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Physics Astrophysics

astro-ph Watch Astrophysics

Sunday 28 June

High Energy Astrophysical Phenomena

Modelling the delayed shock-breakout emission following jet-launching binary neutron star mergers via relativistic magnetohydrodynamic simulations simulations

Matteo Pais, Riccardo Ciolfi and Andrea Pavan

In binary neutron star (BNS) mergers launching a relativistic jet, an electromagnetic (EM) signal is produced when the jet-driven shock breaks out of the merger ejecta. The observed time delay of this shock-breakout (SBO) emission with respect to the gravitational-wave (GW) signal from the merger provides a powerful probe of the physical conditions governing jet launching and early-time jet propagation. Considering different models of jet propagation in realistic post-merger environments, we investigate the SBO emission and corresponding GW-EM delay that would be observed depending on the viewing angle and the assumed ejecta opacity. We performed relativistic MHD simulations of jets propagating through a post-merger environment directly imported from the outcome of a previous BNS merger simulation. We also introduced a specific procedure to faithfully reconstruct the early dynamical ejecta up to their natural front. The evolution was followed in 3D up to 0.6 s and then we continued imposing axisymmetry and an eight times higher resolution. Varying jet launching time and luminosity, we identified three representative models spanning regimes from early breakout to extended jet choking. For each case, we tracked the jet-driven forward shock up to the photosphere and computed the angle-dependent bolometric SBO luminosity, and taking into account non-radial photon propagation, relativistic Doppler shifts, and light-travel-time effects. We considered two opacity values spanning a factor of ten. We find that the GW-EM delay depends only weakly on both the viewing angle and the ejecta opacity, making it, at least for the limited set of configurations considered here, a robust diagnostic for constraining models. Comparing our three cases with GRB 170817A, we find smaller GW-EM delays. Reproducing the same delay will require a broader exploration of the parameter space.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Radial oscillations of quark stars in light of current astrophysical constraints: A comparative study

G. Panotopoulos, A. Rincon and I. Lopes

We investigate the structural and oscillatory properties of isotropic strange quark stars within General Relativity, focusing on three physically motivated equations of state: the color flavor locked (CFL) phase, an interacting quark matter model, and a linear (causal) equation of state. By numerically solving the Tolman Oppenheimer Volkoff and radial perturbation equations, we construct equilibrium stellar sequences and compute oscillation spectra across three representative masses (0.77, 1.40, and 2.00 solar masses). Our analysis is focused on two diagnostics: (i) mass to radius profiles and (ii) radial mode eigenfrequencies with large frequency separations. We compare theoretical predictions against multimessenger constraints from NICER X ray timing of key pulsars, the massive pulsars at two solar masses, and the low mass compact object in HESS J1731–347. All three equations of state yield maximum masses exceeding 2 solar masses with canonical mass radii of (10–12) km, satisfying current observational bounds. Fundamental mode frequencies span (4–7) kHz, with asymptotic large separations differing among the models. These elevated frequencies lie within the detection band of current and next generation gravitational-wave observatories, offering potential asteroseismic signatures for distinguishing strange quark stars from hadronic neutron stars in post merger emission. Our results demonstrate that self bound quark matter naturally accommodates the sub solar mass configuration of HESS J1731–347, reinforcing the viability of strange quark star interpretations.
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Astrophysics of Galaxies

Accelerated gas flow along Ophiuchus B44 filament: Breaking Position-Position-Velocity degeneracy

J. Alves, C. Zucker, C. Lada et al. (+15 more)

(Abridged) Stellar feedback from massive stars in the Upper-Sco has been proposed to have reshaped the gas in the nearby Ophiuchus complex. In this framework, feedback organizes the gas into two filament types based on their orientation relative to the source of feedback: radial (R-type) filaments, aligned radially to the massive stars, and tangential (T-type) filaments, which are orthogonal to the feedback direction. A key prediction of this scenario is that gas within R-type filaments should flow longitudinally away from the massive stars. In this paper, we test this scenario by measuring the three-dimensional gas flow inside the potential R-type filament B44, combining the 3D orientation of the filament from Gaia-based 3D dust maps with radial velocities from CO observations. We find that gas flows longitudinally along the B44 filament away from the massive stars in Upper-Sco with both tracers yielding consistent velocity fields. This result confirms B44 is a R-type filament formed by stellar feedback from Sco-Cen with an implied filament assembly timescale of $\sim$3~Myr, well within the age of the Upper-Sco massive stars. Moreover, we find that the gas motion along B44 and away from the massive stars is accelerated with $a\sim$1.8~km/s/Myr ($\sim 6 \times 10^{-11}$~m/s$^2$). This acceleration is compatible with the accelerations recorded along the Sco-Cen cluster chains over the past $\sim$15~Myr, indicating that B44 is likely a present-day, gas-phase counterpart of the same feedback-driven process that produced those stellar sequences. We further find evidence for a shock at the wind-facing head of the filament, with a deprojected flow Mach number of $\sim$2 and a matching density jump. Our findings demonstrate that Gaia 3D dust maps can lift the line-of-sight ambiguity intrinsic to PPV spectral data, enabling direct deprojection of the gas velocity field in coherent filaments.
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All authors J. Alves, C. Zucker, C. Lada, M. Lombardi, M. Piecka, S. Hutschenreuter, S. Meingast, L. Posch, A. Hacar, K. Tachihara, R. Yamada, C. Swiggum, A. Goodman, R. Wunsch, J. Großschedl, A. Burkert, F. Heitsch, T. Enßlin

Instrumentation and Methods for Astrophysics

Sub-Kelvin Cryogenics for a Super-Pressure Balloon-Borne CMB Polarimeter: Taurus

Jared L. May, Alexandre E. Adler, Jason E. Austermann et al. (+23 more)

