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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 25 June

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

Massive Cosmological Correlators from Flat Space: a Laplace-Space Approach

Nathan Belrhali, Arthur Poisson and Sébastien Renaux-Petel

We develop a new approach to cosmological correlators, built on a simple physical fact: deep inside the Hubble radius every mode oscillates as a flat-space plane wave, the curvature of spacetime making itself felt only as the mode is stretched towards the horizon. A Laplace transform turns this observation into a computational tool, resolving each curved-space mode function into a continuous superposition of plane waves labelled by a dual variable and dressed by a kernel that encodes the spacetime geometry, field content and dynamics. Every time integral then reduces to an elementary flat-space one, yielding simple diagrammatic rules for cosmological correlators. We illustrate the construction on the massive single-exchange correlator. The Laplace representation makes its total- and partial-energy singularities transparent ”from flat space”, and yields a single closed-form, rapidly convergent series valid throughout the entire kinematic domain. Although developed for conformally coupled fields exchanging massive scalars in de Sitter, the approach carries over essentially unchanged to virtually all situations of interest in primordial cosmology.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Laplace Space for Cosmological Correlators

Nathan Belrhali, Arthur Poisson and Sébastien Renaux-Petel

Deep inside the horizon, every cosmological mode oscillates as a flat-space plane wave. A Laplace transform turns this fact into a general method: it resolves each curved-space mode into a superposition of plane waves dressed by a kernel that encodes the spacetime geometry, field content and dynamics, collapsing the time integrals onto flat-space ones. This provides simple diagrammatic rules that turn cosmological correlator diagrams into their flat-space counterparts integrated against Laplace-space kernels. On the paradigmatic massive single exchange, this integral representation makes the energy singularities manifest and evaluates in closed form as a single, rapidly convergent series valid throughout the kinematic domain, with no patching of separate expansions. The Laplace approach sheds conceptual and computational light on cosmological correlators in virtually any theory of the early universe.
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Cosmology and Nongalactic Astrophysics

A solid unification of the dark sector

Jose Beltrán Jiménez, María Pérez Garrote, Florencia A. Teppa Pannia et al. (+1 more)

We construct a unified description of dark matter and dark energy in terms of a single dark component that behaves as a pressureless fluid in the early Universe and undergoes a transition to a solid phase at late times that can support accelerated expansion. A generalized Chaplygin-type solid provides a simple realization of this scenario. The solid nature of the dark medium prevents the instabilities and strong acoustic oscillations that typically arise in perfect-fluid unifications. It also gives rise to distinctive signatures in cosmological perturbations, such as a suppression of structure growth, a nontrivial gravitational slip, and an effective mass for gravitational waves. Since these effects share a common origin in the solid phase, they become relevant only at low redshifts, leaving the high-redshift cosmology essentially unmodified. This demonstrates that a solidly unified dark sector can reproduce the desired background transition from dark matter to dark energy while yielding testable imprints in cosmological perturbations.
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All authors Jose Beltrán Jiménez, María Pérez Garrote, Florencia A. Teppa Pannia, Shinji Tsujikawa

Solar and Stellar Astrophysics

Unveiling Complex Chemistry in Planet-forming Disks with the SKAO

Linda Podio, Lisa Giani, Catherine Walsh et al. (+38 more)

The chemical composition of planets is inherited from that of the natal protoplanetary disk at the time of planet formation. In recent years, we have made huge progress in characterizing disk chemistry. (Sub-)millimeter interferometers, such as ALMA, allowed us to detect emission lines from simple to complex organic molecules and to probe their radial and vertical distribution in disks. On the other hand, JWST has started to unveil the composition of disk ices, and line emission from the innermost disk regions. The advent of SKA will open new domains in the field, by observing emission lines from heavier molecules including heavy carbon chains and rings, and prebiotic molecules with peak emission in the cm range. Moreover, SKA will probe molecular emission from regions which are obscured by dust opacity at mm wavelengths, hence from the disk midplane, and often from the inner 30 au region. These observations will constrain the initial conditions for disk evolution and planet formation, allowing us to predict the chemical composition of the forming planets and their atmospheres. Comparison with forthcoming results on exoplanet atmospheres and on the chemistry of pristine bodies in the Solar System will provide new hints on the origin and evolution of planetary systems including our own.
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All authors Linda Podio, Lisa Giani, Catherine Walsh, Audrey Coutens, Izaskun Jiménez-Serra, Claudio Codella, María José Maureira, Marta De Simone, John D. Ilee, Manuela Lippi, Chin-Fei Lee, Romane Le Gal, Mayank Narang, Giovanni Sabatini, Eleonora Bianchi, Elenia Pacetti, Danai Polychroni, Bihan Banerjee, Paola Caselli, Cecilia Ceccarelli, Amin Farhang, Antonio Garufi, Greta Guidi, Adriano Ingallinera, Stavro L. Ivanovski, Pamela Klaassen, Ana López-Sepulcre, Liton Majumdar, Giulia Perotti, Jaime E. Pineda, Daniel J. Price, Manoj Puravankara, Pablo Rivière-Marichalar, Alvaro Sánchez-Monge, Eugenio Schisano, Paolo M. Simonetti, Leonardo Testi, Claudia Toci, Diego Turrini, Alessio Traficante, Yinhao Wu

Solar and Stellar Astrophysics

Astrochemical Study of Early Embedded Disks

Eleonora Bianchi

The question of how our planet was formed and, more generally, how a planetary system forms is fundamental and has been addressed in a broad range of research domains. However, we still lack a comprehensive understanding of the basic aspects of the process of star and planet formation. In particular, the challenge of measuring the mass and chemical composition of young protostellar disks has, so far, hampered a meaningful comparison with observed exoplanet populations. This will become critical in the near future to interpret the results of European space missions, such as Ariel, which will yield a comprehensive inventory of exoplanetary masses and chemical compositions. Building on recent developments in astrochemistry and data science, this perspective explores future research avenues for the study of young planet-forming disks and introduces the project "Astrochemical Study of Early Embedded Disks" (iSEEDs). By integrating machine learning and data mining with astrochemistry, iSEEDs provides a robust framework to systematically extract the physical conditions and molecular abundances hidden within high-resolution datasets of protostellar environments.
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High Energy Astrophysical Phenomena

