Astrophysics of Galaxies
Galaxy transformation across the cosmic web: The influence zone of filaments
J. A. L. Aguerri and S. Zarattini
The matter distribution in the Universe exhibits a rich variety of structures forming the
cosmic web. These structures arise from the anisotropic gravitational collapse of
primordial density fluctuations and define the pathways along which
galaxies flow from voids to high-density clusters. Local density variations within these structures play a fundamental role in driving the environmental
evolution of
galaxies. To characterise filament boundaries, we analysed
galaxy overdensity profiles around filaments in two
redshift ranges: $0.05 < z < 0.1$ and $0.1 < z < 0.3$. Perpendicular and parallel profiles were derived by averaging
galaxy overdensity as a function of distance. Characteristic scales and central overdensities were then analysed by fitting analytical models, specifically exponential and power-law families. We also introduced normalised density profiles to account for survey incompleteness. The perpendicular overdensity profiles show a nearly constant value in the central regions $D_{fila} < 1$ Mpc, decreasing at distances up to $\approx 10$ Mpc. The mean physical widths (scale radii) at $0.05 < z < 0.1$ and $0.1 < z < 0.3$ are $2.39 \pm 0.69$ and $5.56 \pm 2.29$ Mpc, respectively. This scale difference between
redshift ranges is also evident in the normalised profiles. Conversely, profiles along filaments remain constant at distances larger than $\approx 20$ Mpc from the nearest intersection. Our results show that the influence zone of
cosmic filaments extends up to $\sim 10$ Mpc from their spines. Furthermore, a mild
evolution in structural parameters is observed over the past $\sim 4$ Gyr, suggesting that filaments undergo measurable changes even at relatively low
redshifts.
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High Energy Astrophysical Phenomena
Signatures of Black Hole Spin and Plasma Acceleration in Jet Polarimetry II: Off-Axis Jets
Zachary Gelles, Andrew Chael and Eliot Quataert
We analyze the polarization of optically thin, stationary, axisymmetric black hole jets at scales of order the light cylinder radius. Our work generalizes the face-on results of Gelles et al. (2025) to arbitrary viewing inclination. Due to a combination of geometry and relativistic aberration, the polarization of the jet is not left-right symmetric, and the degree of asymmetry can shed light on both the viewing angle and the
plasma bulk Lorentz factor. We show that there is always a radius in the jet at which the polarization transitions from azimuthal to radial; this radius is different along the spine and limb of the jet. We propose metrics that can be used to constrain the black hole
spin, inclination angle, and
plasma Lorentz factor from these polarimetric signatures, and we discuss the impact of limb-brightening on these measurements. We anticipate that these polarimetric signatures can be studied with current or forthcoming data in M87, NGC 315, NGC 4261, Centaurus A, Cygnus A, and other systems. Observations of the polarization of the base of the counter-jet in higher inclination sources would provide a particularly promising probe of black hole
spin.
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Astrophysics of Galaxies
Testing the Physical Parameter Constraining Power of HCN and HNC with Neural Networks
Erica Behrens, Jeffrey G. Mangum, Mathilde Bouvier et al. (+2 more)
We quantify the utility of HCN and HNC to characterize gas conditions in the nearby starburst
galaxy NGC 253. We use measurements from the Atacama Large Millimeter/Submillimeter Array (ALMA) Large Program ALCHEMI: the ALMA Comprehensive High-resolution Molecular Inventory. Using different subsets of the eight total HCN and HNC transitions measured by ALCHEMI, we test the number and combinations of transitions necessary for constraining the temperature, H$_2$ volume and column densities,
cosmic-ray ionization rate, and beam-filling factor in three representative regions within NGC 253. We use these combinations of HCN and HNC transitions to constrain chemical and radiative transfer models and infer the gas conditions using a
Bayesian nested sampling
algorithm combined with neural network models for increased efficiency. By comparing the shapes of the resulting posterior distributions, as well as the medians and uncertainties for each gas parameter, from each test case to what we obtain with the full set of eight transitions (the control), we quantify how well each test reproduces the control. We find that multiple transitions each of both molecules are required to obtain a median parameter value within a factor of 2 of the control with an uncertainty less than 2-3 times that of the control. We also find that transition combinations that feature a range of upper-state energies are most effective. We show that single transitions, such as HCN J = 1-0 or 3-2, are among the worst-performing combinations and result in parameter values up to an order of magnitude different than the control.
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All authors Erica Behrens, Jeffrey G. Mangum, Mathilde Bouvier, Cosima Eibensteiner, Serena Viti
Earth and Planetary Astrophysics
The Occurrence Rate of Nearby Planetary Companions to Hot Jupiters
Lizhou Sha, Andrew M. Vanderburg, Chelsea X. Huang et al. (+33 more)
Of the > 500 confirmed transiting hot jupiters and approximately 2000 additional candidates today, only ten are known to have nearby companion
planets. The survival of nearby companions means that these hot jupiters cannot have migrated to their present location via dynamically disruptive high-eccentricity migration but instead have undergone disk migration or formed in situ. The occurrence rate for these nearby companions, therefore, constrains the relative efficiency of different hot jupiter formation pathways. Here, we perform a uniform box least-squares search for nearby transiting companions to hot jupiters in the first five years of TESS data. Accounting for observational completeness and detection efficiency, we arrive at an occurrence rate of $(7.6^{+5.5}_{-3.8})\%$, which is a lower limit on the fraction of hot jupiters that underwent disk migration or in situ formation. Comparing this rate with that derived from transit-timing variation searches suggests that hot jupiters are likely mostly aligned with their nearby companions, but their apparently higher incidence of grazing transits may point to a slight preferential misalignment. We also synthesize evidence that hot jupiters with nearby companions may have cold companions at a rate similar to that of other hot jupiters. Comprehensive transit, radial velocity, and
stellar obliquity measurements in hot jupiter systems with nearby companions will be necessary to fully account for the relative prevalence of proposed hot jupiter formation pathways.
