Earth and Planetary Astrophysics
Discovery of an Exterior Third Planet Orbiting $\beta$ Pictoris
Aidan Gibbs, Jean-Baptiste Ruffio, Alexis Bidot et al. (+9 more)
We report the discovery of $\beta$ Pictoris d ($\beta$ Pic d), a third
giant planet in the $\beta$ Pictoris system, which now becomes only the second directly imaged system with more than two confirmed
planets. $\beta$ Pic d was serendipitously detected in JWST/NIRSpec IFU observations. A second epoch of NIRSpec and MIRI/MRS observations confirm the initial discovery. The extracted spectrum shows clear CH$_4$, CO, and H$_2$O absorption features, and $\beta$ Pic d's measured radial velocity is consistent with its orbital position. Radial velocity and astrometry measurements combined with orbital stability simulations suggest a semi-major axis $>$30 au, consistent with $\beta$ Pic d being responsible for carving the inner edge of the $\beta$ Pictoris debris disk. Using effective temperature estimates from atmosphere model grid fits combined with evolutionary models, we estimate a mass of 2–4 $M_\mathrm{Jup}$. $\beta$ Pic d is the first
planet discovered using spectral template matching with moderate-resolution spectroscopy, highlighting its sensitivity to planetary molecular features hidden within bright extrasolar debris disks that are difficult to access with broadband imaging.
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All authors Aidan Gibbs, Jean-Baptiste Ruffio, Alexis Bidot, Travis S. Barman, Clarissa R. Do Ó, Quinn M. Konopacky, Marshall D. Perrin, Aneesh Baburaj, Beck Dacus, Bruce Macintosh, Alexander B. Madurowicz, Jerry W. Xuan
Astrophysics of Galaxies
Red vs. Blue: How metallicity shapes black hole dynamics and mergers in dense star clusters
Saloni Agrawal, Kyle Kremer, Michael Zevin et al. (+6 more)
Dense
star clusters are a well-established environment for the formation of gravitational wave sources through dynamical interactions. Recent LIGO-Virgo-KAGRA (LVK) events such as GW241011 and GW241110 provide some of the best evidence yet for a dynamical origin. However, their relatively low component masses are in tension with predictions from low-
metallicity globular cluster models (which typically produce more massive black holes), hinting that these events may have originated in higher-
metallicity environments. Here we present a new set of Monte Carlo
star cluster simulations with refined coverage in
metallicity, focusing specifically on clusters with [Fe/H] $\geq-1$, similar to the ”red” globular cluster subpopulation observed in most
galaxies. We show that
metallicity has a significant effect on the mass function of black holes and black hole mergers, the total number of black hole mergers per cluster, black hole retention from natal kicks, the mass segregation time for black-hole-driven cluster dynamics, and the merger delay time distribution. We also show that high-
metallicity cluster models produce low-mass hierarchical mergers consistent with the mass ratios and component masses of GW241011 and GW241110, motivating the importance of high-
metallicity clusters in the astrophysical interpretation of future LVK catalogs.
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All authors Saloni Agrawal, Kyle Kremer, Michael Zevin, Cailin Plunkett, Elena González Prieto, Fulya K{\i}roğlu, Christopher E. O'Connor, Frederic A. Rasio, Claire S. Ye
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Multi-peaked high-frequency gravitational waves from PBH-assisted leptogenesis
Debasish Borah and Nayan Das
We study the possibility of probing non-thermal leptogenesis with multi-peaked high-frequency gravitational waves (GW) by considering heavy right-handed
neutrino (RHN) produced from
primordial black hole (PBH) evaporation to be responsible for generating the required
lepton asymmetry. The decay of RHN also produces a GW spectrum due to graviton bremsstrahlung with the corresponding amplitude being enhanced for heavier RHN. The presence of an ultra-light PBH dominated epoch not only ensures sufficient production of RHNs, but also keeps the leptogenesis scenario free from strong washout problem of thermal leptogenesis at very high scale. In addition, the PBH dominated epoch also helps in generating a gravitational bremsstrahlung spectrum distinct from the
stochastic GW background from the thermal bath. Finally, PBH evaporation also brings two separate sources of GW via density perturbation and graviton emission via Hawking evaporation. For the most optimistic scenario with very high scale seesaw consistent with
neutrino mass and leptogenesis, this leads to a multi-peaked GW spectrum with peak frequencies lying in the MHz-EHz range.
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High Energy Astrophysical Phenomena
A Collapsar-Disk Origin for GW190814
Vishal Baibhav, Brian D. Metzger and Lam Hui
GW190814 was a remarkable gravitational-wave (GW) event: a merger between a 23
solar-mass black hole (BH) and a 2.6
solar-mass compact object, with an extreme mass ratio that is difficult to reproduce through standard isolated-binary or dynamical formation channels. Recent work has shown that
neutrino-cooled collapsar disks can become gravitationally unstable and fragment, producing
neutron stars (NSs) or low-mass BHs in orbit around the newly formed central BH. These fragments may subsequently interact, scatter, merge with one another, or inspiral into the central remnant. We propose that GW190814 originated from such a collapsar-disk fragment merging with the central BH. A key prediction of this scenario is a temporal association with a stripped-envelope
supernova preceding the GW event, and we identify the Type Ib
supernova candidate SN2019npv, which occurred inside the GW190814 credible volume approximately 60 days before coalescence, as a possible electromagnetic precursor. Although this delay is too long for a conventional kilonova counterpart, we show that three-body interactions among disk fragments can excite some compact objects to wide orbits and naturally produce merger delays of weeks to months. While GW190814 itself was not expected to produce detectable
tidal-disruption-powered emission, future delayed mergers in this channel could generate luminous transients through either reprocessed kilonova heating or shocks driven as merger ejecta collide with the preceding
supernova ejecta. Finally, treating SN2019npv as the host makes GW190814 a bright standard siren and yields H_0 = 70.5 (+9.2, -6.4) km/s/Mpc.
