Current date: 2026-06-29
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Number of records retrieved: 157
Keyword score statistics
score 11 -- 1 abstracts
score 8 -- 3 abstracts
score 5 -- 1 abstracts
score 4 -- 1 abstracts
score 3 -- 3 abstracts
score 2 -- 8 abstracts
in total -- 17 abstracts
Articles that appeared on 2026-06-29
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[abstract 1 / 17] Wow! (score: 11)
- Title: Exploring the physics behind the observed MAGNETic filaments in large scale RADIO GALAXiesAuthors: Christian M. Fromm, Matthias Kadler, Karl Mannheim,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Recent low-frequency MeerKAT observations of RADIO GALAXies have revealed an unexpected population of thin, highly collimated SYNCHROTRON threads, whose numbers continue to grow with increasing survey depth and sensitivity. These intricate structures display a remarkable diversity of morphologies -- appearing as narrow filaments linking JETs and lobes, as well as ring- or ribbon-like features embedded within the JETs and radio lobes. Despite their ubiquity, the physical origin and stability of these collimated SYNCHROTRON threads remain poorly understood. Proposed mechanisms include shock compression and interactions with the MAGNETo-ionic intracluster medium, MAGNETic flux tube formation, and RECONNECTion-driven MAGNETic filaments. In this work, we investigate the formation and evolution of such MAGNETic filaments using three-dimensional, two-temperature general RELATIVISTIC MAGNETohydrodynamic (GRMHD) simulations of realistically launched JETs from supermassive BLACK HOLEs. From these simulations, we compute synthetic SYNCHROTRON emission maps and polarisation signatures, allowing us to predict the observable characteristics including morphology, brightness profiles, and polarisation patterns. Finally, we assess the detectability and diagnostic potential of these signatures with the Square Kilometre Array Observatory (SKAO), outlining how upcoming SKA observations can distinguish between competing physical models and illuminate the MAGNETic origin of the collimated SYNCHROTRON threads revealed by MeerKAT observations.
[abstract 2 / 17] Wow! (score: 8) - Title: Discriminating BLAZAR emission models with high-energy polarimetry: Multi-band predictions and detectabilityAuthors: Sara Capecchiacci, Ioannis Liodakis, Haocheng Zhang, Michela Negro, Jorge Otero-Santos,Comments:Subjects: astro-ph.HECreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Polarimetric properties of BLAZARs provide key constraints on the acceleration mechanisms powering their RELATIVISTIC JETs, the high-energy emission processes involved, and the composition of the JET itself. We present a multi-band polarimetric study spanning from soft X-rays to gamma-ray energies, considering several bands for current and future missions (0.275 keV, 2-8 keV, 0.5-10 keV, 6-35 keV, 0.2-5 MeV, and 1-100 GeV). Our sample is drawn from the RoboPol monitoring programme, a statistically complete gamma-ray sample including low-, intermediate-, and high-SYNCHROTRON-peaked BLAZARs. Using spectral energy distribution fitting performed with the BJET_MCMC tool, we give predictions on the flux expected for each source in the selected energy bands. We model the polarimetric signatures under three competing emission scenarios: leptonic, hadronic, and hybrid. The detectability of each source was assessed by accounting for the instruments' minimum detectable polarisation (MDP) and by computing the probability of the detection in a blind survey. We show that simultaneous multi-wavelength observations can effectively discriminate between competing emission models due to the difference in the expected polarisation degree. Finally, we derive sensitivity requirements for future gamma-ray polarimetric missions aimed at increasing the number of detectable sources.
