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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 20 January

High Energy Astrophysical Phenomena

Unveiling Hidden Clustering: An Unsupervised Machine Learning Study of Repeating FRB 20220912A

An-Chieh Hsu, Tetsuya Hashimoto, Tomotsugu Goto et al. (+2 more)

Fast Radio Bursts (FRBs) are millisecond-duration radio transients of extragalactic origin. Classifying repeating FRBs is essential for understanding their emission mechanisms, but remains challenging due to their short durations, high variability, and increasing data volume. Traditional methods often rely on subjective criteria and struggle with high-dimensional data. In this study, we apply an unsupervised machine learning framework that combines Uniform Manifold Approximation and Projection (UMAP) and Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) to eight observed parameters from FRB 20220912A. Our analysis reveals three distinct clusters of bursts with varying spectral and fluence properties. Comparisons with clustering studies on other repeaters show that some of our clusters share similar features with sources such as FRB 20201124A and FRB 121102, suggesting possible common emission mechanisms. We also provide qualitative interpretations for each cluster, highlighting the spectral diversity within a single source. Notably, one cluster shows broadband emission and high fluence, which are typically seen in non-repeating FRBs. This raises the possibility that some non-repeaters may be misclassified repeaters due to observational limitations. Our results demonstrate the utility of machine learning in uncovering intrinsic diversity in FRB emission and provide a foundation for future classification studies.
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All authors An-Chieh Hsu, Tetsuya Hashimoto, Tomotsugu Goto, Tomoki Wada, Bjorn Jasper Raquel

Earth and Planetary Astrophysics

Discovery and characterisation of two exoplanets orbiting the metal-poor, solar-type star TOI-5788 with TESS, CHEOPS, and HARPS-N

Ben S. Lakeland, A. Mortier, R. D. Haywood et al. (+48 more)

We present the discovery and characterisation of two transiting exoplanets orbiting the metal-poor, solar-type star TOI-5788. From our analysis of six TESS sectors and a dedicated CHEOPS programme, we identify an inner planet (TOI-5788~b; $P = 6.340758\pm0.000030\,\si{\day}$) with radius $1.528\pm0.075\,\mathrm{R_\oplus}$ and an outer planet (TOI-5788~c; $P = 16.213362\pm0.000026\,\si{\day}$) with radius $2.272\pm0.039\,\mathrm{R_\oplus}$. We obtained 125 radial-velocity spectra from HARPS-N and constrain the masses of TOI-5788~b and~c as $3.72\pm0.94\,\mathrm{M_\oplus}$ and $6.4\pm1.2\,\mathrm{M_\oplus}$, respectively. Although dynamical analyses indicate that a third planet could exist in a stable orbit between 8 and 14 days, we find no evidence of additional planets. Since the TOI-5788 system is one of the few systems with planets straddling the radius gap, and noting that there are even fewer such systems around metal poor stars, it is a promising system to constrain planet formation theories. We therefore model the interior structures of both planets. We find that TOI-5788~b is consistent with being a rocky planet with almost no envelope, or having an atmosphere of a high mean molecular weight. We find that TOI-5788~c is consistent with both gas-dwarf and water-world hypotheses of mini-Neptune formation. We model the atmospheric evolution history of both planets. Whilst both scenarios are consistent with the atmospheric evolution of TOI-5788~c, the gas-dwarf model is marginally preferred. The results of the atmospheric evolution analysis are not strongly dependent on stellar evolution. This makes the system a promising target to test internal structure and atmospheric evolution models.
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All authors Ben S. Lakeland, A. Mortier, R. D. Haywood, S. Ulmer-Moll, Z. Garai, A. Vanderburg, J A. Egger, D. A. Turner, D. Kubyshkina, A. C. M. Correia, H. P. Osborn, L. A. Buchhave, L. Malavolta, A. Bonfanti, W. Boschin, A. Cameron, A. Castro-González, R. Cosentino, M. Damasso, X. Dumusque, D. Ehrenreich, Z. Essack, S. Filomeno, L. Fossati, D. Gandolfi, M. Gillon, C. Hedges, M. López-Morales, G. Lacedelli, M. Lendl, J. Maldonado, G. Mantovan, A. F. Martínez Fiorenzano, P. F. L. Maxted, C. Mordasini, B. Nicholson, S. M. O'Brien, L. Palethorpe, E. Palle, M. Pinamonti, D. Rapetti, I. Ribas, N. C. Santos, A. M. Silva, A. Sozzetti, M. Stalport, G. Szabó, S. Udry, M. Vezie, C. A. Watson, T. G. Wilson

Cosmology and Nongalactic Astrophysics

Evaluating state-of-the-art cloud quantum computers for quantum neural networks in gravitational waves data analysis

Maria-Catalina Isfan, Laurentiu-Ioan Caramete and Ana Caramete

In this work, we explore the possibility of using quantum computers provided for usage in cloud by big companies (such as IBM, IonQ, IQM Quantum Computers, etc.) to run our quantum neural network (QNN) developed for data analysis in the context of LISA Space Mission, developed with the Qiskit library in Python. Our previous work demonstrated that our QNN learns patterns in gravitational wave (GW) data much faster than a classical neural network, making it suitable for fast GW signal detection in future LISA data streams. Analyzing the fees from hardware providers like IBM Quantum, Amazon Braket and Microsoft Azure, we found that the fees for running the first segment of our QNN sum up to \$2000, \$60000, and \$1000000 respectively. Using free plans, we succeed to run the 3-qubit feature map of the QNN for one random data sample on {\fontfamily{qcr} \selectfont ibm\_kyoto} and {\fontfamily{qcr}\selectfont IQM Quantum Computers\_Garnet} quantum computers, obtaining a fidelity of 99%; we could also run the first prediction segment of our QNN on {\fontfamily{qcr} \selectfont ibm\_kyoto}, implemented for 4 qubits, and obtained a prediction accuracy of 20%. We queried providers such as IBM Quantum, Amazon Braket, Pasqal, and Munich Quantum Valley to obtain access to their plans, but, with the exception of Amazon Braket, our applications remain unanswered to this day. Other major setbacks in using the quantum computers we had access to included Qiskit library version issues (as in the cases of IBM Quantum and IQM Quantum Computers) and the frequent unavailability of the devices, as was the case with the Microsoft Azure provider. All the results presented in this paper were accumulated in 2024.
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High Energy Astrophysical Phenomena

X-ray Analysis and Photon-transport Simulations of SMC X-1: A Warped-disc Origin of the Superorbital Modulation

Satoshi Takashima, Hirokazu Odaka, Ryota Tomaru et al. (+3 more)

