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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 4 May

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

Searching for UFOs from the early universe: direct detection prospects for relativistically decoupling dark matter

Stephen E. Henrich, Yann Mambrini and Keith A. Olive

Particles that decouple relativistically from the Standard Model bath during reheating represent a versatile class of well-motivated cold dark matter candidates. In fact, ultrarelativistic decoupling ($T_{\rm FO}\gg m_\chi$) is quite generic for beyond the Standard Model (BSM) heavy portal interactions with strong couplings and relatively low reheating temperatures. In this work, we study the direct detection prospects for ultrarelativistically frozen-out (UFO) candidates, using $Z'$-portal dark matter as a case study. Although typical UFO cross sections are suppressed by a heavy mediator mass scale, we find that experiments such as LZ, XENONnT, PandaX, and DarkSide-50 have already excluded a large portion of the UFO parameter space and there remains viable space above the neutrino fog for $0.4 \text{ GeV} \lesssim m_{\rm DM}\lesssim 1$ TeV. Moreover, SuperCDMS SNOLAB, which is expected to begin collecting data in 2026, should access a large region of UFO parameter space in the 0.5-10 GeV mass range. For heavy BSM portal interactions ($M\gtrsim 1$ TeV), UFOs are typically more accessible to detection than freeze-in candidates due to the comparatively larger cross sections. We also carefully delineate regions of parameter space with degeneracy between UFO and non-relativistic freeze-out. In sum, UFOs are attractive candidates for ongoing and next-generation dark matter detection experiments in a looming post-WIMP era.
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Cosmology and Nongalactic Astrophysics

Euclid preparation. Three-dimensional galaxy clustering in configuration space: Three-point correlation function estimation

Euclid Collaboration: A. Veropalumbo, M. Moresco, F. Marulli et al. (+302 more)

Higher-order correlation functions are firmly established as a fundamental tool for the statistical analysis of clustering in modern galaxy surveys. It was demonstrated that they greatly enrich the information content extracted by two-point statistics, allowing us to break the degeneracies between model parameters and constrain departures from Gaussianity. This paper presents the statistical estimators adopted to evaluate the galaxy three-point correlation function and its numerical implementation within the data analysis pipeline of the Euclid Science Ground Segment. Two different algorithms are adopted to count triplets: a direct and exact counting method capable of providing a robust three-point correlation function measurement for any triangular configuration, and a more efficient method based on spherical harmonic decomposition, designed to address the computational challenges of measuring the three-point statistics for data sets as large as those of the final Euclid survey. The spherical harmonic decomposition estimates the Legendre coefficients of the three-point correlation function up to a finite expansion order. Despite being an approximation, the three-point function measured with this approach satisfies the scientific requirements of the mission. We also introduce, implement, and validate the random split technique, which reduces the computational cost of counting triplets in the reference random sample by a factor of 10, without significantly compromising numerical accuracy. We evaluated the robustness, precision, and accuracy of the numerical estimates through an extensive campaign of validation tests, the results of which are presented. Finally, we quantify the computational requirements and their scaling with the expected size of Euclid data set, showing that a complete three-point analysis of the final Euclid survey is within computational reach.
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All authors Euclid Collaboration: A. Veropalumbo, M. Moresco, F. Marulli, E. Branchini, M. Guidi, A. Farina, A. Pugno, E. Sefusatti, D. Tavagnacco, F. Rizzo, E. Romelli, S. de la Torre, A. Eggemeier, E. Sihvola, M. Viel, N. Aghanim, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, V. F. Cardone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, R. J. Massey, E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, L. Moscardini, C. Neissner, 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, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, V. Allevato, M. Ballardini, C. Benoist, M. Bolzonella, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, L. Gabarra, J. García-Bellido, V. Gautard, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, N. Mauri, R. B. Metcalf, P. Monaco, A. Pezzotta, M. Pöntinen, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Wiesmann, Y. Akrami, G. Alguero, I. T. Andika, G. Angora, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, E. Aubourg, L. Bazzanini, J. Bel, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, H. Böhringer, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, V. Duret, M. Y. Elkhashab, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, F. Fontanot, A. Franco, K. Ganga, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, S. Joudaki, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, M. Lattanzi, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, S. J. Liu, A. Loureiro, M. Magliocchetti, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Migliaccio, M. Miluzio, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, L. Pagano, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, R. Paviot, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, K. Rojas, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, 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, F. Vernizzi, G. Verza, P. Vielzeuf, S. Vinciguerra, N. A. Walton, A. H. Wright

Solar and Stellar Astrophysics

Discovery of the first outbursting hot subdwarf binary: ZTF J0007+4804

E. Stringer, T. Kupfer, K. Deshmukh et al. (+10 more)

Hot subdwarf binaries with white dwarf companions with orbital periods of less than two hours are progenitor candidates for massive single white dwarfs as well as a variety of thermonuclear explosions. Our aim is to determine the binary properties of the hot subdwarf – white dwarf system ZTF J000742.62+480414.51, model its future evolution, and characterize the brightening events seen in TESS photometry. Using data from ZTF and TESS, we performed a Lomb Scargle analysis to find the orbital period and the period of the brightening events. Analysis of time-resolved spectroscopy was combined with light curve modeling to determine the effective temperature, surface gravity, and radius of the primary star, the masses of both stars, and to confirm the presence of an accretion disk. X-ray observations were performed with Swift, and MESA modeling was used to find the future evolution of the system. The kinematics of the system were also calculated. ZTF J000742.62+480414.51 consists of an accreting $0.48\pm0.01\,M_\odot$ white dwarf with a $0.42\pm0.01\,M_\odot$ B-type hot subdwarf acting as a donor. The system exhibits SU UMa type dwarf nova outbursts with a recurrence time of $P_{\mathrm{out}} \approx 9$ days. No X-rays were detected, with an upper limit on the X-ray luminosity of about $3\times10^{31}$ erg/sec. The system lies in the Galactic thin disk, and has an orbital period of $P_{\mathrm{orb}} = 108.72\pm0.01$ minutes. The system has likely formed from a main sequence binary with component masses $\gtrsim2\,\mathrm{M_{\odot}}$ and will likely merge into a single white dwarf, but a thermonuclear explosion cannot be ruled out. ZTF J000742.62+480414.51 consists of a low mass white dwarf actively accreting hydrogen rich material from a B-type hot subdwarf, and is the first hot subdwarf – white dwarf system discovered that produces dwarf nova outbursts.
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All authors E. Stringer, T. Kupfer, K. Deshmukh, T. Maccarone, I. Jackson, A. Kosakowski, C. W. Bradshaw, A. Brown, M. Dorsch, A. Picco, V.S. Dhillon, S. Poshyachinda, S. Awiphan

Earth and Planetary Astrophysics

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) XI: Gas-dust interactions and radial offsets between micron and millimetre-sized grains

