Current date: 2026-08-14
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Number of records retrieved: 666
Keyword score statistics
score 9 -- 1 abstracts
score 7 -- 3 abstracts
score 6 -- 1 abstracts
score 5 -- 1 abstracts
score 4 -- 1 abstracts
score 3 -- 9 abstracts
score 2 -- 16 abstracts
in total -- 32 abstracts
Articles that appeared on 2026-08-14
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[abstract 1 / 32] Wow! (score: 9)
- Title: The emergence of X-ray emission lines during RELATIVISTIC radio-JET formation in the changing-look ACTIVE GALACTIC NUCLEus 1ES 1927+654Authors: Dev R. Sadaula, Sibasish Laha, Eileen T. Meyer, Onic I. Shuvo, Main Pal, Ritesh Ghosh, Matteo Guainazzi, Fabio Pacucci, Stefano Bianchi, Luigi Gallo, Rostom Mbarek, Amelia M. Hankla, Fabio La Franca, Tahir Yaqoob, Megan Masterson, Erin Kara, Missagh Mehdipour, Claudio Ricci, Javier A Garcia, Timothy R. Kallman, Ralf Ballhausen, Mitchell C. Begelman, Alexander Philippov, Suvendu Rakshit, Francesca Panessa, Ehud Behar, S. Bradley Cenko, Federica Ricci, Ilaria Villani, James N. Reeves,Comments:Subjects: astro-ph.HE astro-ph.GA hep-phCreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
We present results from a comprehensive multi-wavelength monitoring campaign of the changing-look ACTIVE GALACTIC NUCLEus 1ES 1927+654 during the onset and evolution of a RELATIVISTIC radio JET ~(May 2022 - August 2025), using observations from XMM-Newton, SWIFT, TNG, ZTF, VLA, and VLBA. The soft X-ray emission lines at ~0.56 keV and ~1 keV have appeared with variable strength and width during the formation of the nascent JET. We note that the ~1 keV feature has been persisting since the post-2017 flare phase. We also report the detection of a broad (~800 eV) FeK emission feature at (6-7) keV in the ~70 ks stacked EPIC-pn spectra, marking the first such detection, which historically was lacking in this source. The joint spectral fitting of XMM-Newton EPIC-pn and RGS data reveals the presence of ionized absorbers in 2022 (log(xi)/(erg cm s^1) ~ 1.5 +- 0.3, N_H ~ 2.5 +- 0.9 x 10^20 cm^-2), but weaker than that detected during the high accretion state in 2018 (Eddington ratio, lambda_Edd > 1). The absorption features further weakened in 2023-2025 and were marginally detectable (N_H <= 10^20 cm^-2). The entire scenario is suggestive of a real-time transition of the accretion flow (from lambda_Edd > 1 to lambda_Edd ~ 0.3) during which the winds become weaker and the JET starts to form and evolve. Furthermore, both the soft X-ray (0.3-2) keV and 5 GHz radio fluxes, which increased by factors of ~10 and ~60, respectively, since 2022, have recently plateaued at elevated levels, indicating a stabilized accretion disk, corona, and JET configuration.
[abstract 2 / 32] Wow! (score: 7) - Title: McFACTS. IV. ElectroMAGNETic Counterparts to AGN-disk-embedded Binary Black Hole MergersAuthors: Emily McPike, Rosalba Perna, K. E. Saavik Ford, Barry McKernan, Harrison E. Cook, Vera Delfavero, Miranda McCarthy, Kaila Nathaniel, Jake Postiglione, Nicolas Posner, Varun Pritmani, Shawn Ray, Richard O'Shaughnessy,Comments: 20 pages, 12 figures, 3 tables; accepted to The Astrophysical JournalSubjects: astro-ph.HECreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
The accretion disks of ACTIVE GALACTIC NUCLEi (AGNs) are promising environments for producing binary BLACK HOLE (BBH) mergers, which have been detected via gravitational waves (GWs) with the LIGO-Virgo-KAGRA (LVK) GW detector network. BBH mergers embedded in AGN disks are unique among GW formation channels in their generic ability to produce electroMAGNETic (EM) counterparts, via interactions between the merger remnant and the surrounding disk gas (though these are not always observable). While such mergers represent valuable multimessenger sources, the lack of predictive statistical models in existing literature currently limits our ability to select possible EM counterparts with GW detections in archival data and in real time using time-domain surveys such as the Zwicky Transient Facility or LSST. Here we employ the Monte Carlo For AGN Channel Testing and Simulation code (McFACTS, https://www.github.com/mcfacts/mcfacts) to predict the bolometric luminosities of JETs and shocks associated with LVK-detectable BBH merger remnants in AGN disks. McFACTS predicts the distribution of GW observables for an underlying BLACK HOLE population and disk model. In this work we present a new capability that simultaneously generates the distribution of bolometric EM luminosities corresponding to these predicted GW detections. Our results are consistent with current observational surveys and indicate that (i) migration in dense, Sirko-Goodman-like disks preferentially produces EM counterparts from high-mass ($\mathscr{M} > 40M_{\odot}$), high-spin remnants across multiple merger generations and (ii) lower chirp mass mergers are more likely to contribute observable counterparts and with shorter emission breakout times in less dense, Thompson-Quataert-Murray-like disks.
[abstract 3 / 32] Wow! (score: 7) - Title: An Evolving Leptonic Jet Model for Delayed Radio Flares in Neutrino BlazarsAuthors: Alina Kochocki, Xavier Rodrigues, Nathan Whitehorn,Comments: 18 pages, 7 figures, submitted to PRDSubjects: astro-ph.HE astro-ph.GACreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
The JETs of BLAZAR ACTIVE GALACTIC NUCLEi (AGN) are promising sites of hadron acceleration and subsequent neutrino production, owing to their extreme intrinsic power and high radiation density. Potential associations of IceCube neutrinos with BLAZARs displaying delayed radio flares, such as TXS~0506+056 and PKS~1424+240, may support this scenario. However, the mechanisms and location of particle acceleration in the JET remain unclear. The 2017 IceCube event associated with TXS 0506+056 was concurrent with the initial peak of a flare in gamma rays, followed by a longer flare at radio frequencies peaking three years later. State-of-the-art single-zone radiative source models focus on the compact high-energy-emitting region, and thus fail to describe this subsequent radio enhancement. In this work, we model the time-domain multi-frequency evolution of TXS 0506+056 by considering electron emission along the physically extended JET. We couple a numerical particle interaction framework with a dynamic description of the temporal and spatial JET evolution down to the parsec scale. We fit the model to multi-wavelength data, including multi-frequency radio light curves. The results suggest that the parsec-scale JET meets a population of older, cooled electrons near the edge of the observable radio core, establishing a causal relation between the initial high-energy emission and trailing radio activity. This spatially and temporally resolved modeling approach can offer new insights into the physical conditions along the JET of flaring neutrino candidate BLAZARs.
