COMMISSIONS 27 AND 42 OF THE IAU
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 4063

                                                 Konkoly Observatory
                                                 Budapest
                                                 11 August 1994 
                                                 HU ISSN 0374 - 0676


     CHROMOSPHERIC INACTIVITY OF DELTA CORONAE BOREALIS IN 1991-93


   Delta CrB (HR 5889) is a chromospherically active giant of spectral type G5 III-IV. In 1985/86
(Fernie 1987) it showed a sinusoidal variability of about 0.06 mag in V and period about 45 days.
This variability persisted in 1987 and 1988, but the period increased at the remarkable rate of some 10
days per year and was accompanied by changes in the amplitude and overall light level (Fernie 1989,
1990). In 1989 the activity ceased, but returned in 1990 with a period of 61 days and amplitude 0.04
mag (Fernie 1991). These effects were interpreted as due to a large spot or spot group drifting in the
photosphere of delta CrB.
   I have continued to monitor delta CrB by means of a program with the Automatic Photoelectric
Telescope Service, and since the last reported observations to JD 2448145 have accumulated another
353 nights of UBV photometry through the 1991, 92, and 93 seasons. Plots of these data show that
through most of this interval delta CrB showed no significant variability, although between JD 2448710
and 2448810 (April - August 1992) there was a weak 0.02 mag variation of period 49 +/- 2 days. As
Table 1 shows, there was no detectable change in the overall light level during these three seasons.
(Cf Fig.3 of Fernie 1990.)


           Table 1
    MEAN SEASONAL VALUES
  Year      <V>      s.e.
1991.289   4.632   +/-0.001
1992.316   4.634   +/-0.002 
1993.327   4.633   +/-0.001

    It is of some interest that the standard deviations of the V magnitudes in each of the three
seasons were 0.008, 0.020, and 0.008 mag respectively. The second value (1992) no doubt reflects
the presence of some variability, but the 0.008 mag for 1991 and 1993 sets an upper limit for the
average observational error of the APT data at this apparent magnitude.

    I do not propose publishing the individual data, but will gladly supply them to anyone who
wants them. Contact me at fernie@astro.utoronto.ca on the Internet.


                          J.D. Fernie
                          David Dunlap Observatory
                          Box 360
                          Richmond Hill, ON L4C 4Y6
                          Canada


References:
Fernie, J.D. 1987, PASP, 99, 183 [BIBCODE 1987PASP...99..183F ]
   -         1989, PASP, 101, 175 [BIBCODE 1989PASP..101..175F ]
   -         1990, PASP, 102, 783 [BIBCODE 1990PASP..102..783F ]
   -         1991, PASP, 103, 1091 [BIBCODE 1991PASP..103.1091F ]




		                  ERRATUM

 Upon Prof. Bidelman's suspicion, it turned out that the new variable star reported in
IBVS No. 3612 had been misidentified. The new small amplitude variable is HD 111829
(instead of HD 111828, as stated in the discovery note).


		                      E. PORETTI
                                Osservatorio Astronomico
                      		Via E. Bianchi, 46
                      		I-22055 Merate (CO)
                     	 	E-mail address: poretti@astmim.mi.astro.it