Papers for Wednesday, Apr 10 2024

Two-body relaxation may drive stars onto near-radial orbits around a massive black hole, resulting in a tidal disruption event (TDE). In some circumstances, stars are unlikely to undergo a single terminal disruption, but rather to have a sequence of many grazing encounters with the black hole. It has long been unclear what is the physical outcome of this sequence: each of these encounters can only liberate a small amount of stellar mass, but may significantly alter the orbit of the star. We study the phenomenon of repeating partial tidal disruptions (pTDEs) by building a semi-analytical model that accounts for mass loss and tidal excitations. In the empty loss cone regime, where two-body relaxation is weak, we estimate the number of consecutive partial disruption that a star can undergo, on average, before being significantly affected by two-body encounters. We find that in this empty loss cone regime, a star will be destroyed in a sequence of weak pTDEs, possibly explaining the tension between the low observed TDE rate and its higher theoretical estimates.

The upcoming new coronographs with deeper contrast limits, together with planned and current high-contrast imaging campaigns will push the detectability limit of protoplanets. These planet-hunting campaigns present a new opportunity to characterize protoplanets and their surrounding environments. However, there are clear uncertainties as to what are the extinction levels at different regions of protoplanetary disks, which will impede our ability to characterize young planets. A correct understanding of the expected extinction together with multiple photometric observations will lead to constraints on the extinction levels, dust growth, disk evolution and protoplanetary accretion rates. In this work, we used hydrodynamic simulations and protoplanetary disk observational constraints obtained from both dust and gas emission to explore the expected extinction maps for continuum filters associated with strong hydrogen lines as tracers of accretion and key broadband photometric filters. We provide a scaling relationship for the extinction as a function of planetary separation and disk mass for three different gas giant masses. We also report values for a subset of disks of interest targetted by multiple imaging campaigns. The described values will be useful for the optimal design of future planet-hunting surveys and for giving context to non-detections in protoplanetary disks and the observed fluxes of point sources along with the birth conditions of protoplanets.

Resonant planetary migration in protoplanetary discs can lead to an interplay between the resonant interaction of planets and their disc torques called overstability. While theoretical predictions and N-body simulations hinted at its existence, there was no conclusive evidence until hydrodynamical simulations were performed. Our primary purpose is to find a hydrodynamic setup that induces overstability in a planetary system with two moderate-mass planets in a first-order 2:1 mean motion resonance. We also aim to analyse the impact of key disc parameters, namely the viscosity, surface density, and aspect ratio, on the occurrence of overstability in this planetary system when the masses of the planets are kept constant. We performed 2D locally isothermal hydrodynamical simulations of two planets, with masses of 5 and 10 $M_{\oplus}$, in a 2:1 resonance. Upon identifying the fiducial model in which the system exhibits overstability, we performed simulations with different disc parameters to explore the effects of the disc on the overstability of the system. We observe an overstable planetary system in our hydrodynamic simulations. In the parameter study, we note that overstability occurs in discs characterised by low surface density and low viscosity. Increasing the surface density reduces the probability of overstability within the system. A limit cycle was observed in a specific viscous model with $\alpha_{\nu} = 10^{-3}$. In almost all our models, planets create partial gaps in the disc, which affects both the migration timescale and structure of the planetary system. We demonstrate the existence of overstability using hydrodynamic simulations but find deviations from the analytic approximation and show that the main contribution to this deviation can be attributed to dynamic gap opening.

Structural disturbances, such as galaxy mergers or instabilities, are key candidates for driving galaxy evolution, so it is important to detect and quantify galaxies hosting these disturbances spanning a range of masses, environments, and cosmic times. Traditionally, this is done by quantifying the asymmetry of a galaxy as part of the concentration-asymmetry-smoothness system, $A_{\rm{CAS}}$, and selecting galaxies above a certain threshold as merger candidates. However, in this work, we show that $A_{\rm{CAS}}$, is extremely dependent on imaging properties -- both resolution and depth -- and thus defining a single $A_{\rm{CAS}}$ threshold is impossible. We analyze an alternative root-mean-squared asymmetry, $A_{\rm{RMS}}$, and show that it is independent of noise down to the average SNR per pixel of 1. However, both metrics depend on the resolution. We argue that asymmetry is, by design, always a scale-dependent measurement, and it is essential to define an asymmetry at a given physical resolution, where the limit should be defined by the size of the smallest features one wishes to detect. We measure asymmetry of a set of $z\approx0.1$ galaxies observed with HST, HSC, and SDSS, and show that after matching the resolution of all images to 200 pc, we are able to obtain consistent $A_{\rm{RMS, 200pc}}$ measurements with all three instruments despite the vast differences in the original resolution or depth. We recommend that future studies use $A_{\rm{RMS, x pc}}$ measurement when evaluating asymmetry, where $x$ is defined by the physical size of the features of interest, and is kept consistent across the dataset, especially when the redshift or image properties of galaxies in the dataset vary.

We report for the first time a sample of 12 supermassive black holes (SMBHs) hosted by low-mass galaxies at cosmic noon, i.e., in a redshift range consistent with the peak of star formation history: $z \sim 1-3$. These black holes are two orders of magnitude too massive for the stellar content of their hosts when compared with the local relation for active galaxies. These overmassive systems at cosmic noon share similar properties with the high-$z$ sources found ubiquitously in recent \textit{James Webb Space Telescope} (\textit{JWST}) surveys (same range of black hole-to-stellar mass ratio, bolometric luminosity, and Eddington ratio). We argue that black hole feedback processes, for which there is possible evidence in five of the sources, and the differing environments in galactic nuclei at these respective epochs play a key role in these overmassive systems. These findings contribute to our understanding of the growth and co-evolution of SMBHs and their host galaxies across cosmic time, offering a link between the early Universe ($z > 4$) observed by \textit{JWST} and observations of the present-day Universe ($z \lesssim 1$).

Unveiling the thermal history of the intergalactic medium (IGM) at $4 \leq z \leq 5$ holds the potential to reveal early onset HeII reionization or lingering thermal fluctuations from HI reionization. We set out to reconstruct the IGM gas properties along simulated Lyman-alpha forest data on pixel-by-pixel basis, employing deep Bayesian neural networks. Our approach leverages the Sherwood-Relics simulation suite, consisting of diverse thermal histories, to generate mock spectra. Our convolutional and residual networks with likelihood metric predicts the Ly$\alpha$ optical depth-weighted density or temperature for each pixel in the Ly$\alpha$ forest skewer. We find that our network can successfully reproduce IGM conditions with high fidelity across range of instrumental signal-to-noise. These predictions are subsequently translated into the temperature-density plane, facilitating the derivation of reliable constraints on thermal parameters. This allows us to estimate temperature at mean cosmic density, $T_{\rm 0}$ with one sigma confidence $\delta T_{\rm 0} \sim 1000{\rm K}$ using only one $20$Mpc/h sightline ($\Delta z\simeq 0.04$) with a typical reionization history. Existing studies utilize redshift pathlength comparable to $\Delta z\simeq 4$ for similar constraints. We can also provide more stringent constraints on the slope ($1\sigma$ confidence interval $\delta {\rm \gamma} \lesssim 0.1$) of the IGM temperature-density relation as compared to other traditional approaches. We test the reconstruction on a single high signal-to-noise observed spectrum ($20$ Mpc/h segment), and recover thermal parameters consistent with current measurements. This machine learning approach has the potential to provide accurate yet robust measurements of IGM thermal history at the redshifts in question.