Taurus is a balloon-borne cosmic microwave background (CMB) experiment designed to operate more than 10,000 transition-edge sensor bolometers at a base temperature near 100 mK during a multi-week stratospheric balloon flight. This platform provides near-space observing conditions while imposing stringent constraints on mass, power, and system robustness, driving the need for a lightweight and highly reliable cryogenic system. To meet these requirements, Taurus employs a multi-stage cryogenic architecture. A 660 L liquid helium tank provides a stable 4 K reservoir, with vapor-cooled shields establishing intermediate stages at approximately 40 K and 80 K. A superfluid helium tank provides an approximately 1.5 K takeoff point for the sub-Kelvin cooling systems. Each of the instrument's three receivers is supported by an independent sub-Kelvin cooling chain that includes closed-cycle 3He sorption refrigerators that cool to 300 mK. These provide the thermal intercept and takeoff for a Chase Research Cryogenics miniature dilution refrigerator that cools the detectors to approximately 100 mK. Here we discuss the requirements and challenges of the Taurus sub-Kelvin cryogenic system and present results of early performance tests.
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All authors Jared L. May, Alexandre E. Adler, Jason E. Austermann, Steven J. Benton, Rick Bihary, Shannon Duff, Malcolm Durkin, Jeffrey P. Filippini, Aurelien A. Fraisse, Thomas Gascard, Sho M. Gibbs, Suren Gourapura, Jon E. Gudmundsson, Johannes Hubmayr, William C. Jones, Ashesh Khatua, Darby McCauley, Johanna M. Nagy, Ivan Padilla, Ricardo R. Rodriguez, John E. Ruhl, M. Shaaf Sarwar, Simon Tartakovsky, Joseph van der List, Michael R. Vissers, Philippe Voyer

Solar and Stellar Astrophysics

Evidence of Supernova Between Formation of Stellar Populations in a Globular Cluster

Evan N. Kirby, Roman Gerasimov, Alice Cai et al. (+3 more)

Globular clusters do not undergo conventional chemical evolution driven by supernova enrichment. Instead, they exhibit unique abundance patterns of the light elements, which cannot be fully explained by any of the proposed enrichment mechanisms. "Normal" stars of low sodium abundances comprise the first population of cluster stars, and "enriched" stars of high sodium abundances, which are found only in globular clusters, comprise the second population. Here we show from a differential line-by-line analysis of stars that span a small range of effective temperature that the globular cluster M92 has higher Fe abundances in second-population (sodium-enhanced) stars than first-population stars. The two populations are well separated in Na, Al, and Fe abundances. The rise in Fe abundance between the first and second stellar populations suggests that M92 was able to retain at least some supernova ejecta, all of which exploded after the first population finished forming. This result provides a lower limit for the time delay between populations.
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All authors Evan N. Kirby, Roman Gerasimov, Alice Cai, Benjamin Coco, Pranav Nalamwar, Lauren Henderson

Solar and Stellar Astrophysics

Distribution of energy release events due to magnetic braiding

David I. Pontin, Klaus Galsgaard and James A. Klimchuk

Energy conversion by reconnection-powered nanoflare heating is one of the leading explanations for the heating of the solar chromosphere and corona. The aim of this paper is to shed light on this mechanism by exploring the magnetic Reynolds number dependence of the energy conversion process. To do this we employ boundary-driven, magnetohydrodynamic, flux-braiding simulations at different magnetic Reynolds numbers ($R_m$), and explore in detail the properties of the individual magnetic energy release events. The properties of the reconnecting current sheets that mediate the energy release are shown to depend on $R_m$. For increasing $R_m$, the current sheets become thinner, more intense, and more numerous. For sufficiently large $R_m$, the current sheets fragment along their length, leading to a sharp cutoff in the current sheet length distribution. The cutoff is consistent with the threshold for non-linear tearing/plasmoid instability. For increasing $R_m$ the magnetic field lines become increasingly tangled, the mean and peak values of the magnetic field strength increase, and the Poynting flux into the domain increases, implying that the heating rate also increases. The global reconnection rate is essentially independent of $R_m$. These results support the braiding mechanism as a viable way to effectively heat the internal portions of coherent flux tubes in the corona.
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Cosmology and Nongalactic Astrophysics

Probing the Baryon Distribution with Fast Radio Bursts

Manisha Caleb, Jéferson A. S. Fortunato, Steffen Hagstotz et al. (+12 more)

Baryonic feedback redistributes matter on small to mid cosmological scales, ultimately limiting inferences from Stage IV galaxy surveys. Direct baryon tracers are crucial for recovering cosmological signals masked by astrophysical effects, and vice versa: galaxy formation and other astrophysical processes must be interpreted cosmologically. Fast radio bursts (FRBs) serve as such tracers: their dispersion measure (DM) records the line-of-sight integrated ionised electron density. The Square Kilometre Array (SKA) will be the only radio telescope capable of detecting many FRBs in the southern hemisphere, significantly enhancing synergy with surveys such as Rubin Observatory. This chapter completes the FRB trilogy by forecasting the SKA's potential to constrain the baryon distribution from cosmological to galactic scales and across cosmic time. We tackle this question by investigating the DM scatter as a function of redshift. We also study the statistical properties of the DM field and its cross-correlation with Stage IV galaxy surveys. Our focus is on cosmic shear and galaxy clustering. This shows that the SKA can play a crucial role in pinpointing baryonic feedback models, thereby greatly enhancing the cosmological constraining power of Stage IV galaxy surveys. Furthermore, we show that the SKA will be able to measure the properties of the circumgalactic medium using the scattering timescale of FRBs. Lastly, the large redshift range of FRB detections with the SKA can improve our understanding of the epoch of reionisation. It may also clarify the mechanism behind FRBs.
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All authors Manisha Caleb, Jéferson A. S. Fortunato, Steffen Hagstotz, Clancy W. James, Joscha N. Jahns-Schindler, Dylan L. Jow, Evan F. Keane, Koustav Konar, Yin-Zhe Ma, Daniele Michilli, Robert Reischke, Amit Seta, Priyanka Singh, Laura G. Spitler, Yidan Wang

High Energy Astrophysical Phenomena

Search for Diffuse Supernova Neutrino Background in the Full KamLAND Dataset with Neural-Network-Based Event Classification

