Instrumentation and Methods for Astrophysics
Charged liquid surface instabilities and detection of Solar neutrino by XENONnT
Sergey Pereverzev
Announcement of detection of
Solar 8B
neutrinos by XENONnT dual-phase detector come with a suite of unexplained detector effects. We expect accumulation of surface charges and charged surface instability resulting in maximal surface elevation and charge density at wire crossing regions, where anomalies were observed. Thou data from these regions were excluded from analysis, surface distortions and charges are present everywhere, which can lead to large systematic errors in small signal detection.
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Instrumentation and Methods for Astrophysics
A Cost-Effective Search for Extraterrestrial Probes in the Solar System
Beatriz Villarroel, Wesley A. Watters, Alina Streblyanska et al. (+3 more)
For centuries, astronomers have discussed the possibility of inhabited worlds - from Herschel's 18th-century observations suggesting Mars may host life, to the systematic search for technosignatures that began in the 1960s using
radio telescopes. Searching for artifacts in the
solar system has received relatively little formal scientific interest and has faced significant technical and social challenges. Automated surveys and new observational techniques developed over the past decade now enable astronomers to survey parts of the sky for anomalous objects. We briefly describe four methods for detecting extraterrestrial artifacts and probes within the
Solar System and then focus on demonstrating one of these. The first makes use of pre-Sputnik images to search for flashes from glinting objects. The second method makes use of space-borne
telescopes to search for artificial objects. A third approach involves examining the reflectance spectra of objects in Earth orbit, in search of the characteristic reddening that may imply long-term exposure of metallic surfaces to space weathering. We focus here on a fourth approach, which involves using Earth's shadow as a filter when searching for optically luminous objects in near-Earth space. We demonstrate a proof-of-concept of this method by conducting two searches for transients in images acquired by the Zwicky Transient Facility (ZTF), which has generated many repeated 30-second exposures of the same fields. In this way, we identified previously uncatalogued events at short angular separations from the center of the shadow, motivating more extensive searches using this technique. We conclude that the Earth's shadow presents a new and exciting search domain for near-Earth SETI.
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All authors Beatriz Villarroel, Wesley A. Watters, Alina Streblyanska, Enrique Solano, Stefan Geier, Lars Mattsson
High Energy Astrophysical Phenomena
Imaging and Polarimetric Signatures of Konoplya-Zhidenko Black Holes with Various Thick Disk
Xinyu Wang, Yukang Wang and Xiao-Xiong Zeng
We investigate the imaging properties of spherically symmetric Konoplya-Zhidenko (KZ) black holes surrounded by geometrically thick
accretion flows, adopting a phenomenological radiatively inefficient
accretion flow (RIAF) model and an analytical ballistic approximation
accretion flow (BAAF) model. General relativistic radiative transfer is employed to compute synchrotron emission from thermal electrons and generate horizon-scale images. For the RIAF model, we analyze the dependence of image morphology on the deformation parameter, observing frequency, and flow dynamics. The
photon ring and central dark region expand with increasing deformation parameter, with brightness asymmetries arising at high inclinations and depending on flow dynamics and emission anisotropy. The BAAF disk produces narrower rings and darker centers, while polarization patterns trace the brightness distribution and vary with viewing angle and deformation, revealing spacetime structure. These results demonstrate that intensity and polarization in thick-disk models provide probes of KZ black holes and near-horizon
accretion physics.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Influence of Fermionic Dark Matter on the Structural and Tidal Properties of Neutron Stars
Monmoy Molla, Masum Murshid and Mehedi Kalam
We investigate the influence of ideal
Fermi gas dark matter on the observable properties of
neutron stars (NSs). Our analysis considers dark matter (DM) particle masses ($\mu$) ranging from $0.2$ GeV to $1$ GeV and various DM mass fractions ($f$). By examining the coexistence of DM and baryonic matter (BM), we explore the formation of either a dense DM core or an extended dark
halo within NSs. Our findings indicate that the resulting DM distribution depends critically on both $\mu$ and $f$. We systematically explore the parameter space of the fermionic DM model using two representative BM equations of state (EoSs) by applying constraints from NS radius measurements by the
Neutron Star Interior Composition Explorer (NICER), observations of $2M_{\odot}$ NSs, and
tidal deformability limits from the LIGO/Virgo Collaboration. This comprehensive analysis enables us to exclude specific ranges of $\mu$ and $f$, demonstrating that the amount of accumulated DM must be relatively small to satisfy current astrophysical constraints.
