Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Euler-Heisenberg actions for gauge-axial background vectors: Hessian diagonalization, sector classification, and applications
Lucas Pereira de Souza
We derive the closed-form one-loop Euler-Heisenberg effective actions for Dirac
fermions coupled simultaneously to classical electromagnetic vector and massive pseudo-vector backgrounds within a controlled quasi-static approximation. Through complete diagonalization of the functional Hessian, we systematically delineate the parameter space into distinct sectors characterized by stability properties and spectral structure. We identify subspaces that encompass and extend results from previous studies into a broader class, admitting propagating axial fields as physically viable regimes; strikingly, we note sectors presenting chirality-asymmetric instability. This addresses long-standing questions regarding the well-defined nature, diagonalizability, and stability of these models. From the effective actions, we derive novel nonperturbative pair-production rates for simultaneously propagating electromagnetic and axial vector backgrounds; remarkably, we find pronounced
vacuum stabilization compared to previous results. Furthermore, we derive the non-perturbative contributions to the
chiral current divergence, which enables dynamical
chiral symmetry breaking and show that the electromagnetic coupling induces instanton-like configurations for the axial field, even when it is not a fundamental gauge field. As a proof-of-concept, we analyze a cosmological toy model of baryogenesis driven by an axial vector, providing numerical estimates that support the viability of this hypothesis. Additionally, we outline qualitative predictions for Weyl/Dirac semi-metals and briefly discuss potential applications in related phenomena, such as
Quark-
Gluon plasma, Electroweak scenarios and the Strong-CP problem.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Ultra-relativistic freeze-out: a bridge from WIMPs to FIMPs
Stephen E. Henrich, Yann Mambrini and Keith A. Olive
We re-examine the case for dark matter (DM) produced by ultra-relativistic freeze-out (UFO). UFO is the mechanism by which Standard Model (SM)
neutrinos decouple from the radiation bath in the early universe at a temperature $T_{d} \approx 1$ MeV. This corresponds to chemical freeze-out without Boltzmann suppression, such that the freeze-out (decoupling) temperature $T_{d}$ is much greater than $m_{\nu}$ and the
neutrinos are therefore ultra-relativistic at freeze-out. While UFO has historically been rejected as a viable mechanism for DM production due to its association with hot DM and the accompanying incompatibility with $\Lambda$CDM, we show that when the approximation of instantaneous reheating after inflation is lifted, UFO can produce cold DM and account for the entire observed relic density in large regions of parameter space. In fact, DM with masses ranging from sub-eV to PeV scales can undergo UFO and be cold before structure formation, given only a simple perturbative, post-inflationary reheating period prior to radiation domination. For some interactions, such as a contact interaction between the
Higgs and DM scalars, there is a seamless transition between the WIMP and FIMP regimes which excludes UFO. However, for many other interactions, such as SM
fermions producing fermionic DM via a heavy scalar or vector mediator, the WIMP to FIMP transition occurs necessarily via a large intermediate region corresponding to UFO. We characterize the general features of UFO in this paper, while we supply a more detailed analysis in a companion paper. We find that UFO during reheating can produce the correct relic density ($\Omega_{\chi}h^2 = 0.12$) for DM masses spanning about 13 orders of magnitude, reheating temperatures spanning 17 orders of magnitude, and beyond the Standard Model (BSM) effective interaction scales spanning 11 orders of magnitude.
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Solar and Stellar Astrophysics
Decoding the RVb Enigma of DF Cyg: Pulsations, Circumstellar Disks, and Post-RGB Evolution Revealed by Multi-Wavelength Observations
Cenk Kayhan and Timur Şahin
This investigation integrates five decades of ground-based photometric data from the AAVSO, AFOEV, ASAS, ASAS-SN, and SuperWASP surveys with recently acquired TESS observations, conducting a multi-wavelength and multi-phase photometric analysis to elucidate the complex nature of DF Cyg. For the first time, we analyze approximately four years of Kepler data alongside TESS observations. Furthermore, TESS observations obtained in 120-second cadence mode, constitute the highest-precision photometric
dataset for DF Cyg to date. By isolating long-term trends in the TESS data, we quantified short-term variations in the fundamental pulsation frequency and its integer harmonics. The two alternating short-term cycles in the TESS light curve facilitated the unambiguous identification of seven previously undetected integer harmonics of the fundamental frequency in the power spectrum, providing critical new insights into the
star's complex pulsation dynamics. A periodogram analysis of the combined ground- and space-based
datasets revealed approximately 35 frequencies linked to both long- and short-term variability mechanisms.
Stellar parameters derived from
Gaia DR3 data specifically, luminosity and radius estimates based on Type II Cepheid PL and PR relations demonstrate consistency with values obtained through SED modeling. Complementary high-resolution spectroscopic analysis of DF Cyg yielded atmospheric parameters of Teff = 4781 K, logg = 1.74 dex, and [FeH] = -0.07 dex, further constraining physical characteristics of the
star. This synthesis of multi-epoch, multi-instrument data advances the understanding of pulsational behavior and evolutionary status in RV Tauri systems. Our findings highlight DF Cyg as a critical
benchmark for its class, as its characteristics bridge the gap between post-RGB systems in the Magellanic Clouds and higher-luminosity post-AGB
stars.
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Earth and Planetary Astrophysics
A JWST Transit of a Jupiter Analog I: Constraints on the Oblateness of Kepler-167e
Ben Cassese, David Kipping, Quentin Changeat et al. (+5 more)
In October 2024 JWST observed a transit of Kepler-167e, a Jupiter-analog
planet on a 1000+ day orbit. These observations, recorded over a long baseline of nearly 60 hours, were designed to search for signatures of planetary oblateness and/or exomoons comparable to Ganymede. In this first in a series of studies analyzing these data we report on constraints on Kepler-167e's oblateness. We explored a large grid of data reduction pipelines and modeling choices, including a new entirely independent reduction pipeline ("katahdin") and two new treatments for limb darkening. We find that under a
Bayesian model comparison framework the data are fit equally well by both spherical and oblate
planet models, and that our ability to constrain the oblateness is negatively impacted by the influence of exposure-long trends. Using the most conservative of our posteriors, we place a 95% upper bound on the projected oblateness of $f<0.097$, which corresponds to a rotation period of $P\geq7.11$ hours if the
planet's
spin axis is aligned with the sky plane. We note, however, that the final bound depends on the choice of reduction pipeline and systematics model, and that our suite of end-to-end analyses produced bounds as low as $f<0.065$ at 95%. We conclude that leveraging JWST to make tighter constraints on planetary oblateness will require further investigation into mitigating exposure-long trends and correlated noise.
