COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                   Number 3108



                                    Konkoly Observatory
                                    Budapest
                                    3 November 1987

                                    HU ISSN 0374-0676


           PULSATION PERIODS IN DELTA SERPENTIS


  The Delta Scuti star delta Ser (HR 5789 = HD 138918 ) was discovered as a
variable star by Millis (1967), based on four nights of observation. He 
obtained a period of 0.13 days and an amplitude of 0.05 magnitudes in V filter.
Valtier (1972) reanalysed the former data obtaining a period of 0.134 days.
  We measured the flux of Delta Ser during eleven nights in 1975 and two
nights in 1975 and two nights in 1979, with the 30 cm Cassegrain-reflector
at the "Mojon del Trigo" Observatory using a standard UBV system.
  The Fourier analysis carried out for our data (Lopez de Coca et al., 1984)
showed two frequencies: 6.4227 c/d as the predominant one and, once the data
were prewhitened for this frequency, the maximum peak appeared at 7.8869 c/d
and the power spectrum after subtracting this second frequency is practically
white noise. The ratio of the two periods is 0.814, which is in good agreement
with the expected theoretical value for the ratio between the first and the
second overtones (Petersen, 1976; Stellingwerf, 1979). A detailed report on
our observations and data analysis will be published elsewhere.


                        P. LOPEZ DE COCA and A. ROLLAND
                        Instituto de Astrofisica de Andalucia
                        Apdo. 2144, Granada, (Spain).


References:

Lopez de Coca, P., Garrido, R. and Rolland, A. 1984, Astron. Astrophys.Suppl.
     Series, 58, 441. [BIBCODE 1984A&AS...58..441L ]
Millis, R.L. 1967, Dissertation, University of Wisconsin.
Petersen, J.O. 1976, in "Multiple Periodic Variable Stars". IAU Colloquium,
     No. 29, Budapest, Vol. 2. p. 195. [BIBCODE 1976ASSL...60..195P ]
Stellingwerf, R.F. 1979, Astrophys. J. 227, 935. [BIBCODE 1979ApJ...227..935S ]
Valtier, J.C. 1972, Astron. Astrophys. 16, 38. [BIBCODE 1972A&A....16...38V ]