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Instrumentation and Methods for Astrophysics
Investigating the Effects of Point Source Injection Strategies on KMTNet Real/Bogus Classification
Dongjin Lee, Gregory S.H. Paek, Seo-Won Chang et al. (+6 more)
Recently, machine learning-based real/bogus (RB) classifiers have demonstrated effectiveness in filtering out artifacts and identifying genuine transients in real-time astronomical surveys. However, the rarity of transient events and the extensive human labeling required for a large number of samples pose significant challenges in constructing training
datasets for RB classification. Given these challenges, point source injection techniques, which inject simulated point sources into optical images, provide a promising solution. This paper presents the first detailed comparison of different point source injection strategies and their effects on classification performance within a simulation-to-reality framework. To this end, we first construct various training
datasets based on Random Injection (RI), Near
Galaxy Injection (NGI), and a combined approach by using the Korea Microlensing
Telescope Network
datasets. Subsequently, we train convolutional neural networks on simulated cutout samples and evaluate them on real, imbalanced
datasets from gravitational wave follow-up observations for GW190814 and S230518h. Extensive experimental results show that RI excels at asteroid detection and bogus filtering but underperforms on transients occurring near
galaxies (e.g.,
supernovae). In contrast, NGI is effective for detecting transients near
galaxies but tends to misclassify variable
stars as transients, resulting in a high false positive rate. The combined approach effectively handles these trade-offs, thereby balancing between detection rate and false positive rate. Our results emphasize the importance of point source injection strategy in developing robust RB classifiers for transient (or multi-messenger) follow-up campaigns.
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All authors Dongjin Lee, Gregory S.H. Paek, Seo-Won Chang, Changwan Kim, Mankeun Jeong, Hongjae Moon, Seong-Heon Lee, Jae-Hun Jung, Myungshin Im
Solar and Stellar Astrophysics
Using Binary Population Synthesis to Calculate the Yields of Low- and Intermediate-Mass Binary Populations at Low Metallicity
Zara Osborn, Amanda Karakas, Devika Kamath et al. (+3 more)
Asymptotic
giant branch (AGB)
stars are important to chemical
evolution at
metallicity $Z \sim 0.0001$ ($\text{[Fe/H]} \approx -2.2$) as they contribute significantly to the production of nitrogen, lead, and
dust in the early Universe. The contribution of AGB
stars to the chemical
evolution of the Universe is often quantified using the chemical yields from single AGB
stars. Binary
evolution challenges our understanding of chemical
evolution as binary phenomena such as mergers and mass transfer episodes can significantly alter the
stellar evolution pathways and yields. In this work, we use binary population synthesis code binary_c to model populations of low and intermediate-mass ($\sim 0.7-7 \, M_{\rm \odot}$)
stars at
metallicity $Z = 0.0001$. Our binary
star populations predict $\sim 37\%$ fewer thermally-pulsing AGB
stars than our single
star populations, leading to a $\sim 40\%$ decrease in the amount of ejected C and a $\sim 35-40\%$ reduction in elements synthesised through the slow
neutron capture process. The uncertainty introduced by the mass-loss from
stellar winds on the AGB makes the impact of binary
evolution on the total amount of ejected N uncertain. The total N yield ejected by our binary
star populations ranges from a $17\%$ to a $36\%$ decrease compared to our single
star populations. However, our binary populations overproduce N by over an order of magnitude during the period $300-700\,$Myr after formation.
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All authors Zara Osborn, Amanda Karakas, Devika Kamath, Robert Izzard, Alex Kemp, Chiaki Kobayashi
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
The window on heavy charged dark matter was never open
Daniele Perri and Glennys Farrar
There is a claim in the literature that charged dark matter particles in the mass range $100 (q_{\rm X}/e)^2~\mathrm{TeV} \leq m_{\rm X} \leq 10^8 (q_{\rm X}/e)~\mathrm{TeV}$ are allowed, based on arguing that heavy charged particles cannot reach the Earth from outside the magnetized region of the Milky Way (Chuzhoy-Kolb, 2009). We point out that this claim fails for physical models for the
Galactic magnetic field. We explicitly confirm our argument by simulating with the software CRPropa the trajectories of heavy charged dark matter in models of the
Galactic magnetic field.
