arXiv subjects

Daniel J. Price

Publications and source records attributed to Daniel J. Price.

At least 37 records · Page 2Linked to original sources

arXiv2026

A benchmark for binary star interaction with a supermassive black hole in general relativity

Most galaxies have supermassive black holes (SMBH) at their centres, surrounded by stars with binary systems also present in this environment. We use two schemes - post-Newtonian (PN) and a scalar perturbation to a background metric to numerically solve the three-body problem of a binary with a SMBH. We test three different PN formulations for the PN scheme: The Einstein-Infeld-Hoffman equation, pair-wise implementation of two-body PN-terms for three bodies and the Arnowitt-Deser-Misner Hamiltonian. We compare these approaches for one million solar mass and one billion solar mass black holes, and find a statistical match between the two approximations for stellar mass binary interacting with a million solar mass black hole. We also perform a statistical study for encounters with this black hole, and find that the higher order PN formulation matches with metric-with-perturbation scheme. However, we find a decrease in separation of the binary, and eccentricity variations between different schemes around the billion solar mass black hole. This behaviour is not present if binary has a large separation or is further away from the black hole due to decreased general-relativistic effects. We find that the pair-wise PN method results in a decrease in separation at pericentre in all test cases irrespective of the distance from the black hole or mass of the black hole, making this the least reliable method for solving this problem. Our work highlights the need for caution when interpreting the results in different formulations around SMBHs. This also shows that when understanding extreme mass ratio inspirals (EMRIs) using simulations, one should beware as the binary gets closer to the black hole.

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arXiv2026

exoALMA XXII: A Two-dimensional Atlas of Deviations from Keplerian Disks

Protoplanetary disks are the birthplaces of planetary systems, and deviations from Keplerian rotation imprinted in disk gas kinematics serve as key tracers of physical processes and the presence of protoplanets within disks. Using the the CO (J=3-2) data from the exoALMA Large Program encompassing 15 disks, we constructed two-dimensional (2D) maps of centroid velocity, line width, and peak intensity, and extracted non-Keplerian deviations by subtracting smooth Keplerian models. This paper provides the first systematic and uniform overview of 2D gas substructures across the entire exoALMA sample. We find that all targets exhibit large-scale deviations from smooth Keplerian disks, displaying a variety of morphologies including spiral-like structures, arc- or ring-like features, and patterns indicative of variations in the emitting surface height. Non-axisymmetric spiral-arm features are detected or suggested in five disks (CQ Tau, MWC 758, HD 135344B, HD 34282, and SY Cha), and are preferentially found in Herbig Ae/Fe systems. In contrast, some other sources (J1852, PDS 66, and V4046 Sgr), despite exhibiting noticeable deviations, appear to be dynamically quieter. This 2D atlas suggests that kinematic substructures are ubiquitous in large ($\gtrsim$ 100 au) protoplanetary disks with ages of a few million years, based on the observations obtained with sufficient sensitivity at moderate-to-high spatial resolution of $\sim$20 au and high velocity resolution of $\sim$0.1 km s$^{-1}$.

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arXiv2026

Dust traps and gas kinematic signatures in a crescent structure of a planet-forming disk

In the past few years, ALMA unveiled a variety of substructures (rings, spirals, crescents) in the continuum emission of most protoplanetary disks imaged at high spatial resolution. While the majority of disks presents axisymmetric ring-like structures in the dust brightness distribution, some sources display asymmetric morphologies (blobs, crescents) that have been often associated to vortices and/or mechanisms generated by the presence of one or more embedded planets. In this brief research report we present the analysis of the arc structure observed in the dust continuum emission of the disk around HD~163296, using high resolution ($\sim$8~au) matched continuum data from ALMA at four wavelengths. We characterize in detail the arc structures and present a kinematic signature observed in the CS(3-2) emission at the same location. Our results indicate that the crescent is caused by differential dust trapping in a local pressure maxima, for which plausible mechanisms can be the presence of a vortex or trapping in a Lagrangian point of the planet-star system.