[abstract 4 / 32] Wow! (score: 7) - Title: X-ray Flaring and Variability in NGC 1275, the Heart of the Perseus ClusterAuthors: Sarah Ketchum, Jon M. Miller, S. W. Allen, Doyee Byun, Tianyin Hu, Missagh Mehdipour, Veronica Tananko, Xin Xiang, Irina Zhuravleva,Comments: Accepted for publication in ApJ LettersSubjects: astro-ph.HE astro-ph.GACreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
NGC 1275 is the central galaxy in the Perseus Cluster. The ACTIVE GALACTIC NUCLEus (AGN) within NGC 1275 is notable for its strong and variable radio activity, tied to the production of radio JETs that inflate large bubbles in the hot intracluster medium (ICM). High spatial resolution X-ray imaging can separate the AGN from the bright ICM, but monitoring the mass accretion rate onto the BLACK HOLE and establishing disk-JET connections in NGC 1275 requires a high cadence. Here, we report on X-ray monitoring of NGC 1275 using data taken over 20 years with the Neil Gehrels SWIFT Observatory. Modeling the temporally constant ICM in each observation allows X-ray emission from accretion onto the BLACK HOLE to be traced reliably, with typical flux errors of $\sim 3\%$. X-ray flaring by a factor of $\sim2$ over mere days is detected starting on MJD 59956 (2023 Feb. 21). The flares imply an emission region consistent with $r \leq 870~(10^{8}~M_{\odot}/M_{BH})~ GM/c^{2}$. The profile of the flaring is inconsistent with simple predictions for tidal disruption events. A flare appears roughly 300 days later in radio monitoring data at 43 GHz. Overall, our results indicate that coordinated, moderate-resolution X-ray imaging and radio monitoring could potentially trace disk-JET connections in the AGN that most vividly impact large-scale structure, and be extended to other sources that impact their hosts.
[abstract 5 / 32] Yes (score: 6) - Title: Ripples in the OCEANS: Broad Line Variability of Little Red DotsAuthors: Madisyn Brooks, Kelcey Davis, Jonathan R. Trump, Raymond C. Simons, Erini Lambrides, Pablo Arrabal Haro, Bren E. Backhaus, Nikko J. Cleri, Steven L. Finkelstein, Mauro Giavalisco, Norman A. Grogin, Michaela Hirschmann, Dale D. Kocevski, Anton M. Koekemoer, Rebecca L. Larson, Ray A. Lucas, Stephen M. Wilkins, Stijn Wuyts, Jorge A. Zavala,Comments: 19 pages, 8 figures, submitted to ApJSubjects: astro-ph.GACreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
Little Red Dots (LRDs) are a unique class of compact, red sources discovered in the JWST extragalactic deep fields. Determining if they are indeed powered by accreting supermassive BLACK HOLEs (SMBHs) is one of the main drivers of the intense study of these objects. Evidence for variability in these objects provides a direct test for the ACTIVE GALACTIC NUCLEus (AGN) nature of their central engine. In this study, we present a variability analysis of 6 LRDs observed by the $R \sim 2700$ OCEANS survey and leverage archival $R \sim 1000$ spectroscopic data from the CEERS and RUBIES surveys. We report marginal detections of $\rm Hα$ broad-line (BL) variability in the LRDs OCEANS-100424/RUBIES-42232 (27\% variability at 2.1$σ$ significance) and OCEANS-35829/RUBIES-49140 (GlimmIr/Irony; 50\% variability at 1.5$σ$ significance). The other 4 LRDs in our sample do not show evidence for BL variability, with a 1$σ$ upper limit of $4.8 \% - 30\%$ variability between their epochs of observations. We also find no evidence ($<1σ$) for continuum variability in our LRD sample. We compare our results to a sample of SDSS-RM QUASARs to determine the probability of our broad $\rm Hα$ variability detections. We find that the probability of reproducing 2 variable and 4 nonvariable QUASARs is $4.71\%$, corresponding to $\sim 2 σ$ departure from typical QUASAR variability. The detection of BL $\rm Hα$ variability in 2 LRDs provides some evidence for the AGN nature of these objects as opposed to pure scattering models.
[abstract 6 / 32] Yes (score: 5) - Title: Large-Scale Dynamos Driven by Shear-Flow-Induced JetsAuthors: B. Tripathi, A. E. Fraser, P. W. Terry, E. G. Zweibel, M. J. Pueschel, R. Fan,Comments: The published article [Nature 649, 848 (2026)] is free to read at https://rdcu.be/eZ7g0Subjects: astro-ph.SR astro-ph.HE physics.flu-dyn physics.plasm-ph physics.space-phCreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
At every scale they occupy, MAGNETic fields affect various phenomena, including STAR FORMATION, COSMIC RAY transport, charged particle acceleration, space weather, transport in planetary atmospheres, and laboratory plasmas. These fields are often generated and sustained by turbulent flows in a process called the dynamo. In 1955, E. N. Parker parameterized the effects of small-scale turbulence to propose a mean-field dynamo theory. The widely used theory reproduces observed large-scale fields but suffers from difficulty in tuning parameters as they are not justified from first principles: Studies of turbulent flows show tangled MAGNETic fields, which are folded and fragmented into small-scale structures due to shear-flow straining. Here, considering a shear flow that is unstable and driven, we develop analytic theory and perform three-dimensional (3D), advanced computer simulations of turbulence with up to 4096 x 4096 x 8192 grid points, showing ab initio generation of quasi-periodic, large-scale MAGNETic fields. The generation occurs via the mean-vorticity effect---an additional mean-field dynamo process postulated in 1990. Crucial to this dynamo is the prior generation of large-scale 3D JETs, robustly produced as topologically protected and exact nonlinear solutions of the MAGNETohydrodynamic equations. The JET-driven dynamo applies to shear-driven laboratory and astrophysical systems. These include binary neutron star mergers, where the reported dynamo likely operates on microsecond timescales to produce in milliseconds some of the strongest MAGNETic fields in the Universe, providing signals for multimessenger astronomy.
[abstract 7 / 32] Yes (score: 4) - Title: Pulsed Infrared Emission from Magnetar 4U 0142+61 Detected by JWSTAuthors: Jeremy Hare, George G. Pavlov, Bettina Posselt, George Younes, Oleg Kargaltsev, Alex van Kooten,Comments: Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We report on a JWST observation of the MAGNETar 4U 0142+61 on 2024 August 18 with the Near-Infrared Camera (NIRCam). NIRCam observed the MAGNETar for 33~min in timing mode, providing a time resolution of 2.5~s. In the F410M filter (pivot wavelength 4.08 $μ$m), we measured the flux density $f_ν= 22.9\pm0.6$ $μ$Jy and detected pulsations at a frequency of $115.059\pm0.035$ mHz, in agreement with the MAGNETar's spin period at the epoch of the JWST observation. The observed pulse profile has one peak per period (although this may be due to the poor time resolution), with a lower limit on the pulsed fraction of about 10\%. We compare the IR pulse profile to the NICER and NUSTAR X-ray pulse profiles and find that the IR peak overlaps with the hard X-ray peak, suggesting a MAGNETospheric origin for the pulsed IR emission.
