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/ H. Lammer [et al.] // Mon. Not. Roy. Astron. Soc. - 2013. - Vol. 430, Is. 2. - P1247-1256, DOI 10.1093/mnras/sts705. - Cited References: 85. - NVE, KGK, MLK and HL acknowledge the support by the FWF NFN project S116 'Pathways to Habitability: From Disks to Active Stars, Planets and Life', and the related FWF NFN subprojects, S116 606-N16 'Magnetospheric Electrodynamics of Exoplanets' and S116607-N16 'Particle/Radiative Interactions with Upper Atmospheres of Planetary Bodies Under Extreme Stellar Conditions'. KGK, HL and PO thank also the Helmholtz Alliance project 'Planetary Evolution and Life'. ML and PO acknowledge support from the FWF project P22950-N16. NVE acknowledges support by the RFBR grant No 12-05-00152-a. The authors also acknowledge support from the EU FP7 project IMPEx (No. 262863) and the EUROPLANET-RI projects, JRA3/EMDAF and the Na2 science working group WG5. The authors thank the International Space Science Institute (ISSI) in Bern, and the ISSI team 'Characterizing stellar- and exoplanetary environments'. Finally, we thank an anonymous referee for interesting suggestions and recommendations which helped to improve the article. . - 10. - ISSN 0035-8711РУБ Astronomy & Astrophysics

Аннотация: The discovery of transiting 'super-Earths' with inflated radii and known masses, such as Kepler-11b-f, GJ 1214b and 55 Cnc e, indicates that these exoplanets did not lose their nebula-captured hydrogen-rich, degassed or impact-delivered protoatmospheres by atmospheric escape processes. Because hydrodynamic blow-off of atmospheric hydrogen atoms is the most efficient atmospheric escape process we apply a time-dependent numerical algorithm which is able to solve the system of 1D fluid equations for mass, momentum and energy conservation to investigate the criteria under which 'super-Earths' with hydrogen-dominated upper atmospheres can experience hydrodynamic expansion by heating of the stellar soft X-rays and extreme ultraviolet (XUV) radiation and thermal escape via blow-off. Depending on orbit location, XUV flux, heating efficiency and the planet's mean density our results indicate that the upper atmospheres of all 'super-Earths' can expand to large distances, so that except for Kepler-11c all of them experience atmospheric mass-loss due to Roche lobe overflow. The atmospheric mass loss of the studied 'super-Earths' is one to two orders of magnitude lower compared to that of 'hot Jupiters' such as HD 209458b, so that one can expect that these exoplanets cannot lose their hydrogen envelopes during their remaining lifetimes.


Доп.точки доступа:
Lammer, H.; Erkaev, N.V.; Еркаев, Николай Васильевич; Odert, P.; Kislyakova, K.G.; Leitzinger, M.; Khodachenko, M.L.

/ K. G. Kislyakova [et al.] // Astrobiology. - 2013. - Vol. 13, Is. 11. - P1030-1048, DOI 10.1089/ast.2012.0958 . - ISSN 1531-1074
Аннотация: We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R Earth and a mass of 10 MEarth, located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×1025 s-1 to ∼5.3×1030 s-1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EOH) to <3 EOH and usually is several times smaller in comparison to the thermal atmospheric escape rates. © 2013 Mary Ann Liebert, Inc.

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Держатели документа:
Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, A-8042 Graz, Austria
Institute of Physics, University of Graz, Graz, Austria
Swedish Institute of Space Physics, Kiruna, Sweden
Institute of Computational Modelling, Siberian Division of the Russian Academy of Sciences, Krasnoyarsk, Russian Federation
SINP, Moscow State University, Moscow, Russian Federation
Polar Geophysical Institute (PGI), Russian Academy of Sciences, Murmansk, Russian Federation
Institute of Astrophysics, University of Vienna, Austria
ИВМ СО РАН

Доп.точки доступа:
Kislyakova, K.G.; Lammer, H.; Holmstrom, M.; Panchenko, M.; Odert, P.; Erkaev, N.V.; Еркаев, Николай Васильевич; Leitzinger, M.; Khodachenko, M.L.; Kulikov, Y.N.; Gudel, M.; Hanslmeier, A.