Origins of Cosmic Rays in the Galactic-extragalactic Transition Energy Range

A. Corstanje, S. Saha, S. Bouma et al. (+28 more)

Cosmic rays arrive at Earth with energies ranging from $10^9$ to over $10^{20}$ eV. One of the open questions in high-energy cosmic ray science concerns the origin of the highest-energy cosmic rays that can be accelerated by Galactic sources, and the transition energy beyond which only extragalactic sources can provide. Measuring the mass composition gives essential information for comparing measurements to source and propagation models, both from the abundances at the source and from the maximum attainable energy which is proportional to the particle charge (and hence its mass). The highest-energy cosmic rays from the Galaxy are found in a range of $10^{16}$ to $10^{18}$ eV which is well suited for radio detection. Building on a decade of experience in measuring cosmic rays at LOFAR, we show that SKA-Low, augmented with an array of small particle detectors, is well suited to advance the field by measuring the mass composition of cosmic rays across this energy range.
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All authors A. Corstanje, S. Saha, S. Bouma, J. Bray, S. Buitink, V. de Henau, E. Dickinson, B. Hare, A. Haungs, H. He, J. Hörandel, T. Huege, C. James, P. Laub, X. Li, H-J. Mathes, K. Mulrey, A. Nelles, F. Schlüter, O. Scholten, R. Spencer, C. Sterpka, K. Terveer, S. Thoudam, G. Trinh, P. Turekova, D. Veberic, K. Watanabe, C. Zhang, P. Zhang, Y. Zhang

Solar and Stellar Astrophysics

Revised orbital parameters of the gamma2 Velorum system

Werner Schmutz, Christian A. Hummel, Gloria Koenigsberger et al. (+2 more)

Context. gamma2 Velorum is the closest and visually brightest Wolf-Rayet binary system. Its eccentric orbit modulates the X-rays observed from the wind-wind interaction, and its large separation allows for spatially resolving both components. Aims. We aim to strengthen the constraints on gamma2 Velorum's properties and, in particular, solve the discrepancy between the eccentricity determined from the emission lines and that from the absorption lines. Methods. We obtained VLT/GRAVITY observations and combined them with earlier spatially-resolved data at different orbital phases. Results. Strong constraints on all orbital parameters were determined and, in particular, we find that e=0.322, close to what was derived from the emission lines. The X-ray light curve declines as s to power -3 after periastron, where s is the separation of the two stars, but its modulation is likely affected by absorption and occultation of the X-ray emitting region at other orbital phases. We find that previous discrepancies in the reddening value can be traced to a brighter K-band magnitude than that predicted by the WR wind models. We conclude E(B-V)=0.02+-0.02 mag. Our now more precise mass and radius values combined with previously determined effective temperatures provide very strong constraints on evolutionary models. The closest match for the O-star is provided by an initial mass M=28.7 Mo rotationally mixed model and a M=32 Mo model for the WR star, with negligible accretion onto the O-star during the WR progenitor's Roche Lobe overflow phase. However, the temperature of the O star is higher and the mass of the WR star is found to be smaller than predicted by the evolutionary tracks for the current epoch, consistent with the well-known "mass-discrepancy problem" in massive stars.
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All authors Werner Schmutz, Christian A. Hummel, Gloria Koenigsberger, Florentin Millour, Joel Sanchez-Bermudez

Instrumentation and Methods for Astrophysics

The SPOTLIGHT Multibeam Real-Time Transient Detection System

Ujjwal Panda, Jayanta Roy, Kshitij Bane et al. (+17 more)

Fast Radio Bursts (FRBs) are among the most enigmatic transient phenomena in the Universe. In order to unravel the mystery behind these events, one requires instruments that possess the ability to search, detect, localise, and capture these events in high resolution over large fields-of-view in real-time. The SPOTLIGHT project is one such backend, leveraging the upgraded Giant Metrewave Radio Telescope (uGMRT) to conduct a commensal search for FRBs and other radio transients, using a dedicated high-performance computing facility, comprised of 90 NVIDIA A100 GPUs and 60 compute servers. Here we present the design, implementation, and performance of SPOTLIGHT's real-time transient search pipeline, a GPU-accelerated system capable of processing up to 2000 post-correlation beams in real time. The pipeline combines AstroAccelerate-powered brute-force dedispersion and single pulse search, with a multi-stage and robust candidate optimisation framework, as well as a triggering system for automatic capture of high-resolution visibility and baseband data. To ensure continuous validation of pipeline performance, we have also developed a real-time signal injection framework capable of injecting synthetic bursts directly into SPOTLIGHT's beamformed data stream. The system operates commensally with routine uGMRT observations, processing data streams in real-time while maintaining high sensitivity to ms-duration transients across dispersion measures extending up to 2000 pc cm$^{-3}$. During its initial deployment in uGMRT Cycle 49 and Cycle 50, the pipeline detected 2870 bursts from 42 known sources, and demonstrated sensitivity consistent with the predicted survey threshold of $\sim$ 0.2 Jy ms. The SPOTLIGHT system establishes a scalable framework for wide-field, low-frequency transient discovery and localisation, and provides a key technological foundation for next-generation radio transient surveys.
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All authors Ujjwal Panda, Jayanta Roy, Kshitij Bane, Chahat Dudeja, Sridhar Gajendran, Param Joshi, Sanjay Kudale, Arpan Pal, Raghav Wani, Karel Adamek, Wes Armour, Kenil Ajudiya, Jayaram Chengalur, Jyotirmoy Das, Nishant Pradeep Deo, Deepak Bhong, Shelton Gnanaraj, Santaji N. Katore, Mekhala Muley, Harshavardhan Reddy

Earth and Planetary Astrophysics

Improving exoplanet mass characterisation with Bayesian model selection using the Learned Harmonic Mean Estimator

Ross S. Dobson, Vincent Van Eylen, Ioanna Manolopoulou et al. (+1 more)

Radial velocity (RV) analyses require modelling choices (such as eccentricity treatment, noise model, velocity trends, and number of planets) that can significantly affect derived planetary masses. Current practice often relies on information criteria to compare and select models, but these have known limitations: they lack the built-in Occam's razor of Bayesian model comparison, and they do not incorporate prior information. Computing the Bayesian evidence needed for Bayes factor model comparison has traditionally required dedicated algorithms such as nested sampling. The learned harmonic mean estimator (LHME) offers an alternative, estimating the Bayesian evidence directly from MCMC posterior samples, with less computational cost and with no modification to the fitting procedure. We present the first application of the LHME to RV model selection, fitting 18 model variants – comparing circular and eccentric orbits, white noise and Gaussian Process noise models, and long-term velocity trends – to six single-planet systems, and 72 variants to a seventh system for an $N$ versus $N+1$ planet model comparison. We find that no single model is universally preferred, reinforcing the need for model comparison to select the most appropriate model for a system, thereby ensuring robust mass characterisation. The LHME, implemented in the open-source harmonic package, makes rigorous Bayesian model comparison accessible to existing MCMC-based RV workflows, and we encourage its wider use for other model comparisons in astrophysics.
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All authors Ross S. Dobson, Vincent Van Eylen, Ioanna Manolopoulou, Kendall Sullivan

