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[Text] / K. G. Kislyakova [et al.] // Astron. Astrophys. - 2014. - Vol. 562. - Ст. A116, DOI 10.1051/0004-6361/201322933. - Cited References: 45. - K.G. Kislyakova, C.P. Johnstone, M.L. Khodachenko, H. Lammer, T. Luftinger and M. Gudel acknowledge the support by the FWF NFN project S116601-N16 "Pathways to Habitability: From Disks to Active Stars, Planets and Life", and the related EWE NFN subprojects, S116 604-N16 "Radiation & Wind Evolution from T Tauri Phase to ZAMS and Beyond". 5116 606-N16 "Magnetospheric Electrodynamics of Exoplanets", and S116607-N16 "Particle/Radiative Interactions with Upper Atmospheres of Planetary Bodies Under Extreme Stellar Conditions". T. Luftinger acknowledges also the support by the FWF project P19962-N16. K. G. Kislyakova, H. Lammer, and P. Odert thank also the Helmholtz Alliance project "Planetary Evolution and Life". P. Odert acknowledges support from the EWE project P22950-N16. The authors also acknowledge support from the EU FP7 project IMPEx (No.262863) and the EUROPLANET-RI projects, JRA3/EMDAF and the Na2 science WG5. N. V. Erkaev acknowledges support by the RFBR grant No 12-05-00152-a. Finally, the authors thank the International Space Science Institute (ISSI) in Bern, and the ISSI team "Characterizing stellar- and exoplanetary environments". This research was conducted using resources provided by the Swedish National Infrastructure for Computing (SNIC) at the High Performance Computing Center North (HPC2N). The authors thank also the anonymous referee for his useful comments. . - ISSN 0004-6361. - ISSN 1432-0746РУБ Astronomy & Astrophysics

Аннотация: Aims. We study the interactions between stellar winds and the extended hydrogen-dominated upper atmospheres of planets. We estimate the resulting escape of planetary pick-up ions from the five "super-Earths" in the compact Kepler-11 system and compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Methods. Assuming the stellar wind of Kepler-11 is similar to the solar wind, we use a polytropic ID hydrodynamic wind model to estimate the wind properties at the planetary orbits. We apply a direct simulation Monte Carlo model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f within a realistic expected heating efficiency range of 15-40%. The same model is used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. From the interaction model, we study the influence of possible magnetic moments, calculate the charge exchange and photoionization production rates of planetary ions, and estimate the loss rates of pick-up H+ ions for all five planets. We compare the results between the five "super-Earths" and the thermal escape rates of the neutral planetary hydrogen atoms. Results. Our results show that a huge neutral hydrogen corona is formed around the planet for all Kepler-11b-f exoplanets. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure and gravitational effects. Non-thermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 "super-Earths" vary between similar to.6.4x10(30) s(-1) and similar to 4.1 x10(31) s(-1), depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of similar to 1.07 x 10(7) g s(-1) and similar to 6.8 x 10(2) g s(-1) respectively, which is a few percent of the thermal escape rates.

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ИВМ СО РАН

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Kislyakova, K.G.; Johnstone, C.P.; Odert, P.; Erkaev, N.V.; Еркаев, Николай Васильевич; Lammer, H.; Luftinger, T.; Holmstrom, M.; Khodachenko, M.L.; Guedel, M.; FWF NFN project [S116601-N16]; EWE NFN subprojects T Tauri Phase [S116 604-N16]; "Magnetospheric Electrodynamics of Exoplanets" [5116 606-N16]; "Particle/Radiative Interactions with Upper Atmospheres of Planetary Bodies Under Extreme Stellar Conditions" [S116607-N16]; FWF project [P19962-N16]; EWE project [P22950-N16]; EU [262863]; EUROPLANET-RI projects [JRA3/EMDAF, Na2 science WG5]; RFBR [12-05-00152-a]

/ P. E. Cubillos [et al.] // Astrophys. J. - 2017. - Vol. 849, Is. 2, DOI 10.3847/1538-4357/aa9019 . - ISSN 0004-637X
Аннотация: The strong, nearly wavelength-independent absorption cross section of aerosols produces featureless exoplanet transmission spectra, limiting our ability to characterize their atmospheres. Here, we show that even in the presence of featureless spectra, we can still characterize certain atmospheric properties. Specifically, we constrain the upper and lower pressure boundaries of aerosol layers, and present plausible composition candidates. We study the case of the bloated Saturn-mass planet WASP-49 b, where near-infrared observations reveal a flat transmission spectrum between 0.7 and 1.0 ?m. First, we use a hydrodynamic upper-atmosphere code to estimate the pressure reached by the ionizing stellar high-energy photons at 10-8 bar, setting the upper pressure boundary where aerosols could exist. Then, we combine HELIOS and Pyrat Bay radiative-transfer models to constrain the temperature and photospheric pressure of atmospheric aerosols, in a Bayesian framework. For WASP-49 b, we constrain the transmission photosphere (hence, the aerosol deck boundaries) to pressures above 10-5 bar (100?solar metallicity), 10-4 bar (solar), and 10-3 bar (0.1?solar) as the lower boundary, and below 10-7 bar as the upper boundary. Lastly, we compare condensation curves of aerosol compounds with the planet's pressure-temperature profile to identify plausible condensates responsible for the absorption. Under these circumstances, we find these candidates: Na2S (at 100? solar metallicity); Cr and MnS (at solar and 0.1?solar); and forsterite, enstatite, and alabandite (at 0.1?solar). © 2017. The American Astronomical Society. All rights reserved.

