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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 9 October

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Collider and direct detection as key probes of asymmetric dark matter: Signals from a compressed Inert Higgs doublet

David Cerdeño, Miguel Escudero, Pietro Ghedini et al. (+4 more)

The cosmic imbalance of particles over antiparticles may be inherited by the dark matter in a certain class of asymmetric dark matter models. In this article, we thoroughly investigate the signatures of the minimal realization of this idea. In this model a new (stable) inert Higgs, $H'$, plays the role of the mediator that facilitates the asymmetry transfer from the visible to the dark sector. It also constitutes a small dark matter sub-component, while the dominant component stems from a singlet scalar asymmetry. A combination of phenomenological and cosmological constraints requires this new inert Higgs doublet to be quite light $46\,{\rm GeV}<m_{H'}< 580\,{\rm GeV}$ and its spectrum rather compressed, $\Delta M = m_{H^\pm}-m_{H_0} \lesssim 1\,{\rm GeV}$ and $\delta m = m_{A_0}-m_{H_0}\lesssim 5\,{\rm MeV}$. Therefore its charged component can be relatively long-lived on collider length-scales. By recasting searches for compressed Higgsinos at the LHC, we derive new limits on this particle and show that, while at present most of the parameter space for this state is still unconstrained, large and key regions of parameter space will be tested at the HL-LHC by a combination of searches for disappearing charged tracks and displaced soft tracks. Quite remarkably, the lifetime of the charged component of the doublet can be correlated with the dark matter interaction rate at direct detection experiments and we show that the next generation of direct detection experiments has a unique sensitivity to the parameter space in the model. The fact that a small neutral mass splitting is a prediction of the asymmetric setup makes it an interesting candidate to account for the high energy nuclear recoil event recently reported by the LZ experiment. More generally, our detailed phenomenological study holds for any dark matter model involving an inert Higgs doublet with mass below 580 GeV.
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All authors David Cerdeño, Miguel Escudero, Pietro Ghedini, Guilherme Guedes, Thomas Hambye, Abel Muñoz-Navarro, Elena Pressendo

Astrophysics of Galaxies

Searching for Nearby Supermassive Black Hole Binaries with GRAVITY

GRAVITY Collaboration: K. Abd El Dayem, N. Aimar, A. Berdeu et al. (+81 more)

We present a systematic interferometric search for close supermassive black hole (SMBH) binaries in 20 nearby type 1 active galactic nuclei (AGN) observed with VLTI/\grav. We investigate parsec-scale asymmetric emission by modeling the squared visibilities and closure phases with a single circular Gaussian component plus a background point source for the central AGN, and searching for additional compact companions through grid-based binary models. The robustness of the search is validated using injection-recovery simulations and point-spread-function diagnostics. Several features are identified in the initial significance maps, but only one candidate out of 20 shows a persistent compact asymmetry, corresponding to an observed incidence of $5\%$. If NGC~3783 is interpreted as a binary AGN, we derive a Poissonian one-sided $1\sigma$ upper limit of $f_{\rm bin}<16.5\%$ for GRAVITY-detectable binaries among bright nearby AGN (K<12.5) at separations of $\sim1$-$100$~pc. Conversely, if the observed asymmetry in NGC~3783 is associated with asymmetric circumnuclear dust emission, the corresponding upper limit on the binary fraction is $f_{\rm bin}<9.2\%$. We compare these results with predictions from the Horizon-AGN simulation, finding comparable binary fractions. We also noted that the expected fraction strongly depends on the assumed distribution of individual SMBH accretion rates within binaries, which is currently unresolved in cosmological models. Our results demonstrate the potential of infrared interferometry to identify parsec-scale binary AGN candidates and motivate future GRAVITY+ observations to expand the sample and follow up known candidates, helping to confirm their nature and distinguish genuine binaries from asymmetric nuclear structures.
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All authors GRAVITY Collaboration: K. Abd El Dayem, N. Aimar, A. Berdeu, J.-P. Berger, G. Bourdarot, W. Brandner, Y. Cao, C. Correia, Q. D'Amato, R. Davies, D. Defrère, A. Drescher, F. Eisenhauer, M. Fabricius, H. Feuchtgruber, S. Flesch, N. M. Förster Schreiber, A. Foschi, Q. Fournier, P. Garcia, R. Garcia Lopez, R. Genzel, S. Gillessen, F. Gonté, X. Haubois, S. F. Hönig, L. C. Ho, M. Houllé, S. Joharle, J. Kammerer, A. Kaufer, P. Kervella, J. Kolb, L. Kreidberg, L. Labadie, S. Lacour, O. Lai, R. Laugier, J.B. Le Bouquin, J. Leftley, R. Li, K. Li, B. Lopez, D. Lutz, F. Mannucci, F. Mang, A. Mérand, F. Millour, M. Montargès, N. Morujão, H. Nowacki, M. Nowak, S. Oberti, J. Osorno, T. Ott, C. Paladini, S. Pappert, T. Paumard, K. Perraut, G. Perrin, R. Petrov, P. O. Petrucci, N. Pourré, S. Rabien, D. C. Ribeiro, S. Robbe-Dubois, M. Sadun Bordoni, J. Sanchez-Bermudez, J. Sauter, M. Scialpi, J. Scigliuto, J. Shangguan, T. Shimizu, F. Soulez, C. Straubmeier, E. Sturm, M. Subroweit, C. Sykes, L. J. Tacconi, P. Thévenet, I. Urso, F. Vincent, J. Woillez, G. Zins

Astrophysics of Galaxies

A first view of interstellar Fe-bearing dust grains with XRISM

I. Psaradaki, L. Corrales, E. Costantini et al. (+8 more)

Understanding the reservoirs of iron (Fe) in our Galaxy is crucial for probing the mechanisms that drive dust grain growth in the interstellar medium (ISM). High-resolution X-ray absorption spectroscopy offers a powerful tool to investigate the chemistry of dust grains, particularly those containing Fe, through spectroscopic features near photoabsorption edges known as X-ray Absorption Fine Structures (XAFS). With the Resolve spectrometer aboard XRISM, we can now examine the Fe K-edge (7.1 keV) owing to its improved spectral resolution in this energy range. This enabled us to probe the dust grain chemistry in high Galactic column densities. In this work, we present a pilot study on dust grain chemistry through the Fe K-edge of the XRISM Performance Verification target GX 340+0. This source is a persistently bright low-mass X-ray binary with a hydrogen column density of 6.6x10^22 cm^-2 along the line of sight, providing sufficient optical depth at the Fe K-edge. By fitting combined dust and gas models, we find that Fe is depleted by 95% into dust along the line of sight towards the source. Moreover, we find evidence that 38% of the solid-phase Fe is in metallic iron, 47% in iron sulfides, and the remainder in silicates. The large contribution from metallic iron and iron sulfides differs from what is typically inferred from X-ray studies of diffuse ISM and may suggest that that these compounds become more significant reservoirs of Fe in higher column density Galactic sightlines.
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All authors I. Psaradaki, L. Corrales, E. Costantini, M. Mehdipour, D. Rogantini, H. Takahasi, R. Ballhausen, P. Chakraborty, T. Nakagawa, R. K. Smith, S. Zeegers