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High Energy Astrophysical Phenomena
First Results from the LSST Shadow Survey: The Restless Luminous Blue Variable AT2017des in the Virgo-Cluster Galaxy, NGC4532
Conor L. Ransome, Bhagya M. Subrayan, David J. Sand et al. (+66 more)
The Legacy Survey of Space and Time (LSST) will start in late-summer 2026, revolutionizing transient astronomy. Here, we present the Dark Energy Camera (DECam) Shadow Survey, which is designed to maximize the science potential of LSST by shadowing LSST observations of local
galaxy-cluster fields, producing a nightly cadence of these fields. The Shadow Survey will discover extremely young
supernovae (SNe), SN precursors, as well as other explosive transients and exotic phenomena, helping to characterize such transients at unprecedented cadence and depth when combined with LSST. We describe our workflow, pipeline, public data releases, and candidate vetting. As an early result of Shadow, we present the fitful luminous blue variable (LBV) eruptions of AT2017des in the Virgo-Cluster
galaxy NGC4532. AT2017des has short-timescale variability (of order 10 days), peaking at around $M_r=-12.5$mag, brighter than normal LBVs, and similar to the more extreme flaring of hot LBVs/SN impostors such as SN2000ch, AT2016blu, and the precursor activity of SN2009ip. Our spectral time-series reveals features typical of these hot LBVs and SN impostors/precursors. Combining our data with long-baseline photometry from additional observatories, we find that the peaks of the outbursts of AT2017des are getting brighter over time, with 2026 peak fluxes being up to 5 times greater than in 2023 and an average brightening of $\sim0.05$ mag yr$^{-1}$. The peaks of AT2017des are more luminous than those of most other LBVs, only being fainter than bright precursors such as SN2009ip, and extreme SN impostors such as AT2016blu. AT2017des may therefore be “ramping up” to a terminal explosion.
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All authors Conor L. Ransome, Bhagya M. Subrayan, David J. Sand, Brian Hsu, Xander J. Hall, Jeniveve Pearson, K. Azalee Bostroem, Jennifer E. Andrews, Joszef Vinko, J. Craig Wheeler, Phillip Noel, Lei Hu, Tomas Cabrera, Stefano Valenti, Wynn V. Jacobson-Galan, Nathan Smith, Alexei V. Filippenko, Mojgan Aghakhanloo, Igor Andreoni, Moira Andrews, Iair Arcavi, Raphael Baer-Way, Emma R. Beasor, Edo Berger, Federica B. Bianco, Peter Blanchard, Thomas G. Brink, Siddarth Chaini, Adrian Crawford, Yize Dong, Joseph Farah, Noah Franz, Sebastian Gomez, Melissa L. Graham, Daichi Hiramatsu, Agoston Horti-David, Griffin Hosseinzadeh, D. Andrew Howell, Philip A. James, Saurabh W. Jha, Charles D. Kilpatrick, Lindsey A. Kwok, Gavin P. Lamb, Amanda R. Lopes, Michael Lundquist, Clara E. Martinez-Vasquez, Thomas Matheson, Curtis McCully, Maryam Modjaz, Gregory S. H. Paek, Antonella Palmese, Avi Patel, Joanne L. Pledger, Aravind P. Ravi, Jeonghee Rho, Krisztian Sarneczky, Manisha Shrestha, Richard Smith, Analia V. Smith Castelli, Monika Soraisam, Jay Strader, Francisco Valdes, Sergiy Vasylyev, V. Ashley Villar, A. Katherina Vivas, Lifan Wang, Samuel D. Wyatt, Kathryn Wynn, WeiKang Zheng
Cosmology and Nongalactic Astrophysics
GalSBI: Forward Modelling Galaxy Clustering and Population
Silvan Fischbacher, Luca Tortorelli, Tomasz Kacprzak et al. (+1 more)
Forward modelling is a powerful approach for analyzing large-scale structure surveys. For this purpose, we extend the GalSBI framework to jointly model the
galaxy population and clustering using an efficient subhalo abundance matching scheme based on optimal transport. We use simulation-based inference to constrain the model parameters by comparing UFig image simulations with DES Y3 imaging data. As a validation, we find that
galaxy photometry and morphology agree well with multi-band imaging data of different depths, namely DES and HSC deep fields.
Galaxy clustering for simulation and data is also in good agreement when comparing the angular power spectrum for different magnitude and color cuts. We further compare simulated
redshift distributions against high-precision photometric
redshifts in HSC deep field imaging of the COSMOS field. We find the
redshift distributions across magnitude cuts to be similar to previous work, however with more realistic uncertainty modelling due to the addition of clustering contribution to sample variance. The agreement of the mean
redshifts with data is very good, between $0.2\sigma$ and $1.6\sigma$ for different magnitude cuts, with sample variance being the dominant uncertainty contributor in bright samples ($<24$ mag) and subdominant compared to
galaxy population model uncertainty in fainter samples. As a byproduct we measure the
galaxy luminosity function and
galaxy-
halo connection, which are broadly consistent with existing literature. The updated GalSBI code and
galaxy population model are publicly available. They enable accurate forward-modelled image simulations with realistic clustering, which can be used to model the effect of sample variance, source clustering,
redshift distributions, and blending in large-scale-structure surveys. This makes GalSBI a powerful tool for the analysis of current and next-generation cosmological
galaxy surveys.
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All authors Silvan Fischbacher, Luca Tortorelli, Tomasz Kacprzak, Alexandre Refregier
Cosmology and Nongalactic Astrophysics
Accurate modeling for 3$\times$2pt analyses in Roman and Rubin: a study of model approximations
Junzhou Zhang, Chihway Chang, Jiachuan Xu et al. (+6 more)
One of the pillars of modern cosmology is the use of
galaxy imaging surveys to extract information from the large-scale structure. In recent surveys, this measurement is typically performed through a 3$\times$2pt analysis, which combines auto- and cross-correlations between
galaxy density and
galaxy weak
lensing. In this paper, we carry out a systematic study of three modeling approximations commonly used in such analyses: 1) applying the Limber approximation, 2) neglecting
redshift-space distortions, and 3) using less accurate models for the nonlinear matter power spectrum. We carry out the study in the context of the final data from two major Stage-IV
galaxy imaging surveys: the Nancy Grace Roman Space
Telescope's High Latitude Imaging Survey and the Vera C. Rubin Observatory's Legacy Survey of Space and Time. To do this, we first validate our modeling pipeline, implemented in the software package CoCoA, against an established code base, CCL. Next, we perform a simulated likelihood analysis to assess the impact of these approximations on the cosmological constraints. We find all three effects to be important; neglecting any of them can induce biases in cosmological constraints approaching or exceeding $1\sigma$, and exceeding $2\sigma$ for Rubin in several cases. Moreover, we explore how the lens-
galaxy sample configuration and scale-cut choice can influence the constraints.
