In this paper, the effect of hot spots movement by accretor surface on the appearance of bolometric light curves for two types of polars - synchronous V808 Aur and asynchronous CD Ind is studied. The analysis was carried out under the assumption of a dipole configuration of the magnetic field, in which the axis of the dipole passes through the accretor center. It is shown that a noticeable shift of the flow maximum at the light curve corresponding to the position of the spots in synchronous polars is determined by a change in the magnitude of mass transfer rate. At the same time, the maximum deviation of the spots from the magnetic poles was 30°. In asynchronous polars, assuming a constant of the mass transfer rate, the spots movement caused by a change in the orientation of the dipole axis relative to the donor has a significant effect on the appearance of light curve. The greatest displacement of the spots from the magnetic poles, which equals to 20°, was observed at the moments when the accretion jet switched from one pole to the other. It is concluded that the comparison of synthetic and observational light curves provides an opportunity to study the physical properties of polars.

Triggered by the MGF detected from the Sculptor galaxy on April 2020, the study described in this proceeding reports the unambiguous identification of a distinct population of 4 local (< 5 Mpc) short GRBs, whose rise time and isotropic energy release are independently inconsistent with the larger short GRB population at >99.9% confidence. These properties, the host galaxies, and non-detection in gravitational waves all point to an extragalactic MGF origin. The inferred volumetric rates for events above 4 × 1044 erg of $$R{\rm{ = }}3.8_{ - 3.1}^{ + 4.0} \times {10^5}Gp{c^{ - 3}}y{r^{ - 1}}$$. These rates imply that some magnetars produce multiple MGFs, providing a source of repeating GRBs. The rates and host galaxies favor common core-collapse supernova as key progenitors of magnetars.

We present interferometric continuum and molecular line emission maps obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of OH231.8+4.2, a well studied bipolar nebula around an asymptotic giant branch (AGB) star that is key to understand the remarkable changes in nebular morphology and kinematics during the short transition from the AGB to the Planetary Nebula (PN) phase. The excellent angular resolution of our maps (∼20 mas ∼30 AU) allows us to scrutinize the central nebular regions of OH231.8+4.2, which hold the clues to understanding how this iconic object assembled its complex nebular architecture. We report, for the first time in this object and others of its kind (i.e. pre-PNe with massive bipolar outflows), the discovery of a rotating circumbinary disk of radius ∼30 AU traced by NaCl, KCl, and H2O emission lines. The disk lies at the base of a young bipolar wind with signs of rotation as well. A compact spatially resolved dust disk is found perpendicular to the bipolar outflow. We also identify a point-like continuum source, which likely represents the central Mira star enshrouded by a ∼3 R* shell or disk of hot (∼1400 K) freshly formed dust. The point source is slightly off-centre from the disk centroid, enabling us for the first time to place constraints to the orbital separation of the central binary system.

T Tauri Stars (TTSs) offer a unique chance to study the physics of non-relativistic accretion engines. In this invited talk, the current status of the field is presented with special emphasis on the predictive power of the numerical simulation of magnetospheric accretion and close binary systems and its impact on astronomical observations.

Close binary evolution is widely invoked to explain the formation of axisymmetric planetary nebulae, after a brief common envelope phase. The evolution of the primary would be interrupted abruptly, its still quite massive envelope being fully ejected to form the PN, which should be more massive than a planetary nebula coming from the same star, were it single. We test this hypothesis by investigating the ionised and molecular masses of a sample consisting of 21 post-common-envelope planetary nebulae, roughly one fifth of their known total population, and comparing them to a large sample of regular planetary nebulae (not known to host close-binaries). We find that post-common-envelope planetary nebulae arising from single-degenerate systems are, on average, neither more nor less massive than regular planetary nebulae, whereas post-common-envelope planetary nebulae arising from double-degenerate systems are considerably more massive, and show substantially larger linear momenta and kinetic energy than the rest. Reconstruction of the common envelope of four objects further suggests that the mass of single-degenerate nebulae actually amounts to a very small fraction of the envelope of their progenitor stars. This leads to the uncomfortable question of where the rest of the envelope is, raising serious doubts on our understanding of these intriguing objects.