The luminous accreting pulsar SMC X-1 is an appropriate target to explore the accretion dynamics. SMC X-1 shows unique quasi-periodic flux variability of 40-65$\,$days known as superorbital modulation. To constrain the accretion structure of SMC X-1 based on timing and spectral study, we have analysed X-ray data of SMC X-1 observed by Suzaku and NuSTAR at various epochs between 2011 and 2022. The spectral analysis shows that the hydrogen column density ($N_\mathrm{H}$) increases from $1.1 \times 10^{22}\,\mathrm{cm^{-2}}$ to $1.24 \times 10^{23}\,\mathrm{cm^{-2}}$ as the flux decreases with the superorbital modulation. The neutral iron K$\alpha$ line at 6.4$\,$keV has a broad width of 0.3$\,$keV, and its equivalent width increases as toward superorbital low states. The line broadening is consistent with Keplerian motion at the inner disc rather than the stellar wind velocity of the donor star. These findings support that the superorbital modulation is a consequence of X-ray attenuation by the warped accretion disc. To test this interpretation, we have conducted photon transport simulations of a system consisting of a neutron star, a warped disc, and optically-thin disc atmosphere. Occultation of the central source by the disc successfully reproduces the observed variations in the equivalent width of neutral iron K$\alpha$ line, pulse profiles, and flux in hard X-rays. Notably, a disc precession angle of approximately $30^\circ$ can account for the observational features. For the radiation pattern of the photon source, the preferred beam width corresponds to a standard deviation of $30^\circ$.
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All authors Satoshi Takashima, Hirokazu Odaka, Ryota Tomaru, Atsushi Tanimoto, Aya Bamba, Toru Tamagawa

Instrumentation and Methods for Astrophysics

Optimising gravitational-wave sky maps for pulsar timing arrays

Kathrin Grunthal, David J. Champion, Eric Thrane et al. (+3 more)

Pulsar timing arrays (PTAs) have recently reported compelling evidence for the presence of a gravitational-wave background signal. Mapping the gravitational-wave background is key to understanding how it is formed, since anisotropy is a tracer for, for example, a supermassive black hole binary origin. In this work we refine the frequentist regularised gravitational-wave mapping analysis developed in our previous work (as part of the MeerKAT PTA 4.5-year data release). We derive a point-spread function describing the angular resolution of a PTA. We investigate how the point spread function changes for different PTA constellations and determine the best possible angular resolution achievable within our framework. Using simulated data, we demonstrate that previous methods do not capture the actual resolution - especially in regions of the sky with a high density of pulsars. We propose an improved scheme that accounts for a variable local resolution and test it using realistic simulations of the latest MeerKAT dataset. We demonstrate that we are able to identify a continuous gravitational wave signal in a region with good pulsar sky coverage with approximately a factor of two increase in significance compared to our previous method.
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All authors Kathrin Grunthal, David J. Champion, Eric Thrane, Rowina S. Nathan, Michael Kramer, Matthew T. Miles

High Energy Astrophysical Phenomena

Rotational enhancement and stability of protoquark stars during thermal evolution

Adamu Issifu, Andreas Konstantinou, Prashant Thakur et al. (+1 more)

We present the first systematic study of rigidly rotating protoquark stars based on isentropic equations of state (EOS) within the density-dependent quark mass (DDQM) framework. Using a quasi-static equilibrium approach, we follow the Kelvin–Helmholtz evolution from hot, lepton-rich matter to a cold, catalyzed quark star (QS). Rotation substantially enhances the maximum stable mass (by up to $\sim 40\%$), equatorial radius, and key rotational observables, with the ratio of rotational kinetic to gravitational potential energy, $T_{\rm kin}/|W|$, reaching $0.18$–$0.19$ near the Keplerian limit, indicating a heightened susceptibility to gravitational-wave–emitting instabilities. Thermal evolution introduces a clear ordering: all stellar properties peak during the lepton-rich stages and decrease monotonically as the star cools. Compared to hadronic stars, rotating proto-QSs exhibit larger radii, higher moments of inertia, and stronger quadrupolar deformation, producing a distinct signature in the mass–radius–spin plane. The EOS parameters are constrained using current astrophysical observations, including mass–radius measurements from HESS~J1731–347 and PSR~J0030+0451, the high-mass constraint from PSR~J0740+6620, and mass-radius constraints inferred from GW170817. The results demonstrate that future multimessenger observations must account for both thermal history and rotation to identify quark matter (QM) in compact stars robustly.
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All authors Adamu Issifu, Andreas Konstantinou, Prashant Thakur, Tobias Frederico

High Energy Astrophysical Phenomena

Secular Evolution of PSR J2021+4026: Long-Term {\gamma}-Ray Flux and Spin-Down Variability Beyond State Transitions

Xue-Zhi Liu, Ming-Yu Ge, Xiao-Ping Zheng et al. (+7 more)

PSR J2021+4026 is a remarkable $\gamma$-ray pulsar exhibiting repeated transitions between high $\gamma$-ray flux (HGF) and low $\gamma$-ray flux (LGF) states. With 17-yr Fermi-LAT monitoring, we reveal persistent secular evolution and enhanced spin-down rate variability within individual emission states – beneath the quasi-periodic state transitions. After removing discrete jumps, the jump-corrected flux $\delta F_\gamma$ shows a three-phase evolution: rise ($+2.02^{+0.17}_{-0.15}\%~\mathrm{yr}^{-1}$), decline ($-3.72^{+0.34}_{-0.47}\%~\mathrm{yr}^{-1}$), and rapid rise ($+14.9^{+6.4}_{-4.4}\%~\mathrm{yr}^{-1}$), with all rates quoted relative to the long-term mean flux $\langle F_\gamma \rangle=7.8\times 10^{-10}\,\mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}$. Moreover, the flux of the LGF state is gradually approaching the stable HGF level at a rate of $+0.72 \pm 0.11\%~\mathrm{yr}^{-1}$. These results demonstrate that secular flux evolution in PSR J2021+4026 operates largely independently of discrete state transitions, yet jointly with them drives the system toward a stable high-flux equilibrium.
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All authors Xue-Zhi Liu, Ming-Yu Ge, Xiao-Ping Zheng, Xiao-Bo Li, Han-Long Peng, Wen-Tao Ye, Bo-Yan Chen, Shi-Jie Zheng, Fang-Jun Lu, Shuang-Nan Zhang

Earth and Planetary Astrophysics

Primitive asteroids in the main belt, Cybele, and Hilda populations from Gaia DR3

Noemie El-Bez-Sebastien, Sonia Fornasier, Antoine Seurat et al. (+1 more)

