Peer Revenue Play credits. Real papers.

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics

astro-ph Watch Astrophysics

Friday 5 June

Cosmology and Nongalactic Astrophysics

Mass-Varying Neutrinos from an Inverse Symmetron

Mainak Baidya, Øyvind Christiansen, Vitor da Fonseca et al. (+2 more)

Neutrinos enter cosmology in different ways and are constrained by distinct observational probes across different epochs: as a relativistic species at high redshift, as a massive but clustering-suppressing component at low redshift, and as a particle physics observable in laboratory experiments. Low (verging on negative) bounds on neutrino mass from galaxy surveys motivate exploration of models where neutrinos may couple to dark energy, causing their mass to vary over cosmic evolution. If the coupling involves an inverse phase transition (symmetry broken, rather than restored, as neutrinos become nonrelativistic) this can tame instabilities in neutrino growth, appear as a lower neutrino mass in galaxy surveys, and add extra suppression to the matter power spectrum. We find that the late-time decoupling shuts down the fifth force and inhibits the excessive growth of neutrino perturbations, thereby eliminating linear-regime instabilities. The model may potentially address the Hubble tension via an early dark energy component localized around the time of recombination.
Read the full abstract

All authors Mainak Baidya, Øyvind Christiansen, Vitor da Fonseca, Eric V. Linder, David F. Mota

Astrophysics of Galaxies

ALMAGAL IX. The chemical complexity of AG318.9477-00.1960: A line-identification template for ALMAGAL

J. Allande, M. T. Beltrán, V. M. Rivilla et al. (+36 more)

We present a detailed molecular line analysis of one of the most chemically rich cores in the ALMAGAL sample, the high-mass core~9 in the AG318.9477-00.1960 clump (AG318-c9), located at a heliocentric distance of \sim 10.4\,\rm kpc. We further assessed whether the emission of selected COMs, that is, ethylene glycol ((CH_2OH)_2; EG), glycolaldehyde (CH_2(OH)CHO; GA), and methyl formate (CH_3OCHO; MF), can be used to trace the innermost regions of hot molecular cores (HMCs). We analysed ALMA Band~6 observations (\sim 217-221GHz). Spectral line identification and local thermodynamic equilibrium modelling were performed using the software MADCUBA. We derived the physical parameters, including the column density (N), excitation temperature (Tex), velocity, line width, and molecular abundances relative to H_2, for all detected species. The chemical inventory of AG318-c9 was compared with that of the HMC G31.41+0.31 (G31). In addition, we performed a pixel-by-pixel analysis of EG, GA, and MF to generate spatially resolved N and Tex maps and corresponding radial profiles.
Read the full abstract

All authors J. Allande, M. T. Beltrán, V. M. Rivilla, Á. López-Gallifa, C. Y. Law, Á. Sánchez-Monge, C. Battersby, M. Benedettini, H. Beuther, C. L. Brogan, L. Bronfman, S. D. Clarke, L. Colzi, D. Elia, F. Fontani, G. A. Fuller, T. R. Hunter, P. T. P. Ho, K. G. Johnston, B. M. Jones, K. -T. Kim, P. D. Klaassen, R. S. Klessen, R. Kuiper, D. C. Lis, C. Mininni, S. Molinari, T. Möller, L. Moscadelli, A. Nucara, S. Pezzuto, P. Schilke, E. Schisano, F. van der Tak, Y. Tang, A. Traficante, S. Walch, Q. Zhang, T. Zhang

Astrophysics of Galaxies

Origin of monolithic high-z galaxies and UV luminosity of mergering high-z galaxies in the cosmological model with non-standard spectrum of density perturbations

Yu.N. Eroshenko, V.N. Lukash, E.V. Mikheeva et al. (+2 more)

The James Webb Space Telescope (JWST) has detected an unexpectedly large number of galaxies at redshifts $z\geq 10$ compared to the predictions of the standard $\Lambda$CDM model. One of possible explanations is the presence of an excess (bump) in the power spectrum of perturbations at the mass scale of these galaxies, which is about $10^{10}M_\odot$. This excess simultaneously shifts the epoch of cosmic reionization to significantly earlier times, in contradiction with observations. Here we show that this defect of the bump model can be avoided if the perturbation spectrum has a cutoff (suppression) at smaller scales, which can be realized by lowering the amplitude of the primordial perturbation spectrum or by considering warm dark matter. With a cutoff present, fewer low-mass halos form and, consequently, fewer stars producing ionizing UV radiation. We also derive the halo merger-rate distribution in the presence of a bump using the extended Press–Schechter (EPS) theory, and verify this distribution against direct $N$-body simulations. Based on this distribution, and under the assumption that mergers trigger starbursts, we compute the UV luminosity function of early galaxies and demonstrate its agreement with available observational data. In the model under consideration, the fraction of early galaxies forming via the monolithic mechanism (through a single large-scale collapse) is significantly increased in comparison with the standard $\Lambda$CDM model, and the first stars appear directly in halos with masses $\geq10^8M_\odot$. We refer to such stars with primordial chemical composition as “Population~IV stars,” to distinguish them from the evolutionary different stellar populations.
Read the full abstract

All authors Yu.N. Eroshenko, V.N. Lukash, E.V. Mikheeva, S.V. Pilipenko, M.V. Tkachev

Astrophysics of Galaxies

Simple cyanides and formylium ions isotopologues in early star-forming molecular cores

