Rommulus Francis Lewis, Hetansh Shah, Amruth Alfred
Over the past few years, Astrophysics has experienced an unprecedented increase in research output, as is evident from the year-over-year increase in the number of research papers put onto the arXiv. As a result, keeping up with progress happening outside our respective sub-fields can be exhausting. While it is impossible to be informed on every single aspect of every sub-field, this paper aims to be the next best thing. We present a summary of statistics for every paper uploaded onto the Astrophysics arXiv over the past year - 2025. We analyse a host of metadata ranging from simple metrics like the number of pages and the most used keywords, as well as deeper, more interesting statistics like the distribution of journals to which papers are submitted, the most used telescopes, the most studied astrophysical objects including GW, GRB, FRB events, exoplanets and much more. We also indexed the authors' affiliations to put into context the global distribution of research and collaboration. Combining this data with the citation information of each paper allows us to understand how influential different papers have been on the progress of the field this year. Overall, these statistics highlight the general current state of the field, the hot topics people are working on and the different research communities across the globe and how they function. We also delve into the costs involved in publications and what it means for the community. We hope that this is helpful for both students and professionals alike to adapt their current trajectories to better benefit the field.
Low-rate Denial-of-Service (LDoS) attacks exploit periodic traffic pulses to trigger congestion while maintaining a low average rate, making them highly stealthy and difficult to distinguish from legitimate bursty traffic using threshold-based or simple statistical detectors. To address this challenge, this paper proposes DELP-Net, an end-to-end Differentiable Entropy Layer Pyramid Network for window-level online LDoS detection directly from raw traffic. DELP-Net combines a multi-scale one-dimensional convolutional pyramid with a differentiable Rényi-entropy-driven attention mechanism to capture distributional regularity and weak repetitive patterns characteristic of LDoS traffic. In addition, an entropy-conditioned temporal convolutional network is employed to model cross-window periodic dependencies in a lightweight manner, together with an entropy-regularized hybrid loss to enhance robustness under complex background traffic. Experiments on the low-rate DoS dataset show that DELP-Net achieves an average F1 score of 0.9877 across six LDoS attack types, with a detection rate of 98.69% and a false-positive rate of 1.15%, demonstrating its effectiveness and suitability for practical online intrusion detection deployments.
We studied the rotational velocities of a sample of blue straggler stars (BSSs) and reference stars belonging to the Galactic globular cluster NGC 1851 using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT. After field decontamination based on radial velocities and proper motions, the final sample of member stars was composed of 15 BSSs and 45 reference stars populating the red giant and horizontal branches of the cluster. In agreement with previous findings, the rotation of the reference stars is negligible in general (lower than 15 km s−1). In contrast, the rotational velocity is high (up to ~150 km s−1) for a subsample of BSSs. We found 4 fast-rotating BSSs (defined as stars that spin faster than 40 km s−1), which corresponds to a percentage of 27 ± 14%. This result delineates a monotonically decreasing trend (instead of a step function) between the percentage of fast-spinning BSSs and the central concentration and density of the host cluster. This supports a scenario in which recent BSS formation preferentially occurs in low-density environments from the evolution of binary systems.
The expansion of the Universe is the basis of modern cosmology. This chapter outlines the theory behind the expansion of the universe, including the cosmological principle, distances, velocities, and accelerations. We provide basic derivations of the key equations and highlight some interesting features, such as superluminal expansion, how pressure increases gravitational attraction, the subtleties of conservation of energy in the expanding universe, and the existence of cosmological horizons.
The orbits of planetary systems can be deformed from their initial configurations due to close encounters with larger astrophysical bodies. Typical candidates for close encounters are stars and binaries. We explore the prospect that if there is a sizeable population of primordial black holes (PBH) in our galaxy, then these may also impact the orbits of exoplanets. Specifically, in a simplified setting, we study numerically how many planetary systems might have a close encounter with a PBH, and analyze the potential changes to the orbital parameters of systems that undergo PBH flybys.
Zi-Li Yue, Cheng-Jian Xiao, H. García-Tecocoatzi
et al.
