What can we learn from GRBs?

We review our recent results on the classification of long and short gamma-ray bursts (GRBs) in different subclasses. We provide observational evidences for the binary nature of GRB progenitors. For long bursts the induced gravitational collapse (IGC) paradigm proposes as progenitor a tight binary system composed of a carbon-oxygen core (COcore) and a neutron star (NS) companion; the supernova (SN) explosion of the COcore triggers a hypercritical accretion process onto the companion NS. For short bursts a NS–NS merger is traditionally adopted as the progenitor. We also indicate additional sub-classes originating from different progenitors: (COcore)–black hole (BH), BH–NS, and white dwarf–NS binaries. We also show how the outcomes of the further evolution of some of these sub-classes may become the progenitor systems of other sub-classes

The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

A model for the population of helium stars in the Galaxy I. Low-mass stars

By means of population synthesis we model the Galactic ensemble of helium stars. It is assumed that all helium stars are formed in binaries. Under this assumption, single helium stars are produced by the mergers of helium remnants of components of close binaries (mainly, by merging helium white dwarfs) and by disruption of binaries with helium components in supernovae explosions. The estimate of the total birthrate of helium stars in the Galaxy is 0.043 yr$^{-1}$, their total number is estimated as $4 \times 10^6$. The rate of binarity in the total sample is 76%. We construct a subsample of low-mass (M_{\rm He} \lesssim 2 \ms) helium stars limited by observational selection effects: stellar magnitude ($V_{\rm He} \leq 16$), ratio of stellar magnitudes of components in binaries ($V_{\rm He}\leq V_{\rm comp}$), lower limit of the semiamplitude of radial velocity that is necessary for discovery of binarity ($K_{min}=30$ km/s). The parameters of this ``observable'' sample are in satisfactory agreement with the parameters of the observed ensemble of sdB stars. In particular, in the selection-limited sample binarity rate is 58%. We analyze the relations between orbital periods and masses of helium stars and their companions in systems with different combinations of components. We expect that overwhelming majority ($\sim 90$%) of unobserved components in binary sdB stars are white dwarfs, predominantly, carbon-oxygen ones.Comment: 16 pages, 6 figures, submitted to Astronomy Reports, fig. 6 corrected, conclusions unchange

THE ROLE OF CHRONIC POLYPOID RHINOSINUSITIS IN OCCURRENCE OF MALIGNANT EPITHELIAL TUMORS OF THE PARANASAL SINUSES AND THE NASAL CAVITY

Growth of occurrence of malignant epithelial tumors of the nasal cavity (NC) and the paranasal sinuses (PNS) is noted. Absolute majority of patients come for treatment with the III and the IV stage of the disease. No trend for decreasing of the untreatedness parameter is observed. Increasing of the efficiency of treatment of patients with cancer depends on timely diagnostics. The main reason of late diagnostics is insufficient oncological alertness of doctors in polyclinics. The issues of therapy tactics at the stage of pre-tumor diseases of the NC and the PNS remain unsolved, while background process that precede development of cancer are morphologically revealed with 56.7 % of patients. One of the most frequently occurred background development processes of the NC and the PNS cancer is chronic polypoid rhinosinusitis (CPR). The degree of occurrence of CPR is high, and the annual growth of its incidence by 2 to 4 % has been observed for the previous 10 years. There are only certain works that view CPR as a pre-cancer disease.The objective of the study is improvement of results of early diagnostics of cancer and optimization of the surgical tactics with pre-cancer diseases of the upper jaw and the PNS.Materials and methods. Retrospective and prospective clinical and morphological analysis of data of 58 patients with benign polypous changes (BPC) and of 182 patients with malignant epithelial tumors (MET)  of the NC and the PNS treated at the Arkhangelsk Regional Clinical Oncology Dispensary from 1980 to 2010 has been performed.Results and discussion The maximum number of patients in both groups is at the age category from 40 to 59 years. Besides, the average age of patients with the BPC was lower than that of the patients with the MET (45.6 ± 2.3 and 54.0 ± 1.5 years old, respectively).Patients of working age prevailed both in the group with the BPC and the group with the MET of the NC and the PNS (19.0 / 81.0 % and 39.6 / 62.1 %, respectively). Males prevailed in the group with the BPC (53.4 % of males and 46.6 % of females), and females prevailed in the group with the MET (39.6 % of males and 60.4 % of females). However, we believe that this controversy to our hypothesis is explained with greater life expectancy of females (females are the prevailing majority in the groups of age category of 70 to 89 years old: 19.8 % are females, 5.3 % are males).The prevailing number of patients with the BPC (77.6 %) lived in cities, and such number in the group of patients with the MET was 54.9 %. The most frequent type of operative treatment of patients with the BPC was electrical maxillar ethmoidectomy that was performed in 82.9 % of cases. Relapse after performance of electrical maxillar ethmoidectomy was demostrated by 2 patients which comprised 4.3 %.In significant number of cases (70,6 % in the group with the BPC and 65.9 % in the group with the MET), the pathological process was localized in the maxillar cavity. Most frequently, glandular-fibrous polyps were revealed (42.1 %), and this morphological structure prevaled with male patients (57.9 % with males and 26.3 % with females); MET of the NC and the PNS, in their turn, also more frequently occurred with males.In 69.0 %, the CPR has been the background for severe epithelial dysplasia, and the CPR, in its turn, was reveled with 39.8 % of patients with the MET.Conclusion. We believe that the data provided prove the key role of the CPR in development of MET of the NC and the PNS