R. D. Taboada, S. Paron, N. C. Martinez et al. (+1 more)

Understanding the chemistry related to the early stages of star formation is of great importance, as it is linked to the beginnings of the most complex chemistry in the interstellar medium. In this context, we investigate the chemical behaviour of simple cyano-bearing molecules and formylium ions isotopologues in a sample of massive infrared-quiet molecular cores. Using archive ALMA Band 7 data of 37 early molecular cores embedded in ATLASGAL clumps, we obtain abundances of HC$_{3}$N, H$^{13}$CN, HN$^{13}$C, H$^{13}$CO$^+$, and HC$^{17}$O$^+$. We used various statistical methods, including hierarchical clustering, to analyse the correlations between molecular abundances, ratios and temperature. We find that HN$^{13}$C, H$^{13}$CO$^{+}$, and HC$^{17}$O$^{+}$ abundances correlate positively with kinetic temperature, suggesting temperature-driven chemical regulation in young massive cores. A similar trend is observed for H$^{13}$CN, although the limited number of detections prevents a definitive conclusion. HC$_3$N abundances show no dependence on temperature within the 40-100 K range, suggesting a chemical steady state between gas-phase production and grain-surface depletion. Similarly, the H$^{13}$CN/HN$^{13}$C ratio, measured in only six regions, suggests no correlation with temperature, differing from findings at lower temperatures. Using a hierarchical clustering method based on abundance ratios, novel in astrochemistry, we identified chemically distinct core groups that align with thermal conditions. Additionally, we provide HC$^{17}$O$^+$ detections for 28 cores-a significant expansion of existing literature-and find evidence that H$^{13}$CO$^{+}$ transitions may have higher optical depths than commonly assumed. These results are important because characterizing the chemical state of early star-forming stages is essential for understanding the onset of the most complex chemistry.
Read the full abstract

All authors R. D. Taboada, S. Paron, N. C. Martinez, M. E. Ortega

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Red noise and evolving signals: a complete frequentist approach to supermassive black hole binary searches with pulsar timing arrays

Xuan Tao, Boris Goncharov, Yiqian Qian et al. (+2 more)

Searches for gravitational waves (GWs) from isolated supermassive black hole binaries (SMBHBs) in pulsar timing array (PTA) data require simultaneous estimation of signal and noise parameters, so the dimensionality of the fit scales with the number of observed pulsars. This computational difficulty is exacerbated when source evolution from GW emission is included, since retaining both Earth and pulsar terms introduces the unknown pulsar distances. Existing frequentist methods such as the $\mathcal{F}$-statistic are restricted to non-evolving sources. In addition, they often rely on a noise covariance estimated from the same data and then held fixed during the signal search, which can bias parameter estimates. We present a Generalized Likelihood Ratio Test and the associated $\mathcal{T}$-statistic that overcomes the aforementioned limitations. This formulation extends earlier work in which the dimensionality of the fitting problem was drastically reduced by semi-analytical maximization of the likelihood over the pulsar phase parameters, followed by efficient global optimization over the remaining parameters using Particle Swarm Optimization. Our simulations demonstrate that for an evolving SMBHB signal with chirp mass $\mathcal{M}=10^{9.2} M_\odot$ and signal-to-noise ratio $20$, this detection statistic achieves a $100\%$ detection probability at a false-alarm probability of $0.06$ in a 30-pulsar timing array, which is characterized by a $100 \mathrm{ns}$ root-mean-square white noise residual and pulsar-specific red noise. For the 30-pulsar timing array at signal-to-noise ratio $10$ and false-alarm probability $0.06$, $\mathcal{T}$ detects $99/100$ realizations, outperforming the $\mathcal{F}_p$ statistic evaluated with the $H_0$-fitted covariance, which detects $71/100$ realizations.
Read the full abstract

All authors Xuan Tao, Boris Goncharov, Yiqian Qian, Yan Wang, Soumya D. Mohanty

Astrophysics of Galaxies

Toward Bayesian photometric cosmic chronometers: Application to VIPERS

Swaraj Pradhan, Pablo Renard, Enrique Gaztanaga et al. (+2 more)

The cosmic chronometer (CC) method provides a direct measurement of the expansion history of the universe, $H(z)$, from the differential ages of passively evolving galaxies. However, most CC analyses rely on high-quality spectroscopy to select passive galaxies, measure age-sensitive spectral features, and control stellar-population systematics. We build on existing works that use the D4000 spectral break as a proxy for measuring galaxy ages and apply it to a photometry-selected galaxy sample from VIPERS PDR2 in the range $0.5 \le z \le 0.8$. Our goal is to extend the scope of the standard CC framework to photometric surveys. To achieve this, we first selected a massive and passive galaxy sample using rest-frame colors and mass. Second, we designed a Bayesian framework to infer full galaxy age posteriors in fine redshift bins, using a D4000-age-metallicity grid from stellar population synthesis models. We marginalized over metallicity, using a Gaussian metallicity prior to break the D4000-age-metallicity degeneracy. Subsequently, we derived age-difference posteriors between redshift bins by convolving their age posteriors. Finally, using the median and errors extracted from the differential age posteriors, we calculated the weighted average $H(z)$ over our selected redshift range. We obtain $H(z=0.65)=93.68\pm28.27\,{\rm (stat.)}\pm10.67\,{\rm (syst.)}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, which is consistent with existing spectroscopic CC measurements and with the $\Lambda$ cold dark matter ($\Lambda$CDM) model prediction from Planck at the same redshift. This result provides a proof of concept for extending direct $H(z)$ measurements from cosmic chronometers to photometric and spectro-photometric surveys, where larger samples can compensate for lower spectral resolution, provided that passive-galaxy selection, metallicity priors, and stellar-population systematics are carefully controlled.
Read the full abstract

All authors Swaraj Pradhan, Pablo Renard, Enrique Gaztanaga, Malgorzata Siudek, Thibaud Moutard

Solar and Stellar Astrophysics

HST observations of chromospheric UV lines in the AGB star R Leo

Maryam Saberi, Donald G. Luttermoser, Graham M. Harper et al. (+3 more)

