Papers for Tuesday, Mar 25 2025

Understanding how and why star formation varies between galaxies is fundamental to our comprehension of galaxy evolution. In particular, the star-formation efficiency (SFE; star-formation rate or SFR per unit cold gas mass) has been shown to vary substantially both across and within galaxies. Early-type galaxies (ETGs) constitute an extreme case, as about a quarter have detectable molecular gas reservoirs but little to no detectable star formation. In this work, we present a spatially-resolved view of the SFE in ten ETGs, combining state-of-the-art Atacama Large Millimeter/submillimeter Array (ALMA) and Multi Unit Spectroscopic Explorer (MUSE) observations. Optical spectroscopic line diagnostics are used to identify the ionized emission regions dominated by star-formation, and reject regions where the ionization arises primarily from other sources. We identify very few regions where the ionization is consistent with pure star formation. Using ${\rm H}\alpha$ as our SFR tracer, we find that previous integrated measurements of the star-formation rate based on UV and 22$\mu$m emission are systematically higher than the SFR measured from ${\rm H}\alpha$. However, for the small number of regions where ionization is primarily associated with star formation, the SFEs are around 0.4 dex higher than those measured in star-forming galaxies at a similar spatial resolution (with depletion times ranging from $10^8$ to $10^{10}$ yr). Whilst the SFE of ETGs is overall low, we find that the SFEs of individual regions within ETGs can be similar to, or higher than, similar sized regions within star-forming galaxies.

The H.E.S.S. telescope has recently detected the total electron-plus-positron ($e^+e^-$) flux up to 40 TeV, finding it to be a featureless and steeply-falling power-law above 1 TeV. This result is in stark tension with standard one-zone models of pulsar $e^+e^-$ injection and diffusion, which predict a hard-spectrum signal above $\sim$10 TeV. We model the local pulsar population, and find 20 sources that would each $individually$ overproduce the H.E.S.S. $e^+e^-$ flux in a one-zone diffusion model. We conclude that $every$ energetic pulsar younger than $\sim$500 kyr must be surrounded by a region of inhibited diffusion ($e.g.$, a supernova remnant, pulsar wind nebula, or TeV halo) that prevents the transport of these $e^+e^-$ to Earth. Because the high-electron density in these regions produces bright synchrotron and inverse-Compton emission, we conclude that all nearby pulsars are detectable as (potentially unassociated) radio, x-ray or $\gamma$-ray sources.

We present spatially-resolved measurements of the ionized gas masses and mass outflow rates for six low-redshift ($z \leq$ 0.02) active galaxies. In this study, we expand our sample to galaxies with more complex gas kinematics modeled as outflows along a galactic disk that is ionized by the active galactic nucleus (AGN) bicone. We use Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) spectroscopy, Wide Field Camera 3 (WFC3) narrow-band imaging, and the photoionization modeling technique that we developed in Revalski et al. (2022) to calculate ionized gas masses using the [O III]/H$\beta$ ratios at each radius. We combine these with existing kinematic models to derive mass and energy outflow rates, which exhibit substantial radial variations due to changes in the outflow velocities. The full sample of 12 galaxies from this series of studies spans 10$^3$ in bolometric luminosity, and we find that the outflows contain ionized gas masses of $M \approx 10^{4.6} - 10^{7.2}$ $M_{\odot}$, reach maximum mass outflow rates of $\dot M_{out} \approx 0.1 - 13$ $M_{\odot}$ yr$^{-1}$, and encompass kinetic energies of $E \approx 10^{52} - 10^{56}$ erg. These energetic properties positively correlate with AGN luminosity. The outflow energetics are less than benchmarks for effective feedback from theoretical models, but the evacuation of gas and injection of energy may still generate long term effects on star-formation in these nearby galaxies. These results highlight the necessity of high spatial resolution imaging and spectroscopy for accurately modeling ionized outflows in active galaxies.

We investigate the nucleosynthesis and kilonova emission based on numerical-relativity binary neutron star merger simulations that incorporate a two-moment neutrino-transport scheme. Unlike in previous works with simpler neutrino treatments, a massive, fast (up to $v=0.3c$), proton-rich neutrino-driven wind develops in the post-merger phase of the simulations as long as the merger remnant does not collapse to a black hole. We evolve the ejecta for 100 days after the merger using 2D ray-by-ray radiation-hydrodynamics simulations coupled in-situ to a complete nuclear network. The most abundant nucleosynthesis products are He, $^{56}$Ni, and $^{56}$Co. We find a total yield of $\sim 10^{-3} M_\odot$ of $^{56}$Ni for all mergers that produce massive neutron star remnants, independently of the mass ratio and equation of state. After a few days, the decay of $^{56}$Ni and later $^{56}$Co becomes the primary source of heating in the matter expanding above the remnant. As a result, the kilonova light curve flattens on timescales of days for polar observation angles. The observation of this effect could serve as smoking gun for the presence of a long-lived neutron star remnant in future kilonova observations.

Ultra-deep optical surveys have reached unprecedented depths, facilitating the study of faint galactic structures. However, the ultraviolet bands, crucial for stellar population studies, remain essentially unexplored at these depths. We present a detailed surface brightness and color analysis of 20 nearby galaxies in the LIGHTS fields observed by GALEX in the FUV and NUV. We adapt and apply a low surface brightness oriented methodology that has proven effective in ultra-deep optical surveys. A novel approach to background subtraction is proposed for UV imaging. Instead of subtracting a constant value from the background, we subtract a Poisson distribution that transforms the background into a pseudo-Gaussian distribution centered at zero. Furthermore, the PSF deconvolution algorithms developed for optical data are applied to our sample, using a novel set of very extended (R=750 arcsec) PSFs for the GALEX bands. This methodology allows us to obtain depths ranging from 28.5 to 30 mag arcsec^{-2}, with reliable surface brightness profiles up to 31 mag arcsec^{-2}. This is about 1 mag deeper than with standard UV techniques. We use the surface brightness and color profiles to show that the application of PSF deconvolution, especially in the FUV, effectively mitigates the excess of light present in the outer regions of certain galaxies compared to the standard GALEX pipeline. This finding is crucial for any accurate stellar population inference from the color profiles. Additionally, a qualitative analysis of the results is presented, with particular emphasis on surface brightness and color properties of the galaxies beyond their optical edges. Our work highlights the importance of developing innovative low surface brightness methods for UV surveys.

The intracluster light (ICL) permeating galaxy clusters is a tracer of the cluster's assembly history, and potentially a tracer of their dark matter structure. In this work we explore the capability of the Euclid Wide Survey to detect ICL using H-band mock images. We simulate clusters across a range of redshifts (0.3-1.8) and halo masses ($10^{13.9}$-$10^{15.0}$ M$_\odot$), using an observationally motivated model of the ICL. We identify a 50-200 kpc circular annulus around the brightest cluster galaxy (BCG) in which the signal-to-noise ratio (S/N) of the ICL is maximised and use the S/N within this aperture as our figure of merit for ICL detection. We compare three state-of-the-art methods for ICL detection, and find that a method that performs simple aperture photometry after high-surface brightness source masking is able to detect ICL with minimal bias for clusters more massive than $10^{14.2}$ M$_\odot$. The S/N of the ICL detection is primarily limited by the redshift of the cluster, driven by cosmological dimming, rather than the mass of the cluster. Assuming the ICL in each cluster contains 15% of the stellar light, we forecast that Euclid will be able to measure the presence of ICL in up to $\sim80000$ clusters of $>10^{14.2}$ M$_\odot$ between $z=0.3$ and 1.5 with a S/N$>3$. Half of these clusters will reside below $z=0.75$ and the majority of those below $z=0.6$ will be detected with a S/N $>20$. A few thousand clusters at $1.3<z<1.5$ will have ICL detectable with a S/N greater than 3. The surface brightness profile of the ICL model is strongly dependent on both the mass of the cluster and the redshift at which it is observed so the outer ICL is best observed in the most massive clusters of $>10^{14.7}$ M$_\odot$. Euclid will detect the ICL at more than 500 kpc distance from the BCG, up to $z=0.7$, in several hundred of these massive clusters over its large survey volume.

Our goal is to estimate the total gas mass in the direction of the Central Molecular Zone (CMZ), quantify the various uncertainties associated, and discuss the implications for the estimates of CR energy densities and dust opacities. The $H_{\rm{I}}$ 21 cm line and the carbon monoxide isotopes ($^{12}\rm{CO}$, $^{13}\rm{CO}$ and $\rm{C}^{18}\rm{O}$) line emission maps are used to derive the total gas column density. The gas in the CMZ is separated from the disk contribution in position and velocity thanks to its different properties in term of velocity dispersion and brightness ratio of CO isotopes. The variations of the $X_{\rm{CO}}$ factors are modelled relying on both theoretical trends from simulations and empirical corrections. We use the new gas column density estimated together with gamma-ray and dust emission measurements to derive the CR energy density and dust opacities, respectively. The $X_{\rm{CO}}$ values in the CMZ range from $(0.32 - 1.37) \ \times$ $10^{20}$ cm$^{-2}$ K$^{-1}$ km$^{-1}$ s, with a distribution that is highly asymmetric and skewed. The median value is $ \rm{\overline{X}_{CO}^{CMZ}} = 0.39 \ \times$ $10^{20}$ cm$^{-2}$ K$^{-1}$ km$^{-1}$ s. The total gas mass in the CMZ is estimated to be $2.3_{-0.3}^{+0.3}\times10^{7} \; \rm{M_{\odot}}$ with $\sim 10 \%$ contribution from the atomic phase. Without removing the disk contamination the total mass is about twice higher, and the atomic gas fraction increases to $\sim30\%$. The cosmic-ray (CR) energy density in the CMZ, assuming a 1/r profile, is higher by a factor of two compared to the previous calculations at TeV energies. Using molecular gas tracers which probes only the densest molecular cores leads to an overestimation of the CR energy density, while ignoring the foreground/background contribution leads to an underestimation of the CR energy density in the CMZ.

[ABRIDGED] DIBs are faint absorption features of mainly unknown origin. Observational constraints on their carriers have been provided in the vast majority of the cases via observations in our Galaxy. Detections in other galaxies are scarce. However, they can further constrain the nature of the carriers by sampling different environments and they can put into test the ubiquity of the molecules creating these features. Using the MUSE data of the LIRG NGC 6240, we mapped the DIB5780 over an almost contiguous area of ~76.96 kpc^2 in the center of the system. We also traced the DIBl6284 over two separate areas toward the north and south of the system, with an extent of ~21.22 kpc^2 and ~31.41 kpc^2 (with a total detected area of ~59.78 kpc^2). This is the first time that the l6284 DIB has been mapped outside our Galaxy. Both maps were compared with the attenuation on the overall stellar population and the ionised gas. Both DIBs are detected in locations with high attenuation (E(B-V)_Gas} > 0.3 and E(B-V)_Stellar >0.1), supporting the connection between DIB carriers and dust. Moreover, when compared with other galaxies, DIBs correlate better with stellar than with the ionised gas attenuation. The DIBl6284 presents a stronger correlation with reddening than the l5780 DIB does that can be attributed to a different nature of the carriers causing these DIBs, or a combined effect of a dependency with the metallicity and the different locations where these DIBs have been measured. In addition, we show that NaI D strongly correlates with both DIBs and advocate the usage of DIBs as a first order tracer for amount of material, in the case where NaI D reaches saturation. The findings here show that DIB carriers can exist and survive in an environment as extreme as a galaxy hosting AGN and allow to envision the possibilities integral field spectrographs have to study DIBs well beyond our Galaxy.

We leverage JWST's superb resolution to derive strong lensing mass maps of 14 clusters, spanning a redshift range of $z\sim0.25 - 1.06$ and a mass range of $M_{500}\sim2-12 \times 10^{14}M_\odot$, from the Strong LensIng and Cluster Evolution (SLICE) JWST program. These clusters represent a small subsample of the first clusters observed in the SLICE program that are chosen based on the detection of new multiple image constraints in the SLICE-JWST NIRCam/F150W2 and F322W2 imaging. These constraints include new lensed dusty galaxies and new substructures in previously identified lensed background galaxies. Four clusters have never been modeled before. For the remaining 10 clusters, we present updated models based on JWST and HST imaging and, where available, ground-based spectroscopy. We model the global mass profile for each cluster and report the mass enclosed within 200 and 500 kpc. We report the number of new systems identified in the JWST imaging, which in one cluster is as high as 19 new systems. The addition of new lensing systems and constraints from substructure clumps in lensed galaxies improves the ability of strong lensing models to accurately reproduce the interior mass distribution of each cluster. We also report the discovery of a candidate transient in a lensed image of the galaxy cluster SPT-CL J0516-5755. All lens models and their associated products are available for download at the Strong Lensing Cluster Atlas Data Base, which is hosted at Laboratoire d'Astrophysique de Marseille.

Areas of massive star formation are strongly influenced by stellar winds and supernovae, therefore, enhanced turbulent flows are expected. We analyse high-quality Karl G. Jansky Very Large Array observations of the neutral hydrogen gas content of DDO 43, a relatively nearby irregular dwarf galaxy. The line wings of neutral hydrogen spectral lines, which provide insights into local enhanced velocity dispersion, are investigated together with far-ultraviolet data, tracing emissions from massive star-forming regions. We find very weak correlations with both higher and lower velocity areas.

