Solar and Stellar Astrophysics
Improving the Physical Interpretability of Gaussian Processes in Stellar Activity Modeling: A Study Case on Photometric Variability Among Stellar Clusters
Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty et al. (+12 more)
Gaussian Processes (GPs) are widely used to model stellar variability in photometric surveys, but a statistically successful fit does not guarantee that the inferred hyperparameters correspond to physically meaningful stellar properties. This is especially important for young, active
stars, whose TESS light curves contain evolving spots, harmonics, and non-sinusoidal variability. We use stellar rotation as a case study to examine when the period hyperparameter of a quasi-periodic GP can be interpreted as a physical rotation period. We introduce a regularized GP likelihood that reweights the covariance-complexity term in the marginal likelihood, reducing the tendency of unconstrained models to converge toward preferred but misleading solutions. We test this framework on 539
stars in IC2602, the Tucana-Horologium Association, Pisces-Eridanus, and GroupX, with independently reported and manually vetted rotation periods. This
benchmark evaluates GP hyperparameter interpretability and automated period recovery with minimal human intervention. We compare regularized and unregularized models across several regularization strengths, {\lambda}, using literature agreement, sector-level diagnostics, and consistency across TESS sectors. Relative to the standard GP likelihood, regularization improves successful rotation-period recovery by an average of 7%. It also generally reduces the median absolute fractional deviation of periods across sectors, showing that the improvement is not limited to catastrophic failures but also mitigates smaller systematic errors. Regularization is particularly beneficial for non-sinusoidal or evolving modulation, where unconstrained GPs may recover harmonics or spurious timescales. These results show that likelihood regularization and cross-sector consistency are practical diagnostics for assessing when GP-based rotation periods are robust.
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All authors Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty, Mark Popinchalk, Jason Lee Curtis, Johanna M. Vos, Alexandrine L'Heureux, Andrew Ayala, Eleanor Johnson, Dawn McCullough, Nicole Munoz, Hannah Park, Xue Weng, Livia Poliquin, Ilhem Lazizi
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Unsupervised Deep Learning Method for Clustering KAGRA O3GK Transient Noise Data
Yubin Kim, Kihyun Jung and Kyujin Kwak
The advent of ground-based gravitational wave detectors has significantly improved the detection of faint gravitational wave signals. However, these detectors are affected by various types of transient noise, known as glitches, which can mimic true gravitational wave signals and limit detector sensitivity. Classifying glitches according to their time-frequency characteristics not only facilitates a deeper understanding of their origins, but also supports their mitigation on data to maintain data quality. While supervised machine learning methods are commonly employed for glitch classification, they require the labelling of training
datasets obtained through manual annotation, a process which is costly and not scalable for evolving detectors. In order to address this challenge, the present study investigates unsupervised deep learning methods for dimensionality reduction and clustering of glitch spectrogram images. In this study, three distinct approaches are applied and compared using data from the KAGRA detector's O3GK run. The findings of this study demonstrate that deep learning-based feature extraction significantly enhances the clustering performance compared to traditional machine learning methods. This study presents an initial analysis of the KAGRA glitch
dataset using unsupervised deep learning, highlighting the potential of this approach for efficient and scalable glitch classification in future observation runs.
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Cosmology and Nongalactic Astrophysics
Chebyshev interpolation in Einstein-Boltzmann codes
Herman Sletmoen
Einstein-Boltzmann codes compute theoretical predictions of cosmological models and rely heavily on interpolation in their independent variables: time $\tau$, wavenumber $k$ and multipole $\ell$. We give a practical summary of interpolation with Chebyshev
polynomials, which converges rapidly for smooth functions and thus pairs naturally with approximation-free Einstein-Boltzmann codes. By solving the perturbations and line-of-sight integrals at Chebyshev nodes in $k$ and $\ell$, we show that Chebyshev
polynomials interpolate to higher precision than traditional cubic splines from fewer explicit solutions. On a set of example spectra for matter and the
cosmic microwave background (CMB), we find up to four orders of magnitude lower interpolation error using the same number of points. For a typical CMB temperature spectrum computed with interpolation in both $k$ and $\ell$, Chebyshev
polynomials converge to $10^{-4}$-$10^{-5}$ relative error with only 50-80 points per variable, while cubic splines approach $10^{-4}$ error with 200 points, translating to a $2.5\times$-$4\times$ speedup. The exact improvement depends on the target function and is generally more dramatic at high precision levels. Standard Chebyshev $\ell$-interpolation needs line-of-sight integrals generalized to non-integer $\ell$, but we show a way to avoid this by rounding the nodes to integers. Chebyshev interpolation is implemented in SymBoltz, which is available at https://github.com/hersle/SymBoltz.jl.
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Astrophysics of Galaxies
Spatially resolved molecular gas conditions in the circumnuclear disc of 3C 84
Bin Jia, Tom Oosterloo, Serena Viti et al. (+1 more)
The brightest cluster
galaxy NGC 1275, at the centre of the Perseus cluster, hosts the
radio-loud AGN 3C 84 and a circumnuclear disc (CND) of cold molecular gas onto which large-scale CO filaments accrete, yet the physical and chemical conditions of the gas in the CND remain poorly constrained. We present a spatially resolved analysis of ALMA CO(2-1), HCN(3-2), and HCO$^+$(3-2) observations at 72 pc. The data are partitioned into beam-sized hexagonal regions and modelled with a
Bayesian framework that couples a neural network emulator of time-dependent chemistry (UCLCHEM) with non-LTE radiative transfer (SpectralRadex) to infer the gas density, kinetic temperature, and
cosmic ray ionisation rate in each region. All three line ratios peak in the inner disc and decline with radius. The inference shows radial gradients in density ($\log_{10} n({\rm H_2}) \approx 6.3$ to $\sim 5$), kinetic temperature (~200 K to ~160 K), and
cosmic ray ionisation rate ($\log_{10}(\zeta/\zeta_0) \approx 4.9$ to $\sim 3$). Despite the powerful
radio AGN, the observed HCN(3-2)/HCO$^+$(3-2) ratio remains $\lesssim 1$ across the disc. Our modelling attributes this to optical depth saturation of HCN(3-2) ($\tau \sim 1$-3), which suppresses the intensity ratio even when the HCN abundance exceeds that of HCO$^+$ by a factor of three or more. The HCN/HCO$^+$ intensity ratio therefore cannot be used as an abundance diagnostic without accounting for optical depth, and a low ratio does not necessarily imply weak AGN influence on the chemistry. Azimuthally resolved profiles suggest a localised HCO$^+$/CO enhancement at the western disc boundary, coinciding with the filament-disc
accretion interface and consistent with shock processing by velocity shear between the infalling filaments and the rotating disc. These results indicate that the CND is shaped by
accretion from its filamentary environment.
