bluuebunny/crossref_metadata_2025_split huggingface dataset:
NGTS and HST insights into the long-period modulation in GW Librae
Authors: Chote P , Gänsicke B T , McCormac J , Aungwerojwit A , Bayliss D , Burleigh M R , Casewell S L , Eigmüller Ph , Gill S , Goad M R , Hermes J J , Jenkins J S , Mukadam A S , Poshyachinda S , Raynard L , Reichart D E , Szkody P , Toloza O , West R G , Wheatley P J 
Published: January 2021

ABSTRACT
Light curves of the accreting white dwarf pulsator GW Librae spanning a 7.5-month period in 2017 were obtained as part of the Next-Generation Transit Survey. This data set comprises 787 h of photometry from 148 clear nights, allowing the behaviour of the long (hours) and short-period (20 min) modulation signals to be tracked from night to night over a much longer observing baseline than has been previously achieved. The long-period modulations intermittently detected in previous observations of GW Lib are found to be a persistent feature, evolving between states with periods ≃ 83 min and 2–4 h on time-scales of several days. The 20 min signal is found to have a broadly stable amplitude and frequency for the duration of the campaign, but the previously noted phase instability is confirmed. Ultraviolet observations obtained with the Cosmic Origin Spectrograph on-board the Hubble Space Telescope constrain the ultraviolet-to-optical flux ratio to ≃5 for the 4 h modulation, and ≲1 for the 20 min period, with caveats introduced by non-simultaneous observations. These results add further observational evidence that these enigmatic signals must originate from the white dwarf, highlighting our continued gap in theoretical understanding of the mechanisms that drive them.
MusE GAs FLOw and Wind V. The dust/metallicity-anisotropy of the circum-galactic medium
Authors: Wendt Martin , Bouché Nicolas F , Zabl Johannes , Schroetter Ilane , Muzahid Sowgat 
Published: January 2021

ABSTRACT
We investigate whether the dust content of the circum-galactic medium (CGM) depends on the location of the quasar sightline with respect to the galaxy major-axis using 13 galaxy-Mg ii absorber pairs (9–81 kpc distance) from the MusE GAs FLOw and Wind (MEGAFLOW) survey at 0.4 &lt; z &lt; 1.4. The dust content of the CGM is obtained from [Zn/Fe] using ultraviolet and visual echelle spectrograph data. When a direct measurement of [Zn/Fe] is unavailable, we estimate the dust depletion from a method that consists in solving for the depletion from multiple singly ionized ions (e.g. Mn ii, Cr ii, and Zn ii) since each ion depletes on dust grains at different rates. We find a positive correlation between the azimuthal angle and [Zn/Fe] with a Pearson’s r = 0.70 ± 0.14. The sightlines along the major axis show [Zn/Fe] &lt; 0.5, whereas the [Zn/Fe] is &gt; 0.8 along the minor axis. These results suggest that the CGM along the minor axis is on average more metal enriched (by ≈ 1 dex) than the gas located along the major axis of galaxies provided that dust depletion is a proxy for metallicity. This anisotropic distribution is consistent with recent results on outflow and accretion in hydro-dynamical simulations.
frost: a momentum-conserving CUDA implementation of a hierarchical fourth-order forward symplectic integrator
Authors: Rantala Antti , Naab Thorsten , Springel Volker 
Published: January 2021