D. Chernyak, T. Eda, M. Eizuka et al. (+63 more)

We report a search for the diffuse supernova neutrino background (DSNB) with the KamLAND detector, targeting electron antineutrinos via inverse beta decay in the neutrino energy range of 8.3 to 30.8 MeV. Using liquid-scintillator exposures of 9.02 kton-year for 8.3 to 9.3 MeV and 9.42 kton-year for 9.3 to 30.8 MeV, we observe seven candidate events after applying a new deep-neural-network-based event classification technique. This result is consistent with the background-only expectation of 16.2 plus or minus 9.4 events, including systematic uncertainties associated with the neural-network selection. A spectral analysis of the energy and radial distributions finds no significant excess attributable to the DSNB. We therefore set 90 percent confidence-level upper limits on the DSNB flux of 38 to 43 per square centimeter per second, depending on the assumed DSNB model. We also derive model-independent 90 percent confidence-level upper limits on the electron-antineutrino flux, obtaining some of the most stringent constraints below 13.3 MeV. Beyond the DSNB search itself, this work demonstrates neural-network-based event classification as a promising approach for suppressing neutron-associated backgrounds in liquid-scintillator neutrino detectors.
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All authors D. Chernyak, T. Eda, M. Eizuka, R. Endo, A. Gando, Y. Gando, T. Hachiya, F. Haneishi, K. Hata, T. Hirai, K. Hosokawa, K. Ichimura, H. Ikeda, K. Inoue, K. Ishidoshiro, Y. Kamei, N. Kawada, Y. Kishimoto, M. Koga, K. Mikami, H. Miyake, K. Mizukoshi, D. Morita, K. Nakamura, R. Nakamura, J. Nakane, Y. Nakano, N. Obata, Y. Ota, K. Saito, I. Sakaki, I. Shimizu, J. Shirai, A. Suzuki, K. Tachibana, A. Takeuchi, K. Tamae, H. Watanabe, Z. Xu, S. Yoshida, S. Umehara, K. Fushimi, K. Kotera, Y. Urano, S. Kurosawa, H. Ozaki, B. E. Berger, B. K. Fujikawa, J. G. Learned, J. Maricic, Z. Li, L. A. Winslow, Y. Efremenko, H. J. Karwowski, D. M. Markoff, W. Tornow, S. Dell'Oro, T. O'Donnell, J. A. Detwiler, S. Enomoto, M. P. Decowski, K. M. Weerman, C. Grant, O. Penek, H. Song, A. Li

Instrumentation and Methods for Astrophysics

PIE-ADA: Physics-Informed Ensemble with Adaptive Data Augmentation for Photometric Transient Classification

Deba Priyo Guha and Fariya Tabassum

The upcoming Large Synoptic Survey Telescope (LSST) is expected to observe approximately 10 million astronomical transient events per night, creating an urgent need for automated classification systems. A key challenge is the extreme class imbalance in transient datasets, where rare event types represent less than 1% of all observations. This paper presents PIE-ADA (Physics-Informed Ensemble with Adaptive Data Augmentation), a framework that generates physically realistic synthetic light curves for underrepresented classes using astrophysically motivated transformations. PIE-ADA applies four augmentation operations, namely correlated noise injection, cosmological time dilation, wavelength-dependent dust extinction, and observation phase shifting, while enforcing physical constraints to prevent unrealistic samples. We extract 271 multi-scale features from six photometric passbands covering statistical, temporal, peak, color, and frequency-domain properties. Evaluated on the PLAsTiCC dataset (7,848 original objects augmented to 8,148 across 14 classes), five classifiers were compared using stratified 5-fold cross-validation. LightGBM achieved the best performance with a weighted log loss of 0.5763 ($\pm$0.0083) and 80.33% accuracy, improving over Random Forest, Extra Trees, and Neural Network baselines by 24-49% in log loss. The framework is computationally efficient, completing the full pipeline in under 37 minutes and classifying individual objects in less than 0.05 seconds, making it suitable for real-time LSST alert processing.
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High Energy Astrophysical Phenomena

SKA-VLBI Probes of High-energy Emission Processes in Relativistic Jets

M. Kadler, E.K. Bempong-Manful, P. G. Edwards et al. (+10 more)

Relativistic jets in the nuclei of active galaxies are ubiquitous sources of high-energy emission. In particular, blazars represent the most luminous persistent X-ray and gamma-ray sources, whose defining characteristics are small jet inclination angles to the line of sight. Blazars can be detected in many cases up to TeV energies and the largest class of TeV emitting extragalactic AGN is represented by high-synchrotron peaked (HSP) BL Lac objects, which are generally comparably faint radio sources. Moreover, evidence has also been accumulated that high-energy cosmic neutrinos detected by IceCube can be associated with blazars. There is an increasing number of suggested blazar-neutrino associations, along with many cases of coincident flaring radio emission, but in a majority of cases, faint blazars on the level of millijanskies or below have to be considered. These high-energy photon and neutrino emission processes hold many unanswered questions including the unknown source of seed-photons for photo-pion production and the infamous Doppler crisis of TeV-emitting BL Lac objects. SKA-VLBI offers the opportunity to achieve superior sensitivity at milliarcsecond resolutions, provided by the combination of the phased SKA-Mid and global VLBI arrays. This opens the possibility to perform high-sensitivity and high-angular resolution imaging and polarimetric probes of faint blazars. The resulting high-fidelity spatially resolved parameterizations of structured jets in bright sources will yield key insights to constrain physical models of high-energy photon and particle emission in AGN jets.
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All authors M. Kadler, E.K. Bempong-Manful, P. G. Edwards, F. Eppel, C. M. Fromm, M. Giroletti, J. Heßdörfer, T. Hovatta, Y. Y. Kovalev, K. Mannheim, R. Ojha, F. Rösch, E. Ros

Earth and Planetary Astrophysics

Giant Planet Atmospheres

Henrik Melin

The giant planets, Jupiter, Saturn, Uranus, and Neptune, all have vibrant and dynamic atmospheres. The iconic belt–zone structure of Jupiter, together with the Great Red Spot, is instantly recognizable. Saturn, with its dramatic ring system and more muted atmosphere, is a formidable jewel in the Solar System. In the outer reaches, the pale blue Uranus and Neptune are found, worlds about which ultimately very little is known. The atmospheres of these planets are dominated by hydrogen and helium, and unlike the Earth, they do not have a solid surface. These differences generate inherently different types of atmospheres, but there are also similarities. For example, the condensation of water, which forms the familiar clouds on Earth, also occurs on the giant planets. Broadly speaking, the atmosphere can be divided into different regimes defined by their temperature gradients. In the troposphere, where weather occurs, the temperatures decrease as a function of increasing altitude as convection moves internal heat upward; the rising material expands and cools. Above this region lies the stratosphere, defined by a positive temperature gradient, where hydrocarbons are heated by ultraviolet radiation from the Sun (analogous to ozone heating in the terrestrial stratosphere), which also drives substantial photochemistry. This is followed by a mesosphere that cools as a function of altitude, a region that is ill-defined at the giant planets. Finally, the upper atmosphere connects to the space environment and is heated by both solar extreme ultraviolet light and auroral processes. The giant planets are energized both by internal heat and by solar heating. These energy inputs, along with the fast rotation rates of these planets, drive dynamics by establishing global circulation patterns and generating both waves and instabilities. [...]
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Instrumentation and Methods for Astrophysics

