COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 273

                                   Konkoly Observatory
                                   Budapest
                                   1968 May 17


  SECONDARY VARIATIONS OF THE FLARE STAR V 1216 SAGITTARII


Observations of the flare star, V 1216 Sagittarii, made at the Boyden
Observatory in 1966 revealed ten flares in 114 hours monitoring (Ref. 1).
During the same session secondary variations of the star's brightness and
colour were sought which are known to occur with amplitudes of a few tenths of
a magnitude in other UV Ceti stars (Ref. 2). The relation between these
secondary variations and the occurrence of flares is unclear. In fact, no
significant evidence of these changes was found in the Boyden 1967 session on
the flare star YZ Canis Minoris, although six flares occurred (Ref. 5).

Differential measures of magnitude and colour of V 1216 Sgr and a nearby
comparison star were made at the 16-inch Nishimura reflector on the night of a
large flare and on five subsequent nights. The results, together with the
observed flares, are shown in Fig. 1. These observations were carried out at
an average air mass of 1.4 at the beginning of a night's monitoring, and mass
extinction coefficients were used when forming mean magnitude and colour
differences for a given night. A check against a second comparison star was
made on four nights.

The general conclusions that may be drawn regarding night-to-night secondary
variations of V 1216 Sgr during this run are (a) that the mall fluctuations in

                          [FIGURE 1]

the B magnitude did not exceed +-0.^m03, and (b) that changes of colour
associated with the large flare in B-V and U-B may have occurred, in the sense
of a slight reddening (~0.^m1) as compared with the star in its less-active
phase. Further work on the constancy of the comparison stars is particularly
desirable.

An approximate UBV sequence, useful for photographic estimates of flare
amplitudes of V 1216 Sgr, was measured on a single night, 15 July 1966. See
Fig. 2 and the Table. The zero points in magnitude and colour were not
determined on the same night, but this will not affect differential measures.
The tabulated values should not be in error by greater than +-0.^m1.

Table
Star         B         B-V     U-B
a           9.^m60    0.^m60  -0.^m30
b          10.65      0.35    -0.15
c          10.70      0.40    -0.25
d          11.80      1.70     1.30
e          12.25      2.00     1.25
f          12.35      1.85     1.55
g          12.75      1.90     1.60
V 1216 Sgr 12.00      1.70     0.95


                          [FIGURE 2]


REFERENCES

(1) A.D. Andrews, Publ. Astr. Soc. Pacific Vol. 78, p. 542 (1966). [BIBCODE 1966PASP...78..542A ]
(2) M. Petit, Journal des Observateurs Vol. 38, P. 354 (1955). [BIBCODE 1955JO.....38..354P ]
(3) A.D. Andrews, I.B.V.S. No. 265 (1968).


Armagh Observatory,
May 7, 1968.
                                    A.D. ANDREWS