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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 27 October

Instrumentation and Methods for Astrophysics

In Search of the Unknown Unknowns: A Multi-Metric Distance Ensemble for Out of Distribution Anomaly Detection in Astronomical Surveys

Siddharth Chaini, Federica B. Bianco and Ashish Mahabal

Distance-based methods involve the computation of distance values between features and are a well-established paradigm in machine learning. In anomaly detection, anomalies are identified by their large distance from normal data points. However, the performance of these methods often hinges on a single, user-selected distance metric (e.g., Euclidean), which may not be optimal for the complex, high-dimensional feature spaces common in astronomy. Here, we introduce a novel anomaly detection method, Distance Multi-Metric Anomaly Detection (DiMMAD), which uses an ensemble of distance metrics to find novelties. Using multiple distance metrics is effectively equivalent to using different geometries in the feature space. By using a robust ensemble of diverse distance metrics, we overcome the metric-selection problem, creating an anomaly score that is not reliant on any single definition of distance. We demonstrate this multi-metric approach as a tool for simple, interpretable scientific discovery on astronomical time series – (1) with simulated data for the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time, and (2) real data from the Zwicky Transient Facility. We find that DiMMAD excels at out-of-distribution anomaly detection – anomalies in the data that might be new classes – and beats other state-of-the-art methods in the goal of maximizing the diversity of new classes discovered. For rare in-distribution anomaly detection, DiMMAD performs similarly to other methods, but may allow for improved interpretability. All our code is open source: DiMMAD is implemented within DistClassiPy: https://github.com/sidchaini/distclassipy/, while all code to reproduce the results of this paper is available here: https://github.com/sidchaini/dimmad/.
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High Energy Astrophysical Phenomena

Shock Acceleration in the Intracluster Medium: Implications of Micromirror Confinement

Rebecca Diesing, Ludwig Böss and Damiano Caprioli

Merging galaxy clusters exhibit strong observational evidence for efficient particle acceleration in the intracluster medium (ICM), particularly in the form of synchrotron-emitting radio relics and halos. Cosmic ray (CR) electrons are likely accelerated (or re-accelerated) at merger and accretion shocks via diffusive shock acceleration (DSA). However, in the presence of the large diffusion coefficients one would naively expect in the rarefied, relatively unmagnetized ICM, this acceleration–in particular, the maximum proton energy ($E_{\rm max}$)–is limited by long acceleration times. On the other hand, recent work on CR transport suggests that the diffusion coefficient can be suppressed in ICM-like environments. In this picture, deviations from local thermodynamic equilibrium can trigger the mirror instability, creating plasma-scale magnetic structures, or "micromirrors," that efficiently scatter CRs. In this paper, we investigate the implications of micromirror confinement for shock acceleration in the ICM. We demonstrate that micromirrors enforce a minimum value of $E_{\rm max} \gtrsim 100$ GeV that does not rely on CR-driven magnetic field amplification. We also discuss micromirror confinement in the context of cosmological simulations and $\gamma$-ray observations, and present a simulation of a Coma-like merging cluster that self-consistently includes CR acceleration at shocks, with an effective diffusion coefficient set by micromirrors. We show that the introduction of micromirrors yields simulated galaxy clusters that remain consistent with $\gamma$-ray observations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

New Bounds on Heavy QCD Axions from Big Bang Nucleosynthesis

Tae Hyun Jung, Takemichi Okui, Kohsaku Tobioka et al. (+1 more)

We study Big Bang Nucleosynthesis (BBN) constraints on heavy QCD axions. BBN offers a powerful probe of new physics that modifies the neutron-to-proton ratio during the process, thanks to the precisely measured primordial Helium-4 abundance. A heavy QCD axion provides an attractive target for this probe, because not only is it a well-motivated hypothetical particle by the strong CP problem, but also it dominantly decays to hadrons if kinematically allowed. A range of its lifetime is thus excluded where the hadronic decays would significantly alter the neutron-to-proton ratio. We compute axion-induced modification of the neutron-to-proton ratio, and obtain robust upper bounds on the axion lifetimes, as low as 0.017 s for the axion mass higher than 300 MeV. Remarkably, this is stronger than projected future CMB bounds via $N_{\rm eff}$. Our bounds are largely insensitive to uncertainties in hadronic cross sections and the axion's branching fractions into various hadrons, as well as to the precise value of the initial axion abundance. We also incorporate, for the first time, several key improvements, such as scattering processes by energetic $K_L$ and secondary hadrons, that can also be important for studying general hadronic injections during BBN, not limited to those from axion decays.
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All authors Tae Hyun Jung, Takemichi Okui, Kohsaku Tobioka, Jiabao Wang

Instrumentation and Methods for Astrophysics

The case for an Astrometric Mission Extension of Euclid. Extending Gaia by 6 magnitudes with Euclid covering one-third of the sky

Luigi "Rolly” BEDIN

The nominal duration of Euclid's main mission is six years, but current best estimates indicate that the observatory has sufficient propellant to operate for up to ~14 years in total. In this work, we advocate dedicating six of these ~8 additional years to repeating the main survey, covering approximately one-third of the sky. This repetition would not only improve the sampling, signal-to-noise, quality, and depth of the survey, but – most importantly – would provide a six-year time baseline between two epochs if executed in the same sequence. The availability of multiple epochs would enable the derivation of proper motions for stars as faint as V~27, i.e., more than five magnitudes fainter than those measured by the Gaia mission. Although it may seem early to propose such a mission extension, in this work we quantitatively illustrate its immense scientific potential. We therefore intend to initiate the technical and scientific discussions early to ensure optimal planning. The here proposed extension would employ only the VIS channel – owing to its superior astrometric capability and depth – while simultaneously using NISP in slitless-spectroscopy mode to enhance the signal-to-noise ratio of first-epoch spectra that would also benefit of proper motions to identify and reject objects within the local Universe.
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Earth and Planetary Astrophysics · Cross-listed from cond-mat.mtrl-sci

Surface Binding Energies for Amorphous Plagioclase Feldspar Calculated using Molecular Dynamics

Amanda Ricketts, Benjamin A. Clouter-Gergen, Anastasis Georgiou et al. (+2 more)

