Papers for Tuesday, Dec 26 2023

Simulating complex astrophysical reacting flows is computationally expensive -- reactions are stiff and typically require implicit integration methods. The reaction update is often the most expensive part of a simulation, which motivates the exploration of more economical methods. In this research note, we investigate how the explicit Runge--Kutta--Chebyshev (RKC) method performs compared to an implicit method when applied to astrophysical reactive flows. These integrators are applied to simulations of X-ray bursts arising from unstable thermonuclear burning of accreted fuel on the surface of neutron stars. We show that the RKC method performs with similar accuracy to our traditional implicit integrator, but is more computationally efficient when run on CPUs.

Traditional spectral energy distribution (SED) fitting techniques face uncertainties due to assumptions in star formation histories and dust attenuation curves. We propose an advanced machine learning-based approach that enhances flexibility and uncertainty quantification in SED fitting. Unlike the fixed NGBoost model used in mirkwood, our approach allows for any sklearn-compatible model, including deterministic models. We incorporate conformalized quantile regression to convert point predictions into error bars, enhancing interpretability and reliability. Using CatBoost as the base predictor, we compare results with and without conformal prediction, demonstrating improved performance using metrics such as coverage and interval width. Our method offers a more versatile and accurate tool for deriving galaxy physical properties from observational data.

We study dual AGN host galaxy morphologies at $z=2$ using the ASTRID simulation, selecting black hole (BH) pairs with small separation ($\Delta r<30\rm{kpc}$), high mass ($M_{\text{BH,12}}>10^7M_\odot$), and luminosity ($L_{\text{bol,12}}>10^{43}\rm{erg/s}$). We kinematically decompose (using MORDOR) $\sim1000$ dual AGN hosts into standard components - a `disk' (thin and thick disk, pseudo-bulge) and 'bulge' (bulge and halo) and define disk-dominated galaxies by the disk-to-total $D/T\geq0.5$. In ASTRID, $60.9\pm2.1\%$ of dual AGN hosts (independent of separation) are disk-dominated, with the $D/T$ distribution peaking at $\sim0.7$. Notably, hosts of BH pairs have similar morphologies (most either both disk or bulge-dominated). In dual-AGN hosts, the $D/T$ increases from $\sim17\% $ at $M_{\rm *}\sim 10^{9} M_{\odot}$ to $ 64\% $ for $M_{\rm *} \sim 10^{11.5} M_{\odot}$, and the pseudo-bulge is the dominant component of the disk fraction at the high mass end. Moreover, dual AGN hosts exhibit a higher fraction of disk/large pseudo-bulge than single-AGN hosts. The Disk-to-Total ratio is approximately constant with BH mass or AGN luminosity. We also create mock images of dual AGN host galaxies, employing morphological fitting software Statmorph to calculate morphological parameters and compare them with our kinematic decomposition results. Around $83.3\pm2.4\%$ of galaxies display disk-like profiles, of which $\sim60.7\pm2.2\%$ are kinematically confirmed as disks. Se\'rsic indices and half-mass radii of dual AGN host galaxies align with observational measurements from HST at $z\sim2$. Around $34\%$ are identified as mergers from the $\text{Gini}-M_{20}$ relation. We find two dual AGN hosted by galaxies that exhibit disk-like se\'rsic index $n_{12}<1$ and $(D/T)_{12}>0.5$, which are in remarkable agreement with properties of recently discovered dual quasars in disk galaxies at $z\sim 2$.

The intrinsic variability due to the magnetic activity of young active stars is one of the main challenges in detecting and characterising exoplanets. We present a method able to model the stellar photosphere and its surface inhomogeneities (starspots) in young/active and fast-rotating stars, based on the cross-correlation function (CCF) technique, to extract information about the spot configuration of the star. Within the Global Architecture of Planetary Systems (GAPS) Project at the Telescopio Nazionale Galileo, we analysed more than 300 spectra of the young planet-hosting star V1298 Tau provided by HARPS-N high-resolution spectrograph. By applying the SpotCCF model to the CCFs we extracted the spot configuration (latitude, longitude and projected filling factor) of this star, and also provided the new RVs time series of this target. We find that the features identified in the CCF profiles of V1298 Tau are modulated by the stellar rotation, supporting our assumption that they are caused by starspots. The analysis suggests a differential rotation velocity of the star with lower rotation at higher latitudes. Also, we find that SpotCCF provides an improvement in RVs extraction with a significantly lower dispersion with respect to the commonly used pipelines, with consequent mitigation of the stellar activity contribution modulated with stellar rotation. A detection sensitivity test, by the direct injection of a planetary signal into the data, confirmed that the SpotCCF model improves the sensitivity and ability to recover planetary signals. Our method enables the modelling of the stellar photosphere, extracting the spot configuration of young/active and rapidly rotating stars. It also allows for the extraction of optimised RV time series, thereby enhancing our detection capabilities for new exoplanets and advancing our understanding of stellar activity.

Recent observations of Rossby waves and other more exotic forms of inertial oscillations in the Sun's convection zone have kindled the hope that such waves might be used as a seismic probe of the Sun's interior. Here we present a 3D numerical simulation in spherical geometry that models the Sun's convection zone and upper radiative interior. This model features a wide variety of inertial oscillations, including both sectoral and tesseral equatorial Rossby waves, retrograde mixed inertial modes, prograde thermal Rossby waves, the recently observed high-frequency retrograde (HFR) vorticity modes, and what may be latitudinal overtones of these HFR modes. With this model, we demonstrate that sectoral and tesseral Rossby waves are ubiquitous within the radiative interior as well as within the convection zone. We suggest that there are two different Rossby-wave families in this simulation that live in different wave cavities: one in the radiative interior and one in the convection zone. Finally, we suggest that many of the retrograde inertial waves that appear in the convection zone, including the HFR modes, are in fact all related, being latitudinal overtones that are mixed modes with the prograde thermal Rossby waves.

