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/ 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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Держатели документа:
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]