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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 23 April

Solar and Stellar Astrophysics

A SPHEREx Pipeline and Spectral Library for Ultracool Dwarfs

Jonathan Gagné, Jacqueline K. Faherty, Azul Ruiz Diaz et al. (+72 more)

We present a Python spectrophotometry extraction tool tailored for fast-moving point sources detected in the SPHEREx mission, and use it to construct a set of 0.75-5.0 $\mu$m low-resolution ($\lambda/\Delta\lambda \sim 50$) spectrophotometry data products based on the SPHEREx Quick Release 2 (QR2) for a set of 6003 L0-Y1 ultracool dwarfs: 2050 known ultracool dwarfs, 3008 known photometric ultracool dwarf candidates, and 947 newly identified ultracool dwarfs. This work more than doubles the number of ultracool dwarfs with spectroscopy, from 3449 to 7402. We provide SPHEREx templates for each spectral subtype and a set of tools to assign automated spectral types. The QR2 data release generates spectrophotometry with an average signal-to-noise per spectral channel above $\sim$10 for most objects with WISE W2 magnitudes of 14.0 mag and brighter. The compiled data set is made available publicly at https://mocadb.ca, where new spectral compilations from future data releases will also be made available as they are published. These new data provide a significant increase in the number of substellar objects for which the 2.4-5.0 $\mu$m window is now accessible, making it possible to probe important molecular chemistry of key CNOS-bearing species for the coolest brown dwarfs. We flag 2668 ultracool dwarfs as candidate young brown dwarfs, 250 as candidate subdwarfs, and 865 as possibly otherwise peculiar for future investigation. The SPIFF library presented here opens the doors to efficient confirmation of candidate substellar objects and follow-up studies of population-level atmospheric properties of cold brown dwarfs.
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All authors Jonathan Gagné, Jacqueline K. Faherty, Azul Ruiz Diaz, Louis-Philippe Coulombe, Thomas P. Bickle, Adam C. Schneider, J. Davy Kirkpatrick, Marc J. Kuchner, Aaron M. Meisner, Dan Caselden, Adam J. Burgasser, Sarah Casewell, Easton J. Honaker, Frank Kiwy, Federico Marocco, Daniella C. Bardalez Gagliuffi, Nikolaj Stevnbak Andersen, Lizzeth Ruiz Arroyo, Bruce Baller, Paul Beaulieu, John Bell, Martin Bilsing, Troy K. Bohling, Guillaume Colin, Giovanni Colombo, Sam Deen, Alexandru Dereveanco, Kevin Dixon, Hugo A. Durantini Luca, Deiby Flores, Christoph Franck, Christopher Fulvi, Michael Gallmann, Jean Marc Gantier, Konstantin Glebov, Léopold Gramaize, Leslie K. Hamlet, Ken Hinckley, Kevin Jablonski, Peter A. Jałowiczor, Martin Kabatnik, Peter Kasprowitz, K Ly, David W. Martin, Naoufel Marzak, Alexander McColgan, Neil J. McEwan, Marianne N. Michaels, William Pendrill, Stéphane Perlin, Ben Pumphrey, James Rabe, Henry Raway, Walter Ruben Robledo, David Roser, Animesh Roy, Arttu Sainio, Vincent Schindler, Manfred Schonau, Jö rg Schümann, Karl Selg-Mann, Andrea Serio, Patrick Smith, Andres Stenner, Christopher Tanner, Melina Thévenot, Vinod Thakur, Mayahuel Torres Guerrero, Maurizio Ventura, Nikita V. Voloshin, Jim Walla, Zbigniew Wȩdracki, Bailey Weyandt, Breck Wilhite, Spartacus Zitouni

Solar and Stellar Astrophysics · Cross-listed from hep-ph

Solar Reflection of Inelastic Dark Matter

Haipeng An and Haoming Nie

Solar-reflected dark matter (SRDM) consists of dark-matter particles up-scattered and accelerated by energetic electrons in the solar interior, producing a high-velocity tail that can enhance signals in direct-detection experiments, especially for MeV-scale masses. We consider an inelastic dark matter (iDM) model, in which solar scattering populates the excited state; subsequent de-excitation in terrestrial detectors releases the mass-splitting energy, substantially helping the energy release of the collision to be larger than the detector threshold. Using detailed Monte Carlo simulations, we generate the velocity and energy distributions of solar-reflected iDM over a range of dark-matter masses $m_\chi$ and mass splittings $\Delta$. We then compute event rates and energy depositions for current xenon and semiconductor experiments. Our results show that these experiments can place new constraints on the parameter space of MeV-scale iDM.
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Instrumentation and Methods for Astrophysics

Fast, Stable, and Physical: Hyperbolic, Magnetic Field-Aligned Diffusion in SPH

Nicholas Owens, James Wadsley, Robert Wissing et al. (+1 more)

In this paper, we introduce the first implementation of magnetic field-aligned hyperbolic diffusion for standard smoothed particle (magneto-)hydrodynamics (SPH), and its linear-exact gradient extension (LESPH). Hyperbolic diffusion differs from traditional parabolic methods by incorporating the physical characteristic speed of diffusing particles and is computationally faster. This work extends it to encompass field-aligned diffusion, linear-exact gradients, and linear reconstruction to limit dissipation. Several standard test problems are presented: a diffusing slab, diffusion around a ring, a Gaussian pulse, and the magneto-thermal instability (MTI). The MTI only grows for for LESPH with reconstruction, and not for SPH. Both LESPH and SPH remain stable while fully aligning diffusion to magnetic fields. LESPH is more accurate and converges faster in the L1 error norm. SPH and LESPH both see improvements when using when also using linear reconstruction. These methods apply to other diffusive transport such as cosmic rays, viscosity, or magnetic resistivity.
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All authors Nicholas Owens, James Wadsley, Robert Wissing, Ben Keller

Instrumentation and Methods for Astrophysics

Euclid Quick Data Release (Q1). AstroVink: A vision transformer approach to find strong gravitational lens systems

Euclid Collaboration: S. H. Vincken, K. Rojas, M. Melchior et al. (+301 more)

