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In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create a new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA-2019-BLG-421/KMT-2019-BLG-2991. The anomalous signal can be explained by either a planet around the lens star or the orbital motion of the source star. For the planetary interpretation, despite many degenerate solutions, the planet is most likely to be a Jovian planet orbiting an M or K dwarf, which is a typical microlensing planet. The discovery proves that the project can indeed increase the sensitivity of historic events and find previously undiscovered signals. [ABSTRACT FROM AUTHOR]

We present relativistic magnetohydrodynamic modelling of jets running into hydrostatic, spherically symmetric cluster atmospheres. For the first time in a numerical simulation, we present model cluster atmospheres based upon the universal pressure profile (UPP), incorporating a temperature profile for a 'typical' self-similar atmosphere described by only one parameter – M 500. We explore a comprehensive range of realistic atmospheres and jet powers and derive dynamic, energetic, and polarimetric data which provide insight into what we should expect of future high-resolution studies of AGN outflows. From the simulated synchrotron emission maps which include Doppler beaming we find sidedness distributions that agree well with observations. We replicated a number of findings from our previous work, such as higher power jets inflating larger aspect-ratio lobes, and the cluster environment impacting the distribution of energy between the lobe and shocked regions. Comparing UPP and β-profiles we find that the cluster model chosen results in a different morphology for the resultant lobes with the UPP more able to clear lobe material from the core; and that these different atmospheres influence the ratio between the various forms of energy in the fully developed lobes. This work also highlights the key role played by Kelvin–Helmholtz instabilities in the formation of realistic lobe aspect ratios. Our simulations point to the need for additional lobe-widening mechanisms at high jet powers, for example jet precession. Given that the UPP is our most representative general cluster atmosphere, these numerical simulations represent the most realistic models yet for spherically symmetric atmospheres. [ABSTRACT FROM AUTHOR]

We derive a corrected analytical solution for the propagation and enhanced phase mixing of torsional Alfvén waves, in a potential magnetic field with exponentially divergent field lines, embedded in a stratified solar corona. Further we develop a code named TAWAS that calculates the analytic solution describing torsional Alfvén waves using idl software language. We then use TAWAS to demonstrate that both our correction to the analytic solution and the inclusion of wave reflection have a significant impact on Alfvén wave damping. We continue to utilize TAWAS by performing a parameter study in order to identify the conditions under which enhanced phase mixing is strongest. We find that phase mixing is the strongest for high frequency Alfvén waves in magnetic fields with highly divergent field lines and without density stratification. We then present a finite difference solver, Wigglewave , which solves the linearized evolution equations for the system directly. Comparing solutions from TAWAS and Wigglewave we see that our analytical solution is accurate within the limits of the WKB approximation but under-reports the wave damping, caused by enhanced phase mixing, beyond the WKB limit. Both TAWAS and Wigglewave solve the linearized governing equations and not the complete non-linear magnetohydrodynamics (MHD) equations. Paper II will consider simulations that solve the full MHD equations including important non-linear effects. [ABSTRACT FROM AUTHOR]

One of the fundamental goals of modern astrophysics is to estimate the physical parameters of galaxies. We present a hierarchical Bayesian model to compute age maps from images in the H α line (taken with Taurus tunable filter, TTF), ultraviolet band (GALEX far UV, FUV), and infrared bands (Spitzer 24, 70, and 160 |$\mu$| m). We present the burst ages for young stellar populations in a sample of nearby and nearly face-on galaxies. The H α to FUV flux ratio is a good relative indicator of the very recent star formation history (SFH). As a nascent star-forming region evolves, the H α line emission declines earlier than the UV continuum, leading to a decrease in the H α/FUV ratio. Using star-forming galaxy models, sampled with a probabilistic formalism, and allowing for a variable fraction of ionizing photons in the clusters, we obtain the corresponding theoretical ratio H α/FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions. We take into account the mean uncertainties and the interrelationships between parameters when computing H α/FUV. We propose a Bayesian hierarchical model where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF) from the observed data (the observed flux ratios H α/FUV). The joint distribution of the parameters is described through independent and identically distributed (i.i.d.) random variables generated through MCMC (Markov Chain Monte Carlo) techniques. [ABSTRACT FROM AUTHOR]

The H2O Southern Galactic Plane Survey (HOPS) has mapped 100 deg² of the Galactic plane for water masers and thermal molecular line emission using the 22 m Mopra telescope. We describe the automated spectral-line fitting pipelines used to determine the properties of emission detected in HOPS data cubes, and use these to derive the physical and kinematic properties of gas in the survey. A combination of the angular resolution, sensitivity, velocity resolution and high critical density of lines targeted make the HOPS data cubes ideally suited to finding precursor clouds to the most massive and dense stellar clusters in the Galaxy. We compile a list of the most massive HOPS ammonia regions and investigate whether any may be young massive cluster progenitor gas clouds. HOPS is also ideally suited to trace the flows of dense gas in the Galactic Centre. We find the kinematic structure of gas within the inner 500 pc of the Galaxy is consistent with recent predictions for the dynamical evolution of gas flows in the centre of the Milky Way. We confirm a recent finding that the dense gas in the inner 100 pc has an oscillatory kinematic structure with characteristic length-scale of 20 pc, and also identify similar oscillatory kinematic structure in the gas at radii larger than 100 pc. Finally, we make all of the above fits and the remaining HOPS data cubes across the 100 deg² of the survey available to the community. [ABSTRACT FROM AUTHOR]

The origin of the low-luminosity radio emission in radio-quiet active galactic nucleus, is unknown. The detection of a positive correlation between the radio and X-ray emission would imply a jet-like origin, similar to that seen in 'hard-state' X-ray binary systems. In our previous work, we found no believable radio variability in the well-known X-ray bright Seyfert 1 galaxy NGC 4051, despite large amplitude X-ray variability. In this study, we have carefully re-analysed radio and X-ray observations using the same methods as our previous work; we again find no evidence for core radio variability. In direct contrast to our findings, another study claim significant radio variability and a distinctive anticorrelation between radio and X-ray data for the same source. The other study report only integral flux values and do not consider the effect of the changing array on the synthesized beam. In both our studies of NGC 4051, we have taken great care to account for the effect that the changing beam size has on the measured radio flux and as a result we are confident that our method gives more accurate values for the intrinsic core radio flux. However, the lack of radio variability we find is hard to reconcile because radio images of NGC 4051 do show jet-like structure. We suggest that the radio structures observed are likely the result of a previous period of higher radio activity and that the current level of radio emission from a compact nuclear jet is low. [ABSTRACT FROM AUTHOR]