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Solar and Stellar Astrophysics
HelioFill: Diffusion-Based Model for EUV Reconstruction of the Solar Farside
Firas Ben Ameur, Rayan Dhib, Yahia Battach et al. (+4 more)
The loss of STEREO-B in 2014 created a persistent blind spot in Extreme Ultraviolet (EUV) imaging of the
solar farside. We present HelioFill, to the authors' knowledge, the first denoising-
diffusion inpainting model that restores full-Sun EUV coverage by synthesizing the STEREO-B sector from Earth-side (SDO) and STEREO-A views. Trained on full-Sun maps from 2011-2014 (when SDO+STEREO-A+B provided 360 degrees coverage), HelioFill couples a latent
diffusion backbone with domain-specific additions: spectral gating, confidence weighting, and auxiliary regularizers, to produce operationally suitable 304 Angstrom reconstructions. On held-out data, the model preserves the observed hemisphere with mean SSIM 0.871 and mean PSNR 25.56 dB, while reconstructing the masked hemisphere with mean SSIM 0.801 and mean PSNR 17.41 dB and reducing boundary error by approximately 21 percent (Seam L2) compared to a state-of-the-art
diffusion inpainting model. The generated maps maintain cross-limb continuity and coronal morphology (loops, active regions, and coronal-hole boundaries), supporting synoptic products and cleaner inner-boundary conditions for coronal/heliospheric models. By filling observational gaps with observationally consistent EUV emission, HelioFill maintains continuity of full-Sun monitoring and complements helioseismic farside detections, illustrating how
diffusion models can extend the effective utility of existing
solar imaging assets for space-weather operations.
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All authors Firas Ben Ameur, Rayan Dhib, Yahia Battach, Andrea Lani, Matteo Parsani, Omar Knio, Stefaan Poedts
Astrophysics of Galaxies
Compact vs. Scattered: Suitability of Southern 6.7GHz Methanol Masers for VLBI astrometry
Lucas J. Hyland, Simon P. Ellingsen and Mark J. Reid
The 6.7~GHz methanol maser transition is exclusively associated with young, high-mass
stars and represents a potential target for astrometric studies, including accurate determination of their distance through trigonometric parallax measurements. There are more than 1000 known 6.7~GHz methanol maser sources in the Milky Way; however, not all are suitable targets for astrometric measurements. We have used the Long Baseline Array to observe 187 southern 6.7~GHz methanol masers and identify 69 sources with one or more maser spots that are sufficiently compact and intense to be suitable targets for very long baseline interferometry astrometry with current instruments. Maser compactness appears to be a strong function of
Galactic position, with masers that are likely in nearby spiral arms being more compact, while those associated with distant arms or the central
Galactic region being less compact - a relationship we associate with scatter broadening. This has implications for astrophysical masers, especially distant ones employed for
Galactic astrometry.
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Instrumentation and Methods for Astrophysics
Studying the Dust Distribution Around Accreting Black Holes with Reverberation Mapping Using PRIMA
Varoujan Gorjian and Michael W. Werner
Variability studies are a powerful tool for studying the structures of unresolved sources. One such type of variability study, called reverberation mapping (RM), established that the dominant source of infrared radiation from an active
galactic nucleus (AGN) was from
dust absorption and re-emission, which demonstrated that the optical brightening and fading of light from the
accretion disk (AD) around a supermassive black hole was followed by a corresponding (delayed) variation at infrared (IR) wavelengths from the surrounding
dust distribution. Since that time a great deal more has been learned about the
dust distribution around ADs, both near the AD in the form of a potential
torus, as well as extended emission in the form of polar
dust outflows. Understanding the
dust distribution is vital to understanding how AGNs affect their host
galaxy as well as the overall energetics of AGNs as ~50% of energy from an AGN comes out in the IR.
Dust RM has been done exclusively in the near-IR (1-5 microns) which traces the inner edge of the
dust near the
dust sublimation radius. Hence extending RM to the mid-IR, especially to the peak of the
dust emission between 25 and 30 microns, allows for an examination of the
dust distribution around ADs and potentially traces the source of the polar
outflow. RM with the proposed PRobe far-Infrared Mission for Astrophysics (PRIMA) can focus on variability monitoring of a sample of low- to high-luminosity AGNs to trace the 25-30 microns emission that is reverberated from the UV/optical AD emission which will be monitored by other space and ground-based observatories and made available to PRIMA users. Then, by detailed modeling of the response of the
dust emission to shorter wavelengths, the distribution of the
dust around an AGN will be revealed and can be linked to the
accretion disk luminosities.