ABSTRACTWe present a novel hierarchical formulation of the fourth-order forward symplectic integrator and its numerical implementation in the GPU-accelerated direct-summation N-body code frost. The new integrator is especially suitable for simulations with a large dynamical range due to its hierarchical nature. The strictly positive integrator sub-steps in a fourth-order symplectic integrator are made possible by computing an additional gradient term in addition to the Newtonian accelerations. All force calculations and kick operations are synchronous so the integration algorithm is manifestly momentum-conserving. We also employ a time-step symmetrization procedure to approximately restore the time-reversibility with adaptive individual time-steps. We demonstrate in a series of binary, few-body and million-body simulations that frost conserves energy to a level of |ΔE/E| ∼ 10−10 while errors in linear and angular momentum are practically negligible. For typical star cluster simulations, we find that frost scales well up to $N_\mathrm{GPU}^\mathrm{max}\sim 4\times N/10^5$ GPUs, making direct-summation N-body simulations beyond N = 106 particles possible on systems with several hundred and more GPUs. Due to the nature of hierarchical integration, the inclusion of a Kepler solver or a regularized integrator with post-Newtonian corrections for close encounters and binaries in the code is straightforward.
Detection of supernova remnants in NGC 4030
Authors: Cid Fernandes R , Carvalho M S , Sánchez S F , de Amorim A , Ruschel-Dutra D 
Published: January 2021

ABSTRACT
MUSE-based emission-line maps of the spiral galaxy NGC 4030 reveal the existence of unresolved sources with forbidden line emission enhanced with respect to those seen in its own H ii regions. This study reports our efforts to detect and isolate these objects and identify their nature. Candidates are first detected as unresolved sources on an image of the second principal component of the H β, [O iii] 5007, H α, [N ii] 6584, [S ii] 6716, 6731 emission-line data cube, where they stand out clearly against both the dominant H ii region population and the widespread diffuse emission. The intrinsic emission is then extracted accounting for the highly inhomogeneous emission-line ‘background’ throughout the field of view. Collisional to recombination line ratios like [S ii]/H α, [N ii]/H α, and [O i]/H α tend to increase when the background emission is corrected for. We find that many (but not all) sources detected with the principal component analysis have properties compatible with supernova remnants (SNRs). Applying a combined [S ii]/H α and [N ii]/H α classification criterion leads to a list of 59 sources with SNR-like emission lines. Many of them exhibit conspicuous spectral signatures of SNRs around 7300 Å, and a stacking analysis shows that these features are also present, except weaker, in other cases. At nearly 30 Mpc, these are the most distant SNRs detected by optical means to date. We further report the serendipitous discovery of a luminous (MV ∼ −12.5), blue, and variable source, possibly associated with a supernova impostor.
Two years of pulsar observations with the ultra-wide-band receiver on the Parkes radio telescope
Authors: Johnston Simon , Sobey C , Dai S , Keith M , Kerr M , Manchester R N , Oswald L S , Parthasarathy A , Shannon R M , Weltevrede P 
Published: January 2021

ABSTRACT
The major programme for observing young, non-recycled pulsars with the Parkes telescope has transitioned from a narrow-band system to an ultra-wide-band system capable of observing between 704 and 4032 MHz. We report here on the initial 2 yr of observations with this receiver. Results include dispersion measure (DM) and Faraday rotation measure (RM) variability with time, determined with higher precision than hitherto, flux density measurements and the discovery of several nulling and mode changing pulsars. PSR J1703−4851 is shown to be one of a small subclass of pulsars that has a weak and a strong mode which alternate rapidly in time. PSR J1114−6100 has the fourth highest |RM| of any known pulsar despite its location far from the Galactic Centre. PSR J1825−1446 shows variations in both DM and RM likely due to its motion behind a foreground supernova remnant.
Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: global and equatorial dynamics
Authors: Tan Xianyu , Showman Adam P 
Published: January 2021

