Astronomische Nachrichten最新文献

Black hole accretion and jet formation are very fundamental and important physical processes in astrophysics. Despite the great progress made in the last decades, our knowledge of the physics of BHs remains highly incomplete. The compact radio cores and/or weak jets are usually observed in nearby LLAGNs, which can help us to better understand and explore the jet and accretion physics due to their proximity and fruitful multi-waveband observations. In this short review, we studied the recent multi-waveband observations of the SMBH activities in LLAGNs and found that the high-resolution millimeter/submillimeter observations are very important for the nearby LLAGNs. The centers of LLAGNs are believed to be powered by hot accretion flow and jets. The aim of this review is to model the multi-wavelength spectral energy distribution (SED) of LLAGNs, and all the data we used here in the literature correspond to the core emission. We found these important features in LLAGNs are hard to fit by pure ADAF or jet models, which implies that they may come from different regions around the SMBH. We usually use the coupled ADAF and jet model to fit the multi-wavelength SED of LLAGNs and found that the submillimeter bump can be naturally modeled by the synchrotron emission of the thermal electrons in ADAF, which is very useful for us to constrain the physical parameters in the accretion disk and jet.

G166.0 + 4.3 (VRO 42.05.01) is a mixed-morphology supernova remnant (SNR) having a different spatial distribution of emission viewed in radio and X-rays. A sharp edge-brightened circular shape of the shell and wing component is visible in radio wavelength, whereas X-ray emission is dominated by a bright spot in the wing, without any edge-brightened structures. The observed shape of this SNR, looking like a shock propagation through the medium of different densities, can be a result of the shock encountering the density discontinuity in the interstellar medium, which makes favorable conditions for the particles' acceleration up to very high energy. Thus, the G166 + 4.3 SNR became a candidate for the investigation of particle acceleration in SNR shocks at high- and very-high energies. At TeV energies, the SHALON telescopes discovered extended emission, with the main contribution to the very-high-energy gamma-ray fluxes given by the regions correlated with the shells visible in the radio energies. But the main contribution to the TeV gamma-ray flux comes from the west part of the SNR, where the maximum of X-ray emission is located. The origin of the very-high-energy gamma-ray emission from G166 + 4.3 SNR is explored.

Low-frequency spectral studies of radio pulsars represent a key method for uncovering their emission mechanisms, magnetospheric structure, and signal interactions with the surrounding interstellar medium (ISM). In recent years, more next-generation low-frequency radio telescopes (e.g., LOFAR, LWA and MWA) have enriched the observational window below 350 MHz, enabling more detailed explorations of the ISM effects, such as absorption and scattering, resulting in diverse spectral behaviors observed across different pulsars. This paper reviews the morphology of pulsar radio spectra, advances in spectral modeling, and the key physical processes governing the low-frequency emission. Looking ahead, next-generation instruments such as SKA-Low—with their unprecedented sensitivity—are expected to resolve outstanding questions in pulsar emission processes, offering insights into the extreme physical regimes governing these exotic objects.

Neutron stars are natural laboratories of cold, dense strong interacting matter. In this article, we briefly review the gravitational waves related to neutron stars. Tidal deformability is a significant value that relates the observation of gravitational waves to the equation of state of cold, dense matter. The implicants of GW170817 and GW190814 are discussed. We also give an outlook for future work.

Active galactic nuclei (AGN) especially of blazar type are among the most luminous objects that have been detected through the whole range of the electromagnetic spectrum. It is generally believed that the powered by the central black hole AGN jets are responsible for the observed features like highly variable non-thermal emission characterized by spectral energy distribution extending from radio frequencies up to very high energy gamma-rays. The investigations of the physical properties of jets as well as the mechanisms of jet launching and localization of emissions in AGN are carried out with multi-wavelength observations of active galaxies at the different activity states to trace the temporal changes of fluxes and spectral behavior. NGC 1275 is one of the nearest and extensively studied active galaxies at the energy range from radio band to very high energy gamma-rays. Its multi-wavelength long-term observations resulted in the broadband spectral energy distribution of NGC 1275 obtained simultaneously or quasi-simultaneously and revealed the short-term and long-term timescale variability of emission fluxes from this AGN. Modeling of the NGC 1275 spectral energy distribution at the different activity states was made to estimate the jet physical parameters which may help to understand the changes in the temporal and spectral behavior of NGC 1275 active galactic nucleus.

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).