SPICE: Scintillation Pipeline for Interferometric Candidate Extraction

Jitendra Salal, Shriharsh Tendulkar and Visweshwar Ram Marthi

We present Scintillation Pipeline for Interferometric Candidate Extraction (SPICE) an automated CASA-based pipeline developed to identify pulsar candidates in Giant Metrewave Radio Telescope (GMRT) and upgraded GMRT (uGMRT) data through their diffractive interstellar scintillation signatures. SPICE integrates flagging, calibration, imaging, and classification, with robust RFI excision, iterative self-calibration with dynamic reference antenna selection, source detection using PyBDSF, and classification based on our earlier development of scintillation-based visibility correlation searches. SPICE is available publicly on github and is archived on Zenodo. We applied SPICE to archival datasets from both legacy GMRT and uGMRT. The pipeline successfully recovered known pulsars such as PSR 0437-4715, PSR B0450-18, and PSR B0329+54, yielding scintillation parameters consistent with expectations. Non-detections in some scans highlight the influence of pervasive RFI, the dependence on the reference antenna, and the intrinsic variability of the scintillation properties. SPICE complements time-domain searches by enabling reproducible scintillation-based candidate identification in interferometric data. Its application to the GMRT archive opens a pathway for discovering compact variable sources and expanding pulsar searches beyond time-domain searches.
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Earth and Planetary Astrophysics

The Maximum Initial Mass

Dario Izzo and Giacomo Acciarini

We introduce the maximum-initial-mass problem as a standalone optimal-control formulation for low-thrust trajectory design and analyze its structure within Pontryagin's framework. For fixed transfer time and final state, the formulation seeks the largest initial mass from which the transfer is feasible, and its necessary conditions imply a full-throttle control law in the nondegenerate case together with the standard primer-vector steering direction. We then establish a correspondence between extremals of the maximum-initial-mass and minimum-time problems, showing that each minimum-time extremal induces a maximum-initial-mass extremal on the associated time interval, and conversely. This viewpoint also clarifies the role of the terminal Hamiltonian condition in indirect formulations of minimum-time problems, which we interpret as a gauge choice rather than an independent necessary condition in the setting considered. Finally, we show that the maximum-initial-mass framework provides a smooth and effective continuation strategy for multiple-revolution low-thrust transfers. Applied to a benchmark GTO-to-GEO transfer, the approach recovers the global minimum-time solution, reveals additional extremal branches, and makes explicit that some trajectories previously reported in the literature correspond to local maxima of transfer time along iso-M curves rather than to local minima.
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Solar and Stellar Astrophysics

Elemental Abundances from Off-center Carbon Burning in Accreting CO White Dwarfs: Implications for SN 2021yfj-like events

Chengyuan Wu, Dongdong Liu, Takashi J. Moriya et al. (+3 more)

SN 2021yfj is a recently discovered interacting supernova that exhibits narrow emission lines of Si, S, and Ar, indicating the presence of circumstellar material (CSM) enriched with these elements surrounding the progenitor prior to the explosion. The origin of SN 2021yfj-like events remains uncertain. Recent work proposed that the SN 2021yfj-like events may stem from the double WD merger scenario, in which the merger of a Si-rich WD with a more massive ONe WD tidally strips about 0.3Msun of Si-rich material to form the CSM. If the merger subsequently triggers a supernova explosion, the interaction between the ejecta and the CSM can reproduce the observed light curve of SN 2021yfj. In this scenario, the progenitor system is a CO WD + He star binary, in which the CO WD accretes He-rich material from the He star. The accumulated material can trigger off-center carbon burning, potentially leading to the formation of a Si-rich WD. However, it remains unclear whether such off-center carbon burning can produce Si, S, and Ar in amounts comparable to those inferred for the CSM of SN 2021yfj. In this work, we simulate the evolution of a CO WD accreting He-rich material using time-dependent mass-accretion rates. Our results show that off-center carbon burning in the accreting CO WD can produce significant amounts of Si and S. We further found that the resulting elemental abundances are strongly affected by the initial carbon abundance of the WD. Based on our results, we suggest that the double WD merger scenario may provide a viable progenitor channel for SN 2021yfj-like events.
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All authors Chengyuan Wu, Dongdong Liu, Takashi J. Moriya, Zhengwei Liu, Heran Xiong, Bo Wang

Earth and Planetary Astrophysics · Cross-listed from nlin.CD

Stable Ballistic Prograde Cyclers in the Three-Body Problem

Shane D. Ross and Michael Roberts-Tsoukkas

We report the first continuous families of stable, ballistic, prograde cycler orbits in the circular restricted three-body problem: periodic trajectories that alternately undergo temporary capture and orbit each primary. We construct continuous families of symmetric cyclers from intersections of the stable and unstable manifold tubes of the $L_1$ Lyapunov orbit and exhibit stable examples across more than two orders of magnitude in mass ratio, from the Sun–Jupiter regime to the equal-mass limit. Linear stability separates naturally into planar and out-of-plane components. A planar-stable branch of every computed family is created simultaneously with a hyperbolic branch in a saddle-center bifurcation of the return map at the family's maximal Jacobi constant, while out-of-plane instability occurs only through isolated parametric resonances. Every computed family contains a subfamily that is linearly stable to both planar and out-of-plane perturbations. These stable cyclers persist into the full three-body problem for sufficiently small third mass. We conjecture that saddle-center birth is universal among cycler families, suggesting that stable cyclers are a generic feature of three-body dynamics.
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Astrophysics of Galaxies

Citizen Science Research with the Square Kilometre Array Observatory (SKAO)

Ananda Hota, Pratik Dabhade, M. J. Hardcastle et al. (+8 more)

Over the past two decades, internet-enabled citizen science research (CSR) has contributed to significant discoveries while involving millions of people in the research process. Our review highlights CSR in extragalactic radio astronomy and emphasises that such approaches will become increasingly relevant across radio astronomy in the era of the Square Kilometre Array (SKA). As astronomical data volumes grow, CSR is converging with Artificial Intelligence and Machine Learning (AI/ML), creating hybrid human-machine frameworks suited to big-data challenges. Two CSR platforms, Radio Galaxy Zoo and RAD@home, demonstrate success: the former excels in large-scale, web-based catalogue creation, while the latter combines structured training with collaborative discovery. Following this, we propose CSR with the SKA, namely SKA@home, with two modes: one purely web-based and the other in collaboratory mode with national training programmes. We argue that CSR can complement, and at times surpass, automated AI/ML pipelines, particularly in identifying rare, intricate, or unexpected features. Illustrative CSR discoveries include an episodic wide-angle-tailed radio galaxy, a jet-galaxy interaction, a collimated synchrotron thread, a twin-ring odd radio circle, and a large-scale shock ahead of a cluster-infalling galaxy. Consistent with the IAU's recognition of CSR as a driver of Astronomy for Development and the United Nations' affirmation of participation in science as a universal human right, both the SKA construction proposal and outreach strategies show commitment to enabling CSR with SKA. The proposed SKA@home would not only enhance the early discovery potential of SKA data but also initiate a deeper and more meaningful connection with society at large.
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All authors Ananda Hota, Pratik Dabhade, M. J. Hardcastle, Stephen Serjeant, C. Konar, Hugh Dickinson, Sabyasachi Pal, Sravani Vaddi, Sagar Sethi, Shubhrangshu Ghosh, Arundhati Purohit

