Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Electromagnetic Radiation from Cosmic-Ray Scatterings on Relic Neutrinos
Gonzalo Herrera and Abraham Loeb
Cosmic-ray scatterings on the
cosmic neutrino background induce a flux of gamma-rays and X-rays from boosted
meson decays and charged
lepton processes. Here we present the first estimate of this flux and its cumulative cosmological contribution. Confronting expectations with
Fermi-LAT diffuse gamma-ray data, we find a limit on the
cosmic neutrino background overdensity at the level of $\eta \lesssim 2 \times 10^{4}$ for a lightest
neutrino mass of $m_{\nu}\gtrsim0.1$ eV, orders of magnitude stronger than current direct laboratory probes, and comparable to constraints on the
cosmic neutrino background obtained with IceCube. We further show that X-ray synchrotron emission from cascade electron-positron pairs in intergalactic
magnetic fields provides a complementary, albeit weaker, constraint. We discuss how anisotropic signatures and future gamma-ray data from CTA could further improve bounds on the relic
neutrino overdensity, approaching in sensitivity the $\Lambda$CDM expected density.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A strongly hyperbolic viscous relativistic hydrodynamics theory with first-order charge current
Federico Schianchi and Fernando Abalos
We extend the first order dissipative relativistic hydrodynamics model of Bemfica-Disconzi-Noronha- Kovtun (BDNK) in order to include the charge number current in full first order expansion with out-of-
equilibrium contribution proportional to the
evolution equation of the ideal fluid. We obtain a fully second order system of partial differential equation (PDE) that can be casted in a fully conservative way. We analyze the hyperbolicity of this model coupled to Einstein field equations using a newly developed technique that allows for hyperbolicity studies without explicit first order reduction. Furthermore, we identify a frame choice where our formulation is causal, stable and with positive
entropy generation for a wide range of equations of state (EoS). Our analysis shows that the inclusion of an out-of-
equilibrium correction to the charge current, plays an important role in guaranteeing the strong hyperbolicity and, therefore, the well-posedness of the system.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Spontaneous particle creation by oscillating compact stars
Adrián del Río and Pau López-Oliver
Quantum field theory predicts that dynamical curved spacetimes can spontaneously excite particle pairs from the
quantum vacuum, a phenomenon extensively studied in expanding universes and in scenarios involving gravitational collapse. In this article, we explore particle creation driven by radial oscillations of 3+1-dimensional spherically symmetric compact objects, such as
neutron stars, using a massless, minimally coupled scalar field as a reference model. We employ a toy model to describe the oscillatory dynamics and its coupling to the field modes, focusing on the resulting effects in the exterior spacetime of the
star. The Bogoliubov coefficients relating the in and out
vacua are computed non-perturbatively using high-precision numerical methods, without relying on weak-field, small-amplitude or small-velocity expansions. This allows us to determine the full particle spectrum and the total particle number in the strong-field and fully relativistic regime. Our analysis confirms the existence of particle creation in this setting and, crucially, reveals a distinct resonance structure in the spectrum.
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High Energy Astrophysical Phenomena
Galactic Center gamma-ray excess from a generic triaxial halo
Leo Qiyuan Hu, Ilias Cholis and Yi-Ming Zhong
Recent studies of
Galactic surveys, such as
Gaia, have revealed that the Milky Way's gravitational potential comes from a matter distribution that is triaxial and rotated with respect to the
Galactic center-Sun axis. This, in turn, could mean that the dark matter
halo also shares these properties. In this work, by fitting to the
Fermi-LAT gamma-ray observations, we test the compatibility of the morphology of the
Galactic Center Excess (GCE) from dark matter annihilation with a triaxial dark matter
halo. In particular, we consider both untilted triaxial
halos and
halos whose principal axes are tilted with respect to the
Galactic disk. In our fits of the
Fermi-LAT data, by testing over a large library of
galactic diffuse emission models, we quantify how the
halo triaxiality and tilt affect the line-of-sight-integrated annihilation signal and, consequently, the preferred GCE spatial templates. We find that the GCE spectrum and inner cuspiness are robust against variations in the triaxiality and tilt of the dark matter
halo. However, in terms of its overall morphology, the GCE in the gamma-ray data can discriminate between choices for the dark matter
halo's triaxiality and tilt. Finally, we find that the GCE is more compatible with originating from a triaxial and tilted
halo of dark matter than originating from a triaxial and tilted
halo of
stars, a result important for understanding the GCE's origin.
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High Energy Astrophysical Phenomena
The origin of isolated millisecond pulsars in non-core-collapsed globular clusters
Raniere de Menezes
A significant fraction of millisecond
pulsars (MSPs) in globular clusters (GCs) are observed as isolated objects, despite the widely accepted scenario in which MSPs are formed through recycling in compact binary systems. The origin of these isolated objects therefore remains an open problem. In this work, we propose a combination of the Heggie–Hills law for hard/soft binaries with companion ablation as a tracer of the fraction of isolated MSPs, $\mathcal{F}_i$, observed in non-core-collapsed GCs. We find $\mathcal{F}_i = (42.49\pm1.62)a_H^{-0.5}\,\%$, where $a_H$ is the Heggie–Hills ionization radius, and that this ionization-driven model is favored over a null hypothesis in which $\mathcal{F}_i$ is independent of $a_H$, with a log Bayes factor of $\ln(BF) > 2.5$, providing significant evidence for a physical dependence of $\mathcal{F}_i$ on $a_H$. Our framework naturally explains the observed overabundance of isolated MSPs in NGC 5139 (aka $\omega$ Centauri) and proposes binary ionization as one of the main mechanisms responsible for the production of isolated MSPs in non-core-collapsed GCs.
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Cosmology and Nongalactic Astrophysics
Cloaking Cosmic Light
Nemanja Kaloper
Light crossing dark domain walls that source a top form coupled to gauge Chern–Simons terms mixing visible and dark $U(1)$ gauge fields generically converts into dark
photons. The effect is entirely localized on the wall and requires no additional ingredients. The conversion rate is a sharp function of the
photon frequency in the wall rest frame, vanishing above the ultraviolet cutoff of the top form sector. Partial cloaking may also induce a rotation of the polarization of transmitted light of order $\Delta\vartheta \sim 10^{-3}$ radians, modify the
cosmic microwave background power spectrum, and violate Etherington's reciprocity relation at low frequencies. These effects can impact cosmological determinations of the Hubble rate.