[Text] / T. Penza [et al.] // Planet Space Sci. - 2008. - Vol. 56, Is. 9. - P1260-1272, DOI 10.1016/j.pss.2008.04.005. - Cited References: 53 . - ISSN 0032-0633РУБ Astronomy & Astrophysics

Аннотация: We investigate the efficiency of the atmospheric mass loss due to hydrodynamic blow-off over the lifetime of the exoplanet HD209458b by studying numerically its hydrogen wind for host star X-ray and EUV (XUV) fluxes between 1 and 100 times that of the present Sun. We apply a time-dependent numerical algorithm which is able to solve the system of hydrodynamic equations straight through the transonic point of the flow including Roche lobe effects. The mass loss rates are calculated as functions of the absorbed energy in the thermosphere. Depending on the heating efficiency for a hydrogen-rich thermosphere the maximum temperature obtained in our study at 1.5R(p1) by neglecting IR cooling is about 5000-10,000 K for heating efficiencies of 10% and 60%, respectively. We find that the upper atmosphere of HD209458b experiences hydrodynamic blow-off even at such low temperatures if one does not neglect gravitational effects caused by the proximity of the planet to its Roche lobe boundary. Depending on the heating efficiency, we find from the solution of the hydrodynamic equations of mass, momentum, and energy balance that energy-limited mass loss rate estimations overestimate the realistic mass loss rate at present time for HD209458b by several times. Using the maximum heating efficiency for hydrogen-rich atmospheres of 60% we find that HD209458b may experience an atmospheric mass loss rate at present time of about 3.5 x 10(10) g s(-1). The mass loss rate evolves to higher values for higher XUV fluxes expected during the early period of the planet's host star evolution, reaching values of several times 10(12) gs(-1). The integrated mass loss is found to be between 1.8% and 4.4% of the present mass of HD209458b. We found that the influence of the stellar tidal forces on atmospheric loss (the Roche lobe effect) is not significant at 0.045 AU. For a similar exoplanet, but at closer orbital distances <= 0.02 AU, the combined effect of the Roche lobe and the high XUV radiation result in much higher thermal loss rates of about 2.6 x 10(11) g s(-1) and even more for early stages. This leads to a total loss over 4 Gyr of 27.5% of the planetary mass. (c) 2008 Elsevier Ltd. All rights reserved.

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Доп.точки доступа:
Penza, T.; Erkaev, N.V.; Еркаев, Николай Васильевич; Kulikov, Y.N.; Langmayr, D.; Lammer, H.; Micela, G.; Cecchi-Pestellini, C.; Biernat, H.K.; Selsis, F.; Barge, P.; Deleuil, M.; Leger, A.

[Text] / N. V. Erkaev [et al.] // Astron. Astrophys. - 2007. - Vol. 472, Is. 1. - P329-334, DOI 10.1051/0004-6361:20066929. - Cited References: 26 . - ISSN 0004-6361РУБ Astronomy & Astrophysics

Аннотация: Context. A study of the mass loss enhancement for very close "Hot Jupiters" due to the gravitational field of the host star is presented. Aims. The influence of the proximity to a planet of the Roche lobe boundary on the critical temperature for blow-off conditions for estimating the increase of the mass loss rate through hydrodynamic blow-off for close-in exoplanets is investigated. Methods. We consider the gravitational potential for a star and a planet along the line that joins their mass centers and the energy balance equation for an evaporating planetary atmosphere including the effect of the stellar tidal force on atmospheric escape. Results. By studying the effect of the Roche lobe on the atmospheric loss from short-periodic gas giants we derived reasonably accurate approximate formulas to estimate atmospheric loss enhancement due to the action of tidal forces on a "Hot Jupiter" and to calculate the critical temperature for the onset of "geometrical blow-off", which are valid for any physical values of the Roche lobe radial distance. Using these formulas, we found that the stellar tidal forces can enhance the hydrodynamic evaporation rate from TreS-1 and OGLE-TR-56b by about 2 fold, while for HD 209458b we found an enhancement of about 50%. For similar exoplanets which are closer to their host star than OGLE-TR-56b, the mass loss enhancement can be even larger. Moreover, we showed that the effect of the Roche lobe allows "Hot Jupiters" to reach blow-off conditions at temperatures which are less than expected due to the stellar X-ray and EUV heating.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Kulikov, Y.N.; Lammer, H.; Selsis, F.; Langmayr, D.; Jaritz, G.F.; Biernat, H.K.

[Text] / M. L. Khodachenko [et al.] // Planet Space Sci. - 2007. - Vol. 55: Symposium on Exoplanets and Planetary Formation (APR 25-30, 2004, Nice, FRANCE), Is. 5. - P631-642, DOI 10.1016/j.pss.2006.07.010. - Cited References: 63 . - ISSN 0032-0633РУБ Astronomy & Astrophysics

