COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1787

                                    Konkoly Observatory
                                    Budapest
                                    1980 May 19


              INFRARED PHOTOMETRY OF ALGOL


The triple system eclipsing binary Algol have been observed over a wide range
of wavelengths -- from X rays to radio. Infrared observations to data have been
at 1.6 microns (Chen and Reuning, 1966); 5 microns (Jameson et al. 1973); 2.2,
3.6, 4.8; and 8.6 microns (Longmore and Jameson, 1975); 2.2 microns (Smyth et
al., 1975); 4.8 microns (Magro et al., 1977); and 10 microns near secondary
minimum (Nadeau et al., 1978). Some of these observations did not have very
much time resolution or contained large statistical errors. These limitations
on the data make it difficult to develop comprehensive theoretical models of
the infrared emission from the system. To provide a better observational
foundation, we have begun a program of infrared observations of Algol with the
1.3-meter telescope and InSb detector'("Otto") at Kitt Peak National
Observatory. Here we present our preliminary results.

All observations have been made during the day with a 23" or 32" aperature.
Beam switching 60" in declination cancelled the infrared background. The
standard star of all observations was Alpha Persei, whose magnitudes are J=
+0.874, H=+0.647, K=+0.565, L=+0.459, and M=+0.36. Extinction correction were
usually small at all wavelengths.

Figures 1-6 summarize the results so far. The phase was calculated from
primary minimum by JD = 2440953.4657+2.8673075 E (Ashbrook, 1976). Figure 1
show a little more than half of the primary eclipse on 10 February 1979 (U.T.).
Complete sets of data were taken every ~5 minutes; the M data was averaged so
each point is roughly 10 minutes apart. Note than the eclipse is fainter and
shallower at longer wavelengths.

                         [FIGURE 1]
                         [FIGURE 2]
                         [FIGURE 3]
                         [FIGURE 4]
                         [FIGURE 5]
                         [FIGURE 6]

Figures 2-6 show light curves: at J, H, K, L, and M bands. (Open circles
indicate marginal data.) From these data, we find that the magnitudes during
primary eclipse are: J=+2.87+-0.01, H=+2.65+-0.01, K=+2.57+-0.01,
L=+2.50+-0.01, M=+2.49+-0.02. During secondary eclipse, the magnitudes are:
J=+2.20+-0.06, H=+2.12+-0.03, K=+2.07+-0.03, L=+2.01+-0.01, and M=+1.98+-0.01.
Outside of eclipses, we determine that J=+2.08+0.04, H=+1.99+0.04,
K=+1.93+-0.06, L=1.89+-0.01, and M=+1.84+-0.01. We had no significant excess
at any wavelengths.

We are continuing observations, especially at M, where the scatter in the data
is the greatest.


MICHAEL ZEILIK, LINDA BAYLISS, PAUL HECKERT
Department of Physics and Astronomy
The University of New Mexico
Albuquerque, New Mexico 87131
U.S.A.

References:

1. Chen, K,-Y. and Reuning, E.G,; Astronomical Journal, vol. 71, 283, 1966 [BIBCODE 1966AJ.....71..283C ]
2. Jameson, R.F., Longmore, A.J., and Crawford, B., Nature, vol. 242, 107, 1973 [BIBCODE 1973Natur.242..107J ]
3. Longmore, A.J. and Jameson, R.F., Mon. Not. R. Astr. Soc., vol. 173, 271,
   1975 [BIBCODE 1975MNRAS.173..271L ]
4. Magro, C.S., Needham, J.D., Phillips, J.P., and Selby, M.J., Mon. Not. R.
   Astr. Soc., vol. 180, 461, 1977 [BIBCODE 1977MNRAS.180..461S ]
5. Nadeau, D., Neugebauer, G., Becklin, E.E., Elfas, J., Ennis, D., Matthews,
   K. and Sellgren, K., Mon. Not. R. Astr. Soc., vol. 184, 523, 1978 [BIBCODE 1978MNRAS.184..523N ]
6. Ashbrook, J., Sky Telesc. 52, 48, 1976