bluuebunny/crossref_metadata_2025_split huggingface dataset:
JWST Transit Spectra. I. Exploring Potential Biases and Opportunities in Retrievals of Tidally Locked Hot Jupiters with Clouds and Hazes
Authors: Lacy Brianna I. , Burrows Adam 
Published: December 2020

Abstract
The atmospheres on tidally locked planets likely exhibit large differences between their day- and night-sides. In this paper, we illustrate how the combined effects of aerosols and day–night temperature gradients shape transit spectra of tidally locked exoplanets and evaluate the implications for retrievals of atmospheric properties. We have developed a new code, Multi-dimensional Exoplanet TransIt Spectra (METIS), which can compute transit spectra for arbitrary longitude–latitude–altitude grids of temperature and pressure. Using METIS, we pair flexible treatments of clouds and hazes with simple parameterized day–night temperature gradients to compute transit spectra and perform retrieval experiments across a wide array of possible exoplanet atmospheric properties. Our key findings are that: (1) the presence of aerosols can increase the effects of day–night temperature gradients on transit spectra; (2) ignoring day–night temperature gradients when attempting to perform Bayesian parameter estimation will return biased results, even when aerosols are present; (3) when a day–night temperature gradient is accounted for in the retrieval, some spectra contain sufficient information to constrain temperatures and the width of the transition from day to night. The presence of clouds and hazes can actually tighten such constraints, but also weaken constraints on metallicity and reference pressure. These last findings are predicated on the assumptions made in parameterizing the day–night atmospheric structure and the assumption of thermochemical equilibrium. Our results imply that this may be a promising avenue to pursue and represent a step toward the larger goal of developing models and theory of adequate complexity to match the superior-quality data that will soon be available.
Transition Region Contribution to AIA Observations in the Context of Coronal Heating
Authors: Schonfeld S. J. , Klimchuk J. A. 
Published: December 2020

Abstract
We investigate the ratio of coronal and transition region intensity in coronal loops observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). Using Enthalpy-based Thermal Evolution of Loops (EBTEL) hydrodynamic simulations, we model loops with multiple lengths and energy fluxes heated randomly by events drawn from power-law distributions with different slopes and minimum delays between events to investigate how each of these parameters influences observable loop properties. We generate AIA intensities from the corona and transition region for each realization. The variations within and between models generated with these different parameters illustrate the sensitivity of narrowband imaging to the details of coronal heating. We then analyze the transition region and coronal emission from a number of observed active regions and find broad agreement with the trends in the models. In both models and observations, the transition region brightness is significant, often greater than the coronal brightness in all six “coronal” AIA channels. We also identify an inverse relationship, consistent with heating theories, between the slope of the differential emission measure (DEM) coolward of the peak temperature and the observed ratio of coronal to transition region intensity. These results highlight the use of narrowband observations and the importance of properly considering the transition region in investigations of coronal heating.
Fermi-LAT Observations of V549 Vel 2017: A Subluminous Gamma-Ray Nova?
Authors: Li Kwan-Lok , Hambsch Franz-Josef , Munari Ulisse , Metzger Brian D. , Chomiuk Laura , Frigo Andrea , Strader Jay 
Published: December 2020

Abstract
We report on the Fermi Large Area Telescope detection (with ≈5.7σ significance) as well as the multiwavelength analysis of the 2017 nova eruption V549 Vel. Unlike the recent shock-powered novae ASASSN-16ma and V906 Car, the optical and γ-ray light curves of V549 Vel show no correlation, likely implying relatively weak shocks in the eruption. Gaia detected a candidate progenitor of V549 Vel and found a parallax measurement of ϖ = 1.91 ± 0.39 mas, equivalent to a mode distance of d ≈ 560 pc (90% credible interval of 380–1050 pc). The progenitor was also observed by the 2MASS and WISE surveys. When adopting the Gaia distance, the spectral energy distribution of the progenitor is close to that of a G-type star. The Swift X-Ray Telescope detected the supersoft X-ray emission of the nova (kT = 30–40 keV) since day 236, and the inferred blackbody size is comparable to that of other novae assuming d ≈ 560 pc (i.e., R
bb ∼ 5 × 108 cm). However, there is also an unknown astrometric excess noise of ϵ

i
= 3.2 mas found in the Gaia data, and the inferred distance becomes controversial. If the Gaia distance is accurate, the γ-ray luminosity of V549 Vel will be as low as L