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All authors Bin Jia, Tom Oosterloo, Serena Viti, Raffaella Morganti
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Testing $f(Q)$ Gravity with DESI DR2 and Strong-Lensing Time Delays
Darshan Kumar, Saibal Ray, Fengge Zhang et al. (+3 more)
Symmetric teleparallel
gravity provides an alternative description of gravitation in which non-metricity replaces
curvature and torsion. Its extension through $f(Q)$
gravity offers a different
geometric description of the late-time expansion of the Universe and its accelerated phase. In this work, we investigate two $f(Q)$ models, a normalized power-law model and a square-root exponential model, and test their ability to describe the late-time expansion history. We constrain the model parameters through Markov chain Monte Carlo analyses using
Cosmic Chronometer measurements, DESI DR2 baryon acoustic oscillations, strong-
lensing time-delay observations, and three Type Ia
supernova compilations, Pantheon$^+$, Union 3.0, and DES Y5. We compare both models with the flat $\Lambda$CDM model using the minimum $\chi^2$, Akaike information criterion, and
Bayesian information criterion. The square-root exponential model provides a better statistical fit than $\Lambda$CDM for the combinations of
Cosmic Chronometer, DESI DR2, and strong-
lensing time-delay data with Pantheon$^+$ and Union 3.0, with improvements in both the goodness of fit and information criteria. The normalized power-law model remains statistically competitive with $\Lambda$CDM for the
supernova-inclusive combinations, although the information criteria do not favor its additional parameter. We also determine the transition
redshift from
cosmic deceleration to acceleration for both models, obtaining consistent values across the different
dataset combinations. The transition
redshifts agree with observational estimates of the
cosmic acceleration epoch. Overall, our results support $f(Q)$
gravity as a viable alternative to $\Lambda$CDM for explaining the late-time accelerated expansion of the Universe without requiring a cosmological constant.
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All authors Darshan Kumar, Saibal Ray, Fengge Zhang, Nisha Rani, Praveen Kumar Dhankar, Jie Zheng
Instrumentation and Methods for Astrophysics
NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II
Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer et al. (+21 more)
NIRC2, the Near Infrared Camera 2 on the Keck II
telescope, was recently upgraded with a new suite of polarimetric observing modes. The new polarimetry modes (referred to as NIRC2-Pol) open up a wide range of new studies, including investigations of
exoplanets, the Galactic center, active galactic
nuclei, and solar system objects. The new modes enabled by the upgrade span the 1.1 to 4.1 micron range (i.e. J through L' bands) and include imaging polarimetry, coronagraphic imaging polarimetry, and spectropolarimetry. NIRC2-Pol is unique, as Keck II is the largest
telescope (10 m) on which AO-fed infrared polarimetry capabilities are available, one of few with L' polarimetric imaging, and the only one where there is both a polarimetric mode and a
vortex coronagraph. Here, we introduce the design of NIRC2-Pol, its capabilities, and its current operational status. We also present its first on-sky results: the first L' polarimetric images of the AB Aurigae circumstellar disk. These images more clearly reveal the disk's iconic spiral arms than previous L' total intensity imaging.
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All authors Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer, Eduardo Marin, Jayke S. Nguyen, Carlos Alvarez, Jaren N. Ashcraft, Mahawa Cisse, Charles-Antoine Claveau, Greg Doppmann, Michael P. Fitzgerald, Matthew Freeman, Trisha Hammen, Ryan Hersey, Nemanja Jovanovic, Scott Lilley, Jessica Lu, James E. Lyke, Keith Matthews, Dimitri Mawet, William Melby, Thomas McIntosh, Max Service, Jacob Taylor
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Global uniqueness of Kerr black hole spin and inclination from a segment of the critical curve
Kenta Hioki
High-resolution observations are expected to probe the
photon-ring structure of black hole images. The critical curve is the geometrically defined limiting locus on the observer's screen toward which successive higher-order
photon subrings accumulate. For a Kerr black hole, the shape of this limiting curve depends on the dimensionless
spin parameter $a$ and the inclination angle $i$. We investigate whether these parameters can be determined uniquely from a connected positive-length segment of the critical curve when the segment's position and orientation on the screen are unknown. For rotating non-extremal Kerr black holes with $0<a<1$ and $0<i\leq\pi/2$, we prove global uniqueness: if two such segments coincide as point sets after orientation-preserving rigid motions of the screen, then their Kerr parameter pairs coincide and the two rigid motions are identical. The proof uses an irreducible implicit
polynomial to show that a segment determines the full algebraic curve containing it and then recovers the parameter pair $(a,i)$ from rigid-motion invariants of that
polynomial.
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Cosmology and Nongalactic Astrophysics
First application of weak lensing peak steepness statistics to HSC Y1 data: effectively probing halo density profiles
Ziwei Li, Xiangkun Liu, Tianyu Zhang et al. (+5 more)
As a new probe, the weak
lensing (WL) peak steepness statistics is sensitive to the density profile of
halos that encodes important information of baryonic feedback and dark matter properties, leading to a promising means to statistically constrain these effects using WL data. In this article, we present its first application to HSC Y1 data to demonstrate the great potential of this new statistics. Within the phenomenological framework of HMcode2016 that attributes the baryonic feedback solely to the reduction of the
halo concentration parameter and focusing on high peaks originated dominantly from massive clusters, our analyses by combining WL peak height and steepness statistics resulted in $S_8=0.76^{+0.08}_{-0.07}$ with the maximum-a-posteriori (MAP) of $0.79$ and low concentrations. Taking the form of the concentration-mass relation as $c(M,z)=A(1+z_{\rm f})/(1+z)$ with $z_{\rm f}$ being the formation
redshift of
halos with mass $M$ at
redshift $z$, we obtain $A=1.93^{+1.33}_{-1.16}$ (MAP=$1.70$) in comparison with $A=3.34^{+1.52}_{-1.74}$ (MAP=3.31) from dark matter only simulated mocks. The result tends to support phenomenologically strong baryonic feedback effects at cluster scales.
