Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Cosmic Birefringence and Axiogenesis
Raymond T. Co, Lawrence J. Hall, Keisuke Harigaya et al. (+1 more)
Recent analyses of Planck and ACT CMB data report a $2\text{-}4\sigma$ hint of isotropic
cosmic birefringence ($\beta \approx 0.3^\circ$), corresponding to a parity-violating rotation of polarization planes that points to potential new physics. We show that both the hint of
cosmic birefringence and the observed baryon asymmetry can be simultaneously explained by the rotation of an
axion-like field. The minimal setup predicts a positive birefringence angle, consistent with the CMB hint, and matter and kination domination ending around a temperature of $\mathcal O(3\text{-}50)$ MeV, making the model falsifiable by astrophysical probes and potentially giving rise to characteristic gravitational-wave signals. We also introduce a mechanism that can exponentially enhance the angular momentum of the rotation generated by the Affleck-Dine mechanism.
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All authors Raymond T. Co, Lawrence J. Hall, Keisuke Harigaya, Taegyu Lee
Astrophysics of Galaxies
CRIMSONS: An Online Tool for Modeling Chemical Enrichment with Stochastic IMF Sampling
Martina Rossi, Lapo Querci, Stefano Ciabattini et al. (+14 more)
Chemical enrichment is a universal process shaped by several interconnected factors, including stellar feedback, the nature of chemical polluters, and the underlying distribution of stellar masses. Three key ingredients are often difficult to treat simultaneously in chemical-
evolution models: the
stochastic sampling of the stellar IMF, uncertainties in stellar nucleosynthesis yields, and pre-enrichment from primordial PopIII
stars. In low
star-formation rate environments, incomplete IMF sampling makes enrichment sensitive to the random presence or absence of massive
supernova progenitors. Here, we present CRIMSONS, the first online tool designed to model chemical enrichment while self-consistently incorporating these three ingredients. The framework allows users to explore different IMFs, stellar population masses and
metallicities, and multiple stellar yield sets. It follows the
evolution of individual
stars and tracks 30 elements(H-Zn), including contributions from SN, AGB
stars, and TypeIa SNe. The current implementation adopts a closed-box framework, neglecting gas flows and spatial mixing, thus providing a controlled setup to isolate the effects of IMF sampling, stellar yields, and PopIII pre-enrichment. With CRIMSONS, we show that incomplete IMF sampling produces large abundance scatter, particularly in low-mass stellar populations. Different yield prescriptions introduce element-dependent variations, while some abundance ratios remain comparatively robust across models. Finally, comparison between models including primordial enrichment and those adopting only a
metallicity floor shows that PopIII pre-enrichment can significantly affect subsequent chemical
evolution. CRIMSONS therefore provides a controlled framework for quantifying the relative impact of
stochastic IMF sampling, nucleosynthetic uncertainties, and primordial pre-enrichment on predicted abundance patterns
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All authors Martina Rossi, Lapo Querci, Stefano Ciabattini, Stefania Salvadori, Irene Vanni, Davide Massari, Edoardo Ceccarelli, Donatella Romano, Viola Gelli, Raffaele Pascale, Alice Mori, Elka Rusta, Ioanna Koutsouridou, Ása Skúladóttir, Laura Magrini, Riano Giribaldi, Jose Schiappacasse-Ulloa
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Quarkyonic matter suppresses neutron-star $g$ modes and reverses their mass trend
Probit J Kalita and Bharat Kumar
Gravity (g) modes are the only
neutron-
star oscillations that report on the composition of dense matter rather than on its stiffness, and work on hybrid
stars has established that a first-order
quark transition raises their frequency. Quarkyonic matter does the opposite.
Quark-nucleon chemical
equilibrium is maintained by the strong interaction, so the
quarks acquire no thermodynamic freedom on an oscillation period and $c_s^2-c_e^2$ reduces to a positive-definite quadratic form in the lepton gradients alone. The nucleon momentum shell stiffens both sound speeds together instead of separating them, so the buoyancy factor collapses by a factor of 9.5 to 19 at an early transition and the core is left only weakly stratified. Solving the $l=2$ relativistic Cowling problem for ten equations of state that share one isoscalar sector, seven quarkyonic and three nucleonic controls at matched
symmetry-energy slope, we found the g-mode confined to the nucleonic shell outside the core, with the horizontal flow that it lives on excluded from the core while the core is displaced almost rigidly. Its frequency falls from 158-522 Hz across the controls to $81-254$~Hz across the quarkyonic models, and by 14% at 1.4$M_\odot$ for the matched pair at $L=50\mev$; more important than the shift, it decreases with mass where the controls rise. Writing each frequency as the dynamical frequency $(GM/R^3)^{1/2}$ times a dimensionless remainder separates structure from composition. The $f$ and $p_1$ trends prove to be inherited from the mass–radius relation; the $g_1$ remainder, constant to $2-9\%$ along a nucleonic sequence, falls by a quarter to a third along a quarkyonic one and departs by a factor of two from the nucleonic $g$-mode relation at fixed compactness and $L/K_0$. These are Cowling values, lower bounds at the ten-per-cent level, and the sign of the trend survives a correction of that size.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Universal $Z^{2/3}/\sqrt{Q_\alpha}$ Scaling Law in Alpha Decay from Nuclei to Neutron-Star Mergers
Hisham Anwer, B. Salah and A. R. Abdulghany
We establish a universal scaling law for $\alpha$-decay half-lives based on the variable $X_a = Z^a/\sqrt{Q_\alpha}$, which collapses experimental and theoretical data spanning over twenty orders of magnitude onto a single linear correlation. Global optimization over the complete set of even-even $\alpha$ emitters reveals a uniquely sharp optimum at $a \simeq 2/3$. This exponent is theoretically motivated by the leading
geometric scaling of heavy
nuclei and emerges quantitatively from the correlated nuclear systematics, driven by the correlated $(Z, Q_\alpha)$
manifold of the nuclear chart. Strikingly, five structurally distinct semi-empirical models and an independent microscopic WKB calculation, when independently optimized with respect to the exponent $a$, yield values clustered around $2/3$, while the corresponding $a=2/3$ correlations remain highly linear without refitting the original model parameters. This emergent scaling law implies smooth variations of decay times along the heavy $r$-process path. We demonstrate analytically that, given a roughly uniform distribution of this variable, the scaling law naturally supports a quasi-power-law radioactive heating rate ($\dot{\epsilon} \propto t^{-1.24}$), consistent with full network calculations. Furthermore, integrating these scaling predictions directly into nuclear source terms for radiative-
diffusion models yields multimessenger observables that accurately reproduce the kilonova AT2017gfo associated with the gravitational-wave event GW170817, demonstrating that the $Z^{2/3}/\sqrt{Q_\alpha}$ scaling coordinate provides a robust tool for modeling the radioactive engines of
neutron-
star mergers.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Event Detection and Finite-Grid Effects at an Imposed Absorbing Boundary in Newtonian Black Hole Orbit Integrations
Gregory M Davis
Numerical classification of black-hole orbits can depend on how prescribed inner capture or absorbing boundaries are implemented. This study investigated how discrete evaluation of such a boundary affects orbit classification. Massless particles were integrated about an isolated Newtonian point mass and initialized at periapsis with an absorbing boundary at rsink = 104RS. Because the Keplerian periapsis q is constant, the expected classification can be analytically determined. A classifier omitting evaluation at initialization can miss particles that already satisfy the removal criterion, but evaluation at t = 0 reproduced the analytic classification on every sampled grid. As the grid resolution increased, the inferred critical periapsis approached the imposed sink radius. These results demonstrate that an apparent critical periapsis can depend on both the imposed boundary and its numerical evaluation, emphasizing the need to distinguish numerical effects from genuine dynamical thresholds.
