bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finding Transitions of Physical Condition in Jets from Observations over the Range of 103–109 Schwarzschild Radii in Radio Galaxy NGC 4261
Authors: Nakahara Satomi , Doi Akihiro , Murata Yasuhiro , Hada Kazuhiro , Nakamura Masanori , Asada Keiichi 
Published: February 2018

Abstract
We report new measurements of jet width and radiation profiles along jets over the range of 103–109 Schwarzschild radius (R
S) in the nearby radio galaxy NGC 4261 using multifrequency Very Long Baseline Array (VLBA) and Very Large Array images. In the VLBA images, we found parabolic-to-conical transition signatures on both the approaching jet and counterjet width profiles at ∼104
R
S from the central engine. A transition in the radiation profile along the approaching jet was also found at ∼104
R
S clearly. Based on the consistency of the transition locations, we conclude that the physical conditions of the NGC 4261 jets change at this distance. Jet flows that change from accelerating to expanding regions were previously found in M87 and NGC 6251 and are presumably present in NGC 4261. Additionally, we found another transition in the radiation profile at ∼3 × 106
R
S in the conical region. NGC 4261 is the first case in which a jet structural transition is suggested in both the approaching and counter jets; this implies that the active galactic nucleus jet collimation process is fundamentally characterized by the global distribution of ambient pressure rather than the local interaction between the jet and the surrounding medium. We discuss the evolution of jet conditions in terms particle acceleration, cooling, dissipation, and jet pressure balance with the surrounding hot gas.
Meterwavelength Single-pulse Polarimetric Emission Survey. IV. The Period Dependence of Component Widths of Pulsars
Authors: Skrzypczak Anna , Basu Rahul , Mitra Dipanjan , Melikidze George I. , Maciesiak Krzysztof , Koralewska Olga , Filothodoros Alexandros 
Published: February 2018

Abstract
The core component width in normal pulsars, with periods (P) > 0.1 s, measured at the half-power point at 1 GHz, has a lower boundary line (LBL) that closely follows the P
−0.5 scaling relation. This result is of fundamental importance for understanding the emission process and requires extended studies over a wider frequency range. In this paper we have carried out a detailed study of the profile component widths of 123 normal pulsars observed in the Meterwavelength Single-pulse Polarimetric Emission Survey at 333 and 618 MHz. The components in the pulse profile were separated into core and conal classes. We found that at both frequencies, the core, as well as the conal component widths versus period, had a LBL that followed the P
−0.5 relation with a similar lower boundary. The radio emission in normal pulsars has been observationally shown to arise from a narrow range of heights around a few hundred kilometers above the stellar surface. In the past the P
−0.5 relation has been considered as evidence for emission arising from last open dipolar magnetic field lines. We show that the P
−0.5 dependence only holds if the trailing and leading half-power points of the component are associated with the last open field line. In such a scenario we do not find any physical motivation that can explain the P
−0.5 dependence for both core and conal components as evidence for dipolar geometry in normal pulsars. We believe the period dependence is a result of a currently unexplained physical phenomenon.
Identification of the Infrared Counterpart of SGR 1935+2154 with the Hubble Space Telescope
Authors: Levan Andrew , Kouveliotou Chryssa , Fruchter Andrew 
Published: February 2018

Abstract
We present deep Hubble Space Telescope observations of a new magnetar source, the soft gamma-repeater SGR 1935+2154, discovered by Swift. We obtained three epochs of observations: while the source was active in 2015 March, during a quiescent period in 2015 August, and during a further active phase in 2016 May. Close to the center of the X-ray error region identified by Chandra, we find a faint (F140W(AB) = 25.3) source, which fades by a factor of ∼2 over the course of 5 months between the first two epochs of observations, before rebrightening during the second active period. If this source is indeed the counterpart to SGR 1935+2154, then it is among the faintest yet located for a magnetar. Our observations are spaced over 1.3 years and enable us to place limits on the source velocity of μ = (60 ± 40) km s−1 kpc−1; observations on timescales of a decade can hence probe proper motion limits smaller than the velocities observed for the majority of pulsars. The comparison of the optical/IR and X-ray light curves of the source suggests that emission in the two regimes is associated but not directly correlated, offering support for a magnetospheric versus a fallback disk origin.
Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf
Authors: Mace Gregory N. , Mann Andrew W. , Skiff Brian A. , Sneden Christopher , Kirkpatrick J. Davy , Schneider Adam C. , Kidder Benjamin , Gosnell Natalie M. , Kim Hwihyun , Mulligan Brian W. , Prato L. , Jaffe Daniel 
Published: February 2018

