bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strong Near-infrared Carbon Absorption in the Transitional Type Ia SN 2015bp*
Authors: Wyatt S. D. , Sand D. J. , Hsiao E. Y. , Burns C. R. , Valenti S. , Bostroem K. A. , Lundquist M. , Galbany L. , Lu J. , Ashall C. , Diamond T. R. , Filippenko A. V. , Graham M. L. , Hoeflich P. , Kirshner R. P. , Krisciunas K. , Marion G. H. , Morrell N. , Persson S. E. , Phillips M. M. , Stritzinger M. D. , Suntzeff N. B. , Taddia F. 
Published: June 2021

Abstract
Unburned carbon is potentially a powerful probe of Type Ia supernova (SN) explosion mechanisms. We present comprehensive optical and near-infrared (NIR) data on the “transitional” Type Ia SN 2015bp. An early NIR spectrum (

days with respect to B-band maximum) displays a striking C i 1.0693 μm line at 11.9 × 103 km s−1, distinct from the prominent Mg ii 1.0927 μm feature, which weakens toward maximum light. SN 2015bp also displays a clear C ii 6580 Å notch early (

days) at 13.2 × 103 km s−1, consistent with our NIR carbon detection. At

, SN 2015bp is less luminous than a normal SN Ia and, along with iPTF 13ebh, is the second member of the transitional subclass to display prominent early-time NIR carbon absorption. We find it unlikely that the C i feature is misidentified He i 1.0830 μm because this feature grows weaker toward maximum light, while the helium line produced in some double-detonation models grows stronger at these times. Intrigued by these strong NIR carbon detections, but lacking NIR data for other SNe Ia, we investigated the incidence of optical carbon in the sample of nine transitional SNe Ia with early-time data (t ≲ −4 days). We find that four display C ii 6580 Å, while two others show tentative detections, in line with the SN Ia population as a whole. We conclude that at least ∼50% of transitional SNe Ia in our sample do not come from sub-Chandrasekhar-mass explosions due to the clear presence of carbon in their NIR and optical spectra.
On a Possible Solution to the Tidal Realignment Problem for Hot Jupiters
Authors: Anderson Kassandra R. , Winn Joshua N. , Penev Kaloyan 
Published: June 2021

Abstract
Hot stars with hot Jupiters have a wide range of obliquities, while cool stars with hot Jupiters tend to have low obliquities. An enticing explanation for this pattern is tidal realignment of the cool host stars, although this explanation assumes that obliquity damping occurs faster than orbital decay, an assumption that needs further exploration. Here we revisit this tidal realignment problem, building on previous work identifying a low-frequency component of the time-variable tidal potential that affects the obliquity but not the orbital separation. We adopt a recent empirically based model for the stellar tidal quality factor and its sharp increase with forcing frequency. This leads to enhanced dissipation at low frequencies, and efficient obliquity damping. We model the tidal evolution of 46 observed hot Jupiters orbiting cool stars. A key parameter is the stellar age, which we determine in a homogeneous manner for the sample, taking advantage of Gaia DR2 data. We explore a variety of tidal histories and futures for each system, finding in most cases that the stellar obliquity is successfully damped before the planet is destroyed. A testable prediction of our model is that hot Jupiter hosts with orbital periods shorter than 2–3 days should have obliquities much smaller than 1°. With the possible exception of WASP-19b, the predicted future lifetimes of the planets range from 108 yr to more than 1010 yr. Thus, our model implies that these hot Jupiters are probably not in immediate danger of being devoured by their host stars while they are on the main sequence.
Comparing the Inner and Outer Star-forming Complexes in the Nearby Spiral Galaxies NGC 628, NGC 5457, and NGC 6946 Using UVIT Observations
Authors: Yadav Jyoti , Das Mousumi , Patra Narendra Nath , Dwarakanath K. S. , Rahna P. T. , McGaugh Stacy S. , Schombert James , Murthy Jayant 
Published: June 2021