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Cosmology and Nongalactic Astrophysics
Statistical Fluctuations as Primordial Correlators in the CMB: Finite Chemical Potential Thermodynamics
Anish Ghoshal, Anupam Mazumdar and Bartłomiej Sikorski
Can primordial cosmological correlations originate from statistical fluctuations of an early-universe thermal system? We connect grand-canonical thermodynamics,
stochastic transport, and gauge-invariant cosmological perturbations for a charged fluid at finite chemical potential. Energy-charge susceptibilities determine
curvature, charge-isocurvature, and cross-correlation amplitudes, while transport sets when each mode leaves
equilibrium. For an isolated, adiabatic conformal
plasma with conserved charge-to-
entropy ratio and power-law
diffusion, diffusive freeze-out yields the universal spectrum $\mathcal P_S(k)\propto k^3$, with $n_{\rm iso}=4$, while equal-time local-
equilibrium curvature-isocurvature covariance vanishes in the conformal source basis. Thus neither finite chemical potential nor replacing Hubble crossing by
diffusion crossing alone yields approximate scale invariance. We evade this obstruction with an open subsystem of massless Dirac
fermions during a sourced quasi-de Sitter phase. There, grand-canonical energy cumulants generate a nearly scale-invariant red
curvature spectrum. A
benchmark gives $\mathcal P_{\zeta_X}(k_\star)=2.10\times10^{-9}$ and $n_s(k_\star)=0.9649$, stays within $0.30%$ of the fitted power law over $0.002\leq k/k_\star\leq4$, and predicts weak negative running and small positive intrinsic non-Gaussianity from higher-order cumulants, $f_{\rm NL}(k_\star)\simeq0.106$ and $g_{\rm NL}(k_\star)\simeq0.0158$. With a two-helicity
vacuum tensor spectrum, the tensor-to-scalar ratio is $r_{t/s}(k_\star)=1.82\times10^{-4}$. This isolates the limitation of isolated conformal thermal seeding and the open-system ingredient needed to overcome it. Thermal energy-charge fluctuations thus provide a calculable source of realistic scalar correlations, while reservoir dynamics, equilibration, and later
curvature-isocurvature transfer must come from a microscopic model.
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Cosmology and Nongalactic Astrophysics
Multi-Stage and Multi-Field Inflation in Random Inflationary Landscapes
Xingang Chen, Lucas Pinol, Zhong-Zhi Xianyu et al. (+1 more)
Generic potentials in an inflationary landscape are typically too steep to support a prolonged period of
cosmic inflation. Atypical flat regions of the landscape are required to support successful inflation. The occurrence of such regions leads broadly to two possibilities: a single prolonged period of slow-roll inflation (which we call single-stage inflation), or multiple shorter periods of inflation separated by transient departures from slow roll (which we call multi-stage inflation), giving rise to primordial features and other departures from the behavior of the simplest slow-roll model. The former is the possibility most commonly assumed when deriving the primordial density fluctuations for the Big Bang model. In this paper, using Gaussian random potentials as a simple model of the inflationary landscape, we study the relative occurrence of these two possibilities. We find a substantial fraction of multi-stage inflationary trajectories in landscapes with field-space dimensions one, two, and three, and this fraction increases with dimensionality at fixed typical landscape
curvature. In constructing the inflationary landscapes and identifying successful inflationary trajectories, we also define several relevant quantities and classify detailed properties of both multi-stage and multi-field inflationary trajectories.
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All authors Xingang Chen, Lucas Pinol, Zhong-Zhi Xianyu, Yisong Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Three-Flavoured Thermal Leptogenesis Without Tuning
Angus Spalding
We investigate thermal leptogenesis in an extension of the Type-I seesaw in which a real singlet scalar couples non-diagonally to the right-handed
neutrinos. The interactions $-y_{ij}\phi N_iN_j$, with $i\neq j$, introduce new sources of CP violation in heavy-
neutrino decays with a negligible enhancement of the standard leptonic washout. We derive an analytic upper bound on the scalar-induced CP asymmetry and present numerical results using fully flavoured Boltzmann equations and the density-
matrix formalism. We show that the observed baryon asymmetry can be generated with a hierarchical right-handed-
neutrino spectrum at the electroweak scale. In the minimal Type-I seesaw, lowering the scale of decay leptogenesis typically requires either a tuned quasi-degeneracy of the right-handed-
neutrino masses or cancellations between the tree-level and one-loop contributions to the light-
neutrino masses, while hierarchical leptogenesis instead requires a high scale that aggravates the
Higgs hierarchy problem. This singlet-scalar extension appears to avoid these tensions, allowing successful leptogenesis with a hierarchical right-handed-
neutrino spectrum down to the electroweak scale.