[abstract 3 / 17] Wow! (score: 8) - Title: A hidden ultra-RELATIVISTIC spine in the JET of a neutrino-associated BLAZARAuthors: Y. Y. Kovalev, F. Eppel, D. C. Homan, A. V. Plavin, P. Benke, A. K. Erkenov, J. L. Gomez, M. Kadler, K. I. Kellermann, P. I. Kivokurtseva, Yu. A. Kovalev, M. L. Lister, V. A. Makeev, A. V. Popkov, A. B. Pushkarev, E. Ros, T. Savolainen, Yu. V. Sotnikova, S. V. Troitsky,Comments: submitted; comments are welcomeSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Supermassive BLACK HOLEs launch powerful JETs of plasma that can accelerate particles to extreme energies, but the physical conditions required to produce high-energy neutrinos remain unknown. In the BLAZAR TXS 0506+056, the first source individually linked to a high-energy neutrino, radio images had seemed to reveal a JET too slow to sustain the extreme conditions required for neutrino production. Here we resolve this tension using long-term radio monitoring, particularly Very Long Baseline Interferometry (VLBI) imaging. We uncover a disturbance in emission propagating with an apparent speed of 21+-1 times the speed of light, that is masked by slower, radio-bright features that dominated earlier analyses. We interpret this as the signature of a stratified JET: an ultra-RELATIVISTIC spine with Lorentz factor Gamma>20 embedded within a slower outer sheath. As the disturbance travels along the spine, it progressively illuminates the sheath, producing the delayed radio flare and naturally accounting for the years-long offset between neutrino and radio emission. The same pattern recurs in a second neutrino-associated event, pointing to a repeatable multi-messenger engine. These findings challenge the standard interpretation of VLBI JET speeds and establish a concrete, testable framework connecting structured JETs to the sources of the Universe's highest-energy neutrinos.
[abstract 4 / 17] Wow! (score: 8) - Title: Parsec-scale polarimetry and kinematics of a spine-sheath JET in the neutrino-BLAZAR TXS 0506+056Authors: F. Eppel, P. Benke, C. Degli Agosti, J. L. Gómez, D. C. Homan, M. Kadler, Y. Y. Kovalev, M. L. Lister, V. A. Makeev, A. V. Plavin, A. B. Pushkarev, E. Ros, T. Savolainen,Comments: 13 pages, 8 figures, submitted to A&ASubjects: astro-ph.HECreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
In 2017, the BLAZAR TXS 0506+056 showed a remarkable gamma-ray outburst simultaneously with a high-energy neutrino detection by IceCube from the same sky region. The significance of this association was found to be on the order of 3 sigma thus providing a strong link between the neutrino emission and the BLAZAR flare. The high-energy flare in TXS 0506+056 was followed by a delayed radio flare, peaking in $\sim2020$ in the aftermath of the neutrino event. We investigate the parsec-scale JET structure and dynamics of TXS 0506+056 using 15 GHz full-POLARIZATION VLBI observations obtained between 2009 and 2025 with the Very Long Baseline Array. Our kinematic analysis reveals moderate superluminal JET speeds of $\sim(1-2)$c and two quasi-stationary components. A new JET component with comparable speed was ejected contemporaneously with the 2017 IceCube neutrino event. The stacked POLARIZATION map is consistent with a stratified spine-sheath JET structure: an inner spine with EVPA aligned with the JET, surrounded by a sheath layer with perpendicular EVPA. Variability in total intensity and POLARIZATION further indicates interaction between these layers, particularly evident in characteristic linear POLARIZATION flares, associated with EVPA rotations of the quasi-stationary components. The multi-layered JET configuration is consistent with previous studies that were able to explain the neutrino emission in this TXS 0506+056 through a spine-sheath JET structure. We suggest that TXS 0506+056 represents an archetypal case and that similar POLARIZATION signatures and geometric light curve flares may be present in other neutrino-emitting sources, potentially offering a solution to the Doppler-crisis phenomenon observed in TeV-emitting BLAZARs.
