bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope
Authors: Turner Jacob E. , Joshi Bhal Chandra , McLaughlin Maura A. , Stinebring Daniel R. 
Published: January 2024

Abstract
We use the upgraded Giant Metrewave Radio Telescope (uGMRT) to measure scintillation arc properties in six bright canonical pulsars with simultaneous dual-frequency coverage. These observations, at frequencies from 300 to 750 MHz, allowed for detailed analysis of arc evolution across frequency and epoch. We perform more robust determinations of frequency dependence for arc curvature, scintillation bandwidth, and scintillation timescale, and comparison between arc curvature and pseudo-curvature than allowed by single-frequency-band-per-epoch measurements, which we find to agree with theory and previous literature. We find a strong correlation between arc asymmetry and arc curvature, which we have replicated using simulations, and attribute to a bias in the Hough transform approach to scintillation arc analysis. Possible evidence for an approximately week-long timescale over which a given scattering screen dominates signal propagation was found by tracking visible scintillation arcs in each epoch in PSR J1136+1551. The inclusion of a 155-minute observation allowed us to resolve the scale of scintillation variations on short timescales, which we find to be directly tied to the amount of interstellar medium sampled over the observation. Some of our pulsars showed either consistent or emerging asymmetries in arc curvature, indicating instances of refraction across their lines of sight. Significant features in various pulsars, such as multiple scintillation arcs in PSR J1136+1551 and flat arclets in PSR J1509+5531, that have been found in previous works, were also detected. The simultaneous multiple-band observing capability of the upgraded GMRT shows excellent promise for future pulsar scintillation work.
Growth of Massive Molecular Cloud Filament by Accretion Flows. I. Slow-shock Instability versus Ambipolar Diffusion
Authors: Abe Daisei , Inoue Tsuyoshi , Inutsuka Shu-ichiro 
Published: January 2024

Abstract
The Herschel Gould Belt Survey showed that stars form in dense filaments in nearby molecular clouds. Recent studies suggest that massive filaments are bound by the slow shocks caused by accretion flows onto the filaments. The slow shocks are known to be unstable to corrugation deformation of the shock front. Corrugation instability could convert the accretion flow's ram pressure into turbulent pressure that influences the width of the filament, which, according to theory, determines the self-gravitational fragmentation scale and core mass. In spite of its importance, the effect of slow-shock instability on star-forming filaments has not been investigated. In addition, the linear dispersion relation obtained from ideal magnetohydrodynamics (MHD) analysis shows that the most unstable wavelength of shock corrugation is infinitesimally small. In the scale of dense filaments, the effect of ambipolar diffusion can suppress the instability at small scales. This study investigates the influence of ambipolar diffusion on the instability of the slow shock. We perform two-dimensional MHD simulations to examine the linear growth of the slow-shock instability, considering the effect of ambipolar diffusion. The results demonstrate that the most unstable scale of slow-shock instability is approximately 5 times the length scale of ambipolar diffusion ℓ
AD calculated using post-shock variables, where ℓ
AD corresponds to the scale where the magnetic Reynolds number for ambipolar diffusivity is unity.
Investigating Period Variability Mechanisms in Eclipsing Binary Stars through Eclipsing Time Variation Analysis: A Case Study of TZ Bootis
Authors: Zervas Konstantinos , Christopoulou Panagiota-Eleftheria , Papageorgiou Athanasios 
Published: January 2024

Abstract
We present an effective strategy for extensive analysis of eclipsing time variations (ETVs) using modern and sophisticated optimization methods that comprise a set of tools to investigate period variability mechanisms in eclipsing binary stars such as the light-time effect, the Applegate mechanism, and mass transfer. We implement these methods for the first time assuming that the above mechanisms can act simultaneously in the puzzling W UMa–type binary star TZ Bootis by using archival and new TESS data spanning 75 yr and reexamining the up-to-date ETVs. Preliminary analysis of the TESS data revealed for the first time the presence of a second binary in agreement with previous spectroscopic data and astrometric results from Gaia DR3. We consider the most credible scenario for the ETV: two stellar circumbinary companions of minimum masses M
3 = 0.5 M
☉ and M
4 = 0.14 M
☉ in highly eccentric orbits e
3 = 0.70 and e
4 = 0.82 with periods P
3 = 38 yr and P
4 = 20 yr along with a 24 yr magnetic activity of the secondary component and a long-term period increase (dP/dt = 1.2 × 10−8 days yr−1), interpreted as a conservative mass transfer from the secondary to the primary component at a rate of dM
1/dt = 3.7 × 10−9 days yr−1. Further spectroscopic observations, analytical modeling of the second pair, and ETV analysis of both pairs are needed to investigate the quadruple nature of the system.
Spectroscopic Imaging of the Sun with MeerKAT: Opening a New Frontier in Solar Physics
Authors: Kansabanik Devojyoti , Mondal Surajit , Oberoi Divya , Chibueze James O. , Engelbrecht N. E. , Strauss R. D. , Kontar E. P. , Botha G. J. J. , Steyn P. J. , Nel Amoré E. 
Published: January 2024

