Earth and Planetary Astrophysics
Evidence for an Atmosphere on the Ultra-Short Period super-Earth HD 3167 b
Brandon Park Coy, Qiao Xue, Megan Weiner Mansfield et al. (+14 more)
'Lava worlds'-Earth-sized
planets hot enough (Teq >~ 1100 K) to melt their dayside silicate surfaces-have emerged as promising candidates for atmospheric detection and characterization. Thermal emission observations show an apparent dichotomy: the hottest lava worlds have colder daysides than the temperature of a maximally emitting bare rock, indicating the likely presence of thick and/or reflective atmospheres while the coldest ones do not. However, where in instellation flux this potential bifurcation occurs is uncertain. We present a JWST MIRI LRS eclipse of the ultra-short period (USP) lava world HD 3167 b (Teq = 1786 K, R = 1.6 Rearth, P = 0.96 d) that helps bridge this gap. We measure the white light eclipse depth to be 38 +/- 11 ppm, more than 5 sigma lower than the expected eclipse depth of a dark, maximally hot bare rock. We use this to derive a dayside brightness temperature that is best explained by the presence of an atmosphere that cools the dayside by reflecting incoming starlight and/or efficiently redistributing heat to the
planet's nightside. An atmosphere is further compatible with the
planet's slight under-density compared to an Earth-like composition. The corresponding dayside emission spectrum is not precise enough to constrain atmospheric composition, motivating follow-up spectroscopic observations with JWST NIRSpec. Lastly, we use our observation and existing data to refine key planetary parameters of the HD 3167 system. HD 3167 b is currently the least irradiated USP super-Earth with evidence for an atmosphere.
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All authors Brandon Park Coy, Qiao Xue, Megan Weiner Mansfield, Jason D. Eastman, Anjali A.A. Piette, Tyler Fairnington, Cole Smith, Michael Zhang, Eliza M.R. Kempton, Jacob L. Bean, Xuan Ji, Peter Gao, Jegug Ih, Daniel D.B. Koll, Rafael Luque, Jaume Orell-Miquel, Edwin S. Kite
Astrophysics of Galaxies
A Forward, Analytic, Differentiable, Geometric (But Inflexible) Lens Model
Paul L. Schechter
We anticipate that hundreds of thousands of distant, strongly gravitationally lensed sources will be detectable with the European Space Agency's (ESA) Euclid mission and the Rubin Observatory Legacy Survey of Space and Time. We consider the virtues and shortcomings of the Singular Isothermal Elliptical Potential (SIEP) with Parallel External Shear (XS_||) for these systems. Its principal virtue is that it admits an analytic forward model that gives image positions and magnifications as functions of the source position (and shape for extended sources). Preliminary experiments suggest a speed-up of a factor in excess of 10,000 compared with conventional models that instead map from the image plane to the source plane and require iteration to converge upon a unique source. A second virtue is that the Witt–Wynne
geometric representation of SIEP+XS_|| permits the quick visual verification of the model's adequacy for a particular lensed system. Unfortunately, the model's strictly elliptical lens equipotential is inconsistent with strictly elliptical surface mass density contours. The Witt–Wynne construction might nonetheless yield a sufficiently good first approximation to accelerate convergence to one's preferred lens model.
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Solar and Stellar Astrophysics
Intermediate-Mass Mergers: A New Scenario for Several FS CMa Stars
Daniela Korcakova, Nela Dvorakova, Iris Bermejo Lozano et al. (+6 more)
We summarise the properties and nature of a peculiar group of B-type
stars called FS CMa
stars. These
stars show the B[e] phenomenon, i.e., their spectra exhibit both forbidden emission lines and infrared excess. Such properties point to an extended circumstellar gas and
dust component. Although the phenomenon has been explained in most B[e]
stars, the origin and nature of FS CMa
stars is disputed. Here, we focus on the merger hypothesis, for which evidence has recently been discovered.
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All authors Daniela Korcakova, Nela Dvorakova, Iris Bermejo Lozano, Gregg A. Wade, Alicia Moranchel Basurto, Pavel Kroupa, Raul Ortega Chametla, Colin Peter Folsom, Ondrej Juhas
Astrophysics of Galaxies
Introducing $\Delta V_{\star-g}$: a new universal kinematic disturbance parameter
Jonah M. Powley, Rebecca J. Smethurst, Chris J. Lintott et al. (+1 more)
We introduce a new kinematic disturbance parameter, $\Delta V_{\star-g}$ (pronounced `DVSG'), which takes advantage of integral field spectroscopy (IFS) to quantify differences between a
galaxy's
stellar and gas velocity maps. The motivation behind $\Delta V_{\star-g}$ is to capture disturbances in the kinematics of a
galaxy that might be missed by alternative methods, while also attempting to minimize bias towards
galaxy properties or features of the IFS data. We first detail the reasons for introducing this parameter, and explain how the $\Delta V_{\star-g}$ value of a
galaxy can be calculated. We then present initial results using $\Delta V_{\star-g}$ to quantify the kinematic disturbance of obscured active
galactic nuclei (AGN) found in the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) survey. We find that there is no statistically significant difference between the $\Delta V_{\star-g}$ distributions of AGN and a control sample (matched in mass and
redshift) of inactive
galaxies. This suggests that AGN triggering may not be preferentially caused by any distinct kinematic disturbance process, or combination of processes, beyond those observed in inactive
galaxies.
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All authors Jonah M. Powley, Rebecca J. Smethurst, Chris J. Lintott, Tobias Géron
Solar and Stellar Astrophysics
JOYS: Launch and destruction of dust in protostellar jets. The case of BHR71-IRS1 with JWST MIRI
Łukasz Tychoniec, Logan Francis, Maria Gabriela Navarro et al. (+24 more)
Protostellar winds can theoretically lift solids from the
planet-forming disks, but direct evidence for launched
dust has been scarce so far. Numerous atomic lines that are unique to mid-infrared (IR) wavelengths reveal refractories eroded from
dust grains and provide information on wind properties in the earliest stages of the
star formation process. We present JWST MIRI-MRS spectral imaging of the inner 2000 au of the BHR71-IRS1 blueshifted side of the
outflow. Atomic line intensities are compared to shock models to constrain the physical conditions and elemental abundances of the outflowing gas.