We have carried out mapping observations of molecular emission lines of HC3N and CH3OH toward two massive cluster-forming clumps, NGC 2264-C and NGC 2264-D, using the Nobeyama 45-m radio telescope. We derive an I (HC3N)/ I (CH3OH) integrated intensity ratio map, showing a higher value at clumps including 2MASS (Two Micron All Sky Survey) point sources at the northern part of NGC 2264-D. Possible interpretations of the I (HC3N)/ I (CH3OH) ratio are discussed. We have also observed molecular emission lines from CCS and N2H+ toward five positions in each clump. We investigate the N (N2H+)/ N (CCS) and N (N2H+)/ N (HC3N) column density ratios among the ten positions in order to test whether they can be used as chemical evolutionary indicators in these clumps. The N (N2H+)/ N (CCS) ratio shows a very high value toward a bright embedded IR source (IRS1), whereas the N (N2H+)/ N (HC3N) ratio at IRS1 is comparable with those at the other positions. These results suggest that ultraviolet radiation affects the chemistry around IRS1. We find that there are positive correlations between these column density ratios and the excitation temperatures of N2H+, which implies the chemical evolution of clumps. These chemical evolutionary indicators likely reflect the combination of evolution along the filamentary structure and evolution of each clump. [ABSTRACT FROM AUTHOR]

We study the distribution and evolution of the stellar mass and the star formation rate (SFR) of the brightest group galaxies (BGGs) over 0.04 < z < 1.3 using a large sample of 407 X-ray galaxy groups selected from the COSMOS, AEGIS, and XMM-LSS fields. We compare our results with predictions from the semi-analytic models based on the Millennium simulation. In contrast to model predictions, we find that, as the Universe evolves, the stellar mass distribution evolves towards a normal distribution. This distribution tends to skew to low-mass BGGs at all redshifts implying the presence of a star-forming population of the BGGs with MS ∼ 1010.5 M⊙ which results in the shape of the stellar mass distribution deviating from a normal distribution. In agreement with the models and previous studies, we find that the mean stellar mass of BGGs grows with time by a factor of ∼2 between z = 1.3 and z = 0.1, however, the significant growth occurs above z = 0.4. The BGGs are not entirely a dormant population of galaxies, as low-mass BGGs in low-mass haloes are more active in forming stars than the BGGs in more massive haloes, over the same redshift range. We find that the average SFR of the BGGs evolves steeply with redshift and fraction of the passive BGGs increases as a function of increasing stellar mass and halo mass. Finally, we show that the specific SFR of the BGGs within haloes with M200 ≤ 1013.4 M⊙ decreases with increasing halo mass at z < 0.4. [ABSTRACT FROM AUTHOR]

Paper XIII of this series presented radial velocities for 406 stars in certain of the Clube Selected Areas, a set of areas systematically arranged in Galactic coordinates. We now complete the survey by providing the radial velocities, mostly obtained at the European Southern Observatory (ESO), of 625 stars in the six southernmost Areas. Each star has been measured at least twice; the mean velocities have standard errors typically of 0.2–0.3 km s−1. Additional observations made from Haute-Provence of many of the stars that are observable from there have helped to identify, and in some instances to characterize, the ∼70 spectroscopic binaries discovered in this programme. The final results of the programme, complementing those given in table 3 of Paper XIII, are summarized in Table 12 , which presents the mean velocities and velocity dispersions in the six southern Areas. It is noted that the difference between Paper XIII and this one as regards the provenance of the radial velocities has led to a small difference in zero-points, which is discussed in Section 3 and needs to be taken into account in any analysis of the combined data. [ABSTRACT FROM AUTHOR]

Three of the six southern Clube Areas that were mainly observed at the European Southern Observatory and whose principal results are given in Paper XVI are marginally observable from Haute-Provence. Additional measurements obtained on several observing runs there enabled orbits to be determined (in most cases rather poorly, owing to the paucity of data) for 30 of the newly discovered spectroscopic-binary systems; they are presented in this paper. One object, HD 33978, seems to be of such significance that special efforts have been made, largely by Drs J. Andersen and H. Lindgren, to obtain additional radial-velocity measurements. That system is shown to be a double-lined binary with a period of only 10.67 d despite one of its components being a late-type giant. The giant star has a projected rotational velocity of almost 40 km s−1; it could be expected to exhibit RS CVn-type photometric variations, which have not yet been observed, in addition to the ‘ellipsoidal variation’, discovered by Hipparcos, which occasioned its designation as VV Lep. [ABSTRACT FROM AUTHOR]

We isolate the spectrum of the secondary component of the composite-binary system 93 Leonis by spectrum subtraction, classify it, and measure the mass ratio of the system. An accurate visual orbit and a well-determined parallax provide reliable measurements of orbital inclination and distance, enabling us to determine precisely the individual masses and other stellar parameters. The primary star is of type ∼G7 III, and the secondary is a rapidly rotating star of type A7 IV. Our photographic spectra at 10 Å mm-1 are invaluable for accurate spectral classification in such cases. By combining 23 measurements of the secondary's velocity with 102 of the primary's and deriving a double-lined orbit, we determine the mass ratio (q = M1/M2) of 93 Leo to be 1.09 ± 0.04. The same value is derived by cross-correlating high-dispersion spectra of 93 Leo B extracted from opposite nodal phases. That value of q is consonant with previous research, but its precision is considerably improved. We show that random errors arising from the cross-correlation of broad, weak features constitute a natural limit to that precision. The derived masses of M1 = 2.2 M[This symbol cannot be presented in ASCII format], M2 = 2.0 M[This symbol cannot be presented in ASCII format] for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log Teff, log L) plane. The giant is almost certainly on its first ascent of the red giant branch, and the dwarf has evolved significantly from the main sequence. The stars fit an isochrone for log(age) = 8.95, about 0.9 Gyr. Metallicity near to solar is suggested by the close correspondence between the component spectra and those of the respective solar-abundance standards. The primary in 93 Leo displays a marked level of chromospheric activity. By combining our high-dispersion spectra we are able to isolate emission in the Ca II K line. The chromospheric material has a small infall velocity, giving rise to a disc-averaged redshift of about 4 km s-1, and an unchanging velocity profile which can be attributed to a large number of small, active events like prominences across the surface. While we can say that there was no perceptible change in the emission strength over an interval of 4 months, we have not made systematic observations to monitor its long-term stability. We contrast the components of 93 Leo with those of α Equ, whose analysis was the subject of Paper 11 in this series. The primary components are very similar, but the two secondary components are extremely different in nature: whereas 93 Leo B is a broad-lined, apparently normal A star, the secondary of α Equ is a sharp-lined Am star of type ∼kA3hA4mA9. We question why that should be, and recommend that a greater emphasis be placed on extracting accurate stellar parameters from the components of spectroscopic binaries as a means towards a better understanding of the vagaries of stellar evolution. 93 Leo has a 9-mag visual companion which appears to be a physical member of the system and to be a single-lined spectroscopic binary with a period of the order of a century. [ABSTRACT FROM AUTHOR]