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Astrophysics of Galaxies
Little Red Dots: One Photometric Tag Concealing Diverse Spectroscopic Flavors of Massive Star Formation and Black Hole Activity
Pablo G. Pérez-González, Guillermo Barro, Stefano Carniani et al. (+61 more)
We compile JWST/NIRSpec prism and MIRI data for 249 Little Red Dots (LRDs) at 2.3<z<9.3, forming a representative spectroscopic subset of NIRCam-selected LRDs. We derive a median stacked spectrum covering rest-frame 0.09-1.2 $\mu$m, with MIRI photometry extending the spectral energy distribution to 4 $\mu$m. Four additional stacks for subsamples defined by optical-to-UV luminosity ratios show that LRDs form a heterogeneous population spanning diverse continuum slopes and line properties. Assuming LRDs host super-massive black holes (BHs) surrounded by dense gas clouds, and
stars accompany this core, we infer masses of $M_{BH}\sim10^{6.0-6.5}$ M$_\odot$ and $M_\bigstar\sim10^{8.3}$ M$_\odot$, corresponding to BH-to-
stellar mass ratios of 1-2%. The stacks show ubiquitous UV and optical FeII emission, indicating a direct view of the broad-line region and high (but sub-Eddington)
accretion ($\lambda_{Edd}=0.6\pm0.2$). We find a significant
stellar contribution in the far-UV, reaching $\sim80$% in the bluest systems. Possible Wolf-Rayet features (HeII$\lambda$4687, nitrogen lines) are identified, tracing a young (3-7 Myr) compact starburst event. We also detect strong Balmer breaks and atypical Balmer, Paschen, [OIII], and optical and near-infrared HeI line ratios, and an absorption at $\sim4550$ Angstrom (probably linked to FeII), all consistent with radiative-transfer effects in high-density gas with warm temperatures (4000-7000 K). We find a diversity of LRD
flavors modulated by the luminosity ratio between between a short ($\lesssim20$ Myr) and intense phase of BH activity, the most extreme stage lasting $\sim3-7$ Myr, characterized by near-Eddington-limit radiation, and a
nuclear and compact starburst dominated by massive
stars (even super-massive, $\mathrm{M}_\mathrm{SMS}\sim10^{5}$ M$_\odot$), all embedded in dense gas with modest
dust content producing a variety of optical depths.
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All authors Pablo G. Pérez-González, Guillermo Barro, Stefano Carniani, Francesco D'Eugenio, George H. Rieke, Roberta Tripodi, Andrew J. Bunker, Xihan Ji, Rui Marques-Chaves, Daniel Schaerer, Giacomo Venturi, Flor Arévalo-González, Santiago Arribas, Pierluigi Rinaldi, Bruno Rodríguez Del Pino, Joris Witstok, Rachana Bhatawdekar, Leindert A. Boogaard, Stephane Charlot, Jacopo Chevallard, Luca Costantin, Mirko Curti, Emma Curtis-Lake, Emanuele Daddi, Kelcey Davis, Mark Dickinson, Callum T. Donnan, Fergus R. Donnan, James S. Dunlop, Daniel J. Eisenstein, Henry C. Ferguson, Román Fernández Aranda, Steven L. Finkelstein, Seiji Fujimoto, Giovanni Gandolfi, Mauro Giavalisco, Norman A. Grogin, Mahmoud Hamed, Michaela Hirschmann, Jeyhan S. Kartaltepe, Dale D. Kocevski, Gene C. K. Leung, Cristina M. Lofaro, Ray A. Lucas, Derek J. McLeod, Jens Melinder, Goran Östlin, Casey Papovich, Laura Pentericci, Borja Pérez-Díaz, Marcia Rieke, Jan Scholtz, Rachel S. Somerville, Thomas M. Stanton, Struan D. Stevenson, Irene Shivaei, Sandro Tacchella, Jonathan R. Trump, Hannah Übler, Xin Wang, Christina C. Williams, Christopher N. A. Willmer, L. Y. Aaron Yung, Yongda Zhu
Astrophysics of Galaxies
Dark matter dynamical friction on binary stars in the faintest dwarf galaxies: I. Analytical approach
Nicolas Esser
We study binary
stars moving through a uniform dark matter background and experiencing dynamical friction. The centre-of-mass motion of the pairs is taken into account. We derive formulas and timescales for the secular
evolution of the orbital parameters for both wide and close binaries. Applying these results to environments typical of the faintest ultra-faint
dwarf galaxies, we show that some binaries undergo significant eccentricity oscillations while their semi-major axes gradually decrease over a Hubble time. At the population level, dynamical friction depletes wide binaries and increases the fraction of highly eccentric systems. Importantly, the effect is not strongest at the highest dark matter densities, since the associated increase in velocity dispersion weakens friction. With future, more detailed theoretical studies and improving observational capabilities, binary
stars may serve as a tool to probe the dark matter content of the faintest
galaxies.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Unitarity violation and restoration in radiative bound-state formation
Marcos M. Flores and Kalliopi Petraki
State-of-the-art calculations motivated by dark matter exhibit severe violation of partial-wave unitarity in the non-relativistic regime in radiative bound-state-formation processes. It has been recently shown, in a model-independent fashion, that unitarity is restored by the proper resummation of the inelastic contributions to the self-energy of the incoming state. In this work, we first derive Kramers-like formulae for individual partial waves, demonstrating that existing calculations of bound-state formation severely violate unitarity. We then discuss how unitarity is restored through the resummation of the absorptive contributions to the incoming-state self-energy, generated by bound-state formation processes, taking into account their analytic structure in the complex momentum plane. Our results can be generalized to a variety of theories and employed in phenomenological studies, such as dark-matter freeze-out, indirect detection and self-interactions.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Warm dark matter from freeze-in at stronger coupling
Duarte Feiteira, Oleg Lebedev and Vinícius Oliveira
We study warm
Higgs portal dark matter (DM) in the framework of freeze-in at stronger coupling. This scenario assumes that the Standard Model thermal bath temperature has always been relatively low, which suppresses dark matter production. As a result, a significant DM-
Higgs coupling is allowed, enabling warm dark matter detection via
Higgs decay at
colliders. We find that the Lyman-{\alpha} bound on the DM mass is particularly strong, excluding masses below 50-100 keV, depending on further details. The shape of the DM momentum distribution is highly non-thermal, with low momenta being effectively cut off, and not captured by the common {\alpha}{\beta}{\gamma}-parametrization.