We present a two-dimensional study of the gas distribution, excitation and kinematics of the OH absorber galaxy IRAS 19154+2704 using Gemini GMOS-IFU observations. Its continuum image shows a disturbed morphology indicative of a past or on-going interaction. The ionised gas emission presents two kinematic components: a narrow ($\sigma\lesssim$300 km s$^{-1}$) component that may be tracing the gas orbiting in the galaxy potential and a broad ($\sigma\gtrsim$500 km s$^{-1}$) component which is produced by an Active Galactic Nucleus (AGN) driven outflow, with velocities reaching $-$500 km s$^{-1}$ which may exceed the escape velocity of the galaxy. The emission-line ratios and BPT diagrams confirm that the gas excitation in the inner $\sim$2 kpc is mainly due the AGN, while in regions farther away, a contribution from star formation is observed. We estimate a mass outflow rate of $\dot{M}_{\rm out}=4.0\pm2.6$ M$_\odot$ yr$^{-1}$ at a distance of 850 pc from the nucleus. The corresponding outflow kinetic power $\dot{E}_{\rm out} = (2.5\pm1.6)\times10^{42}$ erg s$^{-1}$, is only $3\times10^{-4}$ L$_{\rm bol}$ (the AGN luminosity), but the large mass-outflow rate, if kept for a $\sim$10 Myr AGN lifecycle, will expel $\approx10^8$ M$_\odot$ in ionised gas alone. This is the 6th of a series of papers in which we have investigated the kinematics of ULIRGS, most of which are interacting galaxies showing OH Megamasers. IRAS19154 shows the strongest signatures of an active AGN, supporting an evolutionary scenario: interactions trigger AGN that fully appear in the most advanced stages of the interaction.

The superb image quality, stability and sensitivity of the JWST permit deconvolution techniques to be pursued with a fidelity unavailable to ground-based observations. We present an assessment of several deconvolution approaches to improve image quality and mitigate effects of the complex JWST point spread function (PSF). The optimal deconvolution method is determined by using WebbPSF to simulate JWST's complex PSF and MIRISim to simulate multi-band JWST/Mid-Infrared Imager Module (MIRIM) observations of a toy model of an active galactic nucleus (AGN). Five different deconvolution algorithms are tested: (1) Kraken deconvolution, (2) Richardson-Lucy, (3) Adaptive Imaging Deconvolution Algorithm, (4) Sparse regularization with the Condat-V\~u algorithm, and (5) Iterative Wiener Filtering and Thresholding. We find that Kraken affords the greatest FWHM reduction of the nuclear source of our MIRISim observations for the toy AGN model while retaining good photometric integrity across all simulated wavebands. Applying Kraken to Galactic Activity, Torus, and Outflow Survey (GATOS) multi-band JWST/MIRIM observations of the Seyfert 2 galaxy NGC 5728, we find that the algorithm reduces the FWHM of the nuclear source by a factor of 1.6-2.2 across all five filters. Kraken images facilitate detection of a SE to NW $\thicksim$2".5 ($\thicksim$470 pc, PA $\simeq$115\deg) extended nuclear emission, especially in the longest wavelengths. We demonstrate that Kraken is a powerful tool to enhance faint features otherwise hidden in the complex JWST PSF.

Comet nuclei in the outer Solar system are constantly irradiated by cosmic rays at low temperatures. Accumulated high concentrations of radicals can undergo fast recombination with significant heating of cometary surface layers. We present the model of comet activity at large heliocentric distances caused by the recombination of radicals. We found that the considered mechanism can cause activity of comets in distant regions of the Solar system, even at the Oort cloud distances. Outbursts in distant comet reservoirs can be a new source of dust and ice particles contributing to the recently discovered anomalous diffuse light in the cosmic extragalactic background optic light. The orbits of small-radii comets in the Oort cloud are highly influenced by cometary outbursts. This effect may account for the observed decrease in the number of small-radius long-period comets.

The field of fast radio bursts (FRBs) has entered the age of fine characterization as observational results from different radio telescopes become more and more abundant. The large FRB sample is suitable for a statistical study. There is an interesting finding that the waiting-time distributions of very active repeating FRBs show a universal double-peaked feature, with left peaks lower than right ones. Assuming these two peaks are independent and initially comparable, we show that the observed asymmetric shape can be ascribed to the propagational effect in the magnetosphere. An FRB passing through the magnetized plasma will induce the circular motion of charged particles to form a current loop. This further leads to an induced magnetic field with opposite direction respect to the background field. As the effective field strength changes, the scattering absorption probability of the following FRB will be influenced. The absorption can be important under certain physical conditions and bursts with smaller time-lags are easier to be absorbed. Also there will be an imprint on the flux distribution as the scattering optical depth depends on burst luminosity as well.

We revisit the calculation of third order \acp{SIGW} and extend it from a monochromatic primordial power spectrum to a more general log-normal one. We investigate the impact of third order SIGWs on \ac{SNR} of \ac{LISA} and \ac{PTA} observations, and find that third order SIGWs significantly contribute to the total energy density spectrum of \acp{GW} in high-frequency region. For a primordial power spectrum amplitude of $A_{\zeta}=10^{-2}\sim 10^{-1}$, the effects of third order SIGWs lead to a $40\%$ to $400\%$ increase in the SNR for LISA. Additionally, our PTA data analysis reveals that third order SIGWs diminish both the amplitude $A_{\zeta}$ and the peak frequency $f_*$ of the primordial power spectrum.

