Papers for Wednesday, Dec 29 2021

The respective contributions of gas accretion, galaxy interactions, and mergers to the mass assembly of galaxies, their morphological transformations, and the changes in their molecular gas content and star formation activity are still not fully understood. Galaxies with two kinematic components which are manifested as a double-peak (DP) in their emission lines, have been identified in a recent work to play a major role in the morphological transformation towards larger bulges. Notably, star-forming DP galaxies display a central star formation enhancement and are thought to be associated with a sequence of recent minor mergers. In order to probe merger induced star formation, we conducted observations of the molecular gas content of star-forming DP galaxies in the upper part of the main sequence (MS) with the IRAM 30m telescope. In combination with existing molecular gas observations from the literature, we gathered a sample of 41 such galaxies. We succeed in fitting the same kinematic parameters to the optical ionised and molecular gas emission lines for 24 (59\,\%) galaxies. We find a central star formation enhancement which is most likely the result of a galaxy merger or galaxy interactions which is indicated by an excess of gas extinction found in the centre. This star formation is traced by radio continuum emissions of 150 MHz, 1.4 GHz and 3 GHz, which are all three linearly correlated with the CO luminosity described by the same slope. We find a significantly larger amount of molecular gas in the present DP galaxies and larger depletion times. We discard a scenario of large scale instabilities driving gas into the centre and find no direct link between the measured kinematic signatures and inclination. This leads us to conclude that the observed DP galaxies are mostly the result of a recent merger that funnelled molecular gas towards the centre and triggered star formation there.

We apply stellar population synthesis analysis to obtain spatially-resolved archaeological inferences for a large sample of "red and dead" Elliptical galaxies (Classical Ellipticals; CLEs) from the MaNGA/SDSS-IV DR15 survey. From their 2D stellar light and mass maps, we explore the differences between the radial mass and light distributions in the rest-frame bands $g,$ $r,$ and $i$ as functions of look-back time, $t_{\rm lb}$, or redshift, $z$. We characterize these differences through the ratios between the following mass- and light-derived global properties: sizes, concentrations, and effective surface densities. We find that the mass-to-light ratios of these properties change with $t_{\rm lb}$, more the more massive the galaxies are. The CLE galaxy archaeological progenitors are, on average, less compact, concentrated, and dense in light than in mass as $z$ decreases. However, at later times, when also the evolution of the progenitors becomes passive at all radii, there is an upturn in these trends and the differences between mass and light in compactness/concentration decrease towards $z\sim 0$. The trends in the ratios of mass to light sizes agree qualitatively with results from direct observations in galaxy surveys at different redshifts. We discuss the caveats and interpretations of our results, and speculate that the strong structural evolution found in some previous studies for early-type galaxies could be explained partially by photometric changes rather than by intrinsic structural changes.

We report on the three-dimensional (3D) hydrodynamic evolution to iron core-collapse of a rapidly rotating 16 $M_{\odot}$ star. For the first time, we follow the 3D evolution of the angular momentum (AM) distribution in the iron core and convective shell burning regions for the final 10 minutes up to and including gravitational instability and core-collapse. In 3D, we find that convective regions show efficient AM transport that leads to an AM profile that differs in shape and magnitude from $\texttt{MESA}$ within a few shell convective turnover timescales. For different progenitor models, such as those with tightly coupled Si/O convective shells, efficient AM transport in 3D simulations could lead to a significantly different AM distribution in the stellar interior affecting estimates of the natal neutron star or black hole spin. Our results suggest that 3D AM transport in convective and rotating shell burning regions are critical components in models of massive stars and could qualitatively alter the explosion outcome and inferred compact remnant properties.

Exozodiacal dust, warm debris from comets and asteroids in and near the habitable zone of stellar systems, reveals the physical processes that shape planetary systems. Scattered light from this dust is also a source of background flux which must be overcome by future missions to image Earthlike planets. This study quantifies the sensitivity of the Nancy Grace Roman Space Telescope Coronagraph to light scattered by exozodi, the zodiacal dust around other stars. Using a sample of 149 nearby stars, previously selected for optimum detection of habitable exoplanets by space observatories, we find the maximum number of exozodiacal disks with observable \textit{inner} habitable zone boundaries is six and the number of observable outer habitable boundaries is 74. One zodi was defined as the visible-light surface brightness of 22 $m_{\rm V}\ $arcsec$^{-2}$ around a solar-mass star, approximating the scattered light brightness in visible light at the Earth-equivalent insolation. In the speckle limited case, where the signal-to-noise ratio is limited by speckle temporal stability rather than shot noise, the median $5\sigma$ sensitivity to habitable zone exozodi is 12 zodi per resolution element. This estimate is calculated at the inner-working angle of the coronagraph, for the current best estimate performance, neglecting margins on the uncertainty in instrument performance and including a post-processing speckle suppression factor. For an log-norm distribution of exozodi levels with a median exozodi of 3$\times$ the solar zodi, we find that the Roman Coronagraph would be able to make 5$\sigma$ detections of exozodiacal disks in scattered light from 13 systems with a 95\% confidence interval spanning 7-20 systems. This sensitivity allows Roman Coronagraph to complement ground-based measurements of exozodiacal thermal emission and constrain dust albedos.

Deformable Mirrors (DMs) have wide applications ranging from astronomical imaging to laser communications and vision science. However, they often require bulky multi-channel cables for delivering high power to their drive actuators. A low powered DM which is driven in a contactless fashion could provide a possible alternative to this problem.Here, we present a photo-magnetically actuated deformable mirror (PMADM) concept which is actuated in a contactless fashion by a permanent magnet and low power laser heating source. This paper presents the laboratory demonstration of prototype optical surface quality, magnetic control of focus, and COMSOL simulations of its precise photo-control. The PMADM prototype is made of a magnetic composite (polydimethylsiloxane [PDMS] + ferromagnetic $\text{CrO}_\text{2}$) and an optical-quality substrate layer and is 30.48 mm $\times$ 30.48 mm $\times$ 175 $\mu$ m in dimension with an optical pupil diameter of 8 mm. It deforms to 5.76 $\mu$ m when subjected to a 0.12 T magnetic flux density and relaxes to 3.76 $\mu$ m when illuminated by a 50 mW laser. A maximum stroke of 8.78 $\mu$ m before failure is also estimated considering a 3x safety factor. This works also includes simulation of astigmatism generation with the PMADM, a first step in demonstrating control of higher order modes. A fully developed PMADM can have potential application for wavefront corrections in vacuum and space environments.

In this paper, we investigate the cosmological viability of a double scalar field model motivated by warm inflation. To this end, we first set up the theoretical framework in which dark energy, dark matter and inflation are accounted for in a triple unification scheme. We then compute the overall dynamics of the model, analyzing the physical role of coupling parameters. Focussing on the late-time evolution, we test the model against current data. Specifically, using the low-redshift Pantheon Supernovae Ia and Hubble cosmic chronometers measurements, we perform a Bayesian analysis through the Monte Carlo Markov Chains method of integration on the free parameters of the model. We find that the mean values of the free parameters constrained by observations lie within suitable theoretical ranges, and the evolution of the scalar fields provides a good resemblance to the features of the dark sector of the universe. Such behaviour is confirmed by the outcomes of widely adopted selection criteria, suggesting a statistical evidence comparable to that of the standard $\Lambda$CDM cosmology. We finally discuss the presence of large uncertainties over the free parameters of the model and we debate about fine-tuning issues related to the coupling constants.