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All authors Ben Cassese, David Kipping, Quentin Changeat, Daniel A. Yahalomi, Justin Vega, Yayaati Chachan, Billy Edwards, Alex Teachey
Astrophysics of Galaxies
GMCs and Star Formation in the Galaxy: I. Effects of an HII region on a GMC
David Hollenbach, Antonio Parravano and Christopher McKee
The destruction of
Giant Molecular Clouds is a key component in
galaxy evolution. We theoretically model the destruction of GMCs by HII regions, which evaporate ionized gas and eject neutral gas during their expansion. HII regions follow one of three tracks, depending on the EUV luminosity, $S$, of the ionizing OB association: the expansion can stall inside the cloud; it can break out, forming a blister (champagne) flow; or, for $S>S_{\rm com}$, it can result in the formation of a cometary cloud. We present results for the accumulated mass loss, $M_{\rm loss}(t)$, and the final mass loss, $M_{{\rm loss},f}$, by evaporation and ejection for a range of cloud masses ($10^4<M<10^{7}$ M$_\odot$), cloud surface densities ($50<\Sigma<1000$ M$_\odot$ pc$^{-2}$), OB association luminosities ($10^{44}<S<10^{52}$ s$^{-1}$), and off-center position of the association. We do not consider starbursts; our neglect of radiation pressure restricts our treatment to $S<10^{52} [(M/10^6$ M$_\odot)^{0.3})/(\Sigma /100$ M$_\odot$ pc$^{-2}$)] s$^{-1}$, and our neglect of
gravity restricts $(M/10^6$ M$_\odot$)($\Sigma/ 100$ M$_\odot$ pc$^{-2}) < 10$. We find that $M_{{\rm loss},f}$ for the range $0.1 < M_{{\rm loss},f}/M < 0.7$ , is proportional to $S^p$, where $p\sim 0.45-0.75$ depends on $M$, $\Sigma$, and association position. We find analytic fits to $S_{\rm com}$ as a function of $\Sigma$, $M$, and association position. $S> S_{\rm com}$ associations destroy at least 70% of the initial cloud. We find a critical cloud mass $M_{\rm survive}$ above which clouds never become cometary and lose $<$ 70% of their mass via a single association. Low mass clouds mostly lose mass via ejection of neutral gas.
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Cosmology and Nongalactic Astrophysics
Primordial Black Holes from Kinetic Preheating
Peter Adshead, Eve Currens and John T. Giblin Jr
We demonstrate that violent kinetic preheating following inflation can lead to the formation of black holes in the early Universe. In $\alpha$-attractor models with derivative inflaton couplings, nonlinear amplification of field fluctuations drives large spacetime
curvature and gravitational collapse shortly after inflation ends. Using fully general-relativistic
lattice simulations, we find that these dynamics produce black holes with masses of order tens of grams at sub-horizon scales, without requiring large
primordial curvature perturbations. Although such micro-black holes evaporate rapidly via Hawking radiation, their formation modifies the post-inflationary equation of state and their evaporation can successfully reheat the Universe before Big Bang nucleosynthesis. These results identify kinetic preheating as a new, efficient channel for black-hole production and establish a direct connection between inflationary
symmetries and strong-
gravity phenomena at reheating.
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High Energy Astrophysical Phenomena
Plasma flow in force-free magnetospheres: two-fluid model near pulsars and black holes
Morifumi Mizuno, Samuel E. Gralla and Alexander Philippov
Force-free electrodynamics describes the electromagnetic field of the magnetically dominated
plasma found near
pulsars and active black holes, but gives no information about the underlying particles that ultimately produce the observable emission. Working in the two-fluid approximation, we show how particles can be "painted on" to a force-free solution as a function of boundary conditions that encode the particle output of "gap regions" where the force-free approximation does not hold. These boundary conditions also determine the leading parallel electric field in the entire magnetosphere. Our treatment holds in a general (possibly curved) spacetime and is phrased in
language intrinsic to the 1+1 dimensional "field sheet spacetimes" experienced by particles stuck to
magnetic field lines. Besides the new results, this provides an elegant formulation of some standard equations; for example, we show that the zero-gyroradius guiding center approximation is just the Lorentz force law on the field sheet. We derive a general perturbative method and apply it to
pulsar and black hole magnetospheres with radial
magnetic fields to produce fully analytic models that capture key features of the full problem. When applied to more realistic
magnetic field configurations together with simulation-informed boundary conditions for the gap regions, this approach has the potential to provide global magnetosphere models without the need for global particle-in-
cell simulations.
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Astrophysics of Galaxies
Bars in low-density environments rotate faster than bars in dense regions
Natalia Puczek, Tobias Géron, Rebecca J. Smethurst et al. (+1 more)
Does the environment of a
galaxy directly influence the kinematics of its bar? We present observational evidence that bars in high-density environments exhibit significantly slower rotation rates than bars in low-density environments.
