COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2625

                                   Konkoly Observatory
                                   Budapest
                                   13 November 1984

                                   HU ISSN 0374 - 0676



          ON THE He WEAK VARIABLE HD 28843


    Photometric Observations of HD 28843 (=HR 1441) in the ubvy system have
led to the derivation of a period of 1.37390 +- 0.00015 d (Manfroid and Mathys, 1984).
The observations covered a time span of less than two years, from January 1976 to
November 1977.
    Contrarily to what was stated by Manfroid and Mathys, the star was already
known as a variable as early as 1966 (Cousins, 1966). In fact, eight observations
in the V band are available. These V data can be used to refine the period 
determination. V and y magnitude can be compared directly. Several frequency peaks
are obtained when performing the analysis of the complete set of data, both by
a Fourier-Deeming technique and by the method of minimization of the standard
deviation of the observations from a least-square fit by a sine wave and its first 
harmonic (Mathys and Manfroid. 1984). Unlike the former, the latter method allows in
the present case to determine unambiguously the best value of the frequency (Intergal=
0.727901 +- 0.000006 d^-1; the relevant part of the periodogram is shown on Fig. 1).

                              [FIGURE 1]

 FIG. 1 - Part of the periodogram of HD 28843 showing the most probable 
 values of the frequency
                              [FIGURE 2]

 FIG. 2 - Phase diagram for HD 28843 with the period P=1.373813d. Phase 
 origin is JD 2,437,647.336. The solid curve is a least-square fit of the
 observations by a sine wave and its first harmonic. Z: AWJC's 1966 V data.
 Y: Pedersen and Thomsen's y observations, January - February 1976
 (Pedersen and Thomsen, 1977). X: JM and GM's y measurements, November 1977

    A study of the phase diagrams confirms that the alternative values 0.726347
and 0.729453 d^-1 are much less good. Hence we adopt


               P =1.373813 +- 0.000012 d

as the most probable value of the period of HD 28843. The phase diagram obtained
with that period is shown on Fig. 2, together with a least-square fit of the data by a
sine wave and its first harmonic.




J. MANFROID                G. MATHYS                 A.W.J. COUSINS
Institut d'Astrophysique   Institut fur Astronomie   South African Astronomical
5, avenue de Cointe        ETH-Zentrum               Observatory
B-4200 Cointe-Ougree       CH-8092 Zurich            PO Box 9
Belgium                    Switzerland               Observatory, 7935
                                                     South Africa




References:

Cousins, A.W.J. and Stoy, R.H., 1966, R. Obs. Bull. No. 121. [BIBCODE 1966RGOB..121....1C ]
Manfroid, J. and Mathys, G., 1984, Inf. Bull. Var. Stars 2551.
Mathys, G. and Manfroid, J., 1984, submitted to Astron. Astrophys. Suppl. Ser. [BIBCODE 1985A&AS...60...17M ]
Pedersen, H. and Thomsen, B., 1977, Astron. Astrophys. Suppl. Ser. 30, 11. [BIBCODE 1977A&AS...30...11P ]