The role of stellar chromospheres in the chemistry, mass loss, and evolution of cool evolved stars remains poorly understood. We present high-resolution ultraviolet spectra of the nearby Mira-type AGB star R~Leo obtained with STIS on board the Hubble Space Telescope. We focus on two strong chromospheric diagnostics, the Mg\,ii h & k resonance lines and the C\,ii] 2325\,Å\ multiplet, and model their formation with the NLTE radiative-transfer code RH using phase-dependent hydrodynamic atmospheric structures that include pulsation-driven shocks. The observed C\,ii] multiplet ratios imply an electron density of order $10^9\,\mathrm{cm^{-3}}$. The RH contribution functions show that the C\,ii] emission is strongly localized in a compact shock-heated shell at the first temperature peak of the model atmosphere, near $R\simeq1.8~R_{\rm phot}$, where $T\sim10^4$\,K and the local electron density is a few $10^8\,\mathrm{cm^{-3}}$. In contrast, the Mg\,ii h & k lines probe a more extended region ($R< 16~R_{\rm phot}$), with the line cores forming at greater radial distances than the wings. The Mg\,ii h line is reproduced more reliably than the k line, which is more strongly affected by circumstellar and interstellar absorption. As an additional low-opacity kinematic check, the semi-forbidden Al\,ii] $\lambda2669$ line shows a projected stellar-rest-frame blueshift of $\sim6~{\rm km~s^{-1}}$, consistent with shock-related motions expected in Mira atmospheres. Overall, the compact C\,ii] formation region, the extended Mg\,ii contribution functions, and the strong phase dependence of the synthetic Mg\,ii profiles support a picture in which pulsation-driven shocks shape the ultraviolet chromospheric emission lines in Mira variable stars.
Read the full abstract

All authors Maryam Saberi, Donald G. Luttermoser, Graham M. Harper, Theo Khouri, Han Uitenbroek, Wouter Vlemmings

Instrumentation and Methods for Astrophysics

The Universe Observed with Particle Detectors: Astrophysical Legacy of Guido Barbiellini Amidei

Roberto Capuzzo Dolcetta

The development of modern high-energy astrophysics has been deeply intertwined with advances in particle detector technology. Guido Barbiellini Amidei (1943-2024) played a pivotal role in bridging experimental particle physics and astrophysical observation. His scientific career spanned over four decades, from early electron-positron collider experiments at ADONE and LEP (DELPHI) to space based missions such as AGILE, Fermi, and PAMELA. This memorial paper reviews the evolution of high-energy astrophysics as a detector-driven science, highlighting key domains where Barbiellini left an indelible mark: gamma-ray astronomy, cosmic-ray physics, and antimatter studies. We discuss his personal contributions to silicon tracking, calorimetry, data analysis, and his leadership in international collaborations. The conceptual impact of his interdisciplinary approach is examined, and future perspectives in the observation of the high-energy universe are outlined, recognizing that the path forward is built on the foundations he helped lay
Read the full abstract

Solar and Stellar Astrophysics

Study of photometric and spectral variability of the roAp star HD~210684

Viktor Khalack and Catherine Lovekin

This paper studies photometric and spectropolarimetric variability of HD210684 in order to derive its magnetic properties, rotational period, evolutionary stage, and global stellar parameters. The Discrete Fourier Transform is used to measure frequencies and amplitudes of periodic signals present in light curves of HD210684. Evolution models are calculated with MESA, while roAp type pulsations are simulated with GYRE. The values of $T_{eff}$, log(g), $v\sin{i}$, and radial velocity (RV) are derived from the best fit of Balmer line profiles using FITSB2. The Least Square Deconvolution (LSD) method is applied to available Stokes I&V spectra to measure the mean longitudinal magnetic field <Bz> and RV. Detailed analysis of photometric variability reveals rotational modulation with period P=5.02188$\pm$0.00005d and splitting of high-overtone pulsations that corresponds to the same rotational period. Derived <Bz> measurements also show periodic variability with P=5.02188d, but this variability appears to be different from the one predicted by a centred magnetic dipole model. We have determined the inclination angle between the line of sight and the rotation axis to be $i = 31^{\circ} \pm 2^{\circ}$, and the angle between the rotation and magnetic dipole axes as $\beta= 77^{\circ} \pm 3^{\circ}$. Simulations of stellar pulsations constrain $\log T_{eff}$<3.85 and show that our best fitting model depends on whether the observed modes are $\ell = 1$ or $\ell =2$. Considering the derived value of $\beta$, we prefer the best fit model with $\ell =2$ mode, which predicts that HD210684 lies on the main sequence with an age of approximately 1.45Gyr. The best fit of Balmer line profiles has resulted in higher values of $T_{eff}$ and log(g) for spectra acquired at rotational phases $\varphi$= 0.14 - 0.39 suggesting visibility of an area with higher surface temperature.
Read the full abstract

Instrumentation and Methods for Astrophysics

Chhavi: A Python Tool for Converting RAMSES Outputs to VTKHDF for High-Fidelity AMR Visualization

Hemangi C. Varkal, Shubhankar R. Gharote, Munn Vinayak Shukla et al. (+1 more)

RAMSES is an adaptive mesh refinement (AMR) astrophysical simulation code that generates high-resolution multiscale data. However, its native binary output format is not directly compatible with standard visualization tools, making efficient analysis challenging. We present Chhavi, an open-source Python tool that converts RAMSES outputs into the VTKHDF format for direct use in visualization platforms such as ParaView. The tool reconstructs the AMR hierarchy, preserves key physical fields including density, pressure and velocity, and organizes them into a structured representation suitable for multi-resolution visualization. The conversion is validated using the three-dimensional Sedov blast wave test case. Quantitative evaluation through radial profile comparison and Lin's concordance correlation coefficient demonstrates strong agreement between the original and converted datasets, confirming both physical and structural fidelity. Chhavi provides a scalable bridge between RAMSES simulation outputs and modern visualization workflows, supporting efficient and reproducible analysis in computational astrophysics.
Read the full abstract

All authors Hemangi C. Varkal, Shubhankar R. Gharote, Munn Vinayak Shukla, Mehul Pandya

Solar and Stellar Astrophysics

Radial and angular evolution of magnetic cloud signatures in the turbulent solar wind: virtual spacecraft analysis