The well-known cluster of galaxies ZwCl0024+1652 at z ∼ 0.4 lacks an in-depth morphological classification of its central region. While previous studies provide a visual classification of a patched area, we used the public code called gal axy S upport V ector M achine (galsvm) and HST /ACS data as well as the WFP2 master catalogue to automatically classify all cluster members up to 1 Mpc. galsvm analyses galaxy morphologies through support vector machine (SVM). From the 231 cluster galaxies, we classified 97 as early types (ETs) and 83 as late types (LTs). The remaining 51 stayed unclassified (or undecided). By cross-matching our results with the existing visual classification, we found an agreement of 81 per cent. In addition to previous Zwcl0024 morphological classifications, 121 of our galaxies were classified for the first time in this work. In addition, we tested the location of classified galaxies on the standard morphological diagrams, colour–colour and colour–magnitude diagrams. Out of all cluster members, ∼20 per cent are emission-line galaxies, taking into account previous GLACE results. We have verified that the ET fraction is slightly higher near the cluster core and decreases with the clustercentric distance, while the opposite trend has been observed for LT galaxies. We found a higher fraction of ETs (54  per cent) than LTs (46  per cent) throughout the analysed central region, as expected. In addition, we analysed the correlation between the five morphological parameters (Abraham concentration, Bershady–Concelice concentration, asymmetry, Gini, and M20 moment of light) and the clustercentric distance, without finding a clear trend. Finally, as a result of our work, the morphological catalogue of 231 galaxies containing all the measured parameters and the final classification is available in the electronic form of this paper. [ABSTRACT FROM AUTHOR]

HR 3222 is a late-type giant star that has long been known as a spectroscopic binary. A single-lined orbit is readily found; it has a period of 955 d and an eccentricity of 0.33. The spectrum is noticeably composite, especially at short wavelengths; radial-velocity traces show a weak secondary dip that is broadened by a rotational velocity of 18 km s−1. We employ high-dispersion spectroscopy and uncover the secondary spectrum by subtracting from the observed composite one the spectrum of the K0 giant β Gem; the residue is a metallic-line star of type kA8hF2mF4, and measurements of its wavelength displacement from the primary spectrum give a more reliable radial velocity for that component than seems achievable from radial-velocity traces. The mass ratio is . The stars can both be placed on an evolutionary track corresponding to an age of 1.4 Gyr. The fact that the secondary component is a metallic-line star cannot be attributed to the result of tidal effects in this binary system. [ABSTRACT FROM AUTHOR]

We analyse 81 optical spectra of the composite-spectrum binary HD 216572, and show that the primary is a cool giant of type G8 III while the secondary is a double-lined binary consisting of two nearly identical B9 dwarfs in a 1.18-d orbit. The inner system undergoes partial eclipses, whose photometry we model to derive the physical parameters of both secondary stars. The outer system does not eclipse. We isolate the combined spectrum of the secondary by spectral subtraction, and from 48 separate radial-velocity measurements of both secondary components we obtain a triple-lined orbit solution from which we determine the individual masses of all three stars and the inclinations of both the inner and the outer orbits. The period of the outer system is 55 d, which is surprisingly short for a giant star, and our detection of small but non-negligible amounts of variable chromospheric emission in the Ca ii K line is not unlike that detected in other systems with comparably short periods. The secondary components are in a circular orbit and are rotating at about ; although their surface-to-surface separation is only the stars are not noticeably distorted geometrically by such close proximity. All three stars appear to be in synchronous rotation in their respective orbits. We derive fairly accurate Hertzsprung–Russell diagram positions for all three stars and compare them to evolutionary tracks calculated for the respective stellar masses, but cannot reconcile the age of the cool giant with that of the B stars. [ABSTRACT FROM AUTHOR]

HR 1129 is a 4.8-mag star in the constellation Camelopardus, strangely (in view of its brightness) lacking a constellation designation. It has long been known to exhibit a composite spectrum consisting of a late-type primary and an early-type secondary. The radial velocity of the primary is easily measured, and was announced as variable nearly 100 years ago. A preliminary orbit with a period of 6150 d was given for it by one of the present authors in 1990; our new value is 6124 ± 3 d. The system has been resolved by speckle interferometry, but has not been measured systematically by that technique. The spectrum of the primary is found to be very similar to that of α Aqr (G2 Ib), although the parallax shows HR 1129 to be somewhat less luminous. The secondary spectrum has been isolated by subtraction and has proved to be that of a B7 star that is somewhat above the main sequence and may itself already be a giant. We present a comprehensive discussion of the spectra of both stars, and deduce that the system is considerably reddened: . By incorporating 25 measurements of the radial velocity of the secondary, we calculate a double-lined orbit solution which gives the mass ratio for the components as 1.109 ± 0.022; we determine individual masses of (primary) and (secondary). The orbit is viewed at an inclination of ∼ 87°, but there are no eclipses. However, around the phases of conjunction the Mg ii doublet near λ2800 Å, as seen in IUE spectra, exhibits evidence of two circumstellar absorption systems, which we interpret as a wind from the cool giant and a static shell around it. Substantial 100-μm emission recorded by IRAS points to the presence of warm circumbinary dust enveloping the system, and is likely to have originated in the stellar wind. [ABSTRACT FROM AUTHOR]

The spectrum of the secondary component of the bright composite-binary system α Equ, whose visual orbit is already known accurately, is isolated by the method of spectrum subtraction and classified accurately for the first time. The primary is a normal giant of type ∼G7, while the secondary is an Am star of type ∼kA3hA4mA9. The system's mass ratio, q, is determined to be 1.15±0.03 from measurements of the relative radial-velocity displacements between the components. Random and systematic errors in q are evaluated on the basis of the scatter of results derived from sets of spectra obtained from three different sources, and from tests conducted on independent versions of the secondary's spectrum. A spectroscopic analysis of a composite system such as α Equ is strongly challenged by the blending of a great many lines that are common to both spectra. Even when the primary spectrum is thought to have been subtracted adequately, a seemingly unavoidable ghost spectrum of faint residuals can bias wavelength measurements of the secondary's lines. That blending was the principal cause of a history of puzzling and discrepant measurements of q in α Equ. The derived masses of M[sub 1]=2.3 M[sub ⊙], M[sub 2]=2.0 M[sub ⊙] for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log T[sub eff], log L) plane; the stellar points fit a single isochrone (for 0.74 Gyr). Both components are found to be slightly over-luminous compared to normal for their supposed luminosity classes. The giant appears to be commencing its first ascent of the red-giant branch. The dwarf has started to evolve away from the main sequence; its M[sub V] is similar to that of a sub-giant. [ABSTRACT FROM AUTHOR]

Investigates the separation of spectra of the individual components of HR 2030. Luminosity derived from spectra; Strength of the interstellar K line; Existence of a major non-uniformity of the surface of the primary star.