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Astrophysics of Galaxies
The ALPINE-CRISTAL-JWST Survey: Chemical Abundance Comparison Between the ISM and CGM of Main-Sequence Galaxies at z=4-6
Wuji Wang, Andreas L. Faisst, Kyle Finner et al. (+37 more)
Gaseous
halos around
galaxies play an important role in
galaxy evolution. The exchange of metals from the interstellar medium (ISM) to the circumgalactic medium (CGM) are caused by the formation, feedback, and/or merging history of
galaxies. We study the variation in chemical composition between the ISM ($\lesssim3\,$kpc) and CGM ($\sim5-10\,$kpc) for a sample of $M_{\star}>10^{9.5}\,M_{\odot}$ main-sequence
galaxies at $4<z<6$ with both JWST and ALMA observations. Using JWST/NIRSpec integral field spectroscopy, we derive the optical line ratios from the ISM and the CGM for our sample focusing on the typical optical lines used for
metallicity studies. Our comparison shows that the ISM and the CGM have similar chemical abundances. This indicates that the CGM of these typical $4<z<6$
galaxies is enriched to the level of their ISM in the early universe. Using statistical tests, we find that some of the line ratios show marginal differences between the ISM and CGM. Combined with Cloudy modeling, our results suggest that a difference in ionization level (higher for the ISM) is the dominant reason for the observed ratio difference of oxygen line ratios. There is also indication of a deficit in the nitrogen abundance with respect to oxygen in the CGM, which suggests a delay in redistribution of secondary nitrogen. Finally, an enhanced $F_{[\rm CII]\rm 158\mu m}/F_{\rm H\alpha}$ ratio is observed in the CGM, suggesting that feedback and/or mergers play a key role in metal mixing.
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All authors Wuji Wang, Andreas L. Faisst, Kyle Finner, Livia Vallini, Andrea Pallottini, Enrico Veraldi, Bahram Mobasher, Yu-Heng Lin, Giovanni Zamorani, Vicente Villanueva, Sylvain Veilleux, Keerthi Vasan G.C., Hannah Uebler, Akiyoshi Tsujita, Kseniia Telikova, John D. Silverman, Michael Romano, Monica Relano, Francesca Pozzi, Ambra Nanni, Juan Molina, Lun-Jun Liu, Yuan Li, Mahsa Kohandel, Anton M. Koekemoer, Hanae Inami, Edo Ibar, Rodrigo Herrera-Camus, Ali Hadi, Nicol Gutierrez-Vera, Michele Ginolfi, Seiji Fujimoto, Miroslava Dessauges-Zavadsky, Ilse De Looze, Poulomi Dam, Elisabete da Cunha, Mederic Boquien, Roberto J. Assef, Manuel Aravena, David B. Sanders
Astrophysics of Galaxies
ALMA Central Molecular Zone Exploration Survey (ACES) II: 3mm continuum images
Adam Ginsburg, Daniel L. Walker, Ashley T. Barnes et al. (+69 more)
The ALMA Central Molecular Zone Exploration Survey, ACES, has mapped $\gtrsim1000$ square arcminutes at 3 mm toward the center of our
Galaxy. ACES provides the first large-scale, high-resolution ($\sim2.5$") view of the central $\sim200$ parsecs of the Milky Way. In this work, we describe the continuum data processing and present the continuum data products. In the combined mosaic of 45 individual ALMA mosaics, the typical RMS noise achieved is $\sim0.1$ mJy per $\sim2.5$" beam, though there is a tail of substantially higher noise toward regions with bright continuum structure, especially around Sgr A* and Sgr B2. In-band spectral indices are measurable for a small fraction of the brightest and most compact sources, enabling distinction between
dust-dominated and free-free- or synchrotron-dominated sources. To recover emission on large angular scales, we present the GBT MUSTANG-2 Three millimeter Extended
Nucleus Survey (TENS), a new 10"resolution survey of the CMZ, which we combine with the ACES image by feathering. To demonstrate the quality and reliability of the ACES data, we compare to previously-published ALMA data obtained with higher resolution and sensitivity, finding overall good agreement with past results, but some disagreement toward the brightest sources.