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Cosmology and Nongalactic Astrophysics
Tangled $\tau$: Planck CMB Constraints on Flash Reionization
Param Upadhyay, Elisa G. M. Ferreira and Evan McDonough
Recent cosmological tensions have renewed interest in the role of reionization in parameter inference, and flash reionization has been proposed as a transient high-
redshift ionization episode that can increase the Thomson optical depth while remaining compatible with CMB polarization data. In this work, we present the first Markov Chain Monte Carlo analysis of the flash reionization model fit to Planck
cosmic microwave background temperature, polarization, and
lensing data. We perform this analysis using Planck PR4 data in $\Lambda$CDM with flash reionization. We find that CMB data allow a wide range for the
redshift of the flash, $z_{\rm flash}$, but with constraints that are tightly correlated with the peak ionization fraction $x_{\rm flash}$. We find constraints $x_{\rm flash}=0.24 ^{+0.13} _{-0.07}$ and $x_{\rm flash}= 0.15 ^{+0.07} _{ - 0.05}$ for the
benchmark flash reionization scenarios with fixed $z_{\rm flash}=20$ and $25$ respectively. The standard $\Lambda$CDM parameters do not exhibit any significant shifts, and in particular, the total optical depth to reionization is not appreciably changed, with $\tau=0.061 \pm 0.007$ in flash reionization as compared to $\tau=0.059\pm 0.006$ in the standard tanh parametrization. We repeat this analysis for Planck PR3 data in place of PR4, and find that the mild preference for a flash is replaced by 95% CL upper bounds, given by $x_{\rm flash}<0.28$ and $x_{\rm flash}<0.18$ for $z_{\rm flash}=20$ and $25$, respectively, from Planck PR3 data.
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Astrophysics of Galaxies
EPOCHS-DR2 I: Expanded data release and properties of $6.5<z<16.5$ photometrically selected galaxies across NIRCam deep fields covering $\sim700\,\rm arcmin^2$ with the galfind software
Duncan Austin, Christopher J. Conselice, Thomas Harvey et al. (+14 more)
We present the \epochstwo\ sample of $2452$
star forming
galaxies at $6.5<z_{\rm phot}<16.5$ produced using the \galfind\ photometric pipeline across $\sim650-740~\mathrm{arcmin}^2$ in six of the most widely used deep, blank field \jwst/NIRCam imaging surveys. $293$
galaxies are spectroscopically confirmed and a spectroscopic–photometric
redshift comparison yields a normalized median absolute deviation, $\sigma_{\rm NMAD}=0.017$, an $\eta=4.3\%$ outlier rate, and a mean offset $\langle\Delta z\rangle=-0.022$. We find $34$ little red dots (LRDs) with “V–shaped” SEDs, as well as $69$ L–type, $36$ T–type, and $2$ compact Y–type brown dwarf candidates, which we remove from our sample. The fiducial sample yields a flattening $\beta_{\rm UV}-M_{\rm UV}$ relation with only moderately blue median $\beta_{\rm UV}(M_{\rm UV}=-19)=-2.32^{+0.08}_{-0.07}$ at $z\simeq12.5$, implying dust-polluted stellar populations at the highest
redshifts. A “gold” sample of $62$ sources are identified at $z_{\rm phot}>10.5$, $\sim85\%$ of which are without NIRSpec follow-up, including $15$ candidates at $z_{\rm phot}>13.5$ across a diverse range of proper sizes $30\,\rm pc\lesssim r_{\rm c}\lesssim1.5\,\rm kpc$ and UV slopes $-4.0\lesssim\beta_{\rm UV}\lesssim-1.5$. Two very promising candidates stand out, GS-W-4608 and GN-Med-1881, with $\beta_{\rm UV}\lesssim-3$, $\gtrsim1.6\,\rm mag$ \lya\ break colors, and F335M and F410M detections which improve their high-
redshift solution robustness. Complementary to our high-
redshift sample, this public data release provides the community with optical/NIR catalogs, empirical PSFs, and \eazypy, \bagpipes, and \bdfinder\ SED fitting results, enhancing the legacy value of photometric JWST data in the upcoming era of wide-field imaging
datasets with Euclid and Roman.
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All authors Duncan Austin, Christopher J. Conselice, Thomas Harvey, Nathan J. Adams, Louis Quilley, Jordan C. J. D'Silva, Vadim Rusakov, Qiong Li, Lewi Westcott, Caio Goolsby, James Arcidiacono, Kai Madgwick, William J. Roper, Brenda Frye, Norman A. Grogin, Rafael Ortiz III, Rogier Windhorst
Solar and Stellar Astrophysics
Elemental Abundances of Cool Stars: A Spectroscopic Framework Applied to Five Planet-Host Stars
Nicole Gromek, Drew Weisserman, Ryan Cloutier et al. (+2 more)
Stellar elemental abundances provide important constraints on the chemical environments from which
planets form. M and late-K dwarfs are
prime targets for the characterization of small
exoplanets, yet their complex spectra make accurate elemental abundance measurements challenging. In this work, we present a spectral synthesis-based framework to derive detailed abundances for cool
stars from high-resolution, near-infrared spectra. We apply our framework to SPIRou YJHK spectra of five
planet-host
stars–GJ 9827, K2-18, TOI-1201, TOI-1685, and Barnard's
Star–and derive abundances of C, O, Na, Mg, Al, Si, K, Ca, Ti, Cr, Mn, and Fe for all five
stars, plus Sc, V, and Ni for a subset, with typical uncertainties of $\lesssim 0.1$ dex. Our recovered
metallicities and elemental abundances are broadly consistent with expected trends and previous literature analyses of these
stars. We derive stellar ratios of C/O, Mg/Si, Fe/Mg, and Fe/O and find that all five systems are broadly consistent with solar ratios, with the exception of the metal-poor Barnard's
Star ([M/H] $= -0.33 \pm 0.06$ dex), which is substantially iron-poor ([Fe/H] $= -0.722 \pm 0.085$ dex). Our results establish stellar chemical baselines for interior structure and atmospheric studies of these planetary systems with the Hubble Space
Telescope (HST) and James Webb Space
Telescope (JWST), while highlighting the remaining model-dependent limitations of precise abundance analyses for cool
stars.
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All authors Nicole Gromek, Drew Weisserman, Ryan Cloutier, Alexandrine L'Heureux, Charles Cadieux
High Energy Astrophysical Phenomena
PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field IV: X-Ray Variability Analysis
Ross Silver, Francesca Civano, Xiurui Zhao et al. (+31 more)
NuSTAR and XMM-Newton have observed the James Webb Space
Telescope (JWST) North Ecliptic Pole (NEP) Time-Domain Field (TDF) for almost five contiguous years starting in 2019. In that time, the NEP X-ray survey has accumulated 3.5 Ms and 228 ks of quasi-simultaneous NuSTAR and XMM-Newton observations, respectively. This paper presents variability results for the 112 NuSTAR and 453 XMM-Newton sources detected in this field, based solely on the X-ray photometric data. Four NuSTAR sources and 11 XMM-Newton sources varied in at least one band at >=99% confidence. The sources with
redshift measurements show a relationship between luminosity and variability with 74% of variable sources brighter than 5x the sensitivity limit of the survey. This is supported by about 1/3 of sources with more than 400 counts detected being variable and only 4 sources with fewer counts showing variability. Variability timescales are not well determined, but variability amplitude tends to be larger on longer timescales.
