bluuebunny/crossref_metadata_2025_split huggingface dataset:
Normal Modes of Transverse Coronal Loop Oscillations from Numerical Simulations. I. Method and Test Case
Authors: Rial S. , Arregui I. , Oliver R. , Terradas J. 
Published: May 2019

Abstract
The purpose of this work is to develop a procedure to obtain the normal modes of a coronal loop from time-dependent numerical simulations with the aim of better understanding observed transverse loop oscillations. To achieve this goal, in this paper we present a new method and test its performance with a problem for which the normal modes can be computed analytically. In a follow-up paper, the application to the simulations of Rial et al. is tackled. The method proceeds iteratively and at each step consists of (i) a time-dependent numerical simulation followed by (ii) the Complex Empirical Orthogonal Function (CEOF) analysis of the simulation results. The CEOF analysis provides an approximation to the normal mode eigenfunctions that can be used to set up the initial conditions for the numerical simulation of the following iteration, in which an improved normal mode approximation is obtained. The iterative process is stopped once the global difference between successive approximate eigenfunctions is below a prescribed threshold. The equilibrium used in this paper contains material discontinuities that result in one eigenfunction with a jump across these discontinuities and two eigenfunctions whose normal derivatives are discontinuous there. After six iterations, the approximations to the frequency and eigenfunctions are accurate to ≲0.7% except for the eigenfunction with discontinuities, which displays a much larger error at these positions.
Massive Young Stellar Objects and Outflow in the Infrared Dark Cloud G79.3+0.3
Authors: Laws Anna S. E. , Hora Joseph L. , Zhang Qizhou 
Published: May 2019

Abstract
G79.3+0.3 is an infrared dark cloud in the Cygnus-X complex that is home to massive deeply embedded young stellar objects (YSOs). We have produced a Submillimeter Array (SMA) 1.3 mm continuum image and 12CO line maps of the eastern section of G79.3+0.3 in which we detect five separate YSOs. We have estimated physical parameters for these five YSOs and others in the vicinity of G79.3+0.3 by fitting existing photometry from Spitzer, Herschel, and ground-based telescopes to spectral energy distribution models. Through these model fits we find that the most massive YSOs seen in the SMA 1.3 mm continuum emission have masses in the 5–6 M
☉ range. One of the SMA sources was observed to power a massive collimated 12CO outflow extending at least 0.94 pc in both directions from the protostar, with a total mass of 0.83 M
☉ and a dynamical timescale of 23 kyr.
Data-driven Spectroscopy of Cool Stars at High Spectral Resolution
Authors: Behmard Aida , Petigura Erik A. , Howard Andrew W. 
Published: May 2019

Abstract
The advent of large-scale spectroscopic surveys underscores the need to develop robust techniques for determining stellar properties (“labels,” i.e., physical parameters and elemental abundances). However, traditional spectroscopic methods that utilize stellar models struggle to reproduce cool (<4700 K) stellar atmospheres due to an abundance of unconstrained molecular transitions, making modeling via synthetic spectral libraries difficult. Because small, cool stars such as K and M dwarfs are both common and good targets for finding small, cool planets, establishing precise spectral modeling techniques for these stars is of high priority. To address this, we apply The Cannon, a data-driven method of determining stellar labels, to Keck High Resolution Echelle Spectrometer spectra of 141 cool (<5200 K) stars from the California Planet Search. Our implementation is capable of predicting labels for small (<1 R
⊙) stars of spectral types K and later with accuracies of 68 K in effective temperature (T
eff), 5% in stellar radius (R
*), and 0.08 dex in bulk metallicity ([Fe/H]), and maintains this performance at low spectral resolutions (R < 5000). As M dwarfs are the focus of many future planet-detection surveys, this work can aid efforts to better characterize the cool star population and uncover correlations between cool star abundances and planet occurrence for constraining planet formation theories.
On the Measurement of Fundamental Parameters of White Dwarfs in the Gaia Era
Authors: Bergeron P. , Dufour P. , Fontaine G. , Coutu S. , Blouin S. , Genest-Beaulieu C. , Bédard A. , Rolland B. 
Published: May 2019