To understand the potential for observing forming planets and their circumplanetary disks (CPDs) with JWST and ELT, we created mock observations from 3D radiative hydrodynamic simulations and radiative transfer post-processing for planets with 10, 5, 1 Jupiter and 1 Saturn masses with orbital separation of 50 and 30 AU in 0$^{\circ}$, 30$^{\circ}$ and 60$^{\circ}$ inclinations. Instrumental effects were then simulated with Mirage for JWST/NIRCam and NIRISS, MIRISim for JWST/MIRI and SimCADO & SimMETIS for ELT/MICADO and METIS. We found that the longer wavelengths (mid-IR and beyond) are the best to detect CPDs. Longer is the wavelength, the smaller mass planet's CPD could be detected. MIRI on JWST and METIS on ELT offers the best possibility on these telescopes. Specifically, below 3 $\mu$m, only 10 $M_{\mathrm{Jup}}$ planets with their CPDs are detectable with NIRCam and MICADO. 5 $M_{\mathrm{Jup}}$ planets are only detectable if at 30 AU (i.e. closer) orbital separation. Planets above 5 $M_{\mathrm{Jup}}$ with their CPDs are detectable between 3-5 $\mu$m with NIRCam and METIS L/M band, or above 10 $\mu$m with MIRI and METIS N band. For $\leq$ 1 $M_{\mathrm{Jup}}$ planets > 15 $\mu$m are needed, where MIRI uniquely offers imaging capability. We present magnitudes and spectral energy distributions for separate components of the planet+CPD+CSD system, to differentiate the extinction rates of CPDs and CSDs and to provide predictions for observational proposals. Because the CPD turns out to be the main absorber of the planet's emission, especially <10 $\mu$m, this makes the detection of forming planets quite challenging.

Accurate and stable spacecraft pointing is a requirement of many astronomical observations. Pointing particularly challenges nanosatellites because of an unfavorable surface area to mass ratio and proportionally large volume required for even the smallest attitude control systems. This work explores the limitations on astrophysical attitude knowledge and control in a regime unrestricted by actuator precision or actuator-induced disturbances such as jitter. The external disturbances on an archetypal 6U CubeSat are modeled and the limiting sensing knowledge is calculated from the available stellar flux and grasp of a telescope within the available volume. These inputs are integrated using a model-predictive control scheme. For a simple test case at 1 Hz, with an 85 mm telescope and a single 11th magnitude star, the achievable body pointing is predicted to be 0.39 arcseconds. For a more general limit, integrating available star light, the achievable attitude sensing is approximately 1 milliarcsecond, which leads to a predicted body pointing accuracy of 20 milliarcseconds after application of the control model. These results show significant room for attitude sensing and control systems to improve before astrophysical and environmental limits are reached.

For sensitive optical interferometry, it is crucial to control the evolution of the optical path difference (OPD) of the wavefront between the individual telescopes of the array. The OPD between a pair of telescopes is induced by differential optical properties such as atmospheric refraction, telescope alignment, etc. This has classically been measured using a fringe tracker that provides corrections to a piston actuator to account for this difference. An auxiliary method, known as the Piston Reconstruction Experiment (P-REx) has been developed to measure the OPD, or differential 'piston' of the wavefront, induced by the atmosphere at each telescope. Previously, this method was outlined and results obtained from LBT adaptive optics (AO) data for a single telescope aperture were presented. P-REx has now been applied off-line to previously acquired VLT's GRAVITY CIAO wavefront sensing data to estimate the atmospheric OPD for the six VLTI baselines. Comparisons with the OPD obtained from the VLTI GRAVITY fringe tracker were made. The results indicate that the telescope and instrumental noise of the combined VLTI and GRAVITY systems dominate over the atmospheric turbulence contributions. However, good agreement between simulated and on-sky P-REx data indicates that if the telescope and instrumental noise were reduced to atmospheric piston noise levels, P-REx has the potential to reduce the OPD root mean square of piston turbulence by up to a factor of 10 for frequencies down to 1 Hz. In such conditions, P-REx will assist in pushing the sensitivity limits of optical fringe tracking with long baseline interferometers.

Relic galaxies are massive compact quiescent galaxies that formed at high-redshift and remained almost unchanged since then. In this work, we search for analogues to relic galaxies in the TNG50 cosmological simulations to understand relic formation and test the ability of TNG50 to reproduce such rare objects. Using stellar mass, age, radius, quiescence and stellar assembly criteria, we find 5 subhalos in TNG50 that could be potential relic analogues. We compare their properties with other constraints imposed by a sample of 13 observed relic galaxies. We find one analogue in TNG50 that simultaneously satisfies most of the available observational constraints, such as metallicity and morphology. It also shows similarities to the confirmed relic NGC 1277, regarding environment and dark matter fraction. By taking into account a degree of relicness, a second relic analogue may also be considered. However, the central parts of the brightness and density profiles of the analogues are less steep than that of real relic galaxies, possibly due to limited numerical resolution. We identify two formation pathways of relic analogues in TNG50 depending on their environment: they either have their remaining gas stripped during the infall into a cluster at $z \lesssim 1.2$ or consume it before $z > 1.5$. They are then deprived of significant star formation, leaving their stellar populations almost unaltered during the last 9 Gyr. We also find that the analogue progenitors at $z \sim 4$ inhabit more massive halos than progenitors of quiescent galaxies with similar stellar mass at $z \sim 0$.

It has long been established but seldom noticed that we are in a region at least 170 Mpc across in which different types of galaxies show different degrees of alignment with the plane of the de Vaucouleurs Local Supercluster. While clusters of galaxies and radio galaxies at redshifts less than 0.02 are concentrated at low supergalactic latitudes, the most luminous galaxies in the infrared, LIRGs, show little correlation with this plane. The most luminous early-type galaxies are concentrated at low supergalactic latitudes, but similarly luminous spirals are not noticeably so. The cross-correlations of the positions of what might be termed field galaxies with positions of clusters and LIRGs offer a measure of the situation. The mean density at distance 0.5 Mpc from a LIRG is comparable to the mean density at that distance from a cluster of galaxies, but the mean density 5 Mpc from a LIRG is well below the mean density at that distance from a cluster and not much greater than the cosmic mean density. Discussion of issues arising is brief.