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All authors Ziwei Li, Xiangkun Liu, Tianyu Zhang, An Zhao, Chuzhong Pan, Shuo Yuan, Qiao Wang, Zuhui Fan
Solar and Stellar Astrophysics
The Interplay of Magnetic Fields, Turbulence and Vorticity in Core-Collapse Supernovae
David Calvert, Michael Redle, Bibek Gautam et al. (+4 more)
The convective turbulent motion of the fluid below the shock in a core-collapse
supernova stretches and amplifies the
magnetic field of the progenitor
star. The energy contained in the field is sourced from the work done by the fluid on the field which comes at the expense of the fluid's kinetic and internal energy. In addition to the energy exchange with the fluid, the
magnetic field also has a back-reaction upon the fluid via a contribution to the baroclinic vector and thus affects the fluid vorticity. In this paper we explore the interaction of the
magnetic field with the fluid in core-collapse
supernovae using the ELEPHANT code with solar-
metallicity stars of 15 and 20 \msun zero-age main sequence mass and purely toroidal initial
magnetic fields of $B_0 = 0, 10^{10}, and 10^{12}$~G. We find that the
magnetic field in the gain region does not become so large that it alters the global dynamics above the 10% level in the early post-bounce
evolution. The turbulent kinetic energy of the fluid in the gain region is smaller in simulations with a strong initial
magnetic field, but the exact amount of reduction is uncertain due to limitations of the methods for measuring turbulent kinetic energy. The structure of the field in the simulations quickly becomes a tangled mass of flux ropes as soon as convection begins, which leads to a large
magnetic field contribution to the baroclinic vector that dominates over the hydrodynamic contribution. Although governed by very similar transport equations to the
magnetic field, the fluid vorticity and
magnetic field are always close to being randomly aligned at every stage of the
evolution. The enstrophy, which is seen to be closely associated with the turbulent kinetic energy, is found to be reduced in simulations with a strong initial
magnetic field supporting the inference that the
magnetic field reduces the amount of
turbulence in the fluid.
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All authors David Calvert, Michael Redle, Bibek Gautam, Carles J. Stapleford, Carla Frohlich, James P. Kneller, Matthias Liebendoerfer
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The Bondi Dipole in Full Numerical Relativity: a Self-Accelerating Positive-Negative Mass Binary
Nikita M. Shirokov
Bondi showed in 1957 that bodies of opposite active gravitational mass self-accelerate: the negative chases the positive it repels, and the pair runs off together. We evolve this "Bondi dipole" in $3+1$ numerical relativity: two complex scalars share identical Klein-Gordon dynamics; only the phantom enters Einstein's equations with a minus sign – inertial and passive masses positive, active mass negative. Across a
matrix of thirty-four evolutions – runaway pairs, controls, and parameter scans – a mass-matched pair released at rest accelerates as a unit. The midpoint moves $3.00\pm0.01$ by $t=200$ with the separation held to 1%, and reaches a speed of $0.056c$ by $t=400$ with the acceleration steady to 2%; the total signed momentum holds at zero to $\lesssim 1$%. The force is
gravity on both of its axes: $a\propto d^{-2.03\pm0.01}$ over $d=8$ to $20$, $a\propto M^{0.97\pm0.06}$ over a factor $2.5$ in mass, and $a\,d^2/\bar{M}=1$ within 2.4% on the equal-mass ladder. Swapping the sectors inverts the acceleration to two parts in $10^5$; gauge, solver-depth and mesh variations move the drift by $\lesssim 0.01$% and box doubling by 4%; same-sign control pairs hold their centroids to $\lesssim 8\times10^{-4}$ even while merging. The runaway carries no detectable gravitational radiation: the signed dipole cannot radiate, the quadrupole's $\ddot{Q}$ is constant, and the measured $\ell=2$ amplitude falls as $r^{-4.8}$ – near zone, not flux. The phantom
star is, to our knowledge, the first asymptotically flat body of negative ADM mass evolved in numerical relativity; alone it survives to $t=1000$, slowly relaxing outward.
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Astrophysics of Galaxies
Estimator forensics for the wide-binary gravity test: the eccentricity-triple coupling manufactures a pseudo-signal, and a pre-registered protocol for Gaia DR4
Hicham Boufourou
Analyses of Gaia DR3 wide binaries reach opposite verdicts on a claimed low-acceleration anomaly: gamma = Geff/G ~ 1.4 (Chae 2023-2026; Hernandez et al. 2024) versus Newtonian at high significance (Banik et al. 2024; Pittordis et al. 2025), from the same catalogue. We localize the disagreement experimentally. A generative model – Keplerian binaries plus hierarchical triples with photocentre and time-averaging effects – is validated without tuning against Pittordis et al. (2025). Synthetic catalogues of known truth are confronted with three
estimator families: a full-median
estimator, even with a perfect eccentricity correction, recovers gamma = 1.08-1.13 from purely Newtonian universes containing 20-30% residual triples – half-way to the claimed anomaly – while a tail-truncated
estimator and a mixture likelihood recover <= 1.04 and 1.00. An injected MOND-like boost (gamma = 1.4 above 2 kau) is recovered at >= 1.26 by all three: the hypotheses never overlap under robust estimation, so the controversy is decidable. Applying the calibrated
estimators to the 81,088-pair Chae (2024) sample we measure gamma = 1.045 [1.025, 1.068] (2-30 kau), and a joint mixture fit gives gamma = 1.05 [1.04, 1.07] with f_trip = 0.15, consistent with the independent 0.17; gamma = 1.4 is rejected at ~16 sigma. We freeze a pre-registered protocol, time-stamped on Zenodo, for Gaia DR4, where sigma_stat(gamma) < 0.005 will make
estimator systematics fully dominant.
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High Energy Astrophysical Phenomena
A Broadband X-ray Analysis and Optical Counterpart Search of IC5052 ULX
Nabil Brice, Dominic J. Walton, Felix Fürst et al. (+10 more)
We present broadband X-ray spectral and timing analysis of the Ultra-luminous X-ray source (ULX) in IC5052 using simultaneous XMM-Newton and NuSTAR observations from 2022, supplemented by archival 2013 XMM-Newton data. A two-thermal component model, often interpreted as radially-segregated emission from a super-Eddington inner disc and its associated wind, provides a statistically acceptable fit but yields an implausibly high inner disc temperature of $k T_\mathrm{in} \approx 6.4$ keV, inconsistent with even super-Eddington disc models. Including an additional continuum component from either an
accretion column or a Comptonizing corona, as motivated by high S/N observations from other ULXs, provides comparable goodness of fit while allowing plausible inner disc temperatures. The
accretion column model yields $k T_\mathrm{in} \approx 1.2$ keV with the column contributing $F_\mathrm{col} \approx 62\%$ of total flux, while the Comptonizing corona model yields $k T_\mathrm{in} \approx 3.0$ keV with a scattered fraction $\sim 1$, assuming the hotter disc provides the seed
photons. Timing analysis initially challenges both scenarios: the
accretion column model places IC5052 ULX where prior results suggest pulsations may be detectable ($F_\mathrm{col} \sim 62\%$), yet none were detected, while the corona model appears inconsistent with its lack of observed short-timescale variability. However, incorporating spectral information relaxes these constraints, allowing both models to remain physically plausible for IC5052 ULX. Finally, using improved Chandra astrometry, we identified a candidate optical counterpart consistent with an evolved high mass donor. A discrepancy between the optical extinction and X-ray fitted absorption suggests localised X-ray absorption.
