bluuebunny/crossref_metadata_2025_split huggingface dataset:
APOGEE Data Releases 13 and 14: Stellar Parameter and Abundance Comparisons with Independent Analyses
Authors: Jönsson Henrik , Prieto Carlos Allende , Holtzman Jon A. , Feuillet Diane K. , Hawkins Keith , Cunha Katia , Mészáros Szabolcs , Hasselquist Sten , Fernández-Trincado J. G. , García-Hernández D. A. , Bizyaev Dmitry , Carrera Ricardo , Majewski Steven R. , Pinsonneault Marc H. , Shetrone Matthew , Smith Verne , Sobeck Jennifer , Souto Diogo , Stringfellow Guy S. , Teske Johanna , Zamora Olga 
Published: August 2018

Abstract
Data from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high-resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in 2016 August, contained APOGEE data for roughly 150,000 stars, and DR14, released in 2017 August, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements—C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni—the DR14 ASPCAP analyses have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron itself).
APOGEE Data Releases 13 and 14: Data and Analysis
Authors: Holtzman Jon A. , Hasselquist Sten , Shetrone Matthew , Cunha Katia , Prieto Carlos Allende , Anguiano Borja , Bizyaev Dmitry , Bovy Jo , Casey Andrew , Edvardsson Bengt , Johnson Jennifer A. , Jönsson Henrik , Meszaros Szabolcs , Smith Verne V. , Sobeck Jennifer , Zamora Olga , Chojnowski S. Drew , Fernandez-Trincado Jose , Hernandez Anibal Garcia , Majewski Steven R. , Pinsonneault Marc , Souto Diogo , Stringfellow Guy S. , Tayar Jamie , Troup Nicholas , Zasowski Gail 
Published: August 2018

Abstract
The data and analysis methodology used for the SDSS/APOGEE Data Releases 13 and 14 are described, highlighting differences from the DR12 analysis presented in Holtzman et al. Some improvement in the handling of telluric absorption and persistence is demonstrated. The derivation and calibration of stellar parameters, chemical abundances, and respective uncertainties are described, along with the ranges over which calibration was performed. Some known issues with the public data related to the calibration of the effective temperatures (DR13), surface gravity (DR13 and DR14), and C and N abundances for dwarfs (DR13 and DR14) are highlighted. We discuss how results from a data-driven technique, The Cannon, are included in DR14 and compare those with results from the APOGEE Stellar Parameters and Chemical Abundances Pipeline. We describe how using The Cannon in a mode that restricts the abundance analysis of each element to regions of the spectrum with known features from that element leads to Cannon abundances can lead to significantly different results for some elements than when all regions of the spectrum are used to derive abundances.
Exploring Shear-free Ringlet Formation with Direct Simulations of Saturn's B Rings
Authors: Lu Yuxi , Ballouz Ronald-Louis , Richardson Derek C. 
Published: August 2018

Abstract
In this paper, we study the effect of interparticle cohesion in numerical simulations of Saturn’s main rings. Theoretical studies propose that the irregular structure in Saturn’s rings may arise from alternating “solid” and “liquid” ring material. These studies suggest that for sufficiently high interparticle cohesion, shear-free rings around Saturn may form. We use a highly optimized N-body code that models particle self-gravity, soft-sphere collisions, and interparticle cohesion to simulate a patch of Saturn’s rings with periodic boundaries. We present results for nine different cohesion values ranging from 5.0 × 10−2 to 7.0 Pa, dynamical optical depths of 0.8, 1.4, and 1.8, particle material densities of 0.5 and 1 g cm−3, and restitution coefficients of 0.8 and 0.55. Our simulations show a transition of ring particles forming self-gravity wakes to forming structureless uniform distributions of smaller and faster-moving clumps as cohesion increases. The transition from wakes to structureless form occurs at lower inner-particle cohesion values for higher dynamical optical depth. We present an analysis of the physical optical depth, particle number density, and structure characteristics in the simulations at equilibrium. For high cohesion values, energy injection from differential shear causes transient large structures to rotate and collide at high speed, breaking them apart, ultimately limiting the clump size and frustrating the formation of shear-free zones.
Two Warm, Low-density Sub-Jovian Planets Orbiting Bright Stars in K2 Campaigns 13 and 14
Authors: Yu Liang , Rodriguez Joseph E. , Eastman Jason D. , Crossfield Ian J. M. , Shporer Avi , Gaudi B. Scott , Burt Jennifer , Fulton Benjamin J. , Sinukoff Evan , Howard Andrew W. , Isaacson Howard , Kosiarek Molly R. , Ciardi David R. , Schlieder Joshua E. , Penev Kaloyan , Vanderburg Andrew , Stassun Keivan G. , Bieryla Allyson , Butler R. Paul , Berlind Perry , Calkins Michael L. , Esquerdo Gilbert A. , Latham David W. , Murawski Gabriel , Stevens Daniel J. , Petigura Erik A. , Kreidberg Laura , Bristow Makennah 
Published: August 2018