Galactic bars are central, extended structures composed of
stars,
dust and gas, present in approximately 30 to 70 per cent of luminous spiral
galaxies in the local Universe. Recent simulation studies have suggested that the environment can influence the bar rotation rate, $R$, which is used to classify bars as either fast ($1\leq R \leq1.4$) or slow ($R \gt 1.4$). We use estimates of $R$ obtained with the Tremaine-Weinberg method applied to Integral Field Unit spectroscopy from MaNGA and CALIFA. After cross-matching these with the projected neighbour density, $\log\Sigma$, we retain 286
galaxies. The analysis reveals that bars in high-density environments are significantly slower (median $R = 1.65^{+0.13}_{-0.11}$) compared to bars in low-density environments (median $R = 1.39^{+0.09}_{-0.08}$); Anderson-Darling $\textit{p}$-value of $p_{\mathrm{AD}}= 0.002$ ($3.1\,\sigma$). This study marks the first empirical test of the hypothesis that fast bars are formed by global instabilities in isolated
galaxies, while slow bars are triggered by
tidal interactions in dense environments, in agreement with predictions from numerous $\textit{N}$-body simulations. Future studies would benefit from a larger sample of
galaxies with reliable Integral Field Unit data, required to measure bar rotation rates. Specifically, more data are necessary to study the environmental influence on bar formation within dense settings (i.e. groups, clusters and filaments).
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All authors Natalia Puczek, Tobias Géron, Rebecca J. Smethurst, Chris J. Lintott
Astrophysics of Galaxies
The origin of ionized gas in retired galaxies: dynamical clues
Greique A. Valk and Sandro B. Rembold
We investigate the kinematical and dynamical properties of quiescent cluster
galaxies with weak emission lines, referred to as retired (R), and those without emission lines, dubbed passive (P), to better understand the origin of the ionized gas in R
galaxies and what drives the differences between these populations. We stack 2,907 P and 2,387 R
galaxies from 336 relaxed
galaxy clusters to build an ensemble cluster and estimate their projected number density and velocity dispersion profiles, $\sigma_P(R)$, as well as their projected phase-space (PPS) distributions. Additionally, we apply the MAMPOSSt code and the Jeans equation inversion technique to constrain the velocity anisotropy profiles, $\beta(r)$. We find that P
galaxies tend to reside closer to the cluster centres than R
galaxies, and that both populations exhibit similar $\sigma_P(R)$ and $\beta(r)$ profiles, regardless of their
stellar mass,
stellar age, or morphology. The only exception is elliptical R
galaxies, which are marginally more concentrated and display more radial orbits than their P counterparts. PPS analyses indicate that R
galaxies were, on average, accreted later than P
galaxies, except for those with $D_n4000 > 1.86$ or elliptical morphology. These results suggest that R
galaxies, though accreted more recently, have already had enough time to evolve towards a dynamical state more consistent with that of the dynamically relaxed P population. Finally, our findings suggest that the ionized gas in early-type R
galaxies likely originates from
accretion from their own hot gas
haloes, and that its removal triggers the transition toward the P phase over relatively long timescales.
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High Energy Astrophysical Phenomena
The complicated nature of the X-ray emission from the field of the strongly lensed hyperluminous infrared galaxy PJ1053+60 at z=3.549
Carlos Garcia Diaz, Q. Daniel Wang, Kevin C. Harrington et al. (+12 more)
We present an analysis of XMM-Newton X-ray observations of PJ1053+60, a hyperluminous infrared
galaxy (HyLIRG) at z=3.549 that is strongly lensed by a foreground group at z=0.837. We also present GNIRS spectroscopy confirming the presence of an active
galactic nucleus (AGN) to the southwest of PJ1053+60 ($AGN_{SW}$) at $z_{SW}$ = 1.373 $\pm$ 0.006. Using this
redshift prior, we decompose the X-ray spectrum of PJ1053+60 into $AGN_{SW}$ and high-mass X-ray binary (HMXB) components from the HyLIRG. The HMXB component has an unusually high luminosity, $\sim$ 50 times higher than calibration derived from local
galaxies, and a characteristic
photon index likely too flat to be caused by high-mass X-ray binaries at rest frame energies above a few keV. Our 2-D spatial decomposition also suggests a similarly high X-ray HMXB luminosity, although the limited spatial resolution prevents meaningful morphological constraints on the component. We conclude that the enhanced X-ray emission may only be explained by the presence of another AGN ($AGN_{FG}$) embedded in the foreground group
lensing the PJ1053+60 system. The presence of $AGN_{FG}$ is further supported by the detection of a point-like
radio continuum source that coincides with the brightest group
galaxy (BGG) of the foreground lens. Our study demonstrates the limited capability of current X-ray observatories while highlighting the need for higher angular resolution observations to definitively characterize the nature of X-ray emission in distant, strongly lensed HyLIRGs.
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All authors Carlos Garcia Diaz, Q. Daniel Wang, Kevin C. Harrington, James D. Lowenthal, Patrick S. Kamieneski, Eric F. Jimenez-Andrade, Nicholas Foo, Min S. Yun, Brenda L. Frye, Dazhi Zhou, Amit Vishwas, Ilsang Yoon, Belen Alcalde Pampliega, Daizhong Liu, Massimo Pascale
Astrophysics of Galaxies
Shaping the Milky Way. II. The dark matter halo's response to the LMC's passage in a cosmological context
Elise Darragh-Ford, Nicolas Garavito-Camargo, Arpit Arora et al. (+15 more)
The distribution of dark matter in the Milky Way (MW) is expected to exhibit a large-scale dynamical response to the recent infall of the LMC. This event produces a dynamical friction wake and shifts the MW's
halo density center. The structure of this response encodes information about the LMC- MW mass ratio, the LMC's orbit, the MW
halo's pre-infall structure and could provide constraints on dark matter physics. To extract this information, a method to separate these effects and recover the initial shape of the MW's
halo is required. Here, we use basis function expansions to analyze the
halo response in eighteen simulations of MW-LMC-like interactions from the MWest cosmological, dark-matter-only zoom-in simulations. The results show that mergers similar to the LMC consistently generate a significant dipole and a secondary quadrupole response in the
halo. The dipole arises from the host density center displacement and
halo distortions, and its amplitude scales as the square of the MW-LMC mass ratio, peaking 0.2-0.7 Gyr after the LMC's pericenter. The quadrupole's strength depends primarily on the original axis ratios of the host
halo, though contributions from the dynamical friction wake cause it to peak less than 0.3 Gyr before pericenter. Future measurements of both the dipole and quadrupole imprints of the LMC's passage in the density of the MW's
stellar halo should be able to disentangle these effects and provide insight into the initial structure of the MW's
halo, the MW's response, and the mass of the LMC.
