bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light-curve Modulation of Low-mass Stars in K2. I. Identification of 481 Fast Rotators in the Solar Neighborhood
Authors: Saylor Dicy , Lepine Sebastien , Crossfield Ian , Petigura Erik A. 
Published: December 2017

Abstract
The K2 mission is targeting large numbers of nearby (d < 100 pc) GKM dwarfs selected from the SUPERBLINK proper motion survey (μ > 40 mas yr−1, V < 20). Additionally, the mission is targeting low-mass, high proper motion stars associated with the local (d < 500 pc) Galactic halo population also selected from SUPERBLINK. K2 campaigns 0 through 8 monitored a total of 26,518 of these cool main-sequence stars. We used the auto-correlation function to search for fast rotators by identifying short-period photometric modulations in the K2 light curves. We identified 481 candidate fast rotators with rotation periods <4 days that show light-curve modulations consistent with starspots. Their kinematics show low average transverse velocities, suggesting that they are part of the young disk population. A subset (13) of the fast rotators is found among those targets with colors and kinematics consistent with the local Galactic halo population and may represent stars spun up by tidal interactions in close binary systems. We further demonstrate that the M dwarf fast rotators selected from the K2 light curves are significantly more likely to have UV excess and discuss the potential of the K2 mission to identify new nearby young GKM dwarfs on the basis of their fast rotation rates. Finally, we discuss the possible use of local halo stars as fiducial, non-variable sources in the Kepler fields.
Pre-discovery Observations and Orbit of Comet C/2017 K2 (PANSTARRS)
Authors: Hui 許文 Man-To 韜 , Jewitt David , Clark David 
Published: December 2017

Abstract
We present a study of comet C/2017 K2 (PANSTARRS) using pre-discovery archival data taken from 2013 to 2017. Our measurements show that the comet has been marginally increasing in activity since at least 2013 May (heliocentric distance of

pre-perihelion). We estimate the mass-loss rate during the period 2013–2017 as

kg s−1, which requires a minimum active surface area of ∼10–102 km2 for sublimation of supervolatiles such as CO and CO2, by assuming a nominal cometary albedo

. The corresponding lower limit to the nucleus radius is a few kilometers. Our Monte Carlo dust simulations show that dust grains in the coma are

in radius, with ejection speeds from ∼1 to 3 m s−1, and have been emitted in a protracted manner since 2013, confirming estimates by Jewitt et al. The current heliocentric orbit is hyperbolic. Our N-body backward dynamical integration of the orbit suggests that the comet is most likely (with a probability of ∼98%) from the Oort spike. The calculated median reciprocal of the semimajor axis 1 Myr ago was

au−1 (in a reference system centered on the solar-system barycenter).
Protoplanetary Disks in ρ Ophiuchus as Seen from ALMA
Authors: Cox Erin G. , Harris Robert J. , Looney Leslie W. , Chiang Hsin-Fang , Chandler Claire , Kratter Kaitlin , Li Zhi-Yun , Perez Laura , Tobin John J. 
Published: December 2017

Abstract
We present a high angular resolution (

), high-sensitivity (

mJy) survey of the 870 μm continuum emission from the circumstellar material around 49 pre-main-sequence stars in the ρ Ophiuchus molecular cloud. Because most millimeter instruments have resided in the northern hemisphere, this represents the largest high-resolution, millimeter-wave survey of the circumstellar disk content of this cloud. Our survey of 49 systems comprises 63 stars; we detect disks associated with 29 single sources, 11 binaries, 3 triple systems, and 4 transition disks. We present flux and radius distributions for these systems; in particular, this is the first presentation of a reasonably complete probability distribution of disk radii at millimeter wavelengths. We also compare the flux distribution of these protoplanetary disks with that of the disk population of the Taurus–Auriga molecular cloud. We find that disks in binaries are both significantly smaller and have much less flux than their counterparts around isolated stars. We compute truncation calculations on our binary sources and find that these disks are too small to have been affected by tidal truncation and posit some explanations for this. Lastly, our survey found three candidate gapped disks, one of which is a newly identified transition disk with no signature of a dip in infrared excess in extant observations.
Constraining Hot Jupiter Atmospheric Structure and Dynamics through Doppler-shifted Emission Spectra
Authors: Zhang Jisheng , Kempton Eliza M.-R. , Rauscher Emily 
Published: December 2017