ABSTRACTHD 4615/6 is a seventh-magnitude composite-spectrum binary system. It has an orbit of moderate eccentricity (0.43) and a period of 303 d. The system is of course unresolved at the telescope, but we are able to separate the spectra of the component stars and show that they are of types K2 III (HD 4615) and A2.5 V (HD 4616), with a mass ratio (giant:dwarf) of approximately 1.25. The orbital inclination is high, but there are no eclipses. The maximum apparent angular separation is expected to be about 0.009 arcsec. Neither star's rotation is synchronized with the orbital motion. [ABSTRACT FROM AUTHOR]

Multiconjugate adaptive optics (MCAO) stands as an essential technology for the development of future large-aperture solar telescopes. Its primary objective is to empower telescopes to achieve nearly diffraction-limited performance while substantially extending the correction field of view (FoV). Conventional solar MCAO relies on the combination of adaptive optics and high-altitude correction (AO + HAC) modules for multiconjugate correction. However, this architectural approach excels in correction performance primarily at the central position, with performance deteriorating as one moves farther from the centre. Consequently, it results in poor consistency of FoV correction performance. To address these limitations, a new architectural approach was introduced, which combines ground layer AO with HAC (GLAO + HAC). Preliminary results have shown that, compared to AO + HAC, this approach significantly enhances FoV correction uniformity. Building upon these initial findings, this paper undertakes a more extensive research of the GLAO + HAC system. Its objective is to compare various solar MCAO system architectures, including AO + HAC, GLAO + HAC, and general MCAO, to finally propose optimization tailored to GLAO + HAC. Through this analysis, the paper conducts the performance comparison between GLAO + HAC and general MCAO. It underscores that, under equivalent configuration parameters, the differences between these two systems are marginal. However, due to the advantage of the independent control of dual correction modules in GLAO + HAC, it can introduce an optimization strategy by increasing the number of subapertures at the cost of reducing the GLAO guide star sensing FoV. Finally, the results of this strategy demonstrate an obvious enhancement in performance and FoV correction consistency within the GLAO + HAC system. [ABSTRACT FROM AUTHOR]

When starting an N -body simulation of an isolated galaxy, it is desirable to select particles from a distribution function to ensure that the model is in equilibrium. Random sampling from a DF is widely used, but results in a set of particles that differs by shot noise from that intended. This paper presents a method to reduce sampling noise that has been developed by the author in a many collaborations over a number of years. The technique has been partly described in past papers, though the ideas have not previously been gathered together, nor have its advantages been clearly demonstrated in past work. Of course, sampling errors can also be reduced by a brute force increase in the number of particles, but methods to achieve the same effect with fewer particles have obvious advantages. Here we not only describe the method, but also present three sets of simulations to illustrate the practical advantages of reducing sampling error. The improvements are not dramatic, but are clearly worth having. [ABSTRACT FROM AUTHOR]

Observations of real galaxies as well as N -body simulations often indicate the presence of multiple pattern speeds in the disc of a barred spiral galaxy. In this paper we use an accurate frequency extraction algorithm (NAFF) to determine the pattern speeds in an N -body model simulation of a secularly evolving barred spiral galaxy. Then, we compute the manifold spirals under multiple pattern speeds using the algorithm proposed in a previous paper by Efthymiopoulos et al. Our main new results are: (i) We demonstrate that precise frequency extraction algorithms as NAFF allow for a determination of pattern speeds in time windows of length much shorter than the one required by the traditional time-Fourier spectrum of the m = 2 mode. This is particularly convenient in cases where the pattern speeds slowly change in time due to secular evolution in the disc, and/or, the different modes spatially overlap in the disc. (ii) Once we get the frequencies, we compute the approximate gravitational potential, and the manifolds (iii) We show that the observed structures formed by the spiral arms in the simulation (change of form, formation of 'bridges', etc.) can be modelled by manifolds, and that this is consistent with the fact that the bar and spirals have different pattern speeds. [ABSTRACT FROM AUTHOR]

In the Solar system, there exist many non-gravitational perturbations for co-orbital objects, such as the solar radiation pressure, Yarkovsky effect, and so forth. Their effects play important roles in the dynamics of co-orbital objects as they lead to long-term perturbations accumulating. The motivation of this paper is to investigate the general mechanism of the non-gravitational force on the co-orbital motion in the circular restricted three-body problem. We propose an effective method for perturbed co-orbital motions by analysing the locus of the co-orbital objects in a two-dimensional map. Several expressions derived uncover how the non-gravitational force acts on orbital parameters. Taking the Sun–Jupiter system as an example, we implement numerical computations to demonstrate the validity of our results. Numerical computation shows that most of loci of co-orbital motions are in agreement with our conclusions. Some interesting phenomena of perturbed co-orbital motion, such as the co-orbital transition and escape, are found and explained. The results obtained from this paper provide an efficient approach to analyse the evolution of perturbed co-orbital motions. [ABSTRACT FROM AUTHOR]

At present, there is no doubt that relativistic jets observed in active galactic nuclei pass from highly magnetized to weakly magnetized stage, which is observed as a break in the dependence on their width |$d_{\rm jet}(z)$| on the distance z to the central engine. In this paper, we discuss the possibility of observing another break, which should be located at shorter distances. The position of this break can be associated with the region of formation of the dense central core near the jet axis which was predicted both analytically and numerically more than a decade ago, but has not yet received sufficient attention. In this case, the observed width should be determined by the dense core, and not by the total transverse size of the jet. The calculations carried out in this paper, which took into account both the transverse electromagnetic structure of the jet and the change in the spectrum of emitting particles along its axis, indeed showed such behaviour. We also found the evidence of the predicted break in the jet expansion profile using stacked 15 GHz Very Large Baseline Array (VLBA) image of M87 radio jet and constrain the light cylinder radius. [ABSTRACT FROM AUTHOR]

Light emission in the first hours and days following core-collapse supernovae (SNe) is dominated by the escape of photons from the expanding shock-heated envelope. In a preceding paper, Paper I, we provided a simple analytic description of the time-dependent luminosity, L , and colour temperature, T col, valid up to H recombination (T ≈ 0.7 eV), for explosions of red supergiants with convective polytropic envelopes without significant circumstellar medium (CSM). The analytic description was calibrated against 'grey' (frequency-independent) photon diffusion numeric calculations. Here, we present the results of a large set of 1D multigroup (frequency-dependent) calculations, for a wide range of progenitor parameters (mass, radius, core/envelope mass ratios, metalicity) and explosion energies, using opacity tables that we constructed (and made publicly available), including the contributions of bound–bound and bound–free transitions. We provide an analytic description of the small, |${\simeq}10\ \hbox{per cent}$| deviations of the spectrum from blackbody at low frequencies, h ν < 3 T col, and an improved (over Paper I) description of 'line dampening' for h ν > 3 T col. We show that the effects of deviations from initial polytropic density distribution are small, and so are the effects of 'expansion opacity' and deviations from LTE ionization and excitation (within our model assumptions). A recent study of a large set of type II SN observations finds that our model accounts well for the early multiband data of more than 50 per cent of observed SNe (the others are likely affected by thick CSM), enabling the inference of progenitor properties, explosion velocity, and relative extinction. [ABSTRACT FROM AUTHOR]