Dust continuum maps were constructed from PSF-subtracted cubes, and the spectral energy distribution of the
dust was analyzed. The ionized central jet of BHR71-IRS1 is spatially resolved and imaged for the first time, revealing a unique inventory of refractory, volatile, and noble-gas fine-structure lines (Fe, Ni, Co, Cl, S, Ne, Ar). The emission is concentrated along four bright
knots that wiggle along the jet axis. PSF-subtracted continuum maps reveal extended mid-IR continuum emission co-spatial with the jet bullets and within the H$_2$-traced
outflow cone. Spectral energy distributions along the jet are fit together with the extinction, revealing a warm (200-400 K) and a cold (70-90 K)
dust component. The shock modeling constrained by the mid-IR lines indicates a decline in the shock velocity from 70 to 35 km s$^{-1}$ and in the pre-shock density from $>$10$^5$ to $ 4\times 10^4$ cm$^{-3}$ with distance from the protostar. Gas-phase Fe and Ni are measurably depleted relative to
Solar abundances, consistent with a substantial fraction of refractories remaining locked in grains in spite of the shocks. These JWST observations provide direct evidence that
dust is launched in a Class 0 jet and at least partly survives shock processing.
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All authors Łukasz Tychoniec, Logan Francis, Maria Gabriela Navarro, Jakobus M. Vorster, Ewine F. van Dishoeck, Alessio Caratti o Garatti, Korash Assani, Valentin J. M. Le Gouellec, Benoît Tabone, Pamela Klaassen, Adriaan G. M. Janssen, Kay Justtanont, Daniel Harsono, Pooneh Nazari, Simon D. Reyes-Reyes, Katerina Slavicinska, Caroline Gieser, Tyler Bourke, Yao-Lun Yang, Brunella Nisini, Teresa Giannini, Henrik Beuther, R. Devaraj, Thomas P. Ray, Nashanty G. C. Brunken, Yuan Chen, Martijn L. van Gelder
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Post-Newtonian inspiral waveform model for eccentric precessing binaries with higher-order modes and matter effects
Gonzalo Morras, Geraint Pratten, Patricia Schmidt et al. (+1 more)
We introduce pyEFPEHM, a post-Newtonian (PN) inspiral waveform model for eccentric and
spin-precessing compact binaries that includes higher-order modes and matter effects. Accurate and efficient waveform models capturing these effects are essential for probing compact-binary formation channels and exploiting current and future gravitational-wave (GW) observations. pyEFPEHM extends pyEFPE, significantly improving its physical content and accuracy. In particular, we show that above 2.5PN order the quasi-circular contributions to the orbital phasing dominate at each PN order, and incorporate all available higher-order quasi-circular PN corrections to the phasing, including adiabatic
tidal effects. We generalize the multiple-scale analysis solution of the
spin-precession equations, extending it to higher PN orders and including all available quasi-circular corrections. Finally, we add eccentric corrections up to 1PN order in the waveform amplitudes, including the GW multipoles $(l,|m|)=(2,2),(2,1),(2,0),(3,3),(3,2),(3,1),(3,0),(4,4),(4,2),(4,0)$. We validate pyEFPEHM against analytical waveform models and numerical relativity simulations, showing that it provides a robust and computationally efficient description of the inspiral, with good agreement across a broad region of parameter space and up to close to merger. The accuracy degrades in the late inspiral for systems with very unequal masses ($m_2/m_1 \lesssim 0.1$), significant
spins aligned with the orbital angular momentum ($|\chi_\mathrm{eff}| \gtrsim 0.5$), and high eccentricities ($e \gtrsim 0.6$), where the PN expansion is expected to break down. pyEFPEHM represents a significant step toward physically complete and efficient waveform modeling of eccentric and precessing binaries, providing a foundation for future extensions including higher-order corrections, calibration to numerical relativity, and merger ringdown modeling.
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All authors Gonzalo Morras, Geraint Pratten, Patricia Schmidt, Alessandra Buonanno
High Energy Astrophysical Phenomena
Hybrid Simulations of Supersonic Shear Flows: II) Cosmic Ray Viscosity
Naixin Liang and Damiano Caprioli
In this second paper in a series dedicated to characterizing shear layers via 2D hybrid (kinetic ions – fluid electrons) simulations, we study the dynamical role of nonthermal particles (
cosmic rays, CRs), either spontaneously generated or pre-existing. We initialize Kolmogorov-type sinusoidal velocity shear flows unstable to the Kelvin–Helmholtz instability, which evolve nonlinearly into
turbulence. Particles with large gyroradii act as long-range messengers that promote momentum exchange between layers, hence introducing a form of CR viscosity. Even when not energetically dominant, increasing the CR energy density generally enhances momentum transfer, provided that their gyroradii are smaller than the shear lengthscale. We consider flows ranging from subsonic to supersonic and assess the rate of shear dissipation, the partition of the initial kinetic energy among heating, thermal ion acceleration, CR reacceleration, and
magnetic-field amplification, and the maximum energy attained by accelerated particles.
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Astrophysics of Galaxies
Intense and extended CIII] emission suggests a strong outflow in JADES-GS-z14-0
Stefano Carniani, Peter Jakobsen, Giacomo Venturi et al. (+31 more)
JWST has revealed an overabundance of very bright, blue
galaxies at z>10, raising fundamental questions about how
star formation and feedback operate at
Cosmic Dawn. We present new JWST/NIRSpec MSA PRISM/CLEAR spectroscopy of JADES-GS-z14-0 (z=14.18) obtained with the JADES and OASIS programmes. While the rest-frame UV continuum flux level and shape are consistent between the two
datasets, the OASIS spectrum shows a 10$\sigma$ detection of the CIII]$\lambda\lambda1907,1909$ emission line, with a luminosity three times higher than that measured in the JADES data. This difference is naturally explained by the offset in shutter placement between OASIS and JADES, implying that the CIII] emission is spatially displaced by $\sim400$ pc from the
stellar continuum. The non-detection of CIII] in NIRCam medium-band imaging indicates that the emitting region is extended on scales $\gtrsim165$ pc, with a surface brightness below the detection threshold. Interpreting this diffuse, carbon-enriched gas as the result of ongoing or past
outflows, we infer a mass
outflow rate of $\dot{M}_{\rm out}\sim160~{\rm M_\odot\,yr^{-1}}$. We compare it with the
star-formation rate (SFR) and derive a mass-loading factor of $\eta = \dot{M}_{\rm out}/{\rm SFR} = 4-15$, suggesting highly efficient feedback at very early times. Finally, we show that, if
outflows are one of the mechanisms regulating
star formation in JADES-GS-z14-0, the instantaneous
star-formation efficiency in massive
haloes is constrained to $\epsilon_\star\lesssim0.08$. These results support a scenario in which
outflows play a crucial role during the earliest phases of
galaxy formation. Comparing our results with the current theoretical
galaxy formation model, we conclude that a combination of moderate
star-formation efficiency and reduced
dust attenuation can account for the emergence of luminous
galaxies at the highest
redshifts.