We report the initial results of deep eROSITA monitoring of the magnificent seven isolated neutron stars (INSs). Thanks to a combination of high count statistics and good energy resolution, the eROSITA datasets unveil the increasingly complex energy distribution of these presumably simple thermal emitters. For three targets, we report the detection of multiple (in some cases, phase-dependent) spectral absorption features and deviations from the dominant thermal continuum. Unexpected long-term changes of spectral state and timing behaviour have additionally been observed for two INSs. The results pose challenging theoretical questions on the nature of the variations and absorption features and ultimately impact the modeling of the atmosphere and cooling of highly magnetised neutron stars.

Many simulations have been performed to elucidate the formation process of first stars. In first star formation, radiative feedback is a key process in determining stellar masses. However, previous simulations which follow the feedback process don’t resolve the small scale ( 10 AU) to realize long-term calculation, and the structure near massive protostars is still unknown. To clarify how the radiation from the protostar works, we need to resolve small scale and calculate the interaction between the radiation and the dense gas in such a region. As a first step towards understanding the phenomenon in this region, we perform the high-resolution simulation around the massive protostar without radiative transfer. We find that dense gas covers the protostar even in the polar direction and the HII region cannot expand. Solving the radiative transfer for getting accurate results is our future work. We are currently developing the new radiation hydrodynamics code for that.

The magnetar SGR J1830–0645 was discovered in outburst in October 2020. We studied its X-ray properties during the first month of the outburst using XMM–Newton, NuSTAR and Swift observations. The shape and amplitude of the pulse profile varied significantly with energy. The broadband spectrum was well described using two absorbed blackbody components plus a faint power law component at high energies. Phase-resolved spectral analysis of the data suggests that the emission could be attributed to thermal photons from a single heated region with a complex shape on the star surface undergoing resonant Compton scattering on charged particles located in the magnetosphere. Modelling the evolutionary path of the magnetar with our magneto-thermal evolutionary codes indicates that SGR J1830 was born ≈23 kyr ago with a dipolar magnetic field of ∼1015 G, slightly larger than the current value.

Interacting binaries within a common envelope, wherein the primary is a red giant are believed to result in a recently identified evolutionary class – the dusty post-RGB stars. Our SED modeling of eight post-RGBs in the LMC indicates the presence of geometrically thick disks with substantial opening angle in addition to the outer shells. We estimated the total dust mass (and gas mass assuming gas-to-dust ratio) in the disks and shells and set constraints on the dust grain compositions and sizes. The only known Galactic object of this class is the Boomerang nebula. Additionally, we present a DUSTY model of the Boomerang that can serve as a template for 2D modeling of the object using RADMC-3D. 2D modeling is essential to dissect the morphology of the spatially-unresolved post-RGBs in the LMC. These models may then be tested with future HST and ALMA imaging, together with JWST spectroscopy of these objects.

The amount of mass lost by stars during the red-giant branch (RGB) phase is one of the main parameters needed to fully understand later stages of stellar evolution. In spite of its importance, a fully-comprehensive physical understanding of this phenomenon is still missing, and we, mostly, rely on empirical formulations. The Galactic Globular Clusters are ideal targets to derive such formulations, but, until recently, the presence of multiple populations has been a major challenge.

We will discuss the insights on RGB mass loss that can be obtained from the study of the horizontal branch stars in such stellar associations. The estimates obtained via the study of the photometric data will be compared with recent and newly obtained estimates derived for few high metallicity open clusters and a large sample of field stars with asteroseismic techniques.

The surfaces of neutron stars are likely sources of strongly polarized soft X rays due to the presence of strong magnetic fields. Scattering transport in the surface layers is critical to the determination of the emergent anisotropy of light intensity, and is strongly influenced by the complicated interplay between linear and circular polarization information. We have developed a magnetic Thomson scattering simulation to model the outer layers of fully-ionized atmospheres in such compact objects. Here we summarize emergent intensities and polarizations from extended atmospheric simulations, spanning considerable ranges of magnetic colatitudes. General relativistic propagation of light from the surface to infinity is fully included. The net polarization degrees are moderate and not very small when summing over a variety of field directions. These results provide an important foundation for observations of magnetars to be acquired by NASA’s new IXPE X-ray polarimeter and future X-ray polarimetry missions.