Over the past 4 decades, the exploration of planets beyond our solar system has yielded the discovery of over 5600 exoplanets orbiting different stars. Continuous advancements in instrumentation and cutting-edge techniques empower astronomers to unveil and characterize new exoworlds with increasing frequency. Notably, direct imaging, also called high-contrast imaging (HCI), stands out as the only method capable of capturing photons emitted directly from the planetary bodies. This innovative technique proves particularly advantageous for scrutinizing nascent planetary systems, where planets shine brilliantly and emit significant heat during their initial developmental phases. HCI provides comprehensive visuals of the entire system, encompassing the central star, potential circumstellar disks, and any additional companions. However, the complexity of imaging an object 10^6 fainter than its parent star necessitates state-of-the-art instrumentation. HCI demands cutting-edge tools such as exAO systems, telescopes exceeding 8 meters in diameter, coronagraphs, and modern imagers. The pivotal role of post-processing cannot be overstated in the quest for detecting and characterizing planets through HCI. This method has not only facilitated the discovery of numerous planets but has also presented invaluable opportunities to explore the properties of young substellar companions, both planets and brown dwarfs. Insights into their interactions with parent disks or other companions within the system, the composition of their atmospheres, and the identification of still accreting planets, also known as "protoplanets," contribute significantly to our understanding of planet formation scenarios. The continued refinement of HCI promises to unveil further revelations in the captivating field of exoplanetary exploration.

In the context of planet formation, growth from micron-sized grains to kilometer-sized planetesimals is a crucial question. Since the dust growth rate depends on the amount of dust, realizing planet formation scenarios based on dust growth is challenging in environments with low metallicity, i.e. less dust. We investigate dust growth during disk evolution, particularly focusing on the relationship with metallicity. We perform two-dimensional thin-disk hydrodynamic simulations to track the disk evolution over 300 kyr from its formation. The dust motion is solved separately from the gas motion, with its distribution changing due to drag forces from the gas. Dust size growth is also accounted for, with the magnitude of the drag force varying according to the dust size. We employ three models with metallicities of 1.0, 0.1, and 0.01 ${\rm Z}_{\odot}$, i.e. dust-to-gas mass ratios of 10$^{-2}$, 10$^{-3}$, and 10$^{-4}$, respectively. In the disks with the metallicities $\ge0.1$ ${\rm Z}_{\odot}$, the dust radii reach cm sizes, consistent with estimations from the dust growth timescale. Conversely, for the metallicity of 0.01 ${\rm Z}_{\odot}$, the maximum dust size is only 10$^{-2}$ cm, with almost no growth observed across the entire disk scale ($\sim$100 au). At the metallicities $\ge0.1$ ${\rm Z}_{\odot}$, the decoupling between grown dust and gas leads to non-uniform dust-to-gas mass ratios. However, deviations from the canonical value of this ratio have no impact on the gravitational instability of the disk. The formation of dust rings is confirmed in the innermost part of the disk ($\sim$10--30 au). The dust rings where the dust-to-gas mass ratio is enhanced, and the Stokes number reaches $\sim$0.1, are suitable environments for the streaming instability. We conjecture that planetesimal formation occurs through the streaming instability in these dust rings.

Galactic rotation curves have been served as indispensable tools for determining the distribution of mass within galaxies. Despite several advances in precision observations, some discrepancies still persist between the inferred matter distribution from luminosity and observed rotation velocities, often attributed to the presence of dark matter. Traditional parametric models, while insightful, struggle with the complexity of galaxies with prominent bulges or non-circular motions, but in contrast, non-parametric methods offer a promising alternative, adapting to the intricate nature of rotation curves without any prior assumptions. In this work, we employ artificial neural networks to reconstruct rotation curves of 17 spiral galaxies from high-quality data, demonstrating the efficacy of the non-parametric approaches in characterizing galactic dynamics. Our findings underscore the importance of employing diverse methodological approaches to comprehensively understand galactic dynamics in modern astrophysics research. Moreover, the non-parametric reconstruction approach with neural networks presents a promising avenue for further investigations, capable of generating interpolations based on the intrinsic patterns of the data.

We compute the accretion efficiency of small solids, with radii 1 cm $\le$ Rs $\le$ 10 m, on planets embedded in gaseous disks. Planets have masses 3 $\le$ Mp $\le$ 20 Earth masses (Me) and orbit within 10 AU of a solar-mass star. Disk thermodynamics is modeled via three-dimensional radiation-hydrodynamic calculations that typically resolve the planetary envelopes. Both icy and rocky solids are considered, explicitly modeling their thermodynamic evolution. Maximum efficiencies of 1 $\le$ Rs $\le$ 100 cm particles are generally $\lesssim$ 10%, whereas 10 m solids tend to accrete efficiently or be segregated beyond the planet's orbit. A simplified approach is applied to compute the accretion efficiency of small cores, with masses Mp $\le$ 1 Me and without envelopes, for which efficiencies are approximately proportional to Mp^(2/3). The mass flux of solids, estimated from unperturbed drag-induced drift velocities, provides typical accretion rates dMp/dt $\lesssim$ 1e-5 Mearth/yr. In representative disk models with an initial gas-to-dust mass ratio of 70-100 and total mass of 0.05-0.06 Msun, solids' accretion falls below 1e-6 Mearth/yr after 1-1.5 million years (Myr). The derived accretion rates, as functions of time and planet mass, are applied to formation calculations that compute dust opacity self-consistently with the delivery of solids to the envelope. Assuming dust-to-solid coagulation times of approximately 0.3 Myr and disk lifetimes of approximately 3.5 Myr, heavy-element inventories in the range 3-7 Me require that approximately 90-150 Me of solids cross the planet's orbit. The formation calculations encompass a variety of outcomes, from planets a few times the Earth mass, predominantly composed of heavy elements, to giant planets. Peak luminosities during the epoch of solids' accretion range from $\approx$ 1e-7 to $\approx$ 1e-6 times the solar luminosity.

We undertake a project to reexamine microlensing data gathered from high-cadence surveys. The aim of the project is to reinvestigate lensing events with light curves exhibiting intricate anomaly features associated with caustics, yet lacking prior proposed models to explain these features. Through detailed reanalyses considering higher-order effects, we identify that accounting for orbital motions of lenses is vital in accurately explaining the anomaly features observed in the light curves of the lensing events OGLE-2018-BLG-0971, MOA-2023-BLG-065, and OGLE-2023-BLG-0136. We estimate the masses and distances to the lenses by conducting Bayesian analyses using the lensing parameters of the newly found lensing solutions. From these analyses, we identify that the lenses of the events OGLE-2018-BLG-0971 and MOA-2023-BLG-065 are binaries composed of M dwarfs, while the lens of OGLE-2023-BLG-0136 is likely to be a binary composed of an early K-dwarf primary and a late M-dwarf companion. For all lensing events, the probability of the lens residing in the bulge is considerably higher than that of it being located in the disk.

The explosion of core-collapse supernovae (CCSNe) is an extremely challenging problem, and there are still large uncertainties regarding which stars lead to successful explosions that leave behind a neutron star, and which ones will form a black hole instead. In this paper, we simulate 341 progenitors at three different metallicities using spherically symmetric simulations that include neutrino-driven convection via a mixing-length theory. We use these simulations to improve previously derived explosion criteria based on the density and entropy profiles of the pre-supernova progenitor. We also provide numerical fits to calculate the final mass of neutron stars based on either compactness, the location of the Si/Si-O interface, or the Chandrasekhar mass. The neutron star birth mass distribution derived from our 1D+ simulations is bimodal, contrary to what the most popular 1D CCSN simulations have shown so far. We compare the theoretically derived neutron star mass distributions with the observed ones and discuss potential implications for population synthesis studies. We also analyze the black hole mass distribution predicted by our simulations. To be consistent with current models of matter ejection in failed SNe, a large fraction of the envelope must be expelled, leading to small black holes in the low-mass gap. One black hole in this mass region has recently been observed in the GW230529 event by the LIGO-Virgo-KAGRA collaboration. Our results naturally agree with this detection, which the most popular prescriptions for explodability and remnant masses are not able to reproduce. In general, we find that the explosion outcome and mass of the remnant strongly depend on the pre-collapse structure of the progenitor. However, their dependence on the initial mass of the star and the mass of the CO core is highly uncertain and non-linear.