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All authors Elise Darragh-Ford, Nicolas Garavito-Camargo, Arpit Arora, Risa H. Wechsler, Phil Mansfield, Gurtina Besla, Michael S. Petersen, Martin D. Weinberg, Silvio Varela-Lavin, Deveshi Buch, Emily C. Cunningham, Kathryne J. Daniel, Facundo A. Gomez, Kathryn V. Johnston, Chervin F. P. Laporte, Yao-Yuan Mao, Ethan O. Nadler, Robyn Sanderson
Solar and Stellar Astrophysics
Investigating the Role of Protostellar Variability with PRIMA Using Monte Carlo Simulations
Rachel R. Lee, Cara Battersby, Aleksandra Kuznetsova et al. (+5 more)
Evidence suggests that protostellar outbursts likely play a critical role in the
stellar mass assembly process, but the extent of this contribution is not well understood. Using the proposed observing program of PRIMA, a concept far-IR observatory (PRIMA GO Case #43 in Moullet et al. 2023), we examine the probe's ability to unambiguously determine whether or not variable
accretion events dominate the
stellar mass assembly process ($M_{\rm burst}\geq0.5M_{*}$). To do this, we construct multiple protostellar ensembles using Herschel 70$\mu$m flux data and evolve them using a toy Monte Carlo simulation through steady-state and high magnitude
accretion events. Ensembles are observed at various epochs in the
evolution process to conclude how many large amplitude outbursts are observationally recoverable during the proposed program. Based on our synthetic observations and our simulation specifications, we determine that observing a protostellar ensemble of at least 2000 protostars using PRIMA's proposed program is sufficient for determining the importance of protostellar outbursts in the
stellar mass assembly process.
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All authors Rachel R. Lee, Cara Battersby, Aleksandra Kuznetsova, Doug Johnstone, William J. Fischer, Henrik Beuther, Yasuhiro Hasegawa, Marta Sewilo
Earth and Planetary Astrophysics · Cross-listed from physics.ao-ph
Computing the Full Earth System at 1 km Resolution
Daniel Klocke, Claudia Frauen, Jan Frederik Engels et al. (+24 more)
We present the first-ever global simulation of the full Earth system at 1.25 km grid spacing, achieving highest time compression with an unseen number of degrees of freedom. Our model captures the flow of energy, water, and carbon through key components of the Earth system: atmosphere, ocean, and land. To achieve this landmark simulation, we harness the power of 8192 GPUs on Alps and 20480 GPUs on JUPITER, two of the world's largest GH200 superchip installations. We use both the Grace CPUs and Hopper GPUs by carefully balancing Earth's components in a heterogeneous setup and optimizing acceleration techniques available in ICON's codebase. We show how separation of concerns can reduce the code complexity by half while increasing performance and portability. Our achieved time compression of 145.7 simulated days per day enables long studies including full interactions in the Earth system and even outperforms earlier atmosphere-only simulations at a similar resolution.
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All authors Daniel Klocke, Claudia Frauen, Jan Frederik Engels, Dmitry Alexeev, René Redler, Reiner Schnur, Helmuth Haak, Luis Kornblueh, Nils Brüggemann, Fatemeh Chegini, Manoel Römmer, Lars Hoffmann, Sabine Griessbach, Mathis Bode, Jonathan Coles, Miguel Gila, William Sawyer, Alexandru Calotoiu, Yakup Budanaz, Pratyai Mazumder, Marcin Copik, Benjamin Weber, Andreas Herten, Hendryk Bockelmann, Torsten Hoefler, Cathy Hohenegger, Bjorn Stevens
Astrophysics of Galaxies
Quasars acting as Strong Lenses Found in DESI DR1
Everett McArthur, Martin Millon, Meredith Powell et al. (+52 more)
Quasars acting as strong gravitational lenses offer a rare opportunity to probe the
redshift evolution of scaling relations between supermassive black holes and their host
galaxies, particularly the $M_{\mathrm{BH}}$–$M_{\mathrm{host}}$ relation. Using these powerful probes, the mass of the host
galaxy can be precisely inferred from the Einstein radius $\theta_{\mathrm{E}}$. Using 812{,}118
quasars from DESI DR1 ($0.03 \leq z \leq 1.8$), we searched for
quasars lensing higher-
redshift galaxies by identifying background emission-line features in their spectra. To detect these rare systems, we trained a convolutional neural network (CNN) on mock lenses constructed from real DESI spectra of
quasars and emission-line
galaxies (ELGs), achieving a high classification performance (AUC = 0.99). We also trained a regression network to estimate the
redshift of the background ELG. Applying this pipeline, we identified seven high-quality (Grade~A) lens candidates, each exhibiting a strong [O\,ii] doublet at a higher
redshift than the foreground
quasar; four candidates additionally show H$\beta$ and [O\,iii] emission. These results significantly expand the sample of
quasar lens candidates beyond the twelve identified and three confirmed in previous work, and demonstrate the potential for scalable, data-driven discovery of
quasars as strong lenses in upcoming spectroscopic surveys.
