The role of hot low-mass evolved stars (HOLMES) has long been underestimated in various fields of Astronomy. We show here that the population of galaxies with LINER-like spectra is divided among fake AGN (galaxies where the ionization is due to HOLMES) and weak AGN (i.e. the "little monsters"). We also show that the problem of the ionization of the diffuse interstellar gas in galaxies is solved when considering the role of HOLMES.

There are several lines of evidence that active galactic nuclei can be regarded as scaled-up X-ray binaries (XRB). The timescales of the evolutionary phenomena in these two classes are proportional to the black hole masses. Consequently, unlike in the case of XRBs, the evolution of AGNs is too slow to be followed directly. What could be done, however, is to assign particular types of active galaxies to different evolutionary stages observable in XRBs. We found three quasars with clear signatures of a recent transition from radio-loud to radio-quiet state and our own observations confirmed that, despite conspicuous relic large-scale radio structures, their cores can be labelled radio-quiet, anyway. It looks, therefore, that these objects were in the so-called Very High state before and now have shifted to High/Soft state. Analogous transitions in XRBs are well known.

Four variable gamma-ray sources (GeV-TeV) have been associated with binary systems in our Galaxy: the "microquasar" Cygnus X-3 and the "gamma-ray binaries" LS I +61 303, LS 5039 and PSR B1259-63. These objects are all composed of a massive companion star and a compact object of unknown nature, possibly a young pulsar or an accreting black hole. After a brief introduction on gamma-ray astronomy, I will present a comprehensive theoretical model for the high-energy gamma-ray emission and variability in these systems. In this model, the high-energy radiation is produced by inverse Compton scattering of stellar photons on ultra-relativistic electron-positron pairs injected by a young pulsar in gamma-ray binaries and in a relativistic jet in microquasars. I will show that this model explains well the TeV gamma-ray emission observed in LS 5039, but cannot account for the gamma-ray emission in LS I +61 303 and PSR B1259-63. Other processes may dominate in these more complex systems. In Cygnus X-3, the gamma-ray radiation is convincingly reproduced by relativistic Doppler-boosted Compton emission of pairs in a jet. Gamma-ray binaries and microquasars provide a novel environment for the study of pulsar winds and relativistic jets at very small spatial scales.

One of the outstanding subjects of Modern Physics, as the unification of the four fundamental forces in a common scheme of the Quantum Gravity theories, can be studied with high energy photons from astrophysical sources. Search for the Lorentz Invariance Violation (LIV) provides a good observational window on several Quantum Gravity models. The time-of-flight studies with photons are well suited for the detection of tiny effects at the energy Planck scale. Within last few years, all major Gamma-ray experiments have published results on LIV with variable astrophysical sources: Gamma-Ray Bursts (GRBs) with detectors on-board satellites and Active Galactic Nuclei (AGNs) with ground-based experiments. A status of these studies will be reported and the impact on the theoretical landscape will be discussed.

It is generally assumed that outbursts in Low-Mass X-ray Binaries are produced by the same thermal-viscous instability of the accretion disc that drives dwarf-nova outbursts. This assumption is substantiated by the observed properties of transient black-hole binaries although the model itself (the Disc Instability Model - DIM) suffers from some rather serious problems even in the case of dwarf-novae for which it was designed. After a short presentation of the model and its difficulties I will address the question of its applicability to the variability observed in Active Galactic Nuclei and in the recently discovered Intermediate-Mass Black-Hole system HLX-1 in the galaxy ESO 243-49.

It is straightforward to calculate a marginal probability distribution function (PDF) from a certain multivariate PDF. However, the inverse is not trivial: when we have the whole set of marginals, can we reconstruct the original multivariate PDF?
The answer is partially true. The statistical tool for this problem is the copula. I will present the definition, derivation, and construction of copulas in this seminar.
Then, I present its application to the bivariate luminosity function of galaxies as a straightforward example. I will also discuss other possible applications.

Over the last few decades, it has been increasingly clear that there is an extremely compact object at Sgr A* in the center of the galaxy. Some have looked at the theoretical gravitational lensing properties of this object, particularly on stars orbiting the galactic center. In this talk, I explore the possibility that a "boson star" or compact collection of scalar particles, is responsible for the large mass at Sgr A*. This possibility cannot be ruled out by observation of dynamical processes because of the compactness of a boson star. However, I argue that the gravitational lensing properties of a boson star have unique properties and their presence or absence would be strong evidence for or against a boson star in the galactic center.