M. Sangalli, E. K. J. Kilpua, A. Verdini et al. (+3 more)

Interplanetary coronal mass ejections (ICMEs) carry magnetic clouds (MCs), large-scale structures with average radial widths about a fifth of an astronomical unit at Earth's orbit. ICMEs display substructures in white light images and reveal rich dynamics across many spatial scales when directly measured by spacecraft. A spacecraft encounter with an ICME can result in smoothly rotating MC intervals or less organised magnetic obstacle (MO) ones. We investigate how the interplay of expansion, turbulence, and internal cloud dynamics affects magnetic cloud properties, which are reflected in the plasma signatures measured by spacecraft. We perform high-resolution 2.5D MHD simulations of a magnetic flux rope cross-section, which is embedded in the turbulent, expanding solar wind with the expanding box model. We probe the local plasma properties, and thus the flux rope signatures and angular coherence, with virtual spacecraft. Our simulations reproduce clear and stable MC signatures when the flux rope core is intercepted by virtual spacecraft. Disordered MO signatures appear at the edges of the flux rope, and are attributed to both expansion and turbulent transport. We vary some key physical parameters of the flux rope and the environment to understand their effect on the observed coherence and signatures. The pace of the expanding flow controls the angular extent of MC signatures, whereas the intensity of interplanetary turbulence controls how asymmetric and distorted the flux rope appears at 1 AU. The geometry of spacecraft encounters determines whether MC or MO signatures are observed. The presence of a magnetic structure which can result in MO signatures is strongly controlled by the flux rope's initial/early magnetic configuration: MO signatures can only be observed when the axial flux rope field is spatially not well confined by the rope's own magnetic tension, and disappear otherwise.
Read the full abstract

All authors M. Sangalli, E. K. J. Kilpua, A. Verdini, S. W. Good, J. Pomoell, S. Landi

Earth and Planetary Astrophysics

High-Speed Observations of Lunar Impact Flashes

Dale P. Giancono, Hadrien A. R. Devillepoix, Robert M. Howie et al. (+7 more)

Lunar impact flashes provide a direct means of estimating the flux of centimetre-sized meteoroids impacting the lunar surface. However, 25-60 frames per second imaging typical of most monitoring programs limit the ability to resolve the rapid temporal evolution of the impact process, while the integration of Earthshine background restricts the detection of faint flashes. In this work, we present high-speed observations of lunar impact flashes captured at 200 and 250 FPS using the Zadko Telescope in Western Australia. We resolve the light curves of four confirmed events, revealing complex morphologies, some of which are not well modelled by simple exponential decays. One event was simultaneously detected by a second observer using a 50 FPS system, revealing a significantly faster brightness drop in the high-speed data that cannot be explained by spectral differences alone, indicating temporal integration of the vapour plume and subsequent ejecta. Our data also indicates that the initial flash intensity (representing the vapour plume) exhibits significantly less variance across events than the total luminous energy. Furthermore, we found no statistical correlation between the initial luminous energy and the total integrated energy of the flashes in this data, suggesting that the physical mechanism driving the initial vapour expansion may be physically decoupled from the longer-duration glow driven by the cooling ejecta. High temporal resolution combined with high sensitivity are therefore essential for accurately characterising the physical properties of the impactor and distinguishing the initial vapour plume from the subsequent incandescent cooling phase, although a significantly larger dataset is required to definitively constrain these mechanisms.
Read the full abstract

All authors Dale P. Giancono, Hadrien A. R. Devillepoix, Robert M. Howie, Evan Dilley, Bruce Gendre, David Coward, John Moore, Sophie E. Deam, Dean Hooper, Daniel Sheward

Astrophysics of Galaxies

Angular momentum evolution in the CIELO simulations. I. Temporal evolution of gas-stellar misalignments and baryonic merger timing

Catalina Casanueva-Villarreal, Patricia B. Tissera, Nelson Padilla et al. (+4 more)

Gas-stellar kinematic misalignments trace how galaxies assemble and reorient their angular momentum. Although well documented locally, their continuous evolution remains largely unexplored. We aim to characterise the pathways linking aligned, misaligned, and counter-rotating phases, assessing how gas accretion channels and mergers drive reorientation. We analysed 44 central galaxies from the CIELO simulations from z=3.5 to z=0. We defined kinematic episodes using the intrinsic angle, psi, between the star-forming (SF) gas and stellar angular momentum vectors, interpreting these histories by tracking accreted gas origins and evaluating paired statistical contrasts. Nearly 80% of the simulated galaxies are aligned at z=0, yet 86% experience at least one non-aligned episode. Although 19% of non-aligned episodes last >2 Gyr, their durations do not differ significantly from aligned episodes. Abrupt changes in psi coincide with intervals where accreted gas dominates the pre-existing SF reservoir and is highly tilted relative to pre-existing stars. During transitions, the median mass ratio of accreted to pre-existing SF gas rises from 0.57 to 2.14, and the median angular offset increases from 21.2 to 64.6 deg. While relevant mergers cluster near these boundaries, they can drive either alignment or misalignment regardless of mass ratios or orbits. Instead, mergers triggering abrupt transitions typically encounter hosts that are already partially decoupled. In the simulated sample, gas-stellar misalignment is fundamentally driven by reservoir competition. Mergers act as conditional triggers, but a galaxy's ultimate kinematic fate depends strictly on how newly accreted gas couples to, replaces, or mixes with the pre-existing material as it joins the central SF reservoir.
Read the full abstract

All authors Catalina Casanueva-Villarreal, Patricia B. Tissera, Nelson Padilla, Lucas Bignone, Jenny Gonzalez-Jara, Brian Tapia-Contreras, Susana Pedrosa

Instrumentation and Methods for Astrophysics

Second-Generation Fabry-Pérot Unit for CARMENES

Hanna Lina Pleteit, Michael Debus, Sebastian Schäfer et al. (+1 more)