Astrophysics of Galaxies

Cluster Ages to Reconstruct the Milky Way Assembly (CARMA). VI. The age-metallicity relation of in-situ clusters and the age of the Universe

Chiara Zerbinati, Davide Massari, Fernando Aguado-Agelet et al. (+11 more)

Within the homogeneous framework for the derivation of GC ages defined by the CARMA collaboration, we focus on the clusters born in-situ in the MW. As they are the oldest among the old GCs, their absolute age provides constraints about the age of the Universe. Moreover, the shape of their AMR is expected to show the imprints of past merger events, in case these were able to trigger GC formation in the Galaxy. We derive new homogeneous ages for 18 GCs dynamically and/or chemically classified as in-situ, and build the MW AMR from a total sample of 34 GCs. We find that all the selected GCs follow a well defined AMR, with the exception of NGC6642 and Pal1. While the former is likely a member of the LKH merger event, thus putting chronological evidence for the existence of this progenitor on even more robust ground, for the latter we propose an alternative scenario according to which it formed in-situ, but in a metal-depleted region of the Galaxy, possibly due to the interaction with an unspecified merger event. To find evidence of merger-driven GC formation, we use a GMM for the observed age distribution. This is statistically best-fit by 4 components, which we associate with significant events of the MW merger history. Cluster ages were finally calibrated to a more accurate absolute age scale based on asteroseismic measurements of the mass of red giant stars in NGC6791, and the resulting AMR was fit to compute the look-back time for the beginning of cluster formation in the MW. The fit yields t_GC,i=13.59+0.33-0.32 Gyr for initial cluster formation, and tU=13.79+/-0.34 Gyr for the age of the Universe. This value translates to H0=68.72+3.95-3.49(stat.)+2.65-2.32(sys.) km s-1 Mpc-1, where the systematic error comes from a realistic estimate of the zero point uncertainty on the GC absolute ages derived from stellar models.
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All authors Chiara Zerbinati, Davide Massari, Fernando Aguado-Agelet, Cristiano Fanelli, Massimiliano Matteuzzi, Santi Cassisi, Matteo Monelli, Cristiana Spingola, Carme Gallart, Maurizio Salaris, Roger E. Cohen, Edoardo Ceccarelli, Sara Saracino, Elena Pancino

Cosmology and Nongalactic Astrophysics

Where Cluster Galaxies Reside and How Strongly They Lens

Isaque Dutra, Priyamvada Natarajan and Cian Roche

The efficiency of galaxy-galaxy strong lensing (GGSL) in clusters depends jointly on the inner mass distributions of member galaxies and their locations within the cluster potential. Observed GGSL probabilities exceed $\Lambda$CDM predictions by nearly an order of magnitude, but the relative roles of internal structure and environment remain unclear. We disentangle these effects by comparing HST strong-lensing clusters with TNG-Cluster analogs at similar lens redshifts, matched by their primary Einstein radius. For each member, we measure its lensing strength in isolation and when embedded in the cluster field. Members in cluster-critical regions are classified as Major or Minor Perturbers depending on whether they strongly lens in isolation; those in subcritical regions are classified as Intrinsic Lenses, Boosted Lenses, or Inert Members according to whether they lens independently, only with environmental assistance, or not at all. Observed clusters contain 33.7% of selected members in cluster-critical regions, compared with 21.6% in TNG-Cluster, while their Major-to-Minor ratios are similar. Outside these regions, observations contain substantially more Intrinsic and Boosted Lenses and fewer Inert Members, with Boosted Lens fractions of 25.8% and 13.5%, respectively. The discrepancy persists at fixed subhalo mass and after including line-of-sight structure. A mass-conserving contraction mimicking core-collapsed self-interacting dark matter largely recovers the conditional lensing fractions but not cluster-critical occupancy. The GGSL discrepancy therefore reflects both insufficient central concentration in simulated members and differences in their locations within the cluster lensing field.
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Solar and Stellar Astrophysics

A Spectroscopic Census of Cluster White Dwarfs from DESI, LAMOST, and SDSS

David R. Miller, Jeremy Heyl, Huahui Yan et al. (+2 more)

Gaia has substantially expanded the sample of candidate white dwarfs (WDs) in open clusters, but many remain without spectroscopic characterization. We leverage the increasingly extensive archives of large public spectroscopic surveys to identify 62 candidate cluster WDs with available spectra from DESI, LAMOST, and SDSS. After discarding sources with very low S/N and unreliable host clusters, 44 candidates remain, including 37 non-magnetic DA WDs, of which 15 had not previously been characterized in the literature for cluster studies. We find that nine are consistent with single-star origins in their proposed host clusters, increasing the combined cluster DA initial–final mass relation (IFMR) sample to 132 WDs. All lie within $2\sigma$ of the best-fit IFMR from the most comprehensive recent cluster WD sample, suggesting these additions do not require recalibrating the empirical IFMR. One is a likely Hyades tidal-tail WD, providing further evidence that dynamical dispersal helps explain the long-standing WD deficit in the nearest cluster. We further compare WDs with spectra from multiple surveys. Among seven Praesepe WDs observed by both DESI and SDSS, DESI gives higher WD masses in six cases, with a mean difference of $0.067\,\mathrm{M}_\odot$, while the inferred progenitor masses differ by as much as $0.459\,\mathrm{M}_\odot$. More broadly, nine of ten single-star cluster DAs with DESI spectra lie above the empirical IFMR, with a mean final-mass residual of $0.06\pm0.04\,\mathrm{M}_\odot$. These results show that survey-dependent differences can strongly affect cluster WD parameters, and should be considered when combining heterogeneous spectroscopy in empirical IFMR studies.
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All authors David R. Miller, Jeremy Heyl, Huahui Yan, Chengyuan Li, Pier-Emmanuel Tremblay

High Energy Astrophysical Phenomena · Cross-listed from cond-mat.stat-mech

IceCube data for astrophysical neutrinos exhibit q-statistical behavior

Constantino Tsallis and Ugur Tirnakli

Relevant IceCube recent data for astrophysical neutrinos are analyzed. Similarly to cosmic rays and proton-proton LHC collisions, the corresponding spectra are satisfactorily described, for the entire interval of measured energies, through q-Gaussians. This fact reinforces the already available evidence that nonadditive entropies (either of the $S_q$ class or of the $S_{delta}$ one, or even alternative ones) appear to play a crucial role in systems such as black holes and related cosmological phenomena (e.g., dark energy). The IceCube data yield sensibly high values for the momenta-distribution nonadditive index (q \simeq 1.6), in contrast with the cosmic rays values (q \simeq 1.2) and the LHC values (q \simeq 1.1). This fact neatly indicates very-long-ranged space-time correlations. The detailed associated physical mechanisms remain, at the present stage, as an instigating open issue.
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Cosmology and Nongalactic Astrophysics