Abstract
We report the discovery of two planets transiting the bright stars HD 89345 (EPIC 248777106, V = 9.376, K = 7.721) in K2 Campaign 14 and HD 286123 (EPIC 247098361, V = 9.822, K = 8.434) in K2 Campaign 13. Both stars are G-type stars, one of which is at or near the end of its main-sequence lifetime, and the other is just over halfway through its main-sequence lifetime. HD 89345 hosts a warm sub-Saturn (0.66

, 0.11

,

= 1100 K) in an 11.81 day orbit. The planet is similar in size to WASP-107b, which falls in the transition region between ice giants and gas giants. HD 286123 hosts a Jupiter-sized, low-mass planet (1.06

, 0.39

,

= 1000 K) in an 11.17 day, mildly eccentric orbit, with e = 0.255 ± 0.035. Given that they orbit relatively evolved main-sequence stars and have orbital periods longer than 10 days, these planets are interesting candidates for studies of gas planet evolution, migration, and (potentially) reinflation. Both planets have spent their entire lifetimes near the proposed stellar irradiation threshold at which giant planets become inflated, and neither shows any sign of radius inflation. They probe the regime where inflation begins to become noticeable and are valuable in constraining planet inflation models. In addition, the brightness of the host stars, combined with large atmospheric scale heights of the planets, makes these two systems favorable targets for transit spectroscopy to study their atmospheres and perhaps provide insight into the physical mechanisms that lead to inflated hot Jupiters.
The Origin of the Ha-like Structure in Nebular Spectra of Type IIb Supernovae
Authors: Fang 方其 Qiliang 亮 , Maeda Keiichi 
Published: August 2018

Abstract
We investigate the origin of the Hα-like structure seen in late-phase nebular spectra of type IIb supernovae (SNe IIb) at ∼200 days after the explosion. We compare the luminosities of the emission lines of the nebular spectra with the light curve peak magnitudes to reveal their power sources. In this work, we analyze 7 SNe IIb, as well as 2 SNe Ib (SN 2007Y and iPTF 13bvn), which show the Hα-like emission in their nebular spectra. The luminosity of the Hα-like emission shows a tight correlation with the light curve peak magnitude, sharing the same behavior as other nebular lines. This result indicates that the Hα-like emission is powered by the radiative decay of 56Co. The line flux is then expected to roughly follow the mass of the emitting layer. The variation expected from the diversity of the H-rich envelope mass among SNe IIb (reaching nearly to an order of magnitude) is however not seen, suggesting that it is most likely contributed predominantly by [N ii], not by Hα. While further analysis is limited by the available sample size, we find an indication that SNe IIb with a double-peak light curve, which is interpreted as an outcome of the more extended and massive hydrogen envelope, tend to show greater luminosity of the Hα-like feature than those with a single-peak light curve. This behavior indicates a possible additional contribution from Hα. Additionally, we also find a correlation between the [Ca ii]/[O i] ratio and the post-maximum decline rate, indicating that the [Ca ii]/[O i] can be used as a diagnostic for the progenitor mass.
Results from a Systematic Survey of X-Ray Emission from Hydrogen-poor Superluminous SNe
Authors: Margutti R. , Chornock R. , Metzger B. D. , Coppejans D. L. , Guidorzi C. , Migliori G. , Milisavljevic D. , Berger E. , Nicholl M. , Zauderer B. A. , Lunnan R. , Kamble A. , Drout M. , Modjaz M. 
Published: August 2018

Abstract
We present the results from a sensitive X-ray survey of 26 nearby hydrogen-poor superluminous supernovae (SLSNe-I) with Swift, Chandra, and XMM. This data set constrains the SLSN evolution from a few days until ∼2000 days after explosion, reaching a luminosity limit L

x
∼ 1040 erg s−1 and revealing the presence of significant X-ray emission possibly associated with PTF 12dam. No SLSN-I is detected above

