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Active galactic nucleus (AGN) phenomenon and role of jets, powered by the central black hole of AGN, in the feedback of the surroundings on different scales is a matter of detailed multi-wavelength investigations. The long-term observations of AGN are used to reveal the processes taking place in the very proximity to the super-massive black holes. One of the approaches to such studies is to detect the launching of jet components viewed in the radio range and then link it with flaring events detected at higher energy ranges. Tracking the jet-initiated variability events through multiwavelength observations as well as their cross-identification from radio frequencies up to high-energy gamma-rays allows one to locate the regions responsible for the generation of observable features, which can lead to the exploration of the mechanism of jet launching and the origin of emission in the Active Galactic Nucleus. Being nearby and bright, NGC 1275 is one of the extensively studied AGN. This object is very active in the timescales of decades. Multiwavelength long-term observations of NGC 1275 resulted in the detection of different timescale variability from this AGN. For the case of NGC 1275, the cross-correlation of the activity at radio, X-ray, and very high-energy gamma-rays is investigated. The time dependence of the activity of NGC 1275 in the wide energy range was found, which allows one to localize the sites of the emission generation, including one of the very high energies. These multiwavelength long-term studies are highly important for the further advance of the AGN's black hole research and investigations of mechanisms of jet formation.

Blazars are among the most powerful objects in the Universe, whose photon spectrum extends from radio to very high energy gamma-rays (γ-rays). Spectral energy distribution (SED) of blazars has a two-humped shape, whose low-energy part originates from the leptonic mechanism of synchrotron radiation of relativistic electrons in the blazars' jets. It is generally believed that the high-energy part of the spectral energy distribution is of hadronic and leptonic scenarios, but different localization of the source of emission within the core region or far beyond is considered. Also, blazars' emission is characterized by rapid variability at all wavelengths. The tracking of the flaring events at the radio band to connected ones at higher energies may allow localizing emission regions. High-frequency peaked Bl Lacertae type of blazar objects (HBL) are characterized by multi-wavelength variability and SED peaking at the GeV–TeV energy range. Thus, HBL objects have been considered as the best candidate for the sources of very high γ-rays. Mkn 180 is the HBL object with the spectrum that has been measured through radio and X-ray bands to high energy γ-rays. The study of the connection between the outbursts from Mkn 180 viewed from radio to very high energy γ-rays is presented together with its features at the MeV–TeV energy range. These results can help find the parameters for the models of generation of high-energy γ-ray emission in Bl Lac-type objects.

Mkn 180 is the BL Lac object with the spectrum that has been measured through radio and x-ray band to high energy gamma-rays. This object is considered as a potential candidate for the source of high-energy leptonic and/or hadronic cosmic-ray acceleration. Also, it has been proposed to be a GeV–TeV gamma-ray source. The very high energy gamma-rays from Mkn 180 were detected due to the trigger switched on by an optical burst. Mkn 180 was monitored in the optical wave band and in the high and very high energy gamma-rays for a long period and its light curve was obtained. The spectral energy distribution of Mkn 180 blazar was obtained in the wide energy range as well. The spectral energy distributions of blazars consist of two broad peaks. The first, lower frequency peak occurring between radio and soft x-ray energies is due to the synchrotron emissions of relativistic electrons population. Leptonic and hadronic emission mechanisms are considered to describe the second, higher frequency spectrum part between x-ray and VHE gamma-ray energies. The Inverse Compton emissions of the same electrons (synchrotron self-Compton model) or combined with an external Compton mechanism originating from the broad-line region, or the accretion disk are considered in the leptonic scenario. Also, the high energy spectrum part is supposed to be generated due to the processes of photohadronic or hadronuclear interactions of cosmic rays with radiation or matter in the AGN's jet emission region. The multiwavelength observations of Mkn 180 including the GeV–TeV energy data can help to clarify the dominant mechanism of generation of high-energy gamma-ray emission in this object (and whether it can be the source of UHECRs).

Rotational irregularities are one of the prominent observational features that most pulsars exhibit. These glitches, which are sudden increases in spin angular velocity, remains an open problem. In this study, we have investigated the potential role of nontrivial topological defects, specifically in the form of Nambu-Goto type cosmic strings, and its connection to spin irregularities. Such cosmic strings which are one-dimensional topological defects may be formed during various symmetry-breaking and phase transition scenarios and can interact with the neutron stars. In this work, we see that the appearance of such topological defects trapped within the core can lead to the coupling of the string tension with the angular velocity, leading to the abrupt rotational changes observed as pulsar glitches. Further we see, these coupling may generate detectable gravitational waves as a mixture of continuous and burst signals. The evolution of cusps of cosmic strings trapped within neutron stars and the neutron star's mass quadruple moment change due to rotation could produce distinctive gravitational wave signatures, well within the noise cutoff of advLIGO. Our study highlights a potential connection between topological defects, pulsar glitches, and gravitational wave emissions, offering a possible avenue for observationally testing their astrophysical effects.

We have conducted investigations of the structure of interstellar medium towards the star 62 Tau using a very high resolving power (R = $��\lambda �/��\delta �\lambda ��\sim �$170 000) spectrum of ESPRESSO spectrograph. Basic goals of this work are as follows: to search for radial velocity components in the interstellar spectral lines, detectable in the star's spectrum; to measure heliocentric radial velocities (V_r) of the intervening interstellar clouds, to determine Doppler parameter b and the column densities (N) of the atoms and molecules present in the clouds. Using a profile fit procedure we found the components of the atomic and molecular lines with the V_r between $��\approx �$11–18.5 km s$��{�\hspace{0.17em}�}^{�-�1�}�$. Only two main radial velocity components for every spectral feature could be discerned confidently. Thus, it was found that the interstellar matter on this sightline is mostly concentrated in the interstellar clouds with V_r $��\approx �$ 15 and 18 km s$��{�\hspace{0.17em}�}^{�-�1�}�$. The column densities, yielded with the profile fits are in a good agreement with those found earlier by other researchers. The profiles of the interstellar molecular lines (CN, CH and CH$��{�}^{}$