Abstract
We present a coupled 3D atmospheric dynamics and radiative transfer model to predict the disk-integrated thermal emission spectra of transiting exoplanets in edge-on orbits. We calculate spectra at high resolution to examine the extent to which high-resolution emission spectra are influenced by 3D atmospheric dynamics and planetary rotation and to determine whether and how we can constrain thermal structures and atmospheric dynamics through high-resolution spectroscopy. This study represents the first time that the line-of-sight geometry and resulting Doppler shifts from winds and rotation have been treated self-consistently in an emission spectrum radiative transfer model, which allows us to assess the impact of the velocity field on thermal emission spectra. We apply our model to predict emission spectra as a function of orbital phase for three hot Jupiters: HD 209458b, WASP-43b, and HD 189733b. We find net Doppler shifts in modeled spectra due to a combination of winds and rotation at a level of 1–3 km s−1. These Doppler signatures vary in a quasi-sinusoidal pattern over the course of the planets’ orbits as the hot spots approach and recede from the observer’s viewpoint. We predict that WASP-43b produces the largest Doppler shift due to its fast rotation rate. We find that the net Doppler shift in an exoplanet’s disk-integrated thermal emission spectrum results from a complex combination of winds, rotation, and thermal structure. However, we offer a simple method that estimates the magnitude of equatorial wind speeds in hot Jupiters through measurements of net Doppler shifts and lower-resolution thermal phase curves.
Spiky Structures around Reconnection Exhausts in the Solar Wind
Authors: Enžl Jakub , Šafránková Jana , Němeček Zdeněk , Přech Lubomír 
Published: December 2017

Abstract
The paper presents for the first time observations of unusual reconnection events in the solar wind. In all solar wind types, we identify magnetic reconnection exhausts accompanied by one or two side jets. This complex structure is created around a single current sheet and the jet(s) oriented in the same direction as the main exhaust is (are) spatially separated from it. A statistical analysis of reconnection exhausts in Wind observations (422 events) revealed that about 12% of exhausts is accompanied with one side jet and 3% of exhausts is bounded by two side jets, one on each side. Multispacecraft observations of events allow us to conclude that these structures are not consistent with a folding of the reconnection exhaust boundary. A source of these side jets is probably multiple or patchy reconnection at or close to the heliospheric current sheet. We suggest a scenario based on multiple reconnection that would lead to the presence of two side jets. A single jet is caused by a broken X-line consisting of two or more spatially separated parts.
Testing for Shock-heated X-Ray Gas around Compact Steep Spectrum Radio Galaxies
Authors: O’Dea C. P. , Worrall D. M. , Tremblay G. R. , Clarke T. E. , Rothberg B. , Baum S. A. , Christiansen K. P. , Mullarkey C. A. , Noel-Storr J. , Mittal R. 
Published: December 2017

Abstract
We present Chandra and XMM-Newton X-ray, Very Large Array (VLA) radio, and optical observations of three candidate compact steep spectrum (CSS) radio galaxies. CSS sources are of a galactic scale and are presumably driving a shock through the interstellar medium (ISM) of their host galaxy. B3 1445+410 is a low-excitation emission line CSS radio galaxy with possibly a hybrid Fanaroff–Riley FRI/II (or fat double) radio morphology. The Chandra observations reveal a point-like source that is well fit with a power law consistent with the emission from a Doppler boosted core. 3C 268.3 is a CSS broad-line radio galaxy (BLRG) whose Chandra data are consistent spatially with a point source centered on the nucleus and spectrally with a double power-law model. PKS B1017–325 is a low-excitation emission line radio galaxy with a bent double radio morphology. While from our new spectroscopic redshift, PKS B1017−325 falls outside the formal definition of a CSS, the XMM-Newton observations are consistent with ISM emission with either a contribution from hot shocked gas or non-thermal jet emission. We compile selected radio and X-ray properties of the nine bona fide CSS radio galaxies with X-ray detections so far. We find that two out of the nine show X-ray spectroscopic evidence for hot shocked gas. We note that the counts in the sources are low and that the properties of the two sources with evidence for hot shocked gas are typical of the other CSS radio galaxies. We suggest that hot shocked gas may be typical of CSS radio galaxies due to their propagation through their host galaxies.
Interpreting Brightness Asymmetries in Transition Disks: Vortex at Dead Zone or Planet-carved Gap Edges?
Authors: Regály Zs. , Juhász A. , Nehéz D. 
Published: December 2017