, suggesting that the luminous X-ray emission L

x
∼ 1045 erg s−1 associated with SCP 60F6 is not common among SLSNe-I. We constrain the presence of off-axis gamma-ray burst (GRB) jets, ionization breakouts from magnetar engines and the density in the sub-parsec environments of SLSNe-I through inverse Compton emission. The deepest limits rule out the weakest uncollimated GRB outflows, suggesting that if the similarity of SLSNe-I with GRB/SNe extends to their fastest ejecta, then SLSNe-I are either powered by energetic jets pointed far away from our line of sight (θ > 30°), or harbor failed jets that do not successfully break through the stellar envelope. Furthermore, if a magnetar central engine is responsible for the exceptional luminosity of SLSNe-I, our X-ray analysis favors large magnetic fields

G and ejecta masses

, in agreement with optical/UV studies. Finally, we constrain the pre-explosion mass-loss rate of stellar progenitors of SLSNe-I. For PTF 12dam we infer

, suggesting that the SN shock interaction with an extended circumstellar medium is unlikely to supply the main source of energy powering the optical transient and that some SLSN-I progenitors end their lives as compact stars surrounded by a low-density medium similar to long GRBs and type Ib/c SNe.
The Photochemistry of Purine in Ice Analogs Relevant to Dense Interstellar Clouds
Authors: Materese Christopher K. , Nuevo Michel , McDowell Brittiana L. , Buffo Christina E. , Sandford Scott A. 
Published: August 2018

Abstract
The aromatic nitrogen heterocyclic compound purine is the core structural framework of many important biomolecules, particularly nucleobases. Purine and purine derivatives have been observed in carbonaceous chondrites, and it has been hypothesized that the exogenous delivery of these compounds, along with many other biologically relevant compounds, may have played a role in the emergence of life. Numerous experiments in our laboratory have demonstrated that the nucleobases used by life to encode genetic material could have been produced abiotically under astrophysically relevant conditions. Specifically, the UV photoprocessing of pyrimidine and purine in simple ices of astrophysical interest has resulted in the production of all five biological nucleobases, namely, uracil (RNA), cytosine (RNA and DNA), thymine (DNA), adenine (RNA and DNA), and guanine (RNA and DNA). Additionally, follow-up work has examined the photochemistry of pyrimidine in more complex astrophysical ice mixtures to better understand the formation of these compounds under realistic conditions. In this work, we examine the photochemistry of purine in more complex ices of astrophysical interest and compare our results with those from simpler ice mixtures. We also examine the effects of competing parallel synthesis of organic compounds in the ices (unrelated to purine). Finally, we discuss the astrophysical and astrobiological implications of our findings.
The TRENDS High-contrast Imaging Survey. VII. Discovery of a Nearby Sirius-like White Dwarf System (HD 169889)
Authors: Crepp Justin R. , Gonzales Erica J. , Bowler Brendan P. , Morales Farisa , Stone Jordan , Spalding Eckhart , Vaz Amali , Hinz Philip , Ertel Steve , Howard Andrew , Isaacson Howard 
Published: August 2018

Abstract
Monitoring the long-term radial velocity (RV) and acceleration of nearby stars has been proven as an effective method for directly detecting binary and substellar companions. Some fraction of nearby RV trend systems are expected to be comprised of compact objects that likewise induce a systemic Doppler signal. In this paper, we report the discovery of a white dwarf (WD) companion found to orbit the nearby (π = 28.297 ± 0.066 mas) G9 V star HD 169889. High-contrast imaging observations using NIRC2 at the W. M. Keck Observatory and LMIRCam at the Large Binocular Telescope (LBT) Observatory uncover the (ΔH = 9.76 ± 0.16, ΔL′ = 9.60 ± 0.03) companion at an angular separation of 0.″8 (28 au). Thirteen years of precise Doppler observations reveal a steep linear acceleration in the RV time series and place a dynamical constraint on the companion mass of M ≥ 0.369 ± 0.010 M
⊙. This “Sirius-like” system adds to the census of WD companions suspected to be missing from surveys of in the solar neighborhood.
Galileon Intermediate Inflation
Authors: Teimoori Zeinab , Karami Kayoomars 
Published: August 2018