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Instrumentation and Methods for Astrophysics
On the use of the Derivative Approximation for Likelihoods for Gravitational Wave Inference
Josiel Mendonça Soares de Souza and Miguel Quartin
Posterior inference on the more than a dozen parameters governing a gravitational wave (GW) event is challenging. A typical MCMC analysis can take around $100$ CPU hours, and next generation GW observatories will detect many thousands of events. Here we present a thorough comparison of the accuracy and computational cost of the Fisher
Matrix, Derivative Approximation for Likelihoods (DALI) and traditional MCMC methods. We find that using DALI, which extends the traditional Fisher
Matrix (FM) method to higher orders, allows for a good approximation of the posterior with a $55$ times smaller computational cost, and that the cost-benefit of the doublet-DALI is better than that of the triplet-DALI. We also show that the singlet-DALI, a hybrid MCMC-Fisher method, is much more accurate than the traditional FM and 10 times faster than the doublet-DALI. A large effort has been invested in
forecasting the science case of different detector configurations, and the ability of making fast yet accurate estimations of the posteriors is an important step forward. We also introduce version 1.0 of the public GWDALI code, which incorporates automatic differentiation, modern waveforms and an optimized parameter decomposition.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Imprints of a Second Order Electroweak Phase Transition on the Stochastic Gravitational Wave Background
V.K. Oikonomou
In this work we shall study the impact of a second order electroweak phase transition occurring at $\sim 150\,$GeV on the energy spectrum of the
stochastic gravitational background. Specifically, we assume that the non-minimally coupled
Higgs field controls the inflationary era, we find the reheating temperature for the
Higgs inflationary model and we demonstrate that the
Higgs effective potential exhibits a very weak first order phase transition. This weak first order phase transition is an indication that the electroweak phase transition may not actually proceed as a first order phase transition, but it will proceed as a crossover or second order phase transition. This second order phase transition proceeds with the
Higgs field slow-rolling its potential toward to its new minimum. This slow-rolling may deform the radiation domination total equation of state, and the aim of this work is to pinpoint the observational imprints of this total equation of state deformation on the energy spectrum of the
primordial gravitational waves, that affects modes that enter the horizon at temperatures $T\sim 150\,$GeV or lower.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Contribution from Nonlinear Quasi-normal Modes in GW250114
Yuxin Yang, Changfu Shi and Yi-Ming Hu
We report evidence for nonlinear gravitational effects in the ringdown signal of gravitational wave event GW250114. Using
Bayesian inference, we find that the inclusion of a nonlinear quasi-normal mode (220Q), a second-order harmonic predicted by general relativity, is statistically favored over the standard linear model (440 mode) when analyzing the post-merger oscillations. Specifically, models incorporating the 220Q mode yield higher Bayes factors than those including only the linear 440 mode, and produce remnant black hole parameters (mass and
spin) more consistent with full numerical relativity simulations. This suggests that nonlinear mode coupling contributes significantly to the ringdown phase, opening a new avenue to probe strong-field
gravity beyond linear approximations.
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Solar and Stellar Astrophysics
The massive binary system WR 20a: light curve analysis in a colliding wind model
I.I. Antokhin, E.A.Antokhina and A.M. Cherepashchuk
The article presents the results of the analysis of optical light curves of the massive binary system WR 20a (WN 6ha + WN 6ha). The analysis was performed with the binary system model, extending the standard Roche model for the case when both components of the system have powerful
stellar winds. The model takes into account the collision of the winds and the influence of orbital motion on the collision zone. The observational light curves in the BVI filters were taken from previously published papers, in which they were analyzed using the standard Roche model. The main difference between the results of our work and the previous results is that in our model the radii of the components are about 25% smaller. As a consequence, the luminosity of the system in our model decreased by approximately 40%, and the distance to the system by 20%. In addition, the model was able to successfully describe the observed asymmetry of the light curve with respect to the phases of the conjunctions, which is impossible in the standard Roche model. The model light curves were also compared with the observational curves obtained by the TESS satellite and the ASAS-SN project. It was shown that, taking into account recent studies of interstellar extinction in the direction of the young open cluster Westerlund 2, the distance to WR 20a obtained in our calculations is consistent with the hypothesis that WR 20a is a member of the cluster.
