scholarly journals From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context

2018 ◽  
Vol 617 ◽  
pp. A110 ◽  
Author(s):  
Vivien Parmentier ◽  
Mike R. Line ◽  
Jacob L. Bean ◽  
Megan Mansfield ◽  
Laura Kreidberg ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Spectral Features ◽  
Chemical Abundances ◽  
Hot Jupiters ◽  
New Class ◽  
Thermal Structures ◽  
Water Band ◽  
Order Of Magnitude ◽  
Molecular Bond ◽  
Analytical Quantification

Context. A new class of exoplanets has emerged: the ultra hot Jupiters, the hottest close-in gas giants. The majority of them have weaker-than-expected spectral features in the 1.1−1.7 μm bandpass probed by HST/WFC3 but stronger spectral features at longer wavelengths probed by Spitzer. This led previous authors to puzzling conclusions about the thermal structures and chemical abundances of these planets. Aims. We investigate how thermal dissociation, ionization, H− opacity, and clouds shape the thermal structures and spectral properties of ultra hot Jupiters. Methods. We use the SPARC/MITgcm to model the atmospheres of four ultra hot Jupiters and discuss more thoroughly the case of WASP-121b. We expand our findings to the whole population of ultra hot Jupiters through analytical quantification of the thermal dissociation and its influence on the strength of spectral features. Results. We predict that most molecules are thermally dissociated and alkalies are ionized in the dayside photospheres of ultra hot Jupiters. This includes H2O, TiO, VO, and H2 but not CO, which has a stronger molecular bond. The vertical molecular gradient created by the dissociation significantly weakens the spectral features from H2O while the 4.5 μm CO feature remains unchanged. The water band in the HST/WFC3 bandpass is further weakened by the continuous opacity of the H− ions. Molecules are expected to recombine before reaching the limb, leading to order of magnitude variations of the chemical composition and cloud coverage between the limb and the dayside. Conclusions. Molecular dissociation provides a qualitative understanding of the lack of strong spectral features of water in the 1−2 μm bandpass observed in most ultra hot Jupiters. Quantitatively, our model does not provide a satisfactory match to the WASP-121b emission spectrum. Together with WASP-33b and Kepler-33Ab, they seem the outliers among the population of ultra hot Jupiters, in need of a more thorough understanding.

scholarly journals Carbon-loud SDSS BOSS type II quasars at z > 2: high-density gas or secondary production of carbon?

2020 ◽  
Vol 495 (4) ◽  
pp. 4707-4746
Author(s):  
M Silva ◽  
A Humphrey ◽  
P Lagos ◽  
S G Morais
Keyword(s):  
Abundance Ratio ◽  
Systematic Difference ◽  
Sloan Digital Sky Survey ◽  
Type Ii ◽  
Narrow Line ◽  
Chemical Abundances ◽  
Gas Density ◽  
Chemical Enrichment ◽  
Order Of Magnitude ◽  
Nitrogen Abundance

ABSTRACT We study the ultraviolet (UV) emission-line ratios of a sample of 145 type II quasars (QSO2s) from Sloan Digital Sky Survey iii Baryon Oscillation Spectroscopic Survey, and compare against a grid of active galactic nucleus (AGN) photoionization models with a range in gas density, gas chemical abundances, and ionization parameter. Most of the quasars are ‘carbon-loud’, with C  iv/He ii ratios that are unusually high for the narrow-line region, implying higher than expected gas density (>106 cm−3) and/or significantly supersolar-relative carbon abundance. We also find that solar or supersolar nitrogen abundance and metallicity are required in the majority of our sample, with potentially significant variation between objects. Compared to radio galaxies at similar redshifts (HzRGs; z > 2), the QSO2s are offset to higher N  v/He ii, C  iv/He ii, and C iii]/He ii, suggesting systematically higher gas density and/or systematically higher C and N abundances. We find no evidence for a systematic difference in the N/C abundance ratio between the two types of objects. Scatter in the N  iv]/C  iv ratio implies a significant scatter in the N/C abundance ratio among the QSO2s and HzRGs, consistent with differences in the chemical enrichment histories between objects. Interestingly, we find that adopting secondary behaviour for both N and C alleviates the long-standing ‘N  iv] problem’. A subset of the QSO2s and HzRGs also appear to be ‘silicon-loud’, with Si iii] relative fluxes suggesting Si/C and Si/O are an order of magnitude above their solar values. Finally, we propose new UV-line criteria to select genuine QSO2s with low-density narrow-line regions.