A leading candidate for the heating source of chondrules and igneous rims is shock waves. This mechanism generates high relative velocities between chondrules and dust particles. We have investigated the possibility of the chondrule destruction in collisions with dust particles behind a shock wave using a semianalytical treatment. We find that the chondrules are destroyed during melting in collisions. We derive the conditions for the destruction of chondrules and show that the typical size of the observed chondrules satisfies the condition. We suggest that the chondrule formation and rim accretion are different events if they are heated by shock waves.

Research on the solar magnetic field and its effects on solar dynamo mechanisms and space weather events has benefited from the continual improvements in instrument resolution and measurement frequency. The augmentation and assimilation of historical observational data timelines also play a significant role in understanding the patterns of solar magnetic field variation. Within the realm of astronomical data processing, superresolution reconstruction refers to the process of using a substantial corpus of training data to learn the nonlinear mapping between low-resolution and high-resolution images,thereby achieving higher-resolution astronomical images. This paper is an application study in highdimensional non-linear regression. Deep learning models were employed to perform SR modeling on SOHO/MDI magnetograms and SDO/HMI magnetograms, thus reliably achieving resolution enhancement of full-disk SOHO/MDI magnetograms and enhancing the image resolution to obtain more detailed information. For this study, a dataset comprising 9717 pairs of data from April 2010 to February 2011 was used as the training set,1332 pairs from March 2011 were used as the validation set, and 1,034 pairs from April 2011 were used as the test set. After data preprocessing, we randomly cropped 128x128 sub-images as the LR from the full-disk MDI magnetograms, and the corresponding 512x512 sub-images as HR from the HMI full-disk magnetograms for model training. The tests conducted have shown that the study successfully produced reliable 4x super-resolution reconstruction of full-disk MDI magnetograms.The MESR model'sresults (0.911) were highly correlated with the target HMI magnetographs as indicated by the correlation coefficient values. Furthermore, the method achieved the best PSNR, SSIM, MAE and RMSE values, indicating that the MESR model can effectively reconstruct magnetog.

Context. Periodic QSOs are considered as candidates of supermassive binary black hole (BBH) systems in galactic centers. Further confirmation of these candidates may require different lines of observational evidences. Aims. Assuming the Doopler boosting scenario, in this paper we investigate the (coherent) variations of both broad emission lines (BELs) and continuum light curves for active BBH systems surrounding by a circumbinary broad line region (cBLR) and focus on their dependence on the eccentric orbital configuration. Methods. We calculate the variation of continuum light and the Doppler enhanced/weakened photoionization of each BLR cloud according to the motion of BBHs in elliptical orbits, and finally obtain the coherent variation of the continuum and BELs. Results. We find that both the amplitude and variation pattern of the continuum light curves and the evolution of the BEL profiles sensitively depend on the eccentric orbital configuration of BBH systems. If only the secondary BH is active, both the variation amplitudes of continuum light curves and BELs increase with increasing BBH inclination angles and orbital eccentricities, but decrease with increasing BBH mass ratio. If both BHs are active, the asymmetry in the ionization of BLR clouds at different areas caused by the Doppler boosting effect of the secondary BH is weakened due to that of the primary BH at the opposite direction, which leads to systematically smaller variation amplitudes of both continuum light curves and BELs than the cases with only secondary BH activated. Conclusions. The coherent variations of the BEL profiles with the continuum light for those periodic QSOs provide an important way to confirm the existence of BBHs in their center. Future joint analysis of the light curves and multi-epoch observed BEL profiles for periodic QSOs may lead to the identification of a number of BBH systems.

Iron line spectroscopy has been one of the leading methods not only for measuring the spins of accreting black holes but also for testing fundamental physics. Basing on such a method, we present an analysis of a dataset observed simultaneously by NuSTAR and NICER for the black hole binary candidate MAXI J1803-298, which shows prominent relativistic reflection features. Various relxill_nk flavors are utilized to test the Kerr black hole hypothesis. The results obtained from our analysis provide stringent constraints on Johannsen deformation parameter $\alpha_{13}$ with the highest precise to date, namely $\alpha_{13}=0.023^{+0.071}_{-0.038}$ from relxillD_nk and $\alpha_{13}=0.006^{+0.045}_{-0.022}$ from relxillion_nk respectively in 3-$\sigma$ credible lever, where Johannsen metric reduces to Kerr metric when $\alpha_{13}$ vanishes. Furthermore, we investigate the best model-fit results using Akaike Information Criterion and assess its systematic uncertainties.

We investigate the three-dimensional clustering of sources emitting electromagnetic pulses traveling through cold electron plasma, whose radial distance is inferred from their dispersion measure. As a distance indicator, dispersion measure is systematically affected by inhomogeneities in the electron density along the line of sight and special and general relativistic effects, similar to the case of redshift surveys. We present analytic expressions for the correlation function of fast radio bursts (FRBs), and for the galaxy-FRB cross-correlation function, in the presence of these dispersion measure-space distortions. We find that the even multipoles of these correlations are primarily dominated by non-local contributions (e.g. the electron density fluctuations integrated along the line of sight), while the dipole also receives a significant contribution from the Doppler effect, one of the major relativistic effects. A large number of FRBs, $\mathcal{O}(10^{5}\sim10^{6})$, expected to be observed in the Square Kilometre Array, would be enough to measure the even multipoles at very high significance, ${\rm S}/{\rm N} \approx 100$, and perhaps to make a first detection of the dipole (${\rm S}/{\rm N} \approx 10$) in the FRB correlation function and FRB-galaxy cross correlation function. This measurement could open a new window to study and test cosmological models.

Fast coronal mass ejections (CMEs) can drive shock waves capable of accelerating electrons to high energies. These shock-accelerated electrons act as sources of electromagnetic radiation, often in the form of solar radio bursts. Recent findings suggest that radio imaging of solar radio bursts can provide a means to estimate the lateral expansion of CMEs and associated shocks in the low corona. Our aim is to estimate the expansion speed of a CME-driven shock at the locations of radio emission using 3D reconstructions of the shock wave from multiple viewpoints. We estimated the 3D location of radio emission using radio imaging from the Nan\c{c}ay Radioheliograph and the 3D location of the shock. The 3D shock was reconstructed using white-light and extreme ultraviolet images of the CME from the Solar Terrestrial Relations Observatory, Solar Dynamics Observatory, and the Solar and Heliospheric Observatory. The lateral expansion speed of the CME-driven shock at the electron acceleration locations was then estimated using the approximate 3D locations of the radio emission on the surface of the shock. The radio bursts associated with the CME were found to reside at the flank of the expanding CME-driven shock. We identified two prominent radio sources at two different locations and found that the lateral speed of the shock was in the range of $800-1000\,\mathrm{km\,s^{-1}}$ at these locations. Such a high speed during the early stages of the eruption already indicates the presence of a fast shock in the low corona. We also found a larger ratio between the radial and lateral expansion speed compared to values obtained higher up in the corona. The high shock speed obtained is indicative of a fast acceleration during the initial stage of the eruption. This acceleration is most likely one of the key parameters contributing to the presence of metric radio emissions, such as type II radio bursts.

