Papers for Monday, Dec 30 2024

MPI-Rockstar is a massively parallel halo finder based on the Rockstar phase-space temporal halo finder code, which is one of the most extensively used halo finding codes. Compared to the original code, parallelized by a primitive socket communication library, we parallelized it in a hybrid way using MPI and OpenMP, which is suitable for analysis on the hybrid shared and distributed memory environments of modern supercomputers. This implementation can easily handle the analysis of more than a trillion particles on more than 100,000 parallel processes, enabling the production of a huge dataset for the next generation of cosmological surveys. As new functions to the original Rockstar code, MPI-Rockstar supports HDF5 as an output format and can output additional halo properties such as the inertia tensor.

It has been demonstrated that systems of tightly packed inner planets with giant exterior companions tend to have less regular orbital spacings than those without such companions. We investigate whether this observed increase in the gap complexity of the inner systems can be explained solely as the result of secular dynamics caused by the disturbing potential of the exterior companions. Amplification of mutual orbital inclinations in the inner system due to such secular dynamics may lead to the inner system attaining non-mutually transiting geometries, thereby creating artificial observed gaps that result in a higher calculated gap complexity. Using second-order secular theory, we compute time-averaged observed gap complexities along a favorable line of sight for a set of hypothetical systems, both with and without an outer giant. We find that these secular interactions can significantly contribute to the observed gap complexity dichotomy in tightly packed multiple-planet systems.

BL Lacertae is a unique blazar for which the X-ray band can cover either the synchrotron or the inverse Compton, or both parts of the broadband spectral energy distribution. In the latter case, when the spectral upturn is located in the X-ray range, it allows contemporaneous study of the low- and high-energy ends of the electron distribution function. In this work, we study spectral and temporal variability using X-ray and optical observations of the blazar performed with the Neil Gehrels Swift Observatory from 2020 to 2023. The large set of observational data reveals intensive flaring activity, accompanied by spectral changes in both spectral branches. We conclude that the low-energy and high-energy ends of the particle distribution function are characterised by similar variability scales. Additionally, the hard X-ray observations of BL Lacertae performed with the Nuclear Spectroscopic Telescope Array (NuSTAR) confirm a concave spectral curvature for some epochs of the blazar activity and reveal that it can be shifted up to energies of as high as 8 keV. The time-resolved spectral analysis allows us to disentangle X-ray spectral variability features of the synchrotron from inverse Compton components. Despite significant variability of both spectral components, we find only small changes in the position of the spectral upturn. The different slopes and shapes of the X-ray spectrum of BL Lacertae demonstrate that the classification of this source is not constant, and BL Lacertae can exhibit features of either high-, intermediate-, or low-energy peaked blazar in different epochs of observation. This also indicates that the spectral upturn for this blazar can be located not only in the X-ray range of 0.3-10 keV, but also at lower or higher energies.

I discuss here the progress made in the last decade on few of the key open problems in GRB physics. These include: (1) the nature of GRB progenitors, and the outliers found to the collapsar/merger scenarios; (2) Jet structures, whose existence became evident following GRB/GW170817; (3) the great progress made in understanding the GRB jet launching mechanisms, enabled by general-relativistic magneto-hydrodynamic (GR-MHD) codes; (4) recent studies of magnetic reconnection as a valid energy dissipation mechanism; (5) the early afterglow, which may be highly affected by a wind bubble, as well as recent indication that in many GRBs, the Lorentz factor is only a few tens, rather than few hundreds. I highlight some recent observational progress, including major breakthrough in detecting TeV photons and the on-going debate about their origin, polarization measurements, as well as the pair annihilation line recently detected in GRB 221009A, and its implications on the prompt emission physics. I point into some open questions that I anticipate would be at the forefront of GRB research in the next decade.

Solving the inverse problem in spiral galaxies, that allows the derivation of the spatial distribution of dust, gas and stars, together with their associated physical properties, directly from panchromatic imaging observations, is one of the main goals of this work. To this end we used radiative transfer models to decode the spatial and spectral distribution of the nearby face-on galaxies M101 and NGC 3938. In both cases we provide excellent fits to the surface-brightness distributions derived from GALEX, SDSS, 2MASS, Spitzer and Herschel imaging observations. Together with previous results from M33, NGC 628, M51 and the Milky Way, we obtain a small statistical sample of modelled nearby galaxies that we analyse in this work. We find that in all cases Milky Way-type dust with Draine-like optical properties provide consistent and successful solutions. We do not find any "submm excess", and no need for modified dust-grain properties. Intrinsic fundamental quantities like star-formation rates (SFR), specific SFR (sSFR), dust opacities and attenuations are derived as a function of position in the galaxy and overall trends are discussed. In the SFR surface density versus stellar mass surface density space we find a structurally resolved relation (SRR) for the morphological components of our galaxies, that is steeper than the main sequence (MS). Exception to this is for NGC 628, where the SRR is parallel to the MS.

Numerical simulations suggest that dark matter halos surrounding galaxies host numerous small subhalos, which might be detectable by the Fermi-LAT. In this work, we revisit the search for gamma-ray subhalo candidates using the latest Fermi-LAT 4FGL-DR4 catalog. The search is performed by fitting the spectral data of unassociated point sources in the catalog through an unbinned maximum likelihood method. We consider two models in the fitting. One is an empirical function provided by the catalog, and another is a DM model in which DM particles within nearby subhalos annihilate into gamma rays and other Standard Model particles. Based on the fitting results, we identify 32 candidates for which the maximum likelihood value of the DM model fit exceeds that of the empirical function fit. The estimated J-factors of these candidates range from $0.2$ to $5.8 \times 10^{20}\,{\rm GeV^{2}\,cm^{-5}}$, the DM particle masses vary from $30$ to $500\,{\rm GeV}$ and 12 of them are within the range of $[30, 80]\,{\rm GeV}$. Candidate 4FGL J2124.2+1531 is an exception with a J-factor of $4.52 \times 10^{21}\,{\rm GeV^{2}\,cm^{-5}}$ and a particle mass of $3108.44\,{\rm GeV}$. Interestingly, the identified candidates do not overlap with those reported in previous works, and we discuss the possible reasons for the discrepancy. At the current stage, we cannot rule out the possibility that these candidates are gamma-ray pulsars, and further confirmation through multi-band observations is required.