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Earth and Planetary Astrophysics
Resolving star spots on WASP-85 A using high-resolution transit spectroscopy
Vedad Kunovac, Heather Cegla, Hritam Chakraborty et al. (+23 more)
Stellar surface inhomogeneities such as spots and faculae introduce Doppler variations that challenge
exoplanet detection via the radial velocity method. While their impact on disc-integrated spectra is well established, detailed studies of the underlying local line profiles have so far been limited to the Sun. We present an observational campaign targeting the active
star WASP-85 A during transits of its hot Jupiter companion. The transits span two
stellar rotation periods, allowing us to probe the
evolution of active regions. From ground-based photometry we identify seven active regions, six containing dark spots. Using simultaneous ESPRESSO transit spectroscopy, we spatially resolve these regions on the
stellar surface by using the
planet as a probe. We detect significant bisector shape changes, line broadening, and net
redshifts during spot occultations, with velocity shifts of 108-333 m/s (mean uncertainty 50 m/s). The observed broadening is consistent with the Zeeman effect, implying
magnetic field strengths (Stokes $I$) $B$ = 2.7-4.4 kG (mean uncertainty 0.6 kG), comparable to
solar umbrae. Combined with our photometric spot model, this yields lower limits to the disc-integrated field $Bf = 16 \pm 3$ G and $61 \pm 9$ G for the two hemispheres probed – at least three times higher than Sun-as-a-
star values. We also measure centre-to-limb variations in FWHM, line depth, equivalent width, and convective blueshift, which broadly agree with
solar observations and 3D MHD models. This work demonstrates a new way to characterise the surfaces of
exoplanet host
stars, paving the way for future analyses incorporating synthetic line profiles from 3D MHD simulations.
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All authors Vedad Kunovac, Heather Cegla, Hritam Chakraborty, Cis Lagae, David J. A. Brown, Alix Freckelton, Samuel Gill, Mercedes López-Morales, James McCormac, Annelies Mortier, Mathilde Timmermans, Thomas G. Wilson, Romain Allart, Edward M. Bryant, Matthew R. Burleigh, Lauren Doyle, Edward Gillen, James S. Jenkins, Marina Lafarga, Monika Lendl, Mahmoud Oshagh, Vatsal Panwar, Peter P. Pedersen, Amaury Triaud, Richard G. West, Peter J. Wheatley
Astrophysics of Galaxies
PAH Emission Spectra and Band Ratios for Arbitrary Radiation Fields with the Single Photon Approximation
Helena M. Richie and Brandon S. Hensley
We present a new method for generating emission spectra from polycyclic aromatic hydrocarbons (PAHs) in arbitrary radiation fields. We utilize the single-
photon limit for PAH heating and emission to treat individual
photon absorptions as independent events. This allows the construction of a set of single-
photon emission "basis spectra" that can be scaled to produce an output emission spectrum given any input heating spectrum. We find that this method produces agreement with PAH emission spectra computed accounting for multi-
photon effects to within $\simeq10\%$ in the $3-20~{\rm \mu m}$ wavelength range for radiation fields with intensity $U<100$. We use this framework to explore the dependence of PAH band ratios on the radiation field spectrum across grain sizes, finding in particular a strong dependence of the 3.3 to $11.2~\mu$m band ratio on radiation field hardness. A Python-based tool and a set of basis spectra that can be used to generate these emission spectra are made publicly available.
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Instrumentation and Methods for Astrophysics
Optical turbulence forecast for ground-based astronomy and free-space optical communication
Elena Masciadri, Alessio Turchi, Camilo Weinberger et al. (+2 more)
Forecasting optical
turbulence in the Earth's atmosphere has been an ambitious challenge for the astronomical scientific community for several decades. While earlier research primarily focused on whether it was possible to predict optical
turbulence and its vertical distribution, current efforts are more concentrated on the accuracy achievable at different timescales, the efficiency of various
forecasting methods and the contributions of new statistical approaches, such as auto-regression and machine learning to this field. In this contribution, I will present the state of the art of the research conducted by our group, positioned within the international research scenery. Most of our past activity has been primarily focused on ground-based astronomy but recent advancements in space research opened new opportunities for applications in the free-space optical communication.
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All authors Elena Masciadri, Alessio Turchi, Camilo Weinberger, Marlene De Sepibus, Luca Fini
Astrophysics of Galaxies
SS 433 - On flares affecting the slaved accretion disk
Michael Bowler
Variations in the polar angle of the precessing jets in SS 433 are negatively correlated with variations in the speed of the jets. This was established some 20 years ago, based on the analysis of archival data accumulated from 40 years ago. This curious correlation has never been explained. Here I consider a promising mechanism involving the effect of
flares on the slavery of the
accretion disk.
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High Energy Astrophysical Phenomena
SN Ia-CSM 2020aeuh: Massive binary C/O WD merger?
N. N. Chugai
I explore the origin of the circumstellar (CS) shell of the unusual SN Ia 2020aeuh based on the light curve model abd observational constraints. I estimate the $^{56}$Ni mass ($1.1 M\odot$), CS shell mass ($0.04-0.2 M\odot$), radius ($2\times10^{16}$ cm), and expansion velocity $\lesssim 200$ km/s. Large $^{56}$Ni mass and properties of the CS shell are consistent with the scenario of massive binary white
dwarf merger that has been accompanied with the ejection of $\sim 0.1 M\odot$ of matter. It is argued that SN~2020aeuh exploded not earlier than 30 yr after the merger.