We present AstroVink, a vision transformer classifier designed for automated identification of strong lens candidates in Euclid imaging. We build upon the DINOv2 encoder, fine tuned to distinguish between lens and non-lens galaxies. Our base model, trained on simulated strong lens systems and labelled non lenses, recovers 88 of the 110 lens candidates within the top 500 ranked candidates, corresponding to an inspection efficiency of one lens per 5.7 inspected objects in our test set. After the Q1 data release, which yielded about 500 lens candidates, we retrained the model using high confidence lens candidates and new negatives, initially flagged as potential lenses by other classifiers but rejected during visual inspection. The retrained network further improves performance, achieving recovery of all 110 systems within the same ranking and reducing the inspection effort to one lens per 4.5 inspected objects, demonstrating that incorporating real examples significantly enhances model generalisation. An analysis of training subsets revealed that the inclusion of realistic negative examples played a key role in this improvement. Finally, we applied the retrained model to the Q1 original selection of 1.08M targets, followed by a new round of Space Warps citizen science inspection and expert vetting, where we identified a total of eight Grade A and 26 Grade B new lens candidates. These results demonstrate that transformer based architectures can recover strong lens candidates with high efficiency in real Euclid data, while substantially reducing the number of candidates requiring visual inspection.
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All authors Euclid Collaboration: S. H. Vincken, K. Rojas, M. Melchior, N. E. P. Lines, T. E. Collett, A. Verma, P. Holloway, G. Despali, S. Schuldt, R. B. Metcalf, R. Gavazzi, F. Courbin, J. A. Acevedo Barroso, B. Clément, T. Li, D. Sluse, J. Wilde, A. Melo, A. Sonnenfeld, C. Tortora, T. T. Thai, M. Millon, C. Spiniello, A. Manjón-García, M. Meneghetti, B. C. Nagam, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, M. Douspis, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, F. Faustini, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, J. Hoar, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, E. Munari, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, M. Schirmer, P. Schneider, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, E. Zucca, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, L. Gabarra, S. Hemmati, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, N. Mauri, P. Monaco, A. A. Nucita, A. Pezzotta, M. Pöntinen, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, P. Bergamini, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, Y. Charles, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P.-A. Duc, V. Duret, M. Y. Elkhashab, A. Enia, Y. Fang, A. Finoguenov, A. Franco, K. Ganga, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, F. Lepori, G. Leroy, J. Lesgourgues, T. I. Liaudat, S. J. Liu, A. Loureiro, M. Magliocchetti, E. A. Magnier, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, C. Moretti, G. Morgante, K. Naidoo, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, D. Potter, G. W. Pratt, S. Quai, M. Radovich, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, C. Scarlata, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, A. Venhola, D. Vergani, G. Vernardos, G. Verza, S. Vinciguerra, M. Walmsley, N. A. Walton, A. H. Wright

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

Cosmic-Ray Signatures of Annihilating and Semi-Annihilating Dark Matter via One-Step Cascades

Francesco D'Eramo, Silvia Manconi and Tommaso Sassi

We present a framework in which three classes of dark matter number-changing processes can affect both the relic abundance via thermal freeze-out in the early universe and the generation of indirect cosmic-ray signals today. These processes are: (i) direct annihilations into Standard Model final states; (ii) annihilations into metastable on-shell mediators that subsequently decay into Standard Model particles; (iii) semi-annihilation processes featuring a dark matter particle in the final state, accompanied by a metastable mediator. A central element of our analysis is the systematic inclusion of semi-annihilation alongside the more commonly considered channels. This setup is largely model-independent, as we only assume the presence of one or more of these processes with unsuppressed $s$-wave contributions. We analyze representative benchmarks for the dominant decay modes of the mediator and show how the resulting injection spectra for $\gamma$ rays, neutrinos, and cosmic-ray antimatter vary with the relative importance of the three classes of processes. As an application, we evaluate the observable $\gamma$-ray fluxes from dwarf spheroidal galaxies in the GeV-TeV window. Finally, we provide explicit model realizations in which multiple processes coexist, and discuss how their interplay shapes indirect detection signatures. Our results provide a consistent connection between early-universe dynamics and present-day observables, revealing distinctive features that arise when multiple dark matter processes contribute simultaneously.
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Instrumentation and Methods for Astrophysics

The Simons Observatory: Improved Cryogenic Struts for use in the Large Aperture Telescope Receiver

John Orlowski-Scherer, Anna Kofman, Tanay Bhandarkar et al. (+5 more)

The Simons Observatory Large Aperture Telescope Receiver (SO LATR) is a next generation Cosmic Microwave Background camera equipped with > 60, 000 detectors operating at 100 mK. Maintaining these detectors at the correct temperatures and locations requires stiff, cryogenically insulating struts. In this paper we report the design and performance of a novel glue joint in a strut used in the SO LATR to achieve the required performance. We use a tapped hole and set screw to create a profile on the exterior and interior wall of the glue joint, respectively, which greatly increases the strength of that joint by changing the failure mode from adhesive to cohesive. The failure mode of the resulting glue joint is cohesive with a yield strength 10% higher than a comparable smooth-walled design, and an ultimate strength 33% higher. Comparisons of the measured yield strength to the predicted axial load on the strut from simulations results in a factor of safety for the strut of 7. These struts have been installed in the SO LATR for three years and have undergone numerous thermal cycles from 300 K to 100 mK with no evidence of damage to the glue joint.
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All authors John Orlowski-Scherer, Anna Kofman, Tanay Bhandarkar, Mark Devlin, Saianeesh K. Haridas, Jeff Iuliano, Alex Manduca, Robert J. Thornton

High Energy Astrophysical Phenomena

The Effects of Complex Accretion Disk Geometry on Broadened Iron K$\alpha$ Lines

William Surgent and Daniel R. Wilkins

X-rays are emitted from the corona above the orbiting matter of the accretion disk and travel either directly to us or illuminate the disk. This illumination of the inner disk is enhanced by gravitational light bending, which focuses the rays towards the black hole and therefore towards the inner radii of the disk. These rays that hit the inner radii are reflected back to us, and we observe them in the X-ray reflection spectrum. In this work, we create novel general-relativistic ray-tracing simulations to investigate the effects of altering the geometry of the accretion disks of black holes on the most dominant part of the reflection spectrum, the iron K$\alpha$ line. Work demonstrating the effect of disk geometry on the iron line has been performed, though many previous analyses have assumed a simplistic system, consisting of a point-source corona with a flat and infinitesimally thin accretion disk. We extend these models to more realistic accretion disk approximations. These include a constant-aspect-ratio disk, a radiation-pressure-dominated Shakura-Sunyaev disk, an expanded inner disk that has a nonnegligible scale height in its inner regions due to radiation pressure, as well as various warped-disk configurations. Using measurement uncertainties from XRISM, we find that nonnegligible thickness in accretion disks underestimates the black hole spin, coronal height, and inclination angle if fitted with a flat-disk model. The warped-disk model could not be fit with the flat-disk approximation.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Gradient-Produced Neutrinos