CARMENES consists of two high-resolution spectrographs located at the Calar Alto 3.5m telescope, covering the wavelength range from 520nm to 1710 nm. The original Fabry-Perot (FP) units have been essential to track and remove instrumental drift while also improving the wavelength solution provided by the hollow cathode lamps. In this paper we present the second-generation FP unit that has begun operation at Calar Alto in April 2024. It features drastically improved temperature stabilization, additional temperature monitoring, and enhanced optomechanics. Temperature stabilization is improved through better vacuum vessel design, thermal shielding and improved thermal control. The temperature is now monitored with Pt-100 sensors inside the vacuum vessel, one of which is used to drive the temperature control. The new purpose-built optomechanics allow for an improved alignment procedure leading to higher line contrast. The etalon coatings now cover a broader wavelength range, the optics have been upgraded, and the fibers have been updated to an octagonal shape. In laboratory measurements with a Fourier transform spectrometer we compare the FP radial velocity (RV) drift to that of an iodine cell. In a two hour binning we achieve an RMS of the differential RVs of 6cm/s. The new FP unit has already been successfully integrated at CARMENES, with first calibration data indicating improved RV precision.
Read the full abstract

All authors Hanna Lina Pleteit, Michael Debus, Sebastian Schäfer, Ansgar Reiners

Earth and Planetary Astrophysics

Freo Doctor: Atmospheric Modelling for Meteorite Falls and Spacecraft Re-Entries

Hadrien Devillepoix and Martin Cupák

How much does the wind affect the path of meteorite falls? We finely model the lower ~30 km of the atmosphere using Weather Research and Forecasting open source tools at 1 km spatial resolution. Models initialised at different times give different results, which can be used as a proxy for uncertainty. We find that in most cases the differences on the ground positions are significant: median shift for a 1 kg meteorite is 143 m, doubling to 307 m for a 10 g rock, though these vary by over an order of magnitude between events. The differences wind model choice makes on the ground are significantly larger than the typical uncertainty on meteoroid state vector obtained from bright flight observations of the fireball (<100 m), and should be taken into account when predicting meteorite free-fall path to the ground. Unsurprisingly the cases where we see the largest differences coincide with documented extreme weather events. We also find that high spatial resolution models (1 vs. 3 km) tend to perform better. We have successfully used these models to guide field teams to the location of 12 fallen meteorites after fireball observations. We release as open data 1107 models we have calculated for 302 meteorite fall events and spacecraft re-entries around the world.
Read the full abstract

Solar and Stellar Astrophysics

An optimized tidal-trigger model of the QBO, and some implications for the Carrington event

F. Stefani, G.M. Horstmann, G. Mamatsashvili et al. (+1 more)

Magneto-Rossby waves in the solar tachocline are currently being discussed as a potential cause of the quasi-biennial oscillation (QBO). By analyzing sequences of ground-level enhancement (GLE) events and S-flares, the dominant period of the QBO was recently shown to be close to 1.723 years, which is the dominant beat between the periods of the two-planet spring tides of Venus, Earth and Jupiter. We improve upon this model by taking into account the dependence of the three tidally-triggered magneto-Rossby waves on the actual strength of the toroidal field at the tachocline, which we infer from the averaged monthly sunspot number. When optimizing the parameters of this magnetic-field dependence, the correlation of the tidal-forcing function with the 109 extreme solar events reaches values of up to 0.8. This is much higher than the corresponding value for the field-independent tidal forcing function (appr. 0.4), and also higher than the correlation with the sunspot number (appr. 0.56). Based on this improved model, we discuss some interesting parallels between the Carrington event of 1859 and the clustering of strong solar events in summer and autumn 1989. We also make some cautious forecasts for the remainder of cycle 25.
Read the full abstract

All authors F. Stefani, G.M. Horstmann, G. Mamatsashvili, T. Weier

Solar and Stellar Astrophysics

Revealing mixed modes in compressible hydrodynamical simulations of red giant stars

Nils B. de Vries, Arthur Le Saux, Isabelle Baraffe et al. (+4 more)

Mixed modes are observed in many low-mass evolved stars. They provide information about core rotation rates of these stars, which are lower than predicted by stellar evolution models. The mixed modes themselves have been invoked as an angular momentum transport mechanism, but estimating their transport efficiency requires knowledge of their amplitudes. We constrain, for the first time, the mixed mode amplitudes in 2D hydrodynamical simulations of a $1.3M_\odot$ red giant using the code music. We perform two simulations with outer radial truncations at fractional radii $r_o/r_\star = 0.90$ and $r_o/r_\star = 0.98$. We compare the modes in the simulation with those found using both gyre and a dedalus eigenvalue solver. Excellent frequency agreement is found for all p-dominated modes, with minor discrepancies for g-dominated modes, especially in the frequency range $[60, \ 240]\ \mu\mathrm{Hz}$. We find excellent eigenfunction agreement for all modes except those in this frequency range. According to empirical predictions the largest kinetic energies are located around $\nu_{\mathrm{max}} = 312.8\ \mu\mathrm{Hz}$, but in both simulations the modes with frequencies $\nu <50\ \mu\mathrm{Hz}$ have the largest kinetic energies. In the simulation with $r/r_\star = 0.98$, the simulated modes have extrapolated surface velocities comparable to the empirical predictions, with highest surface velocities in a bell-shaped curve peaking around $\nu = 700 \ \mu\mathrm{Hz}$. The extrapolated surface velocities of the low frequency modes are small, and thus hard to observe, but their large kinetic energies deeper in the interior could significantly impact angular momentum transport, which has not yet been investigated.
Read the full abstract

All authors Nils B. de Vries, Arthur Le Saux, Isabelle Baraffe, Thomas Guillet, Richard H. D. Townsend, Armand Leclerc, Adrien Morison

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

Joint probes of dark matter annihilation from neutrino detectors and CMB targets

Ruifeng Leng and Shao-Ping Li

Dark matter (DM) annihilation into neutrinos provides a promising observational channel targeted by current and forthcoming neutrino detectors. However, the detection of such neutrino fluxes alone cannot uniquely determine their astrophysical or cosmological origin, such as the recent observations from Super-Kamiokande that hint at a small excess of electron antineutrino events. We propose that the effective number of neutrino species and the spectral distortion of the cosmic microwave background (CMB) can serve as complementary observables to probe neutrino signatures from DM annihilation. Using a simple model-independent analysis, we determine the detection windows of these cosmic observables that overlap with the experimental sensitivities from the Super-Kamiokande, Jiangmen Underground Neutrino Observatory, Hyper-Kamiokande, and the Deep Underground Neutrino Experiment, showing that joint probes of large DM annihilation to neutrinos with MeV-GeV masses can be achieved by neutrino detectors and CMB experiments.
Read the full abstract