γ
∼ 4 × 1033 erg s−1, making it the least luminous γ-ray nova known so far. This may imply that the shock properties responsible for the γ-ray emission in V549 Vel are different from those of the more luminous events. If the nova is located farther away, it is likely a symbiotic system with a giant companion as the observed progenitor.
Formation of Smaller Anions from CnN− (n = 1–3, 5–7) in the Circumstellar Medium
Authors: Chacko Roby , Banhatti Shreyak , Nrisimhamurty M. , Yadav J. K. , Gupta A. K. , Aravind G. 
Published: December 2020

Abstract
We probe a new pathway for the formation of smaller anions from the temporary negative ion states (anion resonances) of C
n
N− (n = 1–3, 5–7) in the circumstellar envelope of IRC+10216. C
n
N− (n = 1–3, 5–7) anions were collisionally excited to their resonance states and were observed to decay into a variety of smaller anions. The measured kinetic-energy-release distributions for the anionic fragments arising from each of the parent anions indicate a concerted manner of occurrence of these fragments, implying rich dissociation dynamics.

and C2N− were found to be dominant fragments of these anions, suggesting their presence in the external layers of IRC+10216 where UV photons penetrate. C
n
N− (n = 1–3) were also observed to undergo dissociative and nondissociative double-electron detachments, with the former being dominant. The significance of this new pathway in determining the stability and abundance of anions in IRC+10216 is discussed.
Kinematical Signs of Dust Trapping and Feedback in a Local Pressure Bump in the Protoplanetary Disk around HD 142527 Revealed with ALMA
Authors: Yen Hsi-Wei , Gu Pin-Gao 
Published: December 2020

Abstract
We analyzed the archival data of the continuum emission at six wavelengths from 3 to 0.4 mm and 13CO and C18O (1–0, 2–1, and 3–2) lines in the protoplanetary disk around HD 142527 obtained with the Atacama Large Millimeter/submillimeter Array. We performed fitting to the spectral energy distributions obtained at the six wavelengths with the graybody slab models to estimate the distributions of the dust surface density and spectral index of dust absorption coefficient β. We also estimated the distribution of the gas column density by fitting the C18O spectra and measured the disk rotation by fitting the Keplerian disk models to the C18O data. We found super- and sub-Keplerian rotation inside and outside the dust ring in the northwest in the HD 142527 disk, suggestive of the presence of a local pressure bump. In comparison with our estimated dust and gas distributions, the location of the pressure bump is coincident with the region showing a three times higher dust density and a three times lower gas-to-dust mass ratio than the mean values in the disk, suggesting dust trapping in the pressure bump. Nevertheless, there is no correlation between our derived β distribution and the location of the pressure bump. In addition, we found that the width of the dust ring is comparable to or larger than the width of the pressure bump, which could suggest that dust feedback is significant in the pressure bump.
Surface Energy of the Titan Aerosol Analog “Tholin”
Authors: Yu 余馨 Xinting 婷 , Hörst Sarah M. , He Chao , McGuiggan Patricia , Kristiansen Kai , Zhang Xi 
Published: December 2020

Abstract
The photochemical haze produced in the upper atmosphere of Titan plays a key role in various atmospheric and surface processes on Titan. The surface energy, one important physical property of the haze, is crucial for understanding the growth of the haze particles and can be used to predict their wetting behavior with solid and liquid species on Titan. We produced Titan analog haze materials, so-called “tholins,” with different energy sources and measured their surface energies through contact angle and direct force measurements. From the contact angle measurement, we found that the tholins produced by cold plasma and UV irradiation have a total surface energy around 60–70 mJ m−2. The direct force measurement yields a total surface energy of ∼66 mJ m−2 for plasma tholin. The surface energy of tholin is relatively high compared to common polymers, indicating its high cohesiveness. Therefore, the Titan haze particles would likely coagulate easily to form bigger particles, while the haze-derived surface sand particles would need a higher wind speed to be mobilized because of the high interparticle cohesion. The high surface energy of tholins also makes them easily wettable by Titan’s atmospheric hydrocarbon condensates and surface liquids. Thus, the haze particles are likely good cloud condensation nuclei for hydrocarbon clouds (methane and ethane) to nucleate and grow. And if the haze particles are denser compared to the lake liquids, they will likely sink into the lakes instead of forming a floating film to dampen the lake surface waves.
Bimodal Behavior and Convergence Requirement in Macroscopic Properties of the Multiphase Interstellar Medium Formed by Atomic Converging Flows
Authors: Kobayashi Masato I. N. , Inoue Tsuyoshi , Inutsuka Shu-ichiro , Tomida Kengo , Iwasaki Kazunari , Tanaka Kei E. I. 
Published: December 2020