In our Solar system, spin-orbit resonances are common under Sun--planet, planet--satellite and binary asteroid configurations. In this work, high-order and secondary spin-orbit resonances are investigated by taking numerical and analytical approaches. Poincar\'e sections as well as two types of dynamical maps are produced, showing that there are complicated structures in the phase space. To understand numerical structures, we adopt the theory of perturbative treatments to formulate resonant Hamiltonian for describing spin-orbit resonances. Results show that there is an excellent agreement between analytical and numerical structures. It is concluded that the main V-shape structure arising in the parameter space $(\dot\theta,\alpha)$ is sculpted by the synchronous primary resonance, those minute structures inside the V-shape region are dominated by secondary resonances and those structures outside the V-shape region are governed by high-order resonances. At last, the analytical approach is applied to binary asteroid systems (65803) Didymos and (4383) Suruga to reveal their phase-space structures.

We present an initial analysis of Radio Frequency Interference (RFI) flagging statistics from archived Australian SKA Pathfinder (ASKAP) observations for the 'Survey and Monitoring of ASKAP's RFI environment and Trends' (SMART) project. The survey component covers ASKAP's full 700 MHz to 1800 MHz frequency range, including bands not typically used due to severe RFI. In addition to this dedicated survey, we routinely archive and analyse flagging statistics for all scientific observations to monitor the observatory's RFI environment in near real-time. We use the telescope itself as a very sensitive RFI monitor and directly assess the fraction of scientific observations impacted by RFI. To this end, flag tables are now automatically ingested and aggregated as part of routine ASKAP operations for all science observations, as a function of frequency and time. The data presented in this paper come from processing all archived data for several ASKAP Survey Science Projects (SSPs). We found that the average amount of flagging due to RFI across the routinely-used 'clean' continuum science bands is 3%. The 'clean' mid band from 1293 MHz to 1437 MHz (excluding the 144 MHz below 1293 MHz impacted by radionavigation-satellites which is discarded before processing) is the least affected by RFI, followed by the 'clean' low band from 742 MHz to 1085 MHz. ASKAP SSPs lose most of their data to the mobile service in the low band, aeronautical service in the mid band and satellite navigation service in the 1510 MHz to 1797 MHz high band. We also show that for some of these services, the percentage of discarded data has been increasing year-on-year. SMART provides a unique opportunity to study ASKAP's changing RFI environment and informing the implementation of a suite of RFI mitigation techniques.

We investigate the thermodynamics of close encounters between stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGN), during which binary black holes (BBHs) may form. We consider a suite of 2D viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code Athena++. We study formation scenarios where the fluid is either an isothermal gas or an adiabatic mixture of gas and radiation in local thermal equilibrium. We include the effects of viscous and shock heating, as well as optically thick cooling. We co-evolve the embedded BHs with the gas, keeping track of the energetic dissipation and torquing of the BBH by gas and inertial forces. We find that compared to the isothermal case, the minidiscs formed around each BH are significantly hotter and more diffuse, though BBH formation is still efficient. We observe massive blast waves arising from collisions between the radiative minidiscs during both the initial close encounter, and subsequent periapsis periods for successfully bound BBHs. These "disc novae" have a profound effect, depleting the BBH Hill sphere of gas and injecting energy into the surrounding medium. In analysing the thermal emission from these events, we observe periodic peaks in local luminosity associated with close encounters/periapses, with emission peaking in the optical/near-IR. In the AGN outskirts, these outbursts can reach 4% of the AGN luminosity in the IR band, with flares rising over 0.5-1year. Collisions in different disc regions, or when treated in 3D with magnetism, may produce more prominent flares.

We present very-long-baseline interferometry (VLBI) observations of the hyperactive repeating FRB 20220912A using the European VLBI Network (EVN) with an EVN-Lite setup. We detected 150 bursts from FRB 20220912A over two observing epochs in October 2022. Combining the data of these bursts allows us to localise FRB 20220912A to a precision of a few milliarcseconds, corresponding to a transverse scale of less than 10 pc at the distance of the source. The precision of this localisation shows that FRB 20220912A lies closer to the centre of its host galaxy than previously found, although still significantly offset from the host galaxy's nucleus. On arcsecond scales, FRB 20220912A is coincident with a persistent continuum radio source known from archival observations, however, we find no compact persistent emission on milliarcsecond scales. The persistent radio emission is thus likely to be from star-formation in the host galaxy. This is in contrast to some other active FRBs, such as FRB 20121102A and FRB 20190520B.

In this proceedings, we study the possible gravitational impact of primordial black holes (PBHs) or dark matter (DM) clumps on GNSS satellite orbits and gravimeter measurements. It provides a preliminary step to the future exhaustive statistical analysis over 28 years of gravimeter and GNSS data to get constraints over the density of asteroid-mass PBH and DM clumps inside the solar system. Such constraints would be the first to be obtained by direct observation on a terrestrial scale.

The problem of explaining observed soft X-ray fluxes during solar flares, which invokes acceleration of large fraction of electrons, if the acceleration takes places at the solar coronal loop-top, can potentially be solved by postulating that flare at loop-top creates dispersive Alfven waves (DAWs) which propagate towards the foot-points. As DAWs move in progressively denser parts of the loop (due to gravitational stratification) the large fraction of electrons is no longer needed. Here we extend our previous results by considering $f ^{-1}$ frequency spectrum of DAWs and add ${\rm He^{++}}$ ions using fully kinetic particle-in-cell (PIC) simulations. We consider cases when transverse density gradient is in the range ${ 4-40} c/\omega_{\rm { pe}}$ and DAW driving frequency is $0.3-0.6\omega_{\rm { cp}}$. We find that (i) The frequency spectrum case does not affect electron acceleration fraction in the like-to-like cases, but few times larger percentage of ${\rm He^{++}}$ heating is seen due to ion cyclotron resonance; (ii) In cases when counter propagating DAWs collide multiple-times, much larger electron and ion acceleration fractions are found, but the process is intermittent in time. This is because intensive heating (temperature increase) makes the-above-thermal-fraction smaller; Also more isotropic velocity distributions are seen; (iii) Development of kink oscillations occurs when DAWs collide; (iv) Scaling of the magnetic fluctuations power spectrum steepening in the higher-density regions is seen, due to wave refraction. Our PIC runs produce much steeper slopes than the orginal spectrum, indicating that the electron-scale physics has a notable effect of DAW spectrum evolution.