Abstract
We present a far-UV (FUV) study of the star-forming complexes (SFCs) in three nearby galaxies using the Ultraviolet Imaging Telescope. The galaxies are close to face-on and show significant outer disk star formation. Two of them are isolated (NGC 628 and NGC 6946), and one is interacting with distant companions (NGC 5457). We compared the properties of the SFCs inside and outside the optical radius (R
25). We estimated the sizes, star formation rates (SFRs), metallicities, and Toomre Q parameter of the SFCs. We find that the outer disk SFCs are at least 10 times smaller in area than those in the inner disk. The SFRs per unit area (ΣSFR) in both regions have similar mean values, but the outer SFCs have a much smaller range of ΣSFR. They are also metal-poor compared to the inner disk SFCs. The FUV emission is well correlated with the neutral hydrogen gas (H i) distribution and detected within and near several H i holes. Our estimation of the Q parameter in the outer disks of the two isolated galaxies suggests that their outer disks are stable (Q > 1). However, their FUV images indicate that there is ongoing star formation in these regions. This suggests that there may be some nonluminous mass or dark matter in their outer disks, which increases the disk surface density and supports the formation of local gravitational instabilities. In the interacting galaxy, NGC 5457, the baryonic surface density is sufficient (Q < 1) to trigger local disk instabilities in the outer disk.
The Relative Importance of Faraday Rotation and QED Birefringence for the Linear Polarization of X-Rays from Mass-accreting Black Holes
Authors: Krawczynski Henric , Lisalda Lindsey , Gammie Charles F. 
Published: June 2021

Abstract
The upcoming Imaging X-ray Polarimetry Explorer (IXPE; 2–8 keV) and XL-Calibur (15–75 keV) missions will make it possible to measure the linear polarization of X-rays from mass-accreting stellar mass black holes with unprecedented sensitivity, enabling the accurate measurement of percent-level and in some cases even sub-percent-level polarization fractions. The measurements are expected to constrain the spins, inclinations, and the structure of the accretion flows of the observed black holes. The effects of Faraday rotation and birefringence of the quantum electrodynamics vacuum may impact the observable polarization fractions and angles, complicating the interpretation of the results. We estimate the importance of both effects for X-rays from stellar mass and supermassive black holes and discuss the implications of the results for the upcoming IXPE and XL-Calibur observations.
Using Chandra Localizations and Gaia Distances and Proper Motions to Classify Hard X-Ray Sources Discovered by INTEGRAL
Authors: Tomsick John A. , Coughenour Benjamin M. , Hare Jeremy , Krivonos Roman , Bodaghee Arash , Chaty Sylvain , Clavel Maïca , Fornasini Francesca M. , Rodriguez Jerome , Shaw Aarran W. 
Published: June 2021

Abstract
Here, we report on X-ray observations of ten 17–60 keV sources discovered by the International Gamma-Ray Astrophysics Laboratory satellite. The primary new information is sub-arcsecond positions obtained by the Chandra X-ray Observatory. In six cases (IGR J17040-4305, IGR J18017-3542, IGR J18112-2641, IGR J18434-0508, IGR J19504+3318, and IGR J20084+3221), a unique Chandra counterpart is identified with a high degree of certainty, and for five of these sources (all but J19504), Gaia distances or proper motions indicate that they are Galactic sources. For four of these, the most likely classifications are that the sources are magnetic cataclysmic variables (CVs). J20084 could be either a magnetic CV or a high-mass X-ray binary. We classify the sixth source (J19504) as a likely active galactic nucleus (AGN). In addition, we find likely Chandra counterparts to IGR J18010-3045 and IGR J19577+3339, and the latter is a bright radio source and probable AGN. The other two sources, IGR J12529-6351 and IGR J18013-3222, do not have likely Chandra counterparts, indicating that they are transient, highly variable, or highly absorbed.
The X-Ray Properties of Eta Carinae During Its 2020 X-Ray Minimum
Authors: Kashi Amit , Principe David A. , Soker Noam , Kastner Joel H. 
Published: June 2021

