COMMISSIONS 27 AND 42 OF THE IAU
             INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3924

                                                   Konkoly Observatory
                                                   Budapest
                                                   16 August 1993

                                                   HU ISSN 0374 - 0676


                 DISCOVERY OF THE NATURE OF THE
                     VARIATION OF HD 191706


 The eighth magnitude A0V star, HD 191706, was reported to be variable by Veto,
Schoneich, and Rustamov(1980). They had selected it as a comparison star for the study
of the Ap star, HD 191980. They speculated that it might be an eclipsing binary of period
25 days. Since we were also observing that Ap star, we decided to determine the nature
of the variation of HD 191706. Our comparison star was one they used, HD 191879.
 We observed with the 16 inch reflecting telescope at Braeside Observatory near Flagstaff,
Arizona, utilizing the photoelectric photometer with UBV filters, beginning in June 1992.
The first hint that it might be a binary was obtained in early July, 1992. In May 1993, we
obtained our first complete eclipse on JD 2449128. We determine a period of 1.035600d.
Thus, the period is not 25 days, but is close to 1.04 days, which means that the whole
eclipse can be observed from any one location for about two nights every twenty five days.
This was the case, because, in June, in Arizona, the star did not rise high enough for
photometric study until about 11:00 p.m. and the rest of the night was required to record
all of the minimum. The eclipse appears to be total for about 1.87 hours, but the eclipse
is very shallow, about 0.1 magnitudes in V. The observations of our first minimum can
be seen in Figure 1.

                              [FIGURE 1]
                              [FIGURE 2]
 
  There is some indication that the period may be twice the one quoted, or 2.071200
days. That is, on successive nights the depths of the minima seemed slightly different,
which would indicate the presence of primary and secondary minima of almost identical
depth. However, the scatter in these observations is great enough so that we cannot
establish a significant difference between the possible different depths of the minima.
  We propose the following ephemeris:
           
           JD Hel Min (V)=2449128.877 +1.035600xE
                                      +-.000013

  A phase diagram with that period is shown in Figure 2.


	Edward W. BURKE, Jr.   Robert FRIED
	King College           Braeside Observatory
	Bristol, TN 37620      Flagstaff, AZ 86002
	
	Barry ETTER            T. J. KREIDL
	King College           Lowell Observatory
	Bristol, TN 37620      Flagstaff, AZ 86001


Reference:

Veto, B., Schoneich, W., and Rustamov, Y. S.: 1980, Astron. Nach., 301, 317 [BIBCODE 1980AN....301..317V ]


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