COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 950

                                      Konkoly Observatory
                                      Budapest
                                      1974 December 7


           THE CHANGING PERIOD OF HQ LYRAE

     HQ Lyrae (19h23m19s + 42deg20'.5) is listed in the GCVS as a
questioned Mira type star with a period of 322 days. This variable 
was rediscovered by Lucia Dexter at the Maria Mitchell Observatory. 
On the basis of approximately 150 plates taken in recent
years she found a period of 290 days. I then examined the star on
some 700 plates taken between JD21030 and 42300. These indicated
that a constant period will not satisfy all of the observations.
They are best represented by the formula,

        Max. = J.D.2424770 + 289.5n + 30 sin (8deg*n).

The upper portion of the diagram shows the difference between 
observed and computed times of maximum for a constant period of 289.5
days, where the smooth curve represents the function 30 sin (8deg*n). The
lower diagram indicates that the observed (or interpolated) times
of maximum show a spread of +-10 days around the times of predicted
maximum. This spread is smaller than the uncertainty in interpolation 
of time of maximum for some incompletely observed cycles.
     The observations cover a span of 61 cycles after JD_0, the
first actually observed maximum. A number of earlier observations
at cycle -12 are at minimum fainter than the limiting magnitude of
the plates. The previously published JD_0, 28020, is some 20 days
past our observed maximum at that cycle. Our most recent well defined 
maximum, with observations on both the ascending branches of the
light curve, occurred at JD 41880 (cycle 59).



                                        DORRIT HOFFLEIT
                                        Maria Mitchell Observatory
                                        Nantucket, Mass., U.S.A.


                         [FIGURE 1]