We employ an efficient method for identifying gamma-ray sources across the entire sky, leveraging advanced algorithms from Fermi p y, and cleverly utilizing the Galactic diffuse background emission model to partition the entire sky into 72 regions,thereby greatly enhancing the efficiency of discovering new sources throughout the sky through multi-threaded parallel computing. After confirming the reliability of the new method, we applied it for the first time to analyze data from the Fermi Large Area Telescope encompassing approximately 15.41yr of all sky surveys. Through this analysis, we successfully identified 1379 new sources with levels exceeding 4sigma, of which 497 sources exhibited higher significance levels exceeding 5sigma. Subsequently, we performed a systematic analysis of the spatial extension, spectra, and light variation characteristics of these newly identified sources. We identified 21 extended sources and 23 sources exhibiting spectral curvature above 10GeV. Additionally, we identified 44 variable sources above 1GeV.

This paper presents a preliminary investigation into the influence of radial behavior of disk outflow on the structure and dynamics of the broad line region (BLR) in active galactic nuclei (AGNs), with the emphasis on how the mass ejection rate contribute in shaping the broad emission line profiles. Specifically, we analyze how varying the radial efficiency of mass loss from accretion disks, driven by radiative dust-based mechanisms, contribute to the distribution of material in the BLR. By exploring different radial scenarios of disk mass loss behavior, we uncover connections between outflow radial efficiency and emission line profiles, particularly for lowly ionized lines. Our findings reveal that while the observed shape of broad emission lines is partially influenced by the radial behavior of the disk outflow, it ultimately depends more critically on the physical conditions of the clouds and the specific approach adopted to the emissivity for their contribution to the line formation.

The time series of energy and waiting time of magnetar bursts carry important information about the source activity. In this paper, we investigate the memory and dynamical stability of magnetar bursts from four soft gamma repeater (SGR) sources: SGR 1806$-$20, SGR 1900+14, SGR J1935+2154 and SGR J1550$-$5418. Based on the rescaled range analysis, we quantify the memory in magnetar bursts for the first time and find that there exists long-term memory in the time series of both waiting time and energy. We investigate the dynamical stability in the context of randomness and chaos. For all the four SGR samples, we find that the waiting time is not completely random, but the energy of two SGRs is consistent with a total random organization. Furthermore, both waiting time and energy exhibits weak chaos. We also find no significant difference between SGRs and repeating fast radio bursts (FRBs) in the randomness-chaos phase space. The statistical similarity between SGRs and repeating FRBs hints that there may be potential physical connection between these two phenomena.

Accurate measurements of cosmic ray proton flux are crucial for studying the modulation processes of cosmic rays during the solar activity cycle. We present a proton flux measurement method based on ground-based neutron monitor (NM) data and machine learning techniques. After preprocessing the NM data, we use a convolutional neural network (CNN) model to simulate the relationship between the NM observations and proton flux measured by the Alpha Magnetic Spectrometer (AMS-02). We obtain daily proton flux data ranging from 1GV to 100GV for the period from 2011 to 2024, showing that the measured values are in good agreement with the observed ones. In particular, we provide daily proton flux measurements for periods when AMS-02 data are unavailable due to operational reasons. We also perform wavelet analyses on the continuous proton flux data to investigate the relationship between proton flux and solar activity variations, particularly during late 2014 when AMS-02 measurements were missing.

Investigations of trajectories of various objects orbiting the Milky Way (MW) halo with modern precision, achievable in observations by GAIA, requires sophisticated, non-stationary models of the Galactic potential. In this paper we analyze the evolution of the spherical harmonics expansion of MW analogues potential in constrained simulations of the Local Group (LG) from the HESTIA suite. We find that at distances $r>50$~kpc the anisotropic part of the potential demonstrates a significant impact of the environment: ignoring the mass distribution outside the virial radius of the MW results in 20\% errors in the potential quadrupole at these distances. Spherical harmonics vary significantly during the last 6 Gyr. We attribute variations of the potential at $r\ge 30$~kpc to the motions of MW satellites and LG galaxies. We also predict that the anisotropy of the real MW potential should grow with distance in the range $r_\mathrm{vir}<r<500$~kpc, since all realizations of simulated MW-like objects demonstrate such a trend.

The interstellar medium (ISM) is a fundamental component of the Milky Way. Studying its chemical composition and the level of its chemical diversity gives us insight into the evolution of the Milky Way and the role of gas in the Galactic environment. In this paper, we use a novel simulation technique to model the distribution of total hydrogen between gas components, and therefore derive new constraints on the dust depletion and metallicity. We study individual gas components along the lines of sight towards eight bright O/B stars within 1.1 kpc of the Sun using high-resolution HST/STIS absorption spectra (R sim 114 000). We measure the level of dust depletion for these individual components and find components with higher levels of dust depletion compared to Milky Way sightlines in the literature. We find large ranges in the level of dust depletion among components along lines of sight, up to 1.19 dex. Although it is not possible to directly measure the metallicity of individual components due to the saturated and damped Ly-alpha line, we investigate possible metallicity ranges for individual gas components by exploring many different distributions of the total hydrogen gas between components. We select possible combinations of these gas fractions which produce the minimum metallicity difference between components, and for these cases we determine individual metallicities to accuracies that range between sim 0.1 to 0.4 dex. This work shows that full line-of-sight analyses wash out the level of diversity along lines of sight, and that component-by-component studies give a more in-depth understanding of the chemical intricacies of the interstellar medium.