Solar and Stellar Astrophysics

MUSE Imaging Spectroscopy of the Fullerene Planetary Nebula Tc 1

J. R. Walsh, M. J. Barlow, A. Monreal-Ibero et al. (+6 more)

The planetary nebula Tc 1 (PN G345.2 -08.8), one of the rare group of Galactic PNe showing fullerene emission in the infrared, was observed with MUSE wide field mode with adaptive optics, wavelength range 4750-9300A. Extinction, electron temperature (T_e) and density (N_e) images are presented from collisionally excited and recombination line ratios. The nebula has a high surface brightness 12 arcsec core, an elliptical ring of major axis 2.8 arcsec around the central star and some low ionization knots, and an extended halo 55 arcsec in size; between the core and halo is an annulus with intermediate properties, including higher T_e and lower N_e than in the core. The image of optical extinction from H Balmer line ratios is highly structured, and shows an annulus, adjacent to the core, of low extinction, lower than the line-of-sight interstellar extinction. Instrumental effects to account for this anomalously low extinction area are investigated and intrinsic effects from the scattering properties of nebular dust; neither can entirely explain the low-extinction region and the most likely cause is a local non-standard dust reddening law. This low extinction region also shows an anomalously high He I 7281/6678A line ratio, possibly caused by a contaminating line, but none were conclusively identified. The spectrum of the central star was extracted and fitted by a 31000K model atmosphere and is of type O7.5I(f). Over extended regions an enhancement of the detected continuum above the nebular continuum was found, as also seen in some other PNe observed with MUSE. The annulus of low extinction occurs outside the region of strongest fullerene emission, in the zone where N_e declines and T_e rises. A change in dust properties linked to conditions in this transition region between the higher density core nebula and lower density halo is deduced. (Abridged)
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All authors J. R. Walsh, M. J. Barlow, A. Monreal-Ibero, J. Cami, E. Peeters, R. Wesson, J. Bernard-Salas, N. L. J. Cox, G. F. J. Watt

Cosmology and Nongalactic Astrophysics

Methodological Frontiers in 21-cm Intensity Mapping: the Treatment of Systematics and Foreground Contamination

Marta Spinelli, Matilde Barberi-Squarotti, José Luis Bernal et al. (+29 more)

The distribution of neutral hydrogen (HI) in the post-reionization universe traces the cosmic large-scale structure and therefore serves as a powerful cosmological probe. An efficient way to measure its distribution over wide sky areas and redshift ranges is through single-dish intensity mapping, which exploits the autocorrelation signal of each dish in a telescope array while scanning the same sky patch. Thanks to its broad frequency coverage and technical capabilities, SKA-Mid will enable measurements of the integrated 21 cm emission from HI up to redshift $z\sim3$, making single-dish intensity mapping a key observable for probing dark matter and dark energy. Isolating the faint 21 cm cosmological signal without introducing biases is, however, challenging. The 21 cm signal is several orders of magnitude weaker than the astrophysical foregrounds, and its analysis is further affected by instrumental systematics. Overcoming these difficulties requires detailed modelling together with continuous improvements and innovations in data-analysis techniques. Over the past decade, the international community has developed and tested new methods to address current observational challenges and prepare for forthcoming SKA-Mid observations. This chapter reviews recent advances in map-making and component-separation techniques, with particular emphasis on telescope-specific systematics such as beam response and correlated noise. We focus on results obtained in controlled simulation environments, providing a valuable framework for assessing the strengths and limitations of different approaches. Developing robust algorithms capable of accurately handling instrumental effects and sky-model uncertainties is a crucial step toward fully exploiting the cosmological potential of HI intensity-mapping surveys in the SKA Observatory era.
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All authors Marta Spinelli, Matilde Barberi-Squarotti, José Luis Bernal, Somnath Bharadwaj, Victor Bonjean, Philip Bull, Carmelita Carbone, Isabella P. Carucci, Stefano Camera, Suman Chatterjee, Tianyue Chen, Zhaoting Chen, Samir Choudhuri, Devin Crichton, Steven Cunnington, Bianca De Caro, Khandakar Md Asif Elahi, Jose Fonseca, Athanasia Gkogkou, Abhik Ghosh, Keith Grainge, Wenkai Hu, Melis O. Irfan, Yichao Li, Siyambonga Matshawule, Geoff Murphy, Simon Prunet, Mario G. Santos, Jean-Luc Starck, Jingying Wang, Laura Wolz, Zheng Zhang

Instrumentation and Methods for Astrophysics

Time-Domain Synthesis of Gravitational-Wave Detector Glitches using Class-Conditional Derivative Generative Adversarial Networks

Tom Dooney, Mees de Boer, Harsh Narola et al. (+4 more)

Gravitational-wave detectors such as LIGO, Virgo, and KAGRA are highly sensitive instruments susceptible to many noise sources. Short-duration transient noise events, known as glitches, pose a particular challenge for data analysis pipelines, as they can mimic or obscure astrophysical signals. We present GlitchGAN, a class-conditional generative model built on the Conditional Derivative GAN (cDVGAN) architecture, capable of synthesizing seven glitch types from LIGO's third observing run (O3) directly in the time domain. GlitchGAN generalizes effectively, learning to reproduce a diverse glitch space consistent with high-quality DeepExtractor reconstructions, and can generate hybrid glitch morphologies by interpolating across its class-conditioning vector. It generates 1000 glitches in under 22 seconds on a CPU, suitable for detector simulations, mock data challenges, and pipeline validation. Synthetic glitches are validated using the Gravity Spy classifier and UMAP embeddings, both showing strong agreement with real data. To probe residual distributional differences, we train a separate holdout GlitchGAN model and use a downstream CNN to distinguish held-out real glitches from synthetic ones: detectability is high in a clean representation but drops substantially once both populations are injected into realistic detector noise, the condition under which they would typically be used. Despite this, GlitchGAN-generated glitches remain practically useful: augmenting real training sets with synthetic samples matches simple duplication of real data when data is abundant, and increasingly outperforms it as real data becomes scarce. Finally, we highlight a limitation of magnitude-only spectrograms: magnitude Q-transform classifiers can confidently misclassify physically unrealistic glitches from less robust models, underscoring the need for validation methods that preserve phase information.
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All authors Tom Dooney, Mees de Boer, Harsh Narola, Melissa Lopez, Stefano Bromuri, Daniel Stanley Tan, Chris Van Den Broeck