Astrophysics of Galaxies

Evolution of Compact Stellar Systems in Ultralight Dark Matter Halos: Dependence on Stellar and Dark Matter Parameters

Yu-Ming Yang, Xiao-Jun Bi, Long Wang et al. (+1 more)

Compact stellar systems are often used to place stringent constraints on the particle mass of ultralight dark matter (ULDM), as the heating effect induced by wave interference can drive system expansion, potentially bringing them into tension with observations. In a recent study, we pointed out that internal two-body relaxation in these stellar systems may have a significant impact on their evolution in ULDM halos, an effect overlooked in previous studies. Here, we further investigate the influence of stellar metallicity, the Milky Way's tidal field, and the ULDM particle mass on the long-term fate of compact stellar populations. We find that metal-richer systems are generally more resistant to disruption. The tidal field of the Milky Way, by altering the orbital motion of the stellar systems within host ULDM halos, can significantly affect their stability. Furthermore, we find in our simulations that the heating effect becomes stronger with increasing ULDM particle mass when the system size is much smaller than the ULDM de Broglie wavelength $R_{\rm h} \ll \lambda_{\rm dB} $, in contrast to the $\lambda_{\rm dB}\lesssim R_{\rm h}$ case. These results highlight the complexity of the evolution of compact stellar systems in ULDM halos, and suggest that existing constraints derived from the systems, such as ultrafaint dwarf galaxies, may require careful revision.
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All authors Yu-Ming Yang, Xiao-Jun Bi, Long Wang, Peng-Fei Yin

High Energy Astrophysical Phenomena

Neutron Star Mass across Binary Pulsar Subpopulations: Mass-Spin Correlation, Mass Distributions, and Moment of Inertia Effects

Debatri Chattopadhyay

We present a hierarchical Bayesian analysis of the joint mass, spin, and orbital properties of $\sim 50$ Galactic binary radio pulsars with measured neutron star masses, classified by binary type into pulsar-white dwarf (PSR-WD) and double neutron star (DNS) systems. We find moderate evidence for an anti-correlation between neutron star mass and spin period in the pooled recycled population (correlation coefficient $\rho = -0.26$, with $96\%$ of the posterior probability at $\rho<0$; the $90\%$ credible interval excludes zero), robust to the treatment of candidate DNSs and to a radio-detectability selection correction. Although consistent with accretion-driven recycling, the correlation cannot statistically distinguish an accretion origin from a moment of inertia-driven spin-up mechanism, because the neutron star moment of inertia is nearly linear in mass over the observed range. The DNS systems alone instead lean to the positive side expected from the moment-of-inertia mechanism ($\rho=+0.13$), though with only ten systems this is not statistically conclusive. Mass shows no significant correlation with orbital period or inclination, and only a weak one with eccentricity. As a secondary result, neutron stars with helium white dwarf companions are marginally more massive than those with carbon-oxygen/oxygen-neon white dwarf companions ($\Delta \simeq 0.06\,M_\odot$), consistent with more extensive accretion in the helium white dwarf channel. We confirm, in a hierarchical framework, the previously reported correlation between companion mass and orbital eccentricity in double neutron stars ($\rho=+0.82$). We interpret these results within a two-channel picture – accretion-grown PSR-WD versus birth-mass-dominated DNS.
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Instrumentation and Methods for Astrophysics

A Covariance-Aware Framework for Spatially Resolved Exoplanet Biosignature Inference with the Solar Gravitational Lens

Slava G. Turyshev

Assessing possible life on an exoplanet requires spatial, spectral, temporal, and environmental context rather than a threshold detection of one molecule or surface feature. We develop a covariance-aware Solar Gravitational Lens (SGL) framework in which the data product is a time-tagged Stokes spectral cube reconstructed from wavelength-dependent Einstein-ring measurements. The demonstrated calculation is a 0.45-2.40 um Stokes-I reflected-light simulation of an Earth-radius planet at 30 pc, observed from 650 AU with a (128 x 128) raster, 128 simultaneous spectral channels, and $R\simeq70$. A separate 0.40-20 um architecture-level calculation tracks reflected and thermal planet photons, SGL gain, solar-corona noise, instrumental backgrounds, throughput, dwell time, and reconstruction covariance. In the controlled population audit, structural forward-model mismatch preserves the block ordering gas > surface > cloud/path > mineral > calibration/SGL while reducing the combined conditional information gain to 0.83 of the matched-model value. A reconstruction-covariance bracket reduces an (8 x 8) regional coadd gain from 7.77 to 3.00, implying a 6.7-fold dwell penalty. The feasibility results are design scalings, not a mission verdict: imaging and low-resolution mapping are earlier objectives, whereas full regional spectroscopy requires simultaneous acquisition, sub-ppm effective coronal calibration, measured reconstruction covariance, and branch-specific radiometric validation. We show that the SGL offers a uniquely powerful path to surface-resolved mapping, regional spectroscopy, thermal-climate diagnostics, and co-location tests, providing spatial, spectral, temporal, and environmental context that could strengthen assessments of habitability and possible biological activity beyond disk-integrated precursor observations.
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Saturday 27 June

Cosmology and Nongalactic Astrophysics · Cross-listed from physics.gen-ph

Varying Gravity from a Modified Fractional Model: Observational Constraints and Slow-Fast Dynamics

Rami Ahmad El-Nabulsi, Genly Leon, Esteban González et al. (+1 more)

