107B ]
Berdnikov, L. N., 1992e, Astron. and Astrophys. Transactions, 2, 157 [BIBCODE 1992A&AT....2..157B ]
Berdnikov, L. N., 1993,  Pisma v Astron. Zh., 19, 210 [BIBCODE 1993AstL...19...84B ]
Hoffmeister, C., 1944, Astron. Nachr., 274, 177 [BIBCODE 1944AN....274..176H ]
Hoffmeister, C., 1947, Veroff. Sternw. Sonneberg, 1, No. 2
Schmidt, E. G., 1991, Astron. J., 102, 1766 [BIBCODE 1991AJ....102.1766S ]