Abstract
We investigate intermediate inflation in the framework of a Galileon scalar field. To this aim, we first obtain the inflationary observables, including the scalar spectral index, the tensor-to-scalar ratio, the running of the scalar spectral index, as well as the non-Gaussianity parameters. Then, we examine the observational viability of the intermediate inflation within the framework of a Galileon scenario. Our results show that although the prediction of intermediate inflation in the standard framework is completely ruled out by the Planck 2015 observations, it can be put inside the allowed regions of the Planck 2015 TT,TE,EE+lowP data in the Galileon setting. Moreover, we determine the parameter space of the Galileon intermediate inflation for which the model is consistent with the Planck 2015 data. Besides, we derive the consistency relation in the Galileon scenario, and find that it differs from the standard inflation. We also estimate the running of the scalar spectral index and find that it is in well agreement with the 95% CL constraint of the Planck 2015 results. Finally, we evaluate the local, equilateral, orthogonal, and enfolded non-Gaussianity parameters, and conclude that not only is the shape of non-Gaussianity approximately close to the equilateral one, but that it also satisfies the 68% CL bound from the Planck 2015 data.
Relationships between Hi Gas Mass, Stellar Mass, and the Star Formation Rate of HICAT+WISE (H i-WISE) Galaxies
Authors: Parkash Vaishali , Brown Michael J. I. , Jarrett T. H. , Bonne Nicolas J. 
Published: August 2018

Abstract
We have measured the relationships between H i mass, stellar mass, and star formation rate using the Hi Parkes All-Sky Survey Catalog (HICAT) and the Wide-field Infrared Survey Explorer (WISE). Of the 3513 HICAT sources, we find 3.4 μm counterparts for 2896 sources (80%), and provide new WISE-matched aperture photometry for these galaxies. For our principal sample of spiral galaxies with W1 ≤ 10 mag and z ≤ 0.01, we identify H i detections for 93% of the sample. We measure lower H i–stellar mass relationships for H i-selected samples that do not include spiral galaxies with little H i gas. Our observations of the spiral sample show that H i mass increases with stellar mass with a power-law index of 0.35; however, this value is dependent on T-type, which affects both the median and the dispersion of Hi mass. We also observe an upper limit on the H i gas fraction, which is consistent with a halo spin parameter model. We measure the star formation efficiency of spiral galaxies to be constant at 10−9.57 yr−1 ± 0.4 dex for 2.5 orders of magnitude in stellar mass, despite the higher stellar mass spiral showing evidence of quenched star formation.
A Statistical Study to Determine the Origin of Long-duration Gamma-Ray Flares
Authors: Winter L. M. , Bernstein V. , Omodei N. , Pesce-Rollins M. 
Published: August 2018

Abstract
Two scenarios have been proposed to account for sustained ≥30 MeV gamma-ray emission in solar flares: (1) prolonged particle acceleration/trapping involving large-scale magnetic loops at the flare site, and (2) precipitation of high-energy (>300 MeV) protons accelerated at coronal/interplanetary shock waves. To determine which of these scenarios is more likely, we examine the associated soft X-ray flares, coronal mass ejections (CMEs), and solar energetic proton events for (a) the long-duration gamma-ray flares (LDGRFs) observed by the Large Area Telescope on Fermi, and (b) delayed and/or spatially extended high-energy gamma-ray flares observed by the Gamma-ray Spectrometer on the Solar Maximum Mission, the Gamma-1 telescope on the Gamma satellite, and the Energetic Gamma-Ray Experiment Telescope on the Compton Gamma-Ray Observatory. For the Fermi data set of 11 LDGRFs with >100 MeV emission lasting for ≥∼2 hr, we search for associations and reverse associations between LDGRFs, X-ray flares, CMEs, and SEPs, i.e., beginning with the gamma-ray flares and also, in turn, with X-class soft X-ray flares, fast (≥1500 km s−1) and wide CMEs, and intense (peak flux ≥2.67 × 10−3 protons cm−2 s−1 sr−1, with peak to background ratio >1.38) >300 MeV SEPs at 1 au. While LDGRFs tend to be associated with bright X-class flares, we find that only one-third of the X-class flares during the time of Fermi monitoring coincide with an LDGRF. However, nearly all fast, wide CMEs are associated with an LDGRF. These preliminary association analyses favor the proton precipitation scenario, although there is a prominent counter-example of a potentially magnetically well-connected solar eruption with >100 MeV emission for ∼10 hr for which the near-Earth >300 MeV proton intensity did not rise above background.
All Transverse Motion Is Peculiar: Connecting the Proper Motions of Galaxies to the Matter Power Spectrum
Authors: Darling Jeremy , Truebenbach Alexandra E. 
Published: August 2018

