COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2008

                                  Konkoly Observatory
                                  Budapest
                                  1981 August 27

                                  HU ISSN 0374-0676




        HD 200356: A POSSIBLE NEW delta SCUTI STAR



  Since one third of the stars that lie within the limits of the
instability strip are pulsators, (Breger, 1979) whenever an 
observation of a known variable star is made, a systematic search
for detection of new variable stars is carried out (Peniche et
al. 1980, Peniche and Pena 1981). In this case, together with
the observation of the delta Scuti star HR 8006, the star HD 200356
(BD-1d4098) was tested for variability since its spectral type
indicated that it might have features of a delta Scuti pulsator;
Table I presents a summary of the characteristics of the 
observed stars.

                         Table I
--------------------------------------------------------------     
     Star        m_v  Spectrum      alpha(1950)    delta(1950)
--------------------------------------------------------------   
   V=HR8006      6.5     F0         20h52m33s      -1d33'54"
  HD 200356      7.3     F2         21h00m32s      -1d30'24"
C_1 =BD-1d4074   8.0     F5         20h52m21s      -0d53'39"
C_2 =BD-1d4073   8.0     F5         20h52m19.1s    -1d34' 0"
--------------------------------------------------------------

  The photometric observations were made with the 85 cm telescope 
at the San Pedro Martir Observatory, Mexico, a refrigerated
1P21 photomultiplier and Johnson's V filter were utilized. The
sequence C_1, V, C_2 was followed uninterruptedly each night, with
observations of HD 200356 every two cycles. A single observation
consisted of at least five ten second integrations of each star
and two of the sky.
  HD 200356 was observed during the nights of September 28th,
29th, 30th and October 1st, 1980. Figure 1 shows the result of
subtracting the mean of the magnitude of the comparison stars
(interpolated at the time of the observation of the variable)


                          [FIGURE 1]


from the magnitude of HD 200356, along with the sequence of the
difference in magnitudes of the comparison stars for each night.
The probable error in a single observation, estimated from the
comparison stars is +-0.003 mag., time is reported in universal
time and its precision is of 1 minute.
  It is clearly visible from the figure that, although the 
amplitude of the variation of HD 200356 is rather small (0.01 mag.)
it is not a constant star. On each night the calculated standard
deviation of the difference in magnitudes of the comparison stars
is about one half that of the magnitude of the variable star,
moreover, since the magnitude of the comparison stars (8.0) is
fainter than the magnitude of HD 200356 (7.3) the variations seen
in the light curves are real and not due to the atmospheric 
conditions.
  At this moment nothing can be said about the period of this
star, but it is on the order of hours. Hence, due to the 
characteristics shown (spectral type of F2, low amplitude of variation
and a short period on the order of hours) we might conclude that
this star is probably a delta Scuti pulsator; of course more detailed
observations are needed in order to determine its periodic
behaviour.



           S.F. GONZALEZ-BEDOLLA and J.H. PENA
           Universidad Nacional Autonoma de Mexico
           Apdo. Postal 70-264
           Mexico 20, D. F.





References:
Breger, M., 1979 Pub. Astron, Soc. Pac., 91, 5 [BIBCODE 1979PASP...91....5B ]
Peniche, R., Pena, J. H., Sanchez, G., Warman, J.,
      1980, Pub. Astron. Soc. Pac., 92, 300 [BIBCODE 1980PASP...92..300P ]
Peniche, R., Pena, J, H., 1981, Inf. Bull. Var. Stars, No. 1970