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All authors Lizhou Sha, Andrew M. Vanderburg, Chelsea X. Huang, Samuel Christian, Kevin Burdge, Nicholas Saunders, Khalid Barkaoui, Alexander Belinski, Serge Bergeron, Zoë L. de Beurs, Allyson Bieryla, Karen A. Collins, Giuseppe Conzo, Gareb Fernández-Rodríguez, Akihiko Fukui, Davide Gandolfi, Tristan Guillot, Joel D. Hartman, Kai Ikuta, David W. Latham, Jerome P. de Leon, Bob Massey, Gabriel Murawski, Felipe Murgas, Norio Narita, Mohammad Odeh, Enric Palle, Hannu Parviainen, Gabrielle Ross, Richard P. Schwarz, Gregor Srdoc, Chris Stockdale, Samuel N. Quinn, Ian A. Waite, Francis P. Wilkin, George Zhou
Earth and Planetary Astrophysics
A Newly Identified Degeneracy Keeps the Planetary Interpretation Viable for OGLE-2011-BLG-0950
Jiyuan Zhang, Weicheng Zang, Andrzej Udalski et al. (+12 more)
The microlensing event OGLE-2011-BLG-0950 exhibits the well-known “
Planet/Binary” degeneracy, in which distinct lens configurations produce similar light curves but imply substantially different mass ratios between the lens components. A previous study suggested that high-resolution imaging could break this degeneracy through differences in the lens-source relative proper motion. In this work, we identify a new planetary model for this event that arises from a newly identified degeneracy, simultaneously reproducing the observed light curve and remaining consistent with the relative proper motion measured from high-resolution imaging. By combining constraints from the light-curve modeling and high-resolution observations, we infer a lens system consisting of a $\sim 1~M_{\odot}$ host
star orbited by a $\sim 1.5~M_{\rm Jup}$
planet, with a projected separation of about 2 or 8 au, subject to the “Close/Wide” degeneracy. Our reanalysis of the color-magnitude diagram further indicates that the source
star has unresolved companions that contribute non-negligible blended light, highlighting the importance of carefully accounting for source and lens companions in future Roman microlensing analyses. Finally, we show that adopting a single mass–luminosity relation significantly underestimates the uncertainties in the inferred lens properties for host masses $\gtrsim 1~M_{\odot}$.
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All authors Jiyuan Zhang, Weicheng Zang, Andrzej Udalski, Hongjing Yang, Shude Mao, Michał K. Szymański, Igor Soszyński, Radoslaw Poleski, Krzysztof Ulaczyk, Paweł Pietrukowicz, Szymon Kozłowski, Jan Skowron, Przemek Mróz, Sean K. Terry, Andrew Gould
Cosmology and Nongalactic Astrophysics
An efficient model of cosmology dependence in the covariance matrix of the matter power spectrum
Theodore Steele, Robert Smith and Roisin O'Connor
Covariance
matrices are essential cosmological probes of fundamental physics, providing information on numerous fundamental physical parameters and varying with any change in the underlying cosmology. However, this cosmology dependence, while providing excellent information, also makes them computationally intensive to compute, as a new covariance
matrix must explicitly be calculated for every variation in cosmology before comparisons to observational data can be made. In this paper, we develop an efficient model for estimating the parameter dependence of the covariance
matrix of the matter power spectrum by Taylor expanding around a known value of the parameter space. This method allows us to use a relatively small number of input cosmologies, specifically one fiducial cosmology and two further cosmologies for each parameter. We explicitly calculate the covariance
matrices for these cosmologies and then develop a new model that allows us to interpolate from these the form of the covariance
matrix with a cosmology that is located elsewhere in that given parameter space without explicit perturbation theory calculations. This method speeds up covariance
matrix calculations in new cosmologies by orders of magnitude compared to explicit perturbation theory calculations at each point in a given parameter space. Using different approximations, we develop three versions of our interpolated covariance
matrix and validate the model by recreating all of our input cosmologies using all three forms, both with and without super-sample covariance corrections in each case, and show that the models provide robust recreations of the original results, with the different approximations being valid in certain regimes.
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Instrumentation and Methods for Astrophysics
Optomechanical design of the DragonCam microscopic camera
M. J. Clark, M. A. Ravine, M. A. Caplinger et al. (+5 more)
The DragonCam Microscopic Camera is an instrument being developed for NASA's Dragonfly mission [1] to Saturn's moon Titan. The Microscopic Camera will be body-fixed to the Dragonfly vehicle and will image the surface at a distance of about one meter (98.6 cm nominal) with a pixel scale of better than 60 microns/pixel and a nominal 52 degree angle to the Titan surface. With the 4.8 um pixel pitch of the sensor, this is a focal length of about 77.5 mm. To accommodate range variations due to vehicle pose and surface topography, the Microscopic Camera has a focus mechanism to give it a depth of field (DOF) of about 130mm. Since the Microscopic Camera's boresight is tilted by 52{\deg} off the vertical, the optical configuration has a compensating tilted focal plane, taking advantage of the Scheimpflug imaging principle. The optics are all-refractive with nine elements, a six-element stationary group and a three-element moving group. A plano-plano window seals the optics from the environment and also serves as the substrate for a bandpass filter. The optomechanical system is derived from the Mars Hand Lens Imager [11]; the moving group is mounted to a linear slide which is translated via a cam follower by the rotation of a cam driven by a stepper motor. The Microscopic Camera is designed to survive at temperatures as low as -130C without power. The camera is enclosed in a cavity in the foam insulation covering the spacecraft and looking through a single-pane window. Prior to imaging, the camera will be heated to operating temperature (nominal -30C) for proper actuation of the mechanism. STOP analysis has been performed to demonstrate that optical performance is maintained after heating. Software focus merging will be performed in the onboard camera control electronics to minimize image data downlink requirements.