Primitive asteroids include C-, P-, and D-classes, known to be dark and having spectra mostly featureless. They differ in the spectral slope, which ranges from moderate values for C-types, and progressively increases in P- and D-types, the latter being the reddest. While C- and P-types are commonly observed in the asteroid main belt, D-types are commonly found further from the Sun, in the Cybele, Hilda, and Jupiter Trojans regions, and very few are reported in the main belt. This study aims at characterizing the abundance of primordial and red asteroids, belonging to the P-, D-, and Z-classes in the Mahlke et al. (2022) taxonomy, in the 2-5.2 AU region using the third data release by the Gaia mission spectral catalog, which includes more than 60000 spectrophotometric data of asteroids. We have applied the following methodology to identify primordial asteroids in the catalog: 1) selection of objects with signal to noise ratio greater than 20; 2) albedo value less than 12%; 3) chi-squared fit to automatically identify potential D-, Z-, and P-types using Bus-DeMeo and Mahlke taxonomy; 4) visual inspection of every spectrum to confirm the taxonomic classification. Referring to Mahlke taxonomy, we have found 318 new D-types across the main belt, as well as 124 Z-types, and is in agreement with theoretical estimations. We computed the spectral slope in the visible range (0.55 - 0.81 \mu m). We also have identified 265 P-types in the main belt. For the Cybele and Hilda asteroids, we characterize the taxonomic class of all the bodies with SNR higher than 20 in the Gaia catalog, for a total sample of 193 and 180 asteroids, respectively.
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All authors Noemie El-Bez-Sebastien, Sonia Fornasier, Antoine Seurat, Antonin Wargnier

Cosmology and Nongalactic Astrophysics

Frequency shift and viewing direction variations in gravitational lensing

Mikołaj Korzyński and Mateusz Kulejewski

In a gravitational lensing system, the relative transverse velocities of the lens, source, and observer induce a frequency shift in the observed radiation. While this shift is typically negligible in most astrophysical contexts, strategies for its detection have been proposed for both electromagnetic and gravitational waves. This paper provides a rigorous theoretical treatment of the effect, deriving general expressions for the frequency shift within a lensing system embedded in a cosmological spacetime. Our formulation remains valid for arbitrary distances and velocities, including highly relativistic regimes, under any Friedmann-Lemaître-Robertson-Walker metric. Expanding upon previous papers on moving lenses, we provide a detailed analysis of frequency effects induced by lenses moving at relativistic speeds. Furthermore, we extend standard lensing theory by deriving an exact formula for the variation in the source's viewing direction. This result is of interest for strongly anisotropic emitters, such as compact binary systems emitting gravitational waves. Finally, we quantify the apparent misalignment between the lens and the source's two images produced by time-delay effects in lens systems moving with high velocity.
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Instrumentation and Methods for Astrophysics

Prospecting MeerKAT Continuum Data for Enigmatic Radio Sources with Unsupervised Vector-Quantised Variational Autoencoders

Fernando L. Ventura, Kshitij Thorat, Anna Bosman et al. (+2 more)

We present a novel application of Vector quantised variational autoencoders (VQ-VAEs) as an unsupervised tool to probe deep 1.28 GHz radio continuum images taken from the MeerKAT Galaxy Cluster Legacy Survey (MGCLS) and compare their performance to other machine learning methods. We examine the effectiveness of VQ-VAEs in identifying radio continuum sources with anomalous structures in the image-plane domain. We compare performance to a supervised training set and other published anomaly detection methods, focusing especially on simple autoencoders (AE), Memory Unit Autoencoders (MUAE) and a human-in-the-loop software Astronomaly based on bootstrap your own latent (BYOL). Our investigations show that VQ-VAE perform better than simple AEs, are not as accurate as MUAE but are much faster and are also faster and comparable to Astronomaly while not requiring labelled data. We observe that they are able to remove a majority of the typical sources in such data, even when trained in an unsupervised manner on unlabelled data. We also provide our testing set of a large sample of manually labelled radio sources, in particular radio galaxies, taken from the MGCLS at 1.28 GHz. We find VQ-VAEs to be potentially useful as part of automated approaches towards searching through high volumes of data which are key in extracting the full scientific potential of the Square Kilometre Array and its pathfinders.
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All authors Fernando L. Ventura, Kshitij Thorat, Anna Bosman, Roger Deane, Christopher Cleghorn

Astrophysics of Galaxies

Boxy/Peanut Bulges: Comparative Analysis of EGIPS Galaxies and TNG50 Models

Anton Smirnov, Alexander Marchuk, Viktor Zozulia et al. (+2 more)

We investigated the properties of boxy/peanut-shaped (B/PS) bulges in a sample of 71 galaxies from the Edge-on Galaxies in the Pan-STARRS Survey (EGIPS) and 20 simulated galaxies from Illustris TNG50 using multicomponent photometric decomposition. For each real and simulated galaxy, we obtained a suitable photometric model in which the B/PS bulge was represented by a dedicated 2D photometric function. For real galaxies, we found that more flattened X-structures are generally residing in larger B/PS bulges. When tested against the galaxy masses, we verified that both larger bulges and more flattened X-structures are typically found in more massive galaxies. Since large bars are also known to reside in more massive galaxies, we conclude that the flatness of X-structures in larger B/PS bulges has a physical origin, rather than being solely a result of projection effects due to differences in observed bar viewing angles. When comparing the properties of B/PS bulges between EGIPS galaxies and TNG50 galaxies, with bars rotated for different viewing angles, we found that B/PS bulges in TNG50 are considerably smaller and less luminous in terms of total intensity. This is consistent with previous studies of bar properties in TNG50, indicating the B/PS bulges in TNG50 differ from those in real galaxies, as do their parent bars.
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All authors Anton Smirnov, Alexander Marchuk, Viktor Zozulia, Natalia Sotnikova, Sergey Savchenko

Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph

Quasi-linear approach of bi-Kappa distributed electrons with dynamic $\kappa$ parameter. EMEC instability

Pablo S Moya, Roberto E Navarro, Marian Lazar et al. (+3 more)

In recent years, significant progress has been made in the velocity-moment-based quasi-linear (QL) theory of waves and instabilities in plasmas with nonequilibrium velocity distributions (VDs) of the Kappa (or $\kappa$) type. However, the temporal variation of the parameter $\kappa$, which quantifies the presence of suprathermal particles, is not fully captured by such a QL analysis, and typically $\kappa$ remains constant during plasma dynamics. We propose a new QL modeling that goes beyond the limits of a previous approach, realistically assuming that the quasithermal core cannot evolve independently of energetic suprathermals. The case study is done on the electron-cyclotron (EMEC) instability generated by anisotropic bi-Kappa electrons with $A=T_\perp/T_\parallel > 1$ ($\parallel, \perp$ denoting directions with respect to the background magnetic field). The parameter $\kappa$ self-consistently varies through the QL equation of kurtosis (fourth-order moment) coupled with temporal variations of the temperature components, relaxing the constraint on the independence of the low-energy (core) electrons and suprathermal high-energy tails of VDs. The results refine and extend previous approaches. A clear distinction is made between regimes that lead to a decrease or an increase in the $\kappa$ parameter with saturation of the instability. What predominates is a decrease in $\kappa$, i.e., an excess of suprathermalization, which energizes suprathermal electrons due to self-generated wave fluctuations. Additionally, we found that VDs can evolve toward a quasi-Maxwellian shape (as $\kappa$ increases) primarily in regimes with low beta and initial kappa values greater than five. Instability-driven relaxation only partially resolves temperature anisotropy in bi-Kappa electron VDs, as wave fluctuations generally act to further energize suprathermal electrons.
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All authors Pablo S Moya, Roberto E Navarro, Marian Lazar, Peter H Yoon, Rodrigo A López, Stefaan Poedts

