bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low-energy Measurement of the 96Zr(α,n)99Mo Reaction Cross Section and Its Impact on Weak r-process Nucleosynthesis
Authors: Kiss G. G. , Szegedi T. N. , Mohr P. , Jacobi M. , Gyürky Gy. , Huszánk R. , Arcones A. 
Published: February 2021

Abstract
Lighter heavy elements beyond iron and up to around silver can form in neutrino-driven ejecta in core-collapse supernovae and neutron star mergers. Slightly neutron-rich conditions favor a weak r-process that follows a path close to stability. Therefore, the beta decays are slow compared to the expansion timescales, and (α,n) reactions become critical to move matter toward heavier nuclei. The rates of these reactions are calculated with the statistical model and their main uncertainty, at energies relevant for the weak r-process, is the α+nucleus optical potential. There are several sets of parameters to calculate the α+nucleus optical potential leading to large deviations for the reaction rates, exceeding even one order of magnitude. Recently the 96Zr(α,n)99Mo reaction has been identified as a key reaction that impacts the production of elements from Ru to Cd. Here, we present the first cross section measurement of this reaction at energies (6.22 MeV ≤ Ec.m. ≤ 12.47 MeV) relevant for the weak r-process. The new data provide a stringent test of various model predictions which is necessary to improve the precision of the weak r-process network calculations. The strongly reduced reaction rate uncertainty leads to very well-constrained nucleosynthesis yields for Z = 44–48 isotopes under different neutrino-driven wind conditions.
Small-scale Bright Blobs Ejected from a Sunspot Light Bridge
Authors: Li Fuyu , Chen Yajie , Hou Yijun , Tian Hui , Bai Xianyong , Song Yongliang 
Published: February 2021

Abstract
Light bridges (LBs) are bright lanes that divide an umbra into multiple parts in some sunspots. Persistent oscillatory bright fronts at a temperature of ∼105 K are commonly observed above LBs in the 1400/1330 Å passbands of the Interface Region Imaging Spectrograph (IRIS). Based on IRIS observations, we report small-scale bright blobs ejected from the oscillating bright front above a light bridge. Some of these blobs reveal a clear acceleration, whereas the others do not. The average speed of these blobs projected onto the plane of sky is 71.7 ± 14.7 km s−1, with an initial acceleration of 1.9 ± 1.3 km s−2. These blobs normally reach a projected distance of 3–7 Mm from their origin sites. They have an average projected area of 0.57 ± 0.37 Mm2. The blobs were also detected in multiple extreme-ultraviolet passbands of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, but not in the Hα images taken by the New Vacuum Solar Telescope. The typical temperature and electron density of these blobs are around

K and

cm−3, respectively. The estimated kinetic and thermal energies are on the order of

erg and

erg, respectively. These small-scale blobs appear to show three different types of formation processes. They are possibly triggered by induced reconnection or release of enhanced magnetic tension due to interaction of adjacent shocks, local magnetic reconnection between emerging magnetic bipoles on the light bridge and surrounding unipolar umbral fields, and plasma acceleration or instability caused by upward shocks, respectively.
Years-delayed X-Ray Afterglows of TDEs Originated from Wind–Torus Interactions
Authors: Mou Guobin , Dou Liming , Jiang Ning , Wang Tinggui , Guo Fulai , Wang Wei , Wang Hu , Shu Xinwen , He Zhicheng , Zhang Ruiyu , Sun Luming 
Published: February 2021

Abstract
Tidal disruption events (TDEs) occurring in active galactic nuclei (AGNs) are a special class of sources with outstanding scientific significance. TDEs can generate ultrafast winds, which should almost inevitably collide with the preexisting AGN dusty tori. We perform analytical calculations and simulations on the wind–torus interactions and find such a process can generate considerable X-ray afterglow radiation several years or decades later after the TDE outburst. This provides a new origin for the years delayed X-rays in TDEs. The X-ray luminosity can reach 1041−42 erg s−1, and the light curve characteristics depend on the parameters of winds and tori. We apply the model to two TDE candidates, and provide lower limits on the masses of the disrupted stars, as well as rigorous constraints on the gas densities of tori. Our results suggest that the observations of the time delay, spectral shape, luminosity, and the light curve of the X-ray afterglow can be used to constrain the physical parameters of both TDE winds and tori, including the wind velocity, wind density, cloud density, and cloud size.
Peeking Between the Pulses: The Far-UV Spectrum of the Previously Unseen White Dwarf in AR Scorpii
Authors: Garnavich Peter , Littlefield Colin , Lyutikov Maxim , Barkov Maxim 
Published: February 2021