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All authors Junzhou Zhang, Chihway Chang, Jiachuan Xu, Vivian Miranda, Chun-Hao To, Haley Bowden, Kaili Cao, Tim Eifler, Roman HLIS Cosmology PIT
High Energy Astrophysical Phenomena
Signatures of $^{56}$Ni Mixing and Neutron-rich Ejecta in Supernovae
Nikhil Sarin
Supernova lightcurves are often interpreted with one-zone radioactive-decay models that ignore a key variable that can affect interpretation and inferred parameters: the distribution of radioactive material. Using a multi-shell model, we explore the impact of $^{56}$Ni mixing in
supernovae and r-process material in collapsars. Moving $^{56}$Ni outward reduces the overlying
diffusion column, producing faster and brighter rises at fixed $\Mni$, $\Mej$, and $\Ek$, and changes the tail through local gamma-ray leakage. A fast, bright rise is not, by itself, evidence for low ejecta mass or a requirement for engine power, with significant overlap between highly mixed and engine-powered lightcurves. One-zone fits to mixed bolometric light curves produce visually good fits but biased parameters. At fixed opacity, outward mixing is absorbed mainly by low inferred $\Mej$ and high inferred $f_{\rm Ni}$, while $\Mni$ remains stable. If opacity is free, the fully mixed case is recovered with $\kappa^{\rm fit}/\kappa^{\rm input}\simeq0.24$. These shifts affect inferred explosion energies and progenitor mappings, and amplified in photometric fits. Exploring collapsar r-process enrichment, we find that the signature is not always a NIR excess and depends sensitively on the nickel-powered background, radial placement, angular distribution, and viewing angle of
neutron-rich ejecta. In our setup, spherical models often show optical suppression and delayed colour
evolution. Our disk-wind models suggest that fast-rising on-axis GRB-SNe are poor r-process targets for equatorially confined
neutron-rich winds, and become constraining only if the r-process material reaches latitudes $\gtrsim 30^\circ$ from the equatorial plane.
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Astrophysics of Galaxies
Constraints on the Gas Geometry Surrounding Little Red Dots through Narrow-Line Diagnostics
Visal Sok, Erica J. Nelson, Mitchell C. Begelman et al. (+10 more)
Little Red Dots (LRDs) are a recently identified population of high-
redshift sources, with a common interpretation being accreting black holes embedded within a spherical, optically thick gas envelope. Within this framework, some models propose that the continuum arises from the dense-gas envelope, where hard ionizing radiation from the central engine is reprocessed into a
stellar-like photosphere with an effective temperature of $\sim$5000 K. This implies that both the UV continuum and narrow-line emission are then powered by the host
galaxy rather than an exposed central engine. To test whether this is consistent with the observed narrow-line ratios, we analyze multiple line diagnostics for a sample of $\sim$20 LRDs with high signal-to-noise NIRSpec grating spectra. We find that at least 40% of the LRDs have line ratios pointing toward high ionization parameter and electron temperature, with a further 15% also falling in the AGN regime for the Oi/H$\alpha$ diagnostic, indicative of harder ionizing radiation. These line ratios are incompatible with
stellar photoionization from a
star-forming host alone. This suggests lower density channels within the gas envelope through which high energy
photons can escape and excite the surrounding narrow-line emitting gas. At the same time, most LRDs lack strong high-ionization line emission, with He\,ii/H$\beta$ $\lesssim0.1$, consistent with an ionizing spectrum softer than that of a standard AGN. Together, these results disfavour a uniform gas envelope with a covering fraction of unity, and instead point to a more complex geometry that gives rise to anisotropic ionizing radiation.
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All authors Visal Sok, Erica J. Nelson, Mitchell C. Begelman, Jason Dexter, Francesco D'Eugenio, Jenny E. Greene, Joel Leja, Katherine E. Whitaker, Andrew J. Bunker, Pablo G. Pérez-González, Pierluigi Rinaldi, Alberto Torralba, Hannah Übler
Astrophysics of Galaxies
Active galactic nucleus driven jet feedback in cosmologically forming cool-core galaxy clusters I: The effect of hierarchical assembly on intra-cluster medium properties
Rainer Weinberger, Lorenzo Maria Perrone, Christoph Pfrommer et al. (+7 more)
The atmospheres of cool-core
galaxy clusters are excellent probes of astrophysical
plasmas. However, how the interplay between assembly and active
galactic nucleus (AGN) feedback leads to the observed gas profiles remains uncertain. We study the impact of hierarchical assembly on the intra-cluster medium (ICM) in cool-core
galaxy clusters using hydrodynamic simulations as part of the PICO-Cluster project. We compare cosmological zoom simulations employing an explicit AGN jet model against PICO-Cluster simulations with IllustrisTNG kinetic AGN feedback, as well as against isolated
galaxy cluster simulations using jet feedback. The
stellar and gas fractions of our cosmological
galaxy cluster simulations with jet feedback are in excellent agreement with observed
galaxy clusters, and the ICM thermodynamic profiles resemble those of local cool-core
galaxy clusters while those run with IllustrisTNG kinetic AGN feedback do not match these observations. In all simulations, cosmological and isolated, the AGN heating roughly balances the cooling losses, with
star formation being significantly suppressed. The most notable differences between the cosmological and isolated simulations are the resulting velocity and multi-phase structure: gas at radii $> 50$ kpc is shaped by satellite
galaxies rather than jet feedback originating form the central
galaxy. This leads to significant differences in non-thermal pressure support, with only the cosmological simulations being consistent with recent observations. A second notable difference is the abundance of warm ($<10^5$ K) gas beyond the core region, which is absent in our isolated simulation. Our results highlight the need for taking cosmological assembly into account in comparisons of the ICM dynamics and its multi-phase nature, while self-regulation is altered by hierarchical assembly via merger-driven growth of the central supermassive black hole.
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All authors Rainer Weinberger, Lorenzo Maria Perrone, Christoph Pfrommer, Thomas Berlok, Ewald Puchwein, Léna Jlassi, Rosie Talbot, Joseph Whittingham, Rüdiger Pakmor, Volker Springel
Earth and Planetary Astrophysics
C, N, O, S, and photochemistry in a temperate giant planet orbiting a late M dwarf
Michael Zhang, Qiao Xue, Jeehyun Yang et al. (+20 more)
We report the JWST NIRSpec/PRISM transit spectrum of TOI-6894b, an exceptional 420 K sub-Saturn that is one of the rare
giant planets transiting a late M
dwarf. Remarkably, both the light curve and the transit spectrum exhibit almost no
stellar contamination. The spectrum is dominated by prominent absorption features from CH4 and the photochemical product CS2. For the first time in a transit spectrum, NH3 is visually evident, while subtler features from H2O and CO2 can also be seen. We significantly improve upon state-of-the-art photochemical reaction networks, and use our new network to run radiative-convective photochemical ("RCP") models at different
metallicities. These models show that the spectrum–in particular the size of the NH3 and CO2 features relative to the CH4 and H2O features–is most consistent with a
metallicity of 3–10x
solar. Using a semi-free
retrieval framework that perturbs the RCP model's abundance and temperature profiles to fit the data, we find that the
planet's C/O, N/O, and S/N ratios are consistent with
solar values. A grid
retrieval on 1D radiative-convective photochemical
equilibrium (RCPE) models reveals a similar result: [M/H]=0.46 +- 0.08 and C/O=0.69 +- 0.06. The
planet's atmospheric
metallicity, abundance ratios, and bulk metal fraction are all strikingly similar to that of Jupiter, Saturn, and other gas
giant exoplanets, despite orbiting a very low-mass
star.