High Energy Astrophysical Phenomena

A search for Fast Radio Bursts from globular clusters in M49 with FAST

Simon C.-C. Ho, Chris Flynn, Matthew Bailes et al. (+7 more)

The origins of fast radio bursts (FRBs) remain uncertain, although magnetars are a leading progenitor candidate. Because magnetars are thought to form primarily through core-collapse supernovae in young stellar populations, the discovery of FRB 20200120E in a globular cluster (GC) in the nearby galaxy M81 was unexpected given the ancient stellar populations of GCs. Expanding the sample of FRBs localised to nearby galaxies is therefore essential for testing FRB formation channels in old stellar environments. M49 (NGC 4472) is a nearby (~17 Mpc), radio-quiet giant elliptical galaxy in the Virgo cluster hosting about 7000 GCs, making it an ideal target for GC FRB searches. We conducted a 9-hour SnapShotCal observation of M49 using the Five-hundred-meter Aperture Spherical Telescope (FAST) 19-beam receiver, covering approximately 4230 GCs (2.1 hr per GC), and performed a comprehensive single-pulse search over a dispersion measure range of 0-5000 pc cm^-3. No unambiguous astrophysical FRBs were detected. The most significant trigger reached a post-processed signal-to-noise ratio of 8.6 sigma at a dispersion measure of 412.2 pc cm^-3, but is statistically consistent with thermal noise after accounting for the false-alarm rate. We derive a beam-averaged peak flux-density sensitivity of about 16.5 mJy (corresponding to a fluence limit of about 16.5 mJy ms for a 1 ms burst) and place an upper limit on the FRB occurrence rate of 4.7 x 10^-4 FRB GC^-1 hr^-1. Our non-detection constrains only bright bursts above this fluence threshold during the observing window.
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All authors Simon C.-C. Ho, Chris Flynn, Matthew Bailes, Emma Carli, Lei Zhang, Manisha Caleb, Kenneth C. Freeman, Tetsuya Hashimoto, Tomotsugu Goto, James O. Chibueze

Earth and Planetary Astrophysics

Cross-correlation transmission spectroscopy of ultra-hot Jupiters WASP-189b, HAT-P-57b, KELT-17b, and KELT-21b with GIANO-B

P. Meni-Gallardo, J. Orell-Miquel, Gareb Fernández-Rodríguez et al. (+6 more)

Since the discovery of the first exoplanet, significant efforts have been made to characterise their atmospheres. Ultra-hot Jupiters (UHJs) are of particular interest due to their extended and hot atmospheres. Although previous studies have focused on the detection of atomic species at optical wavelengths, near-infrared (NIR) observations offer the potential to detect molecules. In our study, we applied the cross-correlation technique to NIR transmission spectra from \giano. The analysis focuses on the search for H$_2$O, CO, CO$_2$, CH$_4$, HCN, and FeH molecular signals in the atmospheres of four UHJs: HAT-P-57 b, KELT-17 b, KELT-21 b, and WASP-189 b. For the first time, we report results on the NIR transmission spectra of KELT-17b, KELT-21b, and WASP-189b. We report a tentative detection ($3.8\sigma$) of H$_2$O in HAT-P-57 b and a detection ($5.3\sigma$) of FeH in KELT-17~b, which is the third FeH detection ever in a UHJ and with the lowest equilibrium temperature. No molecular signals were found in KELT-21b and WASP-189b, or for other molecules in HAT-P-57b and KELT-17b. The cross-correlation results for HAT-P-57 b, KELT-17 b, KELT-21 b, and WASP-189 b in transmission align with the species detected in the UHJ population. This work underscores the need for further observations to confirm and expand the transmission study of UHJs in the NIR, and the capabilities of high-resolution spectrographs on 4-m-class telescopes.
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All authors P. Meni-Gallardo, J. Orell-Miquel, Gareb Fernández-Rodríguez, H. Parviainen, M. Basilicata, E. Pallé, M. Stangret, I. Carleo, P. Giacobbe

Earth and Planetary Astrophysics

Evidence for possible N2 basal flow beneath Pluto northern Sputnik Planitia

S. Alan Stern, Orkan Umurhan, Gary D. Clow et al. (+4 more)

Sputnik Planitia (SP) on Pluto is a large, predominantly N2 ice-filled basin with a surface area of one million square kilometers; it is among the most spectacular surface features on the planet. The northern extent of SP displays a variety of geomorphological features that can be interpreted as evidence for convective flows in the basin-filling ice sheet. The complete lack of detected craters in SP argues that these processes are ongoing. The convection cells in northern SP also display sharp, darkened boundaries that are bordered by more diffuse, less darkened zones. We hypothesize that these patterns may be explained as evidence of the flow of liquid molecular nitrogen sourced from beneath the glacier. This hypothesis suggests that basal melt of the ice sheet occurs, that this melt reaches the surface before it freezes in transit upward through colder ice, and that the melt has sufficient time before it freezes during flow across the ice surface to fill topographic lows. Here we discuss the evidence on which we base these interpretations, constrain the required physical conditions to create them, and briefly discuss some of their implications.
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All authors S. Alan Stern, Orkan Umurhan, Gary D. Clow, Robert S. Anderson, Alan Howard, Kelsi N. Singer, the New Horizons Team

Astrophysics of Galaxies

HALO II: Constraining Hubble constant $H_{0}$ through continuum delay fitting of Fairall 9

Amit Kumar Mandal, Francisco Pozo Nuñez, Vikram Kumar Jaiswal et al. (+28 more)

