We report observations of the flickering variability of the symbiotic recurrent nova RS Oph at quiescence in five bands (UBVRI). We find evidence of a correlation between the peak-to-peak flickering ...amplitude (ΔF) and the average flux of the hot component (F
av). The correlation is highly significant, with a correlation coefficient of 0.85 and a p-value of ∼10−20. Combining the data from all wavebands, we find a dependence of the type
$\Delta F \propto F_{{\rm av}}^k$
, with power-law index k = 1.02 ± 0.04 for the UBVRI flickering of RS Oph. Thus, the relationship between the amplitude of variability and the average flux of the hot component is consistent with linearity. The rms amplitude of flickering is on average 8 per cent (±2 per cent) of F
av. The detected correlation is similar to that found in accreting black holes/neutron stars and cataclysmic variables. The possible reasons are briefly discussed. The data are available upon request from the authors.
Galactic Structure Toward the Carina Tangent Kaltcheva, N. T.; Golev, V. K.
Publications of the Astronomical Society of the Pacific,
02/2012, Letnik:
124, Številka:
912
Journal Article
Recenzirano
Odprti dostop
ABSTRACT This investigation presents a photometric study of the Galactic structure toward the Carina arm tangent. The field is located between 280° and 286° Galactic longitude and -4° to 4° Galactic ...latitude. All currently available uvbyβ data are used to obtain homogeneous color excesses and distances for more than 260 stars of spectral types O to G. We present revised distances and average extinction for the open clusters and cluster candidates NGC 3293, NGC 3114, Lodén 46, and Lodén 112. The cluster candidate Lodén 112 appears to be a very compact group at a true distance modulus of 11.06 ± 0.11(s.e.) ( 1629 - 80 + 84 pc ), which is significantly closer than previous estimates. We found other OB stars at that same distance and, based on their proper motions, suggest a new OB association at coordinates 282° < l < 285° and -2° < b < 2°. Utilizing BV photometry and spectral classification of the known O-type stars in the very young open cluster Wd 2, we provide a new distance estimate of 14.13 ± 0.16 (s.e.) ( 6698 - 475 + 512 pc ), in excellent agreement with recent distance determinations to the giant molecular structures in this direction. We also discuss a possible connection between the H ii region RCW 45 and the highly reddened B+ star CPD -553036 and provide a revised distance for the luminous blue variable HR Car.
Aims. The distribution of OB stars along with Hα, 12CO, dust infrared emission, and neutral hydrogen is carried out to provide a more complete picture of interactions of the young massive stars and ...the observed supershell GSH 305+01−24. Methods. The studied field is located between 299° ≤ l ≤ 311° and −5° ≤ b ≤ 7°. The investigation is based on nearly 700 O-B9 stars with currently available uvbyβ photometry. The derived stellar physical parameters were used to establish a homogeneous scale for the distances and extinction of light for major apparent groups and layers of foreground and background stars in Centaurus and to study the interaction with the surrounding interstellar medium. Results. The distance to the entire Centaurus star-forming complex is revised, and a maximum of the OB-star distance distribution is found at 1.8 ± 0.4 (rms) kpc. The massive star component of GSH 305+01−24 is identified at about 85−90% completeness up to 11.5−12 mag. The projected coincidence of the OB stars with the shell and the similarities between the shell’s morphology and the OB-star distribution indicate a strong interaction of the stellar winds with the superbubble material. We demonstrate that these stars contribute enough wind injection energy to explain the observed size and expansion velocity of the supershell. The derived stellar ages suggest an age gradient over the Coalsack Loop. Continuous star formation might be taking place within the shell with the youngest stars located toward its periphery, and the open cluster NGC 4755 is the oldest. A layer of very young stars at 1 kpc is detected, and its connection to both GSH 305+01−24 and the foreground GSH 304−00−12 H i shells is investigated.
We present the results of low-resolution optical spectroscopy with OSIRIS/GTC (Optical System for Imaging and Low Resolution Integrated Spectroscopy/Gran Telescopio Canarias) for a sample of ...ultracool dwarfs. For a subsample of seven objects, based on 2 Micron Sky Survey (2MASS) NIR photometric colours, a 'photometric' spectral type is determined and compared to the results of the optical spectroscopy. For the stars, showing Hα line in emission, equivalent widths were measured, and the ratio of Hα to bolometric luminosity were calculated. We find that two dwarfs show the presence of magnetic activity over long periods, LP 326-21 -- quasi-constant-like, and 2MASS J17071830+6439331 -- variable.