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All authors M. J. Clark, M. A. Ravine, M. A. Caplinger, B. A. Lindenfeld, J. D. Laramee, R. S. Bronson, A. D. Giglio, B. G. Crowther
Earth and Planetary Astrophysics
Timescales diagnostics for saving viscous and MHD-driven dusty discs from external photoevaporation
Gabriele Pichierri, Giovanni Rosotti, Rossella Anania et al. (+1 more)
The
evolution of protoplanetary discs is a function of their internal processes and of their environment. It is unclear if angular momentum is mainly removed viscously or by
magnetic winds, or by a combination of the two. While external photoevaporation is expected to influence disc
evolution and dispersal, there are observational limitations towards highly irradiated discs. The interplay between these ingredients and their effect on the gas and
dust distributions are poorly understood. We investigate the
evolution of both the gaseous and solid components of viscous, MHD-wind or hybrid discs, in combination with external FUV-driven mass loss. We test which combinations of parameters protect discs from external irradiation, allowing the solid component to live long enough to allow
planet formation to succeed. We run a suite of 1D simulations of smooth discs with varying initial sizes, levels of viscous and MHD-wind stresses modelled via an $\alpha$ parametrisation, and strengths of the external FUV environment. We track disc radii, various lifetime diagnostics, and the amount of
dust removed by the photoevaporative wind, as a function of the underlying parameters. The biggest role in determining the fate of discs is played by a combination of its ability to spread radially outwards and the strength of FUV-driven erosion. While MHD wind-driven discs experience less FUV erosion due to the lack of spread, they do not live for longer compared to viscously evolving discs, especially at low-to-moderate FUV fluxes, while higher fluxes yield disc lifetimes that are insensitive to the disc's angular momentum transport mechanism. For the solid component, the biggest role is played by a combination of inward drift and removal by FUV winds. This points to the importance of other physical ingredients, such as disc substructures, even in highly-irradiated disc regions, in order to retain solids.
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All authors Gabriele Pichierri, Giovanni Rosotti, Rossella Anania, Giuseppe Lodato
High Energy Astrophysical Phenomena
Broadband Variability Analysis of FSRQ PKS\,0402-362 with Indications of Quasi-Periodic Modulation
Zeeshan Nazir, Sikandar Akbar, Zahir Shah et al. (+2 more)
We present a comprehensive temporal and spectral study of the flat-spectrum
radio quasar PKS~0402$-$362 using
Fermi-LAT/Swift-XRT/UVOT observations spanning from MJD 54686-60321. The $\gamma$-ray light curve exhibits multiple phases of enhanced activity, with the fractional variability parameter ($F_{\mathrm{var}}$) showing larger amplitudes at longer timescales, consistent with variability trends observed in other FSRQs. Statistical analysis of the flux and spectral index distributions using the Anderson–Darling test and histogram fitting reveals that both distributions deviate from a single log-normal form and are better represented by a double log-normal profile, indicating two distinct flux states. A search for quasi-periodic oscillations in the $\gamma$-ray emission using the Lomb–Scargle periodogram identified a significant periodic signal at $\sim$413~days with a confidence level exceeding $3\sigma$. However the proximity of the timescale to one year and limited number of observed cycles prevents a definitive interpretation. Broadband spectral energy distributions for six flux states were modeled using a one-zone leptonic framework incorporating synchrotron, synchrotron self-Compton (SSC), and external Compton (EC) components. The SEDs are well reproduced with physically reasonable parameters: high-flux states exhibit harder electron spectra and lower
magnetic field strengths ($B \sim 0.2--0.6\,\mathrm{G}$), while low-flux states show softer spectra and stronger
magnetic fields ($B \sim 1.3\,\mathrm{G}$). The fitted break energy decreases during high-flux states, suggesting enhanced radiative cooling and a transition toward a particle- or kinetic-energy-dominated jet. These trends are consistent with the “harder-when-brighter” behavior commonly observed in blazars.
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All authors Zeeshan Nazir, Sikandar Akbar, Zahir Shah, Athar A. Dar, Zahoor Malik
Earth and Planetary Astrophysics
Toward Reliable Interpretations of Small Exoplanet Compositions: Comparisons and Considerations of Equations of State and Materials Used in Common Rocky Planet Models
Joseph Schulze, Natalie Hinkel, Wendy Panero et al. (+1 more)
The bulk compositions of small
planets ($R_p< 2 \mathrm{R}_\oplus$) are directly linked to their formation histories, making reliable compositional constraints imperative for testing models of
planet formation and
evolution. Because
exoplanet interiors cannot be directly observed, their make-up must be inferred from mass-radius-composition models that link assumed
stellar abundances to the direct observables: planetary mass and radius. There are a variety of such models in the literature, each adopting different equations of state (EOS) to describe the materials' properties at depth and varying assumptions about the minerals present within the
planets. These EOS+mineral suites provide the foundations for compositional inferences, but they have not yet been systematically compared. In this work, we review several suites, with a detailed description of the basic structure, mineral physics, and materials within standard small
planet models. We show that EOS+mineral suites predict
planet densities whose differences are comparable to current observational uncertainties, which present a challenge for robustly interpreting and classifying small
planets. We apply a powerful small-
planet characterization framework, which illustrates that variations among EOS+mineral suites lead to inconsistent conclusions for both individual
planets and sample-level demographics. Our results demonstrate the need for more careful considerations of the materials and EOS used in mass-radius-composition models, especially given the current focus on finding and characterizing potentially habitable rocky
planets. We conclude with recommendations for best practices so that future interpretations of small
planets and their formation are accurate and consistent.
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All authors Joseph Schulze, Natalie Hinkel, Wendy Panero, Cayman Unterborn
High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Electromagnetic ghosts in pair plasmas
Maxim Lyutikov
Collisions of two weakly nonlinear, $a_0 \ll 1$, counter-propagating EM pulses in pair
plasma leave behind a long-surviving collection of localized waves, an electromagnetic ghost. Waves are trapped (localized) by the random large density fluctuations created by the beat between the pulses. The process is similar to random
plasma density grating and/or Anderson-like wave localization. Structures survive for long, mesoscale times, while the EM energy slowly bleeds through high density walls of the density trap. Large guide
magnetic field, $\omega_B \geq $ few $\omega$, suppresses the formation of the ghosts.
