A5081750356- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Planetary Science and Exploration
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Atmospheric Ozone and Climate
- Space Exploration and Technology
- Space Science and Extraterrestrial Life
- Astronomical and nuclear sciences
- Spacecraft Dynamics and Control
- History and Developments in Astronomy
- Spaceflight effects on biology
- Geomagnetism and Paleomagnetism Studies
- Global Energy and Sustainability Research
- Methane Hydrates and Related Phenomena
- Historical Astronomy and Related Studies
- Spacecraft and Cryogenic Technologies
- Geology and Paleoclimatology Research
- Origins and Evolution of Life
- Geochemistry and Geochronology of Asian Mineral Deposits
- Advanced Frequency and Time Standards
University of Graz
2014-2024
Czech Academy of Sciences, Institute of Physics
2020-2024
Austrian Academy of Sciences
2009-2020
Space Research Institute
2009-2020
Leibniz Institute for Astrophysics Potsdam
2018
Max Planck Institute for Astronomy
2018
Max Planck Society
2018
Nawi Graz
2016
Slovak Academy of Sciences
2009
Astronomical Institute of the Slovak Academy of Sciences
2009
<i>Aims. <i/>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 studies, we estimate position of pressure balance boundary between Coronal Mass Ejection (CME) ram pressures planetary ionosphere for non- or weakly magnetized gas giants at close orbits.<i>Methods. <i/>The thermal atomic hydrogen is calculated by a equation where consider realistic heating efficiency,...
Transit observations of HD 209458b in the stellar Lyman-α(Lyα) line revealed strong absorption both blue and red wings interpreted as hydrogen atoms escaping from planet's exosphere at high velocities. The following sources for were suggested: acceleration by radiation pressure, natural spectral broadening, or charge exchange with wind. We reproduced observation means modeling that includes all aforementioned processes. Our results support a wind velocity ≈400 kilometers per second time...
We investigate the origin and loss of captured hydrogen envelopes from protoplanets having masses in a range between 'sub-Earth'-like bodies 0.1 M⊕ 'super-Earths' with 5 habitable zone at 1 au Sun-like G star, assuming that their rocky cores had formed before nebula gas dissipated. model gravitational attraction accumulation around planet's core as function protoplanetary luminosity during accretion calculate resulting surface temperature by solving hydrostatic structure equations for...
Stimulated by the discovery of a number close-in low-density planets, we generalise Jeans escape parameter taking hydrodynamic and Roche lobe effects into account. We furthermore define $\Lambda$ as value calculated at observed planetary radius mass for planet's equilibrium temperature considering atomic hydrogen, independently atmospheric profile. consider 5 10 $M_{\oplus}$ planets with an 500 1000 K, orbiting early G-, K-, M-type stars. Assuming clear atmosphere comparing rates obtained...
The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known that are surrounded by dense H/He envelopes or contain deep H₂O oceans also hydrogen envelopes. Although these super-Earths orbiting relatively close to their host stars, they have not lost captured nebula-based hydrogen-rich degassed volatile-rich steam protoatmospheres. Thus, it is interesting estimate maximum possible amount of...
There is growing observational and theoretical evidence suggesting that atmospheric escape a key driver of planetary evolution. Commonly, evolution models employ simple analytic formulae (e.g., energy limited escape) are often inaccurate, more detailed physical loss usually only give snapshots an atmosphere's structure difficult to use for evolutionary studies. To overcome this problem, we upgrade already existing upper atmosphere hydrodynamic code produce large grid about 7000 covering...
Abstract Studies of planetary atmospheric composition, variability, and evolution require appropriate theoretical numerical tools to estimate key parameters, among which the mass-loss rate is often most important. In evolutionary studies, it common use energy-limited formula, attractive for its simplicity but ignores important physical effects can be inaccurate in many cases. To overcome this problem, we consider a recently developed grid about 7000 one-dimensional upper-atmosphere...
The ultrafast-rotating (Prot ≈ 0.44 d) fully convective single M4 dwarf V374 Peg is a well-known laboratory for studying intense stellar activity in stable magnetic topology. As an observable proxy the field, we study stability of light curve, hence spot configuration. We also measure occurrence rate flares and coronal mass ejections (CMEs). have analysed spectroscopic observations, BV(RI)C photometry covering 5 yrs, additional RC that expands temporal base over 16 yr. curve suggests almost...
We investigate the loss rates of hydrogen atmospheres terrestrial planets with a range masses and orbital distances by assuming stellar extreme ultraviolet (EUV) luminosity that is 100 times stronger than current Sun. apply 1D upper atmosphere radiation absorption hydrodynamic escape model takes into account ionization, dissociation recombination to calculate mass rates. study effects on thermal hydrogen-dominated super-Earths compare results those obtained energy-limited formula which...