Abstract
Recent submillimeter observations show nonaxisymmetric brightness distributions with a horseshoe-like morphology for more than a dozen transition disks. The most-accepted explanation for the observed asymmetries is the accumulation of dust in large-scale vortices. Protoplanetary disks’ vortices can form by the excitation of Rossby wave instability in the vicinity of a steep pressure gradient, which can develop at the edges of a giant planet–carved gap or at the edges of an accretionally inactive zone. We studied the formation and evolution of vortices formed in these two distinct scenarios by means of two-dimensional locally isothermal hydrodynamic simulations. We found that the vortex formed at the edge of a planetary gap is short-lived, unless the disk is nearly inviscid. In contrast, the vortex formed at the outer edge of a dead zone is long-lived. The vortex morphology can be significantly different in the two scenarios: the vortex radial and azimuthal extensions are ∼1.5 and ∼3.5 times larger for the dead-zone edge compared to gap models. In some particular cases, the vortex aspect ratios can be similar in the two scenarios; however, the vortex azimuthal extensions can be used to distinguish the vortex formation mechanisms. We calculated predictions for vortex observability in the submillimeter continuum with ALMA. We found that the azimuthal and radial extent of the brightness asymmetry correlates with the vortex formation process within the limitations of α-viscosity prescription.
Characterizing Dust Attenuation in Local Star-forming Galaxies: Inclination Effects and the 2175 Å Feature
Authors: Battisti A. J. , Calzetti D. , Chary R.-R. 
Published: December 2017

Abstract
We characterize the influence that inclination has on the shape and normalization in average dust attenuation curves derived from a sample of ∼10,000 local star-forming galaxies. To do this, we utilize aperture-matched multiwavelength data from the Galaxy Evolution Explorer, the Sloan Digital Sky Survey, the United Kingdom Infrared Telescope, and the Two Micron All-sky Survey. We separate our sample into groups according to axial ratio (b/a) and obtain an estimate of their average total-to-selective attenuation

. The attenuation curves are found to be shallower at UV wavelengths with increasing inclination, whereas the shape at longer wavelengths remains unchanged. The highest inclination subpopulation (

) exhibits an NUV excess in its average selective attenuation, which, if interpreted as a 2175 Å feature, is best fit with a bump strength of 17%–26% of the MW value. No excess is apparent in the average attenuation curve of lower inclination galaxies. The differential reddening between the stellar continuum and ionized gas is found to decrease with increasing inclination. We find that higher inclination galaxies have slightly higher values of R

V
, although this is poorly constrained given the uncertainties. We outline possible explanations for these trends within a two component dust model (dense cloud+diffuse dust) and find that they can be naturally explained if carriers of the 2175 Å feature are preferentially destroyed in star-forming regions (UV-bright regions).
Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars
Authors: Namekata Kosuke , Sakaue Takahito , Watanabe Kyoko , Asai Ayumi , Maehara Hiroyuki , Notsu Yuta , Notsu Shota , Honda Satoshi , Ishii Takako T. , Ikuta Kai , Nogami Daisaku , Shibata Kazunari 
Published: December 2017

Abstract
Recently, many superflares on solar-type stars have been discovered as white-light flares (WLFs). The statistical study found a correlation between their energies (E) and durations (τ):

, similar to those of solar hard/soft X-ray flares,

. This indicates a universal mechanism of energy release on solar and stellar flares, i.e., magnetic reconnection. We here carried out statistical research on 50 solar WLFs observed with Solar Dynamics Observatory/HMI and examined the correlation between the energies and durations. As a result, the E–τ relation on solar WLFs (