Astrophysics of Galaxies

The Characteristic Mass and Energy Conversion Efficiency in the Cusp-Core Transition of Dark Matter Haloes: Implications for Scaling Relations and Supernova feedbacks

Michi Shinozaki, Masao Mori, Yuka Kaneda et al. (+1 more)

Galaxies in the nearby Universe, particularly dwarf systems, exhibit inner mass profiles of dark matter haloes that systematically depart from canonical cold dark matter expectations, signalling an interplay between baryonic feedback and the collisionless halo. We update an analytical cusp-core transition model by incorporating the effect of supernova-driven mass loss. Adapting this model to SPARC galaxies, we measure the energy conversion efficiency epsilon, defined as the fraction of supernova feedback energy that is used to change the central dark-matter potential. We find epsilon ~ 0.01 for nearby SPARC galaxies. Building on these measurements, we compare the dynamical energy required for a cusp-core transformation with the feedback energy available over burst cycles and identify a cusp-core transition forbidden region on the halo-stellar mass plane where transformation cannot occur. Galaxies with halo masses from 10^8 to 10^11 M_sun lie outside the forbidden region, whereas ultra-faint dwarf galaxies < 10^8 M_sun, galaxy groups and clusters > 10^11 M_sun fall within it, consistent with their high central densities and the inefficiency of core formation at very low and very high masses. This approach also explains the observed diversity of inner density profiles in low-mass systems, showing that both the star formation rate and the energy conversion efficiency govern them, with the latter emerging as a key parameter setting the strength of the cusp-core transition. Beyond the cusp-core problem, our observationally inferred energy conversion efficiency provides a model independent benchmark that strongly constrains galaxy formation models.
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All authors Michi Shinozaki, Masao Mori, Yuka Kaneda, Kohei Hayashi

Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

RNLE: Residual neural likelihood estimation and its application to gravitational-wave astronomy

Mattia Emma and Gregory Ashton

Simulation-based inference provides a powerful framework for Bayesian inference when the likelihood is analytically intractable or computationally prohibitive. By leveraging machine-learning techniques and neural density estimators, it enables flexible likelihood or posterior modeling directly from simulations. We introduce Residual Neural Likelihood Estimation (RNLE), a modification of Neural Likelihood Estimation (NLE) that learns the likelihood of non-Gaussian noise in gravitational-wave detector data. Exploiting the additive structure of the signal and noise generation processes, RNLE directly models the noise distribution, substantially reducing the number of simulations required for accurate parameter estimation and improving robustness to realistic noise artifacts. The performance of RNLE is demonstrated using a toy model, simulated gravitational-wave signals, and real detector noise from ground based interferometers. Even in the presence of loud non-Gaussian transients, glitches, we show that RNLE can achieve reliable parameter recovery when trained on appropriately constructed datasets. We further assess the stability of the method by quantifying the variability introduced by retraining the conditional density estimator on statistically identical datasets with different optimization seeds, referred to as training noise. This variability can be mitigated through an ensemble approach that combines multiple RNLE models using evidence-based weighting. An implementation of RNLE is publicly available in the sbilby package, enabling its deployment within gravitational-wave astronomy and a broad range of scientific applications requiring flexible, simulation-based likelihood estimation.
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Solar and Stellar Astrophysics

Follow-up of three exocomet-host candidates

P. Muñoz-Cutanda, I. Rebollido, B. Montesinos et al. (+3 more)

Exocomets are small bodies that evaporate when they approach their host star. They are detected through variability of non-photospheric features with spectroscopy and/or asymmetric transits in time-series photometry. In the past four decades ~30 systems have shown such variations, and were therefore classified as exocomet host stars. However, some publications have pointed out mechanisms that might mimic exocometary features, and therefore, careful monitoring is needed to confirm the origin of the observed variability. With this paper we aim to investigate the exocomet nature of the non-photospheric variable features observed in the exocomet candidate stars HD 36546, HD 42111 and HD 85905. All of them have shown some degree of variability, particularly in their Ca II K line. We analysed the non-photospheric Ca II K line features from high-resolution spectra obtained using new NOT/FIES and Mercator/HERMES, and some additional archival spectra of the target stars. The variability was quantified through the changes in the equivalent widths of those features, which are assumed to be of circumstellar origin. Column densities were also estimated for each variable feature. Strong variability was found for HD 85905, consistent with a potential link to exocometary activity. However, the binarity of the system, which we confirmed through interferometric VLTI/PIONIER observations, complicates the interpretation of these signatures and prevents us from drawing definitive conclusions. The remaining two sources do not show any significant variability, but due to the sporadic nature of the exocometary events, we cannot discard the exocomet hypothesis. Further monitoring of the stars will be necessary to carry out a robust determination of the variability patterns and timescales that would completely rule out other scenarios.
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All authors P. Muñoz-Cutanda, I. Rebollido, B. Montesinos, P. Cruz, O. Absil, S. Ertel

Cosmology and Nongalactic Astrophysics

Examination of frequency and scale dependence of CMB hemispherical power asymmetry

Sanjeev Sanyal, Pavan Kumar Aluri and Arman Shafieloo

In this study, we revisit the well-known cosmic microwave background (CMB) anomaly referred to as Hemispherical Power Asymmetry (HPA), using CMB temperature maps from the Planck mission public release 4 (PR4) and the WMAP nine-year data release. Employing the Local Variance Estimator (LVE) method, we systematically reexamine the properties of HPA to investigate possible frequency dependence as well as scale dependence in its amplitude and direction. We model the HPA as a scale-dependent dipole modulation following a power-law form, rather than assuming a scale-invariant case. Our analysis incorporates seven cleaned frequency-specific CMB temperature maps from both the Planck and WMAP missions to test the robustness of the observed asymmetry across instruments and frequency channels. We find that the dipolar modulation characteristic of HPA is present in all cases examined, with consistent estimates of the preferred direction and scale-dependent variation in dipole amplitudes. These results support the conclusion that the observed asymmetry is unlikely to arise from instrumental artifacts or data-processing effects, and instead points toward a persistent large-scale feature of the CMB sky with a possible cosmological origin.
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Cosmology and Nongalactic Astrophysics