We report two anti-reflection (AR) coatings that give better quantum efficiency (QE) than the existing AR coating on the Gaia astrometric field (AF) CCDs. Light being the core of optical astronomy is extremely important for such missions, therefore, the QE of the devices that are used to capture it should be substantially high. To reduce the losses due to the reflection of light from the surface of the CCDs, AR coatings can be applied. Currently, the main component of the Gaia satellite, the AF CCDs use hafnium dioxide (HfO2) AR coating. In this paper, the ATLAS module of the SILVACO software has been employed for simulating and studying the AF CCD pixel structure and several AR coatings. Our findings evidently suggest that zirconium dioxide (ZrO2) and tantalum pentoxide (Ta2O5) will prove to be better AR coatings for broadband astronomical CCDs in the future and will open new avenues for understanding the evolution of the Milky Way.

We investigate the impact of massive primordial black holes (PBHs; $m_{\rm BH}\sim 10^6~M_{\odot}$) on the star formation and first galaxy assembly process using high-resolution hydrodynamical simulations from $z = 1100$ to $z \sim 9$. We find that PBH accretion is self-regulated by feedback, suppressing mass growth unless feedback is weak. PBHs accelerate structure formation by seeding dark matter halos and gravitationally attracting gas, but strong feedback can delay cooling and suppress star formation. In addition, the presence of baryon-dark matter streaming creates an offset between the PBH location and the peaks induced in gas density, promoting earlier and more efficient star formation compared to standard $\Lambda$CDM. By $z \sim 10$, PBH-seeded galaxies form dense star clusters, with PBH-to-stellar mass ratios comparable to observed high-$z$ AGN like UHZ-1. Our results support PBHs as viable SMBH seeds but do not exclude alternative scenarios. We emphasize that PBH-seeding provides a natural explanation for some of the newly-discovered overmassive SMBHs at high redshift, in particular those with extreme ratios of BH-to-dynamical (virial) mass that challenge standard formation channels. Future studies with ultra-deep JWST surveys, the Roman Space Telescope, and radio surveys with facilities such as SKA and HERA will be critical in distinguishing PBH-driven SMBH growth from other pathways.

Recent observations have confirmed the direct association between tidal disruption events (TDEs) and quasi-periodic eruptions (QPEs). In addition, TDE hosts and QPE hosts are statistically found to be similar in their morphological properties and in the strong overrepresentation of post-starburst galaxies. Particularly, both of them show an intriguing preference for extending emission line regions (EELRs), which are indicative of recently faded active galactic nuclei (AGNs). This further suggests that QPEs might be produced following TDEs involving supermassive black holes at a particular stage, when the AGN activity has recently ceased. Moreover, in the framework of "QPEs=EMRI+accretion disk" model, a large fraction of QPE EMRIs are inferred to be quasi-circular from the QPE timing, indicating that they are wet EMRIs that were formed in the AGN disk during a previous AGN phase. Based on these facts, we propose a unified scenario that connects these three phenomena: AGN activities boost both the TDE rate and the formation rate of low-eccentricity EMRIs, consequently TDEs are preferentially found in recently faded AGNs instead of in on-going AGNs due to selection effects, and QPEs are also preferentially found in recently faded AGNs where TDEs frequently feed a misaligned accretion disk to the EMRI.

The dynamics of magnetic fields in the Sun's active regions plays a key role in triggering solar eruptions. Studies have shown that changes in the photosphere's magnetic field can destabilize large-scale structure of the corona, leading to explosive events such as flares and coronal mass ejections (CMEs). This paper delves into the magnetic field evolution associated with a powerful X1.6 class flare that erupted on October 22nd, 2014, from the flare-rich active region NOAA 12192. We utilized high-resolution vector magnetograms from the Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamic Observatory (SDO) to track these changes. Our analysis reveals that a brightening, a precursor to the flare, began near the newly emerged, small-scale bipolar flux regions. During the X1.6 flare, the magnetic flux in both polarities displayed emergence and cancellation. The total current within the active region peaked during the flare. But, it is a non CME event and the ratio of direct to return current value remain close to 1. The large flare in this active region occured when the net current in both polarities attain the same sign. This implies that the Lorentz force, a consequence of the interaction between currents and magnetic fields, would have pushed the field lines together in this scenario. This reconnection of opposing magnetic fields is believed to be the driving force behind major flare occurred in this active region.

As the multiplexing power of spectroscopic instruments increases, so does the need for automated analysis. In practice, the bottleneck for speed is the calculation of model spectra to evaluate the likelihood of candidate parameters. This presentation gives an overview of the steps required for automating spectroscopic analyses, focusing on the speedups achievable by precomputing regular grids of synthetic spectra for on-the-fly interpolation, and a new technique based on precomputed irregular grids capable of tackling problems with much higher dimensionality, as in the case when we are interested in deriving the abundances of multiple elements. Accuracy, ease of use and portability will be discussed.

We report the broadband timing and spectral properties of the neutron star low-mass X-ray binary Aql X-1 during the 2024 outburst with NICER, NuSTAR, and Swift observatories. We detected six thermonuclear X-ray bursts during the NICER and NuSTAR observations, with the observed X-ray burst profiles exhibiting a strong energy dependence. The time-resolved burst spectra indicate the presence of soft excess during the burst, which can be modeled by using a variable persistent emission method ($f_a$ method), or the relxillNS reflection model. We found that the reflection model can contribute $\sim$20% of total emission as observed during the NICER burst. The reflection and blackbody component fluxes are strongly correlated as observed during a burst. The excess emission is possible due to the enhanced mass accretion rate to the neutron star due to the Poynting-Rodertson drag and a fraction of burst emission may be reflected from the disk. The bursts did not show photospheric radius expansion during the peak. Moreover, we examined the burst-free accretion emission in the broadband range with NuSTAR, NICER, and Swift at two epochs of the outburst. The persistent emission showed X-ray reflection feature, which can be well modeled with the relativistic reflection model relxillCp. The inner disk radius (R$_{in}$) is found to be nearly 22 and 10 times $\rm R_{g}$ for two observations, respectively. Assuming that the inner disk is truncated at the magnetospheric radius, the magnetic field strength at the poles of the neutron star is estimated to be $(0.6-1.9) \times 10^9$ G.

The recent DESI results provide increasing evidence that the density of dark energy is time-dependent. I will recall why, from the point of view of fundamental theory,, this result should not be surprising.

Near (~100 pc) and far (~8.7 kpc) relative to the Galactic center, the molecular clouds SgrB2(N) and Orion-KL exhibit different values of the fundamental physical constant mu=m_e/m_p - the electron-to-proton mass ratio. Measured frequency difference between the emission lines of methanol (CH3OH), - J_K_u - J_K_l = 6_3 - 5_2 A+ 542000.981 MHz, 6_3 - 5_2 A- 542081.936 MHz, and 8_0 - 7_-1 E 543076.194 MHz, - observed with the space observatory Herschel toward SgrB2(N) and Orion-KL corresponds to (Sgr-Ori): Delta mu/mu = (-3.7 +/- 0.5)*10^(-7) (1 sigma C.L.). At the same time, comparison of the same methanol lines in Orion-KL with laboratory frequencies shows no significant changes in mu (Ori-lab): Delta mu/mu = (-0.5 +/- 0. 6)*10^(-7), while a comparison between SgrB2(N) and laboratory lines indicates a lower value of mu near the Galactic center (Sgr-lab): Delta mu/mu = (-4.2 +/- 0.7)*10^(-7). The reduced value of mu in SgrB2(N) is not explained by known systematic effects and requires further investigation.

We investigate the future 100 kyr evolution of six selected HTCs to show their basic commonalities and differences in dynamical behaviour. This includes estimating the probability of sungrazing and flipping. We combined three complementary numerical methods to study the dynamical features: the numerical integrations forwards in time, the Lyapunov time estimations, and the Mean Exponential Growth factor of Nearby Orbits (MEGNO). For each comet, we obtain the osculation orbits from the available observations. We then construct swarms of virtual comets as the basis for all dynamical studies. We show that two comets with q<1.3 au achieve the sungrazing state in the future with high probability: 161P with the likelihood of about 80% will be a sungrazing object with q<0.005 au in the next 13 kyr, and 122P with 50% in the next 100 kyr. We found that both these HTCs reach the sungrazing states due to Kozai resonances with other planets than Jupiter; for example, Uranus acts as the agent of Kozai resonance for 161P. We indicate that the high sungrazing probability for both comets is connected with a high likelihood of orbit flipping. The other four HTCs have a slight chance to be sungrazers after 100 kyr (<2.2%); however, three of them can achieve a high flipping probability. We show that the Lyapunov time and MEGNO indicator give a complementary picture of the orbital stability after 10,000 yr. Results allow us to rank comets from the most to least chaotic, where 161P is a particular case with its high probability to disintegrate due to the Kozai mechanism.

As part of the HIERACHY program, we collect the high-SN and high-spectral resolution optical spectra of 25 quasars at $z\approx4-5$ to constrain the C IV evolution at $z\approx 3-5$. In this paper, we report a catalog of 626 (1263) C IV absorption systems (components) at $z\approx3-5$ with a 50% completeness column density of log$(N_{\rm CIV}/\rm cm^{-2}) \approx 12.3$. The HIERACHY/MIKE C IV sample is one of the best C IV absorber samples optimized to study the IGM during the He II reionization epoch. Using 557 (1090) intervening absorption systems (components), we found the column density distribution function of C IV absorption systems with log$(N_{\rm CIV}/\rm cm^{-2})\gtrsim 12.3$ has a broken power-law shape, with the turn-over column density log$(N_{\rm crit}/\rm cm^{-2}) = 13.35^{+0.20}_{-0.19}$, which is close to or smaller than the detection limit of most literature samples. We also found that both comoving path length number density $dn/dX$ and cosmic abundance $\Omega$ for C IV absorption systems with log$(N_{\rm CIV}/\rm cm^{-2})> 13.2$ show an increase (at the 2.2$\sigma$ and 1.4$\sigma$ levels, respectively) from redshift $z\approx5$ to 3, while absorption systems with log$(N_{\rm CIV}/\rm cm^{-2})= 12.3-13.2$ exhibit a constant $dn/dX$ and $\Omega_{\rm CIV}$.

The long-term evolution of relativistic jets in gamma-ray bursts (GRBs), particularly from days to months post-burst, remains a fundamental puzzle in astrophysics. Here, we report our very long baseline interferometry observation of the brightest GRB 221009A from 5 to 26 days post-burst. Combined with released data, we uncover a remarkable two-stage evolution of the jet lateral size. The jet size initially grew slowly but later expanded rapidly, challenging conventional scenarios. The slow-evolving stage provides a robust lower limit on the jet opening angle and direct evidence of jet propagation in the uniform interstellar medium at this period. The synergy analysis of the whole jet size evolution and multi-wavelength emissions uncovers that GRB 221009A harbors an ultra-narrow jet (with a half-opening angle $\simeq$ 0.01-0.03~radian) that propagates through a wind-like medium before encountering the interstellar medium, which finally undergoes lateral spreading after significant deceleration. These findings provide crucial new insights into relativistic jet dynamics and establish GRB 221009A as a unique case study for understanding the complex physics of GRB outflows.

Mass changes due to strong stellar winds and binary mass transfer have a dramatic impact on the consequent evolution of stars. This is generally not accounted for in population synthesis codes which are built using single star evolution models from full stellar evolution codes. We produce a new grid of models using the 1D stellar evolution code \textit{MESA} which includes models with a range of core mass fractions, at each total stellar mass, evolved from core hydrogen exhaustion to the onset of core helium burning. The model grid is used to produce an interpolation table, designed for use in population synthesis codes such as \textit{binary\_c}. We test the interpolation table with a simple integration algorithm to evaluate its capability of reproducing accurate evolutionary tracks. We test our method for stellar masses in the range $M=1-16~\mathrm{M}_\odot$ and show that it successfully reproduces the Hertzpsrung-gap and giant branch lifetime, the core mass at helium ignition and the HR diagram.

Internal-Collision-induced Magnetic Reconnection and Turbulence (ICMART) model is a widely accepted model for explaining how high-magnetization jets produce gamma-ray burst (GRB) prompt emissions. In previous works, we show that this model can produce: 1) light curves with a superposition of fast and slow components; 2) a Band-shaped spectrum whose parameters could follow the typical distribution of GRB observations; 3) both ``hard to soft" and ``intensity tracking" patterns of spectral evolution. In this work, through simulations of a large sample with methods established in previous work, we show that the ICMART model can also explain the observed empirical relationships (here we focus on the Yonetoku and Liang relations), as long as the magnetic field strength in the magnetic reconnection radiation region is proportional to the mass of the bulk shell, and inversely proportional to the initial magnetization factor of the bulk shell. Our results suggest that during extreme relativistic magnetic reconnection events, an increase in magnetic field strength leads to more intense dissipation, ultimately resulting in a weaker residual magnetic field.

Lyman Alpha Emitters (LAEs) are star-forming galaxies that efficiently probe the spatial distribution of galaxies in the high redshift universe. The spatial clustering of LAEs reflects the properties of their individual host dark matter halos, allowing us to study the evolution of the galaxy-halo connection. We analyze the clustering of 5233, 5220, and 3706 LAEs at z = 2.4, 3.1, and 4.5, respectively, in the 9 deg$^2$ COSMOS field from the One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey. After correcting for redshift space distortions, LAE contamination rates, and the integral constraint, the observed angular correlation functions imply linear galaxy bias factors of b = $1.64^{+0.26}_{-0.23}, 1.84^{+0.24}_{-0.22}$, and $2.93^{+0.41}_{-0.36}$, for z = 2.4, 3.1, and 4.5, respectively. The median dark matter halo masses inferred from these measurements are $log(M_h/M_{\odot}) = 11.34^{+0.30}_{-0.31}, 10.94^{+0.26}_{-0.28}$, and $10.83^{+0.26}_{-0.24}$ for the three samples, respectively. The analysis also reveals that LAEs occupy roughly 3-5% of the halos whose clustering strength matches that of the LAEs. The large contrast between this low halo occupation fraction and the high fraction of continuum-selected star-forming galaxies that exhibit Ly$\alpha$ in emission implies that LAEs are unusually luminous for their dark matter masses.

