Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Frequency & Radiative Analysis of Random Yagi-UHF/VHF Phased Array
Luis M. Bres, Luis A. Hernandez and Teviet D. Creighton
This paper investigates a phased array ground station capable of tracking multiple sources, multi-beamforming, electronic steering, easy scaling, and low cost. The project will develop a 20-pair dual-polarized yagi-UHF/VHF phased array with a pseudo-random layout, comparing parameters of random and uniform distributions. We will present several analyses: general analysis for side lobes across both elevation and azimuth, analysis of scaling with number of elements ("element sweep"), electronic beam steering analysis, mechanical beam steering analysis, electro-mechanical beam steering analysis, array density analysis, and reception/transmission spectra analysis.
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High Energy Astrophysical Phenomena
Finite temperature effects on g-modes of inviscid neutron stars
David Morales-Zapien, Prashanth Jaikumar and Thomas Klähn
We study the effect of temperature on secular, compositional $g$-modes in the core of inviscid
neutron stars. Using a
chiral $SU(2)_f$ sigma model, we construct isentropic temperature profiles for hot and dense matter and find that the frequency of the global core $g$-mode's dependence on temperature is governed by the
nuclear symmetry energy slope parameter $L$. As a result, the $g$-mode frequency of a warm
neutron star can be either higher or lower than that of its cold counterpart, depending on $L$. Our results highlight the interplay of thermal effects and composition gradients, and demonstrate the potential of
neutron star $g$-mode observations to constrain the density dependence of the
symmetry energy.
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Earth and Planetary Astrophysics
Secular Light Curve of Exocomet 3I/ATLAS, and its Location on a Comet Evolutionary Diagram
Ignacio Ferrin, Jose Garrido, Charles Triana et al. (+7 more)
In this work we will create the Secular Light Curve (SLC) of exocomet 3I/ATLAS, using the SLC-Methodology (Ferrin 2010-2023). The SLCs give a throve of new information and allow the comparison of exo-comets with comets of our own
solar system. We arrive at the following conclusions: The colors of 3I are consistent and lie inside the area of colors of other comets in our
solar system. The SLC of this comet exhibits a photometric anomaly, a region from -120 to -45 days before perihelion that we interpreted as an eclipse, suggesting that 3I might also be a binary. At -45 days, the SLC changes abruptly its slope, reaching a maximum absolute magnitude of mV(1,1,{\alpha}) = 6.8+-0.1. Using reported estimates derived from 97 papers in the arXiv.org depository for the size,
dust, H2O, CO2, and CO production rates, we calculate the total mass loss. We use the inverse total mass loss, as a proxy for age. The Mass-Loss Age = 0.16 comet years will be plotted in the horizontal axis of a Comet Evolutionary Diagram (CED) while the number of Remaining Returns defined as RR = r/{\Delta}r = 24, will be plotted in the vertical axis of the CED. 3I/ATLAS exocomet lies among the comets of our Oort comet family. We conclude that 3I is a comet of the Oort Cloud, but from a different
stellar system. The Evolutionary Diagram presented in this work shows complexity beyond current understanding
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All authors Ignacio Ferrin, Jose Garrido, Charles Triana, Giuliat Navas, Raul Melia, Santiago Perez, Emiliano Gomez, Jorge Andrey Vargas, Juan Hincapie, Brayan Quintero
Solar and Stellar Astrophysics
Spectroscopic Survey of Faint Planetary-Nebula Nuclei. VIII. The Dwarf Barium Central Star of Kohoutek 1-9
Howard E. Bond, Peter Goodhew, Daniel Stern et al. (+2 more)
In the course of our ongoing survey of faint planetary-nebula
nuclei (PNNi), we obtained optical spectroscopy of the central
star of the little-studied PN Kohoutek~1-9 (K 1-9). Its spectrum is found to be that of a G-type
dwarf with strong absorption features of carbon molecules and s-process elements such as Sr and Ba–a
dwarf barium
star. K 1-9 thus joins a very small group of PNe with barium-
star nuclei. Their likely progenitors are wide binaries in which the primary
star reached the thermally pulsing asymptotic-
giant-branch (AGB) phase, dredged up C and s-process elements from its interior, and transferred enriched material to the companion through a dense
stellar wind. The remnant core is now a hot, optically inconspicuous (pre-)white
dwarf, responsible for ionizing the AGB ejecta, and leaving the optical spectrum dominated by the cool barium
star. We present deep narrow-band images of K 1-9, obtained by accumulating long exposure times using amateur
telescopes. The PN shows a thin-ring morphology, remarkably similar to the "wedding-ring" shapes seen around other members of this class of binary PNNi. The thin ring probably represents material preferentially ejected into the orbital plane of the binary; we note that the PNN is slightly off-center within the ring, as has been predicted theoretically. We suggest several follow-up studies, including precision photometry to search for periodic variations due to starspots on the rotating barium
star, and high-resolution spectroscopy to determine atmospheric parameters of the
star, chemical abundances, and its rotation velocity.
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All authors Howard E. Bond, Peter Goodhew, Daniel Stern, Jonathan Talbot, Gregory R. Zeimann
Solar and Stellar Astrophysics
Modeling YSO Jets in 3D III: Dependence of Accretion and Jet Properties on Stellar Magnetospheric Field Strength and Rotation
Yisheng Tu, Zhi-Yun Li, Zhaohuan Zhu et al. (+1 more)
Observations of Young
Stellar Objects (YSOs) systems reveal a wide diversity of jet properties, from well-collimated bipolar jets to uni-polar jets and systems with no detectable jet. Both prograde and counter-rotating jets are reported, raising questions about how jets are launched and how their properties relate to the underlying
star-disk system. Using 3D non-ideal MHD simulations, we present a suite of models in which jet properties depend sensitively on
stellar rotation and
magnetic field strength. In all models, jets are launched from “two-legged”
magnetic field lines anchored to both the
star and the turbulent, magnetically elevated disk surface, with interactions at the disk surface crucial for mediating the magnetosphere-disk coupling. The axial jet and its surrounding disk wind form a characteristic “spine-tower” structure: the spine is the kinematically-dominated jet along open field lines threading the
star, and the tower is the surrounding toroidal-field–dominated disk wind. The stability of this structure depends on the balance between the spine's stabilizing power and the tower's destabilizing power; if the tower dominates, the disk wind can choke the jet, producing asymmetric or no jets. This relationship allows an upper limit estimate on the toroidal
magnetic field strength in the disk wind-launching region using observed
outflow properties. Counter-rotating jets naturally appear in models, particularly with non-rotating
stars, showing that the classical rotation-poloidal velocity relation does not reliably indicate the jet-launching radius. Instead, it could be used to trace the
stellar rotation rate, offering a potential observational diagnostic of
stellar spin.
