COMMISSION 27 OF THE I. A. U.
                INFORMATION BULLETIN ON VARIABLE STARS
                            Number 3559

                                                       Konkoly Observatory
                                                       Budapest
                                                       4 February 1991

                                                       HU ISSN 0374 - 0676


                 A NEW FORECAST FOR HS HERCULIS

   The first attempt to determine an apsidal period, U, for HS Herculis
was undertaken by Hall and Hubbard (1971). From a preliminary analysis of
observed primary minima, they have computed U=15.5 years. But, soon after
this communication, Martynov (1971) emphasized that the apsidal period 
established by Hall and Hubbard is too short.
   By using his determination, omega = 116 deg for the longitude of periastron
and taking into consideration the spectroscopic value, omega = 37 deg
(see Cesco and Sahade, 1944), Martynov has determined U = 110 years.
   Lastly, Scarfe and Barlow (1974) are of opinion that the available 
photometric data do not put in evidence any effect of apsidal motion "and 
another interpretation of the variation in times of minima is required".
   Now, in Figure 1 we display all O-C differences, which are referring to
the linear ephemeris

         Min.hel.I = JD2440146.6008 + 1.6374333d E.


                            [FIGURE 1]


It is easy to see that the corresponding O-C diagrams for primary and
secondary minima (see Fig. 1) are very likely to be caused by a veritable
apsidal motion, but the length of the apsidal period is difficult to be 
determined.
   Having in view the above presented remarks, we consider that in the
spring of the current year some observers, by performing photoelectric 
observations, could contribute to an apsidal period determination. That is why
we ask for a cooperation in observing the binary system HS Herculis.


                                             IOAN TODORAN

                                             Astronomical Observatory
                                             3400 Cluj-Napoca
                                             Romania



References:

Cesco, C.U., Sahade, G.: 1944, Ap. J., 101, 114. [BIBCODE 1945ApJ...101..114C ]
Hall, D.S., Hubbard, G.S.: 1971, PASP, 83, 459. [BIBCODE 1971PASP...83..459H ]
Martynov, D. Ya.: 1971, Astron. Circ. (in Russian), No. 651. [BIBCODE 1971ATsir.651....1M ]
Scarfe, C.D., Barlow, D.Y.: 1974, PASP, 86, 181. [BIBCODE 1974PASP...86..181S ]