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Cosmology and Nongalactic Astrophysics
Cosmic Tunnels and the Integrated Sachs-Wolfe effect
C. T. Davies, M. Klein, A. Fumagalli et al. (+1 more)
Cosmic voids, vast underdensities in the large-scale structure, offer unique sensitivity to cosmological parameters. However, traditional 3D
galaxy-based void finding is limited by many factors, including uncertainties in the
galaxy-
halo connection and distortions from
redshift errors. Using alternative tracers and new 2D void definitions can alleviate these limitations and be tailored to maximise the signal for specific observables. Here, we introduce
Cosmic Tunnels, a new class of 2D void-like objects traced by
galaxy clusters, corresponding to large underdense lines of sight. We identify
Cosmic Tunnels by applying the tunnel
algorithm to the RASS-MCMF and ACT-MCMF cluster catalogues. We validate their void-like nature by measuring the cross-correlation of
Cosmic Tunnels with
galaxy density contrast maps from the DESI Legacy Survey (measured at 63$\sigma$ significance),
galaxy weak-
lensing maps from DES Y3 (31$\sigma$), and CMB weak-
lensing maps from ACT DR6 (15$\sigma$), all of which show underdense interiors enclosed by compensation ridges, consistent with 3D
galaxy voids, measured at high statistical significance. We also show that the
lensing profiles fit the universal HSW void profile, further validating their void-like nature. We cross-correlate the
Cosmic Tunnels with Planck CMB temperature maps to measure the ISW signal. Using the ACT-MCMF
Cosmic Tunnels, we achieve a 3.6$\sigma$ ISW detection, one of the highest significances ever reported from a single tracer catalogue. These results confirm that
Cosmic Tunnels are robust underdense structures and demonstrate their potential as a new tool for cosmological analyses. Finally, we report a tentative detection of a sign flip in the ISW signal at very low
redshift (z<0.03), consistent with previous studies, challenging the standard $\Lambda\rm{CDM}$ paradigm.
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All authors C. T. Davies, M. Klein, A. Fumagalli, J.J. Mohr
Instrumentation and Methods for Astrophysics
Estimating Flux Densities of Diffuse Cosmological Radio Sources Exploiting Vision Transformers
Nicoletta Sanvitale, Claudio Gheller, Franco Vazza et al. (+3 more)
We present TUNA, a
Vision-
Transformer based network adapted from
segmentation to flux regression for faint, diffuse
radio emission. Trained on LOFAR-like mock observations derived from cosmological simulations, TUNA accurately reconstructs low surface-brightness structures, with only mild smoothing and small brightness-dependent biases. Applied to LOFAR data of the A399 - A401
galaxy cluster system, it recovers the ridge not identifiable in the high resolution observation and matches the low resolution tapered map. These results indicate how TUNA can deliver automated, quantitative surface brightness estimates for diffuse extragalactic sources, enabling scalable analyses for upcoming surveys.
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All authors Nicoletta Sanvitale, Claudio Gheller, Franco Vazza, Federica Govoni, Matteo Murgia, Valentina Vacca
Astrophysics of Galaxies
Unbound Tails and Compressed Heads: A JCMT Study of the SFO 38 Cloud
Puja Porel, Archana Soam, Janik Karoly et al. (+5 more)
SFO 38, located in the Cepheus molecular cloud within the northern part of the HII region IC 1396, is shaped by intense ultraviolet radiation from the nearby O6.5V-type
star HD 206267 and represents a classic example of a bright-rimmed cloud (BRC) undergoing radiatively driven implosion (RDI). While previous studies have examined the southern globule using CS and 13CO (1-0), we present a refined analysis using high-resolution JCMT-HARP observations in the 12CO, 13CO, and C18O (J = 3-2) lines, deriving key physical parameters along with virial mass and
turbulence properties of the southern head. We also perform the first detailed investigation of the northeastern and northwestern tails, determining their morphological dimensions and internal conditions, including excitation temperature, column density, mass, and volume density. Spectral and stability analyses reveal that the tail regions are gravitationally unbound and dynamically expanding, explaining the lack of active
star formation. Our results further shed light on the evolutionary fate of these structures, assessing whether they may accumulate sufficient material to become future sites of
star formation or remain quiescent. Overall, this work highlights the dual role of RDI in this BRC: while it triggers
star formation in the dense head, it simultaneously disperses and dynamically reshapes the extended tails.