The Hubble tension remains one of the most significant unresolved problems in modern cosmology. A key question is whether it may arise from underestimated systematic uncertainties in the different measurement techniques. In this context, new independent methods are of exceptional importance. We therefore pursue a novel approach to determining the Hubble constant, $H_{0}$ based on continuum time delay and spectral energy distribution (SED) modeling in active galactic nuclei (AGNs). Unlike conventional techniques, this method is entirely independent of the cosmic distance ladder and does not require cross-calibration against other distance indicators. As a result, it enables a direct determination of $H_{0}$, free from the arbitrary normalizations that often affect indirect measurements. We conducted a dedicated monitoring campaign of the Seyfert galaxy Fairall 9 and further developed the H0RIZON-AGN model to interpret the resulting observations. The model incorporates the effects of radiation reprocessing in the surrounding cold accretion disk, enabling a more realistic description of the observed continuum delays. Through the simultaneous modeling of the continuum lag-spectrum and the broadband SED of Fairall 9, we derived a Hubble constant of $H_{0}=72.4_{-3.7}^{+3.4} \, \rm km \, s^{-1} \, Mpc^{-1}$. Achieving a measurement precision of approximately 5% from a single source demonstrates the considerable potential of this method for independent determinations of the Hubble constant. Our determination of $H_{0}$ is broadly consistent, within the current uncertainties, with both early- and late-Universe measurements. Future applications of the method to larger datasets, particularly those provided by the Vera Rubin Observatory, are expected to reduce the uncertainty to below 1%, thereby establishing this approach as a powerful independent probe of the Hubble tension.
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All authors Amit Kumar Mandal, Francisco Pozo Nuñez, Vikram Kumar Jaiswal, Mohammad Hassan Naddaf, Bożena Czerny, Swayamtrupta Panda, Paulina Karczmarek, Grzegorz Pietrzyński, Shivangi Pandey, R. Edelson, B. M. Peterson, Michal Zajaček, Alberto Floris, Mary Loli Martínez-Aldama, Michal Dovčiak, Vladimir Karas, Weronika Narloch, Mirosław Kicia, Marek Górski, Mikołaj Kałuszyński, Gergely Hajdu, Piotr Wielgórski, Bartłomiej Zgirski, Cezary Gałan, Wojciech Pych, Radosław Smolec, Ricardo Salinas, Henryka Netzel-Iłkiewicz, Karolina Bąkowska, Wolfgang Gieren, Pierre Kervella

High Energy Astrophysical Phenomena

Stellar black hole binaries from two common envelope evolution phases in triple stellar systems

Lotem Unger and Noam Soker

We propose a triple-star evolutionary channel involving two common envelope evolution (CEE) phases to form close binary black hole (BBH) systems with an average positive effective inspiral spin $\chi_{\rm eff}$ and a tail of systems having $\chi_{\rm eff}<0$, as observed by gravitational wave detectors. $\chi_{\rm eff}$ is the mass-weighted spin of the two merging BHs, and a positive (negative) value indicates an effective spin along (opposite) the orbital angular momentum. The first BH progenitor engulfs a low-mass star during the post-main-sequence evolution. The tertiary star spirals in and spins up the core, which forms the first BH at the first core-collapse supernova (CCSN) explosion. Its spin is along the orbital angular momentum of the inner binary, which can be highly inclined to the outer binary angular momentum. The secondary star later engulfs the BH in a second CEE phase and explodes as a CCSN to form the second BH with a spin that is more aligned with the orbital angular momentum of the two BHs. We use empirically calibrated initial distributions of triple-star systems consisting of two massive stars and impose a hierarchical stability criterion. We compare the predicted ratio of merging BBHs to CCSN explosion rates and find it is up to a factor of 2 larger than the observed rate. This channel can significantly contribute to the population of observed merging BBHs and can explain their qualitative spin distribution.
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Solar and Stellar Astrophysics

Chemical Complexity in the Early Stages of Star Formation in the SKAO Era

Eleonora Bianchi, Mathilde Bouvier, Claudio Codella et al. (+44 more)

About 350 molecules have been identified in the interstellar medium (ISM), including complex molecules relevant to prebiotic chemistry. A remarkable level of molecular diversity has been observed from the earliest stages of star formation, providing the initial chemical inventory inherited by planetary systems. Radio observations have played a pivotal role in these discoveries, starting with the identification of the first polyatomic molecule, $\text{NH}_3$ (Cheung et al. 1968). (Sub-)millimeter observations have revealed complex organic molecules of prebiotic relevance, including formamide ($\text{NH}_2\text{CHO}$), glycolaldehyde ($\text{CH}_2\text{OHCHO}$), and even urea ($(\text{NH}_2)_2\text{CO}$), and hydroxylamine ($\text{NH}_2\text{OH}$), which are possible precursors of RNA nucleotides (Ceccarelli et al. 2023; Jiménez-Serra et al. 2020). However, in dense protostellar regions, dust opacity hampers the detection of molecular emission. Additionally, large molecules and those containing heavy atoms, which have rotational transitions at lower frequencies, often remain inaccessible to current instruments. The Square Kilometre Array Observatory (SKAO) will provide an unprecedented combination of sensitivity and angular resolution at radio wavelengths. This will allow for the detection of prebiotic species and offer new insights into the chemical pathways that shape emerging planetary systems (Jiménez-Serra et al. 2022). This chapter details the scientific questions and advancements that the SKAO, and more specifically, SKA-Mid equipped with the Band 5 receivers, will pursue in the field of astrochemistry, focusing on the chemical complexity in both high-mass and solar-type star-forming regions.
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All authors Eleonora Bianchi, Mathilde Bouvier, Claudio Codella, Laura Colzi, Audrey Coutens, Marta De Simone, Joan Enrique Romero, Gisela Esplugues, Francesco Fontani, Antonio Garufi, Lisa Giani, Arshia Maria Jacob, Izaskun Jiménez-Serra, Marco Padovani, Linda Podio, Albert Rimola, Pablo Rivière Marichalar, Giovanni Sabatini, Andrea Socci, Riccardo Giovanni Urso, Tyler L. Bourke, Gemma Busquet, Paola Caselli, Cecilia Ceccarelli, Tomoya Hirota, John D. Ilee, Valerio Lattanzi, Manuela Lippi, Ana López-Sepulcre, Pierre Marchand, Liton Majumdar, Sabyasachi Pal, Maria Elisabetta Palumbo, Jaime E. Pineda, Manoj Puravankara, Elena Redaelli, Victor M. Rivilla, Basmah Riaz, Álvaro Sánchez-Monge, Silvia Spezzano, Leonardo Testi, Himanshu Tyagi, Claudia Toci, Alessio Traficante, Grazia Umana, Charlotte Vastel, Susanne Wampfler

Cosmology and Nongalactic Astrophysics

Forward-modelling the Tolman and distance-duality tests with IllustrisTNG

Harry Desmond, Tariq Yasin, Richard Stiskalek et al. (+1 more)

The Tolman surface-brightness test and the angular-size distance-duality test are two complementary probes of the same underlying relation between luminosity and angular-diameter distance, $D_L = (1+z)^2 D_A$, as holds in any metric theory of gravity where photon number is conserved. Both tests have recently delivered a priori surprising signals: JWST/ASTRODEEP measurements yield a surface brightness scaling with redshift much flatter than the expected value, and ultracompact radio sources also appear to follow a flatter $D_L/D_A$ scaling with redshift. These results have been suggested to support non-expanding cosmologies, however they are also sensitive to astrophysical and instrumental effects. We test whether these results indicate genuine departures from standard cosmology by forward-modelling observed surface-brightness evolution in the IllustrisTNG cosmological hydrodynamical simulation, with an empirical mock-spectroscopic selection trained on ASTRODEEP. We show that the astrophysical evolution relevant for both tests may be effectively parametrised as a single power-law exponent for the luminosity density as a function of redshift, for which the simulation gives $\gamma=2.23\pm0.20$ across realistic aperture conventions. This value is approximately sufficient to explain both the Tolman and distance-duality signals within standard cosmology and galaxy formation physics, with a small discrepancy for the latter suggesting that radio AGN evolve slightly more strongly than bright galaxies.
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All authors Harry Desmond, Tariq Yasin, Richard Stiskalek, Sebastian von Hausegger

