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.

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 The high-energy environment and atmospheric escape of the mini-Neptune K2-18 b

2020 ◽  
Vol 634 ◽  
pp. L4 ◽  
Author(s):  
Leonardo A. dos Santos ◽  
David Ehrenreich ◽  
Vincent Bourrier ◽  
Nicola Astudillo-Defru ◽  
Xavier Bonfils ◽  
...  
Keyword(s):  
Time Series ◽  
Its Region ◽  
High Energy ◽  
Escape Rate ◽  
Space Telescope ◽  
Atmospheric Escape ◽  
Energy Environment ◽  
In Transit ◽  
Imaging Spectrograph ◽  
Rule Out

K2-18 b is a transiting mini-Neptune that orbits a nearby (38 pc), cool M3 dwarf and is located inside its region of temperate irradiation. We report on the search for hydrogen escape from the atmosphere K2-18 b using Lyman-α transit spectroscopy with the Space Telescope Imaging Spectrograph instrument installed on the Hubble Space Telescope. We analyzed the time-series of fluxes of the stellar Lyman-α emission of K2-18 in both its blue- and redshifted wings. We found that the average blueshifted emission of K2-18 decreases by 67% ± 18% during the transit of the planet compared to the pre-transit emission, tentatively indicating the presence of H atoms escaping vigorously and being blown away by radiation pressure. This interpretation is not definitive because it relies on one partial transit. Based on the reconstructed Lyman-α emission of K2-18, we estimate an EUV irradiation in the range 101 − 102 erg s−1 cm−2 and a total escape rate on the order of 108 g s−1. The inferred escape rate suggests that the planet will lose only a small fraction (< 1%) of its mass and retain its volatile-rich atmosphere during its lifetime. More observations are needed to rule out stellar variability effects, confirm the in-transit absorption, and better assess the atmospheric escape and high-energy environment of K2-18 b.

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.

scholarly journals Quest for the tertiary component in Cyg OB2 #5

2019 ◽  
Vol 627 ◽  
pp. A2
Author(s):  
Gregor Rauw ◽  
Yaël Nazé ◽  
Fran Campos
Keyword(s):  
Light Curve ◽  
High Energy ◽  
Optical Data ◽  
X Ray ◽  
Systemic Velocity ◽  
Short Period ◽  
Velocity Changes ◽  
The Times ◽  
High Energy Emission ◽  
First Time

Aims. The Cyg OB2 #5 system is thought to consist of a short-period (6.6 d) eclipsing massive binary orbited by an OB-star with a period of ~6.7 yr; these stars in turn are orbited by a distant early B-star with a period of thousands of years. However, while the inner binary has been studied many times, information is missing on the other stars, in particular the third star whose presence was indirectly postulated from recurrent modulations in the radio domain. Besides, to this date, the X-ray light curve could not be fully interpreted, for example in the framework of colliding-wind emission linked to one of the systems. Methods. We obtained new optical and X-ray observations of Cyg OB2 #5, which we combined to archival data. We performed a thorough and homogeneous investigation of all available data, notably revisiting the times of primary minimum in photometry. Results. In the X-ray domain, XMM-Newton provides scattered exposures over ~5000 d whilst Swift provides a nearly continuous monitoring for the last couple of years. Although the X-ray light curve reveals clear variability, no significant period can be found hence the high-energy emission cannot be explained solely in terms of colliding winds varying along either the short or intermediate orbits. The optical data reveal for the first time clear signs of reflex motion. The photometry indicates the presence of a 2366 d (i.e. 6.5 yr) period while the associated radial velocity changes are detected at the 3σ level in the systemic velocity of the He II λ 4686 emission line. With the revised period, the radio light curve is interpreted consistently in terms of a wind interaction between the inner binary and the tertiary star. From these optical and radio data, we derive constraints on the physical properties of the tertiary star and its orbit.