Abstract
Solar radio emissions provide several unique diagnostics to estimate different physical parameters of the solar corona, which are otherwise simply inaccessible. However, imaging the highly dynamic solar coronal emissions spanning a large range of angular scales at radio wavelengths is extremely challenging. At gigahertz frequencies, MeerKAT radio telescope is possibly globally the best-suited instrument at present for providing high-fidelity spectroscopic snapshot solar images. Here, we present the first published spectroscopic images of the Sun made using the observations with MeerKAT in the 880–1670 MHz band. This work demonstrates the high fidelity of spectroscopic snapshot MeerKAT solar images through a comparison with simulated radio images at MeerKAT frequencies. The observed images show extremely good morphological similarities with the simulated images. Our analysis shows that below ∼900 MHz MeerKAT images can recover essentially the entire flux density from the large angular-scale solar disk. Not surprisingly, at higher frequencies, the missing flux density can be as large as ∼50%. However, it can potentially be estimated and corrected for. We believe once solar observation with MeerKAT is commissioned, it will enable a host of novel studies, open the door to a large unexplored phase space with significant discovery potential, and also pave the way for solar science with the upcoming Square Kilometre Array-Mid telescope, of which MeerKAT is a precursor.
JWST Imaging of Edge-on Protoplanetary Disks. II. Appearance of Edge-on Disks with a Tilted Inner Region: Case Study of IRAS04302+2247
Authors: Villenave Marion , Stapelfeldt Karl R. , Duchêne Gaspard , Ménard François , Wolff Schuyler G. , Perrin Marshall D. , Pinte Christophe , Tazaki Ryo , Padgett Deborah L. 
Published: January 2024

Abstract
We present James Webb Space Telescope imaging from 2 to 21 μm of the edge-on protoplanetary disk around the embedded young star IRAS04302+2247. The structure of the source shows two reflection nebulae separated by a dark lane. The source extent is dominated by the extended filamentary envelope at ∼4.4 μm and shorter wavelengths, transitioning at 7.7 μm and longer wavelengths to more compact lobes of scattered light from the disk itself. The dark lane thickness does not vary significantly with wavelength, which we interpret as an indication for intermediate-sized (∼10 μm) grains in the upper layers of the disk. Intriguingly, we find that the brightest nebula of IRAS40302 switches side between 12.8 and 21 μm. We explore the effect of a tilted inner region on the general appearance of edge-on disks. We find that radiative transfer models of a disk including a tilted inner region can reproduce an inversion in the brightest nebula. In addition, for specific orientations, the model predicts strong lateral asymmetries, which can occur for more than half possible viewing azimuths. A large number of edge-on protoplanetary disks observed in scattered light show such lateral asymmetries (15/20), which suggests that a large fraction of protoplanetary disks might host a tilted inner region. Stellar spots may also induce lateral asymmetries, which are expected to vary over a significantly shorter timescale. Variability studies of edge-on disks would allow us to test the dominant scenario for the origin of these asymmetries.
Comparative Analysis of Type III Radio Bursts and Solar Flares: Spatial Localization and Correlation with Solar Flare Intensity
Authors: Krupar Vratislav , Kruparova Oksana , Szabo Adam , Nemec Frantisek , Maksimovic Milan , Martinez Oliveros Juan Carlos , Lario David , Bonnin Xavier , Vecchio Antonio , Pulupa Marc , Bale Stuart D. 
Published: January 2024