Ultralight scalars and invisible gravitons

Massimo Giovannini

Unless the tensor to scalar ratio is small enough, the non-adiabatic mode associated with the ultralight bosons may be dangerously comparable with the adiabatic spectrum of curvature inhomogeneities. We point out here that this statement depends on the timeline of the post-inflationary expansion rate. Provided the decelerated evolution is slower than radiation for a sufficiently long period, the relative weight of the non-adiabatic and adiabatic components does not conflict with the direct constraints coming from the large-scale observations. Conversely the presence of ultralight bosons excludes the presence of long stages expanding faster than radiation. The synthesis of the light nuclei and the spectrum of the relic gravitons at high frequencies set the relevant constraints on the duration of the decelerated stages, on the delayed dominance of radiation and on the mass range of the ultralight scalars.
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Earth and Planetary Astrophysics

OGLE-2016-BLG-0523: A Low-mass Brown Dwarf or super-Jupiter in a $>100$ au Orbit

Hongjing Yang, Weicheng Zang, Yoon-Hyun Ryu et al. (+37 more)

To search for very wide-orbit binary-lens events, we cross-match microlensing events detected by OGLE-IV and KMTNet between 2011 and 2024. After removing contaminants from variable stars, we identify OGLE-2016-BLG-0523 as a microlensing event showing two short-lived bumps in its light curve, with the two separated by 8.36 yr. We investigate three scenarios to explain the two bumps, including a binary-lens single-source (2L1S), a single-lens binary-source (1L2S), and two unrelated single-lens single-source events (2$\times$1L1S). The 1L2S interpretation is excluded due to its poorer fit to the data, while the 2$\times$1L1S scenario is disfavored by the low event rate, unphysical total source flux, and unphysical color for one of the two putative sources. For the surviving 2L1S interpretation, the Einstein timescales of the two bumps are $8.343 \pm 0.076$ days and $3.231 \pm 0.047$ days, respectively, implying a binary mass ratio of $q = 0.15$. A Bayesian analysis indicates that the primary lens is most likely a low-mass M dwarf, while the companion is probably a low-mass brown dwarf or super-Jupiter. The inferred projected separation is about 450 au, making the companion the widest low-mass object discovered via microlensing to date. Our discovery highlights both the promise and challenges of identifying very wide, low-mass companions through microlensing. Although upcoming facilities such as Roman and Earth 2.0 space telescopes will improve sensitivity to such events, overcoming degeneracies and distinguishing them from variable phenomena will remain essential for building a robust statistical sample.
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All authors Hongjing Yang, Weicheng Zang, Yoon-Hyun Ryu, Andrzej Udalski, Yuchen Tang, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radoslaw Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, Jiyuan Zhang, Shude Mao, Hongyu Li, Qiyue Qian

High Energy Astrophysical Phenomena

Adiabatic evolution of hadronic neutron stars

Domenico Logoteta, Francesco Zeno Constanzo, Ignazio Bombaci et al. (+3 more)

In this paper we compute several structural properties of static and rotating neutron stars, considering both rigid and differential rotation. To this end, we use a finite-temperature beta-stable equation of state (EOS) extending the zero-temperature hadronic EOS derived by Fortin et al. (2017). We account for the formation of hyperons and the presence of a neutrino-trapped component. Our goal is to provide insights into the long-term evolution of a protoneutron star (PNS) formed after a core-collapse supernova (CCSN) or a remnant resulting from a binary neutron star merger (BNSM). The EOS is derived using a relativistic mean-field quantum many-body theory within the Hartree approximation. Coupling constants are determined using experimental data on hypernuclei and hypernuclear matter to better account for uncertainties in hyperon single-particle potentials. Our EOS models reproduce the typical features of cold neutron stars and PNSs for nucleonic and hyperonic compositions. In particular, they are consistent with measured masses (2.01 M_sun and 2.14 M_sun for PSR J0348+0432 and PSR J0740+6620) and dimensionless tidal deformabilities from GW170817. Thermal contributions act differently depending on composition and rotation state. Finally, our evolutionary scheme provides a simple way to interpret the long-term evolution of BNSM remnants or PNSs from CCSNe, complementing dynamical simulations unable to cover full evolutionary timescales.
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All authors Domenico Logoteta, Francesco Zeno Constanzo, Ignazio Bombaci, Sebastiano Bernuzzi, Albino Perego, David Radice

Astrophysics of Galaxies

A Comprehensive JWST Slitless Spectroscopic Census of $\sim$12,000 Emission-Line Galaxies at Redshift $0\sim9$ in COSMOS

Shuqi Fu, Zijian Zhang, Danyang Jiang et al. (+5 more)

Emission-line galaxies provide key diagnostics of star formation, chemical enrichment, and AGN activity across cosmic time. We present a systematic census of emission-line sources using JWST/NIRCam wide-field slitless spectroscopy (WFSS) from the COSMOS-3D program, which covers a large contiguous area of 0.33 deg$^2$ and provides F444W grism spectroscopy over $3.9$–$5.1\ \mu$m. By combining slitless spectroscopy with deep multi-band imaging data, we construct a homogeneous spectroscopic sample of 12,275 objects at redshift 0–9. The typical $3\sigma$ line-flux limit reaches $3.2\times10^{-18}\ {\rm erg\ s^{-1}\ cm^{-2}}$. To address source confusion inherent to slitless spectroscopy, we develop a multi-step identification framework that combines information from spectra, images, spectral energy distributions, and spatial distributions. We introduce convolutional neural network and large language model to emulate the human identification process and improve efficiency. The resulting catalog provides spectroscopic redshifts, emission-line measurements, and derived physical properties for all sources. The F444W WFSS enables the detection of multiple emission lines, including primarily [O III], H$\alpha$, He I $\lambda10830$, [S III] $\lambda\lambda9531,9069$, Pa$\beta$, Pa$\alpha$, Br$\beta$, PAH, Br$\alpha$, allowing a continuous census of galaxies across cosmic time. We construct composite spectra in several redshift bins and detect a variety of faint spectral features that are difficult to identify in individual spectra, including higher-order hydrogen recombination lines, CO absorption bands, and [Fe II] lines. This catalog provides a key reference dataset for studies of galaxy evolution and AGN activity, and demonstrates the power of WFSS for constructing large, unbiased spectroscopic samples over wide areas. The full catalog will be publicly available online upon publication.
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All authors Shuqi Fu, Zijian Zhang, Danyang Jiang, Jie Chen, Linhua Jiang, Chenxi Bao, Yihe Wang, Ronaldo Laishram