Pulsar timing arrays (PTAs) are essential tools for detecting the stochastic gravitational wave background (SGWB), but their analysis faces significant computational challenges. Traditional methods like Markov-chain Monte Carlo (MCMC) struggle with high-dimensional parameter spaces where noise parameters often dominate, while existing deep learning approaches fail to model the Hellings-Downs (HD) correlation or are validated only on synthetic datasets. We propose a flow-matching-based continuous normalizing flow (CNF) for efficient and accurate PTA parameter estimation. By focusing on the 10 most contributive pulsars from the NANOGrav 15-year dataset, our method achieves posteriors consistent with MCMC, with a Jensen-Shannon divergence below \(10^{-2}\) nat, while reducing sampling time from 50 hours to 4 minutes. Powered by a versatile embedding network and a reweighting loss function, our approach prioritizes the SGWB parameters and scales effectively for future datasets. It enables precise reconstruction of SGWB and opens new avenues for exploring vast observational data and uncovering potential new physics, offering a transformative tool for advancing gravitational wave astronomy.

The detection of a stochastic signal by recent pulsar timing array (PTA) collaborations, including NANOGrav, PPTA, EPTA+InPTA, CPTA and MPTA, has opened a new window to explore gravitational waves (GWs) at nanohertz frequencies. Motivated by the possibility that such a signal could arise from primordial gravitational waves (PGWs), we investigate the implications of tensor non-Gaussianity for the PGW power spectrum. Utilizing PTA data sets, we provide constraints on local-type tensor non-Gaussianity parameter ${F}_{\mathrm{NL}}$. We find $|{F}_{\mathrm{NL}}|\lesssim 7.97$ for a log-normal PGW power spectrum. Our analysis reveals that even moderate tensor non-Gaussianity can lead to significant deviations from standard predictions, thereby offering a novel means to test inflationary scenarios and probe the underlying dynamics of the early Universe. Future multi-band GW observatories, such as LISA, Taiji, and TianQin, will be instrumental in complementing these efforts and further refining our understanding of tensor non-Gaussianity.

Context. The dissolution rate of open clusters (OCs) and integration of their stars into the Milky Way's field population has been previously explored using their age distribution. With the advent of the Gaia mission, we have an exceptional opportunity to revisit and enhance these studies with ages and masses from high quality data. Aims. To build a comprehensive Gaia-based OC mass catalogue which, combined with the age distribution, allows a deeper investigation of the disruption experienced by OCs within the solar neighbourhood. Methods. Masses were determined by comparing luminosity distributions to theoretical luminosity functions. The limiting and core radii of the clusters were obtained by fitting the King function to their observed density profiles. We examined the disruption process through simulations of the build-up and mass evolution of a population of OCs which were compared to the observed mass and age distributions. Results. Our analysis yielded an OC mass distribution with a peak at $log(M)$ = 2.7 dex ($\sim 500 M_{\odot}$), as well as radii for 1724 OCs. Our simulations showed that using a power-law Initial Cluster Mass Function (ICMF) no parameters were able to reproduce the observed mass distribution. Moreover, we find that a skew log-normal ICMF provides a good match to the observations and that the disruption time of a $10^4 M{_\odot}$ OC is $t_4^{tot} = 2.9 \pm 0.4$ Gyr. Conclusions. Our results indicate that the OC disruption time $t_4^{tot}$ is about twice longer than previous estimates based solely on OC age distributions. We find that the shape of the ICMF for bound OCs differs from that of embedded clusters, which could imply a low typical star formation efficiency of $\leq 20\%$ in OCs. Our results also suggest a lower limit of $\sim 60 M{_\odot}$ for bound OCs in the solar neighbourhood.

Five dimensional (5D) uniform inflation describes a de Sitter (or approximate) solution of 5D Einstein equations, with cosmological constant and a 5D Planck scale $M_* \sim 10^9$ GeV. During the inflationary period all dimensions (compact and non-compact) expand exponentially in terms of the 5D proper time. This set-up requires about 40 $e$-folds to expand the fifth dimension from the fundamental length to the micron size. At the end of 5D inflation (or at any given moment during the inflationary phase) one can interpret the solution in terms of 4D fields using 4D Planck units from the relation $M_p^2 = 2 \pi R M_*^3$, which amounts going to the 4D Einstein frame. This implies that if the compactification radius $R$ expands $N$ $e$-folds, then the 3D space would expand $3N/2$ $e$-folds as a result of a uniform 5D inflation. We reexamine the primordial power spectrum predicted by this model and show that it is consistent with Planck's measurements of the comic microwave background. The best-fit to Planck data corresponds to $R \sim 10~\mu$m. A departure of the angular power spectrum predicted by 4D cosmology is visible at multipole moment $\ell \sim 7$.

We apply data-motivated priors on the peak absolute magnitude of Type Ia supernovae ($M$), and on the sound horizon at the drag epoch ($r_d$), to study their impact on the Hubble tension, when compared to the Planck estimated value of the Hubble constant. We use the data from Pantheon$+$, cosmic chronometers, and the latest DESI BAO results for this purpose. We reaffirm the fact that there is a degeneracy between $M$ and $r_d$, and modifying the $r_d$ values to reconcile the Hubble tension also requires a change in the peak absolute magnitude $M$. For certain $M$ and $r_d$ priors, the tension is found to reduce to as low as (1.2-2) $\sigma$.

Dark matter is believed to account for a significant portion of the mass in the universe, exerting a critical influence on the formation and evolution of cosmic structures. This research delves into the processes of annihilation and decay of dark matter particles, which generate observable signals that deepen our comprehension of their characteristics and behaviors. Furthermore, the study explores the potential role of primordial black holes, with a focus on the emissions of Hawking radiation that could offer valuable insights into their distribution and size range. A key aspect of this investigation revolves around the 21 cm signal, a vital tool for scrutinizing the effects of dark matter particles and primordial black hole phenomena on the intergalactic medium. The upcoming Hongmeng mission, featuring a lunar orbital interferometer array, is poised to revolutionize our ability to observe the 21 cm signal. By conducting measurements devoid of atmospheric disturbances, the mission will significantly boost sensitivity to subtle signals associated with dark matter particle annihilation, decay, and primordial black hole emissions. This study assesses the expected performance of the Hongmeng mission in detecting these telltale signs and aims to unveil fresh insights into the nature and interactions of dark matter particles and primordial black hole emissions through a meticulous analysis of the global 21 cm spectrum. The mission holds immense promise for reshaping our understanding of the universe's concealed components.