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arXiv2026

exoALMA XXI: The Morphology and Dynamics of Vertical Flows

Vertical gas flows, such as winds and meridional circulations, are natural outcomes of protoplanetary disk processes and play a critical role in the earliest stages of planet formation. We analyze vertical gas motions in 14 disks as part of the exoALMA Large Program, focusing on the 12CO J=3-2 and 13CO J=3-2 emission lines. Using discminer to model the Keplerian velocity field, we extract line-of-sight velocity residuals and measure the radial and vertical components of the gas motion. Vertical motions are detected in most disks. Two types of patterns emerge: (1) oscillatory up/down flows, likely linked to instabilities, and (2) transitions from downward to upward motions that we interpret as the base of a disk wind. In most cases, the velocity amplitudes are of a few tens of m/s. Two disks, however, MWC758 and CQ Tau, show two spiral velocity features in their residual maps, red- and blue-shifted, which we interpret as vertical velocities reaching up to 350 m/s (0.7 Cs), consistent with gas motion in eccentric disks. Fast upward motions (up to 500 m/s; 1.8 Cs) is also detected in the outer disk of MWC758. Synthetic observations from (magneto)hydrodynamic simulations validate the reliability of our method. Although strong molecular winds appear to be relatively rare in 12CO and 13CO, our study shows that, when traced by deep high spectral resolution line data, protoplanetary disks exhibit ubiquitous vertical flows. However, their overall velocity structure is highly complex, preventing to identify a coherent, dominant physical mechanism driving the vertical motions across all disks, thus requiring further theoretical investigation.

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arXiv2026

exoALMA XX: Tomographic Detection of Embedded Planets in Protoplanetary Disks

The exoALMA Large Program has revealed a wealth of substructures in the dust and molecular line emission of several protoplanetary discs, suggesting that planet formation may unfold within highly dynamic environments. Using synthetic observations of planet-disc interactions and disc instabilities, we demonstrate how the origin of these substructures can be investigated through a tomographic study of molecular lines, extending the scope of the analysis beyond line-centroid kinematics alone. Our results indicate that with only a few hours of ALMA integration at moderate angular resolution ($0.15''-0.30''$), it is possible to identify the key signatures driven by planets more massive than 0.1% of the stellar mass. These signatures manifest not only as deviations from Keplerian motion but also as localized line broadening, enabling accurate constraints on the orbital radius and azimuthal location of the planets. We further show that a diagnostic based on line skewness in spectrally resolved observations can help distinguish between planetary and instability-driven signatures, owing to the distinct degrees of velocity coherence associated with each mechanism. Finally, we apply this tomographic analysis to exoALMA CO line data for the discs of HD 135344B and MWC 758. In HD 135344B, we identify strongly localized velocity and line-width perturbations, suggesting the possibility of three massive planets embedded in the disc: one at $R=95$ au, exterior to the continuum substructures, and two within dust gaps at $R=41$ au and $R=73$ au. For MWC 758, the dominance of vertical-velocity spirals over localized signatures is consistent with predictions from models of moderate disc eccentricities or warps, potentially induced by a substellar companion in the inner regions of the system.

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arXiv2026

exoALMA XIX: Confirmation of Non-thermal Line Broadening in the DM Tau Protoplanetary Disk

Turbulence is expected to transport angular momentum and drive mass accretion in protoplanetary disks. One way to directly measure turbulent motion in disks is through molecular line broadening. DM Tau is one of only a few disks with claimed detection of nonthermal line broadening of 0.25cs-0.33cs, where cs is the sound speed. Using the radiative transfer code mcfost within a Bayesian inference framework that evaluates over five million disk models to efficiently sample the parameter space, we fit high-resolution (0.15", 28 m s-1) 12CO J = 3-2 observations of DM Tau from the exoALMA Large Program. This approach enables us to simultaneously constrain the disk structure and kinematics, revealing a significant nonthermal contribution to the line width of ~0.4cs, inconsistent with purely thermal motions. Using the CO-based disk structure as a starting point, we reproduce the CS J = 7-6 emission well, demonstrating that the CS (which is more sensitive to nonthermal motions than CO) agrees with the turbulence inferred from the CO fit. Establishing a well-constrained background disk model further allows us to identify residual structures in the moment maps that deviate from the expected emission, revealing localized perturbations that may trace forming planets. This framework provides a powerful general approach for extracting disk structure and nonthermal broadening directly from molecular line data and can be applied to other disks with high-quality observations.