Erwin H. Tanin and Yikun Wang

Sufficiently strong electric fields can produce charged-particle pairs via the Schwinger effect. We argue that steep matter-density gradients, as can arise in neutron star interiors, would analogously produce neutrino-antineutrino pairs. We then discuss observational signatures of these gradient-produced (anti)neutrinos and how they could provide new probes of neutron-star structure and baryon-dense QCD.
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Instrumentation and Methods for Astrophysics

Verifying the STIS Time Dependent Sensitivity Trends with the Primary CALSPEC Standards

Daniel Stapleton and Svea Hernandez

The STIS team monitors the time dependent sensitivity (TDS) of each grating with one from a set of three secondary CALSPEC standard stars: GRW+70D5824, AGK+81D266, and BD+28D4211. Here, we use the three primary CALSPEC White Dwarf standard stars, dubbed the standard star "triad" (GD71, GD153, G191B2B), as an independent set of standards to verify the accuracy of STIS TDS corrections derived from the TDS monitoring stars, increasing the sample for each STIS L-mode from one up to three or four standard stars. We focus on triad star observations using the STIS L-mode gratings (e.g., G140L, G230L, etc.) with the same configuration as our standard TDS monitoring programs, and compare the triad observations to the TDS pipeline trends. Our analysis indicates the relative net count rates inferred from the triad standards agree with the TDS trends derived from the TDS monitoring stars with average residuals $<$ 2$\%$ across the full wavelength range of STIS, suggesting our current TDS L-mode trends are reliable and robust. We note that the dispersion in the residuals does vary with wavelength, with the NUV showing the lowest spread ($\pm$ 0.32$\%$ at 2400-2500 Angstroms) and the NIR the largest ($\pm$ 1.32$\%$ at 9500-9900 Angstroms); however, this scatter is also seen in our measurements of the TDS monitoring stars and is more indicative of other instrumental effects. Our findings rule out long term deviations, such as variability in our TDS monitoring stars, within measurement uncertainties.
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Instrumentation and Methods for Astrophysics

Gender equality activities in Astronomical Society of Japan

Aya Bamba, Ayumi Asai, Ryohko Ishikawa et al. (+6 more)

The female ratio in science field, including astronomy, is still quite low in Japan. We, the Astronomical Society of Japan, are making efforts to equalise the gender balance. In this paper, we summarise our statistics, member's thinking shown in our questionnaire, the history and accomplishments of the day-care system during annual meetings, and other activities.
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All authors Aya Bamba, Ayumi Asai, Ryohko Ishikawa, Masayoshi Nobukawa, Hideko Nomura, Kosuke Sato, Hisanori Furusawa, Mami Machida, Sachiko Okumura

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

Determination of the sensitivity of the DEAP-3600 experiment to supermassive charged gravitinos

Michał Olszewski

The lack of discovery of particle dark matter candidates within the favored mass-window range brings in the motivation for the study of new options brought by Planck-mass dark matter models. Extended supergravity theories predict the existence of non-relativistic gravitinos that could at least in part contribute to the missing mass-energy density of the Universe. The feasibility study for the discovery with DEAP-3600 experiment of Planck mass charged gravitino dark matter is presented. Additionally the expected signal events topology within the detector is discussed.
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Solar and Stellar Astrophysics

First measurement of wind line formation regions in an early O-type star

D. Pauli, T.N. Parsons and R.K. Prinja

Massive stars with their strong ionizing radiation and strong stellar winds are the key feedback agents of the universe. Stellar winds of massive stars are often measured by fitting resonance lines in the UV using non-LTE stellar atmosphere models. So far, the line formation regions of these lines have not been measured empirically, preventing a comparison to the model's structures. We aim to conduct the first measurement of the resonance line formation regions in an early-type eclipsing binary in the SMC, namely AzV 75. We employ TESS and ASAS-SN photometry in combination with radial velocity measurements from multi-epoch HST UV spectra to derive the ephemeris. We examine the intensity changes in the C IV and N V resonance lines in the UV and combine them with a light-curve analysis to estimate the region in the wind where these lines are formed. AzV 75 has an orbital period P=165.66d, eccentricity e=0.42, mass ratio q=0.72, and inclination i=85.77{\deg}. With this orbital configuration, no secondary eclipse is expected. We report that the optically thick UV resonance lines exhibit flattening and shortening of the absorption trough, and weakening of their emission features, as they approach the phase of the expected secondary eclipse, while the continuum UV flux appears to remain unaffected. We illustrate that this can be explained by the primary's optically thick wind eclipsing the secondary star. The C IV and N V resonance line formation regions in the primary star extend up to 316 Rsol. The measured extend of the formation regions of resonance lines in a stellar wind are important benchmarks for 1D as well as 3D non-LTE stellar atmosphere models. A first comparison to 1D-stellar atmosphere models indicates that a classical beta-law with an exponent of beta=0.5 instead of beta=0.8 might be favoured for the primary star's velocity field.
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Astrophysics of Galaxies

The impact of hydrogen atom tunneling on aromatic chemistry in TMC-1

Reace H. J. Willis, Thomas H. Speak, Alex N. Byrne et al. (+2 more)

Hydrogen atom tunneling likely plays a substantial role in the gas-phase chemistry of astrochemical environments. To determine the potential effect that it has on the chemical modeling of aromatic molecules, we screened the kida.uva.2024 network, and our own expanded network to find reactions which could be significantly accelerated by hydrogen atom tunneling in the ISM. In total, 64 reactions were identified. The hydrogen abstraction reactions from H$_{2}$ to four key interstellar radicals (C$_{2}$H, OH, CN, and NH$_{2}$) were studied further using newly calculated potential energy surfaces and RRKM analyses to determine rate coefficients for a temperature of 10 K and a density of 2 $\times$ 10$^{4}$ cm$^{-3}$. Despite having low rate coefficients of 1.66 $\times$ 10$^{-15}$, 8.17 $\times$ 10$^{-16}$ and 3.15 $\times$ 10$^{-16}$ $\mathrm{cm^{3}\,s^{-1}}$ the C$_{2}$H, OH, and CN reactions are competitive in the ISM, due to large overall rates caused by the high abundance of molecular hydrogen. The calculated value for the NH$_{2}$ reaction, however, was much smaller and found to be inefficient at ISM conditions. The possible effects of all other considered reactions were studied with simulations using calculated collision limit rate coefficients. Upper and lower bounds were then placed on modeled aromatic abundances using the most significant reactions. Due to the dependence of calculated aromatic abundances on reactions involving c-C$_{6}$H$_{5}^{+}$ and the recent questions surrounding its reactivity, we also explored the abundance variations caused by reactions leading to or involving c-C$_{6}$H$_{5}^{+}$.
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All authors Reace H. J. Willis, Thomas H. Speak, Alex N. Byrne, Christopher N. Shingledecker, Ilsa R. Cooke