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All authors Yisheng Tu, Zhi-Yun Li, Zhaohuan Zhu, Kass Bell
Solar and Stellar Astrophysics
Impacts of Multidimensional Progenitor Perturbations on Core-Collapse Supernova Explosions
Chien-Hui Chen, Eric J. Lentz, W. Raphael Hix et al. (+3 more)
Numerical studies of core-collapse
supernovae have demonstrated the importance of non-radial motions in pre-collapse progenitors on the explosion outcome. We use the CHIMERA
neutrino radiation hydrodynamics code running seven two-dimensional simulations of 15
solar mass progenitors with different progenitor structures introduced by different one and two-dimensional pre-collapse
stellar evolution environments to examine the impacts of
stellar structure and non-spherical motion in the pre-collapse progenitor on the development of explosions. We compare the explosion
evolution of these models in terms of shock dynamics, diagnostic energy,
neutrino heating,
accretion, explosion geometry,
nuclear abundances, and turbulent convection. We also analyze how
stochastic variation impacts our simulations. Contrary to results reported in prior studies examining the impacts of multi-dimensional progenitors, we observe similar shock revival times and explosion development in our simulations despite differences in initial compositions and structures. We find no discernible impact from the
accretion of non-radial perturbations from a multi-D progenitor onto the stalled shock in the revival and strength of explosion, as fully developed
neutrino-driven convection behind the stalled shock is similar for all our models. For models with physically sourced noise in the iron core, a strong oscillation of the shock occurs after bounce and deflects infall laterally, and accelerates the saturation of the lateral turbulent kinetic energy. An examination of model stochasticity shows that any prior expected impacts on explosive outcome due to convection-related perturbations lie below the detectable threshold of numerical variation.
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All authors Chien-Hui Chen, Eric J. Lentz, W. Raphael Hix, J. Austin Harris, Chloe Keeling Sandoval, Stephen W. Bruenn
Solar and Stellar Astrophysics
Near-critical magnetic fields in Kepler red giants
S. Deheuvels, J. Ballot, F. Lignières et al. (+2 more)
The recent seismic detection of
magnetic fields in red
giants cores has given the opportunity to characterize these fields, potentially giving information about their origin and their role in the internal transport of angular momentum. We detect strong deviations from the regular pattern of g-mode periods in eight Kepler red
giants showing $l=1$ doublets. In three of these
stars, the modes show partial suppression. We investigate the
magnetic origin of these features and determine the characteristics of the core fields that can produce such signatures. We need to invoke strong, near-critical fields. Assessing the effects of such fields on the mixed mode frequencies requires a non-perturbative approach. We use and adapt a formalism that was recently proposed following a similar development as the traditional approximation for rotation (TAR). We then compute asymptotic expressions of mixed mode frequencies including
magnetic effects and attempt to reproduce the observed oscillation spectra. We show that for near-critical fields, information can be obtained about the radial profile of the radial field $B_r$, as opposed to weaker fields for which only a weighted average of $B_r^2$ can be measured. For the eight targets, we find that the $l=1$ doublets cannot be identified as the $m=\pm1$ components. Instead, we show that very good fits to all the observations can be obtained by identifying the two components as $m=0$ and $m=1$. These solutions correspond to fields with intensities ranging from 100 to 700 kG that are confined well below the H-burning shell. Our best-fit models for the eight
stars have low masses (1.1-1.2 $M_\odot$) and the maximal size of their convective core during the main sequence approximately corresponds to the radial extent of the measured
magnetic fields. The detected fields could thus have been generated by dynamo action in the main-sequence convective core.
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All authors S. Deheuvels, J. Ballot, F. Lignières, G. Li, M. Villate
Solar and Stellar Astrophysics
A Study of HH 270 with the James Webb Space Telescope
A. N. Ortiz Capeles, A. Noriega-Crespo, A. C. Raga et al. (+4 more)
We present a study of the Herbig-Haro object HH 270 based on observations from the James Webb Space
Telescope (JWST), Subaru
Telescope, and Atacama Large Millimeter/submillimeter Array (ALMA). High-resolution infrared images of H$_2$ and CO were obtained with the NIRCam instrument (JWST) using the F212N (2.12 $\mu$m) and F460M (4.60 $\mu$m) filters, revealing a previously unseen collimated protostellar jet closer to the source, in addition to the very well defined bipolar cavities carved by the
outflow. Newly identified
knots associated with the jet were also detected. Ground-based optical images in the H$\alpha$ (660 nm) emission line, alongside millimeter spectral observations of the (2-1) transition of $^{12}$CO, $^{13}$CO, and C$^{18}$O, further enrich the analysis. The Subaru images show a connection between the optical
outflow in H$\alpha$ and the protostellar jet observed in the infrared. ALMA CO observations trace the kinematics of the entrained molecular gas in the protostellar
outflow and reveal the dense, slow-moving material distributed around the driving source, HH270VLA1. These multi-wavelength observations show evidence of the interaction between the shock-excited jet emission and the molecular
outflow seen at optical, infrared and
radio wavelengths, which provides a detailed view of the complex structure and dynamics of HH 270.
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All authors A. N. Ortiz Capeles, A. Noriega-Crespo, A. C. Raga, M. E. Lebrón, H. Arce, J. L. Morales Ortiz, C. A. Pantoja
Astrophysics of Galaxies
Galactic Archaeology with the Subaru `Ōnohi`ula Prime Focus Spectrograph Strategic Program
Masashi Chiba, Rosemary F. G. Wyse, Evan N. Kirby et al. (+48 more)
The recently commissioned Subaru `Ōnohi`ula
Prime Focus Spectrograph (PFS) will obtain spectra from nearly 2,400 fibers that cover 1.24 square degrees. The 360 night Subaru Strategic Program for PFS is dedicating approximately one-third of its allocation (130 nights) to study the structure and
evolution of
galaxies in the Local Group. This
Galactic Archaeological survey has three pillars. (1) We will determine whether the mass density profiles of
dwarf galaxies are consistent with cusps, as expected for cold dark matter, or cores, as expected from alternative dark matter theories or baryonic feedback. We will deduce the density profiles as a function of radius from modeling of the full line-of-sight velocity and abundance distributions for six
dwarf galaxies. Our total sample will consist of 18,000 member
stars to beyond the nominal
tidal radius of each system. (2) From measurements of the [alpha/Fe] abundance ratio, we will learn the difference in assembly history of the two most massive
galaxies in the Local Group: M31 and the Milky Way. We will observe 30,000 member
stars over 45 square degrees of M31's
halo and outer disk. (3) We will uncover how the most fragile (outer) part of the Milky Way responded to
accretion events both in the distant past (such as
Gaia-Sausage Enceladus) and in more recent history (such as the Sagittarius
dwarf spheroidal
galaxy). To support this study, PFS will provide velocities and
metallicities–from which, in combination with photometry, we will deduce ages–for tens of thousands of main-sequence
stars out to a Galactocentric distance of ~30 kpc.