We present \textsc{AstroLink}, an efficient and versatile clustering algorithm designed to hierarchically classify astrophysically-relevant structures from both synthetic and observational data sets. We build upon \textsc{CluSTAR-ND}, a hierarchical galaxy/(sub)halo finder, so that \textsc{AstroLink} now generates a two-dimensional representation of the implicit clustering structure as well as ensuring that clusters are statistically distinct from the noisy density fluctuations implicit within the $n$-dimensional input data. This redesign replaces the three cluster extraction parameters from \textsc{CluSTAR-ND} with a single parameter, $S$ -- the lower statistical significance threshold of clusters, which can be automatically and reliably estimated via a dynamical model-fitting process. We demonstrate the robustness of this approach compared to \textsc{AstroLink}'s predecessors by applying each algorithm to a suite of simulated galaxies defined over various feature spaces. We find that \textsc{AstroLink} delivers a more powerful clustering performance without suffering from computational drawbacks. With these improvements, \textsc{AstroLink} is ideally suited to extracting a meaningful set of hierarchical and arbitrarily-shaped astrophysical clusters from both synthetic and observational data sets -- lending itself as a great tool for morphological decomposition within the context of hierarchical structure formation.

Giant flares, short explosive events releasing up to 10$^{47}$ erg of energy in the gamma-ray band in less than one second, are the most spectacular manifestation of magnetars, young neutron stars powered by a very strong magnetic field, 10$^{14-15}$ G in the magnetosphere and possibly higher in the star interior. The rate of occurrence of these rare flares is poorly constrained, as only three have been seen from three different magnetars in the Milky Way and in the Large Magellanic Cloud in about 50 years since the beginning of gamma-ray astronomy. This sample can be enlarged by the discovery of extragalactic events, since for a fraction of a second giant flares reach peak luminosities above 10$^{46}$ erg/s, which makes them visible by current instruments up to a few tens of Mpc. However, at these distances they appear similar to, and difficult to distinguish from, regular short gamma-ray bursts (GRBs). The latter are much more energetic events, 10$^{50-53}$ erg, produced by compact binary mergers and originating at much larger distances. Indeed, only a few short GRBs have been proposed, with different levels of confidence, as magnetar giant flare candidates in nearby galaxies. Here we report the discovery of a short GRB positionally coincident with the central region of the starburst galaxy M82. Its spectral and timing properties, together with the limits on its X-ray and optical counterparts obtained a few hours after the event and the lack of an associated gravitational wave signal, qualify with high confidence this event as a giant flare from a magnetar in M82.

We present SCUBA-2/POL-2 850 $\mu$m polarimetric observations of the circumstellar envelope (CSE) of the carbon-rich asymptotic giant branch (AGB) star IRC+10216. Both FIR and optical polarization data indicate grains aligned with their long axis in the radial direction relative to the central star. The 850 $\mu$m polarization does not show this simple structure. The 850 $\mu$m data are indicative, albeit not conclusive, of a magnetic dipole geometry. Assuming such a simple dipole geometry, the resulting 850 $\mu$m polarization geometry is consistent with both Zeeman observations and small-scale structure in the CSE. While there is significant spectral line polarization contained within the SCUBA-2 850 $\mu$m pass-band for the source, it is unlikely that our broadband polarization results are dominated by line polarization. To explain the required grain alignment, grain mineralogy effects, due to either fossil silicate grains from the earlier oxygen-rich AGB phase of the star, or due to the incorporation of ferromagnetic inclusions in the largest grains, may play a role. We argue that the most likely explanation is due to a new alignment mechanism \citep{arXiv:2009.11304} wherein a charged grain, moving relative to the magnetic field, precesses around the induced electric field and therefore aligns with the magnetic field. This mechanism is particularly attractive as the optical, FIR, and sub-mm wave polarization of the carbon dust can then be explained in a consistent way, differing simply due to the charge state of the grains.

The Pierre Auger Observatory is a unique facility designed to study ultra-high energy cosmic rays, with energies up to 10$^{20}$ eV and beyond. The Observatory is located in Argentina and comprises more than 1600 water Cherenkov detectors spread over an area of 3000 square kilometers overlooked by Fluorescence detectors. The first phase of the Observatory's data-taking began in 2004 and continued until the end of 2021. In this contribution, the results from the Phase~I data analysis of the Pierre Auger Observatory are presented. They include, among others, measurements of the cosmic-ray energy spectrum, composition, and arrival direction anisotropy. The Phase~I results from the Pierre Auger Observatory provide major advances in the understanding of the ultra-high energy cosmic ray phenomena and lay the foundation for second-phase studies with the upgraded AugerPrime detector. The status of the AugerPrime upgrade and its performance will be also discussed.