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All authors Adam Ginsburg, Daniel L. Walker, Ashley T. Barnes, Xing Lu, Álvaro Sánchez-Monge, Jaime E. Pineda, Marc W. Pound, Pei-Ying Hsieh, Katharina Immer, Qizhou Zhang, Nazar Budaiev, Savannah R. Gramze, Desmond Jeff, Claire Cook, Alyssa Bulatek, Elisabeth A.C. Mills, John Bally, Laura Colzi, Pablo García, Jonathan D. Henshaw, Izaskun Jiménez-Serra, Ralf S. Klessen, Simon R. Dicker, Steven N. Longmore, Francisco Nogueras-Lara, Víctor M. Rivilla, Miriam G. Santa-Maria, Q. Daniel Wang, Fengwei Xu, Cara Battersby, Paul T. P. Ho, J. M. Diederik Kruijssen, Maya Petkova, Mattia C. Sormani, Robin G. Tress, Jennifer Wallace, J. Armijos-Abendaño, Lucia Armillotta, N. Bijas, Rojita Buddhacharya, Laura A. Busch, Natalie O. Butterfield, Mélanie Chevance, Samuel Crowe, Ana Karla Díaz-Rodríguez, Katarzyna M. Dutkowska, Rubén Fedriani, Christoph Federrath, Simon C. O. Glover, Qi-Lao Gu, Rebecca J. Houghton, Yue Hu, Namitha Issac, Janik Karoly, Mark R. Krumholz, Fu-Heng Liang, Sergio Martín, Farideh Mazoochi, Xing Pan, Dylan Paré, Thushara G.S. Pillai, Denise Riquelme-Vásquez, Anika Schmiedeke, Yoshiaki Sofue, Volker Tolls, Gwenllian M. Williams, Suinan Zhang, Emily Moravec, Charles E. Romero, Brian S. Mason, John Orlowski-Scherer, H Perry Hatchfield
Solar and Stellar Astrophysics
X-Shooting ULLYSES: Massive stars at low metallicity XIV. Properties of SMC late-O and B supergiants reveal the metallicity dependence of winds in the Magellanic Clouds
T. Alkousa, P.A. Crowther, J.M. Bestenlehner et al. (+10 more)
Considering the physics of radiation-driven winds of massive
stars, the wind properties should depend on the metal content of the
stellar atmosphere. Therefore, studying the winds of massive
stars in different
metallicities provides a sanity check on prescriptions that are widely used in evolutionary calculations. We obtained the
stellar and wind properties of a sample of 20 late-O and B supergiants in the Small Magellanic Cloud (SMC) from a quantitative combined UV and optical spectroscopic analysis using CMFGEN. By comparing these properties with those of a Large Magellanic Cloud counterpart study, which has a similar sample and data, and employed the same modelling techniques used in this study, We derived a
metallicity-dependent recipe for wind momentum, which is applicable for $5.4 \leq \log{L_{\rm bol}/L_{\odot}} \leq6.1$ and $14 \leq T_{\rm eff}/{\rm kK} \leq 32$. We find a significant dependence of the wind momentum on the
metallicity, which is largely due to the mass-loss rates. We do not find any evidence of a discontinuity in either the mass-loss rate or the ratio of the terminal wind velocity to the escape velocity between $25$ and $21$~kK, which could be attributed to the bi-stability jump.
Stellar parameters are consistent across different methods and radiative transfer codes, whereas mass-loss rates differ significantly, with our values being generally lower. We find a discrepancy between the evolutionary and spectroscopic masses in $40\%$ of our sample, with the evolutionary mass usually being systematically higher. The mass-loss rates of blue supergiants are far too low to strip the
stellar envelope and the subsequent formation of classical Wolf-Rayet (WR)
stars, leading to the conclusion that luminous blue variable eruptions or binary interactions are necessary to explain the characteristics of the WR population in the SMC.
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All authors T. Alkousa, P.A. Crowther, J.M. Bestenlehner, H. Sana, F. Tramper, J.S. Vink, F. Najarro, A.A.C. Sander, M. Bernini-Peron, L. Oskinova, J.Th. van Loon, R. Kuiper, The XShootU collaboration
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Linking Leptogenesis and Asymmetric Dark Matter: A Testable Framework for Neutrino Mass and the Matter-Antimatter Asymmetry
Henry G. F. McKenna, Juri Smirnov and Martin Gorbahn
We investigate a minimal extension of the Leptogenesis framework that simultaneously explains the observed
baryon asymmetry and dark matter (DM) abundance through the decay of a heavy Majorana
neutrino. In this scenario, CP violation arises from complex Yukawa couplings, enabling the generation of asymmetries in both the Standard Model (SM) and DM sectors. We explore two regimes: (i) wash-in, where an initial dark asymmetry is transferred to SM
leptons by $2 \leftrightarrow 2$ scattering processes; and (ii) co-genesis, featuring a hierarchical coupling structure that allows enhanced CP violation while supporting a low-scale seesaw mechanism at order $\mathcal{O}(2)$ TeV. This setup not only links light
neutrino masses to the Majorana mass term but also suggests that
lepton-number violation may occur at experimentally accessible energy scales. In the co-genesis scenario, we show
spin-independent cross sections for DM heavier than 10 GeV that can be tested in current direct detection experiments and motivate the exploration of cross sections inside the
neutrino fog for lighter DM masses, establishing asymmetric leptogenesis as a predictive
benchmark framework for direct-detection experiments and identifying a new hierarchical-coupling regime enabling TeV-scale leptogenesis.
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High Energy Astrophysical Phenomena
High-resolution Very Large Array Radio Observations of the Boomerang Pulsar Wind Nebula
Paul C. W. Lai, Chi-Yung Ng and Shumeng Zhang
We present a
radio polarimetric study of the Boomerang
pulsar wind nebula G106.65+2.96 with Very Large Array (VLA) observations at the 6 GHz band. Our high-resolution image discovers new small-scale features in the nebula, including an elliptical core of $40''\times20''$ surrounding the central
pulsar and a $2'$-long arc wrapping around the core in the north. The latter shows a gap from the core, and it consists of a bright lobe in the northwest and a tongue-like structure in the northeast. These could be resulting from the
pulsar wind interaction with the environment. Our polarization measurement reveals a highly ordered
magnetic field with toroidal geometry. The small scale features are all highly linearly polarized. In particular, the lobe has a polarization fraction of $\sim$60%, close to the synchrotron limit. This is also much higher than the value measured at a lower frequency, implying significant depolarization. We show that this can be explained by Faraday rotation in the nebula, and we constructed a simple 3D model accordingly to estimate a
magnetic field strength of $\sim$25-70$ \mu$G assuming a median inclination angle of $60^\circ$, which uncertainty arises from the uncertainty in the flux measurement and its distance.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Global Structure in Learned Latent Representations of Confusion-Limited LISA Data
Jericho Cain
Machine learning methods in gravitational wave data analyses depend on the choice of representation and on how structure within that representation is used. Building on previous work using continuous wavelet transform (CWT) autoencoder representations for confusion-limited LISA simulation, we investigate whether source resolvability information is better characterized by local latent geometry or by global latent density. We study this question in a controlled
benchmark with data generation and preprocessing held fixed. Using CWT representations of synthetic confusion-limited LISA segments, we compare geometry based one-class scoring with likelihood-based latent models along with their morphology augmented variants. Likelihood-based scoring consistently outperforms local
manifold-distance methods across three independent seeds, achieving ROC-AUC \(0.8555 \pm 0.0181\) and PR-AUC \(0.9219\pm 0.0118\), compared with ROC-AUC \(0.7663\pm 0.0450\) and PR-AUC \(0.8667\pm 0.0255\) for the geometry baseline. These results suggest that resolvability information in learned latent representations is not fully captured by local latent geometry but instead reflects global properties of the latent distribution. More broadly, this work contributes to representation-aware methods for confusion-foreground characterization in LISA and motivates future studies of coordinate invariance and intrinsic geometry in learned latent spaces.