It remains puzzling why, despite their similar nature, Jupiter and Saturn possess a prograde equatorial jet, whereas Uranus and Neptune have a retrograde one. To understand this discrepancy, we use a 2-D quasi-geostrophic model to explore how the penetration depth of the jet, regulated by Ohmic dissipation, influences jet patterns. When jets penetrate deeply into the planet's interior, the Taylor column height decreases equatorward in the equatorial jet region, yielding a negative gradient of planetary potential vorticity (i.e., a negative beta effect). The tendency to eliminate such a gradient leads to a prograde equatorial jet, as observed on Jupiter and Saturn. In contrast, a relatively shallow system favors retrograde jets along the equator due to the positive beta effect of geometry. If the proposed mechanism applies to Uranus and Neptune, the observed jet structure may suggest the presence of a stratified layer or Ohmic dissipation layer near their surfaces.

We present an interdisciplinary comparison between binary black hole systems and Radio Frequency (RF) Paul Traps, modeling the gravitational binary system as a rotating saddle near its center. This analogy connects these seemingly unrelated systems through the concept of dynamic stability. The rotating saddle potential is analytically tractable, allowing us to prove the existence of bounded charged particle trajectories under certain conditions. By focusing on stellar-mass black holes with a weak electric charge-a feature consistent with specific astrophysical conditions that leaves the spacetime metric largely unaffected but can influence nearby particle interactions-we can neglect complicating factors such as magnetic fields from large accretion disks of heavier black holes or stellar winds. Our simulation results demonstrate that charged particles can exhibit stable, non-orbital trajectories near the center of a binary system with charged stellar-mass black holes, providing unique three-dimensional trapping primarily through gravity. This system is distinctive in the literature for its non-orbital trapping mechanism. While theoretically intriguing, this trapping relies on specific conditions, including nearly identical black hole masses. These types of non-orbital trapping mechanisms could potentially allow for longer-lived plasma configurations, enhancing our ability to detect electromagnetic signatures from these systems. The significance of this work lies in the novel comparison between a laboratory-scale quantum system and a larger astrophysical one, opening new avenues for exploring parallels between microscopic and cosmic phenomena across fourteen orders of magnitude in distance.

We carry out a comprehensive hierarchical multi-scale morphological analysis to search for anomalous behaviour in the large scale matter distribution using convergence map provided by the Atacama Cosmology Telescope (ACT) Data Release 6. We use a suite of morphological statistics consisting of Minkowski functionals, contour Minkowski tensor and Betti numbers for the analysis, and compute their deviations from the ensemble expectations and median values obtained from isotropic $\Lambda$CDM simulations provided by ACT. To assess the statistical significance of these deviations, we devise a general methodology based on the persistence of the deviations across threshold ranges and spatial resolutions, while taking into account correlations among the statistics. From the analysis of the full dataset, and hemispherical regions, we find consistency with isotropic $\Lambda$CDM simulations provided by ACT. Since deviations in smaller sky regions tend to get washed out when averaged over larger regions, we further analyze smaller sky patches. This localized analysis reveals some patches that exhibit statistically significant deviations which we refer to as 'anomalous'. We find that near the CMB cold spot, both the positive and negative density fluctuations are anomalous, at 99% CL and 95% CL respectively. This region also encompasses an anomalous southern spot previously identified in Planck CMB temperature data. We also carry out a comparison of anomalous patches identified here for ACT data with a previous analysis of the convergence map from Planck. We do not find common patches between the two datasets, which suggest that the anomalous behavior of the Planck data arises from noise in the map. Further investigation of the atypical patches using large scale structure surveys is warranted to determine their physical origin.

Black holes (BHs) with masses between $\sim 3-5M_{\odot}$, produced by a binary neutron star (BNS) merger, can further pair up with a neutron star or BH and merge again within a Hubble time. However, the astrophysical environments in which this can happen and the rate of such mergers are open questions in astrophysics. Gravitational waves may play an important role in answering these questions. In this context, we discuss the possibility that the primary of the recent LIGO-Virgo-KAGRA binary GW230529_181500 (GW230529, in short) is the product of a previous BNS merger. Invoking numerical relativity (NR)-based fitting formulas that map the binary constituents' masses and tidal deformabilities to the mass, spin, and kick velocity of the remnant BH, we investigate the potential parents of GW230529's primary. Our calculations using NR fits based on BNS simulations reveal that the remnant of a high-mass BNS merger similar to GW190425 is consistent with the primary of GW230529. This argument is further strengthened by the gravitational wave-based merger rate estimation of GW190425-like and GW230529-like populations. We show that around 18% (median) of the GW190425-like remnants could become the primary component in GW230529-like mergers. The dimensionless tidal deformability parameter of the heavier neutron star in the parent binary is constrained to $67^{+163}_{-61}$ at 90% credibility. Using estimates of the gravitational-wave kick imparted to the remnant, we also discuss the astrophysical environments in which these types of mergers can take place and the implications for their future observations.

We present generative artificial intelligence (AI) to empirically validate fundamental laws of physics, focusing on the Stefan-Boltzmann law linking stellar temperature and luminosity. Our approach simulates counterfactual luminosities under hypothetical temperature regimes for each individual star and iteratively refines the temperature-luminosity relationship in a deep learning architecture. We use Gaia DR3 data and find that, on average, temperature's effect on luminosity increases with stellar radius and decreases with absolute magnitude, consistent with theoretical predictions. By framing physics laws as causal problems, our method offers a novel, data-driven approach to refine theoretical understanding and inform evidence-based policy and practice.

JWST observations, when combined with HST data, promise to improve age estimates of star clusters in nearby spiral galaxies. However, feedback from young cluster stars pushes out the natal gas and dust, making cluster formation and evolution a challenge to model. Here, we use JWST + HST observations of the nearby spiral galaxy NGC 628 to produce spectral energy distribution (SED) templates of compact star clusters spanning 275 nm through 21 {\mu}m. These preliminary SEDs capture the cluster stars and associated gas and dust within radii of 0.12" to 0.67" (corresponding to 6 to 33 pc at the distance of NGC 628). One important finding is that the SEDs of 1, 2, 3, and 4 Myr clusters can be differentiated in the infrared. Another is that in 80-90% of the cases we study, the PAH and H_alpha emission track one another, with the dust responsible for the 3.3 {\mu}m PAH emission largely removed by 4 Myr, consistent with pre-supernova stellar feedback acting quickly on the surrounding gas and dust. Nearly-embedded cluster candidates have infrared SEDs which are quite similar to optically visible 1 to 3 Myr clusters. In nearly all cases we find there is a young star cluster within a few tenths of an arcsec (10 - 30 pc) of the nearly embedded cluster, suggesting the formation of the cluster was triggered by its presence. The resulting age estimates from the empirical templates are compatible both with dynamical estimates based on CO superbubble expansion velocities, and the TODDLERS models which track spherical evolution of homogeneous gas clouds around young stellar clusters.

Cloud-cloud collision (CCC) has been proposed as a mechanism for triggering massive star formation. Observations in the Milky Way and nearby galaxies have revealed the presence of CCCs with collision velocity ($v_{\rm col}$) of 1-40 km/s, and the connection between star formation activity and the properties of colliding clouds has been investigated. In this study, we expand the study to much faster (~100 km/s) CCCs in a nearby colliding galaxies system, the Antennae galaxies. We examine how star formation rate (SFR) on a sub-kpc scale depends on the $v_{\rm col}$ and mass ($M_{\rm mol}$) of giant molecular clouds (GMCs) across the Antennae galaxies, which show diverse star formation activity. Furthermore, to examine the star formation process at a more fundamental level, we also investigate how the star formation efficiency (SFE) of a colliding GMC depends on its $v_{\rm col}$ and $M_{\rm mol}$. SFR is calculated using H$\alpha$ and mid-infrared data. From $\sim2000$ GMCs identified in the CO(1-0) data cube using the ALMA archival data, collision velocities are estimated based on the velocity dispersion among GMCs in a sub-kpc scale region, assuming random motion in three-dimensional space. GMCs are considered to be colliding at a velocity of ~10-150 km/s. We find that regions where high-speed collisions ($v_{\rm col}$~100 km/s) of massive ($M_{\rm mol}$~$10^{7-8}$ $M_\odot$) GMCs are seen show the highest surface density of SFR. Particularly, in the region with $v_{\rm col}$~100 km/s, we find that SFR on a sub-kpc scale increases with increasing $M_{\rm mol}$ in the range of ~$10^{6}$-$10^{8}$ $M_\odot$. The SFE of a colliding cloud is estimated to be 0.1%-3.0% without clear $M_{\rm mol}$ dependence, and the SFE is the lowest at the $v_{\rm col}$~100-150 km/s. These results suggest that the most active star formation in the Antennae galaxies seems to occur due to large GMC mass.

The bolometric radiation from a central body is potentially a powerful driver of atmospheric escape from planets or satellites. When heated above their equilibrium temperatures those satellites, due to their low surface gravity, are be prone to significant atmospheric erosion. Such high temperatures can be reached through a known mechanism: a large ratio of the irradiation to re-radiation opacities of the atmospheric species. We investigate this mechanism for irradiating black-bodies of sub-stellar temperatures and find that specific molecules exist, such as $\rm NH_3$ and $\rm CH_4$, which develop temperature inversions under the irradiation of young post-formation giant planets. These non-isothermal temperature profiles lead to escape rates that can significantly exceed isothermal Parker-model escape rates evaluated at the satellite's equilibrium temperature. Our results indicate that exo-satellites can lose most of their atmospheric mass through this mechanism if the cooling of the exo-satellite's interior is not too rapid. In all scenarios, we find a hierarchical ordering of escape rates of atmospheric species due to thermal decoupling in the upper atmosphere. This thermal decoupling leads to a natural depletion of $\rm CH_4$ and retention of $\rm NH_3$ in our models. We find that giant planets with masses above 2$m_{\rm Jup}$, for cold starts and above 1$m_{\rm Jup}$ in hot start scenarios are able to remove the majority of a Titan analogue's atmosphere. Hence, finding and characterizing exomoon atmospheres in hypothetical future surveys can constrain the post-formation cooling behaviour of giant planets.

We present a novel tensor network algorithm to solve the time-dependent, gray thermal radiation transport equation. The method invokes a tensor train (TT) decomposition for the specific intensity. The efficiency of this approach is dictated by the rank of the decomposition. When the solution is "low-rank," the memory footprint of the specific intensity solution vector may be significantly compressed. The algorithm, following a step-then-truncate approach of a traditional discrete ordinates method, operates directly on the compressed state vector thereby enabling large speedups for low-rank solutions. To achieve these speedups we rely on a recently developed rounding approach based on the Gram-SVD. We detail how familiar SN algorithms for (gray) thermal transport can be mapped to this TT framework and present several numerical examples testing both the optically thick and thin regimes. The TT framework finds low rank structure and supplies up to $\simeq$60$\times$ speedups and $\simeq$1000$\times$ compressions for problems demanding large angle counts, thereby enabling previously intractable SN calculations and supplying a promising avenue to mitigate ray effects.

Fast radio bursts (FRBs) are fierce radio flashes lasting for a few milliseconds from the sky. Although their connection to strongly magnetized neutron stars has been strongly indicated, the exact triggering process and radiation mechanism are still unknown and highly debated. Due to their extremely short duration, the observation of FRBs has long been a difficult task even for large radio telescopes. The difficulty results from the fact that the information obtained in observations is always incomplete, since the telescope always has a limited flux sensitivity and finite operating frequency band. A pressing challenge is to decode the intrinsic features of FRBs from the incomplete observations. Here we establish an efficient methodology to overcome this problem, aiming at effectively correcting for the fluence and frequency cutoffs. Using this method, inverse modeling is performed on a large number of repeating bursts from FRB 20121102A to recover their intrinsic features. It is found that strong bursts intrinsically tend to concentrate their energy in a narrow band, while the spectral range of weak bursts can be either narrow or wide. However, when a weak burst has a broad spectrum, the wing of the spectrum can easily go undetected, resulting in a very narrow spectrum being observed. The narrow spectrum features observed in repeating FRBs are thus an observational selection effect. Underestimation of the burst energy caused by observational cutoffs is also corrected for, and the intrinsic burst energy distribution is re-constructed. It is also found that the bandwidth increases with the increasing central frequency in the Arecibo sample (1.15-1.73 GHz), but such a correlation is not observed in the FAST (1-1.5 GHz) and GBT (4-8 GHz) sample. It indicates the emission pattern of the FRB source might vary across different active periods and frequency bands.

This paper presents a novel approach to the use of Planck telescope data for the systematic search of ultra-bright high-redshift strongly lensed galaxies. These galaxies provide crucial insights into the early universe, particularly during phases of intense star formation. The Planck mission, despite its limited angular resolution, offers a unique opportunity to identify candidate strongly lensed galaxies over a wide area of the sky. This work outlines the methodology used to identify these rare objects, the challenges encountered, and the preliminary results obtained from follow-up observations with higher-resolution instruments.