Аннотация: Atmospheric erosion due to CME-caused ion pick-up is investigated here for the first time for short periodic gas giants (so-called "Hot Jupiters") orbiting close to a star, To study the effect of encountering CMEs produced on the inagnetospheres and atmospheres of "Hot Jupiters" we model possible interaction of dense CME plasma with the exoplanet HD209458b (r(pl) = 1.43r(Jup) M(pl) = 0.69 M(jup)), which orbits a 4.0-5.0 Gyr old Sun-like star at a distance of about 0.045 AU. A numerical hydrodynamic model is applied for calculation of the upper atmospheric density and the hydrogen wind of HD209458b Lis a function of planetocentric distance. Taking into account the similarity of HD209458b's host star to Our Sun we use for the study of the ion production and loss rate of H(+) ions the solar CME plasma parameters and apply a numerical test particle model. Tidal-locking of short periodic exoplanets closely located to their host stars should result in weaker intrinsic planetary magnetic moments, as compared to those of the fast rotating Jupiter type planets at much larger orbits. It is shown that in this case the encountering CME plasma can compress the magnetospheric stand-off distance of short periodic "Hot Jupiters" down to the heights Lit which the ionization and pick-LIP of the planetary neutral atmosphere by the CME plasma flow take place. Assuming for the host star of HD209458b the same CME occurrence rate Lis on the Suit, we estimate possible total mass loss rates of HD2094581b due to its collisions with CMEs over the planet lifetime. It has been found that Under different estimations of the value of a planetary magnetic moment, HD209458b Could have lost over its lifetime the mass from 0-2 up to several times of its present mass M(pl). (c) 2006 Elsevier Ltd. All rights reserved.


Доп.точки доступа:
Khodachenko, M.L.; Lammer, H.; Lichtenegger, H.I.M.; Langmayr, D.; Erkaev, N.V.; Еркаев, Николай Васильевич; Griessmeier, J.M.; Leitner, M.; Penz, T.; Biernat, H.K.; Motschmann, U.; Rucker, H.O.

[Text] / H. . Lammer [et al.] // Astrobiology. - 2007. - Vol. 7, Is. 1. - P185-207, DOI 10.1089/ast.2006.0128. - Cited References: 104 . - ISSN 1531-1074РУБ Astronomy & Astrophysics + Biology + Geosciences, Multidisciplinary

Аннотация: Atmospheric erosion Of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wavelengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 mu m band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O+ ion pick up at orbital distances <= 0.2 astronomical units. We have found that, when exposed to intense XUV fluxes, atmospheres with CO2/N-2 mixing ratios lower than 96% will show an increase in exospheric temperatures and expanded thermosphere-exosphere environments. Hence, they suffer stronger atmospheric erosion, which can result in the total loss of several hundred bars even if an exoplanet is protected by a "magnetic shield" with its boundary located at I Earth radius above the surface. Furthermore, our study indicates that magnetic moments of tidally locked Earth-like exoplanets are essential for protecting their expanded upper atmospheres because of intense XUV radiation against CME plasma erosion. Therefore, we suggest that larger and more massive terrestrial-type exoplanets may better protect their atmospheres against CMEs, because the larger cores of such exoplanets would generate stronger magnetic moments and their higher gravitational acceleration would constrain the expansion of their thermosphere-exosphere regions and reduce atmospheric escape.


Доп.точки доступа:
Lammer, H.; Lichtenegger, H.I.M.; Kulikov, Y.N.; Griessmeier, J.M.; Terada, N.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.; Khodachenko, M.L.; Ribas, I.; Penz, T.; Selsis, F.

[Text] / G. F. Jaritz [et al.] // Astron. Astrophys. - 2005. - Vol. 439, Is. 2. - P771-775, DOI 10.1051/0004-6361:20052946. - Cited References: 32 . - ISSN 0004-6361РУБ Astronomy & Astrophysics

Аннотация: Theoretical studies and recent observational evidence of the expansion of the atmospheres of short-periodic exoplanets show that the atmospheres extend up to several planetary radii. This indicates that the atmospheres experience blow-off conditions. Because of the short orbital distance to their host stars, the expansion of the upper atmosphere is no longer radially symmetric, but depends on the direction to the central body, resulting in a deformation of the expanded atmosphere. We show the connection between atmospheric expansion, tidal forces and effects of the Roche potential and find that HD209458 b, OGLE-TR-10 b and OGLE-TR-111 b are most likely in a state of classical hydrodynamical blow-off because the distance where blow-off can occur is less than the distance to the Lagrangian point L1. On the other hand, OGLE-TR-56 b, OGLE-TR-113 b, OGLE-TR-132 b and TreS-1 experience a geometrical blow-off defined by the Roche lobe as proposed by Lecavelier des Etangs et al. (2004, A&A, 418, L1). Our results have important implications for the evolution of short periodic gas giants, because the Roche lobe overflow of the atmosphere can lead to lower mass loss rates over the exoplanets history, compared to gas giants which experience hydrodynamic expansion and loss unaffected by this boundary. Thus, massive exoplanets like OGLE-TR-56 b in very close orbital distances are subject to geometrical blow-off conditions, this results in a total mass loss for this particular exoplanet of the order of about 3 x 10(-2) M-pl over the planets age, even if current mass loss rates of about 2 x 10(11) g s(-1) are calculated. If the exoplanet effected by the geometrical blow-off is more massive, the mass loss rate is even lower. However, giant exoplanets like HD209458 b, OGLE-TR-10 b and OGLE-TR-111 b at orbital distances of about 0.05 AU may experience classical hydrodynamic blow-off conditions, which can result in higher mass loss rates. Thus, such planets may shrink to their core sizes during the X-ray and EUV active periods of their host stars as proposed by Lammer et al. ( 2003, ApJ, L121, 598) and Bara. e et al. (2004, A& A, 419, L13).