Cosmology and Nongalactic Astrophysics · Cross-listed from math-ph

Unifying spherical convolutions through lifting

J. D. McEwen

We develop a unified description of convolution on the sphere by lifting to the rotation group. A number of definitions of spherical convolution have been proposed, differing in whether the kernel is axisymmetric or directional, whether the output is on the sphere or the rotation group, whether the signals carry spin, and in their computational cost. No unified treatment exists. Regarding the sphere as the homogeneous space $S^2 \cong \text{SO(3)}/\text{SO(2)}$, we lift a spin $s$ field to the rotation group, convolve on $\text{SO(3)}$, and project back to the sphere through the adjoint of the lift for a potentially different spin $s'$. We recover every rotation-equivariant convolution considered previously through constraints on the kernel, spin choices and inclusion or omission of the lift and projection. For maps between fields of fixed input and output spin, we prove that directional kernels, output on the sphere and equivariance cannot be achieved simultaneously. We make explicit that spin fields are sections of associated line bundles, linking the physics and bundle literatures, and express the spin rotation phase as the character of the twist of the section. We present harmonic-space algorithms for the exact and efficient computation of lifted spherical convolutions of band-limited fields by appealing to sampling theorems on the sphere and rotation group. All operators are implemented in the open-source s2conv code, and numerical experiments confirm the reductions and the equivariance of the operators to machine precision. Finally, we illustrate the operators on fields measured on the Earth and on the celestial sky.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Impact of ab initio E1 strength on neutron capture rates along the nickel isotopic chain

Francesca Bonaiti and Joanna E. Sobczyk

Nucleosynthesis simulations of the r-process require neutron capture rates for neutron-rich nuclei, many of which lie beyond experimental reach. Predicting these rates relies on theoretical calculations of the low-energy electric dipole (E1) strength near the neutron threshold. We present the first ab initio computation of the E1 strength along the nickel isotopic chain, for $^{58}$Ni and the even-even isotopes $^{68-80}$Ni. The E1 strength is obtained with the Lorentz integral transform coupled-cluster (LIT-CC) method, extended to axially symmetric reference states to reach open-shell nuclei, using two- and three-nucleon interactions from chiral effective field theory. The approach is benchmarked against the measured photoabsorption cross section of $^{58}$Ni and the E1 strength of $^{68}$Ni. Along the chain we find low-lying E1 strength above the neutron threshold that grows with neutron number. Including it in the reaction code TALYS enhances the neutron capture rates forming $^{68-78}$Ni between 3 and 10 GK, with an effect that increases with temperature and neutron number and an uncertainty dominated by the inversion of the integral transform. For $^{80}$Ni, where strong pygmy dipole strength lies just above threshold, the enhancement sets in already around 0.5 GK. Together, these results open the way to ab initio input for neutron capture rates along isotopic chains far from stability.
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Cosmology and Nongalactic Astrophysics

The Redshift-Space Galaxy Power Spectrum at Two-Loop Order

Oliver H. E. Philcox

Contemporary large-scale structure analyses center around the galaxy power spectrum, modeled with one-loop perturbation theory. This description naturally breaks down at large wavenumbers, prohibiting the extraction of cosmological information from small-scale clustering. In this work, we present a complete model for the redshift-space galaxy power spectrum up to two-loop order, derived in the framework of the Effective Field Theory of Large Scale Structure. This accounts for a wide variety of effects, including fifth-order galaxy bias, redshift-space distortions, small-scale non-linearities, spatial non-locality, long-wavelength bulk flows, coordinate distortions, and stochasticity, involving a total of 49 free coefficients. Our model additionally encodes all deterministic contributions to the one-loop bispectrum and trispectrum (as well as the tree-level quadspectrum and pentaspectrum), which depend on many of the same parameters. We implement the model numerically, using the vegas algorithm to precompute the loop integrals; this allows the full likelihood to be evaluated in milliseconds. The approach is validated using power spectra measured from high-resolution simulations, considering both dark matter and realistic galaxy samples. The extension to two-loop order greatly increases the range of scales over which the power spectrum can be modeled, with $k_{\rm max}$ rising from $0.2h\,\mathrm{Mpc}^{-1}$ to $0.34h\,\mathrm{Mpc}^{-1}$ for a luminous red galaxy sample at $z=0.5$. Much of the additional information is absorbed by the numerous fifth-order biases and counterterms; for this reason, constraints on $\sigma_8$ are not significantly enhanced by the inclusion of two-loop terms. Future work will assess the full implications of the two-loop model for cosmological parameter inference, both alone and in combination with higher-order statistics.
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High Energy Astrophysical Phenomena

Perpendicular transport in isotropic magnetic turbulence. The role of stochastic drifts

F. Pucci, P. Blasi, O. Pezzi et al. (+2 more)

In cosmic ray propagation through turbulent magnetic fields, transport perpendicular to the mean field plays an important role in various astrophysical environments. Numerical simulations have shown that parallel and perpendicular diffusion coefficients exhibit different energy scalings, causing their ratio to increase with energy, but a comprehensive theoretical explanation remains elusive. Here, we investigate perpendicular diffusion using test particle simulations in synthetic isotropic turbulence spanning 6-7 orders of magnitude in wavenumber, together with a theoretical extension of nonlinear guiding center theory that incorporates stochastic drifts. Our approach combines field line random walk and random guiding center drifts to describe perpendicular transport. We find that parallel and perpendicular diffusion coefficients exhibit the same energy scaling only for $r_L \lesssim 10^{-2} L_c$, where $r_L$ is the particle Larmor radius and $L_c$ is the turbulence coherence length. At higher energies, perpendicular diffusion develops a stronger energy dependence, consistently across different turbulence levels. Our theoretical model suggests that this behavior arises from stochastic drifts induced by turbulent magnetic field components parallel to the mean field.
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All authors F. Pucci, P. Blasi, O. Pezzi, C. Evoli, F. Malara