Recent JWST observations of the Fomalhaut debris disk have revealed a significant abundance of dust interior to the outer planetesimal belt, raising questions about its origin and maintenance. In this study, we apply an analytical model to the Fomalhaut system, that simulates the dust distribution interior to a planetesimal belt, as collisional fragments across a range of sizes are dragged inward under Poynting-Robertson (PR) drag. We generate spectral energy distributions and synthetic JWST/MIRI images of the model disks, and perform an extensive grid search for particle parameters -- pertaining to composition and collisional strength -- that best match the observations. We find that a sound fit can be found for particle properties that involve a substantial water ice component, around 50--80% by total volume, and a catastrophic disruption threshold, $Q_D^\star$, at a particle size of $D\!\approx\!30\,$um of 2--4$\,\times\,10^6\,$erg/g. Based on the expected dynamical depletion of migrating dust by an intervening planet we discount planets with masses $>1\,M_\mathrm{Saturn}$ beyond $\sim50\,$au in the extended disk, though a planet shepherding the inner edge of the outer belt of up to $\sim2\,M_\mathrm{Saturn}$ is reconcilable with the PR-drag-maintained disk scenario, contingent upon higher collisional strengths. These results indicate that PR drag transport from the outer belt alone can account for the high interior dust contents seen in the Fomalhaut system, which may thus constitute a common phenomenon in other belt-bearing systems. This establishes a framework for interpreting mid-planetary system dust around other stars, with our results for Fomalhaut providing a valuable calibration of the models.

Cyanogen ($C_2N_2$) was among the many molecules identified in the coma of 67P/Churyumov-Gerasimenko during the Rosetta mission. As a potential parent species of the CN radical, its abundance relative to other species such as HCN should be generalized to comets observed from ground-based facilities. To investigate its presence from infrared spectra in other comets, we developed a new fluorescence model for the $\nu_3$ fundamental band. From new high-resolution infrared spectra of cyanogen, we analyzed the region of the $\nu_3$ band of $C_2N_2$, centered around 4.63 $\mu$m 2158 cm$^{-1}$). In addition to line positions and intensities, ground and excited molecular parameters were obtained. The spectroscopic analysis allowed us to develop a new fluorescence model for cyanogen. Excitation rates of the $\nu_3$ band of cyanogen are presented. An attempt to detect cyanogen in a high-resolution spectrum of comet C/2022 E3 (ZTF) is discussed.

The observed size distributions of solar and stellar flares is found to be consistent with the predictions of the fractal-diffusive self-organized criticality (FD-SOC) model, which predicts power law slopes with universal constants of $\alpha_F=(9/5)=1.80$ for the flux, and $\alpha_E=(5/3)\approx 1.67$ for the fluence, respectively. In this Letter we explore the solar-stellar connection under this aspect, which extends over an unprecedented dynamic range of 13 orders of magnitude between the smallest detected solar nanoflare event ($E_{min}=10^{24}$ erg) and the largest superflare ($E_{max}=10^{37}$ erg) on solar-like G-type stars, observed with the KEPLER mission. The FD-SOC model predicts a scaling law of $L \propto E^{(2/9)}$ for the length scale $L$ as a function of the flare energy $E$, which limits the largest flare size to $L_{max} \lapprox 0.14 R_\odot$ for solar flares, and $L_{stellar} \lapprox 1.04\ R_{\odot}$ for stellar flares on G-type stars. In the overall we conclude that the universality of power laws (and their slopes) is a consequence of SOC properties (fractality, classical diffusion, scale-freeness, volume-flux proportionality), rather than identical physical processes at different wavelengths.

There has been growing evidence that mu and tau neutrinos are noticeably different due to the emergence of muons in core-collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs). Recent theoretical studies also suggest that all flavors of neutrinos and antineutrinos inevitably experience some flavor mixing instabilities including fast neutrino flavor conversions (FFC), which corresponds to one of the collective neutrino oscillations powered by neutrino self-interactions. This represents a need for quantum kinetic treatment in the numerical modeling of neutrino dynamics, which is, however, a formidable computational challenge. In this paper, we present an approximate method to predict asymptotic states of FFC without solving a quantum kinetic equation under a three-flavor framework, in which mu and tau neutrino distributions are not necessarily identical to each other. The approximate method is developed based on a Bhatnagar-Gross-Krook (BGK) relaxation time prescription, capable of capturing essential features of mixing competitions among three different flavor-coherent states. Our proposed scheme is computationally inexpensive and easy to implement in any classical neutrino transport scheme.

Recent studies have proposed that the anisotropy of cosmic rays' arrival directions is conducive to unveiling the local acceleration sites and propagation environment. We built a unified scenario to describe the available observations of the energy spectra and the large-scale anisotropy. In this work, we further investigate the impact of the Sun's motion relative to the local plasma frame on the large-scale anisotropy, i.e. so-called Compton-Getting effect. We find that when considering this effect, the dipole amplitude decreases and the phase slightly deviates from the direction of the local regular magnetic field at tens of TeV energies. At lower energies, when the anisotropy from the density gradient of cosmic rays is small, the influence of the relative motion of the Sun becomes evident. Less than $\sim 200$ GeV, the dipole amplitude rises again and approaches the value of the Compton-Getting effect. Moreover, at several hundreds of GeV, the dipole phase has a flip, which points to the direction of the Compton-Getting effect. In the future, the measurements of anisotropy from $100$ GeV to TeV could testify to this effect.

We investigate the prospects of detecting a stochastic gravitational wave (GW) background from the primordial black hole (PBH) reheating epoch. If PBHs form during a non-standard cosmological phase prior to the radiation-dominated era, they can dominate the energy density of the Universe before evaporating via Hawking radiation. Such PBHs can generate induced GWs that may fall within the detectable range of future interferometry missions: (i) through isocurvature perturbations arising from the inhomogeneous spatial distribution of PBHs, and (ii) through the amplification of adiabatic perturbations triggered by the abrupt transition from PBH domination to radiation domination. We assess the detection prospects of such GW spectra using the signal-to-noise ratio, Fisher forecast analysis, and Markov chain Monte Carlo analysis with mock data from LISA and ET. Our findings reveal that ET exhibits superior sensitivity to both isocurvature- and adiabatic-induced GWs, covering a wide PBH mass range of $M_{\rm in} \in (0.5-4\times 10^7)$ g. However, we find that the relative uncertainties associated with the parameter of the isocurvature source are quite high. LISA, by contrast, is mostly sensitive to the adiabatic source, with $M_{\rm in} \in (2\times10^4-5\times 10^8)$ g. The combined effect of adiabatic and isocurvature sources on ET and LISA provides a multi-stage window into the post-inflationary Universe by constraining PBH mass, energy fraction, and the background equation of state.

If two physical timescales are independent, i.e. they depend on different physics, then (statistically) there is no reason to believe that their values should be equal, even to an order of magnitude. The timescale for abiogenesis $\tau_{AB}$, which depends primarily on prebiotic-chemistry, is expected to be independent of the planetary habitability timescale $\tau_{Hab}$, which depends primarily on the sun and therefore on nuclear forces and gravity. Therefore, we expect that either $\tau_{AB} \ll \tau_{Hab}$ or $\tau_{AB} \gg \tau_{Hab}$. The correct inequality is universal and a single example should suffice to resolve this binary choice. Here I argue that, contrary to a well known anthropic selection effect, our existence (which entails life on Earth) can be considered evidence that the correct choice is the former. A Bayesian analysis, taking into account that our existence is old evidence, implies that the probability of the hypothesis $\tau_{AB} \ll \tau_{Hab}$ is > 0.91, assuming equal priors. The Bayes factor, which depends only on the evidence, is > 10 and suggests strong to decisive support for the short abiogenesis timescale hypothesis, according to the Jeffreys interpretation.

We present a general formalism for studying generalized Holographic Dark Energy (HDE) models in which we use a dimensionless form of the area-entropy of cosmological horizons. The future event horizon is applied though the formalism can also be applied to any other type of the horizon, too. Then, we use our formalism for nonextensive horizon entropies of standard HDE (i.e. Bekenstein-Hawking), and generalized such as Barrow/Tsallis-Cirto, Rényi, Sharma-Mittal, and Kaniadakis as dark energy models of the universe and test them by cosmological data. We find the bounds on the specific entropy model parameters and also apply statistical comparison tool such as the Bayesian evidence criterion in order to favour or disfavour the models against standard $\Lambda$CDM. The main data test results are that all the HDE models under study are statistically disfavoured with respect to $\Lambda$CDM, though at some different levels. The standard HDE seem to be on the same footing as Rényi, Sharma-Mittal, and Kaniadakis HDE models since the latter include only small deviations from HDE model resulting from the series expansion of their extra nonextensivity parameters. However, Barrow and Tsallis-Cirto models, though still disfavoured against $\Lambda$CDM, seem to point out observationally to fulfil an important physical property of extensivity (though still remaining nonadditive) which is in agreement with our previous results of Refs. \cite{Dabrowski:2020atl,PhysRevD.108.103533} and recent claims of Ref. \cite{TSALLIS2025139238}. Finally, the Tsallis-Cirto model parameter is pointing towards the $\Lambda$CDM limit which is singular also at the expense of having much larger value of the holographic dark energy dimensionless parameter $k$ value higher than other models.

Low-metallicity stars preserve the signatures of the first stellar nucleosynthesis events in the Galaxy, as their surface abundances reflect the composition of the interstellar medium from which they were born. Aside from primordial Big Bang nucleosynthesis, massive stars, due to their short lifetimes, dominate the ejecta into the interstellar medium of the early Galaxy. Most of them will end as core-collapse supernova (CCSN) explosions, and typical ejected abundance distributions, e.g. in terms of the alpha-element-to-Fe ratios, reflect these contributions. Essentially all CCSNe contribute 56Fe. Therefore, low-metallicity stars can be used to test whether the abundances of any other elements are correlated with those of Fe, i.e. whether these elements have been co-produced in the progenitor sources or if they require either a different or additional astrophysical origin(s). The present analysis focuses on stars with [Fe/H]<-2, as they probe the earliest formation phase of the Galaxy when only one or very few nucleosynthesis events had contributed their ejecta to the gas from which the lowest metallicity stars form. This was also the era before low and intermediate mass stars (or type Ia supernovae) could contribute any additional heavy elements. Following earlier works into the origin of heavy r-process elements [1], we extend the present study to examine Pearson and Spearman correlations of Fe with Li, Be, C, N, Na, Mg, Si, S, Ca, Ti, Cr, Ni, Zn, Ge, Se, Sr, Zr, Ba, Ce, Sm, Eu, Yb, Lu, Hf, Os, Ir, Pb, Th, and U, using high-resolution stellar abundance data from the SAGA [2] and JINA [3] databases. The main goal is to identify which of the observed elements (i) may have been co-produced with Fe in (possibly a variety of) CCSNe, and which elements require (ii) either a completely different, or (iii) at least an additional astrophysical origin.

One of the manifestations of Lorentz invariance violation (LIV) is vacuum birefringence, which leads to an energy-dependent rotation of the polarization plane of linearly polarized photons arising from an astrophysical source. Here we use the energy-resolved polarization measurements in the prompt $\gamma$-ray emission of five bright gamma-ray bursts (GRBs) to constrain this vacuum birefringent effect. Our results show that at the 95\% confidence level, the birefringent parameter $\eta$ characterizing the broken degree of Lorentz invariance can be constrained to be $|\eta|<\mathcal{O}(10^{-15}-10^{-16})$, which represent an improvement of at least eight orders of magnitude over existing limits from multi-band optical polarization observations. Moreover, our constraints are competitive with previous best bounds from the single $\gamma$-ray polarimetry of other GRBs. We emphasize that, thanks to the adoption of the energy-resolved polarimetric data set, our results on $\eta$ are statistically more robust. Future polarization measurements of GRBs at higher energies and larger distances would further improve LIV limits through the birefringent effect.

The effects of diffraction, reflection and mutual coupling on the spectral smoothness of radio telescopes becomes increasingly important at low frequencies, where the observing wavelength may be significant compared with the antenna or array dimensions. These effects are important for both traditional parabolic antennas, which are prone to the 'standing wave' phenomenon caused by interference between direct and scattered wavefronts, and aperture arrays, such as the SKA-Low, MWA, HERA, and LOFAR which have more complicated scattering geometries and added dependence on pointing direction (scan angle). Electromagnetic modelling of these effects is computationally intensive and often only possible at coarse frequency resolution. Therefore, using the example of SKA-Low station configurations, we investigate the feasibility of parameterising scattering matrices, and separating antenna and array contributions to telescope chromaticity. This allows deeper insights into the effect on spectral smoothness and frequency-dependent beam patterns of differing antenna configurations. Even for the complicated SKA-Low element design, band-limited delay-space techniques appear to produce similar results to brute-force electromagnetic models, and allow for faster computation of station beam hypercubes (position, frequency and polarisation-dependent point spread functions) at arbitrary spectral resolution. As such techniques could facilitate improvements in the design of low-frequency spectral-line surveys, we conduct a simulated Cosmic Dawn experiment using different observing techniques and station configurations.

Solar radio bursts (SRBs) detection is crucial for solar physics research and space weather forecasting. The main challenges faced are noise interference in the spectrum and the diversity of SRBs. However, most research focuses on classifying whether SRBs exist or detecting a single type of SRBs. Existing detection models exhibit deficiencies in the accuracy of SRBs detection. Moreover, existing detection models cannot effectively handle background noise interference in solar radio spectrograms and the significant scale variations among different burst types. This paper proposes a high-performance detection model for solar radio bursts (SRBs) based on Deformable DETR (DEtection TRansformers) called DETR4SBRs. Firstly, this study designed a scale sensitive attention (SSA) module better to address the scale variations of SRBs. Subsequently, this study introduced collaborative hybrid auxiliary training to mitigate the positive-negative sample imbalance issue in Deformable DETR. The experimental results demonstrate that the proposed model achieves a mAP@50 of 83.5% and a recall rate of 99.4% on the SRBs dataset. Additionally, the model exhibits excellent noise-robust performance and can efficiently detect and locate Type II, III, IV, and V SRBs. The model proposed in this study provides robust support for preliminary solar radio burst data processing and has significant implications for space weather forecasting. The source code and data are available on the this https URL and archived on Zenodo.