ABSTRACT
Brown dwarfs, planetary-mass objects and directly imaged giant planets exhibit significant observational evidence for active atmospheric circulation, raising critical questions about mechanisms driving the circulation, its fundamental nature and time variability. Our previous work has demonstrated the crucial role of cloud radiative feedback on driving a vigorous atmospheric circulation using local models that assume a Cartesian geometry and constant Coriolis parameters. In this study, we extend the models to a global geometry and explore properties of the global dynamics. We show that, under relatively strong dissipation in the bottom layers of the model, horizontally isotropic vortices are prevalent at mid-to-high latitudes while large-scale zonally propagating waves are dominant at low latitudes near the observable layers. The equatorial waves have both eastward and westward phase speeds, and the eastward components with typical velocities of a few hundred  m s−1 usually dominate the equatorial time variability. Lightcurves of the global simulations show variability with amplitudes from 0.5 per cent to a few percent depending on the rotation period and viewing angle. The time evolution of simulated lightcurves is critically affected by the equatorial waves, showing wave beating effects and differences in the lightcurve periodicity to the intrinsic rotation period. The vertical extent of clouds is the largest at the equator and decreases poleward due to the increasing influence of rotation with increasing latitude. Under weaker dissipation in the bottom layers, strong and broad zonal jets develop and modify wave propagation and lightcurve variability. Our modelling results help to qualitatively explain several features of observations of brown dwarfs and directly imaged giant planets, including puzzling time evolution of lightcurves, a slightly shorter period of variability in IR than in radio wavelengths, and the viewing angle dependence of variability amplitude and IR colors.
The ASAS-SN catalogue of variable stars IX: The spectroscopic properties of Galactic variable stars
Authors: Jayasinghe T , Kochanek C S , Stanek K Z , Shappee B J , Holoien T W-S , Thompson Todd A , Prieto J L , Dong Subo , Pawlak M , Pejcha O , Pojmanski G , Otero S , Hurst N , Will D 
Published: January 2021

ABSTRACT
The All-Sky Automated Survey for Supernovae provides long baseline (∼4 yr) V-band light curves for sources brighter than V≲ 17 mag across the whole sky. We produced V-band light curves for a total of ∼61.5 million sources and systematically searched these sources for variability. We identified ∼426 000 variables, including ∼219 000 new discoveries. Most (${\sim }74{ per\ cent}$) of our discoveries are in the Southern hemisphere. Here, we use spectroscopic information from LAMOST, GALAH, RAVE, and APOGEE to study the physical and chemical properties of these variables. We find that metal-poor eclipsing binaries have orbital periods that are shorter than metal-rich systems at fixed temperature. We identified rotational variables on the main-sequence, red giant branch, and the red clump. A substantial fraction (${\gtrsim }80{ per\ cent}$) of the rotating giants have large $v$rot or large near-ultraviolet excesses also indicative of fast rotation. The rotational variables have unusual abundances suggestive of analysis problems. Semiregular variables tend to be lower metallicity ($\rm [Fe/H]{\sim }-0.5$) than most giant stars. We find that the APOGEE DR16 temperatures of oxygen-rich semiregular variables are strongly correlated with the WRP − WJK colour index for $\rm T_{eff}\lesssim 3800$ K. Using abundance measurements from APOGEE DR16, we find evidence for Mg and N enrichment in the semiregular variables. We find that the Aluminum abundances of the semiregular variables are strongly correlated with the pulsation period, where the variables with $\rm P\gtrsim 60$ d are significantly depleted in Al.
Photodissociation region diagnostics across galactic environments
Authors: Bisbas Thomas G , Tan Jonathan C , Tanaka Kei E I 
Published: January 2021

ABSTRACT
We present three-dimensional astrochemical simulations and synthetic observations of magnetized, turbulent, self-gravitating molecular clouds. We explore various galactic interstellar medium environments, including cosmic ray ionization rates in the range of ζCR = 10−17–$10^{-14}\, {\rm s}^{-1}$, far-UV intensities in the range of G0 = 1–103 and metallicities in the range of Z = 0.1–$2\, {\rm Z}_{\odot }$. The simulations also probe a range of densities and levels of turbulence, including cases where the gas has undergone recent compression due to cloud–cloud collisions. We examine: (i) the column densities of carbon species across the cycle of C ii, C i, and CO, along with O i, in relation to the H i-to-H2 transition; (ii) the velocity-integrated emission of [C ii] 158 μm, [13C ii] 158 μm, [C i] 609 μm and 370 μm, [O i] 63 μm and 146 μm, and of the first ten 12CO rotational transitions; (iii) the corresponding Spectral Line Energy Distributions; (iv) the usage of [C ii] and [O i] 63 μm to describe the dynamical state of the clouds; (v) the behaviour of the most commonly used ratios between transitions of CO and [C i]; and (vi) the conversion factors for using CO and C i as H2-gas tracers. We find that enhanced cosmic ray energy densities enhance all aforementioned line intensities. At low metallicities, the emission of [C ii] is well connected with the H2 column, making it a promising new H2 tracer in metal-poor environments. The conversion factors of XCO and XC i depend on metallicity and the cosmic ray ionization rate, but not on FUV intensity. In the era of ALMA, SOFIA, and the forthcoming CCAT-prime telescope, our results can be used to understand better the behaviour of systems in a wide range of galactic and extragalactic environments.
The efficiency of grain growth in the diffuse interstellar medium
Authors: Priestley F D , De Looze I , Barlow M J 
Published: January 2021

