COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 362

                               Konkoly Observatory
                               Budapest
                               1969 July 8

      THE MAGNITUDE, COLOR AND SPECTRUM OF RV Sgr (1)

      During our survey of giant N stars (Hidajat, 1965)
in the Palomar-Groningen Variable Star Field 3 (2) (Plaut,
1969), we observed the changes of the color and spectrum of
the variable star RV Sgr. The variations are summarized in
the following table.

JD 2438 000+      V      V-I     M-type Spec.
        964.17   12.1   +4.50        -
        992.05   12.5   +4.73        -
        994.13     -      -          9
        998.16     -      -          8
JD 2439 000+
        001.15     -      -          8
        002.15     -      -          6
        293.27   11.9   +4.18        -
        350.20     -      -         6.5
        351.15     -      -         5-6
        376.06   10.1   +3.25        -
        384.05    9.7   +3.64        -

           The photographic magnitudes and colors listed above
were measured on Kodak 103a-D and I-N plates, exposed behind
GG11 and RG 8 filters respectively to match the V-magnitude
(of the UBV system) and the I-magnitude (of the Kron system).
Pairs of V and I plates were always taken on the same night
with the Bosscha Schmidt telescope. A standard photoelectric
sequence in the field obtained by Wehinger (unpublished)
has been used to calibrate the photometric scales. The
spectral types have been determined on the unwidened
spectral plates (I-N plus RG 8) with a dispersion of
1700A/mm at the atmospheric A-band. The Case system of
classification (Nassau and Velghe, 1964) was used to 
determine the spectral types.
             The magnitude, color and spectrum variations seem
to be in agreement with the finding of Miss Houk (1969), who
shows that a variable with a period of 318 days would have
on the average a spectral type M5 at maximum and M9 or M 10
at minimum.
      We thank Dr. Nancy Houk for providing us with the
A. A. V. S. O. Chart. The support of the photographic material
provided by the Warner and Swasey Observatory is gratefully
acknowledged.



                       TJEN-KIAT TAN
                        B. HIDAJAT
                     Bosscha Observatory
                   Lembang, Java, Indonesia





(1) R. A. - 18h24.6m; Dec. = -33deg21.3' (1950)
(2) R. A. - 18h26m; Dec. = -33.0deg (1950)

Hidajat, B. Inf. Bull. South. Hem. 7, 24, 1965
Houk, N., private communication, 1969
Nassau, J. J, and Velghe, A. G., Ap. J. 139, 190, 1964 [BIBCODE 1964ApJ...139..190N ]
Plaut, L., I. A. U. Symp. 7, 1959 (Ed. by A. Blaauw et al).