According to the Schrödinger-Poisson (SP) equations, fuzzy dark matter (FDM) can form a stable equilibrium configuration, the so-called FDM soliton. The SP system can also determine the evolution of FDM solitons, such as head-on collision. In this paper, we first propose a new adimensional unit of length, time and mass. And then, we simulate the adimensional SP system with $\mathtt{PyUltraLight}$ to study the GWs from post-collision of FDM solitons when the linearized theory is valid and the GW back reaction on the evolution of FDM solitons is ignored. Finally, we find that the GWs from post-collisions have a frequency of (few ten-years)$^{-1}$ or (few years)$^{-1}$ when FDM mass is $m=10^{-18}\rm{eV}/c^2$ or $m=10^{-17}\rm{eV}/c^2$. Therefore, future detection of such GWs will constrain the property of FDM particle and solitons.

In recent years, the jet formation region in active galaxies has been imaged through mm-VLBI in few ideal targets, first and foremost M87. An important leap forward for understanding jet launching could be made by identifying a larger number of suitable objects, characterized by different accretion modes and jet powers. In this article, we present 1 cm and 7 mm VLBI data of a sample of 16 poorly explored radio galaxies, comprising both High-Excitation (HEG) and Low-Excitation Galaxies (LEG) and spanning a large range in radio power. The combination of the sources vicinity (z<0.1) with a large black hole mass ($\log{M_{\rm BH}}$>8.5) results in a high spatial resolution in units of Schwarzschild radii ($<10^3-10^4$ $R_{\rm S}$), necessary for probing the region where the jet is initially accelerated and collimated. We aim at identifying the best candidates for follow-up observations with current and future VLBI facilities. The observations were performed with the High Sensitivity Array, including Effelsberg and the phased-VLA, which has allowed us to characterize the sub-parsec properties of these faint jets and to estimate their core brightness temperature and orientation. The number of sources imaged on scales $\lesssim 10^3$ $R_{\rm S}$ is more than doubled by our study. All targets were detected at both frequencies, and several present two-sided jet structures. Several LEG jets show hints of limb-brightening. The core brightness temperatures are generally below the equipartition value, indicating that equipartition has not yet been reached and/or that the emission is de-boosted. Among LEG, we identify 3C31, 3C66B, and 3C465 as the most promising, combining a relatively high flux density (>50 mJy) with superb spatial resolution (<500 $R_{\rm S}$) at 7 mm. The powerful HEG 3C452 is interesting as well due to its highly symmetric, two-sided jet base.

Aims. In this paper, we searched for multi-wavelength (X-ray, optical and radio) counterparts to the unassociated gamma-ray sources (UGS) of the Fermi 4FGL-DR4 catalog. The main goal is to identify new blazars and/or new active galactic nuclei (AGNs) emitting at GeV energies [like (Narrow Line) Seyfert-1 and radio galaxies]. Methods. We focus on sky regions observed by the Swift satellite that overlap with the reported positions of the UGSs. Since our primary interest lies in extra-galactic sources, we focus on UGSs located outside the Galactic plane (|b| > 10$^{\circ}$). Due to the large number of sources (about 1800 UGS), we developed a pipeline to automatise the search for counterparts and significantly reduce the computational time for the analysis. Our association process begins by identifying potential X-ray counterparts for each UGS; if one is found, we further look for corresponding radio and optical counterparts in the X-ray counterpart error box, thus minimizing ambiguities. Results. Out of the 1284 UGSs in the 4FGL-DR4 catalog, 714 were observed at least once by Swift/XRT. We detected, with a significance of $\geq$ 3$\sigma$, at least one X-ray source within the Fermi error box for 274 of these $\gamma$-ray emitters. Among these, 193 UGSs have a single potential X-ray counterpart (referred to as UGS1), while 81 have multiple potential X-ray counterparts within the Fermi error box (referred to as UGS2). Of the UGS2, 54 have two X-ray counterparts, 11 have three, and the remaining 16 have more than three. Each UGS1 has an optical counterpart, and 113 also could be associated to a radio counterpart. We performed a comparison of the possible counterpart properties with those of the $\gamma$-ray emitters identified by Fermi, with the aim to assess the goodness of our associations.

The recent detection by LHAASO up to 18 TeV of the gamma ray burst GRB 221009A at redshift $z = 0.151$ challenges standard physics because of the strong absorption due to the extragalactic background light (EBL) for photons with energies above 10 TeV. Emission models partially avoiding EBL absorption proposed to explain such an event are unsatisfactory since they require peculiar and contrived assumptions. By introducing in magnetized media the interaction of photons with axion-like particles (ALPs) - which are a generic prediction of most theories extending the standard model of particle physics towards a more satisfying theory - the detection of GRB 221009A can be naturally explained, thereby providing a strong hint at ALP existence.

Earth-like planets in the circumstellar habitable zone (HZ) may have dramatically different climate outcomes depending on their spin-orbit parameters, altering their habitability for life as we know it. We present a suite of 93 ROCKE-3D general circulation models (GCMs) for planets with the same surface conditions and average annual insolation as Earth, but with a wide range of rotation periods, obliquities, orbital eccentricities, and longitudes of periastra. Our habitability metric $f_\mathrm{HZ}$ is calculated based on the temperature and precipitation in each model across grid cells over land. Latin Hypercube Sampling (LHS) aids in sampling all 4 of the spin-orbit parameters with a computationally feasible number of GCM runs. Statistical emulation then allows us to model $f_\mathrm{HZ}$ as a smooth function with built-in estimates of statistical uncertainty. We fit our emulator to an initial set of 46 training runs, then test with an additional 46 runs at different spin-orbit values. Our emulator predicts the directly GCM-modeled habitability values for the test runs at the appropriate level of accuracy and precision. For orbital eccentricities up to 0.225, rotation period remains the primary driver of the fraction of land that remains above freezing and with precipitation above a threshold value. For rotation periods greater than $\sim 20$ days, habitability drops significantly (from $\sim 70$% to $\sim 20$%), driven primarily by cooler land temperatures. Obliquity is a significant secondary factor for rotation periods less than $\sim 20$ Earth days, with a factor of two impact on habitability that is maximized at intermediate obliquity.