We compare the properties of shocked gas in Sgr B2 with maps obtained from 3D simulations of a collision between two fractal clouds. In agreement with 13CO(1-0) observations, our simulations show that a cloud-cloud collision produces a region with a highly turbulent density substructure with an average . Similarly, our numerical multi-channel shock study shows that colliding clouds are efficient at producing internal shocks with velocities of 5 − 50 km s−1 and Mach numbers of ∼ 4 − 40, which are needed to explain the ∼ 10−9 SiO abundances inferred from our SiO(2-1) IRAM observations of Sgr B2. Overall, we find that both the density structure and the shocked gas morphology in Sgr B2 are consistent with a Myr-old cloud-cloud collision. High-velocity shocks are produced during the early stages of the collision and can ignite star formation, while moderate- and low-velocity shocks are important over longer time-scales and can explain the extended SiO emission in Sgr B2.

The unidentified infrared (UIR) bands, whose carriers are thought to be organics, have been widely observed in various astrophysical environments. However, our knowledge of the detailed chemical composition and formation process of the carriers is still limited. We have synthesized laboratory organics named Quenched Nitrogen-included Carbonaceous Composite (QNCC) by quenching plasma produced from nitrogen gas and hydrocarbon solids. Infrared and X-ray analyses of QNCC showed that infrared properties of QNCC well reproduce the UIR bands observed in novae and amine structures contained in QNCC play an important role in the origin of the broad 8 m feature, which characterizes the UIR bands in novae. QNCC is at present the best laboratory analog of organic dust formed around dusty classical novae, which carries the UIR bands in novae via thermal emission process [Endo et al.(2021)].

The Orion Nebula Cluster (ONC) is one of the nearest open clusters, which we can directly compare to numerical simulations. We performed a simulation of star cluster formation similar to the ONC using our new N-body/smoothed particle hydrodynamics code, ASURA+BRIDGE. We found that the hierarchical formation of star clusters via clump mergers can explain the observed three peaks in the stellar age distribution as well as the dynamically anisotropic structures of the ONC.

A four-year sky survey with the use of the eROSITA telescope on board the Spektr-RG observatory will provide the best coverage in the soft (0.5–2 keV) and standard (2–10 keV) X-ray ranges, both in terms of sensitivity and angular resolution. We have analysed the possibility of detecting various types of isolated neutron stars with eROSITA. Among already known objects, eROSITA will be able to detect more than 160 pulsars, 21 magnetars, 7 central compact objects, all seven sources of the Magnificent Seven, and two other X-ray isolated neutron stars during the four-year survey mission.

The decay of the magnetic field in the interior of a magnetar may trigger electron captures by nuclei in the stellar crust, thus providing an internal source of heating. In turn, the onset of electron captures and the heat released are altered by the magnetic field due to the Landau–Rabi quantization of electron motion. The loss of magnetic pressure might also lead to pycnonuclear fusions of the lightest elements. The maximum amount of heat that can be possibly released by each reaction and their location are calculated using nuclear data from both experiments and theoretical predictions of the Brussels-Montreal models based on self-consistent Hartree-Fock-Bogoliubov calculations. Results are found to be consistent with those inferred empirically by comparing neutron-star cooling simulations with observed thermal luminosity of soft gamma-ray repeaters and anomalous X-ray pulsars.

We present an overview of PION, an open-source software project for solving radiation-magnetohydrodynamics equations on a nested grid, aimed at modelling asymmetric nebulae around massive stars. A new implementation of hybrid OpenMP/MPI parallel algorithms is briefly introduced, and improved scaling is demonstrated compared with the current release version. Three-dimensional simulations of an expanding nebula around a Wolf-Rayet star are then presented and analysed, similar to previous 2D simulations in the literature. The evolution of the emission measure of the gas and the X-ray surface brightness are calculated as a function of time, and some qualitative comparison with observations is made.

Thousands of ring-like bubbles appear on infrared images of the Galaxy plane. Most of these infrared bubbles form during expansion of Hii regions around massive stars. However, the physical effects that determine their morphology are still under debate. Namely, the absence of the infrared emission toward the centres of the bubbles can be explained by pushing the dust grains by stellar radiation pressure. At the same time, small graphite grains and PAHs are not strongly affected by the radiation pressure and must be removed by another process. Stellar ultraviolet emission can destroy the smallest PAHs but the photodestruction is ineffective for the large PAHs. Meanwhile, the stellar wind can evacuate all types of grains from Hii regions. In the frame of our chemo-dynamical model we vary parameters of the stellar wind and illustrate their influence on the morphology and synthetic infrared images of the bubbles.