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All authors Michael Zhang, Qiao Xue, Jeehyun Yang, Vighnesh Nagpal, Michael R. Line, Guangwei Fu, Matthew C. Nixon, Jacob L. Bean, Peter Gao, Eliza M.-R. Kempton, Luis Welbanks, Edward M. Bryant, Daniel Bayliss, Madison Brady, Jean-Michel Désert, Vincent Van Eylen, Jonathan J. Fortney, Andrés Jordán, Vivien Parmentier, Caroline Piaulet-Ghorayeb, Elyar Sedaghati, Kevin B. Stevenson, Amaury H.M.J. Triaud
High Energy Astrophysical Phenomena
Modern tidal interaction models for rapid binary population synthesis: II. Binary black hole formation, mergers, and spins
Veome Kapil, Ilya Mandel, Jeff Riley et al. (+3 more)
We present predictions for the merger rates and effective
spin ($\chi_{\rm eff}$) distribution of binary black holes (BBHs) from isolated binary
evolution, using a new self-consistent
tidal dissipation implementation in the rapid binary population synthesis code COMPAS. Most of the first-born black holes (BHs) in our simulated merging BBHs are formed with zero
spins, with the exception of BBHs formed from chemically homogeneous
evolution. The
spins of the second-born BHs with the new model depend significantly on the efficiency of
tidal dissipation and mass transfer history, and crucially, are not always consistent with pre-
supernova synchronization. High-$\chi_{\rm eff}$ binaries preferentially merge at high
redshift due to smaller binary separations at BBH formation and shorter coalescence times, thus rendering them largely inaccessible to current gravitational wave (GW) detectors. We expect the intrinsic
spin distribution of merging BBHs formed from isolated
evolution to be strongly biased toward low $\chi_{\rm eff}$ with current detectors, with a third of systems having $\chi_{\rm eff} < 0.05$ and only $\sim 3\%$ with $\chi_{\rm eff}>0.5$. However, $\chi_{\rm eff}$ will increase as GW detectors become sensitive to higher
redshift sources, with up to $\sim 15\%$ of systems having $\chi_{\rm eff}>0.5$.
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All authors Veome Kapil, Ilya Mandel, Jeff Riley, Evgeni Grishin, Jim Fuller, Emanuele Berti
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
SN1987A Constraints of Light $\boldsymbol{Z'}$ with Non-Mixing Polarisations
Debottam Das, Purusottam Ghosh and Rahul Puri
The observation of
supernova 1987A (SN1987A) provides a unique opportunity to explore new physics beyond the Standard Model (BSM). The production of new particles in the
supernova core could accelerate the cooling process, leading to additional energy loss and consequently reducing the duration of the observed
neutrino burst at detectors. Therefore, any BSM interactions that affect
supernova cooling are subject to stringent constraints from SN1987A observations. In this paper, we revisit the constraints on light gauge
bosons (LGBs) by reassessing the validity of underlying assumptions about the polarisation intermixing. We argue that the intermixing between different polarisation modes is suppressed in the low coupling regime. Using the light gauge
boson in the $L_\mu-L_\tau$ model as an example, we find that considering the independent energy transport of longitudinal and transverse polarisations can lead to significant modifications of the SN1987A bounds on the parameter space.
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Instrumentation and Methods for Astrophysics
Machine Learning and Deep Learning for Exoplanet Detection and Atmospheric Characterization with JWST and the Upcoming Ariel Mission
Muallim Yakubu and Vwavware Oruaode Jude
The detection and atmospheric characterization of
exoplanets have entered a new data-intensive era driven by the James Webb Space
Telescope and the upcoming Ariel mission. Modern surveys produce millions of light curves and high-resolution spectra that overwhelm traditional pipelines, motivating the rapid integration of Machine Learning and Deep Learning methods into the
exoplanet workflow. This review synthesizes the latest progress in applying ML/DL techniques to
exoplanet detection (transit identification, candidate vetting, false-positive rejection) and atmospheric characterization (
retrieval, detrending, cross-correlation, surrogate modelling) in the context of JWST and Ariel. We start with classical
algorithms such as Random Forests and Convolutional Neural Networks, move through
Transformers and Recurrent architectures, then survey modern simulation-based inference using Neural Posterior Estimation and Flow Matching Posterior Estimation with normalizing or continuous normalizing flows. We discuss
benchmark efforts, including the Ariel Machine Learning Data Challenges (2019 to 2025) hosted with NeurIPS, and key JWST case studies such as the WASP-39b Early Release Science programme. Results indicate that DL approaches consistently match or exceed traditional pipelines in both speed and accuracy, while ML-driven
retrievals reduce inference time from CPU-hours to seconds and can accelerate nested-sampling
retrievals by factors of 3-8 without compromising
Bayesian evidence. We identify outstanding challenges interpretability, calibration of uncertainties under noisy data, hybrid modelling, and the generalization of models across instruments and
planet populations and outline a research roadmap spanning the JWST era and beyond into Ariel's launch in 2029.
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Instrumentation and Methods for Astrophysics
Pioneer 10/11 Telemetry Explanatory Almanac
Viktor T. Toth
This document is intended to accompany our first release of edited Pioneer 10/11 telemetry data. The purpose of this data release is to provide a data set for the evaluation of the effect of on-board systematic forces on Pioneer orbits. Telemetry readings were selected for inclusion with this purpose in mind. The files presented here are all in standard formats (tab-delimited ASCII text or Microsoft Excel spreadsheets) and can be utilized using standard data editing tools. We describe the history and availability of the raw telemetry data, documentation that can be used to interpret the data, and the tools we built in order to extract the data. We also describe script programs that were used to generate data files for release, and the manual editing process that was used to bring these data files to their final form.