Among over 1000 known fast radio bursts (FRBs), only three sources - FRB 121102 (R1), FRB 190520 (R2) and FRB 201124 (R3) - have been linked to persistent radio sources (PRS). The observed quasi-steady emission is consistent with synchrotron radiation from a composite of magnetar wind nebula (MWN) and supernova (SN) ejecta. We compute the synchrotron flux by solving kinetic equations for energized electrons, considering electromagnetic cascades of electron-positron pairs interacting with nebular photons. For rotation-powered model, a young neutron star (NS) with age $t_{\rm age}\approx 20\,{\rm yr}$, dipolar magnetic field $B_{\rm dip}\approx (3-5)\times10^{12}\,{\rm G}$ and spin period $P_i\approx 1.5-3\,{\rm ms}$ in an ultra-stripped SN progenitor can account for emissions from R1 and R2. In contrast, R3 requires $t_{\rm age}\approx 10\,{\rm yr}$, $B_{\rm dip}\approx 5.5\times10^{13}\,{\rm G}$ and $P_i\approx 10\,{\rm ms}$ in a conventional core-collapse SN progenitor. For magnetar-flare-powered model, NS aged $t_{\rm age} \approx 25\,/40\,{\rm yr}$ in a USSN progenitor and $t_{\rm age} \approx 12.5\,{\rm yr}$ in a CCSN progenitor explains the observed flux for R1/R2 and R3, respectively. Finally, we constrain the minimum NS age $t_{\rm age,min} \sim 1-3\,{\rm yr}$ from the near-source plasma contribution to observed DM, and $t_{\rm age,min} \sim 6.5-10\,{\rm yr}$ based on the absence of radio signal attenuation.

We present the Active Galactic Nuclei (AGN) catalog from the fourth data release (HDR4) of the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). HETDEX is an untargeted spectroscopic survey. HDR4 contains 345,874 Integral Field Unit (IFU) observations from January 2017 to August 2023 covering an effective area of 62.9 deg2. With no imaging pre-selection, our spectroscopic confirmed AGN sample includes low-luminosity AGN, narrow-line AGN, and/or red AGN down to g~25. This catalog has 15,940 AGN across the redshifts of z=0.1~4.6, giving a raw AGN number density of 253.4 deg-2. Among them, 10,499 (66%) have redshifts either confirmed by line pairs or matched to the Sloan Digital Sky Survey Quasar Catalog. For the remaining 5,441 AGN, 2,083 are single broad line AGN candidates, while the remaining 3,358 are single intermediate broad line (full width at half maximum, FWHM ~ 1200 km s-1) AGN candidates. A total of 4,060 (39%) of the 10,499 redshift-confirmed AGN have emission-line regions $3\sigma$ more extended than the image quality which could be strong outflows blowing into the outskirts of the host galaxies or ionized intergalactic medium.

Existing asteroseismic rotational measurements assume that stars rotate around a single axis. However, tidal torques from misaligned companions, or their possible engulfment, may bring the rotational axis of a star's envelope out of alignment with its core, breaking azimuthal symmetry. I derive perturbative expressions for asteroseismic signatures of such hitherto unexamined rotational configurations, under the ``shellular approximation'' of constant rotation rates on radially stratified mass shells. In the aligned case, the distribution of power between multiplet components is determined by the inclination of the rotational axis; radial differential misalignment causes this to vary from multiplet to multiplet. I examine in particular detail the phenomenology of gravitoacoustic mixed modes as seen in evolved sub- and red giants, where near-resonance avoided crossings may break geometrical degeneracies. Upon applying the revised asteroseismic observational methodology that results from this theoretical discussion to revisit Kepler-56 -- a red giant with a misaligned planetary system -- I find that its core and envelope rotate around different rotational axes. While the rotational axis of its core is indeed misaligned from the orbit normal of its transiting planets (consistently with earlier studies), its envelope's rotational axis is close to lying in the sky plane, and may well be aligned with them. More detailed asteroseismic modelling, and spectroscopic follow-up, will be required to fully elucidate the full spin-orbit geometry of the Kepler-56 system, and potentially discriminate between hypotheses for how it formed.

In this study, we explore how a non-minimal coupling between dark matter and gravity can affect the behavior of dark matter in galaxy clusters. We have considered the case of a disformal coupling, which leads to a modification of the Poisson equation. Building on an earlier work, we expand the analysis considering all possible disformal coupling scenarios and employing various dark matter density profiles. In doing so, we aim to constrain the key parameter in our model, the characteristic coupling length. To achieve this, we analyze data from a combination of strong and weak lensing using three statistical approaches: a single cluster fitting procedure, a joint analysis, and one with stacked profiles. Our findings show that the coupling length is typically very small, thus being fully consistent with general relativity, although with an upper limit at $1\sigma$ which is of the order of $100$ kpc.