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arXiv2025

Evidence for the Keplerian orbit of a close companion around a giant star

Close companions influence stellar evolution through tidal interactions, mass transfer, and mass loss effects. While such companions are detected around young stellar objects, main-sequence stars, red giants, and compact objects, direct observational evidence of close-in companions around asymptotic giant branch (AGB) stars has remained elusive. Here, we present (sub)millimeter time-domain imaging spectroscopy revealing the Keplerian motion of a close-in companion around the AGB star pi1 Gruis. The companion, slightly more massive than the AGB star, is likely a main-sequence star. Unlike more evolved stars with companions at comparable distances, pi1 Gru's companion follows a circular orbit, suggesting an eccentricity-generating mechanism late- or post-AGB. Our analysis suggests that model-predicted circularization rates may be underestimated. Our results highlight the potential of multi-epoch (sub)millimeter interferometry in detecting the Keplerian motion of close companions to giant stars and open avenues for our understanding of tidal interaction physics and binary evolution.

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arXiv2025

Converged simulations of the nozzle shock in tidal disruption events

When debris from a star that experienced a tidal disruption events (TDE) after passing too close to a massive black hole returns to pericenter on the second passage, it is compressed, leading to the formation of nozzle shocks (in the orbital plane) and pancake shocks (perpendicular to the orbital plane). Resolving these shocks is a long-standing problem in the hydrodynamic simulations of parabolic TDEs. Excessive numerical energy dissipation or heating unrealistically expands the stream. In this Letter, we apply adaptive particle refinement to our 3D general relativistic smoothed particle simulations to locally increase the resolution near the pericenter. We achieve resolutions equivalent to $6.55\times10^{11}$ particles, allowing us to converge on the true energy dissipation. We conclude that only $4\times10^{-5}$ of the orbital energy is dissipated in nozzle shocks for a Sun-like star tidally disrupted by a $10^6$ solar-mass black hole, therefore the nozzle shocks are unlikely to be important in the evolution of TDEs.

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arXiv2025

Asymmetric radiation in binary systems: Implications for disk evolution and chemistry

Current models of binary systems often depend on simplified approach of the radiation field, which are unlikely to accurately capture the complexities of asymmetric environments. We investigate the dynamical and chemical implications of a 3D asymmetric radiation field that accounts for the optical properties of sub-structures present in a protoplanetary disk, as well as the inclusion of a secondary radiation source in binary systems. We conducted a series of 3D-SPH hydrodynamical simulations using PHANTOM, coupled with the 3D Monte Carlo radiative transfer code MCFOST, to compute disc temperatures on-the-fly. We explored different binary-disk orientations (0$^o$ and 30$^o$) for an eccentric binary, along with a constant dust-to-gas ratio and dust as a mixture prescription. We also simulated an outburst event as an example of a drastic increase in luminosity. Heating from the secondary star inflates the outer disk, increasing the aspect ratio facing the companion by about 25% in inclined cases compared to 10% in coplanar ones. Dust settling in the mid-plane enhances extinction along the disk plane, making the coplanar case cooler than the inclined one on the side of the disk facing the companion. Besides, heating causes a shift in the snow line for species with freeze-out temperatures below 50 K, depending on the disk-binary inclination and binary phase. During outbursts, the aspect ratio doubles on the star-facing side and increases by 50% on the opposite side in inclined cases. The snow line shift would impact all the species considered in the outburst case. Disk heating in binaries depends on stellar properties, orbital phase, and disk local and global characteristics. This results in temperature asymmetries, especially during secondary star outbursts, leading to variations in aspect ratio and snow lines that can affect chemistry and planet formation.