Flares and CMEs can have deleterious effects on their surroundings: they erode atmospheres of orbiting planets over time also high importance in stellar evolution. Most the CME detections literature are single events found serendipitously sparse for statistical investigation. We aimed to gather a large amount spectral data M-dwarfs drastically increase number known make analysis possible order study properties potential CMEs. Using archive we investigated asymmetric features Balmer-lines,...
The discovery of transiting "super-Earths" with inflated radii and known masses such as Kepler-11b-f, GJ 1214b 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 hydrogen atoms is the most efficient process we apply a time-dependent numerical algorithm which able to solve system 1-D fluid equations for mass, momentum, energy conservation...
Latest research in planet formation indicate that Mars formed within a few million years (Myr) and remained planetary embryo never grew to more massive planet. It can also be expected from dynamical models, most of Mars' building blocks consisted material orbital locations just beyond the ice line which could have contained ~0.1-0.2 wt. % H2O. By using these constraints, we estimate nebula-captured catastrophically outgassed volatile contents during solidification magma ocean apply...
Terrestrial planets formed within gaseous protoplanetary disks can accumulate significant hydrogen envelopes. The evolution of such an atmosphere due to XUV driven evaporation depends on the activity host star, which itself sensitively its rotational evolution, and therefore initial rotation rate. In this Letter, we derive easily applicable method for calculating planetary that combines models a hydrostatic lower hydrodynamic upper atmosphere. We show rate central star is critical importance...
Aims. We study the interactions between stellar winds and extended hydrogen-dominated upper atmospheres of planets. estimate resulting escape planetary pick-up ions from five "super-Earths" in compact Kepler-11 system compare rates with efficiency thermal neutral hydrogen atoms.
We present a uniform analysis of the atmospheric escape rate Neptune-like planets with estimated radius and mass (restricted to $M_{\rm p}<30\,M_{\oplus}$). For each planet we compute restricted Jeans parameter, $\Lambda$, for hydrogen atom evaluated at planetary mass, radius, equilibrium temperature. Values $\Lambda\lesssim20$ suggest extremely high mass-loss rates. identify 27 (out 167) that are simultaneously consistent hydrogen-dominated atmospheres expected exhibit extreme further...
We present a study of plasma conditions in the atmospheres Hot Jupiters HD 209458b and 189733b for an like planet at orbit locations between 0.2 1 au around Sun-like star. discuss how these influence radio emission we expect from their magnetospheres. find that environmental are such cyclotron maser instability (CMI), process responsible generation waves magnetic planets Solar system, most likely will not operate Jupiters. Hydrodynamically expanding possess extended ionospheres whose...
Stellar coronal mass ejections (CMEs) may play an important role in mass- and angular momentum loss of young Sun-like stars. If occurring frequently, they also have a strong effect on planetary evolution by increasing atmospheric erosion. So far it has not been possible to infer the occurrence frequency stellar CMEs from observations. Based their close relation with flares Sun, we develop empirical model combining solar flare-CME relationships flare rates estimate CME activity late-type...
Abstract For the hot exoplanets CoRoT-24b and CoRoT-24c, observations have provided transit radii RT of 3.7 ± 0.4R⊕ 4.9 0.5R⊕, masses ≤5.7M⊕ 28 11M⊕, respectively. We study their upper atmosphere structure escape applying an hydrodynamic model. Assuming ≈ RPL, where RPL is planetary radius at pressure 100 mbar, we obtained for unrealistically high thermally driven rates. This due to planet's temperature low gravity, independent stellar EUV flux. Such rates could last only &lt;100 Myr,...
We present a new observational campaign, DWARF, aimed at detection of circumbinary extrasolar planets using the timing minima low-mass eclipsing binaries. The observations will be performed within an extensive network relatively small to medium-size telescopes with apertures ~20-200 cm. starting sample objects monitored contains (i) binaries M and K components, (ii) short-period sdB or sdO component, (iii) post-common-envelope systems containing WD, which enable determine high precision....
Weak intrinsic magnetic dipole moments of tidally locked close-in giant exoplanets ("hot Jupiters") have been shown in previous studies to be unable provide an efficient magnetospheric protection for their expanding upper atmospheres against the stellar plasma flow, which should lead significant non-thermal atmosphere mass loss. The present work provides a more complete view magnetosphere structure "hot Jupiters," based on paraboloid model (PMM). Besides planetary dipole, PMM considers among...