Доп.точки доступа:
Jaritz, G.F.; Endler, S.; Langmayr, D.; Lammer, H.; Griessmeier, J.M.; Erkaev, N.V.; Еркаев, Николай Васильевич; Biernat, H.K.

[Text] / N. V. Erkaev [et al.] // Astrophys. J. Suppl. Ser. - 2005. - Vol. 157, Is. 2. - P396-401, DOI 10.1086/427904. - Cited References: 48 . - ISSN 0067-0049РУБ Astronomy & Astrophysics

Аннотация: During the past years, more than 130 giant planets were discovered in extrasolar planetary systems. Because of the fact that the orbital distances are very close to their host stars, these planets are embedded in a dense stellar wind, which can pick up planetary ions. We model the stellar wind interaction of the short-periodic exoplanets OGLE-TR-56b and HD 209458b at their orbital distances of approximate to 0.023 AU and approximate to 0.045 AU, by calculating the Alfven Mach number and the magnetosonic Mach number in the stellar wind plasma flow. We then analyze the different plasma interaction regimes around the planetary obstacles, which appear for different stellar wind parameters. Our study shows that the stellar wind plasma parameters like temperature, interplanetary magnetic field, particle density, and velocity near planetary obstacles at orbital distances closer than 0.1-0.2 AU have conditions such that no bow shocks evolve. Our study shows also that these close-in exoplanets are in a submagnetosonic regime comparable to the magnetospheric plasma interaction of the inner satellites of Jupiter and Saturn. Furthermore, we compare the results achieved for both exoplanets with the Jupiter-class exoplanet HD 28185b at its orbital distance of approximate to 1.03 AU. Finally, we also discuss the behavior of the stellar wind plasma flow close to the planetary obstacles of two highly eccentric gas giants, namely, HD 108147b and HD 162020b. Because of their eccentric orbits, these two exoplanets periodically experience both regimes with and without a bow shock. Finally, we simulate the neutral gas density of HD 209458b with a Monte Carlo model. By using the plasma parameters obtained in our study we calculate the ion production and loss rate of H+ with a test particle model. Our simulations yield H+ loss rates for HD 209458b or similar giant exoplanets in orders of about 10(8)-10(9) g s(-1). These ion loss rates are at least 1 order of magnitude lower than the observed loss rate of evaporating neutral H atoms. Our study indicates, that similar gas giants at larger orbital distances have lower ion loss rates. Thus, the dominating component of particle loss of short-periodic Jupiter-class exoplanets will be neutral hydrogen.


Доп.точки доступа:
Erkaev, N.V.; Еркаев, Николай Васильевич; Penz, T.; Lammer, H.; Lichtenegger, H.I.M.; Biernat, H.K.; Wurz, P.; Griessmeier, J.M.; Weiss, W.W.

[Text] / H. . Lammer [et al.] // Astron. Astrophys. - 2009. - Vol. 506, Is. 1. - P399-410, DOI 10.1051/0004-6361/200911922. - Cited References: 46. - The authors thank the anonymous referee for constructive comments and suggestions which helped to improve the paper. H. Lammer, P. Odert, M. Leitzinger, M. L. Khodachenko and A. Hanslmeier gratefully acknowledge the Austrian Fonds zur Forderung der wissenschaftlichen Forschung (FWF grant P19446) for supporting this project. M. Panchenko and M. L. Khodachenko acknowledge also the Austrian Fonds zur Forderung der wissenschaftlichen Forschung (project P20680-N16). H. Lammer, H. I. M. Lichtenegger, H. K. Biernat, Yu. N. Kulikov and N. V. Erkaev thank the AAS "Verwaltungsstelle fur Auslandsbeziehungen" and the RAS. H. Lammer, H. I. M. Lichtenegger, M. L. Khodachenko and Yu. N. Kulikov acknowledge support from the Helmholtz-Gemeinschaft as this research has been supported by the Helmholtz Association through the research alliance "Planetary Evolution and Life". H. Lammer, M. L. Khodachenko, T. Penz, and Yu. N. Kulikov also acknowledge the International Space Science Institute (ISSI; Bern, Switzerland) and the ISSI teams "Evolution of Habitable Planets" and "Evolution of Exoplanet Atmospheres and their Characterization". H. K. Biernat acknowledges additional support due to the Austrian Science Fund under project P20145-N16. The authors also acknowledge fruitful discussions during various meetings related to the Europlanet N2 activities as well as within the N2 Exoplanet discipline working group DWG 7. T. Penz and G. Micela acknowledge support by the Marie Curie Fellowship Contract No. MTKD-CT-2004-002769 of the project "The influence of stellar high radiation on planetary atmospheres". The authors also thank the Austrian Ministry bm:bwk and ASA for funding the CoRoT project. . - ISSN 0004-6361РУБ Astronomy & Astrophysics