High Energy Astrophysical Phenomena

A series of unfortunate events: CHIME/FRB misclassification of a Galactic pulsar as a periodic fast radio burst

The CHIME/FRB Collaboration

In 2022, the CHIME/FRB Collaboration reported the detection of FRB 20191221A, an apparent fast radio burst exhibiting a significant periodicity of 217 ms. Recently, this event has been identified as a series of pulses originating from the known Galactic pulsar PSR J0248+6021. The initial misidentification was caused by an unusual calibration problem with the CHIME telescope, coupled with the atypical characteristics of the pulsar's emission. Here, we detail the issues with the calibration and how it led to a many-degree offset in the pointing of the calculated beams. We describe how we verified that this problem has not affected any other FRB localization, including those reported in the Second CHIME/FRB Catalog, and our newly implemented checks to ensure this mispointing problem does not affect future data.
Read the full abstract

High Energy Astrophysical Phenomena

Infrared Echoes of Precessing Tidal Disruption Events

Hong-Zhou Wu, Shao-Yu Fu, Wen-Long Xu et al. (+2 more)

A tidal disruption event (TDE) occurs when a star is torn apart by a supermassive black hole. The resulting UV/optical flare irradiates parsec-scale dust, producing delayed mid-infrared echoes that persist for years. These echoes provide unique calorimetric probes of the total radiated energy and dust geometry. Existing models usually assume static axisymmetric illumination patterns. However, the TDE accretion disk is likely misaligned and undergoes relativistic precession. In this work, we present a theoretical framework for infrared dust echoes from a precessing TDE disk. The precession will lead to highly variable infrared light curves, which can be revealed by high-cadence observations. The overall profile of the infrared light curves shows double-peaked to single-peaked pattern transitions as a result of the changes in the viewing angle or precession angle. The results indicate that infrared echoes are dynamic tracers of the evolving lighting patterns of the central engine.
Read the full abstract

All authors Hong-Zhou Wu, Shao-Yu Fu, Wen-Long Xu, Chang Zhou, Wei-Hua Lei

Instrumentation and Methods for Astrophysics

Collisional excitation of H$_2$CO by He: Experimental validation of state-of-the-art scattering calculations

Chinmai Sai Jureddy, Sandor Demes, Francesca Tonolo et al. (+2 more)

Non-local thermodynamic equilibrium conditions in the interstellar medium require collisional rate coefficients to model astronomical observations; these are usually determined from theoretical scattering calculations. The aim of this study is to measure experimentally low-temperature pressure-broadening cross-sections for the H$_2$CO-He system in order to validate the theoretical methodology involved in determining new collisional rate coefficients. The experiments employed the chirped-pulse in uniform supersonic flow method, and H$_2$CO is generated in situ by 193 nm excimer laser photolysis of tetrahydrofuran in cold He flows. State-of-the-art calculations are performed by computing a new potential energy surface for the H$_2$CO-He system which is subsequently implemented in scattering calculations using the close-coupling method to derive pressure broadening cross-sections and collisional rate coefficients. Excellent agreement between theory and experiment is obtained, with the calculated values falling within the 95 % confidence intervals of the experimental measurements. Such agreement validates the high accuracy of the theoretical data. Helium constitutes about 20 % relative to H$_2$ in the interstellar medium. The inclusion of collisional rate coefficients for H$_2$CO with He in radiative transfer modelling leads to variations in the excitation temperature of frequently detected rotational lines of up to 12 % in warm regions such as protostars.
Read the full abstract

All authors Chinmai Sai Jureddy, Sandor Demes, Francesca Tonolo, Francois Lique, Ian R. Sims

High Energy Astrophysical Phenomena

LHAASO J1849$-$0002: A Hybrid Lepto-Hadronic Interpretation of PeV Gamma-Ray Emission

Yihan Shi, Yudong Cui and Lili Yang

Recently, LHAASO detected gamma-ray emission from the pulsar wind nebula (PWN) J1849-0001 extending up to approximately 2 PeV, providing strong evidence for PeV particle acceleration. To explain the origin of this ultra-high-energy emission, we investigate three physical scenarios: a pure leptonic model, a hadronic-dominated model, and a hybrid lepto-hadronic model. We show that while both pure leptonic and hadronic-dominated models can reproduce parts of the multiwavelength spectral energy distribution (SED), neither can simultaneously explain the entire dataset, particularly the PeV tail. The leptonic scenario requires an unrealistically high electron cutoff energy, while the hadronic model underpredicts the highest-energy emission. We therefore propose a hybrid model that combines inverse Compton emission from PWN electrons with hadronic interactions between escaped cosmic rays and a nearby molecular cloud. In this framework, a suppressed diffusion coefficient ($\sim 1\%$ of the Galactic average) is required to confine PeV particles in the source vicinity. This model successfully reproduces the full SED, including the approximately 2 PeV emission. We further calculate the associated neutrino flux, and show the sensitivity of NEON to this source. Our results support the interpretation that evolved PWNe embedded in complex environments can act as Galactic PeVatrons.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Lyman-$\alpha$ forest constraints on pure and mixed fuzzy dark matter