scholarly journals High-energy environment of super-Earth 55 Cancri e

2018 ◽  
Vol 615 ◽  
pp. A117 ◽  
Author(s):  
V. Bourrier ◽  
D. Ehrenreich ◽  
A. Lecavelier des Etangs ◽  
T. Louden ◽  
P. J. Wheatley ◽  
...  
Keyword(s):  
Rest Frame ◽  
High Energy ◽  
X Ray ◽  
Short Period ◽  
Chromospheric Emission ◽  
Energy Environment ◽  
Short And Long Term ◽  
Coronal Rain ◽  
Far Ultraviolet

The high-energy X-ray to ultraviolet (XUV) irradiation of close-in planets by their host star influences their evolution and might be responsible for the existence of a population of ultra-short period planets eroded to their bare core. In orbit around a bright, nearby G-type star, the super-Earth 55 Cnc e offers the possibility to address these issues through transit observations at UV wavelengths. We used the Hubble Space Telescope to observe the transit in the far-ultraviolet (FUV) over three epochs in April 2016, January 2017, and February 2017. Together, these observations cover nearly half of the orbital trajectory in between the two quadratures, and reveal significant short- and long-term variability in 55 Cnc chromospheric emission lines. In the last two epochs, we detected a larger flux in the C III, Si III, and Si IV lines after the planet passed the approaching quadrature, followed by a flux decrease in the Si IV doublet. In the second epoch these variations are contemporaneous with flux decreases in the Si II and C II doublets. All epochs show flux decreases in the N V doublet as well, albeit at different orbital phases. These flux decreases are consistent with absorption from optically thin clouds of gas, are mostly localized at low and redshifted radial velocities in the star rest frame, and occur preferentially before and during the planet transit. These three points make it unlikely that the variations are purely stellar in origin, yet we show that the occulting material is also unlikely to originate from the planet. We thus tentatively propose that the motion of 55 Cnc e at the fringes of the stellar corona leads to the formation of a cool coronal rain. The inhomogeneity and temporal evolution of the stellar corona would be responsible for the differences between the three visits. Additional variations are detected in the C II doublet in the first epoch and in the O I triplet in all epochs with a different behavior that points toward intrinsic stellar variability. Further observations at FUV wavelengths are required to disentangle definitively between star-planet interactions in the 55 Cnc system and the activity of the star.

FEATURES OF PHOTOCONDUCTIVITY OF Ge AND Si WITH DISORDERED REGIONS

2010 ◽  
Vol 24 (31) ◽  
pp. 2985-2996 ◽  
Author(s):  
V. YEVSEYEV
Keyword(s):  
Large Scale ◽  
High Energy ◽  
Fast Neutrons ◽  
Potential Relief ◽  
Photoelectrical Properties ◽  
Recombination Centers ◽  
First Time ◽  
High Energy Particles ◽  
Disordered Regions

Influence of large radiation defects — disordered regions on photoconductivity of semiconductors Ge and Si , compensated as a result of an irradiation with fast neutrons and 1 GeV protons, is investigated. For the first time, the combined role of disordered regions and a large-scale potential relief in photoelectrical properties of Ge and Si , irradiated by high energy particles is defined. The model of photoconductivity that takes into consideration disordered regions as specific sensitizing recombination centers and allows formation of the spatial potential relief is developed.

Paleocene isocrinids (Echinodermata: Crinoidea) from the Kauru Formation, South Island, New Zealand

1994 ◽  
Vol 68 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Jeffrey D. Stilwell ◽  
R. Ewan Fordyce ◽  
Peter J. Rolfe
Keyword(s):  
New Zealand ◽  
Storm Surge ◽  
Late Cretaceous ◽  
Fossil Record ◽  
High Energy ◽  
Coarse Grained ◽  
Local Equivalent ◽  
Energy Environment ◽  
First Time