Аннотация: Aims. We study the possible atmospheric mass loss from 57 known transiting exoplanets around F, G, K, and M-type stars over evolutionary timescales. For stellar wind induced mass loss studies, we estimate the position of the pressure balance boundary between Coronal Mass Ejection (CME) and stellar wind ram pressures and the planetary ionosphere pressure for non- or weakly magnetized gas giants at close orbits. Methods. The thermal mass loss of atomic hydrogen is calculated by a mass loss equation where we consider a realistic heating efficiency, a radius-scaling law and a mass loss enhancement factor due to stellar tidal forces. The model takes into account the temporal evolution of the stellar EUV flux by applying power laws for F, G, K, and M-type stars. The planetary ionopause obstacle, which is an important factor for ion pick-up escape from non- or weakly magnetized gas giants is estimated by applying empirical power-laws. Results. By assuming a realistic heating efficiency of about 10-25% we found that WASP-12b may have lost about 6-12% of its mass during its lifetime. A few transiting low density gas giants at similar orbital location, like WASP-13b, WASP-15b, CoRoT-1b or CoRoT-5b may have lost up to 1-4% of their initial mass. All other transiting exoplanets in our sample experience negligible thermal loss (<= 1%) during their lifetime. We found that the ionospheric pressure can balance the impinging dense stellar wind and average CME plasma flows at distances which are above the visual radius of "Hot Jupiters", resulting in mass losses <2% over evolutionary timescales. The ram pressure of fast CMEs cannot be balanced by the ionospheric plasma pressure for orbital distances between 0.02-0.1 AU. Therefore, collisions of fast CMEs with hot gas giants should result in large atmospheric losses which may influence the mass evolution of gas giants with masses
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Доп.точки доступа:
Lammer, H.; Odert, P.; Leitzinger, M.; Khodachenko, M.L.; Panchenko, M.; Kulikov, Y.N.; Zhang, T.L.; Lichtenegger, H.I.M.; Erkaev, N.V.; Еркаев, Николай Васильевич; Wuchterl, G.; Micela, G.; Penz, T.; Biernat, H.K.; Weingrill, J.; Steller, M.; Ottacher, H.; Hasiba, J.; Hanslmeier, A.; Austrian Fonds zur Forderung der wissenschaftlichen Forschung [P19446, P20680-N16]; Helmholtz Association; Austrian Science Fund [P20145-N16]; "The influence of stellar high radiation on planetary atmospheres" [MTKD-CT-2004-002769]

[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]

/ I. F. Shaikhislamov [et al.] // Astrophys. J. - 2014. - Vol. 795, Is. 2, DOI 10.1088/0004-637X/795/2/132 . - ISSN 0004-637X
Аннотация: In the present series of papers we propose a consistent description of the mass loss process. To study in a comprehensive way the effects of the intrinsic magnetic field of a close-orbit giant exoplanet (a so-called hot Jupiter) on atmospheric material escape and the formation of a planetary inner magnetosphere, we start with a hydrodynamic model of an upper atmosphere expansion in this paper. While considering a simple hydrogen atmosphere model, we focus on the self-consistent inclusion of the effects of radiative heating and ionization of the atmospheric gas with its consequent expansion in the outer space. Primary attention is paid to an investigation of the role of the specific conditions at the inner and outer boundaries of the simulation domain, under which different regimes of material escape (free and restricted flow) are formed. A comparative study is performed of different processes, such as X-ray and ultraviolet (XUV) heating, material ionization and recombination, H+ 3 cooling, adiabatic and Lyα cooling, and Lyα reabsorption. We confirm the basic consistency of the outcomes of our modeling with the results of other hydrodynamic models of expanding planetary atmospheres. In particular, we determine that, under the typical conditions of an orbital distance of 0.05AU around a Sun-type star, a hot Jupiter plasma envelope may reach maximum temperatures up to ∼9000K with a hydrodynamic escape speed of ∼9 km s-1, resulting in mass loss rates of ∼ (4-7) · 1010 g s-1. In the range of the considered stellar-planetary parameters and XUV fluxes, that is close to the mass loss in the energy-limited case. The inclusion of planetary intrinsic magnetic fields in the model is a subject of the follow-up paper (Paper II).