Abstract
Following the discovery of the T8 subdwarf WISE J200520.38+542433.9 (Wolf 1130C), which has a proper motion in common with a binary (Wolf 1130AB) consisting of an M subdwarf and a white dwarf, we set out to learn more about the old binary in the system. We find that the A and B components of Wolf 1130 are tidally locked, which is revealed by the coherence of more than a year of V-band photometry phase-folded to the derived orbital period of 0.4967 days. Forty new high-resolution, near-infrared spectra obtained with the Immersion Grating Infrared Spectrometer provide radial velocities and a projected rotational velocity (v sin i) of 14.7 ± 0.7

for the M subdwarf. In tandem with a Gaia parallax-derived radius and verified tidal locking, we calculate an inclination of i = 29° ± 2°. From the single-lined orbital solution and the inclination we derive an absolute mass for the unseen primary (

M
⊙). Its non-detection between 0.2 and 2.5 μm implies that it is an old (>3.7 Gyr) and cool (T
eff < 7000 K) ONe white dwarf. This is the first ultramassive white dwarf within 25 pc. The evolution of Wolf 1130AB into a cataclysmic variable is inevitable, making it a potential SN Ia progenitor. The formation of a triple system with a primary mass >100 times the tertiary mass and the survival of the system through the common-envelope phase, where ∼80% of the system mass was lost, is remarkable. Our analysis of Wolf 1130 allows us to infer its formation and evolutionary history, which has unique implications for understanding low-mass star and brown dwarf formation around intermediate-mass stars.
The Intricate Structure of HH 508, the Brightest Microjet in the Orion Nebula
Authors: Wu Ya-Lin , Close Laird M. , Kim Jinyoung Serena , Males Jared R. , Morzinski Katie M. 
Published: February 2018

Abstract
We present Magellan adaptive optics Hα imaging of HH 508, which has the highest surface brightness among protostellar jets in the Orion Nebula. We find that HH 508 actually has a shorter component to the west, and a longer and knotty component to the east. The east component has a kink at 0.″3 from the jet-driving star θ
1 Ori B2, so it may have been deflected by the wind/radiation from the nearby θ
1 Ori B1B5. The origin of both components is unclear, but if each of them is a separate jet, then θ
1 Ori B2 may be a tight binary. Alternatively, HH 508 may be a slow-moving outflow, and each component represents an illuminated cavity wall. The ionization front surrounding θ
1 Ori B2B3 does not directly face θ
1 Ori B1B5, suggesting that the EUV radiation from θ
1 Ori C plays a dominant role in affecting the morphology of proplyds even in the vicinity of θ
1 Ori B1B5. Finally, we report an Hα blob that might be ejected by the binary proplyd LV 1.
Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey
Authors: Rumbaugh N. , Shen Yue , Morganson Eric , Liu Xin , Banerji M. , McMahon R. G. , Abdalla F. B. , Benoit-Lévy A. , Bertin E. , Brooks D. , Buckley-Geer E. , Capozzi D. , Carnero Rosell A. , Carrasco Kind M. , Carretero J. , Cunha C. E. , D’Andrea C. B. , da Costa L. N. , DePoy D. L. , Desai S. , Doel P. , Frieman J. , García-Bellido J. , Gruen D. , Gruendl R. A. , Gschwend J. , Gutierrez G. , Honscheid K. , James D. J. , Kuehn K. , Kuhlmann S. , Kuropatkin N. , Lima M. , Maia M. A. G. , Marshall J. L. , Martini P. , Menanteau F. , Plazas A. A. , Reil K. , Roodman A. , Sanchez E. , Scarpine V. , Schindler R. , Schubnell M. , Sheldon E. , Smith M. , Soares-Santos M. , Sobreira F. , Suchyta E. , Swanson M. E. C. , Walker A. R. , Wester W. ,   (DES Collaboration)
Published: February 2018

