scholarly journals Narrow, intrinsic C iv absorption in quasars as it relates to outflows, orientation, and radio properties

2019 ◽  
Vol 488 (4) ◽  
pp. 5916-5934
Author(s):  
Robert B Stone ◽  
Gordon T Richards
Keyword(s):  
Radio Emission ◽  
Velocity Distribution ◽  
Spectral Index ◽  
Large Fraction ◽  
Accretion Disc ◽  
Line Of Sight ◽  
Intrinsic Properties ◽  
Disc Model ◽  
Standard Models ◽  
The Relationship

Abstract This work provides evidence that a large fraction of C iv narrow absorption lines (NALs) seen along the line of sight to distant quasars are due to accretion disc winds, while also seeking to understand the relationship between NALs and certain quasar-intrinsic properties. We extend the results from past work in the literature using ${\sim}105\, 000$ NALs from a sample of ${\sim}58\, 000$ SDSS quasars. The primary results of this work are summarized as follows: (1) the velocity distribution (dN/dβ) of NALs is not a function of radio loudness (or even detection) once marginalized by optical/UV luminosity; (2) there are significant differences in the number and distribution of NALs as a function of both radio spectral index and optical/UV luminosity, and these two findings are not entirely interdependent; (3) improvements in quasar systemic redshift measurements and differences in the NAL distribution as a combined function of optical luminosity and radio spectral index together provide evidence that a significant portion of NALs are due to outflows; (4) the results are consistent with standard models of accretion disc winds governed by the LUV–αox relationship and line-of-sight orientation indicated by radio spectral index, and (5) possibly support a magnetically arrested disc model as an explanation for the semistochastic nature of strong radio emission in a fraction of quasars.

Theoretical Approaches to the Functions of Indefinite Pronouns

2017 ◽  
Author(s):  
Martin Haspelmath
Keyword(s):  
Semantic Features ◽  
Semantic Change ◽  
Intrinsic Properties ◽  
Theoretical Approaches ◽  
Mental Spaces ◽  
Logical Semantics ◽  
The Relationship ◽  
Indefinite Pronouns

This chapter focuses on various theoretical approaches to the semantic and syntactic functions of indefinite pronouns. It begins with a discussion of structuralist semantics, which suggests that language is a system whose parts must be defined and described on the basis of their place in the system and their relation to each other, rather than on the basis of their own intrinsic properties. It then considers some of the problems associated with structuralist semantics, including the unclear status of the semantic features; significant overlap of the functions of grammatical items in many areas, including indefinite pronouns; and structuralist semantics makes wrong predictions about semantic change. The chapter proceeds by analysing logical semantics and the issues raised by this approach, along with syntactic approaches, the theory of mental spaces, pragmatic scales and scale reversal. Finally, it explains the relationship between focusing and sentence accent.

On the Relationship between Alonso's Theory of Movement and Wilson's Family of Spatial-Interaction Models

1981 ◽  
Vol 13 (2) ◽  
pp. 217-224 ◽  
Author(s):  
J Ledent
Keyword(s):  
Input Data ◽  
Spatial Interaction ◽  
System Of Equations ◽  
Interaction Models ◽  
Spatial Interaction Models ◽  
Standard Family ◽  
Original Contribution ◽  
Standard Models ◽  
The Relationship

This paper compares the system of equations underlying Alonso's theory of movement with that of Wilson's standard family of spatial-interaction models. It is shown that the Alonso model is equivalent to one of Wilson's four standard models depending on the assumption at the outset about which of the total outflows and/or inflows are known. This result turns out to supersede earlier findings—inconsistent only in appearance—which were derived independently by Wilson and Ledent. In addition to this, an original contribution of this paper—obtained as a byproduct of the process leading to the aforementioned result—is to provide an exact methodology permitting one to solve the Alonso model for each possible choice of the input data.

scholarly journals Investigating hot-Jupiter inflated radii with hierarchical Bayesian modelling

2018 ◽  
Vol 616 ◽  
pp. A76 ◽  
Author(s):  
Marko Sestovic ◽  
Brice-Olivier Demory ◽  
Didier Queloz
Keyword(s):  
Large Fraction ◽  
Population Level ◽  
Mass Range ◽  
Hierarchical Bayesian ◽  
Incident Flux ◽  
Hot Jupiters ◽  
Probabilistic Relation ◽  
Relationship Of ◽  
The Relationship ◽  
Level Analysis