[abstract 5 / 17] Yes (score: 5) - Title: Gamma-ray Bursts in the Radio Sky: the Role of the SKA-VLBIAuthors: Stefano Giarratana, Om Sharan Salafia, Xue-Feng Wu, Jin-Jun Geng, Tao An, Benito Marcote, Marcello Giroletti, Giancarlo Ghirlanda, Tiziana Venturi,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no: AASKAII/Giarratana01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.HECreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Radio observations of $γ$-ray bursts (GRBs) employing the very long baseline interferometry (VLBI) technique provide us with fundamental information on the dynamics and the geometry of the GRB blast wave. With its high angular resolution ($\sim$milli-arcsecond), VLBI allows us to measure the apparent superluminal expansion, to characterise the structure of the JET and to constrain the viewing angle and JET opening angle. While this information is crucial to understand these transient events, such studies have been possible only for three GRBs to date, owing to both the poor sensitivity of current radio facilities and the paucity of close and bright GRBs. In this chapter, we estimate the impact that the SKA-Mid will have on these studies, when included in a VLBI network. We performed a series of dedicated simulations of VLBI observations of GRBs, considering five VLBI networks and the SKA-Mid, both in its AA* and AA4 configurations. We show that including the SKA-Mid in a global-VLBI experiment will: (i) allow us to measure the size and the expansion of a GRB up to a redshift $z\simeq 0.25$ (at a confidence level of $3σ$); (ii) constrain the size $\gtrsim$2 times better than the current global-VLBI array; (iii) improve the localisation precision in Declination from 4 to 30 times; (iv) detect the apparent proper motion of GRBs seen slightly off-axis with a confidence level 3 times better than current VLBI networks. Ultimately, the SKA-Mid will open a new window on a portion of the GRB population that has been inaccessible so far.
[abstract 6 / 17] Yes (score: 4) - Title: The Astrophysics of Fast Radio BurstsAuthors: Alice P. Curtin, Marcin Gawroński, Jason Hessels, Clancy James, Fabian Jankowski, Franz Kirsten, Benito Marcote, Harry Qiu, Robert Reischke, Mawson W. Sammons, Laura G. Spitler, Ben Stappers, Amanda Weltman, The SKA Transients SWG,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Curtin01Subjects: astro-ph.HE astro-ph.COCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Fast radio bursts (FRBs) provide a glimpse of high-energy astrophysical phenomena in other galaxies. They point the way to extreme conditions that are currently undetectable by any other known means. These coherent radio flashes have timescales of microseconds to milliseconds, and inferred energies that are comparable to those of the most extreme bursts seen from Galactic neutron stars. However, the nature of FRB sources remains an open question in astrophysics. Magnetically powered neutron stars known as `MAGNETars' are a leading candidate for explaining the FRB phenomenon, but other plausible progenitors include MAGNETically interacting neutron-star binaries or accreting BLACK HOLEs. The diversity of FRB burst types and their galactic environments hint that multiple mechanisms and progenitor types may be responsible. Here we discuss the ways in which the SKA can uncover the nature of FRBs. In particular, we focus on the key advantages of the SKA: its Southern Hemisphere location and hence overlapping sky coverage with the Vera C. Rubin Observatory, its high sensitivity compared to existing wide-field FRB surveys, its fast search timescales down to tens of $μ$s, and its broad spectral coverage with bands from 50 MHz to 15 GHz. With these capabilities, the SKA will excel in detecting FRB sources across new frequency ranges and timescales. This will aid in a better understanding of the fundamental astrophysics behind FRBs, which will in turn also contribute to their use as cosmological probes, as explored in companion chapters.