J. Olofsson, M. R. Jankovic, S. Marino et al. (+22 more)

The dust observed in debris disks is the result of a collisional cascade initiated from $\sim$ km-sized parent bodies. Using near-infrared to sub-millimeter observations, we can probe particle sizes spanning 2-3 orders of magnitude, and with sufficient angular resolution we can follow the dynamics of these dust particles. Observations taken as part of the ALMA ARKS program allowed for a detailed comparison with near-infrared scattered light observations, at unprecedented resolution. The comparison between the two wavelength regimes reveals that for most gas-bearing debris disks, the distribution of small dust grains peaks outward of the distribution of large dust grains. In this paper we investigate whether gas-dust interactions can explain such radial offsets. We perform numerical simulations and compute surface brightness profiles at several wavelengths to assess which parameters drive these radial offsets. We find that while larger gas masses lead to more efficient outward radial drift, the resulting radial offset strongly depends on the optical depth of the disk, as the drift efficiency directly competes with the particles' collisional lifetime. We also find that increasing the relative number of $\mu$m-sized dust grains usually yields a larger radial offset between scattered light and millimeter observations. Finally, we show that mid-infrared observations can complement near-infrared and sub-millimeter images, and we discuss the formation of secondary rings at near-infrared wavelengths. The angular resolution achieved by the ARKS program has opened a new avenue to study the dynamics of dust particles in debris disks, revealing unexpected differences between the appearance of the disks scattered light and thermal emission. We showed that gas-dust interactions can explain the observed radial offsets and provide pointers as to which parameters have the most significant impact.
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All authors J. Olofsson, M. R. Jankovic, S. Marino, A. V. Krivov, M. Bonduelle, G. Cataldi, Y. Han, A. M. Hughes, T. Löhne, S. Mac Manamon, E. Mansell, L. Matrà, J. Milli, A. A. Sefilian, P. Thébault, B. Zawadzki, M. Booth, C. del Burgo, J. M. Carpenter, Th. Henning, J. B. Lovell, T. Pearce, S. Pérez, D. J. Wilner, M. C. Wyatt

Astrophysics of Galaxies

Environmental Quenching of High-Redshift Galaxies: Interpreting JWST Observations with Simulations

Aleyna Döven, Mohammadreza Ayromlou and Cristiano Porciani

Recent observations of the high-redshift Universe, particularly with JWST, have revealed a population of quenched galaxies that challenges current galaxy formation models, which systematically underpredict their abundance. This discrepancy has been extensively studied for massive systems, motivating revisions to internal quenching mechanisms such as AGN feedback. However, the origin of quenching in lower-mass galaxies at high-z has received far less attention, largely due to previous observational limitations. JWST has now identified low-mass quenched galaxies (${M_{\star}}<10^{10}{\rm M_{\odot}}$). Given this emerging observational evidence, we investigate the viability of environmental quenching as the primary mechanism suppressing star formation in low-mass galaxies at $z>3$. We analyze several simulations, including L-GALAXIES, IllustrisTNG, SIMBA, and TNG-Cluster, jointly comprising more than half a million galaxies at z=5. Across all simulations, quenched systems are overwhelmingly satellites, despite representing less than 10% of the total galaxy population. Satellite quenching increases with host halo mass and decreases with both stellar mass and halocentric distance, showing strong correlations with enhanced ram-pressure exposure and gas depletion. The simulations, particularly L-GALAXIES, produce low-mass quenched galaxies broadly consistent with those observed by JWST. Our results suggest that the recently discovered high-redshift quenched low-mass galaxies are possibly environmentally quenched systems residing in the vicinity of massive halos. According to the simulations, these galaxies are often only temporarily quenched: nearly 90% of them merge within a few hundred megayears, and a small fraction rejuvenate and resume star formation. Extended samples from future observations will enable robust tests of the environmental origin of galaxy quenching in the early Universe.
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Cosmology and Nongalactic Astrophysics

Post-Recombination Fluctuations from a Sequestered Dark Sector

Salvatore Bottaro, Michael Geller, Diego Redigolo et al. (+1 more)

We develop a formalism to characterize the imprints of late-time sources of cosmological fluctuations under the sole assumption that the injection occurs on timescales short compared to the horizon. For post-recombination injections, we derive the general modification of photon geodesics in the presence of scalar, vector, and tensor perturbations, and compute the resulting impact on the Cosmic Microwave Background through the integrated Sachs-Wolfe effect. We show that the signal is generically dominated by instantaneous injections of anisotropic stress. As an application, we consider first-order phase transitions in a sequestered dark sector and show that current observations constrain fractional energy injections at the permille level.
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All authors Salvatore Bottaro, Michael Geller, Diego Redigolo, Maya Tsur

Cosmology and Nongalactic Astrophysics

Comparing Hemispheres: Anisotropy in the deceleration parameter $q_0$

Mauricio Lopez-Hernandez and Josue De-Santiago

We present a hemispherical comparison analysis of the deceleration parameter $q_0$ using the Pantheon+ sample of Type Ia supernovae to test the isotropy of cosmic acceleration and the robustness of redshift corrections. We detect directional variations in $q_0$ across redshift frames. Even in the $z_{\mathrm{HD}}$ frame, where corrections for the CMB dipole and peculiar velocities are applied, a residual dipolar anisotropy persists with $\Delta q_0 = 0.112$ and a maximum signal to noise $S/N = 2.155$, aligned with the CMB dipole direction and decreasing with increasing minimum redshift cut. The anisotropy is stronger in the $z_{\mathrm{hel}}$ and $z_{\mathrm{CMB}}$ frames, where kinematic corrections are incomplete, while the transition to $z_{\mathrm{HD}}$ reduces but does not remove the signal. Inferring the dipole from the supernovae data yields $v_{\odot} = 307.26^{+32.00}_{-22.28},\mathrm{km \, s^{-1}}$ toward $(\mathrm{RA},\mathrm{DEC}) = (156.40^{+4.72}_{-4.71}, -3.38^{+5.54}_{-8.23})^\circ$, mildly discrepant with the Planck CMB dipole at the $\sim 1.9\sigma$ level. When this SNe inferred dipole is incorporated into the redshift correction pipeline, the hemispherical anisotropy is suppressed, with the dipolar pattern disappearing and the maximum signal reduced to $S/N \lesssim 1.75$, while the remaining fluctuations become consistent with statistical noise, suggesting that part of the signal arises from residual mismatches in the modeling of the local velocity field. Since current redshift corrections rely on peculiar velocity reconstructions based on the density field, our results suggest a residual bulk flow not fully captured by these models, highlighting a source of systematic uncertainty in low redshift supernova cosmology.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Metastable strings at PTAs: classical stability analysis

Simone Blasi, Maxime Grandjean and Alberto Mariotti

Metastable strings can arise from a two-step symmetry breaking chain of the type $SU(2) \to U(1) \to 1$.They can decay through quantum tunneling by nucleating a monopole-antimonopole pair, and are prominent candidates for explaining the gravitational wave background detected at Pulsar Timing Arrays (PTAs).We investigate the classical stability of the strings arising in this commonly-considered setup, which serves as a fundamental input for discussing their possible decay channels. We identify the regions of parameter space in which the strings are either classically stable or unstable. Our results show that classical instabilities can impact the parameter space relevant for PTAs. We also discuss the possible fate of the string network in the regions of classical instability.
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Astrophysics of Galaxies