Tracing Cosmological Signature with Doppler Lensing: Insights from Cosmological Simulations

Mubtasim Fuad, Sonia Akter Ema and Md Rasel Hossen

Doppler lensing, a relativistic effect resulting from the peculiar velocities of galaxies along the line of sight, provides insight into the large-scale structure of the Universe. Relativistic simulations are essential for modeling Doppler lensing because they incorporate gravity and motion in spacetime. We compare two relativistic $N$-body simulation frameworks, $\texttt{GEVOLUTION}$ and $\texttt{SCREENING}$, to calculate Doppler lensing convergence in cosmic voids of different sizes and halos of different masses. Our analysis reveals scale-dependent performance: $\texttt{SCREENING}$ shows larger differences in small voids (radius range: 15–25 Mpc/h) with a mean absolute relative difference of 38.5%, due to linearized dynamics failing in nonlinear regimes. Medium voids (25–35 Mpc/h) show better agreement (9.5% mean difference). For large voids (35–45 Mpc/h), $\texttt{SCREENING}$ exhibits intermediate differences (16.9% mean difference) with central instabilities. Moreover, our Doppler convergence analysis with massive halos ($10^{11.5}$–$10^{14} {~h^{-1}\mathrm{M}_\odot}$) demonstrates excellent consistency (1.6–3.6% mean difference). These findings provide clear guidance for simulation choice: $\texttt{GEVOLUTION}$ is recommended for precision studies critical to $\Lambda$CDM or modified gravity tests, while $\texttt{SCREENING}$ offers a computationally efficient alternative for relativistic treatments with large catalogs of voids and halos, assisting future astrophysical surveys.
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Cosmology and Nongalactic Astrophysics

Still Accelerating: Type Ia supernova cosmology is robust to host galaxy age evolution

Phil Wiseman, Brodie Popovic, Mark Sullivan et al. (+14 more)

Type Ia supernovae are a cornerstone of modern cosmology, providing first evidence for cosmic acceleration and new tests of dark energy. Son et al. 2025 (S25) claim a strong redshift evolution in standardized supernova luminosities driven by supernova progenitor age, with dramatic cosmological implications: rapidly evolving dark energy, decelerating expansion, and a $9\sigma$ tension with $\Lambda$CDM. We show that the underpinning evidence required for this conclusion – the supernova progenitor-age dependence, the redshift-dependent age difference, and their combined impact – is either negligible or relies on effects already corrected for in modern supernova analyses. First, the S25 analysis omits the standard host-galaxy stellar mass correction that captures known environmental dependencies that also correlate with stellar age. Applying this correction to the S25 sample, we find no dependence of standardized supernova brightness on host age. Independent data also show no significant difference at low-redshift in standardized brightness between star-forming galaxies and several Gyr older quiescent galaxies of the same stellar mass. Second, the S25 scenario predicts strong redshift evolution of the host-mass effect. Data from the Dark Energy Survey supernova survey measure evolution of $-0.028 \pm 0.034~\mathrm{mag}\,z^{-1}$, consistent with zero and altering the dark-energy equation-of-state measurement ($w$) by $<$0.01 if included. Third, we demonstrate that the claimed $\sim5$~Gyr progenitor age difference between nearby and distant supernovae is overstated by factors of three to five largely due to a conflation of host galaxy age with supernova progenitor age. We conclude that type~Ia supernova cosmology remains robust for current measurements of dark energy.
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All authors Phil Wiseman, Brodie Popovic, Mark Sullivan, Adam G. Riess, Dan Scolnic, Rebecca C. Chen, Tamara M. Davis, Lluís Galbany, Isobel M. Hook, Saurabh W. Jha, Lisa Kelsey, Yukei S. Murakami, Mickaël Rigault, Benjamin M. Rose, Brian Schmidt, Mat Smith, Maria Vincenzi

Astrophysics of Galaxies

SIRIUS: Dark matter cusp evolution in dense dwarf galaxies

Katsuhiro Kaneko, Takayuki R. Saitoh, Yutaka Hirai et al. (+1 more)

Dwarf galaxies have a wide variety of structures, such as dark matter (DM) distribution, stellar-to-halo mass ratio, and stellar density. Recent high-resolution simulations have shown a variety of stellar-to-halo mass ratios for dwarf galaxies with a DM halo mass of $\sim 10^9 M_{\odot}$ at $z=0$. In this study, we performed cosmological $N$-body/smoothed-particle hydrodynamic zoom-in simulations of dwarf galaxies with the highest gas and DM particle mass resolutions of 2.37 $M_{\odot}$ and 12.8 $M_{\odot}$, respectively. The stellar-to-DM halo mass ratio of one of our simulated dwarf galaxies was $\sim 10^{-4}$, typical for satellites of the Milky Way. The stellar mass ($10^5 M_{\odot}$) and half-mass radius (68 pc) were also similar to those of the satellites of the Milky Way. The power-law slope of the DM halo was $\alpha = -1.1$. On the other hand, the other simulated galaxy exhibited a stellar-to-halo mass ratio of $\sim 10^{-3}$ and a steeper power-law slope ($\alpha=-1.9$) than the other; the presence of baryonic matter deepened the cusp. The mass of $>10^6 M_{\odot}$ and a half-mass radius of $\sim 36$ pc of this galaxy were similar to those of ultra-compact dwarf galaxies rather than the satellites of the Milky Way. This DM halo grew in mass earlier than the former one, and the central DM density was higher than that of the other even in the DM-only simulations.
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All authors Katsuhiro Kaneko, Takayuki R. Saitoh, Yutaka Hirai, Michiko S. Fujii

Astrophysics of Galaxies

A jet-gas interaction beyond the host galaxy: detection of a neutral hydrogen outflow at cosmic noon

Renzhi Su, Stephen J. Curran, James R. Allison et al. (+6 more)