Crinoids are reported from the New Zealand Paleocene for the first time and include rare articulated columnals and brachia with pinnules. These specimens of Metacrinus sp. (Isocrinidae) are present in basal, fossiliferous, coarse-grained, quartzose sediments of the Kauru Formation, a few centimeters above schist basement, in the Kakanui Valley, North Otago. The crinoid-bearing facies probably represents earliest onlap or a storm surge onto a wave cut platform; sedimentological and paleontological evidence indicates a moderate- to high-energy environment. The crinoids were most probably buried rapidly while alive or shortly after death. The presence of isocrinids in the Kauru Formation and younger Paleogene strata reveals that the supposed shift of some isocrinids from a shallower to a deeper environment actually occurred much later in the Paleogene, and not the Late Cretaceous as previously supposed. Associated molluscs indicate a mid to upper “Wangaloan” Stage (local), equivalent to mid Paleocene. A summary of the New Zealand crinoid fossil record is presented.

scholarly journals Comparative investigations of equatorial electrodynamics and low-to-mid latitude coupling of the thermosphere-ionosphere system

2006 ◽  
Vol 24 (2) ◽  
pp. 503-513 ◽  
Author(s):  
M. J. Colerico ◽  
M. Mendillo ◽  
C. G. Fesen ◽  
J. Meriwether
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Upper Atmosphere ◽  
Low Latitude ◽  
Brightness Wave ◽  
F Region ◽  
Fabry Perot ◽  
Low Latitudes ◽  
First Time

Abstract. The thermospheric midnight temperature maximum (MTM) is a highly variable, but persistent, large scale neutral temperature enhancement which occurs at low latitudes. Its occurrence can impact many fundamental upper atmospheric parameters such as pressure, density, neutral winds, neutral density, and F-region plasma. Although the MTM has been the focus of several investigations employing various instrumentation including photometers, satellites, and Fabry-Perot interferometers, limited knowledge exists regarding the latitude extent of its influence on the upper atmosphere. This is largely due to observational limitations which confined the collective geographic range to latitudes within ±23°. This paper investigates the MTM's latitudinal extent through all-sky imaging observations of its 6300Å airglow signature referred to by Colerico et al. (1996) as the midnight brightness wave (MBW). The combined field of view of three Southern Hemisphere imaging systems located at Arequipa, Peru, and Tucuman and El Leoncito, Argentina, for the first time extends the contiguous latitudinal range of imager observations to 8° S-39° S in the American sector. Our results highlight the propagation of MBW events through the combined fields of view past 39° S latitude, providing the first evidence that the MTM's effect on the upper atmosphere extends into mid-latitudes. The observations presented here are compared with modeled 6300Å emissions calculated using the NCAR thermosphere-ionosphere-electrodynamic general circulation model (TIEGCM) in conjunction with an airglow code. We report that at this time TIEGCM is unable to simulate an MBW event due to the model's inability to reproduce an MTM of the same magnitude and occurrence time as those observed via FPI measurements made from Arequipa. This work also investigates the origins of an additional low latitude airglow feature referred to by Colerico et al. (1996) as the pre-midnight brightness wave (PMBW) and described as an enhancement in 6300Å emission which occurs typically between 20:00-22:00 LT and exhibits equatorward propagation. We present the first successful simulation of a PMBW event using the TIEGCM and the airglow code. We find that the PMBW's origin is electro-dynamical in nature, resulting from the expected evening decay of the inter-tropical arcs.

scholarly journals Grid of upper atmosphere models for 1–40 M⊕ planets: application to CoRoT-7 b and HD 219134 b,c

2018 ◽  
Vol 619 ◽  
pp. A151 ◽  
Author(s):  
D. Kubyshkina ◽  
L. Fossati ◽  
N. V. Erkaev ◽  
C. P. Johnstone ◽  
P. E. Cubillos ◽  
...  
Keyword(s):  
Mass Loss Rate ◽  
Atmospheric Temperature ◽  
High Energy ◽  
Physical Models ◽  
Upper Atmosphere ◽  
Heating Rates ◽  
Planetary Evolution ◽  
Atmospheric Escape ◽  
Theoretical Evidence ◽  
Atmospheric Loss