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arXiv2025

DAWN. I. Simulating the formation and early evolution of stellar clusters with Phantom N-Body

Context. Simulating stellar dynamics in a molecular cloud environment is numerically challenging due to the strong coupling between young stars and their surrounding gas, and the large range of length and time scales. Aims. This paper is the first of a suite aimed at investigating the complex early stellar dynamics in star-forming regions. We present a new simulation framework which is the key to generating a larger set of simulations, enabling statistical analysis. Methods. Methods originating from the stellar dynamics community, including regularisation and slowdown methods (SDAR), have been added to the hydrodynamical code Phantom to produce simulations of embedded cluster early dynamics. This is completed by a novel prescription of star formation to initialise stars with a low numerical cost, but in a way that is consistent with the gas distribution. Finally, a prescription for H ii region expansion has been added to model the gas removal. Results. We have run testcase simulations following the dynamical evolution of stellar clusters from the cloud collapse to a few Myr. Our new numerical methods fulfil their function by speeding up the calculation. The N-body dynamics with our novel implementation never appear as a bottleneck. Our first simulations show that massive stars largely impact the star formation process and shape the dynamics of the resulting cluster. Depending on the position of these massive stars and the strength of their feedback, they can prematurely dismantle part of the cloud or trigger a second event of cloud collapse, preferentially forming low-mass stars. This stochastic behaviour confirms the need for statistical studies. Conclusions. Our new Phantom N-Body framework enables efficient simulation of the formation and evolution of star clusters. It enables the statistical analysis needed to build models of the dynamical evolution of embedded star clusters.

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arXiv2025

exoALMA. XVIII. Interpreting large scale kinematic structures as moderate warping

The exoALMA program gave an unprecedented view of the complex kinematics of protoplanetary disks, revealing diverse structures that remain poorly understood. We show that moderate disk warps ($\sim 0.5-2^\circ$) can naturally explain many of the observed large-scale velocity features with azimuthal wavenumber $m = 1$. Using a simple model, we interpret line-of-sight velocity variations as changes in the projected Keplerian rotation caused by warping of the disk. While not a unique explanation, this interpretation aligns with growing observational evidence that warps are common. We demonstrate that such warps can also produce spiral structures in scattered light and CO brightness temperature, with $\sim 10$ K variations in MWC 758. Within the exoALMA sample, warp properties correlate with stellar accretion rates, suggesting a link between the inner disc and outer disc kinematics. If warps cause large-scale kinematic structure, this has far reaching implications for turbulence, angular momentum transport, and planet formation.

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arXiv2025

Common envelopes in massive stars III. The obstructive role of radiation transport in envelope ejection

We present 3D radiation hydrodynamics simulations of common-envelope (CE) evolution involving a 12 solar mass red supergiant donor and a 3 solar mass companion. Existing 3D simulations are predominantly adiabatic, focusing strongly on low-mass donors on the red giant and asymptotic giant branches. However, the adiabatic assumption breaks down once the perturbed CE material becomes optically thin or when entering a longer-timescale evolutionary phase after the dynamical plunge-in. This is especially important for high-mass red supergiant donors, which have short thermal timescales, adding significant uncertainty to our understanding of how massive binary stars evolve into gravitational-wave sources, X-ray binaries, stripped-envelope supernovae, and more. We compare our radiation hydrodynamics simulations with an adiabatic simulation from Paper I that is otherwise identical, finding that radiative diffusion strongly inhibits CE ejection. The fraction of ejected mass is roughly half that of the adiabatic case without accounting for recombination energy release. Almost no material is ejected during the dynamical plunge-in, and longer-timescale ejection during the slow spiral-in is suppressed. However, the orbital separation reached at the end of the dynamical plunge-in does not differ significantly. The large amount of remaining bound mass tentatively supports the emerging view that the dynamical plunge-in is followed by a non-adiabatic phase, during which a substantial fraction of the envelope is ejected and the binary orbit may continue to evolve.