Astrophysics of Galaxies

Insights from the stability of methanol maser flare properties I: G9.62+0.20E

S.P. van den Heever and D.J. van der Walt

The brightest 6.7 GHz methanol maser in the Galaxy is associated with the high-mass star-forming region (HMSFR) G009.62+0.20E. Additionally, this methanol maser shows periodic flaring observed at 6.7 and 12.2 GHz. Several models have been hypothesized to explain the periodicity, including periodic accretion, spiral shocks in the gaps of circumbinary disks, pulsating stars, dicke's superradiance, and a colliding wind binary (CWB) system. We analyzed the time series of the 1.22 km s-1 feature of the 6.7 GHz methanol maser spectrum and the 1.25 km s-1 feature of the 12.2 GHz methanol maser spectrum over the monitoring duration of roughly 20 years, to determine an updated period, analyze the stability and repeatability of the flares, the temporal behavior of the flare profile, and the duty cycle of the flare profile based on the updated period. From these results, it is argued for or against any of the mechanisms that have been proposed to explain the periodicity. Lomb-Scargle (LS) and phase dispersion minimization (PDM) methods were used to determine the methanol maser period at 6.7 and 12.2 GHz. Once the period has been determined, phase-folding or period-folding was used to analyze the flare shape, flare stability, and duty cycle of the flares. The periods of the 6.7 and 12.2 GHz methanol masers were determined to be ~ 243.0 +- 0.3 days. The flares are highly repeatable, stable, and show almost identical shapes, as well as their duty cycles. A replicated kernel density estimator (KDE) of the flare shape reproduces the time series very well over a time span of ~ 8000 days. After careful consideration of the proposed mechanisms for periodic methanol masers, we conclude that all but one, the CWB model, have been ruled out as a possible driver of this flare profile. It has also been established that the CWB model can qualitatively explain the flare profile of the periodic methanol masers.
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High Energy Astrophysical Phenomena

TeV Gamma-Ray Emission in the DA 495 Region from HAWC Observations of J1952+2924, J1954+2837, and J1958+2848

R. Alfaro, C. Alvarez, E. Anita-Rangel et al. (+82 more)

Previous observations of the DA 495 region, which contains the pulsar wind nebula (PWN) DA 495 and other very-high-energy (VHE; $>100~\textrm{GeV}$) gamma-ray emitters, showed inconsistent results across different VHE experiments, including differences in the measured flux of DA 495 and in the number of reported sources. Our new dedicated analysis using 3071 days of HAWC data resolves these discrepancies. We identify three extended sources, HAWC J1952+2924 (DA 495), HAWC J1954+2837, and HAWC J1958+2848, all with curved spectra, and find a hint of a fourth source. For DA 495, a multi-wavelength analysis, including our results, radio, X-ray, and other gamma-ray data, reveals that its extended emission is best described by leptonic interactions with an inferred magnetic field of $B\sim10~\mu\textrm{G}$ and that hadronic components are not required. On the other hand, we interpret the other two sources, which have no confirmed counterparts, as TeV halos associated with nearby pulsars, PSR J1954+2836 and PSR J1958+2846, respectively. These results reinforce the interpretation of DA 495 as a leptonic-dominated PWN and add two candidates to the growing population of TeV halos.
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All authors R. Alfaro, C. Alvarez, E. Anita-Rangel, M. Araya, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, P. Bangale, A. Bernal, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, N. Di Lalla, R. Diaz Hernandez, M. A. DuVernois, J. C. Díaz-Vélez, C. Espinoza, N. Fraija, S. Fraija, A. Galván-Gámez, J. A. García-González, F. Garfias, N. Ghosh, A. Gonzalez Muñoz, M. M. González, J. A. González, J. A. Goodman, J. Gyeong, J. P. Harding, I. Herzog, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, S. Kaufmann, D. Kieda, K. Leavitt, W. H. Lee, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, P. E. Mirón-Enriquez, J. A. Morales-Soto, E. Moreno, M. Mostafá, M. Najafi, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, M. Osorio-Archila, E. Ponce, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, M. Roth, A. Sandoval, J. Serna-Franco, M. Shin, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, I. Torres, R. Torres-Escobedo, L. Villaseñor, X. Wang, Z. Wang, I. J. Watson, H. Wu, S. Yu, S. Yun-Cárcamo, X. Zhang, H. Zhou, C. de León

Earth and Planetary Astrophysics

The origin of the large heavy element contents of warm Jupiters

Bertram Bitsch

Planet interior models have revealed that warm Jupiters should harbor large heavy element masses (up to 30-40% of the planetary mass). Within the pebble drift and evaporation scenario, inward drifting pebbles can evaporate and enrich the inner disc with vapor to super-stellar values, accreteable by giant planets. As H$_2$O ice evaporates in the inner disc, while CO$_2$, CH$_4$ and CO evaporate in the outer disc, the enrichment of the disc with vapor decreases with increasing orbital distance. We use the chemcomp code to model the migration and growth of planets via pebble and gas accretion in discs around stars with different masses and discs with different sizes. We show (i) that pebble drift and evaporation can explain the wide range of derived heavy element contents of giant planets. (ii) Giant planets forming around stars with larger disc sizes can accrete larger quantities of heavy elements, because these discs can maintain a high pebble flux for a longer time. (iii) Planets forming or migrating interior to the water ice line can accrete larger amounts of heavy elements via the accretion of vapor enriched gas compared to planets forming in the outer disc regions. (iv) Metal rich stars can allow the formation of planets that are more enriched in heavy elements, if they form in the inner disc regions. Planets forming in the outer disc regions will be - independently of the disc metallicity - much less enriched compared. (v) Planets forming in discs with the same size and total mass, but around stars with higher mass, are only marginally more enriched compared to their counterparts forming around lower mass star. Our study suggests that the trend of increasing total heavy element mass with increasing planetary mass is caused by the accretion of vapor enriched gas in discs with different sizes in the combination with different origins of warm giant planets from the inner and outer disc.
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Astrophysics of Galaxies

A dust-reddened quasar in a [C II]-luminous host at z=6.55

Daming Yang, Joseph F. Hennawi, Rychard Bouwens et al. (+18 more)

Most known quasars at $z>6$ were selected through their rest-frame UV emission. Only a small number of reddened quasars have been identified at these redshifts, leaving their nuclear and host-galaxy properties poorly constrained. We present JWST/NIRSpec spectroscopy and ALMA band 6 observations of the quasar J1440+0019 at $z=6.5488$, revealing its dust-reddened nature and jointly characterizing its nucleus and host galaxy. The continuum is best described by an SMC-like extinction law with $E(B-V)=0.20\pm0.03$. Three absorption systems detected in N V, Si IV, and C IV are blueshifted by approximately $900$–$3600$ km s$^{-1}$ and likely trace an ionized nuclear outflow. The broad Mg II line and extinction-corrected continuum yield a black-hole mass of $\log(M_{\rm BH}/M_\odot)=9.04\pm0.42$, a bolometric luminosity of $L_{\rm bol}\simeq1.1\times10^{47}$ erg s$^{-1}$, and an Eddington ratio of $\lambda_{\rm Edd}\simeq0.8$. ALMA observations further reveal its host galaxy to be among the most [C II]-luminous known at $z>6$, with $L_{\mathrm{[C II]}}=(7.21\pm0.25)\times10^9 L_\odot$. For a fiducial dust temperature of 47 K and emissivity index $\beta=1.6$, the dust continuum implies $L_{\rm TIR}=8.9\times10^{12} L_\odot$ and $M_{\rm dust}=4.0\times10^8 M_\odot$. The inferred dynamical mass places J1440+0019 in the region of the $M_{\rm BH}$–$M_{\rm dyn}$ plane occupied by high-redshift blue quasars. These observations reveal a moderately reddened, rapidly accreting quasar in a luminous, dust-rich host during reionization. Its measured nuclear and host-galaxy properties provide an observational reference for identifying and characterizing similar systems in future systematic searches with wide-area infrared surveys.
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All authors Daming Yang, Joseph F. Hennawi, Rychard Bouwens, Timo Kist, Eduardo Bañados, Hiddo S. B. Algera, Aaron J. Barth, Sarah E. I. Bosman, Frederick B. Davies, Anna-Christina Eilers, Xiaohui Fan, Victoria A. Fawcett, Yuming Fu, Anniek J. Gloudemans, Francesco Guarneri, Bin Jia, Elia Pizzati, Huub Röttgering, Jan-Torge Schindler, Feige Wang, Jinyi Yang