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All authors Masashi Chiba, Rosemary F. G. Wyse, Evan N. Kirby, Judith G. Cohen, László Dobos, Roman Gerasimov, Miho N. Ishigaki, Kohei Hayashi, Carrie Filion, Magda Arnaboldi, Souradeep Bhattacharya, Yutaka Hirai, Chiaki Kobayashi, Yutaka Komiyama, Pete B. Kuzma, Itsuki Ogami, Ana L. Chies-Santos, Nicole L. Klock-Miranda, Federico Sestito, Tamás Budavári, Andrew P. Cooper, Keyi Ding, Ivanna Escala, Elisa G. M. Ferreira, Ortwin Gerhard, Lauren Henderson, Jihye Hong, Shunichi Horigome, Ryota Ikeda, Ryo Ishikawa, Takanobu Kirihara, Zhuohan Li, Mohammad K. Mardini, Nicolas Martin, Yohei Miki, Rin Miyazaki Sakurako Okamoto, Rohan Pattnaik, Kyosuke Sato, Yoshihisa Suzuki, Alexander S. Szalay, Dafa Wardana, Viska Wei, Wenbo Wu, Zhenyu Wu, Xinfeng Xu, Xianhao Ye, Ziqing Ye, Xiangwei Zhang, Gang Zhao, Jingkun Zhao, Xiaosheng Zhao
Instrumentation and Methods for Astrophysics
PEACC - Precision Emitter for 21 cm Array Coherent Calibration
Kalyani Bhopi, Morgan Cole, Mallory Helfenbein et al. (+4 more)
Foreground mitigation remains a central challenge for 21 cm intensity mapping experiments, which require precise, wideband calibration of
telescope beams and gains. We present the Precision Emitter for 21 cm Array Coherent Calibration (PEACC), a digitally synthesized calibration source that generates Gaussian noise across a 1.2 GHz bandwidth, time-synchronized to a 1 pulse-per-second output from a GPS-disciplined oscillator, and optimized for aerial deployment. PEACC uses a dual-source architecture with one unit mounted on an aerial platform and a second reference unit connected directly to the
radio data acquisition system; this configuration enables improved sensitivity in the low-SNR regime and direct phase measurement. The system further supports configurable band selection, allowing adaptation to various 21 cm intensity mapping
telescopes. We validated PEACC through anechoic chamber measurements and by integrating the source on a drone flown over a local
radio dish testbed. In both settings, the correlated channel substantially outperformed the auto-correlation channel across all signal-to-noise regimes of interest, confirming the key advantage of the dual-source architecture. To our knowledge, this is the first published demonstration of a free-space coherent calibration signal synchronized only by clocks, the first deployment of such a source on a drone, and the first published beam measurements made with such a source. Given the growing interest in drone-based calibration for 21 cm arrays, this work establishes the feasibility of high-fidelity digital calibration for next-generation 21 cm instruments, and provides a practical path towards improved foreground control and beam calibration in future arrays.
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All authors Kalyani Bhopi, Morgan Cole, Mallory Helfenbein, Will Tyndall, Audrey Whitmer, Kevin Bandura, Laura Newburgh
Astrophysics of Galaxies
Kozai-driven mass loss of the circumbinary disk in D9 in orbit around the supermassive black hole Sgr A*
Yannick Badoux, Lucas Pouw, Tim van der Vuurst et al. (+1 more)
The supermassive black hole (Sgr A*) in the
Galactic center is surrounded by the S-
star cluster consisting of young
stars on eccentric orbits. Recently, the S-
star binary, called D9, was found to be orbited by a circumbinary disk. Due to the gravitational interaction between Sgr A* and the binary, the disk could be short-lived. We investigate the
evolution of the disk around a
stellar binary while orbiting Sgr A*. We use the AMUSE framework for coupling a
gravity solver (for the binary and Sgr. A*) with a hydrodynamics solver (for the disk). We find that, the disk eventually settles between 5.2$a_{\rm in}$ and 0.28 Hill radii of the binary. Here, $a_{\rm in}$ is the semi-major axis of D9. The inclination of the circumbinary disk follows the binary's, which evolves due to the von Zeipel-Lidov-Kozai (vZLK) mechanism induced by Sgr A*. The mean eccentricity of the disk is approximately in anti-phase with the eccentricity
evolution of the binary. We find a vZLK timescale of $T_\text{vZLK}\approx62.5\,$kyr, which is two orders of magnitude shorter than the value reported by Peisker etal. (2024). As a consequence, D9 has undergone multiple vZLK oscillations in its lifetime of 2.7 Myr. We find the disk shows periodic bursts of mass loss on the vZLK timescale, suggesting that the mass loss itself is in part driven by the vZLK mechanism. The secular
evolution observed in both the binary and the disk are consistent with theoretical predictions. We find the disk loses $\sim$7% $\pm$ 2% of its mass every vZLK cycle. If we extrapolate this mass loss, the disk will have 1% of its current mass left after another $\sim$4 Myr. D9 will then be $\sim$6.7 Myr old, which is on the same order as the current average age of S cluster members. The vZLK-driven mass loss could, therefore, explain the absence of Br$\gamma$ emission from other S cluster members.
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All authors Yannick Badoux, Lucas Pouw, Tim van der Vuurst, Simon Portegies Zwart
Solar and Stellar Astrophysics
Spectroscopic Characterization of WD J000801.25-350450 and its Two Co-Moving Companions
Peter A. Jałowiczor, Thomas P. Bickle, J. Davy Kirkpatrick et al. (+16 more)
We present new spectroscopic data for
Gaia DR3 2309499817384726016 (WD0008-350A) and its two wide, co-moving, low-mass companions. We confirm the white
dwarf is a hydrogen-rich DA, with T$_{\rm eff}$=6200$\pm$90~K and a mass of 0.63$\pm$0.03~M${\odot}$, close to that of the average white
dwarf. Near-infrared spectra of the two
stellar companions to WD0008-350A reveal that the inner companion is an M
dwarf, exhibiting a spectral type of M8. Furthermore, the outer companion is identified as a possible M6 + M9 binary. This paper examines the evidence which suggests the system may be quadruple.