We present upgraded Giant Metrewave Radio Telescope (uGMRT) observations of 0731+438, an \mbox{FR II} radio galaxy at a redshift of 2.429 with two lobes separated by 82 kpc. A blueshifted, faint and broad \mbox{Hi} 21 cm absorption line with velocity full width at half maximum (FWHM) $\sim 600\,\rm km\,s^{-1}$ is detected against the southern radio lobe that is 47 kpc from radio core, indicating a neutral hydrogen outflow associated with jet-gas interaction beyond the host galaxy. The outflow has a mass outflow rate of $\sim\,0.4T_{\rm s}\Omega\rm\, M_\odot\,{\rm yr}^{-1}$, which could increase to $\sim\,4.0T_{\rm s}\Omega\rm\,M_\odot\,{\rm yr}^{-1}$, corresponding to an energy outflow rate of $2.4T_{\rm s}\Omega\times10^{40}$ – $1.5T_{\rm s}\Omega\times10^{41}\,\rm erg\,s^{-1}$, where $T_{\rm s}$ is the spin temperature and $\Omega$ is the solid angle of the outflow. Previous optical observations identified an extended emission line region aligned with the radio axis, ionized by the central Active Galactic Nucleus (AGN). Within this region, a warm and ionized outflow with a mass outflow rate of $\sim\,50\rm\, M_\odot\,{\rm yr}^{-1}$ and an energy outflow rate of $\sim1.7\times10^{43}\,\rm erg\,s^{-1}$ was detected. We propose that both the extended emission line region and the optical outflow are results of synergistic effect between jet and AGN radiation. The AGN likely exerts negative feedback on the host galaxy, as evidenced by the gas expulsion by the jet and the high velocity dispersion of ionized gas observed optically. So far, detections of jet-driven neutral hydrogen outflows remain rare. The high redshift, large outflow radii, substantial mass outflow rate and energy outflow rate of the neutral hydrogen outflow in 0731+438 expand the known parameter space of such outflows.
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All authors Renzhi Su, Stephen J. Curran, James R. Allison, Marcin Słowacki, Minfeng Gu, Vanessa Moss, Yongjun Chen, Zhongzu Wu, Zheng Zheng

High Energy Astrophysical Phenomena

XPE and VLT /FORS2 polarimetry challenge the Seyfert-1.9 classification of MCG-05-23-16

Frédéric Marin, Daniele Tagliacozzo, Francesco Ursini et al. (+21 more)

We report the third observation of the Seyfert-1.9 active galactic nucleus (AGN) MCG-05-23-16 with the Imaging X-ray Polarimetry Explorer (IXPE), together with optical spectro-polarimetry obtained at the Very Large Telescope (VLT), and combined with archival near-ultraviolet, optical and near-infrared polarimetric data. No X-ray polarization was detected in the 2-8 keV band, with a 99% confidence upper limit of $\leq$2.9%, further reduced to $\leq$2.5% when combined with the two past IXPE observations of the same target. Monte Carlo simulations suggest that equatorial coronal models are disfavored if the AGN is indeed a type-1.9/2 AGN, but coronae coplanar to the accretion disk remain consistent if the source is less inclined than previously assumed. VLT/FORS2 data reveal a typical type-2 spectrum in total flux, a broad H$\alpha$ line in polarized flux, and strongly wavelength dependent polarization degree and angle, rotating by nearly 70$^\circ$ across the optical band. Comparison with historical measurements confirms long-term stability of the polarization spectrum and a $\sim$90$^\circ$ rotation in the near-ultraviolet. Interpreting the multi-wavelength polarization relative to the AGN ionization axis indicates that the main obscurer is not a compact circumnuclear torus, but a distant kpc-scale dust lane crossing the galaxy. This result implies that MCG-05-23-16 is in fact a type-1 AGN seen through foreground dust. The low X-ray column density becomes consistent with the absence of polarization, provided that the nuclear inclination is low.
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All authors Frédéric Marin, Daniele Tagliacozzo, Francesco Ursini, Damien Hutsemékers, Mitsuru Kokubo, Thibault Barnouin, Andrea Gnarini, Alessandro Leonardo Lai, Jirí Svoboda, Stefano Bianchi, Vittoria Elvezia Gianolli, Ephraim Gau, Kun Hu, Henric Krawczynski, W. Peter Maksym, Andrea Marinucci, Herman Marshall, Giorgio Matt, Riccardo Middei, Pierre-Olivier Petrucci, Simonetta Puccetti, Nicole Rodriguez, Roberto Serafinelli, Francesco Tombesi

Solar and Stellar Astrophysics

Three-dimensional properties of a coronal shock and the longitudinal distribution of its related solar energetic particles

Yue Zhou, Li Feng, Guanglu Shi et al. (+6 more)

This study aims to investigate the relationship between the spatial-temporal evolution of shock properties and the longitudinal dependence of SEP intensities and spectra. The shock parameters, including the normal speed, oblique angles, compression ratio, and Alfven Mach number, were derived by combining a steady-state solar-wind simulation with the three-dimensional (3D) reconstruction of the shock surface based on multi-view observations. We compared the local shock parameters at the magnetic connecting points with in situ proton intensities and peak spectra to establish the link between shock evolution and SEP characteristics. The shock nose consistently exhibited higher particle-acceleration efficiency with the largest normal speed, compression ratio, and supercritical Alfven Mach number, while the flanks showed delayed transition to supercritical Alfven Mach number with weaker efficiency. The earliest and most rapid proton enhancement of STEREO-B correlated with efficient shock acceleration and prompt magnetic connectivity to the shock. Spectral analysis revealed that proton energy spectra were consistent with the relativistic diffusive shock acceleration (DSA) estimations. The initial shock acceleration began at about 1.4-5 Rsun and caused the widespread longitudinal SEP distribution. The longitudinal dependence of SEP intensity and spectral variations arise from the combined influence of 3D shock properties, magnetic connectivity, and particle transport processes. The agreement between in situ proton indices and relativistic DSA estimations supports DSA in this SEP event and provides insights into the early-stage acceleration at the source region.
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All authors Yue Zhou, Li Feng, Guanglu Shi, Jingnan Guo, Liuguan Ding, Yi Yang, Jianchao Xue, Jun Chen, Weiqun Gan

Earth and Planetary Astrophysics

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) II. The radial structure of debris discs

Yinuo Han, Elias Mansell, Jeff Jennings et al. (+38 more)

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) was recently completed to cover the lack of high-resolution observations of debris discs and to investigate the prevalence of substructures such as radial gaps and rings in a sample of 24 discs. This study characterises the radial structure of debris discs in the ARKS programme. To identify and quantify the disc substructures, we modelled all discs with a range of non-parametric and parametric approaches. We find that of the 24 discs in the sample, 5 host multiple rings, 7 are single rings that display halos or additional low-amplitude rings, and 12 are single rings with at most tentative evidence of additional substructures. The fractional ring widths that we measured are significantly narrower than previously derived values, and they follow a distribution similar to the fractional widths of individual rings resolved in protoplanetary discs. However, there exists a population of rings in debris discs that are significantly wider than those in protoplanetary discs. We also find that discs with steep inner edges consistent with planet sculpting tend to be found at smaller (<100 au) radii, while more radially extended discs tend to have shallower edges more consistent with collisional evolution. An overwhelming majority of discs have radial profiles well-described by either a double power law or double-Gaussian parametrisation. While our findings suggest that it may be possible for some debris discs to inherit their structures directly from protoplanetary discs, there exists a sizeable population of broad debris discs that cannot be explained in this way. Assuming that the distribution of millimetre dust reflects the distribution of planetesimals, mechanisms that cause rings in protoplanetary discs to migrate or debris discs to broaden soon after formation may be at play, possibly mediated by planetary migration or scattering.
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All authors Yinuo Han, Elias Mansell, Jeff Jennings, Sebastian Marino, A. Meredith Hughes, Brianna Zawadzki, Anna Fehr, Jamar Kittling, Catherine Hou, Aliya Nurmohamed, Junu Lee, Allan Cheruiyot, Yamani Mpofu, Mark Booth, Richard Booth, Myriam Bonduelle, Aoife Brennan, Carlos del Burgo, John M. Carpenter, Gianni Cataldi, Eugene Chiang, Steve Ertel, Thomas Henning, Marija R. Jankovic, Ágnes Kóspál, Alexander V. Krivov, Joshua B. Lovell, Patricia Luppe, Meredith A. MacGregor, Sorcha Mac Manamon, Jonathan P. Marshall, Luca Matrà, Julien Milli, Attila Moór, Johan Olofsson, Tim Pearce, Sebastián Pérez, Antranik A. Sefilian, Philipp Weber, David J. Wilner, Mark C. Wyatt