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All authors Nabil Brice, Dominic J. Walton, Felix Fürst, Daniel Stern, Amy H. Knight, Matteo Bachetti, Matthew J. Middleton, Alistair Pagan, Tim P. Roberts, Murray Brightman, Hannah P. Earnshaw, Fiona A. Harrison, Sean N. Pike
High Energy Astrophysical Phenomena
Assessing the Credibility of Gamma-Ray QPO Candidates in 41 TeV-Selected Blazars
Wen-Xin Yang, Yi Liu, Hong-Guang Wang et al. (+2 more)
We analyze quasi-periodic oscillation (QPO) candidates in the 0.1-100 GeV Fermi-LAT light curves of 41 TeV blazars with a conservative, multi-stage timing analysis combining FFT power spectra, red-noise Monte Carlo simulations, false-discovery-rate control, bootstrap period uncertainties, split-sample cross-validation, Lomb-Scargle and WWZ diagnostics, a detection-only sensitivity test, observingwindow checks, and injection-recovery experiments. A first-pass FFT search flags 16 sources above a raw 95% level and six strong candidates after data-quality and split-sample filtering, none satisfying a fully automated multi-method tier. Source-level significance is quantified with forward simulations that preserve the observed sampling and non-Gaussian flux distribution, treating the red-noise slope as a nuisance parameter and never assuming independence of periodogram powers. At simulation-selected reference slopes, only two of the 41 sources reach a raw source-level p < 0.05,only J1555.7+1111 reaches Benjamini-Hochberg significance, and none survives Benjamini-Yekutieli correction. No source survives the conservative slope envelope. Even J1555.7+1111, which the first-pass search flagged as significant but did not rank among its strong candidates, has a global p-value that rises to 7.5*10^-3 under the least favorable slope (~ 0.31 after the full-sample search), so it is not a robust detection. With substantial period uncertainties, a weak observing window, and limited injection-recovery sensitivity, we establish no robust gamma-ray QPO detection: a sampling-faithful red-noise treatment substantially contracts the candidate set, providing an explicit assessment of QPO credibility.
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All authors Wen-Xin Yang, Yi Liu, Hong-Guang Wang, Denis Bastieri, Jun-Hui Fan
High Energy Astrophysical Phenomena · Cross-listed from nucl-ex
Cluster emission and its impact on the r-process nucleosynthesis
Natalia Thomas, Silvia Bara, Thomas Elias Cocolios et al. (+20 more)
Cluster emission is an exotic decay mode between alpha-decay and fission, in which a parent
nucleus emits a cluster of nucleons heavier than an alpha-particle, but lighter than what is usually considered a fission fragment. The properties of cluster emission were investigated by analyzing five high-energy events detected in a spectrum of a mass A = 230 beam produced at ISOLDE (CERN). Under the assumption that these events were caused by cluster emission, the most likely parent-cluster pair responsible for the five high-energy events, was found to be $^{230}Ra$ emitting $^{22}O$, with a branching ratio of $(4.3$ +\- $1.9) \times 10^{-9}$. Four analytical formulas were used to estimate the partial half-lives of cluster emission for a group of
neutron-rich
nuclei. The decay rate was calculated for a selection of cluster
nuclei for each parent isotope. The rates of all decay channels of cluster emission per parent
nucleus were then included in calculations of the r-process nucleosynthesis in a
neutron star merger in order to study the possible impact of cluster emission on the r-process nuclear production. The resulting isotopic abundance distributions were compared to those calculated for a case in which cluster emission was not considered. It was found that the inclusion of cluster emission decay rates from the simple analytical formulas available nowadays does not influence the results of the r-process nucleosynthesis.
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All authors Natalia Thomas, Silvia Bara, Thomas Elias Cocolios, Stephane Goriely, Boris Andel, Andrei N. Andreyev, Alberto Camaiani, James G. Cubiss, Hilde De Witte, Zoe Favier, Michael Heines, Fedor Ivandikov, Jake D. Johnson, Jozef Klimo, Razvan Lica, Jozef Mišt, Chris Page, Riccardo Raabe, Adam Sitarčík, Viktor Van Den Bergh, Piet Van Duppen, Zixuan Yue, Ahmed Youssef
High Energy Astrophysical Phenomena
Probing the Three-Dimensional Structure of a Jet with Faraday Tomography
Sawera Gull, Masaya Kurogi and Keitaro Takahashi
Magnetic fields play a fundamental role in the dynamics and radiation of jets associated with active galactic
nuclei (AGNs), where they accelerate and collimate the relativistic
plasma and produce the observed synchrotron emission. Faraday
tomography is a powerful technique for probing the three-dimensional distribution of
magnetic fields and synchrotron-emitting
plasma along the line of sight, by reconstructing the Faraday Dispersion Function (FDF) from the observed polarization spectrum. To explore what aspects of AGN-jet structure can be revealed by Faraday
tomography, we construct a simple three-dimensional model of an AGN jet that captures its essential features, and compute the resulting FDF for a range of model parameters. The jet is represented as a cylindrical region of uniform thermal-electron density threaded by a coherent helical
magnetic field, to which a random turbulent component can optionally be added. The parameters varied include the inclination angle {\theta} between the jet axis and the line of sight, the wavenumber of the helical field, and the amplitude of the random
magnetic-field component. By systematically varying these parameters, we examine how the underlying
magnetic geometry and
turbulence are encoded in the observable Faraday and polarization structures. The main observational signatures identified by our model include top-bottom asymmetry across the jet, curved or double peaked FDF profiles and increasingly fragmented Faraday depth structure along longer lines of sight, providing potential diagnostics of large scale helical
magnetic fields and small scale turbulent components. These signatures providing a physical framework for interpreting future polarimetric observations of AGN jets from instruments such as LOFAR, MeerKAT, and the VLA.