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All authors Peter A. Jałowiczor, Thomas P. Bickle, J. Davy Kirkpatrick, Sarah L. Casewell, Nicola Gentile Fusillo, Adam C. Schneider, Jonathan Gagné, Jacqueline K. Faherty, Aaron M. Meisner, Marc J. Kuchner, Adam J.Burgasser, Austin Rothermich, Alexia Bravo, Michiharu Hyogo, Mark Popinchalk, Alex J. Brown, Alberto Rebassa-Mansergas, Raquel Murillo-Ojeda, The Backyard Worlds: Planet 9 Collaboration
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Induced Multi-phase Inflation with Reheating: Leptogenesis and Dark Matter Production in Metric versus Palatini
Nilay Bostan, Rafid H. Dejrah, Anish Ghoshal et al. (+1 more)
We study non-minimally coupled scalar-induced multi-phase inflation in metric and Palatini
gravity, considering linear, Brans-Dicke-like, and
Higgs-like sectors. The scalar spectral index lies in the range \( n_s \simeq 0.93 \ \text{--} \ 0.98 \), consistent with Planck and combined Planck+ACT data. The tensor-to-scalar ratio can reach \( r \sim 0.03 \) in metric, whereas Palatini models generically predict \( r \lesssim 10^{-5} \). In the Palatini case, field excursions remain sub-Planckian, and the perturbative unitarity cutoff is raised. Reheating proceeds via perturbative inflaton decays into
Higgs bosons and fermionic dark matter (DM) through the portal coupling \( \lambda_{12} \) and Yukawa coupling \( y_\chi \). Radiative stability of the inflationary plateau constrains the couplings to \( y_\chi, \lambda_{12} \sim 10^{-7} \ \text{--} \ 10^{-3} \), implying \( 4\,\mathrm{MeV} \lesssim T_{\rm rh} \lesssim 10^{15}\,\mathrm{GeV} \). Palatini realizations require smaller couplings and thus a narrower reheating window. Non-thermal DM production $\chi$ from inflaton decays is viable for DM mass \( m_\chi \sim \mathrm{keV} \ \text{--} \ \mathrm{PeV} \) with \( y_\chi \lesssim 10^{-6} \) over large parameter regions. We estimate the inflaton-right-handed
neutrino (RHN) Yukawa coupling \( y_N \) required for successful baryogenesis via non-thermal leptogenesis within a Type-I seesaw framework, for the lightest RHN mass \( M_{N_1} \sim 10^{9} \ \text{--} \ 10^{14}\,\mathrm{GeV} \), provided \( M_{N_1} > T_{\rm max} \), where \( T_{\rm max} \) follows from radiatively consistent reheating. In Palatini scenarios, the lower maximal temperature and tighter stability bounds further restrict the leptogenesis parameter space.
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All authors Nilay Bostan, Rafid H. Dejrah, Anish Ghoshal, Zygmunt Lalak
High Energy Astrophysical Phenomena
High Resolution X-ray Spectroscopy of the Nova-Like Cataclysmic Variable BZ Cam using Chandra HETG: Diagnosis of the ADAF-like (Advective) Hot Flow
Solen Balman, Eric M. Schlegel, Patrick Godon et al. (+2 more)
Nova-likes such as BZ Cam are high state Cataclysmic Variables showing hard X-ray emission that can be characterized with advective hot flows in the inner
accretion disk. We explore Chandra High Energy Transmission Grating (HETG) observations of BZ~Cam for detailed line diagnosis and ionization conditions in the X-ray regime. We mostly find H- and He-like emission lines of Mg, Si, S, and Fe. All He-like line components of forbidden, intercombination and resonance lines are present. The R ratios of selected lines indicate
plasma densities of a few $\times$10$^{12-14}$ cm$^{-3}$ and G ratios reveal temperatures (3-6)$\times$ 10$^6$ K where the Fe lines yield (1-3)$\times$ 10$^7$ K. The H to He line ratios and the R and G ratios show that the
plasma is in a nonequilibrium ionization condition, which is consistent with our previous X-ray results and the
accretion flow in the X-ray region being an ADAF-like (advective) hot flow. Simultaneous fits of the HEG and MEG spectra or the broadband joint spectra of ROSAT, Chandra zero order and NuSTAR yield temperatures 3.4-6.3 keV using a VNEI model of
plasma emission (in XSPEC) or Bremsstrahlung emission. An additional power law is detected above 98% Confidence Level in the broadband analysis. The orbital variations and the broadband spectra show dipping/veiling of the X-rays and an additional warm absorber model with an ionization parameter log($\xi$) = 2.7 is required at the 3$\sigma$ level, along with the VNEI model where the HEG and MEG simultaneous fits yield the log($\xi$) = 3.6 .
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All authors Solen Balman, Eric M. Schlegel, Patrick Godon, Jeremy J. Drake, Edward M. Sion
Earth and Planetary Astrophysics
Observational and Dynamical Constraints on an Unseen Outer Perturber in the GJ 436 Hot Neptune System
Haedam Im, Tiger Lu, Malena Rice et al. (+3 more)
Hot Neptunes in the sub-Jovian desert offer unique insights into planetary system
evolution, retaining signatures of dynamical processes that shaped their present-day architectures. Many of these
planets exhibit polar orbits, yet the mechanisms responsible for these misalignments between the
stellar spin axis and
planet orbit normal remain under debate. GJ 436 b stands among the very few hot Neptunes with both a polar and an eccentric orbit, thereby preserving dynamical signatures that may have otherwise been erased by
tidal circularization. We investigate the unusual orbital architecture of GJ 436, exploring von Zeipel-Lidov-Kozai migration induced by a distant companion as a mechanism to explain the present-day orbit of GJ 436 b. Using $\sim$20 years of archival radial velocity measurements and astrometric data from the Hipparcos-
Gaia Catalog of Accelerations, we constrain a potential companion to $a_{c}<5.4$ AU for $m_{c}>0.05$ $M_{Jup}$ and $a_{c}<64$ AU for $m_{c}>24$ $M_{Jup}$ in the GJ 436 system at the $2\sigma$ confidence level, providing the most stringent constraints to date. We further perform three-body hierarchical secular simulations to determine which companion configurations could reproduce GJ 436 b's present-day orbit within the observationally constrained parameter space. Our dynamical modeling favors sub-Jovian masses on orbits with $a_\mathrm{c} \gtrsim 6.8$ AU, suggesting a substellar perturber. These observational and dynamical constraints can guide future companion searches and illuminate formation mechanisms for hot Neptune desert
planets on polar orbits.