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All authors Everett McArthur, Martin Millon, Meredith Powell, Risa H. Wechsler, Zhiwei Pan, Małgorzata Siudek, Jonas Spiller, Jessica Nicole Aguilar, Steven Ahlen, Abhijeet Anand, Segev BenZvi, Davide Bianchi, David Brooks, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, Arjun Dey, Peter Doel, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Hiram K. Herrera-Alcantar, Klaus Honscheid, Mustapha Ishak, Dick Joyce, Stephanie Juneau, David Kirkby, Theodore Kisner, Anthony Kremin, Ofer Lahav, Claire Lamman, Martin Landriau, Laurent Le Guillou, Marc Manera, Aaron Meisner, Ramon Miquel, Seshadri Nadathur, Nathalie Palanque-Delabrouille, Will Percival, Claire Poppett, Francisco Prada, Ignasi Pérez-Ràfols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Hee-Jong Seo, Joseph Harry Silber, David Sprayberry, Gregory Tarlé, Benjamin Alan Weaver, Rongpu Zhou, Hu Zou
Astrophysics of Galaxies
An Extended, Physically Calibrated FP for Elliptical Galaxies
Tarek Yehia
We present a physically motivated extension of the FP for elliptical
galaxies, derived from the scalar virial
theorem and calibrated using observational data. Starting from the basic
equilibrium condition, we incorporate key physical parameters that govern
galaxy structure and dynamics, namely
stellar mass-to-light ratio, central dark matter fraction, and structural non-homology as traced by the Sersic profile. The resulting model retains the original dependencies on velocity dispersion and surface brightness, but introduces physically interpretable corrections that significantly improve the fit to real data. Using a large
galaxy sample, we demonstrate that this extended FP achieves a higher level of accuracy than the classical form, with all parameters showing strong statistical significance. Our results indicate that the observed FP can be understood as an empirical refinement of the virial prediction, once variations in
stellar populations, dark matter content, and internal structure are taken into account. This work provides a unified framework that bridges theoretical expectations with observed scaling relations in elliptical systems.
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Astrophysics of Galaxies
Star Formation Histories and Stellar Dynamics in the Central Galaxies of RX J0820.9+0752, A1835, and PKS 0745-191
Marie-Joëlle Gingras, B.R. McNamara, Alison L. Coil et al. (+5 more)
We present Keck
Cosmic Web Imager observations of
stellar populations in three
galaxies lying at the centers of cooling flow clusters. All three host rich molecular gas reservoirs and show prominent Balmer absorption from $30-100$ Myr-old
stars consistent with long lasting
star formation. Two systems, A1835 and PKS 0745$-$191, have spatially extended young
stellar populations in their centers with recent
star formation rates of 100 M$_{\odot}$ yr$^{-1}$ and 8 M$_{\odot}$ yr$^{-1}$, respectively. In A1835 we uncover a blueshifted clump of young
stars moving at high speed with respect to the gas and central
galaxy. We suggest these
stars formed in a gaseous
outflow and have since detached from their natal gas and are now falling inward. This result indicates that
star formation is proceeding in a dynamically complex environment shaped by the central
galaxy's motion relative to cooling clouds and the feedback from
radio jets. In RX J0820.9+0752 intermediate-age
stars are found in a filament outside the
nucleus with no discernible
star formation at the center of the
galaxy. All projected
galaxies consist of old
stellar populations with deep D4000 breaks and lack detectable warm gas. While they may interact gravitationally with the central
galaxy, they cannot have donated the upward of $10^{10}~ M_{\odot}$ of molecular gas found in these systems. These results highlight the importance of analyzing spatially resolved
stellar kinematics and
star formation histories in brightest cluster
galaxies, an approach that remains relatively understudied.
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All authors Marie-Joëlle Gingras, B.R. McNamara, Alison L. Coil, Serena Perrotta, Fabrizio Brighenti, S. Peng Oh, H.R. Russell, Wenmeng Ning
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Dark neutron stars from a heavy dark sector
Jacob A. Litterer and João G. Rosa
We study the formation and properties of dark
neutron stars in a scenario where dark matter is made up of (heavy) dark
baryons in a sequestered copy of the MSSM. This scenario naturally explains the coincidence of baryonic and dark matter abundances without the need for tuning particle masses. In particular, the supersymmetry breaking scales in the visible and dark sectors may differ by up to 10-11 orders of magnitude. We argue that dark
neutrons should be the lightest dark
baryons, but that dark
protons may be cosmologically long lived. This allows a small fraction of dark matter to remain ionized until the first
halos start to form, providing cooling mechanisms that foster the gravitational collapse and fragmentation of sub-
halo structures, ultimately resulting in dark
neutron star and black hole formation. For a wide range of model parameters, we find dark
neutron stars with generally smaller mass and radius than ordinary visible sector
neutron stars. We also discuss their potential detectability, particularly through gravitational microlensing and dark
magnetic dipole radiation at
radio frequencies through
photon-dark
photon kinetic mixing.
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Astrophysics of Galaxies
ODIN: Using multiplicity of Lyman-Alpha Emitters to assess star formation activity in dark matter halos
M. Candela Cerdosino, Nelson Padilla, Ana Laura O'Mill et al. (+16 more)
We investigate if systems of multiple Lyman-alpha emitters (LAEs) can serve as a proxy for dark matter
halo mass, assess how their radiative properties relate to the underlying
halo conditions, and explore the physics of
star formation activity in LAEs and its relation to possible physically related companions. We use data from the One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey, which targets LAEs in three narrow
redshift slices. We identify physically associated LAE multiples in the COSMOS field at $z = 2.4$, $z = 3.1$, and $z=4.5$, and use a mock catalog from the IllustrisTNG100 simulation to assess the completeness and contamination affecting the resulting sample of LAE multiples. We then study their statistical and radiative properties as a function of multiplicity, where we adopt the term multiplicity to refer to the number of physically associated LAEs. We find a strong correlation between LAE multiplicity and host
halo mass in the mocks, with higher multiplicity systems preferentially occupying more massive
halos. In both ODIN and the mock sample, we find indications that the mean Ly$\alpha$ luminosity and UV magnitude of LAEs in multiples increase with multiplicity. The
halo-wide LAE surface brightness densities in Ly$\alpha$ and UV increase with multiplicity, reflecting more compact and actively
star-forming environments. The close agreement between the model and ODIN observations supports the validity of the Ly$\alpha$ emission model in capturing key physical processes in LAE environments. Finally, a subhalo-based perturbation induced
star formation model reproduces the minimum subhalo mass distribution in simulations at $z=2.4$, suggesting that local perturbations, rather than the presence of LAE companions, drive
star formation in these systems. For the higher
redshifts, neighbor perturbations do not seem to be the main driver that triggers
star formation.
