COMMISSION 27 OF THE I.A.U.
            INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2811

                                          Konkoly Observatory
                                          Budapest
                                          15 October 1985

                                          HU ISSN 0374 - 0676


             PHOTOELECTRIC PHOTOMETRY OF THE W UMa
                  TYPE VARIABLE STAR FG HYDRAE


  The variable FG Hydrae (BD+3d1979) was discovered by Hoffmeister (1934).
It was classified as a cluster type by Tsesevich (1949) using visual observations.
FG Hydrae was considered by Smith (1954, 1955) as one of the short period
binaries that undergoes complete eclipses. Inspite of the fact that the 
observations taken by Smith did not cover a complete cycle of variation his data
help to define quite well a relatively early epoch. His observations obtained
in 1963 (Smith, 1963) which consist of 306 blue. and 246 yellow observations of
FG Hydrae including data from 11 nights gave a complete light curve of FG
Hydrae and 3 times of minima which are given in Table I.

                    Table I

       Times of minima of FG Hydrae obtained by Smith (1963)

          JD. Hel        Min.     O-C

         2434056.7184    II      +0.0001
            4057.7018    II       0.0000
            4084.5842    II       0.0000

Observations made by Binnendijk (1963) led to a complete light curve and improved period determination.
  FG Hydrae was included in the programme of short period variables running
out at Kottamia Observatory using the 74" reflector.
  The observations were carried out by a one beam photoelectric photometer which
was attached at the cassegrain focus (f/18). Standard B and V filters with EMI
9558 B photomultiplier tube with S-20 photocathode cooled by a propeller fan,
were used through all the intervals of observations. The amplified output of
the tube was fed into a Brown recorder. The times of observations were estimated
from the starting point and the moving mean speed of the strip chart recorder.
Table II lists the pertinent data regarding the variable and comparison stars.

                    Table II

   Star             BD          Spectral type

  FG Hydrae       + deg3 1979   G0V
  Comparison      + deg4 1979   G5V



                               [FIGURE 1]
                               [FIGURE 2]




A total of 395 observations in B and 385 observations in V were obtained 
including the data of 4 nights during Jan and Feb. 1985. The light curves of 
FG Hydrae obtained in both B and V colours are shown in Figures 1 and 2.

  Five times of primary minima and one time of secondary minima were determined
in both B and V colours. Three times of minima are given in Table III.

                    Table III

    J. D.Hel.      Min.  Filter        E       O-C

  2446089.3543      I      V       27821.0   -.0017
       89.3546             B                 -.0014
       90.3678      I      V       27824.0   -.0013
       90.3679             B                 -.0012
       90.5316      II     V       27824.5   -.0014
         .5312             B                 -.0010
  2446109.3822      I      V       27882.0   -.0013
         .3821             B                 -.0014
       10.3654      I      V       27885.0   -.0016
         .3655             B                 -.0015
       11.3491      I      V       27888.0   -.0014
         .3493                               -.0012


The residuals were computed from the following ephemeris

      Min.I = 2436968.7067 + 0.32783433d E




                     H.A. MAHDY, M.A. HAMDY, M.A. SOLIMAN
                     Helwan Observatory, Egypt


References:

Binnendijk, K.I., 1963, Astron.J. 68, 30. [BIBCODE 1963AJ.....68...30B ]
Hoffmeister, C., 1934, Astr.Nachr. 253, 199. [BIBCODE 1934AN....253..195H ]
Smith, H.J., 1954, Astron.J., 59, 196.
Smith, H.J., 1955, Thesis, Harvard University, Cambridge, Massachusetts. [BIBCODE 1955PhDT.........2S ]
Smith, H.J., 1963, Astron.J., 68, 39. [BIBCODE 1963AJ.....68...39S ]
Tsesevich, V.P., 1949, Peremennye Zvezdy, 7, 8.