Abstract
The compact object in the interacting binary AR Sco has widely been presumed to be a rapidly rotating, magnetized white dwarf (WD), but it has never been detected directly. Isolating its spectrum has proven difficult because the spin-down of the WD generates pulsed synchrotron radiation that far outshines the WD’s photosphere. As a result, a previous study of AR Sco was unable to detect the WD in the averaged far-ultraviolet spectrum from a Hubble Space Telescope (HST) observation. In an effort to unveil the WD’s spectrum, we reanalyze these HST observations by calculating the average spectrum in the troughs between synchrotron pulses. We identify weak spectral features from the previously unseen WD and estimate its surface temperature to be 11,500 ± 500 K. Additionally, during the synchrotron pulses, we detect broad Lyα absorption consistent with hot WD spectral models. We infer the presence of a pair of hotspots, with temperatures between 23,000 and 28,000 K, near the magnetic poles of the WD. As the WD is not expected to be accreting from its companion, we describe two possible mechanisms for heating the magnetic poles. The Lyα absorption of the hotspots appears relatively undistorted by Zeeman splitting, constraining the WD’s field strength to be ≲100 MG, but the data are insufficient to search for the subtle Zeeman splits expected at lower field strengths.
Mass-gap Mergers in Active Galactic Nuclei
Authors: Tagawa Hiromichi , Kocsis Bence , Haiman Zoltán , Bartos Imre , Omukai Kazuyuki , Samsing Johan 
Published: February 2021

Abstract
The recently discovered gravitational wave sources GW190521 and GW190814 have shown evidence of BH mergers with masses and spins outside of the range expected from isolated stellar evolution. These merging objects could have undergone previous mergers. Such hierarchical mergers are predicted to be frequent in active galactic nuclei (AGNs) disks, where binaries form and evolve efficiently by dynamical interactions and gaseous dissipation. Here we compare the properties of these observed events to the theoretical models of mergers in AGN disks, which are obtained by performing one-dimensional N-body simulations combined with semi-analytical prescriptions. The high BH masses in GW190521 are consistent with mergers of high-generation (high-g) BHs where the initial progenitor stars had high metallicity, 2g BHs if the original progenitors were metal-poor, or 1g BHs that had gained mass via super-Eddington accretion. Other measured properties related to spin parameters in GW190521 are also consistent with mergers in AGN disks. Furthermore, mergers in the lower mass gap or those with low mass ratio as found in GW190814 and GW190412 are also reproduced by mergers of 2g–1g or 1g–1g objects with significant accretion in AGN disks. Finally, due to gas accretion, the massive neutron star merger reported in GW190425 can be produced in an AGN disk.
White Dwarf Photospheric Abundances in Cataclysmic Variables. I. SS Aurigae and TU Mensae*
Authors: Godon Patrick , Sion Edward M. 
Published: February 2021

Abstract
Chemical abundance studies of cataclysmic variables have revealed high nitrogen to carbon ratios in a number of cataclysmic variable white dwarfs (based on ultraviolet emission and absorption lines), as well as possible carbon deficiency in many secondaries (based on the absence of infrared CO absorption lines). These indicate that the accreted material on the white dwarf surface and the donor itself might be contaminated with CNO processed material. To further understand the origin of this abundance anomaly, there is a need for further chemical abundance study. In the present work, we carry out a far-ultraviolet spectral analysis of the extreme SU UMa dwarf nova TU Men and the U Gem dwarf nova SS Aur using archival spectra. We derive the mass and temperature of the WD using the recently available DR2 Gaia parallaxes. The analysis of HST STIS spectra yields a WD mass

