COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 1054

                                 Konkoly Observatory
                                 Budapest
                                 1975 October 22


      HR6611: AN INTERESTING NEW ECLIPSING BINARY



    HR6611 is an A3m: star (Cowley et al., 1969) which was 
discovered to be eclipsing while being tested for pulsational light
variability. Figure 1 is a plot of the observations obtained using
the photoelectric Volksphotometer on the McDonald Observatory 92cm
telescope. The descending branch of the Light curve was obtained on
June 22, 1975UT in. the Stromgren v filter and the ascending branch
was obtained four days later in Stromgren y. They were pieced 
together assuming that the spectroscopic period, P=3.894 days (Petrie,
1928), applies. The epoch derived is T_0 = JD 2442585.940 +- 0.005.
Stromgren v magnitudes are shown outside of eclipse in Figure 1a
from which we derive an eclipse depth of 0.45 mag in v. All of the
light curves are relative to two comparison stars.
    HR6611 is potentially a very interesting system.  Although
Cowley et al. (1969) classify it as A3m:, Bidelman (Abt and Bidelman,
1969) classifies it as "definitely Am". uvbybeta photometric indices
indicate that the primary is more than a magnitude above the main
sequence making it one of the most luminous Am stars known. Petrie
(1928) derived a mass ratio of 0.89 from the radial velocity curve
but noted that the primary lines were twice as strong as those of the
secondary. He also derived (Petrie, 1950) a magnitude difference 
between the two components of 0.99 mag. and spectral types of A4 and
A7 for the primary and secondary, respectively. Abt (1975) gives
v sin i of 30 and 25 km sec^-1, respectively.
   How do Am abundances increase with increasing luminosity (age)?
HR6611 is composed of two slowly rotating A stars of different mass
and luminosity hence probably different evolutionary states. In 
addition, it is one of the most luminous Am stars known and consequently 
may provide much information concerning the above question.
   We plan to obtain high dispersion spectra during eclipse when
one component will be partially hidden in order to obtain relatively
uncontaminated abundances. In addition, we plan to obtain a complete
light curve and uvbybeta photometry during eclipse to derive individual
temperatures and surface gravities for both components. This, coupled 
with a new radial velocity curve which will yield individual
masses, should be useful in constraining theoretical evolutionary
models.
    I would like to thank Dr. Michel Breger's summer observing
class for obtaining the eclipse egress on June 26, 1975UT.

                    [FIGURE 1]


                            D. W. KURTZ

                       Department of Astronomy
                       and McDonald Observatory
                         University of Texas


References:
Abt, H.A., 1975, Ap.J., 195 405 [BIBCODE 1975ApJ...195..405A ]
Abt, H.A. and Bidelman, W.P. Ap.J., 158, 1091  [BIBCODE 1969ApJ...158.1091A ]
Cowley, A., Cowley, C., Jaschek, M., and Jaschek, C., 1969, A.J., 74, 375 [BIBCODE 1969AJ.....74..375C ]
Petrie, R.M., 1928, Pub.D.A.O. Victoria, 4, 381  [BIBCODE 1928PDAO....4...81P ]
Petrie, R.M., 1950, ibid., 8, 319 [BIBCODE 1950PDAO....8..319P ]