Abstract
We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ∼1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L
bol ∼ 1045–1047 erg s−1 and L/L
Edd ∼ 0.01–1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ∼30%–50% among all

quasars over a baseline of ∼15 yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.
SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR–M∗ Relations on Galaxy Properties
Authors: Pan Hsi-An , Lin Lihwai , Hsieh Bau-Ching , Sánchez Sebastián F. , Ibarra-Medel Héctor , Boquien Médéric , Lacerna Ivan , Argudo-Fernández Maria , Bizyaev Dmitry , Cano-Díaz Mariana , Drory Niv , Gao Yang , Masters Karen , Pan Kaike , Tabor Martha , Tissera Patricia , Xiao Ting 
Published: February 2018

Abstract
The galaxy integrated Hα star formation rate–stellar mass relation, or SFR(global)–M
*(global) relation, is crucial for understanding star formation history and evolution of galaxies. However, many studies have dealt with SFR using unresolved measurements, which makes it difficult to separate out the contamination from other ionizing sources, such as active galactic nuclei and evolved stars. Using the integral field spectroscopic observations from SDSS-IV MaNGA, we spatially disentangle the contribution from different Hα powering sources for ∼1000 galaxies. We find that, when including regions dominated by all ionizing sources in galaxies, the spatially resolved relation between Hα surface density (ΣHα
(all)) and stellar mass surface density (Σ*(all)) progressively turns over at the high Σ*(all) end for increasing M
*(global) and/or bulge dominance (bulge-to-total light ratio, B/T). This in turn leads to the flattening of the integrated Hα(global)–M
*(global) relation in the literature. By contrast, there is no noticeable flattening in both integrated Hα(H ii)–M
*(H ii) and spatially resolved ΣHα
(H ii)–Σ*(H ii) relations when only regions where star formation dominates the ionization are considered. In other words, the flattening can be attributed to the increasing regions powered by non-star-formation sources, which generally have lower ionizing ability than star formation. An analysis of the fractional contribution of non-star-formation sources to total Hα luminosity of a galaxy suggests a decreasing role of star formation as an ionizing source toward high-mass, high-B/T galaxies and bulge regions. This result indicates that the appearance of the galaxy integrated SFR–M
* relation critically depends on their global properties (M
*(global) and B/T) and relative abundances of various ionizing sources within the galaxies.
A Model for Protostellar Cluster Luminosities and the Impact on the CO–H2 Conversion Factor
Authors: Gaches Brandt A. L. , Offner Stella S. R. 
Published: February 2018

Abstract
We construct a semianalytic model to study the effect of far-ultraviolet (FUV) radiation on gas chemistry from embedded protostars. We use the protostellar luminosity function (PLF) formalism of Offner & McKee to calculate the total, FUV, and ionizing cluster luminosity for various protostellar accretion histories and cluster sizes. We2 compare the model predictions with surveys of Gould Belt star-forming regions and find that the tapered turbulent core model matches best the mean luminosities and the spread in the data. We combine the cluster model with the photodissociation region astrochemistry code, 3d-pdr, to compute the impact of the FUV luminosity from embedded protostars on the CO-to-H2 conversion factor, X
CO, as a function of cluster size, gas mass, and star formation efficiency. We find that X
CO has a weak dependence on the FUV radiation from embedded sources for large clusters owing to high cloud optical depths. In smaller and more efficient clusters the embedded FUV increases X
CO to levels consistent with the average Milky Way values. The internal physical and chemical structures of the cloud are significantly altered, and X
CO depends strongly on the protostellar cluster mass for small efficient clouds.
Are DY Persei Stars Cooler Cousins of R Coronae Borealis Stars?
Authors: Bhowmick Anirban , Pandey Gajendra , Joshi Vishal , Ashok N. M. 
Published: February 2018

