COMMISSION 27 OF THE I.A.U.
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 2911

                                                         Konkoly Observatory
                                                         Budapest
                                                         1 July 1986

                                                         HU ISSN 0374 - 0676


                 A NEW BURST OF ACTIVITY IN U CEPHEI

After several years of relative inactivity, large disturbances have
reappeared at all phases in the light curve of the totally-eclipsing Algol.
binary U Cephei. Five-color uvbyI observations made with the 1.0-m Prairie
reflector at Mount Laguna Observatory show appreciable anomalies from 2/3
through 11/12 June 1986. Typical photometric anomalies in primary eclipse
have included excess light near internal contacts, particularly in the 
ultraviolet (where the normal flat-bottomed eclipse turns partial in 
appearance).
At the same time outside eclipse, light levels usually fell, by up to 0.6
or 0.7 mag near phase 0.6 (Olson, 1978, 1985).

                            [FIGURE 1]
                            [FIGURE 2]

   Spot checks on seven nights outside primary eclipse during the above run
showed that the ultraviolet brightness closely matched the lower envelope of
observations made in 1975, when activity was high (Olson, 1978, Figure 3a and
3b). Whatever photospheric changes give rise to these light losses, they
appear to repeat in major bursts. Light curves of primary eclipses on 3/4 and
8/9 June were moderately to fairly highly disturbed, in the author's experience
with this binary. A very slight decline in disturbance was noted in the later
eclipse. Yellow and ultraviolet eclipses for 8/9 June are shown in the
accompanying Figures. The ephemeris used to calculate orbital phases was taken
from Olson et al. (1985).
   The author thanks the U. S. National Science Foundation for continued
support of research on interacting binaries, and the Director and staff of the
Mount Laguna Observatory for their assistance.


                        EDWARD C. OLSON
                        Department of Astronomy
                        University of Illinois
                        1011 W. Springfield, Urbana
                        IL 61801-3000 USA



References:

Olson, E. C. 1978, Astroph, J. 220, 251. [BIBCODE 1978ApJ...220..251O ]
Olson, E. C. 1985, In Interacting Binaries (ed. P. P. Eggleton and
   J. E. Pringle), D. Reidel Publ. Co., p. 127. [BIBCODE 1985ib...proc..127O ]
Olson, E. C., Hickey, J. P., Humes, L., and Paylor, V. 1985, IBVS No. 2707.