Despite the well-established presence of amorphous compounds on planetary bodies such as the Moon and Mercury due to space weathering, the direct effect of atomic arrangement on the surface binding energies (SBEs) of elements on these bodies remains largely unexplored. Accurate SBE values are essential for reliably predicting sputtering yields and the energy distribution of ejecta. Here, we use molecular dynamics simulations to quantify SBEs for the different elements sputtered from amorphous atomic arrangements of the plagioclase feldspar end members, albite and anorthite, and compare to their crystalline counterparts. Results show that while the mean elemental SBEs from amorphous surfaces are not significantly different from their crystalline counterparts, the random orientation in amorphous structures gives rise to a spectrum of bonding configurations, resulting in a distribution of SBEs with a wider range. This contrasts with the clearly discretized set of SBE values associated with the ordered atomic structure of crystalline surfaces. We then consider sputtering by H, He, and a solar wind combination of 96% H and 4% He. For each of these cases, we demonstrate that there is minimal difference (<10% for albite and <20% for anorthite) between the sputtering yields of amorphous and crystalline surfaces. We attribute these results to the presence of the same elemental bonds across different atomic arrangements, which leads to similar mean SBEs and, consequently, comparable sputtering yields.
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All authors Amanda Ricketts, Benjamin A. Clouter-Gergen, Anastasis Georgiou, Deborah Berhanu, Liam S. Morrissey

Earth and Planetary Astrophysics

Rheological Lunar Regolith Simulants

Léonie Gasteiner, Alyona Glazyrina, Naomi Murdoch et al. (+1 more)

Regolith simulants are essential for space research and technology development. Yet, their physical properties often differ from those of true planetary soil, particularly when compared to regolith properties in-situ, that experience notably reduced gravity. We focus on lunar regolith simulants and explore various techniques to modify existing simulants to replicate the mechanical/rheological behavior of Moon regolith in true lunar conditions. Our results are validated against data from in-situ tests conducted during the Luna and Apollo missions, enabling a direct comparison of physical properties of our enhanced simulants to true Lunar regolith, on the Moon. Analyzed in the Mohr-Coulomb model framework, the friction angle of most simulants is generally close to that of true regolith, but the measured cohesion is often higher on the Moon, notably due to the reduced gravity environment. We propose a method to increase the cohesion of an existing simulant and assess the mechanical behavior of our rheological regolith simulant using a standardized geotechnical, shear test. The experimental results are then directly compared to in-situ data, providing a quantitative basis for evaluating the fidelity of the enhanced simulants.
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All authors Léonie Gasteiner, Alyona Glazyrina, Naomi Murdoch, Olfa D'Angelo

Earth and Planetary Astrophysics

Giant Planet Evolution with MESA

Ravit Helled, Simon Müller and Henrik Knierim

The evolution of gaseous planets is a complex process influenced by various physical parameters and processes. In this study, we present critical modifications to the Modules for Experiments in Stellar Astrophysics (MESA) code to enhance its applicability to giant planet modelling. We introduce an equation of state specifically tailored for materials at planetary conditions. The equation of state considers the thermodynamic properties of hydrogen-helium mixtures and heavy elements, improving the accuracy of internal structure calculations. We also present modifications to the radiative opacity to allow the modelling of grains, clouds and opacity windows. Furthermore, we refine the treatment of convective mixing processes in MESA to better replicate convective mixing with the presence of composition gradients. Finally, we add a treatment for helium rain and settling. These modifications aim to enhance the predictive capabilities of MESA for giant planet evolution and are publicly available. We hope that these improvements will lead to a deeper understanding of giant planet evolution in the solar system and beyond.
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Earth and Planetary Astrophysics

HST-COS Transit Spectroscopy of KELT-20b: First Detection of Excess Far-ultraviolet Absorption From an Ultra-hot Jupiter

Patrick R. Behr, Kevin France, Luca Fossati et al. (+4 more)

KELT-20 b is an ultra-hot Jupiter with an equilibrium temperature of $2260$ K orbiting a bright (V =7.6), fast-rotating ($v\sin{i}$=117 km s$^{-1}$) A2 V star. The atmosphere of KELT-20 b has been studied extensively via transmission spectroscopy at optical wavelengths, showing strong hydrogen absorption as well as metals including Na I, Ca II, Fe I, Fe II, Mg I, Si I and Cr II. The atmospheric and ionization conditions of this planet may differ from Jupiter-mass exoplanets due to the relatively weak extreme-ultraviolet radiation from its host star, as the stellar dynamo that generates chromospheric and coronal activity is thought to shut down at spectral types earlier than A4. We present the first spectroscopic observations of KELT-20 b in the far-ultraviolet using the Hubble Space Telescope Cosmic Origins Spectrograph, searching for previously undetected low-ionization and neutral atoms in the upper atmosphere. We find that the FUV transit depth increases with decreasing wavelengths, from $1.88\pm0.04$% at 1600–1760 Å to $2.28\pm0.04$% at 1410–1570 Å, yielding planetary radii of $0.1139\pm0.06$ $R_*$ and $0.1222\pm0.07$ $R_*$, respectively. We report tentative detections of Fe II and N I at $2.4\sigma$ each, and non-detections of C I, S I, Al II, and Si II. We find no evidence for molecular absorption from CO or H$_2$ and no sign of hydrodynamic escape.
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All authors Patrick R. Behr, Kevin France, Luca Fossati, Tommi Koskinen, Patricio E. Cubillos, Arika Egan, P. Wilson Cauley

Cosmology and Nongalactic Astrophysics

The Compressed 3D Lyman-Alpha Forest Bispectrum

Roger de Belsunce, James M. Sullivan and Patrick McDonald

Cosmological studies of the Lyman-Alpha (Lya) forest typically constrain parameters using two-point statistics. However, higher-order statistics, such as the three-point function (or its Fourier counterpart, the bispectrum) offer additional information and help break the degeneracy between the mean flux and power spectrum amplitude, albeit at a significant computational cost. To address this, we extend an existing highly informative compression of the bispectrum, the skew spectra, to the Lya forest. We derive the tree-level bispectrum of Lya forest fluctuations in the framework of effective field theory (EFT) directly in redshift space and validate our methodology on synthetic Lya forest data. We measure the anisotropic cross-spectra between the transmitted flux fraction and all quadratic operators arising in the bispectrum, yielding a set of 26 skew spectra. Using idealized 3D Gaussian smoothing (R=10 Mpc/h), we find good agreement (1-2 sigma level based on the statistical errors of the mocks) with the theoretical tree-level bispectrum prediction for monopole and quadrupole up to k <= 0.17 h/Mpc. To enable the cosmological analysis of Lya forest data from the currently observing Dark Energy Spectroscopic Instrument (DESI), where we cannot do 3D smoothing, we use a line-of-sight smoothing and introduce a new statistic, the shifted skew spectra. These probe non-squeezed bispectrum triangles and avoid locally applying quadratic operators to the field by displacing one copy of the field in the radial direction. Using a fixed displacement of 40 Mpc/h (and line-of-sight smoothing of 10 Mpc/h) yields a similar agreement with the theory prediction. For the special case of correlating the squared (and displaced) field with the original one, we analytically forward model the window function making this approach readily applicable to DESI data.
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Cosmology and Nongalactic Astrophysics