We conduct a systematic search for periodic variables in the hot subdwarf catalogue from Geier et al. 2019 using data from the Zwicky Transient Facility. We present the classification of 67 HW Vir binaries, 496 reflection effect, pulsation or rotation sinusoids, 11 eclipsing signals, and 4 ellipsoidally modulating binaries. Of these, 485 are new discoveries that have not been previously published including a new mass-transferring hot subdwarf binary candidate. These sources were determined by applying the Lomb-Scargle and Box Least Squares periodograms along with manual inspection. We calculated variability statistics on all periodic sources, and compared our results to traditional methods of determining astrophysical variability. We find that $\approx60$% percent of variable targets, mostly sinusoidal variability, would have been missed using the varindex cut of 0.02. Most HW Virs, eclipsing systems and all ellipsoidal variables were recovered with a varindex $> 0.02$. We also find a significant reddening effect, with some variable hot subdwarfs meshing with the main sequence stripe in the Hertzprung-Russell Diagram. Examining the positions of the variable stars in Galactic coordinates, we discover a higher proportion of variable stars within $|b|<25^\circ$ of the Galactic Plane, suggesting that the Galactic Plane may be fertile grounds for future discoveries if photometric surveys can effectively process the the clustered field.

We study the morphologies of 3,964 galaxies and their progenitors with $M_\star > 10^{10} M_\odot$ in the reference EAGLE hydrodynamical simulation from redshifts $z=1$ to $z=0$, concentrating on the redshift evolution of the bar fraction. We apply two convolutional neural networks (CNNs) to classify 35,082 synthetic g-band images across 10 snapshots in redshift. We identify galaxies as either barred or unbarred, while also classifying each sample into one of four morphological types: elliptical (E), lenticular (S0), spiral (Sp), and irregular/miscellaneous (IrrM). We find that the bar fraction is roughly constant between $z = 0.0$ to $z = 0.5$ (32% to 33%), before exhibiting a general decline to 26% out to $z = 1$. The bar fraction is highest in spiral galaxies, from 49% at $z = 0$ to 39% at $z = 1$. The bar fraction in S0s is lower, ranging from 22% to 18%, with similar values for the miscellaneous category. Under 5% of ellipticals were classified as barred. We find that the bar fraction is highest in low mass galaxies ($M_\star \leq 10^{10.5} M_\odot$). Through tracking the evolution of galaxies across each snapshot, we find that some barred galaxies undergo episodes of bar creation, destruction and regeneration, with a mean bar lifetime of 2.24 Gyr. We further find that incidences of bar destruction are more commonly linked to major merging, while minor merging and accretion is linked to both bar creation and destruction.

The article focuses on trajectory design to the trans-Neptunian object (90377) Sedna for launch in 2029-2034. Sedna is currently moving to the perihelion at a distance of around 74 au from the Sun. The perihelion passage is estimated to be in 2073-74. That opens up of opportunities to study such a distant object. Known for its orbit and 10 thousand year period, Sedna is an exciting object for deep space exploration. The current research provides two possible scenarios of transfer to Sedna. A direct flight and flights including gravity assist manoeuvres are considered. The present study showed that a direct flight would be practically unrealistic due to the high total characteristic velocity and the time of flight value. Promising scenarios include gravity assist manoeuvres near Venus, Earth, Jupiter, Saturn and Neptune. The analysis of the close approach to asteroids during the flight to Sedna had been performed. Results of the research presented in this article show that the launch in 2029 provides the best transfer conditions in terms of minimum total characteristic velocity. The analysis shows that with a small additional impulses flybys of the large main-belt asteroids (16) Psyche for launch in 2034 and (20) Massalia for launch in 2029 are possible.

We report on results of high resolution two fluid non-linear simulations of the Rayleigh Taylor Instability (RTI) at the interface between a solar prominence and the corona. These follow results reported earlier by Popescu Braileanu et al. (2021a,b) on linear and early non-linear RTI dynamics in this environment. The simulations use a two fluid model that includes collisions between neutrals and charges, including ionization/recombination, energy and momentum transfer, and frictional heating. High resolution 2.5D magnetized RTI simulations with the magnetic field dominantly normal to and slightly sheared with respect to the prominence plane demonstrate that in a fully developed state of RTI a large fraction of the gravitational energy of a prominence thread can be converted into quasi-turbulent energy of the magnetic field. RTI magnetic energy generation is further accompanied by magnetic and plasma density structure formation, including dynamic formation, break-up, and merging of current sheets and plasmoid sub-structures. The simulations show the role of flow decoupling and ionization/recombination reactions between the neutrals and charges on the structure formation in magnetized RTI. We provide a careful examination of sources and form of numerical dissipation of the evolving magnetic field structures.

We investigate, using a multi-fluid approach, the main properties of standing ion-acoustic modes driven by nonlinear standing Alfv\'en waves. The standing character of the Alfv\'enic pump is because we study the superposition of two identical circularly polarised counter-propagating waves. We consider parallel propagation along the constant magnetic field and we find that left and right-handed modes generate via ponderomotive forces the second harmonic of standing ion-acoustic waves. We demonstrate that parametric instabilities are not relevant in the present problem and the secondary ion-acoustic waves attenuate by Landau damping in the absence of any other dissipative process. Kinetic effects are included in our model where ions are considered as particles and electrons as a massless fluid, and hybrid simulations are used to complement the theoretical results. Analytical expressions are obtained for the time evolution of the different physical variables in the absence of Landau damping. From the hybrid simulations we find that the attenuation of the generated ion-acoustic waves follows the theoretical predictions even under the presence of a driver Alfv\'enic pump. Due to the nonlinear induced ion-acoustic waves the system develops density cavities and an electric field parallel to the magnetic field. Theoretical expressions for this density and electric field fluctuations are derived. The implications of these results in the context of standing slow mode oscillations in coronal loops is discussed.

The Square Kilometre Array (SKA) project is an international cooperation project to build the largest radio telescope worldwide. Data processing is one of the biggest challenges of building the SKA telescope. As a distributed execution framework, the Data Activated Liu Graph Engine (DALiuGE) was proposed to be one of the candidates for addressing the massive data of the SKA. DALiuGE has many distinctive features, but its actual ability to handle scientific data is still not evident. In this paper, we perform an objective evaluation of the usability of DALiuGE concerning the execution performance, developer workload, and implementation difficulty of porting the SAGECal to DALiuGE. The evaluation results showed that the DALiuGE enables fast integration of astronomical software, but there are significant differences in the efficiency of different parallel granularities. Even with the deep optimization of the program, there is still a gap between the current DALiuGE and the traditional MPI in execution performance. Therefore, we come to a preliminary conclusion that the DALiuGE has no performance advantage in batch processing of massive data, while it may be more suitable for application scenarios with more customized computational tasks, such as SKA science regional centers.

We present mid-infrared spectra from our continued monitoring of R Aquarii, the nearest symbiotic Mira, using the Stratospheric Observatory for Infrared Astronomy (SOFIA). New photometric and spectroscipic data were obtained with the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST) in 2018 and 2019 after the system had started its "eclipse", during which it became two magnitudes fainter in the visual. The mid-IR flux, in particular the 10 mu-m silicate feature, have strengthened compared with the previous cycles. Radiative transfer models for the circumstellar dust emission were calculated for the new spectra, and re-calculated for those previously obtained using more appropriate values of the near-IR magnitudes to constrain the properties of the AGB spectra heating the dust. The modeling shows that the luminosity dependence on pulsation phase is not affected by the onset of the eclipse, and that the increase in the mid-IR flux is due to a higher dust density. The models also confirm our earlier results that micron-size grains are present, and that no changes in the grain composition are required to explain the variations in the spectra.

