COMMISSIONS 27 AND 42 OF THE IAU 
        INFORMATION BULLETIN ON VARIABLE STARS 
                     Number 3729

                                   Konkoly Observatory 
                                   Budapest 
                                   14 May 1992 

                                   HU ISSN 0374 - 0676 
 
 
 
     Photometry of alpha Tauri (Dec 1987 to Mar 199Z) 
 
  According to the 4th edition of the General Catalogue 
of Variable Stars (1985-1990) alpha Tau (= Aldebaran = HR 1457) 
is of spectral type K5 III and varies irregularly from visual 
magnitude 0.95 to 0.75. The 4th edition of the Yale Bright 
Star Catalogue (1982) gives V = 0.85, B-V = 1.54 for alpha Tau. 
  In Table I we give photometry of alpha Tau on 13 photometric 
nights. For the most part differential photometry was 
carried out, with transformation to the UBV system by means 
of transformation coefficients derived from differential 
observations of the red-blue pair 27 and 28 LMi (Hall 1983). 
The comparison star beta Ori has V = 0.12, B-V = -0.03 
according to the Bright Star Catalogue, but Guinan et al. 
(1985) found it to be variable by as much as 0.16 mag. For 
the most part our data were reduced with respect to epsilon 
Tau (V = 3.53, B-V = 1.01). Typically 3 differential 
measures were made each night, but on some occasions up to 
7 were made. The light curve is shown in Figure 1. 
 
                          Table I 
                 Photometry of alpha Tau* 
 
Date             <UT>   Julian Date    V             comp 
 
27/28 Dec 1987   0728   2447157.81   0.926+/-0.020   all sky 
23/24 Jan 1988   0818      7184.84   0.887   0.013   beta Ori 
13/14 Feb 1988   0751      7205.83   0.892   0.015   alpha Ori 
 1/2  Mar 1988   0623      7222.77   0.869   0.022   all sky 
 
13/14 Nov 1990   1009      8209.92   0.860   0.006   epsilon Tau 
27/28 Dec 1990   0656      8253.79   0.875   0.008   " 
  3/4 Jan 1991   0617      8260.76   0.893   0.002   " 
  6/7 Mar 1991   0610      8322.76   0.875   0.015   " 
 
12/13 Oct 1991   1127      8542.97   0.860   0.005   " 
 9/10 Nov 1991   0858      8570.87   0.893   0.018   " 
29/30 Dec 1991   0651      8620.79   0.874   0.002   " 
26/27 Jan 1992   0724      8648.81   0.886   0.005   " 
22/23 Mar 1992   0604      8704.75   0.850   0.009   " 
 
      *From observations on 1/2 Mar 1988 and 3/4 Jan 1991, the mean 
       B-V color was measured to be 1.549 +- 0.026. 


                         [FIGURE 1]

 Figure 1  Data from Table I. Data: V-band zero point derived from
 an average of 17 observations of standards per night. Triangles:
 beta Ori used as comparison star. Open circles: epsilon Tau used
 as comparison star. The data were obtained at the 2800-m elevation 
 of Mauna Kea, using a 6-inch reflector and a DC photoelectric system.
 
 
    Since the night of 27/28 Dec 1987 alpha Tau seems to have 
been essentially constant in brightness at V = 0.876 +/- 0.004. 
Excluding 27/28 Dec 1987, when alpha Tau was definitely fainter, 
the standard deviation of the distribution of the other 
points is only +/-0.014 mag, consistent with no variations at 
all given the errors of the individual points. Of course, 
variations could have occurred during the 2 1/2 year gap in 
the light curve. 


                              KEVIN KRISCIUNAS 
 
                              Joint Astronomy Centre 
                              665 Komohana Street 
                              Hilo, Hawaii 96720 USA 
 
References : 
 
Guinan, E. F., McCook, G. P., Harris, W. T., Speranzini, D., 
    and Wacker, S. W. 1985, IBVS No. 2762. 
Hall, D. S. 1983, IAPPP Communic. No. 11, 3.  [BIBCODE 1983IAPPP..11....3H ]