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All authors Puja Porel, Archana Soam, Janik Karoly, Eun Jung Chung, Chang Won Lee, Shinyoung Kim, Shivani Gupta, Neha Sharma
Cosmology and Nongalactic Astrophysics
Probing down to early cosmic epochs using limited redshift ($z\lesssim 1$) optical surveys with host galaxy age and lookback time analysis
Siddharth Kasthurirangan, Meet Panchal, Aparna Joshi et al. (+1 more)
We present a detailed analysis of AGN identification diagnostics and host
galaxy evolution using optical spectral diagnostics using ESO-GOODS-S data. We employ traditional Baldwin-Phillips-Terlevich (BPT) diagrams along with their modern extensions, the Mass-Excitation (MEx) and Colour-Excitation (CEx) diagrams, to classify AGNs from among up to 600+ candidates. We extract the spectral properties utilising an indigenous spectral fitting code. In addition, the code also incorporates inputs from a state-of-the-art
stellar population synthesis model (Bruzual and Charlot, 2003, MNRAS, 344, 1000), extracting the host
galaxy ages and
metallicities as model parameters.
Redshift values for all the studied spectra are obtained from the literature. Using these
redshift values, we are able to assign a 'lookback time' (using standard $\Lambda$CDM cosmological parameters). When this lookback time is combined with the
galaxy ages (from spectral fitting), it enables us to study
galaxy evolution even up to early cosmological epochs ($\sim$13 Gyr), despite restricting the studied field of
galaxies to $z\sim 1$ (lookback time of $\sim$8 Gyr). We conclude that
galaxies ultimately evolving into AGN hosts originate earlier ($\sim$8 Gyr ago) than non-AGN host
galaxies ($\sim$6 Gyr ago). We relate this fact, that AGN hosts date back to an earlier epoch than non-AGN
galaxies, as being likely due to higher
cosmic temperatures at that time, probably enhancing black hole
accretion. We emphasise that host
galaxy age is an additional crucial parameter (apart from cosmological
redshift) in defining our understanding of AGN and
star formation co-
evolution across cosmological time scales.
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All authors Siddharth Kasthurirangan, Meet Panchal, Aparna Joshi, Ganesh Pawar
High Energy Astrophysical Phenomena
A transition from mixed-fuel to pure-helium thermonuclear bursts in Terzan 5 X-3/Swift J174805.3-244637
Lei Zhang, Zhaosheng Li, Yuanyue Pan et al. (+5 more)
We presented a detailed analysis of seven thermonuclear X-ray bursts from Terzan 5 X-3/Swift J174805.3-244637, detected by NICER during the source's 2023 outburst. Our analysis reveals a clear
evolution of burst properties, identifying four non-photospheric radius expansion (non-PRE) bursts, one PRE candidate occurring in a mixed hydrogen/helium environment, and two powerful PRE bursts from pure helium ignition. The time-resolved burst spectra were well described by a model including a variable persistent emission component, quantified by a factor $f_a$, due to the Poynting-Robertson drag. The strength of this interaction scales with burst luminosity: the enhancement is absent ($f_a \approx 1$) in the faintest bursts, becomes modest ($f_a \approx 1.5-2$) for the more luminous non-PRE burst and the PRE candidate, and is very strong ($f_a \approx 6-8$) during the pure-helium PRE bursts. This observed transition from mixed-fuel to pure-helium burning as the local mass
accretion rate dropped below $\sim$10% of the Eddington limit, $\dot{m}_{\rm Edd}$, aligns with theoretical predictions. We verified this scenario with two independent methods. First, at the known distance to Terzan 5, the touchdown luminosities of both the pure helium PRE bursts and the mixed-fuel PRE candidate are consistent with reaching their respective, composition-dependent Eddington limits on the same plausible, massive
neutron star of $\sim 2 M_\odot$. Second, the observed recurrence times of the non-PRE bursts were consistent with predictions for mixed-fuel burning.
