bluuebunny/crossref_metadata_2025_split huggingface dataset:
A solar rotation signature in cosmic dust: Frequency analysis of dust particle impacts on the Wind spacecraft
Authors: Baalmann L. R. , Hunziker S. , Péronne A. , Kirchner J. W. , Glassmeier K.-H. , Malaspina D. M. , Wilson III L. B. , Strähl C. , Chadda S. , Sterken V. J. 
Published: July 2024

Aims. Dust particle impacts on the Wind spacecraft were detected with its plasma wave instrument Wind/WAVES. Frequency analysis on the resulting dust impact time series has revealed spectral peaks indicative of a solar rotation signature. We investigated whether this solar rotation signature is embedded in the interplanetary or in the interstellar dust (ISD) and whether it is caused by co-rotating interaction regions (CIRs), by the sector structure of the interplanetary magnetic field (IMF), or by external effects.
Methods. We performed frequency analysis on different subsets of the data to investigate the origin of these spectral peaks, comparing segments of Wind’s orbit when the spacecraft moved against or with the ISD inflow direction and comparing the time periods of the ISD focusing phase and the ISD defocusing phase of the solar magnetic cycle. A superposed epoch analysis of the number of dust impacts during CIRs was used to investigate the systematic effect of CIRs. Case studies of time periods with frequent or infrequent occurrences of CIRs were performed and compared to synthetic data of cosmic dust impacts affected by CIRs. We performed similar case studies for time periods with a stable or chaotic IMF sector structure. The superposed epoch analysis was repeated for a time series of the spacecraft floating potential.
Results. Spectral peaks were found at the solar rotation period of ∼27 d and its harmonics at 13.5 d and 9 d. This solar rotation signature may affect both interplanetary and interstellar dust. The appearance of this signature correlates with the occurrence of CIRs but not with the stability of the IMF sector structure. The CIRs cause, on average, a reduction in the number of dust impact detections. Periodic changes of the spacecraft’s floating potential were found to partially counteract this reduction by enhancing the instrument’s sensitivity to dust impacts; these changes of the floating potential are thus unlikely to be the cause of the solar rotation signature.
From traffic jams to roadblocks: The outer regions of TW Hya with ALMA Band 8
Authors: Das S. , Kurtovic N. T. , Flock M. 
Published: July 2024

Context. Current ALMA surveys often underestimate protoplanetary disk sizes as many disks have extended low surface-brightness regions that fall below ALMA’s detection limits. To effectively capture faint millimeter continuum emission in these outer regions, increased sensitivity is required.
Aims. In order to gain insights on the connection between disk structure and planet formation, we aim to uncover continuum emission in the outer regions of the disk around TW Hya. Additionally, we aim to investigate the evolution of this disk by studying its dust properties.
Methods. We present Atacama Large Millimeter Array (ALMA) observations of TW Hya at 0.65 mm with ~0.5 arcsecond angular resolution, together with high angular resolution archival observations at 0.87,1.3, 2.1 and 3.1 mm. We constrain the outer disk emission with both image-plane retrieval, and visibility-plane modeling with non-parametric and parametric fitting tools.
Results. Our results confirm emission in the outer disk regions of TW Hya (60 au ≤ R ≤ 110 au) at 0.65, 0.87 and 1.3 mm. With image-plane retrieval, we resolve the new continuum gap and ring, namely D79 and B86, at 0.87 and 1.3 mm. With visibility-plane modeling, we also detect this substructure at 0.65 mm in the form of a quasi-constant emission at the 1σ level. Furthermore, it has a high spectral index of 3.7, which may indicate dust grain sizes <<1 mm. It may be a dust trap or a traffic jam, that has a flux density of ~60 mJy and a mass (1.59 M⊕) that accounts for up to 2% of the dust disk at 0.65 mm.
Conclusions. We confirm the existence of a faint ring in the outer regions of TW Hya at multiple millimeter wavelengths. With visibility-plane modeling, we are able to set constrains that are 3 times better than the resolution of our Band 8 observations.
ASASSN-21js: A multi-year transit of a ringed disc
Authors: Pramono T. H. , Kenworthy M. A. , van Boekel R. 
Published: July 2024

