COMMISSIONS 27 AND 42 OF THE IAU 
            INFORMATION BULLETIN ON VARIABLE STARS 
                       Number 3718
 
                                     Konkoly Observatory 
                                     Budapest 
                                     29 April 1992 
 
                                     HU ISSN 0374 - 0676 
 
 
             NSV 13679: NO ADDITIONAL MINIMUM 
 
 
D. Hoffleit (1991) reported on the unsuccessful search for 
minima on more than 200 Harvard patrol plates taken between 
1898 and 1921. Schlesinger (1925) had found the star barely 
detectable ("missing") on one of his Zone Catalogue 
Allegheny plates (AG 7042 = BD + 49d3511). 
 
There are at least two principal reasons to investigate an 
"object" like this in some detail: 
 
Firstly, we have indications that among eclipsing variables 
totally unusual cases exist more frequently than thought 
hitherto, as for instance objects with strongly varying 
amplitude (e.g. SS Lac, Lehmann 1991) or with nonstellar 
components (e.g. BO Cep, Wenzel 1991). 
 
Secondly, in the course of the search for optical counterparts 
of gamma-ray burst sources the important role of 
photographic plate defects has come to light (see e.g. 
Greiner, Wenzel and Degel 1990, Greiner and Wenzel 1991, 
Hudec 1991). 
 
Therefore I checked the star on 1148 suitable Sonneberg Sky 
Patrol plates taken mainly by P. Ahnert, H. Huth, and B. 
Fuhrmann between 1928 and 1990 (except in 1934 and 1935) 
and additionally on 35 plates of the 400/1600 mm GC 
astrograph from 1974 to 1982. I found no further minimum. 
On the contrary, the star seemed remarkably constant at 
photographic magnitude 9.1m in the system of Hoffleit 
(l.c.). Our investigation can be regarded as a 
chronological continuation of Hoffleit's data. 
 
After all, I conclude that Schlesinger's finding probably 
did originate from a plate blemish:  Take for the value D/P, 
the ratio of the duration of minimum to the period of an 
Algol eclipse curve, the extreme value of 0.01. Then among 
our more than one thousand fairly uniformly distributed 
observations about 10 should lie within the domain of the 
minimum, and some of these should be faint enough to be 
discernible, even if the minimum is distinctly less deep 
than 2.5 mag as was suggested by Hoffleit. If there exists 
a significant secondary minimum, the probability to find 
the object faint would be still higher. If we do not prefer 
to drop this matter and to cancel the star from the list of 
suspected variables, an investigation of Schlesinger's 
suspicious plate by means of microscopic techniques such as 
described by Greiner, Wenzel and Degel (l.c.) might be 
recommended. 
 
 
 
                               W. WENZEL 
                            D O-6400 Sonneberg 
                             Hauptstrasse 40 
 
                                Germany 
 
 
 
References: 
 
Greiner, J.; Wenzel, W., Degel, W.: 1990, Astron. Astrophys. 
    234, p. 251 [BIBCODE 1990A&A...234..251G ]
Greiner, J., Wenzel, W.: 1991, Adv. Space Res. 11, p. 149  [BIBCODE 1991AdSpR..11..149G ]
Hoffleit, D.: 1991, I.B.V.S. No. 3646 
Hudec, R.: 1991, Astron. Inst. Ondrejov Prepr. 123 
Lehmann, T.: 1991, I.B.V.S. No. 3610 
Schlesinger, F.: 1925, Trans. Yale Univ. Obs. 4 
Wenzel, W.: 1991, I.B.V.S. No. 3647