scholarly journals Environmental SEMs: A New Way to Look at Samples

1995 ◽  
Vol 3 (8) ◽  
pp. 14-15
Author(s):  
Don Chernoff ◽  
Mohammad Salim Mujallid
Keyword(s):  
High Vacuum ◽  
Chamber Pressure ◽  
Variable Pressure ◽  
New Class ◽  
The Past ◽  
Order Of Magnitude ◽  
Differential Pumping ◽  
New Applications ◽  
Magnitude Increase ◽  
Environmental Sem

A new class of SEM has evolved over the past few years which provides some startling capabilities never before available to electron microscopists. These instruments, typically referred to as environmental SEMs or variable pressure SEMs. have opened up a host of new applications that are difficult or impossible with a standard SEM. Many of the constraints of sample preparation and handling that exist with a conventional SEM do not apply to environmental SEMs.An environmental SEM functions like a conventional SEM except that you can introduce air or any other gas into the chamber and raise the chamber pressure above the normal high vacuum range of 10-5 or 10-6 Torr. Inmost instruments the vacuum can be raised to as much as 1 Torr. This represents a 6 order of magnitude increase in chamber pressure. Environmental SEMs can achieve this high chamber pressure without damage to the electron source by using differential pumping apertures in the column.

scholarly journals N II λλ5668−5712: A NEW CLASS OF SPECTRAL FEATURES IN ETA CARINAE $^,$

2011 ◽  
Vol 737 (2) ◽  
pp. 70 ◽  
Author(s):  
Andrea Mehner ◽  
Kris Davidson ◽  
Gary J. Ferland
Keyword(s):  
Spectral Features ◽  
Eta Carinae ◽  
New Class

scholarly journals Probing the Interiors of Very Hot Jupiters Using Transit Light Curves

2008 ◽  
Vol 4 (S253) ◽  
pp. 163-169
Author(s):  
Aaron S. Wolf ◽  
Darin Ragozzine
Keyword(s):  
Light Curves ◽  
Small Signal ◽  
Interior Structure ◽  
Love Number ◽  
Hot Jupiters ◽  
Long Baseline ◽  
Future Space ◽  
Order Of Magnitude ◽  
Formation And Evolution ◽  
In Transit

AbstractAccurately understanding the interior structure of extra-solar planets is critical for inferring their formation and evolution and resolving the origin of anomalous planetary radii. The internal density distribution of the planet has a direct effect on the star-planet orbit through the gravitational quadrupole of rotational and tidal bulges, measured by the planetary Love number (k2p, twice the apsidal motion constant). We find that the quadrupole of the planetary tidal bulges dominates the rate of apsidal precession of single very hot Jupiters by more than an order of magnitude over general relativity and the stellar quadrupole. For the shortest-period planets, the planetary interior induces precession of a few degrees per year. By investigating the full photometric signal of apsidal precession, we find that transit timing induces a relatively small signal compared to the changes in transit shapes. With its long baseline of ultra-precise photometry, the future space-based Kepler mission should be able to realistically detect the presence or absence of a core in very hot Jupiters with orbital eccentricities as low as e ~ 0.001. We show that the signal due to k2p is not degenerate with other parameters and has a unique signature on the transit light curve. This technique, outlined in more detail in Ragozzine & Wolf 2008 provides the first readily employed method for directly probing the interiors of extra-solar planets.

scholarly journals Effects of Flux Tubes on Conventional Chromospheric Diagnostics

1980 ◽  
Vol 51 ◽  
pp. 299-299
Author(s):  
Thomas R. Ayres
Keyword(s):  
Magnetic Flux ◽  
High Pressures ◽  
Temperature Inversion ◽  
Microwave Emission ◽  
Energy Budgets ◽  
Chemical Abundances ◽  
Important Distinction ◽  
Flux Tubes ◽  
Order Of Magnitude ◽  
Magnetic Flux Tubes

