Negative / Null Result ReportOpen accessPhysics and Astronomy
A. J. Nayana, R. Margutti, Eli Wiston et al. · 2025 · The Astrophysical Journal Letters
Abstract We present X-ray (0.3–79 keV) and radio (0.25–203 GHz) observations of the most luminous fast blue optical transient (LFBOT) AT 2024wpp at z = 0.0868, spanning 2–280 days after first light. AT 2024wpp shows luminous ( L X ≈ 1.5 × 10 43 erg s −1 ), variable X-ray emission with a Compton hump peaking at δt ≈ 50 days. The X-ray spectrum evolves from a soft ( F ν ∝ ν −0.6 ) to an extremely hard state ( F ν ∝ ν 1.26 ) accompanied by a rebrightening at δt ≈ 50 days. The X-ray emission properties favor an embedded high-energy source shining through asymmetric expanding ejecta. We detect radi
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
W. V. Jacobson-Galán, Luc Dessart, Kyle W. Davis et al. · 2025 · The Astrophysical Journal
Abstract We present analysis of the plateau and late-time phase properties of a sample of 39 Type II supernovae (SNe II) that show narrow, transient, high-ionization emission lines (i.e., “IIn-like”) in their early-time spectra from interaction with confined, dense circumstellar material (CSM). Originally presented by W. V. Jacobson-Galán et al., this sample also includes multicolor light curves and spectra extending to late-time phases of 35 SNe with no evidence for IIn-like features at <2 days after first light. We measure photospheric phase light-curve properties for the distance-correct
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
Davide Faccialà, M. Bonanomi, Bruno Nunes Cabral Tenorio et al. · 2025 · Journal of the American Chemical Society
High Resolution Image Download MS PowerPoint Slide We report a study of the electronic and nuclear relaxation dynamics of the photoexcited RNA base uracil in the gas phase using time-resolved core-level photoelectron spectroscopy together with high-level calculations. The dynamics was investigated by trajectory surface hopping calculations, and the core ionization energies were calculated for geometries sampled from these. The molecule was excited by a UV laser and dynamics probed on the oxygen, nitrogen, and carbon sites by core electron spectroscopy. We find that the main de-excitation chann
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
K. D. Alexander, R. Margutti, Sebastian Gomez et al. · 2026 · The Astrophysical Journal
Abstract Recent observations presented in Y. Cendes et al. show that optically selected tidal disruption events (TDEs) commonly produce delayed radio emission that can peak years after disruption. Here, we explore the multiwavelength properties of a sample of radio-observed optically selected TDEs, to shed light on the physical process(es) responsible for the late-rising radio emission. We combine new late-time X-ray observations with archival optical, UV, X-ray, and radio data to conclude that a diversity of accretion-driven outflows may power the delayed radio emission in TDEs. Our analysis
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
I. Delvecchio, E. Daddi, B. Magnelli et al. · 2025 · Astronomy and Astrophysics
Little red dots (LRDs) are a puzzling population of extragalactic sources whose origin is highly debated. In this work, we performed a comprehensive stacking analysis of NIRCam, MIRI, and ALMA images of a large and homogeneously selected sample of LRDs from multiple JWST Legacy fields. We report clear evidence of hot-dust emission in the median stacked spectral energy distribution (SED) that features a rising near-infrared continuum up to rest-frame λ rest ∼ 3 μm, which is best explained by a standard dusty active galactic nucleus (AGN) structure. Although LRDs are likely to be a heterogeneous
View details →Negative / Null Result ReportOpen accessPhysics and Astronomy
A. M. Farah, A. Vijaykumar, M. Fishbach · 2026 · The Astrophysical Journal Letters
Abstract There is growing evidence from gravitational-wave (GW) observations that some merging black holes (BHs) are created from previous mergers. Using the prediction that these hierarchically merged BHs have dimensionless spin magnitudes of χ ≈ 0.69, we identify a subpopulation in the GW data consistent with a hierarchical-merger origin in dense star clusters. This subpopulation’s primary mass distribution peaks at 17 . 0 − 4.4 + 18.3 M ⊙ , which is approximately twice as large as its secondary mass distribution’s mode ( 10 . 5 − 4.7 + 29.7 M ⊙ ), and its spin tilt distribution is consisten
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Stella Koch Ocker, J. M. Cordes · 2026 · The Astrophysical Journal
Abstract Free electrons in the Galactic interstellar medium (ISM) disperse and scatter coherent radio waves, by amounts that depend on the distance to the radio source. Models of the Galactic electron density are thus widely used to predict distances and scattering of compact radio sources (including pulsars, fast radio bursts, and long-period transients), in addition to mitigating ISM foregrounds in Galactic and extragalactic studies. We use a sample of 171 precise pulsar distances, based entirely on parallaxes and globular cluster associations, as well as scattering measurements of 568 pulsa
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Tim Linden, Thong T. Q. Nguyen, Tim M. P. Tait · 2026 · Journal of Cosmology and Astroparticle Physics
Abstract We model and constrain the unique indirect detection signature produced by dark matter particles that annihilate through a U(1) gauge symmetry into dark photons that subsequently decay into three-photon final states. We focus on scenarios where the dark photon is long-lived, and show that γ-ray probes of celestial objects can set strong constraints on the dark matter/baryon scattering cross section that in many cases surpass the power of current direct detection constraints, and in some cases even peer into the neutrino fog.