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All authors M. Candela Cerdosino, Nelson Padilla, Ana Laura O'Mill, Eric Gawiser, Nicole M. Firestone, M. Celeste Artale, Kyoung-Soo Lee, Changbom Park, Yujin Yang, Caryl Gronwall, Lucia Guaita, Sungryong Hong, Ho Seong Hwang, Woong-Seob Jeong, Ankit Kumar, Jaehyun Lee, Seong-Kook Joshua Lee, Paulina Troncoso Iribarren, Ann Zabludoff
Earth and Planetary Astrophysics
ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY) - II. Time series of Balmer line profiles of Delorme 1(AB)b
Dorian Demars, Mickaël Bonnefoy, Catherine Dougados et al. (+14 more)
Accretion processes in the planetary-mass regime remain poorly constrained, yet they strongly influence
planet formation,
evolution, and the composition of circumplanetary disks (CPDs). We investigate the resolved Balmer hydrogen emission-line profiles and their variability in the ~13Mjup, 30-45 Myr-old companion Delorme to constrain the underlying
accretion mechanisms. Using VLT/UVES, we obtained 31 new epochs of high-resolution optical spectra (330-680 nm, R = 50,000), probing variability from hours to years. We analyze the shape and flux variability of hydrogen emission lines and compare them to two proposed origins: magnetospheric
accretion funnels and localized
accretion shocks. We detect Balmer lines from Halpha to H10 (6564-3799 AA) and a UV continuum excess, both indicative of ongoing
accretion. All features are variable. The hydrogen lines decompose into two static components that vary only in flux. The broader velocity component correlates strongly with the UV excess and is qualitatively consistent with magnetospheric funnel models, but not with shock models. This component dominates the shape variability. The narrower component, which correlates less with the UV excess, is better matched by shock-emission models and drives most of the flux variability. Line fluxes show low variability on hour timescales but up to ~100% over weeks, similar to T Tauri
stars. Our findings support magnetospheric
accretion as the origin of the broad component. The narrow component may arise from
accretion shocks or chromospheric activity. Higher-cadence observations could reveal rotational modulations and help constrain the object's rotation period and
accretion geometry.
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All authors Dorian Demars, Mickaël Bonnefoy, Catherine Dougados, Gayathri Viswanath, Simon C. Ringqvist, Markus Janson, Yuhiko Aoyama, Thanawuth Thanathibodee, Gabriel-Dominique Marleau, Carlo F. Manara, Elisabetta Rigliaco, Judith Szulágyi, Aurora Sicilia-Aguilar, Jérôme Bouvier, Evelyne Alecian, Simon Petrus, Mathis Houllé
Astrophysics of Galaxies
The lives and deaths of faint satellite galaxies around M31
Alex Merrow, Kyle A. Oman and Azadeh Fattahi
We present predictions for proper motions, infall times and times of first pericentric passage for 39 of M31's satellite
galaxies. We estimate these by sampling satellite orbits from cosmological N-body simulations matched on mass, distance and velocity along the line of sight, in addition to properties of the host system. Our predictions are probabilistic based on repeated sampling from the uncertainty distributions of all quantities involved. We use these constraints on the satellites' orbital histories in conjunction with their published
star formation histories to investigate the dominant environmental mechanisms for quenching satellites of M31-like hosts. Around half of the satellites appear to have quenched before their first pericentric passage around M31. Only the most massive satellites (with
stellar masses > 10^8 M_sun) are able to maintain
star formation for up to billions of years after infall. The majority of faint satellites, with
stellar masses < 10^8 M_sun , were likely quenched before entering the M31 system. We compare our results for M31 against predictions for the Milky Way's satellites from the literature; M31's has a more active recent
accretion history with more recently quenched satellites than the Milky Way.
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Earth and Planetary Astrophysics
Dust back-reaction on gas around planets modifies the cold thermal torque
Raúl O. Chametla, Ondřej Chrenko, F. J. Sánchez-Salcedo et al. (+7 more)
A nascent
planet in a gas disk experiences radial migration due to the different torques which act on it. It has recently been shown that the torques produced by the gas and
dust density variations around a non-accreting low-mass
planet, the so-called cold thermal and
dust streaming torques, can surpass each of the other torque components. We investigate how the total torque acting on the
planet is affected by the presence of
dust grains and their aerodynamic back-reaction on gas, while taking into account the cold thermal torque produced by thermal
diffusion in the gas component. We perform high-resolution local and global three-dimensional two-fluid simulations within the pressureless-fluid
dust approximation using the Fargo3D code. We explore the influence of different
dust species parameterized by the Stokes number, focusing on non-accreting protoplanets with masses from one-third the mass of Mars to one Earth mass. The
dust feedback has substantial impact on the asymmetry of the cold thermal lobes (which produce the cold thermal torque). However, the total torque is dominated by the
dust torque when St $>10^{-2}$. The
dust torque becomes more negative over time due to the formation of
dust lobes that resemble the cold thermal lobes that form in the gas component. Therefore, the
dust streaming torque prevails over the cold thermal torque. On the other hand, when St $\leq10^{-2}$, the
dust streaming torque is negligible and thus, the total torque on the
planet comes from the gaseous component of the disk. Our results suggest that a
planet embedded in a gas-
dust disk may experience stagnant migration or inward runaway migration in regions of the protoplanetary disk where the
dust is not fully coupled to the gas. However, this behaviour could change in regions with strong
dust-gas coupling or in the inner transition region of the disk, where the cold thermal torque may become relevant.