Abstract Inspired by the abundant structure near the threshold of the $$D^{(*)}K^{(*)}/\bar{D}^{(*)}K^{(*)},$$ D ( ∗ ) K ( ∗ ) / D ¯ ( ∗ ) K ( ∗ ) , we estimate the strong decay properties of the $$T_{c\bar{s}1}^{f/a}$$ T c s ¯ 1 f / a and $$T_{\bar{c}\bar{s}1}^{f/a}$$ T c ¯ s ¯ 1 f / a with $$I(J^{P})=0/1(1^{+})$$ I ( J P ) = 0 / 1 ( 1 + ) in $$DK^{*}$$ D K ∗ and $$\bar{D}K^{*}$$ D ¯ K ∗ molecular scenarios in the present paper. By employing the effective Lagrangian approach, the widths of the processes $$T_{c\bar{s}1}^{f}\rightarrow D^{*}K, D_{s}^{*}\eta , DK\pi ,$$ T c s ¯ 1 f → D ∗ K , D s ∗ η , D K π , $$T_{c\bar{s}1}^{a}\rightarrow D^{*}K, D_{s}^{*}\pi , DK\pi ,$$ T c s ¯ 1 a → D ∗ K , D s ∗ π , D K π , and $$T_{\bar{c}\bar{s}1}^{f/a}\rightarrow \bar{D}^{*}K, \bar{D}K\pi $$ T c ¯ s ¯ 1 f / a → D ¯ ∗ K , D ¯ K π are estimated. Considering the present estimations, we propose to search for $$T_{c\bar{s}1}^{f/a}$$ T c s ¯ 1 f / a states in $$D^{*}K$$ D ∗ K and $$D_{s}^{*}\pi /D_{s}^{*}\eta $$ D s ∗ π / D s ∗ η mass invariant spectra. Their ratios may serve as an important test of the molecular scenario.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Dalya Baron, Karin M. Sandstrom, Jessica Sutter
et al.
The structure and chemistry of the dusty interstellar medium (ISM) are shaped by complex processes that depend on the local radiation field, gas composition, and dust grain properties. Of particular importance are polycyclic aromatic hydrocarbons (PAHs), which emit strong vibrational bands in the mid-infrared, and play a key role in the ISM energy balance. We recently identified global correlations between PAH band and optical line ratios across three nearby galaxies, suggesting a connection between PAH heating and gas ionization throughout the ISM. In this work, we perform a census of the PAH heating–gas ionization connection using ∼700,000 independent pixels that probe scales of 40–150 pc in 19 nearby star-forming galaxies from the PHANGS survey. We find a universal relation between $\mathrm{log}$ PAH(11.3 μ m/7.7 μ m) and $\mathrm{log}$ ([S ii ]/H α ) with a slope of ∼0.2 and a scatter of ∼0.025 dex. The only exception is a group of anomalous pixels that show unusually high (11.3 μ m/7.7 μ m) PAH ratios in regions with old stellar populations and high starlight-to-dust emission ratios. Their mid-infrared spectra resemble those of elliptical galaxies. Active galactic nucleus hosts show modestly steeper slopes, with a ∼10% increase in PAH(11.3 μ m/7.7 μ m) in the diffuse gas on kiloparsec scales. This universal relation implies an emerging simplicity in the complex ISM, with a sequence that is driven by a single varying property: the spectral shape of the interstellar radiation field. This suggests that other properties, such as gas-phase abundances, gas ionization parameter, and grain charge distribution, are relatively uniform in all but specific cases.
Giant radio quasars (GRQs) are radiatively efficient radio-loud active galactic nuclei that propel large-scale radio jets with projected lengths of more than 0.7 Mpc. We report the discovery of 53 new GRQs within a redshift range of 0.14–2.38, as well as 316 new nongiant extended radio quasars (NGERQs) within a redshift range of 0.037–3.356, from the TIFR GMRT Sky Survey Alternative Data Release 1. The projected lengths of the new GRQs range from 0.7 to ∼2.2 Mpc, and the projected lengths of the new NGERQs range from 67 to 695 kpc. We found that the spectral indices of GRQs are statistically similar to those of NGERQs. We have also investigated the large-scale environmental and jet asymmetry properties of the combined sample, which includes new sources and previously discovered extended radio quasars (ERQs) from the literature. The results indicate that at least 13% of GRQs and 14% of NGERQs in the sample are located in galaxy groups and cluster environments. Similar lower-bound percentages reside near large-scale filamentary structures, with median projected distances of 5.9 and 4.3 Mpc from their respective host quasars. At the current survey noise levels, we find that the projected lengths of ERQs in our sample at z ≥ 1 are smaller than those at z < 1. Furthermore, GRQs at z ≥ 1 exhibit greater arm-length asymmetry compared to NGERQs, which may be attributed to an asymmetric environment.