[abstract 7 / 17] (score: 3) - Title: Collective modes and screening in an electric-MAGNETic dual plasmaAuthors: Hyeong-Chan Kim,Comments: 13 pages, 4 figuresSubjects: physics.plasm-phCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
We study the linear response of an effective RELATIVISTIC two-fluid medium carrying separately conserved electric and MAGNETic charge currents. The model is defined by the duality-symmetric Maxwell equations with electric and MAGNETic sources, together with Lorentz-force dynamics for two fluids with independent inertia and possible Carter-type entrainment. The MAGNETic component is treated as an effective charge-carrying constituent, so the analysis uses only the closed two-fluid equations. Around a homogeneous, neutral, and unMAGNETized background, the transverse electroMAGNETic response contains two stable branches whose cutoffs are set by the electric and MAGNETic plasma frequencies and are exchanged by electric--MAGNETic duality. In the longitudinal sector, entrainment mixes the electric and MAGNETic density oscillations, turns their crossing into an avoided crossing, and gives the stability condition $ κ^2<1 ,$ equivalent to positive definiteness of the two-fluid momentum matrix. Resolving the MAGNETic component into monopole and antimonopole species gives a neutral branch selected by MAGNETic charge conjugation \(C_m\). In this branch the net MAGNETic current vanishes, so the long-range monopole field is absent, while the total MAGNETic density can still produce screened collective response. The resulting picture is that MAGNETic charge can be statically hidden but dynamically visible. A robust observable signature is the density scaling $ω_{\rm coll}^2\simω_{pm}^2\propto n^0_{(m)},$ which may survive dissipative broadening even when sharp ideal-plasma poles are not resolved. We briefly comment on possible dyonic interpretations of MAGNETically neutral composites, but the linear-response results do not rely on that interpretation.
[abstract 8 / 17] (score: 3) - Title: Sawtooth suppression by flux pumping on HBT-EPAuthors: Boting Li, J. P. Levesque, G. A. Navratil, M. E. Mauel,Comments:Subjects: physics.plasm-phCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
This study examines the mechanisms underlying sawtooth suppression in the High Beta Tokamak-Extended Pulse (HBT-EP) device. It is observed that strong-intensity sawtooth activities correlate with reduced-amplitude MHD edge modes which are identified as $m/n=3/1$ external kink modes (XK), while sawtooth suppression correlates with larger and saturated edge mode amplitudes. To further investigate these correlations, the plasma-wall coupling was manipulated by adjusting the positions of the conducting walls in HBT-EP. It was found that strong sawtooth events occur when the normalized wall radius $b/a$ is within a critical value. This implies that the plasma-wall distance must be sufficiently small to ensure effective stabilization of the edge mode. Even slight differences in major radius result in significantly different discharge styles, categorized as ``sawtoothing discharges'' and ``sawtooth-suppressed discharges'' respectively. Through a series of mode structure analyses, we confirm the coexistence and coupling of the $m/n=1/1$ helical core (HC), $m/n=2/1$ tearing mode (TM), and $m/n=3/1$ XK during sawtooth suppression, and that this coupling induces anomalous current broadening. Based on these findings, we conclude that sawtooth suppression in the HBT-EP tokamak is consistent with the process of MAGNETic flux pumping.