Astrophysics of Galaxies

Possible time-variable iron-K$\alpha$ emission in the circumnuclear region of the Circinus galaxy

Aiko Miyamoto, Taiki Kawamuro, Hirokazu Odaka et al. (+2 more)

We present imaging and spatially resolved spectral analyses of eight Chandra data taken for the Circinus galaxy in $\approx$ 22 years to reveal neutral iron-K$\alpha$ emission on a circumnuclear scale ($\sim$ 10–100 pc) and search for time variability in the emission. By simulating and taking account of point-source emission from the active galactic nucleus (AGN), we detect iron-line emission $\sim$ 20–60 pc away from the nucleus, particularly in the eastern and western regions. In the two regions, possible time variability in the line flux was also detected. Our spectral analysis then finds that the observed equivalent widths can reach $\sim$ 2 keV and the slopes of underlying continua are rather inverted with $\Gamma < 0$. These are consistent with a scenario in which the iron emission originates from clouds illuminated by AGN X-rays; our result could provide the first extragalactic example of AGN X-ray echoes. In this scenario, we estimated the physical sizes of the illuminated clouds based on the timescale of variability to be less than 6 pc. Furthermore, we compared the iron emission distribution with the cold molecular distribution inferred by Atacama Large Millimeter/submillimeter Array (ALMA) observation of CO($J$=3–2), revealing that in the region of bright iron-line emission, the molecular emission seems to be weak. This might suggest that the AGN X-ray emission affects the chemical composition in the form of AGN feedback.
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All authors Aiko Miyamoto, Taiki Kawamuro, Hirokazu Odaka, Takuma Izumi, Hironori Matsumoto

Solar and Stellar Astrophysics

HD 26172: an active solar-type subgiant in a close binary system

Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian et al. (+5 more)

We present the first comprehensive photometric and spectroscopic analysis of the RS CVn system HD 26172, robustly determining the previously debated evolutionary state of its primary star. Since this system is a single-lined spectroscopic binary with spot-induced light curve modulations, we derived its physical parameters by combining the TESS light curves, the radial velocity curve from our observations, and the primary-star mass estimates based on three complementary methods.Our results reveal that HD 26172 is a detached binary system composed of a $1.25 \pm 0.32 M_{\odot}$ subgiant and a $0.63 \pm 0.11 M_{\odot}$ main-sequence star. The conclusion of subgiant primary is also supported by the absence of lithium absorption and no observed infrared excess. Using long-term photometry from the KWS survey, we detected a tentative stellar activity cycle of 5635 days with an amplitude of 0.04 mag in HD 26172. Additionally, we identified ten optical flare events exhibiting temporally clustered outburst behavior. The presence of a long-term activity cycle, pronounced starspot activity, and frequent optical flares makes HD 26172 a valuable laboratory for studying magnetic activity in subgiants within close binary systems.
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All authors Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian, Nian-Ping Liu, Jia Zhang, David Mkrtichian, Soonthornthum Boonrucksar, Er-Gang Zha

Cosmology and Nongalactic Astrophysics

Joint constraints on cosmic birefringence and early dark energy from ACT, Planck, DESI, and PantheonPlus

Lu Yin, Guo-Hong Du, Tian-Nuo Li et al. (+1 more)

With the increasing number of high-precision astronomical observations, physical quantities that were previously inaccessible to accurate calculations, such as cosmic birefringence, have once again become a focal point of interest. Such phenomena induce a nonvanishing cross-correlation between the $E$- and $B$-mode polarizations of the cosmic microwave background (CMB), thereby providing a direct observational signature of parity violation. The Chern-Simons coupling between the scalar field in early dark energy (EDE) models and CMB photons is regarded as a plausible mechanism for generating cosmic birefringence. Recent data from the Atacama Cosmology Telescope (ACT) deliver $EB$ measurements at higher multipole moments than those previously achieved by {Planck}, while DESI and PantheonPlus datasets provide new and stringent constraints on the late-time expansion history. Using a joint analysis of {Planck}, DESI DR1, Pantheon+, and ACT data, we perform a full-parameter constraint on the cosmic birefringence effects induced by the EDE-CMB photon coupling. Our results favor a higher Hubble constant, $H_0 = 76.9^{+2.9}_{-2.5}\,\rm km\,s^{-1}\,Mpc^{-1}$, and a relatively large EDE fraction, $f_{\mathrm{EDE}} = 0.232^{+0.074}_{-0.047}$. By comparing the cosmological evolution of this model across different data combinations, we find that the ACT-$EB$ data combined with {Planck} + DESI + PantheonPlus provide good constraints to both early- and late-Universe observations.
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All authors Lu Yin, Guo-Hong Du, Tian-Nuo Li, Xin Zhang

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Cosmological Budget of Entropy from Merging Black Holes

Siyuan Chen, Karan Jani and Thomas W. Kephart

Black holes contain more entropy than any other component of the observable universe. Gravitational-wave observations from LIGO and Virgo have shown evidence of a previously unknown black hole mass range, which provides new information to update the entropy budget. Increases in entropy due to binary black hole mergers, as implied in the second law of thermodynamics, should also be added to the budget. In this study, we update the cosmological entropy budget for black holes in the stellar to lite-intermediate-mass range $(5-300~M_\odot)$, originating from either supernovae or binary mergers, by utilizing a suite of population synthesis models and phenomenological fits derived from numerical relativity. We report three new insights: Firstly, the cumulative entropy from merging black holes surpasses the total entropy from cosmic microwave background photons around the onset of the Over-massive Black Hole Galaxy phase at $z\sim 12$, suggesting that mergers played a more significant role in shaping the thermodynamic state of the early universe than relic radiation. Secondly, if primordial black holes constitute a nonzero fraction of dark matter, their early binary mergers establish an “entropy floor" in the Dark Ages and can dominate the cumulative merger-generated entropy history even for small abundances. Thirdly, by computing the cosmological density parameters, we highlight the thermodynamic asymmetry in black hole mergers, where the production of gravitational-wave energy is inefficient compared to the immense generation of Bekenstein-Hawking entropy.
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Astrophysics of Galaxies

