Connection between orbital modulation of H-alpha and gamma-rays in the Be/X-ray binary LSI+61303

We studied the average orbital modulation of various parameters (gamma-ray flux, H-alpha emission line, optical V band brightness) of the radio- and gamma-ray emitting Be/X-ray binary LSI+61303. Using the Spearman rank correlation test, we found highly significant correlations between the orbital variability of the equivalent width of the blue hump of the H-alpha and Fermi-LAT flux with a Spearman p-value 2e-5, and the equivalent widths ratio EW_B/EW_R and Fermi-LAT flux with p-value 9e-5. We also found a significant anti-correlation between Fermi-LAT flux and V band magnitude with p-value 7.10^{-4}. All these correlations refer to the average orbital variability, and we conclude that the H-alpha and gamma-ray emission processes in LSI+61303 are connected. The possible physical scenario is briefly discussed.Comment: accepted as a Letter in Astronomy and Astrophysic

Narodna nošnja u Brestu (Istra-Ćićarija)

U selu Brestu u istarskoj Ćićariji (općina Buzet) danas je narodna nošnja već gotovo posve iščezla. Do promjena nošnje - koliko se u starinu može doseći - bilo je nekoliko. Kako je Ćićarija i u jezičnom i još više u etnografskom pogledu jedan od najzanimljivijih krajeva Istre, pa kako je u današnjim prilikama ugroženo i ono, što se od narodnoga života i običaja još živo održalo, naročito nošnja, vrijedno je dati njen prikaz. (sa 5 slika

Solar walls for high-performance buildings

Passive solar design can reduce building energy demand for heating, cooling and ventilation, while also contributing to the comfort, well-being and productivity of the building’s occupants. The successful application of passive solar features, such as solar walls, requires a good understanding of the factors influencing their energy performance and a correct assessment of this performance during the design process. This paper discusses some basic design strategies for successful application of solar walls and the factors with the most significant impact on their efficiency. It summarizes the principle results and findings of an experimental study, based on dynamic simulations and test site measurements. The energy performance of various configurations of unvented solar walls was investigated in different climatic conditions. The outcomes of the dynamic simulations were used to develop a simplified quasisteady-state model, which can be used for approximate evaluation of the heat gains and heat losses through an unvented solar wall on a monthly basis. The model is compatible with the monthly method of EN ISO 13790.This work has been supported by The National Science Fund of Bulgaria under projects number ДУНК-01/3 (DUNK-01/3) and ДФНИ Е 02/17 (DFNI E 02/17)

The hydrogen and helium lines of the symbiotic binary Z And during its brightening at the end of 2002

High resolution observations in the region of the lines Halpha, He II 4686 and Hgamma of the spectrum of the symbiotic binary Z And were performed during its small-amplitude brightening at the end of 2002. The profiles of the hydrogen lines were double-peaked. These profiles give a reason to suppose that the lines can be emitted mainly by an optically thin accretion disc. The Halpha line is strongly contaminated by the emission of the envelope, therefore for consideration of accretion disc properties we use the Hgamma line. The Halpha line had broad wings which are supposed to be determined mostly from radiation damping but high velocity stellar wind from the compact object in the system can also contribute to their appearance. The Hgamma line had a broad emission component which is assumed to be emitted mainly from the inner part of the accretion disc. The line He II 4686 had a broad emission component too, but it is supposed to appear in a region of a high velocity stellar wind. The outer radius of the accretion disc can be calculated from the shift between the peaks. Assuming, that the orbit inclination can ranges from 47$^\circ$ to 76$^\circ$, we estimate the outer radius as 20 - 50 R_sun. The behaviour of the observed lines can be considered in the framework of the model proposed for interpretation of the line spectrum during the major 2000 - 2002 brightening of this binary.Comment: 19 pages, 5 figures. Accepted for publication in Astronomy Report

H-alpha observations of the gamma-ray-emitting Be/X-ray binary LSI+61303: orbital modulation, disk truncation, and long-term variability

We report 138 spectral observations of the H-alpha emission line of the radio- and gamma-ray-emitting Be/X-ray binary LSI+61303 obtained during the period of September 1998 -- January 2013. From measuring various H-alpha parameters, we found that the orbital modulation of the H-alpha is best visible in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue hump, and in the radial velocity of the central dip. The periodogram analysis confirmed that the H-alpha emission is modulated with the orbital and superorbital periods. For the past 20 years the radius of the circumstellar disk is similar to the Roche lobe size at the periastron. It is probably truncated by a 6:1 resonance. The orbital maximum of the equivalent width of H-alpha emission peaks after the periastron and coincides on average with the X-ray and gamma-ray maxima. All the spectra are available upon request from the authors and through the CDS.Comment: 11 pages, accepted for publication in A&

H-alpha variability of the recurrent nova T Coronae Borealis

We analyze H-alpha observations of the recurrent nova T CrB obtained during the last decade. For the first time the H-alpha emission profile is analyzed after subtraction of the red giant contribution. Based on our new radial velocity measurements of the H-alpha emission line we estimate the component masses of T CrB. It is found that the hot component is most likely a massive white dwarf. We estimate the inclination and the component masses to be i~67 deg, Mwd = 1.37 +/-0.13 Msun and Msec=1.12 +/-0.23 Msun, respectively. The radial velocity of the central dip in the H-alpha profile changes nearly in phase with that of the red giant's absorption lines. This suggests that the dip is most likely produced by absorption in the giant's wind. Our observations cover an interval when the H-alpha and the U-band flux vary by a factor of ~6, while the variability in B and V is much smaller. Based on our observations, and archival ultraviolet and optical data we show that the optical, ultraviolet and H-alpha fluxes strongly correlate. We argue that the presence of an accretion disc can account for most of the observed properties of T CrB.Comment: 8 pages, 6 EPS figures, to appear in A&