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Institute of Computational Modelling, SB RASKrasnoyarsk, Russian Federation

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Shaikhislamov, I.F.; Khodachenko, M.L.; Sasunov, Y.L.; Lammer, H.; Kislyakova, K.G.; Erkaev, N.V.; Еркаев, Николай Васильевич

/ H. Lammer [et al.] // Origins of Life and Evolution of Biospheres. - 2014. - Vol. 44, Iss. 3. - P239-260, DOI 10.1007/s11084-014-9377-2 . - ISSN 0169-6149
Аннотация: We study the origin and escape of catastrophically outgassed volatiles (H2O, CO2) from exomoons with Earth-like densities and masses of 0.1, 0.5 and 1 M? orbiting an extra-solar gas giant inside the habitable zone of a young active solar-like star. We apply a radiation absorption and hydrodynamic upper atmosphere model to the three studied exomoon cases. We model the escape of hydrogen and dragged dissociation products O and C during the activity saturation phase of the young host star. Because the soft X-ray and EUV radiation of the young host star may be up to ~100 times higher compared to today’s solar value during the first 100 Myr after the system’s origin, an exomoon with a mass < 0.25 M? located in the HZ may not be able to keep an atmosphere because of its low gravity. Depending on the spectral type and XUV activity evolution of the host star, exomoons with masses between ~0.25 and 0.5 M? may evolve to Mars-like habitats. More massive bodies with masses >0.5 M?, however, may evolve to habitats that are a mixture of Mars-like and Earth-analogue habitats, so that life may originate and evolve at the exomoon’s surface.

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Доп.точки доступа:
Lammer, H.; Schiefer, S.-C.; Juvan, I.; Odert, P.; Erkaev, N.V.; Еркаев, Николай Васильевич; Weber, C.; Kislyakova, K.G.; Gudel, M.; Kirchengast, G.; Hanslmeier, A.

/ H. Lammer [et al.] // Mon. Not. R. Astron. Soc. Lett. - 2016. - Vol. 461, Is. 1. - PL62-L66, DOI 10.1093/mnrasl/slw095 . - ISSN 1745-3925
Аннотация: For the hot exoplanets CoRoT-24b and CoRoT-24c, observations have provided transit radii RT of 3.7 ± 0.4R? and 4.9 ± 0.5R?, and masses of ?5.7M? and 28 ± 11M?, respectively. We study their upper atmosphere structure and escape applying an hydrodynamic model. Assuming RT ? RPL, where RPL is the planetary radius at the pressure of 100 mbar, we obtained for CoRoT-24b unrealistically high thermally driven hydrodynamic escape rates. This is due to the planet's high temperature and low gravity, independent of the stellar EUV flux. Such high escape rates could last only for <100 Myr, while RPL shrinks till the escape rate becomes less than or equal to the maximum possible EUV-driven escape rate. For CoRoT-24b, RPL must be therefore located at ?1.9-2.2R? and high altitude hazes/clouds possibly extinct the light at RT. Our analysis constraints also the planet's mass to be 5-5.7M?. For CoRoT-24c, RPL and RT lie too close together to be distinguished in the same way. Similar differences between RPL and RT may be present also for other hot, low-density sub-Neptunes. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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Держатели документа:
Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, Graz, Austria
Institute of Computational Modelling SB RAS, Krasnoyarsk, Russian Federation
Siberian Federal University, Krasnoyarsk, Russian Federation
Thuringer Landessternwarte Tautenburg, Sternwarte 5, Tautenburg, Germany
Institute for Astronomy, University of Vienna, Turkenschanzstrasse 17, Vienna, Austria

Доп.точки доступа:
Lammer, H.; Erkaev, N. V.; Fossati, L.; Juvan, I.; Odert, P.; Cubillos, P. E.; Guenther, E.; Kislyakova, K. G.; Johnstone, C. P.; Luftinger, T.; Gudel, M.

/ P. Cubillos [et al.] // Mon. Not. Roy. Astron. Soc. - 2017. - Vol. 466, Is. 2. - P1868-1879, DOI 10.1093/mnras/stw3103. - Cited References:107. - We thank contributors to SCIPY, MATPLOTLIB (Hunter 2007), the PYTHON programming language, and contributors to the free and open-source community. We thank the anonymous referee for comments that significantly improved the quality of the paper. This research has made use of the Exoplanet Orbit Database and the Exoplanet Data Explorer at exoplanets.org and the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. We acknowledge the Austrian Forschungsforderungsgesellschaft FFG projects 'RASEN' P847963 and 'TAPAS4CHEOPS' P853993, the Austrian Science Fund (FWF) National Research Network projects S11607-N16 and S11604-N16, and the FWF project P27256-N27. NVE acknowledges support by the Russian Foundation for Basic Research grant no. 15-05-00879-a and no. 16-52-14006 ANF-a. . - ISSN 0035-8711. - ISSN 1365-2966РУБ Astronomy & Astrophysics