Aims. The early-type star ASASSN-21js started to fade in 2021, as was detected by the All Sky Automated Survey for Supernovae, undergoing a multi-year eclipse that is still underway. We interpret this event as being due to a structured disc of material transiting in front of the star. The disc is in orbit around a substellar object with the mass and luminosity of a brown dwarf or smaller. We want to determine the expected duration and ending date of the eclipse.
Methods. We modelled a tilted and inclined azimuthally symmetric ring system around an unseen companion and calculated the resulting time-varying light curve as the object transited in front of the star. We made an initial estimate of the ring parameters and used these as inputs to an MCMC algorithm to determine the geometric properties of the rings with associated uncertainties.
Results. The model most consistent with the light curve to date is a two-ring system at high inclination with respect to the line of sight that has a semi-major axis of 71.6 stellar radii. With an estimate of the stellar radius, the transverse velocity is around 0.7 km s−1, which if bound to the star is an orbit with a semi-major axis of around 13 000 au, placing it in the Oort cloud of the parent star. The transit is ongoing and will finish around MJD 61526 (May 1 2027). We encourage the community to continue observing this object in order to understand its properties.
The role of outflows in black-hole X-ray binaries
Authors: Kylafis N. D. , Reig P. 
Published: July 2024

Context. The hot inner flow in black-hole X-ray binaries is not just a static corona rotating around the black hole: it must be partially outflowing. It is therefore a mildly relativistic “outflowing corona”. We have developed a model in which Comptonization takes place in this outflowing corona. In all of our previous work, we assumed a rather high outflow speed of 0.8c.
Aims. Here, we investigate whether an outflow with a significantly lower speed can also reproduce the observations. Thus, in this work we consider an outflow speed of 0.1c or less.
Methods. As in all of our previous work, we used a Monte Carlo code to compute not only the emergent X-ray spectra, but also the time lags that are introduced to the higher-energy photons with respect to the lower-energy ones via multiple scatterings. We also record the angle (with respect to the symmetry axis of the outflow) and the height at which photons escape.
Results. Our results are very similar to those of our previous work, with some small quantitative differences that can be easily explained. We are again able to quantitatively reproduce five observed correlations: (a) the time lag as a function of Fourier frequency, (b) the time lag as a function of photon energy, (c) the time lag as a function of Γ, (d) the time lag as a function of the cutoff energy in the spectrum, and (e) the long-standing radio–X-ray correlation – and all of them with only two parameters, which vary in the same ranges for all the correlations.
Conclusions. Our model does not require a compact, narrow relativistic jet, although its presence does not affect the results. The essential ingredient of our model is the parabolic shape of the Comptonizing corona. The outflow speed plays a minor role. Furthermore, the bottom of the outflow, in the hard state, looks like a “slab” to the incoming soft photons from the disk, and this can explain the observed X-ray polarization, which is along the outflow. In the hard-intermediate state, we predict that the polarization of GX 339−4 will be perpendicular to the outflow.
Luminosity dependence of the multiple cyclotron lines in 4U 0115+63
Authors: Roy Kinjal , Manikantan Hemanth , Paul Biswajit 
Published: July 2024