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Solar and Stellar Astrophysics
Time variations of the mean magnetic flux in active regions of different magneto-morphological classes
Anastasiya Zhukova and Valentina Abramenko
Using a recently suggested magneto-morphological classification (MMC, Abramenko, 2021, MNRAS Vol 507) of
solar active regions (ARs), we explored 3048 ARs, observed from12 May 1996 to 27 December 2021. Magnetograms were acquired with the Michelson Doppler Imager (MDI) on board the
Solar and Heliospheric Observatory (SOHO) and with the Helioseismic and
Magnetic Imager (HMI) on board the
Solar Dynamics Observatory (SDO). ARs were separated between three classes: class A - regular ARs (bipoles which follow the empirical rules compatible with the mean field dynamo theory); class B - irregular ARs (“wrong” bipoles and multipolars); class U - unipolar sunspots. An aim of the present study is to explore time variations of a typical unsigned
magnetic flux of ARs of different classes. The typical flux was acquired as the mean flux over all ARs of a given class observed during one
solar rotation. The time profiles of the mean fluxes for different classes were compared. We found that, except for periods of deep
solar minima, the mean flux of B-class ARs always dominate that of A-class ARs, and, what is the most important, the time profile of B-class ARs is highly intermittent versus the rather smooth and quazi-constant A-class profile. Intermittency implies a direct involvement of
turbulence. We conclude that, through the entire active phase, the Sun is capable of producing regular moderate ARs at a quazi-constant rate along with the production of large and complex irregular ARs in the very intermittent manner. The result is the first observational evidence for the long-standing speculative assumption on the involvement of the convection zone
turbulence into the regular global dynamo-process on a stage of the active regions formation.
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Solar and Stellar Astrophysics
SolARED: Solar Active Region Emergence Dataset for Machine Learning Aided Predictions
Spiridon Kasapis, Eren Dogan, Irina N. Kitiashvili et al. (+6 more)
The development of accurate forecasts of
solar eruptive activity has become increasingly important for preventing potential impacts on space technologies and exploration. Therefore, it is crucial to detect Active Regions (ARs) before they start forming on the
solar surface. This will enable the development of early-warning capabilities for upcoming space weather disturbances. For this reason, we prepared the
Solar Active Region Emergence
Dataset (SolARED). The
dataset is derived from full-disk maps of the Doppler velocity,
magnetic field, and continuum intensity, obtained by the Helioseismic and
Magnetic Imager (HMI) onboard the
Solar Dynamics Observatory (SDO). SolARED includes time series of remapped, tracked, and binned data that characterize the
evolution of acoustic power of
solar oscillations, unsigned
magnetic flux, and continuum intensity for 50 large ARs before, during, and after their emergence on the
solar surface, as well as surrounding areas observed on the
solar disc between 2010 and 2023. The resulting ML-ready SolARED
dataset is designed to support enhancements of predictive capabilities, enabling the development of operational forecasts for the emergence of active regions. The SolARED
dataset is available at https://sun.njit.edu/sarportal/, through an interactive visualization web application.
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All authors Spiridon Kasapis, Eren Dogan, Irina N. Kitiashvili, Alexander G. Kosovichev, John T. Stefan, Jake D. Butler, Jonas Tirona, Sarang Patil, Mengjia Xu
Solar and Stellar Astrophysics
Forecasting Continuum Intensity for Solar Active Region Emergence Prediction using Transformers
Jonas Tirona, Sarang Patil, Spiridon Kasapis et al. (+5 more)
Early and accurate prediction of
solar active region (AR) emergence is crucial for space weather
forecasting. Building on established Long Short-Term
Memory (LSTM) based approaches for
forecasting the continuum intensity decrease associated with AR emergence, this work expands the modeling with new architectures and targets. We investigate a sliding-window
Transformer architecture to forecast continuum intensity
evolution up to 12 hours ahead using data from 46 ARs observed by SDO/HMI. We conduct a systematic ablation study to evaluate two key components: (1) the inclusion of a temporal 1D convolutional (Conv1D) front-end and (2) a novel `Early Detection' architecture featuring
attention biases and a timing-aware loss function. Our best-performing model, combining the Early Detection architecture without the Conv1D layer, achieved a Root Mean Square Error (RMSE) of 0.1189 (representing a 10.6% improvement over the LSTM baseline) and an average advance warning time of 4.73 hours (timing difference of -4.73h), even under a stricter emergence criterion than previous studies. While the
Transformer demonstrates superior aggregate timing and accuracy, we note that this high-sensitivity detection comes with increased variance compared to smoother baseline models. However, this
volatility is a necessary trade-off for operational warning systems: the model's ability to detect micro-changes in precursor signals enables significantly earlier detection, outweighing the cost of increased noise. Our results demonstrate that
Transformer architectures modified with early detection biases, when used without temporal smoothing layers, provide a high-sensitivity alternative for
forecasting AR emergence that prioritizes advance warning over statistical smoothness.
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All authors Jonas Tirona, Sarang Patil, Spiridon Kasapis, Eren Dogan, John Stefan, Irina N. Kitiashvili, Alexander G. Kosovichev, Mengjia Xu
Astrophysics of Galaxies
MARVEL Analysis of the Measured High-resolution Spectra of CO Isotopologues
Timur Grigorev, Yuhang Dai, Max Potter et al. (+3 more)
Carbon monoxide is thought to be the second most abundant molecule in the Universe. This makes observation of both its parent isotopologue ($^{12}$C$^{16}$O) and its stable isotopologues, $^{13}$C$^{16}$O, $^{12}$C$^{18}$O, $^{12}$C$^{17}$O, $^{13}$C$^{18}$O and $^{13}$C$^{17}$O, important in variety of objects. Here the MARVEL (Measured Active Rotational-Vibrational Energy Levels)
algorithm is used to determine precise rotational vibrational energy levels for the five minor isotopologues of carbon monoxide in their electronic ground state. A review of 27 literature sources yields 3716, 1454, 89, 728 and 57 validated transitions for $^{13}$C$^{16}$O, $^{12}$C$^{18}$O, $^{12}$C$^{17}$O, $^{13}$C$^{18}$O and $^{13}$C$^{17}$O, respectively, giving 863, 499, 33, 345 and 45 empirically determined, rotation vibration energy levels, respectively.
