| 1. |
- Boyarchuk, A. A., et al.
(author)
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Scientific problems addressed by the Spektr-UV space project (world space Observatory-Ultraviolet)
- 2016
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In: Astronomy reports (Print). - 1063-7729 .- 1562-6881. ; 60:1, s. 1-42
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Journal article (peer-reviewed)abstract
- The article presents a review of scientific problems and methods of ultraviolet astronomy, focusing on perspective scientific problems (directions) whose solution requires UV space observatories. These include reionization and the history of star formation in the Universe, searches for dark baryonic matter, physical and chemical processes in the interstellar medium and protoplanetary disks, the physics of accretion and outflows in astrophysical objects, from Active Galactic Nuclei to close binary stars, stellar activity (for both low-mass and high-mass stars), and processes occurring in the atmospheres of both planets in the solar system and exoplanets. Technological progress in UV astronomy achieved in recent years is also considered. The well advanced, international, Russian-led Spektr-UV (World Space Observatory-Ultraviolet) project is described in more detail. This project is directed at creating a major space observatory operational in the ultraviolet (115-310 nm). This observatory will provide an effective, and possibly the only, powerful means of observing in this spectral range over the next ten years, and will be an powerful tool for resolving many topical scientific problems.
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| 2. |
- Greiner, J., et al.
(author)
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Gamma-ray burst investigation via polarimetry and spectroscopy (GRIPS)
- 2009
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In: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:1, s. 91-120
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Journal article (peer-reviewed)abstract
- The primary scientific goal of the GRIPS mission is to revolutionize our understanding of the early universe using gamma-ray bursts. We propose a new generation gamma-ray observatory capable of unprecedented spectroscopy over a wide range of gamma-ray energies (200 keV-50 MeV) and of polarimetry (200-1000 keV). The gamma-ray sensitivity to nuclear absorption features enables the measurement of column densities as high as 10(28)cm (-aEuro parts per thousand 2). Secondary goals achievable by this mission include direct measurements of all types of supernova interiors through gamma-rays from radioactive decays, nuclear astrophysics with massive stars and novae, and studies of particle acceleration near compact stars, interstellar shocks, and clusters of galaxies.
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| 3. |
- Fossati, L., et al.
(author)
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Searching for a gas cloud surrounding the WASP-18 planetary system
- 2014
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In: Astrophysics and Space Science. - : Springer Science and Business Media LLC. - 0004-640X .- 1572-946X. ; 354:1, s. 21-28
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Journal article (peer-reviewed)abstract
- Near-UV (NUV) Hubble Space Telescope (HST) observations of the extreme hot-Jupiter WASP-12b revealed the presence of diffuse exospheric gas extending beyond the planet's Roche lobe. Furthermore the NUV observations showed a complete lack of the normally bright core emission of the Mg ii h&k resonance lines, in agreement with the measured anomalously low stellar activity index (logR' (HK) ). Comparisons with other distant and inactive stars, and the analysis of radio and optical measurements of the intervening interstellar medium (ISM), led us to the conclusion that the system is surrounded by a circumstellar gas cloud, likely formed of material lost by the planet. Similar anomalous logR' (HK) index deficiencies might therefore signal the presence of translucent circumstellar gas around other stars hosting evaporating planets; we identified five such systems and WASP-18 is one of them. Both radio and optical observations of the region surrounding WASP-18 point towards a negligible ISM absorption along the WASP-18 line of sight. Excluding the unlikely possibility of an intrinsic anomalously low stellar activity, we conclude that the system is probably surrounded by a circumstellar gas cloud, presumably formed of material lost by the planet. Nevertheless only a far-UV spectrum of the star would provide a definite answer. Theoretical modelling suggests WASP-18b undergoes negligible mass loss, in contrast to the probable presence of a circumstellar gas cloud formed of material lost by the planet. The solution might be the presence either of an extra energy source driving mass loss (e.g., the reconnection of the stellar and planetary magnetic fields inside the planet atmosphere) or of an evaporating third body (e.g., moon).
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| 4. |
- Lammer, H., et al.