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Astrophysics of Galaxies
Little Red Dots on FIRE: Exploring the formation and observational signatures of ultra-compact early galaxies
Niranjan Chandra Roy, Daniel Anglés-Alcázar, Rachel K. Cochrane et al. (+15 more)
Little Red Dots (LRDs) are compact sources with broad Balmer lines, Balmer breaks, anomalous UV emission, rising red continuum, and uncertain origin. We use FIRE cosmological simulations, 3D
dust radiative transfer, and synthetic emission-line data cubes to test whether ultra-compact early
galaxies can reproduce LRD-like observables without invoking AGN. In progenitors of present-day group
halos ($M_{\rm halo} > 10^{13.5} M_{\odot}$), we identify transient phases at $z \approx 4-8$ lasting $\sim 150-400$ Myr in which strong dissipative inflows build massive ($M_{\star} \sim 10^{8.5}-10^{10.5} M_{\odot}$), UV-bright ($-23 \lesssim M_{\rm UV} \lesssim -20$), ultra-compact ($R_{\rm eff} < 300$ pc)
stellar cores with extreme circular velocity ($V_{\rm circ} > 500$ km s$^{-1}$) and consistent with several LRD properties: strong Balmer breaks ($F_{\nu}(4200{\rm \r{A}})/F_{\nu}(3500{\rm \r{A}}) \sim 2$); blue UV beta slopes ($\beta_{\rm UV} \approx -1.25$);
dust masses; ALMA non-detections; and Balmer-line widths up to $\sim 1500$ km s$^{-1}$ broadened by
galaxy-scale dynamics. However,
stellar emission and host-
galaxy kinematics alone do not reproduce the red rest-optical continuum, more extreme Balmer breaks ($\gtrsim 2.5$) and line widths ($\gtrsim 2000$ km s$^{-1}$), or the broad-Balmer/narrow-forbidden-line signature of broad-line AGN. The same ultra-compact conditions efficiently fuel central BHs, suggesting a hybrid
stellar+AGN scenario in which compact
stars explain the UV continuum, Balmer break, and intermediate line widths while AGN supply the red optical continuum and more extreme line properties. With
halo masses $M_{\rm halo} \sim 10^{11-12.5} M_\odot$ and comoving abundance $\sim 2 \times 10^{-5} {\rm cMpc}^{-3}$ (for $\sim 20\%$ duty-cycle at $z \approx 4-8$), ultra-compact
galaxies can contribute to the massive, bright LRD population.
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All authors Niranjan Chandra Roy, Daniel Anglés-Alcázar, Rachel K. Cochrane, Alexander J. Richings, Jonathan Mercedes-Feliz, Christopher C. Hayward, Claude-André Faucher-Giguère, Erini Lambrides, Robert Feldmann, Boon Kiat Oh, Andrew Marszewski, Guochao Sun, Kelcey Davis, Jed McKinney, Caitlin M. Casey, Tanio Díaz-Santos, Madisyn Brooks, Grace Farrell
Astrophysics of Galaxies
Ram-pressure signatures in the dwarf irregular galaxy SextansB revealed by deep MeerKAT HI observations
Brenda Namumba, Neel Kolhe, Francois Hammer et al. (+12 more)
The impact of extremely low-density environments such as the diffuse intergalactic medium (IGM) on the neutral gas distribution of
dwarf galaxies remains poorly explored observationally. We present deep MeerKAT HI 21 cm observations of the Local Group
dwarf irregular
galaxy Sextans B that achieve a spectral resolution of 1.4 km/s and reach column-density sensitivities down to 3.3 x 10^18 cm^-2, allowing us to trace the extended HI disc and faint outer structures. The low-column-density HI distribution is asymmetric and reveals a rosette-like filamentary structure superposed on the HI disc. Comparison with the
stellar distribution shows offsets between the gaseous and
stellar components, with the
stellar disc remaining relatively symmetric while the HI envelope becomes increasingly disturbed. 3D kinematic modelling with TiRiFiC reproduces the global velocity gradient but reveals differences between the approaching and receding sides of the rotation curve at large radii, indicating departures from axisymmetric rotation. While
stellar feedback can produce small-scale cavities and
turbulence in
dwarf galaxies, it cannot generate the filamentary HI structure, the asymmetric outer HI envelope, or the divergence between the approaching and receding rotation curves. This is consistent with interaction with a diffuse IGM. Hydrodynamical simulations tailored to Sextans B show that IGM ram pressure acting on the outer gas disc can produce asymmetric gas distributions, filamentary structures, and kinematic perturbations. The combination of morphological and kinematic signatures suggests that the outer HI disc of Sextans B is affected by ram-pressure interaction with the diffuse IGM in the outskirts of the Local Group. This is the second strong example in the Local Group, after WLM, showing that a very low-density IGM can significantly influence the gas distribution and kinematics of
dwarf galaxies.
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All authors Brenda Namumba, Neel Kolhe, Francois Hammer, Yanbin Yang, Claude Carignan, Roger Ianjamasimanana, Gyula I. G. Józsa, Lourdes Verdes-Montenegro, Haifeng Wang, Hao Chen, Xin Huang, Fortune Ndalama, Amidou Sorgho, Marie Korsaga, Saul P. Phiri
Cosmology and Nongalactic Astrophysics
Revisiting the 'Lensing is Low' Problem with UNIONS
Martine C. T. Campbell, Jack Elvin-Poole, Michael J. Hudson et al. (+11 more)
We present new measurements of the
galaxy-
galaxy lensing (GGL) signal around
Baryon Oscillation Spectroscopic Survey (BOSS) CMASS
galaxies using background sources from the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS). With high-quality imaging of background sources and a survey overlap of approximately 2650 square degrees, we obtain precise large-scale GGL measurements. Building on these new measurements, we revisit the so-called '
lensing is low' problem, wherein
galaxy-
halo connection models calibrated on
galaxy clustering (GC) data over-predict the GGL signal by 20-40% assuming CMB-based cosmological parameters. We model the
galaxy-
halo connection using a
halo occupation distribution (HOD), and perform joint fits to both GGL and GC signals across a wide range of scales, as well as a GC-only fit. In contrast to previous work, we do not find a significant '
lensing is low' effect in the CMASS sample, although the best joint fits are achieved by decreasing the amplitude of the matter power spectrum slightly relative to the Planck cosmological parameters. Overall, we find that two models describe our observables similarly well: one where HOD and cosmological parameters are free, and one where HOD, cosmological, and feedback parameters are free. Importantly, we emphasise the role of large scales in constraining the
lensing is low effect, shifting the narrative away from an exclusively small-scale issue.