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arXiv2025

Radio emission from tidal disruption events produced by the collision between super-Eddington outflows and the circumnuclear medium

In this Letter, we simulate the collision between outflows from the tidal disruption of a 1M$_\odot$ main sequence star around a $10^6$M$_\odot$ black hole and an initially spherically symmetric circumnuclear cloud. We launch super-Eddington outflows self-consistently by simulating the disruption of stars on both bound and unbound initial orbits using general relativistic smoothed particle hydrodynamics. We find shocks formed as early as $\sim 10~$days after the initial stellar disruption produce prompt radio emission. The shock radius ($\approx~10^{17}$~cm), velocity ($\sim 0.15$c) and total energy ($\sim 10^{51}$ erg) in our simulations match those inferred from radio observations of tidal disruption events (TDEs). We ray-trace to produce synthetic radio images and spectra to compare with the observations. While the TDE outflow is quasi-spherical, the synchrotron emitting region is aspherical but with reflection symmetry above and below the initial orbital plane. Our synthetic spectra show continuous decay in peak frequency, matching prompt radio TDE observations. Our model supports the hypothesis that synchrotron radio flares from TDEs result from the collision between outflows and the circumnuclear material.

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arXiv2025

exoALMA VII: Benchmarking Hydrodynamics and Radiative Transfer Codes

Forward modeling is often used to interpret substructures observed in protoplanetary disks. To ensure the robustness and consistency of the current forward modeling approach from the community, we conducted a systematic comparison of various hydrodynamics and radiative transfer codes. Using four grid-based hydrodynamics codes (FARGO3D, Idefix, Athena++, PLUTO) and a smoothed particle hydrodynamics code (Phantom), we simulated a protoplanetary disk with an embedded giant planet. We then used two radiative transfer codes (mcfost, RADMC-3D) to calculate disk temperatures and create synthetic 12CO cubes. Finally, we retrieved the location of the planet from the synthetic cubes using DISCMINER. We found strong consistency between the hydrodynamics codes, particularly in the density and velocity perturbations associated with planet-driven spirals. We also found a good agreement between the two radiative transfer codes: the disk temperature in mcfost and RADMC-3D models agrees within $\lesssim 3~\%$ everywhere in the domain. In synthetic $^{12}$CO channel maps, this results in brightness temperature differences within $\pm1.5$ K in all our models. This good agreement ensures consistent retrieval of planet's radial/azimuthal location with only a few % of scatter, with velocity perturbations varying $\lesssim 20~\%$ among the models. Notably, while the planet-opened gap is shallower in the Phantom simulation, we found that this does not impact the planet location retrieval. In summary, our results demonstrate that any combination of the tested hydrodynamics and radiative transfer codes can be used to reliably model and interpret planet-driven kinematic perturbations.

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arXiv2025

Keplerian motion of a compact source orbiting the inner disc of PDS 70: a third protoplanet in resonance with b and c?

The disc around PDS 70 hosts two directly imaged protoplanets in a gap. Previous VLT/SPHERE and recent James Webb Space Telescope/NIRCam observations have hinted at the presence of a third compact source in the same gap at ~13 au, interior to the orbit of PDS 70 b. We reduce seven published and one unpublished VLT/SPHERE datasets in YJH and K bands, as well as an archival VLT/NaCo dataset in L' band, and an archival VLT/SINFONI dataset in H+K band. We combine angular-, spectral- and reference star differential imaging to search for protoplanet candidates. We recover the compact source in all epochs, consistent with the JWST detection, moving on an arc that can be fit by Keplerian motion of a protoplanet which could be in a resonance with PDS 70 b & c. We find that the spectral slope is overall consistent with the unresolved star and inner disc emission at 0.95--1.65$μ$m, which suggests a dust scattering dominated spectrum. An excess beyond 2.3$μ$m could be thermal emission from either a protoplanet or heated circumplanetary dust, variability, or inner disc contamination, and requires confirmation. While we currently cannot rule out a moving inner disc feature or a dust clump associated with an unseen planet, the data supports the hypothesis of a third protoplanet in this remarkable system.