Are Nucleosynthetic Yields Universal? Interpreting the Multi-Elemental Abundances of Quiescent Galaxies over Cosmic Time Using Milky Way Stars

Aliza G. Beverage, David H. Weinberg, Mariska Kriek et al. (+3 more)

The detailed abundance patterns of quiescent galaxies offer powerful constraints on their formation and evolution. Yet physical insight remains elusive, as nucleosynthetic yields are notoriously uncertain. We introduce a framework that circumvents this problem by using Milky Way abundance trends as empirical proxies for the yields. Applied to quiescent galaxies spanning three redshifts, SDSS ($z\sim0$), LEGA-C ($z\sim0.7$), and JWST/SUSPENSE ($z\sim2$), our approach recovers the $\alpha$- and Fe-peak abundances with a median offset of ~0.05 dex across 14 elements, compared to ~0.23 dex for theoretical yields. The largest discrepancies arise in N, Sr, Ba, and (at $z\sim2$) C, all of which depend on AGB enrichment, a channel we do not explicitly model. We explore the impact of a top-heavy IMF on our predictions and find that it can shift the IMF-averaged core-collapse supernova yields by ~0.05-0.2 dex in a direction that reduces the overall residuals. Surprisingly, the predictions succeed even without modeling the full chemical-evolution history of a galaxy; just Mg and Fe, which trace the relative contributions of core-collapse and Type Ia supernovae, suffice to predict $\alpha$- and Fe-peak elements. The success of the empirical yields, previously demonstrated in dwarf galaxies and the Milky Way disk, and now extended to massive quiescent galaxies, suggests that $\alpha$- and Fe-peak nucleosynthetic yields are largely universal. This lack of complexity makes galaxy abundance patterns highly predictable. Embedding these empirical yields in SPS models will improve inferences on stellar population properties and star formation histories. Moreover, incorporating them into cosmological simulations will produce more observationally motivated predictions.
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All authors Aliza G. Beverage, David H. Weinberg, Mariska Kriek, Nicole Marcelina Gountanis, Andrew B. Newman, Daniel R. Weisz

Astrophysics of Galaxies

Peering down the barrel with DESI DR2: 10 000+ inflows at $z$ < 0.6 reveal how galaxies accrete cold gas

S. Weng, A. Saintonge, M. Pieri et al. (+39 more)

Direct observational constraints on how galaxies acquire their gas remain remarkably limited, hindering our understanding of the baryon cycle. We present a search for down-the-barrel NaI D absorption towards 15.6 million galaxies at $z < 0.6$ in DESI Data Release 2. We use Bayesian evidence ratios to assess whether the absorption requires additional components tracing interstellar gas distinct from the systemic component of the galaxy. We construct a catalogue of 50 088 (27 420) galaxies with moderate (strong) evidence for down-the-barrel absorption. The inferred absorption components are broadly distributed in velocity, with approximately 50% at $v_{\rm flow} < -50$ km/s, 30% within 50 km/s of the systemic velocity and the remaining 20% at $v_{\rm flow} > 50$ km/s. We find strong evidence for a large population of low-velocity, infalling absorbers with velocities $\sim$20 km/s in edge-on galaxies, consistent with radial inflows predicted in simulations. The stronger correlation in early-type galaxies between inflow velocity and stellar velocity dispersion, compared to that with stellar mass, suggests that a portion of these inflows may be associated with accreting satellites. These results reveal the multiple pathways in which galaxies accrete gas at redshift $z < 0.6$ for the first time in a statistically significant sample.
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All authors S. Weng, A. Saintonge, M. Pieri, J. Moustakas, H. Zou, D. Muñoz Santos, J. Yu, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, P. Doel, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A. Gontcho, G. Gutierrez, C. Hahn, S. He, K. Honscheid, T. Hu, R. Joyce, R. Kehoe, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, S. Nadathur, J. A. Newman, W. J. Percival, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, H. Seo, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver

High Energy Astrophysical Phenomena

The SRG/eROSITA diffuse soft X-ray background II. spectra and morphology of the eROSITA bubbles in the western Galactic hemisphere

Michael C. H. Yeung, Martin G. F. Mayer, Andy Strong et al. (+15 more)

The eROSITA bubbles (eRObub) were discovered in 2020 in the first SRG/eROSITA All-Sky Survey, and are among the most extended structures in the X-ray sky. Using eROSITA all-sky maps and spatially resolved spectra, we aim to infer the three-dimensional structure and measure the hot gas properties of the eRObub. We fit spectra binned to a constant S/N and high-S/N spectra from custom regions to examine gas properties in more detail. We fit the morphology of eRObub with a parametrised geometrical model that describes a blast wave propagating into an idealised Galactic halo from the centre. We found the interior of the western eRObub is best characterised by two emission components with relatively uniform temperatures: a hotter component at $kT=0.60\pm0.02$ keV, and a colder one at $kT=0.21^{+0.03}_{-0.01}$ keV, where the latter's emission measure is about five times higher on average. Our spectra suggest sub-solar abundances ($Z=0.2\pm0.1 Z_\odot$), consistent with expectations for the Galactic halo, while we find no conclusive evidence for $\alpha$-element enhancement. In contrast, the North Polar Spur exhibits higher abundances ($Z>0.5 Z_\odot$), which, at face value, disfavours a common origin. We spectrally confirm an apparent cool shell at $kT\sim0.18$-$0.2$ keV surrounding the northern eRObub, assuming collisional ionisation equilibrium. We found no noticeable difference in X-ray emission in regions overlapping with the Fermi Bubbles. Our geometrical model suggests that the horizontal size of both eRObub is well-constrained (semi-minor axis $\sim 6$ kpc), but their vertical extent is uncertain, as the observed X-ray emission is almost insensitive to the existence and location of a bubble cap. Additionally, a tilt ($\sim 30^{\circ}$) towards $l\sim 220^{\circ}$ is needed to reproduce the projected image of the northern eRObub, whereas the southern bubble requires little tilt.
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All authors Michael C. H. Yeung, Martin G. F. Mayer, Andy Strong, Michael J. Freyberg, Gabriele Ponti, Konrad Dennerl, Junjie Mao, Manami Sasaki, Xueying Zheng, Jeremy S. Sanders, Yi Zhang, Jiejia Liu, Liyi Gu, Werner Becker, Frank Haberl, Teng Liu, Andrea Merloni, Peter Predehl

Astrophysics of Galaxies

Built to Rest: The Evolving Star-Forming Main Sequence Requires Episodic Quiescence or Late Assembly

Lucas C. Kimmig, Jesse van de Sande, Rhea-Silvia Remus et al. (+3 more)