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All authors Timur Grigorev, Yuhang Dai, Max Potter, Xiaoyu Xiang, Keyu Zhang, Jonathan Tennyson
High Energy Astrophysical Phenomena
Simulating radio emission from flickering AGN jets: travelling shocks and hotspot brightening
Emma L. Elley, James H. Matthews, Dipanjan Mukherjee et al. (+1 more)
We investigate the impact of flickering variability in jet power on the luminosity and morphology of
radio galaxies. We use a Lagrangian particle method together with relativistic hydrodynamics simulations using the PLUTO code to track the
evolution of electron spectra through particle acceleration at shocks and cooling processes. We introduce an adapted version of this method which improves tracking of adiabatic cooling in regimes where low density jet material mixes with high density from the ambient medium in the lobes. We find that rapid increases in jet power can lead to large increases in hotspot luminosity due to the interaction of a travelling shock structure with the pre-existing shock structure at the jet head. We show that in some cases it may be possible to identify a bright region of emission corresponding to a shock travelling along the jet axis. We find that the time-averaged radiative efficiency of variable jets is similar to their steady counterparts, but find significant departures from this on an instantaneous basis. We suggest that, together with environmental effects and differences in the average powers of jets, variable jet powers may have a significant impact on how we understand the diversity of
radio jets seen in observations and have significant implications for interpretations of jet powers, energy budgets and luminosity-linear size diagrams.
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All authors Emma L. Elley, James H. Matthews, Dipanjan Mukherjee, Bhargav Vaidya
High Energy Astrophysical Phenomena
Tidal capture and repeating partial tidal disruption events of giant stars
Di Wang and Fa-Yin Wang
When an object is scattered near a supermassive black hole (SMBH),
tidal oscillations excited within it reduce its orbital energy, leading to capture by the SMBH. This process, called
tidal capture, can also occur when the object approaches even closer to the SMBH, resulting in a partial
tidal disruption event (pTDE). Previous studies on pTDEs of main-sequence
stars have shown that as the disruption intensifies, dynamical effects dominate over
tidal oscillations, causing the remnant material to acquire a kick velocity instead of being captured by the SMBH. In this work, we performed hydrodynamic numerical simulations of pTDEs involving
giant stars. We found that for weaker disruptions, the dynamical behavior of the remnant material resembles that of main-sequence
stars. However, as the disruptions deepen, the remnant material transitions from gaining energy to losing energy, leading to capture by the SMBH. This behavior markedly differs from that of main-sequence
stars, demonstrating that the presence of a compact core significantly influences the dynamical processes in pTDEs. Our simulations reveal that the energy change of the remnant material strongly correlates with asymmetric mass – lossspecifically, the difference in mass
outflow between the Lagrange points L1 and L2. This suggests that the energy change stems from asymmetric mass loss, consistent with conclusions from previous studies on main-sequence
stars. However, quantitative analysis contradicts earlier models, indicating that the dynamical model of pTDEs requires further refinement. Finally, we discuss the characteristics of repeating pTDEs produced by this process and their potential observability, as well as the implications for the long-term orbital
evolution of high eccentricity extreme mass ratio inspiral systems.
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Earth and Planetary Astrophysics
BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30b
Alastair B. Claringbold, Chloe E. Fisher, James Kirk et al. (+18 more)
We present the JWST NIRSpec/G395H transmission spectrum of the misaligned hot Jupiter HAT-P-30b from 2.8–5.2 $\mu$m as part of the BOWIE-ALIGN survey, a comparative survey designed to probe the link between
planet formation and atmospheric composition in samples of misaligned and aligned hot Jupiters orbiting F-type
stars. Through independent data reductions and
retrieval analyses, we find evidence for absorption features of H$_2$O and CO$_2$ in the atmosphere of HAT-P-30b. Our retrieved abundances are consistent with
equilibrium chemistry, from which we infer a sub-
solar C/O ratio (0.16–0.45), and sub-
solar and sub-
stellar metallicity (0.2–0.8$\times$
solar, compared to a
stellar metallicity of 1.1–1.6$\times$
solar), with muted spectral features. This composition challenges formation models of continuous migration and
accretion within a steady disc of
stellar metallicity, and could be the result of low C/O ratio gas
accretion within the water ice line, low
metallicity accretion due to the trapping of volatiles further out in the disc, or the combined
accretion of low
metallicity gas and carbon-poor solids.
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All authors Alastair B. Claringbold, Chloe E. Fisher, James Kirk, Eva-Maria Ahrer, Anna B. T. Penzlin, Daniel P. Thorngren, Mercedes López-Morales, Peter J. Wheatley, Lili Alderson, Richard A. Booth, Duncan A. Christie, Charlotte Fairman, Nathan J. Mayne, Mason McCormack, Annabella Meech, James E. Owen, Vatsal Panwar, Denis E. Sergeev, Daniel Valentine, Hannah R. Wakeford, Maria Zamyatina
Instrumentation and Methods for Astrophysics
Antarctic Infrared Binocular Telescope: Early Data Release of observations in the 1.4 {\mu}m water-vapor-absorption band
Pu Lin, Haonan Yang, Bin Ma et al. (+12 more)
Ground-based observations around 1.4 $\mu$m are normally limited by strong absorption of telluric water-vapor. However, Dome A, Antarctica has exceptionally dry conditions that offer a unique opportunity for observations in this band. We designed a new filter covering 1.34–1.48 $\mu$m, namely $W'$, and installed it on the Antarctic Infrared Binocular
Telescope (AIRBT) at Dome A in 2025. AIRBT comprises two identical 15 cm optical tube assemblies and two InGaAs cameras equipped with $J$ and $W'$ filters, respectively. With this Early Data Release (EDR), we aim to evaluate the performance of the $W'$ band at Dome A to observe objects with water-vapor features. This EDR covers $\thicksim 20 \ \mathrm{deg^2}$ in the
Galactic plane using $\thicksim 20,000$ images in three nights. For 2 s exposures, the 5 $\sigma$ limiting magnitude histogram peaks at $J \thicksim 11.5$ mag (Vega) and $W' \thicksim 9.9$ mag, respectively. The $J-W'$ vs $J-H$ color-color diagram distinguishes ultracool candidates with water-vapor-absorption features from reddened early type
stars. Furthermore, later-type
stars tend to exhibit stronger water-vapor absorption. Some sources show larger $\Delta W'$ than $\Delta J$ across the three nights, which we attribute to variations of their water-vapor-absorption depth. We conclude that it will be efficient to search for ultracool
stars and estimate their spectral subtypes using $W'$ band imaging at Dome A, where the atmospheric transmission is high and stable.