Cosmology and Nongalactic Astrophysics

Redshift-Dependent Intrinsic Dispersion in the Quasar UV/X-ray Luminosity Relation

Jiaze Gao, Jianping Hu, Yun Chen et al. (+2 more)

Accurate modeling of the intrinsic dispersion in the quasar UV/X-ray luminosity relation is essential for reliable cosmological inference. We investigate its redshift dependence using luminosity distances reconstructed from cosmic chronometer and baryon acoustic oscillation measurements through Gaussian-process (GP) regression. Bayesian model comparison and posterior constraints show that the intrinsic dispersion is not well described by a single redshift-independent constant over $0.7<z<2.6$. It remains approximately constant at $0.7<z<1.6$, but shows an overall decreasing trend in the higher-redshift interval $1.6<z<2.6$, where the redshift-dependent intrinsic-dispersion model is decisively favored. This conclusion remains qualitatively robust against changes in the scaling-relation parameterization, GP kernel, and redshift binning scheme. We further examine its impact on cosmological inference in the flat $\Lambda$CDM model and find that, under the adopted calibration setup, the redshift-dependent intrinsic-dispersion model shifts the posterior median of $\Omega_{\rm m0}$ by $\Delta\Omega_{\rm m0}\simeq 0.025$. This indicates that intrinsic-dispersion modeling is a non-negligible component of the systematic-error budget for quasar cosmology and should be accounted for in future precision analyses.
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All authors Jiaze Gao, Jianping Hu, Yun Chen, Bowen Zhao, Lixin Xu

Instrumentation and Methods for Astrophysics

Frequency Phase Transfer for Future Millimetre Arrays with Arbitrary Frequency Ratios

Senkhosi Simelane, Athol Kemball and Roger Deane

Non-dispersive tropospheric turbulence-induced phase delays enforce significant, often dominant, limitations to the imaging fidelity and dynamic range in (sub-)millimetre astronomy. Frequency Phase Transfer (FPT), which removes such delays from high-frequency data using simultaneous lower-frequency observations, has become increasingly viable with the advent of shared-optical-path multi-band receivers and is a key motivator of the Event Horizon Telescope Collaboration's ambitions to add 86-GHz and 345-GHz bands alongside its existing 230-GHz band. However, existing FPT algorithms break down for non-integer frequency ratios, leaving jump discontinuities in the residual phases. We introduce a new FPT algorithm, phase-wrap counting (PWC), which works for any frequency ratio and clarifies the nature and source of the jump discontinuities left by previous FPT approaches. Using the newly developed High-frequency Inter-band Transfer of Phase Solutions (HITOPS) software package, we apply PWC to a simulated dual-band observation with the Event Horizon Telescope and demonstrate its effectiveness under realistic atmospheric conditions and thermal noise levels. The method successfully calibrates the 230-GHz phases using the 86-GHz phase solutions, outperforming the conventional phase calibration approach in both coherence and peak flux recovery. This result indicates that PWC has the potential to enable the calibration of the 230-GHz band using the 86-GHz band in future EHT operations.
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Cosmology and Nongalactic Astrophysics

Clustering of high-redshift quasars with DESI DR2

M. Charles, P. Martini, A. J. Ross et al. (+46 more)

We present clustering measurements for high-redshift quasars using data from the Dark Energy Spectroscopic Instrument Data Release 2. Our sample consists of quasars with $2.0 < z < 3.5$ in the luminosity range $M_{1450} \leq -19.94$\,mag. We measure the mean quasar bias $b_Q(\bar{z} = 2.48) = 3.61 \pm 0.01$ for the full sample of $\sim 715,000$ quasars and quantify the redshift evolution of quasar bias by dividing the sample into four equal redshift bins. There is strong evolution of the quasar bias with redshift that is well fit by the function $b_Q(z) = a [(1 + z)^2 - 6.565] + b$ with $a=0.230 \pm 0.007$ and $b=2.394 \pm 0.035$, and this fit is also a good match to lower redshift measurements in the literature. This bias evolution is consistent with a characteristic halo mass of $\bar{M}_{\mathrm{h}} \sim 10^{12}\,\mathrm{M_\odot}$ that does not vary significantly with redshift. The inferred duty cycles for quasars in our sample are $f_{\mathrm{duty}} \sim 10^{-2}$, staying mostly constant over redshifts. We investigate the luminosity dependence of quasar clustering by dividing each of our four redshift bins into three luminosity bins. The size of our quasar sample permits the first statistically significant measurement of the luminosity dependence of quasar bias at these redshifts. We measure weak dependence of quasar bias on luminosity at fixed redshift, inconsistent with no dependence, but weaker than predicted by a model in which quasar luminosity is tightly correlated with halo mass. These clustering measurements provide a stringent test for models of active black hole light curves and the black hole-halo connection at high redshift.
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All authors M. Charles, P. Martini, A. J. Ross, D. H. Weinberg, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. Cuceu, A. de la Macorra, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, S. Gontcho A Gontcho, G. Gutierrez, J. Guy, C. Hahn, H. K. Herrera-Alcantar, K. Honscheid, C. Howlett, M. Ishak, R. Joyce, D. Kirkby, A. Kremin, M. Landriau, L. Le Guillou, M. E. Levi, M. Manera, A. Meisner, R. Miquel, J. Moustakas, A. D. Myers, S. Nadathur, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou

High Energy Astrophysical Phenomena · Cross-listed from math.NA

An Arbitrary-Lagrangian-Eulerian solver for relativistic detonation waves

Sara Rinaldi, Olindo Zanotti and Michael Dumbser

In this paper we study the dynamics of relativistic detonation waves theoretically and numerically. The reaction is physically accounted for by an extra term in the definition of the total energy density and by an additional equation for the evolution of the mass fraction of the reactant, while leaving formally unmodified the equations of mass and energy-momentum conservation. In this way, the Rankine-Hugoniot relations maintain the same formal structure of the inert version. For the numerical solution we use a second order finite volume ALE scheme with TVD reconstruction, where the mesh velocity is chosen equal to the shock speed. We also adopt a locally implicit algorithm for the treatment of potentially stiff reaction source terms that arise in the equation of the reactant. We furthermore propose a particularly efficient algorithm for the conversion from the conserved to the primitive variables, which for the relativistic Euler equations is known to be nontrivial. Following this approach, we can successfully solve the Zel'dovich-von Neumann-Doering profile of a relativistsic detonation wave, up to Lorentz factors of the shock front $\gamma_S\sim 7$. Our analysis allowed us to highlight a new special relativistic effect, which has remained unnoticed so far. While in Newtonian detonations the Zel'dovich pressure jump decreases monotonically with the mass flux through the shock front, in the relativistic case it shows a minimum and then rises monotonically as a function of the mass flux. This may have interesting physical implications on the amount of energy that can be extracted from a relativistic detonation wave.
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Astrophysics of Galaxies

Probing Anomalous Microwave Emission with the Square Kilometre Array

Matías Vidal, Simón Casassus, Roke Cepeda-Arroita et al. (+15 more)

Anomalous microwave emission (AME) represents an excess of radiation in the 10-60 GHz range, distinct from synchrotron, free-free, or thermal dust emission. Although most commonly attributed to electric dipole radiation from rapidly rotating small dust grains (spinning dust), alternative mechanisms such as magnetic dipole emission (MDE) remain plausible. The detection of AME across diverse environments, from diffuse interstellar clouds to protoplanetary disks and external galaxies, suggests that multiple physical processes or carriers may contribute to its origin. Understanding AME is essential for both Galactic astrophysics and cosmology, as it constitutes a significant foreground for cosmic microwave background (CMB) studies, potentially biasing measurements. This chapter reviews current theoretical frameworks and observational evidence for AME, highlighting the key outstanding questions concerning its emission mechanisms, carriers, and polarization properties. We discuss how the Square Kilometre Array Observatory (SKAO), through its unprecedented sensitivity, angular resolution, and frequency coverage, will transform AME studies. SKA observations will enable detailed mapping of AME morphology, precise characterisation of its spectral energy distribution, and the identification of its carriers in Galactic and extragalactic environments. By combining SKA-mid data with higher-frequency observations from ALMA and other facilities such as SPHEREx, it will be possible to disentangle competing models and exploit AME as a diagnostic probe of interstellar grain physics and the small-scale structure of the interstellar medium.
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All authors Matías Vidal, Simón Casassus, Roke Cepeda-Arroita, Miguel Cárcamo, Stuart E. Harper, Thiem Hoang, J. A. Rubiño-Martín, Kieran A. Cleary, Clive Dickinson, R. T. Génova-Santos, Gabriel A. Hoerning, Melis O. Irfan, A. Lazarian, Hauyu Baobab Liu, Eric J. Murphy, M. W. Peel, Nathalie Ysard, Zheng Zhang

Earth and Planetary Astrophysics

The ESO SupJup Survey XI. Atmospheric properties of six isolated M- and L-type dwarfs with CRIRES+

C. R. Malcolm, N. Grasser, I. A. G. Snellen et al. (+9 more)

The distinct formation pathways of brown dwarfs and giant exoplanets may be encoded in their atmospheric composition. We present atmospheric retrievals for six isolated brown dwarfs of spectral types M7-L2.5 from the ESO SupJup Survey, aiming to constrain their thermal structures, chemical compositions, and isotope ratios. We analyse CRIRES+ K-band spectra, coupling the radiative transfer code petitRADTRANS with the nested sampling algorithm PyMultiNest under both free and equilibrium chemistry frameworks. The L0 dwarf 2MASS J09532126-1014205 emerges as one of the fastest-rotating ultracool dwarfs known, with $v\sin i = 85.9\pm0.5$ km s$^{-1}$. H$_2$O is strongly detected in all six targets and $^{12}$CO in five, with a marginal $^{12}$CO detection in the ultra-fast L0 rotator consistent with severe rotational broadening. $^{13}$CO is significantly detected in DENIS J060852.8-275358 and tentatively in three further targets. Retrieved compositions are consistent with isolated brown dwarfs: near-solar C/O ratios ($0.51$-$0.63$), predominantly near-solar metallicities, and $^{12}$C/$^{13}$C ratios of ~91-155, at or above the local ISM value, with constraints for the two fastest rotators resting on the spectral fit but not corroborated by a $^{13}$CO cross-correlation peak. The M7 dwarf 2MASS J04341527+2250309 shows discrepant gravity and metallicity values between chemistry frameworks. Apparent H$_2^{18}$O constraints for two targets are found to be spurious, and their H$_2^{(16)}$O/H$_2^{18}$O ratios are presented as lower limits, demonstrating the importance of cross-correlation validation for minor species detections. The near-solar C/O ratios and metallicities, with $^{12}$C/$^{13}$C ratios at or above the ISM value, support a molecular cloud fragmentation origin for the sample. The agreement of $^{12}$C/$^{13}$C between chemistry frameworks supports the robustness of these ratios.
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All authors C. R. Malcolm, N. Grasser, I. A. G. Snellen, S. de Regt, D. González Picos, Y. Zhang, T. Stolker, S. Gandhi, P. Mollière, E. Nasedkin, R. Landman, A. Y. Kesseli

Astrophysics of Galaxies

Start of orbit librations and the bar growth timescale

Ekaterina N. Podzolkova and Anna M. Melnik

We study a dynamical model of the Galaxy with an analytical bar that reproduces the radial velocity $V_R$ profiles as a function of the Galactocentric distance $R$ obtained from the Gaia DR3 data. The model radial velocity profiles show a periodic increase in $V_R$ caused by orbits trapped into libration near the outer Lindblad resonance (OLR). To determine the moment when the librations start, we built a set of additional models differing only in the bar growth time $T_g$. The temporal dependences of the radial velocity $V_R$ in the models with different $T_g$ retain their shape but are shifted relative to each other in time $t$. The shift providing the best agreement between the model dependences is proportional to $T_g$ with the coefficient $k = 0.54 \pm 0.02$. Orbit librations do not start when the bar reaches its full strength, but when it attains only 54% of its maximum strength. Since the maximum bar strength in the models is $Q_b = 0.314$, the librations start when the bar strength reaches $Q_b = 0.170$.
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Cosmology and Nongalactic Astrophysics

Spherical Collapse and Halo Formation in a Cosmology with Decaying Dark Matter and a Semi-Cosmographic Dark Energy

