scholarly journals The Posttransit Tail of WASP-107b Observed at 10830 Å

2021 ◽  
Vol 162 (6) ◽  
pp. 284
Author(s):  
J. J. Spake ◽  
A. Oklopčić ◽  
L. A. Hillenbrand
Keyword(s):  
Three Dimensional ◽  
High Energy ◽  
Stellar Winds ◽  
High Energy Radiation ◽  
Absorption Signal ◽  
Metastable Helium ◽  
Atmospheric Escape ◽  
First Time ◽  
Excess Absorption ◽  
Three Dimensional Simulations

Abstract Understanding the effects of high-energy radiation and stellar winds on planetary atmospheres is vital for explaining the observed properties of close-in exoplanets. Observations of transiting exoplanets in the triplet of metastable helium lines at 10830 Å allow extended atmospheres and escape processes to be studied for individual planets. We observed one transit of WASP-107b with NIRSPEC on Keck at 10830 Å. Our observations, for the first time, had significant posttransit phase coverage, and we detected excess absorption for over an hour after fourth contact. The data can be explained by a comet-like tail extending out to ∼7 planet radii, which corresponds to roughly twice the Roche lobe radius of the planet. Planetary tails are expected based on three-dimensional simulations of escaping exoplanet atmospheres, particularly those including the interaction between the escaped material and strong stellar winds, and have been previously observed at 10830 Å in at least one other exoplanet. With both the largest midtransit absorption signal and the most extended tail observed at 10830 Å, WASP-107b remains a keystone exoplanet for atmospheric escape studies.

Search for helium in the upper atmosphere of the hot Jupiter WASP-127 b using Phoenix/Gemini

2020 ◽  
Author(s):  
Leonardo A. dos Santos ◽  
David Ehrenreich ◽  
Vincent Bourrier ◽  
Romain Allart ◽  
George King ◽  
...  
Keyword(s):  
Large Scale ◽  
High Energy ◽  
Upper Atmosphere ◽  
Metastable Helium ◽  
Atmospheric Escape ◽  
Short Period ◽  
Energy Environment ◽  
In Transit ◽  
First Time ◽  
Hot Jupiter

<div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>Large-scale exoplanet search surveys have shown evidence that atmospheric escape is a ubiquitous process that shapes the evolution and demographics of planets. However, we lack a detailed understanding of this process because very few exoplanets discovered to date could be probed for signatures of atmospheric escape. Recently, the metastable helium triplet at 1.083 μm has been shown to be a viable window for the presence of He-rich escaping envelopes around short-period exoplanets. Our objective is to use, for the first time, the Phoenix spectrograph to search for helium in the upper atmosphere of the inflated hot Jupiter WASP-127 b. We observed one transit and reduced the data manually since there is no pipeline available. We did not find a significant in-transit absorption signal indicative of the presence of helium around WASP-127 b, and set a 90% confidence upper limit for excess absorption at 0.87% in a 0.75 Å passband covering the He triplet. Given the large scale height of this planet, the lack of a detectable feature is likely due to unfavorable photoionization conditions to populate the metastable He I triplet. This conclusion is supported by the inferred low coronal and chromospheric activity of the host star and the old age of the system, which result in a relatively mild high-energy environment around the planet.</p> </div> </div> </div>

scholarly journals Search for helium in the upper atmosphere of the hot Jupiter WASP-127 b using Gemini/Phoenix

2020 ◽  
Vol 640 ◽  
pp. A29 ◽  
Author(s):  
Leonardo A. dos Santos ◽  
David Ehrenreich ◽  
Vincent Bourrier ◽  
Romain Allart ◽  
George King ◽  
...  
Keyword(s):  
Large Scale ◽  
High Energy ◽  
Upper Atmosphere ◽  
Metastable Helium ◽  
Atmospheric Escape ◽  
Short Period ◽  
Energy Environment ◽  
In Transit ◽  
First Time ◽  
Hot Jupiter