Astrophysics of Galaxies

The Dyson Minds 2025 Workshop: SETI around Black Holes

Olivia Curtis, Van Hunter Adams, Daniel Angerhausen et al. (+9 more)

The Dyson Minds 2025 Workshop, held at the Center for Brains, Minds & Machines at MIT and organized by Penn State, MIT, and The Ultraintelligence Foundation, brought together researchers in astrophysics, engineering, artificial intelligence, computer science, and philosophy to examine "Dyson Minds" – large-scale post-biological intelligences powered by energy harvested from supermassive black holes (SMBHs). Building on the ideas of F. J. Dyson (1960, 1966) and I. J. Good (1966), participants explored the physical, engineering, behavioral, and observational consequences of civilizations embodied as machinery operating near the universe's most powerful energy sources. The workshop aimed to develop new observational strategies capable of detecting signatures of such systems. Despite the highly cross-disciplinary scope, discussions centered on how a Dyson Mind might be constructed, how it might behave, and how those factors would shape strategies for the search for extraterrestrial intelligence. Key themes included the thermodynamic, mechanical, and stability limits of Dyson swarms; the trade-offs between power availability and communication latency in distributed minds; and how observability changes depending on whether Dyson Minds act as coherent entities or as loosely coordinated collectives. Across these topics, the consensus was that details of architecture and behavior strongly influence observational signatures. A major recommendation was to apply anomaly-detection methods to archival datasets, including those from WISE, JWST, and the Event Horizon Telescope, to identify unusual sources potentially overlooked by standard reduction pipelines. By integrating insights from multiple disciplines, the meeting advanced concrete, observation-focused strategies for future technosignature searches around SMBHs.
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All authors Olivia Curtis, Van Hunter Adams, Daniel Angerhausen, Joseph Bates, Anamaria Berea, Steven J. Dick, Martin Elvis, Sunil P. Khatri, Richard Linares, Manushaqe Muco, S. Seager, Jason T. Wright

High Energy Astrophysical Phenomena

Testing solitonic boson star interpretations of Sagittarius A* with near-infrared flare astrometry

Xiangyu Wang, Zhenyu Zhang, Hai-Qing Zhang et al. (+2 more)

We use GRAVITY near-infrared (NIR) flare astrometry to test whether Sagittarius A* could be a solitonic boson star. We consider five spherically symmetric solitonic boson-star models with different effective radii, together with the Schwarzschild black hole. Treating the flares as hot spots on circular equatorial orbits, we analyze their centroid motions and images in these spacetimes and use them for parameter fitting. We perform the fitting using both $\chi^2$ analysis and Markov Chain Monte Carlo (MCMC) methods, which yield consistent results: the inferred masses of boson-star models are systematically larger than the established value of $4.3\times10^6M_\odot$. Notably, more diffusive boson stars exhibit imaging properties closer to those of a black hole, leading to mass estimates that are correspondingly closer to the established value. Overall, our results place stringent constraints on solitonic boson star interpretations of Sagittarius A*, although do not completely rule them out.
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All authors Xiangyu Wang, Zhenyu Zhang, Hai-Qing Zhang, Minyong Guo, Bin Chen

High Energy Astrophysical Phenomena

Mitigating Systematic Errors in Parameter Estimation of Binary Black Hole Mergers in O1-O3 LIGO-Virgo Data

Sumit Kumar, Max Melching, Frank Ohme et al. (+3 more)

Systematic errors in the parameter estimation (PE) of gravitational wave (GW) mergers can arise from various sources, including waveform systematics, noise mischaracterization, data analysis artifacts, and other unknown factors. In this study, we analyze selected events from the first three observing runs of the LIGO-Virgo-KAGRA (LVK) collaboration. We choose events that have been flagged in various studies as potentially affected by systematic errors. Here, we reanalyze these events using a couple of parametric models developed in previous work that incorporate uncertainties in both the phase and amplitude of the GW waveform. In this data-driven approach, we apply sufficiently broad priors on the uncertainty parameters to account for potential systematic errors. Our findings show that the proposed method effectively reduces systematic errors, even those arising from data artifacts, such as glitches occurring near a signal and the deglitching process in GW frame files. Similarly, inconsistent results from different waveform models become much more consistent in our framework. One noteworthy event we examine is GW191109\_010717, which is particularly interesting due to its anti-aligned spin properties. We report that, within our framework, the event still exhibits anti-aligned spin characteristics, but the inference results become consistent across raw and deglitched frame files, as well as across the waveform models used for this event (IMRPhenomXPHM, IMRPhenomXO4a, and NRSur7dq4). A similar trend is observed for the event GW200129\_065458, which previously yielded a high, but inconsistent precession parameter among different waveform models. In contrast, we observe a non-zero and consistent value of $\chi_{p}=0.60^{+0.31}_{-0.33}, 0.58^{+0.30}_{-0.29}$ and $0.56^{+0.31}_{-0.28}$ for the IMRPhenomXPHM, IMRPhenomXO4a, and NRSur7dq4 waveform models, respectively.
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All authors Sumit Kumar, Max Melching, Frank Ohme, Harsh Narola, Tom Dooney, Chris Van Den Broeck

Earth and Planetary Astrophysics

Toward Inferring the Surface Fluxes of Biosignature Gases on Rocky Exoplanets from Telescope Spectra

Nicholas F. Wogan, Natasha E. Batalha, Joshua Krissansen-Totton et al. (+5 more)