(author)
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Exoplanet status report: Observation, characterization and evolution of exoplanets and their host stars
- 2010
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In: Solar System Research. - 1608-3423 .- 0038-0946. ; 44:4, s. 290-310
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Journal article (peer-reviewed)abstract
- After the discovery of more than 400 planets beyond our Solar System, the characterization of exoplanets as well as their host stars can be considered as one of the fastest growing fields in space science during the past decade. The characterization of exoplanets can only be carried out in a well coordinated interdisciplinary way which connects planetary science, solar/stellar physics and astrophysics. We present a status report on the characterization of exoplanets and their host stars by reviewing the relevant space- and ground-based projects. One finds that the previous strategy changed from space mission concepts which were designed to search, find and characterize Earth-like rocky exoplanets to: A statistical study of planetary objects in order to get information about their abundance, an identification of potential target and finally its analysis. Spectral analysis of exoplanets is mandatory, particularly to identify bio-signatures on Earth-like planets. Direct characterization of exoplanets should be done by spectroscopy, both in the visible and in the infrared spectral range. The way leading to the direct detection and characterization of exoplanets is then paved by several questions, either concerning the pre-required science or the associated observational strategy.
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| 5. |
- Shematovich, V.I., et al.
(author)
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He2+ transport in the Martian upper atmosphere with an induced magnetic field
- 2013
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In: Journal of Geophysical Research - Space Physics. - : John Wiley & Sons. - 2169-9380 .- 2169-9402. ; 118:3, s. 1231-1242
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Journal article (peer-reviewed)abstract
- Solar wind helium may be a significant source of neutral helium in the Martian atmosphere. The precipitating particles also transfer mass, energy, and momentum. To investigate the transport of He2+ in the upper atmosphere of Mars, we have applied the direct simulation Monte Carlo method to solve the kinetic equation. We calculate the upward He, He+, and He2+ fluxes, resulting from energy spectra of the downgoing He2+ observed below 500 km altitude by the Analyzer of Space Plasmas and Energetic Atoms 3 instrument onboard Mars Express. The particle flux of the downward moving He2+ ions was 1–2 × 106 cm–2 s–1, and the energy flux is equal to 9–10 × 10–3 erg cm–2 s–1. The calculations of the upward flux have been made for the Martian atmosphere during solar minimum. It was found, that if the induced magnetic field is not introduced in the simulations the precipitating He2+ ions are not backscattered at all by the Martian upper atmosphere. If we include a 20 nT horizontal magnetic field, a typical field measured by Mars Global Surveyor in the altitude range of 85–500 km, we find that up to 30%–40% of the energy flux of the precipitating He2+ ions is backscattered depending on the velocity distribution of the precipitating particles. We thus conclude that the induced magnetic field plays a crucial role in the transport of charged particles in the upper atmosphere of Mars and, therefore, that it determines the energy deposition of the solar wind.
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| 6. |
- Shematovich, V.I., et al.
(author)
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Protons and hydrogen atoms transport in the Martian upper atmosphere with an induced magnetic field
- 2011
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116, s. A11320-
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Journal article (peer-reviewed)abstract
- We have applied the Direct Simulation Monte Carlo method to solve the kinetic equation for the H/H+ transport in the upper Martian atmosphere. We calculate the upward H and H+ fluxes, values that can be measured, and the altitude profile of the energy deposition to be used to understand the energy balance in the Martian atmosphere. The calculations of the upward flux have been made for the Martian atmosphere during solar minimum. We use an energy spectrum of the down moving protons in the altitude range 355–437 km adopted from the Mars Express Analyzer of Space Plasma and Energetic Atoms measurements in the range 700 eV–20 keV. The particle and energy fluxes of the downward moving protons were equal to 3.0 × 106 cm−2 s−1 and 1.4 × 10−2 erg cm−2 s−1. It was found that 22% of particle flux and 12% of the energy flux of the precipitating protons is backscattered by the Martian upper atmosphere, if no induced magnetic field is taken into account in the simulations. If we include a 20 nT horizontal magnetic field, a typical field measured by Mars Global Surveyor in the altitude range of 85–500 km, we find that up to 40%–50% of the energy flux of the precipitating protons is backscattered depending on the velocity distribution of the precipitating protons. We thus conclude that the induced magnetic field plays a crucial role in the transport of charged particles in the upper atmosphere of Mars and, therefore, that it determines the energy deposition of the solar wind.
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