One challenge for applying current weak lensing analysis tools to the Nancy Grace Roman Space Telescope is that individual images will be undersampled. Our companion paper presented an initial application of Imcom – an algorithm that builds an optimal mapping from input to output pixels to reconstruct a fully sampled combined image – on the Roman image simulations. In this paper, we measure the output noise power spectra, identify the sources of the major features in the power spectra, and show that simple analytic models that ignore sampling effects underestimate the power spectra of the coadded noise images. We compute the moments of both idealized injected stars and fully simulated stars in the coadded images, and their one- and two-point statistics. We show that the idealized injected stars have root-mean-square ellipticity errors (1–6) × 10−4 per component depending on the band; the correlation functions are ≥2 orders of magnitude below requirements, indicating that the image combination step itself is using a small fraction of the overall Roman second moment error budget, although the fourth moments are larger and warrant further investigation. The stars in the simulated sky images, which include blending and chromaticity effects, have correlation functions near the requirement level (and below the requirement level in a wide-band image constructed by stacking all four filters). We evaluate the noise-induced biases in the ellipticities of injected stars, and explain the resulting trends with an analytical model. We conclude by enumerating the next steps in developing an image coaddition pipeline for Roman. [ABSTRACT FROM AUTHOR]

ω Centauri is considered the most massive globular cluster of the Milky Way and likely the former nuclear star cluster of a Galaxy accreted by the Milky Way. It is speculated to contain an intermediate-mass black hole (IMBH) from several dynamical models. However, uncertainties regarding the location of the cluster centre or the retention of stellar remnants limit the robustness of the IMBH detections reported so far. In this paper, we derive and study the stellar kinematics from the highest-resolution spectroscopic data yet, using the Multi Unit Spectroscopic Explorer (MUSE) in the narrow field mode and wide field mode. Our exceptional data near the centre reveal for the first time that stars within the inner 20 arcsec (∼0.5 pc) counter-rotate relative to the bulk rotation of the cluster. Using this data set, we measure the rotation and line-of-sight velocity dispersion profile out to 120 arcsec with different centres proposed in the literature. We find that the velocity dispersion profiles using different centres match well with those previously published. Based on the counter–rotation, we determine a kinematic centre and look for any signs of an IMBH using the high-velocity stars close to the centre. We do not find any significant outliers >60 km s−1 within the central 20 arcsec, consistent with no IMBH being present at the centre of ω Centauri. A detailed analysis of Jeans' modelling of the putative IMBH will be presented in the next paper of the series. [ABSTRACT FROM AUTHOR]

Stellar coronal sources have been observed in the past not only for their astrophysical interest in the field of binary system evolution and interaction but also for their invaluable roles as benchmarks for plasma spectral models and as calibration sources for high resolution spectroscopic X-ray instruments. These include the gratings on-board Chandra and XMM-Newton , as well as the new generation of high resolution capable-detectors recently flown on-board XRISM and planned for the future also onboard the Athena and the LEM missions. In our previous paper exploiting Chandra /HETG observations of the prototypical coronal source Capella, it has been shown that the centroid energies of the many X-ray emission lines detected in the spectrum of this object change as a function of time due to the Doppler modulation within the binary. This is an effect that needs to be corrected while performing calibrations of high-resolution X-ray instruments. In this paper, we extend our previous work on Capella to other known stellar coronal sources that have been observed with the Chandra /HETG (11 objects in total). We measure in several objects clear trends in the velocity shifts along the orbit of the primary star, meaning that in these sources one of the two star components is largely dominating the high energy emission. In a number of systems the trend in the velocity shift is not obvious. This can be ascribed to the fact that both stellar components contribute significantly to the X-ray emission. [ABSTRACT FROM AUTHOR]

The properties of galaxies in low-density regions of the universe suggest an interplay between galaxy formation and environment. However, the specific reason why this particular large-scale environment influences the evolution of galaxies remains unclear. This paper examines the properties and evolutionary paths of galaxies within cosmic voids using the Illustris TNG300 simulation. The population of void galaxies at z = 0 has a higher star formation rate, a smaller stellar-to-halo-mass ratio, higher gas metallicity, and lower stellar metallicity in comparison with non-void galaxies at fixed stellar mass. Our analysis shows that these differences are mainly due to the characteristics of galaxies classified as satellites, for which the largest differences between void and non-void samples are found. Although the mean number of mergers is similar between void and non-void samples at a fixed stellar mass, void galaxies tend to experience mergers at later times, resulting in a more recent accumulation of accreted stellar mass. While the mean net accreted mass is comparable for high-mass galaxies, low-mass void galaxies tend to exhibit higher fractions of accreted stars than non-void galaxies. This finding challenges the common notion that void galaxies predominantly experience growth with infrequent mergers or interactions. With this paper, we also publicly release our void catalogue as part of the IllustrisTNG project. [ABSTRACT FROM AUTHOR]

Shock boundary layers are regions bounded by a shock wave on the one side and tangential discontinuity on the other side. These boundary layers are commonly observed in astrophysics. For example, they exist in the regions of the interaction of the stellar winds with the surrounding interstellar medium. Additionally, the shock layers (SLs) are often penetrated by the flows of interstellar atoms, as, for instance, in the astrospheres of the stars embedded by the partially ionized interstellar clouds. This paper presents a simple toy model of an SL that aims to qualitatively describe the influence of charge exchange with interstellar hydrogen atoms on the plasma flow in astrospheric SLs. To clearly explore this effect, magnetic fields are neglected, and the geometry is kept as simple as possible. The model explains why the cooling of plasma due to charge exchange in the inner heliosheath leads to an increase in plasma density in front of the heliopause. It also demonstrates that the source of momentum causes changes in the pressure profile within the SL. The paper also discusses the decrease in plasma density near the astropause in the outer SL in the case of layer heating, which is particularly relevant in light of the Voyager measurements in the heliospheric SL. [ABSTRACT FROM AUTHOR]

The upcoming Nancy Grace Roman Space Telescope will carry out a wide-area survey in the near-infrared. A key science objective is the measurement of cosmic structure via weak gravitational lensing. Roman data will be undersampled, which introduces new challenges in the measurement of source galaxy shapes; a potential solution is to use linear algebra-based coaddition techniques such as imcom that combine multiple undersampled images to produce a single oversampled output mosaic with a desired 'target' point spread function (PSF). We present here an initial application of imcom to 0.64 square degrees of simulated Roman data, based on the Roman branch of the Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC) Data Challenge 2 (DC2) simulation. We show that imcom runs successfully on simulated data that includes features such as plate scale distortions, chip gaps, detector defects, and cosmic ray masks. We simultaneously propagate grids of injected sources and simulated noise fields as well as the full simulation. We quantify the residual deviations of the PSF from the target (the 'leakage'), as well as noise properties of the output images; we discuss how the overall tiling pattern as well as Moiré patterns appear in the final leakage and noise maps. We include appendices on interpolation algorithms and the interaction of undersampling with image processing operations that may be of broader applicability. The companion paper ('Paper II') explores the implications for weak lensing analyses. [ABSTRACT FROM AUTHOR]