[abstract 8 / 32] (score: 3) - Title: Quadrupole spectra derived from 2.76 TeV Pb-Pb identified-hadron $\bf v_2(p_t)$ dataAuthors: Thomas A. Trainor,Comments: 23 pages, 20 figures, fix one figure, arXiv admin note: text overlap with arXiv:1610.06256 -- 1610.06256 provides introductory material for this articleSubjects: hep-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
$p_t$-differential quantity $v_2(p_t)$ is meant to measure elliptic flow manifested by a dense QCD medium formed in high-energy nucleus-nucleus collisions. Elliptic flow may be referred to more neutrally as a cylindrical quadrupole component of the transverse motion of particle sources within a collision. As defined, $v_2(p_t)$ relies on an implicit assumption that almost all produced particles emerge from a single source. This article describes a detailed study of the algebraic structure of $v_2(p_t)$. A procedure is developed to derive a common monopole boost (radial flow) value and quadrupole $p_t$ spectra for several hadron species. The method is applied to $v_2(p_t)$ data for three hadron species from 2.76 TeV Pb-Pb collisions. According to available $v_2(p_t)$ data the assumption of a single dominant particle source within A-A collisions is unjustified. Combined with a previous study of quadrupole amplitude variation for 200 GeV $p$-$p$ collisions these results demonstrate that quadrupole structure is related to a novel QCD process separate from projectile-nucleon dissociation and JET production. Given quadrupole evolution it is unlikely that a hydrodynamic description is relevant to that process.
[abstract 9 / 32] (score: 3) - Title: Theoretical Constraints on Neutron Star Superfluidity from Her X-1 PrecessionAuthors: Anton Biryukov, Amir Levinson, Pavel Abolmasov,Comments: Accepted to ApJ. Minor changes addressing referee's commentsSubjects: astro-ph.HECreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
Recent IXPE observations of Her X-1 reveal correlations between flux, POLARIZATION degree, and POLARIZATION angle with its 35-day superorbital cycle. These measurements have been interpreted as strong evidence that the 35-day period is driven by nearly free precession of the neutron star. We show that this interpretation carries far-reaching implications for the dynamics of the crustal superfluid. In particular, maintaining precession over the $\sim 50$-year observational baseline of Her X-1 would require that superfluid vortices remain unpinned for centuries and experience extremely weak mutual friction while traversing the heavy-ion lattice of the inner crust -- conditions that challenge conventional wisdom and standard models of glitch dynamics.
[abstract 10 / 32] (score: 3) - Title: The Delta Resonance in the Neutrino SkyAuthors: Arifa Khatee Zathul, Ke Fang, Francis Halzen, Dan Hooper,Comments:Subjects: astro-ph.HE hep-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
Recent measurements of the diffuse cosmic neutrino flux by IceCube show evidence for a spectral break at an energy near $E_ν\sim 30$ TeV. In this letter, we suggest that this feature may be due to the $Δ$-baryon resonance in $pγ$ interactions. We show that the measured spectrum, including the observed break, can be naturally accommodated by a flux of protons accelerated with a spectrum $dN_p /dE_p \propto E_p^{-3.1}$ interacting with X-rays of typical energy $E_γ \sim 0.3\,{\rm keV}$. We also point out that the presence of this spectral break significantly reduces the contribution of neutrino sources to the isotropic gamma-ray background, alleviating the longstanding tension between these measurements. In the $Δ$-resonance scenario, the gamma rays accompanying neutrino production cascade down to MeV-GeV energies and contribute at the $\sim 10\%$ level to the isotropic gamma-ray background at $\sim 3$~GeV. If our proposal is realized, it may imply that we have identified the dominant sources that produce the extragalactic COSMIC RAYs.
[abstract 11 / 32] (score: 3) - Title: Round-Trip Consistency: Bidirectional Diffusion Models Can Predict Their Own Rollout ErrorsAuthors: Alexander Scheinker,Comments: Code: https://github.com/alexscheinker/round-trip-consistencySubjects: stat.ML cs.LG physics.comp-ph physics.plasm-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
Autoregressive models accumulate error over long rollouts, yet at deployment there is no ground truth to measure it against. We train a single conditional latent diffusion model that steps a dynamical system forward or backward in time via a direction flag, and show that this bidirectionality supplies a measurement-free test-time error signal: rolling forward $i$ steps and then backward $i$ steps must return the model to its start, so the round-trip discrepancy $\mathcal{C}_i$ is a self-supervised proxy for the unobservable rollout error: no ensembles, no held-out data, no governing equations, for one extra rollout. We validate on compressible MAGNETohydrodynamics (MHD), an astrophysical turbulent radiative mixing layer, and natural face videos (CelebV-HQ). On held-out MHD trajectories, $\mathcal{C}_i$ ranks rollout error (Spearman $0.91$-$0.98$ at fixed depth; $0.69 \pm 0.16$ within trajectories), and a simple calibrator fit on training rollouts predicts its magnitude to within $1.14\times$ ($68\%$) and $1.29\times$ ($95\%$) with near-nominal coverage - one nat beyond a depth-only predictor, transferring to all six decoded physical fields. The same signal flags the out-of-distribution Orszag-Tang vortex (AUROC $0.98$; $1.0$ by depth $10$) exactly where sampling-dispersion baselines invert, and it cuts incurred error by $15\%$ at $80\%$ coverage - three times the depth-only baseline. Bidirectional training comes at negative cost, beating direction specialists in both directions, and the backward direction doubles as a fast inverse solver. On LE-PDE-UQ's turbulent Navier-Stokes benchmark, a single bidirectional model reaches accuracy within $1.3\times$ of their ten-model ensemble at a tenth of the training cost, with the best training-free pixel-level calibration. Round-trip consistency turns reversibility into a practical trust signal for generative models.