Astrophysics of Galaxies

A strategy for astrometric quasar selection with Gaia DR3 and its application to discover new luminous $z>2$ quasars

J. Li and J. P. U. Fynbo

We aim to provide a cookbook for purely astrometric selection of quasars with Gaia DR3 and to provide an example of its use for the identification of very luminous $z>2$ quasars. We analyse the Gaia DR3 astrometry of confirmed quasars and stationary sources. We show that the proper motion signal to noise $\mu/\sigma_{\mu}$ follows a Rayleigh-like distribution. We also show the importance of properly taking into account the correlation between proper motions in right ascension and declination, as well as the non-linear error propagation. We adopt the Mahalanobis distance to the null proper-motion hypothesis. A scaled $\chi^2$ distribution with $k=2$ and scale $s=1.1485$ is fitted to Gaia-CRF3; the corresponding $\pm2\sigma$ Gaussian-equivalent threshold is $D^2_{M(\mu)}<7.097$. The final criteria combine this with the parallax condition and $\mathrm{ruwe}<1.4$. Applying the new criteria to the SDSS DR16Q confirmed quasars, the recovery rate is $90.25\%$. The suggested purely astrometric selection significantly improves both completeness and purity compared to other strategies used in the literature, reaching a quasar purity of approximately $95\%$ ($\sim2\sigma$ Gaussian-equivalent). It can be used to improve the selection purity and completeness for future quasar surveys. As an example, we use the suggested strategi to locate 24 very bright $z>2$ quasars without redshifts in the literature. Our proposed astrometric selection strategy recovers 95% of known quasars. Its potential use for new discoveries is demonstrated by the identification of 24 very luminous $z>2$ quasars. Ten of these are new discoveries and for an additional seven we correct the redshifts determined by other methods.}
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Cosmology and Nongalactic Astrophysics

Relaxation Dark Energy: Compositional Dynamics and the Future of Cosmic Acceleration

Gianmassimo Tasinato

If cosmic acceleration is driven by a positive cosmological constant, the universe approaches an eternally accelerating de Sitter state, whose interpretation in quantum gravity remains elusive. We develop a framework in which acceleration is instead a transient stage of dark-sector relaxation towards compositional equilibrium: matter and dark energy approach a stationary density ratio, eventually diluting like pressureless matter. Guided by linear response theory and Onsager's near-equilibrium regression hypothesis, we describe this evolution through a composition variable measuring departure from equilibrium. Extending constant fractional relaxation to the full background evolution yields the dark-energy equation of state $w=w_0a^{-n}$, where $n$ is the relaxation rate per e-fold of expansion. This history connects early dark-energy suppression, an upward phantom crossing and a density maximum to a pressureless scaling future. Using DESI DR2 BAO and Planck distance priors, with and without three alternative supernova compilations, we find a nominal $2.6$–$3.6\sigma$ preference for nonzero relaxation over constant $w$. The composition framework also motivates a constitutive prescription for linear perturbations that remains regular at phantom crossing. Near equilibrium, regular long-wavelength composition disturbances relax at the background rate to leading order, while small-scale fluctuations propagate as damped sound waves. We prove, however, that for separately conserved matter and dark energy, the pointwise constitutive relation cannot sustain a regular, gradient-stable negative-pressure branch throughout its full past evolution. We explore modifications of the pressure response and their consistency with neighbouring homogeneous histories, identifying requirements for extending the near-equilibrium description to the full cosmological evolution.
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Astrophysics of Galaxies

Turbulence modes in molecular clouds in M33: a challenging test of the Brunt-Federrath framework

Raffaele Rani, Ayu Konishi, Kazuyuki Muraoka et al. (+5 more)

Understanding the turbulent structure of molecular clouds is essential for linking galactic environment to the regulation of star formation. Although Galactic molecular clouds have been studied extensively, extending turbulence-mode analysis beyond the Milky Way remains challenging because of the limited spatial resolution and dynamic range of extragalactic observations. We assess the applicability of the Brunt & Federrath (2014; BF14) framework to molecular clouds in M33. We apply BF14 to 128 $^{13}$CO(2-1) clouds, selecting a primary quality-controlled sample of 54 clouds and a more restrictive 25-cloud subsample defined using a stricter extraction-padding criterion (PAD=2) for quantitative analysis.Tests of cloud and noise power spectra, Fourier-space cutoffs, extraction padding, and Monte Carlo uncertainties demonstrate that the retained spatial frequencies are dominated by astrophysical signal and that the inferred turbulence-mode fractions are robust against reasonable analysis choices. Both samples yield consistent distributions of the solenoidal fraction, with mean values of $R \simeq 0.22$ for both samples and median values of $R \simeq 0.18$ and $0.17$, respectively, indicating that compressive motions dominate the turbulent energy budget. No strong systematic variations of $R$ are found with galactocentric distance or tracers of recent star formation. These results demonstrate that, despite the challenging spatial resolution of current extragalactic molecular-line observations, the BF14 framework can be applied reliably to nearby galaxies using spectroscopic observations alone. To our knowledge, this constitutes the first application of the full BF14 formalism to extragalactic molecular-cloud observations.
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All authors Raffaele Rani, Ayu Konishi, Kazuyuki Muraoka, Toby J. T. Moore, David J. Eden, Karan Fernandes, Yueh-Ning Lee, Shih-Ping Lai

Astrophysics of Galaxies

High Resolution Spectro-Polarimetric Observations of the Optical Filaments surrounding NGC 1275 with ESPaDOnS

Benjamin Vigneron, Julie Hlavacek-Larrondo, Luca Fabiani et al. (+6 more)