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All authors Stefano Carniani, Peter Jakobsen, Giacomo Venturi, Francesco D'Eugenio, Tobias J. Looser, Joris Witstok, Christopher N. A. Willmer, Andrea Ferrara, Zihao Wu, Santiago Arribas, Andrew J.Bunker, Stéphane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Daniel J. Eisenstein, Kevin Hainline, Jakob M. Helton, Zhiyuan Ji, Xihan Ji, Benjamin D. Johnson, Mahsa Kohandel, Nimisha Kumari, Roberto Maiolino, Andrea Pallottini, Eleonora Parlanti, Pablo G. Pérez-González, Marcia Rieke, Pierluigi Rinaldi, Brant Robertson, Jan Scholtz, Sandro Tacchella, Hannah Übler, Chris Willot
High Energy Astrophysical Phenomena
Beyond the Diffusion Coefficient: Propagators and Memory in Cosmic Ray Transport
Naixin Liang and S. Peng Oh
Cosmic ray (CR) transport is usually modeled with a single
diffusion coefficient, but this description captures only the growth of the variance and not the full transport process. Distinct transport mechanisms can share the same effective
diffusion coefficient while producing different particle distributions and approaches to the diffusive limit. This limitation is especially relevant in realistic multiphase, structured, and time-dependent media, and is also reflected in observed environmental variations in CR transport near
pulsar wind nebulae,
supernova remnants, and molecular clouds. Particle-tracing studies also show clear departures from standard
diffusion, including both superdiffusion and subdiffusion. We therefore develop a propagator-based framework centered on $P(x,t)$, the probability distribution of particle positions, or equivalently its
Fourier-Laplace transform $P(k,s)$. This object is compact and statistically complete, and naturally exposes
memory: the CR flux can depend on earlier gradients when unresolved trapping or phase changes are coarse-grained away. Using the Montroll-Weiss formalism, we show how to measure $P(k,s)$ directly from trajectories, how to recover the associated
memory kernel, and how to represent broad kernels efficiently with a Prony expansion. Applied to a multiphase medium, the framework shows that slow regions can regulate escape without dominating the total residence-time budget. We also introduce an accelerated Monte Carlo method for coarse-grained transport, and show that if trapping structures evolve while particles are still sampling them, the static long-time limit need not be reached. This paper provides the foundation for future observational applications, particle-tracing measurements, and CR-MHD closures.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Novel Ringdown Tests of General Relativity with Black Hole Graybody Factors
Romeo Felice Rosato, Francesco Crescimbeni, Sophia Yi et al. (+2 more)
We present GreyRing, a new model for the post-merger signal in black-hole binary coalescences based on the graybody factor of the remnant. The model accurately reproduces the full frequency-domain ringdown signal of a large set of comparable-mass, aligned-
spin numerical relativity waveforms, achieving mismatches of order ${\cal O}(10^{-6})$ for the dominant $(\ell,m)=(2,2)$ mode, and typically outperforming state-of-the-art time-domain models. Building on this model, we introduce a novel consistency test of strong
gravity based on the graybody factor: the remnant mass and
spin inferred from GreyRing can be compared with those obtained through standard black hole spectroscopy. This agnostic test relies exclusively on the post-merger signal and does not require the inclusion of overtones or the choice of very early ringdown starting times, combining the advantages of inspiral-merger-ringdown consistency tests and traditional black hole spectroscopy. We apply the test to GW250114 and find that the remnant mass and
spin inferred from GreyRing are consistent with those measured from the full signal. Remarkably, the inferred parameters can be measured with a precision comparable to, or slightly better than, that achieved with standard black-hole spectroscopy. Our graybody-factor waveform model allows for new precision tests of strong
gravity using the ringdown signal.
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All authors Romeo Felice Rosato, Francesco Crescimbeni, Sophia Yi, Emanuele Berti, Paolo Pani
Astrophysics of Galaxies
A Post-starburst Galaxy Undergoing Ram-pressure Stripping at Redshift 3.06
Mingyu Li, Zheng Cai, Bjorn H. C. Emonts et al. (+16 more)
Understanding how
galaxies ignite and extinguish their
star formation remains a cornerstone question in modern astrophysics. Recent JWST surveys have revealed an overabundance of massive quiescent
galaxies in the first billion years of the Universe, challenging current models of
galaxy evolution. In the nearby Universe, ram pressure stripping (RPS) is a major environmental mechanism capable of rapidly shutting down
star formation, yet direct observation remains scarce at
redshift $z\gtrsim1$, and its role at $z>2$ is even poorly constrained by simulations. Here, we utilize JWST and ALMA observations to present direct evidence of RPS in the post-starburst
galaxy A2744-JF-z3, residing in a
galaxy group at
redshift 3.06, the earliest such detection to date. Spectroscopic diagnostics and spectral energy distribution modeling reveal the ongoing removal of cold gas and
dust, coincident with the abrupt cessation of
star formation. Contrary to hydrodynamical simulations that predict a reduced incidence of RPS at high
redshift, our results instead imply that RPS can operate at $z>3$, suggesting a highly
stochastic and impulsive stripping within a clumpy, filamentary intra-group and circumgalactic medium. These observations extend environmental quenching well into the epoch of
galaxy assembly, highlighting RPS as a previously overlooked decisive pathway to rapid quenching in nascent groups and protoclusters in the early Universe.
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All authors Mingyu Li, Zheng Cai, Bjorn H. C. Emonts, Fengwu Sun, Ming Sun, Fuyan Bian, Zihao Li, Xiaojing Lin, Yunjing Wu, Franz E. Bauer, Seiji Fujimoto, Anton M. Koekemoer, Vasily Kokorev, Christopher N. A. Willmer, Eiichi Egami, Xiaohui Fan, J. Xaiver Prochaska, Zechang Sun, Fujiang Yu
Astrophysics of Galaxies
The Shocking Origin of the Flat $EE/BB$ Ratio
Raphael Flauger, Alexei G. Kritsuk and Guanhao Sun
Polarized emission from
dust and synchrotron radiation from the ISM are the dominant foregrounds for CMB polarization and are a major challenge for extracting the
primordial signal on large angular scales. A key characteristic of the
galactic foreground emission is its $EE/BB$ ratio. We argue that MHD shocks play an important role in setting the observed $EE/BB$ ratio. To support this, we first analyze quasi-linear magnetohydrodynamics (MHD) simulations to obtain an $EE/BB$ ratio that increases as $\sim k^2$, then show that with increasing energy injection rates, the $EE/BB$ ratio flattens to a value $\gtrsim 1$, approaching observational results. Looking at the distribution of the velocity divergence, a tail with power law $-7/2$ develops around the same injection rates where the $EE/BB$ ratio flattens. While the system becomes more isotropic, MHD shocks are intrinsically anisotropic and lead to the $E/B$ power asymmetry. We also observe total pressure balance among all our simulations, indicating slow wave dominance. Therefore, in the regime we consider, it is important to go beyond linear MHD equations to understand the foreground radiation.