Space-based photometry missions produce exquisite light curves that contain a wealth of stellar variability on a wide range of timescales. Light curves also typically contain significant instrumental systematics -- spurious, non-astrophysical trends that are common, in varying degrees, to many light curves. Empirical systematics-correction approaches using the information in the light curves themselves have been very successful, but tend to suppress astrophysical signals, particularly on longer timescales. Unlike its predecessors, the PLATO mission will use multiple cameras to monitor the same stars. We present REPUBLIC, a novel systematics-correction algorithm which exploits this multi-camera configuration to correct systematics that differ between cameras, while preserving the component of each star's signal that is common to all cameras, regardless of timescale. Through simulations with astrophysical signals (star spots and planetary transits), Kepler-like errors, and white noise, we demonstrate REPUBLIC's ability to preserve long-term astrophysical signals usually lost in standard correction techniques. We also explore REPUBLIC's performance with different number of cameras and systematic properties. We conclude that REPUBLIC should be considered a potential complement to existing strategies for systematic correction in multi-camera surveys, with its utility contingent upon further validation and adaptation to the specific characteristics of the PLATO mission data

H$_2$CO is a small organic molecule widely detected in protoplanetary disks. As a precursor to grain-surface formation of CH$_3$OH, H$_2$CO is considered an important precursor of O-bearing organic molecules that are locked in ices. Still, since gas-phase reactions can also form H$_2$CO, there remains an open question on the channels by which organics form in disks, and how much the grain versus the gas pathways impact the overall organic reservoir. We present spectrally and spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of several ortho- and para-H$_2$CO transitions toward the bright protoplanetary disk around the Herbig Ae star HD 163296. We derive column density, excitation temperature, and ortho-to-para ratio (OPR) radial profiles for H$_2$CO, as well as disk-averaged values of $N_{\mathrm{T}}\sim4\times 10^{12}$ cm$^{-2}$, $T_{\mathrm{ex}}\sim20$ K, and $\mathrm{OPR}\sim2.7$, respectively. We empirically determine the vertical structure of the emission, finding vertical heights of $z/r\sim0.1$. From the profiles, we find a relatively constant $\mathrm{OPR}\sim2.7$ with radius, but still consistent with $3.0$ among the uncertainties, a secondary increase of $N_{\mathrm{T}}$ in the outer disk, and low $T_{\mathrm{ex}}$ values that decrease with disk radius. Our resulting radial, vertical, and OPR constraints suggest an increased UV penetration beyond the dust millimeter edge, consistent with an icy origin but also with cold gas-phase chemistry. This Herbig disk contrasts previous results for the T Tauri disk, TW Hya, which had a larger contribution from cold gas-phase chemistry. More observations of other sources are needed to disentangle the dominant formation pathway of H$_2$CO in protoplanetary disks.

We review some recent results of general relativistic magnetohydrodynamic (GR-MHD) simulations considering the evolution of geometrically thin disks around a central black hole. Thin disk GR-MHD simulations complement the widely used MAD (Magnetically Arrested Disk) or SANE (Standard And Normal Evolution) approaches of evolving from an initial disk torus. In particular, we discuss the dynamical evolution of the disk, its role in the formation of disk winds or jets, the impact of disk resistivity, and its potential role in generating magnetic flux by an internal disk dynamo. The main characteristics of a thin disk in our approach are the Keplerian rotation of the disk material, which allows to launch disk outflows by the Blandford-Payne magneto-centrifugal effect, in addition to the Blandford-Znajek-driven spine jet from the black hole ergosphere. Thus, for this approach, we neglect disk thermodynamics and radiative effects, concentrating predominantly on the dynamical evolution of the system. Resistive MHD further allows the investigation of physical reconnection and also dynamo action. Magnetic reconnection may generate magnetic islands of plasmoids that are ejected from the disk along with the outflow. We also discussed potential applications of thin disk in explaining the decaying phase of an outburst in black hole X-ray binaries (BH-XRBs). Post-processing of radiation using the simulated dynamical data allows to derive spectra or fluxes, e.g., in the X-ray band, and to derive potential variability characteristics.

Many previous works studied the dynamical timescale mass transfer stability criteria based on the donor response with neglecting the stellar structure of the accretor. In this letter, we investigate the radial response of accretors with mass accumulation and its effect on the binary mass transfer stability. We perform a series of detailed stellar evolution simulations with different types of accretors and obtain the radial variations of stars accreting at different rates. Since the time within which the donor loses half of the original mass has a correlation with the donor mass, we approximately obtain the mean mass transfer rate as a function of mass ratio. Assuming that the common envelope (CE) phase occurs if the accretor radius exceeds the outer Roche lobe radius, we obtain the critical mass ratio of dynamically unstable mass transfer. We find the critical mass ratios for donors filling their Roche lobes at the Main Sequence (MS) and Hertzsprung Gap (HG) stages are smaller than that derived from the radial response of the donor in the traditional way. Our results may suggest that the binary is easier to enter into the CE phase for a donor star at the MS or HG stage than previously believed.

The most promising mechanism of generating primordial black holes (PBHs) is by the enhancement of power spectrum of the primordial curvature perturbation, which is usually accompanied by the the enhancement of non-Gaussianity that crucially changes the abundance of PBHs. In this review I will discuss how non-Gaussianity is generated in single field inflation as well as in the curvaton scenario, and then discuss how to calculate PBH mass function with such non-Gaussianities. I also show non-Gaussianity only has mild effects on the induced gravitational waves (GWs), which gives robust predictions in the mHz and nHz GW experiments.

We analyse the spatial distribution and vertical stratification of the physical parameters of the solar atmosphere when an X-class flare occurs. We made use of observations acquired by the Interferometric Bidimensional Spectropolarimeter instrument when observing the full Stokes parameters for the Fe I 6173 A and Ca II 8542 A transitions. We analysed the observed spectra using the newly developed DeSIRe code to infer the atmospheric parameters at photospheric and chromospheric layers over the entire observed field of view. Our findings reveal that the chromosphere is characterised by temperature enhancements and strong upflows in the flare ribbon area, which indicates that the flaring event is producing hot material that is moving outwards from the Sun. We did not detect any trace of temperature enhancements or strong velocities (of any sign) at photospheric layers, signalling that the impact of the flaring event mainly happens at the middle and upper layers. The information about the magnetic field vector revealed relatively smooth stratifications with height for both magnetic field strength and inclination. Still, when examining the spatial distribution of the magnetic field inclination, we observed the presence of large-scale mixed polarities in the regions where the flare ribbon is located. These results suggest that the interaction between those mixed polarities could be the flare's triggering mechanism.

The Vera C. Rubin Observatory, currently in construction in Chile, will start performing the Legacy Survey of Space and Time (LSST) in 2025 for 10 years. Its 8.4-meter telescope will survey the southern sky in less than 4 nights in six optical bands, and repeatedly generate about 2 000 exposures per night, corresponding to a data volume of about 20 TiB every night. Three data facilities are preparing to contribute to the production of the annual data releases: the US Data Facility will process 35% of the raw data, the UK data facility will process 25% of the raw data and the French data facility, operated by CC-IN2P3, will locally process the remaining 40% of the raw data. In the context of the Data Preview 0.2 (DP0.2), the Data Release Production pipelines have been executed on the DC-2 simulated dataset (generated by the Dark Energy Science Collaboration, DESC). This dataset includes 20 000 simulated exposures, representing 300 square degrees of Rubin images with a typical depth of 5 years. DP0.2 ran at the Interim Data Facility (based on Google cloud), and the full exercise was independently replicated at CC-IN2P3. During this exercise, 3 PiB of data and more than 200 million files were produced. In this contribution we will present a detailed description of the system that we set up to perform this processing campaign using CC-IN2P3's computing and storage infrastructure. Several topics will be addressed: workflow generation and execution, batch job submission, memory and I/O requirements, etc. We will focus on the issues that arose during this campaign and how we addressed them and will present some perspectives after this exercise.