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Earth and Planetary Astrophysics
Topography-Induced Stationary Waves and the Onset of Nightside Warming on Rocky Planets around M-dwarf Stars
Howard Chen, Aida Ildirimzade and Evelyn Macdonald
Among potentially habitable worlds, rocky
planets orbiting M
dwarfs offer the most favorable prospects for atmospheric characterization, yet their climates may differ substantially from those of Earth analogs. In the tidally locked limit, the nightside's tendency to radiatively cool and potentially trap volatiles as permanent ice introduces a strong dependence of habitability on the
planet's surface and atmospheric boundary conditions. We perform a suite of synchronously rotating experiments spanning a wide range of topographic and orographic realizations with different mean elevations and landmass distributions. Across a grid of $p_{\mathrm{N2}} = 0.5$-$8~\mathrm{bar}$ and $F_{\star} = 1200$-$1700~\mathrm{W\,m^{-2}}$, we find that surface relief breaks the flow
symmetry, replacing the circumpolar
vortices with mechanically forced stationary waves. Steep orography produces standing Rossby gyres that strengthen the cross-terminator jet and align vertical uplift with the day–night boundary. These new circulation regimes enhance moisture transport, increasing the infrared optical depth and promoting additional nightside cloud formation, which produces a stronger cloud-greenhouse feedback and lower the critical fluxes required for global planetary deglaciation. Broad, elevated plateaus drive a similarly fragmented but slightly weaker circulation, yielding less effective moisture transport. These results show that the relief and spatial distribution of landmasses, parameters unconstrained for most
exoplanets, can exert strong controls on the climatic bifurcations of tidally locked M-
dwarf exoplanets.
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High Energy Astrophysical Phenomena
IceCube's convex all-sky neutrino spectrum consistent with the magnetically powered corona scenario for active galactic nuclei
Kohta Murase, Shigeo S. Kimura, Mainak Mukhopadhyay et al. (+1 more)
High-energy multimessenger background analyses over the past decade have provided evidence for a population of hidden
neutrino sources that are opaque to GeV-TeV gamma rays, a picture bolstered by recent observations of the nearby active
galaxy NGC 1068. The coronal regions in the hearts of active
galactic nuclei (AGNs) have been proposed as the most promising sites for such hidden nonthermal particle production, and NGC 1068 is expected to be the most
neutrino-active
galaxy for IceCube. We demonstrate that the latest all-sky
neutrino spectrum, exhibiting a spectral bend around 3-30 TeV, is consistent with predictions of the magnetically powered corona scenario, and the models for the all-sky
neutrino flux can simultaneously explain the multimessenger data from NGC 1068 within observational and modeling uncertainties. We further show, in a largely model-independent way, that the contribution from NGC 1068-like sources does not overshoot the observed medium-energy
neutrino flux. Finally, we highlight the key role of the Eddington ratio, which can drive substantial variations in the predicted
neutrino fluxes of nearby AGNs, and we encourage systematic multimessenger searches for the
neutrino-brightest AGNs.
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All authors Kohta Murase, Shigeo S. Kimura, Mainak Mukhopadhyay, Mukul Bhattacharya
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Development of a Cherenkov-Based Time-of-Flight Detector Using Silicon Photomultipliers
Liliana Congedo, Giuseppe De Robertis, Antonio Di Mauro et al. (+11 more)
The aim of this work is to develop high precision Time-of-Flight (TOF) devices based on high refractive index solid Cherenkov radiators read out by silicon photomultipliers (SiPMs). Cherenkov light is
prompt and therefore ideal for reaching the intrinsic timing limits of TOF systems. By utilizing a thin, high-refractive-index radiator a nearly instantaneous signal is generated by particles exceeding the Cherenkov threshold. In order to achieve the ultimate time resolution, we carried out a rigorous optimization of the radiator material and geometry, alongside the efficiency of the optical coupling to the SiPM sensors. The key factors limiting the time resolution were characterized by comprehensive Monte Carlo simulations, subsequently validated against experimental beam test data. We assembled small-scale prototypes instrumented with various Hamamatsu SiPM arrays sensors with pitches ranging from 1.3 to 3 mm coupled with various window materials, such as fused silica and MgF2, featuring various thickness values. The prototypes were successfully tested in beam test campaigns at the CERN-PS T10 beam line. The data were collected with a complete chain of front-end and readout electronics based on either the Petiroc 2A or the Radioroc 2 interfaced to a picoTDC to measure charges and times. By comparing the time measurements with two SiPM arrays we were able to measure a time resolution better than 33.2 ps at the full system level with a charged particle detection efficiency of 100%. Our results demonstrate the expected performance
benchmarks for the charged particle detection efficiency and time resolution and highlight the potential of the developed Cherenkov-based TOF detectors for next-generation particle identification systems.
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All authors Liliana Congedo, Giuseppe De Robertis, Antonio Di Mauro, Mario Giliberti, Francesco Licciulli, Antonio Liguori, Rocco Liotino, Leonarda Lorusso, Mario Nicola Mazziotta, Eugenio Nappi, Nicola Nicassio, Giuliana Panzarini, Roberta Pillera, Giacomo Volpe
High Energy Astrophysical Phenomena
Eccentricity Distribution for Dynamical Gravitational-Wave Merger Channels in The Pinhole Regime
Mor Rozner, Teagan A.Clarke, Isobel M. Romero-Shaw et al. (+1 more)
We argue that various dynamical astrophysical black hole merger channels are expected to result in a common eccentricity distribution at gravitational-wave (GW) frequencies relevant for LIGO/Virgo/KAGRA (LVK) in the high eccentricity limit. This follows from the large separation of scales between the GW regime required for creating eccentric mergers in LVK, and the underlying astrophysical formation environment. Our analytical solution shows exceptional agreement with numerical studies. This finding has important implications for both theoretical studies and ongoing searches for eccentric GW sources.