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Astrophysics of Galaxies
The GMRT archive atomic gas survey – IV. Consistency of the dark matter halo perturbation parameter from morphological and kinematic lopsidedness of galaxies
Prerana Biswas, Narendra Nath Patra and Veselina Kalinova
The lopsidedness of
galaxies is a commonly observed phenomenon, and through different studies, it has been observed that nearly 30% of
galaxies show this phenomenon. In this work, we study morphological lopsidedness in both
stellar and gas disks in the inner and outer regions using
Fourier analysis techniques and compare the results for a sample of nearby
galaxies with different morphologies and environments. Although lopsidedness can result from diverse factors like
tidal interactions, gas
accretion, and internal instability, recent studies suggest it is a common feature that is not solely reliant on rare events, and moderate lopsidedness most likely results from the disk's response to a lopsided dark matter
halo potential. Assuming lopsidedness originates due to a lopsided
halo, we find the morphological and kinematic
halo perturbation parameters in the same radial range. Unlike previous studies, we use 3D kinematic modelled rotation curves for finding kinematic lopsidedness and, hence, kinematic
halo perturbation parameter. Although the detected linear correlation between them is not statistically significant for our small sample of eleven
galaxies, this approach provides a more uniform and physically consistent framework to test the theoretically expected similarity between morphological and kinematic
halo perturbation parameters. Further, within this framework, the discrepancy between them does not appear to depend on the nature of the rotation-curve asymmetry of the two sides of the
galaxy, in contrast to trends seen in earlier studies. In future work, we plan to extend this analysis to a substantially larger sample in order to robustly assess these findings.
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High Energy Astrophysical Phenomena
Distinct First-to-Second Peak Yield Ratios and Timescales Reveal a Sub-dominant Prompt Channel
Yossef Zenati, Paz Beniamini and Kenta Hotokezaka
Stellar abundances reveal non-monotonic [Y/Eu] and [Sr/Eu]
evolution, a systematic decline with increasing [Eu/H] at low
metallicity, a minimum at $[\rm{Eu/H}] \sim -0.3$ and then a rise at high
metallicity. This behavior requires at least three distinct
neutron-capture sources operating on different timescales. We develop a one-zone chemical-
evolution model constraining their typical delay-times, rates, and yield ratios. Reproducing the observed $\rm{[Y/Eu]}$ and $\rm{[Sr/Eu]}$ sequences requires, a delayed $r$-process channel (most likely binary
neutron-
star mergers) dominating Eu production ($\gtrsim 95\%$ of total Eu). A
prompt channel preferentially producing first-peak elements with minimal Eu, explaining the increasing [Y/Eu] at decreasing [Eu/H] below $[\rm{Eu/H}] \lesssim -2.5$; and delayed AGB $s$-process enrichment with delays greater than $t_{min} = 0.3-0.6$\,Gyr reproducing the late-time upturn in Y (Sr). Our model quantitatively reproduces all constraints, including the large $\Delta[\rm{Y/Eu}] \approx 0.6$ dex variation between the late-time rise [Eu/H] and the minimum value, the location of the minimum at [Eu/H] $\sim -0.3$ and late-time rise. The first-to-second peak yield ratios correspond to $[\rm{Y/Eu}] \approx -0.3$ (
prompt) and $\approx -0.8$ (BNS mergers). The observed $\Delta[\rm{Y/Eu}]$ amplitude establishes a model-independent lower limit on the first to second peak yield ratio $\gtrsim 3.4$ between the
prompt and delayed channels, ruling out models with similar
prompt and delayed yield ratios. These results demonstrate that explaining the observed heavy-element abundance patterns requires multiple channels with distinct nucleosynthetic signatures and operational timescales, providing constraints on the relative rates, delay times, and yield patterns of candidate production sites.
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Cosmology and Nongalactic Astrophysics
Model-Independent Analysis of Type Ia Supernova Datasets and Implications for Dark Energy
Zhenyuan Wang and Yun Wang
Recent analyses combining DESI DR2 BAO with CMB and SNe Ia data have reported $2.8$–$4.2\sigma$ evidence for dynamical dark energy, but the significance depends strongly on the
supernova sample, raising the question of whether this signal reflects new physics,
dataset-specific systematics, or the choice of dark energy parameterization. We investigate this question by analyzing four SNe Ia compilations (Pantheon, Pantheon+, DES-Dovekie, and Union3) with DESI DR2 BAO and Planck CMB distance priors, using flux averaging, model-independent expansion rate extraction, parametric ($w_0 w_a$CDM) fits, and a non-parametric reconstruction of the dark energy density ratio $X(z) \equiv \rho_{\rm DE}(z)/\rho_{\rm DE}(0)$. Flux averaging reduces the $\Omega_m$ difference between SNe and DESI from ${\sim}2\sigma$ to ${\sim}1\sigma$ for Pantheon+ and DES-Dovekie. The reconstructed $X(z)$ for DESI DR2 + CMB + SNe is consistent with $\Lambda$CDM for Pantheon, Pantheon+, and DES-Dovekie except at $0.5<z<1$, consistent with Wang & Freese (2026). The largest deviation occurs at $z=2/3$, reaching ${\sim}2.7\sigma$ for Pantheon+ but only $1.6$–$1.7\sigma$ for Pantheon and DES-Dovekie. The $X(z)$ for DESI DR2 + CMB + Union3 is consistent with these within $1\sigma$, but shows an additional $2.4\sigma$ deviation at $z=1/3$ besides the ${\sim}2.7\sigma$ deviation at $z=2/3$. Across all analyses, the departure from $\Lambda$CDM correlates with each
dataset's $\Omega_m$ preference. We demonstrate that a pure $\Lambda$CDM universe with the measured $\Omega_m$ differences can reproduce the observed $X(z)$ pattern, providing a viable alternative interpretation of the observed $X(z) \neq 1$ pattern. Future surveys by Euclid and Roman with sub-percent $\Omega_m$ constraints will be essential to determine whether the signal reflects genuine dark energy
evolution or residual inter-probe $\Omega_m$ inconsistencies.