The star-forming main sequence of galaxies has now been observed out to redshifts of $z\sim6$ and beyond. However, it remains unclear how long typical galaxies remain on or near it as they evolve, and how frequently they return after departing from it. To determine the expected star formation histories, we construct an analytical model to evolve galaxy properties along the star-forming main sequence over time. Our modeled star formation histories and mean ages agree remarkably well with those reconstructed from observational data. Older and more peaked star formation histories arise naturally for more massive galaxies. Simultaneously, we demonstrate that low-mass ($M_*\geq10^{8}\mathrm{M}_\odot$), early-forming ($z>3$) progenitors that remain on the star-forming main sequence must evolve into very massive ($M_*\approx10^{11}\mathrm{M}_\odot$) galaxies today. Consequently, the progenitors of intermediate mass galaxies ($M_*=10^{10}\mathrm{M}_\odot$) must have either formed late ($z<2$) or underwent significant phases ($T>1$Gyr) with suppressed star formation rates ($0.3$dex below the star-forming main sequence). We provide tracks to connect galaxies from $z=6$ to $z=0$ by their star-forming behavior above or below the main sequence. By applying number density arguments to construct evolutionary histories for Milky Way-mass galaxies, we find that they must undergo a significant phase of suppressed star formation, nearing quiescence, or otherwise become too massive. This is particularly true for the Milky Way itself, where we show that the observed presence of a large amount of old stars directly implies a departure from the star-forming main sequence over the majority of its history.
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All authors Lucas C. Kimmig, Jesse van de Sande, Rhea-Silvia Remus, Klaus Dolag, Rebecca Davies, Deanne Fisher

High Energy Astrophysical Phenomena

Wave interference as the origin of the cyclic magnetorotational dynamo in accretion disks: insights from weakly nonlinear theory and local shearing box simulations

Uddipan Banik, Amitava Bhattacharjee and James M. Stone

Long-period cyclic reversals of the large-scale magnetic field are a prominent feature of the dynamo associated with the magnetorotational instability (MRI) in accretion disks, but their physical origin remains unclear. We develop a quasilinear theory (QLT) of the MRI dynamo where the electromotive force (emf) is computed from the linear eigenfunctions under the WKB approximation. The emf depends on the mean field $\mathbf{B}$ more generally than standard mean-field closures allow. In the unstratified case, the leading order contribution to the large-scale dynamo is the shear-current effect: the emf depends on the current $\mathbf{J}$ as $\pmb{\varepsilon} = \pmb{\beta}\cdot\mathbf{J}$, with a tensor $\pmb{\beta}(\mathbf{B},t)$ that oscillates with time $t$ and whose off-diagonal components generate the mean field. The oscillations arise from beats between the two branches of eigenfrequencies. Since the beat frequency varies only weakly with wavenumber, the beats remain coherent and drive the long-period butterfly cycle seen in local shearing box simulations. We predict a dominant cycle period $\sim 30{\left(1+a^2\right)}^{1/2}\,t_{\rm orb}$, with $a$ the vertical-to-radial aspect ratio and $t_{\rm orb}$ the orbital period, and an amplitude scaling $\sim a^2$ before saturation at $a\gtrsim 5$. Both trends agree with zero-net-flux unstratified shearing box simulations with Athena++. A carrier-envelope analysis of the simulation spectra shows that the same interference mechanism extends beyond strict QLT, through higher-order linear combinations of the eigenfrequencies, with observed cycles arising from pairwise beats within this spectral network. These results identify coherent interference between nearly degenerate eigenfrequencies as a key mechanism behind large-scale cyclic dynamos, with implications for magnetic variability in protoplanetary disks, X-ray binaries, and AGNs.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Orbital Nodal Phase as a Pipeline Invariant in Black Hole Timing

Mehmet Baran Ökten

Timing analyses of accreting black holes often package nodal information in ways that depend on benign choices of time and azimuthal convention. We identify the corresponding pipeline-invariant content for slightly tilted circular rings and express it as an orbital nodal phase, $\Delta\psi_{\rm orb}$. In Kerr, this quantity gives the clean geodesic baseline for nodal timing: it equals the nodal precession per orbit, is invariant under the benign remappings considered here, and, for prograde Kerr spin, decreases monotonically with radius outside the innermost stable circular orbit. A fixed-$\Omega_\phi$ transport framework then isolates genuine metric sensitivity from trivial radius drift and provides the natural framework for far-field quadrupolar and higher-multipolar timing-response calculations. Two small analysis-level effects are also identified, namely a second-order bias from coherent radial breathing and the absence of an intrinsic geometric offset from exact slow fixed-$\Omega_\phi$ loops. A limited published-data illustration for GRO J1655$-$40 shows that the observational proxy for $\Delta\psi_{\rm orb}$ can be reconstructed directly from standard reported quasi-periodic oscillation frequencies once an orbital-frequency anchor and an identification convention are specified. Within the thin-ring limit, $\Delta\psi_{\rm orb}$ therefore provides a pipeline-robust reporting quantity and a Kerr-baseline diagnostic for source-level, simulation-level, and strong-gravity comparison applications.
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Cosmology and Nongalactic Astrophysics

Tracing Primordial Gravitational Waves via non-Gaussian Signatures of Halo Bias

Mariam Abdelaziz, Pritha Bari, Sabino Matarrese et al. (+1 more)

Primordial gravitational waves (PGWs) generate scalar density perturbations at second order. Since the induced density contrast is quadratic in the tensor field, it is intrinsically non-Gaussian. We study the imprint of this tensor-induced non-Gaussianity (NG) on the large-scale clustering of dark matter halos through its correction to halo bias. Focusing on inflationary scenarios with a peaked primordial tensor spectrum, we derive the leading scale-dependent contribution sourced by the bispectrum of the induced density field. While yielding a percent-level bias correction for massive low-redshift halos, this effect can reach an $\mathcal{O}(1)$ modulation for rare, high-redshift halos at $z=7$. Notably, the resulting signature exhibits a distinct scale dependence that is not captured by standard primordial non-Gaussianity (PNG) templates. Our results establish halo bias as a novel probe of PGWs through their imprint on the large-scale structure, providing a complementary window into the inflationary epoch.
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All authors Mariam Abdelaziz, Pritha Bari, Sabino Matarrese, Angelo Ricciardone

Instrumentation and Methods for Astrophysics

Foundations for Discovery: A Coordinated Fleet Approach to NASA Astrophysics

Regina Caputo, Francesca M. Civano, Knicole D. Colón et al. (+15 more)