We model the evolution of active galactic nuclei by constructing their radio luminosity functions. We use a set of surveys of varying area and depth, namely the deep COSMOS survey of $1,916$ AGN sources, the wide shallow 3CRR, 7C and 6CE surveys, containing together $356$ AGNs, and the intermediate XXL-North and South fields consisting of $899$ and $1,484$ sources, respectively. We also used the CENSORS, BRL, Wall $\&$ Peacock and Config surveys, consisting respectively of $150$, $178$, $233$ and $230$ sources. Together, these surveys numbered $5,446$ AGN sources and constrained the luminosity functions at high redshift and over a wide range of luminosities (up to $z \approx 3$ and $\log (L / \mathrm{W Hz^{-1}}) \in [22,29])$. We concentrate on parametric methods within the Bayesian framework and show that the luminosity-dependent density evolution (LDDE) model fits the data best, with evidence ratios varying from "strong" ($>10$) to "decisive" ($>100$) according to the Jeffreys interpretation. We determine the number density, luminosity density and kinetic luminosity density as a function of redshift, and observe a flattening of these functions at higher redshifts, not present in simpler models, which we explain by our use of the LDDE model. Finally, we divide our sample into subsets according to the stellar mass of the host galaxies in order to investigate a possible bimodality in evolution. We found a difference in LF shape and evolution between these subsets. All together, these findings point to a physical picture where the evolution and density of AGN cannot be explained well by simple models but require more complex models either via AGN sub-populations where the total AGN sample is divided into subsamples according to various properties such as, for example, optical properties and stellar mass, or via luminosity-dependent functions.

Helium-star models were dynamically evolved into the region of the HR Diagram where R CrB variables are found. The MESA stellar evolution code was able to pick up pulsational instabilities with cycle lengths that are compatible with the periods observed in pulsating R CrB variables. The properties of the computed pulsations hint at their being strange modes.

Context. Ubiquitous small-scale vortical motions are seen to occur in the solar atmosphere both in simulations and observations. They are thought to play a significant role in the local heating of the quiet chromosphere and corona. In a previous paper, we proposed a new method for the automated identification of vortices based on the accurate estimation of curvature centers; this method was implemented in the SWIRL algorithm. Aims. We aim to assess the applicability of the SWIRL algorithm to self-consistent numerical simulations of the solar atmosphere. The highly turbulent and dynamical solar flow poses a challenge to any vortex-detection method. We also conduct a statistical analysis of the properties and characteristics of photospheric and chromospheric small-scale swirling motions in numerical simulations. Methods. We applied the SWIRL algorithm to realistic, three-dimensional, radiative, magneto-hydrodynamical simulations of the solar atmosphere carried out with the CO5BOLD code. In order to achieve statistical validity, we analyzed 30 time instances of the simulation covering 2 h of physical time. Results. The SWIRL algorithm accurately identified most of the photospheric and chromospheric swirls, which are perceived as spiraling instantaneous streamlines of the horizontal component of the flow. Part of the identified swirls form three-dimensional coherent structures that are generally rooted in magnetically dominated intergranular lanes and extend vertically into the chromospheric layers. From a statistical analysis, we find that the average number densities of swirls in the photosphere and chromosphere are 1 Mm-2 and 4 Mm-2, respectively, while the average radius is 50 - 60 km throughout the simulated atmosphere. We also find an approximately linear correlation between the rotational speed of chromospheric swirls and the local Alfv\'en speed. (Abridged)

We investigate whether barred galaxies are statistically more likely to harbour radial molecular gas flows and what effect those flows have on their global properties. Using 46 galaxies from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we identify galaxies hosting optical bars using a combination of the morphological classifications in Galaxy Zoo 2 and HyperLEDA. In order to detect radial molecular gas flows, we employ full 3D kinematic modelling of the ALMaQUEST $^{12}$CO(1-0) datacubes. By combining our bar classifications with our radial bar-flow detections, we find that galaxies classed as barred are statistically more likely to host large-scale radial gas motion compared to their un-barred and edge-on counterparts. Moreover, the majority of barred galaxies require multi-component surface brightness profiles in their best-fit model, indicative of the presence of a resonance system. We find that galaxies classed as barred with radial bar-flow (``barred + radial flow'' subset) are significantly suppressed in global star-formation efficiency compared to barred galaxies without radial bar-flows and the other morphological sub-samples. Our ``barred + radial flow'' subset also possess consistently centrally concentrated molecular gas distributions, with no indication of depleted gas fractions, suggesting that gas exhaustion is not the cause of their suppressed star-formation. Furthermore, these objects have higher median gas densities in their central 1 kpc, implying that a central gas enhancement does not fuel a central starburst in these objects. We propose that dynamical effects, such as the shear caused by the large-scale inflow of gas, acts to gravitationally stabilise the inner gas reservoir.

An initial theoretical attempt to explain the observed decrease of the polytropic/adiabatic index $\gamma$ in the solar corona has been accomplished. The chemical reactions of the ionization-recombination processes in local thermodynamic equilibrium (LTE) of a solar plasma cocktail containing heavy elements are found to cause $1.1 < \gamma \leq 5/3$ in the quiet solar atmosphere. It is also shown that the quiet solar atmosphere is in LTE justifying this theoretical study. This result is obtained by numerically solving the Saha equation and subsequently using a newly derived equation for calculation of the polytropic index from thermodynamic partial derivatives of the enthalpy and pressure with respect to density and temperature. In addition, a comparison between calculated in this way polytropic index and measured from spectroscopic observations of propagating slow magneto-hydrodynamics (MHD) waves in coronal loops shows that LTE ionization accounts for very small part of the observed decrease of $\gamma$ meaning that the solar plasma in the active region is not in LTE as expected. However, the observed dependency of higher polytropic index at higher temperatures is confirmed by the current theoretical approach. It is concluded that to account for the polytropic index decrease in the active regions of the solar corona, it is necessary kinetic non-LTE ionization calculations to be performed.