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Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, Graz, Austria
Federal Research Center Krasnoyarsk Science Center SB RAS, Institute of Computational Modelling, Krasnoyarsk, Russian Federation
Center for Space and Habitability, University of Bern, Sidlerstrasse 5, Bern, Switzerland
Institut fur Geophysik und Meteorologie, Universitat zu Koln, Albertus-Magnus-Platz, Koln, Germany
Max Planck Institute for Astronomy, Konigstuhl 17, Heidelberg, Germany
Department of Astrophysics, University of Vienna, Turkenschanzstrasse 17, Vienna, Austria
Geneva Observatory, University of Geneva, ch. de Maillettes 51, Versoix, Switzerland

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Cubillos, P. E.; Fossati, L.; Erkaev, N. V.; Malik, M.; Tokano, T.; Lendl, M.; Johnstone, C. P.; Lammer, H.; Wyttenbach, A.

/ K. G. Kislyakova [et al.] // Astron. Astrophys. - 2019. - Vol. 623. - Ст. A131, DOI 10.1051/0004-6361/201833941. - Cited References:89. - We acknowledge the support by the Austria Science Fund (FWF) NFN project S116-N16 and the subprojects S11607-N16, S11606-N16 and S11604-N16. P.O., H.L., and N.V.E. acknowledge support from the Austrian Science Fund (FWF) project P25256-N27 "Characterizing Stellar and Exoplanetary Environments via Modeling of Lyman-alpha Transit Observations of Hot Jupiters". N.V.E. also acknowledges support by the RFBR grant No 16-52-14006. M.L.K. also acknowledges FWF projects I2939-N27 and the partial support by the Ministry of Education and Science of Russian federation (Grant No. RFMEFI61617X0084). I.F.S. acknowleges support of Russian Science Foundation project 18-12-00080. The software used in this work was in part developed by the DOE NNSA-ASC OASCR Flash Center at the University of Chicago. This research was conducted using resources provided by the Swedish National Infrastructure for Computing (SNIC) at the High Performance Computing Center North (HPC2N), Umea University, Sweden. The authors are very thankful to Dr. David Ehrenreich for providing the Ly-alpha spectra of GJ 436b, which were used in this article. We would also like to sincerely thank Dr. Vincent Bourrier and Baptiste Lavie for original processing of these spectra. . - ISSN 1432-0746РУБ Astronomy & Astrophysics

Аннотация: Aims. We modeled the transit signatures in the Lyman-alpha (Ly-alpha) line of a putative Earth-sized planet orbiting in the habitable zone (HZ) of the M dwarf GJ 436. We estimated the transit depth in the Ly-alpha line for an exo-Earth with three types of atmospheres: a hydrogen-dominated atmosphere, a nitrogen-dominated atmosphere, and a nitrogen-dominated atmosphere with an amount of hydrogen equal to that of the Earth. For all types of atmospheres, we calculated in-transit absorption they would produce in the stellar Ly-alpha line. We applied it to the out-of-transit Ly-alpha observations of GJ 436 obtained by the Hubble Space Telescope (HST) and compared the calculated in-transit absorption with observational uncertainties to determine if it would be detectable. To validate the model, we also used our method to simulate the deep absorption signature observed during the transit of GJ 436b and showed that our model is capable of reproducing the observations. Methods. We used a direct simulation Monte Carlo (DSMC) code to model the planetary exospheres. The code includes several species and traces neutral particles and ions. It includes several ionization mechanisms, such as charge exchange with the stellar wind, photo- and electron impact ionization, and allows to trace particles collisions. At the lower boundary of the DSMC model we assumed an atmosphere density, temperature, and velocity obtained with a hydrodynamic model for the lower atmosphere. Results. We showed that for a small rocky Earth-like planet orbiting in the HZ of GJ 436 only the hydrogen-dominated atmosphere is marginally detectable with the Space Telescope Imaging Spectrograph (STIS) on board the HST. Neither a pure nitrogen atmosphere nor a nitrogen-dominated atmosphere with an Earth-like hydrogen concentration in the upper atmosphere are detectable. We also showed that the Ly-alpha observations of GJ 436b can be reproduced reasonably well assuming a hydrogen-dominated atmosphere, both in the blue and red wings of the Ly-alpha line, which indicates that warm Neptune-like planets are a suitable target for Ly-alpha observations. Terrestrial planets, on the other hand, can be observed in the Ly-alpha line if they orbit very nearby stars, or if several observational visits are available.

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Univ Vienna, Dept Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria.
Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden.
Russian Acad Sci, Inst Computat Modelling, Siberian Div, Krasnoyarsk 660036, Russia.
Siberian Fed Univ, Krasnoyarsk, Russia.
Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia.
Inst Laser Phys SB RAS, Novosibirsk, Russia.

Доп.точки доступа:
Kislyakova, K. G.; Holmstrom, M.; Odert, P.; Lammer, H.; Erkaev, N., V; Khodachenko, M. L.; Shaikhislamov, I. F.; Dorfi, E.; Gudel, M.; Guedel, Manuel; Kislyakova, Kristina; Austria Science Fund (FWF) NFN project [S116-N16, S11606-N16, S11604-N16, S11607-N16]; Austrian Science Fund (FWF) [P25256-N27]; RFBR [16-52-14006]; FWF [I2939-N27]; Ministry of Education and Science of Russian federation [RFMEFI61617X0084]; Russian Science Foundation [18-12-00080]