COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3354

                                          Konkoly Observatory
                                          Budapest
                                          14 July 1989

                                          HU ISSN 0374-0676


  EPOCHS OF MINIMUM LIGHT FOR WY CANCRI, AM LEONIS, AND RR LEPORIS


An Optec photometer was used on the 41cm David Irons telescope at the
observatory of the Charlotte Amateur Astronomers Club. Differential V
measurements were made. B measurements were not attempted because B curves had
much more scatter in previous observations.  Clear (unfiltered) measurements
proved to be unusable due to the contamination of light from passive red
lighting and scattered light. V curves were used to find epochs of minimum
light. The epochs are given as:

    Star     Hel. J.D.     Method     E      (O-C)

WY Cancri    2447567.6998   Hertz.   1859   -0.0004
AM Leonis    2447567.9076   Hertz.   3875   -0.0005
             2447569.7349   Hertz.   3880   -0.0021
RR Leporis   2447472.7736   BIS.     3546   +0.0029

where Hertz. signifies the Hertzsprung method and BIS. stands for the
bisection of chords technique.

The residuals for WY Cancri were computed using the light elements of Mullis
and Faulkner (1988). Mullis and Faulkner presented two times of minimum light
and a new set of light elements that indicated that the period had changed.
The fact that the residual for WY Cancri presented here is small supports the
period change noted by Mullis and Faulkner. A refined set of light elements
was obtained by combining this epoch of minimum light with those of Mullis and
Faulkner (1988) and Faulkner (1986):

H.J.D. MIN.I=2446025.9019+0.829369608 E.
                      +-1 p.e.   +-10 p.e.

The epochs of minimum light used to get the above light elements, as well as
the residuals, are given in the next table.

Hel. J.D.        E     (O-C)

2446025.9017      0   -0.0002
2446143.6726    142   +0.0002
2447202.7774   1419    0.0000
2447241.7580   1466   +0.0002
2447567.6998   1859   -0.0002

The residuals for AM Leonis were computed from the light elements of Rafert and
Twigg (1980). It should be noted that the eclipse curve from which the second
epoch of minimum light was obtained suffered from an asymmetry, particularly on
the ascending branch. This caused the determined epoch to be slightly early,
giving rise to its more negative residual. Since the residuals of the epochs
presented here are relatively small, it can be concluded that the period of AM
Leonis has remained constant since the observations of Rafert and Twigg.

The residual for RR Leporis was computed based on the light elements of
Bookmyer et al. (1986). Because the residual was about 4 minutes, a new set of
light elements was obtained by combining this epoch of minimum light with those
of Bookmyer et al:

H.J.D. MIN.I=2444226.6627+0.91542890d E
                      +-5 p.e.  +-26 p.e.

Note that this period is 0.088 seconds shorter than that of Bookmyer et al.
The epochs of minimum light used to get the above light elements, as well as
the residuals, are given below.

Hel. J.D.       E       (O-C)

2444226.6635     0    +0.0008
2444231.6968     6    -0.0008
2447472.7736  3546     0.0000


CHRISTOPHER R. MULLIS       DANNY R. FAULKNER
501 Highland Forest Drive   University of South Carolina-Lancaster
Charlotte, NC 28226         Lancaster, SC 29720
U. S. A.                    U. S. A.

References:

Bookmyer, B. B., Faulkner D. R., and Samec, R. G., 1986, 
                                           Inf. Bull. Var. Stars No. 2873.
Faulkner, D. R., 1986, Pub. A. S. P., 98, 605. [BIBCODE 1986PASP...98..690F ]
Mullis, C. R. and Faulkner, D. R., 1988, Inf. Bull. Var. Stars, No. 3206.
Rafert, J. B. and Twigg, L. W., 1980, Mon. Not. R. A. S., 193, 79. [BIBCODE 1980MNRAS.193...79R ]