[abstract 9 / 17] (score: 3) - Title: JWST Reveals Compact Nuclear Starbursts Masquerading as AGNs in Metal-Poor Dwarfs: Where Are the Accreting Intermediate-Mass Black Holes?Authors: William Matzko, Shobita Satyapal, Jeffrey D. Mckaig, Sara Doan, Michael McDonald, Archana Aravindan, Gabriela Canalizo, Jenna M. Cann, Nicholas P. Abel, Omkar Bait, Laura Blecha, Torsten Böker, Thomas Bohn, Jacqueline Fischer, Stephanie LaMassa, Suzanne C. Madden, Mallory Molina, Barry Rothberg, D. Schaerer, Anil Seth, Remington O. Sexton, .,Comments: Comments welcomeSubjects: astro-ph.GACreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
We present JWST/NIRSpec spectroscopy of the low-mass, metal-poor galaxy SDSS~J160135.95+311353.7 (J1601), selected for its extreme mid-infrared colors and compact nuclear emission, placing it within widely used WISE color diagnostics for ACTIVE GALACTIC NUCLEi (AGNs). Despite this selection, we find no evidence for coronal lines, X-ray emission, or variability typically associated with accretion activity. We compare J1601 to SDSS~J120122.30+021108.3 (J1201), a similar but lower-mass, more metal-poor system studied previously (Doan, 2025). Both galaxies host compact nuclear starbursts but differ in their stellar populations and dust properties: J1601 shows CO bandhead absorption indicative of red supergiants, weak nuclear Wolf--Rayet features, and a circumnuclear PAH ring, consistent with a more developed recent starburst, while J1201 is more dust-enshrouded and chemically primitive. Despite these differences, neither system shows evidence for AGN activity, indicating that the absence of accretion is not simply due to evolutionary timing. Photoionization models show that the weakness of high-ionization emission cannot be explained by low metallicity alone, implying a genuine deficit of hard ionizing photons. Crucially, the red mid-infrared colors in both systems originate from compact, unresolved nuclear emission confined to the nuclear star cluster. These results demonstrate that compact nuclear starbursts can mimic AGN-like mid-infrared colors without accretion, and that commonly used AGN diagnostics may not uniquely identify accreting BLACK HOLEs in metal-poor dwarf galaxies. Our findings suggest that such systems may not provide the conditions required for efficient BLACK HOLE growth and/or may lie near or below the regime where BLACK HOLE seeds can form.
[abstract 10 / 17] (score: 2) - Title: Distinguishing Kilonovae from Binary Neutron Star and Neutron Star-Black Hole MergersAuthors: Ish Gupta, Yugesh Bhoge, Rahul Kashyap, Mukul Bhattacharya,Comments: 9 pages, 5 figures, 1 table + AppendixSubjects: astro-ph.HE astro-ph.SRCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Kilonovae (KNe) are most informative when accompanied by a gravitational-wave signal, which can help identify the source as a binary neutron star (BNS) or a neutron star-BLACK HOLE (NSBH) merger. However, future events will also be discovered serendipitously or through follow-up of other transients, without a confident identification of the progenitor. We ask whether the KN light curve alone can distinguish between these two progenitor channels. Using simulated BNS and NSBH populations together with semi-analytic light curve models, we compare their post-peak evolution across the optical $ugrizy$ bands, and quantify the separation between the two classes in each band with the area under the receiver-operating-characteristic curve (AUC). BNS and NSBH KNe populate distinct regions of the post-peak decline distribution, with BNS KNe fading faster in every band. The separation is cleanest in the blue $u$ and $g$ bands $5$ days after peak and in the redder $i$ band $10$ days after peak. Within $5$ days of peak, BNS KNe decline by $\gtrsim 6$ ($\gtrsim 4$) mag in $u$ ($g$) bands, whereas NSBH KNe fade by only $\sim 3$ ($\sim 1$) mag. Over $10$ days in $i$, NSBH KNe decline by $\sim 1$--$2$ mag against $\sim 3$--$6$ mag for BNS. We attribute this to the higher opacity of NSBH ejecta, which lengthens the photon-diffusion time and slows the decline in all bands, while a low opacity blue component drives the rapid early peak and decline of BNS KNe. Although the precise overlap is model-dependent, the qualitative separation persists across variations in the astrophysical population, the NS equation of state, and the controlled variation of ejecta model parameters, establishing the post-peak photometric decline as a viable EM-only diagnostic of whether a KN arose from a BNS or an NSBH merger.