Abstract
We present a critical review of the determination of fundamental parameters of white dwarfs discovered by the Gaia mission. We first reinterpret color–magnitude and color–color diagrams using photometric and spectroscopic information contained in the Montreal White Dwarf Database (MWDD), combined with synthetic magnitudes calculated from a self-consistent set of model atmospheres with various atmospheric compositions. The same models are then applied to measure the fundamental parameters of white dwarfs using the so-called photometric technique, which relies on the exquisite Gaia trigonometric parallax measurements, and photometric data from Panoramic Survey Telescope And Rapid Response System, Sloan Digital Sky Survey, and Gaia. In particular, we discuss at length the systematic effects induced by these various photometric systems. We then study in great detail the mass distribution as a function of effective temperature for the white dwarfs spectroscopically identified in the MWDD, as well as for the white dwarf candidates discovered by Gaia. We pay particular attention to the assumed atmospheric chemical composition of cool, non-DA stars. We also briefly revisit the validity of the mass–radius relation for white dwarfs and the recent discovery of the signature of crystallization in the Gaia color–magnitude diagram for DA white dwarfs. We finally present evidence that the core composition of most of these white dwarfs is, in bulk, a mixture of carbon and oxygen, an expected result from stellar evolution theory, but never empirically well established before.
Unbiased Cosmic Opacity Constraints from Standard Sirens and Candles
Authors: Wei Jun-Jie 
Published: May 2019

Abstract
The observation of Type Ia supernovae (SNe Ia) plays an essential role in probing the expansion history of the universe. But the possible presence of cosmic opacity can degrade the quality of SNe Ia. The gravitational-wave (GW) standard sirens, produced by the coalescence of double neutron stars and black hole–neutron star binaries, provide an independent way to measure the distances of GW sources, which are not affected by cosmic opacity. In this paper, we first propose that combining the GW observations of third-generation GW detectors with SN Ia data in similar redshift ranges offers a novel and model-independent method to constrain cosmic opacity. Through Monte Carlo simulations, we find that one can constrain the cosmic opacity parameter κ with an accuracy of σ

κ
∼ 0.046 by comparing the distances from 100 simulated GW events and 1048 current Pantheon SNe Ia. The uncertainty of κ can be further reduced to ∼0.026 if 800 GW events are considered. We also demonstrate that combining 2000 simulated SNe Ia and 1000 simulated GW events could result in much severer constraints on the transparent universe, for which κ = 0.0000 ± 0.0044. Compared to previous opacity constraints involving distances from other cosmic probes, our method using GW standard sirens and SN Ia standard candles at least achieves competitive results.
First Abundance Measurement of Organic Molecules in the Atmosphere of HH 212 Protostellar Disk
Authors: Lee Chin-Fei , Codella Claudio , Li Zhi-Yun , Liu Sheng-Yuan 
Published: May 2019

Abstract
HH 212 is one of the well-studied protostellar systems, showing the first vertically resolved disk with a warm atmosphere around the central protostar. Here we report a detection of nine organic molecules (including newly detected ketene, formic acid, deuterated acetonitrile, methyl formate, and ethanol) in the disk atmosphere, confirming that the disk atmosphere is, for HH 212, the chemically rich component, identified before at a lower resolution as a “hot corino.” More importantly, we report the first systematic survey and abundance measurement of organic molecules in the disk atmosphere within ∼40 au of the central protostar. The relative abundances of these molecules are similar to those in the hot corinos around other protostars and in Comet Lovejoy. These molecules can be either (i) originally formed on icy grains and then desorbed into gas phase or (ii) quickly formed in the gas phase using simpler species ejected from the dust mantles. The abundances and spatial distributions of the molecules provide strong constraints on models of their formation and transport in star formation. These molecules are expected to form even more complex organic molecules needed for life and deeper observations are needed to find them.
Electron Preacceleration in Weak Quasi-perpendicular Shocks in High-beta Intracluster Medium
Authors: Kang Hyesung , Ryu Dongsu , Ha Ji-Hoon 
Published: May 2019