We investigate a fractional gravity model in which both the Hubble parameter and the gravitational constant evolve dynamically due to fractional renormalization-group effects. The model incorporates a scalar field coupled to a time-varying $G$, generating nonlocal corrections characteristic of fractional–action cosmology. Analytical and numerical solutions reveal oscillatory regimes, cyclic phases, and rapid variations with implications for BBN and early-universe evolution. A robust numerical framework is developed to integrate the regularized system and compare the resulting $H(z)$ evolution with observational data from the Hubble parameter, baryon acoustic oscillations, type Ia supernovae, gravitational lensing, and black hole shadows, thereby enabling a consistent reconstruction of cosmographic quantities. A Bayesian analysis shows that the Fractional model with $\mu=0$ is the only statistically viable variant. The inferred Hubble parameter is stable across models ($h\simeq 0.72$), while the fractional parameters are significantly better constrained in the $\mu=0$ case ($\alpha=1.20^{+0.25}_{-0.14}$, $\zeta=0.43^{+0.39}_{-0.29}$). The dynamical sector yields $m=30.8^{+28.0}_{-20.9}$ and $\Gamma=108.3\pm1.1$, leading to a positive discriminant and a well-determined relaxation timescale $\tau_{\rm rel}\simeq 9$ Gyr, confirming an overdamped regime. Although the $\mu=0$ model attains a slightly lower $\chi^2_{\min}$ than $\Lambda$CDM, the BIC strongly favors $\Lambda$CDM due to its smaller parameter space. Overall, the model reproduces late-time acceleration and mimics $\Lambda$CDM while introducing distinctive cosmographic signatures. The dynamical systems analysis clarifies the stability structure and parameter dependence, indicating that fractional nonlocal corrections may offer new pathways toward addressing the $H_0$ and $S_8$ tensions.
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All authors Rami Ahmad El-Nabulsi, Genly Leon, Esteban González, Kevin Marroquín

Cosmology and Nongalactic Astrophysics · Cross-listed from physics.gen-ph

Scalar Photon Coupling and Modified Photon Evolution: CMB Signatures and Cosmological Constraints

Y. Bisabr

We investigate the constant-$\epsilon$ limit of a photon-sector modification derived from an early-time interaction between a scalar field and radiation. Starting from the underlying scalar–photon coupling, the parameter $\epsilon$ quantifies the departure of the photon energy density from the standard adiabatic scaling, leading in the constant-$\epsilon$ limit to $\rho_{\gamma}\propto a^{-4+\epsilon}$ and to the modified CMB temperature–redshift relation $T(z)=T_{0}(1+z)^{1-\epsilon/4}$. The standard photon sector is recovered for $\epsilon=0$. We implement the corresponding constant-$\epsilon$ background evolution in CLASS and verify that the numerical photon-density evolution reproduces the analytic scaling. We then examine the resulting changes in the recombination history, visibility function and CMB temperature-anisotropy spectrum. These CMB spectra are used only as diagnostic outputs since the coupled scalar–photon perturbation equations are not implemented self-consistently in the numerical calculation and a full CMB likelihood analysis is beyond the scope of the present work. As a preliminary statistical application, we interface the modified CLASS implementation with MontePython and analyze the Pantheon+SH0ES supernova likelihood together with BAO measurements. Within the adopted constant-$\epsilon$ framework, prior choices, data combination and fixed early Universe parameter setup, we obtain $\epsilon=0.0230\pm0.0065$. The posterior is therefore centered on a positive value within this restricted analysis. Because the BAO predictions depend on the model-dependent drag scale and several early-Universe quantities are held fixed, this result should be interpreted as a conditional and preliminary constraint rather than as a full CMB-level determination or evidence for a resolution of the Hubble tension.
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Instrumentation and Methods for Astrophysics

Neural posterior estimation of Galactic Binary signals for the LISA mission

Tanguy Delmond, Natalia Korsakova, Thomas Oberlin et al. (+3 more)

ESA's LISA mission will open a new window onto the gravitational-wave sky by detecting signals from a wide variety of sources in the millihertz frequency band. Among these, galactic binaries are expected to be the most numerous sources observable by LISA. Their analysis and parameter estimation represent a significant challenge, as the signals are expected to strongly overlap in both the time and frequency domains. Conventional Bayesian inference approaches, such as Markov Chain Monte Carlo sampling, are difficult to scale to this setting due to the high dimensionality of the problem and the complicated likelihood landscape which can hinder convergence. In this work, we explore simulation-based inference as a means to perform efficient parameter estimation for single galactic binaries, with a potential extension to the analysis of multiple overlapping sources. Our approach relies on a conditional normalizing flow acting as a neural posterior estimator. The model is trained using samples generated according to a dedicated simulation framework that does not require any likelihood computation. Once trained, the neural posterior estimator enables the generation of thousands of posterior samples per second, again without explicit likelihood evaluation. We first present results for a single source in a narrow frequency band, and then extend the analysis to wider frequency ranges. As a proof of concept, we further investigate the more challenging case of two overlapping sources. These results demonstrate the potential of likelihood-free inference as a scalable alternative to conventional Markov chain Monte Carlo sampling for the analysis of LISA galactic binaries.
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All authors Tanguy Delmond, Natalia Korsakova, Thomas Oberlin, Sylvain Marsat, Antoine Basset, Nicolas Dobigeon

Earth and Planetary Astrophysics

The GAPS programme at TNG LXXV. Validating and confirming Gaia substellar astrometric candidates with HARPS-N

D. Barbato, M. Pinamonti, A. Sozzetti et al. (+22 more)

The astrometric measurements provided by the Gaia space mission represent a key advancement in the search and characterization of exoplanets, helping in particular to solve the mass degeneracy intrinsic to the radial velocity (RV) method. The fact that a fraction of astrophysical false positives contaminates the current catalog of astrometric candidate solutions requires an RV follow-up to validate and confirm such candidates. Within the GAPS programme, we have observed a selected sample of 14 stars having Gaia astrometric solutions compatible with the presence of a substellar companion. The immediate aim of this survey is to identify astrophysical false positives and provide the first RV validation and confirmation of the remaining candidates. We analysed data collected with the HARPS-N spectrograph to identify stellar binary systems from the spectral cross-correlation function profiles. The remaining astrometric candidates were characterized via Markov chain Monte Carlo analysis searching for the best-fit RV solution. Among the stars in our sample with astrometric candidate solutions, we identify 6 as originating from close binary companions mimicking the astrometric motion of distant substellar companions, from which we can estimate an updated value of $43_{-11}^{+13}\%$ for the binary contamination fraction in the Gaia DR3 catalog of astrometric candidates. We validate and confirm the remaining 8 solutions, corresponding to giant and brown dwarf companions with minimum masses between 8 and 62 $M_{\rm Jup}$ and semimajor axes between 0.76 and 1.42 au, providing the first RV characterization for 6 of these candidates and updated orbital solutions for 2 previously confirmed ones.
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All authors D. Barbato, M. Pinamonti, A. Sozzetti, S. Desidera, V. D'Orazi, J. Maldonado, K. Biazzo, L. Naponiello, A. F. Lanza, A. Bignamini, A. S. Bonomo, M. Brogi, L. Cabona, M. Damasso, R. Gratton, L. Mancini, G. Mantovan, D. Nardiello, M. Rainer, G. Guilluy, P. Giacobbe, L. Malavolta, R. Cosentino, W. Boschin, R. Claudi