The extremely luminous infrared galaxy (ELIRG), WISE J090924.01+000211.1 (hereafter; WISE J0909+0002, $z=1.87$) is an extraordinary object with a quasar aspect. This study performs monitoring observations of WISE J0909+0002 with the 105 cm Murikabushi telescope, Okayama and Akeno 50 cm telescopes/MITSuME ($g'$, $R_{\rm c}$, and $I_{\rm c}$ bands), and the SaCRA 55 cm telescope/MuSaSHI ($r$, $i$, and $z$ bands). We obtain the following results by combining the UV/optical light curves of the CRTS, Pan-STARRS, and ZTF archive data, and our observational data: (1) the light curves of WISE J0909+0002 present quasi-periodic (sinusoidal) oscillations with the rest-frame period of $\sim$ 660$-$689 day; (2) the structure functions of WISE J0909+0002 do not show a damped random walk (DRW) trend; (3) the mock DRW light curves present periodic-like trend on rare occasions in 10000 simulations; (4) the relativistic boost scenario is favored, since the relation between variability amplitude and power-law slope ratio is consistent with the theoretical prediction of this scenario, and a substantial parameter space exists between the inclination angles and the black hole mass; (5) the circumbinary disk model is difficult to explain the spectral energy distribution of our target; (6) the significant radio flux density of WISE J0909+0002 is not detected from the VLA FIRST Survey, thus the radio jet precession scenario is ruled out. From our results, the Doppler boost scenario is likely as a cause of the periodic variability, consequently the quasi-periodic oscillations in WISE J0909+0002 is possibly interpreted by a supermassive blackhole binary. Additional observations to investigate the continuity of the periodic trend would bring new insights into mechanisms of the quasi-periodic oscillations and/or ELIRGs.

Significant improvements in our understanding of nuclear $\gamma$-ray line production and instrument performance allow us to better characterize the continuum emission from electrons at energies $\gtrsim$ 300 keV during solar flares. We represent this emission by the sum of a power-law extension of hard X-rays (PL) and a power law times an exponential function (PLexp). We fit the $\gamma$-ray spectra in 25 large flares observed by SMM, RHESSI, and Fermi with this summed continuum along with calculated spectra of all known nuclear components. The PL, PLexp, and nuclear components are separated spectroscopically. A distinct origin of the PLexp is suggested by significant differences between its time histories and those of the PL and nuclear components. RHESSI imaging/spectroscopy of the 2005 January 20 flare, reveals that the PL and nuclear components come from the footpoints while the PLexp component comes from the corona. While the index and flux of the anisotropic PL component are strongly dependent on the flares' heliocentric angle, the PLexp parameters show no such dependency and are consistent with a component that is isotropic. The PLexp spectrum is flat at low energies and rolls over at a few MeV. Such a shape can be produced by inverse Compton scattering of soft X-rays by 10--20 MeV electrons and by thin-target bremsstrahlung from electrons with a spectrum that peaks between 3 -- 5 MeV, or by a combination of the two processes. These electrons can produce radiation detectable at other wavelengths.

We investigate the formation of primordial black holes (PBHs) in an upward step inflationary model, where nonlinearities between curvature perturbations and field fluctuations introduce a cutoff, deviating from the Gaussian case. This necessitates a reevaluation of PBH formation, as $\mathcal{R}$ is not the optimal variable for estimating abundance. Using the extended Press-Schechter formalism, we show that non-Gaussianity modifies both the curvature perturbation profile $\mathcal{R}(r)$ and the integration path in probability space, significantly impacting PBH abundance. Our results reveal that the abundance initially increases with the parameter $h$, which characterizes the relaxation stage after the step. However, beyond a critical value ($h \simeq 5.9$), it sharply declines before rising again. Furthermore, we demonstrate that non-Gaussianity introduces uncertainties in indirect PBH observations via gravitational waves. Notably, we present an example where a positive $f_{\rm NL}$ does not necessarily enhance PBH production, contrary to conventional expectations. Finally, by accounting for non-perturbative effects, we resolve the overproduction of PBHs suggested by pulsar timing array (PTA) data, underscoring the critical importance of incorporating non-Gaussianity in future studies.

We test the standardizability of a homogeneous sample of 41 lower-redshift ($0.00415\leq z \leq 0.474$) active galactic nuclei (AGNs) reverberation-mapped (RM) using the broad H$\alpha$ and H$\beta$ emission lines. We find that these sources can be standardized using four radius$-$luminosity ($R-L$) relations incorporating H$\alpha$ and H$\beta$ time delays and monochromatic and broad H$\alpha$ luminosities. Although the $R-L$ relation parameters are well constrained and independent of the six cosmological models considered, the resulting cosmological constraints are weak. The measured $R-L$ relations exhibit slightly steeper slopes than predicted by a simple photoionization model and steeper than those from previous higher-redshift H$\beta$ analyses based on larger datasets. These differences likely reflect the absence of high-accreting sources in our smaller, lower-redshift sample, which primarily comprises lower-accreting AGNs. The inferred cosmological parameters are consistent within 2$\sigma$ (or better) with those from better-established cosmological probes. This contrasts with our earlier findings using a larger, heterogeneous sample of 118 H$\beta$ AGNs, which yielded cosmological constraints differing by $\gtrsim 2\sigma$ from better-established cosmological probes. Our analysis demonstrates that sample homogeneity$-$specifically, the use of a consistent time-lag determination method$-$is crucial for developing RM AGNs as a cosmological probe.

L328 core has three sub-cores S1, S2, and S3, among which the sub-core S2 contains L328-IRS, a Very Low Luminosity Object (VeLLO), which shows a CO bipolar outflow. Earlier investigations of L328 mapped cloud/envelope (parsec-scale) magnetic fields (B-fields). In this work, we used JCMT/POL-2 submillimeter (sub-mm) polarisation measurements at 850 $\mu$m to map core-scale B-fields in L328. The B-fields were found to be ordered and well-connected from cloud to core-scales, i.e., from parsec- to sub-parsec-scale. The connection in B-field geometry is shown using $Planck$ dust polarisation maps to trace large-scale B-fields, optical and near-infrared (NIR) polarisation observations to trace B-fields in the cloud and envelope, and 850 $\mu$m polarisation mapping core-scale field geometry. The core-scale B-field strength, estimated using the modified Davis-Chandrasekhar-Fermi relation, was found to be 50.5 $\pm$ 9.8 $\mu$G, which is $\sim$2.5 times higher than the envelope B-field strength found in previous studies. This indicates that B-fields are getting stronger on smaller (sub-parsec) scales. The mass-to-flux ratio of 1.1 $\pm$ 0.2 suggests that the core is magnetically transcritical. The energy budget in the L328 core was also estimated, revealing that the gravitational, magnetic, and non-thermal kinetic energies were comparable with each other, while thermal energy was significantly lower.