Abstract
Giant radio relics in the outskirts of galaxy clusters are known to be lit up by the relativistic electrons produced via diffusive shock acceleration (DSA) in shocks with low sonic Mach numbers, M
s ≲ 3. The particle acceleration at these collisionless shocks critically depends on the kinetic plasma processes that govern the injection to DSA. Here, we study the preacceleration of suprathermal electrons in weak, quasi-perpendicular (Q
⊥) shocks in the hot, high-β (β = P
gas/P
B) intracluster medium (ICM) through two-dimensional particle-in-cell simulations. Guo et al. showed that, in high-β Q
⊥-shocks, some of the incoming electrons could be reflected upstream and gain energy via shock drift acceleration (SDA). The temperature anisotropy due to the SDA-energized electrons then induces the electron firehose instability (EFI), and oblique waves are generated, leading to a Fermi-like process and multiple cycles of SDA in the preshock region. We find that such electron preacceleration is effective only in shocks above a critical Mach number

. This means that, in ICM plasmas, Q
⊥-shocks with M
s ≲ 2.3 may not efficiently accelerate electrons. We also find that, even in Q
⊥-shocks with M
s ≳ 2.3, electrons may not reach high enough energies to be injected to the full Fermi-I process of DSA, because long-wavelength waves are not developed via the EFI alone. Our results indicate that additional electron preaccelerations are required for DSA in ICM shocks, and the presence of fossil relativistic electrons in the shock upstream region may be necessary to explain observed radio relics.
On the Anomalous Acceleration of 1I/2017 U1 ‘Oumuamua
Authors: Seligman Darryl , Laughlin Gregory , Batygin Konstantin 
Published: May 2019

Abstract
We show that the P ∼ 8 hr photometric period and the astrometrically measured A
ng ∼ 2.5 × 10−4 cm s−2 non-gravitational acceleration (at r ∼ 1.4 au) of the interstellar object 1I/2017 (‘Oumuamua) can be explained by a nozzle-like venting of volatiles whose activity migrated to track the subsolar location on the object’s surface. Adopting the assumption that ‘Oumuamua was an elongated a × b × c ellipsoid, this model produces a pendulum-like rotation of the body and implies a long semi-axis

. This scale agrees with the independent estimates of ‘Oumuamua’s size that stem from its measured brightness, assuming an albedo of p ∼ 0.1, which is appropriate for ices that have undergone long-duration exposure to the interstellar cosmic-ray flux. Using ray tracing, we generate light curves for ellipsoidal bodies that are subject to both physically consistent subsolar torques and to the time-varying geometry of the Sun–Earth–‘Oumuamua configuration. Our synthetic light curves display variations from chaotic tumbling and changing cross-sectional illumination that are consistent with the observations, while avoiding significant secular changes in the photometric periodicity. If our model is correct, ‘Oumuamua experienced mass loss that wasted ∼10% of its total mass during the ∼100 days span of its encounter with the inner solar system and had an icy composition with a very low [C/O] ≲ 0.003. Our interpretation of ‘Oumuamua’s behavior is consistent with the hypothesis that it was ejected from either the outer regions of a planetesimal disk after an encounter with an embedded M
p ∼ M
Nep planet, or from an exo-Oort cloud.
Consequences of Tidal Dissipation in a Putative Venusian Ocean
Authors: Green J. A. Mattias , Way Michael J. , Barnes Rory 
Published: May 2019

Abstract
The solar tide in an ancient Venusian ocean is simulated using a dedicated numerical tidal model. Simulations with varying ocean depth and rotational periods ranging from −243 to 64 sidereal Earth days are used to calculate the tidal dissipation rates and associated tidal torque. The results show that the tidal dissipation could have varied by more than 5 orders of magnitude, from 0.001 to 780 GW, depending on rotational period and ocean depth. The associated tidal torque is about 2 orders of magnitude below the present day Venusian atmospheric torque, and could change the Venusian daylength by up to 72 days per million years depending on rotation rate. Consequently, an ocean tide on ancient Venus could have had significant effects on the rotational history of the planet. These calculations have implications for the rotational periods of similarly close-in exoplanetary worlds and the location of the inner edge of the liquid water habitable zone.
Effect of the Interstellar Magnetic Field Draping around the Heliopause on the IBEX Ribbon
Authors: Gamayunov Konstantin V. , Heerikhuisen Jacob , Rassoul Hamid K. 
Published: May 2019