Abstract
In an isotropic and homogeneous Hubble expansion, all transverse motion is peculiar. Like the radial peculiar velocities of galaxies, transverse peculiar velocities are a means to trace the density of matter that does not rely on light tracing mass. Unlike radial peculiar velocity measurements that require precise redshift-independent distances in order to distinguish between the Hubble expansion and the observed redshift, transverse peculiar velocities can be measured using redshifts alone as a proxy for distance. Extragalactic proper motions can therefore directly measure peculiar velocities and probe the matter power spectrum. Here we develop two-point transverse velocity correlation statistics and demonstrate their dependence on the matter power spectrum. We predict the power in these correlation statistics as a function of the physical separation, angular separation, and distance of pairs of galaxies and demonstrate that the effect of large-scale structure on transverse motions is best measured for pairs of objects with comoving separations less than about 50 Mpc. Transverse peculiar velocities induced by large-scale structure should be observable as proper motions using long baseline radio interferometry or space-based optical astrometry.
The Next Generation Virgo Cluster Survey (NGVS). XXXI. The Kinematics of Intracluster Globular Clusters in the Core of the Virgo Cluster
Authors: Longobardi Alessia , Peng Eric W. , Côté Patrick , Mihos J. Christopher , Ferrarese Laura , Puzia Thomas H. , Lançon Ariane , Zhang Hong-Xin , Muñoz Roberto P. , Blakeslee John P. , Guhathakurta Puragra , Durrell Patrick R. , Sánchez-Janssen Rúben , Toloba Elisa , Jordán Andrés , Eyheramendy Susana , Cuillandre Jean-Charles , Gwyn Stephen D. J. , Boselli Alessandro , Duc Pierre-Alain , Liu Chengze , Alamo-Martínez Karla , Powalka Mathieu , Lim Sungsoon 
Published: August 2018

Abstract
Intracluster (IC) populations are expected to be a natural result of the hierarchical assembly of clusters, yet their low space densities make them difficult to detect and study. We present the first definitive kinematic detection of an IC population of globular clusters (GCs) in the Virgo cluster, around the central galaxy M87. This study focuses on the Virgo core, for which the combination of Next Generation Virgo Cluster Survey photometry and follow-up spectroscopy allows us to reject foreground star contamination and explore GC kinematics over the full Virgo dynamical range. The GC kinematics changes gradually with galactocentric distance, decreasing in mean velocity and increasing in velocity dispersion, eventually becoming indistinguishable from the kinematics of Virgo dwarf galaxies at R > 320 kpc. By kinematically tagging M87 halo and intracluster GCs, we find that (1) the M87 halo has a smaller fraction (52 ± 3%) of blue clusters with respect to the IC counterpart (77 ± 10%), (2) the (g′−r′)0 versus (i′−z′)0 color–color diagrams reveal a galaxy population that is redder than the IC population, which may be due to a different composition in chemical abundance and progenitor mass, and (3) the ICGC distribution is shallower and more extended than the M87 GCs, yet still centrally concentrated. The ICGC specific frequency, S

N,ICL = 10.2 ± 4.8, is consistent with what is observed for the population of quenched, low-mass galaxies within 1 Mpc from the cluster’s center. The IC population at Virgo’s center is thus consistent with being an accreted component from low-mass galaxies tidally stripped or disrupted through interactions, with a total mass of

.
Nature of Magnetic Holes above Ion Scales: A Mixture of Stable Slow Magnetosonic and Unstable Mirror Modes in a Double-polytropic Scenario?
Authors: Zhang Lei , He Jiansen , Zhao Jinsong , Yao Shuo , Feng Xueshang 
Published: August 2018

Abstract
Magnetic holes are common features with a prominent dip of magnetic field strength in space plasma turbulence. As to their nature, there exists a dispute of explanations among discontinuities, magnetic reconnection, solitons, kinetic-scale electron vortexes, slow waves, and mirror-mode instability. As magnetic holes are often accompanied by thermal anisotropy, at magnetohydrodynamic scales double-polytropic equations can serve as an appropriate description. The reason for the long-lasting dispute lies in the fact that both mirror-mode structures and oblique slow-mode waves are characterized with anticorrelation between plasma density (or temperature) and magnetic field strength, which, as often used in preceding works, is also the characteristic feature of magnetic holes. Therefore, to finally and unambiguously diagnose the nature of magnetic holes above ion scales, we propose to resort to other features, among which v
∥ and its phase relation with

and n behave differently between mirror-mode structures and slow-mode waves. Herewith we establish a model with superposition of both slow and mirror modes to reproduce the observed types of behaviors

. This model inspires new understanding of the nature of magnetic holes: the magnetic hole in reality is not solely contributed by only one mode, but a mixture of the two modes with an adjustable amplitude ratio.