2004/03/17 by A. F. Zakharov, L. C. Popovic, L. Č. Popović +2 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Bulge #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational lens #Gravitational microlensing #Halo #QSOS #Quasar #astro-ph
paper · pdf · doi:10.1051/0004-6361:20034035
published as Astron.Astrophys. 420 (2004) 881-888 · A&A, accepted
arxiv created 2004/03/17 · openalex publication_date 2004/06/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We consider a contribution of microlensing to the X-ray variability of high-redshifted QSOs. Such an effect could be caused by stellar mass objects (SMO) located in a bulge or/and in a halo of this quasar as well as at cosmological distances between an observer and a quasar. Here, we not consider microlensing caused by deflectors in our Galaxy since it is well-known from recent MACHO, EROS and OGLE observations that the corresponding optical depth for the Galactic halo and the Galactic bulge is lower than 10-6. Cosmologically distributed gravitational microlenses could be localized in galaxies (or even in bulge or halo of gravitational macrolenses) or could be distributed in a uniform way. We have analyzed both cases of such distributions. As a result of our analysis, we obtained that the optical depth for microlensing caused by stellar mass objects is usually small for quasar bulge and quasar halo gravitational microlens distributions (). On the other hand, the optical depth for gravitational microlensing caused by cosmologically distributed deflectors could be significant and could reach at . This means that cosmologically distributed deflectors may contribute significantlly to the X-ray variability of high-redshifted QSOs (). Considering that the upper limit of the optical depth () corresponds to the case where dark matter forms cosmologically distributed deflectors, observations of the X-ray variations of unlensed QSOs can be used for the estimation of the dark matter fraction of microlenses.