Measurements of the cosmic redshift drift - the change in redshift of a source over time - will enable independent detection of cosmological expansion thanks to the immense precision soon reached by new facilities such as the Square Kilometer Array Observatory and the Extremely Large Telescope. We conduct the first ever redshift drift computation in fully relativistic cosmological simulations, with the simulations performed with the Einstein Toolkit. We compute the redshift drift over the full skies of 50 synthetic observers in the simulation. We compare all-sky averages for each observer - and across all observers - to the Einstein-de Sitter (EdS) model which represents the large-scale spatially-averaged spacetime of the simulation. We find that at $z\approx0.2$ the mean redshift drift across the sky for all observers deviates from the EdS prediction at the percent level, reducing to $\sim0.1\%$ by $z\approx 1$. However, fluctuations in the redshift drift across the sky are $\sim 10-30\%$ at $z\approx 0.1$ and a few percent at $z\approx 0.5$. Such fluctuations are large enough to potentially exceed the expected precision of upcoming redshift drift measurements. Additionally, we find that along 0.48% of the light rays the redshift drift becomes temporarily positive at very low redshift of $z\lesssim 0.02$. This occurs despite our simulation data being based on a matter-dominated model universe. By including a cosmological constant, we expect a slower growth of structures than in the leading-order EdS space-time, and this may reduce the anisotropy over the observers' skies, although we generally expect our results to hold as order-of-magnitude estimates. Redshift drift is arguably one of the most important measurements to be made by next-generation telescopes. Our results collectively serve as preparation for interpreting such a measurement in the presence of realistic cosmic structures.

We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernovae luminosity distances. Demonstrated using simulated datasets of the complete DESI, LSST and Roman surveys designed for BAO and SNe distance measurements, we show that using our method, the dynamical behaviour of the energy, pressure, equation of state (with its time derivative) of dark energy and the cosmic deceleration function can all be accurately recovered from high-quality data, which allows for robust diagnostic tests for dark energy models.

We present a multiwavelength study of AB Doradus, combining modelling that incorporates a spectropolarimetric magnetic field map with 8.4 GHz radio interferometry to measure the coronal extent and density of this young star. We use the surface magnetic field map to produce a 3D extrapolation of AB Dor's coronal magnetic field. From this model we create synthetic radio images throughout the stellar rotation period which we can compare with the interferometric radio observations. Our models reproduce the two-lobe structure seen in the radio observations. We successfully fit the observed flux magnitude and lobe separation with our model. We conclude that that the features seen in the radio images are a result of centrifugal containment of hot gas at the peak of closed magnetic loops, and that the corona of AB Dor extends to about 8-10 stellar radii, making it much more extended than the present-day solar corona.

We extract key information of dark energy from current observations of BAO, OHD and $H_0$, and find hints of dynamical behaviour of dark energy. In particular, a dynamical dark energy model whose equation of state crosses $-1$ is favoured by observations. We also find that the Universe has started accelerating at a lower redshift than expected.

Chance-aligned sources or blended companions can cause false positives in planetary transit detections or simply bias the determination of the candidate properties. In the era of high-precision space-based photometers, the need for high-spatial resolution images has demonstrated to be critical for validating and confirming transit signals. This already applied to the Kepler mission, it is now applicable to the TESS survey and will be critical for PLATO. We present the results of the AstraLux-TESS survey, a catalog of high-spatial resolution images obtained with the AstraLux instrument (Calar Alto) in the context of the TESS Follow-up Observing Program. We use the lucky-imaging technique to obtain high-spatial resolution images from planet candidate hosts included mostly in two relevant regimes: exoplanet candidates belonging to the level-one requirement of the TESS mission (planets with radii $R<4~R_{\oplus}$), and candidates around intermediate-mass stars. Among the 185 planet host candidate stars observed, we found 13 (7%) to be accompanied by additional sources within 2.2 arcsec separation. Among them, six are not associated to sources in the Gaia DR3 catalog, thus contaminating the TESS light curve. We provide upper limits and probabilities to the possible existence of field contaminants through the sensitivity limits of our images. Among the isolated hosts, we can discard hazardous companions (bright enough to mimic a planetary transit signals) for all their planets. The results from this catalog are key for the statistical validation of small planets (prime targets of the TESS mission) and planets around intermediate-mass stars in the main-sequence. These two populations of planets are hard to confirm with the radial velocity technique. Our results also demonstrate the importance of this type of follow-up observations for future transit missions like PLATO, even in the Gaia era.

In order to test the efficacy of Gamma-ray Bursts (GRBs) as cosmological probes, we the characterize the scatter in the correlations between six pairs of GRB related observables, which have previously also been studied in arXiv:2011.14040. However, some of these observables depend on the luminosity distance, for which one needs to assume an underlying cosmological model. In order to circumvent this circularity problem, we use X-ray and UV fluxes of quasars as distance anchors to calculate the luminosity distance in a model-independent manner, which in turn gets used to calculate the GRB-related quantities. We find that all the six pairs of regression relations show a high intrinsic scatter for both the low and high redshift sample. This implies that these GRB observables cannot be used as model-independent cosmological probes.

Recently published studies suggested that the difference between Universal and Coordinated Time UT1-UTC could reach a large positive value in a few years, making it necessary to introduce a negative leap second into the UTC scale for the first time in its history. Based on the latest UT1 series provided by the International Earth Rotation and Reference Systems Service (IERS) and its prediction, it was shown that the tendency to acceleration of the Earth's rotation observed over past four years most likely will return to the deceleration, which is the usual behavior of the Earth rotational dynamics.

We perform high resolution simulations of forming star clusters as they merge inside giant molecular clouds (GMCs) using hydrodynamics coupled to N-body dynamics to simultaneously model both the gas and stars. We zoom in to previously run GMC simulations and resolve clusters into their stellar and gas components while including the surrounding GMC environment. We find that GMC gas is important in facilitating the growth of clusters in their embedded phase by promoting cluster mergers. Mergers induce asymmetric expansion of the stellar component of the clusters in our simulations. As well, mergers induce angular momentum in the clusters' stellar and gas components. We find that mergers can lead to an increase in the amount of dense gas present in clusters if a background gas distribution is present. We predict that this can lead to new star formation that can change the overall distribution of cluster stars in velocity space. Our results suggest that subcluster mergers in the presence of background gas can imprint dynamical signatures that can be used to constrain cluster formation histories.

The Atmospheric Dispersion Corrector (ADC) of the Gemini Planet Imager (GPI) corrects the chromatic dispersion caused by differential atmospheric refraction (DAR), making it an important optic for exoplanet observation. Despite requiring less than 5 mas of residual DAR to avoid potentially affecting the coronagraph, the GPI ADC averages $\sim7$ and $\sim11$ mas of residual DAR in $H$ and $J$ band respectively. We analyzed GPI data in those bands to find explanations for the underperformance. We found the model GPI uses to predict DAR underestimates humidity's impact on incident DAR, causing on average a 0.54 mas increase in $H$ band residual DAR. Additionally, the GPI ADC consistently undercorrects in $H$ band by about 7 mas, causing almost all the $H$ band residual DAR. $J$ band does not have such an offset. Perpendicular dispersion induced by the GPI ADC, potentially from a misalignment in the prisms' relative orientation, causes 86% of the residual DAR in $J$ band. Correcting these issues could reduce residual DAR, thereby improving exoplanet detection. We also made a new approximation for the index of refraction of air from 0.7 microns to 1.36 microns that more accurately accounts for the effects of humidity.