The James Webb Space Telescope and the future Habitable Worlds Observatory aim to discover exoplanet atmospheric spectra that detect life. Currently, most existing spectral "retrieval" algorithms focus on inferring the abundances of biogenic gases from these spectra. However, abundances are hard to interpret as signatures of life because they are modified by photochemistry, climate, and atmospheric escape. To address this problem, we develop a method for inferring the fluxes of gases at a planetary surface by inverting a coupled photochemical-climate model. As a proof-of-concept, we apply the approach to a synthetic 10-transit JWST NIRSpec Prism spectrum of TRAPPIST-1 e assuming it hosts a biosphere similar to the Archean Earth's. The retrieval confidently detects CO$_2$ and CH$_4$ and can constrain the flux of CH$_4$ into the atmosphere to within approximately 1.5 orders of magnitude (68$\%$ credible interval) provided that TRAPPIST-1's near-UV spectrum is accurately known. We demonstrate how inferred surface gas fluxes naturally fold into a probabilistic assessment of life, finding that ~ 80$\%$ of the surface gas flux posterior is consistent with a CH$_4$-producing metabolism for our nominal test case. As with any inverse problem, these results are conditional on a number of assumptions in our forward model. Overall, we argue that increasing the robustness of life detection on exoplanets requires moving beyond atmospheric abundances toward inference of the surface fluxes that sustain them.
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All authors Nicholas F. Wogan, Natasha E. Batalha, Joshua Krissansen-Totton, Kevin Zahnle, Victoria S. Meadows, Amber V. Young, Evan L. Sneed, Edward W. Schwieterman

Instrumentation and Methods for Astrophysics

Broad-band High-Energy Resolution Hard X-ray Spectroscopy using Transition Edge Sensors at SPring-8

Shinya Yamada, Yuto Ichinohe, Hideyuki Tatsuno et al. (+39 more)

We have succeeded in operating a transition-edge sensor (TES) spectrometer and evaluating its performance at the SPring-8 synchrotron X-ray light source. The TES spectrometer consists of a 240 pixel National Institute of Standards and Technology (NIST) TES system, and 220 pixels are operated simultaneously with an energy resolution of $4$~eV at 6~keV at a rate of about 1~c/s/pixel. The tolerance for high count rates is evaluated in terms of energy resolution and live time fraction, leading to an empirical compromise of about 2 x 10^3 c/s/all pixels with an energy resolution of 5 eV at 6 keV. By utilizing the TES's wide-band spectroscopic capability, simultaneous multi-element analysis is demonstrated for a standard sample. We conducted X-ray absorption near-edge structure (XANES) analysis in fluorescence mode using the TES spectrometer. The excellent energy resolution of the TES enabled us to detect weak fluorescence lines from dilute samples and trace elements that have previously been difficult to resolve due to the nearly overlapping emission lines of other dominant elements. The neighboring lines of As K alpha and Pb L alpha2 of the standard sample were clearly resolved and the XANES of Pb L alpha2 was obtained. Moreover, the X-ray spectrum from the small amount of Fe in aerosols was distinguished from the spectrum of a blank target, which helps us to understand the targets and the environment. These results are the first important step for the application of high resolution TES-based spectroscopy at hard X-ray synchrotron facilities.
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All authors Shinya Yamada, Yuto Ichinohe, Hideyuki Tatsuno, Ryota Hayakawa, Hirotaka Suda, Takaya Ohashi, Yoshitaka Ishisaki, Tomoya Uruga, Oki Sekizawa, Kiyofumi Nitta, Yoshio Takahashi, Takaaki Itai, Hiroki Suga, Makoto Nagasawa, Masato Tanaka, Minako Kurisu, Tadashi Hashimoto, Douglas Bennett, Ed Denison, William Doriese, Malcolm Durkin, Joseph Fowler, Galen O'Neil, Kelsey Morgan, Dan Schmidt, Daniel Swetz, Joel Ullom, Leila Vale, Shinji Okada, Takuma Okumura, Toshiyuki Azuma, Toru Tamagawa, Tadaaki Isobe, Satoshi Kohjiro, Hirofumi Noda, Keigo Tanaka, Akimichi Taguchi, Yuki Imai, Kosuke Sato, Tasuku Hayashi, Teruhiko Kashiwabara, Kohei Sakata

High Energy Astrophysical Phenomena

An RXTE Search for the Sterile Neutrino Decay in Galaxy Clusters

Mark J. Henriksen

We have searched for the 3.55 keV line from sterile neutrino decay using 3.1 megaseconds of RXTE cluster data. A 2.5$\sigma$ excess of emission over a thermal model is found over the energy span of the 3.55 keV line in the combined spectra of the eight clusters that individually have an excess. The residuals are added to increase the signal to noise ratio of the excess, which is then modeled with a Gaussian to simulate the instrumental spectral response. We find a significant correlation (r = 0.76) for a line centered at 3.6 keV with a model flux of 3.07 x 10$^{-5}$ ph cm$^{-2}$ s$^{-1}$. Mixing angle for detected clusters ranges from 0.35 to 6.2 x 10$^{-10}$. The decay rate inferred from the line flux is strongly correlated (r = 0.87) with cluster temperature, which is due to hotter, more massive clusters having a larger amount of dark matter. Approximately half of the decay line total flux comes from the Coma cluster. We fit the Coma cluster spectrum with two different three-component models. The first includes a Gaussian fixed at 3.55 keV to model soft emission. The second three-component model uses a second thermal component to model soft emission. The model fit parameters indicate that the second thermal component is modeling high-energy residuals rather than low ones, where the Gaussian is. Though our line fluxes exceed most reported detections and upper limits, they do not overproduce the dark matter. We conclude that some fraction of the marginally detected excess could be attributed to the decay line since low-temperature thermal emission and systematics fail to model it completely.
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Earth and Planetary Astrophysics

MINDS: Intertwined evolution of dust and gas in large planet-forming disks. A diversity driven by halted pebble drift?