This study utilized LAMOST low-resolution spectra to identify M-type YSOs and characterize their accretion signatures. We measured characteristic features, including hydrogen Balmer, Li {\sc i}, He~{\sc i}, Na {\sc i}, and Ca {\sc ii} lines, as well as molecular absorption bands such as CaH. These features were evaluated for their potential to distinguish between different classes of M-type stars. In addition to the commonly used H$\alpha$ emission and {Li \sc i} $\lambda6708$~Å~absorption, other features such as He~{\sc i}, Na {\sc i}, Ca~{\sc ii} HK and IRT lines, and CN, CaH, and VO bands also show potential for identifying YSOs from M-type dwarfs and giants. Based on key red-band features, we identified over 8,500 M-type YSO candidates from the LAMOST DR8 archive using the random forest technique, with over 2,300 of them likely being classical T Tauri stars (CTTSs). By incorporating $Gaia$ astrometry, 2MASS photometry, and extinction from 3D dust maps, we estimated the basic properties (such as age and mass) of the YSO candidates based on {\sc parsec} models. We also estimated the mass accretion rates of the CTTS candidates using H$\alpha$ emission. The derived accretion rates show a dependence on age and mass similar to that described in previous studies. Significant scatter in mass accretion rates exists even among stars with similar age and mass, which may be partly attributed to variations in $\rm H\alpha$ emission and the veiling.

Over ten mid-infrared (mid-IR) and X-ray models are currently attempting to describe the nuclear obscuring material of active galactic nuclei (AGNs), but many questions remain unresolved. This study aims to determine the physical parameters of the obscuring material in nearby AGNs and explore their relationship with nuclear activity. We selected 24 nearby Seyfert AGNs with X-ray luminosities ranging from $10^{41}$ to $10^{44}$ erg/s, using NuSTAR and Spitzer spectra. Our team fitted the spectra using a simultaneous fitting technique. Then, we compared the resulting parameters with AGN properties, such as bolometric luminosity, accretion rate, and black hole mass. Our analysis shows that dust and gas share a similar structure in most AGNs. Approximately 70% of the sample favors a combination of the X-ray UXclumpy model with the Clumpy and two-phases models at IR wavelengths. We found that linking the half-opening angle and torus angular width parameters from X-ray and mid-IR models helps constrain other parameters and break degeneracies. The study reveals that Sy1 galaxies are characterized by low covering factors, half-opening angles, and column densities but high Eddington rates. In contrast, Sy2 galaxies display higher covering factors and column densities, with a broader range of half-opening angles. We also observed that the distribution of obscuring material is closer to the nucleus in intermediate-luminosity sources, while it is more extended in more luminous AGNs. Our findings reinforce the connection between the properties of gas-dust material within 10 pc and AGN activity. Applying this methodology to a larger sample and incorporating data from facilities such as JWST and XRISM will be crucial in further refining these results.

We study the impact of environmental effects on the measurement of the Hubble constant ($H_0$) from gravitational wave (GW) observations of binary black hole mergers residing in active galactic nuclei (AGNs) near the central supermassive black hole. Using the potential hierarchical triple merger candidate GW190514-GW190521 in AGN J124942.3+344929 with its electromagnetic counterpart ZTF19abanrhr as a multimessenger case study, we demonstrate that environmental effects can be negligible for mergers at approximately tens to hundreds of Schwarzschild radii from the supermassive black hole. We find $H_0=40.9_{-8.9}^{+19.3}\,{\rm km\,s^{-1}\,Mpc^{-1}}$ (median and 68\% credible interval) under a flat prior and flat $\Lambda$CDM cosmology. Incorporating GW170817 prior information improves constraints to $H_0=68.8_{-6.0}^{+7.7}\,{\rm km\,s^{-1}\,Mpc^{-1}}$. We suggest that in general, AGN environments could serve as viable laboratories for cosmological studies from GW observations where environmental effects remain below detection thresholds.

An extinction distribution of the Andromeda Galaxy (M31) is constructed with member stars as tracers by fitting multiband photometric data from UKIRT/WFCAM, PS1, and Gaia DR3. The resulting extinction distribution covers approximately 10 deg$^2$ of M31 with a resolution of approximately 50 arcsec, providing the largest coverage to date based on stellar observations. The derived average extinction, $A_V = 1.17$ mag, agrees well with previous studies. To account for foreground extinction, an extinction map of the Milky Way toward M31 with a resolution of $\sim$ 1.7 arcmin is also constructed, yielding an average extinction of $A_V \approx 0.185$ mag. The results offer a valuable tool for extinction correction in future observations, such as those from the China Space Station Telescope, and provide insights for improving dust models based on the spatial distribution of dust in galaxies like M31.

Blue large-amplitude pulsators (BLAPs), a recently classified type of variable stars, are evolved objects likely formed through interactions between stars in a binary system. However, only two BLAPs with stellar companions have been discovered to date. This paper presents photometric data from the Korea Microlensing Telescope Network (KMTNet) for three BLAPs located in the direction of the Galactic bulge: OGLE-BLAP-006, OGLE-BLAP-007, and OGLE-BLAP-009. The data were collected over eight consecutive years, beginning in 2016, with a high cadence of approximately 15 minutes. Frequency analysis of light variations revealed OGLE-BLAP-006 as a multimode pulsator with a dominant frequency of 37.88 day$^{-1}$ and two new frequencies of 38.25 and 35.05 day$^{-1}$. In contrast, OGLE-BLAP-007 and OGLE-BLAP-009 exhibit single-mode pulsation. By combining the KMTNet data with archival OGLE observations, we investigated pulsation timing variations of the BLAPs using an $O-C$ diagram to identify the light travel time effect caused by the orbital motion of their companions. We found that OGLE-BLAP-006, with no evidence of close companions, has two wide-orbit companions with orbital periods of approximately 4,700 and 6,300 days, making it the third known BLAP in a stellar system; however, no companions were found for OGLE-BLAP-007 and OGLE-BLAP-009. Furthermore, we identified seven other BLAP candidates with wide companions using OGLE data, suggesting that such systems are relatively common. We propose that a BLAP with a wide companion may be a merger remnant of an inner close binary within a hierarchical triple system.

Additional elementary species and primordial black holes are common candidates for dark matter. Their co-existence in the early Universe leads to accretion if particles are heavy. We solve equation of motion affected by expansion which enhances black hole growth rates. They depend upon particles freeze-out time rather than their mass. Taking into account friction we investigate recently suggested baryogenesis mechanism operating via scattering cross-section difference between particles and antiparticles on relativistic symmetric plasma. We find that asymmetry is accumulated at relatively small times which can be used to construct viable particle models.

Hierarchical galactic evolution models predict that mergers drive galaxy growth, producing low surface brightness (LSB) tidal features that trace galaxies' late assembly. These faint structures encode information about past mergers and are sensitive to the properties and environment of the host galaxy. We investigated the relationships between LSB features and their hosts in a sample of 475 nearby massive galaxies spanning diverse environments (field, groups, Virgo cluster) using deep optical imaging from the Canada-France-Hawaii Telescope (MATLAS, UNIONS/CFIS, VESTIGE, NGVS). Using Jafar, an online annotation tool, we manually annotated tidal features and extended stellar haloes, including 199 tidal tails and 100 streams. Geometric and photometric measurements were extracted to analyse their dependence on galaxy mass, environment, and internal kinematics. At our surface brightness limit of 29 mag$\,$arcsec$^{-2}$, tidal features and stellar haloes contribute 2% and 10% of total galaxy luminosity, respectively. Tidal features are detected in 36% of galaxies, with none fainter than 27.8 mag$\,$arcsec$^{-2}$. The most massive galaxies are twice as likely to host tidal debris, and for early-type galaxies their halos are twice as luminous as those in lower-mass systems, a trend not observed in late-type galaxies. Although small-scale interactions increase the frequency of tidal features, the large-scale environment does not influence it. An anticorrelation between this frequency and rotational support is found, but may reflect the mass-driven effect. We release our database of annotated features for deep learning applications. Our findings confirm that galaxy mass is the dominant factor influencing tidal feature prevalence, consistent with hierarchical formation models.

Spectropolarimetry of atomic lines in the spectra of Betelgeuse, and other Red SuperGiants (RSG), presents broad line profiles in linear polarization, but narrow profiles in intensity. Recent observations of the Red SuperGiant RW Cep show, on the other hand, broad intensity profiles, comparable to those in linear polarization. This observation hints that this difference in the Stokes Q/U and I profile widths noted in many RSG is just a temporary situation of the atmosphere of a given star. We propose an explanation for both cases based on the presence of strong velocity gradients larger than the thermal broadening of the spectral line. Using analytical but very simple radiative transfer we can compute intensity line profiles in such scenarios. We find that they qualitatively match the observed broadenings: large gradients are required for the narrow profiles of Betelgeuse, small gradients for the broad profiles of RW Cep. Profile bisectors are also reasonably well explained by this scenario in spite of the simple radiative transfer treatment. These results give a comprehensive explanation of both intensity and polarisation profiles. They provide also comfort to the approximationof a single-scattering event used in explaining the observed linear polarization in the inference of images of the photosphere of Betelgeuse and other Red SuperGiants as RW Cep, $\mu$ Cep and CE Tau. The atmospheres of Red SuperGiants appear to be able, perhaps cyclically, to either produce large velocity gradients that prevent photospheric plasma from reaching the upper atmosphere and that must hinder large events of mass loss, either to leave vertical movements unchanged, letting plasma raising, escaping gravity and forming large dust clouds in the circumstellar environement. The origin of the velocity gradient and its modulation within the atmosphere remains an open question.

Brown dwarfs are failed stars with very low mass (13 to 75 $M_J$), and an effective temperature lower than 2500 K. Thus, they play a key role in understanding the gap in the mass function between stars and planets. However, due to their faint nature, previous searches are inevitably limited to the solar neighbourhood (20 pc). To improve our knowledge of the low mass part of the initial stellar mass function and the star formation history of the Milky Way, it is crucial to find more distant brown dwarfs. Using James Webb Space Telescope (JWST) COSMOS-Web data, this study seeks to enhance our comprehension of the physical characteristics of brown dwarfs situated at a distance of kpc scale. The exceptional sensitivity of the JWST enables the detection of brown dwarfs that are up to 100 times more distant than those discovered in the earlier all-sky infrared surveys. The large area coverage of the JWST COSMOS-Web survey allows us to find more distant brown dwarfs than earlier JWST studies with smaller area coverages. To capture prominent water absorption features around 2.7 $\mu$m, we apply two colour criteria, F115W-F277W+1<F277W-F444W and F277W-F444W>0.9. We then select point sources by CLASS_STAR, FLUX_RADIUS, and SPREAD_MODEL criteria. Faint sources are visually checked to exclude possibly extended sources. We conduct SED fitting and MCMC simulations to determine their physical properties and associated uncertainties. Our search reveals 25 T-dwarf and 2 Y-dwarf candidates, more than any previous JWST brown dwarf searches. They are located from 0.3 kpc to 4 kpc away from the Earth. The cumulative number count of our brown dwarf candidates is consistent with the prediction from a standard double exponential model. Three of our brown dwarf candidates were detected by HST, with transverse velocities $12\pm5$ km s$^{-1}$, $12\pm4$ km s$^{-1}$, and $17\pm6$ km s$^{-1}$.

Context. Proxima Cen b is the prime target for the search of life around a nearby exoplanet by characterizing its atmosphere in reflected light. Due to the very high star/companion contrast (<1E-6), High Dispersion Coronagraphy is the most promising technique to perform such a characterization. Aims. With a maximum separation of 37 mas, Proxima b can be observed with a VLT in the visible. It requires a coronagraph providing high contrast (< 1E-4 ) very close from the star (< 2 {\lambda}/D ) over a broad spectral range (~30%), with a high transmission of the companion (> 50%). We look for an optimal solution that takes benefit of the properties of single-mode fibers. Methods. We introduce the Phase Induced Amplitude Apodizer and Nuller (PIAAN), a coronagraphic integral field unit, designed to feed a diffraction limited spectrograph. It uses a pupil remapping optics with moderate apodization, combined to a single mode fiber integral field unit. It exploits the properties of single mode fibers to null the star light without reducing the companion coupling. The study focuses on a proper tolerance analysis and proposes a wavefront optimization strategy. A prototype is built to demonstrate its performance. Results. We show that the PIAAN can theoretically provide contrasts of 7E-7 and a transmission of 72% at 2 {\lambda}/D over a bandwidth of 30%. A prototype is built and characterized and the proposed wavefront control strategy is also demonstrated in the lab. We reach contrast levels of 3E-5 over the full bandwidth, as expected from the tolerance analysis. Conclusions. We demonstrated the potential of the new PIAAN coronagraph, from simulations to prototype. Its performance will eventually be limited by the XAO capabilities. It is the main coronagraph candidate for the RISTRETTO instrument to observe Proxima Cen b on the VLT and its first technology milestone.