We do a careful investigation of the prospects of dark energy (DE) interacting with cold dark matter (CDM) in alleviating the $S_8$ clustering tension. To this end, we consider various well-known parametrizations of the DE equation of state (EoS), and consider perturbations in both the dark sectors, along with an interaction term. Moreover, we perform a separate study for the phantom and non-phantom regimes. Using CMB, BAO and SNIa datasets, the constraints on the model parameters for each case have been obtained and a generic reduction in the $H_0-\sigma_{8,0}$ correlation has been observed, both for constant and dynamical DE EoS. This reduction, coupled with a significant negative correlation between the interaction term and $\sigma_{8,0}$, contributes to easing the clustering tension by lowering $\sigma_{8,0}$ to somewhere in between the early CMB and late-time clustering measurements for the phantom regime, for almost all the models under consideration. In addition, this is achieved without exacerbating the Hubble tension. In this regard, the CPL and JBP models perform the best in relaxing the $S_8$ tension to $<1\sigma$. However, for the non-phantom regime the $\sigma_{8,0}$ tension tends to have worsened, which reassures the merits of phantom dark energy from latest data. We further do an investigation of the role of RSD datasets and find an overall reduction in tension, with a value of $\sigma_{8,0}$ relatively closer to the CMB value. We finally check if further extensions of this scenario, like the inclusion of the sound speed of dark energy and warm dark matter interacting with DE, can have some effects.

Recently, models of the quasar luminosity function (QLF) rooted on large observational compilations have been produced that, unlike their predecessors, feature a smooth evolution with time. This bypasses the need to assume an ionizing emissivity evolution when simulating helium reionization with observations-based QLF, thus yielding more robust constraints. We combine one such QLF with a cosmological hydrodynamical simulation and 3D multi-frequency radiative transfer. The simulated reionization history is consistently delayed in comparison to most other models in the literature. The predicted intergalactic medium temperature is larger than the observed one at $z \lesssim 3$. Through forward modeling of the He II Lyman-$\alpha$ forest, we show that our model produces an extended helium reionization and successfully matches the bulk of the observed effective optical depth distribution, although it over-ionizes the Universe at $z\lesssim2.8$ as the effect of small-scale Lyman Limit Systems not being resolved. We thoroughly characterize transmission regions and dark gaps in He II Lyman-$\alpha$ forest sightlines. We quantify their sensitivity to the helium reionization, opening a new avenue for further observational studies of this epoch. Finally, we explore the implications for helium reionization of the large number of active galactic nuclei revealed at $z\gtrsim5$ by JWST. We find that such modifications do not affect any observable at $z\leq4$, except in our most extreme model, indicating that the observed abundance of high-$z$ AGNs does not bear consequences for helium reionization.

In this work we study, within the framework of Cowling approximation, the effect of the electric charge on the gravitational wave frequency of fluid oscillation modes of strange quark stars. For this purpose, the dense matter of the stellar fluid is described by the MIT bag model equation of state (EoS), while for the electric charge profile, we consider that the electric charge density is proportional to the energy density. We find that the gravitational wave frequencies change with the increment of electric charge; these effects are more noticeable at higher total mass values. We obtain that the $f$-mode is very sensitive to the change in the electric charge of the star. Furthermore, in the case of the $p_1$ mode, the effect of the electric charge is not very significant. Our results reveal that the study of the fundamental pulsation mode of an electrically charged compact star is very important to distinguish whether compact stars could contain electric charge.

Contact binary may be the progenitor of a red nova that eventually produces a merger event and have a cut-off period around 0.2 days. Therefore, a large number of contact binaries is needed to search for the progenitor of red novae and to study the characteristics of short-period contact binaries. In this paper, we employ the Phoebe program to generate a large number of light curves based on the fundamental parameters of contact binaries. Using these light curves as samples, an autoencoder model is trained, which can reconstruct the light curves of contact binaries very well. When the error between the output light curve from the model and the input light curve is large, it may be due to other types of variable stars. The goodness of fit (R2) between the output light curve from the model and the input light curve is calculated. Based on the thresholds for global goodness of fit (R2), period, range magnitude, and local goodness of fit (R2), a total of 1322 target candidates were obtained.

We write down the force-free electrodynamics (FFE) equations in dipole coordinates, and solve for normal modes corresponding to Alfv\'enic perturbations in the magnetosphere of a neutron star. We show that a single Alfv\'en wave propagating on dipole field lines spontaneously sources a fast magnetosonic (fms) wave at the next order in the perturbation expansion, without needing 3-wave interaction. The frequency of the sourced fms wave is twice the original Alfv\'en wave frequency, and the wave propagates spherically outwards. The properties of the outgoing fms wave can be computed exactly using the usual devices of classical electrodynamics. We extend the calculation to the closed zone of a rotating neutron star magnetosphere, and show that the Alfv\'en wave also sources a spherical fms wave but at the same frequency as the primary Alfv\'en wave.

Gamma-ray burst (GRBs) are the brightest events in the universe. For decades, astrophysicists have known about their cosmological nature. Every year, space missions such as Fermi and SWIFT detect hundreds of them. In spite of this large sample, GRBs show a complex taxonomy in the first seconds after their appearance, which makes it very difficult to find similarities between them using conventional techniques. It is known that GRBs originate from the death of a massive star or from the merger of two compact objects. GRB classification is typically based on the duration of the burst (Kouveliotou et al., 1993). Nevertheless, events such as GRB 211211A (Yang et al., 2022), whose duration of about 50 seconds lies in the group of long GRBs, has challenged this categorization by the evidence of features related with the short GRB population (the kilonova emission and the properties of its host galaxy). Therefore, a classification based only on their gamma-ray duration does not provide a completely reliable determination of the progenitor. Motivated by this problem, Jespersen et al. (2020) and Steinhardt et al. (2023) carried out analysis of GRB light curves by using the t-SNE algorithm, showing that Swift/BAT GRBs database, consisting of light curves in four energy bands (15-25 keV, 25-50 keV, 50-100 keV, 100-350 keV), clusters into two groups corresponding with the typical long/short classification. However, in this case, this classification is based on the information provided by their gamma-ray emission light curves. ClassiPyGRB is a Python 3 package to download, process, visualize and classify GRBs database from the Swift/BAT Instrument (up to July 2022). It is distributed over the GNU General Public License Version 2 (1991). We also included a noise-reduction and an interpolation tools for achieving a deeper analysis of the data.

Neutrino flavor transformation offers a window into the physics of various astrophysical environments, including our Sun and the more exotic environs of core-collapse supernovae and binary neutron-star mergers. Here, we apply an inference framework - specifically: statistical data assimilation (SDA) - to neutrino flavor evolution in the Sun. We take a model for solar neutrino flavor evolution, together with Earth-based neutrino measurements, to infer solar properties. Specifically, we ask what signature of the radially-varying solar electron number density $n_e(r)$ is contained within these Earth-based measurements. Currently, the best estimates of $n_e(r)$ come from the standard solar model. We seek to ascertain, through novel application of the SDA method, whether estimates of the same from neutrino data can serve as independent constraints.

Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionise the study of tidal features. However, the volume of data will far surpass the capacity to inspect each galaxy to identify the feature visually, thereby motivating an urgent need to develop automated detection methods. This paper presents a visual classification of $\sim$2,000 galaxies from the DECaLS survey into different tidal feature categories: arms, streams, shells, and diffuse. Using these labels, we trained a Convolutional Neural Network (CNN) to reproduce the assigned visual classifications. Overall our network performed well and retrieved a median $81.1^{+5.8}_{-6.5}$, $65.7^{+5.0}_{-8.4}$, $91.3^{+6.0}_{-5.9}$, and $82.3^{+1.4}_{-7.9}$ per cent of the actual instances of arm, stream, shell, and diffuse features respectively for just 20 per cent contamination. We verified that the network was classifying the images correctly by using a Gradient-weighted Class Activation Mapping analysis to highlight important regions on the images for a given classification. This is the first demonstration of using CNNs to classify tidal features into sub-categories, and it will pave the way for the identification of different categories of tidal features in the vast samples of galaxies that forthcoming wide-field surveys will deliver.

A strong global magnetic field of young low-mass stars and a high accretion rate are the necessary conditions for the formation of collimated outflows (jets) from these objects. But it is still unclear whether these conditions are also sufficient. We aim to check whether BP Tau, an actively accreting young star with a strong magnetic field, has a jet. We carried out narrowband SII 672 nm imaging and spectroscopic observations of BP Tau and its vicinity. We find that BP Tau is a source of a Herbig-Haro flow (assigned number HH 1181), which includes two HH objects moving from the star in opposite directions and a micro- (counter-) jet of ~ 1" projected length. The flow is oriented along position angle $59 \pm 1$ degree.

Emission lines from Rydberg transitions are detected for the first time from a region close to the surface of Betelgeuse. The H30${\alpha}$ line is observed at 231.905 GHz, with a FWHM ~42 km/s and extended wings. A second line at 232.025 GHz (FWHM ~21 km/s), is modeled as a combination of Rydberg transitions of abundant low First Ionization Potential metals. Both H30${\alpha}$ and the Rydberg combined line X30${\alpha}$ are fitted by Voigt profiles, and collisional broadening with electrons may be partly responsible for the Lorentzian contribution, indicating electron densities of a few 10$^8$cm$^{-3}$. X30${\alpha}$ is located in a relatively smooth ring at a projected radius of 0.9x the optical photospheric radius R$_*$, whereas H30${\alpha}$ is more clumpy, reaching a peak at ~1.4R$_*$. We use a semi-empirical thermodynamic atmospheric model of Betelgeuse to compute the 232 GHz (1.29mm) continuum and line profiles making simple assumptions. Photoionized abundant metals dominate the electron density and the predicted surface of continuum optical depth unity at 232 GHz occurs at ~1.3R$_*$, in good agreement with observations. Assuming a Saha-Boltzmann distribution for the level populations of Mg, Si, and Fe, the model predicts that the X30${\alpha}$ emission arises in a region of radially-increasing temperature and turbulence. Inclusion of ionized C and non-LTE effects could modify the integrated fluxes and location of emission. These simulations confirm the identity of the Rydberg transition lines observed towards Betelgeuse, and reveal that such diagnostics can improve future atmospheric models.

Despite decades of effort, the mechanisms by which the spin axis of a star and the orbital axes of its planets become misaligned remain elusive. Particularly, it is of great interest whether the large spin-orbit misalignments observed are driven primarily by high-eccentricity migration -- expected to have occurred for short-period, isolated planets -- or reflect a more universal process that operates across systems with a variety of present-day architectures. Compact multi-planet systems offer a unique opportunity to differentiate between these competing hypotheses, as their tightly-packed configurations preclude violent dynamical histories, including high-eccentricity migration, allowing them to trace the primordial disk plane. In this context, we report measurements of the sky-projected stellar obliquity ($\lambda$) via the Rossiter-McLaughlin effect for two sub-Saturns in multiple-transiting systems: TOI-5126 b ($\lambda=1\pm 48\,^{\circ}$) and TOI-5398 b ($\lambda=-24^{+14}_{-13} \,^{\circ}$). Both are spin-orbit aligned, joining a fast-growing group of just three other compact sub-Saturn systems, all of which exhibit spin-orbit alignment. Our results strongly suggest that sub-Saturn systems are primordially aligned and become misaligned largely in the post-disk phase through violent dynamical interactions inherent to eccentric migration, as appears to be the case increasingly for other exoplanet populations.

Recently, much attention has been focused on the false-vacuum islands that are flooded by an expanding ocean of true-vacuum bubbles slightly later than most of the other parts of the world. These delayed decay regions will accumulate locally larger vacuum energy density by staying in the false vacuum longer than those already transited into the true vacuum. A false-vacuum island with thus acquired density contrast of a super-horizon size will evolve locally from radiation dominance to vacuum dominance, creating a local baby Universe that can be regarded effectively as a local closed Universe. If such density contrasts of super-horizon sizes can ever grow large enough to exceed the threshold of gravitational collapse, primordial black holes will form similar to those collapsing curvature perturbations on super-horizon scales induced by small-scale enhancements during inflation. If not, such density contrasts can still induce curvature perturbations potentially observable today. In this paper, we revisit and elaborate on the generations of primordial black holes and curvature perturbations from delayed-decayed false-vacuum islands during asynchronous first-order phase transitions with fitting formulas convenient for future model-independent studies.

The Standard Model of particle physics predicts the speed of light to be a universal speed of propagation of massless carriers. However, other possibilities exist -- including Lorentz-violating theories -- where different fundamental fields travel at different speeds. Black holes are interesting probes of such physics, as distinct fields would probe different horizons. Here, we build an exact spacetime for two interacting scalar fields which have different propagation speeds. One of these fields is able to probe the black hole interior of the other, giving rise to energy extraction from the black hole and a characteristic late-time relaxation. Our results provide further stimulus to the search for extra degrees of freedom, black hole instability, and extra ringdown modes in gravitational-wave events.

Recent theoretical progress using multiscale asymptotic analysis has revealed various possible regimes of stratified turbulence. Notably, buoyancy transport can either be dominated by advection or diffusion, depending on the effective P\'eclet number of the flow. Two types of asymptotic models have been proposed, which yield measurably different predictions for the characteristic vertical velocity and length scale of the turbulent eddies in both diffusive and non-diffusive regimes. The first, termed a `single-scale model', is designed to describe flow structures having large horizontal and small vertical scales, while the second, termed a `multiscale model', additionally incorporates flow features with small horizontal scales, and reduces to the single-scale model in their absence. By comparing predicted vertical velocity scaling laws with direct numerical simulation data, we show that the multiscale model correctly captures the properties of strongly stratified turbulence within spatiotemporally-intermittent turbulent patches. Meanwhile its single-scale reduction accurately describes the more orderly layer-like flow outside those patches.

The measurement of the parametrized post-Newtonian parameter $\gamma_{\rm{PPN}}$ is a robust test of general relativity (GR). In some modified theories of gravity, $\gamma_{\rm{PPN}}$ may evolve with the redshift and deviate from one at high redshifts. This means that precise constraints on $\gamma_{\rm{PPN}}$ acquired in the solar system experiments could not be sufficient to test such theories and it is necessary to constrain $\gamma_{\rm{PPN}}$with high precision at high redshifts. However, in many approaches aimed at extragalactic tests of GR, the results might be biased due to entanglement of various factors, such as cosmic curvature, cosmic opacity, and the Hubble constant. Strong lensing systems naturally provide a laboratory to test $\gamma_{\rm{PPN}}$ at galactic scales and high redshifts, but there is degeneracy between measured strength of gravity and cosmic distances in the lensing system. Gravitational waves (GWs) from binary neutron star mergers (standard sirens) provide a direct way to break this degeneracy by providing self-calibrated measurements of the luminosity distance. {We investigate the possibility of estimating $\gamma_{\rm{PPN}}$ by combining well measured strongly lensed systems with GW signals from coalescing neutron stars. Such combination provides a cosmological-model independent, relatively pure and unbiased method for the inference of $\gamma_{\rm{PPN}}$ parameter, avoiding the influence of the above factors and the mass-sheet degeneracy in the lens.} Based on the simulated future 55 lensed quasar systems we demonstrated that the precision of $\gamma_{\rm{PPN}}$ parameter obtained by our method could be of order of $\sim 10^{-2}$. One may reasonably expect that our approach will play an increasingly important role in precise testing the validity of general relativity at galactic scales and high redshifts.