Context. The Be X-ray binary 4U 0115+63 underwent a giant outburst in 2023 with the X-ray luminosity of the source reaching 1038 erg s−1. During the outburst, two target of opportunity observations were made with NuSTAR.
Aims. The main goal of this work is to model the multiple cyclotron scattering features (CRSFs) present in 4U 0115+63 and study their dependence on the luminosity of the source.
Methods. The 3–79 keV broadband X-ray coverage of NuSTAR allowed us to properly model the continuum and investigate the nature of the multiple cyclotron resonance scattering features present in the source spectrum. We used the epoch-folding technique to find the pulsation from the source and also studied the changes in the cyclotron line energy with an order of magnitude variation in the source luminosity.
Results. We detected five cyclotron lines during the 2023 outburst near 12, 16, 24, 34, and 47 keV. The ∼16 keV cyclotron line cannot be harmonically related to the other cyclotron lines at ∼12 keV and ∼24 keV. This indicates the presence of two fundamental lines in the spectrum of 4U 0115+63 at 12 keV and 16 keV.
Conclusions. With the inclusion of the two latest NuSTAR observations, we have expanded the data set of the CRSF line center to encompass a broad range of luminosity. This enables us to comprehensively investigate the relationship between the centroid energy of the cyclotron lines and luminosity. The CRSF line center shows no anticorrelation with luminosity, unlike previously reported. Instead, a weak positive correlation is found in four out of the five detected cyclotron lines of 4U 0115+63. The luminosity variation of the two fundamental CRSFs could be well explained with the prediction from the collisionless shock model. A tentative negative correlation was observed in the fundamental CRSF at 16 keV and its harmonics beyond a “critical luminosity” of 1038 erg/s. This behavior was not present for the 12 keV fundamental CRSF and its harmonic at 24 keV.
Size, albedo, and rotational period of the Hayabusa2# target (98943) 2001 CC21
Authors: Fornasier S. , Dotto E. , Panuzzo P. , Delbo M. , Belskaya I. , Krugly Y. , Inasaridze R. , Barucci M. A. , Perna D. , Brucato J. , Birlan M. 
Published: July 2024

Aims. This study aims to determine the size, albedo, and rotational period of (98943) 2001 CC21, a target of the Hayabusa2 extended mission, using thermal data from the Spitzer Space telescope and ground-based observations.
Methods. The Spitzer data were acquired with the Infrared Spectrograph in the 6–38 μm range, reduced using the Spitzer pipeline, and modeled with the near-Earth asteroid thermal model to determine the asteroid size and albedo. The absolute magnitude and rotational period were determined thanks to new observations carried out at the 3.5 m New Technology Telescope, the 1.2 m Observatoire de Haute Provence, and the 0.7 m Abastumani telescope. Three complete light curves were obtained in 2023 and 2024 at the last-mentioned telescope.
Results. We determine an absolute magnitude of H = 18.94 ± 0.05 and a rotational period of 5.02124±0.00001 hours, with a large light curve amplitude of ∼0.8 mag. at a phase angle of 22°, indicating a very elongated shape with an estimated a/b semiaxis ratio ≥1.7, or a close-contact binary body. The emissivity of 2001 CC21 is consistent with that of silicates, and its albedo is 21.6±1.6%. Finally, the spherical-equivalent diameter of 2001 CC21 is 465±15 m.
Conclusions. The albedo value and emissivity determined here, coupled with results from polarimetry and spectroscopy from the literature, confirm that 2001 CC21 is an S-complex asteroid, and not an L-type one as was previously suggested. The size of 2001 CC21 is less than 500 m, which is smaller than its first size estimation (∼700 m). These results are relevant in preparation of the observing strategy for 2001 CC21 of the Hayabusa2 extended mission.
Tetrahedral grids in Monte Carlo radiative transfer
Authors: Lauwers Arno , Baes Maarten , Camps Peter , Vander Meulen Bert 
Published: July 2024