An interpulse search was carried out in a sample of 96 pulsars observed on the Large Phased Array (LPA) radio telescope in the Pushchino Multibeams Pulsar Search (PUMPS). The pulsar sample is complete for pulsars having a signal-to-noise ratio (S/N) in the main pulse ($MP$) greater than 40. To search for weak interpulses ($IP$), the addition of average profiles over an interval of up to 10 years was used. Interpulses were detected in 12 pulsars (12.5\% of the sample), of which 7 pulsars have an interpulse located near the $180^o$ phase relative to the main pulse (probable orthogonal rotators), and 5 have phases far from $180^o$ (probable coaxial rotators). The amplitude ratios of $IP/MP$ are in the range of 0.004-0.023, the median value is 0.01. Estimates of the observed number of coaxial and orthogonal rotators with $IP/MP \ge 0.01$ do not contradict the model according to which, during evolution, the magnetic axis and the axis of rotation become orthogonal.

Recollimation is a phenomenon of particular importance in the dynamic evolution of jets and in the emission of high-energy radiation. Additionally, the full comprehension of this phenomenon provides insights into fundamental properties of jets in the vicinity of the Active Galactic Nucleus (AGN). Three-dimensional (magneto-)hydrodynamic simulations revealed that the jet conditions at recollimation favor the growth of strong instabilities, challenging the traditional view-supported from two-dimensional simulations-of confined jets undergoing a series of recollimation and reflection shocks. To investigate the stability of relativistic jets in AGNs at recollimation sites, we perform a set of long duration three-dimensional relativistic hydrodynamic simulations with the state-of-the-art PLUTO code, to focus on the development of hydrodynamical instabilities. We explore the non-linear growth of the instabilities and their effects on the physical jet properties as a function of the initial jet parameters: jet Lorentz factor, temperature, opening angle and jet-environment density-contrast. The parameter space is designed to describe low-power, weakly magnetized jets at small distances from the core (around the parsec scale). All collimating jets we simulated develop instabilities. Recollimation instabilities decelerate the jet, heat it, entrain external material, and move the recollimation point to shorter distances from the core. This is true for both conical and cylindrical jets. The instabilities, that are first triggered by the centrifugal instability, appear to be less disruptive in the case of narrower, denser, more relativistic, and warmer jets. These results provide valuable insights into the complex processes governing AGN jets and could be used to model the properties of low-power, weakly magnetized jetted AGNs.

Fast radio bursts (FRBs), millisecond-duration radio transient events, possess the potential to serve as excellent cosmological probes. The FRB redshift distribution contains information about the FRB sources, providing key constraints on the types of engines. However, it is quite challenging to obtain the FRB redshifts due to the poor localization and the faintness of the host galaxies. This reality severely restricts the application prospects and study of the physical origins of FRBs. We propose that the clustering of observed FRBs can be an effective approach to address this issue without needing to accurately model dispersion measure (DM) contributions from the host galaxy and the immediate environment of the source. Using the clustering of $5\times 10^7$ simulated FRBs from future observations with sensitivity similar to the second phase of the Square Kilometre Array, we show that in extragalactic DM space, the redshift distributions can be accurately reconstructed, and the mean redshift for FRBs between 384.8 and 1450.3 $\rm pc\,cm^{-3}$ can be constrained to $\sim\!0.001\pm0.003 (1+z)$. The results demonstrate the potential of FRB clustering to constrain redshift distributions and provide valuable insights into FRB source models and cosmological applications.

Diffuse synchrotron radio sources associated with the intra-cluster medium of galaxy clusters are of special interest at high redshifts to understand the magnetization and particle acceleration mechanisms. El Gordo (EG) is the most massive galaxy cluster at high redshift (0.87), hosts a radio halo and a double radio relic system. We aim to understand the role of turbulence in the origin of the diffuse radio emission by combining radio and X-ray observations. We observed EG with the Upgraded GMRT at 0.3 - 1.45 GHz and obtained the integrated spectra, spatially resolved spectral map, and scaling relations between radio and X-ray surface brightness. We constructed a density fluctuation power spectrum for the central 1 Mpc region using Chandra data. The radio halo and the double relics are detected at all the bands and, in addition, we detect an extension to the eastern relic. The radio halo has a spectral index of $-1.0\pm0.3$ with a possible steepening beyond 1.45 GHz. All the relics have spectral indices of $-1.4$ except the extension of the east relic which has $-2.1\pm0.4$. The radio and X-ray surface brightness point-to-point analysis at bands 3 and 4 show slopes of $0.60\pm0.12$ and $0.76\pm0.12$, respectively. The spectral index and X-ray surface brightness show an anti-correlation. The density fluctuations peak at $\sim 700$ kpc with an amplitude of $(\delta \rho/\rho) =0.15\pm0.02$. We derive the 3D turbulent Mach number of $\sim$ 0.6 from the gas density fluctuations power spectrum, assuming all the fluctuations are attributed to turbulence. The derived properties of EG are in line with the low redshift clusters indicating that fast magnetic amplification proposed in high redshift clusters is at work in EG as well. We have discussed the consistency of the obtained results with the turbulent re-acceleration which might be representative of high redshift merging clusters.

Neural network-based emulators for the inference of stellar parameters and elemental abundances represent an increasingly popular methodology in modern spectroscopic surveys. However, these approaches are often constrained by their emulation precision and domain transfer capabilities. Greater generalizability has previously been achieved only with significantly larger model architectures, as demonstrated by Transformer-based models in natural language processing. This observation aligns with neural scaling laws, where model performance predictably improves with increased model size, computational resources allocated to model training, and training data volume. In this study, we demonstrate that these scaling laws also apply to Transformer-based spectral emulators in astronomy. Building upon our previous work with TransformerPayne and incorporating Maximum Update Parametrization techniques from natural language models, we provide training guidelines for scaling models to achieve optimal performance. Our results show that within the explored parameter space, clear scaling relationships emerge. These findings suggest that optimal computational resource allocation requires balanced scaling. Specifically, given a tenfold increase in training compute, achieving an optimal seven-fold reduction in mean squared error necessitates an approximately 2.5-fold increase in dataset size and a 3.8-fold increase in model size. This study establishes a foundation for developing spectral foundational models with enhanced domain transfer capabilities.

Relativistic jets originating at the center of AGN are embedded in extreme environments with strong magnetic fields and high particle densities, which makes them a fundamental tool for studying the physics of magnetized plasmas. We aim to investigate the magnetic field structure and the pc/sub-pc properties of the relativistic jet in the radio galaxy 3C111. Rotation Measure (RM) studies of nearby radio galaxies, such as this one, provide a valuable tool to investigate transversal magnetic field properties of the synchrotron emission. We model the brightness distribution of the source with multiple 2D Gaussian components to characterize individual emission features. After determining the core shift, we compute the spectral index maps for all the frequency pairs and find different distributions for the core region and the jet with an unusual optically thick/flat feature at 1-2 pc from the core. Using modelfit, we find a total of 56 components at different frequencies. By putting constraints on the size and position, we identify 22 components at different frequencies for which we compute the equipartition magnetic field. We compute the RM at two different triplets of frequencies. At 15.2-21.9-43.8 GHz, we discover high values of RM in the same region where the optically thick/flat feature was found. This can be associated with high electron density at 1-2 pc from the core that we interpreted as originating in a cloud of the clumpy torus. At 5-8.4-15.2 GHz, we find a distribution of the EVPAs and significant RM transverse gradient that provide strong evidence of a helical configuration of the magnetic field, as found in simulations.

Fast Radio Bursts (FRBs) are intense, millisecond-duration radio transients that have recently been proposed to arise from coherent radiation mechanisms within the magnetosphere of neutron stars. Observations of repeating FRBs, including periodic activity and large variations in Faraday rotation measures, suggest that these bursts may have binary system origins, with massive companion. In this work, we investigate how accretion from a massive companion influences the FRB radiation within the magnetosphere of the neutron star. Focusing on two widely accepted pulsar-like coherent radiation mechanisms, we establish the parameter space for neutron stars that allows FRB generation, even in the presence of accreted matter. Our analysis shows that coherent curvature radiation is only viable within a narrow range of parameters, while the magnetic reconnection mechanism operates across a broader range. In both cases, the neutron star must possess a strong magnetic field with strength $\gtrsim 10^{13}$ G. These findings at least indicate that the central engines responsible for producing observable FRBs in binary systems are indeed magnetars.

This study investigates the constraints on ALPs parameters through the photon-ALP oscillation model, based on the high-energy photon propagation characteristics of the gamma-ray burst GRB 221009A. We briefly describe the Primakoff process and use it to derive the oscillation probability. Numerical simulations incorporate the GMF, IGMF, and EBL, utilizing the open-source code gammaALPs to simulate photon propagation from the source to Earth. By employing the chi2 statistical method and segmented spectral fitting of low-energy and high-energy observational data from HXMT-GECAM, the dependence of photon survival probability on ALP mass (ma) and coupling strength (ga) is analyzed. Results show that for the ALP mass range 10^-7 < ma < 10^2 neV, the upper limit on the coupling strength is ga < 0.27 * 10^-11 GeV^-1, improving constraints by one order of magnitude compared to the CAST experiment (6.6 * 10^-11 GeV^-1). Notably, high-energy data exhibit significantly stronger constraining power. This work provides a novel theoretical framework and observational basis for indirectly probing ALPs through extreme astrophysical phenomena.

For monitoring the night sky conditions, wide-angle all-sky cameras are used in most astronomical observatories to monitor the sky cloudiness. In this manuscript, we apply a deep-learning approach for automating the identification of precipitation clouds in all-sky camera data as a cloud warning system. We construct our original training and test sets using the all-sky camera image archive of the Iranian National Observatory (INO). The training and test set images are labeled manually based on their potential rainfall and their distribution in the sky. We train our model on a set of roughly 2445 images taken by the INO all-sky camera through the deep learning method based on the EfficientNet network. Our model reaches an average accuracy of 99\% in determining the cloud rainfall's potential and an accuracy of 96\% for cloud coverage. To enable a comprehensive comparison and evaluate the performance of alternative architectures for the task, we additionally trained three models LeNet, DeiT, and AlexNet. This approach can be used for early warning of incoming dangerous clouds toward telescopes and harnesses the power of deep learning to automatically analyze vast amounts of all-sky camera data and accurately identify precipitation clouds formations. Our trained model can be deployed for real-time analysis, enabling the rapid identification of potential threats, and offering a scaleable solution that can improve our ability to safeguard telescopes and instruments in observatories. This is important now that numerous small and medium-sized telescopes are increasingly integrated with smart control systems to reduce manual operation.

The aim of this paper is to improve our understanding of the heating mechanisms of the solar chromosphere via realistic three-dimensional (3D) modeling of solar magneto-convection, considering the fact that solar plasma contains a significant fraction of neutral gas. For that we performed simulations of the same physically volume of the Sun, namely 5.76x5.76x2.3 Mm^3 (with 1.4 Mm being above the optical surface), at three different resolutions: 20x20x14, 10x10x7 and 5x5x3.5 km^3. At all three resolutions we compare the time series of simulations with/without ambipolar diffusion, as the main non-ideal heating mechanism due to neutrals. We also compare simulations with three different magnetizations: (1) case of a small-scale dynamo; (2) an initially implanted vertical magnetic field of 50 G; (3) an initially implanted vertical field of 200 G, though not all of them are available at all resolutions. We obtain that the average magnetization of the simulations increases with improving resolution. So does the average magnetic Poynting flux, meaning that there is more magnetic energy in the simulation box at higher resolutions. Ambipolar diffusion operates at relatively large scales, which can be actually numerically resolved with the grid scale of the highest resolution simulations as the ones reported here. We consider two ways of evaluating where the ambipolar scales are numerically resolved: (i) a method to evaluate the numerical diffusion of the simulations and compare it to the physical ambipolar diffusion; (ii) an order of magnitude comparison of spatial scales given by the ambipolar diffusion to our grid resolution. At the resolved locations we compare the average temperature in the simulations with/without ambipolar diffusion, and conclude that the plasma is on average about 600 K hotter after 1200 sec of simulation time when the ambipolar diffusion is included.

The search for exoplanetary or star-planet interaction radio signals is a major challenge, as it is one of the only way of detecting a planetary magnetic field. The aim of this article is to demonstrate the relevance of using statistical tools to detect periodic radio signals in unevenly spaced observations. Identification of periodic radio signal is achieved here by a Lomb-Scargle analysis. We first apply the technique on simulated astrophysical observations with controlled simulated noise. This allows for characterizing of spurious detection peaks in the resulting periodograms, as well as identifying peaks due to resonance or beat periods. We then validate this method on a real signal, using ~1400 hours of data from observations of Jupiter's radio emissions by the NenuFAR radio telescope over more than six years to detect jovian radio emissions periodicities (auroral and induced by the Galilean moons). We demonstrate with the simulation that the Lomb-Scargle periodogram allows to correctly identify periodic radio signal, even in a diluted signal. On real measurements, it correctly detects the rotation period of the strong signal produced by Jupiter and the synodic period of the emission triggered by the interaction between Jupiter and its Galilean moon Io, but also maybe weaker signal such as the one produced by the interaction between Jupiter and Europa or between Jupiter and Ganymede. It is important to note that secondary peaks in the Lomb-Scargle periodogram will be observed at the synodic and resonance periods between all the detected signal periodicities (i.e. real signals, but also periodicities in the observation). These secondary peaks can then be used to strengthen the detections of weak signals.