Abstract
The massive binary system Eta Carinae is characterized by intense colliding winds that form shocks and emit X-rays. The system is highly eccentric (e ≃ 0.9), resulting in modulated X-ray emission during its 5.54 yr orbit. The X-ray flux increases in the months prior to periastron passage, exhibiting strong flares, then rapidly declines to a flat minimum lasting a few weeks, followed by a gradual recovery. We present the Neutron Star Interior Composition Explorer telescope spectra obtained before, during, and after the 2020 X-ray minimum, and perform spectral analysis to establish the temporal behavior of the X-ray flux and X-ray-absorbing column density (N
H(t)) for the 2–10 keV and 5–10 keV energy ranges. The latter range is dominated by the stellar wind-collision region and, therefore, these spectral parameters—in particular, N
H(t)—serve as potentially stringent constraints on the binary orientation. We compare the observed N
H(t) results to the behavior predicted by a simple geometrical model in an attempt to ascertain which star is closer to us at periastron: the more massive primary (ω ≃ 240°–270°) or the secondary (ω ≃ 90°). We find that the variations in column density, both far from periastron and around periastron passage, support the latter configuration (ω ≃ 90°). The 2020 X-ray minimum showed the fastest recovery among the last five minima, providing additional evidence for a recent weakening of the primary star’s wind.
Multiphase AGN Winds from X-Ray-irradiated Disk Atmospheres
Authors: Waters Tim , Proga Daniel , Dannen Randall 
Published: June 2021

Abstract
The mechanism of thermal driving for launching mass outflows is interconnected with classical thermal instability (TI). In a recent paper, we demonstrated that as a result of this interconnectedness, radial wind solutions of X-ray-heated flows are prone to becoming clumpy. In this paper, we first show that the Bernoulli function determines whether or not the entropy mode can grow due to TI in dynamical flows. Based on this finding, we identify a critical “unbound” radius beyond which TI should accompany thermal driving. Our numerical disk wind simulations support this result and reveal that clumpiness is a consequence of buoyancy disrupting the stratified structure of steady-state solutions. Namely, instead of a smooth transition layer separating the highly ionized disk wind from the cold phase atmosphere below, hot bubbles formed from TI rise up and fragment the atmosphere. These bubbles first appear within large-scale vortices that form below the transition layer, and they result in the episodic production of distinctive cold phase structures referred to as irradiated atmospheric fragments (IAFs). Upon interacting with the wind, IAFs advect outward and develop extended crests. The subsequent disintegration of the IAFs takes place within a turbulent wake that reaches high elevations above the disk. We show that this dynamics has the following observational implications: dips in the absorption measure distribution are no longer expected within TI zones, and there can be a less sudden desaturation of X-ray absorption lines such as O viii Lyα as well as multiple absorption troughs in Fe xxv Kα.
Likelihood-free Cosmological Constraints with Artificial Neural Networks: An Application on Hubble Parameters and SNe Ia
Authors: Wang Yu-Chen , Xie Yuan-Bo , Zhang Tong-Jie , Huang Hui-Chao , Zhang Tingting , Liu Kun 
Published: June 2021

Abstract
The errors of cosmological data generated from complex processes, such as the observational Hubble parameter data (OHD) and the Type Ia supernova (SN Ia) data, cannot be accurately modeled by simple analytical probability distributions, e.g., a Gaussian distribution. To constrain cosmological parameters from these data, likelihood-free inference is usually used to bypass the direct calculation of the likelihood. In this paper, we propose a new procedure to perform likelihood-free cosmological inference using two artificial neural networks (ANNs), the masked autoregressive flow (MAF) and the denoising autoencoder (DAE). Our procedure is the first to use DAE to extract features from data, in order to simplify the structure of MAF needed to estimate the posterior. Tested on simulated Hubble parameter data with a simple Gaussian likelihood, the procedure shows the capability of extracting features from data and estimating posterior distributions without the need of tractable likelihood. We demonstrate that it can accurately approximate the real posterior, achieve performance comparable to the traditional Markov chain Monte Carlo method, and MAF obtains better training results for a small number of simulation when the DAE is added. We also discuss the application of the proposed procedure to OHD and Pantheon SN Ia data, and use them to constrain cosmological parameters from the non-flat ΛCDM model. For SNe Ia, we use fitted light-curve parameters to find constraints on H
0, Ω
m
, and ΩΛ similar to relevant work, using less empirical distributions. In addition, this work is also the first to use a Gaussian process in the procedure of OHD simulation.
The Abundance of Lead in Four Metal-poor Stars
Authors: Peterson Ruth C. 
Published: June 2021