Context.To understand the structures of complex astrophysical objects, 3D numerical simulations of radiative transfer processes are invaluable. For Monte Carlo radiative transfer, the most common radiative transfer method in 3D, the design of a spatial grid is important and non-trivial. Common choices include hierarchical octree and unstructured Voronoi grids, each of which has advantages and limitations. Tetrahedral grids, commonly used in ray-tracing computer graphics, can be an interesting alternative option.Aims.We aim to investigate the possibilities, advantages, and limitations of tetrahedral grids in the context of Monte Carlo radiative transfer. In particular, we want to compare the performance of tetrahedral grids to other commonly used grid structures.Methods.We implemented a tetrahedral grid structure, based on the open-source library TetGen, in the generic Monte Carlo radiative transfer code SKIRT. Tetrahedral grids can be imported from external applications or they can be constructed and adaptively refined within SKIRT. We implemented an efficient grid traversal method based on Plücker coordinates and Plücker products.Results.The correct implementation of the tetrahedral grid construction and the grid traversal algorithm in SKIRT were validated using 2D radiative transfer benchmark problems. Using a simple 3D model, we compared the performance of tetrahedral, octree, and Voronoi grids. With a constant cell count, the octree grid outperforms the tetrahedral and Voronoi grids in terms of traversal speed, whereas the tetrahedral grid is poorer than the other grids in terms of grid quality. All told, we find that the performance of tetrahedral grids is relatively poor compared to octree and Voronoi grids.Conclusions.Although the adaptively constructed tetrahedral grids might not be favourable in most media representative of astrophysical simulation models, they still form an interesting unstructured alternative to Voronoi grids for specific applications. In particular, they might prove useful for radiative transfer post-processing of hydrodynamical simulations run on tetrahedral or unstructured grids.
FAUST
Authors: Podio L. , Ceccarelli C. , Codella C. , Sabatini G. , Segura-Cox D. , Balucani N. , Rimola A. , Ugliengo P. , Chandler C. J. , Sakai N. , Svoboda B. , Pineda J. , De Simone M. , Bianchi E. , Caselli P. , Isella A. , Aikawa Y. , Bouvier M. , Caux E. , Chahine L. , Charnley S. B. , Cuello N. , Dulieu F. , Evans L. , Fedele D. , Feng S. , Fontani F. , Hama T. , Hanawa T. , Herbst E. , Hirota T. , Jiménez-Serra I. , Johnstone D. , Lefloch B. , Le Gal R. , Loinard L. , Baobab Liu H. , López-Sepulcre A. , Maud L. T. , Maureira M. J. , Menard F. , Miotello A. , Moellenbrock G. , Nomura H. , Oba Y. , Ohashi S. , Okoda Y. , Oya Y. , Sakai T. , Shirley Y. , Testi L. , Vastel C. , Viti S. , Watanabe N. , Watanabe Y. , Zhang Y. , Zhang Z. E. , Yamamoto S. 
Published: July 2024

Context. Recent observations suggest that planet formation starts early, in protostellar disks of ≤105 yr, which are characterized by strong interactions with the environment, such as through accretion streamers and molecular outflows.
Aims. To investigate the impact of such phenomena on the physical and chemical properties of a disk, it is key to understand what chemistry planets inherit from their natal environment.
Methods. In the context of the ALMA large program Fifty AU Study of the chemistry in the disk/envelope system of solar-like protostars (FAUST), we present observations on scales from ∼1500 au to ∼60 au of H2CO, HDCO, and D2CO toward the young planet-forming disk IRS 63.
Results. The H2CO probes the gas in the disk as well as in a large scale streamer (∼1500 au) impacting onto the southeast disk side. We detected for the first time deuterated formaldehyde, HDCO and D2CO, in a planet-forming disk and HDCO in the streamer that is feeding it. These detections allowed us to estimate the deuterium fractionation of H2CO in the disk: [HDCO]/[H2CO] ∼ 0.1 − 0.3 and [D2CO]/[H2CO] ∼ 0.1. Interestingly, while HDCO follows the H2CO distribution in the disk and in the streamer, the distribution of D2CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the southeast disk side, where the streamer crashes onto the disk. In addition, D2CO was detected in two spots along the blue- and redshifted outflow. This suggests that (i) in the disk, HDCO formation is dominated by gas-phase reactions in a manner similar to H2CO, while (ii) D2CO is mainly formed on the grain mantles during the prestellar phase and/or in the disk itself and is at present released in the gas phase in the shocks driven by the streamer and the outflow.
Conclusions. These findings testify to the key role of streamers in the buildup of the disk concerning both the final mass available for planet formation and its chemical composition.
Filling in the blanks
Authors: Callingham Thomas M. , Helmi Amina 
Published: July 2024