AbstractMagnetic flux tubes are usually envisioned as small discrete structures sparsely distributed throughout an otherwise uniform “intertube” medium. An important distinction between the flux tubes and the surrounding atmosphere is the presence of a strong chromospheric temperature inversion at high pressures in the flux tubes, while the intertube component has only a mild, low pressure chromosphere, if any at all. This implies that the flux tubes will be enormously brighter in conventional chromospheric diagnostics than the intertube component. However, the unresolved magnetic elements cover perhaps only 10% of the “quiet” Sun at chromospheric heights. Consequently the intense K and k emission cores are severely diluted. The net result is a weak emission reversal that is not characteristic of either the flux tube or intertube chromosphere. Even in the thermal microwave continuum longward of 100 μm, the flux tubes can contribute significantly to low spatial resolution spectra. Consequently, the spatially averaged microwave emission is also not characteristic of either of the distinct components.If magnetic flux tubes are indeed the dominant class of atmospheric inhomogeneity in the Sun and other cool stars, then single-component interpretations of spatially unresolved data can be completely misleading, especially for inferring important auxiliary quantities, for example chemical abundances, line broadening parameters and chromospheric energy budgets. In the latter case, chromospheric radiative cooling rates derived from empirical mean models could be overestimated by up to an order of magnitude.

scholarly journals Adaptive Framework for Multi-Feature Hybrid Object Tracking

2018 ◽  
Vol 8 (11) ◽  
pp. 2294 ◽  
Author(s):  
Ahmad Khattak ◽  
Gulistan Raja ◽  
Nadeem Anjum
Keyword(s):  
Object Tracking ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Research Paper ◽  
Tracking Accuracy ◽  
Intelligent Decision Making ◽  
New Class ◽  
Intelligent Decision ◽  
Order Of Magnitude ◽  
High Level

Object tracking is a computer vision task deemed necessary for high-level intelligent decision-making algorithms. Researchers have merged different object tracking techniques and discovered a new class of hybrid algorithms that is based on embedding a meanshift (MS) optimization procedure into the particle filter (PF) (MSPF) to replace its inaccurate and expensive particle validation processes. The algorithm employs a combination of predetermined features, implicitly assuming that the background will not change. However, the assumption of fully specifying the background of the object may not often hold, especially in an uncontrolled environment. The first innovation of this research paper is the development of a dynamically adaptive multi-feature framework for MSPF (AMF-MSPF) in which features are ranked by a ranking module and the top features are selected on-the-fly. As a consequence, it improves local discrimination of the object from its immediate surroundings. It is also highly desirable to reduce the already complex framework of the MSPF to save resources to implement a feature ranking module. Thus, the second innovation of this research paper introduces a novel technique for the MS optimization method, which reduces its traditional complexity by an order of magnitude. The proposed AMF-MSPF framework is tested on different video datasets that exhibit challenging constraints. Experimental results have shown robustness, tracking accuracy and computational efficiency against these constraints. Comparison with existing methods has shown significant improvements in term of root mean square error (RMSE), false alarm rate (FAR), and F-SCORE.

scholarly journals Lower bounds to eigenvalues of the Schrödinger equation by solution of a 90-y challenge

2020 ◽  
Vol 117 (28) ◽  
pp. 16181-16186
Author(s):  
Rocco Martinazzo ◽  
Eli Pollak
Keyword(s):  
Lower Bound ◽  
Lower Bounds ◽  
Upper Bound ◽  
Spectral Features ◽  
Numerical Examples ◽  
Tunneling Splittings ◽  
Order Of Magnitude ◽  
Bound Theorem ◽  
Math Phys ◽  
Better Than

The Ritz upper bound to eigenvalues of Hermitian operators is essential for many applications in science. It is a staple of quantum chemistry and physics computations. The lower bound devised by Temple in 1928 [G. Temple,Proc. R. Soc. A Math. Phys. Eng. Sci.119, 276–293 (1928)] is not, since it converges too slowly. The need for a good lower-bound theorem and algorithm cannot be overstated, since an upper bound alone is not sufficient for determining differences between eigenvalues such as tunneling splittings and spectral features. In this paper, after 90 y, we derive a generalization and improvement of Temple’s lower bound. Numerical examples based on implementation of the Lanczos tridiagonalization are provided for nontrivial lattice model Hamiltonians, exemplifying convergence over a range of 13 orders of magnitude. This lower bound is typically at least one order of magnitude better than Temple’s result. Its rate of convergence is comparable to that of the Ritz upper bound. It is not limited to ground states. These results complement Ritz’s upper bound and may turn the computation of lower bounds into a staple of eigenvalue and spectral problems in physics and chemistry.

scholarly journals The origin and evolution of dense regions in the ISM, and their role in spectral features

2012 ◽  
Vol 8 (S292) ◽  
pp. 99-99
Author(s):  
Diego Falceta-Gonçalves
Keyword(s):  
Spectral Line ◽  
Numerical Simulations ◽  
Molecular Clouds ◽  
Spectral Features ◽  
Line Profiles ◽  
Origin And Evolution ◽  
Secular Evolution ◽  
Theoretical Assumptions ◽  
Order Of Magnitude

