The thesis, as its title tells, is mainly devoted to the study of the binary system region of the object SS433. In the first part of the work we summarize the most important published observations of this region as well as the inner part of the jets. We also review some theoretical interpretations of the structure of the binary system and the jets. In the second part of the thesis we focus on selected X-ray and optical observations which were partly collected by ourselves and are presented here for the first time. We use the published data from the Exosat and Ginga X-ray satellites and derive the limits on the mass ratio of the system and the length of the jets. The geometrical models we build are based on a simple Roche model and do not use any assumptions about the shape of the accretion disk what would make the results model-dependent. The length and shape of the primary eclipse of the X-ray jets is used to constrain the relative size of the obscuring body, i.e. the mass-loosing star. It turns out that the effective radius of the star is half of the system separation; this corresponds to the mass ratio of the compact object to the normal star q = Mx/ M* ~ 0.245. The length of the X-ray jets is >= 10^12 cm. Turning to optical observations we first re-analyse the published photometric observations. The derived average light curves for different precessional phases are strikingly asymmetric. We show that the properties of the light curves can be understood if we introduce a new system component. This component is an optically thick outflow of matter from the outer regions of the accretion disk. Such an outflow close to the equatorial plane of the accretion disk - we can call it an excretion disk - can easily explain the observed drifts of the position of the secondary minimum and the asymmetries of the light curves in general. In addition it can provide a natural place for formation of the stationary lines. Our own intensive CCD photometric observations with the Danish-ESO 1.5-m telescope confirm the above presented picture and upgrade it with a detection of sub-day photometric variations. They can be divided into two classes distinguished by their characteristic timescale: ~ 10 minute variations are quite erratic and are likely to originate in the jets, but the longer ones show a nearly periodic character and presumably come from extended corona surrounding the jets. The spectrum of SS433 is rich in emission lines which originate in the jets or in the material between or around the binary components. The only exception is the He II lamda 4686 emission line which is believed to trace the motion of the compact object. So the velocity amplitude of this line is used to calculate the mass function of this single line binary and finally to convert the mass ratio (that we derive from the geometrical models) into masses of the system components. The most important uncertainty in this evaluation comes from inaccurate measurements of the velocity of the He II lamda 4686 line. So we started our own observations of this line with the final goal to understand how and where it is formed; furthermore we would like to confirm or reject the black hole nature of the compact object as suggested if one uses the published value of the velocity amplitude of the line. Our observations of the He II .A4686 emission line with the EMMI spectrograph on ESO's New Technology Telescope are of very high quality. The majority of the spectra show double peaked profiles. The distance between the blue and the red peak is changing with time what is inconsistent with the emission from the accretion disk. Additional observations are needed before the orbital velocity variations of both peaks can be properly constrained. However very preliminary results suggest that the orbital velocity of the compact object is not larger than ~ 145 km/ s what is lower than what is reported in the literature. The above mentioned "most probable" mass ratio q ~ 0.245 corresponds to Mx = 4 M@ and M* ~ 16.4 M@ for the published value of the velocity amplitude. Our observations suggest that these masses should be halved; this brings the mass of the compact object close to the neutron star range. However we believe that these preliminary estimates should not be taken as a firm evidence that the compact object is a neutron star. We should wait for the new spectroscopic data.
|Titolo:||The Binary System SS433|
|Data di pubblicazione:||5-dic-1990|
|Appare nelle tipologie:||8.1 PhD thesis|