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All authors Ross Silver, Francesca Civano, Xiurui Zhao, Samantha Creech, S. P. Willner, Christopher N. A. Willmer, Rogier A. Windhorst, Haojing Yan, Anton M. Koekemoer, Rosalia O'Brien, Rafael Ortiz III, Rolf A. Jansen, Gibson B. Bowling, Payaswini Saikia, W. Peter Maksym, Nico Cappelluti, Francesca Fornasini, Massimo Ricotti, Timothy Carleton, Seth H. Cohen, Rachel Honor, Jake Summers, Jordan C. J. D'Silva, Sibasish Laha, Dan Coe, Christopher J. Conselice, Jose M. Diego, Simon P. Driver, Brenda Frye, Norman A. Grogin, Madeline A. Marshall, Nor Pirzkal, Aaron Robotham, Russell E. Ryan Jr
Cosmology and Nongalactic Astrophysics
Two-dimensional weak lensing shear for cluster mass, concentration, ellipticity and miscentering estimation
Calum Murray, Martin Kilbinger and Constantin Payerne
The effects of weak gravitational
lensing induced by clusters of
galaxies makes it possible to constrain their dark matter distribution. In general mass estimates from weak
lensing are made by compressing the two-dimensional shear-field into one-dimension. In this work we build a forward model of the two-dimensional reduced-shear field around a
galaxy cluster, including the non-Gaussian correlated large-scale structure from N-body simulations, the uncorrelated line-of-sight structure, cluster miscentering and ellipticity. We then use simulation-based inference to obtain posteriors on the cluster mass, concentration, miscentering and ellipticity from the full field. The two-dimensional approach leads to improvements on cluster mass constraints by up to 20%. We show that this is due to a better treatment of the spatially correlated noise across the shear field. There is also significant improvements on the cluster concentration and miscentering. Whilst improvements are also made to the estimation of cluster ellipticity, the constraints are still prior dependent for these individual cluster constraints. We also quantify the impact of the line-of-sight structure on the constraints. Neglecting it underestimates the mass uncertainty by up to a factor of $2$ for the most massive clusters.
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Cosmology and Nongalactic Astrophysics
Merlin: Fast and flexible 3x2pt cosmology with simulation-based inference
Alexandra Wernersson, Guillermo Franco-Abellán and Guadalupe Cañas-Herrera
We present Merlin, a simulation-based inference (SBI) pipeline to perform cosmological analyses of 3x2pt summary statistics:
cosmic shear,
galaxy clustering and the cross-correlation power spectra. Our approach combines Marginal Neural Ratio Estimation (MNRE) with 3x2pt angular power spectra predictions from the cloelib library, although the pipeline is readily extensible to other cosmology libraries. We demonstrate this pipeline on a realistic setting representative of a Stage-IV photometric survey, with a 50-dimensional parameter space describing cosmology and a wide range of systematic effects. We find posteriors that are in excellent agreement with the nested sampler Nautilus, while reducing the number of required CPU-hours by two orders of magnitude. Because the generation of training data and the training of inference networks are decoupled processes, a single simulation bank can be reused to perform inference under different analysis choices, further improving the simulator-efficiency. We illustrate this flexibility by applying scale cuts, varying the survey area, and removing
cosmic shear from the data vector (2x2pt), all at zero extra model evaluations, whereas sampling-based methods need costly re-runs for each case. The Merlin code is publicly available on GitHub.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Ruling out nucleonic direct Urca cooling in low-mass neutron stars using nuclear data
Gabriele Montefusco, Pietro Klausner, Marco Antonelli et al. (+3 more)
Connecting nuclear experiments to
neutron star composition requires controlling the extrapolation of experimental information beyond the densities probed in the laboratory. We combine a broad set of nuclear structure observables and INDRA-FAZIA isospin-transport data within a
Bayesian inference of the dense matter equation of state (EoS). To limit uncontrolled extrapolation to high density, we employ a flexible asymptotically causal metamodel whose
neutron star posteriors are comparable to those obtained with agnostic EoS models. The nuclear structure information is propagated through its full multidimensional distribution of correlated nuclear matter parameters, while the density-dependent INDRA-FAZIA likelihood is evaluated directly along each sampled metamodel
symmetry energy curve. These two sources of laboratory information give compatible constraints on the
symmetry energy, and their combination preserves agreement with finite nuclear observables. When combined with ab initio chiral effective field theory calculations and astrophysical observations, all these constraints substantially improve the determination of central
proton fractions in low-mass
neutron stars, while leaving larger uncertainties for massive
stars. Within the adopted nucleonic metamodel, the reduced probability of large
proton fractions strongly disfavors electronic direct-Urca onset at or below $1.4\,M_\odot$: its posterior probability falls from $\sim20\%$ with chiral and astrophysical constraints alone to below $1\%$ when the laboratory information is included.
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All authors Gabriele Montefusco, Pietro Klausner, Marco Antonelli, Caterina Ciampi, Diego Gruyer, Francesca Gulminelli
Astrophysics of Galaxies
Galaxy evolution in the post-merger regime. V - Atomic gas evolution traced by ALFALFA stacks
Sara L. Ellison, Manasvee Saraf, Leonardo Ferreira et al. (+4 more)
(Abridged) In this work, we investigate the role of atomic hydrogen (HI) gas in the
galaxy merger lifecycle. In order to both identify
galaxies in mergers, as well as to predict their time since coalescence, we present an extension of the MUlti Model Merger Identifier (MUMMI) machine
vision pipeline applied to Dark Energy Camera Legacy Survey (DECaLS) imaging. The new MUMMI-DECaLS catalog contains 19,951 post-mergers, of which 14,638 have robust time post-merger (T_PM) predictions. The MUMMI-DECaLS post-merger
galaxy catalog is cross-matched with the Arecibo Legacy Fast ALFA (ALFALFA) survey. For the 752 post-mergers thus identified, as well as a matched control sample, we produce median spectral stacks of 21~cm emission, finding that the post-mergers are HI deficient by 0.11 dex compared with non-interacting
galaxies. When divided into T_PM bins we find that the HI deficit (or excess) is strongly dependent on both the time since coalescence and whether the
galaxies are
star-forming or quenched.