Massive stars are rare but of paramount importance for their immediate environment and their host galaxies. They lose mass from their birth through strong stellar winds up to their spectacular end of their lives as supernovae. The mass loss changes as they evolve and in some phases it becomes episodic or displays outburst activity. One such phase is the Yellow Hypergiants, in which they experience outbursts due to their pulsations and atmosphere instabilities. This is depicted in photometry as a decrease in their apparent magnitude. The object $\rho$ Cassiopeia (Cas) is a bright and well known variable star that has experienced four major outbursts over the last century, with the most recent one detected in 2013. We derived the light curves from both visual and digital observations and we show that with some processing and a small correction ($\sim0.2$ mag) for the visual the two curves match. This highlights the importance of visual observations both because of the accuracy we can obtain and because they fully cover the historic activity (only the last two of the four outbursts are well covered by digital observations) with a homogeneous approach. By fitting the outburst profiles from visual observations we derive the duration of each outburst. We notice a decreasing trend in the duration, as well as shorter intervals between the outbursts. This activity indicates that $\rho$ Cas may be preparing to pass to the next evolutionary phase.

The radiative and jet power in active galactic nuclei is generated by accretion of material on to supermassive galactic-centre black holes. For quasars, where the radiative power is by definition very high, objects with high radio luminosities form around 10 per cent of the population, although it is not clear whether this is a stable phase. Traditionally, quasars with high radio luminosities have been thought to present jets with edge-brightened morphology (Fanaroff-Riley II - FR II) due to the limitations of previous radio surveys (i.e., FRIs were not observed as part of the quasar population). The LOw Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) with its unprecedented sensitivity and resolution covering wide sky areas has enabled the first systematic selection and investigation of quasars with core-brightened morphology (Fanaroff-Riley I - FR). We carried out a Very Large Array (VLA) snapshot survey to reveal inner structures of jets in selected quasar candidates; 15 (25 per cent) out of 60 sources show clear inner jet structures that are diagnostic of FRI jets and 13 quasars (around 22 per cent) show extended structures similar to those of FRI jets. Black hole masses and Eddington ratios do not show a clear difference between FRI and FRII quasars. FRII quasars tend to have higher jet powers than FRI quasars. Our results show that the occurrence of FRI jets in powerful radiatively efficient systems is not common, probably mainly due to two factors: galaxy environment and jet power.

Suprathermal particles (H and other heavy ions like 4He, 3He, C, O and Fe) are, in general, characterized by the so-called `universal' -1.5 spectral index. However, variation in this spectral index with composition has not been tested critically. In the present investigation, solar cycle variation of individual `quiet' time suprathermal elements is investigated using < ~ 1 MeV/n particle flux data obtained from Ultra Low Energy Isotope Spectrometer on board Advanced Composition Explorer during the solar cycle 23 and 24. The analysis reveals that 4He lags the sunspot numbers in solar cycle 24 by almost 700 days and there is no noticeable lag for the 0.07-0.20 MeV/n 4He during solar cycle 23. Fe, on the other hand, lags the sunspot variation by almost 300 days in cycle 23 while negligible lag is observed in cycle 24. Further, significant changes in spectral slopes are seen for 4He and Fe in the minimum of cycle 24-25 and 23-24 respectively. Although 4He and Fe behave differently, all other elements exhibit random lags in both the solar cycles with respect to sunspot numbers and significant changes in spectral slopes are also not observed. These results suggest the contribution of energetic events in the suprathermal ion pool during `quiet' periods. Although no single generation mechanism is found to be adequate to explain these observations, the contrasting behaviour of 4He and Fe indicates towards sensitive dependence of the generation of suprathermal population on the first ionization potential and mass to charge ratio.

The disclosed satellite metadata as well as previous estimations using Revise Kinematic Precise Point Positioning (RKPPP) approach with L-band data have already demonstrated the continuous yaw steering model used by BDS-3 Medium Earth Orbit (MEO) satellites manufactured by China Academy of Space Technology (CAST) in deep eclipse seasons instead of the orbit normal mode. However, the yaw model has not been validated for MEO satellites manufactured by Shanghai Engineering Center of Microsatellites (SECM), as the horizontal phase center offsets (PCO) approaches zeros, similar for BDS-3 Inclined Geostationary Orbit (IGSO) satellites. In this study, the inter-satellite link (ISL) data were used to estimate the yaw angles of BDS-3 IGSO and MEO satellites with accuracy of around 1.49{\deg} to investigate their yaw behaviors, particularly in the deep eclipse seasons. The estimates confirm that the IGSO and MEO satellites from CAST show the similar yaw behaviors, while the SECM MEO satellites do not fully comply with the attitude law published by China Satellite Navigation Office (CSNO). The attitude transition postpones from that predicted by CSNO yaw law, and occurs when the yaw angle is less than 5{\deg} and the elevation angle of the Sun above the orbital plane (beta angle) crosses 0{\deg}. The transition completes within three minutes with a rate about 0.055{\deg}/s. A model is proposed to predict these behaviors, and the ISL residuals return to normal levels, and became more stable in the adjacent of midnight and noon points. Once the yaw models are used.

New relationships between the orbital period and some parameters of W Ursae Majoris (W UMa) type systems are presented in this study. To investigate the relationships, we calculated the absolute parameters of a sample of 118 systems. For this purpose, we used the parallax values obtained from the Gaia Early Data Release 3 (Gaia EDR3) star catalog for more precise calculations. The other required parameters, including the light curve solutions and the orbital period were derived from previous research. For some relationships, we added 86 systems from another study with an orbital period of less than 0.6 days to our sample, allowing us to increase the number of systems to 204. Therefore, the mass (M) values of each component along with all the other absolute parameters were recalculated for these contact systems. We used the Markov Chain Monte Carlo (MCMC) approach in order to gain the new orbital period-mass relations (P-M) per component, and added the temperature (T) to the process to acquire the new orbital period-temperature (P-T1) relation. We presented the orbital period behavior in terms of log(g) by new relations for each component. We have also obtained a model between the orbital period, the mass of the primary component and temperature (P-M1-T1) using the Artificial Neural Networks (ANN) method. Additionally, we present a model for the relationship between the orbital period and the mass ratio (P-q) by fitting a Multi-Layer Perceptron (MLP) regression model to a sample of the data collected from the literature.

We studied thermal evolution of isolated neutron stars (NSs) including the pion condensation core, with an emphasis on the stiffness of equation of state (EOS). Many temperature observations can be explained by the minimal cooling scenario which excludes the fast neutrino cooling process. However, several NSs are cold enough to require it. The most crucial problem for NS cooling theory is whether the nucleon direct Urca (DU) process is open. The DU process is forbidden if the nucleon symmetry energy is significantly low. Hence, another fast cooling process is required in such an EOS. As the candidate to solve this problem, we consider the pion condensation. We show that the low-symmetry-energy model can account for most cooling observations including cold NSs, with strong neutron superfluidity. Simultaneously, it holds the $2~M_{\odot}$ observations even if the pion condensation core exists. Thus, we propose the possibility of pion condensation, as an exotic state to solve the problem in low-symmetry-energy EOSs. We examined the consistency of our EOSs with other various observations as well.

