Abstract: We discuss the long-term (years) activity of soft X-ray transients. These systems contain a compact object (neutron star, black hole) accreting matter from their low-mass, lobe filling companion. We show how this activity manifests itself in the X-ray spectral region. We pay special attention to the intense outbursts of such systems. We present examples of the light curves of such objects obtained by monitors of X-ray emission (ASM/RXTE and BAT/Swift). These monitors are important instruments for observing the activity on long timescales (even of more than ten years). We show that the X-ray light curves of X-ray transients obtained by the monitors contain various very useful features which can be used for the astrophysical analyzes.

Abstract: Observations of Ellerman bursts (EBs) show them as a small brightenings well observed in different chromospheric lines, both in the optical and UV spectral ranges (H I, Ca II, Mg II). EBs are manifestation of small reconnection processes occurred in the lower solar atmosphere and they can contribute to the chromospheric heating. H-alpha line profiles of EBs exhibit enhanced emission at line-wings even up to a few angstroms from the line core. On the contrary, Ca II and Mg II lines emitted by EBs can be strongly enhanced also in the line cores. We used new UV (IRIS) spectroscopic observations to find models of different EBs observed in the new magnetic flux emergence area. Obtained models of EBs showed that they can be described by one or two component 'hot-spot’ thermal structure.  We found that EBs can be formed in an extended domain of altitudes in the photosphere and/or the chromosphere (400 to 750 km). Our results are consistent with the theory of heating by Joule dissipation in the atmosphere produced by magnetic field reconnection during flux emergence. I will also discuss the new EBs diagnostics possibilities based on the new radio observations in millimeter range obtained in future by ALMA instrument.

Abstract: Massive stars strongly influence their surrounding interstellar medium mainly via photo-ionisation, stellar winds and supernova explosions. These processes are able to sweep up significant amounts of the surrounding gas into cold and dense shells. The shells fragment due to their self-gravity and if they form sufficiently massive stars, the whole process can repeat itself leading to propagating star formation. To circumvent numerical difficulties when modelling this process, we approximate a part of such a shell by an isothermal layer and investigate its fragmentation. The layer is self-gravitating and is confined by external pressure. The importance of self-gravity relative to external pressure is a free parameter in our models. In linear regime of fragmentation, we compare our numerical dispersion relation with analytical estimates found in literature. We follow the fragmentation in the non-linear regime and find that the layer fragments in two qualitatively different ways that were not reported previously. If the external pressure dominates, the layer firstly breaks into gravitationally unbound fragments which merge until they form gravitationally bound objects. On the other hand, if self-gravity dominates, the layer monotonically collapses to bound objects. We use this simple model to provide estimates for fragmenting time and mass of fragments formed in a shell powered by an HII region.

Abstract: Instrumental observations of fireballs, especially those that can produce meteorites, are of great scientific interest and importance because meteorites provide us with a surviving physical record of the formation of our solar system and a direct link to their parent asteroids. Last such event occurred over Upper Austria in the late evening of March 6, 2016 and terminated exactly over Upper Austria-Bavaria border. This -15 magnitude bolide terminated its light very deeply in the atmosphere and heavily fragmented in the last third of its luminous flight, so the fall of a larger number of meteorites of different sizes was almost certain. In spite of a quite bad weather situation over whole Central Europe, this bolide was well recorded optically by 7 Digital Autonomous Fireball Observatories (DAFO) in the Czech part of the European Fireball Network. Apart from these optical records almost all DAFOs in our network provided us with high resolution light curves. It enabled us to get very reliable and complex information about position, dynamics, photometry, absolute timing and initial orbit of this extraordinary event. This case very illustratively demonstrates the capability of our recently modernized fireball network because only scientifically useful records of this extraordinary case were taken by our automated stations. Thanks to it we were also able to predict the possible impact area already second day after the bolide and meteorites could be recovered in this predicted area so soon. The first results based on the analysis of the available records will be presented. Recovery of meteorites and their analysis will be also shortly mentioned.