Gamma-ray bursts (GRBs) comprise of short, bright, energetic flashes of emission from extragalactic sources followed by a longer afterglow phase of decreased brightness. Recent discoveries of very-high-energy (VHE, $\gtrsim 100$ GeV) afterglow emission from GRB 180720B and GRB 190829A by H.E.S.S. have raised questions regarding the emission mechanism responsible. We interpret these observed late-time emission to be the result of inverse Compton emission of ultra-relativistic electrons in the GRB blastwave in an external radiation field, i.e., external Compton (EC), considering both the wind and interstellar medium scenarios. We present predictions of multiwavelength light curves and energy spectra, ranging from optical to VHE, and include the synchrotron and synchrotron self-Compton (SSC) radiation mechanisms as well. We corrected the EC and SSC model for the $\gamma$-ray attenuation by absorption of photons through their interaction with the extragalactic background light (EBL). We compared our results to multiwavelength data and found that EC gives a satisfactory fit for a given set of fixed model parameters for GRB 180720B, whereas SSC result in a better fit for GRB 190829A. For both GRBs a wind environment is preferred over constant density inter-stellar medium, and the Cosmic Microwave Background as the external radiation field. However, with more data and an effective optimisation tool we can find a more robust fit of the model, implying better constraints on the GRB environment and the particle energy requirements for the emission observed at late times. This has consequences for future observations of GRBs at these extreme energies.

Thanks to IXPE , the X-ray spectro-polarimeter launched at the end of 2021, X-ray polarimetry has finally become an extraordinary tool in investigating the physics of accretion in low mass X-ray binaries. Similarly to what happened with gravitational waves, X-ray polarimetry would play a new complementary but at the same time fundamental role in the high-energy astrophysical domain. We summarize here the first 1.5 year results on accreting low-mass X-ray binaries obtained by a huge IXPE observation campaign coordinated with the principal X-ray and Gamma-ray telescopes. Then we compare these results with the theoretical prediction highlighting the unexpected results.

The Roman Space Telescope's Galactic Bulge Time Domain Survey will constitute the most sensitive microlensing survey of the Galactic Bulge to date, opening up new opportunities to search for dark matter (DM). Many extensions of the Standard Model predict the formation of extended DM substructures, such as DM subhalos, boson/axion stars, and halo-dressed primordial black holes. We demonstrate that for such targets, Roman will be sensitive to a broad parameter space up to four orders of magnitude below existing constraints. Our analysis can be readily applied to other extended DM configurations as well.

We make an in-depth analysis of different AGN jet models' signatures, inducing quiescence in galaxies with a halo mass of $10^{12} M_\odot$. Three jet models, including cosmic ray-dominant, hot thermal, and precessing kinetic jets, are studied at two energy flux levels each, compared to a jet-free, stellar feedback-only simulation. We examine the distribution of Mg II, O VI, and O VIII ions, alongside gas temperature and density profiles. Low-energy ions, like Mg II, concentrate in the ISM, while higher energy ions, e.g., O VIII, prevail at the AGN jet cocoon's edge. High-energy flux jets display an isotropic ion distribution with lower overall density. High-energy thermal or cosmic ray jets pressurize at smaller radii, significantly suppressing core density. The cosmic ray jet provides extra pressure support, extending cool and warm gas distribution. A break in the ion-to-mass ratio slope in O VI and O VIII is demonstrated in the ISM-to-CGM transition (between 10-30 kpc), growing smoothly towards the CGM at greater distances.

Magnetar giant flares (MGFs), originating from non-catastrophic magnetars, share noteworthy similarities with some short gamma-ray bursts (GRBs). However, understanding their detailed origin and radiation mechanisms remains challenging due to limited observations. The discovery of MGF GRB 231115A, the second extragalactic magnetar giant flare located in the Cigar galaxy at a luminosity distance of $\sim 3.5$ Mpc, offers yet another significant opportunity for gaining insights into the aforementioned topics. This Letter explores its temporal properties and conducts a comprehensive analysis of both the time-integrated and time-resolved spectra through empirical and physical model fitting. Our results reveal certain properties of GRB 231115A that bear resemblances to GRB 200415A. We employ a Comptonized fireball bubble model, in which the Compton cloud, formed by the magnetar wind with high density $e^{\pm}$, undergoes Compton scattering and inverse Compton scattering, resulting in reshaped thermal spectra from the expanding fireball at the photosphere radius. This leads to dynamic shifts in dominant emission features over time. Our model successfully fits the observed data, providing a constrained physical picture, such as a trapped fireball with a radius of $\sim 1.95 \times 10^{5}$ cm and a high local magnetic field of $2.5\times 10^{16}$ G. The derived peak energy and isotropic energy of the event further confirm the burst's MGF origin and its contribution to the MGF-GRB sample. We also discuss prospects for further gravitational wave detection associated with MGFs, given their high event rate density ($\sim 8\times 10^5\ \rm Gpc^{-3}\ yr^{-1}$) and ultra-high local magnetic field.