Using data from the Complete Nearby ($z_{host}<0.02$) sample of Type Ia Supernovae (CNIa0.02), we discover a linear relation between two parameters derived from the $B-V$ color curves of Type Ia supernovae: the "color stretch" $s_{BV}$ and the rising color slope $s_0^*(B-V)$ after the peak, and this relation applies to the full range of $s_{BV}$. The $s_{BV}$ parameter is known to be tightly correlated with the peak luminosity, and especially for "fast decliners" (dim Type Ia supernovae), and the luminosity correlation with $s_{BV}$ is markedly better than with the classic light-curve width parameters such as $\Delta{m_{15}(B)}$. Thus our new linear relation can be used to infer peak luminosity from $s_0^*$. Unlike $s_{BV}$ (or $\Delta{m_{15}}$), the measurement of $s_0^*(B-V)$ does not rely on the well-determined time of light-curve peak or color maximum, making it less demanding on the light-curve coverage than past approaches.

A new nonthermal phenomenon caused by streaming cosmic rays (CRs) in the universe is proposed. The streaming CRs drive the return current of thermal electrons to compensate for the CR current. Then, electric fields are induced by the resistivity of the return current. It is shown that the resistive electric fields can accelerate secondary electrons generated by the streaming CRs. This is the self-discharge by streaming CRs. In this work, the self-discharge condition and the condition for runaway acceleration of secondary electrons are presented. The self-discharge makes high-energy secondary electrons, resulting in enhancements of ionization and nonthermal emission including K$\alpha$ emission line of neutral irons. After the self-discharge, the return current of thermal electrons is replaced by the electric current of secondary electrons. Since some magnetic field generations and amplifications are driven by the return current of thermal electrons, the self-discharge can significantly influence them.

We present multi-epoch optical and near-infrared observations of the highly reddened, \pion{Fe}{ii} class slow nova V2891 Cygni. The observations span 15 months since its discovery. The initial rapid brightening from quiescence, and the presence of a $\sim$35 day long pre-maximum halt, is well documented. The evidence that the current outburst of V2891 Cyg has undergone several distinct episodes of mass ejection is seen through time-varying P Cygni profiles of the O\,{\sc i} 7773\,$\AA$ line. A highlight is the occurrence of a dust formation event centred around $\sim$+273d, which coincides with a phase of coronal line emission. The dust mass is found to be $\sim0.83-1.25 \times 10^{-10} M_{\odot}$. There is strong evidence to suggest that the coronal lines are created by shock heating rather than by photoionization. The simultaneous occurrence of the dust and coronal lines (with varying velocity shifts) supports the possibility that dust formation is shock-induced. Such a route for dust formation has not previously been seen in a nova, although the mechanism has been proposed for dust formation in some core-collapse supernovae. Analysis of the coronal lines indicates a gas mass and temperature of 8.35--8.42$\times10^{-7}$ M$_\odot$ and $\sim(4.8-9.1)\times10^{5}$~K respectively, and an overabundance of aluminium and silicon. A Case B analysis of the hydrogen lines yields a mass of the ionized gas of ($8.60\pm1.73)\times10^{-5}$ M$_{\odot}$. The reddening and distance to the nova are estimated to be $E(B-V)$ = 2.21$\pm$0.15 and $d$ = 5.50 kpc respectively.

Context: Helioseismic analysis of large-scale flows and structural inhomogeneities in the Sun requires the computation of sensitivity kernels that account for the spherical geometry of the Sun, as well as systematic effects such as line-of-sight projection. Aim: I aim to develop a code to evaluate helioseismic sensitivity kernels for flows using line-of-sight projected measurements. Methods: I decomposed the velocity field in a basis of vector spherical harmonics and computed the kernel components corresponding to the coefficients of velocity in this basis. The kernels thus computed are radial functions that set up a 1.5D inverse problem to infer the flow from surface measurements. I demonstrate that using the angular momentum addition formalism lets us express the angular dependence of the kernels as bipolar spherical harmonics, which may be evaluated accurately and efficiently. Results: Kernels for line-of-sight projected measurements may differ significantly from those that don't account for projection. Including projection in our analysis does not increase the computational time significantly. We demonstrate that it is possible to evaluate kernels for pairs of points that are related through a rotation by linearly transforming the terms that enter the expression of the kernel, and that this result holds even for line-of-sight projected kernels. Conclusion: I developed a Julia code that may be used to evaluate sensitivity kernels for seismic wave travel times computed using line-of-sight projected measurements, which is made freely available under the MIT license.

Relativistic jets are collimated outflows with speeds close to light speed, which are associated with gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and so on. This article mainly overviews recent developments of polarimetric studies of GRBs and their afterglows in the gamma-ray and optical wavebands as well as the first detections of their radio polarization. Polarimetric observations and theoretical modelings can address the emission mechanism, magnetic field structure, and energetics of GRB jets and related collisionless plasma physics. Some of the discussed key physics are common with AGN jets. Furthermore, we mention that polarimetry of AGN jets and protoplanetary disks may be a novel approach to search for ultra-light axion dark matter.

We review novel data analysis techniques developed or adapted for the field of coronal seismology. We focus on methods from the last ten years that were developed for extreme ultraviolet (EUV) imaging observations of the solar corona, as well as for light curves from radio and X-ray. The review covers methods for the analysis of transverse and longitudinal waves; spectral analysis of oscillatory signals in time series; automated detection and processing of large data sets; empirical mode decomposition; motion magnification; and reliable detection, including the most common pitfalls causing artefacts and false detections. We also consider techniques for the detailed investigation of MHD waves and seismological inference of physical parameters of the coronal plasma, including restoration of the three-dimensional geometry of oscillating coronal loops, forward modelling and Bayesian parameter inference.

The Galactic globular cluster system is incomplete, especially in the low latitude regions of the Galactic bulge and disk. We report the physical characterization of twelve star clusters in the Milky Way, most of which are explored here for the first time. Our aim is determining their main physical parameters, such as reddening and extinction, metallicity, age, total luminosity, mean cluster proper motions (PMs), distances, in order to unveil their physical nature. We study the clusters using optical and near-infrared (NIR) datasets. We use the Gaia Early Data Release 3 (EDR3) PMs in order to perform a PM-decontamination procedure and build final catalogues. We match the Gaia EDR3 with the VISTA Variables in the V\'ia L\'actea extended (VVVX) survey and Two Micron All Sky survey (2MASS) in the NIR, in order to construct complete colour-magnitude diagrams (CMDs) and investigate the clusters properties. The extinctions are evaluated using existing reddening maps, spanning $0.09\lesssim A_{Ks}\lesssim 0.86$ mag and $0.89 \lesssim A_{G}\lesssim 4.72$ mag in the NIR and optical, respectively. We obtain their heliocentric distances, that range from about 4 to 20 kpc, placing these clusters at $3\lesssim R_{G}\lesssim 14$ kpc from the Galactic centre. The best PARSEC isochrone fit yields a metallicity range of $-1.8<$[Fe/H]$<+0.3$ and an approximative age range of $2<$Age$<14$ Gyr. We find that all clusters have low-luminosities, with $-6.9<M_{V}<-3.5$ mag. Based on our photometric analysis, we confirm the OC nature for Kronberger100, while we classify Patchick125 as a metal-poor GC, Ferrero54 as a metal-rich GC, and ESO92-18 as a possible old OC or young GC. The classification as GC candidates is also suggested for Kronberger99, Patchick122, Patchick126, Riddle15, FSR190 and Gaia2. We also conclude that Kronberger119 and Kronberger143 might be either old OCs or young GCs.