Cosmic magnification on multi-catalogue Herschel submillimetre galaxies

R. Fernandez-Fernandez, M.M. Cueli, J. González-Nuevo et al. (+6 more)

{Submillimetre galaxies (SMGs) are excellent background sources for magnification-bias studies, but the limited sky coverage in the submillimetre (sub-mm) band constrains their statistical power. Beyond H-ATLAS, Herschel produced additional sub-mm catalogues, though not optimised for spatial statistical lensing analyses.} {Our goal is to refine cosmological constraints from SMG magnification bias by exploiting the full sub-mm sky surveyed by Herschel.} {We expanded the SMG sample by incorporating other Herschel catalogues overlapping SDSS spectroscopic lenses. Random catalogues were generated via kernel density estimation to compute cross-correlations, and Markov Chain Monte Carlo methods were applied to infer astrophysical and cosmological parameters for each catalogue and for the combined dataset.} {We report the first detection of magnification bias in SMGs beyond H-ATLAS, reinforcing the robustness of this observable. Individual Herschel catalogues yield reasonable central values for $\Omega_m$ and $\sigma_8$, although with large uncertainties. The combined analysis, dominated by the more powerful H-ATLAS sample, gives results consistent with $\Lambda$CDM: $\Omega_m = 0.30^{+0.05}_{-0.07}$, $\sigma_8 = 0.80 (+/- 0.07)$, and $h < 0.80$, in better agreement with Planck 2018 than previous non-tomographic studies.} {SMGs are promising tracers for magnification bias, but the narrow sub-mm coverage remains a major limitation. Wider surveys optimised for lensing would enable cross-correlations on larger scales, yielding tighter cosmological constraints.}
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All authors R. Fernandez-Fernandez, M.M. Cueli, J. González-Nuevo, L. Bonavera, D. Crespo, E. Goitia, J.M. Casas, J.A. Cano, M. Migliaccio

Cosmology and Nongalactic Astrophysics

COMAP Pathfinder – Season 2 results IV. A stack on eBOSS/DESI quasars

D.A. Dunne, K.A. Cleary, J.G.S. Lunde et al. (+16 more)

We present a stack of data from the second season of the CO Mapping Array Project (COMAP) Pathfinder on the positions of quasars from eBOSS and DESI. COMAP is a Line Intensity Mapping (LIM) experiment targeting dense molecular gas via CO(1–0) emission at $z\sim3$. COMAP's Season 2 represents a $3\times$ increase in map-level sensitivity over the previous Early Science data release. We do not detect any CO emission in the stack, instead finding an upper limit of $10.0\times 10^{10}\ \mathrm{K\ km\ s^{-1}\ pc^2}$ at 95% confidence within an $\sim 18\ \mathrm{cMpc}$ box. We compare this upper limit to models of the CO emission stacked on quasars and find a tentative ($\sim 3 \sigma$) tension between the limit and the brightest stack models after accounting for a suite of additional sources of experimental attenuation and uncertainty, including quasar velocity uncertainty, pipeline signal loss, cosmic variance, and interloper emission in the LIM data. The COMAP-eBOSS/DESI stack is primarily a measurement of the CO luminosity in the quasars' wider environment and is therefore potentially subject to environmental effects such as feedback. With our current simple models of the galaxy-halo connection, we are thus unable to confidently rule out any models of cosmic CO with the stack alone. Conversely, the stack's sensitivity to these large-scale environmental effects has the potential to make it a powerful tool for galaxy formation science, once we are able to constrain the average CO luminosity via the auto power spectrum (a key goal of COMAP).
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All authors D.A. Dunne, K.A. Cleary, J.G.S. Lunde, D.T. Chung, P.C. Breysse, N.O. Stutzer, J.R. Bond, H.K. Eriksen, J.O. Gundersen, G.A. Hoerning, J. Kim, E.M. Mansfield, S.R. Mason, N. Murray, T.J. Rennie, D. Tolgay, S. Valentine, I.K. Wehus, COMAP Collaboration

Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 6 Results: Redshift Calibration of the Weak Lensing Source Galaxies

B. Yin, A. Amon, A. Campos et al. (+95 more)

Determining the distribution of redshifts for galaxies in wide-field photometric surveys is essential for robust cosmological studies of weak gravitational lensing. We present the methodology, calibrated redshift distributions, and uncertainties of the final Dark Energy Survey Year 6 (Y6) weak lensing galaxy data, divided into four redshift bins centered at $\langle z \rangle = [0.414, 0.538, 0.846, 1.157]$. We combine independent information from two methods on the full shape of redshift distributions: optical and near-infrared photometry within an improved Self-Organizing Map $p(z)$ (SOMPZ) framework, and cross-correlations with spectroscopic galaxy clustering measurements (WZ), which we demonstrate to be consistent both in terms of the redshift calibration itself and in terms of resulting cosmological constraints within 0.1$\sigma$. We describe the process used to produce an ensemble of redshift distributions that account for several known sources of uncertainty. Among these, imperfection in the calibration sample due to the lack of faint, representative spectra is the dominant factor. The final uncertainty on mean redshift in each bin is $\sigma_{\langle z\rangle} = [0.012, 0.008,0.009, 0.024]$. We ensure the robustness of the redshift distributions by leveraging new image simulations and a cross-check with galaxy shape information via the shear ratio (SR) method.
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All authors B. Yin, A. Amon, A. Campos, M. A. Troxel, W. d'Assignies, G. M. Bernstein, G. Camacho-Ciurana, S. Mau, M. R. Becker, G. Giannini, A. Alarcón, D. Gruen, J. McCullough, M. Yamamoto, D. Anbajagane, S. Dodelson, C. Sánchez, J. Myles, J. Prat, C. Chang, M. Crocce, K. Bechtol, A. Ferté, M. Gatti, N. MacCrann, R. Marco, A. Porredón, D. Sánchez Cid, T. Schutt, M. Tabbut, C. To, T. Abbott, M. Aguena, O. Alves, D. Bacon, J. Blazek, S. Bocquet, D. Brooks, R. Camilleri, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, F. Castander, R. Cawthon, C. Conselice, L. da Costa, M. da Silva Pereira, T. Davis, J. De Vicente, S. Desai, H. Diehl, C. Doux, A. Drlica-Wagner, T. Eifler, J. Elvin-Poole, S. Everett, B. Flaugher, P. Fosalba, D. Francis de Souza, J. Frieman, J. Garcia-Bellido, E. Gaztañaga, P. Giles, G. Gutierrez, S. Hinton, D. Hollowood, K. Honscheid, D. Huterer, B. Jain, D. James, K. Kuehn, S. Lee, H. Lin, J. Marshall, J. Mena-Fernández, F. Menanteau, R. Miquel, J. Muir, L. Ofer, R. Ogando, A. Palmese, D. Petravick, A. Plazas Malagón, A. Roodman, R. Rosenfeld, S. Samuroff, E. Sánchez, I. Sevilla, E. Sheldon, T. Shin, M. Smith, E. Suchyta, M. Swanson, G. Tarlé, D. Thomas, V. Vikram, A. Walker, P. Wiseman

Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 6 Results: Clustering-redshifts and importance sampling of Self-Organised-Maps $n(z)$ realizations for $3\times2$pt samples

W. d'Assignies, G. M. Bernstein, B. Yin et al. (+92 more)

This work is part of a series establishing the redshift framework for the $3\times2$pt analysis of the Dark Energy Survey Year 6 (DES Y6). For DES Y6, photometric redshift distributions are estimated using self-organizing maps (SOMs), calibrated with spectroscopic and many-band photometric data. To overcome limitations from color-redshift degeneracies and incomplete spectroscopic coverage, we enhance this approach by incorporating clustering-based redshift constraints (clustering-z, or WZ) from angular cross-correlations with BOSS and eBOSS galaxies, and eBOSS quasar samples. We define a WZ likelihood and apply importance sampling to a large ensemble of SOM-derived $n(z)$ realizations, selecting those consistent with the clustering measurements to produce a posterior sample for each lens and source bin. The analysis uses angular scales of 1.5-5 Mpc to optimize signal-to-noise while mitigating modeling uncertainties, and marginalizes over redshift-dependent galaxy bias and other systematics informed by the N-body simulation Cardinal. While a sparser spectroscopic reference sample limits WZ constraining power at $z>1.1$, particularly for source bins, we demonstrate that combining SOMPZ with WZ improves redshift accuracy and enhances the overall cosmological constraining power of DES Y6. We estimate an improvement in $S_8$ of approximately 10% for cosmic shear and $3\times2$pt analysis, primarily due to the WZ calibration of the source samples.
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All authors W. d'Assignies, G. M. Bernstein, B. Yin, G. Giannini, A. Alarcon, M. Manera, C. To, M. Yamamoto, N. Weaverdyck, R. Cawthon, M. Gatti, A. Amon, D. Anbajagane, S. Avila, M. R. Becker, K. Bechtol, C. Chang, M. Crocce, J. De Vicente, S. Dodelson, J. Fang, A. Ferté, D. Gruen, E. Legnani, A. Porredon, J. Prat, M. Rodriguez-Monroy, C. Sánchez, T. Schutt, I. Sevilla-Noarbe, D. Sanchez Cid, M. A. Troxel, T. M. C. Abbott, F. Andrade-Oliveira, M. Aguena, O. Alves, D. Bacon, J. Blazek, S. Bocquet, D. Brooks, R. Camilleri, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, F. J. Castander, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, S. Desai, P. Doel, C. Doux, A. Drlica-Wagner, T. Eifler, J. Elvin-Poole, S. Everett, B. Flaugher, P. Fosalba, J. Frieman, J. Garcia-Bellido, E. Gaztanaga, P. Giles, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. Huterer, B. Jain, D. J. James, K. Kuehn, O. Lahav, S. Lee, J. L. Marshall, J. Mena-Fernandez, F. Menanteau, R. Miquel, J. Muir, J. Myles, R. L. C. Ogando, A. Palmese, M. Paterno, P. Petravick, A. A. Plazas Malagon, M. Raveri, A. Roodman, S. Samuroff, E. Sanchez, E. Sheldon, T. Shin, M. Smith, E. Suchyta, M. E. C. Swanson, G. Tarle, D. Thomas, V. Vikram, A. R. Walker

Astrophysics of Galaxies

Cosmic Vine: High abundance of massive galaxies and dark matter halos in a forming cluster at z=3.44

Nikolaj B. Sillassen, Shuowen Jin, Georgios E. Magdis et al. (+10 more)

The Cosmic Vine is a massive protocluster at z=3.44 in the JWST CEERS field, offering an ideal laboratory for studying the early phases of cluster formation. Using the data from the DAWN JWST Archive, we conduct a comprehensive study on the large-scale structure, stellar mass function (SMF), quiescent members, and dark matter halos in the Cosmic Vine. First, we spectroscopically confirm 136 galaxies in the Vine at z=3.44, and an additional 47 galaxies belonging to a diffuse foreground structure at z=3.34 which we dub the Leaf. We identify four subgroups comprising the Cosmic Vine and two subgroups within the Leaf. Second, we identified 11 quiescent members with log(M*/Msun)=9.5-11.0, the largest sample of quiescent galaxies in overdense environments at z>3, which gives an enhanced quiescent galaxy number density 2x10^(-4)cMpc^(-3) that is three times above the field level at log(M*/Msun) > 10. Notably, these quiescent members form a tight red sequence on the color-magnitude diagram, making it one of the earliest red sequences known to date. Third, by constructing the SMFs for both star-forming and quiescent members, we find that both SMFs are top-heavy, with a significantly enhanced quiescent fraction at log(M*/Msun)>10.5 compared to field counterparts. The stellar mass-size analysis reveals that star-forming members are more compact at higher masses than their field counterparts. Finally, we estimate a halo mass of log(Mh/Msun)=13.2+-0.3 for the protocluster core, and log(Mh/Msun)=11.9-12.4 for satellite subgroups. The phase-space analysis indicates that three subgroups are likely infalling to the core. This work reveals a high abundance of massive galaxies and dark matter halos in a forming cluster, demonstrating the accelerated assembly of massive galaxies in massive halos when the Universe was less than 2 billion years old.
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All authors Nikolaj B. Sillassen, Shuowen Jin, Georgios E. Magdis, Francesco Valentino, Emanuele Daddi, Raphael Gobat, Malte Brinch, Kei Ito, Tao Wang, Hanwen Sun, Gabriel Brammer, Sune Toft, Thomas Greve