Benoît Tabone, Milou Temmink, Laurens B. F. M. Waters et al. (+25 more)

(Abridged) We aim to investigate the inner regions of large and massive disks orbiting T Tauri stars, thought to be progenitors of systems with wide-orbit planets and possible cases of halted pebble drift. We analyze the MIRI spectra of three disks from the MINDS program: V1094 Sco, DL Tau, and IM Lup. The spectra reveal a striking diversity. V1094 Sco and DL Tau exhibit the highest C$_2$H$_2$/H$_2$O flux ratio in the MINDS sample of T Tauri disks. In V1094 Sco, even cold C$_4$H$_2$ is seen. In contrast, the IM Lup spectrum is dominated by O-bearing species. No one-to-one correspondence is found between the gas in the outer disk, as traced by the C$_2$H/C$^{18}$O flux ratio, and that of the inner disk as traced by the C$_2$H$_2$/H$_2$O flux ratio. To explain these results, we propose a scenario based on a toy model of halted pebble drift. We show that a volatile C/O ratio close to unity and low C and O abundances in inner disks arise only if: (1) ~95$\%$ of the icy grains are blocked in the outer disk, (2) the outer disk is chemically evolved, and (3) the gas in the outer disk has had time to reach the inner disk. DL Tau and perhaps V1094 Sco would be the rare examples for which all these conditions are met. Therefore, a high C$_2$H$_2$/H$_2$O flux ratio in pebble-rich disks would have a different origin than proposed for very-low mass stars, for which fast drift of O-rich pebbles would eventually leave a C-rich inner disk. We also show for the first time that the disks with high C$_2$H$_2$/H$_2$O flux ratio exhibit a prominent silica dust component, a result found in four disks published so far (V1094 Sco, DL Tau, CY Tau, DoAr 33). We propose that the reformation of dust at the sublimation front of silicates in a gas with super-solar (but below unity) C/O ratio leads to a silica stoichiometry (SiO$_2$). In turn, silica is a promising diagnostic of the C/O ratio in the inner disks.
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All authors Benoît Tabone, Milou Temmink, Laurens B. F. M. Waters, Ewine F. van Dishoeck, Andrew Sellek, Pacôme Estève, Nicolas T. Kurtovic, Inga Kamp, Thomas Henning, Danny Gasman, Sierra L. Grant, József Varga, Alice Guerras, Dmitry Semenov, Aditya M. Arabhavi, Alessio Caratti o Garatti, Anne Dutrey, Edwige Chapillon, Stéphane Guilloteau, Manuel Güdel, Hyerin Jang, Till Kaeufer, Jayatee Kanwar, Göran Olofsson, Giulia Perotti, Vincent Piétu, Thomas P. Ray, Marissa Vlasblom

Cosmology and Nongalactic Astrophysics

Informative Priors on Primordial Non-Gaussianity Bias $b_{\phi}$ From Galaxy Formation

Anne Moore, Lucia A. Perez and Elisabeth Krause

Constraining primordial non-Gaussianity via its scale-dependent imprint on galaxy clustering requires knowledge of the bias parameter $b_{\phi}$, which is exactly degenerate with $f^{\rm{loc}}_{\rm{NL}}$ at leading order. To break this degeneracy, current analyses adopt the relation $\left(b_{\phi} = 2\delta_c\left(b_1 - 1\right)\right)$ based on the assumption of a universal mass function. This relation is known to break down for physically motivated galaxy selections, introducing systematic errors in the inferred $f^{\rm{loc}}_{\rm{NL}}$ that scale directly with the assumed $b_{\phi}$ prior. We present a framework to construct physically motivated, observation-conditioned priors on $b_{\phi}$ by marginalizing over galaxy formation uncertainties. We use the CAMELS-SAM simulation suite, augmented by separate Universe simulations, to measure galaxy formation observables, like the stellar mass function (SMF) and the stellar-to-halo mass relationship (SHMR), and $b_{\phi}$ across a range of galaxy formation parameters. From these measurements, we construct a distribution of $b_{\phi}$ conditioned on observations, and we select our galaxy sample to resemble the DESI Emission Line Galaxy (ELG) sample. Conditioning on the SMF or SHMR decreases $\sigma_{b_{\phi}}$ from $0.69$ to $0.08$ and $0.02$ respectively – reductions of $88\%$ and $97\%$ – with consistent results when conditioning on the observed data directly. Despite substantial shifts in the galaxy formation posteriors driven by known SC-SAM discrepancies at high halo masses, the resulting $b_{\phi}$ distributions remain mutually consistent across all observables. The SMF and SHMR are found to carry sufficient constraining power to reduce the galaxy formation uncertainty in $b_{\phi}$ relevant for $f^{\rm{loc}}_{\rm{NL}}$ inference with next-generation spectroscopic surveys
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Accelerating scaling solutions from dark matter particle creation

Sudip Halder, Jaume de Haro, Supriya Pan et al. (+3 more)

This article opens new window to obtain accelerating scaling attractors without any need of dark energy. We study cosmological dynamics in a two-fluid system where pressureless dark matter (DM) undergoes adiabatic particle creation and exchanges energy with a barotropic fluid. Considering six widely used interaction prescriptions, we formulate the corresponding autonomous systems in a compact phase space and perform a unified dynamical analysis. We find that accelerating scaling attractors, namely late-time states where both fluids coexist with fixed energy fractions, arise only when the interaction is controlled by the DM density and energy flows from DM to the second fluid. Such attractors appear in the global and local DM-based interactions, and in the global mixed case, but are entirely absent when the interaction depends on the second fluid or on local mixed terms, which instead drive the universe to a DM-dominated accelerating phase. These results clarify the unique conditions under which matter creation can mimic dark-energy-like behaviour without introducing a dark-energy component.
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All authors Sudip Halder, Jaume de Haro, Supriya Pan, Emmanuel N. Saridakis, Tapan Saha, Subenoy Chakraborty

High Energy Astrophysical Phenomena

Magnetar Engines in Broad-lined Type Ic Supernovae and a Unified Picture for Magnetar-powered Stripped-envelope Supernovae