Abstract
Cowan et al. review how roughly half the elements heavier than iron found in the Sun are produced by rapid neutron capture and half by slow neutron capture, the r- and s-processes. In the Sun, their relative contribution to individual elemental abundances is well understood, except for the lightest and heaviest elements beyond iron. Their contributions are especially uncertain for the heaviest nonradioactive element, lead (Pb, Z = 82). This is constrained by deriving lead abundances in metal-poor stars. For in the most metal-poor halo stars, strontium and heavier elements are found in the solar r-process proportion; s-process elements appear only at metallicities above one-thirtieth solar. In unevolved metal-poor stars of roughly solar heavy-element content, only two UV Pb lines are detectable. Four such stars have high-resolution spectra of the strongest line, Pb ii at 2203.53 Å. Roederer et al. analyzed this line in one star, deriving a lead-to-iron abundance ratio 10 times solar. This and its blueshifted profile suggested strong s-process production. This work analyzes the UV spectra of all four stars. Calculations including a predicted Fe i line blueward of the Pb ii line, and assuming the lead abundance scales with r-process abundances, match all four profiles extremely well. A scaled s-process contribution might improve the match to the much lower lead abundance found in the unevolved star analyzed previously, but its s-process excess is modest. An Fe ii line blends the other lead line, Pb i at 2833.05 Å, which constrains the lead abundance only in the coolest star.
Titan: Earth-like on the Outside, Ocean World on the Inside
Authors: MacKenzie Shannon M. , Birch Samuel P. D. , Hörst Sarah , Sotin Christophe , Barth Erika , Lora Juan M. , Trainer Melissa G. , Corlies Paul , Malaska Michael J. , Sciamma-O’Brien Ella , Thelen Alexander E. , Turtle Elizabeth , Radebaugh Jani , Hanley Jennifer , Solomonidou Anezina , Newman Claire , Regoli Leonardo , Rodriguez Sébastien , Seignovert Benôit , Hayes Alexander G. , Journaux Baptiste , Steckloff Jordan , Nna-Mvondo Delphine , Cornet Thomas , Palmer Maureen Y. , Lopes Rosaly M. C. , Vinatier Sandrine , Lorenz Ralph , Nixon Conor , Czaplinski Ellen , Barnes Jason W. , Sittler Ed , Coates Andrew 
Published: June 2021

Abstract
Thanks to the Cassini–Huygens mission, Titan, the pale orange dot of Pioneer and Voyager encounters, has been revealed to be a dynamic, hydrologically shaped, organic-rich ocean world offering unparalleled opportunities to explore prebiotic chemistry. And while Cassini–Huygens revolutionized our understanding of each of the three “layers” of Titan—the atmosphere, the surface, and the interior—we are only beginning to hypothesize how these realms interact. In this paper, we summarize the current state of Titan knowledge and discuss how future exploration of Titan would address some of the next decade’s most compelling planetary science questions. We also demonstrate why exploring Titan, both with and beyond the Dragonfly New Frontiers mission, is a necessary and complementary component of an Ocean Worlds Program that seeks to understand whether habitable environments exist elsewhere in our solar system.
The Brittle Boulders of Dwarf Planet Ceres
Authors: Schröder Stefan E. , Carsenty Uri , Hauber Ernst , Raymond Carol A. , Russell Christopher T. 
Published: June 2021

Abstract
We mapped all boulders larger than 105 m on the surface of dwarf planet Ceres using images of the Dawn framing camera acquired in the Low Altitude Mapping Orbit. We find that boulders on Ceres are more numerous toward high latitudes and have a maximum lifetime of 150 ± 50 Ma, based on crater counts. These characteristics are distinctly different from those of boulders on asteroid (4) Vesta, an earlier target of Dawn, which implies that Ceres’ boulders are mechanically weaker. Clues to their properties can be found in the composition of Ceres’ complex crust, which is rich in phyllosilicates and salts. As water ice is thought to be present only meters below the surface, we suggest that boulders also harbor ice. Furthermore, the boulder size–frequency distribution is best fit by a Weibull distribution rather than the customary power law, just like for Vesta boulders. This finding is robust in light of possible types of size measurement error.
Between approval and disapproval: Citizens’ views on the invasive tree Ailanthus altissima and its management
Authors: Kowarik Ingo , Straka Tanja M. , Lehmann Mario , Studnitzky Rafael , Fischer Leonie K. 
Published: June 2021