Abstract
We systematically perform hydrodynamics simulations of 20

converging flows of the warm neutral medium (WNM) to calculate the formation of the cold neutral medium (CNM), focusing especially on the mean properties of the multiphase interstellar medium (ISM), such as the mean density on a 10 pc scale. Our results show that convergence in those mean properties requires a 0.02 pc spatial resolution that resolves the cooling length of the thermally unstable neutral medium (UNM) to follow the dynamical condensation from the WNM to the CNM. We also find that two distinct postshock states appear in the mean properties depending on the amplitude of the upstream WNM density fluctuation

(

). When

, the interaction between shocks and density inhomogeneity leads to a strong driving of the postshock turbulence of >3 km s−1, which dominates the energy budget in the shock-compressed layer. The turbulence prevents dynamical condensation by cooling, and the CNM mass fraction remains at ∼45%. In contrast, when

, the CNM formation proceeds efficiently, resulting in the CNM mass fraction of ∼70%. The velocity dispersion is limited to the thermal-instability-mediated level of ∼2–3 km s−1, and the layer is supported by both turbulent and thermal energy equally. We also propose an effective equation of state that models the multiphase ISM formed by the WNM converging flow as a one-phase ISM in the form of P ∝ ργ

eff
, where γ
eff varies from 0.9 (for a large pre-shock Δρ
0) to 0.7 (for a small pre-shock Δρ
0).
591 High-velocity Stars in the Galactic Halo Selected from LAMOST DR7 and Gaia DR2
Authors: Li 李 Yin-Bi 荫碧 , Luo 罗 A-Li 阿理 , Lu 陆由 You-Jun 俊 , Zhang 张 Xue-Sen 学森 , Li 李 Jiao 蛟 , Wang 王 Rui 瑞 , Zuo 左 Fang 芳 , Xiang 向茂 Maosheng 盛 , Ting 丁源 Yuan-Sen 森 , Marchetti Tommaso , Li 李 Shuo 硕 , Wang 王有 You-Fen 芬 , Zhang 张 Shuo 硕 , Hattori Kohei , Zhao 赵永 Yong-Heng 恒 , Zhang 张华 Hua-Wei 伟 , Zhao 赵 Gang 刚 
Published: December 2020

Abstract
In this paper, we report 591 high-velocity star candidates (HiVelSCs) selected from over 10 million spectra of Data Release 7 (DR7) of the Large Sky Area Multi-object Fiber Spectroscopic Telescope and the second Gaia data release, with three-dimensional velocities in the Galactic rest frame larger than 445 km s−1. We show that at least 43 HiVelSCs are unbound to the Galaxy with escape probabilities larger than 50%, and this number decreases to eight if the possible parallax zero-point error is corrected. Most of these HiVelSCs are metal-poor and slightly α-enhanced inner halo stars. Only 14% of them have [Fe/H] > −1, which may be the metal-rich “in situ” stars in the halo formed in the initial collapse of the Milky Way or metal-rich stars formed in the disk or bulge but kinematically heated. The low ratio of 14% implies that the bulk of the stellar halo was formed from the accretion and tidal disruption of satellite galaxies. In addition, HiVelSCs on retrograde orbits have slightly lower metallicities on average compared with those on prograde orbits; meanwhile, metal-poor HiVelSCs with [Fe/H] < −1 have an even faster mean retrograde velocity compared with metal-rich HiVelSCs. To investigate the origins of HiVelSCs, we perform orbit integrations and divide them into four types, i.e., hypervelocity stars, hyper-runaway stars, runaway stars and fast halo stars. A catalog for these 591 HiVelSCs, including radial velocities, atmospheric parameters, Gaia astrometric parameters, spatial positions, and velocities, etc., is available in the China-VO PaperData Repository at doi:10.12149/101038.
The NANOGrav 12.5 yr Data Set: Wideband Timing of 47 Millisecond Pulsars
Authors: Alam Md F. , Arzoumanian Zaven , Baker Paul T. , Blumer Harsha , Bohler Keith E. , Brazier Adam , Brook Paul R. , Burke-Spolaor Sarah , Caballero Keeisi , Camuccio Richard S. , Chamberlain Rachel L. , Chatterjee Shami , Cordes James M. , Cornish Neil J. , Crawford Fronefield , Cromartie H. Thankful , DeCesar Megan E. , Demorest Paul B. , Dolch Timothy , Ellis Justin A. , Ferdman Robert D. , Ferrara Elizabeth C. , Fiore William , Fonseca Emmanuel , Garcia Yhamil , Garver-Daniels Nathan , Gentile Peter A. , Good Deborah C. , Gusdorff Jordan A. , Halmrast Daniel , Hazboun Jeffrey S. , Islo Kristina , Jennings Ross J. , Jessup Cody , Jones Megan L. , Kaiser Andrew R. , Kaplan David L. , Kelley Luke Zoltan , Key Joey Shapiro , Lam Michael T. , W. Lazio T. Joseph , Lorimer Duncan R. , Luo Jing , Lynch Ryan S. , Madison Dustin R. , Maraccini Kaleb , McLaughlin Maura A. , Mingarelli Chiara M. F. , Ng Cherry , Nguyen Benjamin M. X. , Nice David J. , Pennucci Timothy T. , Pol Nihan S. , Ramette Joshua , Ransom Scott M. , Ray Paul S. , Shapiro-Albert Brent J. , Siemens Xavier , Simon Joseph , Spiewak Renée , Stairs Ingrid H. , Stinebring Daniel R. , Stovall Kevin , Swiggum Joseph K. , Taylor Stephen R. , Tripepi Michael , Vallisneri Michele , Vigeland Sarah J. , Witt Caitlin A. , Zhu Weiwei ,   (The NANOGrav Collaboration)
Published: December 2020