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All authors Haedam Im, Tiger Lu, Malena Rice, Quang H. Tran, Gongjie Li, Smadar Naoz
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Testing the Kerr hypothesis beyond the quadrupole with GW241011
Rimo Das, N.V. Krishnendu, M. Saleem et al. (+2 more)
All multipole moments of a Kerr black hole are uniquely determined by its mass and
spin. Gravitational wave observations can test this prediction by measuring
spin-induced multipole moments imprinted on the inspiral phase of compact binary mergers. In this Letter, we show that the recently reported compact binary coalescence GW241011 enables a simultaneous test of deviations in the
spin-induced quadrupole and octupole moments of the binary components from their black hole values. We find no evidence for deviations from the Kerr prediction and place the first constraints on
spin-induced octupole moments of the compact binary. This approach complements tests of the Kerr nature of compact binary merger remnants based on quasinormal mode measurements in the ringdown phase.
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All authors Rimo Das, N.V. Krishnendu, M. Saleem, Chandra Kant Mishra, K.G. Arun
High Energy Astrophysical Phenomena
Even a precessing clock is right twice per orbit – The super-periods of eRO-QPE2 and challenges for quasi-periodic eruption orbital models
R. Arcodia, G. Miniutti, J. Chakraborty et al. (+25 more)
We present O$-$C (“observed minus calculated”) timing analysis of the quasi-periodic eruption (QPE) source eRO-QPE2 with a multi-mission X-ray campaign, which includes 32 observed eruptions spanning a month (i.e. 325 QPE cycles). In relation to
accretion (e.g. disk instability) models, the O-C is consistent with a damped random walk of the QPE recurrence, albeit with highly uncertain parameters. If instead an underlying orbital clock is present, eRO-QPE2 is consistent with a period of $P \sim 2.24$\,h and two hierarchical super-periodic modulations, with periods of $\sim 4.4$\,d ($\sim47$\,P) and $\approx 95$\,d ($\approx 1000$\,P). We found no negative period derivative, with $|\dot{P}| \lesssim 2 \times 10^{-6}$\,s/s at $3\sigma$. This disfavors high-eccentricity WDs and high-mass/eccentricity IMBHs via GW decay. For disk-collision models, where the $\dot{P}$ from gas drag and the QPE integrated energy provide bounds on the local disk density, a main-sequence
star is disfavored as EMRI secondary unless
stellar debris streams are present, while stripped
stars remain allowed. The correlated odd/even O-C disfavors both disk crossings per orbit being observed. Interpreting the data with one observed event per orbit, the short modulation is consistent with apsidal precession for $a \sim 140\,R_g$, $e \approx 0.1$, and $M_{\rm BH} \approx 1.5 \times 10^{5}\,M_\odot$. The longer modulation (much less constrained) is inconsistent with EMRI nodal precession and disk precession is allowed for a limited parameter volume, while there is a solution with a stable hierarchical triple system with an outer massive black hole at $\sim 0.4\,\mathrm{mpc}$ and mass $\sim(0.1-1) \times M_{\rm BH}$. However, no reliable solution can be found with more robust EMRI trajectory models, possibly due to narrow likelihood peaks in a multi-dimensional parameter space with sparse data.
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All authors R. Arcodia, G. Miniutti, J. Chakraborty, A. Franchini, M. Giustini, I. Linial, A. Mummery, L. Bertassi, M. Bonetti, E. Kara, A. Merloni, A. Motta, G. Ponti, E. Quintin, R. Soria, P. Baldini, J. Buchner, M. Dotti, P. C. Fragile, A. Ingram, M. Middleton, C. Panagiotou, A. Sesana, P. Yao, A. Rau, F. M. Vincentelli, M. Guolo, R. Saxton
Instrumentation and Methods for Astrophysics
Learning What's Real: Disentangling Signal and Measurement Artifacts in Multi-Sensor Data, with Applications to Astrophysics
Pablo Mercader-Perez, Carolina Cuesta-Lazaro, Daniel Muthukrishna et al. (+5 more)
Data collected from the physical world is always a combination of multiple sources: an underlying signal from the physical process of interest and a signal from measurement-dependent artifacts from the sensor or instrument. This secondary signal acts as a confounding factor, limiting our ability to extract information about the physics underlying the phenomena we observe. Furthermore, it complicates the combination of observations in heterogeneous or multi-instrument settings. We propose a deep learning framework that leverages overlapping observations, a dual-encoder architecture, and a counterfactual generation objective to disentangle these factors of variation. The resulting representations explicitly separate intrinsic signals from sensor-specific distortions and noise, and can be used for counterfactual view generation, parameter inference unconfounded by measurement distortions, and instrument-independent similarity search. We demonstrate the effectiveness of our approach on astrophysical
galaxy images from the DESI Legacy Imaging Survey (Legacy) and the Hyper Suprime-Cam (HSC) Survey as a representative multi-instrument setting. This framework provides a general recipe for scientific and multi-modal self-supervised pretraining: construct training pairs from overlapping observations of the same physical system, treat sensor- or modality-specific effects as augmentations, and learn invariant representations through counterfactual generation.
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All authors Pablo Mercader-Perez, Carolina Cuesta-Lazaro, Daniel Muthukrishna, Jeroen Audenaert, V. Ashley Villar, David W. Hogg, Marc Huertas-Company, William T. Freeman
Earth and Planetary Astrophysics
Direct Images of CO2 Absorption in the Atmosphere of a Super-Jupiter: Enhanced Metallicity Suggestive of Formation in a Disk
William O. Balmer, Laurent Pueyo, Ashley Messier et al. (+15 more)
It is unclear how directly imaged substellar companions with masses near the deuterium burning limit form, because these objects are rare and their bulk properties are not diagnostic of their formation. In this paper we revisit this problem using JWST/NIRCam coronagraphic images of the 29 Cygni (=HIP 99770) system that reveal the recently-discovered super-Jovian companion 29 Cyg b at wavelengths covering 4-5${\mu}$m for the first time. This object has an uncertain mass that straddles the deuterium burning limit ($M_{\rm b}\simeq15\pm5\,M_{\rm J}$) and a low mass ratio with its early-type host
star ($M_{\rm b}/M_\star\sim0.01$). Absorption from CO$_2$ and CO is apparent at 4.3 and 4.6${\mu}$m in our images. The strength of the CO$_2$ feature relative to CO provides strong evidence, based on empirical comparison with literature observations at these wavelengths and atmospheric modeling, that the companion is enriched in heavier elements compared to the roughly
solar abundances of the host ($Z_{\rm b}/Z_\star=3\pm2$). In addition, we measure the
stellar inclination angle with CHARA/PAVO interferometry: the system is consistent with
spin-orbit
alignment at the $2\,\sigma$ level, with $\Delta i=12\pm6^\circ$. This ensemble of evidence is suggestive of formation within the protoplanetary disk and rapid
accretion of metal-rich material, versus disk fragmentation or capture like higher mass ratio companions. 29 Cyg b shows that
planet formation around early-type
stars can occur on scales at or exceeding the deuterium burning limit, in agreement with the recently revised planetary mass/
metallicity trend that predicts $Z_{\rm pl}/Z_\star=3.3\pm0.5$ at high masses from transiting
planet densities (Chachan et al. 2025).