We investigate the (axial) quasinormal modes of black holes embedded in generic matter profiles. Our results reveal that the axial QNMs experience a redshift when the black hole is surrounded by various matter environments, proportional to the compactness of the matter halo. Our calculations demonstrate that for static black holes embedded in galactic matter distributions, there exists a universal relation between the matter environment and the redshifted vacuum quasinormal modes. In particular, for dilute environments the leading order effect is a redshift $1+U$ of frequencies and damping times, with $U \sim -{\cal C}$ the Newtonian potential of the environment at its center, which scales with its compactness ${\cal C}$.

First stars powered by dark matter (DM) heating instead of fusion can appear in the early Universe from theories of new physics. These dark stars (DSs) can be significantly larger and cooler than early Population III stars, and could seed supermassive black holes (SMBHs). We show that neutrino emission from supermassive DSs provides a novel window into probing SMBH progenitors. We estimate first DS constraints using data from Super-Kamiokande and IceCube neutrino experiments, and consistent with James Webb Space Telescope observations. Upcoming neutrino telescopes offer distinct opportunities to further explore DS properties.

It is known that single-field freeze-in dark matter barely leaves footprints in dark matter direct detection and collider experiments. This situation can be altered in two-field context. In this work we propose a two-field freeze-in dark matter model through Higgs portal. The observed dark matter relic abundance is obtained by a decay of scalar mediator thermalized in the early Universe. While there is a lack of direct dark matter signals, the scalar mediator is in the reach of HL-LHC either through vector boson fusion or Mono-Z channel. Within allowed scalar mass window of 10-50 GeV, we use improved cuts to derive both $2\sigma$ exclusion and $5\sigma$ discovery limits, depending on the value of Higgs portal coupling. If verified, this scalar mediator signal allows us to infer the freeze-in dark matter.

The formation of composite solitons produced by scalar fields without thermal phase transitions in the early Universe is considered. We present numerical simulations of the formation and evolution of soliton structures at the post-inflationary stage. The realistic initial conditions are obtained through the simulation of multiple quantum fluctuations during the inflation epoch. The initial field distributions allow to form local soliton clusters in the early Universe without the need for the thermal production of a soliton network throughout the Universe. We find that in three-dimensional space, the nontrivial composite field structures are formed in the form of <<soliton foam>>, consisting of closed domain walls, domain walls bounded by cosmic strings, and scalar field radiation. The possible cosmological implications of the soliton foam are discussed.

The first and second laws of thermodynamics should lead to a consistent scenario for discussing the cosmological constant problem. In the present study, to establish such a thermodynamic scenario, cosmological equations in a flat Friedmann-Lemaître-Robertson-Walker universe were derived from the first law, using an arbitrary entropy $S_{H}$ on a cosmological horizon. Then, the cosmological equations were formulated based on a general formulation that includes two extra driving terms, $f_{\Lambda}(t)$ and $h_{\textrm{B}}(t)$, which are usually used for, e.g., time-varying $\Lambda (t)$ cosmology and bulk viscous cosmology, respectively. In addition, thermodynamic constraints on the two terms are examined using the second law of thermodynamics, extending a previous analysis [Phys. Rev. D 99, 043523 (2019) (arXiv:1810.11138)]. It is found that a deviation $S_{\Delta}$ of $S_{H}$ from the Bekenstein-Hawking entropy plays important roles in the two terms. The second law should constrain the upper limits of $f_{\Lambda}(t)$ and $h_{\textrm{B}}(t)$ in our late Universe. The orders of the two terms are likely consistent with the order of the cosmological constant $\Lambda_{\textrm{obs}}$ measured by observations. In particular, when the deviation $S_{\Delta}$ is close to zero, $h_{\textrm{B}}(t)$ and $f_{\Lambda}(t)$ should reduce to zero and a constant value (consistent with the order of $\Lambda_{\textrm{obs}}$), respectively, as if a consistent and viable scenario could be obtained from thermodynamics.

The $3+1$ formalism provides a structured approach to analyzing spacetime by separating it into spatial and temporal components. When applied to the Robertson-Walker metric, it simplifies the analysis of cosmological evolution by dividing the Einstein field equations into constraint and evolution equations. It introduces the lapse function $N$ and the shift vector $N^i$, which control how time and spatial coordinates evolve between hypersurfaces. In standard model cosmology, $N = 1$ and $N^i = 0$ for the Robertson-Walker metric. However, the $N$ becomes a function of time when we apply the metric to the minimally extended varying speed of light model. This approach allows for a more direct examination of the evolution of spatial geometry and offers flexibility in handling scenarios where the lapse function and shift vector vary. In this manuscript, we derive the model's $N$ and $N^i$, along with the constraint and evolution equations, and demonstrate their consistency with the existing Einstein equations. We have shown in a previous paper that the possibility of changes in the speed of light in the Robertson-Walker metric is due to cosmological time dilation. Through the $3+1$ formalism, we can make the physical significance more explicit and demonstrate that it can be interpreted as the lapse function. From this, we show that the minimally extended varying speed of light model is consistent.