Astrophysics of Galaxies

The MandelZoom project II: the impact of stellar feedback on black hole accretion through an $\alpha$-disc in dwarf galaxies with a resolved interstellar medium

Eun-jin Shin, Matthew C. Smith, Debora Sijacki et al. (+2 more)

We present a suite of high-resolution simulations to study how different stellar feedback channels regulate the growth of central intermediate-mass black holes (IMBHs) in dwarf galaxies hosting nuclear star clusters (NSCs). We employ a super-Lagrangian refinement scheme to resolve the self-gravity radius of the $\alpha$-accretion disc ($<0.01$~pc) and follow the gas inflows from the interstellar medium (ISM) to the black hole (BH), allowing for the self-consistent emergence of circumnuclear discs (CNDs). In the absence of stellar feedback, as expected, the galactic disc fragments excessively, producing a massive CND. When radiative stellar feedback is included, fragmentation is suppressed, with even more massive CNDs forming and feeding the IMBH. With supernova (SN) feedback only, clustered SNe strongly heat the ISM, yielding both the lowest CND masses and BH accretion rates. When both radiative stellar feedback and SNe are included, the CND becomes intermittent: it survives for $10$–$100$~Myr, and is then destroyed by feedback before being replenished by fresh galactic inflows, while substantial BH growth still takes place. These results highlight the critical importance of accurately modelling the combined effects of key stellar feedback processes to understand IMBH growth. Our simulation suite brackets the likely range of CND states, with IMBHs exhibiting significant growth and systematic spin-up in all dwarf galaxy models explored. These findings bode well for the detection of IMBHs with future observational facilities such as SKA, the Rubin Observatory, and LISA, and make them highly relevant progenitor candidates of the high-redshift supermassive BHs observed by JWST.
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All authors Eun-jin Shin, Matthew C. Smith, Debora Sijacki, Martin A. Bourne, Sophie Koudmani

Cosmology and Nongalactic Astrophysics

Discovery of SN 2025wny: a Strongly Gravitationally Lensed Superluminous Supernova at z = 2.01

Joel Johansson, Daniel A. Perley, Ariel Goobar et al. (+31 more)

We present the discovery of SN 2025wny (ZTF25abnjznp/GOTO25gtq) and spectroscopic classification of this event as the first gravitationally lensed Type I superluminous supernovae (SLSN-I). Deep ground-based follow-up observations resolves four images of the supernova with ~1.7" angular separation from the main lens galaxy, each coincident with the lensed images of a background galaxy seen in archival imaging of the field. Spectroscopy of the brightest point image shows narrow features matching absorption lines at a redshift of z = 2.011 and broad features matching those seen in superluminous SNe with Far-UV coverage. We infer a magnification factor of 20 to 50 for the brightest image in the system, based on photometric and spectroscopic comparisons to other SLSNe-I. SN 2025wny demonstrates that gravitationally-lensed SNe are in reach of ground-based facilities out to redshifts far higher than what has been previously assumed, and provide a unique window into studying distant supernovae, internal properties of dwarf galaxies, as well as for time-delay cosmography.
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All authors Joel Johansson, Daniel A. Perley, Ariel Goobar, Jacob L. Wise, Yu-Jing Qin, Zoë McGrath, Steve Schulze, Cameron Lemon, Anjasha Gangopadhyay, Konstantinos Tsalapatas, Igor Andreoni, Eric C. Bellm, Joshua S. Bloom, Richard Dekany, Suhail Dhawan, Christoffer Fremling, Matthew J. Graham, Steven L. Groom, Daniel Gruen, Xander J. Hall, Mansi Kasliwal, Russ R. Laher, Ragnhild Lunnan, Ashish A. Mahabal, Adam A. Miller, Edvard Mörtsell, Jakob Nordin, Jacob Osman Hjortlund, R. Michael Rich, Reed L. Riddle, Avinash Singh, Jesper Sollerman, Alice Townsend, Lin Yan

Astrophysics of Galaxies

Unveiling the collision between molecular outflows: observational evidence and hydrodynamic simulations

E. Cohen Arazi, P. F. Velázquez, M. E. Ortega et al. (+5 more)

We present an unexplored scenario for interpreting the outflows in the EGO G338.92+0.55 (b) region (hereafter, EGO G338). Within this framework, we investigate the hypothesis that the interaction between two outflows is responsible for the observed morphology and kinematics of this astrophysical object. To explore this possibility, we reanalyse the region using observational molecular line data. We base our analysis on maps of moments 0, 1, and 2 of the CO emission associated with the molecular outflows. Additionally, we conduct three-dimensional hydrodynamic simulations to examine the presence or absence of a collision between two jets. From our numerical results, we produce synthetic CO images to facilitate a direct comparison with observations. The findings of this study provide compelling evidence that the observed morphology and kinematics in the EGO G338 region are the result of a likely collision between two molecular outflows.
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All authors E. Cohen Arazi, P. F. Velázquez, M. E. Ortega, A. Rodríguez-González, E. Alquicira-Peláez, S. Paron, P. Rivera-Ortiz, A. Esquivel

Astrophysics of Galaxies

Galactic bars and active galactic nucleus fuelling in the second half of cosmic history

A. La Marca, M. T. Nardone, L. Wang et al. (+3 more)

We investigate the role of galactic bars in fuelling and triggering Active Galactic Nucleus (AGN) in disc galaxies up to $z\sim 0.8$. We utilise a Deep Learning model, fine-tuned on Galaxy Zoo volunteer classifications, to identify (strongly and weakly) barred and unbarred disc galaxies in Hyper Suprime-Cam Subaru Strategic Program $i$-band images. We select AGN using three independent diagnostics: mid-infrared colours, X-ray detections, and spectral energy distribution (SED) fitting. The SED analysis, performed using CIGALE, quantifies the relative AGN contribution to the total galaxy luminosity ($f_{\rm AGN}$) and the AGN luminosity ($L_{\rm disc}$). We assess the impact of bars by comparing AGN incidence and properties in barred galaxies against carefully constructed redshift-, stellar mass-, and colour-matched unbarred control samples. Our binary AGN classification experiment demonstrates that barred disc galaxies host a higher fraction of AGN compared to their unbarred counterparts, though the significance depends on the AGN selection method, with a more modest excess for SED AGN, and control sample size. This suggests a contributing role for bars in the global AGN budget. The contribution of bars to AGN fuelling appears confined to systems where the AGN has a lower relative contribution to the host galaxy's emission ($f_{\rm AGN} < 0.75$). Crucially, we find a significant dearth of barred disc galaxies hosting AGN with $f_{\rm AGN} > 0.75$, independent of bar strength. Consistent with this, the fraction of barred galaxies among AGN hosts decreases with increasing $L_{\rm disc}$. Combined with previous results, we suggest that bars may contribute to fuelling the population of low-to-moderate luminosity AGN, but major mergers are the principal mechanism for triggering the most powerful and dominant accretion events.
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All authors A. La Marca, M. T. Nardone, L. Wang, B. Margalef-Bentabol, S. Kruk, S. C. Trager