Abstract
We present a comprehensive study of type III radio bursts and their association with solar flares of magnitude M1.0 and larger, as observed by four widely separated spacecraft (Parker Solar Probe, Solar Orbiter, STEREO-A, and Wind). Our main focus is the introduction and validation of two methods for localizing radio bursts using the available multispacecraft data. The first method utilizes intensity fitting with a circular Gaussian distribution, while the second method is based on the time arrival of radio bursts. We demonstrate the effectiveness of these methods through the analysis of a single type III burst event and compare their results with the traditional radio triangulation technique. Furthermore, we conduct a statistical study of 17 type III bursts associated with M- and X-class solar flares in years 2020–2022. Our findings suggest a possible correlation between solar flare intensities and longitudes, with east limb flares tending to be weaker than west limb flares. We also observe a systematic drift of radio burst longitudes toward the east, potentially explained by a poleward component of the local density gradient. Our results suggest a strong correlation between solar flare intensities and radio burst properties, enhancing our understanding of the relationship between solar flares and type III radio bursts.
Small-scale Cosmic-Ray Anisotropy Observed by the GRAPES-3 Experiment at TeV Energies
Authors: Chakraborty M. , Ahmad S. , Chandra A. , Dugad S. R. , Goswami U. D. , Gupta S. K. , Hariharan B. , Hayashi Y. , Jagadeesan P. , Jain A. , Jain P. , Kawakami S. , Koi T. , Kojima H. , Mahapatra S. , Mohanty P. K. , Moharana R. , Muraki Y. , Nakamura T. , Nayak P. K. , Nonaka T. , Oshima A. , Pant B. P. , Pattanaik D. , Paul S. , Pradhan G. S. , Rameez M. , Ramesh K. , Saha S. , Sahoo R. , Scaria R. , Shibata S. , Tabata T. , Takamaru H. , Tanaka K. , Varsi F. , Yamazaki K. , Zuberi M. 
Published: January 2024

Abstract
GRAPES-3 is a mid-altitude (2200 m) and near-equatorial (11.°4N) air shower array, overlapping in its field of view for cosmic-ray observations with experiments that are located in the Northern and Southern Hemispheres. We analyze a sample of 3.7 × 109 cosmic-ray events collected by the GRAPES-3 experiment between 2013 January 1 and 2016 December 31 with a median energy of ∼16 TeV for study of small-scale (<60°) angular-scale anisotropies. We observed two structures, labeled A and B, that deviate from the expected isotropic distribution of cosmic rays in a statistically significant manner. Structure A spans 50°–80° in R.A. and from −15° to 30° in decl. The relative excess observed in structure A is at the level of (6.5 ± 1.3) × 10−4 with a statistical significance of 6.8 standard deviations. Structure B is observed in the R.A. range 110°–140° and at decl. from −10° to 30°. The relative excess observed in this region is at the level of (4.9 ± 1.4) × 10−4 with a statistical significance of 4.7 standard deviations. These structures are consistent with those reported by Milagro, ARGO-YBJ, and HAWC. These observations could provide a better understanding of the sources of cosmic rays, their propagation, and the magnetic structures in our Galaxy.
Studying the Spheromak Rotation in Data-constrained Coronal Mass Ejection Modeling with EUHFORIA and Assessing Its Effect on the B

z
Prediction
Authors: Sarkar Ranadeep , Pomoell Jens , Kilpua Emilia , Asvestari Eleanna , Wijsen Nicolas , Maharana Anwesha , Poedts Stefaan 
Published: January 2024

Abstract
A key challenge in space weather forecasting is accurately predicting the magnetic field topology of interplanetary coronal mass ejections (ICMEs), specifically the north–south magnetic field component (B

z
) for Earth-directed CMEs. Heliospheric MHD models typically use spheromaks to represent the magnetic structure of CMEs. However, when inserted into the ambient interplanetary magnetic field, spheromaks can experience a phenomenon reminiscent of the condition known as the “spheromak tilting instability,” causing its magnetic axis to rotate. From the perspective of space weather forecasting, it is crucial to understand the effect of this rotation on predicting B