Solar and Stellar Astrophysics

The Long-Period Radio Transient and Cataclysmic Variable ASKAP J1745-5051: Evidence for a 15,000 K White Dwarf and a Sub-Stellar Donor

Christian Knigge, Simone Scaringi, Noel Castro Segura et al. (+2 more)

Long-period transients (LPTs) are radio sources that exhibit polarized periodic radio bursts on time-scales of minutes to hours. At least some LPTs are associated with white dwarfs (WDs) in close binary systems. However, the evolutionary connection between LPTs and accreting WDs (aka “cataclysmic variables” [CVs]) has been unclear. The recent discovery of ASKAP J1745-5051 has been a breakthrough: this system is a bona-fide LPT that is also an X-ray emitting magnetic CV (mCV) with P_orb ~ 1.3 hrs. Here, we construct the broad-band far-UV through near-IR SED for the system and show that it is well described by two components: a 15,000 K WD (which dominates the far-UV through optical bands) and a sub-stellar (M_2 ~ 0.05~M_sun, T_eff ~ 1800 K) donor star (which dominates in the K_s band). Our SED-fitting results differ from those in the discovery paper for four reasons: (i) we fix an issue with the treatment of reddening/extinction; (ii) we discard photometric measurements that are irreparably contaminated by an unrelated star located just 0.9" from the target; (iii) we add near-infrared brightness measurements obtained from PSF-fitting photometry on archival VISTA/VHS observations; (iv) we fit the data with synthetic spectra based on model atmospheres (rather than with blackbodies). The inferred WD temperature is reasonable for an accretion-heated primary in a short-period mCV. The sub-stellar nature of the donor suggests that the system is a "period bouncer" that has already evolved past the CV period minimum. The SED fit also yields a distance of d ~ 320 pc, only ~4x larger than that to the nearest confirmed mCV. Since the fraction of the sky swept out by the radio beam is likely to be small, systems like ASKAP J1745-5051 could make up a large percentage of mCVs. This may point towards a connection between LPTs and the “missing” population of period bouncers among CVs.
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All authors Christian Knigge, Simone Scaringi, Noel Castro Segura, Domitilla de Martino, Martina Veresvarska

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Effects of Mirror Dark Matter on Neutron-Star Structure and Tidal Deformability

Jin-Cheng Jiao and Cheng-Ming Li

Mirror dark matter (MDM) can modify neutron-star structure and tidal response through gravitational coupling. In this work, we construct an ordinary-matter equation of state (EOS) by comparing hadronic matter described by the relativistic mean-field NL3\(\omega\rho\) model, and quark matter in the framework of the Nambu–Jona-Lasinio (NJL) model. The stable branch is determined through a Maxwell construction, which serves to connect distinct phases of matter. For the parameter sets considered here, \(m_u=5.2~{\rm MeV}\) is the lowest light current-quark mass in the scanned range that satisfies the \(2M_\odot\) maximum-mass requirement, while \(m_u>5.2~{\rm MeV}\) all yield stable neutron-star configurations without a resolved macroscopic quark core. The small-radius inferences for PSR J0437–4715 and XTE J1814–338, together with the tidal-deformability constraint from GW170817, are sensitive to the dark-matter mass fraction \(f_D\). The commonly used GW170817 interval \(70\lesssim\Lambda_{1.4}\lesssim580\) corresponds approximately to \(0.12\lesssim f_D\lesssim0.88\) in the present model. These results indicate that, even without a macroscopic quark core, MDM can provide an important mechanism for reducing the visible radius and modifying the tidal response of neutron stars.
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Solar and Stellar Astrophysics

Evidence of global periodicity in PSP data: can they be linked to long-period oscillations in solar active regions?

G. Dumbadze, B.M. Shergelashvili, M. Khodachenko et al. (+4 more)

The presence of coherent oscillatory signatures in Parker Solar Probe SWEAP datasets, identified through a series of spectral analyses, is addressed, and their possible connection to oscillatory phenomena in HMI/SDO datasets of active regions is questioned. The goal of the work is to perform a systematic analysis of oscillation spectra applied to SWEAP/PSP time series of various physical quantities. We apply the Lomb-Scargle spectral analysis method to the original, unevenly sampled PSP datasets and to wavelet analyses corresponding to the interpolated, evenly sampled time series. Furthermore, the statistical analysis uses spectra developed for 17 PSP encounters to obtain statistically proven characteristic periodicities. It has been found that, similarly to previously studied spectra in solar active regions with periods above 2 hours, the solar wind datasets manifest sequences of statistically significant periods in the same range in datasets of different physical quantities. It has been found that, similarly to previously studied spectra in solar active regions with periods exceeding 2 hours, the solar wind datasets exhibit sequences of statistically significant periods in the same range across datasets of different physical quantities. Based on the analysis, it is concluded that the spectra exhibit coherent, fixed periodicities in the range of 2-20 hours, with the highest statistical confidence in periods between 4 and 8 hours. It is also vital that the signature of such periods is systematically absent in datasets of PSP orbital trajectory far from the encounter sites. The coherent signal is detectable at the place of the orbital perihelion (when PSP moves almost horizontally with respect to the solar surface) and during approaching and receding phases when PSP flies almost radially.
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All authors G. Dumbadze, B.M. Shergelashvili, M. Khodachenko, L. Westrich, H. Fichtner, A. Reza, S. Poedts

Astrophysics of Galaxies

Insights into Jet-Induced Cloud Disruption in NGC 1316: ALMA Reveals a Spatially Extended Molecular Gas

Kana Morokuma-Matsui, Alexander Y. Wagner, Filippo M. Maccagni et al. (+14 more)

We present ALMA CO($J=1-0$) observations of a nearby radio galaxy NGC1316 at a 100-pc resolution to investigate the impact of AGN jets on the molecular gas. The molecular gas exhibits complex spatial and kinematic distributions, with broad CO line widths ($>50$ km s$^{-1}$) observed in several regions. The interferometric CO flux is only 34%-38% compared to single-dish data, indicating a large fraction of spatially extended molecular gas, especially in the central regions. We identified 24 Giant Molecular Clouds Associations (GMAs) primarily within the “NW Shell” and the “SE Blob”; these GMAs show velocity dispersions approximately twice as high as those in typical star-forming galaxies for their sizes. Analysis of archival ALMA CO($J=2-1$) and CO($J=3-2$) data reveals elevated line ratios ($R_{21} \sim 1$ and $R_{31} \sim 1$) in gas near the jet, whereas, away from the jet, typical values ($R_{21} \sim 0.7$, $R_{31} \sim 0.3$). A multi-wavelength comparison reveals a $\sim$5 kpc warm ionized gas shell that encompasses the molecular NW Shell. The observed energetics and bubble morphology are consistent with an expanding bubble model driven by the jet assuming a jet power of $1.6\times10^{43}$~erg~s$^{-1}$. We propose that the high extended gas fraction results from the destruction of molecular clouds due to interactions with the jet plasma. NGC1316 may be a good example of jet-induced negative feedback through the ablation, dispersal, and rarification of dense molecular clouds through jet-ISM interactions.
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All authors Kana Morokuma-Matsui, Alexander Y. Wagner, Filippo M. Maccagni, Lauranne Lanz, Fumiya Maeda, Jin Koda, Akihiko Hirota, Yutaka Fujita, Kotaro Kohno, Tomoki Morokuma, Tsutomu T. Takeuchi, Kouichiro Nakanishi, Fumi Egusa, Kenji Bekki, Daniel Espada, Bärbel Koribalski, Jing Wang

