Simultaneous UBVRI observations of the cataclysmic variable AE Aquarii: Temperatures and masses of fireballs     

R.K. Zamanov  G.Y. Latev  K.A. Stoyanov  S. Boeva  B. Spassov  S.V. Tsvetkov 《Astronomische Nachrichten》2012,333(8):736-743

We report simultaneous multicolour observations in 5 bands (UBVRI) of the flickering variability of the cataclysmic variable AE Aqr. Our aim is to estimate the parameters (colours, temperature, size) of the fireballs that produce the optical flares. The observed rise times of the optical flares are in the interval 220‐440 s. We estimate the dereddened colours of the fireballs as (U ‐B)₀∼0.8‐1.4, (B ‐V)₀∼0.03‐0.24, and (V ‐I)₀∼0.26‐0.78. We find for the fireballs temperatures of 10000‐25000 K, masses of (7‐90)x10¹⁹ g, and sizes of (3‐7)x10⁹ cm (using a distance of d = 86 pc). These values refer to the peak of the flares observed in the UBVRI bands. The data are available upon request from the authors (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Micro‐PIXE Geochemical Fingerprinting of Nephrite Neolithic Artifacts from Southwest Bulgaria     

Ruslan I. Kostov  Christo Protochristov  Chavdar Stoyanov  Lszl Csedreki  Alíz Simon  Zita Szikszai  Imre Uzonyi  Bisserka Gaydarska  John Chapman 《Geoarchaeology》2012,27(5):457-469

Neolithic artifacts made of nephrite, □Ca₂(Fe,Mg)₅Si₈O₂₂(OH)_2, are found at prehistoric settlements in Bulgaria. This study investigates these objects based on particle induced X‐ray emission using a scanning nuclear microprobe (micro‐PIXE technique). Seven nephrite artifacts from the Neolithic sites of Kovachevo, Bulgarchevo and Galabnik in southwest Bulgaria were analyzed to quantify their composition and to establish if a correlation exists between the distribution of major and trace elements, color, impurities, and texture. The nephrite artifacts are tremolite in composition, with a proposed ultrabasic origin. Based on the geochemical data obtained by micro‐PIXE, we divide the artifacts into Group 1 objects from the Kovachevo site and Group 2 objects from the Galabnik and Bulgarchevo sites. The analytical data and microprobe analyses are compared with geochemical data of nephrite from across the globe. The results are in a good agreement with previous electron microprobe and electron paramagnetic resonance (EPR) spectroscopy data. Our study provides a better understanding of the mineralogy and geochemistry of nephrite artifacts and helps to address questions regarding origin and the distribution of such materials in Bulgaria and other Balkan countries.  相似文献   

Difference between the optical flickering colours of cataclysmic variables and symbiotic recurrent novae     

R. Zamanov  S. Boeva  G. Latev  K. A. Stoyanov  S. V. Tsvetkova 《Astronomische Nachrichten》2015,336(2):189-195

We performed simultaneous observations in 3 bands (U BV) of the flickering variability of the recurrent novae RS Oph and T CrB at quiescence. Using new and published data, we compare the colours of the flickering in cataclysmic variables and symbiotic recurrent novae. We find a difference between the colours of the flickering source in these two types of accreting white dwarfs. The detected difference is highly significant with p ‐values ≈2 x 10^–6 for the distributions of (U – B)₀ colour and p ≈ 3 x 10^–5 on an (U – B) versus (B – V) diagram. The possible physical reasons are briefly discussed. The data are available upon request from the authors. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Tidal interaction in High‐Mass X‐ray Binaries     

K.A. Stoyanov  R.K. Zamanov 《Astronomische Nachrichten》2009,330(7):727-732

Our aim is to investigate tidal interaction in High‐Mass X‐ray Binary stars in order to determine in which objects the rotation of the mass donors is synchronized or pseudosynchronized with the orbital motion of the compact companion. We calculate the pseudosynchronization period (P_ps) and compare it with the rotational period of the mass donors (P_rot). We find that (1) the Be/X‐ray binaries are not synchronized, the mass donors rotate faster than the orbital period and the ratio P_ps/P_rot is 2–300; (2) the giant and supergiant systems are close to synchronization and for them the ratio P_ps/P_rot is 0.3–2 (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Orbital parameters of the high‐mass X‐ray binary 4U 2206+54     

K. A. Stoyanov  R. K. Zamanov  G. Y. Latev  A. Y. Abedin  N. A. Tomov 《Astronomische Nachrichten》2014,335(10):1060-1063

We present new radial velocities of the high‐mass X‐ray binary star 4U 2206+54 based on optical spectra obtained with the Coudé spectrograph at the 2 m RCC telescope of the Rozhen National Astronomical Observatory, Bulgaria in the period November 2011–July 2013. The radial velocity curve of the He I δ6678 Å line is modeled with an orbital period P_orb = 9.568 d and an eccentricity of e = 0.3. These new measurements of the radial velocity resolve the disagreements of the orbital period discussions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Orbital eccentricity of the symbiotic star MWC 560     

R.K. Zamanov  A. Gomboc  K.A. Stoyanov  I.K. Stateva 《Astronomische Nachrichten》2010,331(3):282-285

We present projected rotational velocity measurements of the red giant in the symbiotic star MWC 560, using the high‐resolution spectroscopic observations with the FEROS spectrograph. We find that the projected rotational velocity of the red giant is v sin i = 8.2 ± 1.5 km s^–1, and estimate its rotational period tobe P_rot = 144–306 days. Using the theoretical predictions of tidal interaction and pseudosynchronization, we estimate the orbital eccentricity e = 0.68–0.82. We briefly discuss the connection of our results with the photometric variability of the object (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Gated communities in Bulgaria: interpreting a new trend in post-communist urban development   总被引：1，自引：0，他引：1  

Petar Stoyanov  Klaus Frantz 《GeoJournal》2006,66(1-2):57-63

Private residential neighbourhoods encircled by a wall or fence and cut off from the public by a remote-controlled or guarded gate are not entirely new in Bulgaria. Both ‘dacha’ and leisure settlements of the communist rulers existed in such enclosed developments on the outskirts of Sofia, in mountain resorts, and on the coast of the Black Sea until the end of the 1980s. After the political change in 1989, new types of walled settlements, similar to gated communities in the U.S., began to spring up in Bulgaria, a result of the dramatic and decisive changes in Bulgarian society that are still very much underway today. Seven gated communities, comprising 78 housing units and six projects that are not yet fully completed create an entirely new social context and a residential landscape in the Sofia metropolitan area, which may indicate future residential desires. Ivanyane, situated on the western periphery of Sofia, and Mountain View Village to the southeast, exemplify the two main types of gated communities which are either self-organized by residents or developer-organized. The reasons why these gated communities were built appear to be very similar to those in other places. It can be expected that the demand for this new type of residential living will continue to increase in Sofia’s urban periphery, but it would be unwise to assume that these developments will necessarily provide a positive context for building a new society. The research for this paper was made possible through a project on post-communist urban development approved and financed by the Austrian Ministry of Education, Science and Culture and the Austrian Institute for East and Southeast Europe (Liaison Office in Sofia).  相似文献