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.

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 Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b

Science ◽  
2018 ◽  
Vol 362 (6421) ◽  
pp. 1388-1391 ◽  
Author(s):  
Lisa Nortmann ◽  
Enric Pallé ◽  
Michael Salz ◽  
Jorge Sanz-Forcada ◽  
Evangelos Nagel ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
High Resolution Spectroscopy ◽  
Ultraviolet Region ◽  
Helium Atmosphere ◽  
Atmospheric Escape ◽  
Hot Gas ◽  
Measured Line ◽  
Far Ultraviolet ◽  
Physical And Chemical ◽  
Excess Absorption

Hot gas giant exoplanets can lose part of their atmosphere due to strong stellar irradiation, and these losses can affect their physical and chemical evolution. Studies of atmospheric escape from exoplanets have mostly relied on space-based observations of the hydrogen Lyman-α line in the far ultraviolet region, which is strongly affected by interstellar absorption. Using ground-based high-resolution spectroscopy, we detected excess absorption in the helium triplet at 1083 nanometers during the transit of the Saturn-mass exoplanet WASP-69b, at a signal-to-noise ratio of 18. We measured line blueshifts of several kilometers per second and posttransit absorption, which we interpret as the escape of part of the atmosphere trailing behind the planet in comet-like form.

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 Why an intrinsic magnetic field does not protect a planet against atmospheric escape

2018 ◽  
Vol 614 ◽  
pp. L3 ◽  
Author(s):  
Herbert Gunell ◽  
Romain Maggiolo ◽  
Hans Nilsson ◽  
Gabriella Stenberg Wieser ◽  
Rikard Slapak ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Escape Rate ◽  
Sufficient Condition ◽  
Atmospheric Escape ◽  
Intrinsic Magnetic Field ◽  
Polar Caps ◽  
Wide Range ◽  
Atmospheric Loss ◽  
Planetary Magnetic Field

The presence or absence of a magnetic field determines the nature of how a planet interacts with the solar wind and what paths are available for atmospheric escape. Magnetospheres form both around magnetised planets, such as Earth, and unmagnetised planets, like Mars and Venus, but it has been suggested that magnetised planets are better protected against atmospheric loss. However, the observed mass escape rates from these three planets are similar (in the approximate (0.5–2) kg s−1 range), putting this latter hypothesis into question. Modelling the effects of a planetary magnetic field on the major atmospheric escape processes, we show that the escape rate can be higher for magnetised planets over a wide range of magnetisations due to escape of ions through the polar caps and cusps. Therefore, contrary to what has previously been believed, magnetisation is not a sufficient condition for protecting a planet from atmospheric loss. Estimates of the atmospheric escape rates from exoplanets must therefore address all escape processes and their dependence on the planet’s magnetisation.

scholarly journals Solar Extreme and Far Ultraviolet Radiation Modeling for Aeronomic Calculations

2021 ◽  
Vol 13 (8) ◽  
pp. 1454
Author(s):  
Anatoliy A. Nusinov ◽  
Tamara V. Kazachevskaya ◽  
Valeriya V. Katyushina
Keyword(s):  
Ultraviolet Radiation ◽  
Input Parameter ◽  
Solar Spectrum ◽  
Upper Atmosphere ◽  
Model Calculations ◽  
Radiation Fluxes ◽  
Main Components ◽  
Comparison Of The Results ◽  
Far Ultraviolet ◽  
Radiation Modeling

Modeling the upper atmosphere and ionospheres on the basis of a mathematical description of physical processes requires knowledge of ultraviolet radiation fluxes from the Sun as an integral part of the model. Aeronomic models of variations in the radiation flux in the region of extreme (EUV) and far (FUV) radiation, based mainly on the data of the last TIMED mission measurements of the solar spectrum, are proposed. The EUVT model describes variations in the 5–105 nm spectral region, which are responsible for the ionization of the main components of the earth’s atmosphere. The FUVT model describes the flux changes in the 115–242 nm region, which determines heating of the upper atmosphere and the dissociation of molecular oxygen. Both models use the intensity of the hydrogen Lyman-alpha line as an input parameter, which can currently be considered as one of the main indices of solar activity and can be measured with relatively simpler photometers. A comparison of the results of model calculations with observations shows that the model error does not exceed 1–2% for the FUVT model, and 5.5% for EUVT, which is sufficient for calculating the parameters of the ionosphere and thermosphere.

