COMMISSION 27 OF THE I. A. U.
              INFORMATION BULLETIN ON VARIABLE STARS
                          Number 2551

                                          Konkoly Observatory
                                          Budapest
                                          13 July 1984

                                          HU ISSN 0374-0676

         ON THE PHOTOMETRIC VARIATIONS OF HD 28843 AND HD 29009

  The CP stars HD 28843 = HR 1441 (He weak) and HD 29009 = HR 1449 (B9 Si)
have published photometric periods of respectively 1.37375 days (Pedersen,
1979, based on spectroscopic as well as photometric data) and 3.82 days
(Renson and Manfroid, 1981).
  In spite of the large amplitude of its variations, HD 28843 was not known
to be variable until 1977, and we used it as a comparison star for HD 29009
in several observing runs conducted at that time. Fortunately a second
comparison was included, HD 27563, and differential measurements led us to
derive periods for HD 28843 and HD 29009.
  Analysis of new uvby data obtained in the framework of the Long Term 
Observing Programme at ESO, shoved that HD 27563 is also variable, with a
complex behaviour (Manfroid and Mathys, in preparation), displaying variations
of several hundredths of a magnitude on a time scale of days.
  Careful absolute reduction of all of our old data concerning HD 28843 and
HD 29009, using sophisticated techniques (Manfroid and Heck, 1983) allowed
to study both stars without the interference of HD 27563, and to derive new
periods. Table I shows the repartition of our observations and the telescopes
used. Observations of Pedersen and Thomsen (1977) were included for HD 28843.

                       Table I
Date                   Telescope                Number of observations
                                                HD 28843   HD 29009
November 1977          La Silla Danish 50 cm    42         42
December 1978          La Silla ESO 50 cm                   8
September 1981         La Silla Danish 50 cm                7
January -
February 1976          La Silla Danish 50 cm    11
(Pedersen - Thomsen)
Total                                           53         57
The periods derived from these data are:
HD 28843               P = 1.37390 +- 0.00015 d
HD 29009               P = 3.79864 +- 0.00015 d


                               [FIGURE 1]

 Figure 1   Phase diagram for HD 28843 in u,v,b and y. Phase origin is JD 
 2442778.614 (same as in Pedersen and Thomsen, 1977). (+ Pedersen and 
 Thomsen, January-February 1976, * November 1977)

                               [FIGURE 2]

 Figure 2   Phase diagram for HD 29009 in u,v,b and y. Phase origin is JD 
 2443455.6421. (+ November 1977, * December 1978, (square) September 
 1981, x Long Term Programme)


and lie within the possible ranges quoted by the previous authors. (For
HD 29009, a period of about 3.84 days cannot be definitely excluded; however
this value is much less likely.) The phase diagrams are presented in Figures
1 and 2.
  Additional data from the ESO Long Term Photometric Programme are being
obtained for HD 29009. However the variety of the equipments used so far in
this programme is so large that no refinement of the period could be made.
Analysis and inclusion of those data is under way however (Renson and Manfroid,
in preparation), Figure 2 shows several points of good quality in 1982/83,
which tend to confirm our value of the period of HD 29009.


                  J. MANFROID
               Institut d'Astrophysique
               5, avenue de Cointe
               B-4200 Cointe-Ougree
               Belgium

                  G. MATHYS
               Institut fur Astronomie
               ETH-Zentrum
               CH-8092 Zurich
               Switzerland

References:

Manfroid, J. and Heck, A., 1983, Astron.Astrophys. 120, 302 [BIBCODE 1983A&A...120..302M ]
Pedersen, H., 1979, Astron.Astrophys.Suppl.Ser. 35, 313 [BIBCODE 1979A&AS...35..313P ]
Pedersen, H. and Thomsen, B., 1977, Astron.Astrophys.Suppl.Ser. 30, 11 [BIBCODE 1977A&AS...30...11P ]
Renson, P. and Manfroid, J., 1981, Astron.Astrophys.Suppl.Ser. 44, 23 [BIBCODE 1981A&AS...44...23R ]