High Energy Astrophysical Phenomena

Late-time evolution of the interacting stripped-envelope supernova 2017dio

C. Humina, C. P. Gutiérrez, H. Kuncarayakti et al. (+14 more)

The discovery of stripped-envelope supernovae (SNe) interacting with dense circumstellar medium (CSM) challenges our current understanding of massive star evolution. We present late-time observations of the interacting Type Ic SN 2017dio and investigate its mass-loss mechanism and progenitor channel. We analysed late-time spectra and light curves (LCs) that are dominated by ejecta-CSM interaction. We examined the CSM and the source of the infrared (IR) excess by modelling the radiation produced by the ejecta-CSM interaction and the IR echo from circumstellar dust. In addition, we studied the evolution of spectral features, with a particular emphasis on the Halpha emission line. From the combined analysis of the LCs and spectral properties, we infer that the peak mass-loss rate for the CSM reaches ~0.2 $M_{\odot}/yr$ and that the typical value over most epochs is ~0.06 $M_{\odot}/yr$. The nearby CSM was formed over a period of 4 to 65 years before the explosion. The CSM radius begins at ~$1.3\cdot10^{15}$ cm. The IR excess identified in the LCs is consistent with the radiation from dust with a mass increasing from ~0.001 to ~0.005 $M_{\odot}$ in the case of carbon dust or ~0.005 to ~0.02 $M_{\odot}$ in the case of silicate dust. From IR echo modelling, we estimate an upper limit on the dust mass of $4\cdot10^{-5} M_{\odot}$, which implies an SN progenitor mass-loss rate of $2.4\cdot10^{-5} M_{\odot}/yr$ at the dust evaporation radius determined by the SN peak luminosity (0.017 pc for carbon dust, corresponding to mass loss ~170 years before the explosion). This implies a very rapid increase in the mass-loss rate ahead of the explosion. Although the progenitor of SN 2017dio has lost its helium envelope, it interacted with a hydrogen-rich CSM formed shortly before the explosion, suggesting that this material originated from a companion star rather than the progenitor itself. [Abridged]
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All authors C. Humina, C. P. Gutiérrez, H. Kuncarayakti, T. Nagao, S. González-Gaitán, T. Kangas, T. Kravtsov, K. Maeda, S. Mattila, T. M. Reynolds, L. Tartaglia, S. Benetti, M. Fraser, C. Gall, P. Lundqvist, A. Morales-Garoffolo, M. Stritzinger

High Energy Astrophysical Phenomena

Tracing the Orbital Motion of the Accreting White Dwarf in EX~Hydrae with XRISM/Resolve

Yuken Ohshiro, Yukikatsu Terada, Taichi Ichikawa et al. (+7 more)

Measuring the masses of accreting white dwarfs (WDs) is crucial for understanding their evolution and the physics of accretion. High-resolution X-ray spectroscopy can trace the WD motion through Doppler shifts of emission lines formed close to the WD. We report an 83~ks XRISM/Resolve observation of the intermediate polar EX~Hydrae and measure the orbital modulation of individual Fe K-shell line centroids. The Fe~xxv K$\alpha$ components show coherent orbital modulation, yielding $K_1 = 58.1 \pm 8.5\ \mathrm{km\ s^{-1}}$. This is the first detection of orbital modulation in individual Fe K-shell lines from an accreting WD, made possible by the high spectral resolution of Resolve and its frequent in-orbit gain calibration. The measured $K_1$ is consistent with optical/UV $K_1$ measurements, providing a cross-check that these distinct tracers follow the WD orbital motion. Combining this X-ray measurement with literature orbital parameters, we derive a WD mass of $M_1 = 0.79 \pm 0.04\ M_\odot$. These results demonstrate that high-resolution X-ray spectroscopy can use individual Fe K-shell line centroids to trace WD orbital motion in accreting WDs.
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All authors Yuken Ohshiro, Yukikatsu Terada, Taichi Ichikawa, Yugo Motogami, Manabu Ishida, Koji Mukai, Masayoshi Nobukawa, Takayuki Hayashi, Mariko Kimura, Mai Takeo

Instrumentation and Methods for Astrophysics

Characterization of the RF Board for microwave SQUID multiplexing readout electronics

Junbo Wang, Jianing Dong, Zhekai Cheng et al. (+1 more)

Microwave SQUID multiplexing ($\mu$MUX) is a widely used readout technique for large-scale transition-edge sensor (TES) arrays. It uses radio-frequency (RF) probe tones to interrogate cryogenic resonators, requiring frequency conversion between the baseband electronics and the cryogenic RF signal chain. This work describes the RF Board, a room-temperature frequency-conversion board deployed in the AliCPT $\mu$MUX readout system. The board up-converts 0-4 GHz baseband I/Q signals to the 4-8 GHz RF band for injection into the cryogenic chain and down-converts returned RF signals to baseband I/Q for ADC digitization. For the current 1000-tone operation, with a DAC output tone power of -30 dBm/tone, the required power windows are -35 to -25 dBm/tone for the RF tones transmitted to the cryostat and -45 to -35 dBm/tone at the ADC input for the returned tones. The RF Board is characterized using swept single-tone measurements covering up-conversion, down-conversion, and RF loopback. Based on these measurements, the RF output power is calculated to be -31.06 to -25.53 dBm, satisfying the RF output window. Assuming a representative cryogenic-chain transmission of -40 dB, the loopback result gives an estimated returned power of -45 to -35 dBm, within the target range. These results show that the RF Board meets the wideband frequency-conversion and tone-power requirements for the $\mu$MUX readout system.
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All authors Junbo Wang, Jianing Dong, Zhekai Cheng, Xiangxiang Ren