COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1816

                                Konkoly Observatory
                                Budapest
                                1980 July 14



      INFRARED PHOTOMETRY OF HR 1099 DURING LATE 1979




    The RS CVn type double-lined spectroscopic binary system
HR 1099 (= V711 Tau =ADS2644A) was observed in the near infrared
(mainly J, K and L) at the South African Astronomical Observatory
from 1979 November 17 - December 31. The observations were made
with the 0.75 m telescope, using the Mk II Infrared Photometer
similar to that described by Glass (1973).
    The photometric measures included both the components of
the visual pair ADS 2644 AB and were relative to the same comparison 
star (10 Tau) used for the visual and our previous infrared 
observations (Antonopoulou and Williams 1980, Paper I).
The effects of atmospheric extinction were allowed for using mean
coefficients, but were not significant because of the angular
proximity of the comparison star to the variable. A total of
137 observations was obtained in each colour in 24 nights.
    The phase of each observation was computed according to
the elements:
          T (JD)=2442766.069d + 2.83782d.E,
where the period is the spectroscopically determined orbital
period (Bopp and Fekel 1976) and zero phase corresponds in conjunction 
with the more active component, believed to carry the
spot complex, in front.
    The differential observations, taken as variable minus comparison, 
are plotted against phase and are shown in the Figure.
    It is clearly seen that the phase of the minimum is at
phase 0.95 in agreement with the phase of the minimum given by
the visual data taken at around the same time (Guinan et al. 1979).
This means that the phase of the minimum has shifted by 0.055
forwards, comparing these observations with the ones we took one
year earlier (Paper I).

                   [FIGURE 1]

    The amplitudes of the light variation in J, K and L are
about 0.09 mag, 0.07 mag and 0.06 mag, respectively.
    Assuming the simplified spot model for HR 1099 as described 
in Paper I, our preliminary calculations, from the combination 
of the present infrared data and the visual data given by
Guinan et al. 1979, give the results:
     The spots are 1250K+-700K cooler than the surrounding
photosphere and cover 0.16+-0.02 of the projected area of the
two stars or approximately one third of the hemisphere of the
active component assuming the two components to be the same
size.
     A full discussion will be published later elsewhere.
     We are grateful to the Director and the Staff of the South
African Astronomical Observatory for their help and to the UK
Science Research Council for travel and subsistence.




                      E. ANTONOPOULOU

                      Department of Astronomy
                      University of Edinburgh
                      Royal Observatory
                      Blackford Hill
                      Edinburgh, UK


References:
Antonopoulou, E. and Williams, P.M.,:1980 Ap.and Sp.Sc. 67, 469 [BIBCODE 1980Ap&SS..67..469A ]
Bopp, B.W. and Fekel, F.: 1976 Astron. J. 81, 771 [BIBCODE 1976AJ.....81..771B ]
Glass, I.S.: 1973, M.N.R.A.S. 164, 155 [BIBCODE 1973MNRAS.164..155G ]
Guinan, E.F., McCook, G.P., Fragola, J.L. and Weisenberger,A.G.:
      1979, I.B.V.S. No. 1723