Abstract
In this paper we present, for the first time, the study of low resolution H- and K-band spectra of 7 DY Per type and suspect stars, as well as DY Persei itself. We also observed H- and K-band spectra of 3 R Coronae Borealis (RCB) stars, 1 hydrogen-deficient carbon (HdC) star, and 14 cool carbon stars, including normal giants as comparisons. High 12C/13C and low 16O/18O ratios are characteristic features of majority RCBs and HdCs. We have estimated 16O/18O ratios of the program stars from the relative strengths of the 12C16O and 12C18O molecular bands observed in K-band. Our preliminary analysis suggests that a quartet of the DY Per suspects, along with DY Persei itself, seem to show isotopic ratio strength consistent with that of RCB/HdC stars, whereas two of them do not show significant 13C and 18O in their atmospheres. Our analysis provides further indications that DY Per type stars could be related to the RCB/HdC class of stars.
Kronos and Krios: Evidence for Accretion of a Massive, Rocky Planetary System in a Comoving Pair of Solar-type Stars
Authors: Oh Semyeong , Price-Whelan Adrian M. , Brewer John M. , Hogg David W. , Spergel David N. , Myles Justin 
Published: February 2018

Abstract
We report and discuss the discovery of a significant difference in the chemical abundances of a comoving pair of bright solar-type stars, HD 240430 and HD 240429. The two stars have an estimated 3D separation of ≈0.6 pc (≈0.01 pc projected) at a distance of r ≈ 100 pc with nearly identical 3D velocities, as inferred from Gaia TGAS parallaxes and proper motions, and high-precision radial velocity measurements. Stellar parameters determined from high-resolution spectra obtained with the High Resolution Echelle Spectrometer (HIRES) at the Keck Observatory indicate that the two stars are ∼4 Gyr old. The more metal-rich of the two, HD 240430, shows an enhancement of refractory (

K) elements by ≈0.2 dex and a marginal enhancement of (moderately) volatile elements (

K;

,

,

,

, and

). This is the largest metallicity difference found in a wide binary pair to date. Additionally, HD 240430 shows an anomalously high surface lithium abundance (

), higher than its cooler companion by 0.5 dex. The proximity in phase-space and ages between the two stars suggests that they formed together with the same composition, which is at odds with the observed differences in metallicity and abundance patterns. We therefore suggest that the star HD 240430, “Kronos,” accreted

of rocky material after birth, selectively enhancing the refractory elements as well as lithium in its surface and convective envelope.
Evidence for the Magnetic Breakout Model in an Equatorial Coronal-hole Jet
Authors: Kumar Pankaj , Karpen Judith T. , Antiochos Spiro K. , Wyper Peter F. , DeVore C. Richard , DeForest Craig E. 
Published: February 2018

Abstract
Small, impulsive jets commonly occur throughout the solar corona, but are especially visible in coronal holes. Evidence is mounting that jets are part of a continuum of eruptions that extends to much larger coronal mass ejections and eruptive flares. Because coronal-hole jets originate in relatively simple magnetic structures, they offer an ideal testbed for theories of energy buildup and release in the full range of solar eruptions. We analyzed an equatorial coronal-hole jet observed by the Solar Dynamics Observatory (SDO)/AIA on 2014 January 9 in which the magnetic-field structure was consistent with the embedded-bipole topology that we identified and modeled previously as an origin of coronal jets. In addition, this event contained a mini-filament, which led to important insights into the energy storage and release mechanisms. SDO/HMI magnetograms revealed footpoint motions in the primary minority-polarity region at the eruption site, but show negligible flux emergence or cancellation for at least 16 hr before the eruption. Therefore, the free energy powering this jet probably came from magnetic shear concentrated at the polarity inversion line within the embedded bipole. We find that the observed activity sequence and its interpretation closely match the predictions of the breakout jet model, strongly supporting the hypothesis that the breakout model can explain solar eruptions on a wide range of scales.
Characterizing the Variable Dust Permeability of Planet-induced Gaps
Authors: Weber Philipp , Benítez-Llambay Pablo , Gressel Oliver , Krapp Leonardo , Pessah Martin E. 
Published: February 2018