The Structure of an 80 pc Long Massive Filament

Qian-Ru He, Won-Ju Kim, Gary A. Fuller et al. (+11 more)

Using new Institut de Radioastronomie Millimétrique (IRAM) 30m telescope $\rm N_2H^+$, $\rm C^{18}O$ $J$=1-0 and Atacama Pathfinder Experiment (APEX) telescope $\rm ^{13}CO$ and $\rm C^{18}O$ $J$=2-1 maps together with archival far-infrared continuum data, and $\rm ^{12}CO$, and $\rm ^{13}CO$ $J$=1-0 data, we present a comprehensive analysis of the massive filament CFG024.00$+$0.48 (G24) across clump-to-cloud scales. Our results show that G24 is an $\sim$80 pc giant filament with a total mass of $\sim$$10^5$ M$_{\odot}$. In the different tracers the filament width is measured to be about $\sim$2 times the beam size of the observations, as expected for power-law density distributions, giving beam-deconvolved widths in the range from 0.8 to 2.8 pc. We determine a line-of-sight thickness of $\sim$2.2 pc demonstrating that G24 is not an edge-on, flatten structure. The virial parameter obtained from line mass ($\alpha_{\rm line,vir}=M_{\rm line,vir}/M_{\rm line}$) from the $\rm C^{18}O$ (1-0) data is 0.85, and that obtained from $Herschel$-based H$_2$ column density is 0.52, suggesting G24 is globally close to virial equilibrium. The distribution of the 40 dust clumps appears to have a ”two-tier” fragmentation pattern. For the clump groups, the separation, with a mean/median of 3.68/3.46 pc, is very close to expected length associated with the maximum fragmentation growth rate of $\lambda_{\rm max}=3.55 \pm0.32$ pc estimated for the dust. However, the longitudinal centroid velocity profiles of $\rm C^{18}O$ and $\rm N_2H^+$ show oscillation patterns with wavelengths of 9.8$\pm$0.1 pc and 9.9$\pm$0.1 pc, respectively. This is $\sim$2 times larger than the corresponding values of $\lambda_{\rm max}$ of 4.96$\pm$0.63 pc and 4.65$\pm$1.34 pc, respectively. This suggests that the velocity structure is not dominated by flows directly associated with the fragmentation seen in the dust emission.
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All authors Qian-Ru He, Won-Ju Kim, Gary A. Fuller, Alessio Traficante, Seamus D. Clarke, Yu Gao, Xue-Peng Chen, Min Fang, Ke Wang, En Chen, Tapas Baug, Xiao-Long Wang, Chen Wang, Yong-Xiong Wang

Instrumentation and Methods for Astrophysics

The R2Pub Telescopes for Surveying: An Overview and Performance Evaluation of the System

Xuan Song, Xiaofeng Wang, Jin Zhu et al. (+29 more)

The R2Pub telescope, built by the Beijing Planetarium, is a 60 cm equatorial binocular telescope located at the Daocheng site of Yunnan Observatories in China, at an altitude of about 4700 m. This paper presents an overview of the R2Pub telescope system, including its design, instrumentation, and survey capabilities, and reports an initial evaluation of its system performance. R2Pub is a prime-focus binocular system, with each optical tube covering a field of view of approximately 18 square degrees. It is designed to detect a wide range of transient and variable sources in the local universe, such as variable stars, eclipsing binaries, supernovae, gamma-ray burst afterglows, tidal disruption events, active galactic nuclei, and other unknown transients. The observatory infrastructure, including the dome, equatorial mount, optical tubes, and associated subsystems, has been fully constructed and installed, and the system has entered the commissioning phase. Benefiting from the high-altitude location, good seeing conditions, and dark sky background at the Daocheng site, performance tests during commissioning show that the R2Pub system can reach a 5-sigma limiting magnitude of about 18.7 mag in the Pan-STARRS r' band with a 60 s exposure. Ongoing observations with R2Pub are expected to contribute to studies of variable and transient phenomena and to enhance public outreach in astronomy. The binocular design enables simultaneous dual-band observations, providing instantaneous color information for transient sources and improving the classification and physical characterization of their properties and evolution.
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All authors Xuan Song, Xiaofeng Wang, Jin Zhu, Jian Li, Jincheng Guo, Danfeng Xiang, Xin Li, Cheng Liu, Yuanhang Ning, Zhishuai Ge, Zhenzhen Shao, Xiaochen Zheng, Yi Yang, Lei Zhang, Yaqing Shi, Dongyao Zhao, Xiangyun Zeng, Jun Mo, Tengfei Song, Yufeng Fan, Yu Liu, Jingxing Wang, Shousheng He, Ciren Wangdui, Jujia Zhang, Xuefei Zhang, Kai Ye, Jinming Bai, Xiaojun Jiang, Xiaoming Zhang, Peng Qiu, Jicheng Zhang

Earth and Planetary Astrophysics

Dynamical Origin of (469219) Kamo`oalewa of Tianwen-2 Mission from the Main-Belt: $\nu_6$ Secular Resonance, Flora Family or 3:1 Resonance with Jupiter

Yandong Wang, Shoucun Hu, Jianghui Ji et al. (+1 more)

China's Tianwen-2 mission, launched on 29 May 2025, targets the near-Earth object (469219) Kamo`oalewa, an Earth quasi-satellite trapped in a 1:1 mean-motion resonance with our planet. Determining the origin of Kamo`oalewa is central to understanding the formation pathways and dynamical evolution of Earth's quasi-satellite population. Here we show a strong possibility of main-belt origin for Kamo`oalewa using long-term dynamical simulations. We examine three candidate source regions: the $\nu_6$ secular resonance ($\nu_6$), the 3:1 mean-motion resonance with Jupiter (3:1J MMR), and the Flora family. A total of 42,825 test particles were integrated over 100 Myr. We find that asteroids from all three regions can be transported onto Kamo`oalewa-like orbits, albeit with markedly different efficiencies. Particles originating near the $\nu_6$ show the highest transfer probability (3.31%), followed by the Flora family (2.54%) and the 3:1J MMR (0.39%). We further identify representative dynamical pathways linking these source regions to Earth quasi-satellite orbits. The Tianwen-2 spacecraft is expected to rendezvous with Kamo`oalewa in 2026, performing close-proximity operations and returning samples. The mission will provide decisive observational constraints on the asteroid's composition and physical properties, offering a critical test of its proposed origin.
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All authors Yandong Wang, Shoucun Hu, Jianghui Ji, Jiajun Ying