scholarly journals Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: implications for atmospheric escape on evolutionary timescales

2017 ◽  
Vol 35 (3) ◽  
pp. 721-731 ◽  
Author(s):  
Rikard Slapak ◽  
Audrey Schillings ◽  
Hans Nilsson ◽  
Masatoshi Yamauchi ◽  
Lars-Göran Westerberg ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Polar Region ◽  
Geomagnetic Storms ◽  
Atmospheric Oxygen ◽  
Atmospheric Escape ◽  
Order Of Magnitude ◽  
Ancient Times ◽  
Oxygen Escape ◽  
Atmospheric Loss ◽  
Activity Condition

Abstract. We have investigated the total O+ escape rate from the dayside open polar region and its dependence on geomagnetic activity, specifically Kp. Two different escape routes of magnetospheric plasma into the solar wind, the plasma mantle, and the high-latitude dayside magnetosheath have been investigated separately. The flux of O+ in the plasma mantle is sufficiently fast to subsequently escape further down the magnetotail passing the neutral point, and it is nearly 3 times larger than that in the dayside magnetosheath. The contribution from the plasma mantle route is estimated as  ∼ 3. 9 × 1024exp(0. 45 Kp) [s−1] with a 1 to 2 order of magnitude range for a given geomagnetic activity condition. The extrapolation of this result, including escape via the dayside magnetosheath, indicates an average O+ escape of 3 × 1026 s−1 for the most extreme geomagnetic storms. Assuming that the range is mainly caused by the solar EUV level, which was also larger in the past, the average O+ escape could have reached 1027–28 s−1 a few billion years ago. Integration over time suggests a total oxygen escape from ancient times until the present roughly equal to the atmospheric oxygen content today.

scholarly journals KELT-9 as an Eclipsing Double-lined Spectroscopic Binary: A Unique and Self-consistent Solution to the System

2022 ◽  
Vol 163 (2) ◽  
pp. 40
Author(s):  
Anusha Pai Asnodkar ◽  
Ji Wang ◽  
B. Scott Gaudi ◽  
P. Wilson Cauley ◽  
Jason D. Eastman ◽  
...  
Keyword(s):  
Radial Velocities ◽  
Data Sets ◽  
Dynamical Mass ◽  
Orbital Inclination ◽  
Hot Jupiters ◽  
Atmospheric Escape ◽  
Spectroscopic Binary ◽  
Consistent Solution ◽  
Using Data ◽  
In Transit

Abstract Transiting hot Jupiters present a unique opportunity to measure absolute planetary masses due to the magnitude of their radial velocity signals and known orbital inclination. Measuring planet mass is critical to understanding atmospheric dynamics and escape under extreme stellar irradiation. Here we present the ultrahot Jupiter system KELT-9 as a double-lined spectroscopic binary. This allows us to directly and empirically constrain the mass of the star and its planetary companion without reference to any theoretical stellar evolutionary models or empirical stellar scaling relations. Using data from the PEPSI, HARPS-N, and TRES spectrographs across multiple epochs, we apply least-squares deconvolution to measure out-of-transit stellar radial velocities. With the PEPSI and HARPS-N data sets, we measure in-transit planet radial velocities using transmission spectroscopy. By fitting the circular orbital solution that captures these Keplerian motions, we recover a planetary dynamical mass of 2.17 ± 0.56 M J and stellar dynamical mass of 2.11 ± 0.78 M ⊙, both of which agree with the discovery paper. Furthermore, we argue that this system, as well as systems like it, are highly overconstrained, providing multiple independent avenues for empirically cross-validating model-independent solutions to the system parameters. We also discuss the implications of this revised mass for studies of atmospheric escape.

How atmospheric escape sculped the evolution of the Martian CO2 atmosphere over time

2021 ◽  
Author(s):  
Manuel Scherf ◽  
Herbert Lichtenegger ◽  
Sergey Dyadechkin ◽  
Helmut Lammer ◽  
Raven Adam ◽  
...  
Keyword(s):  
Numerical Models ◽  
Atmospheric Escape ◽  
Ion Escape ◽  
Thermal Escape ◽  
Partial Pressures ◽  
Argon Isotopes ◽  
Atmospheric Loss ◽  
4.1 Ga ◽  
Insight Into ◽  
Volcanic Outgassing