Solar and Stellar Astrophysics

Unveiling stellar (and planetary) internal dynamics with the fully compressible MUSIC code

Arthur Le Saux, Isabelle Baraffe, Thomas Guillet et al. (+8 more)

Multidimensional hydrodynamical simulations have transformed the study of stellar interiors over the past few decades. Most codes developed during that time use the anelastic approximation, which fixes the thermal structure of simulations and filters out sound waves. Many of them also use explicit time integration, which imposes severe constraints on the time step of the simulations. In this context, MUSIC is developed to overcome these limitations. Its main scientific objective is to improve the phenomenological approaches used in 1D stellar evolution codes to describe major hydrodynamical and MHD processes. Here, we review recent applications of the MUSIC code, that focus mainly on convection, convective boundary mixing and waves in stars that possess convective cores, shells and/or envelopes.
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All authors Arthur Le Saux, Isabelle Baraffe, Thomas Guillet, Jane Pratt, Tom Goffrey, Dimitar Vlaykov, Adrien Morison, Jack Morton, Maxime Stuck, Mary Geer Dethero, Nils de Vries

Instrumentation and Methods for Astrophysics

Separation of gain fluctuations and continuum signals in total power spectrometers with application to COMAP

J. G. S. Lunde, P. C. Breysse, D. T. Chung et al. (+11 more)

We describe a time-domain technique for separating $1/f$ gain fluctuations and continuum signal for a total power spectrometer, such as the CO Mapping Array Project (COMAP) Pathfinder instrument. The $1/f$ gain fluctuations of such a system are expected to be common-mode across frequency channels. If the instrument's system temperature is not constant across channels, a continuum signal will exhibit a frequency dependence different from that of common-mode gain fluctuations. Our technique leverages this difference to fit a three-parameter frequency model to each time sample in the time-domain data, separating gain and continuum. We show that this technique can be applied to the COMAP Pathfinder instrument, which exhibits a series of temporally stable resonant noise spikes that effectively act as calibrators, breaking the gain degeneracy with continuum signals. Using both simulations and observations of Jupiter, we explore the effect of a $1/f$ prior for the gain model. We show that the model is capable of cleanly separating Jupiter, a bright continuum source, from the gain fluctuations in the scan. The technique has two applications to COMAP. For the COMAP observations performing line intensity mapping (LIM), the technique better suppresses atmospheric fluctuations and foregrounds than the COMAP LIM pipeline. For the Galactic COMAP observations, which map Galactic continuum signals, the technique can suppress $1/f$ gain fluctuations while retaining all continuum signals. This is demonstrated by the latest COMAP observations of $\lambda$-Orionis, where our method produces far cleaner maps than a destriper alone, typically reducing the noise power by a factor of 7 on beam scales and up to 15 on larger scales.
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All authors J. G. S. Lunde, P. C. Breysse, D. T. Chung, K. A. Cleary, C. Dickinson, D. A. Dunne, J. O. Gundersen, S. E. Harper, G. A. Hoerning, H. T. Ihle, J. W. Lamb, T. J. Pearson, T. J. Rennie, N.-O. Stutzer

Cosmology and Nongalactic Astrophysics

Dynamical friction shear and rotation in Chaplygin cosmology

A. Del Popolo, Saeed Fakhry, Maryam Shiravand et al. (+1 more)

In this study, we build upon the findings of Del Popolo et al. (2013) by further analyzing the influence of dynamical friction on the evolution of cosmological perturbations within the framework of the spherical collapse model (SCM) in a Universe dominated by generalized Chaplygin gas (GCG). Specifically, we investigate how dynamical friction alters the growth rate of density perturbations, the effective sound speed, the equation-of-state parameter www, and the evolution of the cosmic expansion rate. Our results demonstrate that dynamical friction significantly delays the collapse process compared to the standard SCM. Accurate computation of these parameters is crucial for obtaining consistent results and reliable physical interpretations when employing the GCG model. Furthermore, our analysis confirms that the suppression of perturbation growth due to dynamical friction is considerably more pronounced than that caused by shear and rotation, as previously indicated by Del Popolo et al. (2013). This enhanced suppression effectively addresses the instability issues, such as oscillations or exponential divergences in the dark-matter power spectrum, highlighted in linear perturbation studies, such as those by Sandvik et al. (2004).
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All authors A. Del Popolo, Saeed Fakhry, Maryam Shiravand, Morgan Le Delliou

Astrophysics of Galaxies

A targeted radio survey of infrared-selected bow shock candidates

M. Moutzouri, J. Mackey, N. Castro et al. (+8 more)

Bow shocks around massive stars have primarily been detected in IR emission, but radio detections are becoming more frequent with the commissioning of sensitive and large field-of-view interferometers. Radio data probes both thermal and non-thermal emission, thereby constraining the relativistic electron population. We undertook a radio survey for bow shocks based on IR catalogues of candidates, using the VLA and the 100-m Effelsberg Telescope, aiming for new detections and to better characterise the multi-wavelength emission. We used Gaia DR3 to re-calculate spatial motion of the driving stars with respect to the surrounding stellar population. We studied the radio emission from bow shocks using emission maps and spectral-index measurements, and compared our results with data from catalogues and multi-wavelength emission. Of the 24 targets observed with the VLA in the 4-12 GHz band, six were clearly detected (including two previously reported) and 5 possibly detected. A subset of these were also observed and detected with Effelsberg at 4-8 GHz. The VLA-derived spectral index maps indicate non-thermal emission for most sources, but the statistical uncertainties are large for most sources and all Effelsberg observations indicate thermal emission. Assuming thermal emission, we obtain upper limits on the electron density within the shocked layer. We obtained upper limits on radio emission from the bow shock of Zeta Oph at a similar flux level to predictions from MHD simulations. Our survey marks a significant addition to the ca. 10 previously known radio-emitting bow shocks in the literature, and demonstrates that deep, targeted radio surveys can effectively detect IR-selected bow shocks. Follow-up observations of these targets at lower and higher frequencies are encouraged to determine whether any are non-thermal emitters like the bow shocks of BD+43, BD+60 and LS2355. (abridged)
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All authors M. Moutzouri, J. Mackey, N. Castro, Y. Gong, P. Jiménez-Hernández, J. A. Toalá, C. Burger-Scheidlin, M. Rugel, C. Carrasco-González, R. Brose, K.M. Menten

