COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1884

                                   Konkoly Observatory
                                   Budapest
                                   1980 December 12

                                   HU ISSN 0374-0676



                     TAU CYGNI



The star Tau Cyg, reported as suspected Delta Scuti variable
(Pant et al. 1968, Frolov 1970, Kukarkin 1974), was observed
photoelectrically in 6 nights since July 25, 1978 to October 9,
1979 with the UBV photometer described by Piccioni (1972) mounted 
on the 60 cm reflector telescope of the Bologna Observatory.
  Sigma Cygni was used as comparison star. In the Table are
reported the mean UBV magnitudes of Tau Cyg deduced from the

                  Table I
J.D.         N_mis.      V            B-V         U-B
2443715.385   3     3.711+-.006   .411+-.008   .034+-.008
       .425   5     3.709+-.006   .414  .008   .029  .008
2443718.380   4     3.722  .005   .411  .007   .021  .008
       .413   5     3.723  .002   .413  .003   .021  .004
       .445   6     3.717  .002   .411  .003   .019  .004
2443736.431   6     3.722  .002   .420  .002   .011  .003
       .468   2     3.730  .005   .421  .006   .010  .007
2443738.395   5     3.707  .004   .414  .006   .022  .006
       .430   3     3.72   .01    .41   .01    .03   .01
       .452   5     3.703  .007   .408  .008   .019  .008
       .481   4     3.718  .003   .415  .006   .022  .006
       .528   3     3.705  .008   .41   .01    .02   .01
       .554   1     3.71   .01    .42   .01    .02   .01
2443747.355   4     3.704  .004   .417  .005   .022  .006
       .372   4     3.718  .004   .415  .004   .027  .006
2444156.410   5     3.697  .001   .418  .002   .023  .002
       .433   7     3.695  .003   .419  .004   .022  .004
       .468   8     3.694  .003   .416  .003   .022  .003

magnitudes of Sigma Cyg published by Iriarte et al. (1965). A
systematic calibration error of 0.02m could be present in addition 
to the standard errors of the mean.
    The present observations confirm that the star is certainly
variable with an amplitude of about 0.02m; we do not find evindece 
of the period 0.143d suggested by Paraskevopoulos (1921) and
Henroteau (1922).
    Considering all the available observations and the Abt
(1961) remark against a rotational explanation of the variability,
Tau Cyg seems to be a Delta Scuti star of variable-period type
according the Breger (1979) classification with asymmetric light
and velocity curves.
   The authors wish to express the most sincere thanks to Mr.
L. Oculi for his careful technical assistance.







                         C. BARTOLINI

                         A. DAPERGOLAS

                  Istituto di Astronomia dell'Universita
                  di Bologna, Via Zamboni, n.33.
                  40126 Bologna, Italy


References:
Abt, H.A. 1961, Ap.J., 134, 1013 [BIBCODE 1961ApJ...134.1013A ]
Breger,M. 1979, Pub.Astr.Soc.Pac., 91, 5 [BIBCODE 1979PASP...91....5B ]
Frolov, M.S. 1970, I.B.V.S., No. 427
Henroteau, F. 1922, Pub.Dom.Obs.Ottawa, 5, 363
Iriarte, B., Johnson, H.L., Mitchell, R.I., Wisniewski,W.K.,
        1965, Sky and Telescope, 30, 21 [BIBCODE 1965S&T....30...21I ]
Kukarkin, B.V., Kholopov, P.N.,Efremov,Yu.N.,Kukarkina, N.P.,
        Kurochkin, N.E.,Medvedeva,G.I.,Perova,N.B.,Pskovsky,
        Yu,P., Fedorovich,V.P.,Frolov,M.S, 1974, Sec.Suppl.
        to the Third ed. of the Gen.Cat.of Var.Stars
Pant, M.M., Gaur,V.P., Pande, M.C. 1968, Observatory, 88, 221 [BIBCODE 1968Obs....88..221P ]
Paraskevopoulos, J.S. 1921, Ap.J., 53, 144 [BIBCODE 1921ApJ....53..144P ]
Piccioni, A. 1972, Mem.Soc.Astr.It., 43, 159 [BIBCODE 1972MmSAI..43..159P ]