While cities are invasion hotspots, the view of urban residents on non-native species is critically understudied – an important knowledge gap since strategies on biological invasions could gain power by integrating human values, attitudes and perceptions. How citizens perceive the non-native tree Ailanthus altissima (tree of heaven) is unknown despite its abundance in many cities globally and its classification as invasive in many countries. In a quantitative survey with closed questions, we analysed (i) whether residents of Berlin, Germany knew the widespread species, (ii) how they perceived it in different urban situations, (iii) how they accepted different management strategies of it, and (iv) how the sociodemographic background of respondents predicted their preference and acceptability ratings.
In total, we surveyed 196 respondents. Most respondents recognized the tree in a photograph, but few provided its correct name. Citizens’ preferences differed significantly among four urban contexts in which the species was shown, with prevailing approval for trees as a component of designed green spaces and less pronounced preferences for wild-grown trees in other urban spaces. When respondents were asked to indicate how the tree should be managed (three options), we found the most support for removal in problematic cases (‘adaptive on-site’ strategy); some support was found for the ‘leave alone’ strategy and least support for the ‘complete removal’ management strategy. Practitioners with expertise in urban landscaping were more critical of Ailanthus than laypeople. Ordinal logistic regression analyses showed that respondents with a ‘close to nature’ behaviour and attitude had a more positive view on Ailanthus and expressed more support for ‘leave alone’ management. Results demonstrate the importance of citizens’ context dependent views about a widespread invasive species, spanning from approval to disapproval in different situations. We conclude that urban management strategies concerning Ailanthus would gain support from citizens when combining multiple approaches: (i) to control the species in case of realized negative impacts; (ii) to prevent the invasion of the species in areas of conservation concern; and (iii) to develop novel approaches of integrating wild Ailanthus trees into urban green spaces. These insights could support management measures that need to be established due to the EU-Regulation on Invasive Alien Species.
Des villes communistes face à l’éducation prioritaire, entre engagement marqué et refus (1981-1984)
Authors: Heurdier Lydie , Bongrand Philippe 
Published: June 2021

Contrairement à une opinion commune, le Parti communiste français a bien encouragé la mise en place de la politique d’éducation prioritaire créée par le ministre socialiste Alain Savary en 1981-1982. Après l’avoir démontré à partir de la revue officielle du parti, L’école et la nation , l’article analyse la mise en œuvre de cette politique par trois municipalités communistes ayant adopté des postures contrastées. L’étude d’Aubervilliers, Le Havre et Orly, à partir de procès-verbaux de conseils municipaux, de la presse municipale et de témoignages, montre que les relations entre les élus locaux et les enseignants y ont été décisives, les élus disposant en outre d’une large autonomie.
De la décentralisation de l’éducation aux politiques éducatives locales en France : comment traiter en sciences sociales un objet en mutation ?
Authors: Ferhat Ismail 
Published: June 2021

Cette note de synthèse souhaite présenter la manière dont les sciences sociales se sont intéressées à la décentralisation de l’école en France. Elle s’appuie sur une approche quantitative et qualitative de la bibliographie existante en langue française. Objet complexe, puisque le processus est en cours depuis 1982, la décentralisation de l’éducation a longtemps été étudiée à l’intersection de l’analyse savante et de l’expertise des politiques publiques, avant d’être saisie – non sans débat – par les sciences sociales. Avec la reconnaissance accrue des collectivités locales depuis les lois dite Defferre, la question des politiques éducatives locales constitue un thème montant des études.
Bâtir à la vitesse grand V, une solution risquée ?
Authors: Ika Lavagnon , Paché Gilles 
Published: June 2021

Frappés de plein fouet par la pandémie de COVID-19, plusieurs gouvernements ont pris des décisions pour soutenir l’économie. Au Québec, le projet de loi 66 adopté en décembre 2020 met l’accent sur un programme ambitieux de grands projets d’infrastructures, notamment pour en accélérer l’exécution et pour sauver les emplois. Cependant, a-t-on vraiment pris conscience des contraintes temporelles inhérentes à de tels projets ?
Luc de Brabandere : l’homme qui jongle avec les boîtes à penser
Authors: Auger Claudine 
Published: June 2021

Se désignant lui-même comme un philosophe d’entreprise, Luc de Brabandere accompagne les dirigeants dans leur quête de créativité et d’innovation. Point de départ de cette démarche exigeante : distinguer pensée créative et activité d’innovation.