In a previous paper we have suggested that two-armed disc deformation excites two- or three-armed disco-seismic c-mode oscillations by three-mode resonant coupling processes. This might be one of possible causes of the QPOs observed in low-mass X-ray binaries and in black-hole sources. In another previous paper we showed that for these c-mode oscillations to be time periodic, they must satisfy some boundary conditions (regularity conditions) at the sonic point where accretion speed becomes transonic. In this paper we show that these boundary conditions acts so as to dampen the oscillations. This might be favourable for explaining why the QPOs are quasi-periodic. [ABSTRACT FROM AUTHOR]

In this paper, we continue our analysis of the chaotic four-body problem and our study of binary–binary interactions in star clusters. We present a general ansatz-based analytical treatment using statistical mechanics, where each outcome of the four-body problem is regarded as some variation of the three-body problem. For example, when two single stars are produced (the 2 + 1 + 1 outcome), each ejection event is modelled as its own three-body interaction by assuming that the ejections are well separated in time. This is a generalization of the approach adopted in Paper I, based on the density-of-states formalism. There are three possible outcomes for the four-body problem with negative total energies: 2 + 2, 2 + 1 + 1, and 3 + 1. For each outcome, we apply an ansatz-based approach to deriving analytical distribution functions that describe the properties of the products of chaotic four-body interactions involving point particles. To test our theoretical distributions, we perform a set of scattering simulations in the equal-mass point-particle limit using FEWBODY , where we vary the initial ratio of binary semimajor axes. We compare our final theoretical distributions to the simulations for each particular scenario, finding consistently good agreement between the two. The highlights of our results include that binary–binary scatterings act to systematically destroy binaries producing instead a binary and two ejected stars (when the initial binary semimajor axes are similar) or a stable triple (when the initial semimajor axes are very different). The 2 + 2 outcome produces the widest binaries, and the 2 + 1 + 1 outcome produces the most compact binaries. [ABSTRACT FROM AUTHOR]

This document is a correction to a previously published paper titled "Binary black hole mergers from population III stars: uncertainties from star formation and binary star properties." The authors discovered a minor bug in the code used to produce the results shown in various figures. The correction provides the updated figures and lists the changes made to the published version. The authors state that the bug did not significantly affect the results and conclusions of the paper. The main data presented in the paper are publicly available on Zenodo and GitLab. [Extracted from the article]

We identify a source (J1507+3013) with an extended diffuse radio emission around an elliptical galaxy from the Very Large Array (VLA) Faint Images of Radio Sky at Twenty-cm (FIRST) survey. J1507+3013 possesses a morphology similar to the recently identified circular, low-surface-brightness, edge-brightened radio sources commonly known as odd radio circles (ORCs). Such diffuse emissions, as reported in this paper, are also found in mini-haloes and fossil radio galaxies, but the results presented here do not match the properties of mini-haloes or of fossil radio galaxies. The extended emission observed in J1507+3013 around an elliptical galaxy is a very rare class of diffuse emission that is unlike any previously known class of diffuse emission. The extended diffuse emission of J1507+3013 is also detected in the Low Frequency Array (LOFAR) at 144 MHz. J1507+3013 is hosted by an optical galaxy near the geometrical centre of the structure with a photometric redshift of z = 0.079. The physical extent of J1507+3013 is approximately 68 kpc, with a peak-to-peak angular size of 44 arcsec. It shows significantly higher flux densities compared with previously discovered ORCs. The spectral index of J1507+3013 varies between −0.90 and −1.4 in different regions of the diffuse structure, which is comparable to the case for previously discovered ORCs but less steep than for mini-haloes and fossil radio galaxies. If we consider J1507+3013 as a candidate ORC, then this would be the closest and most luminous ORC discovered so far. This paper describes the radio, spectral, and optical/IR properties of J1507+3013 in order to study the nature of this source. [ABSTRACT FROM AUTHOR]

The effect of angular momentum on galaxy formation and evolution has been studied for several decades. Our recent two papers using IllustrisTNG-100 simulation have revealed the acquisition path of the angular momentum from large-scale environment (satellites within hundreds of kpc) through the circumgalactic medium (CGM) to the stellar discs, putting forward the co-rotation scenario across the three distance scales. In real observations, although the rotation signature for the CGM and environmental three-dimensional angular momentum are difficult to obtain, line-of-sight kinematics of group member galaxies and stellar disc kinematics of central galaxies are available utilizing existing group catalogue data and integral field unit (IFU) data. In this paper, we use (1) the group catalogue of SDSS DR7 and MaNGA IFU stellar kinematic maps and (2) the group catalogue of GAMA DR4 data and SAMI IFU stellar kinematic maps, to test if the prediction above can be seen in real data. We found the co-rotation pattern between stellar discs and satellites can be concluded with 99.7 per cent confidence level (∼3σ) when combining the two data sets. And the random tests show that the signal can be scarcely drawn from random distribution. [ABSTRACT FROM AUTHOR]

Astronomical radio-interferometric imaging typically uses published observations of standard flux-calibrator sources to calibrate the spectral response of the instrument. The spectra of standard flux-calibrator sources are usually provided as polynomial models of flux-density as a function of frequency. In this paper we show that there is significant covariance in these polynomial coefficients, and that failing to take this into account leads to significantly larger variance when sampling from the polynomial models. This paper presents polynomial models of calibrator sources that include the covariance structure of the coefficients which are computed using Markov Chain Monte Carlo sampling. In addition a data-free inference technique is presented that can be used to estimate the covariance structure from a simple polynomial model when access to the original data is not available. This data-free technique is compared with estimates of covariance calculated from original observation data. The data-free technique is shown to provide reasonable agreement with covariances calculated from source data. A python package is described that implements this inference, and a catalogue of common flux-calibrator models including covariance is provided. We suggest that when polynomial models of flux-calibrators are used as priors in a Bayesian context, then taking this correlation structure into account will lead to significantly reduced posterior variance. [ABSTRACT FROM AUTHOR]

Tidal streams and stellar shells are naturally formed in galaxy interactions and mergers. The Giant Stellar Stream (GSS), the North-East (NE), and Western (W) stellar shelves observed in Andromeda Galaxy (M31) are examples of these structures and were formed through the merger of M31 and a satellite galaxy. Recent observational papers have provided strong evidence that the shells and GSS originate from a single progenitor. In this paper, we investigate the formation of these two stellar shelves and the detailed nature of their relationship to the GSS. We present numerical simulations of tidal disruption of a satellite galaxy assuming that it is a progenitor of the GSS and the shell system. We represent the progenitor as a dwarf spheroidal galaxy with the stellar mass of 109 M⊙ and evolve its merger with M31 for 3 Gyr to reproduce the chemodynamical properties of the NE and W shelves. We find that an initial metallicity of the progenitor with a negative radial gradient of ΔFeH  = −0.3 ± 0.2 successfully reproduces observed metallicities of the NE, W shelves, and the GSS, showing that all these structures can originate from the same merger event. [ABSTRACT FROM AUTHOR]