Cosmological neutrino mass and abundance measurements are reaching unprecedented precision. Testing their stability versus redshift and scale is a crucial issue, as it can serve as a guide for optimizing ongoing and future searches. Here, we perform such analyses, considering a number of redshift, scale, and redshift-and-scale nodes. Concerning the $k$-space analysis of $\sum m_\nu$, CMB observations are crucial, as they lead the neutrino mass constraints. Interestingly, some data combinations suggest a non-zero value for the neutrino mass with $2\sigma$ significance. The most constraining bound we find is $\sum m_\nu<0.54$ eV at $95\%$ CL in the $[10^{-3}, 10^{-2}]$ $h$/Mpc $k$-bin, a limit that barely depends on the data combination. Regarding the redshift- and scale-dependent neutrino mass constraints, high redshifts ($z>100$) and scales in the range $[10^{-3}, 10^{-1}]$ $h$/Mpc provide the best constraints. The least constraining bounds are obtained at very low redshifts $[0,0.5]$ and also at very small scales ($k>0.1\, h$/Mpc), due to the absence of observations. Highly relevant is the case of the $[100, 1100]$, $[10^{-2}, 10^{-1}]$ $h$/Mpc redshift-scale bin, where a $2$-$3\sigma$ evidence for a non-zero neutrino mass is obtained for all data combinations. The bound from CMB alone at $68\%$ CL is $0.63^{+0.20}_{-0.24}$ eV, and the one for the full dataset is $0.56^{+0.20}_{-0.23}$ eV, clearly suggesting a non-zero neutrino mass at these scales, possibly related to a deviation of the ISW amplitude in this redshift range. Concerning the analysis of $N_{\rm eff}$ in the $k$-space, at intermediate scales ranging from $k=10^{-3}$ $h$/Mpc to $k=10^{-1}$ $h$/Mpc, accurate CMB data provide very strong bounds, the most robust one being $N_{\rm eff}=3.09\pm 0.14$, comparable to the standard expected value without a $k$-bin analysis. [abridged]

Low-mass stellar and substellar companions are indispensable objects for verifying evolutionary models that transition from low-mass stars to planets. Their formation is likely also affected by the surrounding stellar environment. The Fornax-Horologium (FH) association is a recently classified young association in the solar neighbourhood with a dissolving open cluster in its centre. It has not been searched widely for substellar companions and exoplanets with direct imaging. We search for companions of stars in the FH and investigate the formation and evolution of companions during the expansion and dissolution of a star cluster. We conduct a direct-imaging survey of 49 stars in FH with VLT/SPHERE. We present HD 24121B, a companion at the hydrogen-burning limit that orbits star HD 24121 in the core cluster of the FH. The companion is located at a projected angular separation of 2.082 $\pm$ 0.004 arcsec from the central star and has contrasts of $\Delta$H2 = 5.07 $\pm$ 0.05 mag and $\Delta$H3= 4.98 $\pm$ 0.05 mag. We estimate a photometric mass of 74.9 $\pm$ 7.5 $M_J$ for HD 24121B, which places it at the boundary of brown dwarfs and low-mass stars. It is a new benchmark object for evolutionary models at the hydrogen-burning boundary, especially at the age of 30 - 40 Myr. Orbital fitting with joint Gaia and SPHERE relative astrometry found a high eccentricity for HD 24121B. This suggests that it may have undergone dynamic scattering. Future chemical composition measurements such as high-resolution spectroscopic observations will provide more clues on its formation history.

The presence of nine candidate galaxies at $z=17$ and $z=25$ discovered by the \textit{James Webb Space Telescope} in relatively small sky areas, if confirmed, is virtually impossible to reconcile with current galaxy formation model predictions. We show here that the implied UV luminosity density can be produced by a population of primordial black holes (PBH) of mass $M_{\rm PBH} = 10^{4-5} \, M_{\odot}$ residing in low-mass halos ($M_h \approx 10^{7} \, M_{\odot}$), and accreting at a moderate fraction of the Eddington luminosity, $\lambda_E \simeq 0.36$. These sources precede the first significant episodes of cosmic star formation. At later times, as star formation is ignited, PBH emission becomes comparable or subdominant with respect to the galactic one. Such a PBH+galaxy scenario reconciles the evolution of the UV LF from $z=25$ to $z=11$. If ultra-early sources are purely powered by accretion, this strongly disfavours seed production mechanisms requiring the presence of stars (massive/Pop III stars or clusters) or their UV radiation (direct collapse BHs), leaving PBH as the only alternative solution available so far. Alternative explanations, such as isolated, large clusters ($\approx 10^7 \, M_{\odot}$) of massive ($m_\star =10^3 M_{\odot}$) of Pop III are marginally viable, but require extreme and unlikely conditions, that can be probed via UV/FIR emission lines or gravitational waves.

Angular momentum loss through magnetic braking drives the spin-down of low-mass stars and the orbital evolution of various close binary systems. Current theories for magnetic braking, often calibrated for specific types of systems, predict angular momentum loss rates that differ by several orders of magnitude. A unified prescription would provide valuable constraints on the relationship between angular momentum loss, stellar dynamos, and magnetic activity. Recent studies have shown that a saturated, boosted, and disrupted (SBD) magnetic braking prescription can explain the observed increase in the fraction of close white dwarf plus M-dwarf binaries at the fully convective boundary, the period distribution of main-sequence binaries, and the mass distribution of close M-dwarf companions to hot subdwarfs. To analyze whether this prescription also applies to related binaries, we investigated the evolution of cataclysmic variables (CVs) using the SBD magnetic braking model. We implemented the SBD prescription into the stellar evolution code MESA and simulated CV evolution, testing different values for the boosting and disruption parameters over a range of stellar properties. Our model reproduces the observed mass transfer rates and donor mass-radius relation with good accuracy. The evolutionary tracks match the observed boundaries of the orbital period gap and the period minimum for values of boosting and disruption slightly smaller but still consistent with those derived from detached binaries. Angular momentum loss through SBD magnetic braking can explain not only detached binaries but also cataclysmic variables, making it the only current prescription suitable for multiple types of close binary stars. Further testing in other systems is needed, and the semi-empirical convective turnover times currently used for main-sequence stars should be replaced with self-consistent values.

The advent of the multimessenger cosmology marked by the detection of GW170817, gravitational waves from compact objects at cosmological distances demonstrated Standard Sirens as a relevant cosmological probe. In the absence of an electromagnetic counterpart identification, GWs carry valuable information through the dark siren approach, where the source redshift is estimated using galaxy catalogs of potential hosts within the localization volume. However, the dark siren analysis can be affected by galaxy catalog incompleteness at the limits of gravitational-wave detectability, potentially introducing biases in the constraints on cosmological parameters. Focusing on GWs from binary black holes detected by the LIGO, Virgo, and KAGRA collaboration, we explore the possible systematic biases in the measurement of the Hubble constant. These biases may arise from 1) the incompleteness of catalogs due to the apparent magnitude thresholds of optical telescope sensitivity, and 2) the use of incorrect weighting schemes (using star formation or stellar mass as tracers of the host galaxy) for each potential host. We found that an unbiased estimate of $H_0$ can be obtained when the corrected weighting scheme is applied to a complete or volume-limited catalog. The results using stellar mass as a tracer indicate that a percent-level measurement of $H_0$, with a precision of approximately 3%, can be achieved with 100 binary black hole detections by the LVK at O4 and O5 sensitivity. The O5 run provides a slight improvement, reducing the $H_0$ uncertainty by 0.07 km/s/Mpc compared to the O4-like configuration. This precision is achievable by using a complete galaxy catalog that covers the 90% of the localisation probability for each GW detection, with A$_{90\%}$<10 deg$^2$. The $H_0$ precision increases to approximately 6% when it is assumed that every galaxy has an equal probability of being the host.

Recent cosmological observations have revealed growing tensions with the standard $\Lambda$CDM model, including indications of isotropic cosmic birefringence and deviations from $w = -1$ in the dark energy equation of state, as suggested by DESI and supernova measurements. In this paper, we point out that such deviations can arise even from a subdominant energy density component. We then propose a unified framework based on a dynamical axion field that simultaneously accounts for both anomalies, providing a simple and natural extension of the standard $\Lambda$CDM model. In our scenario, the axion field with $2H_0\lesssim m\lesssim 6H_0$, where $H_0$ is the current Hubble constant, induces a nonzero rotation of the CMB polarization plane and modifies the present-day dark energy equation of state. This framework accommodates recent observational data with natural parameter choices, even for a string axion with a decay constant of order $10^{17}\,$GeV.

We investigate the kination-amplified inflationary gravitational-wave background (GWB) interpretation of the signal recently reported by various pulsar timing array (PTA) experiments. Kination is a post-inflationary phase in the expansion history dominated by the kinetic energy of some scalar field, characterized by a stiff equation of state $w=1$. Within the inflationary GWB model, we identify two modes which can fit the current data sets (NANOGrav and EPTA) with equal likelihood: the kination-amplification (KA) mode and the ordinary, non-kination-amplification (no-KA) mode. The multimodality of the likelihood motivates a Bayesian analysis with nested sampling. We analyze the free spectra of current PTA data and mock free spectra constructed with higher signal-to-noise ratios, using nested sampling. The analysis of the mock spectrum designed to be consistent with the best fit to the NANOGrav 15 yr (NG15) data successfully reveals the expected bimodal posterior for the first time while excluding the reheating mode that appears in the fit to the current NG15 data, making a case for our correct treatment of potential multimodal posteriors arising from future PTA data sets. The resultant Bayes factor is $B\equiv Z_\mathrm{no-KA}/Z_\mathrm{KA}=2.9\pm1.9$, indicating comparable statistical significance between the two modes. Given the theoretical model-building challenges of producing highly blue-tilted primordial tensor spectra, the KA mode has the advantage of requiring a less blue primordial spectrum, compared with the no-KA mode. The synergy between future cosmic microwave background polarization, pulsar timing and laser interferometer measurements of gravitational waves will help resolve the ambiguity implied by the multimodal posterior in PTA-only searches.

We consider an axion flux on Earth consistent with emission from the Supernova explosion SN 1987A. Using Chiral Perturbation Theory augmented with an axion, we calculate the energy spectrum of $a + N \to N + \gamma$ as well as $a + N \to N + \pi^0$, where $N$ denotes a nucleon in a water tank, such as the one planned for the Hyper-Kamiokande neutrino detection facility. Our calculations assume the most general axion-quark interactions, with couplings constrained either solely by experimental data, or by specific theory scenarios. We find that even for the QCD axion -- whose interaction strength with matter is at its weakest as compared with axion-like particles -- the expected Čherenkov-light spectrum from neutrino-nucleon interactions is modified in a potentially detectable way. Furthermore, detectability appears significantly more promising for the $N + \pi^0$ final state, as its spectrum peaks an order of magnitude higher and at energies twice as large compared to the $N + \gamma$ counterpart. Given the rarity of SN events where both the neutrino and the hypothetical axion burst are detectable, we emphasize the importance of identifying additional mechanisms that could enhance such signals.

We provide a study of the effects of the Effective Field Theory (EFT) generalisation of stochastic inflation on the production of primordial black holes (PBHs) in a model-independent single-field context. We demonstrate how the scalar perturbations' Infra-Red (IR) contributions and the emerging Fokker-Planck equation driving the probability distribution characterise the Langevin equations for the ``soft" modes in the quasi-de Sitter background. Both the classical-drift and quantum-diffusion-dominated regimes undergo a specific analysis of the distribution function using the stochastic-$\delta N$ formalism, which helps us to evade a no-go theorem on the PBH mass. Using the EFT-induced alterations, we evaluate the local non-Gaussian parameters in the drift-dominated limit.

The study presents an effective approach for deriving and utilizing polarity-based cross-correlation functions to forecast Galactic Cosmic Ray (GCR) fluxes based on solar activity proxies. By leveraging a universal correlation framework calibrated with AMS-02 and PAMELA proton flux data under a numerical model, the methodology incorporates Empirical Mode Decomposition (EMD) and a global spline fit. These techniques ensure robust handling of short-term fluctuations and smooth transitions during polarity reversals. The results have significant potential for space weather applications, enabling reliable GCR flux predictions critical for radiation risk assessments and operational planning in space exploration and satellite missions.

We compute correlation functions of the primordial density perturbations when they couple to a gapless, strongly coupled sector of spectator fields -- ``unparticles" -- during inflation. We first derive a four-point function of conformally coupled scalars for all kinematic configurations in de Sitter, which exchanges an unparticle at tree-level, by performing direct integration using the Mellin-Barnes method. To obtain inflationary bispectra and trispectra, we apply weight-shifting operators to the conformally coupled scalar correlator. We show that the correlators solve differential equations determined by the additional symmetries enjoyed by the unparticle propagator. Based on these differential equations, we are able to discuss the spinning-unparticle exchanges, focusing on two possible cases where the currents or the stress tensor of unparticles are coupled to inflatons, with the help of spin-raising operators. Finally, we study the phenomenology of the resulting shape functions. Depending on the value of the unparticle scaling dimension, we classify three characteristic shapes for the inflationary bispectra, including near-equilateral, near-orthogonal, and a novel shape which appears when the scaling dimensions are close to half-integers. More generally, we find that the leading order squeezed limits are insufficient to conclusively determine the detection of a light particle or unparticle. Only the full shapes of bispectra and trispectra can break this degeneracy.

