COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1747

                                     Konkoly Observatory
                                     Budapest
                                     1980 February 26


           THE BRIGHTNESS INCREASE OF DR TAURI


The star was inspected on 691 blue-sensitive sky patrol plates of Sonneberg
Observatory covering the years from 1931 to January 1980, in order to complete
the light curve of the object given by Chavarria-K.(1). Most of these plates
(n=587, observer H. Huth) were exposed between the years 1952 and 1980. Their
limiting magnitude amounts to about 14.^m0 on the average.

For calibration purposes the chosen comparison stars which include those given
by Kholopov (2) were linked to the UBV-sequence of NGC 1647 (3) situated in the
neighbourhood of DR Tau.

                       [FIGURE 1]

The result of the investigation is shown in Figure 1. There is no doubt that
the star increased in mean brightness during the last 20 years. The continuous
increase which is superimposed by highly short time variations amounts to more
than 3.5m in the blue region. Occasionally the short time variability is
characterized by changes of more than 1.5m per day. The scattered
observations given by other authors (see also (1)) are in agreement with our
results and follow the light curve without contradiction.

The beginning of the increase at 1960 (J.D. 243 7000) can be stated also by
the number of plates on which the star is invisible. The percentage of such
plates in relation to the respective whole number amounts to 80% or 90% in the
years before 1960 and is decreasing continuously to 1980 when the object is
visible on all plates. Therefore and because of the worse limiting magnitude
the plates exposed before 1960 show the star only in phases of maximum
brightness.

The obtained results and a discussion of the light curve in detail will be
published in MVS.


W. GOTZ
Akademie der Wissenschaften der DDR Zentralinstitut fur Astrophysik,
Sternwarte Sonneberg

References:

(1) Chavarria-K. C., 1979, Astron. Astrophys. 79, L18-L21 [BIBCODE 1979A&A....79L..18C ]
(2) Kholopov, P.N., 1951, VS 8, 83
(3) Hoag, A.A., Johnson, H.L., Iriarte, B., Mitchell, R.I., Hallam, K.L.,
   Sharpless, S., 1961, Publ. US Naval Obs., 2nd Ser, Vol. 17., No. VII
   [BIBCODE 1961PUSNO..17....1H ]