[abstract 12 / 32] (score: 3) - Title: Recycled Gas Dominates the Metal-rich Fuel of Supermassive Black HolesAuthors: Dongyun Kwak, Ena Choi, Hannah Jhee, Rachel S. Somerville, Thorsten Naab, Michaela Hirschmann, Jaejin Shin, Jong-Hak Woo,Comments: 14 pages, 1 table, 4 figuresSubjects: astro-ph.GACreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
Understanding the origin and chemical properties of gas accreted by supermassive BLACK HOLEs (SMBHs) is essential for linking BLACK HOLE growth to galaxy evolution. Using a suite of 30 high-resolution cosmological zoom-in simulations, we investigate the chemical properties of gas accreted onto SMBHs in massive galaxies with stellar masses of $10^{10.9-11.9}\,\rm M_\odot$ and BLACK HOLE masses of $10^{8.5-9.7}\,\rm M_\odot$ at $z=0$. By tracing the full cosmological histories of individual gas particles, we identify their origins and enrichment pathways. The accreted gas is classified into four categories: ``early'' gas accreted during the early assembly phase of the main halo, ``external'' gas originating from other galaxies or subhalos, ``recycled'' gas enriched through stellar evolution processes within the primary galaxy, including asymptotic giant branch (AGB) winds and SUPERNOVA ejecta, and ``smooth'' gas accreted from the intergalactic medium. We find that recycled gas dominates the accretion budget and is already metal rich at early epochs. Gas from other origins typically undergoes gradual chemical enrichment within the galactic environment prior to BLACK HOLE accretion. The mean abundance ratios show only weak redshift evolution and are broadly compatible with the high metallicities inferred for QUASAR broad-line regions. Our results suggest that metal-rich gas supply to SMBHs arises naturally from cosmological galaxy evolution and stellar recycling.
[abstract 13 / 32] (score: 3) - Title: Monoenergetic acceleration of charge-neutralized ion bunches to GeV-scale energies by the combination of a high-current electron beam and an ionization frontAuthors: Jiyuan Chen, Jihoon Kim, Roopendra Singh Rajawat, Gennady Shvets,Comments: 6 pages, 3 figuresSubjects: physics.plasm-ph physics.acc-phCreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
Compact heavy ion accelerators have numerous applications, ranging from heavy ion fusion to carbon ion radiotherapy, and testing radiation-hardened electronics. The demand could be met by developing high-gradient traveling wave plasma accelerators of high-charge ($\simμ\mathrm{C}$) RELATIVISTIC ion beams. We will discuss a novel ion acceleration regime -- Counter-propagating ionization Front Acceleration (CFA) -- utilizing counter-propagating Ionization Front (IF) and high-current Relativistic Electron Beam (REB). Theoretical modeling and 3D PIC simulations demonstrate the possibility of using typical REBs produced by induction voltage adders propagating through a gas-filled tube undergoing LASER ionization to achieve acceleration gradients in excess of $\sim 250 {\rm MeV/m}$ while accelerating micro-Coulombs of ions over meters distance. A unique energy conversion mechanism -- from the REB to electroMAGNETic fields to the ions is discussed, as well as the limits on the accelerated ions charge and the degree of its neutralization, acceleration gradient, and ion energy spread.
[abstract 14 / 32] (score: 3) - Title: Gaia parallax bias via spherical harmonics: A Python tool and discussion of possible causesAuthors: Valeri V. Makarov, Ciprian T. Berghea,Comments: Submitted. The parallax-correcting code in Python and graphical presentation is available at https://zenodo.org/records/21708614Subjects: astro-ph.GA astro-ph.CO astro-ph.SRCreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
Parallaxes in Gaia DR3 are known to suffer from a complex set of sky-correlated and magnitude-dependent offsets or biases at the level of a few tens of $μ$as. Estimated from a sample of one million distant QUASARs and AGNs from the CRF catalog, the average offset is negative, but the actual distribution of this important parameter shows significant variations on the sky. We propose a practical method to evaluate the parallax correction as a function of sky position and, optionally, of $G$ magnitude using a spherical harmonic series, and supply a tested Python tool {\tt varpi3.py} available on Zenodo\footnote{ https://zenodo.org/records/21708614}. We find that only the constant $Y_{00}$ term is significantly dependent on magnitude, while the other 80 harmonic terms are either close to zero or flat with magnitude. The directions of the smallest and largest parallax offsets are $(l,b)\simeq(220\degr,+43\degr)$ and $(l,b)\simeq(45\degr,-45\degr)$, which are close to the orientation of the QUASAR density dipole reported in recent publications. Motivated by this curious coincidence, we review possible physical effects resulting in a negative bias of measured parallaxes, including an anisotropic universe with a positive curvature and an orbital aberration component. The proposed method of parallax correction is tested using independent asteroseismology data for four different areas on the sphere. Finally, we show that the parallax zero-point propagates into the CRF proper-motion field through the parallax--proper-motion covariance, biasing the vector spherical harmonic determination of the secular-aberration glide, and hence the Galactocentric acceleration, at the microarcsecond-per-year level.
[abstract 15 / 32] (score: 3) - Title: Photospheric Kelvin--Helmholtz Vortices as Possible Drivers of Coronal Heating: Implications of the DKIST ObservationsAuthors: Katariina Nykyri,Comments: 1 figure, 2 tables, 7 pages without referencesSubjects: astro-ph.SR physics.space-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
The Daniel K. Inouye Solar Telescope (DKIST) has resolved Kelvin--Helmholtz (KH) vortices at photospheric MAGNETic-flux boundaries with a characteristic wavelength of 65 km. I estimate whether these vortices can supply the photospheric driver for cross-scale plasma heating through RECONNECTion across different heights from photosphere to low-corona. Using the simulated MURaM shear, density contrast, and 500 km vertical extent, together with a representative photospheric density, gives a shear-energy density of $1.35\times10^{2}$ J m$^{-3}$ and $2.2\times10^{24}$ erg per characteristic vortex. Magnetic fields $1^\circ$--$7^\circ$ from the exact perpendicular orientation ($ {\bf{B}}\perp{\bf{k}}$) remain KH unstable in an idealized calculation and provide an in-plane component that can be wound or compressed into current layers. The limiting case, in which the center-of-momentum shear reservoir becomes new MAGNETic free energy, gives $b_{\rm cs}=184$ G, identical to the ideal marginal-stability field and equivalent to a $7.6^\circ$ effective twist. This stores at most 135 J m$^{-3}$ in the layers. Using empirical collisionless RECONNECTion heating fractions of 0.28--0.44, the same twist mapped to weakly collisional heights gives ion heating from $\approx$20 eV at the photosphere to $\approx$1.4 keV in the low corona. For an illustrative, snapshot-based KH-active surface fraction of 0.03, quiet-Sun and coronal-hole losses require 5--8\% and 14--21\%, respectively, of the shear reservoir to become RECONNECTing MAGNETic free energy that reaches such heights. Active regions likely require a separate guide-field twist and helicity reservoir. The required upward transport has not been measured by DKIST, but it is directly testable.