ABSTRACT
Grain growth by accretion of gas-phase metals is a common assumption in models of dust evolution, but in dense gas, where the time-scale is short enough for accretion to be effective, material is accreted in the form of ice mantles rather than adding to the refractory grain mass. It has been suggested that negatively charged small grains in the diffuse interstellar medium (ISM) can accrete efficiently due to the Coulomb attraction of positively-charged ions, avoiding this issue. We show that this inevitably results in the growth of the small-grain radii until they become positively charged, at which point further growth is effectively halted. The resulting gas-phase depletions under diffuse ISM conditions are significantly overestimated when a constant grain size distribution is assumed. While observed depletions can be reproduced by changing the initial size distribution or assuming highly efficient grain shattering, both options result in unrealistic levels of far-ultraviolet extinction. We suggest that the observed elemental depletions in the diffuse ISM are better explained by higher initial depletions, combined with inefficient dust destruction by supernovae at moderate ($n_{\rm H}\sim 30 \, {\rm cm}^{-3}$) densities, rather than by higher accretion efficiences.
The ATR-WEE1 kinase module inhibits the MAC complex to regulate replication stress response
Authors: Wang Lili , Zhan Li , Zhao Yan , Huang Yongchi , Wu Chong , Pan Ting , Qin Qi , Xu Yiren , Deng Zhiping , Li Jing , Hu Honghong , Xue Shaowu , Yan Shunping 
Published: January 2021

AbstractDNA damage response is a fundamental mechanism to maintain genome stability. The ATR-WEE1 kinase module plays a central role in response to replication stress. Although the ATR-WEE1 pathway has been well studied in yeasts and animals, how ATR-WEE1 functions in plants remains unclear. Through a genetic screen for suppressors of the Arabidopsis atr mutant, we found that loss of function of PRL1, a core subunit of the evolutionarily conserved MAC complex involved in alternative splicing, suppresses the hypersensitivity of atr and wee1 to replication stress. Biochemical studies revealed that WEE1 directly interacts with and phosphorylates PRL1 at Serine 145, which promotes PRL1 ubiquitination and subsequent degradation. In line with the genetic and biochemical data, replication stress induces intron retention of cell cycle genes including CYCD1;1 and CYCD3;1, which is abolished in wee1 but restored in wee1 prl1. Remarkably, co-expressing the coding sequences of CYCD1;1 and CYCD3;1 partially restores the root length and HU response in wee1 prl1. These data suggested that the ATR-WEE1 module inhibits the MAC complex to regulate replication stress responses. Our study discovered PRL1 or the MAC complex as a key downstream regulator of the ATR-WEE1 module and revealed a novel cell cycle control mechanism.
Polymer modelling unveils the roles of heterochromatin and nucleolar organizing regions in shaping 3D genome organization inArabidopsis thaliana
Authors: Di Stefano Marco , Nützmann Hans-Wilhelm , Marti-Renom Marc A , Jost Daniel 
Published: January 2021