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All authors Martine C. T. Campbell, Jack Elvin-Poole, Michael J. Hudson, Thomas de Boer, Sacha Guerrini, Fabian Hervas-Peters, Hendrik Hildebrandt, Martin Kilbinger, Eugene A. Magnier, Alan W. McConnachie, Charlie T. Mpetha, Romain Paviot, Ludovic Van Waerbeke, Anna Wittje
Astrophysics of Galaxies
The EDGE-CALIFA Survey: Star Formation Efficiency and Galaxy Quenching across 62 Main Sequence, Green Valley, and Red Galaxies
Yu-Hsuan Teng, Alberto D. Bolatto, Peter J. Teuben et al. (+26 more)
We present GBT-EDGE, a new CO(1-0) survey using the Green Bank
Telescope to map 62 nearby (10-140 Mpc)
galaxies spanning the
star-forming main sequence (SFMS), green valley, and red sequence. The
galaxy sample is selected from the CALIFA survey with integral field spectroscopy (IFS), which provides a representative census of local
galactic environments. Combining the CO
dataset with CALIFA's optical IFS measurements, we derive molecular gas masses,
star formation rates (SFR),
metallicities, and
stellar mass densities to measure
star formation efficiency (SFE) and investigate the physical drivers of
galaxy quenching. We obtain a median molecular gas depletion time of $2.10^{+2.35}_{-1.31}$, $6.90^{+17.00}_{-3.67}$, and $127.7^{+201.6}_{-113.4}$ Gyr for our sample of main sequence, green valley, and red
galaxies, respectively, assuming a
Galactic CO-to-H2 conversion factor. By applying various conversion factor prescriptions, we also confirm a systematic decrease of SFE with
galaxy's offset below the SFMS, regardless of the adopted prescription. This suggests that the low SFR in some quenched
galaxies is primarily driven by suppressed SFE rather than an absence of molecular gas. Our results provide evidence that
galaxies below the main sequence can retain substantial molecular gas reservoirs comparable to
star-forming
galaxies, but they exhibit longer depletion times and form
stars inefficiently, possibly due to the combined effects of low gas density and morphological quenching mechanisms.
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All authors Yu-Hsuan Teng, Alberto D. Bolatto, Peter J. Teuben, Erik Rosolowsky, David T. Frayer, Amanda A. Kepley, Sebastian F. Sanchez, Tony Wong, Adam K. Leroy, Dario Colombo, Serena A. Cronin, K. Decker French, Veselina Kalinova, Rebecca C. Levy, Karin M. Sandstrom, Vicente Villanueva, Jorge K. Barrera-Ballesteros, Zein Bazzi, Yixian Cao, Alex Green, Rodrigo Herrera-Camus, Eduardo A. D. Lacerda, Jialu Li, Alejandra Z. Lugo-Aranda, Jocabed Martinez-Lopez, Elizabeth Tarantino, Akshat Tripathi, Carolyn G. Volpert, Di Wen
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Observables and conformal properties of dark matter admixed isentropic neutron stars
Arijit Das, Prashanth Jaikumar, Adarsh Karekkat et al. (+1 more)
We construct an equation of state for isentropic dark-matter-admixed
neutron stars (DMANS) with a hot core and relatively cold crust incorporating self-consistent temperature and DM density profiles for GeV-scale fermionic DM. We show that the enhancement of central
stellar density due to DM accumulation, previously reported for cold
neutron stars, remains robust. Substantial observable effects of DM accumulation arise only for sufficiently massive
stellar configurations. Similar to earlier studies of cold NS, the speed of sound profile is shown to exhibit non-monotonic behavior for sufficiently large DM density in the core. We identify a competition between thermal effects due to nonzero values of
entropy per
baryon and softening effects of the dark sector which drive macroscopic properties and conformality indicators in opposite directions. This competition determines the onset of conformality near the
stellar core and indicates that conformality signatures attributed to
quark-matter in cold NS could be mimicked by DM admixture in isentropic
stars.
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All authors Arijit Das, Prashanth Jaikumar, Adarsh Karekkat, Tanumoy Mandal
Solar and Stellar Astrophysics
Corotating Interaction Regions (CIRs): evolution over a solar lifetime
Rose F. P. Waugh and Moira Jardine
Corotating Interaction Regions (CIRs) are persistent structures in
stellar winds that arise from the interaction between fast and slow wind streams. They are known to generate shocks and high-energy particles, potentially influencing the erosion of planetary atmospheres and space weather conditions. Although extensively studied for the present-day Sun, their
evolution over a
star's lifetime and implications for planetary environments remain less explored. We model the
evolution of CIRs around a
solar-mass
star using a rotational
evolution framework and assess how their location, shape, and particle distributions vary with
stellar age. We find that CIRs form closer to the
star during early
spin-up phases and migrate outward during
spin down, with the minimum CIR radius inversely related to rotation rate. We show that the distribution of high-energy particles produced in CIR shocks varies significantly with age. During the Hadean period, when Earth's atmosphere evolved significantly, CIRs may have generated a number of energetic particles that is \(10^3\) to \(10^7\) times greater than for the present-day Sun. The frequency and strength of CIR-
planet interactions also peak during early rapid rotation phases. Furthermore, we demonstrate from this preliminary study that, for
stars with mass less than 1.4 Msun, whilst CIRs can form within the habitable zone, their shocks always form beyond it. This suggests that energetic particle impacts may rain inward from more distant regions, as with the present-day Sun. These findings have implications for habitability and the
evolution of atmospheres since these particles can alter the chemistry and escape rate of atmospheres.
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Astrophysics of Galaxies
Detection of Variability in Seyfert 2 Galaxies and Measurement of the Optical Scattering Region Size
Natalie Kovacevic, Xinyu Dai, Heechan Yuk et al. (+5 more)
One main theme of the Unification Model of active
galactic nuclei is that there is an obscuring
torus structure blocking the direct view of the central engine for Seyfert 2
galaxies. Here, we present the detection of long-term optical variability for a sample of nearby Seyfert 2s. We found that Seyfert 2s exhibit a relatively low but significant level of variability beyond the constant fluxes established by
galaxies over month to year time scales. The variability is also detected in the structure functions of Seyfert 2s. Assuming a simple variability suppression model by the scattering region and dilution due to host starlight, where the region smooths the unobscured
photon packets from the central engine as the light scatters over the
torus, we estimate AGN scattering region sizes by matching the variability amplitudes of Seyfert 1s to 2s. Our measured scattering sizes are largely consistent with the
torus size measured using their emission properties, suggesting that the scattering region is of a similar size as the
torus. Our results pave the way towards variability as a powerful and independent test for AGN unification models.
