COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER  470


                                 Konkoly Observatory
                                 Budapest
                                 1970 October 8


      GRADIENT DIAGRAM FOR PULSATING VARIABLES

        Comparison of the series of the U,B-and V,B-magnitudes 
for different variable stars indicates in most cases
a regressive dependence. Thus, one can characterize a
variable star by constant light gradients G_u=dU/dB and
G_v= dV/dB. On the gradient diagram (G_u, G_v) variables of
different types form definite sequences (1). The cepheid
sequence is the one mostly studied (2, 3). As to another
pulsating variables they are located above the cepheid
sequence on the gradient diagram as it was shown in the
papers (1,4).
        In this connection series of the phe UBV-magnitudes
of Mira-variables, semi-regular and RV Tau type stars were
studied. The gradients are given in the Table. The Figure

                     [FIGURE 1]

shows the gradient diagram for pulsating variables. One can
see that M,- SR- and RV-variables form a sequenee which is
situated over the cepheids. Inside this sequence RV Tau type
stars distinguish rather well as a rule having G_u > 1,15.
Mira stars and semi-regular variables are not separated and
are located in the left side of the sequence with G_u < 1,15
where there are no RY Tau type stars practically.


        It is interesting that in the new edition of GCVS
(11 ) two of the RV Tau variables given in the Table, SX Her
and UU Her, are classified  as SRd. Actually, UU Her 
gradients typical for semi-regular variables. But SX
according to its location on the gradient diagram, is a 
of the RV Tau type.


                                TABLE

Star            G_u             G_v           Source
                        M
R Boo           0.84            1.03            7
R Cuc           0.89            1.02            8
R Car           0.69            1.02            8
S Car           1.11            0.94            5
X Cen           0.89            0.90            8
U Cet           0.93            1.05            8
o Cet           0.77            0.99            6
S CrB           0.59            1.05            7
X Cyg           0.94            1.04            6
R Dra           0.95            1.03            6
S Her           0.66            0.84            7
SS Her          0.98            1.02            7
R Hya           0.92            0.94            7
R Leo           1.06            0.85            8
RS Lib          0.83            1.03            8
T Nor           0.91            0.87            8
RU Sgr          1.00            0.96            8
R Vir           0.84            1.03            7


                        SR      
T Cen           1.12            1.03            5
W Cyg           0.98            0.98            7
Ch Cyg          1.23            0.90            9
30_g Her        0.94            1.01            7
R Lyr           0.60            1.12            7
L_2 Pup         0.82            0.97            5


                        RV
EQ Cas          1.25            0.77           10
DF Cyg          1.21            0.81           10
V360 Cyg        1.24            0.82           10
SX Her          1.58            0.72           10
UU Her          1.05            0.70           10
AC Her          1.33            0.75           10
EG Lyr          1.31            0.95           10
EP Lyr          1.42            0.72           10
U Mon           1.18            0.86           10
TT Oph          1.80            0.81           10
TX Oph          1.28            0.72           10
UZ Oph          1.04            0.90           10
V453 Oph        1.12            0.78           10
V564 Oph        1.23            0.87           10
R Sge           1.58            0.68           10
R Set           1.33            0.88           10
V Vul           1.52            0.79           10


Kiev, September, 1970

                        I.G. KOLESNIK
                The Main Astronomical Observatory
                of the Ukrainian Academy of Sciences


REFERENCES

(1)  I.G. Kolesnik, F.I.Lukatskaya. Perem. Zvezdy, 17, 224 [BIBCODE 1970PZ.....17..224K ]
     (1970)
(2)  E.S. Kheilo. Inf. Bull. Var. Stars, No. 356 (1969)
(3)  I.G. Kolesnik, E.S. Kheilo. Perem. Zvezdy, 17, 234 (1970). [BIBCODE 1970PZ.....17..234K ]
(4)  F.I. Lukatskaya. Astrometrija and Astrophysika, Kiev
     "Naukova Dumka", 9, (1970).
(5)  O. Eggen. Roy. Obs. Bul., No.29 (1961). [BIBCODE 1961RGOB...29...73E ]
(6)  E. Mendoza. Bol.Obs.Tonantzintla y Takubaya, No.28 (1967). [BIBCODE 1967BOTT....4..114M ]
(7)  J. Smak. Ap J, Suppl. No.89, (1964). 
(8)  A.U. Landolt. PASP, 81, 443 (1969). [BIBCODE 1969PASP...81..443L ]
(9)  B. Cester. Astrophys. Space Sci., 3, 198 (1969). [BIBCODE 1969Ap&SS...3..198C ]
(10) G.W. Preston, W. Krzeminski, J. Smak, J.A. Williams, Ap.J,
     137, 401, (1963). [BIBCODE 1963ApJ...137..401P ]
(11) B.V. Kukarkin, P.N. Kholopov, Yu.N.E'remov, N.P. Kukarkina,
     N.E. Kurochkin, G.I. Medvedeva, N.B. Perova, V.P. Fedorovich
     M.S. Frolov. General Catalogue of Variable Stars. Vol. I
     and II. The third edition, Moscow, 1969.  [BIBCODE 1969gcvs.book.....K ]