Camille Granier, Daniel Grošelj, Luca Comisso
et al.
We investigate the onset of driven collisionless reconnection and plasmoid formation in a magnetically dominated pair plasma, using 2D particle-in-cell simulations. Two force-free flux tubes of radius R are initially pushed together with a prescribed velocity, forming a current sheet whose width shrinks until reconnection sets in. Even in our largest simulation with R ≈ 1600 plasma skin depths, the sheet thickness at reconnection onset is comparable to the skin depth. Plasmoid chains develop when the sheet length-to-width aspect ratio A ≳ 30. In the strongly magnetized limit, the onset of reconnection occurs in roughly 2–6 light-crossing times, depending on the imposed driving timescale, which controls the duration of the thinning phase. In the subsequent nonlinear merging phase, the evolution becomes effectively independent of the initially imposed velocity, leading to magnetic-energy dissipation consistent with a normalized reconnection rate ∼0.1. Our results have important implications for explosive release of magnetic energy in magnetospheres of astrophysical compact objects and their surroundings.
Wenyuan Yu, Nada Al-Haddad, Charles J. Farrugia
et al.
Abstract The aim of this study is to use multispacecraft measurements of interplanetary magnetic clouds (MCs) to better constrain and understand the effect of expansion on their magnetic field properties. We develop a parameter (γ) for comparing magnetic field components measured at multiple spacecraft. We use the minimum variance technique on the magnetic field data to obtain the axial and azimuthal components. The parameter γ acts at the front boundary as a measure of the global difference in the evolution with heliospheric distance of the axial and azimuthal magnetic field components of MCs. Our goal is to determine whether the studied MCs exhibit self-similar expansion and, if so, whether this expansion is predominantly isotropic or radial, based on the estimated γ. Through our analysis of data from multiple spacecraft, we observe a notable consistency in the γ values across the examples examined. We find that the overall expansion of these MCs tends to be isotropic, while the local expansion of MCs, derived from the γ values measured at the rear boundary of MCs, usually shows anisotropic behavior, particularly when the distances between the observations from the two spacecraft are relatively short. This discovery offers insights for refining flux rope models and advancing our comprehension of the expansion processes associated with coronal mass ejections.
Csaba Balazs, Torsten Bringmann, Felix Kahlhoefer
et al.
Dark matter is a fundamental constituent of the universe, which is needed to explain a wide variety of astrophysical and cosmological observations. Although the existence of dark matter was first postulated nearly a century ago and its abundance is precisely measured, approximately five times larger than that of ordinary matter, its underlying identity remains a mystery. A leading hypothesis is that it is composed of new elementary particles, which are predicted to exist in many extensions of the Standard Model of particle physics. In this article we review the basic evidence for dark matter and the role it plays in cosmology and astrophysics, and discuss experimental searches and potential candidates. Rather than targeting researchers in the field, we aim to provide an accessible and concise summary of the most important ideas and results, which can serve as a first entry point for advanced undergraduate students of physics or astronomy.
Abstract General expressions for one-loop contributions associated with lepton-flavor violating decays of the standard model-like Higgs boson $$h\rightarrow e_b^\pm e_a^\mp $$ h → e b ± e a ∓ and gauge boson $$Z\rightarrow e^\pm _b e_a^\mp $$ Z → e b ± e a ∓ are introduced in the unitary gauge. The results are used to discuss these decays as new physics signals in a minimal left-right symmetric model containing only one bidoublet Higgs and a $$SU(2)_R$$ S U ( 2 ) R Higgs doublet accommodating data of neutrino oscillations and $$(g-2)_{\mu }$$ ( g - 2 ) μ . The numerical investigation indicates that some of these decay rates can reach near future experimental sensitivities.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
We present a general procedure for deriving a line-profile model for massive-star X-ray spectra that captures the dynamics of the wind more directly. The basis of the model is the analytic solution to the problem of variable jets in Herbig–Haro objects given by Cantó et al. In deriving our model, we generalize this jet solution to include flows with a prescribed nonzero acceleration for the context of radiatively driven winds. We provide example line profiles generated from our model for the case of sinusoidal velocity and mass-ejection variations. The example profiles show the expected shape of massive-star X-ray emission lines, as well as interesting but complicated trends with the model parameters. This establishes the possibility that observed X-rays could be a result of temporal variations seeded at the wind base, rather than purely generated intrinsically within the wind volume, and can be described via a quantitative language that connects with the physical attributes of those variations, consistently with the downstream momentum-conserving nature of radiatively cooled shocked radial flows.