We study the inflationary phenomenology of a rescaled Einstein-Gauss-Bonnet gravity. In this framework, the gravitational constant of the Einstein-Hilbert term is rescaled due to effective terms active in the high curvature era. Basically, the total theory is an $F(R,G,\phi)$ theory with the Gauss-Bonnet part contributing only a non-minimal coupling to the scalar field, so it is a theory with string theory origins and with a non-trivial $F(R)$ gravity part. The $F(R)$ gravity part in the high curvature regime contributes only a rescaled Einstein-Hilbert term and thus the resulting theory is effectively a rescaled version of a standard Einstein-Gauss-Bonnet theory. We develop the formalism of rescaled Einstein-Gauss-Bonnet gravity, taking in account the GW170817 constraints on the gravitational wave speed. We show explicitly how the rescaled theory affects directly the primordial scalar and tensor perturbations, and how the slow-roll and observational indices of inflation are affected by the rescaling of the theory. We perform a thorough phenomenological analysis of several models of interest and we show that is it possible to obtain viable inflationary theories compatible with the latest Planck data. Also among the studied models there are cases that yield a relatively large blue tilted tensor spectral index and we demonstrate that these models can lead to detectable primordial gravitational waves in the future gravitational wave experiments. Some of the scenarios examined, for specific values of the reheating temperature may be detectable by SKA, LISA, BBO, DECIGO and the Einstein Telescope.

The properties and stability of hydrous phases are key to unraveling the mysteries of the water cycle in Earth's interior. Under the deep lower mantle conditions, hydrous phases transition into a superionic state. However, the influence of the superionic effect on their stability and dehydration processes remains poorly understood. Using ab initio calculations and deep-learning potential molecular dynamics simulations, we discovered a doubly superionic transition in delta-AlOOH, characterized by the highly diffusive behavior of ionic hydrogen and aluminum within the oxygen sub-lattice. These highly diffusive elements contribute significant external entropy into the system, resulting in exceptional thermostability. Free energy calculations indicate that dehydration is energetically and kinetically unfavorable when water exists in a superionic state under core-mantle boundary (CMB) conditions. Consequently, water can accumulate in the deep lower mantle over Earth's history. This deep water reservoir plays a crucial role in the global deep water and hydrogen cycles.

Several models within the framework of Einstein-Gauss-Bonnet gravities are considered with regard their late-time phenomenological viability. The models contain a non-minimally coupled scalar field and satisfy a constraint on the scalar field Gauss-Bonnet coupling, that guarantees that the speed of the tensor perturbations is equal to the speed of light. The late-time cosmological evolution of these Einstein-Gauss-Bonnet models is confronted with the observational data including the Pantheon plus Type Ia supernovae catalogue, the Hubble parameter measurements (cosmic chronometers), data from cosmic microwave background radiation (CMB) and baryon acoustic oscillations (BAO) including the latest measurements from Dark Energy Spectroscopic Instrument (DESI). Among the considered class of models some of them do not fit the CMB and BAO data. However, there exists some models that generate a viable Einstein-Gauss-Bonnet scenario with well-behaved late-time cosmological evolution that fits the observational data essentially better in comparison to the standard $\Lambda$-Cold-Dark-Matter model.

Recently the Dark Energy Survey (DES) Collaboration presented evidence that the equation of state $w$ of the dark energy is varying, or $w \simeq -0.948$ if it is constant. In either case, the dark energy cannot be due to a cosmological constant alone. Here we introduce an ultralight axion (or axion-like particle) with mass $m_\phi \simeq 2 \times 10^{-33}$ eV that has properties that can explain the new $w$ measurement. In particular, $w\ge -1$ in this model, ruling out the $w < -1$ region allowed by the DES data.

Light bosons can form gravitational atoms (GA) around spinning black holes through the superradiance this http URL the black hole to be part of a binary system,the tidal potential of the companion periodically perturbs the GA such that an atomic transition occurs between two of its energy this http URL resonant transition is modeled by the Landau-Zener system,where the orbital frequency of the companion determines the relevant this http URL this work, we study a novel gravitational wave signal originating directly from the atomic transition of the GA in a binary this http URL derive the analytical formulae of both the strain waveform and frequency spectrum of the this http URL further present the GA-binary systems that can have a large signal-to-noise ratio in LISA's frequency this http URL, we discuss the implications of detection of the signal:inferring model parameters,including the boson mass and black hole spin,and computing the phase shift and Doppler shift of the gravitational wave signal for equal mass binaries.

In the Pati-Salam gauge symmetry $SU(4)_c \times SU(2)_L \times SU(2)_R$ (4-2-2, for short), the observed quarks and leptons of each family reside in the bi-fundamental representations $(4,2,1)$ and $({\bar 4},1,2)$. There exist, however, the fundamental representations $(4,1,1)$, $(1,2,1)$ and $(1,1,2)$ and their hermitian conjugates, which show the presence, in principle, of yet to be discovered color triplets that carry electric charge $\pm{e/6}$, and color singlet particles with charges of $\pm{e/2}$. These Standard Model charges are in full accord with the fact that the 4-2-2 model predicts the presence of a topologically stable finite energy magnetic monopole that carries two quanta of Dirac magnetic charge, i.e., $4 \pi/e$, as well as color magnetic charge that is screened beyond the quark confinement scale. The 4-2-2 model therefore predicts the existence of exotic baryons, mesons and leptons that carry fractional ($\pm{e/2}$) electric charges. Since their origin lies in the fundamental representations of 4-2-2, these exotic particles may turn out to be relatively light, in the TeV mass range or so. The 4-2-2 magnetic monopole mass depends on the 4-2-2 symmetry breaking scale which may be as low as a few TeV.

Recently, the Atacama Cosmology Telescope (ACT) DR6 results showed a preference for isotropic cosmic birefringence, which is consistent with the previous analyses using the Planck and WMAP data. Independently, the Dark Energy Spectroscopic Instrument (DESI) DR2 results further support that dark energy is evolving over the history of the universe, enhancing the possibility of new physics in the late-time universe. In this paper, we propose that if domain walls associated with the string axion are formed, the isotropic cosmic birefringence can be explained naturally. Interestingly, avoiding the domain wall problem, the domain wall formation is predicted to be much later than the epoch of recombination. Compared with the previous proposal of kilobyte cosmic birefringence, where domain wall formation occurs before recombination, the predicted rotation angle, $\beta \approx 0.21 c_\gamma$ deg with the anomaly coefficient $c_\gamma \approx 1$, does not suffer from the ambiguity of the population bias. The prediction is in excellent agreement with the ACT (and combined) data regarding cosmic birefringence. This scenario can be probed from the anisotropic birefringence for the photons emitted well after the recombination and the gravitational waves. In addition, the late-time dynamics of the axion contributes to the dark energy component, and we also study the relation to the DESI results.

The identification of gamma-ray induced air showers with Cherenkov telescopes suffers from contamination with a specific class of cosmic ray induced air showers. The predictions for this background show strong discrepancies between the available event generators. In this study, we identify collision events of cosmic rays with atmospheric nuclei in which a large fraction of the original beam energy is transmitted to the electromagnetic part of the shower as the main source for this background. Consequently, we define a pseudorapidity region of interest for hadron collider experiments that corresponds to this background, taking into account the center-of-mass energy. This region of interest is compared with the available datasets and the pseudorapidity coverage of the detectors that recorded it. We find that the LHCf and RHICf detectors are the only ones covering substantial parts of this region of interest and suggest a measurement of the energy spectra of reconstructed neutral pions to be made with this data. Such results could serve as valuable constraints for a future parameter tuning of the event generators to improve the background estimation uncertainties for gamma-ray induced air shower identification.

Modern cosmological theories invoke the idea that all structure in the Universe originates from quantum fluctuations. Understanding the quantum-to-classical transition for these fluctuations is of central importance not only for the foundations of quantum theory, but also for observational astronomy. In my contribution, I review the essential features of this transition, emphasizing in particular the role of Alexei Starobinsky.

We study loop corrections in the effective field theory of inflation with imaginary speed of sound, which has been shown to provide an effective description of multi-field inflationary models characterized by strongly non-geodesic motion and heavy entropic perturbations. We focus on the one-loop corrections to the scalar and tensor power spectra, taking into account all relevant vertices at leading order in derivatives and in slow-roll. We find a power-law dependence of the scalar two-point function on the scale that defines the range of validity of the effective theory, analogous to the enhancement observed in tree-level correlation functions. Even more dramatic, the relative correction to the tensor spectrum is exponentially enhanced, albeit also suppressed in the slow-roll limit. In spite of these large effects, our results show that this class of models can satisfy the requirement of perturbative control and a consistent loop expansion within a range of parameters of phenomenological interest. On the other hand, models predicting large values of the power spectrum on small scales are found to be under strong tension. As a technical bonus, we carefully explain the prescription for the regularization and manipulation of loop integrals in this set-up, where one has a non-trivial domain of integration for time and momentum integrals owing to the regime of validity of the effective field theory. This procedure is general enough to be of potential applicability in other contexts.

When a gravitational shockwave hits a magnetar it creates perturbations of the magnetar magnetic field in a form of a transition radiation. We argue that this radiation can be a novel candidate to explain the origin of fast radio bursts (FRB). A unique feature of the transition radiation on the shockwaves is that normal components of its Maxwell strength `remember' only the spatial `profile' of the shock, not the form of the signal. This fact allows us to determine completely a characteristic initial problem for the perturbations with Cauchy data defined on a null hypersurface just behind the shockwave front. The computations are carried by modeling magnetar as a magnetic dipole. As an illustration we consider shockwaves created by ultrarelativistic objects of two types, by compact sources or by cosmic strings. In the both cases the duration of the engine pulse is determined by an impact distance between the magnetar and the source. We present the angular distribution of the transition radiation flux and show that it is consistent with properties of the FRB engine.

It is very much intriguing if the Planck scale $M_{\rm{Pl}}$ is not a fundamental parameter. The Brans-Dicke gravity is nothing but the theory where the Planck scale $M_{\rm{Pl}}$ is indeed an illusional parameter. The theory predicts a massless scalar boson whose exchanges between matters induce unwanted long range forces. We solve this problem imposing there is no dimensionful parameter in the theory, even at the quantum level. We further extend the theory by including a $R^2$ term and a non-minimal coupling of the Standard Model Higgs to gravity, as their coefficients are dimensionless. This extension provides a heavy inflaton field that is consistent with all cosmological observations, with a potential very similar to that of the Starobinsky model. The inflaton necessarily decays into the massless scalar bosons, resulting in a non-negligible amount of dark radiation in the present universe. We demonstrate that the inflation model yields a sufficiently high reheating temperature for successful leptogenesis, and we also discuss a possible candidate for dark matter.

We propose an explanation for the recently reported ultra-high-energy neutrino signal at KM3NeT, which lacks an identifiable astrophysical source. While decaying dark matter in the Galactic Center is a natural candidate, the observed arrival direction strongly suggests an extragalactic origin. We introduce a multicomponent dark matter scenario in which the components are part of a supermultiplet, with supersymmetry ensuring a nearly degenerate mass spectrum among the fields. This setup allows a heavy component to decay into a lighter one, producing a boosted neutrino spectrum with energy $E_\nu \sim 100$ PeV, determined by the mass difference. The heavy-to-light decay occurs at a cosmological redshift of $z \sim \text{a few}$ or higher, leading to an isotropic directional distribution of the signal.

We show for the first time that warm inflation is feasible with Standard Model (SM) gauge interactions alone. Our model consists of a minimal extension of the SM by a single scalar inflaton field with an axion-like coupling to gluons and a monomial potential. The effects of light fermions, which were previously argued to render warm inflation with the SM impossible, are alleviated by Hubble dilution of their chiral chemical potentials. Our model only features one adjustable combination of parameters and accommodates all inflationary observables. We briefly discuss implications for axion experiments, dark matter, and the strong CP-problem.

In this work, we extend the formalism of second-order relativistic dissipative hydrodynamics, developed previously using Zubarev's non-equilibrium statistical operator formalism. By employing a second-order expansion of the statistical operator in terms of hydrodynamic gradients, we demonstrate that new second-order terms emerge due to the coupling of two-point quantum correlators between tensors of differing ranks, evaluated at distinct space-time points. Such terms arise because the presence of the acceleration vector in the system allows Curie's theorem, which governs symmetry constraints, to be extended for constructing invariants from tensors of different ranks evaluated at distinct space-time points. The new terms are identified in the context of a complete set of second-order equations governing the shear-stress tensor, bulk-viscous pressure, and charge-diffusion currents for a generic quantum system characterized by the energy-momentum tensor and multiple conserved charges. Additionally, we identify the transport coefficients associated with these new terms and derive the Kubo formulas expressing the second-order transport coefficients through two- and three-point correlation functions.

The direct Urca (dUrca) process is a key mechanism driving rapid neutrino cooling in neutron stars, with its baryon density activation threshold determined by the microscopic model for nuclear matter. Understanding how nuclear interactions shape the dUrca threshold is essential for interpreting neutron star thermal evolution, particularly in light of recent studies on exceptionally cold objects. We investigate the impact of incorporating the scalar isovector $\delta$ meson into the neutron star equation of state, which alters the internal proton fraction and consequently affects the dUrca cooling threshold. Since proton superfluidity is known to suppress dUrca rates, we also examine the interplay between the nuclear interaction mediated by the $\delta$ meson and the $^1S_0$ proton pairing gap. We perform a Bayesian analysis using models built within a relativistic mean-field approximation, incorporating constraints from astrophysical observations, nuclear experiments, and known results of \textit{ab initio} calculations of pure neutron matter. We then impose a constraint on the dUrca threshold based on studies of fast-cooling neutron stars. The inclusion of $\delta$ meson expands the range of possible internal compositions, directly influencing the stellar mass required for the central density to reach the dUrca threshold. Furthermore, we observe that the observation of relatively young and cold neutron stars provides insights into $^1S_0$ proton superfluidity in the core of neutron stars.