AbstractIn this work we discuss the turbulent evolution of molecular clouds and the formation of dense structures within. Typically, the clumps evolution occurs apart from the secular evolution of the turbulent mother cloud due to its high density and large inertia. Despite of current theoretical assumptions we show, by means of numerical simulations, that the clump lifetimes are greater than previously thought by more than an order of magnitude. The presence of dense and long-lived clumps modifies the spectral line profiles of clouds, which are strongly related to the determination of Larson's relations. We address the main modifications of these if a realistic distribution of dense structures is taken into account.

scholarly journals LAMOST telescope reveals that Neptunian cousins of hot Jupiters are mostly single offspring of stars that are rich in heavy elements

2017 ◽  
Vol 115 (2) ◽  
pp. 266-271 ◽  
Author(s):  
Subo Dong ◽  
Ji-Wei Xie ◽  
Ji-Lin Zhou ◽  
Zheng Zheng ◽  
Ali Luo
Keyword(s):  
Main Sequence ◽  
The Other ◽  
Heavy Elements ◽  
Main Sequence Stars ◽  
Hot Jupiters ◽  
Transiting Planets ◽  
Short Period ◽  
Data Release ◽  
Order Of Magnitude ◽  
Solar Type

We discover a population of short-period, Neptune-size planets sharing key similarities with hot Jupiters: both populations are preferentially hosted by metal-rich stars, and both are preferentially found in Kepler systems with single-transiting planets. We use accurate Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) stellar parameters for main-sequence stars to study the distributions of short-period (1d<P<10d)Kepler planets as a function of host star metallicity. The radius distribution of planets around metal-rich stars is more “puffed up” compared with that around metal-poor hosts. In two period–radius regimes, planets preferentially reside around metal-rich stars, while there are hardly any planets around metal-poor stars. One is the well-known hot Jupiters, and the other one is a population of Neptune-size planets (2R⊕≲Rp≲6R⊕), dubbed “Hoptunes.” Also like hot Jupiters, Hoptunes occur more frequently in systems with single-transiting planets although the fraction of Hoptunes occurring in multiples is larger than that of hot Jupiters. About 1% of solar-type stars host Hoptunes, and the frequencies of Hoptunes and hot Jupiters increase with consistent trends as a function of [Fe/H]. In the planet radius distribution, hot Jupiters and Hoptunes are separated by a “valley” at approximately Saturn size (in the range of 6R⊕≲Rp≲10R⊕), and this “hot-Saturn valley” represents approximately an order-of-magnitude decrease in planet frequency compared with hot Jupiters and Hoptunes. The empirical “kinship” between Hoptunes and hot Jupiters suggests likely common processes (migration and/or formation) responsible for their existence.

scholarly journals Giant nonvolatile resistive switching in a Mott oxide and ferroelectric hybrid

2019 ◽  
Vol 116 (18) ◽  
pp. 8798-8802 ◽  
Author(s):  
Pavel Salev ◽  
Javier del Valle ◽  
Yoav Kalcheim ◽  
Ivan K. Schuller
Keyword(s):  
Phase Transition ◽  
Electronic Properties ◽  
Real Time ◽  
Resistive Switching ◽  
Structural Phase ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Practical Applications ◽  
New Class ◽  
Order Of Magnitude

Controlling the electronic properties of oxides that feature a metal–insulator transition (MIT) is a key requirement for developing a new class of electronics often referred to as “Mottronics.” A simple, controllable method to switch the MIT properties in real time is needed for practical applications. Here we report a giant, nonvolatile resistive switching (ΔR/R > 1,000%) and strong modulation of the MIT temperature (ΔTc > 30 K) in a voltage-actuated V2O3/PMN-PT [Pb(Mg,Nb)O3-PbTiO3] heterostructure. This resistive switching is an order of magnitude larger than ever encountered in any other similar systems. The control of the V2O3 electronic properties is achieved using the transfer of switchable ferroelastic strain from the PMN-PT substrate into the epitaxially grown V2O3 film. Strain can reversibly promote/hinder the structural phase transition in the V2O3, thus advancing/suppressing the associated MIT. The giant resistive switching and strong Tc modulation could enable practical implementations of voltage-controlled Mott devices and provide a platform for exploring fundamental electronic properties of V2O3.

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