z
at 1 au while implementing the spheromak model for realistic event studies. In this work, we study this by modeling a CME event on 2013 April 11 using the European Heliospheric Forecasting Information Asset. Our results show that a significant spheromak rotation up to 90° has occurred by the time it reaches 1 au, while the majority of this rotation occurs below 0.3 au. This total rotation resulted in poor predicted magnetic field topology of the ICME at 1 au. To address this issue, we further investigated the influence of spheromak density on mitigating rotation. The results show that the spheromak rotation is less for higher densities. Importantly, we observe a substantial reduction in the uncertainties associated with predicting B

z
when there is minimal spheromak rotation. Therefore, we conclude that spheromak rotation adversely affects B

z
prediction in the analyzed event, emphasizing the need for caution when employing spheromaks in global MHD models for space weather forecasting.
An Efficient Algorithm for Astrochemical Systems Using Stoichiometry Matrices
Authors: Motoyama Kazutaka , Krasnopolsky Ruben , Shang Hsien , Aida Kento , Sakane Eisaku 
Published: January 2024

Abstract
Astrochemical simulations are a powerful tool for revealing chemical evolution in the interstellar medium. Astrochemical calculations require efficient processing of large matrices for the chemical networks. The large chemical reaction networks often present bottlenecks for computation because of time derivatives of chemical abundances. We propose an efficient algorithm using a stoichiometry matrix approach in which this time-consuming part is expressed as a loop, unlike the algorithm used in previous studies. Since stoichiometry matrices are sparse in general, the performances of simulations with our algorithm depend on which sparse-matrix storage format is used. We conducted a performance comparison experiment using the common storage formats, including the coordinate format, the compressed column storage format, the compressed row storage (CRS) format, and the sliced ELLPACK format. Experimental results showed that the simulations with the CRS format are the most suitable for astrochemical simulations and about a factor of 2 faster than those with the algorithm used in previous studies. In addition, our algorithm significantly reduces not only the computation time but also the compilation time. We also explore the beneficial effects of parallelization and sparse-matrix reordering in these algorithms.
Bug Found in Gaia query_object Functions of Astroquery’s Python Package
Authors: Sweeney David , Krone-Martins Alberto 
Published: January 2024

Abstract
This research note addresses a bug in the Gaia functionality of the astroquery Python package. The bug, which results in sources in the Gaia catalog not being returned, affects the Gaia.query_object() and Gaia.query_object_async() functions. These rely on the deprecated ADQL BOX function if width or height are specified. These functions are used in published research and as such the bug could affect peer-reviewed results. We advise any researchers using these functions to instead use the Gaia.cone_search() counterparts to these functions or the Gaia.launch_job() functions. The Gaia helpdesk have been contacted and have confirmed the behavior and may update the astroquery documentation in the coming months.
Bioverse: The Habitable Zone Inner Edge Discontinuity as an Imprint of Runaway Greenhouse Climates on Exoplanet Demographics
Authors: Schlecker Martin , Apai Dániel , Lichtenberg Tim , Bergsten Galen , Salvador Arnaud , Hardegree-Ullman Kevin K. 
Published: January 2024

Abstract
Long-term magma ocean phases on rocky exoplanets orbiting closer to their star than the runaway greenhouse threshold—the inner edge of the classical habitable zone—may offer insights into the physical and chemical processes that distinguish potentially habitable worlds from others. The thermal stratification of runaway planets is expected to significantly inflate their atmospheres, potentially providing observational access to the runaway greenhouse transition in the form of a habitable zone inner edge discontinuity in radius–density space. Here, we use Bioverse, a statistical framework combining contextual information from the overall planet population with a survey simulator, to assess the ability of ground- and space-based telescopes to test this hypothesis. We find that the demographic imprint of the runaway greenhouse transition is likely detectable with high-precision transit photometry for sample sizes ≳100 planets if at least ∼10% of those orbiting closer than the habitable zone inner edge harbor runaway climates. Our survey simulations suggest that, in the near future, ESA’s PLATO mission will be the most promising survey to probe the habitable zone inner edge discontinuity. We determine the survey strategies that maximize the diagnostic power of the obtained data and identify as key mission design drivers: (1) a follow-up campaign of planetary mass measurements and (2) the fraction of low-mass stars in the target sample. Observational constraints on the runaway greenhouse transition will provide crucial insights into the distribution of atmospheric volatiles among rocky exoplanets, which may help to identify the nearest potentially habitable worlds.
Effect of Equation of State and Cutoff Density in Smoothed Particle Hydrodynamics Simulations of the Moon-forming Giant Impact
Authors: Hull Scott D. , Nakajima Miki , Hosono Natsuki , Canup Robin M. , Gassmöller Rene 
Published: January 2024

