COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1207

                                                 Konkoly Observatory
                                                 Budapest
                                                 1976 November 23 


      IMPROVED RESULTS FOR SEVEN SAGITTARIUS VARIABLES

The extensive collections of plates at Harvard and at the
Maria Mitchell Observatory cover a sufficient time span for
the detection of changes in period. We are therefore examining
numerous periodic variables for which prior published results
depended on observations made prior to 1960. In the Table, the
first six of the seven listed had last been observed on Harvard
plates taken through 1931, the seventh through 1953. Plates taken 
subsequently, mainly at the Maria Mitchell Observatory since
1956, have confirmed or slightly improved the constant periods
previously found. The time interval represented ranges from 50
to 77 years. Only in two cases are changing periods necessary
to account for the observed times of maximum: for V511 by an
abrupt change at about JD 23950; for V515 by a secular change
in period.
   In the Table the initials in columns 3 and 6 indicate the
people who made the new observations of brightness, or who 
determined the periods: MR, Dr. Marguerite Risley; PR, Pamela
Robinson; CP, Constance Philips; and DH, myself. In all cases
the revised periods depended upon the combination of the new
with the older observations. Although the final determinations
of period, as well as the older ones, are mainly mine, Miss
Robinson and Miss Philips carried out the preliminary computations 
on the stars they had measured which led to the final values. 
Some of the early estimates date back as far as 1899 on
the Harvard plates.
   This work was accomplished under Grant NSF76-15444 from
the U.S. National Science Foundation, for which it is a 
pleasure to express our appreciation.

        Verified or improved periods for seven Sagittarius
                          variables

Var     Period in  New Obs.    Revised Ephemeris         No.    Period Notes
        GCVS         by                JD0+nP+kn^2     Epochs        by

GP Sgr  265.5        PR        40080 +257.5n             122        DH    1
V509       0.53436   PR        41121.770 +0.5343587n   36225        DH+PR
V510     168         PR        42680 +167.9n             187        DH+PR
V511     158.5       MR+DH     23950 -158.5n before JD0   80        DH
                                     +158.2n after JD0   120
V512     196         MR+DH     26500 +196n                97        DH    2
V515     245.7       CP        31635 +246.5n+0.015n^2    114        DH
V1655    245         CP+DH     42980 +245n                78        DH

1. Considerable magnitude scatter in recent observations.
   Attempts by PR to fit the observations to a changing period
   yielded no improvement. The average period given holds fairly
   well from JD 14850 to the present.
2. V512 is too faint at maximum for meaningful observations from
   the Nantucket plates. The previously published JD0 should have
   been 26500, not 26400 as given in GCVS and the original reference 
   (Harvard Annals, 90, 187, 1934).

                          [FIGURE 1]

Figure: Finder charts for the variables tabulated. Width of all
        fields 10', South at top. Markers indicate the variable
        stars, letters, CoD stars to aid in identification of
        field. Left to right, top strip: V510 and V512 Sgr;
        A = CoD -26deg13068, B = -26deg13086.
        Lower strip : V509, V511, GP, V515 and V 1655 Sgr;
        C = -25deg13014, D = -25deg13021, E = -24deg14219, F=-24deg14244,
        G = -25deg13063, H = -25deg13012, and J = -25deg13082.



                                  DORRIT HOFFLEIT

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