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All authors Natalie Kovacevic, Xinyu Dai, Heechan Yuk, Emilia Jaervelae, Tingfeng Yi, Patrick J. Vallely, Benjamin J. Shappee, Francesco Shankar
Cosmology and Nongalactic Astrophysics
Unifying the Dark Sector with the New Generalized Chaplygin Gas: Observational Constraints
Abdulla Al Mamon, Andronikos Paliathanasis and Subhajit Saha
In light of recent cosmological observations, we examine a generalized Chaplygin gas model with a
redshift-dependent exponent as a framework for describing the dark energy and dark matter content of the Universe. Specifically, we treat this fluid as a single unified component and test it against late-time background observational data. We employ Type Ia
supernova data,
cosmic chronometers, and
baryon acoustic oscillations from the second data release of the Dark Energy Spectroscopic Instrument. We perform a
Bayesian analysis for parameter estimation and compare the model with $\Lambda$CDM. We find that the generalized Chaplygin gas provides systematically higher values of the combined likelihood; nevertheless, once the larger number of free parameters is taken into account, both the
Bayesian evidence and the Akaike Information Criterion suggest that the model is statistically indistinguishable from $\Lambda$CDM.
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Earth and Planetary Astrophysics
Observing a 542-day transiting giant with large TTVs: The 2025 transit of HIP 41378 f and new constraints on the outer system
Pietro Leonardi, Alexandre Santerne, Luca Borsato et al. (+27 more)
Characterizing long-period transiting
exoplanets is inherently challenging due to the rarity and long duration of transit events. Yet, these systems provide unique insights into planetary formation, migration, the detection of exomoons, and
primordial atmospheres by occupying a sparsely populated region of the
exoplanet parameter space. The complexity increases further for long-period
planets near mean-motion resonances, where transit timing variations (TTVs) can reach amplitudes of several hours to days. We present a coordinated space- and ground-based observing campaign, using photometry from NEOSSat, multiple LCOGT sites, MuSCAT, MuSCAT3, Tierras and NGTS, to capture the 19-hour transit of the long-period
giant exoplanet HIP 41378 f ($P$ = 542 d, $R$ = 9.5 $R_{\oplus}$) on 31 October 2025. Our transit analysis constrains the time of inferior conjunction to $T_{\mathrm{C}} = 2460980.888 \pm 0.029~\mathrm{BJD_{TDB}}$, occurring $\sim 7$ hours earlier than predicted from its linear ephemeris. This significant offset is consistent with the previously reported TTVs of HIP 41378 f, making it the longest-period
exoplanet known to exhibit measurable TTVs. By combining this new precise measurement to the transit timings of the two outer
planets in the system (HIP 41378 d and HIP 41378 e), we perform a dynamical modeling of the system, using the N-body integrator TRADES, refine the ephemeris of HIP 41378 f, and predict future transit events for all three outer transiting
planets.
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All authors Pietro Leonardi, Alexandre Santerne, Luca Borsato, Salomé Grouffal, Christopher R. Mann, Giampaolo Piotto, Karen A. Collins, Patrick Tamburo, Yugo Kawai, Denise C. Stephens, Juliana García-Mejía, Edward M. Bryant, Krzysztof Sz. Zielinski, Daniel Bayliss, David Charbonneau, Jerome P. de Leon, Gareb Fernández-Rodríguez, Akihiko Fukui, Eric G. Hintz, Keith Horne, Keisuke Isogai, James S. Jenkins, Norio Narita, Ramotholo Sefako, Avi Shporer, Richard P. Schwarz, Gregor Srdoc, Peter Wheatley, Jamie B. Williams, Jorge Fernández Fernández
Cosmology and Nongalactic Astrophysics
DSWIM:Efficient and Stable Deterministic Computation of Warm Inflation Perturbations
Umang Kumar
Warm inflation perturbations are sourced by both thermal and
quantum fluctuations and are commonly computed through
stochastic realizations of the perturbation equations, as implemented in the publicly available code SWIM. Deterministic formulations based on correlation
matrix evolution provide a computationally efficient alternative, but can become numerically ill-conditioned when the perturbation variables evolve over widely different scales. In this work, we extend SWIM by introducing a deterministic module, DSWIM, based on correlation
matrix evolution. We introduce a physically motivated scaling
matrix transformation derived from the effective Hubble scaling of the perturbation variables. The transformed system preserves the
primordial curvature power spectrum exactly while substantially improving the numerical conditioning of the deterministic
evolution equations. Using representative warm inflation models, we show that the scaled framework suppresses numerical artifacts, improves the robustness of the deterministic
evolution, and yields substantial computational speedups while preserving accuracy. We further show that correlated thermal noise contributions arise naturally through the
diffusion matrix structure, resolving previously observed discrepancies between
stochastic and deterministic implementations. Our results establish DSWIM as a numerically robust and computationally efficient framework for computing warm inflation scalar perturbations.
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High Energy Astrophysical Phenomena
Spectral and timing variability of the transient ultraluminous X-ray source NGC 4631 X-4
Sinan Allak, Wei Yu, Lorenzo Ducci et al. (+4 more)
Ultraluminous X-ray sources (ULXs) are among the best laboratories for studying super-Eddington
accretion onto compact objects. We present a detailed spectral and timing analysis of the transient ULX NGC 4631 X-4 using archival Chandra, XMM-Newton, and Swift/XRT observations. The source exhibits pronounced spectral and flux variability on both short and long timescales, with luminosity variations exceeding two orders of magnitude. Its X-ray spectra are well described by absorbed multicolor disk blackbody and power-law models, with characteristic inner disk temperatures of 0.9-1.4 keV and
photon indices of 2.0-2.4. The source does not follow the standard luminosity-temperature relation expected for a geometrically thin, optically thick
accretion disk. No coherent pulsations or quasi-periodic oscillations are detected, while the short-term variability is dominated by aperiodic fluctuations and kilosecond peak-like structures, consistent with clumpy winds and
geometric effects in a super-Eddington
accretion flow. Overall, the spectral and timing properties support super-Eddington
accretion onto a
stellar-mass compact object, although the current data do not allow us to distinguish uniquely between a
neutron star and a
stellar-mass black hole accretor.