Star-forming post-mergers in particular show a strong HI
evolution with T_PM, exhibiting a 0.1 dex MHI excess immediately after coalescence, a 0.3 dex MHI deficit at 0.16 < T_PM < 0.96 Gyr and normal gas masses by ~ 1.5 Gyr after coalescence. On the other hand, despite being matched in
star formation rate, stellar mass and
redshift, quenched post-mergers are HI deficient at both short and long post-coalescence times. Nonetheless, a significant mass of HI (>10^9 M_sun) remains even in these late-time quenched post-mergers, representing a resource which could potentially re-fuel
star formation in the future. Our results demonstrate the complexity of quantifying the HI behaviour in mergers, which depends not only on timing, but also
star-forming status, which can complicate comparisons between different studies and samples.
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All authors Sara L. Ellison, Manasvee Saraf, Leonardo Ferreira, Amelie Saintonge, Dirk Scholte, Jing Wang, Qifeng Huang
High Energy Astrophysical Phenomena
Magnetar magnetothermal evolution with Landau-quantized electrons: enhanced Joule heating due to free electron diamagnetism and the magnetar heating problem
Peter B. Rau
Magnetars are systematically more luminous than other
neutron stars. Previous studies suggest that supporting such high luminosities requires a heat source beyond standard Ohmic dissipation– the “magnetar heating problem”. We previously demonstrated using periodic box simulations that de Haas–van Alphen (dHvA) oscillations of the Landau quantization-induced magnetization in a
neutron star could repeatedly generate large-gradient field components that undergo rapid Ohmic dissipation. Using the QMFM finite volume code developed for this purpose, we perform axisymmetric 2.5D electron magnetohydrodynamics plus thermal
evolution simulations of a realistic
neutron star crust, including all Landau quantization effects, to quantify this enhancement to field dissipation and heating of the
star. We show that Landau quantization effects generate strong, small-scale
magnetic field structures whose dissipation can heat the field-confined equatorial hot spot beyond its temperature in the absence of Landau quantization. Enhanced heating is greatest for weaker initial fields $B\sim10^{14}$ G, for which
magnetic energy is dissipated 30% faster: in this case, the crust cools sufficiently for the dHvA oscillations to reach large amplitudes. For the stronger fields $\gtrsim B\sim5\times10^{14}$ G required to power the most luminous magnetars, the enhancement is modest, as dissipation of these fields heats the crust sufficiently to thermally suppress dHvA oscillations. In cases where heating is significantly enhanced, most of the heat goes into increasing the
neutrino luminosity, and surface
photon luminosity is only slightly increased. For the simple crust-confined fields that we simulated, Landau quantization-enhanced Joule heating is thus insufficient to explain the magnetar heating problem.
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High Energy Astrophysical Phenomena
Luminosity Signatures of Dark Sector Particles from Black Hole Evaporation in Neutron Stars
Ioannis Dalianis and Anastasios Irakleous
Microscopic black holes may form at the centers of
neutron stars through the accumulation and collapse of dark matter. While Standard Model particles produced by Hawking evaporation are efficiently absorbed by the dense stellar medium, sufficiently weakly interacting and long-lived particles can escape and subsequently decay into high-energy
neutrinos,
photons, or charged particles, providing an indirect probe of Hawking radiation. We examine the joint energy–angular distribution of these secondary particles, incorporating mediator propagation, energy-dependent decay, and relativistic decay kinematics. For relativistic mediators, the normalized energy-integrated angular profile becomes approximately independent of the black hole temperature, with its characteristic extent controlled primarily by the combination $c\tau_S/D$ of the mediator lifetime and source distance, as the boost enhancement of the decay length is compensated by relativistic beaming. We demonstrate the viability of this mechanism and illustrate its phenomenology with gravitationally coupled scalars, dark
photons, dark-$Z$
bosons, and heavy neutral leptons. Comparing with monochromatic mediator production from dark matter annihilation, we find that the energy-integrated angular profiles can be nearly degenerate, while the energy spectra and energy-resolved angular distributions remain distinct. These complementary spectral and angular signatures provide targets for high-energy
neutrino and gamma-ray searches.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Gauss–Bonnet running and the de Sitter saddle of quadratic gravity inflation
Ruolin Liu and Niayesh Afshordi
Inflation driven purely by the
quantum running of the
curvature-squared couplings of quadratic
gravity was shown to accommodate the high scalar tilt favored by recent
cosmic microwave background observations, starting from a Euclidean four-sphere at a maximum of the running $R^2$ coupling. That maximum exists only in one renormalization scheme, and is not stationary once the Euler trace anomaly is included. We show that the standard one-loop running, with the usually neglected Gauss–Bonnet coefficient retained, recovers the missing de Sitter state: the Euler running balances the scale dependence of the $R^2$ term at a unique coupling ratio, giving a de Sitter solution that is stationary for the gravitational constraint and for the compact Euclidean action alike, and whose scalaron potential is an extremely flat hilltop ($m^2/H^2\simeq-5\times10^{-10}$) joined to an inverse-linear inflationary plateau. The last $N_*\simeq50$–$60$ $e$-folds are scheme independent, with scalar tilt $n_s\simeq1-4/(3N_*)$, while the tensor-to-scalar ratio, $r$, is set by the number of matter fields that enhance the running. The current tensor bound excludes pure
gravity and sets a minimum matter content, some $4\times10^6$ conformally coupled scalars or $3\times10^5$ vectors—$2.6$ times fewer than the momentum-induced scheme requires—while one-loop control to the end of inflation sets a maximum about ten times higher. Across that window the model predicts $r\gtrsim0.008$ with $0.973\lesssim n_s\lesssim0.978$, within reach of upcoming CMB polarization surveys.