This white paper presents an analysis of Astro2020 science priorities and NASA's future astrophysics mission architecture, advocating for a coordinated fleet of \$1–2B missions, smaller than typical Flagship observatories, but strategically designed to complement them, i.e. a “Next Generation Great Observatories" program. The study addresses opportunities in current mission planning, design, and implementation and proposes a strategic approach to maximize scientific return on investment while strengthening partnerships across NASA divisions, other government organizations, universities, and industry.
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All authors Regina Caputo, Francesca M. Civano, Knicole D. Colón, Brian Humensky, David T. Leisawitz, Avi M. Mandell, Conor A. Nixon, Georgia A. de Nolfo, Jeremy S. Perkins, Elisa V. Quintana, Judith L. Racusin, Joshua E. Schlieder, Albert Y. Shih, Amy A. Simon, Jacob Slutsky, Tonia M. Venters, Jennifer J. Wiseman, Allison A. Youngblood

Astrophysics of Galaxies

AGN STORM 2. XII. Ground-Based Optical Photometry and Lag Measurements of Mrk 817

John W. Montano, Aaron J. Barth, Keith Horne et al. (+40 more)

We present the ground-based imaging campaign and light curves of Markarian 817 as part of the multiwavelength monitoring program AGN STORM\,2. Observations were carried out over 1.4 years in uBgVriz filters, with a median cadence of 0.4 days in g. Reverberation lags are measured using three methods (ICCF, JAVELIN, and PyROA) with the Swift UVW2 band (1928 Å) as the reference light curve. The ICCF centroid lags range from $3.0\pm0.8$ days for the $u$ band up to $7.9\pm1.5$ days for $z$, and are consistent with a $\tau\propto \lambda^{4/3}$ dependence, the relation expected for lamp-post reprocessing by a Shakura-Sunyaev disk. Lags measured with the other methods are systematically shorter, and deviate from a $\lambda^{4/3}$ power-law spectrum at long wavelengths. The lags exceed thin-disk reprocessing predictions by factors of $\sim$3-6, similar to the “disk size discrepancy” seen in other Seyfert galaxies. We divide the campaign into three epochs with different levels of mean luminosity and X-ray obscuring column density and find that the lags vary by as much as a factor of 2 between epochs. The intrinsic spectral energy distribution is bluer and brighter during the first third of the campaign, and the longest continuum reverberation lags are obtained during that period. These results suggest that changes in ionizing luminosity can produce large variations in continuum lags on short timescales by altering the diffuse continuum luminosity emitted by the broad-line region and/or obscuring outflow, although changes in obscuration between the central engine and broad-line region may also contribute to the lag variations.
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All authors John W. Montano, Aaron J. Barth, Keith Horne, Edward M. Cackett, Gisella De Rosa, Yasaman Homayouni, Erin A. Kara, Gerard A. Kriss, Hermine Landt, Gilvan G. Apolonio, Nahum Arav, Benjamin D. Boizelle, Elena Dalla Bonta, Doron Chelouche, Maryam Dehghanian, Rick Edelson, Gary J. Ferland, Carina Fian, CHen Hu, Dragana Ilic, Michael D. Joner, Shai Kaspi, Christopher S. Kochanek, Andjelka B. Kovacevic, Collin Lewin, Sha-Sha Li, Yan-Rong Li, Jun-Rong Liu, Jake A. Miller, Jack M. M. Neustadt, Hagai Netzer, Paolo Ochner, Ethan R. Partington, Alessandro Pizzella, Rachel Plesha, Luka C. Popovic, David Sanmartim, Juan V. Hernandez Santisteban, Marianne Vestergaard, Jack H. F. Wookely, Sen Yang, Zhu-Heng Yao, Fatima Zaidouni

Instrumentation and Methods for Astrophysics

Role of General Users in the Lifecycle of Scientific Software

Bjorn Emonts and the CASA Team

In science, the lifecycle of software products is typically managed with limited resources while facing unlimited demand. Scientific software requirements are necessarily often dominated by internal project specifications and deadlines, but these internal priorities, while beneficial for the community as a whole, do not always align with the individual needs of our ultimate customers: general users. For software products to have the broadest reach, ideally the general user community should be involved in all aspects of the data lifecycle, but reality is that user expectations need to be managed. Based on the lifecycle of the Common Astronomy Software Applications for radio astronomy (CASA), we will show avenues for software teams to interact with general users, even when facing limited resources for user support. We will discuss how involvement of users and user groups in prioritizing software development can benefit both the user community and the software teams. The contents of these proceedings were presented at the 35th conference on Astronomical Data Analysis Software & Systems (ADASS XXXV).
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Instrumentation and Methods for Astrophysics

PDRS : A Linear $\mathcal{O}(N)$ Algorithm for Segmentation of High-Activity Regions in Irregularly Sampled Time Series

Atal Agrawal

Identifying transient high-activity episodes in astronomical time series requires partitioning data into regions of distinct statistical behavior. A widely adopted approach combines Bayesian Blocks with a hill-climbing procedure to isolate high-activity regions, but carries $\mathcal{O}(N^2)$ complexity – a scalability challenge for wide-field surveys like ZTF and the upcoming Rubin Observatory (LSST), where light curves routinely contain thousands of irregularly sampled observations. We present Peak-Driven Region Segmentation (PDRS), a linear-time $\mathcal{O}(N)$ algorithm for rapid extraction of high-activity regions in irregularly sampled data. PDRS seeds candidate regions at statistically significant local maxima and expands them via a gradient-aware multi-source breadth-first search. Saddle-point merging and a median-based filter suppress spurious detections. Functioning as a computationally efficient pre-processing stage, PDRS isolates candidate transient events for downstream analysis. We demonstrate its efficacy on quasar light curves from SDSS Stripe~82 and AGN light curves from ZTF DR23, showing that PDRS identifies candidate high-activity regions comparable to those from Bayesian Blocks at substantially reduced cost. Its domain-agnostic formulation and physically interpretable parameters make PDRS broadly applicable beyond astronomy, including biomedical signals, seismic recordings, and industrial sensor monitoring.
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Solar and Stellar Astrophysics

A Statistical Survey of Faint Solar X-ray Transients Observed by NuSTAR

Reed B. Masek, Lindsay Glesener, Jessie Duncan et al. (+14 more)

In this paper, we use a highly sensitive telescope to characterize solar X-ray transients ranging from microflares in active regions down to weakly energetic brightenings in the quiet Sun. X-rays are closely linked to the initial energy release and immediate heating of solar flares, making them invaluable in understanding their driving processes. NuSTAR is the first long-term, direct focusing hard X-ray observatory to have observed the Sun, offering a unique opportunity to search for and characterize X-ray events from inside and outside active regions that would be otherwise unobservable. We present the first statistical survey of NuSTAR solar observations, characterizing the thermal and possibly nonthermal properties of 113 weakly energetic transients down to $10^{26}$ erg, making this the first to directly compare events from the quiet Sun to those in active regions. Relative to RHESSI microflares, our NuSTAR transients are generally cooler, dimmer, and have slightly steeper spectra. Thermal energy content of active region transients appears to be independent of the volume of emitting plasma for transients produced by active regions. This is in contrast to those from the quiet corona, which on average have lower energy content, smaller emission volumes, and appear cool but bright rather than hot but dim, suggesting a break in trends from traditional microflares. We found no quiet Sun transients with a thermal energy content above $3^{27}$ erg, implying an upper limit on the amount of energy released in plasma above 3 MK by quiescent processes.
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All authors Reed B. Masek, Lindsay Glesener, Jessie Duncan, Kekoa Lasko, Natália Bajnoková, Mary Davenport, Marianne Peterson, Ian Markano, Zasha Avery, Kristopher Cooper, Iain G. Hannah, Brian W. Grefenstette, Stephen M. White, Hugh Hudson, Säm Krucker, David M. Smith, Sarah Paterson