The equation of state of hot neutron star matter of n+p+e+$\mu$ composition in $\beta$-equilibrium is studied for both neutrino-free isothermal and neutrino-trapped isentropic conditions, using the formalism where the thermal evolution is built upon its zero-temperature predictions in a self-consistent manner. The accuracy of the parabolic approximation, often used in the finite temperature calculation of hot neutron star matter, is verified by comparing with the results obtained from the exact evaluation in the neutrino-free neutron star matter. The equation of state of neutrino-trapped isentropic matter at low entropic condition, relevant to the core-collapsing supernovae, is formulated. In the isentropic matter, the particle fractions and equation of state have marginal variance as entropy per particle varies between 1 to 3 (in the unit of k$_B$), but the temperature profile shows marked variation. The isentropes are found to be much less sensitive to the nuclear matter incompressibility, but have a large dependence on the slope parameter L. The bulk properties of the neutron stars predicted by the isentropic equation of state for different entropy are calculated. A model calculation for the early stage evolution of the protoneutron star to neutron star configuration is also given.

With the observed data of the S2 orbit around the black hole Sgr A$^*$ and the Markov Chain Monte Carlo method, we make a constraint on parameters of a disformal Schwarzschild black hole in quadratic degenerate higher-order scalartensor (DHOST) theories. This black hole belongs to a class of non-stealth solutions and owns an extra disformal parameter described the deviation from general relativity. Our results show that the best fit value of the disformal parameter is positive. However, in the range of $1\sigma$, we also find that general relativity remains to be consistent with the observation of the S2 orbit.

Hot axions, thermally produced in the Early Universe, would contribute to dark radiation and are thus subject to present and future constraints from $N_{\rm eff}$. In this paper we quantify the contribution to $N_{\rm eff}$ and its uncertainty in models with axion-gluon couplings from thermal dynamics above the QCD transition. In more detail, we determine the leading-order thermal axion production rate for axion momenta of the order of the temperature adopting three different schemes for the incorporation of the collective dynamics of soft gluons. We show how these three schemes extrapolate differently into the regime of softer axion production, thus giving us a quantitative handle on the theory uncertainty of the rate. Upon solving the Boltzmann equation, we find that this theory uncertainty translates to an uncertainty of at most 0.002 for $N_{\rm eff}$. The uncertainty from common momentum-averaged approximations to the Boltzmann equation is smaller. We also comment on existing rate determinations in the literature and discuss how QCD transition dynamics would need to be integrated into our results.

Constraining the equation of state (EOS) of strongly interacting, dense matter is the focus of intense experimental, observational, and theoretical effort. Chiral effective field theory ($\chi$EFT) can describe the EOS between the typical densities of nuclei and those in the outer cores of neutron stars while perturbative QCD (pQCD) can be applied to properties of deconfined quark matter, both with quantified theoretical uncertainties. However, describing the complete range of densities between nuclear saturation and an almost-free quark gas with a single EOS that has well-quantified uncertainties is a challenging problem. In this work, we argue that Bayesian multi-model inference from $\chi$EFT and pQCD can help bridge the gap between the two theories: we combine the Gaussian random variables that constitute the theories' predictions for the pressure as a function of the density in symmetric nuclear matter. We do this using two Bayesian model mixing procedures: a pointwise approach, and a correlated approach implemented via a Gaussian process (GP), and present results for the pressure and speed of sound in each. The second method produces a smooth $\chi$EFT-to-pQCD EOS. Without input data in the intermediate region, the choice of prior on the EOS, encoded through the GP kernel, as the prior on the EOS function space significantly affects the result in that region. We also discuss future extensions and applications to neutron star matter guided by recent EOS constraints from nuclear theory, nuclear experiment, and multi-messenger astronomy.

A complete canonical formulation of general covariance makes it possible to construct new modified theories of gravity that are not of higher-curvature form, as shown here in a spherically symmetric setting. The usual uniqueness theorems are evaded by using a crucial and novel ingredient, allowing for fundamental fields of gravity distinct from an emergent space-time metric that provides a geometrical structure to all solutions. As specific examples, there are new expansion-shear couplings in cosmological models, a form of modified Newtonian dynamics (MOND) can appear in a space-time covariant theory without introducing extra fields, and related effects help to make effective models of canonical quantum gravity fully consistent with general covariance.

The main limitation for pre-inflationary breaking of Peccei-Quinn (PQ) symmetry is the upper bound on the Hubble rate during inflation from axion isocurvature fluctuations. This leads to a tension between high scale inflation and QCD axions with Grand Unified Theory (GUT) scale decay constants, which reduces the potential for a detection of tensor modes at next generation CMB experiments. We propose a mechanism that excplicitly breaks PQ symmetry via non-minimal coupling to gravity, that lifts the axion mass above the Hubble scale during inflation and has negligible impact on today's axion potential. The initially heavy axion gets trapped at an intermediate minimum during inflation given by the phase of the non-minimal coupling, before it moves to its true CP-conserving minimum after inflation. During this stage it undergoes coherent oscillations around an adiabatically decreasing minimum, which slightly dilutes the axion energy density, while still being able to explain the observed dark matter relic abundance. This scenario can be tested by the combination of next generation CMB surveys like CMB-S4 and LiteBIRD with haloscopes such as ABRACADABRA or CASPEr-Electric.

Several attempts to solve the cosmological constant problem, which concerns the value of the cosmological constant being extremely smaller than the Standard Model mass scales, have introduced a scalar field with a very flat potential that can be approximated as linear around any given position. The scalar field scans the cosmological constant in such a way that the current small value is explained. Recently, Dark Energy Spectroscopic Instrument (DESI) reported the results of the first year. Combining the data with CMB, Pantheon, Union3, and/or DES-SN5YR, there is a preference or anomaly, indicating that the dark energy in the current Universe slightly deviates from that in the $\Lambda$CDM model and varies over time. In this paper, I show that the simple linear potential of a scalar field that may explain the small cosmological constant can explain the DESI anomaly. In particular, the model proposed by the present author in 2108.04246, which relaxes the cosmological constant by the condition that inflation ends, predicts a time-dependence of the dark energy close to the one favored by the data.

Context. At the extreme densities reached in the core of neutron stars, it is possible that quark deconfined matter is produced. The formation of this new phase of strongly interacting matter is likely to occur via a first-order phase transition for the typical temperatures reached in astrophysical processes. The first seeds of quark matter would then form through a process of nucleation within the metastable hadronic phase. Aims. Here we address the role of the thermal fluctuations in the hadronic composition on the nucleation of two-flavour quark matter. Methods. At finite temperature, thermodynamic quantities in a system fluctuate around average values. Being nucleation a local process, it is possible that it occurs in a subsystem whose composition makes the nucleation easier. We will consider the total probability of the nucleation as the product between the probability that a subsystem has a certain hadronic composition different from the average in the bulk, and the nucleation probability in that subsystem. Results. We will show how those fluctuations of the hadronic composition can increase the efficiency of nucleation already for temperatures $\sim (0.1-1)$ keV. However, for temperatures $\lesssim (1-10)$ MeV, the needed overpressure exceeds the maximum pressure reached in compact stars. Finally, for even larger temperatures the process of nucleation can take place, even taking into account finite size effects.