Abstract
A dominant feature in all-sky maps of energetic neutral atoms (ENAs) from NASA’s Interstellar Boundary EXplorer (IBEX) is a ribbon of enhanced fluxes. This ribbon was not predicted before IBEX, but all the up-to-date IBEX observations support a secondary ENA mechanism for the ribbon formation. There are two different classes of the secondary ENA model; the first class assumes a weak pitch angle scattering of energetic protons in the local interstellar medium (LISM), and the second class assumes strong, but spatially localized, scattering. A recent work by Gamayunov et al. strongly supports a “weak scattering” version, and here we extend the scope of the Gamayunov et al. model by using a more realistic interstellar magnetic field (ISMF) from our global MHD-plasma/kinetic-neutral simulation of the heliosphere–LISM interaction in place of the simple analytical model used previously. The main conclusions of our analysis are summarized as follows. (1) Pitch angle scattering of energetic protons in the LISM is not the primary mechanism that controls the width of ribbon. Instead, the ribbon width is mainly determined by draping of the ISMF around the heliopause. (2) The intensity of the ribbon is controlled by pitch angle scattering of energetic protons in the LISM. A model–IBEX comparison suggests that generation of the small-scale local turbulence is suppressed in the LISM. On the other hand, the large-scale interstellar turbulence (LSIT) alone or an interplay between the LSIT and the case of no scattering leads to a good agreement between the model and IBEX fluxes.
Effect of Spherical Equivalent Error on Visual Acuity at Various Distances in Eyes With a Trifocal Intraocular Lens
Authors: Hayashi Ken , Sato Tatshuhiko , Igarashi Chizuka , Yoshida Motoaki 
Published: May 2019

PURPOSE:
To examine the effect of manifest refraction spherical equivalent error on visual acuity at various distances in eyes that received a trifocal intraocular lens (IOL).

METHODS:
Sixty eyes of 30 patients who underwent bilateral implantation of a trifocal IOL (Alcon PanOptix TFNT00; Alcon Laboratories, Inc., Fort Worth, TX) were enrolled. Corrected visual acuity from far to near distances was measured using an all-distance vision tester after simulating the spherical equivalent error by adding spherical lenses with refractive powers of +1.00, +0.50, 0.00, −0.50, and −1.00 diopters (D); addition of a plus lens simulates myopia, whereas addition of a minus lens simulates hyperopia.

RESULTS:

Mean visual acuity at all distances differed significantly among the spherical lens added groups (
P
≤ .0374). Mean distance visual acuity at infinity, 5, and 3 m was significantly worse in all lens added groups (+1.00, +0.50, −0.50, and −1.00 D) than in the no lens group (
P
< .0001). Mean intermediate visual acuity at 1 and 0.7 m did not differ significantly between each of the lens added groups and the no lens group. Mean near visual acuity at 0.3 m was significantly better in the +1.00 and +0.50 D groups and significantly worse in the −0.50 and −1.00 D groups than in the no lens group (
P
≤ .0044).

CONCLUSIONS:
A manifest spherical equivalent error of slight myopia significantly improved near visual acuity but worsened distance visual acuity, whereas that of slight hyperopia worsened both distance and near visual acuity in eyes with trifocal IOLs, suggesting that slight myopia is a better target refraction than slight hyperopia, although emmetropia is the optimum target.

[
J Refract Surg
. 2019;35(5):274–279.]
Underground Drainage Systems and Geothermal Flux
Authors: Badino Giovanni 
Published: May 2019