Jianxiang Liu, Yan Gong and Xingchen Zhou

Fuzzy dark matter (FDM), often realized as an ultralight scalar field, can suppress the growth of small-scale structures and could be strictly tested with Lyman-$\alpha$ forest measurements. In this work, we constrain both pure and mixed FDM models (PFDM and MFDM) using measurements of the one-dimensional (1D) Lyman-$\alpha$ forest flux power spectrum at $z=5.0$, 4.6, and 4.2. We perform cosmological hydrodynamical simulations with modified initial conditions and construct a two-stage neural network emulator for accurate analysis. The first stage predicts the cold dark matter (CDM) 1D flux power spectrum, while the second stage predicts the MFDM effect relative to the CDM baseline. This construction improves the sensitivity to weak FDM effects, enforces the correct CDM limit, and enables robust interpolation across a broad range of FDM masses and fractions. After marginalizing over the intergalactic medium parameters, we obtain the FDM mass $m_{\mathrm{FDM}}>1.9\times10^{-21}~\mathrm{eV}$ at 95% credible level for the PFDM model. For the MFDM model, we find the FDM fraction of dark matter $f_{\mathrm{FDM}}<0.07$, $0.12$, and $0.65$ at 95% credible level for $\log_{10}(m_{\mathrm{FDM}}/\mathrm{eV})=-23.0$, $-22.0$, and $-21.0$, respectively. When $\log_{10}(m_{\mathrm{FDM}}/\mathrm{eV})\gtrsim -20$, the current data do not provide an effective upper limit on $f_{\mathrm{FDM}}$.
Read the full abstract

Cosmology and Nongalactic Astrophysics

From Cosmic Web to Supernova Remnants: Modeling FRB DM to Trace Baryons across Multiple Scales

Zhao Joseph Zhang

Fast radio bursts (FRBs) provide a powerful probe of ionized baryons through their dispersion measures (DMs), but the observed signal contains contributions from the intergalactic medium (IGM), circumgalactic (CGM) gas, host galaxies, and source-local environments. In this thesis, I investigate FRB DMs from cosmic-web to source-local scales using cosmological simulations, zoom-in galaxy simulations, and supernova-remnant (SNR) simulations. Using the CROCODILE simulation suite, I study the DM-$z$ relation, baryon distribution, halo contributions, and host-galaxy DMs. AGN feedback redistributes baryons from halo centers into the diffuse CGM/IGM gas, particularly affecting DM contributions from massive foreground halos. From the simulated DM-$z$ relation, I derive diffuse baryon fractions of $f_{\rm diff}=0.865^{+0.101}_{-0.165}$ and $0.856^{+0.101}_{-0.162}$ for the fiducial and NoBH models. Host-galaxy DM contributions range from below 100 pc cm$^{-3}$ in dwarf galaxies to above 1300 pc cm$^{-3}$ in cluster environments. I also model young magnetars embedded in SNRs using one-dimensional hydrodynamical simulations. The dominant time-variable DM component arises from unshocked ejecta, while the shocked region contributes only a minor fraction. Comparisons with FRB 20190520B and FRB 20121102 suggest source-local DM contributions of tens to hundreds of pc cm$^{-3}$. Most models become transparent to GHz radio emission within 70 yr. In contrast, the shocked region dominates the RM contribution and evolution, with the $11\,M_\odot$ single-star model best reproducing the RM evolution of FRB 20121102. These results demonstrate that FRB dispersion measures must be interpreted as multi-component signals spanning a wide range of physical scales, linking the cosmic web, gaseous halos, host galaxies, and compact-object environments
Read the full abstract

Solar and Stellar Astrophysics

The effect of variable stellar magnetic fields on the spin state of T Tauri stars

Lukas Gehrig and Daniel Steiner

Understanding the stellar spin evolution of young stars is crucial for understanding the evolution of protoplanetary disks and, consequently, the formation of exoplanets. According to stellar spin models, T Tauri stars should evolve toward a spin equilibrium in which the external spin-down torque balances both the external spin-up (accretion) torque and the spin-up due to stellar contraction. A useful reference point along the way to this equilibrium is the "zero-torque state" (ZTS), at which only the external torques cancel out. Recent observations, however, have shown that the spin state of a considerable number of stars is shifted out of the spin equilibrium and the ZTS. We investigate the effects of variable stellar magnetic fields on the stellar spin state of T Tauri stars. [Abstract shortened for arXiv] Temporal variations in the stellar magnetic field can significantly affect the stellar spin state of T Tauri stars. The strength of the effect on the stellar spin state depends on the relation between the timescale of the changing magnetic field, the spin-up timescale, and the viscous timescale of the accretion disk. A developing radiative core on a timescale shorter than the spin-up timescale has a strong effect on the spin state. Stellar magnetic cycles on timescales shorter than the viscous timescale of the inner disk have a weaker effect on the stellar spin state due to a slow back-reaction of the accretion disk. Our results can explain (at least) a part of the stars that are observed out of both states. Further theoretical and observational work is needed to connect accretion, stellar rotation, and magnetic properties in T Tauri stars.
Read the full abstract

High Energy Astrophysical Phenomena

Pulsar searches of Fermi-LAT gamma-ray sources with the MWA

C. P. Lee, N. D. R. Bhat, B. W. Meyers et al. (+2 more)

Searches of unassociated gamma-ray sources in the Fermi-LAT catalogues have led to the discoveries of around a fifth of all known millisecond pulsars (MSPs). These searches have almost exclusively been performed at radio frequencies above 300 MHz, where dispersion and scattering in the interstellar medium are less significant. We report on a shallow survey for pulsars targeting 308 unassociated Fermi-LAT sources in archival Murchison Widefield Array (MWA) observations from the Southern-sky MWA Rapid Two-metre (SMART) pulsar survey at 154 MHz. This is the largest radio survey of unassociated Fermi-LAT sources to date, and only the second to be conducted below 300 MHz after a survey with the Low Frequency Array (LOFAR) that discovered three MSPs. Each source was observed for 20 min by digitally beamforming the MWA tile voltages. Searches were then performed using a new pipeline that implements a semi-coherent dispersion removal scheme for MWA data, enabling greater sensitivities to MSPs than is possible with fully-incoherent dispersion removal (e.g. 2-3 times better sensitivity for dispersion measures between 20-40 pc/cm^3). No new pulsars were identified in the survey, which we attribute to insufficient sensitivity. We estimate flux density limits of approximately 30-220 mJy at 154 MHz (or 0.7-5.2 mJy at 1.4 GHz) for a spin period of 2 ms and a duty cycle of 28%. We discuss how the improved instantaneous sensitivity from the Phase III upgrade of the MWA will increase the number of detectable gamma-ray pulsars by ~30% for the same integration time. The semi-coherent search pipeline we have developed will also be useful for searches of supernova remnants, globular clusters, and pulsar candidates identified in imaging surveys, all of which will help to inform the significance of future surveys with SKA-Low.
Read the full abstract