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Instrumentation and Methods for Astrophysics
A high-isolation wideband channelizer for MKID readouts: a custom HLS implementation on RFSoC
Alberto Hernandez Fernandez, David Diaz Martin, Jose Javier Diaz Garcia et al. (+4 more)
We present a high-performance channelizer for Microwave Kinetic Inductance Detectors (MKIDs), designed to mitigate spectral leakage and scalloping loss through a 50% overlapping polyphase filter bank (PFB). The design is implemented on a Xilinx Zynq UltraScale+ RFSoC ZCU111 using a custom design - primarily in Vitis High-Level Synthesis (HLS), with the time-critical output serializer and glue logic in VHDL - that processes a 4.096 GSPS input stream with a per-branch super-sample rate (SSR) of 16. Rather than relying on aggressive 512 MHz clocking and vendor IP cores, our split-path architecture computes the delayed and non-delayed polyphase branches concurrently, so that the bulk of the channelizer operates at a robust 256 MHz while a single 512 MHz subdomain is confined to the BRAM-to-FFT section. This architectural parallelism enables a deep 16-tap prototype filter that doubles the filter depth of comparable high-speed systems and substantially improves channel isolation. We report the complete internal architecture of the reordering engine that implements the overlap, including two implementation hazards not documented in prior art: a pipeline-stage skew affecting state toggles in HLS, and the state-preservation requirements of a restartable design. The 2/1 overlapped channel response is validated in simulation - recovering the ~3.9 dB scalloping loss of a critically sampled channelizer to below 0.1 dB across the full 2 MHz channel - and characterized systematically with a 100-tone batch frequency sweep, while the parent readout system has been operated cryogenically with an MKID array in an adiabatic demagnetization refrigerator (ADR), identifying individual resonators in total darkness. The result is a resource-efficient, high-isolation
benchmark for wideband frequency-division-multiplexed readouts.
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All authors Alberto Hernandez Fernandez, David Diaz Martin, Jose Javier Diaz Garcia, Roger John Hoyland, Luis Fernando Rodriguez Ramos, Diego Portero Rodriguez, Silvestre Rodriguez Perez
Solar and Stellar Astrophysics · Cross-listed from physics.space-ph
Comprehensive solar eruption analyses enabled by the tools of the SOLER project
Nina Dresing, Jan Gieseler, Markus Baumgartner-Steinleitner et al. (+26 more)
Solar eruptions comprise of a multitude of phenomena such as
flares, coronal mass ejections (CMEs), large-scale coronal waves,
radio bursts, and energetic particles traveling through interplanetary space. These phenomena are observed with a variety of instrumentation, including remote sensing and in-situ detectors. Obtaining a global understanding of a solar eruption often requires the analysis of various of these different
datasets, including a multitude of analysis and modeling tools and a wide range of expertise. Usually, such a comprehensive analysis can only be achieved by a skilled and broad team. The Energetic Solar Eruptions: Data and Analysis Tools (SOLER) project aims at creating a comprehensive analysis platform for the study of solar eruptions that allows a single user to easily apply analysis methods addressing various counterparts of the solar event. Therefore, each partner of the project developed Python-based software, including interfaces in the form of Jupyter Notebooks, which provides application examples and concise step-to-step documentation. In this paper we introduce the comprehensive solar-eruption-analysis infrastructure developed within the SOLER project. We explain where to find the software, how to use it, and give dedicated use-case examples of how to employ selected tools in a combined manner.
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All authors Nina Dresing, Jan Gieseler, Markus Baumgartner-Steinleitner, Carine Briand, Karin Dissauer, Annamaria Fedeli, Robert Jarolim, Jaclyn T. Lang, Diana E. Morosan, Jake A. J Mitchell, Christian Palmroos, Jens Pomoell, Jinge Zhang, Otso Santala, Astrid M. Veronig, Laura Vuorinen, Alexander Warmuth, Oliver Flor, Myrthe Flossie, Emilia K. J. Kilpua, Werner Pötzi, Daniel J. Price, Antonio Gomes, Emil J. Hotti, Ruth A. Hyndman, M. Liebel, Amaia Razquin, Song Tan, Ramio Vainio
Cosmology and Nongalactic Astrophysics
CMB Birefringence from Axion String Networks Calibrated to an AMR Simulation
Mustafa A. Amin, Mudit Jain, Andrew J. Long et al. (+3 more)
A cosmological network of
axion strings may exist in the Universe today. If
axion-like particles couple to electromagnetism, such a network induces spatially varying birefringence in the polarization of the
cosmic microwave background (CMB), which can be probed by current and next-generation CMB experiments. We calibrate a loop-crossing model against a large-scale adaptive-mesh-refinement (AMR) simulation of
axion-string network dynamics in the early Universe and use the calibrated model to predict CMB birefringence from recombination to today. We find that the non-detection of anisotropic birefringence in CMB observations places a strong upper bound on the electromagnetic anomaly coefficient $\mathcal{A}$ that enters the
axion-
photon coupling $g_{a\gamma\gamma} = - \mathcal{A} \alpha_\mathrm{em} / \pi f_a$. A joint analysis of available anisotropic birefringence measurements constrains $|\mathcal{A}| < 0.24$ at 95% C.L., which is independent of the Peccei-Quinn scale $f_a$, assuming that the
axions are hyperlight so that the network survives until today. This limit strongly restricts the high-energy
embedding of hyperlight
axions, excluding the minimal Grand Unified Theory prediction for the electromagnetic anomaly coefficient at high significance. In addition, we discuss the implications of an
axion-string origin for the recently reported evidence of isotropic birefringence.
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All authors Mustafa A. Amin, Mudit Jain, Andrew J. Long, Aden Pugsley, Moira Venegas, Magdalena Whelley
Instrumentation and Methods for Astrophysics
Forward modelling coronagraphic images with a fully physical, differentiable digital twin of MagAO-X: first laboratory results
Matthijs Mars, Sebastiaan Y. Haffert, Louis Desdoigts et al. (+10 more)
Post-processing of high contrast imaging data relies on an accurate model of the stellar point spread function (PSF). Current techniques build this model from the science images themselves, using observational diversity (e.g., angular, spectral or polarimetric diversity), which can cause self-subtraction of the companion signal and constrains the observing strategy. Telemetry-based forward modelling instead builds the stellar PSF model from wavefront sensor data that is already recorded during the observation. The wavefront sensor measures the coherent starlight and can therefore be used to create a PSF model that only models the stellar light and does not reproduce the incoherent light of a companion. We present a fully physical and differentiable digital twin of the focal plane low-order wavefront sensor (FLOWFS) and the coronagraphic science beam of the MagAO-X instrument, implemented in dLux, and calibrate it on laboratory data. When fitted directly to the science images, the model reproduces the coronagraphic PSF down to the
photon and read noise floor of the data. When instead forward modelled from the FLOWFS telemetry alone, the residuals reach $6\times10^{-5}$ of the stellar peak at $5\ \lambda/D$, a factor of 5 below the raw contrast, with the remaining residual set by how well the wavefront estimate transfers from the FLOWFS branch to the science branch of the model. An injected companion at $5\ \lambda/D$ with a peak contrast of $10^{-3}$ is recovered without measurable self-subtraction. We discuss the model improvements currently under development and the path towards on-sky validation.