Mohit Yadav and Tapomoy Guha Sarkar

We investigate nonlinear structure formation in a cosmological model combining one-body decaying dark matter (DDM) with a semi-cosmographic reconstruction of dark energy. In this scenario, a nonrelativistic dark-matter component decays into relativistic dark radiation with decay rate $\Gamma=\tau_{\rm ddm}^{-1}$, while the dark-energy sector is reconstructed directly from the expansion history rather than being fixed to a cosmological constant. Using DESI DR1 BAO and compressed ShapeFit measurements, we constrain the background evolution and propagate the resulting posterior into the nonlinear regime through spherical collapse and halo abundance calculations. This provides a unified framework connecting a reconstructed dark-energy sector and decaying dark matter (DDM) to the nonlinear formation of cosmic structures. We find that the reconstructed dark-energy equation of state can deviate from the $\Lambda$CDM value, $w=-1$, while the critical density threshold for collapse remains close to its standard prediction. The most pronounced signatures emerge in the abundance of massive halos, reflecting modifications to the growth of structure driven by both dark-matter decay and dynamical dark energy. By combining DESI DR1 clustering constraints with halo mass function measurements from the DESI Legacy Imaging Surveys DR9, we obtain joint constraints on the DDM lifetime and dark-energy parameters, demonstrating that halo abundances provide a powerful complementary probe of non-standard dark-sector physics.
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Instrumentation and Methods for Astrophysics

The Line Emission Terahertz Observatory (LETO): Exploring the lifecycle of the ISM and the origins of water

Dimitra Rigopoulou, Peter Roelfsema, William Grainger et al. (+13 more)

The Interstellar Medium (ISM) is the reservoir of baryonic matter from which stars and planetary systems are formed. It is also the repository of the material that is expelled at the end of the stellar evolutionary cycle feeding the baryonic matter reservoir. These evolutionary phases in the ISM together form a complex interplay driving planet and star formation and thus the evolution of our own Milky Way as well as galaxies at low and high redshifts. The design of the Line Emission Terahertz Observatory (LETO) has been optimized to investigate the impact of the ISM on star formation on galactic and extragalactic scales, study the processes that transform gas clouds into stars and planetary systems, and trace the flow of water in the ISM. To achieve these goals, LETO will carry out deep velocity-resolved wide-area spectroscopic observations of key FIR lines in the ISM covering an area of approximately 900 square degrees of the Galactic Plane. To complement our local view LETO will map a large sample of about 200 nearby galaxies in addition to surveys of Galaxies at Cosmic Noon. To shed light on the planet formation process, LETO will study the physical and chemical properties (especially gas mass) of numerous proto-planetary disks and stellar cores through pointed observations of the HD and H2O lines. LETO is a powerful FIR mission building on rich European heritage. To satisfy the requirements for sensitivity, resolving power and mapping speed, LETO utilizes a 3.5m class mirror and several bands with sensitive state-of-the-art multi-pixel heterodyne arrays. The bands together will cover the wavelength range from 56 to 666 micron and with the heterodyne receivers and backends high resolving power spectroscopy a set of key FIR atomic, ionic, and molecular lines can be studied in great detail. The mission is one of several selected for further study in the context of the ESA M8 call.
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All authors Dimitra Rigopoulou, Peter Roelfsema, William Grainger, Chris Pearson, Boon-Kok Tan, Wouter Laauwen, Andrey Baryshev, Vincent Desmaris, Ismael Garcia-Bernete, Javier R. Goicoechea, Leslie Hunt, Georgios Magdis, Miguel Pereira-Santaella, Kamber Schwarz, Bryan Shaugnessy, Martina Wiedner

Astrophysics of Galaxies

Unveiling a cosmic tango: Integral field spectroscopy and numerical simulations of Arp 143's interaction

Hugo Martel, Carmelle Robert, Laurent Drissen et al. (+6 more)

We present spectral data cubes of the interacting galaxy system Arp 143, composed of the ring galaxy NGC 2445 and the lenticular galaxy NGC 2444, obtained with the imaging Fourier transform spectrometer SITELLE at the Canada-France-Hawaii Telescope. Our data allow to probe the kinematics of the interaction and the chemical properties of the ionized gas. Star-forming regions are almost exclusively found in the ring and nucleus of NGC 2445 with the exception of a few very faint ones discovered at the base of the long tidal plume extending north of NGC 2444. Analysis of the H{\alpha} velocity map reveals strong non-circular flows in the ring of NGC 2445, which is expanding. Its nucleus is off-centered with respect to the ring. Oxygen abundance in the ring is on average slightly sub-solar whereas it is close to solar in the nucleus. Broad-band images obtained with the Dragonfly Telephoto array allow to identify the tenuous stellar counterpart of the radio tidal plume. The interaction between the two galaxies is simulated with a chemodynamical evolution code; these simulations suggest that Arp 143 has resulted from a head-on collision between a S0 and a Sc spiral galaxy following a flyby encounter that triggered the formation of the long plume from debris of the disk galaxy.
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All authors Hugo Martel, Carmelle Robert, Laurent Drissen, Charles-Antoine Parent, Prime Karera, Sébastien Vicens-Mouret, Salvador Duarte Puertas, Jorge Iglesias Páramo, José M. Vilchez

Earth and Planetary Astrophysics

Solarsystem: A Validated Lightweight Python Package for Planetary Positions and Solar-Lunar Event Calculations

Ioannis Nasios

This paper presents solarsystem, a validated lightweight and dependency-free Python package for planetary positions and solar-lunar event calculations. The package provides heliocentric and geocentric positions for the major planets, selected dwarf planets, the Centaur Chiron, and the Moon, together with sunrise, sunset, moonrise, moonset, and lunar illumination calculations. Additional functionality includes coordinate transformations between commonly used astronomical reference systems. The implemented algorithms employ analytical models that avoid reliance on external ephemeris datasets, resulting in a portable and computationally efficient solution suitable for a broad range of astronomical applications. An optional precession correction model is included, enabling calculations either in a precession-corrected reference frame or in a fixed epoch framework, depending on user requirements. The numerical performance of solarsystem was evaluated against the JPL DE440 planetary ephemerides using the Skyfield framework as a reference. Validation experiments spanning multiple bodies and extended temporal intervals demonstrate good agreement with the reference ephemerides, with mean planetary longitude and latitude deviations of approximately 0.44 and 0.16 arcminutes, respectively. Additional validation of solar and lunar event calculations yielded timing differences of only a few minutes relative to the reference solutions, while lunar illumination estimates differed by approximately 0.2%. The package can be installed directly through PyPI while the source code, documentation, validation notebooks and example workflows are publicly available through the project repository in https://github.com/IoannisNasios/solarsystem.
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