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Himanshu Chaudhary, Vipin Kumar Sharma, Salvatore Capozzıello et al. · 2026 · The Astrophysical Journal Supplement Series
Abstract Observational data play a pivotal role in identifying cosmological models that are both theoretically consistent and empirically viable. In this work, we investigate the level of preference for dynamical dark energy over a cosmological constant using current late-time observational datasets, including cosmic chronometers (CC), baryon acoustic oscillations from Dark Energy Spectroscopic Instrument (DESI) DR2, and different Type Ia supernova catalogs (Pantheon + , DES-Dovekie, Union3). We analyze various dynamical dark-energy models, including ω CDM, o ω CDM, ω 0 ω a CDM, logarithmic, e
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Lalitwadee Kawinwanichakij, Karl Glazebrook, Themiya Nanayakkara et al. · 2026 · The Astrophysical Journal
Abstract We present the morphological properties of 17 spectroscopically confirmed massive quiescent galaxies ( 10.2 < log ( M * / M ⊙ ) < 11.2 ) at 3.0 < z < 4.3, observed with JWST/NIRSpec and NIRCam. Using Sérsic profile fits to F277W and F444W imaging, we derive the size–mass relation and find typical sizes of ∼0.6–0.8 kpc at M * = 5 × 10 10 M ⊙ , consistent with ∼7× growth from z ∼ 4 to the present, including ∼2× by z ∼ 2. We find tentative evidence that formation history and morphology jointly influence galaxy sizes: late-forming bulge-dominated galaxies appear more compact by ∼0.2–0.3 d
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Zhuoming Zhang, Tengpeng Xu, Yun Chen · 2026 · The Astrophysical Journal
Abstract We present a Bayesian comparative analysis of five cosmological models: ΛCDM, w CDM, w 0 w a CDM, ϕ CDM (with scalar-field dark energy), and an interacting dark energy scenario (the ξ -index model), to investigate dark energy evolution and the Hubble tension. Utilizing the latest data from the second data release of the Dark Energy Spectroscopic Instrument (Baryon Acoustic Oscillations, BAO), Pantheon+ (type Ia supernovae, SNIa), and cosmic microwave background (CMB) data (including lensing) from Planck and the Atacama Cosmology Telescope, we report three key findings. First, the Hubb
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Joss Bland‐Hawthorn, Thor Tepper-García, Oscar Agertz et al. · 2025 · The Astrophysical Journal
Abstract In response to recent observations from JWST and Atacama Large Millimeter Array, we explore a new class of dynamically self-consistent models that mimics a plausible progenitor of the Milky Way over a wide range of disk gas fractions, f gas . The high gas surface densities encourage vigorous star formation, which in turn couples with the gas to drive turbulence. We show that this coupling through momentum recoil drives a random walk of the baryonic potential minimum with respect to total gravitational potential, Φ tot ( R , ϕ , z ). The amplitude of the bulk motion depends on the feed
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Xiangdong Ji, Yang Chen · 2026 · Nuclear Physics B
Momentum current density (MCD) $T^{ij}$ is a general physics concept describing the momentum conservation through momentum flow generated from both the kinetic motion of particles and the interacting forces among them. It has been suggested by M. Polyakov et al. that the MCD in the nucleon, characterized by the form factor $C/D$ of the QCD energy-momentum tensor, can be interpreted as the pressure and shear forces between adjacent parts of the system because the nucleon interior approximates a continuous medium. While intuitively appealing, we find that the interpretation is hard to justify fr
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Tamara Evstafyeva, Nils Peter Siemonsen, William E. East · 2026 · Physical review. D/Physical review. D.
We reinvestigate the stability properties of ultracompact spinning boson stars with a stable light ring using fully nonlinear 3+1 and 2+1 numerical relativity simulations and two different formulations of the Einstein equations. We find no…
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George Yumnam, Parul R. Raghuvanshi, J. D. Budai et al. · 2025 · Cell Reports Physical Science
We provide experimental evidence for the absence of a magnetic moment in bulk RuO 2 , a candidate altermagnetic material, by using a combination of Mössbauer spectroscopy, nuclear forward scattering, inelastic X-ray and neutron scattering,…
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