Instrumentation and Methods for Astrophysics

Improved UVIS Aperture Corrections derived from Focus Diverse PSF Maps

K.Huynh, V.Bajaj, J.Mack et al. (+1 more)

In crowded fields, small-aperture photometry can reduce contamination errors from neighboring sources compared to larger aperture photometry. However, the UVIS encircled energy (EE) varies with detector position and focus variations on orbital timescales for aperture radii less than 10 pixels ($\sim$0.4 arcseconds). Using a set of focus-diverse empirical PSFs by Anderson (2018), we compute 2D spatial maps of the aperture correction between 5-10 pixels and find a maximum change of $\sim$0.01 mag over all focus levels for a given detector position. The upper-left and lower-right corners of the UVIS detector are more focus-sensitive than the rest of the field of view, where the mean correction is systematically $\sim$0.01 mag higher in Amp A for bluer filters (F275W, F336W, F438W) and $\sim$0.01 mag higher in Amp D for redder filters (F606W, F814W) at all focus levels. We test the new aperture correction maps in globular clusters, and we find reduced scatter, better agreement between the two CCDs, and a small shift in the absolute photometry when compared to a single (constant) aperture correction per image. These improvements are specific to photometry with apertures $<$ 10 pixels in radius; results from larger apertures are not affected. Using published EE tables can introduce systematic uncertainties in absolute photometry due to its tendency to vary with detector position and focus level, with larger errors for smaller apertures. Users requiring photometric accuracy better than $\sim$1% for small apertures can use isolated stars in the individual FLT/FLC frames (or PSF cutouts at a similar detector position and focus level) to compute encircled energy corrections and accurately account for the amount of flux at radii larger than their photometric apertures.
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All authors K.Huynh, V.Bajaj, J.Mack, A.Calamida

Astrophysics of Galaxies

MIGHTEE-HI: The HI mass-stellar mass relation of massive galaxies and the HI mass function at 0.25<z<0.5

Hengxing Pan, Matt J. Jarvis, Ian Heywood et al. (+6 more)

The relationship between the already formed stellar mass in a galaxy and the gas reservoir of neutral atomic hydrogen, is a key element in our understanding of how gas is turned into stars in galaxy haloes. In this paper, we measure the $M_{\rm HI}-M_{\star}$ relation based on a stellar-mass selected sample at $0.25 < z < 0.5$ and the MIGHTEE-HI DR1 spectral data. Using a powerful Bayesian stacking technique, for the first time we are also able to measure the underlying bivariate distribution of HI mass and stellar mass of galaxies with $M_\star > 10^{9.5}$ M$_{\odot}$, finding that an asymmetric underlying HI distribution is strongly preferred by our complete samples. We define the concepts of the average of the logarithmic HI mass, $\langle\log_{10}(M_{\rm HI})\rangle$, and the logarithmic average of the HI mass, $\log_{10}(\langle M_{\rm HI}\rangle)$, and find that the difference between $\langle\log_{10}(M_{\rm HI})\rangle$ and $\log_{10}(\langle M_{\rm HI}\rangle)$ can be as large as $\sim$0.5 dex for the preferred asymmetric HI distribution. We observe shallow slopes in the underlying $M_{\rm HI}-M_{\star}$ scaling relations, suggesting the presence of an upper HI mass limit beyond which a galaxy can no longer retain further HI gas. From our bivariate distribution we also infer the HI mass function at this redshift and find tentative evidence for a decrease of 2-10 times in the co-moving space density of the most HI massive galaxies up to $z\sim 0.5$.
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All authors Hengxing Pan, Matt J. Jarvis, Ian Heywood, Tariq Yasin, Natasha Maddox, Mario G. Santos, Maarten Baes, Anastasia A. Ponomareva, Sambatriniaina H. A. Rajohnson

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Observable Signatures of a Quarkyonic Phase in Neutron Stars

Probit J Kalita, Tuhin Malik, Tianqi Zhao et al. (+2 more)

Quarkyonic matter in \(\beta\)-equilibrium is a potential description of cold dense matter in neutron stars (NSs), that introduces non-interacting quarks alongside nucleons and leptons in NS cores. In this paper, we impose observational and theoretical constraints on the model to perform Bayesian inference on it, and find that it is possible to have quarkyonic matter equations of state that satisfy all current astrophysical observations, thereby reinforcing the argument for its use alongside traditional ones. To differentiate between NSs where a quarkyonic phase does and does not appear in the core, we identify some novel signatures based on the mass-radius relation. Focusing on canonical (\(1.4\ \mathrm{M_\odot}\)) NSs, we find the populations of NSs with and without quarkyonic cores show separability on the basis of the slope and curvatures of the mass-radius curve, the central sound speed of the star, and the radius difference between two NSs of \(2\ \mathrm{M_\odot}\) and \(1.4\ \mathrm{M_\odot}\). Our results indicate that observing a neutron star with these signatures matching the values for quarkyonic core NSs would provide a strong evidence for the existence of a quarkyonic phase or a similar crossover transition in its core.
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All authors Probit J Kalita, Tuhin Malik, Tianqi Zhao, Bharat Kumar, James M. Lattimer

Instrumentation and Methods for Astrophysics

Solar flare forecasting with foundational transformer models across image, video, and time-series modalities

S. Riggi, P. Romano, A. Pilzer et al. (+1 more)

We present a comparative study of transformer-based architectures for solar flare forecasting using heterogeneous data modalities, including images, video sequences, and time-series observations. Our analysis evaluates three recent foundational models - SigLIP2 for image encoding, VideoMAE for spatio-temporal video representation, and Moirai2 for multivariate time-series forecasting - applied to publicly available datasets of solar magnetograms from the SDO/HMI mission and soft X-ray fluxes acquired by GOES satellites. All models are trained and validated under consistent data splits and evaluation criteria, with the goal of assessing the strengths and limitations of transformer backbones across spatial and temporal representations of solar activity. We investigate multiple loss formulations (weighted BCE, focal, and score-oriented) and training balance strategies to mitigate class imbalance typical of flare datasets. Results show that while both SigLIP2 and VideoMAE achieve typical performance on image and video data (True Skill Statistic TSS~0.60-0.65), the time-series model Moirai2 reaches superior forecasting skill (TSS~0.74) using irradiance-based temporal evolution alone. These findings highlight the potential of pretrained transformer architectures and cross-modal learning for advancing operational space weather forecasting, paving the way toward unified multimodal models that integrate visual and temporal information.
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All authors S. Riggi, P. Romano, A. Pilzer, U. Becciani