[abstract 11 / 17] (score: 2) - Title: Kinetic theory of the Thermal Farley-Buneman Instability in the E-region ionosphereAuthors: Yakov S. Dimant, Meers M. Oppenheim,Comments: 72 pages, 1 figureSubjects: physics.plasm-phCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
This paper develops a fully kinetic linear theory of the thermal Farley-Buneman instability (TFBI) in the E-region ionosphere with unMAGNETized ions. The TFBI combines spatially uniform E-region plasma instabilities, such as the Farley-Buneman instability (FBI), ion thermal instability (ITI), and electron thermal instability (ETI). Similar collision-dominated plasma processes can also occur in the solar and stellar chromospheres, as well as in other planetary atmospheres. For the first time in the theory of the FBI-related processes, the kinetic description of ions includes the driving electric field, resulting in automatic inclusion of the ITI. This analytic theory has produced a comprehensive linear wave dispersion relation. It is remarkable that, similarly to the oversimplified earlier ion-kinetic studies, this much more general kinetic dispersion relation involves only elementary functions and the standard plasma dispersion function (albeit of several different arguments). This new theory is limited to plasma waves with the frequencies of the order, or larger than, the ion-neutral collision frequency. This inherently kinetic frequency range is of importance for accurate interpretation of radar signals scattered from relatively high E-region altitudes, but at altitudes where ions are unMAGNETized (mostly, below 110 km).
[abstract 12 / 17] (score: 2) - Title: Unveiling the Microhertz Gravitational-Wave Sky with the Square Kilometre Array ObservatoryAuthors: Alexander C. Jenkins, Diego Blas, Joshua W. Foster,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Jenkins01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.CO astro-ph.HE astro-ph.IM gr-qcCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
The gravitational-wave sky is expected to contain a rich variety of sources across a very broad range of frequencies. Much like in electroMAGNETic astronomy, exploring new gravitational-wave frequency bands therefore has the potential to unlock powerful new insights into the Universe. In this chapter, we investigate the prospects for using high-precision timing of binary millisecond pulsars with the Square Kilometre Array Observatory (SKAO) to search for gravitational waves in the microhertz ($μ$Hz) frequency band by targeting resonant gravitational-wave perturbations to the orbits of these binaries. Using only a handful of known systems, we show that SKAO observations can achieve unprecedented sensitivity to microhertz gravitational waves, with the potential to detect inspiralling massive BLACK HOLE binaries in this band. These searches are complementary to conventional pulsar timing array analyses, adding a new dimension to the gravitational-wave science achievable with the SKAO.
[abstract 13 / 17] (score: 2) - Title: Too shy to spin? Cosmic wallflowers as proto-globular clustersAuthors: Floor van Donkelaar, Lucio Mayer, Pedro R. Capelo,Comments: 9 pages, submitted to MNRASSubjects: astro-ph.GA astro-ph.HECreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
We investigate the rotational properties of star-forming clusters at $z \sim 7.6$ in the high-resolution simulation MassiveBlackPS, focusing on two formation channels: clusters forming in galactic discs via gravitational instability and isolated circumgalactic systems, referred to as cosmic wallflowers, born out of cosmic filaments. Using stellar kinematics, we compare their rotational velocities, $v_{\rm rot}$, and rotational support, $v/σ$, to study whether formation environment leaves a clear dynamical imprint. We find a clear separation, wherein cosmic wallflowers systematically have lower rotational velocities and span a wide range in $v/σ$, whereas the identified disc clusters are strongly rotation-dominated and extend to higher $v_{\rm rot}$. When combined with stellar surface densities, a subset of the low-$v_{\rm rot}$ cosmic wallflowers lie surprisingly close to the observed globular cluster population in the Milky Way, whereas disc clusters remain offset. Within the cosmic wallflower population, we identify two regimes: lower-density, weakly rotating systems that overlap with these globular cluster properties, and denser, more rotationally supported systems that likely follow a different evolutionary pathway, possibly linking them to the origin of massive BLACK HOLE seeds at high redshift. We further find that the gas content correlates with this behaviour, with gas-rich cosmic wallflowers preferentially occupying this low-rotation regime. This all suggests that environment and baryonic content together play a key role in setting the initial dynamical state and possible fate of clusters. In particular, weakly rotating, gas-rich cosmic wallflowers emerge as natural proto-globular cluster candidates, potentially evolving towards present-day systems through angular momentum loss and dynamical heating.