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arXiv2025

exoALMA XIV. Gas Surface Densities in the RX J1604.3-2130 A Disk from Pressure-broadened CO Line Wings

The gas surface density is one of the most relevant physical quantities in protoplanetary disks. However, its precise measurement remains highly challenging due to the lack of a direct tracer. In this study, we report the spatially-resolved detection of pressure-broadened line wings in the CO $J=3-2$ line in the RX J1604.3-2130 A transition disk as part of the exoALMA large program. Since pressure-broadened line wings are sensitive to the total gas volume density, we robustly constrain the radial dependence of the gas surface density and midplane pressure in the region located $50-110$ au from the central star, which encompasses the dust ring of the system. The peak radius of the midplane pressure profile matches the dust ring radial location, directly proving radial dust trapping at a gas pressure maximum. The peak gas surface density is $18-44\ {\rm g\ cm^{-2}}$} and decreases at radii interior to and exterior of the dust ring. A comparison of the gas and dust surface densities suggests that the disk turbulence is as low as $α_{\rm turb} \sim 2\times10^{-4}$. Despite dust trapping, the gas-to-dust surface density ratio at the ring peak is { $70-400$}, which implies already-formed protoplanets and/or less efficient dust trapping. The gas surface density drop at radii interior to the ring is consistent with a gas gap induced by a Jupiter-mass planet. The total gas mass within $50 < r < 110$ au is estimated to be $\sim 0.05-0.1\ M_\odot$ ($50-100\ {M_{\rm Jup}}$), suggesting that planetary system formation is possible.

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arXiv2025

exoALMA. XVI. Predicting Signatures of Large-scale Turbulence in Protoplanetary Disks

Turbulent gas motions drive planet formation and protoplanetary disk evolution. However, empirical constraints on turbulence are scarce, halting our understanding of its nature. Resolving signatures of the large-scale perturbations driven by disk instabilities may reveal clues on the origin of turbulence in the outer regions of planet-forming disks. We aim to predict the observational signatures of such large-scale flows, as they would appear in high-resolution Atacama Large Millimeter/submillimeter Array observations of CO rotational lines, such as those conducted by the exoALMA Large Program. Post-processing 3D numerical simulations, we explored the observational signatures produced by three candidate (magneto-)hydrodynamical instabilities to operate in the outer regions of protoplanetary disks: the vertical shear instability (VSI), the magneto-rotational instability (MRI), and the gravitational instability (GI). We found that exoALMA-quality observations should capture signatures of the large-scale motions induced by these instabilities. Mainly, flows with ring, arc, and spiral morphologies are apparent in the residuals of synthetic velocity centroid maps. A qualitative comparison between our predictions and the perturbations recovered from exoALMA data suggests the presence of two laminar disks and a scarcity of ring- and arc-like VSI signatures within the sample. Spiral features produced by the MRI or the GI are still plausible in explaining observed disk perturbations. Supporting these scenarios requires further methodically comparing the predicted perturbations and the observed disks' complex dynamic structure.

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arXiv2025

exoALMA II: Data Calibration and Imaging Pipeline

The exoALMA Large Program was designed to search for subtle kinematic deviations from Keplerian motion, indicative of embedded planets, in high angular and spectral resolution Band 7 observations of $^{12}$CO, $^{13}$CO and CS emission from protoplanetary disks. This paper summarizes the calibration and imaging pipelines used by the exoALMA collaboration. With sources ranging in diameter from 2.4" to 13.8" when probed by $^{12}$CO, multiple antennae configurations were required to maximally recover all spatial information (including the ACA for 7 sources). Combining these datasets warranted particular care in their alignment during calibration and prior to imaging, so as not to introduce spurious features that might resemble the kinematic deviations being investigated. Phase decoherence was found in several datasets, which was corrected by an iterative self-calibration procedure, and we explored the effects of the order of operations of spatial alignment, flux scaling, and self-calibration. A number of different imaging sets were produced for the continuum and line emission, employing an iterative masking procedure that minimizes bias due to non-Keplerian motions in the disk.

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