COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2333

                                   Konkoly Observatory
                                   Budapest
                                   13 May 1983

                                   HU ISSN 0374-0676

            INFRARED VARIABILITY OF HR 7275



   Although Hall's (1976) original classification of the RS CVn stars
included infrared excesses as one criterion, little work has been done to
observe RSCVn stars in the infrared over complete orbital cycles. We report
here infrared photometry of the long-period, non-eclipsing system HR 7275
that clearly shows phase-dependent infrared light curves.
   All observations were carried out with the 1.3-meter telescope at Kitt
Peak National Observatory during the day. We used the InSb photometer "Otto"
with a 20" beam, chopping 60" in declination. Magnitudes were calculated
relative to alpha Lyr, which was taken as 0.0 at JHKL. Because HR 7275 is bright
(V=6), statistical errors in each observation were small, no more than 0.01
mag. Our observations spanned December 1980 to February 1981; most were
clustered in January 1981.

   Figures 1-4 show the results, plotted as the difference (alpha Lyr - HR 7275)
at each filter. The phases were calculated from the ephemeris given by Fried
et al. (1982): HJD = 2431043.57 + 28.59E, which is based on spectroscopy.
Note the clear drop from maximum at phase 0.1 to minimum at phase 0.8. The
amplitude of this infrared distortion wave is 0.11 at J, 0.09 at H, 0.09 at K,
and 0.06 at L.
   The VB observations of Fried et al. (1982) from 1978-1980 show that the
distortion wave of HR 7275 is quasi-periodic, with V amplitudes as large as
0.5 mag and as small as 0.28 mag. Percy and Welch (1982) reported V-band
observations that showed an amplitude of 0.1 mag with minimum at phase 0.45.
The photometric period, which varies, is roughly 27.8 days, significantly
less than the spectroscopic orbital period of 28.59 days.

                           [FIGURE 1]
                           [FIGURE 2]
                           [FIGURE 3]
                           [FIGURE 4]

  Our infrared observations started at about the same time that Fried
et al.'s ended. Their results show that the amplitude was increasing,
reaching about 0.25 mag at V at JD 2444550. Our results fit in well with
their photometric period.
   When combined with visual photometry, infrared observations provide the
necessary data to fit simple starspot models. With visual photometry (UBVR)
obtained at Capilla Peak in Fall 1980, we can model both the temperature and
distribution of starspots. We are in the process of doing so for HR 7275,
using the data reported here.



         M. ZEILIK, R. ELSTON, G. HENSON, P. SMITH

            Dept. of Physics and Astronomy

            The University of New Mexico

               Albuquerque, NM 87131

                      U.S.A.





References:
Fried, R.E., Eaton, J.A., Hall, D.S., Henry, G.W., Lovell, L.P., Krisciunas, K.,
   Chambliss, C.R., Detterline, P.K., Landis H.J., Louth, H., and 
   Skillman, D.R., 1982, Astrophysics and Space Sci., vol. 82, p. 181, 1982.
							[BIBCODE 1982Ap&SS..83..181F ]


Hall, D.S., 1976, IAU Colloquium No. 29, p. 287. [BIBCODE 1976ASSL...60..287H ]


Percy, J.R. and Welch, D.L., 1982, J. Roy. Astro. Soc. Can., vol. 76, p. 185. [BIBCODE 1982JRASC..76..185P ]