[abstract 16 / 32] (score: 3) - Title: Macroscopic Stability of a Rapidly Rotating Theta PinchAuthors: Richard Fitzpatrick,Comments:Subjects: physics.plasm-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
The macroscopic ideal-MHD stability of an axisymmetric mirror device with sonic levels of plasma rotation is analyzed by approximating the plasma equilibrium as a rotating theta pinch possessing an artificial gravity. An eigenmode equation is derived that governs the stability of the equilibrium to small perturbations in the case of an arbitrary plasma angular velocity profile. The stability of the m=1 and m=2 modes is investigated. The plasma is found to be stable to these two modes provided that it is sufficiently short in the axial direction. The critical axial length of the device below which the modes are stabilized first decreases with increasing plasma rotation, attains a minimum value when the rotation is roughly sonic, and then increases with increasing plasma rotation. The value of the plasma rotation off the MAGNETic axis is found to have a significantly stronger effect on the stability of the modes than the value on the MAGNETic axis.
[abstract 17 / 32] (score: 2) - Title: Cosmic Chance Superpositions: Largest Catalog of Quasar-Galaxy Pairs at a Projected Separation of $D \lesssim 20$ kpcAuthors: Labanya Kumar Guha, Raghunathan Srianand, Rajeshwari Dutta,Comments: Accepted for publication in ApJ. 14 Figures, 19 pagesSubjects: astro-ph.GA astro-ph.COCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We present the largest catalogue to date of Galaxies On Top Of Quasars (GOTOQs), systems where the sightline to a background QUASAR passes directly through or very close to a foreground galaxy. Using $\approx$1.1 million QUASAR spectra from SDSS DR16 and the DESI Early Data Release, we identify 1345 unique GOTOQs over the redshift range $0.0045 \leq z \leq 1.09$, more than quadrupling the number previously known. The catalogue combines both absorption agnostic and absorption selected searches, enabling a robust characterization of gas in galaxies at projected separations $D \lesssim 20$ kpc. The GOTOQ emission line ratios indicate that their host galaxies are predominantly normal, star forming disks with typical dust extinctions of $A_V \approx 0.5$ mag. We measure the MgII covering fraction at $D \lesssim 20$ kpc and find it to be remarkably high, $f_c = 98.2^{+1.3}_{-4.5}$ per cent, indicating that these systems trace gas rich, metal enriched regions at the disk-halo interface. The median colour excess towards the QUASAR line of sight, $E(B-V) = 0.087$, is significantly higher than that of typical MgII absorbers, underscoring the dust rich nature of GOTOQ sightlines. From a high signal to noise composite spectrum, we report the first statistical detection of the diffuse interstellar band at $λ4428$ ($W_r = 0.055 \pm 0.011$ angstrom) and at $λ5780$ ($W_r = 0.051\pm 0.012$ angstrom), revealing the presence of complex organic molecules at the disk halo interface. This catalogue provides a powerful reference sample for future multi wavelength studies of gas flows, cold gas, and dust evolution in the inner circumgalactic medium.
[abstract 18 / 32] (score: 2) - Title: Asymptotic scaling theory of electrostatic turbulent transport in MAGNETised fusion plasmasAuthors: T. Adkins, I. G. Abel, M. Barnes, S. Buller, W. Dorland, P. G. Ivanov, R. Meyrand, F. I. Parra, R. Nies, A. A. Schekochihin, J. Squire,Comments: 42 pages, 22 figuresSubjects: physics.plasm-phCreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
Turbulent transport remains one of the principal obstacles to achieving efficient MAGNETic confinement in fusion devices. Two of the dominant drivers of the turbulence are microscale instabilities fuelled by electron- and ion-temperature gradients (ETG and ITG), whose nonlinear saturation determines the cross-field transport of particles and energy. We present a simple asymptotic scaling theory that unifies ETG- and ITG-driven turbulence within a common framework. By balancing the fundamental time scales of linear free energy injection, nonlinear decorrelation, and parallel propagation, the theory isolates the dependence of the heat flux on equilibrium parameters to two key quantities: the parallel system scale and the outer-scale aspect ratio. We show that these quantities encapsulate the essential physics of saturation, leading to distinct predictions for ETG and ITG transport: a cubic scaling with the temperature gradient in the electron channel, and a linear scaling in the ion channel, the latter recovering the ITG scaling recently proposed and numerically verified in axisymmetric geometry by Nies et al. [Phys. Rev. Res. 8, 013295 (2026)]. Extensive nonlinear gyrokinetic simulations confirm that these theoretical predictions in fact hold irrespective of the MAGNETic geometry (slab, tokamak, or stellarator), including the first numerical confirmation of the cubic ETG scaling anticipated by earlier studies. Our theory depends only on the parallel system scale and the outer-scale aspect ratio, and hence provides a physics-based foundation for fast, geometry-aware transport models, offering a pathway toward reactor optimisation in both tokamaks and stellarators.
[abstract 19 / 32] (score: 2) - Title: Probing Dark Matter Halos of High-redshift Quasars via Wide-Field ClusteringAuthors: Hao Meng, Guangping Ye, Huanian Zhang,Comments: 6 figures and 3 tables, resubmittedSubjects: astro-ph.GACreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
High-redshift QUASARs are powerful tracers of both astrophysical processes and large-scale structure in the early Universe. Using a sample of 1,251 spectroscopically confirmed QUASARs and 827 highly reliable photometric QUASAR candidates selected with a machine-learning framework, all at $4.7 \leq z < 6.3$ (excluding $5.4 < z < 5.6$) and with a median luminosity of $M_{1450}\sim -25.5$, we investigate the large-scale environments of QUASARs near the end of cosmic reionization. We measure the projected auto-correlation function of the QUASAR population and derive bias parameters of $b=22.11^{+2.17}_{-2.19}$ and $28.55^{+5.76}_{-5.75}$ for the redshift intervals $4.7\leq z<5.4$ and $5.6\leq z<6.3$, respectively. These correspond to characteristic DARK MATTER halo masses of $\log(M_{ h}/M_\odot)=12.66^{+0.10}_{-0.11}$ and $12.62^{+0.21}_{-0.21}$, respectively. We further estimate QUASAR duty cycles of $0.011^{+0.017}_{-0.007}$ and $0.012^{+0.104}_{-0.011}$ for the two redshift bins. These measurements are consistent with previous studies and the observed $f_{\rm duty}$--$M_{\rm halo}$ relation, indicating that only a small fraction of suitable DARK MATTER halos host optically luminous QUASARs at any given time. The inferred low duty cycles suggest that a substantial fraction of supermassive BLACK HOLE growth may occur during obscured accretion phases. Our results provide new constraints on the connection between high-redshift QUASARs and their host DARK MATTER halos, offering valuable insights into the co-evolution of supermassive BLACK HOLEs and large-scale structure in the early Universe.
