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Regular Variability of the Shape of the Primary Minimum of the Orbital Light Curve of SS 433 with the Phase of the Precessional Period A.M. CHEREPASHCHUK AND S.~. YARLIKOV Shternberg Astronomical Institute The regular variations of the shape of the primary minimum of the orbital 13.082-day light curio of SS 433 with the phase of the 1615~ay precessional period have been discovered by analysis of the photomeuical databank (1755 photometric V-observations during 1979 to 1988~. These vanations with the characteristic period of about 26 days appeared near the moment T3 of the maximum separation of the moving emission lines. They are strongly connected with the phase ~ of the precessional 1615~ay period (see Figure 1, where ^¢ = ~.023. The variations within the period of approximately 26 days (see Figure 2) appeared and disappeared in asymmetry of the primary minimum of orbital light curie and in changing position of the pnmaIy minimum for A¢13 ~ ~ OP.1 (+ 1~.3) relatively the medium phase ~13 = 0 of orbital 13.082-day penod. In view of the fact of such variations the averaging of observations ~ the Unwary minimum for the long interval of phases of the precessional 162.5~ay period (~¢ > 0P.1) can lead to the false appearance of "plate bottom" on the light curve in the puma minimum. The regular vanability of the shape of the primary minimum of the light curve of SS 433 discovered by us redects displacement with the 26-day double orbital period of at least mo hot bright spots on the surface of precessional accretional disk and their eclipse by a "normal" star. One of "these spots can be connected with the ejection of the relativistic collimated jet from the central part of the accretion disk; the second one perhaps is caused by interaction of gas stream conlitlg from a "normal" star with an external border of the precessional accretion disk The precession of the accretion disk causes the change of the relative position of hot spots. Consecutive eclipses of the disk and spots by the "normal" star lead to the appearance and disappearance of asymmetry on 65
66 m 0.5 ~ , AMERICAN AND SOVIET PERSPECTIVES V ~ _ ~ I ~ I ~ ~ r · I' · t ~ ~ ~ ~ r r r , ~ ~ r NO : ~ yr=0.04 ~ ~ y,= 0.98 I I ~I . ~. I . . - - 0 0.5 1 ~13 FIGURE 1 Optical orbital light Curares of SS433 as a function of the precessional period fib. the curve of the eclipse and to the characteristic features on it jUSt as it takes place in cataclysmic variable stars. Quantitative numerical interpretation of the discovered effect will be completed in the future with the help of the light curve synthesis program (Antolthina and CherepashchuL 1987. Astron. Zh 64: 562~.
HIGH-ENERGY ASTROPHYSICS Min I 0.1 ^~13 o -0.1 0.6 0.8 67 (.) (a) I) my () (a) (by , (V v162,5 it) 0.2 lo) Min II 0.1 ~ 0.6 0.8 O 0 -0.1 v13 ~ c,) t4 (-) I' t) 0) () ma_ a` in, , ~ ) · (a) () ' (I 1 v162,5 O.2 (,9 · 0.4 - FIGURE 2 Varations of ~tb13 of the position of the pnmary minimum of optical light curve of SS433 as a function of the phase of the precessional penod.