There is growing observational and theoretical evidence suggesting that atmospheric escape is a key driver of planetary evolution. Commonly, planetary evolution models employ simple analytic formulae (e.g. energy limited escape) that are often inaccurate, and more detailed physical models of atmospheric loss usually only give snapshots of an atmosphere’s structure and are difficult to use for evolutionary studies. To overcome this problem, we have upgraded and employed an existing upper atmosphere hydrodynamic code to produce a large grid of about 7000 models covering planets with masses 1–39 M⊕ with hydrogen-dominated atmospheres and orbiting late-type stars. The modelled planets have equilibrium temperatures ranging between 300 and 2000 K. For each considered stellar mass, we account for three different values of the high-energy stellar flux (i.e. low, moderate, and high activity). For each computed model, we derived the atmospheric temperature, number density, bulk velocity, X-ray and EUV (XUV) volume heating rates, and abundance of the considered species as a function of distance from the planetary centre. From these quantities, we estimate the positions of the maximum dissociation and ionisation, the mass-loss rate, and the effective radius of the XUV absorption. We show that our results are in good agreement with previously published studies employing similar codes. We further present an interpolation routine capable to extract the modelling output parameters for any planet lying within the grid boundaries. We used the grid to identify the connection between the system parameters and the resulting atmospheric properties. We finally applied the grid and the interpolation routine to estimate atmospheric evolutionary tracks for the close-in, high-density planets CoRoT-7 b and HD 219134 b,c. Assuming that the planets ever accreted primary, hydrogen-dominated atmospheres, we find that the three planets must have lost them within a few Myr.

scholarly journals The Hubble PanCET program: an extensive search for metallic ions in the exosphere of GJ 436 b

2019 ◽  
Vol 629 ◽  
pp. A47 ◽  
Author(s):  
L. A. dos Santos ◽  
D. Ehrenreich ◽  
V. Bourrier ◽  
A. Lecavelier des Etangs ◽  
M. López-Morales ◽  
...  
Keyword(s):  
Upper Atmosphere ◽  
Metallic Ions ◽  
Atmospheric Escape ◽  
Extensive Coverage ◽  
Wide Range ◽  
Night Side ◽  
Far Ultraviolet ◽  
In Transit ◽  
Atmospheric Loss ◽  
Excess Absorption

Context. The quiet M2.5 star GJ 436 hosts a warm Neptune that displays an extended atmosphere that dwarfs its own host star. Predictions of atmospheric escape in such planets state that H atoms escape from the upper atmosphere in a collisional regime and that the flow can drag heavier atoms to the upper atmosphere. It is unclear, however, what astrophysical mechanisms drive the process. Aims. Our objective is to leverage the extensive coverage of observations of the far-ultraviolet (FUV) spectrum of GJ 436 obtained with the Cosmic Origins Spectrograph (COS) to search for signals of metallic ions in the upper atmosphere of GJ 436 b, as well as study the activity-induced variability of the star. Methods. We analyzed flux time-series of species present in the FUV spectrum of GJ 436 and successfully performed geocoronal contamination removal in the COS Lyman-α profiles obtained near the Earth’s night-side. Results. GJ 436 displays flaring events with a rate of ~10 d−1. There is evidence for a possibly long-lived active region or longitude that modulates the FUV metallic lines of the star with amplitudes up to 20%. Despite the strong geocoronal contamination in the COS spectra, we detected in-transit excess absorption signals of ~50 and ~30% in the blue and red wings, respectively, of the Lyman-α line. We rule out a wide range of excess absorption levels in the metallic lines of the star during transit. Conclusions. The large atmospheric loss of GJ 436 b observed in Lyman-α transmission spectra is stable over the timescale of a few years, and the red wing signal supports the presence of a variable hydrogen absorption source besides the stable exosphere. The previously claimed in-transit absorption in the Si III line is likely an artifact resulting from the stellar magnetic cycle. The non-detection of metallic ions in absorption could indicate that the escape is not hydrodynamic or that the atmospheric mixing is not efficient in dragging metals high enough for sublimation to produce a detectable escape rate of ions to the exosphere.

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