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All authors Pu Lin, Haonan Yang, Bin Ma, Jinji Li, Haoran Zhang, Michael C. B. Ashley, Zhong-Nan Dong, Lu Feng, Wei Huang, Yi Hu, Zhaohui Shang, Yun Shi, Shijie Sun, Xu Yang, Yong Zhang
High Energy Astrophysical Phenomena
Simulating the quasi-ballistic regime of a short Gamma-Ray Burst jet
Emma Dreas, Andrea Pavan, Riccardo Ciolfi et al. (+1 more)
This study extends the 3D magnetohydrodynamic (MHD) simulation of a jet emerging from a binary
neutron star (BNS) merger presented in Pavan et al. (2023), in which an incipient jet was manually injected into the realistic environment imported from a previous general-relativistic MHD simulation of a merging BNS system. The jet
evolution is followed up to almost 10 seconds without loss of resolution. Our results reveal that the jet faces challenges in penetrating the dense surroundings, leading to a barely successful
outflow that exhibits structural asymmetries and low Lorentz factors. By the end of the extended simulation, 98% of the jet energy is converted to kinetic form and its angular structure is stabilized. The physical quantities inferred thus provide reliable inputs for afterglow emission calculations. This work demonstrates a method for simulating jets in 3D up to nearly ballistic regimes that is general and ready to be applied to any jet in a BNS merger context.
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All authors Emma Dreas, Andrea Pavan, Riccardo Ciolfi, Annalisa Celotti
Cosmology and Nongalactic Astrophysics
Was the Early Universe Quantum? Falsifying Classical Stochastic Inflation
Veronica Sanz
Inflationary cosmology successfully accounts for the observed properties of
primordial fluctuations using
quantum field theory in an expanding background. However, the
quantum nature of these fluctuations has not been experimentally established, since classical
stochastic models could reproduce the observed two-point statistics by construction. Existing approaches to testing
primordial quantumness focus primarily on Bell inequalities, which provide a sharp conceptual criterion but are difficult to implement with cosmological observables. In this work we adopt a falsification-based approach. We define a precise classical hypothesis for the origin of
primordial perturbations (local
stochastic fields admitting a positive probability distribution) and identify inequality constraints that must be satisfied within this class. We show how violations of these classicality inequalities can be probed using realistic cosmological observables, without invoking Bell tests or non-commuting measurement settings. We further identify
symmetry-protected spectator sectors in which
quantum coherence is parametrically preserved during inflation, allowing violations of observable magnitude to survive decoherence. Our results show that large-scale structure and future 21 cm surveys provide a viable and quantitative route to falsifying classical
stochastic descriptions of
primordial fluctuations.
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Astrophysics of Galaxies
The long-term evolution of Ultra Faint Dwarf Galaxies and observational implications
Francesco Flammini Dotti, Roberto Capuzzo-Dolcetta, Giovanni Carraro et al. (+2 more)
Context. In the Local Group,
dwarf spheroidal
galaxies (dSphs) and ultra-faint
dwarf galaxies (UFDs) exhibit large velocity dispersions. These values are generally attributed to the presence of substantial amounts of dark matter (DM), in line with the predictions of the standard model of
galaxy formation. However, alternative, more conservative explanations exist, such as non-virialized dynamical states induced by
tidal interactions, the presence of
stellar streams, and artificial inflation of the velocity dispersion caused by binary-
star orbital motion. Aims. We study the dynamical
evolution of UFDs using purely
stellar ("dry") dynamics, without invoking DM. We dynamically evolve our systems up to a Hubble time and compare our results with observational studies and previous theoretical work. Methods. We employ direct high precision NBODY simulations performed with the NBODY6++GPU code. We explore the role of binaries in inflating the velocity dispersion of low-mass host
galaxies. We also present both the
stellar and dynamical
evolution of the
stellar population, which is necessary to properly interpret our results. Results. We find that, in all our models, the UFD remains globally quasi-stationary for approximately 3000 Myr. Subsequently, the system undergoes mass segregation and experiences a phase resembling core collapse. Red
giants and white
dwarfs (WD) are found to play significant, but distinct, roles. Red
giants provide the dominant contribution to the luminosity, whereas WDs constitute the largest fraction of the non-luminous component, accounting for approximately 13% of the total
stellar population. Finally, if not taken into account properly, velocity dispersion measurements can be strongly biased by the presence of a significant binary population, which can lead to substantial overestimates of velocity dispersion in UFDs
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All authors Francesco Flammini Dotti, Roberto Capuzzo-Dolcetta, Giovanni Carraro, Alessandro Alberto Trani, Rainer Spurzem
Cosmology and Nongalactic Astrophysics
Tracing cosmic structure with neutral hydrogen after the Epoch of Reionization
Jamie Incley and Laura Wolz
We present a study of the transition of Neutral Hydrogen (HI) gas from the end of the Epoch of Reionization (EoR) to late-time large-scale structure. We examine the signature of the transition as traced through the redshifted 21-cm line with SKA-Low at $3 < z < 7$. To do so, we use the semi-numerical simulation 21cmFAST to model the HI during the EoR and add a HI-
halo based post-processing model of the late-time HI. This approach gives a robust estimate of the amplitude of the HI temperature field and predicts the observable power spectrum during the transition period. We find that our simulation pipeline reproduces the expected power spectrum trends from existing observations and theory, in addition to replicating current observational constraints on $\Omega_{\text{HI}}$. Our simulations predict a drop in power of four orders of magnitude between $4 < z < 7$. Assuming an inhomogeneous recombination model, we find a flattening of the power due to lingering neutral islands masking the late-time HI signal for $5 < z< 6.5$. Using SKA-Low deep survey parameters, we find HI power spectrum detectability at scales $k \leq 1$ $h$ Mpc$^{-1}$ for
redshifts $3< z < 7$, even when using the horizon limit to mitigate foregrounds. Our results suggest a sufficient SNR of the HI power spectrum tracing the underlying
halos $z < 5$, which can be used for late-time cosmology. Our results suggest that the resulting $\Omega_{\rm HI}$ constraints can trace different reionization scenarios such as a decreased escape fraction. This study implies that deep SKA-Low observations for $3< z< 7$ will be an important probe to constrain reionization parameters as well as cosmological models.