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Earth and Planetary Astrophysics
Feeding the Circumplanetary Disk: 3D Simulations of Dust Filtration and Accretion in PDS 70 c
Charles H. Gardner, Andrea Isella, Hui Li et al. (+3 more)
How circumplanetary disks (CPDs) capture and retain solids is central to constraining the timescale for formation of rocky satellites and interpreting submillimeter continuum observations around giant
planets. Here, we investigate the transport of gas and dust from the circumstellar disk into the CPD, using PDS 70 as our fiducial example. Based on observation-driven parameters, we perform high-resolution 3D adaptive mesh refinement (AMR) hydrodynamic simulations including a multifluid dust component to study dust
accretion onto
planets with masses of 1 $M_\mathrm{J}$ and 2.5 $M_\mathrm{J}$. We find that the pressure maximum at the gap edge imposes strong, size-dependent dust filtration, drastically lowering the solid content of the accreting flow. The net dust-to-gas mass ratio of the material accreting onto the
planet is reduced by roughly two orders of magnitude relative to the outer disk. Only small grains ($\lesssim 61 \mu$m for the 1 $M_\mathrm{J}$ case and $\lesssim 10 \mu$m for the 2.5 $M_\mathrm{J}$ case) are able to accrete efficiently onto the CPD. Despite this filtering, we show that a continuous inflow of small grains can still deliver sufficient mass to build the observed PDS 70 c CPD or a Galilean-like satellite system within a few million years. Because more massive
planets more effectively prevent the
accretion of large grains, the dust that reaches the CPD is dominated by small particles with low millimeter-wave opacities. Consequently, in the absence of grain growth, interpreting millimeter continuum measurements of CPDs around massive giant
planets may require invoking larger total dust masses than typically assumed.
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All authors Charles H. Gardner, Andrea Isella, Hui Li, Shengtai Li, Gennaro D'Angelo, Adam M. Dempsey
Astrophysics of Galaxies
Reducing False Positives in Strong-Lens Searches with Generalized-Mean Consensus of Machine-Learning Ensembles in the Kilo-Degree Survey
Ziqi Li, Rui Li, Xu Huang et al. (+11 more)
Context. In wide-field surveys, the main challenge is not just classifier sensitivity, but the overwhelming number of false positives. Searching for strong lenses among millions to bilions of
galaxies produces many contaminants, making the bottleneck for follow-up inspection and building statistically useful lens samples. Aims. We aim to improve the purity of strong-lens candidate selection in KiDS DR4 by combining several classifiers. The objective is to retain high completeness for known candidates while substantially reducing the fraction of non-lenses. Methods. We trained convolutional,
Transformer-based, and hybrid classifiers, including Li ResNet+, Swin
Transformer variants, Swin-MLP, and DemiLensNet. Their probabilistic outputs were combined at score level using averaging and a generalized mean consensus. The models were tested on simulated KiDS-like lens images and then evaluated on real KiDS DR4 lens candidates embedded in a non-lens sample. Results. On the simulated test set, ensembles show no advantage over the best single models. On the mixed real KiDS test set, the arithmetic mean reduces the false-positive rate at 90% completeness from 0.016-0.020 (the range spanned by the two best individual models) to 0.011 for the seven-model ensemble. The generalized mean reduces it further, to 0.007. Applied to the full LRG and BG samples at the same 90% completeness level, the generalized mean reduces returned candidates by roughly 50% for LRGs and 70% for BGs, relative to the best single model. After visual inspection, we obtain 170 new high-quality candidates (24 Class A and 146 Class B), together with 1706 Class C candidates. Conclusions. Our results demonstrate that the generalized mean consensus of an ML ensemble strategy provides a practical route to reducing the visual inspection workload while preserving a high recovery rate of promising strong-lens candidates.
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All authors Ziqi Li, Rui Li, Xu Huang, Hui Li, Pufan Liu, Liang Gao, Crescenzo Tortora, Nicola N. Napolitano, Xiaoyue Cao, Ran Li, Liqing Chen, Kang Jiao, Valerio Busillo, Yue Dong
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
A New Probe of Strongly-Interacting Dark Sector using Neutrino Telescopes
Jose A. Macias Cruz, Christopher V. Cappiello, P. S. Bhupal Dev et al. (+1 more)
A confining dark sector modeled after
quantum chromodynamics provides a well-motivated framework for strongly-interacting dark matter. We show that dark vector
mesons in a confining dark sector can be resonantly produced in high-energy
neutrino scattering on the
cosmic neutrino background, generating a distinctive absorption feature in the
cosmic neutrino energy spectrum. Unlike conventional attenuation effects, this feature directly reflects the mass spectrum of dark resonances and can therefore serve as a spectroscopic signature of a strongly-interacting dark sector. We find that a broad range of dark-sector parameter space is within the reach of future
neutrino telescopes, including IceCube-Gen2
Radio. Our proposal thus turns the
cosmic neutrino background into a target for discovering dark-sector resonances, while simultaneously providing a novel probe of dark sector interactions with
neutrinos.
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All authors Jose A. Macias Cruz, Christopher V. Cappiello, P. S. Bhupal Dev, Suchita Kulkarni
Earth and Planetary Astrophysics
Upside down: GJ3090 b the first retrograde exoplanet around an M dwarf detected with NIRPS
Y. Carteret, V. Bourrier, L. Parc et al. (+57 more)
The angle between stellar
spin axis and planetary orbital plane can provide key insights into the formation and dynamical
evolution of planetary systems. In particular, this measurement in multi-
planet systems can be used to further discriminate between different competing migration scenarios. We present six transit observations of the sub-Neptune GJ3090 b obtained with NIRPS and HARPS. GJ3090 b is the inner
planet of a confirmed multi-
planet system orbiting an M dwarf (M2). Using high spectral resolution and high temporal cadence spectroscopic observations, we analyzed the Rossiter-McLaughlin (RM) effect induced by GJ3090 b to determine its orbital obliquity. Through the RM revolutions technique, we find that the
planet is on a retrograde orbit with a derived 3D obliquity of $\psi = 136^{+24}_{-18}\,\mathrm{deg}$. We find no evidence of massive outer planetary or wide stellar binary companions, which disfavors scenarios involving gravitational perturbations from a massive body and instead points toward a primordial misalignment of the protoplanetary disk. Our results establish GJ3090 b as the first
planet on a retrograde orbit discovered around an M dwarf and the first highly misaligned confirmed multi-
planet system without a known massive companion. We further propose late secondary disk
accretion around GJ3090, in which the disk is not expected to be aligned with the stellar
spin axis, followed by disk-driven migration as the most likely mechanisms to explain the observed architecture. This work also illustrates the capability of the RM revolutions technique when applied to near-infrared data to probe orbital architectures of the smallest
planets around M dwarfs that have remained mostly inaccessible.