We analyze archival high spectral resolution ESPaDOnS spectropolarimetric observations (R = $\lambda/\Delta\lambda$ = 68000) of three targeted locations within the filamentary nebula surrounding NGC 1275. We present here the analysis of the main filaments emission lines, namely: [NII]$\lambda6584$, H$\alpha$, and [NII]$\lambda6548$, across our three pointings displaying clear detectable emission, with one also showing additional [SII]$\lambda6716$ and [SII]$\lambda6731$ emission line doublet. Using a Markov Chain Monte-Carlo (MCMC) algorithm and thanks to the exceptionally high spectral resolution of the observations, we resolve for the first time each of the emission lines within one of the pointings into a set of three emission components with a remarkable velocity dispersion contrast ($\sigma_1 \sim 25$ km/s, $\sigma_2 \sim 90$ km/s and $\sigma_3 \sim 208$ km/s). We also perform flux ratios of the three detected emission components, which reveal differences in electron density and ionization sources. Consequently, the ESPaDOnS observations appear to reveal for the first time the overlap of an outer quiescent filament and a central turbulent filament likely affected by the AGN activity at a distance of $\sim 6.8''$ ($\sim 2.5$ kpc) from the central BCG. Finally, ESPaDOnS polarimetric data of one of the pointing allows us to confirm an average linear polarization degree of $\sim 0.15-0.14\%$ and an angle of polarization of $5.3\pm25.7^\circ$ for the optical emission of the filaments, as well as polarization dips associated with the H$\alpha$ emission line and its multiple emission components. We interpret these features and measurements as tentative polarization due to dust scattering.
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All authors Benjamin Vigneron, Julie Hlavacek-Larrondo, Luca Fabiani, Lison Malo, Carter Lee Rhea, Megan Donahue, Jorge Karolt Barrera Ballesteros, Hyunseop Choi, Nadine Manset

Earth and Planetary Astrophysics

Assessing PLATO's Discovery Potential across Different Observing Strategies

Yoshi Nike Emilia Eschen, Michelle Kunimoto, Juan Cabrera et al. (+11 more)

The PLATO mission, planned to launch in spring 2027, will observe a fixed Southern field, LOPS2, for at least 2 years with the goal of discovering and deriving precise parameters for planets as small as Earth around FGK dwarfs and sub-giants. Afterwards, PLATO could continue to monitor the same field or move to a Northern field, LOPN1, overlapping with the Kepler field. We assess these two observing strategies in terms of sensitivity of detecting small and long period planets, and subsequently we estimate yields for both observing strategies. Within this we account for including the Kepler data in the LOPN1 field, monitoring of up to 8 years of the LOPS2 field, and the sensitivity improvement from combining TESS and PLATO data since both fields have been and will be continued to be observed with TESS. We find that by monitoring both fields, and hence more stars, the total number of newly discovered planets is maximised. However, to optimise the number of discovered small and long periods planets, long-term monitoring of one field produces the best results. The combination of Kepler and PLATO data improves detection sensitivities; however, as this only covers a fraction of the LOPN1 field and stellar sample, it improves the yields of small and long period planets only marginally. Hence, to detect and characterise small and long period planets in this sparsely explored exoplanet parameter space, a longer continuous observation of the LOPS2 field is best.
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All authors Yoshi Nike Emilia Eschen, Michelle Kunimoto, Juan Cabrera, Adrien Leleu, Thomas G. Wilson, Heike Rauer, Alex Romanec, François Bouchy, Magali Deleuil, Nicholas Jannsen, Don Pollacco, Toby Rodel, Sophia Sulis, Stéphane Udry

Earth and Planetary Astrophysics

How long could volcanic plumes persist in the Venus atmosphere?

Maureen Cohen, James Holmes, Joanna Egan et al. (+2 more)

Resolving the ambiguity surrounding current Venusian volcanism is a primary objective for upcoming missions like EnVision and VERITAS. This study uses the Venus Planetary Climate Model to simulate the dispersal and detectability of volcanic plumes containing water vapour (H2O), hydrogen chloride (HCl), carbon monoxide (CO), and carbonyl sulphide (OCS) within a three-dimensional atmospheric environment. We model localised gas enhancements at altitudes probed by nightside spectral windows (8.62, 20.91, and 35.45 km above surface). Results indicate that plumes persist longest in the deep atmosphere (8.62 km) at equatorial latitudes, where H2O enhancements remain distinguishable from low background variability for up to 100 hours, forming distinct downstream streaks. In contrast, at 35 km, high intrinsic variability in chemically active species (CO and OCS) driven by atmospheric dynamics obscures plume signatures and chemically inert species disperse within 0.5-2 Earth days. Plumes at high latitudes disperse more rapidly than at low latitudes at all altitudes. We perform sensitivity tests with trace gas increases of 50%, 40%, 30%, 20%, 10%, and 3% above baseline and plume injection times of 6, 12, 28, 38, and 126 hours at all three altitudes and two latitudes. We conclude that observing inert gases, in particular H2O, at low altitudes and latitudes offers the best opportunity for successful plume detection.
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All authors Maureen Cohen, James Holmes, Joanna Egan, Stephen Lewis, Manish R. Patel

Solar and Stellar Astrophysics

Magnetic connectivity from the Sun to the Earth with MHD models II. Impact of input magnetic maps

Barbara Perri, Silke Kennis, Brigitte Schmieder et al. (+1 more)

Connectivity estimation needs to be fast and thus usually relies on semi-empirical models. We previously established that optimised magnetohydrodynamics (MHD) models can also be used to derive magnetic connectivity, yielding good results, especially for complex configurations. However, the modelling is not the only factor that can impact the connectivity estimation. Models' results, both semi-empirical and MHD, depend heavily on the input data used to drive the simulation. In order to quantify this impact on our connectivity estimation, we used 20 different maps by four providers. We selected the period of July 2019, which corresponds to Carrington rotation (CR) number 2219, because it had already been studied in a previous paper. It corresponds to a period of minimum activity, meaning minimal interference from transient structures, but with a high-speed stream and several polarity switches. We have compared our results with in situ data from ACE and developed several visualisation techniques to validate connectivity not only for a specific date but also for a full CR. The choice of the input magnetic map drastically affects the connectivity estimates, with global scores going from 28% global agreement to 63% in the most extreme case. The HMI and GONG maps consistently gave the best connectivity estimations, with more than 50% correct results of the full CR. For this specific period, the GONG-ADAPT maps yielded the least reliable results, with a score below 35%. This is not surprising, as we have shown before that COCONUT required parameter adjustments for these maps. However, WSO maps which showed poor coronal agreement actually provided good connectivity estimates, showing that the Heliospheric Current Sheet (HCS) location is in the end the most crucial parameter for connectivity. Consistent data over a full Carrington rotation are to be favored compared to daily.
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All authors Barbara Perri, Silke Kennis, Brigitte Schmieder, Stefaan Poedts