IC\,4997 is a planetary nebula well known by its variability. We present high-resolution spectra of IC\,4997 obtained in 1993, 2019, and 2020 that reveal changes in the H$\alpha$ and [N\,{\sc ii}] emission line profiles, which had never been reported for this object. The H$\alpha$ P\,Cygni emission profile observed in 1993 changed to a single-peaked profile in 2019--2020, implying that the stellar wind has largely weakened. The very broad H$\alpha$ emission wings narrowed by a factor of $\sim$2 between 1993 and 2019--2020, indicating that the efficiency of the Rayleigh--Raman scattering has noticeably decreased. A high-velocity [N\,{\sc ii}] nebular component detected in 1993 is missing in 2019 and 2020, probably due to a decrease in its electron density. A correlation exists between the strength of the stellar wind and the episodic ($\sim$50--60\,yr) variation in the [O\,{\sc iii}]$\lambda$4363/H$\gamma$ line intensity ratio, suggesting that an episodic, smoothly variable stellar wind is the main cause of the variability of IC\,4997. Monitoring of that intensity ratio and of the H$\alpha$ emission line profile in the coming years and new multiwavelength observations are key to unveiling the ongoing processes in IC\,4997 and constraining the origin of the wind variability.

The TurLab facility is a laboratory, equipped with a 5 m diameter and 1 m depth rotating tank, located in the fourth basement level of the Physics Department of the University of Turin. In the past years, we have used the facility to perform experiments related to the observations of Extreme Energy Cosmic Rays (EECRs) from space using the fluorescence technique for JEM- EUSO missions with the main objective to test the response of the trigger logic. In the missions, the diffuse night brightness and artificial and natural light sources can vary significantly in time and space in the Field of View (FoV) of the telescope. Therefore, it is essential to verify the detector performance and test the trigger logic under such an environment. By means of the tank rotation, a various terrestrial surface with the different optical characteristics such as ocean, land, forest, desert and clouds, as well as artificial and natural light sources such as city lights, lightnings and meteors passing by the detector FoV one after the other is reproduced. The fact that the tank located in a very dark place enables the tests under an optically controlled environment. Using the Mini-EUSO data taken since 2019 onboard the ISS, we will report on the comparison between TurLab and ISS measurements in view of future experiments at TurLab. Moreover, in the forthcoming months we will start testing the trigger logic of the EUSO-SPB2 mission. We report also on the plans and status for this purpose.

In the widely accepted 'Unified Model' solution of the classification puzzle of Active Galactic Nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects and added dusty clumps and polar winds but left the basic picture intact. However, recent high-resolution images of the archetypal type-2 galaxy NGC 1068 suggested a more radical revision. They displayed a ring-like emission feature which the authors advocated to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the type 1-2 dichotomy. Here we present new multi-band mid-infrared images of NGC1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data, our maps locate the central engine below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the Unified Model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre.

We provide observational evidence that galaxy mergers significantly affect stellar kinematics of early-type galaxies (ETGs) such as specific stellar angular momentum within the half-light radius ($\lambda_{R_e}$) and kinematic misalignment ($\psi_\mathrm{mis}$), using MaNGA integral field unit spectroscopic data that are in the Stripe 82 region of the Sloan Digital Sky Survey. In this study, tidal features around ETGs, which are detected in deep coadded images, are used as direct evidence for mergers that occurred recently. In the case of ETGs that do not have dust lanes, $\lambda_{R_e}$ is lower in ETGs with tidal features than in those without tidal features (median $\lambda_{R_e}$: $0.21$ versus $0.39$) in all stellar mass and S\'ersic index ranges except the most massive bin, so that the fraction of ETGs with tidal features in slow rotators is more than twice as large as that in fast rotators ($42\%$ versus $18\%$). Moreover, ETGs with tidal features have larger $\psi_\mathrm{mis}$ than those without tidal features (mean $\psi_\mathrm{mis}$: $28^\circ$ versus $15^\circ$). By contrast, ETGs with dust lanes are fast rotators, and ETGs with both dust lanes and tidal features have the highest $\lambda_{R_e}$ (median $\lambda_{R_e}$: $0.59$) among all ETG categories. In addition, ETGs with dust lanes have small $\psi_\mathrm{mis}$ regardless of the existence of tidal features ($\psi_\mathrm{mis}<7.5^\circ$). Our results can be explained if mergers with different gas fractions generate merger remnants that have different kinematic properties.

Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we search for HI narrow-line self-absorption (HINSA) features in twelve Planck Galactic cold clumps (PGCCs), one starless core L1521B and four star forming sources. Eight of the 12 PGCCs have emission of J=2-1 of cyanoacetylene (HC3N). With an improved HINSA extraction method more robust for weaker and blended features with high velocity resolution, the detection rates of HINSA in PGCCCs are high, at 92% overall (11/12) and 87% (7/8) among sources with HC3N J=2-1 emissions. Combining the data of molecular spectra and Planck continuum maps, we studied the morphologies, abundances and excitations of HI, CO and HC3N in PGCCs. The distribution of HINSA is similar to that of CO emission. HINSA tends to be not detected in regions associated with warm dust and background ionizing radiation, as well as regions associated with stellar objects. The abundances of HI in PGCCs are approximately 3E-4, and vary within a factor of ~3. The non-thermal velocity dispersions traced by C18O J=1-0 and HINSA are consistent with each other (0.1-0.4 km/s), larger than those of HC3N (~0.1 km/s). Carbon chain molecule abundant PGCCs provide a good sample to study HINSA.

It is known that massive stars form as result of the fragmentation of molecular clumps. However, what is not clear is whether this fragmentation gives rise to cores massive enough to form directly high-mass stars, or leads to cores of low and intermediate mass that generate massive stars acquiring material from their environment. Detailed studies towards clumps at early stages of star formation are needed to collect observational evidence that shed light on this issue. The infrared-quiet massive clump AGAL G035.1330-00.7450, located at a distance of 2.1 kpc, is a promising object to study both the fragmentation and the star formation activity at early stages. Using millimeter observations of continuum and molecular lines obtained from the Atacama Large Millimeter Array database at Bands 6 and 7, we study the substructure of this source. The angular resolution of the data at Band 7 is about 0\farcs7, which allow us to resolve structures of about 0.007 pc ($\sim$1500 au). We found that the clump harbours four dust cores (C1-C4) with masses below 3 M$_{\odot}$. Cores C3 and C4 exhibit well collimated, young, and low-mass molecular outflows. C1 and C2 present CH$_3$CN J=13--12 emission, from which we derive rotational temperatures of about 180 and 100 K, and masses of about 1.4 and 0.9 M$_{\odot}$, respectively. The moment 1 map of the CH$_3$CN emission suggests the presence of a rotating disk towards C1, which is confirmed by the CH$_3$OH and CH$_3$OCHO (20-19) emissions. On the other hand, CN N=2-1 emission shows a clumpy and filamentary structure that seems to connect all the cores. These filaments might be tracing the remnant gas of the fragmentation processes taking place within the clump, or gas that is being transported towards the cores, which would imply a competitive accretion scenario.