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All authors William O. Balmer, Laurent Pueyo, Ashley Messier, Evelyn Bruinsma, Jeremy Jones, Klara Matuszewska, Marshall D. Perrin, Julien H. Girard, Jarron M. Leisenring, Kellen Lawson, Roeland P. van der Marel, Jens Kammerer, Aarynn Carter, Mathilde Mâlin, Kimberly Ward-Duong, Kielan K. W. Hoch, Emily Rickman, Sara Seager
High Energy Astrophysical Phenomena
JWST Nebular Spectroscopy of SN 2023qov: Circumstellar Dust Emission in a Normal Type Ia Supernova
Colin W. Macrie, Conor Larison, Huei Sears et al. (+43 more)
We present panchromatic observations of the Type Ia
supernova (SN Ia) 2023qov, ranging from $\sim$2 weeks before to $\sim$1 year after maximum light. JWST near- and mid-infrared spectra at $+$276 and $+$363~days show $\sim$400 K
dust emission that cools by $\sim$75 K between epochs, the first unambiguous spectroscopic detection of
dust emission in a normal SN Ia. We find that the emission is well described by models of carbonaceous
dust placed within $\sim$1 light year of the SN, with a
dust mass of $\sim$$10^{-4}$ M$_{\odot}$. We do not see evidence of active
dust creation, suggesting an infrared light echo by pre-existing circumstellar
dust as the likely source of the emission. The JWST nebular line profiles suggest asymmetric, stratified ejecta, similar to other normal SNe Ia, though a slight double-horn structure in the argon lines indicate a toroidal enhancement. SN 2023qov exhibits a slightly red, fast-declining early light curve ($\Delta m_{15}(B) = 1.47 \pm 0.05$ mag), from which we determine a $^{56}$Ni mass of $M_{56} = 0.21 \pm 0.04$ M$_{\odot}$, and a distance of $d = 36.0 \pm 1.8$ Mpc to the SN and its host, NGC 7029.
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All authors Colin W. Macrie, Conor Larison, Huei Sears, Lindsey A. Kwok, Saurabh W. Jha, Mi Dai, Joel Johansson, Stéphane Blondin, Moira Andrews, K. Auchettl, Carles Badenes, Barnabás Barna, K. Azalee Bostroem, Thomas G. Brink, Kyle W. Davis, Joseph R. Farah, Alexei V. Filippenko, Ori D. Fox, Or Graur, Saarah Hall, D. Andrew Howell, Griffin Hosseinzadeh, Anders Jerkstrand, Reka Konyves-Toth, Christopher Lidman, Keiichi Maeda, Kate Maguire, Bailey Martin, Adam Miller, Megan Newsome, Estefania Padilla Gonzalez, Abigail Polin, Armin Rest, Zoe Rosenberg, David Sand, Michaela Schwab, Matthew Siebert, Mridweeka Singh, Támas Szalai, Tea Temim, Jacco Terwel, Brad Tucker, Jozsef Vinko, Lingzhi Wang, Xiaofeng Wang, WeiKang Zheng
High Energy Astrophysical Phenomena
Repopulating the pair-instability mass gap without sustained growth to massive IMBHs: the case of 47\,Tuc
Debatri Chattopadhyay, Daniel Marín Pina, Mark Gieles et al. (+2 more)
We model the formation and retention of the most massive black hole (BH) in 47~Tuc using the semi-analytical code cBHBd, coupling cluster
evolution with binary BH dynamics and computing merger-remnant masses,
spins, and gravitational-wave
recoil kicks via numerical-relativity surrogate prescriptions. We evolve 80\,000 cluster realisations spanning initial masses, densities, IMFs, and
metallicities, in both a baseline scenario ($m_{\rm max} = 130\,\mathrm{M}_{\odot}$) and an extended-IMF scenario with ${\sim}\,50-110$
primordial BH seeds above the pair-instability gap ($M_{\rm BH} \sim 130-700\,\mathrm{M}_{\odot}$). Selecting models reproducing 47~Tuc's present-day mass and half-mass radius, we find hierarchical mergers alone yield a most massive retained BH of $M_{\rm BH} \sim 45-70\,\mathrm{M}_{\odot}$ with
spin $\chi_{\rm BH} \sim 0.65$, limited to ${\sim}\,1-3$ mergers, as second-generation remnants acquire
spin $\chi \sim 0.7$ that amplifies
recoil kicks in subsequent generations. When
primordial seeds are included, the retained-mass distribution becomes bimodal – in ${\sim}\,90\%$ of realisations all seeds are ejected, but in ${\sim}\,10\%$ a massive seed ($M_{\rm BH} \gtrsim 450\,\mathrm{M}_{\odot}$) survives – while the joint mass-
spin distribution is trimodal; seeds surviving via
stellar-mass BH mergers retain low
spin ($\chi \lesssim 0.3$), whereas seed-seed mergers produce high-mass, high-
spin remnants ($\chi \sim 0.65-0.7$), yielding 90th-percentile retained masses of ${\sim}\,500-1100\,\mathrm{M}_{\odot}$. Both scenarios are consistent with the $3\sigma$ dynamical upper limit of $578\,\mathrm{M}_{\odot}$. Our results favour a dark-remnant subsystem over a single massive IMBH and provide a
spin-mass diagnostic testable with LIGO-Virgo-KAGRA, the Einstein
Telescope,
Cosmic Explorer, and LISA.