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All authors Matthijs Mars, Sebastiaan Y. Haffert, Louis Desdoigts, Joseph D. Long, Rico Landman, Jared R. Males, Laird M. Close, Kyle Van Gorkom, Olivier Guyon, Alexander D. Hedglen, Sandrine Juillard, Jennifer Lumbres, Lauren Schatz
Instrumentation and Methods for Astrophysics
NEXT: The Netherlands EXoplanet Testbed I. Goals and opto-mechanical design
Rico Landman, Sebastiaan Haffert, Louis Desdoigts et al. (+7 more)
We report on the goals, design, and ongoing development of the Netherlands
EXoplanet Testbed (NEXT), a high-contrast imaging testbed under construction in Leiden. NEXT is designed to develop and validate technologies and
algorithms for extreme adaptive optics (XAO) and coronagraphy at the performance levels required by the next generation of high-contrast imagers on the Extremely Large
Telescopes (ELTs) and future space observatories. All powered optics in the common path are custom off-axis parabolas, making the bench fully reflective up to the science cameras, and it operates from the visible to the near-infrared (500-1800 nm). It combines a woofer-tweeter XAO module, using an ALPAO woofer and a Boston Micromachines kilo-DM as tweeter, with a coronagraphic arm that supports common coronagraph architectures and focal-plane wavefront control for dark-hole digging, and reserves space for a suite of wavefront sensors. The design targets a raw contrast of $10^{-7}$ (goal: $10^{-8}$) at $5\lambda/D$ and 800 nm. We present the opto-mechanical design of the testbed, the key trade-offs made to reach these contrast levels, and Fresnel-propagation simulations of its predicted performance.
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All authors Rico Landman, Sebastiaan Haffert, Louis Desdoigts, Matthijs Mars, Dhwanil Patel, Daniel Smith, Remko Stuik, Adam Taras, Elena Tonucci, Yinzi Xin
Instrumentation and Methods for Astrophysics
No need to modulate: On-sky results of a Neural Network enhanced pyramid wavefront sensor and prospects for the ELTs
Rico Landman, Liam Koning, Sebastiaan Y. Haffert et al. (+20 more)
One of the main limitations of ground-based extreme adaptive optics systems (XAO) is the balance between the temporal and
photon noise error. The unmodulated Pyramid Wavefront Sensor (uPWFS) promises significant gains in sensitivity over its modulated counterpart, but its practical use is limited by its linearity range. Nonlinear reconstructors provide a pathway to recover this dynamic range while preserving the sensitivity of the uPWFS, thereby reducing
photon noise and improving contrast. We present the real-time implementation of a Convolutional Neural Network (CNN) reconstructor and show on-sky results with MagAO-X, demonstrating robust and stable correction across diverse atmospheric conditions. Significant gains over default operation are seen in the low and moderate Strehl regimes, while the performance is slightly degraded in the high Strehl regime. We diagnose this in simulation and mainly attribute this to a non-optimized training
dataset for the high-Strehl regime, rather than a fundamental limitation of the approach. Furthermore, initial simulations of the NN-enhanced uPWFS for a downscaled version of the Extremely Large
Telescope (ELT) show substantial gains for fast petal-piston control. These results demonstrate that NN-enhanced wavefront sensing is a viable technology for future high-contrast instruments.
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All authors Rico Landman, Liam Koning, Sebastiaan Y. Haffert, Joseph D. Long, Jared R. Males, Matthijs Mars, Laird M. Close, Olivier Guyon, Warren B. Foster, Kyle Van Gorkom, Alexander D. Hedglen, Parker T. Johnson, Maggie Y. Kautz, Jay K. Kueny, Jialin Li, Joshua Liberman, Miles Lucas, Jennifer Lumbres, Eden A. McEwen, Avalon McLeod, Lauren Schatz, Elena Tonucci, Katie Twitchell
Cosmology and Nongalactic Astrophysics
Gaussian process reconstruction of scalar field dynamics from recent cosmological data
Afaq Maqsood, Sonej Alam and Md. Wali Hossain
We reconstruct the late-time expansion history and dark energy dynamics using available cosmological data. We consider dark energy as an effective minimally coupled canonical scalar field without assuming a specific form for its potential. For reconstruction, we use Gaussian Process (GP) regression with a joint
dataset consisting of 32
cosmic chronometer measurements (CC32), DESI DR2 baryon acoustic oscillation data, three Type Ia
supernova compilations (Pantheon+, Union3, and DES Y5), and compressed CMB distance priors. From the reconstructed Hubble parameter and its derivatives, we obtain the scalar field kinetic and potential energy densities, the equation of state $w(z)$, and the dimensionless slope parameter $|\lambda(z)|$ of the scalar field potential. The reconstructed potential is nearly constant at late times, with $\tilde{V}(0) \simeq 0.68$–$0.70\rho_{c,0}$, close to the dark-energy density in flat $\Lambda$CDM. The kinetic term remains small over $0 \lesssim z \lesssim 2.5$, while $w(z)$ remains close to $-1$ within the uncertainties. Using only CC32 and DESI DR2, we find a mild ($1\sigma$) hint of a phantom-divide crossing near $z\sim0.5$. However, this feature depends on the
supernova compilation and cannot be regarded as a firm conclusion with current data. The slope parameter $|\lambda(z)|$ shows mild
evolution, with present-day central values around $0.8$–$1.0$, but large uncertainties due to its dependence on higher-order derivatives of the expansion history. The
curvature parameter $\Gamma(z)$ requires even higher-order derivatives and is not constrained by current data; therefore, we do not report its reconstruction. Allowing small spatial
curvature, $\Omega_k=0$–$0.02$, changes the results only slightly and remains within the existing uncertainty bands.
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Cosmology and Nongalactic Astrophysics
Dark-to-black super-accretion as a spin-imprinting mechanism for supermassive Kerr black holes
Saeed Fakhry, Nicolas Sanchis-Gual, Jorge Castelo Mourelle et al. (+2 more)
The existence of supermassive black holes with masses $M\gtrsim10^9\,M_{\odot}$ and large dimensionless
spins $\chi\sim0.9-0.99$ at high
redshift remains a challenge to our understanding of the early Universe. In this work, we study the adiabatic co-
evolution of a Kerr black hole seed surrounded by two ultralight scalar dark matter clouds occupying different bound states, and show that this configuration allows the black hole to grow into the supermassive mass range while imprinting a characteristic final
spin. The
evolution proceeds through two stages. During the first stage, a spherical cloud described by the $\ell=0$ mode is completely depleted through a runaway dark-to-black
accretion mechanism on a timescale of hundreds of millions of years for
boson masses $\mu\sim10^{-18}-10^{-17}\,\mathrm{eV}$. Since the accreted material does not carry angular momentum, the black hole
spin is universally driven to $\chi\simeq0$, independently of its initial
spin. Throughout this stage, the second cloud, described by the $\ell=m=1$ mode, remains in the superradiant regime with negligible
evolution. However, once the first stage is completed, this cloud transitions to the accreting regime, rapidly transferring both mass and angular momentum to the black hole. Starting from $\chi\simeq0$, the black hole
spin increases until the
evolution self-consistently saturates close to the threshold $\chi_{\rm sat}$, defined by the condition $\Omega_H(\chi_{\rm sat})=\mu$, on an e-folding timescale of thousands of years, orders of magnitude shorter than the first stage. This final saturation
spin is largely independent of both the initial black hole
spin and the mass of the secondary cloud, providing a
spin-imprinting mechanism in which the primordial
spin is first erased by spherical
accretion and then reset to a value determined only by the
boson mass and the final black hole mass.