with a temperature of 27,750 ± 1000 K for TU Men and a WD mass M
wd ∼ 0.80 ± 0.15 M
⊙ with a temperature of ∼30,000 ± 1000 K for SS Aur. However, the analysis of a FUSE spectrum for SS Aur gives a higher temperature of ∼33,375 ± 1875 K, yielding a higher WD mass of ∼1 ± 0.25 M
⊙, which could be due to the effect of a second hot emitting component present in the short wavelengths of FUSE. Most importantly, based on the white dwarf far-ultraviolet absorption lines, we find that both systems have subsolar carbon and silicon abundances. For TU Men, we also find suprasolar nitrogen abundance, evidence of CNO processing.
Ensuring Robustness in Training-set-based Global 21 cm Cosmology Analysis
Authors: Bassett Neil , Rapetti David , Tauscher Keith , Burns Jack O. , Hibbard Joshua J. 
Published: February 2021

Abstract
We present a methodology for ensuring the robustness of our analysis pipeline in separating the global 21 cm hydrogen cosmology signal from large systematics based on singular value decomposition (SVD) of training sets. We show how traditional goodness-of-fit metrics such as the χ
2 statistic that assess the fit to the full data may not be able to detect a suboptimal extraction of the 21 cm signal when it is fit alongside one or more additional components owing to significant covariance between them. However, we find that comparing the number of SVD eigenmodes for each component chosen by the pipeline for a given fit to the distribution of eigenmodes chosen for synthetic data realizations created from training set curves can detect when one or more of the training sets is insufficient to optimally extract the signal. Furthermore, this test can distinguish which training set (e.g., foreground, 21 cm signal) needs to be modified in order to better describe the data and improve the quality of the 21 cm signal extraction. We also extend this goodness-of-fit testing to cases where a prior distribution derived from the training sets is applied and find that, in this case, the χ
2 statistic and the recently introduced ψ
2 statistic are able to detect inadequacies in the training sets due to the increased restrictions imposed by the prior. Crucially, the tests described in this paper can be performed when analyzing any type of observations with our pipeline.
The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs
Authors: Kirkpatrick J. Davy , Gelino Christopher R. , Faherty Jacqueline K. , Meisner Aaron M. , Caselden Dan , Schneider Adam C. , Marocco Federico , Cayago Alfred J. , Smart R. L. , Eisenhardt Peter R. , Kuchner Marc J. , Wright Edward L. , Cushing Michael C. , Allers Katelyn N. , Bardalez Gagliuffi Daniella C. , Burgasser Adam J. , Gagné Jonathan , Logsdon Sarah E. , Martin Emily C. , Ingalls James G. , Lowrance Patrick J. , Abrahams Ellianna S. , Aganze Christian , Gerasimov Roman , Gonzales Eileen C. , Hsu Chih-Chun , Kamraj Nikita , Kiman Rocio , Rees Jon , Theissen Christopher , Ammar Kareem , Andersen Nikolaj Stevnbak , Beaulieu Paul , Colin Guillaume , Elachi Charles A. , Goodman Samuel J. , Gramaize Léopold , Hamlet Leslie K. , Hong Justin , Jonkeren Alexander , Khalil Mohammed , Martin David W. , Pendrill William , Pumphrey Benjamin , Rothermich Austin , Sainio Arttu , Stenner Andres , Tanner Christopher , Thévenot Melina , Voloshin Nikita V. , Walla Jim , Wędracki Zbigniew ,   The Backyard Worlds: Planet 9 Collaboration
Published: February 2021

Abstract
We present final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs. We combine these with prior studies to build a list of 525 known L, T, and Y dwarfs within 20 pc of the Sun, 38 of which are presented here for the first time. Using published photometry and spectroscopy as well as our own follow-up, we present an array of color–magnitude and color–color diagrams to further characterize census members, and we provide polynomial fits to the bulk trends. Using these characterizations, we assign each object a T
eff value and judge sample completeness over bins of T
eff and spectral type. Except for types ≥T8 and T
eff < 600 K, our census is statistically complete to the 20 pc limit. We compare our measured space densities to simulated density distributions and find that the best fit is a power law (