The equilibrium figure of an inviscid tidally deformed body is the starting point for the construction of many tidal theories such as Darwinian tidal theories or the hydrodynamical Creep tide theory. This paper presents the ellipsoidal equilibrium figure when the spin rate vector of the deformed body is not perpendicular to the plane of motion of the companion. We obtain the equatorial and the polar flattenings as functions of the Jeans and the Maclaurin flattenings, and of the angle $\theta$ between the spin rate vector and the radius vector. The equatorial vertex of the equilibrium ellipsoid does not point toward the companion, which produces a torque perpendicular to the rotation vector, which introduces terms of precession and nutation. We find that the direction of spin may differ significantly from the direction of the principal axis of inertia $C$, so the classical approximation $\mathsf{I}\vec{\omega}\approx C\vec{\omega}$ only makes sense in the neighborhood of the planar problem. We also study the so-called Cassini states. Neglecting the short-period terms in the differential equation for the spin direction and assuming a uniform precession of the line of the orbital ascending node, we obtain the same differential equation as that found by Colombo (1966). That is, a tidally deformed inviscid body has exactly the same Cassini states as a rotating axisymmetric rigid body, the tidal bulge having no secular effect at first order.

We present an analysis of the optical-to-near-IR counterparts of a sample of candidate dusty starbursts at $z>6$. These objects were pre-selected based on the rising trend of their far-infrared-to-sub-millimeter spectral energy distributions and the fact that they are radio-weak. Their precise positions are available through millimeter and/or radio interferometry, which enable us to search for their counterparts in the deep optical-to-near-IR images. The sample include five $z>6$ candidates. Three of them have their counterparts identified, one is still invisible in the deepest images, and one is a known galaxy at $z=5.667$ that is completely blocked by a foreground galaxy. The three with counterparts identified are analyzed using population synthesis model, and their photometric redshifts range from 6.2 to 8.9. Assuming that they are not gravitationally lensed, their total IR luminosities are $10^{13.6-14.0} L_\odot$ and the inferred star formation rates are 4.0--10 $\times 10^3$ $M_\odot$ yr$^{-1}$. The very existence of these dusty starbursts means that the universe must be forming stars intensely very early in time in at least some galaxies, otherwise there would be no enough dust to produce the descendants observed at these redshifts. The inferred stellar masses of their host galaxies, which are at $> 10^{11} M_\odot$ (if not affected by gravitational lensing), present a difficulty in explanation unless we are willing to accept that their progenitors kept forming stars at a rate of $>10^3$ $M_\odot$ yr$^{-1}$ or were formed through intense instantaneous bursts. Spectroscopic confirmation of such these objects will be imperative.

In a recent work (arXiv:2112.11375), Luo and Zhang have asserted that there is a statistically significant angular correlation between IceCube neutrinos (in the energy range of 0.1-3 TeV) and FRBs detected by the CHIME telescope, with 21$\sigma$ significance. We independently verify this claim by counting the total number of neutrino-FRB pairs with angular separations of $< 3 $ degrees, as well as within the observed neutrino error circle, which correspond to the total signal events. This number is then compared to the background, which was obtained by counting the number of coincidences in off-source angular windows with the same solid angle as the signal window. We do not find any statistically significant excess compared to the background. Therefore, we conclude that there is no evidence for an angular correlation between the IceCube neutrinos in the TeV energy range and CHIME FRBs.

We report a novel prediction from single-field inflation that even a tiny step in the inflaton potential can change our perception of primordial non-Gaussianities of the curvature perturbation. Our analysis focuses on the tail of probability distribution generated by an upward step transition between two stages of slow-roll evolution. The nontrivial background dynamics with off-attractor behavior is identified. By using a non-perturbative $\delta N$ analysis, we explicitly show that a highly non-Gaussian tail can be generated by a tiny upward step, even when the conventional nonlinearity parameters $f_{NL}$, $g_{NL}$, etc. remain small. With this example, we demonstrate for the first time the sensitive dependence of non-perturbative effects on the tail of probability distribution. Our scenario has an inconceivable application to primordial black holes by either significantly boosting their abundance or completely forbidding their appearance.

The most exciting future observation in cosmology will feature a monitoring of the cosmic expansion in real time, unlike anything that has ever been attempted before. This campaign will uncover crucial physical properties of the various constituents in the Universe, and perhaps answer a simpler question concerning whether or not the cosmic expansion is even accelerating. An unambiguous yes/no response to this query will significantly impact cosmology, of course, but also the standard model of particle physics. Here, we discuss -- in a straightforward way -- how to understand the so-called `redshift drift' sought by this campaign, and why its measurement will help us refine the standard-model parameters if the answer is `yes.' A `no' answer, on the other hand, could be more revolutionary, in the sense that it might provide a resolution of several long-standing problems and inconsistencies in our current cosmological models. An outcome of zero redshift drift, for example, would obviate the need for a cosmological constant and render inflation completely redundant.

In this paper, we present a new kind of stellar model using the Nariai IV metric. This model can be used to study the strange/quark stars(which is our present interest, though it can also be applicable to neutron stars). We present a mass-radius region where all the regularity conditions, energy conditions, the TOV equation, and stability conditions are satisfied. According to our model, strange stars having mass up to $1.9165M_{\odot}(=2.81 km)$ is stable. A strange star having a mass greater than $1.9165M_{\odot}$ violates the stability conditions. This model can be very useful to predict the radius of strange stars of mass greater than $1 M_{\odot}$.

Hyperon ($Y$) mixing in neutron-star matter brings about a remarkable softening of the equation of state (EoS) and the maximum mass is reduced to a value far less than $2M_{\odot}$. One idea to avoid this "hyperon puzzle in neutron stars" is to assume that the many-body repulsions work universally for every kind of baryons. The other is to take into account the quark deconfinement phase transitions from a hadronic EoS to a sufficiently stiff quark-matter EoS. In the present approach, both effects are handled in a common framework. As well as the hadronic matter, the quark matter with the two-body quark-quark interactions are treated within the Brueckner-Bethe-Goldstone theory beyond the mean field frameworks, where interaction parameters are based on the terrestrial data. The derived mass-radius relations of neutron stars show that maximum masses reach over $2M_{\odot}$ even in the cases of including hadron-quark phase transitions, being consistent with the recent observations for maximum masses and radii of neutron stars by the NICER measurements and the other multimessenger data.