Context. In the solar neighbourhood, only ∼2% of stars in the Gaia survey have a line-of-sight velocity (vlos) contained within the RVS catalogue. These limitations restrict conventional dynamical analysis, such as finding and studying substructures in the stellar halo.
Aims. We aim to present and test a method to infer a probability density function (PDF) for the missing vlos of a star with 5D information within 2.5 kpc. This technique also allows us to infer the probability that a 5D star is associated with the Milky Way’s stellar Disc or the stellar Halo, which can be further decomposed into known stellar substructures.
Methods. We use stars from the Gaia DR3 RVS catalogue to describe the local orbital structure in action space. The method is tested on a 6D Gaia DR3 RVS sample and a 6D Gaia sample crossmatched to ground-based spectroscopic surveys, stripped of their true vlos. The stars predicted vlos, membership probabilities, and inferred structure properties are then compared to the true 6D equivalents, allowing the method’s accuracy and limitations to be studied in detail.
Results. Our predicted vlos PDFs are statistically consistent with the true vlos, with accurate uncertainties. We find that the vlos of Disc stars can be well-constrained, with a median uncertainty of 26 km s−1. Halo stars are typically less well-constrained with a median uncertainty of 72 km s−1, but those found likely to belong to Halo substructures can be better constrained. The dynamical properties of the total sample and subgroups, such as distributions of integrals of motion and velocities, are also accurately recovered. The group membership probabilities are statistically consistent with our initial labelling, allowing high-quality sets to be selected from 5D samples by choosing a trade-off between higher expected purity and decreasing expected completeness.
Conclusions. We have developed a method to estimate 5D stars’ vlos and substructure membership. We have demonstrated that it is possible to find likely substructure members and statistically infer the group’s dynamical properties.
Re-evaluating the cosmological redshift: Insights into inhomogeneities and irreversible processes
Authors: Tremblin P. , Chabrier G. 
Published: July 2024

Aims. Understanding the expansion of the Universe remains a profound challenge in fundamental physics. The complexity of solving general relativity equations in the presence of intricate, inhomogeneous flows has compelled cosmological models to rely on perturbation theory in a homogeneous Friedmann–Lemaître–Robertson-Walker background. This approach accounts for a redshift of light encompassing contributions from both the cosmological background expansion along the photon’s trajectory and Doppler effects at emission due to peculiar motions. However, this computation of the redshift is not covariant, as it hinges on specific coordinate choices that may distort physical interpretations of the relativity of motion.
Methods. In this study we show that peculiar motions, when tracing the dynamics along time-like geodesics, must contribute to the redshift of light through a local volume expansion factor, in addition to the background expansion. By employing a covariant approach to redshift calculation, we address the central question of whether the cosmological principle alone guarantees that the averaged local volume expansion factor matches the background expansion.
Results. We establish that this holds true only in scenarios characterised by a reversible evolution of the Universe, where inhomogeneous expansion and compression modes compensate for one another. In the presence of irreversible processes, such as the dissipation of large-scale compression modes through matter virialisation and associated entropy production, the averaged expansion factor becomes dominated by expansion in voids that can no longer be compensated for by compression in virialised structures. Furthermore, for a universe in which a substantial portion of its mass has undergone virialisation, adhering to the background evolution on average leads to significant violations of the second law of thermodynamics. Our approach shows that entropy production due to irreversible processes during the formation of structures plays the same role as an effective, time-dependent cosmological constant (i.e. dynamical dark energy) without the need to invoke new unknown physics. Our findings underscore the imperative need to re-evaluate the influence of inhomogeneities and irreversible processes on cosmological models, shedding new light on the intricate dynamics of our Universe.
INTEGRAL/IBIS polarization detection in the hard and soft intermediate states of Swift J1727.8−1613
Authors: Bouchet T. , Rodriguez J. , Cangemi F. , Thalhammer P. , Laurent P. , Grinberg V. , Wilms J. , Pottschmidt K. 
Published: July 2024

Aims. Soft γ-ray emission (100 keV–10 MeV) has previously been detected in the hard state of several microquasars. In some sources, this emission was found to be highly polarized and was suggested to be emitted at the base of the jet. Until now, no γ-ray polarization had been found in any other state.
Methods. Using INTEGRAL/IBIS, we studied the soft γ-ray spectral and polarization properties of Swift J1727.8−1613 throughout its outburst.
Results. We detect a highly polarized spectral component in both the hard intermediate state and the early stages of the soft intermediate state above 210 keV. In the hard intermediate state, the polarization angle significantly deviates from the compact jet angle projected onto the sky, whereas in the soft intermediate they are closely aligned. This constitutes the first detection of jet-aligned polarization in the soft γ-ray for a microquasar. We attribute this polarized spectral component to synchrotron emission from the jet, which indicates that some of the jet might persist into the softer states.