Аннотация: We present a uniform analysis of the atmospheric escape rate of Neptune-like planets with estimated radius and mass (restricted to M-p < 30M(circle plus)). For each planet, we compute the restricted Jeans escape parameter, Lambda, for a hydrogen atom evaluated at the planetary mass, radius, and equilibrium temperature. Values of Lambda less than or similar to 20 suggest extremely high mass-loss rates. We identify 27 planets (out of 167) that are simultaneously consistent with hydrogen-dominated atmospheres and are expected to exhibit extreme mass-loss rates. We further estimate the mass-loss rates (L-hy) of these planets with tailored atmospheric hydrodynamic models. We compare L-hy to the energy-limited (maximum-possible high-energy driven) mass-loss rates. We confirm that 25 planets (15 per cent of the sample) exhibit extremely high mass-loss rates (L-hy > 0.1M(circle plus) Gyr(-1)), well in excess of the energy-limited mass-loss rates. This constitutes a contradiction, since the hydrogen envelopes cannot be retained given the high mass-loss rates. We hypothesize that these planets are not truly under such high mass-loss rates. Instead, either hydrodynamic models overestimate the mass-loss rates, transit-timing-variation measurements underestimate the planetary masses, optical transit observations overestimate the planetary radii (due to high-altitude clouds), or Neptunes have consistently higher albedos than Jupiter planets. We conclude that at least one of these established estimations/ techniques is consistently producing biased values for Neptune planets. Such an important fraction of exoplanets with misinterpreted parameters can significantly bias our view of populations studies, like the observed mass-radius distribution of exoplanets for example.

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Держатели документа:
Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
SB RAS, Krasnoyarsk Sci Ctr, Fed Res Ctr, Inst Computat Modelling, Krasnoyarsk 660036, Russia.
Univ Vienna, Dept Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria.
Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.

Доп.точки доступа:
Cubillos, Patricio; Erkaev, N.V.; Еркаев, Николай Васильевич; Juvan, Ines; Fossati, Luca; Johnstone, Colin P.; Lammer, Helmut; Lendl, Monika; Odert, Petra; Kislyakova, Kristina G.; Austrian Forschungsforderungsgesellschaft FFG [P847963, P853993]; Austrian Science Fund (FWF) National Research Network projects [S11607-N16, S11604-N16]; FWF [P27256-N27]; Russian Foundation for Basic Research [15-05-00879-a, 16-52-14006 ANF-a]

[Text] / N. V. Erkaev [et al.] // Mon. Not. Roy. Astron. Soc. - 2017. - Vol. 470, Is. 4. - P4330-4336, DOI 10.1093/mnras/stx1471. - Cited References:54. - The authors thank the anonymous referee for their useful comments. HL, PO and NVE 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'. The authors acknowledge the support by the FWF NFN project S11601-N16 'Pathways to Habitability: From Disks to Active Stars, Planets and Life', and the related FWF NFN subprojects, S11604-N16 'Radiation & Wind Evolution from T Tauri Phase to ZAMS and Beyond' (CJ), S11606-N16 'Magnetospheric Electrodynamics of Exoplanets' (MLK) and S11607-N16 'Particle/Radiative Interactions with Upper Atmospheres of Planetary Bodies Under Extreme StellarConditions' (KK, HL, NVE). DK, LF and NVE acknowledge also the Austrian Forschungsforderungsgesellschaft FFG project 'TAPAS4CHEOPS' P853993. The authors further acknowledge support by the Russian Foundation of Basic Research grants no. 15-05-00879-a (NVE, AVM) and no. 16-52-14006 (NVE, AVM, IFS). MLK also acknowledges support by FWF projects I2939-N27, P25587-N27, P25640-N27 and the Leverhulme Trust Grant IN-2014-016. . - ISSN 0035-8711. - ISSN 1365-2966РУБ Astronomy & Astrophysics

Аннотация: We investigate the interaction between the magnetized stellar wind plasma and the partially ionized hydrodynamic hydrogen outflow from the escaping upper atmosphere of non-magnetized or weakly magnetized hot Jupiters. We use the well-studied hot Jupiter HD 209458b as an example for similar exoplanets, assuming a negligible intrinsic magnetic moment. For this planet, the stellar wind plasma interaction forms an obstacle in the planet's upper atmosphere, in which the position of the magnetopause is determined by the condition of pressure balance between the stellar wind and the expanded atmosphere, heated by the stellar extreme ultraviolet radiation. We show that the neutral atmospheric atoms penetrate into the region dominated by the stellar wind, where they are ionized by photoionization and charge exchange, and then mixed with the stellar wind flow. Using a 3D magnetohydrodynamic (MHD) model, we show that an induced magnetic field forms in front of the planetary obstacle, which appears to be much stronger compared to those produced by the solar wind interaction with Venus and Mars. Depending on the stellar wind parameters, because of the induced magnetic field, the planetary obstacle can move up to approximate to 0.5-1 planetary radii closer to the planet. Finally, we discuss how estimations of the intrinsic magnetic moment of hot Jupiters can be inferred by coupling hydrodynamic upper planetary atmosphere and MHD stellar wind interaction models together with UV observations. In particular, we find that HD 209458b should likely have an intrinsic magnetic moment of 10-20 per cent that of Jupiter.