Abstract
Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can significantly alter the dust dynamics. In this paper, we carry out a systematic study employing long-term numerical simulations aimed at characterizing the critical particle size for retention outside a gap as a function of particle size, as well as various key parameters defining the protoplanetary disk model. To this end, we perform multifluid hydrodynamical simulations in two dimensions, including different dust species, which we treat as pressureless fluids. We initialize the dust outside of the planet’s orbit and study under which conditions dust grains are able to cross the gap carved by the planet. In agreement with previous work, we find that the permeability of the gap depends both on dust dynamical properties and the gas disk structure: while small dust follows the viscously accreting gas through the gap, dust grains approaching a critical size are progressively filtered out. Moreover, we introduce and compute a depletion factor that enables us to quantify the way in which higher viscosity, smaller planet mass, or a more massive disk can shift this critical size to larger values. Our results indicate that gap-opening planets may act to deplete the inner reaches of protoplanetary disks of large dust grains—potentially limiting the accretion of solids onto forming terrestrial planets.
Modulation of Galactic Cosmic Rays in the Inner Heliosphere over Solar Cycles
Authors: Shen Z.-N. , Qin G. 
Published: February 2018

Abstract
The 11- and 22-year modulation of galactic cosmic rays (GCRs) in the inner heliosphere is studied using a numerical model developed by Qin and Shen in 2017. Based on the numerical solutions of Parker’s transport equations, the model incorporates a modified Parker heliospheric magnetic field, a locally static time-delayed heliosphere, and a time-dependent diffusion coefficients model in which an analytical expression of the variation of magnetic turbulence magnitude throughout the inner heliosphere is applied. Furthermore, during solar maximum, the solar magnetic polarity is determined randomly with the possibility of A > 0 decided by the percentage of the solar north polar magnetic field being outward and the solar south polar magnetic field being inward. The computed results are compared at various energies with several GCR observations, e.g., the Interplanetary Monitoring Platform
8 (IMP 8), EPHIN on board the Solar and Heliospheric Observatory (SOHO), Ulysses, and Voyager 1 and 2, and they show good agreement. We show that our model has successfully reproduced the 11- and 22-year modulation cycles.
The Global and Radial Stellar Mass Assembly of Milky Way-sized Galaxies
Authors: Avila-Reese Vladimir , González-Samaniego Alejandro , Colín Pedro , Ibarra-Medel Héctor , Rodríguez-Puebla Aldo 
Published: February 2018

Abstract
We study the global and radial stellar mass assembly of eight zoomed-in Milky Way (MW)-sized galaxies produced in hydrodynamics cosmological simulations. The disk-dominated galaxies (four) show a fast initial stellar mass growth in the innermost parts, driven mostly by in situ star formation (SF), but since z ∼ 2−1, the SF has entered a long-term quenching phase. The outer regions follow this trend but more gently, as they are more external. As a result, the radial stellar mass growth is highly inside-out due to both inside-out structural growth and inside-out SF quenching. The half-mass radius evolves fast; for instance,

(z = 1) < 0.5

(z = 0). Two other runs resemble lenticular galaxies. One also shows a pronounced inside-out growth, and the other one presents a nearly uniform radial mass assembly. The other two galaxies suffered late major mergers. Their normalized radial mass growth histories (MGHs) are very close, but with periods of outside-in assembly during or after the mergers. For all of the simulations, the archaeological radial MGHs calculated from the z = 0 stellar particle age distribution are similar to current MGHs, which shows that the mass assembly by ex situ stars and the radial mass transport do not significantly change their radial mass distributions. Our results agree qualitatively with observational inferences from the fossil record method applied to a survey of local galaxies and from look-back observations of progenitors of MW-sized galaxies. However, the inside-out growth mode is more pronounced, and the

growth is faster in simulations than in observational inferences.