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All authors Raúl O. Chametla, Ondřej Chrenko, F. J. Sánchez-Salcedo, Mauricio Reyes-Ruiz, Clément Baruteau, Alicia Moranchel-Basurto, Joanna Drążkowska, Gabriel-Dominique Marleau, Yasuhiro Hasegawa, Sonia Cornejo
Earth and Planetary Astrophysics
Inferring the physics of protoplanetary disc evolution from the irradiated Cygnus OB2 region – A comparison of viscous and MHD wind-driven scenarios
Jesse Weder, Andrew J. Winter and Christoph Mordasini
Our current understanding has crystallised around two possible
evolution scenarios for protoplanetary discs (turbulent viscosity and magnetohydrodynamic (MHD) wind-driven) - but which dominates remains uncertain. Our aims are twofold: Firstly, we investigate whether a single set of model parameters can reproduce the observational constraints of non-irradiated and irradiated discs. Secondly, we propose a novel approach to break degeneracies between the two
evolution scenarios by studying the relation of
stellar accretion rate and externally driven wind mass-loss rates, which evolve differently depending on the mechanism of angular momentum transport in the outer disc. We evolve synthetic populations of protoplanetary discs using 1D vertically integrated models for both viscous and MHD wind-driven disc
evolution including both internal X-ray and external far ultraviolet (FUV) photoevaporation for both
evolution scenarios. We investigate both weak and strong FUV field environments, where the strong FUV field is calculated based on an environment similar to the Cygnus OB2 association. While both scenarios are able to reproduce observational constraints, our simulations suggest that different parameters are needed for the angular momentum transport to explain disc lifetimes and disc mass -
stellar accretion rate relation in weakly and strongly irradiated regions. We find that the predicted median disc radii are much larger in low FUV environments compared to Cygnus OB2, but also decreasing with time. In the viscous scenario, the median disc radius in a low FUV field environment is ~100au larger than for the MHD wind-driven scenario. We further show that studying
stellar accretion rates and externally driven wind mass-loss rates (provided that they can be isolated from internally driven winds; i.e. MHD wind) is indeed a promising way of disentangling the two
evolution scenarios.
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High Energy Astrophysical Phenomena
Identification and characterization of optical companions to the population of millisecond pulsars in the globular cluster M3
Greta Ettorre, Emanuele Dalessandro, Mario Cadelano et al. (+3 more)
The study of binary millisecond
pulsars (MSPs) in globular clusters (GCs) is a key ingredient to study binary and
stellar evolution under extreme conditions. In this context, an accurate analysis of the optical emission, which is mostly dominated by the companion
star, is essential for a comprehensive characterization of these systems and their role within their environment. In this work, we present a multi-wavelength investigation of five binary MSPs in the
Galactic GC M3 (NGC 5272) using archival Hubble Space
Telescope (HST) data. Our analysis builds on the timing solutions obtained with the FAST
radio Telescope by Li et al. (2024). For each MSP, we carry out precise astrometric cross-matching with the accurate
radio positions to identify potential counterparts. When a match is found, we analyse its location in the colour-magnitude diagrams and compare the results with updated binary
evolution models to infer the system properties. We confirm the identification of the optical companion to M3B, matching the source previously reported by Cadelano et al. (2019), and successfully identify and characterize the optical companions to M3D and M3F. All three are consistent with helium white
dwarfs, as expected from the canonical formation scenario. For M3A and M3E, no reliable counterparts are found, but we place strong upper limits on the brightness and mass of the undetected companion. In the case of M3E, we detect a red object near the
radio position in two F814W observations; however, astrometric measurements over a 15-year baseline reveal a significant proper motion inconsistent with cluster membership, identifying the source as a foreground contaminant. This study highlights the effectiveness of combining precise
radio timing with deep, multi-band HST images to uncover and constrain the nature of MSP companions in GCs, offering insights into their formation and evolutionary histories.
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All authors Greta Ettorre, Emanuele Dalessandro, Mario Cadelano, Cristina Pallanca, Paulo C. C. Freire, Alessandro Ridolfi
Cosmology and Nongalactic Astrophysics
A short blanket for cosmology: the CMB lensing anomaly behind the preference for a negative neutrino mass
Andrea Cozzumbo, Mattia Atzori Corona, Riccardo Murgia et al. (+2 more)
Recent analyses combining
cosmic microwave background (CMB) and
baryon acoustic oscillation (BAO) challenge particle physics constraints on the total
neutrino mass, pointing to values smaller than the lower limit from
neutrino oscillation experiments. To examine the impact of different CMB likelihoods from $\mathit{Planck}$,
lensing potential measurements from $\mathit{Planck}$ and ACT, and BAO data from DESI, we introduce an effective
neutrino mass parameter ($\sum \tilde{m}_{\nu}$) which is allowed to take negative values. We investigate its correlation with two extra parameters capturing the impact of gravitational
lensing on the CMB: one controlling the smoothing of the peaks of the temperature and polarization power spectra; one rescaling the
lensing potential amplitude. In this configuration, we infer $\sum \tilde{m}_{\nu}=-0.018^{+0.085}_{-0.089}~\text{eV}~(68\% ~\text{C.L.})$, which is fully consistent with the minimal value required by
neutrino oscillation experiments. We attribute the apparent preference for negative
neutrino masses to an excess of gravitational
lensing detected by late-time cosmological probes compared to that inferred from $\mathit{Planck}$ CMB angular power spectra. We discuss implications in light of the DESI BAO measurements and the CMB
lensing anomaly.
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All authors Andrea Cozzumbo, Mattia Atzori Corona, Riccardo Murgia, Maria Archidiacono, Matteo Cadeddu
Instrumentation and Methods for Astrophysics
Addressing prior dependence in hierarchical Bayesian modeling for PTA data analysis II: Noise and SGWB inference through parameter decorrelation
Eleonora Villa, Luigi D'Amico, Aldo Barca et al. (+4 more)
Pulsar Timing Arrays (PTA) provide a powerful framework to measure low-frequency gravitational waves, but accuracy and robustness of the results are challenged by complex noise processes that must be accurately modeled. Standard PTA analyses assign fixed uniform noise priors to each
pulsar, an approach that can introduce systematic biases when combining the array. To overcome this limitation, we adopt a hierarchical
Bayesian modeling strategy in which noise priors are parametrized by higher-level hyperparameters. To mitigate the sensitivity of the inferred parameters to the choice of noise hyperprior, we introduce a reparametrization of the hierarchical model based on the orthogonal projection of hyperparameters onto the physical parameter subspace. The transformation is implemented through Normalizing Flows (NFs), which provide an invertible, tractable representation and preserve shrinkage and inter-
pulsar information pooling in the reparametrized model. We also employ i-nessai, a flow-guided nested sampler, to efficiently explore the resulting higher-dimensional parameter space. We apply our method to a minimal 3-
pulsar case study, performing a simultaneous inference of noise and
stochastic gravitational wave background (SGWB) parameters. Despite the limited
dataset, the results consistently show that the reparametrized hierarchical treatment constrains the noise parameters more tightly and partially alleviates the red-noise-SGWB degeneracy, while the orthogonal reparametrization further enhances parameter independence without affecting the correlations intrinsic to the power-law modeling of the physical processes involved.