In the present paper, we consider the process of inverse double Compton (IDC) scattering in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using QED S-matrix formalism for the derivation of a cross-section of direct double Compton (DDC) and assuming detailed balance conditions we give an analytical expression for the cross-section of the IDC process. It is shown that at fixed energies of incident photons the inverse cross-section has no infra-red divergences and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular, by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result the physical frequency profile of the scattered radiation for direct as well as inverse double Compton processes is a function of both the intensity and line shape of the incident photon field.

Multi-fractional theories with integer-order derivatives are simple models of gravitational and matter fields living in spacetimes with variable Hausdorff and spectral dimension, originally proposed as descriptions of spacetimes arising in quantum gravity. In this paper, we pose the question of whether they can serve as an alternative to dark matter. We give a preliminary positive answer. We find the Poisson equation and the Newtonian potential of the multi-fractional theories with integer-order derivatives starting from their covariant modified Einstein's equations. We show that neither the theory $T_v$ with weighted derivatives in the extreme fractional limit nor the theory $T_q$ with $q$-derivatives fit the rotation curve of any of the galaxies NGC7814, NGC6503 and NGC3741 in the SPARC catalogue. The rotation curve of all three galaxies can be explained by purely geometric effects in the theory $T_v$ with weighted derivatives with small fractional corrections when the fractional exponent takes the special value $\alpha=4/3$, but only at large radii.

Simpson-Visser (SV) space-times are the simplest globally regular modifications of the Schwarzschild, Reissner-Nordstrom and other blak-hole solutions of general relativity. They smoothly interpolate between these black holes and traversable wormholes. After a brief presentation of the Schwarzschild-like and Reissner-Nordstrom-like SV geometries, including their Carter-Penrose diagrams, we show that any static, spherically symmetric SV metric can be obtained as an exact solution to the Einstein field equations sourced by a combination of a minimally coupled phantom scalar field with a nonzero potential $V(\phi)$ and a magnetic field in the framework of nonlinear electrodynamics with the Lagrangian $\mathcal {L(F)}$, $\mathcal{F} = F_{\mu\nu} F^{\mu\nu}$ (in standard notations). Explicit forms of $V(\phi)$ and $\mathcal {L(F)}$ are presented for the cases of Schwarzschild-like and Reissner-Nordstrom-like SV metrics.

We propose a new class of cosmological unified dark sector models called ``{\em Generalized Logotropic Models}". They depend on a free parameter $n$. The original logotropic model [P.H. Chavanis, Eur. Phys. J. Plus {\bf 130}, 130 (2015)] is a special case of our generalized model corresponding to $n=1$. In our scenario, the Universe is filled with a single fluid, a generalized logotropic dark fluid (GLDF), whose pressure $P$ includes higher order logarithmic terms of the rest-mass density $\rho_m$. The total energy density $\epsilon$ is the sum of the rest-mass energy density $\rho_m c^2$ and the internal energy density $u$ which play the role of dark matter energy density $\epsilon_m$ and dark energy density $\epsilon_{de}$, respectively. We investigate the cosmological behavior of the generalized logotropic models by focusing on the evolution of the energy density, scale factor, equation of state parameter, decceleration parameter and squared speed of sound. Low values of $n\le 3$ are favored. We also study the asymptotic behavior of the generalized logotropic models. In particular, we show that the model presents a phantom behavior and has three distinct ways of evolution depending on the value of $n$. For $n\le 2$, it leads to a little rip and for $n>2$ to a big rip. We predict the value of the big rip time as a function of $n$ without any free (undetermined) parameter.

In this paper we propose a new approach for the spontaneous breaking and restoration of the $SU(3)_C$ color symmetry in the framework of electroweak symmetry non-restoration (EWSNR) at high temperature, which provides an alternative approach for the Baryogenesis. Due to the exotic high vacuum expectation value (VEV) of the SM Higgs doublet in EWSNR, the color symmetry can be spontaneous broken succeeding the electroweak phase transition whenever there is a negative quartic coupling between the SM Higgs and a scalar color triplet. The color symmetry is then restored at low temperature as the VEV of SM Higgs evolving to small value. We show that the phase transitions related to color breaking and restoration can be first order, and the stochastic gravitational wave (GW) signals are smoking-gun of these processes. We demonstrate the possibility of detecting these GW signals in future GW experiments such as DECIGO and BBO.

The representation of magnetic field as a sum of a toroidal field and a poloidal field has not rarely been used in astrophysics, particularly in relation to stellar and planetary magnetism. In this representation, each toroidal field line lies entirely in a surface, which is named a toroidal field surface. The poloidal field is represented by the curl of another toroidal field and it threads a stack of toroidal field surfaces. If the toroidal field surfaces are either spheres or planes, the poloidal-toroidal (PT) representation is known to have a special property that the curl of a poloidal field is again a toroidal field . We name a PT representation with this property a standard PT representation while one without the property is called a generalized PT representation. In this paper, we have addressed the question whether there are other toroidal field surfaces allowing a standard PT representation than spheres and planes. We have proved that in a three dimensional Euclidean space, there can be no standard toroidal field surfaces other than spheres and planes, which render the curl of a poloidal field to be a toroidal field.

Context. The presence of a magnetic guide field induces several types of anisotropy in solar wind turbulence. The energy cascade rate between scales in the inertial range depends strongly on the direction of this magnetic guide field, splitting the energy cascade according to the parallel and perpendicular directions with respect to magnetic guide field. Aims. Using more than 2 years of Parker Solar Probe (PSP) observations, the isotropy and anisotropy energy cascade rates are investigated. The variance and spectral anisotropy ratios, the kinetic and magnetic energies and the both normalized cross-helicity and residual energy are studied. The connection between the heliocentric distance, the local temperature of the plasma and the energy cascade components is made. Methods. Using exact relations for fully developed magnetohydrodynamic (MHD) turbulence, the incompressible energy cascade rate is computed. In particular, using the isotropy and 2D and slab assumptions, the isotropic, perpendicular and parallel energy cascade rate components are estimated. Results. The variance anisotropy ratios, for both kinetic and magnetic fields, do not exhibit a dependence with respect to the heliocentric distance, $r$. While the kinetic spectral anisotropy ratio shows a dependence with $r$, the magnetic spectral anisotropy does not. A strong correlation between the isotropic and anisotropic energy cascade rates and the temperature is found. A clear dominance of the perpendicular cascades over the parallel cascades as PSP approaches to the Sun is observed. A dominant 2D cascade/geometry over the slab component in slow solar wind turbulence in the largest MHD scales is observed.

The direct detection of cosmic neutrino background (CNB) has been a longstanding challenge in particle physics, due to its low number density and tiny neutrino masses. In this work, we consider the spectrum of the CNB boosted by cosmic rays via the neutrino self-interaction, and calculate the event rate of the boosted CNB-plasmon scattering in term of the dielectric response, which accounts for in-medium screening effect of a condensed matter target. This can be taken as the new direct detection strategy for the CNB in complementary to the traditional one, which captures the CNB on a $\beta$-unstable nucleus. Our result shows that one can either see the event of the CNB for the exposure of per kg$\cdot$year, or puts a strong constraint on the neutrino self-interaction. We further explore the background induced by the sub-MeV dark matter and the boosted super-light dark matter.