High-resolution X-ray spectroscopy is an essential tool in X-ray astronomy, enabling detailed studies of celestial objects and their physical and chemical properties. However, comprehensive mapping of high-resolution X-ray spectra for even simple interstellar and circumstellar molecules is still lacking. In this study, we conducted systematic quantum chemical simulations to predict the C1s X-ray absorption spectra of CN$^+$, CN, and CN$^-$. Our findings provide valuable references for both X-ray astronomy and laboratory studies. We assigned the first electronic peak of CN$^+$ and CN to C1s $\rightarrow \sigma^*$ transitions, while the peak for CN$^-$ corresponds to a C1s $\rightarrow \pi^*$ transition. We further calculated the vibronic fine structures for these transitions using the quantum wavepacket method based on multiconfigurational-level, anharmonic potential energy curves, revealing distinct energy positions for the 0-0 absorptions at 280.7 eV, 279.6 eV, and 285.8 eV. Each vibronic profile features a prominent 0-0 peak, showing overall similarity but differing intensity ratios of the 0-0 and 0-1 peaks. Notably, introducing a C1s core hole leads to shortened C-N bond lengths and increased vibrational frequencies across all species. These findings enhance our understanding of the electronic structures and X-ray spectra of carbon-nitrogen species, emphasizing the influence of charge state on X-ray absorptions.

Recently proposed $SL(2,\mathbb{Z})$ invariant $\alpha$-attractor models have plateau potentials with respect to the inflaton and axion fields. The slope of the potential in the inflaton direction is exponentially suppressed at large values of the inflaton field, but the slope of the potential in the axion direction is double-exponentially suppressed. Therefore, the axion field remains nearly massless and practically does not change during inflation. The inflationary trajectory in such models is stable with respect to quantum fluctuations of the axion field. We show that isocurvature perturbations do not feed into the curvature perturbations during inflation, and argue that such transfer may remain inefficient at the post-inflationary stage.

We explore a concrete realization of a Nelson-Barr model addressing the strong CP problem with suppressed unfavorable corrections. This model has a scalar field that spontaneously breaks discrete symmetry, and its phase component can naturally be relatively light, which we call the Nelson-Barr axion. It has both a tree-level potential and the QCD instanton-induced potential like the QCD axion, each minimizing at the CP-conserving point. While one potential leads to domain wall formation, the other works as a potential bias. This model provides a natural setup for the collapse of the axion domain walls by a potential bias without spoiling a solution to the strong CP problem. We discuss the cosmological implications of domain wall collapses, including dark matter production and gravitational wave emission.

Hořava-Lifshitz gravity (to be precise, its projectable version) is recognized as a renormalizable, unitary, and asymptotically free quantum field theory of gravity. Notably, one of its cosmological predictions is that it can produce scale-invariant primordial density fluctuations and primordial gravitational waves without relying on inflation. In this paper, we investigate the quantum nature of the primordial gravitational waves generated in Hořava-Lifshitz gravity. It has been suggested that, for some inflationary models, the non-classicality of primordial gravitational waves in the squeezed coherent quantum state can be detected using the Hanbury Brown - Twiss (HBT) interferometry. We show that in Hořava-Lifshitz gravity, scale-invariant primordial gravitational waves can be generated during both the radiation-dominated and matter-dominated eras of the Universe. Moreover, the frequency range of their quantum signatures is shown to extend beyond that of inflationary models.

We study the nuclear compositions and neutrino reaction rates in the central region of the core-collapse supernova, assuming the existence of dineutrons ($^2n$) and tetraneutrons ($^4n$). At 100 ms after core bounce, $^2n$ and $^4n$ are more abundant than deuterons within radii of approximately 100 km and 50 km, respectively. Compared to the model ignoring the existence of $^2n$ and $^4n$, the mass fraction of neutrons up to a radius of 100 km reduces. Hence, the neutrino absorption and antineutrino emission rates decrease by approximately 40%-50%. Conversely, those of protons, deuterons, and $^4He$ increase, leading to the increase in the neutrino emission and antineutrino absorption rates by approximately eight times within a radius of 100 km.

We study solutions of the Wheeler DeWitt (WdW) equation in order to recover standard results of cosmological perturbation theory. In mini-superspace, we introduce a dimensionless gravitational coupling $\alpha$ that is typically very small and functions like $\hbar$ in a WKB expansion. We seek solutions of the form $\Psi = e^{iS/\alpha} \psi$ that are the closest quantum analog of a given classical background spacetime. The function $S$ satisfies the Hamilton-Jacobi equation, while $\psi$ obeys a Schrödinger-like equation and has a clear probabilistic interpretation. By using the semiclassical limit we express the relation between $\psi$ and the wavefunction of the universe in perturbation theory, $\psi_P$. We apply our formalism to two main examples. The first is a scalar field with a purely exponential potential, of which particularly simple, scaling solutions are known. The other is a slow-roll scenario expanded in the vicinity of the origin in field space. We discuss possible deviations from the classical background trajectory as well as the higher ``time" derivative terms that are present in the WdW equation but not in the perturbative approach. We clarify the conditional probability content of the wavefunctions and how this is related with the standard gauge fixing procedure in perturbation theory.

One of the simplest extensions of the Standard Model is the Higgs portal extension involving a dark Higgs. Dark sectors that include dark matter candidates, WIMPs, axions, and dark photons, can naturally have this type of interaction, where the dark Higgs is charged under some symmetry, which may or may not be spontaneous broken by the vacuum expectation value. In this paper, using lattice simulations, I show that if the reheating temperature of the Universe is sufficiently high, topological defects such as domain walls and cosmic strings associated with these symmetries are naturally formed even if the symmetries are never restored due to negative thermal mass squareds. This occurs due to the early Universe's non-adiabatic oscillation of the Higgs around the onset of oscillation, which overshoots the origin, and tachyonic instability that enhances fluctuations. The gravitational waves generated by these topological defects may be very significant due to the energetic processes induced by matter effects in the hot and dense Universe irrelevant to the typical energy scale of the dark sector in the vacuum or whether the symmetry is broken in the vacuum. Alongside earlier studies such as usual phase transition, melting domain walls and melting cosmic strings scenarios that assume a symmetric phase in the early Universe, the Higgs portal models naturally predict local overdensities from topological defects, which may induce miniclusters and primordial black holes, as well as the gravitational this http URL phenomena provide novel opportunities to search for such scenarios. I also perform various numerical simulations for the relevant topic including melting domain walls and cosmic strings with inflationary and Gaussian fluctuations, for comparison--which have not been performed previously.