Solar and Stellar Astrophysics

A study of the kinematic and volumetric co-evolution of Earth-directed CMEs

Ashutosh Pattnaik, Nat Gopalswamy, Ranadeep Sarkar et al. (+3 more)

While flare-associated CMEs generally show a strong association between flare X-ray flux and CME kinematics, their volumetric evolution and its link to both kinematics and flare activity remains less explored. In this study, we investigate the volumetric and kinematic co-evolution of ten Earth-directed, flare-associated CMEs using multi-viewpoint observations from STEREO-A, STEREO-B, and SOHO. We perform 3D reconstructions of the CME flux ropes with the Graduated Cylindrical Shell (GCS) model and derive their geometrical parameters. We find that the total CME volume follows a power-law dependence on the leading edge height, and that different structural components expand at different rates, with the ellipsoidal front expanding faster than the conical legs. Furthermore, the volumetric evolution follows a multi-phase pattern: initial overexpansion, a gradual reduction in the expansion rate, and finally saturation at a higher heliocentric distance. This is similar to the well-established three-phase evolution of the CME kinematics. Notably, the second-order derivative of volume with time shows a strong temporal correlation with both CME acceleration and the GOES soft X-ray flux of the associated flare. This is the first study to report such a correspondence between volumetric evolution and flare timing, highlighting the role of flare energy release in governing CME expansion dynamics. Our findings motivate further studies into the coupling between magnetic reconnection and CME volumetric evolution in the corona.
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All authors Ashutosh Pattnaik, Nat Gopalswamy, Ranadeep Sarkar, Hong Xie, Sachiko Akiyama, Grzegorz Michalek

Solar and Stellar Astrophysics · Cross-listed from nucl-th

Structure of the $^8$B and $^8$Li nuclei and the astrophysical $S_{17}(0)$-factor of the $^7$Be($p,\gamma$)$^8$B direct capture process within a three-body model

E.M. Tursunov, D.S. Toshova and S.A. Turakulov

The structure of the ground $(2^+)$ and excited $(1^+)$ bound states of the $^8$B and $^8$Li nuclei is studied within the framework of the $\alpha+^3$He($^3$H)+$p(n)$ three-body potential cluster model based on the hyperspherical Lagrange-mesh method. The two-body realistic potentials have been applied from the literature. Convergent theoretical estimates for the three-body binding energy and matter radius have been obtained with the maximal hypermomentum $K_{max}=22$ and 28 for the ground and excited $1^+$ states, respectively. The ANC value of the virtual transition of the $^8$B nucleus is estimated self-consistently by matching the overlap integral of the $^8$B three-body and the $^7$Be two-body wave functions with it's asymptotics. The obtained values are $0.211$~fm$^{-1/2}$ and $0.739$~fm$^{-1/2}$ in the spin 1 and spin 2 channels, respectively. For the ANC values of the $^8$Li nucleus the estimates $0.220$~fm$^{-1/2}$ and $0.774$~fm$^{-1/2}$ are extracted. The ratio $C^2(^8 {\rm B})/C^2(^8 {\rm Li})=0.912$ implies a breaking of the mirror symmetry of the strong nuclear forces of order 27% due to the Coulomb interaction and the dynamical three-body effects. For the $S_{17}(0)$ -factor an estimate $22.492\pm0.014$ eV b was obtained based on the asymptotic theory developed by D. Baye [Phys. Rev. C 62,065803 (2000)]. The spin 2 channel contributes with $S^{(2)}_{17}(0)=20.838 \pm 0.014$ eV b, while the spin 1 channel yields $S^{(1)}_{17}(0)=1.654 \pm 0.003$ eV b. These results for $S_{17}(0)$ are in a good agreement with the estimate $20.8\pm0.7{\rm(th)}\pm1.4{\rm(exp)}$ eV b of the SF II, but larger than the recommended value $20.5\pm0.70$ eV b of the SF III. At the same time, our estimate is very close to the value 22.4 eV b used in the most successful Solar Model BAR2M [W.~Yang and Z.~Tian, AJ 970 (2024), 38].
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Solar and Stellar Astrophysics

Chromospheric dynamics and the O I 135.6~nm spectral line

Viggo Hansteen, Mats Carlsson, Bart De Pontieu et al. (+1 more)

The O I 135.6 nm spectral line is formed in the chromosphere at the same heights as the Mg II h&k line cores are formed. As the O I line is optically thin, it represents a possibility for measuring the non-thermal velocities in this region without the complications added by optically thick radiative transfer. Numerical models have hitherto strained to reproduce Mg II core line widths, challenging current understanding of chromospheric energetics and dynamics. We aim to construct numerical models, varying physical and numerical parameters in order to asses which of these is most important in setting the Mg II core intensity and width. A set of numerical models of varying resolution, size, magnetic topology and strength are considered and used to synthesize O I line emission and to investigate the constraints that observations of this line place on chromospheric dynamics and densities. We find that, for quiet Sun, while non-thermal motions undeniably provide a source of Doppler broadening and chromospheric mass loading, the average strength of the photospheric magnetic field is the most important parameter in setting the Mg II core width to values within 5 km/s of observed values. Furthermore, for plage, we identify non-equilibrium hydrogen ionization and three dimensional radiative transfer as important ingredients in understanding chromospheric diagnostics and deciphering chromospheric structure.
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All authors Viggo Hansteen, Mats Carlsson, Bart De Pontieu, Daniel Nóbrega-Siverio

Earth and Planetary Astrophysics

Outstanding Questions in Giant Planet Theory

Ravit Helled

Giant planets have key role in shaping planetary systems. Their composition reveals information on the conditions at which planets form, and their interiors serve as natural laboratories to explore the behavior of materials at extreme conditions. They can also host large regular moons that can be habitable. In addition, outside the solar system, giant exoplanets remain the ideal planets for detection and characterization. However, despite decades of investigations, and much progress on both the theoretical and observational fonts, several key open questions remain unanswered. In this short review, I highlight a few open questions in the field with the hope that they can be addressed with future research and observational data.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Hadronic lensing