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All authors Mor Rozner, Teagan A.Clarke, Isobel M. Romero-Shaw, Johan Samsing
Solar and Stellar Astrophysics
HelioSpectrotron 5000: An interactive multi-resolution solar spectral atlas
A.G.M. Pietrow
HelioSpectrotron 5000 (HS5000) is an interactive, multi-resolution
solar spectral atlas designed to facilitate direct comparison between high-resolution reference spectra and observations obtained with a wide range of ground-based instruments. Based on the Hamburg FTS atlas, the HS5000 provides both absolute intensity and continuum-normalized spectra at arbitrary spectral ranges and resolutions, as well as curated line identifications and optional telluric contamination. This framework enables rapid wavelength calibration, line identification, and context image generation.
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Solar and Stellar Astrophysics
21,864 Unresolved, Low-mass Binaries Identified via their Overluminosity in Gaia DR3 and a Catalog of 347,440 Systems within 100 pc of the Sun
Zachary Way, Sébastien Lépine, Jonathan Gagné et al. (+1 more)
The fundamental parameters of a low-mass
star can potentially be determined from its photometry and astrometry. This is complicated by the fact that 10-20 percent of low-mass
stars are predicted to be equal-mass binaries. These unresolved systems appear more luminous compared to single
stars with the same fundamental parameters. We present a method to differentiate binary
stars from single-
star main sequence K and M
dwarfs using their
Gaia DR3 XP spectra. We assemble a training set of
stars which have pristine astrometry and photometry, are located within 100pc of the Sun, and exclude
stars with
Gaia DR3 flags suggesting they may be unequal mass systems, thereby leaving
stars that are predominantly either single- or equal-mass binaries. We then iteratively train Random Forest Regression (RFR) models to predict absolute magnitude and color given the RP spectral coefficients of a
star. After each model, we remove the
stars that have absolute magnitudes significantly brighter than their predicted values. This method converges on a model trained only on single
stars. We then use this model to identify the “overluminous” K and M
stars in
Gaia DR3 within 100 parsecs, with some quality cuts. We find that $\sim13\%$ of the sample is significantly overluminous and assume these to be unresolved binaries. We aggregate several multiplicity surveys across different projected separations and incorporate our overluminous binaries to create a general Catalog of Systems within 100 pc. We use this Catalog to provide lower limits on the multiplicity fraction for
stars between $0.1$ and $0.7~M_{\odot}$.
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All authors Zachary Way, Sébastien Lépine, Jonathan Gagné, Ilija Medan
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Addressing leakage and mode suppression in angular power spectrum estimation for gravitational-wave backgrounds using pulsar timing arrays
Deepali Agarwal, Joseph D. Romano, Yacine Ali-Haïmoud et al. (+1 more)
Mapping gravitational-wave background (GWB) anisotropy with
pulsar timing arrays (PTAs) is affected by harmonic-space mode suppression and mode coupling arising from an array's nonuniform sky response. Spherical harmonic expansions must be truncated at finite multipole l_max^rec, often set to l_max^N_pair$\equiv {\rm int}\left[\sqrt{\text{N_pair}}-1\right]$, where N_pair is the number of distinct
pulsar pairs in an array. This choice is motivated by the counting argument that cross-correlations provide at most N_pair independent constraints. We obtain the multipole l_max^res corresponding to the maximum informative angular scale of a PTA. It is defined such that expansions to l_max^res (approximately) span the space of "observable skies" encoded in the N_pair eigenmaps of the Fisher information
matrix, and therefore depends on the array configuration. We explicitly show that GWB power contained in multipoles l$\gtrsim$l_max^res do not significantly affect analyses that use expansions out to l_max^res, because the PTA response acts as a low-pass filter. In contrast, truncating at l_max^rec< l_max^res leads to leakage of small-scale angular power from l_max^rec<l$\leq$l_max^res. Even choosing l_max^rec=l_max^res, the standard frequentist
estimator of the angular power spectrum C_l remains biased by the modes unobservable by the array. Although we can (partially) debias the standard
estimator – improving its agreement with an injected spectrum – this reduction in bias comes at the expense of an increase in variance, particularly for poorly constrained modes with l$\gg$l_eff. We therefore recommend: (i) using l_max^res for PTA analyses involving spherical harmonic expansions, and (ii) using the debiased standard
estimator for C_l recovery, but only out to multipoles l<l_eff ($\ll$l_max^res) corresponding to sufficiently constrained modes.
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All authors Deepali Agarwal, Joseph D. Romano, Yacine Ali-Haïmoud, Tristan L. Smith
Cosmology and Nongalactic Astrophysics
Cosmic strings and domain walls: the impact of CMB $B$-mode data
Luca Caloni, Ricardo Z. Ferreira, Lara Sousa et al. (+1 more)
We analyse CMB constraints on stable networks of
cosmic strings and domain walls using for the first time full Planck 2018 data together with BICEP/Keck 2018 $B$-mode measurements. The defect-induced anisotropies are computed using the Unconnected Segment Model for Nambu-Goto and Abelian-
Higgs strings, as well as for stable domain walls, and included in a full Markov Chain Monte Carlo analysis jointly varying all $\Lambda$CDM parameters, the tensor-to-scalar ratio, and the string/domain wall tension. No statistically significant evidence for defects is found, although we observe a mild preference for non-zero
cosmic string tension. Our results improve previous constraints on the
cosmic string power spectrum and correct previous CMB analyses with domain walls that overestimated the constraints. In the particular case of strings, the improvement is driven by the $B$-mode data, and is especially pronounced for Abelian-
Higgs strings. We also present forecasts for the Simons Observatory and the LiteBIRD satellite: the former will improve string tension constraints by about a factor of three, while the latter those on the domain wall tension by about a factor of five. Finally, we assess the impact of Nambu-Goto string loops on CMB anisotropies in light of both current and future observations.