) with α = 0.6 ± 0.1. We find that the evolutionary models of Saumon & Marley correctly predict the observed magnitude of the space density spike seen at 1200 K < T
eff < 1350 K, believed to be caused by an increase in the cooling timescale across the L/T transition. Defining the low-mass terminus using this sample requires a more statistically robust and complete sample of dwarfs ≥Y0.5 and with T
eff < 400 K. We conclude that such frigid objects must exist in substantial numbers, despite the fact that few have so far been identified, and we discuss possible reasons why they have largely eluded detection.
Numerical Research on the Effect of the Initial Parameters of a CME Flux-rope Model on Simulation Results
Authors: Shen Fang , Liu Yousheng , Yang Yi 
Published: February 2021

Abstract
Coronal mass ejections (CMEs) are the major drivers of space weather, and an accurate modeling of their initialization and propagation up to 1 au and beyond is an important issue for space weather research and forecasts. In this research, we use the newly developed three-dimensional (3D) flux-rope CME initialization model and 3D IN (interplanetary)-TVD MHD model to study the effect of different CME initial parameters on simulation outputs. The initial CME flux model is established based on the graduated cylindrical shell model. In order to test the influence of the CME initial parameters on the simulation results, we try to run several simulations with different CME initial parameters, then investigate the outputs in interplanetary space. Here, we focus only on cases in which observers are located in the same initial direction of propagation of the CME. Our analysis shows that the parameters specifying the CME initialization in the model, including the initial density, the thickness of CME flux tube, initial mass, and initial magnetic field, have different effects on the simulation results for observers near the Earth and Mars, and on the process of propagation of the CME in interplanetary space. This confirms the important role played by details of the initial implementation of geometric and physical parameters on space weather research and forecasts.
TESS Observations of Cepheid Stars: First Light Results
Authors: Plachy E. , Pál A. , Bódi A. , Szabó P. , Molnár L. , Szabados L. , Benkő J. M. , Anderson R. I. , Bellinger E. P. , Bhardwaj A. , Ebadi M. , Gazeas K. , Hambsch F.-J. , Hasanzadeh A. , Jurkovic M. I. , Kalaee M. J. , Kervella P. , Kolenberg K. , Mikołajczyk P. , Nardetto N. , Nemec J. M. , Netzel H. , Ngeow C.-C. , Ozuyar D. , Pascual-Granado J. , Pilecki B. , Ripepi V. , Skarka M. , Smolec R. , Sódor Á. , Szabó R. , Christensen-Dalsgaard J. , Jenkins J. M. , Kjeldsen H. , Ricker G. R. , Vanderspek R. 
Published: February 2021

Abstract
We present the first analysis of Cepheid stars observed by the TESS space mission in Sectors 1–5. Our sample consists of 25 pulsators: ten fundamental mode, three overtone and two double-mode classical Cepheids, plus three type II and seven anomalous Cepheids. The targets were chosen from fields with different stellar densities, both from the Galactic field and from the Magellanic System. Three targets have 2 minutes cadence light curves available by the TESS Science Processing Operations Center: for the rest, we prepared custom light curves from the full-frame images with our own differential photometric FITSH pipeline. Our main goal was to explore the potential and the limitations of TESS concerning the various subtypes of Cepheids. We detected many low-amplitude features: weak modulation, period jitter, and timing variations due to light-time effect. We also report signs of nonradial modes and the first discovery of such a mode in an anomalous Cepheid, the overtone star XZ Cet, which we then confirmed with ground-based multicolor photometric measurements. We prepared a custom photometric solution to minimize saturation effects in the bright fundamental-mode classical Cepheid, β Dor with the lightkurve software, and we revealed strong evidence of cycle-to-cycle variations in the star. In several cases, however, fluctuations in the pulsation could not be distinguished from instrumental effects, such as contamination from nearby sources, which also varies between sectors. Finally, we discuss how precise light-curve shapes will be crucial not only for classification purposes but also to determine physical properties of these stars.
An open-source, citizen science and machine learning approach to analyse subsea movies
Authors: Anton Victor , Germishuys Jannes , Bergström Per , Lindegarth Mats , Obst Matthias 
Published: February 2021