Context. As of today, hundreds of hot Jupiters have been found, yet the inflated radii of a large fraction of them remain unexplained. A number of mechanisms have been proposed to explain these anomalous radii, however most of these can only work under certain conditions and may not be sufficient to explain the most extreme cases. It is still unclear whether a single mechanism can sufficiently explain the entire distribution of radii, or whether a combination of these mechanisms is needed. Aims. We seek to understand the relationship of radius with stellar irradiation and mass and to find the range of masses over which hot Jupiters are inflated. We also aim to find the intrinsic physical scatter in their radii, caused by unobservable parameters, and to constrain the fraction of hot Jupiters that exhibit inflation. Methods. By constructing a hierarchical Bayesian model, we inferred the probabilistic relation between planet radius, mass, and incident flux for a sample of 286 gas giants. We separately incorporated the observational uncertainties of the data and the intrinsic physical scatter in the population. This allowed us to treat the intrinsic physical scatter in radii, due to latent parameters such as the heavy element fraction, as a parameter to be inferred. Results. We find that the planetary mass plays a key role in the inflation extent and that planets in the range ~0.37−0.98  MJ show the most inflated radii. At higher masses, the radius response to incident flux begins to decrease. Below a threshold of 0.37 ± 0.03  MJ we find that giant exoplanets as a population are unable to maintain inflated radii ≿1.4  RJ but instead exhibit smaller sizes as the incident flux is increased beyond 106 W m−2. We also find that below 1  MJ, there is a cut-off point at high incident flux beyond which we find no more inflated planets, and that this cut-off point decreases as the mass decreases. At incident fluxes higher than ~1.6 × 106 W m−2 and in a mass range 0.37−0.98  MJ, we find no evidence for a population of non-inflated hot Jupiters. Our study sheds a fresh light on one of the key questions in the field and demonstrates the importance of population-level analysis to grasp the underlying properties of exoplanets.

scholarly journals An Accretion-Disc Model for the Algol-Type Eclipsing Binary System AV Del

2011 ◽  
Vol 28 (1) ◽  
pp. 38-45 ◽  
Author(s):  
S. M. R. Ghoreyshi ◽  
J. Ghanbari ◽  
F. Salehi
Keyword(s):  
Binary System ◽  
Radial Velocity ◽  
Outer Radius ◽  
Accretion Disc ◽  
Physical Parameters ◽  
Primary Star ◽  
Eclipsing Binary ◽  
Disc Model ◽  
The Absolute

AbstractThis study inspects the light and radial-velocity curves of the eclipsing binary AV Del. In comparison with other studies already done, the study shows that the absolute elements, fundamental orbital and physical parameters of the system can be determined using the Wilson-Devinney code. Using these parameters, the configuration of the system is presented. Then, an accretion disc model for the system is introduced by using the shellspec code. The results indicate that AV Del is a semi-detached system in which an optically thick accretion disc is surrounding the primary star. The outer radius of the disc is 8.0 R⊙, corresponding to a distance of 1.1 R⊙ from the surface of the secondary. Also, the temperature of the disc is calculated to be T = 5700 K.

scholarly journals Accretion-disc model spectra for dwarf-nova stars

2010 ◽  
Vol 519 ◽  
pp. A117 ◽  
Author(s):  
I. Idan ◽  
J.-P. Lasota ◽  
J.-M. Hameury ◽  
G. Shaviv
Keyword(s):  
Accretion Disc ◽  
Dwarf Nova ◽  
Disc Model

scholarly journals Thermal radio absorption as a tracer of the interaction of SNRs with their environments

2021 ◽  
Vol 653 ◽  
pp. A62
Author(s):  
G. Castelletti ◽  
L. Supan ◽  
W. M. Peters ◽  
N. E. Kassim
Keyword(s):  
Spectral Index ◽  
Supernova Remnants ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Power Laws ◽  
Line Of Sight ◽  
Pulsar Wind Nebulae ◽  
Very Large Array ◽  
Murchison Widefield Array ◽  
Thermal Absorption