The conditions of electron beam welding of VZh172L high-strength nickel alloy in the same combination and with the VZh172 deformed alloy are selected and the mechanical properties and structure of ...welded joints are examined.
Context. NGC 7679 (Mrk 534) is a nearby (z = 0.0177) nearly face-on SB0 luminous infrared Sy2 galaxy in which starburst and AGN activities co-exist. The ionization structure is maintained by both the ...AGN power-law continuum and starburst. The galaxy is a bright X-ray source possessing a low X-ray column density NH < 4 $\times$ 1020 cm-2. Aims. The Compton-thin nature of such unabsorbed objects infers that the simple formulation of the Unified model for SyGs is not applicable in their case. The absorption is likely to originate at larger scales instead of the pc-scale molecular torus. The main goal of this article is to investigate both gas distribution and ionization structure in the circumnuclear region of NGC 7679 in search for the presence of a hidden Sy1-type nucleus, using the O IIIλ5007 luminosity as a tracer of AGN activity. Methods. NGC 7679 was observed with the 2m RCC reflector of the Ukraine National Astronomical Observatory at peak Terskol, Caucasus, Russia. The observations were carried out in October 1996 with the Focal Reducer of the Max-Planck-Institut für Sonnensystemforschung, Germany. All observations were taken with tunable Fabry-Perot narrow-band imaging with spectral FWHM of the Airy profile $\delta\lambda$ between 3 and 4 Å depending on the used wavelength. Results. The O IIIλ5007 emission-line image of the circumnuclear region of NGC 7679 shows elliptical isophotes extended along the PA ≈ 80° in the direction of the counterpart galaxy NGC 7682. There is a maximum of this emission which is shifted ~4 arcsec from the center as defined by the continuum emission. The maximum of ionization by the AGN power-law continuum traced by O IIIλ5007/Hα ratio is displaced by ~13 arcsec eastward from the nucleus. The direction where high ionization is observed at PA ≈ 80° ± 10° coincides with the direction to the companion galaxy NGC 7682 (PA ≈ 72°). On the contrary, at PA ~ 0° the ionization in the circumnuclear region is entirely due to hot stars. Conclusions. Both the ratio $(N_{\rm ph}/N_{\rm ion})_{h\nu\,>\,55\,{\rm eV}} \approx$ 0.2-20 of the number Nph of photons traced by O III to the number Nion of high-energy ionizing photons and the presence of weak and elusive Hα broad wings indicate a hidden AGN. We conclude that the dust and gas in the high ionization direction PA ≈ 80° has a direct view to the central AGN engine. This possibly results in dust/star-formation decay. A large fraction of the unabsorbed Compton-thin Sy2s with O III luminosity $\ga$1041 erg s-1 possesses a hidden AGN source.
The paper clarifies the influence of TIG and EB welding variants and highly temperature-resistant cast nickel super alloy-shaped parts being in a heat-hard enable condition on mechanical properties ...and structure of welded joints of the combinations casting with casting and casting with deformable semi-finished product. The research trackles the problem of short-term durability at temperatures of 20°С and long-term durability at temperatures of 650°C and 1000°C. The filler materials for argon-arc welding and relevant modes for electron-beam welding are selected. They provide a high complex of mechanical properties and an appropriate structure of welded joints.
The conditions of manual argon-arc welding and filler materials were selected and investigations were carried out into the technological, mechanical and corrosion properties and the structure of ...welded joints in the VKNA-1VR intermetallic alloy. The possibilities of repairing casting defects in castings are also investigated.
The paper clarifies the influence of TIG and EB welding variants and highly temperature-resistant nickel superalloy VG159 being in a heat-hardenable condition without post-heat treatment on ...mechanical properties and structure of welded joints. The research trackles the problem of short- and long-term durability at a temperature of 850 and 870°С and covers the issue of resilience. The filler materials for argon-arc welding and relevant modes for electron-beam welding are selected. They provide a high complex of mechanical properties and an appropriate structure of welded joints
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