Abstract
We present a new analysis of the profile data from the 47 millisecond pulsars comprising the 12.5 yr data set of the North American Nanohertz Observatory for Gravitational Waves, which is presented in a parallel paper (Alam et al., hereafter NG12.5). Our reprocessing is performed using “wideband” timing methods, which use frequency-dependent template profiles, simultaneous time-of-arrival (TOA) and dispersion measure (DM) measurements from broadband observations, and novel analysis techniques. In particular, the wideband DM measurements are used to constrain the DM portion of the timing model. We compare the ensemble timing results to those in NG12.5 by examining the timing residuals, timing models, and noise-model components. There is a remarkable level of agreement across all metrics considered. Our best-timed pulsars produce encouragingly similar results to those from NG12.5. In certain cases, such as high-DM pulsars with profile broadening or sources that are weak and scintillating, wideband timing techniques prove to be beneficial, leading to more precise timing model parameters by 10%–15%. The high-precision, multiband measurements of several pulsars indicate frequency-dependent DMs. Compared to the narrowband analysis in NG12.5, the TOA volume is reduced by a factor of 33, which may ultimately facilitate computational speed-ups for complex pulsar timing array analyses. This first wideband pulsar timing data set is a stepping stone, and its consistent results with NG12.5 assure us that such data sets are appropriate for gravitational wave analyses.
OH Evolution in Molecular Clouds
Authors: Tang Ningyu , Li Di , Yue Nannan , Zuo Pei , Liu Tie , Luo Gan , Chen Longfei , Qin Sheng-Li , Wu Yuefang , Heiles Carl 
Published: December 2020

Abstract
We have conducted a OH 18 cm survey toward 141 molecular clouds in various environments, including 33 optical dark clouds, 98 Planck Galactic cold clumps (PGCCs), and 10 Spitzer dark clouds with the Arecibo telescope. The deviations from local thermal equilibrium are common for intensity ratios of both OH main lines and satellite lines. Line intensity of OH 1667 MHz is found to correlate linearly with visual extinction

when

is less than 3 mag. It was converted into OH column density by adopting the excitation temperature derived from Monte Carlo simulations with 1σ uncertainty. The relationship between OH abundance X(OH) relative to H2 and

is found to follow an empirical formula,

Linear correlation is found between OH and 13CO intensity. Besides, nonthermal velocity dispersions of OH and 13CO are closely correlated. These results imply tight chemical evolution and spatial occupation between OH and 13CO. No obvious correlation is found between column density and nonthermal velocity dispersion of OH and H i narrow self-absorption (HINSA), indicating different chemical evolution and spatial volume occupation between OH and HINSA. Using the age information of HINSA analysis, OH abundance X(OH) is found to increase linearly with cloud age, which is consistent with previous simulations. Fourteen OH components without corresponding CO emission were detected, implying the effectiveness of OH in tracing the “CO-dark” molecular gas.
Bridging the Planet Radius Valley: Stellar Clustering as a Key Driver for Turning Sub-Neptunes into Super-Earths
Authors: Kruijssen J. M. Diederik , Longmore Steven N. , Chevance Mélanie 
Published: December 2020