We present new images and continuum spectral analysis for 14 resolved Galactic supernova remnants (SNRs) selected from the 74 MHz Very Large Array Low-Frequency Sky Survey Redux (VLSSr). We combine new integrated measurements from the VLSSr with, when available, flux densities extracted from the Galactic and Extragalactic All-Sky Murchison Widefield Array Survey and measurements from the literature to generate improved integrated continuum spectra sampled from ~15 MHz to ~217 GHz. We present the VLSSr images. When possible we combine them with publicly available images at 1.4 GHz, to analyse the resolved morphology and spectral index distribution across each SNR. We interpret the results and look for evidence of thermal absorption caused by ionised gas either proximate to the SNR itself, or along its line of sight. Three of the SNRs, G4.5+6.8 (Kepler), G28.6−0.1, and G120.1+1.4 (Tycho), have integrated spectra which can be adequately fit with simple power laws. The resolved spectral index map for Tycho confirms internal absorption which was previously detected by the Low Frequency Array, but it is insufficient to affect the fit to the integrated spectrum. Two of the SNRs are pulsar wind nebulae, G21.5−0.9 and G130.7+3.1 (3C 58). For those we identify high-frequency spectral breaks at 38 and 12 GHz, respectively. For the integrated spectra of the remaining nine SNRs, a low frequency spectral turnover is necessary to adequately fit the data. In all cases we are able to explain the turnover by extrinsic thermal absorption. For G18.8+0.3 (Kes 67), G21.8−0.6 (Kes 69), G29.7−0.3 (Kes 75), and G41.1−0.3 (3C 397), we attribute the absorption to ionised gas along the line of sight, possibly from extended H II region envelopes. For G23.3−0.3 (W41) the absorption can be attributed to H II regions located in its immediate proximity. Thermal absorption from interactions at the ionised interface between SNR forward shocks and the surrounding medium were previously identified as responsible for the low frequency turnover in SNR G31.9+0.0 (3C 391); our integrated spectrum is consistent with the previous results. We present evidence for the same phenomenon in three additional SNRs G27.4+0.0 (Kes 73), G39.2–0.3 (3C 396), and G43.3–0.2 (W49B), and derive constraints on the physical properties of the interaction. This result indicates that interactions between SNRs and their environs should be readily detectable through thermal absorption by future low frequency observations of SNRs with improved sensitivity and resolution.

Microstructure of Agglomerates of Nanometer Particles

1995 ◽  
Vol 380 ◽  
Author(s):  
Alfred P. Weber ◽  
James D. Thorne ◽  
Sheldon K. Friedlander
Keyword(s):  
Fractal Dimension ◽  
Laser Ablation ◽  
Coordination Number ◽  
Computer Simulations ◽  
Large Fraction ◽  
Low Density ◽  
Nanometer Particles ◽  
The Relationship

ABSTRACTThe microstructure of an agglomerate can be characterized by the coordination number. The relationship between the fractal dimension and the coordination number of agglomerates of nanometer particles was investigated in experiments and computer simulations. The results for silver agglomerates formed by laser ablation agreed well with the simulations. The coordination number is low for low density fractals because of the large fraction of surface particles which have fewer bonds. The sensitivity of the coordination number to the fractal dimension increases with increasing fractal dimension.

scholarly journals Non-thermal radio emission in Wolf-Rayet stars: is binarity a pre-requisite?

1999 ◽  
Vol 193 ◽  
pp. 348-349
Author(s):  
Sean M. Dougherty
Keyword(s):  
Radio Emission ◽  
Spectral Index ◽  
Thermal Emission ◽  
Radio Observations ◽  
Thermal Radio ◽  
Thermal Radio Emission ◽  
Thermal Emitters

Radio observations of Wolf-Rayet stars currently available in the literature are examined to determine whether binarity is a common feature of WR systems with non-thermal emission. Among 24 stars with observed spectral index values, seven are definite non-thermal emitters, and six others possibly have composite thermal/non-thermal spectra. Stellar companions have been identified in 71% of the non-thermal emitters, strongly supporting a link between non-thermal emission and binarity.

scholarly journals What Mechanism Depolarizes the Emission from the SW Arm of M31?

1990 ◽  
Vol 140 ◽  
pp. 201-202
Author(s):  
E.M. Berkhuijsen ◽  
R. Beck
Keyword(s):  
Radio Emission ◽  
Line Of Sight ◽  
Rotation Measure ◽  
Faraday Effects

Gradients in rotation measure and dispersion in rotation measure, both across the telescope beam, depolarize the radio emission from the SW arm of M31. Faraday effects along the line of sight appear to be negligible.

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