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All authors Debatri Chattopadhyay, Daniel Marín Pina, Mark Gieles, Fabio Antonini, Fotios Fronimos Pouliasis
Astrophysics of Galaxies
Magnetic field alignment with dense cores in the transition between cloud and core scales
Sean Yin, Ayush Pandhi, Rachel Friesen et al. (+7 more)
In a magnetically-dominated model of
star formation, we expect to see
alignments between the
magnetic field orientation of
star-forming dense cores and the cloud-scale
magnetic field. Pandhi et al. (2023) showed instead, however, that the orientation of cores and their angular momentum vectors appear random with respect to the larger-scale
magnetic field, implying that
magnetic fields may play a diminished role in core formation and
evolution. Here, we use higher-resolution
dust polarization data from the B-Fields In
Star-forming Region Observations (BISTRO) survey on the James Clerk Maxwell
Telescope (JCMT) to investigate the change in the
magnetic field orientation from cloud scales to core scales, and reassess any correlations between core-scale
magnetic fields, core orientations and core velocity gradients. We produce a catalog of 79 cores over 14
star-forming regions with averaged core-scale
magnetic field orientations. We find that the core-scale
magnetic field is more disordered compared to the cloud-scale field, as measured by an increased standard deviation in the
magnetic field vector orientations.
Alignment between the core-scale and cloud-scale field varies greatly between regions. Our results are consistent with random
alignments between the core-scale
magnetic field, core orientation, and core velocity gradient, in agreement with the results by Pandhi et al. (2023) for the cloud-scale field. We conclude that there is a clear change in the
magnetic field in the transition from cloud- to core-scales. Our results suggest that the
magnetic field may not play a dominant role in the
evolution of dense cores on core scales.
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All authors Sean Yin, Ayush Pandhi, Rachel Friesen, Simon Coudé, Laura Fissel, Sarah Sadavoy, James Di Francesco, Doug Johnstone, Frédérick Poidevin, Mehrnoosh Tahani
Solar and Stellar Astrophysics
Gaia astrometry disfavors a binary origin for long secondary periods
Cheyanne Shariat, Kareem El-Badry, Morgan MacLeod et al. (+1 more)
Approximately one-third of luminous pulsating red
giant stars exhibit long secondary periods (LSPs): stable photometric variability with periods of several months to years in addition to their much shorter primary pulsation cycles. Now nearly a century after their discovery, the physical origin of LSPs remains unresolved. A leading explanation invokes binarity, in which the LSP corresponds to the orbital period of a low-mass companion responsible for both the photometric variability and the radial-velocity (RV) modulation. We test this hypothesis using a nearby sample of LSP
stars from the
Gaia Focused Product Release, which provides multi-epoch RVs and contemporaneous optical photometry. We find that interpreting the observed RV variability as orbital motion implies companion masses narrowly distributed around $M_2 \approx 0.1~{\rm M_\odot}$ with separations of 1–3 au, placing them squarely in the brown
dwarf desert observed around their
solar-type progenitors. Assuming such companions exist, we then forward-model the astrometric signature expected in
Gaia DR3 and predict systematically elevated RUWE values for nearby LSPs. In contrast, the observed RUWE of nearby LSP
stars is systematically lower than these predictions and consistent with most systems exhibiting LSPs being single. This discrepancy disfavors low-mass
stellar or substellar companions as the dominant origin of LSPs in evolved
stars, motivating a further exploration of alternative
stellar mechanisms.
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All authors Cheyanne Shariat, Kareem El-Badry, Morgan MacLeod, Emily Leiner
Solar and Stellar Astrophysics
Eccentricities of millisecond pulsars with intermediate-mass progenitors
Hagai Bareli and Sivan Ginzburg
One channel to form millisecond
pulsars with CO white
dwarf companions is through the stable Roche-lobe overflow of intermediate-mass ($3\,{\rm M}_\odot\lesssim M\lesssim 5\,{\rm M}_\odot$)
stars at the end of the main sequence (Case A) or the beginning of the hydrogen shell burning phase (Case B). We reproduce previous numerical calculations of this channel and supplement them with a simple analytical model that relates the final orbital period $P(M,m_{\rm wd})$ to the white
dwarf's mass and to its progenitor's initial mass $M$. We also theoretically calculate for the first time the eccentricity $e$ in this process, which is set by the fluctuating gravitational quadrupole moment of the progenitor's convective envelope during Roche-lobe detachment. Intermediate-mass progenitors detach when their non-degenerate cores ignite helium, in contrast to low-mass ($M\lesssim 2\,{\rm M}_\odot$)
stars with degenerate cores that detach when their envelopes become too light to support a burning shell. Despite the order of magnitude higher envelope mass at detachment $m_{\rm e}$ in our case, the eccentricity is barely affected because $e\propto m_{\rm e}^{1/6}$, explaining why intermediate-mass ($m_{\rm wd}\lesssim 0.6\,{\rm M}_\odot)$ CO white
dwarfs have similar eccentricities to lower mass helium white
dwarfs. Massive CO and ONe white
dwarfs ($m_{\rm wd}\gtrsim 0.6\,{\rm M}_\odot)$, on the other hand, probably formed through a different channel of unstable Roche-lobe overflow during helium shell burning (Case C), followed by common envelope inspiral. The measured eccentricities of these massive white
dwarfs remain to be explained.
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Astrophysics of Galaxies
An empirical derivation of the average dust attenuation law at 2<z<7
Giulia Rodighiero, Gaia Edes Esposito, Daniela Calzetti et al. (+12 more)
Dust attenuation affects
galaxy SEDs and introduces uncertainties in
star formation rates,
stellar masses, and
metallicities. Direct spectroscopic constraints at early
cosmic epochs were limited before JWST. We derive the average
dust attenuation law of massive (log10(Mstar/Msun) > 9)
star-forming
galaxies at 2 < z < 7 using JWST spectroscopy. We combine JWST/NIRSpec spectroscopy from JADES with deep multi-wavelength photometry from the ASTRODEEP-JWST catalogues. For approximately 120 mass-selected
galaxies with reliable Balmer decrement (Halpha/Hbeta) measurements, we stack SEDs in bins of Balmer optical depth and derive the selective attenuation curve following Calzetti et al. (1994). JWST/MIRI photometry extends the wavelength coverage into the near-infrared (NIR). The resulting curve spans 0.16-1.14 microns in the rest frame and is well described by a smooth function. We derive R_V approximately 3.98, with Delta R_V = 0.16 indicating its sensitivity to the adopted long-wavelength extrapolation. The average attenuation law agrees remarkably well with the local starburst relation in slope and normalisation, but appears systematically flatter in the ultraviolet than several intermediate-
redshift determinations. We find no significant evidence for a 2175 Angstrom UV bump. Our results provide a direct empirical constraint on the average
dust attenuation law of massive
star-forming
galaxies at 2 < z < 7. This analysis exploits the combined spectroscopic and photometric reach of JWST. Despite variations among individual
galaxies, the ensemble-average behaviour agrees with the local starburst relation, suggesting that the main mechanisms governing
dust attenuation were already operating at early
cosmic times. The relatively shallow UV slope may reflect differences in
dust-
star geometry, radiative-transfer effects, or effective grain-size distributions among
galaxy populations.
