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V. Straizys

Publications and source records attributed to V. Straizys.

26 records · Page 2Linked to original sources
arXiv2008

Young Stars in the Camelopardalis Dust and Molecular Clouds. III. the GL 490 Region

Using the infrared photometry data extracted from the 2MASS, IRAS and MSX databases, 50 suspected young stellar objects (YSOs) are selected from about 37500 infrared objects in the 3x3 deg area with the center at Galactic longitude 142.5 deg and latitude +1.0 deg, in the vicinity of the young stellar object GL 490 in the dark cloud DoH 942 (Dobashi et al. 2005). The spectral energy distributions between 700 nm and 100 mum suggest that most of the selected objects may be YSOs of classes I and II. In the color-magnitude diagram K_s vs. H-K_s the suspected YSOs occupy an area right of the main sequence what can be interpreted as being caused by the effects of luminosity, interstellar and circumstellar reddening and infrared thermal emission in circumstellar envelopes and disks.

astro-ph↗
arXiv2007

Seven-color Vilnius photometry of the open cluster NGC 752

New photoelectric seven-color observations in the Vilnius system are presented for 65 stars in the region of the open cluster NGC 752. Based on individual stars with accurate photometric classifications, we determine the apparent distance modulus (m-M)=8.38 and the mean reddening to the cluster E(Y-V)=0.027, or E(B-V)=0.034. The mean photometric metallicity for the main-sequence stars, [Fe/H]=-0.14, is found to be slightly lower than that derived for the red clump giants, [Fe/H]=-0.08. This difference suggests that red giants in later evolutionary phases may not have zero-age surface values of [Fe/H]. We made use of the least-squares minimization techniques to fit the Padova theoretical isochrones to the CMD, when the binary star population is taken into account. By varying the distance modulus, metallicity and age, the best match has been found between the seven magnitudes and colors of the observed stars and those of model binaries, which gives the distance modulus by 0.2 mag smaller than that derived from individual stars, i.e., (m-M)=8.18, a closely similar metallicity ([Fe/H]=-0.12), and age of 1.6 Gyr. With these results, the fraction of photometric binaries among the main-sequence stars is ~40%.

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arXiv2005

The design and performance of the Gaia photometric system

The European Gaia astrometry mission is due for launch in 2011. Gaia will rely on the proven principles of ESA's Hipparcos mission to create an all-sky survey of about one billion stars throughout our Galaxy and beyond, by observing all objects down to 20th magnitude. Through its massive measurement of stellar distances, motions and multi-colour photometry it will provide fundamental data necessary for unravelling the structure, formation and evolution of the Galaxy. This paper presents the design and performance of the broad- and medium-band set of photometric filters adopted as the baseline for Gaia. The nineteen selected passbands (extending from the ultraviolet to the far-red), the criteria, and the methodology on which this choice has been based are discussed in detail. We analyse the photometric capabilities for characterizing the luminosity, temperature, gravity and chemical composition of stars. We also discuss the automatic determination of these physical parameters for the large number of observations involved, for objects located throughout the entire Hertzsprung-Russell diagram. Finally, the capability of the photometric system to deal with the main Gaia science case is outlined.

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arXiv2003

Interstellar extinction in the direction of the Aquila Rift

The distance dependence of interstellar extinction in the direction of the Aquila Rift is investigated using 473 stars observed in the Vilnius photometric system. Front edge of the dark clouds in the area is found to be at 225$\pm$55 pc and the thickness of the cloud system can be about 80 pc. The maximum extinction A_V in the clouds is close to 3.0 mag. Two stars with larger extinction are found and discussed. Since the new distance of the clouds is larger than the previously accepted distance, the cloud system mass should be increased up to 2.7 10^5 M_sun which is close to the virial mass estimated from the CO velocity dispersion. Additional arguments are given in favor of the genetic relation between the Serpens and the Scorpio-Ophiuchus dark clouds.

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arXiv2002

Kurucz model energy distributions: a comparison with real stars. II. Metal-deficient stars

Energy distributions of synthetic spectra for Kurucz model atmospheres are compared with observed energy distributions of metal-deficient stars of the blue horizontal-branch (BHB), F-G-K subdwarf (SD) and G-K giant (MDG) types. The best coincidence of the synthetic and observed energy curves is found for BHB stars. The largest differences are found in the ultraviolet wavelengths for subdwarfs and cool MDGs. The influence of errors of effective temperatures, gravities and metallicities is estimated.

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arXiv2002

Photometric investigation of the MBM 12 molecular cloud area in Aries. II. Cloud distance

Photoelectric magnitudes and color indices in the Vilnius seven-color system for 152 stars are used to investigate the interstellar extinction in the area of the Aries molecular cloud MBM 12, coinciding with the L1454 and L1457 dust clouds. Spectral types, absolute magnitudes, color excesses, interstellar extinctions and distances of the stars are determined. The plot of interstellar extinction Av versus distance shows that the dust cloud is situated at a distance of 325 pc, at 180 pc from the Galactic plane, and its true diameter is about 11 pc. The interstellar extinction law in the area is found to be normal, typical for the diffuse dust. Ten peculiar or unresolved binary stars and some heavily reddened stars are detected.

astro-ph↗
arXiv2002

CCD photometry and classification of stars in the North America and Pelican nebulae region. I. Moletai photometry

Magnitudes and color indices in the Vilnius seven-color system are measured for 690 stars down to ~13.2 mag in the area of the North America and Pelican nebulae. Spectral types, absolute magnitudes, color excesses, interstellar extinctions and distances of the stars are determined. The plots of interstellar extinction Av versus distance for the North America Nebula and for the dark cloud L935 show that both areas are covered by the same absorbing cloud, situated at a distance of 600 pc. The maximal extinction in the area of the nebula is ~3 mag, while in the dark cloud L935 it is much greater.

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