Since 2008 Fermi-LAT collect full-sky data in gamma. This reveals significant signal in the inner Galaxy - two gamma-ray bubbles, extending 50 degrees above and below the Galactic centre. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze. This lecture are made to introduce structure and morphology of this new phenomena in Galaxy and discuss models of the bubbles origin.

Gamma-Ray Bursts (GRBs) are the brightest sources in the universe, emit mostly in the hard X-ray energy band and have been detected at redshifts up to about 8.1. Thus, they are in principle very powerful probes for cosmology. I shortly review the researches aimed to use GRBs for the measurement of cosmological parameters, which are mainly based on the correlation between spectral peak photon energy and total radiated energy or luminosity. In particular, based on an enriched sample of 110 GRBs, I will provide an update of the analysis by Amati et al. (2008) aimed at extracting information on Ω_M and, to a less extent, on Ω_Λ, from the Ep,i - Eiso correlation. I also briefly discuss the perspectives of using GRBs as cosmological beacons for high resolution absorption spectroscopy of the IGM (e.g., WHIM), and as tracers of the SFR, up to the "dark ages" (z > 6) of the universe.

The Big Bang singularity (together with some others) is one of the key problems in theoretical physics. To understand better the early universe, it is mandatory to investigate its quantum aspects with new fundamental theories. It is therefore essential to experimentally test such theories to allow for a clear discrimination. I would like to show some observable consequences of one of them, namely Loop Quantum Gravity (LQG) and its application to cosmology called Loop Quantum Cosmology (LQC). In this talk, I will firstly introduce some useful cosmological tools, and I will then focus on cosmological perturbations in the framework of LQC, especially the tensorial ones. Finally, I will present some recent results regarding the cosmic inflation within LQC and its consequences on the CMB.

Life on the Earth is determined and affected in surprisingly many different ways by the Sun. The fact that the Earth rotates around the Sun causes the influence of the Sun on Earth to be season dependent. Moreover, our planet also rotates around its own axis so that (on most places on Earth) we strongly depend on the day/night contrast. During the day we can enjoy the light and warmth of `our' star and at night we live in the shadow of our own planet. The weather characteristics are mostly caused by the conditions in the Earth's atmosphere. The formation of clouds, wind and pressure differences can mess up a sunny day completely. Most people do not know more about the weather system on Earth than this and do not realize that the Sun brings more than light and warmth. Apart from the visible light the Sun radiates also in a broad spectrum of other wave lengths. In addition, we also experience a continuous outflow of solar matter emitted in all directions. It gets even more interesting when it turns out that our star is very dynamic and it has a fairly explosive nature and emits now and then enormous magnetic plasma clouds at extremely high velocities in our direction! The whole set of complex effects of the radiation and the plasma stream from the Sun on the Earth and her magnetosphere, our technological systems, our climate and the people determines most of the so-called space weather. The explosions that occur frequently on the Sun and especially the magnetic plasma clouds - the coronal mass ejections (CMEs) - associated to them are the most important solar drivers of the space weather. The detectable effects on Earth appear in a broad spectrum of time and length scales and have various harmful effects for human health and for our technologies. Polar light (aurora) is one of the nicest and least harmful space weather effects but alas, the space weather can also have less amusing effects on Earth. Bad weather conditions in space can hinder or damage satellite operations and communication and navigation systems and even cause power grid outages leading to a variety of tremendous socio-economic losses. Moreover, it causes radiation risks for the crew and passengers on air planes and astronauts in space. Finally, it can influence global climate changes, which is of topical interest today. Since the space weather effects on Earth are mainly determined by the Sun, we will first say something about the most important features of this star. Then we briefly discuss the effects of space weather on Earth. Finally, we search for the causes or sources of the space weather and we focus on the scientific research and the mathematical modeling of the space weather that aims at improving the daily predictions and forecasts.

I will discuss two burning problems of cometary science: 1) what is the characteristic time-scale on which comet nuclei change their rotation periods, and 2) is the nucleus compositionally heterogeneous or homogeneous? Neither property has been well established by observations, although both are of key importance. The former is a proxy for lifetime with respect to centripetal disruption; the latter holds clues about the formation process of comets. The discussion will be based on the results from an extensive mm/submm spectroscopic monitoring of comet 103P/Hartley 2, carried out from the ground in late 2010. I will also briefly summarize the key findings from NASA's EPOXI mission, which approached the comet on Nov. 4.6, 2010 UT.