In this paper, the third of a series of papers, we present well-determined chemical abundances for 124 planetary nebulae (PNe) in the Galactic bulge from deep, long-slit FORS2 spectra from the 8.2 m ESO Very Large telescope (VLT). Prior to this work there were only ∼240 bulge PNe with chemical abundances previously determined over a ∼50 yr period and of highly variable quality. For 34 of these PNe we are presenting their abundances for the first time, which adds ∼14 per cent to the available sample of bulge PNe abundances. The interstellar reddening, physical conditions (electron densities, n e, temperatures, T e), and chemical compositions are derived as single values for each PN but also using different line diagnostics. Selected comparisons with the best literature fluxes for 75 PNe in common reveal that these significant new data are robust, reliable, and internally self-consistent forming the largest independent, high-quality, and well-understood derivation of PNe abundances currently available for study. [ABSTRACT FROM AUTHOR]

With the detection of black hole mergers by the LIGO gravitational wave telescope, there has been increasing interest in the possibility that dark matter may be in the form of solar mass primordial black holes. One of the predictions implicit in this idea is that compact clouds in the broad emission line regions of high-redshift quasars will be microlensed, leading to changes in line structure and the appearance of new emission features. In this paper, the effect of microlensing on the broad emission line region is reviewed by reference to gravitationally lensed quasar systems where microlensing of the emission lines can be unambiguously identified. It is then shown that although changes in Seyfert galaxy line profiles occur on time-scales of a few years, they are too nearby for a significant chance that they could be microlensed, and are plausibly attributed to intrinsic changes in line structure. In contrast, in a sample of 53 high-redshift quasars, 9 quasars show large changes in line profile at a rate consistent with microlensing. These changes occur on a time-scale an order of magnitude too short for changes associated with the dynamics of the emission line region. The main conclusion of the paper is that the observed changes in quasar emission line profiles are consistent with microlensing by a population of solar mass compact bodies making up the dark matter, although other explanations like intrinsic variability are possible. Such bodies are most plausibly identified as primordial black holes. [ABSTRACT FROM AUTHOR]

In this series of papers, we present an emulator-based halo model for the non-linear clustering of galaxies in modified gravity cosmologies. In the first paper, we present emulators for the following halo properties: the halo mass function, concentration–mass relation and halo-matter cross-correlation function. The emulators are trained on data extracted from the forge and bridge suites of N -body simulations, respectively, for two modified gravity (MG) theories: f (R) gravity, and the DGP model, varying three standard cosmological parameters Ωm0, H 0, σ8, and one MG parameter, either |$\bar{f}_{R0}$| or r c. Our halo property emulators achieve an accuracy of |${\lesssim}1\ \hbox{per cent}$| on independent test data sets. We demonstrate that the emulators can be combined with a galaxy–halo connection prescription to accurately predict the galaxy–galaxy and galaxy–matter correlation functions using the halo model framework. [ABSTRACT FROM AUTHOR]

The modelling of astrophysical systems such as binary neutron star mergers or the formation of magnetars from the collapse of massive stars involves the numerical evolution of magnetized fluids at extremely large Reynolds numbers. This is a major challenge for (unresolved) direct numerical simulations which may struggle to resolve highly dynamical features as, e.g. turbulence, magnetic field amplification, or the transport of angular momentum. Sub-grid models offer a means to overcome those difficulties. In a recent paper we presented MInIT, an MHD-instability-induced-turbulence mean-field, sub-grid model based on the modelling of the turbulent (Maxwell, Reynolds, and Faraday) stress tensors. While in our previous work MInIT was assessed within the framework of the magnetorotational instability, in this paper we further evaluate the model in the context of the Kelvin–Helmholtz instability (KHI). The main difference with other sub-grid models (as e.g. the alpha-viscosity model or the gradient model) is that in MInIT, we track independently the turbulent energy density at sub-grid scales, which is used, via a simple closure relation, to compute the different turbulent stresses relevant for the dynamics. The free coefficients of the model are calibrated using well-resolved box simulations of magnetic turbulence generated by the KHI. We test the model against these simulations and show that it yields order-of-magnitude accurate predictions for the evolution of the turbulent Reynolds and Maxwell stresses. [ABSTRACT FROM AUTHOR]

In a companion paper, we introduced a publicly available pipeline to characterize exoplanet atmospheres through high-resolution spectroscopy. In this paper, we use this pipeline to study the biases and degeneracies that arise in atmospheric characterization of exoplanets in near-infrared ground-based transmission spectroscopy. We inject synthetic planetary transits into sequences of SPIRou spectra of the well known M dwarf star Gl 15 A, and study the effects of different assumptions on the retrieval. We focus on (i) mass and radius uncertainties, (ii) non-isothermal vertical profiles, and (iii) identification and retrieval of multiple species. We show that the uncertainties on mass and radius should be accounted for in retrievals and that depth-dependent temperature information can be derived from high-resolution transmission spectroscopy data. Finally, we discuss the impact of selecting wavelength orders in the retrieval and the issues that arise when trying to identify a single species in a multispecies atmospheric model. This analysis allows us to understand better the results obtained through transmission spectroscopy and their limitations in preparation to the analysis of actual SPIRou data. [ABSTRACT FROM AUTHOR]

We present in this paper a public data release of an unprecedentedly large set of core-collapse supernova (CCSN) neutrino emission models, comprising 100 detailed 2D axisymmetric radiation-hydrodynamic simulations evolved out to as late as ∼5 s post-bounce and spanning an extensive range of massive-star progenitors. The motivation for this paper is to provide a physically and numerically uniform benchmark data set to the broader neutrino detection community to help it characterize and optimize subsurface facilities for what is likely to be a once-in-a-lifetime galactic supernova burst event. With this release, we hope to (1) help the international experiment and modelling communities more efficiently optimize the retrieval of physical information about the next galactic CCSN, (2) facilitate the better understanding of core-collapse theory and modelling among interested experimentalists, and (3) help further integrate the broader supernova neutrino community. [ABSTRACT FROM AUTHOR]

Faraday rotation measure (RM) is arguably the most practical observational tracer of magnetic fields in the diffuse circumgalactic medium (CGM). We sample synthetic Faraday rotation skies of Milky Way-like galaxies in TNG50 of the IllustrisTNG project by placing an observer inside the galaxies at a solar circle-like position. Our synthetic RM grids emulate specifications of current and upcoming surveys; the NRAO VLA Sky Survey (NVSS), the Polarisation Sky Survey of the Universe's Magnetism (POSSUM), and a future Square Kilometre Array (SKA1-mid) polarization survey. It has been suggested that magnetic fields regulate the survival of high-velocity clouds. However, there is only a small number of observational detections of magnetized clouds thus far. In the first part of the paper, we test conditions for the detection of magnetized circumgalactic clouds. Based on the synthetic RM samplings of clouds in the simulations, we predict upcoming polarimetric surveys will open opportunities for the detection of even low-mass and distant clouds. In the second part of the paper, we investigate the imprint of the CGM in the all-sky RM distribution. We test whether the RM variation produced by the CGM is correlated with global galaxy properties, such as distance to a satellite, specific star formation rate, neutral hydrogen covering fraction, and accretion rate to the supermassive black hole. We argue that the observed fluctuation in the RM measurements on scales less than 1○, which has been considered an indication of intergalactic magnetic fields, might in fact incorporate a significant contribution of the Milky Way CGM. [ABSTRACT FROM AUTHOR]