AbstractThe 3D genome is characterized by a complex organization made of genomic and epigenomic layers with profound implications on gene regulation and cell function. However, the understanding of the fundamental mechanisms driving the crosstalk between nuclear architecture and (epi)genomic information is still lacking. The plant Arabidopsis thaliana is a powerful model organism to address these questions owing to its compact genome for which we have a rich collection of microscopy, chromosome conformation capture (Hi-C) and ChIP-seq experiments. Using polymer modelling, we investigate the roles of nucleolus formation and epigenomics-driven interactions in shaping the 3D genome of A. thaliana. By validation of several predictions with published data, we demonstrate that self-attracting nucleolar organizing regions and repulsive constitutive heterochromatin are major mechanisms to regulate the organization of chromosomes. Simulations also suggest that interphase chromosomes maintain a partial structural memory of the V-shapes, typical of (sub)metacentric chromosomes in anaphase. Additionally, self-attraction between facultative heterochromatin regions facilitates the formation of Polycomb bodies hosting H3K27me3-enriched gene-clusters. Since nucleolus and heterochromatin are highly-conserved in eukaryotic cells, our findings pave the way for a comprehensive characterization of the generic principles that are likely to shape and regulate the 3D genome in many species.
The search for charmed states of matter
Authors: Ball Philip 
Published: January 2021

Abstract
With the discovery of the Higgs boson in 2012, the Standard Model of particle physics was completed. This description encompasses all known subatomic particles and their interactions. Much of the public interest in high-energy physics now focuses on experimental searches for ‘new physics’ beyond the Standard Model. Yet it would be a mistake to imagine that the Standard Model is now fully understood. Many questions remain about the ways in which known fundamental particles interact and unite, especially at the very high energies needed to produce the most exotic varieties, such as heavy quarks (quarks are the constituents of hadrons, which include the ordinary nuclear particles protons and neutrons) and heavy leptons (leptons are members of the family that includes electrons).
The Beijing Electron-Positron Collider (BEPC), operated by the Chinese Academy of Sciences' Institute of High Energy Physics, is one of the installations that are probing these questions. It has been running since 1988, using a detector called the Beijing Spectrometer (BES). (The site also houses the Beijing Synchrotron Radiation Facility for conducting studies in condensed matter using intense X-rays.) Since 2008, these two instruments have been operating in upgraded form: the BESIII detector and BEPCII accelerator. The facility is now one of the key international centers for investigating the properties and behavior of new exotic hadrons, in particular those that include the charm quark. Italian physicist Luciano Maiani, Director of the European particle physics center CERN in Switzerland from 1999 to 2003, is one of the world leaders in this area of high-energy physics, and played a central role in the identification of the charm quark itself. NSR spoke to him about the aims of the latest work at the BEPCII, and the prospects for new discoveries.
Heart rate: control mechanisms, pathophysiology and assessment of the neurocardiac system in health and disease
Authors: Armstrong R , Wheen P , Brandon L , Maree A , Kenny R -A 
Published: January 2021

Abstract
The monitoring of physiological function and dysfunction is an important principle in modern medicine. Heart rate is a basic example of this type of observation, particularly assessing the neurocardiac system, which entails the autonomic nervous system and intracardiac processes. The neurocardiac axis is an underappreciated and often overlooked system which, if measured appropriately in the clinical setting, may allow identification of patients at risk of disease progression and even mortality. While heart rate itself is a simplistic tool, more information may be gathered through assessing heart rate variability and heart rate recovery time. Studies have demonstrated an association of slow heart rate recovery and lower heart rate variability as markers of elevated sympathetic and lower parasympathetic tone. These parameters have additionally been shown to relate to development of arrhythmia, heart failure, systemic inflammatory processes, ischaemic heart disease and an increased rate of mortality. The aim of this review is to detail how heart rate is homeostatically controlled by the autonomic nervous system, how heart rate can impact on pathophysiological processes, and how heart rate variability and heart rate recovery time may be used in the clinical setting to allow the neurocardiac system to be assessed.