Solar and Stellar Astrophysics

The Near-Ultraviolet Spectra of FU Orionis Accretion Disks

Adolfo S. Carvalho, Lynne A. Hillenbrand, Gregory J. Herczeg et al. (+1 more)

We present the results of the first high-sensitivity NUV (1800 to 3200 Å) survey of FU Ori objects, using the Hubble Space Telescope (HST) STIS spectrograph. We compare new low resolution spectra for 6 sources with predictions from accretion disk models and find that all show emission in excess of the disk model spectrum. The physical properties of the NUV emission excess are very consistent among the sample, with a mean luminosity of $10^{-1.11 \pm 0.4} \ L_\odot$ and temperature of $16400 \pm 2600$ K – despite spanning 0.9 dex in $M_*$, 1.3 dex in $\dot{M}$, and 0.7 dex in $L_\mathrm{acc}$. We use the spectra to conclusively rule out the existence of a hot boundary layer in FU Ori accretion disks. We then discuss the source of the excess emission in the context of recent simulations of FU Ori outbursts and boundary layer accretion. The UV spectra also show the often-seen \ion{C}{2}] 2326 Å\ multiplet and \ion{Mg}{2} 2796/2803 Å\ doublet, as well as the unusual \ion{Fe}{2}] 2507/2509 Å\ doublet, a feature that is not seen in the existing UV spectra of other young stellar objects. We measure and compare the luminosities of these lines in outbursting with those in non-outbursting objects.
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All authors Adolfo S. Carvalho, Lynne A. Hillenbrand, Gregory J. Herczeg, Kevin France

Astrophysics of Galaxies

Validating Open Cluster Candidates with Photometric Bayesian Evidence

Lu Li, Zhaozhou Li and Zhengyi Shao

The thousands of open cluster (OC) candidates identified by the Gaia mission are significantly contaminated by false positives from field star fluctuations, posing a major validation challenge. Based on the Mixture Model for OCs (MiMO), we present a Bayesian framework for validating OC candidates in the color–magnitude diagram. The method compares the Bayesian evidence of two competing models: a single stellar population with field contamination versus a pure field population. Their ratio, the Bayes factor (BF), quantifies the statistical support for cluster existence. Tests on confirmed clusters and random fields show that a threshold of BF > 100 effectively distinguishes genuine clusters from chance field overdensities. This approach provides a robust, quantitative tool for OC validation and catalog refinement. The framework is extendable to multi-dimensional validation incorporating kinematics and is broadly applicable to other resolved stellar systems, including candidate moving groups, stellar streams, and dwarf satellites.
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Astrophysics of Galaxies

The MiMO Catalog: Physical Parameters and Stellar Mass Functions of 1,232 Open Clusters from Gaia DR3

Lu Li, Zhengyi Shao, Zhaozhou Li et al. (+1 more)

We present a homogeneous catalog of 1,232 open clusters with precisely determined ages, metallicities, distances, extinctions, and stellar mass function (MF) slopes, derived from Gaia DR3 data. The parameters are inferred using the Mixture Model for Open clusters (MiMO), a novel Bayesian framework for modeling clusters in the color-magnitude diagram. By explicitly accounting for field-star contamination as a model component, MiMO removes the conventional need for stringent membership preselection, allowing for a more complete inclusion of member stars and thereby enhancing both precision and robustness. Our results broadly agree with existing catalogs but offer improved precision. For each cluster, we provide the best-fit age, metallicity, distance, extinction, and MF slope, along with their full likelihood chains and photometric membership probabilities for individual stars. We further identify an “MF Prime” subsample of 163 clusters with high-quality data, for which the MF estimates are considered most reliable. The catalog and an open-source implementation of MiMO are made publicly available to the community.
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All authors Lu Li, Zhengyi Shao, Zhaozhou Li, Xiaoting Fu

High Energy Astrophysical Phenomena

From Rare Events to a Population: Discovering Overlooked Extragalactic Magnetar Giant Flare Candidates in Archival Fermi Gamma-ray Burst Monitor Data

Aaron C. Trigg, Eric Burns, Michela Negro et al. (+16 more)

Magnetar giant flares (MGFs) are rare, extremely bright bursts of gamma-rays from highly magnetized neutron stars. These events are challenging to identify because, at extragalactic distances, they can appear similar to other astrophysical phenomena. Only a handful have been confidently identified to date, limiting our understanding of their origin and physical properties. This study focuses on expanding the sample of known events and enabling a more detailed characterization of their observational features and intrinsic properties, while introducing significant improvements in the methods used to identify and analyze them. When applied to archival data from the Gamma-ray Burst Monitor (GBM) on the \Fermi Gamma-ray Space Telescope, this approach added four previously unidentified events the known sample, expanding the total to 13 MGFs. This demonstrates both the effectiveness of the method and the likelihood that additional MGFs remain hidden in existing gamma-ray burst catalogs. We utilize this expanded sample to gain a deeper understanding of the broader population of MGFs. We develop a statistical modeling framework that combines previously considered data with modern observations from Fermi/GBM. The model accounts for instrumental sensitivity and the expected diversity in event characteristics. We infer a volumetric rate of events above $1.2\times10^{44}\,\rm{erg}$ of $R_{MGF}=5.5^{+4.5}_{-2.7}\times10^5\rm{Gpc^{-3}yr^{-1}}$. The results show that individual magnetars must produce multiple flares throughout their lifetimes, reinforcing the idea that these are recurring phenomena rather than singular explosive events. Expanding the sample of known MGFs improves our understanding of magnetars and their role in other astrophysical phenomena, including possible links to fast radio bursts, gravitational waves, and the creation of heavy elements in extreme astrophysical environments.
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All authors Aaron C. Trigg, Eric Burns, Michela Negro, Suman Bala, P.N. Bhat, William H. Cleveland, Dmitry D. Frederiks, Adam Goldstein, Boyan A. Hristov, Daniel Kocevski, Niccolò Di Lalla, Stephen Lesage, Bagrat Mailyan, Eliza Neights, Nicola Omodei, Oliver J. Roberts, Lorenzo Scotton, Dmitry S. Svinkin, Joshua Wood