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All authors Luca Caloni, Ricardo Z. Ferreira, Lara Sousa, Clara Winckler
Earth and Planetary Astrophysics
The Orbital Eccentricity–Radius Distribution for Warm, Single Planets in TESS
Tyler R. Fairnington, Jiayin Dong, Chelsea X. Huang et al. (+40 more)
We characterize the radius-dependent eccentricity distribution of 219 warm (P = 8–50 days) systems with only one transiting planetary candidate identified during Sectors 1-69 of the TESS mission. Using the “photoeccentric effect” in a hierarchical
Bayesian framework, we first model the population using discrete planetary size bins (sub-Neptunes, sub-Saturns, and Jovians). We then develop a continuous mixture model with weights governed by a logistic sigmoid function of radius. We find that the warm-single population is best described by two components: a dominant low-eccentricity mode ( <e_low> = 0.039-0.038+0.018) and a secondary dynamically excited mode (<e_high> = 0.466-0.068+0.067). The fraction of
planets belonging to this high-eccentricity component increases strongly with
planet radius, characterized by a transition at a break radius of R_br = 9.2-1.1+1.9 R_e. This trend places warm sub-Saturns predominantly on the same low-eccentricity track as sub-Neptunes. In contrast, warm Jovians (8–16 R_e) are frequently eccentric, with 65-12+13% of the population in the high eccentricity mode. Under the assumption of a two-component model, we see tentative evidence for a bimodal Jovian distribution at ~2.7 sigma. Finally, we identify a non-negligible tail of highly eccentric sub-Neptunes (1–4 R_e), which comprise 16.2-6.4+5.2% of the population, consistent with excitation by non-transiting external companions.
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All authors Tyler R. Fairnington, Jiayin Dong, Chelsea X. Huang, Emma Nabbie, George Zhou, Duncan Wright, Karen A. Collins, David Ciardi, Jon M. Jenkins, David W. Latham, George Ricker, Samuel N. Quinn, Sara Seager, Avi Shporer, Roland Vanderspek, Joshua N. Winn, Khalid Barkaoui, Allyson Bieryla, Lars Buchhave, Dmitry Cheryasov, Jessie Christiansen, Courtney Dressing, Akihiko Fukui, Alexey Garmash, Steven Giacalone, Eric G. Hintz, Steve B. Howell, Keisuke Isogai, Jerome de Leon, Jorge Lillo-Box, Felipe Murgas, Norio Narita, Louise D. Nielsen, Enric Palle, Markus Rabus, Benjamin V. Rackham, Richard P. Schwarz, Gregor Srdoc, Denise C. Stephens, Gavin Wang, Noriharu Watanabe, Francis P. Wilkin, Joe Williams
Astrophysics of Galaxies
The major merger-active galactic nucleus connection up to the cosmic noon
A. La Marca, B. Margalef-Bentabol, L. Wang et al. (+3 more)
Galaxy major mergers are a potential mechanism for triggering active
galactic nuclei (AGN) activity, but their role remains debated, particularly beyond the local Universe. We aim to shed light on the merger-AGN connection at $z=0.5$-$2$, exploiting the multi-wavelength
datasets and James Webb Space
Telescope (JWST) observations in the COSMOS field. We construct a
stellar mass-limited sample and identify AGN via mid-infrared (MIR) colours, X-ray detections, and spectral energy distribution (SED) fitting. We train convolutional neural networks to identify mergers with mock JWST observations. We create non-AGN and non-merger control samples matching the
redshift,
stellar mass, and
star-formation rate distributions of the AGN and mergers. We find AGN to be moderately more frequent in mergers than in non-mergers, with excess ratios ranging from $\sim2.5$ (X-ray AGN) to $\sim1.3$ (MIR) and $\sim 1.1$-1.2 (SED AGN). Similarly, AGN
galaxies show a higher merger fraction ($f_{merg}$) than non-AGN controls. We then study $f_{merg}$ as a function of relative and absolute AGN power, utilising the AGN fraction ($f_{AGN}$) and
accretion disc luminosity (L$_{disc}$) parameters. We uncover a $f_{merg}$-$f_{AGN}$ relation with two regimes: $f_{merg}$ stays roughly flat for less-dominant AGN ($f_{AGN}<0.8$) but increases at $f_{AGN}>0.8$ for the MIR and X-ray AGN, and more gently for SED AGN, where mergers appear to be the main triggering mechanism. Additionally, $f_{merg}$ increases monotonically as a function of L$_{disc}$, for all AGN types, reaching $f_{merg}>50\%$ for the most luminous AGN (L$_{disc} \gtrsim 10^{46}\,{erg\,s^{-1}}$). Overall, our results suggest that major mergers can trigger AGN out to the
cosmic noon at $z\sim2$. Furthermore, the role of major mergers shows a clear dependence on AGN luminosity and remains the principal mechanism for fuelling the most powerful AGN.
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All authors A. La Marca, B. Margalef-Bentabol, L. Wang, S. C. Trager, V. Rodriguez-Gomez, G. Martin
Astrophysics of Galaxies
Simulation of proton radiolysis of H2O and O2 ices with the Nautilus code
Tian-Yu Tu, Valentine Wakelam, Jean-Christophe Loison et al. (+3 more)
The radiolysis effect of
cosmic rays (CRs) plays an important role in the chemistry in molecular clouds. CRs can dissociate the molecules on
dust grains, producing reactive suprathermal species and radicals which facilitate the formation of large molecules. We add the radiolysis process and some relevant reactions into the Nautilus astrochemical code. By adjusting some parameters, we investigate the sensitivity of the simulation results of the H2O ice on the removal of reaction-
diffusion competition, the removal of non-diffusive chemistry, and the desorption energies of the suprathermal species. We find the model, with a few adjustments of the chemistry, can reproduce the steady-state [H2O2]/[H2O] and [O3]/[O2]_0 abundance ratios in the H2O and O2 radiolysis experiments at any CR flux in the experiments. These adjustments in the model do not fully reproduce the fluence required to reach the steady state. It tends also to overestimate the destruction of H2O as measured in H2O radiolysis experiments. We show that reducing the G-values of H2O radiolysis, which implies an increase in the efficiency of immediate reformation of water locally after ion impact, leads to simulated H2O destruction rates closer to the experiments. The effect of reaction-
diffusion competition on the simulation results of H2O ice is significant at $\zeta \lesssim 10^{-14}\ \rm s^{-1}$. The non-diffusive chemistry affects the simulation results at 16 K but not 77K, while the results are sensitive to the desorption energies of suprathermal H, O, O3 and OH at 77 K. Our results show that the steady-state [H2O2]/[H2O] and [O3]/[O2]_0 in experiments can be reproduced by fine-tuning the chemical model, but still call for more constraints on the intermediate pathways in the radiolysis processes, especially the ion chemistry in the ice bulk, as well as activation barriers and branching ratios of the reactions in the network.