F. A. Barone, L. H. C. Borges, G. Flores-Hidalgo
et al.
Abstract In this paper we propose a coupling between the complex scalar field and an external Dirac delta-like planar potential. The coupling is achieved through the Klein–Gordon current normal to the plane where the potential is concentrated. The results are obtained exactly and exhibit many peculiarities. We show that a complex scalar charge does not interact with the potential, but the potential modifies the interaction between two scalar charges if they are placed on opposite sides of the planar potential. When the coupling constant between the potential and the field goes to infinity, the classical field solutions satisfy a kind of MIT boundary conditions along the plane where the potential is concentrated.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Active regions are the brightest structures seen in the solar corona, so their physical properties hold important clues to the physical mechanisms underlying coronal heating. In this work, we present a comprehensive study for a filament-embedding active region as determined from observations from multiple facilities including the Chinese H α Solar Explorer. We find three types of dynamic features that correspond to different thermal and magnetic properties, i.e., the overlying loops—1 MK cool loops, the moss region—2–3 MK hot loops’ footprints, and the sigmoidal filament. The overlying cool loops, which have a potential field, always show Doppler blueshifts at the east footprint and Doppler redshifts at the west, indicating a pattern of “siphon flow.” The moss-brightening regions, which sustain the hot loops that have a moderate sheared field, always show downward Doppler redshifts at the chromosphere, which could be a signature of plasma condensing into the inner region adjacent to the filament. The sigmoidal filament, which has strongly sheared field lines along the polarity inversion line, however, shows a different Doppler velocity pattern in its middle part, i.e., an upward Doppler blueshift at the double- J -shaped stage indicating tether-cutting reconnection during the filament channel formation and then a downward redshift showing the plasma condensation for the sigmoidal filament formation. The present work shows overall properties of the filament-embedding active region, constraining the heating mechanisms of different parts of the active region and providing hints regarding the mass loading of the embedded filament.
Abstract Several new physics scenarios that address anomalies in B-physics predict an enhancement of $$b \rightarrow s \tau \tau $$ b → s τ τ with respect to its Standard Model prediction. Such scenarios necessarily imply modifications of the lifetime ratio $$\tau _{B_{s}}/\tau _{B_{d}}$$ τ B s / τ B d and the lifetime difference $$\Delta \Gamma _{s}$$ Δ Γ s . In this work, we explore indirect bounds provided by these observables over new physics scenarios. We also estimate future projections, showing that future experimental and theoretical improvements on both $$\tau _{B_{s}}/\tau _{B_{d}}$$ τ B s / τ B d and $$\Delta \Gamma _{s}$$ Δ Γ s have the potential to provide bounds competitive with those directly extracted from $$b\rightarrow s \tau \tau $$ b → s τ τ transitions. After performing a model-independent analysis, we apply our results to the particular case of leptoquark mediators proposed to address the $$R_{D^{(*)}}$$ R D ( ∗ ) anomalies.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract Quark has an electric charge either $$-1/3$$ - 1 / 3 or 2/3 and a baryon number 1/3, where the divisions 3’s match the color number. Although the electric charge and the baryon number have a nature distinct from the color charge, the matching is necessary for the standard model or a relevant $$B-L$$ B - L extension consistent at quantum level, since the relevant anomaly $$[SU(2)_L]^2U(1)_A$$ [ S U ( 2 ) L ] 2 U ( 1 ) A for $$A=Y$$ A = Y or $$B-L$$ B - L must vanish. If elementary particles have a new U(1) charge differently from A, such anomaly is not cancelled for each family. However, if we demand that the anomaly is cancelled over all families, this relates the color number to the family number instead of the electric charge and baryon number, and interestingly the family number guides us to a novel U(1) theory. We will discuss the implication of this theory for neutrino mass, recent W-boson mass anomaly, FCNC, and particle colliders.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Fast radio bursts (FRBs) are energetic millisecond phenomena in the radio band. Polarimetric studies of repeating FRBs indicate that many of these sources occupy extreme and complex magnetoionized environments. Recently, a frequency-dependent depolarization has been discovered in several repeating FRBs. However, the temporal evolution of polarization properties is limited by the burst rate and observational cadence of telescopes. In this Letter, the temporal evolution of depolarization in repeating FRB 20201124A is explored. Using the simultaneous variation of rotation measure and dispersion measure, we also measure the strength of a magnetic field parallel to the line of sight. The strength ranges from a few μ G to 10 ^3 μ G. In addition, we find that the evolution of depolarization and magnetic field traces the evolution of rotation measure. Our result supports that the variation of depolarization, rotation measure, and the magnetic field are determined by the same complex magnetoionized screen surrounding the FRB source. The derived properties of the screen are consistent with the wind and the decretion disk of a massive star.