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All authors Sinan Allak, Wei Yu, Lorenzo Ducci, Andrea Santangelo, Aysun Akyuz, Faruk Soydugan, Valery Suleimanov
High Energy Astrophysical Phenomena
A Tentative Double Excess in the Gamma-Ray Spectrum of the Fermi Blazar 4FGL J0604.9-0000
Shi-Ju Kang
Based on 17.75 years of
Fermi-LAT observations, we report a tentative double excess in the gamma-ray spectrum of the blazar 4FGL J0604.9-0000, with peak energies at approximately 1.5 GeV and 11 GeV. The two excesses are modeled as double Gaussian components. For the lower-energy excess, the best-fit centroid is $E_1 = 1.59\pm0.07$ GeV with a width fixed to the instrumental resolution ($\sigma_1 = 0.145$ GeV). For the higher-energy excess, the centroid is $E_2 = 11.15\pm0.61$ GeV and the width is constrained to $\sigma_2 = 1.185$ GeV (about 10% of the peak energy), which is comparable to the
Fermi-LAT energy resolution at that energy. The two features have local significances of $2.6\sigma$ and $3.7\sigma$ (3 dof), respectively. A joint likelihood analysis yields a combined test statistic of TS $\simeq 27$, corresponding to a local significance of approximately $4.3\sigma$ (4 dof, without correction for trials and the look-elsewhere effect) or about $4.8\sigma$ (2 dof). To our knowledge, no other active
galactic nucleus has been reported to show a similar double-excess candidate. The observed energy ratio of $\sim$1:7 is difficult to explain with standard astrophysical emission processes. However, the energies and their ratio are consistent with dark matter annihilation (e.g., $\chi\chi\to\gamma\gamma$ and $\chi\chi\to\gamma\gamma'$) for a particle mass near 11 GeV, making this source a promising target for follow-up observations with next-generation gamma-ray
telescopes.
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Earth and Planetary Astrophysics
Energy-Limited Radiolytic Habitability in the Shallow Martian Subsurface: Implications for ExoMars Rosalind Franklin and Tianwen-3
Dimitra Atri
The surface of Mars is sterilized by ionizing radiation and pervasive oxidants; its shallow subsurface, shielded from ultraviolet light and the most reactive oxidation, may instead preserve habitable conditions. The radiolytic habitable zone (RHZ) hypothesis holds that
galactic cosmic rays can drive water and oxychlorine radiolysis there, generating H2 and oxidants that support chemolithotrophy without sunlight or geothermal heat. We develop a quantitative framework coupling Monte Carlo GCR transport, phase-resolved radiolysis chemistry, water-activity and H2-retention treatments, and microbial maintenance-power constraints for Gale Crater, Oxia Planum, southern Utopia, and Arabia/Mawrth, expressing radiolytic chemical energy as a depth-resolved redox power comparable to the power requirements of life. H2 retention is the dominant control. Sorbed or mineral-associated retention yields 4-6 x 10^-13 W kg^-1 at protected depth (>=10 cm), whereas connected-pore free-gas escape lowers redox power by two to four orders of magnitude. Gale remains inactive under both retention assumptions, consistent with published SAM evolved-gas analyses. Even in retained-H2 active terrains, supported
cell density reaches only 10^3-10^5
cells cm^-3 at subseafloor maintenance powers. The framework predicts a spatially restricted, low-density RHZ, testable by stepped H2 evolved-gas analysis of protected-depth samples from ExoMars Rosalind Franklin, Tianwen-3, or Mars Sample Return.
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Solar and Stellar Astrophysics
Sergey A. Belov, Dmitrii Y. Kolotkov, Akshay V. Mehta et al. (+1 more)
The temporal morphology of
flare light curves encodes the underlying
flare physics, and deviations from the typical
flare profile may indicate the presence of mechanisms not captured by a standard
flare model. To search for such time-domain deviations from a "standard"
flare, we develop an unsupervised Deep Support Vector Data Description (Deep SVDD) model, which learns a compact representation of normal
flares, against which unseen anomalous
flares are identified. The model is trained on synthetic light curves with a "normal"
flare morphology, generated from existing analytical
flare trend models with noise. Using the distribution of normal
flare data, we introduce a probabilistic
Flare Anomaly Index (FLAI) which allows for separating
flare light curves into three distinct classes: normal data (ND), weak anomalies (WA), and strong anomalies (SA). Application of FLAI to the Kepler
flare catalogue (white light) reveals that 36% and 30% of events belong to the WA and SA classes, respectively. For M- and X-class
solar flares from the STIX
flare list, 25% and 32% of events in the 15-25 keV channel are classified as WA and SA, respectively, versus 15% for both WA and SA classes in the 4-10 keV channel. Thus, anomalous
flares appear more frequently in the STIX high-energy channel. These results show that both
solar and
stellar flares often deviate from the normal
flare population used for model training, suggesting departures from the standard
flare scenario, such as modified energy release and dissipation, or the development of wave and oscillatory processes in
flare sites.
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All authors Sergey A. Belov, Dmitrii Y. Kolotkov, Akshay V. Mehta, Laura A. Hayes
Earth and Planetary Astrophysics
A Multiband Study of the HR 4796A Disk in the Optical Using MagAO-X
Jay K. Kueny, Alycia J. Weinberger, Zhe-Yu Daniel Lin et al. (+18 more)
We present total intensity images of the debris disk around HR 4796A from observations spanning 2023 to 2025 with the Magellan extreme adaptive optics instrument (MagAO-X). We detected the disk at high signal-to-noise ratios at $g' (527$ nm), $r' (615$ nm), $i' (762$ nm), and $z' (909 $ nm). Additionally, we present images collected using the "
star-hopping" technique that show the entirety of the disk, including the dramatic forward-scattering at the minor axis. We subjected our images to a battery of modeling techniques to constrain the geometry and photometry of the disk. Leveraging our clear detections of the disk's minor axis, we modeled the scattering phase function (SPF) using a basis of the Legendre
polynomials. To mitigate self-subtraction artifacts in our angular differential imaging, we implemented a forward-modeling pipeline that generates a pixel-based freeform disk forward model leading to a deconvolved image of the disk. Our best-fit disk models reveal: (1) highly forward-scattering SPFs with a minimum at the $\sim65^{\circ}$ scattering angle, (2) a faint
halo of
dust just exterior to the spine of the disk that is not well-described by a broken power law density profile, (3) a red spectral slope for the
dust, and finally (4) a compact, clump-like feature in the freeform disk models. Our empirically-measured SPFs suggest that the scattering is dominated by large, highly-absorptive grains. However, we emphasize the need for testing advanced irregular grain models using our SPFs to learn more about the physical and chemical properties of this complex system.
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All authors Jay K. Kueny, Alycia J. Weinberger, Zhe-Yu Daniel Lin, Joseph D. Long, Jared R. Males, Joshua Liberman, Jialin Li, Sebastiaan Haffert, Laird M. Close, Eden McEwen, Maggie Y. Kautz, Olivier Guyon, Logan Pearce, Parker T. Johnson, Katie Twitchell, Alex Hedglen, Avalon Gower, Warren Foster, Jhen Lumbres, Lauren Schatz, Elena Tonucci