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Astrophysics of Galaxies
Continuous-Time Modelling of Black Hole Binary Evolution with Neural ODEs
Julian Chan, Alessia Gualandris and Payel Das
Pulsar timing arrays (PTAs) can detect the low-frequency
stochastic gravitational-wave background (GWB) generated by an ensemble of supermassive black hole binaries (BHBs). Accurate determination of BHB merger timescales is essential for interpreting GWBs and constraining key astrophysical quantities such as black hole (BH) occupation fractions and
galaxy coalescence rates. High-accuracy $N$-body codes such as Griffin can resolve sub-pc BHB dynamics but are too costly to explore a wide range of initial conditions, motivating the need for surrogate models that emulate their long-term
evolution at much lower computational cost. We investigate neural ordinary differential equations (NODEs) as surrogates for the secular orbital
evolution of BHBs. Our primary contribution is a parameterised NODE (PNODE) trained on an ensemble of $N$-body simulations of
galaxy mergers spanning a two-dimensional parameter space defined by the initial orbital eccentricity and particle resolution $(e_i, N)$, with the learned vector field explicitly conditioned on these parameters. A single PNODE thereby learns a simulation-parameter-conditioned dynamical model for the coupled
evolution of the BH pair's orbital state across the ensemble, yielding smooth trajectories from which stable hardening and eccentricity growth rates can be extracted. The PNODE accurately reproduces the secular
evolution of the specific orbital energy and angular momentum, and the corresponding Keplerian orbital elements, for held-out trajectories, with modest generalisation to a partially unseen high-resolution case. Combining PNODE predictions with semi-analytical prescriptions for
stellar hardening and gravitational-wave emission yields BHB merger timescales consistent with those obtained from direct $N$-body inputs within current theoretical uncertainties.
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Solar and Stellar Astrophysics
BE Lyncis: A Pulsating Star in the Most Eccentric Binary with a Massive Unseen Companion
Jia-Shu Niu, Ying Zhang and Hui-Fang Xue
We report the discovery of an exceptionally eccentric binary system, BE Lyncis (BE Lyn), which might host a compact companion with mass $\gtrsim 2.5~M_{\odot}$. By combining TESS photometry with an extensive set of times of maximum light spanning 39 years, we identify BE Lyn as a high-amplitude $\delta$ Scuti
star in a binary with an orbital period of $\approx15.9$ years and an extraordinary eccentricity of $e=0.9989^{+0.0008}_{-0.0021}$ ($>0.9968$ at 95% confidence) – the most extreme eccentricity reliably measured for any binary system. Dynamical constraints limit the orbital inclination to $i \lesssim 10^{\circ}.1$, implying a companion mass $M_2 \gtrsim 2.5~M_{\odot}$, which identifies the companion as a compact object. This mass points to it most likely being a black hole; if instead it is a rapidly rotating
neutron star, it would be the most massive known. If the black hole interpretation holds, it would be the closest such object to Earth. This system provides a unique laboratory for studying asteroseismology in strong gravitational fields, as well as the formation and
evolution of extremely eccentric binaries. Our work demonstrates the use of the light-travel time effect in a pulsating
star to reveal a compact companion, offering a novel method for detecting black holes in noninteracting binaries.
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Cosmology and Nongalactic Astrophysics
Wenhao Gao, Zhenjie Liu, Zhongxu Zhai et al. (+8 more)
We present a joint analysis of
galaxy clustering and
galaxy–
galaxy lensing measurements from BOSS
galaxies using a simulation-based emulation method combined with a
halo occupation distribution model. Our emulators are constructed with the Aemulus $\nu$ simulations, a suite of $w\nu$CDM $N$-body simulations with massive
neutrinos as independent particle species. We combine small-scale analysis of clustering from $0.1h^{-1}$Mpc to $60.2~h^{-1}$Mpc and
lensing from $1.7h^{-1}$Mpc to $60.2~h^{-1}$Mpc to perform cosmological constraints. We split the BOSS
galaxies into three
redshift bins to measure their clustering and employ
galaxies from Dark Energy Camera Legacy Survey and Hyper Suprime-Cam as source
galaxies to measure
lensing separately. We find that the addition of
lensing significantly improves the constraining power on $S_{8}=\sigma_8(\Omega_m/0.3)^{0.5}$, with a weak improvement for $f\sigma_{8}$. Our results of $f\sigma_{8}$ indicate tensions of around $1\sim4\sigma$ below the results of CMB observations of Planck. For $S_{8}$, our results are also lower than Planck, and the tension can be mitigated when considering possible systematics in
lensing measurement. As a byproduct, our analysis prefers a non-zero
neutrino mass but without strong significance, with the constraining power dominated by the clustering. Given the accuracy and precision of our model and the observational data, it is anticipated that larger and higher-quality spectroscopic
datasets will improve the constraints on this fundamental property in the near future.