The discovery of gravitational wave (GW) events and the detection of electromagnetic counterparts from GW170817 has started the era of multimessenger GW astronomy. The field has been developing rapidly, and in this paper, we discuss the preparation for detecting these events with ESA's Gaia satellite, during the 4th observing run of the LIGO–Virgo–KAGRA (LVK) collaboration that has started on 2023 May 24. Gaia is contributing to the search for GW counterparts by a new transient detection pipeline called GaiaX. In GaiaX , a new source appearing in the field of view of only one of the two telescopes on-board Gaia is sufficient to send out an alert on the possible detection of a new transient. Ahead of O4, an experiment was conducted over a period of about two months. During the two weeks around New Moon in this period of time, the MeerLICHT (ML) telescope located in South Africa tried (weather permitting) to observe the same region of the sky as Gaia within 10 min. Any GaiaX detected transient was published publicly. ML and Gaia have similar limiting magnitudes for typical seeing conditions at ML. At the end of the experiment, we had 11 861 GaiaX candidate transients and 15 806 ML candidate transients, which we further analysed and the results of which are presented in this paper. Finally, we discuss the possibility and capabilities of Gaia contributing to the search for electromagnetic counterparts of gravitational wave events during O4 through the GaiaX detection and alert procedure. [ABSTRACT FROM AUTHOR]

Calibration is the process by which we try to remove atmospheric and instrumental errors that corrupt the observations made by interferometers. Calibration is however an imperfect process and when we calibrate with an incomplete sky model systematics or artefacts manifest in our final images. One of the more striking artefacts that can appear in images are ghost sources. This paper explores these ghost artefacts in greater depth. We are particularly interested in the systematics or artefacts that are created if we partially model extended emission. A theoretical model that utilizes an east–west layout is developed (and empirically validated) that can give insight into the systematics so formed. The results from this study reveal that when we only partially model extended emission then the calibration systematics that form can manifest as extended emission in images. The aforementioned systematics alter the original extended source in various ways; the flux density of the extended source is modified and becomes comparable to the flux density of the source in the calibration sky model and its profile is slightly modified (it becomes more point like). More importantly, we found that the shorter baselines that are more sensitive to extended emission are in general more affected by the calibration systematics than the longer baselines are. In related works, it was found that the number of antennas greatly influence the brightness of the created systematics. For the use case, we investigate in the paper, however, we found this to not be the case. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach to generate samples from target distributions that are difficult to sample from using Markov chain Monte Carlo (MCMC) methods. Traditional MCMC algorithms often face slow convergence due to the difficulty in finding proposals that suit the problem at hand. To address this issue, the paper introduces the approximate posterior ensemble sampler (APES) algorithm, which employs kernel density estimation and radial basis interpolation to create an adaptive proposal, leading to fast convergence of the chains. The APES algorithm's scalability to higher dimensions makes it a practical solution for complex problems. The proposed method generates an approximate posterior probability that closely approximates the desired distribution and is easy to sample from, resulting in smaller autocorrelation times and a higher probability of acceptance by the chain. We compare the performance of the APES algorithm with the affine invariance ensemble sampler with the stretch move in various contexts, demonstrating the efficiency of the proposed method. For instance, on the Rosenbrock function, the APES presented an autocorrelation time 140 times smaller than the affine invariance ensemble sampler. The comparison showcases the effectiveness of the APES algorithm in generating samples from challenging distributions. This paper presents a practical solution to generating samples from complex distributions while addressing the challenge of finding suitable proposals. With new cosmological surveys set to deal with many new systematics, this method offers a practical solution for the upcoming era of cosmological analyses. The algorithms presented in this paper are available at https://github.com/NumCosmo/NumCosmo. [ABSTRACT FROM AUTHOR]

This paper studies the oscillation properties of relativistic, non-self-gravitating tori in the background of a distorted, deformed compact object. This work concentrates on a static and axially symmetric metric containing two quadrupole parameters; relating to the central object and the external fields. This metric may associate the observable effects of these parameters as dynamical degrees of freedom. The astrophysical motivation for choosing such a field is the possibility of constituting a reasonable model for an actual scenario occurring in the vicinity of compact objects. Following our previous works, this paper aims to investigate the radial epicyclic frequency in a perfect fluid disc and not a test particle scenario via a local analysis. To achieve this goal, we employ the vertically integrated technique to be able to treat the equations analytically. The tori configuration is also modelled with Keplerian and non-Keplerian distributions of specific angular momentum. In this set-up, we also discuss the dependence of oscillation properties on the model's variables related to angular momentum distribution and quadrupoles. In the present contribution, we further explore these properties with the possibility of relating oscillatory frequencies to some high-frequency quasi-periodic oscillations models and observed data in some microquasar and neutron star sources, and test the ability of this fluid approach to fit with observational data. [ABSTRACT FROM AUTHOR]

A major puzzle concerning the wide stellar binaries (semimajor axes a ≳ 103 au) in the Solar neighbourhood is the origin of their observed superthermal eccentricity distribution function (DF), which is well approximated by P (e) ∝ e α with α ≈ 1.3. This DF evolves under the combined influence of (i) tidal torques from the Galactic disc and (ii) scattering by passing stars, molecular clouds, and substructure. Recently, it was demonstrated that Galactic tides alone cannot produce a superthermal eccentricity DF from an initially isotropic, non-superthermal one, under the restrictive assumptions that the eccentricity DF was initially of power-law form and then was rapidly phase-mixed toward a steady state by the tidal perturbation. In this paper, we first prove analytically that this conclusion is valid at all times, regardless of these assumptions. We then adopt a thin Galactic disc model and numerically integrate the equations of motion for several ensembles of tidally perturbed wide binaries to study the time evolution in detail. We find that even non-power-law DFs can be described by an effective power-law index α eff which accurately characterizes both their initial and final states, and that a DF with initial (effective or exact) power-law index α i is transformed by Galactic tides into another power law with index α f ≈ (1 + α i)/2 on a time-scale |$\sim 4\, \mathrm{Gyr}\, (a/10^4\mathrm{AU})^{-3/2}$|⁠. In a companion paper, we investigate separately the effect of stellar scattering. As the GAIA data continues to improve, these results will place strong constraints on wide binary formation channels. [ABSTRACT FROM AUTHOR]