All authors C. P. Lee, N. D. R. Bhat, B. W. Meyers, W. van Straten, D. A. Smith

Cosmology and Nongalactic Astrophysics

Inverse-Scattering Reconstruction of Inflation from Scalar and Tensor Primordial Spectra

Jorge Mastache and Allan Hurtado

We develop an inverse-scattering framework to reconstruct the effective inflationary potentials governing scalar and tensor perturbations. By recasting the Mukhanov–Sasaki equation as a Schrödinger-like problem on the half-line, we identify the Bunch–Davies initial condition with the asymptotic Jost solution and show that the freeze-out amplitude of the growing mode is encoded in the corresponding Jost function. This allows the scalar and tensor primordial power spectra to be written in terms of $F^{(s)}_{\nu_s-\frac12}(k)$ and $F^{(t)}_{\nu_t-\frac12}(k)$, respectively, and leads to an inverse-scattering expression for the tensor-to-scalar ratio as a ratio of Jost amplitudes. We then test the reconstruction in the large-$k$ regime using the Born approximation, where the Marchenko equation becomes linear. As benchmarks, we consider a smooth quadratic potential and a step potential that transiently violates slow roll and generates localized features in the primordial spectra. The reconstructed effective potentials reproduce the dominant behavior of $z^{\prime\prime}/z$ and $a^{\prime\prime}/a$ for smooth slow-roll evolution, while localized discrepancies arise in the scalar sector when sharp features induce stronger scattering. Our results show that inverse scattering provides a physically transparent method for connecting features in the primordial spectra to the underlying inflationary dynamics, and that the Jost function acts as a sensitive diagnostic of departures from canonical slow-roll evolution.
Read the full abstract

Instrumentation and Methods for Astrophysics

MOSES – The MONET Star and Exoplanet Spectrograph

S. Schäfer, L. Schmidt, H. Anwand-Heerwart et al. (+2 more)

We introduce MOSES, the new High-Resolution Echelle Spectrograph designated for the 1.2m MONET telescope at McDonald Observatory, Texas, USA. The science drivers are radial velocity experiments and activity monitoring in Sun-like stars. Set for installation in the final quarter of 2026, MOSES features a white pupil design and aims for a spectral resolution greater than 80,000 over the 380-680 nm wavelength range. It incorporates a pixel sampling rate of 3.5 and uses two fibers to facilitate a simultaneous calibration mode. Encased within a vacuum vessel and operating in a temperature-stabilized environment, MOSES is expected to achieve a radial velocity precision below 2 m/s, aided by a Fabry-Pérot etalon calibration system. This paper outlines the implementation of the fiber injection unit, the optical layout of the spectrograph, and the present status of the various subsystems under development.
Read the full abstract

All authors S. Schäfer, L. Schmidt, H. Anwand-Heerwart, D. Jones, A. Reiners

Instrumentation and Methods for Astrophysics

The MICADO first light imager for the ELT: eliminating vibrations and excessive earthquake-loads on specific subsystems

H. Nicklas, S. Schäfer, H. Anwand-Heerwart et al. (+3 more)

Ensuring earthquake resilience is paramount for the upcoming Extremely Large Telescope (ELT). Instruments positioned on the ELT's Nasmyth platform are anticipated to endure substantial seismic accelerations, peaking at 3.6g in specific scenarios. These instruments have to be designed not only to survive such events but also to only require minimal repairs for sustained optimal functionality. This paper presents our approach to mitigate the dynamic forces impacting the rotary platform. This platform hosts various critical components, including cryogenic control units and mosaic detector control systems, essential for the operation of MICADO in its mechanical de-rotating motion. Furthermore, this paper tackles the challenge of minimizing instrument-induced vibrations affecting the telescope's structure. Given that the ELT's optical system, composed of 798 segments, operates very similar to an interferometer, maintaining an extremely stable wavefront is crucial - a key insight learned from the Very Large Telescope Interferometer (VLTI). Our focus is on identifying potential sources of vibration within specific frequency ranges where the telescope demonstrates increased sensitivity. We will explore strategies for mitigating these vibrations to maintain a wavefront error below 50nm.
Read the full abstract

All authors H. Nicklas, S. Schäfer, H. Anwand-Heerwart, J.-O. Dette, J. Witschel, H. Huber

Solar and Stellar Astrophysics

Temperature Diagnostics of Chromospheric Fibrils using DKIST/ViSP Observations: K-Means Clustering Approach

Sanjay Gosain

The chromosphere is a critical layer of the solar atmosphere situated between the photosphere and the corona. Studying its temperature structure is important to understand the complex dynamics and energy-transfer processes between these layers. We investigate the thermodynamic properties of chromospheric fibrils adjacent to a plage region using high-resolution DKIST/ViSP observations of the Ca II 854.2 nm spectral line. We analyze the spectral profiles with the non-LTE inversion code NICOLE combined with K-means clustering. The high spectral and spatial resolution of the DKIST observations allows us to trace thermodynamic properties temperature, density, line-of-sight velocity, and microturbulent velocity along and across the fibrils. We note that while the thermodynamic parameters are retrieved under the assumption of hydrostatic equilibrium, the resulting density and temperature values should be interpreted with the caveat that dynamic and magnetic terms are neglected. The temperature along the fibril length decreases smoothly by about 1000 K from the hotter footpoints toward the mid-axis. The temperature variation across the lateral boundary of fibrils is more abrupt and can vary by several hundreds of degree Kelvin across a megameter. Denser fibrils tend to be associated with cooler, downflowing plasma, while less-dense fibrils do not show this trend. Furthermore, the hotter parts of the fibrils tend to exhibit higher microturbulent velocities than the cooler parts.
Read the full abstract