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All authors Y. Carteret, V. Bourrier, L. Parc, A. Winter, R. Allart, I. de Castro Leão, F. Bouchy, V. M. Passegger, C. Cadieux, P. Lamontagne, É. Artigau, F. Baron, S. C. C. Barros, B. Benneke, X. Bonfils, M. Bryan, B. L. Canto Martins, R. Cloutier, E. Cristo, J. Gagné, N. J. Cook, N. B. Cowan, J. R. De Medeiros, X. Delfosse, R. Doyon, X. Dumusque, D. Ehrenreich, J. I. González Hernández, D. Lafrenière, C. Lovis, L. Malo, C. Melo, L. Mignon, C. Mordasini, F. Pepe, R. Rebolo, J. Rowe, N. C. Santos, D. Ségransan, A. Suárez Mascareño, S. Udry, D. Valencia, G. Wade, K. Al Moulla, R. G. de Souza Barros de Amorim, L. Dang, E. Deibert, D. O. Fontinele, T. Forveille, Y. G. C. Frensch, R. de Lima Gomes, D. Mounzer, S. Pelletier, R. Rosener, B. N. Skinner, A. Srivastava, A. K. Stefanov, V. Vaulato, J. P. Wardenier, D. Weisserman
Instrumentation and Methods for Astrophysics
The Sun can flip the shielding effect of added spacecraft mass
Yasser Maghrbi and Nelson Christensen
Spacecraft structure is usually treated as shielding against energetic particles. We find that the Sun can reverse the effect of adding that structure. Free-falling test masses are the inertial references of gravitational-wave observatories and equivalence-principle experiments; charge accumulated on them couples to stray electric fields and produces acceleration noise that limits sensitivity. In a LISA-like system, increasing the surrounding aluminium from 16 to 24 g cm -2 reduces the stopping-
proton population by (2.3 $\pm$ 0.5)% at solar minimum but increases it by (17.0 $\pm$ 1.0)% at solar maximum, the crossover lying in the deep-solar-minimum regime. Complete 2-24 g cm -2 mass curves show a broad maximum at solar minimum but a monotonic rise at maximum. The reversal arises because added material both attenuates incident
protons and feeds a nuclear-processed population into the stopping-energy window. A first-order projection onto published charging rates gives changes of about -2% and +11% in the net charging rate, affecting charge accumulation, discharge requirements and the associated noise budget. The sign of a structural trade is therefore not fixed by the structure alone.
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High Energy Astrophysical Phenomena
Jet variability in small mass ratio supermassive black hole binaries
Jay V. Kalinani, Manuela Campanelli, Michail Chabanov et al. (+4 more)
We present three-dimensional general relativistic magnetohydrodynamic simulations of a precessing supermassive black hole binary with mass ratio q=1/7, embedded in a circumbinary disk. We investigate how dynamics within the binary cavity launch and shape a relativistic jet to thousands of gravitational radii. The primary black hole dominates both
accretion and jet power, while the smaller black hole repeatedly crosses and shocks the inner
accretion flow. These passages of the secondary drive magnetized gas alternately into the upper and lower jet funnels, producing disturbances that propagate outward as quasi-periodic outflows. Although the inner flow is perturbed twice per orbit, each jet lobe shows one dominant outflow per orbit. On longer timescales, the jet precesses, reverses its
magnetic handedness, and undergoes two weak phases. The first results from a reorientation of the primary
spin and is followed, after the jet recovers, by a reversal in the circulation of the projected
magnetic field. The second weak phase occurs as the secondary's orbit becomes nearly coplanar with the circumbinary disk, reducing the gas and
magnetic flux reaching the primary. Together, these results connect cavity dynamics to large-scale jet variability and predict a set of correlated jet signatures whose relative timing and causal ordering may provide stronger evidence for a small-mass-ratio supermassive black hole binary than any one feature alone.
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All authors Jay V. Kalinani, Manuela Campanelli, Michail Chabanov, Maria Chiara de Simone, Carlos O. Lousto, Helvi Witek, Yosef Zlochower
Astrophysics of Galaxies
A Newly Discovered VVVX Star Cluster Surfing the Galactic Disk
Elisa R. Garro, José G. Fernández-Trincado, Casmir O. Obasi et al. (+15 more)
We report the discovery of Garro 04, a previously unidentified stellar cluster toward the Galactic disc, uncovered as part of the ESO/KMOS VVVX-GalCen Spectroscopic Survey. This object was serendipitously confirmed as a stellar overdensity in the VISTA Variables in the Vía Láctea eXtended (VVVX) survey footprint and subsequently confirmed through medium-resolution $K$-band spectroscopy obtained with the K-band Multi Object Spectrograph (KMOS) at the ESO Very Large
Telescope. The combined photometric and spectroscopic analysis reveals a coherent stellar population with common radial velocities and chemical properties, supporting its classification as a genuine
star cluster rather than a statistical fluctuation of the disk field. We derive the fundamental properties of Garro 04, including its structural parameters, distance, kinematics, and compute its orbital properties, finding that its motion remains confined to the Galactic disk region. Finally, our analysis suggests that Garro~04 is likely an old open cluster, or an object straddling the boundary between the canonical globular and open cluster classifications, with an estimated Age $ = 5 \pm 2$ Gyr and a
metallicity of $\mathrm{[Fe/H]} = -0.5 \pm 0.2$, finding an excellent agreement between the photometric and spectroscopic determinations.
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All authors Elisa R. Garro, José G. Fernández-Trincado, Casmir O. Obasi, Dante Minniti, Matías Gómez, Roberto K. Saito, Javier Alonso-García, Alonso Luna, Valentin D. Ivanov, Maria Gabriela Navarro, Sara Federle, Bernardo P. L. Pereira, Beatriz Barbuy, Devika Bhadrakumar Sindhu, Bruno Dias, Tali Palma, Ilaria Petralia, Sasi Saroon
Instrumentation and Methods for Astrophysics
First Experimental Evaluation of Stray Light Noise Modeling of kilometers-long Beam Tube Arms of Gravitational Wave Detectors
Emilia Chick, Timothy O'Hanlon, Hiro Yamamoto et al. (+3 more)
We present the results of the first experimental evaluation of stray light noise models for LIGO beam tube baffles. We combine the results of a testing campaign at LIGO Livingston and SIS simulations to get a model of backscatter and diffraction noise of select mid-arm baffles. Agreement to within a factor of $3-10$ is found between models and measured gravitational waHe strain. Two distinct regions of well-propagating motion were identified, at approximately $35Hz$ and $90Hz$, and these are visible in the strain signal as broadband features. Peaks with $Q \approx 100-1000$ were also found in the strain signal between $70Hz$ and$100Hz$. These are theorized to come from diffraction noise only, and are modeled using Q-factors measured from the strain. These models are also in good agreement with the strain signal. Other findings on the effect of auxiliary arm systems on stray light noise are discussed.