Solar and Stellar Astrophysics

X-Shooter view of planetary nebulae microstructures I: The case of NGC 7009 knots

L. Konstantinou, S. Akras, K. Bouvis et al. (+4 more)

The properties of NGC 7009 knots are investigated by employing UV-to-near-infrared data from the X-Shooter spectrograph. These structures belong to the category of low-ionization structures (LISs), which are characterized by enhanced emission from low-ionization species and whose origin remains enigmatic. Our main goal is to conduct the first dedicated spectroscopic study of LISs using X-Shooter, that covers a wide spectral range from the UV to the near-IR, simultaneously. As a pilot study, we focus on NGC 7009 to investigate its ionized, atomic, and molecular gas, aiming to better characterize the physical properties of its LISs and explore their largely unexplored molecular content. The spectrum was processed through the ESO Reflex pipeline, and the physical properties of LISs were derived with the latest version of PyNeb. More than 250 emission lines were detected in the spectra of NGC 7009 LISs, including rare, forbidden transitions from low- ionization species such as Fe+ and Ni+, as well as two transitions from P+, identified here for the first time in LISs. The detection of multiple shock tracers, together with the shock excitation of [Fe II] and [O I], as revealed by emission-line diagnostics, supports the presence of shocks at LISs. The richness of the spectrum allowed us to derive electron temperatures and densities at the LISs using both collisionally excited and optical recombination lines. In the near-IR spectrum of the LISs, nine ro-vibrational H2 emission lines were detected, seven of which were reported here for the first time. These lines were used to construct the H2 excitation diagram, providing new insights into the physical conditions of the nebular gas. The excitation of molecular hydrogen is most likely dominated by collisional processes through shocks.
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All authors L. Konstantinou, S. Akras, K. Bouvis, P. Boumis, J. Garcia-Rojas, D.R. Gonçalves, K.N. Gourgouliatos

Instrumentation and Methods for Astrophysics

First Experimental Results of Space Object Detection Using the InteRFeX Array

Bhaskar Ahuja, Thomas Crowther, Steven Tingay et al. (+3 more)

This paper presents the first experimental validation of InteRFeX, a non-uniform receive only (passive) array located at the Nova Systems Space Precinct in Peterborough, Australia, designed for space domain awareness applications. It operates over a frequency range of 70 to 300 MHz and is capable of functioning in a range of observational modes, including as a coherent passive bistatic radar for space surveillance, which is the focus of this work. InteRFeX exploits commercial broadcast transmissions as illuminators of opportunity, combining cross-ambiguity function processing for bistatic range and range-rate retrieval with MUSIC-based direction-of-arrival (DoA) estimation for angular localization. The International Space Station (ISS) serves as the experimental target, with measurements evaluated against Two-Line Element (TLE) orbit predictions. Taking advantage of the dual-polarized array, all four reference–surveillance polarization combinations are evaluated, revealing differences in detection rate and mean signal-to-noise ratio (SNR) over the observation pass, with bistatic-range RMSEs of approximately 1 km relative to the TLE-derived reference. Independently, the MUSIC-based DoA estimates exhibit a mean angular separation of approximately $0.45^\circ$ from the TLE-derived reference directions. The angular deviations are further decomposed into along-track and cross-track components, enabling a more detailed characterization of the DoA offsets relative to the TLE-derived reference trajectory. The processing framework also includes a first-order bistatic link-budget analysis to estimate the expected SNR over the observation geometry. These results demonstrate the feasibility of passive-radar space domain awareness using radio-interferometric array technology and establish the proposed signal-processing pipeline as a basis for a dedicated coherent passive-radar mode within InteRFeX.
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All authors Bhaskar Ahuja, Thomas Crowther, Steven Tingay, Andrew Guidi, Luca Gentile, Marco Martorella

Earth and Planetary Astrophysics

The Hydrological Cycle and Circulation of Tidally-Locked Planets with a Finite Moisture Inventory

Daniel A. Williams, Geoffrey K. Vallis, Stephen I. Thomson et al. (+1 more)

Tidally-locked planets express a range of climate regimes distinct from those found in our solar system. Their atmospheres are often dominated by planetary-wide overturning circulations and super- rotating jets. In this paper we explore the hydrological cycle of such planets and how it might depend on the total inventory of condensate. To this end we use a set of idealised GCM simulations to probe the response of the hydrological cycle to the surface moisture budget in their atmospheres. We find that for low moisture inventories the climate quickly develops a barren day side and a moist night side where the moisture is trapped, as might be expected. For higher moisture inventories the drying of the day side is significantly delayed by the development of a substellar lake just east of the substellar point, which is sustained by the presence of a local thunderstorm-like convective system that persists even after the lake disappears. The timescales for the lake to disappear are millennia, suggesting that even a weak transfer of moisture through surface processes could maintain a moist day side. We also find that adjusting the threshold at which the evaporative rate becomes constrained by the remaining surface liquid depth modifies the longevity of the lake and surrounding day side conditions. These findings have implications for understanding a diverse range of planetary climates and habitability, given the distribution of moisture and presence of a substellar lake.
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All authors Daniel A. Williams, Geoffrey K. Vallis, Stephen I. Thomson, William J. M. Seviour

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

The School on Gravity: from motion to commotion

Vitor Cardoso, Jose María Ezquiaga, Julio Parra-Martinez et al. (+3 more)

Understanding the gravitational interaction is one of the great scientific endeavors of the 21st century. The Nobel Prize-winning discovery of gravitational waves in 2015, and subsequent detections by the LIGO-Virgo-KAGRA Collaboration, have marked a revolutionary step forward in physics and astrophysics by opening an entirely new window for exploring the Universe. Future upgrades to these detectors, along with upcoming facilities such as LISA, the Einstein Telescope, and radio and optical instruments, promise other breakthrough discoveries that the next generation of scientists will need to interpret. The School on Gravity (22–26 June 2026, Copenhagen) aimed to introduce junior scientists–graduate students and advanced undergraduates with a background in general relativity–to a wide range of foundational topics in the exciting new field of gravitational-wave physics. Topics spanned from the theory of motion, to new challenges introduced by quantum physics, to the astrophysics of black holes and source modeling for gravitational-wave detectors. The School on Gravity took place at the legendary Auditorium A of the Niels Bohr Institute, inviting students and lecturers to challenge current paradigms in gravitational physics in the spirit of the quantum revolution that unfolded in this very room. These lecture notes aim at opening up those new ideas presented in Auditorium A to the rest of the scientific community.
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All authors Vitor Cardoso, Jose María Ezquiaga, Julio Parra-Martinez, Laura Sberna, Gustavo J. Turiaci, Lieke van Son