[abstract 14 / 17] (score: 2) - Title: Massive scalar fields in eccentric regime: Detectability and constraints from LISA observations of extreme mass-ratio inspiralsAuthors: Tieguang Zi, Shailesh Kumar, Jun-Kun Zhao, Bao-Min Gu, Fu-Wen Shu,Comments: 24 pages, 9 figures, 4 tablesSubjects: gr-qc astro-ph.HE hep-thCreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Extreme mass-ratio inspirals (EMRIs) are among the prime sources for future space-borne gravitational wave (GW) observatories and provide a useful setting for testing the presence of fundamental fields and possible deviations from general relativity (GR) in both strong and weak gravity regimes. In this work, we study the effect of a massive scalar field on eccentric equatorial EMRI dynamics around Kerr BLACK HOLEs. Considering that the inspiralling stellar-mass object carries a scalar charge and emits scalar radiation together with tensor GWs, we compute the relevant RELATIVISTIC fluxes within the adiabatic treatment of the inspiral. With the solution of the scalar perturbation equation in the frequency domain, the resulting fluxes are presented through the Chebyshev interpolants in order to have the efficient inspiral evolution across the parameter space considered. We quantify the impact of scalar field mass and scalar charge on the orbital evolution and GW signal through phase shifts and waveform mismatches relative to both GR and the massless-scalar scenario. We find that massive scalar radiation can generate significant GW dephasing that increases with orbital eccentricity; however, the scalar flux is suppressed as the scalar field mass is becoming larger. Using a Fisher information matrix (FIM) analysis, we estimate the ability of Laser Interferometer Space Antenna (LISA) to measure or constrain the scalar charge and scalar field mass. Our results indicate that eccentric EMRIs can place meaningful constraints on massive scalar fields and provide a promising as well as important avenue for testing scalar-tensor extensions of gravity in the region of a strong gravitational field.
[abstract 15 / 17] (score: 2) - Title: The Impact and Environment of Massive Stars and Stellar ClustersAuthors: Loren Anderson, Jagadheep D. Pandian, Jyotirmoy Dey, Marco Padovani, Ramlal Unnikrishnan, Annie Zavagno, Grazia Maria Umana, Jakob van den Eijnden, Giovanni Sabatini, Kimberly L. Emig, Alessio Traficante, Álvaro Sánchez-Monge, D. Anish Roshi,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv: 2606.20366)Subjects: astro-ph.GACreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
Massive stars and stellar clusters shape galactic evolution through powerful feedback mechanisms including radiation pressure, photoionization, stellar winds, and COSMIC RAY acceleration. However, their impact remains poorly understood due to observational challenges: they are rare, distant on average, and deeply embedded within dense, dusty environments. Radio observations provide a unique window into these processes, as radio emission penetrates obscuring material and traces both thermal free-free emission from ionized gas and non-thermal SYNCHROTRON emission from shocks and particle acceleration. The Square Kilometre Array (SKA) will revolutionize massive star studies through unprecedented sensitivity and angular resolution. SKA observations will enable detailed characterization of hierarchical structures within HII regions, measurements of physical conditions through hydrogen, helium, and carbon radio recombination lines (RRLs), and detection of non-thermal emission from COSMIC RAY acceleration in star-forming regions. SKA will permit systematic measurements of stellar wind mass-loss rates, studies of photoionized gas kinematics and dynamics, and exploration of photodissociation regions surrounding ultracompact HII regions. Additionally, MAGNETic field strengths can be probed through Zeeman effect observations of RRLs. This chapter discusses the current understanding of massive stars and stellar clusters and their feedback processes. We highlight how SKA observations will advance our knowledge of massive STAR FORMATION, stellar winds, hierarchical structures in HII regions, COSMIC RAY acceleration, and MAGNETic field regulation of STAR FORMATION - providing crucial insights into feedback mechanisms governing the structure and evolution of the Milky Way and galaxies.