Fabrizio Canfora, Cristóbal Corral and Borja Diez

We introduce an analytic approach to study gravitational lensing in the presence of a distribution of hadrons. The situation is analogous to the propagation of photons in a medium with a nontrivial Cooper-pair condensate, where the photon acquires an effective mass term that may depend on the coordinates if the condensate is not homogeneous. As a result, photons generally do not follow null geodesics in the hadronic medium. In this setup, hadrons are described by the nonlinear sigma model minimally coupled to Maxwell theory. The modified Raychaudhuri equation, including hadronic corrections, is derived, along with the integral curves of probe photons in the eikonal approximation. These results are consistent with the theory of gravitational lensing in plasma media, with the advantage that transport properties, such as the refractive index, can be expressed analytically in terms of the hadronic density without assuming a phenomenological modeling thereof. As an example, we study the hadronic lensing produced by an analytic black hole sourced by superfluid pionic vortices, and we obtain the hadronic correction to the deflection angle in the weak-field limit.
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Solar and Stellar Astrophysics

Ellipsoidal modulation and multi-wavelength activity in the pre-cataclysmic binary RX J1553.0+4457

S.-Y. Wu, M. Gritsevich, Q.-H. Lao et al. (+39 more)

RX J1553.0+4457 (TMTS J15530469+4457458) is a detached post-common-envelope binary containing a cool white dwarf and an active late-type companion. We present a multi-wavelength study combining BOOTES multi-band photometry, six sectors of public TESS full-frame imaging, Einstein Probe/FXT X-ray observations, CAFOS optical spectroscopy, and archival ultraviolet-to-mid-infrared photometry. The BOOTES data reveal two short optical flares separated by about 3 h, with amplitudes of roughly 1-1.5 mag and faster decay at shorter wavelengths. The combined TESS light curve shows a stable signal at P = 0.083782 d, consistent with the first harmonic of the known spectroscopic orbital period, and its folded morphology indicates ellipsoidal modulation from a tidally distorted late-type companion rather than an irradiation-dominated waveform. TESS flare energetics lie in the active M-dwarf regime. The Einstein Probe/FXT spectra show a factor of about 4 decline in the 0.3-10 keV flux, mainly associated with decreasing emission measures. The broadband SED is reproduced by a cool white dwarf plus a late-type M dwarf, with no clear hot-continuum or mid-infrared excess. RX J1553.0+4457 is therefore best interpreted as a detached pre-cataclysmic binary whose rapid optical variability is dominated by magnetic activity and whose orbital modulation is ellipsoidal, although a weak wind-fed or intermittent accretion contribution remains possible.
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All authors S.-Y. Wu, M. Gritsevich, Q.-H. Lao, A. J. Castro-Tirado, Z. Li, Y.-D. Hu, I. Pérez-García, R. Sánchez-Ramírez, N. Castro-Segura, E. J. Fernández-García, M. D. Caballero-García, S. Guziy, I. Olivares, J. D. Sakowska, G. García-Segura, D. Hiriart, W. H. Lee, P. J. Meintjes, H. J. van Heerden, A. Martín-Carrillo, L. Hanlon, A. Maury, L. Hernández-García, I. M. Carrasco-García, S. Castillo-Carrión, A. Castellón, S. B. Pandey, C. J. Pérez del Pulgar, A. J. Reina, J.-M. Bai, Y.-F. Fan, C.-J. Wang, Y.-X. Xin, D.-R. Xiong, X.-H. Zhao, J. Mao, B.-L. Lun, K. Ye, C.-Z. Cui, A. F. Valeev, B.-B. Zhang, T.-R. Sun

Earth and Planetary Astrophysics

JWST high-contrast spectroscopy with speckle modelling: Atmospheric retrievals of the T dwarf companion HD 19467 B

Darío González Picos, Tessa van der Post, Sam de Regt et al. (+3 more)

High-contrast, medium-resolution spectroscopy with JWST can resolve molecular and isotopic features in cool substellar atmospheres, but for close-in companions the extracted spectra can be biased by wavelength-dependent residual stellar contamination. We assess the impact of residual speckles on atmospheric inference for the T dwarf companion HD 19467 B and compare the results to the field T dwarf 2MASS J0415-0935. We analyse JWST/NIRSpec G395H spectra ($2.87$–$5.2$$\mu$m; $R\sim2700$) and perform Bayesian atmospheric retrievals with petitRADTRANS coupled to nested sampling using ultranest. We use a flexible, parameterised pressure-temperature profile with free, constant-with-altitude molecular abundances. For HD 19467 B we fit the PSF-subtracted spectrum with a linear model that includes the atmospheric model and a set of speckle spectra from the integral field unit. We detect H$_2$O, CH$_4$, CO, CO$_2$, and NH$_3$ in both atmospheres and measure carbon isotopic ratios from CO isotopologues, finding $^{12}$C/$^{13}$C$=154^{+19}_{-17}$ for HD 19467 B and $^{12}$C/$^{13}$C$=85\pm5$ for 2MASS J0415-0935. Speckle contamination primarily affects the low-frequency spectral shape at $3.0$–$3.7$$\mu$m and can affect retrieved abundances if not accounted for. We obtain seemingly constrained posteriors for some additional species (e.g.\ SiO and H$_2$S) in some cases, but treat these as tentative because cross-correlation does not yield significant detections; PH$_3$ is not detected in either target. Joint fitting of the atmospheric spectrum and the speckle contamination enables native-resolution retrievals of the high-contrast companion HD 19467 B with JWST/NIRSpec without continuum subtraction. Over $2.87$–$5.2$$\mu$m, medium-resolution spectroscopy constrains elemental and isotopic composition; both objects exhibit near-solar metallicity and subsolar C/O ratios.
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All authors Darío González Picos, Tessa van der Post, Sam de Regt, Jean-Baptiste Ruffio, Natalie Grasser, Ignas Snellen

Earth and Planetary Astrophysics

Characterizing the bolometric-photoevaporative transition in young sub-Neptunes with radiation-hydrodynamic simulations

William Misener, Matthäus Schulik, Hilke E. Schlichting et al. (+1 more)

Hydrodynamic atmospheric escape plays a central role in shaping the demographics of small, close-in exoplanets. Two mechanisms have been proposed to drive mass loss: photoevaporation, powered by UV irradiation, and core-powered mass loss, in which a bolometrically heated wind is sustained by cooling from the planetary interior. Although each mechanism can independently reproduce observed exoplanet demographics, both likely operate simultaneously. To quantify their combined impact, we use AIOLOS, a hydrodynamic radiative transfer code, coupled to a planetary evolution model to self-consistently compute atmospheric escape and planetary evolution. We find that as a typical sub-Neptune contracts, it evolves through distinct escape regimes. The youngest, most inflated planets drive a core-powered, bolometrically heated wind because UV radiation cannot reach the bolometric sonic point. This is followed by a transitional regime shaped by both bolometric and UV heating. As radii decrease further, escape rates approach the purely photoevaporative energy limit. We derive analytic scalings for the transition between these regimes, showing that it occurs at smaller radii for lower-mass and more highly irradiated planets, where core-powered escape dominates. Coupling both processes enhances escape even in more massive, cooler sub-Neptunes. We present the first combined mass-loss rates for a range of planet masses and XUV luminosities and show that the thermal structure below the UV absorption radius – set by atmospheric composition – also affects escape rates. These results integrate core-powered and photoevaporative escape into a unified framework, demonstrating that a self-consistent treatment of atmospheric composition, escape, and evolution is essential for understanding small exoplanets.
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All authors William Misener, Matthäus Schulik, Hilke E. Schlichting, James E. Owen

