COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1419

                                                     Konkoly Observatory
                                                     Budapest
                                                     1978 May 5


                      PHOTOMETRY OF AI Phe

AI Phe (BV 1513, HD 6980) was found to be a late-type eclipsing binary by
Strohmeier (1972, IBVS 665), who noted that the period was probably several
days. In order to determine the period and characteristics of the lightcurve
for possible inclusion in the eclipsing binary program at the Copenhagen
University Observatory, a search for eclipses was carried out between
Sept. 1976 and Jan. 1977. The observations were performed with the 50 cm
Danish Telescope at the European Southern Observatory, La Silla, Chile,
equipped with a four-channel spectrophotometer. Filters of the Stromgren uvby
system were employed.
   Observations on 42 nights gave parts of 4 eclipses, and from a preliminary
ephemeris B. Helt (private communication) obtained part of an eclipse in Sept.
1977 with the same instrument.
  The final ephemeris is

                     HJD 2443410.6885 + 24.5923*n.
                                  +-4       +-1

   Primary minimum has a depth in u,v,b,y in the instrumental
system* (which is very close to the standard system) of 1m.24, 1m.05,
0m.83 and 0m.74, respectively. The eclipse lasts almost 13 hours, which is a
fraction of 0.02 of the period, and shows a totality of approximately 80
minutes duration. Only parts of the sides of the secondary minimum were
observed. Their extension gives a depth in y of about 0m.28. Secondary minimum
is displaced to phase 0.46, indicating an accentric orbit. The standard uvby
indices outside eclipse are V=8.609, b-y=0.424, m_1=0.219 and c_1=0.357, with
b-y increasing by about 0m.1 during primary minimum.
   AI Phe is a double-lined spectroscopic binary. M. Imbert (private
communication) has found, from spectra taken with the ESO 1.5 meter telescope
at La Silla, that the primary component is of spectral type G2V, showing rather
broad lines, and that the secondary component is of somewhat later type,
possibly G5. This is consistent with the uvby colours and their variation 
during primary minimum. The difference in spectral type between the components
seems insufficient to explain the large difference in the depths of the two
minima, which is therefore presumably due to the variation of the separation
between the components in an eccentric orbit with e cos omega close to zero.
   Since relatively few late-type long-period eclipsing binaries have been
studied, a full lightcurve will be obtained.


                                 BO REIPURTH

                         Copenhagen University Observatory