[abstract 20 / 32] (score: 2) - Title: Filling The Pockets: The Spherical Nature of 3D Deflagration in Thermonuclear SupernovaeAuthors: S. Shiber, P. Hoeflich, T. Mera, E. Fereidouni, Z. Levy, D. Maci, C. Ashall, E. Baron, M. Shahbandeh, K. Medler, W. B. Hoogendam, C. M. Pfeffer,Comments: 13 pages, 5 figures, 1 table. Published in ApjLSubjects: astro-ph.SR astro-ph.HECreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We investigate thermonuclear explosions within the delayed detonation framework. While spherical delayed detonation models generally reproduce key observational features, a fundamental inconsistency emerges in three dimensions: 3D hydrodynamic simulations exhibit insufficient white dwarf expansion during the deflagration phase. We identify the early deflagration stage, when the burning is dominated by the laminar speed, as a critical phase and explore potential solutions using three-dimensional MAGNETohydrodynamic simulations performed with the FLASH code. In absence of preexisting small-scale velocity fields, hydrodynamical simulations of the early deflagration phase produce large pockets of unburned C/O, leading to inefficient burning. Much of the released energy is deposited into buoyantly rising plumes rather than into the global preexpansion of the white dwarf, which is required to produce the partially burned layers characteristic of SNe Ia. In contrast, when preexisting turbulent velocity fields on scales expected from the smoldering phase are included, the entrainment of burned material into unburned pockets enables the conductive ignition of the surrounding unburned fuel. The effective burning approaches that in spherical models, addressing a long-standing problem in multidimensional deflagration models. For MAGNETic fields considered here, < 1% of the saturation strength, we find that the effective burning rate is dominated by the turbulence. Magnetic fields only marginally suppress the rising of burned plumes and the formation of small structures, leading to a slightly more confined burning region and a reduced burning rate.
[abstract 21 / 32] (score: 2) - Title: A special exact class of three-dimensional equilibria of a MAGNETized plasma exhibiting closed and nested toroidal MAGNETic surfacesAuthors: D. A. Kaltsas, A. I. Kuiroukidis, G. N. Throumoulopoulos,Comments:Subjects: physics.plasm-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We construct a special class of three-dimensional (3D) equilibria with pressure anisotropy which showcase closed, nested toroidal MAGNETic surfaces that are strongly asymmetric in the toroidal direction by applying a sinusoidal perturbation to the axisymmetric Solov'ev equilibrium. They also exhibit distinct closed and nested current-density surfaces. For certain values of the free parameters involved, the perturbations lead to the formation of MAGNETic islands and stochastic areas in the outer plasma region, while well-defined MAGNETic surfaces persist in the inner region. In addition, it is demonstrated that the existence of closed and nested surfaces within the plasma region on which the MAGNETic field modulus is uniform (isoMAGNETic surfaces) is neither necessary nor sufficient for the existence of respective closed and nested MAGNETic surfaces.
[abstract 22 / 32] (score: 2) - Title: Probing Baryonic Feedback Effect with CSST Weak Lensing and Future FRB MeasurementsAuthors: Shuai Feng, Yan Gong, Qi Xiong, Xiaohui Liu, Hengjie Lin, Dingao Hu, Xuelei Chen,Comments: 16 pages, 9 figures, 1 table. Accepted for publication in ApJSubjects: astro-ph.COCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We explore the joint probe on the baryonic feedback effect using the weak lensing measurement from the upcoming Chinese Space-station Survey Telescope (CSST) photometric survey and the dispersion measure (DM) statistics of the fast radio bursts (FRBs) from next-generation radio telescopes, i.e., the Square Kilometre Array (SKA) and the Deep Synoptic Array (DSA-2000). By employing the baryonic halo model, we compute the matter, electron, and matter--electron power spectra, and generate mock data considering realistic noise and systematic effects based on the designs of the telescopes. These mock data are then analyzed using the Markov Chain Monte Carlo (MCMC) method to investigate the parameter constraints. We find that CSST weak lensing alone can constrain the baryonic feedback parameter $\log_{10} T_{\text{AGN}}$ to an accuracy of $3.1\%$, with the sum of neutrino mass bound $\sum m_ν < 0.53\,\mathrm{eV}$. When performing the $3\times2 \,\mathrm{pt}(e,\mathrm{m})$ analysis, the inclusion of FRB DM measurements can significantly improve the precision of $\log_{10} T_{\text{AGN}}$ to $0.4\%$, and will lead to a better constraint on $\sum m_ν$ with an upper limit $< 0.47\,\mathrm{eV}$ by effectively breaking the degeneracy. Our results demonstrate that the joint observation of future FRB DM and weak lensing surveys is a powerful tool for probing the baryonic feedback effect, which is helpful in obtaining robust constraints on the neutrino mass and other important cosmological parameters.
[abstract 23 / 32] (score: 2) - Title: The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. V. When Galaxies Glow with IndustryAuthors: Olivia Curtis, Aidan J. Rowland, Jason T. Wright, Caryl Gronwall, Jakob M. Helton, Joel Leja,Comments: 34 pages, 16 figures, 4 tables, submitted to ApJSubjects: astro-ph.GACreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
We present the most robust stellar population synthesis (SPS)-based search for galaxy-spanning technological waste heat to date, applied to 129 nearby galaxies spanning a wide range of spectral energy distribution (SED) types, including ultraluminous IR galaxies and MIR-luminous ACTIVE GALACTIC NUCLEi (AGN). We incorporate the AGENT Dyson sphere formalism into the Flexible Stellar Population Synthesis code at the stellar population level, so nebular and dust emission respond self-consistently to Dyson sphere reprocessing. With \texttt{Prospector}, we perform a suite of 1,419 injection recovery tests across a range of covering fractions, $α$, where we successfully recover the injected covering fractions (best-fit slope $m = 0.92$) and detect them through Bayesian model selection down to $α\sim 4$--$5\%$ in quiescent galaxies. None of our 129 galaxies prefer a Dyson sphere component, and we place the first per-galaxy 95\% upper limits on warm ($T_{\rm BB} \gtrsim 100$K) swarms, reaching a median $α< 0.3\%$ across quiescent hosts without a dominant AGN. Our injection-calibrated detection rates convert these zero detections into a population bound of $<2.6\%$ of galaxies hosting $α= 25\%$ swarms ($95\%$ confidence). Because survey colors cannot separate waste heat from starbursts and AGN, we develop a scaffold for future searches, running from inexpensive archival screens such as the Balmer decrement and the stellar-to-dynamical-mass offset a swarm leaves behind, through resolved fitting with nuclear excision, to PRIMA FIR photometry that makes targeted JWST imaging decisive. We find that the outskirts of quiescent galaxies are the best hunting grounds for future technosignature searches.