Abstract
The amount of vapor in the impact-generated protolunar disk carries implications for the dynamics, devolatilization, and moderately volatile element isotope fractionation during lunar formation. The equation of state (EoS) used in simulations of the giant impact is required to calculate the vapor mass fraction (VMF) of the modeled protolunar disk. Recently, a new version of M-ANEOS (Stewart M-ANEOS) was released with an improved treatment of heat capacity and expanded experimental Hugoniot. Here, we compare this new M-ANEOS version with a previous version (N-SPH M-ANEOS) and assess the resulting differences in smoothed particle hydrodynamics (SPH) simulations. We find that Stewart M-ANEOS results in cooler disks with smaller values of VMF and in differences in disk mass that are dependent on the initial impact angle. We also assess the implications of the minimum “cutoff” density (ρ

c
), similar to a maximum smoothing length, that is set as a fast-computing alternative to an iteratively calculated smoothing length. We find that the low particle resolution of the disk typically results in >40% of disk particles falling to ρ

c
, influencing the dynamical evolution and VMF of the disk. Our results show that the choice of EoS, ρ

c
, and particle resolution can cause the VMF and disk mass to vary by tens of percent. Moreover, small values of ρ

c
produce disks that are prone to numerical instability and artificial shocks. We recommend that future giant impact SPH studies review smoothing methods and ensure the thermodynamic stability of the disk over simulated time.
Cratering and Tectonic History of the Largest Uranian Satellite, Titania: New Insights Enabled by Image Reprocessing
Authors: Nathan Erica , Head James , Huber Christian 
Published: January 2024

Abstract
From heavily cratered Umbriel to extensively tectonized Miranda, Titania is an intermediary of the Uranian system: heavily cratered, yet tectonically modified. An outstanding mystery in Titania's crater population is its apparent relative lack of large (>30 km) craters. However, progress has been limited by the coverage and quality of images available. Here, we present a new map of Titania enabled by reprocessing Voyager images to reduce the effects of motion blur. Of note, we identify a network of fractures, a set of lineaments that may represent a large multi-ring impact structure, and newly identified catenae. These findings suggest Titania's crater population is missing large craters due to viscous relaxation, tectonic resurfacing, and/or planetocentric debris, and does not necessarily require cryovolcanic resurfacing. In preparation for future missions to the Uranian system, this work presents foundations for identifying imaging targets that can contribute to furthering our understanding of the history and evolution of the Uranian system in a broader context of icy satellite evolution.
Retrievals Applied to a Decision Tree Framework Can Characterize Earthlike Exoplanet Analogs
Authors: Young Amber V. , Crouse Jaime , Arney Giada , Domagal-Goldman Shawn , Robinson Tyler D. , Bastelberger Sandra T. 
Published: January 2024

Abstract
Exoplanet characterization missions planned for the future will soon enable searches for life beyond our solar system. Critical to the search will be the development of life detection strategies that can search for biosignatures while maintaining observational efficiency. In this work, we adopted a newly developed biosignature decision tree strategy for remote characterization of Earthlike exoplanets. The decision tree offers a step-by-step roadmap for detecting exoplanet biosignatures and excluding false positives, based on Earth’s biosphere and its evolution over time. We followed the pathways for characterizing a modern-Earth-like planet and an Archean-Earth-like planet and evaluated the observational trades associated with coronagraph bandpass combinations of designs consistent with the Habitable Worlds Observatory precursor studies. With retrieval analyses of each bandpass (or combination), we demonstrate the utility of the decision tree and evaluate the uncertainty on a suite of biosignature chemical species and habitability indicators (i.e., the gas abundances of H2O, O2, O3, CH4, and CO2). Notably for modern Earth, less than an order of magnitude spread in the 1σ uncertainties was achieved for the abundances of H2O and O2, planetary surface pressure, and atmospheric temperature, with three strategically placed bandpasses (two in the visible and one in the near-infrared). For the Archean, CH4 and H2O were detectable in the visible with a single bandpass.