Abstract
Extrasolar planets with sizes between that of the Earth and Neptune (R
p = 1–4 R⊕) have a bimodal radius distribution. This “planet radius valley” separates compact, rocky super-Earths (R
p = 1.0–1.8 R⊕) from larger sub-Neptunes (R
p = 1.8–3.5 R⊕) hosting a gaseous hydrogen–helium envelope around their rocky core. Various hypotheses for this radius valley have been put forward, which all rely on physics internal to the planetary system: photoevaporation by the host star, long-term mass loss driven by the cooling planetary core, or the transition between two fundamentally different planet formation modes as gas is lost from the protoplanetary disk. Here we report the discovery that the planet radius distribution exhibits a strong dependence on ambient stellar clustering, characterized by measuring the position–velocity phase space density with Gaia. When dividing the planet sample into “field” and “overdensity” subsamples, we find that planetary systems in the field exhibit a statistically significant (p = 5.5 × 10−3) dearth of planets below the radius valley compared to systems in phase space overdensities. This implies that the large-scale stellar environment of a planetary system is a key factor setting the planet radius distribution. We discuss how models for the radius valley might be revised following our findings and conclude that a multiscale, multiphysics scenario is needed, connecting planet formation and evolution, star and stellar cluster formation, and galaxy evolution.
The concept of vegetation class and order in phytosociological syntaxonomy
Authors: Loidi Javier 
Published: December 2020

In order to stabilize the defining concepts of the higher rank syntaxonomic units such as class or order, the criteria of floristic content and unity of origin are enunciated. This is done with the aim of preventing the fragmentation of the large classes and the subsequent typological inflation. For orders, the criterion of specific floristic content is discussed, with orders that have been described to encompass seral secondary forests or the separation of forest vegetation from that which is dominated by shrubs rejected, due to their weak floristic characterization. These criteria have been applied to two forest vegetation classes: the European temperate (Querco-Fagetea) and the Mediterranean (Quercetea ilicis). For the first, it is argued in favor of maintaining a single class for all temperate deciduous forests in Europe instead of dividing them into four. Within this single class five orders are distinguished: Fagetalia, Quercetalia roboris, Quercetalia pubescenti-petraeae, Alno-Fraxinetalia and Populetalia albae, rejecting the orders that have been proposed for secondary forests because they have few characteristic taxa. For the sclerophyllous and macchia forests of Mediterranean Europe, the Quercetea ilicis class can be split into two or three geographical orders, rejecting the Pistacio-Rhamnetalia alaterni as a shrubby physiognomic unit.
Taxonomic reference: Castroviejo S (coord. gen.) (1986–2012) Flora iberica 1–8, 10–15, 17–18, 21. Real Jardín Botánico, CSIC, Madrid, ES.
Syntaxonomic reference: Mucina et al. (2016).
Eastern European Steppe Database
Authors: Vynokurov Denys , Didukh Yakiv , Krasova Olga , Lysenko Hennadiy , Goncharenko Igor , Dmytrash-Vatseba Iryna , Chusova Olga , Shyriaieva Dariia , Kolomiychuk Vitalii , Moysiyenko Ivan 
Published: December 2020

The Eastern European Steppe Database (GIVD ID EU-00-030) includes 6961 vegetation plots of dry grassland vegetation from Eastern Europe (Steppe and Forest-Steppe zones, mountain regions), mainly from Ukraine (4579 relevés), Russia (2403 relevés) and Moldova (203 relevés). 3912 vegetation plots are from different literature sources (66 sources), 219 are from the phytosociological card-index of the M.G. Kholodny Institute of Botany, NAS of Ukraine, 2830 relevés are authors’ relevés. They were established in 1935-2019 years. The database comprises mainly the vegetation of the class Festuco-Brometea (around 95% of the dataset), and a small proportion of Koelerio-Corynephoretea canescentis, Artemisietea vulgaris, Crataego-Prunetea. The taxonomy of vascular species is given according to Cherepanov (1995) for vascular plants, Ignatov and Afonina (1992) for bryophytes and identification guides of the USSR (1971–1978) and Russia (1996, 1998) for lichens. The database is part of the European Vegetation Archive.