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Cosmology and Nongalactic Astrophysics
SN 2022riv in RX J2129: Discovery, Spectroscopic Classification, and Microlensing of a Strongly Lensed Type Ia Supernova from JWST and HST Observations
Birendra Dhanasingham, Patrick L. Kelly, Wenlei Chen et al. (+27 more)
The multiply imaged SN 2022riv was discovered through a search of
galaxy cluster fields as part of a Hubble Space
Telescope (HST) SNAP program to find highly magnified
stars. The
supernova (SN) was detected in the image corresponding to the longest time delay of a
galaxy at
redshift $z=1.522$ strongly lensed by the foreground
galaxy cluster RX J2129.7+0005. Follow up James Webb Space
Telescope (JWST) NIRSpec G140M and PRISM spectroscopy yields a Type Ia SN classification. Using the SALT3-NIR light-curve fitter, we obtain a cosmology-independent measurement of the magnification of $5.35\pm1.01$ for the last-to-arrive image of the SN, with multiple SALT SN spectral time-series models yielding consistent constraints. The last-to-arrive image of SN 2022riv we detect appeared adjacent to the brightest cluster
galaxy (BCG) at a location with an exceptionally high
stellar mass density ($\sim 1-2$ dex higher than that of SN Refsdal), where microlensing is expected to introduce a 20-50% modulation of the magnification. Analyzing six independent lens models of the cluster, we find that four predict the magnification with much greater precision ($p < 0.05$) than would be expected by random chance, given the large effect anticipated from microlensing. Five models yield magnifications of roughly $4-7$ (within $1\sigma$) prior to accounting for microlensing, whereas HoliGRALE favors a significantly higher value of $15.39 \pm 0.85$. After incorporating nominal microlensing, the HoliGRALE prediction is within $1\sigma$ tension with our measurement. A companion paper (Dalrymple et al.) will present constraints on the relative time delay of the image that arrived earlier.
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All authors Birendra Dhanasingham, Patrick L. Kelly, Wenlei Chen, Justin Pierel, Masamune Oguri, Derek Perera, Jose M. Diego, Adi Zitrin, Ashish K. Meena, Mathilde Jauzac, Guillaume Mahler, Elias Mamuzic, Liliya L.R. Williams, Yoon Chan Taak, Anton M. Koekemoer, Thomas J. Broadhurst, Lukas J. Furtak, David Lagattuta, Hayley Williams, Kyle Dalrymple, Alexei V. Filippenko, Christa Gall, Daniel Gilman, Jens Hjorth, Saurabh W. Jha, Conor Larison, Chien-Hsiu Lee, Paolo A. Mazzali, Keren Sharon, Sherry H. Suyu
High Energy Astrophysical Phenomena
A sample of short-lived Galactic radio transients from ASKAP VAST
Akash Anumarlapudi, David L. Kaplan, Natasha Hurley Walker et al. (+6 more)
Galactic radio transients (GRTs) are mysterious short-lived (~days to months)
radio transients that are quiet at all other wavelengths. Until now, roughly half a dozen such sources have been reported, predominantly towards the
Galactic center. However, no unifying properties have been identified among these, leaving their nature, emission mechanism, and even classification poorly understood. Due to the lack of periodic and uniform
radio observations over wide areas of the
Galactic plane until now, the sample size of such transients remained limited. Here, we use
radio observations from the Australian SKA Pathfinder's Variables and Slow Transients survey to discover six new
radio transients along the
Galactic plane that resemble GRTs. Detailed investigation of archival data suggests that these sources may be divided into two classes: sources that exhibit sporadic, pulse-like (minutes)
radio emission, and sources that exhibit long-term (weeks) flaring-type
radio emission. For the short-time variable sources, we draw similarities between optically bright long-period
radio transients and our sample to propose wide-orbit (~days) white
dwarf binaries as underlying sources. For sources that show long-term outbursts, we draw comparisons between
dust-obscured outbursts from WD binaries and our sample. These results could imply that the ongoing wide-field
radio surveys are uncovering
radio emission from sub-populations of WD binaries that were previously unexplored.
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All authors Akash Anumarlapudi, David L. Kaplan, Natasha Hurley Walker, Stella Koch Ocker, Daniel Kelson, Dougal Dobie, Laura Driessen, Tara Murphy, Joshua Pritchard
Astrophysics of Galaxies
A Deep ALMA Survey of the Redshift Distribution of Dusty Star-forming Galaxies
S. J. McKay, A. J. Barger, L. L. Cowie et al. (+1 more)
We present an Atacama Large Millimeter/submillimeter Array (ALMA) spectroscopic follow-up survey of an 870 $\mu$m-selected sample of dusty
star-forming
galaxies (DSFGs) in the GOODS-S field. We use these linescans to identify or confirm spectroscopic
redshifts (spec-zs) for 26 sources. Including spec-zs from the literature, there are now secure or tentative spec-zs for 54 out of 75 DSFGs (72%). At $f_{870}>2.5$ mJy, the sample is 97% spectroscopically complete, allowing us to model the full DSFG
redshift distribution down to nearly the confusion limit for a 15-m
telescope at 850 $\mu$m. This is the highest completeness for an unbiased sample at this flux limit to date. We find that nearly all of the DSFGs in our sample that were targeted with JWST/NIRSpec were spectroscopically identified, without much dependence on near-infrared or submillimeter flux or
redshift. However, only 29% of our sample have JWST spectroscopic coverage. We use the spec-zs to evaluate various photometric
redshift (photo-z) estimates, finding that all methods exhibit an outlier fraction of at least $>20$%. Nearly all of the photo-z methods tend to overshoot the
redshifts, leading to overestimates of the number of DSFGs at high
redshift ($z>4$). Our results suggest that $\lesssim6$% of $f_{870} \geq 2.25$ mJy DSFGs lie at $z>4$ and $\lesssim1$% lie at $z>5$, reflecting a steep decline in the abundance of massive dusty
galaxies in the first 1.5 Gyr.
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All authors S. J. McKay, A. J. Barger, L. L. Cowie, F. E. Bauer
High Energy Astrophysical Phenomena
Spectral index evolution of the limb-brightened jet in 3C 84
L. C. Debbrecht, G. F. Paraschos, E. Ros et al. (+11 more)
Relativistic jets launched by active
galactic nuclei are fundamental for understanding the physics of accreting supermassive black holes and their immediate environment, yet the mechanisms driving jet launching remain uncertain. In this study, we investigate the sub-parsec jet of 3C 84 using multi-epoch, multi-frequency, very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very Long Baseline Array at 22 and 43 GHz. We analyse the
evolution of the spectral index gradient in the core region to relate the observed structure to physical interpretations and to discriminate between competing jet launching models. Furthermore, we examine the impact of the ambient medium and
magnetic field configuration on jet morphology and dynamics over time, and explore their connection to a coinciding $\gamma$-ray
flare. Our spectral analysis reveals significant changes across three epochs, indicating dynamic activity between filamentary structures on sub-parsec scales, evolving
magnetic fields, and a complex interaction with the surrounding medium, all of which shape the innermost jet and may influence its high-energy emission.