<p>Mars likely had a denser atmosphere during the Noachian eon about 3.6 to 4.0 billion years ago (Ga). How dense this atmosphere might have been, and which escape mechanisms dominated its loss are yet not entirely clear. However, non-thermal escape processes and potential sequestration into the ground are believed to be the main drivers for atmospheric loss from the present to about 4.1 Ga.</p> <p>To evaluate non-thermal escape over the last ~4.1 billion years, we simulated the ion escape of Mars' CO<sub>2</sub> atmosphere caused by its dissociation products C and O atoms with numerical models of the upper atmosphere and its interaction with the solar wind (see Lichtenegger et al. 2021; https://arxiv.org/abs/2105.09789). We use the planetward-scattered pick-up ions for sputtering estimates of exospheric particles including <sup>36</sup>Ar and <sup>38</sup>Ar isotopes, and compare ion escape, with sputtering and photochemical escape rates. For solar EUV fluxes ≥3 times the present-day Sun (earlier than ~2.6 Ga) ion escape becomes the dominant atmospheric non-thermal loss process until thermal escape takes over during the pre-Noachian eon (earlier than ~4.0 - 4.1 Ga). If we extrapolate the total escape of CO<sub>2</sub>-related dissociation products back in time until ~4.1 Ga, we obtain a theoretical equivalent to CO<sub>2</sub> partial pressure of more than ~3 bar, but this amount did not necessarily have to be present and represents a maximum that could have been lost to space within the last ~4.1 Ga.</p> <p>Argon isotopes can give an additional insight into the evolution of the Martian atmosphere. The fractionation of <sup>36</sup>Ar/<sup>38</sup>Ar isotopes through sputtering and volcanic outgassing from its initial chondritic value of 5.3, as measured in the 4.1 billion years old Mars meteorite ALH 84001, until the present day can be reproduced for assumed CO<sub>2</sub> partial pressures between ~0.2-3.0 bar, depending on the cessation time of the Martian dynamo (assumed between 3.6-4.0 Ga) - if atmospheric sputtering of Ar started afterwards. The later the dynamo ceased away, the lower the pressure could have been to reproduce <sup>36</sup>Ar/<sup>38</sup>Ar.</p> <p>Prior to ~4.1 Ga (i.e., during the pre-Noachian eon), thermal escape should have been the most important driver of atmospheric escape at Mars, and together with non-thermal losses, might have prevented a stable and dense CO<sub>2</sub> atmosphere during the first ~400 million years. Our results indicate that, while Mars could have been warm and wet at least sporadically between ~3.6-4.1 Ga, it likely has been cold and dry during the pre-Noachian eon (see also Scherf and Lammer 2021; https://arxiv.org/abs/2102.05976).</p>

scholarly journals Stellar flares versus luminosity: XUV-induced atmospheric escape and planetary habitability

2020 ◽  
Vol 500 (1) ◽  
pp. L1-L5
Author(s):  
Dimitra Atri ◽  
Shane R Carberry Mogan
Keyword(s):  
Extreme Ultraviolet ◽  
Wide Energy Range ◽  
X Rays ◽  
Loss Mechanism ◽  
Atmospheric Escape ◽  
Stellar Flares ◽  
Wide Energy ◽  
A Minor ◽  
Atmospheric Loss ◽  
Planetary Habitability

ABSTRACT Space weather plays an important role in the evolution of planetary atmospheres. Observations have shown that stellar flares emit energy in a wide energy range (1030–1038 erg), a fraction of which lies in X-rays and extreme ultraviolet (XUV). These flares heat the upper atmosphere of a planet, leading to increased escape rates, and can result in atmospheric erosion over a period of time. Observations also suggest that primordial terrestrial planets can accrete voluminous H/He envelopes. Stellar radiation can erode these protoatmospheres over time, and the extent of this erosion has implications for the planet’s habitability. We use the energy-limited equation to calculate hydrodynamic escape rates from these protoatmospheres irradiated by XUV stellar flares and luminosity. We use the flare frequency distribution of 492 FGKM stars observed with TESS to estimate atmospheric loss in habitable zone planets. We find that for most stars, luminosity-induced escape is the main loss mechanism, with a minor contribution from flares. However, flares dominate the loss mechanism of ∼20 per cent M4–M10 stars. M0–M4 stars are most likely to completely erode both their proto- and secondary atmospheres, and M4–M10 are least likely to erode secondary atmospheres. We discuss the implications of these results on planetary habitability.

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