) is quite similar to that on stellar superflares (

). However, the durations of stellar superflares are one order of magnitude shorter than those expected from solar WLFs. We present the following two interpretations for the discrepancy: (1) in solar flares, the cooling timescale of WLFs may be longer than the reconnection one, and the decay time of solar WLFs can be elongated by the cooling effect; (2) the distribution can be understood by applying a scaling law (

) derived from the magnetic reconnection theory. In the latter case, the observed superflares are expected to have 2–4 times stronger magnetic field strength than solar flares.
Superorbital Modulation at GeV Energies in the γ-Ray Binary LS I + 61°303
Authors: Xing Yi , Wang Zhongxiang , Takata Jumpei 
Published: December 2017

Abstract
We report the results from our analysis of eight years of the data for the γ-ray binary LS I +61°303, obtained with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. We find a significant dip around the binary’s periastron in the superorbital light curves, and by fitting the light curves with a sinusoidal function, clear phase shifts are obtained. The superorbital modulation seen in the binary has been long known and different scenarios have been proposed. Based on our results, we suggest that the circumstellar disk around the Be companion of this binary may have a non-axisymmetric structure, which rotates at the superorbital period of 1667 days. As a result, the density of the ambient material around the compact star of the binary changes along the binary orbit over the superorbital period, causing the phase shifts in the modulation, and around periastron, the compact star probably enters the Be disk or switches the mode of its emission due to the intereaction with the disk, causing the appearance of the dip. We discuss the implications of this possible scenario to the observed superorbital properties at multiple frequencies.
Modeling UV Radiation Feedback from Massive Stars. I. Implementation of Adaptive Ray-tracing Method and Tests
Authors: Kim Jeong-Gyu , Kim Woong-Tae , Ostriker Eve C. , Skinner M. Aaron 
Published: December 2017

Abstract
We present an implementation of an adaptive ray-tracing (ART) module in the Athena hydrodynamics code that accurately and efficiently handles the radiative transfer involving multiple point sources on a three-dimensional Cartesian grid. We adopt a recently proposed parallel algorithm that uses nonblocking, asynchronous MPI communications to accelerate transport of rays across the computational domain. We validate our implementation through several standard test problems, including the propagation of radiation in vacuum and the expansions of various types of H ii regions. Additionally, scaling tests show that the cost of a full ray trace per source remains comparable to that of the hydrodynamics update on up to

∼

10

3

processors. To demonstrate application of our ART implementation, we perform a simulation of star cluster formation in a marginally bound, turbulent cloud, finding that its star formation efficiency is 12% when both radiation pressure forces and photoionization by UV radiation are treated. We directly compare the radiation forces computed from the ART scheme with those from the M
1 closure relation. Although the ART and M
1 schemes yield similar results on large scales, the latter is unable to resolve the radiation field accurately near individual point sources.
Planet–Planet Occultations in TRAPPIST-1 and Other Exoplanet Systems
Authors: Luger Rodrigo , Lustig-Yaeger Jacob , Agol Eric 
Published: December 2017

Abstract
We explore the occurrence and detectability of planet–planet occultations (PPOs) in exoplanet systems. These are events during which a planet occults the disk of another planet in the same system, imparting a small photometric signal as its thermal or reflected light is blocked. We focus on the planets in TRAPPIST-1, whose orbital planes we show are aligned to

at 90% confidence. We present a photodynamical model for predicting and computing PPOs in TRAPPIST-1 and other systems for various assumptions of the planets’ atmospheric states. When marginalizing over the uncertainties on all orbital parameters, we find that the rate of PPOs in TRAPPIST-1 is about 1.4 per day. We investigate the prospects for detection of these events with the James Webb Space Telescope, finding that ∼10–20 occultations per year of b and c should be above the noise level at 12–15 μm. Joint modeling of several of these PPOs could lead to a robust detection. Alternatively, observations with the proposed Origins Space Telescope should be able to detect individual PPOs at high signal-to-noise ratios. We show how PPOs can be used to break transit timing variation degeneracies, imposing strong constraints on the eccentricities and masses of the planets, as well as to constrain the longitudes of nodes and thus the complete three-dimensional structure of the system. We further show how modeling of these events can be used to reveal a planet’s day/night temperature contrast and construct crude surface maps. We make our photodynamical code available on github (https://github.com/rodluger/planetplanet).
Magnetar-powered Superluminous Supernovae Must First Be Exploded by Jets
Authors: Soker Noam , Gilkis Avishai 
Published: December 2017