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All authors Saeed Fakhry, Nicolas Sanchis-Gual, Jorge Castelo Mourelle, Darío Núñez, Juan Carlos Degollado
Cosmology and Nongalactic Astrophysics
The Primordial power spectrum from the largest to smallest CMB scales
Debabrata Chandra, Dhiraj Kumar Hazra, Arman Shafieloo et al. (+1 more)
We reconstruct the primordial power spectrum (PPS) across the full range of cosmological scales accessible to
Cosmic Microwave Background (CMB) observations. Using the Modified Richardson–Lucy
algorithm, we perform free-form reconstructions through deconvolution of Planck PR3 and PR4, Atacama Cosmology
Telescope (ACT) DR6, and South Pole
Telescope 3G (SPT-3G) D1 data. Across different regularization schemes, we find no evidence for significant deviations from a power-law primordial spectrum. The reconstructed spectra show a strong correlation between Planck and ACT, even at the level of localized features over their overlapping range, $0.07 < k < 0.14\,\mathrm{Mpc}^{-1}$, demonstrating consistency between the two observations. Using a complementary parametric
Bayesian reconstruction, we find that the previously discussed preference for a blueward tilt in the ACT data at small scales is preferred only at the $1\sigma$ level.
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All authors Debabrata Chandra, Dhiraj Kumar Hazra, Arman Shafieloo, Tarun Souradeep
Earth and Planetary Astrophysics
Volatile depletion in rocky planets as a chemical fingerprint of hybrid accretion
Haiyang S. Wang, Anders Johansen, Ziyan Xu et al. (+7 more)
Volatile depletion in rocky
planets relative to their host
stars is commonplace in both the Solar System and exoplanetary systems, yet the connections between
planet formation and composition remain elusive. Here we model devolatilization during pebble
accretion in combination with collisional growth from volatile-depleted planetesimals to explore the formation pathways of Earth and Mars. Using
Bayesian inference, we find that bulk silicate Earth is best reproduced by ${\gtrsim}$75% contribution from two protoplanets formed via pebble
accretion, supplemented by up to $\sim$25% material from planetesimals that are compositionally akin to the asteroid Vesta. Using instead a planetesimal volatile-depletion curve that is not observed among known meteorite parent bodies would allow the planetesimal contribution to reach 40$^{+15}_{-14}$%. In comparison, bulk silicate Mars reflects 27$\pm$5% pebble-accreted material and 73${\pm}$5% Vesta-like planetesimals. We identify volatile depletion as a chemical fingerprint of hybrid
accretion, in which both pebble
accretion and collisional assembly contribute to terrestrial
planet growth. By quantitatively linking formation pathways to volatile budgets, our findings demonstrate how planetary
accretion histories can be inferred from elemental signatures, with broad implications for interpreting the chemical diversity of rocky
exoplanets.
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All authors Haiyang S. Wang, Anders Johansen, Ziyan Xu, Marie-Luise Steinmeyer, Michiel Lambrechts, Elishevah van Kooten, Chao-Chin Yang, Zhaohuan Zhu, Dante S. Lauretta, Martin Bizzarro
High Energy Astrophysical Phenomena
Fingerprints of thermal Comptonization in accreting neutron stars. Plasma-vacuum interplay in cyclotron lines and polarisation
E. Sokolova-Lapa, D. K. Maniadakis, J. J. R. Stierhof et al. (+11 more)
X-ray emission from accreting, strongly magnetised
neutron stars and its pulse-phase variability probe their
magnetic-field geometry,
spin orientation, and emission processes. Whether the radiation emerges mainly from a hot spot or column, and whether its properties are shaped by bulk or thermal Comptonization, remain debated across luminosity regimes. We aim to disentangle intrinsic emission from visibility effects and identify observables characteristic of thermal Comptonization in hot spots and columns. We therefore derived energy-dependent beam patterns and observable signatures without assigning the model to a luminosity regime, focusing on cyclotron-resonance and polarisation effects as tracers of anisotropy. To do so, we computed angle-dependent polarised broadband spectra, including the fundamental cyclotron line, for a homogeneous, self-emitting, magnetised Comptonizing
plasma over a broad parameter range. Accounting for light bending and projection, we obtained phase-dependent fluxes for different geometries and, for hot spots, observed linear polarisation. The beam patterns evolve with energy, driving pulse-profile changes. Near the cyclotron resonance,
plasma-
vacuum interplay produces a narrow central beam and side petals. Their visibility creates geometry-dependent dips, bumps, and M- and W-shaped structures in hot-spot pulsed fraction spectra, but only dips and bumps for columns. Thermally Comptonized cyclotron lines do not reliably trace
plasma temperature;
plasma-induced ellipticity and band averaging reduce observed soft-X-ray linear polarisation to 0-30%. Under typical X-ray
pulsar accretion-channel conditions, thermal Comptonization leaves robust energy-dependent anisotropic signatures. Energy-resolved pulse profiles, pulsed fraction spectra, and polarisation thus provide complementary diagnostics of
neutron star geometry, emission-region shape, and spectral formation.
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All authors E. Sokolova-Lapa, D. K. Maniadakis, J. J. R. Stierhof, E. Ambrosi, A. D'Aì, C. Ferrigno, N. Schettino, M. Middleton, A. Gúrpide, V. Grinberg, G. Lipunova, I. El Mellah, P. Kretschmar, J. Wilms
Astrophysics of Galaxies
Interstellar Aromatic Infrared Bands: IR absorption spectroscopy of the lowest triplet state of naphthalene
Priyanka Arvind Paunikar, Hugo Maurer, Lars Reems et al. (+5 more)
The aromatic infrared bands (AIBs), emission features observed ubiquitously across a wide variety of interstellar objects, are commonly attributed to radiative cooling of highly-excited ground-state vibrational levels of polycyclic aromatic hydrocarbons (PAHs) that are populated after UV absorption and internal conversion. However, for neutral PAHs intersystem crossing to the triplet
manifold, followed by radiative cooling of vibrational levels within the lowest excited triplet state is expected to be a competing relaxation channel. This state differs in vibrational frequencies, transition moments and internal energy, and therefore gives rise to different emission spectra. Despite their significance, neutral PAHs in their triplet states have remained largely unexplored, primarily because of the lack of direct spectroscopic access. Here, we report the first measurement of the infrared absorption spectrum of the lowest triplet state of naphthalene. The spectrum is markedly different from the vibrational spectrum of the singlet electronic ground state, displaying features that can help identifying PAHs in the triplet states in astronomical spectra. We also show that experimental spectra are closely reproduced by anharmonic frequency calculations. These findings serve as a stepping stone for detecting triplet-state PAHs in the interstellar medium and provide a basis for developing more accurate infrared emission models.