Large-scale exoplanet search surveys have shown evidence that atmospheric escape is a ubiquitous process that shapes the evolution and demographics of planets. However, we lack a detailed understanding of this process because very few exoplanets that have been discovered to date could be probed for signatures of atmospheric escape. Recently, the metastable helium triplet at 1.083 μm has been shown to be a viable window for the presence of He-rich escaping envelopes around short-period exoplanets. Our objective is to use, for the first time, the Phoenix spectrograph to search for helium in the upper atmosphere of the inflated hot Jupiter WASP-127 b. We observed one transit and reduced the data manually since no pipeline is available. We did not find a significant in-transit absorption signal indicative of the presence of helium around WASP-127 b, and we set a 90% confidence upper limit for excess absorption at 0.87% in a 0.75 Å passband covering the He triplet. Given the large scale height of this planet, the lack of a detectable feature is likely due to unfavorable photoionization conditions for populating the metastable He I triplet. This conclusion is supported by the inferred low coronal and chromospheric activity of the host star and the old age of the system, which result in a relatively mild high-energy environment around the planet.

scholarly journals Gel Dosimetry with Radio-Fluorogenic Coumarin

2018 ◽  
Author(s):  
Peter A. Sandwall ◽  
Brandt P. Bastow ◽  
Henry B. Spitz ◽  
Howard R. Elson ◽  
Michael Lamba ◽  
...  
Keyword(s):  
Free Radicals ◽  
Carboxylic Acid ◽  
Three Dimensional ◽  
High Energy ◽  
Water Radiolysis ◽  
Gel Dosimetry ◽  
Rate Dependency ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Hydroxyl Free Radicals

In radiotherapy, accurate deposition of energy to the targeted volume is vital to ensure effective treatment. Gel dosimeters are attractive detection systems, as tissue substitutes with potential to yield three-dimensional dose distributions. Radio-fluorogenesis is creation fluorescent chemical products in response to energy deposition from high-energy radiation. This report shares studies of a radio-fluorogenic gel dosimetry system, gelatin with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission, following UV to near UV (365–405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated for this system. The response of the system was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship with a dose-rate dependency and no energy or type dependencies. This report supports the utility of gelatin-C3CA for phantom studies of radio-fluorogenic processes.

scholarly journals High energy gain in three-dimensional simulations of light sail acceleration

2014 ◽  
Vol 105 (8) ◽  
pp. 084105 ◽  
Author(s):  
A. Sgattoni ◽  
S. Sinigardi ◽  
A. Macchi
Keyword(s):  
Three Dimensional ◽  
High Energy ◽  
Energy Gain ◽  
Three Dimensional Simulations

High-resolution RHEED analysis of dynamics of low-temperature superstructure transitions in Ge/Si(001) epitaxial system

2021 ◽  
Vol 33 (11) ◽  
pp. 115603
Author(s):  
Vladimir V Dirko ◽  
Kirill A Lozovoy ◽  
Andrey P Kokhanenko ◽  
Alexander V Voitsekhovskii
Keyword(s):  
Critical Thickness ◽  
Three Dimensional ◽  
Diffraction Method ◽  
High Energy ◽  
Two Dimensional ◽  
A Value ◽  
Wide Range ◽  
Dimensional Growth ◽  
Analysis Of Dynamics ◽  
First Time

Abstract In this paper, we analyze superstructural transitions during epitaxial growth of two-dimensional layers and the formation of quantum dots by the Stranski–Krastanov mechanism in elastically stressed systems by the reflection high-energy electron diffraction method. Detailed dependences of the periodicity parameter N of the 2 × N reconstruction on the effective thickness of the deposited material in a wide range of growth temperatures during epitaxy of germanium on a silicon surface with a crystallographic orientation (001) are obtained. Superstructural transitions and the change in the value of the parameter N at low temperatures of epitaxy in this system have been investigated for the first time. It is shown that the length of dimer rows in such a reconstruction during the growth of pure germanium on silicon can reach a value of no less than N = 11. A relationship is found between the value of the parameter N, determined by elastic strains in the system, and the critical thickness of the transition from two-dimensional to three-dimensional growth. Based on this relationship, a physical mechanism is proposed that explains the nature of the temperature dependence of the critical thickness of the Stranski–Krastanov transition, which has been the subject of constant scientific disputes until now.