The increasing access to autonomously-operated technologies offer vast opportunities to sample large volumes of biological data. However, these technologies also impose novel demands on ecologists who need to apply tools for data management and processing that are efficient, publicly available and easy to use. Such tools are starting to be developed for a wider community and here we present an approach to combine essential analytical functions for analysing large volumes of image data in marine ecological research.
This paper describes the Koster Seafloor Observatory, an open-source approach to analysing large amounts of subsea movie data for marine ecological research. The approach incorporates three distinct modules to: manage and archive the subsea movies, involve citizen scientists to accurately classify the footage and, finally, train and test machine learning algorithms for detection of biological objects. This modular approach is based on open-source code and allows researchers to customise and further develop the presented functionalities to various types of data and questions related to analysis of marine imagery. We tested our approach for monitoring cold water corals in a Marine Protected Area in Sweden using videos from remotely-operated vehicles (ROVs). Our study resulted in a machine learning model with an adequate performance, which was entirely trained with classifications provided by citizen scientists. We illustrate the application of machine learning models for automated inventories and monitoring of cold water corals. Our approach shows how citizen science can be used to effectively extract occurrence and abundance data for key ecological species and habitats from underwater footage. We conclude that the combination of open-source tools, citizen science systems, machine learning and high performance computational resources are key to successfully analyse large amounts of underwater imagery in the future.
Changement de nom de l’organisation et identification organisationnelle. Exploration dans une entreprise tunisienne de télécommunications
Authors: Gharsi-Missaoui Manel , Zaddem Ferid 
Published: February 2021

Bien que les recherches sur le changement du nom de marque 1 de l’organisation soient du ressort du marketing, ce bouleversement affecte également l’organisation en interne. Dans ce travail, nous étudions les effets de ce changement sur l’identification organisationnelle. Notre ambition est de comprendre comment l’identification à l’organisation peut être affectée par le changement de son nom qui est « l’expression la plus simple de l’identité » (Giget, 1989 : 25). Pour répondre à cet objectif, nous avons mené une étude de cas exploratoire dans une entreprise tunisienne de télécommunications. Les résultats de notre recherche montrent que le degré d’identification organisationnelle suite à un tel changement est ambivalent. Ainsi, une diversité d’attitudes et de facteurs liés au changement de nom semblent conduire à une ambivalence du sentiment d’identification à l’entreprise.
Impact of Delayed Time to Treatment on Visual Outcomes in Neovascular AMD: Data From the HARBOR Study
Authors: Goldberg Roger A. , Hill Lauren F. , Davis Tatiana , Ruiz Carlos Quezada 
Published: February 2021

BACKGROUND AND OBJECTIVE:
To determine the potential impact on visual outcomes of delayed treatment initiation in patients with neovascular age-related macular degeneration (nAMD).

PATIENTS AND METHODS:
Post hoc analysis of anti-vascular endothelial growth factor treatment-naïve patients with nAMD from HARBOR. Time to treatment was defined as first ranibizumab injection date minus screening date. Comparisons were made between the prompt (≤ 6 days) versus delayed (> 10 days) treatment groups. Main outcome measures were best-corrected visual acuity (BCVA) change over time, BCVA, number of ranibizumab injections, and proportion of 3-line gainers/losers.

RESULTS:
In HARBOR, more than 50% of patients received their first injection within 7 days of screening, with mean (median) time to treatment of 4.6 (5) and 15.9 (14) days for the prompt and delayed treatment groups, respectively. Mean (95% confidence interval [CI]) BCVA change from baseline to Month 24 was 9.1 (7.4–10.8) and 8.8 (6.7–10.8) Early Treatment Diabetic Retinopathy Study letters in the prompt (n = 395) and delayed (n = 230) treatment groups, respectively. Mean (95% CI) total number of ranibizumab injections for the as-needed arms was 12.4 (11.6–13.3) and 11.4 (10.3–12.4) for the prompt and delayed treatment groups, respectively.

CONCLUSION:
In HARBOR, time from screening to first ranibizumab injection did not seem to significantly affect mean BCVA change or number of injections.

[
Ophthalmic Surg Lasers Imaging Retina
. 2021;52:62–69.]