[abstract 24 / 32] (score: 2) - Title: Why is GN-z11 Bright, Compact, and Nitrogen Enhanced? Insights from UV Absorption and Emission DiagnosticsAuthors: Minami Nakane, Masami Ouchi,Comments: 22 pages, 11 figures, submitted to ApJSubjects: astro-ph.GACreated: 2026-08-12; Updated: 2026-08-14; Datestamp: 2026-08-14
We investigate the UV spectrum of GN-z11, a luminous, compact galaxy with strong nitrogen lines, at $z=10.60$, using deep JWST/NIRSpec high-resolution IFU and medium-resolution MSA spectra assembled from the JADES, SPURS, and GO programs. After optimized reduction and extraction of the IFU data including an evaluation of statistical and systematic uncertainties, we obtain mutually consistent spectra from the high- and medium-resolution observations. After carefully accounting for the data quality limitations, we identify prominent P-Cygni profiles in NV$λ\lambda1238,1243$, SiIV$λ\lambda1394,1403$, and CIV$λ\lambda1548,1550$, together with broad NIV]$λ\lambda1483,1486$ emission (FWHM $\sim1600$ km s$^{-1}$). The P-Cygni profiles resemble those of massive stars such as O-type stars and luminous blue variables (LBVs), while the broad NIV] emission resembles that of nitrogen-sequence Wolf-Rayet (WN) stars. We fit stellar and ACTIVE GALACTIC NUCLEi (AGN) UV spectral models and find that the stellar models are strongly preferred over the AGN models ($Δ$WAIC $=-25$), with the preference driven primarily by the NV P-Cygni profile. These results indicate that the luminous, compact UV continuum of GN-z11 is dominated by massive stars. We derive electron densities from CIII]$λ\lambda1907,1909$, NIII]$λ\lambda1747-1754$, and NIV], with the nitrogen diagnostics extending well beyond the CIII]-based limit and reaching densities of $\gtrsim10^{6.5}$ cm$^{-3}$ for NIV], indicating physically distinct carbon- and nitrogen-emitting nebular components. These findings suggest that the apparent nitrogen enhancement inferred for GN-z11 as a whole may arise when strong narrow nitrogen emission originates from dense gas locally enriched in nitrogen by WN stellar winds and photoionized by nearby massive stars within the same star-forming region.
[abstract 25 / 32] (score: 2) - Title: Infrared imaging of thermally-driven JETs and eddies in planetary-style laboratory turbulenceAuthors: Cy S. David, Remy Monville, Daphne Lemasquerier, Lvcian Vltava, Jonathan M. Aurnou,Comments:Subjects: physics.flu-dynCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
This paper is associated with a poster winner of a 2025 American Physical Society's Division of Fluid Dynamics (DFD) Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available online at the Gallery of Fluid Motion, at https://doi.org/10.1103/APS.DFD.2025.GFM.P012
[abstract 26 / 32] (score: 2) - Title: Elemental Composition Evolution during the 2024 September 30 Solar Eruption: A Comparison of Hot and Cool Plasma Components with Solar Orbiter/SPICE, Hinode/EIS, and Chandrayaan-2/XSMAuthors: Momchil Molnar, Joseph Plowman, Amir Caspi, Ritesh Patel, Arpit Shrivastav, Tania Varesano, Don Hassler, Ryan French, Biswajit Mondal, L. P. Chitta,Comments: Accepted in the Astrophysical JournalSubjects: astro-ph.SRCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
Solar plasma composition differs between the photosphere and corona over a range of timescales, with preferential enhancement of elements with low first ionization potential (FIP). However, the physical origin of the FIP fractionation remains incompletely understood. Furthermore, during flares, the FIP bias also exhibits rapid changes, associated with fast transport of material with different FIP biases. We present novel observations from Solar Orbiter SPICE and EUI, Hinode/EIS, and Chandrayaan-2 XSM instruments, finding rapid abundance changes in the emitting plasma, on timescales of minutes, during the eruptive M7.6-class solar flare observed on 2024 Sept 30. These instruments have wide temperature coverage and find contrasting abundance-evolution patterns between the hotter and cooler plasma components. 3D reconstruction of the active region and additional observations from the Solar Orbiter STIX X-ray telescope show how the hot and cool plasma components, emitting in different spectral regions and observed with the various instruments, sample the plasma composition evolution in distinct locations within the observed flaring plasma. The bright post-flare loop tops observed by SPICE show coronal FIP bias, while the hot plasma observed with XSM exhibits FIP-bias decreasing from coronal to photospheric during the impulsive phase. We interpret these observations as evidence of the X-ray diagnostics seeing hot coronal RECONNECTion outflows mixing with chromospheric plasma as flare loops sequentially energize and relax, explaining why the FIP bias decreases from coronal to a hybrid; and the cool loop tops seen with SPICE show coronal abundances due to coronal material deposited near the looptops.
[abstract 27 / 32] (score: 2) - Title: Time-Domain Benchmark Solutions for Bernstein WavesAuthors: M. Pelkner, K. Hallatschek,Comments:Subjects: physics.plasm-phCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
In previous work, we introduced a semi-analytical method for computing time-domain solutions of linearized Vlasov problems. Rather than representing the plasma response as a sum of residues associated with Landau poles, the method constructs a regularized frequency-domain response spectrum that is subsequently inverted numerically. Explicit applications have so far been limited to unMAGNETized plasmas. In this work, we extend the construction to plasmas with a uniform background MAGNETic field and a Maxwellian equilibrium distribution. We apply the resulting formulation to the electrostatic ion-Bernstein density response of a plasma with kinetic ions and adiabatic electrons, and provide error estimates for truncating both the spectral integration domain and the cyclotron-harmonic expansion. The solution serves as a time-domain reference for damped finite-$k_\parallel$ regimes, in which dispersion-relation roots alone are insufficient for pointwise-in-time verification of simulation codes. Finally, we indicate how the framework can be extended to fully electroMAGNETic problems.
[abstract 28 / 32] (score: 2) - Title: Complex Energy-Dependent Behaviour of Quasi-Periodic Oscillation Observed in GRS 1915+105Authors: Vaibhav Sharma, Ranjeev Misra, V. Jithesh, Shivani Chaudhary, Khushi Jirawala, J S Yadav, Pankaj Jain, N J Juris,Comments: 13 pages, 10 figures, accepted for publication in the Astrophysical JournalSubjects: astro-ph.HECreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We present complex energy-resolved properties of quasi-periodic oscillations (QPOs) in the BLACK HOLE X-ray binary GRS 1915+105 using an observation from the LAXPC instrument onboard AstroSat. Power density spectra (PDSs) are constructed in multiple energy bands and modeled with multi-Lorentzian components to investigate the energy dependence of QPO properties. The QPO frequency shows a modest increase with energy. Dynamic PDS analysis does not reveal clear evidence for time-dependent evolution of the QPO frequency, suggesting that the observed frequency shift is not primarily driven by temporal variability. We perform simultaneous fitting of energy-resolved PDSs and find that a model in which the QPO feature is described by two Lorentzian components provides a better fit. The two components exhibit different evolution in fractional root mean square amplitude as a function of energy. We further examine the phase-lag properties by simultaneously modeling the PDS and the real and imaginary parts of the cross-spectrum and find distinct phase-lag behavior for the two components. Overall, these results indicate that the apparent energy-dependent evolution of the QPO feature may be a result of the presence of more than one variability component.
