COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 395

                                 Konkoly Observatory
                                 Budapest
                                 1969 October 23


       AN RR LYRAE STAR WITH A CHANGING PERIOD

      The variable star discovered by Dr. Dorrit Hoffleit
at 18h 26m 54s and -25deg 15.8' (1900) was examined visually
this summer, under the direction of Dr. Dorrit Hoffleit at
the Maria Mitchell Observatory, on Harvard plates ranging
in Julian Days from 2423948 to 2433858, and on Nantucket,
plates ranging in Julian Days from 2437824 to 2440417. The
brightness of the star varied between 14.0 and 15.7
magnitude.
      The variable is found to be of RR Lyrae, subclass
b type with a period of 0.534829d that operates from J.D.
2423948 to 2433858, and another period of 0.534869 that
operates from J.D.2437824 to 2440417. The later period P'
is related to the earlier period P by the relation

             1/P' = 1/P - 0.000139

      There is an indication of an evolutionary change in
the structure of the star between J.D.2433858 and 2437824,
for which there are no plates available. According to the
graph of the phase of maxima against the Julian Days
(Figure 2) this change took place about 1955-1956.

                      [FIGURE 1]

Figure 1: The light curve obtained for the variable with brightness
expressed in magnitudes as a function of phase of the period.
Dots: Harvard observations; crosses: Nantucket observations;
open circles: Lick observations using the period 0.534829d;
open circles with crosses: Lick observations using the
period 0.534869d.

                      [FIGURE 2]

Figure 2: The phases of maxima expressed in days as a function of Julian
Days for the period 0.534829d. Dots: Harvard  and Nantucket
observations; open circles: Lick observations.

      The Lick Observatory Atlas contains two charts of
the variable. On one chart taken on July 5, 1954, the star
appears to be of magnitude 14.9, and another taken on July
13, 1955 to be of magnitude 15.7. Both observations fit the
light curve using both the early and the late periods; but
the later period of 0.534869d is better, confirming the 
occurrence of the change of the period around 1955.
Using the period 0.534829d, the maxima occur at
phases as shown in Table I.

TABLE I. Observed Maxima on Harvard Plates

J.D.2400000+  Phase   J.D.2400000+  Phase
 26564.347    0.820    31638.315    0.898
 28022.292    0.821    32293.519    0.968
 29520.355    0.831    33836.398    0.774
 30168.536    0.771    33858.326    0.774

Using the period 0.534869d the maxima occur at phases
as shown in Table II.

TABLE II. Observed Maxima on Nantucket Plates

J.D.2400000+  Phase   J.D.2400000+  Phase
 37824.756    0.769    39272.737    0.937
 38612.639    0.808    40000+       0.5 to 0.9

I am deeply indebted to the U.S. National Science
Foundation for the grant to the Maria Mitchell  Observatory
that made this investigation possible.

Nantucket, Massachusetts
October 14, 1969

                           JANET AKYUZ
                       Ege University Observatory
                          Izmir, Turkey