COMMISSIONS 27 AND 42 OF THE IAU
              INFORMATION BULLETIN ON VARIABLE STARS
                          Number 3952

                                               Konkoly Observatory
                                               Budapest
                                               19 November 1993

                                               HU ISSN 0374 - 0676


                      IMPROVED PERIOD OF BH CMi


 BH CMi (BD +2d 1855) was discovered to be variable by Hoffmeister (1934). Recent
photoelectric observations were made by Zakrzewski and Zola in 1989. The incomplete
light curve obtained by them shows that the components of the binary system must
be very distorted, the configuration probably to be contact. Thus Zakrzewski and Zola
(1989) confirmed the classification, made by Soloviev (1955), of BH CMi being a variable
of W-UMa type.
 We decided to observe the star in 1991 in order to obtain a complete coverage of the
light curve and to improve the photometic elements since the ones given by Zakrzewski
and Zola were derived on the basis of only a few minima, determined during few months.
New photoelectric observations were made at Mt. Suhora observatory of the Pedagogical
University. The double beam photometer with Johnson-Morgan filters was used. In the
period between Jan. 16 to Jan. 19 a complete light curve of BH CMi in B and V band s
was obtained. BD +2d 1856 served as the comparison star while BD +2d 1857 was used as
the check star. The light curves are presented graphically in Figure 1, 
where magnitude
denotes the difference between the variable and comparison stars. From the new data we
determined 4 times of minima, 2 moments of the primary minimum and 2 of the secondary
one. These times of minima are listed in Table 1.

           Table 1. New times of minima of BH CMi.

-----------------------------------------
JD Hel   2448274.4066+-0.0002   primary
JD Hel   2448275.5247+-0.0002   primary
JD Hel   2448273.5662+-0.0003   secondary
JD Hel   2448276.3628+-0.0004   secondary
-----------------------------------------

 The new moments of minima combined with those known previously allowed to improve
the period of BH CMi:
        P=0.5594839d+-0.0000025d (from the primary minima)
        P=0.5594869d+-0.0000023d (from the secondary minima)
        P=0.5594848d+-0.0000022d (both primary and secondary)
  Since there are complete B and V light curves available, it is possible to obtain physical
parameters of the system by means of light curve modeling. In order to do this reliably,
spectroscopic observations are also needed.


                           [FIGURE 1]


                          B. ZAKRZEWSKI^1 and S. ZOLA^1,2
                          ^1 Mt. Suhora Observatory
                          Pedagogical University,
                          ul. Podchorazych 2,
                          30-084 Cracow, Poland

                          ^2 Astronomical Observatory
                          Jagiellonian University, ul. Orla 171,
                          30-244 Cracow, Poland



References:
Hoffmeister, C., 1934, A.N., 251, 21 
[CORRECT REFERENCE]		[BIBCODE 1934AN....253..195H ]
Soloviev, A. W.,1955, Astr. Circ., No. 159, 17
Zakrzewski, B., Zola, S.,1989, IBVS, No. 3360