COMMISSION 27 OF THE I. A. U.
                   INFORMATION BULLETIN ON VARIABLE STARS
                                Number 2496

                                                      Konkoly Observatory
                                                      Budapest
                                                      23 March 1984

                                                      HU ISSN 0374-0676


                  AN UV ACTIVE PHENOMENON OF EPSILON AURIGAE


  We have continuously observed Epsilon Aurigae by three colour (U,B and V)
photometry with a 20 cm reflecting telescope at Fukushima University. The
results obtained at the ingress phase have already been reported in I.B.V.S.
No. 2371 and "Epsilon Aurigae Campaign Newsletter", No. 9.
  Continuing these reports we show our results in Figure 1 obtained till the


                                 [FIGURE 1]

 Figure 1   Light curve of epsilon Aur in U,B and V magnitudes. The small 
 arrows along the abscissa represent the predicted dates of 1st, 2nd, 3rd 
 and 4th contacts, respectively, by Gyldenkerne. Note the anomalous 
 brightening near the 3rd contact.


period of the third contact. It is pointed out readily that the anomalous
brightening occured near the end of the totality. It continued for about 40


                            [FIGURE 2]

 Figure 2  Colour variation at the same period as Figure 1. The colours 
 are almost constant within the measured period except the anomalous 
 brightening phase.

                            [FIGURE 3]

 Figure 3   The two-colour diagram of the star after J.D. 2445600. The 
 points are numbered successively and connected by thin lines.



days (J.D. 2445700 ~~ 5740), and its peak coincides wit the time of the third
contact (J.D. 2445709) predicted by Gyldenkerne (1970). Although the brightening
appeared in all colours, it was conspicuous in ultraviolet region. As
already known the colour variation of the star is small, but during the 
period of this brightening it varies appreciably, especially in U-B. The colour
change is illustrated in Figure 2. The two-colour diagram around this variation 
is shown in Figure 3.
   The meaning of this phenomenon cannot be clarified from the photometric
data only, so the spectroscopic observations around its epoch are highly 
desirable.




           TOSIO OKI, IKUO SEKIYA and KATSUNORI HIRAYAMA
               Department of Earth Science
               Fukushima University
               2, Sugumichi Asakawa, Matsukawa-Machi
               Fukushima, Japan 960-12




Reference:
Gyldenkerne, K., 1970., Vistas in Astronomy, 12, 199 [BIBCODE 1970VA.....12..199G ]