We combine pulsar population synthesis with simulation-based inference to constrain the magneto-rotational properties of isolated Galactic radio pulsars. We first develop a flexible framework to model neutron-star birth properties and evolution, focusing on their dynamical, rotational and magnetic characteristics. In particular, we sample initial magnetic-field strengths, $B$, and spin periods, $P$, from log-normal distributions and capture the late-time magnetic-field decay with a power law. Each log-normal is described by a mean, $\mu_{\log B}, \mu_{\log P}$, and standard deviation, $\sigma_{\log B}, \sigma_{\log P}$, while the power law is characterized by the index, $a_{\rm late}$, resulting in five free parameters. We subsequently model the stars' radio emission and observational biases to mimic detections with three radio surveys, and produce a large database of synthetic $P$-$\dot{P}$ diagrams by varying our input parameters. We then follow a simulation-based inference approach that focuses on neural posterior estimation and employ this database to train deep neural networks to directly infer the posterior distributions of the five model parameters. After successfully validating these individual neural density estimators on simulated data, we use an ensemble of networks to infer the posterior distributions for the observed pulsar population. We obtain $\mu_{\log B} = 13.10^{+0.08}_{-0.10}$, $\sigma_{\log B} = 0.45^{+0.05}_{-0.05}$ and $\mu_{\log P} = -1.00^{+0.26}_{-0.21}$, $\sigma_{\log P} = 0.38^{+0.33}_{-0.18}$ for the log-normal distributions, and $a_{\rm late} = -1.80^{+0.65}_{-0.61}$ for the power law at $95\%$ credible interval. Our approach represents a crucial step towards robust statistical inference for complex population-synthesis frameworks and forms the basis for future multi-wavelength analyses of Galactic pulsars.

The correlation between optical and $\gamma$-ray flux variations in blazars reveals a complex behaviour. In this study, we present our analysis of the connection between changes in optical and $\gamma$-ray emissions in the blazar Ton 599 over a span of approximately 15 years, from August 2008 to March 2023. Ton 599 reached its highest flux state across the entire electromagnetic spectrum during the second week of January 2023. To investigate the connection between changes in optical and $\gamma$-ray flux, we have designated five specific time periods, labeled as epochs A, B, C, D, and E. During periods B, C, D, and E, the source exhibited optical flares, while it was in its quiescent state during period A. The $\gamma$-ray counterparts to these optical flares are present during periods B, C, and E, however during period D, the $\gamma$-ray counterpart is either weak or absent. We conducted a broadband spectral energy distribution (SED) fitting by employing a one-zone leptonic emission model for these epochs. The SED analysis unveiled that the optical-UV emission primarily emanated from the accretion disk in quiescent period A, whereas synchrotron radiation from the jet dominated during periods B, C, D, and E. Diverse correlated patterns in the variations of optical and $\gamma$-ray emissions, like correlated optical and $\gamma$-ray flares, could be accounted for by changes in factors such as the magnetic field, bulk Lorentz factor, and electron density. On the other hand, an orphan optical flare could result from increased magnetic field and bulk Lorentz factor.

Many accreting black holes and neutron stars exhibit rapid variability in their X-ray light curves, termed quasi-periodic oscillations (QPOs). The most commonly observed type is the low-frequency ($\lesssim 10$ Hz), type-C QPO, while only a handful of sources exhibit high-frequency QPOs ($\gtrsim 60$ Hz). The leading model for the type-C QPO is Lense-Thirring precession of a hot, geometrically thick accretion flow that is misaligned with the black hole's spin axis. However, existing versions of this model have not taken into account the effects of a surrounding, geometrically thin disc on the precessing, inner, geometrically thick flow. In Bollimpalli et. al 2023, using a set of GRMHD simulations of tilted, truncated accretion discs, we confirmed that the outer thin disc slows down the precession rate of the precessing torus, which has direct observational implications for type-C QPOs. In this paper, we provide a detailed analysis of those simulations and compare them with an aligned truncated disc simulation. We find that the misalignment of the disc excites additional variability in the inner hot flow, which is absent in the comparable aligned-disc simulations. This suggests that the misalignment may be a crucial requirement for producing QPOs. We attribute this variability to global vertical oscillations of the inner torus at epicyclic frequencies corresponding to the transition radius. This explanation is consistent with current observations of higher frequency QPOs in black hole X-ray binary systems.

We investigate the effect of self-interactions on the shape and oscillations of the solitonic core profile of condensed fuzzy dark matter systems without the backdrop of a halo, revealing universal features in terms of an appropriately scaled interaction strength characterizing the crossover between the weakly- and strongly-interacting regimes. Our semi-analytical results are further confirmed by spherically symmetric simulations of the Gross-Pitaevskii-Poisson equations. Inverting our obtained relations, we highlight a degeneracy that could significantly affect constraints on the boson mass in the presence of repulsive boson self-interactions and propose the simultaneous extraction of static and dynamical solitonic features as a way to uniquely constrain both the boson mass and self-interactions.

Inspired by recent advances in observational astrophysics and continued explorations in the field of analog gravity, we discuss the prospect of simulating models of cosmology within the context of synthetic mechanical lattice experiments. We focus on the physics of expanding Universe scenarios described by the Friedmann-Lema\^itre-Robertson-Walker (FLRW) metric. Specifically, quantizing scalar fluctuations in a background FLRW spacetime leads to a quadratic bosonic Hamiltonian with temporally varying pair production terms. Here we present a mapping that provides a one-to-one correspondence between these classes of cosmology models and physical mechanical oscillator systems. As proof-of-principle, we then perform experiments on an actual synthetic lattice system composed of such oscillators. We simulate two different FLRW expansion scenarios driven by inflationary dark energy- and matter-dominated Universes and discuss our experimental results.

We introduce the initiative for Dark Matter in Europe and beyond (iDMEu), a collective effort by a group of particle and astroparticle physicists to set up an online resource meta-repository, a common discussion platform and a series of meetings on everything concerning Dark Matter. This document serves as a status report as well as a citable item concerning iDMEu.

Open-source Large Language Models enable projects such as NASA SciX (i.e., NASA ADS) to think out of the box and try alternative approaches for information retrieval and data augmentation, while respecting data copyright and users' privacy. However, when large language models are directly prompted with questions without any context, they are prone to hallucination. At NASA SciX we have developed an experiment where we created semantic vectors for our large collection of abstracts and full-text content, and we designed a prompt system to ask questions using contextual chunks from our system. Based on a non-systematic human evaluation, the experiment shows a lower degree of hallucination and better responses when using Retrieval Augmented Generation. Further exploration is required to design new features and data augmentation processes at NASA SciX that leverages this technology while respecting the high level of trust and quality that the project holds.