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All authors L. C. Debbrecht, G. F. Paraschos, E. Ros, T. P. Krichbaum, U. Bach, M. A. Gurwell, J. A. Hodgson, M. Janssen, J.-Y. Kim, M. M. Lisakov, N. R. MacDonald, D. G. Nair, J. Oh, J. A. Zensus
High Energy Astrophysical Phenomena
An XMM-Newton Analysis of the Supermassive Black Hole Binary Candidate MCG+11–11–032
Yash A. Gursahani, Tingting Liu, Richard Mushotzky et al. (+2 more)
We investigate the possibility of a binary supermassive black hole system at the center of MCG+11–11–032, a local (z = 0.036) Seyfert 2
galaxy. Prior work with stacked Swift/XRT spectra suggested the presence of two Fe K$\alpha$ lines (at 6.16 keV and 6.56 keV) with 2$\sigma$ confidence. This could be consistent with a prediction of several hydrodynamical models, in which each black hole hosts a mini-disk and contributes one Doppler-shifted Fe K$\alpha$ line to the total spectrum. Another study using a single exposure from Chandra/ACIS did not find evidence for a double line. Here, we conduct follow-up with two epochs of XMM-Newton/EPIC data spaced $\sim$6 months apart. After fitting our spectra with models from the previous two studies, we do not find evidence for a double iron line in either observation. Our best-fit model yields $\Gamma = 1.63^{+0.20}_{-0.21}$ and $N_\text{H}/10^{22} \text{ cm}^{-2} = 17.9^{+2.7}_{-2.4}$ for the first epoch, and $\Gamma = 1.46^{+0.22}_{-0.24}$ and $N_\text{H}/10^{22} \text{ cm}^{-2} = 17.1^{+2.7}_{-2.4}$ for the second. We compare our spectral parameters with those derived in past work on this source, finding broad agreement with prior
datasets. Lastly, we discuss the properties of MCG+11–11–032 alongside samples of Seyfert 2
galaxies from the literature, finding that it is consistent with this population and the single AGN scenario.
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All authors Yash A. Gursahani, Tingting Liu, Richard Mushotzky, Christopher S. Reynolds, Michael Koss
Astrophysics of Galaxies
JWST Observations of Starbursts: Dust Processing in the M82 Superwind
Serena A. Cronin, Alberto D. Bolatto, Helena M. Richie et al. (+39 more)
We present JWST MIRI and NIRCam imaging of the inner ~5 kpc of the M82 superwind at 0.05-0.375” (~0.9-6.5 pc) resolution. Targeted filters probe emission from polycyclic aromatic hydrocarbons (PAHs; F335M, F360M, F770W, F1130W) and continuum (F250M, F360M). The images reveal a network of cool wind filaments traced by PAHs. PAH surface brightness declines with the inverse square of distance to the midplane, suggesting that the incident radiation field from the starburst drives the observed PAH intensity out to 2.5 kpc. The 3.3/11.3 and 3.3/7.7 band ratios show uniformity with distance from the starburst, though comparisons with mid-IR
dust emission models indicate a modest shift toward larger PAHs. Outside the disk, 11.3/7.7 increases moderately, reflecting that PAHs become more neutral with distance from the starburst as they are exposed to a declining radiation field and ionization parameter. Overall, PAHs in the wind are consistent with standard-to-large sizes and standard-to-high ionization states. Including Spitzer and Herschel data, PAH abundance (qPAH) is set at ~1% in the starburst and remains unchanging out to 5 kpc off the disk. This flat qPAH profile suggests that PAHs are shielded from the hot wind, perhaps residing in the surface layers of cool clouds, with possible replenishment from cloud interiors and enrichment of the
halo from previous bursts. In this picture, clouds are not dense enough to promote PAH growth, and they likely undergo radiative cooling and mixing with the hot phase to survive the gauntlet for at least ~20 Myr.
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All authors Serena A. Cronin, Alberto D. Bolatto, Helena M. Richie, Grant P. Donnelly, Rebecca C. Levy, Karl D. Gordon, Elizabeth Tarantino, Martha L. Boyer, Lee Armus, Patricia A. Arens, Leindert A. Boogaard, Daniel A. Dale, Keaton Donaghue, Bruce T. Draine, Sara E. Duval, Kimberly Emig, Deanne B. Fisher, Simon C. O. Glover, Brandon S. Hensley, Rodrigo Herrera-Camus, Ralf S. Klessen, Thomas S.-Y. Lai, Laura Lenkić, Adam K. Leroy, Ashley E. Lieber, Ilse De Looze, Sebastian Lopez, David S. Meier, Elisabeth A.C. Mills, Karin M. Sandstrom, Evan Schneider, Kaitlyn E. Sheriff, Utsav Siwakoti, Evan D. Skillman, J.D.T. Smith, Yu-Hsuan Teng, Todd A. Thompson, Alexander G.G.M. Tielens, Sylvain Veilleux, Vicente Villanueva, Fabian Walter, Paul P. van der Werf
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Not too close! Evaluating the impact of the baseline on the localization of binary black holes by next-generation gravitational-wave detectors
Francesco Iacovelli, Luca Reali, Emanuele Berti et al. (+3 more)
Next-generation (XG) gravitational-wave detectors, such as
Cosmic Explorer (CE) and the Einstein
Telescope (ET), will observe compact binary coalescences at unprecedented rates and signal-to-noise ratios (SNRs). Accurate sky localization of these sources is crucial for several aspects of the science case of CE and ET. The localization of most binary black hole (BBH) signals, which will spend at most a few minutes within the XG detector's effective sensitivity band, will continue to rely primarily on timing triangulation across a network of detectors. A key design choice for triangulation is the baseline between instruments. We investigate how the baseline affects the localization capabilities of a two-detector CE network, analyzing both fixed-parameter injections and a realistic BBH population consistent with the latest GWTC-4 results. For detector-frame total masses up to $\sim\!100\,{\rm M}_\odot$, we find that baselines corresponding to light travel times of $8-11$ ms ($\sim\!2300-3300$ km) offer a reasonable compromise, producing predominantly unimodal or bimodal sky localizations suitable for electromagnetic follow-up and statistical host
galaxy identification and
galaxy cross-correlation studies. Shorter baselines significantly degrade localization, particularly for high SNR events. Crucially, we find that adding a third detector to the network eliminates localization multimodality for a substantial fraction of sources. A network with two CEs and LIGO-India provides unimodal posteriors for a good fraction of events, whereas two CEs plus ET would provide unimodal posteriors for essentially all of them. These considerations should be useful to inform the development of the XG detector network.