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All authors Priyanka Arvind Paunikar, Hugo Maurer, Lars Reems, Alessandra Candian, Sandra Brunken, Jos Oomens, Piero Ferrari, Wybren Jan Buma
Instrumentation and Methods for Astrophysics
Digging dark holes on-sky with the Self-Coherent Camera: Preliminary results
Elena Tonucci, Sebastiaan Y. Haffert, Jared R. Males et al. (+17 more)
Current high-contrast imaging instruments are limited by wavefront errors originating from non-common path aberrations (NCPAs) due, for example, to manufacturing errors in the optics and temperature drifts in the system. These create quasi-static speckles in the final science image that are difficult to distinguish from companions. Therefore, focal plane wavefront sensing and control is needed to suppress speckles. The Self-Coherent Camera (SCC) is a wavefront sensor that allows us to estimate the stellar complex speckle field. In the Fast Atmospheric SCC Technique (FAST), the on-axis starlight hits a coronagraphic focal plane phase mask and is diffracted outside the Lyot stop where it is spatially filtered by a pinhole to create a reference beam. The reference beam and the leaked starlight are recombined on the science plane, creating interference fringes that do not affect the companion, because of incoherence. The focal plane mask was manufactured in-house at Leiden University with Nanoscribe, a micro-3D-printer that uses two-
photon polymerization to achieve sub-micron precision in height. We present preliminary results of the first on-sky closed-loop SCC demonstration with the Magellan Adaptive Optics eXtreme (MagAO-X) instrument on the 6.5-meter Magellan Clay
telescope at Las Campanas Observatory, Chile. We achieve a 1-sigma raw contrast improvement of a factor 10 in the desired dark hole region with FAST closed-loop control. In the future, we will show observations of
stars with companions and use the SCC in post-processing as a Coherent Differential Imaging (CDI) technique to enhance the contrast even further.
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All authors Elena Tonucci, Sebastiaan Y. Haffert, Jared R. Males, Laird M. Close, Kyle van Gorkom, Olivier Guyon, Alexander D. Hedglen, Parker T. Johnson, Maggie Y. Kautz, Jay K. Kueny, Jialin Li, Joshua Liberman, Joseph D. Long, Jennifer Lumbres, Matthijs Mars, Eden A. McEwen, Avalon McLeod, María Eugenia Redondo González, Lauren Schatz, Katie Twitchell
Instrumentation and Methods for Astrophysics
On-sky demonstration of self-learning predictive control with MagAO-X
Sebastiaan Y. Haffert, Jared R. Males, Parker T. Johnson et al. (+13 more)
Direct imaging of
exoplanets is very tricky and requires extremely well corrected wavefronts. Especially low-order order modes are detrimental to the performance of coronagraphs at their inner-working angle. However, that is precisely where conventional AO systems have the highest residuals that are caused by servo-lag errors. This servo-lag error can be reduced with predictive control where the control anticipates the future state of the atmospheric disturbance. We use a self-learning model predictive controller based on the concepts from sub-space predictive control (SPC). We present a novel implementation of the SPC by using an online QR-decomposition based recursive least squares approach. This approach has now been used for self-learning control of vibrations on the MagAO-X instrument. We see on average an Strehl increase of 15 percent and a decrease of the jitter to 0.9 mas. I will discuss how we have implemented the controller and its on-sky perfomance.
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All authors Sebastiaan Y. Haffert, Jared R. Males, Parker T. Johnson, Laird M. Close, Olivier Guyon, Jay Kueny, Joshua Liberman, Joseph D. Long, Miles Lucas, Eden McEwen, Tiffany Nguyen, Adam K. Taras, Kyle Van Gorkom, Maggie Kautz, Katie Twitchell, Lauren Schatz
Instrumentation and Methods for Astrophysics
Sub-diffraction-limited coronagraphic imaging with nano-printed PIAACMC phase masks
Elena Tonucci, Sebastiaan Y. Haffert, Warren B. Foster et al. (+22 more)
Imaging Earth-like
exoplanets in the habitable zone of their host
star is among the main science objectives of future ground-based and space-based observatories. However, the extreme contrast and small separations needed to image such
planets cannot be reached with current technology. The Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is a promising coronagraph to reach this goal. The PIAACMC uses a set of aspheric lenses to apodize the entrance pupil without throughput losses and a phase-shifting focal plane mask for starlight suppression. These allow us to maintain high throughput and achieve a small inner-working angle (IWA), unlocking the capability to observe
exoplanets at the diffraction limit. The masks are manufactured in-house at Leiden University with Nanoscribe, a micro-3D-printer that uses two-
photon polymerization to achieve sub-micron precision in height. We present the first scientific results with a focal plane mask for the PIAACMC on the Magellan Adaptive Optics eXtreme (MagAO-X) instrument for the 6.5-meter Magellan Clay
telescope at Las Campanas Observatory, Chile. We show laboratory and on-sky contrast curves with a broadband z' filter centered at 908 nm with a 14% bandwidth. We use the PIAACMC to detect binary companions at separations ~0.8-5 lambda/D (~23-144 mas). This demonstrates the PIAACMC's capability to observe at the diffraction limit and below, with a sub-lambda/D IWA. Future work includes exploring new mask designs to improve the contrast in broadband light and performing active focal plane wavefront sensing and control.
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All authors Elena Tonucci, Sebastiaan Y. Haffert, Warren B. Foster, Jared R. Males, Olivier Guyon, Laird M. Close, Kyle van Gorkom, Alexander D. Hedglen, Parker T. Johnson, Maggie Y. Kautz, Jay K. Kueny, Rico Landman, Jialin Li, Joshua Liberman, Joseph D. Long, Miles Lucas, Jennifer Lumbres, Matthijs Mars, Eden A. McEwen, Avalon McLeod, Tiffany Nguyen, Logan A. Pearce, María Eugenia Redondo González, Lauren Schatz, Katie Twitchell