The travel times of light signals between two antipodal points on the surface of a compact star are calculated for two different trajectories: a straight line that passes through the center of the star and a semi-circular trajectory that connects the antipodal points along the surface of the star. Interestingly, it is explicitly proved that, for highly dense stars, the longer trajectory (the one that goes along the surface of the star) may be characterized by the {\it shorter} travel time as measured by asymptotic observers. In particular, for constant density stars we determine {\it analytically} the critical value of the dimensionless density-area parameter $\Lambda\equiv 4\pi R^2\rho$ that marks the boundary between situations in which a direct crossing of the star through its center has the shorter travel time and situations in which the semi-circular trajectory along the surface of the star is characterized by the shorter travel time as measured by asymptotic observers [here $\{R,\rho\}$ are respectively the radius of the star and its density].

A consistent and explicit spectral comparison between heterodyne (HD) and direct detection (DD) derived from first principles including the atmospheric transmission and low beam-filling factors could not be found yet in literature but is needed for decisions in technology planification for future infrared interferometry facilities which are e.g. focused on planet formation. This task requires both, high sensitivity continuum and Doppler-resolved emission and absorption line detection in the mid-IR range (N- and Q-bands) at lower source temperatures (300-1000 K). The signal-to-noise ratios (SNRs) are derived for both schemes within the same semi-classical theory, which consists of classical mode theory for coupling to an antenna and occupation of these modes by quanta of three radiation fields, the thermal signal, the thermal background, and for HD also the coherent local oscillator (LO). The effects of very small beam filling factors (interferometry) and atmospheric absorption/emission could be consistently incorporated this way, as well as quantum-noise propagation which allows in HD the consideration of balanced mixers with cross-correlation (CC). Especially, the transition from pre- to post-detection SNRs was considered meticulously. We do this all because the usually cited SNR-expressions were derived for a too simple and unrealistic case, and moreover contain some wrong assumptions. We introduce a novel HD scheme for astronomical interferometry gaining an order of magnitude in sensitivity against conventional HD and calculate that it should trespass the sensitivity of DD interferometry in the N- and Q-bands for a spectral resolution of R=10000, and should do also for R=300 with doable technical improvements. This result encourages to develop broad-band heterodyne technologies for future mid-infrared interferometry facilities and for new instruments at existing facilities.

The Einstein Telescope faces a critical data analysis challenge with correlated noise, often overlooked in current parameter estimation analyses. We address this issue by presenting the statistical formulation of the likelihood function that includes correlated noise for the Einstein Telescope or any detector network. Neglecting these correlations may significantly reduce parameter estimation accuracy, even leading to the failure to reconstruct otherwise resolvable signals. This emphasizes how critical a proper treatment of correlated noise is, as presented in this work, to unlocking the wealth of results promised by the Einstein Telescope.

We analyze the dynamics of the Sun-Earth-Moon system in the context of a particular class of theories of gravity where curvature and matter are nonminimally coupled (NMC). These theories can potentially violate the Equivalence Principle as they give origin to a fifth force and a extra non-Newtonian force that may imply that Earth and Moon fall differently towards the Sun. We show, through a detailed analysis, that consistency with the bound on Weak Equivalence Principle arising from 48 years of Lunar Laser Ranging data, for a range of parameters of the NMC gravity theory, can be achieved via the implementation of a suitable screening mechanism.

We report on the first observation of electroluminescence amplification with a Microstrip Plate immersed in liquid xenon. The electroluminescence of the liquid, induced by alpha-particles, was observed in an intense non-uniform electric field in the vicinity of 8-$\mu$m narrow anode strips interlaced with wider cathode ones, deposited on the same side of a glass substrate. The electroluminescence yield in the liquid reached a value of $(35.5 \pm 2.6)$ VUV photons/electron. We propose ways of enhancing this response with more appropriate microstructures towards their potential incorporation as sensing elements in single-phase noble-liquid detectors.

SM*A*S*H is an extension of the Standard Model of particle physics which has just the minimal number of fields in order to solve six puzzles of particle physics and cosmology in one smash: vacuum stability, inflation, baryon asymmetry, neutrino masses, strong CP, and dark matter. The parameters of SM*A*S*H are constrained by symmetries and requirements to solve these puzzles. This provides various firm predictions for observables which can be confronted with experiments. We discuss the prospects and timeline to scrutinise or smash SM*A*S*H by cosmic microwave background polarisation experiments, axion haloscopes, and future space-borne gravitational wave detectors.

Recent observations from the James Webb Space Telescope have identified a population of massive galaxy sources ($\mathrm{>10^{10}\ M_\odot}$) at $z>7-10$, formed less than 700 Myr after the Big Bang. Such massive galaxies do not have enough time to form within the standard cosmological model, and hence these observations significantly challenge standard cosmology. A number of possible solutions to this problem have been put forward, including an enhancement of the gravitational force in a modified theory of gravity and the claim that massive primordial black holes, which were created in the early universe before galaxy formation, might provide seeds for galaxies and black holes to subsequently form. We discuss two more exotic possibilities. Black holes can persist through a cosmological bounce and constitute large seeds formed in the previous cosmic cycle existing before current galaxy formation. And spikes, both incomplete spikes that occur in the early initial oscillatory regime of general cosmological models and permanent spikes that can form in inhomogeneous models at later times, could provide a mechanism for generating large structures early in the Universe.