V članku opišem pomen interakcije med geotermičnim tokom in mrežo globokega kraškega odvodnjavanja. Problem geotermičnega toka, ki ga prestrežejo vodni kanali, ki v splošnem zaheva tudi izračun temperaturnega polja, obravnavam z inženirskim pristopom, ki pri tem vpelje t.i. faktorje oblike. Tok vode v kraških kanalih zmoti celotno temperaturno polje v okoliškem masivu in sčasoma pritegne nase ves geotermični tok širšega območja. Že majhna količina vode, ki teče v masiv, zmoti temperaturno polje masiva vse do površja. Vpel­java geotermičnega preseka struktur podzemnega odvodnjavanja, omogoča izboljšanje klasične formule za oceno minimalne globine vira geotermalne vode. Tej dodamo faktor povečave, ki je odvisen od razmerja med povprečnim in kritičnim pretokom Qc, ki ga določa geotermični presek. V članku opišem tudi geotermične »stožce senčenja«, ki nastanejo v masivu nad kraškimi kanali. An analysis of the interaction between the geothermal flux and the water or air- deep drainage networks. The problem of geothermal power intercepted by deep structures and, in general, the temperature field calculations, is converted to classical thermo-engineering problems in terms of shape factors. It is shown that the fluid flow in a conduit perturbs the whole deep rock temperature field until the geothermal flux of a large area is focalised onto the conduit. It is shown that either small water masses flowing into a mountain are able to perturb the rock temperature up to the surface, on sizes that do not depend on water mass dimension, but on its depth, and then on enormous volumes. The introduction of the "geothermal cross section" of an underground drainage structure allows us to improve the classical formula of minimum provenance depth of geothermal water. Enlarging factors are applied to the classical estimation in dependence of the ratio between the actual average discharge and the critical discharge Qc, which depends on the conduit geothermal cross section. The geothermal "umbra cones"created in the overlying rock by deep underground structures are described. It is shown that the geothermal flux can play a significant role in the underground drainage phenomenology.
The Montello hill: The “Classical Karst” of the Conglomerate Rocks
Authors: Ferrarese Francesco , Sauro Ugo 
Published: May 2019

Grič Montello je najbrž najbolj tipična morfološka enota krasa, razvitega v konglomeratnih kamninah. Lahko ga štejemo za klasični kras v konglomeratu, primerljivim s klasičnim krasom na apnencu, Tržaškim Krasom. Montello je v tlorisu ovalen, dolg približno 13 km v ZJZ – VSV smeri ter širok okoli 5 km. Razvit je v »montelskem konglomeratu« poznomiocenske starosti (mesinij), ki ga gradijo največ karbonatni prodniki zlepljeni s kalcitnim vezivom, debeline do 2000 m. Montello je oblikovan v cel sistem oblik, nastalih zaradi rečnega uravnavanja in vrezovanja, vidnih na osrednji planoti in sedmih živoskalnih uravnanih teras. Terase so vrezane v pobočje opuščene anticedentne doline. Na rečni uravnavi so se razvile vrtače, večinoma iz grezov pa tudi zaradi točkovnega prenikanja. Vsega skupaj jih je preko 2000. Vrtače na sedmih živoskalnih terasah kažejo različen razvoj in različno velikost glede na starost površja. Kaže, da je bil v začetni fazi morfogeneze vrtač vpliv strukture, to je lezik in razpok, šibak; nasprotno pa je bila poroznost odločujoči dejavnik za razvoj kraškega odtoka. The Montello hill is, probably, the most typical morphounit between the karsts developed in conglomerate rocks. It may be considered the classical karst of the conglomerates comparable with the Classical Karst of limestones: the Carso of Trieste. The Montello hill consists in an elliptical plan figure, elongated for about13 km in a WSW-ENE direction and a width of about 5 km. The rock unit involved is the “Conglomerato del Montello” of late Miocene age (Messinian), mostly composed by carbonate pebbles bound by a calcitic cement, which is 2000 m thick. The Montello is shaped by a complex system of fluvial planation and incision forms in which are distinguishable a main plateau and a stairs of seven planation rock cut terraces. The terraces are cut in the slope of a dead antecedent valley. On the fluvial planation forms, dolines, mostly of the draw down type but also of the point recharge type, have evolved. In total more than 2000 dolines are present. In the seven rock cut terraces the dolines show different development and dimensions according with the ages of the surfaces. In the first morphogenesis of these dolines and of the caves the control of the plan structures as the bedding surfaces and the fractures seems to have been feeble; on the contrary the porosity of the conglomerate has been a determinant factors for the developmente of the karst drainage.