High Energy Radiation from Pulsars

2000 ◽  
Vol 177 ◽  
pp. 427-432 ◽  
Author(s):  
K.S. Cheng
Keyword(s):  
Pair Production ◽  
Production Condition ◽  
Three Dimensional ◽  
High Energy ◽  
Polar Cap ◽  
High Energy Radiation ◽  
Particle Flows ◽  
Consistent Model ◽  
Local Properties ◽  
Vertical Size

AbstractWe propose a three dimensional pulsar magnetosphere model in which the vertical size of the outer gap is first determined by a self-consistent model in which the outer gap is limited by the pair production from collisions of thermal photons produced by polar cap heating of backflow outer gap current and the curvature photons emitted by the gap accelerated charged particles. The transverse size of the outer gap is determined by local pair production condition. In principle, there are two topologically disconnected outer gaps existing in the magnetosphere of a pulsar and both incoming and outgoing particle flows are allowed. And yet double-peak light curves with strong bridges are most common. Using this model and its local properties, we compare the model results with phase-resolved spectra of the Crab pulsar and Geminga.

scholarly journals Young planets under extreme UV irradiation

2018 ◽  
Vol 612 ◽  
pp. A25 ◽  
Author(s):  
D. Kubyshkina ◽  
M. Lendl ◽  
L. Fossati ◽  
P. E. Cubillos ◽  
H. Lammer ◽  
...  
Keyword(s):  
Equilibrium Temperature ◽  
High Energy ◽  
High Energy Radiation ◽  
Hydrodynamic Simulations ◽  
Planetary Evolution ◽  
Atmospheric Escape ◽  
Stellar Radiation ◽  
Extreme Uv ◽  
High Level ◽  
Increasing Temperature

The K2-33 planetary system hosts one transiting ~5 R⊕ planet orbiting the young M-type host star. The planet’s mass is still unknown, with an estimated upper limit of 5.4 MJ. The extreme youth of the system (<20 Myr) gives the unprecedented opportunity to study the earliest phases of planetary evolution, at a stage when the planet is exposed to an extremely high level of high-energy radiation emitted by the host star. We perform a series of 1D hydrodynamic simulations of the planet’s upper atmosphere considering a range of possible planetary masses, from 2 to 40 M⊕, and equilibrium temperatures, from 850 to 1300 K, to account for internal heating as a result of contraction. We obtain temperature profiles mostly controlled by the planet’s mass, while the equilibrium temperature has a secondary effect. For planetary masses below 7–10 M⊕, the atmosphere is subject to extremely high escape rates, driven by the planet’s weak gravity and high thermal energy, which increase with decreasing mass and/or increasing temperature. For higher masses, the escape is instead driven by the absorption of the high-energy stellar radiation. A rough comparison of the timescales for complete atmospheric escape and age of the system indicates that the planet is more massive than 10 M⊕.

scholarly journals Magnetic activity, high-energy radiation and variability: from young solar analogs to low-mass objects

2009 ◽  
Vol 5 (S264) ◽  
pp. 375-384
Author(s):  
Manuel Güdel
Keyword(s):  
Extreme Ultraviolet ◽  
High Energy ◽  
Magnetic Activity ◽  
Energy Output ◽  
Stellar Winds ◽  
High Energy Radiation ◽  
X Ray ◽  
Cool Stars ◽  
Low Mass ◽  
Solar Analogs

AbstractMagnetic activity on cool stars expresses itself in a bewildering variety of radiative and particle output originating from magnetic regions between the photosphere and the corona. Given its origin in evolving magnetic fields, most of this output is variable in time. Radiation in the ultraviolet, the extreme ultraviolet, and the X-ray ranges are important for heating and ionizing upper planetary atmospheres and thus driving atmospheric evaporation. Additionally, stellar winds interact with the upper atmospheres and may lead to further erosion. The stellar high-energy output is therefore a prime factor in determining habitability of planets. We summarize our knowledge of magnetic activity in young solar analogs and lower-mass stars and show how the stellar output changes on evolutionary timescales.

scholarly journals Simulating the chemistry and dynamics of molecular clouds

2009 ◽  
Vol 5 (H15) ◽  
pp. 405-405
Author(s):  
S. C. O. Glover ◽  
C. Federrath ◽  
M.-M. Mac Low ◽  
R. S. Klessen
Keyword(s):  
Molecular Clouds ◽  
Chemical Structure ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Giant Molecular Clouds ◽  
Interstellar Gas ◽  
Density Inhomogeneities ◽  
First Time ◽  
Three Dimensional Simulations

AbstractWe have performed high-resolution three-dimensional simulations of turbulent interstellar gas that for the first time self-consistently follow its coupled thermal, chemical and dynamical evolution. Our simulations have allowed us to quantify the formation timescales for the most important molecules found in giant molecular clouds (H2, CO), as well as their spatial distribution within the clouds. Our results are consistent with models in which molecular clouds form quickly, within 1–2 turbulent crossing times, and emphasize the crucial role of density inhomogeneities in determining the chemical structure of the clouds.

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