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All authors Giulia Rodighiero, Gaia Edes Esposito, Daniela Calzetti, Pietro Benotto, Michele Catone, Paolo Cassata, Giovanni Gandolfi, Laura Bisigello, Stefano Carniani, Alvio Renzini, Irene Shivaei, Benedetta Vulcani, Annagrazia Puglisi, Andrea Enia, Santiago Álvarez-Cordoba
High Energy Astrophysical Phenomena
High-energy neutrino constraints on primordial black holes as dark matter
Mainak Mukhopadhyay and Joaquim Iguaz Juan
Primordial black holes (PBHs) are one of the most appealing dark matter candidates over a wide range of masses and abundances. This broad parameter space has been constrained by a variety of observational probes. In this work, for the first time, we use data from high-energy
neutrino telescopes, like IceCube and ANTARES, to constrain sub-asteroid mass ($\lesssim 10^{18}\,\mathrm{g}$) Schwarzschild PBHs with extended mass functions. We derive limits from the diffuse high-energy
neutrino flux produced by the direct evaporation of PBHs, as well as from the transient signatures associated with PBHs passing in the vicinity of the Earth. While our bounds are slightly weaker than existing constraints from gamma-ray observations, they provide an independent and complementary probe based on observational high-energy
neutrino data. We further show that future detectors such as IceCube-Gen2 and KM3NeT can significantly improve these constraints, potentially excluding PBHs with masses up to $\sim \mathrm{few} \times 10^{18}\,\mathrm{g}$ composing the entirety of dark matter.
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High Energy Astrophysical Phenomena
Time-resolved XRISM spectroscopy reveals the evolution and structure of the corona in MCG-6-30-15
D. R. Wilkins, L. W. Brenneman, A. Ogorzalek et al. (+7 more)
We present a time-resolved analysis of high-resolution spectra of the AGN MCG-6-30-15 obtained by XRISM alongside broadband spectra from NuSTAR and XMM-Newton during a coordinated observing campaign in February 2024. These observations provide some of the most detailed measurements of X-ray reflection from the innermost regions of the
accretion disc around a supermassive black hole, and its
evolution during periods of significant variability. We find that both the X-ray spectrum and its variability can be described by a self-consistent model of the reflection of the coronal X-ray emission from the
accretion disc around a rapidly-spinning (a > 0.93) black hole, in which the observed variability arises from underlying changes in the luminosity, spatial extent and motion of the corona. While the corona is compact, residing within 10rg of the black hole for the majority of the observations, finite spatial extent is required to fully explain the shape of the reflection spectrum. A
flare was observed in the X-ray emission during which the corona expanded to around 15rg and was accelerated away from the black hole reaching a velocity of 0.27c. Around the
flare were short dips in the observed flux, during which the corona was found to have collapsed to a confined region, within 2.5rg of the black hole, enhancing the relativistic effects observed from the inner
accretion disc. We find it is necessary to account for such significant spectral variation in order to obtain accurate measurements of the
spin of the black hole via X-ray reflection spectroscopy.
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All authors D. R. Wilkins, L. W. Brenneman, A. Ogorzalek, A. C. Fabian, E. Behar, R. Boissay-Malaquin, J. A. Garcia, E. B. Hoffman, A. Juranova, D. Rogantini
Astrophysics of Galaxies
The missing ultra-faint satellites of the Milky Way
Isabel M.E. Santos-Santos, Carlos S. Frenk and Julio F. Navarro
We combine the highest resolution N-body simulation of a $\sim10^{12}M_\odot$ $\Lambda$CDM
halo (Aquarius-A) with the semi-analytic model GALFORM to study the full satellite population of Milky Way (MW)-like
galaxies. The model assumes that
galaxies form only in subhalos whose peak circular velocity exceeds the hydrogen-cooling threshold, and predicts that the total number of satellites ever accreted into the main
halo, down to arbitrarily low luminosity, should not exceed a few hundred. The model tracks satellites even after their
halos become unresolved ("orphan"
galaxies), and includes a novel treatment of dark matter and
stellar tidal stripping which takes into account that $\Lambda$CDM subhalos survive
tidal disruption because of their cuspy density profiles. Our results match the massive end of the observed MW satellite mass function and predict that many ultra-faint
dwarfs (UFDs) with $M_V>-5$ are missing from the current MW satellite census. The missing UFDs are predicted to avoid the innermost regions of the host, and have properties overlapping those of the recently-discovered ultra-faint compact MW satellites (UFCSs). If the faintest
dwarfs are initially as compact as UFCSs, our results suggest that many UFCSs should be dark matter-dominated
dwarfs with velocity dispersions $1-3$ km/s which survived disruption because they inhabit the cusp of $\Lambda$CDM subhalos. UFCSs have predicted densities of $10^{10}$-$10^{11}\,M_\odot/$kpc$^3$, higher than those of more extended UFDs. If confirmed, our results provide strong support for the cuspy nature of $\Lambda$CDM
halos and for the hydrogen-cooling threshold for
galaxy formation.
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Earth and Planetary Astrophysics
High-Contrast Imaging of Forming Protoplanets: VLTs, JWST, and the Promise of ELT
Gabriele Cugno and Michael R. Meyer
Planet formation remains a fundamentally important yet poorly understood process. Protoplanetary disks, the birthplaces of planetary systems, exhibit a wide range of substructures that are increasingly interpreted as signatures of interactions with forming
planets. However, the direct detection rate of protoplanets within these disks remains low, leaving critical gaps in our understanding of the physical mechanisms driving their formation and early
evolution. In this chapter, we review recent efforts by the high-contrast imaging community to directly observe forming protoplanets and their immediate environments. These observations aim to provide key constraints on thermal and
accretion processes, planetary growth, and the formation of circumplanetary disks and satellite systems. We also propose a path forward for deriving observational estimates of the
planet mass-to-radius ratio ($M_p/R_p$), a crucial parameter for distinguishing between competing formation models and understanding the thermal
evolution of young
planets. Finally, we highlight how upcoming instruments on the Extremely Large
Telescope (ELT), with their unprecedented combination of high spatial and spectral resolution, will transform our ability to probe
planet formation at the smallest and most critical scales.
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