Noncompact astronomical objects as microlenses
Abstract
The microlensing of the distant stars by neutralino stars has been considered. The neutralino stars have been considered in the recent paper of Gurevich and Zybin, moreover, the stars have been suggested to be regard as a component, carrying a major component of dark matter. The optics of these gravitational microlenses, namely, the gravitational lens equation, its solutions, increasing of images, critical and caustic curves, are analysed by using a clear approximation. The set of model parameters is considered. The first results of observations of microlensing which were presented in the papers of three groups (Alcock et al (1993), Aubourg et al (1993), Udalski et al (1993)) have discovered a phenomenon, predicted in the papers of Byalko (1969) and Paczynsky (1986). A character of the gravitational microlens is unknown till now, although the most widespread hypothesis assumes that they are compact dark objects as brown dwarfs. Nevertheless, they could be presented by another objects, in particular, an existence of the dark objects consisting of the supersymmetrical weakly interacting particles (neutralino) has been recently discussed in the papers of Gurevich and Zybin (1995) and Gurevich et al (1996). The authors shown that the stars could be formed on the early stages of the Universe evolution and to be stable during cosmological timescale. Microlensing of a distant star by a neutralino star is considered in the paper. We consider microlensing by a star in framework of a rough model which is rather clear and we obtain analytical expressions for results. Of course, a more exact model of the gravitational field of neutralino star may be considered, nevertheless, we think that the qualitative estimation of the effect was considered correctly. We approximate the density of distribution mass of a neutralino star in form [ rho_{NeS}(r) = rho_0 frac {{a_0}^2}{r^2}], where r  the current value of a distant from star's center, rho_0  mass density of a neutralino star for distance a_0 from a center, a_0  "radius" netralino star. The detailed analysis of the model is presented in the papers of Zakharov & Sazhin (1996a, 1996b). This research has been supported in part by Russian Foundation of Fundamental Research (grant N 96  02 17434).
 Publication:

Joint European and National Astronomical Meeting
 Pub Date:
 1997
 Bibcode:
 1997jena.confE.318Z