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All authors Wenhao Gao, Zhenjie Liu, Zhongxu Zhai, Jeremy L. Tinker, Jun Zhang, Arka Banerjee, Joseph DeRose, Hong Guo, Yao-Yuan Mao, Kate Storey-Fisher, Risa H. Wechsler
Earth and Planetary Astrophysics
Exploring rotational properties and the YORP effect in asteroid families
Gabriele Bertinelli, Wen-Han Zhou and Paolo Tanga
The long-term dynamical
evolution of asteroid families is governed by the interplay between orbital and rotational
evolution driven by thermal forces and collision. We aim to observationally trace the rotational
evolution of main-belt asteroid families over Gyr timescales. We analyzed rotational properties of 8739 asteroids with
spin period measurements and 3794 asteroids with obliquity determinations across 28 asteroid families spanning ages from 14~Myrs to 3~Gyrs. We introduced a dimensionless timescale that normalizes each asteroid's family age by its classical YORP timescale, enabling direct comparison of rotational states across different evolutionary stages. We examined two key observables: the fraction of slow rotators (periods greater than or equal to 30 hours) and the polarization fraction (the degree to which asteroid
spin poles align correctly with their position in the family's V-shape distribution according to the Yarkovsky theory).
Evolution of both quantities were fitted to identify characteristic transition timescales. We discovered that the slow-rotator fraction increases steeply with $t$ and saturates at $f_{\rm slow} \simeq 0.25$ around a breakpoint $t_{\rm bp} \simeq 20$. This implies a
stochastic YORP timescale $\tau_{\rm YORP,stoc} \simeq 10\,\tau_{\rm YORP}$ by comparison with rotational
evolution models that include tumbling and weakened YORP torques. The polarization fraction reaches a maximum of $\simeq 0.8$ at $t \simeq 16$ and then decays toward the random limit $f_{\rm pol} \rightarrow 0.5$ for $t \gtrsim 20$, indicating an increasing dominance of collisional
spin reorientation over time. The rotation properties within different asteroid families offer crucial clues to rotation
evolution and can serve as a new dimension for age estimation of asteroid families with more data in the LSST era.
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Solar and Stellar Astrophysics
Fates of the sub-stellar objects (FOSSO) I. Fates of the known brown dwarfs in main-sequence–BD binaries
Zhangliang Chen, Hongming Jin, Hongwei Ge et al. (+4 more)
Context. Understanding the survival and orbital
evolution of brown
dwarf (BD) companions during the post-main-sequence (MS)
evolution of their host
stars is increasingly important, especially with recent discoveries of many substellar companions around white
dwarfs (WDs). Aims. We investigate the long-term
evolution and final outcomes of BDs orbiting low-mass MS
stars as these evolve into WDs. By comparing forward-modeling populations with observed WD-BD binaries, we test evolutionary models and predict the existence of yet-undetected systems. Methods. We employ the COMPAS binary population synthesis code to evolve observed MS-BD systems through the post-MS phases of their host
stars into the WD stage, tracking orbital changes driven by mass loss, tides, and common-envelope (CE)
evolution. Results. Our simulations reproduce a period gap in the distribution of detached WD-BD binaries, consistent with observations. We also identify a boundary separating detached and semi-detached systems on the period-mass diagram, located at orbital periods of $\sim$1-2 hours depending on the BD mass. Conclusions. We predict that a subset of currently known MS-BD binaries will survive post-MS
evolution and emerge as detached WD-BD systems, while others will undergo CE
evolution and potentially form cataclysmic variables with BD donors. Our results reproduce the observed period gap in WD-BD binaries and provide quantitative predictions for the role of CE efficiency in shaping their distribution. This work predicts that many WD-BD systems remain undetected, motivating targeted searches with microlensing and high-contrast imaging techniques using next-generation large
telescopes.
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All authors Zhangliang Chen, Hongming Jin, Hongwei Ge, Cong Yu, Kejun Wang, Dichang Chen, Bo Ma
Instrumentation and Methods for Astrophysics · Cross-listed from eess.SY
Report on Earth Observation Missions and Ground Station Management using On-Demand Satellite Operation System
Yuji Sakamoto
Since the launch of its first satellite in 2009, Tohoku University has continuously developed and operated Earth observation satellites and engineering demonstration satellites in the 50cm-class and CubeSat-class (up to 3U). The 50cm-class satellite launched into operation in 2021 enabled efficient operations through cloud-based management functions for both the satellite and ground stations, including automatic command generation. By 2022, up to eight operational satellites were simultaneously managed on a daily basis using three ground stations (Sendai, Hakodate, and Sweden). This paper presents the operational achievements to date and introduces the system that supports efficient satellite operations
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Instrumentation and Methods for Astrophysics · Cross-listed from eess.SY
System Analysis and Pre-Flight Evaluation of Deployable Solar Panels for 3U CubeSat HOKUSHIN-1
Yuji Sakamoto, Masaki Aoi, Sho Suzuki et al. (+8 more)
This paper describes the system design methodology derived from the development and evaluation tests of deployable
solar panels to be mounted on a 3U CubeSat. The study mainly includes structural analysis, thermal analysis, and a review of vibration test results. Hokkaido University is developing the 3U CubeSat HOKUSHIN-1 in collaboration with Tohoku University and Muroran Institute of Technology. Deployable
solar panels are a key technology for future planned lunar exploration missions, as they enable power-intensive communication and propulsion required for orbit control. The satellite also demonstrates a newly developed compact and efficient propulsion system. The satellite has dimensions of approximately 10x10x34 cm, a mass of 3.99 kg, and will be deployed into a circular orbit at an altitude of about 400 km with an orbital inclination of 51.6 degrees from the International Space Station.
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All authors Yuji Sakamoto, Masaki Aoi, Sho Suzuki, Takumi Haga, Shumpei Hosokawa, Yuma Abe, Yuya Tasaki, Tsuyoshi Totani, Sou Nakamura, Masaharu Uchiumi, Shinya Fujita