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All authors Francesco Iacovelli, Luca Reali, Emanuele Berti, Alessandra Corsi, B. S. Sathyaprakash, Digvijay Wadekar
High Energy Astrophysical Phenomena
Sensitivities of Black Hole Images from GRMHD Simulations
Pedro Naethe Motta, Mário Raia Neto, Cora Prather et al. (+1 more)
The advent of high-fidelity imaging of supermassive black holes calls for efficient and robust data-analysis methods. In this work, we use $\texttt{Jipole}$, a differentiable, $\texttt{ipole}$-based radiative transfer code, to enable gradient-based analyses of images generated from state-of-the-art general relativistic magnetohydrodynamic (GRMHD) simulations. We compute image sensitivities, i.e., pixel-wise derivatives of the intensity with respect to model parameters, which form the Jacobian of the forward model and define a local map from parameter space to image space. Using these sensitivities in a mock data analysis, we find that GRMHD-based images generate a structured error landscape for parameter fitting, with anisotropies and local minima, making parameter exploration nontrivial but still tractable when guided by gradient information. We characterize this landscape through the Jacobian and assess the feasibility of gradient-based recovery under idealized, blurred, and noisy conditions. Our results show that automatic differentiation-computed image gradients can guide parameter exploration effectively even in the presence of noise. These findings establish a basis for efficient, high-precision model–data comparisons in black hole imaging and motivate the integration of these sensitivities into advanced inference frameworks.
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All authors Pedro Naethe Motta, Mário Raia Neto, Cora Prather, Alejandro Cárdenas-Avendaño
Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn
RAPRAL v1.0: RAdiation Prediction using RAy tracing and Line-by-line methods for hypersonic air flows
Yuzhe Zhang, Qizhen Hong, Xiaoyong Wang et al. (+1 more)
A new radiation solver, RAPRAL (RAdiation Prediction based on RAy tracing and Line-by-line) implemented in C++, is developed for simulating high-temperature thermochemical nonequilibrium radiative processes. RAPRAL integrates detailed line-by-line spectral modeling with a ray-tracing solution of the radiative transfer equation, enabling accurate resolution of both spectral features and spatial radiation transport. The adopted methods and their implementation are described in detail. To assess the overall capability and accuracy of RAPRAL, we first focus on the computation of atomic and molecular bulk spectral coefficients. Through comparison with the established code in the literature, RAPRAL demonstrates its ability to accurately capture key spectral features across a wide range of conditions. Moreover, RAPRAL is applied to predict afterbody radiative heating in the Fire II flight experiment, based on a two-temperature, 11-species air flowfield. The results demonstrate that the present approach provides reliable predictions of radiative heat flux and effectively captures the dominant radiation mechanisms. Overall, the presented results demonstrate that RAPRAL is a robust tool for simulating radiative processes in hypersonic air flows, and future versions will extend its capabilities to include species relevant to planetary atmospheres.
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All authors Yuzhe Zhang, Qizhen Hong, Xiaoyong Wang, Quanhua Sun
High Energy Astrophysical Phenomena
The nature of tilted supercritical accretion discs
P. Chris Fragile, Matthew J. Middleton, Brooks Brasseur et al. (+2 more)
In this paper, we report on the first 3D general relativistic radiation magnetohydrodynamic simulations of large supercritical
accretion discs that are tilted with respect to the black hole
spin axis. We explore a range of black hole
spin parameters (from $a_* = -0.9$ to 0.9), initial tilts (in the range from $\beta_0 = 0^\circ$ to $30^\circ$), and target mass
accretion rates. We first confirm that, for all the untilted simulations, the Eddington
accretion limit is obeyed ($\dot{M}_\mathrm{BH} \lesssim \dot{M}_\mathrm{Edd}$), consistent with our previous findings. However, for tilted discs we find that the mass
accretion rate can be enhanced by up to a factor of ten and that factor depends linearly on tilt $\dot{M}_\mathrm{BH} \propto \beta_0 \ge \dot{M}_\mathrm{Edd}$. This could be an important aspect in solving the puzzle of the growth of the first supermassive black holes. We also find that for a given tilt, the mass
accretion rate enhancement is proportional to the magnitude of the
spin. Additionally, we find that tilted supercritical
accretion discs are more advective than their untilted counterparts. We attribute all of these differences to the presence of standing shocks in the inner regions of the
accretion flow, a feature unique to tilted discs.
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All authors P. Chris Fragile, Matthew J. Middleton, Brooks Brasseur, Deepika A. Bollimpalli, Zach Smith
Earth and Planetary Astrophysics
Origin and characterization of super-Earths and sub-Neptunes
Léna Parc, Julia Venturini, François Bouchy et al. (+6 more)
Super-Earths and sub-Neptunes represent the most common class of
exoplanets discovered to date in our
galaxy, yet they have no direct analogues in the
Solar System. Since 2014, researchers within the NCCR
PlanetS have made significant contributions to understanding the origin and nature of these small
planets. This chapter provides an overview of the progress made in their detection, characterization, and theoretical interpretation during the 2014-2025 period. The combined data from space-based photometric missions such as Kepler and TESS, together with ground-based radial velocity campaigns using state-of-the-art spectrographs (e.g., HARPS, ESPRESSO, NIRPS), have enabled detailed demographic analyses of these
planets. These observational efforts are complemented by theoretical work exploring their internal structures, bulk compositions, formation and
evolution, shedding light on the physical processes responsible for the observed diversity. As high-precision observations from facilities like JWST begin to probe the atmospheric composition of individual
planets, a more complete picture of super-Earth and sub-Neptune origins is emerging, one that continues to challenge and refine current
planet formation theories.