Jin-Ping Zhu and Bing Zhang

We model the multi-band lightcurves of 80 SNe Ic-BL, including 11 associated with lGRBs, using a magnetar engine model with $^{56}$Ni decay. We find that the data are all consistent with a magnetar central engine, and such a model yields high-quality fits across the sample. The medians with $1\sigma$ regions of the key parameters are $P_{\rm{i}}\sim2.04^{+1.84}_{-0.96}\,{\rm{ms}}$, $B_{\rm{p}}\sim3.96^{+3.28}_{-1.40}\times10^{15}\,{\rm{G}}$, $M_{\rm{ej}}\sim2.30^{+1.48}_{-1.02}\,M_\odot$, and $M_{\rm{Ni}}\sim0.18^{+0.14}_{-0.09}\,M_\odot$, with strong and statistically significant correlations observed for both $M_{\rm{ej}}-P_{\rm{i}}$ (anti-correlation) and $M_{\rm{Ni}}-M_{\rm{ej}}$ (correlation). Comparing the SN Ic-BL samples with and without lGRB association using fitting parameters, we find no significant difference between them, although the GRB-associated sample is slightly brighter, possibly due to an observational bias. Relative to ordinary SNe Ic, SNe Ic-BL have similar $^{56}$Ni and ejecta masses, suggesting comparable pre-SN progenitor properties, with differences possibly arising from the presence of a magnetar engine. In comparison with other possible magnetar-powered SESNe, including SLSNe Ic and FBOTs, we confirm a strong universal $M_{\rm{ej}}-P_{\rm{i}}$ correlation, indicating a common origin. SNe Ic-BL and SLSNe Ic have similar ejecta mass distributions, typically $M_{\rm ej}\gtrsim0.5\,M_\odot$, while FBOTs mostly lie below this value. Differences between SNe Ic-BL and SLSNe Ic may arise from magnetar properties, with SN Ic-BL magnetars rotating faster and having stronger fields. Moreover, the $P_{\rm{i}}-B_{\rm{p}}$ distribution of lGRB magnetars largely overlaps with that of SN Ic-BL magnetars. In connection with binary simulation results, we propose a unified physical classification and progenitor framework for magnetar-powered and ordinary SESNe.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Quantum-information diagnostics of cosmological perturbations with nontrivial sound speed in inflation

Shi-Cheng Liu, Lei-Hua Liu, Bichu Li et al. (+2 more)

In this work, we systematically investigate the quantum-information diagnostics of cosmological perturbations with a nontrivial sound speed, utilizing a normalized open two-mode squeezed-state framework. Rather than introducing new observables, our analysis focuses on how a modified sound speed dynamically reshapes the Schrödinger evolution of the squeezing parameters ($r_k$ and $\phi_k$). We demonstrate how these dynamical changes are inherited by the reduced density matrix of the observable sector. By employing a sound-speed-resonance parametrization, we derive and evaluate the purity, von Neumann entropy, Rényi entropies, and logarithmic negativity. To overcome the intrinsic multiscale stiffness of the post-inflationary equations, we introduce a bounded variable $x = \tanh r_k$ as a partial regularization, which enables reliable numerical simulations exclusively within the inflationary regime. Our numerical results reveal that a nontrivial sound speed significantly suppresses the purity of the reduced state, indicating enhanced effective mixedness. Simultaneously, it strongly amplifies and modulates both the entropic and entanglement diagnostics. More precisely, a nontrivial sound speed postpones the onset of classicality by modulating the decoherence process. Ultimately, we show that a nontrivial sound speed leaves distinct and identifiable quantum-information signatures within the entanglement structure of the early universe.
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All authors Shi-Cheng Liu, Lei-Hua Liu, Bichu Li, Hai-Qing Zhang, Peng-Zhang He

High Energy Astrophysical Phenomena

Gauging the Impact of Cosmic Ray Feedback on the Stellar Initial Mass Function

Margot Fitz Axen, Stella S. R. Offner, Philip F. Hopkins et al. (+1 more)

Cosmic rays (CRs) drive ionization and influence gas dynamics in molecular clouds (MCs), potentially impacting the resulting star formation outcomes. Although previous simulations of individual star formation have included methods for cosmic ray transport (CRT), none have been large enough to resolve the stellar initial mass function (IMF). We conduct numerical simulations following the collapse of a $20000 M_{\odot}$ MC and the subsequent star formation including CRT, both with and without CRs accelerated by winds from the young massive stars, and compare against a non-CRT simulation. We show that after the first massive stars form, the cavity produced by feedback is more pronounced in the CRT simulations because the external CRs are able to propagate inwards and compress the gas into higher density structures. This increases the subsequent star formation in the cloud; by the end of the simulation, the SFE in the CRT simulation including stellar wind CRs is 43 % higher than the non-CRT simulation. The IMF is also top heavy in comparison, with a slope above 1 $M_{\odot}$ that is shallower by $\sim 20$ %. These effects are also present in the simulation without wind-accelerated CRs, but they are not as pronounced; the SFE is only 16 % higher than the non-CRT simulation, and the IMF high-mass slope is shallower by $\sim 10$ %. These results may explain some of the observed top-heavy IMFs, which typically occur in high-CR environments such as the galactic center.
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All authors Margot Fitz Axen, Stella S. R. Offner, Philip F. Hopkins, Michael Y. Grudić

Solar and Stellar Astrophysics

Correlation between active regions' spectra at high radio frequencies and solar flare occurrences

Sara Mulas, Alberto Pellizzoni, Marco Marongiu et al. (+31 more)

High radio frequencies observations with the Italian network of large single-dish radio telescopes resulted in ~450 solar images between 2018 and 2023 in K-band frequency range (18-26 GHz). Solar radio mapping at these frequencies allows the probing of the Active Regions (ARs) chromospheric magnetic field close to the Transition Region, where strong flares and coronal mass ejection events occur. Enhanced magnetic fields up to 1500-2000 G determine anomalous spectra in the ARs brightness compared to pure free-free emission, due to the addition of a steeper gyro-resonance component also associated with circular polarisation up to ~40%. When a significant AR spectral flattening is detected, the probability of a strong flare occurrence within ~30 hours is high (~89% in terms of statistical precision). Despite an approximate weekly cadence of our observations, only ~12% of strong flares are missed/unpredicted within this time interval. Through a correlation analysis, we assess the trade-off on the sensitivity and the robustness of this physics-based flare forecast method.
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All authors Sara Mulas, Alberto Pellizzoni, Marco Marongiu, Adriana Marcucci, Simona Righini, Maria Noemi Iacolina, Elise Egron, Giulia Murtas, Matteo Bachetti, Francesco Berrilli, Alessandro Cabras, Roberto Caocci, Gian Luigi Deiana, Salvatore Luigi Guglielmino, Colby Haggerty, Adelaide Ladu, Sara Loru, Andrea Maccaferri, Pasqualino Marongiu, Andrea Melis, Alessandro Navarrini, Alessandro Orfei, Pierluigi Ortu, Mauro Pili, Tonino Pisanu, Giuseppe Pupillo, Andrea Saba, Luca Schirru, Giampaolo Serra, Caterina Tiburzi, Giuseppe Valente, Alessandra Zanichelli, Pietro Zucca, Mauro Messerotti

Astrophysics of Galaxies

Massive star formation at the Galactic crossroads: Insights from G358.69+0.03 in the Galactic center