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All authors Tian-Yu Tu, Valentine Wakelam, Jean-Christophe Loison, Marin Chabot, Emmanuel Dartois, Yang Chen
Astrophysics of Galaxies
Bar Formation During a Gaia-Sausage-Enceladus-like Merger Event
Bin-Hui Chen, Juntai Shen and Paola Di Matteo
Bars are among the most prominent
galactic structures, yet their formation mechanisms remain incompletely understood. They can form either internally, via dynamical instabilities, or externally, triggered by interactions with other
galaxies. The impact of mergers on bar formation and survival, however, has not been thoroughly investigated. To explore the influence of mergers on bars, we construct a suite of N-body merger pairs where a
Gaia-Sausage-Enceladus-like radially biased satellite disk
galaxy merges with a central disk
galaxy during its bar formation. With the central
galaxy fixed, the satellite varies in merger parameters: the mass ratio $m/M$ relative to the central
galaxy, the impact parameter $b$, and the orbital inclination angle $\theta_i$ relative to the central disk. We find that the bar survival probability decreases with increasing $m/M$. Mergers with $m/M\lesssim1/10$ generally preserve the forming bar, whereas those with ${m/M}\geq1/2$ tend to destroy it, producing more early-type-like remnants. For intermediate mass ratios ($1/5 \leq m/M \leq 1/3$), several models yield “weakening bars”, in which the bar survives the merger but gradually decays during subsequent secular
evolution, possibly due to interactions between nested double bars formed from merger debris. In contrast to $m/M$, $b$ and $\theta_i$ have only secondary and
stochastic effects on bar survival. The different influences of these three merger parameters can be naturally explained by the
tidal force exerted by the satellite on the forming bar, which tends to weaken the bar when the satellite crosses it nearly perpendicular to its major axis.
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Earth and Planetary Astrophysics
LRG-BEASTS: Detection of sodium and evidence for water absorption in the hot Saturn HAT-P-44b
Alastair B. Claringbold, Peter J. Wheatley, James Kirk et al. (+5 more)
We present the low-resolution optical transmission spectrum of the inflated hot Saturn HAT-P-44b. The
planet is a close sibling in radius (1.24 $\mathrm{R_{Jup}}$), temperature (1100 K), and mass (0.35 $\mathrm{M_{Jup}}$) to the exceedingly well-characterized WASP-39b. Using the ACAM instrument on the William Herschel
Telescope (WHT), we obtain a transmission spectrum with sub-scale height precision of 246 ppm, with a wavelength range of 495 – 874 nm and a 20 nm resolution, despite a relatively faint host
star ($V\mathrm{_{mag} = 13.2}$). We detect absorption due to sodium with 3.9$\sigma$ confidence. Atmospheric
retrieval of the transmission spectrum also reveals evidence for \ch{H2O} absorption and Rayleigh scattering from \ch{H2} gas consistent with a cool 800 K atmosphere and a super-
solar metallicity of 7$\substack{+16 \\ -5}$$\times$
solar. Comparison of
retrieval models disfavour the inclusion of a super-Rayleigh scattering slope or high-altitude clouds (at $<1$ mbar) while being agnostic towards the presence of mid-altitude clouds. Our transmission spectrum of HAT-P-44b shows strong similarity to that of its sibling WASP-39b.} This is the tenth
planet in the LRG-BEASTS (Low-Resolution Ground-Based
Exoplanet Atmosphere Survey using Transmission Spectroscopy) survey.
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All authors Alastair B. Claringbold, Peter J. Wheatley, James Kirk, Eva-Maria Ahrer, Ian Skillen, Matteo Brogi, George W. King, James McCormac
Instrumentation and Methods for Astrophysics
Multivariate time-series forecasting of ASTRI-Horn monitoring data: A Normal Behavior Model
Federico Incardona, Alessandro Costa, Farida Farsian et al. (+8 more)
This study presents a Normal Behavior Model (NBM) developed to forecast monitoring time-series data from the ASTRI-Horn Cherenkov
telescope under normal operating conditions. The analysis focused on 15 physical variables acquired by the
Telescope Control Unit between September 2022 and July 2024, representing sensor measurements from the Azimuth and Elevation motors. After data cleaning, resampling, feature selection, and correlation analysis, the
dataset was segmented into fixed-length intervals, in which the first I samples represented the input sequence provided to the model, while the forecast length, T, indicated the number of future time steps to be predicted. A sliding-window technique was then applied to increase the number of intervals. A Multi-Layer Perceptron (MLP) was trained to perform multivariate
forecasting across all features simultaneously. Model performance was evaluated using the Mean Squared Error (MSE) and the Normalized Median Absolute Deviation (NMAD), and it was also benchmarked against a Long Short-Term
Memory (LSTM) network. The MLP model demonstrated consistent results across different features and I-T configurations, and matched the performance of the LSTM while converging faster. It achieved an MSE of 0.019+/-0.003 and an NMAD of 0.032+/-0.009 on the test set under its best configuration (4 hidden layers, 720 units per layer, and I-T lengths of 300 samples each, corresponding to 5 hours at 1-minute resolution). Extending the forecast horizon up to 6.5 hours-the maximum allowed by this configuration-did not degrade performance, confirming the model's effectiveness in providing reliable hour-scale predictions. The proposed NBM provides a powerful tool for enabling early anomaly detection in online ASTRI-Horn monitoring time series, offering a basis for the future development of a prognostics and health management system that supports predictive maintenance.
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All authors Federico Incardona, Alessandro Costa, Farida Farsian, Francesco Franchina, Giuseppe Leto, Emilio Mastriani, Kevin Munari, Giovanni Pareschi, Salvatore Scuderi, Sebastiano Spinello, Gino Tosti