The morphology of radio galaxies can provide significant clues to describe the formation and evolution of galaxies in the Universe. Here, we aim to extract the morphological parameters of radio galaxies and define symmetry criteria as some of the essential factors of their shape explanations. We employed 67 radio galaxies, which include Fanaroff–Riley type 1 and type 2 galaxies, and their radio images from the FIRST and LoTSS surveys. We developed an automatic segmentation process to extract morphological properties such as the size of objects, eccentricity, and orientation of segmented regions from data sets. Using a maximum likelihood estimator, we show that the distributions of sizes follow a power-law function with exponents of −0.39 ± 0.06 and −0.55 ± 0.05 for the FIRST and LoTSS data, respectively. We found that type 2 radio galaxies have slightly lower eccentricities than type 1. We studied the relationships between size, eccentricity, and redshift in scatter plots. The size of galaxies (kpc ^2 ) demonstrates gently growing trends with increasing eccentricity in their scatter plots. We discussed the possible effect of the redshifts of the galaxies on this result. Depending on the number of segmented regions, we defined symmetry criteria based on proximity to the center of a galaxy in the optical band, eccentricity, orientation, and the quarter ( q ) of appearance in the image. We found that the mean symmetry obtained for two segmented regions that mainly emerged in two quarters via the condition of $| {q}^{{\prime} }-q^{\prime\prime} | =2$ has a higher value than those obtained for other cases.
Francisco Ley, Ellen G. Zweibel, Mario Riquelme
et al.
Turbulence driven by active galactic nuclei activity, cluster mergers, and galaxy motion constitutes an attractive energy source for heating the intracluster medium (ICM). How this energy dissipates into the ICM plasma remains unclear, given its low collisionality and high magnetization (precluding viscous heating by Coulomb processes). Kunz et al. proposed a viable heating mechanism based on the anisotropy of the plasma pressure under ICM conditions. The present paper builds upon that work and shows that particles can be heated by large-scale turbulent fluctuations via magnetic pumping. We study how the anisotropy evolves under a range of forcing frequencies, what waves and instabilities are generated, and demonstrate that the particle distribution function acquires a high-energy tail. For this, we perform particle-in-cell simulations where we periodically vary the mean magnetic field B ( t ). When B ( t ) grows (dwindles), a pressure anisotropy P _⊥ > P _∥ ( P _⊥ < P _∥ ) builds up ( P _⊥ and P _∥ are, respectively, the pressures perpendicular and parallel to B ( t )). These pressure anisotropies excite mirror ( P _⊥ > P _∥ ) and oblique firehose ( P _∥ > P _⊥ ) instabilities, which trap and scatter the particles, limiting the anisotropy, and providing a channel to heat the plasma. The efficiency of this mechanism depends on the frequency of the large-scale turbulent fluctuations and the efficiency of the scattering the instabilities provide in their nonlinear stage. We provide a simplified analytical heating model that captures the phenomenology involved. Our results show that this process can be relevant in dissipating and distributing turbulent energy at kinetic scales in the ICM.