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All authors Eleonora Villa, Luigi D'Amico, Aldo Barca, Fatima Modica Bittordo, Francesco Alì, Massimo Meneghetti, Luca Naso
Instrumentation and Methods for Astrophysics
Improving Bayesian inference in PTA data analysis: importance nested sampling with Normalizing Flows
Eleonora Villa, Golam Mohiuddin Shaifullah, Andrea Possenti et al. (+1 more)
We present a detailed study of
Bayesian inference workflows for
pulsar timing array data with a focus on enhancing efficiency, robustness and speed through the use of normalizing flow-based nested sampling. Building on the Enterprise framework, we integrate the i-nessai sampler and
benchmark its performance on realistic, simulated
datasets. We analyze its computational scaling and stability, and show that it achieves accurate posteriors and reliable evidence estimates with substantially reduced runtime, by up to three orders of magnitude depending on the
dataset configuration, with respect to conventional single-core parallel-tempering MCMC analyses. These results highlight the potential of flow-based nested sampling to accelerate PTA analyses while preserving the quality of the inference.
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All authors Eleonora Villa, Golam Mohiuddin Shaifullah, Andrea Possenti, Carmelita Carbone
Earth and Planetary Astrophysics
The interstellar flux gap: From dust to kilometer-scale objects
Eloy Peña-Asensio and Darryl Z. Seligman
Context. Three kilometer-sized interstellar objects (ISOs) have been detected transiting the
Solar System, and spacecraft have directly measured micrometer-scale interstellar
dust (ISD). Yet no intermediate-size interstellar meteoroids have been identified in current meteor surveys. Aims. We test whether a power-law flux extrapolation connecting spacecraft ISD and kilometer-scale ISOs is consistent with meteor surveys, and we quantify the expected interstellar impacting flux based on various observational reports. Methods. We compiled differential fluxes and limits from spacecraft ISD, radar and optical meteor surveys, and theoretical estimates. We evaluated the power-law size-frequency fits, computed the 3I-like flux, and compared measured fluxes to predictions. Results. The spacecraft-measured
dust flux exceeds extrapolations constrained by meteor surveys and kilometer-scale ISOs by $\sim$2-7 orders of magnitude. An $r^{-3.0}$ fit combining spacecraft ISD detections with kilometer-scale ISOs overpredicts the number of meteors with
hyperbolic orbits, whereas slopes of $r^{-2.7}$-$r^{-2.3}$ (derived from radar and optical meteor upper limits, respectively) instead yield interplanetary-to-interstellar flux ratios of $10^{3}$-$10^{6}$. Conclusions. A simple power-law from ISD to ISOs is inconsistent with meteor survey constraints and yields unrealistic predictions for interstellar meteoroids. The data reveal a gap between submicron
dust entrained in the Local Interstellar Cloud (LIC) and macroscopic bodies ejected from planetary systems. This gap may reflect distinct origins and destruction-transport processes rather than a continuous size-frequency distribution. This would imply either the dominance of a small-particle LIC component or the need to reassess spacecraft
dust fluxes.
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Earth and Planetary Astrophysics
Precise Radial Velocities
Jennifer A. Burt, Xavier Dumusque and Samuel Halverson
Precise measurements of a
star's radial velocity (RV) made using extremely stable, high resolution, optical or near infrared spectrographs can be used to determine the masses and orbital parameters of gravitationally-bound extra-
solar planets (
exoplanets). Indeed, RV surveys and follow up efforts have provided the vast majority of published
exoplanet mass measurements and in doing so have enabled studies into
exoplanet interior and atmospheric compositions. Here we review the current state of the RV field, with particular
attention paid to: -The
evolution of precise RV methodologies over the past two decades -Modern RV spectrograph designs that can be calibrated to a stability level of better than 50 cm/s over timescales of years -RV data reduction and post-processing techniques that minimize the impact of instrument systematics and
stellar variability -Techniques for detecting
exoplanets in RV data and disentangling planetary signals from
stellar variability
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Solar and Stellar Astrophysics
Uncertainties in the production of iron-group nuclides in core-collapse supernovae from Monte Carlo variations of reaction rates
Nobuya Nishimura, Carla Froehlich and Thomas Rauscher
Core-collapse
supernovae, occurring at the end of massive
star evolution, produce heavy elements, including those in the iron peak. Although the explosion mechanism is not yet fully understood, theoretical models can reproduce optical observations and observed elemental abundances. However, many
nuclear reaction rates involved in explosive nucleosynthesis have large uncertainties, impacting the reliability of abundance predictions. To address this, we have previously developed a Monte Carlo-based nucleosynthesis code that accounts for reaction rate uncertainties and has been applied to nucleosynthesis processes beyond iron. Our framework is also well suited for studying explosive nucleosynthesis in
supernovae. In this paper, we investigate 1D explosion models using the "PUSH method", focusing on progenitors with varying
metallicities and initial masses around $M_\mathrm{ZAMS} = 16 M_{\odot}$. Detailed post-process nucleosynthesis calculations and Monte Carlo analyses are used to explore the effects of reaction rate uncertainties and to identify key reaction rates in explosive nucleosynthesis. We find that many reactions have little impact on the production of iron-group
nuclei, as these elements are primarily synthesized in the
nuclear statistical
equilibrium. However, we identify a few "key reactions" that significantly influence the production of radioactive
nuclei, which may affect astrophysical observables. In particular, for the production of ${}^{44}$Ti, we confirm that several traditionally studied
nuclear reactions have a strong impact. However, determining a single reaction rate is insufficient to draw a definitive conclusion.
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