Abstract
We analyze recent magnetar light-curve modeling of 38 hydrogen-poor superluminous supernovae (SLSNe) and find that the energies of the explosions themselves, which take place before the magnetar energy is released, are more than what the neutrino-driven explosion mechanism can supply for about half of the systems. These SLSNe must have been exploded by a different process than the delayed neutrino mechanism, most likely the jet feedback mechanism. The conclusion for magnetar modeling of SLSNe is that jets launched at magnetar birth cannot be ignored, not at the explosion itself and not later when mass fall-back might occur. More generally, the present analysis strengthens the call for a paradigm shift from neutrino-driven to jet-driven explosion models of all core collapse supernovae.
Statistical Hierarchy of Varying Speed of Light Cosmologies
Authors: Salzano Vincenzo , Da̧browski Mariusz P. 
Published: December 2017

Abstract
Many varying speed of light (VSL) theories have been developed recently. Here we address the issue of their observational verification in a fully comprehensive way. By using the most updated cosmological probes, we test three different candidates for a VSL theory (Barrow & Magueijo, Avelino & Martins, and Moffat). We consider many different Ansätze for both the functional form of c(z) and the dark energy dynamics. We compare these results using a reliable statistical tool such as the Bayesian evidence. We find that the present cosmological data are perfectly compatible with any of these VSL scenarios, but for the Moffat model there is a higher Bayesian evidence ratio in favor of VSL rather than the c = constant ΛCDM scenario. Moreover, in such a scenario, the VSL signal can help to strengthen constraints on the spatial curvature (with indication toward an open universe), to clarify some properties of dark energy (exclusion of a cosmological constant at

level), and is also falsifiable in the near future owing to peculiar issues that differentiate this model from the standard one. Finally, we apply an information prior and entropy prior in order to put physical constraints on the models, though still in favor Moffat’s proposal.
De la religion tranquille, au fanatisme sacrificiel
Authors: Pommier Gérard 
Published: December 2017

La religion a été le premier mode d’organisation des sociétés humaines. Elle légitimait le pouvoir politique. L’histoire des religions a évolué en allant de l’animisme au polythéisme, puis au monothéisme, pour aboutir à une forme d’athéisme pratique, relayé par une certaine idéalisation de la science. Cela veut-il dire que le sens du sacré va disparaître ? Non, car le fait religieux s’appuie sur des croyances de l’enfance, qui subsisteront sous d’autres formes, notamment grâce à la psychanalyse. Elle révèle à chacun quelle a été sa religion privée, et un sens du sacré coupé de ses attaches communautaires, si souvent aliénantes.
Diseño del modelo de vinculación en una universidad pública en México: desarrollo sustentable y responsabilidad social
Authors: Morales Espinosa Elda Aurora , Vázquez García Angel Wilhelm , Álvarez Morales Aketzalli 
Published: December 2017

Pour la conception d’un modèle le niveau « systémique » devient particulièrement important comme guide de lecture et de mise-en-œuvre des stratégies à encadrer et coordonner. La mondialisation a créé une constante d’induction des identités qui va des pays centrales industrialisés aux pays émergents vers la périphérie. Les effets négatifs de la mondialisation sur la population générale poussent les différents acteurs, les gouvernements, les entreprises, la société civile, et les établissements d’enseignement, à adopter la responsabilité sociale en réponse aux postulats du nouvel ordre économique et social qui se dégage au XXI siècle aux écarts d’inégalité. L’objectif de cette recherche est la délocalisation du débat sur la responsabilité sociale, normalement relié aux affaires, et de l’aborder à partir d’une perspective de l’université publique. Ainsi, on connaitra la mesure dans laquelle les pratiques discursives et la responsabilité sociale, répondent à un modèle d’inclusion sociale. Pour cela nous faisons une révision de la littérature internationale sur les principaux accords dans le domaine du développement durable et de la responsabilité sociale. L’objectif est de proposer un modèle de liens éducatifs pour le développement social, en mettant l’accent sur la durabilité et la responsabilité sociale.