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All authors Léna Parc, Julia Venturini, François Bouchy, Ravit Helled, Caroline Dorn, Adrien Leleu, Yann Alibert, Simon Müller, Haiyang Wang
Solar and Stellar Astrophysics
NGC 1647: A young open cluster with a broad main sequence observed with LAMOST
A. Frasca, M. Qin, J. ALonso-Santiago et al. (+4 more)
In this work we present the results of our analysis of medium-resolution LAMOST spectra of candidate members of the cluster NGC 1647 with the aim of determining the
stellar parameters, activity level, lithium abundance, and to study the cluster properties. We used the code ROTFIT to determine the atmospheric parameters (Teff, logg, and [Fe/H]), radial velocity (Vr), and projected rotation velocity (vsini) for 158 cluster members. Moreover, for
solar-type and cooler
stars (Teff< 6500 K), we calculated the H-alpha and LiI-6708 net equivalent width by means of the subtraction of inactive photospheric templates. We determined the rotation periods for 160
stars by analyzing the available TESS photometry. We found four double-lined spectroscopic systems for which we provide the radial velocities of the two components. The Vr distribution of the cluster members peaks at -5.3 km/s with a dispersion of 1.6 km/s, while the average
metallicity is [Fe/H]=-0.08$\pm$0.08 dex, in line with previous determinations. From the fitting of the spectral energy distribution of 160 likely members we infer the existence of a differential reddening across the cluster field with an average value of $A_V$=1.1 mag. The $A_V$ values show a distinct correlation with the color offset from the lower boundary of the main sequence; conversely, this offset appears to be uncorrelated with vsini. These two findings confirm that differential reddening is the primary driver behind the observed extended Main-Sequence Turn-Off (eMSTO) in this cluster. The age of NGC 1647, obtained from the lithium abundance, is 203$\pm$27 Myr, which is compatible with the values inferred from a gyrochronological approach and the isochrone fitting.
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All authors A. Frasca, M. Qin, J. ALonso-Santiago, G. Catanzaro, J. N. Fu, J. Y. Zhang, A. Bragaglia
Earth and Planetary Astrophysics
The GAPS Programme at TNG. LXXIII. Confirmation of the hot sub-Neptune TOI-4602 b (HD 25295 b), a key target for future atmospheric characterization
C. Di Maio, S. Benatti, D. Locci et al. (+25 more)
Precise mass and radius measurements of small, transitional
exoplanets, such as super-Earths and sub-Neptunes, are essential to constrain their bulk density and formation history, serving as prerequisites for atmospheric characterization. The ArMS Large Programme, carried out within GAPS using the HARPS-N spectrograph at the Telescopio Nazionale Galileo, aims to confirm and characterize transitional
planets in the radius valley through high-precision radial-velocity (RV) measurements. The ultimate goal is to identify ideal targets for atmospheric follow-up observations with next-generation facilities like the James Webb Space
Telescope and the future ESA Ariel satellite. We present the first mass determination of a sub-Neptune
planet using data entirely collected within the ArMS programme, focusing on the validated
planet TOI-4602b. We monitored TOI-4602, which hosts a close-in validated sub-Neptune (P ~ 3.98 d) detected by the Transiting
Exoplanet Survey Satellite (TESS), searching for
planet-induced RV variations. We then performed a joint analysis of these RV measurements together with the TESS photometric data. We determined that TOI-4602b is a sub-Neptune with a radius of Rp = 2.5 Rearth and a mass of Mp = 5.5 Mearth. The resulting bulk density (rho_p = 2.1 ) and atmospheric
evolution modelling suggest the
planet is retaining a tenuous envelope while evolving toward a bare core, consistent with a position immediately above the radius valley. g cm^ -3 Given its bright (V = 8.4) and quiet host
star and the high Transmission Spectroscopy Metric (TSM) value (140 +/- 54), TOI-4602,b is a
prime target for atmospheric characterization. Simulated
retrievals indicate that JWST and Ariel can effectively constrain its atmospheric composition, offering a unique window into the physical processes driving the sub-Neptune to super-Earth transition.
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All authors C. Di Maio, S. Benatti, D. Locci, R. Spinelli, M. Baratella, K. Biazzo, J. Maldonado, A. F. Lanza, C. Dorn, P. E. Cubillos, A. Salmi, A. Maggio, L. Naponiello, F. Marzari, G. Micela, V. Fardella, L. Malavolta, M. Damasso, A. Sozzetti, G. Mantovan, D. Nardiello, I. Carleo, R. Claudi, R. Cosentino, M. Gonzalez, D. Muthukrishna, M. Pinamonti, T. Zingales
High Energy Astrophysical Phenomena
Bright flare in the obscured state of GRS 1915+105 as seen by NICER and Swift
Shuaitongze Zhao, Honghui Liu, Menglei Zhou et al. (+3 more)
We report time-resolved NICER and Swift X-ray spectroscopy of a bright
flare from the black hole X-ray binary GRS 1915+105 during its obscured state, which is characterized by heavy line-of-sight absorption by dense material with complex geometry. In April 2023, an unexpected
flare was detected, with the observed X-ray flux increasing by nearly an order of magnitude relative to the typical obscured-state level. The spectra show pronounced variability, including significant
evolution of the Fe K emission features. Time-resolved spectral modeling indicates that the main
flare is associated with a combination of enhanced intrinsic emission and reduced obscuration. We further find that neutral and ionized reflection components are subject to distinct absorbers, whose evolving visibility implies a stratified absorber-reflector geometry. These properties are consistent with a re-illumination phase following a failed disk wind. A delayed
radio flare detected about 2.5 days later suggests a coupling between
accretion and jet activity.
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All authors Shuaitongze Zhao, Honghui Liu, Menglei Zhou, Swarnim Shashank, Cosimo Bambi, Andrea Santangelo
High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Interaction of Strong Electromagnetic Waves with Unmagnetized Pair Plasmas
Navin Sridhar, Emanuele Sobacchi, Lorenzo Sironi et al. (+3 more)
We investigate analytically and numerically the interaction of strong electromagnetic waves with unmagnetized pair
plasmas. We show that the interaction is governed by a single nonlinearity parameter, $\varepsilon_{\rm p}$, defined as the ratio of the wave strength parameter to the wave frequency in units of the
plasma frequency (with both frequencies measured in the
plasma rest frame prior to the interaction). When $\varepsilon_{\rm p}<1$, the number of wavelengths that propagate through the
plasma without attenuation from induced Compton scattering is approximately $\varepsilon_{\rm p}^{-2/3}$. This attenuation can imprint sub-structures as narrow as a few wavelengths on the pulse profile. When $\varepsilon_{\rm p}>1$, the electromagnetic pulse acts as a relativistic piston and drives a shock into the
plasma. Our results establish a framework for the interaction of strong electromagnetic waves with pair
plasmas, a process relevant for intense
radio pulses from
neutron stars and for next-generation pair
plasma experiments at multi-petawatt
laser facilities.
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All authors Navin Sridhar, Emanuele Sobacchi, Lorenzo Sironi, Masanori Iwamoto, Daniel Grošelj, Brandon K. Russell