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Держатели документа:
Inst Computat Modelling SB RAS, Krasnoyarsk 660036, Russia.
Siberian Fed Univ, Krasnoyarsk 660041, Russia.
Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
Univ Vienna, Inst Astron, Turkenschanzstr 17, A-1180 Vienna, Austria.
Inst Laser Phys SB RAS, Novosibirsk 630090, Russia.

Доп.точки доступа:
Erkaev, N. V.; Odert, P.; Lammer, H.; Kislyakova, K. G.; Fossati, L.; Mezentsev, A. V.; Johnstone, C. P.; Kubyshkina, D. I.; Shaikhislamov, I. F.; Khodachenko, M. L.; Austrian Science Fund (FWF) [P25256-N27]; FWF NFN [S11601-N16, S11604-N16, S11606-N16, S11607-N16]; Austrian Forschungsforderungsgesellschaft FFG [P853993]; Russian Foundation [15-05-00879-a, 16-52-14006]; FWF [I2939-N27, P25587-N27, P25640-N27]; Leverhulme Trust [IN-2014-016]

/ I. F. Shaikhislamov [et al.] // Astrophys. J. - 2018. - Vol. 866, Is. 1. - Ст. 47, DOI 10.3847/1538-4357/aadf39. - Cited References:48. - This work was supported by grant No. 18-12-00080 of the Russian Science Foundation. H.L., L.F., N.D., M.G., K.G.K., C.P.J. acknowledge the Austrian Science Foundation (FWF) project I2939-N27, FWF-NFN projects S11606-N16, WS11607-N16 and S11604-N16. M.L.K. also acknowledges the FWF projects P25587-N27, P25640-N27 and Leverhulme Trust grant IN-2014-016. Parallel computing simulations, key for this study, have been performed at Computation Center of Novosibirsk State University, SB RAS Siberian Supercomputer Center, and Supercomputing Center of the Lomonosov Moscow State University. . - ISSN 0004-637X. - ISSN 1538-4357РУБ Astronomy & Astrophysics

Аннотация: The absorption of stellar radiation observed by HD 209458b in the resonant lines of O I and C II has not yet been satisfactorily explained. We apply a 2D hydrodynamic multi-fluid model that self-consistently describes the expanding planetary wind, driven by stellar XUV radiation and influenced by tidal forces and the surrounding stellar wind. According to this model, HD 209458b has a hydrogen-dominated plasmasphere, expanding beyond the Roche lobe, in the form of two supersonic streams that propagate toward and away from the star. The species heavier than hydrogen and helium are dragged in the escaping material streams and accelerated up to 50 km s(-1). Our simulations show that, assuming solar abundances, O I and C II produce absorption due to the Doppler resonance mechanism at the level of 6%-10%, which is consistent with the observations. Most of this absorption takes place in the streams. The transit depth in the O I and C II lines is unaffected by the stellar wind, unless it is strong enough to form a compact bowshock around the planet and able to redirect all the escaping material to the tail. In this case, the absorption profile becomes asymmetric due to the prominent blueshifted attenuation. Thus, the spectroscopic measurements enable probing of the planetary wind character, as well as the strength of the stellar wind. The computed absorption at wavelengths of the Si III, Mg I, and Mg II lines at solar abundances appears to be much stronger, compared to the observations. This possibly indicates that Si and Mg may be under-abundant in the upper atmosphere of HD 209458b.

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Держатели документа:
Inst Laser Phys SB RAS, Novosibirsk, Russia.
Austrian Acad Sci, Space Res Inst, Graz, Austria.
Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia.
Univ Vienna, Dept Astrophys, Vienna, Austria.
Inst Computat Modelling SB RAS, Krasnoyarsk, Russia.
Siberian Fed Univ, Polytech Inst, Krasnoyarsk, Russia.

Доп.точки доступа:
Shaikhislamov, I. F.; Khodachenko, M. L.; Lammer, H.; Fossati, L.; Dwivedi, N.; Gudel, M.; Kislyakova, K. G.; Johnstone, C. P.; Berezutsky, A. G.; Miroshnichenko, I. B.; Posukh, V. G.; Erkaev, N., V; Ivanov, V. A.; Russian Science Foundation [18-12-00080]; Austrian Science Foundation (FWF) [I2939-N27]; FWF-NFN projects [S11606-N16, WS11607-N16, S11604-N16]; FWF [P25587-N27, P25640-N27]; Leverhulme Trust [IN-2014-016]