Spectro-photometric variability of quasars caused by lensing of diffuse massive substructure: Consequences on flux anomaly and precise astrometric measurements

We investigate the spectro-photometric variability of quasars due to lensing of small mass substructure (from several tens to several hundreds solar masses). The aim of this paper is to explore the milli/microlensing influence on the flux anomaly observed between images of a lensed quasar in different spectral bands and possible influence of small mass structure lensing of non-macrolensed quasars.We find that spectro-photometric variability may be also caused by lensing of small mass diffuse structure and can produce the flux anomaly which is sometimes seen in different images of a lensed quasar. Additionally, we found that the lensing by small mass diffuse structure may produce significant changes in photo-center position of a quasar, and sometimes can split or deviate images of one source that can be detected as separate from the scale from 0.1 to several milliarcseconds. This can be measured ith Gaialike space astrometric missions. We point out a special case where a low redshifted deflector zd = 0.01 is lensing a high redshifted source, for which the variability in the flux and photocenter (several milliarcseconds) may be detected on a relatively short time scale.Comment: 10-pages, 10-figures, 3-table

Stark broadening data for spectral lines of rare-earth elements: Nb III

The electron-impact widths for 15 doubly charged Nb ion lines have been theoretically determined by using the modified semiempirical method. Using the obtained results, we considered the influence of the electron-impact mechanism on line shapes in spectra of chemically peculiar stars and white dwarfs.Comment: 10 pages, 2 figures, 1 table, accepted in Advances in Space Researc

Diagnostics of plasma in the ionospheric D-region: detection and study of different ionospheric disturbance types

Here we discuss our recent investigations of the ionospheric plasma by using very low and low frequency (VLF/LF) radio waves. We give a review of how to detect different low ionospheric reactions (sudden ionospheric disturbances) to various terrestrial and extra-terrestrial events, show their classification according to intensity and time duration, and present some methods for their detections in time and frequency domains. Investigations of detection in time domain are carried out for intensive long-lasting perturbations induced by solar X-ray flares and for short-lasting perturbations caused by gamma ray bursts. We also analyze time variations of signals used in the low ionospheric monitoring after earthquake events. In addition, we describe a procedure for the detection of acoustic and gravity waves from the VLF/LF signal analysis in frequency domain. The research of the low ionospheric plasma is based on data collected by the VLF/LF receivers located in Belgrade, Serbia

Performance requirements for rail fastening systems on European railway network

In order to realize interoperability of railway system, the reconstruction and modernization plan of railway network in the Republic of Serbia should be harmonized with technical requirements of European railway network. The paper presents hierarchical approach to harmonization of legal and technical regulations in the area of railway infrastructure, with special attention drawn to the rail fastening systems. Performance requirements for rail fastening systems were analysed according to the adopted standard series SRPS EN 13481 and SRPS EN 13146