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All authors Lei Zhang, Zhaosheng Li, Yuanyue Pan, Wenhui Yu, Yupeng Chen, Yue Huang, Mingyu Ge, Shu Zhang
Solar and Stellar Astrophysics
Properties of current sheets in two-dimensional tearing-mediated incompressible magnetohydrodynamic turbulence
Chen Shi, Marco Velli, Nikos Sioulas et al. (+1 more)
It is well known that the nonlinear
evolution of magnetohydrodynamic (MHD)
turbulence generates current sheets. In the
solar wind
turbulence, current sheets are frequently observed and they are believed to be an important pathway for the
turbulence energy to dissipate and heat the
plasma. In this study, we perform a comprehensive analysis of current sheets in a high-resolution two-dimensional simulation of balanced, incompressible MHD
turbulence. The simulation parameters are selected such that tearing mode instability is triggered and plasmoids are generated throughout the simulation domain. We develop an automated method to identify current sheets and accurately quantify their key parameters including thickness ($a$), length ($L$), and Lundquist number ($S$). Before the triggering of tearing instability, the current sheet lengths are mostly comparable to the energy injection scale. After the tearing mode onsets, smaller current sheets with lower Lundquist numbers are generated. While power-law scaling relations between $L$ and $a$ and between $a/L$ and $S$ are observed, no clear correlation is found between the upstream
magnetic field strength and thickness $a$. Finally, although the
turbulence energy shows anisotropy between the directions parallel and perpendicular to the local
magnetic field increment, we do not observe a direct correspondence between the shape of the current sheets and that of the
turbulence “eddies.” These results suggest that one needs to be cautious when applying the scale-dependent dynamic
alignment model to the analysis of current sheets in MHD
turbulence.
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All authors Chen Shi, Marco Velli, Nikos Sioulas, Zijin Zhang
High Energy Astrophysical Phenomena
The origin of the spectral versus dynamical age discrepancy in radio galaxies
Larissa Jerrim, Stas Shabala, Ross Turner et al. (+4 more)
We investigate the effect of turbulent
magnetic fields on the observed spectral properties of synchrotron
radio emission in large-scale
radio galaxy lobes. We use three-dimensional relativistic magnetohydrodynamic simulations of fast, high-powered jets to study the structure of the lobe
magnetic fields and how this structure affects the
radio spectrum of the lobes. It has previously been argued that lobe ages inferred from
radio spectra underestimate the true ages of
radio galaxies due to re-acceleration of electrons in the lobe, mixing of electron populations, or the presence of turbulent
magnetic fields in the lobes. We find that the spectral ages with and without accounting for the lobe
magnetic field structure are consistent with each other, suggesting that mixing of radiating populations of different ages is the primary cause of the underestimation of
radio lobe ages. By accounting for the structure of lobe
magnetic fields, we find greater spectral steepening in the equatorial regions of the lobe. We demonstrate that the assumptions of the continuous injection, Jaffe-Perola, and Tribble models for
radio lobe spectra do not hold in our simulations, and we show that young particles with high
magnetic field strengths are the dominant contributors to the overall
radio lobe spectrum.
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All authors Larissa Jerrim, Stas Shabala, Ross Turner, Patrick Yates-Jones, Martin Krause, Georgia Stewart, Chris Power
Solar and Stellar Astrophysics
Abundance Analysis of Chemically Depleted Post-AGB/Post-RGB Binaries with Faint Discs
Maksym Mohorian, Devika Kamath, Meghna Menon et al. (+4 more)
Post-AGB and post-RGB binaries with stable circumbinary discs provide key insights into late
stellar and disc
evolution, revealing how binary interactions shape disc structure and
stellar surface composition. A defining trait of such systems is the observed underabundance of refractory elements in the
stellar photosphere relative to volatile elements – photospheric chemical depletion – resulting from the
star accreting volatile-rich circumstellar gas. In this study, we investigated the link between photospheric depletion and disc
evolution by focusing on post-AGB/post-RGB binaries with low infrared excess (hereafter “faint disc” targets). We analysed high-resolution optical spectra from HERMES/Mercator and UVES/VLT for 6
Galactic and 2 LMC targets. Using E-iSpec, we homogeneously derived atmospheric parameters and chemical abundances of 29 elements from carbon to europium, and included NLTE corrections for 15 elements from carbon to barium that we calculated using pySME and pre-computed grids of departure coefficients. All targets exhibit `saturated' depletion patterns, which we characterised using two-piece linear fits defined by three parameters: initial
metallicity ([M/H]$_0$), turn-off temperature ($T_{\rm turn-off}$), and depletion scale ($\nabla_{\rm 100 K}$). Among several findings, we highlight the bimodal distribution of $T_{\rm turn-off}$ in faint disc targets, which allows classification into two subgroups analogous to full discs with continuous, optically thick
dust ($T_{\rm turn-off}$ > 1 100 K), and transition discs with inner clearing ($T_{\rm turn-off}$ < 1 100 K). Our results imply that faint disc targets likely represent the final stages of disc dissipation, highlighting the diversity of depletion profiles, the complexity of disc-binary interactions, and the need to understand the rarity and
evolution of faint disc systems.
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All authors Maksym Mohorian, Devika Kamath, Meghna Menon, Hans Van Winckel, Mingjie Jian, Anish M. Amarsi, Kateryna Andrych