[abstract 16 / 17] (score: 2) - Title: Discovery of an extremely narrow trail-like feature crossing the Veil Supernova Remnant in deep amateur observationsAuthors: David Martinez-Delgado, Jan-Niklas Pippert, Miguel A. Perez-Torres, Malte Busmann, Emilio J. Alfaro, Mark Hanson, Giuseppe Donatiello, Alexander Zaytsev, Claudia Toci, Claus Gossl, Michael Schmidt, Christoph Ries,Comments: 8 pages, 7 figures, 2 tablesSubjects: astro-ph.GACreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
We report the discovery of an extremely narrow and highly collimated gaseous trail-like structure crossing the eastern region of the Veil Nebula (Cygnus Loop). The feature was first identified in deep narrow-band H-alpha images obtained by a small telescope and was confirmed in more than a dozen publicly available amateur and professional images in the last two decades, rejecting the possibility of being an artifact (e.g., artificial satellite trail). To characterize its structural and luminosity parameters, we applied a model-fitting code originally developed for the analysis of extragalactic stellar tidal streams. The structure is only detected in H-alpha emission, with no detectable counterpart in [SII] or in visible observations, and shows an almost constant brightness and width along its extension. It exhibits a surface brightness of 22.32+/- 0.13 H-alpha mag arcsec^2. Model fitting yields a median width of 1.63", which corresponds to a physical scale of approximately 1200 UA, assuming it is at the same distance (2400 light-years) as the Veil Nebula remnant. We discuss several potential scenarios for the origin of this feature: a Herbig-Haro-like JET, the trail of a high-velocity object, or a non-radiative shock associated with the SUPERNOVA remnant. We rule out the Herbig-Haro scenario, given the absence of a driving stellar source and the lack of [S II] emission. A high-velocity-object wake cannot yet be excluded, particularly if the driver is a compact remnant, but the absence of an obvious source or bow-shock apex and the extremely small, nearly constant width of the structure make a normal runaway-star origin unlikely. The current evidence instead favours a Balmer-dominated non-radiative shock associated with the Cygnus Loop, generated as the SNR blast wave encounters a dense material layer or MAGNETic structure viewed nearly edge-on.
[abstract 17 / 17] (score: 2) - Title: Dynamics of Relativistic Binaries in Structured and Stochastic Environments: A Lagrange-Fourier-Hansen FrameworkAuthors: Lorenz Zwick, Conor Dyson, Brian C. Seymour, János Takátsy, Johan Samsing,Comments: Submitted to PrD. Comments WelcomeSubjects: gr-qc astro-ph.GA astro-ph.HECreated: 2026-06-25; Updated: 2026-06-29; Datestamp: 2026-06-29
We develop a general framework to characterize non-vacuum perturbations to RELATIVISTIC binaries in the gravitational-wave (GW) driven regime, for use in GW parameter estimation studies. The effect of smooth, structured and stochastic perturbations to the binary's motion is reduced to a resonant spectral projection defined on a rolling averaging window, with weights given by Hansen coefficients. This is combined with practical criteria for identifying and evaluating the corresponding dynamical response to perturbations, starting from either analytical models or numerical simulations of binaries in environments. The result is a set of coupled ODEs for the orbital elements that capture epi-cyclic, apsidal and nodal resonances, consistently incorporate feedback from radiation reaction and can be solved efficiently on a coarse time grid. We demonstrate the practical application of the framework in two representative astrophysical scenarios: a compact binary in a variable tidal field and an extreme-mass-ratio inspiral in an accretion disk. We propose the Lagrange-Fourier-Hansen framework as a unified tool for modeling environmental effects in GW templates for eccentric and precessing binary sources, and particularly for bridging the gap between phenomenological prescriptions and realistic models of binaries in environments.
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