Cosmology and Nongalactic Astrophysics

Euclid preparation. CosmoPostProcess: A simulation calibrated framework for weak lensing selection bias in richness-selected galaxy clusters

Euclid Collaboration: R. Ingrao, M. Costanzi, T. Castro et al. (+279 more)

We present CosmoPostProcess, a simulation-based forward-modelling algorithm calibrated to reproduce Euclid optical cluster observables. Its main deliverable is a correction for stacked surface-density profiles, binned in richness and redshift, accounting for selection systematics in richness-selected samples relative to unbiased references. We focus on the Euclid richness definition foreseen for cosmological analyses, which does not apply a colour selection; red-sequence richness is not considered. The algorithm processes $N$-body simulations by painting galaxies with a halo-occupation model and emulating survey detection and richness assignment. We also implement a novel estimate of optical cluster centres from projected galaxy densities, validated against Euclid pipelines. Baryonic effects are included through a correction calibrated on hydrodynamical simulations; the baryon-corrected excess surface density agrees within \(2\,\%\) over \(r\in[0.1,\,5]\,h^{-1}\,\mathrm{Mpc}\). Selection-bias contributions are assessed by varying cosmology and the mass–richness relation. Projection-induced selection bias follows a robust pattern: correlated large-scale structure projected along the line of sight enhances the stacked profile near the one-halo to two-halo transition, peaking at about \(1\,h^{-1}\,\mathrm{Mpc}\) with an amplitude of \(20\!-\!40\,\%\), depending on richness and redshift. The effect is mild at low and intermediate redshift ($z\lesssim0.7$), at the few-percent level, but becomes more relevant at higher redshift ($z\gtrsim0.7$). Baryonic modifications remain sub-dominant outside the core, at about \(2\,\%\) beyond \(r\gtrsim0.3\,h^{-1}\,\mathrm{Mpc}\). The framework delivers radial profile corrections with uncertainties, combining projection-induced selection bias, baryonic physics, and miscentring, to control systematics in Euclid DR1 cluster cosmology. (abridged)
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All authors Euclid Collaboration: R. Ingrao, M. Costanzi, T. Castro, A. Saro, S. Borgani, L. Baumont, M. Aguena, S. Grandis, C. Murray, S. Bhargava, E. Munari, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, H. Degaudenzi, G. De Lucia, F. Dubath, X. Dupac, S. Escoffier, M. Farina, R. Farinelli, S. Farrens, S. Ferriol, F. Finelli, P. Fosalba, M. Frailis, E. Franceschi, M. Fumana, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, E. Maiorano, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, S. Maurogordato, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, 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, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, A. Secroun, E. Sefusatti, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, M. Ballardini, A. Boucaud, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, J. A. Escartin Vigo, J. García-Bellido, T. Gasparetto, S. Hemmati, L. Ingoglia, J. Macias-Perez, M. Magliocchetti, R. Maoli, J. Martín-Fleitas, N. Mauri, P. Monaco, A. Montoro, C. Moretti, A. Pezzotta, M. Pöntinen, I. Risso, E. Sarpa, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, J. A. Acevedo Barroso, Y. Akrami, G. Alguero, I. T. Andika, S. Anselmi, M. Archidiacono, G. Arico, F. Atrio-Barandela, M. Baes, L. Bazzanini, P. Bergamini, D. Bertacca, M. Bethermin, F. Beutler, L. Blot, M. Bonici, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, A. R. Cooray, P. Corcho-Caballero, B. Csizi, O. Cucciati, H. Dannerbauer, T. de Boer, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, V. Duret, M. Y. Elkhashab, Y. Fang, A. Farina, A. Finoguenov, A. Franco, K. Ganga, R. Gavazzi, E. Gaztanaga, Z. Ghaffari, F. Giacomini, F. Gianotti, E. J. Gonzalez, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, N. A. Hatch, C. Hernández-Monteagudo, H. Hildebrandt, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, A. Kovács, I. Kovačić, K. Koyama, S. Kruk, M. C. Lam, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, L. Linke, S. J. Liu, F. Mannucci, C. J. A. P. Martins, M. Migliaccio, M. Miluzio, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, F. Oppizzi, F. Pace, D. Paoletti, F. Passalacqua, K. Paterson, C. Pattison, R. Paviot, D. Potter, G. W. Pratt, S. Quai, M. Radovich, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, A. Schneider, D. Sciotti, E. Sellentin, S. Serjeant, I. Szapudi, K. Tanidis, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, C. Uhlemann, C. Valieri, A. Venhola, D. Vergani, G. Verza, S. Vinciguerra, M. von Wietersheim-Kramsta, N. A. Walton, L. Wang, A. H. Wright

Instrumentation and Methods for Astrophysics

Operating the Fabry-Pérot systems of the European Solar Telescope in multi-aperture mode

G.B. Scharmer, M.G. Löfdahl, J. de la Cruz Rodríguez et al. (+5 more)

We discuss how to optimise the science output of the European Solar Telescope (EST), when used without the wide-field compensation for high-altitude seeing that the EST multi conjugate adaptive optics (MCAO) system will offer. Without MCAO, in particular with the Sun at low elevations or when observing at short wavelengths, high-altitude seeing will strongly attenuate the signal at high spatial frequencies over almost the entire 1 arc min science field-of-view (FOV) of EST. We propose to provide EST with an optional multi-aperture mode, by optically segmenting the 4.2 m aperture into six 1.4 m sub-apertures. This pushes down the root mean square wavefront errors from the high altitude seeing to levels that can more reliably be compensated for with conventional ground-layer adaptive optics and post processing of restored images. This will provide the sustained stable high image quality over a large FOV, needed for obtaining time sequences of spectropolarimetric data. The multi-aperture mode is implemented with low-cost modifications of the camera lenses of the three Fabry-Perot systems that will be used to cover the wavelength range 380-860 nm. Switching between the full-aperture and multi-aperture modes can be done quickly and independently for the three FPI systems. This allows flexible optimisation of EST, taking into account the daily variability and wavelength dependence of seeing. Providing EST with a multi-aperture option represents a value-added aspect that has no negative impact on the EST optical systems or on the FPI systems. It provides a powerful and flexible option that has the potential of significantly improving the quality and amount of its science data before MCAO is operational. We perform simulations and image reconstructions of simulated data to demonstrate the benefits of the multi-aperture option, and provide an optical design to demonstrate its feasibility.
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All authors G.B. Scharmer, M.G. Löfdahl, J. de la Cruz Rodríguez, B. Lindberg, H. Socas-Navarro, D. Kiselman, M. Rempel, J. Leenaarts