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All authors Emilia Chick, Timothy O'Hanlon, Hiro Yamamoto, Denis Martynov. Valery Frolov, Anamaria Effler, Antonios Kontos
High Energy Astrophysical Phenomena
Particle Acceleration in Stratified 2D MRI Turbulence: From Reconnection to First- and Second-Order Fermi and Shear Acceleration
Astor Sandoval, Mario Riquelme and Jorge Cuadra
Low-luminosity
accretion disks around black holes are weakly collisional, potentially enabling nonthermal particle acceleration. Local two-dimensional particle-in-
cell simulations of the stratified magnetorotational instability (MRI) in pair
plasmas by Sandoval et al. (2024; hereafter S24) revealed nonthermal populations with maximum energies proportional to the scale-separation ratio $\omega_{c,0}/\Omega_0$, where $\omega_{c,0}$ and $\Omega_0$ are the initial particle cyclotron and Keplerian frequencies, respectively. We identify the acceleration mechanisms involved and quantify their scale-separation dependence. Acceleration occurs primarily within large-scale current sheets associated with an MRI dynamo. Particles are initially injected by non-ideal electric fields during reconnection driven by plasmoid splitting, attaining energies independently of scale separation. They subsequently undergo rapid first-order Fermi-like acceleration occurring within converging flows between newly formed, separating plasmoids. During this stage, energies grow at a rate proportional to the instantaneous non-relativistic cyclotron frequency, independently of $\omega_{c,0}/\Omega_0$. This fast acceleration rate implies a maximum energy proportional to $\omega_{c,0}/\Omega_0$. Particles then continue interacting repeatedly with plasmoids, undergoing slower, predominantly second-order Fermi acceleration, with a subdominant contribution from shear acceleration. This stage increases particle energies by only a factor of a few over several orbits, regardless of $\omega_{c,0}/\Omega_0$. The combination of these three stages implies a maximum energy proportional to $\omega_{c,0}/\Omega_0$, explaining the scaling found by S24 and suggesting that the MRI may accelerate particles to ultrarelativistic energies in low-luminosity disks. Testing these results in three dimensions remains an important next step.
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Astrophysics of Galaxies
CAVITY: Calar Alto Void Integral-field Treasury surveY: II. Second public data release
B. Bidaran, A. Jiménez, R. García-Benito et al. (+30 more)
Studying
galaxy evolution under the unique environmental conditions of
cosmic voids provides an opportunity to disentangle the role of the large-scale environment in shaping mass assembly (both baryonic and dark matter), regulating
galaxy physical properties, and driving the transformation from
star-forming to quiescent systems. We present the second public data release (DR2) of the Calar Alto Void Integral-field Treasury Survey (CAVITY), an ongoing legacy programme designed to study void
galaxies (VGs) across a range of nearby ($0.005 \leq z \leq 0.050$) voids with different sizes and dynamical stages, providing 200 science-grade optical integral-field spectroscopy (IFS) data cubes. By doubling the number of
galaxies relative to DR1 while maintaining the same selection criteria, DR2 significantly increases the
dataset's statistical power, enabling more robust characterization of
galaxy properties and their correlations with environment. The observations were obtained with the PMAS/PPAK spectrograph on the 3.5-m Calar Alto
telescope using the V500 configuration, covering the optical spectral range of 3745-7500 A at a resolution of 6 A (FWHM). The DR2 VG sample spans a broad range of stellar masses, morphologies, colours, and gas ionisation properties. We describe the sample selection, observing strategy, data reduction pipeline, quality-control procedures, and the public access to the CAVITY
datasets and associated ancillary data on the survey's database. In addition, we present a characterisation of the large- and local-scale environments of CAVITY
galaxies, showing that the 15 surveyed voids encompass a wide variety of sizes,
galaxy richness,
galaxy populations, and local structures, including
galaxy groups. This release comprises 200 IFS data cubes, publicly available together with the master catalogues at the survey's dedicated webpage: https://cavity.caha.es/data/dr2/.
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All authors B. Bidaran, A. Jiménez, R. García-Benito, M. Argudo-Fernández, M. Alcázar-Laynez, S.B. De Daniloff, S. Duarte Puertas, D. Espada, E. Florido, Y. K. González-Koda, I. Pérez, T. Ruiz-Lara, L. Sánchez-Menguiano, G. Torres-Ríos, P. Vásquez-Bustos, S. Verley, A. Zurita, M. A. Canossa-Gosteinski, A. M. Conrado, H. M. Courtois, I. del Moral-Castro, J. Falcón-Barroso, A. Ferré-Mateu, M. Hernández-Sánchez, A. Lugo-Aranda, S. Subramanian, P. Villalba-González, L. Galbany, R. M. González Delgado, R. F. Peletier, S. F. Sánchez, R. van de Weygaert, A. Fernández-Martín
Solar and Stellar Astrophysics
The Role of Non-local Thermal Transport in Flare-Driven Chromospheric Evaporation
Thomas Parmenter, Tony Arber, Sergey Belov et al. (+1 more)
Thermal conduction plays an important role in energy transport during solar
flares.
Flares heat the solar atmosphere to tens of MK which, combined with mean free paths in excess of 1Mm, can cause the heat flux to become non-local. We use the magnetohydrodynamic Lare2d code to simulate a reconnective heating event with three different thermal conduction models: classical Spitzer-Harm (SH) along the
magnetic field, local transport with a heat flux limiter (FL), and the non-local Schurtz, Nicolai, Busquet (SNB) model which is routinely used in
laser-
plasma codes and has been bench- marked against full Vlasov-Fokker-Planck treatment. The
evolution of the atmosphere post heating is compared between simulations using each of these models. Due to a supressed heat flux, SNB gives rise to significantly higher peak temperatures than SH. Further, with SNB transport chromospheric evaporation occurs later and has stronger extreme ultraviolet emission intensity. FL simulations have similar temperature
evolution and chromospheric evaporation to SNB, however different values of the flux limiter work best for peak temperature, downflow velocity and EUV emission intensity, and so there is no one optimal value for all cases. We conclude that the SNB model provides a practicable solution to incorporate non-local thermal transport at MHD scales, which will be crucial to improve the realism and accuracy of the next generation of solar
flare simulations.
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All authors Thomas Parmenter, Tony Arber, Sergey Belov, Tom Goffrey