A. Cheema, V. S. Veena, K. M. Menten et al. (+7 more)

We investigated the high-mass star formation activity in a subregion of the Sagittarius E star-forming complex, centered at (l,b) = (358.69 deg, 0.03 deg), where infrared and radio sources trace a prominent U-shaped structure that has not been identified in previous studies. We used radio continuum data from the Global View on Star Formation (GLOSTAR) survey, which is a wide-band radio (4-8 GHz) survey of the Milky Way that combines data from the Karl G. Jansky Very Large Array and the Effelsberg 100 m telescope. Using BLOBCAT source extraction software, we identified 49 compact radio sources. Based on multiwavelength associations and spectral index estimates, we identified GLOSTAR counterparts to 27 previously confirmed HII regions, detected radio emission from 3 WISE "radio-quiet" candidates, and report 5 new HII region candidates. The derived physical properties indicate that most are relatively evolved HII regions. We find around 50 cold dust clumps, predominantly toward the south and southeast. Mid-infrared flux-ratio maps ([4.5]/[3.6]) show localized shock enhancements along the arc and adjacent clumps, and 15 clumps exhibit SiO emission with broad components indicative of shocks. Together with CO data, the SiO velocity components delineate a continuous (>100 km/s) velocity bridge that links the far dust-lane inflow to the central molecular zone (CMZ) stream. The largest concentration of clumps and compact HII regions lies at this interface. These combined diagnostics favor a scenario in which bar-driven cloud-cloud collision at the far dust-lane-CMZ interface compressed the gas and triggered the observed high-mass star formation.
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All authors A. Cheema, V. S. Veena, K. M. Menten, T. S. Pillai, S. A. Dzib, A. Brunthaler, S. Khan, R. Dokara, M. R. Rugel, Y. Gong

High Energy Astrophysical Phenomena

Delving into the depths of NGC 3783 with XRISM: V. Broad-band modeling of ionized outflows

Keqin Zhao, Jelle S. Kaastra, Liyi Gu et al. (+7 more)

The Seyfert 1 galaxy NGC 3783 hosts a multiphase warm absorber (WA) that has been extensively studied in the X-ray band. High-resolution spectra from 2000-2001 revealed a complex outflow with multiple ionization and velocity components. Two decades later, new XMM-Newton and XRISM observations allow us to investigate the long-term evolution of these outflows. We perform joint spectral modeling of the XMM-Newton/RGS and XRISM/Resolve time-averaged spectra using the pion photoionization code within SPEX. We derive the ionization parameter, column density, turbulent velocity, and outflow velocity for each absorption component, and investigate their thermal stability and Absorption Measure Distribution (AMD) to characterize the physical and dynamical properties of the WA in NGC 3783 in 2024. We compare these results with the 2000-2001 epoch to assess long-term variability, stability, and possible changes in the absorber population. We identify eight WA components spanning log $\xi =$ 1.08-3.38 and outflow velocities of 480-1230 km s$^{-1}$. The ranges of column densities and turbulent velocities remain broadly consistent with the WAs from 2000-2001, but the earlier data contained more low-ionization, high-velocity components. The total column density in 2024 is 1.5 times larger than in 2000-2001, requiring replenishment by fresh material. The dominant Unresolved Transition Array (UTA) absorber (Comp. B3) has increased its column density by a factor of three while maintaining a similar ionization parameter. The WAs in NGC 3783 have undergone significant structural and dynamical evolution over the past 24 years.
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All authors Keqin Zhao, Jelle S. Kaastra, Liyi Gu, Missagh Mehdipour, Megan E. Eckart, Keigo Fukumura, Matteo Guainazzi, Chen Li, Christos Panagiotou, Matilde Signorini

Cosmology and Nongalactic Astrophysics

Saturation Mechanisms in the Interacting Dark Sector

Andronikos Paliathanasis and Kevin J. Duffy

We introduce a family of phenomenological cosmological models featuring an interacting dark sector modulated by a sparseness scale parameter, in order to describe the late-time accelerated expansion of the universe. The sparseness scale, inspired by well-established saturation mechanisms in ecology and biology, is introduced in the interaction as a half-saturation constant that bounds the energy exchange between dark matter and dark energy, controls the dynamical behaviour of the physical variables and can prevent the phantom crossing. We consider three nonlinear interacting models, where two of them recover the linear interacting scenarios when the sparsity parameter vanishes. We examine the phase-space of the cosmological field equations by using the Hubble normalization approach. We determine the stationary points and their stability properties in order to reconstruct the asymptotics behaviour of the field equations. Such an analysis allows us to demonstrate the effects of the sparseness scale on the background dynamics. We test the interacting models with observational data. Specifically, we employ Supernovae catalogues, cosmic chronometers, Baryon Acoustic Oscillation measurements from DESI DR2, and redshift-space distortion measurements of the growth of large-scale structure through the $f$ and $f\sigma_8$ observables. The Bayesian analysis suggests that, for two of the three models, a vanishing sparsity parameter is disfavoured at more than the 95% confidence interval, providing observational support for a nonzero sparseness scale in the dark sector interaction.
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Cosmology and Nongalactic Astrophysics

Impact of Primordial Black Hole population on 21 cm observables at high redshift

Atrideb Chatterjee, Barun Maity and Koushiki

The 21-centimetre (21-cm) signal is one of the most promising probes of the high-redshift Universe. It has typically been modelled without accounting for the effects of active galactic nuclei (AGNs) in the pre-JWST era, primarily due to the lack of observational evidence for AGNs at z > 6. However, following the discovery of several AGNs at redshifts as high as z~ 10 by JWST, it has become imperative to incorporate the impact of these early AGNs when predicting the 21-cm signal. Based on the assumption that these AGNs are seeded by primordial black holes (PBHs), we studied their impact with a semi-numerical model setup. Specifically, we extended the explicitly photon-conserving reionisation framework, SCRIPT, including essential cosmic dawn physics and PBH contributions. This enabled us to compute both the global signal and the power spectrum of the 21-cm line over the redshift range z ~ 30 - 5 within a self-consistent framework. Building on this set-up, we investigated the impact of different PBH mass functions (obeying current observational constraints) on the resulting signal. We find the X-ray heating from PBHs can substantially make the global 21-cm signal shallower and suppress the expected power spectrum amplitude during cosmic dawn. We also find that the choice of mass function plays a crucial role in shaping the 21-cm signal, and can, in fact, lead to significantly different predictions.
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