[abstract 29 / 32] (score: 2) - Title: Differential Obstructions to Curvature-Dependent Conformal TransformationsAuthors: David S. Pereira, Francisco S. N. Lobo, José Pedro Mimoso,Comments: 25 pages, 1 figureSubjects: gr-qcCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
Curvature-dependent conformal rules are local forward assignments on known metrics, but they are not generically local changes of metric variables. We study the nondegenerate class $\widetilde g_{μν}=F(R[g])g_{μν}$, with $F>0$ and $F_R\neq0$. Introducing an independent auxiliary scalar localizes the forward map, while recovering the original metric requires a differential constraint. The complete inverse metric tangent map contains the nonpolynomial projector $ξ^μξ^ν/ξ^2$; hence no differentiable finite-JET inverse, i.e., a formula involving only finitely many derivatives at the same point, exists on an open set of unrestricted metrics. Branchwise functional inverses may nevertheless exist after boundary or Cauchy data are specified. Metric $f(R)$ gravity gives an explicit realization: its local Einstein-frame scalar--tensor representation is a parent theory, whereas a metric-only Einstein-side description requires a differential section governed by a normal operator. We derive the pulled-back classical Hessian and its off-shell embedding term, and in the quadratic model show how constrained Gaussian elimination produces the scalaron nonlocal kernel, the corresponding normal determinant for the displayed measure, and the zero-mode compatibility condition. Exact parent and metric solutions remain equivalent; the obstruction concerns locality and the off-shell variational and fluctuation domains. These results provide a precise framework for assessing curvature-dependent frame transformations in modified gravity and clarify their implications for effective actions, semiclassical analyses, and quantum frame equivalence.
[abstract 30 / 32] (score: 2) - Title: Radio Properties of Narrow-Line and Broad-Line Seyfert 1 GalaxiesAuthors: K. É. Gabányi, S. Komossa, A. Mezősi, E. Forgács-Dajka, S. Frey,Comments: 33 pages, 13 figures, 11 tables. Published in GalaxiesSubjects: astro-ph.GACreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
Narrow-line Seyfert 1 (NLS1) galaxies host ACTIVE GALACTIC NUCLEi (AGN) with narrow optical emission lines of the broad-line region. This is often explained with a relatively lower mass of the central supermassive BLACK HOLE and super-Eddington accretion. We compared the radio properties of large samples of NLS1 and broad-line Seyfert 1 (BLS1) galaxies compiled from the Sloan Digital Sky Survey. We cross-matched the NLS1 and BLS1 samples with the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) sky survey at 1.4 GHz and the first and second epoch data of the Very Large Array Sky Survey (VLASS) at 3 GHz. We calculated the radio spectral indices, the 1.4-GHz radio power, and the radio loudness. We found lower 1.4-GHz radio detection rates for the NLS1 galaxies. The median radio loudness values, the fraction of radio-loud AGN, and the median 1.4-GHz radio power are also lower for the NLS1 sample. The median spectral indices imply a slightly steeper radio spectrum for the NLS1 sample than for the BLS1 sample. Comparison of the STAR FORMATION rates estimated from the radio data and the infrared measurements of the Wide-field Infrared Survey Explorer satellite indicated that more than half of the FIRST- and VLASS-detected NLS1 and BLS1 galaxies contain radio-emitting AGN.
[abstract 31 / 32] (score: 2) - Title: Radio Monitoring of Classical Novae using the ASKAP Variable and Slow Transients SurveyAuthors: Aishani Majumder, David L. Kaplan, Laura N. Driessen, Ashna Gulati, Tara Murphy, Dougal Dobie,Comments:Subjects: astro-ph.HE astro-ph.SRCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We present a search for radio emission from classical novae at 887.5 MHz using data from the Australian SKA Pathfinder Variable And Slow Transient (VAST) survey. We cross-matched 43 optically discovered classical novae that erupted between 2021 September and 2025 November within the 1200-square-degree Galactic survey footprint, and found three which show significant radio emission: V6598 Sgr, V1716 Sco, and V1723 Sco. To analyse their radio light curves, we use both thermal free-free and non-thermal SYNCHROTRON emission models. We fit the data using the Markov chain Monte Carlo (MCMC) method to constrain parameters, including the ejected mass and ejecta velocities for the thermal models, and mass-loss rate, explosion energy, wind velocity, and filling factor for the non-thermal model. All three novae show evidence of non-thermal SYNCHROTRON emission as the dominant emission mechanism at this frequency. We use a broken power law to describe the radial density structure of a non-uniform circumbinary material, which provides a better fit than a standard wind density profile. This strong early-time SYNCHROTRON emission is strong evidence of shock-driven particle acceleration, which may be related to detections of gamma-rays from all three novae as well. In contrast to earlier studies that used multi-frequency data to distinguish between emission models, our analysis is based on single-frequency radio light curves, which can still provide useful constraints on the dominant emission mechanism when interpreted with physically motivated models
[abstract 32 / 32] (score: 2) - Title: Air-water cavity in multi-plunging JET impactsAuthors: Narendra Dev, Hèléne Scolan, J. John Soundar Jerome, Jean-Philippe Matas,Comments: 14 pages, 10 figures, accepted for publication in JFMSubjects: physics.flu-dynCreated: 2026-08-13; Updated: 2026-08-14; Datestamp: 2026-08-14
We report the formation of an original dome-shaped air-water cavity at the impact site of closely-packed plunging water JETs. The injector assembly consists of concentric rings of circular JETs, similar to a shower-head configuration. We infer from high-speed imaging, LASER-induced fluorescence, and optical phase detection probes that the cavity consists of multiple stems and sheets of air that stretch, retract and pinch off to produce bubbles. We also illustrate various bubble production mechanisms in the cavity, along with coalescence and bubble breakup scenarios in the subsequent bubble cloud. Thereby, we describe the wide range of bubble sizes generated by such JETs, from a few micrometers up to about $5$~mm. Measurements of the cavity size are carried out for varying impact velocity, number of JETs, and JET spacing. We propose that this distinctive air-water cavity is generated by liquid entrainment when successive rings of plunging JETs progressively mix with the pool water.
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